defra 8191 baled tyres final1. review the international literature (including peer reviewed reports,...

DEFRA

WR1118: LITERATURE REVIEW OF THE USE OF BALED TYRES IN CONSTRUCTION

WRc Ref: DEFRA8191 MARCH 2010

LITERATURE REVIEW OF THE USE OF BALED TYRES IN CONSTRUCTION

Report No.: DEFRA8191

Date: March 2010

Authors: James Peacock, Liz Lawton, Kathy Lewin, Jane Turrell, Victoria Benson, Ian Johnson, Jörgen Jonnsen

Contract Manager: James Peacock

Contract No.: 15349-0

RESTRICTION: This report has the following limited distribution:

External: Defra

Internal: Authors

Any enquiries relating to this report should be referred to the authors at the following address:

WRc Swindon, Telephone: + 44 (0) 1793 865000 Frankland Road, Blagrove, Fax: + 44 (0) 1793 865001 Swindon, Wiltshire, SN5 8YF. Website: www.wrcplc.co.uk

The contents of this document are subject to copyright and all rights are reserved. No part of this document may be reproduced, stored in a retrieval system or transmitted, in any form or by any means electronic, mechanical, photocopying, recording or otherwise, without the prior written consent of the copyright owner.

This document has been produced by WRc plc.

CONTENTS

EXECUTIVE SUMMARY 1

1. INTRODUCTION 5

1.1 Background 5 1.2 Project Objectives 5 1.3 Definition, arisings and fate 6 1.4 Legislative framework 7

2. METHODOLOGY FOR LITERATURE REVIEW AND DATA ASSESSMENT 9

2.1 Introduction 9 2.2 Methodology 10 2.3 Numbers of papers reviewed 11 2.4 Collation of reports 12 2.5 Collation of data 13

3. LITERATURE REVIEW FINDINGS 15

3.1 Introduction 15 3.2 Contaminants of potential concern 15 3.3 Re-use scenarios 23 3.4 Other factors 27

4. ASSESSMENT OF DATA 29

4.1 Introduction 29 4.2 Assessment of data 31 4.3 Ecotoxicological test data 39 4.4 Overview of key issues 44

5. CONCLUSIONS 47

5.1 Marine 47 5.2 Freshwater 47 5.3 Peat bogs 48 5.4 Overall conclusions 48

6. SUGGESTIONS FOR FURTHER WORK 49

REFERENCES 51

APPENDICES

APPENDIX A ORGANISATIONS CONTACTED FOR ASSESSMENT 59 APPENDIX B ECOTOXICITY DATA AND ENVIRONMENTAL BENCHMARKS

FOR RELEVANT CONTAMINANTS 61 APPENDIX C SUMMARY OF ALL PAPERS REVIEWED 69 APPENDIX D ECOTOXICOLOGY REVIEW 71 APPENDIX E METHODOLOGY FOR ASSESSMENT OF LEACHING

POTENTIAL 92 APPENDIX F COLLATED LEACHING DATA FROM LITERATURE REVIEW 98

LIST OF TABLES

Table 1.1 Fate of end-of-life tyres in the UK in 2008 6 Table 2.1 Summary of source – pathway – receptor approach and relevant

water quality issues for each scenario 10 Table 2.2 Country of origin of reports collected for study 11 Table 3.1 Bulk composition of car and truck tyres 16 Table 3.2 Bulk composition of typical tyre 16 Table 3.3 Hazardous compounds in tyres 17 Table 3.4 Concentration of metals at three sites over a three year period taken

directly from fill (Humphrey and Katz, 2001) 26 Table 4.1 Summary of zinc leaching data at L/S10 32 Table 4.2 Reference summary for data used in Figure 4.1 34 Table B1 Freshwater ecotoxicity data for zinc oxide 61 Table B2 PNECadd values for zinc (EU, 2008b) 63 Table B3 Relevant Environmental Benchmarks for organic compounds 64 Table B4 Relevant Environmental Benchmarks for inorganic compounds 66 Table D1 Study design Kellough (1991) 72 Table D2 Study results Kellough (1991) 73 Table D3 Study design (Birkholz et al., 2003) 75 Table D4 Study results (Birkholz et al., 2003) 76 Table D5 Study design (Day et al., 1993). 76 Table D6 Study results (Day et al., 1993) 78 Table D7 Study design (Nelson et al., 1994) 79 Table D8 Study results (Nelson et al., 1994) 80 Table D9 Study design (Wik et al., 2009) 82 Table D10 Study results (Wik et al., 2009) 83 Table D11 Study design (Moretto, 2007) 85 Table D12 Study results (Moretto, 2007) 85 Table D13 Study design (Collins et al., 2002) 87 Table D14 Study results (Collins et al., 2002) 88 Table E1 Examples of leaching tests (after Environment Agency, 2005) 94

LIST OF FIGURES

Figure 2.1 Source information by year of study 11 Figure 4.1 Zinc oxide solubility pH dependence in seawater and freshwater 33 Figure 4.2 Collated zinc leaching data by pH 33 Figure 4.3 Leaching of zinc compared with total zinc available in tyre 35 Figure 4.4 Leaching of zinc compared with total zinc available in tyre 36 Figure 4.5 Dilution of zinc at various dilutions in a fresh water body 38 Figure E1 Principles of compliance leaching test for granular wastes (BS EN

12457-2) at L/S 10 93 Figure E2 The CEN TC 292 model for comparing contaminant release from

granular materials as a function of pH and L/S ratio (Environment Agency, 2002) 95

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WRc Ref: DEFRA8191/15349-0 March 2010

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EXECUTIVE SUMMARY

BACKGROUND

End-of-life tyres have been used for numerous engineering purposes around the world, although the use of whole baled tyres is less common. The Environmental Permitting Regulations 2010 provides an exemption to allow tyre bales to be re-used for construction, in accordance with the BS PAS 108 protocol,, but this does not yet extend to re-use in an aquatic environment.

The objectives for this study were to:

1. Review the international literature (including peer reviewed reports, grey literature and industry data) and compile information on: the use of baled tyres in construction, whether enclosed in concrete or not; the long term behaviour of the tyres and metals that bind them, when used in a marine

or freshwater environment or an acidic peat bog; the techniques that have been used to assess long-term behaviour and stability of

baled tyres and any associated environmental impacts. 2. Assess any environmental impacts caused by the use of baled tyres when used in

construction and timescales of these.

The literature has been assessed for: in situ studies for relevant schemes; laboratory leaching and ecotoxicity studies, and studies of associated scenarios (e.g. granulated tyres).

FINDINGS Composition

Tyres are manufactured primarily from vulcanised synthetic and natural rubber and a complex mixture of chemicals including zinc oxide (at concentrations of 1 -2 w/w %) and highly aromatic oils. Exact chemical composition varies with tyre type and year of manufacture. Tyres also contain steel beading that is not exposed in baled tyres, and baled tyres used under PAS 108 are strapped together using high tensile steel wires.

Contaminant leaching

When a tyre comes into contact with water, a proportion of the compounds in contact with the water will dissolve. The concentration of the dissolved, leached portion is a key factor when assessing the potential chemical or ecotoxicological impact of tyres in a saline, freshwater or peat bog environment. Tyre leachability increases as the integrity of the tyre is lost, e.g. through ageing or exposure to UV light and ozone, but will depend on the loading rate of tyre material used, the type of tyres and their age or pre-history.

There are few reported studies on the use of baled tyres in aquatic environments. Surrogate leaching test data from tyre chip and shreds had to be included in the review, but over-estimate leaching from tyre bales due to the greater surface area of shredded versus whole tyres.

Whole and shredded tyres leach metals and organic compounds in low concentrations. The potential contaminants of concern are: zinc, iron, manganese, phenols and poly-aromatic

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hydrocarbons (PAHs). Iron and manganese are associated with the steel beading in the centre of the tyre, which are not available for leaching in baled tyres. Evidence indicates that zinc and organic compounds, principally PAHs, are the principal contaminants of concern.

Very few in situ studies reported high concentrations of any contaminants associated with tyres at >50 m from the tyre bales or tyre shred infill, but concentrations above Environmental Quality Standards have been found in water taken from within the tyre bales.

Zinc has been identified as the major component that causes toxic effects. The majority of leachable zinc is released from tyres in the short term, indicating that zinc will initially leach from the tyre surface and the bulk of the tyre structure will remain intact for many years. Zinc leachability increases in acidic pH conditions. The maximum amount of zinc leached in laboratory studies was found to be <1% of the total zinc determined in a tyre (<<1% in most cases), even over long time frames and in acidic conditions.

A few studies have reported the leaching of poly-aromatic hydrocarbons (PAHs) from tyres. One study found that PAHs from tyres can have toxic effects on fish. The use of PAHs in tyre manufacture will be limited from January 2010 under REACH. Although PAHs have a toxic effect on many organisms and have the potential to bioaccumulate, the few field studies available did not show PAHs leaching from tyres above background concentrations, and contributions for tyres was seen to be negligible

Laboratory ecotoxicity data show that leachate generated by tyres is toxic to some species at high loadings. However, there is very limited evidence of adverse affects from leaching of contaminants in actual re-use scenarios.

Marine baled tyre scenario Only a limited number of in situ studies of tyre bales in saline waters have been reported. These indicate the absence of, or very limited effects that can be attributed to leaching of contaminants, including zinc. This probably reflects the large dilution potential of the marine environment and suggests that the risk of contamination from leaching is likely to be low. Successful use of tyres for marine defences and artificial reefs has been reported from the UK. However, further work is required to confirm the resilience of bindings for PAS 108 bales in marine defence, to provide confidence that the tyres cannot come loose in the long term.

Freshwater baled tyre scenario Laboratory-based studies of sensitive freshwater species such as Rainbow trout, indicate that there is potential for adverse effects. Effects are more limited on other fish species of fish and other taxa. One study found this toxicity was reduced with increased water flow. No large scale in situ studies for re-use of tyres in lakes or ponds were available for review and no information was identified on local pH and background contaminant concentrations before tyre bale installation needed to determine impact. Due to the potential leachability of contaminants in the short term we would consider baled tyres to pose a medium risk in the freshwater environment. It is likely that there is a reduction in leachability and risk in the long term although relevant field data are not available to corroborate this.

Peat bog scenario Although in situ data have not been identified for review, the predicted leachability of key contaminants, such as zinc, is high under the low pH conditions of a peat bog. The authors suggest that tyres should not be used in peat bogs until further assessment is made of leaching behaviour in these conditions using data from pH dependent leaching tests and also

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with an appropriate artificial leachant. We would tentatively propose that the risk to peat bog environment from baled tyres is at least medium.

The authors suggest:

collection of fit-for-purpose characterisation data to enable more robust assessments of risk for each re-use scenario e.g. pH dependence leaching data;

further research before tyres are re-used in peat bogs. The risk of leaching is likely to be high due to low pH, high organic matter and low replacement of water;

the long term monitoring is continued at pilot aquatic tyre bale schemes in the UK; and

evidence is obtained to show that tyres bales can be adequately secured in aquatic environment in the long term.

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1. INTRODUCTION

1.1 Background

The move toward sustainable resource management has provided the necessary incentive for the re-use of many wastes that were historically landfilled. The Landfill Directive (1999)1 provided the driver for used tyre recycling and reuse when it specifically banned the disposal of whole used tyres to landfill by 2003 and shredded tyres by 2006. Waste tyres have been used for numerous engineering purposes, for many years around the world. Of specific interest to this project is the re-use of whole tyres in compressed baled blocks and tyres set in concrete used in engineering projects within rivers and coastal sites for bank protection, breakwaters and artificial reefs. In addition, tyre used for ground stabilisation in peat bogs are also considered.

Since 2005, WRAP (the Waste and Resource Action Programme) has been helping to develop and create re-use opportunities for used tyres. To support these aims they have produced a Quality Protocol for tyre-derived rubber products with the Environment Agency. Outside of the protocol, WRAP commissioned the BSI (British Standards Institute) to develop a specification for tyre bales used in construction in collaboration with the tyre re-processing industry. This specification, BSI PAS 108, has helped to put used tyres on a similar footing to other geotechnical materials.

There appears to be a general consensus that the use of baled tyres in such engineering works is generally a low risk activity in the short to medium term, and indeed there are many benefits. However, an independent evaluation of the risks is required to avoid exploitation of a potential re-use route which may compromise the quality of the receiving environment and simply represent a convenient means of disposing of tyres (‘sham recovery’). To help inform this process Defra have commissioned WRc to review the evidence of the potential environmental risks posed by the re-use of baled tyres in construction projects, specifically those in marine and freshwater environments and acidic peat-bogs.

1.2 Project Objectives

The aim of the project was to carry out a review of the international literature on baled tyres used in marine and freshwater environments or within acidic peat bogs. Of particular interest was information on the long-term behaviour and stability of the tyres and metals that bind them in order to assess the environmental impacts posed by these re-use scenarios.

The project specification identified the following objectives for the study.

1. Review the international literature (including peer reviewed reports, grey literature and industry data) and compile information on: the use of baled tyres in construction, whether enclosed in concrete or not; the long term behaviour of the tyres and metals that bind them, when used in a marine

or freshwater environment or an acidic peat bog;

1 European Commission. Council Directive 1999/31/EC on the Landfill of Waste

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the techniques that have been used to assess long-term behaviour and stability of baled tyres and any associated environmental impacts.

2. Assess any environmental impacts caused by the use of baled tyres when used in construction and timescales of these.

1.3 Definition, arisings and fate

A tyre, is considered by the Environment Agency to be “solid, or hollow inflated, rubber ring placed round a wheel of a vehicle to prevent jarring.” or ‘a rubber covering, usually inflated, placed around the wheel to form a soft contact with the road’. Worldwide, 1.1 billion tyres are manufactured for use every year (BLIC, 2001). The average lifespan of a tyre varies from 20 000 to 60 000 miles.

In the UK, 508 000 tonnes (5.1 million tyres) reached the end of their use in 2008 (ETRMA, 2009).

The fate of end-of-life tyres in the UK, as recorded in 2008, is presented in Table 1.1.

Table 1.1 Fate of end-of-life tyres in the UK in 2008

Fate Tonnes (1000s) %

Re-use 39 7.7

Export 49 9.6

Re-treading 52 10

Material recovery 250 49

Energy 95 19

Landfill and unknown 23 4.5

TOTAL 508 -

Source: ETMRA (2009)

Whole tyres were banned from landfill in 2003, excluding tyres for engineering purposes. The ban on shredded tyres was introduced in 2006. Bicycle and large vehicle tyres are still permitted to be accepted to landfill.

The End-of-Life Vehicles (ELV) Directive sets targets for material recovery from passenger vehicles, which was 85% recycling by 2006, increasing to 95% in 2015. Tyres generally make up 3% of an end-of-life vehicle (EC, 2007)

These regulatory drivers have led to a steady increase in re-use and recycling of tyres (WRAP 2008). Waste tyres have been used for numerous engineering purposes e.g. as road base, for many years around the world. Other re-use and recycling options include landfill engineering, re-treading, export, energy recovery and baling of tyres for use in construction projects.

The re-use of tyres, including re-use in construction projects, accounts for 18% of the total re-use market, and this is projected to increase over the coming years (WRAP, 2008). In 2008,

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only 4.5% of fate of tyres was landfill or unknown (WRAP, 2008). This compares to 26% which were stockpiled, landfilled or illegally dumped in 1998 (Environment Agency 1998).

Whereas closed-loop reprocessing of recyclate is feasible for glass and certain polymers, this is not feasible for tyre rubber. Once rubber has been through the vulcanisation process, there are no established techniques for using this rubber to construct new tyres, although partial de-vulcanisation is popular in some countries, such as India.

1.4 Legislative framework

1.4.1 Exemption from Environmental Permitting

Once discarded, tyres are subject to waste legislation under the Framework Directive on Waste 75/442/EEC (as amended). A key element of this legislation is that ‘Member States shall take appropriate measures to encourage the recovery of waste by means of recycling, re-use or reclamation. As a waste, materials cannot be reused for engineering purposes without an Environmental Permit in place or a registered exemption. These exemptions cover tightly defined waste activities that are exempt from the environmental permitting regime, because they are considered to be of low risk or commonly represent low volume activities

Currently there is no exemption for the re-use of tyres in aquatic environments, but baled tyres (limited to 50 tonnes in any single scheme) meeting the PAS108 standard can be used under an U2 exemption under the revised Environmental Permitting Regulations 2010.

1.4.2 PAS 108 standard

Baling of used tyres for engineering projects is quality controlled by the PAS108 standard. A typical baling machine reduces 100 tyre bales to a size of 1.3 x 1.6 x 0.6 m3, to give a density of 680 kg m-3 (WRAP 2007), increasing the density of tyres by a factor of 4-5.

The PAS108 standard was commissioned by WRAP and developed by British Standards Institute (BSI) in collaboration with the tyres reprocessing industry. The publically available standard (PAS) was published in 2007. The PAS108 sets minimum standards for baling of end-of-life tyres for re-use in construction projects, to standardise the approach to baling so the risks can be quantified. Tyre baling ensures tyres are compacted and connected securely, which was a problem with earlier schemes, and led to a ban on using tyres in flood protection schemes in many states in the USA (Collins, 2002).

The PAS 108 standard gives the following uses for baled tyres produced in accordance with the specification:

a) road foundations over soft ground;

b) slope failure repair;

c) lightweight embankment fill;

d) free draining layers behind retaining wall;

e) drainage layers, including landfill engineering applications;

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f) sustainable urban drainage systems.

The PAS108 standard specifies that the binding wires should be high tensile steel wires of a minimum diameter of 3.8 mm (tensile strength 1500 MPa to 1700 MPa), then electro-galvanised to a thickness of at least 3 µm or hot dipped galvanised to a thickness of at least 6 µm.

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2. METHODOLOGY FOR LITERATURE REVIEW AND DATA ASSESSMENT

2.1 Introduction

The aim of the literature review was to compile information on:

the use of baled tyres in construction, whether enclosed in concrete or not;

the long term behaviour of the tyres and metals that bind them, when used in the marine environment, a freshwater environment or an acidic peat bog; and

the techniques that have been used to assess long-term behaviour and stability of baled tyres and any associated environmental impacts.

Relevant data is required to assess the potential risks to the aquatic environment from the scenarios under investigation, namely:

construction of flood defence barriers in both marine and fresh water;

construction of roads over soft ground (e.g. peat) where tyres are placed in the saturated zone;

erosion control in marine and freshwater; and

other uses identified for use in the aquatic environment in including use of tyres for construction of artificial reefs.

Non-baled tyres are outside the scope of the project.

Robust information is needed to inform the source – pathway - receptor risk assessment. Such an assessment also necessitates identifying the contaminants of interest and the collection of information on relevant benchmarks for the assessment. The information requirements therefore include:

composition and leachability of relevant contaminants in tyres. Data from crumbed, shredded and whole tyres are required to assess long-term release after the structural integrity of the tyres had been lost;

release concentrations in marine, freshwater and acidic peat-bog environments (in situ and ex situ studies);

release profile with time (i.e. dependent on the age of the tyres) according to the conditions of the placement;

background concentrations in the placement scenario and/or appropriate environmental thresholds for relevant inorganic and organic contaminants.

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The source-pathway-receptor risk assessment methodology can be summarised as in Table 2.1

Table 2.1 Summary of source – pathway – receptor approach and relevant water quality issues for each scenario

Baled tyres scenario Source/data Pathway Receptor Receiving water characteristics

Marine construction applications (e.g. flood defence, erosion control, artificial reefs)

Saltwater biota

High ionic strength, , high flow rate, oH 7.5-8.4 very high dilution, low organic content

Fresh water construction applications (e.g. flood defence, erosion control)

Freshwater biota

Moderate ionic strength, scenario specific water column replacement rate (river cross-section and flow), high dilution, scenario specific pH (pH 5-9), scenario-specific hardness, low organic content

Construction applications in peat bogs (e.g. road foundation)

Peat bog biota

Low pH, high organic content, low water column replacement, low dilution

Concrete-bound tyres in marine, freshwater or peat bog environment

a) in situ studies:

(i) chemical contamination

(ii) ecotoxicity

b) laboratory testing:

(i) chemical leachability

(ii )ecotoxicity

Direct transfer via leaching

Same as for unbound bales

Same as for unbound bales

Benchmarks for surface water quality assessments – Environmental Quality Standards, (EQSs), Predicted No Effect Concentrations (PNECs),

2.2 Methodology

Literature was collected from as wide a range of sources as was possible in the short timescale of the project. Published, peer reviewed papers from scientific journals were prioritised, but information was also gathered from government departments, public interest groups, trade bodies and individuals. The organisations and individuals contacted for the study are listed in Appendix A.

In addition to direct contact with these organisations, a set of search terms were identified that cover all relevant information criteria to ensure a thorough review of all available pertinent literature. This was searched by means of internet search engines, and scientific journal archives such as Aqualine and the British Library catalogue search (British Library Inside). From the search it emerged that certain figures from academia and industry have conducted a large amount of work on this subject. These people were subsequently contacted directly.

The second phase of data collection involved following up references identified in the first activity phase.

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2.3 Numbers of papers reviewed

Over 150 papers, journals and articles have been reviewed for this study. These are summarised by year of publication in Figure 2.1 and country of origin in Table 2.2. The details of the age of these references is summarised in Table C1 in Appendix C. The majority of papers were published in the last 10 years, but a number of papers (16% of total) were obtained pre-2000.

Year of Study

200914%

200812%

200717%

20069% 2005

8%

2000-200424%

Pre- 200016%

Pre- 2000

2000-2004

2005

2006

2007

2008

2009

Figure 2.1 Source information by year of study

Table 2.2 Country of origin of reports collected for study

Country of origin Number Country of origin Number

Unknown 2 Netherlands 8

Australia 5 New Zealand 1

Belgium 1 Norway 1

Brazil 2 Scotland 2

Canada 2 Sweden 9

Denmark 1 Switzerland 2

Europe 2 Japan 1

France 1 UK 49

Germany 1 USA 13

Ireland 3 Worldwide 2

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The number of large scale in situ studies in Europe relating to baled tyres in aquatic environments can be counted in single figures, and very little data was found from the rest of the world. Baling of tyres for use in construction is still a relatively novel process, having been imported from the USA in the early 2000s. Investigations in to the extent of its use revealed that baled tyres are currently used in construction in UK and Ireland, a small number of states in USA and limited use in Scandinavia. Consequently, studies in to the use of baled tyres is limited. Of the reports quoted in Table 2.2, the only reports on baled tyres were from the UK (12) and USA (3) were directly relevant to baled tyres.

It was therefore necessary to supplement the literature and more importantly the data with analogous uses of tyres, e.g.

use of tyre crumb in sports fields;

use of tyres in sustainable drainage projects; and

use of tyres in children’s playgrounds.

The papers reviewed were generally funded by government departments, industry or public interest groups. The literature obtained can be divided into three categories:

review papers which considered previous research;

original research where laboratory testing was carried out; and

in situ studies carried out with tyres in the environment.

Where possible, original research on which review papers were based was obtained.

2.4 Collation of reports

The literature has been reviewed to provide a source term dataset for the assessment of environmental risk from each scenario. This information is provided in Appendix C and includes (where available) the:

data source; date that information was produced and length of study; tyre type; re-use scenarios for whole tyres in compressed baled blocks and tyres set in concrete in

terms of the type of engineering project and its placement (within rivers and coastal sites for bank protection, breakwaters and artificial reefs and below ground in peat bogs as a ground stabilising materials);

in situ or ex situ evaluation; data available i.e. contaminants monitored, analytical and leaching test methods used; whether baseline conditions were monitored as part of the study; and number of data points.

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2.5 Collation of data

Study types from which data has been collated can be summarised by the following groups:

a) Field information – studies of in situ engineering projects using baled tyres:

ecotoxicological data

chemical leaching test data.

b) Laboratory test data:

ecotoxicological data

chemical leaching test data.

2.5.1 Leaching data

For the assessment of leachability, papers where leachability data had been reported were collated and data extracted. It was not possible to use all the reported leaching test data, as the information required to normalise the results from the test was not always reported. Further background to leaching test principles and methodologies is provided in Appendix E.

In order to have a like-for-like assessment of data, it is necessary to have information on the following:

pH of the eluate used in the leaching test;

the liquid-to-solid (L/S) ratio;

the length of time for the leaching test;

the type of eluate used in the leachate test (salt water, fresh water, distilled water).

Field information which provide data that related to longer term risks is sparse, but laboratory leaching tests can be used to assess worst case leaching. These tests have only been carried out on granulated tyre material and therefore provide a measure of what might leach out in a much longer environmental scenario. Monolithic tests on whole tyres can be undertaken in the laboratory to mimic in situ studies and have the benefit of being undertaken in carefully controlled conditions and known water replacement rates and dilution scenarios.

The evidence from studies on tyres has never been fully assimilated to facilitate identification of those scenarios where re-use could present a measurable environmental impact and the timescales over which this might occur. This study attempts to address this data gap.

As previously discussed, there are many factors influence leaching of contaminants. In order to present data in a unified way LeachXS© was used. LeachXS, is a database/expert decision support system for characterisation and environmental impact assessment based on estimated contaminant release. Using this system, it is possible to summarise leaching test data from a range of different leaching tests.

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Leaching tests can be interpreted in an expert system to provide estimates of the short and long term release of constituents of interest. However, full waste characterisation data is required to achieve this, including full up-flow percolation (DD CEN/TS 14405: 2004) testing and pH dependence (DD CEN/TS 14429:2005 and DD EN 14997: 2006) testing. While data from these leaching behaviour tests were not available, key test conditions such as liquid-to-solid ratio and pH have been identified to enable data from other tests to be analysed using LeachXS©. This dataset is provided in Appendix F.

2.5.2 Ecotoxicity

For the ecotoxicological assessment, papers were scored on a number of factors:

Whether the results were generated using standardised tests; Whether replicates tests were undertaken; Were data based on measured or nominal concentrations Was the paper peer reviewed paper or not; and Did the paper contain all necessary information to allow evaluation of the study.

A literature search for published studies relating to the use of tyre bales in the aquatic environment and their potential impacts on indigenous organisms was carried out and the resulting papers/reports were reviewed. The data collected from the key studies is detailed in the Appendix D for ecotoxicological review, and the main findings from the review summarised in Section 4.5. The review considered the results from both laboratory-based studies and also in situ (field)-based assessments. It should be recognised that in situ assessments will generally have the greatest environmental relevance since they reflect realistic exposure conditions, and were given greater weighting in reaching conclusions regarding each scenario. In laboratory-based assessments there is the potential that adverse effects may be observed because the loading rate of tyres to water is greater than that which would occur in the environment. As a result the concentrations of substances leaching from tyre bales would be overestimated.

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3. LITERATURE REVIEW FINDINGS

3.1 Introduction

This section summarises the key findings of the literature review with respect to identifying and reviewing the principal contaminants of concern and to reviewing information that can be related specifically to the scenarios of interest – i.e. use of tyres in an aquatic environment and factors that influence their potential to leach, such as aging and exposure to ultra-violet light. Other studies have assessed the overall toxic effects to aquatic organisms rather than the leachability of specific contaminants and these are presented in Appendix D, along with details of each referenced study.

Data collated from the literature review have been reviewed separately and are assessed in detail in Section 4.5.

3.2 Contaminants of potential concern

3.2.1 Composition of tyres

Tyres are engineered to be stable in the environment and consist of approximately 45% butyl and natural rubber and 20% carbon black, usually reinforced with steel and textiles, together with trace amounts of various organic additives (BLIC, 2001). Manufacturer-specific formulations mean that there are variations in tyre weight and composition depending on the type of vehicle they are designed for and performance requirements. Typical passenger tyres can contain 30 types of synthetic and natural rubber, eight types of natural rubber, eight types of carbon black, and 40 types of chemicals waxes, oils and pigments as additives (WBCSB, 2008).

Chemical components include silica, sulphur, zinc oxide and copper compounds - to stabilise the rubber matrix and act as reinforcing agents - in addition to a wide range of organic compounds, including oils and specifically polyaromatic hydrocarbons (PAHs). Other metals such as cadmium and lead are present as impurities associated in particular with the zinc oxide.

Hylands and Shulman (2003) reported the bulk composition of car and truck tyres as shown in Table 3.1. Truck tyres contain higher proportion of natural rubber to synthetic rubber. Also, they contain a higher proportion of zinc oxide and metal beading.

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Table 3.1 Bulk composition of car and truck tyres

Material Automobile (%) Trucks (%)

Rubber/elastomers 48 45

Carbon black and silica 22 22

Metal 15 25

Textile 5 -

Zinc oxide 1 2

Sulphur 1 1

Additives 8 -

Typical composition of tyre rubber (Williams et al., 1990 cited in O’Shaughnessy and Garga, 2000) is given in Table 3.2.

Table 3.2 Bulk composition of typical tyre

Compound Weight (kg) Weight (%)

Rubber polymer (SBR) 6.09 62.1

Carbon black 3.04 31

Extender oil 0.19 1.9

Zinc oxide 0.19 1.9

Stearic acid 0.12 1.2

Sulphur 0.11 1.1

Accelerator 0.07 0.7

Total 9.81 99.9

The composition of tyres has changed very little over the past 20 years. However, silica has replaced carbon black to some extent in some tyre mixes (Edskar, 2004).

3.2.2 Hazardous components in tyres

The Working Group of the Basel Convention on the ‘Control of Trans-boundary Movements of Hazardous Wastes and their Disposal’, consider that 1.5% of a tyre’s weight is composed of hazardous compounds based on a Brazilian specification, as shown in Table 3.3.

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Table 3.3 Hazardous compounds in tyres

Chemical Name Remarks Content (%) Content (g) per

tyre

Associated risk

phrases

Copper compounds Alloying constituent of the metallic reinforcing

material (steel cord)

Approx 0.02% 0.14 -

Zinc compounds Zinc oxide, retained in the rubber matrix

Approx 1% 70 R50/53

Cadmium Trace levels, as cadmium compounds

attendant substance of the zinc oxide

Max 0.001% 0.07 R20/21/22; R50/53

Lead/ Lead compounds Trace levels, as attendant substance of

the zinc oxide

Max 0.005% 0.35 R61; R62; R20/22;

R33; R50/53

Acidic solutions or acids in solid form

Stearic acid, in solid form

0.3% 21 -

Organohalogen compounds other than

substances in Appendix to the Basel

convention

Halogen butyl rubber Max 0.1% 7 -

Source: UNEP 2007

Zinc

Zinc occurs naturally in the environment, resulting in natural background concentrations of zinc in all environmental compartments including organisms.

Zinc oxide is used as an additive in tyre manufacture, both as an accelerator for the vulcanisation process (cross linking the rubber polymer with sulphur bridges), and for its structural reinforcement properties. It also limits the degradation of the rubber by UV. Addition of zinc oxide varies according to the tyre specification, but is generally around 1% (or 70g per passenger car tyre). In 1995, the tyre industry accounted for 23% of all zinc oxide use in the EU-15 (total 221 500 tonnes). Other zinc compounds are used in the tyre industry, but generally in low concentrations, with the exception of zinc peroxide (Baumann and Ismeier, 1998).

Zinc oxide is listed in Table 3.2 of the Classification, Labelling and Packaging (CLP) Regulation (2009) and bears risk phrase R50-53 (“very toxic to aquatic organisms, may cause long term adverse effects in the aquatic environment”). Current Environment Agency Guidance on Classification of Hazardous Waste (WM2, Environment Agency, 2008), states that any waste substance or mixture that contains a substance which bears the risk phrase R50-53 at a concentration of >0.25% should be considered hazardous by ecotoxicity (H14). Therefore under current Environment Agency guidance waste tyres are hazardous waste.

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This is at odds with the non-hazardous List of Waste/European Catalogue codes ascribed to end-of-waste tyres (16 01 03). The publication of the European Waste Catalogue predated the reclassification of zinc oxide as an ecotoxic compound. However, reclassification of wastes in line with the transposition of the Waste Framework Directive may need to include end-of-life tyres. This would open the debate as to the appropriateness of using hazardous material in an aquatic environment.

Zinc oxide is insoluble in water (<1.6 mg/100 ml at 30oC), but as an amphoteric element it exhibits very strong pH-dependent leachability with maximum solubility at extreme pH values. Zinc oxide is much less soluble in water compared with other zinc salts including zinc sulphate and zinc chloride, however zinc may be dissolved from zinc oxide solutions to a concentration that is toxic to aquatic organisms (EU, 2008b). These concentrations are displayed in Appendix B. Following the release of zinc oxide into the environment it will be in part transformed into other species of zinc. The further speciation of zinc (complexation, precipitation and sorption) is dependent on the environmental conditions of the receiving environment. Consequently, releases of zinc oxide and other zinc species released will add to the effect of the total amount of zinc in the environment, despite the source of zinc or species of zinc (EU, 2008b). Therefore, the EU have based their risk assessment for zinc oxide on zinc. The PNECs derived for zinc (Appendix B) have been calculated on the basis of toxicity tests that used soluble zinc salts (in particular zinc sulphate and zinc chloride). Also, an “added risk approach” was used since zinc is also an essential element and has a natural background concentration in the environment. This assessment considers only the anthropogenic amount of zinc, i.e. the amount added to the natural background concentration (EU, 2008b).

The current UK Environmental Quality Standard for zinc varies depending on the hardness of the water. As surface waters with a high level of water hardness will generally have a higher pH, zinc leachability will be lowest where the least precautionary EQS applies (i.e. high water hardness).

PAHs

Highly aromatic (HA) oils have been used in tyres for a number of years, both to help in the processing of rubber compounds and for the improved physical properties these oils impart on the tyre, such as improved grip (BLIC, 2005). Highly aromatic oils contain PAHs, many of which are classified as carcinogenic or mutagenic. The use of HA oils containing PAHs are limited from January 2010 under the REACH regulations (EU Regulation (EC) 1907/2006). Highly aromatic (HA) oils typically contain 500 – 700 mg/kg PAHs (0.1-0.3 g per tyre), but this is now restricted to 10 mg/kg PAH (<0.004 g per tyre) from January 2010.

Wik (2008) derived Predicted No Effect Concentrations (PNECs) for both the water column and sediment for tyre wear particles. The PNEC for water was calculated to be 3.9 mg/l and 0.3 g/kg for sediment. Tyre wear particle markers have been found in the water, soil/sediments, air and biota. The maximum Predicted Environmental Concentrations (PECs) for tyre wear particles in water range 0.03 to 56 mg/l and maximum PECs in sediments a range from 0.3 to 155 g/kg dw (Wik, 2008).

PAHs have the tendency to adsorb to sediment where they persist and they also accumulate in biota (KEM, 2002). PAHs can be released from sediments during dredging and other similar activities (KEM, 2002). In an in-situ study, starry flounder (Platichthys stellatus) were exposed to tyre leachate compounds and detectable quantities of benzothiazoles and 2-

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(methymercapto)-benzothiazole (Spies et al., 1987, cited in Evans, 1997). Evans (1997) suggested that this finding indicates that there is the potential for these compounds to be bioaccumulated by organisms in direct contact with sediments.

In studies on tyre granulate used in synthetic turf, zinc and phenols have been demonstrated to leach and affect aquatic and sediment-dwelling organisms if they reach surrounding aquatic environments. However, it was stated that the total amount leached was small, so affects would be localised (KEM, 2007). In an aquatic tyre baling project, the tyres would be submerged or in very close proximity to surface water, potentially enhancing the amount leached compared to with a terrestrial turf project. It should also be noted that in the synthetic turf example the tyres were in granulate form with increased surface area thus enhancing the leaching potential, in a tyre baling project the tyres would be whole reducing the surface area exposed to water and potentially reducing the rate in which that chemicals are leached.

Data on field measurements of PAHs was sparse. Edeskar (2004) reported on a trial where tyre shred had been used in a motorway embankment, and analysed the leachate collected. This found no evidence of any PAH compound measured above background concentrations. Edeskar concluded there is no risk to water from PAHs for tyre shreds, and this is supported by the view of CSTEE (2003) who concluded that the contribution of PAHs to sediments from tyre particles is negligible compared to that from diesel exhausts in EU member states.

Cadmium and lead

As shown in Table 3.3, cadmium and lead can be present in the tyre rubber in very low concentrations (approximately 70 mg/kg and 350 mg/kg per 7 kg tyre, respectively). They are present as trace contaminants in the zinc oxide added to the tyre, and will therefore vary with the concentration of zinc. Both cadmium and lead are given the risk phrase R50/53 - very toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment.

Metal beading

Modern car tyres contain 15 – 25% steel beading. The two principal types of beading used in tyres are zinc and bronze coated wires, and therefore the beading may also be a source of trace amounts of tin and copper. It is not possible to distinguish whether leaching of contaminants is from the tyre itself, the beading or in the case of baled tyres the wrapping wires on the bales.

3.2.3 Leachability of tyres

A wide range of compounds are present in tyres . However, for this review, it is the potential transfer of contaminants from the baled tyres to the aquatic environment that is relevant rather than total concentrations of contaminants in the tyres discussed above. The primary consideration for this review, is therefore which contaminants will leach and at what concentrations. Information on the leachability of contaminants has therefore been sought in order to assess risk to the aquatic environment.

The leachability of substances from a sample matrix is controlled by a number of factors. These are principally:

the liquid to solid ratio (test material to leachant);

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physical conditions such as size and shape of the particle, permeability and porosity;

pH of leachant and buffering capacity of the test material;

availability of constituent for leaching;

the immediate dilution in the system; and

the frequency with which the body or column of water is replaced.

The following section summarises the findings from the literature on total and leachable concentrations of principal contaminants of concern. An independent evaluation of these data is provided in Section 4.

3.2.4 Information on specific contaminants

General comments

Tyres can, to varying degrees, exhibit toxic effects on a range of aquatic organisms. Recent toxicity identification evaluation (Wik, 2007) has identified that this is probably due to zinc and a range of organic compounds. However, it is of note that WiK (2007) used pieces of tyres, so the level of leachates will not be representative of that from whole tyres used in bale projects., Tyre pieces, crumb and granulate will represent a worse case situation for the level of leachates. These are considered in detail below.

Leaching tests on tyre chips indicated that barium, cadmium, chromium, lead, selenium and zinc were found to be the compounds to be of concern in acidic environments (pH 3.5 to 5) and certain types of hydrocarbons (polynuclear aromatic hydrocarbons (PAHs)) may be released under basic conditions (pH 8.0) (Twin City Testing Corp, 1990 cited in O’Shaughnessy and Garga, 2000). Further studies found that tyre chips soaked in different media (i.e. various pHs and ionic strengths), indicated that typical rubber compounds such as zinc and benzothiazoles were leached irrespective of the environmental conditions (Lerner et al., 1993 cited in O’Shaughnessy and Garga, 2000).

The literature has highlighted the following points:

Collins et al. (1995) found that 10 mg of zinc per whole tyre was leached over a 3 month period (see Section 4).

Vershoor (2007) found that emissions of zinc increase over time, as the rubber material breaks down and more ZnO is released, and that standard release profiles for aggregate materials would under-estimate zinc release. These assessments were made on the basis of rubber crumb material.

Blackwell (1995) found leachable concentrations of zinc at over 200 mg/kg at L/S ratio 20 using the US EPA’s toxicity characteristic leaching procedure (TCLP test) using an acidic leachant (pH). Although the exact pH of the leachant is not specified, the standard leachant pH for TCLP is 4.9.

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Al Tabaa et al. (2000) conducted further column tests on shredded tyre samples. The results showed that initially concentrations of 11 mg/l zinc were found, reducing to a constant 6 mg/l at a pH of 5.5. Up to 9 pore concentrations of eluate were passed through the column using ‘extraction fluid’ as tap water resulted in below limit of detection concentrations of zinc and copper. The liquid to solid ratio is not reported. This confirms research elsewhere that found a fairly constant leaching of zinc even after longer exposures.

Much of the laboratory leaching test data is carried out on tyre crumb or shred, either because this is the re-use scenario being studied or impracticalities associated with testing whole tyres. Tests on shredded or granulated will naturally lead to higher levels of leaching due in part to greater surface area exposed to leachant and more exposed metal reinforcement.

Hymands and Schulman (2003) in a report for ETRA reported that “for all regulated metals and organics the results for the post consumer tyres are well below regulatory limits.” However, they do not report the liquid to solid ratio at which this is the case, which is crucial in assessing the impact of used tyres. They also report that ‘several studies are currently underway to determine the impacts of leachates under a broad range of pH conditions’. We have been unable to find any such studies through the literature search.

Dallman et al. (1999) report that of all zinc extracted in leaching test, 75% was extracted in first 24 fours, and 92% after 72 hours.

Lerner et al. (1993) found that leaching of zinc and benzothiazoles leached regardless of environmental conditions (pH and ionic strength of leachant), which appears to contradict the majority of the literature which shows leaching of most contaminants is strongly dependent on factors such as pH.

Laboratory leaching tests cannot not take in to account other environmental factors when considering leaching from tyres. Abernethy et al. (1996) found that tyres taken from an artificial reef in Lake Erie in the US were less toxic than scrap tyres never exposed to the aquatic environment. However this study did not measure chemical leaching from the tyre.

Detectable quantities of benzothiazoles and 2-(methymercapto)-benzothiazole were measured following an in-situ study with flounder exposed to tyre leachate (Spies et al., 1987 cited in Evans, 1997), indicating the potential the sediment could become contaminated by tyre leachate.

Other metals

The review of the literature demonstrated that the information on the leachability of metals other than zinc is extremely sparse.

Humphrey et al. (1997) investigated the use of tyre chip above groundwater. The leaching of metals (and other contaminants) which have a US drinking water standard (antimony, arsenic, barium, beryllium, cadmium, chromium, copper, fluoride, lead, nitrite, selenium, titanium) were tested. This study considered tyre granules, and it was concluded that these metals were associated with the steel bead which would not be exposed in tyre bales unlike when the tyres are granulated. Samples were collected direct from the lined field drain. Average concentrations over a five year period were taken, and it was found

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that concentrations of iron were elevated to between 4 and 28 times the control, and for manganese between 60 and 100 times. All other metals were below respective drinking water limits. The site consisted of five, 33 m length sections 0.6m thick, covered with 0.8-1.4 m soil and 0.13 m asphalt.

In a further study on tyre shreds used for a motorway embankment, it was found that levels of iron and manganese were present, at concentrations 59 and 24 times control. In both of these studies it was found that zinc was not elevated above control concentrations. (Brophy and Graney, 2004)

O’Shaughnessy (1999) found that bench-top lysimeter studies using tyre chips embedded in inert Unimin quartz sand showed increased leaching of aluminium, iron, zinc and manganese. They concluded that the elevated aluminium, iron, and manganese were associated with exposed steel reinforcements on the tyre which would not occur in a tyre baling scenario.

Organic determinands

Due to the wide range of organic compounds used in the manufacture of tyres, leaching of these compounds is complex and the literature shows a large range leaching at very low concentrations.

Leaching of many organic compounds is strongly dependent on pH. Species such as 2(3H)-benzothiazolone will leach at much higher concentrations under acidic or basic conditions than at neutral pH (O’Shaunessy 1999). Kellough et al. (1991) found no trace of PAHs or PCBs tested for whole tyres or shredded tyres. The authors do not report the liquid to solid ratio but used 450 litres of water for one tyre over one week. If we consider a tyre’s mass as 7 kg, this gives an L/S ratio of 64, with no agitation. Sea water was used taken from the Bay of Qunite,

Håøya et al. (2005) investigated the leaching of phenols from tyre shreds in a noise barrier in Norway over a five year period. Many types of phenols are added to tyres to protect the tyre against many forms of degradation processes, making up 1.5% of the tyres weight. The study found that leached concentrations of phenols from field values were in general 10-100 times less than concentrations found from the EN 12457 L/S10 laboratory leaching test.

Hoppe and Mullen (2004) also studied the use of tyre shred in above groundwater table construction, in this case for a motorway embankment. Over the three year period, the study found no increase in concentrations of total organic carbon, or total organic halides.

Humphrey and Katz (2001) found a number of volatile and semi-volatile compounds at very low concentrations in the surrounding ground water in their three year study of tyre shred placed below the ground water table.

Volatile organic compounds (VOCs) identified were: 1,1-dichloro-ethane; 4-methyl-2-pentanone; acetone; benzene; chloroethane; and cis-1,2-di-chloroethane.

Semi-volatile organic compounds (SVOCs) identified were: aniline; phenol; meta- & para- cresol; benzothiazole; and 2(3H)-benzo-thiazolone.

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As these compounds were all released at concentrations below US drinking water standards, the tyre shreds were considered by the authors to be low risk. The net effect of leachability of ecotoxic contaminants will generally be an increase in the toxic effects.

3.3 Re-use scenarios

3.3.1 Use in marine artificial reef applications

Leaching effects

Collins et al. (2002a, 2002b, 2005) have produced numerous reports on an artificial reef constructed from tyres in Poole Bay in 1998. Five hundred tyres were used in the study to form the reef, and the site monitored every two months for colonisation of the reef; organisms were tested for heavy metals. These results were compared to organisms from a concrete control reef. The study found there was no significant (P>0.05) difference in colonising species in the tyre reef when compared with the concrete control reef. The study also found no evidence of any difference in zinc concentrations in species taken from both reefs.

Collins et al. (2005) found that 10 mg zinc would leach from one tyre’s worth of tyre dust over a period of 3 months in seawater.

Research from the USA (Lukens 2004) found that leached concentrations from tyres do not generally breach the US Maximum Concentration limits for drinking water, but secondary limits (iron, magnesium, aluminium, manganese, zinc) were significantly exceeded in some cases. The report concluded “batch leaching tests conducted in laboratory reactors confirm that tires are capable of leaching organic and inorganic materials when continuously submerged in water”.

The most comprehensive account of leaching from tyres in a marine field trial was for the Pevensey Bay project where 350 tyre bales were buried as a substitute for shingle which has to be replenished due to littoral drift (reported in Simm (2005)). The account of leaching behaviour of tyres found that whilst levels of zinc were found within the tyre bale at concentrations above marine EQS, the levels quickly fell just 10 m from the tyres.

Physical effects

Tyres have a density of 1.27 – 1.34 t/m3 (Simm, 2005), giving them partial buoyancy in water (density = 1.00 t/m3 freshwater, 1.03 t/m3 sea water). This increases the need to have tyres properly secured when placed in water, as loose tyres will be moved by water currents.

From the 1950s to the late 1970s, millions of tyres were used for constructing artificial reefs off the coasts Atlantic and Gulf coasts of USA (Mathews 1983). Many of these schemes were poorly designed, which resulted in tyres working loose. In many cases use of these structures lasted only a few years (Feigenbaum, 1989). Most schemes consisted of loose, unballasted tyres which resulted in a poor habitat for fish and algae and coral, as the movement of the tyres dispersed any growth. Tyres can also flex during storms and thus shed rigid epifauna (Collins, 2002).

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Baled tyre schemes have also been unsuccessful in the US where the bales have broken loose. One such scheme in the early 1970s using 75000 used tyres in bundles initially reported positive results with more than 80 species of fish at the first reef constructed. Twenty-five years later most of these tyres were reported as scattered, buried or washed up on the beach (Dugan, 1997).

Lukens (2004) cite over 20 separate examples of tyre reefs, both ballasted and un-ballasted ranging between 1000 and 1 000 000 tyres as being unsuccessful. All unsecured reefs were reported as being unsuccessful. Lukens states that the functional life expectancy of strapping materials has been shown to be significantly less than the tyres themselves. All these schemes were implemented pre-1980s.

Many of the reported washing up of tyres on beaches happened during extreme weather events such as hurricanes, not as common in the UK as in some regions of the US.

Another objection raised to tyres used as reefs is that as the tyres are flexible they do not support hard coral growth. Even when hard corals gain a footing, which they can sometimes do on exposed steel tread cords, they eventually fall off before reaching maturity (Todd Barber, pers comm). The only coral found in UK waters is on the Darwin Mounds located north-west of Cape Wrath, Scotland, and this is therefore not considered a problem for deployment in England and Wales.

Polvinva (1990) found that whilst many artificial reef schemes had been successful in terms of providing habitat for fish, they have not been universally so. Walker (2002) compared three reef types (boulders, concrete and gravel, concrete and tyres). They found that there was no significant difference in total fish or spiny lobster abundance or fish biomass amongst the three reef types.

Foster and Fowler (1992) found that when tyres are properly secured they achieve positive results. Indeed the National Artificial Reef plan of the US Department of Commerce National Oceanic and Atmospheric Administration (2007) stated that where tyres are enclosed in concrete they have produced positive results. However, the plan does not recommend use of tyres in artificial reefs.

Prince et al. (1985) found that after 9 years, tyres used in a marine artificial reef had shown no signs of deterioration and were still functioning well as habitats for fish and periphyton.

Overall, the literature would suggest that whilst toxicity has been seen at high concentrations for some marine organisms, dilution afforded in the sea is such that tyres will chemically have a negligible chemical impact. However, some studies show possible physical effects of the tyres, and raises doubts over whether they can be secured effectively in the longer term.

3.3.2 Use in estuaries

Very few studies were found on the use of tyres in estuaries. Watson and French (1999) considered the use of a tyre raft to stabilise shoreline and prevent loss of woodland in Copperas Bay, Stour estuary. The study found the tyre rafts (placed two high and four deep) were successful in reducing erosion of the salt marsh. The study did not involve any assessment of leaching behaviour or potential ecological impact of tyres. Simm et al. (2004) reported that the rafts were still working effectively four years after placement of the tyres. Hoening (2003) also reported on the effectiveness of tyres for erosion control.

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3.3.3 Use in river and canal projects

Nelson et al. (1994) measured the levels of heavy metals with drinking water standards from tyres, and found that 4.2 mg/kg zinc leached from material. The authors calculated that if the tyres were placed in a canal at a rate of 900 tyres per kilometre, then assuming a canal cross-section of 33.5 m2, this would lead to 0.896 µg/l of zinc being leached above background level. This is assuming static flow conditions, and was therefore considered to be a conservative estimate. However, this report was carried our prior to the advent of tyre baling, which can reduce the volume that tyres occupy, to >100 tyres in 1 m3. In this study 900 tyres were used over a 1 km stretch, the equivalent of 9 PAS108 tyre bales. PAS108 standard tyre bales generally compress tyres to a ratio of between 4-5:1 (PAS108 standard). This increases the density of fill possible with tyres, and will therefore concentrate any leaching seen from these schemes.

In the Branston Island project, 1.2 million tyres were installed as part of a flood defence project. This was one of the largest schemes of its kind implemented in the UK to date. In a report (EA 2007) on the scheme’s impacts, the river chemical and biological quality was monitored during and after the scheme was put in place. Although two large peaks of total and dissolved zinc were observed in the proceeding months of the project, these were not thought to be associated with the tyres. The tyres were covered with a geotextile membrane, and were not all in constant contact with the water. The monitoring of the scheme was ended in 2006, two years after completion of the scheme.

No other literature was obtained on the use of baled tyres in rivers or canals.

3.3.4 Use in peat bogs

Winter et al. (2005) described the construction of roads over soft ground such as peat, and concluded that tyre bales make ideal construction material to spreads loads. Other work has been carried out on the physical properties of baled tyres to show that they are ideal for use over soft ground such as peat bogs where traditional sub-base aggregates would be too dense.

The literature appears to be sparse on leaching characteristics of tyres in peat bogs. Peat bogs are an acidic environment due to high levels of humic and fulvic acids and have a pH of between 3.5 and 5.5.

The only project involving construction of a road over peat in the UK was the B871 Kimbrace-Syre Road, as reported by Mackenzie (2003). The report concludes that baled tyres are a suitable material for construction of roads over soft ground in terms of their physical engineering properties. However, leaching of the tyres in this scenario was not considered.

Humphrey and Katz (2001) compared for tyre derived aggregate (tyre shreds) for three soil types, placed below the groundwater table:

Peat.

Marine clay.

Glacial till.

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At each site 1.4 tonnes of tyre shed were buried below the groundwater table, and samples were taken directly from the tyre fill. The increase in concentrations of leachate taken directly from the tyre fill in comparison to background concentrations is shown in Table 3.4

Table 3.4 Concentration of metals at three sites over a three year period taken directly from fill (Humphrey and Katz, 2001)

Peat Clay Till

Determinand Concentration (mg/l)

Compared to

background

Concentration (mg/l)

Compared to

background

Concentration (mg/l)

Compared to

background

Iron 159 48 59 1.4 122 2.5

Manganese 1.73 2.0 1.34 1.2 4.08 4.5

Zinc 0.571 34 0.150 1.6 0.200 2.2

Levels of zinc and iron were increased in the sample taken from peat in comparison to the background by a factor of 48 and 34, respectively over the 3 year period of the experiment. In contrast, an increase of 1.4 and 1.6 was seen for the clay sample, and 2.5 and 2.2 for the till.

As discussed in previous section, leaching behaviour of tyres is very dependent on pH, and many constituents will leach in larger amounts under acid conditions such as zinc and other metals. There also tends to be little recharge of water in peat bogs, which is the reason they become acidic in the first place.

Peat bogs are very sensitive ecosystems with highly specialist organisms. No ecotoxicological data was found for organisms relevant to peat bogs. No leachability testing specifically using water taken from a peat bog have been conducted using tyres. Many studies have found much higher levels of metals under acidic conditions (pH 5). Al-Tabbaa and Aravinthan (1997) found that all metals were below detection level at neutral pH, but 5 mg/kg and 12 mg/kg for copper and nickel, respectively using the TCLP leaching test, and 0.4 mg/kg and 5 mg/kg, respectively, using the NRA test for 1-4 mm tyre shred.

Studies have shown that species of Daphnia and algae are highly susceptible to these levels of metals. However, no studies appear to have been carried out on peat specific organisms.

3.3.5 Concrete

Ali et al. and Rostami et al. (1993) (as reported by Simm et al. 2005) reported that using tyre crumb in Portland cement mix can significantly decrease the compressive and tensile strength. Simm et al. (2005) also report that Portland cement can be eroded at significant rates (6 mm per year in the most aggressive coastal environments). This type of re-use in not analogous to casing tyre bales in concrete, but was the only information available on the re-use of tyres in concrete.

Stark et al. (1995) reported that concrete-only structures will continue to gain compressive strength over a long period (tens possibly hundreds of years) due to continued hydration of the cement. Where freezing and thawing is not an issue, as in deep aquatic environments, the

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report concludes “Based on the 32 to 34 year performance observations. All concretes exhibited a high level of durability in seawater exposure, regardless of type of Portland cement. The ratio of water to total cementitious material and quantity of air entrainment and pozzolans appears to be of little or no significance in the observed durability of concrete.”

3.4 Other factors

3.4.1 UV degradation

It is widely reported that UV light will degrade tyres. Although tyres degraded by UV will look similar to the naked eye, the degradation process causes micro-fissures in the tyres surface, increasing the surface area of the tyre, and thus possibly increasing leaching, although this has not been extensively studied.

UV light will catalyse the degradation process of tyres; ozone may also cause the degradation of rubber through another mechanism.

PAS108 specifies that tyres should not be left exposed to UV light, as UV light speeds up the degradation. The standard recommends 0.5 m of inert fill to achieve this. This will also have the effect of limited rain water ingress. As PAS108 does not cover tyre bales placed in water, it does not consider UV light passing through water. UV light is partially scattered by water, but a proportion will pass through at least shallow waters.

PAS108 also states that there is ‘no evidence of significant deterioration of tyres buried in the ground, even after many years’, although this statement is not referenced.

3.4.2 Age of tyre

Tyres lose 10-20% of their weight during normal use (Ahlbom and Duus 1994). O’Shaughnessy and Garga (2000) found that leaching from new tyres will be greater than leaching from older tyres. In contrast, Verschoor (2007), found that after artificial aging by high intensity UV, leaching would increase from tyre chips. The difference in the findings is likely to be due to the artificial aging process, which was carried out after the tyres were granulated. These tyre chips were not subjected to three years of continual flushing by rainfall, and this higher level of zinc leachability can be regarded as 3 years worth of leaching of zinc.

3.4.3 Long term effects

Humphrey et al. (2001) conducted a five year study on the leaching behaviour of tyre shred placed above the water table. The experiment measured the concentration of barium, cadmium, chromium, lead, selenium, aluminium, zinc, chlorine, sulphate, iron and manganese, as well as priority VOCs and SVOCs. The study found that no increase in organic contaminants was found or the majority of inorganic components. The study did, however, find increased levels of manganese and some evidence for iron, both of which were released sporadically over the period of the study. It was concluded that the source of these metals was from the steel beading in the tyre, which would not be exposed in baled tyres.

Bauer et al. (2007) reported that aging of tyres can be achieved by heating tyres to 70°C using a fill gas of 50:50 N2 and O2. It was reported that this can artificially age tyres by 6 years in an

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8 week period. This process was designed to test tyre physical properties, however, and leaching properties following the aging process were not reported.

There are anecdotal reports of tyres being intact on vehicles sunk in the second world war (65+ years), but this does not appear to have been studied scientifically, and it is not known how this affects leaching properties of the tyre, or whether tyres will still provide support. Small-scale schemes involving less than 100 tyres have been used for over 100 years with little evidence of environmental damage

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4. ASSESSMENT OF DATA

4.1 Introduction

4.1.1 Methodology

Objective two of this project was to:

“Assess any environmental impacts and timescales of these, caused by the use of baled tyres when used in construction”.

This objective has been undertaken using the available data. The two types of data collated during the literature review have been independently reviewed are:

a) leachability data – laboratory testing and in situ studies;

b) ecotoxicological data laboratory testing and in situ studies.

The source-pathway-receptor type approach has been used to assess the risk to the aquatic environment for specific scenarios, as summarised previously in Table 2.1.

4.1.2 Overview of leachability

As part of the source-pathway-receptor risk assessment process, relevant and robust data are needed to quantify release from the source term.

When a whole baled tyre comes into contact with saline water, freshwater or water within a peat bog, a proportion of the compounds in contact with the water will dissolve. It is this dissolved portion which is of greatest interest when assessing the potential impact of baled tyres. Therefore it is the leachability of tyre which has been used to assess the impact on the quality of the surrounding aquatic environment rather than the total composition of the tyre. It may take many hundreds of years for the whole tyre to breakdown and release all of its components. However, the structural integrity of the bale will have been lost much sooner than complete disintegration. When the tyre bales are no longer fit for the engineering purpose they were initially installed for they will have to be removed and the structure re-built.

The factors that control the leachability of materials are complex and include:

characteristics of the leaching medium (leachant) for example, major ion chemistry, pH, ionic strength, dissolved organic matter content;

length of contact between leachant and sample; particle size of sample; heterogeneity of sample; and

mode of contact; dilution (liquid to solid ratio – L/S2) and replacement of eluate in the system.

2 The liquid-to-solid ratio prevailing during the leaching test, is expressed as quantity of liquid (‘L’) in litres and solid (‘S’) in kg dry matter. L/S is expressed in l kg-1.

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The leaching from a granular material, e.g. granulate tyres, will be different from that of a whole material such as whole baled tyres. However, the use of granulated tests provides an opportunity to accelerate the leaching that might be expected from a whole tyre over time. Leaching using end-over-end shakers at high liquid-to-solid ratios is used in the CEN range of leaching tests (see Appendix D). Constant agitation such as this can accelerate leaching from tyres compared with leaching under environmental conditions.

Ideally, field data would be used to model the leaching behaviour of tyres for any given scenario. A number of studies have been undertaken to this end and are summarised in the following section. Only a handful of field-trial studies have been undertaken on baled tyres, and no direct leaching data could be obtained for baled tyres . Field test data is inevitably site-specific, and it therefore also requires additional information, such as laboratory leaching tests, to support more general conclusions.

In the absence of relevant field test data, laboratory leaching tests can simulate the high liquid-to-solid ratios that can take years or even decades to achieve in the field, within hours or weeks. Leaching tests cannot therefore exactly predict the concentration of a contaminant that will be released in the field but do provide a standardised measure of the dissolved contaminant concentration under specified test conditions. Further background to leaching test principles and methodologies is provided in Appendix E.

4.1.3 Approach

A full assessment of environmental risks involves a number of steps3 including: summarising documentary information, identifying contaminants of potential concern, identifying likely fate and transport of contaminants, identifying receptors and pathways of potential concern, creating a conceptual site model, identifying possible assessment and measurement endpoints and identifying gaps and uncertainties.

The available documentary evidence has been collated in the appendices to this report and the principal contaminants of potential concern have been shown to be: leachable zinc, iron, manganese, iron, copper, cadmium and a number of organic compounds: phenolic compounds and derivatives (such as nonylphenol ethoxylates, 4-tert-octylphenol and bisphenol-A), naphthalene and derivatives, long-chain hydrocarbons (for example n-hexadecane), phthalate plasticisers such as bis(2-ethylhexyl)phthalate and polycyclic aromatic hydrocarbons (PAHs).

The receptors and pathways have been identified in Table 4.1 and the only transport mechanism considered to date has been leachability.

However the dataset is inadequate for a full assessment to be undertaken. There is no information on the maximum availability for leaching of key contaminants or of pH dependent leaching of contaminants across the same material in the same study. Similarly there is little information on the effect of complex leachant matrices such as those encountered in saline water or peat bogs.

3 Ecological Risk Assessment for contaminants in soils. Environment Agency (2008) http://www.environment-agency.gov.uk/subjects/landquality/113813/2143247/?version=1

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CEN TC 292 Working Group 2 has prepared guidance (BS EN 12920) on leaching test selection depending on the waste to be tested and the disposal or reuse scenario to be evaluated as detailed in Appendix E. The authors recommend the use of the CEN TC 292 tool box of tests which enable different factors to be assessed independently but are then considered in a unified approach.

In the absence of a complete, relevant, characterisation dataset, a partial assessment of the data obtained to date has been undertaken.

A number of standard and non-standard leaching tests have been undertaken, and these have been assessed and collated from the literature. These have been summarised and plotted in terms of release of contaminants in terms of the liquid-to-solid ratio and pH of the leaching liquid.

Although availability of CEN standard leaching test data was sparse, a number of useful studies have been collated for leaching using various liquid to solid ratios, leaching liquid, pH and grain size. There is no standard test for leaching from whole tyres, and therefore a range of experimental conditions have been used.

LeachXS© is an expert system for managing and modelling waste characterisation data. It has been developed by ECN (Netherlands), DHI (Denmark) and Vanderbilt University (US), and incorporates:

an Access database of public domain information on leachability and composition,

data management tools allowing comparison of data by waste type or constituent, and

a powerful geochemical speciation/transport model, “ORCHESTRA”.

This programme was used to collate and compare leaching data. Not all functions of LeachXS© could be used as dataset was not appropriate (e.g. no pH dependence test and upflow percolation test data were available or information on key factors such as pH and liquid-to-solid ratios could not be identified for some tests).

4.2 Assessment of data

4.2.1 Leachability

a) Zinc

Zinc has been selected to highlight the extent of the leachability data, as a key parameter for assessing the impact of tyres on the aquatic environment. Zinc also has the most extensive dataset as it is the most frequently reported parameter.

We have collated the data for leachable zinc at liquid to solid ratio 10 at neutral pH. The data shows reasonably good agreement across studies, taking in to account the different experimental conditions (time, size of particle), although results are spread over 4 orders of magnitude.

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Table 4.1 Summary of zinc leaching data at L/S10

Min Max Average RSD%

Zn (mg/kg) 0.04 62 12.27 139.15

It should be noted that in a handful of studies the authors reported that they we unable to extract any zinc at pH 7 (e.g. Al-Tabaa (1997)), and therefore data was not reported.

Inert landfill waste acceptance criteria can be used as a benchmark for leaching. At 4 mg/kg, it can be seen that for the average leached concentration would exceed inert landfill WAC. The maximum value encountered (62 mg Zn/kg) was taken from Verschoor (2007), where the tyres crumbs had been artificially aged 3 years using intense UV light. This study also highlighted that truck tyres will leach zinc at greater rates than car tyres, due to higher concentration of zinc oxide in the original composition for truck tyres (Hylands and Shulman, 2003).

Zinc will be discussed here as an example, but all data are available in Appendix F. Assessment of the literature would also suggest that the zinc is also the most important parameter in terms of toxic effects.

Leachability of zinc can be predicted on the basis of pH and ionic strength of the receiving water. In its pure form zinc oxide is only partially soluble in water. Predicted leaching of zinc, calculated using Visual Minteq© 2.5 is shown in Figure 4.1

Leaching of zinc has been shown to be very pH dependent. Zinc will leach at approximately 50 times higher concentrations in saline water compared with freshwater at the same pH due to the higher ionic strength of seawater. However, leachability will be greater in the lower pH conditions of relevance to many freshwater systems and to peat bog environments. Figure 4.1 shows that zinc oxide solubility will increase by a factor of x100 000 when the pH decreases from 7 to 4.

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Figure 4.1 Zinc oxide solubility pH dependence in seawater and freshwater Data was also collated from studies examining leaching of zinc from tyres. The data was collected from studies using a range of experimental conditions, but the same pH dependence emerges, with predicted zinc solubility highest in acidic conditions. Concentrations are much lower than predicted in the model in Figure 4.1, due to physical constraints of the ZnO bound in the tyre. Data was available from 13 reports for leachable zinc. The results collated from these reports are presented in the plot in Figure 4.2. The plot shows the range of zinc concentrations against pH.

Collated data on leaching of zinc from tyres

0

20

40

60

80

100

120

140

160

180

0 2 4 6 8 10 12 14pH

leac

hed

Zn (m

g/kg

)

Aoki - Infill year 0.6(B,1,1)




Artificial football turf Field1(C,1,1)

New york - CrumbRubber(B,1,1)

Norweigen CrumbRubber(B,1,1)

Rubber crumbs Car tyres 0years old Field(C,1,1)

Rubber infill (cars)(B,1,1)

Rubber product Farm tyres3(C,1,1)

Shredded tyres - salinity test15% salinity(S,1,1)Shredded tyres - virginialeaching test(B,1,1)

Tyre Granulate 2 - for groundwork(B,1,1)

Tyre Shreds - Edeskar(B,2,1)

Figure 4.2 Collated zinc leaching data by pH

-8

-6

-4

-2

0

2

4

6

8

10

12

0 2 4 6 8 10 12 14

pH

log

zinc

sol

ubili

ty (a

q/M

)

Seawater (I=0.6 M)Freshwater (I=0.1 M)

Freshwater

SeawaterPeat bog

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The data are spread over 4 orders of magnitude, which reflects the range of test conditions used to measure leachable zinc, such as length of time of study, liquid-to-solid ratio, and the type of tyre and particle size of tyre shred used in the leaching test. Test conditions for each study are summarised in Table 4.1.

Table 4.2 Reference summary for data used in Figure 4.1

Reference Study Reference L/S ratio Details

Aoki - Infill Aoki T, (2008) Page 53

10 Took samples of tyre crumb from artificial football turfs of varying ages. Varied pH from 3 to 4.5

Dutch Granulates Vershoor (2007) Table 1, p16

10 Leached at L/S 10 for different aged granulated tyres

New York - Crumb Rubber

Lim (2008) Appendix 19

10 Tyre granulate using SPLP method at pH 7 and 4.2

Norwegian Crumb Rubber

Lim (2008) Appendix 19

10 Leached at L/S 10 at ph 7-11 over 24 hours

Rubber crumbs tyres 0 years old Field

Verschoor (2007) p16

10 Leached at L/S 10 for different aged granulated tyres

Rubber infill Hofstra U. (2008) Pages 55-56

0.1-10 & 10

Car tyre granulated rubber infill, NEN 7373 column test and EN 12457-2 at pH’s between 5 and 9.5

Shredded tyres - Virginia leaching test

Ealding (1992) 5 Leached for period 1 hour to 1 year at range of pH (4-8)

Tyre Granulate 1 - for ground work

Edeskär T. (2004/5) Pages 60-66

10

Leached at LS/10 at pH 7 and pH 13.6

Tyre Shreds - for ground work

Edeskär T. (2004/5) Pages 60-66

10

Leached at LS/10 at pH 7

Tyre Shreds - test for ground work

Edeskär T. (2004/5) Appendix XII

10 5 replicates of Shredded tyres leached at LS/10 in neutral conditions.

–Edeskär - Tyre granulates

Edeskär T. (2006) PAPER 2 pages 9-10

10 Leaching according at LS/10 to EN 12457-3 in neutral and alkali conditions

–Edeskär - Tyre Shreds

Edeskär T. (2006) PAPER 2 pages 9-10

2 and 10 Leaching at LS/10 according to EN 12457-1 in neutral conditions

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It is very important to note that all of these data are based on shredded or granulated tyres, and it was not possible to obtain any leach test data on whole tyres. Therefore the amount leached may be considerably over-estimated when considering leaching from whole tyres. This is particularly so due to metal beading (around 11% by weight of the tyre (BLIC, 2001)) which is exposed when tyres are shredded, and which are often zinc coated. This metal beading is not exposed in whole tyres, and where tyres are not exposed to UV light, tyres will not break down to the extent where they will be exposed for hundreds of years (Stevenson, 2004).

It can be seen that for each individual study leachable zinc decreases with increasing pH.

The amount of zinc leached in the laboratory test data is just a fraction of the total zinc available in the tyre. In the most complete dataset reported (BLIC, 2001), the concentration of zinc present in a tyre is 1% and 2%. Figure 4.2 shows the experimental leachable zinc data in comparison with the total zinc. It can be seen that even in the worst-case leaching scenario, less than 1% of the total zinc has leached out. The plot also shows the general decrease in leaching of zinc as pH is increased.

Collated data on leaching of zinc from tyres

0.01

0.1

1

10

100

1000

10000

100000

0 2 4 6 8 10 12 14pH

leac

hed

Zn (m

g/kg

)





Artificial football turf Field1(C,1,1)

New york - CrumbRubber(B,1,1)

Norweigen CrumbRubber(B,1,1)

Rubber crumbs Car tyres 0years old Field(C,1,1)

Rubber infill (cars)(B,1,1)

Rubber product Farm tyres3(C,1,1)

Shredded tyres - salinity test15% salinity(S,1,1)

Shredded tyres - virginialeaching test(B,1,1)

Tyre Granulate 2 - for groundwork(B,1,1)

Figure 4.3 Leaching of zinc compared with total zinc available in tyre

Figure 4.3 shows how leaching of zinc in one study decreases over time (Ealding, 1992). The study found that after initial leaching of zinc over the first week, very little zinc will leach out. This is consistent with field monitoring data (Humphrey, 2006; Collins, 1995) which showed that zinc leaching decreases after a short period (<2 years) of time. Anecdotal evidence would suggest that tyres will not break down over very long periods, and knowledge of the chemistry of tyre formulation would also suggest they will resist degredation. However, there are no studies examining leaching of tyres over long periods (2+ years), so it cannot be stated categorically that further leaching will not occur following the initial flush.

Decrease in zinc leaching from pH 2 -8

Increase in zinc leaching from pH 8 -14

Total zinc at 1-2%

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Leaching of Zn over time at pH 4, 7 and 8

0.01

0.1

1

10

100

1000

0 100 200 300 400

Time (days)

Zn (m

g/kg

)

478

Figure 4.4 Leaching of zinc compared with total zinc available in tyre

Taking the average leached zinc result, it is possible to calculate environmental release for granular tyres under laboratory conditions. As an example, the average release from all data is given as 12 mg/kg in a 24 hour period (duration for which BS EN 12457 leaching test is taken for). If it is considered that this amount will leach in one day per kg of tyre, then Figure 4.4 shows how many tyre bales (each containing 100 tyres) could be placed in a freshwater setting without exceeding the EQS for zinc, which varies depending on hardness of water (taken as 50 µg/kg for water hardness of CaCO3 > 150 mg/l rivers).

This approach has a number of drawbacks, not least the fact that L/S10 leaching as a granular material will grossly overestimate release from a whole tyre in a 24 hour period. However, it may be used as a screening tool as a quick and easy assessment of whether use of bales in a particular location would be suitable, or whether further assessment would be required.

More realistic data may be used in calculations in the model, using leaching from whole tyres. For example Abernethy (1994) found concentrations of zinc of 1.1 mg/kg tyre at a liquid to solid ratio of 42 and at natural pH (7.5 – 8.2) for a period of 14 days. Using this rate of leaching, it can be seen that the number of tyres that can be used before zinc EQS may be exceeded is increased by a factor of 104.

4 This assumes all leaching of zinc occurred in the first 24 hours of the test. If uniform leaching over the 14 days is

assumed, the number of tyre bales that could be used can be increased by a factor of 100.

No increase in leaching after 1 week

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Only one like-for-like study was obtained on tyre crumb leaching in comparison to whole tyres. Collins et al. (1995) found tyre crumb would leach 10 mg per tyre in sea water, whereas whole tyres leached 13 mg per tyre. This is less than would be anticipated with the orders of magnitude increase in surface area that would occur going from whole tyres to tyre crumb.

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Determinand Name Zn User entryConcentration leached from tyre/s 0.0162 mg/l Min number of tyre bales 1 balesL/S10 discharge 2 mg/kg Max number of tyre bales 20 balesUpstream River concentration 0 mg/l Upstream River Minimum Flow 0.1 m3/sEQS 0.05 mg/l Upstream River Maximum Flow 20 m3/sWeight of tyre 7

Number of tyre bales ->River Flow

(m3/s) V 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 200.10 0.16 0.32 0.49 0.65 0.81 0.97 1.13 1.30 1.46 1.62 1.78 1.94 2.11 2.27 2.43 2.59 2.75 2.92 3.08 3.242.19 0.01 0.01 0.02 0.03 0.04 0.04 0.05 0.06 0.07 0.07 0.08 0.09 0.10 0.10 0.11 0.12 0.13 0.13 0.14 0.153.24 0.00 0.01 0.01 0.02 0.02 0.03 0.03 0.04 0.04 0.05 0.05 0.06 0.06 0.07 0.07 0.08 0.08 0.09 0.09 0.104.29 0.00 0.01 0.01 0.02 0.02 0.02 0.03 0.03 0.03 0.04 0.04 0.05 0.05 0.05 0.06 0.06 0.06 0.07 0.07 0.085.34 0.00 0.01 0.01 0.01 0.02 0.02 0.02 0.02 0.03 0.03 0.03 0.04 0.04 0.04 0.05 0.05 0.05 0.05 0.06 0.066.38 0.00 0.01 0.01 0.01 0.01 0.02 0.02 0.02 0.02 0.03 0.03 0.03 0.03 0.04 0.04 0.04 0.04 0.05 0.05 0.057.43 0.00 0.00 0.01 0.01 0.01 0.01 0.02 0.02 0.02 0.02 0.02 0.03 0.03 0.03 0.03 0.03 0.04 0.04 0.04 0.048.48 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0.02 0.02 0.02 0.02 0.03 0.03 0.03 0.03 0.03 0.04 0.049.53 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0.02 0.02 0.02 0.02 0.03 0.03 0.03 0.03 0.03 0.03

10.57 0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.03 0.03 0.03 0.0311.62 0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.03 0.03 0.0312.67 0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.0313.72 0.00 0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.0214.76 0.00 0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0.02 0.02 0.02 0.02 0.0215.81 0.00 0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0.02 0.02 0.02 0.0216.86 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0.02 0.02 0.0217.91 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0.02 0.0218.95 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0.0220.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.02

Dilution Ratio Discharge/River (1 in x)< 1> 1 in 1 < 1 in 10> 1 in 10

Figure 4.5 Dilution of zinc at various dilutions in a fresh water body

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4.2.2 In situ studies

Collins et al. (2002) have reported a project at Penvensey beach, where 40 000 baled tyres were placed on a beach as coastal defence to prevent flooding of low-lying hinterland using tyre bales. Concentrations of zinc were found 1-3 times above marine EQS for zinc (0.5 mg/kg) when taken from the tyre mass at spring tide, but this fell to near background levels just 10 m from the tyres. This reflects the large dilution achieved in a marine environment.

At Branston Island in Lincolnshire over 1 200 000 tyres were used in a flood defence project (see Section 3.3.3). The review concluded that the tyres may not have been the source of the increased levels of zinc, and biological surveys showed that it was difficult to conclude that a negative community response was occurring as a result of leachate inputs from the tyre bale embankment rather than as a result of natural variability, seasonal changes and sampling effort. Monitoring of the scheme ceased in 2006, and as such it is not possible to establish any long term impact of the scheme.

Humphrey and Katz (2001) studied behaviour of tyre shreds when placed below the water table (discussed in previous section). They placed 1.5 tonnes of tyre shreds at three geologically different sites. The review found increased concentration of iron, manganese and zinc in comparison with background concentrations at the three sites. These concentrations decreased to background concentrations within three years at the non-peat sites, and very low levels of all VOCs measured. At all sites, concentrations decreased to near background levels 10 m down gradient of the site. This again confirms that tyres will leach appreciable amounts of contaminants in the first few years, but will decrease markedly over time.

4.3 Ecotoxicological test data

A literature search for published studies relating to the use of tyre bales in the aquatic environment and their potential impacts on indigenous organisms was carried out and the resulting papers/reports were reviewed. The data from the key studies has been detailed in the Appendix C, and the main findings are summarised below. The review has considered the results from both laboratory-based studies and also in situ (field)-based assessments. It should be recognised that in situ assessments will generally have the greatest environmental relevance since they reflect realistic exposure conditions..

4.3.1 Freshwater

The majority of the data on the potential effects of tyre bale use on freshwater organisms are from laboratory-based aquatic toxicity studies. However, there were limited studies that used whole tyres or tyre bales with most studies used tyre plugs, tyre crumb, tyre particles etc instead which probably represent a “worst-case” scenario in terms of potential leaching of contaminants. In contrast, the data from in situ studies are limited.

a) Effects of leachates from tyre materials on freshwater species

In general the available data indicate that the leachates from tyre materials generated in laboratory studies were of relatively low toxicity to the freshwater species tested (Day et al., 1993; Nelson et al., 1994; and Abernethy 1994 and Abernethy et al., 1996 cited in O’Shaughnessy and Garga (2000); Birkholz et al., 2003, ChemRisk, Inc., 2008). However,

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there is some evidence that fish may be more sensitive to leachates from tyre materials than other aquatic organisms. For example an early study by Kellough (1991) reported 100% mortality in the rainbow trout exposed to leachate from tyres, but it was reported that there was outside contamination of the exposure water and fish. Therefore, it is unclear if these mortalities were due to the contaminants in the leachate, increased species sensitivity or poor experimental conditions. Another study by Day et al. (1993), also found that rainbow trout appeared to be more sensitive to the tyre leachate tested than other test species. Furthermore Abernethy (1994), cited in O’Shaughnessy and Garda (2000), recorded 100% mortality in rainbow trout fry following exposure to tyre leachate whilst mortality was not observed in other organisms including other species of fish. In a further study by Abernethy et al. (1996), cited in O’Shaughnessy and Garda (2000), it was found that tyres placed in tanks of flowing water caused no lethal effects to rainbow trout as long as the flow rate was > 1.5 l/min per 600 l of water volume. This emphasises the importance of loading rate of tyre materials on the resulting effects observed in the test species. No large scale in situ studies were available for re-use of tyres in lakes or ponds, where water recharge will be much less than in rivers and canals, however rainbow trout, identified as being sensitive in low flow laboratory tests would not be present in low flow environments. Although other species may show similar sensitivity as the rainbow trout, comparative data were not located.

b) Changes in contaminant leaching (and potential toxicity) with time

Many authors also report that the concentrations of contaminants leaching from tyres (and the resulting toxicity) decreased over time in either repeat studies or following sequential leaching tests. Day et al. (1993) studied the toxicity of leachates from used whole tyres employed as a breakwater in a lake for 10 years to the leachates from new and used tyres on rainbow trout, fathead minnows and the waterflea, D. magna. The leachate from the exposed breakwater tyres was observed to have no toxicity compared with toxic effects observed in the leachate from both new and used tyres. Abernethy et al. (1996) cited in O’Shaughnessy and Garda (2000) found that the toxicity in rainbow trout of leachate from tyres reduced over time. The chemical release was reduced with each subsequent submersion period and considered to be due to a continuous leaching process. Abernethy et al. (1996) cited in O’Shaughnessy and Garda (2000) also compared scrap tyres with tyres that had been used in an artificial reef in a lake. The lake tyres were less toxic than the scrap tyres and the chemicals leached from the tyres used in the reef were present at lower concentrations than the leachate from scrap tyres. Subsequently, Birkholz et al. (2003) investigated the toxicity of leachates from used tyre crumb utilised in playground surfaces on luminescent bacteria (Vibrio fisheri), green algae (Selenastrum capricornutum), waterfleas (Daphnia magna) and fathead minnow (Pimephales promelas). Toxic effects were observed using freshly crumbed tyres but this toxicity reduced over time (i.e. following 3 months in-situ). Finally Wik et al. (2009) carried out six sequential leaching tests using material abraded from used tyres. The leachate from the sixth leaching period was observed to be significantly less toxic than the leachate from the first leaching period. Wik et al. (2009) conducted the toxicity tests on green algae (Pseudokirchneriella subcapitata), waterfleas (D. magna and Ceriodaphnia dubia) and zebra fish eggs (Danio rerio).

Many of the studies identified zinc as being present in the leachate and/or identified it as the contaminant responsible for any toxic effects observed. Nelson et al. (1994) found significantly increased levels of zinc in a tyre leachate compared with control lake water or deionised water. The maximum concentration of zinc measured was 755 µg/l compared with 8.7 µg/l and <4.0 µg/l for the lake water and deionised water, respectively. The current lowest UK long-term EQS (i.e. most conservative EQS as the standards vary due to water hardness, see Appendix B for details) for zinc is 8 µg/l for dissolved zinc and between 8 and 75 µg/l for total

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zinc. The least conservative standard is 50 µg/l for dissolved zinc and 125 to 500 µg/l for total zinc. Therefore, it is anticipated that zinc at 755 µg/l would cause adverse effects to aquatic organisms over the long-term. However, it is important to consider the loading rate used in the study with that which is likely in the receiving water environment. Nelson et al. (1994) calculated the following:

Twenty tyre reefs containing 900 tyres per 1 km of canal with a weight of 8 kg/tyre would result in 7200 kg of tyre material per km of canal. It was estimated that if the cross sectional area of the canal is 33.5 m2, approximately 33 500 000 litres of water would be contained in the 1 km section. The experiments involving the tyre plugs indicated that 755 µg of zinc could be leached from 0.181 kg of tyre material. If this value was used, in the 1 km of canal scenario assuming no flow, the zinc concentration leached from the tyres would be 0.90 µg/l of zinc. This is considered to be the maximum concentration as in most cases there will be a flow of water and the tests using whole tyres showed that zinc concentrations declined over time (Nelson, et al., 1994).

A concentration of total zinc of 0.90 µg/l would be below the most conservative EQS and also under the PNECs derived by the EU, Appendix B. However, it is considered that baling projects may use a significantly higher tyre loading rate than is estimated in the example above.

The Nelson et al. (1994) study also found that cadmium, copper and lead concentrations increased in the tyre leachates compared with the two controls. Cadmium was slightly increased with a concentration of 0.6 µg/l compared with 0.2 and <0.1 µg/l in the lake water and deionised water, respectively. Copper was detected at 5.7-6.7 µg/l compared with <5.0 µg/l for both the controls and lead was increased to 6.7 µg/l compared with <1.0 µg/l for both controls. The current UK freshwater long-term EQSs for cadmium, copper and lead are 5, 1 and 4 µg/l respectively. Therefore, the cadmium levels detected were below the EQS, but both the copper and lead concentrations are slightly above the relevant EQSs, However, this does not take into account the effects of water hardness and dilution. Nelson et al. (1994) found no significant differences between the organic contaminants analysed in the leachate from tyres compared with the controls. In the depuration test conducted by Nelson et al. (1994) the concentration of zinc decreased from 222.6 µg/l (following 30 days submersion) to 131.0 µg/l following 60 days in the water, indicating again that levels of contaminants decrease over time.

The likely role of metals leached from tyre material in toxicity tests was supported in the Nelson et al., 1994 study where the addition of EDTA (a metal chelating agent) were observed to eliminate toxicity effects, whereas without the EDTA toxic effects were observed. However, in the tests carried out by Abernethy (1994), cited in O’Shaughnessy and Garda (2000), where 100% mortality was observed in the rainbow trout, zinc was found to be present at concentrations below those known to be toxic. Sixty two unspecified organic compounds were detected (not all identified), and the toxicity was removed following activated carbon treatment. The toxicity remained following aeration or addition of acid, base, an antioxidant or metal chelating agent. Therefore, the contaminant causing the toxicity was unidentified. Wik et al. (2009) found that following toxicity tests using a leachate from tyre particles, that zinc and lipophilic organic compounds were likely to be causing the toxic effects observed.

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c) Influence of the type of tyre and age/pre-history on tyre bale toxicity

The available data also indicate that there are differences in the toxicity observed in laboratory-based studies depending on the type of tyres used and the age/pre-history of the tyres before their use in tyre bales. On the first point Wik et al. (2009) found relatively large differences in the toxicity between different makes of tyres based on an assessment of tyres manufactured in 2003 by Kimho, compared with tyres manufactured in 1999 and 1992 by Hankook and Good Year, respectively.

Day et al. (1993) found in some tests that used tyres were more toxic than new tyres. It was considered that this could be due to cracks formed in the used tyres from road wear and fatigue which would have increased the surface area available for leaching of contaminants. However, in the same study, but using different types of tyres, the authors found that the leachates from new tyres were more toxic than those from used tyres. It was considered that this could be due to the fact that different types of tyres have slightly different components and hence are likely to result in leachates with different compositions.

It is not clear from the available data if the potential ‘worse case’ tyre type has been used, as the ‘worse case’ has not been identified. However, it is considered unlikely that in a tyre baling scenario that all tyres will be of the same age, level of use or make. Consequently, there is likely to be a mixture of tyre types and age in any one baling project so the leachates would reflect an average situation.

d) Summary

The available data from laboratory-based studies with freshwater species indicates that there is a potential for adverse effects but that this will depend on the loading rate of tyre material used, the type of tyres, the length of placement and the age/pre-history of the tyres. In-situ studies are limited, but the data available for freshwaters indicated little or no effects caused via leaching materials from the tyres. Static laboratory tests have indicated that rainbow trout are more sensitive to tyre leachates, however this sensitivity is reduced when the flow rate is increased. This could indicate that sensitive organisms (such as fish) may be at risk in environments of limited flow. Zinc has been identified as the common contaminant (and a potential toxic agent) in a number of leachates from tyre materials.

4.3.2 Marine

a) Effects of leachates from tyre materials on marine species

The literature review indicated that there were fewer studies relating to the effects of tyres on marine organisms, but these mainly related to in-situ studies. Where tyres have been used as a material for the construction of artificial reefs, there are conflicting data on the effects that these structures have on the marine environment and indigenous organisms. Collins et al. (2002) found that tyres used as reefs did not effect the reef colonisation, but it was observed that there were differences between the colonisation of vertical and horizontal surfaces. However this was probably due to the different water flows around the different structures. In the study, body concentrations of zinc were not elevated in ascidians and bryozoans (relative to control organisms). However elevated zinc body concentrations were found in hydroids taken from the tyre surfaces compared to the samples taken from the control concrete reefs, though the differences in the concentrations were only slight. Clearly one reason for the

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potential absence of effects in marine organisms is the greater possible dilution of contaminants leaching from tyres.

Collins et al. (2002) state that there were early problems with securing the tyre structures to the sea bed, and early tyre reefs could be found to wash to shore following storms. The study stated that this is something that can be easily over come using the appropriate engineering. However, correspondence from the US has stated tyres are not now used for this purpose in most states as they cannot be secured in place. It is also argued that the flexing and chafing of the tyres under wave action prevent fouling and the attachment of epiphytic communities.

The data from Walker et al. (2002) provides contrary evidence in that it found that there were no differences between the fish assemblages around tyre reefs compared to other artificial reef structures. It seems unlikely that fish assemblages would congregate around tyre reefs if there was not a sufficient plant and invertebrate community to support the fish species.

Hartwell (1994) cited in Evans (1997) reported that the toxicity of tyre leachates from cut pieces to sheepshead minnow appear to decrease with increasing salinities. Mortalities were observed in the minnow at higher leachate concentrations and especially at lower salinities. However, the toxicity was reduced with increased leaching period. Evans (1997) also reported effects, (i.e. damage to the brain and eyes) in sheepshead minnow larvae following 1 to 2 days exposure to the leachate in a laboratory test. Mortalities were also observed in tests using grass shrimp and planktonic copepods. The shrimp showed reduced survival in both acute and chronic tests following exposure to leachates from used tyre pieces following 7 day extractions at 5 ppt salinity. However, no mortalities were observed in the subsequent tests using 14 and 21 days extractions at 5 ppt salinity and in any extractions at 15 and 25 ppt salinities. The copepod E. affinis showed toxicity in leachates prepared for all extractions periods at both salinities 5 and 15 ppt, suggesting the E. affinis might be more sensitive than the grass shrimp.

It is important to note that where Collins et al. (2002) conducted UK based studies some of the other authors were based outside the UK and would be using species less relevant to UK waters, this is especially important as there has been some species sensitivity observed in rainbow trout. However, these non-UK data should not be discounted as purely UK data are limited. Overall, it should be recognised that tests using a temperate fish species will be representative of other similar species.

b) Summary

In-situ studies for saline waters indicated little or no effects caused via the leaching of materials from tyre bales. Laboratory studies have shown toxicity, but adverse effects were reduced with increasing salinities. In saline waters the greater dilution available will mitigate any toxic effects from the leaching from tyres. However, there are reports of physical damage being caused with artificial reefs in marine waters coming free and disturbing the natural environment.

4.3.3 Peat bogs

No studies specific to the effects of tyre bales peat on organisms were located, however it is known that decreasing the pH will increase the zinc leaching from the tyres. Peat bogs generally poor species diversity, but without the study data it is not possible to make any accurate assessment on the potential impact of using tyre bales in peat bog environments.

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4.4 Overview of key issues

Using zinc as an example, it can be seen that a range of different testing conditions have been reported to assess leachability from tyres. The pH has the highest impact on the rate of leaching from tyres, but even where this is constant, experimental data still shows a broad range of results. It can be seen, however, that even in highly acidic or alkaline environments over long periods of time, no research has reported greater than 1% of total zinc being leached from the tyre. It was shown in some results that this leached in the short term very rapidly, and decreased after a period of 1 day – 1 year.

Risk tables have been developed for each scenario to give a simple summary of the data collected. The level of risk is indicated in each box using a traffic light system (red for high risk, amber for medium and green for low), with the amount and reliability for this data indicated by the border of each box.

4.4.1 Marine

Artificial Reef

Short term

Medium term

Long term

Physical properties

Leaching properties

= high risk = medium risk = low risk = good data = medium data = insufficient data

Erosion

control

Short term

Medium term

Long term

Physical properties

Leaching properties


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For marine reuse scenarios, it is considered that due to the very high level of dilution afforded, the leaching of tyres is not of environmental concern. However, there is insufficient evidence to show that tyres can be secured safely for long periods (20+ years). For erosion control there is less concern, but evidence is still required for long term stability.

4.4.2 Freshwater

For fresh water applications, tyres have been shown to leach contaminants in the short term, and therefore pose a medium risk. In the long term, leachability will decrease to below background levels from experimental data, but there is little field data to back this up for baled tyres.

Fresh-water

Short term

Medium term

Long term

Flood defence


4.4.3 Peat bog

There is very little information on the re-use of tyres in a peat bog. Laboratory experimental data and modelling would suggest that this will increase leaching of some contaminants (e.g. zinc), and therefore more evidence is required.

Peat-bog

Short term

Medium term

Long term

Roads over soft ground


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5. CONCLUSIONS

5.1 Marine

Leaching of chemicals in marine environments has been reported as low risk, generally due to large dilution of any contaminants released. However, as no data has been identified on leaching behaviour of tyres in the environment in the long term (10+ years) it is not possible to assess whether use of baled tyres presents a long term risk to the marine environment.

Limited data on in situ studies for saline waters indicated the greater dilution available will mitigate any toxic effects caused via the leaching of materials from tyre bales. In saline waters this probably reflects the greater dilution available. .Saltwater laboratory studies have shown toxicity, but adverse effects were reduced with increasing salinities. There is also the potential for contaminants to accumulate in the sediment and affect sediment dwelling organisms, but the majority of the limited available data report on exposure from contaminants via the water column.

Successful use of tyres for marine defences and artificial reefs has been reported from the UK. However, further work is required to confirm the resilience of bindings for PAS 108 bales in marine defence, to provide confidence that the tyres cannot come loose in the long term.

There are very few up-to-date studies of artificial reefs in the very long term (20+ years), but reefs that were initially shown to be successful have subsequently been shown to fail Failure of reefs is generally due to poor ballasting or failure of nylon or steel ties,

5.2 Freshwater

The majority of the data on the potential effects of tyre bale use on freshwater organisms are from laboratory-based aquatic toxicity studies. However, there were limited studies that used whole tyres or tyre bales with most studies used tyre plugs, tyre crumb, tyre particles etc instead which probably represent a “worst-case” scenario in terms of potential leaching of contaminants. In contrast, the data from in-situ studies are limited.

The available data from laboratory-based studies with freshwater species indicates that there is a potential for adverse effects but that this will depend on the liquid-to-solid ratio of the specific scenario of tyre material used, the type of tyres and the age/pre-history of the tyres. In-situ studies are limited, but the data available for freshwaters indicated little or no effects caused via leaching materials from the tyres. Zinc has been identified as the common contaminant (and a potential toxic agent) in a number of leachates from tyre materials. No large scale in situ studies were available for re-use of tyres in lakes or ponds. Some species sensitivity has been identified and some studies have been completed outside the UK, but with the available data should not be discounted.

As with marine use, tyre leachates have been shown to be toxic at some level to fresh-water species, generally at high concentrations and from tyre that have been cut into smaller pieces e.g. tyre crumb, granulate etc. which would present a worst case situation for the level of contaminants leached. No long term monitoring has been carried out on large schemes, although this has shown to be not a risk in short to medium term and limited risk in long term for laboratory studies.

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5.3 Peat bogs

No studies specific to the effects of tyre bales peat on organisms were identified, however it is known that decreasing the pH will increase the zinc leaching from the tyres which is known to increase toxicity in some organisms. Peat bogs generally have poor species diversity, but without the study data it is not possible to make any accurate assessment on the potential impact of using tyre bales in peat bog environments.

t was not possible to obtain any data for this literature review on environmental impact of tyres using peat bog water. One scheme in the UK has been reported as successful in terms of engineering properties, but environmental impact was not considered.

5.4 Overall conclusions

Although a number of leaching tests have been carried out of tyres using a range of eluates, these have been carried out under non-standard conditions, and it is difficult to draw over-all conclusions from the leaching data.

There is no data on how tyres will leach in a peat-bog scenario, and more assessment would be necessary in order to determine whether this activity is low risk.

Tyres have been shown in multiple studies to leach metals and organics in low levels, and this has been shown to be toxic to some species. However, there is very limited evidence of adverse affects from leaching of contaminants in actual re-use scenarios

Steel wires used to bind tyres for PAS 108 were recommended for use in enclosed situations, where tyres will not move should the wires break. Evidence is required to show that tyres can be secured in aquatic environment in the long term.

The authors suggest that tyre bales are not used uncovered when used in flood defence type projects. This will limit the tyres exposure to UV and ozone, and thus decrease the rate of degradation of the tyre. This will also reduce leachate caused by rain intrusion, and minimise risk of tyres coming loose.

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6. SUGGESTIONS FOR FURTHER WORK

No chemical laboratory leaching studies were available for whole baled tyres. Much of the assessment was based on granulated and shredded tyres, which may exaggerate any potential environmental impact. The authors therefore suggest collection of fit for purpose characterisation data to enable a more robust risk assessment to be undertaken for each reuse scenario. Following the procedure detailed in BS EN 14290 and the toolbox of tests developed by CEN TC 292 (waste characterisation) will enable the correct characterisation tests to be identified and used. These will allow the leaching from baled tyres in marine, freshwater and peat bog environments to be predicted and corroboration between studies to be achieved.

The authors suggest that further research is required before tyres are considered for re-use in a peat bog. The assessment has shown that the risk of leaching from peat bogs is likely to be high due to low pH, high organic matter and little recharge of water.

Long term monitoring at schemes at pilot schemes in the UK could be considered where tyre bales have been used in aquatic environments (e.g. Pensevey Bay and Branston Island).

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Simm, J.D., Winter, M.G. and Waite, S. (2008) Design and Specification of tyre bales in construction. Proceedings of the Institution of Civil Engineers. Waste and Resource Management 161(WR2):67-76 (40)

Slater, S. (2006) UK Used Tyre Market 2004. TYR0010. The Waste & Resource Action Programme (WRAP) (54)

Stark, D. (1995) Long-Time Performance of Concrete in a Seawater exposure. Portland Cement Association Research and Development Report RP337 (167)

Stevenson. (2004) Effect of long-term immersion of seawater on NR - A review Stevenson Engineering Research Ltd, Natural Rubber News (171)

Sullivan. (2006) An Assessment of Environmental Toxicity and Potential Contamination from Artificial Turf using Shredded or Crumb Rubber, report for Turfgrass producers international (123)

Svensk Däckåtervinning (2007) Recycled Tyres - material with a great potential. (79)

UNEP (2007) Revised technical guidelines on environmentally sound management of used tyres. Open-ended Working Group of the Basel Convention on the Control of Trans-boundary Movements of Hazardous Wastes and Their Disposal. Sixth session. Geneva 3-7 September 2007. Item 6 (a) (i) of the provisional agenda. UNEP/CHW/OEWG/6/INF/6 (6)

United States Department of Commerce National Oceanic and Atmospheric Administration (2007) National Artificial Reef Plan Guidelines for Siting, Construction, Development, and Assessment of Artificial Reefs (145)

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USEPA (1974) Scrap tyres as Artificial Reefs (146)

Vaco (2009) Environmentally responsible use of rubber granulate from recycled tyres (SBR) as infill in artificial football pitches - Fulfilling the duty of care (Soil Protection Act) (106)

VACO (2009) Zinc Adsorption To Underlays Beneath Artificial Turf - How long does the zinc from the rubber infill remain in the artificial turf field system? (108)

Verschoor, A.J. (2007) Leaching of zinc from rubber infill on artificial turf (football pitches) RIVM Laboratory for Ecological Risk Assessment. RIVM report 601774001/2007. (12)

Verschoor, A.J. and Cleven, R.F.M.J. (2009) Risk assessment of leaching of substances from synthetic polymeric matrices. RIVM Report 711701096/2009 (37)

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Walker, B.K., Henderson, B. and Spieler, R.E. (2002) Fish assemblages associated with artificial reefs of concrete aggregates or quarry stone offshore Miami Beach, Florida, USA. Aquatic Living Resources 15(2):95-105 (120)

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Wik, A., Nilsson, E., Källqvist, T., Tobiesen, A. and Dave, G.(2009) Toxicity assessment of sequential leachates of tire powder using a battery of toxicity tests and toxicity identification evaluations. Chemosphere 77:922-927 (115)

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Wik, A. (2008) When the Rubber Meets the Road Ecotoxicological Hazard and Risk Assessment of Tire Wear Particles, Doctoral Thesis, Department of Plant and Environmental Sciences, Faculty of Science, University of Gothenburg (140)

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Winter, M.G. (2007) The Use of Lightweight Tyre Bales in the Construction of Foundations for Roads Over Soft Ground. TRL (44)

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Winter, M.G. (2008) 121 Tyre Bale Foundations for Roads on Soft Ground. Proceedings of the Second BGA International Conference on Foundations, ICOF2008. (43)

Winter, M.G., Simm, J.D. and Waite, S. (2008) The British Standard Publicly Available Specification for Tyre Bales. EuroGeo4 Paper number 10. (41)

World Trade Organization (2007) Brazil - Measures affecting imports of retreaded tyres. Report of the Panel. WT/DS332/R 12 June 2007 (07-2358) (85)

WRAP (2006a) Case Study 8: Use of tyre bales in embankment core for river Witham Phase 2/3 flood defence contract (125)

WRAP (2006b) Waste Tyres Case Study. Bryn Posteg: Baled tyre substitution of aggregate for landfill sites. TYR0008- Bryn Posteg landfill site. (56)

WRAP (2007a) Case study: tyre bales in an embankment (105)

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WRAP (2008a) Introduction to PAS 108 Specification for the production of tyre bales for use in construction (95)

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Zelibor, J.L. (1991) Leachate from scrap Tyres: RMA TCLP Report, Scrap Tyre Management Council (150)

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APPENDIX A ORGANISATIONS CONTACTED FOR ASSESSMENT

Aliapur British Tyre Manufacturers Association Home ETRA European Tyre Recycling Association automotive tyre and rubber recycling - Paris, France ETRMA HR Wallingford Ltd Research International Rubber Research and Development Board ITMA. Imported Tyre Manufacturer's Association - contact mfe Ministry for the Environment - Manatu Mo Te Taiao National Tyre Distributors Association NTDA Ontario Ministry of the Environment Ontario Tire Stewardship Research in Ocean & Earth Science University of Southampton RMA USA Tyre blocks, Urro blocks, Tyre bales, Tyre recycling, used tyre collection Anglo Environmental Engineering and construction Tyre Recovery Association - providing security, protection and peace of mind for those companies that generate waste tyres UTWG

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APPENDIX B ECOTOXICITY DATA AND ENVIRONMENTAL BENCHMARKS FOR RELEVANT CONTAMINANTS

Direct toxicity testing

Table B1 Freshwater ecotoxicity data for zinc oxide

Species Compound Purity (%) End point Duration (hours)

Conc. (mgZnO/l)

Conc. (mgZn/l)

pH Hardness Reference

Bacteria

Bacteria (Pseudomonas fluorescens)

ZnO 99.9 NOEC (growth inhibition)

16 >100 000 >80 000 7.0 NR EU, 2008

Bacteria (Pseudomonas fluorescens)

ZnO 99.5 NOEC (growth inhibition)

16 >100 000 >80 000 7.0 NR EU, 2008

Algae

EC50 (growth rate)

72 0.17 0.135 8.5 12 EU, 2008

EC50 (biomass) 72 0.043 0.034 8.5 12 EU, 2008

NOEC (growth rate)

72 0.010 0.008 8.5 12 EU, 2008

Green unicellular algae (Selenastrum capricornutum)

ZnO 99.77

NOEC (biomass)

72 <0.005 <0.004 8.5 12 EU, 2008

EC50 (growth rate)

72 0.17 0.136 7.5 24 EU, 2008 Green unicellular algae (Selenastrum capricornutum)

ZnO 99.37

NOEC (growth rate)

72 0.03 0.024 7.5 24 EU, 2008

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Species Compound Purity (%) End point Duration (hours)

Conc. (mgZnO/l)

Conc. (mgZn/l)

pH Hardness Reference

Annelids

- - - - - - - - - -

Molluscs

- - - - - - - - - -

Crustaceans

EC50 (immobilisation)

48 2.2 1.76 7.7 261 EU, 2008 Waterflea (Daphnia magna)

ZnO 99.37

NOEC (immobilisation)

48 0.35 0.28 7.7 261 EU, 2008

Insects

- - - - - - - - - -

Fish

Zebrafish (Brachydanio rerio)

ZnO 99.37 NOLC 96 >5.9 >4.7 7.9 266 EU, 2008

Amphibians

Tadpoles (Bufo bufo japonicus)

ZNO NR EC50 (effect unspecified)

48 - 3.2 7.6 NR EU, 2008

Source: World Health Organisation (2001) Environmental Health Criteria 221. Zinc

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Table B2 PNECadd values for zinc (EU, 2008b)

Environmental compartment PNECadd PNECadd value as Zinc Remark

7.8 µg/l Dissolved zinc Freshwater (hardness >24 mg/l as CaCO3)

PNECadd, aquatic

21 µg/l Total zinc

Freshwater (hardness <24 mg/l as CaCO3)

PNECadd, aquatic softwater 3.1 µg/l Dissolved zinc

49 mg/kg dwt Dry weight of sediment Freshwater sediment PNECadd, sediment

11 mg/kg wwt Wet weight of sediment

STP effluent PNECadd, microorganisms 52 µg/l Dissolved zinc

26 mg/kg dwt Dry weight of soil Soil PNECadd, terrestrial 23 mg/kg wwt Wet weight of soil

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Table B3 Relevant Environmental Benchmarks for organic compounds

UK EQS (µg/l) EC EQS (µg/l) Compound CAS RN FW SW Inland surface

water Other surface

water

EU PNECwater (µg/l)

Benzothiazole 95-16-9 - - - - 2-Hydroxybenzothiazole 934-34-9 - - - - 2-(4-morpholino)benzothiazole 4225-26-7 - - - - Nonylphenol 25154-52-3 AA: 1

MAC: 2.5 AA: 1

MAC: 2.5 - - 0.33

Octylphenol 140-66-9 AA: 1a, b

MAC: 2.5a, b AA: 1a, b

MAC: 2.5a, b AA: 0.1

MAC: NA AA: 0.1

MAC: NA -

Bisphenol A 80-05-7 - - - - 1.6/0.1e Naphthalene 91-20-3 AA: 10c, b

MAC:100a, b AA: 5c, b

MAC: 80a, b AA: 2.4

MAC: NA AA: 1.2

MAC:NA 2.4

Long chain hydrocarbons - - - - - - Dioctylphthalate 117-81-7 AA: 20a, b

MAC: 40a, b AA: 20a, b

MAC: 40a, b AA: 1.3

MAC: NA AA: 1.3

MAC: NA

d

Polycyclic aromatic hydrocarbons (PAHs)

- - - - - -

PAHi: Fluoranthene 206-44-0 AA: 0.2d

MAC: 0.1d AA: 0.002d

MAC: 0.01d AA: 0.1 MAC: 1

AA: 0.1 MAC: 1

-

PAHi: Indeno[1,2,3,-c,d]pyrene 193-39-5 f f AA: 0.002g

MAC: NA AA: 0.002g

MAC: NA -

PAHi: Anthrancene 120-12-7 AA: 0.02d

MAC: 0.1d AA: 0.02d

MAC: 0.1d AA: 0.1

MAC: 0.4 AA: 0.1

MAC: 0.4 0.1

PAHi: Benzo[a]pyrene 50-32-8 AA: 0.03d

MAC: 0.5d AA: 0.03d

MAC: 0.5d AA: 0.05 MAC: 0.1

AA: 0.05 MAC: 0.1

-

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UK EQS (µg/l) EC EQS (µg/l) PAHi: Benzo[b]fluoranthene 205-99-2 f f AA: 0.03h

MAC: NA AA: 0.03h

MAC: -

PAHi: Benzo[ghi]perylene 191-24-2 f f AA: 0.002g

MAC: NA AA: 0.002g

MAC:NA

-

PAHi: Benzo[k]fluoranthene 207-08-9 f f AA: 0.03h

MAC: NA AA: 0.03h

MAC: NAh

-

EQS: Environmental Quality Standard. AA: Annual Average. MAC: Maximum Allowable Concentration. FW: Freshwater. PNEC: Predicted No Effect Concentration. SW: Saline water. a Tentative. b Member States shall bring into force the laws, regulation and administrative provisions to comply with Directive 2008/105/EC by 13 July 2010, refer to the EC EQS. c Statutory. d It is stated that there are a lack of effects at or below the “apparent” water solubility therefore no PNEC can be specified. It is considered that there is no concern for aquatic species exposed via the water phase. e Conservative PNEC taking into account potential endocrine disrupting effects. f Insufficient data to propose an EQS. g Sum concentration of benzo[ghi]perylene and indeno[1,2,3-cd]pyrene. h Sum concentration of benzo[b]fluoranthene and benzo[k]fluoranthene. I PAHs currently with UK EQSs and/or EC EQSs.

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Table B4 Relevant Environmental Benchmarks for inorganic compounds

UK EQS (µg/l) EC EQS (µg/l) Metal CAS RN

FW SW Inland surface water

Other surface water

EU PNECwater (µg/l)

Zinc (dissolved) 7440-66-6 AA: 8 b

AA: 15 c

AA: 50 d

MAC: ND

AA: 10

MAC: ND - - See table ##

Iron (dissolved) 7439-89-6 AA: 1000a

MAC: ND AA: 1000a

MAC: ND - - -

Manganese (dissolved) 7439-96-5 AA: 30 MAC: 300

AA: NR MAC: NR

- - -

Copper (dissolved) 7440-50-8 AA: 0.5 b

AA: 3 l AA: 8 m

AA: 12 g

MAC:ND

AA: 5 a

MAC: ND - - -

Lead (dissolved) 7439-92-1 AA: 4 b

AA:10 c

AA: 20 d

MAC: ND

AA: 25a

MAC: ND AA: 7.2 n

MAC: N/A AA: 7.2 n

MAC: N/A

Cadmium 7440-43-9 AA: 5 a, o

MAC: ND AA: 2.5 a, p

MAC: ND AA: <0.08 q, w

AA: 0.08 r, w

AA: 0.09 e, w

AA: 0.15 s, w

AA: 0.25 t, w

MAC: <0.45 q, w

MAC: 0.45 r, w

MAC: 0.6 e, w

MAC: 0.9 s, w

MAC: 1.5 t, w

AA: 0.2 w

MAC: <0.45 q, w

MAC: 0.45 r, w

MAC: 0.6 e, w

MAC: 0.9 s, w

MAC: 1.5 t, w

0.19 u

0.08 v

Aluminium (reactive aluminium)

7429-90-5 AA: 15h,i

MAC: 10 j

MAC: 25h, k

AA: 15h

MAC: 25h - - -

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AA: Annual Average. MAC: Maximum Allowable Concentration. ND: Not derived. NR: Not required. a Statutory. b When water hardness is 0-50 mg CaCO/l. c When water hardness is 50-150 mg CaCO/l. d When water hardness is >150 mg CaCO/l. e When water hardness is 50-100 mg CaCO/l. f When water hardness is 100-250 mg CaCO/l. g When water hardness is >250 mg CaCO/l. h Tentative. i If pH >6.5. j If pH <6.5. k If pH is >6.5. l When water hardness is 50-200 mg CaCO/l. m When water hardness is 200-250 mg CaCO/l. n Lead and its compounds. o Total. p Dissolved. q When water hardness is <40 mg CaCO/l. r When water hardness is 40-50 mg CaCO/l. s When water hardness is 100-200 mg CaCO/l. t When water hardness is >200 mg CaCO/l. u Dissolved fraction. v PNEC for very soft water. Water hardness 2.7-40 mg CaCO3/l and Dissolved Organic Carbon (DOC) concentration of 2 mg C/l with the additional warning the for sensitive species there is no information that there would be no adverse effects below that PNEC below hardness 5 mg CaCO3/l and DOC 4 mg/l. w Cadmium and its compounds.

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APPENDIX C SUMMARY OF ALL PAPERS REVIEWED

See spreadsheet Study reference summary.xls

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APPENDIX D ECOTOXICOLOGY REVIEW

For the ecotoxicological assessment, papers were scored in terms of their reliability and relevance to the objectives of this project:

Standardised testing Appropriate control Use of replicates Measured or nominal concentration (not often relevant as leachate was used as the

exposure media, containing unknown concentrations of unknown contaminants) Peer reviewed paper or not Detailed methodology Whole tyres or not For reliability and relevance a score of 1 to 4 was used. For reliability, a score of 1-2 was given to studies deemed the most reliable i.e. the authors had used standardised experimental procedure, used replicate samples, the study was published in a peer reviewed journal. A score of 3-4 was given to the least reliable sources i.e. where major errors had occurred in the testing procedure (e.g. contamination of samples and/or controls), inappropriate testing methods had been utilised, no replication of samples, published in source that is not known to have undergone a peer review process. For relevance, a score of 1-2 was given to studies that were deemed relevant to the objectives of this project i.e. the experiments utilised whole tyres in environmentally realistic conditions, a score of 3-4 was given to studies that were deemed of little relevance i.e. they did not consider ecotoxicological effects of tyres leachate etc., however these would not have been included in the detail as they would have added little to the report and final assessment.

A literature search for published studies relating to the use of tyre bales in the aquatic environment and their potential impacts on indigenous organisms was carried out and the resulting papers/reports were reviewed. The data from the key studies are detailed in the Appendix A, and the main findings are summarised in Section 3. The review considered the results from both laboratory-based studies and also in-situ (field)-based assessments. It should be recognised that in-situ assessments will generally have the greatest environmental relevance since they reflect realistic exposure conditions, and were given greater weighting in reaching conclusions regarding each scenario. In laboratory-based assessments there is the potential that adverse effects may be observed because the loading rate of tyres to water is greater than that which would occur in the environment. As a result the concentrations of substances leaching from tyre bales would be overestimated.

AQUATIC TOXICITY

Tyres used underwater are protected from ultraviolet degradation and reported to be in a neutral, stable chemical environment, which is considered to limit leaching (Collins et al., 2002). Tyres have been used for the construction of artificial reefs in North America, the Caribbean, Europe, the Middle East, Asia/Pacific and Australia (Collins et al., 2002). Forty reefs on the east coast on the US has reportedly used 700 000 tyres (Collins et al., 2002). As tyres are buoyant when they were first used for artificial reefs there were issues with them coming free and coming onshore following storms, however, this has been overcome by

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improved engineering and the use of concrete ballasting of the tyre units (Collins et al., 2002). However, use of tyres is banned in the majority of states in the USA for artificial reefs due to their near neutral buoyancy causing them to move very easily unless they are very well secured.

FRESHWATER

Kellough (1991) conducted a series of laboratory studies, the details of which are displayed in Table D1 and Table D2. However, some problems were encountered during the experiment so it is difficult to draw accurate conclusions from the results reported. In the water analysis the concentration of zinc was reported to increase in both the control and test samples, suggesting contamination other than the tyres. The fish used in the bioaccumulation tests were contaminated prior to the start of the study. One hundred percent mortality was observed in the rainbow trout exposed to the tyre water, but mortality was not observed in the controls. However, no effects were observed in the crustaceans or goldfish (used for the bioaccumulation tests). Indicating that rainbow trout could be more susceptible to any contaminants that had been leached from the tyres than the other species tested.

Relevance 1

Reliability 3 or 4

Table D1 Study design Kellough (1991)

Parameter Details Laboratory Loyalist College (Belleville, Ontario) Start date April 1991 Water Water was drawn form the Bay of Quinte by Aqua-Blue Water service

(Belleville, Ontario) for the experiments. Type of tyres Unspecified automobile tyres, but a whole intact tyre was used in one

series and one tyre cut into pieces as to expose the metallic elements was used in another series.

Control Water with tyre material Number of replicates

For the bioaccumulation and toxicity studies 1 aquarium was used, so no replications were carried out.

Experimental set-up

Six 450 litre glass aquaria, A’s for studying bioaccumulation and B’s to study the toxicity. A1: no tyre material A2: one intact tyre immersed in the water A3: one tyre cut into pieces B1: no tyre material B2: one intact tyre immersed in the water B3: one tyre cut into pieces

Species The bioaccumulation study used 100 guppy (Poecilia reticulata), but these were replaced with 75 goldfish (Carassius auratus) the goldfish

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were placed in the aquaria with the tyres. The toxicity study used rainbow trout (Salmo gairdneri) and water fleas (Daphnia magna), water samples from the aquaria (B1, B2 and B3) were taken and used in exposure experiments.

Table D2 Study results Kellough (1991)

Parameter Details Water analysis Little significant differences of concentration of the majority tested.

Concentrations of zinc decreased at day 30, but increased sharply at day 60 with the greatest concentration being 3.1 mg/l in the A3 aquarium water sample. However, in the control the concentration of zinc increased from 0.005 mg/l to 0.68 mg/l within the 60 day test period, indicating a zinc source was present other than the tyres. Boron was observed to be high in concentration in the test tanks, but this could not be explained. No detectable Concentrations of any other compounds tested for were observed in any of the samples taken. No detectable amounts of PAH compounds were found in the water samples, apart from anthracene and chrysene, but these were detected in all three samples, including the control, so their presence was not considered to be due to the tyre material. These two PAHs were the only ones detected in the fish tissue, and detection of napthtalene in A2, was not considered to be due to the tyres as it was detected in the fish taken at day 0.

Toxicity The rainbow trout and water fleas were exposed to water from the three tanks in the “B” series of the experiment. The water was taken at three time intervals, 0, 30 and 60 days. The water was then used in the exposure experiments. There were no mortalities in the water fleas exposed to any of the water (B1, B2 or B3) sampled at 0, 30 or 60 days. Water sampled at day 0 caused no mortalities to the trout and no mortalities were observed in the control water (B1) taken at 30 and 60 days, however 100% mortality was observed in fish within 24 hours of exposure to water from aquaria B2 and B3 at both 30 day and 60 day old water. However, there were very few mortalities observed in the goldfish used in the bioaccumulation test. This could have been due to the trout being for sensitive, however, no firm conclusions were drawn.

Bioaccumulation No significant trends were observed in the metals detected in the fish samples analysed. Zinc concentrations fluctuated and aluminium concentration dropped, however, these changes occurred in all three tanks, including the control. No detectable amounts of polychlorinated biphenyls/organochlorine pesticides (PCBs/OCs) could be observed in any of the samples, apart from in dichlorodiphenyldichloroethylene (DDE). Significant levels were detected in many of the goldfish at day 0, but this was considered to be due to the fish being contaminated prior to the experiment starting.

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ChemRisk, Inc. (2008), conducted a study on tyre wear particles5. They investigated the composition, human exposure and aquatic toxicity. Unfortunately the full results were not available in the interim report, however the species tested green algae, waterfleas and fathead minnows were reported and testing was reported to be carried out under international standard procedures. The road particles were mixed with water and sediment for 24 hours and then the water was allowed to settle and the sediment was removed. The test organisms were then exposed to the water. The tests conducted were all acute tests (24 to 72 hours) and it was concluded that the road particles were “not acutely toxic” (no further details were available) (ChemRisk, Inc., 2008).

Relevance 2-3 (road particles rather than whole tyres)

Reliability 3 (due to lack of study detail, could be improved with availability of data)

Four studies using rubber powder produced from tyre carcases are reported, and none of were reported to indicate toxicity. The first three tests conducted used the green algae Selenastrum capricornutum, the waterflea Daphnia magna and the zebrafish Brachydanio rerio and were carried out according to ISO 8692, 6341 and 7346 testing guidelines, respectively (UNEP, 2007). The fourth test was conducted in 1996, “Determination of Acute Toxicity as per ISO 11268/1 – Observing the effect of tyre powder rubber on a population of earthworm placed in a definite substratum”. No further details on any of the four studies were located.

Later in 2003, a test was carried out in California using rubber crumbs taken from a site where tyres had been disposed. Toxicity was observed in bacteria, green algae, invertebrates and fish (species unspecified). Three months after this initial test, further samples of the rubber crumb were taken from the same site and the subsequent toxicity tests demonstrated a 59% reduction in toxicity (no further details were located) (UNEP, 2007). Without the study details it would be inaccurate to draw any conclusions from these tests, it is also important to note the initial age of the tyre crumb taken from the disposal site was not stated and if the tyres disposed at the site were all the same age and at similar points of degradation. Therefore, the three months could have been longer or shorter than indicated; however, this may be explained in more detail in the original study report.

Relevance 2-3 (rubber powder and crumb rather than whole tyres)

Reliability 3 (due to lack of study detail, could be improved with availability of data)

Birkholz et al. (2003) investigated the toxicity of leachate from tyre crumb used in playgrounds on a number of aquatic species (see Table D3). The composition of the leachate was not reported, but Toxic Units (TU) and Potential Ecotoxic Effects Probe (PEEP) were used to compare the toxicities of the different crumbs to the different species and the effects of ageing of the crumb was also assessed. Birkholz et al. (2003) concluded that even though toxicity to all four species was observed when exposing them to leachate from fresh crumb, this toxicity 5 Tyre wear particles are released from the tyre tread during the use of the tyres (ChemRisk Inc. and DIK Inc.,

2008).

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decreased with time and any leachate would undergo significant dilution (from rain water, snowmelt, the receiving water itself, etc) before entering a water course.

Relevance 2-3 (tyre crumb used in playgrounds rather than whole tyres in an aquatic environment)

Reliability 2 (peer reviewed journal, standardised testing, detailed reporting)

Table D3 Study design (Birkholz et al., 2003)

Parameter Details Laboratory Enviro-Test Laboratories, Edmonton, Alberta, Canada Start date Unspecified, but published in July 2003 Water Freshwater, unspecified Type of tyres Tyre crumb (250 g samples were leached in 1 litre of water to produce

the test leachate). Three types of fresh tyre crumb. Then in another test fresh crumb, crumb that had been aged tyre crumb (in place in the playground for 3 months) and tyre crumb leachate that had been modified by the addition of sewage seed and nutrients and aerated for 5 days).

Control Positive control (lauryl sulphate for the bacteria and sodium chloride for the other species tested)

Number of replicates

Unspecified

Experimental set-up

Once the crumb had been leached into the water the leachate was filtered to remove particulates, then it was used to expose the test species in the standardised method. Serial dilutions of the leachate were used to create the toxic units (TU). The TU is calculated from a probit analysis that produces an EC50, LC50 or IC50 (depending on the effect examined in the specific test) the level is derived and inverted and multiplied by 100. Giving a value that increases with increasing toxicity. Standard toxicity testing were employed either according to Environment Canada or US Environmental Protection Agency guidelines.

Species Luminescent bacteria (Vibrio fisheri); Green algae (Selenastrum capricornutum); Waterflea (Daphnia magna); and Fathead minnow (Pimephales promelas).

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Table D4 Study results (Birkholz et al., 2003)

Parameter Details Water analysis Analysis not carried out Toxicity All samples of fresh tyre crumb were toxic to all four species. There was

a 59% reduction in toxicity exhibited by the tyre crumb leachate that had been in place on playgrounds for 3 months compared with the fresh sample of crumb. The leachate that had been treated with sewage seed and nutrients and then aerated for 5 days showed a 73-86% reduction in toxicity. It was concluded that with ageing of the tyre crumb in-situ and with dilution from rainwater, snow melt, receiving sewers and surface waters the leachate would be ‘non-toxic’.

Bioaccumulation Tests not carried out Day et al. (1993) carried out toxicity testing on a variety of aquatic species using leachates from tyres that had been used in a floating breakwater in a harbour for 10 years, used car tyres and new tyres. Day et al. (1993), found potential variations between the level of toxicity exhibited by tyres manufactured by different companies as well as between new and used tyres. The tyres that had been used as a breakwater for 10 years were found not to cause toxicity, whereas the new and used tyres did cause toxicity. In some cases the used tyres were more toxic than the new tyres, it was suggested that this could have been due to tyre fatigue. When tyres become fatigued they crack which increases the surface area. However, this difference in toxicity could have also been due to the make of tyre. The study does suggest that the toxicity of tyres could decrease over time, but tyre leachate was still toxic to fish following storage for 32 days, indicating once the contaminants are leached from tyres they take time to become non-toxic, however, under certain environmental conditions such as river systems there would be continued dilution.

Relevance 1 (use of whole tyres)


Table D5 Study design (Day et al., 1993).

Parameter Details Laboratory Environment Canada Start date Unspecified. Water Freshwater. Type of tyres There were three types of tyres:

Breakwater tyres obtained from the LaSalle Park Marina floating tyre breakwater situated in Hamilton Harbour, Lake Ontario in-situ since 1981 (immersed for 10 years). Used car tyres. New tyres.

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Control Water without the immersion of any tyre material. Number of replicates

Varied between test.

Experimental set-up

Whole tyres were used for the testing. Nine test species were used in a variety of tests detailed below, test methods used for fish and crustaceans were standard to Environment Canada and the other methods were referenced. In some tests tyre were immersed in water for 5, 10, 20 and 40 days and at the end of each time period water was removed and used in the exposure test. Each test included a minimum of five concentrations of the overlying water (i.e. 0, 6, 12, 25, 50 and 100% concentrated leachate) plus a groundwater control and at least 10 animals were exposed to each concentration. This enabled the authors to calculate at what percent leachate the L(E)C50 was reached for each species. Rainbow trout were also used in tests where the leachate had been stored for 0, 1, 2, 4, 8, 16 and 32 days without a tyre immersed, to test the length of time the leachate remained toxic. Species Test

Rainbow trout (Oncorhynchus mykiss)

96 hour acute lethality test

Fathead minnow (Pimephales promelas)

96 hour acute lethality test

Waterflea (Daphnia magna) 48 hour acute lethality test

Worm (Panagrellua redivivus) Nematode lethality/mutagencity test

Bacteria (Spirillum volutans) Motility inhibition

Bacteria (Photobacterium phosphoreum)

Bioluminescence test

Mutant bacteria (Escherichia coli) Inhibition of enzyme β-galactosidase

Mutant bacteria (Escherichia coli) Inhibition of colour production

Species

Beef heart mitochondria Inhibition of electron transfer

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Table D6 Study results (Day et al., 1993)

Parameter Details Water analysis Analysis not carried out. Toxicity In the fish (fathead minnow and rainbow trout) and crustaceans tests,

exposures to control water and leachate from the breakwater tyres following 5, 10, 20 and 40 day immersion caused no mortalities. The leachate from for the scrap and new tyres following 5, 10, 20 and 40 days immersion caused no mortalities in fathead minnows and daphnia tested. However, the rainbow trout were observed to have a greater sensitivity to the leachates from the new and used tyre leachate, results as follows: leachate from scrap tyres immersed for 5, 10, 20 and 40 days exhibited LC50s of 19.3, 15.1, 16.8 and 11.8% leachate, respectively in rainbow trout. Leachate from new tyres immersed for 5, 10, 20 and 40 days exhibited LC50s of 75.1, 54.6, 52.1 and 80.4% leachate, respectively in the rainbow trout. These results indicate that the leachate from the scrap tyres was of greater toxicity than that from the new tyres. However, the leachate from the new tyres inhibited metabolic function in microorganisms more readily than from the leachate from used tyres, but it was reported that the used tyres used in the experiments carried on bacteria, mitochondria and worms were from a different source than the ones used in the fish and crustacean lethality tests. It was suggested that the make of tyre in this instance could have had an effect on the toxicity. It was also suggested that the increased toxicity observed in the rainbow trout using the used tyres compared with the new tyres could have been due to tyre fatigue as well as different manufacturing processes. Tyres that have been used develop cracks due to flex fatigue which increase the surface area from which toxic compounds may leach. EC50s of 15.8 and 6.6% were reported in P. phosphoreum for the leachate from scrap and new tyres, respectively. Indicating that the leachate from the new tyres is more toxic than from scrap tyres. Inhibition of colour production of 13.7% in E. coli for leachate from scrap tyres, but no responses were observed in either the control or the leachate from the new tyres. This suggests that in this test the scrap tyres are more toxic. In the mitochondrial test the control, leachate form scrap tyres and leachate from new tyres had 93.0, 44.0 and 5% inhibition of control reduction of NAD+, respectively. Indicating that in this test the leachate from the new tyres is again more toxic. In the rainbow trout lethality test using the stored leachate with the immersed tyre removed reported no mortalities in the control in the water stored from 0 to 32 days. LC50s of 15.1, 16.0, 16.8, 18.0, 25.0, 40.5 and 35.4% were reported in scrap tyre leachate stored for 0, 1, 4, 8, 16 and 40 days, respectively. LC50s of 54.6, 54.6, 62.2, 84.7 and 65.7% were reported in new tyres leachate stored for 0, 1, 2, 4 and 8 days, respectively, and no mortalities were observed in the tests carried

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out on new tyre leachate stored 16 and 32 days. Immersing the tyres for 40 days did not increase the toxicity observed in test organisms. Also, the compounds leached from the tyres causing toxicity in rainbow trout persisted for 32 days following the tyres being removed from the water. Tyres that had been submerged and used as breakwater for 10 years did not leach chemicals which were toxic to biota.

Bioaccumulation Test not carried out.

Nelson et al. (1994) conducted toxicity studies (see Table D7 and D8 for details) using leachate from tyre plugs, as well as water analysis, water samples were treated to affect the bioavailability of potential contaminants allowing an assessment to be made on the likely contaminants causing the toxicity. The concentration of zinc was measured over time. Zinc was found at significantly increased concentrations in the tyre leachate, concentrations of cadmium, copper and lead were also increased compared to controls. No differences in the concentrations of organic compounds were detected. Mortality was observed in crustaceans and it was concluded that the majority of toxicity was caused by zinc.

Relevance 1-2 (use of tyre plugs and half tyres)


Table D7 Study design (Nelson et al., 1994)

Parameter Details Laboratory Laboratory unspecified, but the first author is affiliated with

Environmental Sciences Section, Bureau of Reclamation, Denver, Colorado, USA.

Start date Unspecified. Water Water used for the toxicity tests and depuration part of the study was

from Lake Mead, Nevada. The water used for the analysis of organic contaminants test was deionised water.

Type of tyres Tire plugs from nonbias ply tyres were used to determine the toxicity and analysis of organic contaminants studies but half a whole tyre was used for the depuration test.

Control Lake Mead water. Number of replicates

Unspecified.

Experimental set-up

Toxicity test (tyre plugs): Acute 24 hour toxicity according to US EPA guidelines were carried out. Leachate from the tyre plugs was used for the exposures. Tyre plugs were soaked in Lake water for 31 days. Toxicity testing included a baseline toxicity test of tyre leachate diluted with Lake Mead water with aeration, filtration, C18 solid phase extraction (SPE) tests, and pH adjusted samples to test for volatiles, particulate-bound toxicants, non-polar organic compounds, and changes to bioavailability, respectively. Samples were also treated with

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sodium thiosulphate or ethylenediaminetetraacetate (EDTA) to assess metals toxicity. LC50s were calculated and acute toxic units (TUa) were also calculated to compare leachate toxicity to measured concentrations of toxicants. The leachate TUa’s were derived by dividing 100% by the LC50, and the TUa for the individual toxicants were derived by dividing the measured concentration by the LC50 of the acute toxicant. Analysis of organic contaminants (tyre plugs): Tyre plugs were soaked in deionised water for 40 days Depuration study (half a whole tyre): Half a whole tyre was left in an aquaria containing Lake Mead water and aerated for 30 days. After 30 days the tanks were drained, and fresh water was added to the tanks. Water samples were taken and analysed at 30 and 60 days to determine if depuration of materials had occurred.

Species Water flea (Ceriodaphnia dubia) <24 hours old. Fathead minnow (Pimephales promelas) 24-48 hours old.

Table D8 Study results (Nelson et al., 1994)

Parameter Details Water analysis The analytical results from the water used in the toxicity tests showed

the following concentrations of zinc: 8.7, <4.0, 751 and 755 µg/l in Lake Mead dilution water, deionised water, tyre leachate duplicate 1 and tyres leachate duplicate 2, respectively. Cadmium was detected at 0.2, <0.1, 0.6 and 0.6 µg/l, in the respective water and leachate samples. Copper was detected at <5.0, <5.0, 6.7 and 5.7 µg/l in the respective water and leachate samples. Lead was detected at <1.0, <1.0, 6.7 and 6.7 µg/l in the respective water and leachate samples. The analysis of the organic compounds did not detect any analytical differences between the tyre leachate and deionised control. Benzothiozole was detected in both samples (control and leachate) as 1-2 mg/l, indicating that it was being introduced by something else other than the tyre. Other compounds were all below limits of detection (1.0 µg/l). The concentration of zinc in the depuration test was reported to decrease over time (222.6 µg zinc/l at 30 days and 131.0 µg zinc/l following 60 days) indicating that the concentrations of toxicants in tyre reefs would also decrease with continuous leaching by water. It was calculated that the amount of zinc leached per gram of whole tyre was 1.7 µg zinc/g tyre, this was lower than that leached from the tyre plugs, 4.2 µg zinc/g tyre. This was considered to be due to the increased surface area of the plugs. The following was calculated: 20 tyre reefs containing 900 tyres per 1 km of canal and a weight of 8 kg/tyre this would result in 7200 kg of tyre material per km of canal. It was estimated that if the cross sectional

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area of the canal is 33.5 m2, approximately 33500 000 litres of water would be contained in the 1 km section. The experiments involving the tyre plugs indicated that 755 µg of zinc could be leached from 0.181 kg if tyre material. This value was used, in the 1 km of canal scenario assuming no flow, the zinc concentration leached from the tyres would be 0.896 µg/l of zinc. This is considered to be the maximum concentration as in most cases there will be a flow of water and the tests using whole tyres showed that zinc concentrations declined over time.

Toxicity LC50 of 20.3% leachate was reported in C. dubia, but it was not observed to be acutely toxic to the minnows (100% survival was observed in the fish and the blanks and controls). The manipulation of the leachate samples indicated that metals were present. In the 100% leachate in the SPE tests 20% survival was observed in C. dubia (fish were not tested) and in the test using 100% leachate and EDTA there was 100% survival in the C. dubia (fish not tested), indicating that the EDTA removed the toxicity previously exhibited in the C. dubia, it is stated that this demonstrated cationic metal toxicity and a mixture of metals. Chemical analysis of the sample water reported zinc as being present in concentrations likely to cause toxicity and that cadmium, copper and lead were above the background level in the 100% leachate. EDTA is reported to have removed both the zinc and copper, whilst the sodium thiosulphate would remove the copper but not the zinc. The TUa for the leachate test was calculated as 4.9 and an additional zinc bioassay carried out at the same time calculated a TUa of 5.1 for zinc. The authors concluded that the closeness of the two values suggests that the majority of the leachate toxicity is from the zinc.

Bioaccumulation Tests not carried out.

Abernethy (1994) (cited in O’Shaughnessy and Garga, 2000) conducted some freshwater tests. Tyres were submerged in water from which samples were subsequently taken for toxicity testing. The water caused 100% mortality in rainbow trout fry exposed, usually with 48 hours. However, mortality was not observed in the three other species tested including Daphnia magna, Ceriodaphnia and fathead minnows. On analysis the water sample was only found to have zinc present and that was below concentrations known to cause mortality. In further analysis 62 organic compounds were detected, but less than half identified. Toxicity of the water sample was not reduced with aeration, or additions of acid, base, an antioxidant or metal-chelating agent. However, activated carbon completely removed the lethal effects observed, therefore the chemical cause of the toxicity exhibited by the trout fry were unknown (Abernethy, 1994, cited in O’Shaughnessy and Garga, 2000).

A further study conducted by Abernethy et al. (1996) also cited in O’Shaughnessy and Garga, 2000, reported that tyres placed in tanks of flowing water caused no lethal effects to rainbow trout as long as the flow rate was >1.5 l/min per 600 l of water volume. This study also found that the toxicity of the tyres reduced over time, the chemical release was reduced with each subsequent submersion period and considered to be due to a continuous leaching process. In another part of the same study tyres collected from an artificial reef in Lake Erie were observed to be less toxic than scrap tyres which had never be exposed to the aquatic

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environment. The chemicals leached from the tyres used in the reef were much less than those scrap tyres used.

Relevance 1 (use of whole tyres)

Reliability 3 (details of studies reviewed by a second party)

Wik et al. (2009) investigated the effects of leachate form tyre wear particles (from three different tyres) to aquatic organisms. It was reported that the newest tyre was observed to be the most toxic. Toxicity decreased over the sequential leaching period. The Predicted Environmental Concentration/Predicted No Effect Concentration (PEC/PNEC) ratios for the tyre wear particles indicated that adverse effects could occur to the aquatic organism in the receiving water, but the different rubber formulation vary the toxicity. Zinc and lipophilic organic compounds were suggested as being the compounds in the leachate responsible for the toxic responses.

Relevance 2-3 (tyre wear particles rather than whole tyres)


Table D9 Study design (Wik et al., 2009)

Parameter Details Laboratory Norwegian Institute for Water Research in Oslo and the Department of

Plant and Environmental Sciences at the University of Gothenburg. Start date Unspecified. Water Freshwater. Type of tyres Three types of used tyres (manufactured in 2003 (A), 1999 (B) and

1992 (C)). Tyres A, B and C were manufactured by Kimho, Hankook and Good Year, respectively.

Control Freshwater without tyre material. Number of replicates

For each tyre there were two replicates of the leaching and standard procedure were used for the toxicity testing, which would have included replication.

Experimental set-up

Twelve grams of rubber was abraded from each of the three washed tyres using a rasp. Six sequential leaching periods were completed for 5, 9, 20, 7, 5 and 11 days. Standard procedures were used for the toxicity testing. Standard 24-48 hour immobilisation tests were conducted using D. magna. Chronic reproduction tests were carried out using C. dubia. Cell density was examined in a 72 hour test on P. subcapitata and acute toxicity tests were carried out zebra fish eggs. Toxicity Identification Evaluation (TIE) were also carried out to characterise the classes of toxicants. These were done using 1 and 10 g/l tyre leachates after leachings1-3 and of only 10 g/l after leaching 4 and 6. The manipulations included the addition of sodium thiosulphate (STS) (to determine if oxidants

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such as chlorine and some electrophile organic chemicals are causing toxicity and also some cationic metals, e.g. cadmium, copper, silver and mercury), C18 solid phase extraction (SPE) (to determine if lipophilic organic are the cause of toxicity) and ion exchange through a CM column (to determine if cations (metals) are responsible for the toxicity). Water samples were also analysed for zinc.

Species Green algae (Pseudokirchneriella subcapitata). Water fleas (Daphnia magna and Ceriodaphnia dubia). Zebra fish eggs (Danio rerio).

Table D10 Study results (Wik et al., 2009)

Parameter Details Water analysis Test not conducted. Toxicity The toxicity results for zebra fish eggs were removed from the

analysis as there we no consistent toxicity within the concentration range. Apart from at leaching period 1 in tyre A which reported an EC50 (mortality) of 0.55 g/l. In the tests using the other species tested, tyre A (the newest tyre) was reported to be significantly more toxic than tyres B and C, even though previous studies had found new less worn tyres were found to be less toxic than worn older tyres. However, this could be due to the make of tyres. The leachate from the last sequential leaching period (6) was found to significantly less than the leachate from the first sequential leaching period (1). A predicted environmental concentration (PEC) of 0.013 g/l of tyre wear material in road run off had been previously determined. The most sensitive EC50s determined in this study are for C. dubia EC50 (reproduction) for tyre A and the ratio of these EC50s and the PEC are as follows: 0.7, 1.0, 1.0 and 0.1 after leaching period 1, 2, 3 and 6, respectively. For tyres B and C this is ratio is between 0.6-0.01 and 0.2-0.01 for the sequential leaching periods of both tyres, respectively. It was concluded that this indicates that the leachability of toxic compounds differs greatly among the different rubber formulations and tyre wear might cause harmful effects to aquatic organisms such as C. dubia over time. In the TIE tests the toxicity to D. magna of all tyre leachates was significantly reduced by both CM and C18 SPE columns, suggesting that toxicity to a large extent was caused by zinc and lipophilic organic compounds.

Bioaccumulation Test not conducted

Wik and Dave (2006), carried out a study using tyre wear material from 25 tyres. Forty-eight hour EC50 tests on Daphnia magna were conducted on the tyre wear material leachate, these

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EC50s (effect unspecified) ranged from 0.5 to >10.0 g/l. Toxicity identification evaluation (TIE) was used to determine the identity of the toxicants, it was concluded that non-polar organic compounds were causing the majority of the toxic effects. UV light exposure of the filtered leachate was not found to significantly increase the toxicity. However, unfiltered leachate, with the rubber material still present, when exposed to UV was reported to have enhanced toxicity (Wik and Dave, 2006).


Reliability 2 (limited data as abstract only, peer reviewed journal)

Wik and Dave (2009) reported maximum Predicted Environmental Concentrations (PECs) for tyre wear particles in surface waters range from 0.03 to 56 mg/l and in sediments the PECs range from 0.3 to 155 g/kg dw. In previous study Predicted No Effect Concentrations (PNECs) have been determined for C. dubia and P. subcapitata and the using these the PEC/PNEC ratios in water and sediment were reported to be >1, suggesting that the tyre wear concentration is a potential risk to aquatic environment.


Reliability 2 (limited data as abstract only, peer reviewed journal)

Moretto (2007) conducted aquatic toxicity studies using leachates from turf with addition of a number of different granulates (one of them being used tyre rubber). No significant differences in the contaminants were observed between the different granulates in the pilot and the concentrations of contaminants in the in-situ pitch were fairly comparable. The contaminants detected were low and the concentrations fell rapidly over time. The leachate from the turf using tyre rubber granulate filling was considered to have a low impact to the aquatic organisms tested.

Relevance 2-3 (leachate from artificial turf rather than whole tyres)

Reliability 3 (limited toxicity testing data, unclear if peer reviewed)

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Table D11 Study design (Moretto, 2007)

Parameter Details Laboratory EDEMS, France. Start date October 2005 continued for 11 months. Water Rainwater percolating through artificial turf. Type of tyres Used tyre granulate. Control Artificial turf with no granulate filling (pilot). Number of replicates

Unspecified, but the tests were stated to be standardised.

Experimental set-up

Pilot studies were conducted using synthetic turf systems without infill material (control) then four synthetic turf systems with the addition of recycled rubber granulates (tyres), ethylene propylene diene monomer (EPDM) granulates, thermoplastic elastomer (TPE) granulates or rubber granulates (in-situ). All the leachate from these systems were analysed for contaminants and used in toxicity testing. A lysimeter was placed underneath an artificial turf. The turf consisted of used tyre granulates. The rainwater that had percolated through was used in toxicity tests. These tests were carried out after the turf being in place for 3, 3.5, 6 and 7.5 months. This would show any changes any alteration in level of toxicity over the aging of the turf.

Species Waterflea (Daphnia magna) 24 hour immobilisation test. Green algae (Pseudokirchneriella subcapitata) 72 hour growth inhibition test.

Table D12 Study results (Moretto, 2007)

Parameter Details Water analysis Cyanide, phenol and total hydrocarbons concentrations were very low,

most being less than limit of detection (LoD) as were the PAHs tested. The metals Sn, As, Mo and Sb fluctuated over time, but always at low concentration and below the reference guide values in all systems. The metals Al, Ba, Cd, Co, Cr, Cu, Hg, Ni, Pb, Sn and Zn showed a decrease in concentrations over time, with maximum concentration in the first two samples taken in the first month. The concentrations were low to begin with and fell to reach values close to the control, below the reference guide and sometime below the LoD. This indicated that the release of potentially polluting substances takes place n the first month of deployment. Sulphates were found to be slightly greater than the reference guide value at the start of the experiment in the pilot containing the used tyre granulate in the first sampling (within the first month), low concentrations were found in the four pilots, but particularly low concentrations were observed in the in-situ turf. The same was true for NH4

+ in the first month of the pilot.

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No significant differences in the contaminants were observed between the 3 granulates used in the pilots. Concentrations were low and any were slightly higher at the start fell rapidly. The in-situ pitch was fairly comparable.

Toxicity The toxicity unit (100/EC50) for the waterflea (D. magna) were <1 for 3, 3.5, 6 and 7.5 months tests indicating that 50% mortality was not reached using the turf leachate as the exposure media. It was suggested by the author that this showed no toxicity. The algae tests had reported toxicity units of <1.2 for 3.5 and 6 month tests (the tests on algae at 3 months were conducted due to the volume of leachate being insufficient) which corresponded to a 7.5% and 1.6% inhibition at 3.5 and 6 months, respectively, both still no reaching a 50% effect level. However, at 7.5 months the toxicity unit was 1.4 and the reported inhibition was 57.5%, therefore the 50% effect level had been reached. The author attributed this toxicity to external pollution as chemical analyses and results of these same tests on the percolates from indoor pilots had not showed toxic effects. Also, 57.5% was considered by the author to be of low impact.

Bioaccumulation Tests not conducted.

MARINE

Many studies have been conducted on the effects of tyres used for artificial reefs on fish populations; however consideration should also be taken for organisms that colonise the reef structure i.e. the tyres themselves, as they will potentially be exposed to a higher concentration of any substances leaching from the tyres (Collins et al., 2002). Collins et al. (2002) has stated that millions of tyres have been used in marine artificial reef systems around the world and they have been colonised by marine organisms without adverse effects being observed.

Tyres have been found to work well as artificial reefs, as the void space in the tyres enables the construction of the reefs to attract fish. The surfaces of the tyres are colonised by algae and a wide range of faunal species, including corals and shellfish (Collins et al., 1995).

In a study 12 co-located reefs constructed of limestone, quarry boulders, concrete-gravel aggregate or concrete-tyre aggregate offshore of Miami Beach in Florida, USA were examined for the faunal assemblages (Walker et al., 2002). It was reported that there were no significant difference in total fish or spiny lobster abundance or fish biomass between the three reef types. Also, it was reported that there was no evidence to suggest that clustering of fish assemblages by reef type differed between the reef types. Fish abundance data was examined from before the reefs were deployed and compared with data gathered two years following the deployments and it was found that the artificial reefs had increased fish abundance and richness in the surrounding area (Walker et al., 2002).

However, in a recent publication in the US marine artificial reef manual, it has been argued that tyres do not make good habitats for artificial reefs. It should be noted that a lot of this report focused on the tyre reefs that had not been sufficiently secured in place and had moved from the original position of deployment, thus disturbing any growth of epifauna that may have grown and attached itself to the tyre surface. There was also the suggestion that in

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comparison between concrete, coral based rock, painted steel and car tyres found that car tyres were the least suitable material for epifaunal development, specifically for corals. It was considered by the authors that this could be due to components in the tyres that prevent the corals from settling or could cause mortality to new recruits. The article concludes by stating that tyres must be stable in order for fouling or epiphytic communities to attach to the surface. Loose, mobile tyres do not allow invertebrates to grow due to abrasion, chafing and flexing.

Collins et al. (1995), reviews the utilisation of waste tyres in the marine environment and found limited data on the environmental impacts. However, they stated that preliminary results from their own experiments with tyre dust in sea water leaching studies found that zinc was the major leachate (totalling 10 mg/tyre after 3 months). It was also reported by the authors that diluted leachates from the tyre dust showed no significant effects on the growth of the phytoplankton Phaeodactylum and Isocrysis (Collins et al., 1995).

Relevance 2 (review of whole tyres, but tests on tyre dusts)

Reliability 2 (peer reviewed journal)

Collins et al. (2002) conducted a study examining the effects tyres used as an artificial reef on the colonisation of the reefs and the concentration of zinc, copper, lead and cadmium was also analysed in samples of organisms taken from the surface of tyre structures and a concrete control structure. The study design and results are displayed in the Table D13 and D14. The types of tyre structures constructed in this study do not accurately represent how tyres would be used in tyre baling projects.

Relevance 1

Reliability 2

Table D13 Study design (Collins et al., 2002)

Parameter Details Location Poole Bay, off the central south coast of England Start date July 1998 Type of tyre structure

Three types of tyre modules: 1. concrete-filled single tyres, 2. stacks of 6/7 car tyres forming a cylinder filled with concrete

(“rubber rocks”), and 3. open lattice structure (tetrahedral) using either 4 or13 tyres held

together by stainless steel bolts and with the basal tyres filled with concrete.

Control Concrete modules (concrete blocks 20x20x40cm) Number of tyres 500 scrap tyres Reef Eight separate units each 5 m across and 1 m high including tyre and

concrete modules. Monitoring Approximately taken at 2 monthly intervals by scuba diving. Observed

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colonisation, photos were taken and samples of the species colonising the surfaces of the concrete control and tyre modules were taken. Heavy metal analysis was carried out on the samples using flame atomic absorption spectrometry.

Table D14 Study results (Collins et al., 2002)

Parameter Results Species Hydroida: Halecium sp.

Bryozoa: Bugula fabellata Ascidia: Styela clava; Ascidiella aspersa

Metals Zinc, copper, lead and cadmium Effects on species colonisation of structures

The colonisation of the reef modules were examined over a 11 month period and the following observations were it was reported:

o colonisation varied depending on the season, o differences were observed between colonisation on

vertical and horizontal surfaces, which was attributed to greater illumination (supporting more algae), and the horizontal surfaces having more sediment loading.

o The differences between vertical and horizontal surfaces were often increased between structural types (rubber rock and pyramid) than between substrates i.e. concrete or tyre, which was considered by the authors to be likely due to the different water flows around through the structures.

Concentration of metals

Concentrations of zinc were observed in hydroids (Halecium sp.) taken from the surface of the tyre modules compared with those taken from the concrete modules. However, the concentration in zinc in the hydroids on concrete was approximately 90 µg/g and the concentration in hydroids taken from the tyres was approximately 115 µg/g. The concentrations of copper and lead were observed in Halecium as well as cadmium in the bryozoans (Bugula), however these results cannot be explained by the authors as these metals are only minor constituents in tyres.

Stone et al. (1975) cited in Evans (1997) investigated the polychlorinated biphenyls (PCBs), organochlorine pesticides (OCs) and zinc in tissue of fish that had been exposed to tyre leachate. Muscle and liver tissues from ten fish of each species (pinfish, Lagadon rhomboids and the black sea bass, Centropristis striata) were collected before, during (21 days) and at the end of the experiment (101 days for the pinfish and 29 days for the black sea bass). It was reported that no significant differences were observed in the concentration of PCBs or OCs in the tissues from either species tested. However, the pinfish had greater tissue concentrations of both contaminants compared to that of the sea bass. The tissue concentration of zinc was found not to significantly increase in sea bass, but zinc concentrations were increased in the livers of pinfish after 101 days. No significant difference was observed between zinc water concentrations in control and exposure tanks on day 31. Stone et al. (1975) concluded that

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there was no clear relationship between tyre leachates and the concentrations of PCBs, OCs and zinc in black sea bass and pinfish. No mortalities were observed in pinfish following 21 or 101 day exposure. No mortalities were observed in sea bass during the 21 day exposure in either of the two experiments undertaken (one with the two species in a tank together and one with just the sea bass). Mortalities and changes in behaviour were observed in the sea bass following the sampling of the fish at 21 days in the combined experiment. However, the changes in behaviour was attributed to competition for the tyre habitat or dietary deficiencies while the mortalities were attributed to handling and possible disruption of faecal and uneaten food material in the tyres.

Spies et al., 1987, cited in Evans, 1997, reported on a study where Starry flounder (Platichthys stellatus) were exposed to tyre leachate compounds in-situ (San Francisco Bay) and detectable quantities of benzothiazoles and 2-(methymercapto)-benzothiazole were measured.

Evans (1997) reported on two studies (one conducted by Hartwell et al. 1994 and the other by CT&E (1994). These studies investigate the effects of tyre leachate in estuarine waters on the sheepshead minnow, Cyprinodon variegatus. The fish were exposed to cut used tyre (1 cm³ pieces) (Hartwell et al., 1994) and whole used tyres (CT&E, 1994) for three sequential leaching periods, 7, 14 and 21 days at 5, 15, 25 and 35 ppt salinity. The chronic experiments using tyre pieces reported significant mortalities following exposure to 7, 14 and 21 days extractions at 5 ppt salinity and 7 and 14 days extractions at 15 ppt salinity, but not to 21 day extractions at 15 ppt. Chronic LC50 values were not derived. The findings show that mortality decreases with increasing salinity and longer extraction periods. Significant growth effects were observed in fish exposed at 5 ppt salinity following a 21 day extraction period and at 15 ppt salinity following a 14 days extraction period, but not at 25 ppt salinity regardless of the extraction period.

In acute tests mortality was reported following exposure to 7 day extractions at 5 and 15 ppt salinity. Mortalities in acute tests were reported to decrease with increased salinity and decreasing concentrations of leachate. Acute LC50 values for 7 days extraction periods were reported as 10% and 26% leachate for 5 and 15 ppt salinity, respectively, suggesting that greater toxicity was exhibited at the lower salinity (5 ppt). In the experiments using whole tyres mortality was not statistically significant for either extraction or salinity.

In another study reported in Evans (1997) sheepshead minnow larvae were observed to have suffered severe damage to the brain and eye following exposure to tyre leachates at 5 and 25 ppt salinity. It was also reported that neurological alterations in the fish were most pronounced following 1 and 2 day exposure to the leachate from 7 day extraction at 5 and 15 ppt salinity, respectively. Eye damage was increased in fish exposed at 15 ppt salinity for 2 days compared to those exposed at 5 ppt for 1 day. Vacuolated encephalopathy and brain necrosis decreased in frequency or was absent in fish exposed to each successive leachate extraction, increased exposure time and higher salinity.

In the same study grass shrimp, Palaemonetes pugio and the planktonic copepod, Enrytemora affinis were exposed to tyre leachate in estuarine water. The grass shrimp showed significant mortalities in both acute and chronic tests using used tyre pieces following 7 day extractions at 5 ppt salinity. No mortality was observed was observed in subsequent 14 and 21 day extractions at 5 ppt salinity or in any extract at 15 and 25 ppt salinities. The copepod E. affinis exposed to leachate from whole tyres exhibited toxicity after 7, 14 and 21 day extracts prepared at both 5 and 15 ppt.

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PEAT

Limited data were available on the effects on the natural ecology of the use of tyre bales in peat bogs. Unlike the other environments studied, e.g. artificial reefs in the marine environment, contaminants leached from tyre material in peat bogs will be subject to much less dilution by the natural water flow due to the more static conditions experienced in a peat bog. Consequently, there is a potential that these contaminants could build up in the environment and cause greater adverse effects than that seen in a more free flowing environment such as the sea where the dilution would be great and occur rapidly. Sullivan (2006) reports on some direct exposure studies conducted using rubber dust, tyre crumb and tyre chips.

Rubber dust and carbon black were found to be toxic tobacco plant cells when incorporated in their growth media. Rubber dust incorporated at greater than 1% caused 50% or more reduction in plant tissue (Sullivan, 2006). It should be noted that this is an extreme example, whereby the material was incorporated into the growth media. When rubber crumb was mixed with very fine, slightly alkaline sandy loam, to produce concentrations of rubber up to 30%, no increased levels of volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) were detected in the leachate. However, slightly increased levels of boron, sodium and since were found to have leached from acidic sandy loam soil amended with the 30% rubber crumb (Sullivan, 2006).

In another study reported by Sullivan (2006), tyre chips were used as a replacement for peat moss in nursery container media. In one media, 50% of the peat moss was replaces with the chips and in the second 100% was replaced. The remainder of the media was the standard mix consisting of wood chips and sand. It was reported that the media containing the tyre chips had more zinc in the leachate that the control. Nursery plants were observed to grow as the control plants. Only a shrub, Dart’s Gold ninebark showed signs of adverse effects with all plants grown in the media where 100% of the peat moss was replaced with tyre chips. Chlorosis was observed in the ninebark and Billiard spirea, but the authors considered that this could be due to a possible nutrient deficiency. It was concluded that replacing 50% of the peat moss with tyre chips was an acceptable media, but 100% did not retain sufficient water, so was deemed unsuitable (Sullivan, 2006).

A similar study was conducted using ground rubber tyres to mix at varying quantities up to 220% by volume. It was reported that the content of all nutrients other than zinc were within standard concentrations for growth media. The media was set at pHs 5 and 6.5. Petunias grown in 5% or more ground rubber were observed to have significantly decreased dry shoot weights, while the impatiens were not found to have reduced dry root weights until the ground rubber was 10% or greater. These effects were observed at both pHs and the decreased growth was attributed to zinc toxicity and it was concluded that rubber should only be included to growth media of plants that are tolerant to zinc (Sullivan, 2006).

A further study found that peat amended with rubber form tyres for growing corn was only successful when the pH was increased by adding limestone and iron. Raising the pH reduced the availability of zinc leached from the rubber and the additional iron overcame the competition between iron and the remaining available zinc (Sullivan, 2006).

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APPENDIX E METHODOLOGY FOR ASSESSMENT OF LEACHING POTENTIAL

E1 BACKGROUND

This report presents a review of literature and collated data to support assessments of risk to different surface environments from a range of baled tyre reuse scenarios. As part of the source-pathway-receptor risk assessment process, relevant and robust data are needed to quantify release from the source. Modelling potential release to the aqueous environment requires information on the dissolved contaminants, e.g. leachability data. This appendix provides background to the use of leaching test data and to the inter-relationships of data from different test methodologies. It also describes how the data have been used to model risks of surface and groundwater contamination from different scenarios for this assessment elsewhere in the report.

E2 PRINCIPLES

When a solid material comes into contact with a liquid, a proportion of the solid will dissolve. Rainfall passing through soil or fill material, or surface water in direct contact with submerged materials will generate a leachate. The strength of the leachate with respect to dissolved contaminants will depend on a range of physical and chemical factors. Extensive international research has shown that the factors that control the leachability of materials are many and complex. These factors include: characteristics of the leaching medium (leachant) for example, major ion chemistry, pH, dissolved organic matter and ionic strength; length of contact between leachant and sample; particle size of sample; heterogeneity of sample and mode of contact – agitated or otherwise, organic matter contact. An additional key factor is the ratio of waste mass to volume of leachant or liquid-to-solid ratio6. Increasing the liquid-to-solid ratio represents the increased flushing of the waste with water that will occur with time. Thus liquid-to-solid ratio can be used as a surrogate indicator of release with time. The leaching from a granular material, e.g. a shredded tyre, will be different from that of a whole tyre, as used in a tyre bale.

Ideally, field data would be used to model the leaching behaviour of a waste. However, field data for single waste streams are rarely available for realistic timescales. By comparison, laboratory leaching tests can simulate, within hours or weeks, the high liquid-to-solid ratios that can take years or even decades to achieve in the field. Standard European leaching tests developed by CEN (European standard organisation, Comité Europeén de Normalisation) have undergone validation trials to ensure that the data are robust and repeatable by the majority of laboratories accredited to national quality control schemes. Leaching tests cannot therefore exactly predict the concentration of a contaminant that will be released in the field but do provide a standardised measure of the dissolved contaminant concentration under specified test conditions.

One of the most simple leaching tests undertaken across Europe, including the UK is BS EN 12457-2, the landfill waste acceptance criteria compliance test for granular wastes. This is a

6 The liquid-to-solid ratio prevailing during the leaching test, is expressed as quantity of liquid (‘L’) in litres and solid

(‘S’) in kg dry matter. L/S is expressed in l/kg.

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single step leaching test conducted at a liquid-to-solid ratio of 10, i.e. the sample is leached with ten times its dry weight with deionised water over a 24 hour period of agitation. The sample is milled to <4 mm particle size. The eluate analyses in mg/l can be converted to mg/kg on a dry weight basis, taking into account both the liquid-to-solid ratio and the initial moisture content of the sample. The key principles are summarised in Figure E1.

Leachant: Eluate: Leaching fluid added to the The liquid is separated from the

test sample (deionised water solid by centrifugation and/or(DIW) with no pH control). filtration (0.45µm poresize filter),

preserved as appropriate and analysed.Results are reported in mg/l

L/S10: and convereted to mg/kg dry weight.Liquid-to-solid ratio of 10 l/kg Agitate in

i.e.10 litres leachant for end-over-endevery 1 kg waste (on dry shaker for 24 hoursweight/dry solids basis). under specified Natural (own) pH:

test conditions The eluate pH is at, or close to, thatof the waste, as there is no pH control

Waste sample during this batch test. Eluate pH95% sample is <4mm particle size. must be reported to aid interpretation.

Minimum sample size = 90g dry solids).

Figure E1 Principles of compliance leaching test for granular wastes (BS EN 12457-2) at L/S 10

Note: The liquid generated by a laboratory leaching test is termed an eluate to distinguish it from the leachate or percolate generated in the field (e.g. from a landfill or lysimeter)

The two stage compliance leaching test for granular wastes (BS EN 12457-3) is conducted initially at L/S 2, with removal, filtration and reporting of analytical data at L/S 2. The original sample is re-leached at L/S 8 and the eluate filtered and analysed. The cumulative results are calculated in mg/kg over both leaching steps (cumulative leaching at L/S 10 in mg/kg). These tests are examples of compliance leaching tests which are designed to be undertaken routinely and therefore have straightforward methodologies, fast turnaround time and robust enough to be undertaken by different laboratories under different QA regimes. While compliance tests allow pass/fail criteria to be assessed quickly, they have their limitations. CEN Technical Committee 292 on the Characterisation of Waste has developed a range of standard tests to assess leaching behaviour for characterisation purposes. Different working groups have been charged with different remits (e.g. long and short term leaching), such that a ‘tool-box’ of tests is available.

This tool-box is increasingly widely used since many were published in draft form in the 1990s and were written into national legislation implementing the Landfill Directive. In addition uptake has been encouraged globally, such that the US EPA are due to adopt many of the CEN TC 292 tests from 2010. Unfortunately much of the testing that has been reviewed for

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the literature review of baled tyres has not been to CEN standards but to standard tests that pre-date CEN initiatives or to non-standard variants. The range of tests generated by CEN includes methods that enable leaching to be assessed with increasing liquid-to-solid ratio, representing increasing timescales for leaching (e.g. upflow percolation test) and different pH conditions (pH dependence test). By comparison the compliance tests described above have higher liquid-to-solid ratios and no pH control. Details of test methods from the toolbox of tests developed by CEN TC 292 have been described in detail in the Environment Agency’s guidance for the landfill acceptance (Environment Agency, 2005) and relevant information from this guidance is summarised and updated in Table E1.

The authors recommend that any characterisation of leaching behaviour that is subsequently commissioned to fill the gaps in the data requirement for a full baled tyres risk assessment uses these tests.

Table E1 Examples of leaching tests (after Environment Agency, 2005)

Test method Purpose

Compliance tests for granular wastes

BS EN 12457 Parts 1-4:2002. Compliance test for granular waste materials.

Pt 2, L/S 10, <4 mm

Pt 3: L/S 2 and L/S 8 (cumulative L/S 10), <4 mm

To assess leachability under mild extraction conditions at up to L/S 10. The pH of the eluate is not externally controlled during this test, i.e. the eluate pH is determined by the pH of the waste material itself (‘own pH’ or ‘natural pH’). The two-step BS EN 12457-3 is the Iandfill waste acceptance compliance test although there may be technical reasons for using the one-step test (BS EN 12457-2).

The two step test also provides limited leaching behaviour information. Increasing L/S ratio represents increased flushing of the waste with water, correlating with leaching timescales. The two-step test provides basic information about relative timescales for release particularly when placed in the context of data from the upflow percolation test.

Characterisation (leaching behaviour) tests for granular or crushed monolithic wastes

pH dependence tests (DD CEN/TS 14429:2005 and DD EN 14997: 2006)

To determine the effect of falling or increasing pH conditions on leachability of granular wastes. The two test methods cover operations in either continuous pH control or in batch mode. Two main applications are leachability predictions for waste after chemical treatment prior to landfilling or after landfilling, should local porewater/leachate pH conditions change.

A full range of acid/base neutralisation capacity (ANC/BNC) values can be determined from both test methods.

Upflow percolation test (DD CEN/TS 14405: 2004)

To determine the rate of leaching of various contaminants from granular wastes as a function of liquid-to-solid ratio (i.e. relative time). The test conditions approximate to the leaching process occurring when rainwater or other liquids infiltrate and percolate through a granular waste material. Cumulative L/S ratios are 0.1, 0.2, 0.5, 1, 2, 5 and 10. Initial leaching data relate to the low L/S ratios prevailing in landfill and provide context for L/S 2 and L/S 10 data from BS EN 12457:2002 batch tests.

Maximum availability leaching test (EA NEN 7371: 2004)

To determine the potential (maximum) availability of components by leaching under worst-case environmental conditions. Finely ground material is tested at high L/S ratios and with pH control (pH 7 and pH 4). This provides a more realistic maximum for leaching than ‘total’ concentrations determined on hot aqua regia digests. Also see maximum concentration derived from pH dependence test below. Can be used for granular and monolithic wastes.

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Test method Purpose

Characterisation (leaching behaviour) and compliance test for monolithic wastes

Diffusion test (tank test for monolithic wastes) (EA NEN 7375: 2004)

Dynamic Monolithic Leaching Test with Periodic Leachant Renewal, (CEN TC292 WI 292055/prEN 15863)

To assess the leachability of wastes which have been solidified1 for reuse or disposal.

As a characterisation (leaching behaviour) test for monolithic wastes. The test is conducted on samples >40mm in any direction using a volume of leachant approx. 5 times greater than that of the solid. Eight leaching steps are carried out over 64 days. The test is static (no agitation) and is conducted at natural pH (deionised water). Results are generally interpreted on a surface area basis (mg/m2) rather than a liquid-to-solid ratio basis (mg/kg).

As a compliance test: The first four days of the test are completed, eluates analysed and cumulative leaching in mg m-2 compared with the compliance limit values for monolithic wastes.

Note: prEN 15863 is a draft dynamic leaching test in development by CEN TC 292. It is similar to EA NEN 7375, based on seven leaching steps conducted over 36 days

Using standard tests and reporting in consistent units (mg/kg for granular wastes) enables the data to be plotted together as advocated through CEN TC 292’s ‘unified approach to leaching’ for granular waste leaching tests as exemplified by the plots in Figure E2.

Figure E2 The CEN TC 292 model for comparing contaminant release from granular materials as a function of pH and L/S ratio (Environment Agency, 2002)

.The unified approach to data presentation indicates the following:

Left-hand plot: release in mg/kg dry matter as a function of liquid-to-solid ratio. The results for the two step compliance test BS EN 12457-3 are plotted as diamonds. The concentration from the first step is plotted at L/S 2 and cumulative leaching over both steps at L/S 10. Cumulative results from the upflow percolation test are plotted at L/S0.1 to 10. The total concentration and maximum availability for leaching data are dimensionless but plotted here against the y-axis to allow comparison with the leachability data. Usually, as in this example plot, there is a good correlation between the cumulative L/S 10 results from the upflow percolation test with the L/S 10 results from the batch test, even though the methodologies are very different. In other words, although the 24 hour compliance test

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cannot provide detail of the leaching profile with time, it indicates the same level of release by L/S 10 as the more lengthy upflow percolation test.

Right-hand plot: release in mg/kg dry matter as a function of pH. Each step of the pH dependence test is conducted at L/S 10, with individual samples tested at each target pH or with continuous pH modification over the range to be tested. The results of both the pH dependence test (open circles) and the L/S 10 results of the BS EN 12457-2 or 3 compliance test (diamonds) are plotted against the pH measured in the eluate. For leachable determinands that show strong pH-dependency, such as Zn, the data enable leachability to be predicted under different pH conditions. For the situations where the release of a contaminant is controlled by its solubility, the leaching profile with pH will be consistent across different waste matrices. In other words the maximum and minimum leached concentrations will be at approximately the same pH values, although absolute concentrations will vary by waste type. However, every contaminant will exhibit a different pH dependent profile.

Figure E2 shows how data from the less rigorous compliance tests (e.g. BS EN 12457) can be set in the context of background data. Greater confidence can therefore be placed on the batch test approach. In addition the key leaching mechanisms (e.g. solubility control) can be confirmed. In other words, the batch leaching test results only reveal a small part of the leaching story. But the combination of the tests provides more insights into the factors that influence release, which in turn can be used for controlling/ managing the release to the aqueous environment.

E3 SELECTION OF APPROPRIATE LEACHING TEST

The literature review has shown that the leaching data that are relevant to baled tyres are very limited. If further test data are commissioned to complete the gap in the dataset, an exercise needs to be undertaken to determine the most appropriate tests.

CEN TC 292 Working Group 6 has prepared guidance (BS EN 12920) on test selection depending on the waste to be tested and the disposal or reuse scenario to be evaluated. The stepwise approach covers the following:

question to be answered;

description of the scenario;

description of the waste;

determination of the influence of contaminants on release;

modelling of the leaching behaviour;

model validation; and

conclusions and study report.

The focus is therefore to establish the objective of the characterisation exercise and then to use the BS EN 12920 methodology to select the appropriate tests for evaluating environmental performance.

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As part of this process, the approach to testing of construction products under the Construction Product Regulations could be considered.

The selection of scenarios and mode of water/waste contact is a critical initial step. We understand that three basic contaminant release scenarios based on the mode of water contact and the hydraulic properties of construction products have been used in a collaborative study by members of relevant CEN committees in Finland, Denmark and Iceland (Wahlström pers. comm., 2009).

non-permeable product, e.g. roofing material: water flows over the surface of the product;

low permeability product, e.g. bricks, concrete: water enters the matrix by capillary forces;

permeable product, e.g. unbound aggregate: gravity drives infiltration of water into the matrix.

As solid materials, baled tyres will leach in a different way to granular materials. Contaminants will usually diffuse through the matrix of the tyre until the contaminant has been depleted. However, over time, particularly if the tyre has been exposed to ultra-violet light, or has been subjected to mechanical abrasion (e.g. in coastal defences or artificial reefs) the integrity of the rubber will be attacked and begin to break down. Therefore although the impact of crumbed or shredded tyre applications on surface water is outside the scope of this review, the application of granular leaching tests to tyres represents a worst case leaching scenario.

Therefore a combination of approaches including the assessment of granular tyres to represent a worst case may be appropriate. In particular the use of pH dependence tests to assess release of contaminants under the lower pH conditions of peat bogs and the use of scenario specific leachants (e.g. salt water) could be considered.

References

ENV 12920 (2008) Methodology guideline for the determination of the leaching behaviour of waste under specified conditions, CEN/TC 292 WG6.

Environment Agency (2005) Guidance on sampling and testing of wastes to meet waste acceptance procedures, v1, April 2005.

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APPENDIX F COLLATED LEACHING DATA FROM LITERATURE REVIEW

See separate spreadsheet for data summaries

defra 8191 baled tyres final1. review the international literature (including peer reviewed reports,...

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