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Final report Annex 6: Guidance on the notion of ‘major accident’ (Task 6)
Development of an assessment methodology under Article 4 of Directive 2012/18/EU on the control of major-accident hazards involving dangerous substances (070307/2013/655473/ENV.C3)
Report for the European Commission (DG Environment)
AMEC Environment & Infrastructure UK Limited
in association with INERIS and EU-VRi
December 2014
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Copyright and Non-Disclosure Notice
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(©AMEC Environment & Infrastructure UK Limited 2014). save to the extent that
copyright has been legally assigned by us to another party or is used by AMEC under
licence. To the extent that we own the copyright in this report, it may not be copied
or used without our prior written agreement for any purpose other than the purpose
indicated in this report.
The methodology (if any) contained in this report is provided to you in confidence
and must not be disclosed or copied to third parties without the prior written
agreement of AMEC. Disclosure of that information may constitute an actionable
breach of confidence or may otherwise prejudice our commercial interests. Any third
party who obtains access to this report by any means will, in any event, be subject to
the Third Party Disclaimer set out below.
Third-Party Disclaimer
Any disclosure of this report to a third party is subject to this disclaimer. The report
was prepared by AMEC at the instruction of, and for use by, our client named on the
front of the report. It does not in any way constitute advice to any third party who is
able to access it by any means. AMEC excludes to the fullest extent lawfully
permitted all liability whatsoever for any loss or damage howsoever arising from
reliance on the contents of this report. We do not however exclude our liability (if
any) for personal injury or death resulting from our negligence, for fraud or any other
matter in relation to which we cannot legally exclude liability.
Document Revisions
No. Details Date
1 Preliminary version of intermediate report chapter for DG ENV comment
27 March 2014
2 Intermediate report 12 May 2014
3 Intermediate report (revised) 21 July 2014
4 Intermediate report (revised) 11 Sept 2014
5 Draft final report 18 Nov 2014
6 Final report 12 Dec 2014
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List of abbreviations
ADAM Accident Damage Assessment Module
ADR European Agreement Concerning The International Carriage Of Dangerous
Goods By Road
ALARP As Low As Reasonably Practicable
ARIA Analysis, Research and Information about Accidents
BLEVE Boiling Liquid Expanding Vapour Explosion
BOD – COD Biochemical Oxygen Demand – Chemical Oxygen Demand
CE Critical Event
CFD Computational Fluid Dynamics
CLP Classification Labelling Packaging
COMAH Control Of Major Accident Hazards
DA Deterministic Approach
ECHA European Chemicals Agency
e-MARS Major Accident Reporting System
EU European Union
EWGLUP European Working Group on Land Use Planning
F&EI Fire & Explosion Index
GHS Globally Harmonised System
JRC Joint Research Centre
LPG Liquefied Petroleum Gas
LUP Land-Use Planning
MAHB Major Accident Hazard Bureau
MATTE Major Accident To The Environment
MF Material Factor of the Dow’s Fire & Explosion Index
MIMAH Methodology for Identification of Major Accident Hazards
NFPA National Fire Protection Agency
NOEC No Observable Adverse Effects Concentration
PA Probabilistic Approach
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PLG Pressurised Liquefied Gas
RID European Agreement Concerning the International Carriage of Dangerous
Goods by Rail
RMP Risk Management Plan
STOT-SE Specific Target Organ Toxicity (Single Exposure)
USEPA United States Environmental Protection Agency
UVCE Unconfined Vapour Cloud Explosion
Physicochemical parameters
BCF Bioconcentration Factor
EC50 Median Effective Concentration
ΔHr Standard enthalpy of reaction
Kst / Kg Maximum rate of explosion pressure rise for dust clouds/gas
LD50 / LC50 Median Lethal Dose / Median Lethal Concentration
LFL / LEL Lower Flammability Limit / Lower Explosion Limit
LOC Limiting Oxygen Concentration
MIE Minimum Ignition Energy
MTSR Maximum Temperature of the Reaction Synthesis
NOEC No Observed Effect Concentration
Pmax Maximum explosion pressure
Pvap Vapour pressure
ΔTad Adiabatic temperature rise
Teb Boiling point
TMRad Time to maximum rate in adiabatic condition
UFL / UEL Upper Flammability Limit / Upper Explosion Limit
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Contents
List of abbreviations iv
1. Introduction 1
1.1 Purpose of the Report 1
1.2 Scope of Task 6 1
1.3 Structure of the Report 2
2. The Definition of ‘Major Accident’ 3
2.1 Overview 3
2.2 Annex VI of the Seveso Directive 3
2.3 Definitions applied by Member States 5
2.3.1 Belgium 5
2.3.2 Czech Republic and Romania 6
2.3.3 Denmark 7
2.3.4 Finland 8
2.3.5 France 8
2.3.6 Greece 8
2.3.7 United Kingdom 8
2.4 Relevance for the assessment methodology 9
3. Threshold Values for Dangerous Effects 11
3.1 Overview 11
3.2 Generalities on threshold values 11
3.3 Defining level of severity 13
3.4 Defining a level of severity in the context of the assessment methodology 16
3.5 Thermal radiation 18
3.6 Overpressure 20
3.7 Toxic Release 22
4. Member States’ Land-use Planning 30
4.1 Overview 30
4.2 Member States’ land-use planning approaches 31
4.2.1 Background 31
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4.2.2 Restriction of land use by zoning 32
4.2.3 Restriction of land use based on consequence 39
4.2.4 Restriction of Land use based on the probability of Damage 42
4.3 Other criteria for defining major accidents 54
5. Recommendations on Determining Potential for a Major Accident 55
5.1 Overview 55
5.2 Annex VI of the Seveso Directive 55
5.3 Level of harm 55
5.4 Effects thresholds 56
5.5 Land use planning approaches 57
Table 2.1 Comparison of criteria for defining major accidents in Czech Republic and Romania 6 Table 3.1 Scenario relevance for specific phenomena 12 Table 3.2 Overview of phenomena with quantitative values 12 Table 3.3 Possible severity ranking of effects for human health damages 13 Table 3.4 Correspondence between generic level of harm and level of harm selected by Member States 14 Table 3.5 Reversible and irreversible damages in selected Member States 16 Table 3.6 Overview of level of severity for the assessment methodology 17 Table 3.7 Overview of thresholds for thermal radiation (in kW/m2) 19 Table 3.8 Overview of thresholds for overpressure (in mbar) 21 Table 3.9 Comparison of applicable tools for health effects 26 Table 3.10 Comparison of the toxicity thresholds for selected substances under different methodologies 27 Table 3.11 Overview of thresholds for toxic release 28 Table 4.1 Distances reported for inner zones 33 Table 4.2 Safety distance in Finland 34 Table 4.3 Safety distances for specific buildings in Iceland 35 Table 4.4 Distance for natural gas sites and liquid hydrocarbon gas storage warehouses 36 Table 4.5 Type of land use authorised in zones in Catalonia 37 Table 4.6 Safety distances in Catalonia for specific substances and phenomenon 38 Table 4.7 Appropriate safety distances in Sweden 39 Table 4.8 Sensitivity level of buildings in Cyprus 40 Table 4.9 Land use planning decision matrix for new and existing developments 41 Table 4.10 Type of development and zones in Greek land use planning 42 Table 4.11 Values defined for location based risks 44 Table 4.12 Decision matrix for land use based on individual risk 45 Table 4.13 Scale of gravity depending on the number of people involved. 47 Table 4.14 Range of probability scale 47 Table 4.15 Risk matrix in French assessment 48 Table 4.16 Application of zoning in PPRT 49 Table 4.17 Compatibility table for LUP in Italy 50 Table 4.18 HSE assessment per type of building 53 Table 4.19 Decision matrix for HSE in UK 54 Table 5.1 Example of possible reference distances in the context of Article 4 57
Figure 4.1 Social risk calculation in Flanders, the Netherlands and the UK 43 Figure 4.2 Zones restrictions around Seveso sites 45 Figure 4.3 Zone definition from the PPRT process 49 Figure 4.4 Representation of location risk in the Netherlands 51 Figure 4.5 Representation of societal risk in the Netherlands 52
Appendix A References
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1. Introduction
1.1 Purpose of the Report
This report forms part of the outputs of a contract for the European Commission on ‘development of an assessment
methodology under Article 4 of Directive 2012/18/EU on the control of major-accident hazards involving
dangerous substances’. The work has been undertaken by AMEC, INERIS and EU-VRi.
The present report concerns one of a number of specific tasks under the project. It should not be read in isolation,
but in conjunction with the main report and the reports concerning the other project tasks.
1.2 Scope of Task 6
The Article 4 assessment methodology explicitly relates to situations where it is impossible for a substance to cause
“a release of matter or energy that could create a major accident”. (The aim of the overall assessment methodology
is to identify the steps to be followed in order to decide whether a substance or a mixture can cause a major
accident (or not). As such, defining what accidents are to be considered as major accidents is an essential part of
the methodology.
The aim of this task was to develop guidance on the limits above which an accident would be considered “major”,
taking into account the fact that a major accident is already defined in Article 3. The terms of reference for this
project defined two main aspects to be explored in order to gain a better understanding of the concept of a major
accident.
Firstly, to take into account the identification/analysis and comparison of national cut-off values
regularly applied in several Member States in the framework of land-use planning policies. The work
therefore involved analysing such national policies and their respective cut-off values applied to the
various scenarios considered (thermal radiation, overpressure, toxic release, etc.). Conclusions have
been drawn on how these cut-off values may guide the interpretation of the notion of a “major
accident” in the context of Article 4.
Secondly to conduct an analysis and comparison of national definitions and guidance on the notion of
“major accident”, and to draw recommendations from this.
Related to the above, the terms of reference for the project indicate that the criteria listed in Annex VI of the
Directive (which aim to identify major accidents that are subject to notification) could constitute a useful starting
point/framework for specifying the notion of major accident. However, it results from the definition in Article 3
that a major accident covers any “serious danger to human health and to the environment”, which goes beyond the
major accidents subject to notification.
These aspects were approached with the objective of understanding whether and how they could be useful in
informing decision making in the context of Article 4.
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Having undertaken the above analysis, and discussed the findings at a workshop involving experts in the Seveso
directive, it is clear that:
The approaches applied in the context of land use planning for Seveso establishments, and the criteria
used for reporting in Annex VI of the directive are some of the only quantitative measures related to
determining whether a major accident can occur.
However, it is not straightforward or necessarily appropriate to use these approaches to decide on
whether an accident scenario can constitute a major accident. The complexities of how these
approaches are applied, and their limitations, mean that they are probably inappropriate on their own
to form a basis for determining whether a major accident is possible.
Further work is likely to be required before any consensus can be reached on how to determine
whether a major accident is possible based on predictive accident scenarios.
The report includes various material on different methodological approaches, as well as on how the Seveso
Directive is implemented in different member states. This material is only presented in terms of its use in
informing possible assessments under Article 4; it does not reflect any advocacy or criticism of the merits (or
otherwise) of how the Directive is currently being implemented. It is therefore only to be used and understood in
the context of the Article 4 assessment methodology.
1.3 Structure of the Report
This report is structured as follows:
Section 2 presents the information collected on the definition of a major accident;
Section 3 presents a review of some Member States’ legislation in relation to land use planning and
setting safety distances in order to avoid a major accident; and
Section 4 summarises threshold values used in Member States for thermal radiation, overpressure and
toxic release.
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2. The Definition of ‘Major Accident’
2.1 Overview
Article 3 of the Seveso Directive defines a major accident as ‘an occurrence such as major emission, fire or
explosion resulting from uncontrolled developments in the course of the operation of any establishment covered by
this Directive and leading to serious danger to human health or the environment, immediate or delayed, inside or
outside the establishment, and involving one or more dangerous substances’.
Based on this definition, the Joint Research Centre (2005) highlights three criteria to be fulfilled to qualify an accident
as a “major accident”1:
The accident must be initiated by an “uncontrolled development”;
“One or more dangerous substances” listed in Annex I of the Directive must be involved;
The accident must lead to “serious danger” to human health, the environment or the property.
The two first criteria are viewed as relatively unambiguous, unlike the third one about “serious danger”. As the
assessment methodology is aimed at applying across all Member States, it was important to look at additional
elements that could help understanding how the notion of ‘major accident’ could be defined within the context of
Article 4.
For this, a literature review was undertaken in order to identify other elements that could assist in the application of
the Article 3 definition in the context of the assessment methodology including a review of the extent to which
other elements such as Annex VI or Member States’ definitions/interpretations of ‘major accident’ could be used in
the assessment methodology.
Throughout, it should be borne in mind that the definition in Article 3 is the essential starting point. It covers
accidents with effects outside or inside the establishment.
2.2 Annex VI of the Seveso Directive
Article 18 of the Directive requires that a ‘major accident’ meeting the criteria listed in Annex VI of the Directive
has to be reported by Member States to the Commission. As such Annex VI determines criteria for the mandatory
reporting of a major accident to the European Commission. However, these criteria are not equivalent to a
‘definition’ of what constitutes a major accident. Nonetheless, these criteria may be a useful starting point when
attempting to define a major accident within the context of Article 4. They are:
1 Joint Research Centre, 2005, Guidance on the preparation of a safety report to meet the requirements of Directive 96/82/EC as amended by
Directive 2003/105/EC (Seveso II), Institute for the Protection and Security of the Citizen
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“1. Any fire or explosion or accidental discharge of a dangerous substance involving a quantity of at least 5% if
the qualifying laid down in Column 3 of Part 1 or in Column 3 of Part 2 of Annex I.
2. Injury to persons and damage to real estate:
A death;
Six persons injured within the establishment and hospitalised for at least 24 hours;
One person outside the establishment hospitalised for at least 24 hours;
Dwelling(s) outside the establishment damaged and unusable as a result of the accident;
The evacuation or confinement of persons for more than 2 hours (persons × hours): the value is at
least 500; and
The interruption of drinking water, electricity, gas or telephone services for more than 2 hours
(persons × hours): the value is at least 1 000.
3. Immediate damage to the environment:
Permanent or long-term damage to terrestrial habitats:
- 0.5 ha or more of a habitat of environmental or conservation importance protected by legislation;
- 10 or more hectares of more widespread habitat, including agricultural land;
Significant or long-term damage to freshwater and marine habitats:
- 10 km or more of river or canal;
- 1 ha or more of a lake or pond;
- 2 ha or more of delta;
- 2 ha or more of a coastline or open sea;
Significant damage to an aquifer or underground water: 1 ha or more.
4. Damage to property:
Damage to property in the establishment: at least EUR 2,000,000;
Damage to property outside the establishment: at least EUR 500,000.
5. Cross-border damage: any major accident directly involving a dangerous substance giving rise to effects outside
the territory of the Member State concerned.
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2.3 Definitions applied by Member States
Examples of the definition of a major accident applied in several Member States are presented below, note that
these examples are not exhaustive. For a selection of Member States, the following definitions of major accident
have been identified.
2.3.1 Belgium
The Cooperation Agreement2 includes the following definition: an incident such as major emission, fire or
explosion that is the result of uncontrolled developments during the operation of an establishment which falls under
the provisions of this Agreement, and that results in either an immediate or a delayed serious hazard to the health of
persons within or outside the establishment or to the environment and that involves one or several dangerous
substances’.
Further details were identified at federal level.
Federal level
An accident is major if it meets the following criteria3:
The event is the consequence of an uncontrolled development happening during the operation of an
establishment falling under the scope of the Cooperation Agreement. An uncontrolled development is
an anomaly that has developed to such an extent that it is out of control for the operator. In many
cases, it is noted that the speed of the event is a determining for the ‘loss of control’ over the situation;
The event leads to serious danger, either immediate or differed: for individuals inside the Seveso
establishment (employees, sub-contractors or visitors), and /or for individuals outside the Seveso
establishment and or for the environment; and
One or several dangerous substances are involved in the event, the quantity of the substance involved
is not important in the assessment of whether the accident is major.
Some further explanations are provided for serious danger to individuals. These consider either a
bodily injury or health damage4. The effect can be immediate or at a later stage. However chronic
effects due to a long-term exposition to a small concentration of toxic substances are not considered to
be a serious accident.
It is only required that a situation of serious danger ‘appears’ and does not take into account the actual
damages that have arisen from the event. The likely consequences (what could have happened), and
2 Cooperation Agreement Between The Federal Government, The Flemish Region, The Walloon Region And The Brussels
Capital Region Concerning The Control Of Major-Accident Hazards Involving Dangerous Substances, internet link:
http://navigator.emis.vito.be/milnav-consult/consultatie?language=en 3 Service Public Federal, Emploi, Travail et Concertation Social, Accident majeur,
http://www.emploi.belgique.be/defaultTab.aspx?id=6264 4 Service Public Federal, Emploi, Travail et Concertation Sociale, Accident majeur,
http://www.emploi.belgique.be/defaultTab.aspx?id=6264
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not the actual injury or damages (what has happened) are considered when assessing the seriousness of
an accident.
Finally, it is not necessary that the effects are beyond the Seveso establishment boundaries for it to be
considered a major accident.
2.3.2 Czech Republic and Romania
Responses to the survey indicated that the definition of a major accident adopted in these two Member States is
very similar to Annex VI. The details of the definitions are presented in the table below. The text in bold
highlights variations from the text of the Directive.
Table 2.1 Comparison of criteria for defining major accidents in Czech Republic and Romania
Czech Republic1 Romania2
Major accidents caused by hazardous substance or discharged in an amount equal to or exceeding 5 % of any of the quantities of hazardous substances listed in Annex 1 to this Act by section 1 of Table I or II, column 2
n/a
Fatal accidents caused by dangerous substances listed in Annex 1 to this Act Part 1 leading to the formation of one or more of the following events : a) death , b) injury of at least 6 employees or other individuals residing in the building or facility if their hospital stay exceeded 24 hours , c ) injury to at least one person outside the facility or facilities if the hospital exceeds 24 hours ,
Injuries of the persons:
a) a deceased; b) injury of the 6 persons inside the plant and their hospitalization for at least 24 hours; c) injury of one person outside of the plant and the hospitalization at least for 24 hours;
d) damage to one or more dwellings outside object or device that accidentally became uninhabitable , e) The need for evacuation or sheltering of people in buildings for more than two hours , if the total converted time of evacuation or sheltering persons ( persons multiplied by time ) exceeds 500 hours , f) interruption of the supply of drinking water , electricity and thermal energy , gas or telephone services for more than two hours , if the total time converted interruption (number of people multiplied by time ) exceeded 1000 hours .
Causing damage to the property goods: a) causing damages to one/several buildings outside of the plant and destruction of this/those, inhabitable as a result of the accident; b) evacuation and distressing people for more than two hours (persons x hours), calculated value at least 500; c) interruption of the supply services for drinking water, electricity, gas or telecommunications for more than two hours (persons x hours) in the case where the resulted value by multiplication of the affected persons by the numbers of hours of interruption of the above mentioned services, to be at least 1.000;
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Czech Republic1 Romania2
Fatal accidents caused by dangerous substances listed in Annex 1 to this Act , Part 1 , if it results in environmental damage on:
a) areas protected by special regulation (..), i.e. especially protected areas and Natura 2000 zones declared water conservation and protection zones sources of mineral water with an area equal to or greater than 0.5 hectares , b ) the other an area equal to or greater than 10 ha , c ) the watercourse length equal to or greater than 10 km , d ) natural or artificial surface water body without the status of water tank under a special law , an area reaching or exceeding 1 ha .
Fatal accidents caused by dangerous substances listed in Annex 1 to this Act, Part 1, if it results in environmental damage collector, i.e. the geological environment in the saturation zone and elsewhere in the site collection or accumulation of groundwater or groundwater pollution with an area equal to or greater than 1 hour.
Causing immediate harmful effects against the environment: a) permanent damages or on long term on terrestrial habitats:
-0.5 ha or more from an ecological valuable habitat or by conservation, protected by law; -10 ha or more from a more extended habitat, including agricultural land;
b) significant damages or on long term on the surface waters habitats or marines (where is the case, in the damage evaluation process can be made references to the legislation regarding the dangerous substances and chemical mixtures or the lethal concentrations for 50% of the species representatives from the affected environment):
-10 km or more from a river or a channel; -1 ha or more from a lake or a pond; -2 ha or more from a Delta; -2 ha or more from a coastal water body or an open sea;
c) significant damages of an aquifer or ground waters (where is the case, in the evaluation process of the damages can be made references to the legislation regarding dangerous chemical substances and mixtures or the lethal concentrations for 50% of the species representatives of the affected environment):
-1 ha or more
Fatal accidents caused by dangerous substances listed in Annex 1 to this Act , Part 1 , if it results in a) damage to property or equipment originator of a major accident in the amount equal to or exceeding CZK 70 million (current exchange is approx. 1 Euro=26 CZK.) b) damage to property outside the building or equipment accident originator of equal or exceeding 7 million CZK.
Causing damages of the properties: a) damages of the properties from the plant, with a value in RON’s represents the equivalent of at least 0.5 million euro; b) damages of some properties outside of the plant perimeter, with a value in RON’s represents the equivalent of at least 0.2 million euro
Fatal accidents caused by dangerous substances listed in Annex 1 to this Act, Part 1, leading to effects outside the territory of the Czech Republic.
Causing transboundary damages: any accident in which is present a dangerous substance and can produce effects outside of the national territory.
Note 1 Czech Republic national legislation (Act No. 59/2006 coll. on the major accidents prevention
Note 2 Romania, Minister Order No.1084, 22/12/2003 on the Notification procedures which represents major accidents production dangers in which are involved dangerous substances and respectively, of the produced major accidents.
Furthermore, in Czech Republic any accident which includes a significant release of dangerous substance; an
explosion or fire is considered to be a major accident5.
2.3.3 Denmark
Major accidents are defined in the Risk Executive Order (Bekendtgørelse om kontrol med risikoen for større uheld
med farlige stoffe Stk. 5). These are “event on a larger scale, such as emission, fire or explosion resulting from
uncontrolled events in connection with the operation of an establishment subject to this Order in which one or more
5 Survey response
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of the substances mentioned in Annex 1, and, immediately or later may cause significant harm to someone at the
company or outside the company or the environment”6.
2.3.4 Finland
A major accident is an accident that results in permanent injury or prevents people from evacuating their homes or
present location7.
2.3.5 France
A major accident means an occurrence such as a major emission, fire or explosion resulting from uncontrolled
developments in the course of the operation of any establishment covered by the Seveso Directive and leading to
serious danger to human health and/ or the environment, immediate or delayed, outside the establishment, and
involving one or more dangerous substances. Accidents occurring inside the installation are dealt with by the
occupational safety legislation.
2.3.6 Greece
Major accidents can have consequences outside and/or inside an installation. They are not only accidents with
external consequences. In addition, one research article8 argues that an accident can be considered as “major” if it
involves one of the substances included in Annex I of the Seveso Directive in a quantity equal or greater than the
limits provided in that Annex. This interpretation is not easy to implement as an accident does not always involve
the total quantity of the substance present in an establishment.
2.3.7 United Kingdom
Under the COMAH Regulations9, it is considered that a single fatality would be the lower bound cut-off for a major
accident. A guidance document has been published by the Health Safety Executive10 . This document states that
the term ‘major accident’ does not include less serious accidents or other incidents such as authorised discharges of
pollutants as part of the normal operation of plant. Furthermore, an occurrence will be a major accident if it meets
the following conditions:
Results from uncontrolled developments at an establishment to which the Regulations apply; and
Leads to serious danger to people or to the environment, on or off site; and
6 Presentation by Morten R. Østergaard, Danish EPA, Land use planning in the Habour area in the municipality of Aarhus,
DenmarkApplication of a Danish Administration Practice on Land Use Planning, 24 September 2012, Cyprus 7 Niks Jan Dujim, 2009, Acceptance Criteria in Denmark and the EU 8 I.A. Papazoglou, Quantitative Risk Assessment For Accidents At Work In The Chemical Industry And The Seveso II
Directive, System Reliability and Industrial Safety Laboratory 9 Implementing the Seveso Directive in UK national legislation 10 HSE, 2006, A guide to the Control of Major Accident Hazards Regulations 1999 (as amended) (L111)
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Involves one or more dangerous substances defined in the Regulations, irrespective of the quantity
involved.
Further guidance is included to define uncontrolled development and serious danger to people or to the
environment.
As a separate point, an incident will be a major accident if it results in serious danger to the environment. The
UK’s guidelines for what constitutes a ‘major accident to the environment’ provide substantially more elaboration
than the criteria for reporting in Annex VI of the Seveso Directive. Thresholds are defined for each of a number of
different categories of environment11 and for the extent of damage in the event of an accident, which are used in
order to determine whether such an accident would be considered a MATTE (example of thresholds for level of
harm for marine water are included in the Task 3 report).
2.4 Relevance for the assessment methodology
Article 3(13) of the Seveso III Directive provides for the definion of a major accident. Furthermore, Annex VI has
been drafted in order to identify major accidents that need to be reported by Member States to the European
Commission However, Annex VI is not a list of criteria defining a ‘major accident’ which is confirmed by wording
of the relevant mother Article 18 of the Seveso Directive by referring to ‘major accidents meeting the criteria of
Annex VI’. This suggests that it is possible to have major accidents that do not meet the criteria of Annex VI.
This idea is supported by the fact that the extent of consequences of accidents described in the criteria differ from
the extent of accidents that initiated the negotiation for a Seveso Directive at a European level12. In applying the
criteria listed in Annex VI, a major accident may include some events involving dangerous substances that are
classified as occupational accidents. Pey (2009) underlines that regulations and tools that aim at preventing and
controlling major accidents (e.g. external emergency plans, land use planning) focus the attention on accident
scenarios that cause dangerous effects to people or environment outside an industrial site13. Papazoglou, as well as
Heidebrink (2005) add that, in most Member States, scenarios with effects limited to an area inside the
establishment are regulated under legislation other than Seveso Directive (e.g. ATEX Directive, OSHA regulations)
and handled by different competent authorities (e.g. Ministry of Labour) than those responsible for external
safety14.
As a result, it is important to consider Annex VI criteria only as elements guiding the understanding of the concept
of ‘major accident’ for the purpose of the assessment methodology. Feedback from the participants to the workshop
11 Designated land/water sites (national, international and ‘other’), scarce habitats, widespread habitats, aquifers/groundwater,
soil/sediment, built heritage, particular species, marine and freshwater/estuarine habitats. 12 The preamble to the Seveso III Directive highlights that “major accidents often have serious consequences, as evidenced by
accidents like Seveso, Bhopal, Schweizerhalle, Enschede, Toulouse and Buncefield”. 13 Pey A., Lerena P., Suter G., Campos J, 2009, Main differences on Eurpoean regulations in the frame of the Seveso Directive,
Process Safety and Environment Protection 87 14 Papazoglou I.A., Quantitative risk assessment for accidents at work in the chemical industry and the Seveso II Directive
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(October 2014) as well as from the project confirmed that the Annex VI cannot be understood as providing a
definition of ‘major accident of themselves.
While some organisations agreed that they could be a useful starting point for deciding whether a major accident is
possible in the context of Article 4 (because they are based on already-agreed definitions), they are not to be
considered “the definition” of a major accident. Other respondents indicated that going beyond the criteria of
Annex VI for defining a ‘major accident’ was not a suitable approach. One respondent highlighted, referring to
Annex VI, that ‘the concept of a major accident has been legally defined within the Directive since 1982 and
reports of significant problems in applying the definition have not arisen’15.
However the review of definitions of ‘major accident’ applied in Member States, showed variation in the
definitions that have been adopted in a number of Member States. As the assessment methodology under Article 4
is to apply horizontally in all EU Member States, any exclusion of substances from the Seveso Directive following
an assessment would need to be agreed with all Member States. It appears unlikely that those Member States with
additional criteria would agree to an exclusion if the substance in question would still be capable to create major
accidents in accordance with their national provisions. Therefore, it appears to be important to consider the most
stringent requirements at least for the initial screening on whether or not a substance is capable of generating a
major accident. Any subsequent detailed assessment could then further investigate the actual risks.
15 Survey response.
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3. Threshold Values for Dangerous Effects
3.1 Overview
The concept of ‘major accident’ can be defined with reference to its effects and through the comparison of the
national policies and cut-off values that are applied for the following dangerous phenomenon:
Thermal radiation;
Overpressure; and
Toxic release.
3.2 Generalities on threshold values
To assess the consequences of an accident scenario, it is necessary to evaluate the distances by which the
phenomenon’s dangerous effects (i.e. thermal radiation, overpressure and toxic clouds) will give rise to unwanted
effects on human health (e.g. lethality, irreversible damage or reversible damage). The distances can be based on
threshold (or end) values regarding the level of thermal radiation, overpressure or toxic release that may give rise to
the unwanted effects. These values are established on the basis of probit functions that quantify the likelihood of
adverse effects to people at a particular exposure.16
As highlighted in Task 4, the major events (presented in the bow-tie on the fault tree side) are significant effects on
targets (i.e. humans, structures or the environment) from identified dangerous phenomena. The main possible
significant effects in the context of the assessment methodology are the following: thermal radiation, overpressure,
and toxic clouds (affecting humans and the environment).
Table 3.1 summarises the effects that can be assessed for each specific dangerous phenomenon.
16 P.D. Petrolekas and A. Charalambous, Sept 2001, Land use planning considerations in the context of Seveso II Regulations
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Table 3.1 Scenario relevance for specific phenomena
Dangerous Phenomenon Effects
Thermal Radiation Overpressure Toxic Effects
Fireball X X
Flash fire X
Jet fire X
Pool fire X
Vapour Cloud Explosion X X
Toxic Clouds x
Solids Fire x
Source: Roadmaps for LUP
Table 3.2 describes the possible damage of the effects selected and the chemical property of the substance that
would give rise to the effects.
Table 3.2 Overview of phenomena with quantitative values
Property of the substance Effect measured Possible damages
Flammable Thermal radiation Burn to people, damage to property and the installation
Explosive Overpressure Causalities to people, damage to property and the installation
Toxic Toxic release Intoxication of people
Source: Roadmaps for LUP
The European Working Group on Land Use Planning (EWGLUP) has worked on the identified differences in LUP
approaches amongst Member States. Guidelines on land use planning were developed by the EWGLUP17.
In addition, the JRC18 has compiled an overview of Roadmaps for Land-Use Planning for selected Member States
which compared Member States’ approaches to complying with Article 12 of the Seveso II Directive. The JRC
selected five Member States for further analysis19 as examples of different methods of fulfilling Article 12
requirements. The JRC refers to the roadmaps as “decisional routes” bridging the gap between risk analysis and
land-use planning. They present the differences in methodologies and practices in Member States. The
17JRC, 2006, Land use Planning Guidelines in the context of Article 12 of the Seveso II Directive 96/82/EC as amended by
Directive 105/2003/EC. This is referred to in the report as ‘Roadmaps for LUP’ 18 JRC, 2008, Overview of Roadmaps for land-use planning in selected Member States 19 The Netherlands, France, Italy, Germany and the UK
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information presented in the Roadmaps for LUP has been supplemented with information from other pan-European
projects (e.g. ARAMIS20 and ACUTEX21), responses from respondents to the survey for the current project and
additional information on thresholds applied in Member States. These are presented in Sections 3.4, 3.6 and 3.7,
respectively covering thermal radiation, overpressure and toxic release thresholds.
3.3 Defining level of severity
One of the important aspects of the concept of a ‘major accident’ is that it implies a severity which distinguishes it
from other non-major accidents. The assessment methodology needs to define a qualitative level of harm which
corresponds to the concept of major accidents.
The Member States define levels of harm by using concepts such as harmful effects, reversible and irreversible
injuries and lethality. It is important to have a clear understanding of what these mean in order to choose the best
suited corresponding threshold level in undertaking an assessment in the context of Article 4.
There is variation in the level of harm that is taken into account in Member States. In order to compare these
different levels of harms used by Member States, the information gathered for specific Member States has been
classified against a 6-level generic ranking. These generic levels have been defined in accordance with the
information presented in the Roadmaps for LUP and are presented in the table below. A further category has been
created, gathering the various end-values reported for domino effect by Member States.
Table 3.3 Possible severity ranking of effects for human health damages
Level of harm Effects on human targets
Level 1 No effect No injury
Level 2 Small effect Slight injuries without sick leave
Level 3 Reversible injury Injuries leading to hospitalisation
Level 4 Irreversible injury Irreversible injuries or death inside the establishment, reversible injuries outside the establishment
Level 5 Start of lethality Irreversible injuries or death outside the establishment
Level 6 High lethality High number of death inside and outside the establishment
Domino effect
Note: this table is based on information presented in the Roadmaps for LUP (JRC) and information collected on Member States practices
20 ARAMIS, 2004, Accidental risk assessment methodology for industries in the context of the Seveso II Directive, WP2,
Severity evaluation. More information on the ARAMIS project are included in Annex IV (Task 4). 21 In 2006, the ACUTEX project aimed at developing a European methodology for developing Acute Exposure Thresholds
Levels for toxic substance to be applied in major hazard control. As part of the work, the project reviewed the existing levels
or methodologies defined by several countries for toxic substances.
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The objective of this classification is to be able to directly compare the levels of harm established as thresholds in
Member States but also the associated end-values. However, there are some uncertainties surrounding the exact
definition and boundaries of some of the level of harms in Member States. As a result, these tables are not to be
read as presenting absolute equivalents, but rather a comparison of different approaches adopted in Member States.
The correspondence between the generic level of harm and those identified in Member States only indicative and is
presented in Table 3.4.
Table 3.4 Correspondence between generic level of harm and level of harm selected by Member States
Level 1- no effect
Level 2 - small effect
Level 3 - reversible injury
Level 4 - irreversible injury
Level 5 - start of lethality
Level 6 - high lethality
Domino effect
Belgium
Risk Zone - specific measures to limit the accidents consequences
Belgium (Wallonia)
Zone of surveillance (can affect sensitive persons)
Zone of risk (serious consequences)
Zone of immediate danger (irreversible and lethal consequences)
Zone of immediate danger (irreversible and lethal consequences)
Zone for domino effects
Cyprus
Zone III: a-degree burns in a substantial part of the population
Zone II : c-degree burns to 1% of the population
Zone I c-degree burns at a rate of over 50% of the population
Denmark
Threshold values for maximum consequence distance
Estonia
Very dangerous area
France Irreversible effects
Lethal effects (heavy hazards)
Lethal effects (very heavy hazards)
Greece
Zone III - first irreversible effects
Zone II - first death (1% lethality)
Zone I - multiple fatalities
Zone D - domino effects (severe damage to equipment)
Italy Reversible effect
Irreversible effect
Start of lethality
High of lethality Risk of domino
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Level 1- no effect
Level 2 - small effect
Level 3 - reversible injury
Level 4 - irreversible injury
Level 5 - start of lethality
Level 6 - high lethality
Domino effect
Lithuania Reversible injury
Irreversible injury
Beginning lethality High lethality Domino effect
Slovenia Widest impact area
Wider impact area
Inner impact area
Spain Alert Zone (ZA)
Intervention Zone (ZI)
Domino Zone (ZD)
The Netherlands
Where 1% lethality would occur under the most adverse climatological conditions.
UK (in TDU)
50% fatality for offsite planning,
1-5% fatality for LUP
ARAMIS Small or no effect
Reversible effects
Irreversible effects
Start of lethality Domino Effect
Roadmaps for LUP - Non Stationary Radiation No effect Small effects
Reversible effects
Irreversible effects Lethality
Roadmaps for LUP - Stationary Radiation No effect Small effects
Reversible effects
Irreversible effects Lethality
The differences observed between Member States are not a judgement on the levels of safety applied in the member
states or a suggestion that some member states’ approaches are more (or less) protective than others. They are only
used as an illustrative example of the diversity of approaches, and are only applicable in the context of reviewing
possible approaches for the Article 4 assessment methodology. Therefore, the above should not be interpreted as a
statement or an assessment of the implementation of the Seveso Directive in these Member States.
Whilst the level of harm defined as ‘lethality’ or ‘fatality’ is quite clear in that it involves the death of at least one
or several persons, there are more ambiguities in the definition of reversible and irreversible effects.
Some work has recently been published on regulation of industrial risk in the then ‘new’ Member States22. The
report presents for seven Member States the types of damages that are considered to be reversible or irreversible.
Table 3.5 summarises the information reported.
22 JRC, 2007, Risk Mapping of Industrial Hazards in New Member States.
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Table 3.5 Reversible and irreversible damages in selected Member States
Reversible damage Irreversible damage
Member State
Human Infrastructure Environment Human Infrastructure Environment
Bulgaria Injury
Economic loss
Loss of functionality
Public service interruption
Damage to habitat
Economic loss
Death
Disability
Destruction
Uneconomical recovery
Loss of biodiversity
Czech Republic
Injury
Acute effect
Economic loss
Severe damage
Loss of functionality
Economic loss
Public service interruption
Economic loss
Loss of biodiversity
Loss of resource
Death
Canter
Health chronic effect
Destruction Loss of resource
Loss of biodiversity
Cyprus Injury
Acute health effect
Economic loss
Severe damage
Loss of functionality
Economic loss
Public service interruption
Economic loss Death
Chronic health effect
Uneconomical recovery
-
Estonia Injury Severe damage
Economic loss
Public service interruption
- Death Destruction -
Lithuania Injury
Acute health effect
Epidemic
Economic loss
Severe damage
Loss of functionality
Economic loss
Public service interruption
Economic loss
Loss of biodiversity
Loss of resource
Death
Cancer
Chronic health effect
Disability
Destruction
Uneconomical recovery
Economic loss
Loss of biodiversity
Loss of resource
Poland Injury
Acute health effect
Severe damage - Death Destruction -
Romania Injury
Acute health effect
Epidemic
Economic loss
Severe damage
Loss of functionality
Economic loss
Public service interruption
Loss of biodiversity
Death
Cancer
Chronic health effect
Disability
- Loss of biodiversity
Source: JRC, 2007
3.4 Defining a level of severity in the context of the assessment methodology
For the purpose of the assessment methodology, it is recommended that a four level scale of severity could be used.
Table 3.6 presents the thresholds used in the context of the European ARAMIS project, the use of which is
particularly relevant in the context of Article 4 as the results are already well recognised. The thresholds
considered therein are considered to represent the most stringent thresholds used among Member States.
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Table 3.6 Overview of level of severity for the assessment methodology
This four level approach follows the approach of Member States, but presents a reduced range (no effects, high
lethality and domino effects are excluded23) and maps onto the level of severity identified in Member States. The
following correspondence applies: an assessment methodology Level 1 – small effect corresponds to Level 2- small
effects of Table 3.4. Similarly, Level 4 in the table above corresponds to the Level 5 – start of lethality as
presented in Table 3.4.
For the purpose of the assessment methodology, it is important that a qualitative level of harm for a major accident
is set if modelling of accident scenarios is undertaken.
However, it must be highlighted that Level 2 (reversible injuries) is a threshold which could be readily reached for
almost any accident scenario, even for non-dangerous substances. It is also important to take into account the
overlap between Seveso, which covers major accidents (with effects that can be on-site as well as off-site), and the
harm that may occur as a result of industrial accidents which can affect a small number of workers on-site and
which are also covered by other occupational safety and health legislation in the EU. One of the difference
between the issues targeted by Seveso and those addressed by worker protection legislation is the loss of control
and containment that lead to the incident or accident. This loss of control indicates that the potential for a more
serious accident existed and this reflects the motivation behind the Seveso legislation.
For the assessment methodology, it is not considered that the scale of effects can be considered in isolation, but
rather defined in relation to conditions relating to the substance under consideration. For example, the distance at
which the effects threshold (reversible and irreversible injury) is exceeded will be an important factor in
determining whether a particular scenario could lead to a major accident.
23 If the accident has no effect it cannot be a major accident. Moreover any effect over start of lethality is a major accident
(according to the Annex VI criteria) so there is no need to assess worse severity than ‘start of lethality’ in the context of
Article 4.
Level 1 Small effect
Level 2 Reversible injuries
Level 3 Irreversible injuries
Level 4 Start of lethality
Thresholds for overpressure effects (in mbar)
ARAMIS <30 30 - 50 50 - 140 >140
Thresholds for thermal radiation (in kW/m²)
ARAMIS - 60 sec <1.8 1.8 - 3 3 - 5 >5
Thresholds for toxic effects
ARAMIS TEEL1-1 – TEEL-2 TEEL-2 – TEEL-3 >TEEL-3
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3.5 Thermal radiation
Thermal radiation is one of the possible effects from hazardous phenomena. It is generated by the (more or less
rapid) combustion of a flammable or combustible substance.
Table 3.7 presents the threshold values identified during the review of Member States’ practices. The thresholds
values correspond to the levels of harms presented in Table 3.4 and have been assigned to each generic level of
harm according to the definition presented in Table 3.3.
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Table 3.7 Overview of thresholds for thermal radiation (in kW/m2)
Level 1- no effect
Level 2 - small effect
Level 3 - reversible injury
Level 4 - irreversible injury
Level 5 - start of lethality
Level 6 – high lethality
Domino effect
Belgium 2.5 (during 30 sec)
Belgium (Wallonia) 6.4 10 10 8, 32 or 44
Cyprus
3 (Zone III)
6 (Zone II) 15
Denmark 6
Estonia 20 (static), 35 (impulse)
France - human 3 5 8
France - structures 3 5 8 16 20 and 200
Greece * 170 450 1,500
Italy 3 5 7 12.5 12.5
Lithuania 3 5 7 12.5 37.5
Slovenia 1.8 - 3 3-5 > or =5
Spain * 3 5
12 for unprotected equipment, 37 for protected equipment
The Netherlands
12.5 ( 20 sec) or 9.8
UK * 1,800
ARAMIS - 30 sec <3 3-5 5-9 >9 >9
ARAMIS - 60 sec <1.8 1.8 - 3 3-5 >5 >5
Roadmaps for LUP - Non Stationary Radiation - <125 125 - <200 200-350 >350 -
Roadmaps for LUP - Stationary Radiation 1.6 <3 - <5 <3- <5 5 - 7 >7
* in TDU – thermal dose unit
Respondents from the Czech Republic and Portugal indicated that no threshold values have been defined in their
Member States. The 2008 work conducted by the JRC on Roadmaps for LUP in selected Member States concluded
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that overall the ‘divergence of accepted thresholds is not wide’ in the Member States reviewed and it proposed a
default set of values that is presented in the last rows of the table24. The Roadmaps for LUP document makes the
distinction between stationary and non-stationary radiation, however our research found information related mainly
to stationary radiation (which is also most relevant for Seveso establishments).
The table shows that similar thresholds are being relied upon by Member States. It also shows that the most
stringent thresholds are applied in Italy and France with reversible effects starting from 3 kW/m2 and lethality at 7
kW/m2 (for Italy).
In addition, it is interesting to note that few Member States have adopted thresholds for smaller levels of harm (i.e.
Level 2).
If the assessment methodology takes the approach of the most stringent Member State, then Italian values for Level
3 (i.e. reversible effects) should be retained (3 kW/m2). Again, it is not sufficient to consider these types of cut-off
values in isolation in determining whether the potential for a major accident hazard exists. For example, one
person working in a laboratory could be exposed to thermal radiation above such a level, and incur only minor
reversible effects, where the level of harm may be more commensurate with accidents intended to be regulated by
occupational safety legislation. However, if accidents are severe, affect multiple people or the public outside the
site boundary, this is more likely to be classifiable as a major accident.
3.6 Overpressure
Overpressure is the result of a pressure wave. The wave can arise from an explosion, a chemical reaction, a violent
combustion, or a brutal compression or decompression of pressurised gas (e.g. the burst of a bottle of compressed
air).
Table 3.8 presents the threshold values that have been identified during the review of Member States practices.
The thresholds values correspond to the levels of harm presented in Table 3.4 and have been assigned to each
generic level of harm accordingly.
24 JRC, 2008, Overview of Roadmaps for land-use planning in selected Member States
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Table 3.8 Overview of thresholds for overpressure (in mbar)
Level 1- no effect
Level 2 - small effect
Level 3 - reversible injury
Level 4 - irreversible injury
Level 5 - start of lethality
Level 6 – high lethality
Domino effect
Belgium 20
Belgium (Wallonia) 25 50 160
Cyprus 50 140 350
Denmark 50
Estonia 200
France - human 20 50 140 200
France structures 20 50 140 200 200/ 300
Greece 50 140 350
Italy 30 70 140 300 300
Lithuania 30 50 120 530 1,000
Slovenia 20-50 50-140 > or =140
Spain 50 125
160 for atmospheric equipment, 350 for pressurised equipment, 100 for building
The Netherlands 100
ARAMIS <30 30 - 50 50 - 140 >140 >140
Roadmaps for LUP <30 30 - 50 50 - 140 >140
The values reported by France and Italy appear to be the most stringent of those identified. The table shows that
the thresholds values reported by Member States are quite similar, and that both ARAMIS and the JRC report on
Roadmaps for LUP have adopted an identical range of values to use as default values.
In the context of the assessment methodology, the lower range of the values proposed by the ARAMIS project as
default values matches the values of the most stringent Member State and those proposed in the JRC report on
Roadmaps for LUP. These values could be used as the threshold for identifying a major accident due to
overpressure in the context of Article 4. So for example, if Level 3 was to be considered as the relevant level of
harm, the overpressure limit for the purpose of the assessment methodology would be between 30 and 50 mbar.
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3.7 Toxic Release
Toxic release effects result from the absorption of a hazardous toxic substance (or preparation) due to a leak on an
installation, the release of a toxic substance from chemical decomposition during a fire or a chemical reaction.
The JRC report on Roadmaps for LUP found that it was difficult to compare the methods chosen by Member States
to assess the effects from toxic release for the following reasons25:
Countries only agree one threshold, which is the level corresponding to the start of certain effects (for
example irreversible health effects).
There are several existing exposure guidelines and it is not straightforward to choose one rather than
another. In addition there is little data available on effects on humans. Most data is from animal
experimentation extrapolated to humans.
Each of the guidelines and level-setting methodologies cover only a limited number of substances, and
several need to be combined when they sometimes recommend different values.
The effects of the toxic substances can be linked to the dose rather than the concentration. In these
cases, the dose can depend on the concentration value, the exposure time but also others parameters.
The effects will vary according to the person affected, their age and their health conditions.
Threshold levels and Methodologies
There are several existing methodologies that Member States have reported using for assessing toxic effects. The
main ones are described below26.
Acute Exposure Guidelines Levels (AEGL)
This methodology has been developed by the US National Advisory Committee on AEGLs under the US EPA27.
Three levels are defined with exposure times of 10 minutes, 30 minutes, 1 hour, 4 hours and 8 hours:
AEGL-1: the airborne concentration (in ppm) of a substance above which it is predicted that the
general population, including susceptible individuals, could experience notable discomfort, irritation,
or certain asymptomatic non-sensory effects. However, the effects are not disabling and are transient
and reversible upon cessation of exposure.
AEGL-2: the airborne concentration (in ppm) of a substance above which it is predicted that the
general population, including susceptible individuals, could experience irreversible or other serious,
long-lasting adverse health effects or an impaired ability to escape.
25 JRC, 2008, Overview of Roadmaps for land-use planning in selected member States 26 JRC, 2008, Overview of Roadmaps for land-use planning in selected member States 27 American Environmental Protection Agency, Acute Exposure Guidelines Levels,
http://www.epa.gov/oppt/aegl/pubs/define.htm
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AEGL-3: the airborne concentration (in ppm) of a substance above which it is predicted that the
general population, including susceptible individuals, could experience life-threatening health effects
or death.
Dangerous Toxic Load (DTL)
These load levels have been developed by the UK Health and Safety Executive28.
Specified level of toxicity (SLOT): The airborne concentration level at which almost everyone in the
exposed area is likely to suffer severe distress, a substantial fraction of which will require medical
attention, and some people will be seriously injured, requiring prolonged treatment. For highly
susceptible people, the possibility exists that they will be killed.
Significant likelihood of death (SLOD): The airborne concentration level at which the mortality of
50% of an exposed population is predicted.
Emergency Exposure Indices
The indices have been developed in 1991 by the European Centre for Ecotoxicology and Toxicology of
Chemicals29. Apart from two exemplary chemicals, no further values have been developed. Exposure times are 15,
30 and 60 minutes. Three levels are defined:
EEI-1: The maximum airborne concentration below which the exposed population is not likely to
suffer discomfort.
EEI-2: The maximum airborne concentration below which the exposed population is not likely to
suffer irritation.
EEI-3: The airborne concentration below which the exposed population is not likely to be
incapacitated.
Emergency Response Planning Guidelines (ERPG)
These guidelines have been issued by the American Industrial Hygiene Association30. Three levels are defined
with an exposure time of 1 hour:
ERPG-1: The maximum airborne concentration below which it is believed nearly all individuals could
be exposed for up to 1 hour without experiencing more than mild, transient adverse health effects or
without perceiving a clearly defined objectionable odour.
ERPG-2: The maximum airborne concentration below which it is believed nearly all individuals could
be exposed for up to 1 hour without experiencing or developing irreversible or other serious health
effects or symptoms that could impair an individual’s ability to take protective action.
28 Health and Safety Executive, Toxicity levels of chemicals, http://www.hse.gov.uk/chemicals/haztox.htm 29 European Centre for Ecotoxicology and Toxicology of Chemicals , http://www.ecetoc.org/index.php 30 American Industrial Hygiene Association, ERPG Guidelines, 2013 https://www.aiha.org/get-
involved/AIHAGuidelineFoundation/EmergencyResponsePlanningGuidelines/Documents/ERPGIntroText.pdf
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ERPG-3: The maximum airborne concentration below which it is believed nearly all individuals could
be exposed for up to 1 hour without experiencing or developing life-threatening health effects.
Immediately dangerous to life and health (IDLH)
This threshold has been developed by the American National Institute for Occupational Safety and Health and it
represents the maximum concentration in the air of a toxic substance in which a person can be exposed for 30
minutes without any irreversible damages for his/ her health or injuries which can prevent him/her from leaving the
area31.
Intervention guidelines
These guidelines have been issued by the Dutch Competent Authorities in 1999. Three levels for a 1 hour exposure
are defined32.
Life threatening value (LBW): the concentration of a substance above which death or a life threatening
condition may develop within a few days after an exposure of one hour.
Alarming threshold (AGW): the concentration of a substance above which irreversible or other serious
health impairment may occur as a result of acute toxic effects after an exposure of one hour.
Communication guideline value (VRW): the concentration of a substance at which with a high level of
probability will be perceived by the majority of the exposed population as hindrance or above which
minor, quickly reversible health effects may occur after an exposure of one hour. Often this is the
concentration at which exposed people start to complain about the perceived exposure.
Lethal concentration and dose
A series of statistical data have been calculated which set median lethal concentration and median lethal dose33.
LC50 (Median Lethal Concentration 50): is a statistically derived single concentration of a substance
that can be expected to cause death in 50% of animals when administered by the inhalation route
during 4 hours. The LC50 value is expressed in terms of ppm or mg/m3.
LC1 (Median Lethal Concentration 1): The concentration in the air of a toxic substance, which may
cause fatalities to the 1% of the population via inhalation of the substance for duration of 30 minutes.
LD50 (Median Lethal Dose): is a statistically derived single dose of a substance that can be expected to
cause death in 50% of animals when administered by the oral or dermal route. The LD50 value is
expressed in terms of weight of test substance per unit weight of test animal (mg/kg).
31National Institute for Occupational Safety and Health, pages on IDLH, http://www.cdc.gov/niosh/idlh/default.html 32 ACUTEX, Methodology to develop AETLs, January 2006 33 Regulation (EC) No 1272/2008 on the classification, labelling and packaging of substances and mixtures (CLP Regulation)
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SEL and SEI
These thresholds have been developed by the French Ministry of the Environment, for exposure times of 1, 10, 20,
30 and 60 minutes and 2, 4, and 8 hours34.
SEL (Lethal Effects Threshold): concentration for a given exposure period above which mortality can
be observed in the exposed population.
SEI (Irreversible Effects Threshold): concentration for a given exposure period above which
irreversible effects may appear in the exposed population.
SER (Reversible Effects Threshold): concentration for a given exposure period above which reversible
effects may appear in the exposed population.
SP (Perception Threshold): concentration that leads to a sensorial detection of the chemical substance
by the exposed population.
Temporary emergency exposure levels (TEEL)
These levels have been developed by the US Department of Energy and are used in the ARAMIS project for setting
default toxic release thresholds35. Four levels have been defined for a 15 and 60 minutes exposure time, depending
on type of chemicals.
TEEL-0: the threshold concentration below which most people will experience no appreciable risk of
health effects.
TEEL-1: the maximum concentration in air below which it is believed nearly all individuals could be
exposed without experiencing other than mild transient adverse health effects or perceiving a clearly
defined objectionable odour.
TEEL-2: the maximum concentration in air below which it is believed nearly all individuals could be
exposed without experiencing or developing irreversible or other serious health effects or symptoms
that could impair their ability to take protective action.
TEEL-3: the maximum concentration in air below which it is believed nearly all individuals could be
exposed without experiencing or developing life-threatening health effects.
Comparison of threshold levels
Two comparisons of these toxicity threshold levels, relevant for the assessment methodology, have been identified.
In 2006, the ACUTEX project aimed at developing a European methodology for developing Acute Exposure
Thresholds Levels (AETLs) for toxic substance to be applied in major hazard control36. As part of the work, the
project reviewed the existing systems of acute exposure values in order to understand the range of definitions and
34 INERIS, Portail Substances Chimiques, Seuils de toxicite, http://www.ineris.fr/substances/fr/page/23 35 Advanced Technologies and Laboratories International , Protective action criteria,
http://www.atlintl.com/DOE/teels/teel/teel_pdf.html 36 ACUTEX, Methodology to develop AETLs, January 2006
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parameters in current use and to identify the difference between them. The results of the comparison are
reproduced in Table 3.9. This provides helpful guidance on the link between the different existing tools available
and how they can be used to assess a heath effect. It is noticeable that the same tool can be used for health effects
with different levels of harm. For example, EEI-3 is used to assess both irreversible and lethal effects (i.e.
permanent incapacity and lethality).
Table 3.9 Comparison of applicable tools for health effects
Health effect Duration of exposure
1 min
10 min 15 min
20 min
30 min 1 hr 4 hrs 8 hrs Probit
No appreciable risk of health effects, not likely to suffer discomfort
EEI-1
TEEL-0
EEI-1
Objectionable odour TEEL-1
EPRG-1
VRW
Mild effects, discomfort, irritation AEGL-1 EEI-1
TEEL-1
AEGL-1
EEI-1
AEGL-1
EEI-1
EPRG-1
VRW
AEGL-1
AEGL-1
Likely to suffer severe distress SLOT
Medical attention required EEI-2 EEI-2 EEI-2 SLOT
Impairment of an individual’s ability to take protective action or escape
AEGL-2 TEEL-2 EEI-2
AEGL-2
EEI-2
AEGL-2
EPRG-2
EEI-2
AGW
AEGL-2
AEGL-2
Serous health effects, serious injury requiring prolonged treatment
AEGL-2
TEEL-2 EEI-2
AEGL-2
EEI-2
AEGL-2
EPRG-2
EEI-2
AGW
AEGL-2
AEGL-2
SLOT
Immediate or delayed permanent adverse health effects, irreversible health effects
SEI SEI
AEGL-2
TEEL-2
SEI SEI
AEGL-2
SEI
AEGL-2
EPRG-2
AGW
AEGL-2
AEGL-2
Permanent incapacity EEI-3 EEI-3 EEI-3
Life-threatening effects AEGL-3 TEEL-3
AEGL-3 AEGL-3
EPRG-3
LBW
AEGL-3
AEGL-3
Likely to cause death, lethal effects SEL SEL
EEI-3
SEL SEL
EEI-3
SEL
EEI-3
LBW
SLOD
Reproduced from ACUTEX, 2006
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The aim of the ACUTEX project was to define AETLs linked with the existing tools and guidance to measure toxic
effects. For example, for the ACUTEX threshold level 2 (irreversible but not fatal effects), the report found that
there are differences in the effects assessed in different tools: EEI focuses on the prevention of effects leading to
disability while ERPG and AEG focus on the prevention of irreversible and long lasting health effects and
impairment of the ability to escape37.
In addition, the report on Roadmaps for LUP includes a comparison for a selection of chemicals of the results
obtained with IDLH, ERPG and AEGLs. The result of the comparison is presented in Table 3.10.
Table 3.10 Comparison of the toxicity thresholds for selected substances under different methodologies
Substance Thresholds for toxic substances (ppm)
IDLH (30 mins) ERPG3 (1 hr) AEGL-3(1hr)
Ammonia 300 1000 1100
Bromine 3 5 8.5
Chlorine 10 20 20
Hydrogen Chloride 50 100 100
Hydrogen Fluoride 30 50 44
Formaldehyde 20 25 56
Phenol 250 200 Not recommended
Phosgene 2 1 0.75
Sulphur Dioxide 100 15 30
Hydrogen Sulphide 100 100 50
Source: JRC, Roadmaps for LUP
Comparison of thresholds applied in Member States
Table 3.11 presents the thresholds applied by Member States in relation to toxic release. The thresholds values
correspond to the levels of harm presented in Table 3.4 and have been assigned to each generic level of harm
according to the definition presented in Table 3.3.
37 ACUTEX, Methodology to develop AETLs, January 2006.
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Table 3.11 Overview of thresholds for toxic release
Level 1- no effect
Level 2 - small effect
Level 3 - reversible injury
Level 4 - irreversible injury
Level 5 - start of lethality
Level 6 – high lethality
Domino effect
Belgium IDLH
Cyprus IDLH LC1 LC50
Denmark AEGL-3
Estonia IDLH
France SEI SEL 1% SEL 5%
Italy IDLH LC50 LC50
Slovenia ERPG-1 – ERPG-2
ERPG-2 – ERPG-3 ERPG-3
Spain
AEGL 1 –ERPG 1 – TEEL 1
AEGL 2 – ERPG 2 – TEEL 2
The Netherlands D01
UK D50
ARAMIS < TEEL-1 TEEL-1 – TEEL-2
TEEL-2 – TEEL-3 >TEEL-3 >TEEL-3
The table illustrates the diversity of methods used by Member States.
One possible option with regard to the assessment methodology would be to identify the health effects that
constitute the start of a major accident, and using the equivalent level presented in Table 3.9, to ensure that the
substance considered in the assessment methodology does not meet any of the possible thresholds of the tools
available. For example, if it was considered that ‘medical attention required’ is a characteristic of a major accident,
then according to Table 3.9 the assessment must demonstrate that the associated toxicity thresholds (i.e. EEI-2)
cannot be exceeded.
However, it is important to take into account the exposure time as a major accident does not necessarily manifest
effects immediately. The ACUTEX report notes that there are variations in the existing approaches. For example,
the French system uses a time span from 1 to 480 minutes (8 hours). ACUTEX notes that the use of the 480 minute
time span can be problematic as it can be confused with occupational exposure limit (OEL) values that typically
use this time frame38. Finally, the report notes that, in industrial accidents, the release of chemicals would not
typically last more than several minutes, but that in the case of fire, the release of toxic gases can last for days or
weeks.
38 ACUTEX, Methodology to develop AETLs, January 2006
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In the context of the assessment methodology it is appropriate that the assessment demonstrates that the toxicity
thresholds chosen cannot be exceeded under the various exposure times, which may be up to 8 hours if approaches
amongst the different member states are taken into account. Again factors such as the potential to cause off-site
effects for the public (rather than toxic effects on a small number of individuals on-site may need to be taken into
account).
Whilst the focus of this section has been on acute toxicity, it is important to highlight that the Seveso Directive lists
some named carcinogenic and mutagenic substances in Annex I part 2. For carcinogenic and mutagenic substances
that might be considered in the context of Article 4, endpoint values for such health effects should also be
considered in the context of the assessment methodology, and this can be done in a similar manner to e.g. acute
toxicity. However, given the complexities with e.g. dose-response relationships and threshold levels for effects for
CMR substances, no particular threshold values for comparison are presented here. Such assessments should be
done on a case-by-case basis.
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4. Member States’ Land-use Planning
4.1 Overview
Article 13 of the Seveso Directive requires that ‘the objectives of preventing major accidents and limiting the
consequences of such accidents for human health and the environment are taken into account in [...] land-use
policies’.
The approaches adopted by Member States and their Competent Authorities with regard to land-use planning are a
potentially important source of information on the interpretation of the dangerousness of Seveso establishments and
their potential to create major accidents. One of the aims of this Task was to consider national cut-off values
regularly applied in several Member States in the framework of land-use planning policies, and to conclude how
these cut-off values might guide the interpretation of the notion of a “major accident” in the context of Article 4.
The Competent Authorities assess the evaluation of hazard and the analysis of risks created by an establishment
before granting planning permission for new establishments or for developments in the vicinity of existing sites.
The potential for the establishment to create a major accident is an important part of this assessment. For this
assessment, the thresholds values defined by Member States for thermal radiation, overpressure and toxicity effects
are used.
A review of Member States land-use policies was conducted. The information reviewed includes Member States’
reporting under the Seveso Directive, Competent Authorities guidelines, recent pan-European projects on chemical
and industrial risks, and other source of information identified during the literature review. A full list of the
information reviewed is included in Appendix A.
Whilst in some member states, the land use planning approaches are effectively used as a surrogate for what is
considered a major accident, this is not universally true. The links between safety distances and cut-off values used
in land-use planning and the definition of major accident is not clear-cut and there is no direct correlation between
the two. However in the context of the Article 4 assessment methodology, these cut-off values and reference
distances represent some of the only quantitative values available to allow for comparison with estimated effects
distances predicted for relevant accident scenarios.
As has become clear during the course of the project, there are a number of practical and theoretical limitations to
the use of these cut-off values and reference distances in deciding whether a major accident is possible in the
context of Article 4. A key consideration is that safety distances for land use planning are often set by taking into
account local conditions and characteristics such as geographical, social, economic and administrative factors.
These local, site-specific factors are not relevant in the context of the Article 4 assessment methodology.
Since these values show how member states consider the suitability or otherwise of developments near to
establishments where a major accident is possible, and because they include quantitative estimates of distances and
relevant cut-off values for dangerous effects, they may be of help to assessors in the context of Article 4. However,
it is clear that they are not suitable on their own for determining whether a major accident is possible, and so this
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information should be considered as one of a number of elements to take into account when deciding whether
distances to relevant effects calculated for a particular accident scenario constitute a major accident or not.
4.2 Member States’ land-use planning approaches
4.2.1 Background
The European Commission’s land-use planning guidelines describe the most common methods used to assess the
hazard presented by an establishment within land-use planning policies39. They are as follows:
Deterministic approach (also known as consequence-based): The deterministic approach involves
carrying out an assessment of consequences of credible accidents, without taking into account the
likelihood of these accidents. This is in order to avoid uncertainties related to the quantification of the
frequencies of occurrence of the potential accidents40. Under this approach, a scenario is pre-selected
(i.e. a reference scenario), and based on this the modelling of consequences is conducted. The
reference scenario is defined based on expert judgement and historical data and is specific for each
type of establishment. The authorities may require that several reference scenarios are assessed. This
approach involves the definition of effect endpoints (e.g. a tolerability or effect threshold). The
consequences of the accidents are taken into account by calculating the distance at which, for a given
exposure period, the threshold value corresponding to the beginning of the undesired effect is reached.
Using these endpoints, two zones are defined. The inner zone focuses on the immediate boundaries of
the installation and the outer zone is used to separate the installation from densely populated areas or
buildings with sensitive populations.
Probabilistic approach (risk-based): Under this approach, the consequences of potential accidents are
assessed and the likelihood of each scenario occurring is also assessed (thus differing from the
deterministic approach). This method typically consists of five steps:
- Identification of hazards;
- Estimation of the probability of occurrence of the potential accidents;
- Estimation of the extent of consequences of the accidents and their probability;
- Integration into overall risk indices that may include both individual and societal risk; and
- Comparison of the calculated risk with the acceptance criteria.
Under this approach, two types of risk can be calculated: individual risk and societal risk. The risks
defined can be split into categories: typically acceptable, non-acceptable and a region where the risk
can be considered as acceptable but reduction is desired (i.e. ALARP or ALARA). See Figure 4.1 for
a visualisation of these levels.
39 JRC, 2006, Land-Use planning Guidelines in the context of Article 12 of the Seveso II Directive 96/82/EC 40 Institute for Systems Informatics and Safety, 1999, Guidance on Land Use Planning as required by Council Directive
96/82/EC (Seveso II)
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State-of-the-Art approach: This approach is based on the idea that sufficient measures must exist to
protect the population from an accident considered to be the ‘worst conceivable’. The aim is to
operate without imposing any ‘conceivable’ risk to the population outside the establishment by relying
on state of the art technology and additional safety measures. For land use planning, this approach is
translated in the use of zoning, where zones are derived from the consequences of representative
scenarios.
Hybrid approaches (i.e. semi-quantitative approach): The semi-quantitative approach is a sort of
deterministic approach which includes some quantitative (i.e. likelihood) elements. Some elements
are assessed in a quantitative way, while others are assessed qualitatively. See the description for
France below as an example of a hybrid approach in land use planning.
The review of Member States practices on restricting land use in the vicinity of Seveso establishments has
identified two main trends in zoning policies:
1. The restriction of land use by zoning policies based on the type of establishment, surrounding
infrastructures and/or the type of substances involved; and
2. The restriction of land uses by zoning policies based on vulnerability levels.
The latter can be split into two further groups, one defining zones by reference to consequence levels (deterministic
approach) and the other where zones are defined with reference to probability of damage (probabilistic approach).
4.2.2 Restriction of land use by zoning
This practice is based on the principle that uses of land that are not compatible with each other should be separated
by specific distances. Tables have been elaborated that classify the industries into categories and for each a
specific distance is proposed. Some finer categories can be defined and distances specified in accordance with the
substance used in the installation. This approach has been observed in several Member States and Iceland. Table
4.1 presents a summary of the distances identified. These are not directly comparable as they are set with reference
to different variables. For example, in Latvia and Finland, the distances issued are substance and site specific, for
example for natural gas production and storage sites.
The table summarises the distances identified in several Member States for inner zones. It shows that there is a lot
of variation in zoning practices of Member States and that it may be difficult to choose one minimum distance
rather than another without further information.
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Table 4.1 Distances reported for inner zones
Estonia Finland Iceland Latvia Spain (Catalonia)
Sweden
No details on the specific zone
Zone established are up to 200 metres
Substance and building specific
5m
10m
25m
350m
130m
55m
Building specific
1,100 m
330m
For natural gas sites and storage installations
450m
300m
150 m
100m
75m
50m
10-50m
Specific to type of establishment
500m
250m
100m
50m
Specific to type of establishment
200m
500m
1,000m
1,500m
The details of the land use practices in relation to zoning for these countries are set out below.
Estonia
Estonia implements the requirements of the Seveso Directive through their Chemical Act and Planning Act. Local
government has to consult with the Rescue Board which assesses a major accident’s probability for the
establishment and their consequences, and gives recommendations for safe planning. The recommendations are
based on the risk and the methodology developed by the Rescue Board that defines zones and the types of
development that can be accepted in each of these zones.
The assessment is deterministic (i.e. consequence based). The Estonian legislation defines several safety zones
according to specific purposes such as environment protection (e.g. coastal protection), health protection (e.g.
radiation, vibration and noise) or for specific type of establishment (e.g. pressure vessel, gas installation or safety
zone for electrical). The zones established contain distances of up to 200 metres41.
Finland
In Finland, minimum distances are provided as a function of the substance and the tank or storage size. The
distances are calculated for the site boundary but also for residential areas and other areas of public use42. The
values used in Finland are presented in the table below.
41 Presentation by Priit Laaniste, Seveso II and land-use planning in Estonia, Estonian Ministry of the Interior, November 2007 42 Institute for Systems Informatics and Safety, 1999, Guidance on Land Use Planning as required by Council Directive
96/82/EC (Seveso II)
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Table 4.2 Safety distance in Finland
Substance Tank / Storage size
Separation to public roads or site boundary (in metres)
Separation to residential areas, areas of public use or natural sensitivity (in metres)
LPG 5 t 5 15-25
5-50 t 10 35-50
50-200 t 25 50-100
>200 t Safety analysis Safety analysis
Ammonium nitrate 1-5 t 66 100
5-10 t 100 150
10-15 t 133 200
15-30 t 166 250
30-50 t 200 300
50-100 t 233 350
>100 t 266 400
Ammonia >10 t - 400-600
Hydrogen >120 kg - 150
Unstable gases or flammable liquids
5,000 m3 350 -
Other flammable gases or liquids (process unit)
5,000 m3 130 -
Flammable liquids (tanks) 200 m3 55 80
Source: Institute for Systems Informatics and Safety, Guidance on land use planning, 1999
Iceland
In Iceland, safety distances have been established for top-tier establishments. The distances are presented in the
table below.
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Table 4.3 Safety distances for specific buildings in Iceland
Type of building Distance
Hospitals, day-care, large assembly rooms and streets with dense traffic 1,100 metres
Residential areas 1,100 metres
Busy roads and harbours 330 metres
Other buildings and public roads 330 metres
Source: Niks Jan Dujim, Acceptance Criteria in Denmark and the EU
In addition, safety distances have been adopted in the legislation for sites dealing with explosives43. This is not
specific to Seveso sites; however, this can be relevant as explosives are covered by the Seveso Directive.
Latvia
The law on Protective Zones sets out special requirements to restrict the development of residential areas and other
activities in the planning territory in the vicinity of dangerous establishments, as well as restricting dangerous
activities in the vicinity of vulnerable areas.
There is a minimum protective zone of 100m around the buildings of pumping and filling stations for oil and oil
products and other dangerous chemical substances and products, reservoir parks, filling and discharge overpasses,
berths and jetties, heating points, warehouses, storage vessels, and processing and reloading enterprises, where oil,
oil products, dangerous chemical substances or products are kept.
The maximum width of the safety protective zone around pipes, tanks and storage vessels used for oil, oil products,
dangerous chemical substances and products, as well as processing and reloading enterprises is 500m.
In accordance with the law on Protective Zones, the following protective zones must be observed around natural
gas sites and liquid hydrocarbon gas storage warehouses, filling stations and other facilities:
43 Survey response
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Table 4.4 Distance for natural gas sites and liquid hydrocarbon gas storage warehouses
Site Distance of protective zones
Natural gas compressor stations 450m from the external wall of the building or compressor station equipment
Natural gas collection points 300m
Natural gas collector bore-holes located in the natural gas storage area and connected to the collector layer
300m from the bore-hole
Liquid hydrocarbon gas storage warehouses, storage vessels and filling stations
100m
Around gas pipes 75-150 m
Other natural gas and liquid hydrocarbon gas sites 10-50 m
Source: Niks Jan Dujim, Acceptance Criteria in Denmark and the EU
In these protective zones the following activities are prohibited:
The construction of new residential buildings or reconstruction of existing buildings as residential
buildings;
The construction of new sports, educational and recreational buildings and establishments, or the
reconstruction of existing buildings as sports, educational and recreational buildings or establishments;
The construction of playing fields and recreational areas, as well as the organisation of public events;
The siting of petrol filling stations; and
Other operations (or activities) that may interfere with environmental and public safety during the
operation of gas pipes and natural gas and liquid hydrocarbon sites.
Spain
The land use planning system in Spain is based on the definition of three consequences based zones which are
described as follows:
The intervention zone (ZI), the area where immediate protection is justified due to the damage level
caused by the effects of a certain accident.
The alert zone (ZA), the area where immediate protection is not justified (except for critical groups of
the population) due to the damage level caused by the effects of a certain accident. Population within
this area may however perceive the effects of the accident.
The domino zone (ZD), the area where severe damage to property (process and storage equipment) is
expected due to the effects of a certain accident.
In Spain, there is no zone distance set and the basis for defining the limits of the zones are consequences based.
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Catalonia
The regional legislation defines safety zones where land use is regulated. The aim is to ensure that the inhabitants
within these zones can take protective action in case of an accident44. The area affected by the establishment is
known as the no self-protection zone. Inside this zone the ability of the population to take protective measures is
not guaranteed. Its shape and size are fixed by distance to the source of the risk and the severity of possible
accident.
Beyond the ‘no self protection zone’, two further areas are defined by the Catalonian legislation:
The extreme outdoors intensity zone, inside which the negative consequence for people who are
outdoors and other vulnerable elements could be very severe; and
The general sheltering zone which is characterised by land use constraints, preventive measures and
compensatory actions in order to ensure that the population can be warned and can take self-protection
actions.
This set of three zones is known as the assurance of self-protection zone. Land use is controlled within the zones
and specific uses are prohibited in the no self protection zone. These are summarised in Table 4.5.
Table 4.5 Type of land use authorised in zones in Catalonia
Type of uses No self protection zone Extreme outdoors intensity zone General sheltering zone < No self protection zone > No self protection zone
Transport infrastructure
Yes Yes Yes Yes
Industrial Yes (with risk reduction measures)
Yes (with risk reduction measures)
Yes Yes
Services No No Yes (no shopping centres, and limit of 250 persons per buildings)
Yes
Housing No (except for completion urban areas with growth limited by 5% or 500 people)
No (except for completion urban areas with growth limited by 5% or 500 people)
No (except for completion urban areas with growth limited by 5% or 500 people)
Yes
Other uses No No Yes (e.g. park with low density and maximum 500 people attendance)
Yes
Source: Generalitat de Catalunya Departament d’Interior, Relacions Institucionals i Participació, November 2009
44 Generalitat de Catalunya Departament d’Interior, Relacions Institucionals i Participació Direcció General de Protecció Civil
Subdirecció General de Programes en Protecció Civil, November 2009, Land use and spatial planning: criteria for risk
management
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The legislation specifies a generic value for the limit of the ‘no self-protection’ zone which can be revised taking
into account specific information about the dangerous substances used in the installation. The preliminary zone has
a default size of 500 metres. Following the in-depth review of the installation’s characteristics, type of storage and
processes involved, the Competent Authority calculate the extent of potential major accidents and decide whether
the zone perimeter needs to be adjusted. It can either be kept at 500 metres or reduced as follows:
500 metres: Catalonia explained that with a wind speed of 1.5 m/s a toxic cloud can reach a distance of
500 metres in 5.5 minutes. It added that it is generally accepted by risk management experts that at
least 5.5 minutes go by, since the instant when the accidental emission begins, before the affected
population can be warned. This is caused by the uncertainty associated with the first moments of the
emergency and is regarded as unavoidable, even with the best warning techniques. This distance is
also used for establishments whose main function is storage and distribution in large quantities of
flammable gases and liquids obtained from oil distillation.
250 metres: This distance is used for flammable liquefied gases and flammable gases if the storage
area does not qualify as large. It also applies to toxic substances which cannot generate large toxic
clouds because their toxicity level is medium or low, their boiling point is high or because it is
prevented by safety arrangements.
100 metres: This distance is used for flammable or very flammable substances that cannot generate
flammable clouds or deflagrate.
50 metres is used for the remaining cases.
Spain allows for physical barriers to be taken into account and reduces the safety distances from 500m to 250m,
from 250m to 100m and from 100m to 50m. The barriers must resist specific constraints and ensure that beyond
them, specific conditions are met. These are summarised in Table 4.6.
Table 4.6 Safety distances in Catalonia for specific substances and phenomenon
Substance type Dangerous phenomenon
Perimeter of the no self protection zone (in metres)
No preventive actions
With preventive actions
Preventive action
Toxic gases and liquids with low boiling point
Toxic cloud 500 350 Chemical detectors
Extremely flammable liquefied gases
BLEVE 500 250 Physical barriers against thermal radiation and shock wave
Very flammable liquid fuels in large distribution centres
Fires, explosions 500 250 Physical barriers against thermal radiation and shock wave
Very flammable liquids (low boiling point)
Flammable cloud, explosion, jet fire
250 100 Physical barriers against thermal radiation and shock wave
Flammable liquids Pool fire 100 50 Physical barriers against thermal radiation and shock wave
Other Spills causing pollution 50 50 -
Source: Generalitat de Catalunya Departament d’Interior, Relacions Institucionals i Participació, November 2009
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Sweden
In Sweden, the safety distances are provided for 32 different activities. The table below presents some of these
distances. The Swedish legislation considers that these distances are initial values, that can be deviated from
following detailed assessment45. The assessment must take into account reasonable scenarios such as discharges,
fire, smoke from fires, etc.
Table 4.7 Appropriate safety distances in Sweden
Type of infrastructure Distance
Plastic industry 200 m
Paper mill 500 m
Non-organic chemical industry 1,000 m
Oil refinery 1,500 m
Industrial block 50 m
Small industry area 200 m
Industrial area 500 m
Process industry >1,000 m
Source: Guidance on land use planning, 1999
4.2.3 Restriction of land use based on consequence
In the following Member States, zones that restrict land uses are defined by reference to specific effect and
thresholds (as presented in Section 3). For example zone I is the zone where a specific effect would affect a
defined number of people (e.g. 50% if the population affected by c-degree burns in Cyprus, or would reach a
specific threshold 1,200 ppm of toxic release in the Czech Republic). This represents the application of the
consequence based (deterministic) approach for which reference scenarios are assessed. Reference scenarios are
defined by the authorities and the establishment operator. Using the defined threshold values for thermal radiation,
overpressure and toxic release, zones are defined surrounding the establishment.
Cyprus
In Cyprus, the land use planning advisory system takes into account the consequences of major accidents, the type
of developments and the level of sensitivity of the buildings surrounding an establishment.
45 Institute for Systems Informatics and Safety, 1999, Guidance on Land Use Planning as required by Council Directive
96/82/EC (Seveso II)
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Three consequence based zones are defined for land use planning purposes46. The distances of the zones are not
defined but are derived from the consequences of major accidents in agreement with specific endpoints for thermal
radiation, overpressure and toxic cloud:
Zone I is the inner zone where c-degree burns would affect over 50% of the population, severe and
irreparable damage to the supporting structure and walls of buildings or a toxic cloud would cause
death of 50% of the population.
Zone II is the zone where c-degree burns would affect 1% of the population, damage to the supporting
structure and exterior or interior walls of the establishment or a toxic cloud would cause death of 1%
of the population.
Zone III is the zone where a-degree burns would affect a substantial part of the population, damage to
doors and windows, light cracks in the walls and a toxic cloud would create imminent danger to life.
A generic sensitivity level is set for each type of infrastructure, as presented in Table 4.8.
Table 4.8 Sensitivity level of buildings in Cyprus
Sensitivity level 1 Sensitivity level 2 Sensitivity level 3 Sensitivity level 4
Workplaces
Housing, Hotel and holiday accommodation,
Institutional accommodation and education
Institutional accommodation
Parking areas Transport links
Prisons Very large outdoor use by public
Indoor use by public
Outdoor use by public
Source: Presentation by Themistoclis Kyriacou
The sensitivity levels are then adapted by taking into account the specific characteristics of the building and its size.
For example, a workplace with fewer than 100 employees will be rated as level 1 for sensitivity. However, a
workplace providing more than 100 jobs in a building of 3 levels or more will be rated as a sensitivity level 2
because of the number of people involved.
According to the sensitivity level of the buildings surrounding the area and the consequences of accidents reflected
in the zones, the following decision matrix is applied:
46 Presentation by Themistoclis Kyriacou, Labour Inspection Officer, Department of Labour Inspection, Cyprus, Land Use
Planning around Seveso establishments and sitting of new Seveso establishments
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Table 4.9 Land use planning decision matrix for new and existing developments
Sensitivity Level
Existing developments New developments
Zone Ι Zone ΙΙ Zone ΙΙΙ Zone Ι Zone ΙI Zone ΙII
1 POWT PO PO POWT POWT PO
2 POWT POWT PO NO POWT POWT
3 NO POWT POWT NO NO POWT
4 NO NO POWT NO NO NO
Source: Presentation by Themistoclis Kyriacou
Czech Republic
The land use planning procedure for Seveso establishments revolves around the Regional Authority which is
responsible for the prevention of major accidents and is competent for discussing land-use planning applications
and procedures. When notified of a land-use procedure, the Regional Authority transfers an assessment of the risk
of a major accident as submitted by the operator in its safety report to the Construction Authority. Land use
planning decisions or construction permits cannot be issued if the assessment of the risk of a major accident has not
been carried out. The Dutch approach to defining acceptable levels of risk is recommended for operators47.
There are no defined guidelines on setting these zones. However, one example mentioned in a presentation from
the Competent Authorities included the following distances for a steelwork factory involving carbon monoxide
pipelines and storage48:
Internal emergency planning zone (450m / 1200 ppm); and
External emergency planning zone (1400 m / 200 ppm).
There are no set end point values to define a major accident in the Czech Republic49. Any significant release of a
dangerous substance, an explosion or fire can be understood as being a major accident. In addition, the Act
No.59/2006 Coll. on major accident prevention states that if the accident meets one of the criteria listed in the
legislation then it is major (see Section 2.3).
47 Survey response 48 Pavel Danihelka and Pavel Forint, Land-use planning and the SEVESO II directive in the Czech Republic, Ministry of the
Environment, LabR!SK project 49 Survey response
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Greece
The Greek legislation does not require a quantitative risk assessment. However it is common that safety reports
include a risk assessment with a hazard identification, accident frequency calculation, definition of potential
consequences of accidents and risk estimation50. In Greece a typical identification of possible accident scenarios in
an establishment is based on a site-specific hazard analysis. In addition a review of past accidents that have
occurred in similar facilities is conducted. The approach focuses on the worst case scenario.
In order to determine hazard zones, threshold values regarding the level of thermal radiation, overpressure or toxic
dose that may give rise to undesirable effect have been adopted. Greece recommends a set of values that define
four zones within which specific undesirable effects would arise51. Each zone also represents the limits for certain
types of land use. It is compulsory that Zone I does not extend beyond the boundary of the establishment. The
zones defined are presented in Table 4.10.
Table 4.10 Type of development and zones in Greek land use planning
Zone Description Type of development
D Zone of domino effects (severe damage to equipment)
Minimum distance for location of other hazardous establishments
I Zone of multiple fatalities Minimum distance for manufacture, warehouse, open-space activities and recreational areas
II Zone of first death (1% lethality) Minimum distance for public roads, commercial activities, offices and low density housing developments
III Zone of first irreversible effects Minimum distance for residential development and institutional buildings (e.g. schools)
Source: P.D. Petrolekas and A. Charalambous, 2001, Land use planning considerations in the context of Seveso II Regulations
4.2.4 Restriction of Land use based on the probability of Damage
Figure 4.1 has been reproduced from a recent report looking at differences in land use planning approaches in
Member States. It summarises the criteria selected by three Member States to define societal risks and compare
them with the results of a research project (EP112). This corresponds to the risk-based or probabilistic approach to
land-use planning.
50 ShapeRisk Project, 2005, Synthesis document on WP2, Continuity of risk management from work place accident to major
accident 51 P.D. Petrolekas and A. Charalambous, Sept 2001, Land use planning considerations in the context of Seveso II Regulations
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Figure 4.1 Social risk calculation in Flanders, the Netherlands and the UK
Source: Niks Jan Dujim, Acceptance Criteria in Denmark and the EU
Details of Member States practices in relation to defining zones are provided below.
Belgium
Flanders Region
The assessment in Flanders is based on quantitative risk criteria which are the same for new and existing major
hazard establishments. The main aspects of the societal risk assessment are52 :
Employees and hired contractors at the establishment are not considered for the societal risk.
No societal risk criteria have been set for accidents involving less than 10 fatalities, as it is considered
that the location-based criteria must provide the necessary protection for these cases.
Establishments must show that all the necessary preventative measures have been implemented for
smaller accident scenarios (involving fewer than 10 fatalities).
For location-based risks (individual risk), Table 4.11 presents the thresholds associated with the land uses that are
permitted.
52 Niks Jan Dujim, 2009, Acceptance Criteria in Denmark and the EU
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Table 4.11 Values defined for location based risks
Location-based risk per year Land use permitted
<10-5 Commercial activities permitted outside the establishment’s boundary line
<10-6 Residential areas (more than 5 residences) with no vulnerable areas (defined as schools, hospitals, nursing homes and associated land)
<10-7 All types of land use permitted
Source: Niks Jan Dujim, Acceptance Criteria in Denmark and the EU
Walloon Region
The regulation on environmental permitting applies to new establishments or the modification of existing
establishments. For new installations near a Seveso site, the Walloon Region indicates, for each establishment, the
zones in which accident effects damaging to persons or property could occur; these are known as ‘vulnerable
zones’. The Major Risks and Accidents Unit (Walloon Region's coordination and evaluation unit) has issued a
methodology to evaluate the risk of a major accident.
The methodology used is probabilistic. It involves evaluating the risk of major accident combining the estimate of
probability of a dangerous event and the estimate of the effects of this event such as thermal radiation, overpressure
or toxic release53. The societal risk is not taken into account and the ceilings adopted are those which do not result
in irreversible effects for health.
Risk curves are calculated around Seveso establishment. The first 10-6 per year iso-risk curve is known as the
consultation zone. Any land-use in this zone is submitted to advice from the Competent Authority. For decision-
making a matrix has been established which combines the level of risk and the type of buildings and states whether
the permit should be issued or not. The matrix is presented in Table 4.12.
53 RIVM, 2011, An international comparison of four quantitative risk assessment Approaches Benchmark study based on a
fictitious LPG plant
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Table 4.12 Decision matrix for land use based on individual risk
Type of land use
Individual risk
10 -3 to 10-4 per year
10-4 to 10-5 per year
10-5 to 10-6 per year
Type A – Buildings and technical units linked to the geography (e.g. water tower, waste water treatment, windmill)
OK OK OK
Type B – Buildings for a few people, mostly adult and autonomous With caution OK OK
Type C – Buildings for people, mostly adult and autonomous but without number restrictions
Not allowed With caution OK
Type D – Buildings for sensitive people with restricted autonomy Not allowed Not allowed With caution
Source: RIVM, 2011
Denmark
Until 2006, there were no specific guidelines concerning what constitute appropriate safety distances. In 2006, a
Circular setting a minimum distances for all establishments was sent by the Minister for the Environment to all
municipal councils (Circular No 37 of 20 April 2006 on land use planning). The Circular requires municipal
councils to take into account the risk of a major accident before any land use provision is made in a municipal or
local plan affecting areas within 500 m of an establishment.
Following this, the Danish Administration Practice has developed the zoning limitations as shown in the figure
below54.
Figure 4.2 Zones restrictions around Seveso sites
Source: Presentation by Morten R. Østergaard
54 Presentation by Morten R. Østergaard, Danish EPA, Land use planning in the Habour area in the municipality of Aarhus,
DenmarkApplication of a Danish Administration Practice on Land Use Planning, 24 September 2012, Cyprus
Seveso
establishment
Zone 1
Zone 2
Iso risk curve 10-5/year
Iso risk curve 10-6/year
Zone 3
Maximum
consequence
distance
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The zones are defined as follows:
Zone 1: Seveso establishment must have full right of disposal of area, which corresponds to an iso-risk
curve of 10-5 per year.
Zone 2: Neighbouring establishments can be accepted under certain conditions but no vulnerable
buildings can be authorised. The zone corresponds to an iso-risk curve of 10-6 per year.
Zone 3 (i.e. the maximum consequence zone): Neighbouring establishments and vulnerable objects
can be accepted provided that the criteria for societal risk curve are met. No buildings that play a role
in public emergency services or hosting people presenting difficulties for evacuation can be permitted.
The iso-risk curve for zone 1 is based on “location-based risk” that is defined as the risk that a person who is
continually present and unprotected at a given location will die. It does not include consideration of the exposure,
local protection or degree (duration) of presence. The maximum consequence zone is only calculated for scenarios
with a frequency higher than 10-9 per year and it is calculated from the impact level that can lead to life-threatening
and incurable injury55.
France
Since 2003, the French approach is a hybrid method that includes elements of a qualitative assessment in a
quantitative risk analysis. It is based on the identification of bow-tie, fault tree and event tree for many accident
scenarios and the analysis of the performance of the safety barriers put in place for each event. The key element
used for the assessment is the safety report, the results of which are directly used for decision making. The
following qualitative aspects are included56:
Frequency may be assessed using frequency classes;
Fixed end-point values are used to calculate consequence distances;
Various types of consequences such as heat radiation, toxicity and overpressure are assessed
separately (their frequencies are not summed); and
The effects of wind direction and speed are not considered. The safety zones are concentric circles
around the hazard source.
Land use around Seveso establishments is managed by the drafting of a technological risk prevention plan (PPRT),
which evaluates the probability, the intensity of the phenomena and the kinetics for each scenario. It is a flagship
measure of the legislation which aims at protecting people by acting on the existing urbanisation and by
controlling the future land-use planning in the vicinity of top-tier Seveso establishment57.
55 Presentation by Morten R. Østergaard, Danish EPA, Land use planning in the Habour area in the municipality of Aarhus,
DenmarkApplication of a Danish Administration Practice on Land Use Planning, 24 September 2012, Cyprus 56 Niks Jan Dujim, 2009, Acceptance Criteria in Denmark and the EU 57 Clément Lenoble, Clarisse Durand, Introduction of frequency in France following the AZF accident, Journal of Loss
Prevention in the Process Industries, 24 (2011) 227-236
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Endpoint values are used to calculate the intensity of the phenomena for each scenario. The gravity of the effects is
defined by using a scale which depends on the number of victims for each type of effect assessed. The scale is
presented in Table 4.13, the numbers represent number of people affected by the accident.
Table 4.13 Scale of gravity depending on the number of people involved.
Consequence Significant lethal effect Lethal effect Irreversible effect
Seriousness
Disastrous >10 >100 >1000
Catastrophic 1-10 10-100 100-1000
Major <1 1-10 10-100
Serious 0 <1 1-10
Moderate 0 0 <1
Source: Roadmaps for LUP
Other elements are assessed, including the probability. For this a scale of five categories has been adopted to guide
the assessment, and is presented in Table 4.14.
Table 4.14 Range of probability scale
Probability class
Quantitative frequency assessment (per year)
E 0 to 10-5
D 10-4 to 10-5
C 10-3 to 10-4
B 10-2 to 10-3
A 10-2
Source: Clément Lenoble, Clarisse Durand, Introduction of frequency in France following the AZF accident
Once all the elements have been characterised, they are included in a risk matrix defining three levels: unacceptable
(i.e. risk is too high, the installation cannot be authorised), acceptable (i.e. authorisation can be given) and
intermediate (i.e. authorisation can be given after verification that all practicable risk control measures have been
put in place, ALARA).
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Table 4.15 Risk matrix in French assessment
Probability
Gravity
E D C B A
Disastrous ALARA No No No No
Catastrophic OK ALARA No No No
Significant OK ALARA ALARA No No
Serious OK OK ALARA ALARA No
Moderate OK OK ALARA ALARA No
Source: Clément Lenoble, Clarisse Durand, Introduction of frequency in France following the AZF accident
The technological risk prevention plan (PPRT) establishes specific zones as follows:
A dark red zone on which construction is banned and the state can expropriate;
A light red zone where new construction is banned but existing industrial buildings can be extended if
they are protected;
A dark blue zone where new construction is possible depending on the limitations on use or the
protection measures; and
A light blue zone where new construction is possible depending on minor limitations.
The zones are established in relation to the ‘aléas level’ and cumulative probabilities as presented in Table 4.16.
The aléas are defined as the combination of the probability of a dangerous phenomenon and the potential intensity
of its effects. They are calculated for each point of the territory and for each type of effects (thermal radiation,
overpressure and toxic release)58. The cumulative probability is defined in accordance with the information
presented in Table 4.14.
58 Clément Lenoble, Clarisse Durand, Introduction of frequency in France following the AZF accident, Journal of Loss
Prevention in the Process Industries, 24 (2011) 227-236
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Table 4.16 Application of zoning in PPRT
Maximum intensity of the toxic, thermal or overpressure effects on human at a given point
Very serious (significant lethal)
Serious (Lethal)
Significant (Irreversible)
Indirect
Cumulative probability of dangerous phenomena at a given point
>D 5E to D
<5E >D 5E to D
<5E >D
5E to D
<5E All
Aléa level VH+ VH H+ H M+ M Low
Zoning in PPRT Dark red Light red Dark blue Light blue
Source: Roadmaps for LUP
Three aléas maps are drawn, one for each effect (thermal radiation, overpressure and toxic release). The zones are
defined as follows:
Red zones are “ban” zones where future construction is banned. Dark red areas are defined for
expropriation or relinquishments and light red zones for relinquishments.
Blue zones are “limitation” zones, within which protective measures on the future or existing
buildings can be compulsory.
The figure below presents a simplistic representation of the zones as defined by the PPRT process.
Figure 4.3 Zone definition from the PPRT process
Source: Clément Lenoble, Clarisse Durand, Introduction of frequency in France following the AZF accident
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Italy
The risk assessment includes the following steps: the identification, classification and localisation on the map of
vulnerable elements (population, environment, facilities, etc.); the comparison of the defined impact area with the
map of vulnerable elements; the identification of all situations in which the vulnerable elements are located within
the limits of the impact area; and a compatibility judgment for each situation59. The judgment is based on a rating
of the vulnerability of the elements and the gravity of the impact in accordance with specific compatibility tables.
Table 4.17 Compatibility table for LUP in Italy
Frequency /year
Effects
High lethality Beginning of lethality
Heavy injury Light injury
<10-6 DEF CDEF BCDEF ABCDEF
10-4 – 10-6 EF DEF CDEF BCDEF
10-3 – 10-4 F EF DEF CDEF
>10-3 F F EF DEF
Source: Survey response
In this table the letters A, B, etc. stand for specific building category/ type of land use. For example D is residential
area with maximum index of construction 0.5 m3/m2 or area in which there are churches, local markets or similar
activities. F designates that area within the boundaries of the establishment or adjacent to the plant in which no
activity is authorised. Italian legislation (i.e. D.M., 2001, Decree of Italian Ministries 09.05.2001 Minimum safety
requirements relating to town and country planning for areas affected by major accident hazard establishments ,
Official Gazette of the Italian Republic, 138 - S.O. 151, 16.06.2001) describes in details the content of each
building category.
The Netherlands
The approach taken in the Netherlands is risk-based and the assessment is conducted through a Quantitative Risk
Assessment (QRA), for which a methodology has been adopted by the Competent Authorities (i.e. the Purple Book
which has now been replaced by the Bevi). As part of the QRA, three level of individual risk are defined (i.e.
acceptable, as low as reasonably acceptable and non-acceptable).
The Netherlands makes a distinction between individual and societal risk which are defined as follows:
59 JRC, 2008, Overview of Roadmaps for land-use planning in selected Member States
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Individual risk is the likelihood of a person who lives unprotected for 24 hours a day, 365 days a year
at a particular site dying as a result of an accident involving dangerous substances ;and
Societal risk is the probability that a group of more than N persons gets killed due to an accident
deriving from a hazardous installation.
The individual risk is location-based; it is expressed in frequency terms. It includes elements such as the initial
accident frequency, the probability of development, probability of the effects and damage. It is presented in iso-
risk contours over a topographic map of the surrounding on an establishment. The national legislation includes a
set of endpoint values for ‘tolerable’ which is a frequency of 10-6 events/year limit. Figure 4.4 represents an
example of this.
Figure 4.4 Representation of location risk in the Netherlands
Source: Robbert Plarina, 2011
The societal risk is expressed in a number of fatalities per year and is presented as a curve of the number of victims
against the frequency of occurrence. There are not values set in the legislation, and the zones are defined on a case
by case basis. Figure 4.5presents an example of this.
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Figure 4.5 Representation of societal risk in the Netherlands
Source: Robbert Plarina, 2011
The probabilistic approach allows a wider range of modifications to be quantified and reduce the zones, however it
requires additional data (i.e. on failure frequencies particularly) which can be difficult to collect60.
The UK
In the UK, the LUP decisions are taken by the Local Planning Authorities, and advice is produced by the Health
and Safety Executive (HSE). Consequences based zones are defined; the consultation zone is the limit of HSE
interest. Within the consultation zone, three zones are defined as follows:
Inner zone: 10 cpm (10-5 per year), 1800 TDU, 600 mbar;
Middle zone: 1 cpm (10-6 per year), 1000 TDU, 140 mbar; and
Outer zone: 0.3 cpm (3x10-7 per year), 500 TDU, 70 mbar.
The frequency (expressed in chance per million) represents the change per million per year of receiving a
dangerous dose. A decision matrix is then established to identify the developments that are allowed in each zone in
accordance with their sensitivity level.
The HSE defines four sensitivity levels:
60 Presentation by Robbert Plarina, 25 May 2011, Risk based External Safety Regulations in the Netherlands, Seveso
Conference Stockholm.
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Level 1 – Normal working population
Level 2 – General public at home and involved in normal activities
Level 3 – Vulnerable members of the public (children, those with mobility difficulties, those unable to
recognise physical danger)
Level 4 – Large examples of Level 3 or very large outdoor examples of Level 2
These levels of sensitivity correspond to four types of developments:
Type 1 – People at work or parking
Type 2 – Developments for use by the general public
Type 3 – Developments for use by vulnerable people
Type 4 – Very large and sensitive developments
As a general principle the sensitivity level is decreased by one for small examples of a type of development and
increased for large and very large examples of a type of development or where particular features of the
development increase the risk to the population. Table 4.18 provides specific example of cases where negative
advice can be issued for specific type of activities.
Table 4.18 HSE assessment per type of building
Type of activities HSE assessment
A: Residences, hotels, holiday accommodation Negative advice when more than 25 people are exposed to individual risk over 10-5 per year or more than 75 people are exposed to 10-6 per year
B: Workplaces, enterprises, parking areas Negative advice only if the risk from the establishment exceed the normal risk for workplace accidents
C: Shops, meeting rooms, sport and leisure No set rules, advice will be consistent with the principles for category A. Cut-off figures of 100 or 300 people are used for each risk scenario
D: Highly vulnerable or large facilities ( hospitals, schools, large category C facilities involving more than 1000 people)
As for A but the risk criteria are set lower (1/3 of the acceptance criteria) so 0.3 x 10-5 and 0.3 x 10-6
Source: Niks Jan Dujim, Acceptance Criteria in Denmark and the EU
The HSE gives its advice in accordance with the decision matrix reproduced in Table 4.19. DAA stands for ‘don’t
advise against’ the development and AA for ‘advise against’ the development61.
61 HSE’S current approach to land use planning (LUP), http://www.hse.gov.uk/landuseplanning/lupcurrent.pdf
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Table 4.19 Decision matrix for HSE in UK
Level of sensitivity Development in Inner Zone
Development in Middle Zone
Development in Outer Zone
1 DAA DAA DAA
2 AA DAA DAA
3 AA AA DAA
4 AA AA AA
Source: HSE, HSE’S current approach to land use planning (LUP) (http://www.hse.gov.uk/landuseplanning/lupcurrent.pdf)
The HSE has studied societal risk extensively62, but does not have prescriptive criteria it has indicated that it is
working on determining criteria for societal risk. One criterion used is that ‘the risk of an accident involving 50 or
more deaths from a single event should be seen as unacceptable if the expected frequency is greater than once
every 5,000 years’. This is the criteria used for representing the UK in Figure 4.1.
4.3 Other criteria for defining major accidents
As it has been highlighted in Task 4, analysis of past accidents can help in understanding the links that can be made
between the hazard category of a substance and the dangerous phenomena that may be generated further to an
accident involving that substance. It can also help in identifying the type of substances that have been involved in
major accidents as well as recurrent trends or patterns of accidents.
As a result, one step of the assessment methodology could be to show, through a review of the existing accidents
database (e.g. eMARS and ARIA), that the substance proposed has not been involved in any previous industrial
accident. Some databases also record ‘near-misses’ and it might also be appropriate to show that the substance has
not been involved in any ‘near-miss’ cases. However, as set out in the Task 4 report, the absence of past accidents
involving a substance is not on its own sufficient to rule out the possibility of future major accidents.
62 See for example http://www.hse.gov.uk/societalrisk/
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5. Recommendations on Determining Potential for a Major Accident
5.1 Overview
Following the analysis presented in Sections 3 and 4 the following suggestions are made for the use of the
thresholds, cut-off values and safety distances in the context of the assessment methodology.
Several elements have been researched in order to help further understand of the concept of ‘major accident’
beyond the existing definition of Article 3. Whilst it is evident that both Annex VI criteria and safety distances
used in the Member States do not provide a definition of ‘major accident’, they both include elements that may be
helpful for some people in informing the decision making process in the context of Article 4.
5.2 Annex VI of the Seveso Directive
Annex VI lists criteria that characterise major accidents to be reported by Member States to the European
Commission. In the context of the assessment methodology, Member States could compare the results of the
modelling stage (i.e. the effect distances) with some of the criteria for reporting in Annex VI (i.e. those criteria that
are relevant to the effects being studied). Whilst a direct comparison is not possible (the modelling would provide
distances for effects whereas Annex VI lists characteristics of accidents), this step would be the opportunity for the
Member State to demonstrate that the criteria of Annex VI cannot be credibly met for the substance considered. If
it seems credible that at least one of the criteria described in Annex VI could be met, then the substance cannot be
considered as not being able to create a major accident. In contrast, if it seems credible that none of the criteria of
Annex VI could be reached, then further assessment may be required to conclude that there is no potential for a
major accident.
However, this on its own is not necessarily sufficient to demonstrate that a major accident cannot occur. Annex
VI includes criteria for notifying a major accident to the Commission which is not identical to criteria for defining
what is considered to be a major accident. It is important to highlight that the use of Annex VI described here is
limited only to the purpose of the assessment methodology. Respondents to the survey circulated to Seveso experts
and Competent Authorities during the initial phase of this project and participants at the project workshop have
indicated that using the criteria of Annex VI for defining a ‘major accident’ was not a suitable approach on its own.
However, it could provide a useful starting point and so assessors may wish to take these criteria into account, as
one of a number of elements, when drawing conclusions on whether a major accident is impossible in practice for
an Article 4 candidate substance.
5.3 Level of harm
One essential aspect of defining a major accident is deciding on the level of harm which is considered to represent
effects of a major accident.
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A review of some Member States’ practices by the JRC considered different levels of injury for different types of
dangerous phenomena. This review concluded that an ‘irreversible injury’ can correspond to lethality in some
Member States (e.g. Estonia and Poland see Table 3.4). Level 4 (irreversible injury) may in some instances be the
point at which accidents would have effects that equate to a major accident.
Choosing ‘reversible injury’ as the level of harm at which effects of an accident are considered major would be a
strict interpretation. The reversible effects threshold could be readily reached for almost any accident scenario,
even for substances without classification leading to coverage by the Seveso III Directive.
It is important that the level of harm defining a major accident in accordance with the assessment methodology is
agreed by Member States.
It is also important to take into account the overlap between the Seveso Directive, which covers major accidents,
and the harm that may occur as a result of industrial accidents which only affect a small number of workers on-site
covered by other occupational safety and health legislation in the EU (where accidents may not be major).
As a conclusion, for the assessment methodology, it is not considered that the scale of effects can be considered in
isolation. However, the review of member states’ approaches to defining levels of harm may be an element that
assessors wish to take into account in assessments under Article 4. Once again, member states and others are free
to use or disregard this information in their considerations under Article 4. The approaches considered in this
report are not binding or prescriptive.
5.4 Effects thresholds
The review of Member States’ practices has highlighted a range of existing thresholds for thermal radiation,
overpressure and toxic exposure that are used at national level for defining what constitutes a major accident and
for land use planning purposes. Two options are possible for taking these into account in the assessment
methodology:
Conduct the modelling phase of the assessment using the lowest threshold values for relevant effects
amongst the Member States. For example, this would mean that for modelling thermal radiation
effects, the Italian values for Level 3 (i.e. reversible effects) would be retained (3 kW/m2); or
An alternative is to use the default values that have been defined by the pan-European ARAMIS
project. In some cases, these values match those of the most stringent Member States. The advantage
of using the ARAMIS values is that these thresholds are likely to be more readily accepted by Member
States as representing a consensus view, rather than adopting a specific Member State’s approach.
For the assessment methodology, these values may be of use in deciding which effects thresholds should be used
when assessing the consequences of an accident involving a candidate for Article 4. However, once again,
assessors are free to adopt any other approaches that they consider appropriate, recognising that these will need to
be justified to, and accepted by, the Commission and other member states.
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5.5 Land use planning approaches
The review of Member States’ approaches to zoning and setting safety distances in the context of land-use planning
around Seveso establishments has highlighted a lot of variation.
Whilst it is recognised that safety distances used in the context of land use planning do not correlate directly with
distances at which a major accident is concluded to occur (or not), these approaches were covered in the project as
one of the only source of information with quantitative values related to distances and effects of accidents at Seveso
establishments. The aim was to determine whether and how these approaches might guide the interpretation of the
notion of ‘major accident’ in the context of Article 4.
In the context of the assessment methodology under Article 4, one approach would be for the reversible effect
distance from the modelling results to be compared to the shortest distance used in land use planning for similar
effects (as this would provide a more protective/conservative approach). The choice of the distance depends on the
type of substance under assessment and on the type of dangerous effects that may be generated. Reference distances
could mirror those used by Member States, an example of which is summarised in the table below (for Catalonia,
which has the shortest distances for the phenomena listed).
Table 5.1 Example of possible reference distances in the context of Article 4
Dangerous phenomenon Effects to consider Possible distance (m)
Toxic cloud Toxic effects 350
BLEVE Thermal and overpressure effects
200
Fires, explosions Thermal and overpressure effects
200
Flammable cloud, explosion, jet fire Thermal and overpressure effects
100
Pool fire Thermal effects 50
Spills causing pollution - 50
Source: Distances set by Spain (Catalonia)
If the modeled reversible effects distance is lower than the corresponding safety distance, it seems more likely that
a major accident cannot occur. If the reverse situation is observed (i.e. the modelled reversible effects distance is
higher than the corresponding safety distance), a major accident is less likely. However, these distances are clearly
too ‘blunt’ an instrument to be used directly in determining whether a major accident is possible. For example, a
dispersion causing toxic effects could clearly cause a major accident (and severely affect many people) at distances
far less than 350 metres.
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It is recognised that shorter distances used in the context of land use planning (e.g. for restriction of development)
are less ‘protective’ than greater distances. However, in the context of Article 4, if significant effects occur only up
to a short distance from the establishment (e.g. based on modelling of a worst-case scenario), this indicates
relatively lower potential for a major accident. In practice, choosing a distance at which no major accident hazard
is considered possible is a largely arbitrary exercise, and a case-by-case judgement will need to be made by the
assessor.
While the distances used in land-use planning amongst the member states give a useful indication of the range of
distances considered relevant for determining major accident potential, they are not in themselves directly relevant
in determining whether a major accident can occur or not.
It is apparent from the workshop for this project that many experts in the field do not consider land use planning
distances to be a suitable basis for determining whether a major accident can occur in practice. It is also clear that
there are not other reference distances available in the existing literature that allow one to determine – in a general
way – whether a modelled accident could be considered major or not. This is therefore an area where further work
may be required before any consensus can be reached on whether a modelled accident can be considered to be
major or not in the context of Article 4.
December 2014 Doc Reg No. 34075CA016i6
Appendix A References
Reports
ACUTEX, January 2006 , Methodology to develop AETLs
ARAMIS, 2004, Accidental risk assessment methodology for industries in the context of the Seveso II Directive,
WP2, Severity evaluation
Institute for Systems Informatics and Safety, 1999, Guidance on Land Use Planning as required by Council
Directive 96/82/EC (Seveso II)
Clément Lenoble, Clarisse Durand, Introduction of frequency in France following the AZF accident, Journal of
Loss Prevention in the Process Industries, 24 (2011) 227-236
JRC, 2005, Guidance on the preparation of a safety report to meet the requirements of Directive 96/82/EC as
amended by Directive 2003/105/EC (Seveso II), Institute for the Protection and Security of the Citizen
JRC, 2006, Land-Use planning Guidelines in the context of Article 12 of the Seveso II Directive 96/82/EC
JRC, 2007, Risk Mapping of Industrial Hazards in New Member States
JRC, 2008, Overview of Roadmaps for land-use planning in selected member States
Niks Jan Dujim, 2009, Acceptance Criteria in Denmark and the EU
I.A. Papazoglou, Quantitative Risk Assessment For Accidents At Work In The Chemical Industry And The Seveso
II Directive, System Reliability and Industrial Safety Laboratory
P.D. Petrolekas and A. Charalambous, 2001, Land use planning considerations in the context of Seveso II
Regulations
O. Salvi, Risk assessment in decision making related to land-use planning (LUP) as required by the Seveso II
directive
Pavel Danihelka and Pavel Forint, Land-use planning and the SEVESO II directive in the Czech Republic, Ministry
of the Environment, LabR!SK project
ShapeRisk Project, 2005, Synthesis document on WP2, Continuity of risk management from work place accident to
major accident
Presentations
Presentation by Themistoclis Kyriacou, Labour Inspection Officer, Department of Labour Inspection, Cyprus. Land
Use Planning around Seveso establishments and sitting of new Seveso establishments
December 2014 Doc Reg No. 34075CA016i6
Presentation by Priit Laaniste, Seveso II and land-use planning in Estonia, Estonian Ministry of the Interior, November 2007.
Presentation by Morten R. Østergaard, Danish EPA, Land use planning in the Habour area in the municipality of Aarhus,
DenmarkApplication of a Danish Administration Practice on Land Use Planning, 24 September 2012, Cyprus
Presentation by Robbert Plarina, 25 May 2011, Risk based External Safety Regulations in the Netherlands, Seveso
Conference Stockholm
Presentation by Hans-Joachim Uth , Zoning for Land use Planning in Germany and Europe, Federal Environmental
Agency Dessau (FRG)
RIVM, 2011, An international comparison of four quantitative risk assessment Approaches Benchmark study based
on a fictitious LPG plant
Guidelines
Advanced Technologies and Laboratories International, Protective action criteria,
http://www.atlintl.com/DOE/teels/teel/teel_pdf.html
American Environmental Protection Agency, Acute Exposure Guidelines Levels,
http://www.epa.gov/oppt/aegl/pubs/define.htm
American Industrial Hygiene Association, ERPG Guidelines, 2013 https://www.aiha.org/get-
involved/AIHAGuidelineFoundation/EmergencyResponsePlanningGuidelines/Documents/ERPGIntroText.pdf
European Centre for Ecotoxicology and Toxicology of Chemicals , http://www.ecetoc.org/index.php
Generalitat de Catalunya Departament d’Interior, Relacions Institucionals i Participació Direcció General de
Protecció Civil Subdirecció General de Programes en Protecció Civil, November 2009, Land use and spatial
planning: criteria for risk management
Health and Safety Executive, Toxicity levels of chemicals, http://www.hse.gov.uk/chemicals/haztox.htm
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