Environmental risk assessmentDr Stuart DobsonCentre for Ecology & Hydrology, United Kingdom

Reasons for doing international environmental risk assessment:

• high exposure or tonnage production• regional or national contamination• local “hot spots”• transboundary concerns• susceptible populations• “problem” chemicals • global contamination or key ecosystem dysfunction

“the ultimate key aim of [environmental]risk assessment is to prevent further chemicals from becoming major problems by applying lessons learnt at the population and ecosystem end of the spectrum to the lower, screening stages”

Information needed for a full risk assessment:

• population effects data• community effects data• ecosystem effects data

In practice, we have few if any of these

• measured exposure concentrations from a range of habitats/ecosystems

• field studies to give us ….• chronic multiple endpoint/species effects data• acute and sub-acute multiple endpoint/species effects data

Achievable objectives:• international harmonisation on the basic approach (OECD)

• screening of chemicals against a basic set of information

• an estimated “no-observed-effect” concentration

• a predicted “protective” concentration for populations/communities (PNEC)

• a predicted environmental concentration (PEC)

• expression of risk as a ratio PEC/PNEC

Concentration

EXPOSURE EFFECTS

Simple principle of environmental risk assessment

Neither the exposure distribution nor the effects distribution are straightforward to determine

Default exposure estimation:

Refined exposure estimation:

• initial estimate based on tonnage in a region• simple models for degradation• worst case dilution factors• partition models• bioaccumulation models

• base on specific industrial plants or receptors• specific models for region• geographical information incorporated• monitoring

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St Su M E Se

St: surface water (effluent in area is treated) Su: surface water (effluent untreated or unknown)M: estuarine and marine water E: sewage effluent (treated or untreated) Se: sediment

Concentrations of nonylphenol measured in water and sediment

Predicted

Environmental

Concentration

Estimated exposure distribution

Actual exposuredistribution

Exposure distributionrelevant to particularorganisms

• mostly our estimates of environmental concentration are substantially higher than reality

• we can predict locally better than regionally or nationally

• regulators use the conservative worst case to encourage industry to measure levels in the environment

• very little monitoring of chemicals in water, soil etc. is performed globally

• of the monitoring which is done, much of the information is not readily available to IPCS

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ePlot of acute lethal toxicity studies in fish for nonylphenolcompared to sub-lethal NOECs for oestrogenicity

lethal sub-lethal

The effects distribution:• we more usually have acute than longer-term data

• it is a distribution of effects on a limited range of common test species

• it is strongly biased towards temporate climates

• we usually have few data points

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ePlot of acute lethal toxicity studies in fish for nonylphenolcompared to sub-lethal NOECs for oestrogenicity

lethal sub-lethal

Acute to chronic and lethal to sublethal:• commonly we know little of the chronic effects of chemicals

• few endpoints are studied in standard testing

• when sub-lethal endpoints are measured, there are often highly significant effects at concentrations much lower than lethal

We deal with limited data by applying uncertainty factors:• internationally agreed schemes require basic test data for three trophic levels – algae, invertebrates and fish

• lack of any part of the data set attracts an uncertainty factorranging from 10 to 1000 depending on the data

• an uncertainty factor of 10 is always applied because of the very limited data set required

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Concentrations of nonylphenol measured in water and sediment

Lowest acute EC50

Lowest chronic NOEC

Predicted noobserved effect (PNEC)

PEC

With these limitations, what can we achieve?• can we even be confident about risk assessment for well studied chemicals?

• what is the real risk from nonylphenol, for example?

• can we help countries world wide to inform their risk management?

• what have we attempted to do in the IPCS Programmes to overcome the limitations?

Multiple scales

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Plot of estimated and measured concentrationsin surface waters and reported acute toxicity values for 2- butoxyethanol

• only a single measured concentration available

• information on all manufacturing sites in the USA

• the range of toxicity can be compared to modelled concentrations for all sites to give a range of risk factors

• we are still only estimating true risk but increase our confidence in the result

Expanding a limited dataset on exposure ……

Log-logistic distribution of median lethal dose of 10 specieswith determined TLD5

from Baril et al. (1994)

We can use probabilistic methods where the dataset is adequate

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algaeinvertebratesfishupstreamdownstreambioavailablebioavailable

Cu Cr As CCA

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Large datasets establish more reliable no-effect-concentrations …

• the large datasets for copper, chromium and arsenic can establish “true” NOECs

• we can combine measured concentrations to establish risk of copper chrome arsenate wood preservatives

• estimates from the IPCS documents allow us to calculate likely bioavailability to organisms

Incorporation of biology and ecology into the risk assessment …

Beryllium

0.80.1245144.61Grass12.44.435.5vole, field

0.70.1335134.91Grass13.33.224vole, bank

1.60.0632284.81Grass6.3101.11600rabbit

1.70.0572314.61Grass5.7160.22800hare, mountain

1.80.0555324.51Grass5.5184.73330hare, brown

0.30.346651.910Tree shoots3.51620.446750goat, feral

0.30.393545.710Tree shoots3.9902.122925deer, sika

0.30.393045.810Tree shoots3.9907.723100deer, roe

0.40.267667.310Tree shoots2.75352.0200000deer, red

0.20.432441.610Tree shoots4.3583.713500deer, muntjac

0.30.336253.510Tree shoots3.41865.855500deer, fallow

0.20.424942.410Tree shoots4.2633.014900deer, Chinese water

WORST CASE CHRONIC TERb

WORST CASE DIETARY CONSUMPTION (mg/kg/day)

WORST CASE ACUTE TOXICITY/EXPOSURE RATIO (TER)

EXPECTED MAXIMUMCONCENTRATION IN DIET (mg/kg dry weight) c

DIETARY COMPONENT

ESTIMATED FOOD AS % BODY WEIGHT *

ESTIMATED FOOD CONSUMPTION (g dry weight)*

BODY WEIGHT (g fresh weight)

SPECIES

If we have a large enough dataset ….

• we can estimate which species are affected at particular concentrations

• we can define what effects are likely to be seen on communities

Concentration

EXPOSURE EFFECTSNOT

ADAPTED

As

ADAPTED

Species adapt to natural high concentrations of chemicals over time …..

Some communities of species with unique characteristics exist inconcentrations of chemicals which would be lethal to un-adapted communities – they may be of great conservation interest

There are limitations on what advice we can give from the international programmes …

• we might have the range of effects data to estimate toxicity

• we often don’t have enough local exposure data to estimate risk

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Algae: EC50Algae: LOECAlgae: NOECInvertebrates: LC50Invertebrates: LOECInvertebrates: NOECInvertebrates -"Safe concentration"Fish: LC50Fish: LOECFish: NOECFish - "Safe concentration"* - chronicFish behaviour LOEC

Figure 9: Reported toxicity of fluoride to fresh water organisms

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seawaterfresh water; backgroundfresh water; geothermal/volcanicfresh water; local industrial

Figure 5: Reported concentrations of fluoride in surface waters

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Natural: totalNatural: water solubleAnthropogenic: totalAnthropogenic: water soluble

Figure 7: Reported concentrations of fluoride in soil

Conclusions …..

• we can aid countries globally with information to aid risk assessment and risk management

• we could provide better assessment with local information from a range of countries

• exposure data are particularly difficult to obtain

• collaboration to make local information available to the international programmes is invaluable