Environmental risk assessment. Dr Stuart Dobson Centre for Ecology & Hydrology, United Kingdom

Transcription

1 Environmental risk assessment Dr Stuart Dobson Centre for Ecology & Hydrology, United Kingdom

2 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

3 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

4 Information needed for a full risk assessment: measured exposure concentrations from a range of habitats/ecosystems acute and sub-acute multiple endpoint/species effects data chronic multiple endpoint/species effects data field studies to give us. population effects data community effects data ecosystem effects data In practice, we have few if any of these

5 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

6 Simple principle of environmental risk assessment EXPOSURE EFFECTS Concentration Neither the exposure distribution nor the effects distribution are straightforward to determine

7 Default exposure estimation: initial estimate based on tonnage in a region simple models for degradation worst case dilution factors partition models bioaccumulation models Refined exposure estimation: base on specific industrial plants or receptors specific models for region geographical information incorporated monitoring

8 Concentrations of nonylphenol measured in water and sediment 10,000 Concentration µg/litre (µg/kg) 1, Predicted Environmental Concentration 0.01 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

9 Estimated exposure distribution Actual exposure distribution Exposure distribution relevant to particular organisms 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

10 Plot of acute lethal toxicity studies in fish for nonylphenol compared to sub-lethal NOECs for oestrogenicity Concentration µg/litre 1, 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 1 lethal sub-lethal

11 Plot of acute lethal toxicity studies in fish for nonylphenol compared to sub-lethal NOECs for oestrogenicity Concentration µg/litre 1, 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

12 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 factor ranging from 10 to 1000 depending on the data an uncertainty factor of 10 is always applied because of the very limited data set required

13 Concentrations of nonylphenol measured in water and sediment 10,000 Concentration µg/litre (µg/kg) 1, Lowest acute EC50 Lowest chronic NOEC PEC Predicted no observed effect (PNEC) 0.01 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

14 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?

15 Multiple scales

16 Plot of estimated and measured concentrations in surface waters and reported acute toxicity values for 2- butoxyethanol Concentration mg/litre 10,000 1, Expanding a limited dataset on exposure 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 E-005 PECs LC50 we are still only estimating true risk but increase our confidence in the result

17 We can use probabilistic methods where the dataset is adequate Log-logistic distribution of median lethal dose of 10 species with determined TLD5 from Baril et al. (1994)

18 Large datasets establish more reliable no-effect-concentrations concentration µg/litre Cu Cr As CCA algae invertebrates fish upstream downstream bioavailable bioavailable 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

19 Incorporation of biology and ecology into the risk assessment Beryllium SPECIES BODY WEIGHT (g fresh weight) ESTIMATED FOOD CONSUMPTION (g dry weight)* ESTIMATED FOOD AS % BODY WEIGHT * DIETARY COMPONENT EXPECTED MAXIMUM CONCENTRATION IN DIET (mg/kg dry weight) c WORST CASE ACUTE TOXICITY/ EXPOSUR E RATIO (TER) WORST CASE DIETARY CONSUMPTI ON (mg/kg/day) WORST CASE CHRONI C TERb deer, Chinese water Tree shoots deer, fallow Tree shoots deer, muntjac Tree shoots deer, red Tree shoots deer, roe Tree shoots deer, sika Tree shoots goat, feral Tree shoots hare, brown Grass hare, mountain Grass rabbit Grass vole, bank Grass vole, field Grass

20 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

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23 Species adapt to natural high concentrations of chemicals over time.. EXPOSURE NOT ADAPTED EFFECTS As ADAPTED Concentration Some communities of species with unique characteristics exist in concentrations of chemicals which would be lethal to un-adapted communities they may be of great conservation interest

24 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

25 Figure 9: Reported toxicity of fluoride to fresh water organisms 10 3 Concentration (mg fluoride/litre) * * * Algae: EC50 Algae: LOEC Algae: NOEC Invertebrates: LC50 Invertebrates: LOEC Invertebrates: NOEC Invertebrates -"Safe concentration" Fish: LC50 Fish: LOEC Fish: NOEC Fish - "Safe concentration" * - chronic Fish behaviour LOEC 10-1

26 Figure 5: Reported concentrations of fluoride in surface waters 10 2 Concentration (mg fluoride/litre) seawater fresh water; background fresh water; geothermal/volcanic fresh water; local industrial 10-3

27 Figure 7: Reported concentrations of fluoride in soil 10 4 Concentration (mg fluoride/kg) Natural: total Natural: water soluble Anthropogenic: total Anthropogenic: water soluble

28 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