Introduction to the updated CLEA framework reports Ian Martin, Land - PowerPoint PPT Presentation

Introduction to the updated CLEA framework reports Ian Martin, Land Contamination Policy Advisor

Next 60 minutes ● Background ● TOX guidance report (updated CLR9) ● CLEA report (updated CLR10) ● Focus on providing an overview and key changes

Land contamination in England ● Land may be contaminated by previous use, by diffuse pollution, or by its natural state ● Agency (2005) estimated that as many as 325000 sites may be ‘potentially affected’ ● Managing land contamination: 4 Planning regime 4 Part 2A 4 Other such as ‘due diligence’

Estimating risk to human health ● What level of exposure constitutes a minimal or tolerable risk to health? ● How likely is a person living or working on land contamination to be exposed to chemicals from soil?

Adopting a tiered approach Problem Formulation * Stages within each tier of Risk Assessment Hazard Identification Tier 1 Risk Screening * Risk Prioritisation Exposure Assessment Tier 2 Generic Quantitative Risk Assessment * Risk Estimation Tier 3 Detailed Quantitative Risk Assessment * Risk Characterisation Options Appraisal Economics Technology Social Issues Management Risk Management Collect data, iterate processes & monitor

CLEA project objectives ● To develop tools that provide a Government supported methodology that help estimate chronic health risks to people from soil contamination ● To provide generic assessment levels of contamination in soil below which these risks are considered minimal ● To provide a starting point to help assess risks, for instance under Part 2A of the Environmental Protection Act 1990

CLEA project and tools (caveats) h No legal requirement to use in assessing land contamination h Do not cover other types of risk to humans, such as fire, suffocation or explosion, drinking water, or short-term and acute exposures h Do not cover risks to the environment, such as groundwater, ecosystems or buildings h Do not provide a definitive test for telling when human health risks are significant

CLEA project outputs ● CLEA framework reports � Human health toxicological assessment of contaminants in soil (August 2008) � Updated technical background to the CLEA model (August 2008) � CLEA software version 1.03 beta and handbook ● TOX reports and SGV technical notes (in preparation) ● Supporting work � Compilation of chemical data and estimation methods (in preparation) � Vapour Handbook (in collaboration with CIRIA)

TOX guidance report ● Sets out toxicological basis and approaches to deriving health criteria values ● Updates and replaces CLR9 � Comprehensively re-written to improve clarity � Expanded explanation on reviewing tox data and guidance on multiple exposures / dealing with mixtures � Supported by Defra, HPA and FSA ● Defines health criteria values as levels of minimal or tolerable risk to health from long-term human exposure to chemicals in soil

Deriving health based guidance values Toxic effect Response Average man Test species Control LOAEL Sensitive NOAEL man UF UF 0 0 0.1 1 10 100 1000 Dose

Framework to derive HCV ● Collection of data ● Evaluation of data ● Reporting of data � Physical-chemical characteristics � Toxicokinetics � Toxicity � Background intakes ● Differences between threshold / non-threshold toxicity

Threshold and non-threshold toxicity A : Toxicant has no A B threshold. There is some Response risk at any level of exposure. B : Toxicant has a threshold. There is a finite dose below which adverse effects are not discernible. Dose

Threshold HCV h Tolerable daily intake (TDI) is an estimate of the daily intake of a chemical that can be experienced over a lifetime without appreciable health risk h TDI equals point of departure (e.g. NOAEL) divided by uncertainty factor and where possible derived for each exposure route h Existing HCVs should not be adopted naively (there is no hierarchy of sources or simple pick list) h TDSI is the TDI minus non-soil background exposure � MDI is mean daily intake by adults from non-soil sources � Child MDI corrected from adult MDI � Minimum of 50 per cent from soil sources � If no data or information on background exposure are available, assume background is negligible unless qualitative evidence suggests contrary

Non-threshold HCV h Index Dose (ID) is the estimate of the daily intake of a chemical that can be experienced over a lifetime with minimal cancer risk (ALARP principle applies) h Main derivation methods � Apply large UF to Bench Mark Dose (BMDL 10 ) derived from animal study (Defra, UF = 10000) � Quantitative dose-response modelling of human cancer data (Defra, 1 in 100 000 excess lifetime risk) h Threshold effects must also be considered and may drive risk h Comparison with other UK guidelines, it may be disproportionate to enforce a stricter limit for contaminated land than other media h Exceeding an HCV will result in increased risk to health

CLEA report h Replaces CLR10 and provides improved clarity, internal consistency and practical usability h Consolidates previous briefing notes and other guidance into a single report h Reconsiders the generic land-use scenarios and default assumptions used in the CLEA model to derive SGV h Updates the data sets and model algorithms used in the CLEA model based on recent scientific literature

CLEA Model Contaminated Land Exposure Assessment model HUMAN EXPOSURE TO FATE AND TRANSPORT OF CONTAMINANTS IN THE CONTAMINANTS IN SOIL SOIL ENVIRONMENT ENVIRONMENT Predicting how we Understanding and predicting behave on a how contaminants move within contaminated site each environmental according to land-use compartment - air, water, and and the extent to which soil this may lead to exposure to soil contamination for critical receptors (e.g. small children) EVALUATION OF THE RISK Judging the potential risks TO HUMAN HEALTH to health from exposure to ARISING FROM EXPOSURE contaminants in soil

Exposure pathways

Forwards and backwards FORWARD BACKWARD Define Define conceptual model conceptual model Estimate exposure Estimate exposure Mouth Nose Skin Mouth Nose Skin Determine Vary soil concentration contaminant until decision criteria concentration in soil are met from review of Compare with health Compare with health investigation data criteria value criteria value (TDSI or Index Dose) (TDSI or Index Dose) Collect exposure Collect exposure characteristics characteristics and chemical fate and chemical fate and transport data and transport data Decision made after Repeat until exposure comparison of exposure equals health criteria value and health criteria

Managing the uncertainty h Types of uncertainty include parameter, model and scenario uncertainty plus variability h Deterministic and stochastic approaches � Simple generic screening uses deterministic � Detailed assessment may benefit from stochastic h Moving away from maximal exposed individuals to reasonable or more realistic worst-case � Identify common activities or pathways likely to result in exposure and use reasonable worst-case estimates � Identify an unusual (but not unlikely) worst-case activity and use typical case assumptions

Generic land-uses – key changes h Residential � No residential with/without plant uptake � Homegrown produce based on general population � Default building type – small terraced house h Allotment � Children are still critical receptor � Homegrown produce based on high-end grower � No tracked back component h Commercial � Default building type – three storey office (pre-1970)

How much space do you need? h Growing area required for average population consumption rates used in the CLEA model for a family of four is: Annual Household Typical Yields Required Area Category (kg fw m -2 ) (m 2 ) Consumption (kg fw) Green vegetables 16.8 2.8 7.7 Root vegetables 5.7 4.7 1.7 Tuber vegetables 3.0 4.4 0.7 Herbaceous fruit 8.2 5.1 4.0 Shrub fruit 1.5 0.8 1.9 Tree fruit 7.8 1.8 3.9 19.9 h 85 per cent of residential gardens greater than 100 m 2 and 34 per cent greater than 450 m 2 (MAFF 1999)

Generic data sets – extensively revised h Chemical � Simplified (although property adjustments still required) h Soil � Eight soil types defined from UK soil LANDIS database h Human characteristics � Revised height and weight data from Health Survey 2003 � Revised skin area and inhalation rates based on Exposure Factor Handbook � Revised produce consumption rates in line with produce categories used by FSA’s PRISM model h Building � Nine building types based on BRE review

Soil ingestion and dermal contact h Soil ingestion no longer probabilistic distribution � Daily intake for children 100 mg day -1 � Daily intake for adults 50 mg day -1 � Preparation factor added to estimate soil attached to produce h Dermal contact � Briefing Note 1 incorporated � US EPA approach based on empirical absorption factor

Consumption of produce h Produce categories revised and expanded h Generic models are a back-stop to be used only in absence of real data � Inorganic chemicals based on PRISM � Organic chemicals based on suite following review of generic model performance