Contaminated land: dealing with hydrocarbon contamination Assessing risks to human health

Contents of presentation

  CLEA and hydrocarbon-contaminated sites Alternative risk assessment approaches – what options are there?

– – – Method selection Dutch screening values, SNIFFER, RBCA, RISC Workbench, Risc-Human Evaluation Environmental Simulations International

CLEA – a reminder

 Application: determination of Soil Guideline Values for human health in relation to long-term (chronic) exposures to contaminated soil – – For the specified conceptual models Using the specified algorithms Previous CIEH training Environmental Simulations International

CLEA – available tools

   Main reports (CLR 7, 8, 9 and 10) Daughter reports for individual substances – Presently, those of main relevance to hydrocarbon-contaminated sites are the documents for lead and benzo[a]pyrene  A particular hassle for carcinogens CLEA software Environmental Simulations International

CLEA does not

      Function directly as a site-specific risk assessment tool – But the algorithms, exposure parameters and toxicity data can be so used Assess human health risks by all potential pathways Deal with acute exposures (except cyanide) Help in CDM and related assessments Assess risks to other receptors Replace expert judgement Environmental Simulations International

A note on contaminant sources in CLEA

    At surface for soil ingestion, dermal contact, inhalation of dust Directly beneath base of building – Directly under house (for indoor inhalation of vapour) At 1 m depth for outside inhalation of vapour Assumed to be in equilibrium Do these match with the conceptual model for your hydrocarbon-contaminated site?

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Some questions on the exposure calculations

    Are all of the pathways there?

– Groundwater transport isn’t Are the vapour transport algorithms appropriate for the conceptual model Does the dermal uptake algorithm give a suitable assessment for hydrocarbons Is the plant uptake algorithm suitable?

– e.g., US EPA PAH adjustment They may be no problem but we must ask the questions!

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Surf ace Soils Subsurf ace Soils Groundw ater Plant Uptake

A small selection of exposure pathways!

Ingestion by Liv estock Ingestion of Meat Ingestion of Vegetables Soil Ingestion Ingestion of Milk Ingestion of Soil on Vegetables Soil Dermal Contact Ingestion of Eggs Wind Erosion Volatilisation Leaching Atmospheric Dispersion (Dust) Dust Inhalation Atmospheric Dispersion (Vapours) Enclosed Space Accumulation Inhalation of Vapour Ingestion of Suspended Matter Dif f usion into Water Supply Pipes Groundwater Transport Irrigation Discharge to Sea Spray ed Water Ingestion Drinking Water Ingestion Swimming Water Ingestion Seawater Dermal Contact Ingestion of Fish Environmental Simulations International Dust Ingestion Dermal Contact of Suspended Matter Spray ed Water Dermal Contact Shower Water Dermal Contact Swimming Water Dermal Contact Ingestion of Crustacea Dust Dermal Contact Spray ed Water Vapour Inhalation Shower Water Vapour Inhalation Swimming Water Vapour Inhalation Ingestion of Seaweed Ingestion of Freshwater Fish

Groundwater transport and human health?

  In the UK, for risks associated with ground/surface water ingestion, we cannot use a risk-based approach to determine drinking water concentrations – Maximum contaminant concentrations are set out in the Water Regulations (2000) Assessment may also be required when hydrocarbons enter the water source directly or by permeation through pipework Environmental Simulations International

Alternative risk assessment options?

 “ the local authority should be prepared to reconsider any determination based on such use of guideline values if it is demonstrated to the authority’s satisfaction that under some more appropriate method of assessing the risks the local authority would not have determined that the land appeared to be contaminated land.” Environmental Simulations International

Toxicity assessment: carcinogens

  UK & Netherlands uses the Index Dose – The dose which can be considered to present a minimal human health risk from exposure to soil contaminants  Although NL exposure factors are very different US uses the slope factor method – Determines the dose at which there is an acceptable risk of incidence (usually 1 in 10 5 10 6 )  Not accepted by the DoH or Environmental Simulations International

A note on the Dutch screening values

  Easily and widely used – And plenty of hydrocarbon components But – – – Certain pathways only Based on different exposure periods and assumptions to UK approaches Have they been adjusted for the right soil type?

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SNIFFER

  SNIFFER report LQ01 – Guide to good practice for the development of conceptual models and the selection and application of mathematical models of contaminant transport processes in the subsurface [SNIFFER, 2003] Algorithms similar to CLEA but uses some alternatives that may be of interest for hydrocarbon sites  Examples: vapour transport, plant uptake – – Standard land uses directly Other land uses by application of parameters and algorithms Environmental Simulations International

SNIFFER

  Can be used to derive site-specific assessment criteria – Site-specific risk assessment tool (worksheet-based)  Standard land uses directly  Other land uses by application of parameters and algorithms Do not use: – When there is a relevant SGV – – – To derive SGV’s When CLEA can do the same job When the conceptual model makes it inappropriate Environmental Simulations International

RBCA

     ASTM RBCA standard (E2081-00) – Very widely used – Well-documented – US parameters But slope factors are used to determine carcinogenic risk Deterministic Includes soil vapour transport model Includes groundwater transport Environmental Simulations International

RBCA Tool Kit: transport models

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RISC Workbench (BP RISC)

       Compatible with/extends RBCA methodology Slope factors are used to determine carcinogenic risk Good range of defaults for contaminants, aquifers & soil types Probabilistic assessment for many variables Models can be used with stationary free phase contaminants Includes a soil vapour transport model Includes groundwater transport Environmental Simulations International

Risc-Human

      Index Dose is used to calculate risks from genotoxic carcinogens Comprehensive list of pathways & targets Includes a soil vapour transport model Can use subsites and scenarios to store different model runs Large range of organic compounds Probabilistic assessment for many variables Environmental Simulations International

Or a self-coded model?

    Infinitely flexible – Chose the appropriate algorithms Can do probabilistic modelling – Own codes or commercial add-ins  But CLEA PDF’s proprietary QA/QC must be robust Needs good communication with all participating parties Environmental Simulations International

So, which is the right method?

    We can’t tell you – there isn’t a right answer The appropriate risk assessment methodology depends on the conceptual model – Hydrocarbons and other contaminants of concern – Pathways – Suitable algorithms… Beware inappropriate parameterisation Beware inappropriate TDSI and Index Doses – Especially the latter from non-UK sources Environmental Simulations International

Conclusions

   The best tool for any risk assessment job is that with the appropriate conceptual model and sufficient flexibility to enable use of site-specific parameters A wide range of methodologies exist to quantify risks to human health Each has its own approach for the source, exposure routes, transport processes and receptors – Different simplifications – – Different processes Sometimes these differences are subtle, but can lead to significantly different results Environmental Simulations International

Risk assessment methods - some things to question

       Does the user understand the underlying assumptions and conceptual models in the methodology?

Calculation of risk from non-threshold substances The right pathways Reasonable UK exposure parameters Critical receptors Appropriate algorithms (and why chosen) Probabilistic modelling Environmental Simulations International