Assessing Risks to Human Health from Contamination: Decision-making Tools Ian Martin In the next 45 minutes

Illustrate the approach to development of Soil Guideline Values

Provide an update on recent work in the science programme (CLEA UK) Framework for Environmental Risk Management Problem formulation Stages within each tier of risk assessment

Hazard identification

Risk prioritisation Tier 1 Risk screening Identification of consequences

Tier 2 Generic quantitative risk Magnitude of assessment consequences

Tier 3 Detailed Probability of quantitative risk consequences Tiered risk assessment assessment

Significance of the risk

Options appraisal

Guidelines for Environmental Risk Assessment and Management Collect data, iterate processes Risk management (DETR, Environment Agency and IEH, 2000) and monitor Risks from

In the context of evaluating the risk posed by soil contamination, decision-makers need guidance on addressing two key questions:

for a given contaminant, at what level is human intake (from soil) no longer acceptable?

for a given land-use, what might be the typical contaminant intake for adults and children exposed to soil contamination R&D CLR 9, TOX, and Briefing Notes

R&D CLR 9

Framework for deriving Health Criteria Values Basic definitions including intake/uptake, threshold and non-threshold

Definitions of TDI and Index Dose Approach to non-soil background exposure

R&D TOX reports

CLEA Briefing Note 4

integration of assessments via two or more routes into the body Framework for Deriving HCV STEP 1 Chemical characteristics

STEP 2 LITERATURE REVIEW

TOXICITY BACKGROUND DATA EXPOSURE (MDI)

yes Threshold? TDI

no TDSI STEP 3 Index Dose

STEP 4 DERIVE Threshold versus non-threshold

A B A. Toxicant has no threshold, RESPONSE there is some risk at any (%) level of exposure

B. Toxicant has a threshold, there is a finite dose below which adverse effects are no longer discernible

DOSE (mg kg-1 bw d-1) Threshold effects

Tolerable daily intake (TDI)

an estimate of the amount of a contaminant, expressed on a body weight basis, that can be taken in daily over a lifetime without appreciable health risk

Non-soil background taken into account

Tolerable Daily Soil Intake = TDI - MDI Mean Daily Intake based on adult data TDSI calculated internally by the CLEA model 20% rule - if MDI greater than 80% of TDI Non-threshold Index Dose

A dose which can be considered to present minimal human health risk from exposure to soil contaminants

Minimal health risk (but not zero)

Soil considered independently of other sources

ALARP applies

Based on established standards/estimates such as from air or water, which convey a minimal risk (e.g. air quality or water standards derived by EPAQS or WHO) Integration

 CLEA Briefing Note 4  Assume health effects produced by chemical via different entry routes are additive  Do not ignore exposure via routes without HCV  Local action based on strong evidence

 Approaches to solving integration  Treat as simultaneous equation (additive indices)  Assume linear relationship between ADE and soil concentration Risks from Soil Contamination

In the context of evaluating the risk posed by soil contamination, decision-makers need guidance on addressing two key questions:

for a given contaminant, at what level is human intake (from soil) no longer acceptable?

for a given land-use, what might be the typical contaminant intake for adults and children exposed to soil contamination R&D CLR 10, SGV, and Briefing Notes

 R&D CLR 10  Framework for deriving Soil Guideline Values  Defines standard exposure scenarios based on land-use  Describes algorithms that estimate chemical concentration and exposure

 SGV reports

 CLEA Briefing Notes  Note 1: Revised approach to the dermal pathway  Note 2: Revised approach to the indoor air pathway  Note 3: Revised and extended definitions of building types  Note 4: An Update on Deriving Soil Guideline Values Based on Combined Intake from Individual Routes of Exposure

 CLEA 2002 and CLEA UK software Key components of the CLEA model

HUMAN EXPOSURE TO FATE AND OF CONTAMINANTS IN THE CONTAMINANTS IN SOIL SOIL ENVIRONMENT ENVIRONMENT

Predicting how we Understanding and behave on a predicting how contaminated site contaminants move within according to land-use each environmental and the extent to which compartment - air, water, this may lead to and soil exposure to soil contamination for critical receptors (e.g. small children) EVALUATION OF THE RISK TO HUMAN HEALTH ARISING FROM EXPOSURE

Judging the potential risks to health from exposure to contaminants in soil and setting an appropriate level for regulatory “intervention” Exposure pathways Accounting for variability SGVs and DQRA SGVs DQRA

Define Define conceptual model conceptual model Estimate exposure A Estimate exposure

Mouth Nose Skin Mouth Nose Skin Select contaminant Determine concentration in soil contaminant concentration in soil from review of Compare with health Compare with health investigation data criteria value criteria value (TDSI or Index Dose) B (TDSI or Index Dose)

Collect exposure Collect exposure characteristics characteristics and chemical fate and chemical fate and transport data and transport data Basis of Repeat until A = B Soil Decision Guideline Value Recent Developments

CLEA Team expanded in July / August 2005

Mark Hosford, Mammalian Toxicologist

Ian Martin, Exposure Modeller

Publications

SGV for Phenol

Briefing Note 4 on integration

Building Parameters report

Bioaccessibility Workshop report

CLEA UK CLEA UK - Design Specification  Accessibility  Free to the end-user  Easy to install and use (based on Microsoft Excel)  Layered access based on user experience  Flexible  Usable as part of GQRA and DQRA  Most parameters can be tweaked  New chemicals, land-uses, building and soil types can be added  Data can be shared by users using import / export functions  Comprehensive results output and file save options Probabilistic Modelling

 Computationally demanding approach

 Available add-ins for Excel are expensive and complex

 CLEA UK incorporates all the approach described in CLR10 and Briefing Notes

 Latin hypercube sampling used to speed up processing time Start with the Handbook CLEA UK - Run Options

The model can be run in generic assessment mode or site-specific assessment mode by selecting the appropriate button. The simulation can be run to derive a site-specific assessment criterion value in mg.kg-1 OR an ADE/HCV ratio by selecting the appropriate button. CLEA UK - Defining Criteria

You can select land- use, building type or receptor from the drop down menu.

Pathways can be selected or deselected as required for the simulation.

You must enter a pH and an SOM/TOC in the appropriate range to be able to progress to the next step of the wizard process. Selecting the Chemicals to Assess You can select contaminants from the drop down menu Select ‘add’ button to add a contaminant to the simulation Selections about Health Criteria Values & Routes of Entry and integrating assessment criteria cannot be made within this The selected section of the contaminants model. You must appear in the box. make these selections within the Chemical Library for user defined contaminants.

If you are running the simulation in ADE/HCV mode you will need to enter a representative site-specific soil concentration for each contaminant. If running model in ‘site-specific assessment mode’ a soil concentration value will not need to be entered. Reporting

The site name and any other details entered in Step1 of the The type of simulation selected in Step 2 CLEA wizard of the wizard (e.g. Generic Assessment will appear in criteria or Site-specific Assessment) will be displayed in this box. this box.

In site-specific assessment Contaminants selected in mode either a site-specific soil Step 4 of the wizard will The integrated oral and concentration or an ADE/HCV appear in this column. inhalation assessment ratio will be displayed, but not criterion is displayed in this both, depends on selection column. made in CLEA wizard. In generic assessment criteria mode only an ADE/HCV ratio will be displayed. The library land-use selected in step 3 of the Reporting CLEA wizard will be displayed in this box.

The land-use parameter values displayed in this screen will depend on the selections made in Step 3 of the CLEA wizard or if changes were made in the user value maintenance area these will be displayed instead.

The age class and receptors selected within Step 3 of the CLEA wizard will be displayed here. Reporting

The contribution from each pathway to the Average daily Values will only be presented for Dose (ADE) is displayed as a pathways which were selected in Step percentage and a dose. 3 of the CLEA wizard. If N/A is displayed this indicated the pathway was not selected. Adding A Chemical Adding a Concluding Remarks

SGVs are generic assessment criteria:

conceptual exposure models for standard land uses conservative assumptions for soil and chemical parameters which might affect exposure

toxicological assessments that represent a minimal or tolerable risk

CLEA UK supports DQRA within CLR framework.

Technical guidance is a tool to aid decision- making and will not remove uncertainty. Acceptability of Risk

UNSAFE UNSAFE Who decides? UNSAFE Unacceptable ?? UNSAFE What factors UNSAFE are considered? UNSAFE UNSAFE How is this SAFE SAFE decision SAFE Acceptable ?? communicated? SAFE SAFE “ Reports that say that something hasn't happened are always interesting to me, because as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns -- the ones we don't know we don't know. And if one looks throughout the history of our country and other free countries, it is the latter category that tend to be the difficult ones."

Donald Rumsfeld