Development of Approaches for Cumulative Risk Assessment

Objective/Intended Use

This development project modifies existing approaches and generates new ones as needed to apply to cumulative risk (multiple chemicals, multiple exposure pathways and times). This methodology will be available for use in any cumulative risk assessment to help simplify the complexity and improve the feasibility of the effort while retaining the main drivers of the risk. The principle programs this effort will support include Superfund, Pesticides, Drinking Water and Air, although this project fits under the cross-cutting area of cumulative risk and is of high importance to EPA regional risk assessors. This project addresses the practical aspects and supporting tools of cumulative risk assessment, and is relevant to the Risk Assessment Forum project to develop a guidance document for cumulative risk assessment.

Develop a report on approaches for cumulative risk assessment (CRA), including screening and grouping methods and tools for assessing health risks to targeted populations from multiple chemicals from complex exposures. These approaches will enhance the feasibility of CRA by identifying exposure scenarios and chemical subsets with highest likelihood of joint toxicity. Overlapping exposure durations to single and multiple chemicals and overlapping exposures by multiple routes will be specifically addressed. The project will also extend current approaches and tools for CRA by: demonstrating that for many chemicals the scientific bases, methods, and models exist to assess multimedia, multipathway exposures and risks from multiple chemicals relevant to contaminated sites and situations and by developing methods for grouping chemicals and exposure pathways to make more feasible the assessment of overlapping exposures or effects caused by multiple exposure pathways over multiple timeframes.

Abstract

A population focused cumulative health risk assessment of a contaminated site or situation can include the evaluation of toxic risk from multiple chemicals, by multiple pathways, over different time frames of exposure, with multiple sensitive population subgroups, and possibly other factors. Approaches for screening or grouping contaminants or exposures help by reducing the complexity and resource requirements of a cumulative risk assessment in order to make it feasible. This project will develop and demonstrate methods to identify the subset of key components that are likely to drive the risk assessment. A variety of approaches will be used, including chemical properties and weight-of-evidence methods, for grouping chemicals, for quantifying toxicologic interactions, and for focusing on primary exposure scenarios.

Project Status

Work began in April 2001; a revised deadline of July 2004 has been negotiated with the IAG recipient. One example description has been received of screening for mixture risk applied to the Hanford site. Several EPA and outside resources have been identified and information on environmental chemistry has been gathered for most of the chemicals. Toxicity and toxicologic interaction data have been compiled. Completed are: draft mixture risk glossary, draft conceptual models, draft tox screening methods, draft fact sheets for mixture risk concepts and toxicity data on selected contaminants. A skeletal draft of the guidance has been developed.

Project Start Date

04/01/2001

Project Completion Date (Actual/Projected)

05/29/2007