Assessing Exposure for Cumulative Risk Assessment. P. B. Ryan, Emory University, Atlanta, GA; and B. E. Mileson and S. S. Olin, ILSI Risk Science Institute, Washington, DC
Cumulative risk assessments offer a new and important challenge for the exposure assessor relative to single chemical/single medium assessments or even aggregate assessment of exposure to a single chemical. Cumulative risk assessment requires estimation of human exposure to multiple chemicals by multiple routes. Critical to the understanding of cumulative exposure is the need to estimate exposure to all chemicals of interest concurrently, both temporally and spatially. The toxicity profile of the group of chemicals to be evaluated will determine the appropriate time frame, reflect differences in potency of compounds within the group, and possibly provide the framework to account for correlations in the sources of exposure. Before initiating a detailed quantitative cumulative risk assessment, a qualitative assessment should be conducted to ensure that there is a reasonable likelihood of concurrent exposure to the group of chemicals under consideration. Models can be designed to use data on individual chemicals to estimate cumulative exposure using deterministic and/or probabilistic methodologies. Under ideal conditions cumulative exposure assessments would be based on representative sample data for all parameters identified as relevant to the exposures of interest, including exposures via food, water, and air. Data that can be used to characterize exposure to multiple chemicals by multiple routes may be unavailable, and in this case, surrogate data may be used. The presentation of the results of a cumulative exposure assessment should describe the estimated exposure and associated variability and uncertainty for each population, and should describe the contribution of different sources to cumulative exposure.
This work was supported through a cooperative agreement between ILSI RSI and the EPA OPP.
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