US EPA

The implementation of Superfund requires a methodology for estimating health risk from multi-chemical contamination at ambient levels. Most often, the chemical composition of these mixtures is poorly characterized, exposure data are uncertain and toxicologic data on the known components of the mixture are limited. However, a potential human health hazard may exist and the U.S.EPA, state and local governments need to be able to assess the total hazard in order to make decisions on appropriate action.

This report describes a procedure for assessing the risks from chemical mixtures that includes options when different kinds of data are available. Good-quality information on the mixture of concern or a similar mixture should always be used. Less desirable, but still useful approach, is to utilize data on components and their interactions. The quality of exposure and toxicity data must be determined and the uncertainties involved in each risk assessment must be thoroughly discussed. ater contamination is briefly discussed since it is of vital concern as the primary exposure medium for chemical mixtures. The methodology for estimating the human health risk from single chemicals, both carcinogens and systemic toxicants, is reviewed as it forms the basis for the assessment of mixtures.

Stara, J., J. Patterson, K. Blackburn, R. Hertzberg, AND C. DeRosa. Health Risk Assessment of Chemical Mixtures. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/D-89/028 (NTIS PB89222640), 1986.