CURRENT AND FUTURE RISK ASSESSMENT GUIDELINES, POLICY, AND METHODS DEVELOPMENT FOR CHEMICAL-MIXTURES

Humans are typically exposed to low doses of combinations of chemicals rather than to one or two chemicals at a time, yet most of the availa ble toxicity data provide information on single chemicals or binary pa irs, rather than on whole mixtures. The use of existing interactions s tudy data for the quantitative risk assessment of chemical mixtures is problematic. These studies generally lack the necessary statistical c haracterizations to be useful in quantitative risk assessment procedur es. The U.S. EPA developed guidelines for risk assessment for chemical mixtures in 1986 and is currently in the process of making revisions. Significant advances have been made in both the theoretical developme nt and application of procedures such as dose addition, response addit ion, toxicity equivalence factors, comparative potency and interaction s data characterizations. Details on the current revisions to the guid elines are given, along with information on the research efforts that have influenced these revisions or that represent future directions in chemical mixtures risk assessment.