SETTING EXPOSURE STANDARDS - A DECISION-PROCESS

Increased emphasis on routine screening of chemicals for potential neu rotoxicity has resulted in the development of testing guidelines and s tandardized procedures. A multiphased, tiered-testing strategy has bee n proposed by numerous expert panels to evaluate large numbers of chem icals. In a regulatory context, however, a formal tiered-testing appro ach is not used, mostly because of the constraints of differing regula tory authorities and the potential cost of such a testing strategy. In stead, current regulatory decision making utilizes all available anima l and human data to identify a critical adverse effect which is then u sed for setting standards. Although the current decisionmaking process does not use a formal tiered-testing approach, it appears to identify chemicals with neurotoxic effects. An analysis of U.S. Environmental Protection Agency integrated risk information system (IRIS) indicates that about 20% of the chemicals having standards or health advisories are based on neurotoxicity.