APPLYING USEPA RISK ASSESSMENT GUIDANCE IN THE 90S

Over the past decade, risk assessment has become increasingly relied u pon for helping to make environmental management decisions. This trend has been accompanied by research and refinements in basic risk assess ment methodologies to improve our ability to understand and evaluate t he human health risks associated with chemical exposures. Despite this progress, significant uncertainties continue to be associated with th e risk assessment process. These uncertainties typically derive from g aps in available data regarding chemical toxicity, and from difficulti es in reliably estimating the magnitude of chemical exposures. Given t hese limitations, risk assessment is generally most valuable in evalua ting relative risk; for example, when comparing alternatives to achiev ing a specified goal, setting priorities for protecting human health, or establishing procedures for properly allocating resources. Risk ass essment can also be useful for developing regulatory benchmarks such a s permit limits for air or water. In many cases, however, the limitati ons of the risk assessment process make it difficult (if not impossibl e) to reliably estimate an absolute level of risk, especially for a sp ecific individual in an exposed population. In such cases, risk assess ment can be seriously misapplied, and its results misinterpreted. This paper discusses some of the challenges that have been faced by the fi eld of risk assessment during the 1990s. Current trends in risk assess ment, and its use by regulatory agencies in making risk management dec isions, are also described.