DR. ELIZABETH L. ANDERSON: Dr. Whipple has emphasized that risk assessment is on the rise because of policy needs, and I think this is certainly true. Two other points come to mind, and I think they are worth mentioning. First, as the number of our laws increased, scientists searched for their role in the public policy arena. Over time, scientists have become more cautious about making decisions to define a safe level of exposure in the face of scientific uncertainty. Policy makers and lawyers often press science for the answer to what is safe. When faced with considerable uncertainty, scientists are becoming less willing to make these judgments. Final decisions to define safety frequently cannot be based solely on scientific answers but rather must include social and economic considerations in deciding "safety" in terms of how much risk to accept.

In many cases, scientists have started to include threshold as well as non-threshold effects in risk assessment, thus tossing the decision about acceptable risk back to the policy arena for an increasing number of chemicals.