What Is the Risk of the Impossible?

The progression from risk identification to resolution through action or inaction on the part of investigators and policy makers is examined. The cases considered are ones where heated scientific and policy disagreement over the importance-and even the existence-of the risk agent persists or persisted throughout much of the process. Examples include cancer risks from extremely low doses of radiation and cancer from extremely low frequency electromagnetic fields. The decision making process followed in these case studies is explored and the extent to which caution on the part of policy makers may be considered reasonable or unreasonable is discussed. Each of these cases illustrates distinct aspects of the interplay between technical and societal responses to risk that are summarized by: a ban on the perceived risk agent; implementation of the best available technology; and risk assessment and communication. A number of conclusions are drawn that could facilitate a societal dialogue, including greater public participation in the scientific and policy evaluation stages, and the generation of improved guidelines and protocols to manage technological options and risks.