Policy Issues Related to Worst Case Risk Analyses and the Establishment of Acceptable Standards of De Minimis Risk

Abstract

Worst case analyses of risks become important whenever there are wide ranges of uncertainty surrounding estimated risks of technological applications, especially if environmental and societal impacts can reach catastrophic proportions. Risk may be defined as the possible consequences of a decision option times the probability of consequences materializing and special circumstances that may be involved.Increasingly severe magnitudes of consequences resulting from a technological option are sometimes accompanied by increasingly small probabilities that can reach de minimis, or insignificant, levels. Thus, a dilemma exists for policy development as to what the de minimislevel of probability is for those rare combinations of circumstances that can produce worst case consequences. One possible guide is the probability level of fatal accidents individuals routinely accept in their personal activities. Another is the establishment of safety-cost trade-off criteria that take into account equity considerations of the diverse opportunities for saving lives by the allocation of finite financial resources. On November 29, 1978, the Council on Environmental Quality issued implementing regulations for environmental impact statements (40 CFR 1502.22) requiring a worst case analysis, under certain conditions, and an indication of the probability of its occurrence. Difficulties and controversies in implementing the concept of worst case analysis have led the CEQ to reconsider this requirement (48 FR 36486, August 11, 1983). This paper explores a number of policy issues related to worst case analyses within a spectrum of high-consequence/low-probability events and the establishment of acceptable standards of de minimisrisk. Case material is used comparing the catastrophic risk of nuclear power plants with the chronic and accidental risks of using coal to generate electricity.