Determining optimal protective actions for nuclear incidents.

The U.S. Environmental Protection Agency is revising its Protective Action Guides (PAGs), which specify recommended dose levels at which actions should be taken to protect the public during an accident at a nuclear facility. The appropriateness of these PAGs depends on the health risks that could be avoided by the protective actions relative to both the costs and adverse health impacts of taking the actions. According to the optimization principle of radiation protection, the cost of measures designed to protect people from ionizing radiation should be commensurate with the risks avoided. This article evaluates the recommended protective actions with respect to the optimization principle. The evaluation is based on both recent radiation risk estimates and a derivation of the monetary value of a reduction in risk. It is estimated that evacuation of a population sector should be carried out only if the evacuation will reduce the collective dose equivalent to the population by 1 person-Sv or more for every U.S. +34,000 to +250,000 in net evacuation costs. Therefore, the decision to evacuate should be based on the dose that would be avoided by the evacuation and predetermined site-specific evacuation costs, rather than simply projected dose to the population. Findings further suggest that separate PAGs for the thyroid and skin are unnecessary for protecting against stochastic effects because use of the effective dose equivalent concept eliminates the need for these guides. Separate PAGs for specific organs need only ensure that significant nonstochastic effects are prevented.