Title: Planning Protective Action Decision-Making: Evacuate or Shelter-in-Place

Appropriate protective action recommendations or decisions (PARs/PADs) are needed to achieve maximum protection of a population at risk. The factors that affect protective action decisions are complex but fairly well documented. Protective action decisions take into account population distributions, projected or actual exposure to a chemical substance, availability of adequate shelters, evacuation time estimates, and other relevant factors. To choose in-place sheltering, there should be a reasonable assurance that the movement of people beyond their residence, workplace, or school will endanger the health and safety of the public more so than allowing them to remain in place. The decision to evacuate the public should be based on the reasonable assurance that the movement of people to an area outside of an affected area is in the best interest of their health and safety, and is of minimal risk to them. In reality, an evacuation decision is also a resource-dependent decision. The availability of transportation and other resources, including shelters, may factor heavily in the protective action decision-making process. All strategies to protect the health and safety of the public from a release of hazardous chemicals are explicitly considered during emergency decision making. Each institutional facility (such as hospitals, schools, day care centers, correctional facilities, assisted living facilities or nursing homes) in the community should be considered separately to determine what special protective actions may be necessary. Deciding whether to evacuate or to shelter-in-place is one of the most important questions facing local emergency planners responding to a toxic chemical release. That such a complex decision with such important potential consequences must be made with such urgency places tremendous responsibility on the planners and officials involved. Researchers have devoted considerable attention to the evacuation/shelter-in-place protection decision. While several decision aids have been developed, no single approach has achieved widespread acceptance based on validity, utility, and effectiveness (Ujihara 1989, Mannan and Kilpatrick 2000). In the absence of an agreed-upon methodology for making this decision, the best strategy for local emergency planners and officials is a thorough understanding of all the components affecting the decision. This paper summarizes what is currently known about the evacuation/shelter-in-place protection decision and points to available literature that more thoroughly explores the individual components of the decision. The next section summarizes the major issues in protective action decision process. This is followed by a discussion of all the factors that may bear on the protective action decision process. The final section address how to make a protective action decision.