Estimating health risks from natural hazards using risk assessment and epidemiology

Risk assessment is the process of estimating the likelihood that an adverse effect may result from exposure to a specific health hazard. The process traditionally involves hazard identification, dose-response assessment, exposure assessment, and risk characterization to answer "How many excess cases of disease A will occur in a population of size B due to exposure to agent C at dose level D?" For natural hazards, however, we modify the risk assessment paradigm to answer "How many excess cases of outcome Y will occur in a population of size B due to natural hazard event E of severity D?" Using a modified version involving hazard identification, risk factor characterization, exposure characterization, and risk characterization, we demonstrate that epidemiologic modeling and measures of risk can quantify the risks from natural hazard events. We further extend the paradigm to address mitigation, the equivalent of risk management, to answer "What is the risk for outcome Y in the presence of prevention intervention X relative to the risk for Y in the absence of X?" We use the preventable fraction to estimate the efficacy of mitigation, or reduction in adverse health outcomes as a result of a prevention strategy under ideal circumstances, and further estimate the effectiveness of mitigation, or reduction in adverse health outcomes under typical community-based settings. By relating socioeconomic costs of mitigation to measures of risk, we we illustrate that prevention effectiveness is useful for developing cost-effective risk management options.