A semi-quantitative model for risk appreciation and risk weighing

Risk managers need detailed information on (1) the type of effect, (2) the size (severity) of the expected effect(s) and (3) the fraction of the population at risk to decide on well-balanced risk reduction measures. A previously developed integrated probabilistic risk assessment (IPRA) model provides quantitative information on these three parameters. A semi-quantitative tool is presented that combines information on these parameters into easy-readable charts that will facilitate risk evaluations of exposure situations and decisions on risk reduction measures. This tool is based on a concept of health impact categorization that has been successfully in force for several years within several emergency planning programs. Four health impact categories are distinguished: No-Health Impact, Low-Health Impact, Moderate-Health Impact and Severe-Health Impact. Two different charts are presented to graphically present the information on the three parameters of interest. A bar plot provides an overview of all health effects involved, including information on the fraction of the exposed population in each of the four health impact categories. Secondly, a Health Impact Chart is presented to provide more detailed information on the estimated health impact in a given exposure situation. These graphs will facilitate the discussions on appropriate risk reduction measures to be taken.