WHY RANK CHEMICALS BASED ON TOXICITY AND EXPOSURE POTENTIAL?
Health risks are a function of the total dose received by exposed populations from multiple pathways and media. Setting priorities based on chemical toxicity alone will not optimize risk reduction opportunities because substantial differences in the exposure potential of chemicals of similar toxicity are ignored. Substances that are rapidly degraded upon release to the environment are scored the same as substances with long half-lives, even though releases of persistent or bioaccumulative substances result in higher ambient concentrations and total human doses. Indicators of exposure potential can be developed by using measures that determine environmental concentrations of a chemical in different media (such as environmental persistence or bioaccumulation factors), or by using models that estimate the total dose humans acquire as a result of contact with different contaminated media. The best measure of dose would be derived from a comprehensive exposure assessment that addresses the
