EVALUATING TOXIC IMPACT ASSESSMENT METHODS - WHAT WORKS BEST

An analysis was conducted that tested the usefulness of four methods-t oxicity-based scoring, sustainable process index, concentration/toxici ty equivalency, and human toxicity potential-for assessing human healt h impacts of chemical emissions. Each assessment method uses a differe nt model with varying levels of complexity and sophistication to calcu late a toxic equivalency potential. This indicator is a ratio that exp resses human health risks associated with release of a toxic chemical relative to those of an equivalent, equally toxic release of a referen ce chemical. Predicted impacts of the compared toxicants depend on whe ther and how exposure is considered by each evaluation method. Relativ e toxicity scores produced by these methods vary by 3 orders of magnit ude when the same compounds are analyzed; thus, method selection is cr itical. The human toxicity potential method is preferred for comparing toxic emissions. Of the four methods investigated, it incorporates th e mast comprehensive approach to exposure assessment. Pollutants are r anked on the basis of health risks, assessed by using an explicit char acterization of total human exposure to a toxicant.