Analysis of Noncancer Health Risks Associated with Hazardous Air Pollutants

Abstract

Regulatory decisions made by the Environmental Protection Agency (EPA) concerning hazardous air pollutants (HAP) have been based primarily on quantitative assessments of cancer risk. Recently, however, more attention has been focused on effects other than cancer. The EPA has developed new methods to analyze the noncancer health risks associated with exposure to HAP. This paper discusses a newly developed method of analyzing short-term exposure to HAP and evaluating the public health risks resulting from these exposures. In the past, acute noncancer health effects were primarily analyzed on a screening basis. These analyses focused on the worst-case predicted ambient concentrations in comparison with health effects thresholds. Often several worst-case assumptions were factored into such analyses. When these analyses revealed an exceedance of the threshold (as was often the case) the degree of uncertainty was an unacceptable basis for regulatory decision making. The method presented herein represents a substantial improvement in EPA’s ability to analyze the effects of short-term exposure to HAP. Based on the expected exceedance methodology developed for the criteria pollutant program, this method has been adapted to estimate health risks associated with exposure to HAP in terms of expected exceedances of specified health effects thresholds.