The Hazardous Air Pollutant Prioritization System

Abstract

The Hazardous Air Pollution Prioritization System (HAPPS) is used to rank toxic air pollutants as the first step in the Environmental Protection Agency’s regulatory assessment under the Clean Air Act. The purpose of this exercise is to assist in setting the priorities for assessment and focus resources on the chemicals with the greatest potential for public health risks. The HAPPS has evolved over several years based on a system developed at the Oak Ridge National Laboratory and later modified at Argonne National Laboratory. The current system can be run on a personal computer and focuses on air pollutants rather than multimedia exposures. It is designed to rank large numbers of chemicals based on limited, readily available information. Ranking is based on health information and surrogates for population exposure. More specifically, substances are scored on eight factors: oncogenicity, mutagenicity, reproductive and developmental toxicity, acute lethality, other toxic effects, the potential for airborne release (production volume and volatility), bioaccumulation and existing standards. The system possesses a somewhat flexible ranking scheme that can be easily modified to reflect different issues such as concern for acute exposures and the impact of combustion sources on exposure.