New Cost-Effective, Computerized Approachesto Selecting Chemicals for Priority Testing Consideration

Abstract

The Interagency Testing Committee (ITC) was established in 1976 under Section 4(e) of the Toxic Substances Control Act (TSCA). The ITC consists of representatives from 15 member and liaison agencies. The committee recommends chemicals to the U.S. Environmental Protection Agency (EPA) administrator for priority testing consideration and potential rule-making under Section 4(a) of TSCA. Between 1977 and 1983 the ITC conducted five scoring exercises to select existing chemicals for detailed review. These five scoring exercises focused on chemicals of regulatory concern, high-production chemicals, and chemicals recommended by other organizations. In 1986, in preparation for a sixth scoring exercise, we developed new approaches to selecting chemicals for review by the ITC. Expert panels were organized to identify substructures indicative of chemicals with potential to cause adverse health effects or adverse ecological effects. The expert ecological effects panel identified 109 organic chemical substructures that might cause adverse effects to any of eight organism types. These substructures were used to develop a questionnaire which was sent to 86 environmental chemists and toxicologists. Results from this questionnaire were used to reduce the list of substructures identified by the expert panel to 63 substructures with potential to cause adverse ecological effects in one to six organism types. These chemical substructures were used to search a data base of approximately 18 100 discrete organic chemicals. These searches identified about 5200 chemicals which might produce adverse ecological effects. The data base containing 18 100 chemicals was also searched for about 5300 chemicals that were in eleven computer-searchable, environmental-monitoring data bases. These searches identified about 2300 chemicals. The 2300 Chemical Abstracts Service (CAS) numbers for chemicals with potential for environmental exposure were compared with the 5200 CAS numbers for chemicals that might produce adverse ecological effects in order to identify matches. Over 100 chemicals were identified that had both the potential to cause adverse ecological effects and the potential for environmental exposure. A scoring system was developed to rank these chemicals. After obtaining available information on domestic production, many of these chemicals were screened by panels of toxicologists, chemists, ecologists, and engineers to select chemicals of environmental concern for detailed review by the ITC.