Chemical selection by the Interagency Testing Committee: use of computerized substructure searching to identify chemical groups for health effects, chemical fate and ecological effects testing.

Since 1977, the Interagency Testing Committee has convened over 300 meetings, issued 27 semi-annual reports to the Administrator of the US Environmental Protection Agency, screened about 26,000 chemicals, reviewed about 4,500 chemicals and recommended between 5000 and 7600 health effects, chemical fate or ecological effects tests for 114 chemicals and 27 chemical groups. The Committee has used three chemical selection processes to screen and identify chemicals for priority testing consideration. From 1977 to 1980, the Committee's processes consisted of examining large lists of chemicals and designating chemical categories that satisfied generic definitions. From 1980 to 1989, the Committee used sequential exposure and biological scoring processes followed by in-depth review. Since 1989, the Committee has used computerized processes to identify chemical groups that are associated with potentials to cause adverse health or ecological effects or that are likely to involve occupational or environmental exposure and that have common substructures, uses, testing information deficiencies, risk assessment uncertainties, etc. This paper focuses on use of the computerized processes to identify chemical groups containing common substructures that are associated with potentials to cause adverse ecological effects. The purpose of this paper is to describe how: (i) chemical substructures are selected, (ii) substructures are used to identify chemical groups, (iii) groups are processed, and (iv) reliability of the processes that were used to select chemical substructures are being assessed.