The Office of Pollution Prevention and Toxics (OPPT), United States Environmental Protection Agency (EPA) is responsible for administering the Toxic Substances Control Act of 1976 (TSCA). Section 8(b) of TSCA requires the Agency to maintain an inventory of existing chemicals. The current TSCA inventory contains over 70,000 chemicals. From this inventory, a second inventory known as the Chemical Update System (CUS) was created. The CUS inventory contains those chemicals (8,651 as of 1991) in commerce with production volumes of greater than 10,000 pounds per year. Section 4 of TSCA provides for the review, testing, assessment, and regulation of existing chemicals. The screening of large inventories for the purpose of priority setting is time consuming and requires considerable resource time.
The Environmental Effects Branch (EEB) in OPPT is responsible for the environmental assessment of existing chemicals under Section 4 and new chemicals under Section 5. Since 1981, EEB has effectively used QSARs to estimate the inherent toxicity of new chemicals to the aquatic environment. The EEB currently has available 120 QSARs for estimating the acute and/or chronic toxicity values for aquatic vertebrates, invertebrates, and green algae.
In this paper, we propose the use of QSARs as screening tools to assess the inherent toxicity of the chemicals contained in subsets of the TSCA and CUS inventories to the aquatic environment. We will use existing triage and toxicity criteria in OPPT to identify those chemicals of greatest concern.