An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »

Models and Tools Developed by EPA to Assess Hazard under TSCA

On this page you will find an explanation of the methods developed by EPA to predict hazard under the Toxic Substance Control Act (TSCA), with a link to user information.

Learn how to be trained to use these hazard assessment methods – and how to become eligible for expedited review -- through EPA’s Sustainable Futures Initiative.

Ecological Structure-Activity Relationships Program (ECOSAR): Uses quantitative structure-activity relationships (QSAR) to predict the toxicity of untested chemicals based on their structural similarity to chemicals for which aquatic studies are available.

Predictions are based on a library of class-based QSARs within the program overlaid with an expert decision tree for selecting the appropriate chemical class. The program estimates a chemical's toxicity potential based on short and long-term exposure for fish, invertebrates, and aquatic plants along with a limited number of methods for terrestrial and marine organisms.

OncoLogic: Uses mechanism-based structure-activity relationships (SAR) analysis to evaluate cancer potential of untested chemicals based on their structural similarity to chemicals for which studies have been conducted. The rules are incorporated into decision trees that are used along with user input for analysis.

Non-Cancer Health Effects Screening Protocol: Provides user with a procedure of identifying health effects data for the chemical of interest from various public databases and gives insight into various chemical classes associated with health effects of concern.

Analog Identification Methodology (AIM) : Designed to facilitate a data search on a chemical of interest in addition to identification of potential structural analogs and associated data which can be used to support read across approaches and data gap filling.

Chemical Assessment Clustering Engine (ChemACE): Instantly “clusters” chemicals in a large user defined chemical list based on structure. The tool is useful for identifying structural diversity in a chemical inventory and instantly highlighting analogous chemicals for potential read across.

EPA's New Chemical Categories Document: Designed to highlight EPA's accumulated experience in assessing particular substances with shared chemical and toxicological properties. Chemicals whose physical-chemical, toxicological and ecotoxicological properties are likely to be similar or follow a regular pattern as a result of structural similarity may be considered as a group, or ‘category’ of chemicals.