Tox21 is a collaboration among multiple federal Agencies—EPA's National Center for Computational Toxicology, the National Institutes of Environmental Health Sciences (NIEHS)/ National Toxicology Program (NTP), the NIH Chemical Genomics Center (NCGC) and the U.S. Food and Drug Administration (FDA)—working together to develop, validate and translate innovative, high-throughput screening (HTS) chemical testing methods to characterize key steps in toxicity pathways. The goals of the "Tox21 Community" are to investigate the use of these new tools to prioritize substances for further in-depth toxicological evaluation, identify mechanisms of action for further investigation, and develop predictive models for in vivo biological response.

The Tox21 chemical inventory represents a central pillar of the Tox21 project and is unprecedented in its scope, structural diversity, multiple use-scenarios (e.g., pesticides, industrial, food-use, drugs, etc.), and chemical feature characteristics in relation to toxicology. The library consists of approximately equal contributions of more than 3000 physical compound samples mostly procured from commercial sources by each of three Tox21 partners—EPA, NTP, NCGC—for a total of over 10,000 plated compound solutions, spanning more than 8,400 unique chemical substances. Tox21 compounds were selected based on a wide range of criteria, including, but not limited to: environmental hazard or exposure concern based on production volume (industrial chemicals) or occurrence data, availability of animal toxicity study data, food-additives, fragrances, toxicity reference chemicals, and drugs or known bioactive compounds. Additional criteria for chemical selection included physical chemical calculated properties suitable for HTS (MW, volatility, solubility, logP), commercial availability and cost, and DMSO solubility.

To provide user-friendly access to the Tox21 chemical inventory in its entirety, we have developed a dedicated software—the Tox21 Chemical Browser—with enhanced support for browsing and searching of chemical structures. The scope of the browser will eventually expand to support bioassay data as they become available.



File Platform Size MD5 checksum
Tox21ChemBrowser_windows_1_1.exe Windows 20.8 MB 22d87c3613b314e96eaddb5c66f627c9
Tox21ChemBrowser_macos_1_1.dmg Mac OS X 21.1 MB 9d113e43f9f5b61e630274b02249bedb Linux 20.6 MB 809b245729d499fd66032257cfaad118


Please forward all questions and/or comments concerning the data and/or software to Dr. Ruili Huang.

Ver. Date Changes
1.1 Dec 9, 2011
  • Update content to DSSTox v1a
  • Add stereo filters
  • 1.0 Dec 7, 2011 Initial release