Toxicology Testing in the 21st Century (Tox21)

Toxicology in the 21st Century (Tox21) is a federal collaboration among EPA, NIH, including National Center for Advancing Translational Sciences and the National Toxicology Program at the National Institute of Environmental Health Sciences, and the Food and Drug Administration. Tox21 researchers aim to develop better toxicity assessment methods to quickly and efficiently test whether certain chemical compounds have the potential to disrupt processes in the human body that may lead to negative health effects. One of EPA’s contributions to Tox21 are the chemical screening results from the Toxicity Forecaster (ToxCast). Learn more about the mission and goals of the Tox21 program.

Using a high-throughput robotic screening system housed at NCATS, researchers are testing a collection of 10,000 environmental chemicals and approved drugs (called the Tox21 10K library) for their potential to disrupt biological pathways that may result in toxicity. The team prioritizes promising compounds identified from primary screening for further in-depth investigation. Learn more about how the Tox21 program works.


Since Tox21’s inception in 2008, the collaborative research team has developed and validated in vitro cell-based assays (tests) using quantitative high-throughput screening. The researchers have identified, developed, optimized and screened more than 100 assays (tests).

The Tox21 program includes two research phases, structured with guidance from two reports: Toxicology in the 21st Century: The Role of the National Toxicology Program and Toxicity Testing in the 21st Century: A Vision and a Strategy (PDF) (4 pp, 418 K, About PDF)Exit

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