TOXNET is a system of toxicology and environmental health databases developed by the National Library of Medicine. It contains 5 main data files on hazardous substances, chemical carcinogenesis, mutagenicity studies, integrated risk information, and international toxicity estimates. It also contains two literature databases and databases on toxic chemical releases and a chemical dictionary. Users can search individual databases or conduct multi-database searches to find toxicity, health effects, and other information about chemicals.