HazDat, the Agency for Toxic Substances and Disease Registry's Database, is a scientific and administrative database designed "to provide access to information on the release of hazardous substances from Superfund sites or from emergency events and on the effects of hazardous substances on the health of human populations." Most recently updated in mid-January, 1998, the HazDat database includes information on site characteristics, contaminants, exposure rates, and the environmental fate of hazardous substances. In addition, HazDat contains substance-specific information such as metabolites, interactions of substances, susceptible populations, and biomarkers of exposure and effects, among others. Additional data are included from the US Environmental Protection Agency (EPA) Comprehensive Environmental Response, Compensation, and Liability Information System (CERCLIS) database, and thus include site CERCLIS number, site description, latitude/longitude, operable units, and other site information.