EPA's Integrated Risk Information System (IRIS) is a database that contains potential adverse human health effects information that may result from chronic (or lifetime) exposure to specific chemical substances found in the environment. The database (available on the Internet at <http://www.epa.gov/iris> contains qualitative and quantitative health effects information for more than 500 chemical substances that may be used to support the first two steps (hazard identification and dose-response evaluation) of a risk assessment process. When supported by available data, the database provides oral reference doses (RfDs) and inhalation reference concentrations (RfCs) for chronic health effects, and oral slope factors and inhalation unit risks for carcinogenic effects. Combined with specific exposure information, government and private entities can use IRIS data to help characterize public health risks of chemical substances in a site-specific situation and thereby support risk management decisions designed to protect public health.