WASHINGTON (02/23/05) -- The U.S. EPA has established an official reference dose (RfD) of 0.0007 mg/kg/day of perchlorate. This level is consistant with the recommended reference dose included in the National Academy of Science's January 2005 report. A reference dose is a scientific estimate of a daily exposure level that is not expected to cause adverse health effects in humans.

EPA's reference dose for perchlorate will be posted on the agency's online IRIS database, which contains risk information on possible human health effects from exposure to chemical substances in the environment. 

EPA's new RfD translates to a Drinking Water Equivalent Level (DWEL) of 24.5 ppb. A Drinking Water Equivalent Level, which assumes that all of a contaminant comes from drinking water, is the concentration of a contaminant in drinking water that will have no adverse effect with a margin of safety. Because there is a margin of safety built into the RfD and the DWEL, exposures above the DWEL are not necessarily considered unsafe.

Perchlorate has been used in various items, including missile and rocket propellants, munitions and fireworks, flares, automobile airbags and pharmaceuticals. It may also occur naturally and has been found in some fertilizer. Perchlorate has been detected in drinking water in some systems around the country, as well as in certain foods. 

EPA said its Superfund cleanup program plans to issue guidance based on the new RfD.

The perchlorate summary is available on the IRIS web site at: www.epa.gov/iris and at: ww.epa.gov/perchlorate.