Highly Anticipated Perchlorate Report Released
On Tuesday, January 11, 2005 the Committee to Access the Health Implications of Perchlorate Ingestion, convened by the National Research Council at the request of the EPA, DOD, NASA, and the DOE, released their report on the adverse health effects of perchlorate ingestion from clinical, toxicological and public health perspectives. The report also evaluated relevant scientific literature and key findings of the EPA’s 2002 draft risk assessment document on perchlorate. The full report can be found online here.
The committee noted that a no observed-effect level (NOEL) or lowest observed-adverse-effect level (LOAEL) identified from a critical study, is used as the basis for establishing a reference dose for daily oral exposures. The committee decided to use a NOEL rather than a LOAEL as the basis for perchlorate risk assessment. They based their reference daily dose on the identified critical study done by Greer, et al (2002)1 in which healthy men and women were given doses of perchlorate of 0.007 to 0.5 mg/Kg body weight per day for 14 days. In this study, the NOEL was found to be 0.007 mg/Kg/day. Using this amount and applying an uncertainty factor of 10 to protect the most sensitive population (identifi ed as pregnant women who may have hypothyroidism or iodide deficiency), the committee recommended a reference daily dose of perchlorate of 0.0007 mg/Kg of body weight per day from all sources. The EPA’s draft reference daily dose from the 2002 risk assessment was 0.00003 mg/Kg per day. The committee also noted that additional studies are needed, especially long-term, chronic exposure as well as clinical, mechanistic and epidemiological studies.
The release of the report generated a flurry of media reports with widely different safe drinking water levels touted – everything from maximum levels of 3 ppb to 200 ppb. However, as of February 18, 2005, the EPA has set an offi cial reference dose (RfD) of 0.0007mg/kg/day of perchlorate consistant with the National Research Council’s reference dose. The EPA translates the new RfD to a Drinking Water Equivalent Level (DWEL) of 24.5 ppb. As new information becomes available, CAS will post updates at www.caslab.com.
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1 Greer, M/A., G, Goodman, R.C. Pleus, and S.E. Greer. 2002. Health effects assessment for environmental perchlorate contamination: The dose response for inhibition of thyroidal radioiodide uptake in humans. Environ. Health Perspect. 110:927