[CPEO-MEF] PERCHLORATE: EPA Inspector General's office reports

[Lenny Siegel <lennysiegel@gmail.com>]

EPA Office of Inspector
General Scientific Analysis of Perchlorate


Report No. 10-P-0101
April 19, 2010


What We Found

EPA should conduct a cumulative risk assessment to reduce the 
uncertainty in characterizing the public health risk posed by 
perchlorate. A cumulative risk assessment is the current 
state-of-the-art technique for evaluating the public health risk from 
multiple stressors. Over the last two decades, EPA has received numerous 
recommendations to improve environmental risk assessments. In 1997, EPA 
Administrator Carol Browner issued guidance directing EPA to embrace the 
cumulative risk assessment approach on all future major risk 
assessments. Although directed to improve the environmental risk 
assessment process, EPA continues to rely on the outdated single 
chemical risk assessment approach, originally developed in 1954, to 
characterize the risk posed by perchlorate. The single chemical risk 
assessment approach fails to address known sources of scientific 
uncertainty, which lowers the confidence in the perchlorate RfD.

Against established EPA risk assessment procedures, EPA derived the 
perchlorate RfD from a nonadverse biological effect instead of an 
adverse effect. The perchlorate RfD protects against all human 
biological effects from exposure, which is a stricter public health 
criterion than limiting environmental exposure to protect against 
adverse effects in humans. This shift in risk management constitutes a 
significant change in environmental policy.

Based on our scientific analysis, perchlorate is only one of several 
chemicals that stress the thyroid's ability to uptake iodide. The other 
sodium iodide symporter (NIS) stressors include thiocyanate, nitrate, 
and the lack of iodide. All four of these NIS stressors meet EPA's risk 
assessment guidance for conducting a cumulative risk assessment using 
the dose-addition method. Our analysis implemented a cumulative risk 
assessment that found the following: 1) the risk from each of the four 
NIS stressors is not equal; 2) EPA's perchlorate RfD is conservative and 
protective of human health, and further reducing the perchlorate 
exposure below the RfD does not effectively lower risk; 3) increasing 
maternal total iodide intake to healthy levels will reduce the frequency 
and severity of permanent mental deficits in children; and 4) correcting 
moderate and mild iodide deficiency occurring in about 29 percent of the 
U.S. pregnant and nursing population is the most effective approach for 
reducing risk.



To download the entire report, see
http://www.epa.gov/oig/reports/2010/20100419-10-P-0101.pdf

--


Lenny Siegel
Executive Director, Center for Public Environmental Oversight
a project of the Pacific Studies Center
278-A Hope St., Mountain View, CA 94041
Voice: 650/961-8918 or 650/969-1545
Fax: 650/961-8918
<lsiegel@cpeo.org>
http://www.cpeo.org



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