[CPEO-MEF] EPA Sets Reference Dose for Perchlorate

[Lenny Siegel <lsiegel@cpeo.org>]

NEWS RELEASE
U.S. EPA

EPA Sets Reference Dose for Perchlorate

Contact: Cynthia Bergman <bergman.cynthia@epa.gov>

(Washington, D.C.-February 18, 2005) EPA has established an official
reference dose (RfD) of 0.0007 mg/kg/day of perchlorate. This level is
consistent 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, which assumes total intake from both water and
food sources, is appropriate and protective for all populations,
including the most sensitive subgroups. The selected reference dose
contains a full ten-fold uncertainty factor to protect the most
sensitive population, the fetuses of pregnant women who might have
hypothyroidism or iodide deficiency. This uncertainty factor also covers
variability among other human life stages, gender and individual
sensitivities, protecting not only adults, but also other sensitive
subpopulations such as premature neonates, infants and developing children.

Perchlorate exposure has the potential of blocking iodide uptake to the
thyroid gland. NAS identified the non-adverse effect of the inhibition
of iodine uptake as the key biochemical event that precedes the
occurrence of all potential adverse effects of perchlorate exposure.
EPA's RfD is conservative and health protective because it is designed
to prevent the occurrence of any biochemical changes that could lead to
adverse health effects.

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.

EPA's Superfund cleanup program plans to issue guidance based on the new RfD.

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. 

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

For the original press release, go to http://yosemite.epa.gov/opa/admpress.nsf/b1ab9f485b098972852562e7004dc686/c1a57d2077c4bfda85256fac005b8b32!OpenDocument
You may need to cut and paste the URL.

-- 


Lenny Siegel
Director, Center for Public Environmental Oversight
c/o PSC, 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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