[CPEO-MEF] Perchlorate and Nursing infants

[Lenny Siegel <lsiegel@cpeo.org>]

Evaluation of the U.S. EPA/OSWER Preliminary Remediation Goal (PRG) for 
Perchlorate in Groundwater:
Focus on Exposure to Nursing Infants

Gary L. Ginsberg, Dale B. Hattis, R. Thomas Zoeller and Deborah C. Rice
Environmental Health Perspectives
doi:10.1289/ehp.9533 (available at http://dx.doi.org/)
Online 11 December 2006

Abstract

Background: Perchlorate is a common contaminant of drinking water and 
food. It competes with iodide for uptake into the thyroid, thus 
interfering with thyroid hormone production. U.S. EPA's Office of Solid 
Waste and Emergency Response set a groundwater preliminary remediation 
goal (PRG) of 24.5 ug/L to prevent exposure to pregnant women that would 
affect the fetus. This doesn't account for greater exposure that is 
possible in nursing infants, and for the relative source contribution 
(RSC), a factor normally used to lower the PRG due to non-water exposures.

Objectives: To assess whether the OSWER PRG is protective of exposures 
to infants from breastfeeding, and to evaluate the perchlorate RSC.

Methods: Monte Carlo analysis was used to simulate nursing infant 
exposures associated with the OSWER PRG when combined with background 
perchlorate.

Results: The PRG can lead to a 7 fold increase in breast milk 
concentration, causing 90% of nursing infants to exceed the RfD (average 
exceedance 2.8 fold). Drinking water perchlorate must be below 6.9 ug/L 
to keep the median, and below 1.3 ug/L to keep the 90th % nursing infant 
exposure below the RfD. This is 3.6-19 fold below the PRG. Analysis of 
biomonitoring data suggests an RSC of 0.7 for pregnant women, and 0.2 
for nursing infants. Recent data from CDC suggest that the RfD itself 
needs to be reevaluated because of hormonal effects in the general 
population.

Conclusions: The OSWER PRG for perchlorate can be improved by 
considering infant exposures, by incorporating an RSC, and by being 
responsive to any changes in the RfD resulting from the new CDC data.

[Note: "ug" stands for micrograms.]



To link to this article, go to
http://www.ehponline.org/docs/2006/9533/abstract.html

--


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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