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August 29, 2002
New Study Finds Levels of Perchlorate In Drinking Water Insignificant
for Most
Study Released Today
in Environmental Health Perspectives Finds Amount of Chemical in
Water in U.S. Southwest Not a Threat for Thyroid Disease
[RESEARCH TRIANGLE PARK, NC] A new study published today in the
science journal Environmental Health Perspectives found that perchlorate,
a chemical found in drinking water supplies throughout the U.S.
Southwest, should not lead to hypothyroidism in healthy people who
drink water containing low levels of the chemical contaminant. This
new information comes at a time when the U.S. Environmental Protection
Agency is in the midst of developing a reference dose for human
exposure to perchlorate.
Todays study addresses the concern that if exposure to perchlorate
through drinking water causes iodine uptake to be inhibited by too
much for too long, hypothyroidism could result. Although perchlorate
has pharmaceutical uses in the treatment of thyroid disorders related
to its ability to inhibit the uptake of iodine, it was not known
if daily exposure could cause the thyroid to under-perform, according
to the study. Because maternal thyroid hormone levels play a vital
role in fetal brain development, the authors were particularly concerned
about even mild hypothyroidism in pregnant women. Perchlorate is
most commonly used as an oxygen source in rocket propulsion systems
and is found as a contaminant in fertilizers.
The authors, including Monte Greer (the late head of the Endocrinology
Section at Oregon Health & Science University , Portland, Oregon)
and colleagues, evaluated 37 volunteers between 18 and 57 years
of age who drank water containing a fixed amount of perchlorate
four times a day for 14 days. The researchers found that even at
levels 9 to 36 times those normally found in drinking water, the
amount of thyroidal iodine that would be inhibited is physiologically
insignificant for groups with sufficient iodine intake (such as
the U.S. population).
The authors did not estimate a safe level of perchlorate exposure
to iodine-insufficient populations. However, they say that iodine
supplementation should be provided to iodine-insufficient persons
regardless of whether there are known exposures to perchlorate or
other inhibitors of iodine.
EHP is the journal of the National Institute of Environmental Health
Sciences, part of the U.S. Department of Health and Human Services.
More information is available on the Web at http://www.ehponline.org.
Editors note: A full copy of the report is available here
http://ehpnet1.niehs.nih.gov/docs/2002/110p927-937greer/abstract.html
or by fax or e-mail (PDF format) to working media at no charge.
Contact using phone number listed or adams6@niehs.nih.gov
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