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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.
Today’s 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.

Editor’s 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