Chemical in Drinking Water May Create Thyroid Problems

August 2000 -- According to research reported on in the Journal of Occupational and Environmental Medicine (2000;42:777), drinking water that has been contaminated with small amounts of perchlorate--a chemical that is used in the manufacture of rockets, missiles and fireworks, among other products --may be the reason behind higher-than-normal thyroid hormone levels being identified in some newborns in Arizona.

Doctor Ross Brechner, lead author of the study, and chief of the Arizona Department of Health Services, found that mothers who drink water with detectable levels of perchlorate gave birth to babies with elevated levels of thyroid stimulating hormone (TSH), an indicator of the thyroid disorder known as hypothyroidism. In the study, the researchers compared the thyroid levels of infants in Yuma, where the water supply contains perchlorate, and Flagstaff, Arizona, where there is no perchlorate in the water. The infants born in Yuma had high levels of hormones that stimulate the thyroid. This is indicative of thyroid disorder and hypothyroidism. The study, however, does not officially confirm perchlorate as the cause.

Kevin Mayer of the EPA told the Las Vegas Review-Journal, "Nobody disputes that at high levels it will affect the thyroid. The question is what happens at lower levels."

The drinking water from Lake Mead has perchlorate levels of 11 parts per billion, and the EPA currently recommends that drinking water contain no more than 18 parts per billion. No standards have been clearly established regarding safe levels of perchlorate exposure for humans. By late 2000, however, the EPA is expected to issue regulations regarding whether there are any acceptable levels of perchlorate in drinking water.

Perchlorate has migrated from disposal sites in Nevada into Lake Mead, and the Colorado River system, which supplies drinking water for about 20 million people in Arizona, California and Nevada.