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From time to time, I've posted stories about the effects of our continued exposure to perchlorate, a toxic chemical that, in high doses, can decrease thyroid function in humans and is a component of rocket fuel and fireworks.
A new report has found the daily ingestion of perchlorate -- a contaminant present in many public drinking-water supplies -- of up to 0.0007 milligrams per kilogram of body weight -- can occur without adversely affecting the health of even the most sensitive populations. Because perchlorate contamination has been discovered in 35 STATES, and more than 11 MILLION people have perchlorate in their drinking water at concentrations of 4 parts per billion or higher, the EPA is considering a first-ever national standard for "acceptable levels" of the chemical in drinking water. WOW!
Perchlorate inhibits the thyroid's uptake of iodide, which is essential for the production of thyroid hormones. One potential consequence of that effect: Hypothyroidism. The EPA has predicted that an ultimate consequence of that effect is the development of thyroid tumors -- a conclusion the agency based on the occurrence of a few thyroid tumors in rats exposed to perchlorate.
However, a committee of experts formed by the National Academies' National Research Council feels otherwise. They believe perchlorate exposure is unlikely to lead to thyroid tumors in humans, who are much less susceptible to the disruption of thyroid function or formation of thyroid tumors than rats in previous research.
Science Blog January 11, 2005