NPR (National Public Radio) aired a news story on Jan 10, 2005 about the National Research Council's report on the safety of ingested perchlorate. Perchlorate is a chemical used in fuel for rockets and missiles. In high doses, it has been shown to decrease thyroid function in humans. Perchlorate is present in many public drinking-water supplies, in more than 35 states, especially in the southwest.The National Academies' Board on Environmental Studies and Toxicology on the health effects of says daily ingestion of up to 0.0007 milligrams per kilogram of body weight can occur without adversely affecting the health of even the most sensitive populations. That amount is more than 20 times the "reference dose" proposed by the U.S. Environmental Protection Agency in a recent draft risk assessment.
The report is the topic of a one-hour public briefing on Tuesday, Jan. 11. Join the event by listening to a live audio webcast (requires free RealPlayer) and submitting questions using an e-mail form, both accessible on the National-Academies.org home page beginning at 2 p.m. EST
Perchlorate inhibits the uptake of iodine, which is used by the thyroid to produce thyroid hormone. If iodine uptake is inhibited by too much for too long, the result could be hypothyroidism, a condition in which blood levels of thyroid hormone are abnormally low and those of the pituitary hormone thyrotropin (TSH) are abnormally high. Because maternal thyroid hormone level plays a vital role in fetal brain development, the authors say it is important to protect against even mild hypothyroidism in pregnant women.