Perchlorate and thyroid function: what are the environmental issues?

Ammonium perchlorate, used in the solid-propellant of rocket engines, has contaminated some water supplies and represents a potential public health hazard. Its toxicity is the result of the inhibition of the sodium iodide symporter resulting in reduced iodide uptake, possibly leading to reduced production of thyroid hormone. The fetus is the most vulnerable subject. Studies of newborn screening for thyroid function have yielded conflicting results and have not measured perchlorate or iodine intake. Based on short-term clinical studies in adults, less than 0.5 mg perchlorate per 70-kg adult will not lower thyroid uptake of radioiodine, while 1.6 mg/kg per day will lower thyroid uptake by 20%. To avoid interference with thyroid function, the California Office of Environmental Health Hazard Assessment recommended a public health goal of 6 microg perchlorate per liter of drinking water, but approximately three times that concentration is likely to be safe.