Regulating Perchlorate in Drinking Water

Perchlorate has been found to be a drinking water contaminant. It is believed that the pollution sources are from rocket fuels and fire works, as well as occurring naturally in some areas. It is suspected to interfere with thyroid function. The EPA has decided to set a standard for its content in drinking water. The C&E News article of February 7 did not mention what that standard might be, but California has set a limit of no more than 6 mcg per liter. In a separate EPA report, an average of 4 mcg per liter was reported.

The Bush administration had previously decided not to regulate it, but this is being reevaluated by the present administration. The EPA director said that the consideration is being based upon extensive review of the best available science and health needs for the American people.
However, I thought I'd like to know something about the the toxicity of perchlorate with respect to thyroid metabolism, for which it is accused.

Joseph C. Siglin, et al. performed a, "A 90-Day Drinking Water Toxicity Study in Rats of the Environmental Contaminant Ammonium Perchlorate". They found a thyroid change at 10 mg per kilo per day and no change at 1 mg per kilo per day. For convenience, we can eliminate the ammonium contribution to the molecule and just say there was no change at 1 mg per kilo per day for perchlorate.

An average person weighs about 70 kg. Children drinking tap water may weigh as little as 20 kg. Let's take the low children weight. The no-affect level for child would be 20 mg per day. That's 20,000 mcg per day. At 4 mcg per liter, a child drinking 5000 L of water in a day would have no thyroid effect but would certainly be drowned.

In essence, I am not against regulating perchlorate in drinking water, if it is necessary, nor am I against regulating about 16 other chemicals, providing we can show that there is toxicity at the levels for which they currently exist in drinking water. However, my quick calculations above seem to indicate it is even ridiculous to consider it. We also must remember that analytical techniques have developed significantly in the last 50 years, so that we can go down to a gnat's eyelash. However the mere fact that we can find it does not mean that it is significant

This all boils down to the usual consideration of whether regulation is necessary. Let's remember that some of the major problems in employment is the resistance of employers to hire based upon numerous regulations of the federal government.