Perchlorate: low safe level and you're drinking it

Perchlorate, a chemical used in the production of flares, rocket fuel, and munitions, is found in large chunks of the drinking water supply for the western US, in large part because the Colorado river is contaminated.

Naturally, being tasked with regulating environmental safety, the EPA cooprated with industry to study just how risky perchlorate is. To their surprise, as perchlorate had been approved as a thyroid drug many years ago, they found that for newborn rats, there is no safe level of perchorate, and set a limit of one part per billion in drinking water.

So what did industry do? Attack their own study, and lobby the Bush administration for looser standards, with predictable results:

The White House told the EPA to halt further action on the chemical, and arranged for the EPA and three other agencies to sponsor further review by the National Research Council, a federally funded group that vets issues for the government and others. The council, in turn, named a panel of scientists, who did a wide-ranging assessment that included public hearings in 2003 and 2004.

While those hearings resulted in a higher allowed perchlorate content in drinking water, they apparently didn't consider the possibility that perchorate might be consumed in fruits and vegetables which were irrigated with contaminated water:

In fact, however, the EPA's working assumption in such cases is that drinking water accounts for only 20% of people's exposure to a waterborne contaminant. Recent studies indicate that small amounts of the chemical are in a wide variety of fruits and vegetables, possibly from irrigation water, as well as in some dairy products and breast milk.

Such contamination of vegetables and milk is apparently widespread:

Tables 1 and 2 show perchlorate levels in lettuce and bottled water samples, respectively, collected as part of the initial phase of FDA's field assignment, "Collection and Analysis of Food for Perchlorate," that was issued on December 23, 2003, and posted on FDA's website. Lettuce samples were collected at the grower or packing shed while bottled water samples were collected at retail locations. For sample analysis, outermost leaves of each lettuce head were removed, similar to the actions typically taken by a consumer prior to consumption.

Table 3 shows perchlorate levels found in milk samples that were collected and analyzed as part of FDA's research and method development, as well as part of the second phase of FDA's field assignment. All milk samples, except for raw milk samples that were obtained from a research facility in Maryland, were collected at retail.

As a result, many children in the southwest US, or who eat food grown in the southwest, will remain at risk for abnormal thyroid function. Just what we all needed.