A rocket fuel component has been detected in drinking water sources in 18 states. It’s a limited problem the Environmental Protection Agency’s junk science is about to make much worse. U.S. missile and space programs used perchlorate as an oxidizer in solid rocket propellants for decades. At some facilities where it was disposed, perchlorate seeped into groundwater. Some nearby drinking water wells were closed. State and federal officials knew for years perchlorate was in some drinking water. They didn’t worry, though, because the perchlorate was generally below worrisome levels. Now the EPA wants to set the "safe" level of perchlorate in drinking water at effectively one part per billion (ppb). That standard would subject more groundwater to expensive cleanup -- estimated at $6 billion for Department of Defense facilities alone. Lake Mead, serving Las Vegas and Southern California, has perchlorate levels from eight ppb to 16 ppb. That water would need to be diluted with other water at an estimated cost to local water districts of up to $2 billion. Before taxpayers bear billions in costs, a closer look at the situation is warranted. The health effect the EPA is concerned about is hypothyroidism caused by inhibition of iodine uptake by the thyroid gland. At sufficiently high doses, perchlorate reduces the thyroid gland’s ability to take up iodine from the blood. Iodine is essential to the production of thyroid hormones. But the EPA ignores a fundamental tenet of toxicology -- the dose makes the poison. This can be demonstrated by comparing perchlorate’s iodine uptake inhibition to that of nitrate -- a substance that naturally occurs in meats, dairy products and vegetables and that also inhibits the thyroid’s uptake of iodine. A serving of spinach, for example, causes about 300 times more iodine uptake inhibition than the one ppb of perchlorate the EPA says someone might consume in two liters of groundwater. But I haven’t heard of anyone alarmed or harmed by spinach. So what might be a more reasonable perchlorate standard? The good news is much is known about perchlorate’s toxicology. It’s been used to treat patients whose thyroid glands produce too much hormone (hyperthyroidism). Also, workers exposed for an average of five years to "high" levels of perchlorate during manufacturing processes show no changes in blood chemistry or hormone levels. Based on these real-life experiences, the actual safe exposure level for most people may be as high as 12,000 ppb. This level, however, might not fully protect pregnant women and children. But such a level isn’t needed since the highest concentration of perchlorate in ground water is on the order of hundreds of ppb. A 2002 clinical study of men and women of child-bearing age receiving 180-220 ppb perchlorate for two weeks reported no change in the thyroid’s uptake of iodine. Even at much higher doses, the volunteers showed no changes in thyroid hormones and relevant blood chemistry. A 2000 study of school-aged children in Chile reported no thyroid hormone or relevant blood chemistry changes among children exposed to drinking water containing 110 ppb of naturally occurring perchlorate. Instead of using these real-life data, the EPA relied on dubious data from laboratory rat studies. A majority of panelists who reviewed the matter in the EPA’s June 2002 peer review of the studies criticized their design, laboratory practice and data analysis. The EPA simply ignored this criticism. Then, to reach one ppb from the rat data, the EPA arbitrarily divided the dubious results by 300 -- as per the agency’s standard, but non-scientific method of accounting for the uncertainty of extrapolating from experimental animal results to safety standards for humans. It’s not clear why the EPA staff is so determined to set a one ppb standard. One reliable source says some staffers hope to advance their careers by playing a role in the setting of a new and highly visible standard. Others may be sympathetic to the anti-chemical extremists at the Environmental Working Group who not only fearmonger about perchlorate but oppose human testing of perchlorate -- research that helps scientists determine safe levels. The EWG claims human testing is unethical; it’s real worry is that human testing reveals the folly of the EPA’s proposed standard. Capping off this impending travesty are the personal injury lawyers who salivate at the lawsuit potential of the one ppb standard and may be found on the Internet trolling for clients. It doesn’t take a rocket scientist to see that the EPA’s proposed perchlorate standard is needlessly low. But we will need a space program-sized budget to pay for it. Steven Milloy is the publisher of JunkScience.com , an adjunct scholar at the Cato Institute and the author of Junk Science Judo: Self-defense Against Health Scares and Scams (Cato Institute, 2001).