EPA rejects petition to switch from arsenic-contaminated source of fluoride in U.S. drinking water

(http://www.livescience.com/38952-epa-arsenic-petition-response.html) Last May, researchers petitioned the EPA to change the source of fluoride used in U.S. drinking water. The EPA declined that petition this week, saying that the costs of switching fluoride sources would be prohibitive.

Currently, the source of fluoride in most public water supplies is fluorosilicic acid, a byproduct of phosphate fertilizer manufacturing. William Hirzy, a chemistry researcher at the American University in Washington, D.C., who previously worked for the EPA for 27 years, says that records have shown fluorosilicic acid to often be contaminated with arsenic and recommends switching to pharmaceutical-grade sodium fluoride.

Hirzy, who submitted the petition, released a study suggesting that arsenic from fluorosilicic acid could be linked to cancer cases in the U.S. The study erroneously reported that there are about 320 cancer cases caused by ingestion of fluorosilicic acid per year. Hirzy later acknowledged his mistake and stated that the actual figures are closer to three to four cancer cases per year. The EPA published a response in the Federal Register upholding Hirzy's claims that pharmaceutical-grade sodium fluoride contains about 100 times less arsenic than fluorosilicic acid and is therefore 100 times less likely to lead to cancer. However, the EPA defends using the current source of fluoride, as changing to sodium fluoride would not be cost-effective.