U.S. EPA should assess the cumulative health effects of perchlorate exposure rather than a single chemical-risk approach, the agency's inspector general said yesterday.
But tightening what EPA has deemed a safe concentration of perchlorate in drinking water from 24.6 parts per billion to 6 ppb -- the level set by California regulators -- would not provide "a meaningful opportunity to lower the public's risk," the IG report concludes.
Perchlorate is a component of rocket fuel and fireworks that also occurs naturally. It has been found in leafy vegetables and fruit, breast milk and infant formula. Environmentalists have long sought to regulate perchlorate in drinking water because the compound has been known to inhibit the thyroid's iodine uptake and interfere with fetal development at high doses. In the absence of federal action, several states including California have moved forward.
Industry groups argue that exposure to perchlorate at low levels is not harmful and that widespread perchlorate contamination has just come to light because of enhanced technologies capable of detecting perchlorate at minute levels.
EPA announced last year that it would review perchlorate research. During the George W. Bush administration, the agency in 2008 said it would delay its final decision on perchlorate regulation until the National Academy of Sciences studies the matter, but the Obama administration has opted to review past agency decisions on the compound.
A draft of the IG report last year came under fire from environmentalists and public health experts for failing to justify its support of the more liberal drinking water standard.
"Although OIG's use of a cumulative effect approach may have merit, it is inappropriately used to argue against a protective drinking water value for perchlorate," Massachusetts Environmental Protection Department officials wrote. "From a public health perspective and desire to protect children's health, exposures to multiple thyroid toxicants should lower the acceptable exposure value for any single toxicant not the other way around" (Greenwire, May 15, 2009).
The inspector general said there are several other chemicals that also stress the thyroid's ability to uptake iodide, including a lack of iodide. Because of this, the report said, the most effective way to combat the long-term problems associated with iodide-deficiency would be to require that all prenatal vitamins have iodide added and to encourage women to take them during pregnancy and while nursing.
"[L]imiting perchlorate exposure does not effectively address this public health issue," the inspector general said.
Click here to read the report.