In the wake of an influential report issued earlier this year, federal agencies are planning new actions and policies to address perchlorate pollution, government officials said recently.
The Environmental Protection Agency is deciding whether setting a drinking water standard for perchlorate would help protect public health, while the Food & Drug Administration continues to determine how much perchlorate occurs in food. And the Pentagon expects to issue a new policy that will affect cleanup of the chemical at military facilities. Officials from the three agencies described these activities at the American Chemical Society's recent national meeting in Washington, D.C., in sessions sponsored by the Division of Environmental Chemistry.
Perchlorate is a highly soluble component of solid rocket fuel and some munitions. It is also used in roadside flares and fireworks. The compound occurs naturally in rocks, and recent evidence suggests that perchlorate is formed in the atmosphere (C&EN, Feb. 14, page 10). The chemical has been found in drinking water in 34 states, according to EPA.
The reason for concern is that perchlorate can inhibit uptake of iodine by the thyroid and thus may lower the body's level of thyroid hormone. Permanent neurological damage can occur in children with insufficient levels of thyroid hormone.
In January, the National Research Council (NRC) suggested that a safe dose for human ingestion of perchlorate would be 0.7 µg per kilogram of body weight per day (C&EN, Jan. 17, page 13). The exposure level was designed to protect those believed to be most vulnerable to perchlorate's adverse effects: fetuses of pregnant women who have iodide-deficient diets or whose bodies fail to produce enough thyroid hormone.
The NRC report was issued to help settle a dispute that pitted EPA--which proposed stricter cleanup levels--against the Pentagon, the Energy Department, the National Aeronautics & Space Administration, and their contractors, all of which face liability for perchlorate pollution and wanted a more relaxed cleanup standard. EPA adopted the NRC standard, raising the agency's earlier safe dose estimate somewhat from 0.3 µg/kg/day (C&EN, Feb. 28, page 14).
EPA has not yet translated that dose into a parts-per-billion standard that would guide cleanup of perchlorate-contaminated water and soil. And it has not set an allowable level of perchlorate in drinking water.
Perchlorate is on EPA's list of some 50 unregulated contaminants in drinking water, which the agency is reviewing for possible regulation.
By early 2006, EPA will issue a draft decision on whether regulating perchlorate in drinking water would meaningfully reduce the public's risk of adverse effects from exposure to the chemical, said Cynthia C. Dougherty, director of EPA's Office of Ground Water & Drinking Water, at the ACS meeting.
Perchlorate has been found primarily at low levels in drinking water in the U.S., she said. A recent EPA survey found that the chemical occurs on average at concentrations less than 10 ppb, she said, though one locale in Florida had 420 ppb in tap water.
MEANWHILE, FDA is investigating the occurrence of perchlorate in food, said Henry Kim of the Office of Plant & Dairy Foods in the agency's Center for Food Safety & Applied Nutrition. Perchlorate is believed to enter produce that is grown on soil or irrigated with water containing the chemical, Kim pointed out.
In November 2004, FDA posted results of its initial "exploratory" survey of perchlorate in domestically produced milk and lettuce (C&EN, Dec. 6, 2004, page 30). Results of initial tests on U.S.-grown tomatoes, carrots, spinach, and cantaloupes have not been released publicly yet, Kim said, though low levels of perchlorate were found in some samples of each. FDA's methods can detect perchlorate in produce down to 1.0 ppb and in milk as low as 3.0 ppb, Kim said.
For the six foods in the initial survey, the public's average exposure to perchlorate is less than the NRC recommended standard of 0.7 µg/kg/day, Kim said. The preliminary estimate of the public's exposure to perchlorate in foods is undergoing peer review, as required under the federal Information Quality Act, he said.
This first stab at checking for perchlorate in foods was limited, Kim said, and FDA needs more data before it can assess the scope and public health implications of this chemical in foods.
In 2005, FDA has been analyzing 500 samples of both domestic and imported vegetables, fruits and fruit juices, grain products, infant foods and formula, and seafood raised in aquaculture. In addition, the agency is checking for perchlorate in raw milk as well as water and feed given to dairy cows, Kim said.
While FDA continues its analysis of perchlorate in foods, Kim said, it is also studying whether the iodine levels in prenatal vitamins are sufficient to protect fetuses of iodine-deficient women who consume perchlorate in their diet or water.
In addition to the work by EPA and FDA, the Pentagon is formulating a new policy on perchlorate pollution, said Shannon E. Cunniff, special assistant for the Defense Department's Materials of Evolving Regulatory Interest Team. The new guidance will clarify information on the pathways through which people are exposed to perchlorate, Cunniff said at the meeting.
DOD is coordinating with EPA on this policy, which will affect the extent of the cleanup of drinking water and wastewater contaminated with perchlorate from military sources, she said.
PERCHLORATE IS a component of more than 350 types of munitions, including those that make noise or flashes used in training to inure troops to explosions, she said.
To date, two DOD ranges have been shut down because of perchlorate contamination, Cunniff said. Should this happen in "several more locations," the military "will have a real problem," she said, but did not elaborate on what sorts of issues this might entail.
Concern about the public's exposure to perchlorate from DOD activities is exacerbated by "encroachment," new residential or other civilian development that comes right to the property line of military facilities, Cunniff said.
The Pentagon has spent more than $60 million over the past nine or 10 years to address perchlorate contamination, Cunniff continued. She added that more than $40 million of that total has gone toward treatment technology.
DOD is conducting research on chemicals that could be alternatives to perchlorate, Cunniff said. The goal is to find a substance that will provide oxygen in munitions and that is safe and stable.
Meanwhile, the Anniston Army Depot in Alabama is recycling perchlorate being removed from obsolete or aged missiles, Cunniff said. This perchlorate may be sold for use in the commercial blasting industry, she added.
DOD is perceived as the primary source of perchlorate pollution in the U.S. as well as the source with the deepest pockets. "We have been responsible for some pretty big plumes" of the chemical in groundwater, Cunniff said, but the military has not been the source of all perchlorate pollution.
"We'll be responsible for what we're responsible for," Cunniff said, but added that the military will not remediate perchlorate contamination that it did not cause.