The EPA and state health agencies are mandated to set a "reference dose" -- a safe level that would protect even the most at-risk human, and that's what they asked the NAS to recommend, which it now has in a surprising decision on Jan. 10.
The NAS committee recommended a safe dosage level 23 times higher than what the EPA had come up with in its initial risk assessment in 2002 -- even though the NAS committee's broader findings matched many of the conclusions of the EPA and health departments in California and seven other states that have completed their own assessments on perchlorate. The result: The EPA and state health agencies will now reassess their previous recommendations, and the Defense Dept. -- and its contractors -- may be off the hook for cleaning up hundreds of contaminated water systems.
UNSTEADY REFERENCE. "The EPA is going to need to go back and consider their interim guidance," says Bob Hopkins, the spokesperson for the White House's office of Science & Technology Policy, which worked with the EPA, Defense Dept., and the NAS throughout the process. "There's a lot of science [for them] to digest." State health agencies are rethinking their advisories as well. "We're going to be reviewing [the NAS] document very carefully," says Allan Hirsch, spokesperson for the California Office of Environmental Health Hazard Assessment. "If necessary we would revise [California's] public-health goal."
One of the ironies to the whole situation is that few, if any, perchlorate-related health problems have ever been reported in the U.S. or elsewhere, and the NAS and EPA reference doses actually differ by less than one-millionth of a gram. But sufficient consumption of perchlorate can block iodine uptake to the thyroid gland, an essential function in the development of newborns and fetuses.
Arriving at a reference dose can be surprisingly arbitrary. Using clinical evidence, the scientists find a dose that seems to have little or no effect on a healthy adult. But they reach the reference dose by coarsely adjusting for safety's sake -- dividing the dose number by 10 to account for a newborn, for instance, or dividing by 3 if the study didn't involve many people. Of course, what constitutes "many people" for example, is subject to interpretation.
THE FINAL STEP. Because of the subjectivity applied to the clinical data, the reference doses arrived at by the EPA, the various states, and the NAS turn out very differently. "On the big-picture points, the National Academy supported" California's findings, says Hirsch. "But since our [statistical] methodologies weren't exactly the same" the NAS study ended up with a number twice as high as California's.
The EPA still has to translate the reference dose to an appropriate level in drinking water -- the so-called water level. That's the final step in regulation, to be completed by August, 2006. And the difference between the EPA's original dose and the NAS recommendation could determine whether or not hundreds of water systems are cleaned up, says a regulatory analyst with the American Water Works Assn.
True, the EPA has a lot of leeway in arriving at the water level, but if it interprets the NAS dose using the same approach it used in its own 2002 assessment, it would set a level of roughly 24 parts per billion (ppb). Current advisory levels from the EPA and the eight states with advisories or public-health goals range between 1 ppb and 18 ppb.
COMING TO TERMS. Defense contractors like Lockheed Martin (LMT
), Kerr McGee (KMG
), GenCorp's (GY
) AeroJet unit, and American Pacific (APFC
) had already begun paying for water-supply cleanup as the result of legal settlements. But if the EPA follows the NAS recommendation, low-level contamination sites, where perchlorate has seeped over hundreds of miles to taint a city water system will likely go untouched, saving the Defense Dept. and its contractors hundreds of millions of dollars.
The defense industry's response to the NAS recommendation has been surprisingly low-key, considering how much it stands to benefit from less-stringent water regulations. "We endorse the process, and frankly we still need to read the report," says Patrick Corbett of Kerr McGee. Other contractors were equally noncommittal.
All eyes now turn to the EPA to see what water level it will set. The EPA won't comment officially on its regulatory plans, but one agency official says it's quite possible that the EPA will adjust its conversion method, which would lead to a lower level than 24 parts per billion.
Defense may need to dip into its coffers to pay for a water cleanup, but it won't be taking a bath on the costs any time soon. Helm is a reporter for BusinessWeek Online in New York