Wall Street Journal
February Thursday, 2005
EPA's Ruling On Perchlorate Draws Criticism
The Environmental Protection Agency, in a policy decision that may save the Pentagon and defense industry billions of dollars in cleanup costs, adopted a weakened version of the National Academy of Sciences' recommended "safe dose" for perchlorate exposure.
In response, some scientists, environmentalists and members of Congress who are worried that the water contaminant poses a risk to infant-brain development, accused the Bush administration of meddling with the science to help the suspected polluters.
Perchlorate, a main ingredient in solid-rocket fuel and other weapons systems, was discharged into soil and streams by the military and its suppliers throughout the Cold War, and has turned up in water supplies in 35 states.
The current controversy concerns the EPA's adoption of a so-called reference dose for perchlorate, or the daily exposure level for the chemical deemed safe for the most sensitive subpopulations over a lifetime. This is the first step toward the possible setting of a legal water standard for perchlorate.
On Friday, the EPA announced it is officially adopting the reference dose recommended last month by a panel of the National Academy of Sciences' National Research Council, which said adults can safely consume an equivalent of 24 parts per billion of perchlorate in drinking water. In 2002 the EPA proposed its own reference dose for perchlorate of one part per billion, which the agency says it is now discarding.
But in an unusual ripple, the EPA, in translating the NRC's reference dose into a drinking-water limit, said it wasn't following the guidance for how to apply the panel's reference dose that was issued by the NRC panel's chairman, Richard Johnston of the University of Colorado. Dr. Johnston, in public comments last month and again in an interview Friday, stated that in order to translate the NRC reference dose into a drinking-water limit, it is necessary to adjust the NRC dose for an individual's body weight and water-consumption level—in the same way dosages of medicines are routinely adjusted for particular patients' weights.
"So if it's a three-kilogram baby, you adjust [the perchlorate-water limit] down. If it's an 80-kilogram adult, you ' adjust it up," Dr. Johnston explained during a public briefing on Jan. 11. On Friday, he. elaborated on that in an interview: "When you consider the weight and fluid needs of an infant, the perchlorate drinking-water equivalent level is going to be different than for an adult," Dr. Johnston said.
According to an EPA scientist, if the EPA were to follow, Dr. Johnston's advice to translate the NRC's reference dose to protect newborn babies, the agency would have to set a drinking-water limit for perchlorate of roughly four parts per billion.
For its part, the EPA said it interprets the NRC's perchlorate analysis differently than the report's chairman does. William Farland, the EPA's acting chief science officer, said in an interview Friday that "some data" suggest infants are no more sensitive to perchlorate's effects than adults are, and thus babies need no more protection than adults do from the chemical. The NRC's reference dose, Dr. Farland said, is meant to protect the most-sensitive subgroups, in this case pregnant mothers and their fetuses.
Those groups are shielded by an extra safety margin built into the NRC's reference dose, Dr. Farland said. That dose was derived by dividing the perchlorate level that caused ill effects in adult humans by a safety factor of 10.
The EPA's decision not to adjust the drinking-water level for infants makes it less likely the agency will ever set a federal drinking-water standard for the chemical, said some EPA staffers and outside scientists. Very few public water supplies in the U.S. are contaminated with more than 20 parts per billion of perchlorate, and federal law requires the EPA to set drinking-water limits only when the standards will provide significant publichealth benefits. On Friday, both U.S. senators from California, the state most contaminated by perchlorate, urged the EPA to reconsider its reference dose and quickly set a water standard to protect infants.
Thomas Zoeller, a University of Massachusetts neurobiologist who participated in two outside peer reviews of the EPA's perchlorate work sponsored by the agency, said a 24-parts-per-billion drinking-water limit will subject infants to six-times as much perchlorate as deemed safe by the NRC panel. This level could limit the babies' ability to produce thyroid hormone, a crucial biochemical in controlling brain development, Dr. Zoeller said in an interview.
"There is no evidence to support a claim that infants are more or less sensitive to the effect of perchlorate on their thyroid glands than adults," Dr. Zoeller said. "What we do know is that infants drink six times the amount of fluid, per body weight, than adults do, and therefore the 10-fold [safety] factor incorporated by the NRC is 60% accounted for by this difference alone."