The committee based its conclusions largely on a 2002 study in which healthy men and women were given daily doses of perchlorate for two weeks without experiencing any signs of significant thyroid dysfunction -- a finding supported by four other studies of healthy subjects, the committee said. To set a safe threshold, the committee recommended using an "uncertainty factor" of 10 and permitting only one-tenth of the highest doses used in that study.
But environmental activists denounced the findings and released documents that they said showed the committee had been subject to unprecedented pressure by the White House and Defense Department.
"The Defense Department's job is to protect Americans, not threaten our health, but these documents show that it is conspiring with its contractors and the White House to twist the science and avoid cleaning up a chemical that threatens out children's health," said Erik D. Olson of the Natural Resources Defense Council. "We've never seen such a brazen campaign to pressure the National Academy of Sciences to downplay the hazards of a chemical."
The Pentagon referred questions to the White House, which, along with an academy official, dismissed the accusations.
"The academy has an outstanding reputation for objectivity, which is why the administration sought their analysis," said Deputy White House Press Secretary Trent Duffy. "This administration always says decisions should be made on sound science, and they're the experts," he said of the National Academy of Sciences.
The EPA will incorporate the panel's findings in its deliberations as it formulates a national standard, a White House official said.
The nation's largest defense contractor praised the report.
"Lockheed Martin believes the . . . review process is highly credible and we feel the [academy] is in a position to make the best recommendation based on the available science," the company said in a statement.
