Risk Policy Report, an independent newsletter, reported Feb. 28 that the White House Office of Science & Technology Policy is pressuring the Centers for Disease Control to delay the release of a study that tested for perchlorate in human blood samples from the National Health and Nutrition Examination Survey (NHANES). An EPA source told the newsletter that CDC has found levels of perchlorate that "leave no margin of safety" for the public, compared to EPA's current risk limit.

Perchlorate, the explosive ingredient in solid rocket fuel, has contaminated drinking water and soil in at least 35 states, with most of the known contamination coming from military bases and defense contractors. Tests by EWG, academic scientists in Texas and Arizona, state officials in California and the U.S. Food and Drug Administration have found perchlorate in milk, produce and many other foods and animal feed crops from coast to coast. Perchlorate is a thyroid toxin, and animal tests show that even small amounts can disrupt normal growth and development in fetuses, infants and children.

The NHANES study is a followup to a CDC study last year that found perchlorate in the urine of every one of 61 Atlanta residents tested, even though concentrations of perchlorate in the cityÕs drinking water are very low. Last year, scientists at Texas Tech University also found perchlorate in every sample of human milk from 36 mothers.

In a letter to Dr. Julie Gerberding, director of the CDC, EWG Senior Vice President Richard Wiles said the results of the study of Atlanta residents "indicate that food is likely a major source of perchlorate exposure, and that perchlorate exposure is likely to be widespread in the general population."

Although the EPA has no timetable for developing a national drinking water standard for perchlorate, both Massachusetts and California are moving forward with their own safety standards. The proposed standards — 1 part per billion in Massachusetts and 6 ppb in California — are far below EPA's recently adopted risk limit of 24.5 ppb, which is a level used as a guidance for cleaning up perchlorate- contaminated sites. When the EPA announced the risk limit, it acknowledged the need for "national guidance on relative source contribution" — exactly the information the NHANES data could provide.

"In the absence of national safety standards, the CDC should not be sitting on data so clearly needed to protect the public from a chemical that appears to be widespread in drinking water and food," wrote Wiles. "The NHANES perchlorate data should be released immediately."