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EWG Letter to EPA Administrator Johnson Regarding Perchlorate

EWG Letter to EPA Administrator Johnson Regarding Perchlorate

Monday, May 28, 2007

Download the PDF of this letter.

March 29, 2007

Stephen L. Johnson
U.S. Environmental Protection Agency
Ariel Rios Building
1200 Pennsylvania Avenue, N.W.
Washington, D.C. 20460

Dear Administrator Johnson,

We are writing to express significant concerns about the lack of adequate health-protective standards for perchlorate, a dangerous chemical used in rocket fuel that is found in drinking water, groundwater, or soil at hundreds of locations in at least 43 states. Perchlorate is also found in food, dairy milk, human breast milk, and in the bodies of virtually every American.

Recent studies, including one by scientists from the Centers for Disease Control and Boston University, provide strong evidence that this contaminant poses a serious threat to public health. In this study, breast milk from all 49 Boston-area women who provided samples was contaminated with perchlorate. The average level of perchlorate in these samples would expose infants to double the EPA's reference dose (RfD) of 0.7 ug/kg/day, and several times the level that has been found to cause significant thyroid hormone decreases in adult women.

This study confirms earlier research that has also found high levels of perchlorate in breast milk. One recent study that tested dairy milk and breast milk found that the average concentration of perchlorate in breast milk was five times that in dairy milk.

The Boston study also revealed another troubling finding; almost half of the women in the study were not providing adequate levels of iodine to their infants through their breast milk. Iodine is critical to proper thyroid function and can help mitigate perchlorate's risks. The combination of high perchlorate levels and inadequate iodine concentrations in breast milk can leave infants susceptible to significant thyroid disruption, which can impede normal growth and cognitive development. It is also of concern that the women in this study who supplemented their iodine intake through multivitamins and iodized salt didn't necessarily have higher breast milk iodine concentrations, suggesting that protection from perchlorate provided by a mother's adequate iodine intake is not necessarily conferred to her breast-fed infant.

The levels of perchlorate found in breast milk in this study suggest a serious and imminent threat to the normal development and health of potentially all American infants. To protect public health, EPA must adopt a maximum contaminant level for perchlorate in drinking water based on the most recent science, including the 2006 CDC study and the Boston study described above.

The 2006 CDC study showed convincingly, with statistically valid data from a large human population, that perchlorate levels well below the EPA's current RfD cause significant thyroid hormone depression in adult women of childbearing age. With the CDC study showing that even less than 1 ppb perchlorate in water may pose health risks to women, fully protective drinking water standards must be set as low as possible—at no more than 1 ppb—and revised downward as detection and cleanup technology improves.

We urge you to take immediate action to protect American children from serious potential harm as a result of exposure to perchlorate. Please let us know what you will do to address this important public health issue.


Anila Jacob, MD, MPH
Senior Scientist
Environmental Working Group

Richard Wiles
Executive Director
Environmental Working Group

cc: Senator Barbara Boxer
Senator Dianne Feinstein
Senator Frank Lautenberg
Representative Hilda Solis