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Children's Health Protection

Response from Administrator Johnson regarding Preliminary Regulatory Determination on Perchlorate

January 8, 2009
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United States Environmental Protection Agency
Washington, DC 20460

The Administrator

Melanie A. Marty, Ph.D.
Children’s Health Protection Advisory Committee
Cal/EPA, Office of Environmental Health Hazard Assessment
1515 Clay Street, 16th Floor
Oakland, California 94612

Dear Dr. Marty:

I am writing to provide information about the U.S. Environmental Protection Agency’s recent decision relating to perchlorate in drinking water. Your letter of November 3, 2008, sent on behalf of the Children’s Health Protection Advisory Council, expressed concern about the development of the health reference level used to support EPA’s preliminary regulatory determination and asked the Agency to set a maximum contaminant level for perchlorate.

I agree with you that the science on this issue is very complex, and the comments we received on the preliminary regulatory determination raised many important questions. We are therefore withholding a final regulatory determination in order to consult with the National Academy of Sciences on several specific scientific issues that were raised by the CHPAC and other commenters on the preliminary regulatory determination. Specific to your comments, we are asking the NAS to review our use of a physiologically based pharmacokinetic model to assess potential impacts on sensitive subpopulations. We are also asking them to consider the implications of recent biomonitoring studies on our evaluation of exposure to percholorate in drinking water.

States have the ability to establish and enforce drinking water standards, and EPA encourages state-specific situations to be addressed at the local level. The Agency is issuing an interim health advisory to help public health officials and public water systems take appropriate action to address local incidences of percholorate contamination. EPA developed the health advisory level of 15 micrograms per liter (g/L) to address the most sensitive subpopulation identified by the National Research Council – the fetuses of pregnant women – taking into account high-end estimates of perchlorate exposure from both food and consumption of drinking water for this subpopulation.

I assure you that the Agency intends to issue a final regulatory determination for perchlorate in drinking water and will move as expeditiously as possible after considering the results of the NAS review.

Again, thank you for your letter. I appreciate the CHPAC’s continuing interest in this area.



Stephen L. Johnson

Cc: Benjamin H. Grumbles, Assistant Administrator for Water
Ruth McCully, Director, Office of Children’s Health Protection and Environmental Education
Carolyn Hubbard, DFO, CHPAC

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