Regulation of Perchlorate

U.S. Environmental Protection Agency

U.S. EPA is approaching the perchlorate issue in a two-step process. The first involves requiring a nationally representative sampling of drinking water systems to test for perchlorate to determine whether the widespread occurrence of perchlorate requires a national standard. This three-year testing period ended in 2003.

The second phase involves conducting a risk assessment to establish what is called a Reference Dose, which is the amount of perchlorate in drinking water that U.S. EPA considers "safe" if consumed every day. In 2002, U.S. EPA published its draft risk assessment and proposed a Reference Dose of 1 part per billion (ppb) for perchlorate in drinking water, an amount equal to one-half teaspoon of perchlorate in an Olympic-sized pool.

The Reference Dose must be formally adopted before the federal government can develop a national standard - also known as a Maximum Contaminant Level or MCL - for how much perchlorate can be allowed in drinking water. In the process of setting the drinking water standard, U.S. EPA must consider several factors, including the economic and technological feasibility of meeting that standard.

Concerns with U.S. EPA's Process

Most research from human studies was not given adequate consideration, even though the agency's own guidelines sensibly suggest human studies are preferable to animal studies to ascertain human health effects. U.S. EPA made its recommendation for a 1 ppb Reference Dose based mainly on animal studies. In particular, U.S. EPA used a single study on rats which has since been the subject of substantial criticism from renowned scientists and medical experts for being flawed in its design and procedures.

U.S. EPA's interpretations of the results of some studies were different from those of the scientists who actually performed them.

In response to these criticisms, U.S. EPA has called on the National Academy of Sciences (NAS) to review its analysis and the underlying scientific studies which are the basis for the draft Reference Dose.

Next steps for U.S. EPA

  • Independent Peer Review by National Academy of Sciences. A panel of world renowned scientists has been convened by the National Academy of Sciences to conduct a thorough and independent review of U.S. EPA's risk assessment and "draft" Reference Dose. The NAS is expected to publish its report in late 2004 or early 2005.
  • Establish a Final Reference Dose. Based on the results of this report, U.S. EPA is expected to recommend a final Reference Dose for perchlorate in 2005.
  • Establish a National Drinking Water Standard. Based on review of economic, technological and other considerations, U.S. EPA will set a drinking water standard for perchlorate that is as close to the Reference Dose as possible.


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