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Debating Perchlorate

Debating Perchlorate

Humans' consumption of perchlorate in drinking water and foods is a concern for the environmental health community, but perchlorate is considered a small contributor to a larger health problem. A Dec. 30, 2008, letter and analysis from EPA's inspector general that questioned the research approach used by EPA when it set its perchlorate reference dose in February 2005. The letter recommends a cumulative risk assessment approach that examines perchlorate's impact in the context of other chemicals -- including thiocyanate and nitrate -- that, like perchlorate, stress the thyroid's ability to uptake iodide, which can cause permanant mental defects in newborns. The EPA IG's letter asked for scientific comments on the use and application of a cumulative risk assessment to be submitted by March 10, 2009, to the e-mail address Perchlorate_Comments_for_OIG@epa.gov.

The IG's letter and analysis note that humans' diet continuously expose us to all four stressors that act to lower iodide uptake. And while EPA's reference dose has been controversial, it is conservative and does protect human health -- but limiting perchlorate exposure by lowering the drinking water limit will not effectively by itself address the public health issue, the IG concluded.

Perchlorate: A Guide for Consumers, Policymakers and the Media is a Grocery Manufacturers Association Science Policy Paper that examines current science and data for Americans' intake of perchlorate, mainly by ingesting food and drinking water. In high doses, the chemical inhibits uptake of iodide into the thyroid gland, but at low doses it has not been found to affect humans. The paper reviews EPA's Reference Dose, results of 2008 FDA testing for perchlorate in 1,065 samples of food products, a 2007 CDC estimate of adults' daily intake of perchlorate, and FDA's estimate of how much perchlorate is being consumed by various segments of the population, including infants and children. How perchlorate enters foods isn't certain, but it may be from naturally occurring perchlorate or from the use of fertilizer that contains it.

On Jan. 8, 2009, EPA announced it had issued an interim health advisory of 15 parts per billion in drinking water and said it has sought advice from the National Academy of Sciences before making a final determination on whether to issue a national regulation for perchlorate in drinking water. The interim advisory will help state and local officials address local contamination of perchlorate in drinking water, and EPA said it had made a corresponding change in the factors it considers in cleaning up Superfund sites where perchlorate is present. When the agency makes the final regulatory determination, it expects to issue a final health advisory.

The interim level replaced a remediation goal of 24.5 ppb. "This is a sensible step for protecting public health and preserving regulatory options as the science of perchlorate is reviewed," said Benjamin H. Grumbles, EPA's assistant administrator for water. EPA on Oct. 10, 2008, had issued a preliminary regulatory determination in a notice announcing it had decided there is not a "meaningful opportunity for health risk reduction" through a national drinking water regulation for perchlorate. In response, EPA received more than 32,000 comments within three months.

The agency also asked the National Academy of Sciences how it should consider the role of perchlorate in relation to other iodide uptake inhibitors and whether there are "other public health strategies to address this aspect of thyroid health."

This article originally appeared in the February 2009 issue of Occupational Health & Safety.

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