NAS Report on Percholrate Released

Fresh Cut
February 2005

The long awaited report on perchlorate, “Health Implications of Perchlorate Ingestion,” is officially out. It is the tool that policy makers will be using to develop science-based standards to ensure public health. The report is based on an exhaustive review of research on the health effects of perchlorate.

The following are conclusions from the report stated in a National Academy of Science (NAS) news release:

• Environmental releases of perchlorate have been discovered in 35 states, and more than 11 million people have perchlorate in their drinking water at concentrations of 4 parts per billion or higher.

• Daily ingestion of up to 0.0007 milligrams per kilogram of body weight (estimated to be around 20 ppb) can occur without adversely affecting the health of even the most sensitive populations. That amount is more than 20 times the “reference dose” proposed by the U.S. Environmental Protection Agency in a recent draft risk assessment.

• In determining reference dose, the committee recommended using a 2002 clinical study in which groups of healthy men and women were administered perchlorate in daily doses ranging from 0.007 mg/kg to 0.5 mg/kg for 14 days. The study found no statistically significant inhibition of iodide uptake by the thyroid at the 0.007 mg/kg daily dose. The findings in this study are supported by the results in four other studies of healthy subjects, including a six-month study. The committee recommended that an uncertainty factor of 10 be applied to the 0.007 mg/kg per day level to protect the fetuses of pregnant women who might have hypothyroidism or iodide deficiency. This results in the 0.0007 mg/kg per day reference dose recommended in the report.

• Perchlorate inhibits the thyroid’s uptake of iodide, which is essential for the production of thyroid hormones. One potential consequence of that effect is low thyroid hormone production, or hypothyroidism. The committee thinks that perchlorate exposure is unlikely to lead to thyroid tumors in humans.

• The committee emphasized that the reference dose should be based on inhibition of iodide uptake by the thyroid in humans, which is not an adverse effect but the key biochemical event that precedes any health effects caused by perchlorate exposure. The committee called this a “conservative, health-protective approach to perchlorate risk assessment.”

Publicity Expected
While the report will require careful review by anyone choosing to use the findings to develop reasonable standards, it is expected to generate immediate publicity, according to the Produce Marketing Association (PMA). PMA recommends that the following points be considered:

• No one is advising consumers to change their eating habits based on perchlorate. Health experts, including the U.S. Food and Drug Administration recommend that consumers eat a balanced diet, choosing a variety of foods rich in high-fiber grains, fruits, and vegetables.

• Perchlorate is a water quality issue that must be addressed comprehensively by the U.S. government. PMA supports scientific efforts, such as this report, to determine whether this is a public health issue, and if it is, to determine the extent of the problem, appropriate safety levels in food, and appropriate remediation efforts.

• Reference doses for food items would not be the same as for drinking water.

• Perchlorate is a natural and man-made salt formed by adding oxygen molecules to chloride. Widespread perchlorate contamination in the United States was observed after the spring of 1997 when analytical methods were developed that allowed for quantitation down to 4 ppb. Since then, detection of the contaminant in soil, groundwater and drinking water wells has been confirmed in much of the U.S., and sometimes the source for the presence of the compound is unknown.

• Historically, perchlorate has been used as an oxidizer in fireworks, flares and solid rocket fuel. It also has been used in high concentrations to treat a hyperactive thyroid condition known as Graves Disease. The doses used as a medicine are tens of thousands of times greater than the low levels of perchlorate being detected in drinking water today.

Those seeking additional information on perchlorate are encouraged to visit the PMA Web site, where scientific summaries, background documents, and links to government reports on this issue are available. Those in the fresh-cut fruit and vegetable industry with questions should contact the IFPA’s Jim Gorny, Ph.D., vice president of technical and regulatory affairs, at jgorny@ fresh-cuts.org or (530) 756-8900.

© 2005 Columbia Publishing

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