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Perchlorate in Your Drinking Water

How much is too much and who is at risk?


Updated March 18, 2004

Updated March 18, 2004
The national debate on the potential health hazards of perchlorate in our drinking water was further complicated by recent actions of California’s Environmental Protection Agency (EPA). While some applaud the California EPA for taking a first step toward establishing an allowable limit of this perchlorate – a byproduct of rocket fuel production -- in drinking water, environmental groups are alarmed that the level was set at 6 parts per billion.

Environmental groups are quick to point out that a preliminary report from the National Academy of Sciences suggested that the safe level of perchlorate in drinking water should be set no higher than 1 part per billion. The United States EPA, in a draft risk assessment made in 2002, suggested that levels higher than 1 part per billion pose a health risk, especially for fetuses and infants. In contrast, the Defense Department contends that perchlorate at 200 parts per billion has no lasting effect on humans.

Perchlorate is one of only four of the 70 chemicals for which there are public health goals that has a safety factor of 10, rather then the usual safety factors of 100 or 1000. The other three chemicals are lead, nitrates, and fluoride. Currently eight states have advisories for perchlorate in drinking water, ranging from 1 to 18 parts per billion. Massachusetts is using the U.S. EPA guideline of 1 part per billion for its public drinking water standard and has been advising pregnant women, children and people with thyroid disorders not to drink water with higher perchlorate concentrations.

Perchlorate in drinking water is a health concern because it alters the production of thyroid hormones by the body, chemicals that are essential for proper development of the fetus and for normal metabolic functioning of the body. Particularly at risk are people with thyroid conditions, as well as pregnant women and their fetuses. Thyroid dysfunction characterized by hypothyroidism (reduced function of the thyroid gland) can result or be aggravated in persons who already have low thyroid function from consuming perchlorate in drinking water. Fetal and infant development can be retarded by exposure to perchlorate including that contained in breast milk from a mother who is consuming drinking water containing perchlorate.

It is important, especially for those at risk, to be aware that drinking water is not the only potential source of perchlorate in the diet. Beef, lettuce, milk, berries, and other agricultural products may contain perchlorate.

The source of perchlorate of drinking water at many sites, including many of those in California, is the defense industry and the past production of solid rocket propellants using perchlorate. Poor disposal practices, industrial accidents, and agricultural fertilizers are suspected as the sources of contamination of drinking water by perchlorate. Perchlorate has been detected in the public drinking water in at least 22 states. Produce grown in those states that is irrigated by contaminated water has reached around the nation.

Defense contractors -- including Boeing, Lockheed Martin, Aerojet, Kerr-McGee, and McDonnell Douglas -- had opposed California’s regulatory action in the fear that the standard would be too strict. Such action may force expensive cleanups, which these companies may be forced to finance. Clean up of the Colorado River alone, for example, will cost billions, in order to reduce the perchlorate concentrations in this source of drinking water for 15 million Californians.

A detailed report is expected from the National Academy of Sciences later this year. In the meantime, the debate between the Pentagon/Defense Department and various environmental groups continues, with each side disagreeing as to what constitutes safe levels of perchlorate in the nation’s drinking water. The battle also rages on about who will pay for the necessary clean up of sites and water supplies around the country that have been contaminated by this potentially harmful chemical.

As with other chemicals that pose a potential health hazard, the challenge of defining an acceptable level of this contaminant in the drinking water sets two opposing groups of people with significantly different views against each other, with no clear end in sight to this debate. In the meantime, it appears that a portion of the population may be at serious health risk because of the presence of this pollutant in the public drinking water in many areas of the country.

For more information about perchlorate, see:

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