EPA has issued drinking water regulations for more than 90 contaminants. Perchlorate Has Been Found At 395 Sites Including 153 Public Drinking Water Systems

Because information on the extent of perchlorate contamination was not  readily available, we thoroughly reviewed available perchlorate sampling  reports and discussed them with federal and state environmental officials. We identified 395 sites in 35 states, the District of Columbia, and 2  commonwealths of the United States where perchlorate has been found in  drinking water, groundwater, surface water, sediment, or soil. The  perchlorate concentrations ranged from the minimum reporting level of 4  parts per billion to in more than 3.7 million parts per billion—a level found  in groundwater at one of the sites. As shown in figure 2,  our analysis found that, at 110 of the 395 sites, the perchlorate source was  related to propellant manufacturing, rocket motor testing firing, and  explosives testing and disposal at DOD, NASA, and defense-related  industries. EPA officials said the agency does not centrally track or monitor  perchlorate detections or the status of cleanup activities. As a result, it is  difficult to determine the extent of perchlorate contamination in the U.S.  EPA maintains a list of sites where cleanup or other response actions are  underway but the list does not include sites not reported to EPA. Further, states are not required to routinely  notify EPA about perchlorate contamination they discover. Recent Research Indicates that Perchlorate Exposure May be a Concern for Pregnant Women

In our May 2005 review, we conducted a literature search for studies of  perchlorate health risks published from 1998 to 2005 and identified 125  studies on perchlorate and the thyroid. The findings of 26 of these studies indicated that perchlorate had an  adverse effect on thyroid function and human health. In January 2005, the  National Academy of Sciences considered many of these same studies and  concluded that the studies did not support a clear link between  perchlorate exposure and changes in the thyroid function or thyroid  cancer in adults. Consequently, the Academy recommended additional  research into the effect of perchlorate exposure on children and pregnant  women but did not recommend a drinking water standard. For another 29 studies, researchers reviewed several publicly available  human and animal studies and used data derived from these studies to  determine the process by which perchlorate affects the human thyroid and  the highest exposure levels that did not adversely affect humans. About 36 percent of U.S. women have these lower iodine  levels. The study found decreases in a thyroid hormone that helps regulate  the body’s metabolism and is needed for proper fetal neural development  in pregnant women.
Why GAO Did This Study

Perchlorate has been used for decades by the Department of Defense, the National Aeronautics and Space Administration, and the defense industry in manufacturing, testing, and firing missiles and rockets. Other uses include fireworks, fertilizers, and explosives. Perchlorate is readily dissolved and transported in water and has been found in groundwater, surface water, and soil across the country. Perchlorate emerged as a contaminant of concern because health studies have shown that it can affect the thyroid gland, which helps regulate the body's metabolism, and may cause developmental impairment in fetuses of pregnant women. In 2005, EPA set a reference dose of 24.5 parts per billion (ppb)--the exposure level not expected to cause adverse effect in humans. Today's testimony updates GAO's May 2005 report, Perchlorate: A System to Track Sampling and Cleanup Results is Needed, GAO-05-462 . It summarizes GAO's (1) compilation of the extent of perchlorate contamination in the U.S. and (2) review of peer-reviewed studies about perchlorate's health risks. GAO's 2005 report recommended that EPA work to track and monitor perchlorate detections and cleanup efforts. In December 2006, EPA reiterated its disagreement with this recommendation. GAO continues to believe such a system would better inform the public and others about perchlorate's presence in their communities.

What GAO Found

Perchlorate has been found at 395 sites in the U.S.--including 153 public drinking water systems--in concentrations ranging from 4 ppb to more than 3.7 million ppb. More than half the sites are in California and Texas, with the highest concentrations found in Arkansas, California, Texas, Nevada, and Utah. About 28 percent of sites were contaminated by defense and aerospace activities related to propellant manufacturing, rocket motor research and test firing, or explosives disposal. Federal and state agencies are not required to routinely report perchlorate findings to EPA, which does not track or monitor perchlorate detections or cleanup status. EPA recently decided not to regulate perchlorate in drinking water supplies pending further study. GAO reviewed 90 studies of health risks from perchlorate published from 1998 to 2005, and one-quarter indicated that perchlorate had an adverse effect on human health, and thyroid function in particular. In January 2005, the National Academy of Sciences also reviewed several studies and concluded that they did not support a clear link between perchlorate exposure and changes in the thyroid function. The academy did not recommend a drinking water standard but recommended additional research into the effect of perchlorate exposure on children and pregnant women. More recently, a large study by CDC scientists has identified adverse thyroid effects from perchlorate in women with low iodine levels that are found in about 36 percent of U.S. women.