	Background

Perchlorate is a primary ingredient in solid rocket propellant and has been  used for decades by DOD, NASA, and the defense industry in the  manufacturing, testing, and firing of rockets and missiles. The revised draft risk assessment included a proposed reference dose  equivalent to a concentration of 1 part per billion in drinking water, if it is  assumed all exposure comes only from drinking water. The new  reference dose is equivalent to 24.5 parts per billion in drinking water,  assuming that an adult weighing 70 kilograms (or 154 pounds) consumes 2  liters of drinking water per day, and that all perchlorate ingested comes  from drinking water. Perchlorate Has Been Found at Almost 400 Sites across the United States

Various federal and state agencies have reported finding perchlorate at  almost 400 sites in 35 states, the District of Columbia, and 2  commonwealths of the United States in drinking water, surface water,  groundwater, and soil. The concentration levels reported  ranged from 4 parts per billion to more than 3.7 million parts per billion in  groundwater at 1 site, yet roughly two-thirds of sites had concentration  levels at or below 18 parts per billion, the upper limit of EPA’s provisional  cleanup guidance for perchlorate. Federal and state agencies are not  required to routinely report perchlorate findings to EPA, and EPA does not  currently have a formal process to centrally track or monitor perchlorate  detections or the status of a cleanup. As a result, a greater number of sites  may exist in the United States than is presented in this report. Most of the sites and the highest levels of perchlorate were found in a small  number of states. However, the majority of the 395 sites had lower levels of  perchlorate. EPA and State Environmental Agencies Use Federal and State Environmental Laws and Regulations to Respond to Perchlorate

Although there is no federal standard for perchlorate in drinking water or a  federal cleanup standard, EPA and state environmental agencies  authorized by EPA have investigated suspected sites; collected samples  and analyzed for perchlorate; and, when perchlorate is found, cleaned up  or limited perchlorate releases under broad authorities found in various  federal environmental laws and regulations. Further, both EPA and  authorized states have required responsible parties to sample and clean up  perchlorate under other state laws. Parties Responsible for Perchlorate Findings Generally Have Complied with Regulations Requiring Sampling and Cleanup

According to EPA and state officials, private industry and public water  suppliers have generally complied with regulations requiring sampling,  such as those under (1) the RCRA and NPDES permit programs, where  responsible parties have been required to sample and report hazardous  releases to state environmental agencies, or (2) the Safe Drinking Water  Act’s Unregulated Contaminant Monitoring Regulation, which required  sampling for unregulated contaminants, such as perchlorate, between 2001  and 2003. According to EPA and state officials, DOD has been reluctant to (1) sample  on or near active installations because there is no specific federal  regulatory standard for perchlorate or (2) sample where DOD determined  the criteria to sample were not met as outlined in its policy. Of  these, 26 studies found that perchlorate had an adverse effect. The NAS report considered many of the same health risk  studies that we reviewed and concluded that an exposure level higher than  initially recommended by EPA may not adversely affect a healthy adult, but  recommended more study of the effects of perchlorate on pregnant women  and children. The National Academy of Sciences Reported That Evidence Was Insufficient to Show Perchlorate Causes Adverse Effects

In January 2005, NAS issued its report on EPA’s draft health assessment and  the potential health effects of perchlorate. NAS  concluded that an exposure level higher than initially recommended by  EPA may not adversely affect a healthy adult. Objectives, Scope, and Methodology

We identified (1) the estimated extent of perchlorate nationwide; (2) what  actions the federal government, state governments, and responsible parties  have taken to clean up or eliminate the source of perchlorate found; and  (3) what studies of the potential health risks from perchlorate have been  conducted and, where presented, the author’s conclusions or findings on  the health effects of perchlorate. Effects not  studied. A federal district court in California ruled, in  part, that perchlorate is a hazardous waste under RCRA because it is  ignitable, under certain conditions.
Why GAO Did This Study

Perchlorate, a primary ingredient in propellant, has been used for decades in the manufacture and firing of rockets and missiles. Other uses include fireworks, flares, and explosives. Perchlorate has been found in drinking water, groundwater, surface water, and soil in the United States. The National Academy of Sciences (NAS) reviewed studies of perchlorate's health effects and reported in January 2005 that certain levels of exposure may not adversely affect healthy adults but recommended more studies be conducted on the effects of perchlorate exposure in children and pregnant women. GAO determined (1) the estimated extent of perchlorate in the United States, (2) what actions have been taken to address perchlorate, and (3) what studies of perchlorate's health risks have reported.

What GAO Found

Perchlorate contamination has been found in water and soil at almost 400 sites in the United States where concentration levels ranged from a minimum reporting level of 4 parts per billion to millions of parts per billion. More than one-half of all sites were in California and Texas, and sites in Arkansas, California, Texas, Nevada, and Utah had some of the highest concentration levels. Yet, most sites had lower levels of contamination; roughly two-thirds of sites had concentration levels at or below the Environmental Protection Agency's (EPA) provisional cleanup standard of 18 parts per billion. Federal and state agencies are not required to routinely report perchlorate findings to EPA, and EPA does not centrally track or monitor perchlorate detections or the status of cleanup. As a result, a greater number of contaminated sites than we reported may already exist. Although there is no specific federal requirement to clean up perchlorate, EPA and state agencies have used broad authorities under various environmental laws and regulations, as well as state laws and action levels, to sample and clean up and/or require the sampling and cleanup of perchlorate by responsible parties. Further, under certain federal and state environmental laws, private industry may be required to sample for contaminants, such as perchlorate. According to EPA and state officials, private industry and public water suppliers have generally complied with regulations requiring sampling and agency requests to sample. The Department of Defense (DOD) has sampled and cleaned up perchlorate in some locations when required by laws and regulations, but the department has been reluctant to sample on or near active installations under other circumstances. Except where there is a specific legal requirement, DOD's perchlorate sampling policy requires the services to sample only under certain conditions. Cleanup is planned or under way at 51 of the almost 400 perchlorate-contaminated sites identified to date. Since 1998, EPA and DOD have sponsored a number of perchlorate health risk studies using varying study methodologies. We reviewed 90 of these studies that generally examined whether and how perchlorate affected the thyroid. About one-quarter concluded that perchlorate had an adverse effect. In January 2005, NAS reported on the potential health effects of perchlorate and concluded that a total exposure level from all sources, higher than that initially recommended by EPA (a dose equivalent to 1 part per billion in drinking water, assuming that all exposure came from drinking water) may not adversely affect a healthy adult. On the basis of NAS' report, EPA revised its reference dose to a level that is equivalent to 24.5 parts per billion in drinking water (if it is assumed that all exposure comes only from drinking water). The reference dose is not a drinking water standard; it is a scientific estimate of the total daily exposure level from all sources that is not expected to cause adverse effects in humans, including the most sensitive populations.