Perchlorate: EPA Does Not Systematically Track Incidents of	 
Contamination (25-APR-07, GAO-07-797T). 			 
                                                                 
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.	 
-------------------------Indexing Terms------------------------- 
REPORTNUM:   GAO-07-797T					        
    ACCNO:   A68726						        
  TITLE:     Perchlorate: EPA Does Not Systematically Track Incidents 
of Contamination						 
     DATE:   04/25/2007 
  SUBJECT:   Contaminants					 
	     Environmental law					 
	     Environmental legislation				 
	     Environmental policies				 
	     Environmental protection				 
	     Environmental research				 
	     Federal regulations				 
	     Federal/state relations				 
	     Hazardous substances				 
	     Health hazards					 
	     Perchlorates					 
	     Potable water					 
	     Soil remediation					 
	     Standards						 
	     Water pollution					 
	     Water pollution control				 

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GAO-07-797T

   

     * [1]Background
     * [2]Perchlorate Has Been Found At 395 Sites Including 153 Public
     * [3]Recent Research Indicates that Perchlorate Exposure May be a
     * [4]GAO Contacts and Staff Acknowledgments
     * [5]GAO's Mission
     * [6]Obtaining Copies of GAO Reports and Testimony

          * [7]Order by Mail or Phone

     * [8]To Report Fraud, Waste, and Abuse in Federal Programs
     * [9]Congressional Relations
     * [10]Public Affairs

Testimony

Before the Subcommittee on Environment and Hazardous Materials, House
Committee on Energy and Commerce

United States Government Accountability Office

GAO

For Release on Delivery
Expected at 10:00 a.m. EDT
Wednesday, April 25, 2007

PERCHLORATE

EPA Does Not Systematically Track Incidents of Contamination

Statement of John B. Stephenson, Director
Natural Resources and Environment

GAO-07-797T

Mr. Chairman and Members of the Subcommittee:

I am pleased to be here today to discuss our work on perchlorate, a
chemical most commonly used in rocket fuel. A combination of human
activity and natural sources has led to the widespread presence of
perchlorate in the environment. Perchlorate has been used for decades by
the Department of Defense (DOD), the National Aeronautics and Space
Administration (NASA), and the defense industry in the manufacturing,
testing, and firing of missiles and rockets. According to the
Environmental Protection Agency's (EPA) estimates, 90 percent of the
perchlorate produced in the United States is manufactured for use by the
military and NASA, with total typical production quantities averaging
several million pounds per year. Private industry also has used
perchlorate to manufacture automobile airbags, fireworks, flares, and
commercial explosives. Natural sources include certain atmospheric
processes and Chilean nitrate salts (saltpeter) that have been mined and
refined to produce commercial fertilizers for use in the U.S. Perchlorate
forms salts that are readily dissolved and transported in water and that
have been found in groundwater, surface water, and soil across the
country. People are exposed to the perchlorate primarily by ingesting it
in drinking water and food, or by working to manufacture products that
contain the chemical. Health studies have shown that exposure to
perchlorate can affect the thyroid gland, which helps regulate the body's
metabolism, and may cause neurodevelopmental impairment in fetuses of
pregnant women.

In 2003, EPA, DOD, NASA, and the Department of Energy asked the National
Academy of Sciences to review the risks of exposure to perchlorate. In
January 2005, the Academy recommended a reference dose of 0.0007
milligrams of perchlorate per kilogram of body weight per day, an
estimated daily exposure level that is not expected to cause adverse
effects in the children and pregnant women--the most sensitive human
populations. This reference dose equates to a drinking water equivalent
level of 24.5 parts per billion.^1 In February 2005, EPA adopted the
Academy's reference dose for perchlorate, but it has not established a
national federal standard for perchlorate in drinking water or other
regulatory requirements to clean up perchlorate in groundwater, surface
water, or soil, citing the need for additional study about the health
effects of perchlorate exposure.

^1The drinking water equivalent level is based on a reference adult
weighing 70 kilograms (or 154 pounds) drinking 2 liters of water per day,
assuming that all perchlorate exposure comes from drinking water.

My testimony today is based largely on our 2005 report for this Committee
and summarizes (1) our analysis of the estimated extent of perchlorate
found in the United States and (2) the results of our review of published
studies on the health effects of perchlorate.^2 In the 2005 report, we
recommended that EPA develop a tracking system for perchlorate releases
and cleanup efforts across the federal government and state agencies. This
statement also includes information from my February 2007 testimony about
EPA's recent response to our recommendation.^3

To provide an estimate of the extent of perchlorate found in the United
States, we compiled and analyzed data on perchlorate detections from EPA,
DOD, the U.S. Geological Survey, and state agencies. To identify studies
of the potential health risks from perchlorate, who conducted them, and
what methodologies were used, we conducted a literature search for studies
of perchlorate health risks published since 1998, interviewed DOD and EPA
officials on what studies they considered important in assessing
perchlorate health risks, and examined the references of each study for
other studies we had not obtained. We identified 125 studies on
perchlorate and the thyroid, of which we reviewed 90 that were relevant to
our review. A more detailed description of our scope and methodology is
presented in appendix I of our 2005 report.

In summary, we found the following:

           o As of our May 2005 review, perchlorate had been found by federal
           and state agencies in groundwater, surface water, soil, or public
           drinking water systems at almost 400 sites across the country in
           concentrations that ranged from 4 parts per billion (ppb) to more
           than 3.7 million ppb. However, there is not a standardized
           approach to reporting perchlorate data nationwide, therefore there
           may be more contaminated sites than we identified. These sites are
           located across 37 states and U.S. territories, but more than half
           were found in California and Texas. The sources of perchlorate at
           the sites vary, but the greatest known source is defense and
           aerospace activities such as propellant manufacturing, rocket
           motor research and test firing, or explosives disposal. More than
           one-third of the sites were public drinking water systems, where
           perchlorate concentrations ranged from 4 to 420 ppb. Fourteen of
           these 153 public water systems had concentration levels above 24.5
           parts per billion, the drinking water equivalent of EPA's
           perchlorate reference dose. EPA and state officials told us they
           had not cleaned up contaminated public drinking water systems,
           principally because there was no federal drinking water standard
           or specific federal requirement to clean up perchlorate. Further,
           it is difficult to determine the extent of perchlorate in the
           United States or the status of any cleanup actions because EPA
           does not centrally track or monitor perchlorate detections,
           environmental releases, or cleanup activities.
           o Recent research indicates that low-level perchlorate exposure
           may adversely affect the thyroid and increase the risk of
           neurodevelopmental impairment in fetuses of pregnant women. In our
           May 2005 review, we identified and summarized 90 peer-reviewed
           studies published from 1998 to 2005 on the health effects of
           perchlorate. The findings of 26 of these studies indicated that
           perchlorate had an adverse effect on thyroid function and human
           health. Most studies on adult populations were unable to determine
           whether the thyroid was adversely affected, because adverse
           effects of perchlorate on the adult thyroid, such as cancer, may
           happen over longer time periods than are generally observed in a
           research study. In contrast, the adverse effects of perchlorate on
           human development can be more easily studied and measured within
           study time frames, and 18 studies found adverse effects on
           development resulting from maternal exposure to perchlorate. We
           also found that some studies considered the same perchlorate dose
           but found different effects. The precise cause of the different
           results may be attributed to the studies' designs or to the
           physical conditions--such as sex, age, and blood iodine levels--of
           studies' subjects. Such unresolved questions were one of the bases
           for the differing conclusions among EPA, DOD, and other
           researchers on perchlorate doses and human health effects. In its
           January 2005 report, the National Academy of Sciences called for
           additional research on perchlorate exposure to help resolve
           questions about its effect on children and pregnant women. More
           recently, an October 2006 CDC study found that, for women with
           lower iodine levels, perchlorate reduced the thyroid hormone that
           helps regulate metabolism and that plays a part in central nervous
           system development in the fetus.
		   
^2GAO, Perchlorate: A System to Track Sampling and Cleanup Results is
Needed, [11]GAO-05-462 (Washington, D.C.: May 20, 2005).

^3GAO, Environmental Information: EPA Actions Could Reduce the
Availability of Environmental Information to the Public, [12]GAO-07-464T
(Washington, D.C.: February 6, 2007).

           We concluded in our report that EPA needed more reliable
           information on the extent of sites contaminated with perchlorate
           and the status of cleanup efforts, and recommended that EPA work
           with the Department of Defense and the states to establish a
           formal structure for tracking perchlorate information. In December
           2006, EPA reiterated its disagreement with the recommendation
           stating that perchlorate information already exists from a variety
           of other sources. However, we continue to believe that the
           inconsistency and omissions in available data that we found during
           the course of our study underscore the need for a more structured
           and formal tracking system.
		   
		   Background

           According to EPA, perchlorate can interfere with the normal
           functioning of the thyroid gland by competitively inhibiting the
           transport of iodide into the thyroid, which can then affect
           production of thyroid hormones. The fetus depends on an adequate
           supply of maternal thyroid hormone for its central nervous system
           development during the first trimester of pregnancy. The National
           Academy of Sciences reported that inhibition of iodide uptake from
           low-level perchlorate exposure may increase the risk of
           neurodevelopmental impairment in fetuses of high-risk
           mothers--pregnant women who might have iodine deficiency or
           hypothyroidism (reduced thyroid functioning). The Academy
           recognized the differences in sensitivity to perchlorate exposure
           between the healthy adults used in some studies and the most
           sensitive population and the fetuses of these high-risk mothers.
           Consequently, the Academy included a 10-fold uncertainty factor in
           its recommended reference dose to protect these sensitive
           populations. The Academy also called for additional research to
           help determine what effects low-level perchlorate exposure may
           have on children and pregnant women.

           EPA has issued drinking water regulations for more than 90
           contaminants. The Safe Drinking Water Act, as amended in 1996,
           requires EPA to make regulatory determinations on at least five
           unregulated contaminants and decide whether to regulate these
           contaminants with a national primary drinking water regulation.
           The act requires that these determinations be made every five
           years. The unregulated contaminants are typically chosen from a
           list known as the Contaminant Candidate List (CCL), which the act
           also requires EPA to publish every five years. EPA published the
           second CCL on February 24, 2005. On April 11, 2007, EPA announced
           its preliminary determination not to regulate 11 of the
           contaminants on this list. The agency also announced that it was
           not making a regulatory determination for perchlorate because EPA
           believed that additional information may be needed to more fully
           characterize perchlorate exposure and determine whether regulating
           perchlorate in drinking water presents a meaningful opportunity
           for health risk reduction.

           Several federal environmental laws provide EPA and states
           authorized by EPA with broad authorities to respond to actual or
           threatened releases of substances that may endanger public health
           or the environment. For example, the Comprehensive Environmental
           Response, Compensation, and Liability Act of 1980 (CERCLA), as
           amended, authorizes EPA to investigate the release of any
           hazardous substance, pollutant, or contaminant. The Resource
           Conservation and Recovery Act of 1976 (RCRA) gives EPA authority
           to order a cleanup of hazardous waste when there is an imminent
           and substantial endangerment to public health or the environment,
           and one federal court has ruled that perchlorate is a hazardous
           waste under RCRA.^4 The Clean Water Act's National Pollutant
           Discharge Elimination System (NPDES) provisions authorize EPA,
           which may, in turn, authorize states, to regulate the discharge of
           pollutants into waters of the United States. These pollutants may
           include contaminants such as perchlorate. The Safe Drinking Water
           Act authorizes EPA to respond to actual or threatened releases of
           contaminants into public water systems or underground sources of
           drinking water, regardless of whether the contaminant is regulated
           or unregulated, where there is an imminent and substantial
           endangerment to health and the appropriate state and local
           governments have not taken appropriate actions. Under certain
           environmental laws such as RCRA, EPA can authorize states to
           implement the requirements as long as the state programs are at
           least equivalent to the federal program and provide for adequate
           enforcement.

           In addition, some states have their own environmental and water
           quality laws that provide state and local agencies with the
           authority to monitor, sample, and require cleanup of various
           regulated and unregulated hazardous substances that pose an
           imminent and substantial danger to public health. For example, the
           California Water Code authorizes Regional Water Control Boards to
           require sampling of waste discharges and to direct cleanup and
           abatement, if necessary, of any threat to water, including the
           release of an unregulated contaminant such as perchlorate.
           Finally, according to EPA and state officials, at least 9 states
           have established nonregulatory action levels or perchlorate
           advisories, ranging from under 1 part per billion to 18 parts per
           billion, under which responsible parties have been required to
           sample and clean up perchlorate. For example, according to
           California officials, the state of California has a public health
           goal for perchlorate of 6 parts per billion and has used the goal
           to require cleanup at one site.

^4Castaic Lake Water Agency v. Whittaker Corp, 272 F. Supp. 2d 1053 (C.D.
Cal. 2003). The conclusion that perchlorate is a hazardous waste was the
first step in the court's analysis of whether perchlorate is a hazardous
substance under the Comprehensive Environmental Response, Compensation,
and Liability Act (CERCLA). (The definition of hazardous substances under
CERCLA includes hazardous waste under RCRA.)

           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. Roughly one-half of the
           contaminated sites were found in Texas (118) and California (106),
           where both states conducted broad investigations to determine the
           extent of perchlorate contamination. As shown in figure 1, the
           highest perchlorate concentrations were found in five
           states--Arkansas, California, Nevada, Texas, and Utah--where,
           collectively, 11 sites had concentrations exceeding 500,000 parts
           per billion. However, most of the 395 sites did not have such high
           levels of contamination. We found 271 sites where the
           concentration was less than 24.5 parts per billion, the drinking
           water concentration equivalent calculated on the basis of EPA's
           reference dose.

Figure 1: Number of Sites and Maximum Perchlorate Concentrations, by State

According to EPA and state agency officials, the greatest known source of
contamination was defense and aerospace activities. 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. Officials said the source of the contamination at another 58
sites was agriculture, a variety of other commercial activities such as
fireworks and flare manufacturing, and perchlorate manufacturing and
handling. At the remaining sites, state agency officials said the source
of the perchlorate was either undetermined (122 sites) or naturally
occurring (105 sites). Further, all 105 sites with naturally occurring
perchlorate are located in the Texas high plains region where perchlorate
concentrations range from 4 to 59 parts per billion.

Figure 2: Activities Linked to Perchlorate, by Site

Of the sites we identified, 153 were public drinking water systems. The
Safe Drinking Water Act's Unregulated Contaminant Monitoring Regulation
required sampling of public drinking water systems for a 12-month period
between 2001 and 2003. . As of January 2005, 153 (about 4 percent) of
3,722 systems that were sampled and reported reported finding perchlorate
to EPA. Located across 26 states and 2 commonwealths, these 153 sites
accounted for more than one-third of the sites we identified where
perchlorate concentrations reported ranged from 4 parts per billion to 420
parts per billion but averaged less than 10 parts per billion. Only 14 of
the 153 public drinking water systems had concentration levels above 24.5
parts per billion, the drinking water equivalent calculated on the basis
of EPA's revised perchlorate reference dose. California had the most
public water systems with perchlorate, where 58 systems reported finding
perchlorate in drinking water. The highest drinking water perchlorate
concentration of 420 parts per billion was found in Puerto Rico in 2002.
Subsequent sampling in Puerto Rico did not find any perchlorate, and
officials said the source of the initial finding was undetermined.

These 153 public drinking water systems that found perchlorate serve
populated areas, and an EPA official estimated that as many as 10 million
people may have been exposed to the chemical. EPA officials told us they
do not know the source of most of the contamination found in public
drinking water systems, but that 32 systems in Arizona, California, and
Nevada were likely due to previous perchlorate manufacturing at a Kerr
McGee Chemical Company site in Henderson, Nevada. Regional EPA and state
officials told us they did not plan to clean up perchlorate found at
public drinking water sites until EPA establishes a drinking water
standard for perchlorate. In some cases, officials did not plan to clean
up because subsequent sampling was unable to confirm that perchlorate was
present.

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. As a result, EPA officials said they did not always know whether
other federal and state agencies found perchlorate because, as is
generally the case with unregulated contaminants, there is no requirement
for states or other federal agencies to routinely report perchlorate
findings to EPA.

For example, DOD is not required to report to EPA when perchlorate is
found on active installations and facilities. Consequently, EPA region
officials in California said they did not know the Navy found perchlorate
at the Naval Air Weapons Station at China Lake because the Navy did not
report the finding to EPA. Further, states are not required to routinely
notify EPA about perchlorate contamination they discover. For example, EPA
region officials in California said the Nevada state agency did not tell
them perchlorate was found at Rocketdyne, an aerospace facility in Reno,
or that it was being cleaned up. EPA only learned about the perchlorate
contamination when the facility's RCRA permit was renewed.

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. After interviewing DOD and EPA
officials about which studies they considered important in assessing
perchlorate health risks, we reviewed 90 that were relevant to our work.
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.

DOD, EPA, and industry sponsored the majority of the 90 health studies we
reviewed; the remaining studies were conducted by academic researchers and
other federal agencies. Of these 90 studies, 49 were experiments that
sought to determine the effects of perchlorate on humans, mammals, fish,
and/or amphibians by exposing these groups to different doses of
perchlorate over varied time periods and comparing the results with other
groups that were not exposed. Twelve were field studies that compared
humans, mammals, fish, and/or amphibians in areas known to be contaminated
with the same groups in areas known to be uncontaminated. Both types of
studies have limitations: the experimental studies were generally short in
duration, and the field studies were generally limited by the researchers'
inability to control whether, how much, or how long the population in the
contaminated areas was exposed. 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. The 3 remaining studies used another
methodology.^5 Many of the studies we reviewed contained only research
findings, rather than conclusions or observations on the health effects of
perchlorate. Appendix III from our 2005 report provides data on these
studies, including who sponsored them; what methodologies were used; and,
where presented, the author's conclusions or findings on the effects of
perchlorate.

^5The number of study types is greater than the total number of studies
because 3 studies used a combination of experimental design and data
analysis methodologies.

Only 44 of the studies we reviewed had conclusions on whether perchlorate
had an adverse effect. However, adverse effects of perchlorate on the
adult thyroid are difficult to evaluate because they may happen over
longer time periods than can be observed in a typical research study.
Moreover, different studies used the same perchlorate dose amount but
observed different effects, which were attributed to variables such as the
study design type or age of the subjects. Such unresolved questions were
one of the bases for the differing conclusions in EPA, DOD, and academic
studies on perchlorate dose amounts and effects.

The adverse effects of perchlorate on development can be more easily
studied and measured within typical study time frames. Of the studies we
reviewed, 29 evaluated the effect of perchlorate on development, and 18 of
these found adverse effects resulting from maternal exposure to
perchlorate. According to EPA officials, the most sensitive population for
perchlorate exposure is the fetus of a pregnant woman who is also nearly
iodine-deficient. However, none of the 90 studies that we reviewed
considered this population. Some studies reviewed the effect on the
thyroid of pregnant rats, but we did not find any studies that considered
perchlorate's effect on the thyroid of nearly iodine-deficient pregnant
rats.

In January 2005, the National Academy of Sciences issued its report on
EPA's draft health assessment and the potential health effects of
perchlorate. The Academy reported that although perchlorate affects
thyroid functioning, there was not enough evidence to show that
perchlorate causes adverse effects at the levels found in most
environmental samples. Most of the studies that the Academy reviewed were
field studies, the report said, which are limited because they cannot
control whether, how much, or how long a population in a contaminated area
is exposed. The Academy concluded that the studies did not support a clear
link between perchlorate exposure and changes in the thyroid function in
newborns and hypothyroidism or thyroid cancer in adults. In its report,
the Academy noted that only 1 study examined the relationship between
perchlorate exposure and adverse effects on children, and that no studies
investigated the relationship between perchlorate exposure and adverse
effects on vulnerable groups, such as low-birth-weight infants. The
Academy concluded that an exposure level higher than initially recommended
by EPA may not adversely affect a healthy adult. The Academy recommended
that additional research be conducted on perchlorate exposure and its
effect on children and pregnant women but did not recommend that EPA
establish a drinking water standard. To address these issues, in October
2006, CDC researchers published the results of the first large study to
examine the relationship between low-level perchlorate exposure and
thyroid function in women with lower iodine levels. 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.

Mr. Chairman, this concludes my testimony. I would be pleased to answer
any questions that you or other Members of the Subcommittee may have at
this time.

GAO Contacts and Staff Acknowledgments

For further information about this presentation, please contact me, John
Stephenson, at (202) 512-3841 or [email protected] . Contact points
for our Offices of Congressional Relations and Public Affairs may be found
on the last page of this statement. Contributors to this testimony include
Steven Elstein, Assistant Director, and Terrance Horner, Senior Analyst;
Richard Johnson, Alison O'Neill, Kathleen Robertson, and Joe Thompson also
made key contributions.

(360840)

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Highlights of [21]GAO-07-797T , a testimony before the Subcommittee on
Environment and Hazardous Materials, House Committee on Energy and
Commerce

April 25, 2007

PERCHLORATE

EPA Does Not Systematically Track Incidents of Contamination

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.

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.

Number of Sites and Maximum Perchlorate Concentrations, by State

References

Visible links
  11. http://www.gao.gov/cgi-bin/getrpt?GAO-05-462
  12. http://www.gao.gov/cgi-bin/getrpt?GAO-07-464T
  21. http://www.gao.gov/cgi-bin/getrpt?GAO-07-797T
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