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Perchlorate Frequently Asked Questions

California Adopts MCL of 6 ppb


The State of California has adopted a Maximum Contaminant Level for perchlorate in drinking water at 6 parts per billion. The MCL is effective beginning October 18, 2007. Anaheim's water supply is in compliance with the adopted MCL.


Many cities throughout California, as well as in other states, have detected perchlorate in their water supplies. As your water provider, Anaheim Public Utilities would like to reassure you that perchlorate has not affected the safety of your water. Individuals have asked many important questions about perchlorate, and we’d like to share the answers with all our interested customers.


Following are some of the more frequent questions we receive regarding perchlorate. Clicking on the questions below will take you immediately to the answer, or you may scroll down to review all the information.


Q. What is perchlorate?

A. Perchlorate is both a natural and a man-made salt made up of chlorine and oxygen. Today, it is widely used by the military, NASA and the commercial space industry as an ingredient in solid rocket fuel, fireworks and explosives. Perchlorate is naturally present in some fertilizers used in organic farming.


Q. Is perchlorate a health risk?

A. The results of studies conducted so far show that low levels of perchlorate have no adverse effect on human health. At high levels, perchlorate can disrupt iodine uptake in the thyroid gland, which regulates hormone formation. If hormones are not generated, human growth and development could be impacted.


Q. Can perchlorate damage the thyroid gland?

A. Most research indicates that high levels of perchlorate, above 200 parts per billion, can temporarily affect the thyroid’s ability to absorb iodide from the bloodstream. Perchlorate is not stored in any human tissues, so there is not a cumulative effect. Though preliminary research by the United States Environmental Protection Agency (U.S. EPA) indicates that there may be a link between perchlorate and thyroid damage, the January 2005 report released by the National Academy of Sciences (NAS) concludes that thyroid damage due to perchlorate is unlikely.


Q. Is it true that perchlorate was used as a medicine?

A. Yes, in the 1950s, perchlorate was approved by the U.S. Food and Drug Administration as a safe and effective medication to treat people with overactive thyroid glands. It has been replaced in the United States with newer medications, in part because it took enormously high doses to have any effect on the thyroid and these doses had to be given frequently because perchlorate is so rapidly eliminated from the body.


Q. At what level is perchlorate harmful to consume in drinking water?

A. The California Department of Public Health has established a drinking water standard of 6 parts per billion (ppb) effective October 18, 2007. This is the same as the Public Health Goal, which is set to protect persons most sensitive to the effects of perchlorate – individuals with hypothyroidism, pregnant women and infants. To learn more, visit http://www.cdph.ca.gov/certlic/drinkingwater/Pages/Perchlorate.aspx


Q. What was the result of the National Academy of Sciences (NAS) January 2005 report?

A. The NAS report, “Health Implications of Perchlorate Ingestion,” concludes that a dose of 0.007 mg/kg/day would cause no observable effects in the most sensitive individuals. NAS is careful to note that this “reference dose” is not a drinking water standard and that additional work is needed in order to set a drinking water standard. The NAS believes that perchlorate’s impact on the thyroid’s ability to process iodide is temporary and can be mitigated by internal adjustments within the body. The NAS report can be found at http://www.nap.edu/books/0309095689/html/ .


Q. What is the US EPA doing about perchlorate?

A. In December 2008, the US EPA set a Health Reference Advisory of 15 ppb to protect the most sensitive members of the population to help guide cleanup at contaminated sites. In addition, they continue to seek advice from the NAS on possible regulatory action..


Q. Is perchlorate also found in food?

A. The U.S. Food and Drug Administration published results of testing for perchlorate in milk, lettuce and bottled water on November 26, 2004. Perchlorate was found in most samples of milk and lettuce but was rarely detected in bottled water. FDA cautions that the data is preliminary and does not indicate there is a health risk associated with eating lettuce or drinking milk. FDA intends to conduct additional studies and will publish information as it becomes available. You may access the FDA's perchlorate website by clicking on this link: http://www.fda.gov/Food/FoodborneIllnessContaminants/ChemicalContaminants/ucm077572.htm


Q. How much perchlorate is in Anaheim’s drinking water?

A. Recent monitoring shows that perchlorate is below the detection level in all but one well, and as of January 2008, that well has been placed in stand-by mode.

Q. Have any wells in Anaheim been closed because of perchlorate contamination?

A. No wells in Anaheim have been closed because of perchlorate contamination. Some wells, in which perchlorate was detected, have been closed due to pump failures or other maintenance issues. The one remaining well in which perchlorate has been detected has been placed in stand-by mode, which means it will only be used if there is an emergency, such as a major fire.


Q. What are the sources of perchlorate in Anaheim’s water?

A. Extensive studies have been conducted to determine the source of perchlorate in the Orange County Groundwater Basin. The conclusion of local experts is that the perchlorate found in the Orange County Groundwater Basin is thought to have come from the Colorado River. Perchlorate has been present in the Colorado River due to past releases from defense contractor facilities. Although the contamination is mostly cleaned up today, river water has been used to help recharge the groundwater basin since the 1960s. Several investigations have been made to determine if any local sources, including fireworks shows, could have contributed to perchlorate levels in groundwater. At this time there is no evidence that any local source has caused perchlorate contamination.


Q. What can Anaheim do to remove perchlorate?

A. Perchlorate can be removed from groundwater by advanced treatment systems. Staff from Anaheim has met with consultants to estimate what this type of treatment would cost. Treatment of perchlorate could cost up to $50 million and lead to an increase in water rates by 15 to 25 percent.
      Given that
Anaheim’s perchlorate levels are below the PHG that protect the most sensitive persons, we do not believe that it is prudent to invest in treatment systems to remove the low levels of perchlorate from our water supply.
      However, if perchlorate levels were to unexpectedly increase, your Water Utility has already worked with an engineering consultant to identify the treatment systems needed to remove perchlorate.
Anaheim is committed to protecting water quality and stands ready to implement additional treatment if needed.


Q. What is Anaheim doing about this issue?

A. Anaheim will continue to monitor its water supply for perchlorate and maintain a close watch on perchlorate issues throughout the State. If at any time a water supply well contains perchlorate above the state standard, the source will not be used until the perchlorate levels can be reduced.


Q. Should I drink bottled water to be on the safe side?

A. People drink bottled water for a variety of reasons – including convenience, a preference in taste or a perceived belief that bottled water equates to a better quality water. However, you should know that the water quality standards for tap water are actually more stringent than for bottled water.


Q. How does California’s MCL and Public Health Goal of 6 ppb for perchlorate compare to other states?

A. Arizona Department of Environmental Quality has set a "protective health-based guidance level" of 14 ppb.

    Massachusetts Department of Environmental Protection set an MCL of 2 ppb for sensitive individuals (infants, children, pregnant women and persons with hypothyroidism).

    Nevada State Health Division has set a Public Notice Standard of 18 ppb.

    New York has established a notification level of 18 ppb and a "planning level" of 5 ppb..

Q. What about people who drank water with perchlorate above the Public Health Goal?

A. Sensitive individuals, such as pregnant women, infants and persons with hypothyroidism, should consult a health care professional. Most individuals would not be affected by much higher concentrations of perchlorate.


Q. Can low levels of perchlorate cause birth defects?

A. Currently, there are no studies showing perchlorate as a cause of birth defects.


Q. Where can I find more information on perchlorate?

A. You can contact the Environmental Services Manager of Anaheim Public Utilities via e-mail at dwilson@anaheim.net or by phone at 714/765-4277.



Other sources for water quality information, which are not already included above:








Updated: April 7, 2009