About Regulation of Perchlorate

Credible Science Should Lead The Way

Q: What are California's proposed "safe" exposure levels and how were they derived?

A: In 2004, California's Environmental Protection Agency (Cal/EPA) - accounting for perchlorate exposure from water, farm products and cow's milk - adopted a "Public Health Goal" (PHG) for perchlorate in drinking water of 6 ppb, despite ongoing scientific controversy. For example:

  • Studies that show perchlorate begins to affect the thyroid at approximately 245 ppb, and below this level there is no measurable effect. (Studies show levels below 14,000 ppb do inhibit the body's ability to absorb iodine, but even this is not an adverse health effect.)
  • Cal/EPA requested a peer review by a panel of scientists convened by the University of California (UC) to review its own risk assessment on perchlorate;
  • Three UC researchers conducted the review and each disagreed with Cal/ EPA's Office of Environmental Health Hazard Assessment, and one another, on how the state should proceed.


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Q: Are the federal 24.5 ppb Drinking Water Equivalent Level (DWEL) and California's PHG "final" standards?

A: California has set a goal as a first step in setting a standard. At the federal level, U.S. EPA now will need to determine whether to proceed with a national drinking water standard for perchlorate.


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Q: What are the next steps in U.S. EPA's regulatory process for perchlorate?

A: EPA's 24.5 ppb DWEL may be used by officials throughout the agency to make site-specific cleanup or interim drinking water standard decisions involving perchlorate. States and private parties also may look to EPA's RfD and DWEL as they make similar decisions.

At this juncture, EPA is contemplating two regulatory decisions:

First, EPA may revise its 2003 Interim Guidance on perchlorate. That guidance recommended that EPA Regions use a range of 4 ppb to18 ppb for site-specific cleanup decisions or interim drinking water standards. Since EPA's guidance values of 4 ppb to18 ppb were based on older scientific studies and analyses, the agency might choose to change the guidance to reflect its new DWEL.

Second, EPA must decide whether to promulgate a Federal drinking water standard (MCL) for perchlorate. EPA will only proceed with a standard if it determines that perchlorate adversely affects human health, is known or likely to substantially occur in public water systems at frequencies and levels that would cause adverse health effects, and that setting a Federal standard for perchlorate presents a meaningful opportunity to reduce the risk from perchlorate exposure.


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Q: What are the next steps in California's regulatory process for perchlorate?

A: California has set a state Public Health Goal (PHG) for perchlorate of 6 ppb. This accounted for exposure from water as well as from other sources, such as farm products, breast milk and cow's milk.

The California Department of Health Services (DHS) has already begun the process for adopting an enforceable drinking water standard (the MCL) for perchlorate. State law requires that the MCL be set as close to the PHG as is economically and technologically feasible, but does not require the state to investigate the science any further.

Currently, if the level of perchlorate in drinking water exceeds 6 ppb - the "Action Level" set by the DHS as a temporarily acceptable level pending adoption of the MCL - water system operators are required to notify local government agencies. The DHS also recommends that consumers be notified, and that the drinking water source be removed from service, if perchlorate is found at levels 10 times the Action Level. Some drinking water purveyors have already stopped serving drinking water that contains any amount of detectable perchlorate, thereby preventing all potential exposures while the MCL is pending.


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Q: What are the impacts of unnecessarily restrictive standards?

A: The costs of an overly restrictive (i.e., more restrictive than what credible science says is necessary to protect public health) drinking water standard for perchlorate are potentially staggering. California, Nevada and Arizona could be the states most impacted. Overly strict standards would in effect create a "problem" where one does not really exist, forcing citizens, industry and government to incur significant expenses for new treatment plants, retrofitting existing treatment plants, purchasing additional water supplies, lowering reservoir levels and pumping more groundwater from existing sources. This could not only be a substantial expense of resources that could lead to no public health benefit, it could also contribute to a significant water shortage crisis as water supplies are closed because they do not meet the new standards.

Likewise, in California's agriculturally rich areas where water with low amounts of perchlorate is used to irrigate crops, overly restrictive standards could hurt farmers by making their irrigation water scarcer and more expensive. Even more alarming, worried consumers across the country and abroad might avoid buying the crops these farmers grow.


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Q: What is being done now to address perchlorate in drinking water supplies?

A: Perchlorate is being contained, removed and treated at sites where it has been used in the past for manufacturing. New state-of-the-art technologies for removing perchlorate from water have been developed and put into use. Others are being developed or refined. In addition, key members of the aerospace and defense industries, along with the U.S. EPA, the U.S. Department of Defense, and the U.S. Air Force, formed the Perchlorate Study Group in 1993 to fund scientific research so policies could be established to protect public health based on credible science.


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