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Perchlorate
In January 2009, EPA issued an interim health advisory to assist state and local officials in addressing local contamination of perchlorate in drinking water. The interim health advisory level of 15 micrograms per liter (µg/L), or parts per billion (ppb), is based on the reference dose recommended by the National Research Council (NRC) of the National Academy of Sciences (NAS). The Agency is also seeking advice from the NAS before making a final regulatory determination on whether to issue a national regulation for perchlorate in drinking water.
- Interim Drinking Water Health Advisory for Perchlorate PDF (49pp, 406K, About PDF)
December 2008, EPA 822-R-08-25 - Questions and Answers
In October 2008, EPA made a preliminary regulatory determination for perchlorate in drinking water.
EPA has established a reference dose for perchlorate, which is consistent with the reference dose recommended by the National Research Council’s 2005 report.
Additional information about perchlorate can also be found on the EPA Federal Facilities page
Questions and Answers
- Why isn’t EPA making a final regulatory determination?
- What kind of comments did the Agency receive on the Federal Register notice?
- What did the peer reviewers say on their review of EPA’s adaptation and application of the PBPK model to assess effects on sensitive subpopulations?
- What is EPA asking the NAS to do?
- What is the timing for the NAS review and final regulatory determination?
- Why is EPA issuing an interim health advisory?
- What is the basis for EPA’s interim health advisory level of 15 µg/L?
- What comments did EPA get on its peer review of the health advisory?
- How does this decision impact clean up of perchlorate at Superfund sites?
- How frequently is perchlorate found in drinking water?
- How will a public water system know if it has perchlorate in its water?
- How will I know if I have perchlorate in my drinking water?
- How can perchlorate be removed if it gets in my drinking water?
- If I shouldn’t drink water with perchlorate levels above 15 µg/L, does this mean I should also avoid foods that have those concentrations?
Why isn’t EPA making a final regulatory determination?
After reviewing the public comments on the preliminary regulatory determination and peer review comments on a draft health advisory for perchlorate, EPA believes that it would benefit once again from input from the National Academy of Sciences on several specific scientific issues raised by reviewers.
What kind of comments did the Agency receive on the Federal Register notice?
EPA received more than 32,000 comments on the preliminary regulatory determination. The majority of comments were submitted by individuals opposed to the decision using similar language linked to organized write-in campaigns. There were also unique comments that provided additional scientific evaluation of the information EPA used in making the preliminary determination.
- Some commenters supported EPA’s preliminary determination that a national regulation is not needed based on the science and its limited occurrence nationally in water supplies.
- Some commenters questioned EPA’s derivation of the health reference level of 15 µg/L, including the reference dose that served as the basis for the calculation.
- Some commenters questioned EPA’s consideration of the effects of drinking water at the health reference level on infants and children.
- Some commenters questioned the use of a physiologically-based pharmacokinetic (PBPK) model to assess potential effects on sensitive populations.
All of the comments received on the notice can be reviewed on www.regulations.gov. Refer to docket number EPA-HQ-OW-2008-0692.
What did the peer reviewers say on their review of EPA’s adaptation and application of the PBPK model to assess effects on sensitive subpopulations?
EPA’s National Center for Environmental Assessment (NCEA) had its application of the PBPK model, described in the document Inhibition of the Sodium-Iodide Symporter By Perchlorate: An Evaluation of Lifestage Sensitivity Using Physiologically Based Pharmacokinetic (PBPK) Modeling , reviewed by eight peer reviewers. All eight reviewers indicated that the EPA’s description of the PBPK analysis was logical, and clear. Several reviewers identified additional studies for the EPA to consider as input parameters to the model.
What is EPA asking the NAS to do?
EPA is asking the NAS to review several specific scientific issues that were raised by commenters and through peer review. For example, EPA is asking the NAS to evaluate several scientific issues related to its derivation of the Health Reference Level of 15 µg/L; the use of PBPK modeling to evaluate impacts on infants and young children; and the implications of recent biomonitoring studies. The Agency also is asking the NAS how it should consider the role of perchlorate exposure relative to exposure to other compounds that may disrupt thyroid function by inhibiting iodide uptake and if there are other public health strategies to address this aspect of thyroid health. The Agency will post additional information about the review when it is available.
What is the timing for the NAS review and final regulatory determination?
We cannot say at this time when we would expect the NAS review to be completed. The Agency intends to issue a final regulatory determination as soon as possible after receiving and reviewing the NAS report.
Why is EPA issuing an interim health advisory?
EPA believes that it is important to improve public health protection for the most sensitive subpopulation identified by the NAS, the fetuses of pregnant women. Although the Agency is seeking advice from the NAS before making a final regulatory determination, the Agency also recognizes that there is a need for guidance to help public health officials and public water systems take appropriate action to address local incidences of perchlorate contamination. In their comments on the preliminary regulatory determination, the Association of State Drinking Water Administrators and the American Water Works Association both called for the need for a health advisory. The Agency is issuing this interim health advisory to provide protection as it seeks information to help make a final regulatory determination. The Agency expects to issue a final health advisory as part of a final regulatory determination.
- Interim Drinking Water Health Advisory for Perchlorate PDF (49pp, 406K, About PDF)
December 2008, EPA 822-R-08-25
What is the basis for EPA’s interim health advisory level of 15 µg/L?
The interim health advisory level is based on the reference dose recommended by the National Research Council (NRC) as reported in their report Health Implications of Perchlorate Ingestion. EPA adopted the NRC’s recommended reference dose (RfD) of 0.7 ug/kg/day. EPA then calculated the interim health advisory level for perchlorate for the most sensitive subpopulation as identified by the NRC, the fetuses of pregnant women. The interim health advisory level is the estimate of the maximum concentration of perchlorate that can be in the drinking water of a pregnant woman without her total (food and water) exposure exceeding EPA’s RfD for perchlorate. The interim health advisory level takes into account high-end estimates of the amount of perchlorate that may be in her food and of the amount of water she may drink.
What comments did EPA get on its peer review of the health advisory?
EPA had a draft of its health advisory for perchlorate reviewed by four external peer reviewers. The recommendations from the four reviewers ranged from generally supportive with some suggested minor improvements to concerns over gaps in the underlying analysis. The analytical issues identified by the peer reviewers include questions over the adequacy of the analysis to address all of the potentially sensitive sub populations (e.g., iodide deficient pregnant women) and life stages (pre-term and full term infants). Many of the issues raised by the reviewers will be addressed in the Agency’s charge to the NAS.
- Comment-Response Summary Document for Peer Review of Drinking Water Health Advisory for Perchlorate (PDF) (94pp, 474K)
How does this decision impact clean up of perchlorate at Superfund sites?
As a result of the publication of the Interim Health Advisory for perchlorate, the Agency is formally withdrawing the January 26, 2006 guidance it issued regarding perchlorate and sites addressed under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) and the National Oil and Hazardous Substances Contingency Plan (National Contingency Plan or NCP). The January 2006 guidance recommended that Regions consider using a preliminary remediation goal (PRG) of 24.5 ppb (or µg/L). In its place, the Agency now recommends that Regions consider using the interim health advisory level of 15 µg/L as a PRG; consistent with the NCP, the Agency often considers health advisories as “to be considered” (TBC) values for setting cleanup levels. Also, where state regulations establish applicable or relevant and appropriate requirements (ARARs) for perchlorate, these standards should be used as the cleanup level at Superfund sites, unless the ARAR is waived at the site.
How frequently is perchlorate found in drinking water?
Perchlorate was sampled in drinking water supplies as part of the Unregulated Contaminant Monitoring Regulation 1 (UCMR 1) List 1 Assessment Monitoring program. Occurrence data for perchlorate was collected from 3,865 public water supplies between 2001 and 2005. This included all public water supplies serving more than 10,000 people, which together served more than 80% of the population. Approximately 160 (4.1%) of these systems had at least 1 analytical detection of perchlorate (in at least 1 entry/sampling point) at levels greater than or equal to 4 µg/L (the minimum detection level of the test). These 160 systems are located in 26 states and 2 territories and approximately 1.9% (or 637) of the 34,331 samples collected (by these 3,865 public water supplies) had positive detections of perchlorate at levels greater than or equal to 4 µg/L. The average concentration of perchlorate for those samples with positive detections for perchlorate was 9.85 µg/L and the median concentration was 6.40 µg/L. Thirty-one systems had average concentrations greater than or equal to 15 µg/L during the 2001-2005 sampling. Results from UCMR 1 monitoring are available at the site listed below.
How will a public water system know if it has perchlorate in its water?
Systems that were required to monitor for perchlorate as part of UCMR1 will know if they detected perchlorate at levels that exceed the advisory level of 15 µg/L and may have taken action to reduce their levels. Some public water systems have on-going monitoring programs for perchlorate in drinking water. If water systems have not monitored for perchlorate, they can review their source water assessment to determine if there are any potential sources of perchlorate contamination within their source water protection area. If an activity is taking place that could result in perchlorate contamination, they may want to test their water for the presence of perchlorate.
How will I know if I have perchlorate in my drinking water?
You may want to call your drinking water utility or state drinking water program to learn the results of past monitoring or to find out if monitoring is required in your state. While EPA does not regulate perchlorate in drinking water, some public drinking water systems monitored for this contaminant in the past to meet EPA requirements. In addition, California and Massachusetts have issued drinking water standards for perchlorate of 6 µg/L and 2 µg/L, respectively. If there is no requirement for monitoring in your state, you can have your water analyzed by a laboratory that is certified for the analysis of perchorate or similar compounds. An EPA website provides a list of state certification officers or links to certified laboratories in your state. The contacts provided may be able to assist you in finding an appropriate laboratory. You can also call your local public health office to determine if they are aware of any problems with perchlorate in your area.
How can perchlorate be removed if it gets in my drinking water?
Reverse osmosis technology has been certified by NSF International to remove perchlorate from levels as high as 130 µg/L to 4 µg/L or less in drinking water. However, before installing a home treatment unit, we recommend that you contact the manufacturer to determine if the unit can remove perchlorate from your water supply.
If I shouldn’t drink water with perchlorate levels above 15 µg/L, does this mean I should also avoid foods that have those concentrations?
No. The Food and Drug Administration stresses that consumers should maintain a healthy diet consistent with the Dietary Guidelines for Americans, which emphasizes eating a variety of foods across all food groups each day. EPA’s interim health advisory level for perchlorate is based on the most sensitive subpopulation as identified by the NRC, the fetuses of pregnant women. In setting the interim health advisory level, EPA accounted for the amount of perchlorate one may consume in food. If all perchlorate came from drinking water, we estimate a pregnant woman could consume drinking water with 24.5 µg/L of perchlorate and not exceed the perchlorate reference dose. Because it’s easier to control perchlorate exposure from water than it is from a diet consisting of many types of food, EPA is recommending that drinking water contain no more than 15 µg/L of perchlorate. This amount, combined with the amount of perchlorate exposure a pregnant woman may get through her diet, is not expected to exceed the reference dose for perchlorate.