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Peer Review of EPA Draft Human Health and Ecological Risk Assessment of Perchlorate

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Environmental Protection Agency.


Notice of Peer Review Workshop and public comment period.


The U.S. Environmental Protection Agency (EPA) Office of Research and Development is announcing an external peer review workshop to review the revised draft document entitled, “Perchlorate Environmental Contamination: Toxicological Review and Risk Characterization” (NCEA-I-0503). The EPA is also announcing a public comment period for this draft document. The workshop is being organized and convened by the Eastern Research Group, Inc. (ERG), an EPA contractor.


The two-day peer review workshop will begin on Tuesday, March 5, 2002, at 9 a.m. and will end on Wednesday, March 6, 2002, at 4:30 p.m. The 30-day public review and comment period will begin January 9, 2002, and will end February 11, 2002.


The external peer review meeting will be held at a facility in Sacramento, California. To attend the meeting as an observer, please register with ERG via the Internet by visiting You may also register by calling ERG's conference registration line at 781-674-7374 or by faxing a registration request to 781-674-2906. Upon registering, you will be sent an agenda and a logistical fact sheet containing information on the meeting site, overnight accommodations, and ground transportation. The deadline for pre-registration is February 25, 2002. Space is limited, and reservations will be accepted on a first-come, first-served basis. There will be a limited time for oral comments on the revised draft document during the meeting. When registering, please let ERG know if you Start Printed Page 76wish to make a brief statement not to exceed five minutes.

Document Availability: The external review draft of the perchlorate document will be available by January 9, 2002, on EPA's National Center for Environmental Assessment (NCEA) Web site at​ncea. In addition, a compact disk (CD) containing documents cited in the “Perchlorate Environmental Contamination: Toxicological Review and Risk Characterization” report that cannot be readily obtained from the open literature will be available by request as of January 9, 2002. To obtain a copy of the CD, you may contact the EPA Superfund Records Center in San Francisco, California. A shipping and handling fee may apply. The circulation desk phone number for the Superfund Records Center is 415-536-2000. Copies of the perchlorate document and CD are not available from ERG.

Comment Submission: Written comments should be submitted to ERG, Inc., 110 Hartwell Avenue, Lexington, Massachusetts 02421. Comments under 50 pages may be sent via e-mail attachment (in Word, Word Perfect, or PDF) to Written comments must be postmarked by the end of the public comment period (February 11, 2002). Please note that all technical comments received in response to this notice will be placed in a public record. For that reason, commentors should not submit personal information (such as medical data or home address), Confidential Business Information, or information protected by copyright. Due to limited resources, acknowledgments will not be sent.

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Questions regarding registration and logistics should be directed to EPA's contractor, ERG, Inc., at 781-674-7374. For technical inquiries, please contact: Annie Jarabek, U.S. Environmental Protection Agency (MD 52), USEPA Mailroom, Research Triangle Park, NC 27711; telephone 919-541-4847; facsimile 919-541-1818; e-mail

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Perchlorate (ClO4) is an anion that originates as a contaminant in groundwater and surface waters from the dissolution of ammonium, potassium, magnesium, or sodium salts. Perchlorate is exceedingly mobile in aqueous systems and can persist for many decades under typical groundwater and surface water conditions. A major source of perchlorate contamination is the manufacture of ammonium perchlorate for use as the oxidizer component and primary ingredient in solid propellant for rockets, missiles, and fireworks.

EPA's Superfund Technical Support Center issued a provisional reference dose (RfD) for perchlorate in 1992 and a revised provisional RfD in 1995 based on the effects of potassium perchlorate in patients with Graves' disease (an autoimmune disease that results in hyperthyroidism). (An RfD is an estimate of a daily oral human exposure that is anticipated to be without adverse noncancer health effects over a lifetime.) In March 1997, the existing toxicologic database on perchlorate was determined to be inadequate for quantitative human health risk assessment by an external peer review panel. A lack of data on the ecotoxicological effects was also noted. In May 1997, a testing strategy was developed based on the known mode-of-action for perchlorate toxicity (the inhibition of iodide uptake in the thyroid and subsequent perturbations of thyroid hormone homeostasis), and an accelerated research program was initiated to gain a better understanding of the human health effects of perchlorate, examine possible ecological impacts, refine analytical methods, develop treatment technologies, and better characterize the occurrence of perchlorate in groundwater and surface waters.

In December 1998, the National Center for Environmental Assessment (NCEA) developed an external peer review draft document that assessed the human health and ecological risk of perchlorate (“Perchlorate Environmental Contamination: Toxicology Review and Risk Characterization Based on Emerging Information,” NCEA-I-0503). This document presented an updated human health risk assessment that incorporated results of the newly performed health effects studies available as of November 1998 and a screening-level ecological assessment. The human health risk assessment model utilized a mode-of-action approach that harmonized noncancer and cancer approaches to derive a single oral risk benchmark based on precursor effects for both neurodevelopmental and thyroid neoplasia. A workshop was convened in February 1999 in San Bernardino, California, to provide external peer review of that document. Peer reviewers endorsed the conceptual approach proposed by NCEA, but recommended that new analyses be conducted and that several additional studies be planned and performed. NCEA has prepared a revised perchlorate assessment that addresses comments from the 1999 external peer review workshop and incorporates data from additional studies that were either nearing completion at the time of the 1999 review or were recommended at that time. This revised draft document is the subject of the external peer review workshop announced in today's Federal Register notice.

The external peer review panel will consist of a panel of independent scientists selected by EPA's contractor, ERG, from the fields of developmental toxicology, reproductive toxicology, neurotoxicology, immunotoxicology, pharmacokinetics, genetic toxicology, endocrinology, pathology, epidemiology, statistics, ecotoxicology, and environmental transport and biotransformation. Peer reviewers will review the revised human health and ecological risk assessment for perchlorate as well as new studies performed since the 1999 external peer review. Following the external peer review workshop, ERG will prepare a report summarizing the workshop. EPA will address the comments of the external peer reviewers in finalizing the perchlorate risk assessment document and in developing revised toxicity values. The human health and ecological risk assessment may be used in the future to support development of a health advisory or possible drinking water regulations and cleanup decisions at hazardous waste sites. However, any such future decisions would be subject to all applicable statutory and regulatory requirements and policy considerations for use of the assessments under those programs.

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Dated: December 20, 2001.

George W. Alapas,

Acting Director, National Center for Environmental Assessment.

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[FR Doc. 01-32088 Filed 12-31-01; 8:45 am]