Reference Dose for Methylmercury

AGENCY:

Environmental Protection Agency.

ACTION:

Notice of peer-review workshop and public comment period.

SUMMARY:

The U.S. Environmental Protection Agency (EPA) is announcing that Versar, Inc., an EPA contractor for external scientific peer review, will convene a panel of experts and organize and conduct an external peer-review workshop to review the draft document titled, Reference Dose for Methylmercury (NCEA-S-0930). The EPA is also announcing a 30-day public comment period for the draft document. The document was prepared by the EPA's National Center for Environmental Assessment-Washington Office (NCEA-W) within the Office of Research and Development. NCEA will consider the peer-review advice and public comment submissions in revising the document.

DATES:

The peer-review workshop will begin on Wednesday, November 15, 2000, at 9 a.m. and end at 5 p.m. Members of the public may attend as observers, and there will be a limited time for comments from the public in the afternoon. The 30-day public comment period begins October 30, 2000, and ends November 29, 2000.

ADDRESSES:

The external peer-review panel workshop will be held at the Marriott Crystal Gateway Hotel, 1700 Jefferson Davis Highway, Arlington, Virginia 22202, (703) 920-3230. Versar, Inc., an EPA contractor, is organizing, convening, and conducting the peer-review workshop. To attend the workshop, register by November 6, 2000, by calling Versar, Inc. (Ms. Marit Espevik) at (703) 750-3000, ext. 460, or send a facsimile to (703) 642-6954. You also can register via e-mail at espevmar@versar.com. Space is limited, and reservations will be accepted on a first-come, first-served basis. There will be a limited time for comments from the public during the afternoon of the workshop. Please let Versar, Inc. know if you wish to make comments.

The external review draft is available primarily via the Internet on the National Center for Environmental Assessment's home page at http://www.epa.gov/ncea under the What's New and Publications menus. A limited number of paper copies are available from NCEA's Technical Information Staff; telephone: (202) 564-3261; facsimile: (202) 565-0050. If you are requesting a paper copy, please provide your name, mailing address, and the document title, Reference Dose for Methylmercury (NCEA-S-0930). Copies are not available from Versar, Inc.

Comments may be mailed to the Technical Information Staff (8623D), NCEA-W, U.S. Environmental Protection Agency, 1200 Pennsylvania Avenue, NW., Washington, DC 20460, or delivered to the Technical Information Staff at 808 17th Street, NW., 5th Floor, Washington, DC 20006; telephone: (202) 564-3261; facsimile: (202) 565-0050. Comments should be in writing and must be postmarked by November 29, 2000. Please submit one unbound original with pages numbered consecutively, and three copies of the comments. For attachments, provide an index, number pages consecutively with the comments, and submit an unbound original and three copies. Electronic comments may be e-mailed to: nceadc-comment@epa.gov.

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.

FOR FURTHER INFORMATION CONTACT:

For workshop information, registration, and logistics, contact Versar Inc., (Ms. Marit Espevik, telephone: (703) 750-3000, ext. 460; facsimile: (703) 642-6954).

For information about the draft document, contact the Technical Information Staff, NCEA-Washington Office; telephone: (202) 564-3261; facsimile: (202) 565-0050; or e-mail: nceadc-comment@epa.gov.

SUPPLEMENTARY INFORMATION:

In 1997, U.S. EPA issued the Mercury Study Report to Congress (MSRC). Among the assessments in the MSRC was a state-of-the-science evaluation of the health effects of methylmercury. There has been considerable discussion within the scientific community regarding the level of exposure to methylmercury that is likely to be without appreciable risk of adverse health effects. Congress directed EPA through the House Appropriations Report for FY99 to contract with the National Research Council to evaluate the body of data on the health effects of methylmercury, with particular emphasis on new data since the 1997 Mercury Study Report to Congress, and provide recommendations regarding issues relevant to the derivation of an appropriate RfD for methylmercury. EPA has thoroughly reviewed this document, and concurs with the NRC findings and recommendations. The NRC document is used as the basis for the current EPA derivation of the RfD for methylmercury.

Methylmercury is a highly toxic substance; there are a number of adverse health effects associated with methylmercury exposure. Most extensive are the data for neurotoxicity, particularly in developing organisms. Therefore the brain is considered to be the most sensitive target organ for which there are data suitable for derivation of an RfD. The NRC considered three epidemiological longitudinal developmental studies suitable for quantitative risk assessment: the Seychelles Islands, the Faroe Islands, and New Zealand. The Seychelles study has yielded no evidence of impairment related to methylmercury exposure, while both the other studies have found dose-related adverse effects on a number of neuropsychological endpoints. The Faroe Islands study, the larger of the latter two studies, has been extensively peer-reviewed and is used for the derivation of the RfD. The NRC's major finding is that the results of the Faroe Islands study provide a scientifically credible basis on which to base EPA's RfD.

The RfD derived in this assessment is 0.1 ug/kg per day. This is the same as the RfD derived by EPA in 1995 based on an earlier study of a poisoning episode in Iraq, in which data on adverse neurological effects in infants was used as the point of departure for derivation of the RfD.