OEHHA Releases Draft Advisory on Mercury in Fish in Trinity Lake and Other Water Bodies in the Trinity River Watershed

Apr 8, 2005

Release No. 05- 03 April 8, 2005
Contact: Allan Hirsch (916) 324-0995

SACRAMENTO -- The California Environmental Protection Agency's Office of Environmental Health Hazard Assessment (OEHHA) is seeking public comments on a draft fish advisory concerning elevated levels of mercury in fish in Trinity Lake and selected water bodies in the Trinity River watershed in Trinity County.

“The pristine ambience of Trinity County does not change the fact that mercury from past mining activities and other sources was released into the region's waterways, and has accumulated in the fish,” OEHHA Director Dr. Joan Denton said. “The public should still enjoy fishing in the Trinity River watershed, but we recommend that people – especially women of childbearing age and children – carefully monitor how much fish they eat.”

A fact sheet and draft report containing the proposed advisory and OEHHA's evaluation of potential health threats in the fish posed by methylmercury (the most prevalent and toxic form of mercury in fish) are available for viewing and downloading on OEHHA's Web site at www.oehha.ca.gov .

OEHHA staff scientists will make a presentation, answer questions and accept public comments on the draft advisory at a public workshop at 11:30 a.m. on May 3, 2005, at the Victorian Inn Conference Room, 1709 Main Street, Weaverville, California.

Written comments on the draft advisory can be sent until May 9, 2005, to OEHHA's Pesticide and Environmental Toxicology Section, P.O. Box 4010, Sacramento, CA 95812-4010. OEHHA will review all comments, make any appropriate revisions and issue a final advisory.

The draft advisory contains proposed guidelines for consumption of fish from the following Trinity County water bodies: Trinity Lake (also known as Clair Engle Lake), the Trinity River, Lewiston Lake, Coffee Creek, Canyon Creek, Eastman Creek, Eastman Dredge Ponds, Carrville Pond, Crow Creek, Tamarack Creek, the New River and the East Fork Trinity River and its tributaries.

One set of proposed guidelines is for women of childbearing age and children age 17 and younger, who are particularly sensitive to methylmercury. A second set of proposed guidelines is for women beyond their childbearing years and men. Until a final advisory is issued, OEHHA recommends that the public follow the advice in the draft advisory.

The draft advisory contains the following recommendations for women of childbearing age and children age 17 and under:

Limit consumption of all bass from all water bodies named above to one meal a month, and also consumption of Chinook (king) salmon from Trinity Lake, and rivers and creeks draining into the lake, to one meal a month. With the exception of trout from Lewiston Lake and Carrville Pond, consumption of all other sport fish species, including white catfish from all water bodies and trout from any other water body, should be limited to one meal a week. The one-meal-a-week recommendation also applies to salmon from rivers and creeks below Lewiston Lake. Trout from Lewiston Lake and Carrville Pond may be consumed up to three times per week for this population group.

The draft advisory contains the following recommendations for women beyond childbearing years and men:

Limit consumption of all bass from the water bodies named above to one meal a week, and also consumption of Chinook (king) salmon from Trinity Lake, and rivers and creeks draining into the lake, to one meal a week. Consumption of all other sport fish species, including white catfish and trout, should be limited to three meals a week. The three-meal-a-week recommendation also applies to salmon from rivers and creeks below Lewiston Lake.

The draft advisory incorporates the results of fish sampling conducted recently in the Trinity River watershed by the U.S. Geological Survey and the State Water Resources Control Board.

Mercury in fish from the Trinity River watershed originated from the mining of mercury and gold, the majority of which took place from the Gold Rush until approximately 1960. Miners used mercury to extract gold from mined materials and discharged the waste into rivers and streams, where mercury accumulated in the sediment. Bacteria converted the mercury to the more toxic methylmercury, which fish take in from their diet. Methylmercury can accumulate in fish to concentrations many thousands of times greater than mercury levels in the surrounding water.

After entering rivers, streams, and estuaries, mercury accumulates in the sediment. Bacteria convert the inorganic mercury to the more toxic methylmercury, which fish take in from their diet. Methylmercury can accumulate in fish to concentrations many thousands of times greater than mercury levels in the surrounding water.

Women can pass methylmercury on to their fetuses through the placenta, and to infants through breast milk. Excessive exposure to methylmercury may affect the nervous system in children, leading to subtle decreases in learning ability, language skills, attention and/or memory. These effects may occur through adolescence as the nervous system continues to develop. In adults, the most subtle symptoms associated with methylmercury toxicity are numbness or tingling sensations in the hands and feet or around the mouth. Other symptoms at higher levels of exposure could include loss of coordination and vision problems.

The Office of Environmental Health Hazard Assessment is one of six entities within the California Environmental Protection Agency. OEHHA's mission is to protect and enhance public health and the environment by objective scientific evaluation of risks posed by hazardous substances.