OEHHA Releases Draft Advisories on Mercury in Fish in Lower Cosumnes and Mokelumne Rivers

Apr 28, 2006

SACRAMENTO -- The California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment (OEHHA) is seeking public comments on draft fish advisories concerning elevated levels of mercury in some fish in the lower Cosumnes River (Sacramento County) and lower Mokelumne River (San Joaquin County).

“Fish in the lower Cosumnes and Mokelumne rivers are bearing the legacy of decades of mercury releases in those watersheds as a result of gold mining,” OEHHA Director Dr. Joan Denton said. “Women of childbearing age and children should sharply restrict the number and types of fish they eat from those rivers, as well as nearby creeks and sloughs.” Safe Eating Guidelines for Fish and Shellfish from the Lower Mokelumne River.

OEHHA staff scientists will make a presentation, answer questions and accept public comments on the draft advisories at a public workshop to be held at 6:45 p.m. Thursday, May 11, at the Lodi Public Library, 201 W. Locust Street, Lodi.

Written comments on the draft advisories must be received by 5 p.m. on May 29, 2006, at OEHHA’s Pesticide and Environmental Toxicology Branch, 1001 I Street, Sacramento, CA 95812. OEHHA will review all comments, make any appropriate revisions and issue final advisories.

The draft advisories cover the length of the lower Cosumnes River in Sacramento County, both forks of the lower Mokelumne River below Comanche Reservoir to the confluence with the San Joaquin River, and creeks and sloughs that are close to the two rivers.

The advisories contain “safe eating guidelines” for consumption of fish from both rivers. One set of guidelines is for women of childbearing age and children age 17 and younger, who are particularly sensitive to methylmercury. A second set of guidelines is for women beyond their childbearing years and men. Where appropriate, the guidelines identify fish and shellfish species that may be eaten up to two times a week. Until final advisories are issued, OEHHA recommends that the public follow the guidance in the draft advisories.

For the lower Cosumnes River, the draft safe-eating guidelines recommend that women of childbearing age and children 17 years and younger do not eat largemouth, smallmouth or spotted bass, Sacramento pikeminnow, or striped bass exceeding 27 inches in length; and restrict consumption of all other fish and crayfish species to a total of one meal a month. Women beyond childbearing age and men should consume no more than one meal a month of largemouth, smallmouth or spotted bass, or Sacramento pikeminnow; or no more than two meals a month of striped bass (but avoid eating striped bass exceeding 35 inches in length); or no more than one meal a week of crayfish, Sacramento sucker or white catfish. Or, if none of these other fish are eaten, they can safely eat up to two meals a week of bluegill or redear sunfish. Safe Eating Guidelines for Fish and Shellfish from the Lower Cosumnes River.

For the lower Mokelumne River, women of childbearing age and children 17 years and younger should eat no more than one meal a month of all fish species combined (and should not eat striped bass exceeding 27 inches in length); or no more than one meal a week of crayfish. Women beyond childbearing years and men should consume no more than one meal a month of largemouth, smallmouth or spotted bass, or Sacramento pikeminnow; or no more than two meals a month of striped bass (but avoid eating striped bass exceeding 35 inches in length). Or, if none of these other fish are eaten, they can safely eat up to two meals a week of crayfish, bluegill, Sacramento sucker or white catfish.

An exception to the above-stated limits is Asiatic clams from both rivers, which can be safely consumed up to three times a week by men, women and children.

The draft advisories incorporate the results of fish sampling conducted by the State Water Resources Control Board, the University of California, Davis, and the CalFED Bay-Delta Program.

Mercury in fish from these water bodies originated from gold-mining and dredging activity that began during the Gold Rush. Miners used inorganic mercury to extract gold from mined materials and discharged the waste into rivers and streams, where mercury accumulated in the sediment. Bacteria converted 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. Physical contact with the water is safe.

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.

Fish are an important part of a balanced diet, and the American Heart Association recommends the consumption of two meals a week of fish that are low in mercury, such as shrimp, king crab, scallops, farmed catfish, wild ocean salmon, oysters, tilapia, flounder and sole.