OEHHA Releases Draft Advisories on Mercury in Fish in Lake Berryessa and Putah Creek

Feb 17, 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 Lake Berryessa in Napa County, and Putah Creek in Yolo and Solano counties.

“Mercury is prevalent in northern California fish, including some fish from Lake Berryessa and Putah Creek,” OEHHA Director Dr. Joan Denton said. “Fish from these water bodies are safe to eat in moderation, but people – and particularly women of childbearing age and children – should carefully monitor how much fish they eat.”

A fact sheet and draft report containing the proposed advisories and OEHHA’s evaluation of potential health threats posed by consumption of fish containing methylmercury (the most prevalent and toxic form of mercury in fish) are available for viewing and downloading on OEHHA’s Web site, www.oehha.ca.gov, along with fish advisories for other California waterbodies.

OEHHA staff scientists will make a presentation, answer questions and accept public comments on the draft advisories at two public workshops. The first workshop will be from 9:30 a.m. to 11:30 a.m. on February 27, 2006, in the Napa County Board of Supervisors conference room, 1195 Third Street, Napa. The second workshop will be from 6:30 p.m. to 8:30 p.m. on February 28, 2006, at the Winters Library, 201 First Street, Winters.

Written comments on the draft advisories must be received by 5 p.m. on March 20, 2006, at OEHHA’s Pesticide and Environmental Toxicology Branch, 1515 Clay Street, 16th Floor, Oakland, CA 94612. OEHHA will review all comments, make any appropriate revisions and issue final advisories.

The draft Lake Berryessa advisory updates and replaces a 1987 state fish advisory for that water body. The draft Putah Creek advisory is the first for that waterway and covers its entire length from Lake Berryessa to the Yolo Bypass of the Sacramento River.

The draft advisories contain proposed “safe eating guidelines” for consumption of fish from Lake Berryessa and Putah Creek. 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 include “best choices” that identify fish with very low mercury levels that may be consumed up to three times a week or, in some cases, daily. Until final advisories are issued, OEHHA recommends that the public follow the guidance in the draft advisories.

For Lake Berryessa, the draft safe-eating guidelines recommend consumption limits for women of childbearing age and children 17 years and younger of one meal a month of black bass, catfish, or chinook (king) salmon, or one meal a week of bluegill or other sunfish, trout, or kokanee. Women beyond childbearing age and men should consume no more than one meal a week of black bass, catfish, or chinook (king) salmon from Lake Berryessa.

For women beyond childbearing age and men, the “best choices” at Lake Berryessa are trout or kokanee, which may be consumed up to three times a week if no other fish are eaten that week. No fish sampled from Lake Berryessa contained mercury levels low enough for OEHHA to recommend “best choices” for women of childbearing age and children.

For Putah Creek, the levels of mercury in the fish generally were lower. Consumption limits for women of childbearing age and children are one meal a week of black bass, bluegill or other sunfish, carp or goldfish, catfish (including bullheads), crappie, sucker, hitch or crayfish. For women beyond childbearing age and men, eat no more than one meal a week of black bass, crappie or hitch.

The “best choices” for women of childbearing age and children at Putah Creek are trout or Sacramento blackfish, which may be consumed up to three times a week. The “best choices” for women beyond childbearing age and men are trout or Sacramento blackfish, which may be consumed daily, and bluegill or other sunfish, catfish (including bullheads), sucker, carp or goldfish, or crayfish, which may be consumed up to three times a week.

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

The Putah Creek watershed (which includes Lake Berryessa) is rich in mineral deposits, and prospecting for mercury and gold has taken place in the watershed since the mid-1800s. Mercury from natural weathering and mining waste is believed to have entered the area’s water bodies. The region’s numerous geothermal springs also vent mercury into water bodies. Mercury accumulates in the sediment and is converted by bacteria 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.