OEHHA Finalizes Advisory on Mercury in Fish in Lake Berryessa and Putah Creek

Jun 22, 2006

Release No. 06-04
Contact Allan Hirsch
(916) 324-0955

The California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment (OEHHA) has finalized a fish advisory concerning elevated levels of mercury in fish in Lake Berryessa in Napa County, and Putah Creek (including Lake Solano) in Yolo and Solano counties.

“Fish are nutritious and good to eat, but anglers and other fish lovers need to be aware of the presence of mercury in many kinds of fish,” OEHHA Director Dr. Joan Denton said. “Our advisory provides ‘safe eating guidelines’ for Lake Berryessa and Putah Creek fish to help people enjoy fish from those water bodies without putting their health and the health of their children at risk.”

A fact sheet and report containing the advisories and OEHHA’s evaluation of fish from the two water bodies are available for viewing and downloading on OEHHA’s Web site at www.oehha.ca.gov. Cards containing OEHHA’s consumption advice are available at the Lake Berryessa visitor center and headquarters.

The Lake Berryessa advisory updates and replaces a 1987 state fish advisory for that water body. The 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, including Lake Solano.

The advisories contain “safe eating guidelines” for consumption of fish from the water bodies. One set of guidelines is for women of childbearing age and children age 17 and younger, who are particularly sensitive to methylmercury (the most prevalent and toxic form of mercury in fish). 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.

For Lake Berryessa, the safe-eating guidelines recommend consumption limits for women of childbearing age and children 17 years and younger of one meal a month of largemouth, smallmouth or spotted bass, catfish, or chinook (king) salmon; or one meal a week of bluegill or other sunfish, trout, or kokanee. 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 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. As an alternative, women beyond childbearing age and men could have one meal a week of one of the following: largemouth, smallmouth or spotted bass, catfish, or chinook (king) salmon, bluegill or other sunfish.

For Putah Creek, the levels of mercury in the fish generally were lower. The “best choices” for women of childbearing age and children are trout or Sacramento blackfish, which may be consumed up to three times a week. As an alternative, women of childbearing age and children could have one meal a week of one of the following: black bass, bluegill or other sunfish, carp or goldfish, catfish (including bullheads), crappie, sucker, hitch or crayfish.

The “best Putah Creek choices” for women beyond childbearing age and men are trout or Sacramento blackfish, which may be consumed daily, or bluegill or other sunfish, catfish (including bullheads), sucker, carp or goldfish, or crayfish, which may be consumed up to three times a week. As an alternative, this group could have one meal a week of largemouth, smallmouth, or spotted bass, crappie or hitch.

The 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 (including 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.

Fish Advisories