Mining

Mercury in Fish Tissues

Gold Rush mercury a danger in fish,
state says in Sierra warning

Associated Press — 12/16/03
By Don Thompson, staff writer

SACRAMENTO — Mercury used by Gold Rush miners is contaminating fish today, state regulators said Tuesday in their first such warning for Sierra Nevada waterways.

Most people can safely eat limited amounts of the contaminated fish, but children and women of childbearing age should be careful how much they consume, the California Environmental Protection Agency's Office of Environmental Health Hazard Assessment said. Excessive mercury levels can damage the nervous system.

The agency's fish advisory has guidelines for eating fish from Camp Far West Reservoir, Lake Combie, Lake Englebright, Rollins Reservoir, Scotts Flat Reservoir and portions of the South Yuba River, Deer Creek and Bear River in Nevada, Placer and Yuba counties, and from Black Butte, Stony Gorge and East Park reservoirs in Glenn, Tehama and Colusa counties.

Gold miners used mercury to separate gold from sand and gravel. The toxic mercury was allowed to flow into rivers and streams, where it accumulated in the soil.

Over the generations, bacteria convert the inorganic mercury to more dangerous methylmercury, which fish then eat. The department warns that the methylmercury can accumulate in fish in concentrations thousands of times greater than in the surrounding water.

The warning suggests that children and women of childbearing age not eat any bass from Camp Far West Reservoir; eat bass and catfish from the other waterways no more than once or twice a month, depending on where the fish are caught; and eat trout from Deer Creek no more than twice a month.

Adult men and women beyond their childbearing years should eat bass and catfish from the waterways no more than two to four times a month, depending where they're caught, and eat Deer Creek trout no more than four times a month, the advisory says.

For the Black Butte, Stony Gorge and East Park reservoirs, women and children should limit bass to one meal a month and catfish, carp and crappie to two meals per month. Men and older women can safely consume the fish twice as often.

ON THE NET — Office of Environmental Health Hazard Assessment