Dangerous Levels Of Methyl Mercury Found In 74 Californian Lakes
State officials say they are worried about high levels of mercury found in fish caught at Shasta, Whiskeytown and 72 other California lakes and the thousands of anglers who eat their catch from those reservoirs and lakes.
California Water Quality Control Board officials held a public meeting in Redding on Thursday to take comment on setting new regulations to control mercury in lakes such as Shasta and Whiskeytown.
They also plan to set regulations recommending the amount of fish that can be safely eaten from lakes with high levels of mercury.
The six water board staff members at Thursday's hearing outnumbered the audience of four people.
Brian Rasmussen, a hydrologist and geologist at Whiskeytown National Recreation Area who attended the hearing said he was concerned that fish at Whiskeytown had high levels of mercury, but water board officials had not offered to help them advise the public.
"It's a black eye to be on this list," Rasmussen said, referring to a list of 74 reservoirs statewide considered "impaired" because of the high levels of mercury in fish swimming in the lakes.
Lake Britton in eastern Shasta County is on the list, along with Lake Shastina in Siskiyou County, Black Butte Lake in Tehama County and Trinity Lake in Trinity County.
Mercury got into lakes such as Shasta and Whiskeytown from gold mining. Miners used mercury more than a century ago during California's gold rush. Mercury particles also are carried through the air and deposited into lakes by wind and rain, said Carrie Austin, a state water board engineer.
Mercury also is naturally found in springs and soil, Austin said.
The mercury in lakes isn't dangerous to humans until it gets to the bottom of deep lakes, where it turns into methyl mercury and binds to algae eaten by microscopic organisms. Those organisms are eaten by small fish, which are eaten by larger fish such as bass and trout.
As the methyl mercury makes its way up the food chain it accumulates at rates two to five times their previous levels at each stage, Austin said. By the time the methyl mercury reaches game fish such as bass it is sometimes found in concentrations dangerous to humans, she said.
Water board officials say mercury at high levels can cause brain damage, as well as kidney and lung problems in humans and wildlife.
Infants, young children and pregnant women are most at risk from mercury poisoning, according to state officials.
Austin said the board hopes to develop safe consumption levels statewide for fish from the 74 reservoirs and to come up with plans to keep mercury out of reservoirs.
At some lakes, mercury is washed into reservoirs from active and abandoned mines.
Grading or other work could be done to keep mercury from leaching into reservoirs, Austin said.
The state also could encourage stocking lakes with fish that don't tend to accumulate mercury and discourage stocking fish that are good at accumulating mercury, Austin said.
Bass tend to accumulate more mercury than trout, said Rik Rasmussen, who is supervising the process of creating proposed regulations.
"It's really fish-species-specific, to a certain extent," Rasmussen said.
State officials already recommend limiting the amount of fish caught from certain water bodies, such as the San Joaquin-Sacramento Delta. Rasmussen said in those cases, people are encouraged to limit the amount of fish they eat to 17.5 grams per day, or about 8 ounces of fish every other week, he said.