BY JANE KAY
San Francisco Chronicle
Posted on Wed, Sep. 20, 2006
Mercury pollution from power plants and other industrial sources has accumulated in birds, mammals and reptiles across the country, and only cuts in emissions can curtail the contamination, says a report released Tuesday by a national environmental group.
The report is the first major compilation of studies investigating mercury buildup in such wildlife as California clapper rails, bald eagles, common loons and Florida panthers. In all, scientists working with the National Wildlife Federation found 65 studies showing troublesome mercury levels in 40 species.
"From songbirds to alligators, turtles to bats, eagles to polar bears, mercury is accumulating in nearly every link of the food chain," said Catherine Bowes, an author of the report who manages the federation's mercury program in the northeastern states.
According to the study:
• Common loons stopping at Walker Lake in Nevada on their way to Saskatchewan have been contaminated with mercury lingering from past gold mining operations.
• At least one endangered Florida panther has died from mercury poisoning, probably from consuming raccoons with high mercury levels.
• Western and Clarke's grebes in Clear Lake, Calif., have shown altered hormone levels because of mercury poisoning.
• River otters in New York, Maine, Vermont, Massachusetts and Nova Scotia have elevated levels of mercury.
Airborne mercury, which eventually falls to the land and water, comes mostly from coal-fired power plants or medical and trash incinerators. Sewage treatment plants, chlorine-manufacturing plants and runoff from abandoned gold and mercury mines can flow directly into water and wetlands.
Birds and other wildlife eat mercury-contaminated fish as well as insects, crayfish and other small organisms. The mercury accumulates at higher levels up the food chain to raccoons, mink, river otters, panthers and polar bears, the study found.
David Evers, a leading avian ecologist who specializes in contaminants at the nonprofit BioDiversity Research Institute in Gorham, Maine, said mercury-contaminated insects contribute to the high levels of the element in birds, bats and some other wildlife species.
"Traditional, conventional thinking was that the fish food web was the only pathway of concern. But our studies have found that there are other food webs of concern, including insects," Evers said.
Minnesota has cut mercury emissions dramatically over the past 15 years, leading to slightly lower levels in fish. Last spring, the Legislature took another step by requiring the state's three largest coal-fired power plants to reduce mercury emissions by 90 percent by 2015.
The Minnesota Pollution Control Agency, however, said the state has little control over 90 percent of the mercury that falls here because it drifts here from outside the state's borders.
— Dennis Lien