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, Maine's bald eagles,
Canadian 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.
High mercury levels in popular fish such as swordfish and canned albacore
tuna prompted government health warnings in 2004 aimed at pregnant women and
children. Mercury is a neurotoxin that can damage fetuses and cause mental
retardation, learning disabilities, cerebral palsy, blindness and deafness.
The contamination also can kill or harm wildlife. 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
-- 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 Clearlake (Lake County) 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 and in some places are showing such
neurological effects as difficulty in walking. One otter died from 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.
The main source of mercury in humans comes from consuming big predator
fish such as swordfish, shark, king mackerel, tilefish and albacore tuna,
according to the U.S. Environmental Protection Agency.
Birds and other wildlife also 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.
The report from the National Wildlife Federation is consistent with what
California researchers from the U.S. Fish and Wildlife Service, U.S. Geological
Survey and San Francisco Estuary Institute in Oakland have found in California
clapper rails, Caspian and Forster's terns and other shorebirds feeding in the
southern end of San Francisco Bay.
Guadalupe Creek, which flows through San Jose, carries inorganic mercury
from a now-closed mercury mine. The mercury converts to the toxic form,
methylmercury, in the former Cargill salt ponds being restored in the South
Letitia Grenier, a conservation biologist at the San Francisco Estuary
Institute, has researched mercury in songbirds in the wetlands. She praised the
work of Evers and other East Coast researchers.
"It's important for us to open our minds. We should question where there
are other habitats where we could have mercury accumulations. It's great that
we're finally looking at mercury in animals,'' Grenier said.
The National Wildlife Federation issued the study as part of a lobbying
effort for regulations to control mercury emissions at coal-fired power plants
and other sources.
The Electric Reliability Coordinating Council, a trade group for power
generating companies, criticized the study Tuesday as redundant, given past
studies. In a statement, spokesman Scott Segal said emissions of mercury have
been reduced by 40 percent since 1990.
©2006 San Francisco Chronicle