U.S. Water News Online
Near Twin Falls levels are 150 times the highest levels ever found
in lakes in the northeastern U.S.
TWIN FALLS, Idaho -- New research in Idaho shows high
concentrations of toxic mercury in a reservoir that is popular for
its walleye. Some scientists suspect that gold mines across the
border in Nevada are responsible.
Among them is Michael Abbott, an atmospheric scientist with the
Idaho National Laboratory (INL), who spoke to Utah's Statewide
Mercury Work Group, which is grappling with worrisome mercury levels
in at least two water bodies and two species of waterfowl.
In monitoring regional air quality, Abbott found that mercury
levels increased as much as 70 percent when winds blew from the
southwest. The area includes mines belonging to Newmont Mining,
Barrick Goldstrike, Placer Dome and Queenstake Resources.
"The mines are the only sources big enough to cause those peaks,"
Abbott told the Idaho Statesman newspaper.
Since 2002, the Idaho Department of Health and Welfare has warned
people to limit the number of fish they eat that come from the Salmon
Falls Reservoir, south of Twin Falls.
In tests made since August, state Department of Environmental
Quality officials now say they have detected mercury levels in the
reservoir that are 150 times the highest levels ever found in lakes
in the northeastern United States, which have been doused with
mercury from nearby coal-fired power plants.
State environmental regulators say evidence isn't conclusive that
mercury in the reservoir is from the mines. In addition, there's no
specific information about any mercury-related health problems that
may have resulted from exposure to high mercury levels in the Salmon
Still, officials say people should take note.
"Nobody's ever seen a hot spot like this before," said Mike
DuBois, an air quality analyst at the Idaho Department of
Environmental Quality. He also said that other Idaho watersheds could
be at risk if the mines are the reason for the high mercury levels.
His agency wants to single out the origins of the mercury pollution
so that it can begin measures to clean the reservoir.
Utah hopes to learn from Idaho how to monitor and clean up methyl
mercury, a toxic chemical that builds up in the food chain and, if
accumulated in high enough levels, causes neurological damage in
The Nevada gold mines have voluntarily reduced emissions of
mercury by about three-fourths from the levels that were being
emitted before 2002, according to Nevada officials. Mercury is
expelled into the atmosphere when ore is processed. The officials say
the four mines have slashed output from more than 15,000 pounds
annually in 2002 to about 4,000 pounds in 2004.
To cut emissions, the mining companies have installed scrubbers on
smokestacks to capture mercury before it enters the air.
"Monitoring and record keeping, those are the right things to do
and not a huge burden on us," said John Mudge, Newmont Mining's
director of environmental affairs.
The INL's Abbot continues to collect air samples and hopes to
pinpoint the source of the mercury.
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