DIANE DIETZ, THE REGISTER GUARD, JUNE 27, 2006
The last of Oregon’s commercial mercury mines shut down years ago, yet mining is still the major source of mercury pollution in the state’s waterways.
Mercury-laced waters pouring from abandoned mine tunnels and washing out of old mine tailings piles have made it unhealthy to eat a steady diet of some Oregon fish.
Douglas County’s Cooper and Plat I reservoirs and Lane County’s Dorena and Cottage Grove reservoirs are tainted with mercury caused, in part, by the work of miners.
It’s all legacy now.
Mercury mining ceased in the United States 14 years ago, according to the U.S. Geological Survey. Driven by health worries, manufacturers have replaced mercury in thermometers, auto battery switches and paint. Recyclers produce much of the mercury that’s still needed. Domestic consumption continues to drop.
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The mercury in Cottage Grove Lake originates from cinnabar, a naturally occurring ore in Oregon mountains.
At the old mercury mines, such as Black Butte in Lane County and Bonanza in Douglas County, waste mercury-tainted tailings washed into creeks and lakes. In the murky depths, bacteria convert the mercury into a dangerous form: methylmercury.
Plants and bugs draw in this form of mercury, and fish take it on when they eat the plants and bugs. It doesn’t kill the fish. Rather, it concentrates in their muscle tissue.
The accumulation stops at the top of the food chain. In the case of fishing, that’s the bodies of human beings who eat the fish.
Mass poisoning that came to light in the mid-1950s in Japan showed what consuming mercury-laden fish can do. A resin company dumped 27 tons of mercury into Minamata Bay over a 30-year period. More than 3,000 people who ate fish from the bay suffered severe neurological damage. Their children were born with crippling birth defects.
Just this April, Prime Minister Junichiro Koizumi formally apologized to the victims because the government waited decades to stop the pollution.
The fish in Minamata Bay “were 20 to 40 times more contaminated” than Cottage Grove Lake fish, state toxicologist Dave Stone said, but even small amounts can be a risk for children and fetuses.
Methylmercury can be carried in the blood of a pregnant woman to a developing child, can travel through breast milk to a nursing child, can enter the mouth on the fingers of an infant, can enter the bloodstream through the stomach and can pass through the protective blood-brain barrier.
Researchers link exposure to even small amounts of methlymercury to developmental deficits in children, including delayed walking and impaired language, memory and attention span.