A new study adds to the extensive evidence that mercury is prevalent in waterways and fish across America due to mercury emissions from coal-fired power plants and mining in the Sierra. About one-quarter of the fish exceeded mercury levels allowed by the U. S. EPA for the general population -- but which could be harmful to mothers and children if too much is eaten. See the San Francisco Chronicle article here or below.
Study: Mercury found in fish from 291 streams
Dina Cappiello, Associated Press
Thursday, August 20, 2009
(08-20) 04:00 PDT Washington - --
No fish can escape mercury pollution.
That's the take-home message from a federal study of mercury contamination released Wednesday that tested fish from nearly 300 streams across the country. The toxic substance was found in every fish sampled, a finding that underscores how widespread mercury pollution has become.
But while all fish had traces of contamination, only about one-quarter had mercury levels exceeding what the Environmental Protection Agency says is safe for people eating average amounts of fish.
The study by the U.S. Geological Survey is the most comprehensive look to date at mercury in the nation's streams. From 1998 to 2005, scientists collected and tested more than 1,000 fish, including bass, trout and catfish, from 291 U.S. streams.
"This science sends a clear message that our country must continue to confront pollution, restore our nation's waterways and protect the public from potential health dangers," Interior Secretary Ken Salazar said in a statement.
Mercury consumed by eating fish can damage the nervous system and cause learning disabilities in developing fetuses and young children. The main source of mercury to most of the streams tested, according to the researchers, is emissions from coal-fired power plants.
The mercury released from smokestacks here and abroad rains down into waterways, where natural processes convert it into methylmercury - a form that allows the toxin to wind its way up the food chain into fish.
Some of the highest levels in fish were detected in the remote blackwater streams along the coasts of the Carolinas, Georgia, Florida and Louisiana, where bacteria in surrounding forests and wetlands help in the conversion. The second-highest concentration of mercury was detected in largemouth bass from the North Fork of the Edisto River near Fairview Crossroads, S.C.
"Unfortunately, it's the case that almost any fish you test will have mercury now," said Andrew Rypel, a postdoctoral researcher at the University of Mississippi who has studied mercury contamination in fish in the Southeast. He said other research has shown mercury in fish from isolated areas of Alaska and Canada, and species in the deep ocean.
Mercury was also found in high concentrations in Western streams that drain areas mined for mercury and gold. The most contaminated sample came from smallmouth bass from the Carson River at Dayton, Nev., an area tainted with mercury from gold mining. At 58 other streams, most in the West, the acidic conditions created by mining could also be boosting mercury levels, the researchers said.
This article appeared on page A - 6 of the San Francisco Chronicle