Catch a fish in one of America's streams, and there's a good chance it will have at least trace amounts of mercury. The most comprehensive survey to date from the US Geological Survey tested more than 1,000 fish from nearly 300 streams around the nation—and found mercury in every single one of them. The good news? Only about a quarter had levels exceeding what the EPA says is safe for people eating average amounts of fish.
"Unfortunately, it's the case that almost any fish you test will have mercury now," said a researcher at the University of Mississippi. The main source of the toxic substance is emissions from coal-fired power plants. Some of the highest levels were detected in the remote streams along the coasts of the Carolinas, Georgia, Florida, and Louisiana. Excessive amounts of mercury can damage the nervous system and cause learning disabilities in developing fetuses and young children.