The latest study conducted by the U.S. Geological Survey (USGS) definitely poses a few question marks, to say the least; the results were shocking: after testing fish from 291 freshwater streams from the US, all the fish were contaminated with mercury.
"This study shows just how widespread mercury pollution has become in our air, watersheds and many of our fish in freshwater streams," said Interior Secretary Ken Salazar.
No matter how cool it sounds (and is, actually), Mercury is bad for you; really bad. This potent neurotoxin stacks up as you go up the food chain, so you'd expect big predator fish to have higher concentrations. It attacks especially the nervous systems of fetuses and children, but it's effects are considerable on humans too.
The biggest cause of human mercury poisoning in the US is the consumption of fish and shellfish.