What's The Problem? Mercury enters the water from industrial sources, like coal plants. Once in the ocean, it bioaccumulates in marine animals, meaning the higher up on the food chain the animal then the more mercury it is likely to have (e.g., tuna and swordfish). Exposure to mercury, even in small doses, is extremely harmful for wildlife and humans. Once mercury enters the water, it can travel across great distances, making contamination a global problem.
What Can Be Done? Treaty discussions involving the United Nations are underway, which include measures that would use non-mercury alternatives when possible and reduce mercury emissions. Although not a cure all, the European Union enacted an export ban beginning in 2011 and the U.S. Congress enacted a similar export ban in 2013.