Mercury is a naturally occurring element that is found in air, water and soil. It is in many rocks, including coal, which releases mercury into the environment when burned. Coal-burning power plants are the largest human-caused source of mercury emissions to the air in the U.S. Burning hazardous wastes, producing chlorine, breaking mercury products and spilling mercury, as well as the improper treatment and disposal of products or wastes containing mercury, also release it into the environment.

 

Mercury in the air eventually settles into water or onto land where it can be washed into water. A highly toxic form, methylmercury, builds up in fish, shellfish and animals that eat fish. Fish and shellfish are the main sources of methylmercury exposure to humans. Mercury exposure at high levels can harm the brain, heart, kidneys, lungs and immune system of people of all ages, which is why fish advisories are issued to inform and encourage people to continue to eat only fish that are low in methylmercury. (Source: EPA / Photo, liquid mercury: Wikimedia Commons)