But of all the sources of mercury, it is our burning of coal to generate electric power that is the single greatest contributor to the problem. Mercury that naturally occurs in the coal is released during burning and enters the air; it is then precipitated into the oceans, lakes, and rivers by rain. According to the EPA, coal-fired power plants in the United States emit about 48 tons of mercury into the air every year-and more than half of this mercury falls within 10 kilometers of the plant itself. When it reaches the water, microorganisms consume it and convert it into a substance called methylmercury. Into the Food Chain
A study at the University of Tennessee recently rated methylmercury among the most dangerous poisons on Earth (just behind plutonium). It has no known beneficial use, and it accumulates in the muscle tissue of fish, animals, and humans. When minnows eat plankton or algae that is contaminated with methylmercury, it is deposited in their flesh; rger fish prey upon the minnows, and the toxin travels straight up the food chain to our most revered and noble gamefish-the big predators like bass, pike, walleyes, brown trout; and to all the finest food and sport fish of the seas-tuna, swordfish, marlin, halibut. According to the EPA, fish at the top of the aquatic food chain bioaccumulate methylmercury to a level approximately 1 million to 10 million times greater than dissolved concentrations found in surrounding waters.