June 18, 2013
Richard Ellis on ‘Diagnosis: Mercury’
Posted on Nov 28, 2008
The following information comes directly the U.S. Environmental Protection Agency’s Web site:
“Mercury is a naturally occurring element that is found in air, water and soil. It exists in several forms: elemental or metallic mercury, inorganic mercury compounds, and organic mercury compounds. Pure mercury is a liquid metal, sometimes referred to as quicksilver that volatizes readily. When coal is burned, mercury is released into the environment. Coal-burning power plants are the largest human-caused source of mercury emissions to the air in the United States, accounting for over 40 percent of all domestic human-caused mercury emissions. EPA has estimated that about one-quarter of U.S. emissions from coal-burning power plants are deposited within the contiguous U.S. and the remainder enters the global cycle. 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, can also release it into the environment.
“Mercury in the air eventually settles into water or onto land where it can be washed into water. Once deposited, certain microorganisms can change it into methylmercury, a highly toxic form that builds up in fish, shellfish and animals that eat fish. Fish and shellfish are the main sources of methylmercury exposure to humans. Methylmercury builds up more in some types of fish and shellfish than others. The levels of methylmercury in fish and shellfish depend on what they eat, how long they live and how high they are in the food chain.”
Mercury begins its journey upward from the moment it lands on the bottom of the sea (or a river or lake), where it is absorbed by bacteria and converted to methylmercury, after which the now toxic bacteria are ingested by small animals, which themselves are eaten by larger and larger animals until we reach the pinnacle of the food chain, the big fish. These large fish are recognized as the natural pinnacle of the food chain, but, of course, in the same way that humans provide the mercury that works up the food chain, humans have also replaced the big fish as the apex predators. In other words, we are the ultimate beneficiaries of the deadly system we created.
The largest fish—tuna, swordfish, marlins, some sharks—are the top of the food chain, the apex predators. Yellowfin and bigeye tuna are the red-meat tunas that are popularly served in restaurants as grilled tuna steaks, tuna carpaccio, tuna teriyaki and, of course, tuna sushi and sashimi. As top predators (yellowfin and big eye tunas can be six feet long and weigh 400 pounds), these fish have a significant mercury content. The bluefin, the largest tuna of all, will naturally have the most mercury, but because the primary destination for bluefins caught around the world is Japan, Americans don’t give much thought to the mercury content of maguro. For the Japanese market, the bluefin is being so heavily fished in the Mediterranean (a bluefin spawning area) that the World Wildlife Fund has called for a complete shutdown of the tuna fisheries to save the remaining tuna from extinction.
There are fish that are safe to eat. The Monterey Bay Aquarium’s Seafood Watch lists every seafood item regularly consumed in America, and tells you whether it’s safe to eat, ecologically or toxicologically. Among the “Best Choices” are Alaska halibut, anchovies, Arctic char (farmed), bluefish, Pacific cod (the Atlantic cod has been fished to near-extinction), sole, herring, mackerel, Atlantic dorado (mahi-mahi), wild salmon and sardines. In other words, there are plenty of other fish in the sea (and in restaurants); you shouldn’t be eating tuna for health reasons—the tuna’s or yours.
Late in 2008, Island Press published Jane Hightower’s “Diagnosis Mercury: Money, Politics & Poison.” Hightower is a San Francisco doctor whose patients included a woman who complained that “her house seemed to be making her sick;” her symptoms included fatigue, headache, trouble concentrating and hair loss. She felt as if she had a hangover; sometimes she couldn’t get out of bed for a couple of days. To Dr. Hightower’s questions about her diet, the woman said she was a vegetarian and didn’t eat meat, but she ate fish—tuna, swordfish, sushi, sea bass, halibut—at least nine times a week. Testing her, Hightower found that her blood mercury level was 26.0 mcg/l (micrograms per liter), 26 times higher than the EPA guidelines.
A couple brought their 7-year-old son to see Hightower because the boy was experiencing stomachaches, headaches and lethargy, and he turned red when he was in a warm bath. The parents told Hightower that they believed that fish was good for you, so they had been feeding their son canned albacore and yellowfin tuna steadily since he was two. The boy was tested, and found to have a mercury level of about 15mcg/l. When the boy was taken off this dangerous, all-fish diet, his health improved. But, says Hightower, “He will most likely need special education and help for the rest of his life, as he still has difficulty with schoolwork, language skills and social skills.”
Even now, the only warnings given to potential consumers of tuna can be found on the EPA Web site, where pregnant women and nursing mothers are told not to eat tuna because their babies, born and unborn, are susceptible to mercury poisoning. On its “Seafood Watch” handout, based on factors that include species endangerment and human endangerment, the Monterey Bay Aquarium says that one should avoid bluefin tuna.
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