![]() ![]() The symptoms-like numbness in the extremities, weakness, and a narrowing of the field of vision-are well known, and they appear soon after exposure. Diagnosing these cases is clinical child’s play. Mercury’s notoriety as a poison derives from these instances of acute exposure. (Mercury inhalation is still a problem in many workplaces.) ![]() The phrase “as mad as a hatter” harkens back to Victorian England, where mercury was used in haberdasheries. He believed mercury pills would grant him immortality (oops). Mercury probably killed the first Chinese emperor, Qin Shi Huang, in 210 B.C.E. What are the effects of mercury exposure?Ĭases of mercury poisoning go back thousands of years. Photo: Woods Hole Oceanographic Institution That's why predators like tuna have troubling levels of mercury-they eat a lot. When that creature is eaten by bigger creatures, the methylmercury travels up the food chain, collecting in animal tissue in larger and larger amounts. Scientists aren’t quite sure how this conversion occurs, but it probably involves the metabolism of a small but abundant living creature. There, elemental mercury turns into methylmercury. The mercury settles to the ground, where rains eventually wash it to the ocean. Burning fossil fuels releases mercury into the air-around 160 tons per year in the United States. Mercury can also take a less direct route to the sea. “ America’s most polluted lake” is still recovering. I grew up a few miles from New York’s Onondaga Lake, where the Allied Chemical Company disposed of as much as 20 pounds of mercury per day in the mid-20th century. Mercury dumping has been a problem in the United States, too. ![]() (The neurological syndrome caused by severe mercury poisoning is called “Minamata disease” after the tragedy.) The most infamous example occurred in Japan in the 1950s and '60s, when industrial mercury poisoned more than 2,000 people who ate fish from Minamata Bay. In the 19th and 20th centuries, factories dumped massive amounts of methylmercury-the most dangerous form of mercury, bonded to carbon and hydrogen-directly into waterways. The issue gained new urgency last week when a study in the journal Nature showed that mercury concentration at the ocean surface has tripled since the beginning of the industrial era. So what’s a toxic level of mercury in your diet? This has long been a concern, because many fish contain measurable levels of mercury, which can cause profound neurological disease and death if consumed in sufficient amounts. Toxicologists have a saying: “The dose makes the poison.” In other words, there is no such thing as “toxic” or “non-toxic”-it always depends on how much of a substance you consume. It can move throughout your body, where it can penetrate cells in any tissue or organ.This article originally appeared on. When you eat seafood containing methylmercury, more than 95 percent is absorbed, passing into your bloodstream. 60 micrograms for the same portion of canned albacore tuna-and 170 micrograms for swordfish. In comments submitted to federal health officials earlier this year, a group of scientists and policy analysts pointed out that a 6-ounce serving of salmon contains about 4 micrograms of mercury vs. That's why larger, longer-living predators such as sharks and swordfish tend to have more of the toxin than smaller fish such as sardines, sole, and trout. Mercury-containing plants and tiny animals are eaten by smaller fish that are then gobbled up by larger fish, whose tissue accumulates mercury. Geological Survey and Harvard University. Mercury levels in the northern Pacific Ocean have risen about 30 percent over the past 20 years and are expected to rise by 50 percent more by 2050 as industrial mercury emissions increase, according to a 2009 study led by researchers at the U.S. ![]()
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