A study published in the journal Nature Geoscience earlier this year confirmed what scientists have long suspected: Inorganic mercury, which comes from natural sources like volcanoes and geological deposits as well as human activities like coal-burning, is transformed into toxic methylmercury in seawater. Exposure to methylmercury from eating contaminated fish can cause a wide range of neurological symptoms in adults, children and developing fetuses.
“I think of fish as sponges for mercury,” said Jackie Savitz, senior scientist and campaign director for the international ocean conservation and advocacy organization Oceana. “The reason it’s so bad is once mercury gets into the environment, it stays there and magnifies up the food chain. The little critters at the bottom take up a little bit of mercury from zooplankton, and the slightly bigger fish eat them, and so on.” Mercury is found at the highest levels in larger fish, like tuna, swordfish and shark. Low-mercury seafood includes shrimp, salmon, pollock and catfish.
Perhaps the starkest example of the effects of methylmercury poisoning occurred in the Japanese town of Minamata in the 1930s, when a company that made fertilizer and plastics began dumping mercury into the bay where the population fished. In 1956, an epidemic broke out among residents that caused paralysis, convulsions, coma and death. Over time, thousands of children were born with severe deformations, including brain and nervous system damage.
According to the 2005 National Emissions Inventory, coal-burning power plants are the largest human-caused source of mercury emissions to the air in the U.S. “There isn’t much that can be done about mercury getting into the environment from volcanoes,” said Marion Nestle, a professor of nutrition, food studies and public health at New York University and the author of “What to Eat.” “But there is plenty that can be done about emissions from coal-burning power plants. Shutting them off or filtering their emissions would reduce mercury by about 40 percent.”
In adults, mercury poisoning can cause impairment of peripheral vision and thinking; a sensation of pins and needles in the hands, feet and around the mouth; lack of coordination and muscle weakness, according to the Environmental Protection Agency. “You find big sushi eaters start to have numbness or tingling in their fingers, and a loss of concentration,” said Savitz. “They can’t figure out what it is, and doctors have a hard time pinpointing it.”
Exposure in the womb can harm a fetus’ growing brain and nervous system, causing problems with thinking, memory, attention, language and fine motor and visual spatial skills, according to the EPA. A 1999-2000 National Health and Nutrition Examination Survey found that 8 percent of women 16 to 49 years old had concentrations of mercury higher than the EPA’s recommended reference dose.
Blood mercury concentrations can be determined by a blood test, and the typical recommendation is to stop eating all seafood for a certain period of time. Because of the potential harm mercury can have on fetuses, in 2004 the Food and Drug Administration issued three recommendations for women of childbearing age. For more detailed information, Monterey Bay Aquarium’s Seafood Watch provides downloadable guides that identify the types of seafood that contain high levels of mercury, as well as those that are overfished and should be avoided.
Go fish, but go easy
Seafood safety recommendations from the FDA and EPA
Women who may become pregnant, pregnant women, nursing mothers and young children have to be careful with seafood. Here’s what the experts say.
1. Do not eat shark, swordfish, king mackerel or tilefish because they contain high levels of mercury.
2. Eat up to 12 ounces (two average meals) a week of a variety of fish and shellfish that are lower in mercury.
◦ Five of the most commonly eaten seafood varieties that are low in mercury are shrimp, canned light tuna, salmon, pollock and catfish.
◦ Another commonly eaten fish, albacore, or white tuna, has more mercury than canned light tuna. So, when choosing your two meals of fish and shellfish, you may eat up to 6 ounces (one average meal) of albacore tuna per week.
3. Check local advisories about the safety of fish caught by family and friends in your local lakes, rivers and coastal areas. If no advice is available, eat up to 6 ounces (one average meal) per week of fish you catch from local waters, but don’t consume any other fish during that week.
Follow these recommendations when feeding fish and shellfish to your young child, but serve smaller portions.
“I think of fish as sponges for mercury,” said Jackie Savitz, senior scientist and campaign director for the international ocean conservation and advocacy organization Oceana. “The reason it’s so bad is once mercury gets into the environment, it stays there and magnifies up the food chain. The little critters at the bottom take up a little bit of mercury from zooplankton, and the slightly bigger fish eat them, and so on.” Mercury is found at the highest levels in larger fish, like tuna, swordfish and shark. Low-mercury seafood includes shrimp, salmon, pollock and catfish.
Perhaps the starkest example of the effects of methylmercury poisoning occurred in the Japanese town of Minamata in the 1930s, when a company that made fertilizer and plastics began dumping mercury into the bay where the population fished. In 1956, an epidemic broke out among residents that caused paralysis, convulsions, coma and death. Over time, thousands of children were born with severe deformations, including brain and nervous system damage.
According to the 2005 National Emissions Inventory, coal-burning power plants are the largest human-caused source of mercury emissions to the air in the U.S. “There isn’t much that can be done about mercury getting into the environment from volcanoes,” said Marion Nestle, a professor of nutrition, food studies and public health at New York University and the author of “What to Eat.” “But there is plenty that can be done about emissions from coal-burning power plants. Shutting them off or filtering their emissions would reduce mercury by about 40 percent.”
In adults, mercury poisoning can cause impairment of peripheral vision and thinking; a sensation of pins and needles in the hands, feet and around the mouth; lack of coordination and muscle weakness, according to the Environmental Protection Agency. “You find big sushi eaters start to have numbness or tingling in their fingers, and a loss of concentration,” said Savitz. “They can’t figure out what it is, and doctors have a hard time pinpointing it.”
Exposure in the womb can harm a fetus’ growing brain and nervous system, causing problems with thinking, memory, attention, language and fine motor and visual spatial skills, according to the EPA. A 1999-2000 National Health and Nutrition Examination Survey found that 8 percent of women 16 to 49 years old had concentrations of mercury higher than the EPA’s recommended reference dose.
Blood mercury concentrations can be determined by a blood test, and the typical recommendation is to stop eating all seafood for a certain period of time. Because of the potential harm mercury can have on fetuses, in 2004 the Food and Drug Administration issued three recommendations for women of childbearing age. For more detailed information, Monterey Bay Aquarium’s Seafood Watch provides downloadable guides that identify the types of seafood that contain high levels of mercury, as well as those that are overfished and should be avoided.
Go fish, but go easy
Seafood safety recommendations from the FDA and EPA
Women who may become pregnant, pregnant women, nursing mothers and young children have to be careful with seafood. Here’s what the experts say.
1. Do not eat shark, swordfish, king mackerel or tilefish because they contain high levels of mercury.
2. Eat up to 12 ounces (two average meals) a week of a variety of fish and shellfish that are lower in mercury.
◦ Five of the most commonly eaten seafood varieties that are low in mercury are shrimp, canned light tuna, salmon, pollock and catfish.
◦ Another commonly eaten fish, albacore, or white tuna, has more mercury than canned light tuna. So, when choosing your two meals of fish and shellfish, you may eat up to 6 ounces (one average meal) of albacore tuna per week.
3. Check local advisories about the safety of fish caught by family and friends in your local lakes, rivers and coastal areas. If no advice is available, eat up to 6 ounces (one average meal) per week of fish you catch from local waters, but don’t consume any other fish during that week.
Follow these recommendations when feeding fish and shellfish to your young child, but serve smaller portions.
