Typically, people think of fish as a healthy part of a balanced diet. This holds true for some - but not all - types of fish, and definitely not all types of people.
In January, the Food and Drug Administration (FDA) advised pregnant and nursing women, women of childbearing age who may become pregnant, and young children not to eat certain kinds of fish, such as shark, swordfish, king mackerel, and tilefish. These fish contain unsafe levels of mercury, which can be harmful to an unborn baby's or young child's developing nervous system.
Just two months after the FDA released its advisory, the Centers for Disease Control (CDC) issued a report that found the risk of mercury poisoning to be even greater in humans than was previously thought. The report discovered that ten percent of women of childbearing age in the US - nearly six million women - are at risk of giving birth to infants with neurological problems due to mercury exposure in the womb. The National Academy of Sciences estimates that 375,000 babies born each year are at risk for neurological damage, and an estimated 60,000 babies are born with such damage.
Experts were appalled by the CDC's findings, and now believe that not only people who consume large amounts of fish, but rather the general population of fish eaters, are exposed to unsafe levels of mercury.
The national study was the first of its kind to test mercury samples in human blood and hair. All previous US reports had been based solely on fish consumption.
Mercury occurs naturally in charcoal and is released into the air by industrial pollution from power plants, waste incinerators, and industrial processors. After released into the environment, it changes into methylmercury. Once in the air, methylmercury subsequently lands in the oceans, lakes, and streams when it rains or snows. Fish then ingest the mercury, which can cause severe damage to a developing fetus when eaten by a pregnant woman.
Almost all fish ingest some amount of methylmercury. In areas of greater industrial pollution, the levels of methylmercury in local fish are higher. The tolerable limit of methylmercury for human consumption, as set by the FDA, is one part per million (ppm). This level is typically seen in large predator fish like shark and swordfish. In fact, the General Accounting Office has found that over half of the swordfish in the US contain one or more ppm methylmercury.
Recently, the National Wildlife Federation reported that rain in New England contains up to four times the level of mercury considered safe by the federal government for aquatic life. Industrial plants in New England emit 35,000 pounds of mercury into the air each year, but less than a teaspoon of mercury will contaminate a 25-acre lake. But the major source of New England's mercury pollution comes from Midwest plants, which are beyond the control of New England regulators.
Eighty-three percent of New England's rivers, lakes, and streams contain so much mercury that the six regional states have issued warnings to limit consumption of freshwater fish.
Another species of fish that should be of concern to at-risk women and children is tuna. The FDA excluded tuna steaks from their recent advisory, even though tuna can contain harmful amounts of methylmercury. At-risk groups should be advised that fresh tuna steaks and sushi - but not canned tuna - can have greater than one ppm of methylmercury.
The FDA works with state regulation agencies when commercial fish is found to contain levels of methylmercury greater than one ppm. The FDA also regulates fish that is imported, and exports or destroys those that exceed the upper limit or pose a serious health hazard of any kind. Regulation of imported fish is especially important because over 50 percent of the seafood consumed in the US is imported. The Environmental Protection Agency (EPA) recommends that consumers contact their state health department for advice on the safety of fish from local waterways.
The FDA's Center for Food Safety and Applied Nutrition is starting a program to educate pregnant women, women of childbearing age, and their healthcare providers about the risks posed by eating certain kinds of fish to unborn infants.
The government has not only taken the initiative to warn at-risk people about mercury-laden fish, but has also made strides towards reducing the amount of mercury in the air and waters.
The EPA has taken a number of measures to reduce mercury pollution in the US. It has implemented strict regulations for industries that contribute significantly to mercury pollution, including federal bans on mercury additives in paint and pesticides, reduction of mercury in batteries, increased state regulation of mercury emissions and mercury in products, recycling programs, and other voluntary industry actions. And recently, the EPA announced new regulations for power-plant mercury emissions.
Fish is an important part of a healthy diet, and has been associated with decreased risk of heart disease, but "pregnant women should take the advice of the FDA," and limit the amount of fish they eat, especially swordfish, shark, and tuna steak, according to Alice Lichtenstein, D.Sc., professor of nutrition at Tufts School of Nutrition Science and Policy.
The FDA has advised at-risk groups to choose other kinds of seafood like shellfish, canned fish, and smaller ocean or farm-raised fish, and claims women can safely eat 12 ounces of cooked fish per week.
