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Tuna fish sandwiches are a staple in many kids’ lunches. In fact, tuna is the most popular fish in the U.S. 

The good news about tuna’s popularity: Fish is a healthy protein source that’s naturally low in fat and one of the best sources of omega-3 fatty acids, which help prevent heart attacks and lower bad cholesterol (LDLs) while raising good cholesterol (HDLs).

The bad news: Tuna and many other kinds of fish can be contaminated with toxins due to pollution. These toxins are particularly dangerous for children. They can raise a child's risk for cancer, cause brain damage, and disrupt hormonal activity. Even developing babies in the womb can be exposed to — and harmed by — these chemicals.

Fishy Chemicals

Toxic chemicals that contaminate fish have been, and continue to be, put into our environment from manufacturing, agricultural and energy generating activities. Coal-burning power plants release mercury into the air, and it falls into our waterways. Companies also discharge chemical wastes directly into rivers, streams or oceans, as was the case when the General Electric Company (GE) released over a million pounds of polychlorinated biphenyls (PCBs) into the Hudson River in New York during a 30-year period ending in 1977. Pesticides, like DDT and chlordane, travel far and wide on air and water currents. Many of these contaminants persist in the environment for years.

When fish live in polluted waters, they absorb and consume the chemicals in the water, thereby becoming contaminated themselves. As a result, some fish are not healthy to eat and other fish should only be eaten in moderation.

Seafood of greatest concern are the following:

• Predatory and Large Fish (tuna, shark, swordfish, salmon, etc.): These fish tend to accumulate high concentrations of contaminants because they eat large quantities of other contaminated fish over a long life span. By the time predatory fish get large, they have swallowed a lot of toxins.
•  Bottom Feeders (lobsters, mollusks, etc.): Pollutants tend to settle on the bottom of waterways, where these creatures spend most of their lives. Toxins are unlikely to be washed away or biodegrade because of lack of sunlight.
• Fatty Fish (mackerel, salmon, etc.): Some contaminants are stored in fat, so fish and seafood with high fat content are more likely to be contaminated at unhealthy levels.

Chemical contaminants of concern in seafood include:

•  polychlorinated biphenyls (PCBs) 
• polybrominated diphenyl ethers (PBDEs)
• dioxins 
• pesticides, such as DDT and chlordane
• These chemicals are known for their potent health effects and their ability to endure in the environment and the human body for many years. These chemicals, known as Persistent Organic Pollutants (POPs) can take years — even decades — to break down and dissipate. POPs found in fish accumulate in our body fat and can enter the womb and breastmilk. They have been linked to cancer, hormone disruption, brain damage including behavioral problems and intelligence deficits, and reproductive effects. A child exposed to these chemicals through diet or prenatal exposure could face an increased risk of cancer for 20 years. Girls and young women who eat contaminated fish are likely to pass these contaminants onto their children through prenatal exposure.
• methylmercury
• This neurotoxin can cause irreversible damage to the brain and central nervous system and is particularly devastating to the developing brain. Some of the health effects include decreased IQ and attention deficits. Methylmercury does not have the persistence of POPs, which means that reducing exposure by limiting the amount of contaminated fish eaten can make a difference in a matter of months. Since it can cross the placenta and enter breastmilk, women who are considering pregnancy and those who are nursing should avoid fish that are high in mercury.

About Tuna

• As large, predatory fish, tuna are likely to contain high levels of contaminants — particularly mercury, and canned tuna is no exception. The most recent government data shows that canned white (albacore) tuna is the worst, with three times more mercury than canned chunk light tuna. In some cases, mercury levels of canned albacore tuna exceeded the government specified limit. Tuna steaks are also likely to contain unsafe levels of mercury . Fortunately, canned chunk light tuna — which comes from smaller skipjack tuna — actually has lower than average levels of mercury. Even canned chunk light tuna should be eaten in moderation.

Recommendations:

• Children, teenage girls, women considering having children, pregnant women and nursing women should not eat canned white (albacore) tuna or tuna steaks.
• One serving of canned chunk light tuna — about one tuna sandwich for a child, two for an adult — per week is considered safe.

Fish Farms Are Not All Green

Farmed fish may seem like a safer alternative, but that is not always the case. Because farmed fish are raised in close quarters, they must be treated with pesticides and fed antibiotics to minimize lice and disease. In some cases, farming can contribute to environmental pollution of waterways due to waste and pesticides (see below).

Salmon is particularly problematic when farmed. Farmed salmon are fed a fish meal diet that tends to increase the concentration of contaminants in the fish. They have been shown to have higher concentrations of pollutants — up to 10 times more PCBs — than their wild counterparts. Eating farmed salmon more than once a month will increase your cancer risk, according to a study published in the January 2004 issue of Science and co-authored by Healthy Child Science Advisory Committee member, David Carpenter. Farmed salmon originating from European countries have even higher levels of contaminants, Dr. Carpenter and his colleagues have found. Almost all of the Atlantic salmon sold in the U.S. is farmed.

Farmed salmon imported from foreign countries may also be contaminated with other chemicals. Both Chilean and Scottish farmed salmon have been denied entry into the United Kingdom and the U.S., respectively, after the detection of high levels of malachite green, a fabric dye and fungicide banned in the United States. But you can't rely on the federal government to keep the all the tainted fish out — there just aren't enough inspectors to test the billions of pounds of imported fish for banned drugs.

To add insult to injury, farmed salmon are given drugs for an artificial color, because they are not naturally pink due to the diet provided to them. Safety questions have been raised about the impact of the additive canthaxanthin on eyesight. A group of eight consumers in Washington State recently filed a lawsuit against three big grocery store chains for failing to label farmed salmon to indicate the use of artificial colors. Federal regulations require that farmed salmon bear labels stating "artificially colored" or "color added." Though the lawsuit hasn't gone to trial, grocers across the nation have started to label farmed salmon.

* * *

All these nasty chemicals might make you want to forget fish forever. But the health benefits of eating seafood outweigh the risks in most cases. A National Academy of Science study on the health impact of mercury concluded that people should not stop eating fish, but should instead choose fish with lower mercury concentrations.

Who is at Risk?

Bear in mind that we are not equal when it comes to risk from eating contaminated fish. Children, teenage girls and women who may someday become pregnant, pregnant women and women who are breastfeeding must be particularly careful.

•  The fetus, infants and young children are the most vulnerable to the toxins found in fish. Infants and children are more vulnerable than adults to toxic pollutants because their bodies and brains grow and develop throughout childhood. Young children don't have the ability to filter out toxins as effectively as adults, which compounds the risk they face. Research from the Environmental Protection Agency estimates that 630,000 babies are born annually in the U.S. with unsafe levels of mercury in their blood.
•  Women who are pregnant and nursing should be cautious about the type of fish they eat. Contaminants found in fish can be passed from a pregnant woman to her fetus, where they can cause permanent developmental damage. Some of the contaminants are also found in breast milk. Ten percent of women have levels of mercury considered in the danger range, according to the U.S. Centers for Disease Control and Prevention. Dietary changes can reduce blood levels of mercury within a few months.
• All females from birth until after their child-bearing years should be mindful of their fish consumption. Because some chemicals that contaminate fish accumulate and persist in the body for decades, eating safe fish must begin at an early age. A girl or young woman who eats contaminated fish can pass the toxins on to her baby years later.

While men can be overexposed to the contaminants in fish if they eat significant quantities of the worst offenders, environmental health advocates have focused on women and children because even small doses of these chemicals can have a major impact on the development of fetuses, infants and children.

Since young people are not at risk for heart attacks — which a fish diet high in omega-3 fatty acids can prevent, they should avoid contaminated fish, says Dr. Carpenter. Though omega-3 is important for brain development, too, we get enough in a healthy diet. In fact, there are many vegetarian sources of omega-3, such as walnuts, flax seed, and canola.

Isn't Fish Regulated by the Government?

Two federal agencies, the U.S. Food and Drug Administration (FDA) and the U.S. Environmental Protection Agency (EPA) regulate fish and publish advisories on the amount and kind of fish people can consume safely.

• The FDA has set safety limits on the amounts of mercury, PCBs, DDT, chlordane and a number of other pesticides in seafood as well as arsenic in shellfish. FDA advisories apply to commercial fish — that is, fish bought in stores or restaurants.
• The EPA publishes advisories for fish caught in specific bodies of water. They monitor for 39 chemical contaminants, but the vast majority of advisories involve the top five contaminants: mercury, PCBs, chlordane, dioxins, and DDT. EPA issues advisories for fish caught recreationally. Advisories differ widely from place to place, depending on pollution and contamination levels.

Both FDA and EPA recognize the special vulnerability of children, pregnant women, and women of childbearing age to toxins like mercury and make recommendations based on the higher risk these populations face.

Each of these two agencies has its own idea of what's considered "safe" as far as mercury goes. FDA has set the allowable daily intake for methylmercury much higher than EPA and the World Health Organization. The Environmental Working Group (EWG) has issued several reports criticizing FDA's fish advisories as too lax. (See Policy Brief on Mercury Standard.) EWG and other consumer advocates have issued their own guidelines and recommended fish lists using more stringent standards than FDA. We've compared these recommendations and come up with our own.

Meanwhile, who’s watching the farm? Current regulatory law gives us pause. Under the National Aqauculture Act of 1980, the Joint Subcommittee on Aquaculture (JSA) was created as an advisory board to evaluate the industry’s development. JSA is headed by a USDA representative, and there are at least eleven other members from the EPA, FDA, the Department of Interior and the National Science Foundation, among others. The National Oceanic and Atmospheric Administration , or NOAA (part of the Deparment of Commerce, which also sits on JSA), has proposed a new model that would put one agency in charge of aquaculture and allow it to coordinate the various interests and concerns. Meanwhile, aquaculture is regulated by a patchwork of state laws, most of which weren’t written with that industry in mind.

Troubled Waters

Several commercial fishing practices are also causing problems in our oceans. Rapid advances in fishing technology, combined with heavy industry subsidies, has led to overfishing and declining fish stocks worldwide. Approximately twenty-seven million tons of fish and sea life are caught unintentionally each year. This "bycatch", as it is called, is simply discarded. That is about one-quarter of the total catch, according to the Food and Agriculture Organization of the United Nations. Practices like trawling, in which a net is dragged over the ocean floor, harm delicate marine life and disturb the fragile ecosystem. The rising demand for seafood cannot keep pace with the dwindling supply. Several campaigns aiming to reduce the consumption of swordfish, Chilean sea bass, and beluga caviar have received considerable attention.

Large-scale fish and shrimp farms have also created environmental problems. Instead of reducing overfishing, they can actually encourage it. In the case of salmon, each fish consumes several pounds of fish meal (ground-up, wild-caught fish) per pound of its own body weight. Huge amounts of waste, pesticides and antibiotics are released from fish and shrimp farms into the surrounding water, increasing pollution and endangering wild stocks. Escapees from fish farms can also have an impact on wild stocks by interbreeding or competing for food. Salmon farms are having a major impact because of sheer numbers. Salmon is now the third most popular fish in the country, and up to 60 percent of salmon consumed is raised on farms.

Several kinds of genetically engineered (GE) fish are currently under development. These fish have genes "imported" from other fish species (or insects or humans) so that they will grow faster, resist disease, or be able to live under different conditions than they would naturally. Some scientists are expressing concern that escaped GE fish may compete with wild fish for food and mate with them to produce offspring less fit to survive in the wild. The FDA is currently considering whether or not to allow the sale of the first GE fish, a type of salmon. California, Washington, Oregon and Maryland have already passed laws prohibiting GE fish in their open waters.

Which Fish?

Remember that fish is a vital part of a healthy, balanced diet, but we shouldn't have to mix nutrition with toxins. With all the types of chemicals and fish to consider, however, it's easy to be confused about which to choose. We've compiled a Safe Fish Check List to help you choose and prepare fish without exposing your family to dangerous chemicals. There, you'll also find a handy chart to guide your fish selection.

Other Resources

Global Assessment of Organic Contaminants in Farmed Salmon, Science, Vol. 303, No. 5655, 9 Jan 2004 (free registration required).

Tuna Calculator and Brain Food report, Environmental Working Group

Sea Web Aquaculture Clearinghouse

Additional Consumption Recommendations

Online Smart Fish Calculator, Institute for Agriculture and Trade Policy

Seafood Watch Program, Monterey Bay Aquarium

Seafood Smart Choices , Seafood Choices Alliance

Campaigns

Campaign on Genetically Engineered Fish, Center for Food Safety

Caviar Emptor Campaign to Protect and Restore Sturgeon

Take a Pass on Chilean Sea Bass

Government

What You Need to Know About Mercury in Fish and Shellfish, 2004 EPA and FDA Advice For: Women Who Might Become Pregnant, Woman Who are Pregnant, Nursing Mothers and Young Children, March 2004
EPA National Advice on Freshwater Fish for Women and Young Children Gateway to Government Food Safety Information: Consumer Advice on Seafood

Image Courtesy of Jack Parkinson.

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