Contaminated Fish Called Health Risk

By Jessica Kowal

July 15, 2003

Scientists have become increasingly enthusiastic about the health benefits associated with eating fish, particularly as they study the effects of omega-3 fatty acids, or fish oils, on the human body. In the 1970s, these important nutrients were found to prevent heart disease. Omega-3 fatty acids are now also believed to decrease the risk of stroke, to improve infant brain development, and even to ease rheumatoid arthritis, Crohn's disease, psoriasis and postpartum depression.

Nevertheless, there remains a troubling aspect to the good health news: contamination of some species of fish with mercury, PCBs and other chemicals, researchers and government officials say.

And some nutritionists say that lax government regulation of some contaminated fish has confused the public about which fish are safe to eat, which need to be eaten in moderate amounts and which could be dangerous.

The result, some scientists charge, is that Americans are now baffled by changing lists of contaminated species and advisories about what type and how much fish to eat. And the worst outcome of a debate about the safety of fish, many experts worry, is that people may drop fish from their diets entirely rather than figure out the messy details.

The best example of consumer confusion and slow regulatory changes, some experts say, is how the U.S. Food and Drug Administration has addressed the problem of mercury contamination.

In September, after years of debate, the Food and Drug Administration plans to revise its 1970s-era standard for how much mercury in fish is safe. The United States may lower its mercury benchmark, possibly to a Canadian and British standard that is half the level now acceptable to the FDA.

That could affect government advice about popular fish, including fresh and canned tuna, red snapper and halibut, some of which have a fairly high mercury content.

"If you're not regularly getting these fish-based fatty acids in your diet, you're missing out on a health bonanza," said Joyce Nettleton, the author of three books about seafood nutrition. "If I want omega-3s, and I don't want to have to worry about mercury, which ones do I choose? There are choices out there."

The Health Benefits of Fish

Three decades ago, studies found that Greenland Eskimos had remarkably little heart disease, stroke, high blood pressure and arthritis. Scientists subsequently linked these benefits to omega-3 fatty acids, nutrients that are produced by microorganisms in bodies of water and passed to fish in the food chain.

Of the various omega-3 fatty acids, three are especially important biologically: DHA (docosahexanoic acid), EPA (eicosapentaenoic acid) and ALA (alpha-linolenic acid). These are described as "long-chain" fatty acids because their structure comprises more carbon atoms strung together in a chain, according to Margaret Craig-Schmidt, a nutrition and food science professor at Auburn University in Alabama.

During the past three decades scientists have tied several vital health benefits to the omega-3 nutrients found in fish. They prevent heart disease and dramatically reduce the risk of a second heart attack; significantly decrease the risk of stroke for men who eat seafood once a month; ease postpartum depression in women who eat significant amounts of fish, and improve symptoms of inflammatory diseases such as rheumatoid arthritis, rhinitis and psoriasis.

"Not a month or two goes by when we don't have another scientific study about the benefits of long-chain omega-3 fatty acids in our diets," said Charles Santerre, associate professor of foods and nutrition at Indiana's Purdue University.

For pregnant women and children, DHA is the most important omega-3 fatty acid, because it's essential to human brain and eye development. Pregnant and nursing mothers who regularly eat fish rich in omega-3s pass more of these nutrients to their children through the placenta and in breast milk, Craig-Schmidt said. And as further evidence of DHA's importance, two companies began selling infant formula that included DHA and another fatty acid, ARA (arachidonic acid) in early 2002. These supplemented formulas are sold under the brand names Enfamil Lipil and Similac Advance, and cost more than regular infant formula.

But mothers and children can get a fine supply of DHA if they eat certain fattier cold-water fish -- particularly salmon, sardines, herring and mackerel.

Among other species of fish, canned tuna packed in water is a good source of omega-3s, but that same canned tuna, particularly albacore, can also be contaminated with fairly high levels of mercury.

Leaner seafoods, such as cod, pollock, shrimp, clams and oysters, are less fatty and provide less omega-3s, said Jacob Exler, a nutritionist with the U.S. Dept. of Agriculture's Nutrient Data Laboratory.

Mercury and Tuna

Mercury occurs naturally in soil and rock but is released into the atmosphere primarily through volcanic activity, coal combustion and medical waste.

Eventually, it settles at the bottom of oceans, lakes and rivers. Bacteria in bodies of water transform this inorganic mercury into methylmercury, a particularly toxic form, which works its way through the food web.

Because mercury accumulates in the body, long-lived predators such as shark or swordfish have exceptionally high concentrations, as do other large fish, said M. Christopher Newland, a professor in Auburn University's department of experimental psychology who studies the impact of mercury on the nervous system.

The FDA has found relatively high levels of mercury in red snapper, marlin, orange roughy, saltwater bass, freshwater trout and bluefish. But the agency has sampled only limited quantities of these fish, so the typical mercury levels are not well known.

Small, short-lived fish -- again, fish such as sardines and herring -- have the least mercury, as do salmon, king crab, scallops, catfish, oysters and shrimp. The most common farm-raised fish -- namely salmon, trout and catfish -- typically have less mercury contamination than fish caught commercially in the wild, according to experts. But it's important to remember that wild salmon, trout and catfish caught commercially have very low mercury levels, anyway, so the difference is not significant from a health perspective.

In a developing fetus, mercury impairs development of the nervous system and brain. High mercury exposure at any stage of life including in the womb, may speed aging and affect motor skills and learning ability in adults, and may increase the risk of heart disease, Newland said.

The FDA says its advisories about mercury lay out safe, healthy guidelines for fish consumption. In 2001, the FDA told consumers to eat no more than 12 ounces (3/4 pound) of a variety of fish per week, a standard that integrated the Environmental Protection Agency's stricter mercury limits, said David Acheson, chief medical officer in the FDA's Office of Science.

The FDA also has advised the public not to eat four mercury-rich fish: swordfish, shark, king mackerel and tilefish.

But the FDA has taken a less aggressive approach to answering questions about tuna, the most popular fish in America, and a cheap source of protein and omega-3 fatty acids. Some tuna steaks tested by the FDA have mercury levels above the agency's safety standard. Canned tuna has less mercury, but FDA samples found a wide range of mercury content, from undetectable to a level approaching the FDA's unsafe reference point.

The FDA now advises pregnant women to eat no more than one 6-ounce can of tuna each week -- one fat tuna sandwich, say, from a deli.

Some health experts say this still poses too great a risk, and last summer, the FDA's own food advisory committee told the agency to re-examine the tuna-mercury issue. In April, the California Medical Association demanded better labeling of tuna after the Centers for Disease Control and Prevention found high mercury levels in a surprisingly large number of women.

In reply to that and many other studies critical of tuna, the U.S. Tuna Foundation has consistently argued that canned tuna "poses no health risks" and "offers significant health benefits to pregnant women."

As the debate plays out, and as the FDA tests more fish, Nettleton, who has a PhD in nutrition science from the Harvard School of Public Health, advises pregnant women not to risk the purchase of a can of tuna, particularly white albacore tuna, that might be high in mercury.

"Is this the time to play Russian roulette with mercury? If you're really cautious about this, choose other fish," Nettleton said.

There are some better tuna choices. "Chunk light" tuna offered by the major tuna brands and small, troll-caught Pacific albacore tuna and imported Spanish tuna in some specialty food stores have less mercury than white albacore, Nettleton said.

The general public should also be more cautious about mercury in large fish, according to Dr. Jane Hightower, a San Francisco internist. After seeing one patient with hair loss problems, who also ate a lot of fish, Hightower questioned more than 700 patients about their fish intake and found, after blood and hair analysis, that about 80 of these patients had unsafe mercury levels in their bloodstream.

Of this group, 78 percent regularly ate canned tuna, most of it albacore tuna. Some high-income patients also routinely ate ahi tuna steaks, tuna sushi and swordfish, and some suffered from fatigue, muscle aches and hair loss associated with mercury poisoning.

"Essentially, we are eating too much mercury" in fish, said Hightower, who published her study in April 2003.

Newland, the mercury expert from Auburn University, believes the current FDA regulations limiting tuna intake to one can per week is appropriate and safe. He says federal regulators could do more for public health if they would ban commercial sale of the highest-mercury fish, rather than confuse people about detailed lists.

"You can go into a restaurant and get swordfish. That just makes no sense to me," Newland said. "Federal authorities should keep fish that contain a lot of mercury out of the market."

Artificially Colored Salmon

Salmon has very low mercury levels and few other contaminants and is one of the best sources of omega-3 fatty acids. This fish has become increasingly popular in the United States as fresh, farm-raised salmon, mainly imported from South America and Norway, has become very cheap and widely available in supermarkets.

But even salmon has surprised consumers lately.

In grocery stores across the country, and in at least some supermarkets in the metropolitan area, packages of farm-raised salmon -- also called "Atlantic salmon" -- are sporting new labels describing it as "color added" or "color enhanced."

Artificially colored pink salmon? It's true. If not for two additives in their fish food, all farm-raised salmon would be dishwater gray.

About 80 percent of fresh and frozen salmon sold in the U.S. is farmed, and whether it is served as a salmon fillet, a salmon steak, lox or sushi, all of it is colored. The reason is that pink salmon sells; according to consumer studies, people associate richly colored salmon with freshness and quality.

The color issue became a national topic of conversation after an environmental law firm in Seattle filed suit April 23 in state Superior Court to force three national supermarket chains to label the color additives in the farmed salmon, as longtime FDA rules require.

The three grocery chains cited in the lawsuit, Safeway, Albertsons and Kroger Co., do not have stores in New York. But New York City and Long Island stores have begun to change the labels on their farmed salmon in line with the FDA rules.

Wild salmon get their pink-orange-red color by eating shrimp and krill, which feed on algae that produce the colorants, called carotenoids. (Canned salmon is entirely wild salmon). For the farmed fish, which eat pellets of ground-up fish, wheat and other nutrients, the two color additives, canthaxanthin and astaxanthin, mimic the algae's coloring effect.

In the wild, salmon color can vary from ivory white to deep red-orange. For farmed fish, color depends in part on water temperature and diet, but fish farmers can, to some extent, control the hue by altering the amounts of additives in the fish food.

Canthaxanthin has raised health concerns in Europe because high doses cause retinal damage. Earlier this year, European Union regulators told fish farmers to cut canthaxanthin levels to one-third of what is currently allowed by the FDA.

Industry experts say no one could or would eat enough salmon to cause eye damage. They add that problems with canthaxanthin, which is also fed to farmed trout and broiler chickens in the United States, were found mainly in people who consumed the additive in large quantities to give themselves a fake tan. No health risks have been identified in the second additive, astaxanthin, which is approved for use only in fish food.

Stewart Anderson, a global marketing manager for F. Hoffmann La-Roche, the Swiss corporation that dominates the market for these additives, says they are "safe for human consumption" if regulations are followed. The FDA is studying the European decision to see if the United States should change its policy, a senior official in the FDA's Office of Food Safety said.

Even if the public accepts the idea of artificially colored salmon, some environmental groups and wild salmon fishermen, mainly in the Pacific Northwest, argue that consumers should refuse farmed fish for environmental reasons.

Comparing fish farms to pig farms, they say fish farms spread disease-causing waste, and farmed fish genetically weaken wild salmon.

Fish farmers say their industry has improved its environmental record in 20 years in business, and they credit farmed salmon with creating a rapidly growing market for a healthful, less-expensive product.

Contaminants in Sport Fish

Grabbing a fishing pole and catching your supper in a lake or river might sound pleasant. The reality is far different: In dozens of metropolitan area lakes and rivers, fish are contaminated with PCBs, mercury, cadmium, dioxin, DDT and other toxic chemicals.

These contaminants, byproducts of industry or pesticide residue that settle at the bottom of lakes, rivers and reservoirs, can seriously harm infant development, authorities say.

The 2003-2004 state advisory about sport fish points to problems in largemouth and smallmouth bass, walleye, perch, brown bullhead, American eel, carp, American shad, and some trout in 80 of the state's bodies of water.

For example, the New York State Health Department advises that people eat no more than a half-pound per week of bluefish and American eels caught in Long Island Sound, Block Island Sound, Peconic and Gardiners bays, the lower bay of New York Harbor, Jamaica Bay and other Long Island South Shore waters because of PCB contamination.

And it can take six years to clear a high dose of PCBs from a woman's body, so a woman could eat a contaminated fish today, become pregnant next year, nurse her baby nine months later and pass along a higher dose of PCB to her baby than when she ate the fish, said Santerre, the Purdue University professor.

That means that women of childbearing age and children under age 15, in particular, should not eat fish caught by anglers in contaminated waters, according to the New York State Health Department and experts on toxic substances in fish.

Adults other than women and children shouldn't eat more than one meal per week of fish caught in any body of freshwater anywhere in the state or at the mouth of the Hudson River, and some contaminated fish shouldn't be eaten more than once a month, state health officials say.

If you want to go out and catch fish, fine, Santerre said. Check local health advisories, catch a fish and release it. "Then go to the grocery store and get some good, healthy fish," Santerre said.

Jessica Kowal is a freelance writer.

Copyright © 2003, Newsday, Inc.