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Good fish ... bad fish.

Good Fish...Bad Fish

Whether cooked or raw, on your plate or distilled into oil capsules, fish is "hot" these days. Maybe it's a little too hot.

The message to eat more seafood is everywhere; we get it from our doctors, in newspaper articles, on television programs and radio talk shows. In fact, it seems the more we try to cut back on saturated fat in our diets, the more fish we consume.

Does it also mean the more contaminants we put in our bodies?

The health benefits of fish are undeniable. It is an excellent source of protein, B vitamins, and trace minerals. It is also low in saturated fat, yet high in omega-3 fatty acids, which may reduce the risk of heart disease. And in a perfect world that would be just fine.

But there's a problem: Many of the chemicals we introduce into the environment eventually work themselves into lakes, streams, and coastal waters. There, they are ingested by simple forms of marine life and small fish, which in turn are eaten by larger fish. In this way, the chemicals slowly work their way up the food chain. Eventually, they end up in your Blackened Catfish or Trout Almondine.


How serious is the threat from contaminated fish? Larry Skinner, principal fish and wildlife ecologist with the New York Department of Environmental Conservation, puts it this way: "Your chances of getting cancer from eating a weekly eight-ounce meal of trout caught in Lake Ontario is about the same as your lifetime risk of being murdered in the United States today--about 1 in 200." And if you're eating fish caught in New York's Hudson River, Skinner says the odds are even worse.

Fortunately, commercial fishing of trout from Lake Ontario is banned, and you'd have to be desperately hungry to eat a fish caught in the polluted Hudson. But these are only the most blatant examples. To one degree or another, fish from any body of water are potential repositories of industrial chemicals, pesticides, or toxic metals.

Of course, fish can also be tainted with microorganisms or natural toxins. This biological contamination (usually from raw or spoiled fish or shellfish) accounts for about a quarter of all food poisoning cases reported in the U.S. each year.


Industrial Chemicals. Among the worst offenders are polychlorinated biphenyls, or PCBs, which have been used for years in lubricants and coolants. Although the manufacturing of PCBs was banned in the United States in 1979, the pollutant continues to show up in high concentrations in wildlife and fish.

In 1984 researchers at Wayne State and other universities examined infants of women who reported regularly eating an average of two or three meals per week of PCB-contaminated fish from Lake Michigan. At birth, the babies showed weak reflexes and sluggish movements, as well as other signs of "worrisome" behavioral development. [1]

And as if that weren't enough: Most of the estimated cancer risk of eating fish also comes from PCB contamination. [2]

Pesticides. In 1983 the Food and Drug Administration found DDT in 334 of the 386 samples of domestic fish it tested, even though the use of this "probable human carcinogen" was halted in 1972.

But Alan Mearns, an ecologist with the National Oceanographic and Atmospheric Administration (NOAA), says that "DDT levels have declined nationwide, and continue to decline."

Another frequently found fish contaminant and probable cancer-causer is chlordane, which has been widely used to control termites. The "probable" label (which PCBs also have been tagged with) means that the substance causes cancer in animals, but that sufficient evidence in humans is still lacking.

But "sufficient evidence" isn't easy to get. "We don't run controlled cancer studies on humans," explains Sherry Sterling, chief of the Health Sciences section of the Office of Waste Programs Enforcement at the EPA. "We rely on animals as a model for the human system."

Toxic Metals. Low levels of lead, cadmium, chromium, and arsenic frequently turn up in shellfish. Excessive exposure to toxic metals can cause health problems ranging from kidney damage (chromium) and impaired mental development (lead) to cancer (arsenic).

High levels of methyl mercury, another toxic metal, are most often found in large predatory fish such as swordfish, shark, large tuna, halibut, and marlin. Methyl mercury attacks human nerve cells, and can cause numbness and loss of coordination, as well as hearing and visual problems.


Since fish spend their lives immersed in the same waters we use to dump or carry off our chemical contaminants, they're like the "canary in the coal mine," whose sudden death warned miners of dangers in the air.

And, it's becoming increasingly apparent that the "canaries" are taking a pretty stiff beating.

Dr. John D. Harshbarger, director of the Registry of Tumors in Lower Animals at the Smithsonian Institute in Washington, says that fish and shellfish with cancerous tumors have been identified in 25 locations across the country. The "worst," he says, are New York's Hudson River, Ohio's Black River, Washington State's Puget Sound, Boston Harbor, and Ontario's Hamilton Harbor.


To protect consumers from tainted fish sold commercially, the FDA sets "action levels" and "tolerances" for specific contaminants. It can remove from the marketplace fish that exceed these limits.

But the system doesn't come close to safeguarding our seafood supply:

* The FDA has assigned action levels or tolerances to only a dozen or so of the hundreds of contaminants that scientists have identified in fish.

* Government inspectors monitor only a tiny fraction of the fish and shellfish consumed. In 1986 the FDA inspected six pounds of fish for every million pounds eaten.

* Action levels are not legally binding; tolerances, which are, can take years to put in place.

* The scientific basis for standards established in the past is often insufficient. Take DDT. If you eat a daily eight-ounce portion of fish that contains the maximum amount of DDT allowed by the current action level, your risk of getting cancer could be as high as 1 in 1,000, which is unacceptable by all federal standards.

Fortunately, few fish today contain that much pesticide ("Unless, of course, you happen to catch your white croaker off a fishing pier in the Los Angeles area," according to Richard Gossett of the Southern California Coastal Water Research Project).

* Action levels and tolerances are designed to protect "average" consumers, not seafood lovers. But the FDA's definition of "average" is pretty stingy. For example, the tolerance for PCBs is 2 parts per million. But if, once every forty days, you eat more than four ounces of catfish, carp, buffalo fish, fresh water or sea trout, bass, chubs, bluefish, porgy, drum, or mackerel, you're above "average." Not very comforting. [3]

* Federal regulations do not apply to locally- or recreationally-caught fish or shellfish. "I've observed fishermen leaving areas where [state] advisories have been issued, with fish in hand, presumably for consumption," says Thomas Belton of the New Jersey Department of Environmental Protection.

* By law, the FDA's maximum contaminant levels must take into account the economic impact on food-producing industries. This means they inevitably involve some sort of compromise.


Do the dangers of contamination mean we should ignore the health benefits and shun fish and shellfish entirely? Not necessarily.

"There is no need to stop eating seafood," says Dr. Gerald Pollock of the California Department of Health Services. "But to be safe, try to vary your diet."

Nearly three-quarters of the U.S. per capita consumption of commercially-harvested fish and shellfish is made up of canned tuna, fish fillets and steaks (mostly cod, flounder, and pollock), fish sticks, and shrimp. [4] None of these are likely to be very contaminated.

The booby prize for contamination is split between catfish (PCBs and pesticides) and swordfish (mercury). And Cajun food lovers aren't protecting themselves by sticking to "farmed" catfish. Larry Welch, Director of Quality Assurance at Delta Pride, the world's largest catfish processing plant, acknowledges that many catfish are raised in agricultural areas where drifting pesticide sprays and contaminant runoff can be a serious problem.

There's no denying the health benefits of eating fish. But consumers have to weigh those benefits against the long-term, often uncertain risk from chemical contamination.

And while some fish might be "hot," we'd advise you not to "cool" your seafood appetite unnecessarily.

[1] Develop. Psych. 20:523, 1984.

[2] Environ. Sci. Technol. 18:628, 1984.

[3] Environ. Health Perspect. 45:171, 1982.

[4] National Marine Fisheries Service, Fisheries of the U.S., 1986, 1987.

[5] N. Eng. J. Med. 314:707, 1986.
COPYRIGHT 1988 Center for Science in the Public Interest
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Title Annotation:health hazards from eating fish; includes related information
Author:Lefferts, Lisa Y.
Publication:Nutrition Action Healthletter
Date:Oct 1, 1988
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