SHOULD WE EAT FISH?
As we know, fish are an excellent source of complete protein as well as some other exceedingly beneficial nutrients, especially the long-chain omega-3 fatty acids found in the fat of cold-water fish (see NOHA NEWS, Fall 1991). However, persistent manmade chemicals, which are stored in the fat of fish, have accumulated in our lakes and oceans. The levels of these chemicals in the water may seem miniscule. But because they become concentrated in living tissue, highly magnified concentrations can appear in fish, large birds, and our own body fat. It has been calculated that to get as large a dose of polychlorinated biphenyls (PCBs) as one would get from eating two pounds of lake trout, "one would have to drink the Great Lakes water it lives in for 1,000 years."1
Observations such as these prompted widely read magazine Consumer Reports to make waves with a recent article on the safety of eating fish, leaving in its wake a flurry of newspaper articles and fish-store denials. ("Customers arenít getting sick on me," said an officer of one Chicago-area fish wholesaler.2) Though the article concentrated mainly on the problems of spoiled fish, mislabeling, and misinformation from clerks, it did report its own tests for contamination by chemicals such as PCBs, mercury, some pesticides, and, in clams only, lead, cadmium, and arsenic.
The results? "Forty-three percent of our salmon, 50 percent of our whitefish, and 25 percent of our swordfish contained detectable levels of PCBs. Ninety percent of the swordfish also contained detectable amounts of mercury. In some of these fish, the levels we found were significant, posing a possible health hazard to developing fetuses."3 The magazineís samples of flounder and sole were "virtually free of pollutants," but some clam samples were high in lead.
Health hazards from chemicals are usually assessed by means of animal studies, but the results cannot always be accurately translated to effects on humans. For example, one recent study found that humans are four times more sensitive to neurotoxicological effects of PCBs than rodents.4 The same study provided epidemiological evidence of neurotoxic damage to the children of mothers who had eaten Great Lakes fish: poor reflexes and muscle tone at birth, "delay in psychomotor development at 6 to 12 months, and poorer visual recognition memory at 7 months." Such effects often go undetected. According to the Food and Nutrition Board of the Institute of Medicine, National Academy of Sciences, "Under ordinary conditions, [these] effects would not have been recognized by the parents or family physician. They were detected by skilled psychologists trained to measure such endpoints and unaware of the exposure history of the child."5 (Health researchers often focus on markers or "endpoints" as indicators of adverse health effects. Cancer, considered an "easy" endpoint in animal studies, is limited as an endpoint in human studies because of its long lag time Ė as much as forty years.)
Research findings such as these have led investigators to argue that with fish, subtle health effects are more important than cancer and that more innovative research is needed: "The evidence suggests that diverse alterations in the development of offspring resulting from maternal exposure to chemicals that bioaccumulate in fish are more probable and socially devastating than cancer. The chemicals that accumulate in fish generally are neither acute toxicants, powerful human carcinogens, nor genotoxicants. Their mechanisms of action, however, make them developmental toxicants capable of altering the function of critical physiological systems."6
In one new approach to animal research, rats were fed a diet of salmon from a stream feeding into Lake Ontario. Compared to rats fed Pacific salmon or no salmon, they were "hyper-reactive to stressful events such as reductions in food rewards, mild shocks, and novel environments."7 Midwestern waters, it would appear, are no longer the safe, bountiful resource they once were.
Despite their limitations, animal studies do suggest health hazards, often easily missed ones like nerve damage or developmental problems. With birds, "hatchability" and "wasting" (weight loss) are two possible endpoints. Poor hatchability and other deficiencies were found in a 1983 study of Green Bay, Wisconsin, tern chicks contaminated by PCBs and dioxin (widespread in our environment from manufacturing and incineration processes involving chlorine). A later study of less-contaminated Green Bay chicks found better hatchability, but, when continued beyond 17 days, found considerable wasting. By 31 days, 35 percent of the young had died. To the biologists who did the study, this meant that if they had taken only "hatchability . . . as the endpoint, they would have missed the more subtle but equally devastating effects of wasting."8 Hormonal effects have also been found. At the University of Wisconsin, pregnant female rats fed a single meal containing tiny amounts of dioxin produced feminized male offspring.9 Many of these effects didnít show up until the baby rats reached adulthood.
Chemical sensitivity is seen by many as an indicator of societyís overuse of toxic chemicals. According to scientists J.P. Myers and Theo Colborn, of the W. Alton Jones Foundation, chemical sensitivity has been described as a "condition with many adverse health endpoints, the result of reaching a threshold from exposure to a number of chemicals. . . . The increasing number of individuals experiencing chemical sensitivity perhaps in itself is an indication of the inadequacy of pesticide regulation."10
In the sea of government inaction and confusion on fish regulation, the FDA has assumed the role of chief inspector, with its newly created Office of Seafood set up to do mandatory inspections of seafood plants. According to Consumer Reports, however, the FDAís "mandatory program falls short," largely for lack of money.11 With pesticides alone (only one of many chemical contaminants), "under present regulations, a genuine independent review of the health effects of a product never takes place before registration," say Myers and Colborn.12
Should we eat fish? A good answer is difficult, if not impossible. At present, obviously, we cannot rely on the government to protect us. Perhaps the best answer is to stick with those kinds of fish found relatively safe by Consumer Reports and by David Steinman, whose Diet for a Poisoned Planet was reviewed in NOHA NEWS, Winter 1991. Good luck.
1Hileman, Bette, "Great Lakes Cleanup Effort: Much progress, but persistent contamination remain a problem," Chemical & Engineering News, February 8, 1988, p. 30.
2Pratt, Steven, and William Rice, "The taint: Stores respond to Consumer Union charges that fish are contaminated." Chicago Tribune, January 23, 1992, Section 7, p. 4.
3 "Is Our Fish Fit to Eat?" Consumer Reports, February, 1992, pp. 103-14.
4Tilson, H.A., J.L. Jacobson, and W.J. Rogan, "Polychlorinated biphenyls and the developing nervous system: cross species comparisons," Neurotoxicology and Teratology 12:239-48, 1990.
5Cloborn, T.E., "Nontraditional Evaluation of Risk from Fish Contaminants," Proceedings of a Symposium on Issues in Seafood Safety, Farid E. Ahmed, editor, Food and Nutrition Board, Institute of Medicine, National Academy of Sciences, Washington, D.C., 1991, p. 103.
9Myers, J.P., and Theo Colborn, "Immense unknowns characterize the assessment of pesticide risks," Chemical and Engineering News, January 7, 1991, p. 53.
10Myers, J.P., and Theo Colborn, "Blundering questions, weak answers lead to poor pesticide policies, Chemical & Engineering News, January 7, 1991, p. 43.
11Consumer Reports, p. 113.
12Myers and Colborn, "Immense unknowns," p. 54.
Article from NOHA NEWS, Vol. XVII, No. 2, Spring 1992, pages 4-5.