Special to The Japan Times Recently, concern has been expressed in Japan about the contaminants found in whales and other marine mammals. It has been reported that contaminant levels are dangerously high and the government should take steps to reduce the risk to consumers’ health. It may be helpful to consider the experiences in another country where contaminated whale products are also being eaten.
In northern Canada (as well as in Alaska and Greenland), many people living in coastal communities eat large quantities of marine-mammal meat and fat. The Arctic environment contains all the known pollutants occurring in industrial and agricultural regions of the world, as well as having high, but naturally occurring, background levels of such toxic heavy metals as mercury and cadmium. To make matters worse, Arctic animals’ bodies contain large deposits of fat, which is where many of the contaminants accumulate. Northern peoples have a dietary preference and a nutritional need for fat, and so the fat of whales and seals is consumed almost daily. In addition, Arctic animals are long lived, which results in high levels of contaminants being accumulated in their bodies over many years of intake.
When the high levels of environmental contamination became known in Canada through reports similar to those appearing in Japan, understandable concern was expressed by the public. It was widely reported that these contaminants included DDT, dieldrin, chlordane, PCBs, and lead and cadmium-substances believed to cause health problems among people and wildlife.
Not only did contaminant levels in northern peoples’ staple foods exceed tolerable limits contained in national and international guidelines, but they occurred at several times the level found in the foods and bodies of Canadians living in highly polluted industrial regions outside of the north. Furthermore, northern mothers’ milk and their babies’ blood contained very high levels of PCBs (which was to be expected in a region where babies are breastfed many months longer than is usual elsewhere.)
Since the 1970s, government and university scientists, medical researchers and public health professionals in the Arctic nations have published large numbers of reports and held many conferences to consider the health risks people face when consuming relatively large amounts of meat and fat containing high levels of organochlorines and heavy metals. These contaminants are regularly reported to be suspected of causing developmental and neurological abnormalities, and reproductive, kidney, liver, circulatory and immune-system disorders. However, despite considerable research in Alaska, Canada and Greenland, clinical evidence of the predicted ill-health has not been found.
Nevertheless, as a consequence of researchers’ and consumers’ concerns, the Canadian government initiated a comprehensive evaluation of this problem between 1991 and 1997. The resulting 450-page Canadian Arctic Contaminants Assessment Report, published in 1997 and written by more than 80 specialists, includes an exhaustive assessment of the health consequences of consuming foods that contain various heavy metals, radionuclides and organochlorines (including PCBs, DDT, HCH, chlordane, dieldrin and several others).
The results of this study are relevant to consumers’ concerns in Japan. One conclusion is that the well-known health benefits of consuming marine foods far outweigh any potential negative health consequences. Thus “based on insufficient information about the risks and the significantly known benefits of traditional food [marine mammal meat and fat], people were not advised to significantly alter their current diets.”
People are understandably concerned when reading about high PCB or mercury levels in their foods. However, a World Health Organization report indicates that mercury toxicity appears to be blocked by the high levels of selenium found in whale tissues. A 1999 study conducted by the U.S. National Research Council finds no evidence to either support or reject the notion that PCBs, and other so-called enzyme disrupters, in the environment constitute a health risk.
It was noted in a 1992 Government of Quebec study that PCB congeners found in high concentrations in mothers’ milk are quite different from those causing developmental problems in infants and children. Although research continues, the Canadian government report concludes: “The public has been advised to continue eating traditional diets of fish and sea mammals and nursing mothers have been strongly urged to continue breastfeeding.”
Regrettably, we have to accept that there is some risk associated with every activity — even medical procedures like immunization or surgery, or driving a car, engaging in some healthy outdoor sports and frequenting places where others smoke cigarettes. Health assessment requires weighing a variety of considered benefits against the considered risks. Exceeding acceptable daily intake levels of contaminated food is problematic if it occurs every day of a person’s life, but this does not occur in the case of Japanese whale or dolphin consumption.
The Japanese government is advised to be cautious in reacting to hasty and dangerously incomplete reports that contain little to cause concern to consumers who practice the commonsense virtue of eating all types of food in moderation.
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