MadSci Network: General Biology

Re: What makes Inuit women's breast milk so toxic?

Date: Thu Feb 4 13:07:43 2010
Posted By: W Emory Lawrence MD, M.D., Family Practice/Emergency Medicine, Clay County Hospital
Area of science: General Biology
ID: 1260917410.Gb

Thank you for this interesting and thought-provoking question.

I am not aware of any studies related to toxicity of inuit milk, but what you say could well be true. Any substance ingested by mammals can appear in the breast milk, including humans. Toxins that are known to cause problems with marine life include mercury, lead and other heavy metals, dioxins, organophosphates, DDT, and radioactive isotopes from nuclear weapons testing. Toxins are ingested by plankton and algae at the bottom of the food chain and then passed on to the creatures that feed upon them. It is the top predators who accumulate the heaviest burden of toxins because they basically eat everything else. In the Inuit world, this would be your whales, walruses, seals, larger predatory fish, and polar bears. Any or all of these may be staple food items for the traditional Inuits, who occupy a unique niche apart from all other peoples. They are at the top of their food chain, so it is logical to assume they would in fact be at highest risk to accumulate environmental poisons within their bodies.

To answer your question in summary: It is what the Inuit eat that could make their milk toxic.

W Emory Lawrence, MD

[Moderator's Note: I note at least one study of the levels of polychlorinated biphenyls (PCBs) in the breast milk of Inuit women. See:
Dewailly E, Nantel A, Weber JP, Meyer F. (1989) High levels of PCBs in breast milk of Inuit women from arctic Quebec. Bull Environ Contam Toxicol. 43(5):641-6.

In their paper, Dewailly et. al. compare PCB levels in the breast milk of Inuit women living on the east coast of Hudson Bay in Quebec to PCB levels in the breast milk of women of European ancestry living in Quebec City and on the north shore of the St. Lawrence River. The average concentration of PCBs in the breast milk of Inutit women was 111.3 micrograms per liter, while the average concentration of PCBs was 28.4 micrograms per liter in the women of European ancestry. They note that the PCB levels in the Inuit women are among the highest levels ever reported. The authors also note that, "consumption of fish and marine mammals by the Inuit people is markedly higher than in the rest of the Canadian population and in some communities, sea mammals represent a significant part of the diet", and suggest that the PCBs are derived from the fish and sea mammals consumed in Northern Quebec. -- SM]

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