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Dioxin triggers cancer at a smaller dose than any other chemical. PCBs
(polychlorinated biphenyls) are a closely related chemical that also likely
cause cancer. PCBs, when burned, can become dioxin. PCB's and dioxin contribute to
numerous other illnesses in people. However, the pathway from exposure to PCBs
and dioxin to disease is not well understood. Researchers suspect the large
amounts of chlorine in PCBs and dioxins are responsible for the illness.
National PCB studies were performed in the 1970s as part of the National Human
Adipose Tissue Survey (NHATS). Local
and early
NHATS results found PCB levels in African-American populations may have been
greater than those of white populations. Later
studies supported those results, but found that the percentage of the
population with high PCB levels had begun to decrease in 1977, the year PCB
production was banned in the United States.
The PCBs in the Great
Lakes and the Arctic pose the
greatest threat to Native American communities.
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