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Great Lakes Article:

Men who eat fish with pcbs likely to father boys

National Post
01/30/2002

Men who eat fish from the Great Lakes, which are laced with such toxic industrial chemicals as PCBs, conceive a disproportionately high number of sons, according to new research.

The strange effect that PCBs seem to have on sex ratios is poorly understood, but is too significant to pass off as mere coincidence, said Wilfried Karmaus, a professor of epidemiology at the University of Michigan.

He suggested the effect might be due to a disruption of hormone levels in the male reproductive system, which has been documented in other, more severe cases of PCB exposure.

Dr. Karmaus followed nearly 400 families who regularly ate various fish -- walleye, carp, salmon, trout, among others -- they caught in Lake Michigan. Of the 208 children born to the men with the highest PCB content in their blood, 57% of them were boys.

This figure is statistically far higher than the worldwide average sex ratio in which about 52% of newborns are male. Females outnumber males in most populations, though, due to their longer average lifespan and lower mortality rates.

Strangely, the mother's exposure to PCBs had no significant effect on sex ratios, despite the close physiological contact between mother and fetus.

"Being a boy is not a disease," said Dr. Karmaus, the lead researcher on the report in the current Journal of Occupational and Environmental Medicine, "but we can show that there are some health effects on human reproduction from PCBs."

Dr. Karmaus said the phenomenon of skewed birth rates is likely mirrored in fishermen on each of the Great Lakes.

PCBs, or polychlorinated biphenyls, were in wide industrial use from the 1930s to the 1970s, figuring as ingredients in paints, caulking and electrical coolants and insulators. Concern about their toxic effects led to a continent-wide ban on importing and producing PCBs in 1977, but the persistent chemicals decompose at such a slow rate that they are still found at dangerous levels in Great Lakes fish.

The Ontario Ministry of the Environment has issued specific warnings about PCBs in fish and their harmful effects on expectant mothers, but their guide to edible sport fish does not mention effects on male reproductive health.

Mike Wade, a toxicology researcher at Health Canada, said Dr. Karmaus' findings are the latest in the controversial field of sex ratio studies, and they fly in the face of past findings.

"The more boys per girls, in my experience, is kind of novel," Dr. Wade said. "Usually it's the other way around with occupational or drug related factors. For example, guys who are taking chemotherapy tend to have fewer boys than girls."

The explanation for the skewed birth rate around Lake Michigan is probably hormonal, Dr. Karmaus said, but PCBs may also have some as-yet-unknown toxicological effect on the male fetus, which is known to be more fragile than the female.

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