Rio Gomez, I, T Marshall, P Tsai, Y-S Shao and YL Guo. 2002.
Number of boys born to men exposed to polychlorinated biphenyls.
the latest publication tracking the health impacts of cooking oil
contamination by a mixture of PCBs, dioxins and furans in Taiwan
in 1979, del Rio Gomez et al. report that men exposed while
under the age of 20 by the contamination are significantly
less likely to father male off-spring. For men exposed
at an older age, there appears to be no effect.
did they do? del Rio Gomez et al. analyzed the
birth records from 1980 to 1999 of parents exposed to contaminated
cooking oil, calculating the sex ratio of their offspring separately
for men and women. The scientists further divided parents by age
and considered separately those people who had been exposed before
they reached the age of 20 vs. those who were 20-yrs old
or older in 1979.
did they find? Overall, exposed men had fewer male children
than expected. Once del Rio Gomez et al. separated men
by age, it was apparent that this effect was significant only in
men who were less than 20-yrs old at the time of exposure. No effect
of exposure was seen in the sex ratio of exposed women.
overall, exposed men fathered fewer male offspring (p <
0.037), the effect of PCBs appears restricted to men exposed
under the age of 20, for whom the pattern was highly significant
(p < 0.020). Older men did not show an effect (p > 0.60).
does it mean? This is the latest and largest study demonstrating
an effect of dioxin-like compounds on the sex ratio of children
born to exposed parents. Mocarelli
et al. reported a similar pattern in children of parents
exposed in the 1976 Seveso, Italy, chemical plant explosion. As
in this paper, the effect was in men exposed before they reached
consistency of these results gives additional credence to concerns
that contamination by dioxin-like compounds may be having
a broad effect on human sex ratio. Reviews of trends in
the ratio of boys:girls born in several countries, including Denmark,
the US, Canada and the Netherlands,
indicate that the ratio is shifting downward, with fewer boys born
del Rio Gomez et al. point out, the mechanism of action by which
the sex ratio is altered is not yet known. They focus attention
on the fact that dioxin-like compounds are active hormonally, with
estrogenic, anti-estrogenic, and anti-androgenic characteristics.
hypothesize that "dioxin-like compounds might have a negative
effect on the viability of the Y-chromosome carrying sperm or on
the development of XY-fertilised eggs. Furthermore, a relation might
exist between reproductive cells and the aryl hydrocarbon receptors
of dioxin-like compounds, inducing a mutation in proteins that could
result in either a gain or a loss of receptor function, altering
the paths of sex determination."