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Lund (pte035/28.04.2005/12:30) - An environmental pollutant can alter the ratio of sperm carrying male and female chromosomes, according to a new study. A baby's sex is determined by X and Y chromosomes in the sperm. As the BBC http://www.bbc.co.uk reports, Swedish researchers found exposure to a class of pollutants which are a by-product of industrial and agricultural processes increased the Y chromosome sperms. However, the team, from Lund University http://www.lu.se , which studied 149 fishermen, were unable to predict if the effect would lead to more boys being born.
According to lead researcher Aleksander Giwercman, a larger population sample would be needed to confirm it. "We think the fact that exposure to environmentally derived chemicals can change the sex chromosome ratio in sperm is worrying in itself and requires more attention from scientists and the public," he said.
The researchers analysed the effect of exposure to two persistent organochlorine pollutants - DDE and CB-153 - which is most likely to come from eating fatty fish such as salmon. The 20 per cent of men with the highest exposure to DDE compared with the 20 per cent with the lowest exposure had 1.6 per cent more sperm with the Y chromosome, the Human Reproduction journal reported. For CB-153 there was a 0.8 per cent increase.
A second study has also suggested environmental factors can have an effect on male reproductive health. The joint Danish, Finnish and Lithuanian study, also published in Human Reproduction, showed an incident rate of undescended testes, which increases the risk of testicular cancer, in Lithuania of 5.7 per cent. This was lower than the 9 per cent rate in Denmark, but higher than the 2.4 per cent rate in Finland. Data on semen quality and testicular cancer in the Nordic-Baltic region had led the researchers to expect similar rates of undescended testes in Lithuanian and Finnish boys. The fact that this was not so indicated that something in the environment was having an effect on male foetuses developing in the womb. "We need to look more closely at the role of environmental factors, including those that can disrupt the hormone system, and the role of genetics, lifestyle and other factors," said report co-author Niels Jorgensen.
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