8%. The researchers did not study whether the increase in the number of sperm Y led to the birth of more boys. Experts say they can do too little on their own to reduce the effect of pollutants, especially if they live in highly polluted locations.
As a Scandinavian study shows, environmental factors can affect male fertility. They have found that air pollutants appear to affect the ratio of sperm bearing X or Y chromosomes (which determines sex).
The effects of two types of persistent chloroorganic pollutants (POPs) on the sperm of 149 fishermen were evaluated. Some have fished on the east coast of the Baltic Sea, which is contaminated with POPs DDE and CB-153, while others have fished on the west coast, cleaner waters.
It was concluded that the increase in the proportion of sperm containing the Y chromosome is associated with the increase of the concentration of both pollutants in the blood of men.
Following comparison of 20% of fishermen with the highest exposure to pollutants with those with the lowest exposure, DDE pollutant was associated with a 1.6% increase in sperm count with Y chromosome, and CB-153 pollutant with a increase of 0.
One expert, a researcher at the University of Rochester Medical Center in Rochester, N.Y., found flaws in this study because the results explain only a small fraction of the variability in Y chromosome proportion.