Polluted air can not only bring transformation in sperm count, but also to sperm mutation, as found by the researchers from Canada and the US National Centre for Toxicological Research, who studied the impact of polluted air on the mice kept in a shed for 10 weeks.
The study published on Monday in the US Proceedings of the National Academy of Science was carried out by the Health Canada in Hamilton Harbour, and industrial city near Toronto.
The findings supplies substance to ongoing concerns about the effects of air pollution on human health and fertility.
The mice exposed to polluted air kept in a shed downwind of two steel mills and a busy highway had undergone a number of genetic changes as compared to a group of mice kept in house breathing pollutant free filtered air.
After a period of 10 weeks researchers compared both group of mice and surprisingly they found that the mice exposed to polluted air have 60 percent increase in sperm DNA mutation in compared to those exposed to filtered air.
More surprising was the sperm mutation persisted even after the mice were no longer exposed to polluted air.
This led the researchers to conclude that pollution had changed the germ-line cells, which produces sperm.
The researchers say that such changes may alter gene expression and function in offspring of these mice, though they have yet not directly tested it.
“There has been work on the reproductive effects of pollution, but that has largely focused on outcomes of pregnancy, not on male effects,” says Samet, an epidemiologist at the Bloomberg School of Public Health.
“The findings propel us to forward to the next step whether there are any human corollaries to this,” he added further.
The researchers already have established that air pollution causes respiratory and cardiovascular difficulties, developmental defects, and lung cancer in humans. But no work has been done yet that links air pollution to sperm mutation.
Earlier studies found that offspring of wild birds bred near steel mills inherited more DNA mutation comparatively their rural counterparts.
In order to understand the cause of DNA damage in their sperm male mice were put on check by Carole Yauk of Health Canada.
The researchers came on the conclusion that experimental group of mice kept in downwind of two steel mills on a busy highway started to show more signs of DNA damage as compared to control mice breathing fresh air just after three weeks of experiment.
After 10 weeks experimental group had more methylated DNA than controlled group of mice and 16 weeks later the researchers found DNA of experimented group contained more mutation than the controlled ones.
Next task for the researchers are left to determine how the pollution caused the DNA breakage.
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