Air pollution may reduce male birth rate

High rates of air pollution can reduce the number of boys born and may be linked to increased rates of miscarriage, according to research.

Researchers in Brazil studied the proportion of male to female births in different areas of Sao Paulo, one of the most polluted cities in the world.

They found that in the least polluted area of the city, 51.7 per cent of all live births resulted in a boy, while in districts with the worst air quality, only 50.7 per cent of births were male.

The differences were statistically significant, although experts still do not know for certain why pollution affects the male birth rate more than female.

The findings also raise concerns about the effect of the environment on fertility levels.

The Brazilian team also found that male mice exposed to "dirtier" air had reduced sperm counts when compared to those in cages with filtered air.

"Our findings support the concept that air pollution may have a direct negative correlation with sex distribution of exposed populations," the researchers concluded.

In a separate study, the same team found that pregnant mice that were exposed to high levels of air pollution were more likely to lose their babies in the first week of gestation than those caged in cleaner air.

They called for more research into how poor air quality affects the human population.

Air quality levels are much higher in Britain than in Sao Paulo, but researchers there are already concerned that "gender-bender" chemicals in rivers have caused fish to become "feminised".

- INDEPENDENT