Pollution may affect fertility and induce miscarriage

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

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 live births resulted in a boy, while in districts with the worst air-quality, only 50.7 per cent of births were male.

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The Brazilian team also found that male mice who were exposed to "dirtier" air had reduced sperm counts compared with those in cages with filtered air.The same team observed that pregnant mice exposed to high levels of air pollution were more likely to miscarry 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.

British air-quality levels are better than those in Sao Paulo, but researchers are already concerned that "gender-bender" chemicals in rivers have caused fish to become "feminised".