From BBC Health - October 20, 2005 11:22
High levels of air pollution appear to be linked to a reduction in the proportion of male babies being born.
High levels of air pollution are reducing the number of boys born and could be linked to increased rates of miscarriage, research suggests.
A team from Sao Paulo University in Brazil found fewer boys were born in the most polluted areas.
Experiments on mice exposed to high levels of air pollution produced a similar gender imbalance in the pups.
Details were presented to the American Society for Reproductive Medicine annual meeting in Montreal.
It is known that female foetuses tend to be more robust, and able to survive in harsh conditions.
Boy foetuses are more likely to perish in the womb or suffer obstetric complications.
The Sao Paulo team examined birth registries for numbers of babies born between January 2001 and December 2003.
In the least polluted areas 51.7% of the babies born were male - but in the most polluted areas the percentage of males born decreased to 50.7%.
