A new study has found suggestions of air pollution exposure before birth being linked with lower IQ scores of children, with evidence that smog may be harmful to the developing brain, among other health issues.

Researchers carried out a study over 249 children of New York City women who wore backpack air monitors for 48 hours during the last few months of pregnancy. They lived in mostly low-income neighbourhoods in northern Manhattan and the South Bronx, having varying levels of exposure to typical kinds of urban air pollution, mostly from vehicle exhaust.

The children were then given IQ tests at the age of 5, before starting school. Those who were exposed to the most pollution before birth scored an average of four to five points lower than children with less exposure.

That difference means it could affect children's performance in school, said Frederica Perera, the study's lead author and director of the Columbia Center for Children's Environmental Health.

In earlier research, Perera also linked rpenatal exposure to air pollution with genetic abnormalities at birth that would increase risks of cancer, smaller newborn head size, and reduced birth weight.

Her research team has also linked pollution with developmental delays at the age of three, and also with children's asthma.

The research team studied pollutants that can go through the placenta, known scientifically as polycyclic acromatic hydrocarbons. The main sources include vehicle exhaust and factory emissions. Tobacco smoke is also a source, but the mothers in the study were nonsmokers.

Though they took into account other factors that could influence the children's IQ scores, Perera and her team still found a strong evidence from prenatal exposure.

[via Physorg]