Traffic pollution linked to autism?

Traffic pollution has been linked to autism in a new study, indicating that living near busy roads could lead to the condition in children.

A team of scientists from the University of Southern California found that early exposure to traffic pollution could more than double a child's risk of developing autism.

This exposure could happen either while the child is in the womb or during its first year of life, according to the study, which was published in the Archives of General Psychiatry.

According to researchers, children living in homes with the worst air quality due to pollution were three times more at risk of autism than those who resided in homes with the lowest levels of exposure.

The scientists studied data from the US Environmental Protection Agency, and used it to work out what levels of pollution people in different areas of California would have been breathing in.

Experts warn that the implications of these findings could be "large" due to the common nature of air pollution, and the indication that it has "lasting neurological effects".

This comes after a link was discovered between autism and living close to major roads, which supports the new findings.

However, other experts have rubbished the claims, saying that it is unlikely that traffic pollution is a direct cause of autism. 

Uta Frith, a professor of cognitive development at University College London, told BBC News: "It seems to me very unlikely that the association is causal."

"[The study does not] get us any further since it does not present a convincing mechanism by which pollutants could affect the developing brain to result in autism," she said.

Critics of the study pointed out that there are many aspects of daily life that could impact on autism risk, like family history, and it is near-impossible to account for these factors in this study.

This means it is extremely difficult to establish that traffic pollution causes autism.