Traffic pollution 'link' to autism

Living near a busy road is associated with a dramatic increase in the risk of childhood autism, a study has shown.

Early exposure to traffic pollution, either in the womb or during the first year of life, more than doubled a child's chances of having the disorder, scientists found.

Children from homes with the highest air pollution levels were three times more at risk than those from the least exposed homes.

Experts described the finding as "important" but stressed it did not prove a causal link between pollutant chemicals and impaired brain development. Autism is believed to be caused by a combination of genetic and environmental factors. While a number of genetic variants are known to be linked to the disorder, the role played by the environment has been less clear.

Scientists in California set out to investigate a possible link between autism rates and traffic pollution. The Childhood Autism Risks from Genetics and the Environment (Charge) study, published in the latest online edition of the journal Archives of General Psychiatry, looked at data on 245 children without the condition and 279 affected by autism.

Lead scientist Dr Heather Volk, from the Keck School of Medicine at the University of Southern California, said: "This work has broad potential public health implications. We've known for a long time that air pollution is bad for lungs, and especially for children. We're now beginning to understand how air pollution may affect the brain."

In their paper, the authors concluded: "Although additional research to replicate these findings is needed, the public health implications of these findings are large because air pollution exposure is common and may have lasting neurological effects."

However, British experts said the findings should be interpreted with caution. Professor Emily Simonoff, from the Institute of Psychiatry at King's College London, said the way the research was conducted meant the possibility of bias could not be excluded. A number of factors had not been properly taken into account, including father's age and family history of autism.

She said: "This is potentially an important finding and it is therefore essential to consider the strengths and limitations of the study. At present, pregnant women should continue to look after their health during pregnancy but should not be unduly concerned."

Professor Uta Frith, from University College London, said: "It seems to me very unlikely that the association is causal, rather than correlational. Rather than taking the results at face value, I would like to know what it implies to live near a highway. It could imply all sorts of disadvantages, any of which might be associated with increased risk of autism, and with increased risk of other disorders as well."