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Living near a busy road may double the risk of autism, researchers warn
Exposure to air pollution in the womb or during the
first year of life was linked to a dramatic increase
chances of having the disorderChildren from homes with the highest
traffic pollution levels were three times more at risk
23:40 GMT, 26 November 2012
Living near a busy road could double the risk of childhood autism, warn scientists.
They found exposure to air pollution in the womb or during the first year of life was linked to a dramatic increase in a child’s chances of having the disorder.
Children from homes with the highest traffic 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 that traffic pollutants could affect brain development.
Around one in 100 children develops autism but symptoms do not usually become apparent until the second year of life.
Children from homes with the highest traffic pollution levels were three times more at risk than those from the least exposed homes
Autism, or autistic spectrum disorder (ASD), including Asperger’s syndrome, is an umbrella term for a range of developmental disorders that have a lifelong effect on someone’s ability to interact socially and communicate.
An estimated 600,000 children and adults in the UK are affected by ASD. Genes play a role in its development but the impact of environmental factors is less clear.
In a new study scientists in California set out to investigate a possible link between traffic pollution and autism rates, saying they were on the increase.
They looked at data on 279 children affected by autism compared to 245 children without autism matched for age and background.
Air pollution records from the US Environmental Protection Agency were used to estimate exposure to nitrogen dioxide and small sooty particles, both produced from motor vehicle exhausts, at their mothers’ addresses.
Children living in homes with the highest exposure to traffic pollution were three times as likely to have autism as those with least exposure.
The researchers found a twofold increase in risk of autism among children exposed in the womb or during the first year of life to higher levels of air pollution.
Researchers found a two-fold increase in risk of autism among children exposed in the womb or during the first year of life to higher levels of air pollution
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.’ The findings are published online in the journal Archives of General Psychiatry.
Dr Volk said her team assessed a range of factors, including how far people lived from roads, traffic levels, meteorological factors such as wind direction, and information from air quality monitors.
She was especially concerned about exposure to small and very fine pollution particles produced by diesel engines known as PM10s and PM2.5s.
Previous work by Dr Volk’s team found a similar link with autism among children living next to freeways, the US equivalent of motorways.
Dr Volk said: ‘From studies conducted in the lab, we know that we can breathe in tiny particles and they can produce inflammation.
‘Particles have varied composition, and there are many chemicals that can bind to them. The components of these particles could be hazardous to the brain.’
The study 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 were cautious about the findings, saying they did not prove pollution caused autism.
Sophia Xiang Sun, from the Autism Research Centre at Cambridge University, said: ‘Although traffic-related air pollution might be one of the contributing factors to the development of autism, other factors cannot be ruled out.
‘These factors include second-hand smoking during pregnancy, medical conditions related to pregnancy, indoor air pollution, and especially any history of family mental disorders as autism is highly genetic.
‘We know that traffic related air pollution can contribute to many other diseases and conditions, and it is biologically plausible it also has a role in pathways of autism’ she added.
Professor Emily Simonoff, from the Institute of Psychiatry at King’s College London, said the research did not take into account factors such as father’s age and family history of autism.
‘This is potentially an important finding and it is therefore essential to consider the strengths and limitations of the study ‘said Prof Simonoff.
‘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 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.’