CHILDREN who live in cities are at increased risk of developing autism due to a link between the condition and traffic pollution, a new study has found.
The new findings warn that youngsters who live in homes in areas with the highest air pollution levels were up to three times more at risk than those from the least exposed homes.
Early exposure to traffic pollution – either in the womb or during the first 12 months of a child’s life – was said to more than double their chances of having the disorder.
Researchers found evidence that small particles in polluted air, such as nitrogen dioxide, can damage the development of the brain in the womb and in the early years of life when a child’s brain is still growing.
The findings were described by experts in the field as “important”, but they said further research was needed to prove a link between pollutant chemicals and impaired brain development.
Autism, a wide-ranging condition that affects communication and social skills, is believed to be caused by a combination of genetic and environmental factors. While a number of genetic variants have been linked to the disorder, the role played by the environment is still relatively unknown.
Scientists in California set out to investigate a possible link between autism and traffic pollution. The Childhood Autism Risks from Genetics and the Environment study looked at 245 children without the condition and 279 affected by autism.
Official air pollution records were used to estimate exposure to nitrogen dioxide and small, sooty particles produced from motor vehicle exhausts.
Researchers took into account the distance that pregnant women and children lived from busy roads and the levels of pollutants in the air where they lived. Dr Heather Volk, who led the research undertaken by the University of Southern California, said: “We’ve known for a long time that air pollution is bad for lungs, especially for children. We’re now beginning to understand how [it] may affect the brain. We know that we can breathe in tiny particles and they can produce inflammation.
“The public health implications of these findings are large because air pollution exposure is common and may have lasting neurological effects.”
Her team is most concerned about exposure to small particles produced by diesel engines known as PM10s and PM2.5s. Previous studies have linked inhalation of these to heart and lung disease and cancer.
Dr Robert Moffat, director of the National Autistic Society in Scotland, welcomed the research into environmental factors but said further studies were needed to determine how and if issues such as pollution and weather had an impact on autism rates.
Professor Tony Charman, chair in autism education at the Institute of Education, said: “The measured prevalence has risen, but this may or may not be a true increase. Other factors, such as increased awareness among professionals, parents and others might underlie this measured increase.
“The issue of whether this increase is real and, if so, whether and what environmental – as opposed to clinical – factors might explain this, is still an empirical question.”
Sophia Xiang Sun, of the Autism Research Centre at Cambridge University, said: “We know traffic-related air pollution can contribute to many other diseases and conditions and it is biologically plausible it also has a role in autism.”