Exposure to traffic fumes and air pollution can double a mother's risk of giving birth to a child with autism, a new study has found.
Researchers from the Harvard School of Public Health found that contaminants in the air, particularly diesel and mercury, dramatically affect the chance of a child being born with an autism spectrum disorder.
"Our findings raise concerns since, depending on the pollutant, 20 per cent to 60 per cent of the women in our study lived in areas where risk of autism was elevated," said lead scientist Dr Andrea Roberts.
Autism is a developmental disorder that affects around 230,000 Australians. It can be so mild it is barely noticeable or so severe the person requires 24-hour care.
Dr Roberts and her team studied US Environmental Protection Agency data and identified 325 women who had a child with autism and 22,000 with children without the disorder.
They found a clear link between women who were exposed to high levels of pollution while pregnant and those who had an autistic child.
Women in the most polluted locations were twice as likely to give birth to a child with autism than those in area with the lowest levels.
Mercury and diesel pollution were the worst for autism risk, with other types of air contamination, including lead, manganese, methylene chloride and combined metals, having weaker links to the condition.
In all cases, boys were much more likely to be born with autism than girls.
Study co-author Dr Mark Weisskopf said the results highlight the need for more research into the relationship between air pollutants and autism.
"Our results suggest that new studies should begin the process of measuring metals and other pollutants in the blood of pregnant women or newborn children to provide stronger evidence that specific pollutants increase risk of autism," Dr Weisskopf said.
"A better understanding of this can help to develop interventions to reduce pregnant women's exposure to these pollutants."