Children exposed to toxic air pollutants are significantly more likely to develop autism, new research shows.
The study of nearly 1,500 children in China, aged up to three years, found that those exposed to fine particles from some external pollutants were up to 78% more likely to develop autism spectrum disorders.
Vehicle exhaust, road dust and emissions from factories and construction sites are among those pollutants.
The Monash University study was conducted for nine years in Shanghai and involved 1444 children, 124 of whom had autism.
Associate Professor of Melbourne Yuming Guo, who led the research published in Environment International today, said that the causes of autism are complex and not fully understood.
But he said that young brains are more vulnerable to exposure to toxic substances, and studies suggest that brain function and the immune system may be affected.
"These effects could explain the strong link we found between exposure to air pollutants and autism spectrum disorder," he said.
"But more research is needed to explore the associations between air pollution and mental health more broadly."
The research looked at three particle sizes – referred to as PM1 (the smallest variety), PM2.5 and PM10.
Professor Guo said PM1 contributed to an even greater risk of children developing autism, and he hopes the study will lead countries to develop patterns related to the tiny particle, such as those currently in use for some larger particles.
There is no safe level of exposure to air pollutants, which has links to premature births, learning delays and serious health conditions, Guo added.
"All countries should pay attention to reducing air pollution and improving air quality, increasing their quality of life and improving their health outcomes."
The new study is understood as the first to examine the effects of long-term air pollution exposure on autism during the first years of a child's life in developing countries.
More than four million people die each year from air pollution, says the World Health Organization.
The deaths are mainly due to heart disease, stroke, chronic obstructive pulmonary disease, lung cancer and acute respiratory infections in children.