A new study has linked car exhaust fumes to autism.
Researchers at the University of Southern California found that exposure to air pollution in a child's early years may be associated with an increased risk of autism.
The study looked at 279 autistic children along with 245 children who did not have the illness.
Reuters reported that researchers found those children who lived in homes with high levels of air pollution were three times more likely to be autistic than those with the lowest predicted exposure.
"Children exposed to higher levels of traffic-related pollutants during pregnancy or during the first year of life were at increased risk of autism compared to children exposed to the lowest level," said Heather Volk, of the University of Southern California Keck School of Medicine, reported Reuters.
The particulate matter was not measured in the children but are suspected to be linked with the increased risk of illness.
The research also did not look at sources of indoor air pollution, Bloomberg pointed out.
WebMd said that air pollution had already been linked to a variety of health concerns in small children.
The researchers of the current study had already shown that autism is higher in family's that live nearer to highways.
"We are not saying that air pollution causes autism," Volk said, according to HealthDay.
"But it does appear that this may be one potential risk for autism. We are beginning to understand that pollution affects the developing fetus."
The study was published in the Archives of General Psychiatry.