Exposure to air pollution in the womb and the first two years of life may be associated with an increased risk of a child developing autism spectrum disorders (ASDs), new research has found.
ASDs are a range of conditions characterised by social deficits and communication difficulties that typically become apparent early in childhood.
"Autism spectrum disorders are lifelong conditions for which there is no cure and limited treatment options, so there is an urgent need to identify any risk factors that we could mitigate, such as pollution," said lead author Evelyn Talbott, professor of epidemiology at the University of Pittsburgh Graduate School of Public Health in the US.
"Our findings reflect an association, but do not prove causality.
Further investigation is needed to determine possible biological mechanisms for such an association," Talbott noted.
The researchers performed a population-based, case-control study of families with and without ASD living in six southwestern Pennsylvania counties.
They obtained detailed information about where the mothers lived before, during and after pregnancy, and estimated individual exposure to a type of air pollution called PM2.5.
Considered to be the most common and hazardous, this type of pollution refers to particles found in the air that are less than 2.5 micrometres in diameter. It comes from burning wood or coal, car exhaust and other sources.
Based on the child's exposure to concentrations of PM2.5 during the mother's pregnancy and the first two years of life, the researchers found that children who fell into higher exposure groups were at an approximate 1.5-fold greater risk of ASD.
The researchers arrived at the conclusion after accounting for other factors associated with the child's risk for ASD -- such as the mother's age, education and smoking during pregnancy.
The study was published in the journal Environmental Research.