Pollution could be a factor in autism, researchers have found.

　　They say children with autism spectrum disorder (ASD) were more likely to have been exposed to higher levels of certain air toxics during their mothers' pregnancies and the first two years of life compared.

　　The find could help explain the rise in cases.

　　The investigation of children in southwestern Pennsylvania will be presented today at the American Association for Aerosol Research annual meeting in Orlando.

　　'Autism spectrum disorders are a major public health problem, and their prevalence has increased dramatically,' said Evelyn Talbott of Pitt Public Health, who led the research.

　　'Despite its serious social impact, the causes of autism are poorly understood.

　　'Very few studies of autism have included environmental exposures while taking into account other personal and behavioral risk factors.

　　'Our analysis is an addition to the small but growing body of research that considers air toxics as one of the risk factors for ASD.'

　　Dr. Talbott and her colleagues performed a population-based study of families with and without ASD living in six southwestern Pennsylvania counties.