Individuals with high levels of genetic variation and elevated exposure to a type of air pollution may be at an increased risk of developing autism a new analysis shows. The findings showed that environmental factors like exposure to air pollution (ozone nitrogen oxide and particluate matter) contribute to the risk of autism. Genetic factors like copy-number variation -- deletions and duplications of repeated DNA -- also lead to the development of autism. According to the study environmental factors like ozone a harmful air pollutant at the ground level can interact with genetic factors (copy number variation) to produce an even