2017 Yes https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6104398/ Wu, Jianyong North America Experimental Epidemiology Study Students Elementary (K-5) Air pollution Autism spectrum disorder (ASD) Greenness Near-road tree canopy School children We observed inverse associations between several green space metrics and autism prevalence in school districts with high road density, the highly urbanized areas, but not in others. These results suggest that increases of 10% in forest, grassland, average tree canopy and near-road tree canopy are associated with a decrease in autism prevalence of 10%, 10% 11% and 19%, respectively. In contrast, urban land and road density were positively associated with autism prevalence. Our study suggests that green space, specifically tree cover in areas with high road density, may influence autism prevalence in elementary school children beneficially.