PM2.5 as a potential risk factor for autism spectrum disorder: Its possible link to neuroinflammation, oxidative stress and changes in gene expression

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by behavioral deficits including impairments in social communication, social interaction, and repetitive behaviors. Because the etiology of ASD is still largely unknown, there is no cure for ASD thus far. Although it has been established that genetic components play a vital role in ASD development, the influence of epigenetic regulation induced by environmental factors could also contribute to ASD susceptibility. Accumulated evidence has suggested that exposure to atmospheric particulate matter (PM) in polluted air could affect neurodevelopment, thus possibly leading to ASD. Particles with a size of 2.5 μm (PM2.5) or less have been shown to have negative effects on human health, and could be linked to ASD symptoms in children. This review summarizes evidence from clinical and animal studies to demonstrate the possible linkage between PM2.5 exposure and the incidence of ASD in children. An attempt was made to explore the possible mechanisms of this linkage, including changes of gene expression, oxidative stress and neuroinflammation induced by PM2.5 exposure.