"In this cohort study of 2 183 324 births in Ontario, Canada, higher prenatal exposures to sulfate and ammonium components of PM2.5 were statistically associated with increased ASD risk. The second and third trimesters appeared to be sensitive exposure windows."
original paper - https://jamanetwork.com/journals/jamanetworkopen/fullarticle...
"In this cohort study of 2 183 324 births in Ontario, Canada, higher prenatal exposures to sulfate and ammonium components of PM2.5 were statistically associated with increased ASD risk. The second and third trimesters appeared to be sensitive exposure windows."