Interestingly, in our autopsy studies (9, 10), apolipoprotein E allele 4 (APOE4) carriers of the strongest Alzheimer's disease genetic risk factor (110–113) had higher AD Braak stages and the highest risk for suicide associated with lower cumulative exposures to PM2.5 vs. APOE3 carriers. This evidence concerns the gene APOE and Alzheimer disease.