In vivo studies examining the effects of PM exposure in an AD mouse model used female 5xFAD mice with either the ɛ3 or ɛ4 allele of ApoE. The results showed an increase in Aβ oligomers in protein samples, but only in the 5xFAD ApoE ɛ4 mice, suggesting that PM exposure effects on AD pathogenesis can be increased in susceptible genotypes. Here, APOE is linked to Alzheimer disease.