Air pollution and epigenetic aging among Black and White women in the US.

Background: DNA methylation-based measures of biological aging have been associated with air pollution and may link pollutant exposures to aging-related health outcomes. However, evidence is inconsistent and there is little information for Black women.

Objective: We examined associations of ambient particulate matter <2.5 μm and <10 μm in diameter (PM and PM) and nitrogen dioxide (NO) with DNA methylation, including epigenetic aging and individual CpG sites, and evaluated whether associations differ between Black and non-Hispanic White (NHW) women.

Methods: Validated models were used to estimate annual average outdoor residential exposure to PM, PM, and NO in a sample of self-identified Black (n=633) and NHW (n=3493) women residing in the contiguous US. We used sampling-weighted generalized linear regression to examine the effects of pollutants on six epigenetic aging measures (primary: DunedinPACE, GrimAgeAccel, and PhenoAgeAccel; secondary: Horvath intrinsic epigenetic age acceleration [EAA], Hannum extrinsic EAA, and skin & blood EAA) and epigenome-wide associations for individual CpG sites. Wald tests of nested models with and without interaction terms were used to examine effect measure modification by race/ethnicity.

Results: Black participants had higher median air pollution exposure than NHW participants. GrimAgeAccel was associated with both PM and NO among Black participants, (Q4 versus Q1, PM: β=1.09, 95% CI: 0.16-2.03; NO: β=1.01, 95% CI 0.08-1.94) but not NHW participants (p-for-heterogeneity: PM=0.10, NO=0.20). In Black participants, we also observed a monotonic exposure-response relationship between NO and DunedinPACE (Q4 versus Q1, NO: β=0.029, 95% CI: 0.004-0.055; p-for-trend=0.03), which was not observed in NHW participants (p-for-heterogeneity=0.09). In the EWAS, pollutants were significantly associated with differential methylation at 19 CpG sites in Black women and one in NHW women.

Conclusions: In a US-wide cohort study, our findings suggest that air pollution is associated with DNA methylation alterations consistent with higher epigenetic aging among Black, but not NHW, women.