Leukocyte Traits and Exposure to Ambient Particulate Matter Air Pollution in the Women's Health Initiative and Atherosclerosis Risk in Communities Study

Abstract

Background: Inflammatory effects of ambient particulate matter (PM) air pollution exposures may underlie PM-related increases in cardiovascular disease risk and mortality, although evidence of PM-associated leukocytosis is inconsistent and largely based on small, cross-sectional, and/or unrepresentative study populations.

Objectives: Our objective was to estimate PM-leukocyte associations among U.S. women and men in the Women's Health Initiative and Atherosclerosis Risk in Communities study ($n=\mathrm{165,675}$).

Methods: We based the PM-leukocyte estimations on up to four study visits per participant, at which peripheral blood leukocytes and geocoded address-specific concentrations of $\mathrm{PM}\le 10$, $\le 2.5$, and $2.5-10\mu m$ in diameter (${\mathrm{PM}}_{10}$, ${\mathrm{PM}}_{2.5}$, and ${\mathrm{PM}}_{2.5-10}$, respectively) were available. We multiply imputed missing data using chained equations and estimated PM-leukocyte count associations over daily to yearly PM exposure averaging periods using center-specific, linear, mixed, longitudinal models weighted for attrition and adjusted for sociodemographic, behavioral, meteorological, and geographic covariates. In a subset of participants with available data ($n=\mathrm{8,457}$), we also estimated PM-leukocyte proportion associations in compositional data analyses.

Results: We found a $12\text{cells}/\mu L$ (95% confidence interval: $-9$, 33) higher leukocyte count, a 1.2% (0.6%, 1.8%) higher granulocyte proportion, and a $-1.1\%$ ($-1.9\%$, $-0.3\%$) lower $\text{CD}{8}^{+}$ T-cell proportion per $10{\text{-}\mu g/m}^3$ increase in 1-month mean ${\mathrm{PM}}_{2.5}$. However, shorter-duration ${\mathrm{PM}}_{10}$ exposures were inversely and only modestly associated with leukocyte count.

Discussion: The ${\mathrm{PM}}_{2.5}$-leukocyte estimates, albeit imprecise, suggest that among racially, ethnically, and environmentally diverse U.S. populations, sustained, ambient exposure to fine PM may induce subclinical, but epidemiologically important, inflammatory effects. https://doi.org/10.1289/EHP5360.