Long-Term Ambient Air Pollution Exposures and Circulating and Stimulated Inflammatory Mediators in a Cohort of Midlife Adults

Abstract

Background: Chronic exposure to air pollution may prime the immune system to be reactive, increasing inflammatory responses to immune stimulation and providing a pathway to increased risk for inflammatory diseases, including asthma and cardiovascular disease. Although long-term exposure to ambient air pollution has been associated with increased circulating markers of inflammation, it is unknown whether it also relates to the magnitude of inflammatory response.

Objectives: The aim of this study was to examine associations between chronic ambient pollution exposures and circulating and stimulated levels of inflammatory mediators in a cohort of healthy adults.

Methods: Circulating interleukin (IL)-6, C-reactive protein (CRP) ($n=392$), and lipopolysaccharide stimulated production of $\text{IL-}1\beta$, IL-6, and tumor necrosis factor $\left(\text{TNF}\right)\text{-}\alpha$ ($n=379$) were measured in the Adult Health and Behavior II cohort. Fine particulate matter [particulate matter with aerodynamic diameter less than or equal to 2.5 μm (${\mathrm{PM}}_{2.5}$)] and constituents [black carbon (BC), and lead (Pb), manganese (Mn), zinc (Zn), and iron (Fe)] were estimated for each residential address using hybrid dispersion land use regression models. Associations between pollutant exposures and inflammatory measures were examined using linear regression; models were adjusted for age, sex, race, education, smoking, body mass index, and month of blood draw.

Results: There were no significant correlations between circulating and stimulated measures of inflammation. Significant positive associations were found between exposure to ${\mathrm{PM}}_{2.5}$ and BC with stimulated production of IL-6, $\text{IL-}1\beta$, and $\text{TNF-}\alpha$. Pb, Mn, Fe, and Zn exposures were positively associated with stimulated production of $\text{IL-}1\beta$ and $\text{TNF-}\alpha$. No pollutants were associated with circulating IL-6 or CRP levels.

Discussion: Exposure to ${\mathrm{PM}}_{2.5}$, BC, Pb, Mn, Fe, and Zn was associated with increased production of inflammatory mediators by stimulated immune cells. In contrast, pollutant exposure was not related to circulating markers of inflammation. These results suggest that chronic exposure to some pollutants may prime immune cells to mount larger inflammatory responses, possibly contributing to increased risk for inflammatory disease. https://doi.org/10.1289/EHP7089.