Associations of Gestational Exposure to Air Pollution and Polycyclic Aromatic Hydrocarbons with Placental Inflammation

Restricted fetal growth (RFG) is a leading contributor to perinatal mortality and has been associated with gestational exposure to air pollution, such as fine particulate matter (PM_2.5), nitrogen dioxide (NO₂), and polycyclic aromatic hydrocarbons (PAHs). This study examines the association between trimester-specific and weekly means of air pollution throughout gestation and placental inflammatory markers at delivery. In a prospective cohort study of 263 pregnant women in Rochester, NY, we measured interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) in placental tissue and estimated gestational exposure to PM_2.5 and NO₂ using a high-resolution spatial-temporal model. Exposure to PAHs was estimated using urinary 1-hydroxypyrene (1-OHP) concentrations collected once per trimester. Using distributed lag models with a penalized spline function, each interquartile range (2.6 μg/m³) increase in PM_2.5 concentration during gestational weeks 6–11 was associated with decreased placental IL-6 levels (−22.2%, 95% CI: −39.0%, −0.64%). Using multiple linear regression models, each interquartile range increase of 1-OHP was associated with an increase in TNF-α in the first trimester (58.5%, 95% CI: 20.7%, 74.2%), third trimester (22.9%, 95% CI: 0.04%, 49.5%), and entire pregnancy (29.6%, 95%CI: 3.9%,60.6%). Our results suggest gestational exposure to air pollution may alter the inflammatory environment of the placenta at delivery.