Ambient air pollution and inflammatory effects in a Canadian pregnancy cohort

BACKGROUND: Epidemiologic studies have consistently reported associations between air pollution and pregnancy outcomes including preeclampsia and gestational diabetes. However, the biologic mechanisms underlying these relationships remain unclear as few studies have collected relevant biomarker data. We examined relationships between ambient PM(2.5) and NO(2) with markers of inflammation during pregnancy in a prospective cohort of Canadian women. METHODS: We analyzed data from 1170 women enrolled in the Maternal-Infant Research on Environmental Chemicals study. Daily residential PM(2.5) and NO(2) exposures during pregnancy were estimated using satellite-based and land-use regression models and used to create 14-day and 30-day exposure windows before blood-draw. Inflammatory markers C-reactive protein, interleukin-6, interleukin-8, and tumor necrosis factor-α were measured in third trimester plasma samples. Multivariable linear regression was used to estimate associations for an interquartile range (IQR) increase in PM(2.5) and NO(2) and markers of inflammation, while adjusting for individual-level confounders. RESULTS: Fourteen-day (IQR: 6.85 µg/m(3)) and 30-day (IQR: 6.15 µg/m(3)) average PM(2.5) exposures before blood-draw were positively associated with C-reactive protein after adjustment for covariates (24.6% [95% CI = 9.4, 41.9] and 17.4% [95% CI = 1.0, 35.0] increases, respectively). This association was found to be robust in several sensitivity analyses. Neither PM(2.5) nor NO(2) exposures were associated with interleukin-6, interleukin-8, or tumor necrosis factor-α. CONCLUSION: Exposure to ambient PM(2.5) is positively associated with maternal inflammatory pathways in late pregnancy. This may contribute to positive associations between ambient PM(2.5) and risk of adverse pregnancy outcomes.