Relationships between measures of ambient air pollution and markers of inflammation during pregnancy

Abstract

Background Outdoor air pollution can influence important biological processes such as inflammation, and has been shown to increase the risk of adverse pregnancy and birth outcomes. Pregnancy-specific biological processes, such as increased estrogen production and altered metabolism can impair the body’s ability to detoxify air pollution exposures, highlighting the need to study exposures during pregnancy. We examined the relationship between ambient PM2.5 and NO2, with markers of inflammation during pregnancy in a cohort of Canadian women.Methods We analyzed data from 1,397 women enrolled in the Maternal-Infant Research on Environmental Chemicals (MIREC) study, a Canadian pregnancy cohort. Residential PM2.5 and NO2 exposures were estimated using satellite-based and land-use regression models to generate overall pregnancy, and trimester specific averages. Inflammatory markers including C-reactive protein (CRP), interleukin-6 (IL-6), interleukin-8 (IL-8), and tumour Necrosis Factor alpha (TNFα) were measured in third-trimester maternal plasma samples. Multivariable linear regression was used to estimate the effects of an inter-quartile (IQR) change in both PM2.5 and NO2 on markers of inflammation, while adjusting for relevant individual-level confounders, including maternal behaviours, and established predictors of inflammation.Results An IQR (5.42 μg/m3) change in PM2.5 exposure during pregnancy was associated with higher IL-8 levels in the third trimester (5.13% [95% CI: 0.60% – 10.74%]). Exposure to PM2.5 and NO2 (IQR: 19.17ppb) during pregnancy was not significantly associated with other inflammatory makers. Additional analyses examining trimester-specific exposures, non-linear dose-response relationships, and quantitative bias will also be presented.Conclusions We showed that average exposure to PM2.5 during pregnancy was associated with increased third-trimester IL-8 levels, suggesting a possible mechanism through which air pollution exposures may impact the risk of adverse pregnancy and birth outcomes. This work adds to the limited literature on the impact of air pollution on inflammation during pregnancy in a low-exposure cohort.