Pre- and postnatal exposure to PM2.5 and NO2 and blood pressure in children: Results from the ECHO Cohort

BACKGROUND: There is growing interest in understanding the link between early life exposures to ambient air pollution and childhood blood pressure; however, existing findings, largely from single site/cohort studies, are inconclusive.

METHODS: We examined the association between exposures to fine particulate matter (PM2.5) and nitrogen dioxide (NO2) and blood pressure measured at age 5-12 years in 4863 U.S. children from 20 pregnancy cohorts of the NIH ECHO cohort. Point-based residential exposures were derived from spatiotemporal models with a biweekly resolution and averaged over each trimester, the whole pregnancy, and child age 0-2 years. We converted systolic (SBP) and diastolic blood pressure (DBP) to age-, sex-, and height-specific percentiles and classified children with SBP and/or DBP ≥ 90th percentile as high blood pressure (HBP). Associations of PM2.5 (per 5-μ g/m3) or NO2 (per 10-ppb) exposures with blood pressure outcomes were estimated using linear and Poisson regressions adjusted for sociodemographic, lifestyle, temporal, and spatial confounders.

RESULTS: Across windows, mean PM2.5 ranged from 7.6 to 7.9 μ g/m3, and mean NO2 ranged was 8.1-8.8 ppb. We found positive associations of PM2.5 in the first trimester with SBP percentile (β: 1.92, 95 %CI: 0.02, 3.83) and risk of HBP (RR: 1.16, 95 %CI: 1.02, 1.33). Higher PM2.5 exposures averaged over pregnancy and age 0-2 years were also related to elevated SBP percentiles and a higher risk of HBP, but with lower precision. Contrary to our hypotheses, inverse associations of pregnancy average NO2 with both SBP (β: -2.42, 95 %CI: -4.70, -0.14) and DBP (β: -1.94, 95 %CI: -3.81, -0.08) percentiles were suggested.

CONCLUSION: Results reinforce the detrimental effects of PM2.5 on childhood cardiometabolic health, even at low exposure levels. Such findings can inform regulatory policy on acceptable air pollution levels and appropriate controls. The inverse association between prenatal NO2 and blood pressure was counterintuitive and warrants further investigation.