Urban ambient air pollution and blood pressure in schoolchildren in Accra, Ghana.

Ambient air pollution has been linked to elevated blood pressure (BP) in adults, but research is limited among children, particularly in sub-Saharan Africa (SSA). We investigated the potential effects of ambient fine particulate matter (PM2.5), black carbon (BC), and nitrogen dioxide (NO2) exposures on BP in school-aged children in Accra, Ghana's capital and one of the fastest growing cities in SSA. We performed a cross-sectional analysis among 919 (60% girls) schoolchildren aged 7-14 years across 90 elementary schools. Following NIH guideline, we define elevated BP as age, sex, and height specific systolic and/or diastolic BP values at ≥ 90th percentile. PM2.5, BC, and NO2 concentrations at homes and schools were estimated using spatiotemporal land-use regression models developed specifically for Accra using measurement data from 146 sites. Covariate-adjusted associations were estimated using multivariable mixed-effects linear and logistic regression models. The mean SBP and DBP among the children were 107.2 (9.7) and 69.1 (7.1) mmHg, respectively, with one-third of the children having elevated BP. Children's PM2.5 exposure at both home and school were 5-8 times the World Health Organization (WHO) annual guideline of 5 µg/m3, BC levels were above the maximum value in the "good practice statement for BC" (5.1 µg/m3), and NO2 concentrations exceeded the WHO annual guideline of 10 µg/m3 by 11-fold at some locations. Overall, PM2.5, BC, and NO2 were negatively associated with BP after adjustment for demographic and lifestyle covariates. For instance, a 10 unit increase in air pollution at homes was associated with a small decrease in SBP (PM2.5: -0.70 mmHg (95% CI -3.34, 1.94), BC: -4.61 mmHg (95% CI -9.59, 0.37), NO2: -0.19 mmHg (95% CI -0.60, 0.22) and DBP (PM2.5: -0.83 mmHg (95% CI -2.93, 1.28), BC: -4.35 mmHg (95% CI -8.19, -0.50), NO2: -0.14 mmHg (95% CI -0.46, 0.18)). Furthermore, home-level PM2.5 was associated with reduced odds of having elevated BP (OR 0.75 (95% CI 0.39, 1.41)), as was BC (OR 0.35 (95% CI 0.09, 1.39)). This study showed no evidence of pro-hypertensive effect of exposure to PM2.5, BC, and NO2 pollution among schoolchildren in Accra.