Effects of ambient air pollutants and environmental greenness on the incidence of pre-/hypertension in children and adolescents

BACKGROUND: This study estimates long-term effects of air pollution and greenness on the incidence of pre-/hypertension in children and adolescents. METHODS: Exposures to particulate matter <2.5 µm (PM2.5), black carbon (BC) and nitrogen dioxide (NO2) at the residential addresses of 2385 children and adolescents of the IDEFICS/I.Family cohort were estimated using land use regression models; environmental greenness was assessed using the Normalized Difference Vegetation Index (NDVI). Applying g-computation, we estimated the effects of hypothetical reductions of PM2.5, BC, NO2 and increases of NDVI on the incidence of pre-/hypertension over a 6-year period compared to no intervention. RESULTS: The observed risk of developing pre-/hypertension was 14.4%. We found a dose-dependent relationship showing higher risk reductions when imposing lower hypothetical levels or larger percental reductions for the air pollutants. The largest effects were observed for PM2.5, e.g. reducing PM2.5 to ≤10 μg/m3 lowered the risk of developing pre-/hypertension by -10.7 [-14.1, -5.7; 95% bootstrap CI] percentage points compared to no intervention. Effects of BC reductions were less strong, e.g. -5.3 [-10.2, 1.7] when reducing BC to ≤0.8x10-5/m and small (non-significant) effects were found for NO2. Hypothetically increasing NDVI to ≥0.6 lowered the pre-/hypertension risk by -1.5 [-2.9, -0.4]. Sensitivity analyses suggested effects of air pollution mainly on systolic (SBP) but not diastolic blood pressure. CONCLUSIONS: Adherence to recommended levels of air pollutants and increased greenness can help to prevent hypertension among children and adolescents. Efforts to reduce air pollution could thus reduce the cardiovascular disease burden in later life.