Greenness alleviates the effects of ambient particulate matter on the risks of high blood pressure in children and adolescents

Both ambient particulate matter (PM) and decrease of greenness have been suggested as risk factors for high blood pressure (HBP) in children and adolescents. But most evidence were from cross-sectional studies with limited data from prospective cohorts. In this cohort study, we included 588,004 children and adolescents aged 7 to 18 years without HBP from 2005 to 2018 in Beijing (240,081) and Zhongshan (347,923) city of China. The cumulative incidence of HBP was 32.04%, and incidence rate was 14.86 per 100 person-year. After adjustment for confounders, the ten-unit increase in PM1, PM2.5, and PM10 exposure was significantly associated with 43%, 70%, and 43%- higher risks of HBP, respectively, but the 0.1-unit increase in NDVI exposure was significantly associated with a 25% lower risk of HBP. The HRs of PM1 on the HBP risk were 1.486 and 1.150 in the low and the high-level of greenness, and they were 2.635 and 2.507 for PM2.5, and for PM10 1.367 and 1.702 in the two groups. The attributable fraction (AFs) of PM1, PM2.5, and PM10 on HBP incidents were 13.74%, 40.08%, and 15.47% in the low-level of greenness, which simultaneously was higher than those in the high-level of greenness (AF = 4.62%, 17.28%, and 9.96%). The exposure to higher ambient PM air pollution and lower greenness around schools were associated with a higher risk of HBP in children and adolescents, but higher greenness alleviated the adverse effects of ambient PM1 and PM2.5 on the HBP risks. Our findings highlighted a synergic strategy in preventing childhood HBP by decreasing air pollution reduction and improving greenness concurrently.