Blood pressure and pulmonary health effects of ozone and black carbon exposure in young adult runners.

Physical activity has been shown to promote health and well-being, however, exercising in environments with high level of air pollution might increase the risk of cardio-respiratory impairments. In this crossover study, we constructed linear mixed models to investigate the impact of short-term exposure to black carbon (BC) and ozone on blood pressure and pulmonary functions among 30 healthy adult runners after 30-minute run on a clean and polluted route on separate days in August 2015 in Hong Kong. Runners were on average 20.6 years old, with mean body mass index of 20.3 kg/m. Air pollution concentrations were higher in the polluted route than in the clean route, with the highest difference in BC (5.4 μg/m versus 1.3 μg/m). In single-pollutant models, no significant association was found between air pollution and changes in blood pressures, forced vital capacity, forced expiratory volume in 1 s, peak expiratory flow and fractional exhaled nitric oxide, after adjusting for gender, type of route, temperature and relative humidity. When further adjusting for both BC and ozone simultaneously, increment in BC became statistically significantly associated with increase in systolic blood pressure (relative risk = 3.18; 95% CI: 0.24, 6.13) after running exercise. Stratified analysis further shows that the significant adverse association between systolic blood pressure and BC was only observed in the polluted route (e.g., relative risk = 4.51, 95% CI: 0.75, 8.27 in two-pollutant). Our finding of BC is consistent with existing literature, while further studies with greater sample size and longer exposure time are needed to investigate the effects of ozone to cardio-respiratory functions in runners. Given that exercise has clear health benefits, one should consider ways to minimize the air pollution exposure.