摘要
Background:Outdoor physical activity(PA)brings important health benefits,but exposure to polluted air increases health risks.This study aimed to quantify the tradeoff of PA under fine particulate matter(PM_(2.5))air pollution by estimating the optimal PA duration under various pollution levels.Methods:A risk-benefit analysis was performed to estimate the optimal outdoor moderate-intensity PA(MPA)duration under varying PM_(2.5) concentrations.Results:An inverse nonlinear relationship was identified between optimal MPA duration and background PM_(2.5) concentration levels.When background PM_(2.5) concentration increased to 186 μg/m^(3),the optimal outdoor MPA duration decreased to 2.5 h/week,the minimum level recommended by current PA guidelines.When background PM_(2.5) concentration further increased to 235 μg/m^(3),the optimal outdoor MPA duration decreased to 1 h/week.The relationship between optimal MPA duration and background PM_(2.5) concentration levels was stronger when exercising at a location closer to a source of air pollution.Compared to the general adult population,adults aged 60 years and older had substantially steeper curves—the optimal outdoor MPA duration decreased to 2.5 h/week when background PM_(2.5) concentration reached 45 μg/m^(3).Conclusion:The health benefit of outdoor MPA by far outweighs the health risk of PM_(2.5) pollution for the global average urban background concentration(22 μg/m^(3),).This modeling study examined a single type of air pollutant and suffered from measurement errors and estimation uncertainties.Future research should examine other air pollutants and indoor PA,incorporate short-and mid-term health effects of MPA and air pollution into the risk-benefit analysis,and provide estimates specific for high-risk subgroups.
