Short-term joint effects of ambient PM2.5 and O3 on mortality in Beijing, China

Abstract

Introduction: In recent years, air pollution caused by co-occurring PM_2.5 and O₃, named combined air pollution (CAP), has been observed in Beijing, China, although the health effects of CAP on population mortality are unclear.

Methods: We employed Poisson generalized additive models (GAMs) to evaluate the individual and joint effects of PM_2.5 and O₃ on mortality (nonaccidental, respiratory, and cardiovascular mortality) in Beijing, China, during the whole period (2014-2016) and the CAP period. Adverse health effects were assessed for percentage increases (%) in the three mortality categories with each 10-μg/m³ increase in PM_2.5 and O₃. The cumulative risk index (CRI) was adopted as a novel approach to quantify the joint effects.

Results: The results suggested that both PM_2.5 and O₃ exhibited the greatest individual effects on the three mortality categories with cumulative lag day 01. Increases in the nonaccidental, cardiovascular, and respiratory mortality categories were 0.32%, 0.36%, and 0.43% for PM_2.5 (lag day 01) and 0.22%, 0.37%, and 0.25% for O₃ (lag day 01), respectively. There were remarkably synergistic interactions between PM_2.5 and O₃ on the three mortality categories. The study showed that the combined effects of PM_2.5 and O₃ on nonaccidental, cardiovascular, and respiratory mortality were 0.34%, 0.43%, and 0.46%, respectively, during the whole period and 0.58%, 0.79%, and 0.75%, respectively, during the CAP period. Our findings suggest that combined exposure to PM_2.5 and O₃, particularly during CAP periods, could further exacerbate their single-pollutant health risks.

Conclusion: These findings provide essential scientific evidence for the possible creation and implementation of environmental protection strategies by policymakers.

Keywords: Beijing; O3; PM2.5; combined air pollution; joint effects; mortality.