Short-term joint effects of ambient PM(2.5) and O(3) on mortality in Beijing, China

INTRODUCTION: In recent years, air pollution caused by co-occurring PM(2.5) and O(3), 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 O(3) 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/m(3) increase in PM(2.5) and O(3). 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 O(3) 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 O(3) (lag day 01), respectively. There were remarkably synergistic interactions between PM(2.5) and O(3) on the three mortality categories. The study showed that the combined effects of PM(2.5) and O(3) 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 O(3), 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.