Different sized particles associated with all-cause and cause-specific emergency ambulance calls: A multicity time-series analysis in China

Abstract Background Compared with mortality and hospital admission, emergency ambulance calls (EACs) could be a more accurate outcome indicator to reflect the health effects of short-term air pollution exposure. However, such studies have been scarce, especially on a multicity scale in China. Methods We estimated the associations of different diameter particles [i.e., inhalable particulate matter (PM10), coarse particulate matter (PMc), and fine particulate matter (PM2.5)] with EACs for all-cause, cardiovascular, and respiratory diseases in seven Chinese cities. We collected data on EACs and air pollution from 2014 to 2019. We used generalized additive models and random-effects meta-analysis to examine the city-specific and overall associations. Stratified analyses were conducted to examine the effect modifications of gender, age, and season. Results Significant associations of PM10 and PM2.5 with EACs were observed, while the PMc associations were positive but not statistically significant in most analyses. Specifically, each 10 μg/m3 increase in 2-day moving average concentration of PM10 was associated with a 0.25% [95% confidence interval (CI): 0.04%, 0.47%] increase in all-cause EACs, 0.13% (95% CI: −0.01%, 0.26%) in cardiovascular EACs, and 0.35% (95% CI: 0.04%, 0.66%) in respiratory EACs. The corresponding increases in daily EACs for PM2.5 were 0.30% (95% CI, 0.03%, 0.57%), 0.13% (95% CI, −0.07%, 0.33%), and 0.46% (95% CI, 0.01%, 0.92%). Season of the year also modifies the association between particulate matter pollution and EACs. Conclusions Short-term exposure to PM10 and PM2.5 were positively associated with daily all-cause and respiratory-related EACs. The associations were stronger during warm season than cold season. Our findings suggest that the most harmful fraction of particulate matter pollution is PM2.5, which has important implications for current air quality guidelines and regulations in China.