Particulate matter pollution and asthma mortality in China: A nationwide time-stratified case-crossover study from 2015 to 2020.

Background: A national and comprehensive evaluation is lacking on the relationship between short-term exposure to submicron particulate matter (PM) pollution and asthma mortality.

Methods: Data was obtained from 29,553 asthma deaths from the China National Mortality Surveillance System from 2015 to 2020. We used a bilinear interpolation approach to estimate each participant's daily ambient particulate matter pollution and meteorological variables exposure based on their geocoded residential address and a 10 km × 10 km grid from China High Air Pollutants and the fifth generation of European ReAnalysis-Land reanalysis data set. The associations were estimated using a time-stratified case-crossover design and conditional logistic regressions.

Results: Our results revealed significant associations between short-term exposure to various particulate matter and asthma mortality. The 5-day moving average of particulate matter exposure produced the most pronounced effect. Compared to fine particulate matter (PM) and inhalable particulate matter (PM), significantly stronger effects on asthma mortality related to PM pollution were noted. The ERs% for asthma mortality associated with each interquartile range (IQR) increase of exposures to PM (IQR: 19.2 μg/m) was 5.59% (95% CI: 2.11-9.19), which is 14% and 22% higher than that for PM (IQR: 32.0 μg/m, 4.82% (95% CI: 1.84-7.90)) and PM (IQR: 52.2 μg/m, 4.37% (95% CI: 1.16-7.69)), respectively. The estimates remained consistent in various sensitivity analyses.

Conclusions: Our study provided national evidence that acute exposures to various ambient particulate matter pollution can increase mortality due to asthma in China, highlighting stronger associations with ambient PM than PM and PM. China needs to adjust the current ambient air quality standards urgently and pay greater attention to the adverse health effects of PM.