The short-term effects of air pollutants on pneumonia hospital admissions in Lanzhou, China, 2014–2019: evidence of ecological time-series study

This study explored the short-term effects of air pollutants (PM2.5, PM10, SO2, NO2, O38h, and CO) on pneumonia-related hospital admissions in Lanzhou (an ex-heavily polluted city in Northwestern China). A time-series design, with a distributed lag non-linear model (DLNM), was used for statistical analysis. Daily pneumonia hospital admissions data in Lanzhou from January 1, 2014 to December 31, 2019 were collected, in addition to air pollutant and meteorological data. We used DLNM to estimate relative risk (RR), and a 95% confidence interval (CI) of pneumonia hospital admissions was associated with a 10 μg/m3 rise in exposure to air pollutants (per 1 mg/m3 rise in CO). Stratification analysis was also performed according to gender (male and female), age (0–14 years, 15–64 years and ≥ 65 years old), and season (warm season and cold season). A total of 20,071 pneumonia hospital admissions were enrolled for analysis. Pneumonia hospital admissions risk were 1.044 (1.029, 1.060), 1.009 (1.005, 1.013), 1.086 (1.053, 1.121), 1.073 (1.052, 1.093), and 1.157 (1.094, 1.223), respectively, corresponding to a 10 μg/m3 rise in exposure to PM2.5, PM10, SO2, NO2, a 1 mg/m3 rise in exposure to CO. Every 10 μg/m3 increase in O38h was associated with decrease of pneumonia hospital admissions, the RR(95%CI) was 0.949 (0.935, 0.962). The adverse effects for gaseous pollutants (except O38h) on pneumonia hospital admissions were stronger than particulate matter. Six exposure–response curves between air pollutants and pneumonia hospital admissions were approximately linear without thresholds. Female and children aged 0–14 years were more sensitive to the effects of air pollutants, particularly in the cold season. Exposure to air pollutants (except O38h) might be associated with increased risk of pneumonia hospital admissions. The association remained significant after adjusting for other environmental factors.