Air pollution and hospital admissions and deaths due to respiratory infections in megacity of Tehran: A time series analysis

Introduction: Air pollution is one of the main causes for the significant increase of respiratory infections in Tehran. In the present study, we investigated the associations between short-term exposure to ambient air pollutants with the hospital admissions and deaths. Materials and methods: Health data from 39915 hospital admissions and 2459 registered deaths associated with these hospital admissions for respiratory infections were obtained from the Ministry of Health and Medical Education during 2014-2017. We used the distributed lag non-linear model (DLNM) for the analyses. Results: There was a statistically positive association between PM2.5 and AURI in the age group of 16 years and younger at lags 6 (RR 1.31; 1.05-1.64) and 7 (RR 1.50; 1.09-2.06). AURI admissions was associated with O3 in the age group of 16 and 65 years at lag 7 with RR 1.13 (1.00-1.27). ALRI admissions was associated with CO in the age group of 65 years and older at lag 0 with RR 1.12 (1.02-1.23). PM10 was associated with ALRI daily hospital admissions at lag 0 for males. ALRI admissions were associated with NO2 for females at lag 0. There was a positive association between ALRI deaths and SO2 in the age group of 65 years and older at lags 4 and 5 with RR 1.04 (1.00-1.09) and 1.03 (1.00-1.07), respectively. Conclusion: Exposure to outdoor air pollutants including PM10, PM2.5, SO2, NO2, O3, and CO was associated with hospital admissions for AURI and ALRI at different lags. Moreover, exposure to SO2 was associated with deaths for ALRI.