Improvements in ambient PM2.5 exposure was associated with reduced risk of mortality in adults: a longitudinal study

Abstract

Background: Previous epidemiological studies show that long-term exposure to fine particulate air pollution (PM2.5) may increase the risk of mortality. However, evidences concerning the effect of air quality improvements on mortality is scarce. It is crucial to document whether past efforts to reduce air pollution have yielded demonstrable improvements in public health and to better predict whether future efforts will continue to do so. We therefore investigated the relationship of reduction in exposure to long-term ambient PM2.5 with the risk of overall and cause-specific mortality.Methods: We recruited 374,319 Taiwanese adults (aged 18 years or older) who joined a standard medical screening programme between 2001 and 2016. Each participant received at least one medical examination and was followed up till 2019. Vital statuses were obtained from National Death Registry System in Taiwan. PM2.5 concentrations were estimated using a satellite-based spatio-temporal model. The change in PM2.5 (ΔPM2.5) was defined as the difference between the values measured during follow-up and during the immediately preceding medical examination. The time-varying Cox model was used to investigate the effects of ΔPM2.5 on the risk of mortality.Result: The PM2.5 concentration in Taiwan increased during 2002-2004 and began todecrease in 2005. Every 5-µg/m3 decrease in the ambient PM2.5 (i.e., ΔPM2.5 of 5 µg/m3) was associated with a decrease of 64% (95% CI: 64%-65%), 65% (64%-66%), 60% (58%-62%), 62% (59%-64%), 62% (57%-66%), 54% (50%-58%), and 62% (61%-63%) in the risk of mortality from all-cause, cancer, cardiovascular, cerebrovascular, chronic lower respiratory, influenza/pneumonia, and other or unknown disease, respectively. The stratified and sensitivity analyses generally yielded similar results.Conclusion: An improvement in PM2.5 air quality is associated with a decreased risk of mortality. Our findings provided demonstrable evidences for air quality control and public health interventions both in Taiwan and worldwide.