Acute effect of fine particulate matter and respiratory mortality in Changsha, China: a time-series analysis

BACKGROUND: Previous studies have confirmed that exposure to fine particulate matter (PM(2.5)) is associated with respiratory disease mortality. However, due to the differences in PM(2.5) concentration, composition and population susceptibility within different regions, the estimates of the association between PM(2.5) concentration and mortality are different. Moreover, few studies have examined the potential hazard of excessive PM(2.5) exposure in terms of respiratory disease mortality. METHODS: Daily recorded data on meteorological indices, environmental pollutants, and causes of death data in Changsha from January 2015 to December 2018 were obtained. The potential relationship between PM(2.5) concentrations and respiratory disease mortality was determined using distributed lag nonlinear model (DLNM), which includes the relative risk (RR) and cumulative relative risk (CRR) of the lagged effect. The synergistic effects of other air pollutants were also considered. RESULTS: A total of 8,825 cases of respiratory disease mortality occurred in Changsha between 2015 and 2018. The acute effect of PM(2.5) concentration was associated with an increased risk of respiratory disease mortality. Regarding the lag specific effect, a 10 μg/m(3) increase in PM(2.5) concentration on respiratory disease mortality was statistically significant at lag day 0 and lag day 7 with a relative risk of 1.019 (95% CI 1.007- 1.031) and 1.013(95%CI: 1.002-1.024). As for the cumulative lag effect, a 4-day moving average of PM(2.5) concentrations was significantly associated with a cumulative relative risk of 1.027 (95%CI: 1.011-1.031). The single-day lag effect and cumulative 4-day lag effect for male individuals were more significant than those observed in females. The effect of PM(2.5) concentrations and respiratory disease mortality remained statistically significant in the multi-pollutant models (SO(2), NO(2), and O(3)). A higher risk was observed in the cold season than in the warm season. CONCLUSIONS: Our findings show a potential association between exposure to PM(2.5) concentration and respiratory disease mortality in Changsha, with male individuals observed to have particularly higher risk.