Estimating the mutually adjusted health effects of short- and long-term exposure to PM2.5 on respiratory mortality in a population-based study

Short- and long-term exposure to ambient fine particulate matter (PM2.5) increased respiratory mortality. Previous studies have reported the dependence between short- and long-term effects, but most studies have estimated them independently. In this study, the mutually adjusted effects of PM2.5 exposure on respiratory mortality in Sichuan Province, China, were explored using a mixed quasi-Poisson regression model. After adjustment, the estimated effects on respiratory mortality decreased with both short- and long-term PM2.5 exposure, especially under short-term exposure, by 7.44%. A 10 mu g/m3 increase in long-term PM2.5 exposure increased respiratory mortality by 10.42% (95% CI: 7.37%, 13.55%), which was significantly greater than the 1.12% (95% CI: 0.87%, 1.36%) increase in short-term mortality. Females and those under 65 years old suffered from a greater risk when exposed to PM2.5. Greater short-term effects in warm seasons (1.62%; 95% CI: 1.04%, 2.21%) and greater long-term effects in cold seasons (12.99%; 95% CI: 8.22%, 17.33%) were observed. In addition, a greater short-term effect was found using satellite-based PM2.5 concentrations than monitoring-based concentrations. This study indicated that when estimating the effects of short- and long-term PM2.5 exposure, their dependency could not be ignored; otherwise, both effects would be overestimated, especially for short-term effects. A decreasing PM2.5 concentration is beneficial to population health, especially for females and young people.