Associations of long-term joint exposure to various ambient air pollutants with all-cause and cause-specific mortality: evidence from a large population-based cohort study

The association between long-term joint exposure to all kinds of ambient air pollutants and the risk of mortality is not known. Our study prospectively assessed the joint associations of various air pollutants with cause-specific and all-cause mortality risk and identified potential modifying factors affecting these associations. A total of 400,259 individuals aged 40–70 years were included in this study. Information on PM10, PM2.5–10, PM2.5, NO2, and NOx was collected. A weighted air pollution score was calculated to assess joint exposure to the above air pollutants. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox proportional hazards models. During a median of 12.0 years (4,733,495 person-years) of follow-up, 21,612 deaths were recorded, including 7097 deaths from cardiovascular disease and 11,557 deaths from cancer. The adjusted HRs of all-cause mortality were 1.39 (95% CI: 1.29–1.50), 1.86 (95% CI: 1.63–2.13), 1.12 (95% CI: 1.10–1.14), and 1.04 (95% CI: 1.03–1.05) for every 10-ug/m3 increase in PM10, PM2.5, NO2, and NOx, respectively. The adjusted HRs associated with the air pollution score (the highest quintile versus the lowest quintile) were 1.24 (95% CI: 1.19–1.30) for all-cause mortality, 1.33 (95% CI: 1.23–1.43) for cardiovascular mortality, and 1.16 (95% CI: 1.09–1.23) for cancer mortality. Furthermore, we found that the air pollution score was associated with a linear dose–response increase in mortality risk (all P for linearity < 0.001). The findings highlight the importance of a comprehensive assessment of various air pollutants.