The joint effect of long-term exposure to multiple air pollutants on non-accidental and cause-specific mortality: A longitudinal cohort study

The long-term joint impacts of fine particulate matter (PM_2.5), nitrogen dioxide (NO₂), and ozone (O₃) on mortality are inconclusive. To bridge this research gap, we included 283,568 adults from the Taiwan MJ cohort between 2005 and 2016 and linked with the mortality data until 31 May 2019. Participants’ annual average exposures to PM_2.5, NO₂, and O₃ were estimated using satellite-based spatial-temporal models. We applied elastic net-regularised Cox models to construct a weighted environmental risk score (WERS) for the joint effects of three pollutants on non-accidental, cardiovascular, and cancer mortality and evaluated the contribution of each pollutant. The three pollutants jointly raised non-accidental mortality risk with a WERS hazard ratio (HR) of 1.186 (95% CI: 1.118–1.259) per standard deviation increase in each pollutant and weights of 72.8%, 15.2%, and 12.0% for PM_2.5, NO₂, and O₃, respectively. The WERS increased cardiovascular death risk [HR: 1.248 (1.042–1.496)], with PM_2.5 as the first contributor and O₃ as the second. The WERS also elevated the cancer death risk [HR: 1.173 (1.083–1.270)], where PM_2.5 played the dominant role and NO₂ ranked second. Coordinated control of these three pollutants can optimise the health benefits of air quality improvements.