Estimating the vulnerability contribution to 1990-2019 changes in the health burden of ambient air pollution: a global modelling study.

Efforts to reduce the health burden of air pollution focus on reducing pollutant exposure. Less studied are changes in the vulnerability of populations to ambient fine particulate matter (PM2·5) exposure that also affect PM2·5-attributable mortality rates. Vulnerability to PM2·5 is the capacity of a population to be harmed by exposure. Multiple factors affect vulnerability, including pre-existing medical conditions, socioeconomic status, access to and quality of health care, race, and smoking. We aimed to quantify how changes in vulnerability to PM2·5 have affected PM2·5-attributable mortality rate trends between 1990 and 2019. In this global modelling study, we used data on mortality rates from the Global Burden of Disease Study 2021, demographic data from UN Department of Economic and Social Affairs, and PM2·5 concentration data from State of Global Air, to estimate 1990-2019 trends in national PM2·5-attributable mortality rates separately across age and sex categories for 193 countries. We used a demographic model to simulate 1990-2019 PM2·5-attributable mortality rates accounting only for the effect of changes in PM2·5 exposure. The contribution of changes in vulnerability to 1990-2019 PM2·5 mortality rate trends was estimated as the residual change in PM2·5 mortality rates after accounting for the effect of changes in PM2·5 exposure. Between 1990 and 2019, global average age-standardised PM2·5-attributable mortality rates decreased by approximately 45% (140 deaths per 100 000 [95% CI 97-176] in 1990 and 78 deaths per 100 000 [54-98] in 2019). Approximately 48% of the decrease resulted from PM2·5 exposure reductions (1·01 deaths per 100 000 per year [0·65-1·30]), and approximately 52% was from reductions in vulnerability to PM2·5 (1·07 deaths per 100 000 per year [0·78-1·29]). Without vulnerability reductions, 1·7 million additional PM2·5-attributable deaths would have occurred in 2019. Globally, the sensitivity of PM2·5-attributable mortality rates to vulnerability changes was, on average, that a 1·8% reduction in non-PM2·5 mortality rates was associated with a 1% reduction in PM2·5-attributable mortality rates. Given the major contribution reductions in vulnerability to air pollution have made to reducing PM2·5-attributable mortality rates over the past three decades, identifying actions to reduce non-communicable diseases could contribute to reducing future air pollution health burdens. Air quality strategies should consider interventions to further reduce vulnerability, in addition to exposure reductions. EU Horizon Europe.