Urban–Rural Disparity in Ambient PM2.5 Exposure and Attributable Health Burden at the Subnational Scale in Nigeria

Estimating mortality burden attributable to ambient fine particulate matter (PM2.5) exposure requires reliable baseline mortality rates (BMRs), but subnational BMRs are unavailable for many low- and middle-income countries (LMICs), especially in sub-Saharan Africa. Furthermore, changes in PM2.5-attributable health burden at the subnational level and the factors driving them have not been explored. In this study, we estimated the mortality burden attributable to ambient PM2.5 (derived from satellite measurements) in Nigeria at the subnational level using state-specific demographic data and BMRs for noncommunicable diseases, leveraging gross domestic product (GDP) as a surrogate. The annual national PM2.5 average concentration increased from 55.8 ± 9.3 μg/m3 in 2010 to 72.3 ± 16.1 μg/m3 in 2015 and then decreased to 63.8 ± 11.9 μg/m3 in 2021. Rural–urban heterogeneity in PM2.5 exposure reveals air quality in Nigeria as a regional-scale issue. The relative disparities (Z-scores) were within ±1 standard deviation, while the largest absolute disparities within rural and urban settlements ranged from 8.1 μg/m3 to 55.1 μg/m3. The mortality burden increased from 69,410 (95% UI: 51,992–91,767) in 2010 to 157,589 (95% UI: 101,753–236,022) in 2015, and then to 436,626 (95% UI: 243,049–720,727) in 2021. The GDP-derived mortality estimates showed moderate agreement with the Global Burden of Disease estimates for most diseases, indicating their ability to capture broad spatial patterns in mortality burden estimates. Changes in exposure, population size, and baseline mortality increased the overall mortality burden by 16.5%, 26.1%, and 74.7%, respectively, from 2010 to 2021. The findings provide local evidence that PM2.5-attributable mortality will require not only policies to mitigate PM2.5 levels but also measures to address population growth and strengthen health policies to reduce baseline mortality rates and reduce the PM2.5-attributable health burden.