Abstract
BACKGROUND: Despite progress, under-five mortality remains high, especially in Sub-Saharan Africa and South Asia, where around 13,400 children die daily. Environmental pollutants, including PM2.5 from outdoor air and household air pollution, significantly contribute to these preventable deaths. METHODS: This cross-country study combined satellite data with 113 surveys from the IPUMS-DHS dataset (1998-2019) to examine under-five child mortality in 41 developing countries. The integration of Global Annual Particulate Matter with a diameter of 2.5 micrometres or less (PM2.5) Grids from Socioeconomic Data and Applications Center (SEDAC) and geospatial data from the DHS Program enabled a focused analysis of the association between indoor and outdoor air pollution, particularly PM2.5, and child mortality rates using both logistic and multilevel logistic regression models, as well as estimating Population Attributable Fractions (PAF) to quantify the mortality burden attributable to these pollutants. RESULTS: Outdoor air pollution, measured by a one standard deviation increase in PM2.5, significantly increased the risk of child mortality (Odds Ratio [OR]: 1.14; 95% Confidence Interval [CI]: 1.10-1.18; p < 0.001). Moderate and high household air pollution exposure also heightened this risk, with increases of 37% (OR: 1.37; 95% CI: 1.24-1.53; p < 0.001) and 40% (OR: 1.40; 95% CI: 1.26-1.56; p < 0.001), respectively, compared to no exposure. Multilevel models (Models 5a and 10a) produced similar estimates to standard logistic regression, indicating robust associations. Additionally, Population Attributable Fraction analysis revealed that approximately 11.9% of under-five mortality could be prevented by reducing ambient PM2.5 exposure and 12.0% by mitigating household air pollution. The interaction between indoor and outdoor pollution revealed complex dynamics, with moderate and high household exposure associated with a reduction in mortality risk when combined with PM2.5. Geographical disparities were observed, with stronger correlations between outdoor air pollution and child mortality in Africa compared to Asia, and more pronounced impacts in low-income countries. However, household air pollution had stronger association with child mortality in Africa and lower- and middle-income countries. CONCLUSIONS: Our findings could serve as a guide for policy development aimed at reducing under-five mortality, ultimately contributing to the attainment of the Sustainable Development Goal (SDGs).