Spatial modeling of ambient PM2.5 and population exposure in Addis Ababa using land use regression

Abstract

Rapid urban growth in Africa is worsening air pollution in many cities, yet limited air-quality monitoring infrastructure hinders accurate assessment of residents’ exposure. In this study, we applied a land-use regression (LUR) model to estimate annual ambient fine particulate matter (PM 2 . 5 ) concentrations and assess population exposure in Addis Ababa, Ethiopia. Estimated annual PM 2 . 5 concentrations showed substantial spatial variability, ranging from 5.9 to 47.9 μg/m 3 , with a citywide average of 17.3 μg/m 3 . No part of the city met the World Health Organization (WHO) annual air quality guideline of 5 μg/m 3 , and 77% of the area exceeded Interim Target 3 (IT-3; 15 μg/m 3 ). The highest concentrations, exceeding the lowest threshold (IT-1, 35 μg/m 3 ), were observed in the sub-cities of Arada, Addis Ketema, Lideta, and Kirkos, where dense urban development and major transportation corridors are concentrated. The LUR model demonstrated strong performance, with an adjusted R 2 of 0.74 and a root mean square error (RMSE) of 1.85 μg/m 3 . Key predictors included proximity to waste dump sites, green space coverage, and the lengths of primary and secondary roads, reflecting major pollution sources and land-use patterns associated with reduced emissions or improved pollutant dispersion. Model diagnostics showed good internal validity, with low multicollinearity among predictors and no evidence of spatial autocorrelation in the residuals. We further quantified population exposure to PM 2 . 5 by calculating population-weighted concentrations at both city and kebele (the lowest administrative unit) levels. The population-weighted citywide mean concentration was 21.3 μg/m 3 , while kebele-level exposures ranged from 13 to 30 μg/m 3 , highlighting significant disparities in pollution burden across the city. Overall, ambient PM 2 . 5 concentrations substantially exceeded WHO guideline levels, underscoring the urgent need for stronger air quality policies, targeted emission reductions, and urban planning strategies to promote healthier, more equitable living environments.