East African City Centers Show Lower PM2.5 Levels than Their Suburbs

Abstract

Urban air pollution remains a pressing challenge in rapidly developing economies, particularly in data-scarce regions. This study examined air quality in three major East African cities─Kampala, Nairobi, and Dar es Salaam─by integrating low-cost air sensors with satellite data to produce 1 km × 1 km resolution daily PM_2.5 (particulate matter smaller than 2.5 μm) maps from 2019 to 2023. Average PM_2.5 concentrations were 31.4 ± 6.6 μg/m³ around Kampala, 21.7 ± 2.8 μg/m³ around Nairobi, and 33.1 ± 7.4 μg/m³ around Dar es Salaam, indicating moderate to unhealthy levels of air quality. Unexpectedly, urban centers exhibited lower PM_2.5 levels than surrounding suburban area. This discrepancy is likely due to combustion-related activities that occur in the suburbs. Such results suggest that air quality mitigation efforts must extend beyond urban centers to suburban areas, where seasonal vegetation loss and combustion processes may drive pollution spikes. Beyond presenting a scalable approach for monitoring air quality in data-scarce regions, this study highlights the importance of localized strategies for urban air quality management.