Air quality and attributable mortality among city dwellers in Kampala, Uganda: results from 4 years of continuous PM_2.5 concentration monitoring using BAM 1022 reference instrument

Background: Ambient air pollution is a known risk factor for non-communicable diseases and premature mortality. Kampala’s rapid urban growth, biomass and solid waste burning, unpaved roads, and a growing, highly polluting vehicle fleet contribute to poor air quality. Objective: To provide evidence-based estimates of mortality attributable to ambient fine particulate matter (PM2.5) in Kampala. Methods: A time-series design used hourly PM2.5 data (µg/m3) from a Beta Attenuation Monitor (BAM-1022) on the Makerere University School of Public Health rooftop (2018–2021). All-cause (non-accidental) mortality data were obtained from the Uganda Bureau of Statistics and Ministry of Health. The WHO AirQ+ tool was used to estimate attributable mortality relative to WHO guideline and interim targets. Results: The 4-year annual average PM2.5 concentration was 39 µg/m3, with lower levels in rainy seasons. PM2.5 peaks occurred around 09:00 and 21:00, likely reflecting traffic and meteorology; Saturdays had the highest daily average (41.2 µg/m3). Attributable mortality to long-term exposure (above WHO annual guideline of 5 µg/m3) was estimated as 2777 (19.3%), 2136 (17.9%), 1281 (17.9%), and 1063 (19.8%) deaths for 2018–2021, respectively; totaling 7257 deaths over four years. Impact: This first Kampala-specific estimate using WHO’s 5 µg/m3 target shows PM2.5 levels far above guidelines with substantial health impacts, underscoring the need for air quality control measures.