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August 25, 2025Open Access

Spatiotemporal Assessment of PM2. 5 in Senior High Schools in Kumasi, Ghana Using Low-Cost Sensors

VTVictoria Owusu TawiahKwame Nkrumah University of Science and Technology TAThompson AnnorKwame Nkrumah University of Science and Technology EYEdmund I. YambaKwame Nkrumah University of Science and Technology

Key Points

PM2.5 levels exceeded WHO guidelines, averaging 17.18 µg/m³ across six high schools, indicating significant health risks.
The dry season pollution averaged 26.82 µg/m³, highlighting seasonal variations in air quality in Kumasi.
Utilization of low-cost sensors provided valuable insights into air quality, showcasing spatial variations among schools.
Findings emphasize the need for targeted air quality strategies to protect students in vulnerable school environments.

Abstract

Abstract noindent Fine particulate matter (PM2. 5) poses significant health risks, particularly to children; yet, ambient air quality studies in school environments across Kumasi, Ghana, remain limited. This study utilized low-cost Airnote sensors and meteorological data (wind speed and wind direction) from the ERA5-Land Reanalysis to assess levels of PM2. 5 pollution across six senior high schools in Kumasi between 2022 and 2023, capturing spatial and seasonal variability during both the dry and wet seasons. Results revealed an annual median PM2. 5 concentration of 17. 18 \ (\) g/m\ (³\), exceeding the WHO annual guideline of 5 g/m³. Diurnal patterns exhibited bimodal peaks aligned with morning and evening commuting and domestic activities, driven by traffic emissions, biomass burning, and informal waste burning. Pollution levels were notably elevated during weekdays and Saturdays but lower on Sundays. Median concentrations were highest at OKESS (20. 91 g/m³), followed by Adventist (19. 22 g/m³), Sakafia (18. 16 g/m³), and KWG (16. 71 g/m³), while Ibadur (15. 32 g/m³) and KASS (12. 76 g/m³) recorded the lowest levels. Seasonal differences were pronounced: the dry season showed significantly higher pollution (mean = 26. 82 g/m³) than the wet season (mean = 13. 18 g/m³), owing to reduced rainfall and limited atmospheric dispersion. Conditional Bivariate Probability Function (CBPF) analysis and HYSPLIT back-trajectory modeling identified dominant pollution sources, including nearby traffic corridors, domestic combustion activities, unmanaged waste burning, and long-range Saharan dust transport, with clear seasonal shifts in source directionality. Spatial variability in PM2. 5 concentrations was further influenced by land-use characteristics and topography surrounding each school. These findings underscore the need for localized air quality management strategies, particularly in vulnerable environments like schools, to mitigate health risks and enhance urban air quality governance.

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