Spatio–temporal trends of air quality, Kampala City, Uganda, 2020–2022

Abstract Fine particulate matter (PM 2.5 ) is among the health damaging air pollutants; levels >15 µg/m 3 are associated with adverse health effects. We assessed spatio–temporal trends of air quality based on PM 2.5 concentration in Kampala City during January 2020–June 2022. We abstracted PM 2.5 concentrations generated by twenty–four Clarity© Node Solar–Powered monitors from January 1, 2020, to June 30, 2022, from the Clarity© dashboard. We computed 24–hour average PM 2.5 concentrations by combining data from all monitors. Average PM 2.5 concentrations per hour were compared by hour of the day. Seasonal Mann–Kendall statistical test was applied to assess significance of observed trends. Overall, the 24–hour average PM 2.5 concentration from January 1, 2020, to June 30, 2022, was 59 µg/m 3 (range: 18–182 µg/m 3 ). A statistically significant decline in PM 2.5 occurred throughout the assessment period from January 2020 to June 2022 (r = –0.27, p < 0.001). PM 2.5 increased from April to June each year [2020 (55 µg/m 3 , r=0.56, p=0.006), 2021 (45 µg/m 3 , r=0.26, p=0.030), and 2022 (37 µg/m 3 , r=0.37, p=0.030)] and declined from July to September in 2021 (57 µg/m 3 , r=–0.43, p=0.008) and January to March in 2022 (60 µg/m 3 , r=–0.41, p=0.011). PM 2.5 concentration peaked from 10am–midday (74–73 µg/m 3 ) and 8pm–9pm (73–77 µg/m 3 ). PM 2.5 concentrations exceeded targeted safe levels on all days in Kampala City during 2020–2022.