Longitudinal Analysis of Annual PM2.5 Concentration Variations in Blantyre City, Malawi

This study presents current levels of fine particulate matter, with aerodynamic diameter of less than 2.5 micrometre (PM2.5) in the city of Blantyre, Malawi measured between June 2021 to May 2022. PM2.5 measurements were done in 18 different locations (spanning greater than 2 km apart) using Dylos DC1100 PRO Laser Particle Counter (2018 model). The sampling points were; 3 school campuses, 3 hospitals, 3 industrial areas, 3 open markets, 3 residential areas, and 3 commercial/ business centres (CBC) of Blantyre. PM2.5 monitoring was conducted between 10:00-12:00 hours and 15:00-17:00 hours local time. The results showed that the hourly mean PM2.5 concentrations (µg/m3) for the 10:00-12:00 time period were; 43 ± 23 µg/m3 for school campuses, 35 ± 16 µg/m3 for hospitals, 62 ± 38 µg/m3 for industrial areas, 44 ± 26 µg/m3 for markets, 40 ± 21 µg/m3 for residential areas and 35 ± 16 µg/m3 for CBC. The results showed that the hourly mean PM2.5 concentrations (µg/m3) for the 15:00-17:00 time period were; 38 ± 22 µg/m3 for school campuses, 34 ± 18 µg/m3 for hospitals, 57 ± 37 µg/m3 for industrial areas, 42 ± 25 µg/m3 for markets, 36 ± 23 µg/m3 for residential areas and 34 ± 18 µg/m3 for CBC. Significant increases of PM2.5 levels were observed in school campuses, residential areas and CBC during the months of June-October, which are windy and drier. On the other hand, lowest concentration of PM2.5 was observed during the warm season (November-March) across the sampling locations over Blantyre. Based on these findings, this study recommends further investigation of long-term concentration of PM2.5 in Blantyre city because it is hazardous and likely to cause health implications to the local population. Furthermore, interventions should be sought to reduce PM2.5 concentration in the city.