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

Abstract

This study presents current levels of fine particulate matter, with aerodynamic diameter of less than 2.5 micrometre (PM_2.5) in the city of Blantyre, Malawi measured between June 2021 to May 2022. PM_2.5 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. PM_2.5 monitoring was conducted between 10:00-12:00 hours and 15:00-17:00 hours local time. The results showed that the hourly mean PM_2.5 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 PM_2.5 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 PM_2.5 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 PM_2.5 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 PM_2.5 in Blantyre city because it is hazardous and likely to cause health implications to the local population. Furthermore, interventions should be sought to reduce PM_2.5 concentration in the city.