Airborne Particulate Matter Concentrations at Key Transportation Stations in Freetown, Sierra Leone: Compliance With WHO Guidelines

Air pollution, particularly from particulate matter (PM), is a significant public health risk, especially in urban environments where transportation plays a critical role. This study quantifies airborne particulate matter (PM1.0, PM2.5, and PM10) concentrations at key transportation stations (Central and Shell Bus Stations) in Freetown, Sierra Leone. Multifunctional digital air quality monitors (DM502) were used to record measurements during the rainy season in August and at peak traffic hours, spanning three daily intervals: 7:00–11:00 AM, 12:00–4:00 PM, and 5:00–9:00 PM. Our findings reveal elevated levels of particulate matter throughout the study. The average concentrations at the Central Bus Station of 15.40 µg/m³, 27.60 µg/m³, and 31.38 µg/m³ for PM1.0, PM2.5, and PM10, respectively. At Shell Bus Station, these values were notably higher, with averages of 17.71 µg/m³ for PM1.0, 30.33 µg/m³ for PM2.5, and 37.24 µg/m³ for PM10. These average concentrations notably exceed the World Health Organization (WHO) 24-hour guidelines of 15 µg/m³ for PM2.5 and 45 µg/m³ for PM10, indicating deteriorating air quality in these densely populated transit areas. Also, the mean Air Quality Indices (AQI) of PM2.5, and PM10 at Central Bus Station are 95.16 and 26.81 respectively while mean AQI of PM2.5, and PM10 at Shell Bus Station are 90.05 and 32.08 respectively. Significant variations were observed throughout the week, primarily influenced by daily traffic patterns and local activities. Peak PM2.5 levels reached 62.33 µg/m³ at Central Bus Station and 74.67 µg/m³ at Shell Bus Station on Tuesdays. Our analysis underscores the urgent need for improved air quality management strategies in Freetown to mitigate health risks associated with elevated airborne particulate levels. In conclusion, this study serves as a pivotal contribution to understanding air quality dynamics in Freetown's urban transit environment, providing essential data for stakeholders to address public health concerns linked to air pollution. Recommendations include implementing stricter vehicle emissions regulations, enhancing public transportation options, and promoting community awareness initiatives surrounding air quality. These measures are critical in fostering a healthier urban environment for residents and commuters alike.