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Benguema, nestled within Sierra Leone’s Western Area, presents a fascinating case study in urban air quality influenced by its coastal geography and rapid development. Situated at coordinates 8.3215, -13.0724, the town occupies a relatively low-lying terrain, gently sloping towards the Atlantic Ocean. This proximity to the ocean introduces a constant influx of sea breezes, which can both disperse and concentrate pollutants depending on atmospheric conditions. The surrounding landscape is a mix of dense tropical rainforest, transitioning into agricultural land as one moves inland. Benguema’s urban character is evolving, with increasing construction and informal settlements contributing to dust and particulate matter. The city isn’t heavily industrialised, but smaller-scale processing of agricultural products and local artisanal activities contribute to localised emissions. The urban-rural gradient is quite sharp, with significant differences in air quality observed between the town centre and the surrounding rural areas. The prevailing winds, generally southwesterly during the wet season and northeasterly during the dry season, play a crucial role in pollutant transport. The terrain’s limited elevation restricts vertical mixing, potentially exacerbating pollution episodes, particularly during temperature inversions. The coastal location also means susceptibility to humidity and fog, which can trap pollutants near the ground.

Benguema experiences a distinct wet and dry season, profoundly impacting its air quality. The wet season, roughly from May to October, brings heavy rainfall and increased humidity. While rainfall physically washes away some particulate matter, the high humidity can also trap pollutants closer to the ground, creating localised pockets of poor air quality. The southwesterly monsoon winds dominate, bringing moisture from the Atlantic but also potentially transporting pollutants from other coastal regions. November to April marks the dry season, characterised by the harmattan wind – a dry, dusty trade wind blowing from the Sahara Desert. This period consistently sees the poorest air quality in Benguema, as the harmattan carries significant amounts of particulate matter, including PM10 and PM2.5. Temperature inversions are more frequent during the dry season, trapping pollutants and worsening conditions. February and March are typically the most challenging months for respiratory health. Sensitive groups – children, the elderly, and those with pre-existing respiratory conditions – should limit outdoor activity during these months. The wet season offers some respite, but even then, localised pollution from vehicle emissions and small-scale industries remains a concern. Monitoring wind direction and humidity levels is crucial for predicting short-term air quality fluctuations.