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Leicester, nestled within Sierra Leone’s Western Area, occupies a geographically significant position within the broader West African landscape. Located at approximately 8.4604° N, -13.2192° W, the city’s terrain is characterized by gently undulating hills and valleys, typical of the Freetown Peninsula. Its elevation, though modest, contributes to localized microclimates and influences air circulation patterns. The city sits relatively close to the Atlantic Ocean, approximately 20 kilometers away, which introduces maritime influences on humidity and wind direction, though the prevailing winds are often landward. The surrounding landscape is a blend of dense tropical rainforest and agricultural land, with small-scale farming prevalent in the immediate vicinity. This agricultural activity, while vital for local livelihoods, can contribute to particulate matter through burning practices, particularly during land clearing. Further afield, the Freetown peninsula gradually transitions into more rugged terrain. The urban–rural gradient around Leicester is relatively sharp; the city’s footprint is compact, bordered by rural communities engaged in subsistence farming and small-scale trading. The proximity to Freetown, Sierra Leone’s capital and primary industrial hub, means Leicester is indirectly affected by industrial emissions, though the distance mitigates the direct impact. The city’s location within a humid tropical climate zone also means rainfall plays a crucial role in naturally cleansing the air, though this effect is seasonal. The limited industrial presence within Leicester itself means that local sources of pollution are primarily related to transportation and residential activities.

Leicester’s air quality narrative is largely dictated by Sierra Leone’s distinct wet and dry seasons. The dry season, typically spanning November to May, presents the greatest air quality challenges. Reduced rainfall during this period means fewer opportunities for natural pollutant washout, leading to a build-up of particulate matter. The prevailing winds, often weaker during the dry season, can result in stagnant air conditions, particularly in the valleys surrounding the city, fostering temperature inversions where cooler air becomes trapped beneath a layer of warmer air, preventing pollutants from dispersing. Agricultural burning, a common practice for land preparation, intensifies during this period, significantly contributing to smoke and particulate pollution. The months of January and February often experience the poorest air quality due to a combination of these factors. Conversely, the wet season (June to October) brings a significant improvement in air quality. Frequent and often intense rainfall effectively ‘washes’ pollutants from the atmosphere. Higher wind speeds associated with the monsoon season also aid in dispersion. While humidity increases during the wet season, the overall reduction in particulate matter and gaseous pollutants generally makes it a more favourable time for outdoor activities. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, limiting prolonged outdoor exposure and avoiding areas with visible smoke. During the wet season, while air quality improves, the increased humidity can exacerbate existing respiratory issues for some individuals.