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Bol, situated in the Lac Province of Chad, occupies a geographically challenging position within the southern fringes of the Sahara Desert. Located at coordinates 13.4600°N, 14.7400°E, the city’s terrain is predominantly flat, characteristic of the Chadian Basin, with an elevation hovering around 280 meters. This low-lying landscape contributes to limited natural air dispersion. Bol’s proximity to Lake Chad, once one of Africa’s largest lakes, is a defining feature, though the lake has dramatically shrunk in recent decades, exposing vast areas of dried lakebed. This desiccation exacerbates dust storms, a major contributor to particulate matter pollution. The surrounding landscape is a mix of sparse savannah grassland and increasingly arid conditions. While Bol isn’t a major industrial hub, regional agricultural activity – primarily subsistence farming and livestock rearing – contributes to seasonal biomass burning, particularly after harvests. The urban-rural gradient is relatively sharp; Bol represents a concentrated population center amidst a sparsely populated region. The prevailing winds, often carrying dust and sand from the Sahara, further impact air quality. The city’s growth, coupled with limited infrastructure for waste management, adds to localised pollution sources. Understanding this interplay of geographical factors is crucial for addressing Bol’s air quality challenges.

Bol experiences a distinct wet and dry season, heavily influencing its air quality. The dry season, roughly from November to May, is characterised by consistently poor air quality. Harmattan winds, originating from the Sahara, dominate this period, bringing significant amounts of dust and sand, leading to high particulate matter concentrations. January and February are typically the worst months for respiratory health. Temperatures soar during the day, creating stable atmospheric conditions that trap pollutants near the ground. The wet season, from June to October, offers temporary relief. Rainfall suppresses dust and washes away some pollutants, improving air quality. However, increased humidity can also promote the growth of mold and allergens. August and September, while wetter, can still experience localised pollution from post-harvest burning of agricultural waste. Temperature inversions, common during the transition periods between wet and dry seasons, can trap pollutants at ground level. Sensitive groups – children, the elderly, and those with pre-existing respiratory conditions – should limit outdoor activity during the dry season and be mindful of potential allergen spikes during the wet season. Monitoring wind patterns and rainfall is key to predicting pollution episodes.