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Bokoro, nestled within the Hadjer-Lamis region of Chad (coordinates 12.3667° N, 17.0500° E), occupies a geographically significant position on the southern edge of the Chari-Bahr escarpment. The city’s terrain is characterized by undulating plains gradually rising towards the escarpment, resulting in an average elevation of approximately 450 meters above sea level. This location influences local air circulation patterns, often trapping pollutants during periods of low wind. Bokoro’s surrounding landscape is predominantly Sahelian savanna, a transitional zone between the Sahara Desert and the more humid Sudanian woodlands. Extensive agricultural zones, primarily focused on sorghum, millet, and groundnut cultivation, ring the city, contributing to seasonal dust emissions and potential agricultural burning. The Chari River, though not immediately adjacent, exerts a regional influence on humidity and precipitation patterns. The urban–rural gradient around Bokoro is relatively sharp; the city transitions quickly into sparsely populated agricultural lands and pastoral areas. There are no major industrial belts directly impacting Bokoro, but regional trade routes and occasional transport of goods through the area can contribute to localized emissions. The escarpment to the north acts as a barrier, potentially hindering the dispersion of pollutants and creating localized air quality challenges, particularly during dry seasons when wind speeds are lower and temperature inversions are more frequent. The city’s small size (population 15,517) means that local sources, such as vehicle emissions and residential cooking fires, are the primary drivers of air quality concerns.

Bokoro’s air quality follows a distinct seasonal pattern dictated by its Sahelian climate. The dry season, spanning roughly November to May, presents the most significant air quality challenges. Characterized by minimal rainfall and consistently high temperatures, this period is prone to dust storms originating from the Sahara and local agricultural lands. Low wind speeds during these months exacerbate the problem, allowing dust and particulate matter to accumulate. Temperature inversions, common during the cooler nights of the dry season, trap pollutants close to the ground, further degrading air quality. The months of January and February are typically the most problematic, with increased respiratory irritation reported. Conversely, the wet season (June to October) brings a period of relative improvement. Rainfall effectively washes pollutants from the atmosphere, and increased humidity can help to suppress dust. However, the onset of the monsoon season can also bring localized thunderstorms and associated particulate matter. While generally cleaner than the dry season, the wet season can still experience periods of reduced visibility due to fog, particularly in the early morning hours. Sensitive groups, including children, the elderly, and individuals with pre-existing respiratory conditions, should exercise caution during the dry season, limiting outdoor activity during peak dust events and ensuring adequate ventilation indoors. During the wet season, while air quality is generally better, vigilance regarding potential allergens and mold growth is advised.