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Oum Hadjer, situated in the Batha state of Chad at coordinates 13.2944, 19.6914, is a town deeply embedded within the Sahelian zone. The surrounding landscape is predominantly flat to gently undulating savanna, characteristic of this transitional region between the Sahara Desert to the north and the Sudanian savanna to the south. The town’s elevation is relatively low, contributing to limited atmospheric dispersion of pollutants. The Batha region is largely agricultural, with millet, sorghum, and peanuts being key crops. This agricultural activity, while vital to the local economy, introduces particulate matter into the air through land preparation, harvesting, and the burning of crop residue. Oum Hadjer itself is a relatively small urban centre, exhibiting a typical Sahelian urban form – a concentrated core surrounded by a rapidly expanding periphery of residential areas. The urban-rural gradient is sharp, with significant differences in land use and population density. The absence of major industrial belts within Oum Hadjer itself doesn’t preclude regional dust transport from further afield, impacting air quality. Proximity to seasonal watercourses, which can dry up significantly during the dry season, contributes to dust emissions as exposed sediment becomes airborne. The prevailing winds, influenced by the Harmattan from the Sahara, further exacerbate dust levels.

Oum Hadjer experiences a distinct wet and dry season, heavily influencing air quality. The dry season, roughly from November to May, is characterised by consistently poor air quality. The Harmattan winds, blowing from the Sahara, carry substantial amounts of dust and sand, significantly increasing particulate matter concentrations. January to March are typically the worst months, with reduced visibility and heightened respiratory irritation. Temperature inversions, common during cooler nights within the dry season, trap pollutants near the ground, worsening conditions. The onset of the wet season in June brings a temporary improvement. Rainfall suppresses dust, and vegetation growth helps to bind soil particles. However, increased humidity can also promote the growth of molds and fungi, potentially triggering allergic reactions. August and September, the peak of the rainy season, generally offer the best air quality. As the wet season wanes in October and November, dust levels begin to rise again. Sensitive groups – children, the elderly, and those with pre-existing respiratory conditions – should limit outdoor activity during the dry season, particularly in January-March. Wearing masks can provide some protection. Monitoring local conditions and staying indoors during dust storms is crucial.