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Sarh, situated in the Moyen-Chari region of Chad, occupies a pivotal position within the country’s southern expanse. Located at approximately 9.15°N latitude and 18.38°E longitude, the city rests on relatively flat terrain, characteristic of the Sahelian zone. The elevation is modest, generally below 300 meters, contributing to limited natural dispersion of pollutants. Sarh is bisected by the Moyen-Chari River, a seasonal waterway that, while providing a vital water source, can also contribute to localised humidity and potential for stagnant air during the dry season. The surrounding landscape is predominantly savannah grassland, transitioning to more arid conditions further north. Agriculture dominates the regional economy, with significant cultivation of cotton, sorghum, and millet. This agricultural activity, alongside smaller-scale artisanal industries within Sarh itself, represents a key source of particulate matter. The urban-rural gradient is relatively sharp; Sarh is a concentrated urban centre amidst a largely rural backdrop. Dust from unpaved roads and agricultural lands is readily lifted by winds, impacting air quality, particularly as the city expands and encroaches upon these areas. The city’s location within the Sahel makes it vulnerable to long-range transport of dust from the Sahara Desert, exacerbating particulate pollution.

Sarh experiences a distinct wet and dry season, heavily influencing its air quality. The wet season, roughly from June to September, brings temporary relief from dust and particulate matter as rainfall suppresses airborne particles. However, increased humidity can foster mould growth, potentially impacting respiratory health. October marks a transition period with fluctuating conditions. The dry season, spanning from November to May, is when air quality concerns peak. Harmattan winds, originating from the Sahara, carry substantial amounts of dust southward, significantly elevating particulate matter concentrations. January and February are typically the dustiest months, posing risks to vulnerable populations. Temperature inversions, common during cooler nights in the dry season, trap pollutants near ground level, worsening conditions. The hottest months, March and April, can see localised pollution from cooking fires and small-scale industrial activity. Sensitive groups – children, the elderly, and those with pre-existing respiratory conditions – should limit strenuous outdoor activity during the peak dry season. Monitoring wind patterns is crucial; periods of calm winds exacerbate pollution build-up. Avoiding peak hours near busy roads and agricultural burning is advisable.