Laï, situated in the Tandjilé region of Chad, occupies a relatively flat terrain at approximately 580 meters above sea level. This location within the southern Sahelian zone dictates a semi-arid climate, characterized by a distinct wet and dry season. The city’s surrounding landscape is predominantly savannah grassland, interspersed with scattered acacia trees and low shrubs. While no major bodies of water directly border Laï, the Logone River lies to the east, influencing regional humidity levels. Laï functions as a crucial market town and administrative centre for the surrounding agricultural lands, primarily focused on subsistence farming – millet, sorghum, and groundnuts are common crops. The urban-rural gradient is sharp; Laï itself is a concentrated settlement, quickly giving way to rural agricultural activity. Air quality is intrinsically linked to this landscape. Dust from agricultural practices, particularly during the dry season when vegetation cover is minimal, is a significant contributor to particulate matter. The lack of substantial industrial activity within Laï itself mitigates some pollution sources, but regional bushfires during the dry-to-wet transition can transport smoke plumes over the city, impacting air quality. The flat terrain also limits natural dispersion of pollutants, potentially leading to localised build-up.

Laï experiences a pronounced wet and dry season cycle that dramatically influences air quality. The dry season, roughly from November to May, is characterised by consistently high levels of particulate matter. This is due to the lack of rainfall to suppress dust, combined with agricultural activities like land preparation and harvesting. Harmattan winds, blowing from the Sahara, exacerbate the situation, carrying vast quantities of fine dust particles. January to March are typically the months with the poorest air quality. The transition period from dry to wet (May-June) often sees increased smoke from bushfires used for land clearing, creating temporary but significant pollution spikes. The wet season (June to October) offers a reprieve, with rainfall effectively washing away dust and suppressing agricultural dust emissions. However, increased humidity can also promote mould growth, potentially impacting respiratory health. September and October, while generally cleaner, can experience localised flooding which can stir up sediment and contribute to microbial pollutants. Sensitive groups – children, the elderly, and those with respiratory conditions – should limit strenuous outdoor activity during the dry season and be mindful of smoke exposure during the transition period. Monitoring wind direction during bushfire season is crucial.