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Uiraúna, nestled in the heart of Paraíba, Brazil, occupies a unique geographic position within the semi-arid Sertão region. Located at -6.5183 latitude and -38.4122 longitude, the city sits on a relatively flat terrain, typical of the Paraíba Basin, at an elevation of approximately 230 meters. This low-lying landscape contributes to limited natural air dispersion. The surrounding landscape is dominated by *caatinga* vegetation – a thorny scrub forest adapted to drought conditions – and expansive agricultural lands dedicated primarily to subsistence farming and, increasingly, commercial crops like corn and beans. Uiraúna’s air quality is significantly influenced by its rural setting, but also by the increasing vehicular traffic within the urban core and seasonal agricultural burning. The urban-rural gradient is relatively sharp, with the city acting as a regional service centre for smaller, more dispersed rural communities. The lack of substantial industrial belts within Uiraúna itself means that pollution sources are largely diffuse, stemming from domestic fuel combustion (wood and charcoal), dust from unpaved roads, and agricultural practices. Proximity to larger urban centres like Campina Grande (approximately 120km east) can also contribute to regional pollutant transport, though the prevailing wind patterns often mitigate this effect. The climate is hot and semi-arid, exacerbating dust resuspension and pollutant concentration.

Uiraúna experiences a distinct wet and dry season, profoundly impacting air quality. The dry season, spanning roughly August to December, is characterised by minimal rainfall, high temperatures, and strong winds. This period sees a significant increase in particulate matter (PM) due to dust resuspension from agricultural lands and unpaved roads. Agricultural burning, used for land clearing and crop residue management, further degrades air quality during these months, creating hazy conditions. January to April marks the wet season, bringing relief from dust and a reduction in PM levels as rainfall effectively washes pollutants from the atmosphere. However, increased humidity can also foster the growth of molds and allergens, potentially impacting respiratory health. May to July represents a transitional period with moderate temperatures and intermittent rainfall. Temperature inversions, common during the cooler nights of the dry season, trap pollutants near the ground, worsening air quality. Sensitive groups – children, the elderly, and individuals with respiratory conditions – should limit outdoor activity during the peak of the dry season (September-November). Fog, though infrequent, can also exacerbate pollutant concentrations during cooler mornings. Overall, the wet season offers the most favourable conditions for outdoor activities.