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Umburanas, a municipality nestled in the interior of Bahia state, Brazil, occupies a position within the semi-arid Sertão region. Located at -10.7328° latitude and -41.3258° longitude, the city’s terrain is characterised by gently undulating hills and plateaus, typical of the Brazilian Northeast. The elevation is modest, contributing to relatively warm temperatures year-round. Umburanas isn’t directly adjacent to major bodies of water; however, it lies within a network of seasonal rivers and *várzeas* (floodplains) that become prominent during the rainy season. The surrounding landscape is dominated by *caatinga* vegetation – a unique, drought-resistant scrub forest. While Umburanas itself is primarily an agricultural centre, focused on subsistence farming and livestock raising, larger regional agricultural belts dedicated to soy and corn production lie to the south and west, potentially contributing to particulate matter from land preparation and harvesting. The urban-rural gradient is sharp; the city centre is compact, quickly transitioning to rural landscapes. This proximity to agricultural activities, combined with the region’s susceptibility to dust storms and limited rainfall for natural dust suppression, significantly influences local air quality. The lack of significant industrial activity within Umburanas itself means that pollution sources are largely diffuse and related to agricultural practices and biomass burning.

Air quality in Umburanas follows a distinct seasonal pattern dictated by the region’s bimodal rainfall regime. The dry season, typically from August to December, presents the most challenging conditions. Reduced rainfall leads to increased dust resuspension from agricultural lands and unpaved roads, elevating particulate matter concentrations. The lack of precipitation also exacerbates the impact of biomass burning, often used for land clearing and agricultural residue disposal, releasing significant amounts of smoke and pollutants. January to April marks the first rainy season, bringing a temporary improvement in air quality as rainfall washes away particulate matter and suppresses dust. However, increased humidity can also contribute to the formation of mould spores, potentially affecting respiratory health. A secondary, shorter rainy season occurs from May to July, offering further relief. Temperature inversions, common during the cooler, drier months, can trap pollutants near the ground, worsening air quality. Sensitive individuals – children, the elderly, and those with respiratory conditions – should limit strenuous outdoor activity during the dry season, particularly in November and December. Fog, while infrequent, can also trap pollutants. Monitoring wind patterns is crucial; winds from agricultural areas to the south and west can carry pollutants directly over Umburanas.