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Aiuaba, a small municipality nestled in the state of Ceará, Brazil, occupies a unique geographic position within the semi-arid Sertão region. Located at approximately -6.5739 latitude and -40.1239 longitude, the city sits on a relatively flat terrain, typical of the interior of Ceará. The surrounding landscape is characterised by *caatinga* vegetation – a thorny scrubland adapted to prolonged drought conditions. Aiuaba’s elevation is low, contributing to limited natural dispersion of pollutants. The city’s air quality is significantly influenced by its inland location, far removed from the moderating effects of the Atlantic Ocean. While not directly adjacent to major industrial belts, the broader Ceará state experiences agricultural activity, including livestock farming, which can contribute to particulate matter through land use changes and dust. The urban-rural gradient is relatively sharp; Aiuaba itself is a small urban centre surrounded by sparsely populated rural areas. This means localised sources, such as vehicle emissions and small-scale burning of biomass for cooking and heating, have a disproportionately large impact on air quality within the city limits. The lack of significant windbreaks and the flat topography exacerbate the potential for pollutant accumulation, particularly during drier periods. Understanding this interplay of factors is crucial for effective air quality management in Aiuaba.

Aiuaba experiences a distinct wet and dry season, rather than traditional four seasons. Air quality is generally better during the wet season (roughly August to December) when rainfall helps to suppress dust and wash pollutants from the atmosphere. However, increased humidity can also promote the formation of mould spores, potentially impacting respiratory health. The dry season (January to July) presents the greatest air quality challenges. Prolonged drought conditions lead to increased dust resuspension from the *caatinga* landscape and agricultural lands. February and March are typically the driest months, and therefore the period of highest particulate matter concentrations. Temperature inversions, common during the cooler nights of the dry season, trap pollutants near the ground, worsening air quality. Burning of vegetation for land clearing, though often illegal, also contributes to pollution spikes during this time. Sensitive groups – children, the elderly, and individuals with pre-existing respiratory conditions – should limit outdoor activity during the dry season, particularly on days with visible haze. Monitoring wind patterns is crucial; winds from the west and northwest often carry dust from further inland. Staying indoors with windows closed and using air purifiers can offer some protection.