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Banabuiú, nestled in the southeastern corner of Ceará state, Brazil, occupies a geographically significant position within the larger Granito-Açu region. Located at approximately -5.3100 latitude and -38.9208 longitude, the city’s terrain is characterized by undulating hills and valleys, typical of the interior highlands of Ceará. The elevation, though modest, contributes to localized microclimates and influences air circulation patterns. Banabuiú sits inland, approximately 30 kilometers from the Atlantic coastline, benefiting from a semi-arid climate heavily influenced by the trade winds. The surrounding landscape is predominantly scrubland (caatinga), a unique biome adapted to drought conditions, interspersed with small-scale agricultural plots focused on subsistence farming and livestock rearing. This rural character gradually transitions into the urban fabric of Banabuiú, exhibiting a clear urban–rural gradient. While not directly adjacent to major industrial belts, the city’s proximity to larger regional centers like Sobral means it can experience some indirect impacts from industrial emissions transported by prevailing winds. The Rio Banabuiú, a seasonal river, flows through the municipality, providing a vital water source but also potentially contributing to humidity and localized fog formation under certain meteorological conditions. The caatinga vegetation, while generally sparse, can contribute to particulate matter through seasonal leaf fall and occasional wildfires, impacting local air quality. The city’s relatively small size and limited industrial activity mean that local sources, such as vehicle emissions and agricultural practices, are the primary drivers of air pollution.

Banabuiú’s tropical climate dictates a distinct wet and dry season pattern, profoundly influencing its air quality. The dry season, typically spanning from July to November, is characterized by intense solar radiation, low humidity, and persistent trade winds. While these winds generally disperse pollutants, the lack of rainfall means accumulated dust and particulate matter from agricultural activities and unpaved roads remain suspended in the air for extended periods. This can lead to increased respiratory irritation, particularly for individuals with pre-existing conditions. The wet season, from February to June, brings increased rainfall and higher humidity, which naturally scavenges the atmosphere, washing away particulate matter and improving air quality. However, periods of intense rainfall can also lead to flooding, mobilizing dust and sediments, temporarily degrading air quality. Fog formation, though infrequent, can occur during the transition periods between seasons, trapping pollutants near the ground and creating localized air quality concerns. Temperature inversions, while less common than in colder climates, can occasionally occur during the dry season, preventing vertical mixing and concentrating pollutants. The months of September and October, coinciding with the peak of the dry season and agricultural activity, are generally periods to exercise caution regarding outdoor air quality, especially for children, the elderly, and those with respiratory sensitivities. During the wet season, particularly after heavy rainfall events, it’s advisable to avoid prolonged exposure to areas with disturbed soil or standing water.