Massapê, nestled in the state of Ceará, Brazil, occupies a unique position within the semi-arid landscape of the Brazilian Northeast. Located at -3.5228 latitude and -40.3428 longitude, the city sits approximately 180km from the Atlantic coast, influencing its climate and, consequently, its air quality. The terrain is generally flat to gently undulating, characteristic of the Borborema Plateau’s eastern slopes. This flatness hinders natural dispersion of pollutants. The surrounding landscape is dominated by *caatinga* vegetation – a thorny scrub forest adapted to prolonged drought – and scattered agricultural lands, primarily focused on subsistence farming and livestock raising. While not a major industrial hub, regional economic activity centres around agriculture and small-scale commerce. The urban-rural gradient is relatively sharp, with the city acting as a service centre for surrounding rural communities. Dust from agricultural practices and unpaved roads contributes significantly to particulate matter in the air. The lack of substantial elevation and proximity to the coast means limited flushing of pollutants by sea breezes, exacerbating local emissions. The city’s position within a rain shadow further contributes to drier conditions and increased dust suspension. Understanding this geographical context is crucial for addressing Massapê’s air quality challenges.

Massapê experiences a distinct wet and dry season, heavily influencing its air quality. The dry season, typically from August to December, sees a significant deterioration in air quality. Reduced rainfall leads to increased dust resuspension from agricultural lands and unpaved roads, elevating particulate matter concentrations. High temperatures during this period also promote the formation of ground-level ozone, particularly in areas with vehicle traffic. January to April marks the wet season, bringing relief from dust and a temporary improvement in air quality as rainfall washes pollutants from the atmosphere. However, increased humidity can also contribute to mold spore proliferation, impacting respiratory health. May to July represents a transitional period with moderate air quality. Temperature inversions, common during the cooler nights of the dry season, trap pollutants near the ground, worsening conditions. Sensitive groups – children, the elderly, and those with respiratory illnesses – should limit outdoor activity during the peak of the dry season (September-November). Fog, occasionally occurring during the transitional months, can exacerbate particulate matter issues. Monitoring wind patterns is crucial; winds from agricultural areas can carry dust plumes into the city.