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Ribeiro do Amparo, nestled in the state of Bahia, Brazil, occupies a geographically complex position within the broader semi-arid region of the Northeast. Located at coordinates -11.0469, -38.4328, the city sits inland, approximately 80km from the Atlantic coastline. The terrain is characterised by undulating hills and plateaus, typical of the Chapada Diamantina region’s foothills, with an elevation around 250-300m. This inland location, while offering some protection from direct coastal salt spray, means the city is less influenced by moderating sea breezes. The surrounding landscape is dominated by *caatinga* vegetation – a thorny scrubland adapted to prolonged dry periods. Agriculture, primarily subsistence farming and small-scale livestock rearing, is prevalent in the surrounding rural areas, contributing to potential particulate matter from land management practices. While not a major industrial hub, regional agricultural processing (particularly of mangoes, a key local crop) and limited construction activity contribute to localised emissions. The urban-rural gradient is relatively sharp, with a noticeable increase in dust and vehicle emissions as one moves closer to the city centre. The city’s position within a valley can also exacerbate pollution build-up due to limited atmospheric dispersion, particularly during calm weather conditions. This topography, combined with regional climate patterns, significantly influences local air quality.

Ribeiro do Amparo experiences a distinct wet and dry season, rather than traditional four seasons. Air quality is generally better during the wet season (October to March) due to rainfall effectively scavenging particulate matter from the atmosphere. However, increased humidity can also promote the formation of mould spores, potentially impacting respiratory health. The dry season (April to September) presents the greatest air quality challenges. This period is characterised by prolonged drought, increased dust from agricultural lands and unpaved roads, and a higher frequency of wildfires in the surrounding *caatinga*. August and September are typically the months with the poorest air quality due to peak dryness and agricultural burning. Temperature inversions, common during the cooler nights of the dry season, trap pollutants near ground level, exacerbating conditions. Sensitive groups – children, the elderly, and those with pre-existing respiratory conditions – should limit strenuous outdoor activity during these months. Wind patterns, typically easterly, can transport pollutants from agricultural areas westward towards the city. Monitoring wind direction is crucial for predicting pollution episodes. Even during the wet season, localised pollution from vehicle exhaust and construction can be present, requiring continued vigilance.