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Guaiçara, a small municipality nestled in the interior of São Paulo state, Brazil, occupies a gently undulating terrain within the broader Bauru Plateau. Located at coordinates -21.6219, -49.7986, the city’s elevation is approximately 560 meters above sea level, contributing to a moderate climate. The surrounding landscape is predominantly agricultural, characterized by extensive sugarcane and soybean cultivation, typical of the region. This agricultural dominance significantly influences local air quality, with seasonal burning practices and pesticide application being key contributors to particulate matter and volatile organic compound emissions. Guaiçara is not directly adjacent to major bodies of water, though smaller rivers and streams dissect the agricultural lands. The urban-rural gradient is quite sharp; the city centre is compact, quickly transitioning to expansive farmland. While not situated within a major industrial belt, the processing of agricultural products within and around Guaiçara generates localised pollution. The city’s position within a relatively flat basin can occasionally trap pollutants, particularly during periods of atmospheric stability. Prevailing winds generally move from the south-southeast, potentially carrying pollutants from more industrialized areas further east. Understanding this geographical context is crucial for interpreting air quality trends in Guaiçara.

Guaiçara experiences a tropical climate with distinct wet and dry seasons, heavily influencing its air quality. The dry season, typically from May to September, sees a marked increase in particulate matter due to agricultural burning preparing fields for planting. Lower humidity and reduced rainfall exacerbate the concentration of these pollutants, making outdoor activity less favourable during these months, particularly August and September. Sensitive groups – children, the elderly, and those with respiratory conditions – should limit strenuous outdoor exertion. The wet season, from October to April, generally brings improved air quality as rainfall effectively washes pollutants from the atmosphere. However, increased humidity can also foster the growth of molds and fungi, potentially triggering allergic reactions. November and December often experience periods of atmospheric stability, leading to localized pollution build-up from vehicle emissions and small-scale industrial activity. Temperature inversions, common during cooler nights, can trap pollutants near ground level. Fog, prevalent during the cooler months, can also contribute to reduced visibility and increased pollutant concentrations. Overall, the wet season offers better conditions for outdoor activities, but vigilance regarding mold and fungal spores is advised.