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Lençóis Paulista, nestled in the interior of São Paulo state, Brazil, occupies a gently undulating terrain within the larger Bauru Plateau. Its coordinates (-22.5986, -48.8003) place it approximately 290 meters above sea level, a moderate elevation that influences local air circulation. The city is strategically positioned within a significant agricultural zone, heavily reliant on sugarcane and citrus cultivation, with processing facilities concentrated around the urban core. This agricultural activity, alongside smaller industrial pockets, contributes to potential particulate matter and volatile organic compound emissions. The Tietê River flows nearby, though not directly through the city center, offering some limited natural ventilation but also potentially trapping pollutants during temperature inversions. Lençóis Paulista exhibits a clear urban-rural gradient; the city itself is a relatively compact urban center, surrounded by expansive agricultural lands. This proximity means that prevailing winds can carry pollutants from both agricultural burning (seasonal) and industrial sources directly into the populated areas. The surrounding landscape is characterized by rolling hills and patches of preserved Atlantic Forest remnants, offering limited natural filtration. The city’s growth has largely followed the pattern of regional development, focused on agro-industry and related services, shaping its current air quality challenges.

Lençóis Paulista experiences a tropical climate with distinct wet and dry seasons, profoundly impacting air quality. The dry season, typically from May to September, sees a significant increase in particulate matter due to agricultural activities like sugarcane burning for harvest. Lower humidity and reduced rainfall mean pollutants are less effectively washed from the atmosphere, leading to stagnant air conditions. August and September are often the most challenging months for respiratory health. Conversely, the wet season (October to April) brings relief, with frequent rainfall cleansing the air and higher humidity suppressing dust. However, even during the wet season, localized pollution from industrial sources and vehicle emissions remains a concern. Temperature inversions, common during the cooler nights of the dry season, exacerbate pollution by trapping pollutants near ground level. Fog, particularly in the mornings during the transition seasons, can also concentrate pollutants. Sensitive groups – children, the elderly, and those with pre-existing respiratory conditions – should limit strenuous outdoor activity during the dry season and periods of fog. Monitoring wind patterns is crucial; winds from agricultural areas during burning season should prompt increased caution.