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Catanduva, nestled in the interior of São Paulo state, Brazil, occupies a relatively flat portion of the Paraná sedimentary basin at an elevation of approximately 548 meters. This gentle topography, characteristic of the region, facilitates the dispersal of some pollutants but also allows for stagnation under certain meteorological conditions. The city is situated within a broader agricultural landscape, heavily influenced by sugarcane and citrus cultivation, with pockets of industrial activity concentrated around the main urban area. This blend of agricultural practices – involving seasonal burning – and industrial emissions significantly shapes the local air quality profile. The surrounding landscape is predominantly comprised of rolling hills and plains, transitioning into more rugged terrain further west. The Rio Sucuriã, a tributary of the Tietê River, flows near Catanduva, offering limited influence on regional air circulation patterns. The urban-rural gradient is relatively sharp, with a noticeable increase in pollutant concentrations as one moves closer to the city center, driven by vehicular traffic and localized industrial sources. The city’s position within a major agricultural zone means it’s susceptible to long-range transport of pollutants from burning activities in neighboring municipalities, impacting baseline air quality.

Catanduva experiences a distinct wet and dry season, rather than traditional four seasons. Air quality generally improves during the wet season (October to April) due to increased rainfall which effectively washes particulate matter from the atmosphere and suppresses dust. However, high humidity can also contribute to the formation of secondary pollutants. The dry season (May to September) consistently presents the poorest air quality. This is largely due to increased agricultural burning associated with sugarcane harvest preparation, releasing significant amounts of particulate matter (PM2.5 and PM10) and carbon monoxide. Temperature inversions are common during the cooler, drier months, trapping pollutants near the ground. August and September are typically the worst months for air quality, coinciding with peak burning activity. Sensitive groups – children, the elderly, and those with respiratory conditions – should limit strenuous outdoor activity during these periods. Conversely, the wetter months, particularly November and December, offer more favourable conditions for outdoor exercise. Fog, common in the cooler mornings, can exacerbate pollution by trapping pollutants. Monitoring wind patterns is crucial; southerly winds often bring pollutants from more industrialized areas to the north.