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Tupã, nestled in the interior of São Paulo state, Brazil, occupies a gently undulating terrain at an elevation of approximately 540 meters. This positioning within the Paraná-Tietê interfluvial plain significantly influences its air quality. The city is surrounded by a mosaic of agricultural lands, primarily sugarcane and soybean cultivation, alongside patches of *cerrado* vegetation – a tropical savanna ecoregion. While not directly adjacent to major bodies of water, Tupã is influenced by regional humidity patterns originating from the Paraná River basin to the south. The urban-rural gradient is relatively sharp; the city centre is densely populated, transitioning quickly to expansive agricultural fields. This proximity to intensive agriculture is a key factor, as agricultural burning for land preparation and fertilizer application contribute to particulate matter and gaseous pollutant emissions. Furthermore, Tupã’s location along regional transport routes, though not a major industrial hub itself, means it experiences through-traffic contributing to vehicle exhaust. The prevailing winds, generally from the south-southeast, can transport pollutants from more industrialized areas further east towards Tupã, impacting local air quality. The topography, while not mountainous, can create localized pockets where pollutants accumulate, particularly during stable atmospheric conditions. Understanding this interplay of agricultural practices, transport, and regional wind patterns is crucial for assessing and mitigating air pollution in Tupã.

Tupã 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 rainfall scavenging pollutants from the atmosphere and suppressing dust. However, increased humidity can also foster the formation of secondary pollutants. The driest months, May through September, consistently present the poorest air quality. This is largely due to increased agricultural burning for sugarcane harvest preparation, releasing significant amounts of particulate matter (PM2.5 and PM10) and carbon monoxide. Stable atmospheric conditions during these months, characterized by temperature inversions, trap pollutants near the ground, exacerbating the problem. Winds are generally weaker during the dry season, reducing dispersion. August and September are typically the most challenging months for respiratory health. Sensitive groups – children, the elderly, and individuals with pre-existing 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. Monitoring wind direction is important; winds from the east can bring pollutants from more industrialized areas. Local agricultural practices are the dominant driver of seasonal air quality fluctuations in Tupã.