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São Miguel do Iguaçu, nestled in the western state of Paraná, Brazil, occupies a geographically significant position within the Paraná River basin. Its coordinates (-25.3478, -54.2378) place it within a subtropical climate zone, characterized by warm, humid summers and mild winters. The city’s terrain is gently undulating, transitioning from the Paraná River floodplain to slightly higher ground, influencing drainage patterns and localized microclimates. The surrounding landscape is dominated by lush subtropical forests, part of the Atlantic Forest biome, interspersed with agricultural lands – primarily sugarcane and soy cultivation – which contribute to regional air quality dynamics. The Paraná River itself, a major waterway, exerts a moderating influence on local temperatures and humidity. While São Miguel do Iguaçu is a relatively small city with a population of approximately 29,122, it serves as a crucial gateway to the magnificent Iguaçu Falls, a major tourist destination. This tourism generates some localized air pollution from vehicle traffic, though it’s generally less impactful than industrial or agricultural sources. The urban–rural gradient is relatively sharp; the city quickly gives way to extensive agricultural fields and forested areas. The proximity to larger industrial belts in Curitiba, approximately 650 km east, means that occasional long-range transport of pollutants can occur, though this is less frequent than localized emissions. The prevailing winds generally flow from west to east, carrying potential pollutants towards the Atlantic Ocean, but also impacting downwind communities. The elevation, relatively low at around 180 meters above sea level, contributes to temperature inversions during cooler months, potentially trapping pollutants near the ground.

São Miguel do Iguaçu experiences a distinct wet and dry season pattern, significantly impacting air quality throughout the year. The wet season, typically from November to March, brings frequent rainfall and high humidity, generally leading to improved air quality as precipitation washes away particulate matter and dilutes gaseous pollutants. However, intense storms can temporarily elevate particulate levels due to wind-blown dust and soil. The dry season, from April to October, is characterized by lower rainfall and increased sunshine, often accompanied by periods of stagnant air. Temperature inversions are more common during the cooler months (June-August), trapping pollutants closer to the ground, particularly those emitted from agricultural burning practices, a common occurrence as farmers prepare fields for planting. Agricultural activities, including sugarcane harvesting and soy cultivation, release significant amounts of particulate matter and volatile organic compounds (VOCs) into the atmosphere, especially during the dry season. Wind patterns play a crucial role; periods of calm winds exacerbate pollution buildup, while stronger winds disperse pollutants more effectively. Fog, occasionally occurring during the cooler months, can also trap pollutants, reducing visibility and increasing respiratory irritation. Sensitive groups, such as children, the elderly, and individuals with pre-existing respiratory conditions, should exercise caution during periods of stagnant air and agricultural burning, limiting outdoor activity and wearing appropriate masks. The months of August and September often present the most challenging air quality conditions due to a combination of temperature inversions and agricultural practices.