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Embu-Guaçu, nestled within the sprawling metropolitan region of São Paulo, Brazil, occupies a strategically important position in the state’s southeastern quadrant. Located approximately 35 kilometers southwest of the city of São Paulo, its coordinates (-23.8322, -46.8114) place it within a transitional zone between the densely urbanized core and the more rural landscapes of the Paraíba do Sul river basin. The terrain is gently undulating, characterized by rolling hills and valleys, a legacy of the region’s ancient geological formations. Elevation averages around 800 meters above sea level, contributing to a relatively cool climate compared to lower-lying areas of São Paulo. The surrounding landscape is a mosaic of agricultural land – primarily sugarcane and pasture – interspersed with patches of remnant Atlantic Forest. This proximity to agricultural zones introduces localized sources of air pollution, particularly during harvest seasons when burning is sometimes practiced. The urban–rural gradient is noticeable, with Embu-Guaçu exhibiting a mix of residential areas, small-scale industries, and agricultural activities. While not directly adjacent to major rivers, the Paraíba do Sul’s influence moderates the local climate and contributes to humidity levels. The city’s location within the broader São Paulo industrial belt means it is susceptible to pollutants transported from the larger urban center, impacting air quality despite its relatively smaller size and population of approximately 66,970. The prevailing winds, often originating from the south, can carry pollutants northward, affecting local air quality and contributing to regional pollution patterns.

Embu-Guaçu experiences a subtropical climate with distinct wet and dry seasons, significantly influencing its air quality profile. The wet season, typically spanning from October to March, brings increased rainfall and higher humidity, generally leading to improved air quality as precipitation washes away particulate matter and dilutes gaseous pollutants. However, periods of prolonged rainfall can also result in stagnant air conditions, particularly in localized areas, potentially trapping pollutants. The dry season, from April to September, is characterized by lower rainfall, higher temperatures, and increased sunshine. This often leads to a build-up of pollutants, especially during periods of atmospheric stability and temperature inversions, where cooler air is trapped beneath a layer of warmer air, preventing vertical mixing. September and October frequently see the highest concentrations of pollutants due to a combination of factors: reduced rainfall, agricultural burning practices in surrounding areas, and the accumulation of emissions throughout the dry season. During these months, sensitive groups like children, the elderly, and individuals with respiratory conditions should limit prolonged outdoor activity, particularly during the early morning and late afternoon when temperature inversions are most pronounced. Conversely, the months of January and February, with consistent rainfall, generally offer the best air quality for outdoor pursuits. Fog, which occasionally occurs during the cooler months, can also exacerbate air pollution by trapping pollutants near the ground. Maintaining green spaces and promoting sustainable transportation options are crucial for mitigating the impacts of seasonal variations on air quality in Embu-Guaçu.