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Passa Quatro, nestled within the state of Minas Gerais, Brazil, occupies a geographically significant position within the Southeast region. Located at approximately -22.3900 latitude and -44.9669 longitude, the city’s terrain is characterized by undulating hills and valleys typical of the Serra da Mantiqueira foothills. Its elevation, around 850 meters above sea level, contributes to a cooler climate compared to lower-lying areas of Minas Gerais, but also influences atmospheric stability and potential for temperature inversions. The surrounding landscape is a mosaic of agricultural land, primarily dedicated to coffee cultivation and cattle ranching, interspersed with patches of native Cerrado vegetation. This agricultural activity, while vital to the regional economy, can contribute to localized air pollution through the use of fertilizers, pesticides, and emissions from agricultural machinery. Passa Quatro’s proximity to larger urban centers like São Paulo, though relatively distant (approximately 280 km), means it is indirectly affected by regional industrial belts and transportation corridors. The urban–rural gradient is gradual, with smaller settlements and agricultural areas blending seamlessly into the city’s periphery. The lack of major rivers directly adjacent to Passa Quatro means humidity levels are generally lower, impacting atmospheric mixing and potentially exacerbating particulate matter concentrations during drier periods. The city’s compact urban form, with a relatively small population of 16,393, suggests a primarily residential character, though localized commercial activity and agricultural processing facilities likely contribute to air quality variations.

Passa Quatro experiences a tropical savanna climate, exhibiting distinct wet and dry seasons rather than the four traditional seasons. The dry season, typically spanning from April to September, is characterized by lower rainfall and increased sunshine hours. This period often sees a noticeable decline in air quality, primarily due to reduced atmospheric moisture. The drier air inhibits the scavenging effect of rain, allowing particulate matter, including dust from agricultural activities and emissions from vehicles, to accumulate. Temperature inversions, common during the cooler nights of the dry season, trap pollutants near the ground, further worsening air quality. The wet season, from October to March, brings increased rainfall and higher humidity, naturally cleansing the atmosphere and dispersing pollutants. Stronger winds associated with convective storms also aid in ventilation. During the wet season, outdoor activities are generally more pleasant, and air quality improves significantly. However, periods of intense rainfall can lead to soil erosion and the suspension of fine particles, temporarily impacting air quality. Sensitive groups, such as children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, particularly during periods of stagnant air or visible haze. Limiting strenuous outdoor activity during the hottest parts of the day and ensuring adequate ventilation indoors are recommended. The transition periods between wet and dry seasons can be unpredictable, with fluctuating air quality depending on rainfall patterns and wind conditions. Monitoring local weather forecasts and air quality reports is advisable for informed decision-making.