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Carmo, nestled within the state of Rio de Janeiro, Brazil, occupies a geographically complex position at coordinates -21.9339, -42.6089. This small municipality, with a population of approximately 17,198, is situated within the Serra da Mantiqueira mountain range, a significant feature shaping its landscape and influencing its air quality. The terrain is characterized by undulating hills and valleys, contributing to localized microclimates and potential for air stagnation. Carmo’s location is approximately 130 kilometers northwest of Rio de Janeiro city, placing it within a transitional zone between the densely populated urban sprawl of the state capital and the more rural, agricultural landscapes of the interior. The surrounding landscape is a mosaic of rolling pastures, small-scale farms, and patches of Atlantic Forest, a biodiversity hotspot. While not directly adjacent to a major river, Carmo benefits from proximity to smaller streams and tributaries that feed into larger river systems, contributing to regional humidity. The urban–rural gradient is relatively sharp; the municipality itself retains a distinctly rural character, with limited industrial activity concentrated primarily in smaller workshops and agricultural processing facilities. This proximity to agricultural lands, while supporting the local economy, can contribute to seasonal particulate matter from agricultural burning practices, particularly during the drier months. The elevation, averaging around 800 meters above sea level, influences temperature and atmospheric stability, potentially exacerbating air pollution episodes under certain meteorological conditions. The mountainous terrain also creates barriers to wind flow, which can trap pollutants within the valley.

Carmo’s tropical climate dictates a wet and dry seasonal pattern, significantly impacting air quality throughout the year. The dry season, typically spanning from April to September, is often associated with heightened particulate matter concentrations. Reduced rainfall and lower humidity contribute to drier vegetation, increasing the risk of wildfires and agricultural burning, both major sources of smoke and fine particles. Temperature inversions, common during the cooler, drier months (June-August), trap pollutants near the ground, leading to periods of poor air quality. The wet season, from October to March, brings increased rainfall and higher humidity, naturally cleansing the atmosphere and dispersing pollutants. However, intense rainfall events can occasionally lead to increased levels of mold spores and allergens, impacting respiratory health. Wind patterns are generally variable, but during the dry season, weaker winds can exacerbate stagnation events. The months of July and August often present the most challenging air quality conditions due to the combination of temperature inversions, reduced rainfall, and agricultural practices. Sensitive groups, including children, the elderly, and individuals with pre-existing respiratory conditions, should limit prolonged outdoor activity during these periods. During the wet season, while overall air quality improves, those with allergies should monitor pollen counts and take necessary precautions. Maintaining indoor air quality through proper ventilation and air filtration is crucial year-round, particularly during periods of elevated particulate matter.