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Comalapa, Chiapas, nestled within the highlands of southern Mexico, occupies a geographically significant position within the broader Chiapas region. Located at approximately 15.65° N, 92.15° W and an elevation of around 1,750 meters (5,742 feet) above sea level, the city benefits from a temperate, sub-tropical climate influenced by its altitude. The surrounding landscape is dominated by rolling hills and steep slopes, characteristic of the Sierra Madre de Chiapas mountain range. This terrain significantly impacts air circulation; valleys can trap pollutants, while the slopes can channel winds, sometimes dispersing them but also concentrating them in specific microclimates. Comalapa’s proximity to agricultural lands, particularly coffee plantations, is a defining feature. While these plantations contribute to the local economy, agricultural practices, including the use of fertilizers and occasional burning of vegetation, can introduce particulate matter and gaseous pollutants into the air. The urban–rural gradient is relatively sharp, with the city transitioning quickly into agricultural zones. There are no major industrial belts immediately adjacent to Comalapa, reducing the direct impact of heavy industrial emissions. However, regional transportation routes pass nearby, contributing to vehicular pollution. The city’s location within a relatively isolated highland area means that atmospheric dispersion is somewhat limited compared to coastal or lowland regions, potentially exacerbating the effects of local pollution sources. The surrounding forests, while providing some natural air filtration, are also susceptible to deforestation, which can further degrade air quality.

Comalapa’s air quality experiences a distinct seasonal pattern dictated by its tropical climate and the interplay of wet and dry seasons. The dry season, typically spanning from November to April, often sees a slight increase in particulate matter concentrations. This is partly due to reduced rainfall, which limits the natural cleansing effect of precipitation, and increased agricultural burning as farmers prepare fields for planting. Temperature inversions, common during the cooler, drier months, can trap pollutants near the ground, particularly in the mornings. The wet season, from May to October, brings more frequent rainfall, which helps to wash pollutants from the atmosphere, generally leading to improved air quality. However, periods of intense rainfall can also lead to increased humidity, which can exacerbate respiratory issues for sensitive individuals. Fog, particularly during the transition months (April/May and October/November), can also trap pollutants, creating localized pockets of poor air quality. During the wet season, the increased cloud cover can reduce solar radiation, impacting photochemical reactions that contribute to ozone formation. Outdoor activities are generally more favorable during the wet season, particularly in the afternoons after rainfall. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should be mindful of potential particulate matter increases during the dry season and avoid prolonged outdoor exposure during periods of fog or temperature inversions. Agricultural workers should be particularly cautious about exposure to smoke from burning vegetation and take appropriate protective measures.