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San Blas Atempa, nestled within the state of Oaxaca, Mexico, occupies a geographically significant position in the southern highlands. Located at approximately 16.3167° latitude and -95.2167° longitude, the town sits at an elevation of roughly 1,650 meters (5,413 feet) above sea level, contributing to a cooler, often misty climate. The surrounding landscape is characterized by rolling hills and valleys, typical of the Sierra Madre del Sur mountain range. This terrain significantly influences local air circulation patterns; valleys can trap pollutants, while the slopes can channel winds, sometimes dispersing them but also potentially concentrating them in specific areas. San Blas Atempa’s proximity to the larger urban center of Oaxaca City, approximately 30 kilometers to the north, introduces a degree of regional air pollution influence, though the town itself maintains a predominantly rural character. The dominant land use in the immediate vicinity is agriculture, with maize and beans being key crops, and small-scale livestock farming also prevalent. This agricultural activity, while vital to the local economy, can contribute to particulate matter emissions, particularly during burning seasons. The urban–rural gradient is relatively sharp; San Blas Atempa retains a traditional, largely agrarian lifestyle, with limited industrial activity within the town itself. However, the increasing demand for agricultural products and transportation links to Oaxaca City are slowly introducing external factors that can impact air quality, including increased vehicle traffic and potential for larger-scale agricultural operations further afield.

San Blas Atempa’s air quality experiences a distinct seasonal cycle dictated by Oaxaca’s wet and dry seasons. The dry season, typically spanning from November to April, often sees a noticeable increase in particulate matter. This is largely attributable to agricultural practices, specifically the controlled burning of fields to prepare land for planting. While regulated, these burns can release significant amounts of smoke and ash, particularly during periods of low wind speed. Temperature inversions, common during the cooler nights of the dry season, exacerbate this issue by trapping pollutants close to the ground. The wet season, from May to October, brings relief as rainfall washes away accumulated particulate matter and increased humidity helps to settle dust. However, periods of intense rainfall can also lead to localized flooding, which can temporarily release pollutants from saturated soils. Fog, frequently occurring during the transition months (October-November), can also trap pollutants, creating localized pockets of reduced visibility and potentially impacting air quality. During the hottest months (May-June), stagnant air and high temperatures can contribute to ozone formation, although this is generally less of a concern than particulate matter. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, particularly during agricultural burning periods. Limiting outdoor exertion and avoiding areas with visible smoke are advisable. The shoulder seasons, October and April, present a mixed picture, with potential for both fog-related pollution and the lingering effects of agricultural practices.