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Pinotepa Nacional, nestled in the southern coastal plains of Oaxaca, Mexico, occupies a geographically significant position within the larger Tehuantepec Isthmus. Located at approximately 16.34° N, 98.05° W and an elevation of roughly 15 meters (49 feet) above sea level, the city benefits from a relatively flat terrain characteristic of the coastal region. Its proximity to the Pacific Ocean, specifically the Bahía de Pinotepa, exerts a considerable influence on local climate and, consequently, air quality. The surrounding landscape is a mosaic of agricultural lands – primarily sugarcane and maize fields – interspersed with patches of tropical deciduous forest. This agricultural activity, while vital to the local economy, contributes to potential sources of particulate matter, particularly during harvest seasons. The urban–rural gradient transitions rapidly, with the city bordered by these agricultural zones and smaller rural communities. Further inland, the terrain gradually rises towards the Sierra Madre del Sur mountain range, impacting regional wind patterns and potentially trapping pollutants under certain meteorological conditions. There are no major industrial belts immediately adjacent to Pinotepa Nacional; however, the broader Isthmus region experiences some level of industrial activity related to agriculture and processing, which can contribute to transboundary air pollution events. The prevailing easterly trade winds, common to this region, generally disperse pollutants, but their effectiveness is modulated by local topography and seasonal weather patterns. The city’s coastal location also means it is susceptible to sea breezes, which can influence local air circulation and pollutant distribution.

Pinotepa Nacional experiences a tropical wet-and-dry climate, dictating a distinct seasonal pattern in air quality. The dry season, typically spanning from March to May, often sees a slight increase in particulate matter concentrations. This is largely attributable to increased agricultural burning practices as farmers prepare fields for planting, combined with reduced rainfall to wash pollutants from the atmosphere. The lack of consistent rainfall during this period allows dust and smoke to linger. The wet season, from June to October, brings frequent rainfall and higher humidity, naturally cleansing the air and significantly reducing particulate pollution. However, periods of intense rainfall can occasionally lead to localized flooding, which can temporarily release pollutants from inundated areas. November and February represent transitional months, with variable weather patterns. Temperature inversions, though less frequent than in colder climates, can occasionally occur during these months, trapping pollutants closer to the ground, particularly during calmer nights. Wind patterns are generally consistent throughout the year, with easterly trade winds dominating, but their strength and direction can fluctuate. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, particularly during agricultural burning periods. Outdoor activities are generally more favorable during the wet season, although vigilance regarding potential flooding is advised. The combination of agricultural practices and the tropical climate creates a dynamic air quality profile, requiring ongoing monitoring and adaptive strategies to protect public health.