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Mehrān, nestled in the Īlām province of western Iran, occupies a geographically significant position within the Zagros Mountains. Located at approximately 33.1208° N, 46.1642° E, and an elevation of roughly 1,350 meters (4,430 feet) above sea level, the city’s terrain is characterized by steep slopes, rugged valleys, and a generally undulating landscape. The surrounding region is dominated by the expansive Zagros range, a barrier influencing regional weather patterns and air circulation. The city sits near the border with Iraq, and the broader Īlām province is known for its historical significance and agricultural lands, particularly date palm cultivation and cereal farming. This proximity to agricultural zones introduces potential sources of particulate matter, especially during harvest seasons when agricultural burning may occur. The urban–rural gradient around Mehrān is relatively sharp; the city itself is small, transitioning quickly to rural agricultural areas and then to the mountainous terrain. While not directly adjacent to a major river, the region receives significant rainfall, contributing to the overall humidity and influencing atmospheric stability. The lack of extensive industrial belts within immediate proximity is a mitigating factor for air pollution, however, regional industrial activity further east could contribute to transboundary pollution events. The mountainous topography tends to trap pollutants, especially during periods of low wind, creating localized air quality challenges. The city’s relatively isolated location, while offering scenic beauty, also limits dispersal of pollutants.

Mehrān’s air quality experiences a distinct seasonal cycle dictated by its climate and geographical setting. Winters, spanning roughly November to March, are typically the most challenging period. Cold temperatures frequently lead to temperature inversions, where a layer of warm air traps cooler air near the ground, preventing the vertical dispersion of pollutants. This phenomenon, coupled with reduced wind speeds characteristic of winter, results in a build-up of particulate matter and other emissions. Fog, common during these months, further exacerbates the issue by limiting visibility and trapping pollutants. Spring (April-May) brings a gradual improvement as temperatures rise and winds increase, aiding in pollutant dispersal. The increased rainfall during this period also helps to cleanse the atmosphere. Summer (June-August) generally sees the best air quality, with higher temperatures promoting atmospheric mixing and frequent winds. However, occasional dust storms originating from the Arabian Peninsula can impact air quality, introducing coarse particulate matter. Autumn (September-October) marks a transitional period, with decreasing temperatures and increasing humidity. Agricultural activities, including potential burning of crop residues, can contribute to localized pollution spikes. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during winter months, limiting outdoor activity during periods of stagnant air and reduced visibility. During the summer months, while generally cleaner, monitoring for dust storm alerts is advisable. Overall, the period from late November through February presents the greatest air quality concerns in Mehrān.