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Eshtehārd, nestled within Alborz Province, Iran, occupies a geographically significant position approximately 40 kilometers west of Tehran. The city’s coordinates (35.7250° N, 50.3650° E) place it within the foothills of the Alborz Mountains, a range that dramatically influences its climate and air quality. Eshtehārd’s elevation, around 1,600 meters above sea level, contributes to cooler temperatures and increased susceptibility to temperature inversions. The surrounding landscape is characterised by semi-arid plains transitioning into mountainous terrain, with limited natural water bodies in the immediate vicinity. The city is situated within a region experiencing rapid urban expansion, fuelled by migration from rural areas and Tehran’s overflow. This growth has led to increased traffic and construction, contributing to localised pollution. To the east lies the heavily industrialised corridor surrounding Tehran, a significant source of regional pollutants that can be transported to Eshtehārd by prevailing winds. The urban-rural gradient is steep, with agricultural lands to the west and north gradually giving way to denser residential and commercial areas closer to the city centre. This proximity to both agricultural activity (potential for dust and pesticide drift) and industrial zones creates a complex air quality profile.

Eshtehārd’s air quality follows a distinct seasonal pattern. Spring (March-May) often sees moderate pollution levels as temperatures rise and agricultural activities, including burning of crop residue, increase. Winds are variable, sometimes dispersing pollutants, other times trapping them in the valley. Summer (June-August) typically offers the cleanest air, with occasional dust storms originating from western and southwestern regions. Higher temperatures and stronger winds aid in pollutant dispersion, though ozone formation can become a concern during prolonged sunny periods. Autumn (September-November) marks a deterioration in air quality, coinciding with the onset of colder temperatures and increased heating demands. Temperature inversions become more frequent, trapping pollutants near the ground. November is often the most polluted month. Winter (December-February) presents the most challenging conditions. Reduced sunlight, stagnant air masses, and heavy reliance on fossil fuels for heating lead to significant pollutant accumulation. Sensitive groups – children, the elderly, and those with respiratory conditions – should limit outdoor exposure during these months. Fog can exacerbate particulate matter concentrations. Avoiding outdoor activity during calm, cold mornings in winter is advisable.