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Sher, Bihar, nestled in the fertile plains of the Indo-Gangetic Basin, occupies a geographically significant position within a densely populated and agriculturally intensive region of India. Located at approximately 26.3422° N, 84.6210° E, the town’s elevation is relatively low, around 55 meters above sea level, contributing to a tendency for pollutants to accumulate. The surrounding landscape is predominantly flat, characterized by expansive agricultural fields – primarily rice and wheat cultivation – which, while vital for regional food security, can contribute to seasonal particulate matter through crop residue burning. Sher’s proximity to the Ganges River, though providing a crucial water source, also influences local meteorology, impacting wind patterns and humidity levels. The urban–rural gradient around Sher is gradual; the town itself is small, with a population of just over 12,000, but it sits within a larger network of villages and agricultural communities. There are no major industrial belts immediately adjacent to Sher, however, larger industrial areas in nearby cities like Patna can influence regional air quality. The flat terrain and lack of significant topographical features limit natural air dispersion, meaning pollutants released locally, or transported from further afield, tend to linger. The climate is subtropical, with hot, dry summers and a monsoon season, further complicating air quality dynamics. The soil composition, largely alluvial, also impacts dust generation, particularly during drier periods. The overall geographic setting predisposes Sher to challenges in maintaining optimal air quality.

Sher’s air quality follows a distinct seasonal pattern dictated by the region’s subtropical climate and agricultural practices. The pre-monsoon months (March-May) typically experience the poorest air quality. High temperatures exacerbate the formation of ground-level ozone, while stagnant air masses and frequent temperature inversions trap pollutants close to the surface. Agricultural burning of crop residue after the harvest season significantly elevates particulate matter concentrations during this period. The monsoon season (June-September) brings relief, with increased rainfall and stronger winds that naturally cleanse the atmosphere. However, heavy rainfall can also lead to increased humidity and the release of biogenic volatile organic compounds (BVOCs), which can contribute to ozone formation under certain conditions. Post-monsoon (October-November) sees a return to drier conditions, and a resurgence of agricultural burning, again impacting air quality. Winter months (December-February) are often characterized by fog, which further restricts air dispersion and traps pollutants, creating a hazy and potentially unhealthy environment. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the pre-monsoon and post-monsoon periods, limiting outdoor exertion and monitoring for respiratory symptoms. During the foggy winter months, indoor air quality also becomes a concern, necessitating proper ventilation and air purification measures. The interplay of meteorological factors and agricultural practices creates a complex and dynamic air quality profile for Sher.