Mahisi, nestled in the plains of Bihar, India (25.8544° N, 86.4650° E), occupies a geographically significant position within the fertile Gangetic plains. The town’s terrain is predominantly flat, characteristic of the Indo-Gangetic alluvial plain, resulting in minimal elevation changes. This flatness, while conducive to agriculture, unfortunately exacerbates air pollution issues as pollutants tend to accumulate rather than disperse easily. Mahisi lies within a region heavily reliant on agriculture, with surrounding landscapes dominated by rice paddies and other cultivated fields. This agricultural activity, particularly the burning of crop residue after harvest, contributes significantly to seasonal particulate matter pollution. The proximity to the Ganges River, though providing a vital water source, doesn't significantly influence air quality due to the prevailing wind patterns and the scale of agricultural emissions. The urban–rural gradient around Mahisi is gradual; the town itself is relatively small, but it serves as a local market center for surrounding villages, leading to increased vehicular traffic and associated emissions. Further afield, the region is part of a broader industrial belt concentrated in areas like Dhanbad, though Mahisi itself lacks major heavy industries. However, smaller-scale brick kilns and workshops, common in rural Bihar, contribute to localized air pollution. The flat topography and surrounding agricultural lands create a bowl-like effect, trapping pollutants and limiting natural ventilation, a key factor impacting air quality in Mahisi.

Mahisi’s air quality follows a distinct seasonal pattern dictated by the region’s monsoon climate. The dry season, typically spanning October to May, witnesses the most concerning air quality conditions. Post-harvest burning of agricultural residue, a widespread practice in Bihar, releases substantial amounts of particulate matter and other pollutants, leading to peak pollution episodes in November and December. Temperature inversions, common during the colder months, trap these pollutants close to the ground, further worsening the situation. The monsoon season (June to September) brings relief, as consistent rainfall washes away pollutants and strong winds disperse remaining contaminants. However, even during the monsoon, periods of stagnant air and fog, particularly in the mornings, can temporarily degrade air quality. The summer months (April-May) are characterized by high temperatures and dry winds, which can exacerbate the effects of existing pollutants. Spring (March) often sees a gradual improvement as the monsoon approaches, but lingering agricultural burning can still impact air quality. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, particularly during peak burning periods. Limiting outdoor exertion and wearing masks are advisable. During the monsoon, while generally better, periods of fog necessitate similar precautions. The transition months of October and May require vigilance as conditions shift between the dry and wet seasons.