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Thātha, a small town nestled in the Bhojpur district of Bihar, India, occupies a geographically significant position within the fertile Gangetic plains. Located at approximately 25.4988° N latitude and 86.5908° E longitude, the town’s terrain is predominantly flat, characteristic of the Indo-Gangetic alluvial plain. The elevation is relatively low, contributing to a tendency for pollutants to accumulate, particularly during periods of atmospheric stability. Thātha sits near the banks of the Gandak River, a major tributary of the Ganges, which influences local humidity and temperature patterns. The surrounding landscape is overwhelmingly agricultural, with vast stretches of farmland dedicated to rice and maize cultivation, interspersed with smaller villages. This proximity to intensive agricultural practices introduces sources of air pollution, including biomass burning from crop residue and fertilizer application. The urban–rural gradient around Thātha is gradual; the town itself is compact, with limited industrial activity, though it serves as a regional market town, attracting traffic from surrounding rural areas. Further afield, the landscape transitions to slightly undulating terrain, eventually rising towards the Chota Nagpur Plateau, though this is a considerable distance. The flat topography and prevailing wind patterns, often light and variable, can exacerbate air quality issues by limiting pollutant dispersion. The lack of significant natural barriers means that pollutants from distant industrial belts, particularly those in the broader Bihar region, can be transported to Thātha, impacting local air quality.

Thātha’s air quality follows a distinct seasonal pattern dictated by the region’s monsoon climate. The monsoon season, typically spanning from June to September, brings relief from accumulated pollutants due to frequent rainfall and increased wind speeds, effectively flushing the atmosphere. However, the pre-monsoon period (March-May) is often characterized by a significant deterioration in air quality. High temperatures and minimal rainfall create stable atmospheric conditions, leading to temperature inversions where cooler air becomes trapped beneath a layer of warmer air, preventing vertical mixing and trapping pollutants near the ground. Agricultural burning of crop residue after the harvest season (late February to April) further compounds this issue, releasing substantial amounts of particulate matter. The post-monsoon season (October-November) sees a gradual improvement as temperatures begin to cool, but fog formation, particularly in November, can trap pollutants and reduce visibility. Winter months (December-February) are generally cooler, with occasional cold waves, but fog remains a persistent problem, significantly impacting air quality. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the pre-monsoon and winter months, limiting outdoor activities during periods of heavy fog or visible haze. Maintaining indoor air quality through ventilation and air purification can also be beneficial. The monsoon provides a natural cleansing effect, making it the most favourable time for outdoor pursuits.