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Khulna, situated in southwestern Bangladesh within the Khulna Division, occupies a strategic position in the Ganges-Brahmaputra delta region, profoundly shaping its urban character and air quality challenges. The city lies on the banks of the Rupsha and Bhairab rivers, approximately 50 kilometers inland from the Bay of Bengal, with an elevation averaging just 3-5 meters above sea level—making it exceptionally flat and prone to waterlogging. This low-lying terrain, part of the vast Sundarbans mangrove forest periphery, creates a natural basin effect that traps pollutants. Khulna functions as a major industrial and agricultural hub, surrounded by extensive shrimp farming zones and rice paddies, with its urban core transitioning into peri-urban and rural areas along a distinct gradient. The city's location within Bangladesh's industrial belt, particularly for shrimp processing, brick manufacturing, and jute mills, concentrates emission sources near residential zones. Proximity to the Sundarbans, while ecologically significant, does little to mitigate local pollution due to prevailing wind patterns that often stagnate over the urban area. The confluence of river systems and tidal influences from the Bay of Bengal occasionally disperses pollutants but more frequently contributes to high humidity that exacerbates particulate matter formation. This geographic setting—flat, riverine, and industrially active—creates a perfect storm for poor air quality, with limited natural ventilation and persistent emission sources embedded in the urban fabric.

Khulna's air quality follows a pronounced seasonal rhythm dictated by its tropical wet-and-dry climate and monsoon patterns, with pollution peaking dramatically during the cool, dry winter months from November to February. During this period, reduced rainfall, frequent temperature inversions, and calm winds create a stagnant atmospheric layer that traps emissions from brick kilns, industrial exhaust, and domestic biomass burning—compounded by road dust from drier conditions. Sensitive groups, including children, the elderly, and those with respiratory conditions, should minimize outdoor activities, especially in mornings when fog and inversion layers are thickest. The pre-monsoon spring (March-May) brings extreme heat that accelerates photochemical reactions, though occasional thunderstorms provide temporary cleansing. The summer monsoon (June-September) offers the cleanest air, as heavy rains from the Bay of Bengal cyclonic systems wash pollutants from the atmosphere, though high humidity can make residual particulates feel oppressive. Post-monsoon autumn (October) sees a rapid deterioration as rains cease and agricultural burning resumes. For health protection, residents should monitor local air quality advisories, use masks during peak pollution months, and schedule outdoor exercise for monsoon months when dispersion is optimal. The cyclical nature of Khulna's pollution—intense winter haze giving way to monsoon relief—requires adaptive strategies tailored to each season's meteorological quirks.