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Nalua, West Bengal, occupies a geographically significant position within the Ganges Delta, a vast alluvial plain shaped by the mighty Ganges River and its tributaries. Located at approximately 22.1051° N, 88.4619° E, the city’s terrain is predominantly flat, characteristic of the deltaic landscape, with an average elevation of just a few meters above sea level. This low elevation contributes to a susceptibility to flooding, a recurring challenge in the region. Nalua’s proximity to the Hooghly River, a distributary of the Ganges, influences local climate and hydrology, but also presents potential risks related to industrial discharge and waterborne pollutants. The surrounding landscape is a mosaic of agricultural fields – primarily rice paddies and jute cultivation – interspersed with small villages and scattered industrial units. This agricultural belt, while vital for the regional economy, can contribute to air pollution through seasonal burning of crop residue. The urban–rural gradient around Nalua is gradual, with small settlements blending into the agricultural landscape. Further afield, the industrial belt of Howrah and Kolkata exerts an influence, with pollutants potentially transported by prevailing winds. The flat topography and limited natural barriers exacerbate the accumulation of pollutants, particularly during periods of stagnant air. The deltaic soil composition, rich in silt, can also bind with pollutants, affecting long-term soil and water quality. The city’s location within a densely populated region of West Bengal means it is subject to regional pollution trends and transboundary air pollution events.

Nalua’s air quality follows a distinct seasonal pattern dictated by the region’s monsoon climate. The dry season, typically spanning from October to May, witnesses a gradual increase in pollution levels. November and December often experience periods of dense fog, trapping pollutants close to the ground and significantly reducing visibility. Temperature inversions, common during these months, further exacerbate the problem by preventing vertical mixing of the atmosphere. Agricultural burning, a widespread practice after the harvest season, contributes significantly to particulate matter pollution during this period. The monsoon season, from June to September, brings relief as strong winds and frequent rainfall flush out pollutants. However, even during the monsoon, localized pollution from industrial activities and vehicular emissions persists. The pre-monsoon period (April-May) can be particularly challenging, with high temperatures and stagnant air leading to a build-up of pollutants. The humidity also increases, which can worsen respiratory conditions. Sensitive groups, including children, the elderly, and individuals with pre-existing respiratory illnesses, should exercise caution during the dry season, particularly during foggy periods and agricultural burning season (November-December). Outdoor activities are generally more favourable during the monsoon months, although localized pollution hotspots may still exist. The transition periods between seasons often see fluctuating air quality, making it crucial to monitor conditions and adjust outdoor plans accordingly. Maintaining indoor air quality through ventilation and air purification can be beneficial during periods of elevated pollution.