Rishra, a municipality in the Hooghly district of West Bengal, India, occupies a strategically important position on the western bank of the Hooghly River, a major distributary of the Ganges. Located at 22.7100°N latitude and 88.3500°E longitude, the city’s terrain is generally flat, characteristic of the Bengal Delta. Rishra’s elevation is low, making it vulnerable to riverine flooding and influencing local air circulation patterns. The surrounding landscape is a mix of intensely cultivated agricultural land – primarily rice paddies – and burgeoning industrial areas. Historically a riverine trading post, Rishra has evolved into a significant industrial hub, particularly for jute and engineering products. This industrial concentration, coupled with the dense population of 124,577, contributes significantly to localised air pollution. The urban-rural gradient is relatively sharp, with agricultural fields immediately bordering the city limits. The Hooghly River, while providing a transport corridor, also limits atmospheric dispersion of pollutants due to its topographical influence. Proximity to Kolkata, a major metropolitan area, further exacerbates air quality challenges through regional pollutant transport. The prevailing winds, often influenced by the monsoon system, play a crucial role in dispersing or concentrating emissions.

Rishra’s air quality follows a distinct seasonal pattern. The post-monsoon months (October-November) often see a build-up of pollutants as stagnant air masses become trapped after the rains subside, and winter temperatures begin to fall, increasing the likelihood of temperature inversions. These inversions trap particulate matter close to the ground. December to February represents the period of poorest air quality, with cooler temperatures and reduced wind speeds hindering dispersion. The summer months (March-May) bring increased temperatures and convective mixing, which can temporarily improve air quality, but also exacerbate ozone formation due to higher UV radiation. The pre-monsoon season (June-September) is dominated by the southwest monsoon, which brings heavy rainfall and generally washes away pollutants, resulting in the cleanest air. However, increased humidity can also promote secondary pollutant formation. Sensitive groups – children, the elderly, and those with respiratory conditions – should limit outdoor activity during the winter months and periods of stagnant air. Avoiding peak traffic hours and exercising indoors on poor air quality days is advisable. Monitoring local conditions is crucial, as short-term fluctuations can occur.