Kolkata, a metropolitan city in West Bengal has been designated as one of the most polluted cities in the world in terms of ambient air quality. The deteriorated air quality in Kolkata is the outcome of several factors where the vehicular emission has found to be the leading contributor (51.4 per cent) to air pollution followed by industrial emission (24.5 per cent) and dust particles (21.1 per cent) respectively. The limited road spaces, heavy concentration of private motor vehicles, concentration of large number of old vehicles and significant growth of vehicular population are some of the major causes of vehicular emission and resulted pollution in Kolkata. An assessment of vehicular emission have revealed that buses (65 per cent) are the leading contributor of particulate matter which includes large buses with 48.2 per cent and small busses with 17.2 per cent emissions respectively. The major source of emissions of CO and HC are 3 wheelers with 44 per cent and 69 per cent share respectively. Buses are the single largest emitter of oxides of nitrogen accounting for nearly 73 per cent of the fleet emissions. The power generating plants are the biggest industrial source of NOx and SO₂ emissions with 32,232 and 9,964 metric tons per year releasing into the atmosphere. These are also comprises the single largest contributor to NOx and SO2 with 94.2 per cent and 80.5 per cent emissions respectively. Foundry leads to the emission of RPM with 49.4 per cent which was the highest single emitter of RPM followed by brick kilns, power plant coal and battery manufacturing with 17.9 per cent, 14.2 per cent and 11.9 per cent share of emissions respectively. The RPM emission from paved road dust is 45,881 tons per year which is 85 per cent of the total area source of RPM emissions. The other least significant source of air pollution includes open burning of fossil fuel, domestic cooking in slum areas and emission from diesel running trains.