Air pollution becomes acute in Calcutta during winter. Pollutants cannot disperse easily, mainly due to inversion, low wind speed and high congestion. Although Calcutta is known to be one of the world's most polluted cities; available data on pollutant pollution are scanty. So far, data on suspended particulate matter (SPM), SO2, NOx in Calcutta for a couple of years are available. Relatively small amounts of data are available on other parameters like CO, benzene soluble organic matter (BSOM), heavy metals, polynuclear aromatic hydrocarbon (PAH). Almost no data are available on benzene-toluene-xylene (BTX), organolead, heavy metals in inhalable particulate matter (IPM) and acidity of moisture.
Samples were collected from five important street crossings in the core city. The average SPM (Suspended Particulate Mater) concentrations during the winter in 1992, 1993 and 1994 were 982 µg/m3, 1007 µg/m3 and 1181 µg/m3 respectively. High SPM in the city air also showed high BSOM (Benzene Soluble Organic Mater). High BSOM was associated with high value of PAH (Polynuclear Aromatic Hydrocarbons). Twelve PAH compounds were identified and quantified in the city air and some of them are suspected carcinogen. Among the ten heavy metals determined, lead concentration in SPM during winter for Calcutta was high in comparison to other cities of the world. The total organolead concentrations in ambient air were measured and indicated high value of organolead in the city air. The average organolead concentration for 1992, 1993 and 1994 were 303 ng/m3, 299 µg/m3 and 296 µg/m3 respectively. Concentrations of benzene, toluene and xylene were found to be much higher than in other studies elsewhere in the world. The average benzene concentration during winter in 1992, 1994 and 1996 were 1000 µg/m3, 708 µg/m3 and 491 µg/m3 respectively. Various factors like use of kerosene, coal as cooking fuel, coal in use by power plants surrounding the city, large number of cars, poor quality of fuel, bad condition of the city streets, small road area compared to the total city area, high population density, miserable slum conditions of habitation and overall poor socio-economic status of city dwellers are together responsible for the serious air pollution in the city [Chakraborti et al,Current Science, 75(2),123138, 1998].
WHO (World Health Organization) has estimated that the majority of five million children that die from diarrheal diseases in developing world are poor urban families [World Resource Institute (1996). The Urban Environment, Oxford University Press, New York].
SOUND POLLUTION AROUND CALCUTTA