Recent concern for the environment is not only due to natural phenomenon, but the urban, technological fall-outs, which has made people more aware of the environmental issues and their quality. Population beyond the multiple times of the sustaining capacity has made the urban centres polluted, overcrowded and exerted pressures on social and physical amenities.The Concentration of industries in and around urban centres has exposed the urban population to all sorts of risks. These risks can remain unnoticed due to its slow introduction such as increasing the quantity of pollutants in river Ganga, or can be sudden due to some industrial disaster.
Some of the most important urban environmental problems are:
a) Slums and Housing Conditions
b) Air Pollution
Slums, as a consequence of the prevailing socio- economic condition, have now become an essential part of not only million cities of India, but also in medium size cities as well. According to one estimate, about 20 percent of the countries’ urban population resides in the slums. This ratio is high in cities like Kanpur (40%), Lucknow (38.83%), Mumbai (38.30%), Kolkata (35.35%) and Delhi (30.19%). Slum is not only an urban problem. Economically weaker section of rural population, such as landless labour, scheduled caste and tribe population and other social and economically backward communities tend to move to far away large urban centres like Calcutta or Mumbai, or to nearby medium or small urban centres due to compulsions of various kinds in rural areas. Any attempt for the betterment of urban environment makes urban centres more attractive thereby promoting rural-urban migration.
Air, water and noise pollution have their origin in the urban-industrial nuclear complexes. In some cases,pollutants also affect the rural areas, particularly water pollutants. The excessive concentrations of pollutants create conditions, which are beyond tolerance limits and thereby became injurious to human and animal population, their safety, health and properties. In case of air pollution the presence of sulphur dioxide (SO2), Carbon Mono Oxide (CO), fluorides, hydrocarbons, Oxides of Nitrogen and Aldehydes, smoke and dust in large quantities makes sustenance of life dangerous in urban areas. The sources of these pollutants are vehicles, industries and wastes. In an air pollution survey over major cities of India, the highest mean value of SO2 (578mgm3 and 85mgm3 respectively) were found in Kolkata, followed by Mumbai (275 & 83), Delhi (481 & 39), Kanpur (344 & 25), Nagpur (386 & 12), Jaipur (379 & 17) and Madras (106 & 16).
Water pollution, in a way, has more serious consequences because it can easily be transported and can enter in food chain, which may lead to gastric damage. The causes of such pollution may not always be water based. Their origin may be owing to:
Ø Atmospheric dissolved gases leading to acid rain
Ø Decomposition of Animal and Vegetable Wastes
Ø Industrial Wastes
Ø Sewage Discharge
Ø Weathering of Rocks and Soils
Ø Chemical Pesticides
Ø Radioactive Waste
Ø Petroleum Waste.
Presence of these wastes deteriorates the water quality because they stimulate the growth of microorganisms, which often increases the Biological Oxygen Demand (BOD) of the water.
Noise pollution and Solid Waste Disposal are preliminary urban problems. Both these hazards increase with the density of population and the closeness to the centre of the city. Noise pollution can be from vehicles, loudspeakers, music-systems, crackers and the like. Some surveys carried out in some of the urban centres reveals that this pollution is high at road junctions, around railway stations, airports or bus stands. In general, there is a reasonable variation in the level of this pollution within a day. Acceptable levels of noise for various environmental set-ups have been worked out by Indian Standard Institute (ISI). Similarly, the pattern of solid waste generated in cities is directly related to its population size. The urban garbage produced in India per day is about .35 Kg per person. For Kolkata, this average is highest –0.57 Kg per person. But, Mumbai produces the maximum solid waste, followed by Kolkata, Delhi, Madras and Bangalore. Perception studies reveal that tolerance capacity of the population is much more than the scientifically accepted tolerance limits set for this purpose.