Pollution is the effect of undesirable changes in our surroundings that have harmful effects on plants, animals and human beings. This occurs when only short term ecological gains are made at the cost of long term ecological benefits for humanity. During the last few decades we have polluted our air, water and land on which life itself depends with a variety of waste products.
From an ecological point of view, pollutants can be classified as degradable or non-persistent pollutants which can be rapidly broken down by natural process.eg: domestic sewage, discarded vegetables etc., Slowly-degradable or persistent pollutants are pollutants that remain in the environment for many years in an unchanged condition and take decades or longer to degrade.eg:DDT(pesticides) and most plastics. Non-degradable pollutants cannot be degraded by natural processes. Once they are released into the environment they are difficult to eradicate and continue to accumulate.eg: toxic elements like lead or mercury and nuclear wastes.
Pollution is a very wide topic. This thesis focuses on two major pollutions- air and water, and explains in detail the causes, effects and control measures.
Air pollution occurs due to the presence of undesirable solid or gaseous particles in the air in quantities that are harmful to human health and the environment. The air may become polluted by natural causes such as volcanoes, which release ash, dust, sulphur and other gases, or by forest fires that are occasionally caused by lightening. However, unlike pollutants from human activity, naturally-occuring pollutants tend to remain in the atmosphere for a short time and do not lead to permanent atmospheric change.
Air pollution began to increase in the beginning of the twentieth century with the development of transportation systems and large-scale use of petrol and diesel. These severe air quality problems due to the formation of petrochemical smog from the combustion residues of diesel and petrol engines were felt for the first time in Los Angeles. Pollution due to auto- exhaust remains a serious environmental issue in many developed and developing countries, including, India.
The air pollution control act in India was passed in 1981 and the motor vehicle act for controlling air pollution was passed very recently. These laws are intended to prevent the air from becoming over polluted.