Pollution and Pollutants: Classification, Causes, Effects and Sources

 

Classification of Pollution and Pollutants:

Pollution is defined as the presence of impurities or pollutant substances in sufficient concentration levels, causing harmful effects on human beings, animals, plant life or material resources when exposed for a sufficient duration of time, thus reducing the quality of life in the environment.

Pollution is the effect of undesirable changes in our surroundings that have harmful effects on plants, animals and human beings. Pollutants include solid, liquid or gaseous substances present in greater than natural abundance, produce due to human activity, which have a determined effect on our environment.

The nature and concentration of a pollutant determine the severity of its detrimental effects on human health. Impurities released directly from the source of origin are known as primary pollutants, for example, CO, SO₂, NO. When contaminants like HC, NO, O₃, combine in the atmosphere (moisture, sunlight) to form new products like PAN (peroxy acetyl nitrate), petrochemical smog, formaldehyde, which are known as secondary pollutants.

From an ecological perspective, pollutants can be classified as degradable, slowly degradable and non-degradable. The Degradable or called as non-persistent pollutants can be rapidly broken down by natural process. For example domestic sewage, discarded vegetables, 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.

For example, DDT (pesticides) and most plastics. The Non-degradable pollutants cannot be degraded by natural process. Once they are released into the environment they are difficult to eradicate and continue to accumulate: For example, toxic elements like lead or mercury, and nuclear wastes.

Causes:

The ultimate cause of pollution is human activity itself. Pollution is a human contribution to nature. Human activities mainly include: industries for various human needs both directly and indirectly, agriculture for food production and industrial needs, health care for health of human beings and animals, transport for mobility of human beings, dwelling for settlement in city or villages, energy for various direct human and industrial needs.

All of these activities contribute to pollution in one way or other and therefore causes miseries. All of them are aimed to be part of human welfare programmes. Along with welfare, all of them have brought the maladies of pollution.

A vast array of industries can cause pollution contrary to popular perception that only a chemical industry can cause pollution. The nature and intensity of pollution may be different in different industry. In others, it may be invisible, indirect or negligible. In such a broad sense, no industry is free of pollution.

Effects of Pollution:

Pollution produces physical and biological effects that vary from mildly irritating to lethal. The more serious of the two are the biological effects. The physical effects of pollution are those that we can see, but they include effects other than actual physical damage. Oils spills, killing fish birds, coal produce sox, particulates etc., are considered as physical effects. Air pollutants speed the erosion of statues and buildings, which in some instances, destroys works of art.

The most serious result of pollution is its harmful biological effects on human health and on the food-chain of animals, birds, and marine life. Pollution can destroy vegetation that provides food and shelter. It disrupts the balance of nature, and, in extreme cases, can cause the death of humans. Pesticides, which include herbicides and insecticides, can damage crops; kill vegetation; and poison birds, animals, and fish.

Most pesticides are non-selective; they kill or damage life forms other than those intended For example, pesticides used in an effort to control or destroy undesirable vegetation and insects often destroy birds and small animals. The biological effect of water pollution is its danger to our water supplies. Water pollutants are also dangerous to all forms of marine life.

Sources of Pollution:

Nature contributes to pollution by eroding the soil casing silt to build up in streams and by volcanic eruptions that pollute the atmosphere. However, people cause most pollution problems in the world. The main sources of pollutants are agricultural, industrial, municipal and transportation operations. Agricultural pollutants include insecticides, herbicides, pesticides, natural and chemical fertilizers, drainage from animal feedlots, salts from field irrigation, and silts from uncontrolled soil erosion.

Industrial operations produce a wide variety of pollutants. Industrial pollutants include acids from mines and factories, thermal discharges from power plants and radioactive wastes from mining and processing certain ores. Industries create pollutants by producing food, chemicals, metals, petroleum products, and poisons, as well as countless other by-products of our country’s technology.

The primary municipal pollutants are raw or inadequately treated sewage. Other municipal pollutants include refuse, storm-water overflows and salts used on streets in wintertime. Transportation pollutants include emissions from aircraft, trains, waterborne vessels, and cars and trucks. Motor vehicles create most of our air pollutants through their release of unburned fuel vapours (hydrocarbons).