Types Of Pollution Classification Essay

For other uses, see Pollution (disambiguation).

For the academic journal, see Environmental Pollution (journal).

Pollution is the introduction of contaminants into the natural environment that cause adverse change.[1] Pollution can take the form of chemical substances or energy, such as noise, heat or light. Pollutants, the components of pollution, can be either foreign substances/energies or naturally occurring contaminants. Pollution is often classed as point source or nonpoint source pollution. In 2015, pollution killed 9 million people in the world.[2][3]


Air pollution has always accompanied civilizations. Pollution started from prehistoric times when man created the first fires. According to a 1983 article in the journal Science, "soot" found on ceilings of prehistoric caves provides ample evidence of the high levels of pollution that was associated with inadequate ventilation of open fires."[4] Metal forging appears to be a key turning point in the creation of significant air pollution levels outside the home. Core samples of glaciers in Greenland indicate increases in pollution associated with Greek, Roman and Chinese metal production,[5] but at that time the pollution was comparatively small and could be handled by nature.[citation needed]

Urban pollution

The burning of coal and wood, and the presence of many horses in concentrated areas made the cities the primary sources of pollution. The Industrial Revolution brought an infusion of untreated chemicals and wastes into local streams that served as the water supply. King Edward I of England banned the burning of sea-coal by proclamation in London in 1272, after its smoke became a problem.[6][7] But the fuel was so common in England that this earliest of names for it was acquired because it could be carted away from some shores by the wheelbarrow.

It was the industrial revolution that gave birth to environmental pollution as we know it today. London also recorded one of the earlier extreme cases of water quality problems with the Great Stink on the Thames of 1858, which led to construction of the London sewerage system soon afterward. Pollution issues escalated as population growth far exceeded view ability of neighborhoods to handle their waste problem. Reformers began to demand sewer systems, and clean water.[8]

In 1870, the sanitary conditions in Berlin were among the worst in Europe. August Bebel recalled conditions before a modern sewer system was built in the late 1870s:

"Waste-water from the houses collected in the gutters running alongside the curbs and emitted a truly fearsome smell. There were no public toilets in the streets or squares. Visitors, especially women, often became desperate when nature called. In the public buildings the sanitary facilities were unbelievably primitive....As a metropolis, Berlin did not emerge from a state of barbarism into civilization until after 1870."[9]

The primitive conditions were intolerable for a world national capital, and the Imperial German government brought in its scientists, engineers and urban planners to not only solve the deficiencies but to forge Berlin as the world's model city. A British expert in 1906 concluded that Berlin represented "the most complete application of science, order and method of public life," adding "it is a marvel of civic administration, the most modern and most perfectly organized city that there is."[10]

The emergence of great factories and consumption of immense quantities of coal gave rise to unprecedented air pollution and the large volume of industrial chemical discharges added to the growing load of untreated human waste. Chicago and Cincinnati were the first two American cities to enact laws ensuring cleaner air in 1881. Pollution became a major issue in the United States in the early twentieth century, as progressive reformers took issue with air pollution caused by coal burning, water pollution caused by bad sanitation, and street pollution caused by the 3 million horses who worked in American cities in 1900, generating large quantities of urine and manure. As historian Martin Melosi notes, The generation that first saw automobiles replacing the horses saw cars as "miracles of cleanliness.".[11] By the 1940s, however, automobile-caused smog was a major issue in Los Angeles.[12]

Other cities followed around the country until early in the 20th century, when the short lived Office of Air Pollution was created under the Department of the Interior. Extreme smog events were experienced by the cities of Los Angeles and Donora, Pennsylvania in the late 1940s, serving as another public reminder.[13] Air pollution would continue to be a problem in England, especially later during the industrial revolution, and extending into the recent past with the Great Smog of 1952.

Awareness of atmospheric pollution spread widely after World War II, with fears triggered by reports of radioactive fallout from atomic warfare and testing.[14] Then a non-nuclear event, The Great Smog of 1952 in London, killed at least 4000 people.[15] This prompted some of the first major modern environmental legislation, The Clean Air Act of 1956.

Pollution began to draw major public attention in the United States between the mid-1950s and early 1970s, when Congress passed the Noise Control Act, the Clean Air Act, the Clean Water Act and the National Environmental Policy Act.[16]

Severe incidents of pollution helped increase consciousness. PCB dumping in the Hudson River resulted in a ban by the EPA on consumption of its fish in 1974. Long-term dioxin contamination at Love Canal starting in 1947 became a national news story in 1978 and led to the Superfund legislation of 1980.[17] The pollution of industrial land gave rise to the name brownfield, a term now common in city planning.

The development of nuclear science introduced radioactive contamination, which can remain lethally radioactive for hundreds of thousands of years. Lake Karachay, named by the Worldwatch Institute as the "most polluted spot" on earth, served as a disposal site for the Soviet Union throughout the 1950s and 1960s. Chelyabinsk, Russia, is considered the "Most polluted place on the planet".[18]

Nuclear weapons continued to be tested in the Cold War, especially in the earlier stages of their development. The toll on the worst-affected populations and the growth since then in understanding about the critical threat to human health posed by radioactivity has also been a prohibitive complication associated with nuclear power. Though extreme care is practiced in that industry, the potential for disaster suggested by incidents such as those at Three Mile Island and Chernobyl pose a lingering specter of public mistrust. Worldwide publicity has been intense on those disasters.[19] Widespread support for test ban treaties has ended almost all nuclear testing in the atmosphere.[20]

International catastrophes such as the wreck of the Amoco Cadiz oil tanker off the coast of Brittany in 1978 and the Bhopal disaster in 1984 have demonstrated the universality of such events and the scale on which efforts to address them needed to engage. The borderless nature of atmosphere and oceans inevitably resulted in the implication of pollution on a planetary level with the issue of global warming. Most recently the term persistent organic pollutant (POP) has come to describe a group of chemicals such as PBDEs and PFCs among others. Though their effects remain somewhat less well understood owing to a lack of experimental data, they have been detected in various ecological habitats far removed from industrial activity such as the Arctic, demonstrating diffusion and bioaccumulation after only a relatively brief period of widespread use.

A much more recently discovered problem is the Great Pacific Garbage Patch, a huge concentration of plastics, chemical sludge and other debris which has been collected into a large area of the Pacific Ocean by the North Pacific Gyre. This is a less well known pollution problem than the others described above, but nonetheless has multiple and serious consequences such as increasing wildlife mortality, the spread of invasive species and human ingestion of toxic chemicals. Organizations such as 5 Gyres have researched the pollution and, along with artists like Marina DeBris, are working toward publicizing the issue.

Pollution introduced by light at night is becoming a global problem, more severe in urban centres, but nonetheless contaminating also large territories, far away from towns.[21]

Growing evidence of local and global pollution and an increasingly informed public over time have given rise to environmentalism and the environmental movement, which generally seek to limit human impact on the environment.

Forms of pollution

The major forms of pollution are listed below along with the particular contaminant relevant to each of them:

  • Light pollution: includes light trespass, over-illumination and astronomical interference.
  • Littering: the criminal throwing of inappropriate man-made objects, unremoved, onto public and private properties.
  • Noise pollution: which encompasses roadway noise, aircraft noise, industrial noise as well as high-intensity sonar.
  • Soil contamination occurs when chemicals are released by spill or underground leakage. Among the most significant soil contaminants are hydrocarbons, heavy metals, MTBE,[22]herbicides, pesticides and chlorinated hydrocarbons.
  • Radioactive contamination, resulting from 20th century activities in atomic physics, such as nuclear power generation and nuclear weapons research, manufacture and deployment. (See alpha emitters and actinides in the environment.)
  • Thermal pollution, is a temperature change in natural water bodies caused by human influence, such as use of water as coolant in a power plant.
  • Visual pollution, which can refer to the presence of overhead power lines, motorway billboards, scarred landforms (as from strip mining), open storage of trash, municipal solid waste or space debris.
  • Water pollution, by the discharge of wastewater from commercial and industrial waste (intentionally or through spills) into surface waters; discharges of untreated domestic sewage, and chemical contaminants, such as chlorine, from treated sewage; release of waste and contaminants into surface runoff flowing to surface waters (including urban runoff and agricultural runoff, which may contain chemical fertilizers and pesticides); waste disposal and leaching into groundwater; eutrophication and littering.
  • Plastic pollution: involves the accumulation of plastic products in the environment that adversely affects wildlife, wildlife habitat, or humans.


Main article: Pollutant

A pollutant is a waste material that pollutes air, water or soil. Three factors determine the severity of a pollutant: its chemical nature, the concentration and the persistence.

Cost of pollution

Pollution has cost.[23][24][25] Manufacturing activities that cause air pollution impose health and clean-up costs on the whole of society, whereas the neighbors of an individual who chooses to fire-proof his home may benefit from a reduced risk of a fire spreading to their own homes. A manufacturing activity that causes air pollution is an example of a negative externality in production. A negative externality in production occurs “when a firm’s production reduces the well-being of others who are not compensated by the firm."[26] For example, if a laundry firm exists near a polluting steel manufacturing firm, there will be increased costs for the laundry firm because of the dirt and smoke produced by the steel manufacturing firm.[27] If external costs exist, such as those created by pollution, the manufacturer will choose to produce more of the product than would be produced if the manufacturer were required to pay all associated environmental costs. Because responsibility or consequence for self-directed action lies partly outside the self, an element of externalization is involved. If there are external benefits, such as in public safety, less of the good may be produced than would be the case if the producer were to receive payment for the external benefits to others. However, goods and services that involve negative externalities in production, such as those that produce pollution, tend to be over-produced and underpriced since the externality is not being priced into the market.[26]

Pollution can also create costs for the firms producing the pollution. Sometimes firms choose, or are forced by regulation, to reduce the amount of pollution that they are producing. The associated costs of doing this are called abatement costs, or marginal abatement costs if measured by each additional unit.[28] In 2005 pollution abatement capital expenditures and operating costs in the US amounted to nearly $27 million.[29]

Socially Optimal Level of Pollution

Society derives some indirect utility from pollution, otherwise there would be no incentive to pollute. This utility comes from the consumption of goods and services that create pollution. Therefore, it is important that policymakers attempt to balance these indirect benefits with the costs of pollution in order to achieve an efficient outcome.[30]

It is possible to use environmental economics to determine which level of pollution is deemed the social optimum. For economists, pollution is an “external cost and occurs only when one or more individuals suffer a loss of welfare,” however, there exists a socially optimal level of pollution at which welfare is maximized.[31] This is because consumers derive utility from the good or service manufactured, which will outweigh the social cost of pollution until a certain point. At this point the damage of one extra unit of pollution to society, the marginal cost of pollution, is exactly equal to the marginal benefit of consuming one more unit of the good or service.[32]

In markets with pollution, or other negative externalities in production, the free market equilibrium will not account for the costs of pollution on society. If the social costs of pollution are higher than the private costs incurred by the firm, then the true supply curve will be higher. The point at which the social marginal cost and market demand intersect gives the socially optimal level of pollution. At this point, the quantity will be lower and the price will be higher in comparison to the free market equilibrium.[32] Therefore, the free market outcome could be considered a market failure because it “does not maximize efficiency”.[26]

This model can be used as a basis to evaluate different methods of internalizing the externality. Some examples include tariffs, a carbon tax and cap and trade systems.

Sources and causes

Air pollution comes from both natural and human-made (anthropogenic) sources. However, globally human-made pollutants from combustion, construction, mining, agriculture and warfare are increasingly significant in the air pollution equation.[33]

Motor vehicle emissions are one of the leading causes of air pollution.[34][35][36]China, United States, Russia, India[37]Mexico, and Japan are the world leaders in air pollution emissions. Principal stationary pollution sources include chemical plants, coal-fired power plants, oil refineries,[38]petrochemical plants, nuclear waste disposal activity, incinerators, large livestock farms (dairy cows, pigs, poultry, etc.), PVC factories, metals production factories, plastics factories, and other heavy industry. Agricultural air pollution comes from contemporary practices which include clear felling and burning of natural vegetation as well as spraying of pesticides and herbicides[39]

About 400 million metric tons of hazardous wastes are generated each year.[40] The United States alone produces about 250 million metric tons.[41] Americans constitute less than 5% of the world's population, but produce roughly 25% of the world’s CO2,[42] and generate approximately 30% of world’s waste.[43][44] In 2007, China has overtaken the United States as the world's biggest producer of CO2,[45] while still far behind based on per capita pollution - ranked 78th among the world's nations.[46]

In February 2007, a report by the Intergovernmental Panel on Climate Change (IPCC), representing the work of 2,500 scientists, economists, and policymakers from more than 120 countries, said that humans have been the primary cause of global warming since 1950. Humans have ways to cut greenhouse gas emissions and avoid the consequences of global warming, a major climate report concluded. But to change the climate, the transition from fossil fuels like coal and oil needs to occur within decades, according to the final report this year from the UN's Intergovernmental Panel on Climate Change (IPCC).[47]

Some of the more common soil contaminants are chlorinated hydrocarbons (CFH), heavy metals (such as chromium, cadmium–found in rechargeable batteries, and lead–found in lead paint, aviation fuel and still in some countries, gasoline), MTBE, zinc, arsenic and benzene. In 2001 a series of press reports culminating in a book called Fateful Harvest unveiled a widespread practice of recycling industrial byproducts into fertilizer, resulting in the contamination of the soil with various metals. Ordinary municipal landfills are the source of many chemical substances entering the soil environment (and often groundwater), emanating from the wide variety of refuse accepted, especially substances illegally discarded there, or from pre-1970 landfills that may have been subject to little control in the U.S. or EU. There have also been some unusual releases of polychlorinated dibenzodioxins, commonly called dioxins for simplicity, such as TCDD.[48]

Pollution can also be the consequence of a natural disaster. For example, hurricanes often involve water contamination from sewage, and petrochemical spills from ruptured boats or automobiles. Larger scale and environmental damage is not uncommon when coastal oil rigs or refineries are involved. Some sources of pollution, such as nuclear power plants or oil tankers, can produce widespread and potentially hazardous releases when accidents occur.

In the case of noise pollution the dominant source class is the motor vehicle, producing about ninety percent of all unwanted noise worldwide.


Human health

Further information: Soil pollution § Health effects, Toxic hotspots, and List of pollution-related diseases

Adverse air quality can kill many organisms including humans. Ozone pollution can cause respiratory disease, cardiovascular disease, throat inflammation, chest pain, and congestion. Water pollution causes approximately 14,000 deaths per day, mostly due to contamination of drinking water by untreated sewage in developing countries. An estimated 500 million Indians have no access to a proper toilet,[52][53] Over ten million people in India fell ill with waterborne illnesses in 2013, and 1,535 people died, most of them children.[54] Nearly 500 million Chinese lack access to safe drinking water.[55] A 2010 analysis estimated that 1.2 million people died prematurely each year in China because of air pollution.[56] The WHO estimated in 2007 that air pollution causes half a million deaths per year in India.[57] Studies have estimated that the number of people killed annually in the United States could be over 50,000.[58]

Oil spills can cause skin irritations and rashes. Noise pollution induces hearing loss, high blood pressure, stress, and sleep disturbance. Mercury has been linked to developmental deficits in children and neurologic symptoms. Older people are majorly exposed to diseases induced by air pollution. Those with heart or lung disorders are at additional risk. Children and infants are also at serious risk. Lead and other heavy metals have been shown to cause neurological problems. Chemical and radioactive substances can causecancer and as well asbirth defects.

An October 2017 study by the Lancet Commission on Pollution and Health found that global pollution, specifically toxic air, water, soils and workplaces, kill nine million people annually, which is triple the number of deaths caused by AIDS, tuberculosis and malaria combined, and 15 times higher than deaths caused by wars and other forms of human violence.[59] The study concluded that "pollution is one of the great existential challenges of the Anthropocene era. Pollution endangers the stability of the Earth’s support systems and threatens the continuing survival of human societies."[3]


Pollution has been found to be present widely in the environment. There are a number of effects of this:

Environmental health information

The Toxicology and Environmental Health Information Program (TEHIP)[60] at the United States National Library of Medicine (NLM) maintains a comprehensive toxicology and environmental health web site that includes access to resources produced by TEHIP and by other government agencies and organizations. This web site includes links to databases, bibliographies, tutorials, and other scientific and consumer-oriented resources. TEHIP also is responsible for the Toxicology Data Network (TOXNET)[61] an integrated system of toxicology and environmental health databases that are available free of charge on the web.

TOXMAP is a Geographic Information System (GIS) that is part of TOXNET. TOXMAP uses maps of the United States to help users visually explore data from the United States Environmental Protection Agency's (EPA) Toxics Release Inventory and Superfund Basic Research Programs.

Worker productivity

A number of studies show that pollution has an adverse effect on the productivity of both indoor and outdoor workers.[62][63][64]

Regulation and monitoring

Main article: Regulation and monitoring of pollution

To protect the environment from the adverse effects of pollution, many nations worldwide have enacted legislation to regulate various types of pollution as well as to mitigate the adverse effects of pollution.

Pollution control

Pollution control is a term used in environmental management. It means the control of emissions and effluents into air, water or soil. Without pollution control, the waste products from overconsumption, heating, agriculture, mining, manufacturing, transportation and other human activities, whether they accumulate or disperse, will degrade the environment. In the hierarchy of controls, pollution prevention and waste minimization are more desirable than pollution control. In the field of land development, low impact development is a similar technique for the prevention of urban runoff.


Pollution control devices


The earliest precursor of pollution generated by life forms would have been a natural function of their existence. The attendant consequences on viability and population levels fell within the sphere of natural selection. These would have included the demise of a population locally or ultimately, species extinction. Processes that were untenable would have resulted in a new balance brought about by changes and adaptations. At the extremes, for any form of life, consideration of pollution is superseded by that of survival.

For humankind, the factor of technology is a distinguishing and critical consideration, both as an enabler and an additional source of byproducts. Short of survival, human concerns include the range from quality of life to health hazards. Since science holds experimental demonstration to be definitive, modern treatment of toxicity or environmental harm involves defining a level at which an effect is observable. Common examples of fields where practical measurement is crucial include automobile emissions control, industrial exposure (e.g. Occupational Safety and Health Administration (OSHA) PELs), toxicology (e.g. LD50), and medicine (e.g. medication and radiation doses).

"The solution to pollution is dilution", is a dictum which summarizes a traditional approach to pollution management whereby sufficiently diluted pollution is not harmful.[66][67] It is well-suited to some other modern, locally scoped applications such as laboratory safety procedure and hazardous material release emergency management. But it assumes that the dilutant is in virtually unlimited supply for the application or that resulting dilutions are acceptable in all cases.

Such simple treatment for environmental pollution on a wider scale might have had greater merit in earlier centuries when physical survival was often the highest imperative, human population and densities were lower, technologies were simpler and their byproducts more benign. But these are often no longer the case. Furthermore, advances have enabled measurement of concentrations not possible before. The use of statistical methods in evaluating outcomes has given currency to the principle of probable harm in cases where assessment is warranted but resorting to deterministic models is impractical or infeasible. In addition, consideration of the environment beyond direct impact on human beings has gained prominence.

Yet in the absence of a superseding principle, this older approach predominates practices throughout the world. It is the basis by which to gauge concentrations of effluent for legal release, exceeding which penalties are assessed or restrictions applied. One such superseding principle is contained in modern hazardous waste laws in developed countries, as the process of diluting hazardous waste to make it non-hazardous is usually a regulated treatment process.[68] Migration from pollution dilution to elimination in many cases can be confronted by challenging economical and technological barriers.

Greenhouse gases and global warming

Main article: Global warming

Carbon dioxide, while vital for photosynthesis, is sometimes referred to as pollution, because raised levels of the gas in the atmosphere are affecting the Earth's climate. Disruption of the environment can also highlight the connection between areas of pollution that would normally be classified separately, such as those of water and air. Recent studies have investigated the potential for long-term rising levels of atmospheric carbon dioxide to cause slight but critical increases in the acidity of ocean waters, and the possible effects of this on marine ecosystems.

Most polluting industries

The Pure Earth, an international non-for-profit organization dedicated to eliminating life-threatening pollution in the developing world, issues an annual list of some of the world's most polluting industries.[71]

World’s worst polluted places

The Pure Earth issues an annual list of some of the world's worst polluted places.[72]

  • Agbogbloshie, Ghana
  • Chernobyl*, Ukraine
  • Citarum River, Indonesia
  • Dzershinsk*, Russia
  • Hazaribagh, Bangladesh
  • Kabwe*, Zambia
  • Kalimantan, Indonesia
  • Matanza Riachuelo, Argentina
  • Niger River Delta, Nigeria
  • Norilsk*, Russia

See also


  1. ^"Pollution - Definition from the Merriam-Webster Online Dictionary". Merriam-webster.com. 2010-08-13. Retrieved 2010-08-26. 
  2. ^Beil, Laura (15 November 2017). "Pollution killed 9 million people in 2015". Sciencenews.org. Retrieved 1 December 2017. 
  3. ^ abCarrington, Damian (October 20, 2017). "Global pollution kills 9m a year and threatens 'survival of human societies'". The Guardian. Retrieved October 20, 2017. 
  4. ^Spengler, John D.; Sexton, K. A. (1983). "Indoor Air Pollution: A Public Health Perspective". Science. 221 (4605): 9–17 [p. 9]. doi:10.1126/science.6857273. 
  5. ^Hong, Sungmin; et al. (1996). "History of Ancient Copper Smelting Pollution During Roman and Medieval Times Recorded in Greenland Ice". Science. 272 (5259): 246–249 [p. 248]. doi:10.1126/science.272.5259.246. 
  6. ^David Urbinato (Summer 1994). "London's Historic "Pea-Soupers"". United States Environmental Protection Agency. Retrieved 2006-08-02. 
  7. ^"Deadly Smog". PBS. 2003-01-17. Retrieved 2006-08-02. 
  8. ^Lee Jackson, Dirty Old London: The Victorian Fight Against Filth (2014)
  9. ^Cited in David Clay Large, Berlin (2000) pp 17-18
  10. ^Hugh Chisholm (1910). The Encyclopædia Britannica: A Dictionary of Arts, Sciences, Literature and General Information. Encyclopædia Britannica, 11th edition. p. 786. 
  11. ^Patrick Allitt, A Climate of Crisis: America in the Age of Environmentalism (2014) p 206
  12. ^Jeffry M. Diefendorf; Kurkpatrick Dorsey (2009). City, Country, Empire: Landscapes in Environmental History. University of Pittsburgh Press. pp. 44–49. 
  13. ^Fleming, James R.; Knorr, Bethany R. "History of the Clean Air Act". American Meteorological Society. Retrieved 2006-02-14. 
  14. ^Patrick Allitt, A Climate of Crisis: America in the Age of Environmentalism (2014) pp 15-21
  15. ^1952: London fog clears after days of chaos (BBC News)
  16. ^John Tarantino. "Environmental Issues". The Environmental Blog. Archived from the original on 2012-01-11. Retrieved 2011-12-10. 
  17. ^Judith A. Layzer, "Love Canal: hazardous waste and politics of fear" in Layzer, The Environmental Case (CQ Press, 2012) pp: 56-82.
  18. ^Lenssen, "Nuclear Waste: The Problem that Won't Go Away", Worldwatch Institute, Washington, D.C., 1991: 15.
  19. ^Friedman, Sharon M. (2011). "Three Mile Island, Chernobyl, and Fukushima: An analysis of traditional and new media coverage of nuclear accidents and radiation". Bulletin of the atomic scientists. 67 (5): 55–65. doi:10.1177/0096340211421587.
Air pollution in the US, 1973
Blue drain and yellow fish symbol used by the UK Environment Agency to raise awareness of the ecological impacts of contaminating surface drainage.
A visual comparison of the free market and socially optimal outcomes.
Air pollution produced by ships may alter clouds, affecting global temperatures.
An industrial area, with a power plant, south of Yangzhou's downtown, China
Overview of main health effects on humans from some common types of pollution.[49][50][51]
A Mobile Pollution Check Vehicle in India.
Historical and projected CO2 emissions by country (as of 2005).
Source: Energy Information Administration.[69][70]

Environmental Pollution: Pollutants Types, Agents, Classification, General Effects!

In order to meet the basic needs of increased population, the present society has undertaken a series of steps like rapid indus­trialisation, unplanned urbanization, deforestation, over exploi­tation of natural resources etc.

These processes are releasing a variety of extraneous materials and energy into environment in a continuous and uninterrupted manner. Such a disposal which becomes greater than the threshold concentration of a particular substance renders the environment partially or fully unfavour­able for the living world.

This is referred as environmental Pollution. The term pollution is derived from the Latin word Pollutioneum which means to defile or make dirty. The term Pollution has been defined in various ways by various scientists and organisations.

According to U.S. President’s Science Advisory Committee (1966):

“Environmental pollution may be defined as the unfavourable alterations of our surroundings wholly or largely as a byproduct of man’s action through direct or indirect effects of change in energy pattern, radiation levels, chemical and physi­cal constitution and abundance of the organisms”.

According to national Academy of Science, USA (1966), pollution may be de­fined as, “an undesirable change in physical, chemical and bio­logical characteristics of water, air and soil that may harmfully affect human, animal and plant life, industrial progress, living con­ditions and cultural assets.”

According to Odum (1971), “Pollu­tion is an undesirable change in physical, chemical and biologi­cal characteristics of air, water and soil that may harmfully affect the life or create a potential health hazard for living organisms”.

According to Edward (1972) “Pollution is the release of harmful substances or energy into the environment by man in quantities that damage health and resources”. According to tiasmann (1975) “Pollution is the accumulation of substances in the environment or at rates of flow which exceed the capacity of the eco-system to either neutralise or disperse them to harmful levels”.

According to national Environmental Research Council (1976), “Pollution is viewed as the release of substances and energy as waste prod­ucts of human activities which result in harmful changes within the natural environment”.

According to Kudesia, “Pollution is de­fined as the addition of extraneous materials (inorganic, organic, biological or radiological) to water, air or land which adversely affects the natural quality of environment. Pollution is thus, di­rect or indirect change in any component of the environment which is harmful to the living organisms and in particular undesirable for man.

Sometimes, instead of pollution another term “contamina­tion” is used by some scientists. Contamination means the pres­ence of harmful substances or organisms in air, water or soil which may cause diseases or discomfort to the human being. However, the polluted materials need not necessarily be contaminated.


A pollutant may be defined as, “anything, living or non-living or any physical agent (e.g. heat, sound etc.), that in its excess makes any part of the environment undesirable. The polluted water is undesirable for drinking, recreation, visual enjoyment or as an habitat for the aquatic life normal to it.

The polluted air is undesirable for breathing, for the condition of buildings and monuments exposed to it or for animal and plant life. The pol­luted soil and land undesirable for raising food and fodder for animals or for recreation and aesthetic enjoyments”.

In other words, Pollutant may be defined as “constituent in the wrong amount at the wrong place or at the wrong time.” According to the Indian Environment (Protection) Act, 1986, “A pollutant has been defined as any solid, liquid or gaseous substance present in such concentration as may be or tend to be injurious to the environment”.

Commonly speaking, the term pollutant is applied to non-living , man-made substances and other nuisances and it refers to their being in excess in a particular location. For exam­ple, nitrogen, phosphorous and potassium are extensively used in agriculture to increase crop yield but sometimes, these in higher concentration cause pollution in lakes and rivers promoting algal growth. This adverse effect of pollution is more severe when the pollutants are man-made rather than natural preparation.

In short, the unserviceable or residues of things which the humanity manufactures, uses and throws away, can also be regarded as pollutants.

Types of Pollutants:

In terms of eco-system, the pollutants can be classified into two basic groups:

(a) Non-degradable Pollutants:

These are not broken down the natural processes like action of microbes. Most of these Mutants get accumulated in the environment and also get bio­logically magnified as these move along the food chains in an under composed state. These may also react with other com­pounds in the environment to produce toxins.

These can be fur­ther subdivided into two more classes:

(i) Waste:

e.g. glass, plastic, phenolic, aluminum cans etc.

(ii) Poisons:

e.g. radio-active substances, pesticides, smog gases, heavy metals like mercury, lead and their salts.

(b) Degradable pollutants or Bio-degradable Pollutants (Odum 1971):

These are natural organic substances which can be decomposed, removed or consumed and thus, reduced to acceptable levels either by natural processes like biological or microbial action or by some engineered systems, like sewage treat­ment plants.

The degradable pollutants can be further sub-divided into two categories:

(i) Rapidly degradable or non-persistent pollutant:

The degradation of these pollutants is very faster process. For example, the decomposition of sewage and wastes of animals and plants is a faster process. The domestic sewage can be rapidly decomposed by natural processes. However, the problems become complicated when the input into environment get exceeded of the decomposi­tion or dispersal capacity.

(ii) Slowly degradable or persistent pollutant:

The degra­dation of these pollutants is a very slower process. It seems as if the amount of pollutant remains unchanged with time. For example, degradation of synthetic com­pounds and radio-active elements like Iodine 137, Stron­tium 90 or Plutonium 239 takes a longer period of time.

Agents Causing Pollution:

Depending upon the nature of the pollutants and their inter­action with environment process, the pollution caused by differ­ent agents can be classified into the following categories:

(a) Pollution caused by solid wastes.

(b) Pollution caused by liquid wastes.

(c) Pollution caused by gaseous wastes.

(d) Pollution caused by wastes without weights.

(a) Pollution caused by Solid wastes:

The solid wastes in­cludes the pollutants like garbage, rubbish, ashes, large wastes formed due to demolition and construction processes, dead ani­mals wastes, agricultural wastes etc. Prom the above examples, it is clear that the solid wastes may be domestic and industrial in nature.

(b) Pollution caused by liquid wastes:

Oxygen cycle is nicely operated in aquatic system maintaining ecological balance. That is, the dissolved oxygen is used by aquatic living organisms for their respiration and in return, these liberate carbon dioxide. Car­bon dioxide molecules are again used by green plants and algae in the process of photosynthesis.

During photosynthesis, oxygen is again liberated to water which remains in dissolved state. How­ever, if some organic matter (food for bacteria) enters the water course, then bacteria oxidise these materials consuming oxygen from water. At such a condition, if the process of re oxygenation is slower than the process of de-oxygenation, then the river will be devoid of life sustaining dissolved oxygen and aquatic living or­ganisms will die.

The most important source of organic pollutants is sewage which contains faecal matter, urine, kitchen washing and oil wash­ings. Sewage also contains a large number of pathogenic and harmless bacteria. The strength of organic waste material of sew­age is measured in terms of bio-chemical oxygen demand (B.O.D).

The value is expressed in terms of mg. of oxygen per litre of waste for 5 days at 20C. If the volume of B.O.D. is below 1500 mg per litre, the sewage is termed as weak waste, if it is 4000 mg per litre it is medium and above this value it is termed as strong Waste.

However, if liquid industrial wastes containing acids, alka­lis and poisonous substances enter the river, the aquatic life is affected and self-purification system of water is impaired. Pesticides and herbicides which enter water may Kill some organisms or accumulate in fishes which, when consumed by man, pass on the chemicals giving rise to cumulative poisoning.

(c) Pollution caused by Gaseous Wastes:

The gaseous wastes include Carbon monoxide (CO), Sulphur dioxide (SO2), nitrogen dioxide (NO2), Ozone (O3) and smog gases (composed of a com­plex mixture of photochemical oxidation products of hydrocar­bons). These gases are more abundant in the atmosphere of in­dustrial cities.

(d) Pollution from Waste without weight:

This type of pollu­tion is also known as pollution by energy waste; Wastes without weight may be of the following types:

(i) Radio-active

(ii) Heat

(iii) Noise

(i) Radio-active Substance:

Despite of all possible precau­tions in the functioning and maintenance of nuclear reac­tors, it is seen that minute quantity of radio-active waste escapes out into the environment. From the mining opera­tion of the uranium to the use and final disposal of wastes from the reactor, radio-active materials continuously escape out into the environment. Besides, a lot of radio-active wastes enter into environment during the nuclear tests.

(ii) Heat:

A large quantity of waste heat energy is dissipated into environment by the way of hot liquid streams or hot gases released by industries and automobiles.

(iii) Fioise:

The unwanted sound is known as noise. This sources of noise for the general public are the machines in the in­dustry, traffic noise, indiscriminate use of transistor, radios, public address systems, etc.

Classification of Pollution:

Pollution can be classified according to the environment (air, water, and soil) in which it occurs or according to the type of pol­lutant (lead, mercury, carbon dioxide, solid waste, noise, biocide, heat, etc.) by which pollution is caused.

Sometimes, pollution is made to classify into two broad cat­egories:

1. Natural Pollution:

It originates from the natural process.

2. Artificial Pollution:

It originates artificially by the interac­tion in between humanity and environment.

Different types of pollutions are as follows:

1. Air pollution

2. Water pollution

3. Terrestrial pollution

4. Noise pollution

5. Radiation pollution

6. Thermal pollution

7. Industrial pollution

General Effects of Pollution:

Each and every component of environment is influenced by pollution in a number of ways.

The impact of pollution on some biotic and abiotic components may be discussed as below:

(i) Effect on Plants:

Photo-chemical smog’s, sulphur-dioxide (obtained from copper and lead smelter) and hydrogen fluo­ride (obtained from fertiliser manufacturing and aluminum reduction) cause injury to the plants and thereby reduce their growth and vegetation.

In some cases, even when pol­lution levels have been not high enough to produce notice­able injury, the retardation in growth rate may occur. On the whole, the pollutants (air or water pollutant or radiation) bring about complex changes in the plant eco-system, hav­ing effects on one species leading to effects on the other.

(ii) Effect on Animals:

Air pollutants cause eye and respiratory irritation in animals as well as in human beings. Water pol­lutants can endanger aquatic life killing millions of fishes and other animals every year. Sewage, toxic chemicals and diseased animals can make water unfit for use by farm ani­mals.

There are some types of pollutions known to have adverse effects on animals at levels that do not appear to affect human health. Thermal pollution in rivers and lakes can kill fishes. Pesticide levels can reduce reproduction rates through mechanisms like interference in calcium metabo­lism.

(iii) Effect on Human Beings:

Human beings are probably the most concerned about the direct and indirect effects of pol­lution. Sufficiently high levels of pollutants are toxic or even lethal to every human being, although there is a wide range of sensitivities among the human population.

For example, tartar emetic (antimony potassium tartrate) can be lethal at doses as low as 130 mg but some persons have survived doses as high as 15 gm. On the other hand, sufficiently low doses appear to have no toxicological effects.

It is seen that many diseases are water borne and can be checked through the purification of municipal and individual water supplies. Still, the drinking water of most of the world’s population is considerably less safe than that of the devel­oped nations due to inadequacies in public health pro­grammes.

(iv) Effect on materials:

Pollutants can cause deterioration of materials and constructions. Air pollutants like SO2 and H2S04 gas can corrode metals and building materials increasing the frequency of repair and replacement. Water pollutants, like suspended particles or dissolved inorganic compounds can also adversely affect pumps, industrial equipment’s and bridges. The supersonic aircrafts capable of producing sonic booms with pressures of over 100 M/m2, even its noise, can damage buildings and break windows.

(v) Synergism and Antagonism:

Multiple exposure of pollut­ants within or in between classes, may include synergistic or antagonistic biological effects. In many cases, the com­bined effects of two or more pollutants are more severe or even qualitatively different from the individual effects of sepa­rate pollutants. Such a phenomenon is known as synergism. For example, the toxicity of sulphur dioxide can be further increased in the presence of aerosol of soluble salts of ferrous (Iron), manganese and vanadium.

Such an increase in toxicity is known as potentiation. In some cases, the com­bined effects of two pollutants is less rather than more se­vere, and this situation is referred to as antagonism.

For example, the cyanides in industrial wastes are quite poi­sonous to aquatic life and in presence of zinc or cadmium these are extremely poisonous (a synergetic effect) appar­ently, due to the formation of complexes. However, in pres­ence of nickel, a nickel-cyanide complex is formed whose toxicity is comparatively low.

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