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Environmental Pollution (Part - 1) | Environment for UPSC CSE PDF Download

What is Pollution?

Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take 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.


  • Pollutants are the materials or factors that cause adverse effects on the natural quality of any component of the environment.
  • For example, smoke from industries and automobiles, chemicals from factories, radioactive substances from nuclear plants, sewage of houses, and discarded household articles are the common pollutants.

1. Classifications

➤ According to the form in which they persist after release into the environment.

  • Primary pollutants: These persist in how they are added to the environment, e.g. DDT, plastic. 
  • Secondary Pollutants: These are formed by interaction among the primary pollutants, example, peroxyacetyl nitrate (PAN) is formed by the interaction of nitrogen oxides and hydrocarbons.

➤ According to their existence in nature.

  • Quantitative Pollutants: These occur in nature and become pollutant when their concentration reaches beyond a threshold level. E.g. carbon dioxide, nitrogen oxide. 
  • Qualitative Pollutants: These do not occur in nature and are human-made. E.g. fungicides, herbicides, DDT etc.

➤ According to their nature of disposal.

  • Biodegradable Pollutants: Waste products, which are degraded by microbial action. E.g. sewage. 
  • Non-biodegradable Pollutants: Pollutants, which are not decomposed by microbial action. E.g. plastics, glass, DDT, salts of heavy metals, radioactive substances etc.,)

➤ According to origin

  • Natural 
  • Anthropogenic

What are the Causes of pollution?

  • Uncontrolled growth in the human population
  • Rapid industrialization
  • Urbanization
  • Uncontrolled exploitation of nature.
  • Forest fires, radioactivity, volcanic eruptions, strong winds etc.,

Air Pollution

  • Air pollution is aggravated by increasing traffic, growing cities, rapid economic development, and industrialization.
  • 'The presence in the atmosphere of one or more contaminants in such quality and for such duration as it is injurious, or tends to be injurious, to human health or welfare, animal or plant life.'
  • It is the contamination of air by the discharge of harmful substances.
  • Air pollution can cause health problems, damage the environment, property and climate change.

1. Major air pollutants and their sources Carbon monoxide (CO)

  • It is a colourless, odourless gas produced by the incomplete burning of carbon-based fuels including petrol, diesel, and wood.
  • It is also produced from the combustion of natural and synthetic products such as cigarettes.
  • It lowers the amount of oxygen that enters our blood.
  • It can slow our reflexes and make us confused and sleepy.

➤ Carbon dioxide (CO2)

  • It is the principal greenhouse gas emitted due to human activities such as the burning of coal, oil, and natural gases.

➤ Chlorofluorocarbons (CFC)

  • These are gases that are released mainly from air-conditioning systems and refrigeration. 
  • When released into the air, CFCs rise to the stratosphere, where they come in contact with few other gases, which lead to a reduction of the ozone layer that protects the earth from the harmful ultraviolet rays of the sun.

➤ Lead

  • It is present in petrol, diesel, lead batteries, paints, hair dye products, etc. Lead affects children in particular. 
  • It can cause nervous system damage and digestive problems and, in some cases, cause cancer.

➤ Ozone

  • It occurs naturally in the upper layers of the atmosphere. 
  • This important gas shields the earth from the harmful ultraviolet rays of the sun. 
  • However, at the ground level, it is a pollutant with highly toxic effects. 
  • Vehicles and industries are the major sources of ground-level ozone emissions. 
  • Ozone makes our eyes itch, burn, and water. It lowers our resistance to cold and pneumonia. 
  • Nitrogen oxide (Nox) 
  • It causes smog and acid rain. It is produced from burning fuels including petrol, diesel, and coal. 
  • Nitrogen oxide can make children susceptible to respiratory diseases in winters.

➤ Suspended particulate matter (SPM)

  • It consists of solids in the air in the form of smoke, dust, and vapour that can remain suspended for extended periods and is also the main source of haze, reducing visibility. 
  • The finer of these particles, when breathed in can lodge in our lungs and cause lung damage and respiratory problems.

➤ Sulphur dioxide (SO2)

  • It is a gas produced from burning coal, mainly in thermal power plants. 
  • Some industrial processes, such as the production of paper and smelting of metals, produce sulphur dioxide. 
  • It is a major contributor to smog and acid rain. Sulfur dioxide can lead to lung diseases.

2. Smog

  • The term smog was first used (1905) by Dr H A Des Voeux 
  • Smog has been coined from a combination of the words fog and smoke. Smog is a condition of fog that had soot or smoke in it.

➤ The Formation of Smog

  • Photochemical smog (smog) is a term used to describe air pollution resulting from the interaction of sunlight with certain chemicals in the atmosphere.
  • One of the primary components of photochemical smog is ozone.
  • While ozone in the stratosphere protects the earth from harmful UV radiation, ozone on the ground is hazardous to human health.
  • Ground-level ozone is formed when vehicle emissions containing nitrogen oxides (primarily from vehicle exhaust) and volatile organic compounds (from paints, solvents, printing inks, petroleum products, vehicles, etc.) interact in the presence of sunlight.

Environmental Pollution (Part - 1) | Environment for UPSC CSE

  • Smog refers to hazy air that causes difficult breathing conditions. It is a combination of various gases with water vapour and dust.
  • Its occurrences are often linked to heavy traffic, high temperatures, and calm winds. During the winter, wind speeds are low and cause the smoke and fog to stagnate near the ground; hence pollution levels can increase.
  • Smoke particles trapped in the fog gives it a yellow/ black colour, and this smog often settled over cities for many days.
  • Ground-level ozone is formed through a complex reaction involving hydrocarbons, nitrogen oxides, and sunlight. It is formed when pollutants released from gasoline, diesel-powered vehicles and oil-based solvents react with heat and sunlight.

➤ The effects of smog

  • It hampers visibility and harms the environment. 
  • respiratory problems 
  • deaths relating to bronchial diseases. 
  • Heavy smog greatly decreases ultraviolet radiation. 
  • Heavy smog results in decreased natural vitamin D production, leading to a rise in rickets.

3. Indoor air pollution

  • refers to the physical, chemical, and biological characteristics of air in the indoor environment within a home, or an institution or commercial facility.
  • Indoor air pollution is a concern where energy efficiency improvements sometimes make houses relatively airtight, reducing ventilation and raising pollutant levels.
  • Indoor air problems can be subtle and do not always produce easily recognized health impacts.
  • Different conditions are responsible for indoor air pollution in the rural areas and the urban areas.

➤ Rural

  • The rural areas face the greatest threat from indoor pollution, where people rely on traditional fuels such as firewood, charcoal, and cow dung for cooking and heating.
  • Burning such fuels produces large amounts of smoke and other air pollutants in the home's confined space, resulting in high exposure. Women and children are the groups most vulnerable as they spend more time indoors and are exposed to the smoke.
  • Although many hundreds of separate chemical agents have been identified in the smoke from biofuels, the four most serious pollutants are particulates, carbon monoxide, polycyclic organic matter, and formaldehyde.

➤ Urban

  • In urban areas, exposure to indoor air pollution has increased due to a variety of reasons, such as
  • construction of more tightly sealed buildings,
  • reduced ventilation,
  • the use of synthetic materials for building and furnishing and
  • the use of chemical products, pesticides, and household care products.
  • Indoor air pollution can begin within the building or drawn in from outdoors.
  • Other than nitrogen dioxide, carbon monoxide, and lead, several other pollutants affect the air quality.


➤ Volatile organic compounds

  • The main indoor sources are perfumes, hair sprays, furniture polish, glues, air fresheners, moth repellents, wood preservatives, and other products. 
  • Health effect - irritation of the eye, nose and throat, headaches, nausea, and coordination loss. 
  • long term - suspected to damage the liver and other parts of the body.

➤ Tobacco

  • Smoke generates a wide range of harmful chemicals and is carcinogenic.
  • Health effect - burning eyes, nose, and throat irritation to cancer, bronchitis, severe asthma, and decreased lung function.

➤ Biological pollutants

  • includes pollen from plants, mite, and hair from pets, fungi, parasites, and some bacteria. Most of them are allergens and can cause asthma, hay fever, and other allergic diseases.

➤ Formaldehyde

  • Mainly from carpets, particle boards, and insulation foam. It irritates the eyes and nose and allergies.

➤ Radon

  • It is a gas that is emitted naturally by the soil. Due to modern houses having poor ventilation, it is confined inside the house and causes lung cancers.

Do you know

  • Trees are an important part of our world. They provide wood for building and pulp for making paper. They provide habitats (homes) for all sorts of insects, birds and other animals. Many types of fruits and nuts come from trees - including apples, oranges, walnuts, pears and peaches. Even the sap of trees is useful as food for insects and for making maple syrup - yum! 
  • Trees also help to keep our air clean and our ecosystems healthy. We breathe in oxygen and breathe out carbon dioxide. Trees breathe in carbon dioxide and breathe out oxygen. We're perfect partners! 
  • Trees do lots for us, our environment and other plants and animals, but we don't just love trees for practical reasons.
  • Asbestos 
  • Pesticides

4. Fly Ash

  • Ash is produced whenever combustion of solid material takes place.
  • Fly ash is one such residue which rises with the gases into the atmosphere. Fly ash is an excellent powder and tends to travel far in the air. The ash which does not rise is termed as bottom ash.
  • Nearly 73% of India's total installed power generation capacity is thermal, of which 90% is a coal-based generation, with diesel, wind, gas, and steam making up the rest.

➤ Composition

  • Aluminium silicate (in large amounts)
  • Silicon dioxide (SiO2) and
  • Calcium oxide (CaO).
  • Fly ash particles are oxide rich and consist of silica, alumina, oxides of iron, calcium, and magnesium and toxic heavy metals like lead, arsenic, cobalt, and copper.

➤ How is it collected?

  • Fly ash is generally captured by electrostatic precipitators or other particle filtration equipment before the flue gases reach coal-fired power plants' chimneys.

➤ Environmental effects?

  • If fly ash is not captured and disposed of properly, it can considerably pollute air and water.
  • It causes respiratory problems.
  • Fly ash in the air slowly settles on leaves and crops in areas near thermal power plants and lowers the plant yield. 

➤ Advantages

  • Cement can be replaced by fly ash up to 35%, reducing the cost of construction, making roads, etc.
  • Fly ash bricks are light in weight and offer high strength and durability.
  • Fly ash is a better fill material for road embankments and in concrete roads.
  • Fly ash can be used in the reclamation of wastelands.
  • Abandoned mines can be filled up with fly ash.
  • Fly ash can increase the crop yield, and it also enhances the water holding capacity of the land.

➤ Policy measures of MoEF

  • The Ministry of Environment and Forests vide its notification in 2009, has made it mandatory to use Fly Ash based products in all construction projects, road embankment works and low lying landfilling works within 100 km radius of Thermal Power Station.
  • To use Fly Ash in mine filling activities within 50 km radius of Thermal Power Stations.

5. Effects of air pollution

➤ Health effect

  • Effects on Vegetation
    (i) retard photosynthesis.
    (ii) Sulphur dioxide causes chlorosis, plasmolysis, membrane damage and metabolic inhibition.
    (iii) Hydrocarbons such as ethylene cause premature leaf fall, fruit drop, shedding of floral buds, curling petals, and discolouration of sepals.
    (iv) Ozone damage chlorenchyma and thus destructs the foliage in a large number of plants.
  • Effects on Animals 
  • Deterioration of materials 
  • Aesthetic Loss

6. Control Measures

  • Policy measures 
  • Preventive measures
    (i) Selection of suitable fuel (e.g. fuel with low sulphur content) and efficient utilization.
    (ii) Modifications in industrial processes and/or equipment to reduce emission.
    (iii) Selection of the suitable manufacturing site and zoning. e.g. setting of industries at a distance of residential areas, installation of tall chimneys.

➤ Control measures

  • destroying the pollutants by thermal or catalytic combustion
  • conversion of the pollutants to a less toxic form
  • collection of the pollutant 

➤ Different types of air pollutants can be eliminated/minimized by the following methods

  • Control of particulate matter: Two types of devices - arresters and scrubbers are used to remove particulate pollutants from the air. These are arresters and scrubbers.
    (i) Arresters: These are used to separate particulate matters from contaminated air.
    (ii) Scrubbers: These are used to clean air for both specks of dust and gases by passing it through a dry or wet packing material. 

➤ Control of Gaseous Pollutants

  • The gaseous pollutants can be controlled through the techniques of Combustion, absorption and adsorption.
  • Control of Automobile Exhaust
    (i) use of efficient engines (e.g. multipoint fuel injection engine).
    (ii) Catalytic converter filters in the vehicles can convert nitrogen oxide to nitrogen and reduce NOx's potential hazards.
    (iii) use of good quality automobile fuels
    (iv) use of lead-free petrol.
    (v) Use of compressed natural gas (CNG).

7. Government Initiatives

➤ National Air Quality Monitoring Programme

  • In India, the Central Pollution Control Board (CPCB) has been executing a nationwide programme of ambient air quality monitoring known as National Air Quality Monitoring Programme (NAMP).
  • The National Air Quality Monitoring Programme (NAMP) is undertaken in India
    (i) to determine the status and trends of ambient air quality;
    (ii) to ascertain the compliance of NA AQS;
    (iii) to identify non-attainment cities;
    (iv) to understand the natural process of cleaning in the atmosphere; and
    (v) to undertake preventive and corrective measures.
  • Annual average concentration of SOx levels are within the prescribed National Ambient Air Quality Standards (NAAQS).
  • This reduction from earlier levels is due to various measures taken, including the use of CNG in public transport in Delhi, the reduction of sulphur in diesel, and LPG instead of coal as a domestic fuel.
  • A mixed trend is observed in NO2 levels due to various measures taken for vehicular pollution control, such as stricter vehicular emission norms being partially offset by increased NOx levels due to CNG use in urban transport.
  • Total suspended particulates are still a matter of concern in several urban and semi-urban areas.

➤ National Ambient Air Quality Standards (NAAQS)

  • National Ambient Air Quality Standards (NAAQS) were notified in 1982, duly revised in 1994 based on health criteria and land uses.
  • The NAAQS have been revisited and revised in November 2009 for 12 pollutants, which include
    (i) sulphur dioxide (SO2),
    (ii) nitrogen dioxide (NO2),
    (iii) the particulate matter having a size less than 10 microns (PM10),
    (iv) the particulate matter having a size less than 2.5 microns (PM2.5),
    (v) ozone,
    (vi) lead,
    (vii) carbon monoxide (CO),
    (viii) arsenic,
    (ix) nickel,
    (x) benzene,
    (xi) ammonia, and
    (xii) benzopyrene. 

➤ National Air Quality Index

  • National Air Quality Index was launched by the Prime Minister in April, 2015, starting with 14 cities to disseminate air quality information. The AQI has six air quality categories, viz Good, Satisfactory, Moderately polluted, Poor, Very Poor and Severe with the distinct colour scheme. Each of these categories is associated with likely health impacts. AQI considers eight pollutants (PM10, PM2.5, NO2, SO2, CO, O3, NH3 and Pb) for which (up to 24-hourly averaging period) National Ambient Air Quality Standards are prescribed.

8. Air Pollution in India

  • India's air pollution, ranked among the worst in the world is adversely impacting its citizens' lifespan, reducing most Indian lives by over three years - WHO.
  • Over half of India's population – 660 million people – live in areas where fine particulate matter pollution is above India's standards for what is considered safe - 'Economic & Political Weekly.'
  • Of the world's top 20 polluted cities, 13 are in India. Air pollution slashes life expectancy by 3.2 years for the 660 million Indians who live in cities.
  • 2014 global analysis of how nations tackle environmental challenges has ranked India 155 among 177 nations and labelled the country's air quality among the world's worst.
  • India is placed as the "bottom performer" on several dictators such as environmental health impact, air quality, water and sanitation and India's environmental health severely lag behind the BRICS nations - Environmental Performance Index 2014.
  • The Ganga and Yamuna are ranked among the world's 10 most polluted rivers.
  • Despite the National Green Tribunal's directives, civic agencies continue to allow concretization in green belts. Booming real estate and demand for housing units lead to a change of land use and shrinkage of natural conservation zones such as forests, water bodies, wastelands, sanctuaries, and groundwater rechargeable areas.
  • Mindless concretization of the ground and green belts and booming real estate has led to heat island effect - shortwave radiations emanate from concrete surfaces at night time. Concretisation prevents groundwater recharge, thus depleting green cover. Tall buildings also block winds, thereby reducing their cooling effect. Excessive concretization also leads to weakening of trees.
  • The environmental crisis in India is many-sided and multi-faceted, which has to be addressed on different fronts and various actors. We need to harness scientific and social-scientific expertise to develop and promote eco-friendly technologies in construction, energy, water management, industrial production and transportation. Scientific innovation needs to be complemented by legislative change as well as by changes in social behaviour.

9. Measures to control/ mitigate Delhi Air pollution

  • The city needs an implementation strategy to
  • Reduce traffic and vehicles,
  • Cut dieselization,
  • Scale-up integrated public transport,
  • Facilitate walking and cycling,
  • Tax polluting modes,
  • Decide to implement Bharat Stage IV nationwide in 2015 and
  • Euro VI in 2020 and
  • Put controls on other pollution sources.
The document Environmental Pollution (Part - 1) | Environment for UPSC CSE is a part of the UPSC Course Environment for UPSC CSE.
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FAQs on Environmental Pollution (Part - 1) - Environment for UPSC CSE

1. What is environmental pollution?
Ans. Environmental pollution refers to the contamination of the environment by harmful substances or pollutants. These pollutants can be in the form of solid waste, chemicals, gases, or noise, and they can significantly degrade the quality of air, water, and land.
2. What are the different types of environmental pollution?
Ans. There are various types of environmental pollution, including air pollution, water pollution, soil pollution, noise pollution, and light pollution. Each type has its own causes and impacts, but all contribute to the deterioration of the environment and pose risks to human health.
3. What are the main causes of environmental pollution?
Ans. Environmental pollution is mainly caused by human activities. Some of the primary causes include industrial emissions, vehicle exhaust, improper waste disposal, deforestation, use of chemical fertilizers and pesticides, and excessive energy consumption. These activities release pollutants into the environment, leading to pollution.
4. How does environmental pollution affect human health?
Ans. Environmental pollution can have severe effects on human health. Air pollution can cause respiratory problems, allergies, and cardiovascular diseases. Water pollution can lead to waterborne diseases, while soil pollution can contaminate crops and impact food safety. Noise pollution can cause hearing loss and stress-related disorders. Overall, environmental pollution can pose serious risks to human well-being.
5. What can individuals do to reduce environmental pollution?
Ans. Individuals can play a crucial role in reducing environmental pollution. Some steps that can be taken include conserving energy by turning off lights and appliances when not in use, using public transportation or carpooling, recycling and properly disposing of waste, conserving water, planting trees, and using eco-friendly products. Small actions by individuals collectively make a significant impact on reducing pollution levels.
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