Air Pollution Causes and Control of Air Pollution | NCERT Biology Class 12

Air Pollution Causes and Control of Air Pollution
Air Pollution Causes and Control of Air Pollution

Air Pollution Causes and Control of Air Pollution Unit : 10, Chapter – 16

Here we will discuss the topic of ‘Air Pollution Causes and Control of Air Pollution’ for Class 12 based on the pattern of NCERT Class 12 Biology.

Pollution means the introduction of contaminants into the natural environment that cause adverse effects on both living and non-living things. Pollution exists in different forms as chemical substances or energy, like noise, heat or light. Environmental pollution is caused due to the undesirable changes that occur in our surrounding which affect the living organisms to a great extent. The substances, that cause pollution, are known as a pollutant. All these substances may or may not exist already in the environment. If they do exist in the environment, naturally, they do so in a fixed concentration. Whenever concentrations of any of these substances exceed its natural abundance, it becomes a pollutant for the environment. Thus, a pollutant is any substance that is already present in the environment, but due to an increase in its concentration to exceedingly high values, it causes danger to living organisms or the environment. Pollutants can be solid, liquid or gaseous substances that are present in greater concentration than its natural abundance and are produced due to natural or human activities. The threshold limit value (TLV) is a value of a pollutant, which is the permissible limit that can be present in the atmosphere. It is limited to which extent a person is exposed without any adverse effects. TLV can be determined by experimentation on animals, by use of medical knowledge, epidemiology surveys & environmental studies.

Pollutants change the physical and chemical composition of air, water, and soil that becomes unfit for animals and plants. A pollutant may retard the growth rate of plants or animal species or may interfere with human facilities, comfort, and health. Pollutants not only harm the living organisms but also to the property and the environment. For example, acid rain causes harm to marble buildings. Some common pollutants are:

(i) Gases like CO2, SO2, NO2, etc.

(ii) Solid substances like lead, mercury,

(iii) Natural substances like pollen grains,

(vi) Sewage and radioactive substances.

What is Air?

Air is a mixture of certain gases,i.e., 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases. Air also contains a varied amount of water vapour. On average, the water vapours present around and at sea level is 1% and 0.4% over the entire atmosphere.

Air Pollution; Causes of Air Pollution; Control of Air Pollution

Air Pollution

Air pollution means the occurrence of chemicals or compounds (known as pollutants) in the air that destroys the quality of air. The polluted air is harmful to all living things in the atmosphere. Air pollution is majorly caused due to the release of various chemicals into the atmosphere. Air pollution can either be man-made or naturally occurring.

Nowadays, due to continuous industrialisation and modernisation, the biggest source of air pollution is the burning of fossil fuels. For example, when petrol /diesel or coal are burnt to run the vehicles, machines, power plants, etc., there is a release of harmful pollutants into the atmosphere, threatening the survival of all living things around.

There are two major types of air pollutants, gaseous compounds, and compounds in solid form. Some very dangerous pollutants are:

Carbon Monoxide

Sulphur Oxides

Nitrogen Oxides

Carbon Dioxide


Particulate Matter

Radioactive Pollutants

air pollution

Air pollution is caused because of the presence of natural and man-made substances in the air that we breathe.  There are two categories of air pollution: outdoor air pollution and indoor air pollution.

The exposure to pollutants that takes place outside of the built environment is said to be outdoor air pollution. For example:

  • Fine particles that are produced by the burning of fossil fuels (i.e. the coal and petroleum used in energy production) cause a higher level of air pollution.
  • Poisonous gases (sulphur dioxide, nitrogen oxides, carbon monoxide, chemical vapours, etc.)
  • In the Earth’s lower atmosphere, near ground level, ozone is formed when pollutants emitted by cars, power plants, industrial boilers, refineries, chemical plants, and other sources react chemically in the presence of sunlight. This is known as Ground-level ozone which is a harmful air pollutant.
  • Tobacco Smoke

Indoor air pollution occurs due to the exposure to particulates, carbon oxides, and other pollutants present in the indoor air or dust. This includes:

  • Gases like, carbon monoxide, radon, etc.
  • Household products and chemicals
  • Building materials such as asbestos, formaldehyde, lead, etc.
  • Indoor allergens (cockroach and mouse dropping, etc.)
  • Tobacco smoke
  • Mold and pollens

Most of the time, the outdoor air pollutants can make its way inside the buildings by means of open windows, doors, ventilation, etc.

Causes of Air Pollution

  • Air pollution can be caused by both man-made and natural reasons, though the contribution by natural factors is quite negligible.
  • The main culprit of air pollution is human activities. The single most harmful source of air pollution is the unimpeded burning of fossil fuels by mankind. Fossil fuels also are known as non-renewable sources of energy like crude oil, petrol, diesel, coal, etc. are used in almost every process of industrialization, manufacturing, transport and energy generation.
  • In rural areas, a major source of pollution is the burning of crops. In modern agriculture practices, this is actually a useful tool in farming. The uncontrolled crop burning causes significant air pollution.
  • Another source of air pollution which is also a human activity is military resources such as nuclear arsenal and chemical weaponry.
  • Some contribution is given by natural sources also such as forest fires, volcanic activity and methane discharged from cattle. No doubt, the amount of air pollution caused by natural causes is minute when compared to the damage done by man-made causes.

Consequences of Air Pollution

  • Ozone Depletion: The Ozone layer is a belt of natural gases in the stratosphere layer of the atmosphere, that envelope the planet. It protects us from harmful ultraviolet B radiation that is emitted by the sun. The pollutants in the atmosphere can seriously damage the ozone layer. Many holes have appeared in this layer over the last few decades. The ozone layer above Antarctica is particularly facing very serious damage. When the ozone layer is depleted the harmful ultraviolet radiation reaches the surface of the earth and causes skin cancer and eye damage among humans.
  • Smog: Smog is a deadly combination of smoke and fog. It caused when the pollutants in the air, such as carbon particles, condense and mix with the fog. Smog is extremely harmful to humans and the whole environment. It can lead to diseases such as cold, flu, irritation in the eyes, asthma and even lung cancer in the long-term exposure.
  • Acid Rain: Acid Rain is caused when a chemical reaction occurs between air pollutants and water in the atmosphere. Pollutants such as sulphur dioxide and nitrogen oxide are water-soluble and mix with the water for their respective acids in the atmosphere and then precipitate as acid rain. The acidic nature of this rain causes severe damage to the plants, animals, soil and even to the buildings.

Control of Air Pollution

  • Use of Energy efficient appliances: Both at the domestic level and at the industrial level, there is an urgent need for appliances that use energy efficiently, which results in incomplete combustion of fuel, because incomplete combustion causes air pollution.
  • Shifting industries: Another possible solution to reduce the harmful effects of air pollution is to shift the manufacturing plants, factories, and industries to remote areas where there is a low level of population. By doing so, the pollution in urban areas decreases over time.
  • Use of Modern Techniques: With the great advancement in technology, there are many technologies available now, that can help reduce the release of pollutants in the air. Examples of some technologies involve Air filters, scrubbers, precipitators, etc.
  • Shifting to Natural Gases: Instead of using fossil fuels, smokeless fuels should be used in homes and industries. We can switch over to CNG (compressed natural gas) instead of petrol or diesel in the vehicles. This would prove to be a greener and cleaner option in reducing air pollution.
  • Tall chimneys should be installed in factories.
  • Renewable and non-polluting sources of energy like solar energy, wind energy, etc should be used.
  • It is very essential to maintain the automobiles properly and stick to emission control standards.
  • One of the most essential and very cheap methods is planting more and more trees along roadsides and houses.

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Read another Class 12 Biology notes on Carbon Fixation By Chemoautotrophs

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November 22, 2019

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