Air Pollutants

Air pollution refers to any physical, chemical, or biological change in the air. It is the contamination of air by harmful gases, dust, and smoke which affects plants, animals, and humans drastically.

There is a certain percentage of gases present in the atmosphere. An increase or decrease in the composition of these gases is harmful to survival. This imbalance in the gaseous composition has increased Earth’s temperature which is known as global warming.

Environment-related topics are crucial for the UPSC Syllabus. Sections of Geography in general-studies paper-1, Science &Technology and Environment & Ecology of general-studies paper-3 are scoring topics for IAS Exam.

The topic, ‘Air Pollutants’ is important from the Environment and Ecology subject’s perspective. Similarly, there are other related topics that once can refer to for UPSC 2022 preparation:

  1. Stubble Burning
  2. Environment Conventions and Protocols
  3. Vienna Convention for Ozone Protection
  4. Greenhouse Gases
  5. Kyoto Protocol

Air Pollution

Air pollution is defined as the introduction of pollutants, organic molecules, or other unsafe materials into Earth’s atmosphere. This can be in the form of excessive gases like carbon dioxide and other vapours that cannot be effectively removed through natural cycles, such as the carbon cycle or the nitrogen cycle.

What are Air Pollutants?

Pollutants are the substances which cause pollution; air pollution is caused by air pollutants.

Types of Air Pollutants

Primary Pollutants Secondary Pollutants
The pollutants that directly cause air pollution are known as primary pollutants.  The pollutants formed by the intermingling and reaction of primary pollutants are known as secondary pollutants.

Classification of Pollutants

Particulate Pollutants  Gaseous Pollutants
  1. Lead
  2. Fly Ash
  3. Metallic Oxides
  4. Nanoparticles
  1. Carbon monoxide (CO)
  2. Carbon dioxide (CO2)
  3. Chlorofluorocarbons (CFCs)
  4. Ozone (O3)
  5. Nitrogen oxide (NOx)
  6. Sulphur dioxide (SO2)
  • Volatile organic compounds (VOCs)
  • Benzene
  • Ethylene
  • Biological pollutants
  • Asbestos
  • Radon

Particulate Pollutants

The particles that pollute the air by being suspended can be defined as particulate pollutants.

These particles are results of some anthropogenic processes like vehicles, industries, construction sites/activities, etc. or natural sources like pollen, volcanic eruptions, natural gaseous precursors, etc.

  • Their size ranges from 0.001 to 500 micrometers (µm) in diameter.
Heavy Particulate Matter Suspended Particulate Matter Nanoparticulate Matter
  • More than 10 µm
  • Less than 10 µm
  • Less than 0.02 µm
  • Settles down after a point
  • Floats and moves freely with air currents
  • Very light and harmful
  • Form aerosols
  • Particulate pollutants can do vast damage to the human respiratory system.
  • PM 2.5 particles (2.5 µm or less) are declared as one of the most harmful particulate pollutants by the Central Pollution Control Board (CPCB). They are so tiny that they can be detected only with the help of an electron microscope.
  • These fine particulates can be inhaled deep into the lungs and can cause breathing and respiratory problems, irritation, inflammations, and pneumoconiosis (a disease of the lungs caused due to the inhalation of dust. 
    • It is characterized by inflammation, coughing, and fibrosis – excess deposition of fibrous tissue).


  • Lead is one of the most hazardous heavy metals.
  • Lead can cause serious damage to the human body like:
    • Nervous system damage
    • Digestive issues
    • Kidney damage
    • Impacts on intelligence
  • Hence, Lead was banned as an additive to fuels and other products.
  • Lead mixed with water and food can create cumulative poisoning.
  • It has long term effects on children as it lowers intelligence.

Fly Ash

  • Fly Ash is particles of oxides and other heavy metals. The majority of them are aluminum silicate (in large amounts), silicon dioxide (SiO2), and calcium oxide (CaO).
  • Thermal power plants are a major source of Fly Ash pollutants.
  • Its deposition in agricultural fields can cause heavy metal contamination of crops and vegetables. 

The Ministry of Environment and Forests has made it mandatory to use Fly Ash-based products in all construction projects, road embankment works, and low lying landfilling works that are within a 100 km radius of Thermal Power Stations and mine-filling activities within a 50 km radius of Thermal Power Stations.

Nanoparticles (NP)

  • Nanoparticles have diameters less than 100 Nanometers (10-9).
  • NP is responsible for the formation of dust clouds, Ozone depletion, environmental hydroxyl radical concentration, and stratospheric temperature changes.

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Gaseous Pollutants

Gaseous Pollutants Description Impacts
Carbon monoxide (CO)
  • Highly toxic.
  • Produced from internal combustion engines due to incomplete combustion.
  • Other sources are volcanoes, forest fires, etc.
  • Greenhouse gas.
  • Carbon monoxide poisoning.
  • Produces carboxyhemoglobin reducing the oxygen-carrying capacity of the blood.
Carbon dioxide (CO2)
  • Heavier than air.
  • Source are volcanoes, fire, etc.
  • Greenhouse gas.
  • CO2 is an asphyxiant gas (asphyxia: a condition arising when the body is deprived of oxygen, causing unconsciousness or death.).
  • Has other harmful effects if a high concentration of CO2 is inhaled like dizziness, headache, etc.
  • Carbonic rain in high polluted areas.
Chlorofluorocarbons (CFCs)
  • Used in refrigerators, air conditioners, aerosols, etc.
  • Highly destructive to the Ozone layer.
Ozone (O3)
  • Very useful in the Stratosphere but harmful at the ground layer.
  • It’s produced due to industries and vehicles.
  • Greenhouse gas.
  • Has toxic effects.
  • Causes watery and itchy eyes.
Nitrogen oxide (NOx)
  • Various oxides of Nitrogen come under NOX.
  • Caused due to the reaction between oxygen and nitrogen at high temps such as in combustion engines and industries.
  • Aggravates Ashtamatic conditions and other respiratory issues in humans.
  • Plays a major role in the formation of SMOG, acid rain (nitric acid), and the greenhouse effect.
Sulphur dioxide (SO2)
  • Pungent smelling colorless gas produced from mostly volcanic activities, industrial processes, and production of sulphuric acid.
  • Respiratory issues, premature deaths, and death of certain nerves when inhaled.
Volatile Organic Compounds (VOCs)
  • Volatile Organic Compounds (VOCs) are a large group of carbon-based chemicals that easily evaporate at room temperature.
  • Irritations in eyes, skin, nose, and throat.
  • Long-term exposure can cause serious damage to the liver and other organs.
  • Found in petrochemicals and used as a fuel additive
  • Increases cancer risk and a major cause of bone marrow failure.
  • Used in plastic and chemical industries in the production of Polyethylene and other polymers.
  • Excess exposure can cause headaches and dizziness.
  • Ethylene oxide is a carcinogen.
  • Occurs naturally as a fibrous mineral.
  • Prolonged exposure and inhalation can be very harmful and can cause fatal illness.

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Related Links

National Rural Health Mission (NRHM) National Urban Health Mission (NUHM)
Rashtriya Swasthya Bima Yojana (RSBY) UPSC MCQs on Science & Technology
UPSC Calendar 2022 USPC Current Affairs


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