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CBSESecondary School (English Medium) Class 8
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Syllabus

Environmental Issues - Air Pollution and Its Causes

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Topics

  • Air Pollution
  • Causes of Air Pollution
  • Reasons of Air Pollution
  • Ozone Layer: The Protective Shell

Air Pollution:

"Air pollution occurs when harmful substances like gases, particles, and biological molecules are released into the air, negatively impacting human health and the environment."

Air pollution

All the above pictures show large-scale emission of smoke through different agencies. This smoke directly mixes with the atmosphere, disturbing the balance between the constituents of air. This is called air pollution. 

Harmful Substances Released in Air Through Combustion of Fuels:

  • Nitrogen dioxide
  • Carbon dioxide
  • Carbon monoxide
  • Sulfur dioxide
  • Soot

Causes of Air Pollution:

  • Burning of fossil fuels: Fossil fuel burning releases large amounts of sulphur dioxide into the atmosphere. Carbon monoxide, which results from incomplete combustion, is another significant pollutant that contributes to air pollution.
  • Automobiles: Vehicles like cars, trucks, buses, and jeeps emit gases that pollute the air. These emissions are a major source of greenhouse gases and can lead to various health problems.
  • Agricultural Activities: Ammonia, a hazardous gas, is released during farming. Using insecticides, pesticides, and fertilisers releases harmful chemicals into the atmosphere, further contaminating the air.
  • Factories and Industries: Factories and industries are primary sources of pollutants such as carbon monoxide, organic compounds, hydrocarbons, and other chemicals that degrade air quality.
  • Mining Activities: The extraction of minerals through mining releases dust and chemicals into the air. This pollutes the air and affects the health of workers and residents in nearby areas.
  • Domestic Sources: Household items like cleaning products and paints contain toxic chemicals released into the air. For example, the smell from freshly painted walls is due to these chemicals, which can affect breathing and contribute to air pollution.

Reasons of Air Pollution:

I. Natural Reasons

  1. Volcanic Eruptions: Eruptions release gases and materials like hydrogen sulphide, sulphur dioxide, carbon dioxide, and dust into the air.
  2. Earthquakes: Harmful gases and water vapours escape beneath the earth's surface.
  3. Cyclones & Dust Storms: Dust, soil, and microorganisms get mixed into the air.
  4. Forest Fires: Fires emit carbon dioxide, sulphur dioxide, and smoke.
  5. Microbes: Bacteria and fungi spores are present in the air.

II. Man-made Reasons

  1. Fuel Burning: Burning coal, timber, and fuels releases harmful gases like carbon dioxide, carbon monoxide, and sulphur dioxide into the air.
  2. Waste Burning: Open burning of solid and agricultural waste causes air pollution.
  3. Industrialisation: Factories emit large amounts of smoke and pollutants like nitrogen oxide and sulphur compounds.
  4. Atomic Energy: Using radioactive elements in energy plants and blasts releases dangerous radiation into the air.

Ozone Layer – The Protective Shell:

The ozone layer is a protective layer of gas found in the lower part of the stratosphere, a layer of the Earth's atmosphere.

  • Ozone is made up of three oxygen atoms (O₃). The ozone layer acts like a shield that protects all living things on Earth from harmful ultraviolet (UV) rays from the sun.
  • These UV rays can be dangerous because they can cause skin cancer and eye damage and harm plants and animals.
  • The ozone layer absorbs these harmful rays, preventing them from reaching the Earth's surface. 

Threats to the Ozone Layer:

  • Certain human-made chemicals, like chlorofluorocarbons (CFCs), which are used in air conditioners, refrigerators, and aerosol sprays, can destroy the ozone layer.
  • Another chemical called carbon tetrachloride, often used in cleaning products, can also damage the ozone.
  • When these chemicals are released into the air, they rise up to the stratosphere and break down the ozone molecules. This creates holes or thinner spots in the ozone layer, allowing more UV rays to reach the Earth.
  • To help protect the ozone layer, countries around the world have agreed to stop using harmful chemicals like CFCs. To raise awareness about the importance of the ozone layer, September 16th is celebrated as Ozone Protection Day.
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