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Natural Resources

Tutormate > CBSE Syllabus-Class 9th Biology > Natural Resources

4 Air, Water and Soil Pollution

  • Harmful substances like carbon dioxide, carbon monoxide and nitrogen dioxide are usually present in the air in small quantities. Such low concentrations are not harmful to us.
  • Pollution is the presence of unusually high concentrations of harmful substances in the environment.
  • The most common pollution causing health hazard today are the air, water and soil pollution.
  • The pollutants that are responsible for pollution and can be harmful to the health of living organisms are present in quantities more than the amount they can tolerate.
  • Such case of high concentration of pollutants is known as pollution.
  • Pollutant is any substance that is unwanted or harmful and harms the environment.


Presence of undesired substances like oxides of nitrogen and sulphur, suspended particles like unburnt carbon particles and hydrocarbons in increased quantity in the air is called air pollution. Gases that cause air pollution are sulphur dioxide, nitrogen oxides, carbon monoxide, hydrogen sulphide, hydrogen cyanides.
Air pollution could be categorized two types:

  • Natural (e.g., forest fire, dust storm, pollen);
  • Human made (e.g., burning of fossil fuels in homes, industries, vehicles and power plants)

Effects of air pollution:

On human beings:

  • Pollutant gases cause irritation in eyes, throat and lungs. They injure lungs, liver, kidneys, spleen and nervous system. Heart related diseases tend to increase. Many people develop terminal aliments such as cancer.
  • SPM (Suspended Particulate Matter) causes asthma, bronchitis and allergic cold.

On Plants:

  • Many injurious effects such as falling of leaves, reduced growth, degeneration of chlorophyll, mottling of leaves, etc., have been noticed in plants.
  • Lichens are very sensitive to the levels of contaminants, such as sulphur dioxide, present in polluted air.

Acid Rain

  • When fossil fuels such as coal and petroleum products are burnt, they produce oxides of nitrogen and sulphur.
  • On dissolving in rain, these oxides of nitrogen and sulphur form nitric acid and sulphuric acid respectively. This causes acid rain.
  • The acid rainfall severely affects the salmon reproduction and fish yield and also eats into the surface of buildings, eroding the stone (e.g., Taj Mahal) and brick –works.

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