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 Definition: Pollution is defined as the release of toxic or harmful substances into the environment by their natural forces or man and other animals to an extent that causes biological damage to man and his resources. In other words, pollution is the release of harmful substances into the environment, i.e., water, air and land in quantities or to the level that are harmful to man, animals and plants.

The harmful substances that cause pollution in the environment are called pollutants.

There are four main types of pollution. These are

(a)Air pollution

 (b)Noise pollution

 (c) Land pollution

 (d) Water pollution


The major air pollutants, their sources, harmful effects and their control


Air Pollutants Sources Effects
Carbon monoxide


Burning of fuel in cars

other combustion engines

and some industrial processes

It causes suffocation because it combine

with haemoglobin and reduces its ability

to carry oxygen which results in death

Sulphur dioxide



Burning from vehicle’s exhaust,

coal mining and cement factory


It causes impaired health such as the

irritation of eyes, lungs and other respiratory tract diseases. It can cause acid rain.


Nitrogen oxides


 Electrical discharge in air and

Industrial processes


It forms nitric acid with water in air form acid rain which corrodes metallic objects. It irritates the skin and respiratory system.

Smoke and soots



Burning of substances from industries, machines and coal into the air.



Particles can damage lungs and cause discomfort. Soot can cover the leaves of plant thereby reducing photosynthesis. Smoke reduces visibility. It makes buildings black.



Dust particles


Mining, quarries, machines and industrial processes

It irritates respiratory system and cause respiratory diseases such as catarrh and cough.

It reduces visibility. Pollen grains containing dust can affect the lungs resulting in asthma.




Control of Air Pollution


  1. What is environmental pollution?
  2. Mention five sources of air pollution.


Noise pollution

Noise Sources include


Effects of Noise Pollution

or lack of concentration.

Control of Noise


Land Pollutants Sources Effects
(1) Refuse Home, offices, industries and markets (i) It causes offensive odour when the decay.
(2) Sewage Homes and offices (i) It can cause respiratory disorder.

(ii) It results in offensive odour.

(iii) It serves as breeding ground for disease causing organisms.

(3) Metal Scraps Abandoned vehicles and machines (i)            It occupies land space

(ii)           It prevents proper land us.

(4) Pesticides and fertilizes Pesticides sprayed on crops and fertilizers used in soils (i) They destroy useful soil organisms.

(ii). Excess fertilizers can cause soil acidity.

(iii). It can cause the death of aquatic organisms, e.g. fishes

(5) Chemicals, eg. Toxic waste Chemical waste from industries (i) These are poisonous to plants and animals
(6) Glass particles Glass manufacturing or industries using bottles (i) It can cause injury to human skin or body

(ii). It does not decay hence it prevents proper land use.

(7) Crude oil (Oil spillage) Oil drilling, loading or unloading of oil tankers (i) It destroys soil and renders it infertile.

(ii). It destroys plants and animals’ life in water.


  Control of Land Pollution




  1. Mention five common land pollutants.
  2. Suggest ways of controlling the pollutants mentioned


Water Pollutants Sources Effects
(1) Sewage City sewage system (i). It supports the growth of pathogens that can cause diseases, eg. Cholera.

(ii). It make water unfit for human consumption.

(iii). It can kill aquatic organisms.

(iv). It produces unpleasant odours.

(2) Pesticides and Fertilizers Washed by erosion from farms to rivers, streams or ponds (i) It makes water unfit for human consumption.

(ii). It leads to rapid vegetative growth of water plants which makes fishing and movement impossible, eg. Algae bloom.

(iii). It can destroy aquatic organisms, eg. Fish and sea birds.

(3) Chemical Wastes Industries and ships at harbours (i). It can kill aquatic organisms.

(ii). It makes water unfit for human consumption.

(iii). It can accumulate in human body and become toxic later, eg.  Lead and mercury.

(4) Excreta or faeces Humans and animals (i). It produces unpleasant odour

(ii). It serves as a medium for the breeding of pathogens

(5). Crude oil (Oil spillage) Oil drilling, loading and unloading of oil tankers (i) It destroys aquatic plants and animals.

(ii). It makes water unfit for human consumption.

(iii). Food chain is affected.

(iv). It leads to migration of animals.


Control of Water Pollution

(I) There should be efficient and proper sewage disposal system.

(ii) Dumping of refuse or petro-chemical byproducts into rivers, streams or seas should be avoided.

(iii) There should be efficient techniques to deal with or prevent oil spillage.

(iv) Industries should be sited far away from residential areas.

(v) Government or local authorities should strictly monitor all industrial wastes.

(vi) There should be public enlightenment on waste disposal.

(vii) Industrial effluents should be recycled.


Methods of Purifying Water

Methods involved in purifying water include: (i) Boiling (ii) Addition of chemicals, e.g. alum or chlorine (iii) Filtration (iv) Distillation (v) Sterilization using UV light (vi) Boiling (vii) Sedimentation


General Evaluation

  1. Define the term pollution.
  2. State four types of pollution.
  3. Mention three air and noise pollution.
  4. State the effect of air and land pollution.
  5. What is sewage?


Weekend Assignment

  1. The unfavorable alteration of environment due to the addition of impurities is A. pollution B. pollutant C. global warming D.  poisoning
  2. These are causes of water pollution except A. Insects B. Fertilizers C. Sewage D. Petroleum.
  3. Which of the following air pollutant depletes the ozone layer? A. Oxides of sulphur B.  Carbon dioxide C.  Dust D.  Chlorofluorocarbons (CFC)
  4. These are the effects of noise except A. Calmness B. Anxiety C. Short temper D.  High blood pressure.
  5. Which of the following pollutants cause suffocation? A. CO2 B. No2 C. CFC D. sewage.


  1. What are the effects of the following pollution on man? (a) carbon monoxide (b) dust (c) sewage
  2. Highlight five dangers of water pollution.


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