Any undesirable change in the environment due to human activity is pollution. Each activity, human or industrial, discharges some unwanted substances in the environment. The presence of unwanted substances in a concentration which can have an adverse effect on organisms and environment is called pollution.

Although the development and technological growth has given new devices for human comfort it has also added substances that may have adverse effects on life and environment. Thus, an undesirable change in the physical, chemical and biological characteristics of the environment especially air, water and land that may adversely affect human population and the wild life and cultural assets (buildings and monuments) is called pollution.

Depending upon the area or the part of environment affected, pollution may be of the following types:

  1. Air pollution
  2. Water pollution
  3. Land pollution
  4. Noise pollution

Air Pollution

The pollution in air may not be noticed until we see dust or smoke coming out from some source or some foul smell present all around. All human activities from cooking at home to the working of highly mechanized industries contribute to air pollution.

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Water Pollution

The contamination of the water bodies by discharge of pollutants directly or indirectly into them is called water pollution. Water pollution could be due to natural or human activities.

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Fertilizers and pesticides are widely used in agriculture. Their excessive use to increase agricultural yield has led to the phenomenon of eutrophication and biomagnifications, which are serious consequences of water pollution.


With the use of high-yielding varieties of crops, application of fertilizers and pesticides has increased. Excess fertilizers may mix with surface water bodies (surface runoff). The enrichment of water with nutrients such as nitrates and phosphates that triggers the growth of green algae is called eutrophication. This fast growth of algae followed by their decomposition depletes the water body of the dissolved oxygen. As a result, aquatic animals die of oxygen shortage.


Entry of harmful, non-biodegradable chemicals in small concentration and their accumulation in greater concentration in the various levels of a food chain is called biomagnification. Non-biodegradable pesticides, such as DDT are widely used for crop protection. Once they enter the food chain, their concentration keeps on increasing with each trophic level (steps of a food chain). As a result, accumulation of these compounds takes place in the body of top consumers over a period of time.

DDT used in small quantities to kill mosquitoes can enter the food chain and may get concentrated due to its non-biodegradable nature in the body of birds (top consumer). This causes adverse effects, such as weak egg shells, resulting in decreased population.

Control of water pollution

  • Minimise the water by altering the technique involved.
  • Maximum recycling of water after treatment (purification of waste water for reuse).
  • Limiting the quantity of waste water discharge.

Soil Pollution and Land Pollution

Addition of substances that change the quality of soil by making it less fertile and unable to support life is called soil pollution.

Sources of Soil Pollution

  • Domestic sources: plastic bags, kitchen waste, glass bottles and other solid waste.
  • Industrial sources: chemical residue, fly ash, metallic waste
  • Agricultural residues: fertilizers and pesticides

Soil erosion also leads to the degradation of soil due to uprooting of plants and over-grazing.

Noise Pollution

Noise is defined as unwanted sound. It is generally higher in urban and industrial areas than in rural areas. Workers using heavy machinery are exposed to high noise levels for long period of work hours everyday. Intensity of sound is measured in a unit called decibel or dB. The lowest intensity of sound that human ear can hear is 10 dB.

Sources of Noise Pollution

  • Industrial activities
  • Vehicle such as aircraft, trains, automobiles
  • Use of loud speakers and loud music systems at public places
  • Noisy fireworks
  • Increased volume of television

Effects of Noise Pollution

  • Noise pollution can cause serious damage to ears leading to temporary loss of hearing, earache, sometimes even permanent deafness.
  • Noise prevents concentration, increases irritability and causes headache. It may lead to increased blood pressure and irregular heart beat.
  • Ringing of ears (a feeling of sound coming from within the ear in a very quiet environment) is also a result of noise pollution.
  • Noise disturbs sleep and causes slow recovery from sickness.

Preventive Measures and Management

Following steps can be taken to control or minimize noise pollution:

  • Keep the volume of your radio and television low
  • Use automobile horn only in case of emergency
  • Avoid noisy fire crackers
  • Tune and service all machines including automobiles at regular intervals
  • Use of silencers should be mandatory
  • Plant trees, as a green belt around your home is an efficient noise absorber