What is Environmental Pollution?

Environmental pollution occurs due to some unwanted alteration in the surroundings which results in unfavorable effects on all organisms of that surrounding.


A pollutant is a substance that causes pollution. Substances turn into pollutants when they are present in higher concentrations than normal. They occur naturally either in solid, liquid, or gas. It is produced either as an outcome of human activities or naturally. They are difficult to decompose when exposed to the environment. Some examples of such pollutants are plastics, harmful chemicals, nuclear wastes from research institutes or industries, dichlorodiphenyltrichloroethane (DDT), etc.

A contaminant is a substance that does not occur naturally but is introduced by human activities into the atmosphere, affecting its composition.


It is caused by natural resources or nature-based activities, for example, volcanic eruptions, methane gas release from the paddy fields, forest fires, etc.

Man-made Pollution

It is the impact of excessive interference of humans in nature, or activities like burning fuel, industrial effluents, excessive use of pesticides and chemicals, deforestation, etc.

Air Pollution

Atmospheric pollution is of two types: Tropospheric or air pollution and stratospheric pollution.

Earth’s atmosphere consists of five regions, i.e., the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. The troposphere is the lowest region – the region where life sustains. Air pollution causes major damage to this region. The stratosphere is the region lying between the troposphere and the mesosphere - the ozone layer is present in this region. Atmospheric pollution occurs when there is a chemical substance (molecule or compound) building up in the air in unwanted proportions cause harmful effects either directly or indirectly to all living and non-living organisms (such as plants, animals, monuments).

Sources of air pollutants

  • Gaseous air pollutants: Hydrocarbons, ozone, hydrogen sulfide, oxides of S, N, and C.
    • Sulfur oxides: Anthropogenic emissions of sulfides are produced when sulfur-containing coal or fossil fuel is burnt. It is also produced during volcanic eruptions. These pollutants of air pollution cause health effects, like respiratory diseases such as asthma, COVID-19, bronchitis, and emphysema in humans. Sulfur dioxide irritates the eyes, resulting in tears and redness of the eyes.
    • Oxides of nitrogen: Combustion (coal or natural gas) releases oxides of nitrogen such as NO2 and NO into the air. Chemical industries, smokes of tobacco, planes, jets, or rockets also emit these gases. When NO2 is taken in by living organisms, it increases risk factors for all. In plants, it slows down the rate of photosynthesis, and in humans, it causes chronic lung conditions which can be fatal. These oxides also destroy the ozone layer.
    • Hydrocarbons: Hydrocarbons are produced by incomplete combustion of automobile fuel from cars, trucks, etc. Hydrocarbons are a threat to public health as they are carcinogenic. They are also harmful to plants as they cause the breakdown of plant tissues and the shedding of plant parts such as their leaves, flowers, and twigs.
    • Oxides of carbon: CO and CO2 are obtained from incomplete combustion of carbonaceous matter, automobile engines, respiration, burning fossil fuels, and decomposition of limestone, volcanic eruptions, and deforestation.
  • Particulate pollutants: These pollutants of air pollution may include dust, mist, fumes, smoke, smog, etc. It impacts the human respiratory system & causes several respiratory illnesses. They are the carriers of the toxic substances from the atmosphere to the human and cause big hazardous to public health. It causes scattering of sunlight and reduces visibility. It also causes corrosion of metals (when the atmosphere is humid), erosion & soiling of buildings, sculptures, painted surfaces, and soiling of clothes.
  • Fine particulate matter (PM 2.5) is an air pollutant that is a concern for people's health when levels in the air are high. PM 2.5 are tiny particles in the air that reduce visibility and cause the air to appear hazy when levels are elevated.

Effects of air pollution

Green House Effect and Global Warming

Green House Effect is a phenomenon in which the environmental atmosphere confines the heat energy deriving from the sun and stops it from getting away into space and radiates it into the surface of the earth. Green house gases are carbon dioxide, methane, ozone, water vapor, chlorofluorocarbon compounds (CFCs) which captivate the heat and radiate back onto the surface of the earth. It leads to warming up of the earth leading to the warming of the air, this process of warming is called global warming. As a result, the temperature of the earth's atmosphere increases. This phenomenon is known as global warming.

Acid Rain

It composes SO2, NO, NO2, and acidic soot. NO2 and CO2, interact with water vapor in the presence of sunlight to form H2SO4 and HNO3 and this is called Acid rain. Discoloration of the Taj Mahal is the result of acid.

Stratospheric Pollution

Stratospheric pollution is the environmental pollution that results in the depletion of the ozone layer. The ozone layer protects the earth from the UV radiation coming from the sun. This UV radiation dissociates the molecular oxygen present in the environmental atmosphere into free oxygen atoms which then, combine with the other molecular oxygen present in the atmosphere to form a new molecule called ozone. The excess heat released from the sun warms up the stratosphere, decomposing the ozone layer.


  • Any development of an ozone hole that would allow UV radiations from the sun to reach the earth causes many health effects; from a small skin burnt to skin cancer or death.
  • It hampers the cornea and the lens of the eye impacting eyesight or even blindness.
  • It affects plants by causing harmful mutation, damage to chlorophyll, and protein production in them.
  • It also affects the climate badly causing climate change.

Water Pollution

It is the contamination of water with unwanted and hazardous substances. Polluted water has characteristics of bad taste, unpleasant odor color, and unchecked growth of weeds, oil, or grease floating on the surface.

The maximum concentration of some metals in drinking water is as

MetalConcentration limit in ppm

Water Pollutants

SedimentsErosion of soil agriculture and mining.
Plant nutrientsChemical fertilizer, pesticides
MicroorganismsDomestic sewage.
Toxic heavy metalschemical Industries
Organic wastesDomestic sewage, animal waste, decayed animals and plants units, and discharge from food processing units.
PesticidesSubstances used for killing insects, fungi, and weeds.
Radioactive substancesUranium minerals.
HeatWater is used for cooling in industries.

Causes of water pollution

  • Pathogens: They are disease-causing mediums, like harmful bacteria and other pathogens. These pathogens enter the water from domestic sewage and animal excreta. These bacteria cause many gastrointestinal diseases.
  • Organic Wastes: Organic matter like leaves, grass, trash, excessive phytoplankton growth within the water. Decomposition of organic matter by bacteria in water causes depletion of dissolved oxygen in the water that is essential for aquatic life, thus causing risk factors for aquatic life.
  • Chemical Pollutants: Inorganic chemicals like cadmium, nickel, mercury, and their water-soluble salt causes harmful health effects in humans. Humans cannot break down these chemicals; hence it hampers our organs such as kidneys, central nervous system, liver, etc. Organic chemicals polluting air may include oil spills in oceans, polychlorinated biphenyls (PCBs).
  • Biochemical Oxygen Demand (BOD): In a sample of water, it is the total number of oxygen molecules by which bacteria deteriorates the organic matter present in that fixed volume of water. If water has a BOD value of less than 5 ppm, such water is said to be clean water whereas a BOD value of 17 ppm or more indicates that the water is highly polluted.
  • Eutrophication: The process in which there is excessive plant & algal growth, whereby gradually increasing the concentration of plant nutrients, phosphorus, and nitrogen in an aquatic ecosystem, which kills aquatic plants and animals life by limiting it of oxygen for breathing or carbon dioxide, sunlight and nutrient fertilizers for photosynthesis and consequently in the loss of biodiversity.

Effects of water pollution

  • Spotted teeth enamel, caused by drinking water containing above 1 mg/L fluoride leads to fluorosis.
  • Sulfates of Na, K, Mg cause diarrhea in humans.
  • Lead, cadmium, and Hg affect human health by damaging the kidney, liver, brain, and central nervous system.
  • Zinc in water leads to dizziness and diarrhea.
  • Arsenic in fertilizers can cause cramps and paralysis.

Control of Water Pollution

  • Reducing the usage of harmful chemicals from industries, or in agriculture, pesticides. Disposing of toxic chemicals and medical waste, oil spills efficiently.
  • Adsorption, ion exchangers, reverse osmosis, electrodialysis, etc.
  • Sewage Treatment.
  • Water management: Separating the water as biodegradable and non-biodegradable waste. Toxic wastes are usually destroyed by controlled incineration. 

Soil Pollution

Soil pollution occurs when there is the presence of toxic chemicals or contaminants in the soil in higher concentrations than normal.

Sources of soil pollution

  • Overuse of agricultural pollutants, i.e., chemicals like pesticides, fertilizers, bactericides, fumigants, insecticides, herbicides, and fungicides. They are toxic chemicals leading to short-term or long-term communicable or non-communicable diseases. Herbicides can sometimes cause birth defects.
  • Disposal of municipal waste such as food, plastics, etc. Poultries, dairies, and piggery farms produce harmful farm wastes.
  • The disposal of non-degradable industrial solid waste, dumping of nuclear, and radioactive wastes from research institutes, hospitals on a large scale, when not done properly, cause a serious impact on the environment.
  • Deforestation
  • Mining or mineral extraction.

Effects of soil pollution

  • Soil pollutants enter our body through the food chain and thus causes various illness.
  • It affects the fertility of the soil and hence affects food production.
  • It is estimated that soil degradation has released about 3.6 to 4.4 billion tons of carbon dioxide into the atmosphere during the first decade of the 21st century which has resulted in climate change.
  • It has affected the lives of many land animals and also causes desertification.

Control of soil pollution

  • Farmers using manures prepared from animal dung or organic manures.
  • Recycling.
  • Using bio-fertilizers. e.g., BGA (blue-green algae), rhizobium, etc.
  • Installing proper sewage system and waste management.
  • Avoid usage of non-biodegradable materials.
  • Practicing reforestation and afforestation

Noise Pollution

Noise pollution occurs when there are high levels of unpleasant and undesirable sound. Such unpleasant and loud sounds lead to discomfort and health risks in living organisms like deafening, headache, hypertension, cardiovascular disease, blood pressure level, and stress.

Sources of noise pollution

There are many sources of noise pollution. Some of them are traffic, industrial activities and large constructions, loudspeakers, loud music, fireworks, airplanes, etc. Heavy traffic and the continuous vehicle honking sound leads to noise pollution.

A large number of airplanes and air traffic increase has also lead to increased noise pollution. Jet engines exert the maximum level of sound pressure in Decibel. Fireworks are also a major source of noise pollution. Listening to continuous loud music or high decibel sound leads to loss of concentration, temporary or even permanent ear damage if necessary precautions are not taken on time.

Effects of noise pollution

According to the National Park Service (NPS) in the USA, noise pollution has a lot of ill effects. It is causing serious damage to the wildlife, their existence breeding cycle, and rearing. In humans, it causes hypertension and other neurological problems.

Contexts and Application

  • Bachelors in Science in Biology.
  • Bachelors in Environmental Studies.
  • Bachelors in Chemistry.

Practice problems

Q.1 Why is carbon dioxide called a greenhouse gas?

a. Because it traps light

b. Because it traps heat

c. Because it traps gases

d. None

Answer : (b)

Explanation: Carbon dioxide is called a greenhouse gas because it traps heat.

Q. 2 What are the source of gamma rays?

a. Noise pollution

b. Air pollution

c. Soil pollution

d. Radiation pollution

Answer : (d)

Explanation: Radiation pollution is a source of gamma rays.

Q.3 Which of the following is a cause of soil pollution?

a. Acid rain

b. Ozone

c. Radiations

d. None

Answers : (a)

Explanation: Acid rain is a cause of soil pollution.

Q. 4 Which gas is present in the maximum percentage in our environment?

a. Carbon dioxide

b. Carbon monoxide

c. Nitrogen

d. Oxygen

Answer : (c)

Explanation: Nitrogen is present in the maximum percentage in our environment.

Q. 5 Which of the following can be said to be a biodegradable waste?

a. Cotton

b. Wood

c. Paper

d. All of the above

Answer : (d) All of the above.

Explanation: Cotton, wood, paper are all examples of biodegradable waste. They can degrade easily unlike other non-degradable substances such as polythene.

  • Air pollution
  • Water pollution
  • Pollutants
  • Soil erosion
  • Waste management

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