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What is Water Pollution?

Water pollution occurs when harmful substances—often chemicals or microorganisms—contaminate a stream, river, lake, ocean, aquifer, or other body of water, degrading water quality and rendering it toxic to humans or the environment

1. Sources

➤ Types of sources

  • Point Sources
    (i) It is directly attributable to one influence. Here pollutant travels directly from source to water. Point sources are easy to regulate.
  • Diffuse or non-point source.
    (i) It is from various ill-defined and diffuse sources. They vary spatially and temporally and are difficult to regulate.
    (ii) The main sources of water pollution are as follows:
  • Community wastewater: Include discharges from houses, commercial and industrial establishments connected to the public sewerage system. The sewage contains human and animal excreta, food residues, cleaning agents, detergents and other wastes.
    Putrescibility is the process of decomposition of organic matter present in water by microorganisms using oxygen.
  • Industrial Wastes: The industries discharge several inorganic and organic pollutants, which may prove highly toxic to living beings.
  • Agricultural sources
    (i) Fertilizers contain major plant nutrients such as nitrogen, phosphorus and potassium.
    (ii) Excess fertilizers may reach the groundwater by leaching or mixed with surface water of rivers, lakes and ponds by runoff and drainage.
    (iii) Pesticides include insecticides, fungicides, herbicides, nematicides, rodenticides and soil fumigants.
    (iv) They contain a wide range of chemicals such as chlorinated hydrocarbons, organophosphates, metallic salts, carbonates, thiocarbonates, derivatives of acetic acid etc. Many of the pesticides are non-degradable, and their residues have a long life.
    (v) The animal excreta such as dung, wastes from poultry farms, piggeries and slaughterhouses etc. reach the water through runoff and surface leaching during the rainy season.
  • Thermal Pollution: The main sources are the thermal and nuclear power plants. The power plants use water as coolant and release hot waters to the source. Sudden rise in temperature kills fishes and other aquatic animals.
  • Underground water pollution: In India at many places, the groundwater is threatened with contamination due to seepage from industrial and municipal wastes and effluents, sewage channels and agricultural runoff.
  • Marine pollution: Oceans are the ultimate sink of all-natural and human-made pollutants. Rivers discharge their pollutants into the sea. The sewerage and garbage of coastal cities are also dumped into the sea. The other oceanic pollution sources are navigational discharge of oil, grease, detergents, sewage, garbage and radioactive wastes, offshore oil mining, and oil spills.

➤ Oil Spills

  • Oil spills are one of the most dangerous of all water pollutants.
  • Oil spills from tankers at sea or leaks from underground storage tanks on land are tough to control as oil tends to spread very fast, affecting a large area in a short time.
  • On land crude is transported through pipelines or tankers, which can damage and spew out crude oil over the land, thereby contaminating it.
  • Since crude oil is lighter than water, it floats on the surface and poses the threat of swift-spreading fire.
  • Oil spills at sea decrease the water's oxygen level and cause harm to the organisms.
  • Oil spills are also a source of air and groundwater pollution.

2. Effects of Water Pollution

(i) Effects on aquatic ecosystem

  • Polluted water reduces Dissolved Oxygen (DO) content, thereby, eliminates sensitive organisms like plankton, molluscs and fish etc.
  • However, a few tolerant species like Tubifex (annelid worm) and some insect larvae may survive in highly polluted water with low DO content. Such species are recognized as indicator species for polluted water.
  • Biocides, polychlorinated biphenyls (PCBs) and heavy metals directly eliminate sensitive aquatic organisms.
  • Hot waters discharged from industries, when added to water bodies, lowers its DO content.

➤ What is DO, BOD, COD?

  • Presence of organic and inorganic waste in water decreases the water's dissolved oxygen (DO) content. Water having DO content below 8.0 mg L-1 may be considered as contaminated. Water having DO content below. 4.0 mg L-1 is considered to be highly polluted. DO content of water is important for the survival of aquatic organisms. Several factors like surface turbulence, photosynthetic activity, O2 consumption by organisms and decomposition of organic matter are the factors which determine the amount of DO present in water.
  • The higher amounts of waste increase the rates of decomposition and O2 consumption, thereby decreasing water's DO content. The demand for O2 is directly related to increasing input of organic wastes and is empressed as biological oxygen demand (BOD) of water.
  • Water pollution by organic wastes is measured in terms of Biochemical Oxygen Demand (BOD). BOD is the amount of dissolved oxygen needed by bacteria in decomposing the organic wastes present in water. It is expressed in milligrams of oxygen per litre of water.
  • The higher value of BOD indicates low DO content of water. Since BOD is limited to biodegradable materials only, it is not reliable for measuring its pollution load.
  • Chemical oxygen demand (COD) is a slightly better mode used to measure pollution load in the water. It is the measure of oxygen equivalent of the requirement of oxidation of total organic matter (i.e. biodegradable and non-biodegradable) present in water.

(ii) Effects on human health

  • The polluted water usually contains pathogens like virus, bacteria, parasitic protozoa and worms; therefore, it is a source of water-borne diseases like jaundice, cholera, typhoid, amoebiasis etc.
  • Mercury compounds in wastewater are converted by bacterial action into extremely toxic methyl mercury, which can cause numbness of limbs, lips and tongue, deafness, blurring of vision and mental derangement.
  • Minamata disease's cripling deformity due to fish consumption captured from mercury-contaminated Minamata Bay in Japan was detected in 1952.
  • Water contaminated with cadmium can cause itai itai disease, also called ouch-ouch disease (a painful disease of bones and joints) and lung and liver cancer. 
  • The compounds of lead cause anaemia, headache, loss of muscle power and bluish line around the gum.

(iii) Hazards of groundwater pollution

  • Presence of excess nitrate in drinking water is dangerous for human health and may be fatal for infants. 
  • Excess nitrate in drinking water reacts with haemoglobin to form non-functional methaemoglobin and impairs oxygen transport. This condition is called methemoglobinemia or blue baby syndrome.
  • Excess fluoride in drinking water causes neuro-muscular disorders, gastro-intestinal problems, teeth deformity, hardening of bones and stiff and painful joints (skeletal fluorosis).
  • The high concentration of fluoride ions is present in drinking water in 13 states of India. The maximum fluoride level, which the human body can tolerate is 1.5 parts per million (mg/1 of water). Long term ingestion of fluoride ions causes fluorosis.
  • Overexploitation of groundwater may lead to leaching of arsenic from soil and rock sources and contaminate groundwater. Chronic exposure to arsenic causes black foot disease. It also causes diarrhoea, peripheral neuritis, hyperkeratosis and also lung and skin cancer.
  • Arsenic contamination is a serious problem (in tube well-dug areas) in the Ganges Delta, west Bengal causing serious arsenic poisoning to large people. A 2007 study found that over 137 million people in more than 70 countries are probably affected by arsenic drinking water poisoning.

(iv) Biological Magnification
(v) Eutrophication

3. Control Measures

  • Riparian buffers
  • Treatment of sewage water and the industrial effluents should be done before releasing it into water bodies.
  • Hot water should be cooled before release from the power plants
  • Domestic cleaning in tanks, streams and rivers, which supply drinking water, should be prohibited.
  • Excessive use of fertilizers and pesticides should be avoided.
  • Organic farming and efficient use of animal residues as fertilizers.
  • Water hyacinth (an aquatic weed) can purify water by taking some toxic materials and several heavy metals from water.
  • Oil spills in water can be cleaned with the help of bregoli – a by-product of paper industry resembling sawdust, oil zapper, microorganisms.

➤ The steps taken by the Government to address the issues of water pollution include the following

  • Preparation of action plan for sewage management and restoration of water quality in aquatic resources by State Governments;
  • Installation of Online Effluent Monitoring System to check the discharge of effluent directly into the rivers and water bodies;
  • Setting up of monitoring network for assessment of water quality;
  • Action to comply with effluent standards is taken by SPCBs / PCCs to improve the water quality of the rivers;
  • Financial assistance for installation of Common Effluent Treatment Plants for a cluster of Small Scale Industrial units;
  • Issuance of directions for implement at ion of Zero Liquid Discharge;
  • Issuance of directions under Section 5 of Environment (Protection) Act, 1986 to industries and under Section 18(1)(b) of Water (Prevention and Control of Pollution) Act, 1974;

4. Soil Pollution

  • Soil is a thin layer of organic and inorganic materials that covers the Earth's rocky surface. Soil pollution is defined as the 'addition of substances to the soil, which adversely affects soil's physical, chemical and biological properties and reduces its productivity.' 
  • It is a build-up of persistent toxic compounds, chemicals, salts, radioactive materials, or disease-causing agents in the soil which have adverse effects on plant growth, human and animal health. 
  • A soil pollutant is any factor which deteriorates the quality, texture and mineral content of the soil or which disturbs the biological balance of the organisms in the soil.

➤ Causes

  • Indiscriminate use of fertilizers, pesticides, insecticides and herbicides
  • Dumping of large quantities of solid waste
  • Deforestation and soil erosion.
  • Pollution Due to Urbanization

➤ Source

  • Industrial Wastes: The industrial waste includes mercury, lead, copper, zinc, cadmium, cyanides, thiocyanates, chromates, acids, alkalies, organic substances etc. 
  • Pesticides: Pesticides include insecticides, fungicides, algicides, rodenticides, and weedicides sprayed to improve the productivity of agriculture, forestry and horticulture. 
  • Fertilizers and manures: Chemical fertilizers are added to the soil for increasing crop yield. Excessive use of chemical fertilizers reduces the population of soil-borne organisms and the soil's crumb structure, the soil's productivity, and increases salt content of the soil. 
  • Discarded materials: It includes concrete, asphalt, rungs, leather, cans, plastics, glass, discarded food, paper and carcasses. 
  • Radioactive wastes: Radioactive elements from mining and nuclear power plants, find their way into the water and then into the soil. 
  • Other pollutants: Many air pollutants (acid rain) and water pollutants ultimately become part of the soil, and the soil also receives some toxic chemicals during weathering of certain rocks.

➤ Types of Soil Pollution

  • Agricultural Soil Pollution 
  • Pollution due to industrial effluents and solid wastes 
  • Pollution due to urban activities

Effects of soil pollution on

(i) Agriculture

  • Reduced soil fertility
  • Reduced nitrogen fixation
  • Increased erosion
  • Loss of soil and nutrients
  • Reduced crop yield
  • Increased salinity
  • Deposition of silt in tanks and reservoirs

(ii) Health

  • Dangerous chemicals entering underground water 
  • Biomagnification 
  • Release of pollutant gases 
  • Release of radioactive rays causing health problems

(iii) Environment

  • Reduced vegetation
  • Ecological imbalance
  • Imbalance in soil fauna and flora

(iv) Urban areas

  • Clogging of drains 
  • Inundation of areas
  • Foul smell and release of gases 
  • Waste management problems
  • Control measures
  • Reducing chemical fertilizer and pesticide use
  • Use of biopesticides, biofertilizers.
  • Organic farming
  • Four R's: Refuse, Reduce, Reuse, and Recycle
  • Afforestation and Reforestation
  • Solid waste treatment
  • Reduction of waste from construction areas

➤ Four R's

  • Refuse • Instead of buying new containers from the market, use those in the house. Refuse to buy new items though you may think they are prettier than the ones you already have.
  • Reuse • Do not throw away the soft drink cans or the bottles; cover them with homemade paper or paint on them and use them as pencil stands or small vases.
  • Recycle • Use shopping bags made of cloth or jute, which can be used repeatedly. Segregate your waste to make sure that it is collected and taken for recycling.
  • Reduce • Reduce the generation of unnecessary waste, e.g. carry your own shopping bag when you go to the market and put all your purchases directly into it.

5. Noise Pollution

  • Noise pollution is an unpleasant noise created by people or machines that can be annoying, distracting, intrusive, and/or physically painful. 
  • Noise pollution comes from sources such as "road traffic, jet planes, garbage trucks, construction equipment, manufacturing processes, leaf blowers, and boom boxes." 
  • Sound is measured in decibels (dB). An increase of about 10 dB is approximately double the increase in loudness. 
  • A person's hearing can be damaged if exposed to noise levels over 75 dB over a prolonged period of time. The World Health Organization recommends that the sound level indoors should be less than 30 dB.

➤ Ambient Noise Level Monitoring

  • Noise Pollution (Control and Regulation) Rules, 2000 define ambient noise levels for various areas as follows:
    (i) The Government of India on Mar 2011 launched a Real-time Ambient Noise Monitoring Network. Under this network, in phase- I, five Remote Noise Monitoring Terminals have been installed in different noise zones in seven metros (Delhi, Hyderabad, Kolkata, Mumbai, Bangalore, Chennai and Lucknow).
    (ii) In Phase II, another 35 monitoring stations will be installed in the same seven cities. Phase III will cover installing 90 stations in 18 other cities.
    (iii) Phase-III cities are Kanpur, Pune, Surat, Ahmedabad, Nagpur, Jaipur, Indore, Bhopal, Ludhiana, Guwahati, Dehradun, Thiruvananthpuram, Bhubaneswar, Patna, Gandhinagar, Ranchi, Amritsar and Raipur.
    (iv) Silence Zone is an area comprising not less than 100 metres around hospitals, educational institutions, courts, religious places or any other area declared as such by a competent authority.

➤ Impacts of noise

  • Annoyance: It creates annoyance to the receptors due to sound level fluctuations. The a-periodic sound due to its irregular occurrences causes displeasure to hear and annoys.
  • Physiological effects: The physiological features like breathing amplitude, blood pressure, heart-beat rate, pulse rate, blood cholesterol are affected.
  • Loss of hearing: Long exposure to high sound levels cause loss of hearing. This is mostly unnoticed but hurts hearing function.
  • Human performance: The working performance of workers/human will be affected as it distracts the concentration.
  • Nervous system: It causes pain, ringing in the ears, feeling of tiredness, thereby affecting the functioning of the human system.
  • Sleeplessness: It affects the sleeping thereby inducing people to become restless and lose concentration and presence of mind during their activities
  • Material damage: The buildings and materials may get damaged by exposure to infrasonic/ultrasonic waves and even collapsed.


The techniques employed for noise control can be broadly classified as

(i) Control at source

  • Reducing the noise levels from domestic sectors
  • Maintenance of automobiles
  • Control over vibration 
  • Prohibition on the usage of loudspeakers
  • Selection and maintenance of machinery

(ii) Control in the transmission path

  • Installation of barriers
  • Design of building
  • Green belt development (planting of trees)

(iii) Using protective equipment

  • Job rotation
  • Reduced Exposure time
  • Hearing protection
  • Documentation of noise measurements, continuous monitoring and awareness is the need of the hour.

6. Radioactive Pollution

  • Radioactive Pollution: Radioactivity is a phenomenon of spontaneous emission of proton (a-particles), electrons (ß-particles) and gamma rays (short wave electromagnetic waves) due to disintegration of atomic nuclei of some elements. These cause radioactive pollution.
  • Radioactivity: Radioactivity is a property of certain elements (radium, thorium, uranium etc.) to spontaneously emit protons (alpha particles) electrons (beta particles) and gamma rays (short-wave electromagnetic wave) by the disintegration of their atomic nuclei (nuclides).

➤ Types of Radiations

  • Non-ionizing radiations affect only those components which absorb them and have low penetrability. 
  • Ionising radiations have high penetration power and cause breakage of macromolecules.

➤ Types of radiation particles

  • Alpha particles, can be blocked by a piece of paper and human skin.
  • Beta particles can penetrate through the skin, while some glass and metal pieces can be blocked.
  • Gamma rays can penetrate easily to human skin and damage cells on its way through, reaching far, and can only be blocked by a very thick, strong, massive piece of concrete.



  • They include cosmic rays from space and terrestrial radiations from radio-nuclides present in earth's crust such as radium-224, uranium-238, thorium-232, potassium-40, carbon-14, etc.


Atomic explosion (Nuclear fallout)
The nuclear arms use uranium-235 and plutonium-239 for fission and hydrogen or lithium as fusion material. Atomic explosions produce radioactive particles that are thrown high up into the air as huge clouds. These particles are carried to long distances by wind and gradually settle over the earth as fall out or are brought down by rain. The fall out contains radioactive substances such as strontium-90, caesium-137, iodine – 131, etc.

  • Nuclear power plants
  • Nuclear weapon
  • Transportation of nuclear material
  • Disposal of nuclear waste
  • Uranium mining
  • Radiation therapy


The effects of radioactive pollutants depend upon

  • half-life
  • energy-releasing capacity
  • rate of diffusion and
  • rate of deposition of the pollutant.
  • Various environmental factors such as wind, temperature, rainfall also influence their effects.

Period of Radioactivity

Each radioactive nuclide has a constant decay rate. Half-life is the time needed for half of its atoms to decay. The half-life of a radionuclide refers to its period of radioactivity. The half-life may vary from a fraction of a second to thousands of years. The radionuclides with long half-time are the chief source of environmental radioactive pollution. Radiations are of two types about the mode of their action on cells.

(i) Non-ionising radiations

  • They include short-wave radiations such as ultraviolet rays, which forms a part of solar radiation. 
  • They have low penetrating power and affect the cells and molecules which absorb them. 
  • They damage eyes caused by reflections from coastal sand, snow (snow blindness) directly looking towards the sun during an eclipse.
  • They injure the cells of skin and blood capillaries producing blisters and reddening called sunburns.

(ii) Ionising radiations

  • They include X-rays, cosmic rays and atomic radiations (radiations emitted by radioactive elements). 
  • Ionizing radiations have high penetration power and cause breakage of macromolecules.
  • The molecular damage may produce short-range (immediate) or long-range (delayed) effects.
    (i) Short-range effects include burns, impaired metabolism, dead tissues, and the organisms' death.
    (ii) Long-range effects are mutations that increase tumour and cancer incidence, shortening of life-span and developmental changes.
    (iii) The mutated gene can persist in living organisms and may affect their progeny. 
  • The actively dividing cells such as Embryo, foetus, skin, intestinal lining, bone marrow and gamete forming cells are more sensitive to radiation.
  • Some species of animals and plants preferentially accumulate specific radioactive materials. For example, oysters deposit 65Zn, fish accumulate 55Fe, marine animals selectively deposit 90Sr.

➤ Control Measures

  • Prevention is the best control measure as there is no cure available for radiation damage.
    (i) All safety measures should be strictly enforced. Leakage of radioactive elements should be totally checked.
    (ii) Safe disposal of radioactive waste.
    (iii) Regular monitoring through frequent sampling and quantitative analysis. Safety measures against nuclear accidents.
    (iv) Nuclear explosions and use of nuclear weapons should be completely banned.
    (v) Appropriate steps should be taken to protect from occupational exposure.


  • The discarded and end-of-life electronic products ranging from computers, equipment used in Information and Communication Technology (ICT), home appliances, audio and video products and all of their peripherals are popularly known as Electronic waste (E-waste). 
  • E-waste is not hazardous if it is stocked in safe storage or recycled by scientific methods or transported from one place to the other in parts or totality in the formal sector. The e-waste can, however, be considered hazardous if recycled by primitive methods.

➤ E-Waste in India

  • "The Global E-Waste Monitor 2014", 17 lakh tonnes of e-waste generation was reported in the country in 2014. No comprehensive State-wise inventorization of e-waste generation in the country has been done.
  • In India, among top ten cities, Mumbai ranks first in generating e-waste followed by Delhi, Bangalore, Chennai, Kolkata, Ahmadabad, Hyderabad, Pune, Surat and Nagpur. 
  • The 65 cities generate more than 60% of the total generated e-waste, whereas 10 states generate 70% of the total e-waste.
  • Most of the e-waste is recycled in India in unorganized units, which engage a significant workforce. Recovery of metals by primitive means is the most hazardous act.
  • If not carried out properly, can cause damage human beings through inhalation of gases during recycling, contact of the skin with hazardous substances, and contact during acid treatment used in the recovery process.
  • Proper education, awareness, and, most importantly, alternative cost-effective technology need to be provided to provide better means to those who earn the livelihood from this.
  • A holistic approach is needed to address the challenges faced by India in e-waste management. A suitable mechanism needs to be evolved to include small units in an unorganized sector and large organized sector units into a single value chain.
The document Environmental Pollution (Part - 2) | Environment for UPSC CSE is a part of the UPSC Course Environment for UPSC CSE.
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FAQs on Environmental Pollution (Part - 2) - Environment for UPSC CSE

1. What is water pollution?
Ans. Water pollution refers to the contamination of water bodies such as lakes, rivers, oceans, and groundwater by harmful substances, making the water unsuitable for its intended use, whether it is for drinking, bathing, fishing, or irrigation.
2. What are the causes of water pollution?
Ans. Water pollution can be caused by various factors such as industrial waste discharge, sewage and wastewater discharge, agricultural runoff, oil spills, improper disposal of chemicals and hazardous substances, and even natural events like volcanic eruptions or algal blooms.
3. How does water pollution affect the environment?
Ans. Water pollution has severe impacts on the environment. It can lead to the death of aquatic plants and animals, disrupt ecosystems, reduce biodiversity, contaminate the food chain, and degrade water quality. Additionally, polluted water can also harm human health if used for drinking or recreational activities.
4. What are the effects of water pollution on human health?
Ans. Water pollution can have significant health consequences for humans. Consuming contaminated water can lead to various diseases such as diarrhea, cholera, typhoid, hepatitis, and gastrointestinal problems. It can also result in long-term health issues due to exposure to toxic chemicals and heavy metals present in polluted water.
5. How can we prevent water pollution?
Ans. Preventing water pollution requires collective efforts. Some effective measures include treating and managing industrial and domestic wastewater, implementing proper waste disposal practices, promoting sustainable agriculture techniques to reduce pesticide and fertilizer runoff, and raising awareness about the importance of clean water and its conservation. Additionally, stricter regulations and enforcement by governments and industries can also play a crucial role in preventing water pollution.
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