Pollution: A Rising Environmental Problem

ICSE Class 10 · Biology · Chapter 16

What this chapter covers

Pollution, pollutants and the major pollutants
Air pollution
Water pollution
Thermal pollution
Soil pollution
Biomedical waste
Radiation pollution
Noise pollution
Biodegradable and non-biodegradable wastes
Effects of pollution on climate and the environment
Effects on health and other organisms, and measures to control pollution
Swachh Bharat Abhiyan

Key definitions

Pollution is the undesirable change in the physical, chemical or biological characteristics of air, water or soil, caused by the addition of harmful substances or energy, that harms human beings and other living organisms.

A pollutant is any substance or form of energy which, when present in the environment in more than the safe amount, causes pollution.

Air pollution is the presence in the atmosphere of harmful gases, smoke, dust or other particles in amounts that harm human beings, animals, plants or property.

Vehicular pollution is the release of harmful gases and particles from the exhaust of cars, buses, trucks, two-wheelers and auto-rickshaws.

Water pollution is the contamination of rivers, lakes, ponds, groundwater and seas by harmful substances that make the water unfit for drinking, bathing, farming or the survival of aquatic life.

Sewage is the waste water from homes, hotels, hospitals and offices that carries human excreta, food remains, soap and other dissolved and suspended matter.

An oil spill is the release of crude oil or petroleum products into the sea or a river, usually from a damaged tanker, a leaking pipeline or an offshore drilling platform.

Eutrophication is the excessive growth of algae and water plants in a water body that has been enriched with nutrients such as phosphates and nitrates from detergents, sewage and fertiliser run-off.

Biochemical oxygen demand (BOD) is the amount of dissolved oxygen needed by micro-organisms to break down the organic matter present in a given volume of water.

Thermal pollution is the harmful rise in the temperature of a natural water body caused by the discharge of heated water from industries and power plants.

Soil pollution is the addition of harmful substances to the soil that reduce its fertility, harm the organisms living in it and enter food chains through the crops grown on it.

Biomedical waste is any waste produced during the diagnosis, treatment or immunisation of human beings or animals, or during research, that may be infectious or hazardous.

Key points

Pollution is an undesirable change in air, water or soil caused by harmful substances or energy; a pollutant is anything that causes it when above the safe level.
Major pollutants include carbon monoxide, sulphur dioxide, oxides of nitrogen, particulate matter, lead, carbon dioxide and CFCs.
Air pollution comes from vehicles, industries, burning garbage and brick kilns; carbon monoxide forms carboxyhaemoglobin and starves tissues of oxygen.
Water pollution comes from household detergents, sewage, industrial waste and oil spills; nutrients cause eutrophication, and a high BOD signals heavy organic pollution.
Thermal pollution is heated water from power plants and industries; warm water holds less oxygen, so fish suffer.
Soil pollution comes from industrial waste, urban, commercial and domestic waste, and excessive chemical fertilisers.
Biomedical waste, such as used needles, syringes and soiled dressings, spreads infection and must be segregated into colour-coded containers.
Radiation pollution comes from X-rays and radioactive fallout; ionising radiation causes mutations, cancer and birth defects.
Noise pollution from vehicles, industries, construction sites and loudspeakers damages hearing above about 85 dB and causes stress and sleep loss; each 10 dB rise is a tenfold rise in intensity.
Biodegradable wastes (paper, vegetable peels) are broken down by micro-organisms; non-biodegradable wastes (plastics, glass, Styrofoam, DDT) persist.
DDT is non-biodegradable and fat-soluble, so it undergoes biological magnification along food chains and thins the egg shells of birds.
The enhanced greenhouse effect causes global warming, with melting glaciers, rising seas and an erratic monsoon.
Acid rain, from sulphur dioxide and oxides of nitrogen, has a pH below about 5.6 and harms lakes, forests and marble monuments.
CFCs release chlorine that destroys ozone in the stratosphere, letting harmful ultraviolet rays reach the Earth.
Control measures include unleaded petrol and CNG, switching off engines at traffic signals, social forestry, sewage treatment plants, the ban on polythene and plastics, organic farming and the Bharat Stage (Euro Bharat) vehicle norms.

Questions answered

Define pollution and pollutant.

Pollution is the undesirable change in the physical, chemical or biological characteristics of air, water or soil, caused by harmful substances or energy, that harms living organisms. A pollutant is any substance or form of energy which, when present in more than the safe amount, causes pollution.

Name four sources of air pollution named in your syllabus, with one pollutant from each.

Vehicles (carbon monoxide), industries such as thermal power plants (sulphur dioxide), burning garbage (dioxins and soot), and brick kilns (soot and sulphur dioxide).

Why is carbon monoxide poisonous even in small amounts?

Carbon monoxide combines with haemoglobin more than 200 times more readily than oxygen, forming carboxyhaemoglobin. Blood holding carboxyhaemoglobin cannot carry oxygen, so the body's tissues, especially the brain, are starved of oxygen.

What is eutrophication? How do household detergents contribute to it?

Eutrophication is the excessive growth of algae in a water body enriched with nutrients such as phosphates and nitrates. Many detergents contain phosphates, which reach ponds and rivers through drains and act as a fertiliser for algae; when the algae die, their decomposition uses up dissolved oxygen and fish die.

Give two reasons why thermal pollution harms fish.

Warm water holds less dissolved oxygen, and the higher temperature increases the fish's need for oxygen at the same time. Fish eggs and larvae are also very sensitive to heat, so breeding fails.

Name three items of biomedical waste and explain why they must not be mixed with ordinary garbage.

Used needles, syringes and soiled dressings. They may carry infections such as hepatitis B and HIV, and can infect rag-pickers, sanitation workers and animals who handle mixed garbage; used syringes may also be illegally reused.

What is radioactive fallout? Why is radioactive strontium especially harmful?

Radioactive fallout is the settling of radioactive particles from the atmosphere on to land and water after a nuclear explosion or a nuclear plant accident. Radioactive strontium takes the place of calcium in bones and milk, so it stays inside the body and its radiation damages the bone marrow and can cause leukaemia.

A road records 80 dB and a library 40 dB. How many times more intense is the road noise?

The difference is 40 dB. Each 10 dB is a tenfold increase, so the intensity is 10 × 10 × 10 × 10 = 10 000 times greater.

Past board exam questions

ICSE 2027 sample paper · 1 mark

A rabbit in a food chain occupies the position of:

producer
primary consumer
secondary consumer
tertiary consumer

Show answer

primary consumer

ICSE 2027 sample paper · 1 mark

For the past few years there has been irregular rainfall, leading to crop failures and water shortages. This is a result of:

climate change
soil erosion
earth rotation
acid rain

Show answer

climate change

ICSE 2027 sample paper · 1 mark

Kiran lived with his family in the outskirts of a city which had a lot of greenery around. After a few years, a number of factories mushroomed which affected the quality of life of the people living there. The picture shows a crowded industrial area: many factory buildings standing close together, with tall chimneys releasing smoke, storage tanks and trucks in front of them. What message does the picture convey to you?

Show answer

Unplanned industrialisation pollutes the environment; to protect our environment and health, factories should not be constructed near residential areas.

ICSE 2027 sample paper · 2 marks

Show answer

Any two: respiratory diseases (asthma, bronchitis); allergies; skin infections; eye irritation; water-borne diseases.

ICSE 2026 board paper · 1 mark

What does Swachh Bharat Abhiyan aim to achieve in India?

Increase in deforestation to dump waste.
Expansion of landfill areas to accommodate more waste.
Improved sanitation and solid waste management.
Greater industrial waste production.

Show answer

Improved sanitation and solid waste management.

ICSE 2026 sample paper · 5 marks

Give the biological/technical terms for the following: (a) A mixture of smoke and fog. (b) The inner lining of uterus. (c) The pressure that is responsible for the movement of water molecules across the cortical cells of the root. (d) The ground substance present in a chloroplast. (e) The fluid present between the layers of meninges.

Show answer

(a) Smog (b) Endometrium (c) Root pressure (d) Stroma (e) Cerebrospinal fluid

ICSE 2026 sample paper · 5 marks

Choose the odd term out from each of the following set of terms. Mention the category to which the remaining three belong: (a) Sulphur dioxide, Oxygen, Carbon monoxide, Nitrogen dioxide. (b) Pons, Epidermis, Xylem, Phloem. (c) Tympanum, Pinna, Auditory canal, Malleus. (d) Ureter, Urethra, Uterus, Renal Pelvis. (e) Stomata, Lenticles, Cuticle, Root hair.

Show answer

(a) Odd term: Oxygen; the rest are air pollutants. (b) Odd term: Pons; the rest are plant tissues. (c) Odd term: Malleus; the rest are parts of the outer ear. (d) Odd term: Uterus; the rest are parts of the urinary system. (e) Odd term: Root hair; the rest are parts through which transpiration takes place.

ICSE 2026 sample paper · 1 mark

What are non-biodegradable wastes?

Show answer

Non-biodegradable wastes are materials that cannot be broken down (decomposed) by micro-organisms; they persist in the environment and cause pollution, e.g. plastics, glass, DDT.