Types and Sources of Pollution: Air, Water, Thermal, Soil, Biomedical, Radiation and Noise (ICSE Class 10)
Updated 16 October 2026 · Fact-checked
Pollution is an undesirable change in air, water or soil that harms living things. ICSE names seven types: air (vehicles, industries, burning garbage, brick kilns), water (detergents, sewage, industrial waste, oil spills), thermal (hot water from plants), soil (industrial, urban and domestic waste, fertilisers), biomedical waste, radiation (X-rays, fallout) and noise.
Understand Types and Sources of Pollution
Pollution and pollutants. Pollution is any undesirable change in the physical, chemical or biological characteristics of air, water or soil that harms humans and other living things. A pollutant is the agent that causes it. Most pollutants are substances (smoke, sewage, plastics), but some are forms of energy: heat (thermal pollution), sound (noise) and radiation.
1. Air pollution.
| Source | Major pollutants |
|---|---|
| Vehicles | carbon monoxide (CO), nitrogen oxides, unburnt hydrocarbons, soot; lead from leaded petrol |
| Industries | sulphur dioxide, nitrogen oxides, smoke, fly ash |
| Burning garbage | smoke, soot, toxic gases from burning plastics |
| Brick kilns | smoke, soot, CO, sulphur dioxide |
Effects: asthma, bronchitis and other breathing problems, eye irritation, smog, acid rain. Carbon monoxide combines with haemoglobin far more readily than oxygen, forming a stable compound, carboxyhaemoglobin; the blood then carries less oxygen, causing headache, unconsciousness and even death. Smog is worst on cold, still winter days, when the cold air near the ground does not rise and pollutants are trapped.
2. Water pollution.
- Household detergents: phosphates feed algae (algal bloom); decaying algae use up dissolved oxygen.
- Sewage: germs of cholera, typhoid and jaundice; organic matter that uses up oxygen as it decays.
- Industrial waste: toxic chemicals and heavy metals (mercury, lead), which build up in fish and in the people who eat them.
- Oil spills: oil forms a film on the sea, coats birds' feathers (they lose insulation and cannot fly or float) and the gills of fish, and blocks oxygen and light.
3. Thermal pollution. Power plants (including nuclear plants) and industries use water for cooling and release it hot into rivers and lakes. Warm water holds less dissolved oxygen, while aquatic animals need more oxygen when warm, so fish and their eggs die. The pollutant is heat, not a chemical.
4. Soil pollution. Industrial waste (chemicals, fly ash, heavy metals); urban commercial and domestic waste (plastics, glass, metal cans, rotting food); excess chemical fertilisers and pesticides, which harm soil organisms, change soil pH and wash into water bodies. Rainwater seeping through garbage dumps carries harmful substances into the groundwater.
5. Biomedical waste. Waste generated in hospitals, clinics and laboratories during diagnosis and treatment: used and discarded needles and syringes, soiled dressings, blood, body parts, discarded medicines. It can spread infections such as hepatitis B and injure waste pickers, so it must be segregated at source (sharps in puncture-proof containers) and treated, for example by incineration or sterilisation.
6. Radiation pollution. Sources: over-use of X-rays, and radioactive fallout from nuclear plants (leaks, accidents) and nuclear tests. Fallout can be carried far by wind and rain and enter food chains. Effects: mutations, cancers such as leukaemia, burns.
7. Noise pollution. Unwanted loud sound from motor vehicles, industrial establishments, construction sites and loudspeakers (also aircraft). Effects: hearing loss, disturbed sleep, stress, headache, high blood pressure, poor concentration.
Biodegradable and non-biodegradable wastes. Biodegradable wastes (paper, vegetable peels) are broken down by microorganisms; non-biodegradable wastes (plastics, glass, Styrofoam, pesticides such as DDT) are not, and persist in the environment.
Types and Sources of Pollution: key facts
- Sources in the syllabus
Air vehicles, industries, burning garbage, brick kilns Water detergents, sewage, industrial waste, oil spills Soil industrial, urban and domestic waste, chemical fertilisers Noise vehicles, industries, construction, loudspeakers - Learn each list with its type.
- Pollutants that are energy
Thermal heat from cooling water Noise sound Radiation X-rays, radioactive fallout - Name the agent to name the type.
- Key effects
CO carboxyhaemoglobin, less oxygen carried Thermal less dissolved oxygen Sewage cholera, typhoid Biomedical infection, injury from sharps - Give a specific effect.
How to answer Types and Sources of Pollution questions
To answer most questions here, first identify the harmful agent, then name the type of pollution and one specific effect.
- 1Ask: what is actually causing harm? A gas, a liquid, a solid, heat, sound or radiation?
- 2Name the type from the agent: heat → thermal; sound → noise; used syringes → biomedical.
- 3Name the source using the syllabus words (vehicular, industrial, brick kilns, sewage, oil spills).
- 4Give a specific effect (carboxyhaemoglobin, less dissolved oxygen, hearing loss), never just 'pollution' or 'harmful'.
- 5If a number is given (temperature, decibels, oxygen level), compare it with the safe value and say what it means for living things.
Types and Sources of Pollution in real life
The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.
The morning after fireworks
Suppose that after a night of fireworks in your colony, the morning air is hazy, smells of sulphur, and your grandfather, who has asthma, finds it hard to breathe. The bursts were also very loud past midnight.
Name two types of pollution caused and one harmful effect of each.
Try it first, then show the solutionSolution
- Smoke, soot and sulphur dioxide in the air: air pollution, which worsens asthma and irritates the eyes.
- Loud bursts late at night: noise pollution, which disturbs sleep and can damage hearing.
Answer: Air pollution (breathing problems) and noise pollution (disturbed sleep, hearing damage).
Memory hook: Smoke for the lungs, bangs for the ears.
A separate box for needles
Imagine you see a nurse drop a used syringe needle into a hard, sealed plastic box instead of the ordinary dustbin.
Why is this done?
Try it first, then show the solutionSolution
- Used needles are biomedical waste and may carry germs such as hepatitis B virus.
- In an ordinary bin they could prick cleaners and waste pickers and spread infection.
- A puncture-proof container keeps sharps separate until they are treated safely.
Answer: To keep infectious sharps apart so they cannot injure or infect waste handlers.
Memory hook: Sharps go in a box, not in the bin.
Tricks to remember Types and Sources of Pollution
Short memory aids. Say each one aloud once, then use it on a question the same day.
Seven types: A-W-T-S-B-R-N
Air, Water, Thermal, Soil, Biomedical, Radiation, Noise: 'All Women Take Short Breaks Right Now'.
Use it when: Listing the types.
Agent names the type
Heat is thermal, sound is noise, syringes are biomedical.
Use it when: Identifying pollution in a case.
Warm water, worse for fish
Warm water holds less oxygen, but warm fish need more.
Use it when: Thermal pollution.
Types and Sources of Pollution: solved examples
Ordered from board level to HOTS. Try each one before you open the solution.
Example 1: Brick kilns · 1 mark · MCQBoard level
A major air pollutant released by brick kilns is:
(a) chlorofluorocarbons
(b) soot and sulphur dioxide
(c) phosphates
(d) mercury
Try it first, then show the solutionSolution
- Kilns burn coal and other fuels, giving smoke, soot, CO and sulphur dioxide.
Answer: (b) soot and sulphur dioxide
Example 2: Match the source · 2 marks · Short answerBoard level
Name the type of pollution caused by each: (a) a leaking oil tanker at sea; (b) loudspeakers at a late-night function; (c) excess urea fertiliser on a field; (d) blood-stained cotton thrown out by a clinic.
Try it first, then show the solutionSolution
- (a) Water pollution; (b) noise pollution. (1)
- (c) Soil pollution; (d) biomedical waste. (1)
Answer: (a) Water (b) Noise (c) Soil (d) Biomedical
Example 3: Warm water and oxygen · 3 marks · Short answerHarder board level
Suppose river water at 22 °C holds 8.7 mg of dissolved oxygen per litre, but downstream of a factory's cooling-water outlet it is at 32 °C and holds only 7.3 mg per litre.
(a) By how much, and by what percentage, has the dissolved oxygen fallen?
(b) Name the type of pollution.
(c) Explain why fish suffer even more than the fall suggests.
Try it first, then show the solutionSolution
- (a) 8.7 − 7.3 = 1.4 mg per litre, about 1.4 ÷ 8.7 × 100 ≈ 16%. (1)
- (b) Thermal pollution: the pollutant is heat. (1)
- (c) In warmer water fish are more active and need more oxygen, just when less is available. (1)
Answer: (a) 1.4 mg/L, about 16% (b) Thermal (c) Warm fish need more oxygen
Example 4: Birds in an oil spill · 2 marks · Short answerHarder board level
After an oil spill, many seabirds and fish die. Explain how the oil harms (a) seabirds, (b) fish and other sea life.
Try it first, then show the solutionSolution
- (a) Oil coats the feathers, which lose their insulation and waterproofing; the birds cannot fly or float, and swallow oil while cleaning themselves. (1)
- (b) The oil film blocks oxygen from entering the water and light from reaching algae; it also clogs fish gills. (1)
Answer: (a) Feathers coated, birds cannot fly or keep warm (b) Less oxygen and light; gills clogged
Example 5: Too much fertiliser · 3 marks · Short answerHarder board level
A farmer uses chemical fertilisers in much larger amounts than the crop needs. Give two ways this pollutes the soil and one way it affects a pond next to the field.
Try it first, then show the solutionSolution
- Excess fertiliser changes the soil's pH and can make it less fertile over time. (1)
- It harms useful soil organisms such as earthworms and bacteria. (1)
- Rain washes it into the pond, where it feeds an algal bloom; when the algae decay, oxygen is used up and fish die. (1)
Answer: Changes soil pH; harms soil organisms; causes an algal bloom in the pond.
Example 6: Case study: a colony's garbage dump · 4 marks · Case-basedHOTS / competency
Suppose residents of a colony burn their mixed garbage, including plastic bags, in an open plot every evening. A nearby clinic sometimes throws its used syringes and dressings on the same heap.
(a) Name two types of pollution caused.
(b) Why is burning plastic especially harmful?
(c) Give two reasons why the clinic's waste must not go on this heap.
(d) Suggest one better way to deal with the colony's waste.
Try it first, then show the solutionSolution
- (a) Air pollution (smoke from burning garbage) and soil pollution (waste on land); also biomedical waste. (1)
- (b) Burning plastic gives off toxic gases and soot that damage the lungs. (1)
- (c) Used needles and dressings may carry infections such as hepatitis B; sharps can injure people and animals searching the heap. (1)
- (d) Separate biodegradable waste for composting and send plastics for recycling; the clinic must give its biomedical waste for safe treatment. (1)
Answer: (a) Air and soil (biomedical) (b) Toxic gases (c) Infection; injury (d) Segregate, compost, recycle; treat biomedical waste separately
Where students lose marks in Types and Sources of Pollution
The slips examiners see most often, and what to write instead.
Mistake: Carbaminohaemoglobin for carboxyhaemoglobin
CISCE examiners' comments, 2024 Q6(iii): explaining why carbon monoxide is dangerous, candidates gave vague answers or wrote carbamino haemoglobin instead of carboxyhaemoglobin.
Wrong working
CO forms carbaminohaemoglobin.
Right working
CO forms stable carboxyhaemoglobin, cutting off the oxygen supply to tissues.
Do this: Carboxy- for CO; carbamino- is carbon dioxide transport.
Usually costs: 1 mark.
Mistake: Radiation or water pollution for thermal
CISCE examiners' comments, 2025 Q1(xii): for cooling water released back into a stream by nuclear plants, candidates chose radiation pollution or water pollution.
Wrong working
Nuclear plant cooling water: radiation pollution.
Right working
Thermal pollution: the pollutant is heat.
Do this: Name the agent: heat means thermal.
Usually costs: 1 mark.
Mistake: Biomedical confused with biodegradable
CISCE examiners' comments, 2025 Q5(ii): candidates wrote vague answers like 'waste from medicals', gave 'plastic' as the example, or confused biomedical waste with biodegradable waste.
Wrong working
Biomedical waste is waste that decomposes.
Right working
Biomedical waste is waste from hospitals, clinics and laboratories, e.g. used syringes.
Do this: Biomedical = from health care; biodegradable = broken down by microbes.
Usually costs: 1 mark.
Mistake: 'It is noisy' as an effect
CISCE examiners' comments, 2025 Q3(iv): on living near an airport, candidates wrote 'it is noisy' or 'pollution' without naming noise pollution or an effect such as sleep disturbance.
Wrong working
Disadvantage: it is noisy.
Right working
Noise pollution, causing disturbed sleep and hearing damage.
Do this: Name the type and a specific effect on health.
Usually costs: 1 mark each.
Exam tips
- Use the syllabus words for sources: vehicular, industrial, burning garbage, brick kilns.
- Identify thermal, noise and radiation pollution by the energy involved.
- For CO, write 'carboxyhaemoglobin' and 'less oxygen to tissues'.
- Give a named example of biomedical waste: used syringes, needles, soiled dressings.
Practice questions on Types and Sources of Pollution
Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.
Q1 · 1 mark · MCQBoard level
Which of these mainly pollutes the soil rather than the air?
(a) smoke from brick kilns
(b) excess chemical fertiliser on fields
(c) exhaust from vehicles
(d) burning garbageHint
Which one is spread on the ground?
Answer
(b) excess chemical fertiliser on fields
Q2 · 1 mark · Very short answerBoard level
Name two gases released in the exhaust of petrol and diesel vehicles that pollute the air.
Hint
One binds haemoglobin.
Answer
Carbon monoxide and nitrogen oxides (also unburnt hydrocarbons).
Q3 · 2 marks · Very short answerBoard level
What is a pollutant? Name one pollutant that is a form of energy rather than a substance.
Hint
Think of thermal and noise pollution.
Answer
A pollutant is an agent that brings about pollution, harming living things. Heat (or sound, or radiation) is a pollutant that is a form of energy.
Q4 · 2 marks · Short answerHarder board level
A tannery releases waste containing chromium, a toxic heavy metal, into a river whose water is used to irrigate nearby fields. Explain how this pollutes both the water and the soil, and how it may reach people.
Hint
Follow the water from the river to the field to the plate.
Answer
The toxic metal pollutes the river and harms aquatic life. When the water is used for irrigation, the metal is left in the soil, harming soil organisms and fertility. Crops take it up from the soil, and people are exposed by eating the crops or drinking the water.
Q5 · 2 marks · Short answerHarder board level
Suppose the permitted daytime noise level in a residential area is 55 dB, but a sound level meter near a construction site reads 85 dB. By how many decibels is the limit exceeded? Suggest two ways to protect people living nearby.
Hint
Subtract; then think of barriers and timing.
Answer
85 − 55 = 30 dB above the limit. Allow noisy work only in the daytime, use barriers or screens around the site, plant trees as a sound buffer, or fit silencers to machines (any two).
Q6 · 2 marks · Short answerHarder board level
Why are unnecessary X-rays avoided, and why can radioactive fallout from a nuclear accident harm people living far away?
Hint
Ionising radiation; wind and rain.
Answer
X-rays are ionising radiation that can damage cells and cause mutations or cancer, so each exposure should be necessary. Fallout is carried by wind and brought down by rain onto crops and pastures, entering food (for example milk) far from the accident.
Q7 · 2 marks · Short answerHOTS / competency
Smog in a city with many vehicles, brick kilns and garbage fires is often worst on cold, still winter mornings. Suggest a reason.
Hint
Which way does the air move?
Answer
On cold, still mornings the air near the ground is cold and does not rise, and there is no wind to carry pollutants away, so smoke, soot and gases are trapped close to the ground and build up into smog.
Q8 · 3 marks · Short answerHOTS / competency
A town's garbage is dumped in a low-lying open area. Years later, wells nearby give foul, unsafe water. Explain how soil pollution has led to water pollution, and suggest one preventive measure.
Hint
Rain seeps through the heap.
Answer
Rainwater seeping through the rotting garbage dissolves harmful chemicals, metals and germs and carries them down into the groundwater, which feeds the wells. Prevention: segregate and compost or recycle waste, and use lined landfill sites away from water sources.
Test your recall
Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.
1.Four sources of air pollution in the syllabus?Show answer
Vehicles, industries, burning garbage, brick kilns.
2.What does an oil film on the sea stop from entering the water?Show answer
Oxygen from the air (and sunlight).
3.Two diseases spread by water polluted with sewage?Show answer
Cholera and typhoid (also jaundice).
4.Gas that gives firework smoke its choking, sulphur smell?Show answer
Sulphur dioxide.
5.What is the pollutant in thermal pollution?Show answer
Heat.
Types and Sources of Pollution: frequently asked questions
What are the types of pollution in the ICSE Class 10 syllabus?
Air, water, thermal, soil, biomedical waste, radiation and noise pollution, each with named sources, plus biodegradable and non-biodegradable wastes.
Is noise really a pollutant if it leaves nothing behind?
Yes. Unwanted loud sound harms health, causing hearing loss, disturbed sleep, stress and high blood pressure, so it is treated as pollution even though it leaves no residue.
Is carbon monoxide the same kind of pollutant as carbon dioxide?
No. Carbon monoxide comes from incomplete burning and is poisonous: it forms carboxyhaemoglobin and cuts the oxygen supply. Carbon dioxide comes from complete burning; it is not poisonous in this way, but extra CO₂ adds to global warming.