Pollution ICSE Class 9: Types, Sources, Effects and Preventive Measures

What Pollution is about

Weightage: CISCE publishes no chapter weightage and no question-paper layout for ICSE Class 9 Geography. Class IX is examined by your school: one 80-mark paper of 2 hours plus 20 marks of internal assessment (a record file and one project). Pollution is topic 5 of the 2028 syllabus.Source: CISCE ICSE 2028 Geography syllabus, Class IX

Key concepts

Pollution and pollutants

Pollution is the undesirable change in the physical, chemical or biological characteristics of air, water or soil that harms human health, other living things or property.

A pollutant is any substance or form of energy (such as noise, heat or radiation) that causes pollution.

• Biodegradable pollutants can be broken down by bacteria and other natural processes, e.g. sewage, vegetable waste, paper.
• Non-biodegradable pollutants cannot be broken down easily and remain for a very long time, e.g. plastics, DDT, mercury, radioactive waste. They are more dangerous because they accumulate.

Types of pollution in the syllabus: air, water (fresh water and marine), soil, radiation and noise.

Causes behind all types: rapid growth of population, urbanisation, industrialisation, increased use of vehicles and energy, and modern farming with chemicals.

Worked example

(2 marks) Distinguish between biodegradable and non-biodegradable pollutants with one example of each.

Try it first, then show the solutionSolution

1. Biodegradable: broken down by natural processes, e.g. sewage or kitchen waste - 1 mark.
2. Non-biodegradable: not broken down easily, persist and accumulate, e.g. plastic or DDT - 1 mark.

Answer: Biodegradable pollutants, such as sewage and kitchen waste, are broken down by bacteria and natural processes. Non-biodegradable pollutants, such as plastics and DDT, are not broken down easily and remain and accumulate in the environment for long periods.

Air pollution: sources and effects

Sources (syllabus):
1. Vehicular: exhaust from petrol and diesel vehicles releases carbon monoxide (CO), nitrogen oxides (NOx), unburnt hydrocarbons and fine particles (soot).
2. Industrial: factories, thermal power stations and refineries burning coal and oil release sulphur dioxide (SO₂), nitrogen oxides, smoke and dust; some release poisonous gases.
3. Burning of garbage: open burning of waste and plastics releases smoke, fine particles and toxic gases such as dioxins.

Effects on human health:

• Respiratory diseases: asthma, bronchitis, lung infections and, over time, lung cancer; fine particles enter deep into the lungs and blood.
• Carbon monoxide combines with haemoglobin and reduces the oxygen carried by blood, causing headaches and, in high doses, death.
• Irritation of eyes, nose and throat; heart disease.
• Disaster example: in December 1984 a leak of methyl isocyanate gas from a pesticide factory in Bhopal killed thousands of people.

Effects on the environment:

• Acid rain: SO₂ and NOx dissolve in rain to form acids that damage forests, lakes, soils and buildings; sulphur dioxide pollution has discoloured the marble of monuments such as the Taj Mahal.
• Smog: smoke mixed with fog reduces visibility, as in winter in north Indian cities.
• Global warming from carbon dioxide, and ozone depletion from CFCs.
• Damage to crops and reduced plant growth.

Worked example

(3 marks) Name three sources of air pollution and one harmful effect of each.

Try it first, then show the solutionSolution

1. Vehicles: carbon monoxide reduces oxygen in blood - 1 mark.
2. Industries: sulphur dioxide causes acid rain and lung problems - 1 mark.
3. Burning garbage: smoke and toxic gases cause respiratory diseases and smog - 1 mark.

Answer: (1) Vehicles release carbon monoxide, which reduces the oxygen carried by blood. (2) Industries and thermal plants release sulphur dioxide, which causes acid rain and breathing problems. (3) Burning garbage releases smoke and toxic gases that cause respiratory diseases and add to smog.

Water pollution: fresh water and marine

Sources (syllabus):
1. Domestic waste: untreated sewage, kitchen waste and detergents from homes drain into rivers and lakes.
2. Industrial waste: factories (tanneries, chemical, paper, textile and sugar mills) discharge chemicals, dyes, acids, oil and heavy metals such as mercury and lead; power plants release hot water.
(Run-off of fertilisers and pesticides from farms also pollutes water.)

Effects on health:

• Water-borne diseases from sewage-polluted water: cholera, typhoid, jaundice (hepatitis) and diarrhoea.
• Poisoning from heavy metals: mercury in waste water poisoned fish and the people who ate them at Minamata in Japan (Minamata disease).

Effects on the environment:

• Eutrophication: phosphates (detergents) and nitrates (fertilisers) make algae grow rapidly (algal bloom); when they die and decay, bacteria use up the dissolved oxygen, and fish die.
• Biomagnification: non-biodegradable chemicals increase in concentration along food chains.
• Hot water from industries lowers dissolved oxygen (thermal pollution).

Marine pollution: sewage and industrial waste from coastal cities, oil spills from tankers and offshore wells, and plastics that are carried by rivers to the sea. Oil forms a film on the water that blocks sunlight and oxygen, coats the feathers of seabirds and kills fish; plastic is swallowed by turtles, whales and birds, and breaks into microplastics; coral reefs are damaged.

Worked example

(3 marks) Explain how domestic waste and detergents can lead to the death of fish in a lake.

Try it first, then show the solutionSolution

1. Sewage and detergents add nutrients (phosphates) to the lake - 1 mark.
2. Algae grow rapidly (algal bloom); when they die, bacteria decompose them, using up dissolved oxygen - 1 mark.
3. Fish die from lack of oxygen (eutrophication) - 1 mark.

Answer: Domestic sewage and detergents add nutrients such as phosphates to the lake, causing a rapid growth of algae. When the algae die, bacteria decomposing them use up the dissolved oxygen, so fish suffocate and die. This process is called eutrophication.

Soil pollution

Sources (syllabus):
1. Chemical fertilisers: excessive use alters the natural chemistry of the soil, can make it acidic or saline, and kills useful micro-organisms and earthworms, reducing fertility in the long run.
2. Pesticides (insecticides, herbicides, fungicides): many are poisonous and persistent; they kill useful insects and soil organisms and enter food chains. DDT, now banned for farm use in India, is an example of a persistent pesticide.
3. Bio-medical waste: waste from hospitals, clinics and laboratories, such as used syringes, needles, bandages, blood-soaked cotton, expired medicines and body parts. If dumped with ordinary garbage it spreads infection (hepatitis, HIV, tetanus) and harmful chemicals.
(Plastics, industrial waste and mining waste also pollute soil.)

Effects:

• Loss of soil fertility and lower crop yields.
• Harmful chemicals enter crops, then animals and people, causing illness.
• Run-off carries the chemicals into rivers and groundwater.
• Infections spread to rag-pickers, sanitation workers and animals from improperly disposed bio-medical waste.

Safe handling of bio-medical waste: segregate it at source into colour-coded bins, disinfect or incinerate it, and dispose of sharps separately.

Worked example

(2 marks) Why is bio-medical waste dangerous if mixed with ordinary municipal garbage?

Try it first, then show the solutionSolution

1. It contains infected material such as used syringes, needles and blood-soaked dressings - 1 mark.
2. It can spread diseases (hepatitis, HIV, tetanus) to sanitation workers, rag-pickers and animals, and contaminate soil and water - 1 mark.

Answer: Bio-medical waste contains used needles, syringes and dressings carrying germs and chemicals. Mixed with ordinary garbage it can injure and infect sanitation workers, rag-pickers and animals with diseases such as hepatitis and tetanus, and contaminate soil and water.

Radiation and noise pollution

Radiation pollution: the release of harmful high-energy (ionising) radiation into the environment.
Sources (syllabus):
1. X-rays: used in hospitals for diagnosis; frequent or careless exposure is harmful to patients and staff.
2. Radioactive fallout from nuclear plants: accidents release radioactive substances into the air, which settle on land and water. The Chernobyl disaster (1986, in present-day Ukraine) spread fallout across much of Europe; the Fukushima plant in Japan was damaged by the 2011 tsunami. Disposal of radioactive waste is also a problem.
Effects: damage to cells, cancers such as leukaemia, burns, genetic mutations and birth defects; contamination of crops, milk and water for long periods.

Noise pollution: unwanted, loud sound that causes discomfort or harm. Loudness is measured in decibels (dB); every increase of 10 dB means ten times the sound intensity.
Sources (syllabus): traffic (horns, engines), factories (machines), construction sites (drills, pile-drivers), loudspeakers (at functions, processions, festivals) and airports (aircraft taking off and landing).
Effects on health: hearing loss with long exposure to loud noise (above about 85 dB), headaches, stress, irritability, high blood pressure, sleeplessness and lack of concentration (especially for students). Effects on animals: birds and animals are disturbed and may leave their habitats.
Control: India's Noise Pollution (Regulation and Control) Rules, 2000 set limits for residential, commercial, industrial and silence zones (areas around hospitals, schools and courts) and restrict loudspeakers at night.

Worked example

(3 marks) Name three sources of noise pollution and state two of its effects on human health.

Try it first, then show the solutionSolution

1. Sources: traffic, factories, construction sites, loudspeakers, airports (any three) - 1 mark.
2. Effect: hearing loss from prolonged loud noise - 1 mark.
3. Effect: stress, headaches, high blood pressure or sleeplessness - 1 mark.

Answer: Sources include road traffic, construction sites and airports. Prolonged exposure to loud noise can cause permanent hearing loss, and it also causes stress, headaches, high blood pressure and sleeplessness.

Preventive measures

Syllabus measures:
1. Carpools: several people sharing one car for regular journeys reduces the number of vehicles, fuel burnt, exhaust and traffic noise.
2. Promotion of public transport: buses, metro rail and suburban trains carry many people with less fuel per person; electric or CNG buses pollute less.
3. No-smoking zones: banning smoking in public places (offices, schools, hospitals, transport) protects non-smokers from second-hand smoke; Indian law bans smoking in public places.
4. Restricted use of fossil fuels: shifting to solar, wind and hydro power; cleaner fuels such as CNG and LPG; electric vehicles; reduces carbon dioxide, sulphur dioxide and smoke.
5. Saving energy: switching off lights and fans, using LED bulbs and efficient appliances; less electricity means less coal burnt in thermal plants.
6. Encouragement of organic farming: using compost, green manure, crop rotation and natural pest control instead of chemical fertilisers and pesticides prevents soil and water pollution and gives healthier food.

Other measures by type: treat sewage and industrial waste before discharge; install filters, scrubbers and electrostatic precipitators in factories; plant trees as green belts and noise barriers; segregate waste and avoid burning garbage; follow bio-medical waste rules; limit X-ray exposure and use lead aprons; observe silence zones and limit loudspeaker use; reduce, reuse and recycle plastics.

Worked example

(3 marks) Explain how carpools, saving energy and organic farming help reduce pollution.

Try it first, then show the solutionSolution

1. Carpools: fewer vehicles, less fuel burnt, less exhaust and noise - 1 mark.
2. Saving energy: less electricity needed, so less coal burnt in thermal plants - 1 mark.
3. Organic farming: no chemical fertilisers or pesticides, so less soil and water pollution - 1 mark.

Answer: Carpools put fewer vehicles on the road, cutting fuel use, exhaust and noise. Saving energy reduces electricity demand, so thermal power stations burn less coal and emit less smoke and gas. Organic farming replaces chemical fertilisers and pesticides with natural methods, preventing soil and water pollution.

Pollution in real life

Each concept, met in an everyday situation. Read the situation, answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Topics in this chapter

• Air, Water, Soil, Radiation and Noise Pollution and Their Prevention

Pollution: key facts

Five types

Air, water (fresh and marine), soil, radiation, noise

As in the syllabus.

Sources by type

Air	vehicles, industry, burning garbage
Water	domestic, industrial waste
Soil	fertilisers, bio-medical waste, pesticides
Radiation	X-rays, nuclear fallout
Noise	traffic, factories, construction, loudspeakers, airports

Match source to type exactly.

Key pollutants

CO and NOx (vehicles); SO₂ (coal, industry); phosphates (detergents); mercury, lead (industry); DDT (pesticide)

Name the pollutant with its effect.

Decibel rule

$+10dB=10\times soundintensity;+20dB=100\times$

Long exposure above about 85 dB damages hearing.

Preventive measures (syllabus)

Carpools, public transport, no-smoking zones, less fossil fuel, saving energy, organic farming

Link each to the pollution it reduces.

How the school exam asks Pollution

The question patterns to expect, and the method that works for each.

Tricks to remember Pollution

Short memory aids. Say each one aloud once, then use it on a question the same day.

• AWSRN

  A Wise Student Reduces Noise: Air, Water, Soil, Radiation, Noise.

  Use it when: Five types.

• TFCLA

  Noise sources: Traffic, Factories, Construction, Loudspeakers, Airports ('Too Few Can Listen Anymore').

  Use it when: Noise sources from the syllabus.

• C-P-N-F-E-O

  Measures: Carpools, Public transport, No smoking, Fossil fuels cut, Energy saving, Organic farming.

  Use it when: Preventive measures.

Pollution: exam-level solved questions

Ordered from exam level to HOTS. Cover the solution, write your own, then compare step by step.

Case-study practice (Section B style)

Read the situation, then answer every part. In a school exam set on the board pattern this is a 8-mark question split into 2 + 3 + 3 marks.

Where the marks are

How a typical answer is split into step marks. Show every step: a right final answer alone rarely earns full marks.

Where students lose marks in Pollution

The slips examiners see most often, and what to write instead.

• ✗Mistake: Matching sources to the wrong type

  Sources learnt as one list.

  Wrong working

  Pesticides are a source of radiation pollution.

  Right working

  Pesticides cause soil (and water) pollution; X-rays and nuclear fallout cause radiation pollution.

  ✓Do this: Learn the syllabus list type by type.

  Usually costs: 1 mark each.

• ✗Mistake: Vague effects such as 'harmful to health'

  No specific disease or process given.

  ✓Do this: Name it: asthma, cholera, hearing loss, eutrophication, acid rain.

  Usually costs: 1 mark per point.

• ✗Mistake: Measures not linked to a type of pollution

  Lists of good habits written without explanation.

  ✓Do this: Say what each measure reduces: carpools cut vehicle exhaust (air) and noise.

  Usually costs: 1 mark per measure.

• ✗Mistake: Forgetting marine pollution

  Water pollution is treated as rivers only.

  ✓Do this: The syllabus says fresh and marine: add oil spills, plastics and coastal sewage.

  Usually costs: 1 mark.

Practice questions on Pollution

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · MCQExam level

   Which gas from industries is a major cause of acid rain?
   (a) Oxygen
   (b) Sulphur dioxide
   (c) Nitrogen
   (d) Argon

   Hint

   Coal burning.

   Answer

   (b) Sulphur dioxide.

2. Q2 · 1 mark · MCQExam level

   Loudness of sound is measured in:
   (a) hertz
   (b) decibels
   (c) millibars
   (d) watts

   Hint

   dB.

   Answer

   (b) decibels.

3. Q3 · 2 marks · Very short answerExam level

   Name two diseases caused by drinking water polluted with sewage.

   Hint

   Water-borne.

   Answer

   Cholera and typhoid (also jaundice and diarrhoea).

4. Q4 · 2 marks · Very short answerHarder exam level

   How does excessive use of chemical fertilisers harm the soil?

   Hint

   Chemistry and organisms.

   Answer

   It upsets the soil's natural chemistry, can make it acidic or saline, and kills useful micro-organisms and earthworms, so fertility falls in the long run; excess also washes into water bodies.

5. Q5 · 2 marks · Very short answerHarder exam level

   Why is radioactive fallout from a nuclear accident harmful long after the accident?

   Hint

   Long-lived substances.

   Answer

   Some radioactive substances keep giving out radiation for many years. Settling on soil and water, they enter crops, milk and food chains, causing cancers and genetic damage long after the event, as around Chernobyl.

6. Q6 · 2 marks · Very short answerHarder exam level

   State two effects of noise pollution on students.

   Hint

   Learning and health.

   Answer

   (1) Loss of concentration and poorer learning. (2) Headaches, irritability and disturbed sleep (and hearing damage with long exposure).

7. Q7 · 2 marks · Very short answerHarder exam level

   Explain why burning garbage is a cause of air pollution, and suggest a better way to deal with garbage.

   Hint

   Smoke, segregation.

   Answer

   Burning garbage, especially plastics, releases smoke, fine particles and toxic gases that cause respiratory problems. Better: segregate waste at source, compost wet waste and recycle dry waste.

8. Q8 · 3 marks · Short answerHOTS / competency

   A school is located next to a busy airport. A sound meter shows 90 dB during take-offs compared with 60 dB normally. How many times more intense is the take-off noise, and what could the school do?

   Hint

   30 dB = three steps of 10.

   Answer

   30 dB more = 10 × 10 × 10 = 1,000 times the intensity. The school could install sound-insulating windows and walls, plant thick rows of trees as a noise barrier, and request flight-path changes during school hours.

9. Q9 · 2 marks · Very short answerHarder exam level

   Why are no-smoking zones considered a measure against air pollution?

   Hint

   Second-hand smoke.

   Answer

   Tobacco smoke contains harmful gases and particles. Banning smoking in public places keeps indoor and public air cleaner and protects non-smokers, especially children, from inhaling second-hand smoke.

10. Q10 · 3 marks · Short answerHOTS / competency

    'Restricting the use of fossil fuels solves more than one environmental problem.' Explain with three points.

    Hint

    Air, acid rain, warming.

    Answer

    (1) Less burning of coal, petrol and diesel reduces smoke, CO and particulates, improving air quality and health. (2) Less sulphur dioxide and nitrogen oxides means less acid rain damaging forests, lakes and monuments. (3) Less carbon dioxide slows global warming. Using solar, wind and electric transport instead tackles all three.

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. 1.Gas from vehicles that reduces oxygen carried by blood?Show answer

   Carbon monoxide.

2. 2.Process by which nutrients cause algal blooms and fish deaths?Show answer

   Eutrophication.

3. 3.Unit of loudness?Show answer

   Decibel (dB).

4. 4.Two sources of radiation pollution in the syllabus?Show answer

   X-rays; radioactive fallout from nuclear plants.

5. 5.Waste from hospitals is called?Show answer

   Bio-medical waste.

6. 6.Farming without chemical fertilisers and pesticides?Show answer

   Organic farming.

Quick revision checklist

The night before the exam: can you do each of these without looking?

• ☐Air: vehicles (CO, NOx), industry (SO₂, smoke), burning garbage; asthma, acid rain, smog, warming.
• ☐Water: domestic and industrial waste; cholera, typhoid, eutrophication, mercury poisoning; marine: oil spills, plastics.
• ☐Soil: fertilisers, pesticides, bio-medical waste; fertility loss, poisons in food, infection.
• ☐Radiation: X-rays, nuclear fallout; cancer, mutations. Noise: traffic, factories, construction, loudspeakers, airports; hearing loss, stress.
• ☐Measures: carpools, public transport, no-smoking zones, less fossil fuel, saving energy, organic farming.

Pollution: frequently asked questions