Chapter 18: Pollution of air and water

These NCERT Class 8 Science Chapter 18 notes explain pollution of air and water in a clear and structured manner. The chapter focuses on how harmful substances contaminate natural resources and affect human health and the environment.

It discusses causes and effects of air pollution, greenhouse effect, global warming and acid rain. The chapter also explains water pollution, potable water, sewage treatment plants and measures to prevent pollution.

Chapter 18 – Pollution of Air and Water is important for understanding environmental issues and sustainable development. It is highly relevant for school examinations and foundation level competitive preparation.

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1. Introduction: what is pollution?

• Pollution is the contamination of natural resources like air and water.
• When harmful substances mix with air or water, they become polluted.
• Pollution affects human health and the environment.
• It also harms plants and animals.
• Breathing polluted air or drinking dirty water can cause diseases.

2. Air pollution and its meaning

• Air pollution is the presence of harmful substances in air.
• These harmful substances are called air pollutants.
• Polluted air reduces air quality.
• It mainly affects cities and industrial areas.
• Clean air is essential for healthy living.

3. Causes of air pollution

• Smoke from vehicles is a major source of pollution.
• Factories release harmful gases into the air.
• Burning coal, wood and petrol increases pollution.
• Burning garbage releases toxic gases.
• Firecrackers also pollute the air.

4. Common air pollutants

• Carbon monoxide is a poisonous gas released from vehicles.
• Carbon dioxide contributes to global warming.
• Sulphur dioxide and nitrogen dioxide cause acid rain.
• Smoke and dust particles reduce visibility.
• These pollutants harm lungs and environment.

5. Effects of air pollution

• Air pollution causes breathing problems and asthma.
• It leads to eye irritation and lung diseases.
• Smog forms when smoke mixes with fog.
• It contributes to global warming.
• It can also cause acid rain.

6. Greenhouse effect and global warming

• The greenhouse effect occurs when certain gases trap heat in the atmosphere.
• These gases are called greenhouse gases.
• Excess greenhouse gases lead to global warming.
• Carbon dioxide and methane are major greenhouse gases.
• Global warming increases Earth’s temperature.

7. Preventing air pollution

• Use public transport to reduce vehicle smoke.
• Use CNG and electric vehicles.
• Plant more trees to absorb carbon dioxide.
• Avoid burning waste materials.
• Use cleaner fuels for cooking and transport.

8. Water pollution and its meaning

• Water pollution is the contamination of water bodies.
• Rivers, lakes, ponds and seas can get polluted.
• Polluted water is unsafe for drinking and bathing.
• It affects aquatic life.
• Clean water is essential for survival.

9. Causes of water pollution

• Sewage from homes is a major cause.
• Industrial waste releases harmful chemicals.
• Agricultural chemicals like pesticides mix with water.
• Oil spills pollute sea water.
• Dumping garbage into rivers increases pollution.

10. Water pollutants and their impact

• Sewage contains waste and harmful microorganisms.
• Chemicals and pesticides contaminate water.
• Fertilisers increase nutrient levels in water.
• Oil forms a layer on water surface.
• These pollutants harm aquatic plants and animals.

11. Effects of water pollution

• Polluted water spreads diseases like cholera and typhoid.
• It causes diarrhoea and stomach infections.
• Aquatic animals may die due to lack of oxygen.
• Drinking water shortage increases.
• Polluted rivers cannot be used safely.

12. Potable water and purification

• Potable water is water safe for drinking.
• It should be free from germs and harmful chemicals.
• Boiling kills germs present in water.
• Filtration removes suspended particles.
• Chlorination and RO help purify water.

13. Sewage treatment and prevention

• Sewage treatment cleans wastewater before release.
• A sewage treatment plant (STP) removes harmful substances.
• Treated water is safer for the environment.
• Waste should not be dumped into water bodies.
• Using eco-friendly products reduces water pollution.

14. Role of individuals in pollution control

• Save water and avoid wastage.
• Keep surroundings clean.
• Spread awareness about pollution control.
• Follow reduce, reuse and recycle methods.
• Practice environmental responsibility in daily life.

15. Key exam-oriented keywords explained

• Pollution: Contamination of natural resources.
• Air pollution: Presence of harmful substances in air.
• Water pollution: Contamination of water bodies.
• Air pollutants: Harmful substances present in air.
• Sewage: Wastewater from homes and industries.
• Potable water: Water safe for drinking.
• Greenhouse effect: Trapping of heat by gases in atmosphere.
• Global warming: Rise in Earth’s temperature due to greenhouse gases.
• Acid rain: Rain containing harmful acidic gases.
• Sewage treatment plant: Facility that cleans wastewater.

16. One-page summary for quick revision

• Pollution contaminates air and water.
• Air pollution causes respiratory diseases and climate change.
• Water pollution spreads diseases and kills aquatic life.
• Potable water is necessary for health.
• Individual and collective efforts can reduce pollution.

Understanding NCERT Class 8 Science Chapter 18 is essential to learn how pollution affects air, water and life on Earth. The chapter clearly explains causes, effects and preventive measures.

The concepts help students understand environmental responsibility and the importance of conservation. It is highly useful for school exams and foundation competitive preparation.

This completes the NCERT Class 8 Science syllabus. You can now revise all chapters systematically for strong conceptual clarity and exam preparation.

FAQs

Q1. What is pollution?
Pollution is the contamination of natural resources like air and water by harmful substances.

Q2. What are air pollutants?
Air pollutants are harmful gases and particles such as carbon monoxide, sulphur dioxide and dust present in air.

Q3. What is the greenhouse effect?
The greenhouse effect is the trapping of heat in the atmosphere by certain gases, leading to warming of the Earth.

Q4. What is potable water?
Potable water is water that is safe for drinking and free from harmful substances.

Q5. Why is this chapter important for exams?
It explains environmental issues, pollution control and conservation, which are important for school exams and foundation preparation.

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