Kinds, causes and effects of pollution

Six kinds of pollution, their main causes and sources, and effects on health, nature, climate and the economy

Scope: The six kinds of pollution with their causes and effects. The meaning of pollution and its statutory definitions are covered in the note on environmental degradation and pollution.

In one minute

Pollution comes in six main kinds: air, water, soil, noise, thermal and radioactive. Each has its own sources and its own harm.

Most pollution today comes from human activity. Its effects fall on health, nature, the climate and the economy. This is one of the most common long questions in the paper.

Exam focus

Frequency: Frequently asked
Usually asked as: Both (long answer and short answer)

Legal provision

Section 2(b) and (c), Environment (Protection) Act, 1986: an environmental pollutant is a substance in a concentration injurious to environment, and environmental pollution is its presence in the environment.
Section 2(e), Water (Prevention and Control of Pollution) Act, 1974: defines pollution of water, including change in its physical, chemical or biological properties.
Section 2(a) and (b), Air (Prevention and Control of Pollution) Act, 1981: defines an air pollutant, which includes noise, and air pollution.
Section 3(1), Environment (Protection) Act, 1986: the Central Government's power to take measures to prevent, control and reduce pollution of every kind.

Meaning and definition

Pollution is the introduction of harmful substances or energy into the environment beyond what it can absorb. A kind of pollution is named by the part of the environment that is harmed or by the form of the pollutant.

Six kinds of pollutionHow to read this: start at the top box and follow the lines down to the six kinds. Each box gives the typical source.

Pollution
- AirVehicle exhaust, factory smoke, power plants.
- WaterIndustrial effluent, sewage, farm runoff.
- SoilPesticides, industrial waste, poor waste disposal.
- NoiseTraffic, industry, loudspeakers, construction.
- ThermalHot water from power plants and factories.
- RadioactiveNuclear accidents and poor disposal of radioactive waste.

Detailed explanation

Step 1: the six kinds

Kind	What it is	Typical source
Air pollution	Harmful gases and particles released into the air	Vehicles, factories, power plants
Water pollution	Contamination of rivers, lakes and groundwater	Industrial effluent, sewage, farm runoff
Soil pollution	Contamination of land with chemicals or waste	Pesticides, industrial waste, dumping
Noise pollution	Excessive or disturbing sound	Traffic, industry, loudspeakers
Thermal pollution	Sudden rise or fall in the temperature of water	Hot water from power plants
Radioactive pollution	Release of radioactive substances	Accidents, waste disposal

Example. A fertiliser plant near Visakhapatnam releases ammonia into the air (air pollution), pumps washing water into a creek (water pollution), and runs a loud blower all night (noise). One plant, three kinds.

Step 2: causes

Pollution has natural causes, such as volcanic ash and dust storms. Human causes are far larger today.

Industry: factories and power plants release carbon dioxide, nitrogen and sulphur oxides, and toxic chemicals.
Cities and transport: vehicle exhaust, construction dust and loss of green cover.
Farming: fertilisers and pesticides run into soil and water, and livestock give off methane.
Waste: plastic and chemical waste dumped on land or in water.
Mining: dust in the air and toxic substances leaching into soil and water.
Deforestation: fewer trees to absorb pollutants and carbon dioxide, and more soil erosion.
Population growth: more consumption and more waste.

Step 3: effects on health

Air pollution is linked to asthma, bronchitis and heart disease. Polluted water spreads cholera and typhoid. Long exposure to chemicals can cause cancer, and lead and mercury can damage the nervous system.

Example. Children living near a brick-kiln cluster in Telangana cough through the winter months. Smoke and fine dust in the air irritate their lungs.

Step 4: effects on nature, climate and the economy

Nature: habitats are destroyed and species decline. Oil spills, heavy metals and plastics devastate water life. Soil becomes unfit for farming.
Climate: pollution that adds greenhouse gases drives global warming and climate change.
Economy: lost crops, ruined resources and higher health costs.

Step 5: how the law responds

Each kind has its own regulation. The Air Act and the Water Act cover air and water. Noise is treated as an air pollutant and is also governed by rules under the 1986 Act. The 1986 Act gives wide powers for all kinds. Remedies under common law and the Constitution are covered in the notes on those topics.

Don't confuse: natural and human causes

Point	Natural causes	Human (anthropogenic) causes
Examples	Volcanic ash, forest fires started by lightning, dust storms	Factories, vehicles, farm chemicals, waste dumping
Control by law	Hard to control	Can be regulated, penalised and prevented

Inside the concept. A volcanic eruption throws ash into the air. The cause is natural, and no law can stop it.

Just outside it. A cement plant releases dust every day. The cause is human, and the Air Act can regulate it.

Common mistakes

Listing only air and water pollution. There are six kinds in the standard answer.
Forgetting thermal and radioactive pollution.
Leaving out the effects on climate and the economy.
Treating noise as outside pollution law. The Air Act's definition of air pollutant includes noise.

Apply it

Problem

A steel unit near a town emits dust and smoke, releases hot water into a canal and runs heavy machinery at night. A resident group wants to know how many kinds of pollution are involved.

Issue. Which kinds of pollution does the unit cause?

Rule. Pollution may be of air, water, soil, noise, thermal or radioactive kinds.

Application. Dust and smoke are air pollution. Hot water in the canal is thermal pollution, and it may also be water pollution. The night machinery is noise pollution.

Conclusion. Three kinds are involved: air, thermal and noise pollution. The residents can complain under the relevant Acts.

Leading case laws

M.C. Mehta v. Union of India (Taj Trapezium Case) (1997)
Facts. Industrial emissions in the Taj Trapezium Zone damaged the Taj Mahal.

Principle. The Court directed the 292 listed Agra industries to switch to natural gas or stop using coke and coal in the zone and relocate.

Why it matters. It is a leading example of air pollution harming a monument.
Vellore Citizens Welfare Forum v. Union of India (1996)
Facts. Tanneries discharged untreated effluent in five Tamil Nadu districts and polluted land and drinking water around the Palar river.

Principle. Both the precautionary principle and the polluter pays principle are part of the environmental law of the country.

Why it matters. It is a leading example of water and soil pollution and shows who bears the cost.

How to write this answer in the exam

5-mark answer

Meaning of pollution.
Six kinds, one line each.
Main causes.
Main effects.

10-mark answer

Meaning of pollution and statutory definitions.
Table of the six kinds with sources.
Causes: natural, then human (industry, cities, farming, waste, mining, deforestation, population).
Effects on health, nature, climate and the economy.
Legal response in brief.
Two cases: Taj Trapezium and Vellore Citizens.

Key points to remember

Six kinds: air, water, soil, noise, thermal, radioactive.
Human causes dominate: industry, transport, farming, waste, mining, deforestation, population.
Effects: health, nature, climate, economy.
The Air Act definition of air pollutant includes noise.
Taj Trapezium: air pollution and a monument. Vellore: effluent in water and land.

Quick self-test

1. Name the six kinds of pollution.

Air, water, soil, noise, thermal and radioactive.

2. Give two human causes of pollution.

Any two of industry, transport, farming, waste disposal, mining, deforestation and population growth.

3. Is noise within the Air Act definition?

Yes. Section 2(a) includes noise in "air pollutant".