Air pollution refers to the presence of harmful substances (gases, particulates, or biological molecules) in the atmosphere in concentrations that endanger human health, plants, animals, and the environment.
📘 Definition (WHO):
“Air pollution is contamination of the indoor or outdoor environment by any chemical, physical, or biological agent that modifies the natural characteristics of the atmosphere.”
2. Composition of Clean Air
Gas
Percentage by Volume
Nitrogen (N₂)
78.08%
Oxygen (O₂)
20.95%
Argon (Ar)
0.93%
Carbon dioxide (CO₂)
0.04%
Others (Ne, He, CH₄, H₂, O₃, etc.)
Trace amounts
Pollution occurs when this composition is altered by harmful pollutants.
3. Types of Air Pollution
(A) Based on Origin
Type
Description
Examples
Primary pollutants
Emitted directly from identifiable sources
SO₂, CO, NO, hydrocarbons, particulates
Secondary pollutants
Formed by chemical reactions among primary pollutants in the atmosphere
Lead and mercury → brain and nervous system damage.
(B) On Plants
Chlorosis (loss of leaf color).
Reduced photosynthesis due to dust on leaves.
Acid rain → damages leaves and soil nutrients.
Ozone → leaf injury and stunted growth.
(C) On Animals
Ingestion of contaminated fodder.
Acid rain affects aquatic life and food chains.
(D) On Environment and Climate
Smog formation (London-type or photochemical).
Acid rain (from SO₂ and NOₓ).
Ozone layer depletion (due to CFCs).
Global warming (from CO₂, CH₄, N₂O).
Visibility reduction and deterioration of heritage monuments (e.g., Taj Mahal).
7. Control of Air Pollution
(A) Source Control
Use of clean fuels (CNG, LPG, electricity).
Catalytic converters in vehicles.
Electrostatic precipitators in industries to trap particulates.
Scrubbers and filters for flue gases.
Maintenance of engines and machinery.
(B) Technological and Planning Measures
Shift industries away from populated areas.
Promote public transport and non-motorized mobility.
Use of green belt buffers around factories.
Adoption of renewable energy (solar, wind).
Vehicle emission standards (Bharat Stage VI norms in India).
(C) Legal and Policy Measures (India)
Law / Policy
Year
Purpose
Air (Prevention and Control of Pollution) Act
1981
Framework for controlling and monitoring air pollution
Environment (Protection) Act
1986
Umbrella law for environmental protection
National Ambient Air Quality Standards (NAAQS)
2009 (revised)
Specifies safe limits for key pollutants
National Clean Air Programme (NCAP)
2019
Reduce PM₂.₅ and PM₁₀ levels by 40% by 2026
Commission for Air Quality Management (CAQM)
2021
Regulates air quality in NCR and adjoining areas
8. International Efforts
Agreement / Organization
Objective
Stockholm Conference (1972)
First global call for pollution control
UNEP (1972)
United Nations Environment Programme
Montreal Protocol (1987)
Control CFCs and ozone-depleting substances
Kyoto Protocol (1997)
Limit greenhouse gas emissions
Paris Agreement (2015)
Global commitment to combat climate change
WHO Air Quality Guidelines (2021)
Revised global safe limits for key pollutants
9. Air Quality Measurement
Common Parameters (India – CPCB Standards)
Pollutant
Averaging Time
Permissible Limit (µg/m³)
PM₂.₅
24 hours
60
PM₁₀
24 hours
100
SO₂
24 hours
80
NO₂
24 hours
80
CO
8 hours
2 mg/m³
O₃
8 hours
100
Pb
Annual
0.5
AQI (Air Quality Index):
0–50 → Good
51–100 → Satisfactory
101–200 → Moderate
201–300 → Poor
301–400 → Very Poor
401–500 → Severe
10. Preventive and Community Measures
Promote afforestation and urban greenery.
Reduce open burning of waste and crop residue.
Encourage carpooling, public transport, and cycling.
Regular vehicle emission checks.
Awareness campaigns (e.g., “Clean Air for All”, “Beat Air Pollution”).
Citizen participation in air quality monitoring (apps like SAFAR, Sameer).
11. Recent Concerns and Emerging Issues
Indoor air pollution from cooking fuels, incense, mosquito coils.
Microplastics and nanoparticles in air.
Transboundary pollution — e.g., haze over South and Southeast Asia.
Climate change–air pollution nexus (both share common causes).
COVID-19 lockdown provided evidence of improved air quality — highlighting anthropogenic influence.
12. Conclusion
Air pollution is one of the gravest environmental and public health issues of our time. It demands a multi-sectoral approach — combining technology, governance, and citizen responsibility — to ensure clean air for sustainable living.
🌍 “If you can’t see the air, you can’t ignore it — clean air is a human right.”
13. Summary Table (Quick Revision)
Aspect
Key Points
Major pollutants
CO, SO₂, NO₂, PM, O₃, Pb, CFCs
Types
Primary & Secondary
Key effects
Respiratory illness, acid rain, global warming
Key events
London Smog (1952), Bhopal (1984), Delhi Smog
Indian laws
Air Act (1981), EPA (1986), NCAP (2019)
Global treaties
Montreal, Kyoto, Paris
Control measures
Clean fuels, filters, afforestation, public awareness
