Air Pollution
Environment
POLLUTANTS AND THEIR TYPES
Pollutants are elements, molecules or particles that contaminate the air.
• Primary pollutants – Emitted directly from a source.
• Secondary pollutants – Form in the atmosphere through chemical reactions between primary pollutants.
• Quantitative pollutants – Naturally occurring substances that turn harmful when concentration exceeds the threshold.
• Qualitative pollutants – Substances not normally present in the environment and harmful by nature (added by humans).
Air pollution is responsible for 1 in 9 deaths globally and is strongly linked to climate change. Short-lived climate pollutants—methane, black carbon and ground-level ozone—contribute significantly to global warming.
Major air pollutants include CO, CO₂, CFCs, lead, ozone, particulate matter (PM2.5 & PM10), SO₂ and smog.
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NATURAL SOURCES OF AIR POLLUTION
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• Dust from barren lands
• Methane emissions from natural sources
• Radon gas from radioactive decay
• Smoke and CO from wildfires
• Volcanic emissions (sulphur, chlorine, ash)
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ANTHROPOGENIC SOURCES
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• Traditional biomass burning (wood, crop residue, dung)
• Industries and vehicles – major sources of ground-level ozone
• NOx + VOCs (from paints, solvents) + sunlight → photochemical smog
• Fumes from aerosols, varnishes, sprays
• Methane from landfills
• Toxic gases from military activities
• Particulate matter from mining
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INDOOR AIR POLLUTION
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Indoor air can be more polluted than outdoor air.
• Radon – radioactive gas causing lung cancer
• Second-hand smoke – carbon monoxide and fine particles
• Biological pollutants – mould, pollen
• VOCs – from lacquers, pesticides, building materials, furnishings
• Carbon monoxide – from heaters, stoves, vehicles
• Ozone – from UV reactions, high-voltage devices
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NATIONAL AIR QUALITY INDEX (AQI)
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AQI has six categories: Good, Satisfactory, Moderately Polluted, Poor, Very Poor, Severe.
Pollutants considered: PM10, PM2.5, CO, Ozone, NO₂, NH₃, SO₂, Lead.
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NATIONAL AIR QUALITY MONITORING PROGRAMME (NAMP)
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Monitors ambient air quality and ensures compliance with NAAQS.
Pollutants monitored: SO₂, CO, NO₂, PM10, PM2.5, Ozone, Ammonia, Lead, Benzopyrene, Nickel, Benzene, Arsenic.
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NATIONAL CLEAN AIR PROGRAMME (NCAP)
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• Implemented by MoEFCC to reduce PM10 & PM2.5 levels by 20–30% by 2024
• Base year: 2017 | Launch year: 2019
• Coverage: 102 non-attainment cities
• Not legally binding
• Executed by CPCB (statutory body under Water Act, 1974 & Air Act, 1981)
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FLY ASH
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• Residue from coal combustion in thermal power plants
• Bottom ash: settles at the bottom
• Fly ash: escapes with flue gases and collected using ESPs
• Classified as hazardous waste and must be captured
Uses of Fly Ash:
• Replaces Portland cement
• Produces stronger, durable concrete
• Less permeable, resists alkali-silica reactions
• Improves workability and service life
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SMOG
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Smog = smoke + fog.
1. London-type Smog (Sulphurous Smog)
• Occurs in cold conditions
• Coal burning → SO₂ + fog → sulphuric acid droplets
2. Los Angeles-type Smog (Photochemical Smog)
• Occurs on sunny days
• NOx + hydrocarbons + sunlight → ozone, PAN, aldehydes
• Caused mainly by vehicular emissions
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ACID RAIN
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Rain with pH < 5.6 caused by NOx and SO₂ emissions.
Effects:
• Leaching of essential nutrients (Ca, Mg) → reduced soil fertility
• Acidification of lakes → biodiversity loss
• Damage to leaves → reduced photosynthesis
• Slows litter decomposition → harms microorganisms
• Mobilises toxic metals
• Disrupts nitrogen and sulphur cycles
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BHARAT STAGE EMISSION STANDARDS
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• Introduced in 2000 (based on European norms)
• BS III: nationwide since 2010
• BS IV: 13 major cities since 2010; nationwide from 2017
• BS V skipped
• BS VI implemented directly from April 2020
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AIR (PREVENTION AND CONTROL OF POLLUTION) ACT, 1981
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Enacted to implement Stockholm Conference decisions.
Objectives:
• Improve air quality
• Prevent, control and reduce air pollution
Key Provisions:
• Defines air pollutants under Section 2(a)
• Noise added in 1987 amendment
• Section 2(g) → Establishment of CPCB
• SPCBs to be set up for states
• Industries must obtain “consent to operate”
• States prescribe emission standards in line with CPCB
• Before 1988 → enforcement through criminal prosecution
• After 1988 → CPCB/SPCB empowered to close industries
• Citizens’ suit provision added
• Includes noise pollution control
Penalties:
• Non-compliance → imprisonment of 1–6 years + fine
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Subject: Environment
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