Air Pollution
Environment
Pollutants and Their Types
Pollutants are elements, molecules or particles that contaminate the air.
Types of Pollutants
- 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.
Natural Sources of Air Pollution
- Dust from barren lands
- Methane emissions from natural sources
- Radon gas from radioactive decay
- Smoke and CO from wildfires
- Volcanic emissions (sulphur, chlorine, ash)
Anthropogenic Sources
- 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
Indoor Air Pollution
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
National Air Quality Index (AQI)
AQI has six categories: Good, Satisfactory, Moderately Polluted, Poor, Very Poor, Severe.
Pollutants Considered
- PM10
- PM2.5
- CO
- Ozone
- NO₂
- NH₃
- SO₂
- Lead
National Air Quality Monitoring Programme (NAMP)
Monitors ambient air quality and ensures compliance with NAAQS.
Pollutants Monitored
- SO₂
- CO
- NO₂
- PM10
- PM2.5
- Ozone
- Ammonia
- Lead
- Benzopyrene
- Nickel
- Benzene
- Arsenic
National Clean Air Programme (NCAP)
- 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)
Fly Ash
- 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
Smog
Smog = smoke + fog.
London-type Smog (Sulphurous Smog)
- Occurs in cold conditions
- Coal burning → SO₂ + fog → sulphuric acid droplets
Los Angeles-type Smog (Photochemical Smog)
- Occurs on sunny days
- NOx + hydrocarbons + sunlight → ozone, PAN, aldehydes
- Caused mainly by vehicular emissions
Acid Rain
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
Bharat Stage Emission Standards
- 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
Air (Prevention and Control of Pollution) Act, 1981
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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