Air Pollution: Sources, Health Effects and Policy

The scale of the problem

Air pollution is India's largest environmental health risk. The State of Global Air 2024 report linked about 21 lakh deaths in India in 2021 to air pollution (outdoor and household combined).

India's cities: Indian cities dominate global lists of the most polluted cities by PM2.5. Byrnihat (Assam–Meghalaya border) and Delhi topped the IQAir 2024 rankings.

National standards: India's annual PM2.5 standard is 40 µg/m³. The WHO Air Quality Guideline (2021) is 5 µg/m³. Most of India exceeds both.

Economic cost: the Lancet Planetary Health study (2020) estimated losses of about 1.4% of GDP a year from premature deaths and illness.

Major pollutants

• Particulate matter:
• PM10: coarse particles under 10 microns, from dust, construction and roads;
• PM2.5: fine particles under 2.5 microns, which penetrate deep into the lungs and bloodstream. They come from combustion, secondary aerosols and smoke.
• Sulphur dioxide (SO₂): from coal power plants and smelters. It causes acid rain.
• Nitrogen oxides (NOx): from vehicles and power plants. They are precursors of ozone and secondary particles.
• Ground-level ozone (O₃): a secondary pollutant formed from NOx and volatile organic compounds (VOCs) in sunlight. It damages lungs and crop yields.
• Carbon monoxide (CO): incomplete combustion; reduces the blood's oxygen-carrying capacity.
• Ammonia (NH₃): from fertilisers and livestock. It forms secondary particles.
• Lead, benzene and black carbon (soot, which also warms the climate).

Secondary vs primary: primary pollutants are emitted directly; secondary ones form in the atmosphere. A large share of PM2.5 in north India is secondary (sulphates, nitrates, ammonium).

The National Ambient Air Quality Standards (NAAQS, 2009) cover 12 pollutants. The National Air Quality Index (AQI, 2014) has six categories (Good, Satisfactory, Moderate, Poor, Very Poor and Severe) and uses eight pollutants: PM10, PM2.5, NO₂, SO₂, CO, O₃, NH₃ and Pb.

Sources and the north Indian winter

Delhi-NCR's sources (studies such as IIT Kanpur 2016 and TERI–ARAI 2018) include:

• vehicles;
• road and construction dust;
• industry and power plants;
• biomass and waste burning;
• stubble burning in Punjab and Haryana in October–November, whose share of Delhi's PM2.5 can exceed 30–40% on some peak days;
• diwali firecrackers.

Why winters are worst:

• temperature inversions trap pollutants near the ground;
• low wind speeds;
• the Indo-Gangetic Plain is a bowl bounded by the Himalaya;
• stubble burning coincides with the season.

Household pollution: the burning of solid fuels (wood, dung, crop residue) for cooking. PM Ujjwala Yojana (2016) gave over 10 crore LPG connections, but refill rates are low among poor households.

Health impacts

Air pollution causes respiratory diseases (asthma, COPD), heart disease and stroke, lung cancer, low birth weight, and cognitive effects. The IARC classifies outdoor air pollution as a Group 1 carcinogen. The Air Quality Life Index (University of Chicago) estimates that Indians lose about 3.5 years of life expectancy on average, and over 5 years in Delhi, compared with meeting WHO guidelines.

Policy and law

The Air (Prevention and Control of Pollution) Act 1981: enforced by the Central and State Pollution Control Boards. The Jan Vishwas Act 2023 decriminalised some offences, replacing jail terms with penalties.

National Clean Air Programme (NCAP, January 2019):

• the target was a 20–30% reduction in particulate concentrations by 2024 (against 2017). It was revised to 40% in PM10 by 2025–26;
• covers 130 non-attainment cities;
• funding is linked to performance: the Fifteenth Finance Commission grants for million-plus cities, and the PRANA portal;
• the Swachh Vayu Survekshan ranks cities.

Results: PM10 fell in many cities, but critics note that most funds went to dust control rather than combustion sources, and that monitoring in many cities is inadequate.

Delhi-NCR measures:

• the Commission for Air Quality Management (CAQM), made statutory by the CAQM Act 2021, replaced the EPCA;
• the Graded Response Action Plan (GRAP), whose stages are triggered by AQI levels: construction bans, truck entry curbs, odd-even, school closures;
• the Peripheral Expressways to divert trucks;
• shifting industries to PNG;
• stubble management: crop residue machinery subsidies, the Pusa decomposer, ex-situ use for biomass power, and co-firing of biomass pellets in thermal plants (5–10% mandated).

Vehicles:

• India leapfrogged from BS-IV to BS-VI emission norms in April 2020, skipping BS-V;
• CNG in public transport (after the M.C. Mehta case, 1998);
• EV promotion;
• the vehicle scrappage policy (2021);
• E20 ethanol blending.

Power plants: SO₂ emission norms (2015) required flue gas desulphurisation (FGD) units. The deadlines were extended repeatedly. In 2025 the Environment Ministry exempted most plants away from cities and critically polluted areas, citing studies; critics disagreed.

Analysis

The challenge is regional: pollution crosses state boundaries, so city-level plans are not enough. Experts call for airshed-based management across the Indo-Gangetic Plain, with targets for sources (combustion, not just dust) and legally binding, health-based goals.

Stubble burning needs economic solutions:

• crop diversification away from paddy;
• assured markets for residue;
• short-duration varieties (PR-126) that widen the window before wheat sowing.

Fire counts in Punjab fell sharply in 2024 and 2025, but under-reporting due to burning after satellite overpass times has been flagged.

Common prelims traps

• Ozone at ground level is a secondary pollutant.
• India's AQI uses eight pollutants; NAAQS cover 12.
• India moved from BS-IV directly to BS-VI in 2020.
• CAQM replaced EPCA.

Quick self-test

1. *Why is PM2.5 more dangerous than PM10?* It penetrates deeper into the lungs and enters the bloodstream.
2. *What is a temperature inversion?* A warm layer over cooler air near the ground, which traps pollutants.
3. *What does GRAP do?* Triggers graded emergency measures in Delhi-NCR as AQI worsens.

Practice: Mains question

*"Air pollution in north India is a regional problem that needs a regional solution." Discuss with reference to NCAP and the role of CAQM. (250 words)*

Indoor air, noise and other pollution

Indoor air pollution: apart from cooking fuels, indoor pollution comes from:

• mosquito coils and incense;
• tobacco smoke;
• VOCs from paints and furniture;
• radon in some regions.

Women and children face the highest exposure from chulhas.

Noise pollution: governed by the Noise Pollution (Regulation and Control) Rules 2000 under the EPA. Day and night limits are set for industrial, commercial, residential and silence zones: silence zones are within 100 m of hospitals, schools and courts. Loudspeakers are banned between 10 pm and 6 am, except in closed spaces. Chronic noise causes hearing loss, stress, hypertension and sleep disorders.

Light pollution affects nocturnal wildlife, insects, sea turtle hatchlings and astronomy. India's first dark sky reserve is at Hanle (Ladakh), notified in 2022.

International lessons

• Beijing cut PM2.5 by about half between 2013 and 2020. It closed coal plants, switched heating from coal to gas, cut industrial output, and enforced emission rules strictly under a national action plan.
• London moved from the deadly Great Smog (1952) to the Clean Air Act (1956) and later an Ultra Low Emission Zone.
• The common lesson: sustained political will, regional coordination, source-specific targets and strong enforcement.

Key terms

• Non-attainment city: a city that consistently fails to meet NAAQS for five years.
• Airshed: a geographic area where air quality is shaped by common sources and weather.
• Secondary aerosol: a particle formed in the air from gases such as SO₂, NOx and ammonia.
• Black carbon: soot from incomplete combustion that harms health and warms the climate.