The Air We Breathe: Air, Noise and Nuclear Pollution

Air pollution is the contamination of the indoor or outdoor environment by any chemical, physical or biological agent that modifies the natural characteristics of the atmosphere, in the WHO's definition. It kills more Indians than any other environmental risk, it now has a statutory airshed authority and a national programme with a 2026 deadline, and it shares its regulatory family with two quieter hazards: noise, which medicine now ranks among the top three environmental health risks, and nuclear contamination, whose law India rewrote in 2025. This article covers all three, because UPSC increasingly asks them together.

The scale of the crisis

The numbers describe a national emergency. The Centre for Research on Energy and Clean Air found that 204 of 238 monitored cities recorded average PM2.5 above India's National Ambient Air Quality Standard of 40 micrograms per cubic metre, and not a single city met the WHO's safe standard of 5. Ghaziabad (172), Noida (166) and Delhi (163) topped the pollution charts, while Bengaluru, at 39, was the only megacity just under the national limit.

Particulate matter needs a precise definition: PM10 is particles up to 10 microns wide that lodge in the airways, while PM2.5 is fine particles up to 2.5 microns that penetrate deep into the lungs and bloodstream. The Air Quality Life Index (AQLI) estimates that PM2.5 cuts the average Indian's life expectancy by about 3.6 years, a 2021 study linked nearly 116,000 infant deaths to PM2.5 exposure, and pollution-related mortality costs an estimated Rs 2.7 lakh crore a year, about 1.36% of GDP. Black carbon, a major PM2.5 component, even accelerates Himalayan glacier melt and disrupts monsoon patterns, tying air pollution to the water and climate crises.

What fills the air: the sources

India's air pollution has six engines. Fossil-fuel power still generates about 70% of electricity, much of it in ageing, inefficient thermal plants. Vehicular emissions, especially diesel trucks and buses, are the largest year-round urban source. Construction and road dust spikes PM10 in dry months. Household biomass cooking fills rural kitchens with smoke. Open waste burning degrades peri-urban air. And every October-November, stubble burning in Punjab and Haryana sends smoke across the Indo-Gangetic Plain into Delhi's winter inversion, when cold, still air traps pollutants near the ground.

Beyond particles, three gases matter. Nitrogen oxides (NOx) come from vehicles and power plants and drive both smog and acid rain. Sulphur dioxide (SO2) comes mainly from coal combustion. Ground-level ozone is not emitted directly at all: it forms when sunlight cooks NOx and volatile organic compounds together, which is why it peaks on hot, sunny afternoons and defines photochemical smog.

Smog, classical and photochemical

Smog, smoke plus fog, is visible air pollution containing ground-level ozone, particulate matter and nitrogen oxides. The classical (London-type) smog forms in humid, chilly weather from sulphur dioxide, smoke and fog; chemically it is a reducing smog. The photochemical (Los Angeles-type) smog forms in warm, dry, sunny weather when sunlight reacts with nitrogen oxides and unsaturated hydrocarbons from vehicles and factories; it is an oxidising smog whose main poisons are ozone, peroxyacetyl nitrate (PAN), formaldehyde and acrolein. Ozone and PAN are potent eye irritants; high concentrations bring headaches, chest pain and breathing difficulty, and the mixture damages crops, rubber, metals and stonework.

The international answer to smog's chemistry is the Gothenburg Protocol (1999) under the Convention on Long-Range Transboundary Air Pollution. It caps emissions of sulphur dioxide, nitrogen oxides, ammonia and volatile organic compounds (VOCs), the precursors of ground-level ozone and acidification, and its 2012 amendment added PM2.5 and black carbon commitments for 2020. For mains answers, Gothenburg is the model India is urged to copy: binding inter-state compacts with shared targets, since Delhi's smog is made in three states.

The stubble question

Stubble burning is the practice of setting fire to paddy straw left after harvest to clear fields quickly for wheat sowing. It is concentrated in Punjab, Haryana and western UP in the October-November window, when the gap between paddy harvest and wheat sowing is barely three weeks. Burning destroys soil microbes, nitrogen and organic carbon, wastes straw that could become compost or energy, and releases black carbon that warms the climate while choking the plains.

The government's Crop Residue Management (CRM) Scheme (since 2018-19) subsidises machinery, 50% for farmers and 80% for cooperatives and custom hiring centres, with over 3.54 lakh machines distributed and over Rs 4,266 crore released since 2018-19 (Agriculture Ministry review, June 2026). Ex-situ use turns straw into pellets and briquettes, with the power ministry mandating biomass co-firing in coal plants; in-situ options include the PUSA bio-decomposer, a microbial spray that turns straw into compost in 20-25 days. PM JI-VAN Yojana supports second-generation ethanol from crop residue, and the SATAT initiative promotes compressed biogas from farm waste. The durable fix, however, is economic: make residue worth more standing than burning, by correcting the paddy-centric cropping pattern in water-stressed Punjab and Haryana and building a genuine straw economy.

India's clean-air arsenal

The National Clean Air Programme (NCAP), launched in January 2019, is India's first national air-quality framework. It covers about 130 non-attainment cities, cities that consistently breached air-quality standards, with city-specific action plans and over Rs 13,000 crore in performance-linked funding. Its target began as a 20-30% cut in PM10 by 2024 (2017 baseline) and was revised in 2022 to 40% by 2025-26. Progress is mixed: 103 cities cut PM10 in 2024-25 versus baseline, 25 by over 40%, but CREA's 2026 assessment found only 23 of about 100 monitored cities met the revised 40% target.

The Commission for Air Quality Management (CAQM) Act, 2021 created a statutory airshed authority for Delhi-NCR and adjoining areas, replacing fragmented bodies like the EPCA with one body that can direct states, a rare override of federal pollution governance justified by pollution's refusal to respect borders. The Graded Response Action Plan (GRAP) is its emergency arm: an AQI-triggered protocol that escalates construction bans, traffic curbs and industrial shutdowns as air quality slides from 'Poor' to 'Severe+'. Supporting measures include Bharat Stage VI (Phase 2) vehicle norms, the FAME push for electric vehicles, the vehicle-scrappage policy, Pradhan Mantri Ujjwala Yojana's LPG access cutting household smoke, and Swachh Vayu Sarvekshan, the annual ranking of NCAP cities.

Two instruments sharpen the arsenal's aim. SAFAR, the System of Air Quality and Weather Forecasting and Research, is run by the Ministry of Earth Sciences and developed by IITM Pune; it gives real-time air-quality monitoring with one-to-three-day forecasts and location-specific health advisories in cities like Delhi, Mumbai, Pune and Ahmedabad. CAFE norms, the Corporate Average Fuel Efficiency standards notified in 2017 under the Energy Conservation Act, 2001 and implemented by the Bureau of Energy Efficiency, cap the average fuel consumption and carbon dioxide of every carmaker's annual sales, with penalties for breach; they cover petrol, diesel, LPG, CNG, hybrid and electric passenger vehicles and have moved through Phase I (2017 to 2022) and Phase II (2022 to 2027) toward Phase III.

Green crackers: the NEERI alternative

Green crackers are fireworks reformulated to emit significantly less particulate matter and harmful gases than conventional crackers, developed by CSIR-NEERI, the National Environmental Engineering Research Institute. Conventional crackers release barium, aluminium dust, sulphur dioxide and fine particulates that spike PM2.5 during Diwali; green crackers cut these through changed chemistry, using additives that suppress dust, replacing barium nitrate, and reducing aluminium content. They are not emission-free, a point the name sometimes obscures, but they are measurably less polluting per burst.

NEERI's formulations carry brand names worth remembering for prelims: SWAS (safe water releaser), which releases water vapour to suppress dust; SAFAL (safe minimal aluminium), which minimises aluminium use; and STAR (safe thermite cracker), which avoids certain harmful chemicals. The Supreme Court angle is what made them policy: faced with Delhi's Diwali air emergency, the Court restricted firecracker bursting to green crackers in the National Capital Region and has repeatedly tightened the regime, pushing manufacturers toward NEERI-licensed formulations. For mains, green crackers illustrate technology-forcing regulation, where courts and science together shrink the market for the most polluting option without banning celebration itself.

Primary pollutant is a pollutant emitted directly from a source, such as sulphur dioxide from coal burning or carbon monoxide from vehicles. Secondary pollutant is a pollutant formed in the atmosphere when primary pollutants react, the clearest examples being ground-level ozone and peroxyacetyl nitrate in photochemical smog and acid particles formed from sulphur and nitrogen oxides. The distinction matters for policy: cutting a secondary pollutant means cutting its precursors, sometimes in a different city or sector from where the damage appears.

Control technology follows the same logic at the source. Electrostatic precipitators charge and capture fly ash particles in thermal power plants, flue-gas desulphurisation scrubs sulphur dioxide from exhaust gases, and catalytic converters cut nitrogen oxides, carbon monoxide and hydrocarbons from vehicle exhaust. These end-of-pipe tools are necessary, but the AQI story of the previous section shows their limit: they clean individual stacks and tailpipes, while the airshed fills from millions of sources acting together.

Reading the air: the National AQI and the home front

National Air Quality Index (AQI) is a single public number, on a scale of 0 to 500, into which the Central Pollution Control Board converts measured concentrations of eight pollutants, including PM2.5, PM10, nitrogen dioxide, sulphur dioxide, carbon monoxide, ozone, ammonia and lead. Each pollutant first gets a sub-index based on its health breakpoint, and the highest sub-index becomes the day's AQI. It matters because the index, not raw concentration, is what triggers graded emergency action, school and construction decisions, and the health advice citizens actually follow.

Household air pollution is the exposure people face indoors when solid fuels such as firewood, dung, crop residue and coal are burnt for cooking and heating in poorly ventilated homes. It is the indoor twin of the outdoor smog problem: the smoke is trapped where women and young children spend the most hours, so the health burden falls hardest on them. That is why clean cooking is an air-quality policy, not only an energy policy.

The main response is the Pradhan Mantri Ujjwala Yojana (PMUY), which provides LPG connections to women from low-income households so that the first switch away from solid fuel is affordable. The harder second step is refill behaviour: a connection changes exposure only when the cylinder is refilled regularly, so refill prices, distance to distributors and household cash flow decide whether the health gain survives. Every winter in Delhi-NCR, when the AQI crosses into the Severe band, the Graded Response Action Plan (GRAP) stages are invoked or lifted in step with this same index, which is why a single number can shut construction sites and restrict vehicles across an entire airshed.

Noise: the forgotten pollutant

Noise pollution is excessive, unwanted or harmful sound that disrupts the environment and harms health, and medicine now treats it as a crisis, not a nuisance. The European Environment Agency's 2025 data attributes an estimated 66,000 premature deaths a year in Europe to transport noise, and umbrella reviews rank noise among the top three environmental health risks, behind only air pollution and temperature. Chronic exposure raises hypertension, heart-disease and stroke risk, disturbs sleep, impairs children's reading ability, and even disorients whales and dolphins that navigate by echolocation.

Sound is measured in decibels (dB) on a logarithmic scale, so every 10 dB jump feels roughly twice as loud. India's Noise Pollution (Regulation and Control) Rules, 2000 set zone-wise limits enforced by state authorities: industrial areas 75 dB by day and 70 by night, commercial 65/55, residential 55/45, and silence zones, within 100 metres of hospitals, schools and courts, 50/40. The Supreme Court held in 2005 that noise pollution violates Article 21's right to life and that using loudspeakers, even for religious purposes, is not a fundamental right; night-time loudspeaker use (10 pm to 6 am) is restricted. The Air (Prevention and Control of Pollution) Act, 1981 itself defines 'air pollutant' to include noise, and CPCB runs a National Ambient Noise Monitoring Network across major cities. The WHO's 2018 noise guidelines for the European Region, capping road-traffic noise at 53 dB Lden (day-evening-night average) and 45 dB Lnight (night), remain stricter than Indian norms, which is the reform benchmark.

Nuclear contamination: the low-probability, high-consequence pollutant

Nuclear contamination is the deposition of undesirable radioactive material, uranium, plutonium, cesium, iodine isotopes, in air, soil, water or surfaces, altering their natural characteristics. Sources include reactor accidents, weapons testing, and attacks on nuclear facilities. Its signature is persistence: cesium-137's roughly 30-year half-life keeps contaminated farmland unsafe for decades, as Chernobyl's Red Forest and its 2,600 sq km exclusion zone still demonstrate forty years after the 1986 disaster, which killed 28 emergency workers of acute radiation syndrome within months and caused a documented surge in childhood thyroid cancers. Fukushima (2011) displaced over 150,000 people, and its decommissioning will span 30-40 years at a cost of hundreds of billions of dollars.

Containment technology is correspondingly long-horizon. Vitrification fuses high-level waste into stable glass, practised at India's Tarapur, Trombay and Kalpakkam plants; dry-cask storage seals spent fuel in steel-and-concrete casks; and deep geological repositories bury waste for geological time, with Finland's Onkalo the world's first nearing operation, designed to isolate waste for 100,000 years. At Fukushima, the ALPS system treats contaminated water before IAEA-monitored ocean discharge, and robotic systems retrieve the estimated 880 tonnes of fuel debris, work too radioactive for humans.

India rewrote its nuclear law in 2025. The SHANTI Act (Sustainable Harnessing and Advancement of Nuclear Energy for Transforming India), passed in December 2025, repeals the Atomic Energy Act, 1962 and the Civil Liability for Nuclear Damage Act, 2010, consolidating the entire nuclear lifecycle, licensing, decommissioning, waste, emergency response, under one modern statute. Its two landmark shifts are granting the Atomic Energy Regulatory Board (AERB) full statutory status, ending its existence as a mere executive body under the Department of Atomic Energy, and opening plant ownership to private and joint-venture operators while removing the old law's supplier liability that had deterred foreign reactor vendors. Supporting layers include the Safe Disposal of Radioactive Wastes Rules, 1987, BARC's IERMoN real-time radiation surveillance network, and NDMA's nuclear-emergency guidelines.

The global regime rests on the IAEA safeguards system, under which India operates an India-specific safeguards agreement since 2008; the Convention on Nuclear Safety (1994); the post-Chernobyl Early Notification and Assistance Conventions (1986); and the Nuclear Suppliers Group, which gave India a waiver in 2008 though full membership remains elusive. India is not a signatory to the NPT (1968) or CTBT (1996), a consistent position rooted in their discriminatory structure.

One convention deserves a separate mention: the CPPNM, the Convention on the Physical Protection of Nuclear Material and its 2005 amendment, guards nuclear material against theft and sabotage during transport and storage, and India is a party to it.

The way forward

Clean air needs airshed thinking: binding inter-state compacts with joint GRAP triggers, since NCR's smog is a regional product. Make continuous emission monitoring data legally admissible so penalties become automatic rather than inspection-dependent. Build the straw economy so residue pays better than burning, fund municipal Air Quality Cells so NCAP money actually gets spent, and tighten Indian noise norms toward WHO 2018 values. On nuclear, the SHANTI Act's promise, independent regulation plus private capital for a 100 GW-by-2047 target, must now survive its implementation: statutory AERB independence has to be real, waste repositories have to be sited, and emergency drills have to reach beyond plant gates.

Key Terms

• Air pollution: Air pollution is the presence of harmful substances in the atmosphere at concentrations that damage human health, ecosystems, or materials, including PM2.5, PM10, nitrogen dioxide, sulphur dioxide, ozone, and carbon monoxide. Major sources are vehicles, industry, power generation, construction dust, biomass burning, and crop residue burning. It is among the largest environmental health risks globally and a major driver of respiratory and cardiovascular disease. Example: Delhi's winter smog, formed by stubble burning, vehicular emissions, and temperature inversion trapping pollutants, routinely pushes the Air Quality Index into the severe category.
• PM2.5: Fine particulate matter with a diameter of 2.5 micrometres or less, produced by combustion (vehicles, industry, crop burning) and by secondary formation in the atmosphere. Because it penetrates deep into the lungs and enters the bloodstream, it is the most health-damaging air pollutant, linked to respiratory and cardiovascular disease, and India's National Ambient Air Quality Standards set its annual limit at 40 micrograms per cubic metre. It is the headline indicator in India's air quality indices. Example: During Delhi's winter smog episodes, PM2.5 levels routinely exceed safe limits several times over, triggering Graded Response Action Plan restrictions.
• Particulate matter: Particulate matter is the mixture of tiny solid particles and liquid droplets suspended in air, classified by size as PM10 (10 micrometres or less) and the more hazardous PM2.5 (2.5 micrometres or less), which can penetrate deep into the lungs and bloodstream. It arises from combustion, construction dust, stubble burning, industry and natural sources, and is linked to respiratory and cardiovascular disease. Example: Delhi's winter smog is driven by PM2.5 spikes from stubble burning, vehicular emissions and stagnant weather, pushing the Air Quality Index into the severe category.
• Fossil-fuel power: Fossil-fuel power is electricity generated by burning coal, oil or natural gas in thermal power plants. In India it still generates roughly 70 percent of electricity, much of it in ageing and inefficient plants, making it the single largest source of air pollution and carbon emissions in the power sector. It is the baseline that India's energy transition policies seek to reduce through renewables and cleaner technologies. Example: Coal-based thermal plants are the dominant component of India's fossil-fuel power capacity.
• Vehicular emissions: Vehicular emissions are the pollutants released from the exhaust of motor vehicles, including carbon monoxide, nitrogen oxides, particulate matter (PM2.5 and PM10), hydrocarbons and carbon dioxide. They are a leading source of urban air pollution and a significant contributor to greenhouse gas emissions, and older diesel vehicles are disproportionately polluting. Control measures include Bharat Stage VI emission norms, electric vehicle promotion, public transport expansion and graded emergency restrictions. Example: Vehicular emissions are a major reason Delhi enforces the Graded Response Action Plan, including odd even schemes and construction bans, during winter smog episodes.
• Construction and road dust: Construction and road dust refers to the fugitive particulate emissions released by building construction, demolition, excavation, road resurfacing and the movement of vehicles on unpaved surfaces. It is a major source of PM10 and a significant contributor to PM2.5 in Indian cities, where rapid urbanisation keeps construction activity constant. Control measures include water sprinkling, covering of construction material, wind barriers and anti-smog guns, and enforcement agencies suspend construction during severe air-quality episodes. Example: In Delhi-NCR, construction activity is banned under advanced stages of the Graded Response Action Plan when the Air Quality Index enters the severe category.
• Household biomass: Household biomass refers to firewood, dung cakes and crop residues burned in traditional chulhas for cooking and heating in rural homes. It is a major source of indoor air pollution, black carbon emissions and respiratory disease, disproportionately affecting women and children. Government programmes such as the Pradhan Mantri Ujjwala Yojana (2016) have aimed to shift households from biomass to cleaner LPG. Example: The Ujjwala scheme has provided over 10 crore LPG connections since 2016 to move poor households away from cooking with firewood and dung cakes.
• Open waste burning: The uncontrolled burning of municipal solid waste, agricultural residue or industrial refuse in the open, without pollution-control equipment. It is a major source of particulate matter, black carbon, dioxins and furans, and the Solid Waste Management Rules, 2016 prohibit open burning of waste in India. It is both an air-quality and public-health hazard, particularly in urban peripheries. Example: The seasonal burning of crop stubble in Punjab and Haryana is a leading contributor to Delhi's winter air pollution emergency.
• stubble burning: Stubble burning is the practice of setting fire to leftover crop residue, mainly paddy straw, after harvest to clear fields quickly for the next sowing. It releases large amounts of particulate matter (PM2.5 and PM10), carbon monoxide, and other pollutants, and is a major contributor to the severe winter smog in Delhi and the National Capital Region. It is banned by several states and by the Commission for Air Quality Management, though enforcement remains weak. Example: The Commission for Air Quality Management (CAQM) imposes fines and restrictions on stubble burning in Punjab, Haryana, and Uttar Pradesh each winter.
• Ground-level ozone: Ground-level (tropospheric) ozone is a secondary air pollutant formed when nitrogen oxides and volatile organic compounds react in the presence of sunlight, rather than being emitted directly. It is a key ingredient of photochemical smog that irritates the respiratory system, aggravates asthma and damages crops. Unlike the protective ozone layer in the stratosphere, ground-level ozone is harmful to health and vegetation. Example: Ozone levels typically peak on hot, sunny summer afternoons in cities such as Delhi during photochemical smog episodes.
• smog: Smog is the hazardous mixture of smoke and fog formed when pollutants such as particulate matter, nitrogen oxides and volatile organic compounds react in sunlight, as in photochemical smog; it causes respiratory illness, crop damage and visibility loss. It is a recurring PYQ topic alongside the 1999 Gothenburg Protocol on transboundary air pollution. For UPSC it anchors GS-3 environment: air pollution and its mitigation. Example: The National Clean Air Programme (NCAP), launched in 2019.
• classical (London-type) smog: Classical or London-type smog is a reducing smog formed when sulphur dioxide and particulate matter from coal combustion mix with fog in cool, humid conditions. It is chemically distinct from photochemical (Los Angeles-type) smog, which is driven by sunlight acting on vehicle emissions. Example: The Great Smog of London in December 1952, caused by heavy coal burning in stagnant winter air, killed thousands and spurred modern air pollution law.
• photochemical (Los Angeles-type) smog: Photochemical smog, first identified in Los Angeles, forms when nitrogen oxides and volatile organic compounds from vehicles and industry react in strong sunlight. The reactions produce ground-level ozone, peroxyacetyl nitrates and aldehydes, creating a brownish haze that irritates the eyes and lungs. It is typical of warm, sunny cities with heavy traffic and peaks in the afternoon, unlike London-type smog, which is sulphur-based and forms in cold winter conditions. Example: The brownish haze and eye irritation seen in Delhi on hot, sunny afternoons when vehicle exhaust reacts in intense sunlight to form ground-level ozone.
• ozone: Ozone (O3) is a molecule of three oxygen atoms with a dual role in the atmosphere. In the stratosphere it forms the ozone layer that shields life from harmful ultraviolet radiation, while at ground level it is a harmful secondary pollutant. Tropospheric ozone forms when nitrogen oxides and volatile organic compounds react in sunlight, irritating lungs and damaging crops. Example: Ground-level ozone is a key component of photochemical smog in traffic-heavy cities on hot, sunny days.
• Gothenburg Protocol: The Gothenburg Protocol is a 1999 protocol to the 1979 Geneva Convention on Long-range Transboundary Air Pollution that tackles acidification, eutrophication and ground-level ozone. It sets national emission ceilings for sulphur dioxide, nitrogen oxides, volatile organic compounds and ammonia, and was amended in 2012 to cover fine particulate matter (PM2.5) and black carbon. Example: The Protocol is a regional agreement under the UN Economic Commission for Europe, and India is not a party to it.
• Crop Residue Management (CRM) Scheme: The Crop Residue Management (CRM) Scheme is a Central Sector Scheme implemented by the Ministry of Agriculture and Farmers Welfare since 2018-19 to curb stubble burning in Punjab, Haryana, Uttar Pradesh and the NCT of Delhi. It subsidises machinery for in-situ management of paddy straw, giving 50 percent assistance to individual farmers and 80 percent for Custom Hiring Centres run by cooperatives, FPOs, panchayats and rural entrepreneurs, alongside funds for awareness campaigns. The scheme was merged into the Sub-Mission on Agricultural Mechanization in 2022, and by early 2026 over Rs 4,237 crore had been released with more than 3.53 lakh machines distributed. Example: The Happy Seeder, which sows wheat directly into standing paddy stubble, is the flagship machine promoted under the CRM scheme as an alternative to burning.
• Ex-situ: Ex-situ conservation means conserving species outside their natural habitats, such as in zoos, botanical gardens, seed banks, gene banks, aquaria and cryopreservation facilities. It complements in-situ conservation and acts as insurance against extinction when wild habitats are threatened or degraded. It is used for critically endangered species, captive breeding programmes and long term storage of genetic material. Example: Straw is processed ex-situ into pellets and briquettes for biomass co-firing, and seeds are stored ex-situ in seed banks to preserve genetic diversity.
• in-situ: In-situ means at the original site or in its natural place, describing any process carried out where the material already is, rather than removing it to be treated elsewhere. Its opposite is ex-situ, where the material is taken to a different location for treatment. The term is used across ecology, conservation, pollution control, and agriculture. Example: In-situ crop residue management, such as spraying the PUSA bio-decomposer on paddy stubble so it turns into compost in the field itself instead of being burnt.
• PUSA bio-decomposer: The Pusa bio-decomposer is a microbial consortium of seven fungal species developed by ICAR's Indian Agricultural Research Institute, New Delhi, to decompose paddy straw in the field without burning. Supplied as capsules or liquid, it is mixed with water, jaggery and besan and sprayed on stubble, where its enzymes digest cellulose, lignin and pectin, turning the residue into compost in about three to four weeks. Example: Delhi, Punjab, Haryana and Uttar Pradesh sprayed Pusa decomposer on paddy stubble fields in the winters after 2020 as a low-cost alternative to stubble burning, a major driver of seasonal air pollution in the NCR.
• PM JI-VAN Yojana: Pradhan Mantri JI-VAN (Jaiv Indhan-Vatavaran Anukool fasal awashesh Nivaran) Yojana, notified in March 2019 by the Ministry of Petroleum and Natural Gas, provides viability gap funding for second-generation (2G) ethanol projects using lignocellulosic biomass such as crop residue. With an outlay of Rs 1,969.50 crore for 2018-19 to 2023-24, it supports 12 commercial and 10 demonstration plants, helping India meet its ethanol blending targets while reducing stubble burning and import dependence. It aligns with the National Policy on Biofuels, 2018. Example: The 2G ethanol plant at Panipat in Haryana, built by IndianOil, converts rice straw into ethanol for blending with petrol under the Ethanol Blended Petrol programme.
• SATAT: SATAT stands for Sustainable Alternative Towards Affordable Transportation, an initiative launched on 1 October 2018 by the Ministry of Petroleum and Natural Gas. It promotes compressed biogas (CBG) as a clean automotive and industrial fuel made from agricultural residue, cattle dung, press mud and municipal solid waste. Oil marketing companies invite entrepreneurs to set up CBG plants and guarantee offtake of the gas. Example: Under SATAT, CBG produced from paddy straw can be sold to oil companies for use as vehicle fuel, turning a stubble-burning problem into energy.
• non-attainment cities: Non-attainment cities are Indian cities identified by the Central Pollution Control Board as consistently failing to meet the National Ambient Air Quality Standards (NAAQS) over several years. Under the National Clean Air Programme launched in 2019, 131 such cities, including million-plus cities, were taken up for city-specific clean-air action plans targeting road dust, vehicles, industry, domestic fuel, and waste burning. The programme set a target of cutting particulate pollution by up to 40 percent by 2025-26. Example: Delhi, Ghaziabad, and Patna are among the 131 cities covered under the National Clean Air Programme.
• Commission for Air Quality Management (CAQM) Act, 2021: The Commission for Air Quality Management in National Capital Region and Adjoining Areas Act, 2021 creates CAQM as a statutory body to coordinate air-quality management across Delhi, Punjab, Haryana, Rajasthan and Uttar Pradesh. The Commission's directions are binding and prevail over those of the CPCB, state pollution boards and state governments; it can restrict polluting activities, issue codes and guidelines, and impose environment compensation, including on stubble burning. It replaced the earlier Environment Pollution (Prevention and Control) Authority and is accountable to Parliament. Example: CAQM invokes the Graded Response Action Plan (GRAP) to ban construction and restrict diesel vehicles in Delhi-NCR when the Air Quality Index turns severe.
• Bharat Stage VI: Bharat Stage VI (BS-VI) refers to India's emission standards for motor vehicles, which set maximum permissible limits for pollutants such as nitrogen oxides, particulate matter, carbon monoxide and hydrocarbons in vehicle exhaust. India leapfrogged directly from BS-IV to BS-VI nationwide on 1 April 2020, skipping BS-V, making its norms among the strictest in the world at the time. The shift required cleaner BS-VI fuel with very low sulphur content and forced manufacturers to adopt technologies such as diesel particulate filters and selective catalytic reduction. Example: BS-VI cut the permissible nitrogen oxide emissions from diesel cars to 80 mg per km, down from 250 mg per km under BS-IV.
• Pradhan Mantri Ujjwala Yojana: Launched on 1 May 2016 at Ballia, Uttar Pradesh, the Pradhan Mantri Ujjwala Yojana gives free LPG connections, with Rs 1,600 support per connection, to women of Below Poverty Line households to replace smoky chulhas. It aims to cut indoor air pollution and the drudgery of collecting firewood, and it was followed by Ujjwala 2.0 in 2021 for migrant and left-out households. Example: A BPL woman receiving a deposit-free LPG connection under PMUY no longer cooks over biomass smoke linked to respiratory illness; over 9 crore connections have been issued under the scheme.
• Swachh Vayu Sarvekshan: Swachh Vayu Sarvekshan is the Environment Ministry's annual ranking of 130 cities covered under the National Clean Air Programme. Cities are assessed on the measures they take to improve air quality, such as controlling road dust, solid waste and construction waste, curbing vehicular and industrial emissions, and public awareness activities, fostering competition among cities. Example: Lucknow topped the million-plus category in the Swachh Vayu Sarvekshan 2026.
• Noise pollution: Unwanted, excessive or harmful sound that disturbs human activity and damages health. Measured in decibels on a logarithmic scale, where every 10-decibel increase roughly doubles perceived loudness, chronic exposure is linked to hearing loss, hypertension, sleep disturbance and reduced learning in children. Example: Traffic, construction machinery, loudspeakers and Diwali firecrackers are typical sources of noise pollution in Indian cities.
• Noise Pollution (Regulation and Control) Rules, 2000: Rules framed under the Environment (Protection) Act, 1986, that set legally enforceable ambient noise standards for different zones: industrial areas 75 decibels by day and 70 by night, commercial areas 65 and 55, residential areas 55 and 45, and silence zones 50 and 40. Silence zones cover 100 metres around hospitals, educational institutions and courts, and the rules restrict loudspeaker and public-address use, especially at night. Example: State pollution control boards enforce these limits, and the Supreme Court held in 2005 that noise pollution violates the right to life under Article 21.
• silence zones: Under the Noise Pollution (Regulation and Control) Rules, 2000, silence zones are areas of at least 100 metres around hospitals, educational institutions and courts, declared by the competent authority to receive the strictest noise limits. The permissible ambient noise level in a silence zone is 50 dB(A) Leq by day and 40 dB(A) Leq by night. Honking, loudspeakers and construction noise near such zones attract penalties. Example: Use of loudspeakers near a school during examinations can be penalised as a violation of silence-zone norms.
• Article 21: Article 21 guarantees that no person shall be deprived of life or personal liberty except according to procedure established by law. Through judicial interpretation, beginning with Maneka Gandhi (1978), it has expanded to cover dignity, privacy, and a clean environment. It is the most litigated Fundamental Right and central to GS-2 polity. Example: the Supreme Court reading privacy into Article 21 in Justice K.S. Puttaswamy v. Union of India (2017).
• Air (Prevention and Control of Pollution) Act, 1981: The Air (Prevention and Control of Pollution) Act, 1981 is the principal Indian law for controlling air pollution, enacted in the wake of the 1972 Stockholm Conference. It empowers the Central and State Pollution Control Boards to set emission standards, declare air pollution control areas, and require industries to obtain consent before operating. Boards can order closure of polluting units and restrict industrial activity in designated areas. Example: Under this Act the Central Pollution Control Board notifies National Ambient Air Quality Standards, and enforcement actions such as Delhi's Graded Response Action Plan draw on the pollution control machinery it creates.
• National Ambient Noise Monitoring Network: The National Ambient Noise Monitoring Network is a real-time network of noise monitoring stations set up by the Central Pollution Control Board across India's major metro cities, beginning in 2011 with 70 stations in seven cities: Delhi, Mumbai, Kolkata, Chennai, Bengaluru, Hyderabad and Lucknow. It continuously measures ambient noise levels day and night against standards set under the Noise Pollution (Regulation and Control) Rules, 2000. The data is made publicly available and is used to track trends and guide enforcement against noise pollution. Example: Network data showing commercial areas in metros routinely exceeding prescribed limits informed Diwali-time noise advisories.
• Nuclear contamination: The presence of radioactive substances, such as uranium, plutonium, cesium-137 or iodine-131, in air, water, soil or living systems at levels that pose health or ecological risks. It can arise from nuclear weapons testing, reactor accidents, improper waste disposal or uranium mining, and is dangerous because ionizing radiation damages living cells while long-lived isotopes persist for decades to millennia. Clean-up is slow and expensive because contamination spreads through soil and food chains. Example: The 1986 Chernobyl accident released radioactive fallout over large areas of Ukraine and Belarus, leaving an exclusion zone that remains hazardous decades later.
• cesium-137: Cesium-137 is a radioactive isotope of cesium produced by nuclear fission, with a half-life of roughly 30 years. Released by reactor accidents and weapons testing, it contaminates soil and water and keeps affected farmland unsafe for decades. Example: Cesium-137 fallout from the 1986 Chernobyl disaster still contaminates the Red Forest and the 2,600 sq km exclusion zone around the reactor.
• Vitrification: Vitrification is the process of immobilising high level radioactive waste by mixing it with glass forming materials and melting it into stable borosilicate glass blocks. The glass matrix locks the radioactive isotopes in place, preventing them from leaking into the environment for thousands of years, and the blocks are then stored in engineered facilities. It is the internationally accepted method for the long term management of the most hazardous nuclear waste from reprocessing plants. Example: India operates Waste Immobilisation Plants using vitrification at Tarapur and Trombay to treat high level waste from its nuclear fuel reprocessing programme.
• dry-cask storage: Dry-cask storage is a method of interim storage for spent nuclear fuel that has already been cooled in a spent fuel pool, typically for several years. The fuel assemblies are sealed in steel canisters filled with inert gas and placed inside robust steel or concrete casks that provide radiation shielding and passive air cooling through natural convection. It is used worldwide as a safer alternative to overcrowded pools while permanent geological repositories remain unavailable. Example: Independent spent fuel storage installations at nuclear power plants in the United States, where spent fuel is kept in on-site dry casks after initial pool cooling.
• deep geological repositories: Facilities built hundreds of metres underground in stable rock formations for the long-term disposal of high-level radioactive waste. Multiple engineered and natural barriers isolate the waste for thousands of years, until its radioactivity decays to safe levels. They are internationally regarded as the only credible solution for waste that stays hazardous far beyond any human institution's lifespan. Example: Finland's Onkalo facility, built about 450 metres into bedrock at Olkiluoto, is the world's first deep geological repository for spent nuclear fuel.
• Onkalo: The world's first deep geological repository for spent nuclear fuel, built by the company Posiva at the Olkiluoto nuclear site in Finland. Waste will be sealed in copper canisters surrounded by bentonite clay about 400 to 450 metres below ground in stable, nearly two-billion-year-old bedrock, in a multi-barrier system designed to isolate high-level waste safely for up to 100,000 years without active maintenance. It received its operating licence in 2026. Example: Onkalo demonstrates the copper canister, clay buffer and bedrock multi-barrier disposal method that India studies as it develops long-term nuclear waste-management plans.
• ALPS: The Advanced Liquid Processing System, a water-treatment facility at Japan's Fukushima Daiichi nuclear plant that removes most radionuclides (except tritium) from contaminated water before its discharge into the sea. Its operation has been a focal point of international debate over the safety of treated-water release. Example: ALPS-treated water from Fukushima began to be discharged into the Pacific in August 2023 under IAEA monitoring. Example: ALPS-treated water discharge from Fukushima into the Pacific began in August 2023 under IAEA monitoring.
• SHANTI Act: The SHANTI Act (Sustainable Harnessing and Advancement of Nuclear Energy for Transforming India), passed in December 2025, is India's new nuclear law that repeals and consolidates the Atomic Energy Act, 1962 and the Civil Liability for Nuclear Damage Act, 2010. For the first time since Independence it allows private companies and joint ventures to build, own, operate and decommission nuclear power plants, while sensitive activities like fuel production, heavy water manufacture and waste management stay with the state. It gives statutory backing to the Atomic Energy Regulatory Board and replaces the 2010 supplier-liability regime with graded, capacity-linked operator liability. Example: The Act supports India's target of 100 GW of nuclear capacity by 2047.
• Atomic Energy Act, 1962: The Atomic Energy Act, 1962 is the principal law governing the development, control and use of atomic energy in India, replacing the 1948 Act. It vests the Central Government with exclusive authority over atomic energy, restricts disclosure of sensitive information, and keeps uranium and thorium mining and the nuclear fuel cycle under state control. It underpins regulators like the Atomic Energy Regulatory Board and is central to UPSC questions on nuclear governance. Example: A 2015 amendment enabled the Nuclear Power Corporation of India to form joint ventures.
• Civil Liability for Nuclear Damage Act, 2010: The Civil Liability for Nuclear Damage Act, 2010 channels liability for a nuclear accident onto the operator, capped at Rs 1,500 crore, with the government covering compensation beyond that. Its debated Section 17(b) gives the operator a right of recourse against suppliers of defective equipment, which foreign vendors read as supplier liability and cite for staying out of India's reactor market. India joined the global CSC regime in 2016. Example: The supplier-recourse clause has slowed several planned foreign reactor projects.
• Safe Disposal of Radioactive Wastes Rules, 1987: The Safe Disposal of Radioactive Wastes Rules, 1987, notified under the Atomic Energy Act, 1962, regulate the handling, transport and disposal of radioactive waste in India. They require that radioactive waste be disposed of only by persons authorised by the competent authority and in the prescribed manner, preventing contamination of the environment. The framework places waste management under strict regulatory oversight, with the Atomic Energy Regulatory Board supervising compliance. Example: Authorised disposal of spent fuel and contaminated materials from nuclear power plants.
• IERMoN: IERMoN is the Indian Environmental Radiation Monitoring Network, a countrywide real-time radiation surveillance network built by the Bhabha Atomic Research Centre. Using indigenously developed, solar-powered monitoring stations with remote data communication, it enables early detection of any nuclear emergency and lets regulators reassure the public with measured data rather than speculation. Example: During the Fukushima crisis, AERB used IERMoN data from stations across India to confirm that radiation levels stayed at natural background.
• IAEA safeguards: IAEA safeguards are the verification measures through which the International Atomic Energy Agency confirms that a state's declared nuclear material and facilities are used only for peaceful purposes, using inspections, cameras, and material accountancy. Under the NPT they are mandatory for non-nuclear-weapon states; India, a non-signatory, accepted safeguards on its civilian facilities under the 2008 separation plan. For UPSC, safeguards link nuclear energy, the 123 Agreement, and non-proliferation debates. Example: India's 2009 India-specific Safeguards Agreement placing its civilian reactors under IAEA inspection.
• Nuclear Suppliers Group: The Nuclear Suppliers Group (NSG) is a 48-member export-control regime that coordinates controls on civilian nuclear material, equipment, and dual-use technology to prevent weapons proliferation. Formed in response to India's 1974 nuclear test, it first met in London in November 1975. For UPSC, the NSG matters because India, a non-NPT state, won a 2008 waiver enabling civilian nuclear trade but remains blocked from membership, largely by China. Example: The Indo-US civil nuclear deal of 2008 led directly to the NSG's waiver for India, opening global uranium supplies for India's reactors.
• NPT: The Treaty on the Non-Proliferation of Nuclear Weapons (NPT), opened for signature in 1968 and in force since 1970, is the cornerstone of the global nuclear order, with three pillars: non-proliferation, disarmament, and peaceful uses of nuclear energy. It divides states into five recognised nuclear-weapon states and the rest, a structure India has consistently called discriminatory, which is why India has never signed it. India instead pursues civilian nuclear cooperation through the 2008 Nuclear Suppliers Group waiver while staying outside the treaty. Example: India is not a signatory to the NPT (1968) or the Comprehensive Nuclear-Test-Ban Treaty (1996).
• CTBT: The Comprehensive Nuclear-Test-Ban Treaty (CTBT) is a multilateral treaty adopted by the UN General Assembly in 1996 that bans all nuclear explosions, in any environment, for any purpose. It has been signed by 187 states but has not entered into force because 8 of the 44 specifically listed Annex II states have not ratified it: the United States, China, Iran, Israel and Egypt have signed but not ratified, while India, Pakistan and North Korea have not signed. A global International Monitoring System of seismic, hydroacoustic, infrasound and radionuclide stations detects clandestine tests even though the treaty is not in force. Example: The monitoring system detected North Korea's 2017 underground nuclear test within hours, pinpointing its location and estimating its yield.
• Key takeaways: Key takeaways is a quick-revision summary box placed at the end of each article, listing the most exam-relevant points in a short numbered list. It distils definitions, dates, figures, provisions and examples into a form suited for last-minute revision before Prelims and Mains. Together with the article's practice questions, it turns every topic into a self-contained study unit.
• Air Quality Life Index (AQLI): The Air Quality Life Index is a pollution metric developed by the Energy Policy Institute at the University of Chicago (EPIC) that converts fine particulate (PM2.5) concentrations into years of life expectancy lost. Unlike the AQI, which reports pollution as colour-coded categories, the AQLI expresses the health cost in the tangible unit of human life years, based on peer-reviewed research linking long-term PM2.5 exposure to mortality. Example: The AQLI 2025 report estimated that air pollution reduces average Indian life expectancy by 3.5 years, with residents of Delhi-NCR losing 8.2 years relative to the WHO guideline.
• Nitrogen oxides (NOx): A family of air pollutants, chiefly nitric oxide and nitrogen dioxide, formed when fuel burns at high temperatures in vehicles, power plants and industries. They contribute to smog, ground-level ozone and acid rain, and aggravate respiratory illnesses, which is why they are regulated under India's Air (Prevention and Control of Pollution) Act. Example: Vehicular exhaust is the dominant source of nitrogen dioxide in Indian cities, where it is a key driver of winter smog.
• Sulphur dioxide (SO2): Sulphur dioxide is a pungent air pollutant released mainly by burning sulphur-containing fossil fuels such as coal, and by metal smelting. It irritates the respiratory system, aggravates asthma, and oxidises in the atmosphere to form sulphuric acid, making it a principal cause of acid rain. It is a criteria pollutant under India's National Ambient Air Quality Standards. Example: SO2 emissions from coal-based thermal power plants are a major cause of acid rain in industrial regions.
• peroxyacetyl nitrate (PAN): Peroxyacetyl nitrate is a secondary air pollutant formed when nitrogen oxides and volatile organic compounds react in sunlight, and it is a major component of photochemical smog. PAN is a powerful eye irritant and damages plant tissues, stunting crop growth. Because it is stable in cold air, it can travel long distances and spread urban pollution to rural areas. Example: PAN levels spike in cities during hot, sunny, traffic-heavy conditions as part of smog episodes.
• volatile organic compounds (VOCs): Volatile organic compounds are carbon-containing chemicals that evaporate easily at room temperature and enter the air from paints, solvents, fuels, adhesives, furnishings, and vehicle exhaust. Outdoors, they react with nitrogen oxides in sunlight to form ground-level ozone and contribute to photochemical smog; indoors, compounds such as formaldehyde can cause eye, nose, and throat irritation with prolonged exposure. Several VOCs are also known or suspected carcinogens. Example: Benzene from petrol vapour and vehicular emissions is a regulated VOC and a known carcinogen, which is why petrol stations and fuel handling carry strict vapour-recovery norms.
• National Clean Air Programme (NCAP): The National Clean Air Programme is India's first comprehensive national strategy to combat air pollution, launched by the Ministry of Environment, Forest and Climate Change in January 2019. It covers 131 non-attainment cities and sets a target of reducing PM10 concentrations by 40 percent by 2026 over 2017 levels, revised from the original goal of 20-30 percent by 2024. It is implemented through city action plans with a focus on road dust, construction, transport and industrial emissions. Example: Cities such as Kanpur and Lucknow prepared city-specific clean air action plans under NCAP.
• Graded Response Action Plan (GRAP): GRAP is an emergency air-pollution control framework for Delhi-NCR, notified under the Environment (Protection) Act and enforced by the Commission for Air Quality Management. It triggers escalating restrictions as the Air Quality Index worsens across four stages: Stage I (Poor, AQI 201-300), Stage II (Very Poor, AQI 301-400), Stage III (Severe, AQI 401-450) and Stage IV (Severe Plus, AQI above 450). Measures range from banning open waste burning and dust-generating construction in Stage I to halting construction activity, restricting diesel vehicles and closing schools in Stage IV. Example: GRAP Stage IV emergency measures, including a ban on construction and restrictions on polluting trucks, are routinely invoked in Delhi when AQI crosses 450 during winter smog episodes.
• decibels (dB): The unit used to measure sound intensity, on a logarithmic scale where every 10 dB increase represents a tenfold rise in intensity. Because the scale is logarithmic, small numerical increases mean large jumps in loudness. Prolonged exposure above about 85 dB can damage hearing, which is why regulators set zone-wise noise limits. Example: Under India's Noise Pollution Rules, daytime limits are 75 dB for industrial zones, 65 dB for commercial zones, 55 dB for residential zones and 50 dB for silence zones.
• Atomic Energy Regulatory Board (AERB): The Atomic Energy Regulatory Board is India's nuclear and radiation safety regulator, constituted on 15 November 1983 under Section 27 of the Atomic Energy Act, 1962. Its mission is to ensure that the use of ionising radiation and nuclear energy does not pose undue risk to workers, the public, and the environment. It lays down safety standards, licenses nuclear facilities, and oversees radiation safety in medicine and industry, reporting to the Atomic Energy Commission. Example: AERB licenses and inspects India's nuclear power stations, including Kudankulam in Tamil Nadu and Kakrapar in Gujarat, and certifies radiation equipment in hospitals.
• Convention on Nuclear Safety (1994): The Convention on Nuclear Safety is an International Atomic Energy Agency treaty adopted in Vienna on 17 June 1994 and in force since 24 October 1996. It commits parties to maintain a high level of safety at land-based civil nuclear power plants through a legislative and regulatory framework, proper siting, design and construction, safe operation, radiation protection and emergency preparedness. Parties must submit national reports and undergo peer review at review meetings held every three years, making it an incentive convention built on transparency rather than sanctions. Example: India, whose reactors are regulated by the Atomic Energy Regulatory Board, participates in the Convention's triennial review meetings where it reports on its nuclear safety framework.
• Early Notification and Assistance Conventions (1986): These are the two IAEA treaties adopted on 26 September 1986 as a direct response to the Chernobyl disaster of April 1986. The Convention on Early Notification of a Nuclear Accident obliges states to promptly notify the IAEA and any potentially affected states of a nuclear accident with possible transboundary radiological consequences (it entered into force on 27 October 1986). The Convention on Assistance in the Case of a Nuclear Accident or Radiological Emergency sets up a framework for international cooperation and aid, such as equipment, expertise and personnel, during nuclear or radiological emergencies (it entered into force in 1992). Example: The Fukushima Daiichi accident in 2011 triggered notification and assistance mechanisms under both conventions.

• Green crackers: Green crackers are fireworks reformulated by CSIR-NEERI to emit significantly less particulate matter and harmful gases than conventional crackers, through changed chemistry such as dust-suppressing additives and reduced aluminium and barium content. Example: The Supreme Court has restricted NCR Diwali bursting to green crackers to curb the seasonal PM2.5 spike.

• SWAS, SAFAL and STAR: SWAS (safe water releaser), SAFAL (safe minimal aluminium) and STAR (safe thermite cracker) are CSIR-NEERI's branded green-cracker formulations, each reducing emissions through a different chemical route. Example: A SWAS cracker releases water vapour that suppresses the dust its own burst creates.

• CSIR-NEERI: CSIR-NEERI, the National Environmental Engineering Research Institute, is the Council of Scientific and Industrial Research laboratory that developed green-cracker formulations and licenses them to manufacturers. Example: NEERI's emission testing underpins the certification that distinguishes green crackers from conventional ones.

• National Air Quality Index (AQI): The National Air Quality Index (AQI) is a 0 to 500 scale that converts measured concentrations of eight pollutants into one public number, using the highest pollutant sub-index for the day. CPCB categories run from Good to Severe, and the index triggers graded action under GRAP. Example: a Severe day in Delhi-NCR can bring construction bans and vehicle restrictions.
• Household air pollution: Household air pollution is indoor exposure to smoke from solid fuels such as firewood, dung and coal burnt for cooking and heating. It concentrates exposure on women and young children at home. Example: the Pradhan Mantri Ujjwala Yojana tackles it by expanding LPG connections in low-income households.
• Primary pollutant: Primary pollutant is a harmful substance emitted directly from an identifiable source, such as sulphur dioxide from coal or carbon monoxide from vehicles. Control means acting at that source. Example: particulate matter from a factory stack before it reacts in the air.
• Flue-gas desulphurisation: Flue-gas desulphurisation is a scrubbing technology that removes sulphur dioxide from power plant exhaust before it leaves the stack. It cuts acid rain precursors and sulphate particles. Example: fitting flue-gas desulphurisation to coal plants near densely populated airsheds.

Prelims practice