BharatNotes Overview
Air and water pollution are among India's most pressing environmental and public health challenges. India is home to some of the world's most polluted cities -- in recent years, multiple Indian cities have appeared in the top 20 of global PM2.5 rankings. Simultaneously, the CPCB has identified over 350 polluted river stretches across the country, with untreated sewage being the dominant source.
The policy response has been multi-pronged: the National Clean Air Programme (NCAP) targets a 40% reduction in particulate matter by 2026 across 131 non-attainment cities, while Namami Gange has emerged as the flagship river rejuvenation mission. Regulatory frameworks include the Air (Prevention and Control of Pollution) Act, 1981, the Water (Prevention and Control of Pollution) Act, 1974, and the Environment Protection Act, 1986.
For UPSC, this topic is a GS-3 core area. Questions test both factual knowledge (AQI categories, emission norms, BOD/COD) and analytical capacity (policy effectiveness, governance gaps, technology solutions).
Air Pollution — Sources
Vehicular Emissions
- Transport sector contributes approximately 10-40% of urban air pollution depending on the city
- Key pollutants: CO, NOx, PM2.5, hydrocarbons, benzene
- BS-VI emission norms (equivalent to Euro-6) implemented across India from 1 April 2020 -- India leapfrogged from BS-IV directly to BS-VI
- BS-VI mandates: 80% reduction in NOx for diesel vehicles, sulphur content in fuel reduced from 50 ppm (BS-IV) to 10 ppm (BS-VI), On-Board Diagnostics (OBD) systems mandatory, particulate number limits introduced
Industrial Emissions
- Thermal power plants (largest industrial source of SO2, NOx, PM, and mercury)
- Brick kilns (estimated 1.5 lakh units in India; shifting from fixed chimney to zigzag technology)
- Cement, steel, and chemical industries
- Flue Gas Desulphurisation (FGD) mandated for all coal-based thermal power plants -- implementation has been delayed multiple times
Crop Residue Burning (Stubble Burning)
- Concentrated in Punjab and Haryana during the October-November rice harvest season
- Farmers burn an estimated 15-20 million tonnes of paddy straw annually
- Contributes up to 30-40% of Delhi's PM2.5 during peak burning weeks
- Solutions: Happy Seeder (sows wheat directly into rice stubble), Crop Residue Management (CRM) machinery subsidy, bio-decomposer (Pusa Decomposer developed by IARI), ex-situ uses (biomass pellets, bio-CNG, co-firing in power plants)
- Commission for Air Quality Management (CAQM) in NCR and Adjoining Areas (constituted 2021) has statutory powers to enforce measures
Construction Dust
- A significant contributor in rapidly urbanising cities
- Construction and Demolition (C&D) Waste Management Rules, 2016 mandate dust suppression, covered transportation, and recycling of C&D waste
Household Air Pollution
- Burning of biomass fuels (wood, cow dung, crop residue) for cooking in rural households
- Affects an estimated 70 crore Indians
- PM Ujjwala Yojana (PMUY) provides free LPG connections to BPL households; over 10 crore connections distributed
Air Quality Index (AQI)
India's AQI System
Launched by CPCB in 2014 under MoEFCC, the National AQI standardises air quality reporting across India.
Six AQI Categories
| Category | AQI Range | Colour | Health Implication |
|---|---|---|---|
| Good | 0-50 | Green | Minimal impact |
| Satisfactory | 51-100 | Light green | Minor discomfort to sensitive people |
| Moderately Polluted | 101-200 | Yellow | Breathing discomfort for sensitive groups |
| Poor | 201-300 | Orange | Breathing discomfort on prolonged exposure |
| Very Poor | 301-400 | Red | Respiratory illness on prolonged exposure |
| Severe | 401-500 | Maroon | Affects healthy people; serious impact on those with existing diseases |
Eight Pollutants Monitored
PM2.5, PM10, NO2, SO2, CO, O3 (ground-level ozone), NH3 (ammonia), and Pb (lead).
The overall AQI is determined by the worst sub-index among all measured pollutants. A minimum of 3 pollutants must be measured, and one must be either PM2.5 or PM10.
National Ambient Air Quality Standards (NAAQS)
Set by CPCB under the Air Act, NAAQS prescribe permissible limits for 12 pollutants in ambient air.
| Pollutant | Annual average (micrograms per cubic metre) | 24-hour average |
|---|---|---|
| PM2.5 | 40 | 60 |
| PM10 | 60 | 100 |
| SO2 | 50 | 80 |
| NO2 | 40 | 80 |
| CO | -- | 2 mg per cubic metre (8-hour) |
| O3 | -- | 100 (8-hour) |
| Pb | 0.5 | 1.0 |
| NH3 | 100 | 400 |
Non-attainment cities are those that consistently fail to meet NAAQS for PM10 and/or NO2. These cities form the target group for NCAP.
National Clean Air Programme (NCAP)
Key Features
| Parameter | Detail |
|---|---|
| Launched | January 2019 by MoEFCC |
| Cities covered | 131 non-attainment cities across 24 states/UTs |
| Target | 40% reduction in PM10 and PM2.5 concentrations by 2025-26 (from 2017 baseline); revised upward from the initial 20-30% target |
| Approach | City-specific clean air action plans; sector-wise interventions |
| Budget | Rs 10,566 crore allocated to 131 cities for implementation |
Progress and Challenges
- As of 2025, 95 of 131 cities showed improvement in PM10 levels compared to 2017
- However, only 51 cities achieved the initial 20-30% reduction target, and only 23 cities met the revised 40% target
- A 2025-26 assessment found that meeting the 40% reduction target across all 131 cities remains unlikely within the timeline
- Key challenges: insufficient monitoring infrastructure in smaller cities, lack of source apportionment studies, poor enforcement of construction dust norms
GRAP — Graded Response Action Plan (Delhi-NCR)
Structure
GRAP is an emergency response mechanism for the NCR region, implemented by the Commission for Air Quality Management (CAQM). It is triggered based on AQI levels and weather forecasts.
| Stage | AQI Range | Key Actions |
|---|---|---|
| Stage I (Poor) | 201-300 | Ban on open burning, water sprinkling on roads, enforce emission norms |
| Stage II (Very Poor) | 301-400 | Restrict diesel generator use, enhanced road sweeping, control pollution hotspots |
| Stage III (Severe) | 401-450 | Restrict certain vehicles, halt construction at non-compliant sites, remote schooling measures |
| Stage IV (Severe+) | Above 450 | Ban entry of non-essential heavy vehicles, close schools, shut non-essential industries, ban truck entry except essential goods |
GRAP measures are cumulative -- actions under all previous stages continue when a higher stage is invoked. CAQM revised GRAP in 2024 to make it more stringent, with a pre-emptive approach based on AQI forecasts rather than waiting for deterioration to occur.
Bharat Stage Emission Norms
| Norm | Implementation date | Equivalent to | Key improvement |
|---|---|---|---|
| BS-I | 2000 | Euro-1 | First emission standards for vehicles |
| BS-II | 2005 | Euro-2 | Stricter limits on CO, HC, NOx |
| BS-III | 2010 | Euro-3 | Catalytic converters mandatory |
| BS-IV | 2017 (nationwide) | Euro-4 | Significant PM and NOx reduction |
| BS-VI | 1 April 2020 | Euro-6 | 80% NOx reduction (diesel); 10 ppm sulphur; OBD mandatory; real driving emission (RDE) tests |
India skipped BS-V entirely, leapfrogging directly from BS-IV to BS-VI. This was a landmark regulatory decision that brought India's emission standards on par with European norms.
Water Pollution — Sources and Indicators
Major Sources
| Source | Contribution | Key pollutants |
|---|---|---|
| Domestic sewage | ~80% of river pollution | Organic matter, pathogens, nutrients (N, P) |
| Industrial effluents | ~15% | Heavy metals, toxic chemicals, acids/alkalis |
| Agricultural runoff | ~5% | Fertilizers (N, P causing eutrophication), pesticides |
| Urban stormwater | Variable | Oil, grease, suspended solids, microplastics |
Water Quality Indicators
| Indicator | Meaning | Clean water range |
|---|---|---|
| BOD (Biochemical Oxygen Demand) | Oxygen consumed by microbes to decompose organic matter (5 days, 20 degrees C) | Less than 3 mg/L |
| COD (Chemical Oxygen Demand) | Oxygen needed to chemically oxidise all organic and inorganic matter | Less than 10 mg/L |
| DO (Dissolved Oxygen) | Oxygen available for aquatic life | More than 6 mg/L |
| Faecal Coliform | Indicator of pathogenic contamination from human/animal waste | Less than 500 MPN/100mL |
| Total Dissolved Solids (TDS) | Dissolved salts and minerals | Less than 500 mg/L (drinking) |
River Pollution in India
Scale of the Problem
- CPCB has identified 351 polluted river stretches on 323 rivers across India
- Ganga and Yamuna are the most critically studied
- The Yamuna in the Delhi stretch (22 km, representing less than 2% of total length) receives approximately 58% of Delhi's wastewater, resulting in near-zero dissolved oxygen levels during lean flow months
Sewage Treatment Capacity Gap
| Parameter | Data |
|---|---|
| Urban sewage generation | ~72,368 MLD (million litres per day) |
| Installed treatment capacity | ~26,665 MLD |
| Actual treatment | ~20,235 MLD (approximately 28% of generation) |
| Untreated discharge | ~52,133 MLD |
Five states -- Maharashtra, Gujarat, Uttar Pradesh, Delhi, and Karnataka -- account for 60% of total installed treatment capacity, while Bihar, Assam, and northeastern states have negligible infrastructure.
Namami Gange Programme
Overview
| Feature | Detail |
|---|---|
| Launched | June 2014 as a flagship programme under Ministry of Jal Shakti |
| Implementing body | National Mission for Clean Ganga (NMCG) |
| Budget | Allocated Rs 23,424.86 crore from FY 2014-15 to FY 2024-25; Namami Gange Mission-II approved with Rs 22,500 crore till 2026 |
| Coverage | Five main-stem states -- Uttarakhand, UP, Bihar, Jharkhand, West Bengal; and tributaries |
Key Components
| Component | Focus |
|---|---|
| Sewage treatment | Creation of new STPs; rehabilitation of existing non-functional STPs |
| Industrial pollution | Monitoring and closure of Grossly Polluting Industries (GPIs); real-time effluent monitoring |
| River surface cleaning | Removal of floating solid waste using trash skimmers |
| Biodiversity conservation | Conservation of Gangetic dolphins, turtles, and other aquatic fauna |
| Afforestation | Plantation drives along river banks to prevent erosion |
| Ganga rejuvenation | Maintaining ecological flow (e-flow) -- minimum environmental flow standards notified |
Progress (as of 2025)
- Over 300 projects completed; total investment of approximately Rs 40,000 crore
- 25 Sewage Treatment Plants (STPs) commissioned in 2025, treating 530 MLD daily
- Number of GPIs identified and brought under real-time monitoring increased significantly
- Improvement in DO levels observed at several monitoring stations
Challenges
- Sewage infrastructure in smaller towns along tributaries remains weak
- State-level implementation varies significantly
- Encroachments on floodplains continue in several stretches
- River e-flow standards are difficult to enforce when dam operators prioritise irrigation and power
Groundwater Contamination
Arsenic Contamination
- Detected in groundwater in parts of 230 districts across 25 states
- Most affected: West Bengal, Bihar, Jharkhand, Uttar Pradesh, Assam, Manipur
- Source: Natural geological -- dissolution of arsenic-bearing minerals in alluvial aquifers of the Ganga-Brahmaputra-Meghna basin
- Health effects: Arsenicosis (skin lesions, keratosis), increased risk of cancer (bladder, lung, skin)
- WHO permissible limit: 10 micrograms per litre
Fluoride Contamination
- Found in 469 districts across 27 states
- Most affected: Rajasthan, Haryana, Karnataka, Telangana, Gujarat, Punjab, Andhra Pradesh
- Source: Natural dissolution of fluoride-bearing minerals (fluorite, apatite) in hard-rock aquifers
- Health effects: Dental fluorosis (mottled teeth), skeletal fluorosis (bone deformation, crippling)
- Permissible limit: 1.5 mg/L (BIS)
Nitrate Contamination
- 19.8% of groundwater samples exceed permissible limits
- Source: Fertilizer overuse, septic tank leachate, animal waste
- Health effects: Blue baby syndrome (methemoglobinemia) in infants
CPCB and SPCB — Regulatory Framework
Central Pollution Control Board (CPCB)
- Constituted under the Water (Prevention and Control of Pollution) Act, 1974
- Functions: set ambient quality standards (NAAQS, water quality), coordinate with SPCBs, advise the central government, operate national monitoring networks (NAMP for water, CAAQMS for air)
- Chairman appointed by the Central Government
State Pollution Control Boards (SPCBs)
- Implement and enforce pollution control laws at the state level
- Grant Consent to Establish (CTE) and Consent to Operate (CTO) to industries
- Monitor industrial effluent compliance
- Powers to issue closure orders against polluting units
- Key challenge: SPCBs are often understaffed, underfunded, and subject to political pressure
National Green Tribunal (NGT)
- Established under the NGT Act, 2010 for effective and expeditious disposal of cases relating to environmental protection
- Has heard numerous cases on river pollution, air quality, and industrial contamination
- Can impose substantial penalties and direct remedial action
- Proactively monitors Namami Gange, NCAP implementation, and groundwater contamination issues
Remediation Technologies
Air Pollution Control
| Technology | Application |
|---|---|
| Electrostatic Precipitators (ESP) | Remove PM from flue gases in thermal power plants; efficiency up to 99% |
| Bag filters/Fabric filters | Capture fine particles in cement, steel, and chemical industries |
| Flue Gas Desulphurisation (FGD) | Remove SO2 from power plant emissions using limestone slurry (wet FGD) |
| Selective Catalytic Reduction (SCR) | Reduce NOx emissions using ammonia as a reductant |
| Catalytic converters | Fitted in vehicle exhaust to convert CO, NOx, and HC to harmless gases |
| Smog towers | Experimental large-scale air purifiers (Delhi installed two); effectiveness debated |
Water Pollution Treatment
| Technology | Application |
|---|---|
| Activated Sludge Process (ASP) | Most common biological treatment for domestic sewage |
| Sequential Batch Reactor (SBR) | Modified ASP with batch processing; compact footprint |
| Moving Bed Biofilm Reactor (MBBR) | Uses biofilm carriers for high-efficiency biological treatment |
| Constructed Wetlands | Nature-based solution using natural filtration by plants (phytoremediation) |
| Membrane Bioreactor (MBR) | Combines biological treatment with membrane filtration; highest quality effluent |
| Common Effluent Treatment Plant (CETP) | Shared treatment for industrial clusters (mandated for polluting industries) |
Phytoremediation
- Use of plants to absorb, concentrate, or detoxify pollutants from soil and water
- Hyperaccumulator plants like Thlaspi caerulescens (zinc, cadmium) and water hyacinth (heavy metals from water bodies)
- Cost-effective and eco-friendly but slow compared to engineered solutions
Key Government Schemes and Policies Summary
| Scheme/Policy | Year | Focus |
|---|---|---|
| Water Act | 1974 | Prevention and control of water pollution |
| Air Act | 1981 | Prevention and control of air pollution |
| Environment Protection Act | 1986 | Umbrella legislation for environmental protection |
| National River Conservation Plan | 1995 | Conservation of major rivers |
| NAMP (National Air Monitoring Programme) | 1984 | Ambient air quality monitoring network |
| NCAP | 2019 | 40% PM reduction in 131 cities by 2026 |
| Namami Gange | 2014 | Ganga rejuvenation flagship programme |
| BS-VI Norms | 2020 | Vehicular emission standards at par with Euro-6 |
| GRAP | 2017 (revised 2024) | Emergency air quality response for Delhi-NCR |
| CAQM Act | 2021 | Statutory body for air quality management in NCR |
Recent Developments (2024–2026)
NCAP Progress — 26.84% PM Reduction in NCAP Cities (2019–2024)
The National Clean Air Programme (NCAP), launched in January 2019 targeting 131 non-attainment cities, achieved a 26.84% nationwide reduction in PM levels between 2019 and 2024 — approaching the revised target of 40% reduction by 2026. The "Tracing the Hazy Air 2025" report by the Centre for Research on Energy and Clean Air (CREA) found that 41 of 97 assessed NCAP cities met the initial 20–30% PM10 reduction target.
Despite ₹11,211 crore released under NCAP and 15th Finance Commission funds during 2019–2025, utilisation stood at approximately 68% (₹7,594 crore). Delhi remained the most polluted capital city globally, recording annual PM2.5 of 107 µg/m³ in 2024 — nearly 10 times the WHO guideline of 5 µg/m³. Air pollution accounts for over 2 million deaths per year in India (State of Global Air 2024).
UPSC angle: NCAP targets (40% PM reduction by 2026), progress (26.84%), Delhi PM2.5 data, and utilisation challenges are Prelims and Mains data points.
Delhi's Winter Smog — Graded Response Action Plan 2024
Delhi's air quality during October–December 2024 again hit "Severe" and "Severe+" categories under GRAP (Graded Response Action Plan), prompting CAQM (Commission for Air Quality Management in NCR and Adjoining Areas) to enforce Stage 4 restrictions: ban on all construction, entry restriction for BS-III petrol and BS-IV diesel vehicles, and work-from-home mandates.
The principal contributors to Delhi's winter smog identified by IITM Pune's source apportionment studies in 2024 include: local vehicular emissions (28–35%), stubble burning in Punjab/Haryana (contributing 12–50% during peak burning days in October–November), industrial emissions, road dust, and crop residue burning. Punjab burnt approximately 8.3 million tonnes of paddy stubble in 2024 despite state-level subsidies for Happy Seeder machinery.
UPSC angle: GRAP, CAQM, source apportionment of Delhi pollution, and stubble burning policy failures are Mains GS-3 content; GRAP Stage 4 triggers and restrictions are Prelims data.
India's Water Pollution — National Aquatic Monitoring Programme 2024
The Central Pollution Control Board's (CPCB) National Water Quality Monitoring Programme assessed 4,421 water quality monitoring stations across India in 2024. Key findings: Biological Oxygen Demand (BOD) exceeded permissible limits (3 mg/L) in 36% of river stretches monitored; coliform bacteria counts indicated severe faecal contamination in 57% of stations; and heavy metal contamination (lead, chromium, mercury) was found near 23 industrial clusters.
The Namami Gange Mission (budget: ₹20,000 crore) has built sewage treatment capacity of over 4,912 MLD (million litres per day) in the Ganga basin by 2024, against a total sewage generation of over 7,000 MLD — leaving a treatment gap of approximately 2,000 MLD. River Ganga Biological Health Indices improved in 36 of 47 monitored stretches, indicating some recovery.
UPSC angle: CPCB monitoring data, Namami Gange progress (4,912 MLD treatment capacity, budget ₹20,000 crore), BOD standards, and the remaining treatment gap are Prelims and Mains content.
Exam Strategy and Previous Year Relevance
Air and water pollution is a high-frequency topic across both Prelims and Mains.
Prelims focus areas:
- AQI categories and pollutants (6 categories, 8 pollutants)
- BOD vs COD definitions
- NAAQS values for PM2.5 and PM10
- BS-VI implementation date and key features
- NCAP target and number of cities
- GRAP stages and corresponding AQI ranges
- CPCB vs SPCB roles
Mains question patterns:
- "Examine the effectiveness of the National Clean Air Programme in addressing urban air pollution. What reforms are needed?" (GS-3)
- "Discuss the causes of river pollution in India. Critically evaluate the Namami Gange Programme." (GS-3)
- "Stubble burning is a governance failure, not just an environmental problem. Discuss." (GS-3)
- "What is GRAP? How effective has it been in managing Delhi's air quality crisis?" (GS-3)
Key tip: For Mains answers on pollution, always structure your response with: sources of pollution, health/environmental impact, existing policy framework, implementation gaps, and way forward with specific suggestions.
For current affairs on pollution indices, government notifications, and environmental policy updates, visit Ujiyari.com.
