Air quality standards and clean-air governance

Detail

1. National Ambient Air Quality Standards (NAAQS)

• NAAQS (National Ambient Air Quality Standards): legal upper limits for pollutants in the outdoor air we breathe. "Ambient" means the open, outside air, not air inside a factory chimney.
• The Central Pollution Control Board (CPCB) notified them in 2009. They cover 12 pollutants.

• The 12 pollutants: SO₂, NO₂, PM10, PM2.5, ozone (O₃), lead (Pb), carbon monoxide (CO), ammonia (NH₃), benzene, benzo(a)pyrene, arsenic and nickel.

• PM10 / PM2.5 (particulate matter): tiny solid or liquid bits in the air, smaller than 10 or 2.5 micrometres. PM2.5 is about 1/30th the width of a human hair. It goes deep into the lungs and blood.

• The same standard applies to industrial, residential, rural and other areas. Only for NO₂ and SO₂ is there a stricter limit for ecologically sensitive areas.

Pollutant	India NAAQS 2009 (24-hour / annual)	WHO Global Air Quality Guidelines 2021 (24-hour / annual)
PM2.5 (µg/m³)	60 / 40	15 / 5 [2]
PM10 (µg/m³)	100 / 60	45 / 15 [2]

• WHO released its new guidelines on 22 September 2021. They replaced the 2005 guidelines and are stricter, because newer studies show harm even at low levels of pollution [2].
• WHO's annual PM2.5 value is 5 µg/m³. India's annual limit (40) is 8 times looser.
• WHO guidelines are advisory, not binding. India's NAAQS is the legal standard used to judge whether a city is "in attainment" (meets the standard) or not.

2. National Air Quality Index (AQI)

• AQI (Air Quality Index): turns readings of several pollutants into one number and one colour, so the public can understand how clean the air is.
• Launched in April 2015 under the Swachh Bharat Mission ("One Number – One Colour – One Description").
• It uses eight pollutants: PM10, PM2.5, NO₂, SO₂, CO, ozone, ammonia and lead.
• How it is worked out:
• Each pollutant gets a sub-index based on its level compared with the NAAQS.
• The highest sub-index becomes the city's AQI. That pollutant is the "prominent pollutant". In north India in winter, it is usually PM2.5.
• At least three pollutants (one of them PM2.5 or PM10) are needed to report an AQI.

AQI band	Range	Likely health effect
Good	0–50	Minimal impact
Satisfactory	51–100	Minor breathing discomfort for sensitive people
Moderately polluted	101–200	Discomfort for people with lung or heart disease, children, older adults
Poor	201–300	Breathing discomfort for most people on long exposure
Very Poor	301–400	Respiratory illness on long exposure
Severe	401–500	Affects healthy people; serious for the sick

3. Non-attainment cities

• Non-attainment city: a city that failed the NAAQS for PM10 or NO₂ for five years in a row (2011–2015), based on National Air Quality Monitoring Programme data.
• The NCAP list also added million-plus cities (from the 15th Finance Commission air-quality grants) that are not meeting the standards.
• Why most of them are in the Indo-Gangetic Plain (IGP) (Punjab, Haryana, Delhi, UP, Bihar, West Bengal):
• Landlocked basin. The IGP is a low plain between the Himalaya to the north and the Vindhya–peninsular uplands to the south. Polluted air gets trapped between them and cannot easily escape to the sea.
• Winter temperature inversion (a layer of warm air sitting above cooler air near the ground, the reverse of normal):
  • long, clear winter nights → the ground loses heat fast → the air near the ground becomes cold and heavy
  • a warm layer above acts like a lid → smoke and dust cannot rise
  • the mixing height (how high pollutants can spread upward) falls sharply → pollution builds up near the ground and smog forms
• Calm winds. After the monsoon withdraws, winds are weak. The north-westerlies carry smoke from stubble burning in Punjab and Haryana (October–November) towards Delhi.
• Dust. Fine alluvial soil, dry-season road dust, construction dust, and pre-monsoon dust storms from the Thar Desert (Rajasthan) add to PM10.
• Human load. Very high population density, vehicles, brick kilns, coal power plants, and biomass burned for cooking.

4. National Clean Air Programme (NCAP)

• NCAP: India's first national, time-bound plan to reduce air pollution. Launched by the MoEFCC in January 2019.
• Coverage: 131 non-attainment cities, each with its own city action plan. These plans target road dust, waste burning, vehicles, construction and demolition waste, and industry [3]. (Recent official counts say 130 cities for the performance grants [3][4].)
• Target:
• Original goal: cut PM10 and PM2.5 by 20–30% by 2024, compared with 2017.

• Revised goal: cut PM10 by up to 40% by 2025-26, compared with 2017-18 levels.

• Performance-linked funding:

• Money is released based on how much a city actually improves its air quality.

• About ₹13,237 crore in performance-linked grants has been given to 130 cities as gap funding [3][4].

• Results so far (official data):

• 103 of 130 cities showed lower PM10 levels.

• 64 cities cut PM10 by more than 20% [3][4].

• PRANA portal (Portal for Regulation of Air-pollution in Non-Attainment cities): an online dashboard. Cities upload their progress here, and this data is used to rank them [5].

• Swachh Vayu Survekshan (the clean-air survey): an annual ranking of NCAP cities, done in three population categories [5].
• 2025 results (11 award-winning cities) [6]:

Category (population)	Rank 1	Score	Notable action
Over 10 lakh	Indore (Madhya Pradesh)	200/200	Over 16 lakh trees planted; 120 electric + 150 CNG buses
Over 10 lakh	Jabalpur (MP), Rank 2	199/200	11 MW waste-to-energy plant
3–10 lakh	Amravati (Maharashtra)	200/200	340 km of end-to-end paved roads; 19 acres of barren land turned into dense forest
Under 3 lakh	Dewas (MP)	193/200	Industries shifted to cleaner fuels

• Swachh Vayu Diwas is observed on 7 September, which is also the UN International Day of Clean Air for blue skies [7].

5. Delhi-NCR: Graded Response Action Plan (GRAP)

• GRAP: an emergency plan for the whole National Capital Region. Steps become stricter automatically as air quality gets worse.
• First notified in 2017 (by MoEFCC, after Supreme Court orders). It was first enforced by EPCA. It is now run and revised by CAQM.
• Stages are switched on using Delhi's average AQI and weather forecasts. This means action can begin before the air gets worse [8].

Stage	AQI category	Delhi AQI range [8]	Typical measures
I	Poor	201–300	Dust control at construction sites, mechanised road sweeping, water spraying, ban on open waste burning
II	Very Poor	301–400	Limits on diesel generator (DG) sets, higher parking fees to discourage private cars, more buses and metro trips
III	Severe	401–450	Ban on non-essential construction and demolition; limits on older petrol (BS-III) and diesel (BS-IV) vehicles; stone crushers and mining closed
IV	Severe+	>450	Trucks barred from entering Delhi (except those carrying essential goods or running on clean fuel), ban even on public construction projects, possible work-from-home and online schools

• November 2025 revision: the GRAP schedule was made stricter. Measures moved down one stage: Stage IV → III, III → II, II → I. So the same steps now start at a lower AQI [8]. (Earlier revisions came in 2023 and 2024 [8].)

6. Commission for Air Quality Management (CAQM)

• CAQM: a statutory body (one set up by a law). It was created under the Commission for Air Quality Management in National Capital Region and Adjoining Areas Act, 2021.
• It replaced EPCA (Environment Pollution (Prevention and Control) Authority, set up in 1998 on Supreme Court orders).
• Area covered: Delhi-NCR plus the nearby states Punjab, Haryana, Rajasthan and Uttar Pradesh. This covers both the city and the farm areas where stubble is burnt.
• Powers: it can issue binding directions, enforce GRAP, and coordinate between state governments. Its orders override those of state pollution boards on air-quality matters in the region.

7. Debate: airshed vs city-level management

• Airshed: a region that shares the same body of air. Pollution moves freely within it, whatever the state or city borders. The whole IGP acts as one airshed in winter.
• The problem with city-level plans (NCAP):
• A large share of a city's PM2.5 comes from outside its borders, such as stubble smoke, power plants and brick kilns in nearby districts.

• A city cannot control these sources, so city-only plans hit a limit.

• The case for an airshed approach:

• Plan across states, as CAQM partly does for NCR.

• Apply the same idea to the rest of the IGP.

• Other gaps:

• Data gaps. Monitoring stations are crowded into big cities. Small towns and rural areas have very few, even though rural smoke from biomass is high.
• PM10 vs PM2.5. NCAP mainly tracks PM10, which includes a lot of natural dust. Health experts say PM2.5 matters more for health.
• Loose NAAQS. India's limits have not been updated since 2009, while the WHO tightened its guidelines in 2021 [2].

Prelims Hooks

• NAAQS was notified by CPCB in 2009 and covers 12 pollutants. The National AQI uses only 8. Benzene, benzo(a)pyrene, arsenic and nickel are in NAAQS but not in the AQI.
• PM2.5 limits: India 60 / 40 µg/m³ vs WHO 2021 15 / 5 µg/m³ (24-hour / annual) [2].
• AQI order from best to worst: Good → Satisfactory → Moderately polluted → Poor → Very Poor → Severe (401–500). Ammonia and lead are included in the AQI. This is a common trap.
• Non-attainment city: failed NAAQS for PM10 or NO₂ (not PM2.5) for five years in a row, 2011–15.
• NCAP: launched January 2019, run by MoEFCC. Target is up to 40% PM10 cut by 2025-26 (base 2017-18). Cities report on the PRANA portal [5].
• Swachh Vayu Survekshan 2025 winners: Indore (over 10 lakh), Amravati (3–10 lakh), Dewas (under 3 lakh) [6].
• GRAP Stage IV ("Severe+") starts when Delhi AQI is above 450. Stage III covers 401–450 [8].
• CAQM: set up by an Act of 2021, replaced EPCA. It covers Delhi-NCR, Punjab, Haryana, Rajasthan and UP. It does not cover Himachal Pradesh or Uttarakhand.
• Swachh Vayu Diwas is on 7 September [7].

Mains Points

• Geography makes IGP pollution worse: the plain is a landlocked basin hemmed in by the Himalaya. Winter brings temperature inversion, a low mixing height and calm winds. Stubble smoke from Punjab and Haryana and dust from the Thar add to it. As a result, most of India's non-attainment cities are in this one region (GS-I distribution, GS-III environment).
• Policy response with several layers: standards (NAAQS 2009) → public information (AQI 2015) → long-term city plans (NCAP 2019, performance-linked funds, Swachh Vayu Survekshan ranking) → emergency action (GRAP) → a statutory regional body (CAQM 2021). Progress so far: PM10 fell in 103 of 130 cities [3][4].
• Limits: NAAQS is far looser than WHO 2021 values [2]. NCAP focuses on PM10 and on individual cities. There is little monitoring in small towns and rural areas. GRAP is reactive, which is why its repeated tightening (most recently in November 2025) matters [8]. Way forward: airshed-level planning across the IGP, PM2.5-based targets, more monitoring stations, and solving stubble burning at its source (crop diversification, ex-situ use of crop residue).