India Ambient Air Quality Standards
What are India's ambient air quality standards?
India's ambient air limits are the Revised National Ambient Air Quality Standards (NAAQS) of November 2009. They cover 12 pollutants. Most have one limit for industrial, residential, rural and other areas, and SO₂ and NO₂ have tighter annual limits for ecologically sensitive areas notified by the Central Government. The MoEF Gazette archive on PARIVESH lists the notification as G.S.R. 826(E) dated 16/11/2009 [1]. CPCB's reproduction of the table cites a "NAAQS Notification dated 18th November, 2009".
The archive holds only the notification's title, and the Gazette PDF wouldn't open. The values below are therefore taken from Table 1.1 of CPCB's National Ambient Air Quality Status & Trends in India-2010 (January 2012, pp. 1-2), which reproduces the standards.
| # | Pollutant | Averaging time | Industrial, residential, rural & other areas | Ecologically sensitive area | Methods of measurement |
|---|---|---|---|---|---|
| 1 | SO₂, µg/m³ | Annual* / 24 h** | 50 / 80 | 20 / 80 | Improved West and Gaeke; UV fluorescence |
| 2 | NO₂, µg/m³ | Annual* / 24 h** | 40 / 80 | 30 / 80 | Modified Jacob & Hochheiser (Na-arsenite); chemiluminescence |
| 3 | PM10, µg/m³ | Annual* / 24 h** | 60 / 100 | 60 / 100 | Gravimetric; TEOM; beta attenuation |
| 4 | PM2.5, µg/m³ | Annual* / 24 h** | 40 / 60 | 40 / 60 | Gravimetric; TEOM; beta attenuation |
| 5 | Ozone, µg/m³ | 8 h** / 1 h** | 100 / 180 | 100 / 180 | UV photometric; chemiluminescence; chemical method |
| 6 | Lead, µg/m³ | Annual* / 24 h** | 0.50 / 1.0 | 0.50 / 1.0 | AAS/ICP after sampling on EPM 2000 or equivalent filter; ED-XRF using Teflon filter |
| 7 | CO, mg/m³ | 8 h** / 1 h** | 02 / 04 | 02 / 04 | NDIR spectroscopy |
| 8 | Ammonia, µg/m³ | Annual* / 24 h** | 100 / 400 | 100 / 400 | Chemiluminescence; indophenol blue |
| 9 | Benzene, µg/m³ | Annual* | 05 | 05 | GC-based continuous analyser; adsorption/desorption followed by GC |
| 10 | Benzo(a)pyrene (particulate phase only), ng/m³ | Annual* | 01 | 01 | Solvent extraction followed by HPLC/GC |
| 11 | Arsenic, ng/m³ | Annual* | 06 | 06 | AAS/ICP after sampling on EPM 2000 or equivalent filter |
| 12 | Nickel, ng/m³ | Annual* | 20 | 20 | AAS/ICP after sampling on EPM 2000 or equivalent filter |
Note that the units change: CO is in mg/m³, and benzo(a)pyrene, arsenic and nickel are in ng/m³.
How compliance is assessed (notes to the table):
- * Annual: the arithmetic mean of at least 104 measurements a year at a site, taken twice a week, 24-hourly, at uniform intervals.
- ** 24-, 8- or 1-hourly values: these "shall be complied with 98% of the time in a year." For 2% of the time they "may exceed the limits but not on two consecutive days of monitoring."
- Trigger for more monitoring: if results exceed the limits on two consecutive monitoring days, that "shall be considered adequate reason to institute regular or continuous monitoring and further investigation."
CPCB's report says these standards replaced the earlier ones, which were revised on April 11, 1994 and published in the Gazette of India on May 20, 1994. The superseded July 2000 CPCB edition of "Environmental Standards for Ambient Air, Automobiles, Fuels, Industries and Noise" also turns up when you search for these standards. Its ambient air section predates the 2009 standards, so it should not be used for the current limits.
Approach: I searched the archive of MoEF/MoEFCC Gazette notifications (Environmental Standards collection) and CPCB monitoring publications, and took the figures from CPCB's 2010 status report. I couldn't open the official texts themselves: the G.S.R. 826(E) PDF on PARIVESH and the CPCB legal portal page did not respond.
How do they compare with WHO guidelines?
India's NAAQS are much looser than the WHO 2021 Global Air Quality Guidelines (AQG) for particulate matter, NO₂ and SO₂. The PM2.5 annual limit of 40 µg/m³ is eight times the WHO level of 5 µg/m³, and it is above even WHO's least strict interim target (35). The 8-hour ozone limit (100 µg/m³) equals the WHO level. The CO limits are stricter than the WHO short-term values that still apply. WHO's figures come from Table 0.1 and Table 0.2 of the WHO global air quality guidelines (2021), pp. xvii-xviii. The NAAQS figures are the ones from my previous answer (CPCB's reproduction of the November 2009 standards).
| Pollutant | Averaging time | NAAQS (industrial, residential, rural, other) | WHO interim targets 1 / 2 / 3 / 4 | WHO AQG level | Where NAAQS sits |
|---|---|---|---|---|---|
| PM2.5, µg/m³ | Annual | 40 | 35 / 25 / 15 / 10 | 5 | Looser than interim target 1 |
| 24 h | 60 | 75 / 50 / 37.5 / 25 | 15 | Between targets 1 and 2 | |
| PM10, µg/m³ | Annual | 60 | 70 / 50 / 30 / 20 | 15 | Between targets 1 and 2 |
| 24 h | 100 | 150 / 100 / 75 / 50 | 45 | Equals target 2 | |
| O₃, µg/m³ | 8 h | 100 | 160 / 120 / – / – | 100 | Equals AQG level |
| Peak season | none | 100 / 70 / – / – | 60 | No NAAQS equivalent | |
| 1 h | 180 | none in 2021 update | none | No WHO equivalent | |
| NO₂, µg/m³ | Annual | 40 (30 in ecologically sensitive areas) | 40 / 30 / 20 / – | 10 | Equals target 1 (target 2 in sensitive areas) |
| 24 h | 80 | 120 / 50 / – / – | 25 | Between targets 1 and 2 | |
| 1 h | none | n/a | 200 (2005 value, still valid) | No NAAQS equivalent | |
| SO₂, µg/m³ | Annual | 50 (20 in ecologically sensitive areas) | none | none | No WHO annual value |
| 24 h | 80 | 125 / 50 / – / – | 40 | Between targets 1 and 2 | |
| 10 min | none | n/a | 500 (still valid) | No NAAQS equivalent | |
| CO, mg/m³ | 8 h | 2 | n/a | 10 (still valid) | Stricter than WHO |
| 1 h | 4 | n/a | 35 (still valid) | Stricter than WHO | |
| 24 h | none | 7 | 4 | No NAAQS equivalent |
Differences beyond the numbers
- How exceedances are counted: WHO's 24-hour and 8-hour levels are 99th percentiles, which means 3-4 exceedance days a year. The NAAQS short-term values must be met 98% of the time. So even where the numbers are the same (8-hour ozone, for example), the NAAQS allows more exceedance days.
- Ozone: WHO's peak-season level is the average of the daily maximum 8-hour means over the six consecutive months with the highest six-month running average. India has no seasonal ozone standard.
- Interim targets: WHO says that reaching the AQG levels should be the ultimate goal. Where pollution is high, progress through the interim targets "should be considered a critical indicator of improving health conditions" (p. xxi).
- Older WHO values: WHO says its earlier guidelines remain valid for pollutants and averaging times the 2021 update does not cover (p. xviii).
Not compared: Lead, ammonia, benzene, benzo(a)pyrene, arsenic and nickel are not in the 2021 update. WHO refers readers to its earlier volumes for them: Air quality guidelines for Europe (1987 and 2nd edition 2000) and the 2010 indoor air quality guidelines. I did not open those, so I have no WHO figures for these six NAAQS pollutants.
Approach: The datasets I searched hold no WHO guideline values: CPCB National Air Quality Monitoring Programme reports and the EU Ambient Air Quality Directive 2024/2881. So I took the WHO figures from the 2021 guidelines PDF on WHO's IRIS repository. I compared them with the NAAQS values from my previous answer.