Air Quality Standards and Indices in India

Air quality standards and indices in India provide a regulatory and diagnostic framework to monitor, evaluate, and control atmospheric pollution. The Central Pollution Control Board formulates these benchmarks under the Air (Prevention and Control of Pollution) Act, 1981. The National Ambient Air Quality Standards define permissible pollutant thresholds, while the National Air Quality Index translates complex monitoring data into a single numerical value to inform the public about daily air quality levels.

National Ambient Air Quality Standards (NAAQS)

The Central Pollution Control Board (CPCB) notified the first set of ambient air quality standards in 1982. These were revised in 1994 and later updated in November 2009.

Permissible Limits of Pollutants Under NAAQS (2009)

The NAAQS covers 12 identified pollutants. It prescribes uniform standards across industrial, residential, rural, and other areas, with stricter limits for ecologically sensitive zones.

National Air Quality Index (AQI)

The Ministry of Environment, Forest and Climate Change launched the National Air Quality Index (AQI) in April 2015 under the Swachh Bharat Abhiyan initiative. It operates on a “One Number-One Colour-One Description” format.

Tracked Pollutants and Computation

• The National AQI tracks eight criteria pollutants: PM₁₀, PM_2.5, NO_{2, SO_2, CO, O_3, NH_3,} and Pb.
• Calculating an AQI value requires monitoring data for a minimum of three pollutants, with at least one being PM₁₀ or PM_2.5.
• Sub-indices are calculated for individual pollutants using linear interpolation functions, and the overall AQI corresponds to the worst sub-index value among them.

AQI Categories and Associated Health Advisories

Air Quality Monitoring Programs in India

The Central Pollution Control Board coordinates national monitoring programs through manual and continuous monitoring setups.

National Air Quality Monitoring Programme (NAMP)

• The NAMP network covers hundreds of operating stations across states and union territories.
• The system monitors four regular parameters: SO_{2, NO_2, PM_{10}, and PM_2.5.
• Sampling takes place twice a week, yielding 104 observations per year for each station.
• State Pollution Control Boards, Pollution Control Committees, and National Environmental Engineering Research Institute (NEERI) manage network field stations.

Continuous Ambient Air Quality Monitoring Stations (CAAQMS)

• CAAQMS systems provide real-time, automated data streaming to CPCB servers.
• The stations continuously record concentrations of meteorological parameters along with all eight criteria pollutants.
• CAAQMS data feeds the CPCB web portal and mobile applications like SAMEER.

SAFAR (System of Air Quality and Weather Forecasting And Research)

• Developed by the Indian Institute of Tropical Meteorology (IITM), Pune, under the Ministry of Earth Sciences.
• Operational in major metropolitan centers including Delhi, Mumbai, Pune, and Ahmedabad.
• Delivers location-specific air quality forecasts up to 72 hours in advance and models stubble-burning smoke contributions.

National Clean Air Programme (NCAP)

The Ministry of Environment, Forest and Climate Change launched the National Clean Air Programme in January 2019 as a national strategy to tackle air pollution.

Targets and Strategies

• Targets non-attainment cities that consistently failed to meet the NAAQS between 2011 and 2015.
• Set an initial target to reduce particulate matter (PM₁₀ and PM_2.5) by 20% to 30% by 2024, taking 2017 as the baseline year.
• The target was later revised to achieve up to a 40% reduction in PM₁₀ levels or achieve NAAQS standards by 2026 across targeted cities.
• Operates the PRANA (Portal for Regulation of Air-pollution in Non-Attainment cities) portal to monitor physical and financial progress.

Graded Response Action Plan (GRAP)

The Graded Response Action Plan is an emergency intervention mechanism enforced in the National Capital Region (NCR) and adjoining areas during winter pollution episodes.

Institutional Authority and Stages

• The Commission for Air Quality Management (CAQM) in NCR and Adjoining Areas administers and revises the GRAP framework.
• Stage I (Poor, AQI 201–300): Dust suppression measures, strict enforcement of anti-smog guns, and ban on open biomass burning.
• Stage II (Very Poor, AQI 301–400): Ban on coal and firewood use in hotels, regulated diesel generator operations, and enhanced parking fees.
• Stage III (Severe, AQI 401–450): Strict ban on non-essential construction and demolition, ban on plying BS-III petrol and BS-IV diesel four-wheelers.
• Stage IV (Severe+, AQI > 450): Prohibition on the entry of non-essential commercial trucks into Delhi, closure of schools, and shift to work-from-home modes.

Important Facts

• The Central Pollution Control Board is a statutory organisation constituted in September 1974 under the Water (Prevention and Control of Pollution) Act, 1974, and entrusted with powers under the Air Act in 1981.
• NAAQS regulates 12 pollutants, whereas the National Air Quality Index tracks 8 specific pollutants.
• Benzene, Benzo(a)Pyrene, Arsenic, and Nickel are evaluated solely on an annual average basis under the NAAQS.
• Benzo(a)Pyrene, Arsenic, and Nickel are measured in nanograms per cubic meter (ng/m³), while other parameters are measured in micrograms (mug/m³) or milligrams (mg/m³).
• The World Health Organization (WHO) updated its Global Air Quality Guidelines in 2021, recommending an annual PM_2.5 limit of 5 mug/m³ and an annual PM₁₀ limit of 15 mug/m³.
• The Commission for Air Quality Management (CAQM) was established through an Act of Parliament in 2021, replacing the Supreme Court-appointed Environment Pollution (Prevention and Control) Authority (EPCA).
• The SAMEER mobile application provides hourly updates on the National Air Quality Index published by the CPCB.
• IIT Kanpur developed the technical calculation matrix and sub-index formulas for India’s National Air Quality Index.
• Benzene levels are monitored in ambient air because exposure is linked to aplastic anemia and acute myeloid leukemia.
• Benzo(a)Pyrene serves as a marker for polycyclic aromatic hydrocarbon (PAH) emissions generated by incomplete biomass and fossil fuel combustion.
• Non-attainment cities under NCAP are identified when pollutant levels violate NAAQS thresholds for five consecutive years.