Maarg Manthan · Topic 13.11

National Air Quality Index and Comprehensive Environmental Pollution Index

Environment & Ecology › Air, Marine, Noise and Other Pollution · Topic 13.11

The National Air Quality Index (AQI) was launched on 17 September 2014 by the Central Pollution Control Board, under the Swachh Bharat campaign, to give citizens a simple, colour-coded measure of air quality. It turns the concentrations of up to eight pollutants, PM10, PM2.5, nitrogen dioxide, sulphur dioxide, carbon monoxide, ozone, ammonia and lead, into a single number from 0 to 500 and six categories: Good (0 to 50), Satisfactory (51 to 100), Moderately polluted (101 to 200), Poor (201 to 300), Very poor (301 to 400) and Severe (401 to 500). At least three pollutants, one of them PM10 or PM2.5, are needed for a calculation, and the worst sub-index decides the AQI. The Comprehensive Environmental Pollution Index (CEPI) is a CPCB tool, first developed in 2009 and revised in 2016, to rate industrial clusters on air, water and land pollution using factors that include pollutant levels, health effects and the number of people exposed; a score of 70 or more marks a cluster as critically polluted, and 60 to 70 as severely polluted.

5 min read · UPSC Prelims · Environment & Ecology · Air, Marine, Noise and Other Pollution

At a Glance

AQI launched 17 September 2014
Range 0 to 500
Pollutants Eight
Categories Six
CEPI critical score 70 and above
Exam link UPSC Prelims, Environment & Ecology: Air, Marine, Noise and Other Pollution

Where Does It Fit?

This topic follows vehicle norms and explains how air quality and industrial pollution are measured and communicated. It finishes the air pollution part and leads to marine pollution. Previous topic: Bharat Stage Emission Norms. Next topic: Marine Pollution: Sources and Effects.

How Does the National AQI Work?

AQI range	Category and health message
0 to 50	Good: minimal impact
51 to 100	Satisfactory: minor breathing discomfort for sensitive people
101 to 200	Moderately polluted: discomfort for people with lung or heart disease, children and older adults
201 to 300	Poor: breathing discomfort on prolonged exposure
301 to 400	Very poor: respiratory illness on prolonged exposure
401 to 500	Severe: affects healthy people and seriously affects those with existing disease
Method	Sub-index for each pollutant; the highest sub-index is the AQI

What Is the CEPI and How Is It Used?

CEPI: an index developed by CPCB in 2009 to identify polluted industrial clusters
Components: scores for air, water and land pollution based on pollutant levels, human health and ecological effects, and exposure
Critically polluted: score of 70 or more
Severely polluted: score of 60 to 70
Other polluted: score of 50 to 60
First list: in 2009, 88 industrial clusters were assessed and 43 were found critically polluted
Moratorium: new projects in critically polluted areas faced restrictions on expansion until improvement
Revision: a revised method in 2016 improved the assessment

What Else Should You Remember?

AQI pollutants: PM10, PM2.5, NO2, SO2, CO, O3, NH3 and Pb
Minimum data: at least three pollutants and one of them PM
Averaging time: 24-hour averages for most pollutants, 8-hour for CO and ozone
Sub-index: an index value for each pollutant using breakpoints
Dominant pollutant: the pollutant with the highest sub-index
Colour code: green, light green, yellow, orange, red and dark red
SAFAR: System of Air Quality and Weather Forecasting and Research, run by the Ministry of Earth Sciences, gives AQI in major cities
CPCB bulletin: daily AQI for many cities
Real-time stations: continuous monitoring stations across cities report to the CPCB portal
Health advisory: the AQI links numbers to health messages
GRAP link: action stages in Delhi NCR are tied to AQI levels
Other AQIs: the US EPA AQI and UK band systems differ in breakpoints
AQI limitation: shows only a few pollutants and does not capture all toxic air pollutants
Public dashboards: apps now show AQI by location
CEPI purpose: to prioritise industrial clusters for action
Examples: Vapi, Ankleshwar, Angul-Talcher, Ghaziabad and Korba have featured in lists of high scores
Action plans: states prepare plans for improvement of polluted clusters
CPCB: Central Pollution Control Board, a statutory body under the Water Act, 1974
NGT: monitors action on polluted industrial areas
Link to previous: see Bharat Stage Emission Norms
Link to next: see Marine Pollution: Sources and Effects
Link to air pollution: see Causes and Harmful Effects of Air Pollution
Caution: cluster lists and scores are revised, so check the latest CPCB report
Exam hint: learn the six AQI bands with numbers, the eight pollutants and the CEPI cut-offs
AQI and health: each category carries a health message, from no impact to emergency conditions
AQI launch: launched in 2014 as part of the Swachh Bharat campaign, to put air quality in plain view of the public
Hourly updates: many monitoring stations report in near real time to the CPCB portal
Local variation: AQI at a station may not match air quality a few kilometres away
CEPI scoring: a higher CEPI score means a more polluted cluster
Clusters: Industrial clusters are groups of factories in one area, such as chemical or textile belts
Environmental audits: clusters with high CEPI scores are asked for audits and improvement plans

Why Does It Matter for the Exam?

Launch: 2014
Bands: Six
Pollutants: Eight
Current affairs link: GRAP and AQI
Common errors: mixing AQI with NAAQS or CEPI

As an analytical point, an index makes air pollution visible and actionable, but it can hide toxic pollutants not in its list. CEPI similarly helps focus enforcement on industrial hotspots, if updated and acted on.

Why Is This Topic Important?

AQI Public message
CEPI Hotspot rank
Use Action

What Came Next?

The next topic covers marine pollution, its sources and effects. Next topic: Marine Pollution: Sources and Effects.

Key People and Terms

AQI Air Quality Index
Sub-index Pollutant score
CEPI Comprehensive Environmental Pollution Index
SAFAR Air forecast system
NAAQS Air quality standards
GRAP Graded Response Action Plan

Exam Corner

Points to Remember

AQI launched in 2014.
Scale 0 to 500.
Eight pollutants.
CEPI critical: 70 and above.
Highest sub-index decides AQI.

Do Not Confuse With

AQI and NAAQS Public index versus legal standards
AQI and CEPI Air quality versus industrial cluster pollution
Poor and Very poor 201 to 300 versus 301 to 400

Memory Hook

Fifty good, hundred fair, two moderate, three poor, four very poor, five severe.

Mains Angle

Questions ask for categories and cut-offs. These points help.

Purpose Awareness
Limits Few pollutants
Use Action plans

A Question You May Face

An original practice question, not a past paper question.

“Explain the National Air Quality Index and the Comprehensive Environmental Pollution Index and their significance.”

How to Answer

AQI Bands.
CEPI Scores.
Use Action.
Limits Coverage.

GS Relevance

Prelims: AQI categories, pollutants, CEPI scores. GS Paper 3: pollution assessment tools.

Frequently Asked Questions

What is the National Air Quality Index?

The National Air Quality Index, launched by the Central Pollution Control Board on 17 September 2014, converts the concentrations of up to eight air pollutants into a single number from 0 to 500 with six colour-coded categories, from Good to Severe. It gives the public an easy way to understand air quality and its health effects.

Which pollutants are covered by the AQI?

The Indian AQI considers eight pollutants: PM10, PM2.5, nitrogen dioxide, sulphur dioxide, carbon monoxide, ozone, ammonia and lead. Data for at least three pollutants, one of which must be PM10 or PM2.5, is needed for calculating the index, and the pollutant with the highest sub-index decides the AQI value.

What are the AQI categories?

The six categories are Good (0 to 50), Satisfactory (51 to 100), Moderately polluted (101 to 200), Poor (201 to 300), Very poor (301 to 400) and Severe (401 to 500). Each is linked to a colour and a health message, with the higher levels warning that even healthy people may be affected.

What is the Comprehensive Environmental Pollution Index?

The Comprehensive Environmental Pollution Index is a method developed by the CPCB in 2009 and revised in 2016 to score industrial clusters on pollution of air, water and land, taking into account pollutant levels, health and ecological effects and exposure. A score of 70 or more marks a cluster as critically polluted, and it is used to prioritise action.

How is the CEPI used?

CEPI scores are used to identify polluted industrial clusters so that regulators can prioritise them for monitoring, action plans and, in the past, restrictions on new projects. In the first assessment in 2009, 88 clusters were studied and 43 were found critically polluted. States then prepare plans to improve conditions in such areas.

PYQ Practice — Statement Analysis

1 The AQI has six categories.

True

From Good to Severe.

2 An AQI of 350 is Poor.

False

It is Very poor.

3 CEPI scores of 70 or above mark critically polluted areas.