Air quality index

Everything you need to know about Air Quality Index (AQI)

The AQI is an index used for reporting air quality on a daily basis. It informs you about how clean or polluted the air is, and what related health issues you should be worried about. The AQI emphasizes on health effects you may experience within few hours or certain days after inhaling polluted air.

National Air Quality Index (AQI) converts complex air data of eight pollutants into a single number (index value), color and nomenclature.

National Air Quality Index (AQI) was introduced on 17th October 2014 with a view to disseminate information on air quality in a simple comprehendible form for the general population.

How does AQI function?

Let us look at AQI as a standard that runs from 0 to 500. The higher the value of AQI, the higher the level of air pollution and the greater the health concern. For instance, an AQI value of 50 represents decent air quality with little damage to public health, whereas an AQI of 300 represents dangerous air quality.

The measurement of air quality depends on eight pollutants, namely,

  • Particulate Matter (size less than 10 µm) or (PM10),
  • Particulate Matter (size less than 2.5 µm) or (PM2.5),
  • Nitrogen Dioxide (NO2),
  • Sulphur Dioxide (SO2),
  • Carbon Monoxide (CO),
  • Ozone (O3),
  • Ammonia (NH3), and
  • Lead (Pb)

for which temporary (up to 24-hourly averaging period) National Ambient Air Quality Standards are suggested. One need to keep in mind that ambient air quality standards are mentioned separately in India for close to 12 pollutants including the 8 that make up Air Quality Index.

AQI has six categories when it comes to air quality. These are: Good, Satisfactory, Moderately Polluted, Poor, Very Poor and Severe. The AQI values and parallel ambient concentrations (health breakpoints) for the identified eight pollutants are mentioned bellow:

AQI Category, Pollutants and Health Breakpoints  
AQI Category (Range) Categories for the various readings of the pollutant based on the health breakpoint health impacts
 

PM10
24-hr

PM2.5
24-hr

NO2
24-hr

O3
8-hr

CO
8-hr (mg/m3)

SO2
24-hr

NH3
24-hr

Pb
24-hr

Good (0-50)

0-50

0-30

0-40

0-50

0-1.0

0-40

0-200

0-0.5

Satisfactory (51-100)

51-100

31-60

41-80

51-100

1.1-2.0

41-80

201-400

0.5 –1.0

Moderately polluted (101-200)

101-250

61-90

81-180

101-168

2.1- 10

81-380

401-800

1.1-2.0

                 

Poor (201-300)

251-350

91-120

181-280

169-208

10-17

381-800

801-1200

2.1-3.0

Very poor (301-400)

351-430

121-250

281-400

209-748*

17-34

801-1600

1200-1800

3.1-3.5

Severe (401-500)

430 +

250+

400+

748+*

34+

1600+

1800+

3.5+

*One hourly monitoring (for mathematical calculations only)

The AQI index values and health impact associated with it are as follows:

AQI

Associated Health Impacts

Good (0–50)

Minimal Impact

Satisfactory (51–100)

May cause minor breathing discomfort to sensitive people.

Moderately polluted (101–200)

May cause breathing discomfort to people with lung disease such as asthma, and discomfort to people with heart disease, children and older adults.

Poor (201–300)

May cause breathing discomfort to people on prolonged exposure, and discomfort to

 

people with heart disease

Very Poor (301–400)

May cause respiratory illness to the people on prolonged exposure. Effect may be more pronounced in people with lung and heart diseases.

Severe (401-500)

May cause respiratory impact even on healthy people, and serious health impacts on people with lung/heart disease. The health impacts may be experienced even during light physical activity.

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