Daily Air Quality Index (DAQI)

The Daily Air Quality Index (DAQI) tells you about levels of air pollution and provides recommended actions and health advice. The index is numbered 1-10 and divided into four bands, low (1) to very high (10), to provide detail about air pollution levels in a simple way, similar to the sun index or pollen index.

Index and Bands

In the UK most air pollution information services use the index and banding system approved by the Committee on Medical Effects of Air Pollution Episodes (COMEAP). The system uses 1-10 index divided into four bands to provide more detail about air pollution levels in a simple way, similar to the sun index or pollen index.

  • 1-3 (Low)
  • 4-6 (Moderate)
  • 7-9 (High)
  • 10 (Very High)

The overall air pollution index for a site or region is calculated from the highest concentration of five pollutants:

  • Nitrogen Dioxide
  • Sulphur Dioxide
  • Ozone
  • Particles PM2.5
  • Particles < 10µm (PM10)

For more information about the boundaries between index points for each pollutant, visit the Defra UK-AIR Daily Air Quality Index page.

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Health Advice

Latest studies report that:

  • When air pollution is LOW (1-3) effects are unlikely to be noticed even by those who are sensitive to air pollution.
  • When air pollution is MODERATE (4-6) sensitive people may notice mild effects but these are unlikely to need action.
  • When air pollution is HIGH (7-9) sensitive people may notice significant effects and may need to take action.
  • When air pollution is VERY HIGH (10) effects on sensitive people, described for HIGH pollution, may worsen.

Air pollution can cause short-term health effects to sensitive individuals (people who suffer from heart disease or lung diseases, including asthma). Effects on sensitive people can be reduced by spending less time outdoors. 'Reliever' inhalers should lessen effects on asthma sufferers.

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How to use the Daily Air Quality Index

Step 1: Determine whether you (or your children) are likely to be at risk from air pollution. Information on groups who may be affected is provided on the Additional information on the short-term effects of air pollution page on the Defra UK-AIR website. Your doctor may also be able to give you advice.

Step 2: If you may be at-risk, and are planning strenuous activity outdoors, check the air pollution forecast page.

Step 3: Use the health messages corresponding to the highest forecast level of pollution as a guide.

Air Pollution Banding Value Accompanying health messages for at-risk groups and 
the general population
At-risk individuals* General population
Low 1-3 Enjoy your usual outdoor activities. Enjoy your usual outdoor activities.
Moderate 4-6 Adults and children with lung problems, and adults with heart problems, who experience symptoms, should consider reducing strenuous physical activity, particularly outdoors. Enjoy your usual outdoor activities.
High 7-9 Adults and children with lung problems, and adults with heart problems, should reduce strenuous physical exertion, particularly outdoors, and particularly if they experience symptoms. People with asthma may find they need to use their reliever inhaler more often. Older people should also reduce physical exertion. Anyone experiencing discomfort such as sore eyes, cough or sore throat should consider reducing activity, particularly outdoors.
Very High 10 Adults and children with lung problems, adults with heart problems, and older people, should avoid strenuous physical activity. People with asthma may find they need to use their reliever inhaler more often. Reduce physical exertion, particularly outdoors, especially if you experience symptoms such as cough or sore throat.

* Adults and children with heart or lung problems are at greater risk of symptoms. Follow your doctor's usual advice about exercising and managing your condition. It is possible that very sensitive individuals may experience health effects even on Low air pollution days. Anyone experiencing symptoms should follow the guidance provided on the Defra UK-AIR website.

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Boundaries Between Index Points for Each Pollutant

Band Index Ozone Running
8 hourly mean
Nitrogen Dioxide
Hourly Mean
Sulphur Dioxide
15 Minute Mean
PM2.5 Particles
24 Hour Running Mean
PM10 Particles 
24 Hour Running Mean
    µgm-3 µgm-3 µgm-3 µgm-3 µgm-3
  1 0-33 0-67 0-88 0-11 0-16
2 34-66 68-134 89-177 12-23 17-33
3 67-100 135-200 178-266 24-35 34-50
  4 101-120 201-267 267-354 36-41 51-58
5 121-140 268-334 355-443 42-47 59-66
6 141-160 335-400 444-532 48-53 67-75
  7 161-187 401-467 533-710 54-58 76-83
8 188-213 468-534 711-887 59-64 84-91
9 214-240 535-600 888-1064 65-70 92-100
Very High
  10 241 or more 601 or more 1065 or more 71 or more 101 or more

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