Daily Air Quality Index

Index and Bands

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

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

The air quality index is based on the following five pollutants:

  • Nitrogen Dioxide
  • Sulphur Dioxide
  • Ozone
  • Particles < 10 µm (PM10)
  • Particles < 2.5 µm (PM2.5)

For each of these pollutants, a pollution index is calculated, based on its concentration over a specific period of time. Then, the highest of the individual pollutant indices is taken as the Daily Air Quality Index for the site or region.

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 Health Effects of Air Pollution page. Your doctor may also be able to give you advice.

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

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

Air pollution bands and indices µg m3

Ozone

Based on the running 8-hourly mean.

Index 1 2 3 4 5 6 7 8 9 10
Band Low Low Low Moderate Moderate Moderate High High High Very High
µg m-3 0-33 34-66 67-100 101-120 121-140 141-160 161-187 188-213 214-240 241 or more

Nitrogen Dioxide

Based on the hourly mean concentration.

Index 1 2 3 4 5 6 7 8 9 10
Band Low Low Low Moderate Moderate Moderate High High High Very High
µg m-3 0-67 68-134 135-200 201-267 268-334 335-400 401-467 468-534 535-600 601 or more

Sulphur Dioxide

Based on the 15-minute mean concentration.

Index 1 2 3 4 5 6 7 8 9 10
Band Low Low Low Moderate Moderate Moderate High High High Very High
µg m-3 0-88 89-177 178-266 267-354 355-443 444-532 533-710 722-887 888-
1064
1065 or more

PM2.5 Particles

Based on the daily mean concentration for historical data, latest 24 hour running mean for the current day.

Index 1 2 3 4 5 6 7 8 9 10
Band Low Low Low Moderate Moderate Moderate High High High Very High
µg m-3 0-11 12-23 24-35 36-41 42-47 48-53 54-58 59-64 65-70 71 or more

PM10 Particles

Based on the daily mean concentration for historical data, latest 24 hour running mean for the current day.

Index 1 2 3 4 5 6 7 8 9 10
Band Low Low Low Moderate Moderate Moderate High High High Very High
µg m-3 0-16 17-33 34-50 51-58 59-66 67-75 76-83 84-91 91-100 101 or more

Air pollution bandings and health descriptor impacts on sensitive receptor

Air pollution banding Value Accompanying health messages for at-risk individuals* Accompanying health messages for the 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.

Air pollution affects different people in different ways. Anyone experiencing symptoms should follow their doctor's advice.