Air pollution index

The Air Pollution Index (API) can be used to help understand daily air quality and if there are any health effects that may be a concern to the public. The API focuses on the health effects you may experience within a few hours or days after breathing polluted air.

The API measures the five major air pollutants: carbon monoxide, ground-level ozone, nitrogen dioxide, particle pollution (also known as particulate matter) and sulphur dioxide. The Department for Environment, Food & Rural Affairs (DEFRA) has established national air quality standards for each of these pollutants to protect public health.

Banding categories

The purpose of the API is to help you understand how local air quality might affect your health. The API runs from 0 to 10. The higher the API value the greater the level of air pollution and consequently the greater the health concern. This data can be beneficial to individuals whose health is adversely affected by air pollution as the information can be used to adjust daily medication and activities.

The categories are -

  • 1-3 Low - effects are unlikely to be noticed even by individuals who know they are sensitive to air pollution
  • 4-6 Moderate - mild effects unlikely to require actions may be noticed amongst sensitive individuals
  • 7-9 High - sensitive individuals may notice significant effects and action to avoid or reduce these effects may be needed. Asthmatics will find that their ‘reliever’ inhaler is likely to reverse the effects on the lungs
  • 10 Very High - the effects on sensitive individuals described for high levels of pollution may worsen
Index Ozone 8 hourly μg/m3 Nitrogen Dioxide Hourly mean μg/m3 Sulphur Dioxide 15 minute mean μg/m3 Carbon Monoxide 8 hour mean mg/m3  PM10 Particles 24 hour mean μg/m3
Low
1 0-32 0-95 0-88 0-3.8 0-16
2 33-66 96-190 89-176 3.9-7.6 17-32
3 67-99 191-286 177-265 7.7-11.5 33-49
Medium
4 100-126 287-381 266-354 11.6-13.4 50-57
5 127-152  382-476  355-442 43.5-15.4  58-66
6 153-179 478-572  443-531  15.5-17.3  67-74
High
7 180-239 573-635  532-708  17.4-19.2  75-82
8 240-299  363-700  709-886 19.3-21.2  83-91
9 300-359 701-763  887-1063 21.3-23.1 92-99
Very High
10 360 or more 764 or more 1064 or more 23.2 or more 100 or more