Air quality is measured by comparing against a range of health-effects based standards. This page gives information about what this means.

Standards for air pollution are created by setting an acceptable level for concentrations of pollutants in the air over a given time period. They are based on what is known about the effects of each pollutant on health and on the environment. They can also be used as a benchmark to see if air pollution is getting better or worse. Pollution levels exceed a standard when the concentration is higher than that set down by the standard. In order to make useful comparisons between pollutants we often report the number of days that the standard has been exceeded.

A target is set for the maximum number of times a standard can be exceeded over a specific time period.

The objectives adopted in the UK are based on the Air Quality Regulations 2000 and (Amendment) Regulations 2002 for the purpose of Local Air Quality Management. These air quality regulations have adopted the limit values required by EU Daughter Directives on Air Quality into UK law.

A summary of the current UK Air Quality Objectives is provided here.

Summary of Objectives of the National Air Quality Strategy

PollutantObjectiveMeasured asTo be achieved by

Benzene

All Authorities

16.25 µgm3Running Annual Mean31 December 2003

Benzene

Authorities in England and Wales only

5 µgm3Annual Mean31 December 2010

Benzene

Authorities in Scotland and Northern Ireland onlya

3.25 µgm3Running Annual Mean31 December 2010
1,3-Butadiene2.25 µgm3Running Annual Mean31 December 2003

Carbon Monoxide

Authorities in England, Wales and Northern Ireland onlya

10.0 mg/m3Maximum daily running 8 Hour Mean31 December 2003

Carbon Monoxide

Authorities in Scotland only

10.0 mg/m3Running 8 Hour Meanb31 December 2003
Lead0.5 µgm3Annual Mean31 December 2004
0.25 µgm3Annual Mean31 December 2008
Nitrogen Dioxidec

200 µgm3 

Not to be exceeded more than 18 times per year

1 Hour Mean31 December 2005
40 µgm3Annual Mean31 December 2005
Nitrogen Oxides**(V) 30 µgm3Annual Mean31 December 2000
Ozone*

100 µgm3

Not to be exceeded more than 10 times a year

8 hourly running or hourly mean31 December 2005

Particles (PM10)(gravimetric)d

All authorities

50 µgm3

Not to be exceeded more than 35 times per year

Daily Mean31 December 2004
40 µgm3Annual Mean31 December 2004

Particles (PM10)

Authorities in Scotland onlye

50 µgm3

Not to be exceeded more than 7 times per year

Daily Mean31 December 2004
18 µgm3Annual Mean31 December 2004
Sulphur Dioxide

266 µgm3

Not to be exceeded more than 35 times per year

15 Minute Mean31 December 2005

350 µgm3

Not to be exceeded more than 24 times per year

1 Hour Mean31 December 2004

125 µgm3

Not to be exceeded more than 3 times per year

24 Hour Mean31 December 2004
(V) 20 µgm3Annual Mean31 December 2000
(V) 20 µgm3Winter Mean (01 October - 31 March)31 December 2000

Notes:

  • In Northern Ireland none of the objectives are currently in regulation. Air Quality (Northern Ireland) Regulations are scheduled for consultation early in 2003.
  • b. The objectives for nitrogen dioxide are provisional.
  • c. Measured using the European gravimetric transfer sampler or equivalent.
  • d. These 2010 Air Quality Objectives for PM10 apply in Scotland only, as set out in the Air Quality (Scotland) Amendment Regulations 2002.
  • e. These 2010 Air Quality Objectives for PM10 apply in Scotland only, as set out in the Air Quality (Scotland) Amendment Regulations 2002.
  • µgm3 - micrograms per cubic metre
  • mg/m3 - milligrams per cubic metre
  • *Ozone is not included in the Regulations
  • ** Assuming NOx is taken as NO2
  • (V) These standards are adopted for the protection of vegetation and ecosystems. All of the remainder are for the protection of human health.

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New particle objectives for England, Wales, Northern Ireland and Greater London not included in Regulations

RegionObjectiveMeasured asTo be achieved by
Greater London

50 µgm3

Not to be exceeded more than 10 times per year

24-hour Mean31 December 2010
Greater London23 µgm3Annual Mean31 December 2010
Greater London20 µgm3Annual Mean31 December 2015
Rest of England, Wales and Northern Ireland

50 µgm3

Not to be exceeded more than 7 times per year

24-hour Mean31 December 2010
Rest of England, Wales and Northern Ireland20 µgm3Annual Mean31 December 2010