Air Quality Standards

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

Air Quality Standards and Objectives

Standards for air pollution are concentrations over a given time period that are considered to be acceptable in the light of what is scientifically 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.

An exceedence of a standard is a period of time (which is defined in each standard) where the concentration is higher than that set down by the standard. In order to make useful comparisons between pollutants, for which the standards may be expressed in terms of different averaging times, the number of days on which an exceedence has been recorded is often reported.

An objective is the target date on which exceedences of a standard must not exceed a specified number.

The objectives adopted in the UK are defined in the latest Air Quality Strategy for England, Scotland, Wales and Northern Ireland, published on 17th July 2007. Those which are limit values required by EU Daughter Directives on Air Quality have been transposed into UK law through the Air Quality Standards Regulations 2007 which came into force on 15th February 2007.

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

UK Air Quality Objectives for protection of human health, July 2007 - New objectives highlighted in shading
Pollutant	Air Quality Objective		To be achieved by
Pollutant	Concentration	Measured as	To be achieved by
Benzene
All authorities	16.25 µg m^-3	Running annual mean	31 December 2003
England and Wales Only	5.00 µg m^-3	Annual mean	31 December 2010
Scotland and N. Ireland	3.25 µg m^-3	Running annual mean	31 December 2010
1,3-Butadiene	2.25 µg m^-3	Running annual mean	31 December 2003
Carbon Monoxide
England, Wales and N. Ireland	10.0 mg m^-3	Maximum daily running 8-hour mean	31 December 2003
Scotland Only	10.0 mg m^-3	Running 8-hour mean	31 December 2003
Lead	0.5 µg m^-3	Annual mean	31 December 2004
	0.25 µg m^-3	Annual mean	31 December 2008
Nitrogen Dioxide	200 µg m^-3 not to be exceeded more than 18 times a year	1-hour mean	31 December 2005
	40 µg m^-3	Annual mean	31 December 2005
Particles (PM10) (gravimetric)
All authorities	50 µg m^-3, not to be exceeded more than 35 times a year	Daily mean	31 December 2004
	40 µg m^-3	Annual mean	31 December 2004
Scotland Only	50 µg m^-3, not to be exceeded more than 7 times a year	Daily mean	31 December 2010
	18 µg m^-3	Annual mean	31 December 2010
Particles (PM2.5) (gravimetric) *	25 µg m^-3 (target)	Annual mean	2020
All authorities	15% cut in urban background exposure	Annual mean	2010 - 2020
Scotland Only	12 µg m^-3 (limit)	Annual mean	2010
Sulphur dioxide	350 µg m^-3, not to be exceeded more than 24 times a year	1-hour mean	31 December 2004
	125 µg m^-3, not to be exceeded more than 3 times a year	24-hour mean	31 December 2004
	266 µg m^-3, not to be exceeded more than 35 times a year	15-minute mean	31 December 2005
PAH *	0.25 ng m^-3	Annual mean	31 December 2010
Ozone *	100 µg m^-3 not to be exceeded more than 10 times a year	8 hourly running or hourly mean*	31 December 2005

* not included in regulations at present
Shaded data shows new objectives

UK Air Quality Objectives for protection of vegetation and ecosystems, July 2007 - New objectives highlighted in shading
Pollutant	Air Quality Objective		To be achieved by
Pollutant	Concentration	Measured as	To be achieved by
Nitrogen dioxide (for protection of vegetation & ecosystems) *	30 µg m^-3	Annual mean	31 December 2000
Sulphur dioxide (for protection of vegetation & ecosystems) *	20 µg m^-3 20 µg m^-3	Annual mean Winter Average (Oct - Mar)	31 December 2000
Ozone *	18000 µg m^-3.h	AOT40⁺, calculated from 1h values May-July. Mean of 5 years, starting 2010	01 January 2010

* not included in regulations at present
⁺ AOT 40 is the sum of the differences between hourly concentrations greater han 80 µg m^-3 (=40ppb) and 80 µg m^-3, over a given period using only the 1-hour averages measured between 0800 and 2000.
Shaded data shows new objectives

Air Pollution Information Service

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
Carbon Monoxide
Particles < 10µm (PM10)

Air Pollution Forecasts

Air Quality Forecasts are issued on a regional basis for three different area types:

In towns and cities near busy roads
Elsewhere in towns and cities
In rural areas

Forecasts are based on the prediction of air pollution index for the worst-case of the five pollutants listed above, for each region.

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.

More details on effects, including long-term, are available in a free leaflet 'Air Pollution - what it means for your health'.

Air Pollution Bandings and Index and the Impact on the health of People who are Sensitive to Air Pollution

Banding	Index	Health Descriptor
Low	1, 2, or 3	Effects are unlikely to be noticed even by individuals who know they are sensitive to air pollutants
Moderate	4, 5, or 6	Mild effects, unlikely to require action, may be noticed amongst sensitive individuals.
High	7, 8, or 9	Significant effects may be noticed by sensitive individuals and action to avoid or reduce these effects may be needed (e.g. reducing exposure by spending less time in polluted areas outdoors). Asthmatics will find that their 'reliever' inhaler is likely to reverse the effects on the lung.
Very High	10	The effects on sensitive individuals described for 'High' levels of pollution may worsen.

Boundaries Between Index Points for Each Pollutant

Band	Index	Ozone		Nitrogen Dioxide		Sulphur Dioxide		Carbon Monoxide		PM10 Particles
		Running 8 hourly or hourly mean*		hourly mean		15 minute mean		Running 8 hourly mean		Running 24 hour mean
		µgm^-3	ppb	µgm^-3	ppb	µgm^-3	ppb	mgm^-3	ppm	µgm^-3 (Grav. Equiv.)	µgm^-3 (Ref. Equiv.)
Low
	1	0-33	0-16	0-95	0-49	0-88	0-32	0-3.8	0.0-3.2	0-21	0-19
	2	34-65	17-32	96-190	50-99	89-176	33-66	3.9-7.6	3.3-6.6	22-42	20-40
	3	66-99	33-49	191-286	100-149	177-265	67-99	7.7-11.5	6.7-9.9	43-64	41-62
Moderate
	4	100-125	50-62	287-381	150-199	266-354	100-132	11.6-13.4	10.0-11.5	65-74	63-72
	5	126-153	63-76	382-477	200-249	355-442	133-166	13.5-15.4	11.6-13.2	75-86	73-84
	6	154-179	77-89	478-572	250-299	443-531	167-199	15.5-17.3	13.3-14.9	87-96	85-94
High
	7	180-239	90-119	573-635	300-332	532-708	200-266	17.4-19.2	15.0-16.5	97-107	95-105
	8	240-299	120-149	636-700	333-366	709-886	267-332	19.3-21.2	16.6-18.2	108-118	106-116
	9	300-359	150-179	701-763	367-399	887-1063	333-399	21.3-23.1	18.3-19.9	119-129	117-127
Very High
	10	360 or more	180 or more	764 or more	400 or more	1064 or more	400 or more	23.2 or more	20 or more	130 or more	128 or more

* For ozone, the maximum of the 8 hourly and hourly mean is used to calculate the index value.