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
A set of air quality standards and objectives has been developed for several pollutants of concern for human health. Standards are concentrations of pollutants that are considered safe for humans and the environment. Objectives are derived from the standards and are a compromise between what is desirable purely on health grounds and what is practical in terms of feasibility and costs. Each objective has a date by when it must be achieved.
The objectives adopted in Scotland for the purpose of Local Air Quality Management are set out in the Air Quality (Scotland) Regulations 2000, the Air Quality (Scotland) Amendment Regulations 2002 and the Air Quality (Scotland) Amendment Regulations 2016. Similar targets are set at EU level, where there are called limit or target values. These are set out in the European 2008 Ambient Air Quality Directive (2008/50/EC) and transposed into Scottish legislation by the Air Quality Standards (Scotland) Regulations 2010. It is the responsibility of EU Member States to achieve the limit and target values.
A summary of the current UK Air Quality Objectives is provided below.
Summary of objectives of the National Air Quality Strategy
|Pollutant||Air Quality Objective||To be achieved by|
|Authorities in 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|
|Authorities in 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)|
|Scotland Only||50 µg m-3, not to be exceeded more than 7 times a year||24 Hour mean||31 December 2010|
|18 µg m-3||Annual mean||31 December 2010|
|Particles (PM2.5) (gravimetric)|
|Authorities in Scotland Only||10 µg m-3 (limit)||Annual mean||2020|
|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||31 December 2005|
UK Air Quality Objectives for protection of vegetation and ecosystems - July 2007
|Pollutant||Concentration||Air Quality Objective||To be achieved by|
|Oxides of Nitrogen (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
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 currently assessed by Scottish local authorities.
+ AOT 40 is the sum of the differences between hourly concentrations greater than 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.