Frequently asked questions
What are the key air quality pollutants?
The Air Quality (Wales) Regulations 2000 and Air Quality (Amendment)(Wales) Regulations 2002 set air quality objectives for the 7 key pollutants contained within the UK National Air Quality Strategy. The current air quality objectives set in regulation are listed below:
| Pollutant | Concentration | Measured as | Examples of sources | Permitted number of exceedences allowed | Compliance date |
| Benzene* (C6 H6) | 16.25 µg/m3 (5ppb) | Running annual mean | Constituent of petrol emitted as un-burnt fuel or through evaporation (motor vehicles etc). Also present in cigarette smoke. | n/a | 31 Dec 2003 |
| 5 µg/m3 (1.5ppb) | Annual mean | n/a | 31 Dec 2010 | ||
| 1,3-Butadiene* | 2.25 µg/m3 (1 ppb) | Running annual mean | Used in the manufacture of synthetic chemicals and rubber. Also present in cigarette smoke. | n/a | 31 Dec 2003 |
| Carbon monoxide (CO) | 10.00 m g/m3 (8.6ppm) | Maximum daily running 8 hour mean | Vehicle emissions, inefficient combustion of most fuels including gas, coal and oil. | n/a | 31 Dec 2003 |
| Nitrogen dioxide (NO2) | 200 µg/m3 (105ppb) | 1 hour mean | Combustion processes particularly vehicle emissions. | 18 | 31 Dec 2005 |
| 40 µg/m3 (21ppb) | Annual mean | n/a | 31 Dec 2005 | ||
| Lead (pB) | 0.5 µg/m3 | Annual mean | Main source in ambient air from leaded petrol (4 Star) | n/a | 31 Dec 2004 |
| 0.25 µg/m3 | Annual mean ( by 2008) | n/a | 31 Dec 2008 | ||
| Particles (PM 10) | 50 µg/m3 | 24 hour mean | Many sources but particularly from diesel vehicle emissions in towns and cities. | 35 | 31 Dec 2004 |
| 40 µg/m3 | Annual mean | n/a | 31 Dec 2004 | ||
| Sulphur dioxide (SO2) | 350 µg/m3 (132 ppb) | 1 hour mean | Mainly from combustion of fossil fuels. | 24 | 31 Dec 2004 |
| 125 µg/m3 (47 ppb) | 24 hour mean | 3 | 31 Dec 2004 | ||
| 266 µg/m3 (100 ppb) | 15 minute mean | 35 | 31 Dec 2005 | ||
| Key µg/m3 = (microgram per cubic metre of air) mg/m3 = (milligram per cubic metre of air) ppb = (part per billion) or one part of the pollutant per one billion parts of air. ppm = (part per million) or one part of the pollutant per million parts of air. | |||||
For more information on air quality guidelines and statistics please visit the links section.
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Pollution glossary:
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