The national air quality objectives for Wales represent pragmatic thresholds above which the Welsh Government considers the health risks associated with air pollution to be unacceptable. However, air just barely compliant with the objectives should not be considered ‘clean’ and still carries long-term health risks. The lower the concentration of pollutants such as nitrogen dioxide and particulate matter, the lower will be the risks of adverse health effects in the exposed population. Therefore, while compliance with the national air quality objectives is essential, it is desirable to keep levels of pollution as low as reasonable practicable.
National air quality objectives contained in the Air Quality (Wales) Regulations 2000, as amended by the Air Quality (Wales) (Amendment) Regulations 2002
| Pollutant | Air Quality Objective | |
|---|---|---|
| Concentration | Measured as | |
| Benzene | 16.25 µg/m3 | running annual mean |
|
5 µg/m3 |
annual mean | |
| 1,3-Butadiene | 2.25 µg/m3 | running annual mean |
| Carbon Monoxide | 10 mg/m3 | maximum daily running 8-hour mean |
| Lead | 0.25 µg/m3 | annual mean |
| Nitrogen dioxide | 200 µg/m3 not to be exceeded more than 18 times per year | 1-hour mean |
| 40 µg/m3 | annual mean | |
| Particles (PM10) (gravimetric) | 50 µg/m3, not to be exceeded more than 35 times per year | 24-hour mean |
| 40 µg/m3 (WHO guideline 20 µg/m3) |
annual mean | |
| Sulphur Dioxide | 266 µg/m3, not to be exceeded more than 35 times per year | 15-minute mean |
| 350 µg/m3, not to be exceeded more than 24 times per year | 1-hour mean | |
|
125 µg/m3, not to be exceeded more than 3 times per year (WHO guideline 20 µg/m3) |
24-hour mean |
|
Other air quality standards relevant to human health
| Pollutant | EU Limit or target value | |
|---|---|---|
| Concentration | Measured as | |
| Arsenic | 6 ng/m3 | total content in the PM10 fraction average over a calendar year |
| Benzo(a)pyrene | 1 ng/m3 | total content in the PM10 fraction averaged over a calendar year |
| Cadmium | 5 ng/m3 | total content in the PM10 fraction averaged over a calendar year |
| Nickel | 20 ng/m3 | total content in the PM10 fraction averaged over a calendar year |
| Ozone |
120 μg/m3 not to be exceeded on more than 25 days a year averaged over three years (WHO guideline 100 μg/m3) |
maximum daily running 8-hour mean |
| Particles (PM2.5) (gravimetric) |
25 μg/m3 (WHO guideline 10 μg/m3) |
annual mean |