Standards and Objectives

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