Table 1.
Examples of air quality standards for common air pollutants as given in the European Ambient Air Quality Directive (Directive 2008/50/EC) and World Health Organization Air Quality Guidelines (WHO AQG) for the protection of human health
| Air pollutant | EU limit and target value (threshold in µg m−3) | WHO AQG (threshold in µg m−3) |
|---|---|---|
| PM10 a | Annual mean (40) | Annual mean (20) |
| PM10 a | Number of exceedance of 24-h mean (50) | Number of exceedance of 24-h mean (50) |
| PM2.5 b | Annual mean (25) | Annual mean (10) |
| PM2.5 b | – | Number of exceedance of 24-h mean (25) |
| O3 c | Number of exceedance of maximum daily 8-h mean (120) | Number of exceedance of maximum daily 8-h mean (100) |
| NO2 d | Annual mean (40) | Annual mean (40) |
| NO2 d | Number of exceedance of 1-h mean (200) | Number of exceedance of 1-h mean (200) |
| SO2 e | Number of exceedance of 24-h mean (125) | Number of exceedance of 24-h mean (20) |
| COf | Maximum daily 8-h (10,000) | Maximum daily 8-h (10,000) |
aAnnual mean PM10 concentration and number of days with 24-h PM10 concentration over 50 µg m–3 for the protection of human health. The annual mean PM10 concentration does not to exceed 40 µg m–3 (Directive 2008/50/EC) or 20 µg m–3 (WHO AQG). The 24-h PM10 mean concentration does not to exceed 50 µg m–3 (WHO AQG) or more than 35 times a year (EC)
bAnnual mean PM2.5 concentration and numbers of days with 24-h PM2.5 mean concentration over 25 µg m−3 (WHO AQG). The annual mean PM2.5 concentration does not to exceed 25 µg m–3 (EC) or 10 µg m–3 (WHO AQG)
cFor the protection of human health, the Directive 2008/50/EC has introduced a threshold of 120 µg m–3 for the daily maximum 8-h average. The threshold level should not be exceeded on more than 25 times a year. Number of days with daily maximum 8-h O3 concentrations over 100 µg m–3 as limit value for the protection of human health (WHO AQG)
dAnnual mean NO2 concentration and number of hours with NO2 concentrations above 200 µg m−3. The annual mean NO2 concentration does not to exceed 40 µg m–3 (EC and WHO AQG) while the hourly threshold should not be exceeded more than 18 times a year (EC)
eThe 24-h SO2 mean concentration does not to exceed 125 µg m–3 more than 3 times a year (EC) and does not to exceed 20 µg m–3 (WHO AQG). f The Directives have introduced a threshold of 10 mg m–3 for the maximum daily 8-h mean concentration