Historical overview and main features
Concentration limit values
Directive 2008/50/EC fixed limit values on the concentration of pollutants in the air. These values were binding by January 2010, except for PM2.5 which was binding from 1 January 2015. The following concentration limit values were fixed in order to protect human health:
| Pollutant | Limit value |
| Sulphur dioxide SO2 | one hour: 350 microgram/m³* one day: 125 microgram/m³** |
| Nitrogen dioxide NO2 | one hour: 200 microgram/m³*** calendar year: 40 microgram/m³ |
| Benzene | calendar year: 5 microgram/m³ |
| Carbon monoxide | maximum daily 8 hour mean: 10mg/m³ |
| Lead | calendar year: 0,5 microgram/m³ |
| PM10 | one day: 50 microgram/m³**** |
| PM2.5 | calendar year: 25 microgram/m³***** |
*One-hour value for sulphur dioxide may be exceeded 24 times during a calendar year.
** One-day value for sulphur dioxide may be exceeded 3 times per calendar year, without a Member State being in breach of its obligations to respect limit values.
*** One hour value for nitrogen dioxide may be exceeded 18 times during a calendar year.
**** One day limit value for PM10 may be exceeded 35 times during a calendar year.
***** Article 16(2) of Directive 2008/50/EC, together with Annex XIV point E, furthermore, requires the respect, as of 1 January 2015, of a limit value of 25 microgram/m³ per calendar year for PM2.5. As of 2020, this limit value is to be lowered to 20 microgram/m³ per calendar year.