Air pollution limits

Both the World Health Organization (WHO) and the European Union (EU) have established some limit concentrations for key air pollutants above which they may pose some health risks to sensitive populations.

Pollutant WHO limit EU limit
Particulate matter PM10 50 μg/m³ 24-hour mean20 μg/m³ annual mean 50 μg/m³ 24-hour mean40 μg/m³ annual mean
Particulate matter PM2.5 25 μg/m³ 24-hour mean10 μg/m₃ annual mean 25 μg/m³ annual mean
Carbon monoxide (CO) 10 mg/m³ 8-hour mean
Ozone (O3) 100 μg/m³ 8-hour mean 120 μg/m³ 8-hour mean
Nitrogen dioxide (NO2) 200 μg/m³ 1-hour mean40 μg/m³ annual mean 200 μg/m³ hourly mean40 μg/m³ annual mean
Sulphur dioxide (SO2) 500 μg/m³ 10-minute mean20 μg/m³ 24-hour mean 350 μg/m³ hourly mean125 μg/m³ 24-hour mean