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