The World Health Organisation publishes Air Quality Guidelines based on certain pollutants health effects and are there to aid policy makers. The European Union developed their Ambient Air Quality (AAQ) Directives (Directives 2008/50/EC and 2004/107/EC) considering the WHO Guideline figures and the situation in Europe at the time. For some pollutants, they mirror each other exactly (NO2 & CO) whereas for others the WHO guidelines are tighter than EU regulation (SO2, O3 and PM)
Pollutant
Air Quality Guidelines (WHO, 2005)
EU Standards (Directive 2008/50/EC)
no. of EU exceedances allowed in a year
PM2.5
10 µg /m3 annual mean
25 µg /m3 24-hour mean
25 µg /m3 annual mean
-
PM10
20 µg /m3 annual mean
50 µg /m3 24-hour mean
40 µg /m3 annual mean
35
O3
100 µg /m3 8-hour mean
120 µg /m3 8-hour mean
25 averaged over 3 years
NO2
200 µg /m3 1-hour mean
18
SO2
20 µg /m3 24-hour mean
-------------
500 µg /m3 10-minute mean
125 µg /m3 24-hour mean
350 µg /m3 1-hour mean
-----------
3
24
CO
10,000 µg /m3 8-hour mean