Pollutant

Average time

EU

(AQS, 2011)

U.S

(U.S EPA, 2012)

WHO

(WHO, 2006)

SO2 (ppb)

1 hour mean

134

75

-

3 hours mean

-

500

-

24 hours mean

47

140

8

annual mean

-

30

-

NO2 (ppb)

1 hour mean

105

100

106

24 hours mean

-

-

-

annual mean

21

53

21

PM10

(µg∙m−3)

24 hours mean

50

105

50

annual mean

40

-

20

PM2.5

(µg∙m−3)

24 hours mean

-

35

25

annual mean

25

15

10

Ozone (ppb)

1 hour mean

-

120

-

8 hours mean

40

75

50