World Health Organization (WHO) air quality guidelines (AQGs) and estimated reference levels (RLs)
PM10
1 day
Calendar year
45μg/m3
1
5μg/m
3
99th percentile (3-4 exceedance days per year). Updated 2021 guideline
Updated 2021 guideline
PM2.5
1 day
Calendar year
15μg/m
3
5μg/m
3
99th percentile (3-4 exceedance days per year). Updated 2021 guideline
Updated 2021 guideline
O3
Maximum daily 8-hour mean
Peak season (b)
100μg/m
3
60μg/m
3
99th percentile (3-4 exceedance days per year). New 2021 guideline
New 2021 guideline
NO2
1 hour
1 day
Calendar year
200μg/m
3
25μg/m
3
10μg/m
3
99th percentile (3-4 exceedance days per year). New 2021 guideline
Updated 2021 guideline
BaP
Calendar year
0.12ng/m
3
SO2
10 minutes
1 day
500μg/m
3
40μg/m
3
99th percentile (3-4 exceedance days per year). New 2021 guideline
CO
1 hour
Maximum daily 8-hour mean
1 day
30mg/m
3
10mg/m
3
4mg/m
3
99th percentile (3-4 exceedance days per year).
New 2021 guideline
C6H6
Calendar year
1.7μg/m
3
Pb
Calendar year
0.5μg/m
3
As
Calendar year
6.6ng/m
3
Cd
Calendar year
5ng/m
3
(c)
Ni
Calendar year
25ng/m
3
