PM2.5, µg/m³
< 5 †
5-10 ‡
10-15 §
15-20 ¶
20-25 *
25-30
30-35 ⁑
35-40
40-45
45-50
> 50
† WHO guideline ‡ < GLA/WHO Int 4 § WHO Int 3 ¶ UK * WHO Int 2 ⁑ WHO Int 1