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The recommended levels of air pollutants by the WHO air quality guidelines∗.
| Pollutants | Levels |
|---|---|
| PM2.5 | 10 μg/m3 annual mean |
| 25 μg/m324-hour mean | |
|
| |
| PM10 | 20 μg/m3 annual mean |
| 50 μg/m324-hour mean | |
| Ozone (O3) | 100 μg/m38-hour mean |
|
| |
| Nitrogen dioxide (NO2) | 40 μg/m3 annual mean |
| 200 μg/m31-hour mean | |
|
| |
| Sulfur dioxide (SO2) | 20 μg/m324-hour mean |
| 500 μg/m3 10-minute mean | |
∗ Air quality guidelines, global update 2005, World Health Organization, Geneva, 2005.
