WHO revises air quality norms for first time since 2005
- The World Health Organisation (WHO) has announced a tight revision in its air quality guidelines (AQG) on September 23, 2021. This is the first revision in the global air quality by WHO since 2005.
- In the new guidelines, WHO has lowered the acceptable exposure levels to key pollutants, including ozone, nitrogen dioxide, sulfur dioxide, carbon monoxide and particulate matter (PM).
- The revised thresholds of particulate matter “equal or smaller than 10 and 2.5 microns (µm) in diameter” are as follows:
| 24-Hour Exposure (µg/m³) | Year-long Exposure (µg/m³) | |||
| Pollutant | New | Old | New | Old |
| PM2.5 | 15 | 25 | 5 | 10 |
| PM10 | 45 | 50 | 15 | 20 |
Note: µg/m³ denotes micrograms per cubic meter
Source: WHO