Safety standards of particulate matter (PM) in ambient air in different geographical areas
| Agency | PM10 | PM2.5 | Reference |
| World Health Organization (2018) | 20 μg·m−3 (annual) 50 μg·m−3 (24-h) | 10 μg·m−3 (annual) 25 μg·m−3 (24-h) | [2] |
| US Environmental Protection Agency | 50 μg·m−3 (annual) 150 μg·m−3 (24-h) | 12 μg·m−3 (annual) 35 μg·m−3 (24-h) | [28] |
| New South Wales Environment Protection Authority (Australia) | 25 μg·m−3 (annual) 50 μg·m−3 (24-h) | 8 μg·m−3 (annual) 25 μg·m−3 (24-h) | [29] |
| UK and EU | UK/EU: 40 μg·m−3 (annual) 50 μg·m−3 (24-h)# | UK: 25 μg·m−3 (annual) | [30] |
| Scotland: 18 μg·m−3 (annual) 50 μg·m−3 (24-h)¶ | Scotland: 10 μg·m−3 (annual) |
PMx: particles with a 50% cut-off aerodynamic diameter of x µm. #: not to be exceeded more than 35 times a year in the UK; ¶: not to be exceeded more than seven times a year in Scotland.