Fine Particulate Matter PM2.5

Fine particulate matter (PM2.5) is a leading risk factor for premature mortality and morbidity worldwide. According to a Global Burden of Disease Study, outdoor air pollution (including ambient particulate matter) was estimated to cause 6.67 million premature deaths in 2019. [1]

In addition, no safe threshold for PM2.5 has been identified below which no damage to health is observed. [2][3]

An abundance of evidence has supported the adverse effects of short-term and long-term ambient PM2.5 exposure on human health, even at low PM2.5 concentrations. [4]

Therefore, the latest version of the WHO global air quality guidelines published in 2021 has adjusted the recommended limit for outdoor PM2.5 exposure from 10 μg/m3 to 5 μg/m3 for the annual mean exposure and from 25 μg/m3 to 15 μg/m3 for 24-h mean exposure. [5]


Murray C.J., Aravkin A.Y., Zheng P. et al.
:link: Global burden of 87 risk factors in 204 countries and territories, 1990–2019: a systematic analysis for the Global Burden of Disease Study 2019.
Lancet. 2020; 396: 1223-1249

Yu W., Guo Y., Shi L., Li S.
:link: The association between long-term exposure to low-level PM2·5 and mortality in the state of Queensland, Australia: a modelling study with the difference-in-differences approach.
PLoS Med. 2020; 17e1003141

Chen J., Hoek G
:link: Long-term exposure to PM and all-cause and cause-specific mortality: a systematic review and meta-analysis.
Environ Int. 2020; 143105974

Liu C., Chen R., Sera F.
:link: Ambient particulate air pollution and daily mortality in 652 cities.
N Engl J Med. 2019; 381: 705-715

WHO global air quality guidelines: particulate matter (PM2·5 and PM10), ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide.
Date: Sept 22, 2021
Date accessed: November 5, 2021