Effects of urban airborne particulate matter exposure on the human upper respiratory tract microbiome: a systematic review

Table 1 Limit values for PM_2.5 and PM₁₀ daily and annual exposure

Region	Regulation	Limit values	PM_2.5 (µg/m³)	PM₁₀ (µg/m³)
Worldwide	WHO Guidelines, 2005	Daily	25	50
		Annual	10	20
Worldwide	WHO Guidelines, 2021	Daily	15	45
		Annual	5	15
European Union	Directive 2008/50/CE, Ambient Air Quality and cleaner air for Europe	Daily		50
		Annual	25	40
United States of America	National Ambient Air Quality Standard for PM_2.5 and PM₁₀ (Enviromental Protection Agency)	Daily	35	150
		Annual	15
China	Ambient Air Quality Standard, GB 3095-2012	Daily	35^a/75^b	50^a/150^b
		Annual	15^a/35^b	40^a/70^b
Overall		Daily	15–75	45–50
		Annual	5–20^a/35^b	15–40^a/70^b

Note: PM_2.5 and PM₁₀ values recommended by the WHO and established by environmental agencies and governments of the European Union, the United States of America and China
^aUrban areas
^bRural areas

ISSN: 1465-993X