WHO Ambient Air Quality Guidelines

Health Topics

Compound	Guideline Value	Averaging Time
Ozone	120 micrograms/cubic metre (0.06 parts per million)	8 hours
Nitrogen dioxide	200 micrograms/cubic metre (0.11 ppm) 40 to 50 micrograms/cubic metre (0.021 to 0.026 ppm)	1 hour annual
Sulfur dioxide	500 microgrms/cubic metre (0.175 ppm) 125 micrograms/cubic metro (0044 ppm) 50 microgrms per cubicmetre (0.017 ppm)	0 min 24 hours
Particulate matter	^a
Carbon monoxide	100 milligrams/cubic metre (90 ppm)^b 60 mg/cubic metre (50ppm) 30mg/cubic metre (25 ppm) 10mg/cubic metre (10 ppm)	15 min 30 min 1 hour 8 hours
Lead ^c	0.5 to 1.0 micrograms/cubic metre	Annual

No guideline values were set for particulate matter because there is no evident threshold for effects on morbidity and mortality.

The guideline is to prevent carboxyhemoglobin levels in the blood from exceeding 2,5%, The values above are mathematical estimates of some of the CO concentrations and averaging times at which this goal should be achieved.

The guideline for lead was established by WHO in 1987.

Source: Update and revision of the air quality guidelines for Europe.