Air pollution

Air quality guidelines – global update 2005

WHO's work on environmental health provides the basis for global standards in environmental quality and an effective investments for public health such as air quality guidelines and drinking-water quality guidelines.

WHO Air Quality Guidelines (AQG) offer guidance on threshold limits for key air pollutants that pose health risks and provide a reference for setting air pollution targets at regional and national levels to improve air quality.

Air quality guidelines have been published by WHO in 1987 and they were revised in 1997. The 2005 update represents the most current assessment of air pollution health effects, based on an expert evaluation of the scientific evidence. The guidelines offer recommended exposure levels for particulate matter (PM10 and PM2.5), ozone, nitrogen dioxide and sulphur dioxide, as well as a set of interim targets to encourage a progressive improvement in air quality. The result of this work is presented in this document in the form of revised guideline values for selected air pollutants, which are applicable across all WHO regions.

Guideline levels for each pollutant (µg/m3 ):
PM2.5 1 year 10
24 h (99th percentile) 25
PM10 1 year 20
24 h (99th percentile) 50
Ozone, O3 8 h, daily maximum 100
Nitrogen dioxide, NO2 1 yr 40
1 h 200
Sulfur dioxide, SO2 24 h 20
10 min 500

The Executive summary of the revised air quality guidelines is available as per the link below.

WHO Air quality guidelines for particulate matter, ozone, nitrogen dioxide and sulfur dioxide – Global update 2005 – Summary of risk assessment

The full edition of the guidelines is available at: