Air quality guidelines have been published by WHO in 1987 and they were revised in 1997. Given the wealth of new studies on the health effects of air pollution that have been published in the scientific literature since the completion of the second edi¬tion of the Air quality Guidelines for Europe, includ¬ing important new research from low-and middle-income countries where air pollution levels are at their highest, WHO has undertaken to review the accumulated scientific evidence and to consider its implications for its air quality guidelines. 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.
