WHO Global Air Quality Guidelines

"The updated WHO Global Air Quality Guidelines (AQGs) provide recommendations on air quality guideline levels as well as interim targets for six key air pollutants. They also offer qualitative statements on good practices for the management of certain types of particulate matter (PM), for example, black carbon/elemental carbon, ultrafine particles, and particles originating from sand and dust storms, for which there is insufficient quantitative evidence to derive AQG levels."