The WHO also introduced new measurement guidelines for very small particulates which are more dangerous to pulmonary function .
The World Health Organisation revised its air quality guideline levels of sulfur dioxide , nitrogen dioxide and ozone in 2006 in light of new scientific evidence .
The World Health Organisation also introduced new measurement guidelines for very small particulates which are more dangerous to pulmonary function .
The World Health Organisation revised its air quality guideline levels of sulfur dioxide , nitrogen dioxide and ozone in 2006 in light of new scientific evidence .