Introduction Context - While ambient air quality in Europe improved in several respects during the last decades of the 20th century, current levels of air pollution do affect public health. They can cause respiratory diseases and reduce life expectancy.
Three air pollutants have been reviewed by the World Health 0rganization:
	Particulate Matter (PM) is the sum of all particles suspended in air (e.g. dust, ash, soot, tobacco smoke, etc.). Particles vary greatly in size and composition, which does influence how human health is affected. Fine and ultrafine particles tend to be particularly harmful. More...
	Ozone (O3) is a gas formed from other pollutants. Concentrations are often low in busy urban centres and higher in suburban and adjacent rural areas, particularly on sunny days in summer. Exposure to it mainly affects the lungs, but it can also affect the eyes and increase susceptibility to inhaled allergens. More...
	Nitrogen Dioxide (NO2) is an air pollutant produced mainly by road traffic and other combustion processes. It affects particularly populations living near busy roads. Exposure to NO2 may decrease lung function, increase respiratory problems, and affect mortality or disease progression. More...
General issues & Conclusions on air pollutants:
	Overall, risk assessment and guideline setting for air pollutants is made more difficult by uncertainties linked to gaps in knowledge, and differences in the way people respond to air pollutants. Further research and policy action for these and other air pollutants are recommended. More...

This Digest is a faithful summary of the leading scientific consensus reports
produced in 2003 and 2004 by the WHO (World Health Organization):

"Health Aspects of Air Pollution with Particulate Matter, Ozone and Nitrogen Dioxide" (2003) &
"Answers to follow-up questions from CAFE" (2004) More...