Altogether the WHO compiled fine particulate measurement data from its database of more than 4 000 cities in 108 countries.
The concentration of fine particles in Finland averages six micrograms per cubic metre, which is the lowest level on the globe. The level of particles in Estonia, Sweden, Canada, Norway and Iceland are marginally higher.
Countries in the Middle East, Far East and Africa featured at the other end of the scale, with the report underlining the significant air quality problems of emerging countries.
Further information (in Finnish) can be found at the Finnish Meteorological Institute.