Below is information on the current background air quality in some of Europe's major cities based on data taken from http://www.airqualitynow.eu and recorded at 10:40 am GMT May 20.  City Quality Amsterdam  Good [28] Berlin  Good [31] Brussels  Good [25] Krakow  N/A Oslo  N/A Prague  Good [29] London  Very good [11] Madrid  Good [31] Paris  Good [28] Stockholm  Very good [24] Zurich  Good [36] Legend

Below is information on the current background air quality in some of North America's major cities based on data taken from http://www.airnow.gov recorded at 13:35 pm GMT on May 17. 

Below is information on the current background air quality in some of Europe's major cities based on data taken from http://www.airqualitynow.eu and recorded at 8:25 am GMT May 17.  City Quality Amsterdam  Very good [16] Berlin  Very good [23] Brussels  N/A Krakow  N/A Oslo  N/A Prague  Very good [16] London  Very good [19] Madrid  Very good [7] Paris  Good [39] Stockholm  Good [43] Zurich  Very good [8] Legend

Below is information on the current background air quality in some of North America's major cities based on data taken from http://www.airnow.gov recorded at 13:05 pm GMT on May 16.