“…In addition, subway station/ride (urban), mountain/forest (rural) in Australia, and bicycle (rural/suburban) and car (urban/suburban) in Belgium were also measured. These microenvironments have been described more fully in our previous paper (Bhatt et al, 2016a), and were similar to those of other studies (Bolte & Eikelboom, 2012;Frei et al, 2009;Röösli et al, 2010;Urbinello et al, 2014aUrbinello et al, , 2014b. We also evaluated the indoor exposures in airports of both countries, Tullamarine International Airport, Melbourne, and Brussels International Airport, Brussels.…”