“…The magnitude and direction of this bias is widely discussed in the environmental exposure and health effects literature, primarily from the viewpoint of utilising small, portable air pollution sensors to quantify personal exposure directly on an individual level (Steinle et al, 2013Buonanno et al, 2012;Gariazzo et al, 2016;Marek et al, 2016) or mobile devices to assess mobility (Dewulf et al, 2016;Nyhan et al, 2016;Glasgow et al, 2016;Park and Kwan, 2017). While results emerging from these studies are important for understanding the impact of specific mobility patterns (Setton et al, 2008(Setton et al, , 2011Beckx et al, 2009;Dons et al, 2011;Dhondt et al, 2012;Ragettli et al, 2014Ragettli et al, , 2015Brokamp et al, 2016;Smith et al, 2016), for exposure in different micro-environments and for the relative contributions of these to overall personal exposure, up-scaling from this individual level to population level exposure is not straightforward.…”