Figure 3

Black carbon (BC), PM2.5, PM1 and particle number concentrations (PNCs), 1-min aves., measured at the roadsides, and in the playgrounds at 1 m (‘Behind tredge’) and ~ 5 m (‘Playground’) behind the tredges. Boxes indicate median value, lower and upper quartiles, and whiskers show 10th and 90th percentiles.