Left: Galactic distribution of the selected 48 ECC clumps observed by the Hi-GAL project in Galactic latitude and longitude. Right: plan view of the Milky Way (Reid et al. 2014) with the 40 ECC clumps with available distance estimates overplotted. Red and blue symbols indicate the clumps from Category I and II, respectively (see Sect. 3.2 for the definition of these two categories). The position and 1σ width of spiral arms (Reid et al. 2014) are indicated with solid and dotted lines, respectively. The background gray disks with radii of ~4 kpc, ~8 kpc, ~12 kpc, and ~16 kpc indicate the Galactic bar, solar circle, co-rotation of the spiral pattern, and end of major star formation regions, respectively.