Electron density of the star-forming regions in the GRB 980425 host (derived using the [S ii] flux ratio from Christensen et al. 2008 using the calibration of O’Dell et al. 2013 and Osterbrock & Ferland 2006) as a function of their ages from the SED modelling (Christensen et al. 2008). The WR region is both old and dense compared with other regions, which may have helped it to accumulate dust more efficiently. Blue and green crosses mark the regions with n_e > 145 cm^-3 and age ≥6 Myr, respectively (see also Fig. 1).