Dust-corrected metallicity as a function of H I column density. The red dots again represent the main GRB sample but here are size-coded as a function of the SED-derived A_V. The gray-shaded regions represent increasing A_V, marked for each region, assuming the constant DTM_SED ratio derived in this work of log A_V − [log N_HI + [M/H]_tot]= − 21.4. The estimated detection probability for GRBs in each of these A_V ranges is marked as well (see Sect. 4.4 for further details).