Column density ratios in the seven molecular extraction regions of WB67O. Panel (a) shows the measured SO/CS ratios (points) and compares them to the average SO/CS ratio measured in a sample of inner and local Galaxy high-mass star-forming regions (Fontani et al. 2023, dashed line) and to the expected SO/CS ratio obtained by multiplying the local measured value (0.2, dashed line) by the increase in the elemental ratio [O/C]~3.1 (horizontal green line) from the solar circle to R_GC = 23.4 kpc (Méndez-Delgado et al. 2022). Panel (b) shows the same comparison between the measured H¹³CO⁺/HN¹³C ratio and the expected ratio obtained by multiplying the local measured value for the increase in the [O/N] elemental ratio.