  Updating a previous analysis where we used elastic nuclear recoils we study
the Migdal effect to extend to low WIMP masses the direct detection bounds to
operators up to dimension 7 of the relativistic effective field theory
describing WIMP interactions with quarks and gluons. To this aim we include in
our analysis the data of the XENON1T, SuperCDMS, COSINE-100, and DarkSide-50
experiments and assume a standard Maxwellian for the WIMP velocity
distribution. We find that the bounds can reach down to a WIMP mass $\simeq$20
MeV, although in the case of higher-dimension operators the energy scale of the
ensuing constraints may be inconsistent with the validity of the effective
theory.
