I doubt it has anything to do with molecular dipoles. More likely I'd guess ionized radionuclides adsorb onto macroscopic dust particles (or some similar mechanism), which then maintain a net charge imbalance.
Yeah, the wording in the explanation was particular suspect:
> Polarized or polarizable objects are attracted to strong electric fields
Polarizable objects align in an E field, they aren't attracted to the E field. I don't doubt you could contrive a field to move a polarized object, but the wording seems to be confusing an ionized object with a polarized object.
