A "menstrual rag" is a cloth that a woman uses during the time of month when she bleeds from her womb. This means all their attempts to please God fail. This sentence was meant to be shocking. (See: [[rc://en/ta/man/translate/figs-simile]])
This means their sins, as a community, are the reason for their failure. Isaiah compares the iniquities to the wind as the force for their suffering Yahweh's punishment. (See: [[rc://en/ta/man/translate/figs-simile]])