Covenant curses came to Israel because the people defiled their land through sinful behavior.
A menstrual cloth became polluted by contact with a woman's monthly blood flow. This natural process was not sinful, but it made people ceremonially unclean. Any loss of bodily fluids, like blood, sweat (see study note on Ezekiel 44:17–19), or semen, also caused ceremonial uncleanness (see Leviticus 15).