Does dust settle faster when the relative humidity is higher?

Answer 1

Dust is an ionic compound and water is a polar covalent compound. Particles of dust are attracted to water vapor, thus reducing the amount of dust in the air. Rain requires a "seed" upon which to coalesce. If it wasn't for dust, rain could not occur.

Answer 2

Yes, certainly we see more dust floating in dry air than in humid air. Humid air seems to reduce the electrical charges on the dust particles and thus helps them come together and stick up.