"Polvo para hornear" is baking powder, so polvo is not just dust. But my dust masks are also labeled "para polvo", so it appears to include sawdust and construction dust. English treats "powder" as deliberate and/or desirable and "dust" as accidental and/or undesirable, but Spanish doesn't appear to make that distinction.
"Dust" is dirt in English and "a dusting" (a dusting of snow, or icing sugar) seems to be used for positive thin layers of powder. Interestingly, the verb is its own antonym, meaning to remove dust as well as to add dust - "dust the furniture" v "dust the cake (with icing sugar").