Why don't our lungs fill up with dust?

Are skin tags an indication of diabetes? Why don't cattle flee from fire? Do apples stimulate your appetite? Why are some cats great at hunting, and others not? Why doesn't dust fill up our lungs? What is the sediment at the bottom of frozen wine? When did our tail become a coccyx? What causes ringworm? What drives the magnetic field? Dr Chris Smith and Krystal Orderson have all the answers...