dirt isn’t bad for you. If you were to launch dirt in a rocket and it blew up, the rocket parts and fuel would be the most harmful part. you probably consume microscopic amounts of thorium on a regular basis. if you were to mine it or distill it from seawater into concentration to be used in a reactor, yes, it would be harmful, not fissile. If you “breed” Thorium with Uranium 235 or a denatured bomb it becomes fissile (U-233 I think) and in the right reactor self sustaining (paraphrased from the Myths article)