Asbestos, (as-best-as) I know: the tiny microscopic fibers that become airborne are sharp and sickle shaped. They get lodged and hooked in the lung tissue and yes they stay there. The lungs, recognizing an invading substance, makes a protective coating around the fiber, which forms eventual scar tissue, then a specific kind of deadly cancer. Will one exposure mean cancer? I don't think anyone can answer. Also, concete dust from cutting is bad news--it also stays trapped in the lungs and can wreak havoc. Don't stop living or working out of fear though. Use protection (I'm no expert on this end), proceed accordingly, and get the job done.