Ed I couldnt read all the posts to this thread but will later. Im really glad to hear they caught it in time. How long have you been making knives??? How long and how frequent did you wear a mask and if so what type. ??? I bought a dust collector in june and it works ok but allows the fine dust through. I also were a mask with carbon filter, but now just bought the new 3m 6700 series full face . Im in a rought state like you right now just having surgery 10 days ago on my neck so im doing very little.I have done some reading on toxic woods some worse than others. I will go get a high micron filter today for my 1200 cfm dust collector, that will help. I notice when i fire up the collector a small puff of dust goes into the air. I m sure that fine stuff is the bad stuff. Ed I would also like to know what type of wood did you use the most to cause this problem . I know you may not know the ansers to these questions but it may help more of us realize that this dust is really bad for you. Hope you heal fast, I have a long road ahead. kellyw