You've all got me a bit worried now........
I use a mask and dust extraction system.....no problems yet, but I am an asthmatic so time will tell.
Most people I know use it as a core lamination so there is less dust than if its the belly and you are continually working it.
I've got three bows to make using it as the belly. I have to admit it, I don't really like it.......I also find it damn hard to rasp/ scrape etc.