Dust of any kind is one thing, and not good for you. Wearing proper protection is required. Who knows what can be in it... Lead paint? 50 year old emebas, and virouses? If I show up at jobs like that, I leave, and say call me when you're done with that mess, I can do that.... But if you are going to work, or have to work in it, not wearing a mask is just dumb! Demand a mask that fits, and works for the material you're exposed to.
Ohsa has some nice information....
http://www.osha.gov/SLTC/asbestos/ http://www.osha.gov/SLTC/asbestos/checklist.html
