Carbon fiber, fibre glass, FR4 (for PCBs) and other similar materials generate some very nasty dust particles when they machined. The particles are damaging to the lungs in the extreme (as in Asbestos dangerous); they even hang onto clothing and can be carried around you house or place of business harming many.
If you do work them the best way is to have an enclosure which has negative pressure (to keep the dust in) and a dust collector that filters particles down to 0.3 micron.