There have been numerous cases of explosions in Foxcom factories in China : the aluminium powder coming from sanding the iPad cases, if not vented / filtered / ... exploded. I've read so far the toll is over 50 people and 3 workshops.

Then, if powders are dangerous to inhale, even if it is a slightly unlikely event (but you can still get drafts, mishaps, ...) in the long run without proper casing / ventilation / filtering it is just too dangerous to sell to the wide public because the probability is high a dumb * will injure himself and sue you.