There are warning labels on many common household products, which can cause serious injury or even death if not properly used. Doesn't stop people from using it, if they even read the labels in the first place?
Toner by nature is very messy. Even more of a reason to use up as much of it as you can. Most examples of refilling show dumping old toner on a newspaper? I tend to dump old remaining toner directly into a plastic kitchen bag, sealing around the cartridge, outdoors before refilling. Not much different than dumping out the vacuum cleaner canister.
Anyway, this thread has run its purpose. Time to move on.