Are there any hazards involved with the handling of toner?

Answer

 

No (as long as you use your head!).  Here is how HP describes toner.  "Toner is a nontoxic substance composed of plastic, iron, and a small amount of pigment."

Even with that very benign description, still use your head when handling toner.  Use the same common sense you use when you are filling your car with gas (i.e., don't eat it, drink it, purposely inhale large quantities of it, set it on fire... you get the idea).