Originally Posted by c0mfortably_numb
If you can find out what media it is (it can be sand, glass, or metal) just do a google search + MSDS. The MSDS is the Material Safety Data Sheet lists all the possible side effects in coming into contact with said chemical or substance.
My guess would probably just be a mild lung irritant (purely guess) especially for any one with asthma and or allergies. I would not recommend vacuuming the material up either as most household vacuums don't come with HEPA filtration standard. All a vacuum will do is blow the particles back out into the air and possibly into a finer dust, also I would think sweeping would do the same thing.
They're supposed to be iron or brass. My concern is it might seep into the power cable and cause a short. The abrasiveness could cause micro tear in the insulation and eventually can cause arcing or short (this could cause electrical shock to human touching it.)