Zinc is a body-friendly metal needed for prostrate health and does not threaten humans with heavy metal side effects. You would ingest more zinc swallowing a single 50 mg. zinc tablet than many zap sessions. We have customers all over the world and NONE of them have ever complained about our using our handholds or footpads. Zinc will not rust, corrode or tarnish. The large surface area of our electrodes eliminates using sloppy wet paper towels or electrodes. There is plenty of moisture in human skin to promote our zapper pulses. We also have switchable plugs to promote a criss-cross flow of energies from hands to feet. Most other zappers are hard-wired and cannot be reversed. Some units don't even have footpads. We also have an exclusive Body Tester to document zapper effectiveness, which no one else sells.