Not that toxic, unless inhaled (take precautions) or ingested, or heated to high temperature, which produces a toxic gas.

Doping of course can change that.

May require 100+ V AC at 500-2000 Hz. So probably not the right element to implement 4k in! Or for an early education science experiment, unfortunately.

I don't know what the currents would be, proportions or dimensions of epoxy, or much else. Some more research would be required. But in terms of resistive heating creating gas: measure and be careful!