With PFS, Playsand, Blasting grit all we really can count on it that it was screened to a specific uniform size. None of them that we commonly use is rated by the FDA as Potable water source approved filter media. So we don't have any clue as to heavy metals or and other non-desireable contaminate in those anymore than this high desert sand in question. I haven't read about anyone testing Play Sand or PFS.
OP - I suggest use a little common sense as to the collection point i.e.. not near a highway, truck stop, uranium mine, landfill etc. Screen out the scorpions, rinses it good and put it in the tank. Start with a few snails. Then a single healthily fish, if all is good after a wk. add another fish.