Quaternary ammonia is something used to mix with water for a final rinse off of degreaser from cooling conveyors after cleaning them in a Bakery. Quaternary ammonia is what goes in the final rinse water for hand dipped washed glasses at bars. Interestingly to me, metal rinsed with water treated with quaternary ammonia will not rust despite air drying repeatedly. Is it known to be essentially harmless at levels humans certainly consume a little of it? It's been being used for a long time and this Layman guesses yes.