HOW DOES HYDROMX VERIFY IT IS NON-TOXIC? 30/06/2022 by Hydromx is certified nontoxic by FDA regulations. Both Hydromx’s ethylene and propylene versions carry the highest available safety rating from NSF for toxicity. Hydromx-EG (ethylene) carries an NSF HT-2 rating. Hydromx-PG (propylene) has an NSF HT-1 rating. Documentation of these ratings can be found at nsf.com (search for “Hydromx.”)