PG vapor pressure is such that you could potentially just leave open bowls of it instead of needing a vaporizer device.
PG is probably equally effective at disinfection.
PG should have somewhat lower toxicity.
PG is used sometimes in foods as a humectant so it’s relatively available.
About toxicity, tri-glycol is safer than EG because EG is partly metabolized to glyoxal which can permanently form cyclic compounds inside cells. PG is preferentially metabolized to lactic acid before the secondary OH is oxidized, which is why it’s safer, tho yes you could get a small amount of methylglyoxal, so there is that issue, tho methylglyoxal is at least less reactive than glyoxal. The concern I have is that eg, ethoxyethanol is metabolized to ethoxyacetate which is somewhat toxic, and oxidized tri-glycol might be analogous. Note also that ethers eventually get oxidatively cleaved. I’m simplifying a bit here obviously.
Yes, there have been studies, but toxicity studies use high doses in mice to get obvious effects, and then we assume that much lower doses in humans don’t have subtle long-term effects, but the effect of tri-glycol would be limited by the rate of metabolism, and the tri-glycol itself should be safe.
Why?
EG = ethylene glycol, PG = propylene glycol
PG vapor pressure is such that you could potentially just leave open bowls of it instead of needing a vaporizer device.
PG is probably equally effective at disinfection.
PG should have somewhat lower toxicity.
PG is used sometimes in foods as a humectant so it’s relatively available.
About toxicity, tri-glycol is safer than EG because EG is partly metabolized to glyoxal which can permanently form cyclic compounds inside cells. PG is preferentially metabolized to lactic acid before the secondary OH is oxidized, which is why it’s safer, tho yes you could get a small amount of methylglyoxal, so there is that issue, tho methylglyoxal is at least less reactive than glyoxal. The concern I have is that eg, ethoxyethanol is metabolized to ethoxyacetate which is somewhat toxic, and oxidized tri-glycol might be analogous. Note also that ethers eventually get oxidatively cleaved. I’m simplifying a bit here obviously.
Yes, there have been studies, but toxicity studies use high doses in mice to get obvious effects, and then we assume that much lower doses in humans don’t have subtle long-term effects, but the effect of tri-glycol would be limited by the rate of metabolism, and the tri-glycol itself should be safe.