The oral toxicity of propylene glycol is very low, and large quantities are required to incur the dangerous effects described above. The potential for long-term toxicity is also low. In one study, rats were provided with feed containing as much as 5% PG over a period of 104 weeks and they showed no apparent ill effects.
[7] Because of its low chronic oral toxicity, propylene glycol is
generally recognized as safe (GRAS) for use as a direct food additive. Cases of propylene glycol poisoning are related to either inappropriate intravenous use or accidental ingestion of large quantities by children.
[8]
HMMMMM. So the Fda will let us eat it, wash our teeth with it.... BUT we cant smoke it?