http://en.wikipedia.org/wiki/Propylene_glycolSample quote
Propylene glycol
is considered Generally Recognized As Safe
by the U.S. Food and Drug Administration,
and it is used as an humectant (E1520), solvent, and preservative in food and for tobacco products, as well as being the major ingredient in the liquid used in electronic cigarettes (along with vegetable glycerine and, more rarely, PEG 400).
It is also used in pharmaceutical and personal care products.[4]
Propylene glycol is a solvent in many pharmaceuticals, including oral, injectable and topical formulations, such as for diazepam and lorazepam that are insoluble in water, use propylene glycol as a solvent in their clinical, injectable forms[6].
Like ethylene glycol, propylene glycol is able to lower the melting point of water, and so it is used as aircraft de-icing fluid.[4][7]
It is similarly used as automotive antifreeze.[8]
Propylene glycol is an ingredient in the oil dispersant Corexit, used in great quantities during the Deepwater Horizon oil spill[9][10]