What is it and where is it found?
Among its many applications, DG is used as a solvent and humectant. It is also a component in brake fluid, lubricants, wallpaper strippers, artificial fog solutions, and heating fuel. It has also been found in toothpastes and wine.
DG is also a component of cigarette smoke.
How harmful is it and what are the effects?
Unfortunately, it is unclear in the literature as to how dangerous DG when inhaled. Health Canada’s toxicity report does not even mention inhalation as a concern. Studies have been carried out on rats, with the rats forced to inhale DG at various concentrations over several weeks (this only lead to localized irritation). There seem to be no reports of inhalation of DG causing harm to humans (the MSDS has no recommendations regarding serious inhalation).
Ingestion of DG is extremely dangerous. There are many well documented reports of human fatalities on record.
Where can it occur in e-cigarettes?
DG has been found as a contaminant in propylene glycol (it can occur in the production of low grade propylene glycol or low grade nicotine, since DG is used in tobacco processing). When the FDA detected DG in a small sample of E-Cigarettes in 2009 (at lower exposures than would occur with smoking cigarettes) they suggested that this was a serious concern. Though inhalation of DG has not been proven to be overly harmful to humans there have been many fatalities traced to ingesting DG (most of these occurred in contaminated medicines).
What is a recommended threshold for this constituent?
Though the inhalation of this constituent has not been proven to be of great concern it is considered a contaminant and should be avoided.