Today I found a paper reviewing mammalian toxicity of ethylene glycol and propylene glycol (LaKind et al, Critical reviews in Toxicology, 1999). Ethylene glycol is pretty bad, and I wont mention it further. I am not sure how much of this has already been posted in this forum (part has), but I thought that I would list some of the salient points of this article in relation to PG. As this was a review, few details were given about any one study, and the whole article was over 30 pages long, so I distilled hopefully wisely
. Hope you find it useful.
Overall, it looks generally reassuring, especially if the alternative is smoking.
However, e-smokers are definitely a unique population at this point, with a unique kind of exposure, and we will be the source of most future knowledge about long-term exposure to inhaled PG.
- As of the time of publication of this article, there were no reports of deaths caused by PG.
- No oral MLD (minimum lethal dose) for PG in humans has been reported (reported for rats and cats but very high (20g/kg).
- Acute toxicity from PG does not apparently entail well-defined clinical stages. Acute effects include mainly central nervous system consequences, and lactic acidosis from extremely high doses.
- PG has been recommended as an appropriate vehicle for routine administration of bronchodilator drugs (however, the exposure in this case would be shorter than what most e-smokers inhale).
- Few cases of PG intoxication have been reported, in infants and young children, from oral administration, with no deaths reported.
- PG is sometimes used an IV drug vehicle. When administered repeatedly through this route, it may cause renal insufficiency. In vitro studies have shown that continuous exposure to PG studies showed toxicity to human proximal tubule cells.
- In one study, rabbits were exposed to 10% PG aerosol for 20 and 120 minutes. After 20 mins, minimal alterations were reported. After prolonges exposure, pathological alteration of the cilial cells of the trachea were noted. Both durations produced alterations in goblet cells (these cells secrete mucus). A study of 7 dogs exposed to PG inhalation for 15 minutes yielded no hemodynamic effects. The authors of that concluded that, in dogs, PGG is not absorbed via inhalation. (This seems a bit simplistic to me ).
- Then there is what I think is the study mentioned by Tropical Bob in another thread (and also, I believe, by the Ruyan NZ report), where monkeys and rats were exposed to PG vapor for 12 and 18 months, respectively. In rats, except for enhanced growth, no other findings were reported. In monkeys exposed to PG, increased number of red cells and hemoglobin content of blood were reported. However, many monkeys were ill during this time, and these observations were probably unrelated to PG.
Overall, it looks generally reassuring, especially if the alternative is smoking.
However, e-smokers are definitely a unique population at this point, with a unique kind of exposure, and we will be the source of most future knowledge about long-term exposure to inhaled PG.
