By Dr Farsalinos
Included in the response on our critique of the WHO-commissioned e-cigarette review was a section discussing about the difference between lungs and the body (the latter meant to be the digestive tract) in the bio-detoxification systems. This paragraph was copied from a paper by May and Wigand “The Right to Choose: Why Governments Should Compel the Tobacco Industry To Disclose Their Ingredients”, published in the journal Essays of Philosophy. Obviously, this issue has nothing to do with philosophy. Moreover, when I checked the full text of this manuscript, I verified that there was not a single reference to any medical literature cited to support that “chemical reactions of bio-transformation and bio-detoxification do not occur” in the lungs.
By definition, the respiratory tract is one of 3 possible pathways through which environmental contaminants enter the body (the other two being the digestive tract and the skin). It would be a paradox if there were no defence mechanisms. In fact, there is a large array of defence mechanisms throughout the respiratory tract. An overview can be seen here, but there are many more. The lungs have established antioxidant mechanisms. For example glutathione transferases are important in the detoxification of lung carcinogens. Several other enzymatic systems are also present in the lungs, even for nitrosamines. The literature on this issue is very long (examples here, here, here and here). The lungs also have a cytochrome P450 enzymatic system (CYP), which is well known and very important for liver’s detoxification capacities. In some cases, the lung enzymatic systems may actually promote the toxicity of some chemicals rather than inhibiting it, but this is not different from other tissues.
It is true, and I have mentioned it repeatedly, that a GRAS substance for ingestion does not necessarily mean that it is safe for inhalation. However, it neither means that it is not safe. Fortunately in e-cigarettes there is no pyrolysis but heating at significantly lower temperatures. We definitely need more studies to detect whether some substances may be harmful when inhaled and if they can be avoided. However, this does not change the conclusion that e-cigarettes in their current state are by far less harmful that tobacco cigarettes.