Chemical analyses for nicotine impurities on e-liquids: have we learned something important?

Chemical analyses for nicotine impurities on e-liquids: have we learned something important?

A new study about e-cigarettes was published today in the journal “Addiction”. Etter and coworkers evaluated the presence of nicotine metabolites and impurities in 20 samples of commercially available e-liquids.

The study has the known limitations of every chemical analysis: it does not give you any direct information about the results from use; it only gives you indirect evidence about the safety, based on theoretical knowledge or observations from other studies. Additionally, the chemicals analyzed (tobacco alkaloids, see figure 1) would probably not pose any significant additional risk to the user (besides the important finding of absence of ethylene and diethylene glycol). I have always supported that chemical studies, especially on liquid and not vapor, have limited value in evaluating risk of exposure. The authors acknowledge that tests should be mainly focused on vapor.

However, we can derive some useful, but indirect, conclusions from this analysis. Such impurities may come from several sources. One of them is the use of non-USP grade nicotine. This would suggest that manufacturers of these liquids either deliberately (to reduce cost) or unintentionally (being deceived by the supplier) are using low-quality nicotine for their products. This would be really disappointing. The problem would be that, in addition to the above mentioned relatively harmless products, one would reasonably expect to find other impurities too, like nitrosamines. But, as I said, you find something only if you check for it. The difference in cost between pure-grade nicotine and lower-quality would not exceed 5-15 cents per 10ml bottle. I hope manufacturers are not thinking about saving that amount of money, and if some think like this they should be isolated and expelled from the industry. Another source could be the manufacturing process. Perhaps it is environmental exposure, interaction with materials or flavors. We have no data on material safety. Plastics commonly used both for bottles and for the manufacturing of atomizers have not been tested. It is likely that some materials may interact with the liquid and lead to production of toxic chemicals that are subsequently inhaled.

It is important to emphasize that, despite the above-mentioned limitations, even the worst-quality e-cigarette product is probably less harmful that smoking. However, we have a historical opportunity to develop a product that could be almost harmless. Manufacturers should be consumer-sensitive and conscious, check the quality of their supplies, invest on improving the manufacturing process and test their products regularly. If they cannot do these, they shouldn’t be manufacturers. Organizations like AEMSA are playing a major role in developing quality standards of manufacturing, and this will eventually control the market with beneficial effects for the consumers. Further research is certainly needed, on materials, liquid and vapor analysis, including evaluating the effects of use (toxicological and clinical studies). We are seeing a revolution in tobacco harm reduction, and we should obtain all possible benefits from it…

P.S. I am glad that my presentation in TMA congress triggered the interest of Prof. Michael Siegel who wrote an excellent article about misleading “science”. In my presentation I referred to a case report describing lipoid pneumonia “caused by glycerine-based oils” that was published in the journal “Chest”. The German Cancer Society used this publication in order to support that glycerine from e-cigarettes can cause lipoid pneumonia. Unfortunately for them, a high school chemistry teacher knows that glycerine is not a lipid, it is an alcohol. Enjoy the writing of Prof. Siegel here.


Figure 1. Nicotine and other tobacco alkaloids.



Dr Konstantinos Farsalinos



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