A new study finds diacetyl in e-cigarettes but exaggerates risks and fails to discuss about smoking


By Dr Farsalinos

As you all know, I have a strong opinion against the use of diacetyl and acetyl propionyl in e-liquids. In the study we published last year, we made this clear and we analyzed the potential risk from the use of these compounds at high levels (basically, when used as ingredients, or are present as contaminants but at high levels). We emphasized the fact that none should deliberately add these compounds in e-liquids and tests should be conducted to detect potential sources of contamination. All these are, in my opinion, responsible measures to avoid this unnecessary exposure. However, we also presented literature data that tobacco cigarette smoke contains high levels of diacetyl and acetyl propionyl, on average 100 and 10 times higher compared to our samples respectively.

Another study was just published in the journal Environmental Health Perspectives, by researchers from   Harvard T.H. Chan School of Public Health. They evaluated the presence of diacetyl, acetyl propionyl and acetoin in 51 cigarette-like products of different flavors. They found at least 1 of the chemicals in 92% of the samples, with 76% containing diacetyl. The authors recommend urgent action to evaluate the extend of diacetyl exposure from e-cigarettes.

Although I agree that we should know if e-liquids contain diacetyl and acetyl propionyl, I must note that the study has missed some very important points. One is the assessment of the levels found in their samples. The levels presented in Figure 2 are quite low, much lower that what we found in our study. In many cases, levels of these compounds are absolutely minimal, and it is NOT expected to raise any concerns about human health effects. Additionaly, the authors FAILED to mention the presence of these compounds in tobacco cigarette smoke. This omission creates the impression that e-cigarettes are exposing users to a new chemical hazard, while in reality their exposure will be much lower compared to smoking. Finally, the try to argue that the use of the NIOSH-defined safety limits should not be used because they refer to working environment and not to the general population. The latter may include vulnerable people or people with disease. However, we have previously argued that such an argument is irrelevant for a simple reason: e-cigarettes are used by smokers. Whether you are healthy or not, smoking will be a much stronger risk factor for health damage compared to any exposure coming from e-cigarettes (at least at the average levels found in our study and the new study). Thus, this argument is invalid and refers ONLY to never-smokers (and everyone agrees that there is no reason for a never-smokers to use e-cigarettes, whether they contain diacetyl or not).

In conclusion, the article is creating false impressions and exaggerates the potential risk from diacetyl and acetyl propionyl exposure through e-cigarettes. They failed to mention that these chemicals are present in tobacco cigarette smoke and violated a classical toxicological principle that the amount determines the toxicity and the risk.

I have been a strong supporter of removing any diacetyl and acetyl propionyl from e-cigarettes. I maintain the same position today, despite being criticized. These chemicals should not be used in e-liquids. However, we should responsibly and realistically assess the situation. Smokers need to be informed about the risk from continuing smoking versus a risk coming from use of diacetyl containing e-liquids. We should not forget that the risk from discouraging smokers to use e-cigarettes as a smoking cessation tool is higher than the risk of being exposed to diacetyl and acetyl propionyl at the average levels found in this study. 

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