A study carried out by an American research team from the University of California, La Jolla, investigated the harmfulness of e-cigarette on cultured human cells and published their results in the Journal Oral Oncology, last November.
The team, leaded by the Pr Weg Ongkeko from the Department of Otolaryngology-Head and Neck Surgery, produced extracts from e-cigarette’s vapor and tested their effect on epithelial cells. Two kinds of extracts were prepared, one produced by a nicotine-free e-cigarette and another one with nicotine.
Short- (48 hours) and long-term (8 weeks) experiment were conducted on cultured skin and upper aerodigestive tract cells. After exposure, the stage of apoptosis, ie the “degree of cell death”, was assessed by optical measurement of individual cell’s properties after a treatment by intra-cellular dyes and biological assays.
Their results indicate that the cells exposed to e-cigarette vapor, with or without nicotine, show a significantly reduced viability. This means that their potential to maintain themselves or recover after a viral attack was significantly altered in contact with the extract. The cells also showed patterns associated with damaged DNA. Such damages that may be at the origin of the proliferation of abnormal cells and ultimately cause malign tumors.
E-cigarette research is a hot topic and this is once again demonstrated with media running eye-caching slogans as a headline: “Beware! E-cigarettes may lead to cancer“, “E-cigarettes may lead to cancer: study” or “E-cigarettes can cause cancer even when they are nicotine-free, scientists claim“.
Update
Linda Bauld published a comment on December 31, 2015, in The Guardian regarding the alarming headlines. The article, entitled “No, there’s still no evidence e-cigarettes are as harmful as smoking“, debunks poor reportings of this study.
The reader may notice that, despite a co-author remains sceptic with regard to the potential benefit of e-cigarette compared to smoking, the conclusions do not argue for a robust link between their observation and cancer. Instead, they are cautious and employ the expression “the potential carcinogenic effects of e-cigarettes”, while the toxicity of the extracts is significant, based on their results. A recent study conducted on some e-liquids concluded on the absence of significant toxicity, and contradicts the aforementioned research. Such conflicting results indeed deserve further studies.
When interviewed by a Canadian channel, the vaping expert Konstantinos Farsalinos denounced deliberate alarmism on e-cigarette related topics. An alarmism that can either be triggered by the authors themselves or by the media. It was, for example, the case with the presence of Diacetyl in e-liquids when the research team put forward a potential risk of lung disease.
It would have been interesting to compare, on human epithelial cells, “the potential carcinogenic effects” of smoked tobacco extracts along with the nicotine and the nicotine-free e-cigarette extracts, following the same protocole. Tobacco has been recognized the cause of several human cancers and smoking has increased their spectrum to the upper and lower airways and the lungs. Looking for carcinogenic substances in tobacco smoke is probably one of the most tricky task on earth when considering the thousands of potentially harmful substances they contain. The reduced amount of compounds in e-cigarette vapor, compared to tobacco smoke may not hinder the scientists’ task and muffle media’s unsubstantiated fear.
[1] Yu, V., Rahimy, M., Korrapati, A., Xuan, Y., Zou, A. E., Krishnan, A. R., … & Brumund, K. T. (2015). Electronic cigarettes induce DNA strand breaks and cell death independently of nicotine in cell lines. Oral oncology.
