A study by the Centre of Excellence for the acceleration of Harm Reduction (CoEHAR), by researchers at the University of Catania in Italy, found an 80% or less cytotoxic effect in four aerosol e-cigarette liquids than cigarette smoke. They recommend that smokers switching to e-cigarettes as a safer alternative ensure that they use high quality products.
The results of the study, published on 17 April 2022 by Drug Testing & Analysis, showed no contaminants in all e-liquids and a metal content below the levels permitted by the World Health Organisation (WHO) for drinking water.
CoEHAR is a multidisciplinary centre focused on the study of tobacco harm reduction. It includes the Centre for Tobacco Prevention and Treatment and a clinical research organisation, and is supported by the Italian Anti-Smoking Leagueand ECLAT, a research-based company and spin-off of the University of Catania.
The debate over the safety and efficacy of electronic cigarettes demands strong and accurate evidence by the scientific community, wrote CoEHAR in a story released on 21 April 2022.
The growing body of knowledge on alternative nicotine delivery systems and the potential benefits for human health if compared to conventional cigarettes pushed researchers to analyse e-cigarette liquids, which differ in nicotine percentages, type and flavours.
The e-liquids consist largely of propylene glycol and vegetable glycerin, and a smaller part of food chemical flavourings and nicotine (which may also be absent). Substances mixed according to the quality of the liquid or the specific marketing of the product.
The potential risk of e-liquids is connected to the presence or absence of heavy metal residues or nanoplastics and microplastics in the liquids themselves.
By testing some liquids sold in Italy and present also in foreign markets, Coehar researchers analysed four different e-liquids (flavoured with different varieties of tobacco) by Dreamods.
The results of the study showed no contaminants in all e-liquids and a metal content below the levels permitted by WHO for drinking water.
The data is in line with European public authorities quality standards on production and marketing of vaping products.
Once the low risk profile of alternative nicotine delivery system is assessed, the authors of the study believe that the best way to protect the health of vapers is to prefer high quality products.
During the study conducted in CoEHAR labs in Catania, thanks to the collaboration of the spin ECLAT and the use of the most innovative evaluation systems in the world, the researchers – in addition to excluding the presence of contaminants derived from metals and microplastics and nanoplastics – investigated the vapour cytotoxic effect in normal human bronchial epithelial cells by a number of in vitro assays, compared to cigarette smoke.
The exposure system to cigarette smoke and e-cigarette vapour used in the labs off the research centre in Catania reproduce the human exposure of lung cells to the daily use of cigarettes and electronic cigarettes, thus reporting certain and irrefutable results.
Researchers used a smoking machine and a vaping machine to generate respectively the cigarette smoke and the vaping aerosol.
The exposure of bronchial cells to cigarette smoke and e-cigarette vapour was carried out using a biological exposure chamber containing the cells and connected to the machines in order to simulate a physiologically relevant exposure for a smoker or a vape.
The cytotoxicity effect was assessed using two different technologies: Real-Time Cell-based Assay technology (xCELLigence) and High Content Screening technology (Operetta). The latter was also used for the assessment of mitochondria integrity (mitochondria generate most of the chemical energy needed to power the cell’s biochemical reactions ).
Moreover, researchers evaluated the production of reactive oxygen species (ROS) in the aerosol of the four liquids analysed – ‘Dolce Bacco’, ‘Red Bacco’, ‘Deciso’ and ‘Otello’ – and in the cigarette smoke.
Professor Massimo Caruso of the University of Catania and author of the study, is “satisfied with the significantly reduced (about 80% less) cytotoxic effect of the aerosol of all four liquids compared to cigarette smoke”.
The data was confirmed by Professor Giovanni Li Volti, director of CoEHAR who added: “The cells exposed to e-cig vapours also maintained excellent integrity of the mitochondria, highlighting a negligible effect, not significant even on cellular metabolism. Furthermore, no production of reactive oxygen species (ROS) and therefore of oxidative stress in the electronic cigarette aerosol was detected”.
The results increasingly support international data confirming the reduced toxicity of electronic cigarettes compared to conventional smoking and the benefits, in terms of health, for those smokers who decide to use them to quit smoking.
Study details
In vitro cytoxicity profile of e-cigarette liquid samples on primary human bronchial epithelial cells
Massimo Caruso, Alfio Distefano, Rosalia Emma, Pietro Zuccarello, Chiara Copat, Margherita Ferrante, Giuseppe Carota, Roberta Pulvirenti, Riccardo Polosa, Gesualdo Antonio Missale, Sonja Rust, Giuseppina Raciti and Giovanni Li Volti
Author affiliations: University of Catania and GF Ingrassia in Catania, Italy.
Published by Drug Testing & Analysis, on 17 April 2022.
Abstract
Cigarette smoke is associated with severe chronic diseases. The most harmful components of cigarette smoke derive from the combustion process, which are significantly reduced in electronic cigarette aerosol, thus providing a valid option in harm reduction strategies. To develop safer products, it is therefore necessary to screen electronic cigarette liquids (e-liquids) to meet high safety standards defined by government regulations.
The aim of the present study was to evaluate the presence of metal- and plastic-derived contaminants in four different commercial e-liquids with high concentration of nicotine and their cytotoxic effect in normal human bronchial epithelial cells by a number of in vitro assays, in comparison with the 1R6F reference cigarette, using an air-liquid interface (ALI) exposure system. Moreover, we evaluated the effect of aerosol exposure on oxidative stress by measuring the production of reactive oxygen species and mitochondrial potential.
Our results showed no contaminants in all e-liquids and a significantly reduced cytotoxic effect of e-liquid aerosol compared to cigarette smoke as well as a maintained mitochondria integrity. Moreover, no production of reactive oxygen species was detected with e-cigarette aerosol.
In conclusion, these results support the reduced toxicity potential of e-cigs compared to tobacco cigarettes in an in vitro model resembling real life smoke exposure.
See also from the MedicalBrief archives
E-cigarettes: What we know and what we don’t – Cancer Research UK
E-cigarettes: Misconceptions may prevent people from quitting smoking
WHO versus Public Health England over e-cigarettes
E-cigarettes not a substantial gateway to smoking for young people – UK study
Researchers expose the ‘pitiful quality’ of highly cited vaping studies