Vapor from electronic cigarettes is non-toxic to human lung cells under normal usage conditions, according to a British American Tobacco press note citing one of two papers published on Friday.
Even when tests were performed using what was described as ‘extremely unrealistically high doses’, electronic cigarette vapor proved to be significantly less toxic to human lung cells than did cigarette smoke.
And whereas cigarette smoke was cytotoxic even at levels typically observed in real life use, lung cells exhibited low levels of cytotoxicity only after exposing them to an amount of vapor equivalent to a day’s exposure in just one hour.
“We only saw signs of cytotoxicity from the e-cigarette aerosols when we used unrealistically high levels of vapor,” said Dr. Chris Proctor, BAT’s chief scientific officer. “The conservative approach we took means that it is unlikely that normal vaping use would yield cytotoxic effects, even at the low levels observed here.”
The research was due to be published in a special issue on electronic cigarettes in Toxicology Mechanisms and Methods DOI: 10.1080/15376516.2016.1222473.
‘Scientists at British American Tobacco used an advanced lung cell exposure system to investigate the potential adverse effects of e-cigarette vapor on airway tissue compared with cigarette smoke,’ the press note said. ‘A puffing machine was used with human lung cells to compare the potential cytotoxic effects of vapor with cigarette smoke in a way that mimics real-life exposures.
‘The cytotoxicity of the exposed cells was measured using a test called a “neutral red uptake assay”. A neutral red uptake assay involves adding a red dye to cells. Living cells incorporate the red dye into cell components called lysosomes – the cell’s waste disposal system – staining them red. As the cells begin to die, they lose the ability to incorporate this dye and the cells change in colour from red to light pink.
‘A commercially available e-cigarette, Vype ePen, was tested and its potential cytotoxic impact was compared to that of a 3R4F reference cigarette.
‘In order to elicit a cytotoxic response with the Vype e-pen e-cigarette, it was necessary to deliver an estimated daily dose of vapor to the cells in only an hour, which is unlikely to represent levels a consumer would experience. Additionally, the daily dose was calculated by assuming that 100 percent of vapor is deposited in the lungs.
‘The amount of particulate mass from the aerosols deposited on the cells’ surface was also measured to prove that different amounts of smoke or vapor had reached the cells even when there was no or minimal cytotoxic response.’
Meanwhile, in describing the second paper to be published in the special edition of Toxicology Mechanisms and Methods, BAT said that electronic cigarette vapor was much less harmful to lung cells than was cigarette smoke. Laboratory tests had shown that, unlike tobacco smoke, which caused oxidative stress and cell death, electronic cigarette vapor did not. Oxidative stress and cell death were driving factors in the development of many smoking-related diseases such as COPD and lung cancer.
‘Vapor from e-cigarettes has been found to contain significantly lower levels of the toxicants found in cigarette smoke (Chemical Research in Toxicology DOI: 10.1021/acs.chemrestox.6b00188), but suitable lab tests and clinical studies are necessary to understand whether this translates into reductions in biological responses and disease,’ BAT said in a second press note.
‘Researchers at British American Tobacco have developed a standardized way of measuring and comparing the potential of conventional cigarette smoke and e-cigarette vapor to cause oxidative stress in an in vitro model of lung epithelium.
‘To do this they bubbled matched amounts of smoke (from a reference cigarette) or vapor (from Vype ePen or Vype eStick) through cell-growth medium to produce a stock that could be diluted into various concentrations. They then exposed lung epithelial cells to the same concentrations of either smoke or vapor extract and, following exposure, used a panel of commercially available assays to measure and compare the stress responses of the cells.
‘Lung cells exposed to any of the concentrations of cigarette smoke showed signs of oxidative stress and, at higher doses, cytotoxicity. In stark contrast, vapor from e-cigarettes tested had no such effects, even at the highest concentration.’
“These data suggest that exposure to vapor from the e-cigarettes tested induces negligible or no oxidative damage to lung epithelial cells at the range of doses tested,” said Proctor. “This highlights the scale of difference in potency between e-cigarette vapor and cigarette smoke and adds to the weight of evidence on the reduced risk potential of e-cigarettes.”
BAT said that though sensitive enough to detect the damaging pro-oxidant effects of tobacco smoke, the assays used in the study could not detect a response from e-cigarette vapor, which contained comparable levels of nicotine but very low levels of potentially harmful chemicals.
‘These tests are part of a suite of tests being developed to test novel tobacco and nicotine products and could be used to help develop standards for these products in the future,’ BAT said.
‘Many in the public health community believe e-cigarettes offer great potential for reducing the public health impact of smoking. Public Health England, an executive body of the UK Department of Health, recently published a report saying that e-cigarettes are 95 percent safer than cigarettes. The Royal College of Physicians have said that the public can be reassured that e-cigarettes are much safer then smoking and that they should be widely promoted as an alternative to cigarettes, though they also called for more research. Cancer Research UK, Action on Smoking and Health and the British Heart Foundation are also of the view that e-cigarettes are substantially less harmful than smoking.’