E-cigarette vapour does not damage DNA, even at doses 28 times that of equivalent smoke exposure.

Scientists at British American Tobacco used lab-based cellular tests to examine the impact of cigarette smoke and Vype e-cigarette vapour on human lung cells.

The most serious kind of DNA damage is double-strand break, which effectively means that both strands of the DNA molecule have been broken. This is a possible precursor to cancer and potentially lethal to the cell.

'We have been able to show that there is significant DNA damage in human lung cells exposed to smoke, but that this is not case with e-cigarette vapour,' explains Dr James Murphy, Head of Risk Substantiation at British American Tobacco. 'These findings add to evidence on the likely reduced risks of vaping, compared to smoking,' he said.

The research is published in Toxicology Letters.

Double-strand break

Cellular DNA can become damaged when exposed to toxicants, like those in cigarette smoke for example. DNA double-strand break (DSB) in which both strands of the DNA molecule are broken, is the most serious type of DNA damage. The cell attempts to repair the DNA damage by modifying the protein or histone around which the DNA is wrapped. The changes observed in this histone can be used as an indicator of the level of DSB. These changes can be detected using a well-established test called a γH2AX assay.

This test was used to compare the impact of the 3R4F* reference cigarette and Vype ePen and Vype eStick (commercially available e-cigarettes) on human lung cells. This test was used in combination with an exposure system (Vitrocell VC) that allows lung cells to be exposed to aerosol in the lab in a way that mimics exposure in the body when consumers inhale.

This combination of tests allowed for the assessment of the whole aerosol, be it smoke or vapour. Previous studies focused on only the particulate fraction of smoke.

The results show that cigarette smoke induced significant DNA damage in human lung cells, in a dose dependent manner - that is, the higher the dose, the more DNA damage was induced. E-cigarette vapour produced no affect, even when the dose used was 28 times higher than the equivalent smoke exposure.

The results confirm that cigarette smoke is genotoxic (causes genetic damage) and, at higher doses, cytotoxic (can cause cell death). In contrast, e-cigarette vapour is neither genotoxic nor cytotoxic, even at extremely high doses.

'We know that we can be confident in our results because we have shown that e-cigarette aerosol droplets are effectively delivered to cell surfaces in lab-based biological tests,' explains Murphy.

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 the current expert estimate is that using e-cigarettes is around 95% safer than smoking cigarettes, although more research is needed. 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.

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*3R4F is a routinely used reference cigarette developed by the University of Kentucky to ensure consistency in laboratory testing of cigarettes