E-cigarettes -- often touted as a safer alternative to cigarette smoking -- may modify the DNA in the oral cells of users, potentially increasing the risk of cancer.
Introduced to the market in 2004, e-cigarettes are handheld electronic devices that heat a liquid, usually containing nicotine, into an aerosol that the user inhales.
Different flavours of liquids are available, including many that appeal to youth, such as fruit, chocolate and candy.
The popularity of e-cigarettes continue to grow worldwide, but the long-term effects of e-cigarette usage, commonly called "vaping," are unknown.
"We want to characterise the chemicals that vapers are exposed to, as well as any DNA damage they may cause," said Romel Dator, who presented the study in the US at the 256th National Meeting & Exposition of the American Chemical Society (ACS).
According to a 2016 report by the US Surgeon General, 13.5 per cent of middle school students, 37.7 per cent of high school students and 35.8 per cent of young adults (18 to 24 years of age) have used e-cigarettes, compared with 16.4 per cent of older adults (25 years and up).
"It's clear that more carcinogens arise from the combustion of tobacco in regular cigarettes than from the vapor of e-cigarettes," said Silvia Balbo, from the University of Minnesota in the US.
"However, we don't really know the impact of inhaling the combination of compounds produced by this device. Just because the threats are different doesn't mean that e-cigarettes are completely safe," said Balbo.
To characterise chemical exposures during vaping, researchers recruited five e-cigarette users.
They collected saliva samples before and after a 15-minute vaping session and analysed the samples for chemicals that are known to damage DNA.
To evaluate possible long-term effects of vaping, the team assessed DNA damage in the cells of the volunteers' mouths.
The researchers used mass-spectrometry-based methods they had developed previously for a different study in which they evaluated oral DNA damage caused by alcohol consumption.
Researchers identified three DNA-damaging compounds, formaldehyde, acrolein and methylglyoxal, whose levels increased in the saliva after vaping.
Compared with people who do not vape, four of the five e-cigarette users showed increased DNA damage related to acrolein exposure.
The type of damage, called a DNA adduct, occurs when toxic chemicals, such as acrolein, react with DNA. If the cell does not repair the damage so that normal DNA replication can take place, cancer could result.
The researchers plan to follow up this preliminary study with a larger one involving more e-cigarette users and controls.
They also want to see how the level of DNA adducts differs between e-cigarette users and regular cigarette smokers.
"Comparing e-cigarettes and tobacco cigarettes is really like comparing apples and oranges. The exposures are completely different," Balbo said.
"We still don't know exactly what these e-cigarette devices are doing and what kinds of effects they may have on health, but our findings suggest that a closer look is warranted," he said.
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