Two products of electronic cigarettes were found to cause damage on cells that could promote the development of cancer. A new study shows both the nicotine and nicotine-free version of the products damaged the cells and adds to the growing health risks of using e-cigarettes.

The study, published in the journal Oral Oncology, shows that the products that use nicotine caused the worse damage but unfortunately, even the nicotine-free versions have affected the cells. Researchers said their study "strongly suggests that electronic cigarettes are not as safe as their marketing makes them appear to the public."

The team from the Veterans Affairs San Diego Healthcare System created an extract from the vapour of two popular brands of e-cigarettes, which they then used to treat human cells in Petri dishes. Results show that the extract has caused several forms of DNA damage, including DNA strand breaks, on the treated cells.

The double helix that makes up the DNA appears with two long strands of molecules. An individual could be at risk of cancer when the damage has caused one or both of the strands to break apart and results in a failure on the cellular repair process.

"There have been many studies showing that nicotine can damage cells," said lead researcher Dr. Jessica Wang-Rodriquez, a professor of pathology at the University of California, San Diego. "But we found that other variables can do damage as well.”

The researchers believe that nicotine may have not caused the damage alone as the amount of nicotine in e-cigarettes that affected the cells is not sufficient by itself to cause the changes. “There must be other components in the e-cigarettes that are doing this damage,” Wang-Rodriquez said.

The team are now aiming to determine other substances present in e-cigarettes and their specific effects. Earlier studies have already found some harmful chemicals in e-cigarettes, including formaldehyde and diacetyl.

Diacetyl is a common flavouring agent that has been associated to lung disease. It is commonly used in over three-quarters of flavoured e-cigarettes and refill liquids.

However, in the current study, Wang-Rodriquez noted that the cells they analysed in the lab are not completely comparable to a living person’s cells. It means the e-cigarette vapour used in the study could deliver different effects.

In addition, the researchers didn't provide the actual dose of vapour that an e-cigarette user would obtain.

"In this particular study, it was similar to someone smoking continuously for hours on end, so it's a higher amount than would normally be delivered," Wang-Rodriquez said. "What we're looking at now is to dose-control these. We want to know at what dose it causes that critical switch-over to where we see the damage."

However, Wang-Rodriquez said e-cigarettes are not safer than conventional tobacco cigarettes. "Based on the evidence to date, I believe they are no better than smoking regular cigarettes."