In the main part of the experiment, the team used normal epithelial cells, which line organs, glands, and cavities throughout the body, including the mouth and lungs. The scientists tested two types of each e-cigarette: a nicotine and nicotine-free version. Nicotine is what makes smoking addictive. There is also some evidence it can damage cells. The team found that the nicotine versions caused worse damage, but even the nicotine-free vapour was enough to alter cells. “There must be other components in the e-cigarettes that are doing this damage. So we may be identifying other carcinogenic components that are previously undescribed,” Wang-Rodriguez pointed out. The team is now trying to sort out those other substances and their specific effects. There are nearly 500 brands of e-cigarettes on the market, in more than 7,000 flavours. So scientists have their work cut out for them identifying all the potential problems. The study was published in the journal Oral Oncology.