Even short-term use of e-cigarettes may cause cellular inflammation -- an important driver of lung cancer and other respiratory diseases -- in never-smokers, according to a study. Researchers at The Ohio State University in the US found the first evidence of biological changes correlated with e-cigarette use in never-smoker adults.
Using a procedure called bronchoscopy to test for inflammation and smoking-related effects, the study published in the journal Cancer Prevention Research, found a measurable increase in inflammation after four weeks of e-cigarette use, without nicotine or flavours.
Although the magnitude of change was small compared with a control group, the pilot data suggests that even short-term usage can result in inflammatory changes at a cellular level.
Inflammation from smoking is an important driver of lung cancer and other respiratory disease development, the researchers said.
Researchers said any level of cellular inflammation correlated with vaping is concerning because the biological and health effects of e-cigarettes constituents such as propylene glycol and vegetable glycerine -- while "generally regarded as safe" by the US Food and Drug Administration (FDA) when used in foods and cosmetics -- are unknown when heated and inhaled with e-cigarettes.
Researchers note that even in this small study, there were observable effects. "The implication of this study is that longer term use, increased daily use and the addition of flavours and nicotine may promote additional inflammation," said Peter Shields, from The Ohio State University.
"The general perception among the public is that e-cigs are 'safer' than cigarettes. The reality is the industry is changing so fast -- and with minimal regulation -- that usage is outpacing the rate of our scientific understanding.
"It's becoming a public health crisis we should all take very seriously from a general pulmonary health, cancer risk and addiction perspective. E-cigs may be safer than smoking, but that is not the same as safe, and we need to know how unsafe they are," he said.
With the recent reports of lung disease and deaths associated with vaping, the effects of vaping nicotine and marijuana oils makes this research more critical, the researchers said.
The study recruited 30 healthy, non-smoking volunteers to directly assess the impact of tobacco and e-cigarette use on the lungs through bronchoscopy, an outpatient test in which a doctor inserts a thin tube through the nose or mouth to view the airways.
A small sample of lung cells is collected from fluid in the lungs. Participants were randomised to a four-week intervention with e-cigs containing only 50 per cent propylene glycol (PG) or 50 per cent vegetable glycerine (VG) without nicotine or flavours.
Results from these tests were then compared to a separate control group of never-smokers. Researchers did not see levels of inflammation higher than the controls, but there was an increase in inflammation among the users who inhaled more of the e-cigarettes.