A new study on the use of e-cigarettes suggests that when used indoors, users may involuntarily expose non-users to nicotine, although at lower levels than conventional cigarettes.

Tobaccoless e-cigarettes deliver nicotine through an inhaled vapor. When an e-cigarette smoker takes a puff, a nicotine solution inside the device is heated and can be taken into the lungs upon the inhale.

For the study, Maciej Goniewicz of Roswell Park Cancer Institute (RPCI), studied three different brands of e-cigarettes, using a smoking machine in controlled exposure conditions. Goniewicz and his colleagues also compared second-hand exposure of e-cigarette vapor and conventional tobacco smoke.

The research revealed that although e-cigarettes do not emit substantial amounts of carbon monoxide or other toxic compounds, they do emit significant amounts of nicotine, albeit at lower levels than conventional cigarette smoke. However, the amount of nicotine emitted by the e-cigarettes varied by brand.

According to the US Surgeon General, there is no safe level of second-hand tobacco smoke, but there is no official position on second-hand exposure to e-cigarettes.

"To our knowledge, this is one of the first studies to measure the air concentrations of nicotine and volatile organic compounds and compare the emissions from electronic and conventional tobacco cigarettes," said Goniewicz, who is a researcher and assistant professor of oncology in RPCI's Department of Health Behavior. "Our data suggest that secondhand exposure to nicotine from e-cigarettes is on average 10 times less than from tobacco smoke. However, more research is needed to evaluate the health consequences of secondhand exposure to nicotine from e-cigarettes, especially among vulnerable populations including children, pregnant women and people with cardiovascular conditions."

Andrew Hyland of the Department of Health Behavior at RPCI, said the study can help guide policymakers as decisions are made on how to regulate e-cigarettes.

"Questions remain regarding the health impact of e-cigarettes among smokers and nonsmokers. It remains unclear whether young people will see e-cigarette use as a social norm and if e-cigarettes will be used as sources of nicotine in places with smoking bans, thus circumventing tobacco-free laws," Hyland said.