The new study reveals that secondhand smoke from e-cigarettes contains chromium and nickel at levels higher than in traditional cigarettes.
The study - published in the Journal of Environmental Science, Processes and Impacts and led by co-author Prof. Constantinos Sioutas of USC - comes at a time when the World Health Organization (WHO) propose a ban on the use of e-cigarettes indoors.
Prof. Sioutas, along with colleagues at Fondazione IRCCS Instituto Nazionale dei Tumori (the National Institute of Cancer Research) in Milan, Italy, conducted the study to measure the level of exposure to harmful substances in secondhand smoke from e-cigarettes. By doing so, they hoped to provide regulatory authorities with valuable information.
They found that secondhand smoke from e-cigarettes has an overall 10-fold decrease in harmful particles and almost no organic carcinogens, which is likely because they do not burn organic material the way traditional cigarettes do.
But they also found that e-cigarette smoke contains chromium - a toxic element that is not present in traditional cigarettes - and nickel at levels four times higher than normal cigarettes.
The researchers say there were other toxic metals present in e-cigarette smoke, such as lead and zinc, though they were at levels lower than in normal cigarettes.
"Our results demonstrate that overall, electronic cigarettes seem to be less harmful than regular cigarettes, but their elevated content of toxic metals such as nickel and chromium do raise concerns," says Prof. Sioutas.
'Better manufacturing standards could reduce metals in smoke'
The team conducted their experiments in offices and rooms because, according to lead author Arian Saffari, these "are the environments where you're likely to be exposed to secondhand e-cigarette smoke, so we did our testing there to better simulate real-life exposure conditions."
Volunteer participants smoked both regular and e-cigarettes in these environments while the researchers collected particle samples of the indoor air and studied the chemical content.
They compared the smoke from a traditional cigarette brand with some from an Elips Serie C e-cigarette - one of the most popular brands in Europe. As such, they say their results could vary based on which type of cigarettes and e-cigarettes are used.
Commenting on their findings, Saffari says:
"The metal particles likely come from the cartridge of the e-cigarette devices themselves - which opens up the possibility that better manufacturing standards for the devices could reduce the quantity of metals in the smoke. Studies of this kind are necessary for implementing effective regulatory measures."
He adds that because e-cigarettes are relatively new, "there just isn't much research available on them yet."
The study was funded by the Fondazione IRCCS Instituto Nazionale dei Tumori.
In April of this year, the Centers for Disease Control and Prevention (CDC) announced that calls to US poison centers regarding e-cigarettes have soared, mostly due to children under 5 years eating the devices.
Medical News Today recently wrote a feature detailing how policy makers should react to the e-cigarette boom.