In the culture war on cigarette smoking that lingered long after the science and health issues were settled, nothing spoke to the fuzzy, non-evidence-based nature of arguments than claims that second-hand smoke would give someone lung cancer.

Cigarette smoking is annoying and smelly, to be sure, and asthmatics can't be happy in a smoke-filled room any more than non-smokers are, but there are no instances where second-hand smoke has caused cancer. The American Heart Association recently went to war on electronic-cigarettes, a nicotine vapor device, after embracing nicotine patches and lozenges, and some of the claims they made in their policy recommendation defied belief, like that second-hand smoke from e-cigarettes could be just as harmful.

They are not going to like a new study from USC which found an overall 10-fold decrease in exposure to harmful particles, with close-to-zero exposure to organic carcinogens.

That's not to say people should just take them up, there is exposure to some harmful metals in second-hand e-cigarette smoke but while tobacco smoke contains high levels of polycyclic aromatic hydrocarbons – cancer-causing organic compounds – the level of exposure to these substances was reduced to almost zero in second-hand e-cigarette smoke, due to the fact that they do not burn organic material the way old-fashioned cigarettes do.

Trade-off: he toxic element chromium is from traditional cigarettes, as well as nickel at levels four times higher than normal cigarettes, and epidemiologists in modern times have developed a bad habit of exaggerating miniscule findings and claiming 400 percent difference will be meaningful. In addition, several other toxic metals such as lead and zinc were also found in second-hand e-cigarette smoke – though in concentrations lower than for 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," said Constantinos Sioutas, professor at the USC Viterbi School of Engineering, and corresponding author of the study, which was published online on August 22 by the Journal of Environmental Science, Processes and Impacts.

Sioutas and his colleagues at Fondazione IRCCS Instituto Nazionale dei Tumori (National Institute of Cancer Research) in Milan, Italy, began this study with the goal of quantifying the level of exposure to harmful organics and metals in second-hand e-cigarette smoke, in hopes of providing insight for the regulatory authorities.

"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," said Arian Saffari, a PhD student at USC Viterbi and lead author of the paper. "Studies of this kind are necessary for implementing effective regulatory measures. E-cigarettes are so new, there just isn't much research available on them yet."

For this study, the researchers conducted all of the experiments in offices and rooms. While volunteer subjects were smoking regular cigarettes and e-cigarettes, the researchers collected particles in the indoor air and studied the chemical content and sources of the samples.

"Offices and rooms– not laboratories – are the environments where you're likely to be exposed to second-hand e-cigarette smoke, so we did our testing there to better simulate real-life exposure conditions," Saffari said.

Sioutas and Saffari compared the smoke from a common traditional cigarette brand with smoke from an Elips Serie C e-cigarette, one of the most popular European brands. The results could vary based on which type of cigarettes and e-cigarettes are tested, the researchers noted.