E-cigarettes may do more harm than previously thought, according to a report published in the New England Journal of Medicine.

NPR reported last week on a study that found vapor produced by electronic cigarettes can contain a surprisingly high concentration of formaldehyde — a known carcinogen.

Researchers found formaldehyde only when the e-cigarettes were cranked up to their highest voltage levels, which produced between “five-fold and fifteen-fold higher concentrations of formaldehyde than in cigarettes.”

Their findings support the American Heart Association’s policy statement on e-cigarettes released in August 2014.

Dr. Aruni Bhatnagar, professor of medicine at the University of Louisville, chaired the panel of experts who developed the statement.

He said some of the high levels of  chemicals in conventional cigarettes are found in trace levels in e-cigarettes, but formaldehyde and other aldehydes are detected in e-cigarettes.

The main concern with e-cigarettes is that it generates small particulate matter, which is associated with cardiac deaths and respiratory problems when exposed at high levels, he noted.

“There is concern that  these particles when inhaled might have the same toxicity as ambient particles in conventional cigarettes,” Bhatnagar said.

He said people should view e-cigarettes with caution and not just because of the potential health risks.

“The use of e-cigarettes could contend to renormalize smoking and we are concerned that it might erode all the gains in public health that we have made so far,” Bhatnagar said.

He also said that e-cigarettes could fuel addiction by supporting the use of nicotine in places where smoking is already prohibited and recruit a new generation of addicts.

NPR also spoke with Gregory Conley of the American Vaping Association.

Conley said it’s unrealistic for anyone to vape at the high levels recorded in the study because the vapor would be too hot.

“If you hold the button on an e-cigarette for 10 seconds, you could potentially produce 100 times more formaldehyde than you would ever get from a cigarette. But no human vaper would ever vape at that condition, because within one second their lungs would be incredibly uncomfortable,” Conley said.