Tank-system vaping can create temperatures during atomisation high enough to produce levels of the carcinogen formaldehyde comparable to smoking tobacco cigarettes, according to studies cited by the New York Times.

Tank-systems are larger than disposable e-cigarettes. They resemble fountain pens or small torches and vaporise e-liquids quickly, producing thick plumes of steam and “a handful of carcinogens” when atomising temperatures are hot enough, the newspaper reported.
Vapers using the ‘dripping’ method of placing tiny amounts of e-liquid directly onto the heating element atomise at temperatures high enough to produce not only thicker vapor, but also formaldehyde and related toxins at levels approaching conventional cigarettes, states one study cited by the Times.
Dr Alan Shihadeh, project director at Virginia Commonwealth University’s Centre for the Study of Tobacco Products led the research on dripping. A study headed by Dr Maciej Goniewicz, assistant professor of oncology at Roswell Park Cancer Institute in New York, concludes tank systems produce formaldehyde. The Goniewicz study is scheduled for 15 May publication in Nicotine and Tobacco Research. The Shihadeh study is being prepared for submission to the same publication, the Times said.