A new lab test suggests that the use of e-cigarettes at high temperature settings may possibly release more formaldehyde than normal cigarettes.

The research does not prove a health risk – it involved limited testing on just one brand of e-cigarettes and was done in test tubes, not people. It also does not mean e-cigarettes are better or worse than regular ones; tobacco smoke contains dozens of things that can cause cancer.

But it does highlight how little is known about the safety of e-cigarettes – battery-powered devices that heat liquid to deliver nicotine in a vapor rather than from burning tobacco.