San Francisco has officially banned the sales of e-cigarettes until their health effects are made clear.
Officials voted on the move on Tuesday, making it illegal for stores to sell it and for online retailers to deliver.
It is the first city in America to do so.
John Maytham spoke to University of Cape Town's head of the lung clinical research unit (LCRU) Richard van Zyl-Smit.
van Zyl-Smit says the US has particularly seen a huge spike in the use of vapers among teens.
Certainly with the dual device, the amount of nicotine addicted adolescents in the US is staggeringly high.— Richard van Zyl-Smit, Head - UCT lung clinical research unit
I suspect it is not so much the safety compared to tobacco, it is the risk of adolescents starting to vape that they are pushing back against.— Richard van Zyl-Smit, Head - UCT lung clinical research unit
Click on the link below to hear the full conversation...