It's clear that some children have tried electronic cigarettes, but Prof Robert West, director of
tobacco Studies at University College London, says there is no sign they are becoming popular in the UK - the only country he knows where the uptake is monitored closely.
He adds that if and when young people do start smoking e-cigarettes, public health experts will have to study the causes carefully.
"If those young people are people who would have smoked but instead they're using e-cigarettes, then that's a huge public health gain. If they're people who would never have smoked but they've taken up e-cigarettes, frankly in public health terms it's not really an issue - it's like drinking coffee or something, there's no real risk associated with it.
"The real risk is if they start using e-cigarettes and this acts as a gateway into smoking. Now which of those things happens none of us knows at the moment."