Sorting out the science from the smoke in e-cigarette research

London

FROM apple pie to bubbly bubble gum, Irish car bomb or Martian bar - from Mars!, the flavours of electronic cigarette offer something for every taste.

Researchers have counted 7,764 varieties of "vape". That adds up to one of many challenges - from practical constraints to conflicts of interest - in working out how safe e-cigs are, and whether they help smokers quit.