The team hopes their findings will deter people from taking up smoking and debunk the myth that social smoking is harmless. Every cigarette has the potential to cause genetic mutations, Alexandrov says.
Quitting smoking will not reverse these mutations – they leave permanent scars on DNA – but it will prevent the added risk of more mutations
There is good evidence that people who stop smoking have a significantly lower risk of premature death than those who continue, says Simon Chapman at the University of Sydney, Australia.