I t used to be thought that the lungs couldn’t regenerate,” says Dr Charlotte Dean, head of the lung development and disease group at Imperial College London. “But we know now that’s not the case. Broadly speaking, they can repair when you quit smoking.”

Smoking is in effect damaging your lungs, Dean says, and the lungs have a substantial capacity to heal themselves. They have evolved to cope with pollution or getting infected by bacteria or viruses. “Because they’re so vital – you can’t survive without your lungs – they needed to have this capacity,” she says.

Dean says this shouldn’t be used as an excuse to smoke, though; smoking and vaping expose your lungs to more toxic particles than they can cope with.…