According to the World Health Organisation, air pollution causes 7 million premature deaths every year. We’ve known for a long time that air pollution causes lots of health problems, including lung cancer – but exactly how the two were linked was somewhat of mystery. Last week, a team from the Francis Crick Institute and University College London presented findings that shed new light on the role between air pollution and lung cancer. And, in doing so, could make us rethink how cancer develops. Madeleine Finlay speaks to the Guardian’s science correspondent Hannah Devlin about how scientists uncovered this link – and what it might mean for the future of the field.. Help support our independent journalism at theguardian.com/sciencepod