Air pollution has been linked to a swathe of lung cancer-driving DNA mutations, in a study of people diagnosed with the disease despite never having smoked tobacco.

The findings from an investigation into cancer patients around the world helps explain why those who have never smoked make up a rising proportion of people developing the cancer, a trend the researchers called an “urgent and growing global problem”.

The scientists analysed the entire genetic code of lung tumours removed from 871 never-smokers in Europe, North America, Africa and Asia as part of the Sherlock-Lung study. They found that the higher the levels of air pollution in a region, the more cancer-driving and cancer-promoting mutations were present in residents’ tumours.