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”.

Prof Ludmil Alexandrov, a senior author on the study at the University of California in San Diego, said researchers had observed the “problematic trend” but had not understood the cause.

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.