The proportion of people being diagnosed with lung cancer who have never smoked is increasing, with air pollution an “important factor”, the World Health Organization’s cancer agency has said.

Lung cancer in people who have never smoked cigarettes or tobacco is now estimated to be the fifth highest cause of cancer deaths worldwide, according to the International Agency for Research on Cancer (IARC).

Lung cancer in never-smokers is also occurring almost exclusively as adenocarcinoma, which has become the most dominant of the four main subtypes of the disease in both men and women globally, the IARC said.