“Everyone knows that smoking is the leading cause of lung cancer, but not everyone who gets lung cancer is a smoker (or passive smoker), which means that there must be other less well-known causes,” started Dr Morrison.

She added: “After cigarette smoke, the most common cause of primary lung cancer is a gas called ‘radon’.

“This colourless odourless gas, which is a decay product of radioactive substances in rocks and soil, travels up through the ground. It can build up in buildings, including our homes, without being noticed at all.

“In addition, car fumes, containing diesel and nitrogen oxide for example, are known to increase the risk of lung cancer.”

READ MORE: High cholesterol: Pain in hands or feet could be an indication your levels are too high