This is one for anoraks only. Pierre Hainaut of the WHO/IARC and Gerd Pfeifer are experts in the aetiology (causation) of lung cancer via the mutation of the P53 gene. In smokers it is a G to T transversion while in non smokers it is a G to A transversion. The research was of particular interest to the WHO/IARC as this is the final proof, denied by tobacco companies that smoking causes lung cancer. They conclude that it is the case. If the G to T Transversion is never seen in lung cancer then second hand smoke will never cause lung cancer in non smokers. Discuss.