Crarg, My understanding is that a third of those who die from...

Crarg,

My understanding is that a third of those who die from primary lung cancer have never smoked.

The major cause in non-smokers is as a result of breathing xenon or radon gas in the air which results from the breakdown of radioactive particles. From memory xenon tends to accumulate in areas of low disturbance such as rooms in houses and thus the importance of 'airing' your house by having windows open whenever you can.

There will inevitably be an increase in lung cancer cases around the world following the Japanese disaster. Hawaii in particular may tell the story.

Only 12% of those who smoke tobacco actually end up with lung cancer and in general need to have smoked 20 pack years. Emphysema is a more common outcome for most.