I am interested in the fact that the incidence of lung cancer was very low prior to cigarette smoking but that, these days, around 10-15% of lung cancers seem to be unrelated to cigarette smoking. What is the source of these new lung cancers*? In part the finding could be related to early non-recognition of lung cancers but other factors seem to bear on the higher incidence of non-smoking related cancers that has emerged recently.
In the US the second largest cause of lung cancer is exposure to the element radon – most usually as it seeps through the floor of the family home. Radon kills 15,000-22,000 people in the US annually and is responsible for 12% of all lung cancer deaths. Services are available for testing and reducing radon levels in the family home . There is concern if radon levels exceed 4 pico Curies per litre (4pCi/L).
Puzzling recent findings suggest that radon at low concentrations in the home is hermetic for lung cancer – at low enough dosage levels radiation might help repair damaged DNA. These claims don’t challenge the 4pCi/L standard but the fact is that most households are below that level in any event.
By the way, radon concentrations in Australian homes are low – for most households they are marginally above concentrations in the atmosphere. There is however evidence of heightened health risks from radon in the Australian uranium mining industry.
*Of course passive smoking, asbestos and air pollution also cause lung cancers but their effects seem less important than radon exposure. Smoking and radon exposure are however probably synergistic in promoting lung cancers.