Human lung cancer risks from radon - part I- influence from Bystander effects - a microdose analysis

Since the publication of the BEIR VI report in 1999 on health risks from radon, a significantamount of new data has been published showing various mechanisms that mayaffect the ultimate assessment of radon as a carcinogen, at low domestic and workplaceradon levels, in particular the Bystander Effect (BE) and the Adaptive Response radio-protection(AR). We analyzed the microbeam and broadbeam alpha particle data of Miller etal. (1995, 1999), Zhou et al. (2001, 2003, 2004), Nagasawa and Little (1999, 2002), Hei etal. (1999), Sawant et al. (2001a) and found that the shape of the cellular response toalphas is relatively independent of cell species and LET of the alphas. The same alpha particletraversal dose response behavior should be true for human lung tissue exposure toradon progeny alpha particles. In the Bystander Damage Region of the alpha particleresponse, there is a variation of RBE from about 10 to 35. There is a transition regionbetween the Bystander Damage Region and Direct Damage Region of between one andtwo microdose alpha particle traversals indicating that perhaps two alpha particle "hits"are necessary to produce the direct damage. Extrapolation of underground miners lungcancer risks to human risks at domestic and workplace levels may not be valid.