Survival of human lung epithelial cells following in vitro alpha-particle irradiation with absolute determination of the number of alpha-particle traversals of individual cells

Purpose: To throw light on human exposure to domestic radon and radon proge ny, the effects of low doses of alpha-particle irradiation on normal human lung epithelial cells has been studied. At such low exposure levels the con cept of dose is inadequate due to the stochastic variation in the number of alpha-particle traversals per cell. The objective of the current study was to establish an accurate survival curve for human lung epithelial cells wi th absolute determination of the exact number of alpha-particle traversals of individual cells. Materials and methods: irradiation of L132 cells growing in track-etch dete ctor-based cell dishes, was performed using a collimated alpha-particle bea m from a Po-210 source. The number of alpha-particle traversals through eac h individual cell was scored by using a technique of retrospective track-et ch dosimetry. This technique is based upon image matching and mapping of co rresponding cell and alpha-particle track images. The spatial resolution of the hit determination procedure was +/- 0.9 mu m. Results: Surviving fractions of cells (SF) showed strict dependence on the number of nuclear traversals (n), with SF(n) = a exp( - bn), a = 0.957 (+/- 0.046), b = 0.587 (+/- 0.059), R-2 = 98.8%. No significant dependence on t he number of nuclear membrane traversals (m) or the number of cytoplasm tra versals (c) was observed.