Estimates of Cellular Mutagenesis From Cosmic Rays

A parametric track structure model is used to estimate the cross section as a function of particle velocity and charge for mutations at the HGPRT locus in human broblast cell cultures . Experiments that report the fraction of mutations per surviving cell for human lung and skin broblast cells indicate small di erences in the mutation cross section for these two cell lines when di erences in inactivation rates between these cell lines are considered. Using models of cosmic ray transport , the mutation rate at the HGPRT locus is estimated for cell cultures in space ight and rates of about 2 to 10 10 6 per year are found for typical spacecraft shielding. A discussion of how model assumptions may alter the predictions is also presented.