The ionization patterns in molecules, cells, tissues, and the resulting biological harm are distinct from high-energy photon radiation: X-rays and gamma rays, which produce low-linear energy transfer (low-LET) radiation from secondary electrons.
While in space, astronauts are exposed to protons, helium nuclei, and HZE ions, as well as secondary radiation from nuclear reactions from spacecraft parts or tissue.
[4] Although HZE ions make up a small proportion of cosmic rays, their high charge and high energies cause them to contribute significantly to the overall biological impact of cosmic rays, making them as significant as protons in regard to biological impact.
[1] HZE ions can therefore penetrate through thick layers of shielding and body tissue, "breaking the strands of DNA molecules, damaging genes and killing cells".
[1] For HZE ions that originate from solar particle events (SPEs), there is only a small contribution toward a person's absorbed dose of radiation.