Issues in risk assessment from solar particle events

Uncertainties in risk assessment from solar particle events (SPE) include t he role of high linear energy transfer (LET) secondary ions, the assessment of dose-rate effects as they relate to acute injury, the risk of cancer mo rtality and the modification of health effects due to the stress of spacefl ight. We discuss several issues where new knowledge is required for improvi ng estimates of radiation risk from SPE's. Secondary particles such as neut rons and low energy and charge ions (LZE) may dominate radiation risk behin d a storm shelter and their biological effects are poorly understood, espec ially at low dose-rate. Dose-rate modulation of radiation response is also related to genetic pre-disposition an important determinant of radiation se nsitivity. Molecular pathways that control cell death and tissue response h ave been elucidated in recent years and should provide new understanding of dose-rate effects for risk assessment. We consider some of these factors a nd discuss calculations using radiation transport codes, track structure mo dels of energy deposition, and a molecular kinetics approach to model radia tion response. Published by Elsevier Science Ltd.