Speaker
Dr
Francis Cucinotta
(NASA)
Description
Models of radiation carcinogenesis risks from terrestrial radiation or galactic cosmic rays (GCR) and solar particle events (SPE) in space are impacted by various uncertainties related to radiation quality, dose and dose-rate response models, and individual sensitivity. We describe NASA’s approaches to these problems. The use of age and gender specific models with uncertainty assessments based on human epidemiology data for low LET radiation combined with relative biological effectiveness factors (RBEs) and dose- and dose-rate reduction effectiveness factors (DDREF) to extrapolate these results to space radiation exposures are considered the current “state-of-the-art” [1]. The NASA Space Cancer Risk (NSCR) model (2010) [2-3] is based on recent radio-epidemiology data, however a key feature of the NASA model is the formulation of particle fluence and track structure based radiation quality factors for solid cancer and leukemia risk estimates, which are distinct from the ICRP quality factors, and shown to lead to smaller uncertainties in risk estimates. A new Bayesian analysis of uncertainties in the DDREF are summarized in our report. Many persons exposed to radiation on earth as well as astronauts are life-time never-smokers, which is estimated to significantly reduce radiation cancer risks. A key feature of the NASA radiation protection model is the classification of radiation workers by smoking history in setting dose limits. A major challenge to the current approach to cancer risk estimates are Non-Targeted Effects (NTE), which include bystander effects and genomic instability, which has been observed in cell and animal models of cancer risks. NTE’s could lead to significant changes in RBE and DDREF estimates for GCR particles, and distinct risk factors related to individual sensitivity and the potential effectiveness of radiation mitigator’s. We discuss methods to include NTE’s in uncertainty analysis and to design experiments to provide quantitative data for cancer risk assessment models. NSCR-2010 was reviewed by the National Research Council (2012) [1], and a revision to the NASA model, NSCR-2012 that addresses the recommendations from the NRC report.
1. NRC, The National Academy Press, Wash DC, 2012.
2. Cucinotta FA, Chappell LJ, and Kim MY. Space Radiation Cancer Risk Projections and Uncertainties-2010. NASA TP 2011-216155
3. Cucinotta FA et al. Radiat Res 176, 102-114, 2011; Health Phys (in press).
Primary author
Dr
Francis Cucinotta
(NASA)
Co-authors
Ms
Lori Chappell
(USRA)
Dr
Myung-Hee Kim
(USRA)
