Technical Evaluation of the NASA Model for Cancer Risk to Astronauts Due to Space Radiation

This report presents an evaluation of NASA's proposed space radiation cancer risk assessment model and considers the model components, input data (for the radiation types, estimated doses, and epidemiology), and the associated uncertainties. This report also identifies gaps in NASA's current research strategy for reducing the uncertainties in cancer induction risks.

Recent research, much of which has been sponsored by NASA, has focused on understanding and quantifying the radiation health risks posed by space radiation environments. Although many aspects of the space radiation environments are now relatively well characterized, important uncertainties still exist regarding biological effects and thus regarding the level and types of risks faced by astronauts.

Contents
SUMMARY
1 INTRODUCTION
General Cancer Risk Estimation Approach
Evaluating the NASA Model
Proposed NASA Model
Approach to the Committee’s Evaluation
References
2 REVIEW OF NASA MODEL
Introduction
Space Radiation Environments and Transport Models
Galactic Cosmic Rays
Solar Particle Events
Transport Model
Final Comments
Cancer Risk Projection Models
Cancer Mortality Risk Estimation
Transfer from the Japanese to the U.S. Population
Dose and Dose Rate Effectiveness Factor
Risk Models for Never-Smokers
Additional Minor Issues
Uncertainties in Low-Linear Energy Transfer Risk Model
Epidemiological Basis for Radiation-Related Cancer Risk Estimation
Uncertainty-Related Bias
Radiation Risk Protection
Dependence on Atomic Bomb Survivor Data
Miscellaneous Comments
Cancer Risks and Radiation Quality in the Model
Quality Factors for Leukemia and Solid Cancers
Replacement of LET-Based Quality Factors with Track Structure-Based Quality Factors
Risk Cross Sections and Quality Factors
Non-Targeted Effects in the Risk Projection Model
Qualitative Differences Between Low-LET Radiation and Heavy-Ion Biological Effects
Data or Research That Could Improve This Portion of NASA’s Proposed Model
Integration and Completeness of the Model
Model Completeness, Improvements, and Recommendations
References
APPENDIXES
A Statement of Task
B Committee and Staff Biographical Information
C Glossary and Acronyms