Space Radiation and Astronaut Health Managing and Communicating Cancer Risks (2021) / Chapter Skim
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2 Space Radiation and Cancer Risks to Astronauts
2 Space Radiation and Cancer Risks to Astronauts
Pages 33-50
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From page 33... ...
The chapter also includes an over view of both the cancer risk model used by the National Aeronautics and Space Administration (NASA) , which provides the basis for the agency's space radiation health standard, and sex, age, and genetic factors that affect radiation-induced cancer risk.
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From page 34... ...
is the amount of energy that is depos ited in matter (such as biological tissue) per unit distance that the ionizing radiation travels; and • Relative biological effectiveness (RBE)
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CANCER RISK PROJECTION MODELS Ionizing radiation increases the risk of cancer with increasing dose and the effects are cumulative (IARC, 2012)
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Input Data In general, cancer risk models from low-LET radiations are often fitted with data from acute exposures and relatively large doses (typically the Japanese atomic bomb survivor data and specifically the Life Span Study [LSS]
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From page 37... ...
The decision to use ERR indicates that the radiation interacts, in some fashion, with other risk factors that comprise the background risk for a particular cancer. Perhaps the most studied example is for the interactions between radiation exposure and tobacco consumption and their effects on lung cancer risk (ICRP, 2010; NRC, 1999; Pierce et al., 2003)
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, noting that planned career exposure for radiation shall not exceed 3 percent REID for cancer mortality, adjusted for age and sex, as estimated under the current NASA computational model for space radiation cancer risk projections (Cucinotta et al., 2013)
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Evidence suggesting the potential for significant sex differences in radia tion risks of lung cancer (as well as esophagus and stomach) continues to derive primarily from one study -- the study of the Japanese atomic bomb survivors.
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. ICRP specifically noted the following with respect to the application of the system of radiation protection for both sexes for ground-based applications: In view of the uncertainties surrounding the values of tissue weighting factors and the estimate of detriment, the Commission considers it appro priate for radiological protection purposes to use age- and sex-averaged tissue weighting factors and numerical risk estimates.
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. Evidence of the modifying effects of age at exposure on the association between radiation exposure and lung cancer comes primarily from the study of atomic bomb survivors from Japan (Cahoon et al., 2017)
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. The risk for each of 20 radiosensitive tissues is estimated separately according to age at exposure using risk models developed primarily from the LSS of the Japanese atomic bomb survivors.
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population. The NSCR 2012 model has incorporated a set of uncertainty estimates for the biggest uncertainty contributor, which is the radiation quality of the HZE particulate radiations that form the great majority of the astronauts' exposure, which have very high LET, in contrast to the low-LET gamma radiation that was the predominant exposure of the Japanese atomic bomb survivors.
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The effect of other combined stressors of spaceflight on cancer risk. The NASA model includes assumptions for radiation-induced excess risk in relation to time since exposure, for the DDREF, and for radiation quality.
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2019. Sex-specific lung cancer risk among radiation workers in the Million Person Study and patients TB-Fluoroscopy.
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2013. Lung cancer risks from plutonium: An updated analysis of data from the Mayak worker cohort.
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1995. Lung cancer mortality between 1950 and 1987 after exposure to fraction ated moderate-dose-rate ionizing radiation in the Canadian fluoroscopy cohort study and a comparison with lung cancer mortality in the atomic bomb survivors study.
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2019. SC 1-27: Evaluation of sex-specific differences in lung cancer radiation risks and recommendations for use in transfer and projection models.
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2003. Joint effects of radiation and smoking on lung cancer risk among atomic bomb survivors.
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2020. Lung cancer mortality associated with protracted low-dose occupational radiation exposures and smoking behaviors in U
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