Understanding space radiation health effects is critical due to potential increased morbidity and... more Understanding space radiation health effects is critical due to potential increased morbidity and mortality following spaceflight. We evaluated whether there is evidence for excess cardiovascular disease or cancer mortality in early NASA astronauts and if a correlation exists between space radiation exposure and mortality. Astronauts selected from 1959–1969 were included and followed until death or February 2017, with 39 of 73 individuals still alive at that time. Calculated standardized mortality rates for tested outcomes were significantly below U.S. white male population rates, including all-cardiovascular disease (n = 7, SMR = 33; 95% CI, 14–65) and all-cancer (n = 7, SMR = 43; 95% CI, 18–83), as anticipated in a healthy worker population. Space radiation doses for cohort members ranged from 0–78 mGy. No significant associations between space radiation dose and mortality were found using logistic regression with an internal reference group, adjusting for medical radiation. Stati...
Successfully communicating the complex risks associated with radiation exposure is a difficult un... more Successfully communicating the complex risks associated with radiation exposure is a difficult undertaking; communicating those risks within the high-risk context of space travel is uniquely challenging. Since the potential risks of space radiation exposure are not expected to be realized until much later in life, it is hard to draw comparisons between other spaceflight risks such as hypoxia and microgravity-induced bone loss. Additionally, unlike other spaceflight risks, there is currently no established mechanism to mitigate the risks of incurred radiation exposure such as carcinogenesis. Despite these challenges, it is the duty of the Space Radiation Analysis Group (SRAG) at NASA's Johnson Space Center to provide astronauts with the appropriate information to effectively convey the risks associated with exposure to the space radiation environment. To this end, astronauts and their flight surgeons are provided with an annual radiation risk report documenting the astronaut'...
this paper, we first describe the calculation of inactivation and mutation cross sections in the ... more this paper, we first describe the calculation of inactivation and mutation cross sections in the track model. The model is then fit to the several data sets for inactivation and mutation, and the inactivation and mutation probability as a function of ion charge and energy is discussed. Inactivation and Mutation Cross Sections in Track Model
This viewgraph presentation reviews the radiation exposures and risks associated with long-term s... more This viewgraph presentation reviews the radiation exposures and risks associated with long-term spaceflight on the International Space Station. NASA's risk model of cancer mortality is also presented.
Radiation shield design is driven by the need to limit radiation risks while optimizing risk redu... more Radiation shield design is driven by the need to limit radiation risks while optimizing risk reduction with launch mass/expense penalties. Both limitation and optimization objectives require the development of accurate and complete means for evaluating the effectiveness of various shield materials and body-self shielding. For galactic cosmic rays (GCR), biophysical response models indicate that track structure effects lead to substantially different assessments of shielding effectiveness relative to assessments based on LET-dependent quality factors. Methods for assessing risk to the central nervous system (CNS) from heavy ions are poorly understood at this time. High-energy and charge (HZE) ion can produce tissue events resulting in damage to clusters of cells in a columnar fashion, especially for stopping heavy ions. Grahn (1973) and Todd (1986) have discussed a microlesion concept or model of stochastic tissue events in analyzing damage from HZE's. Some tissues, including the...
... interim model. A recently developed proton dose-buildup procedure is used for estimating dose... more ... interim model. A recently developed proton dose-buildup procedure is used for estimating doses. The model considers geomagnetic shielding, magnetic-storm conditions, spacecraft shielding, and body self-shielding. Inputs to ...
Gravitational and space biology bulletin : publication of the American Society for Gravitational and Space Biology, 2003
Estimating the biological risks from space radiation remains a difficult problem because of the m... more Estimating the biological risks from space radiation remains a difficult problem because of the many radiation types including protons, heavy ions, and secondary neutrons, and the absence of epidemiology data for these radiation types. Developing useful biophysical parameters or models that relate energy deposition by space particles to the probabilities of biological outcomes is a complex problem. Physical measurements of space radiation include the absorbed dose, dose equivalent, and linear energy transfer (LET) spectra. In contrast to conventional dosimetric methods, models of radiation track structure provide descriptions of energy deposition events in biomolecules, cells, or tissues, which can be used to develop biophysical models of radiation risks. In this paper, we address the biophysical description of heavy particle tracks in the context of the interpretation of both space radiation dosimetry and radiobiology data, which may provide insights into new approaches to these pr...
High-energy protons in the galactic cosmic rays (GCR)-or generated by nuclear interactions of GCR... more High-energy protons in the galactic cosmic rays (GCR)-or generated by nuclear interactions of GCR heavy-ions with material-are capable of penetrating great thicknesses of shielding to irradiate humans in spacecraft or in lunar or Martian habitats. As protons interact with the nuclei of the elemental constituents of soft tissue and bone, low energy nuclei-target fragments-are emitted into the cells responsible for
Space radiation consists of energetic protons and other heavier ions. During the International Sp... more Space radiation consists of energetic protons and other heavier ions. During the International Space Station program, chromosome aberrations in lymphocytes of astronauts have been analyzed to estimate received biological doses of space radiation. More specifically, pre-flight blood samples were exposed ex vivo to varying doses of gamma rays, while post-flight blood samples were collected shortly and several months after landing. Here, in a study of 43 crew-missions, we investigated whether individual radiosensitivity, as determined by the ex vivo dose–response of the pre-flight chromosome aberration rate (CAR), contributes to the prediction of the post-flight CAR incurred from the radiation exposure during missions. Random-effects Poisson regression was used to estimate subject-specific radiosensitivities from the preflight dose–response data, which were in turn used to predict post-flight CAR and subject-specific relative biological effectiveness (RBEs) between space radiation and ...
High-energy protons in the galactic cosmic rays (GCR)-or generated by nuclear interactions of GCR... more High-energy protons in the galactic cosmic rays (GCR)-or generated by nuclear interactions of GCR heavy-ions with material-are capable of penetrating great thicknesses of shielding to irradiate humans in spacecraft or in lunar or Martian habitats. As protons interact with the nuclei of the elemental constituents of soft tissue and bone, low energy nuclei-target fragments-are emitted into the cells responsible for
Aviakosmicheskaia i ekologicheskaia meditsina = Aerospace and environmental medicine
Many aspects of the interplanetary radiation environment can be simulated using high-energy charg... more Many aspects of the interplanetary radiation environment can be simulated using high-energy charged-particle beams at ground based accelerator facilities. Some of the criteria and parameters used to define science requirements for such simulations are discussed. Some results from a ground-based radiation transport experiment are used to illustrate these considerations.
Understanding space radiation health effects is critical due to potential increased morbidity and... more Understanding space radiation health effects is critical due to potential increased morbidity and mortality following spaceflight. We evaluated whether there is evidence for excess cardiovascular disease or cancer mortality in early NASA astronauts and if a correlation exists between space radiation exposure and mortality. Astronauts selected from 1959–1969 were included and followed until death or February 2017, with 39 of 73 individuals still alive at that time. Calculated standardized mortality rates for tested outcomes were significantly below U.S. white male population rates, including all-cardiovascular disease (n = 7, SMR = 33; 95% CI, 14–65) and all-cancer (n = 7, SMR = 43; 95% CI, 18–83), as anticipated in a healthy worker population. Space radiation doses for cohort members ranged from 0–78 mGy. No significant associations between space radiation dose and mortality were found using logistic regression with an internal reference group, adjusting for medical radiation. Stati...
Successfully communicating the complex risks associated with radiation exposure is a difficult un... more Successfully communicating the complex risks associated with radiation exposure is a difficult undertaking; communicating those risks within the high-risk context of space travel is uniquely challenging. Since the potential risks of space radiation exposure are not expected to be realized until much later in life, it is hard to draw comparisons between other spaceflight risks such as hypoxia and microgravity-induced bone loss. Additionally, unlike other spaceflight risks, there is currently no established mechanism to mitigate the risks of incurred radiation exposure such as carcinogenesis. Despite these challenges, it is the duty of the Space Radiation Analysis Group (SRAG) at NASA's Johnson Space Center to provide astronauts with the appropriate information to effectively convey the risks associated with exposure to the space radiation environment. To this end, astronauts and their flight surgeons are provided with an annual radiation risk report documenting the astronaut'...
this paper, we first describe the calculation of inactivation and mutation cross sections in the ... more this paper, we first describe the calculation of inactivation and mutation cross sections in the track model. The model is then fit to the several data sets for inactivation and mutation, and the inactivation and mutation probability as a function of ion charge and energy is discussed. Inactivation and Mutation Cross Sections in Track Model
This viewgraph presentation reviews the radiation exposures and risks associated with long-term s... more This viewgraph presentation reviews the radiation exposures and risks associated with long-term spaceflight on the International Space Station. NASA's risk model of cancer mortality is also presented.
Radiation shield design is driven by the need to limit radiation risks while optimizing risk redu... more Radiation shield design is driven by the need to limit radiation risks while optimizing risk reduction with launch mass/expense penalties. Both limitation and optimization objectives require the development of accurate and complete means for evaluating the effectiveness of various shield materials and body-self shielding. For galactic cosmic rays (GCR), biophysical response models indicate that track structure effects lead to substantially different assessments of shielding effectiveness relative to assessments based on LET-dependent quality factors. Methods for assessing risk to the central nervous system (CNS) from heavy ions are poorly understood at this time. High-energy and charge (HZE) ion can produce tissue events resulting in damage to clusters of cells in a columnar fashion, especially for stopping heavy ions. Grahn (1973) and Todd (1986) have discussed a microlesion concept or model of stochastic tissue events in analyzing damage from HZE's. Some tissues, including the...
... interim model. A recently developed proton dose-buildup procedure is used for estimating dose... more ... interim model. A recently developed proton dose-buildup procedure is used for estimating doses. The model considers geomagnetic shielding, magnetic-storm conditions, spacecraft shielding, and body self-shielding. Inputs to ...
Gravitational and space biology bulletin : publication of the American Society for Gravitational and Space Biology, 2003
Estimating the biological risks from space radiation remains a difficult problem because of the m... more Estimating the biological risks from space radiation remains a difficult problem because of the many radiation types including protons, heavy ions, and secondary neutrons, and the absence of epidemiology data for these radiation types. Developing useful biophysical parameters or models that relate energy deposition by space particles to the probabilities of biological outcomes is a complex problem. Physical measurements of space radiation include the absorbed dose, dose equivalent, and linear energy transfer (LET) spectra. In contrast to conventional dosimetric methods, models of radiation track structure provide descriptions of energy deposition events in biomolecules, cells, or tissues, which can be used to develop biophysical models of radiation risks. In this paper, we address the biophysical description of heavy particle tracks in the context of the interpretation of both space radiation dosimetry and radiobiology data, which may provide insights into new approaches to these pr...
High-energy protons in the galactic cosmic rays (GCR)-or generated by nuclear interactions of GCR... more High-energy protons in the galactic cosmic rays (GCR)-or generated by nuclear interactions of GCR heavy-ions with material-are capable of penetrating great thicknesses of shielding to irradiate humans in spacecraft or in lunar or Martian habitats. As protons interact with the nuclei of the elemental constituents of soft tissue and bone, low energy nuclei-target fragments-are emitted into the cells responsible for
Space radiation consists of energetic protons and other heavier ions. During the International Sp... more Space radiation consists of energetic protons and other heavier ions. During the International Space Station program, chromosome aberrations in lymphocytes of astronauts have been analyzed to estimate received biological doses of space radiation. More specifically, pre-flight blood samples were exposed ex vivo to varying doses of gamma rays, while post-flight blood samples were collected shortly and several months after landing. Here, in a study of 43 crew-missions, we investigated whether individual radiosensitivity, as determined by the ex vivo dose–response of the pre-flight chromosome aberration rate (CAR), contributes to the prediction of the post-flight CAR incurred from the radiation exposure during missions. Random-effects Poisson regression was used to estimate subject-specific radiosensitivities from the preflight dose–response data, which were in turn used to predict post-flight CAR and subject-specific relative biological effectiveness (RBEs) between space radiation and ...
High-energy protons in the galactic cosmic rays (GCR)-or generated by nuclear interactions of GCR... more High-energy protons in the galactic cosmic rays (GCR)-or generated by nuclear interactions of GCR heavy-ions with material-are capable of penetrating great thicknesses of shielding to irradiate humans in spacecraft or in lunar or Martian habitats. As protons interact with the nuclei of the elemental constituents of soft tissue and bone, low energy nuclei-target fragments-are emitted into the cells responsible for
Aviakosmicheskaia i ekologicheskaia meditsina = Aerospace and environmental medicine
Many aspects of the interplanetary radiation environment can be simulated using high-energy charg... more Many aspects of the interplanetary radiation environment can be simulated using high-energy charged-particle beams at ground based accelerator facilities. Some of the criteria and parameters used to define science requirements for such simulations are discussed. Some results from a ground-based radiation transport experiment are used to illustrate these considerations.
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Papers by Mark Shavers