Space Radiation: The Number One Risk to Astronaut Health beyond Low Earth Orbit

In the paper

“This work showed that chromosome breaks were two-fold more frequent in the Apollo astronauts compared to the Gemini astronauts, suggesting for the first time a link between dose and flight duration.”

In the paper

“in the mouse model, high dose rate proton exposures resulted in comparable effects on the number of circulating white blood cells that subsequently returned to pre-irradiation levels within 30 days following exposure”

In the paper

“The WBC counts did not return to normal levels at the 30-day time point, with proton radiation exposure having the more detrimental effect.”

In the paper

“In a mouse model, T-cells did not become activated following exposure to low doses of SPE-like proton radiation, and the animals were susceptible to a non-toxic bacterial challenge of organisms (Pseudomonas aeruginosa, Klebsiella pneumoniae) that are relatively innocuous and ubiquitous on Earth and have been detected aboard the ISS [65,66].”

What the sources say

• Not checked yetcites [65] Sanzari, 2013, Leukocyte activity is altered in a ground based murine model of microgravity and proton radiation exposure, PLoS One source
• Not checked yetcites [66] Li, 2014, Hindlimb suspension and spe-like radiation impairs clearance of bacterial infections, PLoS One source

In the paper

“With respect to the different qualities of space radiation that may be encountered, the high LET radiation found in the GCR spectrum can directly or indirectly damage biomolecules (e.g., proteins, DNA, lipids), as well as organelles and cellular structures.”

In the paper

“The large ionization power of GCR ions makes them a major health threat to astronauts and constitutes one of the most important barriers impeding plans for interplanetary travel by crewed spacecraft.”

In the paper

“During transit outside of LEO, every cell nucleus within an astronaut would be traversed, on average, by a hydrogen ion every few days and by heavier HZE nuclei (e.g., 16O, 28Si, 56Fe) every few months [12].”

What the sources say

• Not checked yetcites [12] Cucinotta, 1998, The effects of delta rays on the number of particle-track traversals per cell in laboratory and space exposures, Radiat. Res. source

In the paper

“Astronauts traveling on a protracted voyage to Mars may be exposed to SPE radiation events, overlaid on a more predictable flux of GCR.”

In the paper

“The fluence of ionized nuclei that make up GCR is inversely proportional to the solar cycle and decreases by a factor of two during solar maximum [10].”

What the sources say

• Not checked yetcites [10] National Council on Radiation Protection and Measurements (NCRP) (2000). Radiation Protection Guidance for Activities in Low-Earth Orbit, NCRP.

In the paper

“Exploration missions outside of LEO will include interplanetary transits, and shielding provided by the spacecraft may not be able to completely protect astronaut crews from the effects of an SPE.”

In the paper

“Ionized transition metals, such as iron (Z = 26), are biologically harmful, as no reasonable amount of spacecraft material can shield them (Figure 2).”

In the paper

“The main radiation health risks to astronaut crews on exploration missions are degenerative vascular changes, genetic mutations and cancer [2].”

What the sources say

• Not checked yetcites [2] National Council on Radiation Protection and Measurements (NCRP) (2006). Information Needed to Make Radiation Protection Recommendations for Space Missions Beyond Low-Earth Orbit, NCRP.

In the paper

“SPE dose rates are variable over the course of an event and range from zero to 100 mGy/h inside a space vehicle and from zero to 500 mGy/h for an astronaut exposed during an extravehicular activity (EVA) on missions outside of LEO [6].”

What the sources say

• Not checked yetcites [6] Wu, H., Huff, J.L., Casey, R., Kim, M.H., and Cucinotta, F.A. (2013). Evidence Report: Risk of Acute Radiation Syndromes Due to Solar Particle Events, National Aeronautical and Space Agency.

In the paper

“Shielding is an effective countermeasure against solar particle events (SPEs), but is ineffective in protecting crew members from the biological impacts of fast moving, highly-charged galactic cosmic radiation (GCR) nuclei.”

• Also stated in: § 2.1. Galactic Cosmic Radiation · plain

  “Shielding only partially reduces the doses experienced inside a spacecraft, given the penetrating ability of HZE ions [8].”

What the sources say

• Not checked yetcites [8] Cucinotta, 2006, Evaluating shielding effectiveness for reducing space radiation cancer risks, Radiat. Meas. source

In the paper

“GCR nuclei originate from outside our solar system and are high-LET relativistic particles, possessing sufficient energies to penetrate any shielding technology used on current mission vehicles [8].”

What the sources say

• Not checked yetcites [8] Cucinotta, 2006, Evaluating shielding effectiveness for reducing space radiation cancer risks, Radiat. Meas. source

In the paper

“However, the morbidity risk and unique toxicity profiles remain poorly understood.”

In the paper

“No studies to date have adequately assessed the possibility of synergism between high-LET radiation and the stresses of the space environment.”

In the paper

“lack of knowledge about the biological effects of, and responses to, space radiation is the single most important factor limiting the prediction of radiation risk associated with human space exploration”

What the sources say

• Not checked yetcites [3] Committee on the Evaluation of Radiation Shielding for Space Exploration, Aeronautics and Space Engineering Board, Division on Engineering and Physical Sciences, and National Research Council (2008). Managing Space Radiation Risk in the New Era of Space Exploration, National Academies Press.

In the paper

“It remains unclear how moderate to large magnitude SPEs, when combined with continuous GCR exposure, will affect the health and performance of astronaut crews during interplanetary transits.”

In the paper

“Calculation of radiation exposures to astronauts in a detailed and realistic way is challenging because of the complexity of the radiation environment, the shielding effects of the vehicle and/or space suit and human anatomy and physiology.”

In the paper

“Radiation outside of LEO is composed of a toxic milieu of GCR and particles (predominantly protons) expelled from the Sun during SPEs. This mixture of radiation modalities represents the most significant physical impediment to safe human space exploration.”

In the paper

“Exposure to space radiation affects multiple organs and physiological systems in complex ways (Figure 4).”

In the paper

“Exposure to space radiation increases the risks of astronauts developing cancer, experiencing central nervous system (CNS) decrements, exhibiting degenerative tissue effects or developing acute radiation syndrome.”

What the sources say

• Not checked yetcites [4] Cucinotta, F.A., and Durante, M. (2013). Evidence Report: Risk of Radiation Carcinogenesis, National Aeronautical and Space Agency.
• Not checked yetcites [5] Cucinotta, F.A., Wang, H., and Huff, J.L. (2013). Evidence Report: Risk of Acute or Late Central Nervous System Effects from Radiation Exposure, National Aeronautical and Space Agency.
• Not checked yetcites [6] Wu, H., Huff, J.L., Casey, R., Kim, M.H., and Cucinotta, F.A. (2013). Evidence Report: Risk of Acute Radiation Syndromes Due to Solar Particle Events, National Aeronautical and Space Agency.
• Not checked yetcites [7] Huff, J.L., and Cucinotta, F.A. (2013). Evidence Report: Risk of Degenerative Tissue or other Health Effects from Radiation Exposure, National Aeronautical and Space Agency.

In the paper

“SPE radiation and the synergistic effects of spaceflight can place the crew at significant risk for prodromal effects (e.g., nausea and vomiting), skin injury, hematological changes and immune system dysfunction.”

In the paper

“Current space radiation guidelines pertain only to missions in LEO and are not considered relevant for missions beyond LEO. The acceptable levels of risk for space exploration beyond LEO have not been defined at this time and need to be dealt with before sending manned missions to colonize the moon or to deep space, such as a mission to Mars”

What the sources say

• Not checked yetcites [2] National Council on Radiation Protection and Measurements (NCRP) (2006). Information Needed to Make Radiation Protection Recommendations for Space Missions Beyond Low-Earth Orbit, NCRP.

In the paper

“Therefore, in spite of their low flux, HZE ions constitute a deleterious biological threat and contribute a significant amount to the cumulative GCR dose that astronauts will incur outside of LEO.”

In the paper

“Uncertainties with respect to dose toxicity and the complex variation in SPE and GCR spectra likely to be encountered in future exploration missions underscore the need for models that are capable of identifying particle energy and species on an event-by-event basis.”

In the paper

“The resultant radiation-induced increase in oxidative stress levels has been shown to exacerbate some degenerative tissue changes that are normally associated with aging (e.g., cardiovascular disease and cataract formation).”

In the paper

“GCR ions originate from outside our solar system and contain mostly highly energetic protons and alpha particles, with a small component of high charge and energy (HZE) nuclei moving at relativistic speeds and energies [1].”

What the sources say

• Not checked yetcites [1] Simpson, 1983, Elemental and isotopic composition of the galactic cosmic rays, Ann. Rev. Nucl. Part. Sci. source

In the paper

“In addition to GCR, unpredictable and intermittent solar particle events (SPEs) can produce large plasma clouds containing highly energetic protons and some heavy ions that may cause a rapid surge of radiation both outside and within a spacecraft (Figure 1).”

In the paper

“Created by passing through spacecraft shielding, these fission products can deliver a significant fraction of the total mission dose and have the ability to damage critical cellular components when passing through the tissues of the body.”

In the paper

“The interaction of energetic SPE protons and heavy-charged GCR particles with the spacecraft structure can produce an additional, secondary intravehicular radiation hazard.”

In the paper

“Furthermore, the interpretation of animal-based CNS studies that model the space radiation environment is limited and confounds the development of mitigation strategies and countermeasures.”

In the paper

“However, interpretation of these studies is limited by significant individual variability and insufficient statistical power [37,38,39,40].”

What the sources say

• Not checked yetcites [37] Durante, 2003, Chromosome aberration dosimetry in cosmonauts after single or multiple space flights, Cytogenet. Genome Res. source
• Not checked yetcites [38] George, 2001, Chromosome aberrations in the blood lymphocytes of astronauts after space flight, Radiat. Res. source
• Not checked yetcites [39] George, 2004, Chromosome aberrations of clonal origin are present in astronauts’ blood lymphocytes, Cytogenet. Genome Res. source
• Not checked yetcites [40] Horstman, 2005, Space radiation does not induce a significant increase of intrachromosomal exchanges in astronauts’ lymphocytes, Radiat. Environ. Biophys. source

In the paper

“It still remains to be determined whether the higher doses of radiation incurred during future exploration class missions beyond LEO will increase the threat of cancer for astronaut crews [4].”

What the sources say

• Not checked yetcites [4] Cucinotta, F.A., and Durante, M. (2013). Evidence Report: Risk of Radiation Carcinogenesis, National Aeronautical and Space Agency.

In the paper

“During long-duration exploration missions beyond LEO, it is anticipated that multiple SPEs will be encountered.”

In the paper

“Ionizing radiation can damage the CNS, causing changes to cognitive function, inducing fatigue, and generating performance decrements [2,30,42,43,44,45,46,47,48,49,50,51].”

What the sources say

• Not checked yetcites [2] National Council on Radiation Protection and Measurements (NCRP) (2006). Information Needed to Make Radiation Protection Recommendations for Space Missions Beyond Low-Earth Orbit, NCRP.
• Not checked yetcites [30] National Research Council (1990). Health Effects of Exposure to Low Levels of Ionizing Radiation: Beir V, The National Academies Press.
• Not checked yetcites [42] Butler, 2006, Neurocognitive effects of treatment for childhood cancer, Ment. Retard. Dev. Disabil. Res. Rev. source
• Not checked yetcites [43] Castro, 1985, Current considerations in heavy charged-particle radiotherapy: A clinical research trial of the university of california lawrence berkeley laboratory, northern california oncology group, and radiation therapy oncology group, Radiat. Res. Suppl. source
• Not checked yetcites [44] Fabrikant, 1985, Heavy charged-particle bragg peak radiosurgery for intracranial vascular disorders, Radiat. Res. Suppl. source
• Not checked yetcites [45] Napolitano, 1998, Neurological complications of radiotherapy and chemotherapy, J. Neurol. source
• Not checked yetcites [46] Kjellberg, 1983, Bragg-peak proton-beam therapy for arteriovenous malformations of the brain, N. Engl. J. Med. source
• Not checked yetcites [47] Levy, 1989, Stereotactic heavy-charged-particle bragg peak radiosurgery for the treatment of intracranial arteriovenous malformations in childhood and adolescence, Neurosurgery source
• Not checked yetcites [48] Schultheiss, 1995, Radiation response of the central nervous system, Int. J. Radiat. Oncol. Biol. Phys. source
• Not checked yetcites [49] Steinberg, 1990, Stereotactic heavy-charged-particle bragg-peak radiation for intracranial arteriovenous malformations, N. Engl. J. Med. source

In the paper

“Moreover, a second spaceflight apparently does not proportionately increase the yield of aberrations, suggesting a non-additive or even an infra-additive effect, raising the possibility of a radio-adaptive response in crewmembers (i.e., “radiation hormesis”).”

In the paper

“Furthermore, there is only a small probability that low-LET radiation from SPEs will reach high enough doses to cause degenerative tissue effects.”

In the paper

“The linkage between DNA lesions (including point mutations, insertions and deletions, as well as intra- and inter-chromosomal rearrangements) and carcinogenesis is well-established [27].”

What the sources say

• Not checked yetcites [27] National Council on Radiation Protection and Measurements (NCRP) (2010). Potential Impact of Individual Genetic Susceptibility and Previous Radiation Exposure on Radiation Risk for Astronauts, NCRP.

In the paper

“The veracity of data obtained and the reliability of conclusions drawn from ground-based studies using model organisms will benefit substantially from accurately simulating combined exposures to both protons and heavy ions sources.”

In the paper

“Space radiation is the number one risk to astronaut health on extended space exploration missions beyond the Earth’s magnetosphere.”

In the paper

“In general, animal experiments have contributed significantly to our understanding of the mechanisms of disease, but their value in predicting the effectiveness of treatment strategies has limitations [80,81,82].”

What the sources say

• Not checked yetcites [80] Hackam, 2006, Translation of research evidence from animals to humans, JAMA source
• Not checked yetcites [81] Perel, P., Roberts, I., Sena, E., Wheble, P., Briscoe, C., Sandercock, P., Macleod, M., Mignini, L.E., Jayaram, P., and Khan, K.S. (2007). Comparison of treatment effects between animal experiments and clinical trials: Systematic review. BMJ, 334. source
• Not checked yetcites [82] Hackam, D.G. (2007). Translating animal research into clinical benefit. BMJ, 334. source

In the paper

“The ability of humans to realize our potential by becoming a multi-planet species will hinge on, to a large extent, our ability to appropriately understand, manage, mitigate and overcome the significant dangers and health effects of space radiation.”

In the paper

“the selection of a single animal model for specific organ system studies may prove inadequate due to physiological interactions between organ systems that modify specific radiation toxicities.”

In the paper

“Animal studies performed using a ferret model indicate that retching and vomiting occur at doses as low as 50 cGy and can be expected from SPE radiation exposure at doses up to 2 Gy [67,68].”

What the sources say

• Not checked yetcites [67] King, 1988, Characterization of radiation-induced emesis in the ferret, Radiat. Res. source
• Not checked yetcites [68] Sanzari, 2013, Effects of solar particle event proton radiation on parameters related to ferret emesis, Radiat. Res. source

In the paper

“The group concluded that animal models are applicable to the following two stages of radiation research: (1) mechanisms/discovery; and (2) validation.”

What the sources say

• Not checked yetcites [79] Augustine, 2005, Animal models for radiation injury, protection and therapy, Radiat. Res. source