The Health Risks of Extraterrestrial Environments
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Welcome to The Health Risks of Extraterrestrial Environments (THREE), an encyclopedic site whose goal is to present a discussion of the space radiation environment and its health risks to humans. The intent is to make this a good starting point for researchers new to either space, radiation, or both; a source of useful information for established investigators; and a teaching tool for students.

There are links across the top of the website to five distinct pages including the Home page you are reading.

The Encyclopedia link leads to a set of articles covering all aspects of space radiation concern, as well as an introduction to each topic. Early articles contain, in Flash format, slides that were presented to students of the NASA Space Radiation Summer School. Later articles have been written by investigators active in the relevant research area and have been peer reviewed under supervision of an associate editor. These articles may be viewed in PDF format. Click on Recent Articles below for a list of the most recent postings.

Citations to reports and to articles published in the scientific literature, that the associate editors consider to be of interest to the space radiation community, are listed monthly; in most cases, together with a brief description by one of the article authors. The current month's listing may be accessed by clicking on the Current Research Citations link below. These citations are collected and archived on the Bibliography page, sorted by Encyclopedia topics, as a living bibliographic complement to the encyclopedia articles.

Reviews of recently published books on topics related to space radiation may be found under the Book Reviews link below. General news items of interest to the THREE community are listed under the In the News link below.

The Archive is a repository of material kept for reference; the site contains records documenting the history of the NASA Space Radiation Summer School, as well as information from prior Space Radiation Investigators’ Workshops and a history of Featured Articles previously featured under the Featured Article link below. A few important topics are accessible from the Multimedia link; future material will be added as appropriate.

Finally, a glossary of terms related to space radiation research is available on the similarly named page.

The THREE Editorial Board is responsible for oversight of the content and policies for this site. It is hosted by the NASA Johnson Space Center. For further information, including the latest Annual Report, please refer to the links on the left-hand side.

Contributions to any part of THREE, especially submissions for articles, are welcome. Please send your comments and contributions along with your contact information to the THREE Page Editor.

Walter Schimmerling
THREE Chief Editor

  • Current Active Detectors for Dosimetry and Spectrometry on the International Space Station (Article) Cary Zeitlin, Larry Pinsky

    Posted May 5, 2020

  • MicroRNAs (miRNAs), the Final Frontier: The Hidden Master Regulators Impacting Biological Response in All Organisms Due to Spaceflight (Article) Charles Vanderburg, Afshin Beheshti

    Posted March 9, 2020

  • TOPAS-nBio: A Monte Carlo simulation toolkit for cell-scale radiation effects (Article) J. Schuemann, A. McNamara, J. Ramos, J. Perl, K. Held, H. Zhu, S. Incerti, H. Paganetti, B. Faddegon

    Posted December 6, 2019

  • Space Radiation-Induced Cognitive Deficits Following Head-Only, Whole Body, or Body-Only Exposures (Article) Catherine M. Davis and Bernard M. Rabin

    Posted September 11, 2019

  • Track structure and the quality factor for space radiation cancer risk (PDF) Dudley T. Goodhead

    Correction Posted September 28, 2018

  • Abortive apoptosis and its profound effects on radiation‐, chemical‐, and oncogene induced carcinogenesis (PDF) Xinjian Liu, Ian Cartwright, Fang Li, and Chuan-Yuan Li

    Posted June 21, 2018

  • Using Proteomics Approaches to Assess Mechanisms Underlying Low Linear Energy Transfer or Galactic Cosmic Radiation-Induced Cardiovascular Disease (PDF) Zachary D. Brown, Muath Bishawi, and Dawn E. Bowles

    Posted May 21, 2018

  • The Emerging Role of Exosomes in the Biological Processes Initiated by Ionizing Radiation (PDF) Munira A Kadhim, Scott J Bright, Ammar H J Al-Mayah, and Edwin Goodwin

    Posted April 11, 2018

  • Solar Particle Events and Radiation Exposure in Space (PDF) Shaowen Hu

    Posted March 31, 2017

  • An introduction to space radiation and its effects on the cardiovascular system (PDF) Marjan Boerma

    Posted October 13, 2016

  • Precise Genome Engineering and the CRISPR Revolution (Boldly Going Where No Technology Has Gone Before.) (PDF) Eric A. Hendrickson

    Posted April 6, 2016

MicroRNAs (miRNAs), the Final Frontier: The Hidden Master Regulators Impacting Biological Response in All Organisms Due to Spaceflight (PDF)

Charles Vanderburg1, Afshin Beheshti1,2 *
1 Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA, 02142, USA
2 KBRWyle Labs, NASA Ames Research Center, Moffett Field CA, 94035, USA

*Corresponding Author:
Afshin Beheshti, PhD
NASA Ames Research Center
Moffett Field, CA 94035

In the past few decades biological research related to travelling in space has been rapidly growing. The majority of this research is for one purpose, to identify risks to human health that can be caused by the space environment and potential methods to mitigate these risks through development of novel countermeasures. This research will assure safer travel for astronauts involved in current missions on the International Space Station (ISS) and future long-term deep space missions to the moon and Mars. Although such biological research projects have revealed interesting findings that can potentially assist with these missions, the majority of space biology researchers have ignored a key biological factor, the microRNAs (miRNAs) that have emerged as important drivers of biological processes in human health and disease. MiRNAs are a major type of small non-coding RNA (approximately 22nt in length) that have been shown to be regulators of protein expression acting at every step from transcription to translation. One miRNA has the potential to target groups of hundreds of genes. In this comprehensive review, we will cover the history of miRNAs and the biological processes of miRNAs, our systems biology view of miRNAs, and finally the existing knowledge of miRNAs related to space biology. We will discuss the potential use of miRNAs as biological dosimeters for space radiation, the specific role of miRNAs with regard to radiation and microgravity, and the impact miRNAs have on health risks associated with spaceflight.

The new view for molecular biology related to miRNAs. A) Classical view of molecular biology. B) The miRNA related publications over time. Data was gathered from PubMed. The red dotted line shows an exponential fit to the data points. C) The new understanding of molecular biology based on miRNAs.

Donald V. Reames: “Solar Energetic Particles: A Modern Primer on Understanding Sources, Acceleration, and Propagation” (Springer, 2017). (PDF); reviewed by Stephen Kahler.

Research Scholar – Radiation Risk Modeling

The National Institute of Aerospace (NIA) has an immediate opening for a postdoctoral Research Scholar to perform radiobiology studies. The selected candidate will develop models to scale radiation damage from terrestrial radiation exposures. The successful candidate will work as part of a collaborative team on site at NASA Langley Research Center and will be expected to publish results of the work both through internal technical publications and in professional conferences and journals.
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Data Scientist

The HRP team within the Space Radiation Group at NASA Langley has a position open for a data scientist. The selected person will work on the Translational Radiation Research and Countermeasures (TRRaC) project, which is a new project starting in FY21 from the Space Radiation Element within the Human Research Program. Our team would be thankful if you share the position with colleagues and any interested parties.
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This meeting has been cancelled.
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43rd COSPAR Scientific Assembly - COSPAR 2021 Goes Hybrid

Sydney, Australia, 28 January - 4 February 2021 and 24/7 wherever you are
In light of the advice from the Australian Federal Government and with the current travel bans and need to safeguard our space research community at large, COSPAR 2021 will continue as planned, but with the addition of a major on-line component enabling the Assembly to become a hybrid in-person / virtual event. The Assembly will still be held at the same venue, the International Convention Centre Sydney, from Thursday 28 January 2021 through to Thursday 4 February 2021.
The very extensive and indeed excellent program that our Scientific Program Committee assembled for COSPAR-2020 will be carried over to the new dates, along with the line-up of inspirational international and national speakers, the interdisciplinary workshops, as well as immersive social opportunities. We are developing an approach that guarantees that every Interdisciplinary Speaker, oral presentation, poster presentation and workshop will occur at least once in a time zone friendly to attendees. Presentations will be a mix of in-person presentations from Sydney, live streaming and pre-recorded sessions. The new hybrid format will enable all presenters to have the unique opportunity of sharing their science to a much broader audience.
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Radiation Research Society's 66th Annual Meeting goes virtual

Now scheduled for October 18-21, 2020. The 2020 Virtual RRS Annual Meeting will include a complete Annual Meeting experience from the award lectures, symposia, and topical reviews to an interactive exhibit hall and networking opportunities.
By going virtual, we are able to bring you

  • 80+ educational sessions based on high quality science
  • Bonus poster-viewing time with posters and author chat open during and after the meeting
  • Live Q & A with speakers after each session
  • Enhanced exhibitor experiences with optional 1-on-1 video meet-ups
  • Multiple networking forums including virtual lounges, scheduled video calls and chats
  • 30 day access to all sessions, chats and exhibit booths
  • and, of course, no travel hassle or costs!


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ESA-FAIR Space Radiation School

Due to the current situation with COVID-19 PANDEMIA and for the safety of attendees, the 2020 ESA/FAIR Space-Radiation-Summer-School has been cancelled. The school will be rescheduled in 2021, month and day: (TBA). The project team would like to thank all of you for your understanding. Stay safe and healthy!
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RRS, NCI & NASA Collaborative Symposium

This meeting has been cancelled and will be rescheduled for 2021. The organizers have requested that paid registration fees be held for the rescheduled meeting; however, a refund may be obtained by contacting the event organizers. To request a refund please email Katie VanNatta.

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First measurements of the radiation dose on the lunar surface
Shenyi Zhang, Robert f. Wimmer-Schweingruber, Jia Yu, Chi Wang, Qiang Fu, Yongliao Zou, Yueqiang Sun, Chunqin Wang, Donghui Hou, Stephan i. Böttcher, Sönke Burmeister, Lars Seimetz, Björn Schuster, Violetta Knierim, Guohong Shen, Bin Yuan, Henning Lohf, Jingnan Guo, Zigong Xu, Johan l. Freiherr von Forstner, Shrinivasrao r. Kulkarni, Haitao Xu, Changbin Xue, Jun Li, Zhe Zhang, He Zhang, Thomas Berger, Daniel Matthiä, Christine e. Hellweg, Xufeng Hou, Jinbin Cao, Zhen Chang, Binquan Zhang, Yuesong Chen, Hao Geng, Zida Quan. Science Advances 25 Sep 2020:Vol. 6, no. 39, eaaz1334 [9/26/2020]
The Lunar Lander Neutrons and Dosimetry experiment aboard China’s Chang’E 4 lander has made measurements of the radiation exposure to both charged and neutral particles on the lunar surface. We measured an average total absorbed dose rate in silicon of 13.2 ± 1 micro-Gy/hour and a neutral particle dose rate of 3.1 ± 0.5 micro-Gy/hour. The instrumentation is described in:
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Determination of Chromosome Aberrations in Human Fibroblasts Irradiated by Mixed Fields Generated with Shielding
Tony C. Slaba, Ianik Plante, Artem Ponomarev, Zarana S. Patel, Megumi Hada. Radiat Res 1 September 2020; 194 (3): 246–258. [9/26/2020]
To better study biological effects of space radiation using ground-based facilities, the NASA Space Radiation Laboratory (NSRL) at the Brookhaven National Laboratory has been upgraded to rapidly switch ions and energies. This has allowed investigators to design irradiation protocols comprising a mixture of ions and energies more indicative of the galactic cosmic ray (GCR) environment. In this work, human fibroblasts were placed behind 20 g/cm2 aluminum and 10.345 g/cm2 polyethylene and irradiated separately by 344 MeV hydrogen, 344 MeV/n helium, 450 MeV/n oxygen, and 950 MeV/n iron ions at various doses. A multi-scale modeling approach utilizing Geant4, RITRACKS, and RITCARD was developed to predict the formation of chromosome aberrations in these experiments. The multi-scale model described herein is a significant advancement for the computational tools used to predict biological outcomes in cells exposed to highly complex, mixed ion fields related to the GCR environment. Results show that the simulation and experimental data are in good agreement for the complex radiation fields generated by all ions incident on shielding for most data points. Although improvements are needed, the model extends current capabilities for evaluating beam selection and delivery schemes at the NSRL ground-based GCR simulator and for informing NASA risk projection models in the future.
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Cancer incidence risks above and below 1 Gy for radiation protection in space
Hafner L, Walsh L, Schneider U. Life Sci Space Res. 2020 Sep 14. [9/22/2020]
The risk assessment quantities called lifetime attributable risk (LAR) and risk of exposure-induced cancer (REIC) are used to calculate the cumulative cancer incidence risks for astronauts, attributable to radiation exposure accumulated during long term lunar and Mars missions. In order to analyse the impact of a different neutron RBE on the risk quantities, a model for the neutron relative biological effectiveness (RBE) relative to gammas in the Life Span Study (LSS) is developed. The suitability of these risk assessment measures for the use of cancer risk calculation for astronauts as well as the impact of including an excess absolute risk (EAR) baseline scaling and different weightings of the excess risk models is discussed.
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The effect of low temperatures on environmental radiation damage in living systems: Does hypothermia show promise for space travel?
Fukunaga H. Int J Mol Sci. 2020 Sep 1;21(17):E6349. Review.
This literature review provides an overview of the progress to date in the interdisciplinary research field of radiation biology and hypothermia and addresses possible issues related to hypothermic treatments as countermeasures against GCR.
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Suppression of innate immune signaling molecule, MAVS, reduces radiation-induced bystander effect
Rong Jia, Yaxiong Chen, Cong Jia, Burong Hu & Yarong Du (2020) International Journal of Radiation Biology, DOI: 10.1080/09553002.2020.1807642 [8/31/20]
Mitochondrial antiviral signaling (MAVS) protein, located in the mitochondrial out-membrane, is necessary for IFN-beta induction and IFN-stimulated gene expression in response to external stress such as viral invasion and ionizing radiation (IR). Although the involvement of radiation induced bystander effect (RIBE) has been investigated for decades for secondary cancer risk related to radiotherapy, the underlying regulatory mechanisms remain largely unclear, especially the roles played by the immune factors such as MAVS. Our results indicated that the innate immune signaling molecule MAVS in recipient cells participate in RIBE. ROS is an important factor in RIBE via MAVS pathway and MAVS may be a potential target for the precise radiotherapy and radioprotection.
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Mitigation of helium irradiation-induced brain injury by microglia depletion
Allen BD, Syage AR, Maroso M, Baddour AAD, Luong V, Minasyan H, Giedzinski E, West BL, Soltesz I, Limoli CL, Baulch JE, Acharya MM.and published in J Neuroinflammation. 2020 May 19;17(1):159. [8/29/20]
The efficacy of microglial depletion in restoring the cognitive health of mice exposed to cosmic radiation was demonstrated. Specifically, long term feeding of mice with the CSF1R inhibitor to deplete microglia after a single exposure with 30 Gy of (4)HE attenuated the alterations in a battery of neurological, and learning and memory tests in mice when compared to cohorts not given the inhibitor. Collectively data suggest that microglia play a critical role in cosmic radiation-induced cognitive deficits in mice and, that approaches targeting microglial function are poised to provide considerable benefit to the charged-particle exposed brain.
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Do we really need the "detriment" for radiation protection?
Breckow, J. Radiat Environ Biophys 59, 343–348 (2020). [8/29/20]
The purpose of the ICRP detriment concept is to enable a quantitative comparison of stochastic radiation damage for the various organs. For this purpose, the organ-specific nominal risk coefficients are weighted with a function that is intended to express the amount of damage or, respectively, the severity of a disease. This function incorporates a variety of variables that do not depend on radiation parameters, but on characteristics of the disease itself. The question is raised as to whether the rather subtle way of defining the amount of damage is necessary for radiation protection purposes and whether a much simpler relationship can serve for this purpose as well or even better.
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Late effects of 1H + 16O on short-term and object memory, hippocampal dendritic morphology and mutagenesis
Kiffer F, Alexander T, Anderson J, Groves T, McElroy T, Wang J, Sridharan V, Bauer M, Boerma M, Allen A. and published in Front Behav Neurosci. 2020 Jun 26;14:96. [8/28/20]
We exposed 6-month-old male mice to whole-body 1H (0.5 Gy; 150 MeV/n; 18-19 cGy/minute) and an hour later to 16O (0.1Gy; 600 MeV/n; 18-33 Gy/min) at NASA's Space Radiation Laboratory as a galactic cosmic ray-relevant model. Mice were tested for cognitive behavior 9 months after exposure to elucidate late radiation effects. Radiation induced significant deficits in novel object recognition and short-term spatial memory (Y-maze). We detected no general effect of radiation on single-nucleotide polymorphisms in immediate early genes, and genes involved in inflammation but found a higher variant allele frequency in the antioxidants thioredoxin reductase 2 and 3 loci.
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CRaTER observations and permissible mission duration for human operations in deep space
de Wet WC, Slaba TC, Rahmanifard F, Wilson JK, Jordan AP, Townsend LW, Schwadron NA, Spence HE. Life Sci Space Res. 2020 Aug;26:149-62 [8/28/20]
Dose rates observed by the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument were used to obtain the local GCR intensity and composition as a function of time. A response function is constructed that relates observed dose rates to solar modulation potential using a series of Monte Carlo radiation transport calculations. The record of observed solar modulation potential vs. time is then used to calculate a recent historical record of permissible mission duration (PMD) according to NASA's permissible exposure limits (PEL). Tables are provided for extreme values of PMD.
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Sleep Fragmentation Exacerbates Executive Function Impairments Induced by Low Doses of Si Ions
Richard A. Britten, Arriyam S. Fesshaye, Vania D. Duncan, Laurie L. Wellman, and Larry D. Sanford Radiation Research 194(2), 116-123, (30 June 2020). [8/25/20]
Astronauts on deep space missions will be required to work autonomously and thus their ability to perform executive functions could be critical to mission success. In addition to the health risks associated with SR exposure, astronauts have to contend with other stressors, of which inadequate sleep quantity and quality are considered to be major concerns. We have previously shown that a single session of fragmented sleep uncovered latent attentional set shifting (ATSET) performance deficits in rats exposed to protracted neutron irradiation that had no obvious defects in performance under rested wakefulness conditions. It was unclear if the exacerbating impact of sleep fragmentation (SF) only occurs in rats exposed to protracted low dose rate neutron exposures. In this study, we assessed whether SF also unmasks latent ATSET deficits in rats exposed to 5 cGy 600 MeV/n 28Si ions.
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The Roles of Autophagy and Senescence in the Tumor Cell Response to Radiation
Nipa H. Patel, Sahib S. Sohal, Masoud H Manjili, J. Chuck Harrell, David A. Gewirtz. Radiation Research 194(2), 103-115, (30 June 2020). [8/24/20]
Although the scientific literature generally focuses on cell death induced by exposure to ionizing radiation, in fact, the more likely outcomes are responses to evade cell death, such as autophagy and/or senescence. This article explores the roles/involvement of autophagy (cellular self-digestion) and senescence ( a prolonged and durable form of growth arrest) in tumor cells exposed to radiation as a therapeutic modality.
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Space radiation does not alter amyloid or tau pathology in the 3xTg mouse model of Alzheimer's
Owlett L, Belcher EK, Dionisio-Santos DA, Williams JP, Olschowka JA, O'Banion MK Life Sci Space Res. 2020 Nov;27:89-98. Epub2020 Aug 3. [8/9/2020]
Space radiation can cause neuronal damage and degeneration, glial activation, and oxidative stress in the brain. Previous work demonstrated a worsening of Alzheimer’s disease-associated amyloid pathology in male APP/PS1 transgenic mice after HZE exposure. To determine whether tau pathology is altered by HZE particle or proton irradiation, we exposed 3xTg mice, which acquire both amyloid plaque and tau pathology with age, to iron, silicon, or solar particle event (SPE) irradiation at 9 months of age and evaluated behavior and brain pathology at 16 months of age. We found no differences in performance in fear conditioning and novel object recognition tasks between groups of mice exposed to sham, iron (10 and 100 cGy), silicon (10 and 100 cGy), or solar particle event radiation (200 cGy). 200 cGy SPE irradiated female mice had fewer plaques than sham-irradiated females but had no differences in tau pathology. Overall, females had worse amyloid and tau pathology at 16 months of age and demonstrated a reduced neuroinflammatory gene response to radiation. These findings uncover differences between mouse models following radiation injury and corroborate prior reports of sex differences within the 3xTg mouse model.
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Effects of partial- or whole-body exposures to 56Fe particles on brain function and cognitive performance in rats
Cahoon DS, Shukitt-Hale B, Bielinski DF, Hawkins EM, Cacioppo AM, Rabin BM. , Life Sci Space Res. 2020 Nov;27:56-63. Epub 2020 Jul 24. [8/4/2020]
To determine the possible effects that irradiation of the body might have on neuronal function and cognitive performance, rats were given head-only, body-only or whole-body exposures to 56Fe particles. Cognitive performance (novel object recognition, operant responding) was tested in one set of animals; changes in neuronal function (oxidative stress, neuroinflammation) was tested in a second set of rats. The results indicated that there were no consistent differences in either behavioral or neurochemical endpoints as a function of the location of the irradiation.
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Cellular Response to Proton Irradiation: A Simulation Study with TOPAS-nBio
Hongyu Zhu, Aimee L. McNamara, Stephen J. McMahon, Jose Ramos-Mendez, Nicholas T. Henthorn, Bruce Faddegon, Kathryn D. Held, Joseph Perl, Junli Li, Harald Paganetti, Jan Schuemann, Radiation Research, 194(1), 9-21, (13 May 2020) [7/31]
The cellular response to ionizing radiation continues to be of significant interest. DNA is recognized as the critical target for most of the biologic effects of radiation. This work presents an integrated study of simulating cell response after proton irradiation with energies of 0.5–500 MeV (LET of 60–0.2 keV/µm). A model of a whole nucleus with fractal DNA geometry was implemented in TOPAS-nBio for initial DNA damage simulations. A mechanistic repair model was then applied to predict the characteristics of DNA damage repair and dose response of chromosome aberrations. It was found that more than 95% of the DSBs are repaired within the first 24 h and the misrepaired DSB fraction increases rapidly with LET and reaches 15.8% at 60 keV/µm. The dicentric and acentric fragment yields and the dose response of micronuclei formation after proton irradiation were calculated and compared with experimental results.
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Comparative RNA-Seq transcriptome analyses reveal dynamic time-dependent effects of 56Fe, 16O, and 28Si irradiation on the induction of murine hepatocellular carcinoma
Nia AM, Khanipov K, Barnette BL, Ullrich RL, Golovko G, Emmett MR. BMC Genomics. 2020 Jul 1;21(1):453 [7/24/2020]
We performed comparative RNA-Seq transcriptomic analyses to assess the carcinogenic effects of 600 MeV/n 56Fe (0.2 Gy), 1 GeV/n 16O (0.2 Gy), and 350 MeV/n 28Si (0.2 Gy) ions in a mouse model for irradiation-induced hepatocellular carcinoma (HCC). C3H/HeNCrl mice were subjected to total body irradiation to simulate space environment HZE-irradiation, and liver tissues were extracted at five different time points post-irradiation to investigate the time-dependent carcinogenic response at the transcriptomic level. A large number of transcripts were found differentially expressed post-HZE irradiation. Additionally, a handful of novel differentially expressed unannotated transcripts were discovered for each HZE ion. Taken together, these findings may provide a better understanding of biological mechanisms underlying risks for HCC after HZE irradiation and may also have important implications for the discovery of potential countermeasures against and identification of biomarkers for HZE-induced HCC.
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Particle radiation-induced dysregulation of protein homeostasis in primary human and mouse neuronal cells
Shaler T, Lin H, Bakke J, Chen S, Grover A, Chang P Life Sci Space Res (Amst). 2020;25:9-17. [7/24/2020]
Space particle radiations may cause significant damage to proteins and oxidative stress in the cells within the central nervous system and pose a potential health hazard to humans in long-term manned space explorations., We employed a quantitative proteomics method to evaluate the impact of particle-radiation induced alterations in three major pUb-linked chains at lysine residues Lys-48 (K-48), Lys-63 (K-63), and Lys-11 (K-11), and probed for global proteomic changes in mouse and human neural cells that were irradiated with low doses of 250 MeV proton, 260 MeV/u silicon or 1 GeV/u iron ions. The results suggest that the quality of the particle radiation plays a key role in the level, linkage and cell type specificity of protein homeostasis in key populations of neuronal cells.
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Intestinal bacterial indicator phylotypes associate with impaired DNA double-stranded break sensors but augmented skeletal bone micro-structure
Irene Maier, Jared Liu, Paul M Ruegger, Julia Deutschmann, Janina M Patsch, Thomas H Helbich, James Borneman, Robert H Schiestl, Carcinogenesis, Volume 41, Issue 4, April 2020, 483–489 [7/24/2020]
Intestinal microbiota are considered a sensor for molecular pathways, which orchestrate energy balance, immune responses, and cell regeneration. We previously reported that microbiota restriction promoted higher levels of systemic radiation-induced genotoxicity, proliferative lymphocyte activation, and apoptotic polarization of metabolic pathways. Restricted intestinal microbiota (RM) that harbors increased abundance of Lactobacillus johnsonii (LBJ) has been investigated for bacterial communities that correlated radiation-induced genotoxicity.
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Assessing Nonlinearity in Harderian Gland Tumor Induction Using Three Combined HZE-irradiated Mouse Datasets
Lori J. Chappell, S. Robin Elgart, Caitlin M. Milder, Edward J. Semones, Radiation Research, 194(1), 38-51, (24 April 2020) [7/24/2020]
Several nonlinearity assumptions, including nontargeted effects in the low-dose region and cell sterilization in the high dose region, were investigated using the Harderian gland data from Alpen et al. (1993 and 1994), and Chang et al. (2016). While there was some evidence of nonlinearity that was best described using a cell-sterilization model, model fit was not substantially better than the linear model, which was adequate to describe the data. The Harderian gland tumor data do not support the addition of a nontargeted effects term in human cancer risk models.
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A methodology for investigating the impact of medical countermeasures on the risk of exposure induced death
Werneth CM, Slaba TC, Blattnig SR, Huff JL, Norman RB. Life Sci Space Res (Amst). 2020;25:72-102 . [7/16/2020]
Recent meta-analyses have demonstrated the efficacy of medical countermeasures (MCM) in the reduction of background cancer mortality and incidence rates in humans. This manuscript presents a general methodology for incorporating MCM into the NASA Space Radiation Cancer Risk model and includes modifications to the background mortality rates and radiation risk coefficients to numerically quantify the reduction of the Risk of Exposure Induced Death (REID). As an example of the method, data from aspirin and warfarin human cohort studies are employed as MCM in a sensitivity analysis to project the potential reduction in REID for crew members embarking on a one-year deep space mission.
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Protons Show Greater Relative Biological Effectiveness for Mammary Tumorigenesis with Higher ERα- and HER2-Positive Tumors Relative to γ-rays in APCMin/+ Mice
Suman, S., Shuryak, I., Kallakury, B., Brenner, D. J., Fornace, A. J., Jr, Johnson, M. D., & Datta, K. Int J Radiat Oncol Biol Phys. 2020;107(1):202-211. [7/15/2020]
This study provides insight into proton radiation-induced mammary carcinogenesis that has implications for long-duration deep space missions and breast cancer risk in astronauts. In this paper, we demonstrated that the APCMin/+ mouse model has a good signal-to-noise ratio for proton-induced mammary tumorigenesis, which also correlates with dysregulated APC observed in a substantial portion of human breast cancer patients. Our study also establishes that estrogen signaling through ERα and HER2 are actively involved in promoting breast cancer after radiation exposures, so this can provide leads for developing strategies to block aspects of the estrogenic response, which could benefit astronauts as well as radiotherapy patients. Although this study establishes the female APCMin/+ mouse as a relevant model for space radiation-induced mammary tumorigenesis studies, further experiments using GCR and SPE beams are required to address the uncertainties in breast cancer risk modeling for long duration space missions.
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Genomic mapping in outbred mice reveals overlap in genetic susceptibility for HZE ion- and γ-ray-induced tumors.
Edmondson EF, Gatti DM, Ray FA, Garcia EL, Fallgren CM, Kamstock DA, Weil MM. Sci Adv. 2020 Apr;6(16):eaax5940. [6/26/20]
Using a mouse model of genetic diversity, we find that the histotype spectrum of HZE ion-induced tumors is similar to the spectra of spontaneous and γ-ray-induced tumors and that the genomic loci controlling susceptibilities overlap between groups for some tumor types. Where it occurs, this overlap indicates shared tumorigenesis mechanisms regardless of the type of radiation exposure and supports the use of human epidemiological data from γ-ray exposures to predict cancer risks from galactic cosmic rays.
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Investigation of shielding material properties for effective space radiation protection
Naito M, Kodaira S, Ogawara R, Tobita K, Someya Y, Kusumoto T, Kusano H, Kitamura H, Koike M, Uchihori Y, Yamanaka M, Mikoshiba R, Endo T, Kiyono N, Hagiwara Y, Kodama H, Matsuo S, Takami Y, Sato T, Orimo S. Life Sci Space Res. 2020 Aug;26:69-76. Epub 2020 May 23. [6/26/20]
Geant4 Monte Carlo simulations were carried out to investigate the possible shielding materials of aluminum, polyethylene, hydrides, complex hydrides and composite materials for radiation protection in spacecraft by considering two physical parameters, stopping power and fragmentation cross section. The dose reduction with shielding materials was investigated for Fe ions with energies of 500 MeV/n, 1 GeV/n and 2 GeV/n which are around the peak of the GCR energy spectrum. Fe ions easily stop in materials such as polyethylene and hydrides as opposed to materials such as aluminum and complex hydrides including high Z metals with contain little or no hydrogen. Among hydrogenous materials, 6Li10BH4 was one of the more effective shielding materials as a function of mass providing a 20% greater dose reduction compared to polyethylene. Composite materials such as carbon fiber reinforced plastic and SiC composite plastic offer 1.9 times the dose reduction compared to aluminum as well as high mechanical strength. Composite materials have been found to be promising for spacecraft shielding, where both mass and volume are constrained.
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Mitigation of helium irradiation-induced brain injury by microglia depletion.
Allen BD, Syage AR, Maroso M, Baddour AAD, Luong V, Minasyan H, Giedzinski E, West BL, Soltesz I, Limoli CL, Baulch JE, Acharya MM J Neuroinflammation. 2020 May 19;17(1):159. [6/26/20]
Cosmic radiation exposures have been found to elicit cognitive impairments involving a wide-range of underlying neuropathology including elevated oxidative stress, neural stem cell loss, and compromised neuronal architecture. Cognitive impairments have also been associated with sustained microglia activation following low dose exposure to helium ions. Space-relevant charged particles elicit neuroinflammation that persists long-term post-irradiation. Here, we investigated the potential neurocognitive benefits of microglia depletion following low dose whole body exposure to helium ions.
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Solar modulation of the GCR flux and dose rate, observed in space between 1991 and 2019
Life Sciences in Space Research, 26. Dachev, T.P., Tomov, B.T., Matviichuk, Y.N., Dimitrov, P.G., Semkova, J.V., Koleva, R.T., Jordanova, M.M., Bankov, N.G., Shurshakov, V.A. and Benghin, V.V., [6/26/2020]
The paper presents the solar modulation of the long-term galactic cosmic rays (GCR) flux and dose rate variations, observed during 14 space experiments by 10 Bulgarian build Liulin-type spectrometers (LTS). They worked in near Earth space and in the interplanetary radiation environment between January 1991 and January 2019. The major advantage of the data sets are that they are obtained by the electronically identical LTS. The Liulin measurements of about monthly averaged flux and dose rate data are compared with the monthly values of the modulation parameter, reconstructed from the ground based cosmic ray data (Usoskin et al., 2017). A good correlation between the two data sets is observed. As the paper is focused on the L values between 4 and 6.2, only 613,397 measurements are used from more than 12 million. Most of them are available free from the "Unified Web-based Database with Liulin-type Instruments" at
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The Badhwar‐O'Neill 2020 GCR model
Slaba, T. C., & Whitman, K. (2020). Space Weather, 18, e2020SW002456 [6/24/2020]
The galactic cosmic ray environment includes a spectrum of particles from hydrogen through nickel with energies extending beyond hundreds of GeV/n. Accurately characterizing this environment is a critical aspect of mission planning, shield design, and risk assessment. The Badhwar-O'Neill (BON) GCR model is widely used by NASA and other agencies in such applications and has been recently updated. The new model, BON2020, has been calibrated to available balloon and satellite measurements including the high precision data from AMS-02 and PAMELA. Solar modulation (i.e. time dependence) is now characterized by using daily observations from the ACE/CRIS satellite. The average relative error of the BON2020 model compared to all available measurements is <1%, and is shown to be within ±15% of a large fraction of the available measurements (26,269 of 27,646 → 95%).
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Shielding effectiveness: A weighted figure of merit for space radiation shielding
DeWitt JM, Benton ER. Appl Radiat Isot. 2020 Jul;161:109141. Epub 2020 Mar 30.
The risk to space crew health and safety posed by exposure to space radiation is regarded as a significant obstacle to future human exploration missions to the Moon, Mars, and beyond. Engineers developing future spacecraft or planetary surface habitats can benefit from detailed knowledge of a broad range of possible materials that could provide improved protection to space crews from the deleterious effects of prolonged exposure to the space radiation environment. As one step towards providing this knowledge base, we have developed an empirical weighted figure of merit, referred to as shielding effectiveness, that quantifies the ability of a candidate material to shield space crews from the space radiation environment. The preliminary shielding effectiveness values for aluminum, copper, graphite, and water confirm the low Z principle for effective space radiation shielding, and, furthermore, these values tend to be lower when the effectiveness calculation is based on dose equivalent. Of the common materials studied here, at a bulkhead depth of 5 g/cm2, all materials provide a similar level of radiation protection to within standard error.
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Radioprotective effects of induced astronaut torpor and advanced propulsion systems during deep space travel
Squire T, Ryan A, Bernard S. Life Sci Space Res. 2020 Jun 10. [6/23/2020]
This study investigated how the circadian clock and body temperature may contribute to radioprotection during human torpor on deep space missions. It also explored how a decrease in transit time using electrical propulsion could result in decreased radiation dose received by astronauts. Three types of conditions were simulated to investigate the potential radioprotective effect of the circadian clock and decreased temperature on cells being exposed to radiation. These conditions were a strong/weak circadian clock, light exposure and normothermia/hypothermia and torpor. Estimated transit times for a mission to Mars from Earth utilising chemical, nuclear and electrical propulsion systems were generated using the General Mission Analysis Tool (GMAT) and Matlab. Transit times were then input into the National Aeronautics and Space Administration (NASA) Online Tool for the Assessment of Radiation In Space (OLTARIS) computer simulator to estimate doses received by an astronaut for the three propulsion methods. The simulation demonstrated an increase in radioprotection with decreasing temperature with the greatest benefit shown in cells that maintained a strong circadian clock during torpor. This was in contrast to relatively lower radioprotection in cells with a weak clock during normothermia. If torpor weakened the circadian clock a protective effect could be partially restored by an external drive such as lighting schedules to aid entrainment. The propulsion simulation estimated transit times from Earth to Mars were 258 days for chemical propulsion with 165.9mSv received, 209 days for nuclear propulsion with 134.4mSv received and 80 days for electrical propulsion with 51.4mSv received. This study suggests that a state of torpor for astronauts may provide a potential biological radiation protection strategy. Moreover, maintaining a controlled circadian rhythm during torpor conditions may aid radioprotection. Electrical propulsion may limit transit time and subsequently decrease radiation dose to astronauts.
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Absorbed doses from GCR and albedo particles emitted by the lunar surface
Zaman F, Townsend LW, de Wet WC, Schwadron NA, Spence HE, Wilson JK, Jordan AP, Smith SS, Looper MD. Acta Astronaut. 2020 May 28. [Article in Press]. [6/9/2020]
Used the MCNP6 transport code to estimate the angular and energy distribution of albedo particles at an altitude of 50 km to calculate the resulting total absorbed dose rates, which are compared with measurements from the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument aboard the Lunar Reconnaissance Orbiter (LRO) spacecraft. MCNP6 estimates that albedo particles contribute ~20% of the total absorbed dose. Albedo photons account for 9% of the absorbed dose, the highest among albedo species. The estimated dose rates are within 5% of those measured by CRaTER.
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Effects of single-dose protons or oxygen ions on function and structure of the cardiovascular system in male Long Evans rats
Sridharan V, Seawright JW, Landes RD, Cao M, Singh P, Davis CM, Mao XW, Singh SP, Zhang X, Nelson GA, Boerma M. Life Sci Space Res. 2020 Aug;26:62-8. Epub 2020 May 22. [6/1/2020]
This study used rat models to examine long-term effects of single low doses of protons and oxygen ions on function and structure of the heart. Data were obtained from a newly designed study as well as cardiac tissue specimens obtained through tissue sharing. Altogether, radiation induced only minor changes in cardiac function and pathology.
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Space Radiation Biology for "Living in Space"
Furukawa S, Nagamatsu A, Nenoi M, Fujimori A, Kakinuma S, Katsube T, Wang B, Tsuruoka C, Shirai T, Nakamura AJ, Sakaue-Sawano A, Miyawaki A, Harada H, Kobayashi M, Kobayashi J, Kunieda T, Funayama T, Suzuki M, Miyamoto T, Hidema J, Yoshida Y, Takahashi A. Biomed Res Int. 2020 Apr 8;2020:4703286. Review. [5/26/2020]
In the first part of this review, we provide an overview of the space radiation environment and briefly present current and future endeavors that monitor different space radiation environments. We then present research evaluating adverse biological effects caused by exposure to various space radiation environments and how these can be reduced. We especially consider the deleterious effects on cellular DNA and how cells activate DNA repair mechanisms. The latest technologies being developed, e.g., a fluorescent ubiquitination-based cell cycle indicator, to measure real-time cell cycle progression and DNA damage caused by exposure to ultraviolet radiation are presented. Progress in examining the combined effects of microgravity and radiation to animals and plants are summarized, and our current understanding of the relationship between psychological stress and radiation is presented. Finally, we provide details about protective agents and the study of organisms that are highly resistant to radiation and how their biological mechanisms may aid developing novel technologies that alleviate biological damage caused by radiation. Future research that furthers our understanding of the effects of space radiation on human health will facilitate risk-mitigating strategies to enable long-term space and planetary exploration.
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NASA's first ground-based Galactic Cosmic Ray Simulator: Enabling a new era in space radiobiology research
Simonsen LC, Slaba TC, Guida P, Rusek A (2020) and published in PLoS Biol 18(5): e3000669. [5/26/2020]
In June of 2018, thirty-three unique ion-energy beam combinations were delivered in rapid sequential order (under 75 minutes), cumulatively mimicking the GCR environment experienced by shielded astronauts on a deep space mission. The following October, acute and highly fractionated GCR simulation doses were delivered to three animal model systems over four weeks to investigate mixed-field quality and dose-rate effects on the risks of radiogenic cancers, cardiovascular disease, and adverse effects on the central nervous system. In the paper, "NASA's first ground-based Galactic Cosmic Ray Simulator: Enabling a new era in space radiobiology research." The authors describe how the simulator was developed, with a view to balancing the definition of mission-relevant radiation environments, facility limitations and beam selection, required hardware and software upgrades, as well as animal care and handling constraints. NASA's principal investigators utilizing the GCR 33-beam and simplified 5-ion beam simulator now have a reference detailing beam parameters and doses when discussing their experimental results.
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Challenges to the Central Nervous System During Human Spaceflight Missions to Mars
Clément GR, Boyle RD, George KA, Nelson GA, Reschke MF, Williams TJ, Paloski WH. J Neurophysiol. 2020 Apr 15. [Epub ahead of print] Review. [5/21/2020]
During the first 50+ years of human space flight, the primary interest of the neurophysiology community has been to use the sustained, but transient, elimination of gravitational stimulation to better understand the role of the vestibular and somatosensory systems in regulating spatial orientation, eye-head-hand coordination, locomotor control, and motion sickness. The implications of this research has ranged from understanding fundamental neurophysiological mechanisms, to issues in terrestrial medicine, to astronaut performance capabilities at various timeframes during and after missions. However, over the past two decades, as NASA has begun contemplating new missions of unprecedented durations and distances form Earth, a number of new questions have arisen regarding the implications of the neurophysiological and neuropsychological adaptation to the austere, isolated, confined environment that small groups of astronauts would have to endure for many months at a time, as well as the effects of continuous exposure to the low dose rate of highly charged and energetic particles of the omnipresent galactic cosmic radiation on the structure and function of the central nervous system throughout and after these missions. This article reviews the open questions and key results to date of the entire spectrum of neurophysiological studies carried out in recent years.
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Radiation-induced circulating miRNA expression in blood of head and neck cancer patients
Francesca Pasi, Franco Corbella, Ambrogia Baio, Enrica Capelli, Annalisa De Silvestri, Carmine Tinelli & Rosanna Nano. Radiation and Environmental Biophysics (2020) 59:237–244 [5/14/2020]
In recent years, scientists have found evidence confirming the aberrant expression of miRNAs in cancer patients compared to healthy individuals. The growing interest in the identification of non-invasive and specific diagnostic and prognostic molecular markers has identified microRNAs as potential candidates in cancer diagnosis, prognosis and treatment response. This study reports the expression profile of circulating miR-21, -191 and -421 in peripheral blood of head and neck cancer patients. Results showed a modulation of the microRNA expression at different time points after 6 months from the end of therapy. The trends shown in this study confirmed that miRNAs could be useful prognosis markers.
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Individual response of humans to ionising radiation: governing factors and importance for radiological protection
K. E. Applegate, W. Rühm, A. Wojcik, M. Bourguignon, A. Brenner, K. Hamasaki, T. Imai, M. Imaizumi, T. Imaoka, S. Kakinuma, T. Kamada, N. Nishimura, N. Okonogi, K. Ozasa, C. E. Rübe, A. Sadakane, R. Sakata, Y. Shimada, K. Yoshida & S. Bouffler. Radiation and Environmental Biophysics (2020) 59:185–209 [4/22/2020]
This article summarizes initial ICRP workshops, held in Japan, to engage with scientists on current knowledge of individual response to ionizing radiation. The ICRP task group asked a series of questions as part of its mandate to focus its literature review. To summarize, the article discusses what are the ways to quantify the potential impact of individual response to radiation on the incidence of cancers, non-cancer diseases and normal tissue reactions?
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Numerical investigation of radiation shielding properties of polyethylene-based nanocomposite materials in different space environments
Laurenzi S, de Zanet G, Santonicola MG. Acta Astronaut. 2020 Feb 18. [Article in Press] [4/11/2020]
In this study, we numerically investigate the radiation properties of polyethylene-based nanocomposites for space protection using the HZETRN2015 code by NASA. In particular, we analyze the role of single-walled carbon nanotubes (SWCNT) and graphene oxide (GO) nanoplatelets, at different loadings, on the equivalent dose absorbed by the nanocomposites in various radiation fields in space. The choice of polyethylene as the optimal matrix for radiation shielding was confirmed by preliminary studies on different aerospace-grade polymers, aluminium and liquid hydrogen. Simulations were performed for the case of galactic cosmic rays, solar particles events, and for the LEO radiation environment. Composites made of polyethylene and boron carbide particles were also analyzed for comparison with the carbon-filled composites. Results from simulations show that the shielding properties are comparable to the neat polyethylene at low loadings (1–5 wt%) of filler, with the GO nanoplatelets being the best reinforcement for space radiation protection among the investigated fillers.
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Altered Cognitive Flexibility and Synaptic Plasticity in the Rat Prefrontal Cortex after Exposure to Low (≤15 cGy) Doses of 28Si Radiation
Richard A. Britten, Vania D. Duncan, Arriyam Fesshaye, Emil Rudobeck, Gregory A. Nelson, and Roman Vlkolinsky. Radiation Research 193(3), 223-235, (2 February 2020). [4/11/2020]
This study measured cognitive flexibility performance, glutamatergic synaptic transmission and plasticity in the prelimbic area (PrL) of the medial prefrontal cortex (mPFC) of ~10-month-old (at the time of irradiation) male Wistar rats exposed to 1–15 cGy 600 MeV/n 28Si beams. Significantly impaired performance was seen in the simple (SD) and compound discrimination (CD) stages of the attentional set shifting (ATSET) task. However, there was a pronounced non-linear dose response for cognitive impairment The irradiated rats were also screened for performance in a task for unconstrained cognitive flexibility (UCFlex), often referred to as creative problem solving. Exposure to 1, 5 and 10 cGy resulted in a significant reduction in UCFlex performance, in an apparent all-or-none responsive manner. Importantly, performance in the ATSET test was not indicative of UCFlex performance. From a risk assessment perspective, these findings suggest that a value based on a single behavioral end point may not fully represent the cognitive deficits induced by space radiation, even within the cognitive flexibility domain. After completion of the cognitive flexibility testing, in vitro electrophysiological assessments of glutamatergic synaptic transmission and plasticity were performed in slices of the PrL cortex of 10 cGy irradiated rats. There was no obvious correlation between magnitudes of these electrophysiological decrements and the cognitive performance status of the irradiated rats. These data suggest that while radiation-induced changes in synaptic plasticity in the PrL cortex may be associated with cognitive impairment, they are most likely not the sole determinant of the incidence and severity of such impairments.
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Bcl2-induced DNA replication stress promotes lung carcinogenesis in response to space radiation
Xie M, Park D, Sica GL, Deng X. and published in Carcinogenesis. 2020 Mar 11. [Epub ahead of print] [4/11/2020]
Bcl2 not only functions as a potent antiapoptotic molecule but also as an oncogenic protein that induces DNA replication stress. To test the role and mechanism of Bcl2 in high-LET space radiation-induced lung carcinogenesis, we created lung-targeting Bcl2 transgenic C57BL/6 mice using the CC10 promoter to drive Bcl2 expression selectively in lung tissues. Intriguingly, lung-targeting transgenic Bcl2 inhibits ribonucleotide reductase activity, reduces dNTP pool size and retards DNA replication fork progression in mouse bronchial epithelial cells. After exposure of mice to space radiation derived from 56iron, 28silicon or protons, the incidence of lung cancer was significantly higher in lung-targeting Bcl2 transgenic mice than in wild type mice, indicating that Bcl2-induced DNA replication stress promotes lung carcinogenesis in response to space radiation. The findings provide some evidence for the relative effectiveness of space radiation and Bcl-2 at inducing lung cancer in mice.
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Radiation and space flights safety: An insight
Mikhail Ya.Marov. Acta Astronaut. 2020 Mar 16. [4/11/2020]
Cosmic radiation hazard is cornerstone of space flights safety. Different properties of solar electromagnetic and corpuscular radiation with emphasis on its dangerous influence on astronauts and spacecraft equipment and systems are discussed. Solar flares and GCR are of special concern. Geomagnetic storms induced by solar flares affect the ground facilities, social-economic infrastructure and global system operations involving electric power supply, aviation and ground transportation, oil-gas pipelines, geographic information system/data management (GIS), etc. As systems become more complex over time, the impacts of space weather on space flights and humanity in general are likely to increase. We analyze flare complexity and classification depending on their size, duration, morphology or magnetic topology and characteristic corpuscular radiation based on different classification systems as well protective measures to mitigate their consequences.
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The Potential Effects of Radiation on the Gut-Brain Axis
Carli B. Jones, Catherine M. Davis, and Karen S. Sfanos.Radiation Research: March 2020, Vol. 193, No. 3, pp. 209-222 [3/17/2020]
Over the course of a lifetime, humans may be exposed to different types of radiation, typically in the form of low-linear energy transfer (LET) radiation, which is used, for example, in cancer treatment. In addition, astronauts may be exposed to high-LET radiation in outer space. Here, we propose that alterations to the gastrointestinal (GI) microbiota may occur when exposure to either low- or high-LET radiation, and that these alterations may perturb important relationships that exist between the GI microbiota and human health. For example, the GI microbiota can communicate with the brain via various pathways and molecules, such as the enteric nervous system, the vagus nerve, microbial metabolites and the immune system. This relationship has been termed the “gut-brain axis”. Alterations to the composition of the GI microbiome can lead to alterations in its functional metabolic output and means of communication, therefore potentially causing downstream cognitive effects. Consequently, studying how radiation can affect this important network of communication could lead to new and critical interventions, as well as prevention strategies. Herein, we review the evidence supporting a relationship between radiation exposure and disruption of the gut-brain axis as well as summarize strategies that may be used to counter the effects of radiation exposure on the GI microbiome.
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Particle radiation-induced dysregulation of protein homeostasis in primary human and mouse neuronal cells
A, Chang P. Life Sci Space Res. 2020 Feb 21. [3/7/2020]
Space particle radiations may cause significant damage to proteins and oxidative stress in the cells within the central nervous system and pose a potential health hazard to humans in long-term manned space explorations. Dysregulation of the ubiquitin-proteasome system as evidenced by abnormal accumulation of polyubiquitin (pUb) chain linkages has been implicated in several age-related neurodegenerative disorders by mechanisms that may involve the inter-neuronal spread of toxic misfolded proteins, the induction of chronic neuroinflammation, or the inappropriate inhibition or activation of key enzymes, which could lead to dysfunction in, for example, proteolysis, or the accumulation of post-translationally-modified substrates.In this study, we employed a quantitative proteomics method to evaluate the impact of particle-radiation induced alterations in three major pUb-linked chains at lysine residues Lys-48 (K-48), Lys-63 (K-63), and Lys-11 (K-11), and probed for global proteomic changes in mouse and human neural cells that were irradiated with low doses of 250 MeV proton, 260 MeV/u silicon or 1 GeV/u iron ions. We found significant accumulation in K-48 linkage after 1 Gy protons and K-63 linkage after 0.5 Gy iron ions in human neural cells. Cells derived from different regions of the mouse brain (cortex, striatum and mesencephalon) showed differential sensitivity to particle radiation exposure. Although none of the linkages were altered after proton exposure, both K-48 and K-63 linkages in mouse striatal neuronal cells were elevated after 0.5 Gy of silicon or iron ions. Changes were also seen in proteins commonly used as markers of neural progenitor and stem cells, in DNA binding/damage repair and cellular redox pathways. In contrast, no significant changes were observed at the same time point after proton irradiation. These results suggest that the quality of the particle radiation plays a key role in the level, linkage and cell type specificity of protein homeostasis in key populations of neuronal cells.
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Comparison of signaling profiles in the low dose range following low and high LET radiation
Sridharan DM, Chien L-C, Cucinotta FA, Pluth JM. Life Sci Space Res. 2020 Feb [3/7/2020]
In this study we have investigated the kinetics and dose response of DNA double strand breaks (DSB's) for low doses of three different ions at various energies covering a wide spectrum of LET's (11 radiation qualities in all). We performed the work using three different phospho-proteins known to localize to DNA DSB's (γH2AX, pATF2, pSMC1). These phospho-proteins have unique primary activating kinases, which showed novel patterns dependent on dose and radiation quality, with solely ATM mediated phospho-proteins showing a greater persistence.
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Multi-domain cognitive assessment of male mice shows space radiation is not harmful to high-level cognition and actually improves pattern separation
Whoolery CW, Yun S, Reynolds RP, Lucero MJ, Soler I, Tran FH, Ito N, Redfield RL, Richardson DR, Shih HY, Rivera PD, Chen BPC, Birnbaum SG, Stowe AM, Eisch AJ. Sci Rep. 2020 Feb 17;10(1):2737 [3/3/20]
It is understandable that HZE particle exposure is presumed to have a negative influence on some lower and high-level cognitive functions, as many studies support this conclusion. However, our study shows this is not universally true. Mature male mice that receive whole-body exposure to two different HZE particles perform similarly to control mice on many high-level cognitive tasks, reflecting the functional integrity of key neural circuits. Strikingly, mice irradiated with either 56Fe or 28Si actually perform "better" than control mice in both appetitive and aversive pattern separation tasks. Our work urges revisitation of the generally-accepted conclusion that space radiation is detrimental to cognition.
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Radiation engineering analysis of shielding materials to assess their ability to protect astronauts in deep space from energetic particle radiation
Acta Astronaut. 2020 Feb 15. Manning B, Singleterry R. [3/3/20]
This paper is a continuation of a paper written in 2013 (Same title, AA V.91 p.49-54). These papers together look at launch mass to LEO to get astronauts to Mars and back within a GCR proxy total mission exposure limit of 150 mSv effective dose. This paper (AA 2020-Feb-15 preprint) focuses on the difference between spherical vehicles (the original paper) and right circular cylinder vehicles. It also analyzes a whole body personal protection system and the tanking of shielding materials. A newer version of OLTARIS was used along with the latest GCR environment model. As in the previous paper, liquid hydrogen, liquid methane, water, polyethylene, and aluminum are used in the analyses. This paper shows that a single SLS launch of material will get the astronauts to their total proxy limit in about 180 days. No single launch configuration of materials will get an astronaut to 400 days (a typical Mars mission duration in transit). This prompted another study reported on in AIAA SPACE 2018-5360 "Maintaining Human Health for Human-Mars" by Robert Moses, Dennis Bushnell, et. al. that showed it is possible to get humans to and from Mars within the proxy limit; however, transit times of 60 days one-way are necessary. The last item touched on in this paper is an initial investigation of the ray tracing approximation used to convert CAD models of spacecraft to radiation analysis models that can be used in codes like OLTARIS. This is prompting new research in this area.
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Protons show greater relative biological effectiveness for mammary tumorigenesis with higher ERα and HER2 positive tumors relative to γ-rays in APCMin/+ mice
Suman S, Shuryak I, Kallakury B, Brenner DJ, Fornace AJ Jr, Johnson MD, Datta K. Int J Radiat Oncol Biol Phys. 2020 Feb 6. [Epub ahead of print] [2/26/2020]
This study provides insight into proton radiation-induced mammary carcinogenesis that has implications for long-duration deep space missions and breast cancer risk in astronauts. In this paper, we demonstrated that the APCMin/+ mouse model has a good signal-to-noise ratio for proton-induced mammary tumorigenesis, which also correlates with dysregulated APC observed in a substantial portion of human breast cancer patients. Our study also establishes that estrogen signaling through ERα and HER2 are actively involved in promoting breast cancer after radiation exposures, so this can provide leads for developing strategies to block aspects of the estrogenic response, which could benefit astronauts as well as radiotherapy patients. Although this study establishes the female APCMin/+ mouse as a relevant model for space radiation-induced mammary tumorigenesis studies, further experiments using GCR and SPE beams are required to address the uncertainties in breast cancer risk modeling for long duration space missions.
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NASA GeneLab platform utilized for biological response to space radiation in animal models
McDonald JT, Stainforth R, Miller J, Cahill T, da Silveira WA, Rathi KS, Hardiman G, Taylor D, Costes SV, Chauhan V, Meller R, Beheshti A. Cancers (Basel). 2020 Feb 7;12(2):E381 [2/26/2020]
This paper uses the largest number of GeneLab datasets and provides space radiation predictions of biological responses in animal studies. Twenty-eight GeneLab omics datasets were analyzed, associated with both ground-based and spaceflight radiation studies that included in vivo and in vitro approaches. A range of ions from protons to iron particles with doses from 0.1 to 1.0 Gy for ground studies, as well as samples flown in low-Earth orbit with total doses of 1.0 mGy to 30 mGy, were utilized. Distinct biological signatures associating specific ions with specific biological responses due to radiation exposure in space were identified.
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Mathematical model of ATM activation and chromatin relaxation by ionizing radiation
Li Y, Cucinotta FA. Int J Mol Sci. 2020 Feb 12;21(4):E1214. [2/25/2020]
We propose a comprehensive mathematical model to study the dynamics of ionizing radiation induced Ataxia-telangiectasia mutated (ATM) activation that consists of ATM activation through dual mechanisms: the initiative activation pathway triggered by the DNA damage-induced local chromatin relaxation and the primary activation pathway consisting of a self-activation loop by interplay with chromatin relaxation. The model is expressed as a series of biochemical reactions, governed by a system of differential equations and analyzed by dynamical systems techniques. Radiation induced double strand breaks (DSBs) cause rapid local chromatin relaxation, which is independent of ATM but initiates ATM activation at damage sites. Key to the model description is how chromatin relaxation follows when active ATM phosphorylates KAP-1, which subsequently spreads throughout the chromatin and induces global chromatin relaxation. Additionally, the model describes how oxidative stress activation of ATM triggers a self-activation loop in which PP2A and ATF2 are released so that ATM can undergo autophosphorylation and acetylation for full activation in relaxed chromatin. In contrast, oxidative stress alone can partially activate ATM because phosphorylated ATM remains as a dimer. The model leads to predictions on ATM mediated responses to DSBs, oxidative stress, or both that can be tested by experiments.
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Role of Endoplasmic Reticulum and Mitochondrion in Proton Microbeam Radiation-Induced Bystander Effect
Chen Dong, Wenzhi Tu, Mingyuan He, Jiamei Fu, Alisa Kobayashi, Teruaki Konishi, and Chunlin Shao. Radiation Research: January 2020, Vol. 193, No. 1, pp. 63-72. [2/25/2020]
When a small portion of cells in a population of human lung fibroblast MRC-5 cells were precisely irradiated through either the nuclei or cytoplasm with counted microbeam protons, the yield of micronuclei (MN) and the levels of intracellular reactive oxygen species (ROS) in nonirradiated cells neighboring irradiated cells were significantly increased. Our results suggest that the organelles of mitochondria and ER have different roles in RIBE with respect to nuclear and cytoplasmic irradiation, and the function of ER is a prerequisite for mitochondrial activation.
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Characterization of solar energetic particle radiation dose to astronaut crew on deep-space exploration missions
Mertens CJ, Slaba TC. Space Weather. 2019 Dec;17(12):1650-8.) [2/21/2020]
Human radiation exposure from solar energetic particle (SEP) events during deep-space exploration missions has a greater impact on mission planning and operations compared to spaceflight missions to low Earth orbit. In this paper, radiation dose to the blood forming organs (BFO) of astronaut crew are calculated from a set of historical SEP events, using the design of the Orion Multi-Purpose Crew Vehicle (MPCV). The analysis of the BFO doses from the historical events presented in this paper will assist in the design of future space weather architectures by identifying models and measurements needed to expand and extend NASA's existing SEP radiation risk tools.
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Prediction of Cell Survival after Exposure to Mixed Radiation Fields with the Local Effect Model
Radiation Research 193(2), 130-142, (5 December 2019), Tabea Pfuhl, Thomas Friedrich, and Michael Scholz [2/14/2020]
In this paper, the Local Effect Model (LEM) is applied to simulate cell survival after simultaneous irradiation with ions and X-rays. To evaluate the precision of the LEM, the simulation results are compared to existing experimental data. Furthermore, the results are compared to the microdosimetric model by Zaider and Rossi and the Lesion Additivity model by LAM.
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Occam's broom* and the dirty DSB: Cytogenetic perspectives on cellular response to changes in track structure and ionization density
Cornforth MN. Int J Radiat Biol. 2020 Jan 23. [Epub ahead of print] Review. [2/6/2020]
Given equal doses, it is well-known that densely ionizing radiations are more potent in causing a number of biological effects compared to sparsely ionizing radiations, such as x- or gamma rays. According to classical models of radiation action, this results from differences in the spatial distribution of lesions along charged particle tracks. In recent years it has become fashionable instead to explain RBE/LET relationships as being due to “qualitative” differences in the types of molecular lesions that each type of radiation produces at the nanometer level. There is likely a kernel of truth to this idea, but to ignore the fact that such differences result from the distribution of lesions that span sub-micrometer cellular distances is an unjustifiably narrow stance tantamount to employing Occam’s Broom. From a cytogenetic perspective, not only are such spatial considerations indispensable in explaining the impact of ionization density upon higher order biological endpoints, the explanations they provide render arguments based principally on the quality of IR damage largely superfluous.
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Simulating galactic cosmic ray effects: Synergy modeling of murine tumor prevalence after exposure to two one-ion beams in rapid sequence
Huang EG, Wang R, Xie L, Chang P, Yao G, Zhang B, Ham DW, Lin Y, Blakely E, Sachs R. Life Sci Space Res. 2020 Jan 7. [Article in Press] [1/22]
Recent upgrades at the Brookhaven NASA Space Radiation Laboratory (NSRL) now allow mixtures in the form of different one-ion beams delivered in rapid sequence. This paper uses the results of three two-ion mixture experiments to illustrate conceptual, mathematical, computational, and statistical aspects of synergy analyses and also acts as an interim report on the mixture experiments' results. The results were interpreted using the following: (a) accumulated data from HG one-ion accelerator experiments; (b) incremental effect additivity synergy theory rather than simple effect additivity synergy theory; (c) parsimonious models for one-ion dose-effect-relations; and (d), computer-implemented numerical methods encapsulated in freely available open-source customized R software. The main conclusions are the following. As yet, the murine HG tumorigenesis experimental studies show synergy in only one case out of three. Moreover, some theoretical arguments suggest GCR-simulating mixed beams are not likely to be synergistic.
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The German Aerospace Center M-42 radiation detector—A new development for applications in mixed radiation fields.
Berger T, Marsalek K, Aeckerlein J, Hauslage J, Matthiä D, Przybyla B, Rohde M, Wirtz M. Rev Sci Instrum. 2019 Dec 1;90(12):125115. [1/6]
In the last years the Biophysics working group of the Institute of Aerospace Medicine at DLR started the development of a small low power consumption radiation detector system for the measurement of the absorbed dose to be applied in various environments as onboard aircraft, in space and also as a demonstration tool for students. These so called DLR M-42 detectors are based on an electronics design which can easily be adjusted to the user- and mission requirements. M-42 systems were already applied for measurements in airplanes, during two DLR-MAPHEUS rocket missions and have already worked flawlessly on a NASA Balloon flight over New Mexico. In addition, they will be part of the dosimetry suite of the upcoming MARE ( experiment on the NASA Artemis I mission.
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Microgravity and cosmic radiations during space exploration as a window into neurodegeneration on Earth.
Sprugnoli G, Cagle YD, Santarnecchi E. JAMA Neurol. 2019 Nov 25. [Epub ahead of print] [01/02]
Astronauts involved in long-duration spaceflight missions are exposed to microgravity and cosmic radiations, considered responsible of profound changes in brain structure and function. In particular, microgravity is related to cephalad fluid shift that potentially affects protein clearance mechanisms, while cosmic radiations seem to promote the accumulation of amyloid-β in mouse models, and consequently alter hippocampus-related cognition. A pattern of “spaceflight-induced accelerated brain aging” emerges, raising on one hand important issues about astronauts’ health, while, on the other, offering the opportunity to deepen the understanding of neurodegenerative diseases on Earth and develop potential countermeasures.
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Aggressive mammary cancers lacking lymphocytic infiltration arise in irradiated mice and can be prevented by dietary intervention.
Omene C, Ma L, Moore J, Ouyang H, Illa-Bochaca I, Chou W, Patel MS, Sebastiano C, Demaria S, Mao JH, Karagoz K, Gatza ML, Barcellos-Hoff MH. Cancer Immunol Res. 2019 Dec 12. [Epub ahead of print] [12/29]
Using a radiation-genetic mammary chimera model we developed to evaluate how carcinogenesis is affected by radiation-induced, non-mutational processes, we examined the relationship between tumor microenvironment (TME) components and breast cancer phenotypes arising from Trp53-null mammary chimeras as a function of two factors, radiation type and host age. Densely ionizing radiation (DIR), which is present in the space radiation environment and used in radiation oncology, has potentially greater carcinogenic effect compared to sparsely ionizing radiation (SIR) that is prevalent on earth. Because occupational exposure (e.g. astronauts) and most radiotherapy occur in adults, here, we considered age at exposure as a factor. Here we show that compared to our prior studies in 10 week-old mice, the effect of radiation quality was greater in aged mice (10 months old), demonstrating that DIR was more effective than SIR at inducing aggressive tumors. However, tumors arising in both DIR- and SIR-irradiated hosts were characterized by rapid growth rate and an immunosuppressive TME, both of which we have previously reported in young mice. Only tumors arising in irradiated mice were devoid of lymphocytic infiltrates, suggesting that non-mutational, radiation effects promoted immune evasion. This prompted us to use caffeic acid phenethyl ester (CAPE), the major active component in propolis, a honeybee product that possesses immunomodulatory (anti-inflammatory) and anti-cancer properties. CAPE administered post-radiation in the diet of 10-week old mice prevented establishment of aggressive tumors with an immunosuppressive TME. These studies suggest that systemic inflammation and erosion of antitumor immunity elicited by radiation can be targeted after exposure to prevent aggressive tumors.
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Cranial irradiation mediated spine loss is sex-specific and complement receptor-3 dependent in male mice.
Hinkle JJ, Olschowka JA, Love TM, Williams JP, O'Banion MK. Sci Rep. 2019 Dec 11;9(1):18899. [12/26]
Previous rodent studies demonstrated that irradiation induces significant loss in dendritic spine number and alters spine morphology; these changes are associated with behavioral task deficits. In the current study sexual dimorphisms in irradiation-mediated alterations of microglia activation markers and dendritic spine density are described. Moreover, the significant dendritic spine loss observed in male mice following irradiation was complement receptor 3 (CR3)-dependent, revealing a specific and targetable mechanism for radiation effects on synaptic structure.
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Design and dosimetry of a facility to study health effects following exposures to fission neutrons at low dose rates for long durations.
Int J Radiat Biol. 2019 Nov 5. [Epub ahead of print] Borak TB, Heilbronn L, Krumland N, Weil MM. [12/24]
We developed a vivarium in which rodents could be irradiated with neutrons for protracted periods of time. The neutron source is a panoramic irradiator containing 252Cf located in a concrete shielded vault with a footprint of 53 m2. The vault can accommodate sufficient caging to simultaneously irradiate 900 mice and 60 rats for durations up to 400 d at a dose rate of 1 mGy/d and is approved for extended animal husbandry. Mixed field dosimetry was performed using a miniature GM counter and CaF2:Dy thermoluminescent dosimeters (TLD) for photons and tissue-equivalent proportional counters for neutrons. The photon contribution is 20% of the total dose. The uncertainty in the delivered dose is estimated to be ±20%. The dose averaged LET for the charged particle recoil nuclei is 68 keV/µ.
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Effects of chronic exposure to a mixed field of neutrons and photons on behavioral and cognitive performance in mice.
Perez R, Younger S, Bertheau E, Fallgren C, Weil M, Raber J. Behav Brain Res. 2019 Nov 22. [Epub ahead of print] [12/18]
In this study, the effects of high LET radiation delivered at low dose rate which may have relevance to space radiation exposures received by astronauts beyond low Earth orbit were assessed. More specifically, we assessed the effects chronic neutron exposure starting at 60 days of age on behavioral and cognitive performance of BALB/c female and C3H male mice at 600 and 700 days of age. Dose- and time point-dependent effects on various distinct measures of behavioral and cognitive performance of BALB/c female and C3H male mice were revealed. Different outcome measures show distinct dose-response relationships, with some anticipated to worsen performance during space missions, like increased measures of anxiety, while other anticipated to enhance performance, such as increased nest building and object recognition.
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Comments on "New concerns for neurocognitive function during deep space exposures to chronic, low dose rate, neutron radiation."
Bevelacqua JJ, Welsh J, Mortazavi S. eNeuro. 2019 Dec 17. [Epub ahead of print] [12/4]
Evaluations of the biological effects of space radiation must carefully consider the biological system response and the specific nature of the source term. Acharya et al. review neurocognitive function during deep space exposures to chronic, low dose rate, neutron radiation, but do not utilize a source term that reflects the actual space environment in terms of radiation types and their respective energies. In addition, important biological effects including adaptive response to the space radiation environment are not addressed.
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The Future of Low Dose Radiation Research in the United States: Proceedings of a Symposium. Washington, DC: The National Academies Press, 2019
National Academies of Sciences, Engineering, and Medicine; Division on Earth and Life Studies; Nuclear and Radiation Studies Board; Ourania Kosti, Rapporteur
Exposures at low doses of radiation, generally taken to mean doses below 100 millisieverts, are of primary interest for setting standards for protecting individuals against the adverse effects of ionizing radiation. However, there are considerable uncertainties associated with current best estimates of risks and gaps in knowledge on critical scientific issues that relate to low dose radiation. The Nuclear and Radiation Studies Board of the National Academies hosted the symposium on The Future of Low Dose Radiation Research in the United States on May 8 and 9, 2019. The goal of the symposium was to provide an open forum for a national discussion on the need for a long-term strategy to guide a low dose radiation research program in the United States. The symposium featured presentations on low dose radiation programs around the world, panel discussions with representatives from governmental and nongovernmental organizations about the need for a low dose radiation research program, reviews of low dose radiation research in epidemiology and radiation biology including new directions, and lessons to be learned from setting up large research programs in non-radiation research fields. This publication summarizes the presentation and discussion of the symposium.
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Reproductive hazards of space travel in women and men.
Mishra B, Luderer U. Nat Rev Endocrinol. 2019 Oct 14. [Epub ahead of print.[11/16]
This paper reviews the effects of space flight in low earth orbit, cosmic radiation, microgravity, and hypergravity on the reproductive systems of females and males. Studies performed on Earth in which rodents were exposed to experimentally generated high charge and energy particles like those found in cosmic radiation have shown that developing eggs in the ovaries and developing sperm cells in the testes are highly sensitive to destruction by these particles. Exposure to microgravity during space flight and experimental microgravity on Earth disrupts sperm development and testosterone production in rodents, while the male reproductive system seems to adapt to moderate hypergravity. Exposure to microgravity during the second half of pregnancy does not cause major disruptions of fetal development or parturition in rodents. Many gaps remain in our understanding of the reproductive hazards of space travel.
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Physical characteristics at the turnover-points of relative biological effect (RBE) with linear energy transfer (LET).
Jones B, Hill MA. Phys Med Biol. 2019 Oct 30. [Epub ahead of print] [11/13]
This article shows that ions of each lighter element (up to Ferric ions) exert their maximum relative biological effect (RBE) at unique values of ionisation clustering (denoted by a linear energy transfer of LETU). This is the LET value at which RBE (and radiosensitivity) begins to fall with further increases of LET. At LETU the ions are at 0.99 of their fully expressed nuclear charge and share some kinematic properties: a velocity of 3-4 nm.fs-1 per nucleon, or around 6-8 nm.fs-1 per unit Z, dimensions that are relevant to radiochemical changes and to DNA and nucleosome.
These findings differ from conclusions drawn from pooled ionic RBE data, which have previously assumed that the maximum bio-effect of all light ions occured at a LET of around 120 keV per micrometre. There are potential implications for future RBE estimations (based on LET and absorbed dose) in radiotherapy, radioprotection and space travel.
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Meta-analysis of Cognitive Performance by Novel Object Recognition after Proton and Heavy Ion Exposures.
Cacao and Francis A. Cucinotta Radiation Research: November 2019, Vol. 192, No. 5, pp. 463-472. (2019) [11/9]
Experimental studies of cognitive detriments in mice and rats after proton and heavy ion exposures have been performed by several laboratories to investigate possible risks to astronauts exposed to cosmic rays in space travel and patients treated for brain cancers with proton and carbon beams in Hadron therapy. However, distinct radiation types and doses, cognitive tests and rodent models have been used by different laboratories, while few studies have considered detailed dose-response characterizations, including estimates of relative biological effectiveness (RBE). Here we report on the first quantitative meta-analysis of the dose response for proton and heavy ion rodent studies of the widely used novel object recognition (NOR) test, which estimates detriments in recognition or object memory. Our study reveals that linear or linear-quadratic dose-response models of relative risk (RR) do not provide accurate descriptions. However, good descriptions for doses up to 1 Gy are provided by exponentially increasing fluence or dose-response models observed with an LET dependence similar to a classical radiation quality response, which peaks near 100–120 keV/µm and declines at higher LET values. Exponential models provide accurate predictions of experimental results for NOR in mice after mixed-beam exposures of protons and 56Fe, and protons, 16O and 28Si. RBE estimates are limited by available X-ray or gamma-ray experiments to serve as a reference radiation. RBE estimates based on use of data from combined gamma-ray and high-energy protons of low-LET experiments suggest modest RBEs, with values <8 for most heavy ions, while higher values <20 are based on limited gamma-ray data. In addition, we consider a log-normal model for the variation of subject responses at defined dose levels. The log-normal model predicts a heavy ion dose threshold of approximately 0.01 Gy for NOR-related cognitive detriments.
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Acute radiation risk assessment and mitigation strategies in near future exploration spaceflights.
Hu S, Barzilla JE, Semones E. Life Sci Space Res. 2019 Oct 31. [Article in Press] [11/9]
A brief summary of the features of radiation exposure if astronauts encounter severe SPEs beyond Low Earth Orbit (LEO), the evidence of ARS radiobiological studies at exposure levels close to recommended limits, and the shortcomings of previous dose projection approaches for ARS risk assessment. Some ARS biomathematical models, particularly those pertinent to the dose ranges that severe SPEs beyond LEO could generate, are reviewed and evaluated, focusing on their capability to predict the incidence of performance incapacitation and time-phased health effects with subsequent medical care recommendations. Using onboard active dosimeter input for estimating organ doses and likely clinical outcomes for SPEs in real time, a new strategy for ARS assessment and mitigation is described to cope with the potential threats of severe SPEs for planned deep space missions.
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Predictions of cognitive detriments from galactic cosmic ray exposures to astronauts on exploration missions.
Cucinotta FA, Cacao E. Life Sci Space Res. 2019 Oct 16. [Article in Press] [10/16]
For the first-time we report on predictions on cognitive detriments from galactic cosmic ray (GCR) exposures on long-duration space missions outside the protection of the Earth's magnetosphere and solid body shielding. Estimates are based on a relative risk (RR) model of the fluence response for proton and heavy ion in rodent studies using the widely used novel object recognition (NOR) test, which estimates detriments in recognition or object memory. Our recent meta-analysis showed that linear and linear-quadratic dose response models were not accurate, while exponential increasing fluence response models based on particle track structure provided good descriptions of rodent data for doses up to 1 Gy. Using detailed models of the GCR environment and particle transport in shielding and tissue, we predict the excess relative risk (ERR) for NOR detriments for several long-term space mission scenarios. Predictions suggest ERR < 0.15 for most space mission scenarios with ERR<0.1 for 1-year lunar surface missions, and about ERR~0.1 for a 1000 day Mars mission for average solar cycle conditions. We discuss possible implications of these ERR levels of cognitive performance detriments relative to other neurological challenges such as rodent models of Alzheimer's disease (AD), Parkinson's disease (PD) and traumatic brain injury (TBI). Comparisons suggest a small but potentially clinically significant risk for possible space mission scenarios.
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Enhanced GEANT4 Monte Carlo simulations of the space radiation effects on the International Space Station and Apollo missions using high-performance computing environment.
Lund M, Jevremovic T. Acta Astronaut. 2019 Dec;165:219-28. Epub 2019 Sep 19. [10/10]
This paper introduces a new simulation model and application using GEANT4 with multithreading and Message Passing Interface (MPI) that greatly reduces computational time to hours instead of weeks without any post simulation processing based on high-performance computing. This paper also introduces a new set of GEANT4 computational detectors for calculating dose distribution, besides the historically used International Commission of Radiation Units simulation spheres. The computational detectors include a thermoluminescent detector, tissue equivalent proportional counter, and human phantom, along with additional new scorers to calculate dose equivalence based on the International Commission of Radiation Protection standards. This study presents GEANT4 simulations of the dose deposition for the International Space Station and the Apollo 11 and 14 missions, which replicate well the dose measurements during these missions. The simulations of both Apollo missions show consistent doses from galactic cosmic rays and radiation belts with a small variation in dose distribution across the Apollo capsule. The greatest contributor to radiation dose for both Apollo missions in the simulations came from galactic cosmic rays. Simulations of historical solar particle events during an Apollo missions show a solar particle event would not be fatal and below mission limits. These GEANT4 models also provides the values of the dose deposition and dose equivalent for various organs within a human phantom in the International Space Station and Apollo command module, which are developed for the first time using this GEANT4 based application.
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Ethical challenges in human space missions: A space refuge, scientific value, and human gene editing for space.
Szocik K, Norman Z, Reiss MJ. Sci Eng Ethics. 2019 Sep 3. [Epub ahead of print] [10/10]
This article examines some selected ethical issues in human space missions including human missions to Mars, particularly the idea of a space refuge, the scientific value of space exploration, and the possibility of human gene editing for deep-space travel. Each of these issues may be used either to support or to criticize human space missions. We conclude that while these issues are complex and context-dependent, there appear to be no overwhelming obstacles such as cost effectiveness, threats to human life or protection of pristine space objects, to sending humans to space and to colonize space. The article argues for the rationality of the idea of a space refuge and the defensibility of the idea of human enhancement applied to future deep-space astronauts.
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Older Research Citations may be found in the Bibliography.


Basic Concepts of Space Radiation

In order to understand the space radiation risks faced by human explorers, it is necessary to have a clear idea of what it is, where it is, and what happens when space radiation interacts with matter. The articles in this section describe the space radiation environment, the nuclear and atomic interactions with the constituent atoms of materials – especially living materials – in space, and the ways in which energy is deposited in biologically significant molecules.

Some of the articles are taken from the Appendices of a 1998 Strategic Plan I authored during my tenure at NASA and others are presentations given by NASA Summer School faculty. There is a fair amount of overlap, both within this section and between this section and other sections, where the subjects are discussed in greater detail. This is welcome, reflecting as it does, different – and broadening – perspectives on the topics covered.

Walter Schimmerling
THREE Chief Editor

  • The Space Radiation Environment
    • The Natural space Ionizing Radiation Environment* – Patrick O’Neill (Article)
    • Fluence Rates, Delta Rays and Cell Nucleus Hit Rates from Galactic Cosmic Rays – Stanley B Curtis (PDF)
    • Solar Particle Events and Radiation Exposure in Space* – Shaowen Hu (PDF)
  • Interactions of Radiation with Matter
    • Interactions of Radiation with Matter – Walter Schimmerling (Article)
    • Particle Interactions Overview – Lawrence Heilbronn (swf)
    • Physics Summary – Lawrence Heilbronn (swf)
    • Neutron Properties and Definitions – Lawrence Heilbronn (swf)
    • Neutron Lectures Supplement – Lawrence Heilbronn (PDF)
  • Dose and Dose Rate Effectiveness Factors – Walter Schimmerling  (Article)
    • Low LET Physics Topics – Gregory Nelson (swf)  Introduction (PDF)
    • A Note On The Dose-Rate-Effectiveness Factor and its Progeny 
      DDREF -  R.J.M. Fry (PDF)
  • Track Structure
    • Introduction to Track Structure and z*22 - Stanley B. Curtis (PDF)
    • Radiation Quality and Space Radiation Risks – Francis Cucinotta (swf)
    • Development of Monte Carlo Track Structure Codes – Larry Toburen (PDF)
    • Microdosimetry and Detector Responses – Leslie A. Braby (PDF)
    • Interpreting Microdosimetric Spectra – J. F. Dicello and F. A Cucinotta (PDF)
    • Monte Carlo Track Simulations – Michael Dingfelder (PDF)
    • Radiation Track Structure – Dudley T. Goodhead (swf) Abstract (PDF)
  • Elementary Concepts of Shielding – Walter Schimmerling  (PDF)
    • Heavy Ions and Shielding Physics – Lawrence Heilbronn (swf)


Introduction to THREE
Walter Schimmerling

Video presentation of
Research Solutions to Space Radiation Impacts on Human Exploration
Slides in PDF format
Francis A. Cucinotta, Ph.D.
Chief Scientist, Space Radiation Program
NASA Johnson Space Center
Houston, Texas
Aerospace Medicine Grand Rounds
March 23, 2010

Radiation and Human Space Exploration Video
NASA Human Research Program

Radiation tracks and radiation track simulation video
Ianik Plante, Ph.D.
Universities Space Research Association
Division of Space Life Sciences
NASA Johnson Space Center
Houston, Texas

Radiation tracks and radiation track simulation video is excerpted from the article:
Radiation chemistry and oxidative stress (PDF)
Ianik Plante, Ph.D.

Video Presentation of
Space Radiation and Cataracts
Eleanor Blakely
Life Sciences, Lawrence Berkeley National Laboratory
Berkeley, California
July 16, 2003


Glossary derived from:
Human Research Program Integrated Research Plan, Revision A, (January 2009). National Aeronautics and Space Administration, Johnson Space Center, Houston, Texas 77058, pages 232-280.

Exploration Systems Radiation Monitoring Requirements (Sept 2012). Page ii. Ronald Turner.

Report No. 153: Information Needed to Make Radiation Protection Recommendations for Space Missions Beyond Low-Earth Orbit (2006). National Council on Radiation Protection and Measurements, pages 309-318.  Reprinted with permission of the National Council on Radiation Protection and Measurements.

Managing Space Radiation Risk in the New Era of Space Exploration (2008). Committee on the Evaluation of Radiation Shielding for Space Exploration, National Research Council. National Academies Press, pages 111-118.

Contents: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

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AAPM: American Association of Physicists in Medicine.

absolute risk: Expression of excess risk due to exposure as the arithmetic difference between the risk among those exposed and that obtaining in the absence of exposure.

absorbed dose (D): Average amount of energy imparted by ionizing particles to a unit mass of irradiated material in a volume sufficiently small to disregard variations in the radiation field but sufficiently large to average over statistical fluctuations in energy deposition, and where energy imparted is the difference between energy entering the volume and energy leaving the volume. The same dose has different consequences depending on the type of radiation delivered. Unit: gray (Gy), equivalent to 1 J/kg.

ACE: Advanced Composition Explorer Mission, launched in 1997 and orbiting the L1 libration point to sample energetic particles arriving from the Sun and interstellar and galactic sources.  It also provides continuous coverage of solar wind parameters and solar energetic particle intensities (space weather).  When reporting space weather, it can provide an advance warning (about one hour) of geomagnetic storms that can overload power grids, disrupt communications on Earth, and present a hazard to astronauts.

acute effects: short-term biological effects of exposure to radiation, including headaches, dizziness, nausea, and illness that can range from mild to fatal.

acute exposure: Radiation exposure of short duration.

AGS: Alternating Gradient Synchrotron (at Brookhaven National Laboratory).

ALARA (As Low As Reasonably Achievable):  An essential operational safety requirement, as well as a regulatory requirement, that em­phasizes keeping exposure to radiation as low as possible using reasonable methods, and not treating dose limits as “tolerance values”; defined at NASA as limiting radiation exposure to a level that will result in an estimated risk below the limit of the 95 percent confidence level.

albedo: secondary radiation produced by interactions of galactic cosmic rays and high-energy solar protons with matter in the atmosphere or on the surface.

ALL: acute lymphocytic leukemia.

alpha particle: An energetic charged nucleus consisting of two protons and two neutrons. This particle is identical to the 4He nucleus.

ALTEA: Anomalous Long-Term Effects in Astronauts study .

AM: amplitude modulation.

AMA: American Medical Association.

AMAC: American Medical Advisory Committee.

AML: acute myelogenous leukemia.

Amu: atomic mass unit (ALSO: u).

ANLL: acute nonlymphocytic leukemia.

annual risk: The risk in a given year from an earlier exposure. The annual risk (average) from an exposure is the lifetime risk divided by the number of years of expression.

ANP: atrial natriuretic peptide.

ANS: American Nuclear Society.

ANSI: American National Standards Institute.

AU: Astronomical Unit (distance from the Earth to the Sun)

Apoe4: Apoliprotein E isoform 4. Modification of Apo4 is major risk factor in Alzheimer's disease.

apoptosis: A specific mode of cell death (also known as programmed cell death) that can be triggered by exposure to radiation, especially in cells of lymphoid/myeloid or epithelial lineage. Extensive apoptosis contributes to the hematopoietic and gastrointestinal symptoms seen in acute radiation syndrome.

ARC: NASA Ames Research Center.

Ares V/Heavy Lift Launch Vehicle: a NASA vehicle intended to deliver cargo from Earth to low Earth orbit.

ARM: Atmospheric Radiation Measurements.

ascent stage: The pressurized upper stage of the Lunar Lander in which the crew pilots the lander from lunar orbit to the lunar surface and return. The ascent stage takes off from the descent stage, leaving the latter behind on the surface.

AT: ataxia telangiectasia.

ATM: ataxia telangiectasia mutated.

AU: Astronomical Unit (Approx. distance from the Earth to the Sun)

AX-2: NASA Ames Research Center Experimental Suit 2, designed during the Apollo program as a lunar surface hard suit to bend at the waist and rotate in the torso so that the crew member can reach down to the ground with one hand. Fabricated from fiberglass.

AX-5: NASA Ames Research Center Experimental Suit 5, designed during the Space Station Advanced Development program to provide a durable hard suit for extended operations in zero gravity. Fabricated from numerically milled aluminum forgings.

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background radiation: The amount of radiation to which a member of the population is exposed from natural sources, such as terrestrial radiation from naturally-occurring radionuclides in the soil, cosmic radiation originating in outer space, and naturally-occurring radionuclides deposited in the human body. The natural background radiation received by an individual depends on geographic location and living habits. In the United States, the background radiation is on the order of 1 mSv y–1, excluding indoor radon which amounts to ~2 mSv/year on average.

BAF: Booster Applications Facility (the name used to designate the NSRL during planning and construction phases).

BaRyoN: Quark bound state with zero strangeness.

BCC: basal cell carcinoma.

BCD: budget change directive.

BEIR: Biological Effects of Ionizing Radiation. One of a series of reports on the health risks from exposure to low levels of ionizing radiation issued by the Committee to Assess Health Risks from Exposure to Low Levels of Ionizing Radiation, Board on Radiation Effects, Research Division on Earth and Life Studies, National Research Council of the National Academies of Science of the United States, referred to by a Roman number denoting its position in the sequence of reports. At the time of this writing, the latest report is BEIR VII.

BEVALAC: An accelerator system at Lawrence Berkeley National Laboratory consisting of the Bevatron (an early, high-energy synchrotron accelerator constructed in the 1950s and used to discover the antiproton), accelerating particles delivered by the SuperHILAC (first built as the HILAC - Heavy Ion Linear Accelerator - in 1957; along with a similar one at Yale University, the first machine in the US built specifically to accelerate heavy ions, completely rebuilt into the SuperHILAC in 1971). Closed in 1993.

biological end point: effect or response being assessed, e.g., cancer, cataracts.

bipolar device: a type of semiconductor whose operation is based on both majority and minority carriers.

BNL: Brookhaven National Laboratory in Upton (Long Island), New York.

BRCA1: breast cancer 1 tumor suppressor gene.

BRCA2: breast cancer 2 tumor suppressor gene.

BrdU: bromodeoxyuridine.

BRYNTRN: BaRYoN TRaNsport code, a computer code for simulating baryon transport.

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CAD: computer aided design.

CaLV: Cargo Launch Vehicle.

CAM : computerized anatomical man model.

carbon composite: a composite incorporating carbon and other materials for use in lightweight structures, strong enough to substitute for aluminum and other metals in the construction of many parts of a spacecraft, notably the pressure vessel shell. It may incorporate boron, epoxy, polyethylene, hydrogen, or other materials that enhance radiation shielding properties.

CARD: Constellation Architecture Requirements Document; CxP 7000

cargo habitat: a crew habitat that the Lunar Lander carries for delivery to the Lunar Outpost as a key part of the “Outpost-first” strategy considered by NASA as part of the Space Exploration Initiative program.

CB: Control Board.

CDC: Center for Disease Control and Prevention.

CEDE: committed effective dose equivalent.

CENELEC: European Committee for Electrotechnical Standardization.

CEQATR: Constellation Program Environmental Qualification and Acceptance Testing Requirements; CxP 70036

CERN: European Organization for Nuclear Research.

CEV: Crew Exploration Vehicle.

CFR: Code of Federal Regulations.

CHMO: Chief Health And Medical Officer (NASA).

chronic effects: long-lasting effects of exposure to radiation; includes cancer, cataracts, and nervous system damage.

chronic exposure: Radiation exposure over long times (continuous or fractionated).

CI: confidence interval.

CL: confidence level.

CLV: Crew Launch Vehicle.

CME: coronal mass ejection, an explosion of plasma released from the atmosphere (or corona) of the Sun.

CML: chronic myelogenous leukemia.

CNP: cyclic nucleotide phosphatase.

CNS: central nervous system.

Composites: materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct at the macroscopic or microscopic scale within the finished structure.

computerized anatomical male/female: a model of human geometry used to evaluate radiation doses at various points inside the body.

Constellation system: the complete ensemble of launch vehicles, flight vehicles, ground support, support services, and lunar and planetary surface systems associated with the Vision for Space Exploration initiated during the Bush administration.

coronal mass ejection (CME): A transient outflow of plasma from or through the solar corona which may be associated with the generation of solar-particle events.

cosmic-ray modulation: The variation of the observed cosmic-ray intensity as a function of the solar cycle. The cosmic-ray intensity within the solar system is observed to vary approximately inversely with the solar activity cycle that controls the interplanetary magnetic field.

COTS: commercial, off-the-shelf.

CPD: crew passive dosimeter.

CPU: central processor unit.

CRaTER: Cosmic Ray Telescope for the Effects of Radiation.

CRCPD: Conference of Radiation Control Program Directors.

CREME96: Cosmic Ray Effects on Micro-Electronics (1996 revision), a computer code.

cross section (σ): probability per unit particle fluence of a given end point. Unit: cm2.

CT: computed tomography.

CTA: conditioned taste aversion.

CVD: cardiovascular disease.

CW: continuous wave.

CxP: Constellation Program.

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Dr: dose-rate (Gy/hr).

DAAC: Distributed Active Archive Center.

DDREF: dose and dose-rate effectiveness factor (the degree to which both dose and dose rate may influence the biological effects of exposure to a given dose of radiation).

delta rays: Electrons directly ejected from atoms in matter by radiation.

descent stage: The lower stage of the Lunar Lander that includes the descent and landing engines and propellant tanks to serve them. The crew ascending back to lunar orbit in the ascent stage leaves the descent stage behind on the lunar surface.

descent stage habitat: in the descent stage, a pressurized crew habitat in which the crew would live during sortie missions.

deterministic process: process whereby a given event will occur whenever its dose threshold is exceeded.

deterministic effects: early radiation effects usually related to a significant fraction of cell loss, exceeding the threshold for impairment of function in a tissue; so called because the statistical fluctuations in the number of affected cells are very small compared to the number of cells required to reach the threshold (ICRP 1991), above which the severity varies with dose.

detriment: Health detriment is the sum of the probabilities of all the components of health effects. These include in addition to fatal cancer the probability of heritable effects and the probability of morbidity from nonfatal cancer.

DHS: Department of Homeland Security.

DNA: deoxyribonucleic acid.

DOD: Department of Defense.

DOE: Department of Energy.

dose: A general term used when the context is not specific to a particular dose quantity. When the context is specific, the name or symbol for the quantity is used [i.e., absorbed dose (D), mean absorbed dose (DT), dose equivalent (H), effective dose (E), equivalent dose (HT), or organ dose equivalent].

dose equivalent ( H ): Estimate of radiation risk that accounts for differences in the biological effectiveness of different types of charged particles that produce the absorbed dose. H=Q × D, where Q is a quality factor based on the type of radiation (Q = 1 for x-rays). NASA uses Q as specified in ICRP Publication 60 (ICRP, 1991). Unit: sievert (Sv), equivalent to 1 J/kg.

dose limit: A limit on radiation dose that is applied by restricting exposure to individuals or groups of individuals in order to prevent the occurrence of radiation-induced deterministic effects or to limit the probability of radiation related stochastic effects to an acceptable level. For astronauts working in low-Earth orbit, unique dose limits for deterministic and stochastic effects have been recommended by NCRP.

dose rate: Dose delivered per unit time. Can refer to any dose quantity (e.g., absorbed dose, dose equivalent).

dose-response model: A mathematical formulation of the way in which the effect, or response, depends on dose.

dosimeter: A radiation detection device worn or carried by an individual to monitor the individual's radiation exposure. For space activities, a device worn or carried by an astronaut in-flight.

DREF: dose rate effectiveness factor (the degree to which dose rate may influence the biological effects of exposure to a given dose of radiation).

DRM: Design Reference Mission.

DSB: double strand break.

DSNE: Constellation Program Design Specification for Natural Environments; CxP 70023

DTRA: Defense Threat Reduction Agency.

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E: effective dose/ energy.

EAR:excess additive risk (cf. absolute risk).

ED50: dose to cause 50 % of the population to have the effect (e.g., nausea).

EDS: Earth departure stage.

EEG: electroencephalogram.

effective dose ( E ): The sum over specified tissues of the products of the equivalent dose in a tissue (HT) and the tissue weighting factor for that tissue or organ (wT) (i.e., E = wTHT). Effective dose (E) applies only to stochastic effects. Unit: sievert (Sv), equivalent to 1 J/kg.

electron volt (eV): a unit of energy equivalent to 1.602 × 10–19 joules.

ELF: extremely low frequency.

ELR: excess lifetime risk.

EMF: electromagnetic field.

EML: Environmental Measurements Laboratory, New York, NY.

EMS: emergency medical services.

EMU: Extravehicular mobility unit, the space suit developed for space shuttle crews that also serves on the ISS.  The EMU features a hard upper torso and soft lower torso, arms, and legs over the pressure bladder. The entire EMU except the helmets and boots is covered by the thermal micrometeoroid garment.

electron volt (eV): A unit of energy = 1.6 x 10–12 ergs = 1.6 x 10–19 J; 1 eV is equivalent to the energy gained by an electron in passing through a potential difference of 1 V; 1 keV = 1,000 eV; 1 MeV = 1,000,000 eV.

EOS: Earth Observing System.

EPA: Environmental Protection Agency.

equivalent dose ( HT): The product of the mean absorbed dose in an organ or tissue and the radiation weighting factor (wR) of the radiation type of interest. For external exposure wR applies to the radiation type incident on the body.

ERR:excess relative risk.

erythema: A redness of the skin.

ESA: European Space Agency.

ESMD: Exploration Systems Mission Directorate (NASA).

ESP: energetic storm particle.

ESTEC: European Space Research and Technology Centre.

EVCPDS: Extra Vehicle Charged Particle Directional Spectrometer

excess relative risk (ERR): The ratio between the total risk, including the increase due to radiation exposure, and the baseline risk in the absence of radiation exposure; if the excess equals the baseline the relative risk is two.

exposure (technical use): A measure of the ionization produced in air by x or gamma radiation. Exposure is the sum of electric charges on all ions of one sign produced in air when all electrons liberated by photons in a volume of air are completely stopped, divided by the mass of the air in the volume. The unit of exposure in air is the roentgen (R) or in SI units it is expressed in coulombs (C), 1 R = 2.58 x 10–4 C/kg.

exposure (non-technical use): the presentation of an individual or material to radiation likely to deliver a significant dose over a period of time.

EVA: extravehicular activity.

excess risk: the increase in the probability of a certain effect on an individual who has been exposed to a given dose of radiation over the probability of that effect in the absence of radiation exposure.

extravehicular activity: Any activity undertaken by the crew outside a space vehicle or habitat.

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favorable propagation path: A concept suggesting that the Archimedean spiral path from the earth to the sun would connect to a specific solar longitude. It is based on the concept that charged particles travel along the interplanetary magnetic field which is transported out from the sun. For an idealized constant speed solar wind flow, if the interplanetary magnetic field is frozen in the plasma, then the result would form an Archimedean spiral.

FEMA: Federal Emergency Management Agency.

FIRE: First ISCCP Regional Experiment.

first ionization potential: The energy required to remove the least bound electron from an electrically neutral atom. (The ionization potential is usually given in electron volts.)

FISH: fluorescence in situ hybridization.

fluence: (1) ICRU definition : The quotient of dN by da, where dN is the number of particles incident on a sphere of cross-sectional area da (i.e., Φ = dN/da). The unit for fluence is 1/m2, but cm–2 is frequently used; (fluence may be a function of one or more other variables [e.g., Φ (L,t), the distribution of fluence as a function of linear energy transfer (L) and time (t)]. (2) planar fluence (F): The net number of charged particles traversing a given area. Unit: particles/cm2.

fluence rate (dF/dt): Change in fluence over a given small time interval, or the time derivative of the fluence. Unit: 1/m2s.

FLUKA: a general purpose Monte-Carlo computer code for calculations of particle transport and interactions with matter

flux ): Term used historically by the nuclear community for fluence rate and also used for particle flux density, but deprecated by the ICRU convention to eliminate confusion between the terms “particle flux density” and “radiant flux.” See fluence rate.

FM: frequency modulation.

FR: fixed-ratio.

fractionation: The delivery of a given total dose of radiation as several smaller doses, separated by intervals of time.

FSP: fission surface power.

FY: Fiscal Year.

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galactic cosmic rays: the components of galactic cosmic radiation.

galactic cosmic radiation (GCR): The charged-particle radiation outside the Earth magnetosphere comprised of 2 % electrons and positrons, and 98 % nuclei, the latter component consisting (by fluence) of 87 % protons, 12 % helium ions, and 1 % high atomic number, high-energy (HZE) particles.

gamma rays: Short-wavelength electromagnetic radiation of nuclear origin (approximate range of energy: 10 keV to 9 MeV).

GCR: galactic cosmic radiation/ galactic cosmic rays.

GCR: galactic cosmic radiation.

GEANT: A computer application for the simulation of the passage of particles through matter including detector description and simulation.

GEO: Geostationary or Geosynchronous Earth Orbit.

Geostationary Operational Environmental Satellite ( GOES): A satellite in geosynchronous orbit used for monitoring protons. The satellite travel at the same angular speed above the equator as Earth’s rotation and therefore appears stationary when observed from Earth’s surface.

GGTP: gamma-glutamyl transpeptidase.

GI: gastrointestinal.

GLE: ground level event.

GM: geometric mean.

GPM: Global Precipitation Measurement.

gray (Gy): The International System (SI) unit of absorbed dose of radiation, 1 Gy = 1 J kg–1.

gray equivalent (GT or Gy-Eq): The product of DT and Ri, where DT is the mean absorbed dose in an organ or tissue and Ri is a recommended value for relative biological effectiveness for deterministic effects for a given particle type i incident on the body ( GT = Ri × DT). The SI unit is J/kg (NCRP, 2000).

GSD: geometric standard deviation (the standard deviation of the logarithms of a set of random variables, for which the geometric mean is the square root of their product.

GSI(Gesellschaft für Schwerionenforschung): Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany.

GSM: global system for mobile communications.

GT: gray equivalent.

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HACD: Human Adaptation and Countermeasures Division.

HDPE: high-density polyethylene, defined as having a density greater than 0.94 g/cm3.

heavy charged particles: Atomic and subatomic charged particles with masses substantially heavier than that of an electron.

heavy ions: Nuclei of elements heavier than helium such as nitrogen, carbon, boron, neon, argon or iron which are positively charged due to some or all of the atomic electrons having been stripped from them.

HEDS: Human Exploration and Development of Space.

HEFD: Habitability and Environmental Factors Division.

heliocentric: A measurement system with its origin at the center of the sun.

heliolongitude: Imaginary lines of longitude on the sun measured east (left) or west (right) of the central meridian (imaginary north-south line through the middle of the visible solar disk) as viewed from Earth. The left edge of the solar disk is 90°E and the right edge is 90°W.

heliosphere: The magnetic bubble containing the solar system, solar wind, and entire solar magnetic field. It extends beyond the orbit of Pluto.

HEPAD: High Energy Proton and Alpha Detector.

HIDH: Human Integration Design Handbook; NASA/SP-2010-3407

high atomic number, high-energy ( HZE) particles: Heavy ions having an atomic number greater than that of helium (such as nitrogen, carbon, boron, neon, argon or iron ions that are positively charged) and having high kinetic energy.

high-LET: Radiation having a high-linear energy transfer; for example, protons, alpha particles, heavy ions, and interaction products of fast neutrons.

HIMAC: Heavy Ion Medical Accelerator, Chiba Japan.

HMF: heliospheric magnetic field.

HPC: Hydrological Process and Climate.

HPRT: hypoxanthine-guanine phosphoribosyl transferase.

HQ: Headquarters.

HRP: Human Research Program.

HRP CB: Human Research Program Control Board.

HSIR: Constellation Program Human Systems Integration Requirements; CxP 70024

H T : equivalent dose.

HZE: high atomic number and energy.

HZETRN: a transport code developed specifically for high-charge, high-energy particles that is widely used for space radiation shielding and design calculations.

HZE: high atomic number, high energy/ highly energetic, heavy, charged particles.

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IACUC: Institutional Animal Care and Use Committee.

IAEA: International Atomic Energy Agency.

ICNIRP: International Commission on Non-Ionizing Radiation Protection.

ICRP: International Commission on Radiation Protection.

ICRU: International Commission on Radiation Units and Measurements.

IDIQ: Indefinite delivery/indefinite quantity.

IEEE: Institute of Electrical and Electronics engineers.

IL-2: interleukin-2.

IL-6: interleukin-6.

incidence: The rate of occurrence of a disease, usually expressed in number of cases per million .

IND: improvised (or otherwise acquired) nuclear device.

interplanetary magnetic field: The magnetic field in interplanetary space. The interplanetary magnetic field is transported out from the sun via the solar wind.

interplanetary shocks: An abrupt change in the velocity or density of charged particles moving faster than the wave propagation speed in interplanetary space, so that higher velocity components bunch into lower velocity components before these can get out of the way.

ionizing radiation: Any electromagnetic or particulate radiation capable of producing ions, directly or indirectly, in its passage through matter.

ionization: The process by which a neutral atom or molecule acquires a positive or negative charge through the loss or gain of one or more orbital electrons.

IPT: Integrated Product Team.

IRMA: Integrated Risk Management Application.

ISCCP: International Satellite Cloud Climatology Project.

ISS: International Space Station.

ISSMP: ISS Medical Project.

ITA: Internal Task Agreement.

IVCPDS: Intra Vehicle Charged Particle Directional Spectrometer

IV & V: Independent Validation & Verification.

IWG: Investigator Working Group.

IWS: Investigator Workshop.

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JSC: NASA Johnson Space Center.

JWST: James Webb Space Telescope.

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kerma: (an acronym for “Kinetic energy released in materials;” the sum of the initial kinetic energies for all charged particles released by uncharged ionizing radiation in a small sample of material divided by the mass of the sample. Kerma is the same as dose when charged particle equilibrium exists (i.e., when, on the average, the number of charged particles leaving the sample is compensated by an equal number of charged particles entering the sample).

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LAP: latency associated peptide.

LAR: lifetime attributable risk.

LaRC: NASA Langley Research Center.

LAT: Lunar Architecture Team.

latchup: an anomalous state in a semiconductor in which the device no longer responds to input signals.

latent period: Period or state of seeming inactivity between time of exposure of tissue to an injurious agent and an observed response (also time to response or induction period).

LBNL: Lawrence Berkeley National Laboratory.

LCD: liquid crystal display.

LCVG: liquid cooling and ventilation garment.

LDEF: Long Duration Exposure Facility.

LDL: low-density lipoproteins.

LEND: Low Energy Neutron Detector.

LEO (low Earth orbit): the environment in which most recent space missions have been concentrated, where the magnetic field of Earth provides protection against much of the radiation that would be encountered on more distant exploration missions, approximately 300 to 600 mile orbit radius.

LET (linear energy transfer): Measure of the average local energy deposition per unit length of distance traveled by a charged particle in a material. Unit: keV/μm.

lifetime risk: The lifetime probability of suffering from the consequences of a specific health effect. The total risk in a lifetime resulting from an exposure(s) is equal to the average annual risk times the period of expression.

light ions: Nuclei of hydrogen and helium which are positively charged due to some or all of the planetary electrons having been stripped from them.

lineal energy ( y ): The quotient of ε by , where ε is the energy imparted to the matter in a given volume by a single (energy deposition) event and is the mean chord length of that volume ( i.e., y = ε/ l ). The unit for lineal energy is J /m, but keV/ μm is often used in practice (1 keV/µm ~ 1.6x10-10 J/m).

linear energy transfer ( LET): Average amount of energy lost per unit of particle track length as an ionizing particle travels through material, related to the microscopic density distribution of energy deposited in the material and, therefore, a major characteristic of radiation leading to different effects for the same dose of ionizing radiation of different LET on biological specimens or electronic devices.

linear-quadratic model (also linear-quadratic dose-response relationship): expresses the incidence of (e.g., mutation or cancer) as partly directly proportional to the dose (linear term) and partly proportional to the square of the dose (quadratic term).

LIS: local interstellar energy spectrum.

LIS: local interstellar GCR spectrum.

LIS: Local interplanetary Spectra.

LLD: lower limit of detection.

LLU: Loma Linda University.

LLO: low lunar orbit.

lognormal: If the logarithms of a set of values are distributed according to a normal distribution the values are said to have a lognormal distribution, or be distributed log normally.

low-LET: Radiation having a low-linear energy transfer; for example, electrons, x rays, and gamma rays.

LRV: Lunar Roving Vehicle.

LSAC: Life Sciences Applications Advisory Committee.

LSS: Life Span Study.

LSS: Life-Span Study of the Japanese atomic-bomb survivors.

Lunar Lander: the Constellation system vehicle that will travel between the Orion and the surface of the Moon.

LWS: Living With a Star (a NASA program).

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MARIE: Mars Radiation Environment Experiment.

mass stopping power: (see stopping power ).

MAT: Mars Architecture Team.

MCNPX: Monte Carlo N-Particle eXtended.

MDO: Multi-disciplinary Optimization.

mean absorbed (tissue) dose ( DT): The mean absorbed dose in an organ or tissue, obtained by integrating or averaging absorbed doses at points in the organ or tissue.

mean-free path: The average distance between particle collisions with nuclei, atoms or molecules in a material. Also, the average distance between scattering events in interplanetary particle propagation.

MEEP: Mir Environment Effects Payload.

MEO: Medium Earth Orbit.

MeV: Mega-electron Volts: 106 electron volts

mFISH: Multiplex Fluorescence In Situ Hybridization.

Mir: The Russian (previously Soviet) orbital space station.

MISSE: Materials on International Space Station Experiment.

MML: mouse myelogenous leukemia.

MMOP: Multilateral Medical Operations Panel.

MOA: Memorandum of Agreement.

MODIS: Moderate Resolution Imaging Spectrometer.

MORD: Medical Operations Requirements Documents.

MOU: Memorandum of Understanding.

Mrem: millirem.

MRI: magnetic resonance imaging.

MS: Mission Systems

mSv: millisievert.

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N: nucleon.

NAR: Non-Advocate Review.

NAS: National Academy of Sciences.

NASA: National Aeronautics and Space Administration.

NCI: National Cancer Institute.

NCRP: National Council on Radiation Protection and Measurements.

NEDD: Constellation Program Natural Environment Definition for Design; CxP 70044

neutrons: Particles with a mass similar to that of a proton, but with no electrical charge. Because they are electrically neutral, they cannot be accelerated in an electrical field.

NIEL: Non-ionizing energy loss, also called displacement kerma. The total kerma can be divided into an ionizing component and a displacement, or NIEL, component.

NIH: National Institutes of Health.

NM: neutron monitor.

NOAA: National Oceanic and Atmospheric Administration.

noncancer: Health effects other than cancer (e.g., cataracts, cardiovascular disease) that occur in the exposed individual.

Nowcasting: prediction of total doses and the future temporal evolution of the dose once a solar particle event has begun.

NOVICE: Radiation Transport/Shielding Code.

NPR: NASA Procedural Requirements.

NRA: NASA Research Announcement.

NRC: National Research Council.

NRC: Nuclear Regulatory Commission (US).

NSBRI: National Space Biomedical Research Institute.

NSCOR: NASA Specialized Center of Research.

NSF: National Science Foundation.

NSRL: NASA Space Radiation Laboratory (at BNL).

NTE: Non-Targeted Effects.

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OBPR: Office of Biological and Physical Research.

OCHMO: Office of Chief Health and Medical Officer.

organ dose equivalent ( DET): The mean dose equivalent for an organ or tissue, obtained by integrating or averaging dose equivalents at points in the organ or tissue. It is the practice in the space radiation protection community to obtain point values of absorbed dose (D) and dose equivalent (H) using the accepted quality factor-LET relationship [Q(L)], and then to average the point quantities over the organ or tissue of interest by means of computational models to obtain the organ dose equivalent (DET ). For space radiations, NCRP adopted the organ dose equivalent as an acceptable approximation for equivalent dose (HT) for stochastic effects.

Orion Crew Exploration Vehicle: The Constellation system vehicle that will carry passengers in low Earth orbit, or from low Earth orbit to the Moon or Mars, and then back to Earth. Often referred to as CEV; in this report referred to as the Orion crew module.

OSHA: Occupational Safety and Health Administration.

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PC: Probability of Causation.

PCC: premature chromosome condensation.

PCS: personal communication system.

PDF: probability density function.

PDF: probability distribution function.

PE: Project Executive.

PEL (permissible exposure limit): Maximum amount of radiation to which an astronaut may be exposed. For terrestrial workers, PELs are legal limits, defined by OSHA. NASA PELs are set by the chief health and medical officer.

PET: positron emission tomography.

photosphere: The portion of the sun visible in white light. Also the limit of seeing down through the solar atmosphere in white light.

PI: Principal Investigator.

PLR: pressurized lunar rover.

PLSS: personal life support system.

PM: Project Manager.

PP: Project Plan.

PPBE: Planning, Programming, Budgeting and Execution.

PPS: proton prediction system/ pulses per second.

PRD: Passive Radiation Detector; Program Requirements Document.

prevalence: The number of cases of a disease in existence at a given time per unit of population, usually per 100,000 persons.

protons: The nucleus of the hydrogen atom. Protons are positively charged.

protraction: Extending the length of exposure, for example, the continuous delivery of a radiation dose over a longer period of time.

PS: Project Scientist.

PSD: Position-Sensitive Detector; also, Pulse Shape Discrimination.

PVAMU: Prairie View A&M University.

PW: pulsed wave.

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Q: quality factor.

Q(L): quality factor as a function of linear energy transfer.

Qleukemia: quality factor for estimating leukemia risks.

Qsolid: quality factor for estimating solid cancer risks.

QMSFRG: quantum multiple scattering fragmentation model.

quality factor ( Q ): The factor by which absorbed dose (D) at a point is modified to obtain the dose equivalent (H) at the point (i.e., H = Q D), in order to express the effectiveness of an absorbed dose (in inducing stochastic effects) on a common scale of risk for all types of ionizing radiation. There is a specified dependence [Q(L)] of the quality factor (Q) as a function of the unrestricted linear energy transfer (L) in water at the point of interest.

quasithreshold dose: The dose at which the extrapolated straight portion of the dose-response curve intercepts the dose axis at unity survival fraction.

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RAD: Radiation Assessment Detector.

RAM: Radiation Area Monitor.

radiation: 1. The emission and propagation of energy through space or through matter in the form of waves, such as electromagnetic, sound, or elastic waves; 2. The energy propagated through space or through matter as waves; radiation or radiant energy, when unqualified, usually refers to electromagnetic radiation; commonly classified by frequency— Hertzian, infrared, visible, ultraviolet, x and gamma rays; 3. Corpuscular emission, such as alpha and beta particles, or rays of mixed or unknown type, such as cosmic radiation.

radiation quality: A general term referring to the microscopic distribution of of the energy absorbed to yield a given total dose. For example, at resolutions of a few micrometers ionizing events will be more uniformly dispersed for gamma-ray radiation than for the neutron radiation, producing quantitatively different biological effects (see relative biological effectiveness ).

radiation weighting factor ( wR): A factor related to the relative biological effectiveness of different radiations in the calculation of equivalent dose (HT) (see equivalent dose ), independently of the tissue or organ irradiated.

RBE (relative biological effectiveness): Measure of the effectiveness of a specific type of radiation for producing a specific biological outcome, relative to a reference radiation (generally, 250 kVp x-rays). For a defined endpoint, RBE = Dref/Dnew. For HZE particles, RBE generally is greater than 1, meaning that a lower dose of more effective HZE particles will have the same effect as a given dose of the reference radiation.

RCT: Radiation Coordination Team.

RDD: radiological dispersal device.

RDWG: Radiation Discipline Working Group.

regolith: A layer of loose, heterogeneous material covering solid rock on the surface of a moon or planet (including Earth).

REIC: risk of exposure-induced cancer incidence.

REID (risk of exposure induced death): Measure of risk used by NASA as a standard for radiation protection; reflects a calculation of the probability of death due to exposure to radiation in space.

relative biological effectiveness (cf. RBE)

relative risk (cf. excess relative risk)

REM: rapid eye movement.

RF: radiofrequency.

RFI: request for information.

RHIC: Relativistic Heavy Ion Collider (at BNL).

RHO: Radiation Health Officer.

rigidity: The momentum of a charged particle per unit charge. Determines the curvature of the particle’s trajectory in a magnetic field. Two particles with different charge but the same rigidity will travel along a path having the same curvature in a given magnetic field.

risk: The probability of a specified effect or response occurring.

risk coefficient: The increase in the annual incidence or mortality rate per unit dose: (1) absolute risk coefficient is the observed minus the expected number of cases per person year at risk for a unit dose; (2) the relative risk coefficient is the fractional increase in the baseline incidence or mortality rate for a unit dose.

risk cross section: The probability of a particular excess cancer mortality per particle fluence (excluding delta rays).

risk estimate: The number of cases (or deaths) that are projected to occur in a specified exposed population per unit dose for a defined exposure regime and expression period; number of cases per person-gray or, for radon, the number of cases per person cumulative working level month.

roentgen: A unit of radiation exposure. Exposure in SI units is expressed in C kg–1 of air.

ROS: reactive oxygen species.

RRS: radiation Research Society.

RSNA: Radiological Society of North America.

R&T: Research and Technology.

RTG: radioisotope thermoelectric generator.

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SAA: South Atlantic Anomaly.

SACR: Science Advisory Committee on Radiobiology.

SAMPEX: Solar Anomalous and Magnetospheric Particle Explorer.

SAR: specific absorption rate.

SBIR: Small Business Innovation Research.

SCAR: Smoke/Sulfate Clouds and Radiation Experiment.

SCC: squamous cell carcinoma/ small cell cancer.

SCE: sister chromatid exchange.

SCLS: small cell lung carcinoma.

SD: single dose.

SD: standard deviation.

SDO: Solar Dynamic Observatory.

SEC: Space Environment Center. (NOAA).

secondary radiation: radiation that has been generated by the interaction of radiation with the atoms or nuclei of a traversed material.

SEE (single-event effect): a class of effects in which damage results from a single ionizing particle traversing a microelectronic device, rather than the accumulated impact of a large number of particles.

SEE: single event effect/ Space Environment and Effects Program.

SEER: surveillance, epidemiology, and end results.

SET: Space Environment Testbeds.

SEU (single event upset): a change of state caused by ions or electro-magnetic radiation striking a sensitive node in a micro-electronic device.

SFHSS: Space Flight Human Systems Standard; NASA-STD-3001

SGZ: subgranular zone.

SI: International System of Units.

sievert ( Sv): The special name for the SI unit of effective dose (E), equivalent dose (HT), dose equivalent (H), and organ dose equivalent (DT ), 1 Sv = 1 J /kg.

SLSD: Space Life Sciences Directorate (NASA).

S&MA: Safety and Mission Assurance (NASA).

SMD: Science Mission Directorate (NASA).

SMO: Science Management Office (NASA).

SOHO: Solar and Heliospheric Observatory.

Solar cycle: The periodic variation in the intensity of solar activity, as measured, for example, by the numbers of sunspots, flares, CMEs, and SPEs. The average length of solar cycles since 1900 is 11.4 y.

solar flare: The name given to the sudden release of energy (often >1032 ergs) in a relatively small volume of the solar atmosphere. Historically, an optical brightening in the chromosphere, now expanded to cover almost all impulsive radiation from the sun.

solar-particle event (SPE): An eruption at the sun that releases a large number of energetic particles (primarily protons) over the course of hours or days. Signatures of solar energetic-particle events may include significant increases in types of electro­magnetic radiation such as radio waves, x-rays, and gamma rays.

solar wind: The plasma flowing into space from the solar corona. The ionized gas carrying magnetic fields can alter the intensity of the interplanetary radiation.

SOMD: Space Operations Mission Directorate (NASA).

spallation: A high-energy nuclear reaction in which a high-atomic-number target nucleus is struck by a high-energy, light particle (typically a proton); this causes the target nucleus to break up into many components, releasing many neutrons, protons, and higher Z particles.

SPE (cf. solar particle event).

Space Radiation Analysis Group (SRAG): the radiation protection group at NASA’s Johnson Space Center, responsible for radiation monitoring, projecting exposures, and ensuring adherence to principles of ALARA for crews on spaceflight missions.

SPENVIS (SPace ENVironment Information System) : a series of computer programs developed by the European Space Agency for the simulation of radiation effects in flight.

SRA: Society for Risk Analysis.

SRAG: Space Radiation Analysis Group

sRBC: Serum deprivation response factor-related gene product that binds to C-kinase.

SRPE: Space Radiation Program Element (NASA).

SSA: Social Security Administration.

STEREO: Solar-Terrestrial Relations Observatory (NASA mission).

stochastic effects: radiation effects attributed to the consequences of changes caused by radiation in one or a few cells; so called because the statistical fluctuations in the number of initial cells are large compared to the number of cells observed when radiation effects, such as cancer, become manifest (ICRP 1991). The probability of occurrence, rather than the severity, is a function of radiation dose.

stochastic process: process whereby the likelihood of the occurrence of a given event can be described by a probability distribution.

stopping power (lineal stopping power): The quotient of the energy lost (dE) by a charged particle in traversing a distance (dx) in a material. Can also be expressed as mass stopping power by dividing the lineal stopping power by the density (ρ) of the material.

STS: Space Transportation System.

STTR: Small Business Technical Transfer Research.

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TEDE: total effective dose equivalent.

TEPC: tissue equivalent proportional counter.

TGF: transforming growth factor.

TIGER: Grid Generation Code.

tissue weighting factor ( wT): A factor representing the ratio of risk of stochastic effects attributable to irradiation of a given organ or tissue to the total risk when the whole body is irradiated uniformly. The factor is independent of the type of radiation or energy of the radiation.

TLD: thermoluminescent dosimeter.

TMG: thermal micrometeoroid garment.

TMI: Three Mile Island.

TOGA/COARE: Tropical Ocean Global Atmosphere/Coupled Ocean-Atmosphere Experiment.  transport (of radiation): the sequence of interactions between radiation traversing one or more materials and their atoms and nuclei; calculations of the relevant characteristics; transport code: computer program to calculate radiation transport.

trapped radiation: Ionized particles held in place by Earth’s magnetic fields. Also known as the Van Allen belt.

TRL: Technology Readiness Level.

TRMM: Tropical Rainfall Measuring Mission.

TVD: tenth-value distance.

TVL: tenth-value layer.

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UNSCEAR: United Nations Scientific Committee on the Effects Of Atomic Radiation.

US: United States.

USAF: United States Air Force.

US NRC: United States Nuclear Regulatory Commission.

USRA: Universities Space Research Association.

UV: ultraviolet.

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vitreous: The semifluid, transparent substance which lies between the retina and the lens of the eye.

VSE: Vision for Space Exploration.

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WBS: Work Breakdown Structure.

WHO: World Health Organization.

Wind: a NASA spacecraft that observes the Sun and solar wind.

WL: working level.

WLM: working level month (170 h).

w R: radiation weighting factor.

w T: tissue weighting factor.

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Z: atomic number, the number of protons in the nucleus of an atom.

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