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.

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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43rd COSPAR Scientific Assembly

The 43rd COSPAR Scientific Assembly will be held in Sydney, Australia, 15 - 22 August. The abstract deadline is 14 February 2020.
F2.1 Towards space exploration: radiation biological basis Christine E. Hellweg, Guangming Zhou). The interdisciplinary session addresses researchers from the fields of biology, biotechnology, biochemistry, chemistry, physics and medicine dealing with the effects of space relevant radiation qualities alone or in combination with other spaceflight environmental factors such as microgravity on cells, tissues, organs and organisms. Radiation interaction with molecules and track structure geometry are important determinants for the biological outcome. On cellular and tissue level, the complex interplay of cellular responses, starting with DNA damage induction or damages to other cellular components (e.g. membranes, organelles, proteins) and leading to signal transduction, DNA repair, altered gene expression (including microRNA), cell cycle perturbations, cell death, chromosomal aberrations, genomic instability, senescence, differentiation and transformation will be elucidated. Damage escape strategies as well as adaptive responses and bystander effects will also be outlined. Also, cell-type, tissue and organ specific effects of protons and heavy ions resulting in dysfunctions are addressed (such as cataract and cardiovascular and central nervous system effects). The radiation effects on the immune system and its influence on the radiation response in other tissues are important topics in this session. On organismal level, the effects of space relevant radiation qualities not only on mammalian and other vertebrate animal models, but also on plants and invertebrate animals such as insects and nematodes, are topic of this session. This session also covers surveys with human subjects, e.g. detection of chromosomal aberrations in blood lymphocytes. Experiments performed in space and ground-based studies (e.g. at heavy ion accelerators) are discussed in this session.
F2.2: Space Radiation Risk and Counter-measures: Physical and Biophysical Mechanisms, Modelling and Simulations (MSO: Andrea Ottolenghi, DO: Francis A. Cucinotta) is a special session to discuss the results of research activities that can improve space radiation risk assessment. This includes the design of biological and passive and active physical countermeasures in order to reduce cancer risk and understand if non-cancer risks will occur for specific space missions. Particular attention will be given to the mechanisms underlying the dependence of biological effects on the quality of radiation. The session will discuss physical and biophysical multi-scale modeling and simulations with the aim of integrating activities carried on by scientists of different disciplines (physicists, biologists, etc.):
Specific topics are:

  • Physical interaction models and transport and track structure codes, code verification and validation with experimental data.
  • Multi-scale mechanisms, modeling and simulations (at subcellular, cellular, tissue and organism levels) of the biological response to radiation.
  • Systems radiation biology
  • "Omics" investigation of biological systems after radiation exposure
  • Development and implementation of countermeasures, in different mission scenarios.
  • Advanced shielding materials and development of active shielding
  • Risk assessment for cancer morbidity and mortality, with emphasis on chronic exposures and non-targeted effects
  • Risk assessment of early onset effects that have the potential to impact performance during long duration missions, including CNS and cardiovascular diseases, and possible countermeasures.

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Postdoc Positions

There are up to two postdoc positions in radiation modeling open for working with the Space Radiation Group at NASA Langley. The positions are through the National Institute of Aerospace and the postdocs will be working directly with this group on site at NASA Langley.

If you know of anyone looking for a postdoctoral position, please pass this along to them. As you can see from the job announcement, we are open to a wide array of skills and research interests. We are a multidisciplinary group and welcome anyone with the requisite skills and interest in working in space radiation modeling to please apply.

Direct questions to:

Dr. Ryan B. Norman
NASA Langley Research Center
Office: (757) 864-2185
Fax: (757) 864-8911
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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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RITCARD: Radiation-Induced Tracks, Chromosome Aberrations, Repair and Damage
Plante I, Ponomarev A, Patel Z, Slaba T, Hada M. Radiation Research. September 2019, Vol. 192, No. 3, pp. 282-298. [9/30]
Chromosome aberrations (CAs) are one of the effects of radiation exposure and can have implications for human health in the space environment, since they are related to cancer risk. To shed light on the formation and quality of chromosome aberrations in the space environment, many experiments and simulations have been performed using chromosome aberrations in human cells, induced by heavy ions, which are present in galactic cosmic rays (GCRs). In this work, the new simulation program, radiation-induced tracks, chromosome aberrations, repair and damage (RITCARD), is presented. RITCARD is comprised of four parts: a random walk (RW) algorithm for simulating chromosomes in a nucleus; a deoxyribonucleic acid (DNA) damage algorithm; a break repair process; and a function to assess and count chromosome aberrations. Prior to running RITCARD, the code relativistic ion tracks (RITRACKS), is used to simulate detailed radiation track structure and calculate time-dependent differential voxel dose maps in a parallelepiped centered on a cell nucleus. The RITCARD program reads the pre-calculated voxel dose and locates the intersections between the voxels and the chromosomes. Radiation-induced breaks occur strictly at these intersections. When a break occurs in the random walk, the corresponding chromosome piece is cut into two fragments where each has a free end at the position of the break. In the next step, the algorithm simulates the time-dependent rejoining of free end pairs, using different probabilities for pairs originating from a given break (proper) or from different breaks (improper), which results in the formation of fragment sequences. By grouping these sequences, the program determines the number and types of aberrations, based on the criteria used in our experiment. The new program is used to assess the yields of various types of chromosome aberrations in human fibroblast cells for several ions (1H+, 4He2+, 12C6+, 16O8+,20Ne10+, 28Si14+, 48Ti22+ and 56Fe26+) with energies varying from 10 to 1,000 MeV/n. The results show linear and linear-quadratic dose dependence for most chromosome aberrations types. The calculation results were compared with those obtained by fluorescence in situ hybridization (FISH) experiments that were performed by our group. The simulation results also show that the coefficient of the linear part of the dose-dependence curve peaks at an LET value of approximately 100 keV/µm, which evokes a relative biological effectiveness (RBE) peak.
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Space-like 56Fe irradiation manifests mild, early sex-specific behavioral and neuropathological changes in wildtype and Alzheimer's-like transgenic mice.
Liu B, Hinshaw RG, Le KX, Park MA, Wang S, Belanger AP, Dubey S, Frost JL, Shi Q, Holton P, Trojanczyk L, Reiser V, Jones PA, Trigg W, Di Carli MF, Lorello P, Caldarone BJ, Williams JP, O'Banion MK, Lemere CA. Sci Rep. 2019 Aug 20;9(1):12118. [9/24]
This study investigated the effects of exposure to space radiation on behavioral and neuropathological changes in mice. Four-month old Alzheimer’s disease (AD)-like transgenic (Tg) mice and wildtype (WT) littermates were irradiated with a single, whole-body dose of 10 or 50 cGy 56Fe ions (1 GeV/u) at Brookhaven National Laboratory. Sex-, genotype-, and dose-dependent changes in locomotor activity, contextual fear conditioning, grip strength, and motor learning were observed 1.5 months later mostly in Tg mice but not WT mice. Few changes were seen in general health, depression, or anxiety. MicroPET imaging of the translocator protein ligand 2 months post-irradiation showed no radiation-specific change in neuroinflammation, while brain examination indicated that radiation reduced cerebral amyloid-β levels and microglia activation in female Tg mice, modestly increased microhemorrhages in 50 cGy irradiated male WT mice and did not affect synaptic marker levels compared to sham controls. In summary, specific short-term changes in neuropathology and behaviour induced by 56Fe irradiation were observed, possibly having implications for long-term space travel.
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Evaluating the effectiveness of common aerospace materials at lowering the whole body effective dose equivalent in deep space.
Bond DK, Goddard B, Singleterry RC Jr, Bilbao y Leóna S. Acta Astronaut. 2019 Aug 22. [Article in Press] [9/11]
Materials have a primary purpose in the design of space vehicles, such as fuels, walls, racks, windows, etc. Additionally, each will also affect space radiation protection. The shielding capabilities of 59 materials are evaluated for deep space travel, in terms of whole body effective dose equivalent, ED, and number of nucleons per volume#ofNucleonsVolume. The hydrogen rich materials are evaluated further using the number of Hydrogen Atoms per mass and number of Hydrogen Atoms per volume. All evaluated materials, through density, composition, and shielding ability, can be categorized into three groups: metals, polymers and composites, and fuels, hydrides, and liquid gases. The analyses presented in the article shows that a “magic” material is not possible; however polymers and composites should be used instead of metals, if they can serve their primary purpose. Polyethylene and magnesium borohydride are shown to be the best feasible materials from this sample. Thermal neutron absorbers, 6Li and 10B, do not have a significant effect on ED. Alloying of materials, such as aluminum, for strengthening purposes, do not increase ED. Ultimately, a space vehicle is a system of systems and radiation protection must be one of them.
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Nitric Oxide Is Involved in Heavy Ion-Induced Non-Targeted Effects in Human Fibroblasts
Hada M, Saganti PB, Cucinotta FA. Int J Mol Sci. 2019, 20, 4327. [9/4]
We measured chromosomal aberrations (CA) with and without nitric oxide (NO) scavenger in normal skin fibroblasts cells after exposure to 600 MeV/u and 1 GeV/u 56Fe ions, and less than one direct particle traversal per cell nucleus (NO has been reported as a candidate for intercellular signaling for non-targeted effect (NTE) in many studies). Yields of CA were significantly lower in fibroblasts exposed to the NO scavenger compared to controls, suggesting involvement of NO in cell signaling for induction of CA. Media transferred from irradiated cells induced CA in non-irradiated cells, and this effect was abrogated with NO scavengers. Our results strongly support the importance of NTE contributions in the formation of CA at low-particle fluence in fibroblasts.
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Lung cancer progression using fast switching multiple ion beam radiation and countermeasure prevention
Luitel K, Kim SB, Barron S, Richardson JA, Shay JW. Life Sci Space Res. 2019 Aug 1. [Article in Press] [8/28]
We exposed the whole body of a lung cancer susceptible mouse model (K-rasLA-1) to three sequential ion beams: Protons (H) (120 MeV/n) 20 cGy, Helium (He) (250 MeV/n) 5.0 cGy, and Silicon (Si) (300 MeV/n) 5.0 cGy with a dose rate of 0.5 cGy/min and a total dose of 30 cGy in two different orders: 3B-1 (H→He→Si) and 3B-2 (Si→He→H) and used 30 cGy H single-ion beam as a reference. In this study we show that whole-body irradiation with H→He→Si increases the incidence of premalignant lesions and systemic oxidative stress in mice 100 days post-irradiation more than (Si→He→H) and H only irradiation. Additionally, we observed an increase in adenomas with atypia and adenocarcinomas in H→He→Si irradiated mice but not in (Si→He→H) or H (30 cGy) only irradiated mice. When we used the H→He→Si irradiation sequence but skipped a day before exposing the mice to Si, we did not observe the increased incidence of cancer initiation and progression. We also found that a non-toxic anti-inflammatory, anti-oxidative radioprotector (CDDO-EA) reduced H→He→Si induced oxidative stress and cancer initiation almost back to baseline. Thus, exposure to H→He→Si elicits significant changes in lung cancer initiation that can be mitigated using CDDO-EA.
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New concerns for neurocognitive function during deep space exposures to chronic, low dose rate, neutron radiation
Acharya MM, Baulch JE, Klein PM, Baddour AAD, Apodaca LA, Kramar EA, Alikhani L, Garcia C Jr, Angulo MC, Batra RS, Fallgren CM, Borak TB, Stark CEL, Wood MA, Britten RA, Soltesz I, Limoli CL. eNeuro 5 August 2019, 6 (4). 10.1523/ENEURO.0094-19.2019. [8/28]
Using a new, low dose-rate neutron irradiation facility, we have uncovered that realistic, low dose-rate exposures produce serious neurocognitive complications associated with impaired neurotransmission. Chronic (6 month) low-dose (18 cGy) and dose rate (1 mGy/d) exposures of mice to a mixed field of neutrons and photons result in diminished hippocampal neuronal excitability and disrupted hippocampal and cortical long-term potentiation. Furthermore, mice displayed severe impairments in learning and memory, and the emergence of distress behaviors.
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The Combination of Particle Irradiation With the Hedgehog Inhibitor GANT61 Differently Modulates the Radiosensitivity and Migration of Cancer Cells Compared to X-Ray Irradiation
Konings K, Vandevoorde C, Belmans N, Vermeesen R, Baselet B, Walleghem MV, Janssen A, Isebaert S, Baatout S, Haustermans K, Moreels M. Frontiers in Oncology, May 2019, 9, Article N°: 391. [8/26]
Metastasis is still an important cause of mortality in cancer patients and evidence has shown that conventional radiotherapy can increase the formation of metastasizing cells. An important pathway involved in the process of metastasis is the Hedgehog (Hh) signaling pathway. Here, we investigated the effect of X-rays, protons and carbon ions on cell survival, migration and Hh pathway gene expression in prostate cancer (PC3) and medulloblastoma (DAOY) cell lines.
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Pathological effects of ionizing radiation: endothelial activation and dysfunction
Baselet B, Sonveaux P, Baatout S, Aerts A. Cell Mol Life Sciences, Feb 2019, 76 (4): 699-728. [8/26]
The endothelium, a tissue that forms a single layer of cells lining various organs and cavities of the body, especially the heart and blood as well as lymphatic vessels, plays a complex role in vascular biology. It contributes to key aspects of vascular homeostasis and is also involved in pathophysiological processes, such as thrombosis, inflammation, and hypertension. The aim of this review is to summarize the current knowledge on endothelial cell activation and dysfunction after ionizing radiation exposure as a central feature preceding the development of cardiovascular diseases.
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On prognostic estimates of radiation risk in medicine and radiation protection
Ulanowski A, Kaiser JC, Schneider U, Walsh L. Radiation and Environmental Biophysics. August 2019, Volume 58, Issue 3, pp 305–319. [8/2]
Exposure to ionising radiation is known to increase risks of harmful health effects, of which malignant neoplasms receive special attention due to deadly hazards they bring. In many situations of unavoidable radiation exposure, either occupational or medical, risks of additional future health effects are estimated and compared with spontaneous incidence observed in the contemporary population. Correspondingly, the conventional techniques of radiation risk assessment are bound to use of the contemporary demographic and health data and are representative for an average member of the current general population. However, medical patients treated with radiation are unlikely to be similar to the average, mostly healthy, member of the general population; people exposed occupationally, like astronauts, are often selected based on their health status, they undergo periodical medical checks and screenings and due to these they can be hardly represented by the average population member. Use of current, cross-sectional, population statistics for projection of lifetime radiation risks also brings significant uncertainties to the risk estimates due to unknown future changes of health and vital statistics This paper reviews the conventional metrics used to express future radiation risks, demonstrates their limitations and difficulties with their use, and suggest an alternative quantity to express the risk, which is insensitive to competing risks and robust against unknown future changes in the population’s health and demographic data. The authors examine which risk metrics better represent atypical groups, like medical patients or astronauts; are robust to variability of individual properties, pre-selection and screening; and allow risk projections with unknown secular trends.
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Advances in space radiation physics and transport at NASA.
Norbury JW, Slaba TC, Aghara S, Badavi FF, Blattnig SR, Clowdsley MS, Heilbronn LH, Lee K, Maung KM, Mertens CJ, Miller J, Norman RB, Sandridge CA, Singleterry R, Sobolevsky N, Spangler JL, Townsend LW, Werneth CM, Whitman K, Wilson JW, Xu SX, Zeitlin C. Life Sci Space Res. 2019 Jul 10. [Article in Press] Review. [7/31]
This paper describes significant new discoveries and advances made in space radiation physics and transport over the past decade. Some of the most important new developments include the following: 1) The discovery of a minimum in the dose-equivalent versus depth curve; 2) A large contribution to dose from pions; 3) A large contribution of neutrons and light ions to dose equivalent for realistic shield thickness; 4) A realization that there are large and significant gaps in cross section measurements needed for space radiation; 5) Development of 3-dimensional deterministic transport methods; 6) Development of a fully relativistic nuclear fragmentation model; 7) Development of a GCR simulation capability at the NASA Space Radiation Laboratory; 8) Development of an On-Line Tool for the Assessment of Radiation In Space (OLTARIS); 9) Development of a Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) model. Each of these advances contribute significantly to improving our knowledge of space radiation and will help achieve safer long term space travel. The paper is coauthored by 22 scientists from various NASA centers, universities and commercial companies, and includes work funded by NASA’s Human Research Program and Advanced Exploration Systems.
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Update on Galactic Cosmic Ray Integral Flux Measurements in Lunar Orbit With CRaTER
Zeitlin C, Schwadron NA, Spence HE, Jordan AP, Looper MD, Wilson J, Mazur JE, Townsend LW. Space Weather. 19 June 2019:17. [7/30]
We report measurements of increasing intensities of Galactic Cosmic Ray protons and helium ions from 2015 through the end of 2018. The overall decrease in solar activity in this period has led to an increased flux of energetic particles, to levels that are approaching those observed during the previous solar minimum in 2009/2010, which was the deepest minimum of the Space Age. The data have implications for human exploration of deep space, and may provide useful benchmarks for models of cosmic ray fluxes as a function of solar modulation.
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Dose, LET and Strain Dependence of Radiation-Induced 53BP1 Foci in 15 Mouse Strains Ex Vivo. Introducing Novel DNA Damage Metrics
Penninckx S, Cekanaviciute E, Degorre C, Guiet E, Viger L, Lucas S and Costes SV. Radiation Research, 2019:192;1-12. [7/23]
A comprehensive comparative analysis on the repair of radiation-induced DNA damage ex vivo in 15 strains of mice, including 5 inbred reference strains and 10 collaborative-cross strains, of both sexes, totaling 5 million skin fibroblast cells imaged by three-dimensional high-throughput conventional microscopy. Non-immortalized primary skin fibroblasts derived from 76 mice were subjected to increasing doses of both low- and high-LET radiation (X rays; 350 MeV/n 40Ar; 600 MeV/n 56Fe), which are relevant to carcinogenesis and human space exploration. All 15 strains showed the same dose and LET dependence, but strain differences were preserved under various experimental conditions, indicating that the number and sizes of repair domains are modulated by the genetic background of each strain.
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Effects of exposure to 12C and 4He particles on cognitive performance of intact and ovariectomized female rats.
Rabin BM, Miller MG, Larsen A, Spadafora C, Zolnerowich NN, Dell'Acqua LA, Shukitt-Hale B. Life Sci Space Res. 2019 Jul 10. [Article in Press] [7/15]
Exploratory class missions to other planets will include both male and female astronauts. Previous research has indicated that female subjects do not show a disruption of cognitive performance following exposure to HZE particles. Because estrogen can function as a neuroprotectant, the cognitive performance of intact and ovariectomized female rats with estradiol or vehicle implants was tested following exposure to 12C (290 MeV/n) or 4He particles (300 MeV/n). The results indicated that exposure to 12C or 4He particles did not disrupt operant performance in the intact rats. Estradiol implants exacerbated the disruptive effects of radiation on performance. Although estrogen does not appear to function as a neuroprotectant following exposure to space radiation, the data suggest that intact females may be less responsive to the deleterious effects of exposure to space radiation on cognitive performance, possibly due to the effects of estrogen on cognitive performance.
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What does radiation biology tell us about potential health effects at low dose and low dose rates.
Azzam EI. J Radiol Prot. 2019 Jun 19. [Epub ahead of print] [7/2]
The health risks to humans exposed to low dose and low dose rate ionizing radiation remain ambiguous and are the subject of debate. The need to establish risk assessment standards based on the mechanisms underlying low dose/low fluence radiation exposures has been recognized by scholarly and regulatory bodies as critical for reducing the uncertainty in predicting adverse health risks of human exposure to low doses of radiation. Here, a brief review of laboratory-based evidence of molecular and biochemical changes induced by low doses and low dose rates of radiation is presented. In particular, two phenomena, namely bystander effects and adaptive responses that may impact low level radiation health risks are discussed together with the need for further studies. The expansion of this knowledge by considering the important variables that affect the radiation response (e.g., genetic susceptibility, time after exposure), and using the latest advances in experimental models and bioinformatics tools, may guide epidemiological studies towards reducing the uncertainty in predicting the potential health hazards of exposure to low dose radiation.
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Radiation-induced DNA damage cooperates with heterozygosity of TP53 and PTEN to generate high grade gliomas
Todorova PK, Fletcher-Sananikone E, Mukherjee B, Kollipara R, Vemireddy V, Xie XJ, Guida PM, Story MD, Hatanpaa K, Habib AA, Kittler R, Bachoo R, Hromas R, Floyd JR, Burma S. Cancer Res. 2019 May 14. pii: canres.0680.2019 [Epub ahead of print] [6/20]
Using transgenic mouse models, this study uncovers mechanisms by which ionizing radiation, especially particle radiation, promotes the development of lethal brain cancers called glioblastoma. Of special relevance to long-distance space missions, the study clearly shows that high-LET heavy ions carry a much greater carcinogenic risk compared to low-LET protons or X-rays. Importantly, the paper describes a versatile mouse model that can be used in the future for the testing of countermeasures to prevent brain cancer development from radiation exposure.
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Changes in one-carbon metabolism and DNA methylation in the hearts of mice exposed to space environment-relevant doses of oxygen ions (16O)
Miousse IR, Skinner CM, Sridharan V, Seawright JW, Singh P, Landes RD, Cheema AK, Hauer-Jensen M, Boerma M, Koturbash I. Life Sci Space Res. 2019 August; 22, 8-15. [6/20]
Cardiovascular disease constitutes an important threat to humans after space missions beyond the Earth's magnetosphere. We investigated the effects of 16O on the cardiac methylome and one-carbon metabolism in male C57BL/6 J mice. Left ventricles were examined 14 and 90 days after exposure to space-relevant doses of 0.1, 0.25, or 1 Gy of 16O (600 MeV/n). DNA methylation in repetitive elements was elevated, particularly after 90 days, while expression showed first a decrease followed by an increase in transcript abundance. Metabolomics analysis revealed that metabolites involved in homocysteine remethylation, central to DNA methylation, were unaffected by radiation, but the transsulfuration pathway was impacted after 90 days, with a large increase in cystathione levels at the lowest dose.
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Positive impact of low-dose, high-energy radiation on bone in partial- and/or full-weightbearing mice
Bokhari RS, Metzger CE, Black JM, Franklin KA, Boudreaux RD, Allen MR, Macias BR, Hogan HA, Braby LA, Bloomfield SA. npj Microgravity. 2019 Jun 4;5(1):13. [6/10]
We provide evidence for persistent positive impacts of high-LET radiation exposure preceding a period of full or partial weightbearing on bone mass and microarchitecture in the distal femur and, for full weightbearing mice only and more transiently, cortical bone energy absorption values.
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Risks of cognitive detriments after low dose heavy ion and proton exposures
Cucinotta FA, Cacao E. Int J Radiat Biol. 2019 May 23. [Epub ahead of print] [6/5]
Purpose: Heavy ion and proton brain irradiations occur during space travel and in Hadron therapy for cancer. Heavy ions produce distinct patterns of energy deposition in neuron cells and brain tissues compared to X-rays leading to large uncertainties in risk estimates. We make a critical review of findings from research studies over the last 25 years for understanding risks at low dose.
Conclusions: A large number of mouse and rat cognitive testing measures have been reported for a variety of particle species and energies for acute doses. However tissue reactions occur above dose thresholds and very few studies were performed at the heavy ion doses to be encountered on space missions (<0.04 Gy/y) or considered dose-rate effects, such that threshold doses are not known in rodent models. Investigations of possible mechanisms for cognitive changes have been limited by experimental design with largely group specific and not subject specific findings reported. Persistent oxidative stress and activated microglia cells are common mechanisms studied, while impairment of neurogenesis, detriments in neuron morphology, and changes to gene and protein expression were each found to be important in specific studies. Future research should focus on estimating threshold doses carried out with experimental designs aimed at understating causative mechanisms, which will be essential for extrapolating rodent findings to humans and chronic radiation scenarios, while establishing if mitigation are needed.
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Older Research Citations may be found in the Bibliography.


Radiation Risk Management

Space radiation risks are not measured, but predicted. From a practical perspective, it is necessary to address the question of what to do about the probable outcome, once its probability of occurrence has been calculated. The articles in this section discuss the major constraints placed upon space exploration by risk prediction as well as the limitations on the most common conventional means of radiation risk reduction, the use of shielding.

Walter Schimmerling
THREE Chief Editor

  • Radiation Risk Acceptability and Limitations – Francis Cucinotta (PDF)
  • Risk Synthesis: NASA Cancer Risk Models – Francis Cucinotta (swf)
  • Acceptable Risk – Walter Schimmerling  (Article)
  • Radiation Protection - Walter Schimmerling (swf)
  • Radiation Shielding – Ronald Turner   (PDF)
  • The Evolution of Risk Cross Section - Stanley B. Curtis (PDF)
  • Space Radiation Cancer Risk Projections and Uncertainties – 2012 – Francis Cucinotta, Myung-Hee, Y. Kim, Lori J. Chappell (PDF)
  • Probability of Causation for Space Radiation Carcinogenesis following International Space Station, Near Earth Asteroid, and Mars Missions – 2012 – Francis Cucinotta (PDF)
  • Evaluating Shielding Approaches to Reduce Space Radiation Cancer Risks – 2012 – Francis Cucinotta (PDF)


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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