Comparison of dose and risk estimates between ISS Partner Agencies for a 30-day lunar mission.

The International Partner Agencies of the International Space Station (ISS) present a comparison of the ionizing radiation absorbed dose and risk quantities used to characterize example missions in lunar space. This effort builds on previous collaborative work that characterizes radiation environments in space to support radiation protection for human spaceflight on ISS in low-Earth orbit (LEO) and exploration missions beyond (BLEO). A "shielded" ubiquitous galactic cosmic radiation (GCR) environment combined with--and separate from--the transient challenge of a solar particle event (SPE) was modelled for a simulated 30-day mission period. Simple geometries of relatively thin and uniform shields were chosen to represent the space vehicle and other available shielding, and male or female phantoms were used to represent the body's self-shielding. Absorbed dose in organs and tissues and the effective dose were calculated for males and females. Risk parameters for cancer and other outcomes are presented for selected organs. The results of this intracomparison between ISS Partner Agencies itself provide insights to the level of agreement with which space agencies can perform organ dosimetry and calculate effective dose. This work was performed in collaboration with the advisory and guidance efforts of the International Commission on Radiological Protection (ICRP) Task Group 115 and will be presented in an ICRP Report.

European astronaut radiation related cancer risk assessment using dosimetric calculations of organ dose equivalents.

An illustrative sample mission of a Mars swing-by mission lasting one calendar year was chosen to highlight the application of European risk assessment software to cancer (all solid cancer plus leukaemia) risks from radiation exposures in space quantified with organ dose equivalent rates from model calculations based on the quantity Radiation Attributed Decrease of Survival (RADS). The relevant dose equivalent to the colon for radiation exposures from this Mars swing-by mission were found to vary between 198 and 482 mSv. These doses depend on sex and the two other factors investigated here of: solar activity phase (maximum or minimum); and the choice of space radiation quality factor used in the calculations of dose equivalent. Such doses received at typical astronaut ages around 40 years old will result in: the probability of surviving until retirement age (65 years) being reduced by a range from 0.38% (95%CI: 0.29; 0.49) to 1.29% (95%CI: 1.06; 1.56); and the probability of surviving cancer free until retirement age being reduced by a range from 0.78% (95%CI: 0.59; 0.99) to 2.63% (95%CI: 2.16; 3.18). As expected from the features of the models applied to quantify the general dosimetric and radiation epidemiology parameters, the cancer incidence risks in terms of surviving cancer free, are higher than the cancer mortality risks in terms of surviving, the risks for females are higher than for males, and the risks at solar minimum are higher than at solar maximum.

Space agency-specific standards for crew dose and risk assessment of ionising radiation exposures for the International Space Station.

The Partner Agencies of the International Space Station (ISS) maintain separate career exposure limits and shared Flight Rules that control the ionising radiation exposures that crewmembers can experience due to ambient environments throughout their space missions. In low Earth orbit as well as further out in space, energetic ions referred to as galactic cosmic radiation (GCR) easily penetrate spacecraft and spacecraft contents and consequently are always present at low dose rates. Protons and electrons that are trapped in the Earth's geomagnetic field are encountered intermittently, and a rare energetic solar particle event (SPE) may expose crew to (mostly) energetic protons. Space radiation protection goals are to optimize radiation exposures to maintain deleterious late effects at known and acceptable levels and to prevent any early effects that might compromise crew health and mission success. The conventional radiation protection metric effective dose provides a basic framework for limiting exposures associated with human spaceflight and can be communicated to all stakeholders. Additional metrics and uncertainty analyses are required to understand more completely and to convey nuanced information about potential impacts to an individual astronaut or to a space mission. Missions to remote destinations well beyond low Earth orbit (BLEO) are upcoming and bestow additional challenges that shape design and radiation protection needs. NASA has recently adopted a more permissive career exposure limit based upon effective dose and new restrictions on mission exposures imposed by nuclear technologies. This manuscript reviews the exposure limits that apply to the ISS crewmembers. This work was performed in collaboration with the advisory and guidance efforts of International Commission on Radiological Protection (ICRP) Task Group 115 and will be summarized in an upcoming ICRP Report.

The ESA Active Dosimeter (EAD) system onboard the International Space Station (ISS).

Ionizing radiation in general and mixed fields of space radiation in particular pose a risk of serious harm to human health. The risk of such adverse effects increases with the duration of the mission, and for all missions outside the protective properties of the Earth's magnetic field and atmosphere. Accordingly, radiation protection is of central importance for all human spaceflight, which is recognized by all international space agencies. To date various systems, analyze and determine the exposure to ionizing radiation within the environment and to the crew onboard the International Space Station (ISS). In addition to this operational monitoring, experiments and technology demonstrations are carried out. This to further enhance systems capabilities, to prepare for exploratory missions, to the Deep Space Gateway and/or to enable for human presence at other celestial bodies. Subsequently the European Space Agency (ESA) decided early to support the development of an active personal dosimeter. Under the auspices of the European Space Research and Technology Center (ESTEC) together with the European Astronaut Center's (EAC) Medical Operations and Space Medicine (HRE-OM) team, a European industrial consortium was formed to develop, build, and test this system. To complete the ESA Active Dosimeter (EAD) Technology Demonstration in space, EAD components were delivered to ISS with the ESA's space missions 'iriss' and 'proxima' in 2015 and 2016. This marked Phase 1 (2015) and 2 (2016-2017) of the EAD Technology Demonstration to which focus is given in this publication. All EAD systems and their functionalities, the different radiation detector, their properties, and calibrations procedures are described. Emphasis is first on the "iriss" mission of September 2015, that provided a complete set of data for an entire space mission from launch to landing, for the first time. Data obtained during Phase 2 in 2016-2017 are discussed thereafter. Measurements with the active radiation detectors of the EAD system provided data of the absorbed dose, dose equivalent, quality factor as well as the various dose contributions during the crossings of the South Atlantic Anomaly (SAA) and/or resulting from galactic cosmic radiation (GCR). Results of the in-flight cross-calibrations among the internal sensors of the EAD systems are discussed and alternative usage of the EAD Mobile Units as area monitors at various different locations inside the ISS is described.

Towards sustainable human space exploration-priorities for radiation research to quantify and mitigate radiation risks.

Human spaceflight is entering a new era of sustainable human space exploration. By 2030 humans will regularly fly to the Moon's orbit, return to the Moon's surface and preparations for crewed Mars missions will intensify. In planning these undertakings, several challenges will need to be addressed in order to ensure the safety of astronauts during their space travels. One of the important challenges to overcome, that could be a major showstopper of the space endeavor, is the exposure to the space radiation environment. There is an urgent need for quantifying, managing and limiting the detrimental health risks and electronics damage induced by space radiation exposure. Such risks raise key priority topics for space research programs. Risk limitation involves obtaining a better understanding of space weather phenomena and the complex radiation environment in spaceflight, as well as developing and applying accurate dosimetric instruments, understanding related short- and long-term health risks, and strategies for effective countermeasures to minimize both exposure to space radiation and the remaining effects post exposure. The ESA/SciSpacE Space Radiation White Paper identifies those topics and underlines priorities for future research and development, to enable safe human and robotic exploration of space beyond Low Earth Orbit.

The Potential of Physical Exercise to Mitigate Radiation Damage-A Systematic Review.

There is a need to investigate new countermeasures against the detrimental effects of ionizing radiation as deep space exploration missions are on the horizon. Objective: In this systematic review, the effects of physical exercise upon ionizing radiation-induced damage were evaluated. Methods: Systematic searches were performed in Medline, Embase, Cochrane library, and the databases from space agencies. Of 2,798 publications that were screened, 22 studies contained relevant data that were further extracted and analyzed. Risk of bias of included studies was assessed. Due to the high level of heterogeneity, meta-analysis was not performed. Five outcome groups were assessed by calculating Hedges' g effect sizes and visualized using effect size plots. Results: Exercise decreased radiation-induced DNA damage, oxidative stress, and inflammation, while increasing antioxidant activity. Although the results were highly heterogeneous, there was evidence for a beneficial effect of exercise in cellular, clinical, and functional outcomes. Conclusions: Out of 72 outcomes, 68 showed a beneficial effect of physical training when exposed to ionizing radiation. As the first study to investigate a potential protective mechanism of physical exercise against radiation effects in a systematic review, the current findings may help inform medical capabilities of human spaceflight and may also be relevant for terrestrial clinical care such as radiation oncology.

A bespoke health risk assessment methodology for the radiation protection of astronauts.

An alternative approach that is particularly suitable for the radiation health risk assessment (HRA) of astronauts is presented. The quantity, Radiation Attributed Decrease of Survival (RADS), representing the cumulative decrease in the unknown survival curve at a certain attained age, due to the radiation exposure at an earlier age, forms the basis for this alternative approach. Results are provided for all solid cancer plus leukemia incidence RADS from estimated doses from theoretical radiation exposures accumulated during long-term missions to the Moon or Mars. For example, it is shown that a 1000-day Mars exploration mission with a hypothetical mission effective dose of 1.07 Sv at typical astronaut ages around 40 years old, will result in the probability of surviving free of all types of solid cancer and leukemia until retirement age (65 years) being reduced by 4.2% (95% CI 3.2; 5.3) for males and 5.8% (95% CI 4.8; 7.0) for females. RADS dose-responses are given, for the outcomes for incidence of all solid cancer, leukemia, lung and female breast cancer. Results showing how RADS varies with age at exposure, attained age and other factors are also presented. The advantages of this alternative approach, over currently applied methodologies for the long-term radiation protection of astronauts after mission exposures, are presented with example calculations applicable to European astronaut occupational HRA. Some tentative suggestions for new types of occupational risk limits for space missions are given while acknowledging that the setting of astronaut radiation-related risk limits will ultimately be decided by the Space Agencies. Suggestions are provided for further work which builds on and extends this new HRA approach, e.g., by eventually including non-cancer effects and detailed space dosimetry.

The Potential of Fasting and Caloric Restriction to Mitigate Radiation Damage-A Systematic Review.

Detrimental health effects from ionizing radiation to living organisms is one of the key concerns identified and addressed by Radiation Protection institutions, nationally and internationally on Earth and for human spaceflight. Thus, new methods for mitigating the adverse effects of ionizing radiation are urgently needed for terrestrial health and deep space exploration. Caloric restriction and (intermittent-) fasting have been reported to elicit a variety of immediate and long-term physiological effects. The rapidly growing body of evidence of research studies investigating the effects of caloric restriction and dietary fasting points toward a multitude of benefits affecting numerous physiological systems. Therefore, a systematic review was performed to evaluate the evidence of caloric restriction and dietary fasting on the physiological response to ionizing radiation in humans and animals. All experimental studies of humans, animals, and eukaryotic cell lines available in PubMed, Cochrane library, and specialized databases were searched comparing irradiation post-caloric restriction or fasting to a non-nutritionally restricted control group on a broad range of outcomes from molecular to clinical responses. The initial search yielded 2,653 records. The final analysis included 11 studies. Most studies investigated survival rate or cancer occurrence in animals. Included studies did not reveal any benefit from pre exposure caloric restriction, except when performed with post radiation caloric restriction. However, the effects of pre-exposure fasting suggest increased resilience to ionizing radiation.

Evolution of the Health Canada astronaut biodosimetry program with a view toward international harmonization.

Biodosimetry of astronaut lymphocyte samples, taken prior to- and post-flight, provides an important in vivo measurement of radiation-induced damage incurred during space flight which can be included in the medical records of the astronauts. Health Canada has been developing their astronaut biodosimetry program since 2007 and since then has analyzed data from 7 astronauts. While multiple cytogenetic endpoints may be analyzed for the astronauts, the Fluorescent in situ hybridization (FISH) assay is considered to be key for detecting long-lasting stable damage. It is believed that this long-lasting damage is most likely to lead to an increased risk to the health of the astronauts during long-term flights (lasting 6 months or more). The complexity of damage that results from protracted, non-homogeneous radiation exposure, like that found in the space environment, requires a detailed scoring schematic to capture as much information as possible. To that end, this paper outlines the efforts to harmonize the manner in which Health Canada's FISH data are recorded to better facilitate the comparison of results with other international biodosimetry programs.

International Space Station medical standards and certification for space flight participants.

INTRODUCTION: The medical community of the International Space Station (ISS) has developed joint medical standards and evaluation requirements for Space Flight Participants ("space tourists") which are used by the ISS medical certification board to determine medical eligibility of individuals other than professional astronauts (cosmonauts) for short-duration space flight to the ISS. These individuals are generally fare-paying passengers without operational responsibilities. MATERIAL AND CONTEXT: By means of this publication, the medical standards and evaluation requirements for the ISS Space Flight Participants are offered to the aerospace medicine and commercial spaceflight communities for reference purposes. It is emphasized that the criteria applied to the ISS spaceflight participant candidates are substantially less stringent than those for professional astronauts and/or crewmembers of visiting and long-duration missions to the ISS. CONCLUSIONS: These medical standards are released by the government space agencies to facilitate the development of robust medical screening and medical risk assessment approaches in the context of the evolving commercial human spaceflight industry.