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Space Radiation Element

The Space Radiation Element (SRE) seeks to characterize human health outcomes associated with space radiation exposure, helping NASA to build strategies that protect astronaut health and ensure safe human spaceflight.

The aurora australis above the southern Indian Ocean

Space Radiation Risks

NASA has identified the following health concerns from space radiation as high research priorities

Increased risk of cancers:

The evidence for cancer risks from humans exposed to radiation is extensive for doses above 100 millisieverts (mSv). There are uncertainties for lower doses and in transferring risks between populations with different genetic and dietary attributes.

Human epidemiology can be applied to space exposures; however, there are additional uncertainties related to the quality of radiation in space, while the doses to be expected on space missions are well understood. Reducing the uncertainties in risk assessment is required before a mission to Mars can be undertaken and has led to a number of investigations on carcinogenesis and degenerative diseases.

The large uncertainties in risk projection models will only be reduced by improving basic understanding of the underlying biological processes and their disruption by space radiation. It is unlikely that the radiation risk problem for space exploration will be solved by a simple countermeasure, such as shielding or radio protective drugs. The risk will be understood and controlled only with more basic research in the field of cancer induction by charged particles.  [Learn More]

Changes in motor function and behavior; neurological disorders:

At this time, reliable projections for central nervous system risks from space radiation exposure cannot be made due to limited data on the effects of high radiation on the nervous system. The existing animal and cellular data show that space-like radiation can produce molecular, structural, functional, and behavioral effects at doses comparable to reference mission projections.

If human responses closely resemble those in animal models, the possibility exists for impacts on mission operations and/or late degenerative changes. However, the significance of these results in terms of space flight operational performance or morbidity to astronauts has not been explained.

Computer simulations and systems biology approaches may be helpful in providing the necessary data and knowledge to evaluate the similarity between animal and human response mechanisms. Findings based on rodent models may need to be validated in higher species such as non-human primates.

A vigorous research program will be required to solve these problems and must rely on new approaches to risk assessment and countermeasure validation because the unique properties of the CNS and its modes of impairment are intrinsically different than those associated with cancer risks. [Learn More]

Degenerative tissue defects such as cataracts, circulatory diseases, and digestive diseases:

The association between ionizing radiation exposure and the long-term development of degenerative tissue effects such as heart disease, cataracts, immunological changes, and premature aging is well-established for moderate to high doses of radiation. The majority of this evidence is derived from epidemiological studies on the atomic bomb survivors, radiotherapy patients, and occupationally exposed workers and is supported by laboratory studies using animal models and studies of cataracts in astronauts.

The risks for these diseases from low dose-rate exposures are much more difficult to assess due to their multifactorial nature and long latency periods where animals must be observed; therefore, these risks remain debatable for ISS or short-term lunar missions but are more likely in long-term lunar or Mars missions. It also remains unclear whether low-dose exposures influence the same biological pathways that have been shown to be involved in disease progression following moderate- to high-dose radiation exposures.

Research to address the possible role of chronic inflammation and increased oxidative stress associated with space radiation exposure will need to be conducted. As mission duration increases, there could be degenerative risks to other tissues related to digestive diseases and pulmonary changes that become a concern. [Learn More]

Acute radiation risks from a major solar or galactic cosmic ray event:

The biological effects of space radiation, including acute radiation risks (ARS), are a significant concern for human spaceflight. The primary data that are currently available are derived from analyses of medical patients and persons accidentally exposed to high doses of radiation. High doses of radiation can induce profound radiation sickness and death. Lower doses of radiation induce symptoms that are much milder physiologically but that pose operational risks that may be equally serious. Both scenarios have the potential to seriously affect crew health and/or prevent the completion of mission objectives.

NASA has established short-term dose limits to prevent clinically significant deterministic health effects, including performance degradation in flight. Radiation protection must be provided in the form of shielding and operational dosimetry and monitoring, as well as biological countermeasures when traveling outside of the protective magnetosphere of Earth. Predictive models support the evaluation of crew risks, operational requirements and decisions, and the efficient design of vehicle shelters to minimize exposures.

As future NASA missions once again extend beyond lower Earth orbit and now for longer durations, there is reasonable concern that a compromised immune system due to high skin doses from a solar particle event may lead to increased risks. Research data specific to the space flight environment are being compiled to quantify the magnitude of this increased risk and to develop appropriate predictive models and protection strategies. In addition, clinically relevant biological countermeasures are being identified and validated for spaceflight. [Learn More]

Learn more about these and other risks to humans posed by spaceflight at NASA’s Human Research Roadmap.