Commentary 23

NCRP Commentary No. 23, Radiation Protection for Space Activities: Supplement to Previous Recommendations

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This National Council on Radiation Protection and Measurements (NCRP) Commentary supplements previous recommendations from NCRP that underlie the current National Aeronautics and Space Administration (NASA) standards for radiation protection of crew members during space activities.

For exposure to space radiation, protection standards for missions in low-Earth orbit (LEO) were approved by NASA in 2007 and a recent revision of these standards was approved by NASA in 2014. These protection standards have been applied to past and current missions on the International Space Station (ISS), which have been of relatively short duration of up to six months. There is now the possibility of longer-duration missions on the ISS and additionally the need for design and planning of potential future exploratory missions, which involve travel beyond LEO such as to Mars. This Commentary focuses on the implications of extended LEO missions in a general manner, particularly with regard to uncertainties in the knowledge of the health effects and the biological effectiveness of exposures to galactic cosmic rays in space, specifically to high atomic number and high-energy particles such as iron. The following topics are addressed:

• Application of the existing NASA standard used for current LEO missions to extended LEO missions.
• Application of the existing NASA standard used for current LEO missions to exploratory missions.
• The potential for inclusion of recent scientific knowledge on cardiovascular disease and central nervous system (CNS) dysfunction or disease in radiation protection standards for space missions.
• The high priority research areas needed to address uncertainties in the estimation of radiation risk for NASA space missions.
• Ethical considerations and principles that may bear on the application of NCRP advice on radiation protection for space activities.

The conclusions and recommendations contained in this Commentary are based on the current state of knowledge and experiences related to the possible health effects of space radiations. It is anticipated that additional research, along the lines proposed in this Commentary, will lead to further enhancement of the current NASA cancer risk projection model and refinement in the evaluation of the risk of exposure-induced death for cancer as well as consideration of CNS and cardiovascular effects.