Space Radiation

AbstractThe most critical biomedical risks of space habitation are (1) carcinogenesis caused by radiation, (2) loss of bone mass or density, (3) poor psychosocial adaptation, and (4) clinical manifestations of trauma or acute medical problems. Because of the unique problems and the potential long‐term consequences, radiation is frequently considered the most serious of these for long‐duration space missions, and cancer is the major risk followed by damage to the central nervous system. Radiative hazards in space have been discussed in depth by a Task Group of the National Research Council along with overall research strategies.The term radiation in the present context refers specifically to directly and indirectly ionizing radiation, including X rays, gamma rays, neutrons, ions, and other somewhat esoteric particles such as muons and pions. Radiation is a natural part of our environment on the surface of Earth. Biological organisms in general, and humans in particular, have adapted to the normal radiative environment at Earth's surface and certainly have even benefited from the radiation. At the same time, those radiations also initiate biological damage ranging from sunburn to cancer. Earth's atmosphere and its magnetic field act as excellent radiative shields by reducing the levels of radiation. As one goes farther away from Earth's surface into orbit or toward outer space, the radiative level generally increases in intensity and changes in the types and energies of the radiation. It is known that the radiative dose rates for personnel in space are significantly higher than on Earth's surface. There has been little experience with regard to the biological consequences of healthy people exposed to these types of radiation for protracted periods of time. Best estimates indicate, however, that the additional exposure to higher energy radiation beyond that on Earth's surface or above the present allowable limits for radiation workers could result in significant risks of cancer or other serious diseases.Because of higher level of exposures and the potential for long‐term negative consequences, radiation has been categorized as the worst biomedical risk of long‐duration space missions. At the same time, using an appropriate programmatic strategy and focused research, the risks of radiation in space should be reduced to levels comparable to or less than those of other hazards.