Health threat from cosmic rays radiation resulting from particle interactions within the vitreous humor. This phenomenon has been replicated on Earth by scientists at various institutions. As the duration of the longest Apollo flights was less than two weeks, the astronauts had limited cumulative exposures and a corresponding low risk for radiation carcinogenesis. In addition, there were only 24 such astronauts, making statistical analysis of any potential health effects problematic. In the above discussion dose equivalents is units of Sievert (Sv) are noted, however the Sv is a unit for comparing cancer risks for different types of ionizing radiation. For CNS effects absorbed doses in
Acute radiation syndrome are not designed to evaluate acute radiation syndrome. To help avoid confusion between these quantities, absorbed dose is measured in units of grays (in SI, unit symbol Gy) or rads (in CGS), while the others are measured in sieverts (in SI, unit symbol Sv) or rems (in CGS). 1 rad = 0.01 Gy and 1 rem = 0.01 Sv. In most of the acute exposure scenarios that lead to radiation sickness, the bulk of the radiation is external whole-body gamma, in which case the absorbed, equivalent and effective doses are all equal. There are exceptions, such as the Therac-25 accidents