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
Ionizing radiation and dose quantities in SI and non-SI units. The relationships of the ICRP dose quantities are shown in the accompanying diagram. Ionizing radiation has many industrial, military, and medical uses. Its usefulness must be balanced with its hazards, a compromise that has shifted over time. For example, at one time, assistants in shoe shops used X-rays to check a child's shoe size, but this practice was halted when the risks of ionizing radiation were better understood. Neutron radiation is essential to the working of nuclear reactors and nuclear weapons. The penetrating power of x-ray, gamma, beta, and positron radiation is