The most common units are ion pairs per centimeter of air or per micron of water or tissue. Specific ionization is very important in considerations of internal exposure to alpha and beta radiation. The range of an alpha particle in tissue is limited to a very few microns, therefore a great deal of ionization takes place in a very small volume producing a highly concentrated volume of damaged tissue. By the same token, the external hazard from alpha radiation is negligible because in most cases the alpha particle will not penetrate the outer layers of dead skin. Beta radiation has a specific ionization considerably less than alpha radiation and much smaller mass, which makes its range considerably greater.
Beta radiation is both external and internal hazard.
The external effect is usually in the form of a burn which closely resembles a thermal burn, but takes longer to heal. Some high energy beta particles can penetrate deeply enough into tissue to be a hazard to internal body organs, even when it is from an external source. The specific ionization of gamma radiation is less by orders of magnitude. However, its high penetrating ability makes it a hazard to any organ in the body. Somatic and genetic effects of radiation Acute somatic effects of radiation include skin burns, vomiting, hair loss, temporary sterility or subfertility in men, and blood changes.