For example, bone marrow is more sensitive than skin cells to radiation-induced cancer. Because the cancers can occur anytime in the exposed person's lifetime, these studies can take seventy years or more to complete. For example, the largest and scientifically most valuable epidemiologic study of radiation effects has been the ongoing study of the Japanese atomic bomb survivors. Radiation may alter the DNA within any cell. Cell damage and death that result from mutations in somatic cells occur only in the organism in which the mutation occurred and are therefore termed somatic or nonheritable effects.
Cancer is the most notable long-term somatic effect.
Genetic effects may not appear until many generations later. The genetic effects of radiation were first demonstrated in fruit flies in the 1920s. Like cancers, the genetic effects of radiation are impossible to distinguish from mutations due to other causes. Today at least 1,300 diseases are known to be caused by a mutation. During the period studied by the Advisory Committee, there was considerable debate among the scientific community over both the extent and the consequences of radiation-induced mutations.