Within months of Roentgen's discovery of X rays, severe adverse effects were 
reported, but not well publicized. As a result, over the next two decades, 
fluoroscope operators suffered lethal skin carcinomas. Later, case reports 
appeared concerning leukemia in radiation workers, and infants born with severe 
mental retardation after their mothers had been given pelvic radiotherapy early 
in pregnancy. Fluoroscopy and radiotherapy for benign disorders continued to be 
used with abandon until authoritative reports were published on the adverse 
effects of ionizing radiation by the U.S. NAS-NRC and the UK MRC in 1956. 
Meanwhile, exposure to the atomic bombs in Japan had occurred and epidemics of 
delayed effects began to be recognized among the survivors: cataracts (1949), 
leukemia (1952) and severe mental retardation among newborn infants after 
intrauterine exposure (1952). No statistically significant excess of germ-cell 
genetic effects was detected by six clinical measurements (1956), the F1 
mortality (1981), cytogenetic studies (1987) or biochemical genetic studies 
(1988). Somatic cell effects were revealed by long-lasting chromosomal 
aberrations in peripheral lymphocytes (1968), and somatic cell mutations were 
found at the glycophorin A locus in erythrocytes (1992). Molecular biology is a 
likely focus of new studies based on the function of the gene for ataxia 
telangiectasia (1995), a disorder in which children have severe, even lethal 
acute radiation reactions when given conventional doses of radiotherapy for 
lymphoma, to which they are prone. Also, obligate heterozygote female relatives 
can be studied for increased susceptibility to radiation-induced breast cancer, 
as suggested by clinical studies. The tumor registries in Hiroshima and Nagasaki 
now provide incidence data that show the extent of increases in eight common 
cancers and no increase in eight others (1994). The possibility of very late 
effects of A-bomb exposure is suggested by recent reports of increased 
frequencies of hyperparathyroidism, parathyroid cancers and certain causes of 
death other than cancer.