Answer to Question #3996 Submitted to "Ask the Experts"

Could you provide a reference that shows a lack of gonadal effects due to radiation in the survivors of Hiroshima? I am an ED (emergency department) doctor and frequently order CT (computerized tomography) scans to evaluate for appendicitis. Lately the residents have been ordering ultrasounds (which are never diagnostic and must almost always be followed by a CT scan anyway). They are arguing that they want to spare the gonads of the patient from the radiation of the CT scan. I surmise from reading many of the answers on your website that there really is no evidence of gonadal damage from the radiation dose provided during diagnostic CT scanning. I would very much like a reference to support this for my upcoming talk.

I am not aware of any references that discuss gonadal effects of radiation in the survivors of Hiroshima. However, the Committee on the Biological Effects of Ionizing Radiation, BEIR V (NAS/NRC 1990), reviewed the effects of radiation exposure to both the testis and ovaries. For the testis, they estimated a threshold dose equivalent for induction of temporary sterility in the adult human testis of 0.15 Sv (15 rem), and for permanent sterility of 3.5 Sv (350 rem) when received as a single exposure. These determinations are based on a number of sources, including Fabrikant (1972), Hall (1987), and UNSCEAR (1982). You might also want to check out Rowley, et. al. (1974) and UNSCEAR (2001).

Since doses as low as 0.15 Sv (15 rem) to the testis have been shown to cause at least a temporary decrease in sperm count, there may be cause for concern since typical CT doses are in the range of 0.03 to 0.05 Sv (3 to 5 rem). This is especially pertinent when more than one CT procedure performed on an individual results in multiple doses to the testis.

Kenneth L. Miller, CHP, CMHP

References:

1. National Academy of Sciences/National Research Council. Health effects of exposure to low levels of ionizing radiation. Report of the Advisory Committee on the Biological Effects of Ionizing Radiation, BEIR V. Washington, DC: National Academy Press; 1990.
    
2. Fabrikant JI. Radiobiology. Chicago, IL: Year Book Medical; 1972.
    
3. Hall E. Radiobiology for the radiologist. New York, NY: Harper & Row; 1987.
    
4. United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). Ionizing radiation: Sources and biological effects. New York, NY: United Nations; 1982.
    
5. Rowley MJ, Leach DR, Warner AW, Heller CG. Effect of graded doses of ionizing radiation on the human testis. Radiation Research 59:665-678; 1974.
    
6. United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). Hereditary effects of radiation. New York, NY: United Nations; 1982.
    
7. Health effects of exposure to low levels of ionizing radiation. Report of the Advisory Committee on the Biological Effects of Ionizing Radiation, BEIR V. Washington, DC: National Academy Press; 1990.