RERF Findings in Brief
Radiation Exposure and Cancer
The risk of cancer increases significantly with radiation exposure for leukemia and most organ sites including the esophagus, stomach, colon, lung, female breast, ovary, brain, thyroid, and bladder. The largest increase in risk is found for leukemia. For other sites such as the rectum, pancreas, uterus, prostate, and kidney data suggest a possible increase in risk but the results are not statistically significant (Ozasa et al., 2012; Preston et al., 2007). Nevertheless, for all types of solid cancer combined there is a nearly 50% increase in risk at a dose of 1 Gray (Gy).
Radiation interacts with certain risk factors. For example, the risk associated with radiation for developing lung cancer is higher for light-to-moderate smokers compared to non-smokers and is dependent on smoking intensity (Furukawa et al., 2010). On the other hand, there is no clear evidence that the degree of radiation risk for breast, bladder or colon cancer is modified by other risk factors.
Those exposed in childhood have a notably higher risk of leukemia, thyroid cancer, and non-melanoma skin cancers than those exposed later in life. Moreover, radiation-associated increases in cancer risks persist throughout life regardless of age at exposure (Preston et al., 2007; Furukawa et al., 2012).
At present there is no evidence to support that those exposed prenatally have greater risk to develop cancer in adulthood compared to those exposed as children (Preston et al., 2008).
Radiation Exposure and Other Health Effects
Higher levels (doses above 0.5 Gy) of radiation exposure are associated with an elevated risk of both stroke and heart disease, and these findings are supported by a variety of clinical and laboratory data showing that various circulatory disease risk factors are also associated with radiation dose. There is uncertainty in the degree of risk at lower doses (Shimizu et al., 2010).
Recent data suggest the threshold of vision-impaired cataracts is much lower than the presumed threshold level (2-5 Gy) that was used for many years for radiation protection purposes. More protective eye safety standards are being implemented as a result of these new findings (Neriishi et al., 2012).
Thyroid nodules (benign and malignant) increase linearly with radiation dose. The increase is greater for those exposed in younger age (Imaizumi et al., 2006).
Excess risk was detected for uterine fibroids, which may be additional evidence indicating that benign tumor growths are possible effects of radiation exposure (Wong et al., 1993).
Increased risk of mental retardation and decrements in intelligence more generally were observed among those exposed prenatally to higher doses of radiation (100-300 mGy and above) between 8 and 25 weeks of gestation (Otake et al., 1996).
Genetic Effects of Radiation Exposure
Currently, there is no evidence that the offspring of survivors are at higher risk of developing cancer or other disease compared to the offspring of unexposed parents (Izumi et al., 2003). Furthermore, molecular analyses to search for radiation-associated inherited mutations in blood cells have also been negative (Nakamura, 2006). However 30-40 more years of follow-up are needed for definitive evidence regarding radiation risk in offspring.
Furukawa K, Preston DL, Lönn S, Funamoto S, Yonehara S, Matsuo T, Egawa H, Tokuoka S, Ozasa K, Kasagi F, Kodama K, Mabuchi K., Radiation and smoking effects on lung cancer incidence among atomic bomb survivors., Radiat Res. 2010 Jul;174(1):72-82.
Furukawa K, Preston D, Funamoto S, Yonehara S, Ito M, Tokuoka S, Sugiyama H, Soda M, Ozasa K, Mabuchi K., Long-term trend of thyroid cancer risk among Japanese atomic-bomb survivors: 60 years after exposure., Int J Cancer. 2012 Jul 31. doi: 10.1002/ijc.27749. [Epub ahead of print]
Imaizumi M, Usa T, Tominaga T, Neriishi K, Akahoshi M, Nakashima E, Ashizawa K, Hida A, Soda M, Fujiwara S, Yamada M, Ejima E, Yokoyama N, Okubo M, Sugino K, Suzuki G, Maeda R, Nagataki S, Eguchi K., Radiation dose-response relationships for thyroid nodules and autoimmune thyroid diseases in Hiroshima and Nagasaki atomic bomb survivors 55-58 years after radiation exposure., JAMA. 2006 Mar 1;295(9):1011-22.
Izumi S, Suyama A, Koyama K. Radiation-related mortality among offspring of atomic bomb survivors: a half-century of follow-up. Int J Cancer 107:292-97; 2003.
Nakamura N. Genetic effects of radiation in atomic-bomb survivors and their children: past, present and future. J Radiat Res (Japan) 47(Suppl.):B67-B73; 2006.
Neriishi K, Nakashima E, Akahoshi M, Hida A, Grant EJ, Masunari N, Funamoto S, Minamoto A, Fujiwara S, Shore RE., Radiation dose and cataract surgery incidence in atomic bomb survivors, 1986-2005., Radiology. 2012 Oct;265(1):167-74. Epub 2012 Aug 8.
Ozasa K, Shimizu Y, Suyama A, Kasagi F, Soda M, Grant EJ, Sakata R, Sugiyama H, Kodama K., Studies of the mortality of atomic bomb survivors, Report 14, 1950-2003: an overview of cancer and noncancer diseases, Radiat Res. 2012 Mar;177(3):229-43. Epub 2011 Dec 15.
Preston D, Cullings H, Suyama A, Funamoto S, Nishi N, Soda M, Mabuchi K, Kodama K, Kasagi F, Shore RE. Solid cancer incidence in atomic bomb survivors exposed in utero or as young children. J Natl Cancer Inst 100:428-36; 2008.
Shimizu Y, Kodama K, Nishi N, Kasagi F, Suyama A, Soda M, Grant EJ, Sugiyama H, Sakata R, Moriwaki H, Hayashi M, Konda M, Shore RE., Radiation exposure and circulatory disease risk: Hiroshima and Nagasaki atomic bomb survivor data, 1950-2003., BMJ. 2010 Jan 14;340:b5349. doi: 10.1136/bmj.b5349.
Suzuki G, Cullings H, Fujiwara S, Matsuura S, Kishi T, Ohishi W, Akahoshi M, Hayashi T, Tahara E. LTA 252GG and GA genotypes are associated with diffuse-type noncardia gastric-cancer risk in the Japanese population. Heliobacter 14:571-79; 2009.
Wong FL, Yamada M, Sasaki H, Kodama K, Akiba S, Shimaoka K, Hosoda Y, Noncancer disease incidence in the atomic bomb survivors: 1958-1986, Radiat Res 135:418-30, 1993