|Fig. 1: Pripyat, a town affected by the Chernobyl disaster, displays a radioactive sign. (Source: Wikimedia Commons)|
An increase in cancer incidence after nuclear disasters has been studied and documented in the 20th century. The findings from this research have given the scientific community a greater understanding of how radiation affects the human body. These findings have also guided radiation protection around the world. Evidence has shown that though nuclear disasters may result in an increase in cancer incidence, not every accident may have consequences quite as devastating.
When the power plant at Chernobyl caught fire in 1986, it spit radioactive particles into the air over Western Russia, Ukraine, and what is now Belarus.  Fig. 1 shows a radioactive sign on display around this area in Pripyat. About 80% of the particles were short-lived isotopes of iodine and most of the rest were cesium isotopes.  Many people ingested the radioactive iodine from cow's milk after iodine was dropped onto plants that were eaten by cows.  The iodine then proceeded to enter their milk.  The iodine was concentrated in the thyroid gland after consumption. 
Evidence of cancer has appeared after the Chernobyl accident. As stated by Urban, a significant increase in thyroid cancer occurred after the disaster.  Children are susceptible to thyroid cancer from radioactive iodine because of their small thyroid glands.  Dr. Vasily S. Kazakov of the Belarus Ministry of Health in Minsk performed a study on thyroid cancer in children in regions affected by the Chernobyl accident.  In Gomel, the most contaminated region studied after the nuclear catastrophe, thyroid cancer rates significantly increased in the years following the disaster.  Before the Chernobyl disaster, there were about one or two cases of thyroid cancer in children each year.  Approximately 38 cases were recorded in 1991 alone. The cases recorded were particularly striking because of the aggressiveness of some of the children's cancers. 
In 1945, the United States dropped one bomb on Hiroshima and one bomb on Nagasaki. Though the blasts were horrific and a large number of people died in the bombings, many survived their radiation in the aftermath of the attacks.  As stated by Dong, Japan's Radiation Effects Research Foundation (RERF) played a pivotal role in cancer research after the bombings.  The cancer data from radiation survivors now underpins every radiation protection system in the world.  The RERF estimates that out of the nearly 100,000 atomic survivors tracked, only 853 cases of cancerous tumors can be attributed to the bombs. 
In a separate study, atomic bomb survivors exposed in the womb have been found to have developed tumors.  According to the RERF, about 5% of these may be attributable to radiation, though this number rises to 11% when limited to those receiving more than .005 sieverts (Sv) of radiation. 
As noted by Mitchel, there was no increase in cancer after the Three Mile Island accident in 1979.  Studies have shown no significant difference in the overall rate of cancer deaths compared with the general population after the Three Mile Island nuclear accident.  The University of Pittsburgh's Graduate School of Public Health said that their study "provides no consistent evidence that radioactivity released during the nuclear accident has had a significant impact on the overall mortality experience of these residents."  The study concluded that dose-response relationships, however, cannot be definitively excluded. 
© Lauren Murphy. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 G. Kolata, "A Cancer Legacy from Chernobyl," New York Times, 3 Sep 92.
 O. Urban, "Health Consequences from the Chernobyl Incident," Physics 241, Stanford University, Winter 2016.
 P. Voosen, "Hiroshima and Nagasaki Cast Long Shadows Over Radiation Science," New York Times, 11 Apr 11.
 C. Dong, "Long-term Health Effects of the Atomic Bombings in Japan," Physics 241, Stanford University, Winter 2016.
 M. Mitchel, "The Three Mile Island's Impact on U.S. Nuclear Industry," Physics 241, Stanford University, Winter 2017.
 M. L. Wald, "Normal Cancer Rate Found Near Three Mile Island Plant," New York Times, 1 Nov 02.