The bombing of the Japanese cities Hiroshima and Nagasaki by the United States in 1945 was the first and only use of nuclear weapons against civilian targets. A series of studies began in its aftermath to measure the impact of the fallout, in terms of both the radiation dose to which the victims were exposed and the effects of this exposure on DNA and health in general.
Continuing research that started in the 1980s under the leadership of physicist Sérgio Mascarenhas, Full Professor at the University of São Paulo (USP), Brazilian scientists have published an article in the journal PLOS ONE describing a method of precise measurement of the radiation dose absorbed by the bones of victims of the nuclear bombs dropped on Japan.
The investigation was conducted during the postdoctoral research of Angela Kinoshita, currently a professor at Universidade do Sagrado Coração in Bauru, São Paulo State.
As Kinoshita explained, the study is unique insofar as it used samples of human tissue from victims of the bomb dropped on Hiroshima.
On the strength of this research, he [Oswaldo Baffa] was invited to teach at Harvard University in the United States. Before leaving for the US, however, he decided to go to Japan to try to obtain samples of bones from victims of the nuclear bombs and test his method on them.
“They gave me a jawbone, and I decided to measure the radiation right there, at Hiroshima University,” he said. “I needed to prove experimentally that my discovery was genuine.”
Mascarenhas succeeded in demonstrating that a dosimetric signal could be obtained from the sample even though the technology was still rudimentary and there were no computers to help process the results. The research was presented at the American Physical Society’s annual March Meeting, where it made a strong impression. Mascarenhas brought the samples to Brazil, where they remain.
Thanks to this combination of techniques, they were able to measure a dose of approximately 9.46 grays (Gy), which is high in Baffa’s view. “About half that dose, or 5 Gy, is fatal if the entire body is exposed to it,” he said.