I4U News (EUA)

Scientists measure radiation dose in bone from the victim of hiroshima bombing

Publicado em 29 abril 2018

Atomic bombings of Hiroshima and Nagasaki in 1945 resulted in horrific casualties and devastation. Approximately 200,000 people died in the bombings while many survivors were severely disfigured.

Scientists already know that radiation exposure has harmful effects on humans. But the level of radiation dose to which the victims were exposed and the effects of this exposure on DNA and health in general are still unclear. In a latest study, Brazilian researchers describe how they used a sophisticated technique and took precise measurement of the radiation dose absorbed by the bones of victims of the nuclear bombs dropped on Japan.

"We used a technique known as electron spin resonance spectroscopy to perform retrospective dosimetry. Currently, there's renewed interest in this kind of methodology due to the risk of terrorist attacks in countries like the United States," said Oswaldo Baffa, a Professor at the University of São Paulo.

"Imagine someone in New York planting an ordinary bomb with a small amount of radioactive material stuck to the explosive. Techniques like this can help identify who has been exposed to radioactive fallout and needs treatment."

For the study, researchers used the jawbone of a Hiroshima bombing victim and removed millimeter-scale pieces of it. The samples were then exposed to radiation by using a technique called the additive dose method.

“We added radiation to the material and measure the rise in the dosimetric signal,” explained Baffa. “We then constructed a curve and extrapolated from that the initial dose, when the signal was presumably zero. This calibration method enabled us to measure different samples, as each bone and each part of the same bone has a different sensitivity to radiation, depending on its composition.”

By using this combination of techniques, researchers were able to calculate a dose of approximately 9.46 grays (Gy), which is higher than anticipated. Researchers say that exposure to about half of that dose or 5gy is enough to kill a person.

"The measurement we obtained in this latest study is more reliable and up to date than the preliminary finding.” Physicist Sérgio Mascarenhas from University of São Paulo said.

Thanks to the advances, researchers are now able to distinguish the signal of radiation dose absorbed during the nuclear attack from the so-called background signal. The background signal is produced by various things and can mix with signal corresponding to the radiation dose.

"There were serious doubts about the feasibility of using this methodology to determine the radiation dose deposited in these samples, because of the processes involved in the episode,” said researcher Angela Kinoshita. "The results confirm its feasibility and open up various