NEW TECHNIQUE REVEALS LEVELS OF HIROSHIMA RADIATION
In the 70-plus years since the US dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki, several studies have examined the levels of radiation to which victims were exposed, using techniques ranging from longterm studies of mutation in the DNA of survivors, to measuring the luminescence of quartz grains in brick fragments. But now a team at the University of São Paulo (USP) in Brazil has successfully completed the first such study using actual human tissue.
To do this, they employed a technique called ‘electron spin resonance spectrometry’. The research was conducted by postdoctoral researcher Angela Kinoshita, under the supervision of USP’s Prof Oswaldo Baffa, and builds upon 1970s research by Prof Sérgio Mascarenhas, also of the University of São Paulo.
Mascarenhas discovered that exposure to radiation leaves bones weakly magnetised. If levels of background radiation are known, the extent of this so- called ‘paramagnetism’ can be measured to reveal a bone’s age. This means that if the age of the bone is known, it can be measured to determine how much radiation it has been exposed to.
Some four decades on, with the benefit of more advanced equipment, Baffa and Kinoshita were able to take such readings from tiny fragments of a victim’s jawbone, and determine that the individual had been exposed to approximately 9.46 Grays – almost twice the fatal dose. These findings tally with the results of previous studies, demonstrating the new technique’s potential as a means of triaging possible victims of radiation exposure.
“Imagine someone in New York planting an ordinary bomb with a small amount of radioactive material stuck to the explosive,” said Baffa. “Techniques like this can help identify who has been exposed to radioactive fallout and needs treatment.”
LEFT: Jawbone of victim from Hiroshima
BELOW: A destroyed Hiroshima after the bomb was dropped in 1945