Hiroshima victim’s jawbone reveals new levels of nuclear radiation

The new study performed by Brazilian researchers at the University of São Paulo is the first to measure direct blast radiation exposure, effectively using a victim’s jawbone as a dosimeter - a device used to measure an absorbed dose of ionizing radiation.

Physicist Sergio Mascarenhas went to Hiroshima 27 years after the bombing to see if he could obtain remains from victims and test their radiation level. “Exposure to radiation makes human bone magnetic, and that magnetic memory existed in the bones of atomic bombing victims years after the explosion,” Mascarenhas said.

During the final stage of World War II, the United States detonated two nuclear weapons over the Japanese cities of Hiroshima and Nagasaki on 6 August and 9 August 1945, respectively. The A-bomb nicknamed “Little Boy” that blew over Hiroshima instantly killed 45,000 people and would go on to claim the lives of thousands more as a result of nuclear fallout.

In a novel research, scientists have now  measured how much radiation was absorbed by the bones of one of the casualties, who was less than a mile away from where the bomb was set off.

In 1972 Mascarenhas obtained samples of bones from a few victims, including a jawbone from a person who was less than a mile away from where the bomb, code-named "Little Boy," dropped. He was able to test the bones and estimate how much radiation they absorbed, but technology at the time could not help him decipher specifically how much radiation was present.

The physicist took the remains to his native country, where they remained in storage for decades until two other Brazilian scientists recently decided to test them again with better technology.

Oswaldo Baffa, one of the scientists, said the jawbone showed 9.46 grays of radiation. Grays is the unit of measure for the amount of radiation absorbed by an object or person.

The finding means the amount of radiation found in the jawbone was more than enough to kill a person. About 5 grays of whole body radiation can kill a person. When a person undergoes radiation treatment for cancer, about 2 to 3 grays of radiation are centered on a specific part of the body.

The scientists believed their data is “timely and significant” due to the number of threats countries, including the US, receive regarding atomic bombs.

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

The scientist said he tested the bone by crushing a part of it with a mortar and pestle and exposing portions of the sample to various levels of radiation. The sample was then tested using a spectrometer and other techniques to determine the amount of radiation.

Mascarenhas, now in his 90s and retired, has not given up on his research.

“The measurement we obtained in this latest study is more reliable and up-to-date than the preliminary finding, but I’m currently evaluating a methodology that’s about a thousand times more sensitive than [electronic] spin resonance,” he told Brazilian media. “We’ll have news in a few months.”

Little Boy held about 140 pounds of uranium, which underwent nuclear fission when it exploded as planned nearly 2,000 feet above the Japanese city. The blast released 16 kilotons of explosive force, causing unspeakable damage in the area. According to one estimate, at least 50,000 people were killed and an equal number were injured that day. Nearly 70 per cent of the city’s buildings were destroyed, leaving many homeless.