Scientific tests on a shirt worn by a 16-year-old girl who was exposed to rain containing radioactive materials that fell after the Hiroshima atomic bombing on Aug. 6, 1945, known as “black rain,” continue to detect slight amounts of cesium 137 more than 70 years after the attack.

The girl, Toyoko Kubota, washed the shirt for physical education classes a number of times on a washboard, but could not remove the dark stains left after her exposure to the rain. After marriage, she changed her surname to Matsumiya. She is now 89 and lives in Mihara, Hiroshima Prefecture.

At the time of the bombing she was a student at Nishi Girls’ High School, which was closed after the nuclear attack. When the bomb fell she was on the second floor of her school building, which was located in Higashikanon-machi, now part of the city’s Nishi Ward, about 1.3 kilometers from the hypocenter.

The teen was trapped under debris from the building but managed to free herself despite injuries. After that, she was exposed to the black rain near the school. Fatigued and with a high fever and anemia she lay down to rest, but managed to survive.

Kiyoshi Shizuma, 69, a professor emeritus at Hiroshima University and an expert in radiation physics, has been studying the radioactive fallout from the bomb — including the radioactivity of the black rain that was triggered by the bombing.

The storage room at Hiroshima Peace Memorial Museum holds many A-bombed artifacts that show traces of the black rain. In 2016, Shizuma received permission from the museum to measure the radiation found on four pieces of A-bombed clothing at Hiroshima University.

In addition to the girl’s shirt, a small amount of cesium-137 was also detected on a sailor-style school uniform, a burned shirt and a loincloth. The items were believed to have been exposed to the black rain in present-day Naka Ward and Nishi Ward.

It is thought the black rain and its radioactive fallout affected a wide area of the city, not only downtown Hiroshima. How far it reached and what impact it had on humans are still debated.

Shizuma later reported his findings from the radiation tests to a study group focused on A-bombed artifacts at the museum. He also shared the results in an article in the group’s journal.

“I would like to uncover the facts that have yet to be clarified, as much as possible,” said Shizuma, whose grandfather was killed in the atomic bombing. The professor’s father was also exposed to radiation as he entered the city center shortly after the attack.

This monthly feature focuses on topics and issues covered by the Chugoku Shimbun, the largest newspaper in the Chugoku region. The original article was published on June 25.

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