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Katsuko Saruhashi turned radioactive fallout into a scientific legacy

Today’s Google Doodle celebrates Japanese geochemist Katsuko Saruhashi, whose research helped reveal the insidious spread of radioactive fallout from the US nuclear testing ground in the Pacific. If she were still alive, today would have been her 98th birthday.

In 1957, Saruhashi became the first woman to receive a PhD in chemistry in Japan. Her work focused on measuring the molecules in seawater — like carbon dioxide, oxygen, and also radioactive molecules like cesium-137.

Just twelve years before she received her PhD, the United States dropped atomic bombs that devastated the cities of Hiroshima and Nagaski, and the US continued to unleash a torrent of radioactive fallout in the Pacific as it tested bigger and bigger bombs. By 1958, the US had exploded 67 nuclear devices around the Marshall Islands — leaving a long legacy of contamination behind.

Saruhashi worked at the Central Meteorological Observatory in Tokyo to develop more sensitive methods of measuring radioactive fallout. It was a challenging task, says Toshihiro Higuchi, a historian at Georgetown University and expert on Cold War science. “The amount of fallout that we are talking about is really tiny, and then we are talking about the vast ocean,” he says.

Saruhashi and her colleagues discovered that fallout didn’t disperse evenly in the ocean.

The concentrations of radioactive cesium near Japan, for example, were much higher than the concentrations along the west coast of the US. The team proposed that the high levels were because Japan is downstream of the Pacific nuclear testing ground. But others suspected that the measurements might be off, Higuchi says. “There was a controversy over her argument that the radioactive fallout in seawater was more than what they used to think.”

To settle the dispute, the US Atomic Energy Commission funded a lab swap.

Saruhashi took a six month leave of absence from her work at the Central Meteorological Observatory in Japan, and visited Scripps Institute of Oceanography. There, she and oceanographer Ted Folsom compared their methods and discovered that Saruhashi’s technique was spot on: the two teams’ methods produced almost identical results.

Saruhashi worked to support female scientists, and in 1958 co-founded the Society of Japanese Women Scientists, which pushed for nuclear disarmament and peace. “She was very conscious of the social responsibility of scientists in general,” Higuchi says. Saruhashi died in 2007.

But she left behind a legacy of scientific research, including an award called the Saruhashi Prize for top natural scientists who are women. “She was a trailblazer,” Higuchi says.

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