Katsuko Saruhashi

Katsuko Saruhashi (1920 to 2007) was a Japanese geochemist who built tools for some of the first measurements of carbon dioxide in seawater and later showed the dangers of radioactive fallout and how far it travels. Born in Tokyo, she left a secure job at an insurance firm at 21 to study chemistry at the Imperial Women's College of Science, graduated in 1943 and joined the Meteorological Research Institute, where she worked with her mentor Yasuo Miyake. In 1957 she became the first woman to earn a science doctorate from the University of Tokyo, with a dissertation on carbonic matter in natural water. Her 1955 table gave oceanographers a way to find the composition of three carbonic acid substances from water temperature, pH and salinity. With Miyake she measured caesium-137 and strontium-90 in seawater and found much higher levels in the western North Pacific, a result tied to nuclear testing there and later checked against American measurements at Scripps. She also worked to raise the number and standing of women scientists in Japan, founding the Society of Japanese Women Scientists and the Saruhashi Prize.