Dr. Walter John Jr., 99, of San Francisco, California, passed away April 14, 2023. A distinguished aerosol physicist, he conducted groundbreaking air pollution research, studying airborne particles and designing instruments to measure air pollution. A Research Scientist at the California Department of Public Health from 1974 to 1992, Walter headed the aerosol and microscopy laboratories. He subsequently founded the company Particle Science and held two patents for measurement equipment he developed. He was Senior Physicist and Nuclear Reactor Research Group leader at Lawrence Livermore National Laboratory from 1958 to 1971, researching experimental nuclear physics.

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Walter is survived by his wife of 69 years, Carol Salin John, of San Francisco; children Kenneth John (Kathy) of Arlington, VA, Leslie John (Greg Blackman) of Media, PA, Laura Ryle (Clint) of Santa Cruz, CA, and Claudia Shearer of San Francisco; and grandchildren Augie Blackman, Rachel Blackman, Rebecca Hoskins (Ward), Dean Shearer, and Luke Shearer.

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