Glen R. Cass; Caltech Professor Specialized in Airborne Pollutants

Glen R. Cass, 54, an expert on pollution who helped identify the mix of airborne chemicals that pollute urban areas such as Los Angeles, died July 30 of cancer at Duke University Hospital in Durham, N.C.

Cass specialized in the control of airborne particles, photochemical oxidants and improved visibility. In 1999, he initiated a study of airborne particles at 500 sites around the world, including seven in China. The study, called Operation Blue Sky, factored into China's 2008 Olympic bid.

The Pasadena-born Cass graduated from USC, earned his master's degree at Stanford and his doctorate at Caltech, where he taught for 24 years before joining the faculty at the Georgia Institute of Technology.

Cass served on several advisory committees for government agencies. His research included work for the Environmental Protection Agency, the California Air Resources Board, NASA, the Department of Defense, Exxon and the Ford Foundation.