Arie Jan Haagen-Smit

In the late 1940s, the city of Los Angeles grew fearful over a burgeoning cloud of smog with a baffling origin. Meanwhile, Arie Jan Haagen-Smit, a researcher at the California Institute of Technology, sat in a laboratory extracting chemical compounds responsible for flavor in pineapples.

In 1948, he decided to use the same lab technique to distill answers from the sky, collecting condensed smog from several hundred cubic feet of air. Analysis of the liquid revealed aldehydes, acids, and organic peroxides.

These chemicals, Haagen-Smit concluded, were created when hydrocarbons produced by oil refineries and automobiles interacted with compounds in the atmosphere.

Following his discovery, Haagen-Smit worked with the city to take on industry, urging factories to filter their smokestacks and pushing automobile plants to develop devices to limit exhaust vapors.

“I felt I was competent in chemistry, but not in government,” he said. “However, the job had to be done, and I never walk away from anything.”