IRVINE, Calif. (AP) — James Pitts, a pioneering smog researcher whose work spurred California’s ground-breaking clean-air regulations, died Thursday at age 93, his wife said.

Pitts died in his sleep at his home in Irvine, according to his wife and fellow professor at the University of California, Irvine, Barbara Finlayson-Pitts.

Pitts began researching air pollution in the 1950s at the University of California, Riverside. At the time, the causes and dangers of smog weren’t well-understood.

He helped create the Statewide Air Pollution Research Center and directed it for 18 years. His team built the first smog chamber to study photochemical smog.

It was visited by scientists and politicians from around the world.

Pitts joined his wife at UC Irvine in 1994.

Pitts co-authored nearly 400 scientific books and publications. He also served on panels at the California Air Resources Board.

Gov. Jerry Brown lauded Pitts’ contributions to the state’s environmental health.

“Jim was one of the key pioneers in cleaning up air pollution in California and we’ll all miss him,” Brown said in a statement.

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