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.

READ MORE: 'Positivity, Acceptance And Love': Lodi Announces Location Of City's First-Ever Pride Festival

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.

READ MORE: Fans Back In Stands At All American Speedway In Roseville

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.

MORE NEWS: 1 Injured In Highway 50 Crash That Caused Major Backups In Sacramento

(TM and © Copyright 2014 CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2014 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)