Premieres Tuesday, Aug. 26, 2025 at 9 p.m. on KPBS TV / PBS app
Midcentury Los Angeles was a boomtown. People came for economic opportunities, Hollywood glamour, and the sunny, beautiful weather. But when thick, choking clouds threatened to tarnish its appeal, a commission was created to determine the source of the smog. Initially, the focus was on curbing emissions from a new chemical plant, but it became clear the problem was bigger than one factory. In 1947, Los Angeles County established the Air Pollution Control District (APCD), the first regulatory agency of its kind in the nation. Although inspectors ticketed factories and vehicles that emitted visible smoke, the problem continued.
L.A.’s unique geography was partly to blame. Mountains surround the city, trapping pollution, while hot air from nearby deserts pushes it downward. But understanding this was small consolation to Angelenos, especially when, in 1948, similar conditions trapped pollution in the industrial town of Donora, Pennsylvania, and killed at least 20 people. L.A. leaders felt a heightened urgency to solve the problem — and the solution came from a surprising place.
Arie Haagen-Smit, a plant chemist at Caltech, was working on distilling the essence of pineapple flavor for Dole when L.A. farmers noticed that their crops were dying at an unusual rate. Determined to find the cause, he used distilling techniques to reduce the smoggy L.A. air to a few drops of liquid and was surprised to discover large concentrations of ozone, a harmful form of oxygen. Haagen-Smit deduced that evaporated hydrocarbons in gasoline, activated by the city’s abundant sunlight, reacted with other chemicals in the air to create ozone. Having finally solved the mystery, he called his discovery “photochemical smog.”
Haagen-Smit faced immediate pushback from the petroleum and auto industries. For decades, he would fight alongside county officials and environmental groups like SOS (“Stamp Out Smog”), run by a group of Beverly Hills mothers who brought their children to meetings in gas masks. While the auto industry claimed they could do nothing, an early prototype of the catalytic converter showed promise in eliminating hydrocarbons before they could turn into ozone.
Advocates didn’t back down, and in 1967, Governor Ronald Reagan created the California Air Resources Board, the first agency to require emissions standards on vehicles as a condition for sale. Los Angeles also spearheaded a lawsuit against the automakers, alleging a conspiracy to delay the development of emissions technology. Finally, carmakers agreed to stop suppressing emissions technology in a 1969 settlement with the Nixon administration.
California led the way, but political pressure to address environmental concerns was mounting nationwide, culminating in the first Earth Day in 1970. Soon after, President Nixon created the Environmental Protection Agency and passed the Clean Air Act of 1970, which set strict emissions targets for all new vehicles by 1975. Despite carmakers’ objections, they were forced to develop technology, including viable catalytic converters and unleaded gasoline, in order to comply with the regulations. These changes resulted in profound benefits on air quality and health to this day.
Today, Angelenos still live with occasional smog, but it is vastly reduced and car pollution is less than 1% of what it was when Haagen-Smit began his fight. A tale of tenacity, scientific ingenuity, and political skill, "Clearing the Air: The War on Smog" proves that solutions to environmental questions could transcend partisanship. The fight took decades, but Los Angeles changed the world.
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ABOUT THE PARTICIPANTS:
Mustafa Santiago Ali is a 24-year veteran of the EPA and founding member of the EPA Office of Environmental Justice. He currently serves as the Executive Vice President for the National Wildlife Federation.
Ann Carlson is Professor of Environmental Law and Founding Director of the Emmett Institute on Climate Change and the Environment at UCLA. Dr. Carlson is a leading scholar of climate change and air pollution law and policy and the co-editor of Lessons from the Clean Air Act: Building Durability and Flexibility into U.S. Climate and Energy Policy.
Merlin Chowkwanyun is Assistant Professor of Sociomedical Sciences at the Mailman School of Public Health, Columbia University, and author of "All Health Politics is Local: Battles for Community Health in the Mid-Century United States."
Chip Jacobs is a Pasadena-based journalist and co-author, with William J. Kelly, of "Smogtown: The Lung Burning History of Pollution in Los Angeles." His reporting and opinion pieces have been published and/or aired in the Los Angeles Times, Los Angeles Daily News, The New York Times, CNN, L.A. Weekly, and other outlets.
Mary Nichols is the former Chair of the California Air Resources Board, serving under Governors Brown (1975–82, 2010–18), Schwarzenegger (2007–10) and Newsom (2019–20). As an environmental lawyer for over 45 years, Nichols has played key roles in California and the nation’s progress toward healthy air and in crafting California’s internationally recognized climate action plan.
Christopher Wells is Professor of Environmental Studies and Chair of Environmental History at Macalester College. He is the author of "Car Country: An Environmental History" (2012) and editor of Environmental Justice in Postwar America: A Documentary Reader (2018).
Watch On Your Schedule: AMERICAN EXPERIENCE "Clearing the Air: The War on Smog" will stream for free simultaneously with broadcast on all station-branded PBS platforms, including PBS.org and the PBS app, available on iOS, Android, Roku, Apple TV, Amazon Fire TV, Android TV, Samsung Smart TV, Chromecast and VIZIO.
The film will also be available for streaming with closed captioning in English and Spanish on the AMERICAN EXPERIENCE website.
