Los Angeles’ skyline is often defined by its most recognizable features: the Hollywood Sign, its downtown skyscrapers… And the grayish cloud that frequently settles over the horizon. While the city’s smog is certainly not a pleasant view, contrary to popular belief, it is far less severe than in the 1960s and 1970s, when it was deeply toxic.
That transformation is at the heart of Smog and Sunshine: The Surprising Story of How Los Angeles Cleaned Up Its Air, written by Ann Carlson, Shirley Shapiro Professor of Environmental Law at UCLA and founding director of the Emmett Institute on Climate Change and the Environment.
In a recent interview, Carlson reflects on how L.A. moved from some of the worst air pollution levels in the world to becoming one of the most studied environmental success stories.
366 Days of Contamination
Back in the 1960s, “there were 286 days that Southern California violated ozone standards.” Lead concentrations in the atmosphere were up to 50 times higher than today, exposing residents to levels of pollution that would now be considered catastrophic.
Carbon monoxide pollution was so extreme that in 1964, the region exceeded legal air quality standards on all 366 days of that year (which was a leap year). By the 1970s, “we’d have smog alerts on more than half of the days of the year”.
From a pineapple experiment to the Clean Air Act
Caltech scientist Arie Haagen-Smit, a plant biochemist studying pineapples, was drawn into air pollution research when SoCal’s crops began suffering unexplained damage. To investigate, he built one of the first controlled “smog chamber” experiments, combining car emissions with sunlight exposure under laboratory conditions.
He discovered that smog formed in the atmosphere when vehicle pollutants reacted with sunlight, producing a toxic chemical mix, the first clear scientific proof that air pollution was more than a byproduct of emissions.
From there, Mary Nichols played a key role in implementing catalytic converters, a technology that would later become a global standard, while Juana Gutierrez and the Mothers of East L.A., drew attention to environmental injustice, successfully opposing polluting facilities in marginalized communities.
By the 1980’s, Congressman Henry Waxman strengthened the Clean Air Act through federal legislation, reinforcing the regulatory framework that enabled long-term improvements.
Los Angeles smog and air quality today
While the grey cloud is still a city staple, the city is no longer defined by constant smog alerts. Despite the air quality challenges (particularly from wildfire smoke and heavy transport emissions), the contrast with its past is dramatic.
The transformation reflects decades of scientific research, regulatory action, and public pressure working in tandem.
