One sunny summer day in 1943, a blue-brown haze descended upon the city of Los Angeles. It smelled like bleach, made people’s eyes sting and drove almost everyone indoors. It was so bad that some residents thought they were under a chemical warfare attack.

This was Los Angeles’ first episode of “photochemical” smog. In one of the great success stories of scientific activism, researchers determined the source of L.A. smog, persuaded industry that their science was right, and worked tirelessly until civic leaders took necessary regulatory action to prevent it.

But it’s a success story that seems increasingly hard to repeat. Despite continued reports of poor air quality in U.S. cities, leading to more than 100,000 premature deaths in 2011 and disproportionately affecting black and Hispanic Americans, the Environmental Protection Agency has loosened regulation of our air. Changes include reversing guidance that limits toxic air pollution from major sources, disbanding its review panel on particulate air pollution and now moving to limit the types of scientific studies used to set air quality standards. Scientists criticize these actions—but how can they effectively enact change in an administration that doesn’t listen to science? We can start by taking a look at how scientists in the past managed to get rid of photochemical smog

After continual smog episodes in the 40s, citizens demanded the government take action, and in 1947 the California Air Pollution Control Act gave cities the authority to create and enforce their own air pollution regulations. In L.A., chemist and entrepreneur Arnold Beckman and biochemist Arie Haagen-Smit teamed up to find out what the nasty smog really was.

At the time, everyone thought the smog was caused by sulfur dioxide, which had been plaguing many cities, like London and New York, as a consequence of coal plants and backyard incinerators. But when Beckman and Haagen-Smit condensed polluted L.A. air into a few drops of smelly brown liquid, they found organic peroxides, not sulfur dioxide. Haggen-Smit thought these peroxides were from incomplete combustion of gasoline, and therefore that car emissions were to blame for LA’s smog.

Continuing this research while on sabbatical, Haagen-Smit found that hydrocarbons and nitrous oxides—volatile organic compounds (VOCs) released from burning gasoline—can react to form a peroxide called ozone. But the reaction happens only if sunlight is around to help out. When it’s high up in the atmosphere, ozone protects us by filtering out dangerous UV rays from the sun. But near the surface, it can be harmful to human health. Due to L.A.’s geography, vehicle emissions do not quickly dissipate, and the sunny California days changed the city from paradise to environmental disaster.

After his sabbatical, Haagen-Smit returned to academia for a time, but never stopped thinking about smog. When the auto, oil and gas industries disputed his claims and the media continued to report that incinerators cause smog, he fought back. According to Beckman, Haagen-Smit was “a man of great courage, who was never afraid to meet head-on anyone who challenged the validity of his scientific work.” So, when given the opportunity to study smog in an industry setting and implement solutions, Haagen-Smit gave up his academic studies again.

From the 1950’s into the 1970s both Haagen-Smit and Beckman worked with multiple organizations at the city, state and federal level. They collected air pollution data, developed policy recommendations, and discussed their findings with virtually everyone.

As a member of the L.A. Chamber of Commerce, Beckman rallied businesses to support their cause. In the halls of Caltech, Haagen-Smit gave public lectures explaining exactly where smog comes from. Mixing together seemingly innocuous gases, he filled flasks with smog and made his audience cry. His demos convinced the public; there was no denying Haagen-Smit made the same stuff L.A. residents had come to know well. Beckman also advertised their research with mobile air quality monitoring stations—basically motor homes with science equipment—used to collect air quality data throughout L.A.’s neighborhoods.

By showing people exactly how smog was formed and letting them witness the science for themselves, Haagen-Smit and Beckman forged a bond with the L.A. community. Residents of L.A. and other parts of California continued to pressure their government, this time armed with arguments founded in solid science.

Fortunately, the discovery of a simple way to eliminate smog happened in parallel with Haagen-Smit’s work. By 1954, another scientist had invented the catalytic converter and engineered one that could be retrofitted to car exhaust systems, removing hydrocarbons and nitrous oxides from tailpipe emissions.

Though their efforts to change the auto industry were met with great resistance, Beckman and Haagen-Smit valued each incremental step forward. In the last decade of his life, Arie Haagen-Smit fought fiercely with auto industry researchers to implement catalytic converters and make commonsense changes that limit ozone pollution. And eventually he won them over, making friends of the industry scientists. But with the industry’s bottom line at stake, the battle continued into the late 1960s, when Beckman met with Henry Ford II to personally deliver the arguments for curbing tailpipe emissions.

By 1970, concern about air pollution of all kinds became a nationwide issue, and Beckman and Haagen-Smit’s research received much attention. The Clean Air Act of 1970 and the establishment of the Environmental Protection Agency (EPA) began a new era in environmental regulation. As a member of the National Air Pollution Board, Beckman worked closely with the EPA to create air pollution regulations. Haagen-Smit chaired California’s first motor vehicle pollution control board and air resources board, at one point banning Volkswagen sales in California until their emissions compliance was certified.

At the same time, the Justice department sued the auto industry, claiming that they conspired to delay the use of catalytic converters. Faced with litigation, the auto industry slowly added catalytic converters to vehicles. By 1975 the EPA mandated the use of catalytic converters on every new vehicle. And finally, testing of vehicle emissions began in the 1980s.

With these regulations, ozone-related smog episodes declined significantly. While ozone pollution and hazy L.A. days haven’t gone away completely, smog is no longer killing crops and forcing otherwise healthy people to take shelter.

Scientists understood the cause of L.A. smog in the early 1950s and simultaneously developed the technology needed to solve the smog problem. Yet the fight to implement their solution lasted for over 20 years. And it took a lot more than science to solve the smog problem. It took scientists with the courage to step out of their labs and into new, sometimes unfamiliar roles—policymaker, public speaker, activist and friend.

Without Beckman’s commitment to policy and Haagen-Smit tenacity with the auto industry, change would have been even slower. Without the public, both citizens and local businesses, on their side, politicians probably wouldn’t have paid as much attention, or backed scientific research when it was needed. And without friendship, Haagen-Smit may not have continued smog research at all; he almost returned to academia after his initial success analyzing liquefied smog, but was convinced by Beckman to persevere.

Now, while the EPA, fails to properly address current concerns about air pollution, scientists need to not only do excellent science, but continue to step out of the lab to share, or perhaps defend, their results.

Industries will always resist change when their profits are affected—but these companies are made up of people who will often listen. While it may not seem like it all the time, there are civic leaders and policy makers who actually listen. Scientists must speak up.

Not every step forward will be huge. Not everyone will listen. But that doesn’t mean we can’t stop trying. Even after over 20 years, Beckman and Haagen-Smit never did.