The Clean Air Act Has Saved Millions Of Lives—But Gaps Remain

In the 1960s, the urban air pollution crisis in America had reached a fever pitch: Cities were shrouded in smog, union steelworkers were demanding protections for their health, and the Department of Justice was mounting an antitrust lawsuit against the Detroit automakers for conspiracy to pollute.

But all that changed when Richard Nixon signed the Clean Air Act of 1970. The law set national limits for six major pollutants, established stringent emissions standards for vehicles, and required the latest pollution-limiting technology for industrial facilities. It was widely recognized as innovative, landmark legislation because it was evidence-based, future-proofed, and it had teeth.

Since the Clean Air Act took effect, emissions of the most common pollutants have fallen by around 80%. The law has saved millions of lives and trillions of dollars. An EPA analysis showed that the Clean Air Act’s benefits outweigh its costs by a factor of 30. Thanks to this policy, the United States enjoys some of the cleanest air in the world.

But five decades on, has the Clean Air Act protected everyone? And can a policy designed for the problems of urban, mid-century cities protect our health in the face of climate change?

The Road To The Clean Air Act Passes Through Pittsburgh

In many ways, the story of the Clean Air Act starts in Pittsburgh, Pennsylvania, decades before the federal law was signed. In the 1940s and 1950s, Pittsburgh was the steel manufacturing capital of the world. Steel mills and blast furnaces lined the banks of the city’s famous three rivers, burning bituminous coal from the surrounding hills and pouring dark smoke from brick chimneys and smokestacks.

“[Pittsburgh] was one of the most heavily-polluted places on the entire planet,” says Matt Mehalik, executive director of the advocacy nonprofit Breathe Project.

The smoke and dust hung so thick in the air that they blotted out the sun, and the city had to light streetlights in the middle of the day for people to conduct their business in town. Metallic ash settled on homes and stripped paint from residents’ cars. Even hanging laundry to dry on clotheslines was a risk.

“Sometimes you’d look up and you’d run out and you’d take the wet clothes back off the line because you can see the soot and stuff coming in,” says Art Thomas, a long-time Pittsburgh-area resident and former employee of U.S. Steel. “If you didn’t get them off the lines, you had to wash your clothes again.”

The pollution was considered the price that residents had to pay for Pittsburgh’s prosperity, but the public health effects weren’t well understood yet.

Then, in 1948, a wake-up call came from a small milltown called Donora in a river valley south of Pittsburgh. A blanket of warm air, known as a temperature inversion, settled over the river valley like a lid, trapping cooler air—and air pollution from Donora’s industrial plants—close to the ground for five days. By the time the inversion broke and the smog lifted, 20 people had died, and another 6,000 had been sickened out of a town of 14,000.

“It was a truly horrific watershed moment in the history of the United States,” Mehalik says. “That Donora smog incident … set into motion various efforts to control air pollution.”

The following year, in 1949, Allegheny County, where Pittsburgh is located, adopted its first air pollution control law. Over the 20 years that followed, much of the thick, visible smoke in the city cleared—and regulators honed new expertise in air pollution control. The results were dramatic: In 1949, an average of 170 tons of dust was falling on every square mile in Allegheny County each month. By 1969, that number fell to 38 tons.

“A lot that went into the policies that were set by the EPA when it was created in the 1970s grew from that experience trying to tame pollution here in Pittsburgh,” Mehalik says.

“Where There’s Pollution, There’s Cancer”

While many experts tout the Clean Air Act as one of the most successful environmental policies in the history of the United States, it is also widely acknowledged that it has failed to address the pollution hotspots in many communities of color and high-poverty neighborhoods.

Perhaps the most well known of these is an area dubbed “Cancer Alley,” along the Mississippi River, between Baton Rouge and New Orleans in Louisiana. It’s a stretch of 184 river miles where more than 300 industrial facilities, most of them petrochemical plants, emit hazardous air pollutants. One of the most significant of these is ethylene oxide, a colorless gas used to make products like plastics and antifreeze. It’s a known carcinogen that increases the risk of blood and breast cancers.

Dr. Kim Terrell and Gianna St. Julien are researchers at the Tulane Environmental Law Clinic and co-authors of a 2022 study that linked higher cancer rates to pollution in Cancer Alley. Their research found cancer rates 35% to 40% higher than the national average in some communities. It affirmed what local residents had been saying for decades.

“People have always been saying, ‘Hey, where there’s pollution, there’s cancer,’” Terrell says. “And our study confirms that, yes, where there’s pollution in Louisiana, there’s cancer.”

Lisa Jordan directs Tulane’s Environmental Law Clinic. She says the reason hotspots like Cancer Alley can exist is because “there’s just not really a program in the Clean Air Act that’s specifically designed to monitor and protect every community from breathing toxic air.”

The Clean Air Act has two main ways of addressing pollution. The first is the National Ambient Air Quality Standards program. It requires state, local, and tribal air agencies, which are responsible for implementing the Clean Air Act, to monitor and limit six common pollutants, like lead and particulate matter, in their ambient air. Under this program, pollution standards are clear, monitoring methods are well-established, and compliance is relatively straightforward: A region either meets the standard, or it doesn’t. If it falls short, it has to submit a special plan to the EPA showing how it will comply. If that fails, it triggers sanctions.

The second big way the Clean Air Act addresses pollution is by limiting emissions of 188 less-common “hazardous air pollutants,” largely from major industrial facilities. The approach is two-pronged: First, the EPA requires facilities to use the latest and best pollution control technologies. Then, it looks at what health risks remain after those controls are in place, to determine if more stringent standards are needed. But, unlike with the six common pollutants, hazardous air pollutants are not continually monitored in the ambient air.

Terrell says that may make it possible for there to be dangerous concentrations of these hazardous air pollutants.

“There is no substitute for air monitoring in communities because you can have control technologies that don’t work as well as you thought, or you could have leaks or other sources of fugitive emissions that you’re not accounting for,” Terrell says. “So you don’t know what people are exposed to unless you actually measure that exposure.”

That said, hazardous air pollutants are notoriously hard to measure. But recently, environmental engineers at Johns Hopkins used a mobile lab to measure actual concentrations of ethylene oxide in Cancer Alley. They found levels of the gas 10 times higher than EPA estimates–and a thousand times higher than what’s considered safe for long-term exposure.

Wildfire Smoke And A Clean Air Loophole

The Clean Air Act was designed to clean up urban air pollution emitted from smokestacks and tailpipes. So events like wildfires present a problem. And as wildfires have increased and the wildfire season has gotten longer, jurisdictions have turned to a carveout to help them comply with air quality standards.

It’s known as the “exceptional events rule,” and it allows air agencies to ask the EPA to grant an exception when there’s a pollution event, like a wildfire, that’s out of their control. The exception allows an agency to comply with the National Ambient Air Quality Standards, even if the measured pollution would have pushed a region over the legal limit.

When an air agency is granted an exceptional event, the pollution attributed to that event remains viewable for research purposes, but it no longer factors into the region’s “design value.” The design value is how the EPA determines if an area is in compliance with pollution limits or not.

Public health reporter Molly Peterson says that in terms of government accountability, that’s like erasing the pollution from the record. She worked on an investigative series for The Guardian about the use of exceptional events, which was published last year. Her team’s analysis found that 21 million Americans live in areas where an exceptional event has allowed regulators to report that air was cleaner than it was. And it’s likely trending upwards: In 2016, air agencies across the United States flagged 19 wildfires as potential exceptional events. In 2020, they flagged 65.

“It just seems like it might be worth counting,” Peterson says of the air pollution that’s deemed an exception. “If nobody’s responsible for an airborne problem, then no one’s going … to apply more resources to it.”

Peterson believes new legal frameworks may be necessary to address poor air quality driven by climate change.

“The Clean Air Act is still this absolutely amazing piece of legislation, without which we wouldn’t be breathing and without which my skies in Los Angeles wouldn’t be clear right now,” Peterson says. “Even so, circumstances have changed, and the law hasn’t been able to take notice of that yet.”

This article was written by Susan Scott Peterson.

Further Reading

• An EPA overview of the Clean Air Act, including its history, the roles of science and government, and more.
• Read more about the Donora smog incident that inspired the Clean Air Act via the American Journal of Public Health.