Regulations have cleaned up cars, power plants and factories, leaving cleaner air while economies have grown.
Cavan Images/Josh Campbell via Getty ImagesRichard E. Peltier, UMass Amherst
The Trump administration is “reconsidering” more than 30 air pollution regulations, and it offered industries a brief window to apply for exemptions that would allow them to stop following many air quality regulations immediately if approved. All of the exemptions involve rules finalized in 2024 and include regulations for hazardous air pollutants that cause asthma, heart disease and cancer.
The results – if regulations are ultimately rolled back and if those rollbacks and any exemptions stand up to court challenges – could impact air quality across the United States.
“Reconsideration” is a term used to review or modify a government regulation. While Environmental Protection Agency Administrator Lee Zeldin provided few details, the breadth of the regulations being reconsidered affects all Americans. They include rules that set limits for pollutants that can harm human health, such as ozone, particulate matter and volatile organic carbon.
Zeldin wrote on March 12, 2025, that his deregulation moves would “roll back trillions in regulatory costs and hidden “taxes” on U.S. families.“
What Zeldin didn’t say is that the economic and health benefits from decades of federal clean air regulations have far outweighed their costs. Some estimates suggest every $1 spent meeting clean air rules has returned $10 in health and economic benefits.
How far America has come, because of regulations
In the early 1970s, thick smog blanketed American cities and acid rain stripped forests bare from the Northeast to the Midwest.
Air pollution wasn’t just a nuisance – it was a public health emergency. But in the decades since, the United States has engineered one of the most successful environmental turnarounds in history.
Thanks to stronger air quality regulations, pollution levels have plummeted, preventing hundreds of thousands of deaths annually. And despite early predictions that these regulations would cripple the economy, the opposite has proven true: The U.S. economy more than doubled in size while pollution fell, showing that clean air and economic growth can – and do – go hand in hand.
The numbers are eye-popping.
An Environmental Protection Agency analysis of the first 20 years of the Clean Air Act, from 1970 to 1990, found the economic benefits of the regulations were about 42 times greater than the costs.
The EPA later estimated that the cost of air quality regulations in the U.S. would be about US$65 billion in 2020, and the benefits, primarily in improved health and increased worker productivity, would be around $2 trillion. Other studies have found similar benefits.
That’s a return of more than 30 to 1, making clean air one of the best investments the country has ever made.
Science-based regulations even the playing field
The turning point came with the passage of the Clean Air Act of 1970, which put in place strict rules on pollutants from industry, vehicles and power plants.
These rules targeted key culprits: lead, ozone, sulfur dioxide, nitrogen oxides and particulate matter – substances that contribute to asthma, heart disease and premature deaths. An example was the removal of lead, which can harm the brain and other organs, from gasoline. That single change resulted in far lower levels of lead in people’s blood, including a 70% drop in U.S. children’s blood-lead levels.
Air Quality regulations lowered the amount of lead being used in gasoline, which also resulted in rapidly declining lead concentrations in the average American between 1976-1980. This shows us how effective regulations can be at reducing public health risks to people.USEPA/Environmental Criteria and Assessment Office (1986)
The results have been extraordinary. Since 1980, emissions of six major air pollutants have dropped by 78%, even as the U.S. economy has more than doubled in size. Cities that were once notorious for their thick, choking smog – such as Los Angeles, Houston and Pittsburgh – now see far cleaner air, while lakes and forests devastated by acid rain in the Northeast have rebounded.
Comparison of growth areas and declining emissions, 1970-2023.EPA
And most importantly, lives have been saved. The Clean Air Act requires the EPA to periodically estimate the costs and benefits of air quality regulations. In the most recent estimate, released in 2011, the EPA projected that air quality improvements would prevent over 230,000 premature deaths in 2020. That means fewer heart attacks, fewer emergency room visits for asthma, and more years of healthy life for millions of Americans.
The economic payoff
Critics of air quality regulations have long argued that the regulations are too expensive for businesses and consumers. But the data tells a very different story.
EPA studies have confirmed that clean air regulations improve air quality over time. Other studies have shown that the health benefits greatly outweigh the costs. That pays off for the economy. Fewer illnesses mean lower health care costs, and healthier workers mean higher productivity and fewer missed workdays.
The EPA estimated that for every $1 spent on meeting air quality regulations, the United States received $9 in benefits. A separate study by the non-partisan National Bureau of Economic Research in 2024 estimated that each $1 spent on air pollution regulation brought the U.S. economy at least $10 in benefits. And when considering the long-term impact on human health and climate stability, the return is even greater.
Hollywood and downtown Los Angeles in 1984: Smog was a common problem in the 1970s and 1980s.Ian Dryden/Los Angeles Times/UCLA Archive/Wikimedia Commons, CC BY
The next chapter in clean air
The air Americans breathe today is cleaner, much healthier and safer than it was just a few decades ago.
Yet, despite this remarkable progress, air pollution remains a challenge in some parts of the country. Some urban neighborhoods remain stubbornly polluted because of vehicle emissions and industrial pollution. While urban pollution has declined, wildfire smoke has become a larger influence on poor air quality across the nation.
That means the EPA still has work to do.
If the agency works with environmental scientists, public health experts and industry, and fosters honest scientific consensus, it can continue to protect public health while supporting economic growth. At the same time, it can ensure that future generations enjoy the same clean air and prosperity that regulations have made possible.
By instead considering retracting clean air rules, the EPA is calling into question the expertise of countless scientists who have provided their objective advice over decades to set standards designed to protect human lives. In many cases, industries won’t want to go back to past polluting ways, but lifting clean air rules means future investment might not be as protective. And it increases future regulatory uncertainty for industries.
The past offers a clear lesson: Investing in clean air is not just good for public health – it’s good for the economy. With a track record of saving lives and delivering trillion-dollar benefits, air quality regulations remain one of the greatest policy success stories in American history.
This article, originally published March 12, 2025, has been updated with the administration’s offer of exemptions for industries.Richard E. Peltier, Professor of Environmental Health Sciences, UMass Amherst
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Black holes, like the one in this illustration, can spray powerful jets.
S. Dagnello (NRAO/AUI/NSF), CC BY-SADavid Garofalo, Kennesaw State University
One of the most powerful objects in the universe is a radio quasar – a spinning black hole spraying out highly energetic particles. Come too close to one, and you’d get sucked in by its gravitational pull, or burn up from the intense heat surrounding it. But ironically, studying black holes and their jets can give researchers insight into where potentially habitable worlds might be in the universe.
As an astrophysicist, I’ve spent two decades modeling how black holes spin, how that creates jets, and how they affect the environment of space around them.
What are black holes?
Black holes are massive, astrophysical objects that use gravity to pull surrounding objects into them. Active black holes have a pancake-shaped structure around them called an accretion disk, which contains hot, electrically charged gas.
The plasma that makes up the accretion disk comes from farther out in the galaxy. When two galaxies collide and merge, gas is funneled into the central region of that merger. Some of that gas ends up getting close to the newly merged black hole and forms the accretion disk.
There is one supermassive black holeat the heart of every massive galaxy.
Black holes and their disks can rotate, and when they do, they drag space and time with them – a concept that’s mind-boggling and very hard to grasp conceptually. But black holes are important to study because they produce enormous amounts of energy that can influence galaxies.
How energetic a black hole is depends on different factors, such as the mass of the black hole, whether it rotates rapidly, and whether lots of material falls onto it. Mergers fuel the most energetic black holes, but not all black holes are fed by gas from a merger. In spiral galaxies, for example, less gas tends to fall into the center, and the central black hole tends to have less energy.
One of the ways they generate energy is through what scientists call “jets” of highly energetic particles. A black hole can pull in magnetic fields and energetic particles surrounding it, and then as the black hole rotates, the magnetic fields twist into a jet that sprays out highly energetic particles.
Magnetic fields twist around the black hole as it rotates to store energy – kind of like when you pull and twist a rubber band. When you release the rubber band, it snaps forward. Similarly, the magnetic fields release their energy by producing these jets.
The accretion disk around a black hole can form a jet of hot, energetic particles surrounded by magnetic field lines.NASA, ESA, and A. Feild (STScI), CC BY
These jets can speed up or suppress the formation of stars in a galaxy, depending on how the energy is released into the black hole’s host galaxy.
Rotating black holes
Some black holes, however, rotate in a different direction than the accretion disk around them. This phenomenon is called counterrotation, and some studies my colleagues and I have conducted suggest that it’s a key feature governing the behavior of one of the most powerful kinds of objects in the universe: the radio quasar.
Radio quasars are the subclass of black holes that produce the most powerful energy and jets.
You can imagine the black hole as a rotating sphere, and the accretion disk as a disk with a hole in the center. The black hole sits in that center hole and rotates one way, while the accretion disk rotates the other way.
This counterrotation forces the black hole to spin down and eventually up again in the other direction, called corotation. Imagine a basketball that spins one way, but you keep tapping it to rotate in the other. The tapping will spin the basketball down. If you continue to tap in the opposite direction, it will eventually spin up and rotate in the other direction. The accretion disk does the same thing.
Since the jets tap into the black hole’s rotational energy, they are powerful only when the black hole is spinning rapidly. The change from counterrotation to corotation takes at least 100 million years. Many initially counterrotating black holes take billions of years to become rapidly spinning corotating black holes.
So, these black holes would produce powerful jets both early and later in their lifetimes, with an interlude in the middle where the jets are either weak or nonexistent.
When the black hole spins in counterrotation with respect to its accretion disk, that motion produces strong jets that push molecules in the surrounding gas close together, which leads to the formation of stars.
But later, in corotation, the jet tilts. This tilt makes it so that the jet impinges directly on the gas, heating it up and inhibiting star formation. In addition to that, the jet also sprays X-rays across the galaxy. Cosmic X-rays are bad for life because they can harm organic tissue.
For life to thrive, it most likely needs a planet with a habitable ecosystem, and clouds of hot gas saturated with X-rays don’t contain such planets. So, astronomers can instead look for galaxies without a tilted jet coming from its black hole. This idea is key to understanding where intelligence could potentially have emerged and matured in the universe.
Black holes as a guide
By early 2022, I had built a black hole model to use as a guide. It could point out environments with the right kind of black holes to produce the greatest number of planets without spraying them with X-rays. Life in such environments could emerge to its full potential.
Looking at black holes and their role in star formation could help scientists predict when and where life was most likely to form.
Where are such conditions present? The answer is low-density environments where galaxies had merged about 11 billion years ago.
These environments had black holes whose powerful jets enhanced the rate of star formation, but they never experienced a bout of tilted jets in corotation. In short, my model suggested that theoretically, the most advanced extraterrestrial civilization would have likely emerged on the cosmic scene far away and billions of years ago.
David Garofalo, Professor of Physics, Kennesaw State University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
The Role of Bike Lanes in Shaping Modern Urban Development
Bike lanes in urban areas promote sustainability, improve mobility, boost economic growth, enhance public health, and increase property values, symbolizing a shift toward inclusive community-focused city planning.
Cycle path in the city park. Bicycle sign on the road.
As cities continue to grow and urban spaces evolve, the integration of bike lanes has emerged as a transformative element in urban development. Beyond just providing a space for cyclists, bike lanes symbolize a shift toward sustainable, inclusive, and community-focused city planning.
Sustainability and Environmental Benefits Bike lanes contribute to reducing carbon emissions by encouraging more people to opt for cycling over driving. This not only lowers air pollution but also supports greener urban environments.
Improved Urban Mobility Cities with well-designed bike lane networks experience enhanced traffic flow. By reducing congestion and offering safe zones for cyclists, bike lanes create a more balanced transportation ecosystem.
Economic Growth Bike-friendly cities often see increased local business activity. Cyclists are more likely to stop and shop at small businesses along their routes, boosting neighborhood economies.
Health and Community Well-being Encouraging cycling promotes physical activity, improving public health. Additionally, bike lanes foster a sense of community by creating shared, accessible spaces for all residents.
Urban Aesthetic and Property Value Bike lanes enhance the visual appeal of cities and often lead to increased property values in surrounding areas. They signal modern, forward-thinking development, attracting young professionals and families.
Bike lanes are more than just pavement—they are investments in a city’s future. By prioritizing sustainable transit, healthier lifestyles, and economic growth, urban planners can create cities that thrive for generations. To embrace the future of urban living, integrating bike lanes into development plans must remain a top priority.
Call to Action Join the movement for sustainable cities by supporting bike lane initiatives in your community. Together, we can build cities that benefit everyone.
Image Credit: Adobe Stock
Learn more about Bike Lanes…
Check out these sites related to biking and urban development:
CicLAvia: CicLAvia catalyzes vibrant public spaces, active transportation, and good health through car-free streets. https://www.ciclavia.org/
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Neither party – Democrats nor Republicans – is doing a better job at fixing crime.
Carl Ballou – iStock/Getty Images PlusJustin de Benedictis-Kessner, Harvard Kennedy School and Christopher S. Warshaw, George Washington University
Following George Floyd’s death at the hands of police in Minneapolis in 2020, the U.S. has undergone a national reckoning over crime prevention and police reform.
Across the country, calls went out from activists to rethink the scope and role of the police. Some on the left vowed to “defund” the police. Others on the right promised to instead “back the blue” and maintain or increase police funding.
This rhetorical tug-of-war unfolded while many cities across the country grappled with spiking crime rates during the first months of the COVID-19 pandemic.
Blaming crime on Democratic city leaders was a centerpiece of Donald Trump’s 2024 presidential campaign. He repeatedly made claims about crime spikes in recent years without evidence or context.
More recently, Republican congressional leaders have called several Democratic mayors from across the country to testify before Congress about their sanctuary city policies that are aimed at protecting noncitizens from deportation. These congressional politicians have asserted that these Democratic mayors – Brandon Johnson of Chicago, Mike Johnston of Denver, Michelle Wu of Boston, and Eric Adams of New York – have “created a public safety nightmare” in their cities by allowing immigrants without legal authorization to stay there.
Journalists and politicians on both sides of the aisle have claimed that local election results over the past four years in places like San Francisco and Los Angeles reflect a widespread frustration with Democratic policies on crime in cities.
Under this argument, Democratic city leaders need to change their approach on crime to satisfy voters. It’s become a political axiom of sorts that policies championed largely by Democratic city leaders over the past half decade have resulted in rising crime levels.
As researchers of politics and public policy, we wanted to figure out if that was true.
A New York Times headline from June 8, 2022, linking crime rates and the Democratic Party.The New York Times
Neither party does a better job
As any student of introductory statistics learns, correlation doesn’t imply causation. Looking at increases or decreases in crime rates in Republican or Democratic cities and claiming either party is to blame would be making exactly this error: confusing correlation with causation.
We put to the test the argument that one side or the other is better at fighting crime in our research published in January 2025. By employing three decades of data on mayoral elections from across the country, we were able to disentangle city leaders’ partisanship from other features of cities.
Contrary to much of the political rhetoric and media coverage aimed at most Americans, our results show that neither party is doing a better job at actually causing crime to decrease.
In Dallas, Mayor Eric Johnson has claimed that Democratic leaders aren’t taking public safety seriously and that the Democratic Party is “with the criminals.” Johnson switched from being a Democrat to a Republican in 2023 and attributes his decision at least partially to this partisan difference on crime and policing and the seriousness with which he takes this policy issue.
But our research shows that Johnson’s and others’ claims about Democratic cities becoming more dangerous just aren’t true: Mayors from the Democratic Party aren’t making cities any more – or less – dangerous than mayors from the Republican Party.
Nor, it turns out, is there any support for claims by some progressive Democrats that they would reduce the role – and enormous budgets – of police departments in cities across the country.
When we examined the number of sworn police officers in cities and how much money those cities spend on the police, Democratic and Republican mayors alike have had surprisingly little influence on police department budgets or sizes.
In other words, Democrats aren’t cutting police budgets, nor are Republicans increasing police budgets. Most cities have increased police budgets in the past few years, possibly due to pressure from police unions.
Dallas Mayor Eric Johnson speaks during the second day of the 2024 Republican National Convention in Milwaukee on July 16, 2024.Andrew Caballero-Reynolds/AFP via Getty Images
‘Crime is nonpartisan’
It turns out that campaign promises from both sides of the partisan aisle about crime and policing have little bearing on what’s happening on the ground in most cities and police departments across the country.
Neither party is doing a better job at reducing crime. Nor is either party actually addressing the ballooning financial cost of local police forces in the U.S., nor the long-term reputational costs from police misconduct for trust in the police and government more broadly.
As others have said: crime is nonpartisan.
Crime has decreased across the U.S. during the past three decades overall, and the isolated cities where crime has increased recently can reverse these temporary trends.
Partisan blame narratives do little to actually lower crime and make neighborhoods safer, though.
There are real evidence-backed policies that reduce crime – such as youth jobs programs in Chicago and Boston. Other policies reduce racial disparities in the criminal justice system – such as alternative 911 response programs that use unarmed behavioral health workers to respond to some types of emergencies.
These policies and interventions might not be as slogan-worthy as “defund the police” or “back the blue.” Nor is implementing these policies as politically convenient as blaming sanctuary city mayors. But research shows that they work and can move cities toward the shared goal of improved public safety for their residents.Justin de Benedictis-Kessner, Associate Professor of Public Policy, Harvard Kennedy School and Christopher S. Warshaw, Professor of Political Science, George Washington University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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