The worst 10 hotspots for fine particle air pollution in the US have been revealed by The Guardian in an analysis using cutting-edge modelling.
America’s top spot is not a traffic-clogged metropolis or renowned heavy industry zone but a small town surrounded by farmland and mountains.
These findings – based on a model developed by a team of researchers at institutions including the University of Washington – show that, across the contiguous US, the neighborhoods burdened by the worst pollution are overwhelmingly the same places where Black and Hispanic populations live. Race is more of a predictor of air pollution exposure than income level, researchers have found.
“What we’re seeing here is segregation,” said Julian Marshall, professor of environmental engineering at the University of Washington, co-director of the Center for Air, Climate and Energy Solutions and one of the team of researchers that created the computer model. “You have segregation of people and segregation of pollution.”
The fine particles of air pollution emitted by cars, factories, wildfires and dusty agricultural activities, known to researchers as PM2.5, are small enough to travel deep into the lungs and into the bloodstream, increasing death rates from causes like respiratory disease, heart attacks and strokes. New research is showing they are associated with a surprising array of health impacts, ranging from miscarriages and Covid-19 to kidney damage and blood infections.
This top 10 is based on data recorded between 2011 and 2015, the most recent years available for the national model. The age of the data is typical for current air pollution studies performed by academics. Researchers say pollution patterns tend to remain relatively steady over the years.
Check your own neighborhood’s air pollution in our interactive tool. And read on for the nation’s worst hotspots.
10. Central areas in Birmingham, Alabama
Birmingham has long been known as one of the nation’s most racially divided (or segregated) cities. And Black neighborhoods are breathing air far worse than that in white areas just a few miles away, according to the Guardian’s analysis.
The most polluted tracts, a central band running north-east to south-west through the city’s core, turned out to have populations that were 95% Black.
Over the city’s long industrial history as an iron and steel hub, the dirtiest industries have tended to be located where property values are the lowest – and where the people had the least political clout to push back against it, according to the non-profit Greater-Birmingham Alliance to Stop Pollution (Gasp).
“These factors, while race-neutral on their face, absolutely contribute to the disproportionate site placement of these facilities near Black neighborhoods,” wrote environmental justice advocate Spencer Bowley in an analysis for Gasp.
“The white areas are where the lowest pollution levels are,” Michael Hansen, the non-profit’s executive director, told the Guardian.
And he said, where dirty industries are located usually “corresponds to the T” with the locations of Black communities.
9. A semi-circle of neighborhoods in central Atlanta
The map of the most polluted air in Atlanta looks remarkably similar to the near-century-old, federal redlining maps that once categorized certain areas of the city as “hazardous”, based on racist factors such as how many Black or “foreign-born” people lived there.
Homes in the areas – including large sections of north-west and south-east of central Atlanta – were dubbed too risky for investment and excluded from federal loan insurance. In the decades that followed, freeways and polluting facilities tended to be sited in those areas because the minority communities that lived there didn’t have the political or social clout to stop their construction.
While some of these intercity communities have since gentrified, the hotspot data shows the areas with the most air pollution are still the ones that faced redlining and real estate discrimination so many decades ago. Overall, they are 68% Black and only 25% white.
“We’re talking about the bullseye in the very center of Atlanta,” said Brian Gist, an attorney with the Atlanta-based Southern Environmental Law Center. “The area is the confluence of two major interstates. You have a lot of cars and it’s in a downtown area, so there’s a lot of traffic there.”
Another cluster of polluted census tracts borders the Atlanta airport, which ranks as the busiest air terminal in the world. Black people also make up the largest racial group in these areas.
“It’s true all over the country that, a lot of the time, we put our highways through African American communities,” said Gist. “That’s the story these maps tell.”
8. Semi-rural areas in central Pennsylvania
The air pollution epicenters in this central Pennsylvania region differ from others around the nation. Instead of urban agglomerations, they are more like freckles scattered across the land.
They also have a higher share of white residents compared with other hotspots – overall, the central Pennsylvania areas with the highest fine particle air pollution are 84% white. There is a lot of agriculture in the area, but it is also a transportation thoroughfare and is dotted with clusters of industry, including food processing plants, metals fabricators and plastics manufacturing.
7. A swath of the St Louis Metro Area
In metropolitan St Louis, the areas with the highest air pollution tend to sit north of Delmar Blvd – the racial and socioeconomic dividing line known as the “Delmar Divide”. They stretch from the northern part of the city of St Louis across the Mississippi River and into impoverished communities in East St Louis.
Overall, the populations in neighborhoods with the highest PM2.5 levels were 52% Black, compared to 22% for other areas of the same counties.
The region’s air is affected by a number of energy plants that still use coal, including one a few miles north of the most polluted neighborhoods.
“We are ringed by power plants,” said Steve Mahfood, a former director of the Missouri department of natural resources, who now sits on the boards of numerous environmental nonprofits studying air pollution in the region. “We have three of the 10 most polluting power plants in the nation.”
6. A large portion of Houston
Environmentalist Robert Bullard was not surprised that central Houston lies in a cloud of pollution. The college where he teaches, Texas Southern University, sits in the middle of it.
The historically Black university, along with numerous communities of color, is located inside a ring of freeways. They are also just west of one of the nation’s busiest ports and petrochemical processing centers. Not only is Houston an oil industry infrastructure hub, its residents top the national chart for the most vehicle miles travelled every day.
In the most polluted census tracts in Houston, 80% of residents are people of color.
Bullard, known as a founding father of the environmental justice movement, has documented in 18 books how neighborhoods with the highest pollution are invariably those with the most people of color, lowest incomes and least access to healthcare. He said it was a geographic pattern that repeats itself over and over in the US.
“The polluting facilities are all located in our neighborhoods,” said Bullard. “And then when we start looking at which communities are most likely to have elevated asthma, respiratory problems, diabetes, heart disease, stroke or Covid, it’s like, ‘Oh my God, it’s the same map!’ That’s what we’re mad about.”
5. A central swath of Indianapolis, Indiana
The city that hosts the famous Indianapolis 500 raceway has long had an affinity for autos. As in Houston, federal statistics show that residents here drive more than almost any other metro area.
For years, the region has also been dealing with the side-effects: high levels of air pollution blanketing much of Indianapolis’s central core.
Professor Gabriel Filippelli, director of Indiana University’s Environmental Resilience Institute, says transportation sources are to blame for much of the city’s fine particulate pollution.
“We are famous for being the crossroads of America,” said Filippelli, who has been setting up a network of monitors to measure the air pollution moment-to-moment and sharing it with residents in a real-time map. “We have a ton of roads that go through here,” noting that the city sits in a bullseye of national highways.
This is worsened, he said, by the fact that there is no emissions testing of vehicles and a very underdeveloped public transit system.
“Whatever is spewing out the tailpipes, it’s perfectly legal in our backwards state,” he said.
Reviewing the map created by the Guardian using the CACES model, Filippelli recognized many of the neighborhoods of Indianapolis where people of color are living with high levels of pollution.
However, there were some details of the map’s estimates that he said did not jibe with his own measurements and observations. For instance, the very center of the city – which houses the university and some government buildings but few actual residents – shows up as not being as polluted as nearby neighborhoods. Filippelli believes the pollution there is actually worse than shown.
Professor Marshall, who helped develop the model, acknowledged that CACES’s estimates of pollution at the granular, census tract level cannot be expected to be perfect in every location. But the model combines the best available science, including views from space, to fill in the whole map, he said.
“The EPA cannot measure in every neighborhood,” he said. In lieu of that, “our predictions are a best guess”.
4. North-west Indiana industrial zones
While considered a distant suburb of Chicago, north-west Indiana is a giant industrial pollution hub in its own right. The most polluted portion of the region, including most of Gary and the city of East Chicago, has long been a mecca of the steel industry. While job cuts in recent decades have left some parts abandoned and blighted, many factories still operate. Air pollution experts have faulted the state of Indiana for its lack of controls on emissions. It leads the nation in the amount of industrial toxic pollution emissions per square mile, according to a 2021 EPA report, cited by the Chicago Tribune.
Heavily polluted areas are also where many of the people of color live. Tracts estimated to be among the most polluted had 60% non-white populations.
3. Chicago’s South and West Sides
Cheryl Johnson, a longtime environmental justice activist for Chicago’s heavily polluted South Side, has won numerous battles to stem air pollution sources in her neighborhood.
Along with areas on the west side of metropolitan Chicago, the neighborhoods that make up the South Side – such as Back of the Yards and Riverdale – are where majority Black and Hispanic residents have had to live alongside some of the region’s dirtiest industries. Now these neighborhoods have the third highest levels of fine particulate pollution in the nation.
Johnson has fought to eliminate stockpiles of pet coke, a byproduct of oil refining, that were stored at the nearby port and sending clouds of toxic black dust into her neighborhood. But every time one problem is solved, she said, it seems like another dirty industry moves into the area.
“We have landfills, industrial facilities, hazardous waste sites, sewage treatment plants, chemical processing facilities, chemical disposal, underground contamination,” she said. “It’s everywhere.”
Johnson’s Altgeld Gardens neighborhood, on the far South Side of Chicago, is burdened with fine particulate pollution above the EPA limit of 12 micrograms of particulate matter per cubic meter (µg/m3).
“If you are poor and Black and your education system is poor and Black, you’re the first to be dumped on,” Johnson said.
2. South Los Angeles
The maze of freeway interchanges, railyards and warehouses in South Los Angeles has long served as a dumping ground for industry.
In this cluster of landlocked neighborhoods and small cities – including Compton, Maywood and Paramount – residents like Felipe Aguirre live with air that has regularly exceeded the EPA limit of 12 µg/m3.
Compared with those living across town in Bel Air, South LA’s residents – who are majority Black and Hispanic – breathe 50% more of this pollution. Meanwhile, Bel Air is 87% white and residents have life expectancies as much as a dozen years longer than those in South LA.
As an activist, Aguirre has battled to close major industrial plants, including a battery recycling facility in Vernon that was spewing toxic lead into local backyards. But he admits that the gains are tenuous: new polluters, such as several distribution centers for Amazon and other shipping companies, keep trucks flowing through the area.
The political divisions that separate the many tiny cities mean that the mostly Hispanic workers who live in Aguirre’s town of Maywood often have no voting power over where industry is placed by the next city over.
“The companies not only have a seat at the table, they own the table, they serve the meals and they make us clean up the dishes,” said Aguirre.
1. Bakersfield area, California
The area around Bakersfield, an agricultural town in California’s Central Valley 100 miles north of Los Angeles, has the most unhealthful air in America.
Bakersfield is in an unlucky location, surrounded by mountains that trap toxic farming chemicals, dust, truck and train fumes and oil-drilling exhaust, as well as pollution blowing south from other parts of the populous state, according to local air experts. Environmentalists charge that local air regulators have worsened the situation with lax enforcement against industrial polluters.
The worst census tracts in Bakersfield had up to 16 micrograms of fine particulate pollution per cubic meter over the years studied – well above the threshold set by the EPA requiring remediating action. The entire region around the south end of California’s Central Valley has failed to meet the Clean Air Act’s targets for most of the last 25 years.
Environmentalists from the region sought help from California legislators last year, saying local regulators had been “favoring industry at the expense of public health”.
“Federal civil rights laws could apply to the city for allowing a disproportionate amount of air pollution to fall on to communities of color and disadvantaged populations, while other communities receive the benefits of programs aimed at cleaning the air,” said Perry Elerts, staff attorney with Leadership Council for Justice and Accountability, one of a host of environmental groups working to get the air in the area cleaned up.
A coalition of groups represented by the legal non-profit Earthjustice is suing the EPA to ensure it enforces the Clean Air Act and takes action to bring pollution levels down. The coalition filed two suits charging that regulators have done little more than create “a series of weak state plans that collect dust on federal desks for years”.
Residents such as Emprezz Nontzikelelo, who lives in the most polluted corner of the region, face diseases associated with poor air quality, such as asthma, pneumonia and chronic obstructive pulmonary disorder.
“What a mess we live in here,” said the 77-year-old. For years the dirtiest industries, transportation facilities and freeways were sited in the part of town home to the densest populations of minorities and low-income people.
“Those who have an illusion of power feel like our lives don’t have any value and we are expendable,” she said. “They expect us to die early from this air pollution. It’s deliberate. They put everything over here to ensure that we breathe the worst air.”
Emma De La Rosa, 29, an environmental justice activist with the Leadership Council for Justice and Accountability, is working to make sure that it is not always the neighborhoods of color that end up housing the dirtiest industries. The group recently lost a battle to stop the city of Bakersfield from approving a major new distribution warehouse, expected to bring a surge in diesel truck traffic, in one of the most polluted corners of the city, which is mostly populated by low-income Latinos.
But De La Rosa and other activists are determined to keep fighting until everyone in the region can enjoy healthy air, which De La Rosa said will require regulators to give much more attention to the neighborhoods currently bearing the brunt of the pollution.
“Someday I would like to be able to look up and see the mountains all around my city,” she said. “I would like residents to be able to enjoy their neighborhoods without the fear of an asthma attack and walk their city without concern of truck traffic running them over.”
Methodology
To identify hotspots, The Guardian looked at the clusters of census tracts with the highest long term averages for estimated PM2.5. In California, the state with the nation’s worst air pollution, these were above the current EPA action level of 12 micrograms per cubic meter (µg/m3.) In other parts of the country, the cutoff was just below the action level at 11.5 µg/m3.
The air pollution map and the hotspots calculations are based on a model, created by the Center for Air, Climate and Energy Solutions (CACES), which estimates the total levels of fine particulate matter (PM2.5) for census blocks throughout the contiguous US. The modeling technique was developed through research by Sun-Young Kim, Matthew Bechle, Lianne Sheppard, Adam A. Szpiro, and Julian Marshall of University of Washington; and Steve Hankey of Virginia Tech.
CACES bases its estimates on publicly available PM2.5 concentration measurements from EPA monitors, and uses information about land use (for example, locations of major and minor roads; elevation; and whether an area is urban or rural) and satellite-derived estimates of air pollution and land cover to predict concentrations at locations where there are no measuring devices. Estimates were generated for each census block with population greater than zero, and then population-weighted to obtain an average estimate for each census tract
The Guardian looked at the average annual levels for the most recent five-year period available: 2011 - 2015. We overlaid racial demographic data, using US Census data from the American Community Survey 5-year estimates for 2011 - 2015.
The pollution estimates for each individual census tract represent a “best guess” based on the available data. The results for census tracts in metropolitan regions where there are hotspots are confirmed by other government and nonprofit studies.
In order to narrow the list of most polluted locations for the Top 10, some discretion was required as many areas have similar levels, particularly toward the bottom of the list. Specifically, California's Inland Empire around Riverside County, the Pittsburgh PA area and an industrial area north of Cincinnati were considered for inclusion, but missed the cut.
Special thanks to Professor Julian Marshall and Alvin Chang for advising on this project.
Check your own neighborhood’s air pollution in our interactive tool. And read our story about how air pollution disproportionately affects people of color.
