Unequal air: The pollution legacy of segregation and the freeway boom in Los Angeles
This is the first story in AfroLA’s solutions-reported climate change series, 2035. How do political moves toward energy equity shape a city, a region—and its people—that have historically struggled with social and economic inequity? Read more about the series here.
On a blue-sky day in Los Angeles, perhaps after a rainstorm, puffy white clouds drift lazily over the rooftops. In some parts of town, you might even be able to smell the sea. In other neighborhoods, the smell of car exhaust pervades even on the nicest of days. Looking out at the skyline on a bad air day means seeing a layer of grayish-brown hanging over the city. The buildings are hazy, if they’re visible at all. Asthma flares up.
While the skies change from day to day, one thing stays the same: traffic. With more than 500 miles of freeway in Los Angeles County and a total of roughly 235 million miles driven daily in the region, vehicles and their supporting infrastructure are front and center in the L.A. ecosystem. Around the clock, Angelenos are in their cars, walking through underpasses and living near the city’s ubiquitous freeways.
“We all suffer from traffic here, from congestion,” said Geoff Boeing, professor of urban planning and spatial analysis at the University of Southern California Price School of Public Policy. “Part of my interest in this is as an L.A. resident myself. We all suffer from air pollution here—we just don’t all suffer equally.”
He’s one of the authors of a study published this year showing that people who drive less are exposed to more air pollution.
“If you know much about Los Angeles geography or history, it’s not a paradox at all,” said Boeing. “What it’s telling us is that people who live in Bel Air drive a lot and are exposed to little air pollution at home. People who live in Pico Union or South Central drive less because they own fewer vehicles—they have less access to mobility—but they’re exposed to tons of air pollution.”
“We all suffer from traffic here, from congestion…We all suffer from air pollution here—we just don’t all suffer equally.”—Geoff Boeing, USC urban planning professor
The study controlled for factors like income, wealth, where people live and how close they are to things like freight and freeways. They found that all else equal, the residents who are exposed to the most vehicular air pollution at home are the ones who drive less.
“On average, white commuters traverse tracts that are far more non-white than the tracts where most white commuters live,” he said. “This disparity does not exist in the opposite direction. On average, nonwhite commuters do not travel through tracts that are substantially whiter than their home tracts.”
Regardless of income, places with more residents of color have more vehicular air pollution than places with more white residents. In essence, drivers are externalizing the costs of driving onto the communities they drive through, and residents of color are bearing more of the environmental and health burdens. This unequal relationship is no surprise; in fact, it’s by design.
“I think one thing that’s important to keep in mind is the history of freeway building in Los Angeles, how the freeway revolts worked here, which communities were able to block the freeways and which communities weren’t and how that matches almost perfectly the air pollution and racial composition patterns we still see today,” said Boeing.
Generations of racist urban planning divided L.A.’s Black and Latine neighborhoods and prevented movement of the same communities out of areas near major roadways and other polluting infrastructure. For years now, residents have paid the price with their health.
Understanding vehicular air pollution
Vehicles like cars and trucks can pollute the air in a number of different ways, and studies of vehicular pollution from across the country can help us understand what’s happening in L.A.
“We try to look at what patterns are repeated nationally,” said Julian Marshall, professor of civil and environmental engineering at the University of Washington, who did some of his early research in L.A. “Each pollutant has its own story. It has different sources; it has different spatial patterns. Things differ by pollutant and by state and over time.”
Emissions from gas-powered vehicles can form nitrogen oxides (NOx). NOx is a combination of two gases: nitrogen dioxide (NO2) and nitric oxide (NO). NO2 has a strong odor and reddish-brown color. It’s also one of the six “criteria pollutants” known to be harmful to human health that are regulated by the Environmental Protection Agency under the Clean Air Act.
“Fundamentally what we’re looking at is segregation in terms of where people live and where the pollution is.”—Julian Marshall, University of Washington professor of civil and environmental engineering
If a person is exposed to NO2—from living near a busy road, or standing behind a truck when it belches exhaust fumes—it can irritate their airways, making it harder to breathe and exacerbating conditions like asthma. Studies have shown that NO2 may even contribute to the development of asthma, particularly in children.
“The Clean Air Act has reduced average concentrations and that change has reduced disparities in absolute terms, but much less so in relative terms,” Marshall said.
As an example, if levels of all pollutants were cut in half, everyone’s air would be cleaner. The most exposed people and least exposed would both be breathing better. However, the disparity between those groups would still remain.
“Fundamentally, what we’re looking at is segregation in terms of where people live and where the pollution is,” Marshall said.
So the air is cleaner now than it used to be, thanks to air quality regulations. But people of color across the country, and in L.A., are still breathing air that is less clean than their white counterparts.
“Many people would say, ‘Well, these are disparities by race, but that’s just race as a proxy for income, right?’ And the answer is no, not really,” said Marshall. “The differences by race are distinct from and larger than the differences by income. And if you statistically correct for income, you get disparities by race across the income spectrum and they’re nearly unchanged.”
Another criteria pollutant is ground-level ozone. Gas-powered cars and trucks don’t directly emit ozone. However, what they do emit—NOx, carbon monoxide (CO) and volatile organic compounds—help to create it, as shown in a comprehensive 1999 report backed by the National Research Council.
This is important as it means that along with the direct-to-individual types of pollution, there are also more indirect pathways to poor health resulting from vehicular emissions. A 2018 study in North Carolina showed that when Black children with asthma were exposed to even low levels of ozone, their lung function worsened, despite using an inhaler to control their symptoms.
A third criteria pollutant is called particulate matter, a blend of microscopic airborne liquids and solids. Soot, dust, and pollen are all examples. Vehicle exhaust, brake dust and tire wear, among other things, can all contribute to particulate matter concentrations near roadways.
There are many sizes of particulates, and not all are currently regulated. Coarse particulate matter (PM10-2.5) measures between 10 and 2.5 micrometers in diameter, while fine particulate matter is under 2.5 micrometers. Both are well-studied and included in the criteria pollutant list. A 2017 study of children and young adults on Medicaid found that exposure to PM10-2.5 was associated with asthma. In some cases, the young people’s asthma was severe enough that it required treatment in a hospital.
Ultrafine particles, on the other hand, are less than 100 nanometers in diameter. There are currently no regulatory standards for them.
“The smallest of the smallest”: The problem with ultrafine particles
“I’ve come to believe that there’s an important issue hidden in the air pollution problem, which is these ultrafines, that is not being addressed sufficiently, and there’s a very large population who lives near highways or major roadways that’s being exposed,” said Doug Brugge, professor of occupational and environmental health at the University of Connecticut School of Medicine. “If, as I think, the evidence pretty strongly suggests it’s adversely affecting their health, then how do we get that onto the policy agenda? How do we raise awareness and how do we start doing something to reduce their exposure and risks?”
Brugge believes there need to be more long-term exposure and mortality studies that specifically look at ultrafine particles. However, they can be tough to track. They condense and evaporate, and people are constantly moving in and out of fields of exposure, he explained.
The ultrafine particles that can be found near highways are typically combustion products coming out of the exhaust pipes of gas- and diesel-powered vehicles.
“Mostly they come out as very hot, semi-volatile gases that condense and form very, very tiny particles. Ultrafine particles are the smallest of the smallest particles in the air,” Brugge said.
Some are smaller than 10 nanometers in diameter, comparable to the size of large molecules. He said that gives them some particularly worrisome properties, like the ability to cross biological barriers in a way large particles can’t.
“The one I like to point to is, if you’re breathing them in, they will go up the olfactory nerve at the back of your nose and directly into your brain. I’m convinced that’s been shown—that these particles are accumulating in our brains from breathing them in,” Brugge said. “I think there’s still questions about exactly how much health risk that constitutes, but they travel around the body in ways that the larger particles would have a hard time doing. So, there’s a lot of reasons to be concerned about them.”
Brugge and fellow researchers did a controlled exposure study of traffic-related air pollution focusing on ultrafines in Boston, at a place in the city where two major highways intersect, as happens in many parts of L.A. There is a housing development at the intersection with a community room inside.
“We had people spend two hours there on three consecutive Monday mornings and we randomly adjusted the conditions either to let all the pollution in, a little bit of the pollution in, or keep almost all of it out,” he said.
They used high-efficiency particulate absorbing (HEPA) filters and controlled air flow into the room through windows and doors. Each day, after low, medium or high exposure, they checked participants’ blood pressure. Research has shown that exposure to PM2.5 can raise blood pressure in as little as two hours. In the ultrafines study, Brugge’s team found that participants’ blood pressure corresponded to their exposure levels.
“Every research study has limitations, but to me that was the strongest evidence that there is a direct causal link between the air pollution that people are exposed to and their blood pressure,” he said.
In a 2016 study using blood samples, he and his fellow researchers identified links between ultrafine exposure and inflammatory biomarkers that can signify a risk for cardiovascular problems like atherosclerosis, heart attacks and strokes, similar to known risks from exposure to fine particulate matter.
A 2022 study to which Marshall contributed found that average exposure to ultrafine particles in the U.S. is a third higher for racial-ethnic minority individuals than it is for white individuals, compared to the total national average. The greatest disparities can often be found in cities.
So, once again, while reducing emissions across the board would have a positive effect, it wouldn’t close the exposure gap by targeting the communities who need the most help.
“If you keep doing what you’ve been doing, you’ll keep getting what you’ve been getting,” said Marshall. “The approaches that are in the Clean Air Act will tend to continue this sort of thing happening and that conclusion, of course, is not new. That’s what environmental justice groups have been saying for years, decades, generations in some cases. But our modeling work is consistent with that.”
Getting into the weeds about different types of air pollution and their effects is important, as it can help residents and policymakers better understand the public health and infrastructure choices they are faced with. For example, if a city is looking at building low-income housing near a highway, or an offramp into a neighborhood, Brugge hopes vehicular air pollution will be on the list of topics to consider.
“Bringing this issue into discussions about development I think is critical and I don’t think happens enough,” said Brugge. “In the neighborhoods where we’ve worked for 15 years, it comes up…but the few of us like me can’t be everywhere for every building for every new highway development—it’s too much. It’s got to be systematized and made part of a standard process.”
Whereas solutions to the air pollution problem have yet to be systematized, many of the causes have long been entrenched in policy and practice.
“A lot of the infrastructure that we did build was very explicitly racist—there’s no controversy about that. They were open about that at the time. It was part of their explicit stated goals,” said Boeing. “We use that same infrastructure today. There’s a legacy that was shaped by those decisions.”
In many cases, U.S. freeways were built knowing their construction would decimate neighborhoods and disenfranchise Black and Brown individuals from access to both healthy spaces and economic opportunities.
Redlining, racial covenants and housing segregation in L.A.
“This is a story that is the same across the country,” said Katherine Cabrera of the Greenlining Institute, a California-based nonprofit focusing on economic opportunity and the environment. “Highways were constructed because of the legacy of redlining often directly through communities of color, resulting in the disinvestment of these neighborhoods.”
For Cabrera, the deeply troubled history of Southern California’s transportation infrastructure is personal.
“I grew up next to the [State Route] 60 freeway in the Inland Empire,” said Cabrera. Back in the 90s, it was an agricultural area, and a predominantly Latine and immigrant community.
Over the years, agriculture was replaced by warehouses, “which meant more trucks, more pollution,” she said. “These individuals were also the same individuals not only being exposed to pollutants, but also suffering from exploitative working conditions through the logistics industry. This is what really led me to question—why is my community being disproportionately burdened by the impacts of climate and environmental justice while wealthier and less diverse communities nearby are not?”
The placement of polluting industries, waste products and supporting infrastructure in communities of color can be defined as environmental racism, a term coined by civil rights leader Benjamin Chavis in the 1980s. In a 1994 paper, “The Legacy of American Apartheid and Environmental Racism,” Robert Bullard expanded the definition to include “any policy, practice, or directive that differentially affects or disadvantages (whether intended or unintended) individuals, groups or communities based on race or color.”
“It starts with decision-making, in terms of not taking those concerns into consideration—the air quality and associated health risks—due to environmental racism, particularly if you’re looking at urban areas,” said Regan Patterson, assistant professor of civil and environmental engineering at UCLA.
Segregation in L.A. was the result of white supremacy officially codified or unofficially upheld by policy-makers and residents alike. From discriminatory housing practices to the routing of freeways through neighborhoods, generations of Black Angelenos were denied equal access to economic opportunities, green space, property and more.
Despite the 1917 case Buchanan v. Warley, in which the U.S. Supreme Court unanimously decided that a Louisville ordinance preventing a Black man from owning a house on a predominantly white block violated the Fourteenth Amendment, segregation continued across the country at the local level through practices like the issuing of racial covenants and redlining.
A racial or restrictive covenant was a clause written into a deed preventing the sale of land or property to people who weren’t white. A covenant could last for decades with the intent of cementing white ownership and control of neighborhoods, and preventing them from becoming mixed-race.
In 1924, the National Association of Real Estate Boards wrote in its Code of Ethics that realtors “should never be instrumental in introducing into a neighborhood a character of property or occupancy, members of any race or nationality, or individuals whose presence will clearly be detrimental to property values in that neighborhood.”
Backed by those in real estate and repeatedly upheld by Supreme Courts at both the state and federal levels, covenants were widely used in L.A. through the 1940s. According to a Los Angeles Historic Resources Survey report from 2018, their prominence began to fade following the 1948 Supreme Court Shelley v. Kraemer ruling, which held that the enforcement of covenants by courts violated the Equal Protection Clause. But some remained in place until the passage of the 1968 Fair Housing Act, which finally made them illegal.
Decades prior, in the midst of the Great Depression, the New Deal saw the creation of several new federal agencies, including both the Home Owners Loan Corporation in 1933 and the Federal Housing Administration in 1934. In order to help struggling homeowners, the HOLC established a system to grant low-interest loans. However, the loans were often tied to a newly-developed, map-based risk rating system for neighborhoods. The lowest-risk neighborhoods were outlined in blue or green, neighborhoods deemed to be “in decline” were outlined in yellow, and “hazardous” neighborhoods were colored red.
“Through this policy of redlining, it became clear from the maps that the primary indicator of risk was race,” said Cabrera.
Because of restrictive covenants and other discriminatory housing practices, Black residents mainly lived in the vicinity of Central Avenue, from Downtown to South L.A. Redlined areas in L.A. included this Central Avenue corridor, along with West Adams and Jefferson Park, meaning these residents were often prevented from receiving federal aid.
The FHA eventually adopted the same redlining system, largely barring Black residents from mortgage assistance and construction loans even after the end of World War II.
“By the postwar years, African Americans had become the most intensely segregated of all nonwhite groups in Los Angeles,” the report reads. Even today, L.A.’s Black neighborhoods “are rooted in discriminatory practices and the community’s triumphs over them.”
Connecting and destroying: L.A.’s freeway boom
Following the creation of the Interstate Highway System in 1956, freeways began springing up across the country, despite warnings that large-scale transportation and other “urban renewal” projects would likely displace hundreds of thousands of families and cause the greatest potential harm to low-income, elderly and minority residents.
L.A. had already been planning additional roadways since the 1940s, but likewise saw a renewed interest in freeways throughout the 1950s and 1960s, primarily to connect white communities with economic centers and one another. However, with construction plans came pushback.
One of the roads that was never built was the proposed Beverly Hills Freeway, which would have crossed some of the city’s wealthiest neighborhoods. Homeowners took their significant political and social power to battle and succeeded in preventing the freeway’s construction.
In spite of overwhelming attendance at planning meetings and vocal opposition to proposed plans, Eastside Los Angeles working-class communities weren’t so lucky.
“It’s differential access to power along racial and class lines,” said Patterson. “Where freeways were routed disproportionately impacted poor communities of color, particularly Black and Latine communities.”
In a massive construction undertaking, the East Los Angeles Interchange was built on the ruins of residential streets in Boyle Heights, where today the I-5, I-10, U.S. 101 and S.R. 60 freeways connect to form an enormous, traffic-clogged artery.
As a result, said Cabrera, “Over 2,000 homes were actually destroyed to make way for freeways in the community of Boyle Heights, destroying their economy, their culture and locking in pollution for the community.”
In Pasadena, freeway construction of the I-210 freeway displaced about 2,600 residents whose homes were bulldozed to make way for the new route. In the San Fernando Valley, another freeway development resulted in the displacement of about 900 residents. In both cases, multiple routes for the freeways were proposed, according to a study published earlier this year. The cities ultimately chose to pursue the options with the greatest consequences—social, economic and environmental—for neighborhoods of color, some of which had been previously redlined.
“I would say that those considerations weren’t taken into effect because there was a lack of care, and actually wanting to either reinforce segregation or to adversely impact those communities,” said Patterson. “When you think about who freeways were supposed to serve, they were serving white flight. So, the communities that went to the suburbs were leaving the urban core, where communities of color were left and subsequently disinvested. It was intentional.”
Communities were carved up by freeways, residents’ connections to economic centers were severed, and neighborhoods with their own distinct histories and cultures were divided. These Angelenos were left surrounded by pollution-emitting vehicles driven by people from other parts of town, who were just passing through.
A stark reminder of this legacy lies in the maps that have played a part at various stages of L.A.’s history, said Cabrera. If you overlay the California EPA map (identifying communities’ pollution vulnerability), a 1939 redlining map and even Los Angeles County’s COVID-19 vulnerability map, the similarities are impossible to ignore. In a 2022 study, researchers found that contemporary air pollution levels show an association with an area’s historic HOLC grade—whether it was green, blue, yellow or redlined.
“I think this is why it’s important to unpack why racial equity matters and why we must be explicit and intentional with talking about race when we talk about the environment,” said Cabrera.
These public health consequences are the legacy of decades of discriminatory actions that go beyond redlining, racial covenants and transportation infrastructure projects. In a recent study published, researchers used the ambient concentrations of two pollutants, NO2 and PM10–2.5 to look into the historical factors behind the unequal air pollution exposure we see today.
For generations, federal, state and local policies and practices have led to greater numbers of Black, Asian and Latine individuals living in more densely-populated and more polluted areas. For example, Black land loss in the 20th century, combined with greater economic opportunities to be found in cities, led to families moving out of rural areas. Additionally, polluting infrastructure from refineries to factories is disproportionately located near or in Black communities.
“Systemic racism is systemic,” said Marshall. “Addressing disparities will be harder because it’s not just one or two sectors of the economy.”
Clearing the air
Many of the systems we’re currently working with have been set up to shift the cost, or the burden, away from those reaping the benefits.
One question we need to ask, said Marshall: “How do we move forward in a way that works in our democracy and reflects current inequalities and is anti-racist and eliminates those disparities—doesn’t accept them, doesn’t turn a blind eye toward them?”
Back in 2020, California Gov. Gavin Newsom announced a goal of having all new passenger cars and trucks sold in the state be zero-emission by 2035.
In 2021, the Los Angeles Department of Water and Power, in partnership with the National Renewable Energy Laboratory, released a study evaluating the economic costs and public health benefits of a totally clean-energy future for the city, along with potential pathways to reach that goal within the next 10 to 20 years. Its scenarios were based on different combinations of options for power generation and consumption, like natural gas, rooftop solar, renewable energy credits and transmission lines.
Using 2012 as a baseline, researchers investigated how these pathways could affect air pollutant emissions throughout the city, specifically nitrogen oxides and fine particulate matter. They found that all options could lead to significant emissions reductions, including from the transportation sector, which would likewise mean better public health outcomes and lower health costs for residents.
“When we’ve looked at what will address the problem, you need location-specific solutions, which are different from what’s in the Clean Air Act,” said Marshall. “You have to go to the overburdened communities and reduce pollution there. Plain and simple.”
He and Patterson partnered on a 2022 study that could point in the right direction. If emission reductions and other strategies specifically target communities with the greatest disparities, there’s a better chance of eliminating the racial-ethnic differences in air pollution exposure. If emissions are just reduced across the board, you’d have to get to zero emissions in order to eliminate the disparities.
The work also has to be community-driven, said Patterson. That doesn’t mean the most burdened communities should be tasked with fixing the problems alone, just that the lived experiences of people who are in these communities need to be sought out and heard.
Patterson was lead author of a 2019 study on the effects on air pollution when freeways are rerouted and replaced with different infrastructure. After the Cypress Freeway, which divided West Oakland, was damaged in the 1989 Loma Prieta earthquake, community activists pushed for the freeway to be rerouted rather than repaired. It’s an innovative approach to an accidental change in circumstance that could lend ideas for future solutions. The infrastructure we have now doesn’t have to be the infrastructure we always have to live with, and communities can lead the way.
“Existing transportation funding structures and project pipelines favor a top-down, siloed approach and as a result, transportation policies often fail to meet the specific needs of frontline communities,” said Cabrera. “But when we talk to folks on the ground, we know that the communities want to take advantage of the available funds and policies. I think the key thing here is they have been excluded from the decision-making processes that impact their lives.”
Greenlining has resources for community members and others to use, including the Achieving Resilient Mobility report and the Clean Mobility Equity playbook. Statewide, California has its Transformative Climate Communities Program, which aims to support pollution-affected communities in guiding their own recovery.
Earlier this year, Transportation Secretary Pete Buttigieg announced the first 45 awardees of the five-year, $1 billion federal Reconnecting Communities Pilot Program, backed by the bipartisan infrastructure bill. The grants are intended to help communities who were negatively impacted by historic transportation infrastructure decisions, including $30 million to the city of Long Beach and $2 million to Pasadena, where freeway construction in the 70s displaced about 4,000 low-income residents and residents of color. It aligns with a Biden Administration initiative to invest in communities disproportionately affected by pollution.
Boeing said incentivizing working from home to discourage commutes from white, wealthy communities, enacting tolls or congestion pricing, (which L.A. is considering) and building low-income housing in more unburdened areas, like Bel Air, Beverly Hills and South Pasadena could also be community-minded solutions.
“It’s the society that sets us up in this situation where taking part in these systems—this infrastructure—harms other people,” said Boeing.
On a smaller scale, there are a few practical options for reducing direct air pollution exposure, said Brugge. In buildings with HVAC systems, you can upgrade the filters or change the recirculation so less pollution gets through. If there’s no forced air ventilation in a home, an air purifier could be an option.
Since 2016, L.A. has mandated that all new homes within 1,000 feet of a freeway have high-efficiency air filtration systems, but it relies on landlords to comply and doesn’t necessarily protect residents already in place.
What all these options share is the notion that community-led and supported plans need to be at the heart of any sustainable solutions.
“So often nowadays we just act like the infrastructure we’ve got, the urban patterns we’ve got—which have been given to us—they’re just natural, they’re just the way things are, but they’re not. Things were planned by other human beings, often for pretty problematic reasons,” said Boeing. “We can have a desegregated society. We can walk around one of the finest climates on the planet. But none of this comes without tradeoffs, and unless we make driving not our singleminded priority in all transportation planning, none of that will come to pass.”
This story was supported by a Diversity Reporting Grant from the National Association of Science Writers.