In the 1930s, the federal Home Owners' Loan Corporation (HOLC) made maps of thousands of cities across the United States. Each neighborhood was color-coded according to the perceived security of prospective lenders’ investments.

In Brooklyn’s map, the area around the Navy Yard was colored in bright red, signifying a “D” rating — the lowest possible. An accompanying report listed undesirable features like the nearby shipyard and Brooklyn Bridge — and describes the neighborhood’s residents, who were mainly Italian and Black merchants and laborers. A “great many” received government assistance.

“An area of poor properties and shifting population of questionable character and occupation,” the report by the HOLC, a government-sponsored group, read. Like so many neighborhoods inhabited by immigrants, people of color and people living in poverty, the area had been redlined, cutting residents off from homeownership and discouraging investment.

Fair housing laws of the 1960s officially ended redlining, but the longtail effects of the inequity continue to show up within the old boundaries. New research links the historical discrimination, coupled with generational harm caused by land-use policies, with modern-day pollution.

A map of Brooklyn. Neighborhoods are shaded in different colors.

The Home Owners' Loan Corporation used racist criteria to grade neighborhoods on their lending security.

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The Home Owners' Loan Corporation used racist criteria to grade neighborhoods on their lending security.
Mapping Inequality Project

The once-redlined neighborhood surrounding the Navy Yard, for example, has some of the highest rates of nitrogen dioxide (NO2) — a toxic byproduct found in car exhaust — in the entire city, according to the new findings by University of California, Berkeley, professors. It also has elevated levels of particulate matter 2.5 (PM2.5), tiny particles emitted from motor vehicles — like the trucks that chug along on the Brooklyn Queens Expressway overhead — and industrial sites.

It’s not just the Navy Yard, either. The Berkeley researchers found that throughout the New York metro area, neighborhoods deemed “unfavorable” nearly a century ago are more polluted on average than other communities mapped out by the federal authority, typically along racial lines.

A photo of trucks moving on a highway

Trucks inch along the Brooklyn Queens Expressway in a neighborhood with a high concentration of air pollution.

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Trucks inch along the Brooklyn Queens Expressway in a neighborhood with a high concentration of air pollution.
Jaclyn Jeffrey-Wilensky

On average, the worst-rated neighborhoods have about 32% higher concentrations of NO2 compared with the best-rated neighborhoods. PM2.5, or particle pollution, varies just 6% between redlined and favorably rated neighborhoods — but experts say even small differences in the pollutant’s concentrations can have a major impact on residents’ health. Exposure to these tiny particles is linked to hospital visits for asthma and heart disease, as well as to premature death — all of which disproportionately affect New Yorkers of color and Black New Yorkers in particular, according to city data.

“When it comes to environmental disparities in our country, the past is really with us today,” said Dr. Joshua Apte, coauthor on the pollution study and assistant professor of civil and environmental engineering at the University of California, Berkeley. “These decisions that have been made over centuries and decades still resonate today and in the air we breathe.”

Environmental justice advocates said the findings, published in March in the journal Environmental Science and Technology Letters, underscore the need for new spending to remedy the legacy of harm tied both to redlining and land-use policies, including the siting of power plants and highways near communities of color. Such results also point to the need for faster investment in renewable energies, as communities marginalized long ago continue to pay a price, even as such discrimination has long since been outlawed, according to the advocates.

"No coincidence"

Past research has linked redlining to many other environmental and health disparities. On average, residents of formerly redlined neighborhoods are sicker, have more pregnancy and birth complications, are more vulnerable to extreme heat and die younger than their neighbors living in areas with more favorable ratings from the Home Owners' Loan Corporation. Many have also borne the brunt of COVID-19 hospitalizations and deaths.

The unfavorable ratings were based on the proportion of nonwhite or immigrant residents in a neighborhood, as well as the presence of preexisting sources of pollution. They made it harder for Black families and other residents of redlined neighborhoods to buy homes, build wealth and escape poverty, contributing to poorer overall health. The designation also made redlined areas appealing targets for highways, peaking power plants, waste transfer stations and heavy industry — all of which produce harmful emissions.

“It's no coincidence that these neighborhoods that are experiencing extremely high concentrations of traffic-related air pollution, are the same neighborhoods where kids are getting more sick with asthma,” said Dr. Stephanie Lovinsky-Desir, chief of pediatrics in the division of pediatric pulmonology at Columbia University’s Irving Medical Center.

For the Berkeley study, the researchers matched the government-made maps with emissions and census data from 2010. They calculated NO2 and PM2.5 levels for each census block and compared the average concentrations of these pollutants at each government rating — ”A,” “B,” “C” or “D.”

Across all the cities originally mapped by the government, redlined neighborhoods were exposed to more NO2 and PM2.5 than neighborhoods with higher ratings. Even among inhabitants of same-rated areas, the study found, residents of color tended to be more exposed to these pollutants than their white neighbors — suggesting that redlining isn’t solely to blame for racial disparities in air pollution exposure.

These trends bore out in the New York metro area, too: Both pollutants were more concentrated in neighborhoods with the worst government ratings. Bergen County, New Jersey, and the Bronx both had especially large differences between differently-rated neighborhoods. Staten Island and Manhattan, meanwhile, had more modest variations.

Differences between individual neighborhoods are more extreme. Residents of the neighborhood surrounding the Navy Yard, which includes two New York City Housing Authority complexes, are exposed to nearly three times the NO2 concentration as those dwelling in Riverdale, which mainly received ‘A’ and ‘B’ ratings from the HOLC.

Plenty of neighborhoods don’t follow the trends, though: much of Staten Island’s west shore received a ‘D’ designation from the Home Owners' Loan Corporation, but the region has below-average levels of the two pollutants.

“A snapshot”

Experts and local environmental justice advocates alike said the results are validating but unsurprising.

“It corroborates what we in frontline communities have known for a long time,” said Arif Ullah, executive director of South Bronx Unite, an environmental advocacy group working in a neighborhood with a high burden of air pollution and the highest rate of pediatric asthma hospital admissions in the entire city.

“This has all resulted in toxic, poisonous air,” he said of the city planning decisions that led to the construction of multiple highways, waste transfer stations and peaker power plants in the neighborhood. “We breathe this air on a daily basis. Our community has been paying the price for breathing that air.”

Dr. Joan Casey, an assistant professor of environmental health sciences at Columbia University’s Mailman School of Public Health, praised the study but cautioned against drawing a direct cause-and-effect relationship between the corporation’s grades and 21st-century air pollution. After all, she said, pre-existing pollution sources may have helped earn a neighborhood its "D" grade in the first place. The data is also from 2010, Casey noted, and neighborhood demographics and air pollution exposure have changed since then.

“They're looking at a snapshot,” she said. “It could be really interesting to know how these disparities shifted between 1930 and modern day, or even into 2020 and going forward.”

Highways and industrial sites aren’t the only sources of dangerous air pollution: gas stoves and heaters can contribute, too, says Dr. Gary Adamkiewicz, associate professor in the department of environmental health at Harvard’s T.H. Chan School of Public Health.

There are lots of different ways that we see disproportionate exposures in practice in the real world

Dr. Gary Adamkiewicz, Harvard’s T.H. Chan School of Public Health

“Whether it’s poor housing or a neighborhood with a lot of traffic, there are lots of different ways that we see disproportionate exposures in practice in the real world,” he said.

Experts and environmental justice advocates both called on elected officials to protect already overburdened neighborhoods from new pollution sources. Sonal Jessel, policy director at WE ACT for Environmental Justice, urged city and state officials to make strides away from fossil fuels and toward renewable energy as a way to reduce emissions and invest in underserved communities.

A New York State Assembly bill currently in committee would require developers to include special consideration for low-income communities and communities of color in their environmental impact statements. Lawmakers are also trying to secure $15 billion worth of climate justice funding in the upcoming state budget.The funds would pay for energy-efficient low-income housing, electrified school buses and renewable energy infrastructure, among other projects.

“No more polluting gas in your home, no more dirty peaker plants creating horrible air quality,” Jessel said.

The Environmental Protection Agency should also lower the acceptable threshold for PM2.5 from 12 micrograms per cubic meter to 8, said Casey, referring to the air quality standards states must aim for under the Clean Air Act. Casey added that even small decreases in air pollution can have an enormous effect on health.

“If we reduced [PM2.5] just 1 microgram per meter cubed across the city, we could be preventing myocardial infarction, asthma attacks, premature mortality,” she said. “It can translate into better health even at these low levels.”

Ken Alston, Jr., who teaches at a school near the Navy Yard, had an even simpler suggestion.

“Don't put schools next to massive highways,” he said. “That would be a start.”