Chapter 6.1 · The air you're assigned · Report

Air pollution

The national traffic-pollution percentile of census tracts, modeled for 2020, has a correlation of −0.41 with the Area Deprivation Index across tracts but +0.19 within counties.

Author: Vishal Singh
Affiliation: NYU Stern
Published: 9 October 2026

Every estimate of the chapter with its interval and every figure as a table, generated from the chapter's data files. Table n of this report is figure n of the chapter. The same report as Markdown: report.md.

Identification

Title

Air pollution

Label

The air you're assigned

Chapter

6.1 (Part VI, Environment, connection and well-being; An American life)

Question

Who breathes the most polluted air, by neighborhood deprivation, race and historical redlining grade?

Dek

The national traffic-pollution percentile of census tracts, modeled for 2020, has a correlation of −0.41 with the Area Deprivation Index across tracts but +0.19 within counties.

Grain

neighborhoods

Status

published

Published

9 October 2026

Updated

not revised

Data sources

EPA EJScreen. EPA EJScreen 2024, tract file (Zenodo archive, release 2.32): national percentiles of 13 indicators on 2020 tracts; air quality modeled for 2020, toxic releases for 2021; years: 2024 (indicators); ACS 2018-2022 (demographics); weights: none (modeled indicators); tract population weights from the ACS
Area Deprivation Index. Neighborhood Atlas Area Deprivation Index 2023, national rank, tract values; years: 2023 release (version 4.0.1; built on ACS 2019-2023); weights: ACS 2019-2023 tract population
American Community Survey. ACS 2019-2023 tract population, race-alone and Hispanic or Latino shares, poverty rate; years: 2019-2023 (5-year); weights: Census Bureau survey weights applied upstream
CDC PLACES. CDC PLACES 2024 release, tract estimates of current asthma and COPD among adults (BRFSS 2022); years: 2024 release (tracts); 2025 release (ZCTAs, 2023 data year); weights: none (model-based estimates); ACS tract population
Mapping Inequality (HOLC maps). Mapping Inequality digitized HOLC maps (1935 to 1940), grades A to D, matched to 2020 tracts by area; years: 1930s-1940s maps (2023 digitization); weights: none (map polygons)

Canonical URL

https://vishalsingh.org/zipcode/air-pollution

Markdown

https://vishalsingh.org/zipcode/air-pollution/report.md

BibTeX

@misc{singh2026airpollution,
  author = {Singh, Vishal},
  title = {Air pollution},
  year = {2026},
  url = {https://vishalsingh.org/zipcode/air-pollution},
  note = {In ZIP Code Destiny. Published 9 October 2026.}
}

Principal estimates

The facts the dek and the opening prose cite, in order of appearance. Every fact is in the table of all estimates below.

Estimand	Population	Period	Value	Interval	n	Weights	Source	Fact id
population-weighted correlation of the tract Traffic proximity national percentile with the ADI national rank, county-cluster bootstrap interval	residents of tracts with a Traffic proximity percentile and an ADI rank	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	−0.41	95% CI −0.49 to −0.33	82,198 tracts	ACS 2019-2023 tract population	EPA EJScreen	ptraf_adi
population-weighted correlation of the tract Traffic proximity national percentile with the ADI national rank, after removing each county's population-weighted mean from both (counties with at least 5 tracts), county-cluster bootstrap interval	residents of tracts in counties with at least 5 tracts that have a Traffic proximity percentile and the ADI national rank	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	+0.19	95% CI 0.15 to 0.22	79,730 tracts	ACS 2019-2023 tract population	EPA EJScreen	ptraf_adi_within
population-weighted mean of the tract Traffic proximity national percentile in an ADI decile (deciles hold equal numbers of tracts), county-cluster bootstrap interval	residents of tracts in the least deprived of the ten ADI deciles (decile 1)	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	75	95% CI 68 to 79	8,149 tracts	ACS 2019-2023 tract population	EPA EJScreen	ptraf_adi_d1
population-weighted mean of the tract Traffic proximity national percentile in an ADI decile (deciles hold equal numbers of tracts), county-cluster bootstrap interval	residents of tracts in the most deprived of the ten ADI deciles (decile 10)	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	39	95% CI 35 to 42	8,203 tracts	ACS 2019-2023 tract population	EPA EJScreen	ptraf_adi_d10
population-weighted correlation of the tract Traffic proximity national percentile with the ADI national rank, metropolitan tracts only, county-cluster bootstrap interval	residents of metropolitan tracts with a Traffic proximity percentile and the ADI national rank	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	−0.31	95% CI −0.40 to −0.21	66,593 tracts	ACS 2019-2023 tract population	EPA EJScreen	ptraf_adi_metro
population-weighted correlation of the tract Traffic proximity national percentile with the tract poverty rate, county-cluster bootstrap interval	residents of tracts with a Traffic proximity percentile and the tract poverty rate	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	+0.07	95% CI 0.04 to 0.11	82,818 tracts	ACS 2019-2023 tract population	EPA EJScreen	ptraf_pov
population-weighted correlation of the tract NO₂ national percentile with the tract's Hispanic or Latino share, county-cluster bootstrap interval	residents of tracts with a NO₂ percentile and a race and ethnicity share	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	+0.40	95% CI 0.35 to 0.46	83,003 tracts	ACS 2019-2023 tract population	EPA EJScreen	no2_hisp
population-weighted correlation of the tract NO₂ national percentile with the tract's Hispanic or Latino share after removing each county's population-weighted mean from both, county-cluster bootstrap interval	residents of tracts in counties with at least 5 tracts that have a NO₂ percentile and a race and ethnicity share	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	+0.23	95% CI 0.21 to 0.26	80,548 tracts	ACS 2019-2023 tract population	EPA EJScreen	no2_hisp_within

Findings

Traffic pollution ranks at a mean national percentile of 75 in the tenth of census tracts that are least deprived by the Area Deprivation Index (ADI) and 39 in the tenth that are most deprived. Across tracts, the correlation between the traffic percentile and the ADI rank is −0.41 (95% CI −0.49 to −0.33). Within a county the correlation is +0.19 (95% CI 0.15 to 0.22), so compared only with the other tracts of its county, a more deprived tract tends to rank higher on traffic. Among metropolitan tracts alone the correlation is still negative (−0.31 (95% CI −0.40 to −0.21)), and with the tract poverty rate in place of the ADI it is +0.07 (95% CI 0.04 to 0.11) across all tracts. For NO₂, diesel PM and traffic, the percentiles rise with the Hispanic share and with the Black share of a tract, across tracts and within counties. The correlation of the NO₂ percentile with Hispanic share is +0.40 (95% CI 0.35 to 0.46) across tracts and +0.23 (95% CI 0.21 to 0.26) within counties.

A percentile ranks a tract against other tracts and does not give a concentration. Every statement in this chapter is about tracts or about the residents of groups of tracts. None describes what an individual breathes, because people leave their tract during the day and the indicators are modeled estimates for particular years.

What the pollution indicators measure

The indicators come from the Environmental Protection Agency's EJScreen. EPA removed the tool from its website in 2025, and the chapter uses the archived copy of the final 2024 release kept on Zenodo.[1] The tract file is on 2020 census tracts, as are the ADI, the American Community Survey (ACS) estimates for 2019 to 2023 and the CDC PLACES file used later, so the files join on the tract identifier with no crosswalk. Connecticut tracts carry the planning-region codes in all of them.

EPA's technical documentation dates each air indicator.[1] Fine particulate matter (PM₂.₅, in micrograms per cubic meter) and ozone (the annual mean of the ten highest daily maximum eight-hour readings, in parts per billion) are for 2020 and combine monitor readings with an air-quality model. NO₂ (parts per billion) is a 2020 estimate built from satellite data and a regression model. Diesel particulate matter (micrograms per cubic meter) is EPA's 2020 estimate from its air toxics screening. Toxic releases to air are a toxicity-weighted concentration modeled from 2021 reports, and traffic proximity is an index of 2020 traffic counts on nearby major roads, weighted by distance. The release has no air-toxics cancer-risk index. Besides the 6 air indicators, the file carries 4 indicators of proximity and discharge (Superfund sites, risk-management facilities, hazardous-waste facilities and wastewater) and 3 of old housing and infrastructure (housing built before 1960 as a proxy for lead paint, underground storage tanks and drinking-water violations), 13 in all. Each is a modeled or calculated value and none is a monitor reading at the tract.

Each indicator also comes as a national percentile. EPA's documentation describes percentiles ranked across block groups, but the percentiles in this file rank tracts, so a percentile is the share of tracts with a lower value. A percentile compares a tract with other tracts and says nothing about the level of a pollutant. The first and third quartiles of tract PM₂.₅ are 7.3 and 9.0 micrograms per cubic meter, so small differences in concentration separate tracts by many percentile points.

EJScreen has no PM₂.₅ or ozone estimate for the 1,524 tracts with residents in Alaska, Hawaii and Puerto Rico. A missing value is not a value of zero, so the analysis leaves those tracts out and every comparison covers the same places. It uses the 83,008 tracts of the contiguous states and the District of Columbia that have a positive ACS population, and they hold 330.1 million residents. 810 of those tracts have no ADI rank, and comparisons with the ADI leave them out, so 82,198 tracts have both a traffic percentile and an ADI rank. Means and correlations are population-weighted, with intervals from a bootstrap that redraws whole counties.

Pollution percentiles fall as deprivation rises

Table 1 sorts tracts into tenths by the ADI national rank, with the first tenth the least deprived, and averages the pollution percentile of the tracts in each tenth. Every line falls from the first tenth to the ninth and edges up in the tenth. For traffic the means are 75 in the first tenth, 35 (95% CI 32 to 38) in the ninth and 39 in the tenth.

Across the tracts with both values the correlation with the ADI rank is −0.41 (95% CI −0.49 to −0.33) for traffic, −0.38 (95% CI −0.45 to −0.30) for diesel PM, −0.18 (95% CI −0.27 to −0.10) for NO₂ and −0.18 (95% CI −0.29 to −0.06) for PM₂.₅. Higher deprivation goes with lower pollution percentiles across the country, most strongly for traffic and diesel PM.

Table 1. Traffic pollution ranks at a mean national percentile of 75 in the least deprived tenth of tracts and 39 in the most deprived

A gap in percentiles is a gap in rank. For PM₂.₅ the mean percentiles are 64 (95% CI 52 to 73) in the first tenth, 44 (95% CI 41 to 47) in the ninth and 48 (95% CI 44 to 51) in the tenth. The mean PM₂.₅ concentration is 9.6 (95% CI 8.7 to 10.4) micrograms per cubic meter in the least deprived tenth and 8.1 (95% CI 7.9 to 8.2) in the most deprived. The intervals describe which places are in the file and leave out the error in EPA's models.

Metropolitan tracts keep the fall, and the sign reverses within counties

Among metropolitan tracts the fall persists for traffic and diesel PM. One explanation is that the most deprived tracts are rural and that rural air ranks cleaner. Table 2 tests it in three tabs. The share of residents living in small-town and rural tracts, as the USDA classifies tracts, rises from 0.6% (95% CI 0.4% to 1.1%) in the least deprived tenth to 20.3% (95% CI 18.4% to 22.3%) in the ninth and eases to 18.5% (95% CI 16.2% to 21.0%) in the tenth, and it is 6.9% of residents overall. Those tracts hold a minority of residents in every tenth.

Among metropolitan tracts alone the traffic percentile still falls from 76 (95% CI 69 to 80) in the first tenth to 48 (95% CI 45 to 50) in the ninth. Diesel PM falls from 71 (95% CI 64 to 76) to 47 (95% CI 44 to 50).

The correlations of traffic and diesel PM with the ADI rank are −0.31 (95% CI −0.40 to −0.21) and −0.28 (95% CI −0.36 to −0.19) among metropolitan tracts, against −0.41 and −0.38 in all tracts. For NO₂ and PM₂.₅ the metropolitan correlations are −0.09 (95% CI −0.17 to 0.00) and −0.10 (95% CI −0.22 to 0.03), small and with intervals that include zero, and most of the fall in the metropolitan lines comes across the first three tenths. Leaving out the small-town, rural and micropolitan tracts changes the correlation less for traffic and diesel PM than for NO₂ and PM₂.₅, so rural tracts account for more of the national fall in the NO₂ and PM₂.₅ percentiles than of the traffic and diesel PM falls.

Table 2. The fall in traffic and diesel PM percentiles with deprivation persists among metropolitan tracts, and the sign reverses when tracts are compared within a county

The sign also depends on how deprivation is measured. The ADI descends from an index of census measures that includes median home value and median gross rent,[2] so places with high housing costs read as less deprived, a limit that Chapter 1.1, What the deprivation index measures takes up. These data do not isolate that component, but the tract poverty rate does not show the negative sign. Across all tracts it correlates +0.07 (95% CI 0.04 to 0.11) with the traffic percentile and +0.18 (95% CI 0.15 to 0.21) with the NO₂ percentile.

It depends as well on which tracts are compared. Across all tracts, the comparison mixes places: a deprived tract in one county is compared with a less deprived tract in another county, which can differ in traffic, industry and housing costs. Within a county, each tract is compared only with the other tracts of its county, by removing the county's population-weighted mean from both variables. In that comparison, over the 79,730 tracts of counties that have enough tracts to compare, the ADI rank correlates +0.19 (95% CI 0.15 to 0.22) with the traffic percentile, +0.19 (95% CI 0.15 to 0.23) with diesel PM and +0.28 (95% CI 0.25 to 0.31) with NO₂. The poverty rate correlates +0.27 (95% CI 0.24 to 0.29) with the traffic percentile. Within a county, more deprived tracts have higher pollution percentiles.

Across counties the relation runs the other way. The correlation between a county's mean traffic percentile and its mean ADI rank is −0.66 (95% CI −0.73 to −0.58) across 3,095 counties, each weighted by its residents. The fall across the country reflects differences between counties.

Early environmental-justice research documented waste facilities sited in Black communities in the South.[3] The same indicators that fall with the ADI rise with the racial and ethnic composition of a tract. Table 3 repeats the tenths design with the share of residents who are Hispanic or Latino, of any race, and the share who are Black or African American alone, of any ethnicity. The groups overlap, because a Hispanic resident can be Black, and they are 19.0% and 12.1% of residents.

The NO₂ percentile averages 33 (95% CI 30 to 36) in the tenth of tracts with the lowest Hispanic share and 73 (95% CI 68 to 76) in the tenth with the highest, and it averages 38 (95% CI 35 to 41) and 58 (95% CI 53 to 63) across Black-share tenths. Tracts with the same share go to the same tenth, so the lowest Black-share tenth holds all 8,815 tracts with no Black alone residents and the second holds correspondingly fewer.

Table 3. Pollution percentiles rise with the Hispanic share of a tract, from 33 to 73 for NO₂ across deciles, and with its Black share up to the fifth decile and in the tenth

In every panel the Hispanic-share lines rise from the second tenth to the tenth, and the Black-share lines rise through the fifth tenth, change little to the ninth and rise again in the tenth for traffic, diesel PM and NO₂. Across tracts, Hispanic share correlates +0.40 (95% CI 0.35 to 0.46) with the NO₂ percentile, +0.34 (95% CI 0.26 to 0.41) with diesel PM, +0.33 (95% CI 0.27 to 0.40) with traffic and +0.32 (95% CI 0.22 to 0.40) with PM₂.₅.

Black share correlates +0.14 (95% CI 0.10 to 0.19) with NO₂, +0.18 (95% CI 0.13 to 0.23) with diesel PM and +0.17 (95% CI 0.12 to 0.22) with traffic, and +0.06 (95% CI 0.00 to 0.12) with PM₂.₅, which is close to zero. For NO₂, diesel PM and traffic the correlations with both shares stay positive when states are redrawn instead of counties.

The correlations persist within counties. There the NO₂ percentile correlates +0.23 (95% CI 0.21 to 0.26) with Hispanic share and +0.17 (95% CI 0.14 to 0.21) with Black share, and the traffic percentile +0.19 (95% CI 0.16 to 0.21) and +0.16 (95% CI 0.14 to 0.19).

To see whether race and deprivation each go with pollution on their own, a joint model puts them together. In a weighted regression of the traffic percentile on the ADI rank, Hispanic share and Black share, each variable measured from its county mean and scaled to one standard deviation, the coefficients are +0.06 (95% CI 0.02 to 0.10) for the ADI rank, +0.17 (95% CI 0.14 to 0.21) for Hispanic share and +0.15 (95% CI 0.12 to 0.19) for Black share.

For NO₂ they are +0.16 (95% CI 0.13 to 0.19), +0.18 (95% CI 0.15 to 0.21) and +0.12 (95% CI 0.08 to 0.16). All are positive, and the ADI rank is the weakest for traffic.

With the poverty rate in place of the ADI rank, the traffic coefficients are +0.19 (95% CI 0.17 to 0.21) for poverty, +0.14 (95% CI 0.10 to 0.17) for Hispanic share and +0.10 (95% CI 0.07 to 0.14) for Black share. Within a county, poverty and the racial and ethnic composition of a tract each go with higher pollution percentiles, and these data do not rank them.

Weighting tracts by the residents of a group describes where the group lives. The tract of the average Hispanic resident has an NO₂ percentile of 63 (95% CI 59 to 67), that of the average Black alone resident 56 (95% CI 52 to 60), and that of the average resident 50 (95% CI 47 to 53). These are averages over tracts of residence and not measurements of individuals. A national model that attributes PM₂.₅ exposure to the consumption of goods and services finds that Black and Hispanic residents are exposed to more particulate matter than their own consumption accounts for, and non-Hispanic white residents to less.[4]

Hazards stack in the same tracts

Single indicators understate a tract's burden when hazards coincide. Count, for each tract, how many of the 5 hazards PM₂.₅, diesel PM, NO₂, traffic proximity and toxic releases to air have a national percentile of at least 75. Table 4 shows the mean count by tenth for 82,993 tracts.

The count rises from 0.8 (95% CI 0.6 to 1.0) in the lowest Black-share tenth to 1.7 (95% CI 1.4 to 2.0) in the highest, and from 0.6 (95% CI 0.5 to 0.7) to 2.3 (95% CI 1.8 to 2.8) across Hispanic-share tenths. The Black-share line is flat from the sixth tenth to the ninth, so the highest tenth stands apart.

Across ADI tenths the count falls from 2.1 (95% CI 1.7 to 2.5) to 1.0 (95% CI 0.8 to 1.2). Ozone is not counted, because it forms in the air from other pollutants and does not mark a local source as the five counted hazards do. Adding it as a sixth hazard gives the same ordering of the three lines.

Table 4. Residents of tracts in the highest Black-share decile live with 1.7 stacked air hazards on average, against 0.8 in the lowest, and the score falls across deprivation deciles

The second view shows the share of residents living in tracts with 3 or more stacked hazards. It is 10% (95% CI 6% to 15%) in the lowest Black-share tenth and 32% (95% CI 23% to 40%) in the highest, and 6% (95% CI 4% to 10%) and 49% (95% CI 35% to 61%) across Hispanic-share tenths.

Two components summarize the indicators

The indicators overlap, and principal components summarize them. The analysis standardizes each of the 13 national percentiles to mean zero and standard deviation one across the 80,754 tracts that have all of them, counts every tract once, and finds the weighted combinations of the indicators that capture the most variance. The first component holds 38.6% (95% CI 36.2% to 41.7%) of the variance and the second 11.7% (95% CI 10.5% to 13.1%). A population-weighted version gives almost the same components, with 37.1% in the first.

The first component has positive weights on every indicator except drinking-water violations, and the largest are on diesel PM (+0.40 (95% CI 0.38 to 0.41)), traffic proximity (+0.40 (95% CI 0.39 to 0.41)), hazardous-waste facilities (+0.39 (95% CI 0.37 to 0.40)) and NO₂ (+0.38 (95% CI 0.36 to 0.39)). It marks tracts that are dense and close to roads and facilities, and the chapter calls it the urban-industrial component.

The second weights underground storage tanks (+0.55 (95% CI 0.33 to 0.66)), lead paint (+0.45 (95% CI 0.33 to 0.56)) and drinking-water violations (+0.32 (95% CI 0.19 to 0.43)) positively and PM₂.₅ (−0.47 (95% CI −0.55 to −0.38)) and ozone (−0.31 (95% CI −0.38 to −0.16)) negatively, so it separates tracts with old housing and infrastructure from tracts with high PM₂.₅ and ozone (Table 5). The sign of a component is arbitrary, and the names describe the weights without testing them.

Table 5. The first component weights diesel PM, traffic, hazardous-waste facilities and NO₂ most, and the second weights storage tanks, lead paint and drinking-water violations against PM₂.₅ and ozone

The deprivation index relates differently to the two kinds of indicator. Storage tanks correlate +0.25 (95% CI 0.13 to 0.36) with the ADI rank and lead paint +0.16 (95% CI 0.06 to 0.26), against negative correlations for most of the air indicators.

The urban-industrial component is highest in a few dense counties

Table 6 averages the tract scores on the first component within each county, weighting tracts by population. Cook County, Illinois, has the highest mean (+1.69, in standard deviations of the tract score), followed by Hudson County, New Jersey (+1.67), and New York County (+1.58). The independent city of St. Louis (+1.50) and the Bronx (+1.45) come next.

Los Angeles County has rank 6 among the mapped counties. The median county scores −1.2, so most counties sit below the tract average. The map covers 3,094 counties. The 49 gray counties are in Alaska and Hawaii, where EJScreen has no PM₂.₅ or ozone estimate, or are counties where fewer than 50% of residents live in tracts with all indicators. Puerto Rico is not drawn.

Table 6. The urban-industrial component is highest in Cook County, Illinois, and in dense counties around New York, and below the tract average in most counties

Table 7 lists the correlation of each of the 13 indicators with the ADI rank, Hispanic share and Black share. It shades a cell by the wider of two 95% intervals, one from a bootstrap over counties and one from a bootstrap over states, and the counts below require both to exclude zero. Of the 6 air indicators, 4 correlate negatively with the ADI rank: ozone, diesel PM, NO₂ and traffic. The PM₂.₅ correlation is negative under the county bootstrap and its interval includes zero when states are redrawn, and the correlation for toxic releases to air cannot be told from zero.

5 correlate positively with Hispanic share, all but toxic releases, and 4 with Black share: diesel PM, NO₂, traffic and toxic releases. The PM₂.₅ and ozone cells for Black share include zero. Of the 3 old-housing and infrastructure indicators, 1 is clearly positive with the ADI rank, lead paint. Storage tanks are positive under the county bootstrap and include zero when states are redrawn, and the interval for drinking-water violations includes zero.

Table 7. Pollution percentiles correlate negatively with deprivation for 4 of 6 air indicators and positively with Hispanic share for 5

Modeled asthma does not follow the urban-industrial component

If the urban-industrial component tracked illness, modeled asthma would rise with it. CDC PLACES estimates the prevalence of current asthma among adults for every tract from a model fitted to the 2022 Behavioral Risk Factor Surveillance System, with age, sex, race and ethnicity, education and county poverty as inputs.[5] A tract's value therefore reflects who lives there and where, and a correlation of PLACES values with the ADI or with race shares is partly built into the model. The tract file has no intervals, and Chapter 7.1, Health behaviors and the supply of care discusses the same limit for other PLACES measures.

Table 8 ranks tracts in twentieths on each of three measures. Modeled asthma is highest in the lowest twentieth on the urban-industrial component (11.2% (95% CI 11.1% to 11.3%)) and lowest in the highest (9.9% (95% CI 9.7% to 10.5%)). It rises from 9.7% (95% CI 9.5% to 9.9%) to 11.0% (95% CI 10.6% to 11.5%) across lead-paint twentieths, and from 9.0% (95% CI 8.9% to 9.3%) to 12.7% (95% CI 12.4% to 12.9%) across deprivation twentieths.

Across tracts the urban-industrial component correlates −0.10 (95% CI −0.18 to 0.00) with modeled asthma and −0.37 (95% CI −0.42 to −0.32) with modeled COPD, the lead-paint percentile correlates +0.27 (95% CI 0.20 to 0.34) with asthma, and the ADI rank +0.53 (95% CI 0.48 to 0.58). The deprivation line is the one most closely tied to the model's inputs, and the flat-to-falling urban-industrial line says nothing about illness itself, because the values are modeled.

Table 8. Modeled asthma prevalence is highest in the lowest twentieth of tracts on the urban-industrial component (11.2%) and rises with the lead-paint percentile and with deprivation

Tracts graded D in the 1930s have higher traffic, NO₂ and diesel percentiles

Between 1935 and 1940 the Home Owners' Loan Corporation drew residential security maps for cities and graded neighborhoods from A, labeled best, to D, labeled hazardous.[6] The grades in general are the subject of Chapter 5.2, Home value, income and redlining, and this chapter uses them to look at air only. Each tract takes the grade that covers most of its area, among tracts where graded polygons cover at least 50% of the tract. 10,950 tracts qualify, holding 37.9 million residents in 215 counties.

Pooled across those counties, the traffic percentile steps up from 78 (95% CI 75 to 80) in grade A tracts to 86 (95% CI 83 to 89) in grade D tracts. NO₂ goes from 73 (95% CI 70 to 76) to 86 (95% CI 83 to 89), and diesel PM from 73 (95% CI 69 to 77) to 86 (95% CI 81 to 89).

The stacked-hazard score goes from 2.3 (95% CI 2.0 to 2.5) to 3.2 (95% CI 2.8 to 3.5). PM₂.₅ moves less, from 56 (95% CI 49 to 63) to 60 (95% CI 51 to 69), and the two pooled intervals overlap. Pooled gaps mix the differences between grades with the differences between the cities that were graded.

Comparing tracts within the same county separates the two. In the 199 counties that hold more than one grade, grade D tracts rank 3.9 (95% CI 2.7 to 5.1) points above grade A tracts on the traffic percentile, 9.7 (95% CI 7.2 to 12.2) on NO₂, 5.1 (95% CI 3.9 to 6.5) on diesel PM and 1.1 (95% CI 0.2 to 2.0) on PM₂.₅, and their stacked-hazard score is 0.6 (95% CI 0.4 to 0.7) higher (Table 9). Each within-county gap is smaller than the pooled gap, and the PM₂.₅ gap is the smallest with an interval that excludes zero. A comparison of the same grades across U.S. cities with modeled NO₂ and PM₂.₅ for 2010 also finds higher NO₂ in grade D than in grade A neighborhoods, and a smaller difference for PM₂.₅.[7] The graded tracts are dense urban cores, so even grade A tracts rank above the national middle for traffic and NO₂.

Table 9. Within the same county, tracts graded D in the 1930s rank 3.9 points above grade A tracts on the traffic percentile and 9.7 points on NO₂, and the stacked-hazard score is 0.6 higher

Causal evidenceBoundary design; difference-in-differences

Whether redlining and traffic shape the air a neighborhood receives

The comparisons above describe tracts and do not test whether a grade changed the air. Two studies use designs that bear on parts of the question, and a third, in the next box, follows hazardous-waste sites over time.

Salazar-Miranda and coauthors compared neighborhoods on either side of HOLC boundaries within cities, a boundary design. The lower-graded side has higher current and projected heat and flood risk, less tree canopy and less permeable ground.[8] Their outcomes are climate risks and not air pollution, so they do not test whether the grade changed air quality.

Currie and Walker compared births to mothers living near toll plazas with births to mothers living farther from them, before and after E-ZPass reduced congestion at the plazas, a difference-in-differences design. Prematurity and low birth weight fell among mothers near the plazas relative to mothers farther away, which suggests that traffic congestion near a road harms infants.[9] It concerns plazas that adopted electronic tolling and does not say how much of a neighborhood's air pollution comes from a 1930s grade.

Under the standardized index the ends of the traffic gradient no longer differ

Over the 75,058 tracts that have a traffic percentile and all four rankings, the mean traffic percentile under the ADI falls from 75 (95% CI 69 to 80) in the least deprived tenth to 38 (95% CI 35 to 41) in the most deprived, with a rank correlation between tenth and mean of −0.96 (Table 10). Under the standardized index the line falls into the middle tenths and climbs back at the deprived end, so the two ends, 62 (95% CI 58 to 65) and 59 (95% CI 55 to 64), have overlapping intervals and the rank correlation is −0.31. Under median household income the mean falls from 62 (95% CI 58 to 66) to 50 (95% CI 46 to 53) and rises again toward the deprived end (rank correlation −0.70), and under the bachelor's degree share it falls from 69 (95% CI 65 to 72) to 48 (95% CI 42 to 53) (−0.87). Under the rule in Chapter 9.1, How far one ranking goes the standardized index changes this gradient, since its ends do not differ, and income changes its shape, while the degree share leaves it unchanged, with a rank correlation that moves by less than 0.1.

Table 10. Traffic proximity is steadily better toward the more deprived end under the ADI; the two ends do not differ detectably under the standardized index, and it is better at the more deprived end but uneven along the way under the income ranking

What these data cannot show

Percentiles rank tracts and do not give a level of exposure, and a percentile cannot say whether a concentration meets a health guideline. The indicators are EPA model output for 2020 and 2021 with their own error, assigned to tracts from finer geography. The negative link between deprivation and pollution percentiles depends on the measure of deprivation and on the comparison, and each comparison answers a different question. The ADI includes home values and rents, the poverty rate does not, and a within-county comparison holds the metropolitan area fixed while it discards differences between areas.

Everything here is ecological. The shares of Hispanic and Black residents are ACS estimates for 2019 to 2023 without margins of error, the two groups overlap, and a tract average does not describe any one of its residents. Counties in one state share traffic, industry and climate, so the county bootstrap gives intervals narrower than one that redraws whole states. With states redrawn the correlation of the traffic percentile with the ADI rank is −0.41 (95% CI −0.52 to −0.25), which still excludes zero, and that of the PM₂.₅ percentile is −0.18 (95% CI −0.38 to 0.10), which includes it.

The principal components are a description. They use national percentiles, which discard the differences in concentration, and they cover only the tracts with all indicators, so Alaska, Hawaii and Puerto Rico are absent. County scores are means of modeled tract values. PLACES values are modeled from survey responses and demographic inputs, they are crude prevalence among adults, and asthma and COPD depend on age and smoking in ways the tract file does not separate. The HOLC comparison is among graded urban cores, matches a 1930s polygon to a 2020 tract by area, and describes the residents of today. It cannot separate what the grades did from the features of the neighborhoods that surveyors graded, and the box above shows what the available designs do and do not cover.

Tables

Table 1. Traffic pollution ranks at a mean national percentile of 75 in the least deprived tenth of tracts and 39 in the most deprived

Mean national percentile of four EJScreen air indicators by decile of the Area Deprivation Index national rank, population-weighted, census tracts

conf_high	conf_low	decile	estimate	hazard	n_units
79.18	68.05	1	74.70	Traffic proximity	8,149
71.29	58.96	2	65.23	Traffic proximity	8,293
60.23	53.49	3	56.92	Traffic proximity	8,205
53.77	48.87	4	51.45	Traffic proximity	8,184
50.34	44.93	5	47.72	Traffic proximity	8,416
47.13	41.66	6	44.43	Traffic proximity	8,052
44.32	38.17	7	41.19	Traffic proximity	8,161
40.55	35.39	8	38.01	Traffic proximity	8,288
37.53	32.20	9	34.92	Traffic proximity	8,247
42.13	35.42	10	38.99	Traffic proximity	8,203
75.36	62.13	1	69.69	Diesel PM	8,149
71.11	59.70	2	65.61	Diesel PM	8,293
61.41	54.39	3	58.14	Diesel PM	8,205
56.45	50.53	4	53.64	Diesel PM	8,184
52.62	46.70	5	49.71	Diesel PM	8,416
49.53	43.50	6	46.55	Diesel PM	8,052
46.27	39.94	7	43.07	Diesel PM	8,161
42.12	36.95	8	39.46	Diesel PM	8,288
38.91	33.80	9	36.35	Diesel PM	8,247
42	35.94	10	39.13	Diesel PM	8,203
67.58	54.21	1	61.37	NO₂	8,146
63.92	51.85	2	58.08	NO₂	8,292
56.05	48.39	3	52.30	NO₂	8,204
53.46	47.20	4	50.45	NO₂	8,184
51.82	45.39	5	48.71	NO₂	8,416
50.96	44.17	6	47.59	NO₂	8,052
49.47	42.09	7	45.71	NO₂	8,161
46.95	40.92	8	43.89	NO₂	8,288
45.25	39.68	9	42.52	NO₂	8,247
50.71	44.27	10	47.64	NO₂	8,203
73.24	52.34	1	64.27	PM₂.₅	8,149
65.84	47.61	2	56.82	PM₂.₅	8,293
56.99	47.69	3	52.29	PM₂.₅	8,205
54.11	47.20	4	50.75	PM₂.₅	8,184
51.99	46.09	5	49.21	PM₂.₅	8,416
51.28	44.87	6	48.16	PM₂.₅	8,052
50.70	44.20	7	47.40	PM₂.₅	8,161
47.38	41.64	8	44.47	PM₂.₅	8,288
46.62	41.50	9	44.06	PM₂.₅	8,247
50.97	44.29	10	47.76	PM₂.₅	8,203

Note: National percentiles rank modeled values, so a gap in percentiles is not a gap in concentrations: the mean PM₂.₅ concentration is 9.6 micrograms per cubic meter in the least deprived decile and 8.1 in the most deprived.

Note: Each point rests on the tracts of a decile that have a value for the indicator, and the tooltip gives the count. The 1,524 tracts with residents in Alaska, Hawaii and Puerto Rico have no PM₂.₅ or ozone estimate and are outside the analysis, and 810 tracts in it have no ADI rank.

Note: The Area Deprivation Index descends from an index that includes median home value and median gross rent, so it rates dense, high-cost metropolitan tracts as less deprived than their incomes suggest.

Source: EPA EJScreen 2024, Area Deprivation Index 2023 and ACS 2019-2023; population-weighted means, modeled estimates

Data: vishalsingh.org/zipcode/report/air-pollution/figures/air_vs_deprivation.json

Table 2. The fall in traffic and diesel PM percentiles with deprivation persists among metropolitan tracts, and the sign reverses when tracts are compared within a county

Three views of the link between the Area Deprivation Index and national pollution percentiles: rural share, metropolitan tracts only, and correlations by comparison

Table 2.1. Rural share

The share of residents in small-town and rural tracts rises from 0.6% in the least deprived decile to 20.3% in the ninth and 18.5% in the tenth

Share of residents living in small-town and rural tracts by decile of the Area Deprivation Index national rank, population-weighted

conf_high	conf_low	decile	n_units	rural
1.10	0.400	1	8,077	0.600
1.40	0.700	2	8,222	1
1.70	1	3	8,064	1.30
2.80	1.80	4	8,050	2.20
4.20	2.90	5	8,271	3.50
6.90	5	6	7,946	5.90
10.30	7.80	7	8,077	8.90
15.50	12.50	8	8,207	13.90
22.30	18.40	9	8,214	20.30
21	16.20	10	8,194	18.50

Table 2.2. Metropolitan tracts only

Among metropolitan tracts alone the traffic percentile still falls from 76 to 48 and diesel PM from 71 to 47, while the correlations for NO₂ and PM₂.₅ shrink to −0.09 and −0.10

Mean national percentile of four air indicators by decile of the Area Deprivation Index national rank, all tracts and metropolitan tracts only, population-weighted

conf_high	conf_low	decile	estimate	hazard	n_units	series
79.18	68.05	1	74.70	Traffic proximity	8,149	All tracts
71.29	58.96	2	65.23	Traffic proximity	8,293	All tracts
60.23	53.49	3	56.92	Traffic proximity	8,205	All tracts
53.77	48.87	4	51.45	Traffic proximity	8,184	All tracts
50.34	44.93	5	47.72	Traffic proximity	8,416	All tracts
47.13	41.66	6	44.43	Traffic proximity	8,052	All tracts
44.32	38.17	7	41.19	Traffic proximity	8,161	All tracts
40.55	35.39	8	38.01	Traffic proximity	8,288	All tracts
37.53	32.20	9	34.92	Traffic proximity	8,247	All tracts
42.13	35.42	10	38.99	Traffic proximity	8,203	All tracts
79.79	69.40	1	75.65	Traffic proximity	7,879	Metropolitan tracts
71.89	60.29	2	66.37	Traffic proximity	7,945	Metropolitan tracts
61.48	54.76	3	58.28	Traffic proximity	7,676	Metropolitan tracts
55.86	50.82	4	53.44	Traffic proximity	7,427	Metropolitan tracts
53.17	47.75	5	50.40	Traffic proximity	7,330	Metropolitan tracts
51.12	45.58	6	48.42	Traffic proximity	6,665	Metropolitan tracts
50.69	44.36	7	47.60	Traffic proximity	6,166	Metropolitan tracts
49.78	44.36	8	47.14	Traffic proximity	5,549	Metropolitan tracts
50.34	44.52	9	47.55	Traffic proximity	4,817	Metropolitan tracts
56.28	49.08	10	52.93	Traffic proximity	5,139	Metropolitan tracts
75.36	62.13	1	69.69	Diesel PM	8,149	All tracts
71.11	59.70	2	65.61	Diesel PM	8,293	All tracts
61.41	54.39	3	58.14	Diesel PM	8,205	All tracts
56.45	50.53	4	53.64	Diesel PM	8,184	All tracts
52.62	46.70	5	49.71	Diesel PM	8,416	All tracts
49.53	43.50	6	46.55	Diesel PM	8,052	All tracts
46.27	39.94	7	43.07	Diesel PM	8,161	All tracts
42.12	36.95	8	39.46	Diesel PM	8,288	All tracts
38.91	33.80	9	36.35	Diesel PM	8,247	All tracts
42	35.94	10	39.13	Diesel PM	8,203	All tracts
76.27	63.75	1	70.76	Diesel PM	7,879	Metropolitan tracts
72.08	61.58	2	67.05	Diesel PM	7,945	Metropolitan tracts
63.41	56.48	3	60.05	Diesel PM	7,676	Metropolitan tracts
59.21	53.22	4	56.28	Diesel PM	7,427	Metropolitan tracts
56.03	50.15	5	53.15	Diesel PM	7,330	Metropolitan tracts
54.05	48.05	6	51.04	Diesel PM	6,665	Metropolitan tracts
52.79	46.25	7	49.48	Diesel PM	6,166	Metropolitan tracts
50.75	45.10	8	47.96	Diesel PM	5,549	Metropolitan tracts
50.21	44.25	9	47.41	Diesel PM	4,817	Metropolitan tracts
54.37	46.45	10	50.87	Diesel PM	5,139	Metropolitan tracts
67.58	54.21	1	61.37	NO₂	8,146	All tracts
63.92	51.85	2	58.08	NO₂	8,292	All tracts
56.05	48.39	3	52.30	NO₂	8,204	All tracts
53.46	47.20	4	50.45	NO₂	8,184	All tracts
51.82	45.39	5	48.71	NO₂	8,416	All tracts
50.96	44.17	6	47.59	NO₂	8,052	All tracts
49.47	42.09	7	45.71	NO₂	8,161	All tracts
46.95	40.92	8	43.89	NO₂	8,288	All tracts
45.25	39.68	9	42.52	NO₂	8,247	All tracts
50.71	44.27	10	47.64	NO₂	8,203	All tracts
67.98	55.13	1	62.30	NO₂	7,876	Metropolitan tracts
64.62	53.25	2	59.20	NO₂	7,944	Metropolitan tracts
57.75	49.76	3	53.86	NO₂	7,675	Metropolitan tracts
55.46	49.30	4	52.47	NO₂	7,427	Metropolitan tracts
54.41	47.81	5	51.10	NO₂	7,330	Metropolitan tracts
54.38	47.18	6	50.78	NO₂	6,665	Metropolitan tracts
54.58	46.54	7	50.48	NO₂	6,166	Metropolitan tracts
54.22	47.16	8	50.68	NO₂	5,549	Metropolitan tracts
55.82	48.80	9	52.48	NO₂	4,817	Metropolitan tracts
62.79	55.61	10	59.35	NO₂	5,139	Metropolitan tracts
73.24	52.34	1	64.27	PM₂.₅	8,149	All tracts
65.84	47.61	2	56.82	PM₂.₅	8,293	All tracts
56.99	47.69	3	52.29	PM₂.₅	8,205	All tracts
54.11	47.20	4	50.75	PM₂.₅	8,184	All tracts
51.99	46.09	5	49.21	PM₂.₅	8,416	All tracts
51.28	44.87	6	48.16	PM₂.₅	8,052	All tracts
50.70	44.20	7	47.40	PM₂.₅	8,161	All tracts
47.38	41.64	8	44.47	PM₂.₅	8,288	All tracts
46.62	41.50	9	44.06	PM₂.₅	8,247	All tracts
50.97	44.29	10	47.76	PM₂.₅	8,203	All tracts
73.63	53.27	1	65.02	PM₂.₅	7,879	Metropolitan tracts
66.11	48.04	2	57.46	PM₂.₅	7,945	Metropolitan tracts
57.63	48.12	3	52.91	PM₂.₅	7,676	Metropolitan tracts
55.43	48.45	4	52.03	PM₂.₅	7,427	Metropolitan tracts
54.20	48.03	5	51.20	PM₂.₅	7,330	Metropolitan tracts
54.48	48.07	6	51.20	PM₂.₅	6,665	Metropolitan tracts
55.59	48.80	7	52.08	PM₂.₅	6,166	Metropolitan tracts
54.13	47.55	8	50.83	PM₂.₅	5,549	Metropolitan tracts
55.03	48.33	9	51.78	PM₂.₅	4,817	Metropolitan tracts
59.38	50.89	10	55.33	PM₂.₅	5,139	Metropolitan tracts

Table 2.3. Correlations by comparison

The correlation of the traffic percentile with the ADI rank is −0.41 across the tracts that have both and +0.19 within counties

Population-weighted correlation of four national pollution percentiles with the ADI national rank and with the tract poverty rate, in three comparisons

comparison	conf_high	conf_low	hazard	measure	n	r
All tracts	−0.331	−0.492	Traffic proximity	Area Deprivation Index rank	82,198	−0.413
All tracts	0.112	0.037	Traffic proximity	Poverty rate	82,818	0.075
Metropolitan tracts	−0.208	−0.398	Traffic proximity	Area Deprivation Index rank	66,593	−0.306
Metropolitan tracts	0.200	0.123	Traffic proximity	Poverty rate	67,063	0.162
Within counties	0.225	0.149	Traffic proximity	Area Deprivation Index rank	79,730	0.188
Within counties	0.288	0.244	Traffic proximity	Poverty rate	80,353	0.267
All tracts	−0.301	−0.452	Diesel PM	Area Deprivation Index rank	82,198	−0.377
All tracts	0.098	0.025	Diesel PM	Poverty rate	82,818	0.064
Metropolitan tracts	−0.192	−0.364	Diesel PM	Area Deprivation Index rank	66,593	−0.280
Metropolitan tracts	0.180	0.098	Diesel PM	Poverty rate	67,063	0.141
Within counties	0.226	0.147	Diesel PM	Area Deprivation Index rank	79,730	0.188
Within counties	0.272	0.226	Diesel PM	Poverty rate	80,353	0.250
All tracts	−0.103	−0.266	NO₂	Area Deprivation Index rank	82,193	−0.182
All tracts	0.209	0.145	NO₂	Poverty rate	82,816	0.178
Metropolitan tracts	0.004	−0.173	NO₂	Area Deprivation Index rank	66,588	−0.085
Metropolitan tracts	0.277	0.215	NO₂	Poverty rate	67,060	0.247
Within counties	0.305	0.252	NO₂	Area Deprivation Index rank	79,725	0.279
Within counties	0.340	0.301	NO₂	Poverty rate	80,350	0.321
All tracts	−0.060	−0.289	PM₂.₅	Area Deprivation Index rank	82,198	−0.176
All tracts	0.072	0.003	PM₂.₅	Poverty rate	82,821	0.038
Metropolitan tracts	0.029	−0.222	PM₂.₅	Area Deprivation Index rank	66,593	−0.102
Metropolitan tracts	0.103	0.025	PM₂.₅	Poverty rate	67,065	0.064
Within counties	0.112	0.008	PM₂.₅	Area Deprivation Index rank	79,730	0.063
Within counties	0.105	0.035	PM₂.₅	Poverty rate	80,355	0.073

Source: EPA EJScreen 2024, Area Deprivation Index 2023 and ACS 2019-2023; population-weighted means, modeled estimates

Data: vishalsingh.org/zipcode/report/air-pollution/figures/rural_share_and_pm25.json

Table 3. Pollution percentiles rise with the Hispanic share of a tract, from 33 to 73 for NO₂ across deciles, and with its Black share up to the fifth decile and in the tenth

Mean national percentile of four EJScreen air indicators by decile of the tract's Hispanic or Latino share and of its Black alone share, population-weighted

conf_high	conf_low	decile	estimate	group	hazard	n_units
33.11	27.53	1	30.28	Hispanic or Latino share	Traffic proximity	8,295
37.41	32.83	2	35.08	Hispanic or Latino share	Traffic proximity	8,301
42.07	37.43	3	39.80	Hispanic or Latino share	Traffic proximity	8,301
46.83	42.22	4	44.55	Hispanic or Latino share	Traffic proximity	8,301
51.21	46.17	5	48.74	Hispanic or Latino share	Traffic proximity	8,300
54.44	48.92	6	51.80	Hispanic or Latino share	Traffic proximity	8,300
58.25	51.88	7	55.26	Hispanic or Latino share	Traffic proximity	8,301
61.57	54.47	8	58.22	Hispanic or Latino share	Traffic proximity	8,301
65.67	58.11	9	62.12	Hispanic or Latino share	Traffic proximity	8,298
73.75	61.15	10	67.72	Hispanic or Latino share	Traffic proximity	8,300
38.13	30.82	1	34.38	Black alone share	Traffic proximity	8,811
41.66	33.58	2	37.52	Black alone share	Traffic proximity	7,786
49.06	40.54	3	44.80	Black alone share	Traffic proximity	8,301
54.03	46.09	4	50.15	Black alone share	Traffic proximity	8,301
57.57	50.14	5	54.04	Black alone share	Traffic proximity	8,301
59.11	51.61	6	55.41	Black alone share	Traffic proximity	8,300
57.72	51.71	7	54.72	Black alone share	Traffic proximity	8,301
57.64	51.82	8	54.74	Black alone share	Traffic proximity	8,299
57.05	51.07	9	54.11	Black alone share	Traffic proximity	8,300
63.65	56.11	10	60.09	Black alone share	Traffic proximity	8,298
34.27	29.53	1	31.90	Hispanic or Latino share	Diesel PM	8,295
37.78	33.56	2	35.65	Hispanic or Latino share	Diesel PM	8,301
41.92	37.69	3	39.83	Hispanic or Latino share	Diesel PM	8,301
46.83	42.35	4	44.62	Hispanic or Latino share	Diesel PM	8,301
51.98	46.55	5	49.36	Hispanic or Latino share	Diesel PM	8,300
55.05	49.39	6	52.40	Hispanic or Latino share	Diesel PM	8,300
58.95	52.77	7	56.06	Hispanic or Latino share	Diesel PM	8,301
62.36	55.56	8	59.19	Hispanic or Latino share	Diesel PM	8,301
66.91	59.68	9	63.61	Hispanic or Latino share	Diesel PM	8,298
74.51	61.29	10	68.86	Hispanic or Latino share	Diesel PM	8,300
38.10	30.66	1	34.37	Black alone share	Diesel PM	8,811
41.66	34.07	2	37.81	Black alone share	Diesel PM	7,786
48.49	40.80	3	44.63	Black alone share	Diesel PM	8,301
53.41	45.86	4	49.76	Black alone share	Diesel PM	8,301
57.92	50.84	5	54.49	Black alone share	Diesel PM	8,301
60.10	52.85	6	56.63	Black alone share	Diesel PM	8,300
59.47	53.58	7	56.62	Black alone share	Diesel PM	8,301
59.25	53.41	8	56.45	Black alone share	Diesel PM	8,299
58.75	52.52	9	55.78	Black alone share	Diesel PM	8,300
65.14	56.84	10	61.15	Black alone share	Diesel PM	8,298
35.63	29.91	1	32.64	Hispanic or Latino share	NO₂	8,300
37.85	33.41	2	35.66	Hispanic or Latino share	NO₂	8,300
40.50	36.41	3	38.47	Hispanic or Latino share	NO₂	8,299
44.55	40.42	4	42.50	Hispanic or Latino share	NO₂	8,300
48.59	43.65	5	46.07	Hispanic or Latino share	NO₂	8,301
52	46.50	6	49.30	Hispanic or Latino share	NO₂	8,300
56.32	50.50	7	53.53	Hispanic or Latino share	NO₂	8,301
61.67	55.20	8	58.61	Hispanic or Latino share	NO₂	8,301
66.71	60.36	9	63.74	Hispanic or Latino share	NO₂	8,301
76.39	67.95	10	72.62	Hispanic or Latino share	NO₂	8,300
40.85	34.68	1	37.81	Black alone share	NO₂	8,813
42.45	36.05	2	39.17	Black alone share	NO₂	7,786
48.13	41.45	3	44.78	Black alone share	NO₂	8,300
52.13	45.61	4	48.97	Black alone share	NO₂	8,299
56.35	50.06	5	53.35	Black alone share	NO₂	8,301
57.99	51.28	6	54.73	Black alone share	NO₂	8,300
57.40	51.41	7	54.50	Black alone share	NO₂	8,301
57.79	51.05	8	54.50	Black alone share	NO₂	8,301
57.51	49.72	9	53.74	Black alone share	NO₂	8,301
62.87	53.48	10	58.35	Black alone share	NO₂	8,301
42.72	37.18	1	39.90	Hispanic or Latino share	PM₂.₅	8,300
41.66	37.05	2	39.37	Hispanic or Latino share	PM₂.₅	8,301
43.40	39.08	3	41.23	Hispanic or Latino share	PM₂.₅	8,301
46.77	41.99	4	44.43	Hispanic or Latino share	PM₂.₅	8,301
49.67	44.33	5	47.04	Hispanic or Latino share	PM₂.₅	8,301
52.85	46.43	6	49.59	Hispanic or Latino share	PM₂.₅	8,300
56.43	48.56	7	52.56	Hispanic or Latino share	PM₂.₅	8,301
60.75	51.13	8	56.22	Hispanic or Latino share	PM₂.₅	8,301
67.09	56.02	9	62.01	Hispanic or Latino share	PM₂.₅	8,301
76.80	60.46	10	69.44	Hispanic or Latino share	PM₂.₅	8,301
49.02	40.71	1	44.78	Black alone share	PM₂.₅	8,815
48.02	40.19	2	44	Black alone share	PM₂.₅	7,786
52.73	43.89	3	48.27	Black alone share	PM₂.₅	8,301
55.36	46.28	4	50.74	Black alone share	PM₂.₅	8,301
57.32	48.36	5	52.76	Black alone share	PM₂.₅	8,301
58.38	49.06	6	53.58	Black alone share	PM₂.₅	8,300
57.34	49.22	7	53.36	Black alone share	PM₂.₅	8,301
57.32	49.17	8	53.42	Black alone share	PM₂.₅	8,301
55.94	48.20	9	52.14	Black alone share	PM₂.₅	8,301
58.29	48.65	10	53.65	Black alone share	PM₂.₅	8,301

Note: Deciles hold nearly equal numbers of tracts, and tracts with the same share go to the same decile. The lowest Black-share decile therefore holds all 8,815 tracts with no Black alone residents, and the second holds fewer than a tenth of the tracts.

Note: Hispanic or Latino residents can be of any race and Black alone residents can be of any ethnicity, so the two groups overlap. Both shares are ACS 2019-2023 tract estimates.

Note: Weighting each tract by its number of Hispanic or Latino residents instead, the mean NO₂ percentile is 63; weighting by Black alone residents it is 56, and weighting by all residents it is 50. These are averages over tracts of residence and not measurements of individuals.

Note: The analysis covers the contiguous states and the District of Columbia, because EJScreen has no PM₂.₅ or ozone estimate for the 1,524 tracts in Alaska, Hawaii and Puerto Rico.

Source: EPA EJScreen 2024 and ACS 2019-2023; population-weighted means, modeled estimates

Data: vishalsingh.org/zipcode/report/air-pollution/figures/air_by_race_deciles.json

Table 4. Residents of tracts in the highest Black-share decile live with 1.7 stacked air hazards on average, against 0.8 in the lowest, and the score falls across deprivation deciles

Mean number of five air hazards in the top quarter of tracts, by decile of tract Black alone share, Hispanic or Latino share and ADI national rank, population-weighted, up to 82,993 tracts

conf_high	conf_low	decile	estimate	measure	n_units	sorted_by
0.990	0.640	1	0.800	score	8,809	Black alone share
15.06	6.03	1	10.17	heavy	8,809	Black alone share
1.04	0.650	2	0.840	score	7,786	Black alone share
17.05	6.94	2	11.71	heavy	7,786	Black alone share
1.27	0.830	3	1.04	score	8,300	Black alone share
22.10	10.42	3	16.08	heavy	8,300	Black alone share
1.43	0.980	4	1.20	score	8,299	Black alone share
25.58	13.37	4	19.37	heavy	8,299	Black alone share
1.58	1.12	5	1.35	score	8,301	Black alone share
28.92	16.40	5	22.71	heavy	8,301	Black alone share
1.68	1.17	6	1.43	score	8,300	Black alone share
31.73	18.17	6	25.08	heavy	8,300	Black alone share
1.57	1.16	7	1.36	score	8,301	Black alone share
28.24	17.10	7	22.71	heavy	8,301	Black alone share
1.60	1.16	8	1.38	score	8,299	Black alone share
28.79	17.03	8	22.94	heavy	8,299	Black alone share
1.59	1.16	9	1.37	score	8,300	Black alone share
30.34	17.82	9	24.06	heavy	8,300	Black alone share
2	1.40	10	1.70	score	8,298	Black alone share
40.20	23.19	10	31.97	heavy	8,298	Black alone share
0.750	0.470	1	0.600	score	8,295	Hispanic or Latino share
9.79	3.68	1	6.44	heavy	8,295	Hispanic or Latino share
0.720	0.530	2	0.620	score	8,300	Hispanic or Latino share
8.77	4.74	2	6.68	heavy	8,300	Hispanic or Latino share
0.850	0.650	3	0.750	score	8,299	Hispanic or Latino share
10.63	6	3	8.29	heavy	8,299	Hispanic or Latino share
1.01	0.780	4	0.890	score	8,300	Hispanic or Latino share
14.68	8.62	4	11.60	heavy	8,300	Hispanic or Latino share
1.21	0.930	5	1.07	score	8,300	Hispanic or Latino share
18.85	10.90	5	14.90	heavy	8,300	Hispanic or Latino share
1.34	1	6	1.17	score	8,300	Hispanic or Latino share
22.30	12.90	6	17.60	heavy	8,300	Hispanic or Latino share
1.53	1.14	7	1.34	score	8,301	Hispanic or Latino share
27.59	16.80	7	22.27	heavy	8,301	Hispanic or Latino share
1.78	1.30	8	1.54	score	8,301	Hispanic or Latino share
34.26	20.32	8	27.64	heavy	8,301	Hispanic or Latino share
2.07	1.55	9	1.82	score	8,298	Hispanic or Latino share
42.31	27.17	9	35.04	heavy	8,298	Hispanic or Latino share
2.79	1.84	10	2.34	score	8,299	Hispanic or Latino share
60.69	34.80	10	48.84	heavy	8,299	Hispanic or Latino share
2.49	1.67	1	2.13	score	8,146	Area Deprivation Index rank
56.35	29.54	1	44.46	heavy	8,146	Area Deprivation Index rank
2.26	1.34	2	1.79	score	8,292	Area Deprivation Index rank
47.03	22.05	2	34.58	heavy	8,292	Area Deprivation Index rank
1.63	1.16	3	1.38	score	8,204	Area Deprivation Index rank
30.43	17.64	3	24.07	heavy	8,204	Area Deprivation Index rank
1.39	1.03	4	1.21	score	8,184	Area Deprivation Index rank
23.21	13.37	4	18.35	heavy	8,184	Area Deprivation Index rank
1.30	0.920	5	1.11	score	8,416	Area Deprivation Index rank
21.04	10.84	5	15.92	heavy	8,416	Area Deprivation Index rank
1.24	0.850	6	1.04	score	8,052	Area Deprivation Index rank
20.28	9.73	6	14.88	heavy	8,052	Area Deprivation Index rank
1.22	0.780	7	0.980	score	8,161	Area Deprivation Index rank
19.91	8.44	7	13.88	heavy	8,161	Area Deprivation Index rank
1.04	0.710	8	0.870	score	8,288	Area Deprivation Index rank
16.11	7.58	8	11.47	heavy	8,288	Area Deprivation Index rank
0.970	0.660	9	0.800	score	8,247	Area Deprivation Index rank
14.70	6.77	9	10.40	heavy	8,247	Area Deprivation Index rank
1.17	0.790	10	0.980	score	8,203	Area Deprivation Index rank
19.56	9.71	10	14.49	heavy	8,203	Area Deprivation Index rank

Views: Mean number of stacked hazards (measure = score); Share of residents with three or more (measure = heavy).

Note: Deciles hold nearly equal numbers of tracts, tracts with the same value go to the same decile, and the lowest Black-share decile holds all 8,815 tracts with no Black alone residents. Bands are 95% intervals from a bootstrap over counties. The lines are not monotone in every step: the Black-share line is level from the sixth to the ninth decile and the deprivation line rises slightly in the tenth.

Note: Ozone is not counted. It forms in the air from other pollutants and does not mark a local source, as the other five hazards do. A count of six that adds ozone has the same ordering across the three lines.

Note: The analysis covers the contiguous states and the District of Columbia, because EJScreen has no PM₂.₅ or ozone estimate for the 1,524 tracts in Alaska, Hawaii and Puerto Rico.

Note: Hispanic or Latino residents can be of any race and Black alone residents can be of any ethnicity, so the groups overlap.

Source: EPA EJScreen 2024 and ACS 2019-2023; population-weighted means, modeled estimates

Data: vishalsingh.org/zipcode/report/air-pollution/figures/stacked_exposure.json

Table 5. The first component weights diesel PM, traffic, hazardous-waste facilities and NO₂ most, and the second weights storage tanks, lead paint and drinking-water violations against PM₂.₅ and ozone

Weights of the 13 standardized EJScreen percentiles on the first two principal components, 80,754 tracts, each tract counted once

group	indicator	pc1	pc1_high	pc1_low	pc2	pc2_high	pc2_low
Air	PM2.5	0.220	0.260	0.170	−0.470	−0.380	−0.550
Air	Ozone	0.250	0.280	0.220	−0.310	−0.160	−0.380
Air	Diesel PM	0.400	0.410	0.380	−0.020	0.050	−0.080
Air	Nitrogen dioxide	0.380	0.390	0.360	0.040	0.110	−0.030
Air	Traffic proximity	0.400	0.410	0.390	0.020	0.080	−0.050
Air	Toxic releases to air	0.230	0.260	0.200	0.090	0.280	−0.200
Proximity and discharge	Superfund proximity	0.230	0.260	0.210	0.220	0.300	0.130
Proximity and discharge	Risk-management facilities	0.260	0.280	0.210	−0.080	0.110	−0.330
Proximity and discharge	Hazardous-waste facilities	0.390	0.400	0.370	0	0.070	−0.060
Proximity and discharge	Wastewater discharge	0.220	0.250	0.190	−0.040	0.060	−0.150
Old housing and infrastructure	Lead paint (housing built before 1960)	0.140	0.170	0.100	0.450	0.560	0.330
Old housing and infrastructure	Underground storage tanks	0.150	0.260	0.030	0.550	0.660	0.330
Old housing and infrastructure	Drinking-water violations	−0.080	−0.020	−0.120	0.320	0.430	0.190

Note: Weights are the entries of unit-length eigenvectors of the correlation matrix, so they are the weights on standardized percentiles. A population-weighted version gives almost the same components: the first holds 37.1% of the variance.

Note: The first component is labeled by its largest weights and the second by its largest positive weights; the labels are descriptions, not findings.

Source: EPA EJScreen 2024, national percentiles of the 13 indicators; principal components of the correlation matrix, each tract once, modeled estimates

Data: vishalsingh.org/zipcode/report/air-pollution/figures/pca_loadings.json

Table 6. The urban-industrial component is highest in Cook County, Illinois, and in dense counties around New York, and below the tract average in most counties

Population-weighted county mean of the tract score on the first principal component of 13 EJScreen percentiles, in standard deviations of the tract score

No inline rows: the values of Table 6 are in /data/air-pollution/pc1_map.json.

Note: A county is mapped when at least 50% of its residents live in tracts with all 13 indicators. Gray counties have no score: Alaska and Hawaii (no PM₂.₅ or ozone estimate), and a few counties where fewer tracts have all of them. Puerto Rico has no PM₂.₅ or ozone estimate and is not drawn.

Note: Connecticut is drawn as its eight legacy counties, with tracts assigned to them by the staged crosswalk. Scores are county means of modeled tract values and carry no sampling interval.

Note: The key runs from the first to the 99th percentile of the county scores, and counties outside that range take the colors of its two ends; the tooltip gives the value.

Source: EPA EJScreen 2024, first principal component of the 13 national percentiles; population-weighted county means, modeled estimates

Data: vishalsingh.org/zipcode/report/air-pollution/figures/pc1_map.json

Table 7. Pollution percentiles correlate negatively with deprivation for 4 of 6 air indicators and positively with Hispanic share for 5

Population-weighted correlation of 13 EJScreen national percentiles with the ADI national rank, Hispanic or Latino share and Black alone share, across tracts

against	conf_high	conf_low	county_high	county_low	group	indicator	n	r	state_high	state_low
Area Deprivation Index	0.101	−0.378	−0.060	−0.289	Air	PM2.5	82,198	−0.176	0.101	−0.378
Hispanic or Latino share	0.422	0.069	0.396	0.217	Air	PM2.5	83,008	0.315	0.422	0.069
Black alone share	0.240	−0.075	0.118	0	Air	PM2.5	83,008	0.060	0.240	−0.075
Area Deprivation Index	−0.044	−0.361	−0.132	−0.352	Air	Ozone	82,198	−0.244	−0.044	−0.361
Hispanic or Latino share	0.445	0.172	0.418	0.236	Air	Ozone	83,008	0.336	0.445	0.172
Black alone share	0.063	−0.167	−0.010	−0.122	Air	Ozone	83,008	−0.066	0.063	−0.167
Area Deprivation Index	−0.254	−0.455	−0.301	−0.452	Air	Diesel PM	82,198	−0.377	−0.254	−0.455
Hispanic or Latino share	0.457	0.173	0.409	0.258	Air	Diesel PM	82,998	0.340	0.457	0.173
Black alone share	0.277	0.087	0.227	0.131	Air	Diesel PM	82,998	0.179	0.277	0.087
Area Deprivation Index	−0.047	−0.286	−0.103	−0.266	Air	Nitrogen dioxide	82,193	−0.182	−0.047	−0.286
Hispanic or Latino share	0.455	0.340	0.455	0.345	Air	Nitrogen dioxide	83,003	0.402	0.447	0.340
Black alone share	0.245	0.058	0.189	0.098	Air	Nitrogen dioxide	83,003	0.145	0.245	0.058
Area Deprivation Index	−0.247	−0.516	−0.331	−0.492	Air	Traffic proximity	82,198	−0.413	−0.247	−0.516
Hispanic or Latino share	0.419	0.219	0.401	0.267	Air	Traffic proximity	82,998	0.333	0.419	0.219
Black alone share	0.289	0.057	0.220	0.116	Air	Traffic proximity	82,998	0.167	0.289	0.057
Area Deprivation Index	0.147	−0.063	0.130	−0.001	Air	Toxic releases to air	82,198	0.064	0.147	−0.063
Hispanic or Latino share	0.087	−0.135	0.054	−0.135	Air	Toxic releases to air	83,008	−0.037	0.087	−0.109
Black alone share	0.221	0.101	0.202	0.115	Air	Toxic releases to air	83,008	0.162	0.221	0.101
Area Deprivation Index	−0.102	−0.302	−0.141	−0.273	Proximity and discharge	Superfund proximity	82,198	−0.210	−0.102	−0.302
Hispanic or Latino share	0.213	0.048	0.200	0.062	Proximity and discharge	Superfund proximity	82,998	0.134	0.213	0.048
Black alone share	0.152	0.006	0.123	0.027	Proximity and discharge	Superfund proximity	82,998	0.077	0.152	0.006
Area Deprivation Index	0.219	0.001	0.177	0.016	Proximity and discharge	Risk-management facilities	82,198	0.100	0.219	0.001
Hispanic or Latino share	0.324	0.103	0.315	0.174	Proximity and discharge	Risk-management facilities	82,998	0.248	0.324	0.103
Black alone share	0.200	0.090	0.185	0.092	Proximity and discharge	Risk-management facilities	82,998	0.142	0.200	0.090
Area Deprivation Index	−0.154	−0.497	−0.266	−0.450	Proximity and discharge	Hazardous-waste facilities	82,198	−0.363	−0.154	−0.497
Hispanic or Latino share	0.405	0.128	0.358	0.192	Proximity and discharge	Hazardous-waste facilities	82,998	0.274	0.405	0.128
Black alone share	0.259	0.015	0.185	0.079	Proximity and discharge	Hazardous-waste facilities	82,998	0.131	0.259	0.015
Area Deprivation Index	0.035	−0.172	−0.014	−0.170	Proximity and discharge	Wastewater discharge	82,198	−0.092	0.035	−0.172
Hispanic or Latino share	0.207	−0.070	0.164	−0.036	Proximity and discharge	Wastewater discharge	82,998	0.073	0.207	−0.070
Black alone share	0.126	0.007	0.112	0.011	Proximity and discharge	Wastewater discharge	82,998	0.061	0.126	0.007
Area Deprivation Index	0.342	0.040	0.258	0.060	Old housing and infrastructure	Lead paint (housing built before 1960)	82,198	0.160	0.342	0.040
Hispanic or Latino share	0.131	−0.087	0.107	−0.058	Old housing and infrastructure	Lead paint (housing built before 1960)	83,008	0.019	0.131	−0.087
Black alone share	0.126	0.002	0.113	0.007	Old housing and infrastructure	Lead paint (housing built before 1960)	83,008	0.062	0.126	0.002
Area Deprivation Index	0.461	−0.039	0.365	0.126	Old housing and infrastructure	Underground storage tanks	82,198	0.253	0.461	−0.039
Hispanic or Latino share	0.320	−0.294	0.104	−0.177	Old housing and infrastructure	Underground storage tanks	83,008	−0.037	0.320	−0.294
Black alone share	0.317	0.216	0.298	0.243	Old housing and infrastructure	Underground storage tanks	83,008	0.271	0.317	0.216
Area Deprivation Index	0.209	−0.109	0.142	−0.024	Old housing and infrastructure	Drinking-water violations	80,047	0.063	0.209	−0.109
Hispanic or Latino share	0.166	−0.142	0.077	−0.098	Old housing and infrastructure	Drinking-water violations	80,758	−0.017	0.166	−0.142
Black alone share	0.062	−0.107	0.027	−0.065	Old housing and infrastructure	Drinking-water violations	80,758	−0.020	0.062	−0.107

Note: Indicators are tract-level national percentiles; several are modeled estimates. Correlations use all tracts that have both values, so the count varies by cell. The data table gives the county and state intervals next to the wider one that the figure uses.

Note: Hispanic or Latino residents can be of any race and Black alone residents can be of any ethnicity, so the two columns overlap.

Source: EPA EJScreen 2024, Area Deprivation Index 2023 and ACS 2019-2023; population-weighted correlations, modeled estimates

Data: vishalsingh.org/zipcode/report/air-pollution/figures/air_correlation_strip.json

Table 8. Modeled asthma prevalence is highest in the lowest twentieth of tracts on the urban-industrial component (11.2%) and rises with the lead-paint percentile and with deprivation

Modeled prevalence of current asthma among adults by twentieth of tracts on three measures, population-weighted, 80,754 tracts with all 13 percentiles

conf_high	conf_low	estimate	n_units	ranked_on	twentieth
11.28	11.08	11.17	4,033	Urban-industrial component	1
10.93	10.79	10.86	4,034	Urban-industrial component	2
10.80	10.66	10.73	4,034	Urban-industrial component	3
10.71	10.56	10.64	4,033	Urban-industrial component	4
10.64	10.47	10.56	4,034	Urban-industrial component	5
10.62	10.45	10.53	4,034	Urban-industrial component	6
10.57	10.38	10.47	4,033	Urban-industrial component	7
10.50	10.29	10.40	4,034	Urban-industrial component	8
10.52	10.29	10.41	4,034	Urban-industrial component	9
10.49	10.27	10.38	4,034	Urban-industrial component	10
10.50	10.24	10.37	4,033	Urban-industrial component	11
10.54	10.24	10.39	4,034	Urban-industrial component	12
10.60	10.24	10.41	4,034	Urban-industrial component	13
10.60	10.26	10.42	4,033	Urban-industrial component	14
10.71	10.32	10.50	4,034	Urban-industrial component	15
10.85	10.36	10.59	4,034	Urban-industrial component	16
11.04	10.45	10.73	4,033	Urban-industrial component	17
11.03	10.24	10.61	4,034	Urban-industrial component	18
11.18	10.05	10.53	4,034	Urban-industrial component	19
10.47	9.68	9.87	4,034	Urban-industrial component	20
9.89	9.55	9.72	4,736	Lead-paint percentile	1
9.88	9.61	9.74	3,292	Lead-paint percentile	2
10.01	9.76	9.88	4,082	Lead-paint percentile	3
10.17	9.93	10.05	4,012	Lead-paint percentile	4
10.33	10.11	10.22	4,027	Lead-paint percentile	5
10.47	10.27	10.38	3,987	Lead-paint percentile	6
10.66	10.46	10.56	3,953	Lead-paint percentile	7
10.75	10.55	10.65	3,976	Lead-paint percentile	8
10.81	10.60	10.71	4,014	Lead-paint percentile	9
10.86	10.68	10.77	4,007	Lead-paint percentile	10
10.93	10.71	10.82	4,043	Lead-paint percentile	11
10.96	10.72	10.84	4,046	Lead-paint percentile	12
10.93	10.66	10.80	4,076	Lead-paint percentile	13
10.95	10.67	10.81	4,108	Lead-paint percentile	14
10.96	10.59	10.77	4,123	Lead-paint percentile	15
11.01	10.63	10.81	4,180	Lead-paint percentile	16
11.05	10.58	10.80	4,203	Lead-paint percentile	17
11.18	10.61	10.88	3,379	Lead-paint percentile	18
11.26	10.60	10.90	4,214	Lead-paint percentile	19
11.47	10.59	10.99	4,216	Lead-paint percentile	20
9.29	8.87	9.05	4,164	ADI national rank	1
9.66	9.24	9.43	3,873	ADI national rank	2
9.88	9.57	9.72	3,982	ADI national rank	3
10.08	9.77	9.93	4,135	ADI national rank	4
10.24	9.91	10.07	3,814	ADI national rank	5
10.40	9.99	10.18	4,039	ADI national rank	6
10.35	10.04	10.20	3,933	ADI national rank	7
10.42	10.15	10.29	4,053	ADI national rank	8
10.49	10.25	10.37	4,132	ADI national rank	9
10.58	10.33	10.46	3,708	ADI national rank	10
10.65	10.42	10.53	4,205	ADI national rank	11
10.78	10.55	10.67	3,968	ADI national rank	12
10.83	10.61	10.72	4,078	ADI national rank	13
10.97	10.79	10.87	3,828	ADI national rank	14
11.12	10.92	11.02	4,143	ADI national rank	15
11.22	11.03	11.12	3,897	ADI national rank	16
11.36	11.17	11.27	4,080	ADI national rank	17
11.58	11.37	11.47	4,042	ADI national rank	18
11.92	11.65	11.78	4,017	ADI national rank	19
12.92	12.44	12.68	3,947	ADI national rank	20

Note: PLACES estimates for tracts come from a model fitted to survey responses, with age, sex, race and ethnicity, education and county poverty as inputs, applied to each tract's population; they are not counts of cases. The lead-paint indicator and the ADI are built from the same Census survey as the population inputs, which makes their lines partly mechanical.

Note: Each twentieth holds equal numbers of tracts on its own measure, so the three lines do not describe the same tracts. The tract file carries no intervals for PLACES values.

Source: CDC PLACES 2024 release (modeled estimates from BRFSS 2022), EPA EJScreen 2024 and ADI 2023; population-weighted means

Data: vishalsingh.org/zipcode/report/air-pollution/figures/asthma_vs_exposure.json

Table 9. Within the same county, tracts graded D in the 1930s rank 3.9 points above grade A tracts on the traffic percentile and 9.7 points on NO₂, and the stacked-hazard score is 0.6 higher

Difference from grade A in the same county in the mean national percentile of four air indicators and in the mean stacked-hazard score, by dominant HOLC grade of the tract, population-weighted

conf_high	conf_low	contrast	estimate	grade	label	measure	n_units
n/a	n/a	within	0	A	Grade A	Traffic proximity (percentile)	672
1.78	−0.180	within	0.810	B	Grade B	Traffic proximity (percentile)	2,246
3.15	0.860	within	2.06	C	Grade C	Traffic proximity (percentile)	5,054
5.12	2.67	within	3.91	D	Grade D	Traffic proximity (percentile)	2,978
80.28	74.52	pooled	77.55	A	Grade A	Traffic proximity (percentile)	672
84.21	78.81	pooled	81.74	B	Grade B	Traffic proximity (percentile)	2,246
87.02	80.11	pooled	84.16	C	Grade C	Traffic proximity (percentile)	5,054
88.62	82.79	pooled	86.34	D	Grade D	Traffic proximity (percentile)	2,978
n/a	n/a	within	0	A	Grade A	NO₂ (percentile)	672
6.41	2.47	within	4.46	B	Grade B	NO₂ (percentile)	2,246
8.76	4.48	within	6.67	C	Grade C	NO₂ (percentile)	5,054
12.20	7.23	within	9.74	D	Grade D	NO₂ (percentile)	2,978
76.36	69.73	pooled	73.03	A	Grade A	NO₂ (percentile)	672
81.99	74.96	pooled	78.72	B	Grade B	NO₂ (percentile)	2,246
85.72	79.03	pooled	82.73	C	Grade C	NO₂ (percentile)	5,054
89.21	82.52	pooled	86.36	D	Grade D	NO₂ (percentile)	2,978
n/a	n/a	within	0	A	Grade A	Diesel PM (percentile)	672
2.19	0.240	within	1.24	B	Grade B	Diesel PM (percentile)	2,246
3.57	1.71	within	2.70	C	Grade C	Diesel PM (percentile)	5,054
6.45	3.92	within	5.14	D	Grade D	Diesel PM (percentile)	2,978
76.57	68.93	pooled	73.05	A	Grade A	Diesel PM (percentile)	672
81.66	72.33	pooled	77.41	B	Grade B	Diesel PM (percentile)	2,246
84.97	75.26	pooled	81.17	C	Grade C	Diesel PM (percentile)	5,054
89.44	80.50	pooled	86.02	D	Grade D	Diesel PM (percentile)	2,978
n/a	n/a	within	0	A	Grade A	PM₂.₅ (percentile)	672
0.880	−0.010	within	0.420	B	Grade B	PM₂.₅ (percentile)	2,246
1.28	0.030	within	0.670	C	Grade C	PM₂.₅ (percentile)	5,054
2.02	0.250	within	1.13	D	Grade D	PM₂.₅ (percentile)	2,978
62.68	49.05	pooled	55.85	A	Grade A	PM₂.₅ (percentile)	672
61.24	47.08	pooled	54.02	B	Grade B	PM₂.₅ (percentile)	2,246
68.58	46.88	pooled	58.11	C	Grade C	PM₂.₅ (percentile)	5,054
69.39	51.02	pooled	60.02	D	Grade D	PM₂.₅ (percentile)	2,978
n/a	n/a	within	0	A	Grade A	Stacked air hazards (0 to 5)	672
0.340	0.050	within	0.200	B	Grade B	Stacked air hazards (0 to 5)	2,246
0.500	0.240	within	0.380	C	Grade C	Stacked air hazards (0 to 5)	5,054
0.720	0.420	within	0.580	D	Grade D	Stacked air hazards (0 to 5)	2,978
2.52	2.04	pooled	2.29	A	Grade A	Stacked air hazards (0 to 5)	672
2.87	2.29	pooled	2.60	B	Grade B	Stacked air hazards (0 to 5)	2,246
3.35	2.57	pooled	3	C	Grade C	Stacked air hazards (0 to 5)	5,054
3.50	2.85	pooled	3.19	D	Grade D	Stacked air hazards (0 to 5)	2,978

Views: Within the same county (contrast = within); All graded tracts, pooled (contrast = pooled).

Note: Differences in the first view come from a population-weighted regression of the tract value on grade with county fixed effects, so only counties that hold more than one grade inform them. Grade A is the baseline and has no interval. The pooled view compares tracts across 215 counties.

Note: The HOLC maps cover the dense urban cores of cities, so even grade A tracts sit above the national median for traffic and NO₂. The comparison is among graded tracts and does not compare graded with ungraded places.

Note: A tract graded D today holds residents of today and not those of the 1930s. Grades A to D follow the original map labels, and areas graded E or F or left blank are set aside. Other outcomes by grade, including the Area Deprivation Index, are in the chapter on home value, income and redlining.

Source: Mapping Inequality HOLC maps (1935-1940) matched to 2020 tracts, EPA EJScreen 2024 and ACS 2019-2023; population-weighted means, modeled estimates

Data: vishalsingh.org/zipcode/report/air-pollution/figures/air_by_holc_grade.json

Table 10. Traffic proximity is steadily better toward the more deprived end under the ADI; the two ends do not differ detectably under the standardized index, and it is better at the more deprived end but uneven along the way under the income ranking

Mean national percentile of the tract (0 to 100) by tenth of tracts ranked four ways, over the 75,058 tracts that have all four rankings

bin	conf_high	conf_low	estimate	n_units	ranking
1	79.56	68.90	75.19	7,443	Area Deprivation Index
2	71.26	59.32	65.46	7,502	Area Deprivation Index
3	59.60	53.30	56.51	7,581	Area Deprivation Index
4	53.59	48.52	51.12	7,540	Area Deprivation Index
5	50.45	44.98	47.82	7,439	Area Deprivation Index
6	46.62	41.19	43.85	7,666	Area Deprivation Index
7	43.38	37.87	40.60	7,364	Area Deprivation Index
8	39.90	34.91	37.48	7,543	Area Deprivation Index
9	36.96	31.87	34.46	7,451	Area Deprivation Index
10	41.45	35.04	38.37	7,529	Area Deprivation Index
1	65.41	57.70	61.82	7,505	Standardized index
2	57.72	51.44	54.67	7,506	Standardized index
3	52.94	47.38	50.22	7,506	Standardized index
4	50.03	44.40	47.29	7,506	Standardized index
5	47.16	41.13	44.12	7,506	Standardized index
6	46.44	40.16	43.32	7,505	Standardized index
7	46.71	39.55	43.22	7,506	Standardized index
8	48.60	40.85	44.75	7,506	Standardized index
9	53.91	45.99	50.05	7,506	Standardized index
10	63.52	54.66	59.23	7,506	Standardized index
1	65.51	57.85	61.94	7,507	Median household income
2	58.96	51.85	55.48	7,506	Median household income
3	56.86	49.16	53.02	7,504	Median household income
4	53.49	45.72	49.64	7,525	Median household income
5	51.26	43.99	47.69	7,487	Median household income
6	48.65	41.47	45.08	7,505	Median household income
7	46.60	40.03	43.36	7,506	Median household income
8	47.91	41.10	44.47	7,505	Median household income
9	48.18	41.77	45.03	7,507	Median household income
10	52.84	46.36	49.77	7,506	Median household income
1	71.73	64.88	68.59	7,505	Bachelor's degree share
2	61.91	55.58	58.83	7,505	Bachelor's degree share
3	57.49	51.88	54.71	7,509	Bachelor's degree share
4	54.17	48.72	51.49	7,500	Bachelor's degree share
5	51.50	45.69	48.62	7,507	Bachelor's degree share
6	48.45	42.33	45.49	7,507	Bachelor's degree share
7	44.50	38.05	41.30	7,510	Bachelor's degree share
8	43.52	36.17	39.78	7,512	Bachelor's degree share
9	44.05	35.82	39.86	7,494	Bachelor's degree share
10	52.94	42.31	47.64	7,509	Bachelor's degree share

Note: Least and most deprived tenth: ADI 75 and 38, rank correlation −0.96; standardized index 62 and 59, −0.31; median household income 62 and 50, −0.70; bachelor's degree share 69 and 48, −0.87.

Note: The standardized index applies the ADI's coefficients to its measures after standardizing each one, so home value and income carry less weight than in the ADI. Income and degree share are single census measures, each ranked from the highest value to the lowest.

Source: EPA EJScreen 2024, Area Deprivation Index 2023 and ACS 2019-2023; population-weighted means, modeled estimates; ADI 2023 and ACS 2019-2023 tract tables (B19013, B15003 and the 15 rebuilt ADI measures)

Data: vishalsingh.org/zipcode/report/air-pollution/figures/alt_rankings.json

All estimates

Every fact in facts.json (165), sorted by id. The same values as JSON: facts.json.

Fact id	Value	Unit	Estimand	Population	Period	Interval	n	Weights	Source	Note
adi_asthma	+0.53	correlation coefficient	population-weighted correlation of the tract's modeled prevalence of current asthma among adults with the ADI national rank, county-cluster bootstrap interval	residents of tracts in the PCA with a PLACES estimate for current asthma	PLACES 2024 release (BRFSS 2022); EJScreen 2024; ACS 2019-2023	95% CI 0.48 to 0.58	80,038 tracts	ACS 2019-2023 tract population	CDC PLACES	PLACES prevalence is a model-based estimate from survey responses, so it is not a measured rate.
alt_adi_least	75	Mean national percentile of the tract (0 to 100)	population-weighted mean of the tract's traffic-proximity national percentile; 95% intervals from a bootstrap over counties	the least deprived tenth of tracts ranked by Area Deprivation Index, among the tracts with all four rankings	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 69 to 80	7,443 tracts	ACS 2019-2023 tract population	EPA EJScreen
alt_adi_most	38	Mean national percentile of the tract (0 to 100)	population-weighted mean of the tract's traffic-proximity national percentile; 95% intervals from a bootstrap over counties	the most deprived tenth of tracts ranked by Area Deprivation Index, among the tracts with all four rankings	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 35 to 41	7,529 tracts	ACS 2019-2023 tract population	EPA EJScreen
alt_adi_rho	−0.96	rank correlation	Spearman rank correlation between bin order and bin mean, each bin counted once	the bins of tracts ranked by Area Deprivation Index	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			each bin counted once	EPA EJScreen
alt_degree_least	69	Mean national percentile of the tract (0 to 100)	population-weighted mean of the tract's traffic-proximity national percentile; 95% intervals from a bootstrap over counties	the least deprived tenth of tracts ranked by Bachelor's degree share, among the tracts with all four rankings	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 65 to 72	7,505 tracts	ACS 2019-2023 tract population	EPA EJScreen
alt_degree_most	48	Mean national percentile of the tract (0 to 100)	population-weighted mean of the tract's traffic-proximity national percentile; 95% intervals from a bootstrap over counties	the most deprived tenth of tracts ranked by Bachelor's degree share, among the tracts with all four rankings	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 42 to 53	7,509 tracts	ACS 2019-2023 tract population	EPA EJScreen
alt_degree_rho	−0.87	rank correlation	Spearman rank correlation between bin order and bin mean, each bin counted once	the bins of tracts ranked by Bachelor's degree share	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			each bin counted once	EPA EJScreen
alt_income_least	62	Mean national percentile of the tract (0 to 100)	population-weighted mean of the tract's traffic-proximity national percentile; 95% intervals from a bootstrap over counties	the least deprived tenth of tracts ranked by Median household income, among the tracts with all four rankings	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 58 to 66	7,507 tracts	ACS 2019-2023 tract population	EPA EJScreen
alt_income_most	50	Mean national percentile of the tract (0 to 100)	population-weighted mean of the tract's traffic-proximity national percentile; 95% intervals from a bootstrap over counties	the most deprived tenth of tracts ranked by Median household income, among the tracts with all four rankings	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 46 to 53	7,506 tracts	ACS 2019-2023 tract population	EPA EJScreen
alt_income_rho	−0.70	rank correlation	Spearman rank correlation between bin order and bin mean, each bin counted once	the bins of tracts ranked by Median household income	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			each bin counted once	EPA EJScreen
alt_n_places	75,058	tracts	count of tracts in the common sample of the ranking comparison	tracts with the outcome and all four rankings	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (full count)	EPA EJScreen
alt_rho_cut	0.9	absolute rank correlation	threshold between a steady and an uneven gradient	the rule for changed gradients (docs/RANKING_SWITCH_RULE.md)	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (a fixed rule)	EPA EJScreen
alt_rho_margin	0.1	absolute rank correlation	smallest move in the rank correlation that counts as a change of shape	the rule for changed gradients (docs/RANKING_SWITCH_RULE.md)	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (a fixed rule)	EPA EJScreen
alt_std_least	62	Mean national percentile of the tract (0 to 100)	population-weighted mean of the tract's traffic-proximity national percentile; 95% intervals from a bootstrap over counties	the least deprived tenth of tracts ranked by Standardized index, among the tracts with all four rankings	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 58 to 65	7,505 tracts	ACS 2019-2023 tract population	EPA EJScreen
alt_std_most	59	Mean national percentile of the tract (0 to 100)	population-weighted mean of the tract's traffic-proximity national percentile; 95% intervals from a bootstrap over counties	the most deprived tenth of tracts ranked by Standardized index, among the tracts with all four rankings	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 55 to 64	7,506 tracts	ACS 2019-2023 tract population	EPA EJScreen
alt_std_rho	−0.31	rank correlation	Spearman rank correlation between bin order and bin mean, each bin counted once	the bins of tracts ranked by Standardized index	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			each bin counted once	EPA EJScreen
asth_adi_t1	9.0%	percent of adults with current asthma (modeled)	population-weighted mean of the tract's modeled crude prevalence of current asthma among adults, within a twentieth of tracts, county-cluster bootstrap interval	residents of tracts in the least deprived twentieth of tracts on the ADI national rank	PLACES 2024 release (BRFSS 2022)	95% CI 8.9% to 9.3%	4,164 tracts	ACS 2019-2023 tract population	CDC PLACES
asth_adi_t20	12.7%	percent of adults with current asthma (modeled)	population-weighted mean of the tract's modeled crude prevalence of current asthma among adults, within a twentieth of tracts, county-cluster bootstrap interval	residents of tracts in the most deprived twentieth of tracts on the ADI national rank	PLACES 2024 release (BRFSS 2022)	95% CI 12.4% to 12.9%	3,947 tracts	ACS 2019-2023 tract population	CDC PLACES
asth_ldp_t1	9.7%	percent of adults with current asthma (modeled)	population-weighted mean of the tract's modeled crude prevalence of current asthma among adults, within a twentieth of tracts, county-cluster bootstrap interval	residents of tracts in the lowest twentieth of tracts on the lead-paint percentile	PLACES 2024 release (BRFSS 2022)	95% CI 9.5% to 9.9%	4,736 tracts	ACS 2019-2023 tract population	CDC PLACES
asth_ldp_t20	11.0%	percent of adults with current asthma (modeled)	population-weighted mean of the tract's modeled crude prevalence of current asthma among adults, within a twentieth of tracts, county-cluster bootstrap interval	residents of tracts in the highest twentieth of tracts on the lead-paint percentile	PLACES 2024 release (BRFSS 2022)	95% CI 10.6% to 11.5%	4,216 tracts	ACS 2019-2023 tract population	CDC PLACES
asth_pc1_t1	11.2%	percent of adults with current asthma (modeled)	population-weighted mean of the tract's modeled crude prevalence of current asthma among adults, within a twentieth of tracts, county-cluster bootstrap interval	residents of tracts in the lowest twentieth of tracts on the urban-industrial component	PLACES 2024 release (BRFSS 2022)	95% CI 11.1% to 11.3%	4,033 tracts	ACS 2019-2023 tract population	CDC PLACES
asth_pc1_t20	9.9%	percent of adults with current asthma (modeled)	population-weighted mean of the tract's modeled crude prevalence of current asthma among adults, within a twentieth of tracts, county-cluster bootstrap interval	residents of tracts in the highest twentieth of tracts on the urban-industrial component	PLACES 2024 release (BRFSS 2022)	95% CI 9.7% to 10.5%	4,034 tracts	ACS 2019-2023 tract population	CDC PLACES
black_share_all	12.1%	percent of residents	population-weighted mean of the tract share of residents who are Black or African American alone (of any ethnicity)	residents of the tracts in the analysis	ACS 2019-2023		83,008 tracts	ACS 2019-2023 tract population	American Community Survey
corridor_bronx	+1.45	standard deviations of the tract-level component 1 score	population-weighted county mean of the tract component 1 score (scaled to unit variance across tracts)	residents of Bronx County, New York	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023		346 tracts	ACS 2019-2023 tract population	EPA EJScreen
corridor_hudson	+1.67	standard deviations of the tract-level component 1 score	population-weighted county mean of the tract component 1 score (scaled to unit variance across tracts)	residents of Hudson County, New Jersey	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023		182 tracts	ACS 2019-2023 tract population	EPA EJScreen
corridor_la_rank	6	rank among mapped counties (1 = highest mean score)	rank of Los Angeles County by population-weighted county mean of the tract component 1 score	mapped counties	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (rank)	EPA EJScreen
corridor_newyork	+1.58	standard deviations of the tract-level component 1 score	population-weighted county mean of the tract component 1 score (scaled to unit variance across tracts)	residents of New York County, New York	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023		300 tracts	ACS 2019-2023 tract population	EPA EJScreen
corridor_q50	−1.2	standard deviations of the tract-level component 1 score	median over mapped counties of the population-weighted county mean of the tract component 1 score (each county counts once)	mapped counties	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023		3,094 counties	none (each county counts once)	EPA EJScreen
corridor_stlouis	+1.50	standard deviations of the tract-level component 1 score	population-weighted county mean of the tract component 1 score (scaled to unit variance across tracts)	residents of the independent city of St. Louis, Missouri	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023		104 tracts	ACS 2019-2023 tract population	EPA EJScreen
corridor_top	+1.69	standard deviations of the tract-level component 1 score	population-weighted county mean of the tract component 1 score (scaled to unit variance across tracts)	residents of the county with the highest mean score	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023		1,318 tracts	ACS 2019-2023 tract population	EPA EJScreen
dslpm_adi	−0.38	correlation coefficient	population-weighted correlation of the tract Diesel PM national percentile with the ADI national rank, county-cluster bootstrap interval	residents of tracts with a Diesel PM percentile and an ADI rank	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI −0.45 to −0.30	82,198 tracts	ACS 2019-2023 tract population	EPA EJScreen
dslpm_adi_metro	−0.28	correlation coefficient	population-weighted correlation of the tract Diesel PM national percentile with the ADI national rank, metropolitan tracts only, county-cluster bootstrap interval	residents of metropolitan tracts with a Diesel PM percentile and the ADI national rank	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI −0.36 to −0.19	66,593 tracts	ACS 2019-2023 tract population	EPA EJScreen
dslpm_adi_within	+0.19	correlation coefficient	population-weighted correlation of the tract Diesel PM national percentile with the ADI national rank, after removing each county's population-weighted mean from both (counties with at least 5 tracts), county-cluster bootstrap interval	residents of tracts in counties with at least 5 tracts that have a Diesel PM percentile and the ADI national rank	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.15 to 0.23	79,730 tracts	ACS 2019-2023 tract population	EPA EJScreen
dslpm_black	+0.18	correlation coefficient	population-weighted correlation of the tract Diesel PM national percentile with the tract's Black alone share, county-cluster bootstrap interval	residents of tracts with a Diesel PM percentile and a race and ethnicity share	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.13 to 0.23	82,998 tracts	ACS 2019-2023 tract population	EPA EJScreen
dslpm_hisp	+0.34	correlation coefficient	population-weighted correlation of the tract Diesel PM national percentile with the tract's Hispanic or Latino share, county-cluster bootstrap interval	residents of tracts with a Diesel PM percentile and a race and ethnicity share	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.26 to 0.41	82,998 tracts	ACS 2019-2023 tract population	EPA EJScreen
dslpm_metro_d1	71	national percentile of the tract (0 to 100)	population-weighted mean of the tract Diesel PM national percentile, metropolitan tracts only, ADI deciles of all tracts, county-cluster bootstrap interval	residents of metropolitan tracts (RUCA codes 1 to 3) in ADI decile 1 of all tracts	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 64 to 76	7,879 tracts	ACS 2019-2023 tract population	EPA EJScreen
dslpm_metro_d9	47	national percentile of the tract (0 to 100)	population-weighted mean of the tract Diesel PM national percentile, metropolitan tracts only, ADI deciles of all tracts, county-cluster bootstrap interval	residents of metropolitan tracts (RUCA codes 1 to 3) in ADI decile 9 of all tracts	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 44 to 50	4,817 tracts	ACS 2019-2023 tract population	EPA EJScreen
heavy_black_hi	32%	percent of residents living in tracts with three or more stacked hazards	population-weighted share of residents in tracts with three or more of the five air hazards in the top quarter, county-cluster bootstrap interval	residents of tracts in decile 10 of the Black alone share	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 23% to 40%	8,298 tracts	ACS 2019-2023 tract population	EPA EJScreen
heavy_black_lo	10%	percent of residents living in tracts with three or more stacked hazards	population-weighted share of residents in tracts with three or more of the five air hazards in the top quarter, county-cluster bootstrap interval	residents of tracts in decile 1 of the Black alone share	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 6% to 15%	8,809 tracts	ACS 2019-2023 tract population	EPA EJScreen
heavy_hisp_hi	49%	percent of residents living in tracts with three or more stacked hazards	population-weighted share of residents in tracts with three or more of the five air hazards in the top quarter, county-cluster bootstrap interval	residents of tracts in decile 10 of the Hispanic or Latino share	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 35% to 61%	8,299 tracts	ACS 2019-2023 tract population	EPA EJScreen
heavy_hisp_lo	6%	percent of residents living in tracts with three or more stacked hazards	population-weighted share of residents in tracts with three or more of the five air hazards in the top quarter, county-cluster bootstrap interval	residents of tracts in decile 1 of the Hispanic or Latino share	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 4% to 10%	8,295 tracts	ACS 2019-2023 tract population	EPA EJScreen
heavy_min	3	air hazards	a tract is heavily stacked when this many of the five hazards or more are in the top quarter; a definition	tracts	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (definition)	EPA EJScreen
hisp_share_all	19.0%	percent of residents	population-weighted mean of the tract share of residents who are Hispanic or Latino (of any race)	residents of the tracts in the analysis	ACS 2019-2023		83,008 tracts	ACS 2019-2023 tract population	American Community Survey
holc_cover_min	50%	percent of the tract's area	a tract is graded when polygons graded A to D cover at least this share of its area; a definition	2020 tracts	HOLC maps of 1935 to 1940			none (definition)	Mapping Inequality (HOLC maps)
ldpnt_adi	+0.16	correlation coefficient	population-weighted correlation of the tract Lead paint (housing built before 1960) national percentile with the ADI national rank, county-cluster bootstrap interval	residents of tracts with a Lead paint (housing built before 1960) percentile and an ADI rank	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.06 to 0.26	82,198 tracts	ACS 2019-2023 tract population	EPA EJScreen
ldpnt_asthma	+0.27	correlation coefficient	population-weighted correlation of the tract's modeled prevalence of current asthma among adults with the lead-paint percentile, county-cluster bootstrap interval	residents of tracts in the PCA with a PLACES estimate for current asthma	PLACES 2024 release (BRFSS 2022); EJScreen 2024; ACS 2019-2023	95% CI 0.20 to 0.34	80,674 tracts	ACS 2019-2023 tract population	CDC PLACES	PLACES prevalence is a model-based estimate from survey responses, so it is not a measured rate.
map_cover_min	50%	percent of the county's residents	a county is mapped when residents of tracts with all 13 indicators are at least this share of its residents; a definition	counties	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (definition)	EPA EJScreen
n_adi_missing	810	tracts	count of tracts with a missing ADI national rank	tracts in the analysis with no ADI rank (every block group suppressed)	ADI 2023			none (full count)	Area Deprivation Index
n_air_adi_neg	4	indicators	count of air indicators whose correlation with the ADI national rank is negative with an interval that excludes zero under the county bootstrap and under the bootstrap that redraws states	EJScreen indicators in the group: the 6 air indicators	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (count of indicators)	EPA EJScreen
n_air_black_pos	4	indicators	count of air indicators whose correlation with the Black alone share is positive with an interval that excludes zero under the county bootstrap and under the bootstrap that redraws states	EJScreen indicators in the group: the 6 air indicators	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (count of indicators)	EPA EJScreen
n_air_hisp_pos	5	indicators	count of air indicators whose correlation with the Hispanic or Latino share is positive with an interval that excludes zero under the county bootstrap and under the bootstrap that redraws states	EJScreen indicators in the group: the 6 air indicators	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (count of indicators)	EPA EJScreen
n_air_ind	6	indicators	number of air indicators; a definition	EJScreen air indicators (PM₂.₅, ozone, diesel PM, NO₂, traffic proximity, toxic releases to air)	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (definition)	EPA EJScreen
n_between_counties	3,095	counties	count of counties in the county-level correlation	counties with at least one tract that has a traffic-proximity percentile and an ADI rank	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (full count)	EPA EJScreen
n_black_zero	8,815	tracts	count of tracts with a Black alone share of zero	tracts in the analysis with no Black alone residents in the ACS 2019-2023 estimate	ACS 2019-2023			none (full count)	American Community Survey
n_indicators	13	indicators	number of national-percentile indicators entering the correlation strip and the PCA	EJScreen environmental indicators in the staged extract	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (definition)	EPA EJScreen
n_map_counties	3,094	counties	count of mapped counties	counties and county equivalents on the map sprite with a component 1 score	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (full count)	EPA EJScreen
n_map_nodata	49	counties	count of map units with no component 1 score	counties and county equivalents on the map sprite without a score	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (full count)	EPA EJScreen
n_no_pm25	1,524	tracts	count of tracts with a missing PM₂.₅ percentile	tracts with a positive population and no PM₂.₅ or ozone value (all in Alaska, Hawaii and Puerto Rico), left out of the analysis	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (full count)	EPA EJScreen	Missing is not zero: EPA's fused air-quality surfaces cover the contiguous states and the District of Columbia.
n_old_adi_pos	1	indicators	count of old-housing and infrastructure indicators whose correlation with the ADI national rank is positive with an interval that excludes zero under the county bootstrap and under the bootstrap that redraws states	EJScreen indicators in the group: the 3 old-housing and infrastructure indicators	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (count of indicators)	EPA EJScreen
n_old_ind	3	indicators	number of old-housing and infrastructure indicators; a definition	EJScreen old-housing and infrastructure indicators (lead paint, storage tanks, drinking water)	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (definition)	EPA EJScreen
n_pca	80,754	tracts	count of tracts in the PCA	tracts in the analysis with all 13 percentiles (drinking-water violations are missing for some tracts)	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (each tract counts once)	EPA EJScreen
n_prox_ind	4	indicators	number of proximity and discharge indicators; a definition	EJScreen proximity and discharge indicators (Superfund sites, risk-management facilities, hazardous-waste facilities, wastewater discharge)	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (definition)	EPA EJScreen
n_ptraf_adi	82,198	tracts	count of tracts in the correlation of the traffic percentile with the ADI rank	tracts with a traffic-proximity percentile and an ADI rank (tracts without an ADI rank are left out)	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (full count)	EPA EJScreen
n_ptraf_adi_within	79,730	tracts	count of tracts in the within-county correlation of the traffic percentile with the ADI rank	tracts with a traffic-proximity percentile and an ADI rank in counties with at least 5 such tracts	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (full count)	EPA EJScreen
n_stack_tracts	82,993	tracts	count of tracts with PM₂.₅, diesel PM, NO₂, traffic and toxic-release percentiles	tracts in the analysis with all five air percentiles	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (full count)	EPA EJScreen
n_tracts	83,008	tracts	count of tracts in the analysis	2020 census tracts in the contiguous states and the District of Columbia with an EJScreen record and a positive 2019-2023 population	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (full count)	EPA EJScreen	Statistics about one indicator use the tracts that have a value for it; each correlation lists its own count.
no2_adi	−0.18	correlation coefficient	population-weighted correlation of the tract NO₂ national percentile with the ADI national rank, county-cluster bootstrap interval	residents of tracts with a NO₂ percentile and an ADI rank	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI −0.27 to −0.10	82,193 tracts	ACS 2019-2023 tract population	EPA EJScreen
no2_adi_metro	−0.09	correlation coefficient	population-weighted correlation of the tract NO₂ national percentile with the ADI national rank, metropolitan tracts only, county-cluster bootstrap interval	residents of metropolitan tracts with a NO₂ percentile and the ADI national rank	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI −0.17 to 0.00	66,588 tracts	ACS 2019-2023 tract population	EPA EJScreen
no2_adi_within	+0.28	correlation coefficient	population-weighted correlation of the tract NO₂ national percentile with the ADI national rank, after removing each county's population-weighted mean from both (counties with at least 5 tracts), county-cluster bootstrap interval	residents of tracts in counties with at least 5 tracts that have a NO₂ percentile and the ADI national rank	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.25 to 0.31	79,725 tracts	ACS 2019-2023 tract population	EPA EJScreen
no2_black	+0.14	correlation coefficient	population-weighted correlation of the tract NO₂ national percentile with the tract's Black alone share, county-cluster bootstrap interval	residents of tracts with a NO₂ percentile and a race and ethnicity share	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.10 to 0.19	83,003 tracts	ACS 2019-2023 tract population	EPA EJScreen
no2_black_d1	38	national percentile of the tract (0 to 100)	population-weighted mean of the tract NO₂ national percentile within a decile of tracts by Black alone share, county-cluster bootstrap interval	residents of tracts in decile 1 of the Black alone share of residents (deciles hold equal numbers of tracts)	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 35 to 41	8,813 tracts	ACS 2019-2023 tract population	EPA EJScreen
no2_black_d10	58	national percentile of the tract (0 to 100)	population-weighted mean of the tract NO₂ national percentile within a decile of tracts by Black alone share, county-cluster bootstrap interval	residents of tracts in decile 10 of the Black alone share of residents (deciles hold equal numbers of tracts)	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 53 to 63	8,301 tracts	ACS 2019-2023 tract population	EPA EJScreen
no2_black_within	+0.17	correlation coefficient	population-weighted correlation of the tract NO₂ national percentile with the tract's Black alone share after removing each county's population-weighted mean from both, county-cluster bootstrap interval	residents of tracts in counties with at least 5 tracts that have a NO₂ percentile and a race and ethnicity share	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.14 to 0.21	80,548 tracts	ACS 2019-2023 tract population	EPA EJScreen
no2_hisp	+0.40	correlation coefficient	population-weighted correlation of the tract NO₂ national percentile with the tract's Hispanic or Latino share, county-cluster bootstrap interval	residents of tracts with a NO₂ percentile and a race and ethnicity share	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.35 to 0.46	83,003 tracts	ACS 2019-2023 tract population	EPA EJScreen
no2_hisp_d1	33	national percentile of the tract (0 to 100)	population-weighted mean of the tract NO₂ national percentile within a decile of tracts by Hispanic or Latino share, county-cluster bootstrap interval	residents of tracts in decile 1 of the Hispanic or Latino share of residents (deciles hold equal numbers of tracts)	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 30 to 36	8,300 tracts	ACS 2019-2023 tract population	EPA EJScreen
no2_hisp_d10	73	national percentile of the tract (0 to 100)	population-weighted mean of the tract NO₂ national percentile within a decile of tracts by Hispanic or Latino share, county-cluster bootstrap interval	residents of tracts in decile 10 of the Hispanic or Latino share of residents (deciles hold equal numbers of tracts)	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 68 to 76	8,300 tracts	ACS 2019-2023 tract population	EPA EJScreen
no2_hisp_within	+0.23	correlation coefficient	population-weighted correlation of the tract NO₂ national percentile with the tract's Hispanic or Latino share after removing each county's population-weighted mean from both, county-cluster bootstrap interval	residents of tracts in counties with at least 5 tracts that have a NO₂ percentile and a race and ethnicity share	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.21 to 0.26	80,548 tracts	ACS 2019-2023 tract population	EPA EJScreen
no2_joint_adi	+0.16	within-county standard deviations of the NO₂ percentile per within-county standard deviation of the predictor	coefficient on the ADI national rank in a population-weighted regression of the tract NO₂ national percentile on the ADI national rank, the Hispanic or Latino share, the Black alone share, with each county's population-weighted mean removed from every variable and each variable scaled to a standard deviation of one, errors clustered on county	residents of tracts in counties with at least 5 tracts that have every variable in the model	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.13 to 0.19	79,725 tracts	ACS 2019-2023 tract population	EPA EJScreen	A descriptive association within counties, not a causal estimate.
no2_joint_black	+0.12	within-county standard deviations of the NO₂ percentile per within-county standard deviation of the predictor	coefficient on the Black alone share in a population-weighted regression of the tract NO₂ national percentile on the ADI national rank, the Hispanic or Latino share, the Black alone share, with each county's population-weighted mean removed from every variable and each variable scaled to a standard deviation of one, errors clustered on county	residents of tracts in counties with at least 5 tracts that have every variable in the model	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.08 to 0.16	79,725 tracts	ACS 2019-2023 tract population	EPA EJScreen	A descriptive association within counties, not a causal estimate.
no2_joint_hisp	+0.18	within-county standard deviations of the NO₂ percentile per within-county standard deviation of the predictor	coefficient on the Hispanic or Latino share in a population-weighted regression of the tract NO₂ national percentile on the ADI national rank, the Hispanic or Latino share, the Black alone share, with each county's population-weighted mean removed from every variable and each variable scaled to a standard deviation of one, errors clustered on county	residents of tracts in counties with at least 5 tracts that have every variable in the model	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.15 to 0.21	79,725 tracts	ACS 2019-2023 tract population	EPA EJScreen	A descriptive association within counties, not a causal estimate.
no2_pov	+0.18	correlation coefficient	population-weighted correlation of the tract NO₂ national percentile with the tract poverty rate, county-cluster bootstrap interval	residents of tracts with a NO₂ percentile and the tract poverty rate	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.15 to 0.21	82,816 tracts	ACS 2019-2023 tract population	EPA EJScreen
no2_res_all	50	national percentile of the tract (0 to 100)	mean over tracts of the NO₂ national percentile, each tract weighted by the number of residents in the group (tract grain, not an individual's exposure), county-cluster bootstrap interval	all residents of the tracts in the analysis	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 47 to 53	83,003 tracts	ACS 2019-2023 tract count of residents in the group	EPA EJScreen
no2_res_black	56	national percentile of the tract (0 to 100)	mean over tracts of the NO₂ national percentile, each tract weighted by the number of residents in the group (tract grain, not an individual's exposure), county-cluster bootstrap interval	Black or African American residents who report that race alone (of any ethnicity) of the tracts in the analysis	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 52 to 60	74,190 tracts	ACS 2019-2023 tract count of residents in the group	EPA EJScreen
no2_res_hisp	63	national percentile of the tract (0 to 100)	mean over tracts of the NO₂ national percentile, each tract weighted by the number of residents in the group (tract grain, not an individual's exposure), county-cluster bootstrap interval	Hispanic or Latino residents (of any race) of the tracts in the analysis	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 59 to 67	80,460 tracts	ACS 2019-2023 tract count of residents in the group	EPA EJScreen
pc1_asthma	−0.10	correlation coefficient	population-weighted correlation of the tract's modeled prevalence of current asthma among adults with the urban-industrial component (PC1), county-cluster bootstrap interval	residents of tracts in the PCA with a PLACES estimate for current asthma	PLACES 2024 release (BRFSS 2022); EJScreen 2024; ACS 2019-2023	95% CI −0.18 to 0.00	80,674 tracts	ACS 2019-2023 tract population	CDC PLACES	PLACES prevalence is a model-based estimate from survey responses, so it is not a measured rate.
pc1_copd	−0.37	correlation coefficient	population-weighted correlation of the tract's modeled prevalence of COPD among adults with the urban-industrial component (PC1), county-cluster bootstrap interval	residents of tracts in the PCA with a PLACES estimate for COPD	PLACES 2024 release (BRFSS 2022); EJScreen 2024; ACS 2019-2023	95% CI −0.42 to −0.32	80,674 tracts	ACS 2019-2023 tract population	CDC PLACES	PLACES prevalence is a model-based estimate from survey responses, so it is not a measured rate.
pc1_diesel	+0.40	weight on the standardized Diesel PM percentile in component 1 (unit-length eigenvector)	eigenvector entry of component 1 (signs fixed so that the traffic weight on component 1 and the storage-tank weight on component 2 are positive), county-cluster bootstrap interval	tracts with all 13 EJScreen percentiles	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.38 to 0.41	80,754 tracts	none (each tract counts once)	EPA EJScreen
pc1_hazwaste	+0.39	weight on the standardized Hazardous-waste facilities percentile in component 1 (unit-length eigenvector)	eigenvector entry of component 1 (signs fixed so that the traffic weight on component 1 and the storage-tank weight on component 2 are positive), county-cluster bootstrap interval	tracts with all 13 EJScreen percentiles	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.37 to 0.40	80,754 tracts	none (each tract counts once)	EPA EJScreen
pc1_no2	+0.38	weight on the standardized Nitrogen dioxide percentile in component 1 (unit-length eigenvector)	eigenvector entry of component 1 (signs fixed so that the traffic weight on component 1 and the storage-tank weight on component 2 are positive), county-cluster bootstrap interval	tracts with all 13 EJScreen percentiles	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.36 to 0.39	80,754 tracts	none (each tract counts once)	EPA EJScreen
pc1_traffic	+0.40	weight on the standardized Traffic proximity percentile in component 1 (unit-length eigenvector)	eigenvector entry of component 1 (signs fixed so that the traffic weight on component 1 and the storage-tank weight on component 2 are positive), county-cluster bootstrap interval	tracts with all 13 EJScreen percentiles	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.39 to 0.41	80,754 tracts	none (each tract counts once)	EPA EJScreen
pc1_var	38.6%	percent of the variance of the 13 standardized percentiles	eigenvalue share of component 1 of the correlation matrix of the 13 percentiles, each tract counted once, county-cluster bootstrap interval	tracts with all 13 EJScreen percentiles	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 36.2% to 41.7%	80,754 tracts	none (each tract counts once)	EPA EJScreen
pc1_var_w	37.1%	percent of the variance of the 13 standardized percentiles	eigenvalue share of component 1 when the standardization and the correlation matrix use population weights	tracts with all 13 EJScreen percentiles, each weighted by its residents	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023		80,754 tracts	ACS 2019-2023 tract population	EPA EJScreen
pc2_lead	+0.45	weight on the standardized Lead paint (housing built before 1960) percentile in component 2 (unit-length eigenvector)	eigenvector entry of component 2 (signs fixed so that the traffic weight on component 1 and the storage-tank weight on component 2 are positive), county-cluster bootstrap interval	tracts with all 13 EJScreen percentiles	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.33 to 0.56	80,754 tracts	none (each tract counts once)	EPA EJScreen
pc2_ozone	−0.31	weight on the standardized Ozone percentile in component 2 (unit-length eigenvector)	eigenvector entry of component 2 (signs fixed so that the traffic weight on component 1 and the storage-tank weight on component 2 are positive), county-cluster bootstrap interval	tracts with all 13 EJScreen percentiles	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI −0.38 to −0.16	80,754 tracts	none (each tract counts once)	EPA EJScreen
pc2_pm25	−0.47	weight on the standardized PM2.5 percentile in component 2 (unit-length eigenvector)	eigenvector entry of component 2 (signs fixed so that the traffic weight on component 1 and the storage-tank weight on component 2 are positive), county-cluster bootstrap interval	tracts with all 13 EJScreen percentiles	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI −0.55 to −0.38	80,754 tracts	none (each tract counts once)	EPA EJScreen
pc2_tanks	+0.55	weight on the standardized Underground storage tanks percentile in component 2 (unit-length eigenvector)	eigenvector entry of component 2 (signs fixed so that the traffic weight on component 1 and the storage-tank weight on component 2 are positive), county-cluster bootstrap interval	tracts with all 13 EJScreen percentiles	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.33 to 0.66	80,754 tracts	none (each tract counts once)	EPA EJScreen
pc2_var	11.7%	percent of the variance of the 13 standardized percentiles	eigenvalue share of component 2 of the correlation matrix of the 13 percentiles, each tract counted once, county-cluster bootstrap interval	tracts with all 13 EJScreen percentiles	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 10.5% to 13.1%	80,754 tracts	none (each tract counts once)	EPA EJScreen
pc2_water	+0.32	weight on the standardized Drinking-water violations percentile in component 2 (unit-length eigenvector)	eigenvector entry of component 2 (signs fixed so that the traffic weight on component 1 and the storage-tank weight on component 2 are positive), county-cluster bootstrap interval	tracts with all 13 EJScreen percentiles	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.19 to 0.43	80,754 tracts	none (each tract counts once)	EPA EJScreen
pm25_adi	−0.18	correlation coefficient	population-weighted correlation of the tract PM₂.₅ national percentile with the ADI national rank, county-cluster bootstrap interval	residents of tracts with a PM₂.₅ percentile and an ADI rank	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI −0.29 to −0.06	82,198 tracts	ACS 2019-2023 tract population	EPA EJScreen
pm25_adi_d1	64	national percentile of the tract (0 to 100)	population-weighted mean of the tract PM₂.₅ national percentile in an ADI decile (deciles hold equal numbers of tracts), county-cluster bootstrap interval	residents of tracts in the least deprived of the ten ADI deciles (decile 1)	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 52 to 73	8,149 tracts	ACS 2019-2023 tract population	EPA EJScreen
pm25_adi_d10	48	national percentile of the tract (0 to 100)	population-weighted mean of the tract PM₂.₅ national percentile in an ADI decile (deciles hold equal numbers of tracts), county-cluster bootstrap interval	residents of tracts in the most deprived of the ten ADI deciles (decile 10)	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 44 to 51	8,203 tracts	ACS 2019-2023 tract population	EPA EJScreen
pm25_adi_d9	44	national percentile of the tract (0 to 100)	population-weighted mean of the tract PM₂.₅ national percentile in an ADI decile (deciles hold equal numbers of tracts), county-cluster bootstrap interval	residents of tracts in the ninth of the ten ADI deciles (decile 9)	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 41 to 47	8,247 tracts	ACS 2019-2023 tract population	EPA EJScreen
pm25_adi_metro	−0.10	correlation coefficient	population-weighted correlation of the tract PM₂.₅ national percentile with the ADI national rank, metropolitan tracts only, county-cluster bootstrap interval	residents of metropolitan tracts with a PM₂.₅ percentile and the ADI national rank	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI −0.22 to 0.03	66,593 tracts	ACS 2019-2023 tract population	EPA EJScreen
pm25_adi_state	−0.18	correlation coefficient	population-weighted correlation of the tract PM₂.₅ national percentile with the ADI national rank, bootstrap interval from redrawing whole states	residents of tracts with a PM₂.₅ percentile and the ADI national rank	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI −0.38 to 0.10	82,198 tracts	ACS 2019-2023 tract population	EPA EJScreen
pm25_black	+0.06	correlation coefficient	population-weighted correlation of the tract PM₂.₅ national percentile with the tract's Black alone share, county-cluster bootstrap interval	residents of tracts with a PM₂.₅ percentile and a race and ethnicity share	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.00 to 0.12	83,008 tracts	ACS 2019-2023 tract population	EPA EJScreen
pm25_hisp	+0.32	correlation coefficient	population-weighted correlation of the tract PM₂.₅ national percentile with the tract's Hispanic or Latino share, county-cluster bootstrap interval	residents of tracts with a PM₂.₅ percentile and a race and ethnicity share	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.22 to 0.40	83,008 tracts	ACS 2019-2023 tract population	EPA EJScreen
pm25_q25	7.3	micrograms of PM₂.₅ per cubic meter, annual average	25th percentile of the tract concentrations (each tract counts once)	tracts with a modeled PM₂.₅ value	air quality modeled for 2020		83,008 tracts	none (each tract counts once)	EPA EJScreen
pm25_q75	9.0	micrograms of PM₂.₅ per cubic meter, annual average	75th percentile of the tract concentrations (each tract counts once)	tracts with a modeled PM₂.₅ value	air quality modeled for 2020		83,008 tracts	none (each tract counts once)	EPA EJScreen
pm25_ug_d1	9.6	micrograms of PM₂.₅ per cubic meter, annual average	population-weighted mean of the tract's modeled PM₂.₅ concentration, county-cluster bootstrap interval	residents of tracts in the least deprived ADI decile	air quality modeled for 2020; ADI 2023	95% CI 8.7 to 10.4	8,149 tracts	ACS 2019-2023 tract population	EPA EJScreen
pm25_ug_d10	8.1	micrograms of PM₂.₅ per cubic meter, annual average	population-weighted mean of the tract's modeled PM₂.₅ concentration, county-cluster bootstrap interval	residents of tracts in the most deprived ADI decile	air quality modeled for 2020; ADI 2023	95% CI 7.9 to 8.2	8,203 tracts	ACS 2019-2023 tract population	EPA EJScreen
pop_frame	330.1 million	people	sum of tract population	residents of the tracts in the analysis	ACS 2019-2023			none (full count)	American Community Survey
ptraf_adi	−0.41	correlation coefficient	population-weighted correlation of the tract Traffic proximity national percentile with the ADI national rank, county-cluster bootstrap interval	residents of tracts with a Traffic proximity percentile and an ADI rank	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI −0.49 to −0.33	82,198 tracts	ACS 2019-2023 tract population	EPA EJScreen
ptraf_adi_between	−0.66	correlation coefficient	correlation across counties of the county's population-weighted mean traffic percentile with its population-weighted mean ADI rank, each county weighted by its residents, bootstrap interval over counties	residents of counties, one point per county with at least one tract that has a traffic-proximity percentile and an ADI rank	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI −0.73 to −0.58	3,095 counties	ACS 2019-2023 county population (sum of tract population)	EPA EJScreen
ptraf_adi_d1	75	national percentile of the tract (0 to 100)	population-weighted mean of the tract Traffic proximity national percentile in an ADI decile (deciles hold equal numbers of tracts), county-cluster bootstrap interval	residents of tracts in the least deprived of the ten ADI deciles (decile 1)	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 68 to 79	8,149 tracts	ACS 2019-2023 tract population	EPA EJScreen
ptraf_adi_d10	39	national percentile of the tract (0 to 100)	population-weighted mean of the tract Traffic proximity national percentile in an ADI decile (deciles hold equal numbers of tracts), county-cluster bootstrap interval	residents of tracts in the most deprived of the ten ADI deciles (decile 10)	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 35 to 42	8,203 tracts	ACS 2019-2023 tract population	EPA EJScreen
ptraf_adi_d9	35	national percentile of the tract (0 to 100)	population-weighted mean of the tract Traffic proximity national percentile in an ADI decile (deciles hold equal numbers of tracts), county-cluster bootstrap interval	residents of tracts in the ninth of the ten ADI deciles (decile 9)	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 32 to 38	8,247 tracts	ACS 2019-2023 tract population	EPA EJScreen
ptraf_adi_metro	−0.31	correlation coefficient	population-weighted correlation of the tract Traffic proximity national percentile with the ADI national rank, metropolitan tracts only, county-cluster bootstrap interval	residents of metropolitan tracts with a Traffic proximity percentile and the ADI national rank	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI −0.40 to −0.21	66,593 tracts	ACS 2019-2023 tract population	EPA EJScreen
ptraf_adi_state	−0.41	correlation coefficient	population-weighted correlation of the tract Traffic proximity national percentile with the ADI national rank, bootstrap interval from redrawing whole states	residents of tracts with a Traffic proximity percentile and the ADI national rank	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI −0.52 to −0.25	82,198 tracts	ACS 2019-2023 tract population	EPA EJScreen
ptraf_adi_within	+0.19	correlation coefficient	population-weighted correlation of the tract Traffic proximity national percentile with the ADI national rank, after removing each county's population-weighted mean from both (counties with at least 5 tracts), county-cluster bootstrap interval	residents of tracts in counties with at least 5 tracts that have a Traffic proximity percentile and the ADI national rank	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.15 to 0.22	79,730 tracts	ACS 2019-2023 tract population	EPA EJScreen
ptraf_black	+0.17	correlation coefficient	population-weighted correlation of the tract Traffic proximity national percentile with the tract's Black alone share, county-cluster bootstrap interval	residents of tracts with a Traffic proximity percentile and a race and ethnicity share	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.12 to 0.22	82,998 tracts	ACS 2019-2023 tract population	EPA EJScreen
ptraf_black_within	+0.16	correlation coefficient	population-weighted correlation of the tract Traffic proximity national percentile with the tract's Black alone share after removing each county's population-weighted mean from both, county-cluster bootstrap interval	residents of tracts in counties with at least 5 tracts that have a Traffic proximity percentile and a race and ethnicity share	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.14 to 0.19	80,544 tracts	ACS 2019-2023 tract population	EPA EJScreen
ptraf_hisp	+0.33	correlation coefficient	population-weighted correlation of the tract Traffic proximity national percentile with the tract's Hispanic or Latino share, county-cluster bootstrap interval	residents of tracts with a Traffic proximity percentile and a race and ethnicity share	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.27 to 0.40	82,998 tracts	ACS 2019-2023 tract population	EPA EJScreen
ptraf_hisp_within	+0.19	correlation coefficient	population-weighted correlation of the tract Traffic proximity national percentile with the tract's Hispanic or Latino share after removing each county's population-weighted mean from both, county-cluster bootstrap interval	residents of tracts in counties with at least 5 tracts that have a Traffic proximity percentile and a race and ethnicity share	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.16 to 0.21	80,544 tracts	ACS 2019-2023 tract population	EPA EJScreen
ptraf_joint_adi	+0.06	within-county standard deviations of the Traffic proximity percentile per within-county standard deviation of the predictor	coefficient on the ADI national rank in a population-weighted regression of the tract Traffic proximity national percentile on the ADI national rank, the Hispanic or Latino share, the Black alone share, with each county's population-weighted mean removed from every variable and each variable scaled to a standard deviation of one, errors clustered on county	residents of tracts in counties with at least 5 tracts that have every variable in the model	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.02 to 0.10	79,730 tracts	ACS 2019-2023 tract population	EPA EJScreen	A descriptive association within counties, not a causal estimate.
ptraf_joint_black	+0.15	within-county standard deviations of the Traffic proximity percentile per within-county standard deviation of the predictor	coefficient on the Black alone share in a population-weighted regression of the tract Traffic proximity national percentile on the ADI national rank, the Hispanic or Latino share, the Black alone share, with each county's population-weighted mean removed from every variable and each variable scaled to a standard deviation of one, errors clustered on county	residents of tracts in counties with at least 5 tracts that have every variable in the model	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.12 to 0.19	79,730 tracts	ACS 2019-2023 tract population	EPA EJScreen	A descriptive association within counties, not a causal estimate.
ptraf_joint_hisp	+0.17	within-county standard deviations of the Traffic proximity percentile per within-county standard deviation of the predictor	coefficient on the Hispanic or Latino share in a population-weighted regression of the tract Traffic proximity national percentile on the ADI national rank, the Hispanic or Latino share, the Black alone share, with each county's population-weighted mean removed from every variable and each variable scaled to a standard deviation of one, errors clustered on county	residents of tracts in counties with at least 5 tracts that have every variable in the model	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.14 to 0.21	79,730 tracts	ACS 2019-2023 tract population	EPA EJScreen	A descriptive association within counties, not a causal estimate.
ptraf_jointb_black	+0.10	within-county standard deviations of the Traffic proximity percentile per within-county standard deviation of the predictor	coefficient on the Black alone share in a population-weighted regression of the tract Traffic proximity national percentile on the tract poverty rate, the Hispanic or Latino share, the Black alone share, with each county's population-weighted mean removed from every variable and each variable scaled to a standard deviation of one, errors clustered on county	residents of tracts in counties with at least 5 tracts that have every variable in the model	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.07 to 0.14	80,353 tracts	ACS 2019-2023 tract population	EPA EJScreen	A descriptive association within counties, not a causal estimate.
ptraf_jointb_hisp	+0.14	within-county standard deviations of the Traffic proximity percentile per within-county standard deviation of the predictor	coefficient on the Hispanic or Latino share in a population-weighted regression of the tract Traffic proximity national percentile on the tract poverty rate, the Hispanic or Latino share, the Black alone share, with each county's population-weighted mean removed from every variable and each variable scaled to a standard deviation of one, errors clustered on county	residents of tracts in counties with at least 5 tracts that have every variable in the model	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.10 to 0.17	80,353 tracts	ACS 2019-2023 tract population	EPA EJScreen	A descriptive association within counties, not a causal estimate.
ptraf_jointb_pov	+0.19	within-county standard deviations of the Traffic proximity percentile per within-county standard deviation of the predictor	coefficient on the tract poverty rate in a population-weighted regression of the tract Traffic proximity national percentile on the tract poverty rate, the Hispanic or Latino share, the Black alone share, with each county's population-weighted mean removed from every variable and each variable scaled to a standard deviation of one, errors clustered on county	residents of tracts in counties with at least 5 tracts that have every variable in the model	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.17 to 0.21	80,353 tracts	ACS 2019-2023 tract population	EPA EJScreen	A descriptive association within counties, not a causal estimate.
ptraf_metro_d1	76	national percentile of the tract (0 to 100)	population-weighted mean of the tract Traffic proximity national percentile, metropolitan tracts only, ADI deciles of all tracts, county-cluster bootstrap interval	residents of metropolitan tracts (RUCA codes 1 to 3) in ADI decile 1 of all tracts	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 69 to 80	7,879 tracts	ACS 2019-2023 tract population	EPA EJScreen
ptraf_metro_d9	48	national percentile of the tract (0 to 100)	population-weighted mean of the tract Traffic proximity national percentile, metropolitan tracts only, ADI deciles of all tracts, county-cluster bootstrap interval	residents of metropolitan tracts (RUCA codes 1 to 3) in ADI decile 9 of all tracts	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 45 to 50	4,817 tracts	ACS 2019-2023 tract population	EPA EJScreen
ptraf_pov	+0.07	correlation coefficient	population-weighted correlation of the tract Traffic proximity national percentile with the tract poverty rate, county-cluster bootstrap interval	residents of tracts with a Traffic proximity percentile and the tract poverty rate	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.04 to 0.11	82,818 tracts	ACS 2019-2023 tract population	EPA EJScreen
ptraf_pov_within	+0.27	correlation coefficient	population-weighted correlation of the tract Traffic proximity national percentile with the tract poverty rate, after removing each county's population-weighted mean from both (counties with at least 5 tracts), county-cluster bootstrap interval	residents of tracts in counties with at least 5 tracts that have a Traffic proximity percentile and the tract poverty rate	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.24 to 0.29	80,353 tracts	ACS 2019-2023 tract population	EPA EJScreen
redline_counties	215	counties	count of counties	counties with at least one graded tract in the analysis	HOLC maps of 1935 to 1940			none (full count)	Mapping Inequality (HOLC maps)
redline_dslpm_a	73	national percentile of the tract (0 to 100)	mean of the tract diesel PM national percentile, population-weighted, county-cluster bootstrap interval	residents of tracts whose dominant 1930s HOLC grade is A	HOLC maps of 1935 to 1940; air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 69 to 77	672 tracts	ACS 2019-2023 tract population	EPA EJScreen
redline_dslpm_d	86	national percentile of the tract (0 to 100)	mean of the tract diesel PM national percentile, population-weighted, county-cluster bootstrap interval	residents of tracts whose dominant 1930s HOLC grade is D	HOLC maps of 1935 to 1940; air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 81 to 89	2,978 tracts	ACS 2019-2023 tract population	EPA EJScreen
redline_fe_counties	199	counties	count of counties that inform a within-county contrast between grades	counties with graded tracts of at least two different grades	HOLC maps of 1935 to 1940			none (full count)	Mapping Inequality (HOLC maps)
redline_fe_dslpm	5.1	national percentile points, grade D minus grade A	coefficient on grade D, against grade A, in a population-weighted regression of the tract diesel PM national percentile on grade dummies with county fixed effects, bootstrap interval over counties	residents of graded tracts in counties that hold more than one grade	HOLC maps of 1935 to 1940; air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 3.9 to 6.5	10,950 tracts	ACS 2019-2023 tract population	EPA EJScreen
redline_fe_no2	9.7	national percentile points, grade D minus grade A	coefficient on grade D, against grade A, in a population-weighted regression of the tract NO₂ national percentile on grade dummies with county fixed effects, bootstrap interval over counties	residents of graded tracts in counties that hold more than one grade	HOLC maps of 1935 to 1940; air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 7.2 to 12.2	10,950 tracts	ACS 2019-2023 tract population	EPA EJScreen
redline_fe_pm25	1.1	national percentile points, grade D minus grade A	coefficient on grade D, against grade A, in a population-weighted regression of the tract PM₂.₅ national percentile on grade dummies with county fixed effects, bootstrap interval over counties	residents of graded tracts in counties that hold more than one grade	HOLC maps of 1935 to 1940; air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.2 to 2.0	10,950 tracts	ACS 2019-2023 tract population	EPA EJScreen
redline_fe_ptraf	3.9	national percentile points, grade D minus grade A	coefficient on grade D, against grade A, in a population-weighted regression of the tract traffic national percentile on grade dummies with county fixed effects, bootstrap interval over counties	residents of graded tracts in counties that hold more than one grade	HOLC maps of 1935 to 1940; air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 2.7 to 5.1	10,950 tracts	ACS 2019-2023 tract population	EPA EJScreen
redline_fe_stack	0.6	air hazards in the top quarter of tracts (0 to 5), grade D minus grade A	coefficient on grade D, against grade A, in a population-weighted regression of the tract stacked-hazard score on grade dummies with county fixed effects, bootstrap interval over counties	residents of graded tracts in counties that hold more than one grade	HOLC maps of 1935 to 1940; air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.4 to 0.7	10,950 tracts	ACS 2019-2023 tract population	EPA EJScreen
redline_n	10,950	tracts	count of tracts with a dominant grade	2020 tracts in the analysis at least half covered by HOLC polygons graded A to D	HOLC maps of 1935 to 1940; EJScreen 2024			none (full count)	Mapping Inequality (HOLC maps)
redline_no2_a	73	national percentile of the tract (0 to 100)	mean of the tract NO₂ national percentile, population-weighted, county-cluster bootstrap interval	residents of tracts whose dominant 1930s HOLC grade is A	HOLC maps of 1935 to 1940; air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 70 to 76	672 tracts	ACS 2019-2023 tract population	EPA EJScreen
redline_no2_d	86	national percentile of the tract (0 to 100)	mean of the tract NO₂ national percentile, population-weighted, county-cluster bootstrap interval	residents of tracts whose dominant 1930s HOLC grade is D	HOLC maps of 1935 to 1940; air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 83 to 89	2,978 tracts	ACS 2019-2023 tract population	EPA EJScreen
redline_pm25_a	56	national percentile of the tract (0 to 100)	mean of the tract PM₂.₅ national percentile, population-weighted, county-cluster bootstrap interval	residents of tracts whose dominant 1930s HOLC grade is A	HOLC maps of 1935 to 1940; air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 49 to 63	672 tracts	ACS 2019-2023 tract population	EPA EJScreen
redline_pm25_d	60	national percentile of the tract (0 to 100)	mean of the tract PM₂.₅ national percentile, population-weighted, county-cluster bootstrap interval	residents of tracts whose dominant 1930s HOLC grade is D	HOLC maps of 1935 to 1940; air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 51 to 69	2,978 tracts	ACS 2019-2023 tract population	EPA EJScreen
redline_pop	37.9 million	people	sum of tract population	residents of the graded tracts	ACS 2019-2023			none (full count)	American Community Survey
redline_ptraf_a	78	national percentile of the tract (0 to 100)	mean of the tract traffic national percentile, population-weighted, county-cluster bootstrap interval	residents of tracts whose dominant 1930s HOLC grade is A	HOLC maps of 1935 to 1940; air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 75 to 80	672 tracts	ACS 2019-2023 tract population	EPA EJScreen
redline_ptraf_d	86	national percentile of the tract (0 to 100)	mean of the tract traffic national percentile, population-weighted, county-cluster bootstrap interval	residents of tracts whose dominant 1930s HOLC grade is D	HOLC maps of 1935 to 1940; air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 83 to 89	2,978 tracts	ACS 2019-2023 tract population	EPA EJScreen
redline_stack_a	2.3	air hazards in the top quarter of tracts (0 to 5)	mean of the stacked-exposure score, population-weighted, county-cluster bootstrap interval	residents of tracts whose dominant 1930s HOLC grade is A	HOLC maps of 1935 to 1940; air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 2.0 to 2.5	672 tracts	ACS 2019-2023 tract population	EPA EJScreen
redline_stack_d	3.2	air hazards in the top quarter of tracts (0 to 5)	mean of the stacked-exposure score, population-weighted, county-cluster bootstrap interval	residents of tracts whose dominant 1930s HOLC grade is D	HOLC maps of 1935 to 1940; air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 2.8 to 3.5	2,978 tracts	ACS 2019-2023 tract population	EPA EJScreen
rural_all	6.9%	percent of residents living in small-town and rural tracts	population-weighted share of residents in tracts coded 7 to 10 in the USDA Rural-Urban Commuting Area scheme	residents of all tracts with a RUCA code	RUCA 2010 codes on 2020 tracts; ACS 2019-2023		82,124 tracts	ACS 2019-2023 tract population	Area Deprivation Index
rural_hi	18.5%	percent of residents living in small-town and rural tracts	population-weighted share of residents in tracts coded 7 to 10 in the USDA Rural-Urban Commuting Area scheme, county-cluster bootstrap interval	residents of tracts in ADI decile 10 with a RUCA code (Connecticut has none)	RUCA 2010 codes on 2020 tracts; ADI 2023; ACS 2019-2023	95% CI 16.2% to 21.0%	8,194 tracts	ACS 2019-2023 tract population	Area Deprivation Index
rural_lo	0.6%	percent of residents living in small-town and rural tracts	population-weighted share of residents in tracts coded 7 to 10 in the USDA Rural-Urban Commuting Area scheme, county-cluster bootstrap interval	residents of tracts in ADI decile 1 with a RUCA code (Connecticut has none)	RUCA 2010 codes on 2020 tracts; ADI 2023; ACS 2019-2023	95% CI 0.4% to 1.1%	8,077 tracts	ACS 2019-2023 tract population	Area Deprivation Index
rural_peak	20.3%	percent of residents living in small-town and rural tracts	population-weighted share of residents in tracts coded 7 to 10 in the USDA Rural-Urban Commuting Area scheme, county-cluster bootstrap interval	residents of tracts in ADI decile 9 with a RUCA code (Connecticut has none)	RUCA 2010 codes on 2020 tracts; ADI 2023; ACS 2019-2023	95% CI 18.4% to 22.3%	8,214 tracts	ACS 2019-2023 tract population	Area Deprivation Index
stack_adi_hi	1.0	air hazards in the top quarter of tracts (0 to 5)	population-weighted mean of the stacked-exposure score within a decile of tracts, county-cluster bootstrap interval	residents of tracts in decile 10 of the ADI rank	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.8 to 1.2	8,203 tracts	ACS 2019-2023 tract population	EPA EJScreen
stack_adi_lo	2.1	air hazards in the top quarter of tracts (0 to 5)	population-weighted mean of the stacked-exposure score within a decile of tracts, county-cluster bootstrap interval	residents of tracts in decile 1 of the ADI rank	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 1.7 to 2.5	8,146 tracts	ACS 2019-2023 tract population	EPA EJScreen
stack_black_hi	1.7	air hazards in the top quarter of tracts (0 to 5)	population-weighted mean of the stacked-exposure score within a decile of tracts, county-cluster bootstrap interval	residents of tracts in decile 10 of the Black alone share	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 1.4 to 2.0	8,298 tracts	ACS 2019-2023 tract population	EPA EJScreen
stack_black_lo	0.8	air hazards in the top quarter of tracts (0 to 5)	population-weighted mean of the stacked-exposure score within a decile of tracts, county-cluster bootstrap interval	residents of tracts in decile 1 of the Black alone share	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.6 to 1.0	8,809 tracts	ACS 2019-2023 tract population	EPA EJScreen
stack_cut	75	national percentile	a hazard counts as stacked when the tract's national percentile is at or above this cutoff (the top quarter of tracts); a definition	tracts	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (definition)	EPA EJScreen
stack_hisp_hi	2.3	air hazards in the top quarter of tracts (0 to 5)	population-weighted mean of the stacked-exposure score within a decile of tracts, county-cluster bootstrap interval	residents of tracts in decile 10 of the Hispanic or Latino share	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 1.8 to 2.8	8,299 tracts	ACS 2019-2023 tract population	EPA EJScreen
stack_hisp_lo	0.6	air hazards in the top quarter of tracts (0 to 5)	population-weighted mean of the stacked-exposure score within a decile of tracts, county-cluster bootstrap interval	residents of tracts in decile 1 of the Hispanic or Latino share	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.5 to 0.7	8,295 tracts	ACS 2019-2023 tract population	EPA EJScreen
stack_n_haz	5	air hazards	number of air hazards in the stacked score; a definition	PM₂.₅, diesel PM, NO₂, traffic proximity and toxic releases to air	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023			none (definition)	EPA EJScreen
ust_adi	+0.25	correlation coefficient	population-weighted correlation of the tract Underground storage tanks national percentile with the ADI national rank, county-cluster bootstrap interval	residents of tracts with a Underground storage tanks percentile and an ADI rank	air indicators modeled for 2020 (toxic releases for 2021), population and deprivation 2019-2023	95% CI 0.13 to 0.36	82,198 tracts	ACS 2019-2023 tract population	EPA EJScreen

Definitions

National percentile: A neighborhood's position in the national ordering, given as the share of all neighborhoods that fall below it. A higher percentile means a higher value than more of the rest of the country.
Area Deprivation Index (ADI): A score that ranks neighborhoods by income, education, employment and housing conditions drawn from the American Community Survey. In this book a higher national percentile means a more deprived neighborhood.
Census tract: A small area drawn by the Census Bureau to stand in for a neighborhood. Boundaries are redrawn after each decennial census.
Modeled estimate: A figure produced by a statistical model instead of a direct count or measurement, usually for small areas where direct data are thin, borrowing strength from surveys, neighboring areas or other data. Neighboring areas can share errors, so single extremes call for caution.
Population-weighted: Averaged so that each place counts in proportion to its number of residents, which lets a large county move the result more than a small one. An unweighted average counts every place equally.
Bootstrap interval: A range for an estimate found by recomputing it on many random resamples of the data and reading the range from the results. It shows how much the estimate would vary from sample to sample.
Principal components: A method that combines many correlated measures into a few summary scores, ordered by how much of the variation among places each captures. The first component is the single weighted combination that captures the most.
HOLC grade: A letter from A to D that the Home Owners' Loan Corporation gave neighborhoods on its 1930s maps, with A labeled best and D hazardous. The maps are known as redlining maps.
Ecological inference: Drawing conclusions about individuals from data about places or groups. A pattern across counties need not hold for the people inside them.

Methods

This chapter compares census tracts on the national percentiles of EPA's EJScreen 2024 air indicators, set against the Area Deprivation Index, race and ethnicity, rural or metropolitan status, PLACES asthma and COPD, and the grades of the 1930s HOLC maps. The indicators are EPA model output for 2020 and 2021, not monitor readings, and each percentile is the share of tracts with a lower value. The tracts in Alaska, Hawaii and Puerto Rico that lack PM2.5 and ozone are left out, and the HOLC comparisons cover only tracts that the digitized maps grade. Estimates are modeled and carry no sampling error beyond the bootstrap intervals, which describe which places are in the file.

Where the air indicators come from

Air indicators are the national percentiles in EPA's EJScreen 2024 tract file, as archived on Zenodo (release 2.32, after EPA removed the tool in 2025). EPA's documentation describes percentiles ranked across block groups; the percentiles in this file rank tracts (their unweighted mean is close to 50), so a percentile is the share of tracts with a lower value.

EPA's documentation dates PM2.5, ozone, NO2 and diesel PM to 2020, toxic releases to air to 2021 and traffic to 2020 traffic counts; PM2.5 is in micrograms per cubic meter, ozone and NO2 in parts per billion, diesel PM in micrograms per cubic meter, and traffic and toxic releases are indices. The indicators are EPA model output, not monitor readings.

Figure explained here: Figure 1

Which tracts are included and how they are weighted

The tract file is on 2020 tracts, like the tract atlas and PLACES, and joins on the 11-character GEOID without a crosswalk (Connecticut carries planning-region codes in all of them); the 686 territory rows of EJScreen are not on the spine and drop out.

PM2.5 and ozone are missing for all tracts in Alaska, Hawaii and Puerto Rico (the tracts with residents in those places are left out of the analysis), and diesel PM is missing for Alaska.

A tract is kept when its ACS 2019-2023 population is positive, and every mean and correlation weights tracts by that population.

How the groups and exposure measures are defined

Deciles and twentieths hold nearly equal numbers of tracts, and tracts tied on the sorting variable share a bin, so the lowest Black-share decile holds all tracts with a share of zero.

Race and ethnicity shares come from the ACS tract file: Hispanic or Latino of any race, and Black or African American alone of any ethnicity, so the groups overlap.

The stacked score counts how many of PM2.5, diesel PM, NO2, traffic proximity and toxic releases to air have a national percentile of 75 or more. Ozone is left out because it forms in the air from other pollutants and does not mark a local source; a count of six that adds it keeps the same ordering of the three sorting variables.

Rural tracts are USDA RUCA codes 7 to 10 and metropolitan tracts codes 1 to 3, from the staged geography file (2010 revised codes mapped to 2020 tracts by largest land overlap); Connecticut has no code.

PLACES values are model-based estimates of crude prevalence among adults.

Figures explained here: Figure 3, Figure 4, Figure 2 and Figure 8

How redlining grades are matched to tracts

HOLC polygons graded A to D are intersected with 2020 tracts in an equal-area projection; a tract takes the grade covering most of its area when graded polygons cover at least half of it.

The pooled grade means compare tracts across counties; the within-county contrasts come from a population-weighted regression of the tract value on grade with county fixed effects.

Figure explained here: Figure 9

How intervals and correlations are computed

Intervals for means and correlations are 95% percentile intervals from 2,000 draws of whole counties with replacement (seed 12345); Connecticut counts as its nine planning regions.

Three kinds of interval differ. The coefficients of the within-county joint models are weighted least squares with errors clustered on county and t intervals. Two correlations in the limits section (traffic and PM2.5 against the ADI rank) and the old-housing, air and race counts of the correlation strip redraw whole states instead, with the same number of draws and seed; the strip shades a cell by the wider of its county and state intervals, and a count requires both intervals to exclude zero. The county-level correlation of mean traffic percentile with mean ADI rank bootstraps counties, and the grade contrasts within counties bootstrap counties as well.

Correlations are population-weighted Pearson correlations. Within-county correlations subtract each county's population-weighted mean from both variables and use counties with at least 5 tracts that have both values.

Estimates are modeled and carry no sampling error beyond these bootstraps, which describe which places are in the file.

Figure explained here: Figure 7

How the principal components and the map are built

The PCA standardizes the 13 percentiles to mean zero and standard deviation one across the 80,754 tracts that have all 13, counts each tract once, and takes the eigenvectors of the correlation matrix; the intervals redraw whole counties, rebuild the matrix and match eigenvectors to the full-sample components. County scores are the population-weighted means of the tract scores on the first component; a county is mapped when at least 50% of its residents live in tracts with all 13 indicators.

Puerto Rico is not drawn on maps.

Figures explained here: Figure 5 and Figure 6

Four rankings of the same places

The comparison follows the book's ranking switch rule, fixed on October 28, 2026 before any of these gradients was computed. The main gradient of the chapter is recomputed under four rankings of the same places, with the outcome, period, weights, bins and intervals unchanged: the published ADI; a standardized index that applies the ADI's coefficients to its measures after standardizing each one across tracts; median household income; and the share of adults 25 and older with a bachelor's degree or more. The three alternatives come from ACS tract estimates for 2019 to 2023, the period of the ADI.

All four rankings use the same places, the 75,058 tracts that have the outcome and all four rankings, so the ADI panel can differ slightly from the chapter's main figure. Tracts enter only if they have every input of the standardized index, which leaves out tracts without a median rent, home value or mortgage cost.

A pattern counts as changed when the worse end switches sides, when the two ends differ under one ranking and not the other, or when the rank correlation of bin order and bin mean falls on the other side of 0.9 and moves by at least 0.1.

Figure explained here: Figure 10

What these data cannot show

References

Fitzgerald, William; Gehrke, Gretchen (Environmental Data & Governance Initiative) (2025). EPA Environmental Justice Screening Tool (EJScreen) data, 2015-2024. Zenodo, version 1, January 29, 2025; the record includes EPA's EJScreen Technical Documentation, version 2.3, revised July 31, 2024. doi:10.5281/zenodo.14767363
Singh, Gopal K. (2003). Area deprivation and widening inequalities in US mortality, 1969-1998. American Journal of Public Health 93(7): 1137-1143. doi:10.2105/ajph.93.7.1137
Bullard, Robert D. (1990). Dumping in Dixie: Race, Class, and Environmental Quality. Westview Press, Boulder, CO.
Tessum, Christopher W.; Apte, Joshua S.; Goodkind, Andrew L.; Muller, Nicholas Z.; Mullins, Kimberley A.; Paolella, David A.; Polasky, Stephen; Springer, Nathaniel P.; Thakrar, Sumil K.; Marshall, Julian D.; Hill, Jason D. (2019). Inequity in consumption of goods and services adds to racial-ethnic disparities in air pollution exposure. Proceedings of the National Academy of Sciences 116(13): 6001-6006. doi:10.1073/pnas.1818859116
Greenlund, Kurt J.; Lu, Hua; Wang, Yan; Matthews, Kevin A.; LeClercq, Jennifer M.; Lee, Benjamin; Carlson, Susan A. (2022). PLACES: Local Data for Better Health. Preventing Chronic Disease 19: 210459. doi:10.5888/pcd19.210459
Nelson, Robert K.; Winling, LaDale; Marciano, Richard; Connolly, Nathan; et al. (2023). Mapping Inequality: Redlining in New Deal America. American Panorama, ed. Robert K. Nelson and Edward L. Ayers, Digital Scholarship Lab, University of Richmond. dsl.richmond.edu/panorama/redlining/
Lane, Haley M.; Morello-Frosch, Rachel; Marshall, Julian D.; Apte, Joshua S. (2022). Historical Redlining Is Associated with Present-Day Air Pollution Disparities in U.S. Cities. Environmental Science & Technology Letters 9(4): 345-350. doi:10.1021/acs.estlett.1c01012
Salazar-Miranda, Arianna; Conzelmann, Claire; Phan, Toan; Hoffman, Jeremy (2024). Long-term effects of redlining on climate risk exposure. Nature Cities 1(6): 436-444. doi:10.1038/s44284-024-00076-y
Currie, Janet; Walker, Reed (2011). Traffic Congestion and Infant Health: Evidence from E-ZPass. American Economic Journal: Applied Economics 3(1): 65-90. doi:10.1257/app.3.1.65
Mohai, Paul; Saha, Robin (2015). Which came first, people or pollution? Assessing the disparate siting and post-siting demographic change hypotheses of environmental injustice. Environmental Research Letters 10(11): 115008. doi:10.1088/1748-9326/10/11/115008

Provenance

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data/staged/svi/svi_tract2020_2022.parquet	17,740,415	cb3860d8edc2aaf1f2a02211a58f7a0b80457eb6ad9a37b5ec8abb2d5da9da10	e371a4a696d5bed05d54ad7c5b6ca2504508805b847ec415c2322be7f66ec2b2

Outputs

File	SHA-256
facts.json	08d2673946006133096b425bfb53d0134f0fa5d125180516c34ade93d4e8693a
figures/air_by_holc_grade.json	8deca0cce4090c781c707ca8faf4ed46347be2749e2af8552d56f4be245de821
figures/air_by_race_deciles.json	fe6c97d0faa05d3b4a776c10908210090bf1176814b3016d1f7817d8a25e6e2d
figures/air_correlation_strip.json	da717b75ad02951025e46984c4a4d255d4830ef3854c6074dd75c1d1d512bbfc
figures/air_vs_deprivation.json	f39920e02e942de8030bc8e4d33c42062e9a7775403ac2ca2f7adc7647c2dcb9
figures/alt_rankings.json	fb9b7c1a5a852c52c286a80d9fd5a275f943fc01e710b5e3f23814aacf966268
figures/asthma_vs_exposure.json	df2ab99b05283c073498dc67389978013e9c83033b25f65a202d3b2ca23b881c
figures/pc1_map.json	4a6d9a3c3d9cb5ea01905f9585991a5068941517ac354c37262f347c535cc51a
figures/pca_loadings.json	775a3e114afad55a5698d5e6cdfd613f340c4d7f734d170aa739cdda3d88fd10
figures/rural_share_and_pm25.json	9d07dee60f3c20cb84cfe3e9e804c417c15bc921328be265e4532630b69f42e2
figures/stacked_exposure.json	740c00d123abd178ee61cbc69af4fe6e164aa4c8bf4a4d71ebe237c15c221dda
meta.json	369d449df1b378856e56f3c593f938cb3e46c815420d8544c8e2237d4aed43e1
public/data/air-pollution/pc1_map.json	42a309c754c9455e1a4180b45a6bba4e3bb9bd58e1fd138707d85e4663c339e0
refs.json	2af03780c82338c01d793ceef467a7e0d8296a83ad69eb166349300dcb22ee0a

Machine formats

Report (Markdown): https://vishalsingh.org/zipcode/air-pollution/report.md
Every estimate (JSON): https://vishalsingh.org/zipcode/report/air-pollution/facts.json
Table 1, figure "air_vs_deprivation" (JSON): https://vishalsingh.org/zipcode/report/air-pollution/figures/air_vs_deprivation.json
Table 2, figure "rural_share_and_pm25" (JSON): https://vishalsingh.org/zipcode/report/air-pollution/figures/rural_share_and_pm25.json
Table 3, figure "air_by_race_deciles" (JSON): https://vishalsingh.org/zipcode/report/air-pollution/figures/air_by_race_deciles.json
Table 4, figure "stacked_exposure" (JSON): https://vishalsingh.org/zipcode/report/air-pollution/figures/stacked_exposure.json
Table 5, figure "pca_loadings" (JSON): https://vishalsingh.org/zipcode/report/air-pollution/figures/pca_loadings.json
Table 6, figure "pc1_map" (JSON): https://vishalsingh.org/zipcode/report/air-pollution/figures/pc1_map.json
Table 7, figure "air_correlation_strip" (JSON): https://vishalsingh.org/zipcode/report/air-pollution/figures/air_correlation_strip.json
Table 8, figure "asthma_vs_exposure" (JSON): https://vishalsingh.org/zipcode/report/air-pollution/figures/asthma_vs_exposure.json
Table 9, figure "air_by_holc_grade" (JSON): https://vishalsingh.org/zipcode/report/air-pollution/figures/air_by_holc_grade.json
Table 10, figure "alt_rankings" (JSON): https://vishalsingh.org/zipcode/report/air-pollution/figures/alt_rankings.json
Payload of "pc1_map" (JSON): https://vishalsingh.org/zipcode/data/air-pollution/pc1_map.json
Index of every report: https://vishalsingh.org/zipcode/llms.txt; all reports in one file: https://vishalsingh.org/zipcode/llms-full.txt

Identification

Principal estimates

Findings

What the pollution indicators measure

Pollution percentiles fall as deprivation rises

Metropolitan tracts keep the fall, and the sign reverses within counties

Pollution percentiles rise with the Hispanic and Black share of a tract

Hazards stack in the same tracts

Two components summarize the indicators

The urban-industrial component is highest in a few dense counties

Most air indicators correlate negatively with deprivation and positively with Hispanic and Black share

Modeled asthma does not follow the urban-industrial component

Tracts graded D in the 1930s have higher traffic, NO₂ and diesel percentiles

Under the standardized index the ends of the traffic gradient no longer differ

What these data cannot show

Tables

Table 1. Traffic pollution ranks at a mean national percentile of 75 in the least deprived tenth of tracts and 39 in the most deprived

Table 2. The fall in traffic and diesel PM percentiles with deprivation persists among metropolitan tracts, and the sign reverses when tracts are compared within a county

Table 2.1. Rural share

Table 2.2. Metropolitan tracts only

Table 2.3. Correlations by comparison

Table 3. Pollution percentiles rise with the Hispanic share of a tract, from 33 to 73 for NO₂ across deciles, and with its Black share up to the fifth decile and in the tenth

Table 4. Residents of tracts in the highest Black-share decile live with 1.7 stacked air hazards on average, against 0.8 in the lowest, and the score falls across deprivation deciles

Table 5. The first component weights diesel PM, traffic, hazardous-waste facilities and NO₂ most, and the second weights storage tanks, lead paint and drinking-water violations against PM₂.₅ and ozone

Table 6. The urban-industrial component is highest in Cook County, Illinois, and in dense counties around New York, and below the tract average in most counties

Table 7. Pollution percentiles correlate negatively with deprivation for 4 of 6 air indicators and positively with Hispanic share for 5

Table 8. Modeled asthma prevalence is highest in the lowest twentieth of tracts on the urban-industrial component (11.2%) and rises with the lead-paint percentile and with deprivation

Table 9. Within the same county, tracts graded D in the 1930s rank 3.9 points above grade A tracts on the traffic percentile and 9.7 points on NO₂, and the stacked-hazard score is 0.6 higher

Table 10. Traffic proximity is steadily better toward the more deprived end under the ADI; the two ends do not differ detectably under the standardized index, and it is better at the more deprived end but uneven along the way under the income ranking

All estimates

Definitions

Methods

Where the air indicators come from

Which tracts are included and how they are weighted

How the groups and exposure measures are defined

How redlining grades are matched to tracts

How intervals and correlations are computed

How the principal components and the map are built

Four rankings of the same places

What these data cannot show

References

Provenance

Machine formats