Chapter 6.1 · The air you're assigned

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

Within a county, the correlation between a census tract's traffic-pollution percentile and its rank on the Area Deprivation Index (ADI) is +0.19. Compared only with the other tracts of its county, a more deprived tract therefore tends to rank higher on traffic, an index of the traffic on nearby major roads weighted by distance. Ranked against every tract in the country instead, the more deprived tract tends to rank lower. Both statements describe tracts with the same EPA estimates for 2020 and the same index. They differ in which tracts each one is compared with.

Across the country, more deprived tracts rank lower on traffic

The pollution measures are national percentiles, and a tract's percentile is the share of tracts with a lower value. Sorted into tenths by ADI rank, the least deprived tenth of tracts has a mean traffic percentile of 75 and the most deprived tenth a mean of 39, with each tract weighted by its residents. Across the tracts that have both values, the correlation between the traffic percentile and the ADI rank is −0.41 (95% CI −0.49 to −0.33). The lines for diesel particulate matter (diesel PM), nitrogen dioxide (NO₂) and fine particulate matter (PM₂.₅) also fall from the first tenth to the ninth. Higher deprivation goes with lower pollution percentiles across the country, most strongly for traffic and diesel PM.

Figure 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

Mean national percentile of the tract (0 to 100)

Decile of the Area Deprivation Index national rank (1 = least deprived, 10 = most deprived)

Show data

Data for Traffic pollution ranks at a mean national percentile of 75 in the least deprived tenth of tracts and 39 in the most deprived
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

Every line falls from the least deprived tenth of tracts on the left to the ninth and edges up in the tenth, and the traffic and diesel lines fall furthest. Each point is the population-weighted mean national percentile of the tracts in one tenth of the ADI rank, with 95% intervals from resampling whole counties, and the traffic line is drawn in colour. Values in Table 1.

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

How we know

The indicators come from EPA's EJScreen, a tool EPA removed from its website in 2025, and the chapter uses the archived copy of the final 2024 release.[1] The four indicators here are EPA's modeled estimates for 2020, and none is a monitor reading at the tract. The analysis covers the 83,008 tracts of the contiguous states and the District of Columbia with residents in the American Community Survey for 2019 to 2023, and they hold 330.1 million people. Alaska, Hawaii and Puerto Rico are left out because EJScreen has no PM₂.₅ or ozone estimate for their tracts. Means and correlations are population-weighted, and the intervals come from a bootstrap that redraws whole counties. The qualification that changes the reading is what a percentile measures. It ranks a tract against other tracts and does not give a concentration, so a gap in percentiles is a gap in rank. The report gives every estimate with its interval and sample size.

Compared within a county, the sign reverses

The national comparison mixes places. It sets a deprived tract in one county against a less deprived tract in another, and the counties can differ in traffic, industry and housing costs. The within-county comparison sets each tract only against the other tracts of its county, by subtracting the county's population-weighted mean from both measures. Over the 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 and +0.28 (95% CI 0.25 to 0.31) with the NO₂ percentile. 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), with each county weighted by its residents. The fall across the country reflects differences between counties.

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. It correlates +0.07 (95% CI 0.04 to 0.11) with the traffic percentile across all tracts and +0.27 (95% CI 0.24 to 0.29) within counties. Leaving out the small-town, rural and micropolitan tracts does not remove the fall for traffic. Among metropolitan tracts alone, the correlation of the traffic percentile with the ADI rank is still negative, at −0.31 (95% CI −0.40 to −0.21).

Figure 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

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

Area Deprivation Index rank
Poverty rate

Traffic proximity

Diesel PM

NO₂

PM₂.₅

Correlation with the tract's national percentile

For the ADI rank the dots sit left of zero across all tracts and among metropolitan tracts and right of zero within counties, though the whiskers for NO₂ and PM₂.₅ among metropolitan tracts include zero. For the poverty rate the dots sit right of zero in all three comparisons. Within counties, each tract is compared with the other tracts of its county, and counties with fewer than five tracts are left out. Whiskers are 95% intervals from a bootstrap over counties.

Show data

Data for 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, Correlations by comparison
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

For the ADI rank the dots sit left of zero across all tracts and among metropolitan tracts and right of zero within counties. The whiskers for NO₂ and PM₂.₅ among metropolitan tracts include zero. For the poverty rate the dots sit right of zero in all three comparisons. Each dot is a population-weighted correlation with a tract's national percentile, with 95% intervals from resampling whole counties, and the within-county comparison leaves out counties with too few tracts. The other tabs show the share of residents in small-town and rural tracts by tenth and the metropolitan lines. Values in Table 2.

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

Within counties, race and 1930s grades go with higher percentiles

The within-county comparison also carries the patterns by race and ethnicity. Hispanic share here counts residents who are Hispanic or Latino, of any race, and Black share counts residents who are Black or African American alone, of any ethnicity, so the groups overlap. Within counties, 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. In a within-county model that holds the ADI rank, Hispanic share and Black share together, all three go with a higher traffic percentile, and the ADI rank is the weakest of them. With the poverty rate in place of the ADI rank, poverty and the racial and ethnic composition of a tract each go with higher pollution percentiles, and these data do not rank them.

Between 1935 and 1940 the Home Owners' Loan Corporation drew maps that graded city neighborhoods from A, labeled best, to D, labeled hazardous.[3] Each tract takes the grade that covers most of its area, among tracts where graded areas cover at least 50% of the tract. Compared with grade A tracts in the same county, grade D tracts rank 3.9 (95% CI 2.7 to 5.1) percentile points higher on traffic and 9.7 (95% CI 7.2 to 12.2) points higher on NO₂. Each within-county gap is smaller than the gap pooled across all graded tracts, which mixes the differences between grades with the differences between the cities that were graded. The graded tracts are dense urban cores, so even grade A tracts rank above the national middle for traffic and NO₂. The grades in general are the subject of Chapter 5.2, Home value, income and redlining.

Figure 3

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

Traffic proximity (percentile)

NO₂ (percentile)

Diesel PM (percentile)

PM₂.₅ (percentile)

Stacked air hazards (0 to 5)

Difference from grade A in the same county (units named in each panel title)

Show data

Data for 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, Within the same county
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
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
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
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
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

Within a county, dots move right from grade A, the baseline at zero, to grade D for every measure, and the PM₂.₅ differences are the smallest. Each dot is the difference from grade A tracts in the same county, from a population-weighted comparison that uses only counties holding more than one grade, with 95% intervals from resampling whole counties. The second view shows the grade means pooled across all graded tracts. Values in Table 9.

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

Taken together, the national fall in pollution percentiles with the ADI describes how counties differ from one another. Inside a county, tracts that are more deprived, that have a higher Hispanic or Black share, or that were graded D in the 1930s have higher traffic and NO₂ percentiles. These comparisons describe tracts and do not test whether a grade changed the air. None describes what an individual breathes, because people leave their tract during the day and the indicators are modeled.

What this cannot tell you

A percentile cannot say whether a concentration meets a health guideline, and the indicators are EPA model output with their own error, which the intervals leave out. Counties in one state share traffic, industry and climate, so intervals that redraw whole states are wider. With states redrawn, the correlation of the PM₂.₅ percentile with the ADI rank is −0.18 (95% CI −0.38 to 0.10), which includes zero. Everything here is ecological, and a tract average does not describe any one of its residents.

Go deeper

The report: every estimate with its interval and sample size.
Tables: every figure of the report as a table.

Reading paths that include this chapter:

Data sources

EPA EJScreenEPA 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 2021Years: 2024 (indicators); ACS 2018-2022 (demographics) · Weights: none (modeled indicators); tract population weights from the ACS · License: Public domain (U.S. EPA); archived copy on Zenodo
Area Deprivation IndexNeighborhood Atlas Area Deprivation Index 2023, national rank, tract valuesYears: 2023 release (version 4.0.1; built on ACS 2019-2023) · Weights: ACS 2019-2023 tract population · License: Free for non-commercial use; cite the Neighborhood Atlas and Kind and Buckingham
American Community SurveyACS 2019-2023 tract population, race-alone and Hispanic or Latino shares, poverty rateYears: 2019-2023 (5-year) · Weights: Census Bureau survey weights applied upstream · License: Public domain (U.S. Census Bureau)
CDC PLACESCDC 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 · License: Public domain (CDC, U.S. Department of Health and Human Services)
Mapping Inequality (HOLC maps)Mapping Inequality digitized HOLC maps (1935 to 1940), grades A to D, matched to 2020 tracts by areaYears: 1930s-1940s maps (2023 digitization) · Weights: none (map polygons) · License: CC BY-NC-SA 4.0 (cite Nelson and coauthors)

All data sources

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
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/

How to cite

@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.}
}