Abstract
Rationale & Objective
Fine particulate matter (PM2.5) is associated with increased mortality and disproportionately affects minoritized patients with kidney failure, particularly Black patients. Among patients with kidney failure, we tested whether neighborhood characteristics (racial and ethnic segregation, socioeconomic deprivation, and built environment) modified the association between PM2.5 exposure and mortality, overall and by race and ethnicity.
Study Design
Cohort study (2003-2019).
Setting & Participants
National registry for patients with kidney failure.
Exposures
Annualized PM2.5 concentrations (high, > 9 μg/m3), segregation scores (Theil’s H method), deprivation scores (American Community Survey), and built environment factors (medically underserved areas [MUA] and urbanicity) by patients’ residential ZIP code at dialysis initiation.
Outcome
All-cause mortality.
Analytical Approach
We used multivariable Cox regression with shared state-level frailty to quantify whether neighborhood factors modify the association between PM2.5 and mortality, overall and stratified by race and ethnicity.
Results
High PM2.5 (vs low) was differentially associated with mortality among patients with kidney failure residing in neighborhoods characterized by high segregation (adjusted hazard ratio [aHR], 1.17; 95% confidence interval [CI], 1.15-1.19; Pinteraction high vs low < 0.001), high deprivation (aHR, 1.17; 95% CI, 1.15-1.19; Pinteraction high vs low < 0.001), MUA (aHR, 1.15; 95% CI, 1.13-1.16; Pinteraction = 0.005), and high-density urban (HDU) areas (aHR, 1.14; 95% CI, 1.12-1.15; Pinteraction < 0.001). These differential associations were most prominent among Black patients ([high segregation: aHR, 1.25; 95% CI, 1.21-1.29; Pinteraction high vs low = 0.006], [high deprivation: aHR, 1.26; 95% CI, 1.22-1.30; Pinteraction high vs low < 0.001], [MUA: aHR, 1.22; 95% CI, 1.19-1.26; Pinteraction = 0.02], [HDU areas: aHR, 1.23; 95% CI, 1.20-1.26; Pinteraction < 0.001])
Limitations
Outdoor PM2.5 may not reflect individual-level exposures.
Conclusions
High levels of PM2.5 were associated with increased mortality risk among patients with kidney failure residing in neighborhoods characterized by high segregation, high deprivation, MUAs, and HDU areas, particularly among Black patients. Nephrologists should consider closer monitoring of patients, particularly those from minoritized groups who reside in these high-risk neighborhoods, to help mitigate the adverse effects of PM2.5 and reduce related mortality.
Index Words: Residential neighborhood air pollution, segregation, deprivation, mortality, kidney failure
Plain-language Summary
Exposure to high levels of fine particulate matter (PM2.5), a form of air pollution, disproportionately affects minoritized patients with kidney failure, particularly Black patients. Residential neighborhood characteristics may explain both the overall association between PM2.5 exposure and mortality and the racial and ethnic differences in this association among patients with kidney failure in the United States. In this study, we found that high PM2.5 levels were associated with increased mortality risk in neighborhoods characterized by high segregation and high deprivation, medically underserved areas, and HDU areas. These associations were most prominent among Black patients with kidney failure. Our findings underscore the need for clinicians to identify and monitor high-risk populations to reduce mortality risk related to PM2.5, particularly among Black patients.
Exposure to elevated levels of fine particulate matter (aerodynamic diameter < 2.5 μm [PM2.5]) is associated with increased mortality among patients with kidney failure.1 One potential mechanistic pathway involves PM2.5-induced systemic inflammation, which contributes to cardiovascular and respiratory comorbidities, ultimately increasing the risk of mortality in these individuals.1,2
Additionally, the mortality risk associated with PM2.5 disproportionately affects minoritized patients with kidney failure, particularly Black patients.1 These disparities are believed to be driven in part by variations in the distributions of pre-existing comorbidities and epigenetic aging.3,4 However, these variations may not fully explain the deleterious association between PM2.5 and mortality, nor the racial differences observed in this association.
Residential neighborhood characteristics may play a significant role in these associations, as they have in other health care disparities.5,6 For instance, highly segregated neighborhoods often experience disinvestment,7, 8, 9, 10, 11 resulting in fewer resources,6,12 elevated PM2.5 levels,13, 14, 15, 16, 17 and higher mortality risk, particularly among the Black population.18,19 Neighborhood deprivation, reflected in indicators such as wealth, income, education, occupation, and housing, captures broader socioeconomic disadvantages and is associated with adverse health outcomes.20, 21, 22, 23, 24 Highly deprived neighborhoods may lack access to adequate health care,23 while also being burdened with high PM2.5 levels,25 further increasing mortality risk,22 especially for Black individuals.22 Moreover, built environment factors, such as the presence of parks and high vehicle traffic, also influence PM2.5 exposure.26,27 Increased green spaces can promote physical activity and improve mental health,28 whereas high traffic volumes contribute to vehicle emissions, deteriorating air quality.27 Furthermore, individuals in medically underserved areas (MUAs) and urban settings may face additional challenges that heighten their susceptibility to the harmful effects of PM2.5 on mortality.29 Therefore, it is plausible that neighborhood factors interact with environmental exposure to PM2.5, contributing to increased mortality. We hypothesize that these social and physical neighborhood characteristics modify the association between PM2.5 and mortality, disproportionately impacting minoritized patients, particularly Black patients with kidney failure.
In this national study of patients with kidney failure, we (1) tested whether neighborhood factors (racial and ethnic segregation, neighborhood deprivation, and built environment factors [eg, parks, vehicle counts, MUA designation, and urbanicity types]) modify the associations between PM2.5 and mortality and (2) stratified the aforementioned associations by race and ethnicity.
Methods
Study Population and Data Source
We leveraged data from the United States Renal Data System (USRDS) to identify a cohort of 814,608 patients (age ≥ 18 years) diagnosed with kidney failure in the United States (US), who initiated dialysis between January 1, 2003, and December 31, 2019. The United States Renal Data System is a national registry that provides comprehensive information on all patients with kidney failure in the US, including information from the Center for Medicare & Medicaid Services (CMS) Medical Evidence form (CMS-2728) and Medicare billing claims.30 Patient characteristics, comorbidities, and body mass index were extracted from CMS-2728 at dialysis initiation.30 The study population was limited to patients with kidney failure whose primary payer was Medicare (Medicare Fee-for-Services) and whose race and ethnicity were categorized into one of the following categories: non-Hispanic (NH) Asian (Asian hereafter), NH Black (Black hereafter), Hispanic, or NH White (White hereafter).
The Institutional Review Board at the New York University Grossman School of Medicine reviewed our study and determined it to be exempt (s22-00535), because participants could not be identified.
Air Pollution
We obtained PM2.5 levels (2003-2019) from the Centers for Disease Control and Prevention National Environmental Public Health Tracking Network.31 Daily PM2.5 levels were annualized at the census tract level and averaged at the ZIP code level,32 which were then linked to the 5-digit residential ZIP code of patients at the time of dialysis initiation. We used the current annual National Ambient Air Quality standards set by the US Environmental Protection Agency (EPA) to define low (≤ 9 μg/m3) and high (> 9 μg/m3) PM2.5 concentrations.33 ZIP codes served as proxies for patients’ residential neighborhoods, consistent with prior research.5,6
Neighborhood Factors
Residential racial and ethnic segregation
We used the Multigroup Entropy Index (Thiel’s H) method to quantify racial and ethnic segregation (segregation hereafter).5 This method is known for its robustness in measuring segregation across multiple racial and ethnic groups.34, 35, 36 The calculation included three steps: (1) extracting population-specific race and ethnicity counts within ZIP Code Tabulation Areas (ZCTAs) from American Community Survey 5-year estimates; (2) assessing the diversity within ZCTAs; and (3) examining the distribution of racial and ethnic populations within counties (Item S1: Calculations).34, 35, 36
We then assigned segregation scores to patients based on their 5-digit residential ZIP code at dialysis initiation. Segregation scores were categorized into tertiles, based on prior studies: low (< 3.4), medium (≥ 3.4 and < 11.6), and high (≥ 11.6).5,6,18,37, 38, 39, 40, 41
Neighborhood deprivation index
We extracted census-tract-level neighborhood deprivation index (NDI) scores (deprivation hereafter), a composite measure derived from 10 American Community Survey variables, using the “ndi” R statistical software package.20,42,43 NDI scores were weighted using population weights and aggregated at the ZIP code level,20,42, 43, 44 then linked with the residential 5-digit ZIP code of patients. They were then further divided into tertiles of low (≤ −0.11), medium (> −0.11 to ≤ 0.59), and high (> 0.59), based on prior literature.18,37, 38, 39, 40, 41 A higher NDI score indicates a greater degree of socioeconomic deprivation.
Built Environment Factors
Parks and daily vehicle counts
The ZCTA-level number of parks (2018-2020) and daily vehicle count (1963-2019) were obtained from the National Neighborhood Data Archive of the Inter-University Consortium for Political and Social Research at the University of Michigan.45,46 These data were categorized into low or high groups and then linked to each patient’s 5-digit residential ZIP code at dialysis initiation.
Medically underserved areas
We assessed geographic health care accessibility using the Health Resources and Services Administration’s medically underserved area (MUA) designation.47 This designation identifies contiguous geographic areas with insufficient health care resources based on: the number of primary care physicians, the percentage of individuals living below the federal poverty level, the percentage of individuals aged ≥ 65 years, and infant mortality rates.47 We spatially aligned the ZCTA centroids and MUAs to identify ZCTAs that fall within MUAs, and linked them to the residential 5-digit ZIP code of patients at dialysis initiation.
Urbanicity
We obtained urbanicity types from the modified 2017-2021 Rural-Urban Commuting Area Codes defined by the US Department of Agriculture.48,49 These modified urbanicity types divided the metropolitan core into 2 subcategories based on the population and land area distribution: high-density urban (HDU) areas and suburban areas.48 We then classified the residential ZIP codes of patients into four urbanicity types: HDU, suburban, rural, and small town.48
Mortality
We obtained data on all-cause mortality from the USRDS, which captures information from multiple sources, including the CMS Medicare Enrollment Database, CMS forms 2746 (Death Notification form) and 2728, the Organ Procurement and Transplantation Network transplant follow-up form, the CROWN-Web database, and inpatient claims.1 Patients with kidney failure were followed from the date of dialysis initiation until the earliest occurrence of any of the following events: death, loss of Medicare eligibility, or the end of the study (December 31, 2019).
Statistical Analyses
We used the Kaplan-Meier method to estimate the unadjusted cumulative incidence of mortality by PM2.5 and race and ethnicity. We used complementary log-log plots and Schoenfeld residuals to test the proportional hazards assumption. We then used multivariable Cox proportional hazard models with shared state-level frailty to50: (1) test whether neighborhood factors (segregation, NDI, and various built environmental factors) modify the association between PM2.5 and mortality, using interaction terms and Wald; and (2) stratify the associations by race and ethnicity, using interaction terms and Wald tests to test differences by neighborhood factors within each racial and ethnic group. All models were adjusted for patient demographics other than race and ethnicity (age, sex, body mass index, and employment status), dialysis-related factors (pre-kidney failure nephrology care, cause of kidney failure), existing comorbidities (cancer, hypertension, diabetes, peripheral vascular disease, cerebrovascular disease, atherosclerotic heart disease, congestive heart failure, chronic obstructive pulmonary disease, illicit drug use, alcohol use, and tobacco use), assessments of functional status (ability to walk, residence in an institutionalized setting, and the need for assistance with daily activities), and neighborhood-level factors (% of residents with ≥ high school degree, % of residents with ≥ bachelor’s degree, and median household income). Variables were selected based on previous research.1,51, 52, 53, 54
Sensitivity Analysis
We assessed the robustness of our results through the following sensitivity analysis: (1) using Cox proportional hazards models without shared state-level frailty; (2) restricting analyses to individuals aged > 66 years; (3) adjusting for urbanicity types; (4) using a prior EPA cutoff of > 12 μg/m3 to define high PM2.5 concentrations; and (5) examining whether neighborhood factors are associated with mortality among individuals exposed to low PM2.5 levels.
All statistical analyses were conducted using SAS (v9.4 [SAS Institute]), Stata 17 MP (StataCorp LLC), R statistical software (version 4.0.3, R Foundation for Statistical Computing), and Quantum Geographic Information System (QGIS; v3.30).55 Statistical significance was defined as a 2-sided P value < 0.05.
Results
Study Population
Among 814,608 patients with kidney failure who initiated dialysis, the mean age was 62.4 years (±SD, 15.1), 43.7% were female, 4.9% were Asian, 35.0% were Black, 14.8% were Hispanic, and 45.2% were White. Additionally, 46.3% had diabetes, 30.3% had hypertension as the cause of kidney failure, and 47.5% had pre-kidney failure nephrology care (Table 1).
Table 1.
Characteristics of Patients With Kidney Failure (Aged ≥ 18 years) Initiating Dialysis Between 2003 and 2019, Stratified By Race and Ethnicity and Residential Neighborhood PM2.5 levels (N = 814,608).
| Patient Characteristics | Patients N = 814,608 |
Asian N = 39,872 |
Black N = 285,399 |
Hispanic N = 120,798 |
White N = 368,539 |
||||
|---|---|---|---|---|---|---|---|---|---|
| PM2.5a | |||||||||
| Low N = 10,225 |
High N = 29,647 |
Low N = 53,537 |
High N = 231,862 |
Low N = 41,436 |
High N = 79,362 |
Low N = 119,575 |
High N = 248,964 |
||
| Age in y, mean (SD) | 62.4 (15.1) | 61.9 (15.3) | 63.6 (15.6) | 58.7 (14.7) | 58.7 (14.9) | 59.9 (14.8) | 58.9 (14.5) | 66.4 (14.4) | 66.3 (14.4) |
| Age group, y, N (%) | |||||||||
| 18-34 | 39,931 (4.9) | 589 (5.8) | 1602 (5.4) | 3,592 (6.7) | 15,320 (6.6) | 2,437 (5.9) | 5,069 (6.4) | 3,699 (3.1) | 7,623 (3.1) |
| 35-49 | 119,737 (14.7) | 1,532 (15.0) | 3,749 (12.6) | 10,300 (19.2) | 46,417 (20.0) | 7,098 (17.1) | 14,122 (17.8) | 11,452 (9.6) | 25,067 (10.1) |
| 50-64 | 267,013 (32.8) | 3,335 (32.6) | 8,966 (30.2) | 20,156 (37.6) | 84,801 (36.6) | 15,621 (37.7) | 31,647 (39.9) | 33,184 (27.8) | 69,303 (27.8) |
| ≥ 65 | 387,927 (47.6) | 4,769 (46.6) | 15,330 (51.7) | 19,489 (36.4) | 85,324 (36.8) | 16,280 (39.3) | 28,524 (35.9) | 71,240 (59.6) | 146,971 (59.0) |
| Female, N (%) | 356,348 (43.7) | 4,647 (45.4) | 13,100 (44.2) | 24,848 (46.4) | 111,891 (48.3) | 17,192 (41.5) | 33,775 (42.6) | 46,408 (38.8) | 104,487 (42.0) |
| BMI in kg/m2, mean (SD) | 29.0 (7.9) | 26.3 (6.4) | 25.2 (6.0) | 29.9 (8.2) | 29.7 (8.3) | 29.1 (7.3) | 28.6 (7.1) | 29.2 (7.7) | 28.8 (7.8) |
| BMI group, N (%) | |||||||||
| ≤ 25 | 283,280 (34.8) | 5,065 (49.5) | 17,127 (57.8) | 16,325 (30.5) | 75,385 (32.5) | 12,945 (31.2) | 26,994 (34.0) | 39,793 (33.3) | 89,646 (36.0) |
| 26-30 | 230,410 (28.3) | 2,891 (28.3) | 7,706 (26.0) | 14,466 (27.0) | 62,285 (26.9) | 12,949 (31.3) | 25,608 (32.3) | 33,976 (28.4) | 70,529 (28.3) |
| > 30 | 300,918 (36.9) | 2,269 (22.2) | 4,814 (16.2) | 22,746 (42.5) | 94,192 (40.6) | 15,542 (37.5) | 26,760 (33.7) | 45,806 (38.3) | 88,789 (35.7) |
| Employment status, N(%) | |||||||||
| Unemployed | 183,879 (22.6) | 2,399 (23.5) | 7,635 (25.8) | 15,285 (28.6) | 66,077 (28.5) | 10,918 (26.3) | 25,910 (32.6) | 17,850 (14.9) | 37,805 (15.2) |
| Employed | 98,960 (12.1) | 1,776 (17.4) | 4,247 (14.3) | 7,637 (14.3) | 29,009 (12.5) | 4,916 (11.9) | 8,247 (10.4) | 14,625 (12.2) | 28,503 (11.4) |
| Retired | 473,215 (58.1) | 5,123 (50.1) | 14,893 (50.2) | 27,692 (51.7) | 120,060 (51.8) | 22,001 (53.1) | 37,435 (47.2) | 81,616 (68.3) | 164,395 (66.0) |
| Other | 58,554 (7.2) | 927 (9.1) | 2,872 (9.7) | 2,923 (5.5) | 16,716 (7.2) | 3,601 (8.7) | 77,70 (9.8) | 5,484 (4.6) | 18,261 (7.3) |
| Cause of Kidney Failure, N (%) | |||||||||
| Diabetes mellitus | 377,050 (46.3) | 5,445 (53.3) | 14,865 (50.1) | 23,922 (44.7) | 101,370 (43.7) | 25,836 (62.4) | 50,143 (63.2) | 49,994 (41.8) | 105,475 (42.4) |
| Hypertension | 246,469 (30.3) | 2,421 (23.7) | 8,236 (27.8) | 19,834 (37.0) | 88,205 (38.0) | 8,269 (20.0) | 16,304 (20.5) | 33,472 (28.0) | 69,728 (28.0) |
| Glomerulonephritis | 67,452 (8.3) | 1,312 (12.8) | 3,422 (11.5) | 4,052 (7.6) | 17,923 (7.7) | 3,200 (7.7) | 5,525 (7.0) | 10,648 (8.9) | 21,370 (8.6) |
| Other | 123,637 (15.2) | 1,047 (10.2) | 3,124 (10.5) | 5,729 (10.7) | 24,364 (10.5) | 4,131 (10.0) | 7,390 (9.3) | 25,461 (21.3) | 52,391 (21.0) |
| Comorbidities, N (%) | |||||||||
| Cancer | 53,095 (6.5) | 387 (3.8) | 978 (3.3) | 387 (3.8) | 978 (3.3) | 1,608 (3.9) | 2,426 (3.1) | 11,361 (9.5) | 21,929 (8.8) |
| Peripheral vascular disease | 93,318 (11.5) | 607 (5.9) | 1,744 (5.9) | 607 (5.9) | 1,744 (5.9) | 4,867 (11.7) | 7,799 (9.8) | 15,605 (13.1) | 37,146 (14.9) |
| Cerebrovascular disease | 74,916 (9.2) | 807 (7.9) | 2,244 (7.6) | 807 (7.9) | 2,244 (7.6) | 3,037 (7.3) | 5,610 (7.1) | 10,315 (8.6) | 24,275 (9.8) |
| Atherosclerotic heart disease | 99,450 (12.2) | 1,347 (13.2) | 3,069 (10.4) | 1,347 (13.2) | 3,069 (10.4) | 5,420 (13.1) | 7,250 (9.1) | 20,690 (17.3) | 36,311 (14.6) |
| CHF | 247,297 (30.4) | 2,275 (22.2) | 7,210 (24.3) | 2,275 (22.2) | 7,210 (24.3) | 11,060 (26.7) | 20390 (25.7) | 36,713 (30.7) | 85,598 (34.4) |
| COPD | 65,634 (8.1) | 326 (3.2) | 1,073 (3.6) | 326 (3.2) | 1,073 (3.6) | 1,889 (4.6) | 2,716 (3.4) | 13,636 (11.4) | 28,161 (11.3) |
| Drug use | 10,663 (1.3) | 27 (0.3) | 50 (0.2) | 27 (0.3) | 50 (0.2) | 349 (0.8) | 646 (0.8) | 1,046 (0.9) | 1,660 (0.7) |
| Alcohol use | 12,194 (1.5) | 43 (0.4) | 98 (0.3) | 43 (0.4) | 98 (0.3) | 528 (1.3) | 1,071 (1.3) | 1,843 (1.5) | 3,339 (1.3) |
| Tobacco use | 47,793 (5.9) | 255 (2.5) | 628 (2.1) | 255 (2.5) | 628 (2.1) | 1,357 (3.3) | 2,094 (2.6) | 7,591 (6.3) | 15,647 (6.3) |
| Functional impairment | 95,724 (11.8) | 971 (9.5) | 3,196 (10.8) | 971 (9.5) | 3,196 (10.8) | 4,951 (11.9) | 8,860 (11.2) | 16,294 (13.6) | 30,615 (12.3) |
| Institutionalized | 50,788 (6.2) | 350 (3.4) | 12,62 (4.3) | 350 (3.4) | 1,262 (4.3) | 1,844 (4.5) | 3,096 (3.9) | 9,785 (8.2) | 17,799 (7.1) |
| Pre-kidney failure nephrology care, N (%) | 386,985 (47.5) | 6,959 (68.1) | 13,998 (47.2) | 6,959 (68.1) | 13,998 (47.2) | 21,643 (52.2) | 31,051 (39.1) | 76,291 (63.8) | 111,242 (44.7) |
| Residential neighborhood Factors, N (%)b | |||||||||
| Percent with a high school degree or higher | |||||||||
| ≤ 84.2% | 270,428 (33.2) | 2,711 (26.5) | 12,747 (43.0) | 2,711 (26.5) | 12,747 (43.0) | 23,473 (56.7) | 53,935 (68.0) | 18,543 (15.5) | 52,441 (21.1) |
| 84.3%-91.5% | 272,445 (33.5) | 3,278 (32.1) | 8,342 (28.1) | 3,278 (32.1) | 8,342 (28.1) | 10,400 (25.1) | 15,435 (19.4) | 39,413 (33.0) | 82,747 (33.2) |
| > 91.5% | 271,542 (33.3) | 4,236 (41.4) | 8,558 (28.9) | 4,236 (41.4) | 8,558 (28.9) | 7,534 (18.2) | 9,990 (12.6) | 61,585 (51.5) | 113,724 (45.7) |
| Percent with bachelor’s degree or higher | |||||||||
| ≤ 22.1% | 273,488 (33.6) | 2,095 (20.5) | 6,494 (21.9) | 2,095 (20.5) | 6,494 (21.9) | 19,811 (47.8) | 41,797 (52.7) | 27,183 (22.7) | 61,550 (24.7) |
| 22.2%-36.7% | 270,156 (33.2) | 3,661 (35.8) | 9,075 (30.6) | 3,661 (35.8) | 9,075 (30.6) | 12,959 (31.3) | 19,618 (24.7) | 44,800 (37.5) | 82,653 (33.2) |
| > 36.7% | 270,771 (33.2) | 4,469 (43.7) | 14,078 (47.5) | 4,469 (43.7) | 14,078 (47.5) | 8,637 (20.9) | 17,945 (22.6) | 47,558 (39.8) | 104,709 (42.1) |
| Median Household Income ($) | |||||||||
| ≤ $53,197 | 269,700 (33.1) | 1,180 (11.6) | 3,318 (11.2) | 1,180 (11.6) | 3,318 (11.2) | 15,522 (37.5) | 27,382 (34.5) | 23,482 (19.7) | 54,976 (22.1) |
| $53,198-$74,434 | 272,377 (33.5) | 2,957 (29.0) | 8,053 (27.2) | 2,957 (29.0) | 8,053 (27.2) | 15,817 (38.3) | 25,459 (32.1) | 48,556 (40.6) | 87,661 (35.2) |
| > $74,434 | 272,062 (33.4) | 6,076 (59.5) | 18,268 (61.6) | 6,076 (59.5) | 18,268 (61.6) | 10,009 (24.2) | 26,505 (33.4) | 47,436 (39.7) | 106,208 (42.7) |
| Racial and ethnic segregation, N (%)c | |||||||||
| Low segregation | 269,700 (33.1) | 3,789 (37.1) | 11,115 (37.5) | 14,616 (27.3) | 45,211 (19.5) | 12,302 (29.7) | 20953 (26.4) | 58,626 (49.0) | 104,829 (42.1) |
| Medium segregation | 272,377 (33.5) | 5,112 (50.0) | 11,057 (37.3) | 21,925 (41.0) | 63,958 (27.6) | 19,464 (47.0) | 24455 (30.8) | 45,103 (37.7) | 79,003 (31.7) |
| High segregation | 272,062 (33.4) | 1,324 (12.9) | 7,475 (25.2) | 16,996 (31.7) | 122,693 (52.9) | 9,670 (23.3) | 33954 (42.8) | 15,846 (13.3) | 65,132 (26.2) |
| Neighborhood deprivation, N (%)d | |||||||||
| Low deprivation | 269,700 (33.1) | 5,404 (52.9) | 14,480 (48.8) | 13,714 (25.6) | 40,639 (17.5) | 8,718 (21.0) | 16,538 (20.8) | 55,965 (46.8) | 116,089 (46.6) |
| Medium deprivation | 272,377 (33.5) | 3,480 (34.0) | 9,703 (32.7) | 20,139 (37.6) | 68,711 (29.6) | 14,353 (34.6) | 23,834 (30.0) | 44,773 (37.4) | 86,554 (34.8) |
| High deprivation | 272,062 (33.4) | 1,341 (13.1) | 5,464 (18.4) | 19,684 (36.8) | 122,512 (52.8) | 18,365 (44.3) | 38,990 (49.1) | 18,837 (15.8) | 46,321 (18.6) |
| Number of parks, N (%)e | |||||||||
| 1-11 | 409,532 (50.3) | 4,055 (39.7) | 13,470 (45.4) | 23,888 (44.6) | 114,964 (49.6) | 17,580 (42.4) | 38,724 (48.8) | 62,097 (51.9) | 134,754 (54.1) |
| ≥ 12 | 405,076 (49.7) | 6,170 (60.3) | 16,177 (54.6) | 29,649 (55.4) | 116,898 (50.4) | 23,856 (57.6) | 40,638 (51.2) | 57,478 (48.1) | 114,210 (45.9) |
| Daily vehicle traffic, N (%)f | |||||||||
| Low (≤ 199,068) | 433,077 (53.2) | 5,124 (50.1) | 16,298 (55.0) | 22,620 (42.3) | 127,521 (55.0) | 18,344 (44.3) | 43,113 (54.3) | 58,974 (49.3) | 141,083 (56.7) |
| High (> 199,068) | 381,531 (46.8) | 5,101 (49.9) | 13,349 (45.0) | 30,917 (57.7) | 104,341 (45.0) | 23,092 (55.7) | 36,249 (45.7) | 60,601 (50.7) | 107,881 (43.3) |
| MUA, N (%)g | |||||||||
| Not MUA | 488,156 (59.9) | 7,370 (72.1) | 22,102 (74.6) | 26,180 (48.9) | 117,661 (50.7) | 19,314 (46.6) | 417,38 (52.6) | 72,076 (60.3) | 181,715 (73.0) |
| MUA | 326,452 (40.1) | 2,855 (27.9) | 7,545 (25.4) | 27,357 (51.1) | 114,201 (49.3) | 22,122 (53.4) | 37,624 (47.4) | 47,499 (39.7) | 672,49 (27.0) |
| Urbanicity, N (%)h | |||||||||
| High-density urban | 467,378 (57.4) | 7,077 (69.2) | 24,145 (81.4) | 32,037 (59.8) | 142,227 (61.3) | 23,128 (55.8) | 62,241 (78.4) | 50,986 (42.6) | 125,537 (50.4) |
| Suburban | 301,806 (37.0) | 2,852 (27.9) | 52,56 (17.7) | 18,596 (34.7) | 78,531 (33.9) | 15,874 (38.3) | 16,067 (20.2) | 57,749 (48.3) | 106,881 (42.9) |
| Rural | 14,291 (1.8) | 153 (1.5) | 140 (0.5) | 980 (1.8) | 2,218 (1.0) | 951 (2.3) | 530 (0.7) | 3,630 (3.0) | 5,689 (2.3) |
| Small town | 31,133 (3.8) | 143 (1.4) | 106 (0.4) | 1,924 (3.6) | 8,886 (3.8) | 1,483 (3.6) | 524 (0.7) | 7,210 (6.0) | 10,857 (4.4) |
Abbreviations: BMI = body mass index; CHF = congestive heart failure; COPD = chronic obstructive pulmonary disease; MUA = medically underserved areas; SD = standard deviation.
PM2.5 obtained from the Centers for Disease Control and Prevention. National Environmental Public Health Tracking Network; low ≤ 9 μg/m3, and high > 9 μg/m3 concentrations per US EPA cutoffs.
Neighborhood-level factors were extracted from the American Community Survey (ACS) 5-year estimates for every 5 years.
Segregation levels are calculated based on Iceland’s Multigroup Entropy Index, using patients’ 5-digit ZIP code as a proxy for neighborhoods. Tertiles of neighborhood segregation scores were used to identify high-, medium, and low-segregation neighborhoods.
Neighborhood deprivation scores (census tract level) were obtained from the “ndi” package in R, and averaged at the ZIP code level using population weights. Tertiles of neighborhood deprivation scores were used to identify high-, medium-, and low-deprivation neighborhoods.
National Neighborhood Data Archive (NaNDA): Parks by ZIP Code Tabulation Area, United States, 2018. Ann Arbor, MI: Inter-university Consortium for Political and Social Research [distributor], December 7, 2020. https://doi.org/10.3886/E119803V1.
National Neighborhood Data Archive (NaNDA): Traffic Volume by ZIP Code Tabulation Area, United States, 1963-2019. Ann Arbor, MI: Inter-university Consortium for Political and Social Research [distributor], January 20, 2022. https://doi.org/10.3886/E160261V1.
From the Health Resources & Services Administration (HRSA); https://data.hrsa.gov/data/download.
This classification modified the original 2010 Rural-Urban Commuting Area Codes (RUCA) Codes defined by the United States Department of Agriculture (USDA).
We identified 6,199 residential neighborhoods, of which 96% had ≥ 11 patients with kidney failure residing in them. Among Black, Hispanic, and White patients, those exposed to high PM2.5 were more likely to be female and less likely to have received pre-kidney failure nephrology care compared with those exposed to low PM2.5 (Table 1).
PM2.5 and Mortality by Race and Ethnicity
The unadjusted 5-year cumulative incidence of mortality was higher for those exposed to high PM2.5 for all racial and ethnic groups except for Hispanic patients (Fig 1A-D): Asian (high, 57.7%; low, 51.3%; PLog-rank < 0.001), Black (high, 54.8%; low, 49.2%; PLog-rank < 0.001), and White (high, 75.3%; low, 71.9%; PLog-rank < 0.001).
Figure 1.
Unadjusted cumulative incidence of mortality stratified by residential neighborhood PM2.5 levels and race and ethnicity ([A] Asian, [B] Black, [C] Hispanic, [D] White] among patients with kidney failure (age ≥ 18 years) initiating dialysis (2003-2019).
After adjustment, the strength of the association between PM2.5 and mortality among patients with kidney failure differed by race and ethnicity (Pinteraction < 0.001). Among Asian (adjusted hazard ratio [aHR], 1.16; 95% confidence interval [CI]; 1.11-1.21); Black (aHR, 1.22; 95% CI, 1.20-1.24); Hispanic (aHR, 1.02; 95% CI, 1.00-1.04); and White (aHR, 1.12; 95% CI, 1.11-1.14) patients, exposure to high PM2.5 was associated with increased mortality risk compared with individuals of the same racial and ethnic group exposed to low PM2.5 (Table 2).
Table 2.
The Role of Race and Ethnicity and Neighborhood Characteristics in Modifying the Association Between Residential Neighborhood PM2.5 and Mortality Among Patients With Kidney Failure (Aged ≥ 18 Years) Initiating Dialysis (2003-2019; N = 814,608)
| Characteristic | Adjusted hazard ratio (aHR) (95% confidence interval) of Mortality |
|
|---|---|---|
| Low PM2.5 | High PM2.5 | |
| Race and ethnicitya | ||
| Asian | Reference | 1.16 (1.11-1.21) |
| Black | Reference | 1.22 (1.20-1.24) |
| Hispanic | Reference | 1.02 (1.00-1.04) |
| White | Reference | 1.12 (1.11-1.14) |
| P-value for interactionh | < 0.001 | |
| Segregation Levelb | ||
| Low | Reference | 1.10 (1.09-1.12) |
| Medium | Reference | 1.13 (1.12-1.15) |
| High | Reference | 1.17 (1.15-1.19) |
| P-value for interactionh | <0.001 | |
| NDIc | ||
| Low | Reference | 1.11 (1.09-1.12) |
| Medium | Reference | 1.12 (1.10-1.13) |
| High | Reference | 1.17 (1.15-1.19) |
| P-value for interactionh | <0.001 | |
| Number of Parksd | ||
| 1-11 | Reference | 1.13 (1.12-1.15) |
| ≥ 12 | Reference | 1.13 (1.11-1.14) |
| P-value for interactionh | 0.58 | |
| Daily vehicle traffice | ||
| Low (≤ 199,068) | Reference | 1.10 (1.09-1.12) |
| High (>199,068) | Reference | 1.13 (1.11-1.14) |
| P-value for interactionh | 0.002 | |
| MUAf | ||
| Not MUA | Reference | 1.12 (1.11-1.13) |
| MUA | Reference | 1.15 (1.13-1.16) |
| P-value for interactionh | 0.005 | |
| Urbanicityg | ||
| High-density urban | Reference | 1.14 (1.12-1.15) |
| Suburban | Reference | 1.12 (1.10-1.13) |
| Rural | Reference | 1.20 (1.14-1.26) |
| Small town | Reference | 1.04 (1.00-1.07) |
| P-value for interactionh | < 0.001 | |
Abbreviations: MUA = medically underserved areas; NDI = neighborhood deprivation index. Statistically significant associations (P < 0.05) are in bold.
Multilevel Cox models with state-level shared frailty. All models adjusted for age, sex, cause of kidney failure, employment status, body mass index (BMI), nephrology care, comorbidities (cancer, hypertension, diabetes, peripheral vascular disease, atherosclerotic heart disease, congestive heart failure, chronic obstructive pulmonary disease, drug use, alcohol use, tobacco use), functional status, and neighborhood factors (education and income). Neighborhood factors were excluded from models with NDI. Models included a clustering term at the patient’s state of residence.
PM2.5 obtained from the Centers for Disease Control and Prevention. National Environmental Public Health Tracking Network; low = ≤ 9 μg/m3, and high > 9 μg/m3 concentrations.
Race and ethnicity: non-Hispanic White, non-Hispanic Black, Hispanic, and non-Hispanic Asian (Asian American, Native Hawaiian, and Pacific Islander).
Segregation levels are calculated based on Iceland’s Multigroup Entropy Index, using patients’ 5-digit ZIP code as a proxy for neighborhoods. Tertiles of neighborhood segregation scores were used to identify high-, medium, and low-segregation neighborhoods.
Neighborhood deprivation scores (census tract level) were obtained from the “ndi” package in R, and averaged at the ZIP code level using population weights. Tertiles of neighborhood deprivation scores were used to identify high-, medium-, and low-deprivation neighborhoods.
National Neighborhood Data Archive (NaNDA): Parks by ZIP Code Tabulation Area, United States, 2018. Ann Arbor, MI: Inter-university Consortium for Political and Social Research [distributor], December 7, 2020. https://doi.org/10.3886/E119803V1.
National Neighborhood Data Archive (NaNDA): Traffic Volume by ZIP Code Tabulation Area, United States, 1963-2019. Ann Arbor, MI: Inter-university Consortium for Political and Social Research [distributor], January 20, 2022. https://doi.org/10.3886/E160261V1.
Health Resources & Services Administration (HRSA); https://data.hrsa.gov/data/download.
This classification modified the original 2010 Rural-Urban Commuting Area Codes (RUCA) Codes defined by the United States Department of Agriculture (USDA).
P-value for the interaction between PM2.5 and race and ethnicity; PM2.5 and segregation levels; PM2.5 and deprivation levels; PM2.5 and number of parks; PM2.5 and daily vehicle traffic; PM2.5 and MUA; PM2.5 and urbanicity.
Neighborhood Factors and the Association Between PM2.5 and Mortality
Residential racial and ethnic segregation
After adjustment, the strength of the association between PM2.5 and mortality among patients with kidney failure differed by segregation level (Pinteraction < 0.001; Table 2). Among patients with kidney failure residing in high-segregation neighborhoods, those exposed to high PM2.5 had a 1.17-fold increased mortality risk (95% CI, 1.15-1.19), compared with individuals of the same neighborhood segregation level exposed to low PM2.5. This association was strongest among those residing in high-segregation neighborhoods (Table 2).
NDI
After adjustment, the strength of the association between PM2.5 and mortality among patients with kidney failure differed by deprivation levels (Pinteraction < 0.001; Table 2). Among patients with kidney failure residing in high-deprivation neighborhoods, those exposed to high PM2.5 had a 1.17-fold increased mortality risk (95% CI, 1.15-1.19) compared with individuals of the same neighborhood deprivation level exposed to low PM2.5. This association was strongest among those residing in high-deprivation neighborhoods (Table 2).
Built Environment Factors
Parks and daily vehicle counts
The strength of the association between PM2.5 and mortality among patients with kidney failure did not differ by park quantity, but it did differ by traffic level (Pinteraction = 0.002; Table 2). Among patients with kidney failure residing in neighborhoods with heavy daily vehicle traffic, those exposed to high PM2.5 had a 1.13-fold increased mortality risk (95% CI, 1.11-1.14; Table 2) compared with those exposed to low PM2.5.
MUAs
The strength of the association between PM2.5 and mortality among patients with kidney failure differed by MUA designation (Pinteraction = 0.005). Among patients with kidney failure residing in MUAs, those exposed to high PM2.5 (compared with those exposed to low PM2.5) had a 1.15-fold increased mortality risk (95% CI, 1.13-1.16) compared with those exposed to low PM2.5. This association was strongest among those residing in MUAs (Table 2).
Urbanicity
The strength of the association between PM2.5 and mortality among patients with kidney failure differed by urbanicity (Pinteraction < 0.001). Among patients with kidney failure residing in HDU and rural neighborhoods, those exposed to high PM2.5 had a 1.14-fold (95% CI, 1.12-1.15) and 1.20-fold (95% CI, 1.14-1.26) increased mortality risk, respectively, compared with individuals of the same neighborhoods exposed to low PM2.5 (Table 2).
Role of Neighborhood Factors on Racial and Ethnic Differences in PM2.5 and Mortality
When stratified by race and ethnicity, the association between PM2.5 and mortality differed across racial and ethnic groups (Table 3). Particularly, among Black patients with kidney failure, those exposed to high PM2.5 had an increased risk of mortality when residing in neighborhoods characterized by high segregation (aHR, 1.25; 95% CI, 1.21-1.29; Pinteraction = 0.006), high deprivation (aHR, 1.26; 95% CI, 1.22-1.30; Pinteraction < 0.001), heavy daily traffic (aHR, 1.22; 95% CI, 1.18-1.26; Pinteraction = 0.02), MUAs (aHR, 1.22; 95% CI, 1.19-1.26; Pinteraction = 0.02), high density (aHR, 1.23; 95% CI, 1.20-1.26), and suburban neighborhoods (aHR, 1.17; 95% CI, 1.13-1.20; Pinteraction < 0.001) compared with individuals of the same neighborhoods exposed to low PM2.5. Similar associations between PM2.5 and mortality were observed among Asian patients residing in rural neighborhoods (aHR, 1.48; 95% CI, 1.00-2.21; Pinteraction = 0.19) and those in areas with fewer parks (aHR, 1.21; 95% CI, 1.12-1.30; Pinteraction = 0.04), as well as among Hispanic (aHR, 1.21; 95% CI, 1.01-1.45; Pinteraction = 0.007) and White patients (aHR, 1.13; 95% CI, 1.07-1.20; Pinteraction = 0.02) residing in rural neighborhoods compared with individuals of the same neighborhoods exposed to low PM2.5 (Table 3).
Table 3.
The Role of Residential Neighborhood Characteristics in Modifying the Association Between Residential Neighborhood PM2.5 and Mortality Among Patients With Kidney Failure (Aged ≥ 18 Years) Initiating Dialysis (2003-2019), Stratified by Race and Ethnicity (N = 814,608)
| Charcateristic | Adjusted hazard ratio (aHR) (95% confidence interval) of mortality |
|||||||
|---|---|---|---|---|---|---|---|---|
| Asian N = 39,872 |
Black N = 285,399 |
Hispanic N = 120,798 |
White N = 368,539 |
|||||
| PM2.5a | ||||||||
| Low | High | Low | High | Low | High | Low | High | |
| Segregation levelb | ||||||||
| Low | Reference | 1.08 (1.01-1.16) | Reference | 1.16 (1.12-1.20) | Reference | 0.99 (0.95-1.03) | Reference | 1.13 (1.11-1.14) |
| Medium | Reference | 1.18 (1.10-1.26) | Reference | 1.18 (1.15-1.22) | Reference | 1.08 (1.05-1.12) | Reference | 1.13 (1.11-1.15) |
| High | Reference | 1.20 (1.07-1.34) | Reference | 1.25 (1.21-1.29) | Reference | 1.03 (0.99-1.08) | Reference | 1.16 (1.13-1.19) |
| P-value for interactionh | 0.11 | 0.006 | 0.08 | 0.12 | ||||
| NDIc | ||||||||
| Low | Reference | 1.10 (1.04-1.17) | Reference | 1.18 (1.14-1.23) | Reference | 1.08 (1.03-1.13) | Reference | 1.11 (1.09-1.12) |
| Medium | Reference | 1.18 (1.09-1.27) | Reference | 1.13 (1.10-1.17) | Reference | 1.03 (0.99-1.07) | Reference | 1.14 (1.12-1.16) |
| High | Reference | 1.19 (1.06-1.33) | Reference | 1.26 (1.22-1.30) | Reference | 1.02 (0.99-1.05) | Reference | 1.20 (1.17-1.23) |
| P-value for interactionh | 0.19 | <0.001 | 0.16 | < 0.001 | ||||
| Number of Parksd | ||||||||
| 1-11 | Reference | 1.21 (1.12-1.30) | Reference | 1.19 (1.16-1.22) | Reference | 1.06 (1.03-1.10) | Reference | 1.13 (1.11-1.15) |
| ≥ 12 | Reference | 1.11 (1.04-1.17) | Reference | 1.20 (1.17-1.23) | Reference | 1.02 (0.99-1.05) | Reference | 1.14 (1.12-1.16) |
| P-value for interactionh | 0.04 | 0.55 | 0.07 | 0.52 | ||||
| Daily Vehicle Traffice | ||||||||
| Low (≤ 199,068) | Reference | 1.14 (1.06-1.22) | Reference | 1.17 (1.14-1.20) | Reference | 1.07 (1.04-1.11) | Reference | 1.12 (1.10-1.14) |
| High (> 199,068) | Reference | 1.12 (1.05-1.19) | Reference | 1.22 (1.18-1.26) | Reference | 0.98 (0.95-1.01) | Reference | 1.12 (1.10-1.14) |
| P-value for interactionh | 0.68 | 0.02 | <0.001 | 0.94 | ||||
| MUAf | ||||||||
| Not MUA | Reference | 1.14 (1.08-1.20) | Reference | 1.17 (1.14-1.20) | Reference | 1.06 (1.02-1.09) | Reference | 1.13 (1.11-1.15) |
| MUA | Reference | 1.16 (1.07-1.26) | Reference | 1.22 (1.19-1.26) | Reference | 1.02 (0.99-1.05) | Reference | 1.14 (1.12-1.16) |
| P-value for interactionh | 0.68 | 0.02 | 0.08 | 0.51 | ||||
| Urbanicityg | ||||||||
| High-density urban | Reference | 1.16 (1.10-1.23) | Reference | 1.23 (1.20-1.26) | Reference | 1.05 (1.01-1.08) | Reference | 1.15 (1.13-1.16) |
| Suburban | Reference | 1.10 (1.01-1.20) | Reference | 1.17 (1.13-1.20) | Reference | 1.03 (1.00-1.07) | Reference | 1.13 (1.12-1.15) |
| Rural | Reference | 1.48 (1.00-2.21) | Reference | 1.13 (0.99-1.29) | Reference | 1.21 (1.01-1.45) | Reference | 1.13 (1.07-1.20) |
| Small town | Reference | 0.88 (0.58-1.36) | Reference | 1.06 (0.97-1.15) | Reference | 0.81 (0.68-0.95) | Reference | 1.06 (1.02-1.11) |
| P-value for interactionh | 0.19 | < 0.001 | 0.007 | 0.02 | ||||
Abbreviations: MUA = medically underserved areas; NDI = neighborhood deprivation index. Statistically significant associations (P < 0.05) are in bold.
Multilevel Cox models with state-level shared frailty. All models adjusted for age, sex, cause of kidney failure, employment status, body mass index (BMI), nephrology care, comorbidities (cancer, hypertension, diabetes, peripheral vascular disease, atherosclerotic heart disease, congestive heart failure, chronic obstructive pulmonary disease, drug use, alcohol use, tobacco use), functional status, and neighborhood factors (education & income).). Neighborhood factors were excluded from models with NDI. Models included a clustering term at the patient’s state of residence.
PM2.5 obtained from the Centers for Disease Control and Prevention. National Environmental Public Health Tracking Network; low = ≤ 9 μg/m3, and high > 9 μg/m3 concentrations.
Segregation levels are calculated based on Iceland’s Multigroup Entropy Index, using patients’ 5-digit ZIP code as a proxy for neighborhoods. Tertiles of neighborhood segregation scores were used to identify high-, medium, and low-segregation neighborhoods.
Neighborhood deprivation scores (census tract level) were obtained from the “ndi” package in R, and averaged at the ZIP code level using population weights. Tertiles of neighborhood deprivation scores were used to identify high-, medium, and low-deprivation neighborhoods.
National Neighborhood Data Archive (NaNDA): Parks by ZIP Code Tabulation Area, United States, 2018. Ann Arbor, MI: Inter-university Consortium for Political and Social Research [distributor], December 7, 2020. https://doi.org/10.3886/E119803V1.
National Neighborhood Data Archive (NaNDA): Traffic Volume by ZIP Code Tabulation Area, United States, 1963-2019. Ann Arbor, MI: Inter-university Consortium for Political and Social Research [distributor], January 20, 2022. https://doi.org/10.3886/E160261V1.
Health Resources & Services Administration (HRSA); https://data.hrsa.gov/data/download.
This classification modified the original 2010 Rural-Urban Commuting Area Codes (RUCA) Codes defined by the United States Department of Agriculture (USDA).
P-value for the interaction between PM2.5 and segregation levels; PM2.5 and deprivation levels; PM2.5 and number of parks; PM2.5 and daily vehicle traffic; PM2.5 and MUA; PM2.5 and urbanicity.
Sensitivity Analysis
Our findings were robust to the following sensitivity analyses: (1) using Cox proportional hazards models without shared state-level frailty (Tables S1, 2); (2) restricting the cohort to individuals aged > 66 years (Tables S3, 4); (3) adjusting for urbanicity (Table S5); (4) defining high PM2.5 using the previous EPA threshold (Tables S6, 7); and (5) examining whether residence in MUAs, suburban, rural, and small town areas was associated with increased mortality risk when exposed to low PM2.5 levels (Table S8).
Discussion
In this national study involving 814,608 patients with kidney failure, exposure to higher PM2.5 was associated with an increased mortality risk among those residing in neighborhoods characterized by high segregation (1.17-fold), high deprivation (1.17-fold), MUA designation (1.15-fold), and HDU areas (1.14-fold), compared with those exposed to lower PM2.5 levels. There was a differential impact of PM2.5 exposure by race and ethnicity, where Black patients exposed to high (vs low) PM2.5 experienced the greatest mortality risk when residing in neighborhoods characterized by high segregation (1.25-fold), high deprivation (1.26-fold), neighborhoods characterized as MUAs (1.22-fold), and HDU areas (1.23-fold).
Our findings of increased mortality risk among residents of high-segregation neighborhoods exposed to high PM2.5 levels are consistent with prior research.11,56,57 Patients residing in these neighborhoods often experience elevated PM2.5 exposure,58,59 which contributes to increased mortality risk.60,61 This association could be attributed to the upstream causes of segregation, including discriminatory zoning and redlining,62 which creates an uneven distribution of resources and the formation of neighborhoods characterized by poor social conditions,62 including a high concentration of polluting industries.61 Additionally, living near major roads or areas with heavy vehicle traffic can reduce air quality because of increased vehicle emissions.27 Long-term exposure to vehicle emissions has been associated with higher rates of emergency visits, hospital admissions, and increased mortality in the literature.27 However, built environments with more green spaces, such as a higher number of parks, have been linked to a reduced mortality risk associated with exposure to high levels of PM2.5.26 In our study, we observed this association between heavy vehicle traffic and mortality, but not with the number of parks. This could be attributed to other unexplored factors at play, such as the synergistic impact of green spaces with neighborhood urbanicity, which was beyond the scope of our study to test.
Moreover, it is well established that residing in MUAs is associated with inadequate health care resources,29 and a limited availability of qualified health care providers and facilities.63 However, prior research has highlighted the role of urbanization in mitigating the adverse effects of elevated PM2.5 by improving the quality and accessibility of health services and increasing awareness of healthy lifestyles.64 Therefore, it is plausible that the observed association between increased PM2.5 levels and mortality in MUA neighborhoods could be, in part, driven by rurality. Rurality may impede access to and utilization of health care services, which is associated with poorer health outcomes and increased mortality.65,66 Interestingly, we also found that among patients with kidney failure, particularly Black patients, the mortality risk was higher among those exposed to high PM2.5 and residing in high-density or suburban areas compared with those exposed to low PM2.5. This could be because of increasing environmental risk factors or behavioral changes with increasing urbanization, independent of health care access, which may also amplify the deleterious effects of PM2.5 on mortality.64 However, further research is required to disentangle the role of health care access and environmental risk factors by means of neighborhood urbanicity.
Additionally, when stratified by race and ethnicity, there was a differential impact such that Black patients exposed to high levels of PM2.5 experienced increased mortality, especially in neighborhoods characterized by high segregation, high deprivation, and poor built environments. Historically, segregation has perpetuated racial hierarchies and exclusions,17 particularly affecting Black populations.5 Prior studies noted that high-segregation neighborhoods that are predominantly Black had a higher concentration of polluting industries,67 which may contribute to increased mortality risk. Additionally, Black patients residing in deprived neighborhoods are often exposed to a range of socioeconomic stressors,68,69 which, compounded by exposure to elevated PM2.5,70 can lead to adverse health conditions,71, 72, 73 affecting psychosocial well-being, quality of life, and mortality.74 We observed similar associations between exposure to high PM2.5 and increased mortality among Asian and White patients, possibly because of reasons similar to those affecting Black patients.
Surprisingly, we found no associations between high PM2.5 exposure and increased mortality among Hispanic patients, except in HDU, suburban, and rural neighborhoods. Moreover, increasing levels of neighborhood deprivation were associated with increased mortality among Asian, Black, and White patients exposed to high PM2.5, which was not observed for Hispanic patients. The Hispanic population is highly heterogeneous (eg, US-born vs foreign-born),75 which may also contribute to variation in observed effects. The results could also reflect the “Hispanic paradox,”76 potentially driven by underreporting of comorbid conditions and the healthy migrant effect.76 A previous study has shown that foreign-born Mexican Americans have a lower risk of mortality compared with US-born non-Hispanic White individuals.77 However, more research is warranted to better understand these associations.
Ultimately, addressing the racial and ethnic differences in the impact of PM2.5 on mortality among patients with kidney failure may require multifaceted interventions and environmental policies. At the national level, efforts should focus on greater investment in segregated neighborhoods, improving the built environment (including green spaces and health care access),26,29 and reducing vehicle traffic.27 At the clinician level, this involves closely monitoring patients from high-risk neighborhoods to mitigate PM2.5-related mortality. Clinicians concerned about their patients’ exposure to air pollution might consider implementing air pollution screening tools to assess indoor and outdoor exposure levels and provide targeted interventions.78 These could include home air pollution monitors, air purifiers, upgraded ventilation systems, regular mask usage, provision of educational materials,63,79 and forming partnerships with local community organizations and policymakers to reduce the observed racial and ethnic differences in mortality.79 Additionally, increasing access to primary health care providers in MUAs and maintaining engagement with current providers may help reduce mortality risk even in areas with high PM2.5 levels.80
Our study has several notable strengths, including a large cohort using national registry data spanning over 17 years to quantify the association between PM2.5 and mortality with linkage to neighborhood characteristics. However, our study must be considered in light of its limitations. First, we used residential ZIP codes as proxies for neighborhoods because of data availability. Despite the possibility of spatial misclassification and systematic biases,78 ZIP codes are frequently used to define residential neighborhoods.81,82 Second, we relied on outdoor PM2.5 measurements, which may not capture the total PM2.5 exposure experienced by patients from other sources, such as smoking, cooking, and workplace environments. Nevertheless, outdoor PM2.5 remains a major contributor to overall exposure.83 Third, we only considered PM2.5 and various neighborhood characteristics at the initiation of dialysis and assumed them to remain constant over time. However, this assumption could be challenged if patients relocated to new neighborhoods with differing PM2.5 levels and neighborhood characteristics.
In conclusion, we found that high PM2.5 exposure was associated with an increased mortality risk in neighborhoods characterized by high segregation, high socioeconomic deprivation, and those that are medically underserved and HDU areas. These associations were observed among Asian, Hispanic, and White patients, but were most prominent among Black patients. Clinicians should consider closer monitoring of patients residing in these high-risk neighborhoods to reduce PM2.5-related mortality risk, particularly among Black patients with kidney failure.
Article Information
Authors’ Full Names and Academic Degrees
Yiting Li, MPH, Gayathri Menon, MHS, Jane J. Long, MD, Malika Wilson, MD, MBA, Byoungjun Kim, PhD, Mario P. DeMarco, MD, MPH, Babak J. Orandi MD, PhD, MSc, Sunjae Bae MD, PhD, Wenbo Wu PhD, Yijing Feng, MHS, Terry Gordon, PhD, George D. Thurston, ScD, Dorry L. Segev MD, PhD, and Mara A. McAdams-DeMarco, PhD
Authors’ Contributions
Concept and design: MMD, YL; acquisition, analysis, and interpretation of data: MMD, YL, GH, JL, BK, MMD, BO, SB, WW, TG, GT; statistical analysis: LY; obtained funding: MMD, DS; administrative, technical, or material support: LY, GM; supervision: MDM, DS. Each author made significant intellectual contributions to the drafting or revision of the manuscript and takes responsibility for the work as a whole, ensuring that any questions regarding the accuracy or integrity of any part of the work are thoroughly investigated and resolved.
Support
None.
Financial Disclosure
The authors declare that they have no relevant financial interests.
Disclaimer
The data reported here have been supplied by the United States Renal Data System (USRDS). The interpretation and reporting of these data are the responsibility of the author(s) and in no way should be seen as an official policy or interpretation of the US government.
Data Sharing
The datasets used and/or analyzed during the current study are available from the United States Renal Data System (USRDS) upon Data Use Agreement (DUA) approval. Per the DUA between the authors and USRDS, the rerelease of the data or the deposition of data into publicly available repositories or to individuals is not allowed.
Peer Review
Received December 21, 2024. Evaluated by 1 external peer reviewer, with direct editorial input from an Associate Editor and the Editor-in-Chief. Accepted in revised form July 14, 2025.
Footnotes
Complete author and article information provided before references.
Item S1. Calculations: Racial and Ethnic Segregation Score Models Based on Iceland’s Entropy Approach
Table S1. Cox Proportional Hazards Model—without Shared State-Level Frailty.
The role of race and ethnicity and neighborhood characteristics in modifying the association between residential neighborhood PM2.5 and mortality among patients with kidney failure (aged ≥ 18 years) initiating dialysis (2003-2019; N = 814,608)
Table S2: Cox Proportional Hazards Model—Without Shared State-Level Frailty.
The role of residential neighborhood characteristics in modifying the association between residential neighborhood PM2.5 and mortality among patients with kidney failure (aged ≥18) initiating dialysis (2003-2019; N = 814,608)
Table S3: Sensitivity Analysis—Aged > 66 years.
The role of race and ethnicity and neighborhood characteristics in modifying the association between residential neighborhood PM2.5 and mortality among patients with kidney failure (aged > 66 years) initiating dialysis (2003-2019; N = 345,718)
Table S4: Sensitivity Analysis—Aged >66 years.
The role of residential neighborhood characteristics in modifying the association between residential neighborhood PM2.5 and mortality among patients with kidney failure (aged > 66 years) initiating dialysis (2003-2019; N = 345,718)
Table S5: Sensitivity Analysis—Adjusting for Urbanicity.
The role of residential neighborhood characteristics in modifying the association between residential neighborhood PM2.5 and mortality among patients with kidney failure (aged ≥ 18 years) initiating dialysis (2003-2019; N = 814,608)
Table S6: Sensitivity Analysis—Previous Environmental Protection Agency (EPA) Cutoff for High PM2.5 > 12 μg/m3.
The role of race and ethnicity and neighborhood characteristics in modifying the association between residential neighborhood PM2.5 and mortality among patients with kidney failure (aged ≥18 years) initiating dialysis (2003-2019; N = 814,608)
Table S7: Sensitivity Analysis—Previous Environmental Protection Agency (EPA) Cutoff for high PM2.5 > 12 μg/m3.
The role of residential neighborhood characteristics in modifying the association between residential neighborhood PM2.5 and mortality among patients with kidney failure (aged ≥ 18 years) initiating dialysis (2003-2019; N = 814,608)
Table S8: Cox Proportional Hazards Model—Low PM2.5 Neighborhoods.
The role of residential neighborhood characteristics in modifying the association between residential neighborhood low PM2.5 and mortality among patients with kidney failure (aged ≥ 18 years) initiating dialysis (2003-2019; N = 224,773)
Supplementary Materials
/Item S1, Tables S1-S8.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
/Item S1, Tables S1-S8.

