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    Chapter 13.6

    Air pollution and the vote

    Tracts with more diesel exposure voted more Democratic in 2020, by 24.8 points per standard deviation of exposure, but only 4.9 points once race, income, education and density are held fixed.

    DraftFigures and numbers may change as the analysis is rebuilt.what is still being checked

    Still being checked: the release years of the deprivation and asthma values and of the American Community Survey values in the tract atlas, and which archived copy of EJScreen version 2.3 the atlas was built from. The atlas file records none of them.

    The tenth of census tractsCensus tractA Census Bureau neighborhood area, usually home to between 1,200 and 8,000 people. Tract boundaries were redrawn after the 2010 census and again after 2020. with the most diesel exhaust in the air had a Democratic two-party margin of +49.1 (95% CI 42.4 to 55.8)+49.1 percentage points of Democratic two-party marginEstimandvote-weighted mean tract margin; 95% interval clustered by countyInterval95% CI 42.4 to 55.8n8,114Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts in decile 10 of diesel exposurePeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies pointsPercentage pointThe unit for the difference between two percentages. A change from one share to another is stated in points, not in percent, so that absolute and relative change are not confused. in the 2020 presidential election, against −29.8 (95% CI −32.2 to −27.4)−29.8 percentage points of Democratic two-party marginEstimandvote-weighted mean tract margin; 95% interval clustered by countyInterval95% CI −32.2 to −27.4n8,114Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts in decile 1 of diesel exposurePeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies points in the tenth with the least, a gap of 78.978.9 percentage points of Democratic two-party marginEstimanddifference in vote-weighted mean margin, top decile minus bottom decile; 95% interval clustered by countyInterval95% CI 71.8 to 86.1n16,228Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts in the top and bottom decile of diesel exposurePeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies points. The margin difference per standard deviationStandard deviationA measure of how far values typically fall from their average. A larger standard deviation means the values are more spread out. of diesel exposure shrinks when tracts are compared on who lives in them: 42% (95% CI 36% to 48%)42% percent of the no-controls diesel coefficientEstimandratio of the diesel coefficient with race, income and education held fixed to the diesel coefficient with no controls (ratio of point estimates); 95% interval from a county bootstrap (2,000 replicates)Interval95% CI 36% to 48%n81,134Weightsnone (ratio of estimates)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies of the no-controls coefficient remains with race, income and education held fixed, and 20% (95% CI 12% to 27%)20% percent of the no-controls diesel coefficientEstimandratio of the diesel coefficient with race, income, education and density held fixed to the diesel coefficient with no controls (ratio of point estimates); 95% interval from a county bootstrap (2,000 replicates)Interval95% CI 12% to 27%n81,134Weightsnone (ratio of estimates)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies once population density is added. The four air measures in the chapter move together, so the data cannot say which one carries the difference that remains. The chapter also compares neighborhood deprivation, modeled asthma prevalence and survey support for EPA enforcement. The asthma figures are modeled estimates and not measured health outcomes, a distinction that the section on asthma explains.

    The margin is the Democratic vote minus the Republican vote as a share of the two, so a positive value is a Democratic lead. The votes come from precinct returns that a land-cover model allocated to 2020 census tracts [1], so each tract's margin is an estimate and not a count. Pollution comes from EJSCREENEJSCREENThe Environmental Protection Agency's environmental justice screening tool. It combines pollution and hazard measures, such as fine particles and diesel exhaust, with the demographics of each neighborhood.. Diesel exposure is its modeled annual average concentration of diesel particulate matter in the tract's air, in micrograms per cubic meter, and the other measures are modeled annual averages of fine particles and nitrogen dioxide and a traffic proximity score (vehicles per day on nearby major roads, weighted by distance).The EPA removed EJSCREEN from its website in February 2025. Public Environmental Data Partners hosts a reconstruction of version 2.32.3 EJScreen version numberEstimandversion of the tool, identified from the indicators and values in the atlasWeightsnone (identifier)Populationthe EPA EJScreen release identified in the tract atlasPeriodreleased July 2024SourceEJScreen, released in July 2024 with air data modeled for 2020 [2]. Of the 82,76582,765 census tractsEstimandcount of tractsWeightsnone (count)Populationtracts in the 2020 tract atlasPeriod2020 presidential electionSourcePrecinct votes on census geographies tracts in the atlas, 81,61781,617 census tractsEstimandcount of tractsWeightsnone (count)Populationtracts in the atlas with more than 100 estimated votesPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies have more than 100100 votesEstimanda tract is kept when its estimated presidential votes exceed this numberWeightsnone (constant)Populationcensus tractsPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies estimated votes, and 81,13481,134 census tractsEstimandcount of tractsWeightsnone (count)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies of those have every pollution measure, control and land area that the models need. They lie in 4747 statesEstimandcount of statesWeightsnone (count)Populationstates with at least one tract in the samplePeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies states and carry 155.1 million155.1 million votesEstimandsum of tract presidential votes in the sampleWeightsnone (sum of votes)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies votes, and each tract counts in proportion to its votes. The unit is a neighborhood, and the last section returns to what that allows.

    The margin rises with diesel exposure

    Figure 1 sorts the tracts into ten equal groups by diesel exposure and shows the margin in each, with each row labeled by its decile and median exposure. The point estimates rise with each step. The deciles below the fifth lean Republican and the deciles above it lean Democratic, and the fifth decile, with a median exposure of 0.140.14 micrograms per cubic meter of diesel particulate matterEstimandmedian across tracts in the decilen8,113Weightsnone (each tract counts once)Populationcensus tracts in decile 5 of diesel exposurePeriodEJScreen 2.3, 2020 modeled air dataSourceEJScreen micrograms per cubic meter of diesel particulate matter, is an even split within its interval (+1.4 (95% CI −1.8 to 4.7)+1.4 percentage points of Democratic two-party marginEstimandvote-weighted mean tract margin; 95% interval clustered by countyInterval95% CI −1.8 to 4.7n8,113Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts in decile 5 of diesel exposurePeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies points). The intervals are widest in the top two deciles. The tenth-decile tracts sit in 112112 countiesEstimandcount of counties with at least one tract in the decileWeightsnone (count)Populationcensus tracts in decile 10 of diesel exposurePeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies counties, against 1,8241,824 countiesEstimandcount of counties with at least one tract in the decileWeightsnone (count)Populationcensus tracts in decile 1 of diesel exposurePeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies counties for the first decile, and the intervals allow for tracts in one county resembling each other.

    Figure 1

    The Democratic margin rises from −29.8 points in the tenth of tracts with the least diesel exposure to +49.1 points in the tenth with the most

    Democratic minus Republican share of the two-party 2020 presidential vote, percentage points; vote-weighted mean by decile of tract diesel particulate exposure, each row labeled with the decile and its median exposure in micrograms per cubic meter; 95% intervals clustered by county

    Show data
    Data for The Democratic margin rises from −29.8 points in the tenth of tracts with the least diesel exposure to +49.1 points in the tenth with the most
    conf_highconf_lowdeciledecile_labeldiesel_medianmarginn
    −27.42−32.2311 (0.04 µg/m³)0.042−29.828,114
    −26.24−31.3122 (0.07)0.068−28.788,113
    −19.39−24.1833 (0.09)0.092−21.788,113
    −7.48−13.2544 (0.12)0.118−10.368,114
    4.68−1.8355 (0.14)0.1441.428,113
    12.456.1566 (0.17)0.1719.308,113
    21.7314.9977 (0.20)0.20318.368,114
    30.0722.6288 (0.24)0.24426.348,113
    40.1128.2499 (0.31)0.31134.188,113
    55.8442.391010 (0.48)0.47749.128,114
    The margin rises with each step from the tenth of tracts with the least diesel exposure to the tenth with the most, and the interval of the fifth decile includes zero. Dots are vote-weighted mean margins and whiskers are 95% intervals that allow tracts in one county to resemble each other.Note: Deciles of diesel exposure hold equal numbers of tracts; ties are broken by census tract code.Note: Tracts with 100 or fewer votes are left out. Intervals treat counties as the units that vary. They do not include error in the allocation of precinct votes to tracts or in the modeled pollution values.Source: Precinct votes allocated to census tracts (Fekrazad 2025), 2020 presidential election; EPA EJScreen version 2.3 (2024 release, 2020 air data); American Community Survey tract data (vintage not recorded in the atlas); vote-weighted, full counts of tracts, no sampling weights

    The tenth decile differs from the first in more than the air (Figure 2). The white-alone share of residents is 36%36% percent (share of residents who are white alone)Estimandvote-weighted mean of the tract share of residents who are white alonen8,114Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts in decile 10 of diesel exposurePeriod2020 votes; ACS tract sharesSourcePrecinct votes on census geographies in the tenth decile against 79%79% percent (share of residents who are white alone)Estimandvote-weighted mean of the tract share of residents who are white alonen8,114Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts in decile 1 of diesel exposurePeriod2020 votes; ACS tract sharesSourcePrecinct votes on census geographies in the first, the Hispanic share is 33%33% percent (share of residents who are Hispanic)Estimandvote-weighted mean of the tract share of residents who are Hispanicn8,114Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts in decile 10 of diesel exposurePeriod2020 votes; ACS tract sharesSourcePrecinct votes on census geographies against 9%9% percent (share of residents who are Hispanic)Estimandvote-weighted mean of the tract share of residents who are Hispanicn8,114Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts in decile 1 of diesel exposurePeriod2020 votes; ACS tract sharesSourcePrecinct votes on census geographies, and the median tract holds 5,1675,167 people per square kilometerEstimandmedian across tracts in the decilen8,114Weightsnone (each tract counts once)Populationcensus tracts in decile 10 of diesel exposurePeriod2020 votes; ACS tract population and land areaSourcePrecinct votes on census geographies people per square kilometer against 1414 people per square kilometerEstimandmedian across tracts in the decilen8,114Weightsnone (each tract counts once)Populationcensus tracts in decile 1 of diesel exposurePeriod2020 votes; ACS tract population and land areaSourcePrecinct votes on census geographies. Income peaks in decile 66 decile of diesel exposureEstimanddecile with the highest vote-weighted mean tract incomeWeightsnone (identifier)Populationcensus tractsPeriod2020 votes; ACS tract incomesSourcePrecinct votes on census geographies and the college share is nearly flat from there. Diesel exposure moves with density, and across tracts the correlation of exposure with the log of density is +0.68 (95% CI 0.66 to 0.71)+0.68 correlation coefficient, from −1 to +1Estimandvote-weighted correlation across tracts of diesel exposure with log population density; 95% interval from a county bootstrap (2,000 replicates)Interval95% CI 0.66 to 0.71n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriodEJScreen 2.3, 2020 modeled air data; ACS populationSourceEJScreen. Holding these traits fixed means comparing tracts that resemble each other on them.

    The Area Deprivation IndexArea Deprivation IndexA ranking of neighborhoods built from income, education, employment and housing measures in the American Community Survey. Higher ranks mean more deprived neighborhoods. ranks neighborhoods from the least to the most deprived [3], and its mean national rank falls from 62.5 (95% CI 60.9 to 64.2)62.5 Area Deprivation Index national rank (1 = least deprived, 100 = most deprived)Estimandvote-weighted mean rank; 95% interval clustered by countyInterval95% CI 60.9 to 64.2n8,076Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts in decile 1 of diesel exposure with an ADI rankPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourceArea Deprivation Index in the first decile of diesel exposure to 22.2 (95% CI 16.2 to 28.2)22.2 Area Deprivation Index national rank (1 = least deprived, 100 = most deprived)Estimandvote-weighted mean rank; 95% interval clustered by countyInterval95% CI 16.2 to 28.2n8,073Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts in decile 10 of diesel exposure with an ADI rankPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourceArea Deprivation Index in the tenth, against 44.8 (95% CI 42.2 to 47.4)44.8 Area Deprivation Index national rank (1 = least deprived, 100 = most deprived)Estimandvote-weighted mean rank; 95% interval clustered by countyInterval95% CI 42.2 to 47.4n80,849Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationall sample tracts with an ADI rankPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourceArea Deprivation Index for all tracts weighted by votes. The index is built from income, education, employment and housing measures, so it overlaps with the controls in the vote models. Chapter 13.3, Deprivation and mobility (planned) asks how deprivation itself relates to the vote, and Chapter 13.1, Measures of hardship compared sets several hardship measures side by side.

    Figure 2

    Higher-diesel tracts are denser, less white and more Hispanic, and income peaks at decile 6 while college share stays nearly flat after it

    Characteristics of the tracts in each decile of diesel particulate exposure (8,113 or 8,114 tracts per decile): shares of residents (percent), income (dollars) and deprivation rank averaged by votes, density and exposure as medians

    Decile of diesel exposureDiesel PM, median (µg/m³)Democratic margin (points)White alone (%)Black alone (%)Hispanic (%)College degree (%)Median household incomeDeprivation rank (100 = most)People per km², median
    1 (least)0.04−29.8795925$70k62.514
    20.07−28.8787928$78k59.144
    30.09−21.87771032$87k52.2152
    40.12−10.47281136$95k47.1427
    50.14+1.467111340$98k45.0821
    60.17+9.362131541$102k42.71,080
    70.20+18.457141742$101k41.41,394
    80.24+26.353151942$100k39.41,669
    90.31+34.247142542$98k34.42,354
    10 (most)0.48+49.136133342$97k22.25,167
    Show data
    Data for Higher-diesel tracts are denser, less white and more Hispanic, and income peaks at decile 6 while college share stays nearly flat after it
    adiblackcollegedecile_labeldensity_mediandiesel_medianhispanicincomemarginnwhite
    62.535.3525.501 (least)13.950.0429.3969.75−29.828,11478.60
    59.127.1027.58244.190.0688.8978.14−28.788,11378.46
    52.197.0332.123152.30.09210.0587.46−21.788,11376.60
    47.108.3836.504426.80.11811.0894.75−10.368,11472.38
    45.0310.7239.565821.20.14412.8898.501.428,11366.65
    42.6612.7541.4961079.70.17114.56102.19.308,11361.82
    41.4013.5141.9371394.10.20317.16100.618.368,11456.66
    39.3815.1842.4081669.10.24418.6999.8526.348,11352.93
    34.4414.4642.2092354.40.31124.5197.5634.188,11347.12
    22.2112.7542.0710 (most)5167.40.47733.4396.6249.128,11435.99
    Density and the Democratic margin rise and the white share falls from each decile to the next, while income peaks in decile 6 and the college share changes little after it. Each row is a decile of tracts by diesel exposure; shares, income and deprivation rank are vote-weighted means of tract values, and density and exposure are medians.Note: Deciles of diesel exposure hold equal numbers of tracts; ties are broken by census tract code.Note: Shares, incomes and ranks are means of tract values weighted by votes. They describe the tracts in each decile, so the table shows no interval.Note: The atlas labels the white share as white alone. Together the white, Black and Hispanic shares never exceed a tract's whole population, so the white share appears to leave out Hispanic residents, but the atlas file does not say so.Note: The Area Deprivation Index has no rank for a small number of tracts, which are left out of that column.Source: Precinct votes allocated to census tracts (Fekrazad 2025), 2020 presidential election; EPA EJScreen version 2.3 (2024 release, 2020 air data); American Community Survey tract data (vintage not recorded in the atlas); vote-weighted, full counts of tracts, no sampling weights; Area Deprivation Index national rank (Neighborhood Atlas; release year not recorded in the atlas file)

    Controls shrink every gap, and fine particles end near zero

    Figure 3 regresses the tract margin on each exposure. Each exposure is standardized, so a coefficient is the difference in the margin, in points, between tracts one standard deviation apart in exposure. One standard deviation of diesel exposure is 0.140.14 micrograms per cubic meter of diesel particulate matterEstimandstandard deviation across tracts (unweighted)Weightsnone (each tract counts once)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriodEJScreen 2.3, 2020 modeled air dataSourceEJScreen micrograms per cubic meter. For the other exposures it is 3.53.5 parts per billion of nitrogen dioxideEstimandstandard deviation across tracts (unweighted)Weightsnone (each tract counts once)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriodEJScreen 2.3, 2020 modeled air dataSourceEJScreen parts per billion of nitrogen dioxide, 2.12.1 micrograms per cubic meter of fine particlesEstimandstandard deviation across tracts (unweighted)Weightsnone (each tract counts once)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriodEJScreen 2.3, 2020 modeled air dataSourceEJScreen micrograms per cubic meter of fine particles and 2.4 million2.4 million traffic proximity score (annual average daily traffic on major roads divided by distance)Estimandstandard deviation across tracts (unweighted)Weightsnone (each tract counts once)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriodEJScreen 2.3, 2020 highway countsSourceEJScreen on the traffic proximity score. Tracts count in proportion to their votes, and the intervals are clustered by countyClustered standard errorsStandard errors that allow answers within the same group, such as the same county or the same week, to be related. They are wider than ordinary errors when members of a group resemble each other., so they allow tracts in one county to resemble each other.

    The diesel coefficient is 24.8 (95% CI 21.5 to 28.0)24.8 percentage points of Democratic two-party margin per standard deviation of the exposureEstimandweighted least squares coefficient on the standardized diesel particulate matter exposure, with no controls; 95% interval clustered by countyInterval95% CI 21.5 to 28.0n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies points with no controls and 10.3 (95% CI 8.1 to 12.6)10.3 percentage points of Democratic two-party margin per standard deviation of the exposureEstimandweighted least squares coefficient on the standardized diesel particulate matter exposure, with race, income and education held fixed; 95% interval clustered by countyInterval95% CI 8.1 to 12.6n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies points with the white, Black and Hispanic shares of residents, the college share and median household income held fixed. Adding the log of population density lowers it further, to 4.9 (95% CI 2.6 to 7.2)4.9 percentage points of Democratic two-party margin per standard deviation of the exposureEstimandweighted least squares coefficient on the standardized diesel particulate matter exposure, with race, income, education and density held fixed; 95% interval clustered by countyInterval95% CI 2.6 to 7.2n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies points. Traffic proximity goes from 24.7 (95% CI 19.2 to 30.2)24.7 percentage points of Democratic two-party margin per standard deviation of the exposureEstimandweighted least squares coefficient on the standardized traffic proximity exposure, with no controls; 95% interval clustered by countyInterval95% CI 19.2 to 30.2n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies points to 12.2 (95% CI 9.0 to 15.3)12.2 percentage points of Democratic two-party margin per standard deviation of the exposureEstimandweighted least squares coefficient on the standardized traffic proximity exposure, with race, income and education held fixed; 95% interval clustered by countyInterval95% CI 9.0 to 15.3n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies with the demographic controls and 8.7 (95% CI 6.1 to 11.3)8.7 percentage points of Democratic two-party margin per standard deviation of the exposureEstimandweighted least squares coefficient on the standardized traffic proximity exposure, with race, income, education and density held fixed; 95% interval clustered by countyInterval95% CI 6.1 to 11.3n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies with density added. Nitrogen dioxide goes from 24.3 (95% CI 22.3 to 26.3)24.3 percentage points of Democratic two-party margin per standard deviation of the exposureEstimandweighted least squares coefficient on the standardized nitrogen dioxide exposure, with no controls; 95% interval clustered by countyInterval95% CI 22.3 to 26.3n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies points to 10.1 (95% CI 8.3 to 11.9)10.1 percentage points of Democratic two-party margin per standard deviation of the exposureEstimandweighted least squares coefficient on the standardized nitrogen dioxide exposure, with race, income and education held fixed; 95% interval clustered by countyInterval95% CI 8.3 to 11.9n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies and then 3.6 (95% CI 1.5 to 5.8)3.6 percentage points of Democratic two-party margin per standard deviation of the exposureEstimandweighted least squares coefficient on the standardized nitrogen dioxide exposure, with race, income, education and density held fixed; 95% interval clustered by countyInterval95% CI 1.5 to 5.8n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies. Fine particles are the exception, with a coefficient of 8.8 (95% CI 5.3 to 12.2)8.8 percentage points of Democratic two-party margin per standard deviation of the exposureEstimandweighted least squares coefficient on the standardized fine particles (pm2.5) exposure, with no controls; 95% interval clustered by countyInterval95% CI 5.3 to 12.2n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies points with no controls, 0.9 (95% CI −1.4 to 3.1)0.9 percentage points of Democratic two-party margin per standard deviation of the exposureEstimandweighted least squares coefficient on the standardized fine particles (pm2.5) exposure, with race, income and education held fixed; 95% interval clustered by countyInterval95% CI −1.4 to 3.1n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies with the demographic controls and −0.7 (95% CI −2.8 to 1.4)−0.7 percentage points of Democratic two-party margin per standard deviation of the exposureEstimandweighted least squares coefficient on the standardized fine particles (pm2.5) exposure, with race, income, education and density held fixed; 95% interval clustered by countyInterval95% CI −2.8 to 1.4n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies with density, so once tracts are compared on who lives in them the fine-particle interval includes zero.

    The four exposures are correlated, so the first four rows of each panel do not say which one matters. Diesel exposure moves with traffic proximity and nitrogen dioxide (correlationsCorrelationA number from minus 1 to plus 1 for how closely two measures move together in a straight-line pattern. Zero means no straight-line pattern; a correlation does not say that one measure causes the other. of +0.68+0.68 correlation coefficient, from −1 to +1Estimandvote-weighted correlation across tracts of diesel exposure with traffic proximity; 95% interval from a county bootstrap (2,000 replicates)Interval95% CI 0.58 to 0.77n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriodEJScreen 2.3, 2020 modeled air dataSourceEJScreen and +0.72+0.72 correlation coefficient, from −1 to +1Estimandvote-weighted correlation across tracts of diesel exposure with nitrogen dioxide; 95% interval from a county bootstrap (2,000 replicates)Interval95% CI 0.66 to 0.76n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriodEJScreen 2.3, 2020 modeled air dataSourceEJScreen across tracts). In the joint row, where all four enter one model with the controls and density, only traffic proximity has an interval above zero: it keeps 8.7 (95% CI 5.6 to 11.7)8.7 percentage points of Democratic two-party margin per standard deviation of the exposureEstimandcoefficient on standardized traffic in one model with diesel, traffic, nitrogen dioxide and fine particles together, plus race, income, education and density; 95% interval clustered by countyInterval95% CI 5.6 to 11.7n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies points while diesel falls to 1.31.3 percentage points of Democratic two-party margin per standard deviation of the exposureEstimandcoefficient on standardized diesel in one model with diesel, traffic, nitrogen dioxide and fine particles together, plus race, income, education and density; 95% interval clustered by countyInterval95% CI −2.1 to 4.6n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies, an interval that includes zero, so the data cannot say which exposure carries the difference.

    Figure 3

    Controls shrink the Democratic gap for every pollutant, and with all four exposures in one model traffic proximity keeps 8.7 points while diesel falls to 1.3

    Difference in the Democratic two-party margin (percentage points) per standard deviation of tract exposure, by pollutant and set of controls; 81,134 tracts; 95% intervals clustered by county

    • No controls
    • Race, income, education
    • Plus density
    • All four together
    • County fixed effects

    Diesel particulate matter

    Traffic proximity

    Nitrogen dioxide

    Fine particles (PM2.5)

    Margin per SD of exposure (points)

    Show data
    Data for Controls shrink the Democratic gap for every pollutant, and with all four exposures in one model traffic proximity keeps 8.7 points while diesel falls to 1.3
    conf_highconf_lowestimatenpollutantspecification
    27.9921.5224.7581,134Diesel particulate matterNo controls
    12.568.1110.3481,134Diesel particulate matterRace, income, education
    7.212.604.9081,134Diesel particulate matterPlus density
    4.64−2.051.2981,134Diesel particulate matterAll four together
    8.895.267.0781,134Diesel particulate matterCounty fixed effects
    30.2219.1924.7081,134Traffic proximityNo controls
    15.359.0412.2081,134Traffic proximityRace, income, education
    11.296.088.6981,134Traffic proximityPlus density
    11.725.598.6581,134Traffic proximityAll four together
    8.564.646.6081,134Traffic proximityCounty fixed effects
    26.2822.3524.3181,134Nitrogen dioxideNo controls
    11.868.2910.0781,134Nitrogen dioxideRace, income, education
    5.801.463.6381,134Nitrogen dioxidePlus density
    1.85−3.40−0.77781,134Nitrogen dioxideAll four together
    7.805.166.4881,134Nitrogen dioxideCounty fixed effects
    12.245.268.7581,134Fine particles (PM2.5)No controls
    3.09−1.370.85981,134Fine particles (PM2.5)Race, income, education
    1.36−2.80−0.72181,134Fine particles (PM2.5)Plus density
    0.309−3.76−1.7281,134Fine particles (PM2.5)All four together
    2.53−2.430.05081,134Fine particles (PM2.5)County fixed effects
    Diesel, traffic proximity and nitrogen dioxide have intervals above zero in every row except the joint model, and fine particles have an interval that includes zero once controls are added. In the joint row only traffic proximity has an interval above zero. Each panel is one pollutant and each dot is the coefficient from a vote-weighted regression of the tract margin on the standardized exposure, with the controls named on the row; in the joint row the coefficient is that pollutant's in a model with all four. One standard deviation of diesel exposure is 0.14 micrograms per cubic meter.Note: Controls are the white, Black and Hispanic shares of residents, the college share and median household income; density is the log of people per square kilometer. The joint row enters all four exposures in one model with the controls and density.Note: The county fixed effects row is a different comparison and not a further control: it uses the same controls and density and compares tracts only within their own county.Note: Intervals treat counties as the units that vary. They do not include error in the allocation of precinct votes to tracts or in the modeled pollution values.Source: Precinct votes allocated to census tracts (Fekrazad 2025), 2020 presidential election; EPA EJScreen version 2.3 (2024 release, 2020 air data); American Community Survey tract data (vintage not recorded in the atlas); vote-weighted, full counts of tracts, no sampling weights

    Population density is closely tied to the Democratic vote across American places [4]. Entering density as 2020 binsEstimandnumber of equal-size bins of log density that replace the log term in the robustness modelWeightsnone (constant)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies equal-size bins in place of the log term gives a diesel coefficient of 3.4 (95% CI 1.1 to 5.8)3.4 percentage points of Democratic two-party margin per standard deviation of the exposureEstimanddiesel coefficient with race, income and education held fixed and density entered as 20 equal-size bins instead of a log term; 95% interval clustered by countyInterval95% CI 1.1 to 5.8n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies points. Clustering the intervals by state in place of county gives 4.9 (95% CI 0.2 to 9.6)4.9 percentage points of Democratic two-party margin per standard deviation of the exposureEstimandsame coefficient as diesel with race, income, education and density held fixed, with the interval clustered by state (47 clusters)Interval95% CI 0.2 to 9.6n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies points for the diesel coefficient with density, and the lower bound is near zero.

    Comparing tracts inside the same county, with a fixed effectFixed effectsRegression terms that give each group, such as each country or each year, its own baseline. The other coefficients then compare respondents within the same group. for each county and the same controls and density, gives 7.1 (95% CI 5.3 to 8.9)7.1 percentage points of Democratic two-party margin per standard deviation of the exposureEstimandweighted least squares coefficient on the standardized diesel particulate matter exposure, within county, with race, income, education and density held fixed; 95% interval clustered by countyInterval95% CI 5.3 to 8.9n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies points for diesel, 6.5 (95% CI 5.2 to 7.8)6.5 percentage points of Democratic two-party margin per standard deviation of the exposureEstimandweighted least squares coefficient on the standardized nitrogen dioxide exposure, within county, with race, income, education and density held fixed; 95% interval clustered by countyInterval95% CI 5.2 to 7.8n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies points for nitrogen dioxide and 6.6 (95% CI 4.6 to 8.6)6.6 percentage points of Democratic two-party margin per standard deviation of the exposureEstimandweighted least squares coefficient on the standardized traffic proximity exposure, within county, with race, income, education and density held fixed; 95% interval clustered by countyInterval95% CI 4.6 to 8.6n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies points for traffic. The point estimates for diesel and nitrogen dioxide are larger than the pooled ones with density, and the point estimate for traffic is smaller.The within-county coefficient minus the pooled coefficient with density is +2.2 (95% CI −0.4 to 5.3)+2.2 percentage points of Democratic two-party margin per standard deviation of the exposureEstimandwithin-county coefficient on the standardized diesel exposure minus the pooled coefficient with race, income, education and density; 95% interval from a county bootstrap (2,000 replicates)Interval95% CI −0.4 to 5.3n81,134Weightsnone (difference of two weighted least squares coefficients)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies points for diesel, an interval that includes zero, +2.8 (95% CI 0.5 to 5.3)+2.8 percentage points of Democratic two-party margin per standard deviation of the exposureEstimandwithin-county coefficient on the standardized nitrogen dioxide exposure minus the pooled coefficient with race, income, education and density; 95% interval from a county bootstrap (2,000 replicates)Interval95% CI 0.5 to 5.3n81,134Weightsnone (difference of two weighted least squares coefficients)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies points for nitrogen dioxide and −2.1 (95% CI −4.4 to −0.1)−2.1 percentage points of Democratic two-party margin per standard deviation of the exposureEstimandwithin-county coefficient on the standardized traffic proximity exposure minus the pooled coefficient with race, income, education and density; 95% interval from a county bootstrap (2,000 replicates)Interval95% CI −4.4 to −0.1n81,134Weightsnone (difference of two weighted least squares coefficients)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies points for traffic. A within-county comparison removes every difference between counties, including the urban-rural contrast, but it is not a comparison of neighbors. Tracts in one county range from dense cores to suburbs, which is why density stays in the model. Chapter 12.6, Suburbs and density (planned) takes up the density gradient in the vote directly.

    Figure 4 moves the question to counties. A tract model of the margin on race, income and education, with no pollution term, predicts each tract's margin, and the residual margin is the actual margin minus that prediction. The map averages the residual over each county's tracts by votes, which smooths the noise in single tract estimates and lets the map use county shapes. Diesel exposure for a county is the same vote-weighted average of its tract values.

    Figure 4

    The residual margin after race, income and education averages −15.9 points in southern counties and +14.5 points in northeastern counties, weighted by votes

    Residual margin: tract Democratic two-party margin minus the margin predicted from tract race, income and education, averaged over each county's tracts by votes, percentage points; county diesel exposure in micrograms per cubic meter

    Loading county values

    Residual margin after race, income and education (percentage points)

    More RepublicanMore Democratic

    Values outside −40 to +40 take the end colors.

    No data (3,143 counties)

    Select a class to show only those places.

    Hover or tap a county for its value, or search by name. Zoom with the buttons on the map, then drag to move it.

    • Alaska draws as no data. Its election returns are reported by election district, and the district codes cannot be matched to boroughs and census areas.
    Red counties voted more Republican than race, income and education predict, and blue counties more Democratic, across 3,096 counties. Switch views to hold density fixed as well, or to see diesel exposure, which is highest in New York, Kings, Bronx and Queens Counties in New York City and in Hudson County, New Jersey, where county means run from 0.56 to 0.75 micrograms per cubic meter.Note: Hawaii, Connecticut and the District of Columbia draw as no data (Hawaii has no tract vote estimates, the tract atlas has no rows for Connecticut, and it has no white share for DC tracts), and so does any county without a tract of more than 100 votes.Note: County values are averages of modeled tract values, so they carry the errors of both models. No interval is shown on the map.Source: Precinct votes allocated to census tracts (Fekrazad 2025), 2020 presidential election; EPA EJScreen version 2.3 (2024 release, 2020 air data); American Community Survey tract data (vintage not recorded in the atlas); vote-weighted county means of tract values, full counts, no sampling weights

    The residual margin has a strong regional component. Counties in the South average −15.9−15.9 percentage points of Democratic two-party marginEstimandmean over counties, weighted by county votes, of the residual margin net of race, income and education (a positive value is more Democratic than the model predicts)n1,419Weightsvotes cast in the county, 2020 presidential electionPopulationcounties of the South census region in the samplePeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies points and counties in the Northeast +14.5+14.5 percentage points of Democratic two-party marginEstimandmean over counties, weighted by county votes, of the residual margin net of race, income and education (a positive value is more Democratic than the model predicts)n209Weightsvotes cast in the county, 2020 presidential electionPopulationcounties of the Northeast census region in the samplePeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies points, and 61%61% percent of the vote-weighted variance of the county residual marginEstimandshare of the vote-weighted variance of the county residual margin (net of race, income and education) that lies between states: one minus the ratio of the within-state variance to the total variancen3,096Weightsvotes cast in the county, 2020 presidential electionPopulationcounties with at least one tract in the samplePeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographiesNoteA descriptive ratio of variances with no interval. of the variance of the residual, weighted by county votes, lies between states.

    Figure 5 plots each county's diesel exposure against its residual margin. Across counties weighted by their votes, the residual correlates with county diesel exposure at +0.26 (95% CI 0.17 to 0.34)+0.26 correlation coefficient, from −1 to +1Estimandcorrelation across counties, weighted by county votes, of county diesel exposure with the county mean residual margin after a tract model of race, income and education; 95% interval from a county bootstrap (2,000 replicates)Interval95% CI 0.17 to 0.34n3,096Weightsvotes cast in the county, 2020 presidential electionPopulationcounties with at least one tract in the samplePeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies, so counties with more exposure vote more Democratic than the demographic model predicts. Counting each county once, the correlation is +0.27 (95% CI 0.25 to 0.30)+0.27 correlation coefficient, from −1 to +1Estimandunweighted correlation across counties (each county counts once) of county diesel exposure with the county mean residual margin after a tract model of race, income and education; 95% interval from a county bootstrap (2,000 replicates)Interval95% CI 0.25 to 0.30n3,096Weightsnone (each county counts once)Populationcounties with at least one tract in the samplePeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies. When density also enters the model that produces the residual, the vote-weighted correlation is +0.08 (95% CI −0.02 to 0.17)+0.08 correlation coefficient, from −1 to +1Estimandcorrelation across counties, weighted by county votes, of county diesel exposure with the county mean residual margin after a tract model of race, income, education and density; 95% interval from a county bootstrap (2,000 replicates)Interval95% CI −0.02 to 0.17n3,096Weightsvotes cast in the county, 2020 presidential electionPopulationcounties with at least one tract in the samplePeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies, which includes zero, and the unweighted correlation is −0.06 (95% CI −0.09 to −0.03)−0.06 correlation coefficient, from −1 to +1Estimandunweighted correlation across counties (each county counts once) of county diesel exposure with the county mean residual margin after a tract model of race, income, education and density; 95% interval from a county bootstrap (2,000 replicates)Interval95% CI −0.09 to −0.03n3,096Weightsnone (each county counts once)Populationcounties with at least one tract in the samplePeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies, which does not, so the sign of the density-adjusted correlation depends on whether large counties count more. Within states, the vote-weighted correlation is +0.18 (95% CI 0.01 to 0.41)+0.18 correlation coefficient, from −1 to +1Estimandcorrelation across counties, weighted by county votes, of county diesel exposure with the county mean residual margin after a tract model of race, income and education, both measured from their vote-weighted state means (within-state); 95% interval from resampling the 47 states (2,000 replicates)Interval95% CI 0.01 to 0.41n3,096Weightsvotes cast in the county, 2020 presidential electionPopulationcounties with at least one tract in the samplePeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies net of race, income and education and −0.07 (95% CI −0.21 to 0.16)−0.07 correlation coefficient, from −1 to +1Estimandcorrelation across counties, weighted by county votes, of county diesel exposure with the county mean residual margin after a tract model of race, income, education and density, both measured from their vote-weighted state means (within-state); 95% interval from resampling the 47 states (2,000 replicates)Interval95% CI −0.21 to 0.16n3,096Weightsvotes cast in the county, 2020 presidential electionPopulationcounties with at least one tract in the samplePeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies with density added, with intervals that resample the states.

    Figure 5

    County diesel exposure correlates at +0.26 with the residual margin after race, income and education, and at +0.08 (interval includes zero) with density added

    Each dot is a county: its mean diesel exposure (averaged over tracts by 2020 votes) against its residual margin, the Democratic two-party margin minus the margin predicted from race, income and education, in percentage points; correlations across 3,096 counties weighted by county votes

    • Dot area: Votes for president, 2020430,0001,500,0004,300,000
    Show data
    Data for County diesel exposure correlates at +0.26 with the residual margin after race, income and education, and at +0.08 (interval includes zero) with density added
    CountyDiesel exposure (µg/m³)Residual margin (points)Residual margin, density held fixed (points)Votes for president, 2020
    Autauga, AL0.099−37.1−34.327,770
    Baldwin, AL0.079−39.1−36.2109,679
    Barbour, AL0.048−21.7−4.610,518
    Bibb, AL0.061−31.6−21.99,595
    Blount, AL0.078−38.5−33.627,588
    Bullock, AL0.040+10.2+37.94,613
    Butler, AL0.059−25.1−7.69,488
    Calhoun, AL0.091−25.8−24.350,980
    Chambers, AL0.080−22.0−11.115,284
    Cherokee, AL0.073−29.5−22.012,301
    Chilton, AL0.075−36.1−29.019,310
    Choctaw, AL0.034−15.7+7.67,464
    Clarke, AL0.041−22.4−1.513,135
    Clay, AL0.052−32.7−17.46,930
    Cleburne, AL0.077−38.4−26.57,227
    Coffee, AL0.048−37.5−31.822,275
    Colbert, AL0.107−17.4−17.327,886
    Conecuh, AL0.047−16.9+7.36,441
    Coosa, AL0.048−21.2−1.15,479
    Covington, AL0.039−36.8−27.517,430
    Crenshaw, AL0.035−33.3−14.96,617
    Cullman, AL0.090−36.4−34.641,851
    Dale, AL0.044−33.3−25.619,738
    Dallas, AL0.067−10.5+4.617,864
    DeKalb, AL0.073−34.6−27.629,356
    Elmore, AL0.072−34.4−29.941,030
    Escambia, AL0.054−29.5−16.815,910
    Etowah, AL0.097−24.6−25.147,728
    Fayette, AL0.051−34.1−20.88,766
    Franklin, AL0.057−36.0−25.912,578
    Geneva, AL0.043−39.6−29.512,545
    Greene, AL0.059+5.7+37.64,775
    Hale, AL0.051−19.7+3.56,772
    Henry, AL0.040−34.9−19.59,298
    Houston, AL0.070−38.1−36.146,173
    Jackson, AL0.073−25.9−19.623,636
    Jefferson, AL0.194−18.3−15.8325,762
    Lamar, AL0.047−31.6−18.77,193
    Lauderdale, AL0.085−22.8−21.744,339
    Lawrence, AL0.073−27.2−17.216,031
    Lee, AL0.087−37.8−31.571,065
    Limestone, AL0.112−29.6−25.649,235
    Lowndes, AL0.057−2.4+27.96,835
    Macon, AL0.064+0.7+25.98,723
    Madison, AL0.118−26.4−23.0194,767
    Marengo, AL0.048−24.2−0.610,900
    Marion, AL0.061−31.4−23.713,807
    Marshall, AL0.076−41.1−37.639,655
    Mobile, AL0.150−24.0−24.2181,166
    Monroe, AL0.040−17.7−0.410,668
    Montgomery, AL0.145−24.7−18.698,448
    Morgan, AL0.124−31.2−30.853,722
    Perry, AL0.043+0.8+31.85,230
    Pickens, AL0.046−21.4−0.29,668
    Pike, AL0.047−36.5−20.213,841
    Randolph, AL0.059−42.5−27.810,837
    Russell, AL0.090−10.3−3.521,329
    St. Clair, AL0.109−30.2−29.844,441
    Shelby, AL0.128−46.2−42.5114,950
    Sumter, AL0.058−3.8+28.86,291
    Talladega, AL0.080−19.6−13.135,663
    Tallapoosa, AL0.054−31.2−19.720,991
    Tuscaloosa, AL0.118−25.9−22.189,347
    Walker, AL0.087−28.7−25.031,170
    Washington, AL0.038−34.1−13.08,876
    Wilcox, AL0.039−2.4+26.45,903
    Winston, AL0.056−34.7−26.911,284
    Apache, AZ0.016+16.7+54.635,171
    Cochise, AZ0.049−19.7−5.760,391
    Coconino, AZ0.072+9.6+27.773,274
    Gila, AZ0.038−11.5+4.027,663
    Graham, AZ0.039−28.7−12.514,995
    Greenlee, AZ0.019−35.2+1.53,685
    La Paz, AZ0.071−17.9+5.16,546
    Maricopa, AZ0.256−3.0−7.52,067,902
    Mohave, AZ0.074−18.1−20.4104,667
    Navajo, AZ0.040−6.5+17.251,767
    Pima, AZ0.159+7.1+10.1519,220
    Pinal, AZ0.131−7.2−6.6184,398
    Santa Cruz, AZ0.048+4.7+30.619,556
    Yavapai, AZ0.073−10.5−6.0143,219
    Yuma, AZ0.162−14.3−10.569,651
    Arkansas, AR0.074−21.5−10.76,292
    Ashley, AR0.050−29.0−16.47,926
    Baxter, AR0.061−14.0−11.221,007
    Benton, AR0.090−25.8−22.0119,903
    Boone, AR0.051−16.3−13.417,114
    Bradley, AR0.043−31.9−9.73,654
    Calhoun, AR0.040−32.4−6.32,182
    Carroll, AR0.042−5.9+7.911,797
    Chicot, AR0.062−22.2−0.34,103
    Clark, AR0.086−14.0+0.58,395
    Clay, AR0.091−14.6−8.85,183
    Cleburne, AR0.052−24.0−17.712,680
    Cleveland, AR0.045−31.3−12.43,600
    Columbia, AR0.056−36.9−22.88,616
    Conway, AR0.100−10.1+2.08,685
    Craighead, AR0.125−26.5−24.938,511
    Crawford, AR0.117−25.3−22.824,093
    Crittenden, AR0.180−13.8−8.316,367
    Cross, AR0.106−24.5−16.86,942
    Dallas, AR0.051−23.5−4.52,649
    Desha, AR0.070−19.0+4.34,164
    Drew, AR0.055−30.4−12.46,908
    Faulkner, AR0.106−21.5−19.054,428
    Franklin, AR0.073−20.0−9.87,129
    Fulton, AR0.053−14.3+0.25,119
    Garland, AR0.062−13.9−11.644,199
    Grant, AR0.054−26.7−18.28,191
    Greene, AR0.103−17.5−19.616,100
    Hempstead, AR0.078−32.9−16.56,845
    Hot Spring, AR0.090−16.7−9.912,557
    Howard, AR0.059−34.2−17.64,837
    Independence, AR0.072−22.4−14.514,512
    Izard, AR0.042−27.7−12.45,810
    Jackson, AR0.100−18.4−7.55,091
    Jefferson, AR0.093−10.8−1.124,796
    Johnson, AR0.084−20.2−9.59,541
    Lafayette, AR0.047−31.1−10.82,679
    Lawrence, AR0.101−14.6−8.45,857
    Lee, AR0.076−17.7+1.12,848
    Lincoln, AR0.054−21.9−6.73,875
    Little River, AR0.066−35.4−18.25,177
    Logan, AR0.048−17.5−9.58,182
    Lonoke, AR0.098−22.0−21.430,699
    Madison, AR0.037−22.6−5.77,351
    Marion, AR0.041−12.4−2.07,503
    Miller, AR0.118−30.3−28.416,527
    Mississippi, AR0.102−19.7−10.712,342
    Monroe, AR0.091−23.3+1.72,816
    Montgomery, AR0.035−19.8−0.83,873
    Nevada, AR0.065−24.2−3.23,358
    Newton, AR0.030−15.7+2.93,998
    Ouachita, AR0.109−19.0−5.19,629
    Perry, AR0.054−11.5+1.74,627
    Phillips, AR0.076−12.0+6.26,242
    Pike, AR0.046−36.5−18.04,246
    Poinsett, AR0.101−20.0−15.37,521
    Polk, AR0.039−29.8−17.68,490
    Pope, AR0.100−25.2−21.224,432
    Prairie, AR0.085−28.7−9.53,495
    Pulaski, AR0.154−6.9−4.6169,926
    Randolph, AR0.076−17.9−10.86,812
    St. Francis, AR0.123−14.4−0.37,108
    Saline, AR0.100−21.7−21.556,960
    Scott, AR0.036−28.1−13.03,551
    Searcy, AR0.036−27.0−9.34,019
    Sebastian, AR0.092−20.8−20.847,138
    Sevier, AR0.058−35.9−19.25,202
    Sharp, AR0.059−13.6−5.37,566
    Stone, AR0.039−17.1−3.55,938
    Union, AR0.057−29.6−18.116,607
    Van Buren, AR0.042−14.1−1.97,807
    Washington, AR0.092−3.1+0.594,275
    White, AR0.083−26.5−22.130,885
    Woodruff, AR0.086−16.2+7.12,476
    Yell, AR0.056−27.7−13.06,741
    Alameda, CA0.250+21.4+21.4767,729
    Alpine, CA0.012+26.8+71.0741
    Amador, CA0.052+2.6+11.522,308
    Butte, CA0.133+8.5+10.7102,023
    Calaveras, CA0.049+4.6+16.427,159
    Colusa, CA0.078−20.1+8.37,962
    Contra Costa, CA0.161+22.9+23.3581,271
    Del Norte, CA0.024−0.7+7.411,452
    El Dorado, CA0.067+3.4+6.8115,597
    Fresno, CA0.369−9.6−6.9364,089
    Glenn, CA0.100−16.9−7.711,296
    Humboldt, CA0.054+42.2+48.768,824
    Imperial, CA0.180−4.7+7.255,690
    Inyo, CA0.021+0.6+25.69,480
    Kern, CA0.318−17.1−15.6305,129
    Kings, CA0.268−19.2−16.643,863
    Lake, CA0.031+28.5+35.528,808
    Lassen, CA0.020−25.9−9.411,980
    Los Angeles, CA0.401+12.5+10.14,256,459
    Madera, CA0.225−13.6−1.853,736
    Marin, CA0.077+54.1+54.9155,764
    Mariposa, CA0.030−0.5+24.010,277
    Mendocino, CA0.031+47.4+61.943,333
    Merced, CA0.302−0.9+5.190,569
    Modoc, CA0.015−23.4+2.34,338
    Mono, CA0.014+27.3+57.36,737
    Monterey, CA0.093+25.7+30.6163,789
    Napa, CA0.101+32.4+34.772,042
    Nevada, CA0.058+28.7+34.764,806
    Orange, CA0.316−13.3−16.21,521,670
    Placer, CA0.211−3.9−5.4234,940
    Plumas, CA0.022+17.6+37.811,256
    Riverside, CA0.271−4.1−3.9997,214
    Sacramento, CA0.234+10.4+6.0716,929
    San Benito, CA0.100+19.1+25.428,876
    San Bernardino, CA0.353−7.1−5.6840,486
    San Diego, CA0.234+2.9+1.31,601,471
    San Francisco, CA0.307+33.3+25.2439,813
    San Joaquin, CA0.265+3.3+1.6288,024
    San Luis Obispo, CA0.070+13.8+17.3159,755
    San Mateo, CA0.125+30.3+29.4373,511
    Santa Barbara, CA0.116+20.0+20.6200,147
    Santa Clara, CA0.202+10.1+11.3849,568
    Santa Cruz, CA0.078+54.1+54.6143,698
    Shasta, CA0.090−7.5−8.492,846
    Sierra, CA0.020+11.3+42.41,930
    Siskiyou, CA0.029+5.2+25.223,439
    Solano, CA0.151+15.3+15.2205,888
    Sonoma, CA0.095+52.5+53.1268,261
    Stanislaus, CA0.269−0.2−2.9214,859
    Sutter, CA0.151−15.4−13.342,604
    Tehama, CA0.098−16.0−4.328,787
    Trinity, CA0.010+26.5+52.96,262
    Tulare, CA0.312−16.4−11.5146,843
    Tuolumne, CA0.040+8.3+15.430,395
    Ventura, CA0.165+11.7+10.8422,731
    Yolo, CA0.190+12.7+18.296,830
    Yuba, CA0.143−9.6−5.729,816
    Adams, CO0.312+15.0+11.1236,740
    Alamosa, CO0.050−13.7+6.67,808
    Arapahoe, CO0.268+9.9+5.7350,172
    Archuleta, CO0.015−10.8+12.49,144
    Baca, CO0.022−45.1−8.92,225
    Bent, CO0.036−21.5+13.92,274
    Boulder, CO0.122+38.6+41.4206,111
    Broomfield, CO0.238+18.7+15.846,632
    Chaffee, CO0.016+10.8+29.813,718
    Cheyenne, CO0.020−51.0−10.41,136
    Clear Creek, CO0.025+13.0+37.86,548
    Conejos, CO0.014−14.2+24.94,333
    Costilla, CO0.010+5.3+54.42,094
    Crowley, CO0.030−34.5−8.21,750
    Custer, CO0.009−14.1+13.63,635
    Delta, CO0.029−13.8+2.519,370
    Denver, CO0.462+32.4+28.7393,776
    Dolores, CO0.011−26.3+8.81,449
    Douglas, CO0.166−12.9−13.0231,605
    Eagle, CO0.029+14.9+38.626,745
    Elbert, CO0.048−22.8−9.318,983
    El Paso, CO0.117−13.2−15.9378,813
    Fremont, CO0.026−11.6−5.125,557
    Garfield, CO0.041+5.8+24.530,904
    Gilpin, CO0.021+15.1+36.14,186
    Grand, CO0.017+7.0+33.49,870
    Gunnison, CO0.018+20.3+46.211,190
    Hinsdale, CO0.005−13.8+33.5632
    Huerfano, CO0.022+5.5+35.44,406
    Jackson, CO0.013−37.8+4.6876
    Jefferson, CO0.185+18.0+14.2376,131
    Kiowa, CO0.022−41.1−2.2903
    Kit Carson, CO0.026−35.8−4.63,871
    Lake, CO0.015+5.3+25.43,961
    La Plata, CO0.030+15.7+32.335,667
    Larimer, CO0.146+13.7+14.1224,264
    Las Animas, CO0.028−0.8+26.47,961
    Lincoln, CO0.028−46.7−12.32,651
    Logan, CO0.070−27.8−17.510,532
    Mesa, CO0.093−8.8−11.990,623
    Mineral, CO0.006−19.7+29.4756
    Moffat, CO0.034−35.2−30.97,026
    Montezuma, CO0.021−9.2+9.415,500
    Montrose, CO0.043−20.2−10.124,922
    Morgan, CO0.109−26.5−14.013,744
    Otero, CO0.049−15.0+0.79,576
    Ouray, CO0.009+20.3+52.54,020
    Park, CO0.013+3.1+24.712,285
    Phillips, CO0.033−43.4−12.12,485
    Pitkin, CO0.014+34.5+60.711,957
    Prowers, CO0.044−35.8−19.45,561
    Pueblo, CO0.101+2.0+5.188,239
    Rio Blanco, CO0.015−42.7−7.13,691
    Rio Grande, CO0.022−22.1+1.36,305
    Routt, CO0.028+28.3+47.816,876
    Saguache, CO0.011+18.8+61.53,389
    San Juan, CO0.007+23.9+68.5562
    San Miguel, CO0.008+36.5+69.25,147
    Sedgwick, CO0.058−41.9−8.01,446
    Summit, CO0.026+36.8+52.418,479
    Teller, CO0.016−20.1−8.916,962
    Washington, CO0.031−45.5−11.73,008
    Weld, CO0.190−9.6−7.3166,255
    Yuma, CO0.033−54.2−18.94,981
    Kent, DE0.108−0.5+1.087,021
    New Castle, DE0.183+18.2+16.2287,633
    Sussex, DE0.079−0.8+2.3129,356
    Alachua, FL0.146−1.4+5.7142,988
    Baker, FL0.080−37.4−31.114,082
    Bay, FL0.092−30.7−33.893,213
    Bradford, FL0.073−29.0−22.613,704
    Brevard, FL0.120−9.8−15.5360,580
    Broward, FL0.285−7.9−9.9959,445
    Calhoun, FL0.036−29.1−14.46,537
    Charlotte, FL0.092+0.2−6.7116,560
    Citrus, FL0.080−7.0−10.193,403
    Clay, FL0.124−26.3−29.9124,589
    Collier, FL0.115−26.4−26.5208,285
    Columbia, FL0.086−24.8−19.833,092
    DeSoto, FL0.076−18.1−7.412,676
    Dixie, FL0.043−17.7−8.78,173
    Duval, FL0.201−16.9−19.5494,212
    Escambia, FL0.120−17.9−20.5170,856
    Flagler, FL0.093−9.6−12.171,871
    Franklin, FL0.036−16.3+0.56,874
    Gadsden, FL0.058−2.6+16.223,763
    Gilchrist, FL0.051−21.7−13.39,702
    Glades, FL0.056−34.8−10.95,212
    Gulf, FL0.036−32.4−17.08,172
    Hamilton, FL0.065−25.6−5.75,567
    Hardee, FL0.070−38.5−21.28,500
    Hendry, FL0.069−31.6−14.012,943
    Hernando, FL0.105−5.6−10.9109,147
    Highlands, FL0.072−20.7−17.352,232
    Hillsborough, FL0.216−15.2−15.4713,279
    Holmes, FL0.044−35.5−26.19,078
    Indian River, FL0.098−11.8−15.097,740
    Jackson, FL0.051−27.7−15.322,456
    Jefferson, FL0.049−2.2+15.98,468
    Lafayette, FL0.039−45.1−26.93,661
    Lake, FL0.133−11.1−11.9211,284
    Lee, FL0.127−11.7−16.1393,618
    Leon, FL0.120−6.5−1.2161,120
    Levy, FL0.057−16.7−5.823,196
    Liberty, FL0.033−26.1−3.43,566
    Madison, FL0.052−19.5−2.69,393
    Manatee, FL0.147−10.5−15.1217,471
    Marion, FL0.119−12.3−12.6204,736
    Martin, FL0.129−13.7−16.698,969
    Miami-Dade, FL0.286−42.6−39.11,154,200
    Monroe, FL0.059−9.7−8.948,122
    Nassau, FL0.101−27.0−24.858,920
    Okaloosa, FL0.082−34.2−37.1116,748
    Okeechobee, FL0.075−26.7−20.215,984
    Orange, FL0.255−9.1−6.7649,086
    Osceola, FL0.167−12.8−5.7172,793
    Palm Beach, FL0.192−4.5−7.5774,179
    Pasco, FL0.137−8.6−13.4302,673
    Pinellas, FL0.184+3.9−5.9556,668
    Polk, FL0.146−15.3−15.7344,106
    Putnam, FL0.069−19.8−13.836,403
    St. Johns, FL0.126−25.3−24.5177,026
    St. Lucie, FL0.136−5.5−8.9172,340
    Santa Rosa, FL0.078−28.1−30.3107,193
    Sarasota, FL0.132+0.2−5.6271,167
    Seminole, FL0.212−14.4−14.6261,618
    Sumter, FL0.170−17.7−22.092,538
    Suwannee, FL0.059−31.6−20.721,057
    Taylor, FL0.050−33.6−20.810,135
    Union, FL0.062−32.5−24.76,251
    Volusia, FL0.135−2.7−7.3308,100
    Wakulla, FL0.048−15.6−7.818,133
    Walton, FL0.062−34.3−28.043,795
    Washington, FL0.046−29.4−19.312,335
    Appling, GA0.049−33.5−21.68,341
    Atkinson, GA0.042−36.7−15.03,155
    Bacon, GA0.052−44.8−32.84,668
    Baker, GA0.036−28.7+1.21,555
    Baldwin, GA0.072−18.7−10.418,283
    Banks, GA0.097−37.1−30.98,784
    Barrow, GA0.175−29.0−29.637,921
    Bartow, GA0.179−28.0−27.950,434
    Ben Hill, GA0.073−27.3−21.26,560
    Berrien, GA0.048−33.0−22.27,743
    Bibb, GA0.170−14.0−10.369,327
    Bleckley, GA0.063−40.5−30.75,706
    Brantley, GA0.046−32.1−24.27,746
    Brooks, GA0.051−20.3−3.67,100
    Bryan, GA0.099−29.6−23.421,340
    Bulloch, GA0.068−31.9−22.130,084
    Burke, GA0.053−13.7+6.010,684
    Butts, GA0.130−28.3−23.611,771
    Calhoun, GA0.038−16.0+9.12,194
    Camden, GA0.099−18.3−13.823,688
    Candler, GA0.051−31.7−16.04,431
    Carroll, GA0.104−27.0−25.154,450
    Catoosa, GA0.165−21.8−27.332,593
    Charlton, GA0.055−45.2−26.74,566
    Chatham, GA0.140−12.2−9.9133,420
    Chattahoochee, GA0.051−21.1−5.21,582
    Chattooga, GA0.089−23.1−19.810,050
    Cherokee, GA0.156−30.7−33.2144,830
    Clarke, GA0.168+2.0+8.151,333
    Clay, GA0.035−26.5+3.01,434
    Clayton, GA0.184+5.2+7.8111,190
    Clinch, GA0.043−34.1−11.52,864
    Cobb, GA0.230−20.7−18.8393,747
    Coffee, GA0.064−34.4−23.515,214
    Colquitt, GA0.062−44.3−33.816,083
    Columbia, GA0.127−30.9−30.780,581
    Cook, GA0.081−36.0−24.17,035
    Coweta, GA0.117−33.1−30.976,798
    Crawford, GA0.067−23.1−10.96,102
    Crisp, GA0.108−40.8−28.28,039
    Dade, GA0.096−23.4−18.77,434
    Dawson, GA0.091−44.4−38.516,081
    Decatur, GA0.050−25.9−14.011,627
    DeKalb, GA0.255+3.2+7.0370,006
    Dodge, GA0.053−38.7−25.28,070
    Dooly, GA0.080−26.3−3.64,105
    Dougherty, GA0.090−17.1−9.935,296
    Douglas, GA0.159−13.8−8.369,121
    Early, GA0.039−29.6−5.85,187
    Echols, GA0.045−59.6−33.61,441
    Effingham, GA0.092−34.0−29.931,570
    Elbert, GA0.073−26.4−15.29,171
    Emanuel, GA0.048−33.0−16.99,501
    Evans, GA0.052−35.6−20.74,247
    Fannin, GA0.049−27.5−20.814,865
    Fayette, GA0.121−33.3−26.771,994
    Floyd, GA0.134−27.8−25.441,648
    Forsyth, GA0.163−48.4−45.0129,176
    Franklin, GA0.108−38.2−32.210,765
    Fulton, GA0.273−14.0−9.0518,228
    Gilmer, GA0.054−31.4−23.616,510
    Glascock, GA0.048−42.4−28.01,566
    Glynn, GA0.089−23.0−19.341,984
    Gordon, GA0.156−31.5−29.424,066
    Grady, GA0.051−29.3−16.410,707
    Greene, GA0.074−38.0−20.811,247
    Gwinnett, GA0.231−21.8−18.5413,865
    Habersham, GA0.069−42.1−37.120,453
    Hall, GA0.157−34.9−33.590,517
    Hancock, GA0.049+5.5+32.14,133
    Haralson, GA0.097−31.9−30.314,248
    Harris, GA0.068−37.5−24.819,991
    Hart, GA0.087−27.5−22.212,727
    Heard, GA0.059−25.0−16.15,391
    Henry, GA0.179−14.8−10.8122,762
    Houston, GA0.117−29.7−29.474,819
    Irwin, GA0.054−42.7−24.04,168
    Jackson, GA0.172−37.7−34.837,673
    Jasper, GA0.081−36.5−23.57,644
    Jeff Davis, GA0.051−40.8−28.85,771
    Jefferson, GA0.057−11.4+9.47,642
    Jenkins, GA0.048−21.4−3.73,455
    Johnson, GA0.046−25.0−11.44,100
    Jones, GA0.083−17.6−11.214,966
    Lamar, GA0.088−31.0−23.39,039
    Lanier, GA0.048−40.8−27.42,844
    Laurens, GA0.064−32.0−22.522,729
    Lee, GA0.062−46.9−38.616,729
    Liberty, GA0.083−0.9+5.421,257
    Lincoln, GA0.054−25.7−10.64,650
    Long, GA0.059−20.6−5.65,656
    Lowndes, GA0.104−30.0−25.246,355
    Lumpkin, GA0.064−32.1−26.015,531
    McDuffie, GA0.085−27.4−15.910,455
    McIntosh, GA0.077−18.00.06,696
    Macon, GA0.069−8.2+14.84,662
    Madison, GA0.090−27.9−21.314,936
    Marion, GA0.045−22.1−0.93,624
    Meriwether, GA0.065−19.9−5.310,878
    Miller, GA0.038−45.3−24.02,835
    Mitchell, GA0.045−22.4−5.78,963
    Monroe, GA0.126−34.4−22.915,492
    Montgomery, GA0.042−38.8−21.93,966
    Morgan, GA0.101−34.0−20.311,707
    Murray, GA0.073−29.7−27.515,389
    Muscogee, GA0.133−14.7−13.980,509
    Newton, GA0.158−13.8−9.754,239
    Oconee, GA0.125−34.4−25.725,168
    Oglethorpe, GA0.071−25.2−11.28,131
    Paulding, GA0.144−24.2−26.185,385
    Peach, GA0.117−25.3−15.212,549
    Pickens, GA0.071−28.9−26.717,116
    Pierce, GA0.058−44.8−36.99,048
    Pike, GA0.071−35.2−29.810,720
    Polk, GA0.101−30.8−26.017,399
    Pulaski, GA0.060−38.0−30.74,059
    Putnam, GA0.070−41.2−27.011,855
    Quitman, GA0.033−20.2+3.91,106
    Rabun, GA0.036−33.0−18.89,568
    Randolph, GA0.038−36.4−5.93,074
    Richmond, GA0.150−3.5−1.987,014
    Rockdale, GA0.179−9.5−3.044,686
    Schley, GA0.045−35.2−19.72,275
    Screven, GA0.050−22.0−2.26,628
    Seminole, GA0.041−30.7−16.63,884
    Spalding, GA0.123−21.5−20.130,116
    Stephens, GA0.088−25.6−24.611,884
    Stewart, GA0.035−21.3+11.41,990
    Sumter, GA0.072−27.2−10.912,150
    Talbot, GA0.057−4.3+22.53,522
    Taliaferro, GA0.059+8.0+37.2928
    Tattnall, GA0.048−45.2−30.78,183
    Taylor, GA0.061−32.1−11.33,839
    Telfair, GA0.046−30.8−11.64,333
    Terrell, GA0.056−13.0+6.94,416
    Thomas, GA0.061−29.5−19.721,853
    Tift, GA0.106−37.4−31.216,283
    Toombs, GA0.057−44.2−33.710,914
    Towns, GA0.039−35.0−25.17,983
    Treutlen, GA0.048−26.5−11.43,077
    Troup, GA0.106−28.8−21.930,049
    Turner, GA0.074−29.7−11.43,792
    Twiggs, GA0.067−15.5+5.54,444
    Union, GA0.044−27.6−21.015,556
    Upson, GA0.069−18.8−14.612,905
    Walker, GA0.112−23.3−25.029,354
    Walton, GA0.153−36.3−35.451,095
    Ware, GA0.096−32.2−27.214,192
    Warren, GA0.062−13.8+10.82,651
    Washington, GA0.061−25.9−4.79,459
    Wayne, GA0.064−36.3−29.012,778

    Showing the first 500 of 3096 rows.

    Counties with similar diesel exposure differ by tens of points in residual margin. Each dot is a county, and the lines are binned means over tenths of counties ordered by exposure, weighted by votes and counting each county once, with 95% intervals from resampling states. Net of race, income and education the binned means counting each county once rise from the third tenth to the tenth. With density also held fixed, the tenth with the least exposure has the highest means under both weightings. Within states, the correlation is +0.18 net of race, income and education and −0.07 with density added.Note: Binned means group counties into tenths by diesel exposure. The number of counties in each bin is in the tooltip.Note: Hawaii, Connecticut and the District of Columbia, and counties without a tract of more than 100 votes, are left out. County values are averages of modeled tract values, so they carry the errors of both models.Note: Intervals on the binned means resample the states. They do not include error in the allocation of precinct votes to tracts or in the modeled pollution values.Source: Precinct votes allocated to census tracts (Fekrazad 2025), 2020 presidential election; EPA EJScreen version 2.3 (2024 release, 2020 air data); American Community Survey tract data (vintage not recorded in the atlas); vote-weighted county means of tract values, full counts, no sampling weights

    Modeled asthma cannot register local air

    A modeled health estimate is computed from other data by a formula. A measured health outcome is a count or an answer recorded for the people who live in the place. The asthma figures in this chapter are of the first kind: the CDC's PLACES estimates of current asthma among adults [5] are modeled and not measured, so they cannot show an effect of local air. PLACES fits a multilevel model to survey answers, with the age, sex, race and education of respondents and the poverty rate of the county as inputs, and applies it to each tract's population [5]. One tract's estimate differs from another's through its demographic mix and its county, and not through its local air.

    Modeled prevalence is 11.0% (95% CI 11.0% to 11.1%)11.0% percent of adults with current asthma (model-based tract estimate)Estimandvote-weighted mean of the tract estimate; 95% interval clustered by countyInterval95% CI 11.0% to 11.1%n8,114Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts in decile 1 of diesel exposurePeriodPLACES release not recorded in the atlas fileSourceCDC PLACES in the first decile of diesel exposure and 9.9% (95% CI 9.6% to 10.3%)9.9% percent of adults with current asthma (model-based tract estimate)Estimandvote-weighted mean of the tract estimate; 95% interval clustered by countyInterval95% CI 9.6% to 10.3%n8,114Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts in decile 10 of diesel exposurePeriodPLACES release not recorded in the atlas fileSourceCDC PLACES in the tenth. Per standard deviation of diesel exposure, prevalence differs by −0.25 (95% CI −0.35 to −0.14)−0.25 percentage points of adults with current asthma per standard deviation of diesel exposureEstimandweighted least squares coefficient of the tract asthma estimate on standardized diesel exposure, with no controls; 95% interval clustered by countyInterval95% CI −0.35 to −0.14n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriodPLACES release not recorded in the atlas fileSourceCDC PLACES points with no controls, by 0.04 (95% CI −0.04 to 0.12)0.04 percentage points of adults with current asthma per standard deviation of diesel exposureEstimandweighted least squares coefficient of the tract asthma estimate on standardized diesel exposure, with race, income and education held fixed; 95% interval clustered by countyInterval95% CI −0.04 to 0.12n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriodPLACES release not recorded in the atlas fileSourceCDC PLACES points with race, income and education held fixed and by −0.02 (95% CI −0.11 to 0.07)−0.02 percentage points of adults with current asthma per standard deviation of diesel exposureEstimandweighted least squares coefficient of the tract asthma estimate on standardized diesel exposure, with race, income, education and density held fixed; 95% interval clustered by countyInterval95% CI −0.11 to 0.07n81,134Weightsvotes cast in the tract, 2020 presidential election (pres_tot)Populationcensus tracts with more than 100 votes in 2020 and complete pollution, control and land-area dataPeriodPLACES release not recorded in the atlas fileSourceCDC PLACES points with density added. The difference is negative with no controls and its interval includes zero once race, income and education are held fixed, as expected when the model is built from demographic inputs. The pattern describes how the modeled values line up with diesel exposure and does not test whether exposure affects asthma. Chapter 13.4, Health outcomes and the vote (planned) looks at small-area health outcomes and the vote more broadly.

    The support gap shrinks within party

    The Cooperative Election Study asked respondents in 2020 whether they support strengthening the Environmental Protection Agency's enforcement of the Clean Air Act and the Clean Water Act even if it costs U.S. jobs. The item names two statutes and a cost in jobs, so it measures more than support for the agency, and it does not ask about local pollution or health. Among the 57,41157,411 respondentsEstimandcount of respondentsWeightsnone (count)PopulationCES 2020 respondents with an answer on the EPA enforcement item, a seven-point party ID and a county in the tract samplePeriod2020SourceCooperative Election Study respondents in 2,6302,630 countiesEstimandcount of counties with a respondentWeightsnone (count)PopulationCES 2020 respondents with an answer on the EPA enforcement item, a seven-point party ID and a county in the tract samplePeriod2020SourceCooperative Election Study counties who gave an answer and a party ID and live in a county with tracts in the sample, weighted support is 59.7% (95% CI 58.5% to 60.8%)59.7% percent supporting stronger EPA enforcement of the Clean Air Act and Clean Water Act, even if it costs U.S. jobsEstimandweighted share; 95% interval clustered by countyInterval95% CI 58.5% to 60.8%n57,411WeightsCES 2020 weight (weight)PopulationCES 2020 respondents with an answer on the EPA enforcement item, a seven-point party ID and a county in the tract samplePeriod2020SourceCooperative Election Study. Respondents in the fifth whose counties have the most diesel exposure are more supportive, 69.5% (95% CI 67.2% to 71.8%)69.5% percent supporting stronger EPA enforcement of the Clean Air Act and Clean Water Act, even if it costs U.S. jobsEstimandweighted share; 95% interval clustered by countyInterval95% CI 67.2% to 71.8%n11,482WeightsCES 2020 weight (weight)PopulationCES respondents in the highest fifth of county diesel exposurePeriod2020SourceCooperative Election Study against 51.2% (95% CI 49.8% to 52.7%)51.2% percent supporting stronger EPA enforcement of the Clean Air Act and Clean Water Act, even if it costs U.S. jobsEstimandweighted share; 95% interval clustered by countyInterval95% CI 49.8% to 52.7%n11,483WeightsCES 2020 weight (weight)PopulationCES respondents in the lowest fifth of county diesel exposurePeriod2020SourceCooperative Election Study in the fifth whose counties have the least, and they are more often Democrats, 59.0% (95% CI 56.0% to 62.0%)59.0% percent Democratic (party ID 1 to 3)Estimandweighted share; 95% interval clustered by countyInterval95% CI 56.0% to 62.0%n11,482WeightsCES 2020 weight (weight)PopulationCES respondents in the highest fifth of county diesel exposurePeriod2020SourceCooperative Election Study against 32.3% (95% CI 30.9% to 33.7%)32.3% percent Democratic (party ID 1 to 3)Estimandweighted share; 95% interval clustered by countyInterval95% CI 30.9% to 33.7%n11,483WeightsCES 2020 weight (weight)PopulationCES respondents in the lowest fifth of county diesel exposurePeriod2020SourceCooperative Election Study. Support is 86.1% (95% CI 85.3% to 86.9%)86.1% percent supporting stronger EPA enforcement of the Clean Air Act and Clean Water Act, even if it costs U.S. jobsEstimandweighted share; 95% interval clustered by countyInterval95% CI 85.3% to 86.9%n28,671WeightsCES 2020 weight (weight)PopulationDemocratic respondents (seven-point party ID, leaners included)Period2020SourceCooperative Election Study among Democrats, 59.7% (95% CI 58.0% to 61.4%)59.7% percent supporting stronger EPA enforcement of the Clean Air Act and Clean Water Act, even if it costs U.S. jobsEstimandweighted share; 95% interval clustered by countyInterval95% CI 58.0% to 61.4%n8,643WeightsCES 2020 weight (weight)PopulationIndependent respondents (seven-point party ID, leaners included)Period2020SourceCooperative Election Study among independents and 30.6% (95% CI 29.5% to 31.7%)30.6% percent supporting stronger EPA enforcement of the Clean Air Act and Clean Water Act, even if it costs U.S. jobsEstimandweighted share; 95% interval clustered by countyInterval95% CI 29.5% to 31.7%n20,097WeightsCES 2020 weight (weight)PopulationRepublican respondents (seven-point party ID, leaners included)Period2020SourceCooperative Election Study among Republicans, with leaners counted in their party.

    Figure 6 fits a linear probability modelLinear probability modelA regression of a yes-or-no outcome on predictors, fitted by least squares so that each coefficient is a change in the probability of yes. The book weights it and reports robust standard errors. of support on standardized county diesel exposure, with survey weightsSurvey weightsNumbers that scale each respondent so the sample matches the population on known traits such as age, race, education and region. A weighted average counts a respondent with a large weight for more than one with a small weight. and errors clustered by county. For all respondents the coefficient is 6.4 (95% CI 5.3 to 7.6)6.4 percentage points of support per standard deviation of county diesel exposureEstimandweighted linear probability model coefficient on standardized county diesel exposure, specification: no controls; 95% interval clustered by countyInterval95% CI 5.3 to 7.6n57,411WeightsCES 2020 weight (weight)Populationall respondents in the CES 2020 samplePeriod2020SourceCooperative Election Study points per standard deviation with no controls, 1.3 (95% CI 0.9 to 1.7)1.3 percentage points of support per standard deviation of county diesel exposureEstimandweighted linear probability model coefficient on standardized county diesel exposure, specification: party id and demographics; 95% interval clustered by countyInterval95% CI 0.9 to 1.7n57,411WeightsCES 2020 weight (weight)Populationall respondents in the CES 2020 samplePeriod2020SourceCooperative Election Study points with party ID and demographics held fixed and −0.4 (95% CI −1.1 to 0.4)−0.4 percentage points of support per standard deviation of county diesel exposureEstimandweighted linear probability model coefficient on standardized county diesel exposure, specification: plus county density; 95% interval clustered by countyInterval95% CI −1.1 to 0.4n57,411WeightsCES 2020 weight (weight)Populationall respondents in the CES 2020 samplePeriod2020SourceCooperative Election Study with the density of the county added. Among Democrats it is 0.0 (95% CI −0.8 to 0.8)0.0 percentage points of support per standard deviation of county diesel exposureEstimandweighted linear probability model coefficient on standardized county diesel exposure, specification: no controls; 95% interval clustered by countyInterval95% CI −0.8 to 0.8n28,671WeightsCES 2020 weight (weight)Populationdemocrats in the CES 2020 samplePeriod2020SourceCooperative Election Study with no controls and 0.2 (95% CI −0.6 to 1.0)0.2 percentage points of support per standard deviation of county diesel exposureEstimandweighted linear probability model coefficient on standardized county diesel exposure, specification: party id and demographics; 95% interval clustered by countyInterval95% CI −0.6 to 1.0n28,671WeightsCES 2020 weight (weight)Populationdemocrats in the CES 2020 samplePeriod2020SourceCooperative Election Study with controls. Among Republicans it is 4.3 (95% CI 2.4 to 6.2)4.3 percentage points of support per standard deviation of county diesel exposureEstimandweighted linear probability model coefficient on standardized county diesel exposure, specification: no controls; 95% interval clustered by countyInterval95% CI 2.4 to 6.2n20,097WeightsCES 2020 weight (weight)Populationrepublicans in the CES 2020 samplePeriod2020SourceCooperative Election Study with no controls, 3.0 (95% CI 1.2 to 4.8)3.0 percentage points of support per standard deviation of county diesel exposureEstimandweighted linear probability model coefficient on standardized county diesel exposure, specification: party id and demographics; 95% interval clustered by countyInterval95% CI 1.2 to 4.8n20,097WeightsCES 2020 weight (weight)Populationrepublicans in the CES 2020 samplePeriod2020SourceCooperative Election Study with controls and 1.0 (95% CI −1.4 to 3.4)1.0 percentage points of support per standard deviation of county diesel exposureEstimandweighted linear probability model coefficient on standardized county diesel exposure, specification: plus county density; 95% interval clustered by countyInterval95% CI −1.4 to 3.4n20,097WeightsCES 2020 weight (weight)Populationrepublicans in the CES 2020 samplePeriod2020SourceCooperative Election Study once county density is added. With county density added every group's interval includes zero. The fifth of respondents in the most exposed counties live in only 5454 countiesEstimandcount of counties with a respondent in the groupWeightsnone (count)PopulationCES respondents in the highest fifth of county diesel exposurePeriod2020SourceCooperative Election Study counties, so large urban counties make up that end of the exposure range.

    Figure 6

    Support for EPA enforcement rises with county diesel exposure, but the rise shrinks within party and its interval includes zero with county density held fixed

    Percentage-point difference in support for strengthening EPA enforcement of the Clean Air Act and Clean Water Act even if it costs U.S. jobs, per standard deviation of county diesel exposure; 57,411 respondents in 2,630 counties, 2020; 95% intervals clustered by county

    • All respondents
    • Democrats
    • Independents
    • Republicans

    No controls

    Party ID and demographics

    Plus county density

    Support per SD of diesel (points)

    Show data
    Data for Support for EPA enforcement rises with county diesel exposure, but the rise shrinks within party and its interval includes zero with county density held fixed
    conf_highconf_lowestimategroupnspecification
    7.575.306.43All respondents57,411No controls
    1.740.8611.30All respondents57,411Party ID and demographics
    0.369−1.12−0.377All respondents57,411Plus county density
    0.829−0.7730.028Democrats28,671No controls
    0.955−0.6200.168Democrats28,671Party ID and demographics
    0.568−1.77−0.603Democrats28,671Plus county density
    4.811.343.08Independents8,643No controls
    3.51−0.1771.66Independents8,643Party ID and demographics
    1.18−4.11−1.47Independents8,643Plus county density
    6.162.394.27Republicans20,097No controls
    4.781.182.98Republicans20,097Party ID and demographics
    3.40−1.420.991Republicans20,097Plus county density
    For all respondents the coefficient falls from 6.4 points with no controls to 1.3 with party ID and demographics held fixed and −0.4 with county density added, and every group's interval includes zero at that last step. Each dot is a weighted linear probability model coefficient. The first panel uses no controls, the second holds fixed the seven-point party ID, race, education, income, age and gender, and the third adds the log density of the county. One standard deviation of county diesel exposure across respondents is 0.12 micrograms per cubic meter. Democrats, independents and Republicans include leaners, and each row is estimated on that group alone.Note: The CES is an opt-in panel, so its intervals are model based. County exposure is a county value assigned to each respondent, not an exposure the respondent was measured to have.Note: It is a different CES item from the one on giving the EPA power to regulate carbon dioxide.Source: Cooperative Election Study 2020 wave, item on strengthening EPA enforcement of the Clean Air Act and Clean Water Act, weighted with the CES survey weight; county diesel exposure from EPA EJScreen version 2.3 averaged over tracts by 2020 votes

    What these data cannot show

    The estimates describe places in one election. They do not say how the residents of a tract voted, because a pattern across areas can differ from the pattern among the people in them [6] (ecological inferenceEcological inferenceDrawing a conclusion about individuals from data on groups or places, such as counties. A pattern across counties can differ from the pattern among the people who live in them.). The vote in each tract is an allocation of precinct returns by a land-cover model and each pollution value is modeled, so the estimates carry errors that the intervals leave out. The exposures and the vote are both from 2020, so the data cannot say whether pollution changes how people vote, whether people who vote a certain way settle near sources, or whether the siting of sources follows political power, a claim the environmental justice literature makes [7].

    Holding traits fixed is partial. The controls come from the American Community Survey and carry sampling error, and density enters as one summary of urban form. The four exposures move together, so the data cannot say which one the coefficients reflect, and the county residual varies strongly between states, so a correlation across counties can reflect regional differences that the data cannot separate from exposure. Coverage is 4747 statesEstimandcount of statesWeightsnone (count)Populationstates with at least one tract in the samplePeriod2020 presidential election; EJScreen 2.3 air data for 2020SourcePrecinct votes on census geographies states, because Alaska, Hawaii and Connecticut have no tract vote estimates and the District of Columbia lacks the white share that the controls need. The survey comparison assigns a county exposure to each respondent and cannot see how much air pollution a respondent breathes. The vote is the presidential margin in one election, so the data say nothing about turnout, down-ballot races or votes on local environmental measures, and they hold no local political context, so they cannot say why tracts with more exposure vote as they do.


    Data sources

    • Precinct votes on census geographiesPrecinct votes allocated to 2020 census tracts (Fekrazad 2025) with the ACS demographics of the tract atlas (ACS years not recorded), 2020 presidential electionYears: 2016 and 2020 (contiguous United States only) · Weights: votes cast in the tract (pres_tot); full counts of tracts, no sampling weights · License: CC0 (data doi:10.7910/DVN/Z8TSH3), as stated in the project README.
    • EJScreenEPA EJScreen version 2.3 (July 2024; modeled air data for 2020), tract values in the atlas; EPA removed the tool in February 2025 and the archived copy is not recordedYears: Version as distributed with the tract atlas file. · Weights: none (tract values) · License: US government data. The EPA removed EJScreen from its website in February 2025, so the archived copy is the source to cite.
    • Area Deprivation IndexArea Deprivation Index national rank, tract values in the atlas; release year not recordedYears: Vintage as distributed with the tract and ZCTA atlas files. · Weights: none (tract values) · License: The Neighborhood Atlas may restrict commercial use and redistribution; read its terms before publishing derived tract values.
    • CDC PLACESCurrent asthma among adults, model-based tract estimates in the atlas; release year not recordedYears: Release as distributed with the tract and ZCTA atlas files. · Weights: none (tract values) · License: US government data, open access.
    • Cooperative Election StudyCooperative Election Study 2020 wave; support for strengthening EPA enforcement of the Clean Air Act and Clean Water Act even if it costs U.S. jobsYears: 2006-2024 (every year; self-reported turnout is available in the 10 even years) · Weights: weight (single wave) · License: See the provider's terms of use.

    All data sources

    Methods

    Sample: census tracts in the tract atlas (82,765 tracts in 47 states and the District of Columbia; Alaska and Hawaii have no tract vote estimates, and the tract atlas has no rows for Connecticut) with more than 100 estimated presidential votes in 2020, a two-party margin, all four pollution measures, the five controls and a land area above zero: 81,134 tracts in 47 states and 3,096 counties, carrying 155.1 million votes. The District of Columbia drops out because the atlas has no white share for its tracts. Vote: precinct returns allocated to 2020 tracts by Regionalized Land Cover Regression (Fekrazad 2025), fractional votes; margin = 100 (D minus R) over (D plus R). Pollution: tract values of EPA EJScreen version 2.3 (July 2024) in the atlas: diesel particulate matter (micrograms per cubic meter; 2020 AirToxScreen), traffic proximity (annual average daily traffic on major roads within 10 kilometers divided by distance; 2020 highway counts), nitrogen dioxide (parts per billion; NASA satellite model, 2020) and fine particles (micrograms per cubic meter; 2020). EPA removed EJScreen from its website on 5 February 2025. The atlas does not record the version or the archived copy; version 2.3 is identified from the values (the fine-particle range and the nitrogen dioxide maximum match the 2.3 documentation, and the median diesel value is close to the documented median, which is a block-group value while the atlas holds tract values, so the atlas diesel range is narrower than the documented one). Controls: white, Black and Hispanic shares of residents, college share and median household income are American Community Survey tract values; the atlas does not record the survey years. Estimands: the vote-weighted mean margin by decile of diesel exposure (equal numbers of tracts); the coefficient of the margin on each exposure standardized with the unweighted standard deviation across tracts; the share of the raw diesel coefficient that remains after controls (a ratio of point estimates); the within-county coefficient minus the pooled coefficient with density; and, across counties, the correlation of county diesel exposure with the county residual margin (the tract margin minus the margin predicted by a weighted least squares model with no pollution term, on the demographic controls alone or with log density added, averaged over the county's tracts by votes). Weights: tract presidential votes. Estimator: weighted least squares; controls are the shares of white, Black and Hispanic residents, the college share and median household income; density is the log of people per square kilometer; the within-county estimate removes the vote-weighted county mean from every variable before fitting. Interval method: 95%, clustered by county (3,096 clusters); the retained shares and the within-county differences use a county bootstrap (2,000 replicates, seed 12345, the same resampled counties for every model); correlations across tracts and counties use a county bootstrap (2,000 replicates, seed 12345); county correlations are reported weighted by county votes and unweighted, because the weighting decides the sign of the density-adjusted one; within-state correlations (county diesel exposure and the county residual margin each measured from its vote-weighted state mean, correlated with county votes as weights) and the binned means of the county residual margin over tenths of counties ordered by diesel exposure (weighted by county votes, or counting each county once) resample the 47 states (2,000 replicates, seed 12345); the share of the variance of the county residual margin that lies between states is one minus the ratio of the vote-weighted within-state variance to the total variance and has no interval; the state-clustered interval on the diesel coefficient uses 47 clusters. Intervals are model based and do not include error in the vote allocation or in the modeled pollution. The atlas does not record how EJScreen block-group values were turned into tract values (diesel and fine particles are tract values in the source). Deprivation: Area Deprivation Index national rank. Asthma: CDC PLACES current asthma among adults, a model-based estimate that cannot vary with local air (its inputs are demographic and geographic). The release years of the ADI and PLACES values are not recorded in the atlas. CES: 2020 wave, respondents with an answer on the item on strengthening EPA enforcement of the Clean Air Act and Clean Water Act even if it costs U.S. jobs (support_epa_airwater, from the source item enviro_airwateracts, coded 1 for support), a seven-point party ID and a county in the tract sample (57,411 respondents in 2,630 counties); weighted least squares on a 0 or 100 outcome with the survey weight; county exposure is the vote-weighted county mean of tract diesel exposure. Suppression: tracts with 100 or fewer votes are dropped; no survey cell rests on fewer than 30 respondents; tract deciles and county values are full counts of tracts and counties.

    References

    1. Fekrazad, Amir (2025). A dataset of US precinct votes allocated to Census geographies with precision. Scientific Data 12: 794. doi:10.1038/s41597-025-05140-3
    2. US Environmental Protection Agency (2024). EJScreen Technical Documentation for Version 2.3 (revised July 31, 2024). Office of Environmental Justice and External Civil Rights, Washington, DC. epa.gov/system/files/documents/2024-07/ejscreen-tech-doc-version-2-3.pdf
    3. Kind, Amy J. H.; Buckingham, William R. (2018). Making Neighborhood-Disadvantage Metrics Accessible: The Neighborhood Atlas. New England Journal of Medicine 378: 2456-2458. doi:10.1056/NEJMp1802313
    4. Rodden, Jonathan A. (2019). Why Cities Lose: The Deep Roots of the Urban-Rural Political Divide. Basic Books, New York.
    5. 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
    6. Robinson, W. S. (1950). Ecological Correlations and the Behavior of Individuals. American Sociological Review 15(3): 351-357.
    7. Mohai, Paul; Pellow, David; Roberts, J. Timmons (2009). Environmental Justice. Annual Review of Environment and Resources 34: 405-430. doi:10.1146/annurev-environ-082508-094348

    How to cite

    @misc{singh2026airpollutionandthevote,
      author = {Singh, Vishal},
      title = {Air pollution and the vote},
      year = {2026},
      url = {https://vishalsingh.org/politics/air-pollution-and-the-vote},
      note = {In The Public Mind. Published 30 September 2026.}
    }

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