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Table 4 Comparison of regression results for nitrate in community water systems using city- and county-level demographics

From: Environmental justice and drinking water quality: are there socioeconomic disparities in nitrate levels in U.S. drinking water?

Variable City Demographics County Demographics
Percent change (95% CI) p-value Percent change (95% CI) p-value
Percent Black, non-Hispanica −0.4 (−0.7, −0.2) 0.0016 −0.7 (−1.1, −0.3) 0.001
Percent Hispanica 0.3 (0.1, 0.5) 0.017 0.9 (0.6, 1.3) < 0.0001
Percent povertya −0.2 (−0.6, 0.1) 0.170 −1.9 (−2.5, −1.2) < 0.0001
Percent home ownershipa −0.4 (−0.6, −0.2) 0.0004 0.3 (−0.3, 0.8) 0.325
Percent urban householdsa 0.2 (0.1, 0.3) < 0.0001 0.1 (0.0, 0.2) 0.222
System size: Smallb 11.8 (5.5, 18.5) 0.0002 11.4 (5.2, 18.0) 0.0002
System size: Mediumb 12.3 (3.8, 21.5) 0.004 14.1 (5.6, 23.3) 0.0009
System size: Largeb 22.8 (12.2, 34.4) < 0.0001 29.7 (18.6, 41.8) < 0.0001
System size: V. Largeb 21.2 (−2.5, 50.5) 0.083 34.7 (8.7, 67.1) 0.007
Source water: Groundwaterc 35.8 (24.9, 47.7) < 0.0001 35.2 (24.4, 47.0) < 0.0001
Percent croplanda 0.5 (0.3, 0.6) < 0.0001 0.4 (0.2, 0.6) < 0.0001
Livestock per 100 acresa 0.1 (0.0, 0.2) 0.123 0.1 (−0.1, 0.2) 0.313
Region: Northeastd 62.3 (−8.8, 189) 0.100 −13.8 (−52.2, 55.5) 0.622
Region: Southd 48.2 (−13.8, 155) 0.155 −3.2 (−44.7, 69.6) 0.910
Region: Westd 82.1 (2.4, 224) 0.041 −42.9 (−67.5, 0.2) 0.051
  1. Notes: Percent change in nitrate concentration from pooled regression results using city- and county-level demographic, land use, and water system characteristics. Analyses based only on CWSs with available information about both the cities and counties served (N = 19,987). Models include state-specific random intercepts and a fixed intercept term
  2. aContinuous predictor, table estimates reflect effect of one-unit change in the predictor
  3. bReferent group: very small systems. cReferent group: surface water. dReferent group: Midwest