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Table 5 Regression results for nitrate in community water systems stratified by region

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

Variable

Midwesta (n = 8869)

Northeasta (n = 6572)

Southa (n = 14,452)

Westa (n = 9573)

Percent Change (95% CI)

p-value

Percent Change (95% CI)

p-value

Percent Change (95% CI)

p-value

Percent Change (95% CI)

p-value

Percent Black, non-Hispanicb

−0.4 (−1.6, 0.7)

0.481

−1.1 (−2.4, 0.2)

0.101

−1.2 (−1.5, −1.0)

< 0.0001

1.0 (−0.9, 2.9)

0.289

Percent Hispanicb

−0.8 (−1.5, 0.0)

0.045

4.0 (3.1, 5.0)

< 0.0001

1.9 (1.6, 2.2)

< 0.0001

1.4 (1.1, 1.7)

< 0.0001

Percent povertyb

0.8 (−0.4, 2.0)

0.181

−3.8 (−5.0, −2.6)

< 0.0001

−0.6 (−1.2, 0.1)

0.116

−1.7 (−2.4, −1.0)

< 0.0001

Percent home ownershipb

0.4 (−0.4, 1.2)

0.331

--e

 

0.5 (0.0, 1.0)

0.063

−1.3 (−1.9, −0.7)

< 0.0001

Percent urban householdsb

−0.4 (−0.6, −0.3)

< 0.0001

0.2 (0.1, 0.4)

0.003

0.1 (0.0, 0.2)

0.083

--e

 

System size: Smallc

33.0 (23.2, 43.6)

< 0.0001

30.4 (18.2, 44.0)

< 0.0001

−8.9 (−15.0, −2.5)

0.011

3.5 (−4.5, 12.3)

0.402

System size: Mediumc

54.4 (36.6, 74.5)

< 0.0001

27.3 (9.6, 48.0)

0.002

−14.8 (−21.8, −7.2)

0.0003

18.5 (3.9, 35.2)

0.012

System size: Largec

103 (74.1, 137)

< 0.0001

35.9 (13.5, 62.6)

0.0008

−11.2 (−20.5, −0.9)

0.036

38.8 (21.0, 59.1)

< 0.0001

System size: V. Largec

223 (102, 418)

< 0.0001

23.1 (−18.5, 85.9)

0.324

−14.8 (−33.6, 9.3)

0.208

98.6 (47.3, 168)

< 0.0001

Source water: Groundwaterd

−14.8 (−27.3, −0.1)

0.049

53.3 (34.7, 74.4)

< 0.0001

−16.6 (−24.3, −8.1)

0.0003

139 (115, 167)

< 0.0001

Percent croplandb

−0.2 (−0.3, 0.0)

0.100

1.4 (0.8, 2.1)

< 0.0001

1.4 (1.2, 1.6)

< 0.0001

0.5 (0.2, 0.7)

0.0006

Livestock per 100 acresb

0.1 (−0.1, 0.2)

0.304

0.7 (0.3, 1.1)

0.0005

−0.1 (−0.3, 0.0)

0.085

1.7 (1.2, 2.2)

< 0.0001

  1. Note: Percent change in nitrate concentration from pooled regression results using county-level demographic, land use, and water system characteristics in each of the four U.S. regions. Models include state-specific random intercepts and a fixed intercept term
  2. aFor a visual depiction of which states are in each U.S. region, refer to Fig. 1
  3. bContinuous predictor, table estimates reflect effect of one-unit change in the predictor
  4. cReferent group: very small systems. dReferent group: surface water. eNot included in final model
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Environmental Health

ISSN: 1476-069X