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Table 6 Regression for factors associated with arsenic concentration (μg/L) in community water systems (CWS), 2005-2007, San Joaquin Valley, CA (n=464)

From: Environmental justice implications of arsenic contamination in California’s San Joaquin Valley: a cross-sectional, cluster-design examining exposure and compliance in community drinking water systems

Variable Model Aa Model Ba Model Cb Model D (< 200 Conections) Model E (≥ 200 Connections)
Constant 20.0 (6.7, 33.3) 11.2 (6.1, 16.4) 9.7 (−11.8, 31.3) 18.2 (−11.9, 49.1) 8.7 (−11.7, 49.1)
% People of Color   −0.01 (−0.11, 0.08) −0.02 (−.13, 0.09) −0.17* (−0.36, 0.02) .03 (−0.09, 0.15)
% Home ownership -.14 (−0.34, 0.05)   −0.27** (−0.50, -0.05) −0.43** (−0.84, -0.03) -.19* (−0.40, 0.02)
Groundwater or combinedc    11.4*** (7.5, 15.2) 11.5*** (6.1, 16.9) 8.4*** (4.2, 12.6)
Private non-PUC regulatedd    5.6* (−1.0, 12.2) 8.5** (0.73, 16.3) 1.2 (−5.4, 7.9)
Publicd    6.9** (0.61, 13.11) 7.5* (−0.76, 15.8) 6.4* (−0.99, 13.8)
< 200 service connections    2.6 (−1.2, 6.5) na na
2006e    2.8** (0.52, 5.1) 4.4** (0.27, 8.4) 1.8 (−.76, 4.3)
2007e    1.2 (−0.51, 2.9) 2.4* (−0.11, 4.9) .52 (−1.8, 2.9)
Summer/fall    -.27 (−1.9, 1.4) .43 (−3.1, 4.0) -.27 (−2.1, 1.5)
Valley f    −1.4 (−6.5, 3.7) 6.4 (−2.3, 14.9) −4.4 (−10.6, 1.8)
Foothills f    6.9* (0.32, 13.5) 12.1*** (3.9, 20.4) 5.1 (−1.0, 11.3)
  1. Regression with robust standard errors, clustered by CWS. Coefficients represent the estimated difference in mean concentration at the system-level associated with a unit change in the covariate (95% CI); na=not applicable, as no CWSs in this model run contains this factor, or all CWSs have this factor.
  2. aUnadjusted models, all CWSs included; bAdjusted model, all CWSs included; c Surface water is referent category; combined refers to combination of groundwater and surface water sources; dPrivately owned PUC-regulated CWS as referent category; e 2005 is referent year; f Mountains is referent category.
  3. * p < .10, ** p < .05, *** p < .01; R2 in Model B = .08; R2 in Model C = .09.