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Table 2 Agreement* between arsenic measures, overall and by type of water source

From: Water quality monitoring records for estimating tap water arsenic and nitrate: a validation study

  Radius (maximum distance between residence and water source, miles)
  0.5 1 2 3 4 5 6 7 8 9 10
All residences (N = 107)            
% with monitoring data in radius 30 58 78 89 92 93 98 99 100 100 100
Agreement*            
All sources in radius            
   Mean 0.49 0.30 0.32 0.20 0.18 0.15 0.12 0.04 0.05 0.08 0.09
   Maximum 0.51 0.26 0.26 0.21 0.24 0.20 0.16 0.12 0.15 0.16 0.17
   Most recent 0.49 0.33 0.13 0.10 0.17 0.07 0.20 0.17 0.24 0.25 0.31
Closest source only            
   Mean 0.49 0.35 0.19 0.11 0.10 0.09 0.11 0.11 0.13 0.13 0.13
   Maximum 0.47 0.36 0.19 0.11 0.10 0.09 0.10 0.10 0.12 0.12 0.12
   Most recent 0.49 0.35 0.17 0.09 0.08 0.08 0.09 0.09 0.11 0.11 0.11
Residences on a public system† (N = 89)            
% with monitoring data in radius 31 60 81 89 91 93 98 99 100 100 100
Agreement* (mean, all sources in radius) 0.41 0.21 0.29 0.24 0.22 0.15 0.09 0.02 0.03 0.08 0.09
Residences with a private well‡(N = 18)            
% with monitoring data in radius 22 50 61 89 94 94 100 100 100 100 100
Agreement* (mean, all sources in radius) 1.0 0.68 0.67 0.22 0.32 0.32 0.35 0.25 0.27 0.29 0.32
  1. * Correlation (Spearman's rho) between arsenic levels measured in tap water of individual residences and selected summary measures estimated for that home using public water quality monitoring data and geographic information systems (GIS).
  2. Water system served by wells, surface sources or other sources with federally-mandated monitoring.
  3. ‡ Individual or shared private well, not subject to federally-mandated monitoring.