Table 2

Correlation coefficients between measured PCE concentrations in water samples and model-generated estimates

No. of Samples
 Spearman Correlation Coefficient
 P-Value
All Samples
 88
 0.48
 < 0.001




According to:


Complexity of pipe configurationa


     Simple
 31
 0.51
 0.003
     Complex
 57
 0.38
 0.003




Magnitude of flowa


     High (> 19 homes)
 19
 0.37
 0.1
     Medium (3–19 homes)
 33
 0.30
 0.09
     Low (< = 2 homes)
 36
 0.54
 0.0007




Position along pipea


     End
 44
 0.44
 0.003
     Beginning/Middle
 44
 0.44
 0.003




Overestimated housing densitya


     Yes
 25
 0.52
 0.008
     No
 63
 0.47
 0.0001




Season sampleda


     Spring
 74
 0.50
 < 0.0001
     Autumn
 14
 0.58
 0.03




Water fixture sampleda


     Tap or spigot
 10
 0.84
 0.002
     Hydrant
 18
 0.34
 0.2
     Unknown
 60
 0.38
 0.003




Sampling personnela


     Sampler 1
 69
 0.45
 0.0001
     Sampler 2
 18
 0.57
 0.01
     Sampler 3
 1
 ---b
 ---b




Towna


     Barnstable
 7
 ---c
 ---c
     Bourne
 16
 0.53
 0.03
     Brewster
 7
 0.018
 1.0
     Chatham
 6
 0.39
 0.4
     Falmouth
 6
 0.49
 0.3
     Provincetown
 5
 ---c
 ---c
     Sandwich
 9
 0.53
 0.1
     Plymouth
 25
 0.56
 0.003
     Wareham
 7
 0.48
 0.3




Pipe installation yeara


     1968–1972
 23
 0.42
 0.05
     1973–1976
 32
 0.56
 0.0008
     1977–1980
 33
 0.37
 0.03

a See text for definitions and further description.

b Analyses were not conducted because of the small sample size.

c Analyses were not conducted because all water samples had undetectable PCE levels.

Spence et al. Environmental Health 2008 7:24   doi:10.1186/1476-069X-7-24