Manoj K. Mohanty and Baojie Zhang
Department of Mining and Mineral Resources
Engineering
Southern Illinois University at Carbondale
ISTC Research Symposium – September 9, 2009





Introduction
Objective
Project Methodology
Data Compilation
Data Analysis
 Individual correlation coefficients (r)
 Hypothesis testing
 Multiple regression analysis




Monthly Average Concentrations
Conclusions
Recommendations
Acknowledgements
2
3
Causes of Birth Defects
Illustration by Electronic Illustrators Group.
http://medical-dictionary.thefreedictionary.com/Birth+Defects
4
US Corn-belt
Past studies indicate:
• Illinois- among the highly nitrate
contaminated states.
• Atrazine was detected in146 streams
out of 149 sampled in the Midwestern
states.
• Iowa study- Higher rates of intrauterine
growth retardation (IUGR) with higher
level of atrazine in drinking water
• Indiana study- Detrimental effects of
disinfectant byproducts.
Source:
http://en.wikipedia.org/wiki/Grain_Belt
5
To investigate the correlation of incidence rates of various negative
reproductive outcomes with the concentration of key agrochemical
based contaminants and disinfectant byproducts in drinking water
used in Illinois.
Negative reproductive outcomes:
Drinking Water Contaminants:
•
Nitrate
• Birth defects
•
Nitrite
• Adverse pregnancy outcomes
•
Atrazine
• Preterm births
•
Total trihalomethanes (TTHM)
•
Five haloacetic acids (HAA5)
6
1. Central Nervous System Defects
•
Anencephalus
•
Encephalocele
•
Hydrocephalus
•
Microcephalus
•
Spina bifida
2. Cardiovascular System Defects
•
Aortic valve stenosis
•
Atrial septal defect
•
Coarctation of aorta
•
Common truncus
•
Ebstein anomaly
•
Endocardial cushion defect
•
Hypoplastic left heart syndrome
•
Patent ductus arteriosus
•
Pulmonary artery anomalies
•
Pulmonary valve atresia and stenosis
•
Tetralogy of Fallot
•
Transposition of great arteries
•
Tricuspid valve atresia and stenosis
•
Ventricular septal defect
3. Respiratory System Defects
•
Lung agenesis/hypoplasia
4. Alimentary Tract Defects
• Biliary atresia
• Choanal atresia
• Cleft lip
• Cleft palate
• Esophageal atresia
• Hirschsprung disease
• Pyloric stenosis
• Rectal or large intestinal atresia/stenosis
5. Genitourinary System Defects
• Bladder exstrophy
• Hypospadias
• Obstructive genitourinary defect
• Renal agenesis/hypoplasia
• Epispadias
6. Musculoskeletal Defects
• Club foot
• Congenital hip dislocation
• Diaphragmatic hernia
• Gastroschisis
• omphalocele
• Reduction deformity
7. Chromosomal Defects
• Down syndrome
• Edward syndrome
• Patau syndrome
7
1. Very low birth weight
4. Perinatal deaths
2. Serious Congenital Infections
5. Endocrine Metabolic or Immune Disorder
•
Chlamydia
•
Adrenogenital syndrome
•
Congenital syphilis
•
Gystic fibrosis
•
Congenital tetanus
•
Immune deficiency disease
•
Cytomegalovirus
•
Inborn errors of metabolism
•
Gonorrhea
•
Neonatal hypothyroidism
•
Group B streptococcus
6. Fetal Alcohol Syndrome
•
Hepatitis B virus
7. Other Adverse Pregnancy Outcomes
•
Herps
•
Cerebral lipidoses
•
Listeriosis
•
Choriretinitis
•
Rubela
•
Endocardial fiberoelastosis
•
Sepsis
•
Intrauterine growth retardation
3. Blood Disorder
•
Neurofibromatosis
•
Coagulation
•
Occlusion of cerebral arteries
•
Constitutional aplastic anemia
•
Retinopathy of prematurity
•
Hereditary hemolytic anemia
•
Strabismus
•
Leukomia
8
1.
2.
3.
4.
Negative reproductive outcome (NRO) data for each
county in Illinois for the five year period: 1998-2002.
Drinking-water contaminant data from community water
supplies (CWS) for the same time period.
Correlation coefficients (r) between individual NRO and
drinking water contaminants based on sample data and
hypothesis testing.
Multiple regression analysis to investigate the correlations
and their statistical significance by considering all five
water contaminants simultaneously.
9
Example County: ADAMS
Birth Defects
Central Nervous System Defects
Cardiovascular System Defects
Respiratory System Defects
Alimentary Tract Defects
Genitourinary System Defects
Musculoskeletal Defects
Chromosomal Defects
Total
Incidence
Cases
Rate
5
12.0
52
125.1
3
7.2
7
16.8
17
40.9
16
38.5
4
9.6
104
249.9
10
2
County
Birth Defect Rates
for Each County
Adams
Alexander
Bond
Boone
Brown
Bureau
Calhoun
Carroll
Cass
Champaign
Christian
Clark
Clay
Clinton
Coles
Cook
Crawford
Cumberland
DeKalb
DeWitt
Douglas
DuPage
Edgar
Edwards
Effingham
Fayette
Ford
Franklin
Fulton
Gallatin
Greene
Grundy
Hamilton
Hancock
Hardin
Henderson
Henry
Iroquois
Jackson
Jasper
Jefferson
Jersey
JoDaviess
Johnson
Kane
Kankakee
Case
104
8
14
127
3
48
3
18
39
176
61
8
18
47
74
6113
12
10
181
31
27
1202
16
6
85
29
20
33
71
1
24
49
11
15
3
5
74
32
49
13
50
23
12
6
774
154
1
Rate
249.9
121.9
148.9
426.2
112.8
228.7
119.1
203.2
406.1
158.4
304.8
83.9
196.6
241.3
249.9
144.7
111.9
158.7
322.2
298.0
182.8
184.2
147.6
156.6
368.5
231.4
230.1
142.8
352.0
30.4
286.1
202.7
245.1
135.4
138.9
135.0
259.5
177.9
147.3
233.9
211.3
193.8
101.6
89.5
200.7
200.3
95% CI
Lower
Upper
204.2
302.8
52.6
240.2
81.4
249.8
355.3
507.1
23.3
329.6
168.6
303.2
24.6
348.1
120.5
321.2
288.8
555.2
135.8
183.6
233.1
391.5
36.2
165.4
116.5
310.7
177.3
320.9
196.2
313.7
48.5
240.6
57.8
195.5
76.1
291.8
277.0
372.7
202.5
423.0
120.4
265.9
153.2
368.1
84.4
239.8
57.5
340.9
294.4
455.7
154.9
332.3
140.5
355.4
98.3
200.6
274.9
444.0
0.8
169.4
183.3
425.7
150.0
268.0
122.4
438.6
75.8
223.3
28.6
405.9
43.8
315.2
203.7
325.7
121.7
251.2
109.0
194.7
124.6
400.0
156.8
278.5
122.9
290.9
52.5
177.5
32.9
194.9
186.9
215.4
170.0
234.6
2
County
Lee
Livingston
Logan
McDonough
McHenry
McLean
Macon
Macoupin
Madison
Marion
Marshall
Mason
Massac
Menard
Mercer
Monroe
Montgomery
Morgan
Moultrie
Ogle
Peoria
Perry
Piatt
Pike
Pope
Pulaski
Putnam
Randolph
Richland
Rock Island
St. Clair
Saline
Sangamon
Schuyler
Scott
Shelby
Stark
Stephenson
Tazewell
Union
Vermilion
Wabash
Warren
Washington
Wayne
White
Case
51
55
55
41
485
356
254
65
385
72
27
32
4
10
32
31
38
78
35
137
382
17
12
23
0
7
14
36
12
339
363
33
383
4
8
30
18
104
216
15
93
1
34
16
13
11
1
Rate
275.1
223.7
326.1
276.1
240.6
356.0
340.3
235.1
231.0
273.6
396.1
350.9
42.1
149.3
336.8
183.1
221.8
371.6
369.0
452.4
290.6
139.4
139.3
241.8
0.0
150.8
425.6
185.8
121.2
324.9
202.5
215.1
303.7
106.9
259.0
246.8
485.6
346.0
274.3
144.3
161.2
14.2
326.5
190.1
126.9
133.8
95% CI
Lower
Upper
204.8
361.7
168.5
291.2
245.7
424.5
198.1
374.5
219.6
263.0
320.0
395.0
299.7
384.8
181.5
299.7
208.5
255.3
214.0
344.5
261.0
576.3
240.0
495.4
11.5
107.7
71.6
274.6
230.4
475.5
124.4
259.9
156.9
304.4
293.7
463.8
257.0
513.1
379.8
534.8
262.2
321.2
81.2
223.2
72.0
243.3
153.3
362.8
0.0
227.9
60.6
310.6
232.7
714.1
130.1
257.2
62.6
211.6
291.2
361.4
182.2
224.5
148.1
302.1
274.1
335.7
29.1
273.6
111.8
510.3
166.5
352.4
287.8
767.5
282.7
419.3
239.0
313.5
80.8
238.0
130.1
197.5
0.4
78.9
226.1
456.2
108.7
308.7
67.6
217.0
66.8
239.5
11
For all 102 counties in Illinois over the period of 1998-2002:
Negative
Reproductive
Outcomes
Number of
Incidences
Incidence
Rate Range
Birth Defects
17,379
0 to 485.6
Adverse Pregnancy
38,738
0 to 540.7
Preterm Birth
89,097
358.3 to1462.9
12
County: ADAMS
Nitrate Data
CWS
No. of
Observation
1
2
3
4
5
6
7
8
9
20
5
19
18
5
5
9
20
5
Observed
Value
(mg/L)
8.057
3.360
6.348
5.318
2.200
2.302
0.820
6.167
2.704
Total
106
2.641
Population
Served
159
883
1066
248
45000
600
1812
4890
98
54,756
Detection
Limit
(mg/L)
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
Censored
Value
(mg/L)
8.057
3.360
6.348
5.318
2.200
2.302
0.876
6.167
2.704
2.643
13
County: ADAMS
Nitrite Data
CWS
No. of
Observation
1
2
3
4
5
6
7
8
9
Total
20
5
19
18
5
5
9
20
5
106
Observed
Detection Censored
Population
Value
Limit
Value
Served
(mg/L)
(mg/L)
(mg/L)
0.00
159
0.1
0.10
0.02
883
0.1
0.12
0.00
1066
0.1
0.10
0.00
248
0.1
0.10
0.00
45000
0.1
0.11
0.00
600
0.1
0.10
0.00
1812
0.1
0.10
0.00
4890
0.1
0.10
0.00
98
0.1
0.10
0.000
54,756
0.109
14
Nitrite Data for
Each County
County
Number
Population
Adams
Alexander
Bond
Boone
Brown
Bureau
Calhoun
Carroll
Cass
Champaign
Christian
Clark
Clay
Clinton
Coles
Cook
Crawford
Cumberland
DeKalb
DeWitt
Douglas
DuPage
Edgar
Edwards
Effingham
Fayette
Ford
Franklin
Fulton
Gallatin
Greene
Grundy
Hamilton
Hancock
Hardin
Henderson
Henry
Iroquois
Jackson
Jasper
Jefferson
Jersey
JoDaviess
Johnson
Kane
106
20
13
89
10
130
22
79
36
142
72
158
15
64
63
273
123
37
201
46
34
172
114
18
41
25
56
4
52
56
54
138
N/A
42
10
70
236
222
13
20
1
11
135
15
324
56735
6349
13102
32718
629
26658
4963
10012
10353
162942
29743
10306
7647
30480
43574
3832774
11028
4801
73449
11741
6208
321168
12540
4036
18931
14279
10614
39018
24412
4221
10107
29928
8621
10897
17471
6442
36242
20194
26074
10117
40045
13007
22289
5885
388361
Observed
Mean
0.0003
0.0063
0.0000
0.0000
0.0000
0.0080
0.0000
0.0000
0.0000
0.0078
0.0018
0.0401
0.1854
0.0144
0.0084
0.0001
0.0025
0.0276
0.0001
0.0025
0.0336
0.0034
0.0835
0.0404
0.0008
0.0000
0.0028
0.0000
0.0008
0.0025
0.0000
0.0001
N/A
0.0014
0.0000
0.0000
0.0068
0.0126
0.0000
0.0000
0.0000
0.0000
0.0010
0.0000
0.0010
Censored
Mean
0.1085
0.0466
0.1000
0.1102
0.1000
0.1026
0.1020
0.1111
0.1000
0.0438
0.1171
0.1220
0.2737
0.1401
0.0566
0.1015
0.1022
0.1063
0.0998
0.1009
0.1253
0.1007
0.0959
0.2042
0.1113
0.1162
0.1092
0.1000
0.1123
0.1013
0.1000
0.0857
N/A
0.1354
0.1000
0.1065
0.1373
0.1169
0.1976
0.1000
0.1000
0.1000
0.1022
0.1000
0.1014
County
Number
Population
Lee
Livingston
Logan
Macon
Macoupin
Madison
Marion
Marshall
Mason
Massac
McDonough
McHenry
McLean
Menard
Mercer
Monroe
Montgomery
Morgan
Moultrie
Ogle
Peoria
Perry
Piatt
Pike
Pope
Pulaski
Putnam
Randolph
Richland
Rock Island
Saline
Sangamon
Schuyler
Scott
Shelby
St. Clair
Stark
Stephenson
Tazewell
Union
Vermilion
Wabash
Warren
Washington
Wayne
106
91
132
50
39
131
24
99
35
18
58
302
146
24
104
25
55
31
25
206
241
13
64
108
4
23
35
82
22
279
5
83
10
25
91
33
22
109
344
15
129
55
49
7
22
30558
28328
19623
96575
25433
221024
40498
13180
16038
6803
21714
179319
121079
7695
16957
21017
18417
25552
14287
32631
160075
17714
10248
11279
4413
7348
6086
21967
8118
117776
24808
149308
3070
5537
22893
201705
6332
48979
107229
10089
52518
9196
18735
8234
10815
Observed
Mean
0.0000
0.0248
0.0325
0.0127
0.0013
0.0073
0.0555
0.0000
0.0000
0.0000
0.0008
0.0034
0.0022
0.0000
0.0412
0.0026
0.0000
0.0005
0.0552
0.0000
0.0009
0.0163
0.0212
0.0008
0.0000
0.0020
0.0000
0.0093
0.0000
0.0047
0.0000
0.0000
0.0000
0.0000
0.0025
0.0055
0.0348
0.0001
0.0063
0.0000
0.0081
0.0006
0.0102
0.0317
0.0018
Censored
Mean
0.1017
0.0865
0.1290
0.1097
0.1327
0.0598
0.1611
0.1149
0.1062
0.1000
0.0977
0.1288
0.0757
0.1000
0.1294
0.1113
0.1708
0.1070
0.1217
0.1040
0.0438
0.1343
0.1210
0.1632
0.1000
0.1000
0.1000
0.1039
0.1953
0.1021
0.1140
0.1043
0.1000
0.1000
0.1020
0.0313
0.1270
0.1760
0.1012
0.1000
0.1020
0.1003
0.1152
0.0524
15
0.1722
Contaminants
Number of
in Drinking
Measurements
Water
Nitrate
10,967
Nitrite
9,909
Atrazine
5,504
TTHM
7,409
HAA5
4,407
Observed
Concentration
Range
Censored
Concentration
Range
0 to 4.90
mg/L
0 to 0.190
mg/L
0 to 1.02
µg/L
0.213 to 84.8
µg/L
0 to 64.9
µg/L
0.043 to 4.91
mg/L
0.031 to 0.274
mg/L
0.156 to 1.185
µg/L
0.947 to 84.9
µg/L
1.00 to 64.9
µg/L
Observed
Censored
Average IL
Average IL
Concentration Concentration
0.652
mg/L
0.003
mg/L
0.067
ug/L
23.3
µg/L
10.4
µg/L
0.709
mg/L
0.100
mg/L
0.343
µg/L
23.2
µg/L
10.6
µg/L
MCL
10 mg/L
1
mg/L
3
µg/L
80
µg/L
60
µg/L
16

Correlation Analysis
where,
SSxy=
SSxx=
SSyy=
xi: contaminant concentration for each county
yi: rate of negative reproductive outcome for each county

Hypothesis testing
where n represents the number of county water contaminant
concentration values and r is the sample correlation
coefficient
17
Sample correlation coefficient and hypothesis testing results
BD
APO
PB
t-BD
t-APO
t-PB
Absolute t-critical; α=0.2; =80
Significant Correlation
Nitrate
Nitrate
(Observed data) (Censored data)
0.163
0.164
0.032
0.033
0.062
0.062
1.476
1.491
0.288
0.296
0.553
0.555
1.294
1.294
BD only
BD only
BD: Birth defect; APO: Adverse Pregnancy Outcome; PB: Preterm Birth
18
Statistically Significant Correlations
Nitrate Nitrite Atrazine TTHM HAA5
Based
on Observed
Contaminant Data
Based
on Censored
Contaminant Data
BD
APO
BD
APO
PB
PB
PB
PB
BD
PB
PB
BD
PB
BD: Birth defect; APO: Adverse Pregnancy Outcome; PB: Preterm Birth
19
Multiple Regression Analysis
Adverse Pregnancy Outcomes
First Step - All Variables Entered
R2 = 0.3576
DF
Regression
Error
Total
20
61
81
Variable
Value
Sum of
Squares
336543.96
604648.99
941192.96
Final Step – Significant Variables
R2 = 0.2824
Mean
Square
16827.20
9912.28
F Ratio
Prob(F)
1.6976
0.0590
DF
Regression
Error
Total
Standard
t-ratio
Prob(t)
Variable
Error
Intercept
341.5898
17.5006
19.5188
0.0000
Intercept
X1
-12.2542
28.1969
-0.4346
0.6654
X4
X2
-22.8035
21.5956
-1.0559
0.2952
X5
X3
-24.6700
34.9375
-0.7061
0.4828
X1*X2
X4
-126.7511
34.0797
-3.7193
0.0004
X1*X4
X5
125.3061
39.7763
3.1503
0.0025
X2*X3
X1^2
2.8801
11.5610
0.2491
0.8041
X2*X5
X1*X2
-19.7633
18.4164
-1.0731
0.2874
X4*X5
X1*X3
6.5454
20.3016
0.3224
0.7483
X4^2
X1*X4
58.8689
21.5424
2.7327
0.0082
X1*X5
-31.8425
32.2058
-0.9887
0.3267
X2^2
-2.2452
7.4131
-0.3029
0.7630
X2*X3
14.7828
15.8718
0.9314
0.3553
X2*X4
59.0453
30.2566
1.9515
0.0556
X2*X5
-44.6522
23.1555
-1.9284
0.0585
X3^2
4.7412
9.0755
0.5224
0.6033
X3*X4
-21.0662
43.3601
-0.4858
0.6288
X3*X5
35.8869
34.8607
1.0294
0.3073
X4^2
52.4069
15.9505
3.2856
0.0017
X4*X5
-81.2761
25.2204
-3.2226
0.0020
X5^2
10.5416
19.8922
0.5299
0.5981
X1: Nitrate mg/L; X2: Nitrite mg/L; X3: Atrazine, ug/L; X4: TTHM ug/L; X5: HAA5 ug/L; L
8
73
81
Value
336.3542
-92.9137
80.8744
-26.9575
41.7613
20.4827
-19.6211
-50.5058
46.5344
Sum of
Squares
265786.12
675406.84
941192.96
Mean
Square
33223.26
9252.15
F
Ratio
3.5909
Standard
Error
13.3080
26.0995
27.8310
13.2648
11.0803
11.3337
9.6265
14.1453
13.1761
t-ratio
Prob(t)
25.2745
-3.5600
2.9059
-2.0323
3.7690
1.8072
-2.0382
-3.5705
3.5317
0.0000
0.0007
0.0048
0.0458
0.0003
0.0749
0.0452
0.0006
0.0007
Prob(F)
0.0015
20
No. of
County
Data
82
Initial
R2
0.206
Final
R2
0.132
F-ratio
1.90
Critical
F-value
1.85
Significant main
factors
X3, X4,X4^2
Significant factor
interactions
X1*X3,X1*X4, X4*X5
BD
Censored
82
0.163
0.092
1.95
2.02
X4,X4^2
X1*X4, X4*X5
APO
Observed
82
0.358
0.286
3.65
1.76
X2,X4,X5,X3^2,X4
^2
X1*X4,X2*X5,X4*X5
APO
Censored
82
0.358
0.282
3.59
1.76
X4, X5, X4^2
X1*X2,X1*X4,X2*X3
X2*X5,X4*X5,
PB
Observed
82
0.166
0.110
1.97
1.92
X5, X1^2
X1*X2,X1*X4,X2*X5
PB
Censored
82
0.206
0.118
2.58
2.02
X2,X3,X5,X4^2
NA
BD
Observed
Final
X1: nitrate; X2: nitrite; X3: atrazine; X4: TTHM and X5:HAA5
BD: Birth defect; APO: Adverse Pregnancy Outcome; PB: Preterm Birth
21
22
23
24
25
26




As much as 16.3%, 35.8% and 20.6% of the variability
in the rates of birth defects, adverse pregnancy
outcomes and preterm births is explained by five
contaminants (nitrate, nitrite, atrazine, TTHM and
HAA5) in public drinking water supplies in IL.
TTHM, HAA5 and Nitrate- statistically significant for all
three categories of negative reproductive outcomes.
Nitrite is significant for APO and PB only.
Atrazine is significant for all three categories of
negative reproductive outcomes except the BD model
based on censored data and PB model based on
observed data.
27





The monthly average concentrations of all three agrochemical based contaminants are much higher in surface
water based CWS.
Concentration of disinfectant byproducts are more in the
GW based water supplies.
Atrazine concentration peaks in the months of May/Juneagrees well with past studies.
The peak monthly average concentrations (118 μg/L in May
and 98 μg/L in November) for TTHM are well above the
corresponding MCL of 80 μg/L .
The peak concentrations of HAA5 of 75 μg/L in May and
100 μg/L in November for HAA5 are well above the
corresponding MCL of 60μg/L .
28



Surface water based CWS and Ground water based
CWS may be separately examined.
For developing meaningful correlations for some of the
individual BD and APO, a data set covering a much
longer time period (maybe 10 to 20 years) will be
required.
A much more comprehensive study using controlled
experiments in future should include all known factors
contributing to various negative reproductive outcomes
to develop predictive models for each or at least some of
them.
29





Illinois Sustainable Technology Center
United States Geological Survey
Illinois Environmental Protection Agency
Illinois Department of Public Health
Indiana University Medical Research Center
30
31
32
33
Correlation among the exploratory variables
Nitrate Nitrite Atrazine
Statistically Significant
Contaminant Based
on Observed Data
Statistically Significant
Contaminant Based
on Censored Data
TTHM
HAA5 HAA5
TTHM
TTHM HAA5 HAA5
TTHM
HAA5
HAA5
TTHM
Atrazine Atrazine
HAA5
TTHM
Atrazine Atrazine
Nitrate
Nitrite
34

Occurrence of a specific adverse outcome is assumed to be a rare event, therefore
such occurrences are assumed to follow a Poisson distribution. Where there are a
large number of birth defect cases, the confidence interval is narrow, indicating that
the rate is stable. Where there are few birth defect cases, the confidence interval
becomes very wide, indicating that the rate is not very stable.
- where Y is the observed number of events, Yl and Yu are lower and upper
confidence limits for Y respectively, c²n,a is the chi-square quantile for upper tail
probability a on n degrees of freedom.
35
36
37
38
Correlation Analysis based on Observed Contaminant
Nitrate
Nitrite
Atrazine
BD
0.163
-0.074
0.038
APO
0.032
-0.210
0.115
PB
0.062
-0.006
0.166
t-BD
1.476
-0.661
0.342
t-APO
0.288
-1.922
1.033
t-PB
0.553
-0.053
1.503
Absolute t-critical; α=0.2; =80
1.294
1.294
1.294
Significant Correlation
BD only
APO only
PB only
Correlation Analysis based on Censored Contaminant
Nitrate
Nitrite
Atrazine
BD
0.164
-0.048
-0.023
APO
0.033
-0.156
0.013
PB
0.062
-0.177
0.189
t-BD
1.491
-0.429
-0.206
t-APO
0.296
-1.408
0.120
t-PB
0.555
-1.605
1.723
Absolute t-critical; α=0.2; =80
1.294
1.294
1.294
Significant Correlation
BD only
APO and PB PB only
Data
TTHM
-0.132
-0.073
0.161
-1.194
-0.659
1.461
1.294
PB only
Data
TTHM
-0.136
-0.072
0.160
-1.224
-0.644
1.450
1.294
PB only
HAA5
-0.174
-0.060
0.207
-1.583
-0.533
1.889
1.294
BD and PB
HAA5
-0.175
-0.058
0.211
-1.588
-0.518
1.931
1.294
BD and PB
39
Nitrate
Nitrite
Atrazine
TTHM
HAA5
t-HAA5
t-TTHM
t-Atrazine
t-Nitrite
t-Nitrate
Absolute t-critical; α=0.25; =80
Significant Correlation
Nitrate
Nitrite
Atrazine
TTHM
HAA5
Correlation among the Explanatory Variables based on Observed Data
Nitrate
Nitrite
Atrazine
TTHM
1.000
-0.008
0.067
-0.139
-0.008
1.000
0.135
0.068
0.067
0.135
1.000
0.365
-0.139
0.068
0.365
1.000
-0.088
0.168
0.380
0.686
-0.794
-1.259
0.599
-0.076
1.294
TTHM
1.523
0.610
1.215
-0.076
1.294
Nitrite, HAA5
3.678
3.506
1.215
0.599
1.294
TTHM, HAA5
8.441
3.506
0.610
-1.259
1.294
HAA5, Atrazine and Nitrate
Correlation among the Explanatory Variables based on Censored Data
Nitrate
Nitrite
Atrazine
TTHM
1.000
-0.138
0.002
-0.145
-0.138
1.000
0.042
0.142
0.002
0.042
1.000
0.303
-0.145
0.142
0.303
1.000
-0.096
0.206
0.310
0.677
t-HAA5
-0.862
t-TTHM
-1.312
t-Atrazine
0.018
t-Nitrite
-1.242
t-Nitrate
Absolute t-critical; α=0.25; =80
1.294
Significant Correlation
Nitrite, TTHM HAA5,
1.881
1.285
0.375
2.912
2.848
HAA5
-0.088
0.168
0.380
0.686
1.000
8.441
3.678
1.523
-0.794
1.294
TTHM and Atrazine
HAA5
-0.096
0.206
0.310
0.677
1.000
8.231
8.231
2.848
2.912
0.375
1.285
1.881
-1.242
0.018
-1.312
-0.862
1.294
1.294
1.294
1.294
TTHM, Nitrate TTHM, HAA5 HAA5, Atrazine and Nitrate, Nitrite TTHM, Atrazine, Nitrite
40