ISTC Research Symposium – September 9, 2009

Correlations of Agrochemical Residues in Drinking Water and Birth Defects in IL

Manoj K. Mohanty and Baojie Zhang

Department of Mining and Mineral Resources EngineeringSouthern Illinois University at Carbondale

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Introduction Objective Project Methodology Data Compilation Data Analysis

Individual correlation coefficients (r) Hypothesis testing Multiple regression analysis

Monthly Average Concentrations Conclusions Recommendations Acknowledgements

Outline

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Introduction

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Introduction (cont.)

Illustration by Electronic Illustrators Group.http://medical-dictionary.thefreedictionary.com/Birth+Defects

Causes of Birth Defects

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Introduction (cont.)

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

US Corn-belt

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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.

Objective

Negative reproductive outcomes:• Birth defects • Adverse pregnancy outcomes • Preterm births

Drinking Water Contaminants:• Nitrate• Nitrite • Atrazine• Total trihalomethanes (TTHM)• Five haloacetic acids (HAA5)

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List of Birth Defects 1. Central Nervous System Defects 4. Alimentary Tract Defects• Anencephalus • Biliary atresia• Encephalocele • Choanal atresia• Hydrocephalus • Cleft lip• Microcephalus • Cleft palate• Spina bifida • Esophageal atresia2. Cardiovascular System Defects • Hirschsprung disease• Aortic valve stenosis • Pyloric stenosis• Atrial septal defect • Rectal or large intestinal atresia/stenosis• Coarctation of aorta 5. Genitourinary System Defects• Common truncus • Bladder exstrophy• Ebstein anomaly • Hypospadias • Endocardial cushion defect • Obstructive genitourinary defect• Hypoplastic left heart syndrome • Renal agenesis/hypoplasia• Patent ductus arteriosus • Epispadias• Pulmonary artery anomalies 6. Musculoskeletal Defects• Pulmonary valve atresia and stenosis • Club foot• Tetralogy of Fallot • Congenital hip dislocation• Transposition of great arteries • Diaphragmatic hernia• Tricuspid valve atresia and stenosis • Gastroschisis• Ventricular septal defect • omphalocele3. Respiratory System Defects • Reduction deformity• Lung agenesis/hypoplasia 7. Chromosomal Defects

• Down syndrome• Edward syndrome• Patau syndrome

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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

LIST OF ADVERSE PREGNANCY OUTCOMES (APO)

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1. Negative reproductive outcome (NRO) data for each county in Illinois for the five year period: 1998-2002.

2. Drinking-water contaminant data from community water supplies (CWS) for the same time period.

3. Correlation coefficients (r) between individual NRO and drinking water contaminants based on sample data and hypothesis testing.

4. Multiple regression analysis to investigate the correlations and their statistical significance by considering all five water contaminants simultaneously.

Project Methodology

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Birth DefectsIncidence

Cases RateCentral Nervous System Defects 5 12.0Cardiovascular System Defects 52 125.1

Respiratory System Defects 3 7.2Alimentary Tract Defects 7 16.8

Genitourinary System Defects 17 40.9Musculoskeletal Defects 16 38.5Chromosomal Defects 4 9.6

Total 104 249.9

Birth Defect Data

Example County: ADAMS

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County 95% CI2

County 95% CI2

Case Rate1 Lower Upper Case Rate1 Lower Upper Adams 104 249.9 204.2 302.8 Lee 51 275.1 204.8 361.7

Alexander 8 121.9 52.6 240.2 Livingston 55 223.7 168.5 291.2 Bond 14 148.9 81.4 249.8 Logan 55 326.1 245.7 424.5

Boone 127 426.2 355.3 507.1 McDonough 41 276.1 198.1 374.5 Brown 3 112.8 23.3 329.6 McHenry 485 240.6 219.6 263.0 Bureau 48 228.7 168.6 303.2 McLean 356 356.0 320.0 395.0 Calhoun 3 119.1 24.6 348.1 Macon 254 340.3 299.7 384.8 Carroll 18 203.2 120.5 321.2 Macoupin 65 235.1 181.5 299.7 Cass 39 406.1 288.8 555.2 Madison 385 231.0 208.5 255.3

Champaign 176 158.4 135.8 183.6 Marion 72 273.6 214.0 344.5 Christian 61 304.8 233.1 391.5 Marshall 27 396.1 261.0 576.3

Clark 8 83.9 36.2 165.4 Mason 32 350.9 240.0 495.4 Clay 18 196.6 116.5 310.7 Massac 4 42.1 11.5 107.7

Clinton 47 241.3 177.3 320.9 Menard 10 149.3 71.6 274.6 Coles 74 249.9 196.2 313.7 Mercer 32 336.8 230.4 475.5 Cook 6113 144.7 48.5 240.6 Monroe 31 183.1 124.4 259.9

Crawford 12 111.9 57.8 195.5 Montgomery 38 221.8 156.9 304.4 Cumberland 10 158.7 76.1 291.8 Morgan 78 371.6 293.7 463.8

DeKalb 181 322.2 277.0 372.7 Moultrie 35 369.0 257.0 513.1 DeWitt 31 298.0 202.5 423.0 Ogle 137 452.4 379.8 534.8

Douglas 27 182.8 120.4 265.9 Peoria 382 290.6 262.2 321.2 DuPage 1202 184.2 153.2 368.1 Perry 17 139.4 81.2 223.2 Edgar 16 147.6 84.4 239.8 Piatt 12 139.3 72.0 243.3

Edwards 6 156.6 57.5 340.9 Pike 23 241.8 153.3 362.8 Effingham 85 368.5 294.4 455.7 Pope 0 0.0 0.0 227.9

Fayette 29 231.4 154.9 332.3 Pulaski 7 150.8 60.6 310.6 Ford 20 230.1 140.5 355.4 Putnam 14 425.6 232.7 714.1

Franklin 33 142.8 98.3 200.6 Randolph 36 185.8 130.1 257.2 Fulton 71 352.0 274.9 444.0 Richland 12 121.2 62.6 211.6

Gallatin 1 30.4 0.8 169.4 Rock Island 339 324.9 291.2 361.4 Greene 24 286.1 183.3 425.7 St. Clair 363 202.5 182.2 224.5 Grundy 49 202.7 150.0 268.0 Saline 33 215.1 148.1 302.1

Hamilton 11 245.1 122.4 438.6 Sangamon 383 303.7 274.1 335.7 Hancock 15 135.4 75.8 223.3 Schuyler 4 106.9 29.1 273.6 Hardin 3 138.9 28.6 405.9 Scott 8 259.0 111.8 510.3

Henderson 5 135.0 43.8 315.2 Shelby 30 246.8 166.5 352.4 Henry 74 259.5 203.7 325.7 Stark 18 485.6 287.8 767.5

Iroquois 32 177.9 121.7 251.2 Stephenson 104 346.0 282.7 419.3 Jackson 49 147.3 109.0 194.7 Tazewell 216 274.3 239.0 313.5 Jasper 13 233.9 124.6 400.0 Union 15 144.3 80.8 238.0

Jefferson 50 211.3 156.8 278.5 Vermilion 93 161.2 130.1 197.5 Jersey 23 193.8 122.9 290.9 Wabash 1 14.2 0.4 78.9

JoDaviess 12 101.6 52.5 177.5 Warren 34 326.5 226.1 456.2 Johnson 6 89.5 32.9 194.9 Washington 16 190.1 108.7 308.7

Kane 774 200.7 186.9 215.4 Wayne 13 126.9 67.6 217.0 Kankakee 154 200.3 170.0 234.6 White 11 133.8 66.8 239.5

Birth Defect Rates for Each County

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Birth Defect Data Summary

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

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Water Contaminant Data

County: ADAMSNitrate Data

CWSNo. of

Observation

ObservedValue (mg/L)

PopulationServed

DetectionLimit

(mg/L)

CensoredValue(mg/L)

1 20 8.057 159 0.1 8.0572 5 3.360 883 0.1 3.3603 19 6.348 1066 0.1 6.3484 18 5.318 248 0.1 5.3185 5 2.200 45000 0.1 2.2006 5 2.302 600 0.1 2.3027 9 0.820 1812 0.1 0.8768 20 6.167 4890 0.1 6.1679 5 2.704 98 0.1 2.704

Total 106 2.641 54,756 2.643

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Water Contaminant Data (cont.)

County: ADAMSNitrite Data

CWSNo. of

Observation

Observed Value(mg/L)

Population Served

Detection Limit

(mg/L)

Censored Value(mg/L)

1 20 0.00 159 0.1 0.102 5 0.02 883 0.1 0.123 19 0.00 1066 0.1 0.104 18 0.00 248 0.1 0.105 5 0.00 45000 0.1 0.116 5 0.00 600 0.1 0.107 9 0.00 1812 0.1 0.108 20 0.00 4890 0.1 0.109 5 0.00 98 0.1 0.10

Total 106 0.000 54,756 0.109

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Nitrite Data for Each County

County Number Population Observed Censored

County Number Population Observed Censored

Mean Mean Mean Mean Adams 106 56735 0.0003 0.1085 Lee 106 30558 0.0000 0.1017

Alexander 20 6349 0.0063 0.0466 Livingston 91 28328 0.0248 0.0865 Bond 13 13102 0.0000 0.1000 Logan 132 19623 0.0325 0.1290 Boone 89 32718 0.0000 0.1102 Macon 50 96575 0.0127 0.1097 Brown 10 629 0.0000 0.1000 Macoupin 39 25433 0.0013 0.1327 Bureau 130 26658 0.0080 0.1026 Madison 131 221024 0.0073 0.0598

Calhoun 22 4963 0.0000 0.1020 Marion 24 40498 0.0555 0.1611 Carroll 79 10012 0.0000 0.1111 Marshall 99 13180 0.0000 0.1149 Cass 36 10353 0.0000 0.1000 Mason 35 16038 0.0000 0.1062

Champaign 142 162942 0.0078 0.0438 Massac 18 6803 0.0000 0.1000 Christian 72 29743 0.0018 0.1171 McDonough 58 21714 0.0008 0.0977

Clark 158 10306 0.0401 0.1220 McHenry 302 179319 0.0034 0.1288 Clay 15 7647 0.1854 0.2737 McLean 146 121079 0.0022 0.0757

Clinton 64 30480 0.0144 0.1401 Menard 24 7695 0.0000 0.1000 Coles 63 43574 0.0084 0.0566 Mercer 104 16957 0.0412 0.1294 Cook 273 3832774 0.0001 0.1015 Monroe 25 21017 0.0026 0.1113

Crawford 123 11028 0.0025 0.1022 Montgomery 55 18417 0.0000 0.1708 Cumberland 37 4801 0.0276 0.1063 Morgan 31 25552 0.0005 0.1070

DeKalb 201 73449 0.0001 0.0998 Moultrie 25 14287 0.0552 0.1217 DeWitt 46 11741 0.0025 0.1009 Ogle 206 32631 0.0000 0.1040 Douglas 34 6208 0.0336 0.1253 Peoria 241 160075 0.0009 0.0438 DuPage 172 321168 0.0034 0.1007 Perry 13 17714 0.0163 0.1343 Edgar 114 12540 0.0835 0.0959 Piatt 64 10248 0.0212 0.1210

Edwards 18 4036 0.0404 0.2042 Pike 108 11279 0.0008 0.1632 Effingham 41 18931 0.0008 0.1113 Pope 4 4413 0.0000 0.1000

Fayette 25 14279 0.0000 0.1162 Pulaski 23 7348 0.0020 0.1000 Ford 56 10614 0.0028 0.1092 Putnam 35 6086 0.0000 0.1000

Franklin 4 39018 0.0000 0.1000 Randolph 82 21967 0.0093 0.1039 Fulton 52 24412 0.0008 0.1123 Richland 22 8118 0.0000 0.1953

Gallatin 56 4221 0.0025 0.1013 Rock Island 279 117776 0.0047 0.1021 Greene 54 10107 0.0000 0.1000 Saline 5 24808 0.0000 0.1140 Grundy 138 29928 0.0001 0.0857 Sangamon 83 149308 0.0000 0.1043

Hamilton N/A 8621 N/A N/A Schuyler 10 3070 0.0000 0.1000 Hancock 42 10897 0.0014 0.1354 Scott 25 5537 0.0000 0.1000 Hardin 10 17471 0.0000 0.1000 Shelby 91 22893 0.0025 0.1020

Henderson 70 6442 0.0000 0.1065 St. Clair 33 201705 0.0055 0.0313 Henry 236 36242 0.0068 0.1373 Stark 22 6332 0.0348 0.1270

Iroquois 222 20194 0.0126 0.1169 Stephenson 109 48979 0.0001 0.1760 Jackson 13 26074 0.0000 0.1976 Tazewell 344 107229 0.0063 0.1012 Jasper 20 10117 0.0000 0.1000 Union 15 10089 0.0000 0.1000

Jefferson 1 40045 0.0000 0.1000 Vermilion 129 52518 0.0081 0.1020 Jersey 11 13007 0.0000 0.1000 Wabash 55 9196 0.0006 0.1003

JoDaviess 135 22289 0.0010 0.1022 Warren 49 18735 0.0102 0.1152 Johnson 15 5885 0.0000 0.1000 Washington 7 8234 0.0317 0.0524

Kane 324 388361 0.0010 0.1014 Wayne 22 10815 0.0018 0.1722

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Contaminants in Drinking

Water

Number of Measurements

Observed Concentration

Range

Censored Concentration

Range

Observed Average IL

Concentration

Censored Average IL

ConcentrationMCL

Nitrate 10,967 0 to 4.90mg/L

0.043 to 4.91 mg/L

0.652mg/L

0.709mg/L 10 mg/L

Nitrite 9,909 0 to 0.190mg/L

0.031 to 0.274 mg/L

0.003mg/L

0.100mg/L

1mg/L

Atrazine 5,504 0 to 1.02µg/L

0.156 to 1.185 µg/L

0.067ug/L

0.343µg/L

3µg/L

TTHM 7,409 0.213 to 84.8 µg/L

0.947 to 84.9 µg/L

23.3µg/L

23.2µg/L

80 µg/L

HAA5 4,407 0 to 64.9µg/L

1.00 to 64.9µg/L

10.4µg/L

10.6µg/L

60 µg/L

Summary Water Contaminant Data

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Correlation Analysis

where, SSxy=

SSxx=

SSyy=

xi: contaminant concentration for each county 

yi: rate of negative reproductive outcome for each county

Hypothesis testing

Data Analysis

where n represents the number of county water contaminant concentration values and r is the sample correlation coefficient

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 Nitrate

(Observed data)Nitrate

(Censored data)BD 0.163 0.164APO 0.032 0.033PB 0.062 0.062 t-BD 1.476 1.491 t-APO 0.288 0.296 t-PB 0.553 0.555

Absolute t-critical; α=0.2; =80 1.294 1.294Significant Correlation BD only BD only

Sample correlation coefficient and hypothesis testing results

Data Analysis (cont.)

BD: Birth defect; APO: Adverse Pregnancy Outcome; PB: Preterm Birth

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  Nitrate Nitrite Atrazine TTHM HAA5

Based on Observed

Contaminant Data BD APO PB PBBDPB

Based on Censored

Contaminant Data BDAPO PB PB PB

BD PB

Statistically Significant Correlations

Data Analysis (cont.)

BD: Birth defect; APO: Adverse Pregnancy Outcome; PB: Preterm Birth

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Multiple Regression AnalysisAdverse Pregnancy Outcomes First Step - All Variables Entered Final Step – Significant Variables R2 = 0.3576 R2 = 0.2824 DF Sum of

Squares Mean Square

F Ratio Prob(F) DF Sum of Squares

Mean Square

F Ratio

Prob(F)

Regression 20 336543.96 16827.20 1.6976 0.0590 Regression 8 265786.12 33223.26 3.5909 0.0015 Error 61 604648.99 9912.28 Error 73 675406.84 9252.15 Total 81 941192.96 Total 81 941192.96 Variable Value Standard

Error t-ratio Prob(t) Variable Value Standard

Error t-ratio Prob(t)

Intercept 341.5898 17.5006 19.5188 0.0000 Intercept 336.3542 13.3080 25.2745 0.0000 X1 -12.2542 28.1969 -0.4346 0.6654 X4 -92.9137 26.0995 -3.5600 0.0007 X2 -22.8035 21.5956 -1.0559 0.2952 X5 80.8744 27.8310 2.9059 0.0048 X3 -24.6700 34.9375 -0.7061 0.4828 X1*X2 -26.9575 13.2648 -2.0323 0.0458 X4 -126.7511 34.0797 -3.7193 0.0004 X1*X4 41.7613 11.0803 3.7690 0.0003 X5 125.3061 39.7763 3.1503 0.0025 X2*X3 20.4827 11.3337 1.8072 0.0749 X1^2 2.8801 11.5610 0.2491 0.8041 X2*X5 -19.6211 9.6265 -2.0382 0.0452 X1*X2 -19.7633 18.4164 -1.0731 0.2874 X4*X5 -50.5058 14.1453 -3.5705 0.0006 X1*X3 6.5454 20.3016 0.3224 0.7483 X4^2 46.5344 13.1761 3.5317 0.0007 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 X 1 : N it r a te m g /L ; X 2 : N i tr i t e m g / L ; X 3 : A t r a z i n e , u g /L ; X 4 : T T H M u g /L ; X 5 : H A A 5 u g / L ; L

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No. of County

DataInitial

R2

Final R2

Final

Critical F-value

Significant main factors

Significant factor interactionsF-ratio

BD Observed

82 0.206 0.132 1.90 1.85 X3, X4,X4^2 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*X3X2*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

X1: nitrate; X2: nitrite; X3: atrazine; X4: TTHM and X5:HAA5

Regression Analysis: Summary Results

BD: Birth defect; APO: Adverse Pregnancy Outcome; PB: Preterm Birth

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Month-wise Concentration of the Water Contaminant-Atrazine

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Month-wise Concentration of the Water Contaminant-Nitrate

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Month-wise Concentration of the Water Contaminant-Nitrite

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Month-wise Concentration of the Water Contaminant-TTHM

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Month-wise Concentration of the Water Contaminant-HAA5

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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.

Conclusions

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The monthly average concentrations of all three agro-chemical 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/June-agrees 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 .

Conclusions (cont.)

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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.

Recommendations

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Illinois Sustainable Technology Center United States Geological Survey Illinois Environmental Protection Agency Illinois Department of Public Health Indiana University Medical Research Center

Acknowledgements

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Questions

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Reserve Slides

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Results (cont.)

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  Nitrate Nitrite Atrazine TTHM HAA5Statistically Significant

Contaminant Based on Observed Data   HAA5

TTHM HAA5

HAA5 Atrazine

TTHM Atrazine

Statistically Significant Contaminant Based on Censored Data TTHM HAA5

TTHM HAA5

HAA5 Atrazine Nitrate

TTHM Atrazine Nitrite

Results (cont.)

Correlation among the exploratory variables

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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.

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Results

37

Results

38

Results

39

Results

Nitrate Nitrite Atrazine TTHM HAA5BD 0.163 -0.074 0.038 -0.132 -0.174APO 0.032 -0.210 0.115 -0.073 -0.060PB 0.062 -0.006 0.166 0.161 0.207t-BD 1.476 -0.661 0.342 -1.194 -1.583t-APO 0.288 -1.922 1.033 -0.659 -0.533t-PB 0.553 -0.053 1.503 1.461 1.889Absolute t-critical; α=0.2; g=80 1.294 1.294 1.294 1.294 1.294Significant Correlation BD only APO only PB only PB only BD and PB

Nitrate Nitrite Atrazine TTHM HAA5BD 0.164 -0.048 -0.023 -0.136 -0.175APO 0.033 -0.156 0.013 -0.072 -0.058PB 0.062 -0.177 0.189 0.160 0.211t-BD 1.491 -0.429 -0.206 -1.224 -1.588t-APO 0.296 -1.408 0.120 -0.644 -0.518t-PB 0.555 -1.605 1.723 1.450 1.931Absolute t-critical; α=0.2; g=80 1.294 1.294 1.294 1.294 1.294Significant Correlation BD only APO and PB PB only PB only BD and PB

Correlation Analysis based on Observed Contaminant Data

Correlation Analysis based on Censored Contaminant Data

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Results (cont.)Nitrate Nitrite Atrazine TTHM HAA5

Nitrate 1.000 -0.008 0.067 -0.139 -0.088Nitrite -0.008 1.000 0.135 0.068 0.168Atrazine 0.067 0.135 1.000 0.365 0.380TTHM -0.139 0.068 0.365 1.000 0.686HAA5 -0.088 0.168 0.380 0.686 1.000

t-HAA5 -0.794 1.523 3.678 8.441t-TTHM -1.259 0.610 3.506 8.441t-Atrazine 0.599 1.215 3.506 3.678t-Nitrite -0.076 1.215 0.610 1.523t-Nitrate -0.076 0.599 -1.259 -0.794Absolute t-critical; α=0.25; g=80 1.294 1.294 1.294 1.294 1.294Significant Correlation TTHM Nitrite, HAA5 TTHM, HAA5 HAA5, Atrazine and Nitrate TTHM and Atrazine

Nitrate Nitrite Atrazine TTHM HAA5Nitrate 1.000 -0.138 0.002 -0.145 -0.096Nitrite -0.138 1.000 0.042 0.142 0.206Atrazine 0.002 0.042 1.000 0.303 0.310TTHM -0.145 0.142 0.303 1.000 0.677HAA5 -0.096 0.206 0.310 0.677 1.000

t-HAA5 -0.862 1.881 2.912 8.231t-TTHM -1.312 1.285 2.848 8.231t-Atrazine 0.018 0.375 2.848 2.912t-Nitrite -1.242 0.375 1.285 1.881t-Nitrate -1.242 0.018 -1.312 -0.862Absolute t-critical; α=0.25; g=80 1.294 1.294 1.294 1.294 1.294Significant Correlation Nitrite, TTHM HAA5, TTHM, Nitrate TTHM, HAA5 HAA5, Atrazine and Nitrate, Nitrite TTHM, Atrazine, Nitrite

Correlation among the Explanatory Variables based on Observed Data

Correlation among the Explanatory Variables based on Censored Data