Short-term Methods for Estimating

the Chronic Toxicity of Effluents and

Receiving Waters to Freshwater

Organisms 

Fourth Edition

October 2002
U.S. Environmental Protection Agency

Office of Water (4303T)

1200 Pennsylvania Avenue, NW

Washington, DC 20460

EPA-821-R-02-013
ii

DISCLAIMER

The Engineering and Analysis Division, of the Office of Science and Technology, has reviewed and

approved this report for publication. Neither the United States Government nor any of its employees, contractors,

or their employees make any warranty, expressed or implied, or assumes any legal liability or responsibility for any

third party’s use of or the results of such use of any information, apparatus, product, or process discussed in this

report, or represents that its use by such party would not infringe on privately owned rights.
iii

CONTENTS

Page

Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x

Section Number Page

1. Introduction ................................................................... 1

2. Short-Term Methods for Estimating Chronic Toxicity .................................. 3

Introduction ................................................................ 3

Types of Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Static Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Advantages and Disadvantages of Toxicity Test Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

3. Health and Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

General Precautions .......................................................... 7

Safety Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

General Laboratory and Field Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Disease Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Safety Manuals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Waste Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

4. Quality Assurance .............................................................. 9

Introduction ................................................................ 9

Facilities, Equipment, and Test Chambers ........................................ 9

Test Organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Laboratory Water Used for Culturing and Test Dilution Water . . . . . . . . . . . . . . . . . . . . . . . . 9

Effluent and Receiving Water Sampling and Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Test Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Quality of Test Organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Food Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Acceptability of Short-Term Chronic Toxicity Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Analytical Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Calibration and Standardization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Replication and Test Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Variability in Toxicity Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Test Precision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Demonstrating Acceptable Laboratory Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Documenting Ongoing Laboratory Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Reference Toxicants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Record Keeping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

5. Facilities, Equipment, and Supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

General Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Test Chambers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Cleaning Test Chambers and Laboratory Apparatus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Apparatus and Equipment for Culturing and Toxicity Tests . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Reagents and Consumable Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Test Organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

6. Test Organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Test Species . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
iv

Sources of Test Organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Life Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Laboratory Culturing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Holding and Handling Test Organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Transportation to the Test Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Test Organism Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

7. Dilution Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Types of Dilution Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Standard, Synthetic Dilution Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Use of Receiving Water as Dilution Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Use of Tap Water as Dilution Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Dilution Water Holding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

8. Effluent and Receiving Water Sampling, Sample Handling,

 and Sample Preparation for Toxicity Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Effluent Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Effluent Sample Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Effluent Sampling Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Receiving Water Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Effluent and Receiving Water Sample Handling, Preservation, and Shipping . . . . . . . . . . . . . 32

Sample Receiving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Persistence of Effluent Toxicity During Sample Shipment and Holding . . . . . . . . . . . . . . . . . 33

Preparation of Effluent and Receiving Water Samples for Toxicity Tests . . . . . . . . . . . . . . . . 33

Preliminary Toxicity Range-Finding Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Multi-concentration (Definitive) Effluent Toxicity Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Receiving Water Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

9. Chronic Toxicity Test Endpoints and Data Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Endpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Relationship Between Endpoints Determined by

 Hypothesis Testing and Point Estimation Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Precision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Data Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Choice of Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Hypothesis Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Point Estimation Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

10. Report Preparation and Test Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Report Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Test Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

11. Test Method: Fathead Minnow, Pimephales promelas, Larval

Survival and Growth Test Method 1000.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

 Scope and Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

 Summary of Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

 Interferences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

 Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

 Apparatus and Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

 Reagents and Consumable Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

 Effluent and Receiving Water Collection, Preservation, and Storage . . . . . . . . . . . . . . . . . . 65

 Calibration and Standardization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

 Quality Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

 Test Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

 Summary of Test Conditions and Test Acceptability Criteria . . . . . . . . . . . . . . . . . . . . . . . . 72

 Acceptability of Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

 Data Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
v

 Precision and Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

12. Test Method: Fathead Minnow, Pimephales promelas, Embryo-larval

Survival and Teratogenicity Test Method 1001.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

 Scope and Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

 Summary of Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

 Interferences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

 Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

 Apparatus and Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

 Reagents and Consumable Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

 Effluent and Receiving Water Collection, Preservation, and Storage . . . . . . . . . . . . . . . . . . 116

 Calibration and Standardization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

 Quality Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

 Test Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

 Summary of Test Conditions and Test Acceptability Criteria . . . . . . . . . . . . . . . . . . . . . . . . 124

 Acceptability of Test Result . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

 Data Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

 Precision and Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

13. Test Method: Daphnid, Ceriodaphnia dubia, Survival and

Reproduction Test Method 1002.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

 Scope and Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

 Summary of Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

 Interferences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

 Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

 Apparatus and Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

 Reagents and Consumable Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

 Effluent and Receiving Water Collection, Preservation, and Storage . . . . . . . . . . . . . . . . . . 154

 Calibration and Standardization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

 Quality Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

 Test Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

 Summary of Test Conditions and Test Acceptability Criteria . . . . . . . . . . . . . . . . . . . . . . . . 161

 Acceptability of Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161

 Data Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

 Precision and Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189

14. Test Method: Green Alga, Selenastrum capricornutum, Growth

Test Method 1003.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197

 Scope and Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197

 Summary of Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197

 Interferences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197

 Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197

 Apparatus and Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198

 Reagents and Consumable Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199

 Effluent and Receiving Water Collection, Preservation, and Storage . . . . . . . . . . . . . . . . . . 203

 Calibration and Standardization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

 Quality Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

 Test Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

 Summary of Test Conditions and Test Acceptability Criteria . . . . . . . . . . . . . . . . . . . . . . . . 208

 Acceptability of Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208

 Data Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212

 Precision and Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224

Cited References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231

Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
vi

A. Independence, Randomization, and Outliers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246

B. Validating Normality and Homogeneity of Variance Assumptions . . . . . . . . . . . . . . . . . . . . . 252

C. Dunnett's Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269

D. T test with Bonferroni's Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281

E. Steel's Many-one Rank Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287

F. Wilcoxon Rank Sum Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291

G. Fisher's Exact Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297

H. Single Concentration Toxicity Test - Comparison of Control

with 100% Effluent or Receiving Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306

I. Probit Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309

J. Spearman-Karber Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312

K. Trimmed Spearman-Karber Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317

L. Graphical Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321

M. Linear Interpolation Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324

Cited References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334
vii

FIGURES

SECTIONS 1-10 

Number Page

1. Control charts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2. Flowchart for statistical analysis of test data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

SECTION 11

Number Page

1. Data form for the fathead minnow, Pimephales promelas,

larval survival and growth test. Routine chemical and

physical determinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

2. Mortality data for the fathead minnow, Pimephales promelas,

larval survival and growth test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

3. Weight data for the fathead minnow, Pimephales promelas,

larval survival and growth test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

4. Summary data for the fathead minnow, Pimephales promelas,

larval survival and growth test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

5. Flowchart for statistical analysis of fathead minnow,

Pimephales promelas, larval survival data by hypothesis

testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

6. Flowchart for statistical analysis of fathead minnow,

Pimephales promelas, larval survival data by point estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

7. Plot of survival proportion data in Table 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

8. Output for USEPA Probit Analysis program, Version 1.5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

9. Flowchart for statistical analysis of fathead minnow,

Pimephales promelas, larval growth data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

10. Plot of weight data from fathead minnow, Pimephales

promelas, larval survival and growth test for point

estimate testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

11. Plot of raw data, observed means, and smoothed means for

the fathead minnow, Pimephales promelas, growth data

in Tables 2 and 18 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
viii

SECTION 11 (Continued)

Number Page

12. ICPIN program output for the IC25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

13. ICPIN program output for the IC50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

SECTION 12

Number Page

1. Data form for the fathead minnow, Pimephales promelas,

embryo-larval survival and teratogenicity test. Routine

chemical and physical determinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

2. Data form for the fathead minnow, Pimephales promelas,

embryo-larval survival and teratogenicity test. Survival

and terata data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122

3. Summary data for the fathead minnow, Pimephales promelas,

embryo-larval survival and teratogenicity test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

4. Flowchart for statistical analysis of fathead minnow,

Pimephales promelas, embryo-larval data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

5. Plot of fathead minnow, Pimephales promelas, total mortality

data from the embryo-larval test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

6. Output for USEPA Probit Analysis program, Version 1.5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

SECTION 13

Number Page

1. Examples of a test board and randomizing template . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152

2. Data form for the daphnid, Ceriodaphnia dubia, survival

and reproduction test. Routine chemical and physical

determinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159

3. Data form for the daphnid, Ceriodaphnia dubia, survival

and reproduction test. Daily summary of data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162

4. Flowchart for statistical analysis of the daphnid,

Ceriodaphnia dubia, survival data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

5. Output for USEPA Trimmed Spearman-Karber program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
ix

SECTION 13 (Continued)

Number Page

6. Flowchart for statistical analysis of the daphnid,

Ceriodaphnia dubia, reproduction data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173

7. Plot of number of young per adult female from a daphnid,

Ceriodaphnia dubia, survival and reproduction test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174

8. Plot of raw data, observed means, and smoothed means for

the daphnid, Ceriodaphnia dubia, reproductive data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

9. Example of ICPIN program output for the IC25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187

10. Example of ICPIN program output for the IC50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

SECTION 14

Number Page

1. Data form for the green alga, Selenastrum capricornutum,

 growth test. Routine chemical and physical

determinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

2. Data form for the green alga, Selenastrum capricornutum,

growth test, cell density determinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209

3. Flowchart for statistical analysis of the green alga,

Selenastrum capricornutum, growth response data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213

4. Plot of log10 transformed cell count data from the green

alga, Selenastrum capricornutum, growth response test in

Table 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215

5. Plot of raw data and observed means for the green alga,

Selenastrum capricornutum, growth data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223

6. ICPIN program output for the IC25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226

7. ICPIN program output for the IC50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227
x

TABLES

SECTIONS 1-10 

Number Page

1. National interlaboratory study of chronic toxicity

test precision, 1991: Summary of responses using

a reference toxicant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

2. National interlaboratory study of chronic toxicity

test precision, 2000: Precision of responses using

effluent, receiving water, and reference toxicant

sample types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

3. Preparation of synthetic freshwater using reagent

grade chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

4. Preparation of synthetic freshwater using

mineral water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

5. Percent unionized NH3 in aqueous ammonia solutions:

Temperatures 15-26°C and pH 6.0-8.9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

6. Variability criteria (upper and lower PMSD bounds) for 

sublethal hypothesis testing endpoints submitted under 

NPDES permits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

SECTION 11

Number Page

1. Summary of test conditions and test acceptability

criteria for fathead minnow, Pimephales promelas,

larval survival and growth toxicity tests with

effluents and receiving waters (Test Method 1000.0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

2. Summary of survival and growth data for fathead minnow,

Pimephales promelas, larvae exposed to a reference

toxicant for seven days . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

3. Fathead minnow, Pimephales promelas, survival data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

4. Centered observations for Shapiro-Wilk's example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

5. Ordered centered observations for the

Shapiro-Wilk's example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

6. Coefficients and differences for Shapiro-Wilk's example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

7. ANOVA table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
xi

SECTION 11 (Continued)

Number Page

8. ANOVA table for Dunnett's Procedure example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

9. Calculated t values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

10. Data for Probit Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

11. Fathead minnow, Pimephales promelas, growth data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

12. Centered observations for Shapiro-Wilk's example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

13. Ordered centered observations for Shapiro-Wilk's example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

14. Coefficients and differences for Shapiro-Wilk's example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

15. ANOVA table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

16. ANOVA table for Dunnett's Procedure example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

17. Calculated t values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

18. Fathead minnow, Pimephales promelas, mean growth response

after smoothing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

19. Precision of the fathead minnow, Pimephales promelas,

larval survival and growth test, using NaPCP as a

reference toxicant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

20. Combined frequency distribution for survival NOECs

for all laboratories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

21. Combined frequency distribution for weight NOECs

for all laboratories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

22. Precision of point estimates for various sample types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

23. Frequency distribution of hypothesis testing results

for various sample types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

SECTION 12

Number Page

1. Summary of test conditions and test acceptability criteria

for fathead minnow, Pimephales promelas, embryo-larval

survival and teratogenicity toxicity tests with effluents

and receiving waters (Test Method 1001.0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
xii

SECTION 12 (Continued)

Number Page

2. Data from fathead minnow, Pimephales promelas, embryo-larval

toxicity test with ground water effluent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130

3. Fathead minnow, Pimephales promelas, embryo-larval total

mortality data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

4. Centered observations for Shapiro-Wilk's example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

5. Ordered centered observations for the Shapiro-Wilk's example . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

6. Coefficient and differences for the Shapiro-Wilks example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

7. Assigning ranks to the control and 3.125% effluent

concentration for the Steel's Many-One Rank Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

8. Table of ranks for Steel's Many-One Rank Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

9. Rank sums . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

10. Data for Probit Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

11. Precision of the fathead minnow, Pimephales promelas,

embryo-larval survival and teratogenicity test, using

cadmium as a reference toxicant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138

12. Precision of the fathead minnow, Pimephales promelas,

embryo-larval, survival and teratogenicity toxicity test,

 using diquat as a reference toxicant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

13. Precision of the fathead minnow, Pimephales promelas,

embryo-larval survival and teratogenicity static-renewal

test conducted with trickling filter effluent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

SECTION 13

Number Page

1. Nutrient stock solutions for maintaining algal stock

cultures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147

2. Final concentration of macronutrients and micronutrients

in the culture medium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148

3. Summary of test conditions and test acceptability

criteria for daphnid, Ceriodaphnia dubia, survival

and reproduction toxicity tests with effluents

and receiving waters (Test Method 1002.0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
xiii

SECTION 13 (Continued)

Number Page

4. Summary of survival and reproduction data for the

daphnid, Ceriodaphnia dubia, exposed to an effluent

for seven days . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

5. Format of the 2x2 contingency table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

6. 2x2 contingency table for control and 25% effluent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170

7. Data for Trimmed Spearman-Karber Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170

8. The daphnid, Ceriodaphnia dubia, reproduction data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171

9. Centered observations for Shapiro-Wilk's example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

10. Ordered centered observations for Shapiro-Wilk's example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

11. Coefficients and differences for Shapiro-Wilk's example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178

12. ANOVA table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

13. ANOVA table for Dunnett's Procedure example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

14. Calculated t values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

15. Daphnid, Ceriodaphnia dubia, reproduction mean

response after smoothing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184

16. Single laboratory precision of the daphnid, Ceriodaphnia

dubia, survival and reproduction test, using NaPCP as a

reference toxicant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190

17. The daphnid, Ceriodaphnia dubia, seven-day survival and

reproduction test precision for a single laboratory using

NaPCP as the reference toxicant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191

18. Interlaboratory precision for the daphnid, Ceriodaphnia

dubia, survival and reproduction test with copper

spiked effluent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

19. Interlaboratory precision data for the daphnid,

Ceriodaphnia dubia, summarized for eight reference

toxicants and effluents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194

20. Precision of point estimates for various sample types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195

21. Frequency distribution of hypothesis testing results for

various sample types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
xiv

SECTION 14

Number Page

1. Nutrient stock solutions for maintaining algal stock

cultures and test control cultures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201

2. Final concentration of macronutrients and micronutrients

in the culture medium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

3. Summary of test conditions and test acceptability criteria

for green alga, Selenastrum capricornutum, growth toxicity

tests with effluents and receiving waters (Test Method 1003.0) . . . . . . . . . . . . . . . . . . . . . . . . . . . 210

4. Green alga, Selenastrum capricornutum, growth

response data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212

5. Centered observations for Shapiro-Wilk's example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214

6. Ordered centered observations for Shapiro-Wilk's example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216

7. Coefficients and differences for Shapiro-Wilk's example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216

8. ANOVA table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218

9. ANOVA table for Dunnett's Procedure example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220

10. Calculated t values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220

11. Algal mean growth response after smoothing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222

12. Single laboratory precision of the green alga,

Selenastrum capricornutum, 96-h toxicity tests,

using the reference toxicant cadmium chloride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228

13. Precision of point estimates for various sample types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229

14. Frequency distribution of hypothesis testing results for

various sample types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
1

SECTION 1

INTRODUCTION

1.1 This manual describes chronic toxicity tests for use in the National Pollutant Discharge Elimination System

(NPDES) Permits Program to identify effluents and receiving waters containing toxic materials in chronically toxic

concentrations. The methods included in this manual are referenced in Table IA, 40 CFR Part 136 regulations and,

therefore, constitute approved methods for chronic toxicity tests. They are also suitable for determining the toxicity

of specific compounds contained in discharges. The tests may be conducted in a central laboratory or on-site, by the

regulatory agency or the permittee.

1.2 The data are used for NPDES permits development and to determine compliance with permit toxicity limits. 

Data can also be used to predict potential acute and chronic toxicity in the receiving water, based on the LC50,

NOEC, IC50 or IC25 (see Section 9, Chronic Toxicity Endpoints and Data Analysis) and appropriate dilution,

application, and persistence factors. The tests are performed as a part of self-monitoring permit requirements,

compliance biomonitoring inspections, toxics sampling inspections, and special investigations. Data from chronic

toxicity tests performed as part of permit requirements are evaluated during compliance evaluation inspections and

performance audit inspections.

1.3 Modifications of these tests are also used in toxicity reduction evaluations and toxicity identification

evaluations to identify the toxic components of an effluent, to aid in the development and implementation of toxicity

reduction plans, and to compare and control the effectiveness of various treatment technologies for a given type of

industry, irrespective of the receiving water (USEPA, 1988c; USEPA, 1989b; USEPA 1989c; USEPA, 1989d; 

USEPA, 1989e; USEPA, 1991a; USEPA, 1991b; and USEPA, 1992).

1.4 This methods manual serves as a companion to the acute toxicity test methods for freshwater and marine

organisms (USEPA, 2002a), the short-term chronic toxicity test methods for marine and estuarine organisms

(USEPA, 2002b), and the manual for evaluation of laboratories performing aquatic toxicity tests (USEPA, 1991c). 

In 2002, EPA revised previous editions of each of the three methods manuals (USEPA, 1993a; USEPA, 1994a;

USEPA, 1994b).

1.5 Guidance for the implementation of toxicity tests in the NPDES program is provided in the Technical Support

Document for Water Quality-based Toxics Control (USEPA, 1991a).

1.6 These freshwater short-term toxicity tests are similar to those developed for marine and estuarine organisms to

evaluate the toxicity of effluents discharged to marine and estuarine waters under the NPDES permit program. 

Methods are presented in this manual for three species of freshwater organisms from three phylogenetic groups. 

The methods are all static renewal type seven-day tests except the green alga, Selenastrum capricornutum, test

which lasts four days. 

1.7 The three species for which test methods are provided are the fathead minnow, Pimephales promelas; the

daphnid, Ceriodaphnia dubia; and the green alga, Selenastrum capricornutum. 

 

1.7.1 Two of the methods incorporate the chronic endpoint of growth in addition to lethality and one incorporates

reproduction. The fathead minnow, Pimephales promelas, embryo-larval survival and teratogenicity test

incorporates teratogenic effects in addition to lethality. The green alga, Selenastrum capricornutum, growth test has

the advantage of a relatively short exposure period (96 h).

1.8 The validity of the freshwater chronic methods in predicting adverse ecological impacts of toxic discharges

was demonstrated in field studies (USEPA, 1984; USEPA, 1985b; USEPA, 1985c; USEPA, 1985d; USEPA, 1986a;

USEPA, 1986b; USEPA, 1986c; USEPA, 1986d; Birge et al., 1989; and Eagleson et al., 1990).
2

1.9 The use of any test species or test conditions other than those described in the methods summary tables in this

manual shall be subject to application and approval of alternate test procedures under 40 CFR 136.4 and 40 CFR

136.5.

1.10 These methods are restricted to use by, or under the supervision of, analysts experienced in the use or conduct

of aquatic toxicity tests and the interpretation of data from aquatic toxicity testing. Each analyst must demonstrate

the ability to generate acceptable test results with these methods using the procedures described in this methods

manual.

1.11 This manual was prepared in the established EMSL-Cincinnati format (USEPA, 1983). 
3

SECTION 2 

SHORT-TERM METHODS FOR ESTIMATING CHRONIC TOXICITY

2.1 INTRODUCTION

2.1.1 The objective of aquatic toxicity tests with effluents or pure compounds is to estimate the "safe" or "no

effect" concentration of these substances, which is defined as the concentration which will permit normal

propagation of fish and other aquatic life in the receiving waters. The endpoints that have been considered in tests

to determine the adverse effects of toxicants include death and survival, decreased reproduction and growth,

locomotor activity, gill ventilation rate, heart rate, blood chemistry, histopathology, enzyme activity, olfactory

function, and terata. Since it is not feasible to detect and/or measure all of these (and other possible) effects of toxic

substances on a routine basis, observations in toxicity tests generally have been limited to only a few effects, such as

mortality, growth, and reproduction. 

2.1.2 Acute lethality is an obvious and easily observed effect which accounts for its wide use in the early period of

evaluation of the toxicity of pure compounds and complex effluents. The results of these tests were usually

expressed as the concentration lethal to 50% of the test organisms (LC50) over relatively short exposure periods

(one-to-four days). 

2.1.3 As exposure periods of acute tests were lengthened, the LC50 and lethal threshold concentration were

observed to decline for many compounds. By lengthening the tests to include one or more complete life cycles and

observing the more subtle effects of the toxicants, such as a reduction in growth and reproduction, more accurate,

direct, estimates of the threshold or safe concentration of the toxicant could be obtained. However, laboratory

life-cycle tests may not accurately estimate the "safe" concentration of toxicants because they are conducted with a

limited number of species under highly controlled, steady-state conditions, and the results do not include the effects

of the stresses to which the organisms would ordinarily be exposed in the natural environment. 

2.1.4 An early published account of a full life-cycle, fish toxicity test was that of Mount and Stephan (1967). In

this study, fathead minnows, Pimephales promelas, were exposed to a graded series of pesticide concentrations

throughout their life cycle, and the effects of the toxicant on survival, growth, and reproduction were measured and

evaluated. This work was soon followed by full life-cycle tests using other toxicants and fish species.

2.1.5 McKim (1977) evaluated the data from 56 full life-cycle tests, 32 of which used the fathead minnow,

Pimephales promelas, and concluded that the embryo-larval and early juvenile life-stages were the most sensitive

stages. He proposed the use of partial life-cycle toxicity tests with the early life-stages (ELS) of fish to establish

water quality criteria. 

2.1.6 Macek and Sleight (1977) found that exposure of critical life-stages of fish to toxicants provides estimates of

chronically safe concentrations remarkably similar to those derived from full life-cycle toxicity tests. They reported

that "for a great majority of toxicants, the concentration which will not be acutely toxic to the most sensitive life

stages is the chronically safe concentration for fish, and that the most sensitive life stages are the embryos and fry". 

Critical life-stage exposure was considered to be exposure of the embryos during most, preferably all, of the

embryogenic (incubation) period, and exposure of the fry for 30 days post-hatch for warm water fish with

embryogenic periods ranging from one-to-fourteen days, and for 60 days post-hatch for fish with longer

embryogenic periods. They concluded that in the majority of cases, the maximum acceptable toxicant concentration

(MATC) could be estimated from the results of exposure of the embryos during incubation, and the larvae for 30

days post-hatch. 

2.1.7 Because of the high cost of full life-cycle fish toxicity tests and the emerging consensus that the ELS test data

usually would be adequate for estimating chronically safe concentrations, there was a rapid shift by aquatic

toxicologists to 30 - 90-day ELS toxicity tests for estimating chronically safe concentrations in the late 1970s. In
4

1980, USEPA adopted the policy that ELS test data could be used in establishing water quality criteria if data from

full life-cycle tests were not available (USEPA, 1980a). 

2.1.8 Published reports of the results of ELS tests indicate that the relative sensitivity of growth and survival as

endpoints may be species dependent, toxicant dependent, or both. Ward and Parrish (1980) examined the literature

on ELS tests that used embryos and juveniles of the sheepshead minnow, Cyprinodon variegatus, and found that

growth was not a statistically sensitive indicator of toxicity in 16 of 18 tests. They suggested that the ELS tests be

shortened to 14 days posthatch and that growth be eliminated as an indicator of toxic effects. 

2.1.9 In a review of the literature on 173 fish full life-cycle and ELS tests performed to determine the chronically

safe concentrations of a wide variety of toxicants, such as metals, pesticides, organics, inorganics, detergents, and

complex effluents, Woltering (1984) found that at the lowest effect concentration, significant reductions were

observed in fry survival in 57%, fry growth in 36%, and egg hatchability in 19% of the tests. He also found that fry

survival and growth were very often equally sensitive, and concluded that the growth response could be deleted

from routine application of the ELS tests. The net result would be a significant reduction in the duration and cost of

screening tests with no appreciable impact on estimating MATCs for chemical hazard assessments. Benoit et al.

(1982), however, found larval growth to be the most significant measure of effect, and survival to be equally or less

sensitive than growth in early life-stage tests with four organic chemicals. 

2.1.10 Efforts to further reduce the length of partial life-cycle toxicity tests for fish without compromising their

predictive value have resulted in the development of an eight-day, embryo-larval survival and teratogenicity test for

fish and other aquatic vertebrates (USEPA, 1981; Birge et al., 1985), and a seven-day larval survival and growth

test (Norberg and Mount, 1985). 

2.1.11 The similarity of estimates of chronically safe concentrations of toxicants derived from short-term,

embryo-larval survival and teratogenicity tests to those derived from full life-cycle tests has been demonstrated by

Birge et al. (1981), Birge and Cassidy (1983), and Birge et al. (1985).

2.1.12 Use of a seven-day, fathead minnow, Pimephales promelas, larval survival and growth test was first

proposed by Norberg and Mount at the 1983 annual meeting of the Society for Environmental Toxicology and

Chemistry (Norberg and Mount, 1983). This test was subsequently used by Mount and associates in field

demonstrations at Lima, OH (USEPA, 1984), and at many other locations. Growth was frequently found to be more

sensitive than survival in determining the effects of complex effluents. 

2.1.13 Norberg and Mount (1985) performed three single toxicant fathead minnow larval growth tests with zinc,

copper, and DURSBAN®, using dilution water from Lake Superior. The results were comparable to, and had

confidence intervals that overlapped with, chronic values reported in the literature for both ELS and full life-cycle

tests. 

2.1.14 Mount and Norberg (1984) developed a seven-day cladoceran partial life-cycle test and experimented with a

number of diets for use in culturing and testing the daphnid, Ceriodaphnia reticulata (Norberg and Mount, 1985). 

As different laboratories began to use this cladoceran test, it was discovered that apparently more than one species

was involved in the tests conducted by the same laboratory. Berner (1986) studied the problem and determined that

perhaps as many as three variant forms were involved and it was decided to recommend the use of the more

common Ceriodaphnia dubia rather than the originally reported Ceriodaphnia reticulata. The method was adopted

for use in the first edition of the freshwater short-term chronic methods (USEPA, 1985e). 

2.1.15 The green alga, Selenastrum capricornutum, bottle test was developed, after extensive design, evaluation,

and application, for the National Eutrophication Research Program (USEPA, 1971). The test was later modified for

use in the assessment of receiving waters and the effects of wastes originating from industrial, municipal, and

agricultural point and non-point sources (USEPA, 1978a).
5

2.1.16 The use of short-term toxicity tests including subchronic and chronic tests in the NPDES Program is

especially attractive because they provide a more direct estimate of the safe concentrations of effluents in receiving

waters than was provided by acute toxicity tests, at an only slightly increased level of effort, compared to the fish

full life-cycle chronic and 28-day ELS tests and the 21-day daphnid, Daphnia magna, life-cycle test.

2.2 TYPES OF TESTS

2.2.1 The selection of the test type will depend on the NPDES permit requirements, the objectives of the test, the

available resources, the requirements of the test organisms, and effluent characteristics such as fluctuations in

effluent toxicity.

2.2.2 Effluent chronic toxicity is generally measured using a multi-concentration, or definitive test, consisting of a

control and a minimum of five effluent concentrations. The tests are designed to provide dose-response

information, expressed as the percent effluent concentration that affects the hatchability, gross morphological

abnormalities, survival, growth, and/or reproduction within the prescribed period of time (four to seven days). The

results of the tests are expressed in terms of the highest concentration that has no statistically significant observed

effect on those responses when compared to the controls or the estimated concentration that causes a specified

percent reduction in responses versus the controls.

2.2.3 Use of pass/fail tests consisting of a single effluent concentration (e.g., the receiving water concentration or

RWC) and a control is not recommended. If the NPDES permit has a whole effluent toxicity limit for acute

toxicity at the RWC, it is prudent to use that permit limit as the midpoint of a series of five effluent concentrations. 

This will ensure that there is sufficient information on the dose-response relationship. For example, the effluent

concentrations utilized in a test may be: (1) 100% effluent, (2) (RWC + 100)/2, (3) RWC, (4) RWC/2, and (5)

RWC/4. More specifically, if the RWC = 50%, appropriate effluent concentrations may be 100%, 75%, 50%, 25%,

and 12.5%. 

2.2.4 Receiving (ambient) water toxicity tests commonly employ two treatments, a control and the undiluted

receiving water, but may also consist of a series of receiving water dilutions. 

2.2.5 A negative result from a chronic toxicity test does not preclude the presence of toxicity. Also, because of the

potential temporal variability in the toxicity of effluents, a negative test result with a particular sample does not

preclude the possibility that samples collected at some other time might exhibit chronic toxicity.

2.2.6 The frequency with which chronic toxicity tests are conducted under a given NPDES permit is determined by

the regulatory agency on the basis of factors such as the variability and degree of toxicity of the waste, production

schedules, and process changes. 

2.2.7 Tests recommended for use in this methods manual may be static non-renewal or static renewal. Individual

methods specify which static type of test is to be conducted. 

2.3 STATIC TESTS

2.3.1 Static non-renewal tests - The test organisms are exposed to the same test solution for the duration of the test.

2.3.2 Static-renewal tests - The test organisms are exposed to a fresh solution of the same concentration of sample

every 24 h or other prescribed interval, either by transferring the test organisms from one test chamber to another, or

by replacing all or a portion of solution in the test chambers.
6

2.4 ADVANTAGES AND DISADVANTAGES OF TOXICITY TEST TYPES

2.4.1 STATIC NON-RENEWAL, SHORT-TERM TOXICITY TESTS:

Advantages:

1. Simple and inexpensive.

2. Very cost effective in determining compliance with permit conditions.

3. Limited resources (space, manpower, equipment) required; would permit staff to perform many more

tests in the same amount of time.

4. Smaller volume of effluent required than for static renewal or flow-through tests.

Disadvantages:

1. Dissolved oxygen (DO) depletion may result from high chemical oxygen demand (COD), 

biological oxygen demand (BOD), or metabolic wastes. 

2. Possible loss of toxicants through volatilization and/or adsorption to the exposure vessels.

3. Generally less sensitive than static renewal, because the toxic substances may degrade or be adsorbed,

thereby reducing the apparent toxicity. Also, there is less chance of detecting slugs of toxic wastes, or

other temporal variations in waste properties.

2.4.2 STATIC RENEWAL, SHORT-TERM TOXICITY TESTS:

Advantages:

1. Reduced possibility of DO depletion from high COD and/or BOD, or ill effects from 

metabolic wastes from organisms in the test solutions.

2. Reduced possibility of loss of toxicants through volatilization and/or adsorption to the 

exposure vessels. 

3. Test organisms that rapidly deplete energy reserves are fed when the test solutions are 

renewed, and are maintained in a healthier state.

Disadvantages:

1. Require greater volume of effluent than non-renewal tests.

2. Generally less chance of temporal variations in waste properties. 
7

SECTION 3

HEALTH AND SAFETY

3.1 GENERAL PRECAUTIONS

3.1.1 Each laboratory should develop and maintain an effective health and safety program, requiring an ongoing

commitment by the laboratory management. This program should include (1) a safety officer with the responsibility

and authority to develop and maintain a safety program, (2) the preparation of a formal, written, health and safety

plan, which is provided to each of the laboratory staff, (3) an ongoing training program on laboratory safety, and (4)

regularly scheduled, documented, safety inspections.

3.1.2 Collection and use of effluents in toxicity tests may involve significant risks to personal safety and health. 

Personnel collecting effluent samples and conducting toxicity tests should take all safety precautions necessary for

the prevention of bodily injury and illness which might result from ingestion or invasion of infectious agents,

inhalation or absorption of corrosive or toxic substances through skin contact, and asphyxiation due to lack of

oxygen or presence of noxious gases.

3.1.3 Prior to sample collection and laboratory work, personnel will determine that all necessary safety equipment

and materials have been obtained and are in good condition.

3.1.4 Guidelines for the handling and disposal of hazardous materials must be strictly followed.

3.2 SAFETY EQUIPMENT

3.2.1 PERSONAL SAFETY GEAR

3.2.1.1 Personnel should use safety equipment, as required, such as rubber aprons, laboratory coats, respirators,

gloves, safety glasses, hard hats, and safety shoes. Plastic netting on glass beakers, flasks, and other glassware

minimizes breakage and subsequent shattering of the glass.

3.2.2 LABORATORY SAFETY EQUIPMENT

3.2.2.1 Each laboratory (including mobile laboratories) should be provided with safety equipment such as first aid

kits, fire extinguishers, fire blankets, emergency showers, chemical spill clean up kits, and eye fountains.

3.2.2.2 Mobile laboratories should be equipped with a telephone or other means to enable personnel to summon

help in case of emergency.

3.3 GENERAL LABORATORY AND FIELD OPERATIONS

3.3.1 Work with effluents should be performed in compliance with accepted rules pertaining to the handling of

hazardous materials (see safety manuals listed in Section 3, Health and Safety, Subsection 3.5). It is recommended

that personnel collecting samples and performing toxicity tests not work alone. 

3.3.2 Because the chemical composition of effluents is usually only poorly known, they should be considered as

potential health hazards, and exposure to them should be minimized. Fume and canopy hoods over the toxicity test

areas must be used whenever possible. 

3.3.3 It is advisable to cleanse exposed parts of the body immediately after collecting effluent samples.

3.3.4 All containers are to be adequately labeled to indicate their contents.
8

3.3.5 Staff should be familiar with safety guidelines on Material Safety Data Sheets for reagents and other

chemicals purchased from suppliers. Incompatible materials should not be stored together. Good housekeeping

contributes to safety and reliable results.

3.3.6 Strong acids and volatile organic solvents employed in glassware cleaning must be used in a fume hood or

under an exhaust canopy over the work area.

3.3.7 Electrical equipment or extension cords not bearing the approval of Underwriter Laboratories must not be

used. Ground-fault interrupters must be installed in all "wet" laboratories where electrical equipment is used.

3.3.8 Mobile laboratories should be properly grounded to protect against electrical shock.

3.4 DISEASE PREVENTION

3.4.1 Personnel handling samples which are known or suspected to contain human wastes should be immunized

against tetanus, typhoid fever, polio, and hepatitis B. 

3.5 SAFETY MANUALS

3.5.1 For further guidance on safe practices when collecting effluent samples and conducting toxicity tests, check

with the permittee and consult general safety manuals, including USEPA (1986e) and Walters and Jameson (1984).

3.6 WASTE DISPOSAL

3.6.1 Wastes generated during toxicity testing must be properly handled and disposed of in an appropriate manner. 

Each testing facility will have its own waste disposal requirements based on local, state, and Federal rules and

regulations. It is extremely important that these rules and regulations be known, understood, and complied with by

all persons responsible for, or otherwise involved in performing the toxicity testing activities. Local fire officials

should be notified of any potentially hazardous conditions.
9

SECTION 4

QUALITY ASSURANCE

4.1 INTRODUCTION

4.1.1 Development and maintenance of a toxicity test laboratory quality assurance (QA) program (USEPA, 1991a)

requires an ongoing commitment by laboratory management. Each toxicity test laboratory should (1) appoint a

quality assurance officer with the responsibility and authority to develop and maintain a QA program; (2) prepare a

quality assurance plan with stated data quality objectives (DQOs); (3) prepare a written description of laboratory

standard operating procedures (SOPs) for culturing, toxicity testing, instrument calibration, sample chain-of-custody

procedures, laboratory sample tracking system, glassware cleaning, etc.; and (4) provide an adequate, qualified

technical staff for culturing and testing the organisms, and suitable space and equipment to assure reliable data.

4.1.2 QA practices for toxicity testing laboratories must address all activities that affect the quality of the final

effluent toxicity test data, such as: (1) effluent sampling and handling; (2) the source and condition of the test

organisms; (3) condition of equipment; (4) test conditions; (5) instrument calibration; (6) replication; (7) use of

reference toxicants; (8) record keeping; and (9) data evaluation. 

4.1.3 Quality control practices, on the other hand, consist of the more focused, routine, day-to-day activities

carried out within the scope of the overall QA program. For more detailed discussion of quality assurance and

general guidance on good laboratory practices and laboratory evaluation related to toxicity testing, see FDA, (1978);

USEPA, (1979d), USEPA (1980b), USEPA (1980c), and USEPA (1991c); DeWoskin (1984); and Taylor (1987).

4.1.4 Guidance for the evaluation of laboratories performing toxicity tests and laboratory evaluation criteria may

be found in USEPA (1991c).

4.2 FACILITIES, EQUIPMENT, AND TEST CHAMBERS

4.2.1 Separate test organism culturing and toxicity testing areas should be provided to avoid possible loss of

cultures due to cross-contamination. Ventilation systems should be designed and operated to prevent recirculation

or leakage of air from chemical analysis laboratories or sample storage and preparation areas into organism

culturing or testing areas, and from testing and sample preparation areas into culture rooms.

4.2.2 Laboratory and toxicity test temperature control equipment must be adequate to maintain recommended test

water temperatures. Recommended materials must be used in the fabrication of the test equipment which comes in

contact with the effluent (see Section 5, Facilities, Equipment and Supplies; and specific toxicity test method).

4.3 TEST ORGANISMS

4.3.1 The test organisms used in the procedures described in this manual are the fathead minnow, Pimephales

promelas, the daphnid, Ceriodaphnia dubia, and the green alga, Selenastrum capricornutum. The fish and

invertebrates should appear healthy, behave normally, feed well, and have low mortality in the cultures, during

holding, and in test controls. Test organisms should be positively identified to species (see Section 6, Test

Organisms).

4.4 LABORATORY WATER USED FOR CULTURING AND TEST DILUTION WATER

4.4.1 The quality of water used for test organism culturing and for dilution water used in toxicity tests is extremely

important. Water for these two uses should come from the same source. The dilution water used in effluent toxicity

tests will depend in part on the objectives of the study and logistical constraints, as discussed in detail in Section 7,

Dilution Water. For tests performed to meet NPDES objectives, synthetic, moderately hard water should be used. 
10

The dilution water used for internal quality assurance tests with organisms, food, and reference toxicants should be

the water routinely used with success in the laboratory. Types of water are discussed in Section 5, Facilities,

Equipment and Supplies. Water used for culturing and test dilution should be analyzed for toxic metals and

organics at least annually or whenever difficulty is encountered in meeting minimum acceptability criteria for

control survival and reproduction or growth. The concentration of the metals Al, As, Cr, Co, Cu, Fe, Pb, Ni, and

Zn, expressed as total metal, should not exceed 1 mg/L each, and Cd, Hg, and Ag, expressed as total metal, should

not exceed 100 ng/L each. Total organochlorine pesticides plus PCBs should be less than 50 ng/L (APHA, 1992). 

Pesticide concentrations should not exceed USEPA's Ambient Water Quality chronic criteria values where

available. 

4.5 EFFLUENT AND RECEIVING WATER SAMPLING AND HANDLING

4.5.1 Sample holding times and temperatures of effluent samples collected for on-site and off-site testing must

conform to conditions described in Section 8, Effluent and Receiving Water Sampling, Sample Handling, and

Sample Preparation for Toxicity Tests. 

4.6 TEST CONDITIONS

4.6.1 Water temperature should be maintained within the limits specified for each test. The temperature of test

solutions must be measured by placing the thermometer or probe directly into the test solutions, or by placing the

thermometer in equivalent volumes of water in surrogate vessels positioned at appropriate locations among the test

vessels. Temperature should be recorded continuously in at least one test vessel for the duration of each test. Test

solution temperatures should be maintained within the limits specified for each test. DO concentration and pH

should be checked at the beginning of each test and daily throughout the test period.

4.7 QUALITY OF TEST ORGANISMS

4.7.1 The health of test organisms is primarily assessed by the performance (survival, growth, and/or reproduction)

of organisms in control treatments of individual tests. The health and sensitivity of test organisms is also assessed

by reference toxicant testing. In addition to documenting the sensitivity and health of test organisms, reference

toxicant testing is used to initially demonstrate acceptable laboratory performance (Subsection 4.15) and to

document ongoing laboratory performance (Subsection 4.16). 

4.7.2 Regardless of the source of test organisms (in-house cultures or purchased from external suppliers), the

testing laboratory must perform at least one acceptable reference toxicant test per month for each toxicity test

method conducted in that month (Subsection 4.16). If a test method is conducted only monthly, or less frequently, a

reference toxicant test must be performed concurrently with each effluent toxicity test.

4.7.3 When acute or short-term chronic toxicity tests are performed with effluents or receiving waters using test

organisms obtained from outside the test laboratory, concurrent toxicity tests of the same type must be performed

with a reference toxicant, unless the test organism supplier provides control chart data from at least the last five

monthly short-term chronic toxicity tests using the same reference toxicant and control conditions (see Section 6,

Test Organisms).

4.7.4 The supplier should certify the species identification of the test organisms, and provide the taxonomic

reference (citation and page) or name(s) of the taxonomic expert(s) consulted.

4.7.5 If routine reference toxicant tests fail to meet test acceptability criteria, then the reference toxicant test must

be immediately repeated. 
11

4.8 FOOD QUALITY

4.8.1 The nutritional quality of the food used in culturing and testing fish and invertebrates is an important factor

in the quality of the toxicity test data. This is especially true for the unsaturated fatty acid content of brine shrimp

nauplii, Artemia. Problems with the nutritional suitability of the food will be reflected in the survival, growth, and

reproduction of the test organisms in cultures and toxicity tests. Artemia cysts, and other foods must be obtained as

described in Section 5, Facilities, Equipment, and Supplies. 

4.8.2 Problems with the nutritional suitability of food will be reflected in the survival, growth, and reproduction of

the test organisms in cultures and toxicity tests. If a batch of food is suspected to be defective, the performance of

organisms fed with the new food can be compared with the performance of organisms fed with a food of known

quality in side-by-side tests. If the food is used for culturing, its suitability should be determined using a short-term

chronic test which will determine the affect of food quality on growth or reproduction of each of the relevant test

species in culture, using four replicates with each food source. Where applicable, foods used only in chronic

toxicity tests can be compared with a food of known quality in side-by-side, multi-concentration chronic tests, using

the reference toxicant regularly employed in the laboratory QA program.

4.8.3 New batches of food used in culturing and testing should be analyzed for toxic organics and metals or

whenever difficulty is encountered in meeting minimum acceptability criteria for control survival and reproduction

or growth. If the concentration of total organochlorine pesticides exceeds 0.15 mg/g wet weight, or the

concentration of total organochlorine pesticides plus PCBs exceeds 0.30 μg/g wet weight, or toxic metals (Al, As,

Cr, Cd, Cu, Pb, Ni, Zn, expressed as total metal) exceed 20 μg/g wet weight, the food should not be used (for

analytical methods see AOAC, 1990 and USDA, 1989). For foods (e.g., such as YCT) which are used to culture

and test organisms, the quality of the food should meet the requirements for the laboratory water used for culturing

and test dilution water as described in Section 4.4 above.

4.9 ACCEPTABILITY OF SHORT-TERM CHRONIC TOXICITY TESTS

4.9.1 For the tests to be acceptable, control survival in fathead minnow, Pimephales promelas, and the daphnid,

Ceriodaphnia dubia, tests must be 80% or greater. At the end of the test, the average dry weight of surviving

seven-day-old fathead minnows in control chambers must equal or exceed 0.25 mg. In Ceriodaphnia dubia

controls, 60% or more of the surviving females must have produced their third brood in 7 ± 1 days, and the number

of young per surviving female must be 15 or greater. In algal toxicity tests, the mean cell density in the controls

after 96 h must equal or exceed 1 x 106

 cells/mL and not vary more than 20% among replicates. If these criteria are

not met, the test must be repeated.

4.9.2 An individual test may be conditionally acceptable if temperature, DO, and other specified conditions fall

outside specifications, depending on the degree of the departure and the objectives of the tests (see test condition

summaries). The acceptability of the test would depend on the experience and professional judgment of the

laboratory investigator and the reviewing staff of the regulatory authority. Any deviation from test specifications

must be noted when reporting data from the test. 

4.10 ANALYTICAL METHODS

4.10.1 Routine chemical and physical analyses for culture and dilution water, food, and test solutions must include

established quality assurance practices outlined in USEPA methods manuals (USEPA, 1979a and USEPA, 1979b).

4.10.2 Reagent containers should be dated and catalogued when received from the supplier, and the shelf life

should not be exceeded. Also, working solutions should be dated when prepared, and the recommended shelf life

should be observed.
12

4.11 CALIBRATION AND STANDARDIZATION

4.11.1 Instruments used for routine measurements of chemical and physical parameters such as pH, DO,

temperature, and conductivity, must be calibrated and standardized according to instrument manufacturer's

procedures as indicated in the general section on quality assurance (see USEPA Methods 150.1, 360.1, 170.1, and

120.1 in USEPA, 1979b). Calibration data are recorded in a permanent log book. 

4.11.2 Wet chemical methods used to measure hardness, alkalinity and total residual chlorine must be standardized

prior to use each day according to the procedures for those specific USEPA methods (see USEPA Methods 130.2

and 310.1 in USEPA, 1979b).

4.12 REPLICATION AND TEST SENSITIVITY

4.12.1 The sensitivity of the tests will depend in part on the number of replicates per concentration, the

significance level selected, and the type of statistical analysis. If the variability remains constant, the sensitivity of

the test will increase as the number of replicates is increased. The minimum recommended number of replicates

varies with the objectives of the test and the statistical method used for analysis of the data.

4.13 VARIABILITY IN TOXICITY TEST RESULTS

4.13.1 Factors which can affect test success and precision include (1) the experience and skill of the laboratory

analyst; (2) test organism age, condition, and sensitivity; (3) dilution water quality; (4) temperature control; and (5)

the quality and quantity of food provided. The results will depend upon the species used and the strain or source of

the test organisms, and test conditions, such as temperature, DO, food, and water quality. The repeatability or

precision of toxicity tests is also a function of the number of test organisms used at each toxicant concentration. 

Jensen (1972) discussed the relationship between sample size (number of fish) and the standard error of the test, and

considered 20 fish per concentration as optimum for Probit Analysis.

4.14 TEST PRECISION

4.14.1 The ability of the laboratory personnel to obtain consistent, precise results must be demonstrated with

reference toxicants before they attempt to measure effluent toxicity. The single-laboratory precision of each type of

test to be used in a laboratory should be determined by performing at least five tests with a reference toxicant.

4.14.2 Test precision can be estimated by using the same strain of organisms under the same test conditions and

employing a known toxicant, such as a reference toxicant.

4.14.3 Interlaboratory precision data from a 1991 study of chronic toxicity tests with two species using the

reference toxicants potassium chloride and copper sulfate are shown in Table 1. Table 2 shows interlaboratory

precision data from a study of three chronic toxicity test methods using effluent, receiving water, and reference

toxicant sample types (USEPA, 2001a; USEPA, 2001b). The effluent sample was a municipal wastewater spiked

with KCl, the receiving waster sample was a river water spiked with KCl, and the reference toxicant sample

consisted of moderately-hard synthetic freshwater spiked with KCl. Additional precision data for each of the tests

described in this manual are presented in the sections describing the individual test methods.
13

TABLE 1. NATIONAL INTERLABORATORY STUDY OF CHRONIC TOXICITY TEST PRECISION, 1991: 

SUMMARY OF RESPONSES USING A REFERENCE TOXICANT1

________________________________________________________________________________________

Organism Endpoint No. Labs % Effluent2

 SD CV(%)

________________________________________________________________________________________

Pimephales Survival, NOEC 146 NA NA NA

promelas Growth, IC25 124 4.67 1.87 40.0

Growth, IC50 117 6.36 2.04 32.1

Growth, NOEC 142 NA NA NA

________________________________________________________________________________________

Ceriodaphnia Survival, NOEC 162 NA NA NA

dubia Reproduction, IC25 155 2.69 1.96 72.9

Reproduction, IC50 150 3.99 2.35 58.9

 Reproduction, NOEC 156 NA NA NA

________________________________________________________________________________________

1 From a national study of interlaboratory precision of toxicity test data performed in 1991 by the Environmental

Monitoring Systems Laboratory- Cincinnati, U.S. Environmental Protection Agency, Cincinnati, OH 45268.

Participants included Federal, state, and private laboratories engaged in NPDES permit compliance monitoring. 2 Expressed as % effluent; in reality it was a reference toxicant (KCl) but was not known by the persons conducting

the tests.
14

TABLE 2. NATIONAL INTERLABORATORY STUDY OF CHRONIC TOXICITY TEST PRECISION, 2000:

PRECISION OF RESPONSES USING EFFLUENT, RECEIVING WATER, AND REFERENCE

TOXICANT SAMPLE TYPES1

.

Organism Endpoint Number of Tests2 CV (%)3

Pimephales promelas Growth, IC25 73 20.9

Ceriodaphnia dubia Reproduction, IC25 34 35.0

Selenastrum capricornutum

(with EDTA) Growth, IC25 21 34.3

Growth, IC50 22 32.2

Selenastrum capricornutum (without

EDTA) Growth, IC25 21 58.5

Growth, IC50 22 58.5

1 From EPA’s WET Interlaboratory Variability Study (USEPA, 2001a; USEPA, 2001b). 2 Represents the number of valid tests (i.e., those that met test acceptability criteria) that were used in the analysis

of precision. Invalid tests were not used. 3 CVs based on total interlaboratory variability (including both within-laboratory and between-laboratory components

of variability) and averaged across sample types. IC25s or IC50s were pooled for all laboratories to calculate the

CV for each sample type. The resulting CVs were then averaged across sample types. 

4.14.4 Additional information on toxicity test precision is provided in the Technical Support Document for Water

Quality-based Control (see pp. 2-4, and 11-15 in USEPA, 1991a).

4.14.5 In cases where the test data are used in Probit Analysis or other point estimation techniques (see Section 9,

Chronic Toxicity Test Endpoints and Data Analysis), precision can be described by the mean, standard deviation,

and relative standard deviation (percent coefficient of variation, or CV) of the calculated endpoints from the

replicated tests. In cases where the test data are used in the Linear Interpolation Method, precision can be estimated

by empirical confidence intervals derived by using the ICPIN Method (see Section 9, Chronic Toxicity Test

Endpoints and Data Analysis). However, in cases where the results are reported in terms of the No-Observed-Effect

Concentration (NOEC) and Lowest-Observed-Effect Concentration (LOEC) (see Section 9, Chronic Toxicity Test

Endpoints and Data Analysis) precision can only be described by listing the NOEC-LOEC interval for each test. It

is not possible to express precision in terms of a commonly used statistic. However, when all tests of the same

toxicant yield the same NOEC-LOEC interval, maximum precision has been attained. The "true" no effect

concentration could fall anywhere within the interval, NOEC ± (NOEC minus LOEC).

4.14.6 It should be noted here that the dilution factor selected for a test determines the width of the NOEC-LOEC

interval and the inherent maximum precision of the test. As the absolute value of the dilution factor decreases, the

width of the NOEC-LOEC interval increases, and the inherent maximum precision of the test decreases. When a

dilution factor of 0.3 is used, the NOEC could be considered to have a relative variability as high as ± 300%. With

a dilution factor of 0.5, the NOEC could be considered to have a relative variability of ± 100%. As a result of the

variability of different dilution factors, USEPA recommends the use of the dilution factor of 0.5 or greater. 

Other factors which can affect test precision include: test organism age, condition, and sensitivity; temperature
15

control; and feeding.

4.15 DEMONSTRATING ACCEPTABLE LABORATORY PERFORMANCE

4.15.1 It is a laboratory's responsibility to demonstrate its ability to obtain consistent, precise results with reference

toxicants before it performs toxicity tests with effluents for permit compliance purposes. To meet this requirement,

the intralaboratory precision, expressed as percent coefficient of variation (CV%), of each type of test to be used in

the laboratory should be determined by performing five or more tests with different batches of test organisms, using

the same reference toxicant, at the same concentrations, with the same test conditions (i.e., the same test duration,

type of dilution water, age of test organisms, feeding, etc.), and the same data analysis methods. A reference

toxicant concentration series (0.5 or higher) should be selected that will consistently provide partial mortalities at

two or more concentrations.

4.16 DOCUMENTING ONGOING LABORATORY PERFORMANCE

4.16.1 Satisfactory laboratory performance is demonstrated by performing at least one acceptable test per month

with a reference toxicant for each toxicity test method conducted in the laboratory during that month. For a given

test method, successive tests must be performed with the same reference toxicant, at the same concentrations, in the

same dilution water, using the same data analysis methods. Precision may vary with the test species, reference

toxicant, and type of test. Each laboratory’s reference toxicity data will reflect conditions unique to that facility,

including dilution water, culturing, and other variables; however, each laboratory’s reference toxicity results should

reflect good repeatability.

4.16.2 A control chart should be prepared for each combination of reference toxicant, test species, test conditions,

and endpoints. Toxicity endpoints from five or six tests are adequate for establishing the control charts. Successive

toxicity endpoints (NOECs, IC25s, LC50s, etc.) should be plotted and examined to determine if the results (X1) are

within prescribed limits (Figure 1). The chart should plot logarithm of concentration on the vertical axis against the

date of the test or test number on the horizontal axis. The types of control charts illustrated (see USEPA, 1979a) are

used to evaluate the cumulative trend of results from a series of samples, thus reference toxicant test results should

not be used as a de facto criterion for rejection of individual effluent or receiving water tests. For endpoints that are

point estimates (LC50s and IC25s), the cumulative mean ( ) and upper and lower control limits (± 2S) are re- X ̄

calculated with each successive test result. Endpoints from hypothesis tests (NOEC, NOAEC) from each test are

plotted directly on the control chart. The control limits would consist of one concentration interval above and below

the concentration representing the central tendency. After two years of data collection, or a minimum of 20 data

points, the control chart should be maintained using only the 20 most recent data points.

4.16.3 Laboratories should compare the calculated CV (i.e., standard deviation / mean) of the IC25 for the 20 most

recent data points to the distribution of laboratory CVs reported nationally for reference toxicant testing (Table 3-2

in USEPA, 2000b). If the calculated CV exceeds the 75th percentile of CVs reported nationally, the laboratory

should use the 75th and 90th percentiles to calculate warning and control limits, respectively, and the laboratory

should investigate options for reducing variability. Note: Because NOECs can only be a fixed number of discrete

values, the mean, standard deviation, and CV cannot be interpreted and applied in the same way that these

descriptive statistics are interpreted and applied for continuous variables such as the IC25 or LC50. 

4.16.4 The outliers, which are values falling outside the upper and lower control limits, and trends of increasing or

decreasing sensitivity, are readily identified. In the case of endpoints that are point estimates (LC50s and IC25s), at

the P0.05 probability level, one in 20 tests would be expected to fall outside of the control limits by chance alone. If

more than one out of 20 reference toxicant tests fall outside the control limits, the laboratory should investigate

sources of variability, take corrective actions to reduce identified sources of variability, and perform an additional

reference toxicant test during the same month. Control limits for the NOECs will also be exceeded occasionally,

regardless of how well a laboratory performs. In those instances when the laboratory can document the cause for

the outlier (e.g., operator error, culture health or test system failure), the outlier should be excluded from the future

calculations of the control limits. If two or more consecutive tests do not fall within the control limits, the results
16

must be explained and the reference toxicant test must be immediately repeated. Actions taken to correct the

problem must be reported.

4.16.5 If the toxicity value from a given test with a reference toxicant falls well outside the expected range for the

other test organisms when using the standard dilution water and other test conditions, the laboratory should

investigate sources of variability, take corrective actions to reduce identified sources of variability, and perform an

additional reference toxicant test during the same month. Performance should improve with experience, and the

control limits for endpoints that are point estimates should gradually narrow. However, control limits of ± 2S will

be exceeded 5% of the time by chance alone, regardless of how well a laboratory performs. Highly proficient

laboratories which develop very narrow control limits may be unfairly penalized if a test result which falls just

outside the control limits is rejected de facto. For this reason, the width of the control limits should be considered in

determining whether or not a reference toxicant test result falls “well” outside the expected range. The width of the

control limits may be evaluated by comparing the calculated CV (i.e., standard deviation / mean) of the IC25 for the

20 most recent data points to the distribution of laboratory CVs reported nationally for reference toxicant testing

(Table 3-2 in USEPA, 2000b). In determining whether or not a reference toxicant test result falls “well” outside the

expected range, the result also may be compared with upper and lower bounds for ±3S, as any result outside these

control limits would be expected to occur by chance only 1 out of 100 tests (Environment Canada, 1990). When a

result from a reference toxicant test is outside the 99% confidence intervals, the laboratory must conduct an

immediate investigation to assess the possible causes for the outlier. 

4.16.6 Reference toxicant test results should not be used as a de facto criterion for rejection of individual effluent

or receiving water tests. Reference toxicant testing is used for evaluating the health and sensitivity of organisms

over time and for documenting initial and ongoing laboratory performance. While reference toxicant test results

should not be used as a de facto criterion for test rejection, effluent and receiving water test results should be

reviewed and interpreted in the light of reference toxicant test results. The reviewer should consider the degree to

which the reference toxicant test result fell outside of control chart limits, the width of the limits, the direction of the

deviation (toward increased test organism sensitivity or toward decreased test organism sensitivity), the test

conditions of both the effluent test and the reference toxicant test, and the objective of the test.

4.17 REFERENCE TOXICANTS

4.17.1 Reference toxicants such as sodium chloride (NaCl), potassium chloride (KCl), cadmium chloride (CdCl2),

copper sulfate (CuSO4), sodium dodecyl sulfate (SDS), and potassium dichromate (K2Cr2O7), are suitable for use in

the NPDES Program and other Agency programs requiring aquatic toxicity tests. EMSL-Cincinnati hopes to release

USEPA-certified solutions of cadmium and copper for use as reference toxicants through cooperative research and

development agreements with commercial suppliers, and will continue to develop additional reference toxicants for

future release. Standard reference materials can be obtained from commercial supply houses, or can be prepared

inhouse using reagent grade chemicals. The regulatory agency should be consulted before reference toxicant(s) are

selected and used.
17

Figure 1. Control charts. (A) hypothesis testing results; (B) point estimates (LC, EC, or IC).

X ̄ '

j

n

i'1

Xi

n

S '

j

n

i'1

Xi

2 &

(j

n

i'1

Xi)

2

n

n&1

Where: Xi = Successive toxicity values from toxicity tests.

n = Number of tests.

X ̄ = Mean toxicity value.

S = Standard deviation.
18

4.18 RECORD KEEPING

4.18.1 Proper record keeping is important. A complete file should be maintained for each individual toxicity test

or group of tests on closely related samples. This file should contain a record of the sample chain-of-custody; a

copy of the sample log sheet; the original bench sheets for the test organism responses during the toxicity test(s);

chemical analysis data on the sample(s); detailed records of the test organisms used in the test(s), such as species,

source, age, date of receipt, and other pertinent information relating to their history and health; information on the

calibration of equipment and instruments; test conditions employed; and results of reference toxicant tests. 

Laboratory data should be recorded on a real-time basis to prevent the loss of information or inadvertent

introduction of errors into the record. Original data sheets should be signed and dated by the laboratory personnel

performing the tests.

4.18.2 The regulatory authority should retain records pertaining to discharge permits. Permittees are required to

retain records pertaining to permit applications and compliance for a minimum of 3 years [40 CFR 122.41(j)(2)].
19

SECTION 5

FACILITIES, EQUIPMENT, AND SUPPLIES

5.1 GENERAL REQUIREMENTS

5.1.1 Effluent toxicity tests may be performed in a fixed or mobile laboratory. Facilities must include equipment

for rearing and/or holding organisms. Culturing facilities for test organisms may be desirable in fixed laboratories

which perform large numbers of tests. Temperature control can be achieved using circulating water baths, heat

exchangers, or environmental chambers. Water used for rearing, holding, acclimating, and testing organisms may

be ground water, receiving water, dechlorinated tap water, or reconstituted synthetic water. Dechlorination can be

accomplished by carbon filtration, or the use of sodium thiosulfate. Use of 3.6 mg (anhydrous) sodium

thiosulfate/L will reduce l.0 mg chlorine/L. After dechlorination, total residual chlorine should be non-detectable. 

Air used for aeration must be free of oil and toxic vapors. Oil-free air pumps should be used where possible. 

Particulates can be removed from the air using BALSTON® Grade BX or equivalent filters, and oil and other

organic vapors can be removed using activated carbon filters (BALSTON®, C-1 filter, or equivalent).

5.1.2 The facilities must be well ventilated and free from fumes. Laboratory ventilation systems should be

checked to ensure that return air from chemistry laboratories and/or sample holding areas is not circulated to test

organism culture rooms or toxicity test rooms, or that air from toxicity test rooms does not contaminate culture

areas. Sample preparation, culturing, and toxicity test areas should be separated to avoid cross contamination of

cultures or toxicity test solutions with toxic fumes. Air pressure differentials between such rooms should not result

in a net flow of potentially contaminated air to sensitive areas through open or loosely- fitting doors. Organisms

should be shielded from external disturbances.

5.1.3 Materials used for exposure chambers, tubing, etc., that come in contact with the effluent and dilution water

should be carefully chosen. Tempered glass and perfluorocarbon plastics (TEFLON®) should be used whenever

possible to minimize sorption and leaching of toxic substances. These materials may be reused following

decontamination. Containers made of plastics, such as polyethylene, polypropylene, polyvinyl chloride, TYGON®,

etc., may be used as test chambers or to ship, store and transfer effluents and receiving waters, but they should not

be reused unless absolutely necessary, because they could carry over adsorbed toxicants from one test to another, if

reused. However, these containers may be repeatedly reused for storing uncontaminated waters, such as deionized

or laboratory-prepared dilution waters and receiving waters. Glass or disposable polystyrene containers can be used

for test chambers. The use of large ($ 20 L) glass carboys is discouraged for safety reasons. 

5.1.4 New plastic products of a type not previously used should be tested for toxicity before initial use by

exposing the test organisms in the test system where the material is used. Equipment (pumps, valves, etc.) which

cannot be discarded after each use because of cost, must be decontaminated according to the cleaning procedures

listed below (see Section 5, Facilities, Equipment and Supplies, Subsection 5.3.2). Fiberglass and stainless steel, in

addition to the previously mentioned materials, can be used for holding, acclimating, and dilution water storage

tanks, and in the water delivery system, but once contaminated with pollutants the fiberglass should not be reused. 

All material should be flushed or rinsed thoroughly with the test media before using in the test.

5.1.5 Copper, galvanized material, rubber, brass, and lead must not come in contact with culturing, holding,

acclimation, or dilution water, or with effluent samples and test solutions. Some materials, such as several types of

neoprene rubber (commonly used for stoppers), may be toxic and should be tested before use. 

5.1.6 Silicone adhesive used to construct glass test chambers absorbs some organochlorine and organophosphorus

pesticides, which are difficult to remove. Therefore, as little of the adhesive as possible should be in contact with

water. Extra beads of adhesive inside the containers should be removed. 
20

5.2 TEST CHAMBERS

5.2.1 Test chamber size and shape are varied according to size of the test organism. Requirements are specified in

each toxicity test method.

5.3 CLEANING TEST CHAMBERS AND LABORATORY APPARATUS

5.3.1 New plasticware used for sample collection or organism exposure vessels does not require thorough cleaning

before use. It is sufficient to rinse new sample containers once with dilution water before use. New glassware must

be soaked overnight in 10% acid (see below) and rinsed well in deionized water and dilution water.

5.3.2 All non-disposable sample containers, test vessels, tanks, and other equipment that have come in contact with

effluent must be washed after use to remove contaminants as described below. 

1. Soak 15 min in tap water and scrub with detergent, or clean in an automatic dishwasher.

2. Rinse twice with tap water.

3. Carefully rinse once with fresh, dilute (10%, V:V) hydrochloric or nitric acid to remove scale, metals

and bases. To prepare a 10% solution of acid, add 10 mL of concentrated acid to 90 mL of deionized

water. 

4. Rinse twice with deionized water.

5. Rinse once with full-strength, pesticide-grade acetone to remove organic compounds (use a fume hood

or canopy).

6. Rinse three times with deionized water.

5.3.3 Special requirements for cleaning glassware used in the green alga, Selenastrum capricornutum, toxicity tests

(Method 1003.0, Section 14). Prepare all graduated cylinders, test flasks, bottles, volumetric flasks, centrifuge

tubes and vials used in algal assays as follows: 

1. Wash with non-phosphate detergent solution, preferably heated to $ 50°C. Brush the inside of flasks

with a stiff-bristle brush to loosen any attached material. The use of a commercial laboratory glassware

washer or heavy-duty kitchen dishwasher (under-counter type) is highly recommended.

2. Rinse with tap water.

3. Test flasks should be thoroughly rinsed with acetone and a 10% solution (by volume) of reagent grade

hydrochloric acid (HCl). It may be advantageous to soak the flasks in 10% HCl for several days. Fill

vials and centrifuge tubes with the 10% HCl solution and allow to stand a few minutes; fill all larger

containers to about one-tenth capacity with HCl solution and swirl so that the entire surface is bathed.

4. Rinse twice with MILLIPORE® MILLI-Q® OR QPAKTM2, or equivalent, water.

5. New test flasks, and all flasks which through use may become contaminated with toxic organic

substances, must be rinsed with pesticide-grade acetone or heat-treated before use. To thermally 

degrade organics, place glassware in a high temperature oven at 400°C for 30 min. After cooling, go to

7. If acetone is used, go to 6.

6. Rinse thoroughly with MILLIPORE® MILLI-Q® or QPAKTM2, or equivalent water, and dry in an 105°C

oven. All glassware should be autoclaved before use and between uses.

7. Cover the mouth of each chamber with aluminum foil or other closure, as appropriate, before storing.

5.3.4 The use of sterile, disposable pipets will eliminate the need for pipet washing and minimize the possibility of

contaminating the cultures with toxic substances.

5.3.5 All test chambers and equipment must be thoroughly rinsed with the dilution water immediately prior to use

in each test. 
21

5.4 APPARATUS AND EQUIPMENT FOR CULTURING AND TOXICITY TESTS

5.4.1 Apparatus and equipment requirements for culturing and testing are specified in each toxicity test method. 

Also, see USEPA, 2002a.

5.4.2 WATER PURIFICATION SYSTEM

5.4.2.1 A good quality, laboratory grade deionized water, providing a resistance of 18 megaohm-cm, must be

available in the laboratory and in sufficient quantity for laboratory needs. Deionized water may be obtained from

MILLIPORE® Milli-Q®, MILLIPORE® QPAKTM2 or equivalent system. If large quantities of high quality

deionized water are needed, it may be advisable to supply the laboratory grade deionizer with preconditioned water

from a Culligan®, Continental®, or equivalent mixed-bed water treatment system.

5.5 REAGENTS AND CONSUMABLE MATERIALS

5.5.1 SOURCES OF FOOD FOR CULTURE AND TOXICITY TESTS

1. Brine shrimp, Artemia sp., cysts -- Many commercial sources of brine shrimp cysts are available.

2. Frozen adult brine shrimp, Artemia -- Available from most pet supply shops or other commercial

sources.

3. Flake fish food -- TETRAMIN® and BIORIL® are available from most pet shops.

4. Trout chow -- Available from commercial sources.

5. Cereal leaves, CEROPHYLL® or equivalent -- Available from commercial sources.

6. Yeast -- Packaged dry yeast, such as Fleischmann's, or equivalent, can be purchased at the local grocery

store or commercial sources.

7. Alfalfa Rabbit Pellets -- Available from feed stores as Purina rabbit chow.

8. Algae - Available from commercial sources.

5.5.1.1 All food should be tested for nutritional suitability and chemically analyzed for organochlorine pesticides,

PCBs, and toxic metals (see Section 4, Quality Assurance).

5.5.2 Reagents and consumable materials are specified in each toxicity test method section. Also, see Section 4,

Quality Assurance.

5.6 TEST ORGANISMS

5.6.1 Test organisms should be obtained from inhouse cultures or from commercial suppliers (see specific test

method; Section 4, Quality Assurance; and Section 6, Test Organisms).

5.7 SUPPLIES

5.7.1 See test methods (see Sections 11-14) for specific supplies.
22

SECTION 6

TEST ORGANISMS

6.1 TEST SPECIES

6.1.1 The species used in characterizing the chronic toxicity of effluents and/or receiving waters will depend on the

requirements of the regulatory authority and the objectives of the test. It is essential that good quality test organisms

be readily available throughout the year from inhouse or commercial sources to meet NPDES monitoring

requirements. The organisms used in the toxicity tests must be identified to species. If there is any doubt as to the

identity of the test organism, representative specimens should be sent to a taxonomic expert to confirm the

identification.

6.1.2 Toxicity test conditions and culture methods for the species listed in Subsection 6.1.3 are provided in this

manual also, see USEPA, 2002a.

6.1.3 The organisms used in the short-term chronic toxicity tests described in this manual are the fathead minnow,

Pimephales promelas, the daphnid, Ceriodaphnia dubia (Berner, 1986), and the green alga, Selenastrum

capricornutum. 

6.1.4 Some states have developed culturing and testing methods for indigenous species that may be as sensitive, or

more sensitive, than the species recommended in Subsection 6.1.3. However, USEPA allows the use of indigenous

species only where state regulations require their use or prohibit importation of the recommended species in

Subsection 6.1.3. Where state regulations prohibit importation of non-native fishes or the use of recommended test

species, permission must be requested from the appropriate state agency prior to their use.

6.1.5 Where states have developed culturing and testing methods for indigenous species other than those

recommended in this manual, data comparing the sensitivity of the substitute species and the one or more

recommended species must be obtained in side-by-side toxicity tests with reference toxicants and/or effluents, to

ensure that the species selected are at least as sensitive as the recommended species. These data must be submitted

to the permitting authority (State or Region) if required. USEPA acknowledges that reference toxicants prepared

from pure chemicals may not always be representative of effluents. However, because of the observed and/or

potential variability in the quality and toxicity of effluents, it is not possible to specify a representative effluent.

6.1.6 Guidance for the selection of test organisms where the salinity of the effluent and/or receiving water requires

special consideration is provided in the Technical Support Document for Water Quality-based Toxics Control

(USEPA, 1991a).

1. Where the salinity of the receiving water is < 1‰, freshwater organisms are used regardless of the

salinity of the effluent.

2. Where the salinity of the receiving water is $ 1‰, the choice of organisms depends on state water

quality standards and/or permit requirements.

6.2 SOURCES OF TEST ORGANISMS

6.2.1 The test organisms recommended in this manual can be cultured in the laboratory using culturing and

handling methods for each organism described in the respective test method sections. The fathead minnow,

Pimephales promelas, culture method is given in Section 11 and not repeated in Section 12. Also, see USEPA

(2002a).
23

6.2.2 Inhouse cultures should be established wherever it is cost effective. If inhouse cultures cannot be maintained

or it is not cost effective, test organisms or starter cultures should be purchased from experienced commercial

suppliers (see USEPA, 2002a).

6.2.3 Starter cultures of the green algae, Selenastrum capricornutum, S. minutum, and Chlamydomonas reinhardti

are available from commercial suppliers.

6.2.4 Because the daphnid, Ceriodaphnia dubia, must be cultured individually in the laboratory for at least seven

days before the test begins, it will be necessary to obtain a starter culture from a commercial source at least three

weeks before the test is to begin if they are not being cultured inhouse.

6.2.5 If, because of their source, there is any uncertainty concerning the identity of the organisms, it is advisable to

have them examined by a taxonomic specialist to confirm their identification. For detailed guidance on

identification, see the individual test methods.

6.2.6 FERAL (NATURAL OCCURRING, WILD CAUGHT) ORGANISMS

6.2.6.1 The use of test organisms taken from the receiving water has strong appeal, and would seem to be a logical

approach. However, it is generally impractical and not recommended for the following reasons:

1. Sensitive organisms may not be present in the receiving water because of previous exposure to the

effluent or other pollutants.

2. It is often difficult to collect organisms of the required age and quality from the receiving water.

3. Most states require collecting permits, which may be difficult to obtain. Therefore, it is usually more

cost effective to culture the organisms in the laboratory or obtain them from private, state, or Federal

sources. The fathead minnow, Pimephales promelas, the daphnid, Ceriodaphnia dubia, and the green

alga, Selenastrum capricornutum, are easily cultured in the laboratory or readily available

commercially.

4. The required QA/QC records, such as the single laboratory precision data, would not be available.

5. Since it is mandatory that the identity of the test organism be known to species level, it would be

necessary to examine each organism caught in the wild to confirm its identity. This would usually be

impractical or, at the least, very stressful to the organisms.

6. Test organisms obtained from the wild must be observed in the laboratory for a minimum of one week

prior to use, to assure that they are free of signs of parasitic or bacterial infections and other adverse

effects. Fish captured by electroshocking must not be used in toxicity testing.

6.2.6.2 Guidelines for collecting natural occurring organisms are provided in USEPA (1973), USEPA (1990) and

USEPA (1993b).

6.2.7 Regardless of their source, test organisms should be carefully observed to ensure that they are free of signs of

stress and disease, and in good physical condition. Some species of test organisms can be obtained from

commercial stock certified as "disease-free".

6.3 LIFE STAGE

6.3.1 Young organisms are often more sensitive to toxicants than are adults. For this reason, the use of early life

stages, such as larval fish, is required for all tests. In a given test, all organisms should be approximately the same

age and should be taken from the same source. Since age may affect the results of the tests, it would enhance the

value and comparability of the data if the same species in the same life stages were used throughout a monitoring

program at a given facility.
24

6.4 LABORATORY CULTURING

6.4.1 Instructions for culturing and/or holding the recommended test organisms are included in the respective test

methods (also, see USEPA, 2002a).

6.5 HOLDING AND HANDLING TEST ORGANISMS

6.5.1 Test organisms should not be subjected to changes of more than 3°C in water temperature in any 12 h period

or 2 units of pH in any 24-h period.

6.5.2 Organisms should be handled as little as possible. When handling is necessary, it should be done as gently,

carefully, and quickly as possible to minimize stress. Organisms that are dropped or touch a dry surface or are

injured during handling must be discarded. Dipnets are best for handling larger organisms. These nets are

commercially available or can be made from small-mesh nylon netting, silk batting cloth, plankton netting, or

similar material. Wide-bore, smooth glass tubes (4 to 8 mm ID) with rubber bulbs or pipettors (such as

PROPIPETTE®) should be used for transferring smaller organisms such as larval fish.

6.5.3 Holding tanks for fish are supplied with good quality water (see Section 5, Facilities, Equipment, and

Supplies) with flow-through rate of at least two tank volumes per day. Otherwise use a recirculation system where

water flows through an activated carbon or undergravel filter to remove dissolved metabolites. Culture water can

also be piped through high intensity ultraviolet light sources for disinfection, and to photodegrade dissolved

organics.

6.5.4 Crowding must be avoided because it will stress the organisms and lower the DO concentrations to

unacceptable levels. The solution of oxygen depends on temperature and altitude. The DO must be maintained at a

minimum of 4.0 mg/L. Aerate gently if necessary.

6.5.5 The organisms should be observed carefully each day for signs of disease, stress, physical damage, or

mortality. Dead and abnormal organisms should be removed as soon as observed. It is not uncommon for some

fish mortality (5-10%) to occur during the first 48 h in a holding tank because of individuals that refuse to feed on

artificial food and die of starvation. Organisms in the holding tanks should generally be fed as in the cultures (see

culturing methods in the respective methods).

6.5.6 Fish should be fed as much as they will eat at least once a day with live brine shrimp nauplii, Artemia, or

frozen adult brine shrimp, or dry food (frozen food should be completely thawed before use). Adult brine shrimp

can be supplemented with commercially prepared food such as TETRAMIN® or BIORIL® flake food, or equivalent. 

Excess food and fecal material should be removed from the bottom of the tanks at least twice a week by siphoning.

6.5.7 A daily record of feeding, behavioral observations, and mortality should be maintained.

6.6 TRANSPORTATION TO THE TEST SITE

6.6.1 Organisms are transported from the base or supply laboratory to a remote test site in culture water or standard

dilution water in plastic bags or large-mouth screw-cap (500 mL) plastic bottles in styrofoam coolers. Adequate DO

is maintained by replacing the air above the water in the bags with oxygen from a compressed gas cylinder, and

sealing the bags or by use of an airstone supplied by a portable pump. The DO concentration must not fall below

4.0 mg/L.

6.6.2 Upon arrival at the test site, the organisms are transferred to receiving water if receiving water is to be used

as the test dilution water. All but a small volume of the holding water (approximately 5%) is removed by siphoning

and replaced slowly over a 10 to 15 minute period with dilution water. If receiving water is to be used as the

dilution water, caution must be exercised in exposing the test organisms to it, because of the possibility that it might

be toxic. For this reason, it is recommended that only approximately 10% of the test organisms be exposed initially
25

to the dilution water. If this group does not show excessive mortality or obvious signs of stress in a few hours, the

remainder of the test organisms may be transferred to the dilution water.

6.6.3 A group of organisms must not be used for a test if they appear to be unhealthy, discolored, or otherwise

stressed, or if mortality appears to exceed 10% preceding the test. If the organisms fail to meet these criteria, the

entire group must be discarded and a new group obtained. The mortality may be due to the presence of toxicity, if

the receiving water is used as dilution water, rather than a diseased condition of the test organisms. If the

acclimation process is repeated with a new group of test organisms and excessive mortality occurs, it is

recommended that an alternative source of dilution water be used.

6.7 TEST ORGANISM DISPOSAL

6.7.1 When the toxicity test(s) is concluded, all test organisms (including controls) should be humanely destroyed

and disposed of in an appropriate manner.
26

SECTION 7

DILUTION WATER

7.1 TYPES OF DILUTION WATER

7.1.1 The type of dilution water used in effluent toxicity tests will depend largely on the objectives of the study. 

7.1.1.1 If the objective of the test is to estimate the absolute chronic toxicity of the effluent, a synthetic (standard)

dilution water is used. If the test organisms have been cultured in water which is different from the test dilution

water, a second set of controls, using culture water, should be included in the test.

7.1.1.2 If the objective of the test is to estimate the chronic toxicity of the effluent in uncontaminated receiving

water, the test may be conducted using dilution water consisting of a single grab sample of receiving water (if

non-toxic), collected either upstream and outside the influence of the outfall, or with other uncontaminated natural

water (ground or surface water) or standard dilution water having approximately the same characteristics (hardness,

alkalinity, and conductivity) as the receiving water. Seasonal variations in the quality of receiving waters may

affect effluent toxicity. Therefore, the pH, alkalinity, hardness, and conductivity of receiving water samples should

be determined before each use. If the test organisms have been cultured in water which is different from the test

dilution water, a second set of controls, using culture water, should be included in the test.

7.1.1.3 If the objective of the test is to determine the additive or mitigating effects of the discharge on already

contaminated receiving water, the test is performed using dilution water consisting of receiving water collected

immediately upstream or outside the influence of the outfall. A second set of controls, using culture water, should

be included in the test.

7.1.2 An acceptable dilution water is one which is appropriate for the objectives of the test; supports adequate

performance of the test organisms with respect to survival, growth, reproduction, or other responses that may be

measured in the test (i.e., consistently meets test acceptability criteria for control responses); is consistent in quality;

and does not contain contaminants that could produce toxicity. Receiving waters, synthetic waters, or synthetic

waters adjusted to approximate receiving water characteristics may be used for dilution provided that the water

meets the above listed qualifications for an acceptable dilution water. USEPA (2000a) provides additional guidance

on selecting appropriate dilution waters.

7.1.3 When dual controls (one control using culture water and one control using dilution water) are used (see

Subsections 7.1.1.1 - 7.1.1.3 above), the dilution water control should be used to determine test acceptability. It is

also the dilution water control that should be compared to effluent treatments in the calculation and reporting of test

results. The culture water control should be used to evaluate the appropriateness of the dilution water source. 

Significant differences between organism responses in culture water and dilution water controls could indicate

toxicity in the dilution water and may suggest an alternative dilution water source. USEPA (2000a) provides

additional guidance on dual controls.

7.2 STANDARD, SYNTHETIC DILUTION WATER

7.2.1 Standard, synthetic dilution water is prepared with deionized water and reagent grade chemicals or mineral

water (Tables 3 and 4). The source water for the deionizer can be ground water or tap water.

7.2.2 DEIONIZED WATER USED TO PREPARE STANDARD, SYNTHETIC, DILUTION WATER

7.2.2.1 Deionized water is obtained from a MILLIPORE® MILLI-Q®, MILLIPORE® QPAKTM

2 or equivalent

system. It is advisable to provide a preconditioned (deionized) feed water by using a Culligan®, Continental®, or
27

equivalent system in front of the MILLIPORE® System to extend the life of the MILLIPORE® cartridges (see

Section 5, Facilities, Equipment, and Supplies). 

7.2.2.2 The recommended order of the cartridges in a four-cartridge deionizer (i.e., MILLI-Q® System or

equivalent) is (1) ion exchange, (2) ion exchange, (3) carbon, and (4) organic cleanup (such as ORGANEX-Q®, or

equivalent) followed by a final bacteria filter. The QPAKTM

2 water system is a sealed system which does not allow

for the rearranging of the cartridges. However, the final cartridge is an ORGANEX-Q® filter, followed by a final

bacteria filter. Commercial laboratories using this system have not experienced any difficulty in using the water for

culturing or testing. Reference to the MILLI-Q® systems throughout the remainder of the manual includes all

MILLIPORE® or equivalent systems. 

7.2.3 STANDARD, SYNTHETIC FRESHWATER

7.2.3.1 To prepare 20 L of synthetic, moderately hard, reconstituted water, use the reagent grade chemicals in

Table 3 as follows:

1. Place 19 L of MILLI-Q®, or equivalent, water in a properly cleaned plastic carboy.

2. Add 1.20 g of MgSO4, 1.92 g NaHCO3, and 0.080g KCl to the carboy.

3. Aerate overnight.

4. Add 1.20 g of CaSO4•2H20 to 1 L of MILLI-Q® or equivalent deionized water in a separate flask. Stir

on magnetic stirrer until calcium sulfate is dissolved, add to the 19 L above, and mix well.

5. For Ceriodaphnia dubia culturing and testing, add sufficient sodium selenate (Na2SeO4) to provide 2

mg selenium per liter of final dilution water.

6. Aerate the combined solution vigorously for an additional 24 h to dissolve the added chemicals and

stabilize the medium.

7. The measured pH, hardness, etc., should be as listed in Table 3.

TABLE 3. PREPARATION OF SYNTHETIC FRESHWATER USING REAGENT GRADE CHEMICALS1

Water Reagent Added (mg/L)2 Approximate Final Water Quality

Type AlkaNaHCO3 CaSO4•2H2O MgSO4 KCl pH3 Hardness4

 linity4

Very soft 12.0 7.5 7.5 0.5 6.4-6.8 10-13 10-13

Soft 48.0 30.0 30.0 2.0 7.2-7.6 40-48 30-35

Moderately

 Hard 96.0 60.0 60.0 4.0 7.4-7.8 80-100 57-64

Hard 192.0 120.0 120.0 8.0 7.6-8.0 160-180 110-120

Very hard 384.0 240.0 240.0 16.0 8.0-8.4 280-320 225-245

1 Taken in part from Marking and Dawson (1973). 2 Add reagent grade chemicals to deionized water. 3 Approximate equilibrium pH after 24 h of aeration. 4 Expressed as mg CaCO3/L.

7.2.3.2 If large volumes of synthetic reconstituted water will be needed, it may be advisable to mix 1 L portions of

concentrated stock solutions of NaHCO3, MgSO4, and KCl for use in preparation of the reconstituted waters.

7.2.3.3 To prepare 20 L of standard, synthetic, moderately hard, reconstituted water, using mineral water such as

PERRIER® Water, or equivalent (Table 4), follow the instructions below.
28

1. Place 16 L of MILLI-Q® or equivalent water in a properly cleaned plastic carboy.

2. Add 4 L of PERRIER® Water, or equivalent.

3. Aerate vigorously for 24 h to stabilize the medium.

4. The measured pH, hardness and alkalinity of the aerated water will be as indicated in Table 4.

5. This synthetic water is referred to as diluted mineral water (DMW) in the toxicity test methods.

 TABLE 4. PREPARATION OF SYNTHETIC FRESHWATER USING MINERAL WATER1

Approximate Final Water Quality

Volume of Proportion 

Water Mineral Water of Mineral AlkaType Added (mL/L)2 Water (%) pH3 Hardness4 linity4

Very soft 50 2.5 7.2-8.1 10-13 10-13

Soft 100 10.0 7.9-8.3 40-48 30-35

Moderately Hard 200 20.0 7.9-8.3 80-100 57-64

Hard 400 40.0 7.9-8.3 160-180 110-120

Very hard5 --- --- --- --- ---

1 From Mount et al. (1987), and data provided by Philip Lewis, EMSL-Cincinnati, OH. 2 Add mineral water to Milli-Q® water, or equivalent, to prepare Diluted Mineral Water (DMW). 3 Approximate equilibrium pH after 24 h of aeration. 4 Expressed as mg CaCO3/L. 5 Dilutions of PERRIER® Water form a precipitate when concentrations equivalent to "very hard water" are

aerated. 

7.3 USE OF RECEIVING WATER AS DILUTION WATER

7.3.1 If the objectives of the test require the use of uncontaminated receiving water as dilution water, and the

receiving water is uncontaminated, it may be possible to collect a sample of the receiving water upstream of, or

close to, but outside of the zone influenced by the effluent. However, if the receiving water is contaminated, it may

be necessary to collect the sample in an area "remote" from the discharge site, matching as closely as possible the

physical and chemical characteristics of the receiving water near the outfall.

7.3.2 The sample should be collected immediately prior to the test, but never more than 96 h before the test begins. 

Except where it is used within 24 h, or in the case where large volumes are required for flow through tests, the

sample should be chilled to 0-6°C during or immediately following collection, and maintained at that temperature

prior to use in the test.

7.3.3 Receiving water containing debris or indigenous organisms that may be confused with or attack the test

organisms should be filtered through a sieve having 60 mm mesh openings prior to use.

7.3.4 Where toxicity-free dilution water is required in a test, the water is considered acceptable if test organisms

show the required survival, growth, and reproduction in the controls during the test. 

7.3.5 The regulatory authority may require that the hardness of the dilution water be comparable to the receiving

water at the discharge site. This requirement can be satisfied by collecting an uncontaminated receiving water with

a suitable hardness, or adjusting the hardness of an otherwise suitable receiving water by addition of reagents as

indicated in Table 3.
29

7.4 USE OF TAP WATER AS DILUTION WATER

7.4.1 The use of tap water as dilution water is discouraged unless it is dechlorinated and passed through a

deionizer and carbon filter. Tap water can be dechlorinated by deionization, carbon filtration, or the use of sodium

thiosulfate. Use of 3.6 mg/L (anhydrous) sodium thiosulfate will reduce 1.0 mg chlorine/L (APHA, 1992). 

Following dechlorination, total residual chlorine should not exceed 0.01 mg/L. Because of the possible toxicity of

thiosulfate to test organisms, a control lacking thiosulfate should be included in toxicity tests utilizing thiosulfatedechlorinated water.

7.4.2 To be adequate for general laboratory use following dechlorination, the tap water is passed through a

deionizer and carbon filter to remove toxic metals and organics, and to control hardness and alkalinity.

7.5 DILUTION WATER HOLDING

7.5.1 A given batch of dilution water should not be used for more than 14 days following preparation because of

the possible build-up of bacterial, fungal, or algal slime growth and the problems associated with it. The container

should be kept covered and the contents should be protected from light.
30

SECTION 8

EFFLUENT AND RECEIVING WATER SAMPLING, SAMPLE HANDLING,

AND SAMPLE PREPARATION FOR TOXICITY TESTS

8.1 EFFLUENT SAMPLING

8.1.1 The effluent sampling point should be the same as that specified in the NPDES discharge permit (USEPA,

1988a). Conditions for exception would be: (l) better access to a sampling point between the final treatment and

the discharge outfall; (2) if the processed waste is chlorinated prior to discharge, it may also be desirable to take

samples prior to contact with the chlorine to determine toxicity of the unchlorinated effluent; or (3) in the event

there is a desire to evaluate the toxicity of the influent to municipal waste treatment plants or separate wastewater

streams in industrial facilities prior to their being combined with other wastewater streams or non-contact cooling

water, additional sampling points may be chosen. 

8.1.2 The decision on whether to collect grab or composite samples is based on the objectives of the test and an

understanding of the short and long-term operations and schedules of the discharger. If the effluent quality varies

considerably with time, which can occur where holding times are short, grab samples may seem preferable because

of the ease of collection and the potential of observing peaks (spikes) in toxicity. However, the sampling duration

of a grab sample is so short that full characterization of an effluent over a 24-h period would require a prohibitively

large number of separate samples and tests. Collection of a 24-h composite sample, however, may dilute toxicity

spikes, and average the quality of the effluent over the sampling period. Sampling recommendations are provided

below (also see USEPA, 2002a).

8.1.3 Aeration during collection and transfer of effluents should be minimized to reduce the loss of volatile

chemicals.

8.1.4 Details of date, time, location, duration, and procedures used for effluent sample and dilution water

collection should be recorded.

8.2 EFFLUENT SAMPLE TYPES

8.2.1 The advantages and disadvantages of effluent grab and composite samples are listed below:

8.2.1.1 GRAB SAMPLES

 Advantages: 

1. Easy to collect; require a minimum of equipment and on-site time. 

2. Provide a measure of instantaneous toxicity. Toxicity spikes are not masked by dilution. 

 Disadvantages: 

1. Samples are collected over a very short period of time and on a relatively infrequent basis. The

chances of detecting a spike in toxicity would depend on the frequency of sampling and the probability

of missing a spike is high.

8.2.1.2 COMPOSITE SAMPLES

Advantages:

1. A single effluent sample is collected over a 24-h period.
31

2. The sample is collected over a much longer period of time than a single grab sample and contains all

toxicity spikes.

Disadvantages:

1. Sampling equipment is more sophisticated and expensive, and must be placed on-site for at least 24 h.

2. Toxicity spikes may not be detected because they are masked by dilution with less toxic wastes. 

8.3 EFFLUENT SAMPLING RECOMMENDATIONS

8.3.1 When tests are conducted on-site, test solutions can be renewed daily with freshly collected samples, except

for the green alga, Selenastrum capricornutum, test which is not renewed. 

8.3.2 When tests are conducted off-site, a minimum of three samples are collected. If these samples are collected

on Test Days 1, 3, and 5, the first sample would be used for test initiation, and for test solution renewal on Day 2. 

The second sample would be used for test solution renewal on Days 3 and 4. The third sample would be used for

test solution renewal on Days 5, 6, and 7. 

8.3.3 Sufficient sample volume must be collected to perform the required toxicity and chemical tests. A 4-L (1-

gal) CUBITAINER® will provide sufficient sample volume for most tests.

8.3.4 THE FOLLOWING EFFLUENT SAMPLING METHODS ARE RECOMMENDED:

8.3.4.1 Continuous Discharges

8.3.4.1.1 If the facility discharge is continuous, a single 24-h composite sample is to be taken. 

8.3.4.2 Intermittent discharges 

8.3.4.2.1 If the facility discharge is intermittent, a composite sample is to be collected for the duration of the

discharge but not more than 24 hours.

8.4 RECEIVING WATER SAMPLING

8.4.1 Logistical problems and difficulty in securing sampling equipment generally preclude the collection of

composite receiving water samples for toxicity tests. Therefore, based on the requirements of the test, a single grab

sample or daily grab sample of receiving water is collected for use in the test.

8.4.2 The sampling point is determined by the objectives of the test. In rivers, samples should be collected from

mid-stream and at mid-depth, if accessible. In lakes the samples are collected at mid-depth.

8.4.3 To determine the extent of the zone of toxicity in the receiving water downstream from the outfall, receiving

water samples are collected at several distances downstream from the discharge. The time required for the effluentreceiving-water mixture to travel to sampling points downstream from the outfall, and the rate and degree of

mixing, may be difficult to ascertain. Therefore, it may not be possible to correlate downstream toxicity with

effluent toxicity at the discharge point unless a dye study is performed. The toxicity of receiving water samples

from five stations downstream from the discharge point can be evaluated using the same number of test vessels and

test organisms as used in one effluent toxicity test with five effluent dilutions. 
32

8.5 EFFLUENT AND RECEIVING WATER SAMPLE HANDLING, PRESERVATION, AND SHIPPING

8.5.1 Unless the samples are used in an on-site toxicity test the day of collection (or hand delivered to the testing

laboratory for use on the day of collection), they should be chilled and maintained at 0-6°C until used to inhibit

microbial degradation, chemical transformations, and loss of highly volatile toxic substances.

8.5.2 Composite samples should be chilled as they are collected. Grab samples should be chilled immediately

following collection.

8.5.3 If the effluent has been chlorinated, total residual chlorine must be measured immediately following sample

collection.

8.5.4 Sample holding time begins when the last grab sample in a series is taken (i.e., when a series of four grab

samples are taken over a 24-h period), or when a 24-h composite sampling period is completed. If the data from

the samples are to be acceptable for use in the NPDES Program, the lapsed time (holding time) from sample

collection to first use of each grab or composite sample must not exceed 36 h. EPA believes that 36 h is adequate

time to deliver the samples to the laboratories performing the test in most cases. In the isolated cases, where the

permittee can document that this delivery time cannot be met, the permitting authority can allow an option for onsite testing or a variance for an extension of shipped sample holding time. The request for a variance in sample

holding time, directed to the USEPA Regional Administrator under 40 CFR 136.3(e) should include supportive data

which show that the toxicity of the effluent sample is not reduced (e.g., because of volatilization and/or sorption of

toxics on the sample container surfaces) by extending the holding time beyond more than 36 h. However, in no

case should more than 72 h elapse between collection and first use of the sample. In static-renewal tests, each grab

or composite sample may also be used to prepare test solutions for renewal at 24 h, 48 h, and/or 72 h after first use,

if stored at 0-6°C, with minimum head space, as described in Subsection 8.5. If shipping problems (e.g.,

unsuccessful Saturday delivery) are encountered with renewal samples after a test has been initiated, the permitting

authority may allow the continued use of the most recently used sample for test renewal. Guidance for determining

the persistence of the sample is provided in Subsection 8.7.

8.5.5 To minimize the loss of toxicity due to volatilization of toxic constituents, all sample containers should be

"completely" filled, leaving no air space between the contents and the lid. 

8.5.6 SAMPLES USED IN ON-SITE TESTS 

8.5.6.1 Samples collected for on-site tests should be used within 24 h.

8.5.7 SAMPLES SHIPPED TO OFF-SITE FACILITIES 

8.5.7.1 Samples collected for off-site toxicity testing are to be chilled to 0-6°C during or immediately after

collection, and shipped iced to the performing laboratory. Sufficient ice should be placed with the sample in the

shipping container to ensure that ice will still be present when the sample arrives at the laboratory and is unpacked. 

Insulating material should not be placed between the ice and the sample in the shipping container unless required to

prevent breakage of glass sample containers.

8.5.7.2 Samples may be shipped in one or more 4-L (l-gal) CUBITAINERS® or new plastic "milk" jugs. All

sample containers should be rinsed with source water before being filled with sample. After use with receiving

water or effluents, CUBITAINERS® and plastic jugs are punctured to prevent reuse. 

8.5.7.3 Several sample shipping options are available, including Express Mail, air express, bus, and courier

service. Express Mail is delivered seven days a week. Saturday and Sunday shipping and receiving schedules of

private carriers vary with the carrier. 
33

8.6 SAMPLE RECEIVING

8.6.1 Upon arrival at the laboratory, samples are logged in and the temperature is measured and recorded. If the

samples are not immediately prepared for testing, they are stored at 0-6°C until used.

8.6.2 Every effort must be made to initiate the test with an effluent sample on the day of arrival in the laboratory,

and the sample holding time should not exceed 36 h unless a variance has been granted by the NPDES permitting

authority.

8.7 PERSISTENCE OF EFFLUENT TOXICITY DURING SAMPLE SHIPMENT AND HOLDING

8.7.1 The persistence of the toxicity of an effluent prior to its use in a toxicity test is of interest in assessing the

validity of toxicity test data, and in determining the possible effects of allowing an extension of the holding time. 

Where a variance in holding time (> 36 h, but # 72 h) is requested by a permittee, (see Subsection 8.5.4 above),

information on the effects of the extension in holding time on the toxicity of samples must be obtained by

comparing the results of multi-concentration chronic toxicity tests performed on effluent samples held 36 h with

toxicity test results using the same samples after they were held for the requested, longer period. The portion of the

sample set aside for the second test should be held under the same conditions as during shipment and holding.

8.8 PREPARATION OF EFFLUENT AND RECEIVING WATER SAMPLES FOR TOXICITY TESTS

8.8.1 When aliquots are removed from the sample container, the head space above the remaining sample should be

held to a minimum. Air which enters a container upon removal of sample should be expelled by compressing the

container before reclosing, if possible (i.e., where a CUBITAINER® is used), or by using an appropriate discharge

valve (spigot). 

8.8.2 With the daphnid, Ceriodaphnia dubia, and fathead minnow, Pimephales promelas, tests, effluents and

receiving waters should be filtered through a 60-μm plankton net to remove indigenous organisms that may attack

or be confused with the test organisms (see the daphnid, Ceriodaphnia dubia, test method for details). Receiving

waters used in green alga, Selenastrum capricornutum, toxicity tests must be filtered through a 0.45-μm pore

diameter filter before use. It may be necessary to first coarse-filter the dilution and/or waste water through a nylon

sieve having 2- to 4-mm mesh openings to remove debris and/or break up large floating or suspended solids. 

Because filtration may increase the dissolved oxygen (DO) in the effluent, the DO should be checked both before

and after filtering. Low dissolved oxygen concentrations will indicate a potential problem in performing the test. 

Caution: filtration may remove some toxicity.

8.8.3 If the samples must be warmed to bring them to the prescribed test temperature, supersaturation of the

dissolved oxygen and nitrogen may become a problem. To avoid this problem, samples may be warmed slowly in

open test containers. If DO is still above 100% saturation after warming to test temperature, samples should be

aerated moderately (approximately 500 mL/min) for a few minutes using an airstone. If DO is below 4.0 mg/L after

warming to test temperature, the solutions must be aerated moderately (approximately 500 mL/min) for a few

minutes, using an airstone, until the DO is within the prescribed range ($4.0 mg/L). Caution: avoid excessive

aeration. 

8.8.4 The DO concentration in the samples should be near saturation prior to use. Aeration may be used to bring

the DO and other gases into equilibrium with air, minimize oxygen demand, and stabilize the pH. However,

aeration during collection, transfer, and preparation of samples should be minimized to reduce the loss of volatile

chemicals. 

8.8.4.1 Aeration during the test may alter the results and should be used only as a last resort to maintain the

required DO. Aeration can reduce the apparent toxicity of the test solutions by stripping them of highly volatile

toxic substances, or increase their toxicity by altering pH. However, the DO in the test solutions should not be

allowed to fall below 4.0 mg/L.
34

8.8.4.2 In static tests (renewal or non-renewal), low DOs may commonly occur in the higher concentrations of

wastewater. Aeration is accomplished by bubbling air through a pipet at a rate of 100 bubbles/min. If aeration is

necessary, all test solutions must be aerated. It is advisable to monitor the DO closely during the first few hours of

the test. Samples with a potential DO problem generally show a downward trend in DO within 4 to 8 h after the test

is started. Unless aeration is initiated during the first 8 h of the test, the DO may be exhausted during an unattended

period, thereby invalidating the test.

8.8.5 At a minimum, pH, conductivity, and total residual chlorine are measured in the undiluted effluent or

receiving water, and pH and conductivity are measured in the dilution water.

8.8.5.1 It is recommended that total alkalinity and total hardness also be measured in the undiluted effluent test

water, receiving water, and the dilution water.

8.8.6 Total ammonia is measured in effluent and receiving water samples where toxicity may be contributed by unionized ammonia (i.e., where total ammonia $ 5 mg/L). The concentration (mg/L) of un-ionized (free) ammonia in

a sample is a function of temperature and pH, and is calculated using the percentage value obtained from Table 5,

under the appropriate pH and temperature, and multiplying it by the concentration (mg/L) of total ammonia in the

sample.

8.8.7 Effluents and receiving waters can be dechlorinated using 6.7 mg/L anhydrous sodium thiosulfate to reduce 1

mg/L chlorine (APHA, 1992). Note that the amount of thiosulfate required to dechlorinate effluents is greater than

the amount needed to dechlorinate tap water (see Section 7, Dilution Water, Subsection 7.4.1). Since thiosulfate

may contribute to sample toxicity, a thiosulfate control should be used in the test in addition to the normal dilution

water control.

8.8.8 Mortality or impairment of growth or reproduction due to pH alone may occur if the pH of the sample falls

outside the range of 6.0 - 9.0. Thus, the presence of other forms of toxicity (metals and organics) in the sample may

be masked by the toxic effects of low or high pH. The question about the presence of other toxicants can be

answered only by performing two parallel tests, one with an adjusted pH, and one without an adjusted pH. 

Freshwater samples are adjusted to pH 7.0 by adding 1N NaOH or 1N HCl dropwise, as required, being careful to

avoid overadjustment.
35

TABLE 5. PERCENT UNIONIZED NH3 IN AQUEOUS AMMONIA SOLUTIONS: TEMPERATURES 15-

26°C AND pH 6.0-8.91

pH TEMPERATURE (°C)

15 16 17 18 19 20 21 22 23 24 25 26

6.0 0.0274 0.0295 0.0318 0.0343 0.0369 0.0397 0.0427 0.0459 0.0493 0.0530 0.0568 0.0610

6.1 0.0345 0.0372 0.0400 0.0431 0.0464 0.0500 0.0537 0.0578 0.0621 0.0667 0.0716 0.0768

6.2 0.0434 0.0468 0.0504 0.0543 0.0584 0.0629 0.0676 0.0727 0.0781 0.0901 0.0901 0.0966

6.3 0.0546 0.0589 0.0634 0.0683 0.0736 0.0792 0.0851 0.0915 0.0983 0.1134 0.1134 0.1216

6.4 0.0687 0.0741 0.0799 0.0860 0.0926 0.0996 0.107 0.115 0.124 0.133 0.143 0.153

6.5 0.0865 0.0933 0.1005 0.1083 0.1166 0.1254 0.135 0.145 0.156 0.167 0.180 0.193

6.6 0.109 0.117 0.127 0.136 0.147 0.158 0.170 0.182 0.196 0.210 0.226 0.242

6.7 0.137 0.148 0.159 0.171 0.185 0.199 0.214 0.230 0.247 0.265 0.284 0.305

6.8 0.172 0.186 0.200 0.216 0.232 0.250 0.269 0.289 0.310 0.333 0.358 0.384

6.9 0.217 0.234 0.252 0.271 0.292 0.314 0.338 0.363 0.390 0.419 0.450 0.482

7.0 0.273 0.294 0.317 0.342 0.368 0.396 0.425 0.457 0.491 0.527 0.566 0.607

7.1 0.343 0.370 0.399 0.430 0.462 0.497 0.535 0.575 0.617 0.663 0.711 0.762

7.2 0.432 0.466 0.502 0.540 0.581 0.625 0.672 0.722 0.776 0.833 0.893 0.958

7.3 0.543 0.586 0.631 0.679 0.731 0.786 0.845 0.908 0.975 1.05 1.12 1.20

7.4 0.683 0.736 0.793 0.854 0.918 0.988 1.061 1.140 1.224 1.31 1.41 1.51

7.5 0.858 0.925 0.996 1.07 1.15 1.24 1.33 1.43 1.54 1.65 1.77 1.89

7.6 1.08 1.16 1.25 1.35 1.45 1.56 1.67 1.80 1.93 2.07 2.21 2.37

7.7 1.35 1.46 1.57 1.69 1.82 1.95 2.10 2.25 2.41 2.59 2.77 2.97

7.8 1.70 1.83 1.97 2.12 2.28 2.44 2.62 2.82 3.02 3.24 3.46 3.71

7.9 2.13 2.29 2.46 2.65 2.85 3.06 3.28 3.52 3.77 4.04 4.32 4.62

8.0 2.66 2.87 3.08 3.31 3.56 3.82 4.10 4.39 4.70 5.03 5.38 5.75

8.1 3.33 3.58 3.85 4.14 4.44 4.76 5.10 5.46 5.85 6.25 6.68 7.14

8.2 4.16 4.47 4.80 5.15 5.52 5.92 6.34 6.78 7.25 7.75 8.27 8.82

8.3 5.18 5.56 5.97 6.40 6.86 7.34 7.85 8.39 8.96 9.56 10.2 10.9

8.4 6.43 6.90 7.40 7.93 8.48 9.07 9.69 10.3 11.0 11.7 12.5 13.3

8.5 7.97 8.54 9.14 9.78 10.45 11.16 11.90 12.7 13.5 14.4 15.2 16.2

8.6 9.83 10.5 11.2 12.0 12.8 13.6 14.5 15.5 16.4 17.4 18.5 19.5

8.7 12.07 12.9 13.8 14.7 15.6 16.6 17.6 18.7 19.8 21.0 22.2 23.4

8.8 14.7 15.7 16.7 17.8 18.9 20.0 21.2 22.5 23.7 25.1 26.4 27.8

8.9 17.9 19.0 20.2 21.4 22.7 24.0 25.3 26.7 28.2 29.6 31.1 32.6

1 Table provided by Teresa Norberg-King, ERL, Duluth, Minnesota. Also see Emerson et al. (1975), Thurston et

al. (1974), and USEPA (1985a).

8.9 PRELIMINARY TOXICITY RANGE-FINDING TESTS

8.9.1 USEPA Regional and State personnel generally have observed that it is not necessary to conduct a toxicity

range-finding test prior to initiating a static, chronic, definitive toxicity test. However, when preparing to perform a

static test with a sample of completely unknown quality, or before initiating a flow-through test, it is advisable to

conduct a preliminary toxicity range-finding test.

8.9.2 A toxicity range-finding test ordinarily consists of a down-scaled, abbreviated static acute test in which

groups of five organisms are exposed to several widely-spaced sample dilutions in a logarithmic series, such as
36

100%, 10.0%, 1.00%, and 0.100%, and a control, for 8-24 h. Caution: if the sample must also be used for the fullscale definitive test, the 36-h limit on holding time (see Subsection 8.5.4) must not be exceeded before the definitive

test is initiated.

8.9.3 It should be noted that the toxicity (LC50) of a sample observed in a range-finding test may be significantly

different from the toxicity observed in the follow-up chronic definitive test because: (1) the definitive test is longer;

and (2) the test may be performed with a sample collected at a different time, and possibly differing significantly in

the level of toxicity.

8.10 MULTI-CONCENTRATION (DEFINITIVE) EFFLUENT TOXICITY TESTS 

8.10.1 The tests recommended for use in determining discharge permit compliance in the NPDES program are

multi-concentration, or definitive, tests which provide (1) a point estimate of effluent toxicity in terms of an IC25,

IC50, or LC50, or (2) a no-observed-effect-concentration (NOEC) defined in terms of mortality, growth,

reproduction, and/or teratogenicity and obtained by hypothesis testing. The tests may be static renewal or static

non-renewal.

8.10.2 The tests consist of a control and a minimum of five effluent concentrations. USEPA recommends the use

of a $0.5 dilution factor for selecting effluent test concentrations. Effluent test concentrations of 6.25%, 12.5%,

25%, 50%, and 100% are commonly used, however, test concentrations should be selected independently for each

test based on the objective of the study, the expected range of toxicity, the receiving water concentration, and any

available historical testing information on the effluent. USEPA (2000a) provides additional guidance on choosing

appropriate test concentrations.

8.10.3 When these tests are used in determining compliance with permit limits, effluent test concentrations should

be selected to bracket the receiving water concentration. This may be achieved by selecting effluent test

concentrations in the following manner: (1) 100% effluent, (2) [RWC + 100]/2, (3) RWC, (4) RWC/2, and (5)

RWC/4. For example, where the RWC = 50%, appropriate effluent concentrations may be 100%, 75%, 50%, 25%,

and 12.5%. 

8.10.4 If acute/chronic ratios are to be determined by simultaneous acute and short-term chronic tests with a single

species, using the same sample, both types of tests must use the same test conditions, i.e., pH, temperature, water

hardness, salinity, etc.

8.11 RECEIVING WATER TESTS

8.11.1 Receiving water toxicity tests generally consist of 100% receiving water and a control. The total hardness

of the control should be comparable to the receiving water.

8.11.2 The data from the two treatments are analyzed by hypothesis testing to determine if test organism survival

in the receiving water differs significantly from the control. Four replicates and 10 organisms per replicate are

required for each treatment (see Summary of Test Conditions and Test Acceptability Criteria in the specific test

method).

8.11.3 In cases where the objective of the test is to estimate the degree of toxicity of the receiving water, a multiconcentration test is performed by preparing dilutions of the receiving water, using a $ 0.5 dilution series, with a

suitable control water.
37

SECTION 9

CHRONIC TOXICITY TEST ENDPOINTS AND DATA ANALYSIS

9.1 ENDPOINTS

9.1.1 The objective of chronic aquatic toxicity tests with effluents and pure compounds is to estimate the highest

"safe" or "no-effect concentration" of these substances. For practical reasons, the responses observed in these tests

are usually limited to hatchability, gross morphological abnormalities, survival, growth, and reproduction, and the

results of the tests are usually expressed in terms of the highest toxicant concentration that has no statistically

significant observed effect on these responses, when compared to the controls. The terms currently used to define

the endpoints employed in the rapid, chronic and sub-chronic toxicity tests have been derived from the terms

previously used for full life-cycle tests. As shorter chronic tests were developed, it became common practice to

apply the same terminology to the endpoints. The terms used in this manual are as follows:

9.1.1.1 Safe Concentration - The highest concentration of toxicant that will permit normal propagation of fish and

other aquatic life in receiving waters. The concept of a "safe concentration" is a biological concept, whereas the

"no-observed-effect concentration" (below) is a statistically defined concentration.

9.1.1.2 No-Observed-Effect-Concentration (NOEC) - The highest concentration of toxicant to which organisms

are exposed in a full life-cycle or partial life-cycle (short-term) test, that causes no observable adverse effects on the

test organisms (i.e., the highest concentration of toxicant in which the values for the observed responses are not

statistically significantly different from the controls). This value is used, along with other factors, to determine

toxicity limits in permits.

9.1.1.3 Lowest-Observed-Effect-Concentration (LOEC) - The lowest concentration of toxicant to which organisms

are exposed in a life-cycle or partial life-cycle (short-term) test, which causes adverse effects on the test organisms

(i.e., where the values for the observed responses are statistically significantly different from the controls).

9.1.1.4 Effective Concentration (EC) - A point estimate of the toxicant concentration that would cause an

observable adverse affect on a quantal, "all or nothing," response (such as death, immobilization, or serious

incapacitation) in a given percent of the organisms, calculated by point estimation techniques. If the observable

effect is death or immobility, the term, Lethal Concentration (LC), should be used (see Subsection 9.1.1.5). A

certain EC or LC value might be judged from a biological standpoint to represent a threshold concentration, or

lowest concentration that would cause an adverse effect on the observed response.

9.1.1.5 Lethal Concentration (LC) - The toxicant concentration that would cause death in a given percent of the

test population. Identical to EC when the observed adverse effect is death. For example, the LC50 is the

concentration of toxicant that would cause death in 50% of the test population.

9.1.1.6 Inhibition Concentration (IC) - The toxicant concentration that would cause a given percent reduction in a

non-quantal biological measurement for the test population. For example, the IC25 is the concentration of toxicant

that would cause a 25% reduction in mean young per female or in growth for the test population, and the IC50 is the

concentration of toxicant that would cause a 50% reduction.

9.2 RELATIONSHIP BETWEEN ENDPOINTS DETERMINED BY HYPOTHESIS TESTING AND

POINT ESTIMATION TECHNIQUES

9.2.1 If the objective of chronic aquatic toxicity tests with effluents and pure compounds is to estimate the highest

"safe or no-effect concentration" of these substances, it is imperative to understand how the statistical endpoints of

these tests are related to the "safe" or "no-effect" concentration. NOECs and LOECs are determined by hypothesis

testing (Dunnett's Test, a t test with the Bonferroni adjustment, Steel's Many-one Rank Test, or the Wilcoxon Rank
38

Sum Test with the Bonferroni adjustment), whereas LCs, ICs, and ECs are determined by point estimation

techniques (Probit Analysis, Spearman-Karber Method, Trimmed Spearman-Karber Method, Graphical Method or

Linear Interpolation Method). There are inherent differences between the use of a NOEC or LOEC derived from

hypothesis testing to estimate a "safe" concentration, and the use of a LC, EC, IC, or other point estimates derived

from curve fitting, interpolation, etc.

9.2.2 Most point estimates, such as the LC, IC, or EC, are derived from a mathematical model that assumes a

continuous dose-response relationship. By definition, any LC, IC, or EC value is an estimate of some amount of

adverse effect. Thus the assessment of a "safe" concentration must be made from a biological standpoint rather than

with a statistical test. In this instance, the biologist must determine some amount of adverse effect that is deemed to

be "safe", in the sense that from a practical biological viewpoint it will not affect the normal propagation of fish and

other aquatic life in receiving waters.

9.2.3 The use of NOECs and LOECs, on the other hand, assumes either (1) a continuous dose-response

relationship, or (2) a non-continuous (threshold) model of the dose-response relationship.

9.2.3.1 In the case of a continuous dose-response relationship, it is also assumed that adverse effects that are not

"statistically observable" are also not important from a biological standpoint, since they are not pronounced enough

to test as statistically significant against some measure of the natural variability of the responses.

9.2.3.2 In the case of non-continuous dose-response relationships, it is assumed that there exists a true threshold, or

concentration below which there is no adverse effect on aquatic life, and above which there is an adverse effect. 

The purpose of the statistical analysis in this case is to estimate as closely as possible where that threshold lies.

9.2.3.3 In either case, it is important to realize that the amount of adverse effect that is statistically observable

(LOEC) or not observable (NOEC) is highly dependent on all aspects of the experimental design, such as the

number of concentrations of toxicant, number of replicates per concentration, number of organisms per replicate,

and use of randomization. Other factors that affect the sensitivity of the test include the choice of statistical

analysis, the choice of an alpha level, and the amount of variability between responses at a given concentration.

9.2.3.4 Where the assumption of a continuous dose-response relationship is made, by definition some amount of

adverse effect might be present at the NOEC, but is not great enough to be detected by hypothesis testing. 

9.2.3.5 Where the assumption of a non-continuous dose-response relationship is made, the NOEC would indeed be

an estimate of a "safe" or "no-effect" concentration if the amount of adverse effect that appears at the threshold is

great enough to test as statistically significantly different from the controls in the face of all aspects of the

experimental design mentioned above. If, however, the amount of adverse effect at the threshold were not great

enough to test as statistically different, some amount of adverse effect might be present at the NOEC. In any case,

the estimate of the NOEC with hypothesis testing is always dependent on the aspects of the experimental design

mentioned above. For this reason, the reporting and examination of some measure of the sensitivity of the test

(either the minimum significant difference or the percent change from the control that this minimum difference

represents) is extremely important.

9.2.4 In summary, the assessment of a "safe" or "no-effect" concentration cannot be made from the results of

statistical analysis alone, unless (1) the assumptions of a strict threshold model are accepted, and (2) it is assumed

that the amount of adverse effect present at the threshold is statistically detectable by hypothesis testing. In this

case, estimates obtained from a statistical analysis are indeed estimates of a "no-effect" concentration. If the

assumptions are not deemed tenable, then estimates from a statistical analysis can only be used in conjunction with

an assessment from a biological standpoint of what magnitude of adverse effect constitutes a "safe" concentration. 

In this instance, a "safe" concentration is not necessarily a truly "no-effect" concentration, but rather a concentration

at which the effects are judged to be of no biological significance.
39

9.2.5 A better understanding of the relationship between endpoints derived by hypothesis testing (NOECs) and

point estimation techniques (LCs, ICs, and ECs) would be very helpful in choosing methods of data analysis. 

Norberg-King (1991) reported that the IC25s were comparable to the NOECs for 23 effluent and reference toxicant

data sets analyzed. The data sets included short-term chronic toxicity tests for the fathead minnow, Pimephales

promelas, and the daphnid, Ceriodaphnia dubia. Birge et al. (1985) reported that LC1s derived from Probit

Analysis of data from short-term embryo-larval tests with reference toxicants were comparable to NOECs for

several organisms. Similarly, USEPA (1988d) reported that the IC25s were comparable to the NOECs for a set of

daphnid, Ceriodaphnia dubia, chronic tests with a single reference toxicant. However, the scope of these

comparisons was very limited, and sufficient information is not yet available to establish an overall relationship

between these two types of endpoints, especially when derived from effluent toxicity test data.

9.3 PRECISION

9.3.1 HYPOTHESIS TESTS

9.3.1.1 When hypothesis tests are used to analyze toxicity test data, it is not possible to express precision in terms

of a commonly used statistic. The results of the test are given in terms of two endpoints, the No-Observed- Effect

Concentration (NOEC) and the Lowest-Observed-Effect Concentration (LOEC). The NOEC and LOEC are limited

to the concentrations selected for the test. The width of the NOEC-LOEC interval is a function of the dilution

series, and differs greatly depending on whether a dilution factor of 0.3 or 0.5 is used in the test design. Therefore,

USEPA recommends the use of the $ 0.5 dilution factor (see Section 4, Quality Assurance). It is not possible to

place confidence limits on the NOEC and LOEC derived from a given test, and it is difficult to quantify the

precision of the NOEC-LOEC endpoints between tests. If the data from a series of tests performed with the same

toxicant, toxicant concentrations, and test species, were analyzed with hypothesis tests, precision could only be

assessed by a qualitative comparison of the NOEC-LOEC intervals, with the understanding that maximum precision

would be attained if all tests yielded the same NOEC-LOEC interval. In practice, the precision of results of

repetitive chronic tests is considered acceptable if the NOECs vary by no more than one concentration interval

above or below a central tendency. Using these guidelines, the "normal" range of NOECs from toxicity tests using

a 0.5 dilution factor (two-fold difference between adjacent concentrations), would be four-fold.

9.3.2 POINT ESTIMATION TECHNIQUES

9.3.2.1 Point estimation techniques have the advantage of providing a point estimate of the toxicant concentration

causing a given amount of adverse (inhibiting) effect, the precision of which can be quantitatively assessed

(1) within tests by calculation of 95% confidence limits, and (2) across tests by calculating a standard deviation and

coefficient of variation.

9.3.2.2 It should be noted that software used to calculate point estimates occasionally may not provide associated

95% confidence intervals. This situation may arise when test data do not meet specific assumptions required by the

statistical methods, when point estimates are outside of the test concentration range, and when specific limitations

imposed by the software are encountered. USEPA (2000a) provides guidance on confidence intervals under these

circumstances.

9.4 DATA ANALYSIS

9.4.1 ROLE OF THE STATISTICIAN

9.4.1.1 The use of the statistical methods described in this manual for routine data analysis does not require the

assistance of a statistician. However, the interpretation of the results of the analysis of the data from any of the

toxicity tests described in this manual can become problematic because of the inherent variability and sometimes

unavoidable anomalies in biological data. If the data appear unusual in any way, or fail to meet the necessary

assumptions, a statistician should be consulted. Analysts who are not proficient in statistics are strongly advised to

seek the assistance of a statistician before selecting the method of analysis and using any of the results. 
40

9.4.1.2 The statistical methods recommended in this manual are not the only possible methods of statistical

analysis. Many other methods have been proposed and considered. Certainly there are other reasonable and

defensible methods of statistical analysis for this kind of toxicity data. Among alternative hypothesis tests some,

like Williams' Test, require additional assumptions, while others, like the bootstrap methods, require computerintensive computations. Alternative point estimation approaches most probably would require the services of a

statistician to determine the appropriateness of the model (goodness of fit), higher order linear or nonlinear models,

confidence intervals for estimates generated by inverse regression, etc. In addition, point estimation or regression

approaches would require the specification by biologists or toxicologists of some low level of adverse effect that

would be deemed acceptable or safe. The statistical methods contained in this manual have been chosen because

they are (1) applicable to most of the different toxicity test data sets for which they are recommended, (2) powerful

statistical tests, (3) hopefully "easily" understood by nonstatisticians, and (4) amenable to use without a computer, if

necessary.

9.4.2 PLOTTING THE DATA

9.4.2.1 The data should be plotted, both as a preliminary step to help detect problems and unsuspected trends or

patterns in the responses, and as an aid in interpretation of the results. Further discussion and plotted sets of data

are included in the methods and the Appendices.

9.4.3 DATA TRANSFORMATIONS

9.4.3.1 Transformations of the data, (e.g., arc sine square root and logs), are used where necessary to meet

assumptions of the proposed analyses, such as the requirement for normally distributed data.

9.4.4 INDEPENDENCE, RANDOMIZATION, AND OUTLIERS

9.4.4.1 Statistical independence among observations is a critical assumption in all statistical analysis of toxicity

data. One of the best ways to insure independence is to properly follow rigorous randomization procedures. 

Randomization techniques should be employed at the start of the test, including the randomization of the placement

of test organisms in the test chambers and randomization of the test chamber location within the array of chambers. 

Discussions of statistical independence, outliers and randomization, and a sample randomization scheme, are

included in Appendix A.

9.4.5 REPLICATION AND SENSITIVITY

9.4.5.1 The number of replicates employed for each toxicant concentration is an important factor in determining

the sensitivity of chronic toxicity tests. Test sensitivity generally increases as the number of replicates is increased,

but the point of diminishing returns in sensitivity may be reached rather quickly. The level of sensitivity required

by a hypothesis test or the confidence interval for a point estimate will determine the number of replicates, and

should be based on the objectives for obtaining the toxicity data.

9.4.5.2 In a statistical analysis of toxicity data, the choice of a particular analysis and the ability to detect

departures from the assumptions of the analysis, such as the normal distribution of the data and homogeneity of

variance, is also dependent on the number of replicates. More than the minimum number of replicates may be

required in situations where it is imperative to obtain optimal statistical results, such as with tests used in

enforcement cases or when it is not possible to repeat the tests. For example, when the data are analyzed by

hypothesis testing, the nonparametric alternatives cannot be used unless there are at least four replicates at each

toxicant concentration.

9.4.6 RECOMMENDED ALPHA LEVELS

9.4.6.1 The data analysis examples included in the manual specify an alpha level of 0.01 for testing the

assumptions of hypothesis tests and an alpha level of 0.05 for the hypothesis tests themselves. These levels are
41

common and well accepted levels for this type of analysis and are presented as a recommended minimum

significance level for toxicity test data analysis.

9.5 CHOICE OF ANALYSIS

9.5.1 The recommended statistical analysis of most data from chronic toxicity tests with aquatic organisms follows

a decision process illustrated in the flowchart in Figure 2. An initial decision is made to use point estimation

techniques (the Probit Analysis, the Spearman-Karber Method, the Trimmed Spearman-Karber Method, the

Graphical Method, or Linear Interpolation Method) and/or to use hypothesis testing (Dunnett's Test, the t test with

the Bonferroni adjustment, Steel's Many-one Rank Test, or the Wilcoxon Rank Sum Test with the Bonferroni

adjustment). NOTE: For the NPDES Permit Program, the point estimation techniques are the preferred

statistical methods in calculating end points for effluent toxicity tests. If hypothesis testing is chosen,

subsequent decisions are made on the appropriate procedure for a given set of data, depending on the results of the

tests of assumptions, as illustrated in the flowchart. A specific flow chart is included in the analysis section for each

test.

9.5.2 Since a single chronic toxicity test might yield information on more than one parameter (such as survival,

growth, and reproduction), the lowest estimate of a "no-observed-effect concentration" for any of the responses

would be used as the "no-observed-effect concentration" for each test. It follows logically that in the statistical

analysis of the data, concentrations that had a significant toxic effect on one of the observed responses would not be

subsequently tested for an effect on some other response. This is one reason for excluding concentrations that have

shown a statistically significant reduction in survival from a subsequent hypothesis test for effects on another

parameter such as reproduction. A second reason is that the exclusion of such concentrations usually results in a

more powerful and appropriate statistical analysis. In performing the point estimation techniques recommended in

this manual, an all-data approach is used. For example, data from concentrations above the NOEC for survival are

included in determining ICp estimates using the Linear Interpolation Method.

9.5.3 ANALYSIS OF GROWTH AND REPRODUCTION DATA

9.5.3.1 Growth data from the fathead minnow, Pimephales promelas, larval survival and growth test are analyzed

using hypothesis testing or point estimation techniques according to the flowchart in Figure 2. The above

mentioned growth data may also be analyzed by generating a point estimate with the Linear Interpolation Method. 

Data from effluent concentrations that have tested significantly different from the control for survival are excluded

from further hypothesis tests concerning growth effects. Growth is defined as the dry weight per original number of

test organisms when group weights are obtained. When analyzing the data using point estimation techniques, data

from all concentrations are included in the analysis. 

9.5.3.2 Reproduction data from the daphnid, Ceriodaphnia dubia, survival and reproduction test are analyzed

using hypothesis testing or point estimation techniques according to the flowchart in Figure 2. In hypothesis testing,

data from effluent concentrations that have significantly lower survival than the control, as determined by Fisher's

Exact test, are not included in the hypothesis tests for reproductive effects. Data from all concentrations are

included when using point estimation techniques.

9.5.4 ANALYSIS OF ALGAL GROWTH RESPONSE DATA

9.5.4.1 The growth response data from the green alga, Selenastrum capricornutum, toxicity test, after an

appropriate transformation, if necessary, to meet the assumptions of normality and homogeneity of variance, may be

analyzed by hypothesis testing according to the flowchart in Figure 2. Point estimates, such as the IC25 and IC50,

would also be appropriate in analyzing algal growth data.
42

9.5.5 ANALYSIS OF MORTALITY DATA

9.5.5.1 Mortality data are analyzed by Probit Analysis, if appropriate, or other point estimation techniques (i.e., the

Spearman-Karber Method, the Trimmed Spearman-Karber Method, or the Graphical Method) (see Appendices I-L

and the discussion below). The mortality data can also be analyzed by hypothesis testing, after an arc sine square

root transformation (see Appendix B-F), according to the flowchart in Figure 2.

9.5.5.2 Mortality data from the daphnid, Ceriodaphnia dubia, survival and reproduction test are analyzed by

Fisher's Exact Test (Appendix G) prior to the analysis of the reproduction data. The mortality data may also be

analyzed by Probit Analysis, if appropriate or other methods (see Subsection 9.5.5.1).
43

Figure 2. Flowchart for statistical analysis of test data
44

9.6 HYPOTHESIS TESTS

9.6.1 DUNNETT'S PROCEDURE

9.6.1.1 Dunnett's Procedure is used to determine the NOEC. The procedure consists of an analysis of variance

(ANOVA) to determine the error term, which is then used in a multiple comparison procedure for comparing each

of the treatment means with the control mean, in a series of paired tests (see Appendix C). Use of Dunnett's

Procedure requires at least three replicates per treatment to check the assumptions of the test. In cases where the

numbers of data points (replicates) for each concentration are not equal, a t test may be performed with Bonferroni's

adjustment for multiple comparisons (see Appendix D), instead of using Dunnett's Procedure.

9.6.1.2 The assumptions upon which the use of Dunnett's Procedure is contingent are that the observations within

treatments are normally distributed, with homogeneity of variance. Before analyzing the data, these assumptions

must be tested using the procedures provided in Appendix B.

9.6.1.3 If, after suitable transformations have been carried out, the normality assumptions have not been met,

Steel's Many-one Rank Test should be used if there are four or more data points (replicates) per toxicant

concentration. If the numbers of data points for each toxicant concentration are not equal, the Wilcoxon Rank Sum

Test with Bonferroni's adjustment should be used (see Appendix F).

9.6.1.4 Some indication of the sensitivity of the analysis should be provided by calculating (1) the minimum

difference between means that can be detected as statistically significant, and (2) the percent change from the

control mean that this minimum difference represents for a given test.

9.6.1.5 A step-by-step example of the use of Dunnett's Procedure is provided in Appendix C.

9.6.2 T TEST WITH THE BONFERRONI ADJUSTMENT

9.6.2.1 A t test with Bonferroni's adjustment is used as an alternative to Dunnett's Procedure when the number of

replicates is not the same for all concentrations. This test sets an upper bound of alpha on the overall error rate, in

contrast to Dunnett's Procedure, for which the overall error rate is fixed at alpha. Thus Dunnett's Procedure is a

more powerful test.

9.6.2.2 The assumptions upon which the use of the t test with Bonferroni's adjustment is contingent are that the

observations within treatments are normally distributed, with homogeneity of variance. These assumptions must be

tested using the procedures provided in Appendix B.

9.6.2.3 The estimate of the safe concentration derived from this test is reported in terms of the NOEC. A

step-by-step example of the use of the t test with Bonferroni's adjustment is provided in Appendix D.

9.6.3 STEEL'S MANY-ONE RANK TEST

9.6.3.1 Steel's Many-one Rank Test is a multiple comparison procedure for comparing several treatments with a

control. This method is similar to Dunnett's Procedure, except that it is not necessary to meet the assumption of

normality. The data are ranked, and the analysis is performed on the ranks rather than on the data themselves. If

the data are normally or nearly normally distributed, Dunnett's Procedure would be more sensitive (would detect

smaller differences between the treatments and control). For data that are not normally distributed, Steel's

Many-one Rank Test can be much more efficient (Hodges and Lehmann, 1956).

9.6.3.2 It is necessary to have at least four replicates per toxicant concentration to use Steel's test. Unlike Dunnett's

procedure, the sensitivity of this test cannot be stated in terms of the minimum difference between treatment means

and the control mean that can be detected as statistically significant.
45

9.6.3.3 The estimate of the safe concentration is reported as the NOEC. A step-by-step example of the use of

Steel's Many-one Rank Test is provided in Appendix E.

9.6.4 WILCOXON RANK SUM TEST WITH THE BONFERRONI ADJUSTMENT

9.6.4.1 The Wilcoxon Rank Sum Test with the Bonferroni Adjustment is a nonparametric test for comparing

treatments with a control. The data are ranked and the analysis proceeds exactly as in Steel's Test except that

Bonferroni's adjustment for multiple comparisons is used instead of Steel's tables. When Steel's test can be used

(i.e., when there are equal numbers of data points per toxicant concentration), it will be more powerful (able to

detect smaller differences as statistically significant) than the Wilcoxon Rank Sum Test with Bonferroni's

adjustment.

9.6.4.2 The estimate of the safe concentration is reported as the NOEC. A step-by-step example of the use of the

Wilcoxon Rank Sum Test with Bonferroni Adjustment is provided in Appendix F.

9.6.5 A CAUTION IN THE USE OF HYPOTHESIS TESTING

9.6.5.1 If in the calculation of an NOEC by hypothesis testing, two tested concentrations cause statistically

significant adverse effects, but an intermediate concentration did not cause statistically significant effects, the results

should be used with extreme caution.

9.7 POINT ESTIMATION TECHNIQUES

9.7.1 PROBIT ANALYSIS

9.7.1.1 Probit Analysis is used to estimate the LC1, LC50, EC1, or EC50 and the associated 95% confidence

interval. The analysis consists of adjusting the data for mortality in the control, and then using a maximum

likelihood technique to estimate the parameters of the underlying log tolerance distribution, which is assumed to

have a particular shape.

9.7.1.2 The assumption upon which the use of Probit Analysis is contingent is a normal distribution of log

tolerances. If the normality assumption is not met, and at least two partial mortalities are not obtained, Probit

Analysis should not be used. It is important to check the results of Probit Analysis to determine if use of the

analysis is appropriate. The chi-square test for heterogeneity provides one good test of appropriateness of the

analysis. The computer program (see Appendix I) checks the chi-square statistic calculated for the data set against

the tabular value, and provides an error message if the calculated value exceeds the tabular value.

9.7.1.3 A discussion of Probit Analysis, and examples of computer program input and output, are found in

Appendix I. 

9.7.1.4 In cases where Probit Analysis is not appropriate, the LC50 and associated confidence interval may be

estimated by the Spearman-Karber Method (Appendix J) or the Trimmed Spearman-Karber Method (Appendix K). 

If the test results in 100% survival and 100% mortality in adjacent treatments (all or nothing effect), the LC50 may

be estimated using the Graphical Method (Appendix L).

9.7.2 LINEAR INTERPOLATION METHOD

9.7.2.1 The Linear Interpolation Method (see Appendix M) is a procedure to calculate a point estimate of the

effluent or other toxicant concentration [Inhibition Concentration, (IC)] that causes a given percent reduction (e.g.,

25%, 50%, etc.) in the reproduction or growth of the test organisms. The procedure was designed for general

applicability in the analysis of data from short-term chronic toxicity tests.
46

9.7.2.2 Use of the Linear Interpolation Method is based on the assumptions that the responses (1) are

monotonically non-increasing (the mean response for each higher concentration is less than or equal to the mean

response for the previous concentration), (2) follow a piecewise linear response function, and (3) are from a

random, independent, and representative sample of test data. The assumption for piecewise linear response cannot

be tested statistically, and no defined statistical procedure is provided to test the assumption for monotonicity. 

Where the observed means are not strictly monotonic by examination, they are adjusted by smoothing. In cases

where the responses at the low toxicant concentrations are much higher than in the controls, the smoothing process

may result in a large upward adjustment in the control mean.

9.7.2.3 The inability to test the monotonicity and piecewise linear response assumptions for this method makes it

difficult to assess when the method is, or is not, producing reliable results. Therefore, the method should be used

with caution when the results of a toxicity test approach an "all or nothing" response from one concentration to the

next in the concentration series, and when it appears that there is a large deviation from monotonicity. See

Appendix M for a more detailed discussion of the use of this method and a computer program available for

performing calculations.
47

SECTION 10

REPORT PREPARATION AND TEST REVIEW

10.1 REPORT PREPARATION

The following general format and content are recommended for the report: 

10.1.1 INTRODUCTION 

 1. Permit number

 2. Toxicity testing requirements of permit

 3. Plant location

 4. Name of receiving water body

 5. Contract Laboratory (if the tests are performed under contract)

a Name of firm

b. Phone number

c. Address

6. Objective of test

10.1.2 PLANT OPERATIONS

 1. Product(s)

 2. Raw materials

 3. Operating schedule

 4. Description of waste treatment

 5. Schematic of waste treatment

 6. Retention time (if applicable)

 7. Volume of waste flow (MGD, CFS, GPM)

 8. Design flow of treatment facility at time of sampling

10.1.3 SOURCE OF EFFLUENT, RECEIVING WATER, AND DILUTION WATER

 1. Effluent Samples 

a. Sampling point (including latitude and longitude)

b. Collection dates and times 

c. Sample collection method

d. Physical and chemical data 

e. Mean daily discharge on sample collection date

f. Lapsed time from sample collection to delivery

g. Sample temperature when received at the laboratory

 2. Receiving Water Samples

a. Sampling point (including latitude and longitude)

b. Collection dates and times

c. Sample collection method

d. Physical and chemical data

e. Streamflow (at time of sampling)

f. Sample temperature when received at the laboratory

g Lapsed time from sample collection to delivery

 3. Dilution Water Samples 

a. Source
48

b. Collection date(s) and time(s)

c. Pretreatment

d. Physical and chemical characteristics 

10.1.4 TEST METHODS 

 1. Toxicity test method used (title, number, source)

 2. Endpoint(s) of test

 3. Deviation(s) from reference method, if any, and the reason(s) 

 4. Date and time test started 

 5. Date and time test terminated 

 6. Type and volume of test chambers 

 7. Volume of solution used per chamber 

 8. Number of organisms per test chamber 

 9. Number of replicate test chambers per treatment 

10. Acclimation of test organisms (temperature mean and range) 

11. Test temperature (mean and range)

12. Specify if aeration was needed

13. Feeding frequency, and amount and type of food

14. Specify if (and how) pH control measures were implemented

 

10.1.5 TEST ORGANISMS 

 1. Scientific name and how determined

 2. Age 

 3. Life stage 

 4. Mean length and weight (where applicable) 

 5. Source 

 6. Diseases and treatment (where applicable) 

 7. Taxonomic key used for species identification 

10.1.6 QUALITY ASSURANCE

 1. Reference toxicant used routinely; source

 2. Date and time of most recent reference toxicant test, test results, and current control chart

 3. Dilution water used in reference toxicant test 

 4. Results (NOEC or, where applicable, LOEC, LC50, EC50, IC25 and/or IC50); report percent minimum

significant difference (PMSD) calculated for sublethal endpoints determined by hypothesis testing in

reference toxicant test

 5. Physical and chemical methods used 

10.1.7 RESULTS 

 1. Provide raw toxicity data in tabular form, including daily records of affected organisms in each

concentration (including controls) and replicate, and in graphical form (plots of toxicity data)

 2. Provide table of LC50s, NOECs, IC25, IC50, etc. (as required in the applicable NPDES permit)

 3. Indicate statistical methods used to calculate endpoints

 4. Provide summary table of physical and chemical data

 5. Tabulate QA data

 6. Provide percent minimum significant difference (PMSD) calculated for sublethal endpoints
49

10.1.8 CONCLUSIONS AND RECOMMENDATIONS

 1. Relationship between test endpoints and permit limits

 2. Actions to be taken

10.2 TEST REVIEW

10.2.1 Test review is an important part of an overall quality assurance program (Section 4) and is necessary for

ensuring that all test results are reported accurately. Test review should be conducted on each test by both the

testing laboratory and the regulatory authority. 

10.2.2 SAMPLING AND HANDLING 

10.2.2.1 The collection and handling of samples are reviewed to verify that the sampling and handling procedures

given in Section 8 were followed. Chain-of-custody forms are reviewed to verify that samples were tested within

allowable sample holding times (Subsection 8.5.4). Any deviations from the procedures given in Section 8 should

be documented and described in the data report (Subsection 10.1). 

10.2.3 TEST ACCEPTABILITY CRITERIA

10.2.3.1 Test data are reviewed to verify that test acceptability criteria (TAC) requirements for a valid test have

been met. Any test not meeting the minimum test acceptability criteria is considered invalid. All invalid tests must

be repeated with a newly collected sample. 

10.2.4 TEST CONDITIONS

10.2.4.1 Test conditions are reviewed and compared to the specifications listed in the summary of test condition

tables provided for each method. Physical and chemical measurements taken during the test (e.g., temperature, pH,

and DO) also are reviewed and compared to specified ranges. Any deviations from specifications should be

documented and described in the data report (Subsection 10.1).

10.2.4.2 The summary of test condition tables presented for each method identify test conditions as required or

recommended. For WET test data submitted under NPDES permits, all required test conditions must be met or the

test is considered invalid and must be repeated with a newly collected sample. Deviations from recommended test

conditions must be evaluated on a case-by-case basis to determine the validity of test results. Deviations from

recommended test conditions may or may not invalidate a test result depending on the degree of the departure and

the objective of the test. The reviewer should consider the degree of the deviation and the potential or observed

impact of the deviation on the test result before rejecting or accepting a test result as valid. For example, if

dissolved oxygen is measured below 4.0 mg/L in one test chamber, the reviewer should consider whether any

observed mortality in that test chamber corresponded with the drop in dissolved oxygen.

10.2.4.3 Whereas slight deviations in test conditions may not invalidate an individual test result, test condition

deviations that continue to occur frequently in a given laboratory may indicate the need for improved quality control

in that laboratory. 

10.2.5 STATISTICAL METHODS

10.2.5.1 The statistical methods used for analyzing test data are reviewed to verify that the recommended

flowcharts for statistical analysis were followed. Any deviation from the recommended flowcharts for selection of

statistical methods should be noted in the data report. Statistical methods other than those recommended in the

statistical flowcharts may be appropriate (see Subsection 9.4.1.2), however, the laboratory must document the use of

and provide the rationale for the use of any alternate statistical method. In all cases (flowchart recommended
50

methods or alternate methods), reviewers should verify that the necessary assumptions are met for the statistical

method used. 

10.2.6 CONCENTRATION-RESPONSE RELATIONSHIPS

10.2.6.1 The concept of a concentration-response, or more classically, a dose-response relationship is “the most

fundamental and pervasive one in toxicology” (Casarett and Doull, 1975). This concept assumes that there is a

causal relationship between the dose of a toxicant (or concentration for toxicants in solution) and a measured

response. A response may be any measurable biochemical or biological parameter that is correlated with exposure

to the toxicant. The classical concentration-response relationship is depicted as a sigmoidal shaped curve, however,

the particular shape of the concentration-response curve may differ for each coupled toxicant and response pair. In

general, more severe responses (such as acute effects) occur at higher concentrations of the toxicant, and less severe

responses (such as chronic effects) occur at lower concentrations. A single toxicant also may produce multiple

responses, each characterized by a concentration-response relationship. A corollary of the concentration-response

concept is that every toxicant should exhibit a concentration-response relationship, given that the appropriate

response is measured and given that the concentration range evaluated is appropriate. Use of this concept can be

helpful in determining whether an effluent possesses toxicity and in identifying anomalous test results.

10.2.6.2 The concentration-response relationship generated for each multi-concentration test must be reviewed to

ensure that calculated test results are interpreted appropriately. USEPA (2000a) provides guidance on evaluating

concentration-response relationships to assist in determining the validity of WET test results. All WET test results

(from multi-concentration tests) reported under the NPDES program should be reviewed and reported according to

USEPA guidance on the evaluation of concentration-response relationships (USEPA, 2000a). This guidance

provides review steps for 10 different concentration-response patterns that may be encountered in WET test data. 

Based on the review, the guidance provides one of three determinations: that calculated effect concentrations are

reliable and should be reported, that calculated effect concentrations are anomalous and should be explained, or that

the test was inconclusive and the test should be repeated with a newly collected sample. It should be noted that the

determination of a valid concentration-response relationship is not always clear cut. Data from some tests may

suggest consultation with professional toxicologists and/or regulatory officials. Tests that exhibit unexpected

concentration-response relationships also may indicate a need for further investigation and possible retesting. 

10.2.7 REFERENCE TOXICANT TESTING

10.2.7.1 Test review of a given effluent or receiving water test should include review of the associated reference

toxicant test and current control chart. Reference toxicant testing and control charting is required for documenting

the quality of test organisms (Subsection 4.7) and ongoing laboratory performance (Subsection 4.16). The reviewer

should verify that a quality control reference toxicant test was conducted according to the specified frequency

required by the permitting authority or recommended by the method (e.g., monthly). The test acceptability criteria,

test conditions, concentration-response relationship, and test sensitivity of the reference toxicant test are reviewed to

verify that the reference toxicant test conducted was a valid test. The results of the reference toxicant test are then

plotted on a control chart (see Subsection 4.16) and compared to the current control chart limits (± 2 standard

deviations).

10.2.7.2 Reference toxicant tests that fall outside of recommended control chart limits are evaluated to determine

the validity of associated effluent and receiving water tests (see Subsection 4.16). An out of control reference

toxicant test result does not necessarily invalidate associated test results. The reviewer should consider the degree

to which the reference toxicant test result fell outside of control chart limits, the width of the limits, the direction of

the deviation (toward increasing test organism sensitivity or toward decreasing test organism sensitivity), the test

conditions of both the effluent test and the reference toxicant test, and the objective of the test. More frequent

and/or concurrent reference toxicant testing may be advantageous if recent problems (e.g., invalid tests, reference

toxicant test results outside of control chart limits, reduced health of organism cultures, or increased within-test

variability) have been identified in testing. 
51

10.2.8 TEST VARIABILITY

10.2.8.1 The within-test variability of individual tests should be reviewed. Excessive within-test variability may

invalidate a test result and warrant retesting. For evaluating within-test variability, reviewers should consult EPA

guidance on upper and lower percent minimum significant difference (PMSD) bounds (USEPA, 2000b). 

10.2.8.2 When NPDES permits require sublethal hypothesis testing endpoints from Methods 1000.0,1002.0, or

1003.0 (e.g., growth or reproduction NOECs and LOECs), within-test variability must be reviewed and variability

criteria must be applied as described in this section (10.2.8.2). When the methods are used for non-regulatory

purposes, the variability criteria herein are recommended but are not required, and their use (or the use of alternative

variability criteria) may depend upon the intended uses of the test results and the requirements of any applicable

data quality objectives and quality assurance plan.

10.2.8.2.1 To measure test variability, calculate the percent minimum significant difference (PMSD) achieved in

the test. The PMSD is the smallest percentage decrease in growth or reproduction from the control that could be

determined as statistically significant in the test. The PMSD is calculated as 100 times the minimum significant

difference (MSD) divided by the control mean. The equation and examples of MSD calculations are shown in

Appendix C. PMSD may be calculated legitimately as a descriptive statistic for within-test variability, even when

the hypothesis test is conducted using a non-parametric method. The PMSD bounds were based on a representative

set of tests, including tests for which a non-parametric method was required for determining the NOEC or LOEC. 

The conduct of hypothesis testing to determine test results should follow the statistical flow charts provided for each

method. That is, when test data fail to meet assumptions of normality or heterogeneity of variance, a nonparametric method (determined following the statistical flowchart for the method) should be used to calculate test

results, but the PMSD may be calculated as described above (using parametric methods) to provide a measure of test

variability. 

10.2.8.2.2 Compare the PMSD measured in the test with the upper PMSD bound variability criterion listed in

Table 6. When the test PMSD exceeds the upper bound, the variability among replicates is unusually large for the

test method. Such a test should be considered insufficiently sensitive to detect toxic effects on growth or

reproduction of substantial magnitude. A finding of toxicity at a particular concentration may be regarded as

trustworthy, but a finding of "no toxicity" or "no statistically significant toxicity" at a particular concentration

should not be regarded as a reliable indication that there is no substantial toxic effect on growth or reproduction at

that concentration.

10.2.8.2.3 If the PMSD measured for the test is less than or equal to the upper PMSD bound variability criterion in

Table 6, then the test's variability measure lies within normal bounds and the effect concentration estimate (e.g.,

NOEC or LOEC) would normally be accepted unless other test review steps raise serious doubts about its validity.

10.2.8.2.4 If the PMSD measured for the test exceeds the upper PMSD bound variability criterion in Table 6, then

one of the following two cases applies (10.2.8.2.4.1, 10.2.8.2.4.2).

10.2.8.2.4.1 If toxicity is found at the permitted receiving water concentration (RWC) based upon the value of the

effect concentration estimate (NOEC or LOEC), then the test shall be accepted and the effect concentration estimate

may be reported, unless other test review steps raise serious doubts about its validity.

10.2.8.2.4.2 If toxicity is not found at the permitted RWC based upon the value of the effect concentration estimate

(NOEC or LOEC) and the PMSD measured for the test exceeds the upper PMSD bound, then the test shall not be

accepted, and a new test must be conducted promptly on a newly collected sample.

10.2.8.2.5 To avoid penalizing laboratories that achieve unusually high precision, lower PMSD bounds shall also

be applied when a hypothesis test result (e.g., NOEC or LOEC) is reported. Lower PMSD bounds, which are based

on the 10th percentiles of national PMSD data, are presented in Table 6. The 10th percentile PMSD represents a

practical limit to the sensitivity of the test method because few laboratories are able to achieve such precision on a
52

regular basis and most do not achieve it even occasionally. In determining hypothesis test results (e.g., NOEC or

LOEC), a test concentration shall not be considered toxic (i.e., significantly different from the control) if the relative

difference from the control is less than the lower PMSD bounds in Table 6. See USEPA, 2000b for specific

examples of implementing lower PMSD bounds. 

10.2.8.3 To assist in reviewing within-test variability, EPA recommends maintaining control charts of PMSDs

calculated for successive effluent tests (USEPA, 2000b). A control chart of PMSD values characterizes the range of

variability observed within a given laboratory, and allows comparison of individual test PMSDs with the

laboratory’s typical range of variability. Control charts of other variability and test performance measures, such as

the MSD, standard deviation or CV of control responses, or average control response, also may be useful for

reviewing tests and minimizing variability. The log of PMSD will provide an approximately normal variate useful

for control charting.

TABLE 6. VARIABILITY CRITERIA (UPPER AND LOWER PMSD BOUNDS) FOR SUBLETHAL

HYPOTHESIS TESTING ENDPOINTS SUBMITTED UNDER NPDES PERMITS.1

Test Method Endpoint Lower PMSD Bound Upper PMSD Bound

Method 1000.0, Fathead Minnow Larval

Survival and Growth Test growth 12 30

Method 1002.0, Ceriodaphnia dubia

Survival and Reproduction Test reproduction 13 47

Method 1003.0, Selenastrum

capricornutum Growth Test growth 9.1 29

1

 Lower and upper PMSD bounds were determined from the 10th and 90th percentile, respectively, of PMSD data

from EPA’s WET Interlaboratory Variability Study (USEPA, 2001a; USEPA, 2001b).
53

SECTION 11

TEST METHOD

FATHEAD MINNOW, PIMEPHALES PROMELAS,

LARVAL SURVIVAL AND GROWTH TEST 

METHOD 1000.0

11.1 SCOPE AND APPLICATION

11.1.1 This method estimates the chronic toxicity of effluents and receiving water to the fathead minnow,

Pimephales promelas, using newly hatched larvae in a seven-day, static renewal test. The effects include the

synergistic, antagonistic, and additive effects of all the chemical, physical, and biological components which

adversely affect the physiological and biochemical functions of the test organisms. 

11.1.2 Daily observations on mortality make it possible to also calculate acute toxicity for desired exposure periods

(i.e., 24-h, 48-h, 96-h LC50s).

11.1.3 Detection limits of the toxicity of an effluent or pure substance are organism dependent.

11.1.4 Brief excursions in toxicity may not be detected using 24-h composite samples. Also, because of the long

sample collection period involved in composite sampling, and because the test chambers are not sealed, highly

degradable or highly volatile toxicants present in the source may not be detected in the test. 

11.1.5 This test method is commonly used in one of two forms: (1) a definitive test, consisting of a minimum of

five effluent concentrations and a control, and (2) a receiving water test(s), consisting of one or more receiving

water concentrations and a control. 

11.2 SUMMARY OF METHOD

11.2.1 Fathead minnow, Pimephales promelas, larvae are exposed in a static renewal system for seven days to

different concentrations of effluent or to receiving water. Test results are based on the survival and weight of the

larvae. 

11.3. INTERFERENCES

11.3.1 Toxic substances may be introduced by contaminants in dilution water, glassware, sample hardware, and

testing equipment (see Section 5, Facilities, Equipment and Supplies).

11.3.2 Adverse effects of low dissolved oxygen (DO) concentrations, high concentrations of suspended and/or

dissolved solids, and extremes of pH, alkalinity, or hardness, may mask the presence of toxic substances.

11.3.3 Improper effluent sampling and sample handling may adversely affect test results (see Section 8, Effluent

and Receiving Water Sampling, Sample Handling, and Sample Preparation for Toxicity Tests). 

11.3.4 Pathogenic and/or predatory organisms in effluent samples or receiving water that is used for dilution may

affect test organism survival and confound test results. When pathogen interference is suggested by observation

(11.3.4.1) and data evaluations (11.3.4.2) and confirmed by parallel testing (11.3.4.4), steps should be taken to

minimize pathogen interference to the extent that test results are not confounded by mortality due to pathogens. 

Pathogen control techniques that do not require modification of effluent samples, such as use of the modified test

design described in Subsection 11.3.4.5, are recommended for controlling pathogen interference. Upon approval by

the regulatory authority, analysts also may use additional pathogen control techniques that require sample

modification (11.3.4.6) provided that parallel testing of altered and unaltered samples further confirms the presence
54

of pathogen interference and demonstrates successful pathogen control (11.3.4.6). 

11.3.4.1 A typical indication that pathogen interference has occurred in a WET test is when test organisms exhibit

“sporadic mortality”. This sporadic morality phenomenon is characterized by an unexpected concentrationresponse relationship (i.e., effects that do not increase with increasing effluent concentration) and organism survival

that varies greatly among replicates and among effluent dilutions (USEPA, 2000a). The observed sporadic

mortality among replicates may occur in receiving water controls, lower effluent concentrations, and occasionally in

full-strength effluent on day 3 or day 4 of the chronic test. When sporadic mortality occurs, a fungal growth may

appear directly on the fish, especially in the gill area. The fungus has not been definitively identified, but the fungal

growth appears to be compatible with Saprolegnea sp. (Downey et al., 2000). Microbiological evaluations on

receiving waters, the fish, and the food indicated the ubiquitous nature of pathogenic organisms (e.g., Flexibacter

spp., Aeromonas hydrophila), and eradicating them from the test through the decontamination of the fish and their

food has not been practical (Geis et al., 2000). 

11.3.4.2 When pathogen interference is suspected, a series of data evaluations are required. The test data must be

reviewed to determine a cause for any unexpected concentration-response pattern and subsequently to determine the

validity of calculated results (USEPA, 2000a). USEPA (2000a) provides guidance on reviewing concentrationresponse relationships including specific response patterns that may indicate pathogen effects. Each treatment

(including the control) should be evaluated for an unusually high mortality response and unevenness of mortalities

among replicates. Within-treatment coefficient of variation (CVs) for survival of >40% in effluent or receiving

water treatments but relatively small for control replicates in a standard reconstituted water may be an indication of

pathogen interference. Receiving water controls from improper preparation or collection also should be evaluated.

11.3.4.3 Because of the ubiquitous nature of the pathogens or predatory organisms, all test equipment, glassware,

and pipettes must be kept clean and dry when not in use. Use of separate glassware, pipettes, and siphons for each

concentration is recommended to minimize cross contaminating replicates of all treatments. Care also should be

taken to properly clean test chambers by removing excess food, dead fish larvae, and other debris prior to daily

renewal (see Subsection 11.10.7). When proper laboratory hygiene and filtration through a 2-4 mm mesh opening

(Subsection 8.8.2) do not eliminate the sporadic mortality, the analyst should determine the source and confirm

pathogen interference using parallel testing (11.3.4.4). 

11.3.4.4 Parallel tests should be conducted using reconstituted water and receiving water as diluents with the

effluent to confirm that the test results are due to pathogen interference and to determine the source of pathogens in

the test. This determination is an important step in controlling pathogen interference. When the dilution water

exhibits the interference (i.e., pathogen interference is not observed in the test using reconstituted laboratory water

for dilution), reconstituted laboratory water instead of receiving waters should be used to eliminate the interference. 

However, if receiving water is required, the analyst may modify the test design to control pathogen interference

(Subsection 11.3.4.5) or treat the dilution water prior to testing to remove the interference (Subsection 11.3.4.6). If

pathogen interference is due to pathogens in the effluent (i.e., pathogen interference is still observed in the test using

reconstituted laboratory water for dilution), it is recommended that the analyst modify the test design to control

pathogen interference (Subsection 11.3.4.5). Upon approval by the regulatory authority, analysts also may use

various sample sterilization techniques to control pathogen interference (11.3.4.6) provided that parallel testing of

altered and unaltered samples further confirms the presence of pathogen interference and demonstrates successful

pathogen control.

11.3.4.5 When data evaluation indicates that sporadic mortality has occurred as described in Subsections 11.3.4.1 -

11.3.4.2, the test design can be modified as described below to control pathogen interference. The use of 2 fish per

20 ml in each 1 ounce plastic cup test solution or 2 fish per 50 ml in each 4 ounce plastic cup can be used rather

than 10 fish per test chamber. The total number of fish tested remains unchanged (i.e., 40 per treatment). At test

initiation, for each test concentration and replicate, the test cups must be labeled to easily recombine the fish to the

original replicate at the end of the test. For example, for replicate A, each of the five plastic test cups would be

identified as subreplicate A1, A2, A3, A4, and A5 repeating the pattern for subsequent replicates (e.g., for replicate

B, each cup would be identified as subreplicate B1, B2, B3, B4, and B5). At test termination, all test organisms
55

from the five A subreplicates are combined for a survival and weight determination. Document the recombination

of replicates in records.

11.3.4.5.1 All test chambers must be randomized using a template for randomization or by using a table of random

numbers. Test chambers are randomized once at the beginning of the test (see Subsection 11.10.2.3). When using

templates, a number of different templates should be prepared, so that the same template is not used for every test. 

Randomization procedures must be documented with daily records.

11.3.4.5.2 When adding or transferring the larvae to test chambers, the amount of excess water added to the

chambers should be kept to a minimum to avoid unnecessary dilution of the test concentrations. The fish in each test

chamber should be fed 0.1 mL of a concentrated suspension of newly hatched (less than 24-h old) brine shrimp

nauplii three times daily at 4 h intervals, or 0.15 mL should be fed twice daily at an interval of 6 h. (NOTE: to

prevent low dissolved oxygen levels, the amount of food added to cups should be adjusted to account for the

modified test design that uses smaller test chambers). Dead test organisms should be removed as soon as they are

observed.

11.3.4.5.3 Fish are transferred to new or clean test chambers daily. At the time of the daily renewal of the test

solutions, the fish are transferred to a new test chamber containing fresh test solution using a pipette which has at

least a 5mm bore diameter. Separate pipettes should be used for each treatment. Water transfer is kept to a

minimum by allowing the fish to swim out of the pipette into the new test chamber. Any potential injury to

individual fish should be recorded on the test sheets.

11.3.4.5.4 At test termination, the surviving larvae in each chamber must be counted and all subreplicates within a

replicate (e.g., A1, A2, A3, A4, and A5) combined. For example, all test cups (within a treatment) labeled A would

be combined for a survival and dry weight determination.

11.3.4.6 When parallel testing has confirmed pathogen interference, the regulatory authority may allow

modifications of the effluent samples or receiving water diluent to remove or inactivate the pathogens (Subsection

11.3.4.6.1 - 11.3.4.6.4). Techniques that control pathogen interference without modifying the effluent sample

(11.3.4.5) are recommended, but they may not always be able to minimize pathogen interference to the extent that

test results are not confounded by mortality due to pathogens. Therefore, regulatory authorities may allow

appropriate pathogen control techniques (including those that modify the effluent sample) on a case-by-case basis. 

TIE approaches (USEPA, 1991b; USEPA, 1992) and the following procedures (Subsection 11.3.4.6.1 - 11.3.4.6.4)

can be used alone or in combination to ascertain the adverse influence on tests caused by pathogens. Prior to

routine use of pathogen control techniques that modify the sample, the effects of pathogenic bacteria and the

effectiveness of the selected pathogen control technique must be confirmed by parallel and simultaneous testing of

the technique with altered and unaltered samples.

11.3.4.6.1 Use of ultra-violet light to irradiate the sample. The rate of pumping specified by the manufacturer of

the apparatus should be used (provided that adequate disinfection is achieved), and the life of the UV light source

must follow manufacturers’ recommendations and be documented. For example, one liter of water can be irradiated

for 20 min using an 8 watt UV light (Aquatic Ecosystems, Apopka, FL) prior to use each day of the test. Light

sources have limited lifetimes and their effectiveness will decrease with age. The delivery pump and the light source

should be on the same electrical circuit to ensure that when power is interrupted both terminate operation. QA/QC

procedures should be put into place to assure that the light source is on at the beginning and at the end of the

procedure. Treatment of the large volumes of water necessary for test dilution also may be impractical. Caution:

Since the effluent or receiving water samples must be passed through the UV sterilizer and then test treatments

prepared, there may be potential effects of UV light on the sample. UV exposure may increase or decrease toxicity

from other pollutants in the sample. UV treatment is known to cause photoactivation of some organic compounds,

which may increase toxicity. UV treatment also is known to cause the photochemical breakdown of certain organic

compounds, which could decrease toxicity (if the parent compound is toxic) or increase toxicity (if reaction

products are toxic). These effects should be considered in the selection of pathogen control strategies, and the

analyst should attempt to minimize these effects to the extent reasonably practicable. The effectiveness of UV for
56

sterilization may decrease with turbid or stained samples. Bacteria can escape exposure by being lodged in crevices

of particulate matter in the sample. All toxicity tests using a sterilized sample must include a blank preparation

consisting of similarly sterilized laboratory water.

11.3.4.6.2 Ultra-filtration through a 0.22 μm pore diameter filter (such as Gelman Suprocap®) may be conducted on

sample aliquots before daily use. Samples may need to be filtered through a glass fiber filter prior to the 0.22 μm

filter. This is time consuming and volume restricted. Treatment of the large volumes of water necessary for test

dilution may be impractical. Caution: Since the effluent or receiving water samples must be passed through the

filter, the effect of filtering must be evaluated. Filtration can remove toxicity if toxic components of the sample are

bound to particles (USEPA, 1991b; 1992). The removal of suspended solids also may influence the bioavailability

of chemical pollutants. These effects should be considered in the selection of pathogen control strategies, and the

analyst should attempt to minimize these effects to the extent reasonably practicable. The removal of toxicity by

filtration must be evaluated for each sample by testing samples before and after filtration. All toxicity tests using a

sterilized sample also must include a blank preparation consisting of similarly sterilized reconstituted laboratory

water. 

11.3.4.6.3 Use of chlorination and dechlorination. In some cases, pathogens can survive the chlorination/

dechlorination process and the pathogenic effects may increase due to lack of competition from other organisms.

Sufficient data must be collected and documented to determine the effective dosage required. Caution: Chlorination

of effluent samples could cause unknown effects on the sample. Chlorination could increase or decrease sample

toxicity by oxidizing organic compounds or forming chlorination by-products. These effects should be considered

in the selection of pathogen control strategies, and the analyst should attempt to minimize these effects to the extent

reasonably practicable. Toxicity tests conducted with the addition of chlorine and subsequent dechlorination

(USEPA, 1991b; 1992) to either effluent or receiving water samples also must include a blank preparation

consisting of similarly treated laboratory water.

11.3.4.6.4 Use of antibiotics. The addition of wide spectrum antibiotics has been effective in removing the

pathogen effect (Downey et al., 2000). Antibacterial treatment such as those commonly used in aquaculture or

home aquarium maintenance (e.g., oxytetracycline, chloramphenicol, and actinomycin) may be effective. Sufficient

data must be collected to determine the effective dosage required. Caution: While antibiotics are effective, easy to

use, inexpensive, and readily available, the antibiotic treatment may alter the sample in unknown or undesirable

ways and may make the sample too cloudy. Large volumes of a sample may need to be treated. These effects

should be considered in the selection of pathogen control strategies, and the analyst should attempt to minimize

these effects to the extent reasonably practicable. All toxicity tests using antibiotic treatments also must include

treatment blanks of similarly prepared laboratory water.

11.3.5 Food added during the test may sequester metals and other toxic substances and confound test results. 

Daily renewal of solutions, however, will reduce the probability of reduction of toxicity caused by feeding.

11.3.6 pH drift during the test may contribute to artifactual toxicity when ammonia or other pH-dependent

toxicants (such as metals) are present. As pH increases, the toxicity of ammonia also increases (see Subsection

8.8.6), so upward pH drift may increase sample toxicity. For metals, toxicity may increase or decrease with

increasing pH. Lead and copper were found to be more acutely toxic at pH 6.5 than at pH 8.0 or 8.5, while nickel

and zinc were more toxic at pH 8.5 than at pH 6.5 (USEPA, 1992). In situations where sample toxicity is confirmed

to be artifactual and due to pH drift (as determined by parallel testing as described in Subsection 11.3.6.1), the

regulatory authority may allow for control of sample pH during testing using procedures outlined in Subsection

11.3.6.2. It should be noted that artifactual toxicity due to pH drift is not likely to occur unless pH drift is large

(more than 1 pH unit) and/or the concentration of some pH-dependent toxicant in the sample is near the threshold

for toxicity. 

11.3.6.1 To confirm that toxicity is artifactual and due to pH drift, parallel tests must be conducted, one with

controlled pH and one with uncontrolled pH. In the uncontrolled-pH treatment, the pH is allowed to drift during the

test. In the controlled-pH treatment, the pH is maintained using the procedures described in Subsection 11.3.6.2. 
57

The pH to be maintained in the controlled-pH treatment (or target pH) will depend on the objective of the test. If

the objective of the WET test is to determine the toxicity of the effluent in the receiving water, the pH should be

maintained at the pH of the receiving water (measured at the edge of the regulatory mixing zone). If the objective

of the WET test is to determine the absolute toxicity of the effluent, the pH should be maintained at the pH of the

sample upon completion of collection (as measured on an aliquot removed from the sample container).

11.3.6.1.1 During parallel testing, the pH must be measured in each treatment at the beginning (i.e., initial pH) and

end (i.e., final pH) of each 24-h exposure period. For each treatment, the mean initial pH (e.g., averaging the initial

pH measured each day for a given treatment) and the mean final pH (e.g., averaging the final pH measured each day

for a given treatment) must be reported. pH measurements taken during the test must confirm that pH was

effectively maintained at the target pH in the controlled-pH treatment. For each treatment, the mean initial pH and

the mean final pH should be within ± 0.2 pH units of the target pH. Test procedures for conducting toxicity

identification evaluations (TIEs) also recommend maintaining pH within ± 0.2 pH units in pH-controlled tests

(USEPA, 1992).

11.3.6.1.2 Total ammonia also should be measured in each treatment at the outset of parallel testing. Total

ammonia concentrations greater than 5 mg/L in the 100% effluent are an indicator that toxicity observed in the test

may be due to ammonia (USEPA, 1992). 

11.3.6.1.3 Results from both of the parallel tests (pH-controlled and uncontrolled treatments) must be reported to

the regulatory authority. If the uncontrolled test meets test acceptability criteria and shows no toxicity at the

permitted instream waste concentration, then the results from this test should be used for determining compliance. 

If the uncontrolled test shows toxicity at the permitted instream waste concentration, then the results from the pHcontrolled test should be used for determining compliance, provided that this test meets test acceptability criteria

and pH was properly controlled (see Subsection 11.3.6.1.1). 

11.3.6.1.4 To confirm that toxicity observed in the uncontrolled test was artifactual and due to pH drift, the results

of the controlled and uncontrolled-pH tests are compared. If toxicity is removed or reduced in the pH-controlled

treatment, artifactual toxicity due to pH drift is confirmed for the sample. To demonstrate that a sample result of

artifactual toxicity is representative of a given effluent, the regulatory authority may require additional information

or additional parallel testing before pH control (as described in Subsection 11.3.6.2) is applied routinely to

subsequent testing of the effluent. 

11.3.6.2 The pH can be controlled with the addition of acids and bases and/or the use of a CO2-controlled

atmosphere over the test chambers. pH is adjusted with acids and bases by dropwise adding 1N NaOH or 1N HCl

(see Subsection 8.8.8). The addition of acids and bases should be minimized to reduce the amount of additional

ions (Na or Cl) added to the sample. pH is then controlled using the CO2-controlled atmosphere technique. This

may be accomplished by placing test solutions and test organisms in closed headspace test chambers, and then

injecting a predetermined volume of CO2 into the headspace of each test chamber (USEPA, 1991b; USEPA, 1992);

or by placing test chambers in an atmosphere flushed with a predetermined mixture of CO2 and air (USEPA, 1996). 

Prior experimentation will be needed to determine the appropriate CO2/air ratio or the appropriate volume of CO2 to

inject. This volume will depend upon the sample pH, sample volume, container volume, and sample constituents. 

If more than 5% CO2 is needed, adjust the solutions with acids (1N HCl) and then flush the headspace with no more

than 5% CO2 (USEPA, 1992). If the objective of the WET test is to determine the toxicity of the effluent in the

receiving water, CO2 is injected to maintain the test pH at the pH of the receiving water (measured at the edge of the

regulatory mixing zone). If the objective of the WET test is to determine the absolute toxicity of the effluent, CO2 is

injected to maintain the test pH at the pH of the sample upon completion of collection. USEPA (1991b; 1992) and

Mount and Mount (1992) provide techniques and guidance for controlling test pH using a CO2-controlled

atmosphere. In pH-controlled testing, control treatments must be subjected to all manipulations that sample

treatments are subjected to. These manipulations must be shown to cause no lethal or sublethal effects on control

organisms. In pH-controlled testing, the pH also must be measured in each treatment at the beginning and end of

each 24-h exposure period to confirm that pH was effectively controlled at the target pH level. 
58

11.4 SAFETY

11.4.1 See Section 3, Health and Safety.

11.5 APPARATUS AND EQUIPMENT

11.5.1 Fathead minnow and brine shrimp culture units -- see USEPA, 1985a and USEPA, 2002a. This test

requires 240-360 larvae. It is preferable to obtain larvae from an in-house fathead minnow culture unit. If it is not

feasible to culture fish in-house, embryos or newly hatched larvae can be shipped in well oxygenated water in

insulated containers.

11.5.2 Samplers -- automatic sampler, preferably with sample cooling capability, that can collect a 24-h composite

sample of 5 L.

11.5.3 Sample containers -- for sample shipment and storage (see Section 8, Effluent and Receiving Water

Sampling, Sample Handling, and Sample Preparation for Toxicity Tests). 

11.5.4 Environmental chamber or equivalent facility with temperature control (25 ± 1°C).

11.5.5 Water purification system -- MILLIPORE MILLI-Q®, deionized water or equivalent (see Section 5,

Facilities, Equipment, and Supplies). 

11.5.6 Balance -- analytical, capable of accurately weighing to 0.00001 g.

11.5.7 Reference weights, Class S -- for checking performance of balance. Weights should bracket the expected

weights of the weighing pans and the expected weights of the pans plus fish. 

11.5.8 Test chambers -- four borosilicate glass or non-toxic disposable plastic test chambers are required for each

concentration and control. Test chambers may be 1 L, 500 mL or 250 mL beakers, 500 mL plastic cups, or

fabricated rectangular (0.3 cm thick) glass chambers, 15 cm x 7.5 cm x 7.5 cm. To avoid potential contamination

from the air and excessive evaporation of test solutions during the test, the chambers should be covered with safety

glass plates or sheet plastic (6 mm thick). 

11.5.9 Volumetric flasks and graduated cylinders -- Class A, borosilicate glass or non-toxic plastic labware,

10-1000 mL for making test solutions. 5.10 

11.5.10 Volumetric pipets -- Class A, 1-100 mL. 

11.5.11 Serological pipets -- 1-10 mL, graduated. 

11.5.12 Pipet bulbs and fillers -- PROPIPET®, or equivalent. 

11.5.13 Droppers, and glass tubing with fire polished edges, 4 mm ID -- for transferring larvae. 

11.5.14 Wash bottles -- for rinsing small glassware and instrument electrodes and probes.

11.5.15 Thermometers, glass or electronic, laboratory grade -- for measuring water temperatures. 

11.5.16 Bulb-thermograph or electronic-chart type thermometers -- for continuously recording temperature. 

11.5.17 Thermometers, National Bureau of Standards Certified (see USEPA Method 170.1, USEPA, 1979b) -- to

calabrate laboratory themometers.
59

11.5.18 Meters, pH, DO, and specific conductivity -- for routine physical and chemical measurements.

11.5.19 Drying oven -- 50-105° C range for drying larvae.

11.6 REAGENTS AND CONSUMABLE MATERIALS

11.6.1 Sample containers -- for sample shipment and storage (see Section 8, Effluent and Receiving Water

Sampling, Sample Handling, and Sample Preparation for Toxicity Tests).

11.6.2 Data sheets (one set per test) -- for recording data.

11.6.3 Vials, marked -- 24 per test, containing 4% formalin or 70% ethanol to preserve larvae (optional).

11.6.4 Weighing boats, aluminum -- 24 per test.

11.6.5 Tape, colored -- for labeling test chambers.

11.6.6 Markers, waterproof -- for marking containers, etc.

11.6.7 Reagents for hardness and alkalinity tests -- see USEPA Methods 130.2 and 310.1, USEPA, 1979b. 

11.6.8 Buffers, pH 4, pH 7, and pH 10 (or as per instructions of instrument manufacturer) -- for instrument

calibration (see USEPA Method 150.1, USEPA, 1979b).

11.6.9 Specific conductivity standards -- see USEPA Method 120.1, USEPA, 1979b. 

11.6.10 Membranes and filling solutions for DO probe (see USEPA Method 360.1, USEPA, 1979b), or reagents --

for modified Winkler analysis.

11.6.11 Laboratory quality control samples and standards -- for calibration of the above methods.

11.6.12 Reference toxicant solutions (see Section 4, Quality Assurance).

11.6.13 Ethanol (70%) or formalin (4%) -- for use as a preservative for the fish larvae. 

11.6.14 Reagent water -- defined as distilled or deionized water that does not contain substances which are toxic to

the test organisms (see Section 5, Facilities, Equipment, and Supplies).

11.6.15 Effluent, receiving water, and dilution water -- see Section 7, Dilution Water; and Section 8, Effluent and

Receiving Water Sampling, Sample Handling, and Sample Preparation for Toxicity Tests.

11.6.16 Brine Shrimp, Artemia, Nauplii -- for feeding cultures and test organisms

11.6.16.1 Newly-hatched Artemia nauplii are used as food (see USEPA, 2002a) for fathead minnow, Pimephales

promelas, larvae in toxicity tests and frozen brine shrimp and flake food are used in the maintenance of continuous

stock cultures. Although there are many commercial sources of brine shrimp cysts, the Brazilian or Colombian

strains are currently preferred because the supplies examined have had low concentrations of chemical residues and

produce nauplii of suitably small size. 

11.6.16.2 Each new batch of brine shrimp, Artemia, cysts must be evaluated for size (Vanhaecke and Sorgeloos,

1980, and Vanhaecke et al., 1980) and nutritional suitability (see Leger et al., 1985; Leger et al., 1986) against

known suitable reference cysts by performing a side by side larval growth test using the "new" and "reference"

cysts. The "reference" cysts used in the suitability test may be a previously tested and acceptable batch of cysts. A
60

sample of newly-hatched Artemia nauplii from each new batch of cysts should be chemically analyzed. The

Artemia cysts should not be used if the concentration of total organochlorine exceeds 0.15 μg/g wet weight or the

total concentration of organochlorine pesticides plus PCBs exceeds 0.30 μg/g wet weight. (For analytical methods

see USEPA, 1982).

11.6.16.3 Artemia nauplii are obtained as follows: 

1. Add 1 L of seawater, or a solution prepared by adding 35.0 g uniodized salt (NaCl) or artificial sea

salts to 1 L deionized water, to a 2-L separatory funnel, or equivalent.

2. Add 10 mL Artemia cysts to the separatory funnel and aerate for 24-h at 27EC. (Hatching time varies

with incubation temperature and the geographic strain of Artemia used) (see USEPA, 1991b; USEPA,

2002a and ASTM, 1993).

 3. After 24 h, cut off the air supply in the separatory funnel. Artemia nauplii are phototactic, and will

concentrate at the bottom of the funnel if it is covered for 5-10 min. To prevent mortality, do not leave

the concentrated nauplii at the bottom of the funnel more than 10 min without aeration.

4. Drain the nauplii into a beaker or funnel fitted with a # 150 μm Nitex® or stainless steel screen, and

rinse with deionized water, or equivalent, before use.

11.6.16.4 Testing Artemia nauplii as food for toxicity test organisms.

11.6.16.4.1 The primary criterion for acceptability of each new supply of brine shrimp cysts is the ability of the

nauplii to support good survival and growth of the fathead minnow larvae (see Subsection 11.12). The larvae used

to evaluate the suitability of the brine shrimp nauplii must be of the same geographical origin, species, and stage of

development as those used routinely in the toxicity tests. Sufficient data to detect differences in survival and growth

should be obtained by using three replicate test vessels, each containing a minimum of 15 larvae, for each type of

food.

11.6.16.4.2 The feeding rate and frequency, test vessels, volume of control water, duration of the test, and age of

the nauplii at the start of the test, should be the same as used for the routine toxicity tests.

11.6.16.4.3 Results of the brine shrimp nutrition assay, where there are only two treatments, can be evaluated

statistically by use of a t test. The "new" food is acceptable if there are no statistically significant differences in the

survival and growth of the larvae fed the two sources of nauplii.

11.6.17 TEST ORGANISMS, FATHEAD MINNOWS, PIMEPHALES PROMELAS

11.6.17.1 Newly hatched fish less than 24 h old should be used for the test. If organisms must be shipped to the

testing site, fish up to 48 h old may be used, all hatched within a 24-h window.

11.6.17.2 If the fish are kept in a holding tank or container, most of the water should be siphoned off to

concentrate the fish. The fish are then transferred one at a time randomly to the test chambers until each chamber

contains ten fish. Alternately, fish may be placed one or two at a time into small beakers or plastic containers until

they each contain five fish. Three (minimum of two) of these beakers/plastic containers are then assigned to

randomly-arranged control and exposure chambers.

11.6.17.2.1 The fish are transferred directly to the test vessels or intermediate beakers/plastic containers, using a

large-bore, fire-polished glass tube (6 mm to 9 mm I.D. X 30 cm long) equipped with a rubber bulb, or a large

volumetric pipet with tip removed and fitted with a safety type bulb filler. The glass or plastic containers should

only contain a small volume of dilution water.

11.6.17.2.2 It is important to note that larvae should not be handled with a dip net. Dipping small fish with a net

may result in damage to the fish and cause mortality.
61

11.6.17.3 The test is conducted with a minimum of four test chambers at each toxicant concentration and control. 

Fifteen (minimum of ten) embryos are placed in each replicate test chamber. Thus 60 (minimum of 40) fish are

exposed at each test concentration.

11.6.17.4 Sources of organisms

11.6.17.4.1 Fathead minnows, Pimephales promelas, may be obtained from commercial biological supply houses. 

Fish obtained from outside sources for use as brood stock or in toxicity tests may not always be of suitable age and

quality. Fish provided by supply houses should be guaranteed to be of (1) the correct species, (2) disease free, (3)

in the requested age range, and (4) in good condition. This can be done by providing the record of the date on

which the eggs were laid and hatched, and information on the sensitivity of contemporary fish to reference

toxicants.

11.6.17.5 Inhouse Sources of Fathead Minnows, Pimephales promelas

11.6.17.5.1 Problems in obtaining suitable fish from outside laboratories can be avoided by developing an inhouse

laboratory culture facility. Fathead minnows, Pimephales promelas, can be easily cultured in the laboratory from

eggs to adults in static, recirculating, or flow-through systems. The larvae, juveniles, and adult fish should be kept

in 60 L (15 gal) or 76 L (20 gal) rearing tanks supplied with reconstituted water, dechlorinated tap water, or natural

water. The water should be analyzed for toxic metals and organics quarterly (see Section 4, Quality Assurance). 

11.6.17.5.1.1 If a static or recirculating system is used, it is necessary to equip each tank with an outside activated

carbon filter system, similar to those sold for tropical fish hobbyists (or one large activated carbon filter system for a

series of tanks) to prevent the accumulation of toxic metabolic wastes (principally nitrite and ammonia) in the water. 

11.6.17.5.2 Flow-through systems require large volumes of water and may not be feasible in some laboratories. 

The culture tanks should be shielded from extraneous disturbances using opaque curtains, and should be isolated

from toxicity testing activities to prevent contamination. 

11.6.17.5.3 To avoid the possibility of inbreeding of the inhouse brood stock, fish from an outside source should

be introduced yearly into the culture unit.

11.6.17.5.4 Dissolved oxygen -- The DO concentration in the culture tanks should be maintained near saturation,

using gentle aeration with 15 cm air stones if necessary. Brungs (1971), in a carefully controlled long-term study,

found that the growth of fathead minnows was reduced significantly at all dissolved oxygen concentrations below

7.9 mg/L. Soderberg (1982) presented an analytical approach to the re-aeration of flowing water for culture

systems.

11.6.17.5.5 Culture Maintenance 

11.6.17.5.5.1 Adequate procedures for culture maintenance must be followed to avoid poor water quality in the

culture system. The spawning and brood stock culture tanks should be kept free of debris (excess food, detritus,

waste, etc.) by siphoning the accumulated materials (such as dead brine shrimp nauplii or cysts) from the bottom of

the tanks daily with a glass siphon tube attached to a plastic hose leading to the floor drain. The tanks are more

thoroughly cleaned as required. Algae, mostly diatoms and green algae, growing on the glass of the spawning tanks

are left in place, except for the front of the tank, which is kept clean for observation. To avoid excessive build-up of

algal growth, the walls of the tanks are periodically scraped. The larval culture tanks are cleaned once or twice a

week to reduce the mass of fungus growing on the bottom of the tank.

11.6.17.5.5.2 Activated charcoal and floss in the tank filtration systems should be changed weekly, or more often if

needed. Culture water may be maintained by preparation of reconstituted water or use of dechlorinated tap water. 

Distilled or deionized water is added as needed to compensate for evaporation.
62

11.6.17.5.5.3 Before new fish are placed in tanks, salt deposits are removed by scraping or with 5% acid solution,

the tanks are washed with detergent, sterilized with a hypochlorite solution, and rinsed well with hot tap water and

then with laboratory water. 

11.6.17.5.6 Obtaining Embryos for Toxicity Tests

11.6.17.5.6.1 Embryos can be shipped to the laboratory from an outside source or obtained from adults held in the

laboratory as described below. 

11.6.17.5.6.2 For breeding tanks, it is convenient to use 60 L (15 gal) or 76 L (20 gal) aquaria. The spawning unit

is designed to simulate conditions in nature conducive to spawning, such as water temperature and photoperiod. 

Spawning tanks must be held at a temperature of 25 ± 2°C. Each aquarium is equipped with a heater, if necessary, a

continuous filtering unit, and spawning substrates. The photoperiod for the culture system should be maintained at

16 h light and 8 h darkness. For the spawning tanks, this photoperiod must be rigidly controlled. A convenient

photoperiod is 5:00 AM to 9:00 PM. Fluorescent lights should be suspended about 60 cm above the surface of the

water in the brood and larval tanks. Both DURATEST® and cool-white fluorescent lamps have been used, and

produce similar results. An illumination level of 50 to 100 ft-c is adequate.

11.6.17.5.6.3 To simulate the natural spawning environment, it is necessary to provide substrates (nesting

territories) upon which the eggs can be deposited and fertilized, and which are defended and cared for by the males. 

The recommended spawning substrates consist of inverted half-cylinders, 7.6 cm × 7.6 cm (3 in × 3 in) of Schedule

40 PVC pipe. The substrates should be placed equi-distant from each other on the bottom of the tanks.

11.6.17.5.6.4 To establish a breeding unit, 15-20 pre-spawning adults six to eight months old are taken from a

"holding" or culture tank and placed in a 76-L spawning tank. At this point, it is not possible to distinguish the

sexes. However, after less than a week in the spawning tank, the breeding males will develop their distinct

coloration and territorial behavior, and spawning will begin. As the breeding males are identified, all but two are

removed, providing a final ratio of 5-6 females per male. The excess spawning substrates are used as shelter by the

females. 

11.6.17.5.6.5 Sexing of the fish to ensure a correct female/male ratio in each tank can be a problem. However, the

task usually becomes easier as experience is gained (Flickinger, 1966). Sexually mature females usually have large

bellies and a tapered snout. The sexually mature males are usually distinguished by their larger overall size, dark

vertical color bands, and the spongy nuptial tubercles on the snout. Unless the males exhibit these secondary

breeding characteristics, no reliable method has been found to distinguish them from females. However, using the

coloration of the males and the presence of enlarged urogenital structures and other characteristics of the females,

the correct selection of the sexes can usually be achieved by trial and error. 

11.6.17.5.6.6 Sexually immature males are usually recognized by their aggressive behavior and partial banding. 

These undeveloped males must be removed from the spawning tanks because they will eat the eggs and constantly

harass the mature males, tiring them and reducing the fecundity of the breeding unit. Therefore, the fish in the

spawning tanks must be carefully checked periodically for extra males. 

11.6.17.5.6.7 A breeding unit should remain in their spawning tank about four months. Thus, each brood tank or

unit is stocked with new spawners about three times a year. However, the restocking process is rotated so that at

any one time the spawning tanks contain different age groups of brood fish. 

11.6.17.5.6.8 Fathead minnows spawn mostly in the early morning hours. They should not be disturbed except for

a morning feeding (8:00 AM) and daily examination of substrates for eggs in late morning or early afternoon. In

nature, the male protects, cleans, and aerates the eggs until they hatch. In the laboratory, however, it is necessary to

remove the eggs from the tanks to prevent them from being eaten by the adults, for ease of handling, for purposes of

recording embryo count and hatchability, and for the use of the newly hatched young fish for toxicity tests. 
63

11.6.17.5.6.9 Daily, beginning six to eight hours after the lights are turned on (11:00 AM - 1:00 PM), the

substrates in the spawning tanks are each lifted carefully and inspected for embryos. Substrates without embryos

are immediately returned to the spawning tank. Those with embryos are immersed in clean water in a collecting

tray, and replaced with a clean substrate. A daily record is maintained of each spawning site and the estimated

number of embryos on the substrate.

11.6.17.5.6.10 Three different methods are described for embryo incubation.

1. Incubation of Embryos on the Substrates: Several (2-4) substrates are placed on end in a circular

pattern (with the embryos on the innerside) in 10 cm of water in a tray. The tray is then placed in a

constant temperature water bath, and the embryos are aerated with a 2.5 cm airstone placed in the

center of the circle. The embryos are examined daily, and the dead and fungused embryos are

counted, recorded, and removed with forceps. At an incubation temperature of 25°C, 50% hatch

occurs in five days. At 22°C embryos incubated on aerated tiles require 7 days for 50% hatch.

2. Incubation of Embryos in a Separatory Funnel: The embryos are removed from the substrates with a

rolling action of the index finger ("rolled off") (Gast and Brungs, 1973), their total volume is

measured, and the number of embryos is calculated using a conversion factor of approximately 430

embryos/mL. The embryos are incubated in about 1.5 L of water in a 2 L separatory funnel

maintained in a water bath. The embryos are stirred in the separatory funnel by bubbling air from the

tip of a plastic micro-pipette placed at the bottom, inside the separatory funnel. During the first two

days, the embryos are taken from the funnel daily, those that are dead and fungused are removed, and

those that are alive are returned to the separatory funnel in clean water. The embryos hatch in four

days at a temperature of 25°C. However, usually on day three the eyed embryos are removed from the

separatory funnel and placed in water in a plastic tray and gently aerated with an air stone. Using this

method, the embryos hatch in five days. Hatching time is greatly influenced by the amount of

agitation of the embryos and the incubation temperature. If on day three the embryos are transferred

from the separatory funnel to a static, unaerated container, a 50% hatch will occur in six days (instead

of five) and a 100% hatch will occur in seven days. If the culture system is operated at 22°C, embryos

incubated on aerated tiles require seven days for 50% hatch. 

3. Incubation in Embryo Incubation Cups: The embryos are "rolled off" the substrates, and the total

number is estimated by determining the volume. The embryos are then placed in incubation cups

attached to a rocker arm assembly (Mount, 1968). Both flow-through and static renewal incubation

have been used. On day one, the embryos are removed from the cups and those that are dead and

fungused are removed. After day one only dead embryos are removed from the cups. During the

incubation period, the eggs are examined daily for viability and fungal growth, until they hatch. 

Unfertilized eggs, and eggs that have become infected by fungus, should be removed with forceps

using a table top magnifier-illuminator. Non-viable eggs become milky and opaque, and are easily

recognized. The non-viable eggs are very susceptible to fungal infection, which may then spread

throughout the egg mass. Removal of fungus should be done quickly, and the substrates should be

returned to the incubation tanks as rapidly as possible so that the good eggs are not damaged by

desiccation. Hatching takes four to five days at an optimal temperature of 25°C. Hatching can be

delayed several (two to four) days by incubating at lower temperatures. A large plastic tank receiving

recirculating water from a temperature control unit, can be used as a water bath for incubation of

embryos.

11.6.17.5.6.11 Newly-hatched larvae are transferred daily from the egg incubation apparatus to small rearing

tanks, using a large bore pipette, until the hatch is complete. New rearing tanks are set up on a daily basis to

separate fish by age group. Approximately 1500 newly hatched larvae are placed in a 60-L (15 gal) or 76-L (20 gal)

all-glass aquarium for 30 days. A density of 150 fry per liter is suitable for the first four weeks. The water

temperature in the rearing tanks is allowed to follow ambient laboratory temperatures of 20-25°C, but sudden,

extreme variations in temperature must be avoided. 
64

11.6.17.5.7 Food and Feeding

11.6.17.5.7.1 The amount of food and feeding schedule affects both growth and egg production. The spawning

fish and pre-spawners in holding tanks usually are fed all the adult frozen brine shrimp and tropical fish flake food

or dry commercial fish food (No. l or No. 2 granules) that they can eat (ad libitum) at the beginning of the work day

and in the late afternoon (8:00 AM and 4:00 PM). The fish are fed twice a day (twice a day with dry food and once

a day with adult shrimp) during the week and once a day on weekends. 

11.6.17.5.7.2 Fathead minnow larvae are fed freshly-hatched brine shrimp (Artemia) nauplii twice daily until they

are four weeks old. Utilization of older (larger) brine shrimp nauplii may result in starvation of the young fish

because they are unable to ingest the larger food organisms (see Subsection 11.6.16 or USEPA, 2002a for

instructions on the preparation of brine shrimp nauplii).

11.6.17.5.7.3 Fish older than four weeks are fed frozen brine shrimp and commercial fish starter (#l and #2), which

is ground fish meal enriched with vitamins. As the fish grow, larger pellet sizes are used, as appropriate. (Starter,

No. 1 and N. 2 granules, U.S. Fish and Wildlife Service Formulation Specification Diet SD9-30). Newly hatched

brine shrimp nauplii, and frozen adult brine shrimp are fed to the fish cultures in volumes based on age, size, and

number of fish in the tanks.

11.6.17.5.7.4 Fish in the larval tanks (from hatch to 30 days old) are fed commercial starter fish food at the

beginning and end of the work day, and newly hatched brine shrimp nauplii (from the brine shrimp culture unit)

once a day, usually mid-morning and mid-afternoon. 

11.6.17.5.7.5 Attempts should be made to avoid introducing Artemia cysts and empty shells when the brine shrimp

nauplii are fed to the fish larvae. Some of the mortality of the larval fish observed in cultures could be caused from

the ingestion of these materials.

11.6.17.5.8 Disease Control 

11.6.17.5.8.1 Fish are observed daily for abnormal appearance or behavior. Bacterial or fungal infections are the

most common diseases encountered. However, if normal precautions are taken, disease outbreaks will rarely, if

ever, occur. Hoffman and Mitchell (1980) have put together a list of some chemicals that have been used

commonly for fish diseases and pests.

11.6.17.5.8.2 In aquatic culture systems where filtration is utilized, the application of certain antibacterial agents

should be used with caution. A treatment with a single dose of antibacterial drugs can interrupt nitrate reduction

and stop nitrification for various periods of time, resulting in changes in pH, and in ammonia, nitrite and nitrate

concentrations (Collins et al., 1976). These changes could cause the death of the culture organisms. 

11.6.17.5.8.3 Do not transfer equipment from one tank to another without first disinfecting tanks and nets. If an

outbreak of disease occurs, any equipment, such as nets, airlines, tanks, etc., which has been exposed to diseased

fish should be disinfected with sodium hypochlorite. Also to avoid the contamination of cultures or spread of

disease, each time nets are used to remove live or dead fish from tanks, they are first sterilized with sodium

hypochlorite or formalin, and rinsed in hot tap water. Before a new lot of fish is transferred to culture tanks, the

tanks are cleaned and sterilized as described above. 

11.6.17.5.8.4 It is recommended that chronic toxicity tests be performed monthly with a reference toxicant. Newly

hatched fathead minnow larvae less than 24 h old are used to monitor the chronic toxicity of the reference toxicant

to the test fish produced by the culture unit (see Section 4, Quality Assurance).
65

11.6.17.5.9 Record Keeping

11.6.17.5.9.1 Records, kept in a bound notebook, include: (l) type of food and time of feeding for all fish tanks; (2)

time of examination of the tiles for embryos, the estimated number of embryos on the tile, and the tile position

number; (3) estimated number of dead embryos and embryos with fungus observed during the embryonic

development stages; (4) source of all fish; (5) daily observation of the condition and behavior of the fish; and (6)

dates and results of reference toxicant tests performed (see Section 4, Quality Assurance).

11.7 EFFLUENT AND RECEIVING WATER COLLECTION, PRESERVATION, AND STORAGE

11.7.1 See Section 8, Effluent and Receiving Water Sampling, Sample Handling, and Sample Preparation for

Toxicity Tests.

11.8 CALIBRATION AND STANDARDIZATION

11.8.1 See Section 4, Quality Assurance. 

11.9 QUALITY CONTROL

11.9.1 See Section 4, Quality Assurance. 

11.10 TEST PROCEDURES

11.10.1 TEST SOLUTIONS 

11.10.1.1 Receiving Waters 

11.10.1.1.1 The sampling point is determined by the objectives of the test. Receiving water toxicity is determined

with samples used directly as collected or after samples are passed through a 60 μm NITEX® filter and compared

without dilution, against a control. Using four replicate chambers per test, each containing 250 mL, and 400 mL for

chemical analyses, would require approximately 1.5 L or more of sample per test per day. 

11.10.1.2 Effluents 

11.10.1.2.1 The selection of the effluent test concentrations should be based on the objectives of the study. A

dilution factor of 0.5 is commonly used. A dilution factor of 0.5 provides precision of ± 100%, and testing of

concentrations between 6.25% and 100% effluent using only five effluent concentrations (6.25%, 12.5%, 25%,

50%, and 100%). Test precision shows little improvement as the dilution factor is increased beyond 0.5, and

declines rapidly if a smaller dilution factor is used. Therefore, USEPA recommends the use of the $ 0.5 dilution

factor.

11.10.1.2.2 If the effluent is known or suspected to be highly toxic, a lower range of effluent concentrations should

be used (such as 25%, 12.5%, 6.25%, 3.12%, and 1.56%). If a high rate of mortality is observed during the first

1 to 2 h of the test, additional dilutions should be added at the lower range of effluent concentrations.

11.10.1.2.3 The volume of effluent required for daily renewal of four replicates per concentration, each containing

250 mL of test solution, is approximately 2.5 L. Sufficient test solution (approximately 1500 mL) is prepared at

each effluent concentration to provide 400 mL additional volume for chemical analyses at the high, medium, and

low test concentrations. If the sample is used for more than one daily renewal of test solutions, the volume must be

increased proportionately.

11.10.1.2.4 Tests should begin as soon as possible, preferably within 24 h of sample collection. The maximum

holding time following retrieval of the sample from the sampling device should not exceed 36 h for off-site toxicity
66

tests unless permission is granted by the permitting authority. In no case should the sample be used for the first time

in a test more than 72 h after sample collection (see Section 8, Effluent and Receiving Water Sampling, Sample

Handling, and Sample Preparation for Toxicity Tests).

11.10.1.2.5 Just prior to test initiation (approximately 1 h) the temperature of sufficient quantity of the sample to

make the test solutions should be adjusted to the test temperature and maintained at that temperature during the

addition of dilution water.

11.10.1.2.6 The DO of the test solutions should be checked prior to the test initiation. If any of the solutions are

supersaturated with oxygen, all of the solutions and the control should be gently aerated. If any solution has a DO

concentration below 4.0 mg/L, all of the solutions and the control must be gently aerated.

11.10.1.3 Dilution Water

11.10.1.3.1 Dilution water may be uncontaminated receiving water, a standard synthetic (reconstituted) water, or

some other uncontaminated natural water (see Section 7, Dilution Water).

11.10.2 START OF THE TEST 

11.10.2.1 Label the test chambers with a marking pen. Use of color-coded tape to identify each treatment and

replicate is helpful. A minimum of five effluent concentrations and a control are used for each effluent test. Each

treatment (including the control) must have a minimum of four replicates. 

11.10.2.2 Tests performed in laboratories that have in-house fathead minnow breeding cultures should use larvae

less than 24 h old. When eggs or larvae must be shipped to the test site from a remote location, it may be necessary

to use larvae older than 24 h because of the difficulty in coordinating test organism shipments with field operations. 

However, in the latter case, the larvae must not be more than 48 h old at the start of the test and must all be within

24 h of the same age. 

11.10.2.3 Randomize the position of test chambers at the beginning of the test (see Appendix A). Maintain the

chambers in this configuration throughout the test. Preparation of a position chart may be helpful.

11.10.2.4 The larvae are pooled and placed one or two at a time into each randomly arranged test chamber or

intermediate container in sequential order, until each chamber contains 15 (minimum of 10) larvae, for a total of

60 larvae (minimum of 40) for each concentration (see Appendix A). The test organisms should come from a pool

of larvae consisting of at least three separate spawnings. The amount of water added to the chambers when

transferring the larvae should be kept to a minimum to avoid unnecessary dilution of the test concentrations. 

11.10.2.4.1 The chambers may be placed on a light table to facilitate counting the larvae.

11.10.3 LIGHT, PHOTOPERIOD, AND TEMPERATURE

11.10.3.1 The light quality and intensity should be at ambient laboratory levels, which is approximately 10-20

μE/m2

/s, or 50 to 100 foot candles (ft-c), with a photoperiod of 16 h of light and 8 h of darkness. The water

temperature in the test chambers should be maintained at 25 ± 1o

C.

11.10.4 DISSOLVED OXYGEN (DO) CONCENTRATION

11.10.4.1 Aeration may affect the toxicity of effluents and should be used only as a last resort to maintain

satisfactory DO concentrations. The DO concentrations should be measured in the new solutions at the start of the

test (Day 0) and before daily renewal of the test solutions on subsequent days. The DO concentrations should not

fall below 4.0 mg/L (see Section 8, Effluent and Receiving Water Sampling, Sample Handling, and Sample

Preparation for Toxicity Tests). If it is necessary to aerate, all concentrations and the control should be aerated. 
67

The aeration rate should not exceed 100 bubbles/min, using a pipet with an orifice of approximately 1.5 mm, such

as a 1-mL, KIMAX® serological pipet, or equivalent. Care should be taken to ensure that turbulence resulting from

aeration does not cause undue physical stress to the fish. 

11.10.5 FEEDING 

11.10.5.1 The fish in each test chamber are fed 0.1 g (approximately 700 to 1000) of a concentrated suspension of

newly hatched (less than 24-h old) brine shrimp nauplii three times daily at 4-h intervals or, as a minimum, 0.15 g

are fed twice daily at an interval of 6 h. Equal amounts of nauplii must be added to each replicate chamber to

reduce variability in larval weight. Sufficient numbers of nauplii should be provided to assure that some remain

alive in the test chambers for several hours, but not in excessive amounts which will result in depletion of DO below

acceptable levels (below 4.0 mg/L).

11.10.5.2 The feeding schedule will depend on when the test solutions are renewed. If the test is initiated after

12:00 PM, the larvae may be fed only once the first day. On following days, the larvae normally would be fed at

the beginning of the work day, at least 2 h before test solution renewal, and at the end of the work day, after test

solution renewal. However, if the test solutions are changed at the beginning of the work day, the first feeding

would be after test solution renewal in the morning, and the remaining feeding(s) would be at the appropriate

intervals. The larvae are not fed during the final 12 h of the test.

11.10.5.3 The nauplii should be rinsed with freshwater to remove salinity before use (see USEPA, 2002a). At

feeding time pipette about 5 mL (5 g) of concentrated newly hatched brine shrimp nauplii into a 120 mesh nylon net

or plastic cup with nylon mesh bottom. Slowly run freshwater through the net or rinse by immersing the cup in a

container of fresh water several times. Resuspend the brine shrimp in 10 mL of fresh water in a 30 mL beaker or

simply set the cup of washed brine shrimp in 1⁄4 inch of fresh water so that the cup contains about 10 mL of water. 

Allow the container to set for a minute or two to allow dead nauplii and empty cysts to settle or float to the surface

before collecting the brine shrimp from just below the surface in a pipette for feeding. Distribute 2 drops (0.1 g) of

the brine shrimp to each test chamber. If the survival rate in any test chamber falls below 50%, reduce the feeding

in that chamber to 1 drop of brine shrimp at each subsequent feeding.

11.10.6 OBSERVATIONS DURING THE TEST 

11.10.6.1 Routine Chemical and Physical Determinations

11.10.6.1.1 DO is measured at the beginning and end of each 24-h exposure period in at least one test chamber at

each test concentration and in the control.

11.10.6.1.2 Temperature and pH are measured at the end of each 24-h exposure period in at least one test chamber

at each test concentration and in the control. Temperature should also be monitored continuously or observed and

recorded daily for at least two locations in the environmental control system or the samples. Temperature should be

measured in a sufficient number of test vessels at least at the end of the test to determine the temperature variation in

the environmental chamber.

11.10.6.1.3 The pH is measured in the effluent sample each day before new test solutions are made.

11.10.6.1.4 Conductivity, alkalinity and hardness are measured in each new sample (100% effluent or receiving

water) and in the control.

11.10.6.1.5 Record all the measurements on the data sheet (Figure 1)
68

11.10.6.2 Routine Biological Observations

11.10.6.2.1 The number of live larvae in each test chamber are recorded daily (Figure 2) , and the dead larvae are

discarded.

11.10.6.2.2 Protect the larvae from unnecessary disturbance during the test by carrying out the daily test

observations, solution renewals, and removal of dead larvae, carefully. Make sure the larvae remain immersed

during the performance of these operations.
69

Discharger: Test Dates:

Location: Analyst:

Conc:

Day

1 2 3 4 5 6 7 Remarks

Temp.

D.O. Initial

Final

pH Initial

Final

Alkalinity

Hardness

Conductivity

Chlorine

Conc:

Day

1 2 3 4 5 6 7 Remarks

Temp.

D.O. Initial

Final

pH Initial

Final

Alkalinity

Hardness

Conductivity

Chlorine

Conc:

Day

1 2 3 4 5 6 7 Remarks

Temp.

D.O. Initial

Final

pH Initial

Final

Alkalinity

Hardness

Conductivity

Chlorine

Figure 1. Data form for the fathead minnow, Pimephales promelas, larval survival and growth test. Routine

chemical and physical determinations.
70

Discharger: Test Dates:

Location: Analyst:

Conc:

Day

1 2 3 4 5 6 7 Remarks

Temp.

D.O. Initial

Final

pH Initial

Final

Alkalinity

Hardness

Conductivity

Chlorine

Conc:

Day

1 2 3 4 5 6 7 Remarks

Temp.

D.O. Initial

Final

pH Initial

Final

Alkalinity

Hardness

Conductivity

Chlorine

Conc:

Day

1 2 3 4 5 6 7 Remarks

Temp.

D.O. Initial

Final

pH Initial

Final

Alkalinity

Hardness

Conductivity

Chlorine

Figure 1. Data form for the fathead minnow, Pimephales promelas, larval survival and growth test. Routine

chemical and physical determinations (CONTINUED).
71

Discharger: Test Dates:

Location: Analyst:

No. Surviving Organisms

Conc: Rep. No. Day

Control: 1 2 3 4 5 6 7 Remarks

Conc:

Conc:

Conc:

Conc:

Conc:

Conc:

Conc:

Comments:

Figure 2. Survival data for the fathead minnow, Pimephales promelas, larval survival and growth test.
72

11.10.7 DAILY CLEANING OF TEST CHAMBERS

11.10.7.1 Before the daily renewal of test solutions, uneaten and dead Artemia, dead fish larvae, and other debris

are removed from the bottom of the test chambers with a siphon hose. Alternately, a large pipet (50 mL) fitted with

a rubber bulb can be used. Because of their small size during the first few days of the tests, larvae are easily drawn

into the siphon tube or pipet when cleaning the test chambers. By placing the test chambers on a light box,

inadvertent removal of larvae can be greatly reduced because they can be more easily seen. If the water siphoned

from the test chambers is collected in a white plastic tray, the larvae caught up in the siphon can be retrieved and

returned to the chambers. Any incidence of removal of live larvae from the test chambers during cleaning, and

subsequent return to the chambers, should be noted in the records. 

11.10.8 TEST SOLUTION RENEWAL

11.10.8.1 Freshly prepared solutions are used to renew the tests daily immediately after cleaning the test chambers. 

For on-site toxicity studies, fresh effluent or receiving water samples should be collected daily, and no more than 24

h should elapse between collection of the samples and their use in the tests (see Section 8, Effluent and Receiving

Water Sampling, Sample Holding, and Sample Preparation for Toxicity Tests). For off-site tests, a minimum of

three samples are collected, preferably on days one, three, and five. Maintain the samples in the refrigerator at 0-

6o

C until used.

11.10.8.2 For test solution renewal, the water level in each chamber is lowered to a depth of 7 to 10 mm, which

leaves 15 to 20% of the test solution. New test solution (250 mL) should be added slowly by pouring down the side

of the test chamber to avoid excessive turbulence and possible injury to the larvae. 

11.10.9 TERMINATION OF THE TEST 

11.10.9.1 The test is terminated after seven days of exposure. At test termination, dead larvae are removed and

discarded. The surviving larvae in each test chamber (replicate) are counted and immediately prepared as a group

for dry weight determination, or are preserved as a group in 70% ethanol or 4% formalin. Preserved organisms are

dried and weighed within 7 days. For safety, formalin should be used under a hood.

11.10.9.2 For immediate drying and weighing, place live larvae onto a 500 μm mesh screen in a large beaker to

wash away debris that might contribute to the dry weight. Each group of larvae is rinsed with deionized water to

remove food particles, transferred to a tared weighing boat that has been properly labeled, and dried at 60o

C, for 24

h or at 100o

C for a minimum of 6 h. Immediately upon removal from the drying oven, the weighing boats are

placed in a dessicator until weighed, to prevent the absorption of moisture from the air. All weights should be

measured to the nearest 0.01 mg and recorded on data sheets (Figure 3). Subtract tare weight to determine the dry

weight of the larvae in each replicate. For each test chamber, divide the final dry weight by the number of original

larvae in the test chamber to determine the average individual dry weight and record on the data sheet (Figure 3). 

For the controls, also calculate the mean weight per surviving fish in the test chamber to evaluate if weights met test

acceptability criteria (See Section 11.11). Average weights should be expressed to the nearest 0.001 mg.

11.10.9.3 Prepare a summary table as illustrated in Figure 4.

11.11 SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA

11.11.1 A summary of test conditions and test acceptability criteria is presented in Table 1.
73

Discharge:____________________ Test Date(s): ________________ Drying Temperature (EC): _______________ Location: ____________________ Weighing Date:________________ Drying Time (h): _______________________ Analyst: ____________________________ ___________________________________________________________________________  A B B-A C (B-A)/C RemarksConc: Rep. Wgt. of Dry wgt: Total dry No. of Mean dry wgt  No. tare tare and wgt of original of larvae  (mg) larvae larvae larvae (mg)  (mg) (mg) (mg) Control ______ _______ _________ __________ ________ ___________ ________________________ ______ _______ _________ __________ ________ ___________ ________________________ ______ _______ _________ __________ ________ ___________ ________________________ ______ _______ _________ __________ ________ ___________ ________________________Conc: ______ _______ _________ __________ ________ ___________ ________________________ ______ _______ _________ __________ ________ ___________ ________________________ ______ _______ _________ __________ ________ ___________ _______________________________________ _______ _________ __________ ________ ___________ ________________________Conc: ______ _______ _________ __________ ________ ___________ ________________________ ______ _______ _________ __________ ________ ___________ ________________________ ______ _______ _________ __________ ________ ___________ _______________________________________ _______ _________ __________ ________ ___________ ________________________Conc: ______ _______ _________ __________ ________ ___________ ________________________ ______ _______ _________ __________ ________ ___________ ________________________ ______ _______ _________ __________ ________ ___________ _______________________________________ _______ _________ __________ ________ ___________ ________________________Conc: ______ _______ _________ __________ ________ ___________ ________________________ ______ _______ _________ __________ ________ ___________ ________________________ ______ _______ _________ __________ ________ ___________ _______________________________________ _______ _________ __________ ________ ___________ ________________________Conc: ______ _______ _________ __________ ________ ___________ ________________________ ______ _______ _________ __________ ________ ___________ ________________________ ______ _______ _________ __________ ________ ___________ _______________________________________ _______ _________ __________ ________ ___________ ________________________Figure 3. Weight data for the fathead minnow, Pimephales promelas, larval survival and growth test. From USEPA (1989a).
74

Discharger: Test Dates: 

Location: Analyst: 

TREATMENT CONTROL

NO. LIVE LARVAE

SURVIVAL

(%)

MEAN DRY WGT

OF LARVAE (MG)

± SD

TEMPERATURE

RANGE (EC)

DISSOLVED

OXYGEN RANGE

 (MG/L)

HARDNESS

CONDUCTIVITY

COMMENTS:

Figure 4. Summary data for the fathead minnow, Pimephales promelas, larval survival and growth test. 
75

TABLE 1. SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA FOR

FATHEAD MINNOW, PIMEPHALES PROMELAS, LARVAL SURVIVAL AND GROWTH

TOXICITY TESTS WITH EFFLUENTS AND RECEIVING WATERS (TEST METHOD

1000.0)1

1. Test type: Static renewal (required)

2. Temperature (o

C): 25 ± 1oC (recommended)

Test temperatures must not deviate (i.e., maximum minus

minimum temperature) by more than 3o

C during the test

(required)

3. Light quality: Ambient laboratory illumination (recommended)

4. Light intensity: 10-20 μE/m2

/s (50-100 ft-c)(ambient laboratory levels)

(recommended)

5. Photoperiod: 16 h light, 8 h darkness (recommended)

6. Test chamber size: 500 mL (recommended minimum)

7. Test solution volume: 250 mL (recommended minimum) 

8. Renewal of test 

solutions: Daily (required) 

9. Age of test organisms: Newly hatched larvae less than 24 h old. If shipped, not

more than 48 h old, 24 h range in age (required) 

10. No. larvae per test chamber: 10 (recommended) 

11. No. replicate chambers 

per concentration: 4 (required minimum)

12. No. larvae per

concentration: 40 (required minimum) 

13. Source of food: Newly hatched Artemia nauplii (less than 24 h old)

(required) 

14. Feeding regime: On days 0-6, feed 0.1 g newly hatched (less than 24-h old)

brine shrimp nauplii three times daily at 4-h intervals or, as a

minimum, 0.15 g twice daily at 6-h intervals (at the

beginning of the work day prior to renewal, and at the end of

the work day following renewal). Sufficient nauplii are

added to provide an excess. (recommended)

1

 For the purposes of reviewing WET test data submitted under NPDES permits, each test condition listed

above is identified as required or recommended (see Subsection 10.2 for more information on test review).

Additional requirements may be provided in individual permits, such as specifying a given test condition

where several options are given in the method.
76

TABLE 1. SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA FOR

FATHEAD MINNOW, PIMEPHALES PROMELAS, LARVAL SURVIVAL AND GROWTH

TOXICITY TESTS WITH EFFLUENTS AND RECEIVING WATERS (TEST METHOD

1000.0) (CONTINUED)

 

15. Cleaning: Siphon daily, immediately before test solution renewal (required)

16. Aeration: None, unless DO concentration falls below 4.0 mg/L. Rate should

not exceed 100 bubbles/minimum (recommended) 

17. Dilution water: Uncontaminated source of receiving or other natural water,

synthetic water prepared using MILLIPORE MILLI-Q® or

equivalent deionized water and reagent grade chemicals, or DMW

(see Section 7, Dilution Water) (available options)

18. Test concentrations: Effluents: 5 and a control (required minimum)

Receiving Water: 100% receiving water (or minimum of 5) and a

control (recommended) 

19. Dilution factor: Effluents: $ 0.5 (recommended) 

Receiving waters: None or $ 0.5 (recommended) 

20. Test duration: 7 days (required) 

21. Endpoints: Survival and growth (weight) (required) 

22. Test acceptability

criteria: 80% or greater survival in controls; average dry weight per

surviving organism in control chambers equals or exceeds 0.25 mg

(required) 

23. Sampling requirements: For on-site tests, samples collected daily, and used within 24 h of

the time they are removed from the sampling device; For off-site

tests, a minimum of three samples (e.g., collected on days one, three

and five) with a maximum holding time of 36 h before first use (see

Section 8, Effluent and Receiving Water Sampling, Sample

Handling, and Sample Preparation for Toxicity Tests, Subsection

8.5.4) (required) 

24. Sample volume required: 2.5 L/day (recommended) 
77

11.12 ACCEPTABILITY OF TEST RESULTS

11.12.1 For the test results to be acceptable, survival in the controls must be at least 80%. The average dry weight

per surviving control larvae at the end of the test must equal or exceed 0.25 mg.

11.13 DATA ANALYSIS

11.13.1 GENERAL 

11.13.1.1 Tabulate and summarize the data. A sample set of survival and growth response data is shown in Table

2.

TABLE 2. SUMMARY OF SURVIVAL AND GROWTH DATA FOR FATHEAD MINNOW,

PIMEPHALES PROMELAS, LARVAE EXPOSED TO A REFERENCE TOXICANT FOR

SEVEN DAYS1

Proportion of

NaPCP Survival in Replicate Mean Avg Dry Wgt (mg) In Mean

Conc. Chambers Prop. Replicate Chambers Dry Wgt

 (μg/L) A B C D Surv A B C D (mg)

0 1.0 1.0 0.9 0.9 0.95 0.711 0.662 0.646 0.690 0.677

32 0.8 0.8 1.0 0.8 0.85 0.517 0.501 0.723 0.560 0.575

64 0.9 1.0 1.0 1.0 0.975 0.602 0.669 0.694 0.676 0.660

128 0.9 0.9 0.8 1.0 0.90 0.566 0.612 0.410 0.672 0.565

256 0.7 0.9 1.0 0.5 0.775 0.455 0.502 0.606 0.254 0.454

512 0.4 0.3 0.4 0.2 0.325 0.143 0.163 0.195 0.099 0.150

1 Four replicates of 10 larvae each.

11.13.1.2 The endpoints of toxicity tests using the fathead minnow, Pimephales promelas, larvae are based on the

adverse effects on survival and growth. The LC50, the IC25, and the IC50 are calculated using point estimation

techniques (see Section 9, Chronic Toxicity Test Endpoints and Data Analysis). LOEC and NOEC values for

survival and growth are obtained using a hypothesis testing approach such as Dunnett's Procedure (Dunnett, 1955)

or Steel's Many-one Rank Test (Steel, 1959; Miller, 1981) (see Section 9). Separate analyses are performed for the

estimation of the LOEC and NOEC endpoints and for the estimation of the LC50, IC25 and IC50. Concentrations

at which there is no survival in any of the test chambers are excluded from the statistical analysis of the NOEC and

LOEC for survival and growth, but included in the estimation of the LC50, IC25, and IC50. See the Appendices for

examples of the manual computations, and examples of data input and program output. 

11.13.1.3 The statistical tests described here must be used with a knowledge of the assumptions upon which the

tests are contingent. Tests for normality and homogeneity of variance are included in Appendix B. The assistance

of a statistician is recommended for analysts who are not proficient in statistics. 
78

11.13.2 EXAMPLE OF ANALYSIS OF FATHEAD MINNOW, PIMEPHALES PROMELAS, SURVIVAL

DATA

11.13.2.1 Formal statistical analysis of the survival data is outlined in Figures 5 and 6. The response used in the

analysis is the proportion of animals surviving in each test or control chamber. Separate analyses are performed for

the estimation of the NOEC and LOEC endpoints and for the estimation of the LC50, EC50, and IC endpoints. 

Concentrations at which there is no survival in any of the test chambers are excluded from statistical analysis of the

NOEC and LOEC, but included in the estimation of the IC, EC, and LC endpoints.

11.13.2.2 For the case of equal numbers of replicates across all concentrations and the control, the evaluation of the

NOEC and LOEC endpoints is made via a parametric test, Dunnett's Procedure, or a nonparametric test, Steel's

Many-one Rank Test, on the arc sine square root transformed data. Underlying assumptions of Dunnett's

Procedure, normality and homogeneity of variance, are formally tested. The test for normality is the Shapiro-Wilk's

Test, and Bartlett's Test is used to test for homogeneity of variance. If either of these tests fails, the nonparametric

test, Steel's Many-one Rank Test, is used to determine the NOEC and LOEC endpoints. If the assumptions of

Dunnett's Procedure are met, the endpoints are estimated by the parametric procedure.

11.13.2.3 If unequal numbers of replicates occur among the concentration levels tested, there are parametric and

nonparametric alternative analyses. The parametric analysis is a t test with the Bonferroni adjustment (see

Appendix D). The Wilcoxon Rank Sum Test with the Bonferroni adjustment is the nonparametric alternative (see

Appendix F).

11.13.2.4 Probit Analysis (Finney, 1971; see Appendix I) is used to estimate the concentration that causes a

specified percent decrease in survival from the control. In this analysis, the total mortality data from all test

replicates at a given concentration are combined. If the data do not fit the Probit analysis, the Spearman-Karber

Method, the Trimmed Spearman-Karber Method, or the Graphical Method may be used (see Appendices I-L).
79

Figure 5. Flowchart for statistical analysis of the fathead minnow, Pimephales promelas, larval survival data by

hypothesis testing.
80

Figure 6. Flowchart for statistical analysis of the fathead minnow, Pimephales promelas, larval survival data by

point estimation. 
81

 TABLE 3. FATHEAD MINNOW, PIMEPHALES PROMELAS, SURVIVAL DATA

NaPCP Concentration (μg/L)

Replicate Control 32 64 128 256 512 

A 1.0 0.8 0.9 0.9 0.7 0.4 

 RAW B 1.0 0.8 1.0 0.9 0.9 0.3 

C 0.9 1.0 1.0 0.8 1.0 0.4 

D 0.9 0.8 1.0 1.0 0.5 0.2 

 ARC SINE A 1.412 1.107 1.249 1.249 0.991 0.685 

 TRANS- B 1.412 1.107 1.412 1.249 1.249 0.580 

 FORMED C 1.249 1.412 1.412 1.107 1.412 0.685 

D 1.249 1.107 1.412 1.412 0.785 0.464 

 

Mean( ) Y ̄ 1.330 1.183 1.371 1.254 1.109 0.604 i

Si

2 0.0088 0.0232 0.0066 0.0155 0.0768 0.0111

i 1 2 3 45 6

11.13.2.5 Example of Analysis of Survival Data 

11.13.2.5.1 This example uses the survival data from the Fathead Minnow Larval Survival and Growth Test (Table

2). The proportion surviving in each replicate must first be transformed by the arc sine square root transformation

procedure described in Appendix B. The raw and transformed data, means and variances of the transformed

observations at each toxicant concentration and control are listed in Table 3. A plot of the survival proportions is

provided in Figure 7.

11.13.2.6 Test for Normality

11.13.2.6.1 The first step of the test for normality is to center the observations by subtracting the mean of all

observations within a concentration from each observation in that concentration. The centered observations are

summarized in Table 4. 

11.13.2.6.2 Calculate the denominator, D, of the statistic: 

D ' Σ

n

i'1

(Xi

&X)  ̄ 2

Where: Xi = the ith centered observation 

 

X ̄ = the overall mean of the centered observations 

n = the total number of centered observations
82

Figure 7. Plot of survival proportion data in Table 3.
83

TABLE 4. CENTERED OBSERVATIONS FOR SHAPIRO-WILK'S EXAMPLE 

NaPCP Concentration (μg/L)

Replicate Control 32 64 128 256 512

A 0.082 -0.076 -0.122 -0.005 -0.118 0.081 

B 0.082 -0.076 0.041 -0.005 0.140 -0.024 

C -0.081 0.229 0.041 -0.147 0.303 0.081 

D -0.081 -0.076 0.041 0.158 -0.324 -0.140 

TABLE 5. ORDERED CENTERED OBSERVATIONS FOR THE SHAPIRO-WILK'S EXAMPLE

i X(i) i X(i)

1 -0.324 13 -0.005 

2 -0.147 14 0.041 

3 -0.140 15 0.041 

4 -0.122 16 0.041 

5 -0.118 17 0.081 

6 -0.081 18 0.081 

7 -0.081 19 0.082 

8 -0.076 20 0.082 

9 -0.076 21 0.140 

10 -0.076 22 0.158 

11 -0.024 23 0.229 

12 -0.005 24 0.303 

11.13.2.6.3 For this set of data: n = 24 

X ̄ ' 1

24 (0.000) ' 0.000

D = 0.4265

11.13.2.6.4 Order the centered observations from smallest to largest 

X(1) # X(2) # ... # X(n)

where X(i) denotes the ith ordered observation. The ordered observations for this example are listed in Table 5. 

11.13.2.6.5 From Table 4, Appendix B, for the number of observations, n, obtain the coefficients a1, a2, ... ak where

k is n/2 if n is even and (n-1)/2 if n is odd. For the data in this example, n = 24 and k = 12. The ai

 values are listed in

Table 6.
84

TABLE 6. COEFFICIENTS AND DIFFERENCES FOR SHAPIRO-WILK'S EXAMPLE

i ai X(n-i+1) - X(i)

1 0.4493 0.627 X(24) - X(1)

2 0.3098 0.376 X(23) - X(2)

3 0.2554 0.298 X(22) - X(3)

4 0.2145 0.262 X(21) - X(4)

5 0.1807 0.200 X(20) - X(5)

6 0.1512 0.163 X(19) - X(6)

7 0.1245 0.162 X(18) - X(7)

8 0.0997 0.157 X(17) - X(8)

9 0.0764 0.117 X(16) - X(9)

10 0.0539 0.117 X(15) - X(10)

11 0.0321 0.065 X(14) - X(11)

12 0.0107 0.000 X(13) - X(12)

1.13.2.6.6 Compute the test statistic, W, as follows: 

W ' 1

D ['

k

i'1

ai(X (n&i%1)&X (i))]

2

The differences X(n-i+1) - X(i) are listed in Table 6. For the data in this example, 

W ' 1

0.4265 (0.6444)2'0.974

11.13.2.6.7 The decision rule for this test is to compare W as calculated in Section 13.2.6.6 to a critical value

found in Table 6, Appendix B. If the computed W is less than the critical value, conclude that the data are not

normally distributed. For the data in this example, the critical value at a significance level of 0.01 and n = 24

observations is 0.884. Since W = 0.974 is greater than the critical value, conclude that the data are normally

distributed. 

11.13.2.7 Test for Homogeneity of Variance 

11.13.2.7.1 The test used to examine whether the variation in mean proportion surviving is the same across all

toxicant concentrations including the control, is Bartlett's Test (Snedecor and Cochran, 1980). The test statistic is as

follows:

B'

[('

P

i'1

Vi)ln S ̄2

& '

P

i'1

VilnS 2

i ]

C
85

Where: Vi

 = degrees of freedom for each toxicant concentration and control, Vi = (ni - 1) 

 ni

 = the number of replicates for concentration i 

 ln = loge

 i = 1, 2, ..., p where p is the number of concentrations including the control

 S ̄2 '

('

P

i'1

ViS 2

i )

'

P

i'1

Vi

 C ' 1%(3(p&1))&1

['

P

i'1

1

Vi

&('

P

i'1

Vi)

&1

]

11.13.2.7.2 For the data in this example (see Table 3), all toxicant concentrations including the control have the

same number of replicates (ni

 = 4 for all i). Thus, Vi = 3 for all i. 

11.13.2.7.3 Bartlett's statistic is therefore: 

B ' [(18)ln(0.0236)&3'

P

i'1

ln(S 2

i )]/1.1296

= [18(-3.7465) - 3(-24.7516)]/1.1296 

= 6.8178/1.1296 

= 6.036 

11.13.2.7.4 B is approximately distributed as chi-square with p - 1 degrees of freedom, when the variances are in

fact the same. Therefore, the appropriate critical value for this test (from a table of chi-square distribution), at a

significance level of 0.01 with five degrees of freedom, is 15.086. Since B = 6.036 is less than the critical value of

15.086, conclude that the variances are not different. 

11.13.2.8 Dunnett's Procedure 

11.13.2.8.1 To obtain an estimate of the pooled variance for the Dunnett's Procedure, construct an ANOVA table

as described in Table 7.
86

TABLE 7. ANOVA TABLE

Source df Sum of Squares Mean Square(MS) 

(SS) (SS/df) 

Between p - 1 SSB S = SSB/(p-1) 2

B

Within N - p SSW = SSW/(N-p) S 2

W

Total N - 1 SST 

Where: p = number toxicant concentrations including the control

N = total number of observations n1 + n2 ... + np

ni = number of observations in concentration i 

SSB ' ' Between Sum of Squares

P

i'1

T 2

i /ni

&G 2/N

SST ' ' Total Sum of Squares

P

i'1

'

ni

j'1

Y 2

ij &G 2

/N

SSW ' SST&SSB Within Sum of Squares

G = the grand total of all sample observations, G ' '

P

i'1

Ti

Ti = the total of the replicate measurements for concentration i 

Yij = the jth observation for concentration i (represents the proportion surviving for toxicant concentration 

 i in test chamber j) 

11.13.2.8.2 For the data in this example: 

 n1 = n2 = n3 = n4 = n5 = n6 = 4 

N = 24 

T1 = Y11 + Y12 + Y13 + Y14 = 5.322 

T2 = Y21 + Y22 + Y23 + Y24 = 4.733 

T3 = Y31 + Y32 + Y33 + Y34 = 5.485 

T4 = Y41 + Y42 + Y43 + Y44 = 5.017 

T5 = Y51 + Y52 + Y53 + Y54 = 4.437 

T6 = Y61 + Y62 + Y63 + Y64 = 2.414 
87

TABLE 8. ANOVA TABLE FOR DUNNETT'S PROCEDURE EXAMPLE

Source df Sum of Squares Mean Square(MS)

(SS) (SS/df)

Between 5 1.574 0.315 

Within 18 0.426 0.024 

Total 23 2.002 

t

i ' (Y ̄

1&Y ̄i

)

Sw (1/n1) % (1/ni

)

G = T1 + T2 + T3 + T4 + T5 + T6 = 27.408 

 

SSB ' j

P

i'1

T 2

i

ni

& G 2

N

' 1

4

(131.495) & (27.408)2

24 ' 1.574

SST ' j

p

i'1

j

ni

j'1

Y 2

ij & G 2

N

 

' 33.300& (27.408)2

24 ' 2.000

 

SSW ' SST&SSB = 2.000 - 1.574 = 0.4260 

 SB

2

 = SSB/(p-1) = 1.574/(6-1) = 0.3150 

SW

2

 = SSW/(N-p) = 0.426/(24-6) = 0.024 

11.13.2.8.3 Summarize these calculations in the ANOVA table (Table 8).

11.13.2.8.4 To perform the individual comparisons, calculate the t statistic for each concentration, and control

combination as follows:

Where: = mean proportion surviving for concentration i Y ̄ i
88

t

2 ' (1.330&1.183)

[0.155 (1/4) % (1/4)]

' 1.341

TABLE 9. CALCULATED T VALUES

NaPCP Concentration (μg/L) i ti

32 2 1.341

64 3 -0.374

128 4 0.693

256 5 2.016

512 6 6.624

Y ̄ = mean proportion surviving for the control 1

SW = square root of the within mean square 

n1 = number of replicates for the control 

ni = number of replicates for concentration i. 

11.13.2.8.5 Table 9 includes the calculated t values for each concentration and control combination. In this

example, comparing the 32 μg/L concentration with the control the calculation is as follows:

11.13.2.8.6 Since the purpose of this test is to detect a significant reduction in proportion surviving, a one-sided

test is appropriate. The critical value for this one-sided test is found in Table 5, Appendix C. For an overall alpha

level of 0.05, 18 degrees of freedom for error and five concentrations (excluding the control) the critical value is

2.41. The mean proportion surviving for concentration i is considered significantly less than the mean proportion

surviving for the control if ti

 is greater than the critical value. Since t6 is greater than 2.41, the 512 μg/L

concentration has significantly lower survival than the control. Hence the NOEC and the LOEC for survival are

256 μg/L and 512 μg/L, respectively.

11.13.2.8.7 To quantify the sensitivity of the test, the minimum significant difference (MSD) that can be detected

statistically may be calculated.

MSD ' d Sw (1/n1) % (1/n)

Where: d = the critical value for Dunnett's procedure

SW = the square root of the within mean square

n = the common number of replicates at each concentration 

(this assumes equal replication at each concentration)

 n1 = the number of replicates in the control.
89

11.13.2.8.8 In this example:

MSD ' 2.41(0.155) (1/4) % (1/4)

= 2.41 (0.155)(0.707)

= 0.264

11.13.2.8.9 The MSD (0.264) is in transformed units. To determine the MSD in terms of percent survival, carry

out the following conversion. 

 1. Subtract the MSD from the transformed control mean. 

 1.330 - 0.264 = 1.066 

 2. Obtain the untransformed values for the control mean and the difference calculated in 1. 

 [Sine ( 1.330) ]2

 = 0.943 

 [Sine ( 1.066) ]2

 = 0.766 

 3. The untransformed MSD (MSDu) is determined by subtracting the untransformed values from 2. 

 MSDu = 0.943 - 0.766 = 0.177 

11.13.2.8.10 Therefore, for this set of data, the minimum difference in mean proportion surviving between the

control and any toxicant concentration that can be detected as statistically significant is 0.177.

11.13.2.8.11 This represents a decrease in survival of 19% from the control.
90

TABLE 10. DATA FOR PROBIT ANALYSIS

NaPCP Concentration (μg/L)

Control 32 64 128 256 512

Number Dead 2 6 1 4 9 27

Number Exposed 40 40 40 40 40 40

11.13.2.9 Calculation of the LC50 

11.13.2.9.1 The data used for the Probit Analysis is summarized in Table 10. To perform the Probit Analysis, run

the USEPA Probit Analysis Program. An example of the program input and output is supplied in Appendix I.

11.13.2.9.2 For this example, the chi-square test for heterogeneity was not significant, thus Probit Analysis appears

appropriate for this data.

11.13.2.9.3 Figure 8 shows the output data for the Probit Analysis of the data in Table 10 using the USEPA Probit

Program.

11.13.3 EXAMPLE OF ANALYSIS OF FATHEAD MINNOW, PIMEPHALES PROMELAS, GROWTH DATA

11.13.3.1 Formal statistical analysis of the growth data is outlined in Figure 9. The response used in the statistical

analysis is mean weight per original organism for each replicate. Because this measurement is based on the number

of original organisms exposed (rather than the number surviving), the measured response is a combined survival and

growth endpoint that can be termed biomass. An IC estimate can be calculated for the growth data via a point

estimation technique (see Section 9, Chronic Toxicity Test Endpoints and Data Analysis). Hypothesis testing can

be used to obtain the NOEC for growth. Concentrations above the NOEC for survival are excluded from the

hypothesis test for growth effects.

11.13.3.2 The statistical analysis using hypothesis tests consists of a parametric test, Dunnett's Procedure, and a

nonparametric test, Steel's Many-one Rank Test. The underlying assumptions of the Dunnett's Procedure, normality

and homogeneity of variance, are formally tested. The test for normality is the Shapiro-Wilk's Test and Bartlett's

Test is used to test for homogeneity of variance. If either of these tests fails, the nonparametric test, Steel's

Many-one Rank Test, is used to determine the NOEC and LOEC endpoints. If the assumptions of Dunnett's

Procedure are met, the endpoints are determined by the parametric test.

11.13.3.3 Additionally, if unequal numbers of replicates occur among the concentration levels tested there are

parametric and nonparametric alternative analyses. The parametric analysis is a t test with the Bonferroni

adjustment (see Appendix D). The Wilcoxon Rank Sum Test with the Bonferroni adjustment is the nonparametric

alternative (see Appendix F).
91

Probit Analysis of Fathead Minnow Larval Survival Data 

Proportion

Observed Responding

Number Number Proportion Adjusted for

Conc. Exposed Resp. Responding Controls

Control 40 2 0.0500 0.0000

32.0000 40 6 0.1500 0.0779

64.0000 40 1 0.0250 -.0577

128.0000 40 4 0.1000 0.0237

256.0000 40 9 0.2250 0.1593

512.0000 40 27 0.6750 0.6474

Chi - Square for Heterogeneity (calculated) = 4.522

Chi - Square for Heterogeneity 

 (Tabular value at 0.05 level) = 7.815

Probit Analysis of Fathead Minnow Larval Survival Data

Estimated LC/EC Values and Confidence Limits

 Exposure Lower Upper

Point Conc. 95% Confidence Limits

LC/EC 1.00 127.637 34.590 195.433

LC/EC 50.00 422.696 345.730 531.024

Figure 8. Output for USEPA Probit Analysis Program, Version 1.5
92

Figure 9. Flowchart for statistical analysis of fathead minnow, Pimephales promelas, larval growth data. 
93

TABLE 11. FATHEAD MINNOW, PIMEPHALES PROMELAS, GROWTH DATA

NaPCP Concentration (μg/L)

Replicate Control 32 64 128 256 512

 A 0.711 0.517 0.602 0.566 0.455 -

 B 0.662 0.501 0.669 0.612 0.502 -

 C 0.646 0.723 0.694 0.410 0.606 -

 D 0.690 0.560 0.676 0.672 0.254 -

Mean( ) 0.677 0.575 0.660 0.565 0.454 - Y ̄ i

S 0.00084 0.01032 0.00162 0.01256 0.0218 - 2

i

i 1 2 34 5 6

 TABLE 12. CENTERED OBSERVATIONS FOR SHAPIRO-WILK'S EXAMPLE 

NaPCP Concentration (μg/L)

Replicate Control 32 64 128 256 

A 0.034 -0.058 -0.058 0.001 0.001

B -0.015 -0.074 0.009 0.047 0.048

C -0.031 0.148 0.034 -0.155 0.152

D 0.013 -0.015 0.016 0.107 -0.200

11.13.3.4 The data, mean and variance of the observations at each concentration including the control are listed in

Table 11. A plot of the weight data for each treatment is provided in Figure 10. Since there is significant mortality

in the 512 μg/L concentration, its effect on growth is not considered.

11.13.3.5 Test for Normality

11.13.3.5.1 The first step of the test for normality is to center the observations by subtracting the mean of all the

observations within a concentration from each observation in that concentration. The centered observations are

summarized in Table 12.
94

Figure 10. Plot of weight data from fathead minnow, Pimephales promelas, larval survival and growth test for point es
95

TABLE 13. ORDERED CENTERED OBSERVATIONS FOR SHAPIRO-WILK'S EXAMPLE 

i X(i) i X(i)

1 -0.200 11 0.009

2 -0.155 12 0.013

3 -0.074 13 0.016

4 -0.058 14 0.034

5 -0.058 15 0.034

6 -0.031 16 0.047

7 -0.015 17 0.048

8 -0.015 18 0.107

9 0.001 19 0.148

10 0.001 20 0.152

11.13.3.5.2 Calculate the denominator, D, of the test statistic:

D ' j

n

i'1

(Xi

&X ̄)

2

Where: Xi = the ith centered observation 

X ̄ = the overall mean of the centered observations 

n = the total number of centered observations 

For this set of data, n = 20

X ̄ ' 1

20 (0.004) ' 0.000

D = 0.1414

11.13.3.5.3 Order the centered observations from smallest to largest 

 X(1) # X(2) # ... # X(n)

Where X(i) is the ith ordered observation. These ordered observations are listed in Table 13.

11.13.3.5.4 From Table 4, Appendix B, for the number of observations, n, obtain the coefficients a1, a2, ..., ak

where k is n/2 if n is even and (n-1)/2 if n is odd. For the data in this example, n = 20 and k = 10. The ai values are

listed in Table 14.
96

TABLE 14. COEFFICIENTS AND DIFFERENCES FOR SHAPIRO-WILK'S EXAMPLE

i ai X(n-i+1) - X(i)

1 0.4734 0.352 X(20) - X(1)

2 0.3211 0.303 X(19) - X(2)

3 0.2565 0.181 X(18) - X(3)

4 0.2085 0.106 X(17) - X(4)

5 0.1686 0.105 X(16) - X(5)

6 0.1334 0.065 X(15) - X(6)

7 0.1013 0.049 X(14) - X(7)

8 0.0711 0.031 X(13) - X(8)

9 0.0422 0.012 X(12) - X(9)

10 0.0140 0.008 X(11) - X(10)

11.13.3.5.5 Compute the test statistic, W, as follows:

W ' 1

D [j

k

i'1

ai(X (n&i%1)&X (i))]2

the differences X(n-i+1) - X(i) are listed in Table 14. For this set of data:

W ' 1

0.1414 (0.3666)2 ' 0.9505

11.13.3.5.6 The decision rule for this test is to compare W with the critical value found in Table 6, Appendix B. If

the computed W is less than the critical value, conclude that the data are not normally distributed. For this example,

the critical value at a significance level of 0.01 and 20 observations (n) is 0.868. Since W = 0.9505 is greater than

the critical value, the conclusion of the test is that the data are normally distributed.

11.13.3.6 Test for Homogeneity of Variance 

11.13.3.6.1 The test used to examine whether the variation in mean dry weight is the same across all toxicant

concentrations including the control, is Bartlett's Test (Snedecor and Cochran, 1980). The test statistic is as follows:

B '

[(j

P

i'1

Vi)lnS ̄2

&j

P

i'1

Viln S 2

i ]

C

Where: Vi = degrees of freedom for each toxicant concentration and control, Vi

 = (ni - 1)

ni = the number of replicates for concentration i.
97

ln = loge

i = 1, 2, ..., p where p is the number of concentrations including the control

S ̄2 '

(j

P

i'1

ViS 2

i )

j

P

i'1

Vi

 C ' 1%(3(p&1))&1

[j

P

i'1

1/Vi&(j

P

i'1

Vi)

&1

]

11.13.3.6.2 For the data in this example, (see Table 11) all toxicant concentrations including the control have the

same number of replicates (ni

 = 4 for all i). Thus, Vi = 3 for all i.

11.13.3.6.3 Bartlett's statistic is therefore:

B ' [(15)ln(0.00947)&3j

P

i'1

ln(S 2

i )]/1.133

 = [15(-5.9145) - 3(-26.2842]/1.133 

= 8.8911/1.133 

= 7.847 

11.13.3.6.4 B is approximately distributed as chi-square with p - 1 degrees of freedom, when the variances are in

fact the same. Therefore, the appropriate critical value for this test, at a significance level of 0.01 with four degrees

of freedom, is 13.277. Since B = 7.847 is less than the critical value of 13.277, conclude that the variances are not

different.

11.13.3.7 Dunnett's Procedure

11.13.3.7.1 To obtain an estimate of the pooled variance for the Dunnett's Procedure, construct an ANOVA table

as described in Table 15.
98

TABLE 15. ANOVA TABLE

Source df Sum of Squares Mean Square(MS)

(SS) (SS/df)

 

Between p - 1 SSB S = SSB/(p-1) 2

B

 

Within N - p SSW S = SSW/(N-p) 2

W

Total N - 1 SST

Where: p = number toxicant concentrations including the control 

N = total number of observations n1 + n2 ... + np

ni = number of observations in concentration i 

SSB ' j Between Sum of Squares

P

i'1

T 2

i /ni

&G 2

/N

SST ' ' Total Sum of Squares

P

i'1

'

ni

j'1

Y 2

ij &G 2

/N

SSW ' SST&SSB Within Sum of Squares 

G = the grand total of all sample observations, G ' j

P

i'1

Ti

Ti = the total of the replicate measurements for concentration i

Yij = the jth observation for concentration i (represents the mean dry weight of the fish for toxicant

concentration i in test chamber j) 

11.13.3.7.2 For the data in this example:

n1 = n2 = n3 = n4 = n5 = 4 

N = 20 

T1 = Y11 + Y12 + Y13 + Y14 = 2.709 

T2 = Y21 + Y22 + Y23 + Y24 = 2.301 
99

TABLE 16. ANOVA TABLE FOR DUNNETT'S PROCEDURE EXAMPLE

Source df Sum of Squares Mean Square(MS)

(SS) (SS/df)

Between 4 0.1270 0.0318

Within 15 0.1417 0.0094

Total 19 0.2687

T3 = Y31 + Y32 + Y33 + Y34 = 2.641 

T4 =Y41 + Y42 + Y43 + Y44 = 2.260 

T5 = Y51 + Y52 + Y53 + Y54 = 1.817 

G=T1 + T2 + T3 + T4 + T5 = 11.728

SSB ' j

P

i'1

T 2

i /ni

&G 2

/N

' 1

4

(28.017) & (11.728)2

20 ' 0.1270

 SST ' '

P

i'1

'

ni

j'1

Y 2

ij &G 2

/N

' 7.146 & (11.728)2

20 ' 0.2687

SSW ' SST&SSB = 0.2687 - 0.1270 = 0.1417 

SB

2 = SSB/(p-1) = 0.1270/(5-1) = 0.0318

 

SW

2 = SSW/(N-p) = 0.041/(20-5) = 0.0094 

11.13.3.7.3 Summarize these calculations in the ANOVA table (Table 16).

11.13.3.7.4 To perform the individual comparisons, calculate the t statistic for each concentration, and control

combination as follows: 

t

i ' (Y ̄

1&Y ̄i

)

Sw (1/n1)%(1/ni

)

Where: = mean dry weight for toxicant concentration i Y ̄ i

 
100

 = mean dry weight for the control Y ̄1

SW = square root of the within mean square

n1 = number of replicates for the control

ni = number of replicates for concentration i.

11.13.3.7.5 Table 17 includes the calculated t values for each concentration and control combination. In this example,

comparing the 32 μg/L concentration with the control the calculation is as follows:

t

2 ' (0.677&0.575)

[0.097 (1/4)%(1/4)]

' 1.487

TABLE 17. CALCULATED T VALUES 

NaPCP

Concentration i ti

(μg/L)

32 2 1.487

64 3 0.248

128 4 1.632

256 5 3.251

11.13.3.7.6 Since the purpose of this test is to detect a significant reduction in mean weight, a one-sided test is

appropriate. The critical value for this one-sided test is found in Table 5, Appendix C. For an overall alpha level of

0.05, 15 degrees of freedom for error and four concentrations (excluding the control) the critical value is 2.36. The

mean weight for concentration "i" is considered significantly less than the mean weight for the control if ti

 is greater

than the critical value. Since t5 is greater than 2.36, the 256 μg/L concentration had significantly lower growth than

the control. Hence the NOEC and the LOEC for growth are 128 μg/L and 256 μg/L, respectively.

11.13.3.7.7 To quantify the sensitivity of the test, the minimum significant difference (MSD) that can be

statistically detected may be calculated:

MSD ' d Sw (1/n1) % (1/n)

Where: d = the critical value for the Dunnett's Procedure

SW = the square root of the within mean square

n = the common number of replicates at each concentration 

(this assumes equal replication at each concentration) 

n1 = the number of replicates in the control. 
101

11.13.3.7.8 In this example:

MSD ' 2.36(0.052) (1/4) % (1/4)

= 2.36 (0.097) (0.707)

= 0.162

11.13.3.7.9 Therefore, for this set of data, the minimum difference that can be detected as statistically significant is

0.162 mg. 

11.13.3.7.10 This represents a 24% reduction in mean weight from the control.

11.13.3.8 Calculation of the IC

11.13.3.8.1 The growth data in Table 2 modified to be mean weights per original number of fish are utilized in this

example. As seen in Table 2 and Figure 11, the observed means are not monotonically non-increasing with respect

to concentration (the mean response for each higher concentration is not less than or equal to the mean response for

the previous concentration, and the responses between concentrations do not follow a linear trend). Therefore, the

means are smoothed prior to calculating the IC. In the following discussion, the observed means are represented by

 and the smoothed means by Mi Y ̄ . i

11.13.3.8.2 Starting with the control mean, = 0.677, we see that > . Set M1 Y ̄ = Comparing to , 1 Y ̄1 Y ̄2 Y ̄1 Y ̄2 Y ̄3

Y ̄ < . 2 Y ̄3

11.13.3.8.3 Calculate the smoothed means:

 M2 = M3 = ( + )/2 = 0.618 Y ̄2 Y ̄3

 

11.13.3.8.4 For the remaining observed means, M3 > > > . Thus, M4 becomes , M5 Y ̄ becomes etc., 4 Y ̄5 Y ̄6 Y ̄4 Y ̄5

for the remaining concentrations. Table 18 contains the smoothed means, and Figure 11 provides a plot of the

smoothed concentration response curve.
102

Figure 11. Plot of raw data, observed means, and smoothed means for the fathead minnow, Pimephales promelas, growth data 
103

TABLE 18. FATHEAD MINNOW, PIMEPHALES PROMELAS, MEAN GROWTH RESPONSE AFTER

SMOOTHING

NaPCP Response Smoothed

Conc i means, means, Mi Y ̄ i

(μg/L) (mg) (mg)

Control 1 0.677 0.677

32 2 0.575 0.618

64 3 0.660 0.618

128 4 0.565 0.565

256 5 0.454 0.454

512 6 0.150 0.150

11.13.3.8.5 An IC25 and an IC50 can be estimated using the Linear Interpolation Method. A 25% reduction in

weight, compared to the controls, would result in a mean dry weight of 0.508 mg, where M1(1 - p/100) = 0.677(1 -

25/100). A 50% reduction in weight, compared to the controls, would result in a mean weight of 0.339 mg, where

M1(1 - p/100) = 0.677(1 - 50/100). Examining the smoothed means and their associated concentrations (Table 18),

the response 0.508 mg is bracketed by C4 = 128 μg/L and C5 = 256 μg/L. For the 50% reduction (0.339 mg), the

response (0.339 μg) is bracketed by C5 = 256 μg/L and C6 = 512 μg/L.

11.13.3.8.6 Using the equation in Section 4.2 from Appendix M, the estimate of the IC25 is calculated as follows:

ICp ' Cj

%[M1(1&p/100)&Mj]

(C(j%1)&Cj)

(M(j%1)&Mj

)

IC25 ' 128%[0.677(1&25/100)&0.565] (256&128)

(0.454&0.565)

= 194 μg/L

11.13.3.8.7 Using the equation in Section 4.2 of Appendix M the estimate of the IC50 is calculated as follows:

ICp ' Cj

%[M1(1&p/100)&Mj]

(C(j%1)&Cj)

(M(j%1)&Mj

)

IC50 ' 256%[0.677(1&50/100)&0.454] (512&256)

(0.150&0.454)

= 353 μg/L
104

Conc. ID 1 2 3 4 5 6

Conc. Tested 0 32 64 128 256 512

Response 1 0.711 0.517 0.602 0.566 0.455 0.143

Response 2 0.662 0.501 0.669 0.612 0.502 0.163

Response 3 0.646 0.723 0.694 0.410 0.606 0.195

Response 4 0.690 0.560 0.676 0.672 0.254 0.099

*** Inhibition Concentration Percentage Estimate ***

Toxicant/Effluent: NaPCP

Test Start Date: Example Test Ending Date: 

Test Species: Fathead minnows

Test Duration: 7-d

DATA FILE: fhmanual.icp

OUTPUT FILE: fhmanual.i25

Conc. Number Concentration Response Std. Pooled

ID Replicates μg/l Means Dev. Response Means

1 4 0.000 0.677 0.029 0.677

2 4 32.000 0.575 0.102 0.618

3 4 64.000 0.660 0.040 0.618

4 4 128.000 0.565 0.112 0.565

5 4 256.000 0.454 0.148 0.454

6 4 512.000 0.150 0.040 0.150

The Linear Interpolation Estimate: 193.9503 Entered P Value: 25

Number of Resamplings: 80

The Bootstrap Estimates Mean: 186.4935 Standard Deviation: 52.6094

Original Confidence Limits: Lower: 107.0613 Upper: 285.6449

Expanded Confidence Limits: Lower: 54.9278 Upper: 340.6617

Resampling time in Seconds: 1.81 Random Seed: 1272173518

Figure 12. ICPIN program output for the IC25.

11.13.3.8.8 When the ICPIN program was used to analyze this set of data, requesting 80 resamples, the estimate of

the IC25 was 193.9503 μg/L. The empirical 95% confidence interval for the true mean was (54.9278 μg/L,

340.6617 μg/L). The computer program output for the IC25 for this data set is shown in Figure 12.

11.13.3.8.9 When the ICPIN program was used to analyze this set of data for the IC50, requesting 80 resamples,

the estimate of the IC50 was 353.2884 μg/L. The empirical 95% confidence interval for the true mean was

208.4723 μg/L and 418.5276 μg/L. The computer program output is shown in Figure 13.
105

Conc. ID 1 2 3 4 5 6

Conc. Tested 0 32 64 128 256 512

Response 1 0.711 0.517 0.602 0.566 0.455 0.143

Response 2 0.662 0.501 0.669 0.612 0.502 0.163

Response 3 0.646 0.723 0.694 0.410 0.606 0.195

Response 4 0.690 0.560 0.676 0.672 0.254 0.099

*** Inhibition Concentration Percentage Estimate ***

Toxicant/Effluent: NaPCP

Test Start Date: Example Test Ending Date: 

Test Species: Fathead minnows

Test Duration: 7-d

DATA FILE: fhmanual.icp

OUTPUT FILE: fhmanual.i50

Conc. Number Concentration Response Std. Pooled

ID Replicates μg/l Means Dev. Response Means

1 4 0.000 0.677 0.029 0.677

2 4 32.000 0.575 0.102 0.618

3 4 64.000 0.660 0.040 0.618

4 4 128.000 0.565 0.112 0.565

5 4 256.000 0.454 0.148 0.454

6 4 512.000 0.150 0.040 0.150

The Linear Interpolation Estimate: 353.2884 Entered P Value: 50

Number of Resamplings: 80

The Bootstrap Estimates Mean: 345.1108 Standard Deviation: 37.0938

Original Confidence Limits: Lower: 262.7783 Upper: 394.0629

Expanded Confidence Limits: Lower: 208.4723 Upper: 418.5276

Resampling time in Seconds: 1.87 Random Seed: 1126354766

Figure 13. ICPIN program output for the IC50.
106

TABLE 19. PRECISION OF THE FATHEAD MINNOW, PIMEPHALES PROMELAS, LARVAL SURVIVAL

AND GROWTH TEST, USING NAPCP AS A REFERENCE TOXICANT1,2

Chronic

NOEC LOEC Value 

Test (μg/L) (μg/L) (μg/L)

1 256 512 362

2 128 256 181

3 256 512 362

4 128 256 181

5 128 256 181

 n: 5 5 5

 Mean: NA NA 253.4

1

 From Pickering, 1988.

2

 For a discussion of the precision of data from chronic toxicity tests,

 (see Section 4, Quality Assurance). 

11.14 PRECISION AND ACCURACY

11.14.1 PRECISION – Data on single-laboratory and multilaboratory precision are described below (Subsections

11.14.1.1 and 11.14.1.2). Single-laboratory precision is a measure of the reproducibility of test results when tests

are conducted using a specific method under reasonably constant conditions in the same laboratory. Singlelaboratory precision is synonymous with the terms within-laboratory precision and intralaboratory precision. 

Multilaboratory precision is a measure of the reproducibility of test results from different laboratories using the

same test method and analyzing the same test material. Multilaboratory precision is synonymous with the term

interlaboratory precision. Interlaboratory precision, as used in this document, includes both within-laboratory and

between-laboratory components of variability. In recent multilaboratory studies, these two components of

interlaboratory precision have been displayed separately (termed within-laboratory and between-laboratory

variability) and combined (termed total interlaboratory variability). The total interlaboratory variability that is

reported from these studies is synonymous with interlaboratory variability reported from other studies where

individual variability components are not separated.

11.14.1.1 Single-Laboratory Precision

11.14.1.1.1 Information on the single-laboratory precision of the fathead minnow larval survival and growth test is

presented in Table 19. The range of NOECs was only two concentration intervals, indicating good precision.

11.14.1.1.2 EPA evaluated within-laboratory precision of the Fathead Minnow, Pimephales promelas, Larval

Survival and Growth Test using a database of routine reference toxicant test results from 19 laboratories (USEPA,

2000b). The database consisted of 205 reference toxicant tests conducted in 19 laboratories using a variety of

reference toxicants including: cadmium, chromium, copper, potassium chloride, sodium chloride, sodium

pentachlorophenate, and sodium dodecyl sulfate. Among the 19 laboratories, the median within-laboratory CV

calculated for routine reference toxicant tests was 26% for the IC25 growth endpoint. In 25% of laboratories, the

within-laboratory CV was less than 21%; and in 75% of laboratories, the within-laboratory CV was less than 38%. 
107

11.14.1.2 Multilaboratory Precision

11.14.1.2.1 A multilaboratory study of Method 1000.0 described in the first edition of this manual (USEPA,

1985e), was performed using seven blind samples over an eight month period (DeGraeve et. al., 1988). In this

study, each of the 10 participating laboratories was to conduct two tests simultaneous with each sample, each test

having two replicates of 10 larvae for each of five concentrations and the control. Of the 140 tests planned, 135

were completed. Only nine of the 135 tests failed to meet the acceptance criterion of 80% survival in the controls. 

Of the 126 acceptable survival NOECs reported, an average of 41% were median values, and 89% were within one

concentration interval of the median (Table 20). For the growth (weight) NOECs, an average of 32% were at the

median, and 84% were within one concentration interval of the median (Table 21). Using point estimate techniques,

the precision (CV) of the IC50 was 19.5% for the survival data and 19.8% for the growth data. If the mean weight

acceptance criterion of 0.25 mg for the surviving control larvae, which is included in this revised edition of the

method, had applied to the test results of the interlaboratory study, one third of the 135 tests would have failed to

meet the test criteria (Norberg-King, personal communication and 1989 memorandum; DeGraeve et al., 1991). 

11.14.1.2.2 In 2000, EPA conducted an interlaboratory variability study of the Fathead Minnow, Pimephales

promelas, Larval Survival and Growth Test (USEPA, 2001a; USEPA, 2001b). In this study, each of 27 participant

laboratories tested 3 or 4 blind test samples that included some combination of blank, effluent, reference toxicant,

and receiving water sample types. The blank sample consisted of moderately-hard synthetic freshwater, the effluent

sample was a municipal wastewater spiked with KCl, the receiving water sample was a river water spiked with KCl,

and the reference toxicant sample consisted of moderately-hard synthetic freshwater spiked with KCl. Of the 101

Fathead Minnow Larval Survival and Growth tests conducted in this study, 98.0% were successfully completed and

met the required test acceptability criteria. Of 24 tests that were conducted on blank samples, none showed false

positive results for survival endpoints, and only one resulted in false positive results for the growth endpoint,

yielding a false positive rate of 4.35%. Results from the reference toxicant, effluent, and receiving water sample

types were used to calculate the precision of the method. Table 22 shows the precision of the IC25 for each of these

sample types. Averaged across sample types, the total interlaboratory variability (expressed as a CV%) was 20.9%

for IC25 results. Table 23 shows the frequency distribution of survival and growth NOEC endpoints for each

sample type. For the survival endpoint, NOEC values spanned four concentrations for the reference toxicant sample

type and two concentrations for the effluent and receiving water sample types. The percentage of values within one

concentration of the median was 97.2%, 100%, and 100% for the reference toxicant, effluent, and receiving water

sample types, respectively. For the growth endpoint, NOEC values spanned five concentrations for the reference

toxicant sample type and four concentrations for the effluent and receiving water sample types. The percentage of

values within one concentration of the median was 86.1%, 91.7%, and 76.9% for the reference toxicant, effluent,

and receiving water sample types, respectively. 

11.14.2 ACCURACY 

11.14.2.1 The accuracy of toxicity tests cannot be determined.
108

TABLE 20. COMBINED FREQUENCY DISTRIBUTION FOR SURVIVAL NOECs FOR ALL

LABORATORIES1

NOEC Frequency (%) Distribution

Tests with Two Reps Tests with Four Reps

Sample Median ± 12 > 23 Median ± 12 > 23

1. Sodium Pentachlorophenate (A) 35 53 12 57 29 14 

2. Sodium Pentachlorophenate (B) 42 42 16 56 44 0 

3. Potassium Dichromate (A) 47 47 6 75 25 0 

4. Potassium Dichromate (B) 41 41 18 50 50 0 

5. Refinery Effluent 301 26 68 6 78 22 0 

6. Refinery Effluent 401 37 53 10 56 44 0 

7. Utility Waste 501 56 33 11 56 33 11 

1

 From DeGraeve et al., 1988. 

2

 Percent of values at one concentration interval above or below the median. Adding this percentage to the percent 

of values at the median yields the percent of values within one concentration interval of the median. 3 Percent of values two or more concentration intervals above or below the median.
109

TABLE 21. COMBINED FREQUENCY DISTRIBUTION FOR WEIGHT NOECs FOR ALL

LABORATORIES1

NOEC Frequency (%) Distribution

Tests with Two Reps Tests with Four Reps

Sample Median ± 12 > 23 Median ± 12 > 23 

1. Sodium Pentachlorophenate (A) 59 41 0 57 43 0

2. Sodium Pentachlorophenate (B) 37 63 0 22 45 33

3. Potassium Dichromate (A) 35 47 18 88 0 12

4. Potassium Dichromate (B) 12 47 41 63 25 12

5. Refinery Effluent 301 35 53 12 75 25 0

6. Refinery Effluent 401 37 47 16 33 56 11

7. Utility Waste 501 11 61 28 33 56 11

1

 From DeGraeve et al., 1988.

2

 Percent of values at one concentration interval above or below the median. Adding this percentage to the

percent of values at the median yields the percent of values within one concentration interval of the median. 3 Percent of values two or more concentration intervals above or below the median.
110

TABLE 22. PRECISION OF POINT ESTIMATES FOR VARIOUS SAMPLE TYPES1

Test Endpoint Sample Type

CV (%)2

Within-lab3 Between-lab4 Total5

IC25 Reference toxicant 10.0 17.2 19.9

Effluent 19.1 12.9 23.1

Receiving water - - 19.8

Average 14.6 15.0 20.9

1 From EPA’s WET Interlaboratory Variability Study (USEPA, 2001a; USEPA, 2001b). 2 CVs were calculated based on the within-laboratory component of variability, the between-laboratory

component of variability, and total interlaboratory variability (including both within-laboratory and betweenlaboratory components). For the receiving water sample type, within-laboratory and between-laboratory

components of variability could not be calculated since the study design did not provide within-laboratory

replication for this sample type. 3 The within-laboratory component of variability for duplicate samples tested at the same time in the same

laboratory. 4 The between-laboratory component of variability for duplicate samples tested at different laboratories.. 5 The total interlaboratory variability, including within-laboratory and between-laboratory components of

variability. The total interlaboratory variability is synonymous with interlaboratory variability reported from

other studies where individual variability components are not separated. 
111

TABLE 23. FREQUENCY DISTRIBUTION OF HYPOTHESIS TESTING RESULTS FOR VARIOUS

SAMPLE TYPES1

Test Endpoint Sample Type

Median

NOEC

Value

% of Results at

the Median

% of Results

±12

% of Results 

$23

Survival NOEC Reference toxicant 50% 75.0 22.2 2.78

Effluent 12.5% 76.9 23.1 0.00

Receiving water 25% 69.2 30.8 0.00

Growth 

NOEC Reference toxicant 50% 58.3 27.8 13.9

Effluent 12.5% 66.7 25.0 8.33

Receiving water 12.5% 30.8 46.1 23.1

1 From EPA’s WET Interlaboratory Variability Study (USEPA, 2001a; USEPA, 2001b). 2 Percent of values at one concentration interval above or below the median. Adding this percentage to the

percent of values at the median yields the percent of values within one concentration interval of the median. 3 Percent of values two or more concentration intervals above or below the median.
112

SECTION 12

TEST METHOD

FATHEAD MINNOW, PIMEPHALES PROMELAS,

EMBRYO-LARVAL SURVIVAL AND TERATOGENICITY TEST

METHOD 1001.0

12.1 SCOPE AND APPLICATION

12.1.1 This method estimates the chronic toxicity of whole effluents and receiving water to the fathead minnow,

Pimephales promelas, using embryos in a seven-day, static renewal test. The effects include the synergistic,

antagonistic, and additive effects of all the chemical, physical, and biological components which adversely affect

the physiological and biochemical functions of the test organisms. The test is useful in screening for teratogens

because organisms are exposed during embryonic development.

12.1.2 Daily observations on mortality make it possible to also calculate the acute toxicity for desired exposure

periods (i.e., 24-h, 48-h, 96-h LC50s).

12.1.3 Detection limits of the toxicity of an effluent or pure substance are organism dependent.

12.1.4 Brief excursions in toxicity may not be detected using 24-h composite samples. Also, because of the long

sample collection period involved in composite sampling, and because the test chambers are not sealed, highly

degradable and highly volatile toxicants, in the source may not be detected in the test. 

12.1.5 This test method is commonly used in one of two forms: (1) a definitive test, consisting of a minimum of

five effluent concentrations and a control, and (2) a receiving water test(s), consisting of one or more receiving

water concentrations and a control. 

12.2 SUMMARY OF METHOD

12.2.1 Fathead minnow, Pimephales promelas, embryos are exposed in a static renewal system to different

concentrations of effluent or to receiving water for seven days, starting shortly after fertilization of the eggs. Test

results are based on the total frequency of both mortality and gross morphological deformities (terata). 

12.3 INTERFERENCES

12.3.1 Toxic substances may be introduced by contaminants in dilution water, glassware, sample hardware, and

testing equipment (see Section 5, Facilities, Equipment, and Supplies).

12.3.2 Adverse effects of low dissolved oxygen (DO), high concentrations of suspended and/or dissolved solids,

and extremes of pH may mask the presence of toxic substances.

12.3.3 Improper effluent sampling and sample handling may adversely affect test results (see Section 8, Effluent

and Receiving Water Sampling, Sample Handling, and Sample Preparation for Toxicity Tests). 

12.3.4 Pathogenic and/or predatory organisms in the dilution water and effluent may affect test organism survival

and confound test results.

12.3.5 pH drift during the test may contribute to artifactual toxicity when ammonia or other pH-dependent

toxicants (such as metals) are present. As pH increases, the toxicity of ammonia also increases (see Subsection

8.8.6), so upward pH drift may increase sample toxicity. For metals, toxicity may increase or decrease with
113

increasing pH. Lead and copper were found to be more acutely toxic at pH 6.5 than at pH 8.0 or 8.5, while nickel

and zinc were more toxic at pH 8.5 than at pH 6.5 (USEPA, 1992). In situations where sample toxicity is confirmed

to be artifactual and due to pH drift (as determined by parallel testing as described in Subsection 12.3.5.1), the

regulatory authority may allow for control of sample pH during testing using procedures outlined in Subsection

12.3.5.2. It should be noted that artifactual toxicity due to pH drift is not likely to occur unless pH drift is large

(more than 1 pH unit) and/or the concentration of some pH-dependent toxicant in the sample is near the threshold

for toxicity. 

12.3.5.1 To confirm that toxicity is artifactual and due to pH drift, parallel tests must be conducted, one with

controlled pH and one with uncontrolled pH. In the uncontrolled-pH treatment, the pH is allowed to drift during the

test. In the controlled-pH treatment, the pH is maintained using the procedures described in Subsection 12.3.5.2. 

The pH to be maintained in the controlled-pH treatment (or target pH) will depend on the objective of the test. If

the objective of the WET test is to determine the toxicity of the effluent in the receiving water, the pH should be

maintained at the pH of the receiving water (measured at the edge of the regulatory mixing zone). If the objective

of the WET test is to determine the absolute toxicity of the effluent, the pH should be maintained at the pH of the

sample upon completion of collection (as measured on an aliquot removed from the sample container).

12.3.5.1.1 During parallel testing, the pH must be measured in each treatment at the beginning (i.e., initial pH) and

end (i.e., final pH) of each 24-h exposure period. For each treatment, the mean initial pH (e.g., averaging the initial

pH measured each day for a given treatment) and the mean final pH (e.g., averaging the final pH measured each day

for a given treatment) must be reported. pH measurements taken during the test must confirm that pH was

effectively maintained at the target pH in the controlled-pH treatment. For each treatment, the mean initial pH and

the mean final pH should be within ±0.2 pH units of the target pH. Test procedures for conducting toxicity

identification evaluations (TIEs) also recommend maintaining pH within ± 0.2 pH units in pH-controlled tests

(USEPA, 1992).

12.3.5.1.2 Total ammonia also should be measured in each treatment at the outset of parallel testing. Total

ammonia concentrations greater than 5 mg/L in the 100% effluent are an indicator that toxicity observed in the test

may be due to ammonia (USEPA, 1992). 

12.3.5.1.3 Results from both of the parallel tests (pH-controlled and uncontrolled treatments) must be reported to

the regulatory authority. If the uncontrolled test meets test acceptability criteria and shows no toxicity at the

permitted instream waste concentration, then the results from this test should be used for determining compliance. 

If the uncontrolled test shows toxicity at the permitted instream waste concentration, then the results from the pHcontrolled test should be used for determining compliance, provided that this test meets test acceptability criteria

and pH was properly controlled (see Subsection 12.3.6.1.1). 

12.3.5.1.4 To confirm that toxicity observed in the uncontrolled test was artifactual and due to pH drift, the results

of the controlled and uncontrolled-pH tests are compared. If toxicity is removed or reduced in the pH-controlled

treatment, artifactual toxicity due to pH drift is confirmed for the sample. To demonstrate that a sample result of

artifactual toxicity is representative of a given effluent, the regulatory authority may require additional information

or additional parallel testing before pH control (as described in Subsection 12.3.5.2) is applied routinely to

subsequent testing of the effluent. 

12.3.5.2 The pH can be controlled with the addition of acids and bases and/or the use of a CO2-controlled

atmosphere over the test chambers. pH is adjusted with acids and bases by dropwise adding 1N NaOH or 1N HCl

(see Subsection 8.8.8). The addition of acids and bases should be minimized to reduce the amount of additional

ions (Na or Cl) added to the sample. pH is then controlled using the CO2-controlled atmosphere technique. This

may be accomplished by placing test solutions and test organisms in closed headspace test chambers, and then

injecting a predetermined volume of CO2 into the headspace of each test chamber (USEPA, 1991b; USEPA, 1992);

or by placing test chambers in an atmosphere flushed with a predetermined mixture of CO2 and air (USEPA, 1996). 

Prior experimentation will be needed to determine the appropriate CO2/air ratio or the appropriate volume of CO2 to

inject. This volume will depend upon the sample pH, sample volume, container volume, and sample constituents. 
114

If more than 5% CO2 is needed, adjust the solutions with acids (1N HCl) and then flush the headspace with no more

than 5% CO2 (USEPA, 1992). If the objective of the WET test is to determine the toxicity of the effluent in the

receiving water, CO2 is injected to maintain the test pH at the pH of the receiving water (measured at the edge of the

regulatory mixing zone). If the objective of the WET test is to determine the absolute toxicity of the effluent, CO2 is

injected to maintain the test pH at the pH of the sample upon completion of collection. USEPA (1991b; 1992) and

Mount and Mount (1992) provide techniques and guidance for controlling test pH using a CO2-controlled

atmosphere. In pH-controlled testing, control treatments must be subjected to all manipulations that sample

treatments are subjected to. These manipulations must be shown to cause no lethal or sublethal effects on control

organisms. In pH-controlled testing, the pH also must be measured in each treatment at the beginning and end of

each 24-h exposure period to confirm that pH was effectively controlled at the target pH level. 

12.4 SAFETY

12.4.1 See Section 3, Health and Safety. 

12.5 APPARATUS AND EQUIPMENT

12.5.1 Fathead minnow and brine shrimp culture units -- See Section 11, Fathead Minnow, Pimephales Promelas,

Larval Survival and Growth Test, and USEPA, 2002a. To test effluent toxicity on-site or in the laboratory,

sufficient numbers of newly fertilized eggs must be available, preferably from a laboratory fathead minnow culture

unit. If necessary, embryos can be shipped in well oxygenated water in insulated containers. In cases where

shipping is necessary, up to 48-h old embryos may be used for the test.

12.5.2 Samplers -- automatic sampler, preferably with sample cooling capability, that can collect a 24-h composite

sample of 5 L or more.

12.5.3 Sample containers -- for sample shipment and storage (see Section 8, Effluent and Receiving Water

Sampling, Sample Handling, and Sample Preparation for Toxicity Tests). 

12.5.4 Environmental chamber or equivalent facility with temperature control (25 ± 1EC). 

12.5.5 Water purification system -- MILLIPORE MILLI-Q®, deionized water or equivalent (see Section 5,

Facilities, Equipment, and Supplies).

12.5.6 Balance -- analytical, capable of accurately weighing to 0.00001 g.

12.5.7 Reference weights, Class S -- for checking performance of balance. Weights should bracket the expected

weights of material to be weighed.

12.5.8 Test chambers -- four borosilicate glass or disposable, non-toxic plastic labware, per test solution, such as: 

500-mL beakers; 100 mm x 15 mm or 100 mm x 20 mm glass or disposable polystyrene Petri dishes; or 12-cm OD,

stackable "Carolina" culture dishes. The chambers should be covered with safety glass plates or sheet plastic during

the test to avoid potential contamination from the air and excessive evaporation of the test solutions during the test.

12.5.9 Dissecting microscope, or long focal length magnifying lens, hand or stand supported -- for examining

embryos and larvae in the test chambers.

12.5.10 Light box, microscope lamp, or flashlight -- for illuminating chambers during examination and observation

of embryos and larvae. 

12.5.11 Volumetric flasks and graduated cylinders -- Class A, borosilicate glass or non-toxic plastic labware,

10-1000 mL, for making test solutions.
115

12.5.12 Volumetric pipets -- Class A, 1-100 mL. 

12.5.13 Serological pipets -- 1-10 mL, graduated.

12.5.14 Pipet bulbs and fillers -- PROPIPET®, or equivalent. 

12.5.15 Droppers, and glass tubing with fire polished edges, 2-mm ID -- for transferring embryos, and 4-mm ID --

for transferring larvae. 

12.5.16 Wash bottles -- for washing embryos from substrates and containers and for rinsing small glassware and

instrument electrodes and probes.

12.5.17 Thermometers, glass or electronic, laboratory grade -- for measuring water temperatures.

12.5.18 Bulb-thermograph or electronic-chart type thermometers -- for continuously recording temperature.

12.5.19 Thermometer, National Bureau of Standards Certified (see USEPA Method 170.1, USEPA 1979b) -- to

calibrate laboratory thermometers.

12.5.20 Meters, pH, DO, and specific conductivity -- for routine physical and chemical measurements.

12.6 REAGENTS AND CONSUMABLE MATERIALS

12.6.1 Sample containers -- for sample shipment and storage (see Section 8, Effluent and Receiving Water

Sampling, Sample Handling and Sample Preparation for Toxicity Tests).

12.6.2 Data sheets (one set per test) -- for recording data.

12.6.3 Tape, colored -- for labelling test chambers.

12.6.4 Markers, waterproof -- for marking containers, etc.

12.6.5 Reagents for hardness and alkalinity tests -- see USEPA Methods 130.2 and 310.1, USEPA 1979b. 

12.6.6 Membranes and filling solutions for DO probe (see USEPA Method 360.1, USEPA 1979b), or reagents --

for modified Winkler analysis. 

12.6.7 Standard pH buffers, pH 4, pH 7, and pH 10 (or as per instructions of instrument manufacturer) -- for

instrument calibration (see USEPA Method 150.1, USEPA 1979b). 

12.6.8 Specific conductivity standards -- see USEPA Method 120.1, USEPA 1979b.

12.6.9 Laboratory quality control samples and standards -- for calibration of the above methods.

12.6.10 Reference toxicant solutions -- see Section 4, Quality Assurance.

12.6.11 Reagent water -- defined as distilled or deionized water which does not contain substances which are toxic

to the test organisms (see Section 5, Facilities, Equipment, and Supplies). 

12.6.12 Effluent, receiving water, and dilution water -- see Section 7, Dilution Water; and Section 8, Effluent and

Receiving Water Sampling, Sample Handling, and Sample Preparation for Toxicity Tests.
116

12.6.13 TEST ORGANISMS, FATHEAD MINNOWS, PIMEPHALES PROMELAS

12.6.13.1 Fathead minnow embryos, less than 36-h old, are used for the test. The test is conducted with four

(minimum of three) test chambers at each toxicant concentration and control. Fifteen (minimum of ten) embryos are

placed in each replicate test chamber. Thus 60 (minimum of 30) embryos are exposed at each test concentration and

360 (minimum of 180) embryos would be needed for a test consisting of five effluent concentrations and a control.

12.6.13.2 Sources of Organisms

12.6.13.2.1 It is recommended that the embryos be obtained from inhouse cultures or other local sources if at all

possible, because it is often difficult to ship the embryos so that they will be less than 36 h old for beginning the

test. Receipt of embryos via Express Mail, air express, or other carrier, from a reliable outside source is an

acceptable alternative, but they must not be over 48 h old when used to begin the test.

12.6.13.2.2 Culturing methods for fathead minnows, Pimephales promelas, are described in Section 6, Section 11

and in USEPA, 2002a.

12.6.13.2.3 Fish obtained from outside sources (see Section 5, Facilities, Equipment, and Supplies) such as

commercial biological supply houses for use as brood stock should be guaranteed to be (1) of the correct species,

(2) disease free, (3) in the requested age range, and (4) in good condition. This can be done by providing the record

of the date on which the eggs were laid and hatched, and information on the sensitivity of the contemporary fish to

reference toxicants. 

12.6.13.3 Obtaining Embryos for Toxicity Tests from Inhouse Cultures.

12.6.13.3.1 Spawning substrates with the newly-spawned, fertilized embryos are removed from the spawning tanks

or ponds, and the embryos are separated from the spawning substrate by using the index finger and rolling the

embryos gently with a circular movement of the finger (see Gast and Brungs, 1973). The embryos are then

combined and washed from the spawning substrate onto a 400 μm NITEX® screen, sprayed with a stream of

deionized water to remove detritus and food particles, and back-washed with dilution water into a crystallizing dish

for microscopic examination. Damaged and infertile eggs are discarded.

12.6.13.3.2 The embryos from three or more spawns are pooled in a single container to provide a sufficient

number to conduct the tests. These embryos may be used immediately to start a test inhouse or may be transported

for use at a remote location. When transportation is required, embryos should be taken from the substrates within

12 h of spawning. This permits off-site tests to be started with less than 36-h old embryos. Embryos should be

transported or shipped in clean, opaque, insulated containers, in well aerated or oxygenated fresh culture or dilution

water, and should be protected from extremes of temperature and any other stressful conditions during transport.

Instantaneous changes of water temperature when embryos are transferred from culture unit water to test dilution

water, or from transport container water to on-site test dilution water, should be less than 2EC. Sudden changes in

pH, dissolved ions, osmotic strength, and DO should be avoided.

12.7 EFFLUENT AND RECEIVING WATER COLLECTION, PRESERVATION, AND STORAGE

12.7.1 See Section 8, Effluent and Receiving Water Sampling, Sample Handling, and Sample Preparation for

Toxicity Tests.

12.8 CALIBRATION AND STANDARDIZATION

12.8.1 See Section 4, Quality Assurance.
117

12.9 QUALITY CONTROL

12.9.1 See Section 4, Quality Assurance.

12.10 TEST PROCEDURES

12.10.1 TEST SOLUTIONS 

12.10.1.1 Receiving Waters 

12.10.1.1.1 The sampling point is determined by the objectives of the test. Receiving water toxicity is determined

with samples used directly as collected or after samples are passed through a 60 μm NITEX® filter and compared

without dilution, against a control. Using four replicate chambers per test, each containing 100 mL, and 400 mL for

chemical analysis, would require approximately one liter, or more, of sample per test day.

12.10.1.2 Effluents

12.10.1.2.1 The selection of the effluent test concentrations should be based on the objectives of the study. A

dilution factor of 0.5 is commonly used. A dilution factor of 0.5 provides precision of ± 100%, and testing of

concentrations between 6.25% and 100% effluent using only five effluent concentrations (6.25%, 12.5%, 25%,

50%, and 100%). Improvements in precision decline rapidly if the dilution factor is increased beyond 0.5 and

precision declines rapidly if a smaller dilution factor is used. Therefore, USEPA recommends the use of the $

0.5 dilution factor.

12.10.1.2.2 If the effluent is known or suspected to be highly toxic, a lower range of effluent concentrations should

be used (such as 25%, 12.5%, 6.25%, 3.12%, and 1.56%). If a high rate of mortality is observed during the first

1 to 2 h of the test, additional dilutions should be added at the lower range of effluent concentrations.

12.10.1.2.3 The volume of effluent required for daily renewal of four replicates per concentration, each containing

100 mL of test solution, is 1.5 L. Sufficient test solution (approximately 1000 mL) is prepared at each effluent

concentration to provide 400 mL additional volume for chemical analyses. If the sample is used for more than one

daily renewal of test solutions, the volume must be increased proportionately. 

12.10.1.2.4 Tests should begin as soon as possible, preferably within 24 h of sample collection. The maximum

holding time following retrieval of the sample from the sampling device should not exceed 36 h for the off-site

toxicity tests unless permission is granted by the permitting authority. In no case should the sample be used for the

first time in a test more than 72 h after sample collection (see Section 8, Effluent and Receiving Water Sampling,

Sample Handling, and Sample Preparation for Toxicity Tests).

12.10.1.2.5 Just prior to test initiation (approximately 1 h) the temperature of sufficient quantity of the sample to

make the test solutions should be adjusted to the test temperature and maintained at that temperature during the

addition of dilution water. 

12.10.1.2.6 The DO of the test solutions should be checked prior to test initiation. If any of the solutions are

supersaturated with oxygen, all of the solutions and the control should be gently aerated. If any solution has a DO

below 4.0 mg/L, all of the solutions and the control must be gently aerated.

12.10.1.3 Dilution Water

12.10.1.3.1 Dilution water may be uncontaminated receiving water, a standard synthetic (reconstituted) water, or

some other uncontaminated natural water (see Section 7, Dilution Water).
118

12.10.1.3.2 If the hardness of the test solutions (including the control) does not equal or exceed 25 mg/L as

CaCO3, it may be necessary to adjust the hardness by adding reagents for synthetic softwater as listed in Table 3,

Section 7. In this case parallel tests should be conducted, one with the hardness adjusted and one unadjusted.

12.10.2 START OF THE TEST

12.10.2.1 Label the test chambers with a marking pen and use color-coded tape to identify each treatment and

replicate. A minimum of five effluent concentrations and a control are used for each effluent test. Each treatment

(including the control) should have four (minimum of three) replicates.

12.10.2.2 Tests performed in laboratories that have inhouse fathead minnow breeding cultures must initiate tests

with embryos less than 36 h old. When the embryos must be shipped to the test site from a remote location, it may

be necessary to use embryos older than 36 h because of the difficulty of coordinating test organism shipments with

field operations. However, in the latter case, the embryos must not be more than 48 h old at the start of the test and

should all be within 24 h of the same age.

12.10.2.3 Randomize the position of the test chambers at the beginning of the test (see Appendix A). Maintain the

chambers in this configuration throughout the test. Preparation of a position chart may be helpful. 

12.10.2.4 The test organisms should come from a pool of embryos consisting of at least three separate spawnings. 

Gently agitate and mix the embryos to be used in the test in a large container so that eggs from different spawns are

thoroughly mixed. 

12.10.2.5 Using a small bore (2 mm ID) glass tube, the embryos are placed one or two at a time into each

randomly arranged test chamber or intermediate container in sequential order, until each chamber contains 15

(minimum of 10) embryos, for a total of 60 (minimum of 30) embryos for each concentration (see Appendix A). 

The amount of water added to the chambers when transferring the embryos to the compartments should be kept to a

minimum to avoid unnecessary dilution of the test concentrations. 

12.10.2.6 After the embryos have been distributed to each test chamber, examine and count them. Remove and

discard damaged or infertile eggs and replace with new undamaged embryos. Placing the test chambers on a light

table may facilitate examining and counting the embryos.

12.10.3 LIGHT, PHOTOPERIOD AND TEMPERATURE 

12.10.3.1 The light quality and intensity should be at ambient laboratory levels, which is approximately 10-20

μE/m2

/s, or 50 to 100 foot candles (ft-c), with a photoperiod of 16 h of light and 8 h of darkness. The water

temperature in the test chambers should be maintained at 25 ± 1EC. 

12.10.4 DISSOLVED OXYGEN (DO) CONCENTRATION

12.10.4.1 Aeration may affect the toxicity of effluents and should be used only as a last resort to maintain

satisfactory DO concentrations. The DO concentrations should be measured in the new solutions at the start of the

test (Day 0) and before daily renewal of the new solutions on subsequent days. The DO concentrations should not

fall below 4.0 mg/L (see Section 8, Effluent and Receiving Water Sampling, Sample Handling, and Sample

Preparation for Toxicity Tests). If it is necessary to aerate, all concentrations and the control should be aerated. 

The aeration rate should not exceed 100 bubbles/min, using a pipet with an orifice of approximately 1.5 mm, such

as a l-mL KIMAX® serological Pipet, or equivalent. Care should be taken to ensure that turbulence resulting from

the aeration does not cause undue physical stress to the embryos.

12.10.5 FEEDING 

12.10.5.1 Feeding is not required.
119

12.10.6 OBSERVATIONS DURING THE TEST

12.10.6.1 Routine Chemical and Physical Determinations

12.10.6.1.1 DO is measured at the beginning and end of each 24-h exposure period in at least one test chamber at

each test concentrations and in the control.

12.10.6.1.2 Temperature and pH are measured at the end of each 24-h exposure period in at least one test chamber

at each test concentration and in the control. Temperature should also be monitored continuously or observed and

recorded daily for at least two locations in the environmental control system or the samples. Temperature should be

measured in a sufficient number of test vessels, at least at the end of the test, to determine temperature variation in

the environmental chamber.

12.10.6.1.3 The pH is measured in the effluent sample each day before new test solutions are made.

12.10.6.1.4 Conductivity, alkalinity and hardness are measured in each new sample (100% effluent or receiving

water) and in the control.

12.10.6.2 Record all the measurements on the data sheet (Figure 1).

12.10.6.3 Routine Biological Observations 

12.10.6.3.1 At the end of the first 24 h of exposure, before renewing the test solutions, examine the embryos. 

Remove the dead embryos (milky colored and opaque) and record the number (Figure 2). If the rate of mortality

(including those with fungal infection) exceeds 20% in the control chambers, or if excessive non-concentrationrelated mortality occurs, terminate the test and start a new test with new embryos. 

12.10.6.3.2 At 25EC, hatching may begin on the fourth day. After hatching begins, count the number of dead and

live embryos and the number of hatched, dead, live, and deformed larvae, daily. Deformed larvae are those with

gross morphological abnormalities such as lack of appendages, lack of fusiform shape (non-distinct mass), lack of

mobility, a colored, beating heart in an opaque mass, or other characteristics that preclude survival. Count and

remove dead embryos and larvae as previously discussed and record the numbers for all of the test observations

(Figure 2). Upon hatching, deformed larvae are counted as dead.

12.10.6.3.3 Protect the embryos and larvae from unnecessary disturbance during the test by carrying out the daily

test observations, solution renewals, and removal of dead organisms carefully. Make sure that the test organisms

remain immersed during the performance of the above operations.

12.10.7 DAILY CLEANING OF TEST CHAMBERS

12.10.7.1 Since feeding is not required, test chambers are not cleaned daily unless accumulation of particulate

matter at the bottom of the chambers causes a problem.

12.10.8 TEST SOLUTION RENEWAL 

12.10.8.1 Freshly prepared solutions are used to renew the tests daily. For on-site toxicity studies, fresh effluent or

receiving water samples should be collected daily, and no more than 24 h should elapse between collection of the

samples and their use in the tests (see Section 8, Effluent and Receiving Water Sampling, Sample Handling and

Sample Preparation for Toxicity Tests). For off-site tests, a minimum of three samples are collected, preferably on

days one, three, and five. Maintain the samples in the refrigerator at 0-6EC until used.

12.10.8.2 The test solutions are renewed immediately after removing dead embryos and/or larvae. During the

daily renewal process, the water level in each chamber is lowered to a depth of 7 to 10 mm, which leaves 15 to 20%

of the test solution. New test solution should be added slowly by pouring down the side of the test chamber to

avoid excessive turbulence and possible injury to the embryos or larvae. 
120

Discharger: Test Dates:

Location: Analyst:

Control:

Day

1 2 3 4 5 6 7 Remarks

Temp.

D.O. Initial

Final

pH Initial

Final

Alkalinity

Hardness

Conductivity

Chlorine

Conc:

Day

1 2 3 4 5 6 7 Remarks

Temp.

D.O. Initial

Final

pH Initial

Final

Alkalinity

Hardness

Conductivity

Chlorine

Conc:

Day

1 2 3 4 5 6 7 Remarks

Temp.

D.O. Initial

Final

pH Initial

Final

Alkalinity

Hardness

Conductivity

Chlorine

Figure 1. Data form for the fathead minnow, Pimephales promelas, embryo-larval survival and teratogenicity

test. Routine chemical and physical determinations.
121

Discharger: Test Dates:

Location: Analyst:

Control:

Day

1 2 3 4 5 6 7 Remarks

Temp.

D.O. Initial

Final

pH Initial

Final

Alkalinity

Hardness

Conductivity

Chlorine

Conc:

Day

1 2 3 4 5 6 7 Remarks

Temp.

D.O. Initial

Final

pH Initial

Final

Alkalinity

Hardness

Conductivity

Chlorine

Conc:

Day

1 2 3 4 5 6 7 Remarks

Temp.

D.O. Initial

Final

pH Initial

Final

Alkalinity

Hardness

Conductivity

Chlorine

Figure 1. Data form for the fathead minnow, Pimephales promelas, embryo-larval survival and teratogenicity

test. Routine chemical and physical determinations (CONTINUED)
122

Discharger: Test Dates:

Location: Analyst:

Conc: Rep.

No.

Condition of

Embryo/larvae

Day

12 3 4 5 6 7

Control

1 Live/dead

Terata

2 Live/dead

Terata

3 Live/dead

Terata

4 Live/dead

Terata

Treatment 1 Live/dead

Terata

2 Live/dead

Terata

3 Live/dead

Terata

4 Live/dead

Terata

Treatment 1 Live/dead

Terata

2 Live/dead

Terata

3 Live/dead

Terata

4 Live/dead

Terata

Treatment 1 Live/dead

Terata

2 Live/dead

Terata

3 Live/dead

Terata

4 Live/dead

Terata

Figure 2. Data form for the fathead minnow, Pimephales promelas, embryo-larval survival and teratogenicity

test. Survival and terata data.
123

Discharger: Test Dates:

Location: Analyst:

Conc: Rep.

No.

Condition of

Embryo/larvae

Day

12 3 4 5 6 7

Treatment 1 Live/dead

Terata

2 Live/dead

Terata

3 Live/dead

Terata

4 Live/dead

Terata

Treatment 1 Live/dead

Terata

2 Live/dead

Terata

3 Live/dead

Terata

4 Live/dead

Terata

Comments:

Figure 2. Data form for the fathead minnow, Pimephales promelas, embryo-larval survival and teratogenicity

test. Survival and terata data (CONTINUED).
124

12.10.9 TERMINATION OF THE TEST 

12.10.9.1 The test is terminated after seven days of exposure. Count the number of surviving, dead, and deformed

larvae, and record the numbers of each (Figure 2). The deformed larvae are treated as dead in the analysis of the

data. Keep a separate record of the total number and percent of deformed larvae for use in reporting the

teratogenicity of the test solution.

12.10.9.2 Prepare a summary of the data as illustrated in Figure 3.

12.11 SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA

12.11.1 A summary of test conditions and test acceptability criteria is presented in Table 1.

12.12 ACCEPTABILITY OF TEST RESULTS

12.12.1 For the test results to be acceptable, survival in the controls must be at least 80%.
125

Discharger: Test Dates: 

Location: Analyst: 

Treatment Control

No. dead

embryos and

larvae

No. terata

Total

mortality

(dead and

deformed)

Total

mortality (%)

Terata (%)

Hatch (%)

Comments:

Figure 3. Summary data for the fathead minnow, Pimephales promelas, embryo-larval survival and

teratogenicity test. 
126

TABLE 1. SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA FOR

FATHEAD MINNOW, PIMEPHALES PROMELAS, EMBRYO-LARVAL SURVIVAL AND

TERATOGENICITY TOXICITY TESTS WITH EFFLUENTS AND RECEIVING WATERS

(TEST METHOD 1001.0)1

 

 1. Test type: Static renewal (required) 

2. Temperature: 25 ± 1EC (recommended)

Test temperatures must not deviate (i.e., maximum minus

minimum temperature) by more than 3EC during the test

(required)

3. Light quality: Ambient laboratory illumination (recommended) 

4. Light intensity: 10-20 μE/m2

/s or 50-100 ft-c (ambient laboratory levels)

(recommended) 

5. Photoperiod: 16 h light, 8 h dark (recommended) 

6. Test chamber size: 150 mL (recommended minimum) 

7. Test solution volume: 70 mL (recommended minimum) 

8. Renewal of test solutions: Daily (required)

9. Age of test organisms: Less than 36-h old embryos (Maximum of 48-h if shipped)

(required)

10. No. embryos per test chamber: 15 (recommended) 

10 (required minimum) 

11. No. replicate test 

chambers per concentration: 4 (recommended)

3 (required minimum) 

12. No. embryos per concentration: 60 (recommended)

30 (required minimum) 

13. Feeding regime: Feeding not required 

14. Aeration: None unless DO falls below 4.0 mg/L (recommended) 

1

 For the purposes of reviewing WET test data submitted under NPDES permits, each test condition listed above

is identified as required or recommended (see Subsection 10.2 for more information on test review). Additional

requirements may be provided in individual permits, such as specifying a given test condition where several

options are given in the method.
127

 TABLE 1. SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA FOR 

FATHEAD MINNOW, PIMEPHALES PROMELAS, EMBRYO-LARVAL SURVIVAL AND

TERATOGENICITY TOXICITY TESTS WITH EFFLUENTS AND RECEIVING WATERS

(TEST METHOD 1001.0) (CONTINUED)

 

15. Dilution water: Uncontaminated source of receiving or other natural water,

synthetic water prepared using MILLIPORE MILLI-Q® or

equivalent deionized water and reagent grade chemicals or

DMW (see Section 7, Dilution Water). The hardness of the

test solutions should equal or exceed 25 mg/L (CaCO3) to

ensure hatching success (available options)

16. Test concentrations: Effluents: 5 and a control (required minimum)

Receiving waters: 100% receiving water (or minimum of

5) and a control (recommended) 

17. Dilution factor: Effluents: $ 0.5 (recommended) 

Receiving waters: None, or $ 0.5 (recommended) 

18. Test duration: 7 days (required) 

19. Endpoint: Combined mortality (dead and deformed organisms)

(required) 

20. Test acceptability criteria: 80% or greater survival in controls (required) 

21. Sampling requirements: For on-site tests, samples collected daily and used within

24 h of the time they are removed from the sampling

device. For off-site tests, a minimum of three samples

(e.g., collected on days one, three, and five) with a

maximum holding time of 36 h before first use (see

Section 8, Effluent and Receiving Water Sampling, Sample

Handling, and Sample Preparation for Toxicity Tests,

Subsection 8.5.4) (required) 

22. Sample volume required: 1.5 to 2.5 L/day depending on the volume of test solutions

used (recommended) 

 
128

12.13 DATA ANALYSIS

12.13.1 GENERAL

12.13.1.1 Tabulate and summarize the data (Figure 3).

12.13.1.2 The endpoints of this toxicity test are based on total mortality, combined number of dead embryos, and

dead and deformed larvae. The EC1 is calculated using Probit Analysis (Finney, 1971; see Appendix I). Separate

analyses are performed for the estimation of LOEC and NOEC endpoints and for the estimation of the EC1

endpoint. Concentrations at which there is no survival in any of the test chambers are excluded from the statistical

analysis of the NOEC and LOEC, but included in the estimation of the EC1 endpoint. See the Appendices for

examples of the manual computations and examples of data input and output for the computer programs.

12.13.1.3 The statistical tests described here must be used with a knowledge of the assumptions upon which the

tests are contingent. The assistance of a statistician is recommended for analysts who are not proficient in statistics.

12.13.2 EXAMPLE OF ANALYSIS OF FATHEAD MINNOW EMBRYO-LARVAL SURVIVAL AND

TERATOGENICITY DATA

12.13.2.1 Formal statistical analysis of the total mortality data is outlined on the flowchart in Figure 4. The

response used in the analysis is the total mortality proportion in each test or control chamber. Separate analyses are

performed for the estimation of the NOEC and LOEC endpoints and for the estimation of the EC endpoint. 

Concentrations at which there is 100% total mortality in all of the test chambers are excluded from statistical

analysis of the NOEC and LOEC, but included in the estimation of the EC1 endpoint.

12.13.2.2 For the case of equal numbers of replicates across all concentrations and the control, the evaluation of

the NOEC and LOEC endpoints is made via a parametric test, Dunnett's Procedure, or a nonparametric test, Steel's

Many-one Rank Test, on the arc sine square root transformed data. Underlying assumptions of Dunnett's

Procedure, normality and homogeneity of variance, are formally tested. The test for normality is the Shapiro-Wilk's

Test, and Bartlett's Test is used to test for homogeneity of variance. If either of these tests fails, the nonparametric

test, Steel's Many-one Rank Test, is used to determine the NOEC and LOEC endpoints. If the assumptions of

Dunnett's Procedure are met, the endpoints are estimated by the parametric procedure.

12.13.2.3 If unequal numbers of replicates occur among the concentration levels tested, there are parametric and

nonparametric alternative analyses. The parametric analysis is a t test with the Bonferroni adjustment

(see Appendix D). The Wilcoxon Rank Sum Test with the Bonferroni adjustment is the nonparametric alternative

(see Appendix F).

12.13.2.4 Probit Analysis (Finney, 1971) is used to estimate the concentration that causes a specified percent

decrease in survival from the control. In this analysis, the total mortality data from all test replicates at a given

concentration are combined.
129

Figure 4. Flowchart for statistical analysis of fathead minnow, Pimephales promelas, embryo-larval data. 
130

12.13.2.5 The data for this example are listed in Table 2. Total mortality, expressed as a proportion (combined

total number of dead embryos, dead larvae and deformed larvae divided by the number of embryos at start of test),

is the response of interest. The total mortality proportion in each replicate must first be transformed by the arc sine

square root transformation procedure described in Appendix B. The raw and transformed data, means and variances

of the transformed observations at each effluent concentration and control are listed in Table 3. A plot of the data

is provided in Figure 5. Since there is 100% total mortality in replicates for the 50.0% concentration, it is not

included in this statistical analysis and is considered a qualitative mortality effect.

 TABLE 2. DATA FROM FATHEAD MINNOW, PIMEPHALES PROMELAS, EMBRYO-LARVAL

TOXICITY TEST WITH GROUND WATER EFFLUENT

Effluent No. Dead at Test Deformed at Test Dead + Deformed

Conc. Eggs at Termination Termination at Termination

(%) Start No. % No. % No. %

Control 10 0 0 0 0 0 0

10 2 20 0 0 2 20

 10 0 0 0 0 0 0

 10 1 10 0 0 1 10

3.125 10 0 0 0 0 0 0

10 0 0 1 10 1 10

10 0 0 0 0 0 0

10 1 10 0 0 1 10

6.25 10 0 0 0 0 0 0

 10 0 0 0 0 0 0

 10 0 0 0 0 0 0

 10 0 0 1 10 1 10

12.5 10 0 0 0 0 0 0

10 0 0 0 0 0 0

10 0 0 0 0 0 0

 10 1 10 0 0 1 10

25.0 10 1 10 9 90 10 100

 10 2 20 8 80 10 100

 10 2 20 8 80 10 100

 10 1 10 4 40 5 50

50.0 10 4 40 6 60 10 100

 10 3 30 7 70 10 100

 10 5 50 5 50 10 100

 10 3 30 7 70 10 100
131

Figure 5. Plot of fathead minnow, Pimephales promelas, total mortality data from the embryo-larval test.
132

D ' '

n

i'1

(Xi

&X ̄)

2

TABLE 3. FATHEAD MINNOW, PIMEPHALES PROMELAS, EMBRYO-LARVAL TOTAL

MORTALITY DATA 

Effluent Concentration (%)

Replicate Control 3.125 6.25 12.5 25.0 50.0

 RAW A 0.00 0.00 0.00 0.00 1.00 1.00

B 0.20 0.10 0.00 0.00 1.00 1.00

C 0.00 0.00 0.00 0.00 1.00 1.00

D 0.10 0.10 0.10 0.10 0.50 1.00

 ARC SINE A 0.159 0.159 0.159 0.159 1.412 -

 TRANS- B 0.464 0.322 0.159 0.159 1.412 -

 FORMED C 0.159 0.159 0.159 0.159 1.412 -

D 0.322 0.322 0.322 0.322 0.785 -

Mean( ) Y ̄ 0.276 0.241 0.200 0.200 1.255 i

S 0.022 0.009 0.007 0.007 0.098 2

i

i 1 234 5

12.13.2.6 Test for Normality 

12.13.2.6.1 The first step of the test for normality is to center the observations by subtracting the mean of all

observations within a concentration from each observation in that concentration. The centered observations are

summarized in Table 4.

TABLE 4. CENTERED OBSERVATIONS FOR SHAPIRO-WILK'S EXAMPLE 

 

Effluent Concentration (%)

Replicate Control 3.125 6.25 12.5 25.0 50.0

A -0.117 -0.082 -0.041 -0.041 0.157 - 

B 0.188 0.081 -0.041 -0.041 0.157 - 

C -0.117 0.081 -0.041 -0.041 0.157 - 

D 0.046 -0.082 0.122 0.122 -0.470 - 

12.13.2.6.2 Calculate the denominator, D, of the statistic:

 Where: Xi = the ith centered observation

X ̄ = the overall mean of the centered observations
133

n = the total number of centered observations

12.13.2.6.3 For this set of data, n = 20

X ̄ ' 1

20 (&0.003) ' 0.000

D = 0.4261

12.13.2.6.4 Order the centered observations from smallest to largest

 X(1) # X(2) # ... # X(n)

where X(i) denotes the ith ordered observation. The ordered observations for this example are listed in Table 5.

TABLE 5. ORDERED CENTERED OBSERVATIONS FOR THE SHAPIRO-WILK'S EXAMPLE

i X(i) i X(i)

1 -0.470 11 -0.041

2 -0.117 12 0.046

3 -0.117 13 0.081

4 -0.082 14 0.081

5 -0.082 15 0.122

6 -0.041 16 0.122

7 -0.041 17 0.157

8 -0.041 18 0.157

9 -0.041 19 0.157

10 -0.041 20 0.188

12.13.2.6.5 From Table 4, Appendix B, for the number of observations, n, obtain the coefficients a1, a2, ..., ak

where k is n/2 if n is even and (n-1)/2 if n is odd. For the data in this example, n = 20 and k = 10. The ai values are

listed in Table 6.
134

W ' 1

D ['

k

i'1

ai(X (n&i%1)&X (i))]

2

TABLE 6. COEFFICIENTS AND DIFFERENCES FOR THE SHAPIRO-WILK'S EXAMPLE 

i ai X(n-i+1) - X(i)

1 0.4734 0.658 X(20) - X(1)

2 0.3211 0.274 X(19) - X(2)

3 0.2565 0.274 X(18) - X(3)

4 0.2085 0.239 X(17) - X(4)

5 0.1686 0.204 X(16) - X(5)

6 0.1334 0.163 X(15) - X(6)

7 0.1013 0.122 X(14) - X(7)

8 0.0711 0.122 X(13) - X(8)

9 0.0422 0.087 X(12) - X(9)

10 0.0140 0.000 X(11) - X(10)

12.13.2.6.6 Compute the test statistic, W, as follows:

The differences X(n-i+1) - X(i) are listed in Table 6. For the data in this example,

W ' 1

0.4261 (0.6004)2

= 0.846

12.13.2.6.7 The decision rule for this test is to compare W as calculated in Section 13.2.6.6 to a critical value

found in Table 6, Appendix B. If the computed W is less than the critical value, conclude that the data are not

normally distributed. For the data in this example, the critical value at a significance level of 0.01 and n = 20

observations is 0.868. Since W = 0.846 is less than the critical value, conclude that the data are not normally

distributed.

12.13.2.6.8 Since the data do not meet the assumption of normality, Steel's Many-one Rank Test will be used to

analyze the total mortality data.

12.13.2.7 Steel's Many-one Rank Test 

12.13.2.7.1 For each control and concentration combination, combine the data and arrange the observations in

order of size from smallest to largest. Assign the ranks (1, 2, ..., 8) to the ordered observations with a rank of

1 assigned to the smallest observation, rank of 2 assigned to the next larger observation, etc. If ties occur when

ranking, assign the average rank to each tied observation.

12.13.2.7.2 An example of assigning ranks to the combined data for the control and 3.125% effluent concentration

is given in Table 7. This ranking procedure is repeated for each control/concentration combination. The complete

set of rankings is summarized in Table 8. The control group ranks are next summed for each effluent concentration

pairing, as shown in Table 9. 
135

TABLE 7. ASSIGNING RANKS TO THE CONTROL AND 3.125% EFFLUENT CONCENTRATION

FOR STEEL'S MANY-ONE RANK TEST

Transformed Effluent

Rank Proportion Concentration

Mortality (%)

2.5 0.159 Control

2.5 0.159 Control

2.5 0.159 3.125

2.5 0.159 3.125

6 0.322 Control

6 0.322 3.125

6 0.322 3.125

8 0.464 Control

TABLE 8. TABLE OF RANKS FOR STEEL'S MANY-ONE RANK TEST

Effluent Concentration (%)

Repl. Control 3.125 6.25 12.5 25.0 

A 0.159 (2.5,3,3,1.5) 0.159 (2.5) 0.159 (3) 0.159 (3) 1.412 (7)

B 0.464 (8,8,8,4) 0.322 (6) 0.159 (3) 0.159 (3) 1.412 (7)

C 0.159 (2.5,3,3,1.5) 0.159 (2.5) 0.159 (3) 0.159 (3) 1.412 (7)

D 0.322 (6,6.5,6.5,3) 0.322 (6) 0.322 (3) 0.159 (3) 0.785 (5)

TABLE 9. RANK SUMS

Effluent Control

Concentration (%) Rank Sum

3.125 19

6.25 20.5

12.5 20.5

25.0 10

12.13.2.7.3 For this example, we want to determine if the total mortality in any of the effluent concentrations is

significantly higher than the total mortality in the control. If this occurs, the rank sum of the control would be

significantly less than the rank sum at that concentration. Thus we are only concerned with comparing the control

rank sum for each pairing with the various effluent concentrations with some "minimum" or critical rank sum, at or

below which the concentration total mortality would be considered significantly greater than the control. At a

signficance level of 0.05, the minimum rank sum in a test with four concentrations (excluding the control) and four

replicates per concentration is 10 (see Table 5, Appendix E).
136

12.13.2.7.4 Since the control rank sum for the 25.0% effluent concentration pairing is equal to the critical value,

the total proportion mortality in the 25.0% concentration is considered significantly greater than that in the control. 

Since no other rank sums are less than or equal to the critical value, no other concentrations have signficantly higher

total proportion mortality than the control. Hence the NOEC is 12.5% and the LOEC is 25.0%. 

12.13.2.8 Calculation of the LC50

12.13.2.8.1 The data used for the Probit Analysis is summarized in Table 10. To perform the Probit Analysis, run

the USEPA Probit Analysis Program. An example of the program input and output is supplied in Appendix I.

12.13.2.8.2 For this example, the chi-square test for heterogeneity was not significant. Thus Probit Analysis

appears appropriate for this data. 

12.13.2.8.3 Figure 6 shows the output data for the Probit Analysis of the data from Table 10 using the USEPA

Probit Program. 

TABLE 10. DATA FOR PROBIT ANALYSIS 

Effluent Concentration (%)

Control 3.125 6.25 12.5 25.0 50.0

Number Dead 3 1 0 1 6 15

Number Exposed 40 40 40 40 40 40

12.14 PRECISION AND ACCURACY

12.14.1 PRECISION 

12.14.1.1 Single-laboratory Precision

12.14.1.1.1 Data shown in Tables 11 and 12 indicate that the precision of the embryo-larval survival and

teratogenicity test, expressed as the relative standard deviation (or coefficient of variation, CV) of the LC1 values,

was 62% for cadmium (Table 11) and 41% for Diquat (Table 12).

12.14.1.1.2 Precision data are also available from four embryo-larval survival and teratogenicity tests on trickling

filter pilot plant effluent (Table 13). Although the data could not be analyzed by Probit Analysis, the NOECs and

LOECs obtained using Dunnett's Procedure were the same for all four tests, 7% and 11% effluent, respectively,

indicating maximum precision in terms of the test design. 

12.14.1.2 Multilaboratory Precision

12.14.1.2.1 Data on the multilaboratory precision of this test are not yet available.

12.14.2 ACCURACY

12.14.2.1 The accuracy of toxicity tests cannot be determined.
137

USEPA PROBIT ANALYSIS PROGRAM

USED FOR CALCULATING LC/EC VALUES

Version 1.5

Probit Analysis of Fathead Minnow Embryo-Larval Survival

and Teratogenicity Data

 Proportion

 Observed Responding

 Number Number Proportion Adjusted for

 Conc. Exposed Resp. Responding Controls

 Control 20 2 0.1000 0.0000

 0.5000 20 2 0.1000 0.0174

 1.0000 20 1 0.0500 -.0372

 2.0000 20 4 0.2000 0.1265

 4.0000 20 16 0.8000 0.7816

 8.0000 20 20 1.0000 1.0000

Chi - Square for Heterogeneity (calculated) = 0.441

Chi - Square for Heterogeneity (tabular value) = 7.815

Probit Analysis of Fathead Minnow Embryo-Larval Survival

and Teratogenicity Data

 Estimated LC/EC Values and Confidence Limits

 Exposure Lower Upper

Point Conc. 95% Confidence Limits

LC/EC 1.00 1.346 0.453 1.922

LC/EC 50.00 3.018 2.268 3.672

Figure 6. Output for USEPA Probit Program, Version 1.5.
138

TABLE 11. PRECISION OF THE FATHEAD MINNOW, PIMEPHALES PROMELAS, 

EMBRYO-LARVAL SURVIVAL AND TERATOGENICITY TEST, USING CADMIUM AS

A REFERENCE TOXICANT1,2

Test LC13 95% Confidence NOEC4

(mg/L) Limits (mg/L)

1 0.014 0.009 - 0.018 0.012

2 0.006 0.003 - 0.010 0.012

3 0.005 0.003 - 0.009 0.013

4 0.003 0.002 - 0.004 0.011

5 0.006 0.003 - 0.009 0.012

N 5 5

Mean 0.0068 NA

SD 0.0042 

CV(%) 62 NA

 

1 Tests conducted by Drs. Wesley Birge and Jeffrey Black, University of Kentucky, Lexington, under a

cooperative agreement with the Bioassessment and Ecotoxicology Branch, EMSL, USEPA, Cincinnati,

OH. 2 Cadmium chloride was used as the reference toxicant. The nominal concentrations, expressed as cadmium

(mg/L), were: 0.01, 0.032, 0.100, 0.320, and 1.000. The dilution water was reconstituted water with a

hardness of 100 mg/L as calcium carbonate, and a pH of 7.8. 3 Determined by Probit Analysis. 4 Highest no-observed-effect concentration determined by independent statistical analysis (2X2 Chi-square

Fisher's Exact Test). NOEC range of 0.011 - 0.013 represents a difference of one exposure concentration.
139

TABLE 12. PRECISION OF THE FATHEAD MINNOW, PIMEPHALES PROMELAS,

EMBRYO-LARVAL, SURVIVAL AND TERATOGENICITY TOXICITY TEST, USING

DIQUAT AS A REFERENCE TOXICANT1,2

 Test LC13 95% Confidence

 (mg/L) Limits

1 0.58 0.32 - 0.86

2 2.31 --

4

3 1.50 1.05 - 1.87

4 1.71 1.24 - 2.09

5 1.43 0.93 - 1.83

N 5

Mean 1.51 

SD 0.62 

CV(%) 41.3 

1 Tests conducted by Drs. Wesley Birge and Jeffrey Black, University of Kentucky, Lexington, under a

cooperative agreement with the Bioassessment and Ecotoxicology Branch, EMSL, USEPA, Cincinnati,

OH. 2 The Diquat concentrations were determined by chemical analysis. The dilution water was reconstituted

water with a hardness of 100 mg/L as calcium carbonate, and a pH of 7.8. 3 Determined by Probit Analysis. 4 Cannot be calculated.
140

TABLE 13. PRECISION OF THE FATHEAD MINNOW, PIMEPHALES PROMELAS, EMBRYO-LARVAL

SURVIVAL AND TERATOGENICITY STATIC-RENEWAL TEST CONDUCTED WITH

TRICKLING FILTER EFFLUENT1,2,3

Test NOEC LOEC

No. (% Effluent) (% Effluent)

17 11

27 11

37 11

47 11

1 Data provided by Timothy Neiheisel, Bioassessment and Ecotoxiology Branch, EMSL, USEPA, Cincinnati, OH. 2 Effluent concentrations used: 3, 5, 7, 11 and 16% 3 Maximum precision achieved in terms of NOEC-LOEC interval. For a discusssion of the precision of data from

chronic toxicity tests (see Section 4, Quality Assurance).
141

SECTION 13

TEST METHOD

DAPHNID, CERIODAPHNIA DUBIA,

SURVIVAL AND REPRODUCTION TEST

METHOD 1002.0

13.1 SCOPE AND APPLICATION

13.1.1 This method measures the chronic toxicity of effluents and receiving water to the daphnid, Ceriodaphnia

dubia, using less than 24 h old neonates during a three-brood (seven-day), static renewal test. The effects include

the synergistic, antagonistic, and additive effects of all the chemical, physical, and biological components which

adversely affect the physiological and biochemical functions of the test organisms.

13.1.2 Daily observations on mortality make it possible to also calculate acute toxicity for desired exposure periods

(i.e., 24-h, 48-h, and 96-h LC50s). 

13.1.3 Detection limits of the toxicity of an effluent or pure substance are organism dependent. 

13.1.4 Brief excursions in toxicity may not be detected using 24-h composite samples. Also, because of the long

sample collection period involved in composite sampling, and because the test chambers are not sealed, highly

degradable or highly volatile toxicants in the source may not be detected in the test. 

13.1.5 This test method is commonly used in one of two forms: (1) a definitive test, consisting of a minimum of

five effluent concentrations and a control, and (2) a receiving water test(s), consisting of one or more receiving

water concentrations and a control. 

13.2 SUMMARY OF METHOD

13.2.1 Ceriodaphnia dubia are exposed in a static renewal system to different concentrations of effluent, or to

receiving water, until 60% or more of surviving control females have three broods of offspring. Test results are

based on survival and reproduction. If the test is conducted as described, the surviving control organisms should

produce 15 or more young in three broods. If these criteria are not met at the end of 8 days, the test must be

repeated. 

13.3 INTERFERENCES

13.3.1 Toxic substances may be introduced by contaminants in dilution water, glassware, sample hardware, and

testing equipment (see Section 5, Facilities, Equipment, and Supplies).

13.3.2 Improper effluent sampling and handling may adversely affect test results (see Section 8, Effluent and

Receiving Water Sampling, Sample Handling, and Sample Preparation for Toxicity Tests). 

13.3.3 Pathogenic and/or predatory organisms in the dilution water and effluent may affect test organism survival

and confound test results.

13.3.4 The amount and type of natural food in the effluent or dilution water may confound test results.

13.3.5 Food added during the test may sequester metals and other toxic substances and confound test results. 

Daily renewal of solutions, however, will reduce the probability of reduction of toxicity caused by feeding.
142

13.3.6 pH drift during the test may contribute to artifactual toxicity when ammonia or other pH-dependent

toxicants (such as metals) are present. As pH increases, the toxicity of ammonia also increases (see Subsection

8.8.6), so upward pH drift may increase sample toxicity. For metals, toxicity may increase or decrease with

increasing pH. Lead and copper were found to be more acutely toxic at pH 6.5 than at pH 8.0 or 8.5, while nickel

and zinc were more toxic at pH 8.5 than at pH 6.5 (USEPA, 1992). In situations where sample toxicity is confirmed

to be artifactual and due to pH drift (as determined by parallel testing as described in Subsection 13.3.6.1), the

regulatory authority may allow for control of sample pH during testing using procedures outlined in Subsection

13.3.6.2. It should be noted that artifactual toxicity due to pH drift is not likely to occur unless pH drift is large

(more than 1 pH unit) and/or the concentration of some pH-dependent toxicant in the sample is near the threshold

for toxicity. 

13.3.6.1 To confirm that toxicity is artifactual and due to pH drift, parallel tests must be conducted, one with

controlled pH and one with uncontrolled pH. In the uncontrolled-pH treatment, the pH is allowed to drift during the

test. In the controlled-pH treatment, the pH is maintained using the procedures described in Subsection 13.3.6.2. 

The pH to be maintained in the controlled-pH treatment (or target pH) will depend on the objective of the test. If

the objective of the WET test is to determine the toxicity of the effluent in the receiving water, the pH should be

maintained at the pH of the receiving water (measured at the edge of the regulatory mixing zone). If the objective

of the WET test is to determine the absolute toxicity of the effluent, the pH should be maintained at the initial pH of

the sample upon completion of collection (as measured on an aliquot removed from the sample container).

13.3.6.1.1 During parallel testing, the pH must be measured in each treatment at the beginning (i.e., initial pH) and

end (i.e., final pH) of each 24-h exposure period. For each treatment, the mean initial pH (e.g., averaging the initial

pH measured each day for a given treatment) and the mean final pH (e.g., averaging the final pH measured each day

for a given treatment) must be reported. pH measurements taken during the test must confirm that pH was

effectively maintained at the target pH in the controlled-pH treatment. For each treatment, the mean initial pH and

the mean final pH should be within ±0.2 pH units of the target pH. Test procedures for conducting toxicity

identification evaluations (TIEs) also recommend maintaining pH within ±0.2 pH units in pH-controlled tests

(USEPA, 1992).

13.3.6.1.2 Total ammonia also should be measured in each treatment at the outset of parallel testing. Total

ammonia concentrations greater than 5 mg/L in the 100% effluent are an indicator that toxicity observed in the test

may be due to ammonia (USEPA, 1992). 

13.3.6.1.3 Results from both of the parallel tests (pH-controlled and uncontrolled treatments) must be reported to

the regulatory authority. If the uncontrolled test meets test acceptability criteria and shows no toxicity at the

permitted instream waste concentration, then the results from this test should be used for determining compliance. 

If the uncontrolled test shows toxicity at the permitted instream waste concentration, then the results from the pHcontrolled test should be used for determining compliance, provided that this test meets test acceptability criteria

and pH was properly controlled (see Subsection 13.3.6.1.1). 

13.3.6.1.4 To confirm that toxicity observed in the uncontrolled test was artifactual and due to pH drift, the results

of the controlled and uncontrolled-pH tests are compared. If toxicity is removed or reduced in the pH-controlled

treatment, artifactual toxicity due to pH drift is confirmed for the sample. To demonstrate that a sample result of

artifactual toxicity is representative of a given effluent, the regulatory authority may require additional information

or additional parallel testing before pH control (as described in Subsection 13.3.6.2) is applied routinely to

subsequent testing of the effluent. 

13.3.6.2 The pH can be controlled with the addition of acids and bases and/or the use of a CO2-controlled

atmosphere over the test chambers. pH is adjusted with acids and bases by dropwise adding 1N NaOH or 1N HCl

(see Subsection 8.8.8). The addition of acids and bases should be minimized to reduce the amount of additional

ions (Na or Cl) added to the sample. pH is then controlled using the CO2-controlled atmosphere technique. This

may be accomplished by placing test solutions and test organisms in closed headspace test chambers, and then

injecting a predetermined volume of CO2 into the headspace of each test chamber (USEPA, 1991b; USEPA, 1992);
143

or by placing test chambers in an atmosphere flushed with a predetermined mixture of CO2 and air (USEPA, 1996). 

Prior experimentation will be needed to determine the appropriate CO2/air ratio or the appropriate volume of CO2 to

inject. This volume will depend upon the sample pH, sample volume, container volume, and sample constituents. 

If more than 5% CO2 is needed, adjust the solutions with acids (1N HCl) and then flush the headspace with no more

than 5% CO2 (USEPA, 1992). If the objective of the WET test is to determine the toxicity of the effluent in the

receiving water, CO2 is injected to maintain the test pH at the pH of the receiving water (measured at the edge of the

regulatory mixing zone). If the objective of the WET test is to determine the absolute toxicity of the effluent, CO2 is

injected to maintain the test pH at the pH of the sample upon completion of collection. USEPA (1991b; 1992) and

Mount and Mount (1992) provide techniques and guidance for controlling test pH using a CO2-controlled

atmosphere. In pH-controlled testing, control treatments must be subjected to all manipulations that sample

treatments are subjected to. These manipulations must be shown to cause no lethal or sublethal effects on control

organisms. In pH-controlled testing, the pH also must be measured in each treatment at the beginning and end of

each 24-h exposure period to confirm that pH was effectively controlled at the target pH level. 

13.4 SAFETY

13.4.1 See Section 3, Health and Safety. 

13.5 APPARATUS AND EQUIPMENT

13.5.1 Ceriodaphnia and algal culture units -- See Ceriodaphnia and algal culturing methods below and algal

culturing methods in Section 14 and USEPA, 2002a. 

13.5.2 Samplers -- automatic sampler, preferably with sample cooling capability, capable of collecting a 24-h

composite sample of 5 L or more.

13.5.3 Sample containers -- for sample shipment and storage (see Section 8, Effluent and Receiving Water

Sampling, Sample Handling, and Sample Preparation for Toxicity Tests).

13.5.4 Environmental chambers, incubators, or equivalent facilities with temperature control (25 ± 1EC).

13.5.5 Water purification system -- MILLIPORE MILLI-Q®, deionized water or equivalent (see Section 5,

Facilities, Equipment, and Supplies).

13.5.6 Balance -- analytical, capable of accurately weighing 0.00001 g.

13.5.7 Reference weights, Class S -- for checking performance of balance. Weights should bracket the expected

weights of the material to be weighed.

13.5.8 Test chambers -- 10 test chambers are required for each concentration and control. Test chambers such as

30-mL borosilicate glass beakers or disposable polystyrene cups are recommended because they will fit in the

viewing field of most stereoscopic microscopes. The glass beakers and plastic cups are rinsed thoroughly with

dilution water before use. To avoid potential contamination from the air and excessive evaporation of the test

solutions during the test, the test vessels should be covered with safety glass plates or sheet plastic (6 mm thick).

13.5.9 Mechanical shaker or magnetic stir plates -- for algal cultures. 

13.5.10 Light meter -- with a range of 0-200 μE/m2

/s (0-1000 ft-c). 

13.5.11 Fluorometer (optional) -- equipped with chlorophyll detection light source, filters, and photomultiplier

tube (Turner Model 110 or equivalent).

13.5.12 UV-VIS spectrophotometer (optional) -- capable of accommodating 1-5 cm cuvettes. 
144

13.5.13 Cuvettes for spectrophotometer -- 1-5 cm light path.

13.5.14 Electronic particle counter (optional) -- Coulter Counter, ZBI, or equivalent, with mean cell (particle)

volume determination. 

13.5.15 Microscope with 10X, 45X, and 100X objective lenses, 10X ocular lenses, mechanical stage, substage

condensor, and light source (inverted or conventional microscope) -- for determining sex and verifying

identification.

13.5.16 Dissecting microscope, stereoscopic, with zoom objective, magnification to 50X -- for examining and

counting the neonates in the test vessels.

13.5.17 Counting chamber -- Sedgwick-Rafter, Palmer-Maloney, or hemocytometer.

13.5.18 Centrifuge (optional) -- plankton, or with swing-out buckets having a capacity of 15-100 mL.

13.5.19 Centrifuge tubes -- 15-100 mL, screw-cap. 

13.5.20 Filtering apparatus -- for membrane and/or glass fiber filters. 

13.5.21 Racks (boards) -- to hold test chambers. It is convenient to use a piece of styrofoam insulation board, 50

cm x 30 cm x 2.5 cm (20 in x 12 in x 1 in), drilled to hold 60 test chambers, in six rows of 10 (see Figure 1). 

13.5.22 Light box -- for illuminating organisms during examination. 

13.5.23 Volumetric flasks and graduated cylinders -- class A, borosilicate glass or non-toxic plastic labware,

10-1000 mL, for culture work and preparation of test solutions.

13.5.24 Pipettors, adjustable volume repeating dispensers -- for feeding. Pipettors such as the Gilson

REPETMAN®, Eppendorf, Oxford, or equivalent, provide a rapid and accurate means of dispensing small volumes

(0.1 mL) of food to large numbers of test chambers.

13.5.25 Volumetric pipets -- class A, 1-100 mL. 

13.5.26 Serological pipets -- 1-10 mL, graduated.

13.5.27 Pipet bulbs and fillers -- PROPIPET®, or equivalent. 

13.5.28 Disposable polyethylene pipets, droppers, and glass tubing with fire-polished edges, $ 2mm ID -- for

transferring organisms. 

13.5.29 Wash bottles -- for rinsing small glassware and instrument electrodes and probes. 

13.5.30 Thermometer, glass or electronic, laboratory grade, -- for measuring water temperatures. 

13.5.31 Bulb-thermograph or electronic-chart type thermometers -- for continuously recording temperature. 

13.5.32 Thermometer, National Bureau of Standards Certified (see USEPA Method 170.1, USEPA 1979b) -- to

calibrate laboratory thermometers.

13.5.33 Meters, DO, pH, and specific conductivity -- for routine physical and chemical measurements.
145

13.6 REAGENTS AND CONSUMABLE MATERIALS

13.6.1 Sample containers -- for sample shipment and storage (see Section 8, Effluent and Receiving Water

Sampling, Sample Handling, and Sample Preparation for Toxicity Tests).

13.6.2 Data sheets (one set per test) -- for recording the data.

13.6.3 Vials, marked -- for preserving specimens for verification (optional).

13.6.4 Tape, colored -- for labeling test vessels.

13.6.5 Markers, waterproof -- for marking containers.

13.6.6 Reagents for hardness and alkalinity tests -- see USEPA Methods 130.2 and 310.1, USEPA, 1979b. 

13.6.7 Buffers, pH 4, pH 7, and pH 10 (or as per instructions of instrument manufacturer) -- for instrument

calibration check (see USEPA Method 150.1, USEPA, 1979b). 

13.6.8 Specific conductivity standards -- see USEPA Method 120.1, USEPA, 1979b.

13.6.9 Membranes and filling solutions for DO probe (see USEPA Method 360.1, USEPA, 1979b), or reagents --

for modified Winkler analysis.

13.6.10 Laboratory quality control samples and standards -- for calibration of the above methods. 

13.6.11 Reference toxicant solutions -- see Section 4, Quality Assurance.

13.6.12 Reagent water -- defined as distilled or deionized water that does not contain substances which are toxic to

the test organisms (see Section 5, Facilities, Equipment, and Supplies).

13.6.13 Effluent, surface water, and dilution water -- see Section 7, Dilution Water; and Section 8, Effluent and

Receiving Water Sampling, Sample Handling, and Sample Preparation for Toxicity Tests.

13.6.14 Trout chow, yeast, and CEROPHYL® food (or substitute food) -- for feeding the cultures and test

organisms.

13.6.14.1 Digested trout chow, or substitute flake food (TETRAMIN®, BIORIL®, or equivalent), is prepared as

follows: 

1. Preparation of trout chow or substitute flake food requires one week. Use starter or No. 1 pellets

prepared according to current U.S. Fish and Wildlife Service specifications. 

2. Add 5.0 g of trout chow pellets or substitute flake food to 1 L of MILLI-Q® water. Mix well in a

blender and pour into a 2-L separatory funnel. Digest prior to use by aerating continuously from the

bottom of the vessel for one week at ambient laboratory temperature. Water lost due to evaporation is

replaced during digestion. Because of the offensive odor usually produced during digestion, the vessel

should be placed in a fume hood or other isolated, ventilated area.

3. At the end of digestion period, place in a refrigerator and allow to settle for a minimum of 1 h. Filter

the supernatant through a fine mesh screen (i.e., NITEX® 110 mesh). Combine with equal volumes of

supernatant from CEROPHYLL® and yeast preparations (below). The supernatant can be used fresh,

or frozen until use. Discard the sediment.
146

13.6.14.2 Yeast is prepared as follows: 

1. Add 5.0 g of dry yeast, such as FLEISCHMANN'S® Yeast, Lake State Kosher Certified Yeast, or

equivalent, to 1 L of MILLI-Q® water.

2. Stir with a magnetic stirrer, shake vigorously by hand, or mix with a blender at low speed, until the

yeast is well dispersed.

3. Combine the yeast suspension immediately (do not allow to settle) with equal volumes of supernatant

from the trout chow (above) and CEROPHYLL® preparations (below). Discard excess material. 

13.6.14.3 CEROPHYLL® is prepared as follows: 

1. Place 5.0 g of dried, powdered, cereal or alfalfa leaves, or rabbit pellets, in a blender. Cereal leaves,

CEROPHYLL®, or equivalent are available from commercial sources. Dried, powdered, alfalfa leaves

may be obtained from health food stores, and rabbit pellets are available at pet shops.

2. Add 1 L of MILLI-Q® water. 

3. Mix in a blender at high speed for 5 min, or stir overnight at medium speed on a magnetic stir plate.

4. If a blender is used to suspend the material, place in a refrigerator overnight to settle. If a magnetic

stirrer is used, allow to settle for 1 h. Decant the supernatant and combine with equal volumes of

supernatant from trout chow and yeast preparations (above). Discard excess material.

13.6.14.4 Combined yeast-cerophyl-trout chow (YCT) is mixed as follows: 

1. Thoroughly mix equal (approximately 300 mL) volumes of the three foods as described above.

2. Place aliquots of the mixture in small (50 mL to 100 mL) screw-cap plastic bottles and freeze until

needed.

3. Freshly prepared food can be used immediately, or it can be frozen until needed. Thawed food is

stored in the refrigerator between feedings, and is used for a maximum of two weeks. Do not store

frozen over three months.

4. It is advisable to measure the dry weight of solids in each batch of YCT before use. The food should

contain 1.7-1.9 g solids/L. Cultures or test solutions should contain 12-13 mg solids/L.

13.6.15 Algal food -- for feeding the cultures and test organisms.

13.6.15.1 Algal Culture Medium is prepared as follows: 

1. Prepare (five) stock nutrient solutions using reagent grade chemicals as described in Table 1.

2. Add 1 mL of each stock solution, in the order listed in Table 1, to approximately 900 mL of MILLI-Q®

water. Mix well after the addition of each solution. Dilute to 1 L, mix well. The final concentration

of macronutrients and micronutrients in the culture medium is given in Table 2.

3. Immediately filter the medium through a 0.45 μm pore diameter membrane at a vacuum of not more

than 380 mm (15 in.) mercury, or at a pressure of not more than one-half atmosphere (8 psi). Wash

the filter with 500 mL deionized water prior to use.

4. If the filtration is carried out with sterile apparatus, filtered medium can be used immediately, and no

further sterilization steps are required before the inoculation of the medium. The medium can also be

sterilized by autoclaving after it is placed in the culture vessels.

5. Unused sterile medium should not be stored more than one week prior to use, because there may be

substantial loss of water by evaporation. 
147

TABLE 1. NUTRIENT STOCK SOLUTIONS FOR MAINTAINING ALGAL STOCK CULTURES 

STOCK COMPOUND AMOUNT DISSOLVED IN

SOLUTION 500 mL MILLI-Q® WATER

1. MACRONUTRIENTS

A. MgCl2@6H2O 6.08 g

CaCl2@2H2O 2.20 g

NaNO3 12.75 g

B. MgSO4@7H2O 7.35 g

C. K2HPO4 0.522 g

D. NaHCO3 7.50 g

2. MICRONUTRIENTS

H3BO3 92.8 mg

MnCl2@4H2O 208.0 mg

ZnCl2 1.64 mg1

FeCl3@6H2O 79.9 mg

CoCl2@6H2O 0.714 mg2

Na2MoO4@2H2O 3.63 mg3

CuCl2@2H2O 0.006 mg4

Na2EDTA@2H2O 150.0 mg

Na2SeO4 1.196 mg5

1 ZnCl2 - Weigh out 164 mg and dilute to 100 mL. Add 1 mL of this solution to Stock 2,

micronutrients. 2 CoCl2@6H2O - Weigh out 71.4 mg and dilute to 100 mL. Add 1 mL of this solution to Stock

2, micronutrients. 3 Na2MoO4@2H2O - Weigh out 36.6 mg and dilute to 10 mL. Add 1 mL of this solution to

Stock 2, micronutrients. 4 CuCl2@2H2O - Weigh out 60.0 mg and dilute to 1000 mL. Take 1 mL of this solution and

dilute to 10 mL. Take 1 mL of the second dilution and add to Stock 2, micronutrients. 5 Na2SeO4 - Weigh out 119.6 mg and dilute to 100 mL. Add 1 mL of this solution to Stock 2,

micronutrients.
148

TABLE 2. FINAL CONCENTRATION OF MACRONUTRIENTS AND MICRONUTRIENTS IN THE

CULTURE MEDIUM

MACRONUTRIENT CONCENTRATION ELEMENT CONCENTRATION

(mg/L) (mg/L) 

NaNO3 25.5 N 4.20 

MgCl2@6H2O 12.2 Mg 2.90 

CaCl2@2H2O 4.41 Ca 1.20 

MgSO4@7H2O 14.7 S 1.91 

K2HPO4 1.04 P 0.186 

NaHCO3 15.0 Na 11.0 

 K 0.469 

 C 2.14 

MICRONUTRIENT CONCENTRATION ELEMENT CONCENTRATION

(μg/L) (μg/L) 

H3BO3 185.0 B 32.5 

MnCl2@4H2O 416.0 Mn 115.0

ZnCl2 3.27 Zn 1.57 

CoCl2@6H2O 1.43 Co 0.354

CuCl2@2H2O 0.012 Cu 0.004 

Na2MoO4@2H2O 7.26 Mo 2.88 

FeCl3@6H2O 160.0 Fe 33.1 

Na2EDTA@2H2O 300.0 -- ----

Na2SeO4 2.39 Se 0.91 
149

13.6.15.2 Algal Cultures 

13.6.15.2.1 See Section 6, Test Organisms, for information on sources of "starter" cultures of Selenastrum

capricornutum, S. minutum, and Chlamydomonas reinhardti.

13.6.15.2.2 Two types of algal cultures are maintained: "stock" cultures, and "food" cultures.

13.6.15.2.2.1 Establishing and Maintaining Stock Cultures of Algae: 

1. Upon receipt of the "starter" culture (usually about 10 mL), a stock culture is initiated by aseptically

transferring one milliliter to each of several 250-mL culture flasks containing 100 mL algal culture

medium (prepared as described above). The remainder of the starter culture can be held in reserve for

up to six months in a refrigerator (in the dark) at 4EC.

2. The stock cultures are used as a source of algae to initiate "food" cultures for Ceriodaphnia dubia

toxicity tests. The volume of stock culture maintained at any one time will depend on the amount of

algal food required for the Ceriodaphnia dubia cultures and tests. Stock culture volume may be

rapidly "scaled up" to several liters, if necessary, using 4-L serum bottles or similar vessels, each

containing 3 L of growth medium. 

3. Culture temperature is not critical. Stock cultures may be maintained at 25EC in environmental

chambers with cultures of other organisms if the illumination is adequate (continuous "cool-white"

fluorescent lighting of approximately 86 ± 8.6 μE/m2

/s, or 400 ft-c). 

4. Cultures are mixed twice daily by hand.

5. Stock cultures can be held in the refrigerator until used to start "food" cultures, or can be transferred to

new medium weekly. One-to-three milliliters of 7-day old algal stock culture, containing

approximately 1.5 X 106

 cells/mL, are transferred to each 100 mL of fresh culture medium. The

inoculum should provide an initial cell density of approximately 10,000-30,000 cells/mL in the new

stock cultures. Aseptic techniques should be used in maintaining the stock algal cultures, and care

should be exercised to avoid contamination by other microorganisms.

6. Stock cultures should be examined microscopically weekly, at transfer, for microbial contamination. 

Reserve quantities of culture organisms can be maintained for 6-12 months if stored in the dark at 4EC. 

It is advisable to prepare new stock cultures from "starter" cultures obtained from established outside

sources of organisms (see Section 6, Test Organisms) every four to six months.

13.6.15.2.2.2 Establishing and Maintaining "Food" Cultures of Algae: 

1. "Food" cultures are started seven days prior to use for Ceriodaphnia dubia cultures and tests. 

Approximately 20 mL of 7-day-old algal stock culture (described in the previous paragraph),

containing 1.5 X 106

 cells/mL, are added to each liter of fresh algal culture medium (i.e., 3 L of

medium in a 4-L bottle, or 18 L in a 20-L bottle). The inoculum should provide an initial cell density

of approximately 30,000 cells/mL. Aseptic techniques should be used in preparing and maintaining

the cultures, and care should be exercised to avoid contamination by other microorganisms. However,

sterility of food cultures is not as critical as in stock cultures because the food cultures are terminated

in 7-10 days. A one-month supply of algal food can be grown at one time, and stored in the

refrigerator.

2. Food cultures may be maintained at 25EC in environmental chambers with the algal stock cultures or

cultures of other organisms if the illumination is adequate (continuous "cool-white" fluorescent

lighting of approximately 86 ± 8.6 μE/m2

/s or 400 ft-c). 

3. Cultures are mixed continuously on a magnetic stir plate (with a medium size stir bar) or in a

moderately aerated separatory funnel, or are mixed twice daily by hand. If the cultures are placed on a

magnetic stir plate, heat generated by the stirrer might elevate the culture temperature several degrees. 

Caution should be exercised to prevent the culture temperature from rising more than 2-3EC.
150

13.6.15.2.3 Preparing Algal Concentrate for Use as Ceriodaphnia dubia Food:

1. An algal concentrate containing 3.0 to 3.5 X 107

 cells/mL is prepared from food cultures by

centrifuging the algae with a plankton or bucket-type centrifuge, or by allowing the cultures to settle in

a refrigerator for at least three weeks and siphoning off the supernatant.

2. The cell density (cells/mL) in the concentrate is measured with an electronic particle counter,

microscope and hemocytometer, fluorometer, or spectrophotometer (see Section 14, Green Alga,

Selenastrum capricornutum Growth Test), and used to determine the dilution (or further

concentration) required to achieve a final cell count of 3.0 to 3.5 X 107

/mL.

3. Assuming a cell density of approximately 1.5 X 106

 cells/mL in the algal food cultures at 7 days, and

100% recovery in the concentration process, a 3-L, 7-10 day culture will provide 4.5 X 109

 algal cells. 

This number of cells would provide approximately 150 mL of algal cell concentrate (1500 feedings at

0.1 mL/feeding) for use as food. This would be enough algal food for four Ceriodaphnia dubia tests.

4. Algal concentrate may be stored in the refrigerator for one month.

13.6.15.3 Food Quality

13.6.15.3.1 USEPA recommends Fleishmann's® yeast, Cerophyll®, trout chow, and Selenastrum capricornutum as

the preferred Ceriodaphnia dubia food combination. This recommendation is based on extensive data developed by

many laboratories which indicated high Ceriodaphnia dubia survival and reproduction in culturing and testing. The

use of substitute food(s) is acceptable only after side-by-side tests are conducted to determine that the quality of the

substitute food(s) is equal to the USEPA recommended food combination based on survival and reproduction of

Ceriodaphnia dubia.

13.6.15.3.2 The quality of food prepared with newly acquired supplies of yeast, trout chow, dried cereal leaves,

algae, and/or any substitute food(s) should be determined in side-by-side comparisons of Ceriodaphnia dubia

survival and reproduction, using the new food and food of known, acceptable quality, over a seven-day period in

control medium. 

13.6.16 TEST ORGANISMS, DAPHNIDS, CERIODAPHNIA DUBIA

13.6.16.1 Cultures of test organisms should be started at least three weeks before the brood animals are needed, to

ensure an adequate supply of neonates for the test. Only a few individuals are needed to start a culture because of

their prolific reproduction. 

13.6.16.2 Neonates used for toxicity tests must be obtained from individually cultured organisms. Mass cultures

may be maintained, however, to serve as a reserve source of organisms for use in initiating individual cultures and

in case of loss of individual cultures.

13.6.16.3 Starter animals may be obtained from commercial sources and may be shipped in polyethylene bottles. 

Approximately 40 animals and 3 mL of food are placed in a l-L bottle filled full with culture water for shipment. 

Animals received from an outside source should be transferred to new culture media gradually over a period of 1-2

days to avoid mass mortality. 

13.6.16.4 It is best to start the cultures with one animal, which is sacrificed after producing young, mounted on a

microscope slide, and retained as a permanent slide mount to facilitate identification and permit future reference. 

The species identification of the stock culture should be verified by preparing slide mounts, regardless of the

number of animals used to start the culture. The following procedure is recommended for making slide mounts of

Ceriodaphnia dubia (modified from Beckett and Lewis, 1982):

 1. Pipet the animal onto a watch glass.

 2. Reduce the water volume by withdrawing excess water with the pipet.
151

 3. Add a few drops of carbonated water (club soda or seltzer water) or 70% ethanol to relax the specimen

so that the post-abdomen is extended. (Optional: with practice, extension of the postabdomen may be

accomplished by putting pressure on the cover slip).

 4. Place a small amount (one to three drops) of mounting medium on a glass microscope slide. The

recommended mounting medium is CMCP-9/10 Medium, prepared by mixing two parts of CMCP-9

with one part of CMCP-10 stained with enough acid fuchsin dye to color the mixture a light pink. For

more viscosity and faster drying, CMC-10 stained with acid fuchsin may be used.

 5. Using forceps or a pipet, transfer the animal to the drop of mounting medium on the microscope slide.

 6. Cover with a 12 mm round cover slip and exert minimum pressure to remove any air bubbles trapped

under the cover slip. Slightly more pressure will extend the postabdomen. 

 7. Allow mounting medium to dry.

 8. Make slide permanent by placing varnish around the edges of the coverslip.

 9. Identify to species (see Pennak, 1978; Pennak, 1989; and Berner, 1986).

10. Label with waterproof ink or diamond pencil.

11. Store for permanent record.

13.6.16.5 Mass Culture

13.6.16.5.1 Mass cultures are used only as a "backup" reservoir of organisms. 

13.6.16.5.2 One-liter or 2-L glass beakers, crystallization dishes, "battery jars," or aquaria may be used as culture

vessels. Vessels are commonly filled to three-fourths capacity. Cultures are fed daily. Four or more cultures are

maintained in separate vessels and with overlapping ages to serve as back-up in case one culture is lost due to

accident or other unanticipated problems, such as low DO concentrations or poor quality of food or laboratory

water.

13.6.16.5.3 Mass cultures which will serve as a source of brood organisms for individual culture should be

maintained in good condition by frequent renewal with new culture medium at least twice a week for two weeks. 

At each renewal, the adult survival is recorded, and the offspring and the old medium are discarded. After two

weeks, the adults are also discarded, and the culture is re-started with neonates in fresh medium. Using this

schedule, 1-L cultures will produce 500 to 1000 neonate Ceriodaphnia dubia each week.

13.6.16.6 Individual Culture

13.6.16.6.1 Individual cultures are used as the immediate source of neonates for toxicity tests.

13.6.16.6.2 Individual organisms are cultured in 15 mL of culture medium in 30-mL (1 oz) plastic cups or 30-mL

glass beakers. One neonate is placed in each cup. It is convenient to place the cups in the same type of board used

for toxicity tests (see Figure 1).
152

1 3 5246

312546

413652

536124

215364

641352

531624

152463

214653

364215

1 3 5246

312546

413652

536124

215364

641352

531624

152463

214653

364215

10 20 30 40 50 60

9 19 29 39 49 59

8 18 28 38 48 58

7 17 27 37 47 57

6 16 26 36 46 56

5 15 25 35 45 55

4 14 24 34 44 54

3 13 23 33 43 53

2 12 22 32 42 52

1 11 21 31 41 51

In each of

the 10 cups,

is one

culture

parent with

at least 8

young per

female/cup

Figure 1. Examples of a test board and randomizing template: 1) test board with positions for six columns of ten

replicate test chambers with each position numbered for recording results on data sheets, 2) cardboard

randomizing template prepared by randomly drawing numbers (1-6) for each position in a row across

the board, and 3) test board (1) placed on top of the randomizing template (2) for the purpose of

assigning the position of test treatments (1-6) within each block (row on the test board). Following

placement of test chambers, test organisms are allocated using blocking by known parentage. Test

organisms from a single brood cup are distributed to each treatment within a given block (row on the

test board). 
153

13.6.16.6.3 Organisms are fed daily (see Subsection 13.6.16.9) and are transferred to fresh medium a minimum of

three times a week, typically on Monday, Wednesday, and Friday. On the transfer days, food is added to the new

medium immediately before or after the organisms are transferred.

13.6.16.6.4 To provide cultures of overlapping ages, new boards are started weekly, using neonates from adults

which produce at least eight young in their third or fourth brood. These adults can be used as sources of neonates

until 14 days of age. A minimum of two boards are maintained concurrently to provide backup supplies of

organisms in case of problems.

13.6.16.6.5 Cultures which are properly maintained should produce at least 20 young per adult in three broods

(seven days or less). Typically, 60 adult females (one board) will produce more than the minimum number of

neonates (120) required for two tests.

13.6.16.6.6 Records should be maintained on the survival of brood organisms and number of offspring at each

renewal. Greater than 20% mortality of adults, or less than an average of 20 young per female would indicate

problems, such as poor quality of culture media or food. Cultures that do not meet these criteria should not be used

as a source of test organisms.

13.6.16.7 Culture Medium 

13.6.16.7.1 Moderately hard synthetic water prepared using MILLIPORE MILLI-Q® or equivalent deionized water

and reagent grade chemicals or 20% DMW is recommended as a standard culture medium (see Section 7, Dilution

Water).

13.6.16.8 Culture Conditions

13.6.16.8.1 The daphnid, Ceriodaphnia dubia, should be cultured at a temperature of 25 ± 1EC.

13.6.16.8.2 Day/night cycles prevailing in most laboratories will provide adequate illumination for normal growth

and reproduction. A photoperiod of 16-h of light and 8-h of darkness is recommended. Light intensity should be

10-20 μE/m2

/s or 50 to 100 ft-c. 

13.6.16.8.3 Clear, double-strength safety glass or 6 mm plastic panels are placed on the culture vessels to exclude

dust and dirt, and reduce evaporation. 

13.6.16.8.4 The organisms are delicate and should be handled as carefully and as little as possible so that they are

not unnecessarily stressed. They are transferred with a pipet of approximately 2-mm bore, taking care to release the

animals under the surface of the water. Any organism that is injured during handling should be discarded.

13.6.16.9 Food and Feeding

13.6.16.9.1 Feeding the proper amount of the right food is extremely important in Ceriodaphnia dubia culturing. 

The key is to provide sufficient nutrition to support normal reproduction without adding excess food which may

reduce the toxicity of the test solutions, clog the animal's filtering apparatus, or greatly decrease the DO

concentration and increase mortality. A combination of Yeast, CEROPHYLL®, and Trout chow (YCT), along with

the unicellular green alga, Selenastrum capricornutum, will provide suitable nutrition if fed daily.

13.6.16.9.2 Other algal species (such as S. minutum or Chlamydomonas reinhardti), other substitute food

combinations (such as Flake Fish Food), or different feeding rates may be acceptable as long as performance criteria

are met and side-by-side comparison tests confirm acceptable quality (see Subsection 13.6.15.3).

13.6.16.9.3 Cultures should be fed daily to maintain the organisms in optimum condition so as to provide

maximum reproduction. Stock cultures which are stressed because they are not adequately fed may produce low
154

numbers of young, large numbers of males, and/or ephippial females. Also, their offspring may produce few young

when used in toxicity tests. 

13.6.16.9.4 Feed as follows:

1. If YCT is frozen, remove a bottle of food from the freezer 1h before feeding time, and allow to thaw. 

2. YCT food mixture and algal concentrates should both be thoroughly mixed by shaking before

dispensing. 

3. Mass cultures are fed daily at the rate of 7 mL YCT and 7 mL algae concentrate/L culture. 

4. Individual cultures are fed at the rate of 0.1 mL YCT and 0.1 mL algae concentrate per 15 mL culture. 

5. Return unused YCT food mixture and algae concentrate to the refrigerator. Do not re-freeze YCT. 

Discard unused portion after two weeks. 

13.6.16.10 It is recommended that chronic toxicity tests be performed monthly with a reference toxicant. Daphnid,

Ceriodaphnia dubia, neonates less than 24 h old, and all within 8 h of the same age are used to monitor the chronic

toxicity of the reference toxicant to the Ceriodaphnia dubia produced by the culture unit (see Section 4, Quality

Assurance).

13.6.16.11 Record Keeping

13.6.16.11.1 Records, kept in a bound notebook, include (1) source of organisms used to start the cultures, (2) type

of food and feeding times, (3) dates culture were thinned and restarted, (4) rate of reproduction in individual

cultures, (5) daily observations of the condition and behavior of the organisms in the cultures, and (6) dates and

results of reference toxicant tests performed (see Section 4, Quality Assurance).

13.7 EFFLUENT AND RECEIVING WATER COLLECTION, PRESERVATION, AND STORAGE

13.7.1 See Section 8, Effluent and Receiving Water Sampling, Sample Handling, and Sample Preparation for

Toxicity Tests.

13.8 CALIBRATION AND STANDARDIZATION

13.8.1 See Section 4, Quality Assurance.

13.9 QUALITY CONTROL

13.9.1 See Section 4, Quality Assurance.

13.10 TEST PROCEDURES

13.10.1 TEST SOLUTIONS

13.10.1.1 Receiving Waters 

13.10.1.1.1 The sampling point is determined by the objectives of the test. Receiving water toxicity is determined

with samples used directly as collected or after samples are passed through a 60 μm NITEX® filter and compared

without dilution, against a control. For a test consisting of single receiving water and control, approximately 600

mL of sample would be required for each test, assuming 10 replicates of 15 mL, and sufficient additional sample for

chemical analysis. 
155

13.10.1.2 Effluents

13.10.1.2.1 The selection of the effluent test concentrations should be based on the objectives of the study. A

dilution factor of 0.5 is commonly used. A dilution factor of 0.5 provides precision of ± 100%, and testing of

concentrations between 6.25% and 100% effluent using only five effluent concentrations (6.25%, 12.5%, 25%,

50%, and 100%). Improvements in precision decline rapidly if the dilution factor is increased beyond 0.5, and

precision declines rapidly if a smaller dilution factor is used. Therefore, USEPA recommends the use of the $

0.5 dilution factor.

13.10.1.2.2 If the effluent is known or suspected to be highly toxic, a lower range of effluent concentrations should

be used (such as 25%, 12.5%, 6.25%, 3.12%, and 1.56%). If a high rate of mortality is observed during the first

1 to 2 h of the test, additional dilutions should be added at the lower range of effluent concentrations. 

13.10.1.2.3 The volume of effluent required for daily renewal of 10 replicates per concentration, each containing

15 mL of test solution, with a dilution series of 0.5, is approximately 1 L/day. A volume of 15 mL of test solution is

adequate for the organisms, and will provide a depth in which it is possible to count the animals under a

stereomicroscope with a minimum of re-focusing. Ten test chambers are used for each effluent dilution and for the

control. Sufficient test solution (approximately 550 mL) is prepared at each effluent concentration to provide 400

mL additional volume for chemical analyses at the high, medium, and low test concentrations. 

13.10.1.2.4 Tests should begin as soon as possible, preferably within 24 h of sample collection. The maximum

holding time following retrieval of the sample from the sampling device should not exceed 36 h for off-site toxicity

tests unless permission is granted by the permitting authority. In no case should the sample be used for the first time

in a test more than 72 h after sample collection (see Section 8, Effluent and Receiving Water Sampling, Sample

Handling, and Sample Preparation for Toxicity Tests).

13.10.1.2.5 Just prior to test initiation (approximately one h) the temperature of sufficient quantity of the sample to

make the test solutions should be adjusted to the test temperature and maintained at that temperature during the

preparation of the test solutions.

13.10.1.2.6 The DO of the test solutions should be checked prior to test initiation. If any of the solutions are

supersaturated with oxygen, all of the solutions and the control should be gently aerated. If any solution has a DO

concentration below 4.0 mg/L, all the solutions and the control must be gently aerated.

13.10.1.3 Dilution Water

13.10.1.3.1 Dilution water may be uncontaminated receiving water, a standard synthetic (reconstituted) water, or

some other uncontaminated natural water (see Section 7, Dilution Water).

13.10.2 START OF THE TEST 

13.10.2.1 Label the test chambers with a marking pen. Use of color-coded tape to identify each treatment and

replicate is helpful. A minimum of five effluent concentrations and a control are used for each effluent test. Each

treatment (including the control) must have ten replicates.

13.10.2.2 The test chambers must be randomly assigned to a board using a template (Figure 1) or by using random

numbers (see Appendix A). Randomizing the position of test chambers as described in Figure 1 (or equivalent) will

assist in assigning test organisms using blocking by known parentage (Subsection 13.10.2.4). A number of different

templates should be prepared, and the template used for each test should be identified on the data sheet. The same

template must not be used for every test.

13.10.2.3 Neonates less than 24 h old, and all within 8 h of the same age, are required to begin the test. The

neonates must be obtained from individual cultures using brood boards, as described above in Subsection 13.6.16.6,
156

Individual Culture (also see Section 6, Test Organisms). Neonates must be taken only from adults in individual

cultures that have eight or more young in their third or subsequent broods. These adults can be used as brood stock

until they are 14 days old. If the neonates are held more than one or two hours before using in the test, they should

be fed (0.1 mL YCT and 0.1 mL algal concentrate/15 mL of media). Record the age range of test organisms,

source, and feeding of neonates on test data sheets.

13.10.2.4 Ten brood cups, each with 8 or more young, are randomly selected from a brood board for use in setting

up a test. To start the test, neonates from these ten brood cups are distributed to each test chamber in the test board

(one per test chamber). Test organisms must be assigned to test chambers using a block randomization procedure,

such that offspring from a single female are distributed evenly among the treatments, appearing once in every test

concentration. This arrangement is referred to as “blocking by known parentage”. The technique used to achieve

blocking by known parentage should be recorded in the test data report. One effective technique is to block

randomize the test board as described in Figure 1 and transfer one neonate from the first brood cup to each of the six

test chambers in the first row on the test board. One neonate from the second brood cup is then transferred to each

of the six test chambers in the second row on the test board. This process is continued until each of the 60 test

chambers contains one neonate. The set of six test chambers (one for each test treatment) containing organisms

derived from a single female parent is referred to as a block. When using the technique described in Figure 1, each

row of the test board will represent a block.

13.10.2.4.1 The brood cups and test chambers may be placed on a light table to facilitate counting the neonates. 

However, care must be taken to avoid temperature increase due to heat from the light table.

13.10.2.4.2 Following the allocation of test organisms to the test board, additional neonates might remain in the ten

brood cups that were selected for test setup. These additional neonates may be discarded, used as future culture

organisms if needed, or used to start additional tests (provided that at least 6 neonates remain and these neonates

continue to meet test organism age requirements).

13.10.2.5 Blocking by known parentage allows the performance of each test organism to be tracked to its parent

culture organism. This technique ensures that any brood effects (i.e., differences in test organism fecundity or

sensitivity attributable to the source of parentage) are evenly distributed among the test treatments. Also, by

knowing the parentage of each test organism, blocks consisting largely of males can be omitted from all test

treatments at the end of the test (see Subsection 13.13.1.4), decreasing variability among replicates.

13.10.3 LIGHT, PHOTOPERIOD, AND TEMPERATURE 

13.10.3.1 The light quality and intensity should be at ambient laboratory levels, approximately 10-20 μE/m2

/s, or

50 to 100 ft-c, with a photoperiod of 16 h of light and 8 h of darkness. 

13.10.3.2 It is critical that the test water temperature be maintained at 25 ± 1EC to obtain three broods in seven

days. 

13.10.4 DISSOLVED OXYGEN (DO) CONCENTRATION

13.10.4.1 Aeration may affect the toxicity of effluents and should be used only as a last resort to maintain

satisfactory DO concentrations. The DO concentrations should be measured in the new solutions at the start of the

test (Day 0) and before daily renewal of the test solutions on subsequent days. The DO concentration should not

fall below 4.0 mg/L (see Section 8, Effluent and Receiving Water Sampling, Sample Handling, and Sample

Preparation for Toxicity Tests). Aeration is generally not practical during the daphnid, Ceriodaphnia dubia, test. If

the DO in the effluent and/or dilution water is low, aerate gently before preparing the test solutions. The aeration

rate should not exceed 100 bubbles/min using a pipet with an orifice of approximately 1.5 mm, such as a 1 ml

KIMAX® serological pipet, or equivalent. Care should be taken to ensure that turbulence resulting from aeration

does not cause undue physical stress to the organisms.
157

13.10.5 FEEDING 

13.10.5.1 The organisms are fed when the test is initiated, and daily thereafter. Food is added to the fresh medium

immediately before or immediately after the adults are transferred. Each feeding consists of 0.1 mL YCT and

0.1 mL Selenastrum capricornutum concentrate/15 mL test solution (0.1 mL of algal concentrate containing 3.0-3.5

X 107

 cells/mL will provide 2-2.3 X 105 cells/mL in the test chamber). 

13.10.5.2 The YCT and algal suspension can be added accurately to the test chambers by using automatic

pipettors, such as Gilson, Eppendorf, Oxford, or equivalent. 

13.10.6 OBSERVATIONS DURING THE TEST 

13.10.6.1 Routine Chemical and Physical Determinations 

13.10.6.1.1 DO is measured at the beginning and end of each 24-h exposure period in at least one test chamber at

each test concentration and in the control.

13.10.6.1.2 Temperature and pH are measured at the end of each 24-h exposure period in at least one test chamber

at each test concentration and in the control. Temperature should be monitored continuously or observed and

recorded daily for at least two locations in the environmental control system or the samples. Temperature should be

measured in sufficient number of test vessels at least at the end of the test to determine the temperature variation in

the environmental chamber.

13.10.6.1.3 The pH is measured in the effluent sample each day before new test solutions are made.

13.10.6.1.4 Conductivity, alkalinity and hardness are measured in each new sample (100% effluent or receiving

water) and in the control.

13.10.6.1.5 Record the data on data sheet (Figure 2).

13.10.6.2 Routine Biological Observations

13.10.6.2.1 Three or four broods are usually obtained in the controls in a 7-day test conducted at 25 ± 1EC. A

brood is a group of offspring released from the female over a short period of time when the carapace is discarded

during molting. In the controls, the first brood of two-to-five young is usually released on the third or fourth day of

the test. Successive broods are released every 30 to 36 h thereafter. The second and third broods usually consist of

eight to 20 young each. The total number of young produced by a healthy control organism in three broods often

exceeds 30 per female. In this three-brood test, offspring from fourth or higher broods should not be counted and

should not be included in the total number of neonates produced during the test.

13.10.6.2.2 The release of a brood may be inadvertently interrupted during the daily transfer of organisms to fresh

test solutions, resulting in a split in the brood count between two successive days. For example, four neonates of a

brood of five might be released on Day 3, just prior to test solution renewal, and the fifth released just after renewal,

and counted on Day 4. Partial broods, released over a two-day period, should be counted as one brood.

13.10.6.2.3 Each day, the live adults are transferred to fresh test solutions, and the numbers of live young are

recorded (see data form, Figure 3). The young can be counted with the aid of a stereomicroscope with substage

lighting. Place the test chambers on a light box over a strip of black tape to aid in counting the neonates. The

young are discarded after counting.

13.10.6.2.4 Some of the effects caused by toxic substances include, (1) a reduction in the number of young

produced, (2) young may develop in the brood pouch of the adults, but may not be released during the exposure
158

period, and (3) partially or fully developed young may be released, but are all dead at the end of the 24-h period. 

Such effects should be noted on the data sheets (Figure 3). 

13.10.6.2.5 Protect the daphnids, Ceriodaphnia dubia, from unnecessary disturbance during the test by carrying

out the daily test observations, solution renewals, and transfer of females carefully. Make sure the females remain

immersed during the performance of these operations.

13.10.7 DAILY PREPARATION OF TEST CHAMBERS

13.10.7.1 The test is started (Day 0) with new disposable polystyrene cups or precleaned 30-mL borosilicate glass

beakers that are labeled and color-coded with tape. Each following day, a new set of plastic cups or precleaned

glass beakers is prepared, labeled, and color-coded with tape similar to the original set. New solutions are placed in

the new set of test chambers, and the test organisms are transferred from the original test chambers to the new ones

with corresponding labels and color-codes. Each day, previously used glass beakers are recleaned (see Section 5,

Facilities, Equipment, and Supplies) for the following day, and previously used plastic cups are discarded.
159

Discharger: Test Dates:

Location: Analyst:

Control:

Day

1 2 3 4 5 6 7 Remarks

Temp.

D.O. Initial

Final

pH Initial

Final

Alkalinity

Hardness

Conductivity

Chlorine

Conc:

Day

1 2 3 4 5 6 7 Remarks

Temp.

D.O. Initial

Final

pH Initial

Final

Alkalinity

Hardness

Conductivity

Chlorine

Conc:

Day

1 2 3 4 5 6 7 Remarks

Temp.

D.O. Initial

Final

pH Initial

Final

Alkalinity

Hardness

Conductivity

Chlorine

Figure 2. Data form for the daphnid, Ceriodaphnia dubia, survival and reproduction test. Routine chemical

and physical determinations.
160

Discharger: Test Dates:

Location: Analyst:

Control:

Day

1 2 3 4 5 6 7 Remarks

Temp.

D.O. Initial

Final

pH Initial

Final

Alkalinity

Hardness

Conductivity

Chlorine

Conc:

Day

1 2 3 4 5 6 7 Remarks

Temp.

D.O. Initial

Final

pH Initial

Final

Alkalinity

Hardness

Conductivity

Chlorine

Conc:

Day

1 2 3 4 5 6 7 Remarks

Temp.

D.O. Initial

Final

pH Initial

Final

Alkalinity

Hardness

Conductivity

Chlorine

Figure 2. Data form for the daphnid, Ceriodaphnia dubia, survival and reproduction test. Routine chemical

and physical determinations (CONTINUED).
161

13.10.8 TEST SOLUTION RENEWAL 

13.10.8.1 Freshly prepared solutions are used to renew the test daily. For on-site toxicity studies, fresh effluent or

receiving water samples should be collected daily, and no more than 24 h should elapse between collection of the

samples and their use in the tests (see Section 8, Effluent and Receiving Water Sampling, Sample Handling, and

Sample Preparation for Toxicity Tests). For off-site tests, a minimum of three samples are collected, preferably on

days one, three, and five. No more than 36 h should elapse between collection of the sample and the first use in the

test. Maintain the samples in the refrigerator at 0-6EC until used.

13.10.8.2 New test solutions are prepared daily, and the test organisms are transferred to the freshly prepared

solutions using a small-bore (2 mm) glass or polyethylene dropper or pipet. The animals are released under the

surface of the water so that air is not trapped under the carapace. Organisms that are dropped or injured are

discarded. 

13.10.9 TERMINATION OF THE TEST 

13.10.9.1 Tests should be terminated when 60% or more of the surviving control females have produced their third

brood, or at the end of 8 days, whichever occurs first. Because of the rapid rate of development of Ceriodaphnia

dubia, at test termination all observations on organism survival and numbers of offspring should be completed

within two hours. An extension of more than a few hours in the test period would be a significant part of the brood

production cycle of the animals, and could result in additional broods. In this three-brood test, offspring from fourth

or higher broods should not be counted and should not be included in the total number of neonates produced during

the test.

13.10.9.2 Count the young, conduct required chemical measurements, and complete the data sheets (Figure 3).

13.10.9.3 Any animal not producing young should be examined to determine if it is a male (Berner, 1986). In

most cases, the animal will need to be placed on a microscope slide before examining (see Subsection 13.6.16.4).

13.10.9.3.1 In general, the occurrence of males in healthy, well-maintained individual cultures is rare. In

interlaboratory testing of the Ceriodaphnia dubia Survival and Reproduction Test, males were identified in only 7%

(9 of 126 tests) of tests conducted (USEPA, 2001a). The number of males identified in these tests ranged from 1 to

12. In five tests containing a large number of males (4-12), laboratories conducting those tests also noted that

organism cultures were experiencing or recovering from some stress. Since male production in cladoceran

populations is generally associated with conditions of environmental stress (Pennak, 1989), culture conditions

should be examined whenever males are identified in a test.

13.11 SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA

13.11.1 A summary of test conditions and test acceptability criteria is presented in Table 3.

13.12 ACCEPTABILITY OF TEST RESULTS

13.12.1 For the test results to be acceptable, at least 80% of all control organisms must survive, and 60% of

surviving control females must produce at least three broods, with an average of 15 or more young per surviving

female.
162

Discharger: Analyst:

Location: Test Start-Date/Time: 

Date Sample Collected: Test Start-Date/time: 

Replicate

Number of

Young

Number

of Adults

Young

per Adult

1 2 3 4 5 6 7 8 9 10

Conc. Day

1

2

3

4

5

6

7

Total

Replicate

Number of

Young

Number

of Adults

Young

per Adult

1 2 3 4 5 6 7 8 9 10

Conc. Day

1

2

3

4

5

6

7

Total

Replicate

Number of

Young

Number

of Adults

Young

per Adult

1 2 3 4 5 6 7 8 9 10

Conc. Day

1

2

3

4

5

6

7

Total

Figure 3. Data form for the daphnid, Ceriodaphnia dubia, survival and reproduction test. Daily summary

of data.
163

Discharger: Analyst:

Location: Test Start-Date/Time: 

Date Sample Collected: Test Start-Date/time: 

Replicate

Number of

Young

Number

of Adults

Young

per Adult

1 2 3 4 5 6 7 8 9 10

Conc. Day

1

2

3

4

5

6

7

Total

Replicate

Number of

Young

Number

of Adults

Young

per Adult

1 2 3 4 5 6 7 8 9 10

Conc. Day

1

2

3

4

5

6

7

Total

Replicate

Number of

Young

Number

of Adults

Young

per Adult

1 2 3 4 5 6 7 8 9 10

Conc. Day

1

2

3

4

5

6

7

Total

Figure 3. Data form for the daphnid, Ceriodaphnia dubia, survival and reproduction test. Daily summary

of data (CONTINUED).
164

TABLE 3. SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA FOR

DAPHNID, CERIODAPHNIA DUBIA, SURVIVAL AND REPRODUCTION TOXICITY TESTS

WITH EFFLUENTS AND RECEIVING WATERS (TEST METHOD 1002.0)1

1. Test type: Static renewal (required) 

2. Temperature (EC): 25 ± 1EC (recommended) 

Test temperatures should not deviate (i.e., maximum

minus minimum temperature) by more than 3EC

during the test (required) 

3. Light quality: Ambient laboratory illumination (recommended) 

4. Light intensity: 10-20 μE/m2

/s, or 50-100 ft-c 

(ambient laboratory levels) (recommended) 

5. Photoperiod: 16 h light, 8 h dark (recommended) 

6. Test chamber size: 30 mL (recommended minimum)

7. Test solution volume: 15 mL (recommended minimum)

8. Renewal of test solutions: Daily (required) 

9. Age of test organisms: Less than 24 h; and all released within a 8-h period

(required)

10. No. neonates per 

test chamber: 1 Assigned using blocking by known parentage

(Subsection 13.10.2.4) (required)

11. No. replicate test 

chambers per concentration: 10 (required minimum) 

12. No. neonates per 

test concentration: 10 (required minimum)

13. Feeding regime: Feed 0.1 mL each of YCT and algal suspension per

test chamber daily (recommended) 

14. Cleaning: Use freshly cleaned glass beakers or new plastic cups

daily (recommended) 

15. Aeration: None (recommended) 

16. Dilution water: Uncontaminated source of receiving or other natural

water, synthetic water prepared using MILLIPORE

MILLI-Q® or equivalent deionized water and reagent

grade chemicals or DMW (see Section 7, Dilution

Water) (available options)

1

 For the purposes of reviewing WET test data submitted under NPDES permits, each test condition listed

above is identified as required or recommended (see Subsection 10.2 for more information on test review). 

Additional requirements may be provided in individual permits, such as specifying a given test condition

where several options are given in the method. 
165

 TABLE 3. SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA FOR

DAPHNID, CERIODAPHNIA DUBIA, SURVIVAL AND REPRODUCTION TOXICITY

TESTS WITH EFFLUENTS AND RECEIVING WATERS (TEST METHOD 1002.0)

(CONTINUED)

17. Test concentrations: Effluents: 5 and a control (required minimum)

Receiving Water: 100% receiving water (or minimum

of 5) and a control (recommended) 

18. Dilution factor: Effluents: $ 0.5 (recommended) 

 Receiving Waters: None or $ 0.5 (recommended) 

19. Test duration: Until 60% or more of surviving control females have

three broods (maximum test duration 8 days)

(required) 

20. Endpoints: Survival and reproduction (required) 

21. Test acceptability criteria: 80% or greater survival of all control organisms and

an average of 15 or more young per surviving female

in the control solutions. 60% of surviving control

females must produce three broods (required)

22. Sampling requirements: For on-site tests, samples collected daily and used

within 24 h of the time they are removed from the

sampling device. For off-site tests, a minimum of

three samples (e.g., collected on days one, three, and

five) with a maximum holding time of 36 h before

first use (see Section 8, Effluent and Receiving Water

Sampling, Sample Handling, and Sample Preparation

for Toxicity Tests, Subsection 8.5.4) (required) 

23. Sample volume required: 1 L/day (recommended) 
166

TABLE 4. SUMMARY OF SURVIVAL AND REPRODUCTION DATA FOR THE DAPHNID,

CERIODAPHNIA DUBIA, EXPOSED TO AN EFFLUENT FOR SEVEN DAYS 

No. of Young per Adult No.

Effluent Replicate Live

Concentration 1 2 3 4 5 6 7 8 9 10 Adults

(%)

Control 27 30 29 31 16 15 18 17 14 27 10 

1.56 32 35 32 26 18 29 27 16 35 13 10 

3.12 39 30 33 33 36 33 33 27 38 44 10 

6.25 27 34 36 34 31 27 33 31 33 31 10 

12.5 10 13 7 7 7 10 10 16 12 2 10 

25.0 0 0 0 0 0 0 0 0 0 0 2 

13.13 DATA ANALYSIS

13.13.1 GENERAL

13.13.1.1 Tabulate and summarize the data. A sample set of survival and reproduction data is listed in Table 4.

13.13.1.2 The endpoints of toxicity tests using the daphnid, Ceriodaphnia dubia, are based on the adverse effects

on survival and reproduction. The LC50, the IC25, the IC50 and the EC50 are calculated using point estimation

techniques, and LOEC and NOEC values for survival and reproduction are obtained using a hypothesis test

approach such as Fisher's Exact Test (Finney, 1948; Pearson and Hartley, 1962), Dunnett's Procedure (Dunnett,

1955) or Steel's Many-one Rank Test (Steel, 1959; Miller, 1981) (see Section 9, Chronic Toxicity Test Endpoints

and Data Analysis). Separate analyses are performed for the estimation of the LOEC and NOEC endpoints and for

the estimation of the LC50, IC25, IC50 and EC50. Concentrations at which there is no survival in any of the test

chambers are excluded from the statistical analysis of the NOEC and LOEC for reproduction, but included in the

estimation of the LC50, IC25, IC50, and EC50. See the Appendices for examples of the manual computations,

program listings, and examples of data input and program output.

13.13.1.3 The statistical tests described here must be used with a knowledge of the assumptions upon which the

tests are contingent. Tests for normality and homogeneity of variance are included in Appendix B. The assistance

of a statistician is recommended for analysts who are not proficient in statistics. 

13.13.1.4 At the end of the test, if 50% or more of the surviving organisms in a block are identified as males, the

entire block must be excluded from data analysis for the reproduction endpoint (i.e., calculation of the reproduction

NOEC and IC25 as described in Subsection 13.13.3), but may be used in the analysis of the survival endpoint (i.e.,

calculation of the survival NOEC and LC50 as described in Subsection 13.13.2). For blocks having fewer than 50%

of surviving organisms identified as males, the males (not the entire block) must be excluded from the analysis of

reproduction (i.e., calculation of the reproduction NOEC and IC25 as described in Subsection 13.13.3), but may be

used in the analysis of survival (i.e., calculation of the survival NOEC and LC50 as described in Subsection

13.13.2). Note that the exclusion of males from the analysis of reproduction may create unequal sample sizes

among the concentrations, influencing the statistical methods chosen for analysis of reproduction (Figure 6). 

Determinations regarding test acceptability criteria for survival and reproduction (Subsection 13.12) must be made

prior to exclusion of any blocks. In addition to these test acceptability criteria, if fewer than eight replicates in the
167

control remain after excluding males and blocks with 50% or more of surviving organisms identified as males, the

test is invalid and must be repeated with a newly collected sample. 

13.13.2 EXAMPLE OF ANALYSIS OF THE DAPHNID, CERIODAPHNIA DUBIA, SURVIVAL DATA 

13.13.2.1 Formal statistical analysis of the survival data is outlined on the flowchart in Figure 4. The response

used in the analysis is the number of animals surviving at each test concentration. Separate analyses are performed

for the estimation of the NOEC and LOEC endpoints and for the estimation of the EC50, LC50, IC25, or IC50

endpoints. Concentrations at which there is no survival in any of the test chambers are excluded from the statistical

analysis of the NOEC and LOEC, but included in the estimation of the LC, EC, and IC endpoints.

13.13.2.2 Fisher's Exact Test is used to determine the NOEC and LOEC endpoints. It provides a conservative test

of the equality of any two survival proportions assuming only the independence of responses from a Bernoulli

(binomial) population. Additional information on Fisher's Exact Test is provided in Appendix G.
168

Figure 4. Flowchart for statistical analysis of the daphnid, Ceriodaphnia dubia, survival data.
169

TABLE 5. FORMAT OF THE 2x2 CONTINGENCY TABLE

Number of Number of 

Successes Failures Observations 

Condition 1 a A - a A 

Condition 2 b B - b B 

Total a + b [(A+B) - a - b] A + B

13.13.2.3 Probit Analysis (Finney, 1971; Appendix I) is used to estimate the concentration that causes a specified

percent decrease in survival from the control. In this analysis, the total number dead at a given concentration is the

response.

13.13.2.4 Example of Analysis of Survival Data 

13.13.2.4.1 The data in Table 4 will be used to illustrate the analysis of survival data from the daphnid,

Ceriodaphnia dubia, Survival and Reproduction Test. As can be seen from the data in Table 4, there were no

deaths in the 1.56%, 3.12%, 6.25%, and 12.5% concentrations. These concentrations are obviously not different

from the control in terms of survival. This leaves only the 25% effluent concentration to be tested statistically for a

difference in survival from the control.

13.13.2.5 Fisher's Exact Test

13.13.2.5.1 The basis for Fisher's Exact Test is a 2x2 contingency table. From the 2x2 table prepared by

comparing the control and the effluent concentration, determine statistical significance by looking up a value in the

table provided in Appendix G (Table G.5). However, to use this table the contingency table must be arranged in the

format illustrated in Table 5.

13.13.2.5.2 Arrange the table so that the total number of observations for row one is greater than or equal to the

total for row two (A $ B). Categorize a success such that the proportion of successes for row one is greater than or

equal to the proportion of successes for row two (a/A $ b/B). For these data, a success may be 'alive' or 'dead'

whichever causes a/A $ b/B. The test is then conducted by looking up a value in the table of significance levels of

b and comparing it to the b value given in the contingency table. The table of significance levels of b is included in

Appendix G, Table G.5. Enter Table G.5 in the section for A, subsection for B, and the line for a. If the b value of

the contingency table is equal to or less than the integer in the column headed 0.05 in Table G.5, then the survival

proportion for the effluent concentration is significantly different from that of the control. A dash or absence of

entry in Table G.5 indicates that no contingency table in that class is significant.

13.13.2.5.3 To compare the control and the effluent concentration of 25%, the appropriate contingency table for

the test is given in Table 6.

13.13.2.5.4 Since 10/10 $ 3/10, the category 'alive' is regarded as a success. For A = 10, B = 10 and, a = 10, under

the column headed 0.05, the value from Table G.5 is b = 6. Since the value of b (b = 3) from the contingency table

(Table 6), is less than the value of b (b = 6) from Table G.5 in Appendix G, the test concludes that the proportion
170

TABLE 7. DATA FOR TRIMMED SPEARMAN-KARBER ANALYSIS

Effluent Concentration (%)

Control 1.56 3.12 6.25 12.5 25.0 

Number Dead 0 0 0 0 0 8 

Number Exposed 10 10 10 10 10 10 

surviving in the 25% effluent concentration is significantly different from the control. Thus the NOEC for survival

is 12.5% and the LOEC is 25%. 

TABLE 6. 2x2 CONTIGENCY TABLE FOR CONTROL AND 25% EFFLUENT

Number of

Alive Dead

Number of

Observations

Condition 1 10 0 10

Condition 2 3 7 10

Total 13 7 20

13.13.2.6 Calculation of the LC50 

13.13.2.6.1 The data used for the Trimmed Spearman-Karber Method are summarized in Table 7. To perform the

Trimmed Spearman-Karber Method, run the USEPA Trimmed Spearman-Karber Program. An example of the

program input and output is supplied in Appendix J.

13.13.2.6.2 For this example, with only one partial mortality, Trimmed Spearman-Karber analysis appears

appropriate for this data.

13.13.2.6.3 Figure 5 shows the output for the Trimmed Spearman-Karber Analysis of the data in Table 7 using the

USEPA Program.

13.13.3 EXAMPLE OF ANALYSIS OF THE DAPHNID, CERIODAPHNIA DUBIA, REPRODUCTION 

DATA

13.13.3.1 Formal statistical analysis of the reproduction data is outlined on the flowchart in Figure 6. The

response used in the statistical analysis is the number of young produced per adult female, which is determined by

taking the total number of young produced until either the time of death of the adult or the end of the experiment,

whichever comes first. In this three-brood test, offspring from fourth or higher broods should not be counted and

should not be included in the total number of neonates produced during the test. An animal that dies before
171

producing young, if it has not been identified as a male, would be included in the analysis with zero entered as the

number of young produced. The subsequent calculation of the mean number of live young produced per adult

female for each toxicant concentration provides a combined measure of the toxicant's effect on both mortality and

reproduction. An IC estimate can be calculated for the reproduction data using a point estimation technique (see

Section 9, Chronic Toxicity Test Endpoints and Data Analysis). Hypothesis testing can be used to obtain an NOEC

for reproduction. Concentrations above the NOEC for survival are excluded from the hypothesis test for

reproduction effects.

13.13.3.2 The statistical analysis using hypothesis tests consists of a parametric test, Dunnett's Procedure, and a

nonparametric test, Steel's Many-one Rank Test. The underlying assumptions of the Dunnett's Procedure, normality

and homogeneity of variance, are formally tested using the Shapiro Wilk's Test for normality, and Bartlett's Test for

homogeneity of variance. If either of these tests fails, a nonparametric test, Steel's Many-one Rank Test, is used to

determine the NOEC and LOEC. If the assumptions of Dunnett's Procedure are met, the endpoints are determined

by the parametric test.

13.13.3.3 Additionally, if unequal numbers of replicates occur among the concentration levels tested there are

parametric and nonparametric alternative analyses. The parametric analysis is a t test with the Bonferroni

adjustment (see Appendix D). The Wilcoxon Rank Sum Test with the Bonferroni adjustment is the nonparametric

alternative (see Appendix F).

13.13.3.4 The data, mean, and variance of the observations at each concentration including the control are listed in

Table 8. A plot of the number of young per adult female for each concentration is provided in Figure 7. Since there

is significant mortality in the 25% effluent concentration, its effect on reproduction is not considered.

TABLE 8. THE DAPHNID, CERIODAPHNIA DUBIA, REPRODUCTION DATA

Effluent Concentration (%)

Replicate Control 1.56 3.12 6.25 12.5 

1 27 32 39 27 10

2 30 35 30 34 13

3 29 32 33 36 7

4 31 26 33 34 7

5 16 18 36 31 7

6 15 29 33 27 10

7 18 27 33 33 10

8 17 16 27 31 16

9 14 35 38 33 12

10 27 13 44 31 2

Mean Y'I 22.4 26.3 34.6 31.7 9.4 

Si

2 48.0 64.0 23.4 8.7 15.1 

i 1 2 34 5
172

TRIMMED SPEARMAN-KARBER METHOD. VERSION 1.5 

 DATE: 1 TEST NUMBER: 2 DURATION: 7 Days 

 TOXICANT: effluent 

 SPECIES: Ceriodaphnia dubia

 RAW DATA: Concentration Number Mortalities 

 --- ---- (%) Exposed 

 .00 10 0

 1.25 10 0 

 3.12 10 0 

 6.25 10 0 

 12.5 10 0 

 25.0 10 8 

 SPEARMAN-KARBER TRIM: 20.00 % 

 SPEARMAN-KARBER ESTIMATES: LC50: 19.28 

 95% CONFIDENCE LIMITS 

 ARE NOT RELIABLE. 

 NOTE: MORTALITY PROPORTIONS WERE NOT MONOTONICALLY INCREASING. 

 ADJUSTMENTS WERE MADE PRIOR TO SPEARMAN-KARBER ESTIMATION. 

Figure 5. Output for USEPA Trimmed Spearman-Karber program.
173

Figure 6. Flowchart for the statistical analysis of the daphnid, Ceriodaphnia dubia, reproduction

data.
174

Figure 7. Plot of number of young per adult female from a daphnid, Ceriodaphnia dubia, survival and reproduction test.
175

TABLE 9. CENTERED OBSERVATIONS FOR SHAPIRO-WILK'S EXAMPLE

Effluent Concentration (%)

Replicate Control 1.56 3.12 6.25 12.5

1 4.6 5.7 4.4 -4.7 0.6

2 7.6 8.7 -4.6 2.3 3.6 

3 6.6 5.7 -1.6 4.3 -2.4 

4 8.6 -0.3 -1.6 2.3 -2.4 

5 -6.4 -8.3 1.4 -0.7 -2.4 

6 -7.4 2.7 -1.6 -4.7 0.6 

7 -4.4 0.7 -1.6 1.3 0.6 

8 -5.4 -10.3 -7.6 -0.7 6.6 

9 -8.4 8.7 3.4 1.3 2.6 

10 4.6 -13.3 9.4 -0.7 -7.4 

13.13.3.5 Test for Normality

13.13.3.5.1 The first step of the test for normality is to center the observations by subtracting the mean of all the

observations within a concentration from each observation in that concentration. The centered observations are

summarized in Table 9.

13.13.3.5.2 Calculate the denominator, D, of the test statistic: 

D ' '

n

i'1

(Xi

&X ̄)

2

 Where: Xi = the ith centered observation

 

 = the overall X ̄ mean of the centered observations 

 n = the total number of centered observations.

For this set of data,

n = 50 

X ̄ ' 1

50 (0.0) ' 0.0

D = 1433.4 
176

W ' 1

D ['

k

i'1

ai

(X (n&i%1)&X (i))]

2

W ' 1

1433.4 (37.3)2 ' 0.97

13.13.3.5.3 Order the centered observations from smallest to largest 

 X(1) # X(2) # ...# X(n)

 Where X(i) is the ith ordered observation. These ordered observations are listed in Table 10.

13.13.3.5.4 From Table 4, Appendix B, for the number of observations, n, obtain the coefficients a1, a2, ..., ak where

k is n/2 if n is even and (n-1)/2 if n is odd. For the data in this example, n = 50, k = 25. The ai

 values are listed in

Table 11.

13.13.3.5.5 Compute the test statistic, W, as follows: 

The differences X(n-i+1) - X(i) are listed in Table 11. 

For this set of data: 

 
177

 TABLE 10. ORDERED CENTERED OBSERVATIONS FOR SHAPIRO-WILK'S EXAMPLE 

 iX(i) i X(i)

1 -13.3 26 0.6 

2 -10.3 27 0.6 

3 -8.4 28 0.7 

4 -8.3 29 1.3 

5 -7.6 30 1.3 

6 -7.4 31 1.4 

7 -7.4 32 2.3 

8 -6.4 33 2.3 

9 -5.4 34 2.6 

10 -4.7 35 2.7 

11 -4.7 36 3.4 

12 -4.6 37 3.6 

13 -4.4 38 4.3 

14 -2.4 39 4.4 

15 -2.4 40 4.6 

16 -2.4 41 4.6 

17 -1.6 42 5.7 

18 -1.6 43 5.7 

19 -1.6 44 6.6 

20 -1.6 45 6.6 

21 -0.7 46 7.6 

22 -0.7 47 8.6 

23 -0.7 48 8.7 

24 -0.3 49 8.7 

25 0.6 50 9.4 
178

TABLE 11. COEFFICIENTS AND DIFFERENCES FOR SHAPIRO-WILK'S EXAMPLE

i ai X(n-i+1) - X(i)

1 0.3751 22.7 X(50) - X(1)

2 0.2574 19.0 X(49) - X(2)

3 0.2260 17.1 X(48) - X(3)

4 0.2032 16.9 X(47) - X(4)

5 0.1847 15.2 X(46) - X(5)

6 0.1691 14.0 X(45) - X(6)

7 0.1554 14.0 X(44) - X(7)

8 0.1430 12.1 X(43) - X(8)

9 0.1317 11.1 X(42) - X(9)

10 0.1212 9.3 X(41) - X(10)

11 0.1113 9.3 X(40) - X(11)

12 0.1020 9.0 X(39) - X(12)

13 0.0932 8.7 X(38) - X(13)

14 0.0846 6.0 X(37) - X(14)

15 0.0764 5.8 X(36) - X(15)

16 0.0685 5.1 X(35) - X(16)

17 0.0608 4.2 X(34) - X(17)

18 0.0532 3.9 X(33) - X(18)

19 0.0459 3.9 X(32) - X(19)

20 0.0386 3.0 X(31) - X(20)

21 0.0314 2.0 X(30) - X(21)

22 0.0244 2.0 X(29) - X(22)

23 0.0174 1.4 X(28) - X(23)

24 0.0104 0.9 X(27) - X(24)

25 0.0035 0.0 X(26) - X(25)

13.13.3.5.6 The decision rule for this test is to compare W with the critical value found in Table 6, Appendix B. If

the computed W is less than the critical value, conclude that the data are not normally distributed. For this example,

the critical value at a significance level of 0.01 and 50 observations (n) is 0.930. Since W = 0.97 is greater than the

critical value, the conclusion of the test is that the data are normally distributed. 

13.13.3.6 Test for Homogeneity of Variance 

13.13.3.6.1 The test used to examine whether the variation in number of young produced is the same across all

effluent concentrations including the control, is Bartlett's Test (Snedecor and Cochran, 1980). The test statistic is as

follows: 

 B '

[('

P

i'1

Vi)lnS ̄2

& '

P

i'1

VilnS 2

i ]

C

 Where: Vi = degrees of freedom for each effluent concentration and control, Vi = (ni - 1) 

p = number of levels of effluent concentration and control 
179

S ̄2 '

('

P

i'1

ViS 2

i )

'

P

i'1

Vi

C ' 1%(3(p&1))&1 ['

P

i'1

1

Vi

&('

P

i'1

Vi

)

&1

]

ni = the number of replicates for concentration i 

 ln = loge

i = 1, 2, ..., p where p is the number of concentrations including the control 

13.13.3.6.2 For the data in this example (see Table 8), all effluent concentrations including the control have the

same number of replicates (ni

 = 10 for all i). Thus, Vi = 9 for all i.

13.13.3.6.3 Bartlett's statistic is therefore: 

B ' [(45)ln(31.8)&9'

P

i'1

ln(S 2

i )]/1.04

= [45(3.46) - 9(16.061)]/1.04 

 = 11.15/1.04 

 = 10.72 

13.13.3.6.4 B is approximately distributed as chi-square with p - 1 degrees of freedom, when the variances are in

fact the same. Therefore, the appropriate critical value for this test, at a significance level of 0.01 with four degrees

of freedom, is 13.3. Since B = 10.7 is less than the critical value of 13.3, conclude that the variances are not

different. 

13.13.3.7 Dunnett's Procedure 

13.13.3.7.1 To obtain an estimate of the pooled variance for the Dunnett's Procedure, construct an ANOVA table as

described in Table 12.
180

TABLE 12. ANOVA TABLE

Source df Sum of Squares Mean Square(MS) 

(SS) (SS/df) 

 

Between p - 1 SSB = SSB/(p-1) 

 

Within N - p SSW = SSW/(N-p) 

Total N - 1 SST 

Where: p = number effluent concentrations including the control 

N = total number of observations n1 + n2 ... + np

ni = number of observations in concentration i 

 Between Sum of Squares SSB ' '

P

i'1

T 2

i

ni

& G 2

N

 SST ' ' Total Sum of Squares

P

i'1

'

ni

j'1

Y 2

ij & G 2

N

 SSW ' SST&SSB Within Sum of Squares

G = the grand total of all sample observations, G ' '

P

i'1

Ti

T i = the total of the replicate measurements for concentration i 

Yij = the jth observation for concentration i (represents the number of young produced by female j in

effluent concentration i)

13.13.3.7.2 For the data in this example:

n1 = n 2 = n 3 = n 4 = n5 = 10 

N = 50 

T1 = Y11 + Y 12 + . . . + Y110 = 224 

T2 = Y21 + Y 22 + . . . + Y210 = 263 
181

TABLE 13. ANOVA TABLE FOR DUNNETT'S PROCEDURE EXAMPLE 

Source df Sum of Squares Mean 

Square(MS)

(SS) (SS/df)

Between 4 3887.88 971.97

Within 45 1433.40 31.85

Total 49 5321.28

T3 = Y31 + Y 32 + . . . + Y310 = 346 

T4 = Y41 + Y 42 + . . . + Y410 = 317 

T5 = Y51 + Y 52 + . . . + Y510 = 94 

G = T1 + T2 + T3 + T4 + T5 = 1244 

SSB ' '

P

i'1

T 2

i

ni

& G 2

N

t

2 ' (22.4&26.3)

[5.64 ( 1

10)%( 110)]

' -1.55

SST ' '

P

i'1

'

ni

j'1

Y 2

ij & G 2

N

' 36,272& (1244)2

50 '5321.28

 SSW ' SST&SSB = 5321.28 - 3887.88 = 1433.40 

 SB

2

 = SSB/(p-1) = 3887.88/(5-1) = 971.97 

 SW

2

 = SSW/(N-p) = 1433.40/(50-5) = 31.85 

13.13.3.7.3 Summarize these calculations in an ANOVA table (Table 13).
182

t

i ' (Y ̄

1&Y ̄

i

)

Sw ( 1

n1

)%( 1

ni

)

t

2 ' (22.4&26.3)

[5.64 ( 1

10)%( 110)]

' -1.55

TABLE 14. CALCULATED T VALUES

Effluent Concentration (%) i ti

1.56 2 -1.55 

3.12 3 -4.84 

6.25 4 -3.69 

12.5 5 5.16 

13.13.3.7.4 To perform the individual comparisons, calculate the t statistic for each concentration and control

combination as follows:

Where: = mean number of young produced for effluent concentration i Y ̄ i

 = mean number of young produced for the control Y ̄1

 SW = square root of within mean square 

 n1 = number of replicates for the control 

 ni = number of replicates for concentration i. 

Since we are looking for a decrease in reproduction from the control, the mean for concentration i is subtracted from

the control mean in the t statistic above. However, if we were looking for an increased response over the control,

the control mean would be subtracted from the mean at a concentration. 

13.13.3.7.5 Table 14 includes the calculated t values for each concentration and control combination. In this

example, comparing the 1.56% concentration with the control the calculation is as follows: 

13.13.3.7.6 Since the purpose of this test is to detect a significant reduction in mean reproduction, a one-sided test

is appropriate. The critical value for this one-sided test is found in Table 5, Appendix C. Since an entry for 45

degrees of freedom for error is not provided in the table, the entry for 40 degrees of freedom for error, an alpha level

of 0.05 and four concentrations (excluding the control) will be used, 2.23. The mean reproduction for concentration

"i" is considered significantly less than the mean reproduction for the control if ti

 is greater than the critical value. 
183

Since t5 is greater than 2.23, the 12.5% concentration has significantly lower reproduction than the control. Hence

the NOEC and the LOEC for reproduction are 6.25% and 12.5%, respectively.

13.13.3.7.7 To quantify the sensitivity of the test, the minimum significant difference (MSD) that can be

statistically detected may be calculated:

MSD ' d Sw ( 1

n1

)%(

1

n

)

Where: d = the critical value for the Dunnett's Procedure 

SW = the square root of the within mean square 

n = the common number of replicates at each concentration (this assumes equal replication at each

concentration) 

n1 = the number of replicates in the control. 

13.13.3.7.8 In this example:

MSD ' 2.23(5.64) ( 1

10)%( 110)

 = 2.23 (5.64) (0.447)

= 5.62

13.13.3.7.9 Therefore, for this set of data, the minimum difference that can be detected as statistically significant is

5.62. 

13.13.3.7.10 This represents a 25% decrease in mean reproduction from the control.

13.13.3.8 Calculation of the IC

13.13.3.8.1 The reproduction data in Table 4 are utilized in this example. As can be seen from Figure 8, the

observed means are not monotonically non-increasing with respect to concentration. Therefore, the means must be

smoothed prior to calculating the IC.

13.13.3.8.2 Starting with the observed control mean, Y'1= 22.4, and the observed mean for the lowest effluent

concentration,Y'2= 26.3, we see that Y'1 is less than Y'2 .

13.13.3.8.3 Calculate the smoothed means:

 

 M1 = M2 = (Y'1+Y'2)/2 = 24.35

 
184

TABLE 15. DAPHNID, CERIODAPHNIA DUBIA, REPRODUCTION MEAN RESPONSE AFTER

SMOOTHING

Response Smoothed

Effluent Means, Yi Means, Mi

Conc. (%) i (young/female) (young/female)

Control 1 22.4 28.75

1.56 2 26.3 28.75

3.12 3 34.6 28.75

6.25 4 31.7 28.75

12.5 5 9.4 9.40

25.0 6 0.0 0.00

13.13.3.8.4 Since Y'3= 34.6 is larger than M2, average Y'3 with the previous concentrations: 

 

M1 = M2 = M3 = (M1 + M2 +Y'3)/3 = 27.7.

13.13.3.8.5 Additionally,Y'4 = 31.7 is larger than M3, and is pooled with the first three means. Thus:

(M1 + M2 + M3 +Y'4)/4 = 28.7 = M1 = M2 = M3 = M4

13.13.3.8.6 Since M4 > Y'5 = 9.4, set M5 = 9.4. Likewise, M5 > Y'6 = 0, and M6 becomes 0. Table 15 contains the

smoothed means and Figure 8 gives a plot of the smoothed means and the interpolated response curve.

13.13.3.8.7 Estimates of the IC25 and IC50 can be calculated using the Linear Interpolation Method. A 25%

reduction in reproduction, compared to the controls, would result in a mean reproduction of 21.56 young per adult,

where M1(1 - p/100) = 28.75(1 - 25/100). A 50% reduction in reproduction, compared to the controls, would result

in a mean reproduction of 14.38 young per adult, where M1(1 - p/100) = 28.75(1 - 50/100). Examining the

smoothed means and their associated concentrations (Table 15), the two effluent concentrations bracketing 21.56

young per adult are C4 = 6.25% effluent and C5 = 12.5% effluent. The two effluent concentrations bracketing a

response of 14.38 young per adult are also C4 = 6.25% and C 5 = 12.5%.
185

Figure 8. Plot of raw data, observed means, and smoothed means for the daphnid, Ceriodaphnia dubia, reproductive data.
186

13.13.3.8.8 Using equation from Section 4.2 in Appendix M, the estimate of the IC25 is as follows:

ICp ' Cj

%[M1(1& p

100)&Mj

]

(C(j%1)&Cj)

(M(j%1)&Mj

)

IC25 ' 6.25%[28.75(1& 25

100)&28.75] (12.5&6.25)(9.40&28.75)

= 8.57% effluent

13.13.3.8.9 The estimate of the IC50 is as follows:

ICp ' Cj

%[M1(1& p

100)&Mj

]

(C(j%1)&Cj)

(M(j%1)&Mj

)

IC50 ' 6.25%[28.75(1& 50

100)&28.75] (12.5&6.25)(9.40&28.75)

 = 10.89% effluent

13.13.3.8.10 When the ICPIN program was used to analyze this data set for the IC25, requesting 80 resamples, the

estimate of the IC25 was 8.5715% effluent. The empirical 95% confidence interval for the true mean was 8.3112%

and 9.0418% effluent. The computer output for this data set is provided in Figure 9.

13.13.3.8.11 When the ICPIN program was used to analyze this data set for the IC50, requesting 80 resamples, the

estimate of the IC50 was 10.8931% effluent. The empirical 95% confidence interval for the true mean was

10.4373% and 11.6269% effluent. The computer output for this data set is provided in Figure 10.
187

Conc. ID 1 2 3 4 5 6

------------------------------------------------------------------------

Conc. Tested 0 1.56 3.12 6.25 12.5 25.0

------------------------------------------------------------------------

Response 1 27 32 39 27 10 0

Response 2 30 35 30 34 13 0

Response 3 29 32 33 36 7 0

Response 4 31 26 33 34 7 0

Response 5 16 18 36 31 7 0

Response 6 15 29 33 27 10 0

Response 7 18 27 33 33 10 0

Response 8 17 16 27 31 16 0

Response 9 14 35 38 33 12 0

Response 10 27 13 44 31 2 0

------------------------------------------------------------------------

*** Inhibition Concentration Percentage Estimate ***

Toxicant/Effluent: Effluent

Test Start Date: Example Test Ending Date: 

Test Species: Ceriodaphnia dubia

Test Duration: 7-d

DATA FILE: cdmanual.icp

OUTPUT FILE: cdmanual.i25

-----------------------------------------------------------------------

Conc. Number Concentration Response Std. Pooled

 ID Replicates % Means Dev. Response Means

-----------------------------------------------------------------------

 1 10 0.000 22.400 6.931 28.750

 2 10 1.560 26.300 8.001 28.750

 3 10 3.120 34.600 4.835 28.750

 4 10 6.250 31.700 2.946 28.750

 5 10 12.500 9.400 3.893 9.400

 6 10 25.000 0.000 0.000 0.000

-----------------------------------------------------------------------

The Linear Interpolation Estimate: 8.5715 Entered P Value: 25

-----------------------------------------------------------------------

Number of Resamplings: 80

The Bootstrap Estimates Mean: 8.5891 Standard Deviation: 0.1831

Original Confidence Limits: Lower: 8.3112 Upper: 9.0418

Resampling time in Seconds: 2.53 Random Seed: -641671986

Figure 9. Example of ICPIN program output for the IC25. 
188

Conc. ID 1 2 3 4 5 6

------------------------------------------------------------------------

Conc. Tested 0 1.56 3.12 6.25 12.5 25.0

------------------------------------------------------------------------

Response 1 27 32 39 27 10 0

Response 2 30 35 30 34 13 0

Response 3 29 32 33 36 7 0

Response 4 31 26 33 34 7 0

Response 5 16 18 36 31 7 0

Response 6 15 29 33 27 10 0

Response 7 18 27 33 33 10 0

Response 8 17 16 27 31 16 0

Response 9 14 35 38 33 12 0

Response 10 27 13 44 31 2 0

------------------------------------------------------------------------

*** Inhibition Concentration Percentage Estimate ***

Toxicant/Effluent: Effluent

Test Start Date: Example Test Ending Date: 

Test Species: Ceriodaphnia dubia

Test Duration: 7-d

DATA FILE: cdmanual.icp

OUTPUT FILE: cdmanual.i50

-----------------------------------------------------------------------

Conc. Number Concentration Response Std. Pooled

 ID Replicates % Means Dev. Response Means

-----------------------------------------------------------------------

 1 10 0.000 22.400 6.931 28.750

 2 10 1.560 26.300 8.001 28.750

 3 10 3.120 34.600 4.835 28.750

 4 10 6.250 31.700 2.946 28.750

 5 10 12.500 9.400 3.893 9.400

 6 10 25.000 0.000 0.000 0.000

-----------------------------------------------------------------------

The Linear Interpolation Estimate: 10.8931 Entered P Value: 50

-----------------------------------------------------------------------

Number of Resamplings: 80

The Bootstrap Estimates Mean: 10.9316 Standard Deviation: 0.3357

Original Confidence Limits: Lower: 10.4373 Upper: 11.6269

Resampling time in Seconds: 2.58 Random Seed: 172869646

Figure 10. Example of ICPIN program output for the IC50.
189

13.14 PRECISION AND ACCURACY

13.14.1 PRECISION – Data on single-laboratory and multilaboratory precision are described below (Subsections

13.14.1.1 and 13.14.1.2). Single-laboratory precision is a measure of the reproducibility of test results when tests

are conducted using a specific method under reasonably constant conditions in the same laboratory. Singlelaboratory precision is synonymous with the terms within-laboratory precision and intralaboratory precision. 

Multilaboratory precision is a measure of the reproducibility of test results from different laboratories using the

same test method and analyzing the same test material. Multilaboratory precision is synonymous with the term

interlaboratory precision. Interlaboratory precision, as used in this document, includes both within-laboratory and

between-laboratory components of variability. In recent multilaboratory studies, these two components of

interlaboratory precision have been displayed separately (termed within-laboratory and between-laboratory

variability) and combined (termed total interlaboratory variability). The total interlaboratory variability that is

reported from these studies is synonymous with interlaboratory variability reported from other studies where

individual variability components are not separated.

13.14.1.1 Single-Laboratory Precision

13.14.1.1.1 Information on the single-laboratory precision of the daphnid, Ceriodaphnia dubia, survival and

reproduction test is based on the NOEC and LOEC values from nine tests with the reference toxicant sodium

pentachlorophenate (NaPCP) is provided in Table 16. The NOECs and LOECs of all tests fell in the same

concentration range, indicating maximum possible precision. Table 17 gives precision data for the IC25 and IC50

values for seven tests with the reference toxicant NaPCP. Coefficient of variation was 41% for the IC25 and 28%

for the IC50.

13.14.1.1.2 Ten sets of data from six laboratories met the acceptability criteria, and were statistically analyzed

using nonparametric procedures to determine NOECs and LOECs. 

13.14.1.1.3 EPA evaluated within-laboratory precision of the daphnid, Ceriodaphnia dubia, Survival and

Reproduction Test using a database of routine reference toxicant test results from 33 laboratories (USEPA, 2000b). 

The database consisted of 393 reference toxicant tests conducted in 33 laboratories using a variety of reference

toxicants including: cadmium, copper, potassium chloride, sodium chloride, and sodium pentachlorophenate. 

Among the 33 laboratories, the median within-laboratory CV calculated for routine reference toxicant tests was 27%

for the IC25 reproduction endpoint. In 25% of laboratories, the within-laboratory CV was less than 17%; and in

75% of laboratories, the within-laboratory CV was less than 45%.
190

TABLE 16: SINGLE LABORATORY PRECISION OF THE DAPHNID, CERIODAPHNIA DUBIA,

SURVIVAL AND REPRODUCTION TEST, USING NAPCP AS A REFERENCE

TOXICANT1,2

Test NOEC LOEC Chronic

(mg/L) (mg/L) Value

(mg/L)

13 0.25 0.50 0.35

24 0.20 0.60 0.35

3 0.20 0.60 0.35

45 0.30 0.60 0.42

5 0.30 0.60 0.42

6 0.30 0.60 0.42

7 0.30 0.60 0.42

8 0.30 0.60 0.42

9 0.30 0.60 0.42

1

 For a discussion of the precision of data from chronic toxicity tests see Section 4, Quality Assurance. 2 Data from Tests performed by Philip Lewis, Aquatic Biology Branch, EMSL-Cincinnati, OH. Tests were

conduted in reconstituted hard water (hardness = 180 mg CaC03/L; pH - 8.1). 3 Concentrations used in Test 1 were: 0.03, 0.06, 0.12, 0.25, 0.50, 1.0 mg NaPCP/L. 4 Concentrations used in Tests 2 and 3 were: 0.007, 0.022, 0.067, 0.020, 0.60 mg NaPCP/L. 5 Concentrations used in Tests 4 through 9 were: 0.0375, 0.075, 0.150, 0.30, 0.60 mg NaPCP/L.
191

 TABLE 17. THE DAPHNID, CERIODAPHNIA DUBIA, SEVEN-DAY SURVIVAL AND 

REPRODUCTION TEST PRECISION FOR A SINGLE LABORATORY USING NAPCP AS

THE REFERENCE TOXICANT (USEPA, 1991a)

Test Number NOEC (mg/L) IC25 (mg/L) IC50 (mg/L)

19 0.30 0.3754 0.4508

46A 0.20 0.0938 0.2608

46B 0.20 0.2213 0.2879

49 0.20 0.2303 0.2912

55 0.20 0.2306 0.3177

56 0.10 0.2241 0.2827

 n 7 7 7

 Mean NA 0.2157 0.2953

 CV(%) NA 41.1 27.9
192

13.14.1.2 Multilaboratory Precision 

13.14.1.2.1 A multilaboratory study was performed by the Aquatic Biology Branch, EMSL-Cincinnati in 1985e,

involving a total of 11 analysts in 10 different laboratories (Neiheisel et. al., 1988; USEPA, 1988e). Each analyst

performed one-to-three seven-day tests using aliquots of a copper-spiked effluent sample, for a total of 25 tests. 

The tests were performed on the same day in all participating laboratories, using a pre-publication draft of Method

1002.0. The NOECs and LOECs for these tests were within one concentration interval which, with a dilution factor

of 0.5, is equivalent to a two-fold range in concentration (Table 18).

13.14.1.2.2 A second multilaboratory study of Method 1002.0 (using the first edition of this manual; USEPA,

1985c), was coordinated by Battelle, Columbus Division, and involved 11 participating laboratories (Table 19)

(DeGraeve et al., 1989). All participants used 10% DMW (10% PERRIER® Water) as the culture and dilution

water, and used their own formulation of food for culturing and testing the Ceriodaphnia dubia. Each laboratory

was to conduct at least one test with each of eight blind samples. Each test consisted of 10 replicates of one

organism each for five toxicant concentrations and a control. Of the 116 tests planned, 91 were successfully

initiated, and 70 (77%) met the survival and reproduction criteria for acceptability of the results (80% survival and

nine young per initial female). If the reproduction criteria of 15 young/female, used in this edition of the method,

had been applied to the results of the interlaboratory study, 22 additional tests would have been unacceptable. The

overall precision (CV) of the test was 27% for the survival data (7-day LC50s) and 37.5% and 39.0% for the

reproduction data (IC50s and IC25s, respectively).

13.14.1.2.3 In 2000, EPA conducted an interlaboratory variability study of the daphnid, Ceriodaphnia dubia,

Survival and Reproduction Test (USEPA, 2001a; USEPA, 2001b). In this study, each of 34 participant laboratories

tested 3 or 4 blind test samples that included some combination of blank, effluent, reference toxicant, and receiving

water sample types. The blank sample consisted of moderately-hard synthetic freshwater, the effluent sample was a

municipal wastewater spiked with KCl, the receiving water sample was a river water spiked with KCl, and the

reference toxicant sample consisted of moderately-hard synthetic freshwater spiked with KCl. Of the 122

Ceriodaphnia dubia Survival and Reproduction tests conducted in this study, 82.0% were successfully completed

and met the required test acceptability criteria. Of 27 tests that were conducted on blank samples, none showed

false positive results for survival endpoints, and only one resulted in false positive results for the growth endpoint,

yielding a false positive rate of 3.70%. Results from the reference toxicant, effluent, and receiving water sample

types were used to calculate the precision of the method. Table 20 shows the precision of the IC25 for each of these

sample types. Averaged across sample types, the total interlaboratory variability (expressed as a CV%) was 35.0%

for IC25 results. Table 21 shows the frequency distribution of survival and growth NOEC endpoints for each

sample type. For the survival endpoint, NOEC values spanned three concentrations for the reference toxicant and

effluent sample types and two concentrations for the receiving water sample type. The percentage of values within

one concentration of the median was 97.2%, 91.3%, and 100% for the reference toxicant, effluent, and receiving

water sample types, respectively. For the growth endpoint, NOEC values spanned five concentrations for the

reference toxicant sample type, three concentrations for the effluent sample type, and two concentrations for the

receiving water sample type. The percentage of values within one concentration of the median was 83.3%, 100%,

and 100% for the reference toxicant, effluent, and receiving water sample types, respectively. 

13.14.2 ACCURACY

13.14.2.1 The accuracy of toxicity tests cannot be determined.
193

TABLE 18. INTERLABORATORY PRECISION FOR THE DAPHNID, CERIODAPHNIA DUBIA,

SURVIVAL AND REPRODUCTION TEST WITH COPPER SPIKED EFFLUENT (USEPA,

1988e) 

Endpoints (% Effluent)

Reproduction Survival

Analyst Test NOEC LOEC NOEC LOEC 

3 1 12 25 25 50 

4 1 6 12 12 25 

4 2 6 12 25 50 

5 1 6 12 12 25 

5 2 12 25 12 25 

6 1 12 25 25 50 

6 2 6 12 25 50 

10 1 6 12 12 25 

10 2 6 12 12 25 

11 1 12 25 25 50 
194

TABLE 19. INTERLABORATORY PRECISION DATA FOR THE DAPHNID, CERIODAPHNIA 

DUBIA, SUMMARIZED FOR EIGHT REFERENCE TOXICANTS AND EFFLUENTS

(USEPA, 1991a)

Test Material Mean IC50 CV% Mean IC25 CV%

 

 Sodium chloride 1.34 29.9 1.00 34.3

 Industrial 3.6 83.3 3.2 78.1

 Sodium chloride 0.96 57.4 0.09 44.4

 Pulp and Paper 60.0 28.3 47.3 27.0

 Potassium dichromate 35.8 30.8 23.4 32.7

 Pulp and Paper 70.2 7.5 55.7 12.2 

 Potassium dichromate 53.2 25.9 29.3 46.8

 Industrial 69.8 37.0 67.3 36.7

n 88

Mean 37.5 39.0

Standard Deviation 23.0 19.1
195

TABLE 20. PRECISION OF POINT ESTIMATES FOR VARIOUS SAMPLE TYPES1

Test Endpoint Sample Type

CV (%)2

Within-lab3 Between-lab4 Total5

IC25 Reference toxicant - - -

Effluent 17.4 27.6 32.6

Receiving water - - 37.4

Average 17.4 27.6 35.0

1 From EPA’s WET Interlaboratory Variability Study (USEPA, 2001a; USEPA, 2001b). 2 CVs were calculated based on the within-laboratory component of variability, the between-laboratory

component of variability, and the total interlaboratory variability (including both within-laboratory and

between-laboratory components). For the reference toxicant sample type a majority of the results were

outside of the test concentration range, so precision estimates were not calculated. For the receiving water

sample type, within-laboratory and between-laboratory components of variability could not be calculated

since the study design did not provide within-laboratory replication for this sample type. 3 The within-laboratory (intralaboratory) component of variability for duplicate samples tested at the same

time in the same laboratory. 4 The between-laboratory component of variability for duplicate samples tested at different laboratories. 5 The total interlaboratory variability, including within-laboratory and between-laboratory components of

variability. The total interlaboratory variability is synonymous with interlaboratory variability reported

from other studies where individual variability components are not separated. 
196

TABLE 21. FREQUENCY DISTRIBUTION OF HYPOTHESIS TESTING RESULTS FOR VARIOUS

SAMPLE TYPES1

Test Endpoint Sample Type

Median

NOEC

Value

% of Results at

the Median

% of Results

±12

% of Results 

$23

Survival NOEC Reference toxicant 100% 97.2 0.00 2.78

Effluent 25% 65.2 26.1 8.70

Receiving water 25% 90.0 10.0 0.00

Growth 

NOEC Reference toxicant 100% 72.2 11.1 16.7

Effluent 12.5% 70.8 29.2 0.00

Receiving water 25% 70.0 30.0 0.00

1 From EPA’s WET Interlaboratory Variability Study (USEPA, 2001a; USEPA, 2001b). 2 Percent of values at one concentration interval above or below the median. Adding this percentage to the

percent of values at the median yields the percent of values within one concentration interval of the median. 3 Percent of values two or more concentration intervals above or below the median.
197

SECTION 14

TEST METHOD

GREEN ALGA, SELENASTRUM CAPRICORNUTUM, GROWTH TEST

METHOD 1003.0

14.1 SCOPE AND APPLICATION

14.1.1 This method measures the chronic toxicity of effluents and receiving water to the freshwater green alga,

Selenastrum capricornutum, in a four-day static test. The effects include the synergistic, antagonistic, and additive

effects of all the chemical, physical, and biological components which adversely affect the physiological and

biochemical functions of the test organisms. 

14.1.2 Detection limits of the toxicity of an effluent or pure substance are organism dependent.

14.1.3 Brief excursions in toxicity may not be detected using 24-h composite samples. Also, because of the long

sample collection period involved in composite sampling, and because the test chambers are not sealed, highly

degradable or highly volatile toxicants present in the source may not be detected in the test.

14.1.4 This test method is commonly used in one of two forms: (1) a definitive test, consisting of a minimum of

five effluent concentrations and a control, and (2) a receiving water test(s), consisting of one or more receiving

water concentrations and a control.

14.1.5 This test is very versatile because it can also be used to identify wastewaters which are biostimulatory and

may cause nuisance growths of algae, aquatic weeds, and other organisms at higher trophic levels. 

14.2 SUMMARY OF METHOD

14.2.1 A green alga, Selenastrum capricornutum, population is exposed in a static system to a series of

concentrations of effluent, or to receiving water, for 96 h. The response of the population is measured in terms of

changes in cell density (cell counts per mL), biomass, chlorophyll content, or absorbance. 

14.3 INTERFERENCES

14.3.1 Toxic substances may be introduced by contaminants in dilution water, glassware, sample hardware, and

testing equipment (see Section 5, Facilities, Equipment, and Supplies).

14.3.2 Adverse effects of high concentrations of suspended and/or dissolved solids, color, and extremes of pH may

mask the presence of toxic substances.

14.3.3 Improper effluent sampling and handling may adversely affect test results (see Section 8, Effluent and

Receiving Water Sampling, Sample Handling, and Sample Preparation for Toxicity Tests).

14.3.4 Pathogenic organisms and/or planktivores in the dilution water and effluent may affect test organism

survival and growth, and confound test results. 

14.3.5 Nutrients in the effluent or dilution water may confound test results. 

14.4 SAFETY

14.4.1 See Section 3, Safety and Health. 
198

14.5 APPARATUS AND EQUIPMENT

14.5.1 Laboratory Selenastrum capricornutum culture unit -- see culturing methods below and USEPA, 2002a. To

test effluent toxicity, sufficient numbers of log-phase-growth organisms must be available. 

14.5.2 Samplers -- automatic sampler, preferably with sample cooling capability, that can collect a 24-h composite

sample of 5 L or more. 

14.5.3 Sample containers -- for sample shipment and storage (see Section 8, Effluent and Receiving Water

Sampling, Sample Handling, and Sample Preparation for Toxicity Tests). 

14.5.4 Environmental chamber, incubator, or equivalent facility -- with "cool-white" fluorescent illumination (86 ±

8.6 μE/m2

/s, 400 ± 40 ft-c, or 4306 lux) and temperature control (25 ± 1EC). 

14.5.5 Mechanical shaker -- capable of providing orbital motion at the rate of 100 cycles per minute (cpm). 

14.5.6 Light meter -- with a range of 0-200 μE/m2

/s (0-1000 ft-c). 

14.5.7 Water purification system -- MILLIPORE MILLI-Q®, deionized water or equivalent (see Section 5,

Facilities, Equipment, and Supplies). 

14.5.8 Balance -- analytical, capable of accurately weighing 0.00001 g. 

14.5.9 Reference weights, class S -- for checking performance of balance. 

14.5.10 Volumetric flasks and graduated cylinders -- class A, 10-1000 mL, borosilicate glass, for culture work and

preparation of test solutions. 

14.5.11 Volumetric pipets -- class A, 1-100 mL. 

14.5.12 Serological pipets -- 1-10 mL, graduated. 

14.5.13 Pipet bulbs and fillers -- PROPIPET®, or equivalent. 

14.5.14 Wash bottles -- for rinsing small glassware, instrument electrodes, and probes. 

14.5.15 Test chambers -- four 125 or 250 mL borosilicate, Erlenmeyer flasks, with foam plugs or stainless steel or

Shumadzu closures. For special glassware cleaning requirements (see Section 5, Facilities, Equipment, and

Supplies).

14.5.16 Culture chambers -- 1-4 L borosilicate, Erlenmeyer flasks. 

14.5.17 Thermometers, glass or electronic, laboratory grade -- for measuring water temperatures. 

14.5.18 Bulb-thermograph or electronic-chart type thermometers -- for continuously recording temperature. 

14.5.19 Thermometer, National Bureau of Standards Certified, (see USEPA Method 170.1, USEPA, 1979b) -- to

calibrate laboratory thermometers. 

14.5.20 Meters, pH and specific conductivity -- for routine physical and chemical measurements.

14.5.21 Tissue grinder -- for chlorophyll extraction. 
199

14.5.22 Fluorometer (Optional) -- equipped with chlorophyll detection light source, filters, and photomultiplier

tube (Turner Model 110 or equivalent).

14.5.23 UV-VIS spectrophotometer -- capable of accommodating 1-5 cm cuvettes. 

14.5.24 Cuvettes for spectrophotometer -- 1-5 cm light path. 

14.5.25 Electronic particle counter (Optional) -- Coulter Counter, Model ZBI, or equivalent, with mean cell

(particle) volume determination.

14.5.26 Microscope -- with 10X, 45X, and 100X objective lenses, 10X ocular lenses, mechanical stage, substage

condenser, and light source (inverted or conventional microscope).

14.5.27 Counting chamber -- Sedgwick-Rafter, Palmer-Maloney, or hemocytometer.

14.5.28 Centrifuge -- with swing-out buckets having a capacity of 15-100 mL.

14.5.29 Centrifuge tubes -- 15-100 mL, screw-cap. 

14.5.30 Filtering apparatus -- for membrane and/or glass fiber filters. 

14.6 REAGENTS AND CONSUMABLE MATERIALS

14.6.1 Sample containers -- for sample shipment and storage (see Section 8, Effluent and Receiving Water

Sampling, Sample Handling, and Sample Preparation for Toxicity Tests).

14.6.2 Data sheets (one set per test) -- for recording data.

14.6.3 Tape, colored -- for labeling test chambers.

14.6.4 Markers, waterproof -- for marking containers, etc. 

14.6.5 Reagents for hardness and alkalinity tests -- see USEPA Methods 130.2 and 310.1, USEPA, 1979b.

14.6.6 Buffers pH 4, pH 7, and pH 10 (or as per instructions of instrument manufacturer) for instrument calibration

(see USEPA Method 150.1, USEPA, 1979b).

14.6.7 Specific conductivity standards (see USEPA Method 120.1, USEPA, 1979b).

14.6.8 Standard particles -- such as chicken or turkey fibroblasts or polymer microspheres, 5.0 ± 0.03 μm diameter,

65.4 μm3

 volume, for calibration of electronic particle counters.

14.6.9 Membranes and filling solutions for DO probe (see USEPA Method 360.1, USEPA, 1979b), or reagents --

for modified Winkler analysis.

14.6.10 Laboratory quality control samples and standards -- for calibration of the above methods.

14.6.11 Reference toxicant solutions -- see Section 4, Quality Assurance.

14.6.12 Reagent water -- defined as distilled or deionized water that does not contain substances which are toxic to

the test organisms (see Section 5, Facilities, Equipment, and Supplies). 
200

14.6.13 Effluent or receiving water and dilution water -- see Section 7, Dilution Water; and Section 8, Effluent and

Receiving Water Sampling, Sample Handling, and Sample Preparation for Toxicity Testing.

14.6.14 Acetone -- pesticide-grade or equivalent. 

14.6.15 Dilute (10%) hydrochloric acid -- carefully add 10 mL of concentrated HCl to 90 mL of MILLI-Q® water. 

14.6.16 TEST ORGANISMS, GREEN ALGA, SELENASTRUM CAPRICORNUTUM

14.6.16.1 Selenastrum capricornutum, a unicellular coccoid green alga, is the test organism. The genus and

species name of this organism was formally changed to Pseudokirchneriella subcapitata (Hindak, 1990), however,

the method manual will continue to refer to Selenastrum capricornutum to maintain consistency with previous

versions of the method.

14.6.16.2 Algal Culture Medium is prepared as follows: 

14.6.16.2.1 Prepare (five) stock nutrient solutions using reagent grade chemicals as described in Table 1. 

14.6.16.2.2 Add 1 mL of each stock solution, in the order listed in Table 1, to approximately 900 mL of MILLI-Q®

water. Mix well after the addition of each solution. Dilute to 1 L, mix well, and adjust the pH to 7.5 ± 0.1, using

0.1N NaOH or HCl, as appropriate. The final concentration of macronutrients and micronutrients in the culture

medium is given in Table 2.

14.6.16.2.3 Immediately filter the pH-adjusted medium through a 0.45 μm pore diameter membrane at a vacuum of

not more than 380 mm (15 in.) mercury, or at a pressure of not more than one-half atmosphere (8 psi). Wash the

filter with 500 mL deionized water prior to use.

14.6.16.2.4 If the filtration is carried out with sterile apparatus, filtered medium can be used immediately, and no

further sterilization steps are required before the inoculation of the medium. The medium can also be sterilized by

autoclaving after it is placed in the culture vessels. If a 0.22 μg filter is used no sterilization is needed.

14.6.16.2.5 Unused sterile medium should not be stored more than one week prior to use, because there may be

substantial loss of water by evaporation.

14.6.16.2.6 When prepared according to Table 1, the micronutrient stock solution contains

ethylenediaminetetraacetic acid (EDTA). EPA requires the addition of EDTA to nutrient stock solutions when

conducting the Selenastrum capricornutum Growth Test and submitting data under NPDES permits. The use of

EDTA improves test method performance by reducing the incidence of false positives and increasing test method

precision. In interlaboratory testing of split samples analyzed with and without the addition of EDTA, false positive

rates were 0.00% with EDTA and 33.3% without EDTA (USEPA, 2001a). Interlaboratory variability, expressed as

the CV for IC25 values, was 34.3% with EDTA and 58.5% without EDTA (USEPA, 2001a). While the addition of

EDTA improves test performance, EPA also cautions that the addition of EDTA may cause the Selenastrum

capricornutum Growth Test to underestimate the toxicity of metals. Regulatory authorities should consider this

possibility when selecting test methods for monitoring effluents that are suspected to contain metals. As

recommended in EPA’s Technical Support Document for Water Quality-Based Toxics Control (USEPA, 1991a),

the most sensitive of at least three test species from different phyla should be used for monitoring the toxicity of

effluents. 
201

 TABLE 1. NUTRIENT STOCK SOLUTIONS FOR MAINTAINING ALGAL STOCK CULTURES AND

TEST CONTROL CULTURES

STOCK COMPOUND AMOUNT DISSOLVED IN

SOLUTION 500 mL MILLI-Q® WATER

1. MACRONUTRIENTS

A. MgCl2@6H2O 6.08 g

CaCl2@2H2O 2.20 g

NaNO3 12.75 g

B. MgSO4@7H2O 7.35 g

C K2HPO4 0.522 g

D. NaHCO3 7.50 g

2. MICRONUTRIENTS

H3BO3 92.8 mg

MnCl2@4H2O 208.0 mg 

ZnCl2 1.64 mg1

FeCl3@6H2O 79.9 mg 

CoCl2@6H2O 0.714 mg2

Na2MoO4@2H2O 3.63 mg3

CuCl2@2H2O 0.006 mg4

Na2EDTA@2H2O 150.0 mg

Na2SeO4 1.196 mg5

1 ZnCl2 - Weigh out 164 mg and dilute to 100 mL. Add 1 mL of this solution to Stock 2, micronutrients. 2 CoCl2@6H2O - Weigh out 71.4 mg and dilute to 100 mL. Add 1 mL of this solution to Stock 2,

micronutrients. 3 Na2MoO4@2H2O - Weigh out 36.6 mg and dilute to 10 mL. Add 1 mL of this solution to Stock 2,

micronutrients. 4 CuCl2@2H2O - Weigh out 60.0 mg and dilute to 1000 mL. Take 1 mL of this solution and dilute to 10 mL. 

Take 1 mL of the second dilution and add to Stock 2, micronutrients. 5 Na2SeO4 - Weigh out 119.6 mg and dilute to 100 mL. Add 1 mL of this solution to Stock 2,

micronutrients.
202

 TABLE 2. FINAL CONCENTRATION OF MACRONUTRIENTS AND MICRONUTRIENTS IN THE

CULTURE MEDIUM

MACRONUTRIENT CONCENTRATION ELEMENT CONCENTRATION

(mg/L) (mg/L)

NaNO3 25.5 N 4.20 

MgCl2@6H2O 12.2 Mg 2.90 

CaCl2@2H2O 4.41 Ca 1.20 

MgSO4@7H2O 14.7 S 1.91 

K2HPO4 1.04 P 0.186 

NaHCO3 15.0 Na 11.0 

 K 0.469 

 C 2.14 

MICRONUTRIENT CONCENTRATION ELEMENT CONCENTRATION

(μg/L) (μg/L)

H3BO3 185.0 B 32.5 

MnCl2@4H2O 416.0 Mn 115.0

ZnCl2 3.27 Zn 1.57 

CoCl2@6H2O 1.43 Co 0.354

CuCl2@2H2O 0.012 Cu 0.004 

Na2MoO4@2H2O 7.26 Mo 2.88 

FeCl3@6H2O 160.0 Fe 33.1 

Na2EDTA@2H2O 300.0 -- ----

Na2SeO4 2.39 Se 0.91 
203

14.6.16.3 Stock Algal Cultures

14.6.16.3.1 See Section 6, Test Organisms, for information on sources of "starter" cultures of the green alga,

Selenastrum capricornutum.

14.6.16.3.2 Upon receipt of the "starter" culture (usually about 10 mL), a stock culture is initiated by aseptically

transferring 1 mL to a culture flask containing control algal culture medium (prepared as described above). The

volume of stock culture medium initially prepared will depend upon the number of test flasks to be inoculated later

from the stock, or other planned uses, and may range from 25 mL in a 125 mL flask to 2 L in a 4-L flask. The

remainder of the starter culture can be held in reserve for up to six months in a refrigerator (in the dark) at 4EC. 

14.6.16.3.3 Maintain the stock cultures at 25 ± 1EC, under continuous "Cool-White" fluorescent lighting of 86 ±

8.6 μE/m2

/s (400 ± 40 ft-c). Shake continuously at 100 cpm or twice daily by hand.

14.6.16.3.4 Transfer 1 to 2 mL of stock culture weekly to 50 - 100 mL of new culture medium to maintain a

continuous supply of "healthy" cells for tests. Aseptic techniques should be used in maintaining the algal cultures,

and extreme care should be exercised to avoid contamination. Examine the stock cultures with a microscope for

contaminating microorganisms at each transfer.

14.6.16.3.5 Viable unialgal culture material may be maintained for long periods of time if placed in a refrigerator

at 4EC. 

14.6.16.4 It is recommended that chronic toxicity tests be performed monthly with a reference toxicant. Algal cells

four to seven days old are used to monitor the chronic toxicity (growth) of the reference toxicant to the algal stock

produced by the culture unit (see Section 4, Quality Assurance, Subsection 4.17).

14.6.16.5 Record Keeping

14.6.16.5.1 Records, kept in a bound notebook, include (1) dates culture media was prepared, (2) source of

"starter" cultures, (3) date stock cultures were started, (4) cell density in stock cultures, and (5) dates and results of

reference toxicant tests performed (see Section 4, Quality Assurance).

14.7 EFFLUENT AND RECEIVING WATER COLLECTION, PRESERVATION, AND STORAGE 

14.7.1 See Section 8, Effluent and Receiving Water Sampling, Sample Handling, and Sample Preparation for

Toxicity Tests.

14.8 CALIBRATION AND STANDARDIZATION

14.8.1 See Section 4, Quality Assurance.

14.9 QUALITY CONTROL

14.9.1 See Section 4, Quality Assurance.

14.10 TEST PROCEDURES

14.10.1 TEST SOLUTIONS

14.10.1.1 Receiving Waters

14.10.1.1.1 The sampling point is determined by the objectives of the test. Receiving water toxicity is determined

with samples used directly as collected or after samples are passed through a 60 μm NITEX® filter and compared
204

without dilution against a control. Using four replicate chambers per test, each containing 100 mL and 400 mL for

chemical analyses, would require approximately 1 L or more of sample for the test. 

14.10.1.2 Effluents 

14.10.1.2.1 The selection of the effluent test concentrations should be based on the objectives of the study. A

dilution factor of 0.5 is commonly used. A dilution factor of 0.5 provides precision of ± 100%, and testing of

concentrations between 6.25% and 100% effluent using five effluent concentrations (6.25%, 12.5%, 25%, 50%, and

100%). Improvements in precision decline rapidly if the dilution factor is increased beyond 0.5 and precision

declines rapidly if a smaller dilution factor is used. Therefore, USEPA recommends using a $ 0.5 dilution

factor. 

14.10.1.2.2 If the effluent is known or suspected to be highly toxic, a lower range of effluent concentrations should

be used (such as 25%, 12.5%, 6.25%, 3.12%, and 1.56%). If a high rate of mortality is observed during the first

1 to 2 h of the test, additional dilutions should be added at the lower range of the effluent concentrations.

14.10.1.2.3 The volume of effluent required for the test is 1 to 2 L. Sufficient test solution (approximately 900 or

1500 mL) is prepared at each effluent concentration to provide 400 mL additional volume for chemical analyses at

the high, medium, and low test concentrations. There is no daily renewal of test solution. 

14.10.1.2.4 Tests should begin as soon as possible, preferably within 24 h of sample collection. The maximum

holding time following retrieval of the sample from the sampling device should not exceed 36 h for off-site toxicity

tests unless permission is granted by the permitting authority. In no case should the sample be usedfor the first time

in a test more than 72 h after sample collection (see Section 8, Effluent and Receiving Water Sampling, Sample

Handling, and Sample Preparation for Toxicity Tests).

14.10.1.2.5 Just prior to test initiation (approximately 1 h) the temperature of sufficient quantity of the sample to

make test solutions should be adjusted to the test temperature and maintained at that temperature during the addition

of dilution water.

14.10.1.2.6 The DO of the test solutions should be checked prior to test initiation. If any of the solutions are

supersaturated with oxygen, all of the solutions and the control should be gently aerated. If or any solution has a

DO concentration below 4.0 mg/L, all of the solutions and the control must be gently aerated.

14.10.1.2.7 Effluents may be toxic and/or nutrient poor. "Poor" growth in an algal toxicity test, therefore, may be

due to toxicity or nutrient limitation, or both. To eliminate false negative results due to low nutrient concentrations,

1 mL of each stock nutrient solution is added per liter of effluent prior to use in preparing the test dilutions. Thus,

all test treatments and controls will contain at a minimum the concentration of nutrients in the stock culture medium. 

14.10.1.2.8 If samples contain volatile substances, the test sample should be added below the surface of the

dilution water towards the bottom of the test container through an appropriate delivery tube.

14.10.1.3 Dilution Water

14.10.1.3.1 Dilution water may be stock culture medium, any uncontaminated receiving water, a standard synthetic

(reconstituted) water, or some other natural water (see Section 7, Dilution Water). However, if water other than the

stock culture medium is used for dilution water, 1 mL of each stock nutrient solution should be added per liter of

dilution water. Natural waters used as dilution water must be filtered through a prewashed filter, such as a GF/A,

GF/C, or equivalent filter, that provides 0.45 μm particle size retention. 

14.10.1.3.2 If the growth of the algae in the test solutions is to be measured with an electronic particle counter, the

effluent and dilution water must be filtered through a GF/A or GF/C filter, or other filter providing 0.45 μm particle
205

size retention, and checked for "background" particle count before it is used in the test. Glass-fiber filters generally

provide more rapid filtering rates and greater filtrate volume before plugging. 

14.10.1.4 Preparation of Inoculum 

14.10.1.4.1 The inoculum is prepared no more than 2 to 3 h prior to the beginning of the test, using Selenastrum

capricornutum harvested from a four- to-seven-day stock culture. Each milliliter of inoculum must contain enough

cells to provide an initial cell density of approximately 10,000 cells/mL (± 10%) in the test flasks. Assuming the

use of 250 mL flasks, each containing 100 mL of test solution, the inoculum must contain 1,000,000 cells/mL. 

14.10.1.4.2 Estimate the volume of stock culture required to prepare the inoculum. As an example, if the four-toseven-day-old stock culture used as the source of the inoculum has a cell density of 2,000,000 cells/mL, a test

employing 24 flasks, each containing 100 mL of test medium and inoculated with a total of 1,000,000 cells, would

require 24,000,000 cells or 15 mL of stock solution (24,000,000/2,000,000) to provide sufficient inoculum. It is

advisable to prepare a volume 20% to 50% in excess of the minimum volume required, to cover accidental loss in

transfer and handling. 

14.10.1.4.3 Prepare the inoculum as follows:

1. Centrifuge 15 mL of stock culture at 1000 x g for 5 min. This volume will provide a 50% excess in

the number of cells. 

2. Decant the supernatant and resuspend the cells in 10 mL of control medium.

3. Repeat the centrifugation and decantation step, and resuspend the cells in 10 mL control medium.

4. Mix well and determine the cell density in the algal concentrate. Some cells will be lost in the

concentration process. 

5. Determine the density of cells (cells/mL) in the stock culture (for this example, assume 2,000,000 per

mL).

6. Calculate the required volume of stock culture as follows:

Volume (mL) of Number test flasks Volume of test 10,000

Stock Culture = to be used × Solutions/flask × cells/mL

Required Cell density (cells/mL) in the stock culture

= 24 flasks × 100 mL/flask × 10,000 cells/mL 

2,000,000 cells/mL 

= 12.0 mL Stock Culture 

7. Dilute the cell concentrate as needed to obtain a cell density of 1,000,000 cells/mL, and check the cell

density in the final inoculum. 

8. The volume of the algal inoculum should be considered in calculating the dilution of toxicant in the

test flasks. 

14.10.2 START OF THE TEST 

14.10.2.1 Label the test chambers with a marking pen and use the color-coded tape to identify each treatment and

replicate. A minimum of five effluent concentrations and a control are used for each effluent test. Each treatment 

(including the control) should have a minimum of four replicates.

14.10.2.2 Randomize the position of the test flasks at the beginning of the test (see Appendix A). Preparation of a

position chart may be helpful.
206

14.10.2.3 The test begins when the algae are added to the test flasks. Mix the inoculum well, and add 1 mL to the

test solution in each randomly arranged flask. Make a final check of the cell density in three of the test solutions at

time "zero" (within 2 h of the inoculation). 

14.10.2.3.1 Alkalinity, hardness, and conductivity are measured at the beginning of the test in the high, medium,

and low effluent concentrations and control before they are dispensed to the test chambers and the data recorded on

the data sheet (Figure 1).

Discharger: Test Dates: 

Location: Analyst: 

 

Effluent Concentration

Parameter Control Remarks

Temperature

pH

Alkalinity

Hardness

Conductivity

Chlorine

Figure 1. Data form for the green alga, Selenastrum capricornutum, growth test. Routine chemical and

physical determinations.

14.10.3 LIGHT, PHOTOPERIOD, AND TEMPERATURE 

14.10.3.1 Test flasks are incubated under continuous illumination at 86 ± 8.6 μE/m2

/s (400 ± 40 ft-c), at 25 ± 1EC,

and should be shaken continuously at 100 cpm on a mechanical shaker or twice daily by hand. Flask positions in

the incubator should be randomly rotated each day to minimize possible spatial differences in illumination and

temperature on growth rate. If it can be verified that test specifications are met at all positions, this need not be

done.

14.10.4 DISSOLVED OXYGEN (DO) CONCENTRATION

14.10.4.1 Because of the continuous illumination of the test flasks, DO concentration should never be a problem

during the test and no aeration will be required.

14.10.5 OBSERVATIONS DURING THE TEST

14.10.5.1 Routine Chemical and Physical Determinations

14.10.5.1.1 Temperature should be monitored continuously or observed and recorded daily for at least two

locations in the environmental control system or the samples. Temperature should be checked in a sufficient

number of test vessels at least at the end of the test to determine variability in the environmental chamber.

14.10.5.1.2 Temperature and pH are measured at the end of each 24-h exposure period in at least one test flask at

each concentration and in the control.
207

14.10.5.1.3 Record all the measurements on the data sheet (Figure 1).

14.10.5.2 Biological Observations

14.10.5.2.1 Toxic substances in the test solutions may degrade or volatilize rapidly, and the inhibition in algal

growth may be detectable only during the first one or two days in the test. It may be desirable, therefore, to

determine the algal growth response daily. Otherwise, biological observations are not required until the test is

terminated and the test solutions are not renewed during the test period.

14.10.6 TERMINATION OF THE TEST 

14.10.6.1 The test is terminated 96 h after initiation. The algal growth in each flask is measured by one of the

following methods: (a) cell counts, (b) chlorophyll content, or (c) turbidity (light absorbance). 

14.10.6.2 Cell counts 

14.10.6.2.1 Automatic Particle Counters 

14.10.6.2.1.1 Several types of automatic electronic and optical particle counters are available for use in the rapid

determination of cell density (cells/mL) and mean cell volume (MCV) in μm3

/cell. The Coulter Counter is widely

used and is discussed in detail in USEPA (1978b). 

14.10.6.2.1.2 If biomass data are desired for algal growth potential measurements, a Model ZM Coulter Counter is

used. However, the instrument must be calibrated with a reference sample of particles of known volume. 

14.10.6.2.1.3 When the Coulter Counter is used, an aliquot (usually 1 mL) of the test culture is diluted 10X to 20X

with a l% sodium chloride electrolyte solution, such as ISOTON®, to facilitate counting. The resulting dilution is

counted using an aperture tube with a 100-μm diameter aperture. Each cell (particle) passing through the aperture

causes a voltage drop proportional to its volume. Depending on the model, the instrument stores the information on

the number of particles and the volume of each, and calculates the mean cell volume. The following procedure is

used: 

1. Mix the algal culture in the flask thoroughly by swirling the contents of the flask approximately six

times in a clockwise direction, and then six times in the reverse direction; repeat the two-step process

at least once.

2. At the end of the mixing process, stop the motion of the liquid in the flask with a strong brief reverse

mixing action, and quickly remove 1 mL of cell culture from the flask with a sterile pipet. 

3. Place the aliquot in a counting beaker, and add 9 mL (or 19 mL) of electrolyte solution (such as

Coulter ISOTON®). 

4. Determine the cell density (and MCV, if desired).

14.10.6.2.2 Manual microscope counting method 

14.10.6.2.2.1 Cell counts may be determined using a Sedgwick-Rafter, Palmer-Maloney, hemocytometer, inverted

microscope, or similar methods. For details on microscope counting methods, see APHA (1992) and USEPA

(1973). Whenever feasible, 400 cells per replicate are counted to obtain ± 10% precision at the 95% confidence

level. This method has the advantage of allowing for the direct examination of the condition of the cells. 

14.10.6.3 Chlorophyll Content 

14.10.6.3.1 Chlorophyll may be estimated in-vivo fluorometrically, or in-vitro either fluorometrically or

spectrophotometrically. In-vivo fluorometric measurements are recommended because of the simplicity and

sensitivity of the technique and rapidity with which the measurements can be made (Rehnberg et al., 1982). 
208

14.10.6.3.2 The in-vivo chlorophyll measurements are made as follows: 

1. Adjust the "blank" reading of the fluorometer using the filtrate from an equivalent dilution of effluent

filtered through a 0.45 μm particle retention filter.

2. Mix the contents of the test culture flask by swirling successively in opposite directions (at least three

times), and remove 1 mL of culture from the flask with a sterile pipet.

3. Place the aliquot in a small disposable vial and record the fluorescence as soon as the reading

stabilizes. (Do not allow the sample to stand in the instrument more than 1 min). 

4. Discard the sample.

14.10.6.3.3 For additional information on chlorophyll measurement methods, (see APHA, 1992).

14.10.6.4 Turbidity (Absorbance) 

14.10.6.4.1 A second rapid technique for growth measurement involves the use of a spectrophotometer to

determine the turbidity, or absorbance, of the cultures at a wavelength of 750 nm. Because absorbance is a complex

function of the volume, size, and pigmentation of the algae, it would be useful to construct a calibration curve to

establish the relationship between absorbance and cell density. 

14.10.6.4.2 The algal growth measurements are made as follows: 

1. A blank is prepared as described for the fluorometric analysis. 

2. The culture is thoroughly mixed as described above.

3. Sufficient sample is withdrawn from the test flask with a sterile pipet and transferred to a 1- to 5-cm

cuvette.

4. The absorbance is read at 750 nm and divided by the light path length of the cuvette, to obtain an

“absorbance-per-centimeter” value.

5. The 1-cm absorbance values are used in the same manner as the cell counts.

14.10.6.5 Record the data as indicated in Figure 2.

14.11 SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA

14.11.1 A summary of test conditions and test acceptability criteria is presented in Table 3.

14.12 ACCEPTABILITY OF TEST RESULTS

14.12.1 For the test results to be acceptable, the mean algal cell density in the control flasks must exceed 1 X 106

cells/mL at the end of the test, and the coefficient of variation (CV, calculated as standard deviation X 100 / mean)

for algal cell density among the control replicates must not exceed 20%.
209

Discharger: Test Dates: 

Location: Analyst: 

Cell Density Measurement Treatment 

Concentration Replicate Mean Comments

1234

 Control 

 Conc:

 Conc:

 Conc:

 Conc:

 Conc:

Comments:

 Figure 2. Data form for the green alga, Selenastrum capricornutum, growth test, cell density determinations.
210

 TABLE 3. SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA FOR

GREEN ALGA, SELENASTRUM CAPRICORNUTUM, GROWTH TOXICITY TESTS

WITH EFFLUENTS AND RECEIVING WATERS (TEST METHOD 1003.0)1

1. Test type: Static non-renewal (required)

2. Temperature: 25 ± 1EC (recommended) 

Test temperatures must not deviate (i.e., maximum

minus minimum temperature) by more than 3°C

during the test (required)

3. Light quality: "Cool white" fluorescent lighting (recommended) 

4. Light intensity: 86 ± 8.6 μE/m2/s (400 ± 40 ft-c or 4306 lux)

(recommended) 

5. Photoperiod: Continuous illumination (required) 

6. Test chamber size: 125 mL or 250 mL (recommended)

7. Test solution volume: 50 mL or 100 mL2

 (recommended)

8. Renewal of test solutions: None (required) 

9. Age of test organisms: 4 to 7 days (required)

10. Initial cell density in 

test chambers: 10,000 cells/mL (recommended) 

11. No. replicate chambers 

per concentration: 4 (required minimum)

12. Shaking rate: 100 cpm continuous, or twice daily by hand

(recommended)

13. Aeration: None (recommended) 

14. Dilution water: Algal stock culture medium, enriched

uncontaminated source of receiving or other natural

water, synthetic water prepared using MILLIPORE

MILLI-Q® or equivalent deionized water and

reagent grade chemicals, or DMW (see Section 7,

Dilution Water) (available options)

1

 For the purposes of reviewing WET test data submitted under NPDES permits, each test condition listed

above is identified as required or recommended (see Subsection 10.2 for more information on test

review). Additional requirements may be provided in individual permits, such as specifying a given test

condition where several options are given in the method. 2

 For tests not continuously shaken use 25 mL in 125 mL flasks and 50 mL in 250 mL flasks. 
211

 TABLE 3. SUMMARY OF TEST CONDITIONS AND TEST ACCEPTABILITY CRITERIA FOR

GREEN ALGA, SELENASTRUM CAPRICORNUTUM, GROWTH TOXICITY TESTS WITH

EFFLUENTS AND RECEIVING WATERS (TEST METHOD 1003.0) (CONTINUED) 

 15. Test concentrations: Effluents: 5 and a control (required minimum) 

Receiving Water: 100% receiving water (or minimum of

5) and a control (recommended) 

16. Test dilution factor: Effluents: $ 0.5 (recommended) 

Receiving Waters: None or $ 0.5 (recommended) 

17. Test duration: 96 h (required) 

18. Endpoint: Growth (cell counts, chlorophyll fluorescence,

absorbance, or biomass) (required) 

19. Test acceptability 

criteria:3 Mean cell density of at least 1 X 106

 cells/mL in the

controls; and variability (CV%) among control replicates

less than or equal to 20% (required) 

20. Sampling requirements: For on-site tests, one sample collected at test initiation,

and used within 24 h of the time it is removed from the

sampling device. For off-site tests, holding time must not

exceed 36 h before first use (see Section 8, Effluent and

Receiving Water Sampling, Sample Handling, and

Sample Preparation for Toxicity Tests, Subsection 8.5.4)

(required) 

21. Sample volume required: 1 or 2 L depending on test volume (recommended) 

3

 If the test is conducted under non-NPDES applications (i.e., data are not submitted under NPDES

permits) and used without EDTA in the nutrient stock solution, the test acceptability criteria are a mean

cell density of at least 2 X 105

 cells/mL in the controls, and variability (CV%) among control replicates

less than or equal to 20%. 
212

14.13 DATA ANALYSIS

14.13.1 GENERAL 

14.13.1.1 Tabulate and summarize the data. A sample set of algal growth response data is shown in Table 4.

 TABLE 4. GREEN ALGA, SELENASTRUM CAPRICORNUTUM, GROWTH RESPONSE DATA

Toxicant Concentration (μg Cd/L)

Replicate Control 5 10 20 40 80 

A 1209 1212 826 493 127 49.3 

B 1180 1186 628 416 147 40.0 

C 1340 1204 816 413 147 44.0 

Log10 A 3.082 3.084 2.917 2.693 2.104 1.693

Trans- B 3.072 3.074 2.798 2.619 2.167 1.602 

formed C 3.127 3.081 2.912 2.616 2.167 1.643 

Mean( ) 3.094 3.080 2.876 2.643 2.146 1.646 Y ̄ i

14.13.1.2 The endpoints of toxicity tests using the green alga, Selenastrum capricornutum, are based on the

adverse effects on cell growth (see Section 9, Chronic Toxicity Test Endpoints and Data Analysis). The EC50, the

IC25, and the IC50 are calculated using the point estimation techniques, and LOEC and NOEC values for growth

are obtained using a hypothesis testing approach such as Dunnett's Procedure (Dunnett, 1955) or Steel's Many-one

Rank Test (Steel, 1959; Miller, 1981). Separate analyses are performed for the estimation of the LOEC and NOEC

endpoints and for the estimation of the EC50, IC25, and IC50. See the Appendices for examples of the manual

computations, and examples of data input and program output. 

14.13.1.3 The statistical tests described here must be used with a knowledge of the assumptions upon which the

tests are contingent. Tests for normality and homogeneity of variance are included in Appendix B. The assistance

of a statistician is recommended for analysts who are not proficient in statistics. 

14.13.2 EXAMPLE OF ANALYSIS OF ALGAL GROWTH DATA 

14.13.2.1 Formal statistical analysis of the growth data is outlined on the flowchart in Figure 3. The response used

in the statistical analysis is the number of cells per milliliter per replicate. Separate analyses are performed for the

estimation of the NOEC and LOEC endpoints and for the estimation of the IC25 and IC50 endpoints.

14.13.2.2 The statistical analysis using hypothesis tests consists of a parametric test, Dunnett's Procedure, and a

nonparametric test, Steel's Many-one Rank Test. The underlying assumptions of the Dunnett's Procedure, normality

and homogeneity of variance, are formally tested. The test for normality is the Shapiro-Wilk's Test, and Bartlett's

Test is used to test for homogeneity of variance. If either of these tests fails, the nonparametric test, Steel's

Many-one Rank Tests, is used to determine the NOEC and LOEC endpoints. If the assumptions of Dunnett's

Procedure are met, the endpoints are determined by the parametric test.
213

Figure 3. Flowchart for statistical analysis of the green alga, Selenastrum capricornutum, growth response data.
214

14.13.2.3 Additionally, if unequal numbers of replicates occur among the concentration levels tested there are

parametric and nonparametric alternative analyses. The parametric analysis is a t test with the Bonferroni

adjustment (see Appendix D). The Wilcoxon Rank Sum Test with the Bonferroni adjustment is the nonparametric

alternative (see Appendix F).

14.13.2.4 Data from an algal growth test with cadmium chloride will be used to illustrate the statistical analysis. 

The cell counts were log10 transformed in an effort to stabilize the variance for the ANOVA analysis. The raw data,

log10 transformed data, mean and standard deviation of the observations at each concentration including the control

are listed in Table 4. A plot of the log10 transformed cell counts for each treatment is provided in Figure 4.

14.13.2.5 Test for Normality

14.13.2.5.1 The first step of the test for normality is to center the observations by subtracting the mean of all the

observations within a concentration from each observation in that concentration. The centered observations are

summarized in Table 5.

 TABLE 5. CENTERED OBSERVATIONS FOR SHAPIRO-WILK'S EXAMPLE 

 Toxicant Concentration (μg Cd/L) 

Replicate Control 5 10 20 40 80 

A -0.012 0.004 0.041 0.050 -0.042 0.047 

B -0.022 -0.006 -0.078 -0.024 0.021 -0.044 

C 0.033 0.001 0.036 -0.027 0.021 -0.003 

14.13.2.5.2 Calculate the denominator, D, of the test statistic:

D ' '

n

i'1

(Xi

&X)

2

 Where: Xi = the ith centered observation 

 

 X& = the overall mean of the centered observations 

 n = the total number of centered observations. 

For this set of data, n = 18 

 

X ' 1

18(0.000) ' 0.000

 D = 0.0214 

14.13.2.5.3 Order the centered observations from smallest to largest: 

 X(1) # X(2) # ... # X(n)

Where X(i) is the ith ordered observation. These ordered observations are listed in Table 6.
215

Figure 4. Plot of the log10 transformed cell count data from the green alga, Selenastrum capricornutum, growth response test i
216

 TABLE 6. ORDERED CENTERED OBSERVATIONS FOR SHAPIRO-WILK'S EXAMPLE

i X(i) i X(i)

1 -0.078 10 0.001 

2 -0.044 11 0.004 

3 -0.042 12 0.021 

4 -0.027 13 0.021 

5 -0.024 14 0.033 

6 -0.022 15 0.036 

7 -0.012 16 0.041 

8 -0.006 17 0.047 

9 -0.003 18 0.050 

W ' 1

D['

k

i'1

ai(X (n&i%1)&X (i))]

2

 TABLE 7. COEFFICIENTS AND DIFFERENCES FOR SHAPIRO-WILK'S EXAMPLE

i ai X(n-i+1) - X(i)

1 0.4886 0.128 X(18) - X(1)

2 0.3253 0.091 X(17) - X(2)

3 0.2553 0.083 X(16) - X(3)

4 0.2027 0.063 X(15) - X(4)

5 0.1587 0.057 X(14) - X(5)

6 0.1197 0.043 X(13) - X(6)

7 0.0837 0.033 X(12) - X(7)

8 0.0496 0.010 X(11) - X(8)

9 0.0163 0.004 X(10) - X(9)

14.13.2.5.4 From Table 4, Appendix B, for the number of observations, n, obtain the coefficients a1 , a 2, ..., a k

where k is n/2 if n is even and (n-1)/2 if n is odd. For the data in this example, n = 18 , k = 9. The a i values are

listed in Table 7.

14.13.2.5.5 Compute the test statistic, W, as follows: 

The differences X(n-i+1) - X(i) are listed in Table 7.
217

W ' 1

0.0214(0.1436)2 ' 0.964

For this set of data:

14.13.2.5.6 The decision rule for this test is to compare W with the critical value found in Table 6, Appendix B. If

the computed W is less than the critical value, conclude that the data are not normally distributed. For this example,

the critical value at a significance level of 0.01 and 18 observations (n) is 0.858. Since W = 0.964 is greater than

the critical value, the conclusion of the test is that the data are normally distributed. 

14.13.2.6 Test for Homogeneity of Variance 

14.13.2.6.1 The test used to examine whether the variation in mean cell count is the same across all toxicant

concentrations including the control, is Bartlett's Test (Snedecor and Cochran, 1980). The test statistic is as follows: 

B '

[('

P

i'1

Vi)ln S ̄2& '

P

i'1

Viln S 2

i ]

C

 Where: Vi = degrees of freedom for each toxicant concentration and control, Vi

 = (ni - 1) 

p = number of levels of toxicant concentration including the control

ni = the number of replicates for concentration i 

ln = loge

i = 1, 2, ..., p, where p is the number of concentrations including the control

S ̄2 '

('

P

i'1

ViS 2

i )

'

P

i'1

Vi

C ' 1%(3(p&1))&1 ['

P

i'1

1

Vi

&('

P

i'1

Vi)

&1

]

14.13.2.6.2 For the data in this example, (see Table 4) all toxicant concentrations including the control have the

same number of replicates (ni

 = 3 for all i). Thus, Vi = 2 for all i. 

14.13.2.6.3 Bartlett's statistic is therefore: 

 B '

[(12)ln(0.0018)&2 '

P

i'1

ln(S 2

i )]

1.194

= [12(-6.3200) - 2(-41.9082)]/1.194 

= 7.9764/1.194 

= 6.6804
218

TABLE 8. ANOVA TABLE

Source df Sum of Squares Mean Square(MS) 

(SS) (SS/df) 

 

Between p - 1 SSB SB

2

 = SSB/(p-1) 

Within N - p SSW SW

2 = SSW/(N-p) 

Total N - 1 SST 

14.13.2.6.4 B is approximately distributed as chi-square with p - 1 degrees of freedom, when the variances are in

fact the same. Therefore, the appropriate critical value for this test, at a significance level of 0.01 with five degrees

of freedom, is 15.09. Since B = 6.6804 is less than the critical value of 15.09, conclude that the variances are not

different. 

14.13.2.7 Dunnett's Procedure 

14.13.2.7.1 To obtain an estimate of the pooled variance for Dunnett's Procedure, construct an ANOVA table as

described in Table 8.

Where: p = number of toxicant concentrations including the control 

N = total number of observations n1 + n 2 ... + n p

n i

 = number of observations in concentration i 

SSB ' ' Between Sum of Squares

P

i'1

T 2

i

ni

& G 2

N

SST ' ' Total Sum of Squares

P

i'1

'

ni

j'1

Y 2

ij & G 2

N

SSW ' SST&SSB Within Sum of Squares 

G = the grand total of all sample observations, G ' '

P

i'1

Ti

Ti = the total of the replicate measurements for concentration i 

Yij = the jth observation for concentration i (represents the cell count for toxicant concentration i in test

chamber j) 
219

14.13.2.7.2 For the data in this example: 

n1 = n 2 = n 3 = n 4 = n 5 = n 6 = 3 

N = 18 

T1 = Y11 + Y12 + Y13 = 9.281 

T2 = Y21 + Y22 + Y23 = 9.239 

T3 = Y31 + Y32 + Y33 = 8.627 

T4 = Y41 + Y42 + Y43 = 7.928 

T5 = Y51 + Y52 + Y53 = 6.438 

T6 = Y61 + Y62 + Y63 = 4.938 

G =T1 + T2 + T3 + T4 + T5 + T6 = 46.451 

SSB ' '

P

i'1

T 2

i

ni

& G 2

N

' 1

3

(374.606) & (46.451)

18

2

' 4.997

SST ' '

P

i'1

'

ni

j'1

Y 2

ij & G 2

N

' 124.890 & (46.451)2

18 ' 5.018

SSW ' SST&SSB = 5.018 - 4.997 = 0.0210 

SB

2 = SSB/(p-1) = 4.996/(6-1) = 0.9990 

SW

2

 = SSW/(N-p) = 0.021/(18-6) = 0.0018 

14.13.2.7.3 Summarize these calculations in the ANOVA table (Table 9).
220

t

i ' (Y ̄

1&Y ̄i

)

Sw ( 1

n1

)%( 1

ni

)

t

2 ' (3.094&3.080)

[0.0424 (1/3)%(1/3)]

' 0.405

TABLE 10. CALCULATED T VALUES

Toxicant Concentration i ti

(μg Cd/L) 

5 2 0.405 

10 3 6.300 

20 4 13.035 

40 5 27.399 

80 6 41.850 

TABLE 9. ANOVA TABLE FOR DUNNETT’S PROCEDURE EXAMPLE

Source df Sum of Squares Mean Square (MS)

(SS) (SS/df)

Between 5 4.997 0.999

Within 12 0.021 0.0018

Total 17 5.017

14.13.2.7.4 To perform the individual comparisons, calculate the t statistic for each concentration, and control

combination as follows:

Where: = mean cell count for toxicant concentration i Y ̄ i

Y ̄ = mean cell count for the control 1

 SW = square root of the within mean square 

 n1 = number of replicates for the control 

 ni

 = number of replicates for concentration i.

14.13.2.7.5 Table 10 includes the calculated t values for each concentration and control combination. In this

example, comparing the 5 μg/L concentration with the control the calculation is as follows:
221

MSD ' d Sw (1/n1)%(1/n)

14.13.2.7.6 Since the purpose of this test is to detect a significant reduction in mean cell count, a one-sided test is

appropriate. The critical value for this one-sided test is found in Table 5, Appendix C. For an overall alpha level of

0.05, 12 degrees of freedom for error and five concentrations (excluding the control) the critical value is 2.50. The

mean count for concentration i is considered significantly less than the mean count for the control if ti

 is greater than

the critical value. Since t 3, t 4, t 5 and t 6 are greater than 2.50, the 10, 20, 40 and 80 μg/L concentrations have

significantly lower mean cell counts than the control. Hence the NOEC and the LOEC for the test are 5 μg/L and

10 μg/L, respectively. 

14.13.2.7.7 To quantify the sensitivity of the test, the minimum significant difference (MSD) that can be

statistically detected may be calculated.

Where: d = the critical value for Dunnett's Procedure 

 SW = the square root of the within mean square 

 n = the common number of replicates at each concentration (this assumes equal replication at each

concentration) 

 n1 = the number of replicates in the control. 

14.13.2.7.8 In this example:

MSD ' 2.50(0.0424) (1/3)%(1/3)

= 2.50 (0.0424)(0.8165)

= 0.086

14.13.2.7.9 The MSD (0.086) is in transformed units. An approximate MSD in terms of cell count per 100 mL

may be calculated via the following conversion.

1. Subtract the MSD from the transformed control mean. 

3.094 - 0.086 = 3.008 

2. Obtain the untransformed values for the control mean and the difference calculated in 1. 

10(3.094) = 1241.6 

10(3.008) = 1018.6 

3. The untransformed MSD (MSDu) is determined by subtracting the untransformed values from 2. 

MSUu = 1241.6 - 1018.6 = 223 

14.13.2.7.10 Therefore, for this set of data, the minimum difference in mean cell count between the control and

any toxicant concentration that can be detected as statistically significant is 223.

14.13.2.7.11 This represents a decrease in growth of 18% from the control. 
222

TABLE 11. ALGAL MEAN GROWTH RESPONSE AFTER SMOOTHING

Response Smoothed 

Toxicant Concentration i means, mean, Mi Y ̄ i

(μg Cd/L) (cells/mL) (cells/mL)

Control 1 1243 1243

5 2 1201 1201

10 3 757 757

20 4 441 441

40 5 140 140

80 6 44 44

14.13.2.8 Calculation of the ICp

14.13.2.8.1 The growth data in Table 4 are utilized in this example. Table 11 contains the means for each toxicant

concentration. As can be seen, the observed means are monotonically non-increasing with respect to concentration. 

Therefore, it is not necessary to smooth the means prior to calculating the ICp. See Figure 5 for a plot of the

response curve.

14.13.2.8.2 An IC25 and IC50 can be estimated using the Linear Interpolation Method (Appendix M). A 25%

reduction in cell count, compared to the controls, would result in a mean count of 932 cells, where M1(1-p/100) =

1243(1-25/100). A 50% reduction in cell count, compared to the controls, would result in a mean count of 622

cells. Examining the means and their associated concentrations (Table 11), the response, 932 cells, is bracketed by

C2 = 5 μg Cd/L and C3 = 10 μg Cd/L. The response, 622 cells, is bracketed by C3 = 10 μg Cd/L and C4 = 20 μg

Cd/L.

14.13.2.8.3 Using the equation from section 4.2 of Appendix M, the estimate of the IC25 is calculated as follows:

ICp ' C j

%[M 1(1&p/100)&M j]

(C (j%1)&Cj)

(M (j%1)&M j

)

IC25 ' 5%[1243(1&25/100)&1201] (10&5)

(757&1201)

= 8μg Cd/L.

14.13.2.8.4 The IC50 estimate is 14 μg Cd/L:

IC25 ' 6.25%[28.75(1&25/100)&28.75] (12.5&6.25)

(9.40&28.75)

IC50 ' 10%[1243(1&50/100)&757] (20&10)

(441&757)

= 14 μg Cd/L.
223

Figure 5. Plot of raw data and observed means for the green alga, Selenastrum capricornutum, growth data.
224

14.13.2.8.5 When the ICPIN program was used to analyze this set of data, requesting 80 resamples, the estimate of

the IC25 was 8.0227μg Cd/L. The empirical 95% confidence interval for the true mean was 6.4087 μg Cd/L and

10.0313 μg Cd/L. The ICPIN computer program output for the IC25 for this data set is shown in Figure 6.

14.13.2.8.6 When the ICPIN program was used to analyze this set of data, requesting 80 resamples, the estimate of

the IC50 was 14.2774 μg Cd/L. The empirical 95% confidence interval for the true mean was 9.7456 μg Cd/L and

18.5413 μg Cd/L. The computer program output for the IC50 for this data set is shown in Figure 7.

14.13.3 BIOSTIMULATION

14.13.3.1 Where the growth response in effluent (or surface water) exceeds growth in the control flasks, the

percent stimulation, S(%), is calculated as shown below. Values which are significantly greater than the control

indicate a possible degrading enrichment effect on the receiving water (Walsh et al., 1980):

S (%) ' T&C

C

x 100

Where: T = Mean effluent or surface water response

C = Mean control response

14.14 PRECISION AND ACCURACY

14.14.1 PRECISION – Data on single-laboratory and multilaboratory precision are described below (Subsections

14.14.1.1 and 14.14.1.2). Single-laboratory precision is a measure of the reproducibility of test results when tests

are conducted using a specific method under reasonably constant conditions in the same laboratory. Singlelaboratory precision is synonymous with the terms within-laboratory precision and intralaboratory precision. 

Multilaboratory precision is a measure of the reproducibility of test results from different laboratories using the

same test method and analyzing the same test material. Multilaboratory precision is synonymous with the term

interlaboratory precision. Interlaboratory precision, as used in this document, includes both within-laboratory and

between-laboratory components of variability. In recent multilaboratory studies, these two components of

interlaboratory precision have been displayed separately (termed within-laboratory and between-laboratory

variability) and combined (termed total interlaboratory variability). The total interlaboratory variability that is

reported from these studies is synonymous with interlaboratory variability reported from other studies where

individual variability components are not separated.

14.14.1.1 Single-Laboratory Precison

14.14.1.1.1 Data from repetitive 96-h toxicity tests conducted with cadmium chloride as the reference toxicant,

using medium containing EDTA, are shown in Table 12. The precision (CV) of the 10 EC50s was 10.2%.

14.14.1.1.2 EPA evaluated within-laboratory precision of the green alga, Selenastrum capricornutum, Growth Test

using a database of routine reference toxicant test results from nine laboratories (USEPA, 2000b). The database

consisted of 85 reference toxicant tests conducted in 9 laboratories using a variety of reference toxicants including:

copper, sodium chloride, and zinc. Among the 9 laboratories, the median within-laboratory CV calculated for

routine reference toxicant tests was 26% for the IC25 growth endpoint. In 25% of laboratories, the withinlaboratory CV was less than 25%; and in 75% of laboratories, the within-laboratory CV was less than 39%. 

14.14.1.2 Multilaboratory Precision

14.14.1.2.1 In 2000, EPA conducted an interlaboratory variability study of the green alga, Selenastrum

capricornutum, Growth Test (USEPA, 2001a; USEPA, 2001b). In this study, each of 11 participant laboratories

tested 4 blind test samples that included some combination of blank, effluent, reference toxicant, and receiving

water sample types. The blank sample consisted of moderately-hard synthetic freshwater, the effluent sample was a
225

municipal wastewater spiked with KCl, the receiving water sample was a river water spiked with KCl, and the

reference toxicant sample consisted of moderately-hard synthetic freshwater spiked with KCl. Each sample was

tested with and without the addition of EDTA. Of the 44 Selenastrum capricornutum Growth tests conducted with

EDTA, 63.6% were successfully completed and met the required test acceptability criteria. Of the 44 tests

conducted without EDTA, 65.9% were successfully completed and met the required test acceptability criteria. Of

five tests that were conducted on blank samples with the addition of EDTA, none showed false positive results for

the growth endpoint. Of 6 tests that were conducted on blank samples without the addition of EDTA, 2 showed

false positive results for the growth endpoint, yielding a false positive rate of 33.3%. Results from the reference

toxicant, effluent, and receiving water sample types were used to calculate the precision of the method. Table 13

shows the precision of the IC25 for each of these sample types. Averaged across sample types, the total

interlaboratory variability (expressed as a CV%) was 34.3% and 58.5% for IC25 results in tests with EDTA and

without EDTA, respectively. Table 14 shows the precision of growth NOEC endpoints for each sample type. 

NOEC values for tests with EDTA spanned three concentrations for the effluent sample type and four

concentrations for the reference toxicant and receiving water sample types. NOEC values for tests without EDTA,

spanned six concentrations for the reference toxicant sample type, four concentrations for the effluent sample type,

and two concentrations for the receiving water sample type. The percentage of values within one concentration of

the median for tests conducted with EDTA was 85.7%, 100%, and 85.7% for the reference toxicant, effluent, and

receiving water sample types, respectively. The percentage of values within one concentration of the median for

tests conducted without EDTA was 40.0%, 50.0%, and 100% for the reference toxicant, effluent, and receiving

water sample types, respectively. 

14.14.2 ACCURACY 

14.14.2.1 The accuracy of toxicity tests cannot be determined.
226

Conc. ID 1 2 3 4 5 6

Conc. Tested 0 5 10 20 40 80

Response 1 1209 1212 826 493 127 49.3

Response 2 1180 1186 628 416 147 40.0

Response 3 1340 1204 816 413 147 44.0

*** Inhibition Concentration Percentage Estimate ***

Toxicant/Effluent: Cadmium

Test Start Date: Example Test Ending Date: 

Test Species: Selenastrum capricornutum

Test Duration: 96 h

DATA FILE: scmanual.icp

OUTPUT FILE: scmanual.i25

Conc. Number Concentration Response Std. Pooled

 ID Replicates μg/l Means Dev. Response Means

 1 3 0.000 1243.000 85.247 1243.000

 2 3 5.000 1200.667 13.317 1200.667

 3 3 10.000 756.667 111.541 756.667

 4 3 20.000 440.667 45.347 440.667

 5 3 40.000 140.333 11.547 140.333

 6 3 80.000 44.433 4.665 44.433

The Linear Interpolation Estimate: 8.0227 Entered P Value: 25

Number of Resamplings: 80

The Bootstrap Estimates Mean: 8.1627 Standard Deviation: 0.4733

Original Confidence Limits: Lower: 7.2541 Upper: 8.9792

Expanded Confidence Limits: Lower: 6.4087 Upper: 10.0313

Resampling time in Seconds: 1.65 Random Seed: -1575623987

Figure 6. ICPIN program output for the IC25.
227

Conc. ID 1 2 3 4 5 6

Conc. Tested 0 5 10 20 40 80

Response 1 1209 1212 826 493 127 49.3

Response 2 1180 1186 628 416 147 40.0

Response 3 1340 1204 816 413 147 44.0

*** Inhibition Concentration Percentage Estimate ***

Toxicant/Effluent: Cadmium

Test Start Date: Example Test Ending Date: 

Test Species: Selenastrum capricornutum

Test Duration: 96 h

DATA FILE: scmanual.icp

OUTPUT FILE: scmanual.i50

Conc. Number Concentration Response Std. Pooled

 ID Replicates μg/l Means Dev. Response Means

 1 3 0.000 1243.000 85.247 1243.000

 2 3 5.000 1200.667 13.317 1200.667

 3 3 10.000 756.667 111.541 756.667

 4 3 20.000 440.667 45.347 440.667

 5 3 40.000 140.333 11.547 140.333

 6 3 80.000 44.433 4.665 44.433

The Linear Interpolation Estimate: 14.2774 Entered P Value: 50

Number of Resamplings: 80

The Bootstrap Estimates Mean: 14.2057 Standard Deviation: 1.1926

Original Confidence Limits: Lower: 12.1194 Upper: 16.3078

Expanded Confidence Limits: Lower: 9.7456 Upper: 18.5413

Resampling time in Seconds: 1.65 Random Seed: -1751550803

Figure 7. ICPIN program output for the IC50.
228

 TABLE 12. SINGLE LABORATORY PRECISION OF THE GREEN ALGA,

SELENASTRUM CAPRICORNUTUM, 96-H TOXICITY TESTS, USING THE

REFERENCE TOXICANT CADMIUM CHLORIDE (USEPA, 1991a)

Test Number EC50 (mg/L)

1 2.3

2 2.4

3 2.3

4 2.8

5 2.6

6 2.1

7 2.1

8 2.1

9 2.6

10 2.4

n 10.0

Mean 2.37

CV (%) 10.2
229

TABLE 13. PRECISION OF POINT ESTIMATES FOR VARIOUS SAMPLE TYPES1

Test Endpoint Sample Type

CV (%)2

Within-lab3 Between-lab4 Total5

IC25 Reference toxicant 10.9 20.8 23.5

(with EDTA) Effluent 39.5 8.48 40.4

Receiving water - - 38.9

Average 25.2 14.6 34.3

IC25 Reference toxicant 25.6 83.6 87.5

(without EDTA) Effluent 21.0 60.3 63.9

Receiving water - - 24.1

Average 23.3 72.0 58.5

1 From EPA’s WET Interlaboratory Variability Study (USEPA, 2001a; USEPA, 2001b). 2 CVs were calculated based on the within-laboratory component of variability, the between-laboratory

component of variability, and the total interlaboratory variability (including both within-laboratory and

between-laboratory components). For the receiving water sample type, within-laboratory and betweenlaboratory components of variability could not be calculated since the study design did not provide withinlaboratory replication for this sample type. 3 The within-laboratory (intralaboratory) component of variability for duplicate samples tested at the same

time in the same laboratory. 4 The between-laboratory component of variability for duplicate samples tested at different laboratories. 5 The total interlaboratory variability, including within-laboratory and between-laboratory components of

variability. The total interlaboratory variability is synonymous with interlaboratory variability reported from

other studies where individual variability components are not separated. 
230

TABLE 14. FREQUENCY DISTRIBUTION OF HYPOTHESIS TESTING RESULTS FOR VARIOUS

SAMPLE TYPES1

Test Endpoint Sample Type

Median

NOEC

Value

% of Results at

the Median

% of Results

±12

% of Results 

$23

Growth NOEC Reference toxicant 25% 57.1 28.6 14.3

(with EDTA) Effluent 6.25% 42.9 57.1 0.00

Receiving water 12.5% 28.6 57.1 14.3

Growth NOEC Reference toxicant 18.8% -

4 40.0 60.0

(without EDTA) Effluent 18.8% -

4 50.0 50.0

Receiving water 6.25% 75.0 25.0 0.00

1 From EPA’s WET Interlaboratory Variability Study (USEPA, 2001a; USEPA, 2001b). 2 Percent of values at one concentration interval above or below the median. Adding this percentage to the

percent of values at the median yields the percent of values within one concentration interval of the median. 3 Percent of values two or more concentration intervals above or below the median. 4 The median NOEC fell between test concentrations, so no test results fell precisely on the median.
231

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USEPA. 1985c. Validity of effluent and ambient toxicity tests for predicting biological impact, Scippo Creek, Circleville,

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USEPA. 1985d. Validity of effluent and ambient toxicity tests for predicting biological impact, Ohio River, near

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USEPA. 1986b. Validity of effluent and ambient toxicity tests for predicting biological impact, Naugatuck River,

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estuarine organisms. Weber, C.I., W.B. Horning, D.J. Klemm, T.W. Neiheisel, P.A. Lewis, E.L. Robinson,

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USEPA. 1989b. Methods for aquatic toxicity identification evaluations: Phase II toxicity identification procedures. D.I.

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USEPA. 1992. Toxicity identification evaluations: characterization of chronically toxic effluents, Phase I: Toxicity

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USEPA. 1993b. Fish field and laboratory methods for evaluating the biological integrity of surface waters. Klemm, D.J., 

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APPENDICES

Page

A. Independence, Randomization, and Outliers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246

1. Statistical Independence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246

2. Randomization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246

3. Outliers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251

B. Validating Normality and Homogeneity of Variance Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . 252

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252

2. Tests for Normal Distribution of Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252

3. Test for Homogeneity of Variance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265

4. Transformations of the Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266

C. Dunnett's Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269

1. Manual Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269

2. Computer Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275

D. T test with the Bonferroni Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281

E. Steel's Many-one Rank Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287

F. Wilcoxon Rank Sum Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291

G. Fisher's Exact Test with the Bonferroni Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297

H. Single Concentration Toxicity Test - Comparison of Control with

100% Effluent or Receiving Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306

I. Probit Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309

J. Spearman-Karber Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312

K. Trimmed Spearman-Karber Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317

L. Graphical Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321

M. Linear Interpolation Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324

1. General Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324

2. Data Summary and Plots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324
245

APPENDICES (CONTINUED)

Page

3. Monotonicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324

4. Linear Interpolation Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324

5. Confidence Intervals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325

6. Manual Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326

7. Computer Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329

Cited References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334
246

APPENDIX A

INDEPENDENCE, RANDOMIZATION, AND OUTLIERS

1. STATISTICAL INDEPENDENCE

1.1 Dunnett's Procedure and the t test with Bonferroni's adjustment are parametric procedures based on the

assumptions that (1) the observations within treatments are independent and normally distributed, and (2) that the

variance of the observations is homogeneous across all toxicant concentrations and the control. Of the three

possible departures from the assumptions, non-normality, heterogeneity of variance, and lack of independence,

those caused by lack of independence are the most difficult to resolve (see Scheffe, 1959). For toxicity data,

statistical independence means that given knowledge of the true mean for a given concentration or control,

knowledge of the error in any one actual observation would provide no information about the error in any other

observation. Lack of independence is difficult to assess and difficult to test for statistically. It may also have

serious effects on the true alpha or beta level. Therefore, it is of utmost importance to be aware of the need for

statistical independence between observations and to be constantly vigilant in avoiding any patterned experimental

procedure that might compromise independence. One of the best ways to help ensure independence is to follow

proper randomization procedures throughout the test. 

2. RANDOMIZATION 

2.1 Randomization of the distribution of test organisms among test chambers and the arrangement of treatments

and replicate chambers is an important part of conducting a valid test. The purpose of randomization is to avoid

situations where test organisms are placed serially into test chambers, or where all replicates for a test concentration

are located adjacent to one another, which could introduce bias into the test results.

2.2 An example of randomization of the distribution of test organisms among test chambers, and an example of

randomization of arrangement of treatments and replicate chambers are described using the Fathead Minnow Larval

Survival and Growth test. For the purpose of the example, the test design is as follows: five effluent concentrations

are tested in addition to the control. The effluent concentrations are as follows: 6.25%, 12.5%, 25.0%, 50.0%, and

100.0%. There are four replicate chambers per treatment. Each replicate chamber contains ten fish.

2.3 RANDOMIZATION OF FISH TO REPLICATE CHAMBERS EXAMPLE

2.3.1 Consider first the random assignment of the fish to the replicate chambers. The first step is to label each of

the replicate chambers with the control or effluent concentration and the replicate number. The next step is to

assign each replicate chamber four double-digit numbers. An example of this assignment is provided in Table A.1. 

Note that the double digits 00 and 97 through 99 were not used.
247

TABLE A.1. RANDOM ASSIGNMENT OF FISH TO REPLICATE CHAMBERS EXAMPLE

ASSIGNED NUMBERS FOR EACH REPLICATE CHAMBER

Assigned Numbers Replicate Chamber

01, 25, 49, 73 Control, replicate chamber 1 

02, 26, 50, 74 Control, replicate chamber 2

03, 27, 51, 75 Control, replicate chamber 3

04, 28, 52, 76 Control, replicate chamber 4

05, 29, 53, 77 6.25% effluent, replicate chamber 1

06, 30, 54, 78 6.25% effluent, replicate chamber 2

07, 31, 55, 79 6.25% effluent, replicate chamber 3

08, 32, 56, 80 6.25% effluent, replicate chamber 4

09, 33, 57, 81 12.5% effluent, replicate chamber 1

10, 34, 58, 82 12.5% effluent, replicate chamber 2

11, 35, 59, 83 12.5% effluent, replicate chamber 3

12, 36, 60, 84 12.5% effluent, replicate chamber 4

13, 37, 61, 85 25.0% effluent, replicate chamber 1

14, 38, 62, 86 25.0% effluent, replicate chamber 2

15, 39, 63, 87 25.0% effluent, replicate chamber 3

16, 40, 64, 88 25.0% effluent, replicate chamber 4

17, 41, 65, 89 50.0% effluent, replicate chamber 1

18, 42, 66, 90 50.0% effluent, replicate chamber 2

19, 43, 67, 91 50.0% effluent, replicate chamber 3

20, 44, 68, 92 50.0% effluent, replicate chamber 4

21, 45, 69, 93 100.0% effluent, replicate chamber 1

22, 46, 70, 94 100.0% effluent, replicate chamber 2

23, 47, 71, 95 100.0% effluent, replicate chamber 3

24, 48, 72, 96 100.0% effluent, replicate chamber 4

2.3.2 The random numbers used to carry out the random assignment of fish to replicate chambers are provided in

Table A.2. The third step is to choose a starting position in Table A.2, and read the first double digit number. The

first number read identifies the replicate chamber for the first fish taken from the tank. For the example, the first

entry in row 2 was chosen as the starting position. The first number in this row is 37. According to Table A.1, this

number corresponds to replicate chamber 1 of the 25.0% effluent concentration. Thus, the first fish taken from the

tank is to be placed in replicate chamber 1 of the 25.0% effluent concentration.

2.3.3 The next step is to read the double digit number to the right of the first one. The second number identifies

the replicate chamber for the second fish taken from the tank. Continuing the example, the second number read in

row 2 of Table A.2 is 54. According to Table A.1, this number corresponds to replicate chamber 2 of the 6.25%

effluent concentration. Thus, the second fish taken from the tank is to be placed in replicate chamber 2 of the

6.25% effluent concentration.
248

TABLE A.2. TABLE OF RANDOM NUMBERS (Dixon and Massey, 1983)

 10 09 73 25 33 76 52 01 35 86 34 67 35 43 76 80 95 90 91 17 39 29 27 49 45

 37 54 20 48 05 64 89 47 42 96 24 80 52 40 37 20 63 61 04 02 00 82 29 16 65

 08 42 26 89 53 19 64 50 93 03 23 20 90 25 60 15 95 33 47 64 35 08 03 36 06

 99 01 90 25 29 09 37 67 07 15 38 31 13 11 65 88 67 67 43 97 04 43 62 76 59

 12 80 79 99 70 80 15 73 61 47 64 03 23 66 53 98 95 11 68 77 12 27 17 68 33

 66 06 57 47 17 34 07 27 68 50 36 69 73 61 70 65 81 33 98 85 11 19 92 91 70

 31 06 01 08 05 45 57 18 24 06 35 30 34 26 14 86 79 90 74 39 23 40 30 97 32

 85 26 97 76 02 02 05 16 56 92 68 66 57 48 18 73 05 38 52 47 18 62 38 85 79

 63 57 33 21 35 05 32 54 70 48 90 55 35 75 48 28 46 82 87 09 83 49 12 56 24

 73 79 64 57 53 03 52 96 47 78 35 80 83 42 82 60 93 52 03 44 35 27 38 84 35

 98 52 01 77 67 14 90 56 86 07 22 10 94 05 58 60 97 09 34 33 50 50 07 39 98

 11 80 50 54 31 39 80 82 77 32 50 72 56 82 48 29 40 52 42 01 52 77 56 78 51

 83 45 29 96 34 06 28 89 80 83 13 74 67 00 78 18 47 54 06 10 68 71 17 78 17

 88 68 54 02 00 86 50 75 84 01 36 76 66 79 51 90 36 47 64 93 29 60 91 10 62

 99 59 46 73 48 87 51 76 49 69 91 82 60 89 28 93 78 56 13 68 23 47 83 41 13

 65 48 11 76 74 17 46 85 09 50 58 04 77 69 74 73 03 95 71 86 40 21 81 65 44

 80 12 43 56 35 17 72 70 80 15 45 31 82 23 74 21 11 57 82 53 14 38 55 37 63

 74 35 09 98 17 77 40 27 72 14 43 23 60 02 10 45 52 16 42 37 96 28 60 26 55

 69 91 62 68 03 66 25 22 91 48 36 93 68 72 03 76 62 11 39 90 94 40 05 64 18

 09 89 32 05 05 14 22 56 85 14 46 42 75 67 88 96 29 77 88 22 54 38 21 45 98

 91 49 91 45 23 68 47 92 76 86 46 16 28 35 54 94 75 08 99 23 37 08 92 00 48

 80 33 69 45 98 26 94 03 68 58 70 29 73 41 35 53 14 03 33 40 42 05 08 23 41

 44 10 48 19 49 85 15 74 79 54 32 97 92 65 75 57 60 04 08 81 22 22 20 64 13

 12 55 07 37 42 11 10 00 20 40 12 86 07 46 97 96 64 48 94 39 28 70 72 58 15

 63 60 64 93 29 16 50 53 44 84 40 21 95 25 63 43 65 17 70 82 07 20 73 17 90

 61 19 69 04 46 26 45 74 77 74 51 92 43 37 29 65 39 45 95 93 42 58 26 05 27

 15 47 44 52 66 95 27 07 99 53 59 36 78 38 48 82 39 61 01 18 33 21 15 94 66

 94 55 72 85 73 67 89 75 43 87 54 62 24 44 31 91 19 04 25 92 92 92 74 59 73

 42 48 11 62 13 97 34 40 87 21 16 86 84 87 67 03 07 11 20 59 25 70 14 66 70

 23 52 37 83 17 73 20 88 98 37 68 93 59 14 16 26 25 22 96 63 05 52 28 25 62

 04 49 35 24 94 75 24 63 38 24 45 86 25 10 25 61 96 27 93 35 65 33 71 24 72

 00 54 99 76 54 64 05 18 81 59 96 11 96 38 96 54 69 28 23 91 23 28 72 95 29

 35 96 31 53 07 26 89 80 93 45 33 35 13 54 62 77 97 45 00 24 90 10 33 93 33

 59 80 80 83 91 45 42 72 68 42 83 60 94 97 00 13 02 12 48 92 78 56 52 01 06

 46 05 88 52 36 01 39 09 22 86 77 28 14 40 77 93 91 08 36 47 70 61 74 29 41

 32 17 90 05 97 87 37 92 52 41 05 56 70 70 07 86 74 31 71 57 85 39 41 18 38

 69 23 46 14 06 20 11 74 52 04 15 95 66 00 00 18 74 39 24 23 97 11 89 63 38

 19 56 54 14 30 01 75 87 53 79 40 41 92 15 85 66 67 43 68 06 84 96 28 52 07

 45 15 51 49 38 19 47 60 72 46 43 66 79 45 43 59 04 79 00 33 20 82 66 95 41

 94 86 43 19 94 36 16 81 08 51 34 88 88 15 53 01 54 03 54 56 05 01 45 11 76

 98 08 62 48 26 45 24 02 84 04 44 99 90 88 96 39 09 47 34 07 35 44 13 18 80

 33 18 51 62 32 41 94 15 09 49 89 43 54 85 81 88 69 54 19 94 37 54 87 30 43

 80 95 10 04 06 96 38 27 07 74 20 15 12 33 87 25 01 62 52 98 94 62 46 11 71

 79 75 24 91 40 71 96 12 82 96 69 86 10 25 91 74 85 22 05 39 00 38 75 95 79

 18 63 33 25 37 98 14 50 65 71 31 01 02 46 74 05 45 56 14 27 77 93 89 19 36

 74 02 94 39 02 77 55 73 22 70 97 79 01 71 19 52 52 75 80 21 80 81 45 17 48

 54 17 84 56 11 80 99 33 71 43 05 33 51 29 69 56 12 71 92 55 36 04 09 03 24

 11 66 44 98 83 52 07 98 48 27 59 38 17 15 39 09 97 33 34 40 88 46 12 33 56

 48 32 47 79 28 31 24 96 47 10 02 29 53 68 70 32 30 75 75 46 15 02 00 99 94

 69 07 49 41 38 87 63 79 19 76 35 58 40 44 01 10 51 82 16 15 01 84 87 69 38
249

TABLE A.3. EXAMPLE OF RANDOM ASSIGNMENT OF FIRST TEN FISH TO REPLICATE

CHAMBERS

Fish Assignment

First fish taken from tank 25.0% effluent, replicate chamber 1

Second fish taken from tank 6.25% effluent, replicate chamber 2

Third fish taken from tank 50.0% effluent, replicate chamber 4

Fourth fish taken from tank 100.0% effluent, replicate chamber 4

Fifth fish taken from tank 6.25% effluent, replicate chamber 1

Sixth fish taken from tank 25.0% effluent, replicate chamber 4

Seventh fish taken from tank 50.0% effluent, replicate chamber 1

Eighth fish taken from tank 100.0% effluent, replicate chamber 3

Ninth fish taken from tank 50.0% effluent, replicate chamber 2

Tenth fish taken from tank 100.0% effluent, replicate chamber 4

TABLE A.4 RANDOM ASSIGNMENT OF REPLICATE CHAMBERS TO POSITIONS: EXAMPLE

LABELING THE POSITIONS WITHIN THE WATER BATH

12 3 4 5 6

78 910 11 12

13 14 15 16 17 18

19 20 21 22 23 24

2.3.4 Continue in this fashion until all the fish have been randomly assigned to a replicate chamber. In order to fill

each replicate chamber with ten fish, the assigned numbers will be used more than once. If a number is read from

the table that was not assigned to a replicate chamber, then ignore it and continue to the next number. If a replicate

chamber becomes filled and a number is read from the table that corresponds to it, then ignore that value and

continue to the next number. The first ten random assignments of fish to replicate chambers for the example are

summarized in Table A.3.

2.3.5 Four double-digit numbers were assigned to each replicate chamber (instead of one, two, or three doubledigit numbers) in order to make efficient use of the random number table (Table A.2). To illustrate, consider the

assignment of only one double-digit number to each replicate chamber: the first column of assigned numbers in

Table A.1. Whenever the numbers 00 and 25 through 99 are read from Table A.2, they will be disregarded and the

next number will be read.

2.4 RANDOMIZATION OF REPLICATE CHAMBERS TO POSITIONS EXAMPLE

2.4.1 Next consider the random assignment of the 24 replicate chambers to positions within the water bath (or

equivalent). Assume that the replicate chambers are to be positioned in a four row by six column rectangular array. 

The first step is to label the positions in the water bath. Table A.4 provides an example layout.
250

2.4.2 The second step is to assign each of the 24 positions four double-digit numbers. An example of this

assignment is provided in Table A.5. Note that the double digits 00 and 97 through 99 were not used.

TABLE A.5. RANDOM ASSIGNMENT OF REPLICATE CHAMBERS TO POSITIONS: EXAMPLE

ASSIGNED NUMBERS FOR EACH POSITION

Assigned Numbers Position

01, 25, 49, 73 1

02, 26, 50, 74 2

03, 27, 51, 75 3

04, 28, 52, 76 4

05, 29, 53, 77 5

06, 30, 54, 78 6

07, 31, 55, 79 7

08, 32, 56, 80 8

09, 33, 57, 81 9

10, 34, 58, 82 10

11, 35, 59, 83 11

12, 36, 60, 84 12

13, 37, 61, 85 13

14, 38, 62, 86 14

15, 39, 63, 87 15

16, 40, 64, 88 16

17, 41, 65, 89 17

18, 42, 66, 90 18

19, 43, 67, 91 19

20, 44, 68, 92 20

21, 45, 69, 93 21

22, 46, 70, 94 22

23, 47, 71, 95 23

24, 48, 72, 96 24

2.4.3 The random numbers used to carry out the random assignment of replicate chambers to positions are

provided in Table A.2. The third step is to choose a starting position in Table A.2, and read the first double-digit

number. The first number read identifies the position for the first replicate chamber of the control. For the

example, the first entry in row 10 of Table A.2 was chosen as the starting position. The first number in this row was

73. According to Table A.5, this number corresponds to position 1. Thus, the first replicate chamber for the control

will be placed in position 1. 

2.4.4 The next step is to read the double-digit number to the right of the first one. The second number identifies

the position for the second replicate chamber of the control. Continuing the example, the second number read in

row 10 of Table A.2 is 79. According to Table A.5, this number corresponds to position 7. Thus, the second

replicate chamber for the control will be placed in position 7.

2.4.5 Continue in this fashion until all the replicate chambers have been assigned to a position. The first four

numbers read will identify the positions for the control replicate chambers, the second four numbers read will

identify the positions for the lowest effluent concentration replicate chambers, and so on. If a number is read from

the table that was not assigned to a position, then ignore that value and continue to the next number. If a number is

repeated in Table A.2, then ignore the repeats and continue to the next number. The complete randomization of
251

replicate chambers to positions for the example is displayed in Table A.6.

TABLE A.6. RANDOM ASSIGNMENT OF REPLICATE CHAMBERS TO POSITIONS:

EXAMPLE ASSIGNMENT OF ALL 24 POSITIONS

Control 100.0% 6.25% 6.25% 6.25% 12.5% 

Control 12.5% Control 25.0% 12.5% 25.0% 

100.0% 50.0% 100.0% Control 100.0% 25.0% 

50.0% 50.0% 25.0% 50.0% 12.5% 6.25%

2.4.6 Four double-digit numbers were assigned to each position (instead of one, two, or three) in order to make

efficient use of the random number table (Table A.2). To illustrate, consider the assignment of only one doubledigit number to each position: the first column of assigned numbers in Table A.5. Whenever the numbers 00 and

25 through 99 are read from Table A.2, they will be disregarded and the next number will be read.

3. OUTLIERS

3.1 An outlier is an inconsistent or questionable data point that appears unrepresentative of the general trend

exhibited by the majority of the data. Outliers may be detected by tabulation of the data, plotting, and by an

analysis of the residuals. An explanation should be sought for any questionable data points. Without an

explanation, data points should be discarded only with extreme caution. If there is no explanation, the analysis

should be performed both with and without the outlier, and the results of both analyses should be reported.

3.2 Gentleman-Wilk's A statistic gives a test for the condition that the extreme observation may be considered an

outlier. For a discussion of this, and other techniques for evaluating outliers, see Draper and John (1981).
252

APPENDIX B

VALIDATING NORMALITY AND HOMOGENEITY OF VARIANCE ASSUMPTIONS

1. INTRODUCTION

1.1 Dunnett's Procedure and the t test with Bonferroni's adjustment are parametric procedures based on the

assumptions that the observations within treatments are independent and normally distributed, and that the variance

of the observations is homogeneous across all toxicant concentrations and the control. These assumptions should be

checked prior to using these tests, to determine if they have been met. Tests for validating the assumptions are

provided in the following discussion. If the tests fail (if the data do not meet the assumptions), a nonparametric

procedure such as Steel's Many-one Rank Test may be more appropriate. However, the decision on whether to use

parametric or nonparametric tests may be a judgment call, and a statistician should be consulted in selecting the

analysis.

2. TEST FOR NORMAL DISTRIBUTION OF DATA

2.1 SHAPIRO-WILK'S TEST

2.1.1 One formal test for normality is the Shapiro-Wilk's Test (Conover, 1980). The test statistic is obtained by

dividing the square of an appropriate linear combination of the sample order statistics by the usual symmetric

estimate of variance. The calculated W must be greater than zero and less than or equal to one. This test is

recommended for a sample size of 50 or less. If the sample size is greater than 50, the Kolmogorov "D" statistic

(Stephens, 1974) is recommended. An example of the Shapiro-Wilk's test is provided below. 

2.2 The example uses growth data from the Fathead Minnow Larval Survival and Growth Test. The same data are

used in the discussion of the homogeneity of variance determination in Paragraph 3 and Dunnett's Procedure in

Appendix C. The data, the mean and variance of the observations at each concentration, including the control, are

listed in Table B.1.

TABLE B.1. FATHEAD LARVAL, PIMEPHALES PROMELAS, LARVAL GROWTH DATA 

(WEIGHT IN MG) FOR THE SHAPIRO-WILK'S TEST 

NaPCP Concentration (μg/L) 

Replicate Control 32 64 128 256

 A 0.711 0.646 0.669 0.629 0.650

 B 0.662 0.626 0.669 0.680 0.558

 C 0.718 0.723 0.694 0.513 0.606

 D 0.767 0.700 0.676 0.672 0.508

Mean( ) Y ̄ 0.714 0.674 0.677 0.624 0.580 i

Si

2 0.0018 0.0020 0.0001 0.0059 0.0037

i 1 2 3 45

2.3 The first step of the test for normality is to center the observations by subtracting the mean of all the

observations within a concentration from each observation in that concentration. The centered observations are

listed in Table B.2.
253

D ' '

n

i'1

(Xi&X ̄)

2

TABLE B.2. EXAMPLE OF SHAPIRO-WILK'S TEST: CENTERED OBSERVATIONS

NaPCP Concentration (μg/L)

Replicate Control 32 64 128 256

A -0.003 -0.028 -0.008 0.005 0.070

B -0.052 -0.048 -0.008 0.056 -0.022

C 0.004 0.049 0.017 -0.111 0.026

D 0.053 0.026 -0.001 0.048 -0.072

2.4 Calculate the denominator, D, of the test statistic:

Where: Xi

 = the centered observations and &X is the overall mean of the centered observations. For this set of data,

&X = 0, and D = 0.0412. 

2.5 Order the centered observations from smallest to largest.

 X(1) # X(2) # ... # X(n)

where X(i) denotes the ith ordered observation. The ordered observations are listed in Table B.3.

TABLE B.3. EXAMPLE OF THE SHAPIRO-WILK'S TEST: ORDERED OBSERVATIONS

i X(i) i X(i)

1 -0.111 11 0.004

2 -0.072 12 0.005

3 -0.052 13 0.017

4 -0.048 14 0.026

5 -0.028 15 0.026

6 -0.022 16 0.048

7 -0.008 17 0.049

8 -0.008 18 0.053

9 -0.003 19 0.056

10 -0.001 20 0.070

2.6 From Table B.4, for the number of observations, n, obtain the coefficients a1, a2, ..., ak, where k is n/2 if n is

even, and (n-1)/2 if n is odd. For the data in this example, n = 20, k = 10. The ai

 values are listed in Table B.5.
254

TABLE B.4. COEFFICIENTS FOR THE SHAPIRO-WILK'S TEST (Conover, 1980)

Number of Observations

i±n 23 4 5 6 7 8 9 10

 1 0.7071 0.7071 0.6872 0.6646 0.6431 0.6233 0.6052 0.5888 0.5739

 2 - 0.0000 0.1667 0.2413 0.2806 0.3031 0.3164 0.3244 0.3291

 3- - - 0.0000 0.0875 0.1401 0.1743 0.1976 0.2141

 4- - - - - 0.0000 0.0561 0.0947 0.1224

 5- - - - - - - 0.0000 0.0399

Number of Observations 

i±n 11 12 13 14 15 16 17 18 19 20

 1 0.5601 0.5475 0.5359 0.5251 0.5150 0.5056 0.4968 0.4886 0.4808 0.4734

 2 0.3315 0.3325 0.3325 0.3318 0.3306 0.3209 0.3273 0.3253 0.3232 0.3211

 3 0.2260 0.2347 0.2412 0.2460 0.2495 0.2521 0.2540 0.2553 0.2561 0.2565

 4 0.1429 0.1586 0.1707 0.1802 0.1878 0.1939 0.1988 0.2027 0.2059 0.2085

 5 0.0695 0.0922 0.1099 0.1240 0.1353 0.1447 0.1524 0.1587 0.1641 0.1686

 6 0.0000 0.0303 0.0539 0.0727 0.0880 0.1005 0.1109 0.1197 0.1271 0.1334

 7 - - 0.0000 0.0240 0.0433 0.0593 0.0725 0.0837 0.0932 0.1013

 8 - - - - 0.0000 0.0196 0.0359 0.0496 0.0612 0.0711

 9 - - - - - - 0.0000 0.0163 0.0303 0.0422

10 - - - - - - - - 0.0000 0.0140

 

Number of Observations

i±n 21 22 23 24 25 26 27 28 29 30

 

 1 0.4643 0.4590 0.4542 0.4493 0.4450 0.4407 0.4366 0.4328 0.4291 0.4254

 2 0.3185 0.3156 0.3126 0.3098 0.3069 0.3043 0.3018 0.2992 0.2968 0.2944

 3 0.2578 0.2571 0.2563 0.2554 0.2543 0.2533 0.2522 0.2510 0.2499 0.2487

 4 0.2119 0.2131 0.2139 0.2145 0.2148 0.2151 0.2152 0.2151 0.2150 0.2148

 5 0.1736 0.1764 0.1787 0.1807 0.1822 0.1836 0.1848 0.1857 0.1864 0.1870

 6 0.1399 0.1443 0.1480 0.1512 0.1539 0.1563 0.1584 0.1601 0.1616 0.1630

 7 0.1092 0.1150 0.1201 0.1245 0.1283 0.1316 0.1346 0.1372 0.1395 0.1415

 8 0.0804 0.0878 0.0941 0.0997 0.1046 0.1089 0.1128 0.1162 0.1192 0.1219

 9 0.0530 0.0618 0.0696 0.0764 0.0923 0.0876 0.0923 0.0965 0.1002 0.1036

10 0.0263 0.0368 0.0459 0.0539 0.0610 0.0672 0.0728 0.0778 0.0822 0.0862

11 0.0000 0.0122 0.0228 0.0321 0.0403 0.0476 0.0540 0.0598 0.0650 0.0697

12 - - 0.0000 0.0107 0.0200 0.0284 0.0358 0.0424 0.0483 0.0537

13 - - - - 0.0000 0.0094 0.0178 0.0253 0.0320 0.0381

14 - - - - - - 0.0000 0.0084 0.0159 0.0227

15 - - - - - - - - 0.0000 0.0076

 
255

TABLE B.4. COEFFICIENTS FOR THE SHAPIRO WILK'S TEST (CONTINUED)

Number of Observations

i±n 31 32 33 34 35 36 37 38 39 40

 1 0.4220 0.4188 0.4156 0.4127 0.4096 0.4068 0.4040 0.4015 0.3989 0.3964

 2 0.2921 0.2898 0.2876 0.2854 0.2834 0.2813 0.2794 0.2774 0.2755 0.2737

 3 0.2475 0.2462 0.2451 0.2439 0.2427 0.2415 0.2403 0.2391 0.2380 0.2368

 4 0.2145 0.2141 0.2137 0.2132 0.2127 0.2121 0.2116 0.2110 0.2104 0.2098

 5 0.1874 0.1878 0.1880 0.1882 0.1883 0.1883 0.1883 0.1881 0.1880 0.1878

 6 0.1641 0.1651 0.1660 0.1667 0.1673 0.1678 0.1663 0.1686 0.1689 0.1691

 7 0.1433 0.1449 0.1463 0.1475 0.1487 0.1496 0.1505 0.1513 0.1520 0.1526

 8 0.1243 0.1265 0.1284 0.1301 0.1317 0.1331 0.1344 0.1356 0.1366 0.1376

 9 0.1066 0.1093 0.1118 0.1140 0.1160 0.1179 0.1196 0.1211 0.1225 0.1237

10 0.0899 0.0931 0.0961 0.0988 0.1013 0.1036 0.1056 0.1075 0.1092 0.1108

11 0.0739 0.0777 0.0812 0.0844 0.0873 0.0900 0.0924 0.0947 0.0967 0.0986

12 0.0585 0.0629 0.0669 0.0706 0.0739 0.0770 0.0798 0.0824 0.0848 0.0870

13 0.0435 0.0485 0.0530 0.0572 0.0610 0.0645 0.0677 0.0706 0.0733 0.0759

14 0.0289 0.0344 0.0395 0.0441 0.0484 0.0523 0.0559 0.0592 0.0622 0.0651

15 0.0144 0.0206 0.0262 0.0314 0.0361 0.0404 0.0444 0.0481 0.0515 0.0546

16 0.0000 0.0068 0.0131 0.0187 0.0239 0.0287 0.0331 0.0372 0.0409 0.0444

17 - - 0.0000 0.0062 0.0119 0.0172 0.0220 0.0264 0.0305 0.0343

18 - - - - 0.0000 0.0057 0.0110 0.0158 0.0203 0.0244

19 - - - - - - 0.0000 0.0053 0.0101 0.0146

20 - - - - - - - - 0.0000 0.0049

Number of Observations 

i±n 41 42 43 44 45 46 47 48 49 50

 1 0.3940 0.3917 0.3894 0.3872 0.3850 0.3830 0.3808 0.3789 0.3770 0.3751

 2 0.2719 0.2701 0.2684 0.2667 0.2651 0.2635 0.2620 0.2604 0.2589 0.2574

 3 0.2357 0.2345 0.2334 0.2323 0.2313 0.2302 0.2291 0.2281 0.2271 0.2260

 4 0.2091 0.2085 0.2078 0.2072 0.2065 0.2058 0.2052 0.2045 0.2038 0.2032

 5 0.1876 0.1874 0.1871 0.1868 0.1865 0.1862 0.1859 0.1855 0.1851 0.1847

 6 0.1693 0.1694 0.1695 0.1695 0.1695 0.1695 0.1695 0.1693 0.1692 0.1691

 7 0.1531 0.1535 0.1539 0.1542 0.1545 0.1548 0.1550 0.1551 0.1553 0.1554

 8 0.1384 0.1392 0.1398 0.1405 0.1410 0.1415 0.1420 0.1423 0.1427 0.1430

 9 0.1249 0.1259 0.1269 9,1278 0.1286 0.1293 0.1300 0.1306 0.1312 0.1317

10 0.1123 0.1136 0.1149 0.1160 9.1170 0.1180 0.1189 0.1197 0.1205 0.1212

11 0.1004 0.1020 0.1035 0.1049 0.1062 0.1073 0.1085 0.1095 0.1105 0.1113

12 0.0891 0.0909 0.0927 0.0943 0.0959 0.0972 0.0986 0.0998 0.1010 0.1020

13 0.0782 0.0804 0.0824 0.0842 0.0860 0.0876 0.0892 0.0906 0.0919 0.0932

14 0.0677 0.0701 0.0724 0.0745 0.0765 0.0783 0.0801 0.0817 0.0832 0.0846

15 0.0575 0.0602 0.0628 0.0651 0.0673 0.0694 0.0713 0.0731 0.0748 0.0764

16 0.0476 0.0506 0.0534 0.0560 0.0584 0.0607 0.0628 0.0648 0.0667 0.0685

17 0.0379 0.0411 0.0442 0.0471 0.0497 0.0522 0.0546 0.0568 0.0588 0.0608

18 0.0283 0.0318 0.0352 0.0383 0.0412 0.0439 0.0465 0.0489 0.0511 0.0532

19 0.0188 0.0227 0.0263 0.0296 0.0328 0.0357 0.0385 0.0411 0.0436 0.0459

20 0.0094 0.0136 0.0175 0.0211 0.0245 0.0277 0.0307 0.0335 0.0361 0.0386

21 0.0000 0.0045 0.0087 0.0126 0.0163 0.0197 0.0229 0.0259 0.0288 0.0314

22 - - 0.0000 0.0042 0.0081 0.0118 0.0153 0.0185 0.0215 0.0244

23 - - - - 0.0000 0.0039 0.0076 0.0111 0.0143 0.0174

24 - - - - - - 0.0000 0.0037 0.0071 0.0104

25 - - - - - - - - 0.0000 0.0035
256

W ' 1

D ['

k

i'1

ai (X (n&i%1)&X (i))]

2

2.7 Compute the test statistic, W, as follows: 

The differences, X(n-i+1) - X(i), are listed in Table B.5.

2.8 The decision rule for this test is to compare the critical value from Table B.6 to the computed W. If the

computed value is less than the critical value, conclude that the data are not normally distributed. For this example,

the critical value at a significance level of 0.01 and 20 observations (n) is 0.868. The calculated value, 0.959, is not

less than the critical value. Therefore, conclude that the data are normally distributed.

TABLE B.5. EXAMPLE OF THE SHAPIRO-WILK'S TEST: TABLE OF COEFFICIENTS AND

DIFFERENCES

 iai X(n-i+1) - X(i)

1 0.4734 0.181 X(20) - X(1)

2 0.3211 0.128 X(19) - X(2)

3 0.2565 0.105 X(18) - X(3)

4 0.2085 0.097 X(17) - X(4)

5 0.1686 0.076 X(16) - X(5)

6 0.1334 0.048 X(15) - X(6)

7 0.1013 0.034 X(14) - X(7)

8 0.0711 0.025 X(13) - X(8)

9 0.0422 0.008 X(12) - X(9)

10 0.0140 0.005 X(11) - X(10)

2.9 In general, if the data fail the test for normality, a transformation such as to log values may normalize the data. 

After transforming the data, repeat the Shapiro-Wilk's Test for normality.

2.10 KOLMOGOROV "D" TEST

2.10.1 A formal two-sided test for normality is the Kolmogorov "D" Test. The test statistic is calculated by

obtaining the difference between the cumulative distribution function estimated from the data and the standard

normal cumulative distribution function for each standardized observation. This test is recommended for a sample

size greater than 50. If the sample size is less than or equal to 50, then the Shapiro Wilk's Test is recommended. An

example of the Kolmogorov "D" test is provided below.

2.10.2 The example uses reproduction data from the daphnid, Ceriodaphnia dubia, Survival and Reproduction

Test. The observed data and the mean of the observations at each concentration, including the control, are listed in

Table B.7.

2.10.3 The first step of the test for normality is to center the observations by subtracting the mean of all the

observations within a concentration from each observation in that concentration. The centered observations for the

example are listed in Table B.8.
257

TABLE B.6. QUANTILES OF THE SHAPIRO-WILK'S TEST STATISTIC (Conover, 1980)

 n 0.01 0.02 0.05 0.10 0.50 0.90 0.95 0.98 0.99

 3 0.753 0.756 0.767 0.789 0.959 0.998 0.999 1.000 1.000

 4 0.687 0.707 0.748 0.792 0.935 0.987 0.992 0.996 0.997

 5 0.686 0.715 0.762 0.806 0.927 0.979 0.986 0.991 0.993

 6 0.713 0.743 0.788 0.826 0.927 0.974 0.981 0.986 0.989

 7 0.730 0.760 0.803 0.838 0.928 0.972 0.979 0.985 0.988

 8 0.749 0.778 0.818 0.851 0.932 0.972 0.978 0.984 0.987

 9 0.764 0.791 0.829 0.859 0.935 0.972 0.978 0.984 0.986

10 0.781 0.806 0.842 0.869 0.938 0.972 0.978 0.983 0.986

11 0.792 0.817 0.850 0.876 0.940 0.973 0.979 0.984 0.986

12 0.805 0.828 0.859 0.883 0.943 0.973 0.979 0.984 0.986

13 0.814 0.837 0.866 0.889 0.945 0.974 0.979 0.984 0.986

14 0.825 0.846 0.874 0.895 0.947 0.975 0.980 0.984 0.986

15 0.835 0.855 0.881 0.901 0.950 0.975 0.980 0.984 0.987

16 0.844 0.863 0.887 0.906 0.952 0.976 0.981 0.985 0.987

17 0.851 0.869 0.892 0.910 0.954 0.977 0.981 0.985 0.987

18 0.858 0.874 0.897 0.914 0.956 0.978 0.982 0.986 0.988

19 0.863 0.879 0.901 0.917 0.957 0.978 0.982 0.986 0.988

20 0.868 0.884 0.905 0.920 0.959 0.979 0.983 0.986 0.988

21 0.873 0.888 0.908 0.923 0.960 0.980 0.983 0.987 0.989

22 0.878 0.892 0.911 0.926 0.961 0.980 0.984 0.987 0.989

23 0.881 0.895 0.914 0.928 0.962 0.981 0.984 0.987 0.989

24 0.884 0.898 0.916 0.930 0.963 0.981 0.984 0.987 0.989

25 0.888 0.901 0.918 0.931 0.964 0.981 0.985 0.988 0.989

26 0.891 0.904 0.920 0.933 0.965 0.982 0.985 0.988 0.989

27 0.894 0.906 0.923 0.935 0.965 0.982 0.985 0.988 0.990

28 0.896 0.908 0.924 0.936 0.966 0.982 0.985 0.988 0.990

29 0.898 0.910 0.926 0.937 0.966 0.982 0.985 0.988 0.990

30 0.900 0.912 0.927 0.939 0.967 0.983 0.985 0.988 0.990

31 0.902 0.914 0.929 0.940 0.967 0.983 0.986 0.988 0.990

32 0.904 0.915 0.930 0.941 0.968 0.983 0.986 0.988 0.990

33 0.906 0.917 0.931 0.942 0.968 0.983 0.986 0.989 0.990

34 0.908 0.919 0.933 0.943 0.969 0.983 0.986 0.989 0.990

35 0.910 0.920 0.934 0.944 0.969 0.984 0.986 0.989 0.990

36 0.912 0.922 0.935 0.945 0.970 0.984 0.986 0.989 0.990

37 0.914 0.924 0.936 0.946 0.970 0.984 0.987 0.989 0.990

38 0.916 0.925 0.938 0.947 0.971 0.984 0.987 0.989 0.990

39 0.917 0.927 0.939 0.948 0.971 0.984 0.987 0.989 0.991

40 0.919 0.928 0.940 0.949 0.972 0.985 0.987 0.989 0.991

41 0.920 0.929 0.941 0.950 0.972 0.985 0.987 0.989 0.991

42 0.922 0.930 0.942 0.951 0.972 0.985 0.987 0.989 0.991

43 0.923 0.932 0.943 0.951 0.973 0.985 0.987 0.990 0.991

44 0.924 0.933 0.944 0.952 0.973 0.985 0.987 0.990 0.991

45 0.926 0.934 0.945 0.953 0.973 0.985 0.988 0.990 0.991

46 0.927 0.935 0.945 0.953 0.974 0.985 0.988 0.990 0.991

47 0.928 0.936 0.946 0.954 0.974 0.985 0.988 0.990 0.991

48 0.929 0.937 0.947 0.954 0.974 0.985 0.988 0.990 0.991

49 0.929 0.937 0.947 0.955 0.974 0.985 0.988 0.990 0.991

50 0.930 0.938 0.947 0.955 0.974 0.985 0.988 0.990 0.991 
258

TABLE B.7. CERIODAPHNIA DUBIA REPRODUCTION DATA FOR THE KOLMOGOROV "D"

TEST

Effluent Concentration (%)

Replicate Control 1.56 3.12 6.25 12.5 25.0

1 27 32 39 27 19 10

2 30 35 30 34 25 13

3 29 32 33 36 26 7

4 31 26 33 34 17 7

5 16 18 36 31 16 7

6 15 29 33 27 21 10

7 18 27 33 33 23 10

8 17 16 27 31 15 16

9 14 35 38 33 18 12

10 27 13 44 31 10 2

Mean 22.4 26.3 34.6 31.7 19.0 9.4

TABLE B.8. CENTERED OBSERVATIONS FOR KOLMOGOROV “D” EXAMPLE

Effluent Concentration (%)

Replicate Control 1.56 3.12 6.25 12.5 25.0

1 4.6 5.7 4.4 -4.7 0.0 0.6

2 7.6 8.7 -4.6 2.3 6.0 3.6

3 6.6 5.7 -1.6 4.3 7.0 -2.4

4 8.6 -0.3 -1.6 2.3 -2.0 -2.4

5 -6.4 -8.3 1.4 -0.7 -3.0 -2.4

6 -7.4 2.7 -1.6 -4.7 2.0 0.6

7 -4.4 0.7 -1.6 1.3 4.0 0.6

8 -5.4 -10.3 -7.6 -0.7 -4.0 6.6

9 -8.4 8.7 3.4 1.3 -1.0 2.6

10 4.6 -13.3 9.4 -0.7 -9.0 -7.4
259

2.10.4 Order the centered observations from smallest to largest:

 X(1) # X(2) # ... # X(n)

where X(i) denotes the ith ordered observation, and n denotes the total number of centered observations. The

ordered observations for the example are listed in Table B.9.
260

TABLE B.9. EXAMPLE CALCULATION OF THE KOLMOGOROV "D" STATISTIC

i X(i) zi pi Di

+ Di-

1 -13.3 -2.51 0.0060 0.0107 0.0060

2 -10.3 -1.94 0.0262 0.0071 0.0095

3 -9.0 -1.70 0.0446 0.0054 0.0113

4 -8.4 -1.58 0.0571 0.0096 0.0071

5 -8.3 -1.57 0.0582 0.0251 -0.0085

6 -7.6 -1.43 0.0764 0.0236 -0.0069

7 -7.4 -1.40 0.0808 0.0359 -0.0192

8 -7.4 -1.40 0.0808 0.0525 -0.0359

9 -6.4 -1.21 0.1131 0.0369 -0.0202

10 -5.4 -1.02 0.1539 0.0128 0.0039

11 -4.7 -0.89 0.1867 -0.0034 0.0200

12 -4.7 -0.89 0.1867 0.0133 0.0034

13 -4.6 -0.87 0.1922 0.0245 -0.0078

14 -4.4 -0.83 0.2033 0.0300 -0.0134

15 -4.0 -0.75 0.2266 0.0234 -0.0067

16 -3.0 -0.57 0.2843 -0.0176 0.0343

17 -2.4 -0.45 0.3264 -0.0431 0.0597

18 -2.4 -0.45 0.3264 -0.0264 0.0431

19 -2.4 -0.45 0.3264 -0.0097 0.0264

20 -2.0 -0.38 0.3520 -0.0187 0.0353

21 -1.6 -0.30 0.3821 -0.0321 0.0488

22 -1.6 -0.30 0.3821 -0.0154 0.0321

23 -1.6 -0.30 0.3821 0.0012 0.0154

24 -1.6 -0.30 0.3821 0.0179 -0.0012

25 -1.0 -0.19 0.4247 -0.0080 0.0247

26 -0.7 -0.13 0.4483 -0.0150 0.0316

27 -0.7 -0.13 0.4483 0.0017 0.0150

28 -0.7 -0.13 0.4483 0.0184 -0.0017

29 -0.3 -0.06 0.4761 0.0072 0.0094

30 0.0 0.00 0.5000 0.0000 0.0167

31 0.6 0.11 0.5438 -0.0271 0.0438

32 0.6 0.11 0.5438 -0.0105 0.0271

33 0.6 0.11 0.5438 0.0062 0.0105

34 0.7 0.13 0.5517 0.0150 0.0017

35 1.3 0.25 0.5987 -0.0154 0.0320

36 1.3 0.25 0.5987 0.0013 0.0154

37 1.4 0.26 0.6026 0.0141 0.0026

38 2.0 0.38 0.6480 -0.0147 0.0313

39 2.3 0.43 0.6664 -0.0164 0.0331

40 2.3 0.43 0.6664 0.0003 0.0164

41 2.6 0.49 0.6879 -0.0046 0.0212

42 2.7 0.51 0.6950 0.0050 0.0117

43 3.4 0.64 0.7389 -0.0222 0.0389

44 3.6 0.68 0.7517 -0.0184 0.0350

45 4.0 0.75 0.7734 -0.0234 0.0401

46 4.3 0.81 0.7910 -0.0243 0.0410

47 4.4 0.83 0.7967 -0.0134 0.0300
261

zi ' X (i)

s

and s 2 ' '[X (i)

]

2

(n&1)

 TABLE B.9. EXAMPLE CALCULATION OF THE KOLMOGOROV "D" STATISTIC (CONTINUED)

i X(i) zi pi Di

+ Di-

48 4.6 0.87 0.8078 -0.0078 0.0245

49 4.6 0.87 0.8078 0.0089 0.0078

50 5.7 1.08 0.8599 -0.0266 0.0432

51 5.7 1.08 0.8599 -0.0099 0.0266

52 6.0 1.13 0.8708 -0.0041 0.0208

53 6.6 1.25 0.8944 -0.0111 0.0277

54 6.6 1.25 0.8944 0.0056 0.0111

55 7.0 1.32 0.9066 0.0101 0.0066

56 7.6 1.43 0.9236 0.0097 0.0069

57 8.6 1.62 0.9474 0.0026 0.0141

58 8.7 1.64 0.9495 0.0172 -0.0005

59 8.7 1.64 0.9495 0.0338 -0.0172

60 9.4 1.77 0.9616 0.0384 -0.0217

2.10.5 The next step is to standardize the ordered observations. Let zi denote the standardized value of the ith

ordered observation. Then, 

For the example, s = 5.3, and the standardized observations are listed in Table B.9.

2.10.6 From Table B.10, obtain the value of the standard normal cumulative distribution function (standard normal

CDF) at zi

. Denote this value as p i. Note that negative z are not listed in Table B.10. The value of the standard

normal CDF at a negative number is one minus the value of the standard normal CDF at the absolute value of that

number. For example, since the value of the standard normal CDF at 3.21 is 0.9993, the value of the standard

normal CDF at -3.21 is 1 - 0.9993 = 0.0007. The pi

 values for the example data are listed in Table B.9.
262

TABLE B.10. P IS THE VALUE OF THE STANDARD NORMAL CUMULATIVE DISTRIBUTION

AT Z

zp zp z p z p

0.00 0.5000 0.41 0.6591 0.82 0.7939 1.23 0.8907

0.01 0.5040 0.42 0.6628 0.83 0.7967 1.24 0.8925

0.02 0.5080 0.43 0.6664 0.84 0.7995 1.25 0.8944

0.03 0.5120 0.44 0.6700 0.85 0.8023 1.26 0.8962

0.04 0.5160 0.45 0.6736 0.86 0.8051 1.27 0.8980

0.05 0.5199 0.46 0.6772 0.87 0.8078 1.28 0.8997

0.06 0.5239 0.47 0.6808 0.88 0.8106 1.29 0.9015

0.07 0.5279 0.48 0.6844 0.89 0.8133 1.30 0.9032

0.08 0.5319 0.49 0.6879 0.90 0.8159 1.31 0.9049

0.09 0.5359 0.50 0.6915 0.91 0.8186 1.32 0.9066

0.10 0.5398 0.51 0.6950 0.92 0.8212 1.33 0.9082

0.11 0.5438 0.52 0.6985 0.93 0.8238 1.34 0.9099

0.12 0.5478 0.53 0.7019 0.94 0.8264 1.35 0.9115

0.13 0.5517 0.54 0.7054 0.95 0.8289 1.36 0.9131

0.14 0.5557 0.55 0.7088 0.96 0.8315 1.37 0.9147

0.15 0.5596 0.56 0.7123 0.97 0.8340 1.38 0.9162

0.16 0.5636 0.57 0.7157 0.98 0.8365 1.39 0.9177

0.17 0.5675 0.58 0.7190 0.99 0.8389 1.40 0.9192

0.18 0.5714 0.59 0.7224 1.00 0.8413 1.41 0.9207

0.19 0.5753 0.60 0.7257 1.01 0.8438 1.42 0.9222

0.20 0.5793 0.61 0.7291 1.02 0.8461 1.43 0.9236

0.21 0.5832 0.62 0.7324 1.03 0.8485 1.44 0.9251

0.22 0.5871 0.63 0.7357 1.04 0.8508 1.45 0.9265

0.23 0.5910 0.64 0.7389 1.05 0.8531 1.46 0.9279

0.24 0.5948 0.65 0.7422 1.06 0.8554 1.47 0.9292

0.25 0.5987 0.66 0.7454 1.07 0.8577 1.48 0.9306

0.26 0.6026 0.67 0.7486 1.08 0.8599 1.49 0.9319

0.27 0.6064 0.68 0.7517 1.09 0.8621 1.50 0.9332

0.28 0.6103 0.69 0.7549 1.10 0.8643 1.51 0.9345

0.29 0.6141 0.70 0.7580 1.11 0.8665 1.52 0.9357

0.30 0.6179 0.71 0.7611 1.12 0.8686 1.53 0.9370

0.31 0.6217 0.72 0.7642 1.13 0.8708 1.54 0.9382

0.32 0.6255 0.73 0.7673 1.14 0.8729 1.55 0.9394

0.33 0.6293 0.74 0.7704 1.15 0.8749 1.56 0.9406

0.34 0.6331 0.75 0.7734 1.16 0.8770 1.57 0.9418

0.35 0.6368 0.76 0.7764 1.17 0.8790 1.58 0.9429

0.36 0.6406 0.77 0.7794 1.18 0.8810 1.59 0.9441

0.37 0.6443 0.78 0.7823 1.19 0.8830 1.60 0.9452

0.38 0.6480 0.79 0.7852 1.20 0.8849 1.61 0.9463

0.39 0.6517 0.80 0.7881 1.21 0.8869 1.62 0.9474

0.40 0.6554 0.81 0.7910 1.22 0.8888 1.63 0.9484
263

TABLE B.10. P IS THE VALUE OF THE STANDARD NORMAL CUMULATIVE DISTRIBUTION

AT Z (CONTINUED)

z p z p z p z p 

 1.64 0.9495 2.05 0.9798 2.46 0.9931 2.87 0.9979

 1.65 0.9505 2.06 0.9803 2.47 0.9932 2.88 0.9980

 1.66 0.9515 2.07 0.9808 2.48 0.9934 2.89 0.9981

 1.67 0.9525 2.08 0.9812 2.49 0.9936 2.90 0.9981

 1.68 0.9535 2.09 0.9817 2.50 0.9938 2.91 0.9982

 1.69 0.9545 2.10 0.9821 2.51 0.9940 2.92 0.9982

 1.70 0.9554 2.11 0.9826 2.52 0.9941 2.93 0.9983

 1.71 0.9564 2.12 0.9830 2.53 0.9943 2.94 0.9984

 1.72 0.9573 2.13 0.9834 2.54 0.9945 2.95 0.9984

 1.73 0.9582 2.14 0.9838 2.55 0.9946 2.96 0.9985

 1.74 0.9591 2.15 0.9842 2.56 0.9948 2.97 0.9985

 1.75 0.9599 2.16 0.9846 2.57 0.9949 2.98 0.9986

 1.76 0.9608 2.17 0.9850 2.58 0.9951 2.99 0.9986

 1.77 0.9616 2.18 0.9854 2.59 0.9952 3.00 0.9987

 1.78 0.9625 2.19 0.9857 2.60 0.9953 3.01 0.9987

 1.79 0.9633 2.20 0.9861 2.61 0.9955 3.02 0.9987

 1.80 0.9641 2.21 0.9864 2.62 0.9956 3.03 0.9988

 1.81 0.9649 2.22 0.9868 2.63 0.9957 3.04 0.9988

 1.82 0.9656 2.23 0.9871 2.64 0.9959 3.05 0.9989

 1.83 0.9664 2.24 0.9875 2.65 0.9960 3.06 0.9989

 1.84 0.9671 2.25 0.9878 2.66 0.9961 3.07 0.9989

 1.85 0.9678 2.26 0.9881 2.67 0.9962 3.08 0.9990

 1.86 0.9686 2.27 0.9884 2.68 0.9963 3.09 0.9990

 1.87 0.9693 2.28 0.9887 2.69 0.9964 3.10 0.9990

 1.88 0.9699 2.29 0.9890 2.70 0.9965 3.11 0.9991

 1.89 0.9706 2.30 0.9893 2.71 0.9966 3.12 0.9991

 1.90 0.9713 2.31 0.9896 2.72 0.9967 3.13 0.9991

 1.91 0.9719 2.32 0.9898 2.73 0.9968 3.14 0.9992

 1.92 0.9726 2.33 0.9901 2.74 0.9969 3.15 0.9992

 1.93 0.9732 2.34 0.9904 2.75 0.9970 3.16 0.9992

 1.94 0.9738 2.35 0.9906 2.76 0.9971 3.17 0.9992

 1.95 0.9744 2.36 0.9909 2.77 0.9972 3.18 0.9993

 1.96 0.9750 2.37 0.9911 2.78 0.9973 3.19 0.9993

 1.97 0.9756 2.38 0.9913 2.79 0.9974 3.20 0.9993

 1.98 0.9761 2.39 0.9916 2.80 0.9974 3.21 0.9993

 1.99 0.9767 2.40 0.9918 2.81 0.9975 3.22 0.9994

 2.00 0.9772 2.41 0.9920 2.82 0.9976 3.23 0.9994

 2.01 0.9778 2.42 0.9922 2.83 0.9977 3.24 0.9994

 2.02 0.9783 2.43 0.9925 2.84 0.9977 3.25 0.9994

 2.03 0.9788 2.44 0.9927 2.85 0.9978 3.26 0.9994

 2.04 0.9793 2.45 0.9929 2.86 0.9979 3.27 0.9995

 
264

TABLE B.10. P IS THE VALUE OF THE STANDARD NORMAL CUMULATIVE DISTRIBUTION

AT Z (CONTINUED)

z p z p z p z p 

3.28 0.9995 3.46 0.9997 3.64 0.9999 3.82 0.9999

3.29 0.9995 3.47 0.9997 3.65 0.9999 3.83 0.9999

3.30 0.9995 3.48 0.0997 3.66 0.9999 3.84 0.9999

3.31 0.9995 3.49 0.9998 3.67 0.9999 3.85 0.9999

3.32 0.9995 3.50 0.9998 3.68 0.9999 3.86 0.9999

3.33 0.9996 3.51 0.9998 3.69 0.9999 3.87 0.9999

3.34 0.9996 3.52 0.9998 3.70 0.9999 3.88 0.9999

3.35 0.9996 3.53 0.9998 3.71 0.9999 3.89 0.9999

3.36 0.9996 3.54 0.9998 3.72 0.9999 3.90 1.0000

3.37 0.9996 3.55 0.9998 3.73 0.9999 3.91 1.0000

3.38 0.9996 3.56 0.9998 3.74 0.9999 3.92 1.0000

3.39 0.9997 3.57 0.9998 3.75 0.9999 3.93 1.0000

3.40 0.9997 3.58 0.9998 3.76 0.9999 3.94 1.0000

3.41 0.9997 3.59 0.9998 3.77 0.9999 3.95 1.0000

3.42 0.9997 3.60 0.9998 3.78 0.9999 3.96 1.0000

3.43 0.9997 3.61 0.9998 3.79 0.9999 3.97 1.0000

3.44 0.9997 3.62 0.9999 3.80 0.9999 3.98 1.0000

3.45 0.9997 3.63 0.9999 3.81 0.9999 3.99 1.0000

2.10.7 Next, calculate the following differences for each ordered observation:

Di

+ = (i/n) - pi

Di- =pi - [(i-1)/n]

The differences for the example are listed in Table B.9.

2.10.8 Obtain the maximum of the Di

+, and denote it as D+. Obtain the maximum of the Di-, and denote it as D-. 

For the example, D+ = 0.0525, and D- = 0.0597.

2.10.9 Next, obtain the maximum of D+ and D-, and denote it as D. For the example, D = 0.0597.

2.10.10 The test statistic, D*, is calculated as follows:

D * ' D( n&0.01% 0.85

n

)

For the example, D* = 0.4684.

2.10.11 The decision rule for the two tailed test is to compare the critical value from Table B.11 to the computed

D*. If the computed value is greater than the critical value, conclude that the data are not normally distributed. For

this example, the critical value at a significance level of 0.01 is 1.035. The calculated value, 0.4684, is not greater

than the critical value. Thus, the conclusion of the test is that the data are normally distributed.

2.10.12 In general, if the data fail the test for normality, a transformation such as the log transformation may

normalize the data. After transforming the data, repeat the Kolmogorov "D" test for normality.
265

TABLE B.11. CRITICAL VALUES FOR THE KOLMOGOROV "D" TEST

 

Alpha Critical

Level Value

 

0.010 1.035

0.025 0.955

0.050 0.895

0.100 0.819

0.150 0.775

 

TABLE B.12. FATHEAD LARVAL GROWTH DATA (WEIGHT IN MG) USED FOR BARTLETT'S

TEST FOR HOMOGENEITY OF VARIANCE

NaPCP Concentration (μg/L)

Replicate Control 32 64 128 256

A 0.711 0.646 0.669 0.629 0.650 

B 0.662 0.626 0.669 0.680 0.558 

C 0.718 0.723 0.694 0.513 0.606 

D 0.767 0.700 0.676 0.672 0.508 

 

Mean( ) Y ̄ 0.714 0.674 0.677 0.624 0.580 i

Si

2 0.0018 0.0020 0.0001 0.0059 0.0037 

I 1 2 34 5

3. TEST FOR HOMOGENEITY OF VARIANCE

3.1 For Dunnett's Procedure and the t test with Bonferroni's adjustment, the variances of the data obtained from

each toxicant concentration and the control are assumed to be equal. Bartlett's Test is a formal test of this

assumption. In using this test, it is assumed that the data are normally distributed.

3.2 The data used in this example are growth data from a Fathead Minnow Larval Survival and Growth Test, and

are the same data used in Appendices C and D. These data are listed in Table B.12, together with the calculated

variance for the control and each toxicant concentration.

3.3 The test statistic for Bartlett's Test (Snedecor and Cochran, 1980) is as follows:

 B '

[('

P

i'1

Vi)ln S ̄2

& '

P

i'1

Viln S 2

i ]

C

Where: Vi

 = degrees of freedom for each toxicant concentration and control
266

p = number of levels of toxicant concentration including the control

ln = loge

i = 1, 2, ..., p where p is the number of concentrations

ni = the number of replicates for concentration i.

S ̄2 '

('

P

i'1

ViS 2

i )

'

P

i'1

Vi

C ' 1%[3(p&1)]&1 ['

P

i'1

1

Vi

&('

P

i'1

Vi)

&1

]

3.4 Since B is approximately distributed as chi-square with p - 1 degrees of freedom when the variances are equal,

the appropriate critical value is obtained from a table of the chi-square distribution for p - 1 degrees of freedom and

a significance level of 0.01. If B is less than the critical value then the variances are assumed to be equal.

3.5 For the data in this example, Vi

 = 3, p = 5, = 0.0027, and C = 1.133. The calculated B value is: S ̄ 2

B '

(15)[ln(0.0027)]&3'

P

i'1

ln(S 2

i )

1.133

' 15(&5.9145)&3(&32.4771)

1.133

 = 7.691 

3.6 Since B is approximately distributed as chi-square with p - 1 degrees of freedom when the variances are equal,

the appropriate critical value for the test is 13.277 for a significance level of 0.01. Since B = 7.691 is less than the

critical value of 13.277, conclude that the variances are not different.

4. TRANSFORMATIONS OF THE DATA 

4.1 When the assumptions of normality and/or homogeneity of variance are not met, transformations of the data

may remedy the problem, so that the data can be analyzed by parametric procedures, rather than by nonparametric

technique such as Steel's Many-one Rank Test or Wilcoxon's Rank Sum Test. Examples of transformations include

log, square root, arc sine square root, and reciprocals. After the data have been transformed, Shapiro-Wilk's and

Bartlett's tests should be performed on the transformed observations to determine whether the assumptions of

normality and/or homogeneity of variance are met.

4.2 ARC SINE SQUARE ROOT TRANSFORMATION (USEPA, 1993)

4.2.1 For data consisting of proportions from a binomial (response/no response; live/dead) response variable, the

variance within the ith treatment is proportional to Pi

 (1 - Pi), where Pi is the expected proportion for the treatment. 

This clearly violates the homogeneity of variance assumption required by parametric procedures such as Dunnett's

Procedure or the t test with Bonferroni's adjustment, since the existence of a treatment effect implies different values

of Pi

 for different treatments, i. Also, when the observed proportions are based on small samples, or when Pi is
267

close to zero or one, the normality assumption may be invalid. The arc sine square root (arc sine ) transformation P

is commonly used for such data to stabilize the variance and satisfy the normality requirement.

4.2.2 Arc sine transformation consists of determining the angle (in radians) represented by a sine value. In the

case of arc sine square root transformation of mortality data, the proportion of dead (or affected) organisms is taken

as the sine value, the square root of the sine value is calculated, and the angle (in radians) for the square root of the

sine value is determined. Whenever the proportion dead is 0 or 1, a special modification of the arc sine square root

transformation must be used (Bartlett, 1937). An explanation of the arc sine square root transformation and the

modification is provided below.

4.2.3 Calculate the response proportion (RP) at each effluent concentration, where:

 RP = (number of surviving or "unaffected" organisms)/(number exposed)

 Example: If 12 of 20 animals in a given treatment replicate survive:

 RP = 12/20 

= 0.60

4.2.4 Transform each RP to its arc sine square root, as follows: 

4.2.4.1 For RPs greater than zero or less than one: 

 Angle (radians) = arc sine RP

 Example: If RP = 0.60: 

 Angle = arc sine 0.60

= arc sine 0.7746

= 0.8861 radians 

4.2.4.2 Modification of the arc sine square root when RP = 0: 

 Angle (in radians) = arc sine 1/4 N

 Where: N = Number of animals/treatment replicate
268

 Example: If 20 animals are used: 

 Angle = arc sine 1/80

= arc sine 0.1118 

= 0.1120 radians 

4.2.4.3 Modification of the arc sine square root when RP = 1.0:

 Angle = 1.5708 radians - (radians for RP = 0) 

 Example: Using above value: 

 Angle = 1.5708 - 0.1120 

 = 1.4588 radians
269

TABLE C.1. FATHEAD MINNOW, PIMEPHALES PROMELAS, LARVAL GROWTH DATA

(WEIGHT IN MG) USED FOR DUNNETT'S PROCEDURE

NaPCP Concentration (μg/L)

Replicate Control 32 64 128 256 

A 0.711 0.517 0.602 0.566 0.455 

B 0.662 0.501 0.669 0.612 0.502 

C 0.646 0.723 0.694 0.410 0.606 

D 0.690 0.560 0.676 0.672 0.254 

Mean( ) Y ̄ 0.677 0.575 0.660 0.565 0.454 i

Total(Ti) 2.709 2.301 2.641 2.260 1.817 

APPENDIX C

DUNNETT'S PROCEDURE

1. MANUAL CALCULATIONS

1.1 Dunnett's Procedure (Dunnett, 1955; Dunnett, 1964) is used to compare each concentration mean with the

control mean to decide if any of the concentrations differ from the control. This test has an overall error rate of

alpha, which accounts for the multiple comparisons with the control. It is based on the assumptions that the

observations are independent and normally distributed and that the variance of the observations is homogeneous

across all concentrations and control (see Appendix B for a discussion on validating the assumptions). Dunnett's

Procedure uses a pooled estimate of the variance, which is equal to the error value calculated in an analysis of

variance. Dunnett's Procedure can only be used when the same number of replicate test vessels have been used at

each concentration and the control. When this condition is not met, a t test with Bonferroni's adjustment is used

(see Appendix D).

1.2 The data used in this example are growth data from a Fathead Minnow Larval Survival and Growth Test, and

are the same data used in Appendices B and D. These data are listed in Table C.1.

1.3 One way to obtain an estimate of the pooled variance is to construct an ANOVA table including all sums of

squares, using the following formulas:

Where: p = number of effluent concentrations including:

Total Sum of Squares SST ' '

ij

Yij

2

&G 2

/N

Between Sum of Squares SSB ' '

i

Ti

2

/ni

&G 2

/N
270

SST ' '

ij

Yij

2

&G 2

/N

SSB ' '

i

Ti

2

/ni&G 2/N

SSW ' SST&SSB

SSW ' SST&SSB Within Sum of Squares

G = the grand total of all sample observations; G ' '

P

i'1

Ti

Ti = the total of the replicate measurements for concentration i

N = the total sample size; N ' '

i

ni

ni = the number of replicates for concentration i 

 

Yij = the jth observation for concentration i 

1.4 For the data in this example: 

 n1 = n2 = n 3 = n 4 = n 5 = 4

 N = 20

 T1 = Y11 + Y12 + Y 13 + Y 14 = 2.709

 T2 = Y21 + Y22 + Y 23 + Y 24 = 2.301

 T3 = Y31 + Y32 + Y 33 + Y 34 = 2.641

 T4 = Y41 + Y42 + Y 43 + Y 44 = 2.260

 T5 = Y51 + Y52 + Y 53 + Y 54 = 1.817

 G = T1 + T2 + T 3 + T 4 + T 5 = 11.728 

 = 7.146 - (11.728)2

/20 

 = 0.2687

= 1⁄4 (28.017 - 11.728)2

/20 

= 0.1270

= 0.2687 - 0.1270 

= 0.1417
271

 TABLE C.2. ANOVA TABLE FOR DUNNETT'S PROCEDURE

Source df Sum of Mean Square (MS)

Squares (SS) (SS/df)

 

Between p - 1 SSB SB

2

 = SSB/(p-1)

Within N - p SSW SW

2 = SSW/(N-p)

Total N - 1 SST

 TABLE C.3. COMPLETED ANOVA TABLE FOR DUNNETT'S PROCEDURE

Source df SS Mean Square

Between 5 - 1 = 4 0.1270 0.0318

Within 20 - 5 = 15 0.1417 0.0094

Total 19 0.2687

t

i ' (Y ̄

1&Y ̄

i

)

Sw (1/n1)%(1/ni

)

1.5 Summarize these data in the ANOVA table (Table C.2).

1.6 Summarize data for ANOVA (Table C.3).

1.7 To perform the individual comparisons, calculate the t statistic for each concentration and control combination,

as follows: 

Where: &Yi

 = mean for concentration i

 &Y1 = mean for the control

 Sw = square root of the within mean square 

 n1 = number of replicates in the control

ni

 = number of replicates for concentration i. 
272

TABLE C.4. CALCULATED T VALUES

NaPCP 

Concentration i ti

 

(μg/L) 

32 2 1.487 

64 3 0.248 

128 4 1.633 

256 5 3.251 

1.8 Table C.4 includes the calculated t values for each concentration and control combination.

1.9 Since the purpose of the test is only to detect a decrease in growth from the control, a one-sided test is

appropriate. The critical value for the one-sided comparison (2.36), with an overall alpha level of 0.05, 15 degrees

of freedom and four concentrations excluding the control is read from the table of Dunnett's "T" values (Table C.5;

this table assumes an equal number of replicates in all treatment concentrations and the control). The mean weight

for concentration i is considered significantly less than the mean weight for the control if ti

 is greater than the critical

value. Since T5 is greater than 2.36, the 256 μg/L concentration has significantly lower growth than the control. 

Hence the NOEC and LOEC for growth are 128 μg/L and 256 μg/L, respectively.
273

TABLE C.5. DUNNETT'S "T" VALUES (Miller, 1981)

(One-tailed)dαk

v 

k α = .05 α = 0.1

1 2 3 4 5 6 7 8 9 1 2 3 45 6 7 8 9

5 2.02 2.44 2.58 2.85 2.98 3.08 3.16 3.24 3.30 3.37 3.90 4.21 4.43 4.50 4.73 4.85 4.94 5.036 1.94 2.34 2.56 2.71 2.83 2.92 3.00 3.07 3.12 3.14 3.61 4.88 4.07 4.21 4.33 4.43 4.51 4.397 1.89 2.27 2.48 2.62 2.73 2.82 2.89 2.95 3.01 3.00 3.42 3.56 3.83 3.96 4.07 4.15 4.23 4.308 1.86 2.22 2.42 2.55 2.56 2.74 2.81 2.87 2.92 2.90 3.20 3.51 3.67 3.79 3.18 3.96 4.03 4.099 1.83 2.18 2.37 2.50 2.60 2.68 2.75 2.81 2.86 2.82 3.19 3.40 3.55 3.86 3.75 3.82 3.89 3.9410 1.81 2.15 2.34 2.47 2.56 2.64 2.70 2.76 2.81 2.76 3.11 3.31 3.45 3.56 3.64 3.71 3.78 3.8311 1.80 2.13 2.31 2.44 2.53 2.60 2.67 2.72 2.77 2.72 3.06 3.25 3.38 3.46 3.56 3.63 3.69 3.7412 1.78 2.11 2.29 2.41 2.50 2.58 2.64 2.59 2.74 2.68 3.01 3.19 3.32 3.42 3.50 3.56 3.62 3.6713 1.77 2.09 2.27 2.39 2.48 2.55 2.61 2.68 2.71 2.65 2.97 3.15 3.27 3.37 3.44 3.91 3.56 3.6114 1.76 2.08 2.25 2.37 2.46 2.53 2.59 2.64 2.69 2.62 2.94 3.11 3.23 3.32 3.40 3.46 3.51 3.5615 1.75 2.07 2.24 2.36 2.44 2.51 2.57 2.62 2.67 2.60 2.91 3.08 3.20 3.29 3.36 3.42 3.47 3.5216 1.75 2.06 2.23 2.34 2.43 2.50 2.56 2.61 2.65 2.58 2.38 3.05 3.17 3.28 3.33 3.39 3.44 3.4817 1.74 2.05 2.22 2.33 2.42 2.49 2.54 2.59 2.64 2.57 2.86 3.03 3.14 3.23 3.30 3.36 3.41 3.4518 1.73 2.04 2.21 2.32 2.41 2.48 2.53 2.58 2.62 2.55 2.84 3.01 3.12 3.21 3.27 3.33 3.38 3.4019 1.73 2.03 2.20 2.31 2.40 2.47 2.52 2.57 2.61 2.54 2.83 2.99 3.10 3.18 3.25 3.31 3.36 3.4020 1.72 2.03 2.19 2.30 2.30 2.46 2.51 2.56 2.60 2.53 2.81 2.97 3.08 3.17 3.23 3.29 3.34 3.4024 1.71 2.01 3.17 2.28 2.36 2.43 2.48 2.53 2.57 2.40 2.77 2.92 3.03 3.11 3.17 3.22 3.27 3.3130 1.70 1.99 2.15 2.25 2.33 2.40 2.45 2.50 2.54 2.46 2.72 2.87 2.97 3.05 3.11 3.16 3.21 3.2440 1.68 1.97 2.13 2.23 2.31 2.37 2.42 2.47 2.51 2.42 2.68 2.32 2.92 2.99 3.06 3.10 3.14 3.1860 1.67 1.95 2.10 2.21 2.28 2.35 2.39 2.44 2.48 2.39 2.64 2.78 2.87 2.94 3.08 3.04 3.06 3.12120 1.86 1.93 2.08 2.18 2.26 2.32 2.37 2.41 2.45 2.36 2.60 2.73 2.82 2.90 2.94 2.90 3.03 3.06α 1.64 1.92 2.06 2.16 2.23 2.29 2.34 2.33 2.42 2.33 2.56 2.68 2.77 2.34 2.90 2.93 2.97 3.00
274

MSD ' d Sw (1/n1)%(1/n)

MSD ' 2.36(0.097)[3 (1/4)%(1/4)] ' 2.36(0.097)( 2/4)

Percent Reduction ' MSDu

Controlu

x 100

1.10 To quantify the sensitivity of the test, the minimum significant difference (MSD) may be calculated. The formula is

as follows: 

Where: d = critical value for the Dunnett's Procedure 

Sw = the square root of the within mean square 

n = the number of replicates at each concentration, assuming an equal number of replicates at all treatment

concentrations

n1 = number of replicates in the control 

For example:

 = 2.36 (0.097)(0.707) 

 = 0.162

1.11 For this set of data, the minimum difference between the control mean and a concentration mean that can be detected

as statistically significant is 0.087 mg. This represents a decrease in growth of 24% from the control.

1.11.1 If the data have not been transformed, the MSD (and the percent decrease from the control mean that it represents)

can be reported as is. 

1.11.2 In the case where the data have been transformed, the MSD would be in transformed units. In this case carry out

the following conversion to determine the MSD in untransformed units. 

1.11.2.1 Subtract the MSD from the transformed control mean. Call this difference D. Next, obtain untransformed values

for the control mean and the difference, D. 

MSDu = controlu - Du

Where: MSDu = the minimum significant difference for untransformed data

Controlu = the untransformed control mean 

Du = the untransformed difference

1.11.2.2 Calculate the percent reduction from the control that MSDu represents as: 

 
275

1.11.3 An example of a conversion of the MSD to untransformed units, when the arc sine square root transformation was

used on the data, follows: 

 Step 1. Subtract the MSD from the transformed control mean. As an example, assume the data in Table C.1

were transformed by the arc sine square root transformation. Thus: 

 0.677 - 0.162 = 0.515

 Step 2. Obtain untransformed values for the control mean (0.677) and the difference (0.515) obtained in Step

1 above. 

 [ Sine (0.677)]2

 = 0.392

 [ Sine (0.515)]2

 = 0.243

 Step 3. The untransformed MSD (MSDu) is determined by subtracting the untransformed values obtained in

Step 2. 

MSDu = 0.392 - 0.243 = 0.149 

In this case, the MSD would represent a 38.0% decrease in survival from the control [(0.149/0.392)(100)]. 

2. COMPUTER CALCULATIONS

2.1 This computer program incorporates two analyses: an analysis of variance (ANOVA), and a multiple comparison of

treatment means with the control mean (Dunnett's Procedure). The ANOVA is used to obtain the error value. Dunnett's

Procedure indicates which toxicant concentration means (if any) are statistically different from the control mean at the 5%

level of significance. The program also provides the minimum difference between the control and treatment means that

could be detected as statistically significant, and tests the validity of the homogeneity of variance assumption by Bartlett's

Test. The multiple comparison is performed based on procedures described by Dunnett (1955).

2.2 The source code for the Dunnett's program is structured into a series of subroutines, controlled by a driver routine. 

Each subroutine has a specific function in the Dunnett's Procedure, such as data input, transforming the data, testing for

equality of variances, computing p values, and calculating the one-way analysis of variance. 

2.3 The program compares up to seven toxicant concentrations against the control, and can accommodate up to 50

replicates per concentration.

2.4 If the number of replicates at each toxicant concentration and control are not equal, a t test with Bonferroni's

adjustment is performed instead of Dunnett's Procedure (see Appendix D).

2.5 The program was written in IBM-PC FORTRAN by Computer Sciences Corporation, 26 W. Martin Luther King

Drive, Cincinnati, OH 45268. A compiled executable version of the program can be obtained from EMSL-Cincinnati by

sending a written request to EMSL at 3411 Church Street, Cincinnati, OH 45244.
276

2.6 DATA INPUT AND OUTPUT

2.6.1 Reproduction data from a daphnid, Ceriodaphnia dubia, survival and reproduction test (Table C.6) are used to

illustrate the data input and output for this program.

TABLE C.6. SAMPLE DATA FOR DUNNETT'S PROGRAM CERIODAPHNIA DUBIA

REPRODUCTION DATA

Effluent Concentration (%)

Replicate Control 1.56 3.12 6.25 12.5

1 27 32 39 27 10 

2 30 35 30 34 13 

3 29 32 33 36 7

4 31 26 33 34 7

5 16 18 36 31 7

6 15 29 33 27 10 

7 18 27 33 33 10 

8 17 16 27 31 16 

9 14 35 38 33 12 

10 27 13 44 31 2 

2.6.2 Data Input

2.6.2.1 When the program is entered, the user is asked to select the type of data to be entered: 

1. Response proportions, like survival or fertilization proportions.

2. Counts and measurements, like offspring counts, cystocarp counts or weights.

2.6.2.2 After the type of data is chosen, the user has the following options: 

1. Create a data file

2. Edit a data file

3. Perform analysis on existing data set

4. Stop

2.6.2.3 When Option 1 (Create a data file) is selected for counts and measurements, the program prompts the user for the

following information:

1. Number of concentrations, including control 

2. For each concentration: 

- number of observations 

- data for each observation 

2.6.2.4 After the data have been entered, the user may save the file on a disk, and the program returns to the menu (see

below).

2.6.2.5 Sample data input is shown in Figure C.1.
277

EMSL Cincinnati Dunnett Software

Version 1.5

1) Create a data file

2) Edit a data file

3) Perform ANOVA on existing data

4) Stop

Your choice ? 1

Number of groups, including control ? 5

Number of observations for group 1 ? 10

Enter the data for group 1 one observation at a time.

NO. 1? 27

NO. 2? 30

NO. 3? 29

NO. 4? 31

NO. 5? 16

NO. 6? 15

NO. 7? 18

NO. 8? 17

NO. 9? 14

NO. 10? 27

Number of observations for group 2 ? 10

Do you wish to save the data on disk ?y

Disk file for output ? cerio

 

Figure C.1. Sample Data Input for Dunnett's Program for Reproduction Data from Table C.6.
278

2.6.3 Program Output

2.6.3.1 When Option 3 (Perform analysis on existing data set) is selected from the menu, the user is asked to select the

transformation desired, and indicate whether they expect the means of the test groups to be less or greater than the mean for

the control group (see Figure C.2).

2.6.3.2 Summary statistics (Figure C.3) for the raw and transformed data, if applicable, the ANOVA table, results of

Bartlett's Test, the results of the multiple comparison procedure and the minimum detectable difference are included in the

program output.
279

EMSL Cincinnati Dunnett Software

Version 1.5

1) Create a data file

2) Edit a data file

3) Perform analysis on existing data set

4) Stop

Your choice ? 3

File name ? cerio

Available Transformations

1) no transform

2) square root

3) log10

Your choice ? 1

Dunnett's test as implemented in this program is

a one-sided test. You must specify the direction

the test is to be run; that is, do you expect the

means for the test groups to be less than or

greater than the mean for the control group mean.

Direction for Dunnett's test : L=less than, G=greater than ? L

Figure C.2. Example of Choosing Option 3 from the Menu of the Dunnett Program. 
280

Ceriodaphnia Reproduction Data from Table C.6

Summary Statistics and ANOVA

 Transformation = None

 Group n Mean s.d. CV%

 

1 = control 10 22.4000 6.9314 30.9

 2 10 26.3000 8.0007 30.4

 3 10 34.6000 4.8351 14.0

 4 10 31.7000 2.9458 9.3

 5* 10 9.4000 3.8930 41.4

 

*) the mean for this group is significantly less than the control 

 mean at alpha = 0.05 (1-sided) by Dunnett's test

Minimum detectable difference for Dunnett's test = -5.628560

This difference corresponds to -25.13 percent of control

Between concentrations

Sum of squares = 3887.880000 with 4 degrees of freedom.

Error mean square = 31.853333 with 45 degrees of freedom.

Bartlett's test p-value for equality of variances = .029

Do you wish to restart the program ?

Figure C.3. Example of Program Output for the Dunnett's Program Using the Reproduction Data from Table C.6. 

 
281

APPENDIX D

T TEST WITH BONFERRONI'S ADJUSTMENT

1. The t test with Bonferroni's adjustment is used as an alternative to Dunnett's Procedure when the number of replicates is

not the same for all concentrations. This test sets an upper bound of alpha on the overall error rate, in contrast to Dunnett's

Procedure, for which the overall error rate is fixed at alpha. Thus, Dunnett's Procedure is a more powerful test.

2. The t test with Bonferroni's adjustment is based on the same assumptions of normality and homogeneity of variance as

Dunnett's Procedure (see Appendix B for testing these assumptions), and, like Dunnett's Procedure, uses a pooled estimate

of the variance, which is equal to the error value calculated in an analysis of variance.

3. An example of the use of the t test with Bonferroni's adjustment is provided below. The data used in the example are

the same as in Appendix C, except that the third replicate from the 256 μg/L concentration is presumed to have been lost. 

Thus, Dunnett's Procedure cannot be used. The weight data are presented in Table D.1.

 TABLE D.1. FATHEAD MINNOW, PIMEPHALES PROMELAS, LARVAL GROWTH DATA

(WEIGHT IN MG) USED FOR THE T-TEST WITH BONFERRONI'S ADJUSTMENT

NaPCP Concentration (μg/L)

Replicate Control 32 64 128 256 

A 0.711 0.517 0.602 0.566 0.455 

B 0.662 0.501 0.669 0.612 0.502 

C 0.646 0.723 0.694 0.410 (LOST) 

D 0.690 0.560 0.676 0.672 0.254 

Mean( ) Y ̄ 0.677 0.575 0.660 0.565 0.404 

Total(Ti) 2.709 2.301 2.641 2.260 1.211 

3.1 One way to obtain an estimate of the pooled variance is to construct an ANOVA table including all sums of squares,

using the following formulas:

Where: p = number of effluent concentrations including the control

N = the total sample size; N ' '

i

ni

ni = the number of replicates for concentration i

 Total Sum of Squares SST ' '

ij

Yij

2

&G 2

/N
282

SSB ' '

i

Ti

2

/ni&G 2/N

SST ' '

ij

Yij

2

&G 2

/N

SSW ' SST&SSB

 Between Sum of Squares SSB ' '

i

Ti

2

/ni&G 2/N

 Within Sum of Squares SSW ' SST&SSB

Where: G = The grand total of all sample observations; G ' '

P

i'1

Ti

 

Ti = The total of the replicate measurements for concentration i 

 

 Yij = The jth observation for concentration i 

3.2 For the data in this example:

n1 = n2 = n 3 = n 4 = 4

T1 = Y11 + Y12 + Y 13 + Y 14 = 2.709

T2 = Y21 + Y22 + Y 23 + Y 24 = 2.301 

T3 = Y31 + Y32 + Y 33 + Y 34 = 2.641 

T4 = Y41 + Y42 + Y 43 + Y 44 = 2.260

T5 = Y51 + Y52 + Y 53 + Y 54 = 1.211

G = T1 + T2 + T3 + T 4 + T 5 = 11.122

 

= 6.668 - (11.122)2

 /19 

= 0.158 

= 6.779 - (11.122)2

/19 

= 0.269
283

TABLE D.3. COMPLETED ANOVA TABLE FOR THE T-TEST WITH BONFERRONI'S ADJUSTMENT

Source df SS Mean Square

Between 5 - 1 = 4 0.158 0.0395 

Within 19 - 5 = 14 0.111 0.0029 

Total 18 0.269

t

i ' (Y ̄

1&Y ̄

i

)

Sw (1/n1)%(1/ni

)

= 0.269 - 0.158 

= 0.111 

3.3 Summarize these data in the ANOVA table (Table D.2): 

 TABLE D.2. ANOVA TABLE FOR BONFERRONI'S ADJUSTMENT

Source df Sum of Mean Square (MS)

Squares (SS) (SS/df)

Between p - 1 SSB SB

2 = SSB/(p-1)

Within N - p SSW SW

2 = SSW/(N-p)

Total N - 1 SST

3.4 Summarize these data in the ANOVA table (Table D.3):

3.5 To perform the individual comparisons, calculate the t statistic for each concentration and control combination, as

follows:

Where: = mean for each concentration Y ̄ i

Y ̄ = mean for the control 1

Sw = square root of the within mean square 
284

n1 = number of replicates in the control. 

ni = number of replicates for concentration i. 

3.6 Table D.4 includes the calculated t values for each concentration and control combination.

TABLE D.4. CALCULATED T VALUES

NaPCP 

Concentration i ti

(μg/L) 

32 2 1.623

64 3 0.220 

128 4 1.782 

256 5 4.022 

3.7 Since the purpose of the test is only to detect a decrease in growth from the control, a one-sided test is appropriate. 

The critical value for the one-sided comparison (2.510), with an overall alpha level of 0.05, fourteen degrees of freedom

and four concentrations excluding the control, was obtained from Table D.5. The mean weight for concentration "i" is

considered significantly less than the mean weight for the control if ti

 is greater than the critical value. Since t5 is greater

than 2.510, the 256 μg/L concentration has significantly lower growth than the control. Hence the NOEC and LOEC for

growth are 128 μg/L and 256 μg/L, respectively.
285

 TABLE D.5. CRITICAL VALUES FOR "T" FOR THE T TEST WITH BONFERRONI'S ADJUSTMENT 

P = 0.05 CRITICAL LEVEL, ONE TAILED 

 df K = 1 K = 2 K = 3 K = 4 K = 5 K = 6 K = 7 K = 8 K = 9 K = 10

 1 6.314 12.707 19.002 25.452 31.821 38.189 44.556 50.924 57.290 63.657

 2 2.920 4.303 5.340 6.206 6.965 7.649 8.277 8.861 9.408 9.925 3 2.354 3.183 3.741 4.177 4.541 4.857 5.138 5.392 5.626 5.841 4 2.132 2.777 3.187 3.496 3.747 3.961 4.148 4.315 4.466 4.605 5 2.016 2.571 2.912 3.164 3.365 3.535 3.681 3.811 3.927 4.033 6 1.944 2.447 2.750 2.969 3.143 3.288 3.412 3.522 3.619 3.708 7 1.895 2.365 2.642 2.842 2.998 3.128 3.239 3.336 3.422 3.500 8 1.860 2.307 2.567 2.752 2.897 3.016 3.118 3.206 3.285 3.356 9 1.834 2.263 2.510 2.686 2.822 2.934 3.029 3.111 3.185 3.250 10 1.813 2.229 2.406 2.634 2.764 2.871 2.961 3.039 3.108 3.170 11 1.796 2.301 2.432 2.594 2.719 2.821 2.907 2.981 3.047 3.106 12 1.783 2.179 2.404 2.561 2.681 2.730 2.863 2.935 2.998 3.055 13 1.771 2.161 2.380 2.533 2.651 2.746 2.827 2.897 2.950 3.013 14 1.762 2.145 2.360 2.510 2.625 2.718 2.797 2.864 2.924 2.977 15 1.754 2.132 2.343 2.490 2.603 2.694 2.771 2.837 2.895 2.947 16 1.746 2.120 2.329 2.473 2.584 2.674 2.749 2.814 2.871 2.921 17 1.740 2.110 2.316 2.459 2.567 2.655 2.729 2.793 2.849 2.899 18 1.735 2.101 2.305 2.446 2.553 2.640 2.712 2.775 2.830 2.879 19 1.730 2.094 2.295 2.434 2.540 2.626 2.697 2.759 2.813 2.861 20 1.725 2.086 2.206 2.424 2.528 2.613 2.684 2.745 2.798 2.846 21 1.721 2.080 2.278 2.414 2.518 2.602 2.672 2.732 2.785 2.832 22 1.718 2.074 2.271 2.406 2.509 2.592 2.661 2.721 2.773 2.819 23 1.714 2.069 2.264 2.398 2.500 2.583 2.651 2.710 2.762 2.808 24 1.711 2.064 2.258 2.391 2.493 2.574 2.642 2.701 2.752 2.797 25 1.709 2.060 2.253 2.385 2.486 2.566 2.634 2.692 2.743 2.788 26 1.706 2.056 2.248 2.379 2.479 2.559 2.627 2.684 2.734 2.779 27 1.704 2.052 2.243 2.374 2.473 2.553 2.620 2.677 2.727 2.771 28 1.702 2.049 2.239 2.369 2.468 2.547 2.613 2.670 2.720 2.764
286

 TABLE D.5. CRITICAL VALUES FOR "T" FOR THE T TEST WITH BONFERRONI'S ADJUSTMENT

P = 0.05 CRITICAL LEVEL, ONE TAILED (CONTINUED)

df K = 1 K = 2 K = 3 K = 4 K = 5 K = 6 K = 7 K = 8 K = 9 K = 10 29 1.700 2.046 2.235 2.364 2.463 2.541 2.607 2.664 2.713 2.757 30 1.698 2.043 2.231 2.360 2.458 2.536 2.602 2.658 2.707 2.750 31 1.696 2.040 2.228 2.356 2.453 2.531 2.597 2.652 2.701 2.745 32 1.694 2.037 2.224 2.352 2.449 2.527 2.592 2.647 2.696 2.739 33 1.693 2.035 2.221 2.349 2.445 2.523 2.587 2.643 2.691 2.734 34 1.691 2.033 2.219 2.346 2.442 2.519 2.583 2.638 2.686 2.729 35 1.690 2.031 2.216 2.342 2.438 2.515 2.579 2.634 2.682 2.724 36 1.689 2.029 2.213 2.340 2.435 2.512 2.575 2.630 2.678 2.720 37 1.688 2.027 2.211 2.337 2.432 2.508 2.572 2.626 2.674 2.716 38 1.686 2.025 2.209 2.334 2.429 2.505 2.568 2.623 2.670 2.712 39 1.685 2.023 2.207 2.332 2.426 2.502 2.565 2.619 2.667 2.708 40 1.684 2.022 2.205 2.329 2.424 2.499 2.562 2.616 2.663 2.705 50 1.676 2.009 2.189 2.311 2.404 2.478 2.539 2.592 2.638 2.678 60 1.671 2.001 2.179 2.300 2.391 2.463 2.324 2.576 2.621 2.661 70 1.667 1.995 2.171 2.291 2.381 2.453 2.513 2.564 2.609 2.648 80 1.665 1.991 2.166 2.285 2.374 2.446 2.505 2.556 2.600 2.639 90 1.662 1.987 2.162 2.280 2.369 2.440 2.499 2.549 2.593 2.632 100 1.661 1.984 2.158 2.276 2.365 2.435 2.494 2.544 2.588 2.626 110 1.659 1.982 2.156 2.273 2.361 2.432 2.490 2.540 2.583 2.622 120 1.658 1.980 2.153 2.270 2.358 2.429 2.487 2.536 2.580 2.618Infinite 1.645 1.960 2.129 2.242 2.327 2.394 2.450 2.498 2.540 2.576 d.f. = Degrees of freedom for MSE (Mean Square Error) from ANOVA. K = Number of concentrations to be compared to the control.
287

TABLE E.1. EXAMPLE OF STEEL'S MANY-ONE RANK TEST: DATA FOR THE DAPHNID,

CERIODAPHNIA DUBIA, 7-DAY CHRONIC TEST

No.

Effluent Replicate Live

Concentration 1 2 3 4 5 6 7 8 9 10 Adults

Control 20 26 26 23 24 27 26 23 27 24 10

3% 13 15 14 13 23 26 0 25 26 27 9

6% 18 22 13 13 23 22 20 22 23 22 10

12% 14 22 20 23 20 23 25 24 25 21 10

25% 9 0 9 7 6 10 12 14 9 13 8

50% 0 0 0 0 0 0 0 0 0 0 0

APPENDIX E

STEEL'S MANY-ONE RANK TEST

1. Steel's Many-one Rank Test is a nonparametric test for comparing treatments with a control. This test is an alternative

to Dunnett's Procedure, and may be applied to data when the normality assumption has not been met. Steel's Test requires

equal variances across the treatments and the control, but it is thought to be fairly insensitive to deviations from this

condition (Steel, 1959). The tables for Steel's Test require an equal number of replicates at each concentration. If this is not

the case, use Wilcoxon's Rank Sum Test, with Bonferroni's adjustment (see Appendix F).

2. For an analysis using Steel's Test, for each control and concentration combination, combine the data and arrange the

observations in order of size from smallest to largest. Assign the ranks to the ordered observations (1 to the smallest, 2 to

the next smallest, etc.). If ties occur in the ranking, assign the average rank to the observation. (Extensive ties would

invalidate this procedure). The sum of the ranks within each concentration and within the control is then calculated. To

determine if the response in a concentration is significantly different from the response in the control, the minimum rank

sum for each concentration and control combination is compared to the significant values of rank sums given later in this

section. In this table, k equals the number of treatments excluding the control and n equals the number of replicates for

each concentration and the control.

3. An example of the use of this test is provided below. The test employs reproduction data from a Ceriodaphnia dubia

7-day, chronic test. The data are listed in Table E.1. Significant mortality was detected via Fisher's Exact Test in the 50%

effluent concentration. The data for this concentration is not included in the reproduction analysis.

4. For each control and concentration combination, combine the data and arrange the observations in order of size from

smallest to largest. Assign ranks (1, 2, 3,..., 16) to the ordered observations (1 to the smallest, 2 to the next smallest, etc.). 

If ties occur in the ranking, assign the average rank to each tied observation. 

5. An example of assigning ranks to the combined data for the control and 3% effluent concentration is given in Table E.2. 

This ranking procedure is repeated for each control and concentration combination. The complete set of rankings is listed

in Table E.3. The ranks are then summed for each effluent concentration, as shown in Table E.4.
288

TABLE E.2. EXAMPLE OF STEEL'S MANY-ONE RANK TEST: ASSIGNING 

RANKS TO THE CONTROL AND 3% EFFLUENT CONCENTRATION

Rank Number of Young Control or % Effluent

Produced

10 3

2.5 13 3

2.5 13 3

4 14 3

5 15 3

6 20 Control 

8 23 Control 

8 23 Control 

8 23 3 

10.5 24 Control 

10.5 24 Control 

12 25 3 

15 26 Control 

15 26 Control 

15 26 Control 

15 26 3 

15 26 3 

19 27 Control 

19 27 Control 

19 27 3 

TABLE E.3. TABLE OF RANKS

Replicate Control1 Effluent Concentration (%)

(Organism) 3 6 12 25

1 20 (6,4.5,3,11) 13 (2.5) 18 (3) 14 (1) 9 (5)

2 26 (15,17,17,17) 15 (5) 22 (7.5) 22 (6) 0 (1)

3 26 (15,17,17,17) 14 (4) 13 (1.5) 20 (3) 9 (5)

4 23 (8,11.5,8.5,12.5) 13 (2.5) 13 (1.5) 23 (8.5) 7 (3)

5 24 (10.5,14.5,12,14.5) 23 (8) 23 (11.5) 20 (3) 6 (2)

6 27 (19,19.5,19.5,19.5) 26 (15) 22 (7.5) 23 (8.5) 10 (7)

7 26 (15,17,17,17) 0 (1) 20 (4.5) 25 (14.5) 12 (8)

8 23 (8,11.5,8.5,12.5) 25 (12) 22 (7.5) 24 (12) 14 (10)

9 27 (19,19.5,19.5,19.5) 26 (15) 23 (11.5) 25 (14.5) 9 (5)

10 24 (10.5,14.5,12,14.5) 27 (19) 22 (7.5) 21 (5) 13 (9)

1

 Control ranks are given in the order of the concentration with which they were ranked.
289

 TABLE E.4. RANK SUMS 

 ________________________________________________

Effluent Rank Sum 

Concentration 

(%) 

 ________________________________________________

3 84 

 6 64 

12 76 

25 55 

 ________________________________________________

6. For this set of data, determine if the reproduction in any of the effluent concentrations is significantly lower than the

reproduction by the control organisms. If this occurs, the rank sum at that concentration would be significantly lower than

the rank sum of the control. Thus, compare the rank sums for the reproduction of each of the various effluent

concentrations with some "minimum" or critical rank sum, at or below which the reproduction would be considered to be

significantly lower than the control. At a probability level of 0.05, the critical rank in a test with four concentrations and ten

replicates is 76 (see Table E.5 , for R=4).

7. Comparing the rank sums in Table E.4 to the appropriate critical rank, the 6%, 12% and 25% effluent concentrations are

found to be significantly different from the control. Thus the NOEC and LOEC for reproduction are 3% and 6%,

respectively.
290

TABLE E.5. SIGNIFICANT VALUES OF RANK SUMS: JOINT CONFIDENCE COEFFICIENTS OF

0.95 (UPPER) and 0.99 (LOWER) FOR ONE-SIDED ALTERNATIVES (Steel, 1959)

k = number of treatments (excluding control)

n 23 45 6 7 8 9

 

4 11 10 10 10 10 -- -- --

-- -- -- -- -- -- -- --

5 18 17 17 16 16 16 16 15

15 -- -- -- -- -- -- --

6 27 26 25 25 24 24 24 23

23 22 21 21 -- -- -- --

7 37 36 35 35 34 34 33 33

32 31 30 30 29 29 29 29

8 49 48 47 46 46 45 45 44

43 42 41 40 40 40 39 39

9 63 62 61 60 59 59 58 58

56 55 54 53 52 52 51 51

10 79 77 76 75 74 74 73 72

71 69 68 67 66 66 65 65

11 97 95 93 92 91 90 90 89

87 85 84 83 82 81 81 80

12 116 114 112 111 110 109 108 108

105 103 102 100 99 99 98 98

13 138 135 133 132 130 129 129 128

125 123 121 120 119 118 117 117

14 161 158 155 154 153 152 151 150

147 144 142 141 140 139 138 137

15 186 182 180 178 177 176 175 174

170 167 165 164 162 161 160 160

16 213 209 206 204 203 201 200 199

196 192 190 188 187 186 185 184

17 241 237 234 232 231 229 228 227

223 219 217 215 213 212 211 210

18 272 267 264 262 260 259 257 256

252 248 245 243 241 240 239 238

19 304 299 296 294 292 290 288 287

282 278 275 273 272 270 268 267

20 339 333 330 327 325 323 322 320

315 310 307 305 303 301 300 299
291

APPENDIX F

WILCOXON RANK SUM TEST

1. Wilcoxon's Rank Sum Test is a nonparametric test, to be used as an alternative to Steel's Many-one Rank Test when the

number of replicates are not the same at each concentration. A Bonferroni's adjustment of the pairwise error rate for

comparison of each concentration versus the control is used to set an upper bound of alpha on the overall error rate, in

contrast to Steel's Many-one Rank Test, for which the overall error rate is fixed at alpha. Thus, Steel's Test is a more

powerful test.

2. An example of the use of the Wilcoxon Rank Sum Test is provided in Table F.1. The data used in the example are the

same as in Appendix E, except that two males are presumed to have occurred, one in the control and one in the 12%

effluent concentration. Thus, there is unequal replication for the reproduction analysis.

3. For each concentration and control combination, combine the data and arrange the values in order of size, from smallest

to largest. Assign ranks to the ordered observations (a rank of 1 to the smallest, 2 to the next smallest, etc.). If ties in rank

occur, assign the average rank to each tied observation. 

TABLE F.1. EXAMPLE OF WILCOXON'S RANK SUM TEST: DATA FOR THE DAPHNID,

CERIODAPHNIA DUBIA, 7-DAY CHRONIC TEST

No.

Effluent Replicate Live

Concentration 1 2 3 4 5 6 7 8 9 10 Adults

Cont M 26 26 23 24 27 26 23 27 24 10

3% 13 15 14 13 23 26 0 25 26 27 9

6% 18 22 13 13 23 22 20 22 23 22 10

12% 14 22 20 23 M 23 25 24 25 21 10

25% 9 0 9 7 6 10 12 14 9 13 8

50% 0 00 0 0 0 0 0 0 0 0

4. An example of assigning ranks to the combined data for the control and 3% effluent concentration is given in Table F.2. 

This ranking procedure is repeated for each of the three remaining control versus test concentration combinations. The

complete set of ranks is listed in Table F.3. The ranks are then summed for each effluent concentration, as shown in

Table F.4.

5. For this set of data, determine if the reproduction in any of the effluent concentrations is significantly lower than the

reproduction by the control organisms. If this occurs, the rank sum at that concentration would be significantly lower than

the rank sum for the control. Thus, compare the rank sums for the reproduction of each of the various effluent

concentrations with some "minimum" or critical rank sum, at or below which the reproduction would be considered to be

significantly lower than the control. At a probability level of 0.05, the critical rank in a test with four concentrations and

nine replicates in the control is 72 for those concentrations with ten replicates, and 60 for those concentrations with nine

replicates (see Table F.5, for K = 4).

6. Comparing the rank sums in Table F.4 to the appropriate critical rank, the 6%, 12% and 25% effluent concentrations are

found to be significantly different from the control. Thus, the NOEC and LOEC for reproduction are 3% and 6%,

respectively.
292

TABLE F.2. EXAMPLE OF WILCOXON'S RANK SUM TEST: ASSIGNING 

RANKS TO THE CONTROL AND EFFLUENT CONCENTRATIONS 

Rank Number of Young Control or % Effluent 

Produced 

10 3

2.5 13 3

2.5 13 3

4 14 3

5 15 3

7 23 Control 

7 23 Control 

7 23 3

9.5 24 Control

9.5 24 Control

11 25 3

14 26 Control

14 26 Control

14 26 Control

14 26 3

14 26 3

18 27 Control

18 27 Control

18 27 3
293

TABLE F.3. TABLE OF RANKS

Replicate Control1 Effluent Concentration (%)

(Organism) 3 6 12 25 

1 M 13 (2.5) 18 (3) 14 (1) 9 (5)

2 26 (14,16,15,16) 15 (5) 22 (6.5) 22 (4) 0 (1)

3 26 (14,16,15,16) 14 (4) 13 (1.5) 20 (2) 9 (5)

4 23 (7,10.5,6.5,11.5) 13 (2.5) 13 (1.5) 23 (6.5) 7 (3)

5 24 (9.5,13.5,10,13.5) 23 (7) 23 (10.5) M 6 (2)

6 27 (18,18.5,17.5,18.5) 26 (14) 22 (6.5) 23 (6.5) 10 (7)

7 26 (14,16,15,16) 0 (1) 20 (4) 25 (12.5) 12 (8)

8 23 (7,10.5,6.5,11.5) 25 (11) 22 (6.5) 24 (10) 14 (10)

9 27 (18,18.5,17.5,18.5) 26 (14) 23 (10.5) 25 (12.5) 9 (5)

10 24 (9.5,13.5,10,13.5) 27 (18) 22 (6.5) 21 (3) 13 (9)

1

 Control ranks are given in the order of the concentration with which they were ranked.

TABLE F.4. RANK SUMS 

Effluent Rank Sum No. of Critical 

Concentration Replicates Rank Sum 

3 79 10 72 

6 57 10 72 

12 58 9 60 

25 55 10 72 
294

TABLE F.5. CRITICAL VALUES FOR WILCOXON'S RANK SUM TEST WITH BONFERRONI'S

ADJUSTMENT OF ERROR RATE FOR COMPARISON OF "K" TREATMENTS VERSUS

A CONTROL FIVE PERCENT CRITICAL LEVEL (ONE-SIDED ALTERNATIVE:

TREATMENT CONTROL)

K No. Replicates No. of Replicates Per Effluent Concentration

in Control 

3 4 5 6 7 8 9 10 

1 3 6 10 16 23 30 39 49 59

4 6 11 17 24 32 41 51 62

5 7 12 19 26 34 44 54 66

6 8 13 20 28 36 46 57 69

7 8 14 21 29 39 49 60 72

8 9 15 23 31 41 51 63 72

9 10 16 24 33 43 54 66 79

10 10 17 26 35 45 56 69 82

2 3 -- -- 15 22 29 38 47 58

4 -- 10 16 23 31 40 49 60

5 6 11 17 24 33 42 52 63

6 7 12 18 26 34 44 55 66

7 7 13 20 27 36 46 57 69

8 8 14 21 29 38 49 60 72

9 8 14 22 31 40 51 62 75

10 9 15 23 32 42 53 65 78

3 3 -- -- -- 21 29 37 46 57

4 -- 10 16 22 30 39 48 59

5 -- 11 17 24 32 41 51 62

6 6 11 18 25 33 43 53 65

7 7 12 19 26 35 45 56 68

8 7 13 20 28 37 47 58 70

9 7 13 21 29 39 49 61 73

10 8 14 22 31 41 51 63 76
295

TABLE F.5. CRITICAL VALUES FOR WILCOXON'S RANK SUM TEST WITH

BONFERRONI'S ADJUSTMENT OF ERROR RATE FOR COMPARISON OF "K"

TREATMENTS VERSUS A CONTROL FIVE PERCENT CRITICAL LEVEL

(ONE-SIDED ALTERNATIVE: TREATMENT CONTROL) (CONTINUED)

K No. Replicates No. of Replicates Per Effluent Concentration

in Control 

3 4 5 6 7 8 9 10

4 3 -- -- -- 21 28 37 46 56

4 -- -- 15 22 30 38 48 59

5 -- 10 16 23 31 40 50 61

6 6 11 17 24 33 42 52 64

7 6 12 18 26 34 44 55 67

8 7 12 19 27 36 46 57 69

9 7 13 20 28 38 48 60 72

10 7 14 21 30 40 50 62 75

5 3 -- -- -- -- 28 36 46 56

4 -- -- 15 22 29 38 48 58

5 -- 10 16 23 31 40 50 61

6 -- 11 17 24 32 42 52 63

7 6 11 18 25 34 43 54 66

8 6 12 19 27 35 45 56 68

9 7 13 20 28 37 47 59 71

10 7 13 21 29 39 49 61 74

6 3 -- -- -- -- 28 36 45 56

4 -- -- 15 21 29 38 47 58

5 -- 10 16 22 30 39 49 60

6 -- 11 16 24 32 41 51 63

7 6 11 17 25 33 43 54 65

8 6 12 18 26 35 45 56 68

9 6 12 19 27 37 47 58 70

10 7 13 20 29 38 49 60 73

7 3 -- -- -- -- -- 36 45 56

4 -- -- -- 21 29 37 47 58

5 -- -- 15 22 30 39 49 60

6 -- 10 16 23 32 41 51 62

7 -- 11 17 25 33 43 53 65

8 6 11 18 26 35 44 55 67

9 6 12 19 27 36 46 58 70

10 7 13 20 28 38 48 60 72
296

TABLE F.5. CRITICAL VALUES FOR WILCOXON'S RANK SUM TEST WITH

BONFERRONI'S ADJUSTMENT OF ERROR RATE FOR COMPARISON OF

"K" TREATMENTS VERSUS A CONTROL FIVE PERCENT CRITICAL

LEVEL (ONE-SIDED ALTERNATIVE: TREATMENT CONTROL)

(CONTINUED)

K No. Replicates No. of Replicate Per Effluent Concentration

in Control 

3 4 5 6 7 8 9 10 

8 3 -- -- -- -- -- 36 45 55 

4 -- -- -- 21 29 37 47 57 

5 -- -- 15 22 30 39 49 59 

6 -- 10 16 23 31 40 51 62 

7 -- 11 17 24 33 42 53 64 

8 6 11 18 25 34 44 55 67 

9 6 12 19 27 36 46 57 69 

10 6 12 19 28 37 48 59 72 

9 3 -- -- -- -- -- -- 45 55 

4 -- -- -- 21 28 37 46 57 

5 -- -- 15 22 30 39 48 59 

6 -- 10 16 23 31 40 50 62 

7 -- 10 17 24 33 42 52 64 

8 -- 11 18 25 34 44 55 66 

9 6 11 18 26 35 46 57 69 

10 6 12 19 28 37 47 59 71 

10 3 -- -- -- -- -- -- 45 55 

4 -- -- -- 21 28 37 46 57 

5 -- -- 15 22 29 38 48 59 

6 -- 10 16 23 31 40 50 61 

7 -- 10 16 24 32 42 52 64 

8 -- 11 17 25 34 43 54 66 

9 6 11 18 26 35 45 56 68 

10 6 12 19 27 37 47 58 71 
297

APPENDIX G

FISHER'S EXACT TEST

1. Fisher's Exact Test (Finney, 1948; Pearson and Hartley, 1962) is a statistical method based on the

hypergeometric probability distribution that can be used to test if the proportion of successes is the same in two

Bernoulli (binomial) populations. When used with the Ceriodaphnia dubia data, it provides a conservative test of

the equality of any two survival proportions assuming only the independence of responses from a Bernoulli

population. Additionally, since it is a conservative test, a pair-wise comparison error rate of 0.05 is suggested rather

that an experiment-wise error rate.

2. The basis for Fisher's Exact Test is a 2×2 contingency table. However, in order to use this table the contingency

table must be arranged in the format shown in Table G.1. From the 2×2 table, set up for the control and the

concentration you wish to compare, you can determine statistical significance by looking up a value in the table

provided later in this section. 

TABLE G.1. FORMAT FOR CONTINGENCY TABLE

Number of

Number of

Successes Failures Observations

Row 1 a A - a A 

Row 2 b B - b B 

Total a + b [(A + B) - a - b] A + B 

3. Arrange the table so that the total number of observations for row one is greater than or equal to the total for row

two (A $ B). Categorize a success such that the proportion of successes for row one is greater than or equal to the

proportion of successes for row two (a/A $ b/B). For the Ceriodaphnia dubia survival data, a success may be 'alive'

or 'dead', whichever causes a/A $ b/B. The test is then conducted by looking up a value in the table of significance

levels of b and comparing it to the b value given in the contingency table. The table of significance levels of b is

Table G.5. Enter Table G.5 in the section for A, subsection for B, and the line for a. If the b value of the

contingency table is equal to or less than the integer in the column headed 0.05 in Table G.5, then the survival

proportion for the effluent concentration is significantly different from the survival proportion for the control. A

dash or absence of entry in Table G.5 indicates that no contingency table in that class is significant. 

4. To illustrate Fisher's Exact Test, a set of survival data (Table G.2) from the daphnid, Ceriodaphnia dubia,

survival and reproduction test will be used. 

5. For each control and effluent concentration construct a 2x2 contingency table.

6. For the control and effluent concentration of 1% the appropriate contingency table for the test is given in

Table G.3.
298

TABLE G.2. EXAMPLE OF FISHER'S EXACT TEST: CERIODAPHNIA DUBIA MORTALITY DATA 

Effluent

Concentration (%) No. Dead Total1

Control 1 9

1 0 10

3 0 10

6 0 10

12 0 10

25 10 10

1

 Total number of live adults at the beginning of the test. 

 7. Since 10/10 > 8/9, the category 'alive' is regarded as a success. For A = 10, B = 9 and, a = 10, under the column

headed 0.05, the value from Table G.5 is b = 5. Since the value of b (b = 8) from the contingency table (Table G.3),

is greater than the value of b (b = 5) from Table G.5, the test concludes that the proportion of survival is not

significantly different for the control and 1% effluent.

8. The contingency tables for the combinations of control and effluent concentrations of 3%, 6%, 12% are identical

to Table G.3. The conclusion of no significant difference in the proportion of survival for the control and the level

of effluent would also remain the same.

9. For the combination of control and 25% effluent, the contingency table would be constructed as Table G.4. The

category 'dead' is regarded as a success, since 10/10 > 1/9. The b value (b = 1) from the contingency table

(Table G.4) is less than the b value (b = 5) from the table of significance levels of b (Table G.5). Thus, the percent

mortality for 25% effluent is significantly greater than the percent mortality for the control. Thus, the NOEC and

LOEC for survival are 12% and 25%, respectively.

TABLE G.3. 2×2 CONTINGENCY TABLE FOR CONTROL AND 1% EFFLUENT

Number of

Number of 

Alive Dead Observations 

 

1% Effluent 10 0 10

Control 8 1 9

Total 18 1 19
299

Table G.4. 2x2 CONTINGENCY TABLE FOR CONTROL AND 25% EFFLUENT 

Number of

Number of

Dead Alive Observations

 

25% Effluent 10 0 10 

Control 1 8 9 

Total 11 8 19 
300

 TABLE G.5. SIGNIFICANT LEVELS OF B: VALUES OF B (LARGE TYPE) AND

CORRESPONDING PROBABILITIES (SMALL TYPE)1

α α 0-05 0-025 0-01 0-005 0-05 0-025 0-01 0-005

A=8 8 4 -038 3 -013 2 -003 2 -003

A=3 B=3 3 0 -050 —— 7 2 -020 2 -020 1 -005+ 0 -001

 6 1 -020 1 -020 0 -003 0 -003

5 0 -013 0 -013 

A=4 B=4 4 1 -014 1 -014 —— —— 4 0 -038 

 3 4 0 -029 —— —— —— 7 8 3 -026 2 -007 2 -007 1 -001

7 2 -035- 1 -009 1 -009 0 -001

A=5 B=5 5 1 -024 1 -024 0 -004 0 -004 6 1 -032 0 -006 0 -006 

 4 0 -024 1 -024 —— —— 5 0 -019 0 -019 

 4 5 1 -048 0 -008 0 -008 —— 6 8 2 -015- 2 -015- 1 -003 1 -003

 4 0 -040 —— —— —— 7 1 -016 1 -016 0 -002 0 -002

 3 5 0 -018 0 -018 —— —— 6 0 -009 0 -009 0 -009 

 2 5 0 -048 —— —— —— 5 0 -028 —— —— 

 5 8 2 -035- 1 -007 1 -007 0 -001

7 1 -032 0 -005- 0 -005- 0 -005-

A=6 B=6 6 2 -030 1 -008 1 -008 0 -001 6 0 -016 0 -016 —— 

5 1 -040 0 -008 0 -008 —— 5 0 -044 —— —— 

 4 0 -030 —— —— —— 4 8 1 -018 1 -018 0 -002 0 -002

 5 6 1 -015+ 0 -015+ 0 -002 0 -002 7 0 -010+ 0 -010+ —— 

5 0 -013 0 -013 —— —— 6 0 -030 —— —— 

4 0 -045+ —— —— —— 3 8 0 -006 0 -006 0 -006

 4 6 1 -033 0 -005- 0 -005- 0 -005- 7 0 -024 0 -024 —— 

 5 0 -024 0 -024 —— —— 2 8 0 -022 0 -022 —— 

 3 6 0 -012 0 -012 —— —— A=9 9 5 -041 4 -015- 3 -005- 3 -005-

5 0 -048 —— —— —— 8 3 -025- 3 -025- 2 -008 1 -002

 2 6 0 -036 —— —— —— 7 2 -028 1 -008 1 -008 0 -001

6 1 -025- 1 -025- 0 -005- 0 -005-

A=7 B=7 7 3 -035- 2 -010+ 1 -002 1 -002 5 0 -015- 0 -015- —— 

6 1 -015- 1 -015- 0 -002 0 -002 4 0 -041 —— —— 

5 1 -010+ 0 -010+ —— —— 8 9 4 -029 3 -009 3 -009 2 -002

4 0 -035- —— —— —— 8 3 -043 2 -013 1 -003 1 -003

 6 7 2 -021 2 -021 1 -005- 1 -005- 7 2 -044 1 -012 0 -002 0 -002

6 1 -025+ 0 -004 0 -004 0 -004 6 1 -036 0 -007 0 -007

5 0 -016 0 -016 —— —— 5 0 -020 0 -020 —— 

4 0 -049 —— —— —— 7 9 3 -019 3 -019 2 -005 2 -005-

 5 7 2 -045+ 1 -010+ 0 -001 0 -001 8 2 -024 2 -024 1 -006 0 -001

6 1 -045+ 0 -008 0 -008 —— 7 1 -020 1 -020 0 -003 0 -003

5 0 -027 —— —— —— 6 0 -010+ 0 -010+ —— 

 7 1 -024 1 -024 —— 0 -003 5 0 -029 —— —— 

6 0 -015+ 0 -015+ 0 -003 —— 6 9 3 -044 2 -011 1 -002 1 -002

5 0 -045+ —— —— —— 8 2 -047 1 -011 0 -001 0 -001

7 0 -008 0 -008 0 -008 —— 7 1 -035- 0 -006 0 -006

6 0 -033 —— —— —— 6 0 -017 0 -017 —— 

7 0 -028 —— —— —— 5 0 -042 —— —— 

1 The table shows:(1) In bold type, for given a, A and B, the value of b ([a) which is just significant at the probability level

quoted (one-tailed test); and (2) In small type, for given A, B and r = a + b, the exact probability (if there is independence) that

b is equal to or less than the integer shown in bold type. From Pearson and Hartley (1962). 
301

TABLE G.5. SIGNIFICANT LEVELS OF B: VALUES OF B (LARGE TYPE) AND CORRESPONDING

PROBABILITIES (SMALL TYPE)1

 (CONTINUED) 

α

Probability

α

Probability

0-05 0-025 0-01 0-005 0-05 0-025 0-01 0-005

A=9 B=5 9 2 -027 1 -005- 1 -005- 1 -005- A=10 B=4 10 1 -011 1 -011 0 -001 0 -001

8 1 -023 1 -023 0 -003 0 -003 9 1 -041 0 -005- 0 -005- 0 -005-

7 0 - 0 -010+ —— —— 8 0 - 0 -015- —— ——

6 0 -028 —— —— —— 7 0 - —— —— ——

 4 9 1 -014 1 -014 0 -001 0 -001 3 10 1 -038 0 -003 0 -003 0 -003

8 0 -007 0 -007 0 -007 —— 9 0 -014 0 -014 —— ——

7 0 -021 0 -021 —— —— 8 0 - —— —— ——

6 0 -049 —— 0 -005 —— 2 10 0 - 0 -015+ —— ——

 3 9 1 - 0 -005- 0 -005- 0 -005- 9 0 - —— —— ——

8 0 -018 0 -018 —— ——

7 0 - —— —— ——

 2 9 0 -018 0 -018 —— —— A=11 B=11 11 7 - 6 -018 5 -006 4 -002

10 5 -032 4 -012 3 -004 3 -004

9 4 -040 3 -015- 2 -004 2 -004

A=10 B=10 10 6 -043 5 -016 4 -005+ 3 -002 8 3 -043 2 -015- 1 -004 1 -004

9 4 -029 3 -010- 3 -010 2 -003 7 2 -040 1 -012 0 -002 0 -002

8 3 - 2 -012 1 -003 1 -003 6 1 -032 0 -006 0 -006 ——

7 2 - 1 -010- 1 -010- 0 -002 5 0 -018 0 -018 —— ——

6 1 -029 0 -005+ 0 -005+ —— 4 0 - —— —— ——

5 0 -016 0 -016 —— —— 10 11 6 - 5 -012 4 -004 4 -004

4 0 -043 —— —— —— 10 4 -021 4 -021 3 -007 2 -002

 9 10 5 -033 4 -011 3 -003 3 -003 9 3 -024 3 -024 2 -007 1 -002

9 4 - 3 -017 2 -005- 2 -005- 8 2 -023 2 -023 1 -006 0 -001

8 2 -019 2 -019 1 -004 1 -004 7 1 -017 1 -017 0 -003 0 -003

7 1 - 1 -015- 0 -002 0 -002 6 1 -043 0 -009 0 -009 ——

6 1 -040 0 -008 0 -008 —— 5 0 -023 0 -023 —— ——

5 0 -022 0 -022 —— —— 9 11 5 -026 4 -008 4 -008 3 -002

 8 10 4 -023 4 -023 3 -007 2 -002 10 4 -038 3 -012 2 -003 2 -003

9 3 -032 2 -009 2 -009 1 -002 9 3 -040 2 -012 1 -003 1 -003

8 2 -031 1 -008 1 -008 0 -001 8 2 - 1 -009 1 -009 0 -001

7 1 -023 1 -023 0 -004 0 -004 7 1 - 1 -025- 0 -004 0 -004

6 0 -011 0 -011 —— —— 6 0 -012 0 -012 —— ——

5 0 -029 —— —— —— 5 0 -030 —— —— ——

 7 10 3 - 3 -015- 2 -003 2 -003 8 11 4 -018 4 -018 3 -005- 3 -005-

9 2 -018 2 -018 1 -004 1 -004 10 3 -024 3 -024 2 -006 1 -001

8 1 -013 1 -013 0 -002 0 -002 9 2 -022 2 -022 1 -005- 1 -005-

7 1 -036 0 -006 0 -006 —— 8 1 - 1 -015- 0 -002 0 -002

6 0 -017 0 -017 —— —— 7 1 -037 0 -007 0 -007 ——

5 0 -041 —— —— —— 6 0 -017 0 -017 —— ——

 6 10 3 -036 2 -008 2 -008 1 -001 5 0 -040 —— —— ——

9 2 -036 1 -008 1 -008 0 -001 7 11 4 -043 3 -011 2 -002 2 -002

8 1 -024 1 -024 0 -003 0 -003 10 3 -047 2 -013 1 002 1 -002

7 0 - 0 -010+ —— —— 9 2 -039 1 -009 1 -009 0 -001

6 0 -026 —— —— —— 8 1 - 1 -025- 0 -004 0 -004

 5 10 2 -022 2 -022 1 -004 1 -004 7 0 - 0 -010+ —— ——

9 1 -017 1 -017 0 -002 0 -002 6 0 - 0 -025- —— ——

8 1 - 0 -007 0 -007 —— 6 11 3 - 2 006 2 -006 1 -001

7 0 - 0 -019 —— —— 10 2 - 1 -005+ 1 -005+ 0 -001

6 0 - —— —— —— 9 1 - 1 -018 0 -002 0 -002
302

TABLE G.5. SIGNIFICANT LEVELS OF B: VALUES OF B (LARGE TYPE) AND CORRESPONDING

PROBABILITIES (SMALL TYPE)1

 (CONTINUED) 

α Probability α Probability

0-05 0-025 0-01 0-005 0-05 0-025 0-01 0-005

A=11 B=6 8 1 -043 0 -007 0 -007 —— A=12 B=9 7 1 -037 0 -007 0 -007 ——

7 0 -017 0 -017 —— —— 6 0 -017 0 -017 —— ——

6 0 -037 —— —— —— 5 0 -039 —— —— ——

 5 11 2 -018 2 -018 1 -003 1 -003 8 12 5 -049 4 -014 3 -004 3 -004

10 1 -013 1 -013 0 -001 0 -001 11 3 -018 3 -018 2 -004 2 -004

9 1 -036 0 -005- 0 -005- 0 -005- 10 2 -015+ 2 -015+ 1 -003 1 -003

8 0 -013 0 -013 —— —— 9 2 -040 1 -010- 1 -010- 0 -001

7 0 -029 —— —— —— 8 1 -025- 1 -025- 0 -004 0 -004

 4 11 1 -009 1 -009 1 -009 0 -001 7 0 -010+ 0 -010+ —— ——

10 1 -033 0 -004 0 -004 0 -004 6 0 -024 0 -024 —— ——

9 0 -011 0 -011 —— —— 7 12 4 -036 3 -009 3 -009 2 -002

8 0 -026 —— —— —— 11 3 -038 2 -010- 2 -010- 1 -002

 3 11 1 -033 0 -003 0 -003 0 -003 10 2 -029 1 -006 1 -006 0 -001

10 0 -011 0 -011 —— —— 9 1 -017 1 -017 0 -002 0 -002

9 0 -027 —— —— —— 8 1 -040 0 -007 0 -007 ——

 2 11 0 -013 0 -013 —— —— 7 0 -016 0 -016 —— ——

10 0 -038 —— —— —— 6 0 -034 —— —— ——

 6 12 3 -025- 3 -025- 2 -005- 2 -005-

11 2 -022 2 -022 1 -004 1 -004

A=12 B=12 12 8 -047 7 -019 6 -007 5 -002 10 1 -013 1 -013 0 -002 0 -002

11 6 -034 5 -014 4 -005- 4 -005- 9 1 -032 0 -005- 0 -005- 0 -005-

10 5 -045- 4 -018 3 -006 2 -002 8 0 -011 0 -011 —— ——

9 4 -050- 3 -020 2 -006 1 -001 7 0 -025- 0 -025- —— ——

8 3 -050- 2 -018 1 -005- 1 -005- 6 0 -050- —— —— ——

7 2 -045- 1 -014 0 -002 0 -002 5 12 2 -015- 2 -015 1 -002 1 -002

6 1 -034 0 -007 0 -007 —— 11 1 -010- 1 -010- 1 -010- 0 -001

5 0 -019 0 -019 —— —— 10 1 -028 0 -003 0 -003 0 -003

4 0 -047 —— —— —— 9 0 -009 0 -009 0 -009 ——

 11 12 7 -037 6 -014 5 -005- 5 -005- 8 0 -020 0 -020 —— ——

11 5 -024 5 -024 4 -008 3 -002 7 0 -041 —— —— ——

10 4 -029 3 -010+ 2 -003 2 -003 4 12 2 -050 1 -007 1 -007 0 -001

9 3 -030 2 -009 2 -009 1 -002 11 1 -027 0 -003 0 -003 0 -003

8 2 -026 1 -007 1 -007 0 -001 10 0 -008 0 -008 0 -008 ——

7 1 -019 1 -019 0 -003 0 -003 9 0 -019 0 -019 —— ——

6 1 -045- 0 -009 0 -009 —— 8 0 -038 —— —— ——

5 0 -024 0 -024 —— —— 3 12 1 -029 0 -002 0 -002 0 -002

 10 12 6 -029 5 -010 5 -010- 4 -003 11 0 -009 0 -009 0 -009 ——

11 5 -043 4 -015+ 3 -005- 3 -005- 10 0 -022 0 -022 —— ——

10 4 -048 3 -017 2 -005- 2 -005- 9 0 -044 —— —— ——

9 3 -046 2 -015- 1 -004 1 -004 2 12 0 -011 0 -011 —— ——

8 2 -038 1 -010+ 0 -002 0 -002 11 0 -033 —— —— ——

7 1 -026 0 -005- 0 -005- 0 -005-

6 0 -012 0 -012 —— ——

5 0 -030 —— —— —— A=13 B=13 13 9 -048 8 -020 7 -007 6 -003

 9 12 5 -021 5 -021 4 -006 3 -002 12 7 -037 6 -015+ 5 -006 4 -002

11 4 -029 3 -009 3 -009 2 -002 11 6 -048 5 -021 4 -008 3 -002

10 3 -029 2 -008 2 -008 1 -002 10 4 -024 4 -024 3 -008 2 -002

9 2 -024 2 -024 1 -006 0 -001 9 3 -024 3 -024 2 -008 1 -002

8 1 -016 1 -016 0 -002 0 -002 8 2 -021 2 -021 1 -006 0 -001
303

TABLE G.5. SIGNIFICANT LEVELS OF B: VALUES OF B (LARGE TYPE) AND CORRESPONDING

PROBABILITIES (SMALL TYPE)1

 (CONTINUED) 

α

Probability

α

Probability

0-05 0-025 0-01 0-005 0-05 0-025 0-01 0-005

A=13 B=13 7 2 -048 1 -015+ 0 -003 0 -003 A=13 B=7 11 2 -022 2 -022 1 -004 1 -004

6 1 -037 0 -007 0 -007 —— 10 1 -012 1 -012 0 -002 0 -002

5 0 -020 0 -020 —— —— 9 1 -029 0 -004 0 -004 0 -004

4 0 -048 —— —— 8 0 -010+ 0 -010+ —— ——

 12 1 8 -039 7 -015- 6 -005+ 5 -002 7 0 -022 0 -022 —— ——

1 6 -027 5 -010- 5 -010- 4 -003 6 0 -044 —— —— ——

1 5 -033 4 -013 3 -004 3 -004 6 13 3 -021 3 -021 2 -004 2 -004

1 4 -036 3 -013 2 -004 2 -004 12 2 -017 2 -017 1 -003 1 -003

9 3 -034 2 -011 1 -003 1 -003 11 2 -046 1 -010- 1 -010- 0 -001

8 2 -029 1 -008 1 -008 0 -001 10 1 -024 1 -024 0 -003 0 -003

7 1 -020 1 -020 0 -004 0 -004 9 1 -050- 0 -008 0 -008 ——

6 1 -046 0 -010- 0 -010- —— 8 0 -017 0 -017 —— ——

5 0 -024 0 -024 —— —— 7 0 -034 —— —— ——

 11 1 7 -031 6 -011 5 -003 5 -003 5 13 2 -012 2 -012 1 -002 1 -002

1 6 -048 5 -018 4 -006 3 -002 12 2 -044 1 -008 1 -008 0 -001

1 4 -021 4 -021 3 -007 2 -002 11 1 -022 1 -022 0 -002 0 -002

1 3 -021 3 -021 2 -006 1 -001 10 1 -047 0 -007 0 -007 ——

9 3 -050- 2 -017 1 -004 1 -004 9 0 -015- 0 -015- —— ——

8 2 -040 1 -011 0 -002 0 -002 8 0 -029 —— —— ——

7 1 -027 0 -005- 0 -005- 0 -005- 4 13 2 -044 1 -006 1 -006 0 -000

6 0 -013 0 -013 —— —— 12 1 -022 1 -022 0 -002 0 -002

0 -030 —— —— 11 0 -006 0 -006 0 -006 ——

 10 1 6 -024 6 -024 5 -007 4 -002 10 0 -015- 0 -015- —— ——

1 5 -035- 4 -012 3 -003 3 -003 9 0 -029 —— —— ——

1 4 -037 3 -012 2 -003 2 -003 3 13 1 -025 1 -025 0 -002 0 -002

1 3 -033 2 -010+ 1 -002 1 -002 12 0 -007 0 -007 0 -007 ——

9 2 -026 1 -006 1 -006 0 -001 11 0 -018 0 -018 —— ——

8 1 -017 1 -017 0 -003 0 -003 10 0 -036 —— —— ——

7 1 -038 0 -007 0 -007 —— 2 13 0 -010- 0 -010- 0 -010- ——

6 0 -017 0 -017 —— —— 12 0 -029 —— —— ——

 5 0 -038 —— ——

 9 1 5 -017 5 -017 4 -005- 4 -005-

1 4 -023 4 -023 3 -007 2 -001 A=14 14 10 -049 9 -020 8 -008 7 -003

1 3 -022 3 -022 2 -006 1 -001 13 8 -038 7 -016 6 -006 5 -002

1 2 -017 2 -017 1 -004 1 -004 12 6 -023 6 -023 5 -009 4 -003

9 2 -040 1 -010+ 0 -001 0 -001 11 5 -027 4 -011 3 -004 3 -004

8 1 -025- 1 -025- 0 -004 0 -004 10 4 -028 3 -011 2 -003 2 -003

7 0'-010+ 0 -010+ —— —— 9 3 -027 2 -009 2 -009 1 -002

6 0 -023 0 -023 —— —— 8 2 -023 2 -023 1 -006 0 -001

5 0 -049 —— —— 7 1 -016 1 -016 0 -003 0 -003

 8 1 5 -042 4 -012 3 -003 3 -003 6 1 -038 0 -008 0 -008 ——

1 4 -047 3 -014 2 -003 2 -003 5 0 -020 0 -020 —— ——

1 3 -041 2 -011 1 -002 1 -002 4 0 -049 —— —— ——

1 2 -029 1 -007 1 -007 0 -001 13 14 9 -041 8 -016 7 -006 6 -002

9 1 -017 1 -017 0 -002 0 -002 13 7 -029 6 -011 5 -004 5 -004

8 1 -037 0 -006 0 -006 —— 12 6 -037 5 -015+ 4 -005+ 3 -002

7 0 -015- 0 -015- —— —— 11 5 -041 4 -017 3 -006 2 -001

6 0 -032 —— —— 10 4 -041 3 -016 2 -005- 2 -005-

 7 1 4 -031 3 -007 3 -007 2 -001 9 3 -038 2 -013 1 -003 1 -003

1 3 -031 2 -007 2 -007 1 -001 8 2 -031 1 -009 1 -009 0 -001
304

 TABLE G.5. SIGNIFICANT LEVELS OF B: VALUES OF B (LARGE TYPE) AND CORRESPONDING

PROBABILITIES (SMALL TYPE)1

 (CONTINUED) 

α

Probability

α

Probability

0-05 0-025 0-01 0-005 0-05 0-025 0-01 0-005

A=14 7 1 -021 1 -021 0 -004 0 -004 A=14 B=7 14 4 -026 3 -006 3 -006 2 -001

6 1 -048 0 -010+ —— —— 13 3 -025 2 -006 2 -006 1 -001

5 0 -025- 0 -025- —— —— 12 2 -017 2 -017 1 -003 1 -003

 12 1 8 -033 7 -012 6 -004 6 -004 11 2 -041 1 -009 1 -009 0 -001

1 6 -021 6 -021 5 -007 4 -002 10 1 -021 1 -021 0 -003 0 -003

1 5 -025+ 4 -009 4 -009 3 -003 9 1 -043 0 -007 0 -007 ——

1 4 -026 3 -009 3 -009 2 -002 8 0 -015- 0 -015- —— ——

1 3 -024 3 -024 2 -007 1 -002 7 0 -030 —— —— ——

9 2 -019 2 -019 1 -005- 1 -005- 6 14 3 -018 3 -018 2 -003 2 -003

8 2 -042 1 -012 0 -002 0 -002 13 2 -014 2 -014 1 -002 1 -002

7 1 -028 0 -005+ 0 -005+ —— 12 2 -037 1 -007 1 -007 0 -001

6 0 -013 0 -013 —— —— 11 1 -018 1 -018 0 -002 0 -002

5 0 -030 —— —— —— 10 1 -038 0 -005+ 0 -005+ ——

 11 1 7 -026 6 -009 6 -009 5 -003 9 0 -012 0 -012 —— ——

1 6 -039 5 -014 4 -004 4 -004 8 0 -024 0 -024 —— ——

1 5 -043 4 -016 3 -005- 3 -005- 7 0 -044 —— —— ——

1 4 -042 3 -015- 2 -004 2 -004 5 14 2 -010+ 2 -010+ 1 -001 1 -001

1 3 -036 2 -011 1 -003 1 -003 13 2 -037 1 -006 1 -006 0 -001

9 2 -027 1 -007 1 -007 0 -001 12 1 -017 1 -017 0 -002 0 -002

8 1 -017 1 -017 0 -003 0 -003 11 1 -038 0 -005- 0 -005- 0 -005-

7 1 -038 0 -007 0 -007 —— 10 0 -011 0 -011 —— ——

6 0 -017 0 -017 —— —— 9 0 -022 0 -022 —— ——

5 0 -038 —— —— —— 8 0 -040 —— —— ——

 10 1 6 -020 6 -020 5 -006 4 -002 4 14 2 -039 1 -005- 1 -005- 1 -005-

1 5 -028 4 -009 4 -009 3 -002 13 1 -019 1 -019 0 -002 0 -002

1 4 -028 3 -009 3 -009 2 -002 12 1 -044 0 -005- 0 -005- 0 -005-

1 3 -024 3 -024 2 -007 1 -001 11 0 -011 0 -011 —— ——

1 2 -018 2 -018 1 -004 1 -004 10 0 -023 0 -023 —— ——

9 2 -040 1 -011 0 -002 0 -002 9 0 -041 —— —— ——

8 1 -024 1 -024 0 -004 0 -004 3 14 1 -022 1 -022 0 -001 0 -001

7 0 -010- 0 -010- 0 -010- —— 13 0 -006 0 -006 0 -006 ——

6 0 -022 0 -022 —— —— 12 0 -015- 0 -015- —— ——

5 0 -047 —— —— —— 11 0 -029 —— —— ——

 9 1 6 -047 5 -014 4 -004 4 -004 2 14 0 -008 0 -008 0 -008 ——

1 4 -018 4 -018 3 -005- 3 -005- 13 0 -025 0 -025 —— ——

1 3 -017 3 -017 2 -004 2 -004 12 0 -050 —— —— ——

1 3 -042 2 -012 1 -002 1 -002

1 2 -029 1 -007 1 -007 0 -001

9 1 -017 1 -017 0 -002 0 -002

8 1 -036 0 -006 0 -006 —— A=15 B=15 15 11 -050- 10 -021 9 -008 8 -003

7 0 -014 0 -014 —— —— 14 9 -040 8 -018 7 -007 6 -003

6 0 -030 —— —— —— 13 7 -025+ 6 -010+ 5 -004 5 -004

 8 1 5 -036 4 -010- 4 -010- 3 -002 12 6 -030 5 -013 4 -005- 4 -005-

1 4 -039 3 -011 2 -002 2 -002 11 5 -033 4 -013 3 -005- 3 -005-

1 3 -032 2 -008 2 -008 1 -001 10 4 -033 3 -013 2 -004 2 -004

1 2 -022 2 -022 1 -005- 1 -005- 9 3 -030 2 -010+ 1 -003 1 -003

1 2 -048 1 -012 0 -002 0 -002 8 2 -025+ 1 -007 1 -007 0 -001

9 1 -026 0 -004 0 -004 0 -004 7 1 -018 1 -018 0 -003 0 -003

8 0 -009 0 -009 0 -009 —— 6 1 -040 0 -008 0 -008 ——

7 0 -020 0 -020 —— —— 5 0 -021 0 -012 —— ——

6 0 -040 —— —— —— 4 0 -050- —— —— ——
305

 TABLE G.5. SIGNIFICANT LEVELS OF B: VALUES OF B (LARGE TYPE) AND

CORRESPONDING PROBABILITIES (SMALL TYPE)1

 (CONTINUED) 

α

Probability

α

Probability

0-05 0-025 0-01 0-005 0-05 0-025 0-01 0-005

A=15 B=14 15 10 -042 9 -017 8 -006 7 -002 A=15 B=9 13 4 -042 3 -013 2 -003 2 -003

14 8 -031 7 -013 6 -005- 6 -005- 12 3 -032 2 -009 2 -009 1 -002

13 7 -041 6 -017 5 -007 4 -002 11 2 -021 2 -021 1 -005- 1 -005-

12 6 -046 5 -020 4 -007 3 -002 10 2 -045- 1 -011 0 -002 0 -002

11 5 -048 4 -020 3 -007 2 -002 9 1 -024 1 -024 0 -004 0 -004

10 4 -046 3 -018 2 -006 1 -001 8 1 -048 0 -009 0 -009 ——

9 3 -041 2 -014 1 -004 1 -004 7 0 -019 0 -019 —— ——

8 2 -033 1 -009 1 -009 0 -001 6 0 -037 —— —— ——

7 1 -022 1 -022 0 -004 0 -004 8 15 5 -032 4 -008 4 -008 3 -002

6 1 -049 0 -011 —— —— 14 4 -033 3 -009 3 -009 2 -002

5 0 -025+ —— —— —— 13 3 -026 2 -006 2 -006 1 -001

 13 15 9 -035- 8 -013 7 -005- 7 -005- 12 2 -017 2 -017 1 -003 1 -003

14 7 -023 7 -023 6 -009 5 -003 11 2 -037 1 -008 1 -008 0 -001

13 6 -029 5 -011 4 -004 4 -004 10 1 -019 1 -019 0 -003 0 -003

12 5 -031 4 -012 3 -004 3 -004 9 1 -038 0 -006 0 -006 ——

11 4 -030 3 -011 2 -003 2 -003 8 0 -013 0 -013 —— ——

10 3 -026 2 -008 2 -008 1 -002 7 0 -026 —— —— ——

9 2 -020 2 -020 1 -005+ 0 -001 6 0 -050- —— —— ——

8 2 -043 1 -013 0 -002 0 -002 7 15 4 -023 4 -023 3 -005- 3 -005-

7 1 -029 0 -005+ 0 -005+ —— 14 3 -021 3 -021 2 -004 2 -004

6 0 -013 0 -013 —— —— 13 2 -014 2 -014 1 -002 1 -002

5 0 -031 —— —— —— 12 2 -032 1 -007 1 -007 0 -001

 12 15 8 -028 7 -010- 7 -010- 6 -003 11 1 -015+ 1 -015+ 0 -002 0 -002

14 7 -043 6 -016 5 -006 4 -002 10 1 -032 0 -005- 0 -005- 0 -005-

13 6 -049 5 -019 4 -007 3 -002 9 0 -010+ 0 -010+ —— ——

12 5 -049 4 -019 3 -006 2 -002 8 0 -020 0 -020 —— ——

11 4 -045+ 3 -017 2 -005- 2 -005- 7 0 -038 —— —— ——

10 3 -038 2 -012 1 -003 1 -003 6 15 3 -015+ 3 -015+ 2 -003 2 -003

9 2 -028 1 -007 1 -007 0 -001 14 2 -011 2 -011 1 -002 1 -002

8 1 -018 1 -018 0 -003 0 -003 13 2 -031 1 -006 1 -006 0 -001

7 1 -038 0 -007 0 -007 —— 12 1 -014 1 -014 0 -002 0 -002

6 0 -017 0 -017 —— —— 11 1 -029 0 -004 0 -004 0 -004

5 0 -037 —— —— —— 10 0 -009 0 -009 0 -009 ——

 11 15 7 -022 7 -022 6 -007 5 -002 9 0 -017 0 -017 —— ——

14 6 -032 5 -011 4 -003 4 -003 8 0 -032 —— —— ——

13 5 -034 4 -012 3 -003 3 -003 5 15 2 -009 2 -009 2 -009 1 -001

12 4 -032 3 -010+ 2 -003 2 -003 14 2 -032 1 -005- 1 -005- 1 -005-

11 3 -026 2 -008 2 -008 1 002 13 1 -014 1 -014 0 -001 0 -001

10 2 -019 2 -019 1 -004 1 -004 12 1 -031 0 -004 0 -004 0 -004

9 2 -040 1 -011 0 -002 0 -002 11 0 -008 0 -008 0 -008 ——

8 1 -024 1 -024 0 -004 0 -004 10 0 -016 0 -016 —— ——

7 1 -049 0 -010- 0 -010- —— 9 0 -030 —— —— ——

6 0 -022 0 -022 —— —— 4 15 2 -035+ 1 -004 1 -004 1 -004

5 0 -046 —— —— —— 14 1 -016 1 -016 0 -001 0 -001

 10 15 6 -017 6 -017 5 -005- 5 -005- 13 1 -037 0 -004 0 -004 0 -004

14 5 -023 5 -023 4 -007 3 -002 12 0 -009 0 -009 0 -009 ——

13 4 -022 4 -022 3 -007 2 -001 11 0 -018 0 -018 —— ——

12 3 -018 3 -018 2 -005- 2 -005- 10 0 -033 —— —— ——

11 3 -042 2 -013 1 -003 1 -003 3 15 1 -020 1 -020 0 -001 0 -001

10 2 -029 1 -007 1 -007 0 -001 14 0 -005- 0 -005- 0 -005- 0 -005-

9 1 -016 0 -016 0 -002 0 -002 13 0 -012 0 -012 —— ——

8 1 -034 0 -006 0 -006 —— 12 0 -025- 0 -025- —— ——

7 0 -013 1 -013 —— —— 11 0 -043 —— —— ——

6 0 -028 —— —— —— 2 15 0 -007 0 -007 0 -007 ——

 9 15 6 -042 5 -012 4 -003 4 -003 14 0 -022 0 -022 —— ——

14 5 -047 4 -015- 3 -004 3 -004 13 0 -044 —— —— ——
306

F ' S1

2

S2

2

where S1

2 > S22

TABLE H.1. CERIODAPHNIA DUBIA REPRODUCTION DATA FROM AN EFFLUENT SCREENING

TEST

Replicate

1 2 3 4 5 6 7 8 9 10 &X S2

Control 36 38 35 35 28 41 37 33 . . 35.4 14.5

100% Effluent 23 14 21 7 12 17 23 8 18 . 15.9 36.6

F ' 36.61

14.55

 APPENDIX H

SINGLE CONCENTRATION TOXICITY TEST - COMPARISON OF CONTROL

WITH 100% EFFLUENT OR RECEIVING WATER

1. To statistically compare a control with one concentration, such as 100% effluent or the instream waste

concentration, a t-test is the recommended analysis. The t-test is based on the assumptions that the observations are

independent and normally distributed and that the variances of the observations are equal between the two groups.

2. Shapiro Wilk's test may be used to test the normality assumption (see Appendix B for details). If the data do not

meet the normality assumption, the nonparametric test, Wilcoxon's Rank Sum Test, may be used to analyze the data. 

An example of this test is given in Appendix F. Since a control and one concentration are being compared, the K =

1 section of Table F.5 contains the needed critical values.

3. The F test for equality of variances is used to test the homogeneity of variance assumption. When conducting

the F test, the alternative hypothesis of interest is that the variances are not equal.

4. To make the two-tailed F test at the 0.01 level of significance, put the larger of the two variances in the

numerator of F.

5. Compare F with the 0.005 level of a tabled F value with n1 - 1 and n 2 - 1 degrees of freedom, where n1 and n2

are the number of replicates for each of the two groups. 

6. A set of Ceriodaphnia dubia reproduction data from an effluent screening test will be used to illustrate the F

test. The raw data, mean and variance for the control and 100% effluent are given in Table H.1.

7. Since the variability of the 100% effluent is greater than the variability of the control, S2

 for the 100% effluent

concentration is placed in the numerator of the F statistic and S2

 for the control is placed in the denominator.

8. There are 9 replicates for the effluent concentration and 8 replicates for the control. Thus, the numerator

degrees of freedom is 8 and the denominator degrees of freedom is 7. For a two-tailed test at the 0.01 level of
307

t ' Y ̄

1&Y ̄2

Sp

1

n1

% 1

n2

Sp ' (n1&1)S1

2

%(n2&1)S 2

2

n1%n2&2

t ' 35.4&15.9

5.13 1

8

% 1

9

' 7.82

Sp ' (8&1)14.5%(9&1)36.6

(8%9&2) ' 5.13

significance, the critical F value is obtained from a table of the F distribution (Snedecor and Cochran, 1980). The

critical F value for this test is 8.68. Since 2.52 is not greater than 8.68, the conclusion is that the variances of the

control and 100% effluent are homogeneous. 

9. EQUAL VARIANCE T-TEST

9.1 To perform the t-test, calculate the following test statistic: 

Where: = Mean for the control Y ̄1

Y ̄ = Mean for the effluent concentration 2

S1

2 = Estimate of the variance for the control 

S2

2 = Estimate of the variance for the effluent concentration

n1 = Number of replicates for the control 

n2 = Number of replicates for the effluent concentration 

9.2 Since we are usually concerned with a decreased response from the control, such as a decrease in survival or a

decrease in reproduction, a one-tailed test is appropriate. Thus, compare the calculated t with a critical t, where the

critical t is at the 5% level of significance with n1 + n2 - 2 degrees of freedom. If the calculated t exceeds the critical

t, the mean responses are declared different.

9.3 Using the data from Table H.1 to illustrate the t-test, the calculation of t is as follows:

Where:
308

t ' Y ̄

1&Y ̄2

S 2

1

n1

%

S 2

2

n2

df ) ' (n1&1) (n2&1)

(n2&1) C2

%(1&C)

2

(n1&1)

C '

S 2

1

n1

S 2

1

n1

%

S 2

2

n2

9.4 For an 0.05 level of significance test with 15 degrees of freedom the critical t is 1.754 (Note: Table D.5 for K

= 1 includes the critical t values for comparing two groups). Since 7.82 is greater than 1.754, the conclusion is that

the reproduction in the 100% effluent concentration is significantly lower than the control reproduction.

10. UNEQUAL VARIANCE T-TEST 

10.1 If the F test for equality of variance fails, the t-test is still a valid test. However, the denominator of the t statistic

is adjusted as follows:

Where: = Mean for the control Y ̄1

Y ̄ = Mean for the effluent concentration 2

S1

2

 = Estimate of the variance for the control 

S2

2

 = Estimate of the variance for the effluent concentration 

n1 = Number of replicates for the control 

n2 = Number of replicates for the effluent concentration 

10.2 Additionally, the degrees of freedom for the test are adjusted using the following formula: 

Where: 

10.3 The modified degrees of freedom is usually not an integer. Common practice is to round down to the nearest

integer.

10.4 The t-test is then conducted as the equal variance t-test. The calculated t is compared to the critical t at the

0.05 significance level with the modified degrees of freedom. If the calculated t exceeds the critical t, the mean

responses are found to be statistically different.
309

APPENDIX I

PROBIT ANALYSIS

1. This program calculates the EC1 and EC50 (or LC1 and LC50), and the associated 95% confidence intervals. 

2. The program is written in IBM PC Basic for the IBM compatible PC by Computer Sciences Corporation, 26 W.

Martin Luther King Drive, Cincinnati, OH 45268. A compiled, executable version of the program can be obtained

from EMSL-Cincinnati by sending a written request to EMSL at 3411 Church Street, Cincinnati, OH 45244.

2.1 Data input is illustrated by a set of total mortality data (Figure I.1) from a fathead minnow embryo-larval

survival and teratogenicity test. The program requests the following input:

1. Desired output of abbreviated (A) or full (F) output? (Note: only abbreviated output is shown below.)

2. Output designation (P = printer, D = disk file). 

3. Title for the output.

4. The number of exposure concentrations.

5. Toxicant concentration data.

2.2 The program output for the abbreviated output includes the following: 

1. A table of the observed proportion responding and the proportion responding adjusted for the controls

(see Figure I.2).

2. The calculated chi-square statistic for heterogeneity and the tabular value. This test is one indicator of

how well the data fit the model. The program will issue a warning when the test indicates that the data

do not fit the model.

3. Estimated LC1 and LC50 values and associated 95% confidence intervals (see Figure I.2).
310

USEPA PROBIT ANALYSIS PROGRAM

USED FOR CALCULATING LC/EC VALUES

Version 1.5

Do you wish abbreviated (A) or full (F) input/output? A

Output to printer (P) or disk file (D)? P

Title ? Example of Probit Analysis

Number responding in the control group = ? 2

Number of animals exposed in the concurrent control group = ? 20

Number of exposure concentrations, exclusive of controls ? 5

Input data starting with the lowest exposure concentration

Concentration = ? 0.5

Number responding = ? 2

Number exposed = ? 20

Concentration = ? 1.0

Number responding = ? 1

Number exposed = ? 20

Concentration = ? 2.0

Number responding = ? 4

Number exposed = ? 20

Concentration = ? 4.0

Number responding = ? 16

Number exposed = ? 20

Concentration = ? 8.0

Number responding = ? 20

Number exposed = ? 20

Number Number

 Number Conc. Resp. Exposed

1 0.5000 2 20 

2 1.0000 1 20

3 2.0000 4 20

4 4.0000 16 20

5 8.0000 20 20

Do you wish to modify your data ? N

The number of control animals which responded = 2

The number of control animals exposed = 20

Do you wish to modify these values ? N

Figure I.1. Sample Data Input for USEPA Probit Analysis program, Version 1.5.
311

Example of Probit Analysis

Proportion 

Observed Responding

Number Number Proportion Adjusted for

Conc. Exposed Resp. Responding Controls 

Control 20 2 0.1000 0.0000

0.5000 20 2 0.1000 0.0174

1.0000 20 1 0.0500 -.0372

2.0000 20 4 0.2000 0.1265

4.0000 20 16 0.8000 0.7816

8.0000 20 20 1.0000 1.0000

Chi - Square for Heterogeneity (calculated) = 0.441

Chi - Square for Heterogeneity 

 (tabular value at 0.05 level) = 7.815

Example of Probit Analysis

 Estimated LC/EC Values and Confidence Limits

Exposure Lower Upper

Point Conc. 95% Confidence Limits

LC/EC 1.00 1.346 0.453 1.922

LC/EC 50.00 3.018 2.268 3.672

Figure I.2. USEPA Probit Analysis Program Used for Calculating LC/EC Values, Version 1.5.
312

APPENDIX J

SPEARMAN-KARBER METHOD

1. The Spearman-Karber Method is a nonparametric statistical procedure for estimating the LC50 and the

associated 95% confidence interval (Finney, 1978). The Spearman-Karber Method estimates the mean of the

distribution of the log10 of the tolerance. If the log tolerance distribution is symmetric, this estimate of the mean is

equivalent to an estimate of the median of the log tolerance distribution.

2. If the response proportions are not monotonically non-decreasing with increasing concentration (constant or

steadily increasing with concentration), the data must be smoothed. Abbott's procedure is used to "adjust" the

concentration response proportions for mortality occurring in the control replicates.

3. Use of the Spearman-Karber Method is recommended when partial mortalities occur in the test solutions, but the

data do not fit the Probit model.

4. To calculate the LC50 using the Spearman-Karber Method, the following must be true: 1) the smoothed

adjusted proportion mortality for the lowest effluent concentration (not including the control) must be zero, and 2)

the smoothed adjusted proportion mortality for the highest effluent concentration must be one.

5. To calculate the 95% confidence interval for the LC50 estimate, one or more of the smoothed adjusted

proportion mortalities must be between zero and one.

6. The Spearman-Karber Method is illustrated below using a set of mortality data from a Fathead Minnow Larval

Survival and Growth test. These data are listed in Table J.1.

TABLE J.1. EXAMPLE OF SPEARMAN-KARBER METHOD: MORTALITY DATA FROM A

FATHEAD MINNOW LARVAL SURVIVAL AND GROWTH TEST (40 ORGANISMS

PER CONCENTRATION)

 

Effluent Number of Mortality

Concentration Mortalities Proportion

 

Control 2 0.05

6.25% 2 0.05 

12.5% 0 0.00 

25.0% 0 0.00

50.0% 26 0.65

100.0% 40 1.00 

 

7. Let p0, p1, ..., pk denote the observed response proportion mortalities for the control and k effluent

concentrations. The first step is to smooth the pi

 if they do not satisfy p0 # p1 # ... # pk. The smoothing process

replaces any adjacent pi

's that do not conform to p0 # p1 # ... # pk with their average. For example, if pi is less than

pi-1 then:
313

p s

i&1 ' p si ' (pi

%pi&1)

2

Where: pi

s

 = the smoothed observed proportion mortality for effluent concentration i.

7.1 For the data in this example, because the observed mortality proportions for the control and the 6.25% effluent

concentration are greater than the observed response proportions for the 12.5% and 25.0% effluent concentrations,

the responses for these four groups must be averaged:

p s

0 ' p s1 ' p s2 ' p s3 ' 0.05%0.05%0.00%0.00

4 ' 0.104 ' 0.025

7.2 Since p4 = 0.65 is larger than p3

s

, set p4

s

 = 0.65. Similarly, p5 = 1.00 is larger than p4

s

, so set p5

s

 = 1.00. 

Additional smoothing is not necessary. The smoothed observed proportion mortalities are shown in Table J.2.

8. Adjust the smoothed observed proportion mortality in each effluent concentration for mortality in the control

group using Abbott's formula (Finney, 1971). The adjustment takes the form:

Where: pi

a

 = (pi

s

 - p0

s

) / (1 - p0

s

)

p0

s

 = the smoothed observed proportion mortality for the control

pi

s

 = the smoothed observed proportion mortality for effluent concentration i.

8.1 For the data in this example, the data for each effluent concentration must be adjusted for control mortality

using Abbott's formula, as follows:

p a

0 ' p a1 ' p a2 ' p a3 ' p s

1 &p s0

1&p s

0

' 0.025&0.025

1&0.025 ' 0.00.975 ' 0.0

p a

4 '

p s

4 &p s0

1&p s

0

' 0.650&0.025

1&0.025 ' 0.06250.975 '0.641

p a

5 ' p s

5 &p s0

1&p s

0

' 1.000&0.025

1&0.025 ' 0.9750.975 ' 1.000

The smoothed, adjusted response proportions for the effluent concentrations are shown in Table J.2. A plot of the

smoothed, adjusted data is shown in Figure J.1.

9. Calculate the log10 of the estimated LC50, m, as follows:

m' '

k&1

i'1

(p a

i%1)(xi

%xi%1)

2

Where: pi

a

 = the smoothed adjusted proportion mortality at concentration i

Xi

 = the log10 of concentration i

k = the number of effluent concentrations tested, not including the control.
314

9.1 For this example, the log10 of the estimated LC50, m, is calculated as follows:

 m = [(0.000 - 0.000) (0.7959 + 1.0969)]/2 +

[(0.000 - 0.000) (1.0969 + 1.3979)]/2 +

[(0.641 - 0.000) (1.3979 + 1.6990)]/2 +

[(1.000 - 0.641) (1.6990 + 2.0000)]/2

= 1.656527 

 TABLE J.2. EXAMPLE OF SPEARMAN-KARBER METHOD: SMOOTHED, ADJUSTED

MORTALITY DATA FROM A FATHEAD MINNOW LARVAL SURVIVAL AND

GROWTH TEST

 

Smoothed,

Smoothed Adjusted

Effluent Mortality Mortality Mortality

Concentration Proportion Proportion Proportion

 

Control 0.05 0.025 0.000

6.25% 0.05 0.025 0.000

12.5% 0.00 0.025 0.000

25.0% 0.00 0.025 0.000

50.0% 0.65 0.650 0.641

100.0% 1.00 1.000 1.000

 

10. Calculate the estimated variance of m as follows:

V(m) ' '

k&1

i'2

p a

i (1&p ai )(Xi%1%Xi&1)

2

4(ni

&1)

Where: Xi = the log10 of concentration i

ni = the number of organisms tested at effluent concentration i 

 

pi

a = the smoothed adjusted observed proportion mortality at effluent concentration i

k = the number of effluent concentrations tested, not including the control.

10.1 For this example, the estimated variance of m, V(m), is calculated as follows:

 V(m) = (0.000)(1.000)(1.3979 - 0.7959)2

/4(39) +

(0.000)(1.000)(1.6990 - 1.0969)2

/4(39) +

(0.641)(0.359)(2.0000 - 1.3979)2

/4(39)

= 0.00053477
315

Figure J.1. Plot of the smoothed, adjusted data for the fathead minnow larval survival and growth test.
316

1.656527±2 0.00053477 ' (1.610277, 1.702777)

11. Calculate the 95% confidence interval for m: m±2.0 V(m)

11.1 For this example, the 95% confidence interval for m is calculated as follows:

12. The estimated LC50 and a 95% confidence interval for the estimated LC50 can be found by taking base10

antilogs of the above values.

12.1 For this example, the estimated LC50 is calculated as follows:

LC50 = antilog(m) = antilog(1.656527) = 45.3%.

12.2 The limits of the 95% confidence interval for the estimated LC50 are calculated by taking the antilogs of the

upper and lower limits of the 95% confidence interval for m as follows:

lower limit: antilog(1.610277) = 40.8%

upper limit: antilog(1.702777) = 50.4%
317

APPENDIX K

TRIMMED SPEARMAN-KARBER METHOD

1. The Trimmed Spearman-Karber Method is a modification of the Spearman-Karber Method, a nonparametric

statistical procedure for estimating the LC50 and the associated 95% confidence interval (Hamilton et al, 1977). 

Appendix The Trimmed Spearman-Karber Method estimates the trimmed mean of the distribution of the log10 of the

tolerance. If the log tolerance distribution is symmetric, this estimate of the trimmed mean is equivalent to an

estimate of the median of the log tolerance distribution.

2. If the response proportions are not monotonically non-decreasing with increasing concentration (constant or

steadily increasing with concentration), the data must be smoothed. Abbott's procedure is used to "adjust" the

concentration response proportions for mortality occurring in the control replicates.

3. Use of the Trimmed Spearman-Karber Analysis is recommended only when the requirements for the Probit

Method and the Spearman-Karber Method are not met.

4. To calculate the LC50 using the Trimmed Spearman-Karber Method, the smoothed, adjusted, observed

proportion mortalities must bracket 0.5.

5. To calculate the 95% confidence interval for the LC50 estimate, one or more of the smoothed, adjusted, observed

proportion mortalities must be between zero and one.

6. Let p 0, p 1, ..., p k denote the observed proportion mortalities for the control and the k effluent concentrations. 

The first step is to smooth the pi

 if they do not satisfy p 0 # p 1 # ... # p k. The smoothing process replaces any

adjacent pi

's that do not conform to p 0 # p 1 # ... # p k, with their average. For example, if pi is less than pi-1 then:

Where: pi

s

-1 = pi

s

 = (pi + pi-1)/2

pi

s

 = the smoothed observed proportion mortality for effluent concentration i.

7. Adjust the smoothed observed proportion mortality in each effluent concentration for mortality in the control

group using Abbott's formula (Finney, 1971). The adjustment takes the form:

Where: pi

a = (pis

 - p0

s

) / (1 - p0

s

)

p0

s = the smoothed observed proportion mortality for the control

pi

s = the smoothed observed proportion mortality for effluent concentration i.

8. Calculate the amount of trim to use in the estimation of the LC50 as follows:

Where: Trim = max(p1

a

, 1-pk

a

)

p1

a = the smoothed, adjusted proportion mortality for the lowest effluent concentration, exclusive of

the control

pk

a

 = the smoothed, adjusted proportion mortality for the highest effluent concentration

k = the number of effluent concentrations, exclusive of the control.

The minimum trim should be calculated for each data set rather than using a fixed amount of trim for each data set.
318

9. Due to the intensive nature of the calculation for the estimated LC50 and the calculation of the associated 95%

confidence interval using the Trimmed Spearman-Karber Method, it is recommended that the data be analyzed by

computer.

10. A computer program which estimates the LC50 and associated 95% confidence interval using the Trimmed

Spearman-Karber Method, can be obtained from EMSL-Cincinnati by sending a written request to EMSL, 3411

Church Street, Cincinnati, OH 45244.

11. The Trimmed Spearman-Karber program automatically performs the following functions:

a. Smoothing.

b. Adjustment for mortality in the control.

c. Calculation of the necessary trim.

d. Calculation of the LC50.

e. Calculation of the associated 95% confidence interval.

12. To illustrate the Trimmed Spearman-Karber method using the Trimmed Spearman-Karber computer program, a

set of data from a Fathead Minnow Larval Survival and Growth test will be used. The data are listed in Table K.1.

TABLE K.1. EXAMPLE OF TRIMMED SPEARMAN-KARBER METHOD: MORTALITY DATA

FROM A FATHEAD MINNOW LARVAL SURVIVAL AND GROWTH TEST 

(40 ORGANISMS PER CONCENTRATION)

 

Effluent Number of Mortality

Concentration Mortalities Proportion

% 

Control 2 0.05

6.25 0 0.00 

12.5 2 0.05 

25.0 0 0.00

50.0 0 0.00

100.0 32 0.80 

 

12.1 The program requests the following input (Figure K.1):

a. Output destination (D = disk file, P = printer).

 b. Control data.

c. Data for each toxicant concentration.

12.2 The program output includes the following (Figure K.2):

a. A table of the concentrations tested, number of organisms exposed, and mortalities.

b. The amount of trim used in the calculation.

c. The estimated LC50 and the associated 95% confidence interval.
319

A:>spearman 

 TRIMMED SPEARMAN-KARBER METHOD. VERSION 1.5 

 

ENTER DATE OF TEST: 

1

ENTER TEST NUMBER: 

2

WHAT IS TO BE ESTIMATED?

(ENTER "L" FOR LC50 AND "E" FOR EC50) 

 L 

ENTER TEST SPECIES NAME: 

Fathead minnow

ENTER TOXICANT NAME: 

Effluent 

ENTER UNITS FOR EXPOSURE CONCENTRATION OF TOXICANT:

%

ENTER THE NUMBER OF INDIVIDUALS IN THE CONTROL: 

 40 

ENTER THE NUMBER OF MORTALITIES IN THE CONTROL: 

2 

ENTER THE NUMBER OF CONCENTRATIONS 

(NOT INCLUDING THE CONTROL; MAX = 10): 

5 

ENTER THE 5 EXPOSURE CONCENTRATIONS (IN INCREASING ORDER): 

6.25 12.5 25 50 100

ARE THE NUMBER OF INDIVIDUALS AT EACH EXPOSURE CONCENTRATION EQUAL(Y/N)?

y 

ENTER THE NUMBER OF INDIVIDUALS AT EACH EXPOSURE CONCENTRATION: 40 

 

ENTER UNITS FOR DURATION OF EXPERIMENT 

(ENTER "H" FOR HOURS, "D" FOR DAYS, ETC.): 

Days 

ENTER DURATION OF TEST: 

7 

ENTER THE NUMBER OF MORTALITIES AT EACH EXPOSURE CONCENTRATION: 0 2 0 0 32 

 

WOULD YOU LIKE THE AUTOMATIC TRIM CALCULATION(Y/N)? 

 y 

Figure K.1. Example input for Trimmed Spearman-Karber Method.
320

TRIMMED SPEARMAN-KARBER METHOD. VERSION 1.5 

DATE: 1 TEST NUMBER: 2 DURATION: 7 Days 

TOXICANT: effluent 

SPECIES: fathead minnow

RAW DATA: Concentration Number Mortalities 

 --- ---- (%) Exposed 

.00 40 2 

6.25 40 0

12.50 40 2

25.00 40 0

50.00 40 0

100.00 40 32

SPEARMAN-KARBER TRIM: 20.41% 

SPEARMAN-KARBER ESTIMATES: LC50: 77.28 

95% CONFIDENCE LIMITS 

ARE NOT RELIABLE. 

NOTE: MORTALITY PROPORTIONS WERE NOT MONOTONICALLY INCREASING. 

ADJUSTMENTS WERE MADE PRIOR TO SPEARMAN-KARBER ESTIMATION. 

Figure K.2. Example output for Trimmed Spearman-Karber Method.
321

p s

0 ' p s1 ' p s2 ' p s3 ' 0.05%0.00%0.00%0.00

4 ' 0.054 ' 0.0125

APPENDIX L

GRAPHICAL METHOD

1. The Graphical Method is used to calculate the LC50. It is a mathematical procedure which estimates the LC50

by linearly interpolating between points of a plot of observed percent mortality versus the base 10 logarithm (log10)

of percent effluent concentration. This method does not provide a confidence interval for the LC50 estimate and its

use is only recommended when there are no partial mortalities. The only requirement for the Graphical Method is

that the observed percent mortalities bracket 50%.

2. For an analysis using the Graphical Method the data must first be smoothed and adjusted for mortality in the

control replicates. The procedure for smoothing and adjusting the data is detailed in the following steps.

3. The Graphical Method is illustrated below using a set of mortality data from an Fathead Minnow Larval Survival

and Growth test. These data are listed in Table L.1.

TABLE L.1. EXAMPLE OF GRAPHICAL METHOD: MORTALITY DATA FROM A FATHEAD

MINNOW LARVAL SURVIVAL AND GROWTH TEST (40 ORGANISMS PER

CONCENTRATION)

 

Effluent Number of Mortality

Concentration Mortalities Proportion

% 

Control 2 0.05

6.25 0 0.00 

12.5 0 0.00 

25.0 0 0.00

50.0 40 1.00

100.0 40 1.00 

 

4. Let p 0, p 1, ..., p k denote the observed proportion mortalities for the control and the k effluent concentrations. 

The first step is to smooth the p i if they do not satisfy p 0 # p 1 # ... # pk. The smoothing process replaces any

adjacent pi

's that do not conform to p 0 # p 1 # ... # p k with their average. For example, if pi is less than pi-1 then:

p s

i&1 ' p si ' (pi

%pi&1)/2

Where: pi

s

 = the smoothed observed proportion mortality for effluent concentration i.

4.1 For the data in this example, because the observed mortality proportions for the 6.25%, 12.5%, and 25.0%

effluent concentrations are less than the observed response proportion for the control, the values for these four

groups must be averaged:

4.2 Since p4 = p5 = 1.00 are larger then 0.0125, set p4

s

 = p5

s

 = 1.00. Additional smoothing is not necessary. The

smoothed observed proportion mortalities are shown in Table L.2.
322

TABLE L.2. EXAMPLE OF GRAPHICAL METHOD: SMOOTHED, ADJUSTED MORTALITY

DATA FROM A FATHEAD MINNOW LARVAL SURVIVAL AND GROWTH TEST

 

Smoothed,

Smoothed Adjusted

Effluent Mortality Mortality Mortality

Concentration Proportion Proportion Proportion

% 

Control 0.05 0.0125 0.00

6.25 0.00 0.0125 0.00

12.5 0.00 0.0125 0.00

25.0 0.00 0.0125 0.00

50.0 1.00 1.0000 1.00

100.0 1.00 1.0000 1.00

 

5. Adjust the smoothed observed proportion mortality in each effluent concentration for mortality in the control

group using Abbott's formula (Finney, 1971). The adjustment takes the form:

p a

i ' (p si &p s0 ) /(1&p s0 )

Where: p0

s = the smoothed observed proportion mortality for the control

 pi

s = the smoothed observed proportion mortality for effluent concentration i.

5.1 Because the smoothed observed proportion mortality for the control group is greater than zero, the responses

must be adjusted using Abbott's formula, as follows:

p a

0 ' p a1 ' p a2 ' p a3 ' p s

1 &p s0

1&p s

0

' 0.0125&0.0125

1 & 0.0125 ' 0.00.9875 ' 0.0

p a

4 ' p a5 ' p s

4 &p s0

1&p s

0

' 1.00 & 0.0125

1 &0.0125 ' 0.98750.9875 ' 1.00

A table of the smoothed, adjusted response proportions for the effluent concentrations are shown in Table L.2.

5.2 Plot the smoothed, adjusted data on 2-cycle semi-log graph paper with the logarithmic axis (the y axis) used for

percent effluent concentration and the linear axis (the x axis) used for observed percent mortality. A plot of the

smoothed, adjusted data is shown in Figure L.1.

6. Locate the two points on the graph which bracket 50% mortality and connect them with a straight line.

7. On the scale for percent effluent concentration, read the value for the point where the plotted line and the 50%

mortality line intersect. This value is the estimated LC50 expressed as a percent effluent concentration.

7.1 For this example, the two points on the graph which bracket the 50% mortality line (0% mortality at 25%

effluent, and 100% mortality at 50% effluent) are connected with a straight line. The point at which the plotted line

intersects the 50% mortality line is the estimated LC50. The estimated LC50 = 35% effluent.
323

Figure L.1 Plot of the smoothed adjusted response proportions for fathead minnow, Pimephales promelas, survival data.
324

APPENDIX M

LINEAR INTERPOLATION METHOD

1. GENERAL PROCEDURE

1.1 The Linear Interpolation Method is used to calculate a point estimate of the effluent or other toxicant

concentration that causes a given percent reduction (e.g., 25%, 50%, etc.) in the reproduction or growth of the test

organisms (Inhibition Concentration, or IC). The procedure was designed for general applicability in the analysis of

data from short-term chronic toxicity tests, and the generation of an endpoint from a continuous model that allows a

traditional quantitative assessment of the precision of the endpoint, such as confidence limits for the endpoint of a

single test, and a mean and coefficient of variation for the endpoints of multiple tests.

1.2 The Linear Interpolation Method assumes that the responses (1) are monotonically non-increasing, where the

mean response for each higher concentration is less than or equal to the mean response for the previous

concentration, (2) follow a piecewise linear response function, and (3) are from a random, independent, and

representative sample of test data. If the data are not monotonically nonincreasing, they are adjusted by smoothing

(averaging). In cases where the responses at the low toxicant concentrations are much higher than in the controls, the

smoothing process may result in a large upward adjustment in the control mean. Also, no assumption is made about

the distribution of the data except that the data within a group being resampled are independent and identically

distributed.

2. DATA SUMMARY AND PLOTS

2.1 Calculate the mean responses for the control and each toxicant concentration, construct a summary table, and

plot the data.

3. MONOTONICITY

3.1 If the assumption of monotonicity of test results is met, the observed response means ( ) should stay the same Y ̄ i

or decrease as the toxicant concentration increases. If the means do not decrease monotonically, the responses are

"smoothed" by averaging (pooling) adjacent means.

3.2 Observed means at each concentration are considered in order of increasing concentration, starting with the

control mean ( ). If the mean observed response at the lo Y ̄ west toxicant concentration ( ) is equal to or smaller 1 Y ̄2

than the control mean ( ), it is used as the response. If it Y ̄ is larger than the control mean, it is averaged with the 1

control, and this average is used for both the control response (M1) and the lowest toxicant concentration response

(M2). This mean is then compared to the mean observed response for the next higher toxicant concentration ( ). Y ̄3

Again, if the mean observed response for the next higher toxicant concentration is smaller than the mean of the

control and the lowest toxicant concentration, it is used as the response. If it is higher than the mean of the first two,

it is averaged with the first two, and the mean is used as the response for the control and two lowest concentrations of

toxicant. This process is continued for data from the remaining toxicant concentrations. A numerical example of

smoothing the data is provided below. (Note: Unusual patterns in the deviations from monotonicity may require an

additional step of smoothing). Where decrease monotonically, the become Mi Y ̄ without smoothing. i Y ̄ i

4. LINEAR INTERPOLATION METHOD

4.1 The method assumes a linear response from one concentration to the next. Thus, the ICp is estimated by linear

interpolation between two concentrations whose responses bracket the response of interest, the (p) percent reduction

from the control.

4.2 To obtain the estimate, determine the concentrations CJ and CJ+1 which bracket the response M1 (1 - p/100),

where M1 is the smoothed control mean response and p is the percent reduction in response relative to the control
325

ICp ' CJ % [ M1 (1 & p/100) & MJ ] (CJ % 1 & CJ

)

(MJ % 1 & MJ

)

response. These calculations can easily be done by hand or with a computer program as described below. The

linear interpolation estimate is calculated as follows:

Where: CJ = tested concentration whose observed mean response is greater than M1(1 - p/100).

CJ + 1 = tested concentration whose observed mean response is less than M1(1 - p/100).

M1 = smoothed mean response for the control.

MJ = smoothed mean response for concentration J.

MJ + 1 = smoothed mean response for concentration J + 1.

p = percent reduction in response relative to the control response.

ICp = estimated concentration at which there is a percent reduction from the smoothed mean control

response. The ICp is reported for the test, together with the 95% confidence interval

calculated by the ICPIN.EXE program described below.

4.3 If the CJ is the highest concentration tested, the ICp would be specified as greater than CJ. If the response at the

lowest concentration tested is used to extrapolate the ICp value, the ICp should be expressed as a less than the lowest

test concentration.

5. CONFIDENCE INTERVALS

5.1 Due to the use of a linear interpolation technique to calculate an estimate of the ICp, standard statistical methods

for calculating confidence intervals are not applicable for the ICp. This limitation is avoided by use a technique

known as the bootstrap method as proposed by Efron (1982) for deriving point estimates and confidence intervals.

5.2 In the Linear Interpolation Method, the smoothed response means are used to obtain the ICp estimate reported

for the test. The bootstrap method is used to obtain the 95% confidence interval for the true mean. In the bootstrap

method, the test data Yji is randomly resampled with replacement to produce a new set of data Yji*, that is statistically

equivalent to the original data, but a new and slightly different estimate of the ICp (ICp*) is obtained. This process is

repeated at least 80 times (Marcus and Holtzman, 1988) resulting in multiple "data" sets, each with an associate ICp*

estimate. The distribution of the ICp* estimates derived from the sets of resampled data approximates the sampling

distribution of the ICp estimate. The standard error of the ICp is estimated by the standard deviation of the

individual ICp* estimates. Empirical confidence intervals are derived from the quantiles of the ICp* empirical

distribution. For example, if the test data are resampled a minimum of 80 time, the empirical 2.5% and the 97.5%

confidence limits are approximately the second smallest and second largest ICp* estimates (Marcus and Holtzman,

1988). 

5.3 The width of the confidence intervals calculated by the bootstrap method is related to the variability of the data. 

When confidence intervals are wide, the reliability of the IC estimate is in question. However, narrow intervals do

not necessarily indicate that the estimate is highly reliable, because of undetected violations of assumptions and the

fact that the confidence limits based on the empirical quantiles of a bootstrap distribution of 80 samples may be

unstable.

5.4 The bootstrapping method of calculating confidence intervals is computationally intensive. For this reason, all

of the calculations associated with determining the confidence intervals for the ICp estimate have been incorporated

into a computer program. Computations are most easily done with a computer program such as the revision of the
326

BOOTSTRP program (USEPA, 1988; USEPA, 1989) which is now called "ICPIN" which is described below in

subsection 7.

6. MANUAL CALCULATIONS

6.1 DATA SUMMARY AND PLOTS

6.1.1 The data used in this example are the Ceriodaphnia dubia reproduction data used in the example in Section

13. Table M.1 includes the raw data and the mean reproduction for each concentration. Data are included for all

animals tested regardless of death of the organism. If an animal died during the test without producing young, a zero

is entered. If death occurred after producing young, the number of young produced prior to death is entered. A plot

of the data is provided in Figure M.1.

TABLE M.1. CERIODAPHNIA DUBIA REPRODUCTION DATA 

Effluent Concentration (%)

Replicate Control 1.56 3.12 6.25 12.5 25.0

1 27 32 39 27 10 0

2 30 35 30 34 13 0

3 29 32 33 36 70

4 31 26 33 34 70

5 16 18 36 31 70

6 15 29 33 27 10 0

7 18 27 33 33 10 0

8 17 16 27 31 16 0

9 14 35 38 33 12 0

10 27 13 44 31 2 0

Mean ( ) Y ̄ 22.4 26.3 34.6 31.7 9.4 0 i

i 1 2 3 4 56

6.2 MONOTONICITY

6.2.1 As can be seen from the plot in Figure M.1, the observed means are not monotonically non-increasing with

respect to concentration. Therefore, the means must be smoothed prior to calculating the IC.

6.2.2 Starting with the control mean Y'1 = 22.4 and Y'2 = 26.3, we see that Y'1 < Y'2 . Calculate the smoothed means:

M1 ' M2 ' (Y ̄

1 % Y ̄2)/2 ' 24.35

6.2.3 Since Y'3 = 34.6 is larger than M2, average Y'3 with the previous concentrations:

6.2.4 Additionally, Y'4 = 31.7 is larger than M3, and is pooled with the first three means. Thus, 

M1 ' M2 ' M3 ' M4 ' ( M1 % M2 % M3 % Y ̄

4 )/4 ' 28.7
327

Figure M.1. Plot of raw data, observed means, and smoothed means for the daphnid, Ceriodaphnia dubia, reproductive data.
328

TABLE M.2. CERIODAPHNIA DUBIA REPRODUCTION MEAN RESPONSE AFTER

SMOOTHING

Effluent Response Smoothed 

Concentration Mean (Yi

) Mean (Mi)

% i (Young/female) (Young/female)

Control 1 22.4 28.75

1.56 2 26.3 28.75

3.12 3 34.6 28.75

6.25 4 31.7 28.75

12.5 5 9.4 9.40

25.0 6 0.0 0.00

6.2.5 Since M4 > Y'5 = 9.4, set M5 = 9.4. Likewise, M5 > Y'6 = 0 and M6 becomes 0. Table M.2 contains the 

smoothed means and Figure M.1 gives a plot of the smoothed response curve.

6.3 LINEAR INTERPOLATION

6.3.1 Estimates of the IC25 and IC50 are calculated using the Linear Interpolation Method. A 25% reduction in

reproduction, compared to the controls, would result in a mean reproduction of 21.56 young per adult, where M1(1-

p/100) = 28.75(1-25/100). A 50% reduction in reproduction, compared to the controls, would result in a mean

reproduction of 14.38 young per adult, where M1(1-p/100) = 28.75(1-50/100). Examining the smoothed means and

their associated concentrations (Table M.2), the two effluent concentrations bracketing the reproduction of 21.56

young per adult are C4 = 6.25% effluent and C5 = 12.5% effluent. The two effluent concentrations bracketing a

response of 14.38 young per adult are also C4 = 6.25% effluent and C5 = 12.5% effluent. 

6.3.2 Using Equation 1 from 4.2, the estimate of the IC25 is calculated as follows:

ICp ' CJ % [ M1 (1 & p/100) & MJ ] (CJ % 1 & CJ

)

(MJ % 1 & MJ

)

 

IC25 ' 6.25 % [28.75 (1 & 25/100) & 28.75] (12.5 & 6.25)

(9.40 & 28.75)

= 8.57% effluent

6.3.3 Using the equation from section 4.2, the estimate of the IC50 is calculated as follows:

ICp ' CJ % [ M1 (1 & p/100) & MJ ] (CJ % 1 & CJ

)

(MJ % 1 & MJ

)

 IC50 ' 6.25 % [28.75 (1 & 50/100) & 28.75] (12.5 & 6.25)

(9.40 & 28.75)

= 10.89% effluent
329

6.4 CONFIDENCE INTERVALS

6.4.1 Confidence intervals for the ICp are derived using the bootstrap method. As described above, this method

involves randomly resampling the individual observations and recalculating the ICp at least 80 times, and

determining the mean ICp, standard deviation, and empirical 95% confidence intervals. For this reason, the

confidence intervals are calculated using a computer program called ICPIN. This program is described below and is

available to carry out all the calculations of both the interpolation estimate (ICp) and the confidence intervals.

7. COMPUTER CALCULATIONS

7.1 The computer program, ICPIN, prepared for the Linear Interpolation Method was written in TURBO PASCAL

for IBM compatible PCs. The program (version 2.0) has been modified by Computer Science Corporation, Duluth,

MN with funding provided by the Environmental Research Laboratory, Duluth, MN (Norberg-King, 1993). The

program was originally developed by Battelle Laboratories, Columbus, OH through a government contract supported

by the Environmental Research Laboratory, Duluth, MN (USEPA, 1988). To obtain the program and supporting

documentation, send a written request to EMSL-Cincinnati at 3411 Church Street, Cincinnati, OH 45244.

7.2 The ICPIN.EXE program performs the following functions: 1) it calculates the observed response means (Yi

)

(response means); 2) it calculates the standard deviations; 3) checks the responses for monotonicity; 4) calculates

smoothed means (Mi

) (pooled response means) if necessary; 5) uses the means, Mi, to calculate the initial ICp of

choice by linear interpolation; 6) performs a user-specified number of bootstrap resamples between 80 and 1000 (as

multiples of 40); 7) calculates the mean and standard deviation of the bootstrapped ICp estimates; and 8) provides an

original 95% confidence intervals to be used with the initial ICp when the number of replicates per concentration is

over six and provides both original and expanded confidence intervals when the number of replicates per

concentration are less than seven (Norberg-King, 1993).

7.3 For the ICp calculation, up to twelve treatments can be used (which includes the control). There can be up to 40

replicates per concentration, and the program does not require an equal number of replicates per concentration. The

value of p can range from 1% to 99%.

7.4 DATA INPUT

7.4.1 Data is entered directly into the program onscreen. A sample data entry screen in shown in Figure M.2. The

program documentation provides guidance on the entering and analysis of data for the Linear Interpolation Method

(Norberg-King, 1993).

7.4.2 The user selects the ICp estimate desired (e.g., IC25 or IC50) and the number of resamples to be taken for the

bootstrap method of calculating the confidence intervals. The program has the capability of performing any number

of resamples from 80 to 1000 as multiples of 40. However, Marcus and Holtzman (1988) recommend a minimum of

80 resamples for the bootstrap method be used and at least 250 resamples are better (Norberg-King, 1993).

7.5 DATA OUTPUT.

7.5.1 The program output includes the following (Figures M.3 and M.4):

1. A table of the concentration identification, the concentration tested and raw data response for each

replicate and concentration.

2. A table of test concentrations, number of replicates, concentration (units), response means (Y ̄i

),

standard deviations for each response mean, and the pooled response means (smoothed means; Mi

).

3. The linear interpolation estimate of the ICp using the means (Mi

). Use this value for the ICp estimate.

4. The mean ICp and standard deviation from the bootstrap resampling.

5. The confidence intervals calculated by the bootstrap method for the ICp. Provides an original 95%

confidence intervals to be used with the initial ICp when the number of replicates per concentration is
330

over six and provides both original and expanded confidence intervals when the number of replicates

per concentration are less than seven.

7.6 ICPIN program output for the analysis of the Ceriodaphnia dubia reproduction data in Table M.1 is provided in

Figures M.3 and M.4.

7.6.1 When the ICPIN program was used to analyze this set of data, requesting 80 resamples, the estimate of the

IC25 was 8.57% effluent. The empirical 95% confidence intervals for the true mean were 8.30% to 8.85% effluent.

7.6.2 When the ICPIN program was used to analyze this set of data, requesting 80 resamples, the estimate of the

IC50 was 10.89% effluent. The empirical 95% confidence intervals for the true mean were 10.36% to 11.62%

effluent.
331

ICp Data Entry/Edit Screen Current File:

Conc. ID1 2 3 4 5 6

Conc. Tested

Conc. Tested

Response 1

Response 2

Response 3

Response 4

Response 5

Response 6

Response 7

Response 8

Response 9

Response 10

Response 11

Response 12

Response 13

Response 14

Response 15

Response 16

Response 17

Response 18

Response 19

Response 20

F10 for Command Menu Use arrow Keys to Switch Fields

Figure M.2. ICp data entry/edit screen. Twelve concentrating identifications can be used. Data for concentrations

are entered in columns 1 through 6. For concentrations 7 through 12 and responses 21-40 the data is

entered in additional fields of the same screen.
332

Conc. ID 1 2 3 4 5 6

Conc. Tested 0 1.56 3.12 6.25 12.5 25.0

Response 1 27 32 39 27 10 0

Response 2 30 35 30 34 13 0

Response 3 29 32 33 36 7 0

Response 4 31 26 33 34 7 0

Response 5 16 18 36 31 7 0

Response 6 15 29 33 27 10 0

Response 7 18 27 33 33 10 0

Response 8 17 16 27 31 16 0

Response 9 14 35 38 33 12 0

Response 10 27 13 44 31 2 0

*** Inhibition Concentration Percentage Estimate ***

Toxicant/Effluent: 

Test Start Date: app M Test Ending Date: 

Test Species: Ceriodaphnia dubia

Test Duration: 7-d

DATA FILE: cerioman.icp

OUTPUT FILE: cerioman.i25

Conc. Number Concentration Response Std. Pooled

 ID Replicates % Means Dev. Response Means

 1 10 0.000 22.400 6.931 28.750

 2 10 1.560 26.300 8.001 28.750

 3 10 3.120 34.600 4.835 28.750

 4 10 6.250 31.700 2.946 28.750

 5 10 12.500 9.400 3.893 9.400

 6 10 25.000 0.000 0.000 0.000

The Linear Interpolation Estimate: 8.5715 Entered P Value: 25

Number of Resamplings: 80

The Bootstrap Estimates Mean: 8.6014 Standard Deviation: 0.1467

Original Confidence Limits: Lower: 8.3040 Upper: 8.8496

Resampling time in Seconds: 2.53 Random Seed: -1652543090

Figure M.3. Example of ICPIN program output for the IC25.
333

Conc. ID 1 2 3 4 5 6

Conc. Tested 0 1.56 3.12 6.25 12.5 25.0

Response 1 27 32 39 27 10 0

Response 2 30 35 30 34 13 0

Response 3 29 32 33 36 7 0

Response 4 31 26 33 34 7 0

Response 5 16 18 36 31 7 0

Response 6 15 29 33 27 10 0

Response 7 18 27 33 33 10 0

Response 8 17 16 27 31 16 0

Response 9 14 35 38 33 12 0

Response 10 27 13 44 31 2 0

*** Inhibition Concentration Percentage Estimate ***

Toxicant/Effluent: 

Test Start Date: app M Test Ending Date: 

Test Species: Ceriodaphnia dubia

Test Duration: 7-d

DATA FILE: cerioman.icp

OUTPUT FILE: cerioman.i50

Conc. Number Concentration Response Std. Pooled

 ID Replicates % Means Dev. Response Means

 1 10 0.000 22.400 6.931 28.750

 2 10 1.560 26.300 8.001 28.750

 3 10 3.120 34.600 4.835 28.750

 4 10 6.250 31.700 2.946 28.750

 5 10 12.500 9.400 3.893 9.400

 6 10 25.000 0.000 0.000 0.000

The Linear Interpolation Estimate: 10.8931 Entered P Value: 50

Number of Resamplings: 80

The Bootstrap Estimates Mean: 10.9108 Standard Deviation: 0.3267

Original Confidence Limits: Lower: 10.3618 Upper: 11.6201

Resampling time in Seconds: 2.58 Random Seed: 340510286

Figure M.4. Example of ICPIN program output for the IC50.
334

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