Analytical Feasibility Support Document for the Second Six-Year Review of 

Existing National Primary Drinking Water Regulations
Office of Water (4607M)

EPA 815-B-09-003 

October 2009 

www.epa.gov/safewater
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

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Acknowledgments

Thanks to Mr. Shawn Kassner and Dr. Mark Carter (formerly) of Environmental 

Resource Associates (ERA; now ERA - A Waters Company) for sharing their expertise and their 

PT data.
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Executive Summary

The Safe Drinking Water Act (SDWA), as amended in 1996, requires the Environmental 

Protection Agency (EPA) to review and revise, if appropriate, existing National Primary 

Drinking Water Regulations (NPDWRs). Review involves consideration of five key elements, 

as appropriate: health effects, analytical and treatment feasibility, implementation-related issues, 

occurrence and exposure, and economic impact. This report addresses the analytical feasibility 

aspect of the review which has been based on the laboratories' analytical performance data 

generated as part of the EPA's certification program for drinking water laboratories. This 

analytical feasibility assessment is based jointly on the recent analytical performance data 

collected during the second six year review as well as on earlier data collected during the first six 

year review. Efforts are also made to determine if the analytical performance assessments based 

on the laboratory data are supported by the approval of improved methods or revision of existing 

methods since the last review. The goal is to create a comprehensive document that addresses all 

regulated chemical analytes for which data are available.

Analytical Performance Assessment Based on the Laboratories' Analytical Performance Data

The Practical Quantitation Level (PQL) assessments are presented by way of linear 

regressions that plot laboratory passing rate versus true concentration. The PQL is defined as 

"the lowest achievable level of analytical quantitation during routine laboratory operating 

conditions within specified limits of precision and accuracy" (50 FR 46902, November 13, 

1985). It has been set at the concentration where 75% of laboratories are predicted to meet 

acceptance criteria. PQL determination can be a useful tool in assessing whether promulgated 

PQLs can be reduced as a result of improved laboratory performance over time. 

The Six-Year 1 laboratory passing rate data were generated during the EPA-administered 

Performance Evaluation (PE) Program from the late 1980s through late 1999, at which time, the 

laboratory performance program became privatized under the direction of the National 

Environmental Laboratory Accreditation Conference (NELAC; now The NELAC Institute - 

TNI). The current report includes PQL assessments for all available Six-Year 1 PE data and 

more recent laboratory passing rate data that were generated under the TNI Proficiency Testing 

(PT) program. Environmental Resource Associates (ERA) was the only provider of PT samples 

to the testing laboratories that was willing to share PT data with EPA. ERA estimates that during 

the period from late 1999 through 2006, they have accounted for approximately 50% of all PT

results nationwide. 

For non-radionuclides, the ERA dataset encompasses the period from late 1999 through 

2004. ERA data for radionuclides were generated from 2002-2006. Note that for the 

radionuclides, limitations of laboratory performance at low concentrations is generally not an 

issue, as PQLs can be lowered, if necessary, by increasing sample volume and/or radiological 

analysis duration. Thus, though the radionuclide PT data are evaluated in this report (see 

Appendix B) for completeness, no conclusions are drawn regarding changes to PQLs. 

The results for the regulated analytes are broken down into two categories based on the 

limitation of the PQL for setting the Maximum Contaminant Level (MCL) at the time of 
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promulgation: 1) analytes with MCL equal to the current PQL, and thus the PQL is limiting; or 

2) analytes with MCL greater than the current PQL and thus it is technically feasible to reduce an 

MCL. PQL assessment for this second group of analytes can indicate the potential for MCL 

reduction beyond the current PQL. Using this as a framework, the PQL assessments based on 

the PT/PE data were made and are presented in this report for a total of 66 analytes. Four 

analytes could not be analyzed for the reasons stated: acrylamide, epichlorohydrin, 2,3,7,8-

TCDD (dioxin) lacked PE/PT data, and chlorite has no PQL. The recommendations for PQL 

assessment are as follows:

• For 25 analytes, the PQL is equal to the MCL and hence the PQL is limiting. Of these 25 

analytes, PQL assessment indicates that:

– The PQL can be reduced for 9 analytes: benzene, carbon tetrachloride, chlordane, 

1,2-dichloroethane, 1,2-dichloropropane, hexachlorobenzene, tetrachloroethylene, 

1,1,2-trichloroethane, and trichloroethylene; 

– The PQL might be considered for reduction for 8 analytes: alachlor, antimony, 1,2-

dibromo-3-chloropropane (DBCP), heptachlor, heptachlor epoxide, lindane, 

toxaphene, and vinyl chloride; and 

– PT data do not support reduction of the PQL or data are inconclusive or insufficient 

to reach a conclusion for 8 analytes: benzo(a)pyrene, bromate, dichloromethane, 

di(2-ethylhexyl)phthalate (DEHP), ethylene dibromide (EDB), pentachlorophenol, 

polychlorinatedbiphenyls (PCBs), and thallium. 

• For 41 analytes, the PQL is less than the MCL; hence the MCL can be reduced. For these 

41 analytes, PQL assessment indicates that:

– The PQL can be reduced further (beyond the current PQL) for 11 analytes: barium, 

1,4-dichlorobenzene, cis-1,2-dichloroethylene, 1,1-dichloroethylene, ethylbenzene, 

monochlorobenzene, nitrite, styrene, toluene, 1,2,4-trichlorobenzene, and 1,1,1-

trichloroethane; 

– The PQL might be considered for further reduction for 6 analytes: atrazine, 

carbofuran, trans-1,2-dichloroethylene, hexachlorocyclopentadiene, methoxychlor, 

and 2,4,5-TP (Silvex); and

– PE/PT data do not support further reduction of the PQL or data are inconclusive or 

insufficient to reach a conclusion for 24 analytes: arsenic, beryllium, cadmium, 

chromium, copper, cyanide, dalapon, 1,2-dichlorobenzene, 2,4-dichlorophenoxyacetic 

acid (2,4-D), di(2-ethylhexyl)adipate, dinoseb, diquat, endothall, endrin, fluoride, 

glyphosate, lead, mercury, nitrate, oxamyl, picloram, selenium, simazine, and 

xylenes. 

Analytical Performance Assessment Based on New Methods Approval/Revision of Existing 

Methods

For those analytes with new methods, improved analytical performance (and hence, 

possible reduction of the PQL) may be suggested by lower detection limits from new methods. 

The existence of new methods with lower detection limits may not directly translate to improved 
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analytical performance, however. It is possible that only a small number of laboratories will use 

a new method, or it may take time for the method to be utilized to its full effectiveness.

Improved analytical performance (and hence, possible PQL reduction) may also be 

supported by the approval and availability of new or revised analytical methods with lower 

MDLs (note that in some analytical methods, the term DL is used instead of MDL, but these 

quantities are essentially equivalent). For 15 regulated analytes, new methods have been 

approved. For 12 of these analytes (bromate, carbofuran, 2,4-D, dalapon, dinoseb, fluoride, 

mercury, nitrite, oxamyl, pentachlorophenol, picloram and 2,4,5-TP), the MDLs are lower (or 

their range of MDLs includes values that are lower) than those from earlier-approved methods. 

In two cases (atrazine and cyanide), the methods are proprietary and are not readily available; 

hence, MDLs are not known, and comparison cannot be made. Lastly, in one case (nitrate), new 

or revised methods do not indicate a lower MDL. 

Overall, the results show that only for 20 of the 66 analytes evaluated in this report, 

laboratory performance data was sufficient to qualitatively conclude that the PQL can be 

lowered. For 14 analytes there were indications for a lower PQL but for the remaining 32 either 

the data were inconclusive or insufficient to draw a conclusion. Furthermore, for only 3 of the 

20 analytes for which PQL could be lowered, the improved analytical performance was 

supported by new and improved methods approval. For others, there was either no correlation or 

correlation could not be made due to insufficient data. 
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Abbreviations and Acronyms 

μg/L Micrograms per liter

mg/L Milligrams per liter

Der. Derivatization

ACVT Automated Cold Vapor Technique 

AES Atomic Emission Spectrometry 

APG Analytical Products Group, Inc. 

ASTM American Society for Testing and Materials

CASRN Chemical Abstracts Service Registry Number

CBI Confidential Business Information 

CCGC Capillary Column Gas Chromatography 

CUV Coupled Ultraviolet 

CVAAS Cold Vapor Atomic Absorption Spectrometry 

CVAFS Cold Vapor Atomic Fluorescence Spectrometry

CFR Code of Federal Regulations

2,4-D 2,4-Dichlorphenoxyacetic acid

DAI Direct Aqueous Injection

DBCP 1,2-Dibromo-3-chloropropane 

DCBP Decachlorobiphenyl 

DEHA Di(2-ethylhexyl)adipate

DEHP Di(2-ethylhexyl)phthalate

DL Detection Limit

ECD Electron Capture Detection 

ECGC Electron Capture Gas Chromatography 

EDB Ethylene Dibromide (1,2-dibromoethane) 

ELCD Electrolytic Conductivity Detector

EPA United States Environmental Protection Agency 

ERA Environmental Resource Associates (name changed to ERA - A 

Waters Company, effective July 10, 2009) 

FD Fluorescence Detection

FR Federal Register

GC Gas Chromatography 

GFAA Graphite Furnace Atomic Absorption 

HPLC High Performance Liquid Chromatography 

IC Ion Chromatography 

ICP Inductively Coupled Plasma 

ICR Information Collection Request 

I-EE Ion-Exchange Extraction

I-ELSE Ion-Exchange Liquid/Solid Extraction 

IMDL Interlaboratory Method Detection Limit

LLE Liquid/Liquid Extraction 

LLED Liquid/Liquid Extraction and Derivatization 

LLMED Liquid/Liquid Microextraction and Derivatization 

L/S Liquid/Solid

LSE Liquid/Solid Extraction
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MCL Maximum Contaminant Level

MCLG Maximum Contaminant Level Goal

MDL Method Detection Limit

ME Microextraction

ML Minimum Level

MLPD Multi-Laboratory Performance Data

MRL Minimum Reporting Level

MS Mass Spectrometry

NDWAC National Drinking Water Advisory Council 

NELAC National Environmental Laboratory Accreditation Conference 

NERL National Exposure Research Laboratory 

N-PD Nitrogen-Phosphorus Detector 

NPDWR National Primary Drinking Water Regulation

OLS Ordinary Least Squares

PCB Polychlorinatedbiphenyl 

PDAUVD Photodiode Array Ultraviolet Detector 

PE Performance Evaluation

PID Photoionization Detector 

PQL Practical Quantitation Level

PT Proficiency Testing

QA Quality Assurance 

QC Quality Control 

RDL Regulatory Detection Limit

SD Standard Deviation(s) 

SDWA Safe Drinking Water Act

TNI The NELAC Institute

TT Treatment Technique 

2,4,5-TP 2-(2,4,5-Trichlorophenoxy)propionic acid 

U.S.C. United States Code 

USEPA United States Environmental Protection Agency 

UVD Ultraviolet Detection

VOC Volatile Organic Compound 
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Executive Summary ...................................................................................................................... ii

Abbreviations and Acronyms ...................................................................................................... v

1.0 Introduction ....................................................................................................................... 1

2.0 Background ....................................................................................................................... 2

3.1 BIAS ............................................................................................................................................................ 9

2.3 OPERATIONAL DETAILS OF THE PE/PT PROGRAMS..................................................................................... 6

2.4 EFFORTS MADE TO OBTAIN PT DATA......................................................................................................... 8

3.0 Representativeness of Available Data PT ....................................................................... 8

2.1 RELATIONSHIP BETWEEN SDWA REQUIREMENTS AND ANALYTICAL METHODS ....................................... 2

2.2 PQL DETERMINATION METHODS FOR THE SDWA CONTAMINANTS........................................................... 3

3.2 PRECISION ................................................................................................................................................... 9

3.3 THE REGRESSION MODEL..........................................................................................................................10

4.0 Identification of Regulated Analytes for PQL Assessment ......................................... 11

5.0 Second Six-Year Review PQL Assessment Methodology............................................ 15

5.1 DATA AVAILABLE FOR PQL ASSESSMENT................................................................................................15

5.2 CALCULATING NATIONAL PASSING RATES ...............................................................................................19

5.3 REGRESSION PLOTS...................................................................................................................................20

6.0 Results of PQL Assessment ............................................................................................ 21

6.1 ANALYTES WITH MAXIMUM CONTAMINANT LEVEL (MCL) EQUAL TO THE CURRENT PQL AND THUS THE 

PQL IS LIMITING......................................................................................................................................................22

6.1.1 PQL Assessment Supports Reduction of the Current PQL ..................................................................22

Benzene ..............................................................................................................................................................23

Results of the Methods Comparison .......................................................................................................................... 23

Results of the PQL Analysis...................................................................................................................................... 23

Conclusion for Benzene............................................................................................................................................. 24

Carbon Tetrachloride ........................................................................................................................................25

Results of the Methods Comparison .......................................................................................................................... 25

Results of the PQL Analysis...................................................................................................................................... 25

Conclusion for Carbon Tetrachloride ........................................................................................................................ 26

Chlordane ..........................................................................................................................................................27

Results of the Methods Comparison .......................................................................................................................... 27

Results of the PQL Analysis...................................................................................................................................... 27

Conclusion for Chlordane.......................................................................................................................................... 28

1,2-Dichloroethane (Ethylene dichloride) .........................................................................................................29

Results of the Methods Comparison .......................................................................................................................... 29

Results of the PQL Analysis...................................................................................................................................... 29

Conclusion for 1,2-Dichloroethane............................................................................................................................ 30

1,2-Dichloropropane..........................................................................................................................................31

Results of the Methods Comparison .......................................................................................................................... 31

Results of the PQL Analysis...................................................................................................................................... 31

Conclusion for 1,2-Dichloropropane ......................................................................................................................... 32

Hexachlorobenzene............................................................................................................................................33

Results of the Methods Comparison .......................................................................................................................... 33

Results of the PQL Analysis...................................................................................................................................... 33

Conclusion for Hexachlorobenzene ........................................................................................................................... 34

TABLE OF CONTENTS

Acknowledgments.......................................................................................................................... i
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Tetrachloroethylene ...........................................................................................................................................35

Results of the Methods Comparison .......................................................................................................................... 35

Results of the PQL Analysis...................................................................................................................................... 35

Conclusion for Tetrachloroethylene........................................................................................................................... 36

1,1,2-Trichloroethane ........................................................................................................................................37

Results of the Methods Comparison .......................................................................................................................... 37

Results of the PQL Analysis...................................................................................................................................... 37

Conclusion for 1,1,2-Trichloroethane........................................................................................................................ 38

Trichloroethylene ...............................................................................................................................................39

Results of the Methods Comparison .......................................................................................................................... 39

Results of the PQL Analysis...................................................................................................................................... 39

Conclusion for Trichloroethylene .............................................................................................................................. 40

6.1.2 PQL Assessment May Support Reduction of the Current PQL............................................................41

Alachlor..............................................................................................................................................................41

Results of the Methods Comparison .......................................................................................................................... 41

Results of the PQL Analysis...................................................................................................................................... 41

Conclusion for Alachlor............................................................................................................................................. 42

Antimony ............................................................................................................................................................43

Results of the Methods Comparison .......................................................................................................................... 43

Results of the PQL Analysis...................................................................................................................................... 43

Conclusion for Antimony .......................................................................................................................................... 44

1,2-Dibromo-3-chloropropane (DBCP).............................................................................................................45

Results of the Methods Comparison .......................................................................................................................... 45

Results of the PQL Analysis...................................................................................................................................... 45

Conclusion for 1,2-Dibromo-3-chloropropane .......................................................................................................... 46

Heptachlor .........................................................................................................................................................47

Results of the Methods Comparison .......................................................................................................................... 47

Results of the PQL Analysis...................................................................................................................................... 47

Conclusion for Heptachlor......................................................................................................................................... 48

Heptachlor Epoxide ...........................................................................................................................................49

Results of the Methods Comparison .......................................................................................................................... 49

Results of the PQL Analysis...................................................................................................................................... 49

Conclusion for Heptachlor Epoxide........................................................................................................................... 50

Lindane ..............................................................................................................................................................51

Results of the Methods Comparison .......................................................................................................................... 51

Results of the PQL Analysis...................................................................................................................................... 51

Conclusion for Lindane ............................................................................................................................................. 52

Toxaphene..........................................................................................................................................................53

Results of the Methods Comparison .......................................................................................................................... 53

Results of the PQL Analysis...................................................................................................................................... 53

Conclusion for Toxaphene......................................................................................................................................... 54

Vinyl Chloride....................................................................................................................................................55

Results of the Methods Comparison .......................................................................................................................... 55

Results of the PQL Analysis...................................................................................................................................... 55

Conclusion for Vinyl Chloride................................................................................................................................... 56

6.1.3 PQL Assessment Does Not Support Reduction of the Current PQL or Data are Insufficient to Reach a 

Conclusion. ........................................................................................................................................................57

Benzo(a)pyrene ..................................................................................................................................................57

Results of the Methods Comparison .......................................................................................................................... 57

Results of the PQL Analysis...................................................................................................................................... 57

Conclusion for Benzo(a)pyrene ................................................................................................................................. 58

Bromate..............................................................................................................................................................59

Results of the Methods Comparison .......................................................................................................................... 59

Results of the PQL Analysis...................................................................................................................................... 59

Conclusion for Bromate............................................................................................................................................. 60

Dichloromethane (Methylene chloride) .............................................................................................................61

Results of the Methods Comparison .......................................................................................................................... 61

Results of the PQL Analysis...................................................................................................................................... 61

Conclusion for Dichloromethane............................................................................................................................... 62
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Di(2-ethylhexyl)phthalate (DEHP) ....................................................................................................................63

Results of the Methods Comparison .......................................................................................................................... 63

Results of the PQL Analysis...................................................................................................................................... 63

Conclusion for Di(2-ethylhexyl)phthalate ................................................................................................................. 64

Ethylene dibromide (EDB)................................................................................................................................. 65

Results of the Methods Comparison .......................................................................................................................... 65

Results of the PQL Analysis...................................................................................................................................... 65

Conclusion for Ethylene Dibromide .......................................................................................................................... 66

Pentachlorophenol.............................................................................................................................................67

Results of the Methods Comparison .......................................................................................................................... 67

Results of the PQL Analysis...................................................................................................................................... 67

Conclusion for Pentachlorophenol............................................................................................................................. 68

Polychlorinatedbiphenyls (PCBs) as Decachlorobiphenyl (DCBP)..................................................................69

Results of the Methods Comparison .......................................................................................................................... 69

Results of the PQL Analysis...................................................................................................................................... 70

Conclusion for Polychlorinatedbiphenyls.................................................................................................................. 70

Thallium .............................................................................................................................................................71

Results of the Methods Comparison .......................................................................................................................... 71

Results of the PQL Analysis...................................................................................................................................... 71

Conclusion for Thallium............................................................................................................................................ 72

6.2 ANALYTES WITH MAXIMUM CONTAMINANT LEVEL (MCL) GREATER THAN THE CURRENT PQL AND 

THUS IT IS TECHNICALLY FEASIBLE TO REDUCE AN MCL.......................................................................................73

6.2.1 PQL Assessment Supports Reduction of the Current PQL ..................................................................73

Barium................................................................................................................................................................73

Results of the Methods Comparison .......................................................................................................................... 73

Results of the PQL Analysis...................................................................................................................................... 73

Conclusion for Barium .............................................................................................................................................. 74

1,4-Dichlorobenzene ..........................................................................................................................................75

Results of the Methods Comparison .......................................................................................................................... 75

Results of the PQL Analysis...................................................................................................................................... 75

Conclusion for 1,4-Dichlorobenzene ......................................................................................................................... 76

cis-1,2-Dichloroethylene....................................................................................................................................77

Results of the Methods Comparison .......................................................................................................................... 77

Results of the PQL Analysis...................................................................................................................................... 77

Conclusion for cis-1,2-Dichloroethylene ................................................................................................................... 78

1,1-Dichloroethylene..........................................................................................................................................79

Results of the Methods Comparison .......................................................................................................................... 79

Results of the PQL Analysis...................................................................................................................................... 79

Conclusion for 1,1-Dichloroethylene......................................................................................................................... 80

Ethylbenzene ......................................................................................................................................................81

Results of the Methods Comparison .......................................................................................................................... 81

Results of the PQL Analysis...................................................................................................................................... 81

Conclusion for Ethylbenzene..................................................................................................................................... 82

Monochlorobenzene (Chlorobenzene) ...............................................................................................................83

Results of the Methods Comparison .......................................................................................................................... 83

Results of the PQL Analysis...................................................................................................................................... 83

Conclusion for Monochlorobenzene.......................................................................................................................... 84

Nitrite (as N) ......................................................................................................................................................85

Results of the Methods Comparison .......................................................................................................................... 85

Results of the PQL Analysis...................................................................................................................................... 85

Conclusion for Nitrite ................................................................................................................................................ 86

Styrene................................................................................................................................................................87

Results of the Methods Comparison .......................................................................................................................... 87

Results of the PQL Analysis...................................................................................................................................... 87

Conclusion for Styrene .............................................................................................................................................. 88

Toluene...............................................................................................................................................................89

Results of the Methods Comparison .......................................................................................................................... 89

Results of the PQL Analysis...................................................................................................................................... 89

Conclusion for Toluene ............................................................................................................................................. 90
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1,2,4-Trichlorobenzene ......................................................................................................................................91

Results of the Methods Comparison .......................................................................................................................... 91

Results of the PQL Analysis...................................................................................................................................... 91

Conclusion for 1,2,4-Trichlorobenzene ..................................................................................................................... 92

1,1,1-Trichloroethane ........................................................................................................................................93

Results of the Methods Comparison .......................................................................................................................... 93

Results of the PQL Analysis...................................................................................................................................... 93

Conclusion for 1,1,1-Trichloroethane........................................................................................................................ 94

6.2.2 PQL Assessment May Support Reduction of the Current PQL............................................................95

Atrazine ..............................................................................................................................................................95

Results of the Methods Comparison .......................................................................................................................... 95

Results of the PQL Analysis...................................................................................................................................... 95

Conclusion for Atrazine............................................................................................................................................. 96

Carbofuran.........................................................................................................................................................97

Results of the Methods Comparison .......................................................................................................................... 97

Results of the PQL Analysis...................................................................................................................................... 97

Conclusion for Carbofuran ........................................................................................................................................ 98

trans-1,2-Dichloroethylene ................................................................................................................................99

Results of the Methods Comparison .......................................................................................................................... 99

Results of the PQL Analysis...................................................................................................................................... 99

Conclusion for trans-1,2-Dichloroethylene ............................................................................................................. 100

Hexachlorocyclopentadiene.............................................................................................................................101

Results of the Methods Comparison ........................................................................................................................ 101

Results of the PQL Analysis.................................................................................................................................... 101

Conclusion for Hexachlorocyclopentadiene ............................................................................................................ 102

Methoxychlor ...................................................................................................................................................103

Results of the Methods Comparison ........................................................................................................................ 103

Results of the PQL Analysis.................................................................................................................................... 103

Conclusion for Methoxychlor.................................................................................................................................. 104

2-(2,4,5-Trichlorophenoxy)propanoic acid (2,4,5-TP; Silvex) ........................................................................105

Results of the Methods Comparison ........................................................................................................................ 105

Results of the PQL Analysis.................................................................................................................................... 105

Conclusion for 2,4,5-TP........................................................................................................................................... 106

6.2.3 PQL Assessment Does Not Support Reduction of the Current PQL or Data are Insufficient to Reach a 

Conclusion .......................................................................................................................................................107

Arsenic .............................................................................................................................................................107

Results of the Methods Comparison ........................................................................................................................ 107

Results of the PQL Analysis.................................................................................................................................... 107

Conclusion for Arsenic ............................................................................................................................................ 108

Beryllium..........................................................................................................................................................109

Results of the Methods Comparison ........................................................................................................................ 109

Results of the PQL Analysis.................................................................................................................................... 109

Conclusion for Beryllium ........................................................................................................................................ 110

Cadmium..........................................................................................................................................................111

Results of the Methods Comparison ........................................................................................................................ 111

Results of the PQL Analysis.................................................................................................................................... 111

Conclusion for Cadmium......................................................................................................................................... 112

Chromium ........................................................................................................................................................113

Results of the Methods Comparison ........................................................................................................................ 113

Results of the PQL Analysis.................................................................................................................................... 113

Conclusion for Chromium ....................................................................................................................................... 114

Copper..............................................................................................................................................................115

Results of the Methods Comparison ........................................................................................................................ 115

Results of the PQL Analysis.................................................................................................................................... 115

Conclusion for Copper............................................................................................................................................. 116

Cyanide ............................................................................................................................................................117

Results of the Methods Comparison ........................................................................................................................ 117

Results of the PQL Analysis.................................................................................................................................... 117

Conclusion for Cyanide ........................................................................................................................................... 118
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Dalapon............................................................................................................................................................119

Results of the Methods Comparison ........................................................................................................................ 119

Results of the PQL Analysis.................................................................................................................................... 119

Conclusion for Dalapon........................................................................................................................................... 120

1,2-Dichlorobenzene ........................................................................................................................................121

Results of the Methods Comparison ........................................................................................................................ 121

Results of the PQL Analysis.................................................................................................................................... 121

Conclusion for 1,2-Dichlorobenzene ....................................................................................................................... 122

2,4-Dichlorophenoxyacetic acid (2,4-D)..........................................................................................................123

Results of the Methods Comparison ........................................................................................................................ 123

Results of the PQL Analysis.................................................................................................................................... 123

Conclusion for 2,4-D ............................................................................................................................................... 124

Di(2-ethylhexyl)adipate (DEHA) .....................................................................................................................125

Results of the Methods Comparison ........................................................................................................................ 125

Results of the PQL Analysis.................................................................................................................................... 125

Conclusion for DEHA ............................................................................................................................................. 126

Dinoseb ............................................................................................................................................................127

Results of the Methods Comparison ........................................................................................................................ 127

Results of the PQL Analysis.................................................................................................................................... 127

Conclusion for Dinoseb ........................................................................................................................................... 128

Diquat ..............................................................................................................................................................129

Results of the Methods Comparison ........................................................................................................................ 129

Results of the PQL Analysis.................................................................................................................................... 129

Conclusion for Diquat.............................................................................................................................................. 130

Endothall..........................................................................................................................................................131

Results of the Methods Comparison ........................................................................................................................ 131

Results of the PQL Analysis.................................................................................................................................... 131

Conclusion for Endothall......................................................................................................................................... 132

Endrin ..............................................................................................................................................................133

Results of the Methods Comparison ........................................................................................................................ 133

Results of the PQL Analysis.................................................................................................................................... 133

Conclusion for Endrin.............................................................................................................................................. 134

Fluoride............................................................................................................................................................135

Results of the Methods Comparison ........................................................................................................................ 135

Results of the PQL Analysis.................................................................................................................................... 135

Conclusion for Fluoride........................................................................................................................................... 136

Glyphosate .......................................................................................................................................................137

Results of the Methods Comparison ........................................................................................................................ 137

Results of the PQL Analysis.................................................................................................................................... 137

Conclusion for Glyphosate ...................................................................................................................................... 138

Lead ................................................................................................................................................................. 139

Results of the Methods Comparison ........................................................................................................................ 139

Results of the PQL Analysis.................................................................................................................................... 139

Conclusion for Lead ................................................................................................................................................ 140

Mercury............................................................................................................................................................141

Results of the Methods Comparison ........................................................................................................................ 141

Results of the PQL Analysis.................................................................................................................................... 141

Conclusion for Mercury........................................................................................................................................... 142

Nitrate (as N) ...................................................................................................................................................143

Results of the Methods Comparison ........................................................................................................................ 143

Results of the PQL Analysis.................................................................................................................................... 143

Conclusion for Nitrate ............................................................................................................................................. 144

Oxamyl (Vydate) ..............................................................................................................................................145

Results of the Methods Comparison ........................................................................................................................ 145

Results of the PQL Analysis .................................................................................................................................... 145

Conclusion for Oxamyl............................................................................................................................................ 146

Picloram...........................................................................................................................................................147

Results of the Methods Comparison ........................................................................................................................ 147

Results of the PQL Analysis.................................................................................................................................... 147

Conclusion for Picloram.......................................................................................................................................... 148
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Selenium...........................................................................................................................................................149

Results of the Methods Comparison ........................................................................................................................ 149

Results of the PQL Analysis.................................................................................................................................... 149

Conclusion for Selenium ......................................................................................................................................... 150

Simazine ...........................................................................................................................................................151

Results of the Methods Comparison ........................................................................................................................ 151

Results of the PQL Analysis.................................................................................................................................... 151

Conclusion for Simazine.......................................................................................................................................... 152

Xylenes (total) ..................................................................................................................................................153

Results of the Methods Comparison ........................................................................................................................ 153

Results of the PQL Analysis.................................................................................................................................... 153

Conclusion for Xylenes ........................................................................................................................................... 154

7.0 Summary ........................................................................................................................ 155

8.0 References ...................................................................................................................... 165

Appendix A: Listing of New and Updated Analytical Methods .......................................... A-1

Appendix B: Radionuclide Regressions ................................................................................. B-1

ALPHABETICAL LIST OF ANALYTE PROFILES

1,1,1-Trichloroethane .................................................................................................................................. 93 

1,1,2-Trichloroethane .................................................................................................................................. 37 

1,1-Dichloroethylene .................................................................................................................................. 79 

1,2,4-Trichlorobenzene ............................................................................................................................... 91 

1,2-Dibromo-3-chloropropane (DBCP ....................................................................................................... 45 

1,2-Dichlorobenzene ................................................................................................................................. 121 

1,2-Dichloroethane (Ethylene ..................................................................................................................... 29 

1,2-Dichloropropane ................................................................................................................................... 31 

1,4-Dichlorobenzene ................................................................................................................................... 75 

2,4,5-TP (Silvex) ....................................................................................................................................... 105 

2,4-Dichlorophenoxyacetic acid (2,4-D) .................................................................................................. 123 

Alachlor ...................................................................................................................................................... 41 

Antimony .................................................................................................................................................... 43 

Arsenic ...................................................................................................................................................... 107 

Atrazine ....................................................................................................................................................... 95 

Barium ........................................................................................................................................................ 73 

Benzene ....................................................................................................................................................... 23 

Benzo(a)pyrene ........................................................................................................................................... 57 

Beryllium .................................................................................................................................................. 109 

Bromate ....................................................................................................................................................... 59 

Cadmium ................................................................................................................................................... 111 

Carbofuran .................................................................................................................................................. 97 

Carbon Tetrachloride .................................................................................................................................. 25 

Chlordane .................................................................................................................................................... 27 

Chromium ................................................................................................................................................. 113 

cis-1,2-Dichloroethylene ............................................................................................................................. 77 

Copper ....................................................................................................................................................... 115 

Cyanide ..................................................................................................................................................... 117 

Dalapon ..................................................................................................................................................... 119 
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Di(2-ethylhexyl)adipate (DEHA) ............................................................................................................. 125 

Di(2-ethylhexyl)phthalate (DEHP) ............................................................................................................. 63 

Dichloromethane (Methylene chloride) ...................................................................................................... 61 

Dinoseb ..................................................................................................................................................... 127 

Diquat ........................................................................................................................................................ 129 

Endothall ................................................................................................................................................... 131 

Endrin ........................................................................................................................................................ 133 

Ethylbenzene ............................................................................................................................................... 81 

Ethylene dibromide (EDB) ......................................................................................................................... 65 

Fluoride ..................................................................................................................................................... 135 

Glyphosate ................................................................................................................................................ 137 

Heptachlor ................................................................................................................................................... 47 

Heptachlor Epoxide .................................................................................................................................... 49 

Hexachlorobenzene ..................................................................................................................................... 33 

Hexachlorocyclopentadiene ...................................................................................................................... 101 

Lead .......................................................................................................................................................... 139 

Lindane ....................................................................................................................................................... 51 

Mercury ..................................................................................................................................................... 141 

Methoxychlor ............................................................................................................................................ 103 

Monochlorobenzene (Chlorobenzene) ........................................................................................................ 83 

Nitrate (as N)............................................................................................................................................. 143 

Nitrite (as N) ............................................................................................................................................... 85 

Oxamyl (Vydate) ...................................................................................................................................... 145 

Pentachlorophenol ....................................................................................................................................... 67 

Picloram .................................................................................................................................................... 147 

Polychlorinatedbiphenyls (PCBs) as Decachlorobiphenyl (DCBP) ........................................................... 69 

Selenium ................................................................................................................................................... 149 

Simazine .................................................................................................................................................... 151 

Styrene ........................................................................................................................................................ 87 

Tetrachloroethylene .................................................................................................................................... 35 

Thallium ...................................................................................................................................................... 71 

Toluene ....................................................................................................................................................... 89 

Toxaphene ................................................................................................................................................... 53 

trans-1,2-Dichloroethylene ......................................................................................................................... 99 

Trichloroethylene ........................................................................................................................................ 39 

Vinyl Chloride ............................................................................................................................................ 55 

Xylenes (total) ........................................................................................................................................... 153 
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LIST OF EXHIBITS

Exhibit 1: Summary of Differences Between EPA’s PE Program and NELAC’s PT Program .... 7

Exhibit 2: U.S. EPA National Primary Drinking Water Standards and Related Information ..... 11

Exhibit 3: Availability of Six-Year 1 PE Data and Six-Year 2 PT Data for Regulated Analytes 16

Exhibit 4: Analytical Methods for Benzene................................................................................. 23

Exhibit 5: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Benzene .......................... 24

Exhibit 6: Analytical Methods for Carbon Tetrachloride ............................................................ 25

Exhibit 7: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Carbon Tetrachloride ...... 26

Exhibit 8: Analytical Methods for Chlordane .............................................................................. 27

Exhibit 9: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Chlordane ....................... 28

Exhibit 10: Analytical Methods for 1,2-Dichloroethane ............................................................. 29

Exhibit 11: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – 1,2-Dichloroethane ....... 30

Exhibit 12: Analytical Methods for 1,2-Dichloropropane ........................................................... 31

Exhibit 13: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – 1,2-Dichloropropane ..... 32

Exhibit 14: Analytical Methods for Hexachlorobenzene............................................................. 33

Exhibit 15: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Hexachlorobenzene ...... 34

Exhibit 16: Analytical Methods for Tetrachloroethylene ............................................................ 35

Exhibit 17: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Tetrachloroethylene ...... 36

Exhibit 18: Analytical Methods for 1,1,2-Trichloroethane ......................................................... 37

Exhibit 19: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – 1,1,2-Trichloroethane ... 38

Exhibit 20: Analytical Methods for Trichloroethylene ................................................................ 39

Exhibit 21: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Trichloroethylene ......... 40

Exhibit 22: Analytical Methods for Alachlor .............................................................................. 41

Exhibit 23: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Alachlor ........................ 42

Exhibit 24: Analytical Methods for Antimony ............................................................................ 43

Exhibit 25: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Antimony ...................... 44

Exhibit 26: Analytical Methods for DBCP .................................................................................. 45

Exhibit 27: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – DBCP ............................ 46

Exhibit 28: Analytical Methods for Heptachlor........................................................................... 47

Exhibit 29: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Heptachlor .................... 48

Exhibit 30: Analytical Methods for Heptachlor Epoxide ............................................................ 49

Exhibit 31: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Heptachlor Epoxide ...... 50
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Exhibit 32: Analytical Methods for Lindane ............................................................................... 51

Exhibit 33: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Lindane ......................... 52

Exhibit 34: Analytical Methods for Toxaphene........................................................................... 53

Exhibit 35: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Toxaphene .................... 54

Exhibit 36: Analytical Methods for Vinyl Chloride .................................................................... 55

Exhibit 37: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Vinyl Chloride .............. 56

Exhibit 38: Analytical Methods for Benzo(a)pyrene ................................................................... 57

Exhibit 39: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Benzo(a)pyrene ............ 58

Exhibit 40: Analytical Methods for Bromate............................................................................... 59

Exhibit 41: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Bromate ........................ 60

Exhibit 42: Analytical Methods for Dichloromethane................................................................. 61

Exhibit 43: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Dichloromethane .......... 62

Exhibit 44: Analytical Methods for Di(2-ethylhexyl)phthalate ................................................... 63

Exhibit 45: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Di(2-ethylhexyl)phthalate

....................................................................................................................................................... 64

Exhibit 46: Analytical Methods for Ethylene Dibromide ............................................................ 65

Exhibit 47: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Ethylene Dibromide ..... 66

Exhibit 48: Analytical Methods for Pentachlorophenol .............................................................. 67

Exhibit 49: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Pentachlorophenol ........ 68

Exhibit 50: Analytical Methods for PCBs: As Decachlorobiphenyl .......................................... 69

Exhibit 51: Analytical Methods for PCBs: As Aroclors ............................................................. 69

Exhibit 52: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – PCBs ............................. 70

Exhibit 53: Analytical Methods for Thallium .............................................................................. 71

Exhibit 54: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Thallium ....................... 72

Exhibit 55: Analytical Methods for Barium ................................................................................ 73

Exhibit 56: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Barium .......................... 74

Exhibit 57: Analytical Methods for 1,4-Dichlorobenzene ........................................................... 75

Exhibit 58: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – 1,4-Dichlorobenzene .... 76

Exhibit 59: Analytical Methods for cis-1,2-Dichloroethylene .................................................... 77

Exhibit 60: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – cis-1,2-Dichloroethylene

....................................................................................................................................................... 78

Exhibit 61: Analytical Methods for 1,1-Dichloroethylene .......................................................... 79

Exhibit 62: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – 1,1-Dichloroethylene .... 80
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Exhibit 63: Analytical Methods for Ethylbenzene ....................................................................... 81

Exhibit 64: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Ethylbenzene ................ 82

Exhibit 65: Analytical Methods for Monochlorobenzene ........................................................... 83

Exhibit 66: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Monochlorobenzene ...... 84

Exhibit 67: Analytical Methods for Nitrite (as N) ....................................................................... 85

Exhibit 68: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Nitrite ............................ 86

Exhibit 69: Analytical Methods for Styrene ................................................................................ 87

Exhibit 70: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Styrene .......................... 88

Exhibit 71: Analytical Methods for Toluene ............................................................................... 89

Exhibit 72: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Toluene ......................... 90

Exhibit 73: Analytical Methods for 1,2,4-Trichlorobenzene ....................................................... 91

Exhibit 74: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – 1,2,4-Trichlorobenzene 92

Exhibit 75: Analytical Methods for 1,1,1-Trichloroethane ......................................................... 93

Exhibit 76: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – 1,1,1-Trichloroethane ... 94

Exhibit 77: Analytical Methods for Atrazine............................................................................... 95

Exhibit 78: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Atrazine ........................ 96

Exhibit 79: Analytical Methods for Carbofuran .......................................................................... 97

Exhibit 80: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Carbofuran .................... 98

Exhibit 81: Analytical Methods for trans-1,2-Dichloroethylene ................................................. 99

Exhibit 82: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – trans-1,2-

Dichloroethylene ......................................................................................................................... 100

Exhibit 83: Analytical Methods for Hexachlorocyclopentadiene .............................................. 101

Exhibit 84: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – 

Hexachlorocyclopentadiene ........................................................................................................ 102

Exhibit 85: Analytical Methods for Methoxychlor .................................................................... 103

Exhibit 86: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Methoxychlor ............. 104

Exhibit 87: Analytical Methods for 2,4,5-TP (Silvex) .............................................................. 105

Exhibit 88: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – 2,4,5-TP (Silvex) ........ 106

Exhibit 89: Analytical Methods for Arsenic .............................................................................. 107

Exhibit 90: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Arsenic ........................ 108

Exhibit 91: Analytical Methods for Beryllium .......................................................................... 109

Exhibit 92: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Beryllium .................... 110

Exhibit 93: Analytical Methods for Cadmium........................................................................... 111
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Exhibit 94: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Cadmium .................... 112

Exhibit 95: Analytical Methods for Chromium ......................................................................... 113

Exhibit 96: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Chromium ................... 114

Exhibit 97: Analytical Methods for Copper............................................................................... 115

Exhibit 98: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Copper ........................ 116

Exhibit 99: Analytical Methods for Cyanide ............................................................................. 117

Exhibit 100: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Cyanide ..................... 118

Exhibit 101: Analytical Methods for Dalapon ........................................................................... 119

Exhibit 102: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Dalapon .................... 120

Exhibit 103: Analytical Methods for 1,2-Dichlorobenzene ....................................................... 121

Exhibit 104: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – 1,2-Dichlorobenzene 122

Exhibit 105: Analytical Methods for 2,4-D ............................................................................... 123

Exhibit 106: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – 2,4-D ......................... 124

Exhibit 107: Analytical Methods for Di(2-ethylhexyl)adipate .................................................. 125

Exhibit 108: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – DEHA ....................... 126

Exhibit 109: Analytical Methods for Dinoseb ........................................................................... 127

Exhibit 110: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Dinoseb ..................... 128

Exhibit 111: Analytical Methods for Diquat ............................................................................. 129

Exhibit 112: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Diquat ....................... 130

Exhibit 113: Analytical Methods for Endothall ......................................................................... 131

Exhibit 114: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Endothall .................. 132

Exhibit 115: Analytical Methods for Endrin ............................................................................. 133

Exhibit 116: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Endrin ....................... 134

Exhibit 117: Analytical Methods for Fluoride ........................................................................... 135

Exhibit 118: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Fluoride .................... 136

Exhibit 119: Analytical Methods for Glyphosate ...................................................................... 137

Exhibit 120: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Glyphosate ................ 138

Exhibit 121: Analytical Methods for Lead ................................................................................ 139

Exhibit 122: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Lead .......................... 140

Exhibit 123: Analytical Methods for Mercury........................................................................... 141

Exhibit 124: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Mercury .................... 142

Exhibit 125: Analytical Methods for Nitrate ............................................................................. 143
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Exhibit 126: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Nitrate ....................... 144

Exhibit 127: Analytical Methods for Oxamyl ........................................................................... 145

Exhibit 128: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Oxamyl ..................... 146

Exhibit 129: Analytical Methods for Picloram .......................................................................... 147

Exhibit 130: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Picloram .................... 148

Exhibit 131: Analytical Methods for Selenium ......................................................................... 149

Exhibit 132: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Selenium ................... 150

Exhibit 133: Analytical Methods for Simazine ......................................................................... 151

Exhibit 134: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Simazine ................... 152

Exhibit 135: Analytical Methods for Xylenes ........................................................................... 153

Exhibit 136: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Xylenes ..................... 154

Exhibit 137: Second Six-Year Review Analytical Feasibility Assessment Summary Analytes 

with MCL Equal to the Current PQL, and thus the PQL is Limiting - 25 Analytes ................... 157

Exhibit 138: Second Six-Year Review Analytical Feasibility Assessment Summary Analytes 

with MCL Greater than the Current PQL and Thus it is Technically Feasible to Reduce the MCL 

- 41 Analytes ............................................................................................................................... 160

Appendix A

Exhibit A-1: New or Revised Analytical Methods since 2000; Review of NPDWRs under 40 

CFR §§141.23, 141.24, and 141.131 .......................................................................................... A-1

Appendix B

Exhibit B-1: U.S. EPA National Primary Drinking Water Standards and Related Information – 

Radionuclides .............................................................................................................................. B-1

Exhibit B-2: Availability of Six-Year 1 PE Data and Six-Year 2 PE/PT Data for Radionuclides

..................................................................................................................................................... B-3

Exhibit B-3: Evaluation of ERA PT Data – Gross Alpha .......................................................... B-4

Exhibit B-4: Evaluation of ERA PT Data – Radium-226 .......................................................... B-5

Exhibit B-5: Evaluation of ERA PT Data – Radium-228 .......................................................... B-6

Exhibit B-6: Evaluation of ERA PT Data – Uranium................................................................ B-7

Exhibit B-7: Evaluation of ERA PT Data – Gross Beta ............................................................ B-8

Exhibit B-8: Evaluation of ERA PT Data – Barium-133 .......................................................... B-9

Exhibit B-9: Evaluation of ERA PT Data – Cobalt-60 ............................................................ B-10

Exhibit B-10: Evaluation of ERA PT Data – Cesium-134 ...................................................... B-11

Exhibit B-11: Evaluation of ERA PT Data – Cesium-137 ...................................................... B-12

Exhibit B-12: Evaluation of ERA PT Data – Iodine-131 ........................................................ B-13
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Exhibit B-13: Evaluation of ERA PT Data – Strontium-89 .................................................... B-14

Exhibit B-14: Evaluation of ERA PT Data – Strontium-90 .................................................... B-15

Exhibit B-15: Evaluation of ERA PT Data – Tritium.............................................................. B-16

Exhibit B-16: Evaluation of ERA PT Data – Zinc-65 ............................................................. B-17
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1.0 Introduction

The Safe Drinking Water Act (SDWA), as amended in 1996, requires the Environmental 

Protection Agency (EPA) to review and revise, if appropriate, existing National Primary 

Drinking Water Regulations (NPDWRs). As part of the review, EPA developed a protocol 

document (USEPA, 2003a) that describes the process and strategy EPA uses to review existing 

NPDWRs in order to meet its statutory requirement. The protocol was based on the 

recommendations from the National Drinking Water Advisory Council (NDWAC), internal 

Agency deliberations, and discussions with the diverse stakeholders involved in drinking water 

and its protection. The protocol enables EPA to target those NPDWRs that are the most 

appropriate candidates for revision and thus efficiently utilize its resources. As part of the 

review, and where appropriate, EPA reviews the following key technical elements to make 

decisions regarding regulatory changes: health effects assessments; technology assessments 

(analytical feasibility and treatment technology); other regulatory revisions (e.g., monitoring and 

reporting); occurrence and exposure analyses; and available economic information. This 

document discusses the analytical feasibility aspect of the second Six-Year Review.

Analytical feasibility assessment is one of the key components of regulations review 

because the analytical feasibility may have been the limiting factor in setting the Maximum 

Contaminant Level (MCL) for some of the existing NPDWRs or because the health effects 

reviews may indicate a potential change in the Maximum Contaminant Level Goal (MCLG). 

This document examines analytical method performance over time by determining if the 

Practical Quantitation Levels (PQLs) may have changed since promulgation. The PQL is 

defined as "the lowest achievable level of analytical quantitation during routine laboratory 

operating conditions within specified limits of precision and accuracy" (50 FR 46902, November 

13, 1985) and is derived from the laboratory accreditation studies performed as part of the 

drinking water laboratory certification program. Data from these studies was referred to as 

Performance Evaluation (PE) data while the program was under EPA oversight until 1999, and 

as Proficiency Testing (PT) data when the program was privatized with the National 

Environmental Laboratory Accreditation Conference (NELAC) providing oversight. 

Analytical method performance is also assessed by comparing the Method Detection 

Limits (MDLs) of the analytical methods which were available at the time of promulgation to 

those of the currently approved methods. The purpose is to determine if PQL changes based on 

the PE/PT data are also supported by the approval and availability of new/improved methods to 

the testing laboratories. 

For the first Six-Year Review, EPA performed PQL assessments for 40 analytes that met

either of the following two criteria: 

• First, for those contaminants where the MCL is currently limited by analytical feasibility 

(i.e., the MCL is set at the PQL) and the MCLG is still appropriate, EPA evaluated the 

currently approved methods for those contaminants and available PE data to determine 

whether it might be possible to lower the PQL and hence set an MCL that is closer to the 

MCLG.
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• The second circumstance under which EPA re-evaluated the PQL was for contaminants 

identified under the Six-Year health effects technical review as having potential changes 

to their MCLG. Because the information for the health effects review was not completely 

available at the time the analytical methods analysis began, EPA took a broad-brush 

approach and included a number of contaminants that may not have needed a 

reassessment of their analytical feasibility.

In this document, PQL assessments are presented for all regulated contaminants for 

which data was available, using both the original data from the first Six-Year Review (all 

available data for regulated analytes; not just the 40 prioritized for Six-Year 1) and the new data 

for the second Six-Year Review, and on approval and availability of new and improved methods. 

The goal is to create a comprehensive document regarding laboratory analytical performance for 

regulated analytes based on available approaches. 

During the course of this study, EPA noted that for the Six Year Review 2 it did not have 

sufficient data or the data was inconclusive to actually recalculate any PQLs for the reasons 

discussed later in the report. PE/PT results were either not available below the current PQL, the 

concentrations of interest, or the results were inconclusive/inadequate regarding a potential to 

revise PQL. This limited EPA to use the data only to indicate a potential trend (qualitative 

assessment) for PQL revision. In view of this, EPA explored the use of two other sources of 

information regarding the potential to revise PQL: the minimum reporting levels (MRLs) in the 

Six Year Review Information Collection Request (ICR) data set and the MDL multiplier 

approach. These approaches and their results are discussed in a separate document prepared by 

EPA entitled: Development of Estimated Quantitation Levels for the Six-Year Review of 

National Primary Drinking Water Regulations (USEPA, 2009). 

2.0 Background 

2.1 Relationship Between SDWA Requirements and Analytical Methods

Section 1401(1)(C)(i) of SDWA (as amended in 1996); 42 U.S.C. § 300f(1)(C)(i), states 

that an MCL for a national primary drinking water regulation is set "if, in the judgment of the 

Administrator, it is economically and technologically feasible to ascertain the level of such 

contaminant in water in public water systems." According to SDWA, NPDWRs include "criteria 

and procedures to assure a supply of drinking water which dependably complies with such 

maximum contaminant levels; including accepted methods of quality control and testing 

procedures to insure compliance with such levels" [§1401(1)(D) of SDWA; 42 U.S.C. § 

300f(1)(D)]. Except in certain circumstances, EPA is to set the MCL as close to the MCLG as is 

feasible with the best available technologies (Section 1412 (b)(4)(B)) of SDWA. The MCLs for 

several SDWA contaminants were set at levels higher than MCLGs due to the limits of the 

analytical feasibility at that time. Since the promulgation of pre-1996 SDWA NPDWRs, newer 

analytical methods and updated methods for measuring SDWA contaminants have been 

approved. The approval of newer analytical techniques may have provided laboratories with the 

analytical capability to measure some contaminants at lower levels. In addition, some 
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laboratories may have improved in their ability to measure at lower levels using the same 

methods that were originally promulgated.

 In considering analytical methods for use in compliance monitoring, EPA evaluates the 

overall sensitivity of the techniques. In previous regulations, EPA has used two measures of 

analytical capability, the MDL and the PQL. 

• The MDL is a measure of method sensitivity. The MDL is defined at 40 CFR Part 136 

Appendix B as "the minimum concentration of a substance that can be reported with 99% 

confidence that the analyte concentration is greater than zero." MDLs can be operator, 

method, laboratory, and matrix-specific. Due to normal day-to-day and run-to-run 

analytical variability, MDLs may not be reproducible within a laboratory or between 

laboratories. The regulatory significance of the MDL is that EPA uses the MDL to 

determine when a contaminant is considered to be detected and it can be used to calculate 

a PQL for that contaminant. 

• The PQL is defined as "the lowest achievable level of analytical quantitation during 

routine laboratory operating conditions within specified limits of precision and accuracy" 

(56 FR 46902, November 13, 1985). The Agency has used the PQL to estimate or 

evaluate the minimum concentration at which most laboratories can be expected to 

reliably measure a specific chemical contaminant during day-to-day analyses of drinking 

water samples. The PQL is a means of integrating information on the performance of the 

approved analytical methods into the development of a drinking water regulation (52 FR 

25690, July 8, 1987). The PQL incorporates the following (50 FR 46880, November 13, 

1985; 52 FR 25690, July 8, 1987; 54 FR 22062, May 22, 1989): 

- quantitation, 

- precision and bias, 

- normal operations of a laboratory, and 

- the fundamental need to have a sufficient number of laboratories available to conduct 

compliance monitoring analyses. 

 In some cases, the quantitation level for a particular analyte may have been the limiting 

factor in the determination of the MCL for that analyte. This could be especially true for 

contaminants with MCLGs of zero. In addition, there are several SDWA contaminants with nonzero MCLGs that have their MCL set at the PQL.

2.2 PQL Determination Methods for the SDWA Contaminants 

Historically, EPA has used two main approaches to determine a PQL for SDWA 

analytes. One approach (and the preferred approach) used data from laboratory Performance 

Evaluation (PE studies, now called PT or Proficiency Testing studies). Although the primary use 

of the PE/PT data was for EPA’s laboratory certification, the data were also used as a secondary 

data source for many years to develop PQLs when the spike concentrations were in the 

appropriate concentration range. The derivation of the PQL involved determining the 
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concentration of an analyte at which 75% of all participating laboratories achieved results within 

a specified range around the spike value. 

 A PQL derived in such a manner is considered a stringent target for routine laboratory 

performance because:

• PE/PT samples are prepared in reagent water and therefore do not contain the matrix

interferences that may occur in field samples.

• Laboratories analyze only a small number of samples for the study and are aware that the 

samples are for the purposes of performance evaluation (i.e., they are not "blind" 

samples).

 

 In deriving a PQL from the laboratory performance data, the Agency typically sets a 

fixed percentage or 2 sigma (2 standard deviation) acceptance window around the known 

concentration (or spike value) of the samples. While the acceptance limits for inorganics 

typically range from 15 to 30% (40 CFR §141.23(k)(3)(ii)), the acceptance limits for organics 

generally range from 20 to 50% (40 CFR §141.24(f)(17)(i) and 40 CFR §141.24(h)(19)(i)). 

Several SDWA analytes have acceptance limits of 2 sigma (2 standard deviations). The 

percentage of laboratories achieving results within the specified acceptance window (y-axis) is 

plotted against the known spike concentration of the PE/PT samples (x-axis). Linear regression 

or graphical analysis is performed to determine the concentration at which 75% of the 

participating laboratories achieve acceptable results.

In the absence of PE/PT data, EPA has relied on the MDL multiplier method. In this 

approach, a PQL is calculated by multiplying the EPA-derived MDL by a factor of 5 or 10. The 

5 or 10 multiplier is used to account for the variability and uncertainty that can occur at the 

MDL. The MDL multiplier method was mostly used in the early years of rule development for 

NPDWRs when insufficient PE/PT data were available. Once sufficient data became available, 

most of the PQLs that were developed using the MDL multiplier were validated using PE/PT

data. 

There are advantages and disadvantages for each of these approaches. Some of the 

advantages and disadvantages for these PQL derivation approaches are as follows: 

(1) PE/PT data to derive a new PQL 

 Advantages - 

• Uses inter-laboratory data collected at concentrations near the MCL.

• More representative of what methods are being used for the analysis of that contaminant. 

• May be the preferred approach for contaminants with MCLGs of zero because MCLs for 

these contaminants are set at the PQL and EPA strives to use their preferred approach in 

these cases. 
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Disadvantages - 

• The PQL derived for each contaminant is affected by EPA’s choice of “an acceptable 

level of precision.” Acceptance criteria are not the same for all methods or contaminants. 

These levels have been set at + 10% or more (see Exhibit 2).

• PT data from 1999 and earlier are obtained from varying numbers of laboratories; hence 

some passing rates may represent dozens of laboratories, while others may represent very 

few laboratories. Despite this, linear regression treats each national passing rate equally. 

Further, passing rates of near 100% can influence the regression line in such a manner as 

to “mask” low passing rates below 75%. For example, if at higher concentrations the 

passing rates are all at or near 100%, but at lower concentrations near the PQL there are 

several passing rates well below 75%, the resultant regression line may still predict 

greater than 75% of laboratories to pass over the entire range of true (or spike)

concentrations even though the data near the PQL demonstrate that this may not be the 

case.

• During Six Year 1, some stakeholders felt that the PQL may be influenced by the set of 

data used (i.e., using data from all laboratories as opposed to only using data from EPA 

State and Regional laboratories, which was the case with Six Year 1 data). 

• Some stakeholders felt that the laboratory performance may be skewed because PE/PT

samples may be treated as special samples that are critical for laboratory certification.

• The derivation of PQLs from laboratory performance data is a resource- and timeintensive process. 

• PE/PT data are generated as part of the drinking water laboratory certification program 

which is designed to test precision and accuracy around the MCL. Therefore, 

concentrations representing laboratory performance at orders of magnitude below the 

current MCL are generally not represented. 

(2) The MDL-Multiplier Approach 

 Advantage

• It is a relatively easy and straightforward process 

Disadvantages

• A PQL derived from the MDL using a multiplier to account for laboratory variability and 

uncertainty may not be practical or realistic.

• Several methods with varying MDLs may be approved for the same contaminant and it 

can be difficult to decide which Method/MDL to select for the PQL calculation. 
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2.3 Operational Details of the PE/PT Programs 

PE studies were an integral part of EPA's certification program for drinking water 

laboratories for over 20 years (thru 1999). Historically, performance studies were conducted 

semi-annually by EPA for all current and proposed drinking water contaminants. Although the 

studies were conducted semi-annually, for certification purposes, laboratories were only required 

to demonstrate acceptable performance once a year (40 CFR 141.23(k)(3) and 141.24(f)(17)). 

PE study samples (spike samples) were sent to all laboratories that conduct drinking water 

analyses, including utility laboratories, commercial laboratories, and State and EPA Regional 

laboratories. Samples or sample concentrates that were analyzed, contained all SDWA analytes 

and analytes that were being considered for regulation under the SDWA.

As part of these studies, EPA’s National Exposure Research Laboratory (NERL) in 

Cincinnati, Ohio, sent participating laboratories a set of stable sample concentrates in sealed 

glass ampules, a data reporting form, and appropriate instructions. Each laboratory produced the 

study samples by diluting a measured quantity of the specific concentrates to volume with 

reagent water. The laboratory then analyzed the samples using an EPA-approved method of 

their choice. The completed reporting form was sent to EPA for evaluation, the data were 

carefully reviewed per Quality Assurance/Quality Control (QA/QC) procedures, entered into a 

database, and a fully detailed report was then returned to each laboratory. The responsible State 

or EPA office contacted those laboratories that demonstrated potential problems.

 Performance Evaluation studies are no longer performed by EPA. In December 1999, the 

PT program was privatized, with NELAC providing oversight to what is now referred to as the 

PT program. NELAC is a cooperative association of State and Federal agencies and, in 2006, 

NELAC and the Institute for National Environmental Laboratory Accreditation combined to 

form The NELAC Institute (TNI). For the purposes of this document, “NELAC” is used to 

represent both NELAC and TNI. PT data services under the NELAC's program are provided by 

private companies that prepare and provide PT samples (spiked at concentrations in accordance 

with NELAC policies) to analytical laboratories as part of maintaining laboratory accreditation. 

Approximately 10-12 such PT providers (e.g., Environmental Resource Associates – ERA) exist 

nationwide. PT providers also compile the results of the PT analyses for use by NELAC. 

Privatization of the PT program made it harder for the Agency to obtain PT data. As a 

result, during the second six year review, only one PT provider (ERA) was willing to share 

national pass/fail rates with EPA (see Section 2.4 for further discussion). ERA provided EPA 

with general summary statistics and national failure rates; however, no information regarding 

laboratory identification was shared, thereby maintaining laboratory confidentiality. Depending 

on the analyte and/or concentration, the PT data from ERA may represent more than 70 

laboratories at any single concentration. According to ERA personnel, since December 1999, 

when the PT process was privatized, ERA has accounted for approximately 50% of all PT results 

nationwide. 

A laboratory either passes or fails for each analyte based upon the Acceptance Limits 

(NELAC now refers to these as Acceptance Criteria) for each analyte. Acceptance Criteria can 

be percentage based (e.g., + 30% of the spiked, or true value), standard deviation-based (e.g., + 2 
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standard deviations, as described in Section 5.2), or based on average and range of replicate 

analyses (radionuclides only). In certain cases (e.g., volatile organic compounds - VOCs) the 

acceptance criteria may differ depending on the concentration (e.g., + 40% for spike 

concentrations <10 μg/L and + 20% for concentrations > 10 μg/L).

The key differences between EPA’s PE program and the current NELAC PT program in 

terms of the utility of the data for PQL assessment are described in Exhibit 1. For PQL 

assessment, the most significant implication of the differences between the two programs is that, 

while more laboratories and more spiking concentrations are represented in the NELAC PT data, 

fewer analytes have data at or below their PQL. As the PE/PT programs were designed for the 

purpose of laboratory accreditation, both programs exhibited shortcomings with respect to the 

use of the data for PQL assessment. As far as the data from the NELAC PT program is 

concerned, EPA would have benefitted if a) data from all PT providers were available, and b) 

additional spike concentrations for PT samples were selected below the current PQLs.

Exhibit 1: Summary of Differences Between EPA’s PE Program and NELAC’s PT

Program1 

Laboratory Accreditation 

Program Feature During EPA PE Period During NELAC PT Period

Number of Laboratories 

Participating

Wide range but typically 10 - 60 

laboratories per concentration

Wide range but typically 10 - 70 

laboratories per concentration

Types of Laboratories 

Participating

EPA Regional and State 

laboratories - Narrow spectrum of 

laboratories and relatively 

uniform in performance

Public Water System, academic 

and private with some EPA 

regional and State laboratories - 

Broad spectrum of laboratories 

with wide performance range 

Number of True (Spike) 

Concentrations Evaluated/ 

analyte

Approximately 10 - 30 59 - 60

Number of True (Spike) 

Concentrations Below the PQL

Of the 66 analytes which had PE 

data for PQL assessment, 39 

analytes had data < the current 

PQL2

Of the 66 analytes which had PT 

data for PQL assessment, 22 

analytes had data < the current

PQL

Amount of Data Available to EPA 

for PQL Assessment (% of the 

National PT data)

Percentage unknown Approximately 50% of the 

national PT data

Data Broken Down by Analytical 

Method?

Yes No

1 Excludes radionuclides

2 Passing rates at or below the PQL could not be calculated for dalapon, DEHA, endothall or simazine 

because the NELAC regression coefficients that are used to calculate national passing rates (see 

Section 5.2) are not valid at or below the PQL for these four analytes. As a result only 35 of the 39 analytes 

have passing rates at or below the PQL

 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

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2.4 Efforts Made to Obtain PT Data

The following is a summary of efforts that were made by EPA to obtain nationallyrepresentative PT data from the private firms that now provide PT services and/or directly from 

NELAC:

EPA first searched the websites of various PT providers to find out if the laboratory 

performance data was posted on-line. Although, some PT providers (e.g., APG of Belpre, OH) 

posted various PT statistics online, it did not include the passing/failing rates at each spike 

concentration which was needed for PQL assessment. At that point, requests for data were sent 

or discussed with PT Providers, members of the NELAC PT Committee and members of the 

NELAC PT Board. Only basic information was requested: the contaminant name being tested; 

the concentration of the PT sample; the number of labs in the PT round (no names or IDs, just 

the total number); and the number of labs that passed and/or number of labs that failed at each 

concentration. In all contacts, it was made clear that EPA needed just this basic information and 

would not require the identity of any individual lab, etc., and would not require the disclosure of 

what could be considered confidential business information (CBI). 

After multiple attempts, it was made clear by NELAC and the PT providers contacted 

that the data were considered to be CBI and therefore, could not be released. One exception to 

this was the PT provider ERA of Arvada, Colorado. ERA willingly and quickly sent their failure 

rates, true concentrations and basic summary statistics to EPA in August 2004. Note that ERA 

provided summary statistics and national failure rates as cited above, and no information 

regarding laboratory identification or other CBI was provided by ERA. Although APG also 

provided to EPA many hundreds of pages of analyzed data from the PT program across the 

country, it did not include the passing/failing rates at each concentration that were needed for 

PQL assessment. 

3.0 Representativeness of Available PT Data

 During the period when the available Six-Year 2/ERA data were generated, there were

approximately 10-12 companies that provided PT data services nationwide (a review of the TNI 

website indicates that that number is smaller in 2009). Only one of these providers, ERA, was 

willing to provide their pass/fail rates to EPA. According to ERA personnel, since December 

1999, when the PT process was privatized, they account for approximately 50% of all PT results 

nationwide. As described in Section 2.4, substantial efforts were made to obtain additional PT 

data to no avail. The assessments made in this report are based on PT data that were available, 

and this limitation is recognized. The refusal of other PT providers/NELAC to provide results 

raises some questions about the validity of the data set available to EPA. In other words, is the 

available data set sufficient to perform the assessments herein? The issues can be divided into 

three broad areas: bias, precision, and the regression model. 
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3.1 Bias 

 The refusal of providers other than ERA to provide data introduces potential nonresponse bias. If ERA procedures and results are different from that of other providers, the data 

may not be representative. Because no data are available from the other providers, it is difficult 

to quantify the potential bias. EPA considered options to evaluate the potential bias: 

• Compare ERA’s data to existing EPA data from the first Six-Year Review. EPA can test 

whether the percentage of laboratories passing is significantly different for individual 

analytes. However, because laboratory performance tends to improve over time, the 

degree of difference between ERA and other providers from Six-Year 1 becomes 

confounded. 

• Collect and compare any available information about the procedures used by ERA and 

the other providers. This includes the processes used to identify and collect data from 

laboratories, quality control measures, and analytical approaches. Given the lack of 

response from other PT providers, this is not likely to be feasible. 

 EPA could use this information to evaluate the results from ERA. EPA could make 

subjective judgments about the potential sign and magnitude of the bias, and might also conduct 

sensitivity analyses to explore the potential impact of the non-response bias on the results. 

3.2 Precision

For EPA to determine whether the available data are adequate for its analysis, EPA 

needed to establish data quality objectives for its analysis. An important data quality objective 

that is affected by the size of the sample is the precision of the estimates made with the sample. 

EPA could consider: 

• The margin of error the Agency is willing to tolerate. The data are used to estimate 

regression parameters and a predicted regression line. A prediction interval can be 

estimated for the regression line. EPA could specify the size of this prediction interval, 

and might also want to consider the size of the confidence interval for each parameter of 

the regression model. 

• The confidence level the Agency requires for its estimates. Confidence levels are 

usually expressed as 1-α, where α is the probability of a type I error. In other words, the 

probability that the prediction interval includes the true regression line is 1-α percent. It 

is common to estimate either a 95 percent or 99 percent prediction interval. 

 Sampling is not the only source of uncertainty in the analysis, as is discussed in the next 

section. But EPA also considered the impact of the sample size on the regression error. This 

requires a subjective judgment regarding the level of error EPA is willing to tolerate; the Agency 

could then consider the impact the margin of error may have on the PQL determination through a 

sensitivity analysis.
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3.3 The Regression Model

The PT data are used to estimate a simple linear regression using ordinary least squares 

(OLS). The regression of the percentage of laboratories passing at the spiked concentrations of 

an analyte is used in recalculation of the PQL. The standard results of the theory of linear 

regression is not entirely suited for sample surveys. The theory assumes the population is 

infinite, or that the observed finite population is drawn from an infinite superpopulation. This 

implies that sampling error is not the only source of error in a regression estimate. In fact, the 

error of the regression estimate consists of three parts, as discussed below. 

The use of a sample is one potential source of error. It is useful to think of the regression 

as an estimate of the conditional mean of the percentage of laboratories passing. The average 

estimate of the mean across repeated samples will equal the true population mean. But the mean 

of a specific sample may differ from the population mean. The second source of error is in the 

estimated parameters of the regression model. The regression is of the form (Weisberg, 1985): 

(1) Yi = β0 + β1xi + εi

Where:

Yi = Dependent variable for observation i. (e.g., laboratory passing rate for true concentration

i); 

β0 = Intercept or constant which tells us the expected value of Y when X is equal to zero. (e.g., 

the observed concentration in a sample that has not been spiked); 

β1 = The slope, or the change in Y for a change in x;

xi = The independent variable for observation i (the true concentration for observation i); 

εi = Random error, or the difference between the observed passing rate and the model's 

prediction. It is due to random error or variables excluded from the model. (Which, 

ideally, are not correlated with the independent variables.)

It is estimated by:

(2) Ŷi = b0 + b1x

Where: 

Ŷi = The fitted value predicted by the model. 

The parameters b0 and b1 are unbiased estimates of β0 and β1 (the true parameters), but 

they can differ for a particular finite population. 

Finally, the error of an individual prediction has a third component, the difference 

between the observed percentage for a true concentration and the average percentage for that 

concentration. This is εi in equation (1). The parts of the error are independent, so the variance 

of the prediction error is the sum of the three variances. Even if the regression estimate is based 

on the entire (finite) population, these last two components of error remain. 
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4.0 Identification of Regulated Analytes for PQL Assessment

 For the first Six-Year analytical feasibility review, EPA focused on assessing whether the 

PQL had changed since promulgation for a subset of the 68 chemical NPDWRs. EPA identified 

and performed the analytical feasibility analysis for a total of 40 NPDWRs based on the 

priorities discussed in Section 1.0. 

For the second Six-Year analytical feasibility review, EPA’s goal is to create a 

comprehensive document that includes PQL assessments for all regulated analytes for which PT 

data are available. Exhibit 2 summarizes these analytes, along with their range of MDLs, current 

PQL, how the PQL was determined, their MCLG, MCL, and the current acceptance criteria for 

PT. 

Exhibit 2: U.S. EPA National Primary Drinking Water Standards and Related 

Information1

Analyte

CASRN

EPA MDL or 

Range 

(mg/L)2

PQL

(mg/L)

How PQL 

Determined?

MCLG

(mg/L)

MCL or TT

(mg/L)

Acceptance 

Criteria

Acrylamide

79-06-1 N/A N/A N/A Zero TT3 N/A

Alachlor

15972-60-8 

0.000005 - 

0.000225 0.002 IMDL x 10 Zero 0.002 + 45%

Antimony

7440-36-0 

0.00002 - 

0.0008 0.006 PE Data 0.006 0.006 + 30%

Arsenic

7440-38-2 

0.0001 -

0.008 0.003 PE Data Zero 0.010 + 30%

Atrazine

1912-24-9 

0.000003 - 

0.0024 0.001 PE Data 0.003 0.003 + 45%

Barium

7440-39-3 

0.00004 -

0.001 0.15 PE Data 2 2 + 15%

Benzene

71-43-2 

0.00001 - 

0.00004 0.005 RDL x 10 Zero 0.005 + 20% or 40%

Benzo[a]pyrene

50-32-8 

0.000016 - 

0.00023 0.0002 PE Data Zero 0.0002 Mean + 

2 Std Dev

Beryllium

7440-41-7 

0.00002 - 

0.0003 0.001 PE Data 0.004 0.004 + 15%

Bromate 

15541-45-4 

0.00012 - 

0.00144 0.01 N/A Zero 0.01

Mean + 

2 Std Dev

(changed to 

+ 30%, 2007) 

Cadmium

7440-43-9 

0.00003 - 

0.001 0.002 PE Data 0.005 0.005 + 20%

Carbofuran

1563-66-2 

0.000043 -

0.00052

(note: lower 

bound = DL)

0.007 IMDL x 10 0.04 0.04 + 45%

Carbon tetrachloride

56-23-5 

0.000002 - 

0.00021 0.005 PE Data Zero 0.005 + 20% or 40%

Chlordane

57-74-9 

0.000001 – 

0.000224 0.002 IMDL x 10 0.002 0.002 + 45%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

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Analyte

CASRN

EPA MDL or 

Range 

(mg/L)2

PQL

(mg/L)

How PQL 

Determined?

MCLG

(mg/L)

MCL or TT

(mg/L)

Acceptance 

Criteria

Chlorite

7758-19-2 

0.00045 - 

0.01 N/A N/A 0.8 1.0 +30%

Chromium (total) 

Cr III: 16065-83-1 

Cr VI: 18540-29-9 

0.00008 - 

0.004 0.01 PE Data 0.1 0.1 + 15%

Copper

7440-50-8 

0.00001 - 

0.003 0.05 PE Data 1.3 TT5 Action level 

1.3 + 10% 

Cyanide 

(as free cyanide)

57-12-5 

N/A 0.1 PE Data 0.2 0.2 + 25%

Dalapon

75-99-0 

0.000024 - 

0.0013 0.01 MDL x 10 0.2 0.2 Mean +

2 Std Dev

1,2-Dibromo-3-

chloropropane (DBCP)

96-12-8 

0.000006 - 

0.00001 0.0002 IMDL x 10 Zero 0.0002 + 40%

1,2-Dichlorobenzene 

(o-Dichlorobenzene)

95-50-1 

0.00002 - 

0.00005 0.005 MDL survey 

and PE Data 0.6 0.6 + 20% or 40%

1,4-Dichlorobenzene 

(p-Dichlorobenzene) 

106-46-7 

0.00001 - 

0.00004 0.005 PE Data 0.075 0.075 + 20% or 40%

1,2-Dichloroethane 

(Ethylene dichloride)

107-06-2 

0.00002 - 

0.00006 0.005 PE Data Zero 0.005 + 20% or 40%

1,1-Dichloroethylene

75-35-4 

0.00004 - 

0.00012 0.005 PE Data 0.007 0.007 + 20% or 40%

cis-1,2-

Dichloroethylene

156-59-2 

0.00001 - 

0.00012 0.005 MDL survey 

and PE Data 

0.07 0.07 + 20% or 40%

trans-1,2-

Dichloroethylene

156-60-5 

0.00003 - 

0.00006 0.005 MDL survey 

and PE Data 0.1 0.1 + 20% or 40%

Dichloromethane 

(Methylene chloride)

75-09-2 

0.00001 - 

0.00009 0.005 PE Data Zero 0.005 + 20% or 40%

2,4-

Dichlorophenoxyacetic 

acid (2,4-D)

94-75-7 

0.000055 - 

0.0013 0.005 Raised to 

near MCL 0.07 0.07 + 50%

1,2-Dichloropropane

78-87-5 

0.00001 - 

0.00004 0.005 MDL survey 

and PE Data Zero 0.005 + 20% or 40%

Di(2-ethylhexyl)adipate 

(DEHA)

103-23-1 

0.00009 - 

0.01182 0.006 MDL x 10 0.4 0.4 Mean +

2 Std Dev

Di(2-ethylhexyl) 

phthalate (DEHP)

117-81-7 

0.00046 - 

0.00225 0.006 PE Data Zero 0.006 Mean +

2 Std Dev

Dinoseb

88-85-7 

0.000081 - 

0.0015 0.002 MDL x 10 0.007 0.007 Mean +

2 Std Dev

Diquat

85-00-7 0.00072 0.004 PE Data 0.02 0.02 Mean +

2 Std Dev

Endothall

145-73-3 

0.0007 - 

0.00179 0.09 MDL x 10 0.1 0.1 Mean +

2 Std Dev
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

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Analyte

CASRN

EPA MDL or 

Range 

(mg/L)2

PQL

(mg/L)

How PQL 

Determined?

MCLG

(mg/L)

MCL or TT

(mg/L)

Acceptance 

Criteria

Endrin

72-20-8 

0.000002 - 

0.00034 0.0001 MDL x 10 0.002 0.002 + 30%

Epichlorohydrin

106-89-8 N/A N/A N/A Zero TT3 N/A

Ethylbenzene

100-41-4 

0.00001 - 

0.00006 0.005 MDL survey 

and PE Data 0.7 0.7 + 20% or 40%

Ethylene dibromide 

(EDB)

106-93-4 

0.000007 - 

0.000032 0.00005 IMDL x 5 Zero 0.00005 + 40%

Fluoride

16984-48-8 0.009 - 0.01 0.5 PE Data 4 4 + 10%

Glyphosate

1071-83-6 

0.00599 - 

0.006 0.06 PE Data 0.7 0.7 Mean +

2 Std Dev

Heptachlor

76-44-8 

0.0000015 - 

0.00015 0.0004 IMDL x 10 Zero 0.0004 + 45%

Heptachlor epoxide

1024-57-3 

0.000001 - 

0.000202 0.0002 IMDL x 10 Zero 0.0002 + 45%

Hexachlorobenzene

118-74-1 

0.000001 - 

0.00013 0.001 PE Data Zero 0.001 Mean +

2 Std Dev

Hexachlorocyclopentadiene

77-47-4 

0.000004 - 

0.00016 0.001 PE Data 0.05 0.05 Mean +

2 Std Dev

Lead

7439-92-1 

0.00002 - 

0.0007 0.005 PE Data Zero TT5

, Action level = 

0.015 + 30%

Lindane

58-89-9 

0.000002 - 

0.00015 0.0002 MDL x 10 0.0002 0.0002 + 45%

Mercury (Inorganic)

7439-97-6 

0.0000018 - 

0.0002 0.0005 PE Data 0.002 0.002 + 30%

Methoxychlor

72-43-5 

0.000003 - 

0.00096 0.01 Raised to 

near MCL 0.04 0.04 + 45%

Monochlorobenzene 

(Chlorobenzene)

108-90-7 

0.00001 - 

0.00004 0.005 MDL x 10 0.1 0.1 + 20% or 40%

Nitrate (as N)

14797-55-8 0.002 - 0.008 0.4 PE Data 10 10 + 10%

Nitrite (as N)

14797-65-0 0.001 - 0.004 0.4 PQL for 

nitrate 1 1 + 15%

Oxamyl (Vydate)

23135-22-0 

0.000044 - 

0.00086 0.02 MDL x 10 0.2 0.2 Mean +

2 Std Dev

Pentachlorophenol

87-86-5 

0.000014 - 

0.0016 0.001 PE Data Zero 0.001 + 50%

Picloram

1918-02-1 

Not 

Recovered - 

0.001

0.001 DL x 10 0.5 0.5 Mean +

2 Std Dev

Polychlorinated 

biphenyls (PCBs) as 

Decachlorobiphenyl 

(DCBP)

1336-36-3 

As 

Decachlorobiphenyl 

(DCBP): 

0.00008

As Aroclors: 

0.000012 - 

0.0156

0.0005 PE Data Zero 0.0005 + 100%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

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Analyte

CASRN

EPA MDL or 

Range 

(mg/L)2

PQL

(mg/L)

How PQL 

Determined?

MCLG

(mg/L)

MCL or TT

(mg/L)

Acceptance 

Criteria

Selenium

7782-49-2 

0.0005 - 

0.0079 0.01 PE Data 0.05 0.05 + 20%

Simazine

122-34-9 

0.000008 - 

0.0068 0.0007 MDL x 10 0.004 0.004 Mean +

2 Std Dev

Styrene

100-42-5 

0.00001 - 

0.0001 0.005 MDL survey

and PE Data 0.1 0.1 + 20% or 40%

2,3,7,8-TCDD (Dioxin)

1746-01-6 

1.E-8

(note: value 

is an ML)

3 x 10-8 MDL x 5 Zero 3 x 10-8 Mean +

2 Std Dev

Tetrachloroethylene

127-18-4 

0.000002 - 

0.00014 0.005 MDL survey 

and PE Data Zero 0.005 + 20% or 40%

Thallium

7440-28-0 

0.00001 - 

0.0007 0.002 PE Data 0.0005 0.002 + 30%

Toluene

108-88-3 

0.00001 - 

0.00011 0.005 MDL survey 

and PE Data 1 1 + 20% or 40%

Toxaphene

8001-35-2 

0.00013 - 

0.0017 0.003 PE Data Zero 0.003 + 45%

2,4,5-TP (Silvex)

93-72-1 

0.000018 - 

0.0018 0.005 Raised to 

near MCL 0.05 0.05 + 50%

1,2,4-Trichlorobenzene

120-82-1 

0.00002 - 

0.0002 0.005 MDL x 10 0.07 0.07 + 20% or 40%

1,1,1-Trichloroethane

71-55-6 

0.000005 - 

0.00008 0.005 DL x 10 0.2 0.2 + 20% or 40%

1,1,2-Trichloroethane

79-00-5 

0.000012 - 

0.0001 0.005 PE Data 0.003 0.005 + 20% or 40%

Trichloroethylene

79-01-6 

0.000002 - 

0.00019 0.005 PE Data Zero 0.005 + 20% or 40%

Vinyl chloride

75-01-4 

0.00001 - 

0.00018 0.002 MLPD Zero 0.002 + 40%

Xylenes (total)

1330-20-7 

0.00001 - 

0.00013 0.005 MDL survey 

and PE Data 10 10 + 20% or 40%

1 Definitions

Chemical Abstracts Services Registry Number (CASRN) 

Maximum Contaminant Level (MCL) – The highest level of a contaminant that is allowed in drinking water. MCLs 

are set as close to MCLGs as feasible using the best available treatment technology and taking cost into 

consideration. MCLs are enforceable standards.

Treatment technique (TT) – A required process intended to reduce the level of a contaminant in drinking water.

DL = Detection Limit

IMDL = Interlaboratory Method Detection Limit

MDL = Method Detection Limit

ML = Minimum Level

MLPD = Multi-laboratory Performance Data

PQL = Practical Quantitation Level

RDL = Regulatory Detection Limit

2 The MDLs and/or ranges were obtained from the individual analytical methods developed by EPA; non-EPA 

methods are not represented. Therefore, the MDL ranges presented may not represent the entire range of 

possible values. Methods can be found at the National Environmental Methods Index website (NEMI, 2008).

3 Each water system must certify, in writing to the state (using third-party or manufacturers certification) that when it 

uses acrylamide and/or epichlorohydrin to treat water, the combination (or product) of dose and monomer level 
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does not exceed the levels specified, as follows: Acrylamide = 0.05% dosed at 1 mg/L (or equivalent); 

Epichlorohydrin = 0.01% dosed at 20 mg/L (or equivalent).

4 MDL range for chlordane including α− and γ−chlordane and trans-nonachlor. 

5 Lead and copper are regulated by a Treatment Technique that requires systems to control the corrosiveness of 

their water. If more than 10% of tap water samples exceed the action level, water systems must take additional 

steps. For copper, the action level is 1.3 mg/L, and for lead is 0.015 mg/L. From 40 CFR Part 140 revised as of 

July 1, 2003, and EPA 816-F-03-016 June 2003 (USEPA, 2003b). 

6 MDL range for PCBs is from EPA Method 508A only. Other methods (505, 508.1 and 525.2) are screening 

methods and are not used for comparison to MCLs.

PQL values and the basis for their determination can be found at 50 FR 46880, November 13, 1985; 52 FR 25690. 

July 8, 1987; 53 FR 31516, August 18, 1988; 54 FR 22062, May 22, 1989; 55 FR 30370, July 25, 1990; 56 FR 

3526, January 30, 1991; 57 FR 31776, July 17, 1992; 63 FR 69390, December 16, 1998; and EPA-815-R-00-010: 

“Analytical Methods Support Document For Arsenic In Drinking Water” (USEPA, 1999).

Acceptance criteria are available at: http://www.nelac-institute.org/ and at 40 CFR 141.24(f)(17)(i), 40 CFR 

141.24(h)(19)(i)(B), 40 CFR 141.23(k)(3)(ii), 40 CFR 141.89(a)(1)(ii)(A), 40 CFR 141.89(a)(1)(ii)(B) and 40 CFR 

141.131(b)(2)(ii). 

5.0 Second Six-Year Review PQL Assessment Methodology 

5.1 Data Available for PQL Assessment 

Qualitative PQL assessments are based on all available laboratory performance data from 

Six-Year 1 and from one major PT provider (ERA) that was willing to share PT data with EPA. 

Exhibit 3 summarizes the availability of Six-Year 1 PE data and Six-Year 2 PT data and whether 

data are available at or below the PQL for each analyte. Having data below the PQL is 

considered to be important in concluding whether a PQL could be reduced, regardless of how 

high passing rates are above the PQL. For non-radionuclides, the ERA dataset encompasses the 

period from late 1999 through 2004. ERA data for radionuclides were generated from 2002-

2006. 

A review of new or revised analytical methods that have been approved by EPA for the 

analysis of regulated analytes was undertaken for the period of 2000 through 2007. The approval 

and availability of these analytical methods might indicate an improvement in laboratory 

analytical performance. New and updated methods for the regulated analytes are discussed in 

each contaminant profile in Section 6. A complete listing of new and updated analytical methods 

is provided in Appendix A. 

Regression plots for radionuclides based on laboratory performance data obtained from 

ERA (for the period 2002-2006) are presented in Appendix B. Radionuclides were not included 

in the Six-Year 1 review and therefore, no data are available. Note that for the radionuclides, 

limitations of laboratory performance at low concentrations is generally not an issue, as PQLs 

can be lowered, if necessary, by increasing sample volume and/or radiological analysis duration. 

Thus, though the radionuclide PT data are evaluated in this report for completeness, no 

conclusions are drawn regarding changes in PQLs. 
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Exhibit 3: Availability of Six-Year 1 PE Data and Six-Year 2 PT Data for Regulated 

Analytes

Analyte

CASRN In Six-Year 1 Data? In Six-Year 2 ERA Data 

1999-2004?

Acrylamide

79-06-1 No No 

Alachlor

15972-60-8 Yes, some data < PQL Yes, no data < PQL

Antimony

7440-36-0 Yes, some data < PQL1 Yes, no data < PQL

Arsenic

7440-38-2 Yes, some data < PQL1 Yes, no data < PQL

Atrazine

1912-24-9 Yes, some data < PQL1 Yes, no data < PQL

Barium

7440-39-3 Yes, some data < PQL1 Yes, no data < PQL

Benzene

71-43-2 Yes, some data < PQL Yes, some data < PQL

Benzo[a]pyrene

50-32-8 Yes, no data < PQL Yes, no data < PQL

Beryllium

7440-41-7 Yes, some data < PQL Yes, no data < PQL

Bromate 

15541-45-4 Yes, some data < PQL Yes, some data < PQL

Cadmium

7440-43-9 Yes, no data < PQL Yes, no data < PQL

Carbofuran

1563-66-2 Yes, some data < PQL Yes, no data < PQL

Carbon tetrachloride

56-23-5 Yes, some data < PQL Yes, some data < PQL

Chlordane

57-74-9 Yes, some data < PQL Yes, no data < PQL

Chlorite

7758-19-2 Yes, but no PQL Yes, but no PQL

Chromium (total) 

Cr III: 16065-83-1 

Cr VI: 18540-29-9 

Yes, no data < PQL Yes, no data < PQL

Copper

7440-50-8 Yes, some data < PQL1 Yes, no data < PQL

Cyanide 

(as free cyanide)

57-12-5 

Yes, only one datum = 

PQL; no data < PQL Yes, no data < PQL

Dalapon

75-99-0 

Yes, some data < PQL; 

passing rates below 

PQL could not be 

calculated 2

Yes, no data < PQL

1,2-Dibromo-3-chloropropane (DBCP)

96-12-8 Yes, some data < PQL Yes, some data < PQL

1,2-Dichlorobenzene 

(o-Dichlorobenzene)

95-50-1 

Yes, no data < PQL Yes, no data < PQL
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Analyte

CASRN In Six-Year 1 Data? In Six-Year 2 ERA Data 

1999-2004?

1,4-Dichlorobenzene 

(p-Dichlorobenzene) 

106-46-7 

Yes, some data < PQL Yes, some data < PQL

1,2-Dichloroethane (Ethylene 

dichloride)

107-06-2 

Yes, some data < PQL1 Yes, some data < PQL

1,1-Dichloroethylene

75-35-4 Yes, no data < PQL Yes, some data < PQL

cis-1,2-Dichloroethylene

156-59-2 Yes, no data < PQL Yes, some data < PQL

trans-1,2-Dichloroethylene

156-60-5 Yes, no data < PQL Yes, some data < PQL

Dichloromethane (Methylene chloride)

75-09-2 Yes, no data < PQL Yes, no data < PQL

2,4-Dichlorophenoxyacetic acid (2,4-D)

94-75-7 Yes, some data < PQL Yes, no data < PQL

1,2-Dichloropropane

78-87-5 Yes, no data < PQL Yes, some data < PQL

Di(2-ethylhexyl)adipate (DEHA)

103-23-1 

Yes, some data < PQL; 

passing rates below 

PQL could not be 

calculated 2

Yes, no data < PQL

Di(2-ethylhexyl) phthalate (DEHP)

117-81-7 Yes, some data < PQL Yes, no data < PQL

Dinoseb

88-85-7 Yes, no data < PQL Yes, no data < PQL

Diquat

85-00-7 Yes, no data < PQL Yes, no data < PQL

Endothall

145-73-3 

Yes, some data < PQL; 

passing rates below 

PQL could not be 

calculated 2

Yes, no data < PQL

Endrin

72-20-8 Yes, no data < PQL1 Yes, no data < PQL

Epichlorohydrin

106-89-8 No No 

Ethylbenzene

100-41-4 Yes, no data < PQL Yes, some data < PQL

Ethylene dibromide (EDB)

106-93-4 Yes, no data < PQL Yes, no data < PQL

Fluoride

16984-48-8 Yes, some data < PQL Yes, no data < PQL

Glyphosate

1071-83-6 Yes, no data < PQL Yes, no data < PQL

Heptachlor

76-44-8 Yes, some data < PQL Yes, no data < PQL

Heptachlor epoxide

1024-57-3 Yes, some data < PQL Yes, no data < PQL

Hexachlorobenzene

118-74-1 Yes, some data < PQL Yes, some data < PQL

Hexachlorocyclopentadiene

77-47-4 Yes, some data < PQL Yes, no data < PQL
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Analyte

CASRN In Six-Year 1 Data? In Six-Year 2 ERA Data 

1999-2004?

Lead

7439-92-1 Yes, some data < PQL1 Yes, no data < PQL

Lindane

58-89-9 Yes, some data < PQL1 Yes, no data < PQL

Mercury (Inorganic)

7439-97-6 Yes, no data < PQL Yes, no data < PQL

Methoxychlor

72-43-5 Yes, some data < PQL Yes, no data < PQL 

Monochlorobenzene (Chlorobenzene)

108-90-7 Yes, no data < PQL Yes, some data < PQL

Nitrate (as N)

14797-55-8 Yes, no data < PQL Yes, no data < PQL

Nitrite (as N)

14797-65-0 Yes, some data < PQL Yes, no data < PQL

Oxamyl (Vydate)

23135-22-0 Yes, some data < PQL Yes, no data < PQL

Pentachlorophenol

87-86-5 Yes, some data < PQL Yes, no data < PQL

Picloram

1918-02-1 Yes, no data < PQL Yes, no data < PQL

Polychlorinated biphenyls (PCBs) as 

Decachlorobiphenyl (DCBP)

1336-36-3 

Yes, some data < PQL Yes, no data < PQL

Selenium

7782-49-2 Yes, some data < PQL1 Yes, no data < PQL

Simazine

122-34-9 

Yes, some data < PQL; 

passing rates below 

PQL could not be 

calculated 2

Yes, no data < PQL

Styrene

100-42-5 Yes, no data < PQL Yes, some data < PQL

2,3,7,8-TCDD (Dioxin)

1746-01-6 No Yes, no data < PQL; only 

one spike level

Tetrachloroethylene

127-18-4 Yes, no data < PQL Yes, some data < PQL

Thallium

7440-28-0 Yes, some data < PQL Yes, no data < PQL

Toluene

108-88-3 Yes, no data < PQL Yes, some data < PQL

Toxaphene

8001-35-2 Yes, some data < PQL Yes, no data < PQL

2,4,5-TP (Silvex)

93-72-1 Yes, some data < PQL1 Yes, no data < PQL

1,2,4-Trichlorobenzene

120-82-1 Yes, no data < PQL Yes, some data < PQL

1,1,1-Trichloroethane

71-55-6 Yes, some data < PQL Yes, some data < PQL

1,1,2-Trichloroethane

79-00-5 Yes, no data < PQL Yes, some data < PQL

Trichloroethylene

79-01-6 Yes, no data < PQL Yes, some data < PQL
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Analyte

CASRN In Six-Year 1 Data? In Six-Year 2 ERA Data 

1999-2004?

Vinyl chloride

75-01-4 Yes, no data < PQL Yes, some data < PQL

Xylenes (total)

1330-20-7

Yes, no data < PQL Yes, some data < PQL

1 Means passing rates for Six-Year 1 data were calculated for this report, as these analytes were not 

evaluated in the March 2003 report, and acceptance criteria are percentage-based, not + 2 S.D. 2 Means passing rates for Six-Year 1 data at or below the PQL could not be calculated for this report, as 

these analytes were not evaluated in the March 2003 report, acceptance criteria are + 2 S.D., and 

available regression coefficients are not valid at or below the PQL.

5.2 Calculating National Passing Rates 

ERA provided national failure rates that were converted into passing rates by subtracting 

the percent of laboratories failing from 100%. Six-Year 1 PT data for the 40 analytes that were 

prioritized for analysis in the March 2003 report had been compiled (and passing rates 

calculated) in 2003 from original printed output from participating laboratories and EPA 

archives. In a few cases, some of the original data could not be used because the original hard 

copies were not legible. For analytes that were evaluated in the March 2003 report, the passing 

rates and true concentrations were taken directly from the report. In addition, passing rates were 

calculated for analytes that were not prioritized for the 2003 Six-Year 1 PQL Assessment using 

the Six-Year 1 data.

The Acceptance Criteria that were set forth in various FR notices during the time of the 

generation of the Six-Year 1 data were used to calculate the passing rates. However, while this 

was a relatively straightforward procedure for analytes with percentage-based acceptance criteria 

(e.g., + 30%), fourteen analytes have acceptance criteria of +2 standard deviations (SD) about 

the estimated mean recovery for each PT study. The mean and acceptance criteria must be 

calculated by using coefficients that were applicable during the generation of the Six-Year 1 PE 

data; these coefficients are not available from EPA at this time. The equations are:

• Mean = a*T + b

• SD = c*T + d

Where a, b, c, and d are the coefficients, and T is the true or spiked concentration. 

 Coefficients that were published by the NELAC in 2002 were available for this 

assessment; however it is not clear whether these coefficients were in place during the generation 

of the Six-Year 1 data. Re-calculation of passing rates for several of these analytes using the 

2002 NELAC coefficients indicated considerable agreement in passing rates, although values 

were different in some cases (there was no apparent pattern to the values that were not in 

agreement). This suggested that the coefficients may not have changed or at least not changed 

substantially from the 1990s to 2002; however this is uncertain. Since eight of the 14 analytes 

with acceptance criteria of + 2 SD were evaluated in the March 2003 report, and acceptance 

criteria had, apparently, been provided by EPA at that time, the Six-Year 1 regressions for these 
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eight analytes are taken directly from the data in the March 2003 report. These eight analytes 

are: benzo(a)pyrene, di(2-ethylhexyl)phthalate, diquat, glyphosate, hexachlorobenzene, 

hexachlorocyclopentadiene, oxamyl, and picloram. The remaining six of 14 analytes that had 

not been prioritized for inclusion in the March 2003 report are: bromate, dalapon, di(2-

ethylhexyl)adipate, dinoseb, endothall, and simazine. Passing rates for these six analytes were 

calculated using the 2002 NELAC coefficients. As a result, there is some uncertainty associated 

with the Six-Year 1 PT data analysis for these six analytes. 

It should be noted that for dalapon, di(2-ethylhexyl)adipate, endothall, and simazine, 

passing rates for data below the PQL were not determined, as the 2002 NELAC criteria are only 

valid over specific concentration ranges, and the ranges did not extend below the PQLs for these 

analytes.

5.3 Regression Plots

The PQL assessments are illustrated using linear regressions that plot laboratory passing 

rate versus true concentration. The PQL often has been set at the concentration where 75% of 

laboratories are predicted to meet acceptance criteria. The number of laboratories that 

participated in the Six-Year 1 PT studies for the regulated analytes ranged from approximately 

10 to more than 60, with approximately 10 to 30 different concentrations evaluated. The number 

of laboratories that participated in the ERA PT studies from 1999-2004 for the regulated analytes 

ranged from approximately 10 to more than 70, with 59-60 different concentrations evaluated.

In cases where the acceptance criteria vary with concentration, the data points that were 

less than 10 μg/L and those that were greater than or equal to 10 μg/L are plotted as independent 

data populations, as the variable acceptance criteria tend to result in two "clusters" of data. The 

following sections present the results of the regressions used in Six-Year 1, the regressions of the 

1999-2004 ERA PT data, and any methods that have been approved for these analytes since 

2000. The ERA data comprise approximately 50% of the nationwide PT data, while the PT data 

used in Six-Year 1 was from state and EPA laboratories across the country. Several analytes in 

Exhibit 1 could not be evaluated in this report for a number of reasons. These include:

• Acrylamide: No PT data available.

• Chlorite: Chlorite has no promulgated PQL. 

• Epichlorohydrin: No PT data available.

• 2,3,7,8-Tetrachlorodibenzodioxin (TCDD – dioxin): Only one data point in the ERA data 

set, and no Six-Year 1 PT data. 
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6.0 Results of PQL Assessment

EPA used two very different approaches to assess improvements in laboratory analytical 

performance over time: 1) evaluating data from the laboratory accreditation studies performed 

as part of the drinking water laboratory certification program (PE/PT data), and 2) comparing 

performance of the analytical methods available for compliance monitoring at the time of 

promulgation to those available currently. For analytes with no new methods, analytical 

performance was measured solely by PE/PT data. For those analytes with new methods, 

analytical performance was measured by PE/PT data, but may be supported by lower detection 

limits from new methods. The existence of new methods with lower detection limits may not 

directly translate to improved analytical performance, however. It is possible that only a small 

number of laboratories will use a new method, or it may take time for the method to be utilized 

to its full effectiveness.

Despite of using this two-step approach, EPA had difficulty in making a quantitative 

assessment of the improvements in laboratory performance over time. There were severe

limitations in the laboratory accreditation studies data, i.e. PE/PT results were either not 

available below the current PQL, the concentrations of interest, or the results were 

inconclusive/inadequate regarding a potential to revise the PQL. As a result, EPA did not have 

sufficient data to recalculate any PQLs with certainty. Instead, EPA used the data to indicate 

potential (qualitative assessment) for PQL revision. 

For each analyte, MDLs from EPA-approved methods are compared and a PQL 

assessment is presented by means of linear regression of both the Six-Year 1 dataset and the 

ERA dataset from Six-Year 2. Note that MDLs from proprietary methods (i.e., analytical 

methods not developed by EPA) are not included in the MDL comparison, as they are not readily 

available. A qualitative conclusion is drawn by presenting a recommendation of whether a PQL 

might be reduced. The discussion includes an indication of whether an analyte was evaluated in 

the March 2003 report (e.g., included for discussion, but PE data were not necessarily regressed), 

whether the Six-Year 1 data were regressed in the March 2003 report (e.g., analyte was included 

and the PE data were regressed), how the true concentrations relate to the PQL, and how the PE 

data from Six-Year 1 and the ERA PT data from Six-Year 2 may suggest or not suggest potential 

changes to the PQL.

The results for the regulated analytes are broken down into two categories based on the 

limitation of the PQL for setting MCL at the time of promulgation: 1) analytes with Maximum 

Contaminant Level (MCL) equal to the current PQL, and thus the PQL is limiting; or 2) analytes 

with MCL greater than the current PQL and thus it is technically feasible to reduce an MCL. 

PQL assessment for these analytes can indicate the potential for MCL reduction beyond the 

current PQL. The PQL assessments were made and are presented in this report for a total of 66 

analytes. Four analytes could not be analyzed for the reasons stated: acrylamide, 

epichlorohydrin, 2,3,7,8-TCDD (dioxin) lacked PE/PT data, and chlorite has no PQL. 

 Using this as a framework, the following sub-categories are used to summarize the results 

of PQL analysis. These categorizations were made based on a visual inspection of the 

regressions. In some cases, even though the regression line(s) were above the 75% passing rate, 
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several factors, including poor performance above the PQL or lack of data below the PQL led to 

a conclusion that perhaps the PQL should not be reduced. In addition, consideration was given 

to recent laboratory performance as indicated by the ERA data. For example, if the older SixYear 1 data indicated that the PQL should not be reduced, and if the more recent ERA data 

indicated better performance, this was a factor in making the overall determination as to whether 

or not a PQL could be reduced. 

• Analytes with MCL equal to the current PQL, and thus the PQL is limiting 

- PQL assessment supports reduction of the current PQL; 

- PQL assessment may support reduction of the current PQL; and 

- PQL assessment does not support reduction of the current PQL, or data are 

inconclusive or insufficient to reach a conclusion 

• Analytes with MCL greater than the current PQL and thus it is technically feasible to 

reduce an MCL

- PQL assessment supports reduction of the current PQL;

- PQL assessment may support reduction of the current PQL; and 

- PQL assessment does not support reduction of the current PQL, or data are 

inconclusive or insufficient to reach a conclusion.

Note that the qualitative conclusions presented in this report are not necessarily identical 

to the conclusions that were documented in the March 2003 report. Rather, a new assessment is 

made herein considering the advantages and disadvantages of the PQL concept, the availability 

of PT data in the vicinity of and/or below the PQL, and outliers. The qualitative conclusions are 

based primarily on data that are in the vicinity of and/or below the PQL (for most of the VOCs, 

this corresponds to concentrations <10 μg/L). Only the current evaluations of the Six-Year 1 and 

Six-Year 2/ERA data are presented in this report.

 

6.1 Analytes with Maximum Contaminant Level (MCL) Equal to the Current PQL and 

Thus the PQL is limiting 

Twenty-five analytes have an MCL that is set at the PQL. As a result, PQL assessment is 

required to determine whether an MCL might be lowered in the future. These 25 analytes can be 

further categorized into the three groups mentioned in Section 6.0 depending on whether or not 

the PT assessments support the reduction of the current PQL. 

6.1.1 PQL Assessment Supports Reduction of the Current PQL

Of the 25 analytes mentioned above, nine analytes have an existing PQL that is equal to 

the MCL and their PE/PT data suggest that the PQL could be lower. 
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Benzene 

Results of the Methods Comparison

Exhibit 4 summarizes the MDLs for benzene as documented in EPA-developed analytical 

methods. No updated or new analytical methods have been approved for the analysis of benzene 

in drinking water samples during the years 2000-2007. 

Exhibit 4: Analytical Methods for Benzene

MCL = 0.005 mg/L Current PQL = 0.005 mg/L DL = 0.0005 mg/L 

Acceptance Criteria = + 20% or 40%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

502.2 CCGC with PID/ELCD 0.01

524.2 CCGC/MS 0.03 - 0.04

Notes: The regulatory DL for volatile organic compounds is listed at 40 CFR 

141.24(k)(17)(ii)(C). Acceptance Criteria for volatile organic compounds are listed at 40 CFR 

141.24(f)(17)(i).

Results of the PQL Analysis 

The current PQL for benzene is 5 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets 

are regressed separately (see Exhibit 5). The Six-Year 1 PE data for benzene were regressed as 

part of the March 2003 report. Note that the acceptance criteria are + 40% at spike 

concentrations below 10 μg/L and + 20% at or above 10 μg/L; hence the data are regressed as 

two independent populations. Two of the 17 spike values from the Six-Year 1 data set are below 

the current PQL of 5 μg/L. Eight of the 60 spike values from the Six-Year 2/ERA data set are 

less than the current PQL. All of the passing rates for the Six-Year 1 and Six-Year 2/ERA data 

sets are at or above 75%. 
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Exhibit 5: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Benzene

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25

True Value (ug/L)

% Laboratories Passing

ERA Data Below 10 ug/L ERA Data At or Above 10 ug/L PQL

Six-Year 1 Data Below 10 ug/L Six-Year 1 Data At or Above 10 ug/L 10 ug/L Acceptance Criteria Boundary

75% Passing Rate

Acceptance Criteria

= + 20%

Acceptance Criteria

= + 40%

Current PQL 

= 5 ug/L

75%

Conclusion for Benzene

The high laboratory passing rates (well above 75%) at concentrations below the current 

PQL of 5 μg/L for both the Six-Year 1 and Six-Year 2/ERA data sets suggest that the PQL could 

be lower. Although there are limited Six-Year 1 data below the PQL, laboratory passing rates 

below and in the vicinity of the PQL are well above 75%, which supports the conclusion that the 

PQL could be lower. No new or revised methods that may be expected to improve analytical 

performance in the vicinity of the current PQL (and hence suggest possible reduction of the 

PQL) have been approved from 2000-2007.
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Carbon Tetrachloride 

Results of the Methods Comparison

Exhibit 6 summarizes the MDLs for carbon tetrachloride as documented in EPAdeveloped analytical methods. No updated or new analytical methods have been approved for 

the analysis of carbon tetrachloride in drinking water samples during the years 2000-2007. 

Exhibit 6: Analytical Methods for Carbon Tetrachloride

MCL = 0.005 mg/L Current PQL = 0.005 mg/L DL = 0.0005 mg/L 

Acceptance Criteria = + 20% or 40%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

502.2 CCGC with PID/ELCD 0.01 - 0.02

524.2 CCGC/MS 0.08 - 0.21

551.1 LLE/GC w/ ECD 0.002 -

0.050

Notes: The regulatory DL for volatile organic compounds is listed at 40 CFR 

141.24(k)(17)(ii)(C). Acceptance Criteria for volatile organic compounds are listed at 40 CFR 

141.24(f)(17)(i).

Results of the PQL Analysis

The current PQL for carbon tetrachloride is 5 μg/L. The Six-Year 1 and Six-Year 2/ERA 

data sets are regressed separately (see Exhibit 7). The Six-Year 1 PE data for carbon 

tetrachloride were evaluated but were not regressed as part of the March 2003 report. Note that 

the acceptance criteria are + 40% at spike concentrations below 10 μg/L and + 20% at or above 

10 μg/L; hence the data are regressed as two independent populations. One of the 17 spike 

values from the Six-Year 1 data set is below the current PQL of 5 μg/L. Nine of the 60 Six-Year 

2/ERA spike values are below the current PQL. Nearly all of the passing rates for the Six-Year 1 

and Six-Year 2/ERA data sets are above 75% (with the exception of two Six-Year 2/ERA 

passing rates). 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 26

Exhibit 7: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Carbon Tetrachloride

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14 16 18 20

True Value (ug/L)

% Laboratories Passing

ERA Data Below 10 ug/L ERA Data At or Above 10 ug/L PQL

Six-Year 1 Data Below 10 ug/L Six-Year 1 Data At or Above 10 ug/L 10 ug/L Acceptance Criteria Boundary

75% Passing Rate

Acceptance Criteria

= + 20%

Acceptance Criteria

= + 40%

Current PQL 

= 5 ug/L

75%

Conclusion for Carbon Tetrachloride

The high laboratory passing rates (well above 75%) at concentrations below the current 

PQL of 5 μg/L for both the Six-Year 1 and Six-Year 2/ERA data sets suggest that the PQL could 

be lower. Although there is only one Six-Year 1 datum below the PQL, laboratory passing rates 

below and in the vicinity of the PQL are well above 75%, which supports the conclusion that the 

PQL could be lower. No new or revised methods that may be expected to improve analytical 

performance in the vicinity of the current PQL (and hence suggest possible reduction of the 

PQL) have been approved from 2000-2007.
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 27

Chlordane 

Results of the Methods Comparison

Exhibit 8 summarizes the MDLs for chlordane as documented in EPA-developed 

analytical methods (note that the MDLs in Exhibit 8 represent ranges for chlordane, α-chlordane, 

γ-chlordane, cis-nonachlor and trans-nonachlor). No updated or new analytical methods have 

been approved for the analysis of chlordane in drinking water samples during the years 2000-

2007. 

Exhibit 8: Analytical Methods for Chlordane 

MCL = 0.002 mg/L Current PQL = 0.002 mg/L DL = 0.0002 mg/L 

Acceptance Criteria = + 45%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

505 ME and GC 0.006 - 0.14

508 GC/ECD 0.0016 –

0.0041

508.1 LSE and ECGC 0.001 –

0.004

525.2 LSE and CCGC/MS 0.05 – 0.22

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for chlordane is 2 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets 

are regressed separately (see Exhibit 9). The Six-Year 1 PE data for chlordane were evaluated in 

the March 2003 report; however, these data were not regressed in the report. Three of the 20 

spike values from the Six-Year 1 data set are below the current PQL of 2 μg/L. No Six-Year 

2/ERA data are below the current PQL. All of the Six-Year 1 passing rates and all but two of the 

Six-Year 2/ERA passing rates exceed 75%.
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 28

Exhibit 9: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Chlordane 

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14 16 18 20

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 45%

Current PQL 

= 2 ug/L

75%

Conclusion for Chlordane

The high laboratory passing rates (well above 75%) at concentrations below the current 

PQL of 5 μg/L for the Six-Year 1 data set suggest that the PQL could be lower. Although there 

are no Six-Year 2/ERA data below the PQL, laboratory passing rates in the vicinity of the PQL 

are well above 75% which may support the Six-Year 1 data conclusion that the PQL could be 

lower. No new or revised methods that may be expected to improve analytical performance in 

the vicinity of the current PQL (and hence suggest possible reduction of the PQL) have been 

approved from 2000-2007. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 29

1,2-Dichloroethane (Ethylene dichloride) 

Results of the Methods Comparison

Exhibit 10 summarizes the MDLs for 1,2-dichloroethane as documented in EPAdeveloped analytical methods. No updated or new analytical methods have been approved for 

the analysis of 1,2-dichloroethane in drinking water samples during the years 2000-2007. 

Exhibit 10: Analytical Methods for 1,2-Dichloroethane

MCL = 0.005 mg/L Current PQL = 0.005 mg/L DL = 0.0005 mg/L 

Acceptance Criteria = + 20% or 40%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

502.2 CCGC with PID/ ELCD 0.03

524.2 CCGC/MS 0.02 - 0.06

Notes: The regulatory DL for volatile organic compounds is listed at 40 CFR 

141.24(k)(17)(ii)(C). Acceptance Criteria for volatile organic compounds are listed at 40 CFR 

141.24(f)(17)(i).

Results of the PQL Analysis

 The current PQL for 1,2-dichloroethane is 5 μg/L. The Six-Year 1 and Six-Year 2/ERA 

data sets are regressed separately (see Exhibit 11). The Six-Year 1 PE data for 1,2-

dichloroethane were evaluated but were not regressed as part of the March 2003 report. Note 

that the acceptance criteria are + 40% at spike concentrations below 10 μg/L and + 20% at or 

above 10 μg/L; hence the data are regressed as two independent populations. One of the 17 

spike values from the Six-Year 1 data set is below the current PQL of 5 μg/L. Seven of the 60 

Six-Year 2/ERA spike values are below the current PQL. All of the passing rates for the SixYear 1 and Six-Year 2/ERA data are above 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 30

Exhibit 11: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – 1,2-Dichloroethane

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14 16 18 20

True Value (ug/L)

% Laboratories Passing

ERA Data Below 10 ug/L ERA Data At or Above 10 ug/L PQL

Six-Year 1 Data Below 10 ug/L Six-Year 1 Data At or Above 10 ug/L 10 ug/L Acceptance Criteria Boundary

75% Passing Rate

Acceptance Criteria

= + 20%

Acceptance Criteria

= + 40%

Current PQL 

= 5 ug/L

75%

Conclusion for 1,2-Dichloroethane

The high laboratory passing rates (well above 75%) at concentrations below the current 

PQL of 5 μg/L for both the Six-Year 1 and Six-Year 2/ERA data sets suggest that the PQL could 

be lower. Although there is only one Six-Year 1 datum below the PQL, laboratory passing rates 

below and in the vicinity of the PQL are well above 75%, which supports the conclusion that the 

PQL could be lower. No new or revised methods that may be expected to improve analytical 

performance in the vicinity of the current PQL (and hence suggest possible reduction of the 

PQL) have been approved from 2000-2007.
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 31

1,2-Dichloropropane 

Results of the Methods Comparison

Exhibit 12 summarizes the MDLs for 1,2-dichloropropane as documented in EPAdeveloped analytical methods. No updated or new analytical methods have been approved for 

the analysis of 1,2-dichloropropane in drinking water samples during the years 2000-2007. 

Exhibit 12: Analytical Methods for 1,2-Dichloropropane 

MCL = 0.005 mg/L Current PQL = 0.005 mg/L DL = 0.0005 mg/L 

Acceptance Criteria = + 20% or 40%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

502.2 CCGC with PID/ ELCD 0.01 - 0.03

524.2 CCGC/MS 0.02 - 0.04

Notes: The regulatory DL for volatile organic compounds is listed at 40 CFR 

141.24(k)(17)(ii)(C). Acceptance Criteria for volatile organic compounds are listed at 40 CFR 

141.24(f)(17)(i).

Results of the PQL Analysis

The current PQL for 1,2-dichloropropane is 5 μg/L. The Six-Year 1 and Six-Year 2/ERA 

data sets are regressed separately (see Exhibit 13). The Six-Year 1 PE data for 1,2-

dichloropropane were evaluated but were not regressed as part of the March 2003 report. Note 

that the acceptance criteria are + 40% at spike concentrations below 10 μg/L and + 20% at or 

above 10 μg/L; hence the data are regressed as two independent populations. No Six-Year 1 data 

are available below the current PQL of 5 μg/L. Nine of the 60 spike values in the Six-Year 

2/ERA data set are below the current PQL. All of the passing rates are above 75% (with the 

exception of one passing rate equal to 75%). 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 32

Exhibit 13: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – 1,2-Dichloropropane 

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14 16 18 20

True Value (ug/L)

% Laboratories Passing

ERA Data Below 10 ug/L ERA Data At or Above 10 ug/L PQL

Six-Year 1 Data Below 10 ug/L Six-Year 1 Data At or Above 10 ug/L 10 ug/L Acceptance Criteria Boundary

75% Passing Rate

Acceptance Criteria

= + 20%

Acceptance Criteria

= + 40%

Current PQL 

= 5 ug/L

75%

Conclusion for 1,2-Dichloropropane

The high laboratory passing rates (well above 75%) at concentrations below the current 

PQL of 5 μg/L for the Six-Year 2/ERA data set suggests that the PQL could be lower. Although 

there are no Six-Year 1 data below the PQL, laboratory passing rates in the vicinity of the PQL 

are well above 75% which may support the Six-Year 2/ERA data conclusion that the PQL could 

be lower. No new or revised methods that may be expected to improve analytical performance 

in the vicinity of the current PQL (and hence suggest possible reduction of the PQL) have been 

approved from 2000-2007. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 33

Hexachlorobenzene 

Results of the Methods Comparison

Exhibit 14 summarizes the MDLs for hexachlorobenzene as documented in EPAdeveloped analytical methods. No updated or new analytical methods have been approved for 

the analysis of hexachlorobenzene in drinking water samples during the years 2000-2007. 

Exhibit 14: Analytical Methods for Hexachlorobenzene

MCL = 0.001 mg/L Current PQL = 0.001 mg/L DL = 0.0001 mg/L 

Acceptance Criteria = Mean + 2 Std Dev

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

505 ME and GC 0.002

508 GC/ECD 0.0077

508.1 L/S Extraction and ECGC 0.001

525.2 LSE and CCGC/MS 0.049 - 0.13

551.1 LLE/GC w/ ECD 0.001 -

0.003

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for hexachlorobenzene is 1 μg/L. The Six-Year 1 and Six-Year 2/ERA 

data sets are regressed separately (see Exhibit 15). The Six-Year 1 PE data for 

hexachlorobenzene were evaluated but were not regressed as part of the March 2003 report. 

Eight of the 14 spike Six-Year 1 values are below the current PQL of 1 μg/L. Nine of the 60 

Six-Year 2/ERA spike values are below the current PQL. Nearly all of the passing rates for the 

Six-Year 1 and Six-Year 2/ERA hexachlorobenzene data are above 75% (with the exception of 

two Six-Year 2/ERA passing rates). 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 34

Exhibit 15: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Hexachlorobenzene

Conclusion for Hexachlorobenzene

The high laboratory passing rates (generally well above 75%) at concentrations below 

and in the vicinity of the current PQL of 1 μg/L for both the Six-Year 1 and Six-Year 2/ERA 

data sets suggest that the PQL could be lower. No new or revised methods that may be expected 

to improve analytical performance in the vicinity of the current PQL (and hence suggest possible 

reduction of the PQL) have been approved from 2000-2007.

0

10

20

30

40

50

60

70

80

90

100

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= Mean + 2 SD

Current PQL 

= 1 ug/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 35

Tetrachloroethylene

Results of the Methods Comparison

Exhibit 16 summarizes the MDLs for tetrachloroethylene as documented in EPAdeveloped analytical methods. No updated or new analytical methods have been approved for 

the analysis of tetrachloroethylene in drinking water samples during the years 2000-2007. 

Exhibit 16: Analytical Methods for Tetrachloroethylene

MCL = 0.005 mg/L Current PQL = 0.005 mg/L DL = 0.0005 mg/L 

Acceptance Criteria = + 20% or 40%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

502.2 CCGC with PID/ELCD 0.02 - 0.05

524.2 CCGC/MS 0.05 - 0.14

551.1 LLE/GC w/ ECD 0.002 -

0.008

Notes: The regulatory DL for volatile organic compounds is listed at 40 CFR 

141.24(k)(17)(ii)(C). Acceptance Criteria for volatile organic compounds are listed at 40 CFR 

141.24(f)(17)(i).

Results of the PQL Analysis

The current PQL for tetrachloroethylene is 5 μg/L. The Six-Year 1 and Six-Year 2/ERA 

data sets are regressed separately (see Exhibit 17). The Six-Year 1 PE data for 

tetrachloroethylene were evaluated but were not regressed as part of the March 2003 report. 

Note that the acceptance criteria are + 40% at spike concentrations below 10 μg/L and + 20% at 

or above 10 μg/L; hence the data are regressed as two independent populations. No Six-Year 1 

data are available below the current PQL of 5 μg/L. Thirteen of the 60 spike values in the SixYear 2/ERA data set are below the current PQL. All but two of the passing rates are above 75%. 

Furthermore, the regression lines are also well above 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 36

Exhibit 17: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Tetrachloroethylene

Conclusion for Tetrachloroethylene

The high laboratory passing rates (well above 75%) at concentrations below the current 

PQL of 5 μg/L for the Six-Year 2/ERA data set suggests that the PQL could be lower. Although 

there are no Six-Year 1 data below the PQL, laboratory passing rates in the vicinity of the PQL 

are well above 75% which may support the Six-Year 2/ERA data conclusion that the PQL could 

be lower. No new or revised methods that may be expected to improve analytical performance 

in the vicinity of the current PQL (and hence suggest possible reduction of the PQL) have been 

approved from 2000-2007.

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14 16 18 20

True Value (ug/L)

% Laboratories Passing

ERA Data Below 10 ug/L ERA Data At or Above 10 ug/L PQL

Six-Year 1 Data Below 10 ug/L Six-Year 1 Data At or Above 10 ug/L 10 ug/L Acceptance Criteria Boundary

75% Passing Rate

Acceptance Criteria

= + 20%

Acceptance Criteria

= + 40%

Current PQL 

= 5 ug/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 37

1,1,2-Trichloroethane 

Results of the Methods Comparison

Exhibit 18 summarizes the MDLs for 1,1,2-trichloroethane as documented in EPAdeveloped analytical methods. No updated or new analytical methods have been approved for 

the analysis of 1,1,2-trichloroethane in drinking water samples during the years 2000-2007. 

Exhibit 18: Analytical Methods for 1,1,2-Trichloroethane

MCL = 0.005 mg/L Current PQL = 0.005 mg/L DL = 0.0005 mg/L 

Acceptance Criteria = + 20% or 40%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

502.2 CCGC with PID/ ELCD 0.04

524.2 CCGC/MS 0.03 - 0.10

551.1 LLE/GC w/ ECD 0.012 -

0.017

Notes: The regulatory DL for volatile organic compounds is listed at 40 CFR 

141.24(k)(17)(ii)(C). Acceptance Criteria for volatile organic compounds are listed at 40 CFR 

141.24(f)(17)(i).

Results of the PQL Analysis

The current PQL for 1,1,2-trichloroethane is 5 μg/L. The Six-Year 1 and Six-Year 

2/ERA data sets are regressed separately (see Exhibit 19). The Six-Year 1 PE data for 1,1,2-

trichloroethane were evaluated but were not regressed as part of the March 2003 report. Note 

that the acceptance criteria are + 40% at spike concentrations below 10 μg/L and + 20% at or 

above 10 μg/L; hence the data are regressed as two independent populations. No Six-Year 1 data 

are available below the current PQL of 5 μg/L. Twelve of the 60 spike values in the Six-Year 

2/ERA data are below the current PQL. All of the passing rates are above 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 38

Exhibit 19: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – 1,1,2-Trichloroethane

0 2 4 6 8 10 12 14 16 18 20

True Value (ug/L)

ERA Data Below 10 ug/L ERA Data At or Above 10 ug/L PQL

Six-Year 1 Data Below 10 ug/L Six-Year 1 Data At or Above 10 ug/L 10 ug/L Acceptance Criteria Boundary

75% Passing Rate

Conclusion for 1,1,2-Trichloroethane

The high laboratory passing rates (well above 75%) at concentrations below the current 

PQL of 5 μg/L for the Six-Year 2/ERA data set suggests that the PQL could be lower. Although 

there are no Six-Year 1 data below the PQL, laboratory passing rates in the vicinity of the PQL 

are well above 75% which may support the Six-Year 2/ERA data conclusion that the PQL could 

be lower. No new or revised methods that may be expected to improve analytical performance 

in the vicinity of the current PQL (and hence suggest possible reduction of the PQL) have been 

approved from 2000-2007. 

0

10

20

30

40

50

60

70

80

90

100

% Laboratories Passing

Acceptance Criteria

= + 20%

Acceptance Criteria

= + 40%

Current PQL 

= 5 ug/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 39

Trichloroethylene

Results of the Methods Comparison

Exhibit 20 summarizes the MDLs for trichloroethylene as documented in EPA-developed 

analytical methods. No updated or new analytical methods have been approved for the analysis 

of trichloroethylene in drinking water samples during the years 2000-2007. 

Exhibit 20: Analytical Methods for Trichloroethylene

MCL = 0.005 mg/L Current PQL = 0.005 mg/L DL = 0.0005 mg/L 

Acceptance Criteria = + 20% or 40%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

502.2 CCGC with PID/ ELCD 0.01 - 0.06

524.2 CCGC/MS 0.02 - 0.19

551.1 LLE/GC w/ ECD 0.002 -

0.042

Notes: The regulatory DL for volatile organic compounds is listed at 40 CFR

141.24(k)(17)(ii)(C). Acceptance Criteria for volatile organic compounds are listed at 40 CFR 

141.24(f)(17)(i).

Results of the PQL Analysis

The current PQL for trichloroethylene is 5 μg/L. The Six-Year 1 and Six-Year 2/ERA 

data sets are regressed separately (see Exhibit 21). The Six-Year 1 PE data for trichloroethylene 

were evaluated but were not regressed as part of the March 2003 report. Note that the 

acceptance criteria are + 40% at spike concentrations below 10 μg/L and + 20% at or above 10 

μg/L; hence the data are regressed as two independent populations. No Six-Year 1 data are 

below the current PQL of 5 μg/L. Six of the 60 spike values in the Six-Year 2/ERA data are 

below the current PQL. All but one of the passing rates are above 75%. Furthermore, the 

regression lines are also well above 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 40

Exhibit 21: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Trichloroethylene 

Conclusion for Trichloroethylene

The high laboratory passing rates (well above 75%) at concentrations below the current 

PQL of 5 μg/L for the Six-Year 2/ERA data set suggests that the PQL could be lower. Although 

there are no Six-Year 1 data below the PQL, laboratory passing rates in the vicinity of the PQL 

are well above 75% which may support the Six-Year 2/ERA data conclusion that the PQL could 

be lower. No new or revised methods that may be expected to improve analytical performance 

in the vicinity of the current PQL (and hence suggest possible reduction of the PQL) have been 

approved from 2000-2007.

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14 16 18 20

True Value (ug/L)

% Laboratories Passing

ERA Data Below 10 ug/L ERA Data At or Above 10 ug/L PQL

Six-Year 1 Data Below 10 ug/L Six-Year 1 Data At or Above 10 ug/L 10 ug/L Acceptance Criteria Boundary

75% Passing Rate

Acceptance Criteria

= + 20%

Acceptance Criteria

= + 40%

Current PQL 

= 5 ug/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 41

6.1.2 PQL Assessment May Support Reduction of the Current PQL

Of the 25 analytes mentioned in Section 6.1, eight analytes have an existing PQL that is 

equal to the MCL and their PE/PT data suggest that the PQL could possibly be lower.

Alachlor 

Results of the Methods Comparison

Exhibit 22 summarizes the MDLs for alachlor as documented in EPA-developed 

analytical methods. No updated or new analytical methods have been approved for the analysis 

of alachlor in drinking water samples during the years 2000-2007. 

Exhibit 22: Analytical Methods for Alachlor 

MCL = 0.002 mg/L Current PQL = 0.002 mg/L DL = 0.0002 mg/L 

Acceptance Criteria = + 45%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

505 ME and GC 0.225

507 GC/N-PD 0.14

508.1 LSE and ECGC 0.009

525.2 LSE and CCGC/MS 0.069 - 0.16

551.1 LLE/GC w/ ECD 0.005 - 

0.025

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for alachlor is 2 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets 

are regressed separately (see Exhibit 23). The Six-Year 1 PE data for alachlor were evaluated in 

the March 2003 report; however, these data were not regressed in that report. Four of the 20 

spike values from the Six-Year 1 data set are below the current PQL of 2 μg/L. However, none 

of the Six-Year 2/ERA data are below the current PQL. The percentage of laboratories passing 

is variable, ranging from 71.4% to 100%. The Six-Year 1 passing rates generally exceed 75% 

(with the exception of one spike value) and all of the Six-Year 2/ERA passing rates are greater 

than or equal to 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 42

Exhibit 23: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Alachlor 

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14 16 18 20

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 45%

Current PQL 

= 2 ug/L

75%

Conclusion for Alachlor

The Six-Year 1 laboratory passing rates below and in the vicinity of the PQL of 2 μg/L 

are above 75% with one exception. Given the lack of Six-Year 2/ERA data below the PQL, but 

passing rates above 75% in the vicinity of the PQL, a reduction of the PQL may be considered. 

No new or revised methods that may be expected to improve analytical performance in the 

vicinity of the current PQL (and hence suggest possible reduction of the PQL) have been 

approved from 2000-2007.
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 43

Antimony

Results of the Methods Comparison

Exhibit 24 summarizes the MDLs for antimony as documented in EPA-developed 

analytical methods. Updates to two methods have been approved for the analysis of antimony in 

drinking water samples during the years 2000-2007 (see Exhibit A-1). These updates are 

associated with administrative and technical changes or clarifications that are not expected to 

improve analytical performance near the PQL. 

Exhibit 24: Analytical Methods for Antimony 

MCL = 0.006 mg/L Current PQL = 0.006 mg/L DL = 0.0004-0.003mg/L

Acceptance Criteria = +30%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL mg/L

200.8 ICP/MS 0.00002 -

0.0004

200.9 GFAA 0.0008

Notes: Regulatory DLs for inorganic compounds are listed at 40 CFR 141.23(a)(4)(i). 

Acceptance Criteria for inorganic compounds are listed at 40 CFR 141.23(k)(3)(ii).

Results of the PQL Analysis

 The current PQL for antimony is 0.006 mg/L. The Six-Year 1 and Six-Year 2/ERA data 

sets are regressed separately (see Exhibit 25). The Six-Year 1 PE data for antimony were not 

evaluated in the March 2003 report. Two of the 20 spike values from the Six-Year 1 data are 

below the current PQL of 0.006 mg/L. No Six-Year 2/ERA data are below the current PQL. All 

of the passing rates in both data sets exceed 75%. The regression lines are also well above 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 44

Exhibit 25: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Antimony

90

100

0

10

20

30

40

50

60

70

80

0.00 0.02 0.04 0.06 0.08 0.10 0.12

True Value (mg/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 30%

Current PQL 

= 0.006 mg/L

75%

Conclusion for Antimony

Given the availability of limited data below the current PQL of 0.006 mg/L, but relatively 

high laboratory passing rates (above 75%) just below and in the vicinity of the PQL for the SixYear 1 data, and above 75% passing rates in the vicinity of the PQL for the Six-Year 2/ERA 

data, a reduction of the PQL may be considered. No new or revised methods that may be 

expected to improve analytical performance in the vicinity of the current PQL (and hence 

suggest possible reduction of the PQL) have been approved from 2000-2007. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 45

1,2-Dibromo-3-chloropropane (DBCP) 

Results of the Methods Comparison

Exhibit 26 summarizes the MDLs for 1,2-dibromo-3-chloropropane as documented in 

EPA-developed analytical methods. No updated or new analytical methods have been approved 

for the analysis of DBCP in drinking water samples during the years 2000-2007. 

Exhibit 26: Analytical Methods for DBCP

MCL = 0.0002 mg/L Current PQL = 0.0002 mg/L DL = 0.00002 mg/L 

Acceptance Criteria = + 40%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

504.1 ME and GC 0.01

551.1 LLE/GC w/ ECD 0.006 -

0.009

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for DBCP is 0.2 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets 

are regressed separately (see Exhibit 27). The Six-Year 1 PE data for DBCP were evaluated but 

were not regressed as part of the March 2003 report. One of the 14 spike values from the SixYear 1 data is below the current PQL of 0.2 μg/L. Three of the 60 Six-Year 2/ERA spike values 

are below the current PQL. All of the passing rates for the Six-Year 1 and Six-Year 2/ERA data 

are above 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

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Exhibit 27: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – DBCP

Conclusion for 1,2-Dibromo-3-chloropropane

Given the limited data below the current PQL of 0.2 μg/L but high laboratory passing 

rates (well above 75%) just below and in the vicinity of the PQL for both Six-Year 2/ERA and 

Six-Year 1 data set, a reduction of the PQL may be considered. No new or revised methods that 

may be expected to improve analytical performance in the vicinity of the current PQL (and hence 

suggest possible reduction of the PQL) have been approved from 2000-2007.

0

10

20

30

40

50

60

70

80

90

100

0.0 0.5 1.0 1.5 2.0 2.5 3.0

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 40%

Current PQL 

= 0.2 ug/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 47

Heptachlor 

Results of the Methods Comparison

Exhibit 28 summarizes the MDLs for heptachlor as documented in EPA-developed 

analytical methods. No updated or new analytical methods have been approved for the analysis 

of heptachlor in drinking water samples during the years 2000-2007. 

Exhibit 28: Analytical Methods for Heptachlor 

MCL = 0.0004 mg/L Current PQL = 0.0004 mg/L DL = 0.00004 mg/L 

Acceptance Criteria = + 45%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

505 ME and GC 0.003

508 GC/ECD 0.0015

508.1 LSE and ECGC 0.005

525.2 LSE and CCGC/MS 0.059 - 0.15

551.1 LLE/GC w/ ECD 0.002 -

0.081

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for heptachlor is 0.4 μg/L. The Six-Year 1 and Six-Year 2/ERA data 

sets are regressed separately (see Exhibit 29). The Six-Year 1 PE data for heptachlor were 

evaluated but were not regressed as part of the March 2003 report. Three of the 19 spike values 

in the Six-Year 1 data set are below the current PQL of 0.4 μg/L. None of the Six-Year 2/ERA

data are below the current PQL. Although all of the Six-Year 1 passing rates, along with both 

regression lines, are well above 75%, the Six-Year 2/ERA passing rates display significant 

variability. Furthermore, three of the Six-Year 2/ERA passing rates are below 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

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Exhibit 29: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Heptachlor

90

100

0

10

20

30

40

50

60

70

80

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 45%

Current PQL 

= 0.4 ug/L

75%

Conclusion for Heptachlor

Given the availability of limited data below the current PQL of 0.4 μg/L, but relatively 

high laboratory passing rates (well above 75%) below and in the vicinity of the PQL for the SixYear 1 data, and a lack of data below the PQL for the Six-Year 2/ERA data, a reduction of the 

PQL may be considered. The passing rates in the vicinity of the PQL for the Six-Year 2/ERA 

data are variable which may not support the Six-Year 1 data conclusion that the PQL might be 

reduced. No new or revised methods that may be expected to improve analytical performance in 

the vicinity of the current PQL (and hence suggest possible reduction of the PQL) have been 

approved from 2000-2007.
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 49

Heptachlor Epoxide

Results of the Methods Comparison

Exhibit 30 summarizes the MDLs for heptachlor epoxide as documented in EPAdeveloped analytical methods. No updated or new analytical methods have been approved for 

the analysis of heptachlor epoxide in drinking water samples during the years 2000-2007. 

Exhibit 30: Analytical Methods for Heptachlor Epoxide 

MCL = 0.0002 mg/L Current PQL = 0.0002 mg/L DL = 0.00002 mg/L 

Acceptance Criteria = + 45%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

505 ME and GC 0.004

508 GC/ECD 0.0059

508.1 LSE and ECGC 0.001

525.2 LSE and CCGC/MS 0.048 - 0.13

551.1 LLE/GC w/ ECD 0.002 -

0.202

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for heptachlor epoxide is 0.2 μg/L. The Six-Year 1 and Six-Year 

2/ERA data sets are regressed separately (see Exhibit 31). The Six-Year 1 PE data for 

heptachlor epoxide were evaluated but were not regressed as part of the March 2003 report. 

Three of the 19 spike values in the Six-Year 1 data are below the current PQL of 0.2 μg/L. None 

of the Six-Year 2/ERA data are below the current PQL. Although all of the Six-Year 1 passing 

rates, along with both regression lines, are well above 75%, the Six-Year 2/ERA passing rates 

displayed significant variability. Furthermore, two of the Six-Year 2/ERA passing rates near the 

PQL are below 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

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Exhibit 31: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Heptachlor Epoxide 

Conclusion for Heptachlor Epoxide

Given the availability of limited data below the current PQL of 0.2 μg/L, but relatively 

high laboratory passing rates (mostly >90%) below and in the vicinity of the PQL for the SixYear 1 data, and a lack of data below the PQL for the Six-Year 2/ERA data, a reduction of the 

PQL may be considered. The passing rates in the vicinity of the PQL for the Six-Year 2/ERA 

data are highly variable which may not support the Six-Year 1 data conclusion that the PQL 

might be reduced. No new or revised methods that may be expected to improve analytical 

performance in the vicinity of the current PQL (and hence suggest possible reduction of the 

PQL) have been approved from 2000-2007.

0

10

20

30

40

50

60

70

80

90

100

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 45%

Current PQL 

= 0.2 ug/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 51

Lindane 

Results of the Methods Comparison

Exhibit 32 summarizes the MDLs for lindane as documented in EPA-developed 

analytical methods. No updated or new analytical methods have been approved for the analysis 

of lindane in drinking water samples during the years 2000-2007. 

Exhibit 32: Analytical Methods for Lindane

MCL = 0.0002 mg/L Current PQL = 0.0002 mg/L DL = 0.00002 mg/L 

Acceptance Criteria = + 45%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

505 ME and GC 0.003

508 GC/ECD 0.006

508.1 LSE and ECGC 0.006

525.2 LSE and CCGC/MS 0.047 - 0.15

551.1 LLE/GC w/ ECD 0.002 -

0.017

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for lindane is 0.2 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets 

are regressed separately (see Exhibit 33). The Six-Year 1 PE data for lindane were not evaluated 

in the March 2003 report. Three of the 20 spike values in the Six-Year 1 data set are less than or 

equal to the current PQL of 0.2 μg/L. None of the Six-Year 2/ERA data are below the current 

PQL. All the passing rates in both data sets are above 75%. Furthermore, the regression lines 

are also well above 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 52

Exhibit 33: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Lindane

Conclusion for Lindane

Given the availability of limited data below the current PQL of 0.2 μg/L, but relatively 

high laboratory passing rates (well above 75%) below and in the vicinity of the PQL for the SixYear 1 data, and a lack of data below the PQL for the Six-Year 2/ERA data, a reduction of the 

PQL may be considered. The passing rates in the vicinity of the PQL for the Six-Year 2/ERA 

data are somewhat variable, but all above 75%, which may support the Six-Year 1 data 

conclusion that the PQL might be reduced. No new or revised methods that may be expected to 

improve analytical performance in the vicinity of the current PQL (and hence suggest possible 

reduction of the PQL) have been approved from 2000-2007. 

0

10

20

30

40

50

60

70

80

90

100

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 45%

Current PQL 

= 0.2 ug/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 53

Toxaphene 

Results of the Methods Comparison

Exhibit 34 summarizes the MDLs for toxaphene as documented in EPA-developed 

analytical methods. No updated or new analytical methods have been approved for the analysis 

of toxaphene in drinking water samples during the years 2000-2007. 

Exhibit 34: Analytical Methods for Toxaphene 

MCL = 0.003 mg/L Current PQL = 0.003 mg/L DL = 0.001 mg/L 

Acceptance Criteria = + 45%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

505 ME and GC 1.0

508 GC/ECD

Listed in 

Method; no 

MDLs

determined

508.1 LSE and ECGC 0.13

525.2 LSE and CCGC/MS 1.0 - 1.7

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for toxaphene is 3 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets 

are regressed separately (see Exhibit 35). The Six-Year 1 PE data for toxaphene were evaluated 

but were not regressed in the March 2003 report. Three of the 20 spike values in the Six-Year 1 

data set are less than the current PQL of 3 μg/L. None of the Six-Year 2/ERA data are below the 

current PQL. All of the Six-Year 1 passing rates and regression line are well above 75%. 

Although the Six-Year 2/ERA data display some variability (and two of the passing rates are 

below 75%), the regression line is well above the 75% threshold. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 54

Exhibit 35: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Toxaphene 

Conclusion for Toxaphene

Given the availability of limited data below the current PQL of 3 μg/L, but relatively 

high laboratory passing rates (well above 75%) below and in the vicinity of the PQL for the SixYear 1 data, and a lack of data below the PQL for the Six-Year 2/ERA data, a reduction of the 

PQL may be considered. The passing rates in the vicinity of the PQL for the Six-Year 2/ERA 

data are somewhat variable but all above 75%, which may support the Six-Year 1 data 

conclusion that the PQL might be reduced. No new or revised methods that may be expected to 

improve analytical performance in the vicinity of the current PQL (and hence suggest possible 

reduction of the PQL) have been approved from 2000-2007. 

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14 16 18 20

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 45%

Current PQL 

= 3 ug/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 55

Vinyl Chloride

Results of the Methods Comparison

Exhibit 36 summarizes the MDLs for vinyl chloride as documented in EPA-developed 

analytical methods. No updated or new analytical methods have been approved for the analysis 

of vinyl chloride in drinking water samples during the years 2000-2007. 

Exhibit 36: Analytical Methods for Vinyl Chloride

MCL = 0.002 mg/L Current PQL = 0.002 mg/L DL = 0.0005 mg/L 

Acceptance Criteria = + 40%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

502.2 CCGC with PID/ ELCD 0.01 - 0.18

524.2 CCGC/MS 0.04 - 0.17

Notes: The regulatory DL for volatile organic compounds is listed at 40 CFR 

141.24(k)(17)(ii)(C). Acceptance Criteria for volatile organic compounds are listed at 40 CFR 

141.24(f)(17)(i).

Results of the PQL Analysis

The current PQL for vinyl chloride is 5 μg/L. The Six-Year 1 and Six-Year 2/ERA data 

sets are regressed separately (see Exhibit 37). The Six-Year 1 PE data for vinyl chloride were 

evaluated but were not regressed as part of the March 2003 report. No Six-Year 1 data are 

available below the current PQL of 5 μg/L. Two of the 60 spike values in the Six-Year 2/ERA

data are below the current PQL (a third is equal to the PQL). All of the passing rates are above 

75% (with the exception of one passing rate that is equal to 75%). Furthermore, the regression 

lines are well above 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 56

Exhibit 37: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Vinyl Chloride

Conclusion for Vinyl Chloride

Given the availability of limited data below the current PQL of 2 μg/L, but relatively 

high laboratory passing rates (well above 75%) below and in the vicinity of the PQL for the SixYear 2/ERA data, and a lack of data below the PQL for the Six-Year 1 data, a reduction of the 

PQL may be considered. The passing rates in the vicinity of the PQL for the Six-Year 1 data are 

variable, but all are >75%, which may support the Six-Year 2/ERA data conclusion that the PQL 

might be reduced. No new or revised methods that may be expected to improve analytical 

performance in the vicinity of the current PQL (and hence suggest possible reduction of the 

PQL) have been approved from 2000-2007.

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30 35

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 40%

Current PQL 

= 2 ug/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

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Page 57

6.1.3 PQL Assessment Does Not Support Reduction of the Current PQL or Data are 

Insufficient to Reach a Conclusion.

Of the 25 analytes mentioned in Section 6.1, eight analytes have an existing PQL that is 

equal to the MCL and their PE/PT data either indicate that the PQL should not be lower or their 

PE/PT data are insufficient to reach a conclusion.

Benzo(a)pyrene

Results of the Methods Comparison

Exhibit 38 summarizes the MDLs for benzo(a)pyrene as documented in EPA-developed 

analytical methods. No updated or new analytical methods have been approved for the analysis 

of benzo(a)pyrene in drinking water samples during the years 2000-2007. 

Exhibit 38: Analytical Methods for Benzo(a)pyrene

MCL = 0.0002 mg/L Current PQL = 0.0002 mg/L DL = 0.00002 mg/L 

Acceptance Criteria = Mean + 2 Std Dev

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

525.2 LSE and CCGC/MS 0.032 - 0.23

550 LLE/HPLC w/ CUV and FD 0.029

550.1 LSE/HPLC w/ CUV and FD 0.016

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

 The current PQL for benzo(a)pyrene is 0.2 μg/L. The Six-Year 1 and Six-Year 2/ERA 

data sets are regressed separately (see Exhibit 39). The Six-Year 1 PE data for benzo(a)pyrene 

were regressed as part of the March 2003 report. None of the Six-Year 1 or the Six-Year 2/ERA

data set are below the current PQL of 0.2 μg/L. All of the passing rates in the Six-Year 1 data 

are above 75% while several passing rates in the Six-Year 2/ERA data are less than or equal to 

75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

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Exhibit 39: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Benzo(a)pyrene

0

10

20

30

40

50

60

70

80

90

100

0.0 0.5 1.0 1.5 2.0 2.5 3.0

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= Mean + 2 SD

Current PQL 

= 0.2 ug/L

75%

Conclusion for Benzo(a)pyrene

Although the laboratory passing rates for the Six-Year 1 data set are above 75%, the 

passing rates for the Six-Year 2/ERA data set are low in the vicinity of the PQL of 0.2 μg/L. It 

may not be appropriate to recommend lowering of the PQL due to the lack of data below the 

current PQL for both data sets and the variability of the Six-Year 2/ERA passing rates. No new 

or revised methods that may be expected to improve analytical performance in the vicinity of the 

current PQL (and hence suggest possible reduction of the PQL) have been approved from 2000-

2007. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 59

Bromate

Results of the Methods Comparison

Exhibit 40 summarizes the MDLs for bromate as documented in EPA-developed 

analytical methods. Four new analytical methods have been approved for the analysis of 

bromate in drinking water samples during the years 2000-2007 (EPA Methods 317.0 (Rev. 2.0), 

321.8, 326.0, and ASTM D6581-00 [Federal Register, Vol. 71, No. 2, p. 388, January 4, 2006; 

see Exhibit A-1]). The MDLs/DLs for bromate by EPA Methods 317.0, 321.8 and 326.0 are 

lower than those for EPA Method 300.1, suggesting that laboratory performance at low 

concentrations may improve through use of Methods 317.0, 321.8 and 326.0. Since the new 

ASTM method is proprietary, it is uncertain whether new MDLs may be lower than those for 

other methods. Note that the acceptance criteria for bromate are given as +2 SD. NELAC 

changed the acceptance criteria to +30% in March 2007, but +2 SD were in place during the 

generation of the PT data used in this report. 

Exhibit 40: Analytical Methods for Bromate 

MCL = 0.010 mg/L Current PQL = 0.01 mg/L DL = N/A 

Acceptance Criteria = Mean + 2 Std Dev

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL mg/L

300.1 IC 0.00128 -

0.00144

317.0 IC with postcolumn reagent 0.00012 –

0.00098

321.8 IC/ICP/MS 0.0003 (DL)

326.0 IC with suppressor acidified postcolumn reagent 0.00017 –

0.0012 (DL)

Notes: EPA has not provided a regulatory DL for bromate in the CFR. Acceptance Criteria for 

disinfection byproducts are listed at 40 CFR 141.131(b)(2)(ii). As of April 1, 2007, the 

Acceptance Criteria for bromate were changed to + 30% (71 FR 388 1/4/2006).

Results of the PQL Analysis

The current PQL for bromate 10 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets are 

regressed separately (see Exhibit 41). The Six-Year 1 PE data for bromate were not evaluated in 

the March 2003 report. Three of the nine spike values in the Six-Year 1 data set are below the 

current PQL of 10 μg/L. One of the 60 spike values in the Six-Year 2/ERA data set is below the 

PQL. Three of the Six-Year 1 concentrations and two of the Six-Year 2/ERA concentrations 

have passing rates of less than 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 60

Exhibit 41: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Bromate

Conclusion for Bromate 

Although many of the laboratory passing rates for both the Six-Year 1 and Six-Year 

2/ERA data sets are >75%, it may not be appropriate to recommend lowering of the PQL due to 

the low passing rates below the current PQL of 10 μg/L for the Six-Year 1 data set and the 

variability of the Six-Year 2/ERA data set in the vicinity of the PQL. However, the approval of 

EPA Methods 317.0 (Rev. 2.0) and 326.0 for the analysis of bromate provides lower MDLs that 

were achievable by use of other approved methods. This may lead to an overall improvement in 

analytical performance in the vicinity of the current PQL and could suggest possible reduction of 

the PQL. 

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= Mean + 2 SD

Current PQL 

= 10 ug/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 61

Dichloromethane (Methylene chloride)

Results of the Methods Comparison

Exhibit 42 summarizes the MDLs for dichloromethane as documented in EPA-developed 

analytical methods. No updated or new analytical methods have been approved for the analysis 

of dichloromethane in drinking water samples during the years 2000-2007. 

Exhibit 42: Analytical Methods for Dichloromethane 

MCL = 0.005 mg/L Current PQL = 0.005 mg/L DL = 0.0005 mg/L 

Acceptance Criteria = + 20% or 40%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

502.2 CCGC with PID/ ELCD 0.01 - 0.02

524.2 CCGC/MS 0.03 - 0.09

Notes: The regulatory DL for volatile organic compounds is listed at 40 CFR 

141.24(k)(17)(ii)(C). Acceptance Criteria for volatile organic compounds are listed at 40 CFR 

141.24(f)(17)(i).

Results of the PQL Analysis

The current PQL for dichloromethane is 5 μg/L. The Six-Year 1 and Six-Year 2/ERA 

data sets are regressed separately (see Exhibit 43). The Six-Year 1 PE data for dichloromethane 

were evaluated but not regressed in the March 2003 report. Note that the acceptance criteria are 

+ 40% at spike concentrations below 10 μg/L and + 20% at or above 10 μg/L; hence the data are

regressed as two independent populations. None of the Six-Year 1 or the Six-Year 2/ERA data 

are below the current PQL of 5 μg/L. All but one of the passing rates in the Six-Year 1 data are 

above 75%. Two of the passing rates in the Six-Year 2/ERA data are equal to 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

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Exhibit 43: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Dichloromethane

Conclusion for Dichloromethane

Although most laboratory passing rates for both the Six-Year 1and Six-Year 2/ERA data 

sets are high (well above 75%) in the vicinity of the current PQL of 5 μg/L, it may not be 

appropriate to recommend lowering of the PQL due to the lack of data below the current PQL. 

No new or revised methods that may be expected to improve analytical performance in the 

vicinity of the current PQL (and hence suggest possible reduction of the PQL) have been 

approved from 2000-2007.

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14 16 18 20

True Value (ug/L)

% Laboratories Passing

ERA Data Below 10 ug/L ERA Data At or Above 10 ug/L PQL

Six-Year 1 Data Below 10 ug/L Six-Year 1 Data At or Above 10 ug/L 10 ug/L Acceptance Criteria Boundary

75% Passing Rate

Acceptance Criteria

= + 20%

Acceptance Criteria

= + 40%

Current PQL 

= 5 ug/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 63

Di(2-ethylhexyl)phthalate (DEHP)

Results of the Methods Comparison

Exhibit 44 summarizes the MDLs for di(2-ethylhexyl)phthalate as documented in EPAdeveloped analytical methods. No updated or new analytical methods have been approved for 

the analysis of DEHP in drinking water samples during the years 2000-2007. 

Exhibit 44: Analytical Methods for Di(2-ethylhexyl)phthalate 

MCL = 0.006 mg/L Current PQL = 0.006 mg/L DL = 0.0006 mg/L 

Acceptance Criteria = Mean + 2 Std Dev

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

506 LLE or LSE and GC/PID 2.25

525.2 LSE and CCGC/MS 0.46 - 1.3

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for DEHP is 6 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets are 

regressed separately (see Exhibit 45). The Six-Year 1 PE data for DEHP were regressed as part 

of the March 2003 report. Two of the 18 spike values in the Six-Year 1 data set are below the 

current PQL of 6 μg/L. None of the Six-Year 2/ERA data are below the current PQL. Four 

concentrations from the Six-Year 1 data set (two below the current PQL and two in the vicinity 

of the current PQL) have passing rates of less than or equal to 75%. Three of the Six-Year 

2/ERA passing rates are less than or equal to 75%. 
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Exhibit 45: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Di(2-

ethylhexyl)phthalate 

ERA Data PQL Six-Year 1 Data 75% Passing Rate

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30 35 40 45 50

True Value (ug/L)

% Laboratories Passing

Acceptance Criteria

= Mean + 2 SD

Current PQL 

= 6 ug/L

75%

Conclusion for Di(2-ethylhexyl)phthalate

Given the low laboratory passing rates below and in the vicinity of the PQL of 6 μg/L for 

the Six-Year 1 data set and the lack of data below the PQL and the variability of the Six-Year 

2/ERA data set, it is may not be appropriate to recommend lowering of the PQL. No new or 

revised methods that may be expected to improve analytical performance in the vicinity of the 

current PQL (and hence suggest possible reduction of the PQL) have been approved from 2000-

2007. 
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Ethylene dibromide (EDB) 

Results of the Methods Comparison

Exhibit 46 summarizes the MDLs for ethylene dibromide as documented in EPAdeveloped analytical methods. No updated or new analytical methods have been approved for 

the analysis of EDB in drinking water samples during the years 2000-2007. 

Exhibit 46: Analytical Methods for Ethylene Dibromide

MCL = 0.00005 mg/L Current PQL = 0.00005 mg/L DL = 0.00001 mg/L 

Acceptance Criteria = + 40%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

504.1 ME and GC 0.01

551.1 LLE/GC w/ ECD 0.007 -

0.032

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for EDB is 0.05 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets 

are regressed separately (see Exhibit 47). The Six-Year 1 PE data for EDB were evaluated but 

not regressed in the March 2003 report. None of the Six-Year 1 or the Six-Year 2/ERA PT data 

for EDB are below the current PQL of 0.05 μg/L. Nearly all of the passing rates in the Six-Year 

1 and Six-Year 2/ERA data set are above 75% (with the exception of three passing rates equal to 

75%). 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

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Exhibit 47: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Ethylene Dibromide

Conclusion for Ethylene Dibromide

Although most passing rate of laboratories for both Six-Year 2/ERA and Six-Year 1 data 

sets are high (> 75%), it may not be appropriate to recommend lowering of the PQL due to the 

lack of data below or in the vicinity of the current PQL of 0.05 μg/L. The variability in the 

passing rates for both data sets further supports this recommendation. No new or revised 

methods that may be expected to improve analytical performance in the vicinity of the current 

PQL (and hence suggest possible reduction of the PQL) have been approved from 2000-2007.

0

10

20

30

40

50

60

70

80

90

100

0.0 0.5 1.0 1.5 2.0 2.5

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 40%

Current PQL 

= 0.05 ug/L

75%
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Pentachlorophenol 

Results of the Methods Comparison

Exhibit 48 summarizes the MDLs for pentachlorophenol as documented in EPAdeveloped analytical methods. Updates to one method (ASTM D5317-98) have been approved 

for the analysis of pentachlorophenol in drinking water samples during the years 2000-2007 (see 

Exhibit A-1). These updates are minor technical revisions that are not anticipated to improve 

analytical performance near the PQL. In addition, a new method, EPA Method 515.4, was 

approved (Federal Register, Vol. 67, No. 209, p. 65888, October 29, 2002; see Exhibit A-1). 

The low end of the MDL range for pentachlorophenol by EPA Method 515.4 is lower than that 

obtained from other approved methods, which suggests that laboratory performance at low 

concentrations may be improved through use of Method 515.4. 

Exhibit 48: Analytical Methods for Pentachlorophenol 

MCL = 0.001 mg/L Current PQL = 0.001 mg/L DL = 0.00004 mg/L 

Acceptance Criteria = + 50%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

515.1 GC/ECD 0.032

515.2 LSE and GC/ECD 0.16

515.3 LLED and GC/ELCD 0.021 -

0.085

515.4 LLMED and GC/ECD 0.014 –

0.084

525.2 LSE and CCGC/MS 0.72 - 1.0

555 HPLC/PDAUVD 0.15 - 1.6

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for pentachlorophenol is 1 μg/L. The Six-Year 1 and Six-Year 2/ERA 

data sets are regressed separately (see Exhibit 49). The Six-Year 1 PE data for 

pentachlorophenol were regressed as part of the March 2003 report. Only one of the 16 spike 

values in the Six-Year 1 data set is below the current PQL of 1 μg/L. None of the Six-Year 

2/ERA data are below the current PQL. Passing rates for both data sets are highly variable.
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Exhibit 49: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Pentachlorophenol

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70 80 90 100

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 50%

Current PQL 

= 1 ug/L

75%

Conclusion for Pentachlorophenol

Given the limited data below the PQL of 1 μg/L (only one Six-Year 1 datum just below 

the PQL) and the high variability in the passing rates in the vicinity of the PQL for both the SixYear 1 and the Six-Year 2/ERA data sets, it may not be appropriate to recommend lowering of 

the PQL. However, the approval of EPA Method 515.4 for the analysis of pentachlorophenol 

provides a lower MDL than was achievable by use of other approved methods. This may lead to 

an overall improvement in analytical performance in the vicinity of the current PQL and could 

suggest possible reduction of the PQL. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

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Polychlorinatedbiphenyls (PCBs) as Decachlorobiphenyl (DCBP) 

Results of the Methods Comparison

Exhibits 50 and 51 summarize the MDLs for polychlorinatedbiphenyls as documented in 

EPA-developed analytical methods. Note that the PE/PT data and the MCL for PCBs are based 

on PCBs as decachlorobiphenyl. Performing this analysis involves a perchlorination step that 

converts mono- to octa-chlorinated biphenyl to the completely chlorinated perchlorobiphenyl or 

decachlorobiphenyl (see EPA Method 508A below). However, PCBs may also be quantitated as 

carbon:chlorine mass ratio groups known as aroclors. EPA Method 508A must be used for 

compliance if aroclor screening (e.g., qualitative identification) indicates the presence of PCBs. 

Available MDLs for both groups are given in Exhibits 50 and 51. No updated or new analytical 

methods have been approved for the analysis of PCBs in drinking water samples during the years 

2000-2007. 

Exhibit 50: Analytical Methods for PCBs: As Decachlorobiphenyl

MCL = 0.0005 mg/L Current PQL = 0.0005 mg/L DL = 0.0001 mg/L 

Acceptance Criteria = + 100%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

508A Perchlorination/GC (2-Chlorobiphenyl as source) 0.08

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Exhibit 51: Analytical Methods for PCBs: As Aroclors

MCL = 0.0005 mg/L Current PQL = 0.0005 mg/L DL = 0.00008-0.02 mg/L 

Acceptance Criteria = + 100%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

505 ME and GC 0.08 - 15.0

508 GC/ECD No MDLs

508.1 LSE and ECGC 0.012 -

0.044

525.2 LSE and CCGC/MS 0.018 - 0.56

Notes: Regulatory DLs for PCBs as Aroclors are listed at 40 CFR 141.24(h)(13)(2).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B). 

Note that use of these methods is only permitted for screening of drinking water samples. 

Demonstration of compliance with the MCL if Aroclors are detected must be performed in 

accordance with EPA Method 508A (see Exhibit 50).
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

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Results of the PQL Analysis

The current PQL for PCBs is 0.5 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets are 

regressed separately (see Exhibit 52). The Six-Year 1 PE data for PCBs were evaluated but were 

not regressed as part of the March 2003 report. Only one of the 11 spike values in the Six-Year 

1 data set is below the current PQL of 0.5 μg/L. None of the Six-Year 2/ERA data are below the 

current PQL. Passing rates in the vicinity of the current PQL are highly variable.

Exhibit 52: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – PCBs

0

10

20

30

40

50

60

70

80

90

100

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 100%

Current PQL 

= 0.5 ug/L

75%

Conclusion for Polychlorinatedbiphenyls

Although the Six-Year 2/ERA laboratory passing rates are high (well above 75%), given 

the low laboratory passing rates and decreasing trend in laboratory passing rates below and in the 

vicinity of the PQL of 0.5 μg/L for the Six-Year 1 data set and the lack of data below the PQL 

for the Six-Year 2/ERA data set, it may not be appropriate to recommend lowering of the PQL. 

No new or revised methods that may be expected to improve analytical performance in the 

vicinity of the current PQL (and hence suggest possible reduction of the PQL) have been 

approved from 2000-2007. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

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Thallium

Results of the Methods Comparison

Exhibit 53 summarizes the MDLs for thallium as documented in EPA-developed 

analytical methods. No updated or new analytical methods have been approved for the analysis 

of thallium in drinking water samples during the years 2000-2007. 

Exhibit 53: Analytical Methods for Thallium 

MCL = 0.002 mg/L Current PQL = 0.002 mg/L DL = 0.0003-0.001 mg/L 

Acceptance Criteria = + 30%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL mg/L

200.8 ICP/MS 0.00001 -

0.0003

200.9 GFAA 0.0007

Notes: Regulatory DLs for inorganic compounds are listed at 40 CFR 141.23(a)(4)(i).

Acceptance Criteria for inorganic compounds are listed at 40 CFR 141.23(k)(3)(ii).

Results of the PQL Analysis

The current PQL for thallium is 0.002 mg/L. The Six-Year 1 and Six-Year 2/ERA data 

sets are regressed separately (see Exhibit 54). The Six-Year 1 PE data for thallium were 

evaluated but were not regressed in the March 2003 report. Only one of the 19 spike values in 

the Six-Year 1 data set is less than the current PQL of 0.002 mg/L. None of the Six-Year 2/ERA

data are below the current PQL. Nearly all of the passing rates in both data sets are above 75% 

(with the exception of two passing rates in the Six-Year 2/ERA data that are equal to 75%). In 

addition, both regression lines are well above 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

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Exhibit 54: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Thallium

0

10

20

30

40

50

60

70

80

90

100

0.00 0.01 0.01 0.02 0.02 0.03 0.03 0.04 0.04

True Value (mg/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 30%

Current PQL 

= 0.002 mg/L

75%

Conclusion for Thallium

Although the Six-Year 1 laboratory passing rates are high (above 75%) below and in the 

vicinity of the PQL of 0.002 mg/L, given the lack of data below the PQL and the lower

laboratory passing rates in the vicinity of the PQL for the Six-Year 2/ERA data set, it may not be 

appropriate to recommend lowering of the PQL. No new or revised methods that may be 

expected to improve analytical performance in the vicinity of the current PQL (and hence 

suggest possible reduction of the PQL) have been approved from 2000-2007. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

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6.2 Analytes with Maximum Contaminant Level (MCL) Greater Than the Current 

PQL and Thus it is Technically Feasible to Reduce an MCL

The analytes in this category have an existing PQL that is less than the MCL. If new 

health information were to become available for any of these analytes, causing EPA to consider 

reducing the MCL, the existing PQL would not hinder reduction of the MCL (to the level of the 

current PQL). Forty-one analytes fit into this category. These 41 analytes can be further 

categorized into the three groups mentioned in Section 6.0 depending on whether or not the 

PE/PT assessments support the further reduction of the current PQL. 

6.2.1 PQL Assessment Supports Reduction of the Current PQL

Of the 41 analytes mentioned above, 11 analytes have an existing PQL that is less than 

the MCL and their PE/PT data suggest that the PQL could be lower. 

Barium

Results of the Methods Comparison

Exhibit 55 summarizes the MDLs for barium as documented in EPA-developed analytical 

methods. Updates to three methods have been approved for the analysis of barium in drinking 

water samples during the years 2000-2007 (see Exhibit A-1). These updates are associated with 

administrative and technical changes or clarifications that are not expected to improve analytical 

performance near the PQL. The updated methods are proprietary and are not listed in Exhibit 55. 

Exhibit 55: Analytical Methods for Barium 

MCL = 2 mg/L Current PQL = 0.15 mg/L DL = 0.002-0.1 mg/L 

Acceptance Criteria = + 15%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL mg/L

200.7 ICP-AES 0.001

200.8 ICP/MS 0.00004 -

0.0008

Notes: Regulatory DLs for inorganic compounds are listed at 40 CFR 141.23(a)(4)(i). 

Acceptance Criteria for inorganic compounds are listed at 40 CFR 141.23(k)(3)(ii).

Results of the PQL Analysis

The current PQL for barium is 0.15 mg/L. The Six-Year 1 and Six-Year 2/ERA data sets 

are regressed separately (see Exhibit 56). The Six-Year 1 PE data for barium were not evaluated 

in the March 2003 report. Two of the 19 spike values in the Six-Year 1 data set are below the 

current PQL of 0.15 mg/L. No Six-Year 2/ERA data are below the current PQL. With the 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 74

exception of one spike value in the Six-Year 1 data, all of the passing rates exceed 75%. Both 

the Six-Year 1 and ERA regression lines are well above 75%. 

Exhibit 56: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Barium

0

10

20

30

40

50

60

70

80

90

100

0.00 0.40 0.80 1.20 1.60 2.00 2.40 2.80

True Value (mg/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 15%

Current PQL 

= 0.15 mg/L

75%

Conclusion for Barium 

The high laboratory passing rates (well above 75%) at just below and in the vicinity of 

the current PQL of 15 mg/L for the Six-Year 1 data set suggest that the PQL could be lower; 

however any reduction might be small due to the lower passing rate at the lowest spike 

concentration. Although there are no Six-Year 2/ERA data below the PQL, laboratory passing 

rates in the vicinity of the PQL are also high, which may support the Six-Year 1 data conclusion 

that the PQL could be lower. No new or revised methods that may be expected to improve 

analytical performance in the vicinity of the current PQL (and hence suggest possible reduction 

of the PQL) have been approved from 2000-2007. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

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1,4-Dichlorobenzene

Results of the Methods Comparison

Exhibit 57 summarizes the MDLs for 1,4-dichlorobenzene as documented in EPAdeveloped analytical methods. No updated or new analytical methods have been approved for 

the analysis of 1,4-dichlorobenzene in drinking water samples during the years 2000-2007. 

Exhibit 57: Analytical Methods for 1,4-Dichlorobenzene

MCL = 0.075 mg/L Current PQL = 0.005 mg/L DL = 0.0005 mg/L 

Acceptance Criteria = + 20% or 40%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

502.2 CCGC with PID/ ELCD 0.01 - 0.04

524.2 CCGC/MS 0.03 - 0.04

Notes: The regulatory DL for volatile organic compounds is listed at 40 CFR 

141.24(k)(17)(ii)(C). Acceptance Criteria for volatile organic compounds are listed at 40 CFR 

141.24(f)(17)(i).

Results of the PQL Analysis

The current PQL for 1,4-dichlorobenzene is 5 μg/L. The Six-Year 1 and Six-Year 

2/ERA data sets are regressed separately (see Exhibit 58). The Six-Year 1 PE data for 1,4-

dichlorobenzene were evaluated but were not regressed as part of the March 2003 report. Note 

that the acceptance criteria are + 40% at spike concentrations below 10 μg/L and + 20% at or 

above 10 μg/L; hence the data are regressed as two independent populations. One of the 17 

spike values from the Six-Year 1 data is below the current PQL of 5 μg/L. Nine of the 60 SixYear 2/ERA spike values are at or below the current PQL. All of the passing rates for the SixYear 1 and Six-Year 2/ERA data are well above 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

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Exhibit 58: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – 1,4-Dichlorobenzene

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14 16 18 20

True Value (ug/L)

% Laboratories Passing

ERA Data Below 10 ug/L ERA Data At or Above 10 ug/L PQL

Six-Year 1 Data Below 10 ug/L Six-Year 1 Data At or Above 10 ug/L 10 ug/L Acceptance Criteria Boundary

75% Passing Rate

Acceptance Criteria

= + 20%

Acceptance Criteria

= + 40%

Current PQL 

= 5 ug/L

75%

Conclusion for 1,4-Dichlorobenzene

The high laboratory passing rates (well above 75%) at concentrations below the current 

PQL of 5 μg/L for both the Six-Year 1 and Six-Year 2/ERA data sets suggest that the PQL could 

be lower. Although there is only one Six-Year 1 datum below the PQL, laboratory passing rates 

below and in the vicinity of the PQL are well above 75%, which supports the Six-Year 2/ERA 

data conclusion that the PQL could be lower. No new or revised methods that may be expected 

to improve analytical performance in the vicinity of the current PQL (and hence suggest possible 

reduction of the PQL) have been approved from 2000-2007. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

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cis-1,2-Dichloroethylene

Results of the Methods Comparison

Exhibit 59 summarizes the MDLs for cis-1,2-dichloroethylene as documented in EPAdeveloped analytical methods. No updated or new analytical methods have been approved for 

the analysis of cis-1,2-dichloroethylene in drinking water samples during the years 2000-2007. 

Exhibit 59: Analytical Methods for cis-1,2-Dichloroethylene

MCL = 0.07 mg/L Current PQL = 0.005 mg/L DL = 0.0005 mg/L 

Acceptance Criteria = + 20% or 40%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

502.2 CCGC with PID/ ELCD 0.01 - 0.05

524.2 CCGC/MS 0.06 - 0.12

Notes: The regulatory DL for volatile organic compounds is listed at 40 CFR 

141.24(k)(17)(ii)(C). Acceptance Criteria for volatile organic compounds are listed at 40 CFR 

141.24(f)(17)(i).

Results of the PQL Analysis

The current PQL for cis-1,2-dichloroethylene is 5 μg/L. The Six-Year 1 and Six-Year 

2/ERA data sets are regressed separately (see Exhibit 60). The Six-Year 1 PE data for cis-1,2-

dichloroethylene were not evaluated as part of the March 2003 report. Note that the acceptance 

criteria are + 40% at spike concentrations below 10 μg/L and + 20% at or above 10 μg/L; hence 

the data are regressed as two independent populations. No Six-Year 1 data are available below 

the current PQL of 5 μg/L. Five of the 60 spike values in the Six-Year 2/ERA data are below the 

current PQL. All of the passing rates are above 75% (with the exception of one passing rate 

equal to 75%). 
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Exhibit 60: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – cis-1,2-

Dichloroethylene

Conclusion for cis-1,2-Dichloroethylene

The high laboratory passing rates (well above 75%) at concentrations below the current 

PQL of 5 μg/L for the Six-Year 2/ERA data set suggest that the PQL could be lower. Although 

there are no Six-Year 1 data below the PQL, laboratory passing rates in the vicinity of the PQL 

are also high, which may support the Six-Year 2/ERA data conclusion that the PQL could be 

lower. No new or revised methods that may be expected to improve analytical performance in 

the vicinity of the current PQL (and hence suggest possible reduction of the PQL) have been 

approved from 2000-2007.

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30 35 40 45 50

True Value (ug/L)

% Laboratories Passing

ERA Data Below 10 ug/L ERA Data At or Above 10 ug/L PQL

Six-Year 1 Data Below 10 ug/L Six-Year 1 Data At or Above 10 ug/L 10 ug/L Acceptance Criteria Boundary

75% Passing Rate

Acceptance Criteria

= + 20%

Acceptance Criteria

= + 40%

Current PQL 

= 5 ug/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

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1,1-Dichloroethylene

Results of the Methods Comparison

Exhibit 61 summarizes the MDLs for 1,1-dichloroethylene as documented in EPAdeveloped analytical methods. No updated or new analytical methods have been approved for 

the analysis of 1,1-dichloroethylene in drinking water samples during the years 2000-2007. 

Exhibit 61: Analytical Methods for 1,1-Dichloroethylene

MCL = 0.007 mg/L Current PQL = 0.005 mg/L DL = 0.0005 mg/L 

Acceptance Criteria = + 20% or 40%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

502.2 CCGC with PID/ ELCD 0.04 - 0.1

524.2 CCGC/MS 0.05 - 0.12

Notes: The regulatory DL for volatile organic compounds is listed at 40 CFR 

141.24(k)(17)(ii)(C). Acceptance Criteria for volatile organic compounds are listed at 40 CFR 

141.24(f)(17)(i).

Results of the PQL Analysis

 The current PQL for 1,1-dichloroethylene is 5 μg/L. The Six-Year 1 and Six-Year 

2/ERA data sets are regressed separately (see Exhibit 62). The Six-Year 1 PE data for 1,1-

dichloroethylene were evaluated but were not regressed as part of the March 2003 report. Note 

that the acceptance criteria are + 40% at spike concentrations below 10 μg/L and + 20% at or 

above 10 μg/L; hence the data are regressed as two independent populations. No Six-Year 1 data 

are available below the current PQL of 5 μg/L. Ten of the 60 spike values in the Six-Year 

2/ERA data are below the current PQL. While three of the four regression lines are above the 

75% passing rate threshold, a few passing rates (all above the current PQL) are below 75%. One 

of the Six-Year 1 spike values (equal to 11.7 μg/L) has a passing rate of just under 20%. This 

causes the Six-Year 1 regression line to cross below the 75% threshold. This potential outlier 

represents 56 laboratories, of which 45 failed. It is possible (but uncertain) that this low passing 

rate is not due to poor laboratory performance but rather to an erroneous PE sample or other 

aberration, since low “national” passing rates around 20% are very uncommon. The more recent

Six-Year 2/ERA data support generally high laboratory performance. 
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Exhibit 62: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – 1,1-Dichloroethylene 

Conclusion for 1,1-Dichloroethylene

The high laboratory passing rates (well above 75%) at concentrations below the current 

PQL of 5 μg/L for the Six-Year 2/ERA data set suggest that the PQL could be lower. Although 

there are no Six-Year 1 data below the PQL, laboratory passing rates in the vicinity of the PQL 

are also high, which may support the Six-Year 2/ERA data conclusion that the PQL could be 

lower. No new or revised methods that may be expected to improve analytical performance in 

the vicinity of the current PQL (and hence suggest possible reduction of the PQL) have been 

approved from 2000-2007. 

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14 16 18 20

True Value (ug/L)

% Laboratories Passing

ERA Data Below 10 ug/L ERA Data At or Above 10 ug/L PQL

Six-Year 1 Data Below 10 ug/L Six-Year 1 Data At or Above 10 ug/L 10 ug/L Acceptance Criteria Boundary

75% Passing Rate

Acceptance Criteria

= + 20%

Acceptance Criteria

= + 40%

Current PQL 

= 5 ug/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

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Ethylbenzene

Results of the Methods Comparison

Exhibit 63 summarizes the MDLs for ethylbenzene as documented in EPA-developed 

analytical methods. No updated or new analytical methods have been approved for the analysis 

of ethylbenzene in drinking water samples during the years 2000-2007. 

 

Exhibit 63: Analytical Methods for Ethylbenzene

MCL = 0.7 mg/L Current PQL = 0.005 mg/L DL = 0.0005 mg/L 

Acceptance Criteria = + 20% or 40%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

502.2 CCGC with PID/ ELCD 0.01 - 0.04

524.2 CCGC/MS 0.03 - 0.06

Notes: The regulatory DL for volatile organic compounds is listed at 40 CFR 

141.24(k)(17)(ii)(C). Acceptance Criteria for volatile organic compounds are listed at 40 CFR 

141.24(f)(17)(i).

Results of the PQL Analysis

The current PQL for ethylbenzene is 5 μg/L. The Six-Year 1 and Six-Year 2/ERA data 

sets are regressed separately (see Exhibit 64). The Six-Year 1 PE data for ethylbenzene were not 

evaluated as part of the March 2003 report. Note that the acceptance criteria are + 40% at spike 

concentrations below 10 μg/L and + 20% at or above 10 μg/L; hence the data are regressed as 

two independent populations. No Six-Year 1 data are available below the current PQL of 5 

μg/L. Eighteen of the 60 spike values in the Six-Year 2/ERA data are below the current PQL. 

All of the passing rates are above 75% (with the exception of one passing rate equal to 75%). 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

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Exhibit 64: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Ethylbenzene

100

0

10

20

30

40

50

60

70

80

90

0 2 4 6 8 10 12 14 16 18 20

True Value (ug/L)

% Laboratories Passing

ERA Data Below 10 ug/L ERA Data At or Above 10 ug/L PQL

Six-Year 1 Data Below 10 ug/L Six-Year 1 Data At or Above 10 ug/L 10 ug/L Acceptance Criteria Boundary

75% Passing Rate

Acceptance Criteria

= + 20%

Acceptance Criteria

= + 40%

Current PQL 

= 5 ug/L

75%

Conclusion for Ethylbenzene

The high laboratory passing rates (well above 75%) at concentrations below the current 

PQL of 5 μg/L for the Six-Year 2/ERA data set suggest that the PQL could be lower. Although 

there are no Six-Year 1 data below the PQL, laboratory passing rates in the vicinity of the PQL 

are also high, which may support the Six-Year 2/ERA data conclusion that the PQL could be 

lower. No new or revised methods that may be expected to improve analytical performance in 

the vicinity of the current PQL (and hence suggest possible reduction of the PQL) have been 

approved from 2000-2007. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 83

Monochlorobenzene (Chlorobenzene)

Results of the Methods Comparison

Exhibit 65 summarizes the MDLs for monochlorobenzene as documented in EPAdeveloped analytical methods. No updated or new analytical methods have been approved for 

the analysis of monochlorobenzene in drinking water samples during the years 2000-2007. 

Exhibit 65: Analytical Methods for Monochlorobenzene

MCL = 0.1 mg/L Current PQL = 0.005 mg/L DL = 0.0005 mg/L 

Acceptance Criteria = + 20% or 40%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

502.2 CCGC with PID/ELCD 0.01 - 0.02

524.2 CCGC/MS 0.03 - 0.04

Notes: The regulatory DL for volatile organic compounds is listed at 40 CFR 

141.24(k)(17)(ii)(C). Acceptance Criteria for volatile organic compounds are listed at 40 CFR 

141.24(f)(17)(i).

Results of the PQL Analysis

The current PQL for monochlorobenzene is 5 μg/L. The Six-Year 1 and Six-Year 2/ERA 

data sets are regressed separately (see Exhibit 66). The Six-Year 1 PE data for 

monochlorobenzene were not evaluated as part of the March 2003 report. Note that the 

acceptance criteria are + 40% at spike concentrations below 10 μg/L and + 20% at or above 10 

μg/L; hence the data are regressed as two independent populations. No Six-Year 1 data are 

available below the current PQL of 5 μg/L. Three of the 60 spike values in the Six-Year 2/ERA

data set are below the current PQL. All of the passing rates are above 75%, and all four 

regression lines are well above 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 84

Exhibit 66: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Monochlorobenzene

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30 35 40 45 50

True Value (ug/L)

% Laboratories Passing

ERA Data Below 10 ug/L ERA Data At or Above 10 ug/L PQL

Six-Year 1 Data Below 10 ug/L Six-Year 1 Data At or Above 10 ug/L 10 ug/L Acceptance Criteria Boundary

75% Passing Rate

Acceptance Criteria

= + 20%

Acceptance Criteria

= + 40%

Current PQL 

= 5 ug/L

75%

Conclusion for Monochlorobenzene

The high laboratory passing rates (well above 75%) at concentrations below the current 

PQL of 5 μg/L for the Six-Year 2/ERA data set suggest that the PQL could be lower. Although 

there are no Six-Year 1 data below the PQL, laboratory passing rates in the vicinity of the PQL 

are also high, which may support the Six-Year 2/ERA data conclusion that the PQL could be 

lower. No new or revised methods that may be expected to improve analytical performance in

the vicinity of the current PQL (and hence suggest possible reduction of the PQL) have been 

approved from 2000-2007. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 85

Nitrite (as N)

Results of the Methods Comparison

Exhibit 67 summarizes the MDLs for nitrite as documented in EPA-developed analytical 

methods. Updates to eleven methods and two new methods (EPA Method 300.1 and ASTM 

D6508, rev. 2) have been approved for the analysis of nitrite in drinking water samples during 

the years 2000-2007 (Federal Register, Vol. 67, No. 205, p. 65220, October 23, 2002; Federal 

Register, Vol. 72, No. 47, p. 11200, March 12, 2007; see Exhibit A-1). The updates to methods 

are associated with administrative and technical changes or clarifications that are not expected to 

improve analytical performance near the PQL. The MDL for EPA Method 300.1 is lower than 

that for EPA Method 300.0 which suggests that laboratory performance at low concentrations 

may be improved through use of Method 300.1. Since the new ASTM method is proprietary, it 

is uncertain whether new MDLs may be lower than those for other methods; in addition, the 

updated methods are proprietary and are not listed in Exhibit 67. 

Exhibit 67: Analytical Methods for Nitrite (as N)

MCL = 1 mg/L Current PQL = 0.4 mg/L DL = 0.004-0.103 mg/L 

Acceptance Criteria = + 15%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL mg/L

300.0 IC 0.004

300.1 IC 0.001

353.2 Auto Colorimetry No MDL

Notes: Regulatory DLs for inorganic compounds are listed at 40 CFR 141.23(a)(4)(i). 

Acceptance Criteria for inorganic compounds are listed at 40 CFR 141.23(k)(3)(ii).

Results of the PQL Analysis

The current PQL for nitrite is 0.4 mg/L. The Six-Year 1 and Six-Year 2/ERA data sets 

are regressed separately (see Exhibit 68). The Six-Year 1 PE data for nitrite were not evaluated 

in the March 2003 report. Five of the 20 spike values in the Six-Year 1 data set are less than the 

current PQL of 0.4 mg/L. No Six-Year 2/ERA data are below the current PQL. All of the 

passing rates are above 75% and both regression lines are also well above 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 86

Exhibit 68: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Nitrite

Conclusion for Nitrite

The high laboratory passing rates (above 75%) at concentrations below the current PQL 

of 5 μg/L for the Six-Year 1 data set suggest that the PQL could be lower. Although there are no 

Six-Year 2/ERA data below the PQL, laboratory passing rates in the vicinity of the PQL are also 

high, which may support the Six-Year 1 data conclusion that the PQL could be lower. In 

addition, the approval of EPA Method 300.1 for the analysis of nitrite provides a lower MDL 

than was achievable by use of EPA Method 300.0. This may lead to an overall improvement in 

analytical performance in the vicinity of the current PQL and could suggest possible reduction of 

the PQL.

0

10

20

30

40

50

60

70

80

90

100

0.0 0.5 1.0 1.5 2.0 2.5

True Value (mg/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 15%

Current PQL 

= 0.4 mg/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 87

Styrene

Results of the Methods Comparison

Exhibit 69 summarizes the MDLs for styrene as documented in EPA-developed 

analytical methods. No updated or new analytical methods have been approved for the analysis 

of styrene in drinking water samples during the years 2000-2007. 

Exhibit 69: Analytical Methods for Styrene

MCL = 0.1 mg/L Current PQL = 0.005 mg/L DL = 0.0005 mg/L 

Acceptance Criteria = + 20% or 40%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

502.2 CCGC with PID/ELCD 0.01 - 0.1

524.2 CCGC/MS 0.04 - 0.06

Notes: The regulatory DL for volatile organic compounds is listed at 40 CFR 

141.24(k)(17)(ii)(C). Acceptance Criteria for volatile organic compounds are listed at 40 CFR 

141.24(f)(17)(i).

Results of the PQL Analysis

The current PQL for styrene is 5 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets are 

regressed separately (see Exhibit 70). The Six-Year 1 PE data for styrene were not evaluated as 

part of the March 2003 report. Note that the acceptance criteria are + 40% at spike 

concentrations below 10 μg/L and + 20% at or above 10 μg/L; hence the data are regressed as 

two independent populations. No Six-Year 1 data are available below the current PQL of 5 

μg/L. Six of the 60 spike values in the Six-Year 2/ERA data are below the current PQL. All of 

the passing rates are above 75% (with the exception of one passing rate equal to 75%). 

Furthermore, the regression lines are well above 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 88

Exhibit 70: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Styrene

Conclusion for Styrene

The high laboratory passing rates (75% or above) at concentrations below the current 

PQL of 5 μg/L for the Six-Year 2/ERA data set suggest that the PQL could be lower. Although 

there are no Six-Year 1 data below the PQL, laboratory passing rates in the vicinity of the PQL 

are also high, which may support the Six-Year 1 data conclusion that the PQL could be lower. 

No new or revised methods that may be expected to improve analytical performance in the 

vicinity of the current PQL (and hence suggest possible reduction of the PQL) have been 

approved from 2000-2007. 

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14 16 18 20

True Value (ug/L)

% Laboratories Passing

ERA Data Below 10 ug/L ERA Data At or Above 10 ug/L PQL

Six-Year 1 Data Below 10 ug/L Six-Year 1 Data At or Above 10 ug/L 10 ug/L Acceptance Criteria Boundary

75% Passing Rate

Acceptance Criteria

= + 20%

Acceptance Criteria

= + 40%

Current PQL 

= 5 ug/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 89

Toluene

Results of the Methods Comparison

Exhibit 71 summarizes the MDLs for toluene as documented in EPA-developed 

analytical methods. No updated or new analytical methods have been approved for the analysis 

of toluene in drinking water samples during the years 2000-2007. 

Exhibit 71: Analytical Methods for Toluene 

MCL = 1 mg/L Current PQL = 0.005 mg/L DL = 0.0005 mg/L 

Acceptance Criteria = + 20% or 40%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

502.2 CCGC with PID/ELCD 0.01 - 0.02

524.2 CCGC/MS 0.08 - 0.11

Notes: The regulatory DL for volatile organic compounds is listed at 40 CFR 

141.24(k)(17)(ii)(C). Acceptance Criteria for volatile organic compounds are listed at 40 CFR 

141.24(f)(17)(i).

Results of the PQL Analysis

The current PQL for toluene is 5 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets are 

regressed separately (see Exhibit 72). The Six-Year 1 PE data for toluene were evaluated but 

were not regressed as part of the March 2003 report. Note that the acceptance criteria are + 40% 

at spike concentrations below 10 μg/L and + 20% at or above 10 μg/L; hence the data are

regressed as two independent populations. No Six-Year 1 data are available below the current 

PQL of 5 μg/L. Nine of the 60 spike values in the Six-Year 2/ERA data are below the current 

PQL. All of the passing rates and all four regression lines are above 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 90

Exhibit 72: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Toluene

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25

True Value (ug/L)

% Laboratories Passing

ERA Data Below 10 ug/L ERA Data At or Above 10 ug/L PQL

Six-Year 1 Data Below 10 ug/L Six-Year 1 Data At or Above 10 ug/L 10 ug/L Acceptance Criteria Boundary

75% Passing Rate

Acceptance Criteria

= + 20%

Acceptance Criteria

= + 40%

Current PQL 

= 5 ug/L

75%

Conclusion for Toluene 

The high laboratory passing rates (well above 75%) at concentrations below the current 

PQL of 5 μg/L for the Six-Year 2/ERA data set suggest that the PQL could be lower. Although 

there are no Six-Year 1 data below the PQL, laboratory passing rates in the vicinity of the PQL 

are also high, which may support the Six-Year 2/ERA data conclusion that the PQL could be 

lower. No new or revised methods that may be expected to improve analytical performance in 

the vicinity of the current PQL (and hence suggest possible reduction of the PQL) have been 

approved from 2000-2007. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 91

1,2,4-Trichlorobenzene

Results of the Methods Comparison

Exhibit 73 summarizes the MDLs for 1,2,4-trichlorobenzene as documented in EPAdeveloped analytical methods. No updated or new analytical methods have been approved for 

the analysis of 1,2,4-trichlorobenzene in drinking water samples during the years 2000-2007. 

Exhibit 73: Analytical Methods for 1,2,4-Trichlorobenzene

MCL = 0.07 mg/L Current PQL = 0.005 mg/L DL = 0.0005 mg/L 

Acceptance Criteria = + 20% or 40%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

502.2 CCGC with PID/ELCD 0.02 - 0.08

524.2 CCGC/MS 0.04 - 0.20

Notes: The regulatory DL for volatile organic compounds is listed at 40 CFR 

141.24(k)(17)(ii)(C). Acceptance Criteria for volatile organic compounds are listed at 40 CFR 

141.24(f)(17)(i).

Results of the PQL Analysis

The current PQL for 1,2,4-trichlorobenzene is 5 μg/L. The Six-Year 1 and Six-Year 

2/ERA data sets are regressed separately (see Exhibit 74). The Six-Year 1 PE data for 1,2,4-

trichlorobenzene were not evaluated as part of the March 2003 report. Note that the acceptance 

criteria are + 40% at spike concentrations below 10 μg/L and + 20% at or above 10 μg/L; hence 

the data are regressed as two independent populations. No Six-Year 1 data are available below 

the current PQL 5 μg/L. Six of the 60 spike values in the Six-Year 2/ERA data are below the 

current PQL. All but four of the Six-Year 2/ERA passing rates are above 75%. Furthermore, the 

four regression lines are well above 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 92

Exhibit 74: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – 1,2,4-

Trichlorobenzene

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25

True Value (ug/L)

% Laboratories Passing

ERA Data Below 10 ug/L ERA Data At or Above 10 ug/L PQL

Six-Year 1 Data Below 10 ug/L Six-Year 1 Data At or Above 10 ug/L 10 ug/L Acceptance Criteria Boundary

75% Passing Rate

Acceptance Criteria

= + 20%

Acceptance Criteria

= + 40%

Current PQL 

= 5 ug/L

75%

Conclusion for 1,2,4-Trichlorobenzene

The high laboratory passing rates (>80%) at concentrations below the current PQL of 5 

μg/L for the Six-Year 2/ERA data set suggest that the PQL could be lower. Although there are 

no Six-Year 1 data below the PQL, laboratory passing rates in the vicinity of the PQL are also 

high, which may support the Six-Year 2/ERA data conclusion that the PQL could be lower. No 

new or revised methods that may be expected to improve analytical performance in the vicinity 

of the current PQL (and hence suggest possible reduction of the PQL) have been approved from 

2000-2007. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 93

1,1,1-Trichloroethane 

Results of the Methods Comparison

Exhibit 75 summarizes the MDLs for 1,1,1-trichloroethane as documented in EPAdeveloped analytical methods. No updated or new analytical methods have been approved for 

the analysis of 1,1,1-trichloroethane in drinking water samples during the years 2000-2007. 

Exhibit 75: Analytical Methods for 1,1,1-Trichloroethane

MCL = 0.07 mg/L Current PQL = 0.005 mg/L DL = 0.0005 mg/L 

Acceptance Criteria = + 20% or 40%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

502.2 CCGC with PID/ ELCD 0.01 - 0.03

524.2 CCGC/MS 0.04 - 0.08

551.1 LLE/GC w/ ECD 0.005 -

0.012

Notes: The regulatory DL for volatile organic compounds is listed at 40 CFR 

141.24(k)(17)(ii)(C). Acceptance Criteria for volatile organic compounds are listed at 40 CFR 

141.24(f)(17)(i).

Results of the PQL Analysis

The current PQL for 1,1,1-trichloroethane is 5 μg/L. The Six-Year 1 and Six-Year 

2/ERA data sets are regressed separately (see Exhibit 76). The Six-Year 1 PE data for 1,1,1-

trichloroethane were evaluated but were not regressed as part of the March 2003 report. Note 

that the acceptance criteria are + 40% at spike concentrations below 10 μg/L and + 20% at or 

above 10 μg/L; hence the data are regressed as two independent populations. One of the 17 

spike values from the Six-Year 1 data is below the current PQL of 5 μg/L. Ten of the 60 SixYear 2/ERA spike values are below the current PQL. All of the passing rates for the Six-Year 1 

and Six-Year 2/ERA data are above 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 94

Exhibit 76: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – 1,1,1-Trichloroethane

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14 16 18 20

True Value (ug/L)

% Laboratories Passing

ERA Data Below 10 ug/L ERA Data At or Above 10 ug/L PQL

Six-Year 1 Data Below 10 ug/L Six-Year 1 Data At or Above 10 ug/L 10 ug/L Acceptance Criteria Boundary

75% Passing Rate

Acceptance Criteria

= + 20%

Acceptance Criteria

= + 40%

Current PQL 

= 5 ug/L

75%

Conclusion for 1,1,1-Trichloroethane

The high laboratory passing rates (generally >90%) at concentrations below the current 

PQL of 5 μg/L for both the Six-Year 1 and Six-Year 2/ERA data sets suggest that the PQL could 

be lower. Although there is only one Six-Year 1 datum below the PQL, laboratory passing rates 

below and in the vicinity of the PQL are well above 75%, which supports the conclusion that the 

PQL could be lower. No new or revised methods that may be expected to improve analytical 

performance in the vicinity of the current PQL (and hence suggest possible reduction of the 

PQL) have been approved from 2000-2007. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 95

6.2.2 PQL Assessment May Support Reduction of the Current PQL

Of the 41 analytes mentioned in Section 6.2, six analytes have an existing PQL that is 

less than the MCL and their PE/PT data suggest that the PQL could possibly be lower. 

Atrazine

Results of the Methods Comparison

Exhibit 77 summarizes the MDLs for atrazine as documented in EPA-developed 

analytical methods. No updated methods have been approved for the analysis of atrazine in 

drinking water samples during the years 2000-2007; however, a new method, Syngenta AG-625, 

was approved (Federal Register, Vol. 67, No. 209, p. 65888, October 29, 2002; see Exhibit A-1). 

Since the method is proprietary, the MDL/DL for atrazine by Syngenta AG-625 is not known, 

but the Federal Register notice indicates that this method “meets EPA’s criteria for method 

performance.” Thus, it is uncertain whether new MDLs may be lower than those for other 

methods. 

Exhibit 77: Analytical Methods for Atrazine

MCL = 0.003 mg/L Current PQL = 0.001 mg/L DL = 0.0001 mg/L 

Acceptance Criteria = + 45%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

505 ME and GC 2.4

507 GC/N-PD 0.015

508.1 LSE and ECGC 0.003

525.2 LSE and CCGC/MS 0.065 -

0.081

551.1 LLE/GC w/ ECD 0.082 -

0.121

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for atrazine is 1 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets 

are regressed separately (see Exhibit 78). The Six-Year 1 PE data for atrazine were not 

evaluated in the March 2003 report. Three of the 20 spike values in the Six-Year 1 data are 

below the current PQL of 1 μg/L. No Six-Year 2/ERA data are below the current PQL. With 

the exception of one spike value, all of the Six-Year 1 passing rates exceed 75%, while the SixYear 2/ERA passing rates are more variable. Both regression lines are well above 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 96

Exhibit 78: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Atrazine

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 45%

Current PQL 

= 1 ug/L

75%

Conclusion for Atrazine

Given the limited data below the current PQL of 1 μg/L but generally high laboratory 

passing rates (mostly above 75%) below and in the vicinity of the PQL for the Six-Year 1 data 

set, a reduction of the PQL may be considered. The Six-Year 2/ERA data exhibit some 

variability, but laboratory passing rates in the vicinity of the PQL are generally >75% and may 

also support PQL reduction. While a new method, Syngenta AG-625, was approved for the 

analysis of atrazine in 2002, the method is proprietary and it is not known whether the DLs 

and/or MDLs from this method could lead to an overall improvement in analytical performance 

in the vicinity of the current PQL and suggest possible reduction of the PQL. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 97

Carbofuran 

Results of the Methods Comparison

Exhibit 79 summarizes the MDLs for carbofuran as documented in EPA-developed 

analytical methods. No updated methods have been approved for the analysis of carbofuran in 

drinking water samples during the years 2000-2007; however, a new method, EPA Method 

531.2, was approved (Federal Register, Vol. 67, No. 209, p. 65888, October 29, 2002; see 

Exhibit A-1). The range of DLs/MDLs for carbofuran by EPA Method 531.2 is approximately 

one order of magnitude less than the MDL from EPA Method 531.1, which suggests that 

laboratory performance at low concentrations may be improved through use of Method 531.2. 

Exhibit 79: Analytical Methods for Carbofuran 

MCL = 0.04 mg/L Current PQL = 0.007 mg/L DL = 0.0009 mg/L 

Acceptance Criteria = + 45%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

531.1 DAI/HPLC w/ Der. 0.52

531.2 DAI/HPLC w/ Der. 0.043 - 

0.058 (DL)

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for carbofuran is 7 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets 

are regressed separately (see Exhibit 80). The Six-Year 1 PE data for carbofuran were evaluated 

in the March 2003 report; however, these data were not regressed in that report. Two of the 20 

spike values in the Six-Year 1 data are below the current PQL of 7 μg/L. No Six-Year 2/ERA

data are below the current PQL. The Six-Year 1 passing rates were all well above 75%; however 

the passing rates for the Six-Year 2/ERA data are more variable. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 98

Exhibit 80: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Carbofuran 

0

10

20

30

40

50

60

70

80

90

100

0 30 60 90 120 150

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 45%

Current PQL 

= 7 ug/L

75%

Conclusion for Carbofuran

Given the limited data below the current PQL of 7 μg/L but generally high laboratory 

passing rates (above 75%) below and in the vicinity of the PQL for the Six-Year 1 data set, a 

reduction of the PQL may be considered. The Six-Year 2/ERA data exhibit some variability, 

with laboratory passing rates in the vicinity of the PQL ranging from less than 70% to 100% 

which may not support the Six-Year 1 data conclusion that the PQL could be lower. The range 

of DLs/MDLs for carbofuran by recently-approved EPA Method 531.2 is approximately one 

order of magnitude lower than the MDL from EPA Method 531.1. This may lead to an overall 

improvement in analytical performance in the vicinity of the current PQL and could suggest 

possible reduction of the PQL. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 99

trans-1,2-Dichloroethylene

Results of the Methods Comparison

Exhibit 81 summarizes the MDLs for trans-1,2-dichloroethylene as documented in EPAdeveloped analytical methods. No updated or new analytical methods have been approved for 

the analysis of trans-1,2-dichloroethylene in drinking water samples during the years 2000-2007. 

Exhibit 81: Analytical Methods for trans-1,2-Dichloroethylene

MCL = 0.1 mg/L Current PQL = 0.005 mg/L DL = 0.0005 mg/L 

Acceptance Criteria = + 20% or 40%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

502.2 CCGC with PID/ ELCD 0.03 - 0.06

524.2 CCGC/MS 0.03 - 0.06

Notes: The regulatory DL for volatile organic compounds is listed at 40 CFR 

141.24(k)(17)(ii)(C). Acceptance Criteria for volatile organic compounds are listed at 40 CFR 

141.24(f)(17)(i).

Results of the PQL Analysis

The current PQL for trans-1,2-dichloroethylene is 5 μg/L. The Six-Year 1 and Six-Year 

2/ERA data sets are regressed separately (see Exhibit 82). The Six-Year 1 PE data for trans-1,2-

dichloroethylene were not evaluated as part of the March 2003 report. Note that the acceptance 

criteria are + 40% at spike concentrations below 10 μg/L and + 20% at or above 10 μg/L; hence 

the data are regressed as two independent populations. No Six-Year 1 data are available below 

the current PQL of 5 μg/L. Three of the 60 spike values in the Six-Year 2/ERA data set are 

below the current PQL. All but two of the passing rates are above 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

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Exhibit 82: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – trans-1,2-

Dichloroethylene

Conclusion for trans-1,2-Dichloroethylene

Given the limited data below the current PQL of 5 μg/L but generally high laboratory 

passing rates (well above 75%) below and in the vicinity of the PQL for the Six-Year 2/ERA

data set and in the vicinity of the PQL for the Six-Year 1 data set, a reduction of the PQL may be 

considered. The Six-Year 2/ERA data exhibit some variability, with laboratory passing rates in 

the vicinity of the PQL ranging from slightly below 75% to 100%; which may support the SixYear 1 data conclusion that the PQL could be lower. No new or revised methods that may be 

expected to improve analytical performance in the vicinity of the current PQL (and hence 

suggest possible reduction of the PQL) have been approved from 2000-2007.

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30 35 40 45 50

True Value (ug/L)

% Laboratories Passing

ERA Data Below 10 ug/L ERA Data At or Above 10 ug/L PQL

Six-Year 1 Data Below 10 ug/L Six-Year 1 Data At or Above 10 ug/L 10 ug/L Acceptance Criteria Boundary

75% Passing Rate

Acceptance Criteria

= + 20% Acceptance Criteria

= + 40%

Current PQL 

= 5 ug/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

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Hexachlorocyclopentadiene 

Results of the Methods Comparison

Exhibit 83 summarizes the MDLs for hexachlorocyclopentadiene as documented in EPAdeveloped analytical methods. No updated or new analytical methods have been approved for 

the analysis of hexachlorocyclopentadiene in drinking water samples during the years 2000-

2007. 

Exhibit 83: Analytical Methods for Hexachlorocyclopentadiene 

MCL = 0.05 mg/L Current PQL = 0.001 mg/L DL = 0.0001 mg/L 

Acceptance Criteria = Mean + 2 Std Dev

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

505 ME and GC 0.13

508 GC/ECD No MDL

508.1 LSE and ECGC 0.004

525.2 LSE and CCGC/MS 0.072 - 0.16

551.1 LLE/GC w/ ECD 0.016 -

0.018

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for hexachlorocyclopentadiene is 1 μg/L. The Six-Year 1 and Six-Year 

2/ERA data sets are regressed separately (see Exhibit 84). The Six-Year 1 PE data for 

hexachlorocyclopentadiene were evaluated but were not regressed as part of the March 2003 

report. Six of the 20 spike values in the Six-Year 1 data set are below the current PQL of 1 μg/L. 

No Six-Year 2/ERA data are below the current PQL. All but one of the Six-Year 1 passing rates, 

along with the Six-Year 1 regression line, are above 75%; however, the Six-Year 2/ERA passing 

rates are more variable, with several passing rates below 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

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Exhibit 84: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – 

Hexachlorocyclopentadiene

Conclusion for Hexachlorocyclopentadiene

Given the generally high laboratory passing rates (all but one well above 75%) below and 

in the vicinity of the current PQL of 1 μg/L for the Six-Year 1 data set, a reduction of the PQL 

may be considered. The Six-Year 2/ERA data exhibit some variability, with laboratory passing 

rates in the vicinity of the PQL ranging from less than 70% to 100%, which may not support the 

Six-Year 1 data conclusion that the PQL could be lower. No new or revised methods that may 

be expected to improve analytical performance in the vicinity of the current PQL (and hence 

suggest possible reduction of the PQL) have been approved from 2000-2007. 

0

10

20

30

40

50

60

70

80

90

100

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= Mean + 2 SD

Current PQL 

= 1 ug/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

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Page 103

Methoxychlor

Results of the Methods Comparison

Exhibit 85 summarizes the MDLs for methoxychlor as documented in EPA-developed 

analytical methods. No updated or new analytical methods have been approved for the analysis 

of methoxychlor in drinking water samples during the years 2000-2007. 

Exhibit 85: Analytical Methods for Methoxychlor 

MCL = 0.04 mg/L Current PQL = 0.01 mg/L DL = 0.0001 mg/L 

Acceptance Criteria = + 45%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

505 ME and GC 0.96

508 GC/ECD 0.022

508.1 LSE and ECGC 0.003

525.2 LSE and CCGC/MS 0.033 - 0.13

551.1 LLE/GC w/ ECD 0.008 -

0.026

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for methoxychlor is 10 μg/L. The Six-Year 1 and Six-Year 2/ERA data 

sets are regressed separately (see Exhibit 86). The Six-Year 1 PE data for methoxychlor were

evaluated but were not regressed as part of the March 2003 report. Four of the 20 spike values in 

the Six-Year 1 methoxychlor PE data are below the current PQL of 10 μg/L. All of the passing 

rates are above 75%. None of the Six-Year 2/ERA values are below the current PQL and the 

data exhibit more variability. The Six-Year 1 regression line is well above 75%; however, the 

Six-Year 2/ERA regression line predicts a decrease in passing rates with an increase in spike 

values. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

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Exhibit 86: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Methoxychlor 

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70 80 90 100

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 45%

Current PQL 

= 10 ug/L

75%

Conclusion for Methoxychlor

Given the generally high laboratory passing rates (well above 75%) below and in the 

vicinity of the current PQL of 10 μg/L for the Six-Year 1 data set, a reduction of the PQL may be 

considered. The Six-Year 2/ERA data exhibit some variability, with laboratory passing rates in 

the vicinity of the PQL generally above 80%; however, there is more variability at higher 

concentrations and a predicted downward trend at higher concentrations. Overall, the Six-Year 2 

data may not support the Six-Year 1 data conclusion that the PQL could be lower. No new or 

revised methods that may be expected to improve analytical performance in the vicinity of the 

current PQL (and hence suggest possible reduction of the PQL) have been approved from 2000-

2007. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 105

2-(2,4,5-Trichlorophenoxy)propanoic acid (2,4,5-TP; Silvex)

Results of the Methods Comparison

Exhibit 87 summarizes the MDLs for 2-(2,4,5-trichlorophenoxy)propanoic acid as 

documented in EPA-developed analytical methods. Updates to one method have been approved 

for the analysis of 2,4,5-TP in drinking water samples during the years 2000-2007 (see Exhibit 

A-1). These updates are minor technical revisions that are not anticipated to improve analytical 

performance near the PQL. In addition, a new method, EPA Method 515.4 was approved 

(Federal Register, Vol. 67, No. 209, p. 65888, October 29, 2002; see Exhibit A-1). The MDL for 

2,4,5-TP by EPA Method 515.4 is somewhat lower than that obtained from other EPA methods, 

which suggests that laboratory performance at low concentrations may be improved through use 

of Method 515.4. 

Exhibit 87: Analytical Methods for 2,4,5-TP (Silvex) 

MCL = 0.05 mg/L Current PQL = 0.005 mg/L DL = 0.0002 mg/L 

Acceptance Criteria = + 50%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

515.1 GC/ECD 0.21

515.2 LSE and GC/ECD 0.16

515.3 LLED and GC/ELCD 0.072 - 0.14

515.4 LLMED and GC/ECD 0.018 –

0.033

555 HPLC/PDAUVD 0.37 - 1.8

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for 2,4,5-TP is 5 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets 

are regressed separately (see Exhibit 88). The Six-Year 1 PE data for 2,4,5-TP were not 

evaluated in the March 2003 report. Three of the 20 spike values in the Six-Year 1 PE data are 

less than the current PQL of 5 μg/L. No Six-Year 2/ERA data are below the current PQL. 

While the passing rates for both data sets are fairly variable, all of the Six-Year 1 passing rates 

are above 75% (with the exception of one passing rate that is equal to 75%). One passing rate in 

the Six-Year 2/ERA data is below 75%. Both the Six-Year 1 and Six-Year 2/ERA regression 

lines are above 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

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Exhibit 88: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – 2,4,5-TP (Silvex) 

0

10

20

30

40

50

60

70

80

90

100

0 30 60 90 120 150

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 50%

Current PQL 

= 5 ug/L

75%

Conclusion for 2,4,5-TP

Given the limited data below the current PQL of 5 μg/L but generally high laboratory 

passing rates (well above 75%) below and in the vicinity of the PQL for the Six-Year 1 data set 

and in the vicinity of the PQL for the Six-Year 2/ERA data, a reduction of the PQL may be 

considered. The Six-Year 2/ERA data exhibit some variability, with laboratory passing rates in 

the vicinity of the PQL ranging from less than 70% to 100%; which may not support the SixYear 1 data conclusion that the PQL could be lower. In addition, EPA Method 515.4 has a lower 

range of MDLs compared to previously-approved methods. This may lead to an overall 

improvement in analytical performance in the vicinity of the current PQL and could suggest 

possible reduction of the PQL. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 107

6.2.3 PQL Assessment Does Not Support Reduction of the Current PQL or Data are 

Insufficient to Reach a Conclusion

Of the 41 analytes mentioned in Section 6.2, 24 analytes have an existing PQL that is less 

than the MCL and their PE/PT data either indicate that the PQL should not be lower or their 

PE/PT data are insufficient to reach a conclusion.

Arsenic

Results of the Methods Comparison

Exhibit 89 summarizes the MDLs for arsenic as documented in EPA-developed 

analytical methods. Updates to eight methods have been approved for the analysis of arsenic in 

drinking water samples during the years 2000-2007 (see Exhibit A-1). These updates are 

associated with administrative and technical changes or clarifications that are not expected to 

improve analytical performance near the PQL. The updated methods are proprietary and are not 

listed in Exhibit 89.

Exhibit 89: Analytical Methods for Arsenic

MCL = 0.010 mg/L Current PQL = 0.003 mg/L DL = 0.005-0.0014 mg/L 

Acceptance Criteria = + 30%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL mg/L

200.7 ICP-AES 0.008

200.8 ICP/MS 0.0001 -

0.0014

200.9 GFAA 0.0005

Notes: Regulatory DLs for inorganic compounds are listed at 40 CFR 141.23(a)(4)(i). 

Acceptance Criteria for inorganic compounds are listed at 40 CFR 141.23(k)(3)(ii).

Results of the PQL Analysis

The current PQL for arsenic is 0.003 mg/L. The Six-Year 1 and Six-Year 2/ERA data 

sets are regressed separately (see Exhibit 90). The Six-Year 1 PE data for arsenic were not 

evaluated in the March 2003 report. Four of the 26 spike values in the Six-Year 1 data set are 

below the current PQL of 0.003 mg/L. No Six-Year 2/ERA data are below the current PQL. 

With the exception of two spike values, all of the Six-Year 1 passing rates exceed 75%. The low 

passing rate just below the PQL is of concern, however. In general, many of the passing rates 

around the PQL are highly variable. Furthermore, some of the Six-Year 2/ERA passing rates 

above the PQL are below 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 108

Exhibit 90: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Arsenic

Conclusion for Arsenic

Given the relative lack of data below the current PQL of 0.003 mg/L, the downward trend 

in laboratory passing rates below the PQL for the Six-Year 1 data set, and the lack of data in the

vicinity of the PQL for the Six-Year 2/ERA dataset, it may not be appropriate to recommend 

lowering of the PQL. No new or revised methods that may be expected to improve analytical 

performance in the vicinity of the current PQL (and hence suggest possible reduction of the 

PQL) have been approved from 2000-2007.

0

10

20

30

40

50

60

70

80

90

100

0.00 0.03 0.06 0.09 0.12 0.15

True Value (mg/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 30%

Current PQL 

= 0.003 mg/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 109

Beryllium

Results of the Methods Comparison

Exhibit 91 summarizes the MDLs for beryllium as documented in EPA-developed 

analytical methods. Updates to five methods have been approved for the analysis of beryllium in 

drinking water samples during the years 2000-2007 (see Exhibit A-1). These updates are 

associated with administrative and technical changes or clarifications that are not expected to 

improve analytical performance near the PQL. The updated methods are proprietary and are not 

listed in Exhibit 91.

Exhibit 91: Analytical Methods for Beryllium

MCL = 0.004 mg/L Current PQL = 0.001 mg/L DL = 0.00002-0.0003 mg/L 

Acceptance Criteria = + 15%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL mg/L

200.7 ICP-AES 0.0003

200.8 ICP/MS 0.00002 -

0.0003

200.9 GFAA 0.00002

Notes: Regulatory DLs for inorganic compounds are listed at 40 CFR 141.23(a)(4)(i).

Acceptance Criteria for inorganic compounds are listed at 40 CFR 141.23(k)(3)(ii).

Results of the PQL Analysis

 The current PQL for beryllium is 0.001 mg/L. The Six-Year 1 and Six-Year 2/ERA data 

sets are regressed separately (see Exhibit 92). The Six-Year 1 PE data for beryllium were 

regressed as part of the March 2003 report. Four of the 19 spike values in the Six-Year 1 data set 

are below the current PQL of 0.001 mg/L. No Six-Year 2/ERA data are below the current PQL 

of 0.001 mg/L. The four concentration values from the Six-Year 1 data set that are below the 

current PQL also have passing rates of less than 75%. The Six-Year 2/ERA data in the vicinity 

of the current PQL have variable passing rates. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 110

Exhibit 92: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Beryllium

0

10

20

30

40

50

60

70

80

90

100

0.000 0.005 0.010 0.015 0.020 0.025

True Value (mg/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 15%

Current PQL 

= 0.001 mg/L

75%

Conclusion for Beryllium

Given the relative lack of data and the downward trend in laboratory passing rates below 

the current PQL of 0.001 mg/L for the Six-Year 1 data set and the lack of data and high 

variability below the PQL for the Six-Year 2/ERA dataset, it may not be appropriate to 

recommend lowering of the PQL. No new or revised methods that may be expected to improve 

analytical performance in the vicinity of the current PQL (and hence suggest possible reduction 

of the PQL) have been approved from 2000-2007.
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 111

Cadmium 

Results of the Methods Comparison

Exhibit 93 summarizes the MDLs for cadmium as documented in EPA-developed 

analytical methods. Updates to one method have been approved for the analysis of cadmium in 

drinking water samples during the years 2000-2007 (see Exhibit A-1). These updates are 

associated with administrative and technical changes or clarifications that are not expected to 

improve analytical performance near the PQL. The updated method is proprietary and is not 

listed in Exhibit 93.

Exhibit 93: Analytical Methods for Cadmium 

MCL = 0.005 mg/L Current PQL = 0.002 mg/L DL = 0.0001-0.001 mg/L 

Acceptance Criteria = + 20%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL mg/L

200.7 ICP-AES 0.001

200.8 ICP/MS 0.00003 -

0.0005

200.9 GFAA 0.00005

Notes: Regulatory DLs for inorganic compounds are listed at 40 CFR 141.23(a)(4)(i). 

Acceptance Criteria for inorganic compounds are listed at 40 CFR 141.23(k)(3)(ii).

Results of the PQL Analysis

 The current PQL for cadmium is 0.002 mg/L. The Six-Year 1 and Six-Year 2/ERA data 

sets are regressed separately (see Exhibit 94). The Six-Year 1 PE data for cadmium were 

evaluated but not regressed in the March 2003 report. None of the Six-Year 1 or the Six-Year 

2/ERA data are below the current PQL of 0.002 mg/L. However, all of the passing rates, as well 

as the two regression lines, are well above 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 112

Exhibit 94: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Cadmium

Conclusion for Cadmium

Although laboratory passing rates are high (well above 75%) for the Six-Year 1 and SixYear 2/ERA data sets, given the lack of data below the current PQL of 0.002 mg/L for both data 

sets, it may not be appropriate to recommend lowering of the PQL. No new or revised methods 

that may be expected to improve analytical performance in the vicinity of the current PQL (and 

hence suggest possible reduction of the PQL) have been approved from 2000-2007. 

0

10

20

30

40

50

60

70

80

90

100

0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040 0.045 0.050

True Value (mg/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 20%

Current PQL 

= 0.002 mg/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 113

Chromium

Results of the Methods Comparison

Exhibit 95 summarizes the MDLs for chromium as documented in EPA-developed 

analytical methods. Updates to three methods have been approved for the analysis of chromium 

in drinking water samples during the years 2000-2007 (see Exhibit A-1). These updates are 

associated with administrative and technical changes or clarifications that are not expected to 

improve analytical performance near the PQL. The updated methods are proprietary and are not 

listed in Exhibit 95.

Exhibit 95: Analytical Methods for Chromium 

MCL = 0.1 mg/L Current PQL = 0.01 mg/L DL = 0.001-0.007 mg/L 

Acceptance Criteria = + 15%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL mg/L 

200.7 ICP-AES 0.004

200.8 ICP/MS 0.00008 -

0.0009

200.9 GFAA 0.0001

Notes: Regulatory DLs for inorganic compounds are listed at 40 CFR 141.23(a)(4)(i).

Acceptance Criteria for inorganic compounds are listed at 40 CFR 141.23(k)(3)(ii).

Results of the PQL Analysis

 The current PQL for chromium is 0.01 mg/L. The Six-Year 1 and Six-Year 2/ERA data 

sets are regressed separately (see Exhibit 96). The Six-Year 1 PE data for chromium were 

evaluated but not regressed in the March 2003 report. None of the Six-Year 1 or the Six-Year 

2/ERA data for chromium are below the current PQL of 0.01 mg/L. However, all of the passing 

rates, as well as the two regression lines, are well above 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

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Exhibit 96: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Chromium

Conclusion for Chromium

Although laboratory passing rates are high (well above 75%) for the Six-Year 1 and SixYear 2/ERA data sets, given the lack of data below the current PQL of 0.01 mg/L for both data 

sets, it may not be appropriate to recommend lowering of the PQL. No new or revised methods 

that may be expected to improve analytical performance in the vicinity of the current PQL (and 

hence suggest possible reduction of the PQL) have been approved from 2000-2007. 

0

10

20

30

40

50

60

70

80

90

100

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20

True Value (mg/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 15%

Current PQL 

= 0.01 mg/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 115

Copper 

Results of the Methods Comparison

Exhibit 97 summarizes the MDLs for copper as documented in EPA-developed analytical 

methods. Updates to six methods have been approved for the analysis of copper in drinking 

water samples during the years 2000-2007 (see Exhibit A-1). These updates are associated with 

administrative and technical changes or clarifications that are not expected to improve analytical 

performance near the PQL. The updated methods are proprietary and are not listed in Exhibit 97. 

Exhibit 97: Analytical Methods for Copper 

Action Level = 1.3 mg/L Current PQL = 0.05 mg/L DL = N/A 

Acceptance Criteria = + 10%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL mg/L

200.7 ICP-AES 0.003

200.8 ICP/MS 0.00001 -

0.0005

200.9 GFAA 0.0007

Notes: EPA has not provided a regulatory DL for copper in the CFR. The Acceptance Criteria

for copper are listed at 40 CFR 141.89(a)(1)(ii)(B).

Results of the PQL Analysis

The current PQL for copper is 0.05 mg/L. The Six-Year 1 and Six-Year 2/ERA data sets 

are regressed separately (see Exhibit 98). The Six-Year 1 PE data for copper were not evaluated 

in the March 2003 report. One of the 19 spike values in the Six-Year 1 data set is below the 

current PQL of 0.05 mg/L. No Six-Year 2/ERA data are below the PQL. The single

concentration value less than the PQL corresponds to a passing rate of less than 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 116

Exhibit 98: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Copper

Conclusion for Copper 

 Although laboratory passing rates are high (above 75% just above the PQL) for the SixYear 1 and Six-Year 2/ERA data sets, given the lack of data below the current PQL of 0.05 mg/L 

for both data sets (with the exception of one laboratory passing rate below 75%), it may not be 

appropriate to recommend lowering of the PQL. No new or revised methods that may be 

expected to improve analytical performance in the vicinity of the current PQL (and hence 

suggest possible reduction of the PQL) have been approved from 2000-2007.

0

10

20

30

40

50

60

70

80

90

100

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

True Value (mg/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 10%

Current PQL 

= 0.05 mg/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 117

Cyanide 

Results of the Methods Comparison

Exhibit 99 summarizes the MDLs for cyanide as documented in EPA-developed 

analytical methods. Updates to nine methods and four new methods (Kelada 01, QuikChem 10-

204-00-1-X, OIA-1677 and ASTM D6888-04) have been approved for the analysis of cyanide in 

drinking water samples during the years 2000-2007 (67 FR 65220, October 23, 2002, 67 FR 

65888, October 29, 2002, 72 FR 11200, March 12, 2007; see Exhibit A-1). While the updates 

are associated with administrative and technical changes or clarifications that are not expected to 

improve analytical performance near the PQL, the new methods may improve analytical 

performance near the PQL; however, because the newly-approved methods are proprietary, the 

MDLs/DLs from these methods are not known. In addition, the updated methods are proprietary 

and are not listed in Exhibit 99. 

Exhibit 99: Analytical Methods for Cyanide 

MCL = 0.2 mg/L Current PQL = 0.1 mg/L DL = 0.0005-0.05 mg/L 

Acceptance Criteria = + 25%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL mg/L

335.4 Semi-Auto Colorimetry No MDL

Notes: Regulatory DLs for inorganic compounds are listed at 40 CFR 141.23(a)(4)(i).

Acceptance Criteria for inorganic compounds are listed at 40 CFR 141.23(k)(3)(ii).

Results of the PQL Analysis

The current PQL for cyanide is 0.1 mg/L. The Six-Year 1 and Six-Year 2/ERA data sets 

are regressed separately (see Exhibit 100). The Six-Year 1 PE data for cyanide were not 

evaluated in the March 2003 report. One of the 20 spike concentrations from the Six-Year 1 data 

set is equal to the PQL; however, none of these data are below the current PQL of 0.1 mg/L. No

Six-Year 2/ERA data are below the current PQL. Several passing rates are below 75%.
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 118

Exhibit 100: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Cyanide 

0

10

20

30

40

50

60

70

80

90

100

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

True Value (mg/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 25%

Current PQL 

= 0.1 mg/L

75%

Conclusion for Cyanide

Given the variable laboratory passing rates for the Six-Year 1 and Six-Year 2/ERA data 

sets and the lack of data below the current PQL of 0.1 mg/L for both data sets (with the 

exception of one laboratory passing rate from the Six-Year 1 data set just above 75% at the 

PQL), it may not be appropriate to recommend lowering of the PQL. Although four new 

methods have been approved for the analysis of cyanide, DLs/MDLs are not available for these 

methods since they are proprietary. Hence it is not known whether use of these newly-approved 

methods could improve laboratory performance at low concentrations and potentially affect the 

PQL. While four new methods have been approved for the analysis of cyanide in drinking water, 

the methods are proprietary and it is not known whether the DLs and/or MDLs from this method 

could lead to an overall improvement in analytical performance in the vicinity of the current 

PQL and suggest possible reduction of the PQL. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 119

Dalapon 

Results of the Methods Comparison

Exhibit 101 summarizes the MDLs for dalapon as documented in EPA-developed 

analytical methods. No updated methods have been approved for the analysis of dalapon in 

drinking water samples during the years 2000-2007; however, two new methods, EPA Method 

515.4 and EPA Method 552.3 were approved (Federal Register, Vol. 67, No. 209, p. 65888, 

October 29, 2002, Federal Register, Vol. 72, No. 47, p. 11200, March 12, 2007; see Exhibit A1). The ranges of MDLs for dalapon by EPA Method 515.4 and 552.3 are lower than most of the 

MDLs from other methods, which suggests that laboratory performance at low concentrations 

may be improved through use of Methods 515.4 and 552.3. 

Exhibit 101: Analytical Methods for Dalapon 

MCL = 0.2 mg/L Current PQL = 0.01 mg/L DL = 0.001 mg/L 

Acceptance Criteria = Mean + 2 Std Dev

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

515.1 GC/ECD 1.3

515.3 LLED and GC/ELCD 0.53 - 0.97

515.4 LLMED and GC/ECD 0.054 –

0.074

552.1 I-ELSE/GC w/ ECD 0.32

552.2 LLED/GC w/ ECD 0.119

552.3 LLMED/GC w/ ECD 0.024 - 0.14

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for dalapon is 10 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets 

are regressed separately (see Exhibit 102). The Six-Year 1 PE data for dalapon were not 

evaluated in the March 2003 report. None of the Six-Year 2/ERA data for dalapon are below the 

PQL, and passing rates for Six-Year 1 data below the PQL could not be calculated as the 

NELAC regression coefficients are not valid over that range. However, all of the passing rates, 

as well as the two regression lines, are well above 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 120

Exhibit 102: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Dalapon 

Conclusion for Dalapon

Although laboratory passing rates are high (above 75%) for the Six-Year 1 and Six-Year 

2/ERA data sets, given the lack of data below the current PQL of 10 μg/L for both data sets, it 

may not be appropriate to recommend lowering of the PQL. However, the approval of EPA 

Methods 515.4 and 552.3 for the analysis of dalapon provides lower MDLs than were achievable

by use of other approved methods. This may lead to an overall improvement in analytical

performance in the vicinity of the current PQL and could suggest possible reduction of the PQL. 

0

10

20

30

40

50

60

70

80

90

100

0 30 60 90 120 150

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= Mean + 2 SD

Current PQL 

= 10 ug/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 121

1,2-Dichlorobenzene

Results of the Methods Comparison

Exhibit 103 summarizes the MDLs for 1,2-dichlorobenzene as documented in EPAdeveloped analytical methods. No updated or new analytical methods have been approved for 

the analysis of 1,2-dichlorobenzene in drinking water samples during the years 2000-2007. 

Exhibit 103: Analytical Methods for 1,2-Dichlorobenzene

MCL = 0.6mg/L Current PQL = 0.005 mg/L DL = 0.0005 mg/L 

Acceptance Criteria = + 20% or 40%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

502.2 CCGC with PID/ELCD 0.02 - 0.05

524.2 CCGC/MS 0.03 - 0.05

Notes: The regulatory DL for volatile organic compounds is listed at 40 CFR 

141.24(k)(17)(ii)(C). Acceptance Criteria for volatile organic compounds are listed at 40 CFR 

141.24(f)(17)(i).

Results of the PQL Analysis

The current PQL for 1,2-dichlorobenzene is 5 μg/L. The Six-Year 1 and Six-Year 

2/ERA data sets are regressed separately (see Exhibit 104). The Six-Year 1 PE data for 1,2-

dichlorobenzene were not evaluated in the March 2003 report. Note that the acceptance criteria 

are + 40% at spike concentrations below 10 μg/L and + 20% at or above 10 μg/L; hence the data 

were regressed as two independent populations. None of the Six-Year 1 or the Six-Year 2/ERA

data are below the current PQL of 5 μg/L. However, all of the passing rates for the two data sets 

are well above 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 122

Exhibit 104: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – 1,2-Dichlorobenzene

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25

True Value (ug/L)

% Laboratories Passing

ERA Data Below 10 ug/L ERA Data At or Above 10 ug/L PQL

Six-Year 1 Data Below 10 ug/L Six-Year 1 Data At or Above 10 ug/L 10 ug/L Acceptance Criteria Boundary

75% Passing Rate

Acceptance Criteria

= + 20%

Acceptance Criteria

= + 40%

Current PQL 

= 5 ug/L

75%

Conclusion for 1,2-Dichlorobenzene

Although laboratory passing rates are high (well above 75% in the vicinity of the PQL) 

for the Six-Year 1 and Six-Year 2/ERA data sets, given the lack of data below the current PQL 

of 5 μg/L for both data sets, it may not be appropriate to recommend lowering of the PQL. No 

new or revised methods that may be expected to improve analytical performance in the vicinity 

of the current PQL (and hence suggest possible reduction of the PQL) have been approved from 

2000-2007.
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 123

2,4-Dichlorophenoxyacetic acid (2,4-D)

Results of the Methods Comparison

Exhibit 105 summarizes the MDLs for 2,4-dichlorophenoxyacetic acid as documented in 

EPA-developed analytical methods. Updates to one method have been approved for the analysis 

of 2,4-D in drinking water samples during the years 2000-2007 (see Exhibit A-1). These updates 

are minor technical revisions that are not anticipated to improve analytical performance near the 

PQL. In addition, a new method, EPA Method 515.4 was approved (Federal Register, Vol. 67, 

No. 209, p. 65888, October 29, 2002; see Exhibit A-1). The MDL for 2,4-D by EPA Method 

515.4 is somewhat lower than that obtained from other EPA methods, which suggests that 

laboratory performance at low concentrations may be improved through use of Method 515.4. 

Exhibit 105: Analytical Methods for 2,4-D 

MCL = 0.07 mg/L Current PQL = 0.005 mg/L DL = 0.0001 mg/L 

Acceptance Criteria = + 50%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

515.1 GC/ECD 0.078

515.2 LSE and GC/ECD 0.28

515.3 LLED and GC/ELCD 0.35 - 0.36

515.4 LLMED and GC/ECD 0.055 -

0.066

555 HPLC/PDAUVD 0.34 - 1.3

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for 2,4-D is 5 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets are 

regressed separately (see Exhibit 106). The Six-Year 1 PE data for 2,4-D were not evaluated in 

the March 2003 report. Only one of the 20 spike values in the Six-Year 1 data set and none of 

the Six-Year 2/ERA data are below the current PQL of 5 μg/L. Several passing rates are below 

75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 124

Exhibit 106: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – 2,4-D 

0

10

20

30

40

50

60

70

80

90

100

0 30 60 90 120 150

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 50 %

Current PQL 

= 5 ug/L

75%

Conclusion for 2,4-D

Given the variable laboratory passing rates for the Six-Year 1 and Six-Year 2/ERA data 

sets and the lack of data below the current PQL of 5 μg/L for both data sets (with the exception 

of one laboratory passing rate from the Six-Year 1 data set just above 75%), it may not be 

appropriate to recommend lowering of the PQL. However, the approval of EPA Method 515.4 

for the analysis of 2,4-D provides a lower MDL that was achievable by use of other approved 

methods. This may lead to an overall improvement in analytical performance in the vicinity of 

the current PQL and could suggest possible reduction of the PQL. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 125

Di(2-ethylhexyl)adipate (DEHA)

Results of the Methods Comparison

Exhibit 107 summarizes the MDLs for di(2-ethylhexyl)adipate as documented in EPAdeveloped analytical methods. No updated or new analytical methods have been approved for 

the analysis of DEHA in drinking water samples during the years 2000-2007. 

Exhibit 107: Analytical Methods for Di(2-ethylhexyl)adipate 

MCL = 0.4 mg/L Current PQL = 0.006 mg/L DL = 0.0006 mg/L 

Acceptance Criteria = Mean + 2 Std Dev

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

506 LLE or LSE and GC/PID 11.82

525.2 LSE and CCGC/MS 0.09 - 1.3

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for DEHA is 6 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets are 

regressed separately (see Exhibit 108). The Six-Year 1 PE data for DEHA were not evaluated in 

the March 2003 report. None of the Six-Year 2/ERA data for DEHA are below the current PQL

of 6 μg/L and passing rates for Six-Year 1 data below the PQL could not be calculated as the 

NELAC regression coefficients are not valid over that range. However, all but two of the 

passing rates for the two data sets are above 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 126

Exhibit 108: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – DEHA

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30 35 40 45 50

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= Mean + 2 SD

Current PQL 

= 6 ug/L

75%

Conclusion for DEHA

Although laboratory passing rates are high (well above 75% in the vicinity of the PQL) 

for the Six-Year 1 data set, given the variable laboratory passing rates for the Six-Year 2/ERA 

data set and the lack of data below the current PQL of 6 μg/L for both the Six-Year 1 and SixYear 2/ERA data sets, it may not be appropriate to recommend lowering of the PQL. No new or 

revised methods that may be expected to improve analytical performance in the vicinity of the 

current PQL (and hence suggest possible reduction of the PQL) have been approved from 2000-

2007.
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 127

Dinoseb

Results of the Methods Comparison

Exhibit 109 summarizes the MDLs for dinoseb as documented in EPA-developed 

analytical methods. No updated methods have been approved for the analysis of dinoseb in 

drinking water samples during the years 2000-2007; however, a new method, EPA Method 515.4 

was approved (Federal Register, Vol. 67, No. 209, p. 65888, October 29, 2002; see Exhibit A-1). 

The MDL range for dinoseb by EPA Method 515.4 is lower than that obtained from other EPA 

methods, which suggests that laboratory performance at low concentrations may be improved 

through use of Method 515.4. 

Exhibit 109: Analytical Methods for Dinoseb 

MCL = 0.007 mg/L Current PQL = 0.002 mg/L DL = 0.0002 mg/L 

Acceptance Criteria = Mean + 2 Std Dev

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

515.1 GC/ECD 0.33

515.2 LSE and GC/ECD 0.28

515.3 LLED and GC/ELCD 0.75 - 0.82

515.4 LLMED and GC/ECD 0.081 –

0.166

555 HPLC/PDAUVD 0.26 - 1.5

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for dinoseb is 2 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets 

are regressed separately (see Exhibit 110). The Six-Year 1 PE data for dinoseb were not 

evaluated in the March 2003 report. None of the Six-Year 1 or the Six-Year 2/ERA data are 

below the current PQL of 2 μg/L. In general, many of the passing rates around the PQL are 

highly variable. Although all of the passing rates in the Six-Year 1 data are above 75%, three 

passing rates in the Six-Year 2/ERA data are below 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 128

Exhibit 110: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Dinoseb

Conclusion for Dinoseb

 Although laboratory passing rates are high (well above 75% in the vicinity of the PQL) 

for the Six-Year 1 data set, given the variable laboratory passing rates for the Six-Year 2/ERA 

data set and the lack of data below the current PQL of 2 μg/L for both the Six-Year 1 and SixYear 2/ERA data sets, it may not be appropriate to recommend lowering of the PQL. However, 

the approval of EPA Method 515.4 for the analysis of dinoseb provides a lower MDL than was 

achievable by use of other approved methods. This may lead to an overall improvement in 

analytical performance in the vicinity of the current PQL and could suggest possible reduction of 

the PQL. 

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30 35 40 45 50

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= Mean + 2 SD

Current PQL 

= 2 ug/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 129

Diquat

Results of the Methods Comparison

Exhibit 111 summarizes the MDLs for diquat as documented in EPA-developed 

analytical methods. No updated or new analytical methods have been approved for the analysis 

of diquat in drinking water samples during the years 2000-2007. 

Exhibit 111: Analytical Methods for Diquat 

MCL = 0.02 mg/L Current PQL = 0.004 mg/L DL = 0.0004 mg/L 

Acceptance Criteria = Mean + 2 Std Dev

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

549.2 LSE/HPLC w/ UVD 0.72

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for diquat is 4 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets are 

regressed separately (see Exhibit 112). The Six-Year 1 PE data for diquat were evaluated but 

were not regressed in the March 2003 report. None of the Six-Year 1 or the Six-Year 2/ERA

data are below the current PQL of 2 μg/L. All of the passing rates in the Six-Year 1 data are 

above 75%; meanwhile, five passing rates in the Six-Year 2/ERA data are less than or equal to 

75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 130 

Exhibit 112: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Diquat

Conclusion for Diquat 

Although laboratory passing rates are high (above 75% in the vicinity of the PQL) for the 

Six-Year 1 data set, given the variable laboratory passing rates for the Six-Year 2/ERA data set 

and the lack of data below the current PQL of 4 μg/L for both the Six-Year 1 and Six-Year 

2/ERA data sets, it may not be appropriate to recommend lowering of the PQL. No new or 

revised methods that may be expected to improve analytical performance in the vicinity of the 

current PQL (and hence suggest possible reduction of the PQL) have been approved from 2000-

2007. 

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30 35 40 45

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= Mean + 2 SD

Current PQL 

= 4 ug/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 131

Endothall

Results of the Methods Comparison

Exhibit 113 summarizes the MDLs for endothall as documented in EPA-developed 

analytical methods. No updated or new analytical methods have been approved for the analysis 

of endothall in drinking water samples during the years 2000-2007. 

Exhibit 113: Analytical Methods for Endothall 

MCL = 0.1 mg/L Current PQL = 0.09 mg/L DL = 0.009 mg/L 

Acceptance Criteria = Mean + 2 Std Dev

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

548.1 I-EE/Methylate and GC/MS 0.7 - 1.79

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for endothall is 90 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets 

are regressed separately (see Exhibit 114). The Six-Year 1 PE data for endothall were not 

evaluated in the March 2003 report. None of the Six-Year 2/ERA data for endothall are below 

the PQL and passing rates for Six-Year 1 data below the PQL could not be calculated as the 

NELAC regression coefficients are not valid over that range. All but one of the passing rates in 

the Six-Year 1 data are above 75%; meanwhile, four passing rates in the Six-Year 2/ERA data 

are less than or equal to 75%. Note that the 0% passing rate near 220 ug/L from the Six-Year 1 

data was a study that consisted of only one laboratory. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 132

Exhibit 114: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Endothall

0

10

20

30

40

50

60

70

80

90

100

0 50 100 150 200 250 300 350 400 450 500

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= Mean + 2 SD

Current PQL 

= 90 ug/L

75%

Conclusion for Endothall

Although laboratory passing rates are high (well above 75% in the vicinity of the PQL) 

for the Six-Year 1 data set, given the variable laboratory passing rates for the Six-Year 2/ERA 

data set and the lack of data below the current PQL of 90 μg/L for both the Six-Year 1 and SixYear 2/ERA data sets, it may not be appropriate to recommend lowering of the PQL. No new or 

revised methods that may be expected to improve analytical performance in the vicinity of the 

current PQL (and hence suggest possible reduction of the PQL) have been approved from 2000-

2007.
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 133

Endrin

Results of the Methods Comparison

Exhibit 115 summarizes the MDLs for endrin as documented in EPA-developed 

analytical methods. No updated or new analytical methods have been approved for the analysis 

of endrin in drinking water samples during the years 2000-2007. 

Exhibit 115: Analytical Methods for Endrin

MCL = 0.002 mg/L Current PQL = 0.0001 mg/L DL = 0.00001 mg/L 

Acceptance Criteria = + 30%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

505 ME and GC 0.063

508 GC/ECD 0.0062

508.1 LSE and ECGC 0.007

525.2 LSE and CCGC/MS 0.16 - 0.34

551.1 LLE/GC w/ ECD 0.002 -

0.003

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for endrin is 0.1 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets 

are regressed separately (see Exhibit 116). The Six-Year 1 PE data for endrin were not evaluated 

in the March 2003 report. None of the Six-Year 1 or the Six-Year 2/ERA data are below the 

current PQL of 0.1 μg/L. One passing rate for the Six-Year 1 data is below 75%; however, the 

Six-Year 2/ERA passing rates are more variable, with several passing rates below 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 134

Exhibit 116: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Endrin

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5 6

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 30%

Current PQL 

= 0.1 ug/L

75%

Conclusion for Endrin

Given the variable laboratory passing rates in the vicinity of the current PQL of 0.1 μg/L 

and the lack of data below the current PQL for both the Six-Year 1 and Six-Year 2/ERA data 

sets, it may not be appropriate to recommend lowering of the PQL. No new or revised methods 

that may be expected to improve analytical performance in the vicinity of the current PQL (and 

hence suggest possible reduction of the PQL) have been approved from 2000-2007. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 135

Fluoride

Results of the Methods Comparison

Exhibit 117 summarizes the MDLs for fluoride as documented in EPA-developed analytical 

methods. Updates to eleven methods and two new methods (EPA Method 300.1 and ASTM 

D6508, rev. 2) have been approved for the analysis of fluoride in drinking water samples during 

the years 2000-2007 (Federal Register, Vol. 72, No. 47, p. 11200, March 12, 2007; see Exhibit 

A-1). The updates are associated with administrative and technical changes or clarifications that 

are not expected to improve analytical performance near the PQL. The updated methods are 

proprietary and are not listed in Exhibit 117. The MDL for EPA Method 300.1 is slightly lower 

than that for EPA Method 300.0, which suggests that laboratory performance at low 

concentrations may be improved through use of Method 300.1. Since the new ASTM method is 

proprietary, it is uncertain whether new MDLs may be lower than those for other methods. 

Exhibit 117: Analytical Methods for Fluoride 

MCL = 4 mg/L Current PQL = 0.5 mg/L DL = N/A 

Acceptance Criteria = + 10%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL mg/L

300.0 IC 0.01

300.1 IC 0.009

Notes: EPA has not provided a regulatory DL for fluoride in the CFR. Acceptance Criteria for 

inorganic compounds are listed at 40 CFR 141.23(k)(3)(ii).

Results of the PQL Analysis

The current PQL for fluoride is 0.5 mg/L. The Six-Year 1 and Six-Year 2/ERA data sets 

are regressed separately (see Exhibit 118). The Six-Year 1 PE data for fluoride were evaluated 

but were not regressed as part of the March 2003 report. One of the 20 spike values in the SixYear 1 data set is below the current PQL of 0.5 mg/L. No Six-Year 2/ERA data are below the 

current PQL. All but one of the Six-Year 1 passing rates are above 75%. Furthermore, two of 

the Six-Year 2/ERA passing rates are below 75%. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 136

Exhibit 118: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Fluoride

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5 6 7 8

True Value (mg/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 10%

Current PQL 

= 0.5 mg/L

75%

Conclusion for Fluoride

Given the variable laboratory passing rates for the Six-Year 1 and Six-Year 2/ERA data 

sets in the vicinity of the current PQL of 0.5 mg/L and the lack of data below the PQL for both 

data sets (with the exception of one laboratory passing rate from the Six-Year 1 data set slightly 

below the PQL), it may not be appropriate to recommend lowering of the PQL. However, the 

approval of EPA Method 300.1 for the analysis of fluoride provides a slightly lower MDL than 

was achievable by use of other approved methods. This may lead to a slight improvement in 

analytical performance in the vicinity of the current PQL and could suggest possible reduction of 

the PQL. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 137

Glyphosate

Results of the Methods Comparison

Exhibit 119 summarizes the MDLs for glyphosate as documented in EPA-developed 

analytical methods. No updated or new analytical methods have been approved for the analysis 

of glyphosate in drinking water samples during the years 2000-2007. 

Exhibit 119: Analytical Methods for Glyphosate 

MCL = 0.7 mg/L Current PQL = 0.06 mg/L DL = 0.006 mg/L 

Acceptance Criteria = Mean + 2 Std Dev

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

547 DAI/HPLC w/ Der. and FD 5.99 - 6.00

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for glyphosate is 60 μg/L. The Six-Year 1 and Six-Year 2/ERA data 

sets are regressed separately (see Exhibit 120). The Six-Year 1 PE data for glyphosate were 

evaluated but not regressed in the March 2003 report. None of the Six-Year 1 or the Six-Year 

2/ERA data are below the current PQL of 60 μg/L. All but one of the passing rates in the SixYear 1 data are above 75%; however, several passing rates in the Six-Year 2/ERA data are less 

than or equal to 75%. 
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Exhibit 120: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Glyphosate 

0

10

20

30

40

50

60

70

80

90

100

0 100 200 300 400 500 600 700 800

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= Mean + 2 SD

Current PQL 

= 60 ug/L

75%

Conclusion for Glyphosate

Given the variable laboratory passing rates for the Six-Year 2/ERA data set and the lack 

of data below or in the vicinity of the current PQL of 60 μg/L for both the Six-Year 1 and SixYear 2/ERA data sets, it may not be appropriate to recommend lowering of the PQL. No new or 

revised methods that may be expected to improve analytical performance in the vicinity of the 

current PQL (and hence suggest possible reduction of the PQL) have been approved from 2000-

2007.
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Lead

Results of the Methods Comparison

Exhibit 121 summarizes the MDLs for lead as documented in EPA-developed analytical 

methods. Updates to three methods have been approved for the analysis of lead in drinking 

water samples during the years 2000-2007 (see Exhibit A-1). These updates are associated with 

administrative and technical changes or clarifications that are not expected to improve analytical 

performance near the PQL. The updated methods are proprietary and are not listed in Exhibit 

121. 

Exhibit 121: Analytical Methods for Lead 

Action Level = 0.015 mg/L Current PQL = 0.005 mg/L DL = 0.001 mg/L 

Acceptance Criteria = + 30%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL mg/L

200.8 ICP/MS 0.00002 -

0.0006

200.9 GFAA 0.0007

Notes: The regulatory DL for lead is listed at 40 CFR 141.89(a)(1)(iii). Note that the DL is 

referred to as the “method detection limit” in the CFR. The Acceptance Criteria for lead are 

listed at 40 CFR 141.89(a)(1)(ii)(A).

Results of the PQL Analysis

The current PQL for lead is 5 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets are 

regressed separately (see Exhibit 122). The Six-Year 1 PE data for lead were not evaluated in 

the March 2003 report. Four of the 20 spike values in the Six-Year 1 data set are less than or 

equal to the current PQL of 5 μg/L. No Six-Year 2/ERA data are below the PQL. Three of the 

Six-Year 1 concentration values had passing rates of less than 75%. 
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Exhibit 122: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Lead

Conclusion for Lead

Given the relative lack of data and the downward trend in laboratory passing rates below 

the current PQL of 5 μg/L for the Six-Year 1 data set and the lack of data below the PQL for the 

Six-Year 2/ERA dataset, it may not be appropriate to recommend lowering of the PQL. No new 

or revised methods that may be expected to improve analytical performance in the vicinity of the 

current PQL (and hence suggest possible reduction of the PQL) have been approved from 2000-

2007.

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70 80 90 100

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 30%

Current PQL 

= 5 ug/L

75%
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Mercury

Results of the Methods Comparison

Exhibit 123 summarizes the MDLs for mercury as documented in EPA-developed analytical 

methods. Updates to three methods have been approved for the analysis of mercury in drinking 

water samples during the years 2000-2007 (see Exhibit A-1). These updates are associated with 

administrative and technical changes or clarifications that are not expected to improve analytical 

performance near the PQL. The updated methods are proprietary and are not listed in Exhibit 

123. However, a new method, EPA Method 245.7, rev. 2.0, was approved (Federal Register,

Vol. 72, No. 47, p. 11200, March 12, 2007; see Exhibit A-1). The MDL from this method is 

significantly lower than the MDLs from other methods, suggesting that laboratory performance 

at low concentrations may improve through use of Method 245.7. 

Exhibit 123: Analytical Methods for Mercury

MCL = 0.002 mg/L Current PQL = 0.0005 mg/L DL = 0.0002 mg/L 

Acceptance Criteria = + 30%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL mg/L

200.8 ICP/MS 0.0002

245.1 CVAAS No MDL

245.2 ACVT No MDL

245.7 CVAFS 0.0000018

Notes: Regulatory DLs for inorganic compounds are listed at 40 CFR 141.23(a)(4)(i).

Acceptance Criteria for inorganic compounds are listed at 40 CFR 141.23(k)(3)(ii).

Results of the PQL Analysis

The current PQL for mercury is 0.0005 mg/L. The Six-Year 1 and Six-Year 2/ERA data 

sets are regressed separately (see Exhibit 124). The Six-Year 1 PE data for mercury were 

evaluated but not regressed in the March 2003 report. None of the Six-Year 1 or the Six-Year 

2/ERA data are below the current PQL of 0.0005 mg/L. (One of the Six-Year 1 values is equal 

to 0.000506 mg/L, just above the PQL.) All but one of the passing rates in the Six-Year 1 data 

set and all of the passing rates in the Six-Year 2/ERA data set are above 75%. 
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Exhibit 124: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Mercury

0

10

20

30

40

50

60

70

80

90

100

0.000 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009

True Value (mg/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 30%

Current PQL 

= 0.0005 mg/L

75%

Conclusion for Mercury

Given the variable laboratory passing rates the vicinity of the current PQL of 0.5 mg/L 

for the Six-Year 1 data set and the lack of data below the PQL for both the Six-Year 1 and SixYear 2/ERA data sets (with the exception of one laboratory passing rate from the Six-Year 1 data 

set just below the PQL), it may not be appropriate to recommend lowering of the PQL. 

However, the approval of EPA Method 245.7 (Rev 2.0) for the analysis of mercury provides a 

significantly lower MDL than was achievable by use of other approved methods. This may lead 

to an overall improvement in analytical performance in the vicinity of the current PQL and could 

suggest possible reduction of the PQL. 
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Nitrate (as N)

Results of the Methods Comparison

Exhibit 125 summarizes the MDLs for nitrate as documented in EPA-developed analytical 

methods. Updates to ten methods and two new methods (EPA Method 300.1 and ASTM D6508, 

rev. 2) have been approved for the analysis of nitrate in drinking water samples during the years 

2000-2007 (Federal Register, Vol. 67, No. 205, p. 65220, October 23, 2002; Federal Register, 

Vol. 72, No. 47, p. 11200, March 12, 2007; see Exhibit A-1). The updates are associated with 

administrative and technical changes or clarifications that are not expected to improve analytical 

performance near the PQL. The updated methods are proprietary and are not listed in Exhibit 

125. In addition, MDL data for nitrate by EPA Method 300.1 indicate a higher MDL than is 

obtained from EPA Method 300.0, which does not suggest that laboratory performance at low 

concentrations may be improved through use of Method 300.1. 

Exhibit 125: Analytical Methods for Nitrate 

MCL = 10 mg/L Current PQL = 0.4 mg/L DL = 0.01-1 mg/L 

Acceptance Criteria = + 10%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL mg/L

300.0 IC 0.002

300.1 IC 0.008

353.2 Auto Colorimetry No MDL

Notes: Regulatory DLs for inorganic compounds are listed at 40 CFR 141.23(a)(4)(i).

Acceptance Criteria for inorganic compounds are listed at 40 CFR 141.23(k)(3)(ii).

Results of the PQL Analysis

The current PQL for nitrate is 0.4 mg/L. The Six-Year 1 and Six-Year 2/ERA data sets 

are regressed separately (see Exhibit 126). The Six-Year 1 PE data for nitrate were not evaluated 

in the March 2003 report. None of the Six-Year 1 or the Six-Year 2/ERA data are below the 

current PQL of 0.4 mg/L, although several of the Six-Year 1 values are just above the PQL. 

Several of the passing rates (especially in the Six-Year 1 data set) are below 75%. 
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Exhibit 126: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Nitrate

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14 16

True Value (mg/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 10%

Current PQL 

= 0.4 mg/L

75%

Conclusion for Nitrate

Given the variable laboratory passing rates for the Six-Year 1 and Six-Year 2/ERA data 

sets and the lack of data below the current PQL of 0.4 mg/L for both data sets, it may not be 

appropriate to recommend lowering of the PQL. No new or revised methods that may be 

expected to improve analytical performance in the vicinity of the current PQL (and hence 

suggest possible reduction of the PQL) have been approved from 2000-2007.
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Oxamyl (Vydate)

Results of the Methods Comparison

Exhibit 127 summarizes the MDLs for oxamyl as documented in EPA-developed 

analytical methods. No updated methods have been approved for the analysis of oxamyl in 

drinking water samples during the years 2000-2007; however, a new method, EPA Method 

531.2, was approved (Federal Register, Vol. 67, No. 209, p. 65888, October 29, 2002; see 

Exhibit A-1). The range of DLs for oxamyl by EPA Method 531.2 are lower than the MDL from

EPA Method 531.1, suggesting that laboratory performance at low concentrations may improve 

through use of Method 531.2. 

Exhibit 127: Analytical Methods for Oxamyl 

MCL = 0.2 mg/L Current PQL = 0.02 mg/L DL = 0.002 mg/L 

Acceptance Criteria = Mean + 2 Std Dev

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

531.1 DAI/HPLC w/ Der. 0.86

531.2 DAI/HPLC w/ Der. 0.044 - 

0.065 (DL)

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for oxamyl is 20 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets 

are regressed separately (see Exhibit 128). The Six-Year 1 PE data for oxamyl were regressed as 

part of the March 2003 report. Seven of the 20 spike values in the Six-Year 1 data set are below 

the current PQL of 20 μg/L; however, none of the Six-Year 2/ERA data are below the current 

PQL. Passing rates, particularly in the Six-Year 1 data, are highly variable.
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Exhibit 128: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Oxamyl 

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70 80

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= Mean + 2 SD

Current PQL 

= 20 ug/L

75%

Conclusion for Oxamyl

Given the variable laboratory passing rates in the vicinity of the current PQL of 20 μg/L 

for the Six-Year 1 and Six-Year 2/ERA data sets and the lack of data below the PQL for the SixYear 2 data set, it may not be appropriate to recommend lowering of the PQL. The approval of 

EPA Method 531.2 for the analysis of oxamyl provides a lower range of MDLs than was 

achievable by use of other approved methods. This may lead to an overall improvement in 

analytical performance in the vicinity of the current PQL and could suggest possible reduction of 

the PQL. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

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Picloram

Results of the Methods Comparison

Exhibit 129 summarizes the MDLs for picloram as documented in EPA-developed 

analytical methods. Updates to one method have been approved for the analysis of picloram in 

drinking water samples during the years 2000-2007 (see Exhibit A-1). These updates are minor 

technical revisions that are not anticipated to improve analytical performance near the PQL. In 

addition, a new method, EPA Method 515.4 was approved (Federal Register, Vol. 67, No. 209, 

p. 65888, October 29, 2002; see Exhibit A-1). The MDL for picloram by EPA Method 515.4 is 

lower than those obtained from other approved methods, suggesting that laboratory performance 

at low concentrations may improve through use of Method 515.4. 

Exhibit 129: Analytical Methods for Picloram

MCL = 0.5 mg/L Current PQL = 0.001 mg/L DL = 0.0001 mg/L 

Acceptance Criteria = Mean + 2 Std Dev

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

515.1 GC/ECD 0.15

515.2 LSE and GC/ECD 0.35

515.3 LLED and GC/ELCD 0.47 - 1.0

515.4 LLMED and GC/ECD 0.055 –

0.076

555 HPLC/PDAUVD

Not 

Recovered - 

0.5

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for picloram is 1 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets 

are regressed separately (see Exhibit 130). The Six-Year 1 PE data for picloram were evaluated 

but not regressed in the March 2003 report. None of the Six-Year 1 or the Six-Year 2/ERA data 

are below the current PQL of 1 μg/L. The passing rates begin to drop below 75% approaching 

the PQL. 
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Exhibit 130: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Picloram

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70 80

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= Mean + 2 SD

Current PQL 

= 1 ug/L

75%

Conclusion for Picloram

Although the laboratory passing rates for both the Six-Year 1 and Six-Year 2/ERA data 

sets are generally high, given the lower laboratory passing rates in the vicinity of the current 

PQL of 1 μg/L and the lack of data below the PQL for both data sets, it may not be appropriate 

to recommend lowering of the PQL. However, the approval of EPA Method 515.4 for the 

analysis of picloram provides a lower MDL than was achievable by use of other approved

methods. This may lead to an overall improvement in analytical performance in the vicinity of 

the current PQL and could suggest possible reduction of the PQL. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

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Selenium

Results of the Methods Comparison

Exhibit 131 summarizes the MDLs for selenium as documented in EPA-developed 

analytical methods. Updates to four methods have been approved for the analysis of selenium in 

drinking water samples during the years 2000-2007 (see Exhibit A-1). These updates are 

associated with administrative and technical changes or clarifications that are not expected to 

improve analytical performance near the PQL. 

Exhibit 131: Analytical Methods for Selenium

MCL = 0.05 mg/L Current PQL = 0.01 mg/L DL = 0.002 mg/L 

Acceptance Criteria = + 20%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL mg/L

200.8 ICP/MS 0.0005 -

0.0079

200.9 GFAA 0.0006

Notes: Regulatory DLs for inorganic compounds are listed at 40 CFR 141.23(a)(4)(i).

Acceptance Criteria for inorganic compounds are listed at 40 CFR 141.23(k)(3)(ii).

Results of the PQL Analysis

The current PQL for selenium is 0.01 mg/L. The Six-Year 1 and Six-Year 2/ERA data 

sets are regressed separately (see Exhibit 132). The Six-Year 1 PE data for selenium were not 

evaluated in the March 2003 report. Only one of the 20 spike values in the Six-Year 1 data set is 

below the current PQL of 0.01 mg/L. No Six-Year 2/ERA data are below the current PQL. All 

of the passing rates are well above 75%. Furthermore, both regression lines are also well above 

75%. 
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Exhibit 132: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Selenium

0

10

20

30

40

50

60

70

80

90

100

0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10

True Value (mg/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= + 20%

Current PQL 

= 0.01 mg/L

75%

Conclusion for Selenium

Although the laboratory passing rates for both the Six-Year 1 and Six-Year 2/ERA data 

sets are generally high, given the lack of data below the PQL of 0.01 mg/L for both data sets 

(with the exception of one value from the Six-Year 1 data set just below the PQL), it may not be 

appropriate to recommend lowering of the PQL. No new or revised methods that may be 

expected to improve analytical performance in the vicinity of the current PQL (and hence 

suggest possible reduction of the PQL) have been approved from 2000-2007.
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Simazine

Results of the Methods Comparison

Exhibit 133 summarizes the MDLs for simazine as documented in EPA-developed 

analytical methods. No updated or new analytical methods have been approved for the analysis 

of simazine in drinking water samples during the years 2000-2007. 

Exhibit 133: Analytical Methods for Simazine

MCL = 0.004 mg/L Current PQL = 0.0007 mg/L DL = 0.00007 mg/L 

Acceptance Criteria = Mean + 2 Std Dev

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

505 ME and GC 6.8

507 GC/N-PD 0.014

508.1 LSE and ECGC 0.008

525.2 LSE and CCGC/MS 0.045 - 0.18

551.1 LLE/GC w/ ECD 0.121 -

0.187

Notes: Regulatory DLs for synthetic organic compounds are listed at 40 CFR 141.24(h)(18).

Acceptance Criteria for synthetic organic compounds are listed at 40 CFR 141.24(h)(19)(i)(B).

Results of the PQL Analysis

The current PQL for simazine is 0.7 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets 

are regressed separately (see Exhibit 134). The Six-Year 1 PE data for simazine were not 

evaluated in the March 2003 report. None of the Six-Year 2/ERA data are below the current 

PQL of 0.7 μg/L and passing rates for Six-Year 1 data below the PQL could not be calculated as 

the NELAC regression coefficients are not valid over that range. All of the passing rates in the 

Six-Year 1 data are above 75%; however, several passing rates in the Six-Year 2/ERA data are 

less than or equal to 75%. 
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Exhibit 134: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Simazine

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30 35 40

True Value (ug/L)

% Laboratories Passing

ERA Data PQL Six-Year 1 Data 75% Passing Rate

Acceptance Criteria

= Mean + 2 SD

Current PQL 

= 0.7 ug/L

75%

Conclusion for Simazine

Although the laboratory passing rates for the Six-Year 1 data set are generally high (well 

above 75%), given the lack of data below the PQL of 0.7 μg/L for both the Six-Year 1 and SixYear 2/ERA data sets and the variability in laboratory passing rates in the vicinity of the PQL for 

the Six-Year 2 data set, it may not be appropriate to recommend lowering of the PQL. No new 

or revised methods that may be expected to improve analytical performance in the vicinity of the 

current PQL (and hence suggest possible reduction of the PQL) have been approved from 2000-

2007.
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Xylenes (total)

Results of the Methods Comparison

Exhibit 135 summarizes the MDLs for xylenes as documented in EPA-developed 

analytical methods. No updated or new analytical methods have been approved for the analysis 

of xylenes in drinking water samples during the years 2000-2007. 

Exhibit 135: Analytical Methods for Xylenes

MCL = 10 mg/L Current PQL = 0.005 mg/L DL = 0.0005 mg/L 

Acceptance Criteria = + 20% or 40%

EPA Methods Approved for the Analysis of Drinking Water

Method Technique MDL μg/L

502.2 CCGC with PID/ ELCD 0.01 - 0.02

524.2 CCGC/MS 0.03 - 0.13

Notes: The regulatory DL for volatile organic compounds is listed at 40 CFR 

141.24(k)(17)(ii)(C). Acceptance Criteria for volatile organic compounds are listed at 40 CFR 

141.24(f)(17)(i).

Results of the PQL Analysis

The current PQL for xylenes is 5 μg/L. The Six-Year 1 and Six-Year 2/ERA data sets 

are regressed separately (see Exhibit 136). The Six-Year 1 PE data for xylenes were evaluated 

but were not regressed as part of the March 2003 report. Note that the acceptance criteria are + 

40% at spike concentrations below 10 μg/L and + 20% at or above 10 μg/L; hence the data are

regressed as two independent populations. No Six-Year 1 data are available below the current 

PQL of 5 μg/L. Only one of the 60 spike values in the Six-Year 2/ERA data set is below the 

current PQL. All of the passing rates for the Six-Year 1 data set are above 75%; however the 

passing rates for the Six-Year 2/ERA data set are more variable.
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Exhibit 136: Evaluation of Six-Year 1 and Six-Year 2/ERA PT Data – Xylenes

Conclusion for Xylenes

Although the laboratory passing rates for the Six-Year 1 data set are generally high (well 

above 75%), given the lack of data below the PQL of 5 μg/L for the Six-Year 1 data set and the 

variability in laboratory passing rates for the Six-Year 2 data set, it may not be appropriate to 

recommend lowering of the PQL. No new or revised methods that may be expected to improve 

analytical performance in the vicinity of the current PQL (and hence suggest possible reduction 

of the PQL) have been approved from 2000-2007.

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30 35 40 45 50

True Value (ug/L)

% Laboratories Passing

ERA Data Below 10 ug/L ERA Data At or Above 10 ug/L PQL

Six-Year 1 Data Below 10 ug/L Six-Year 1 Data At or Above 10 ug/L 10 ug/L Acceptance Criteria Boundary

75% Passing Rate

Acceptance Criteria

= + 20%

Acceptance Criteria

= + 40%

Current PQL 

= 5 ug/L

75%
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7.0 Summary

This document examines analytical method performance over time by determining if the 

Practical Quantitation Levels (PQLs) may have changed since promulgation. PQL assessments 

are presented by means of linear regression of available Six-Year 1 data and the ERA dataset 

from Six-Year 2. A qualitative conclusion is drawn by presenting a recommendation of whether 

a PQL might be reduced. In addition, analytical method performance is also assessed by 

comparing the Method Detection Limits (MDLs) of the analytical methods which were available 

at the time of promulgation to those of the currently approved methods. 

Exhibit 137 provides summary observations from this review of PE data that were 

compiled in the first Six-Year Review and of ERA’s 1999-2004 PT data. It also includes a 

notation as to whether any recently-approved analytical methods or updates (i.e., from 2000-

2007) are available for these analytes that might indicate improved laboratory performance at 

low concentrations. Lastly, a recommendation as to whether a PQL can be reduced is provided 

(these analytes are italicized). Note that the entries in the “Current Evaluation of Six-Year 1 

Data” column are not necessarily identical to the conclusions that were documented in the March 

2003 report. Rather, a new assessment is made herein considering the advantages and 

disadvantages of the PQL concept, the availability of PE/PT data in the vicinity of and/or below 

the PQL, and outliers. The qualitative conclusions are based primarily on data that are in the 

vicinity of and/or below the PQL (for most of the VOCs, this corresponds to concentrations <10 

μg/L). Only the current evaluations of the Six-Year 1 and Six-Year 2/ERA data are presented in 

this report. 

The overall assessment decision presented in the final column of Exhibit 137 consists of 

the following possible outcomes: 

• Regulated Contaminants with Existing PQL Lower than the MCL

- PQL assessment supports reduction of the current PQL; 

- PQL assessment may support reduction of the current PQL; and 

- PQL assessment does not support reduction of the current PQL, or data are 

inconclusive or insufficient to reach a conclusion 

• Regulated Contaminants for Which the MCL is Set at the PQL, and thus, the PQL is 

Limiting

- PQL assessment supports reduction of the current PQL; 

- PQL assessment may support reduction of the current PQL; and

- PQL assessment does not support reduction of the current PQL, or data are 

inconclusive or insufficient to reach a conclusion. 

 The recommendation to not reduce the PQL/MCL (or not to reduce it further in cases 

where the PQL < MCL) could be related to many factors, since each of the Six-Year 1 and ERA 

data sets may reflect one or more of the following traits:

• No PE/PT data are available at or below the PQL;
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Page 156

• Laboratory performance is poor near the PQL;

• Laboratory performance is highly variable over the range of concentrations analyzed. 

 The data sets may suggest entirely opposite recommendations, in that one data set may 

suggest that the PQL could be reduced while the other may suggest the opposite. Hence there is 

no simple, succinct way to reflect the reason why a recommendation of “No change to the PQL” 

was obtained, although a lack of data at or below the PQL for both data sets implies that the data 

are insufficient to support a reduction in the PQL. However, in a case such as this, laboratory 

performance across the range of concentrations analyzed is still a contributing factor in the 

recommendation. 

 

 As shown in Exhibit 137, of the 66 analytes that could be analyzed in this report 

(acrylamide, epichlorohydrin, 2,3,7,8-TCDD (dioxin) could not be analyzed due to a lack of 

PE/PT data, and chlorite has no PQL), the qualitative recommendations for PQL assessment

break down as follows: 

• For 25 analytes, the PQL is equal to the MCL and hence PQL is limiting. Of these 25 

analytes, PQL assessment indicates that:

– The PQL can be reduced for 9 analytes: benzene, carbon tetrachloride, chlordane, 

1,2-dichloroethane, 1,2-dichloropropane, hexachlorobenzene, tetrachloroethylene, 

1,1,2-trichloroethane, and trichloroethylene; 

– The PQL might be considered for reduction for 8 analytes: alachlor, antimony, 1,2-

dibromo-3-chloropropane, heptachlor, heptachlor epoxide, lindane, toxaphene, and 

vinyl chloride; and 

– PE/PT data do not support reduction of the PQL or data are inconclusive or 

insufficient to reach a conclusion for 8 analytes: benzo(a)pyrene, bromate, 

dichloromethane, di(2-ethylhexyl)phthalate, ethylene dibromide, pentachlorophenol, 

polychlorinatedbiphenyls (PCBs), and thallium. 

• For 41 analytes, the PQL is less than the MCL; hence the MCL can be reduced. For these 

41 analytes, PQL assessment indicates that:

– The PQL can be reduced further (beyond the current PQL) for 11 analytes: barium, 

1,4-dichlorobenzene, cis-1,2-dichloroethylene, 1,1-dichloroethylene, ethylbenzene, 

monochlorobenzene, nitrite, styrene, toluene, 1,2,4-trichlorobenzene, and 1,1,1-

trichloroethane; 

– The PQL might be considered for further reduction for 6 analytes: atrazine, 

carbofuran, trans-1,2-dichloroethylene, hexachlorocyclopentadiene, methoxychlor, 

and 2,4,5-TP (Silvex); and

– PE/PT data do not support further reduction of the PQL or data are inconclusive or 

insufficient to reach a conclusion for 24 analytes: arsenic, beryllium, cadmium, 

chromium, copper, cyanide, dalapon, 1,2-dichlorobenzene, 2,4-dichlorophenoxyacetic 

acid, di(2-ethylhexyl)adipate, dinoseb, diquat, endothall, endrin, fluoride, glyphosate, 

lead, mercury, nitrate, oxamyl, picloram, selenium, simazine, and xylenes. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 157

Several factors often require that these assessments be made qualitatively rather than 

quantitatively. The regression of PE/PT data vs. passing rate can be affected by high passing 

rates even when there are also passing rates that are well below the 75% threshold (e.g., a large 

number of passing rates >90% will “offset” passing rates below 75%, resulting in a regression 

line that is well above 75% across the range of spike concentrations). Thus, even when the 

regression line is above the 75% passing rate threshold, a few relatively low passing rates, 

particularly near the PQL, may be considered to be more important than much higher passing 

rates at other concentrations. In some cases, the recommendation resulting from the Six-Year 1 

data set is opposite from that resulting from the ERA data set. In these cases, the more recent 

ERA data may drive the recommendation. The variable acceptance criteria (based on analyte 

concentration) for several analytes (most of the VOCs) also confound the issue. In these cases, 

the passing rates below 10 μg/L are often much higher than those at or above 10 μg/L. Passing 

rates of less than 75% may occur above 10 μg/L, while much higher passing rates are often

observed below 10 μg/L.

 Exhibits 137 and 138 summarize the qualitative assessment for potential PQL reduction 

for the Six-Year 1 and Six-Year 2/ERA datasets individually and include a final qualitative 

recommendation considering both datasets. These exhibits also include an indication of whether 

new or updated analytical methods might be expected to improve analytical performance in the 

vicinity of the current PQL. Exhibit 137 summarizes the PQL assessments for the 25 analytes

that have an MCL set at the current PQL, and thus the PQL is limiting. Exhibit 138 summarizes 

the PQL assessments for the 41 analytes that have an MCL that is greater than the current PQL, 

and thus it is technically feasible to reduce an MCL. Analytical method performance assessment 

for these analytes can indicate the potential for MCL reduction beyond the current PQL. 

Exhibit 137: Second Six-Year Review Analytical Feasibility Assessment Summary

Analytes with MCL Equal to the Current PQL, and thus the PQL is Limiting - 25 Analytes 

Analyte

Current 

PQL 

(mg/L)

New or Updated 

Methods?

PQL Assessment Results

Current 

Evaluation of 

Six-Year 1 

Data

Current 

Evaluation of 

Six-Year 2

(ERA 1999-

2004) Data

Overall Qualitative 

Recommendation

Alachlor 0.002 No

Data may 

support lower 

PQL

No data <

current PQL; 

passing rates 

high in vicinity 

of current PQL

Reduction of current PQL may 

be supported

Antimony 0.006

Yes - not expected 

to improve 

analytical 

performance in 

vicinity of current 

PQL

Data may 

support lower 

PQL

No data <

current PQL; 

passing rates 

high in vicinity 

of current PQL

Slight reduction of current PQL 

may be supported

Benzene 0.005 No Data support 

lower PQL

Data support 

lower PQL

Reduction of current PQL 

supported
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 158

Analyte

Current 

PQL 

(mg/L)

New or Updated 

Methods?

PQL Assessment Results

Current 

Evaluation of 

Six-Year 1 

Data

Current 

Evaluation of 

Six-Year 2

(ERA 1999-

2004) Data

Overall Qualitative 

Recommendation

Benzo(a)pyrene 0.0002 No No data <

current PQL

No data <

current PQL No change to current PQL

Bromate 0.01

Yes – may improve 

analytical 

performance in 

vicinity of current 

PQL. New 

methods 317.0 and 

326.0 have lower 

MDLs.

Data indicate no 

change to 

current PQL

Data indicate 

no change to 

current PQL

No change to current PQL

Carbon tetrachloride 0.005 No Data support 

lower PQL

Data support 

lower PQL

Reduction of current PQL 

supported

Chlordane 0.002 No Data support 

lower PQL

No data <

current PQL; 

passing rates 

generally high

in vicinity of 

current PQL

Reduction of current PQL 

supported

1,2-Dibromo-3-

chloropropane (DBCP) 0.0002 No

Data may 

support lower 

PQL

Data may 

support lower 

PQL

Slight reduction of current PQL 

may be supported

1,2-Dichloroethane 

(Ethylene dichloride) 0.005 No Data support 

lower PQL

Data support 

lower PQL

Reduction of current PQL 

supported

Dichloromethane

(Methylene Chloride) 0.005 No No data <

current PQL

No data <

current PQL No change to current PQL

1,2-Dichloropropane 0.005 No

No data < PQL; 

passing rates 

high in vicinity 

of current PQL

Data support 

lower PQL

Reduction of current PQL 

supported

Di(2-ethylhexyl) phthalate 

(DEHP) 0.006 No

Data indicate no 

change to 

current PQL

No data <

current PQL No change to current PQL

Ethylene Dibromide 

(EDB) 0.00005 No No data <

current PQL

No data <

current PQL No change to current PQL

Heptachlor 0.0004 No Data support 

lower PQL

No data <

current PQL; 

passing rates 

variable in 

vicinity of 

current PQL

Reduction of current PQL may 

be supported

Heptachlor epoxide 0.0002 No Data support 

lower PQL

No data <

current PQL; 

passing rates 

variable in 

vicinity of 

current PQL

Reduction of current PQL may 

be supported

Hexachlorobenzene 0.001 No Data support 

lower PQL

Data support 

lower PQL

Reduction of current PQL 

supported

Lindane 0.0002 No

Data may 

support lower 

PQL

No data <

current PQL; 

passing rates 

high in vicinity 

of current PQL

Reduction of current PQL may 

be supported
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 159

Analyte

Current 

PQL 

(mg/L)

New or Updated 

Methods?

PQL Assessment Results

Current 

Evaluation of 

Six-Year 1 

Data

Current 

Evaluation of 

Six-Year 2

(ERA 1999-

2004) Data

Overall Qualitative 

Recommendation

Pentachlorophenol 0.001

Yes - may improve 

analytical 

performance in 

vicinity of current 

PQL. New method 

515.4 has capability 

of a lower MDL.

Data indicate no 

change to 

current PQL

No data <

current PQL No change to current PQL

PCBs as DCBP 0.0005 No

Data indicate no 

change to 

current PQL

No data <

current PQL No change to current PQL

Tetrachloroethylene 0.005 No

No data <

current PQL; 

passing rates 

high in vicinity 

of current PQL

Data support 

lower PQL

Reduction of current PQL 

supported

Thallium 0.002 No

Data may 

support lower 

PQL

No data <

current PQL No change to current PQL

Toxaphene 0.003 No Data support 

lower PQL

No data <

current PQL; 

passing rates 

variable in 

vicinity of 

current PQL

Reduction of current PQL may 

be supported

1,1,2-Trichloroethane 0.005 No

No data <

current PQL; 

passing rates 

high in vicinity 

of current PQL

Data support 

lower PQL

Reduction of current PQL 

supported

Trichloroethylene 0.005 No

No data <

current PQL; 

passing rates 

high in vicinity 

of current PQL

Data support 

lower PQL

Reduction of current PQL 

supported

Vinyl chloride 0.002 No

No data <

current PQL; 

passing rates 

high in vicinity 

of current PQL

Data may 

support lower 

PQL

Reduction of current PQL may 

be supported
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 160

Exhibit 138: Second Six-Year Review Analytical Feasibility Assessment Summary

Analytes with MCL Greater than the Current PQL and Thus it is Technically Feasible to 

Reduce the MCL - 41 Analytes 

Analyte

Current 

PQL 

(mg/L)

New or Updated 

Methods?

PQL Assessment Results

Current 

Evaluation of 

Six-Year 1 

Data

Current 

Evaluation of 

Six-Year 2 

(ERA 1999-

2004) Data

Overall Qualitative 

Recommendation

Arsenic 0.003

Yes - not expected 

to improve 

analytical 

performance in 

vicinity of current 

PQL

Data indicate no 

change to 

current PQL

No data <

current PQL No change to current PQL

Atrazine 0.001

Yes – Effect on 

performance 

unknown. DL from 

new method 

needed to assess 

effect on analytical 

performance in 

vicinity of current 

PQL

Data may 

support lower 

PQL

No data <

current PQL; 

passing rates 

variable in 

vicinity of 

current PQL

Reduction of current PQL may 

be supported

Barium 0.15

Yes - not expected 

to improve 

analytical 

performance in 

vicinity of current 

PQL

Data support 

slightly lower 

PQL

No data <

current PQL; 

passing rates 

high in vicinity 

of current PQL

Slight reduction of current PQL 

supported

Beryllium 0.001

Yes - not expected 

to improve 

analytical 

performance in 

vicinity of current 

PQL

Data indicate no 

change to 

current PQL

No data <

current PQL No change to current PQL

Cadmium 0.002

Yes - not expected 

to improve 

analytical 

performance in 

vicinity of current 

PQL

No data <

current PQL

No data <

current PQL No change to current PQL

Carbofuran 0.007

Yes - may improve 

analytical 

performance in 

vicinity of current 

PQL. New method 

531.2 has lower 

MDL.

Data support 

lower PQL

No data <

current PQL; 

passing rates 

variable in 

vicinity of 

current PQL

Reduction of current PQL may 

be supported

Chromium 0.01

Yes - not expected 

to improve 

analytical 

performance in 

vicinity of current 

PQL

No data <

current PQL

No data <

current PQL No change to current PQL

Copper 0.05

Yes - not expected 

to improve 

analytical 

performance in 

vicinity of current 

PQL

Data indicate no 

change to 

current PQL

No data <

current PQL No change to current PQL
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 161

Analyte

Current 

PQL 

(mg/L)

New or Updated 

Methods?

PQL Assessment Results

Current 

Evaluation of 

Six-Year 1 

Data

Current 

Evaluation of 

Six-Year 2 

(ERA 1999-

2004) Data

Overall Qualitative 

Recommendation

Cyanide (as free cyanide) 0.1

Yes – effect on 

performance 

unknown. DLs from 

new method(s) 

needed to assess 

effect on analytical 

performance in 

vicinity of current 

PQL

No data < 

current PQL

No data <

current PQL No change to current PQL

Dalapon 0.01

Yes – may improve 

analytical 

performance in 

vicinity of current 

PQL. MDL from 

new methods 515.4 

and 552.3 are lower 

than previous MDLs

Cannot 

determine 

passing rates 

for data <

current PQL

No data <

current PQL No change to current PQL

1,2-Dichlorobenzene 

(o-Dichlorobenzene) 0.005 No No data <

current PQL

No data <

current PQL No change to current PQL

1,4-Dichlorobenzene 

(p-Dichlorobenzene) 0.005 No Data support 

lower PQL

Data support 

lower PQL

Reduction of current PQL 

supported

1,1-Dichloroethylene 0.005 No

No data <

current PQL; 

passing rates 

high in vicinity 

of current PQL

Data support 

lower PQL

Reduction of current PQL 

supported

cis-1,2-dichloroethylene 0.005 No

No data <

current PQL; 

passing rates 

high in vicinity 

of current PQL

Data support 

lower PQL

Reduction of current PQL 

supported

trans-1,2-

Dichloroethylene 0.005 No

No data <

current PQL; 

passing rates 

high in vicinity 

of current PQL

Data may 

support lower 

PQL; passing 

rates generally 

high in vicinity 

of current PQL

Reduction of current PQL may 

be supported

2,4-Dichlorophenoxyacetic acid (2,4-D) 0.005

Yes - may improve 

analytical 

performance in 

vicinity of current 

PQL. New method 

515.4 has lower 

MDL.

Data indicate no 

change to 

current PQL

No data <

current PQL No change to current PQL

Di(2-ethylhexyl) adipate 

(DEHA) 0.006 No

Cannot 

determine 

passing rate for

data < current 

PQL

No data <

current PQL No change to current PQL

Dinoseb 0.002

Yes - may improve 

analytical 

performance in 

vicinity of current 

PQL. New method 

515.4 has lower 

MDL.

No data <

current PQL

No data <

current PQL No change to current PQL
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 162

Analyte

Current 

PQL 

(mg/L)

New or Updated 

Methods?

PQL Assessment Results

Current 

Evaluation of 

Six-Year 1 

Data

Current 

Evaluation of 

Six-Year 2 

(ERA 1999-

2004) Data

Overall Qualitative 

Recommendation

Diquat 0.004 No No data <

current PQL

No data <

current PQL No change to current PQL

Endothall 0.09 No

Cannot 

determine 

passing rate for 

data < current 

PQL

No data <

current PQL No change to current PQL

Endrin 0.0001 No No data <

current PQL

No data <

current PQL No change to current PQL

Ethylbenzene 0.005 No

No data <

current PQL; 

passing rates 

high in vicinity 

of current PQL

Data support 

lower PQL

Reduction of current PQL 

supported

Fluoride 0.5

Yes – may improve 

analytical 

performance in 

vicinity of current 

PQL. MDL from 

new method 300.1 

is slightly lower 

than MDL from 

300.0.

Insufficient data 

< current PQL

No data <

current PQL No change to current PQL

Glyphosate 0.06 No No data <

current PQL

No data <

current PQL No change to current PQL

Hexachlorocyclopentadiene 0.001 No

Data may 

support lower 

PQL

No data <

current PQL; 

passing rates 

variable in 

vicinity of 

current PQL

Reduction of current PQL may 

be supported

Lead 0.005

Yes - not expected 

to improve 

analytical 

performance in 

vicinity of current 

PQL

Data indicate no 

change to 

current PQL

No data <

current PQL No change to current PQL

Mercury 0.0005

Yes – may improve 

analytical 

performance in 

vicinity of current 

PQL. MDL from 

new method 245.7 

is significantly lower 

than previous MDLs

Data indicate no 

change to 

current PQL

No data <

current PQL No change to current PQL

Methoxychlor 0.01 No Data support 

lower PQL

No data <

current PQL; 

passing rates 

variable in 

vicinity of 

current PQL

Reduction of current PQL may 

be supported

Monochlorobenzene 

(Chlorobenzene) 0.005 No

No data <

current PQL; 

passing rates 

high in vicinity 

of current PQL

Data support 

lower PQL

Slight reduction of current PQL 

supported
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 163

Analyte

Current 

PQL 

(mg/L)

New or Updated 

Methods?

PQL Assessment Results

Current 

Evaluation of 

Six-Year 1 

Data

Current 

Evaluation of 

Six-Year 2 

(ERA 1999-

2004) Data

Overall Qualitative 

Recommendation

Nitrate (as N) 0.4

Yes - not expected 

to improve 

analytical 

performance in 

vicinity of current 

PQL. MDL from 

new method 300.1 

is higher than that 

from 300.0.

No data <

current PQL

No data <

current PQL No change to current PQL

Nitrite (as N) 0.4

Yes - may improve 

analytical 

performance in 

vicinity of current 

PQL. MDL from 

new method 300.1 

is lower than 

previous MDLs

Data support 

lower PQL

No data <

current PQL; 

passing rates 

high in vicinity 

of current PQL

Reduction of current PQL 

supported

Oxamyl (Vydate) 0.02

Yes - may improve 

analytical 

performance in 

vicinity of current 

PQL. MDL from 

new method 531.2 

is lower than 

previous MDLs

Data indicate no 

change to 

current PQL

No data <

current PQL No change to current PQL

Picloram 0.001

Yes - may improve 

analytical 

performance in 

vicinity of current 

PQL. New method 

515.4 has lower 

MDL.

No data <

current PQL

No data <

current PQL No change to current PQL

Selenium 0.01

Yes - not expected 

to improve 

analytical 

performance in 

vicinity of current 

PQL

Insufficient data 

< current PQL

No data <

current PQL No change to current PQL

Simazine 0.0007 No

Cannot 

determine 

passing rate for 

data < current 

PQL

No data <

current PQL No change to current PQL

Styrene 0.005 No

No data <

current PQL; 

passing rates 

high in vicinity 

of current PQL

Data support 

lower PQL

Reduction of current PQL 

supported

Toluene 0.005 No

No data <

current PQL; 

passing rates 

high in vicinity 

of current PQL

Data support 

lower PQL

Reduction of current PQL 

supported
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 164

Analyte

Current 

PQL 

(mg/L)

New or Updated 

Methods?

PQL Assessment Results

Current 

Evaluation of 

Six-Year 1 

Data

Current 

Evaluation of 

Six-Year 2 

(ERA 1999-

2004) Data

Overall Qualitative 

Recommendation

2,4,5-TP (Silvex) 0.005

Yes - may improve 

analytical 

performance in 

vicinity of current 

PQL. New method 

515.4 has capability 

of a lower MDL.

Data support 

lower PQL

No data <

PQL; passing 

rates variable 

in vicinity of 

current PQL

Reduction of current PQL may 

be supported

1,2,4-Trichlorobenzene 0.005 No

No data <

current PQL; 

passing rates 

high in vicinity 

of current PQL

Data support 

lower PQL

Reduction of current PQL 

supported

1,1,1-Trichloroethane 0.005 No Data support 

lower PQL

Data support 

lower PQL

Reduction of current PQL 

supported

Xylenes (total) 0.005 No No data <

current PQL

Data indicate 

no change to 

current PQL

No change to current PQL

Improved analytical performance (and hence, possible PQL reduction) may also be 

supported by the approval and availability of new or revised analytical methods with lower 

MDLs (note that in some analytical methods, the term DL is used instead of MDL, but these 

quantities are essentially equivalent). For 15 regulated analytes, new methods have been 

approved. For 12 of these analytes (bromate, carbofuran, 2,4-D, dalapon, dinoseb, fluoride, 

mercury, nitrite, oxamyl, pentachlorophenol, picloram and 2,4,5-TP), the MDLs are lower (or 

their range of MDLs includes values that are lower) than those from earlier-approved methods. 

In two cases (atrazine and cyanide), the methods are proprietary and are not readily available; 

hence, MDLs are not known, and comparison cannot be made. Lastly, in one case (nitrate), new 

or revised methods do not indicate a lower MDL. 

Overall, the results show that only for 20 of the 66 analytes evaluated in this report, 

laboratory performance data was sufficient to qualitatively conclude that the PQL can be 

lowered. For 14 analytes there were indications for a lower PQL but for the remaining 32 either 

the data were inconclusive or insufficient to draw a conclusion. Furthermore, for only 3 of the 

20 analytes for which PQL could be lowered, the improved analytical performance was 

supported by new and improved methods approval. For others, there was either no correlation or 

correlation could not be made due to insufficient data. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 165

8.0 References

NEMI. 2008. National Environmental Methods Index, available on the Internet at: 

http://www.nemi.gov/apex/f?p=237:1:1342350837485455; accessed March, 2008.

USEPA. 1985a. National Primary Drinking Water Regulations; Volatile Synthetic Organic

Chemicals; Final Rule and Proposed Rule. Federal Register. Vol. 50, No. 219, p. 46880, 

November 13, 1985. 

USEPA. 1985b. National Primary Drinking Water Regulations; Volatile Synthetic Organic

Chemicals; Proposed Rule. Federal Register. Vol. 50, No. 219, p. 46902, November 13, 1985. 

USEPA. 1987. National Primary Drinking Water Regulations – Synthetic Organic Chemicals;

Monitoring for Unregulated Contaminants; Final Rule. Federal Register. Vol. 52, No. 130, 

p. 25690, July 8, 1987. 

USEPA. 1988. Drinking Water Regulations; Maximum Contaminant Level Goals and National 

Primary Drinking Water Regulations for Lead and Copper; Proposed Rule. Federal Register. 

Vol. 53, No. 160, p. 31516, August 18, 1988. 

USEPA. 1989. National Primary and Secondary Drinking Water Regulations; Synthetic Organic 

Chemicals and Inorganic Chemicals; Proposed Rule. Federal Register. Vol. 55, No. 143, p. 

30370, July 25, 1990. 

USEPA. 1990. National Primary and Secondary Drinking Water Regulations; Proposed Rule. 

Federal Register. Vol. 54, No. 97, p. 22062, May 22, 1989. 

USEPA. 1991a. National Primary Drinking Water Regulations – Synthetic Organic Chemicals

and Inorganic Chemicals; Monitoring for Unregulated Contaminants; National Primary 

Drinking Water Regulations Implementation; National Secondary Drinking Water 

Regulations; Final Rule. Federal Register. Vol. 56, No. 30, p. 3526, January 30, 1991. 

USEPA. 1991b. Drinking Water; National Primary Drinking Water Regulations; Radionuclides; 

Proposed Rule. Federal Register. Vol. 56, No. 138, p. 33050, July 18, 1991. 

USEPA. 1992. National Primary and Secondary Drinking Water Regulations – Synthetic 

Organic Chemicals and Inorganic Chemicals; National Primary Drinking Water Regulations 

Implementation Federal Register. Vol. 57, No. 138, p. 31776, July 17, 1992. 

USEPA. 1998. National Primary Drinking Water Regulations: Disinfectants and Disinfection 

Byproducts; Final Rule. Federal Register. Vol. 63, No. 241, p. 69390, December 16, 1998. 

USEPA. 1999. Analytical Methods Support Document For Arsenic In Drinking Water, EPA815-R-00-010, December. 

USEPA. 2000. National Primary Drinking Water Regulations; Radionuclides; Final Rule. 

Federal Register. Vol. 65, No. 236, p. 76708, December 7, 2000. 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page 166

USEPA. 2002a. Guidelines Establishing Test Procedures for the Analysis of Pollutants Under 

the Clean Water Act; National Primary Drinking Water Regulations; and National Secondary 

Drinking Water Regulations; Methods Update; Final Rule. Federal Register. Vol. 67, p. 

65220, October 23, 2002. 

USEPA. 2002b. Unregulated Contaminant Monitoring Regulation: Approval of Analytical 

Method for Aeromonas; National Primary and Secondary Drinking Water Regulations: 

Approval of Analytical Methods for Chemical and Microbiological Contaminants; Final Rule. 

Federal Register. Vol. 67, p. 65888, October 29, 2002. 

USEPA. 2003a. EPA Protocol for the Review of Existing National Primary Drinking Water 

Regulations, EPA-815-R-03-002, June 2003. 

USEPA. 2003b. National Primary Drinking Water Standards, EPA-816-F-03-016, June 2003. 

USEPA. 2003c. Analytical Feasibility Support Document for the Six-Year Review of National 

Primary Drinking Water Regulations, EPA-815-R-03-003, March 2003. 

USEPA. 2006. National Primary Drinking Water Regulations: Stage 2 Disinfectants and 

Disinfection Byproducts Rule; Final Rule. Federal Register. Vol. 71, p. 388, January 4, 2006. 

USEPA. 2007. Guidelines Establishing Test Procedures for the Analysis of Pollutants Under the 

Clean Water Act; National Primary Drinking Water Regulations; and National Secondary 

Drinking Water Regulations; Analysis and Sampling Procedures; Final Rule. Federal Register. 

Vol. 72, p. 11200, March 12, 2007. 

USEPA. 2009. Development of Estimated Quantitation Levels for the Six-Year Review of 

National Primary Drinking Water Regulations. Draft; in preparation. 

Weisberg, S. 1985. Applied Linear Regression, New York: John Wiley & Sons, Inc.
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page A-1 

Appendix A: Listing of New and Updated Analytical Methods

 Exhibit A-1 lists analytical methods that have been developed or revised and approved 

for the analysis of drinking water during the years 2000 – 2007. In many cases, the new methods 

or revisions to existing methods are not expected to significantly improve laboratory 

performance at low concentration (i.e., in the vicinity of the current PQL). Many of the revisions 

relate to clarifications to technical language, solvent replacements to improve safety, or other 

administrative changes/clarifications that are not expected to affect analytical performance. 

Improved analytical performance (and hence, possible PQL reduction) may also be 

supported by the approval and availability of new or revised analytical methods with lower 

MDLs (note that in some analytical methods, the term DL is used instead of MDL, but these 

quantities are essentially equivalent). For 15 regulated analytes, new methods have been 

approved. For 12 of these analytes (bromate, carbofuran, 2,4-D, dalapon, dinoseb, fluoride, 

mercury, nitrite, oxamyl, pentachlorophenol, picloram and 2,4,5-TP), the MDLs are lower (or 

their range of MDLs includes values that are lower) than those from earlier-approved methods. 

In two cases (atrazine and cyanide), the methods are proprietary and are not readily available; 

hence, MDLs are not known, and comparison cannot be made. Lastly, in one case (nitrate), new 

or revised methods do not indicate a lower MDL. 

Exhibit A-1: New or Revised Analytical Methods since 2000; Review of NPDWRs under 

40 CFR §§141.23, 141.24, and 141.131 

Revised/ 

New Method Old Method NPDWR/Contaminant(s) Notes

Source: Guidelines Establishing Test Procedures for the Analysis of Pollutants Under the Clean Water 

Act; National Primary Drinking Water Regulations; and National Secondary Drinking Water Regulations; 

Methods Update; Final Rule. Federal Register, Vol. 67, No. 205, p. 65220, October 23, 2002. Initial rule 

notices, including direct final rule and proposed rule published January 16, 2001: Federal Register, Vol. 

66, p. 3466 and Federal Register, Vol. 66, p. 3526, respectively.1

D2972-97C D2972-93C

arsenic Methods updates from 1999 Annual 

Book of ASTM Standards, Vols. 11.01 

and 11.02; revisions to 141.23(k)(1) 

inorganic analysis; per FR notice, 

these do not contain substantive 

changes in procedures or 

instrumentation, rather, they focus on 

safety factors; see §141.23. Examples 

of minor technical changes are 

recommendations for the handling of 

hazardous materials and safer or 

better ways to conduct certain 

hazardous or complicated analytical 

procedures. Some of the ASTM 

methods have been augmented (cont.) 

D2972-97B D2972-93B

D3645-97B D3645-93B beryllium

D2036-98A D2036-91A

cyanide

D2036-98B D2036-91B

D4327-97 D4327-91 fluoride, nitrate, nitrite

D3559-96D D3559-95D lead

D3223-97 D3223-91 mercury

D3859-98A D3859-93A selenium
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page A-2 

Exhibit A-1: New or Revised Analytical Methods since 2000; Review of NPDWRs under 

40 CFR §§141.23, 141.24, and 141.131

Revised/ 

New Method Old Method NPDWR/Contaminant(s) Notes

D3859-98B D3859-93B

with additional tables of method 

performance data.” No further methodspecific explanations were provided.

3120 B

no name/number change

arsenic, barium, beryllium, 

chromium, copper

Methods updates from Standard 

Methods for the Examination of Water 

and Wastewater, 20th Ed., 1998; 

revisions to 141.23(k)(1) Inorganic 

analysis; per FR notice changes are 

editorial and technical clarifications; 

see §141.23. More specifically, the 

initial Federal Register notice (66 FR 

3466) explains that : “Of the 71 

Standard Methods included in today’s 

rule, 52 methods are unchanged from 

previous versions. The remaining 19 

methods contain minor editorial 

changes or technical clarifications. 

Some of these revisions are minor 

modifications or voluntary but useful 

options, such as better explanations on 

conducting a specific step in the 

method; recommendations for safer 

handling or disposal of hazardous 

reagents; and options to use 

alternative procedures, reagents, or 

equipment.” Only the 13 methods 

listed to the left apply to this Second 

Six-Year Review of NPDWRs. 

4500-CN- C 

cyanide

4500-CN- G 

4500-CN- E 

4500-CN- F 

4110 B fluoride, nitrate, nitrite

4500-F- B,D

4500-F- C fluoride

4500-F- E 

4500-NO3 - F 

nitrate, nitrite

4500-NO3 - E 

4500-NO3 - D nitrate

4500-NO2 - B nitrite

Source: Unregulated Contaminant Monitoring Regulation: Approval of Analytical Method for 

Aeromonas; National Primary and Secondary Drinking Water Regulations: Approval of Analytical 

Methods for Chemical and Microbiological Contaminants. Federal Register, Vol. 67, No. 209, p. 65888, 

October 29, 2002. Proposed rule: Federal Register, Vol. 67, p. 10532, March 7, 2002.

EPA Method 

515.4 none

2,4-D (as acid, salts and esters), 

2,4,5-TP (Silvex), dinoseb, 

pentachlorophenol, picloram and 

dalapon

Available at: 

http://www.epa.gov/safewater/methods

/; see §141.24. New method. Method 

515.4 is a Gas Chromatography 

method that was initially approved for 

Unregulated Contaminant Monitoring 

Regulation analyses. 

EPA Method 

531.2 none carbofuran and oxamyl

Available at: 

http://www.epa.gov/safewater/methods

/; see §141.24. New method. This 

method improves sample preservation 

procedures that are required under 

EPA Method 531.1 and SM 6610, and 

updates the method (cont.) 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page A-3 

Exhibit A-1: New or Revised Analytical Methods since 2000; Review of NPDWRs under 

40 CFR §§141.23, 141.24, and 141.131

Revised/ 

New Method Old Method NPDWR/Contaminant(s) Notes

performance tables using data 

generated with more up to date 

equipment. Accuracy, precision and 

detection limit data generated using 

this method is superior to that 

generated with either of the currently 

approved methods. 

Syngenta 

AG-625 none atrazine

“Atrazine in Drinking Water by 

Immunoassay”, February 2001 

available from Syngenta Crop 

Protection, Inc., 410 Swing Road, Post 

Office Box 18300, Greensboro, NC 

27419, Phone number (336) 632–

6000; see §141.24. New method. 

This is an industry-developed method 

that meets EPA’s criteria for method 

performance, and is “a satisfactory 

compliance method for atrazine in 

drinking water.”

Kelada 01 none

cyanide

‘‘Kelada Automated Test Methods for 

Total Cyanide, Acid Dissociable 

Cyanide, And Thiocyanate’’, Revision 

1.2, August 2001, EPA # 821–B–01–

009 for cyanide is available from the 

National Technical Information Service 

(NTIS), PB 2001–108275, 5285 Port 

Royal Road, Springfield, VA 22161; 

800–553–6847; see § 141.23. New 

method. Validated in both single and 

multi-laboratory validation studies, 

Kelada 01 is “a satisfactory compliance 

method for total cyanide in drinking 

water.”

QuikChem 

10–204–00–

1–X 

none

‘‘Digestion and distillation of total 

cyanide in drinking and wastewaters 

using MICRO DIST and determination 

of cyanide by flow injection analysis’’, 

Revision 2.1, November 30, 2000 for 

cyanide is available from Lachat 

Instruments, 6645 W. Mill Rd., 

Milwaukee, WI 53218; 414–358–4200; 

see §141.23. New method. 

Validated in both single and multilaboratory validation studies, 

QuikChem 10-204-00-1-X is “a 

satisfactory compliance method for 

total cyanides in drinking water.”
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page A-4 

Exhibit A-1: New or Revised Analytical Methods since 2000; Review of NPDWRs under 

40 CFR §§141.23, 141.24, and 141.131

Revised/ 

New Method Old Method NPDWR/Contaminant(s) Notes

Source: National Primary Drinking Water Regulations: Stage 2 Disinfectants and Disinfection 

Byproducts Rule; Final Rule. Federal Register, Vol. 71, No. 2, p. 388, January 4, 2006. Proposed Rule: 

Federal Register, Vol. 68, No. 159, p. 49548, August 18, 2003. 

EPA Method 

317.0 rev 2.0 300.1 bromate and chlorite

EPA Method 317.0 Revision 2 uses the 

EPA Method 300.1 technology, but it 

adds a postcolumn reactor that 

provides a more sensitive and specific 

analysis for bromate than is obtained 

using EPA Method 300.1. 

Several advantages of this method:

(1) Very few ions react with ODA to 

form compounds that are detected by 

the UV/Vis detector. This makes the 

method less susceptible to 

interferences for bromate.

(2) The UV/Vis detector is very 

sensitive to the chromophore, so lower 

concentrations of bromate can be 

detected and quantitated. (Bromate 

concentrations can be reliably 

quantitated as low as 1 μg/L using this 

detector versus 5 μg/L for EPA Method 

300.1.)

(3) Since the front part of the analysis 

is the same as EPA Method 300.1, 

bromate, chlorite, and bromide can be 

determined in the same analysis.

EPA Method 

321.8 bromate

The advantage of this method is that it 

is very specific and sensitive to 

bromate. The single laboratory 

detection limit presented in the method 

is 0.3 μg/L.

EPA Method 

326.0 bromate and chlorite

Method provides higher quality 

bromate data than the currently 

approved EPA Method 300.1 when 

bromate concentrations are below 10 

μg/ L. EPA anticipates the number of 

laboratories using this method will 

increase as utilities become aware of 

the method’s sensitivity and begin to 

request it be used for their samples.

EPA Method 

327.0 rev 1.1 chlorite (daily monitoring only)

EPA Method 327.0 offers advantages

over the currently approved methods in

that it is not subject to positive

interferences from other chlorine (cont.) 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page A-5 

Exhibit A-1: New or Revised Analytical Methods since 2000; Review of NPDWRs under 

40 CFR §§141.23, 141.24, and 141.131

Revised/ 

New Method Old Method NPDWR/Contaminant(s) Notes

species and it is easier to use. See § 

141.131.

SM 4500-

ClO2 E and 

E-00

chlorite (daily monitoring only)

Standard Methods Section 4500–ClO2

contains the methods for determining

chlorine dioxide residuals and chlorite

and it includes method 4500–ClO2E.

On–Line Version of Standard Methods 

[were] ... cited in addition to the 19th 

editions in order to allow flexibility for 

the water systems performing the 

analyses.

ASTM D 

6581-00 bromate and chlorite

This method uses the same 

procedures as EPA Method 300.1 (the 

method promulgated in the Stage 1

DBPR) and thus is considered

equivalent to the approved method. 

The ASTM method includes 

interlaboratory study data that were not 

available when EPA Method 300.1 was 

published. The study data demonstrate 

good precision and low bias for all 

analytes.

Source: Guidelines Establishing Test Procedures for the Analysis of Pollutants Under the Clean Water 

Act; National Primary Drinking Water Regulations; and National Secondary Drinking Water Regulations; 

Analysis and Sampling Procedures; Final Rule. Federal Register, Vol. 72, No. 47, p. 11200, March 12, 

2007. Proposed rules: Federal Register, Vol. 68, p. 49548, August 18, 2003 and Federal Register, Vol. 

69, p. 18166, April 6, 2004. 

OIA-1677, 

DW

none for 

drinking 

water

cyanide

EPA–821–R–99–013, August 1999 

Method OIA–1677, DW ‘‘Available 

Cyanide by Flow Injection, Ligand 

Exchange, and Amperometry,’’ 

January 2004 is technically equivalent 

to Method OIA–1677, which is 

currently approved for determination of 

available cyanide in the NPDES 

program (64 FR 73414; December 30, 

1999). Method OIA–1677, DW only 

differs from OIA– 1677 in having (a) 

updated contact information, and (b) 

less method modification flexibility 

(references to performance-based 

modifications have been removed). 

Therefore the validation data on OIA–

1677 is applicable to OIA– 1677, DW. 

See § 141.23.
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page A-6 

Exhibit A-1: New or Revised Analytical Methods since 2000; Review of NPDWRs under 

40 CFR §§141.23, 141.24, and 141.131

Revised/ 

New Method Old Method NPDWR/Contaminant(s) Notes

ASTM 

D6888-04 none

ASTM Method D6888–04 uses a 

similar technology to Method OIA–

1677. ASTM D6888-03 was proposed 

with OIA–1677, but later refined and 

proposed as ASTM D6888-04 in 70 FR 

7909, February 16, 2005. See § 

141.23.

D1179-99(B) D1179-93(B) fluoride

ASTM Method updates “incorporate 

minor technical and/or editorial 

revisions that improve the methods.” 

See § 141.23.

D1688-02(A) D1688-95(A)

copper

D1688-02(B) D1688-95(B)

D2972-03(B) D2972-97(B)

arsenic

D2972-03(C) D2972-97(C)

D3223-02 D3223-97 mercury

D3559-03(D) D3559-96(D) lead

D3645-03(B) D3645-97(B) beryllium

D3697-02 D3697-92 antimony

D3859-03(A) D3859-98(A)

selenium

D3859-03(B) D3859-98(B)

D3867-99(B) D3867-90(B) nitrate, nitrite

D4327-03 D4327-97 fluoride, nitrate, nitrite

D5317-98 

(2003) D5317-93 2,4-D, 2,4,5-TP, 

pentachlorophenol, picloram

ASTM Method updates “incorporate 

minor technical and/or editorial 

revisions that improve the methods.” 

See § 141.24.

D6508, Rev. 

2 none fluoride, nitrate, nitrite

A new method that employs capillary 

ion electrophoresis to determine 

common anions in wastewater and 

drinking water. “Test Method for 

Determination of Dissolved Inorganic 

Anions in Aqueous Matrices Using 

Capillary Ion Electrophoresis and 

Chromate Electrolyte” (Method D6508, 

Rev. 2) appears to provide an 

acceptable technological alternative to 

ion chromatography and wet chemical 

methods in terms of method 

performance and is equivalent to (cont.) 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page A-7 

Exhibit A-1: New or Revised Analytical Methods since 2000; Review of NPDWRs under 

40 CFR §§141.23, 141.24, and 141.131

Revised/ 

New Method Old Method NPDWR/Contaminant(s) Notes

other approved methods in the working 

range.

3111 B-99 3111 B [19th] copper

Standard Methods updates include: 

“...a number [with]... no changes from 

previously approved version, some 

incorporate minor technical and 

editorial revisions to improve userfriendliness, update references, and 

correct errors.” .” See § 141.23.

3112 B-99 3112 B [19th] mercury

3113 B-99 3113 B [19th]

antimony, arsenic, barium, 

beryllium, cadmium, chromium, 

copper, lead, selenium

3114 B-97 3114 B [19th] arsenic, selenium

3120 B-99 3120 B [20th] arsenic, barium, beryllium, 

chromium, copper

4110 B-00 4110 B [20th] fluoride, nitrate, nitrite

4500-CN E99

4500-CN E 

[20th]

4500-CN F cyanide 4500-CN F 

[20th]

4500-CN G994500-CN G 

[20th]

4500-F-B-97 4500-F-B 

[20th]

4500-F-C-97 fluoride 4500-F-C 

[20th]

4500-F-D-97 4500-F-D 

[20th]

4500-NO2 B00

4500-NO2 B 

[20th] nitrite

4500-NO3-E00

4500-NO3- E 

[20th]

nitrate, nitrite

4500-NO3-F00

4500-NO3-F 

[20th]

EPA Method 

245.7 rev 2.0

245.7 

revision 1.0 mercury

Reagent and instrumentation changes; 

MDL is significantly lower than those 

from other methods.

EPA Method 

552.3 rev 1.0 New Method dalapon MDL range is lower than MDLs from 

most other methods.
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page A-8 

Exhibit A-1: New or Revised Analytical Methods since 2000; Review of NPDWRs under 

40 CFR §§141.23, 141.24, and 141.131

Revised/ 

New Method Old Method NPDWR/Contaminant(s) Notes

EPA Method 

300.1 none fluoride, nitrate, nitrite

EPA Method 300.1 is extended to use 

for these NPDWRs, to provide greater 

flexibility to laboratories and allows 

them to reduce analytical costs.

1. A proposed and a direct final rule (DFR) for these methods were published simultaneously on January 

16, 2001. This was done to ensure that public input requirements were met, and if no public comments 

were received on the DFR, then a second revised final rule would not have been needed. The details of 

the rule were contained in the DFR (66 FR 3466), and the required public comment request and 

explanation of the combined proposal and DFR publication was provided in the proposed rule (66 FR 

3526).
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page B-1 

Appendix B: Radionuclide Regressions

Radionuclides are a unique group of substances, as their measurement requires a unique 

analytical technology compared to other analytes. MDLs and PQLs for radionuclides in drinking 

water are affected by three major factors:

• Type of detector;

• Volume of sample available;

• Duration of analysis 

Thus, for the radionuclides, limitations of laboratory performance at low concentrations 

is generally not an issue, as MDLs and PQLs can be lowered, if necessary, by increasing sample

volume and/or radiological analysis duration. The radionuclides for which PT data were 

available from ERA (2002-2006) are included in this report for completeness; however no 

conclusions regarding PQL assessment are made (note that Barium-133, Cobalt-60 and Zinc-65 

do not have promulgated PQLs per 58 FR, 33050, July 18, 1991 and 65 FR 76752, December 7, 

2000). Exhibit B-1 summarizes the regulated radionuclides, along with their current PQL, how 

the PQL was determined, their MCLG, MCL, and the current acceptance criteria for PT. 

Acceptance criteria for radionuclides are based on both the average of three analyses and the 

range of values obtained from three analyses (μ = the assigned value). Exhibit B-2 summarizes 

the availability of PE and PT data and whether data are available at or below the PQL for each 

radionuclide. 

Exhibit B-1: U.S. EPA National Primary Drinking Water Standards and Related 

Information – Radionuclides

Analyte

Regulatory 

Detection 

Limit (pCi/L) 1

PQL

(pCi/L)

How PQL 

Determined? MCLG MCL

Acceptance 

Criteria (pCi/L); μ = 

assigned value2

Gross Alpha 3 15 PE data Zero 15 pCi/L

Average – 3-20 

pCi/L: μ + 8.66; >20-

<75 pCi/L: μ + 0.433μ

Range - 3-20 pCi/L: 

21.8; >20-<75 pCi/L: 

1.09μ

Radium-226 1 5 PE data Zero

5 pCi/L (Ra226 and Ra228)

Average – 1-20 

pCi/L: μ + 0.260μ 

Range - 1-20 pCi/L: 

0.654μ

Radium-228 1 5 PE data Zero

5 pCi/L (Ra226 and Ra228)

Average – 1-20 

pCi/L: μ + 0.433μ 

Range - 1-20 pCi/L: 

1.09μ

Uranium N/A 5 PE data Zero 30 ug/L

Average – 2-35 

pCi/L: μ + 5.20; >35-

<70 pCi/L: μ + 0.173μ

Range – 2-35 pCi/L: 

13.1; >35-<70 pCi/L: 

0.436μ

Beta particle and 

photo emitters See individual constituents listed below 4 millirem/ 

year (total) See below
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page B-2 

Analyte

Regulatory 

Detection 

Limit (pCi/L) 1

PQL

(pCi/L)

How PQL 

Determined? MCLG MCL

Acceptance 

Criteria (pCi/L); μ = 

assigned value2

Gross Beta 4 30 PE data Zero N/A

Average – 4-50 

pCi/L: μ + 8.66; >50-

<65 pCi/L: μ + 17.3

Range - 4-50 pCi/L: 

21.8; >50-<65 pCi/L: 

43.6

Barium-133 N/A N/A PE data Zero N/A

Average – 9-50 

pCi/L: μ + 8.66; >50-

<110 pCi/L: 

μ + 0.173μ 

Range - 9-50 pCi/L: 

21.8; >50-<110 

pCi/L: 0.436μ

Cesium-134 10 10 PE data Zero N/A

Average – 10-96 

pCi/L: μ + 8.66; 

Range - 10-96 pCi/L: 

21.8

Cesium-137 N/A 10 PE data Zero N/A

Average – 20-100 

pCi/L: μ + 8.66; 

>100-<240 pCi/L: 

μ + 0.0866μ

Range - 20-100 

pCi/L: 21.8; >100-

<240 pCi/L: 0.218μ

Cobalt-60 N/A N/A PE data Zero N/A

Average – 10-100 

pCi/L: μ + 8.66; 

>100-<120 pCi/L: 

μ + 0.0866μ

Range - 10-100 

pCi/L: 21.8; >100-

<120 pCi/L: 0.218μ

Iodine-131 1 20 PE data Zero N/A

Average – 1-15 

pCi/L: μ + 3.46; >15-

<30 pCi/L: μ + 5.20μ

Range - 1-215 pCi/L: 

8.72; >15-<30 pCi/L: 

13.1

Strontium-89 10 5 PE data Zero N/A

Average – 10-70 

pCi/L: μ + 8.66; 

Range - 10-70 pCi/L: 

21.8

Strontium-90 2 5 PE data Zero N/A

Average – 2-45 

pCi/L: μ + 8.66; 

Range – 2-45 pCi/L: 

21.8

Tritium 1,000 1,200 PE data Zero N/A

Average – 1,000-

4,000 pCi/L: μ +

294μ0.0933; >4,000-

<32,000 pCi/L: 

μ + 0.173μ

Range – 1,000-

4,000 pCi/L: 

741μ0.0933; >4,000-

<32,000 pCi/L: 

0.436μ
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page B-3 

Analyte

Regulatory 

Detection 

Limit (pCi/L) 1

PQL

(pCi/L)

How PQL 

Determined? MCLG MCL

Acceptance 

Criteria (pCi/L); μ = 

assigned value2

Zinc-65 N/A N/A PE data Zero N/A

Average – 30-50 

pCi/L: μ + 8.66; >50-

<360 pCi/L: 

μ + 0.173μ 

Range - 30-50 pCi/L: 

21.8; >50-<

pCi/L: 0.436μ

1 Regulatory Detection Limits for radionuclides can be found at FR 65 76708, December 7, 2000. 

Corresponding PQLs can be found at: 58 FR, 33050, July 18, 1991. Note that the PQL for Strontium-89 

from 1991 is less than the regulatory DL from 2000.

2 Acceptance criteria are available at: http://www.nelac-institute.org and are subject to change over time.

360 

Exhibit B-2: Availability of Six-Year 1 PE Data and Six-Year 2 PE/PT Data for 

Radionuclides

Analyte In Six-Year 1 Data?1 In Six-year 2 ERA Data 

2002-2006?

Gross Alpha Not available Yes, some data < PQL

Radium-226 Not available Yes, some data < PQL

Radium-228 Not available Yes, some data < PQL

Uranium Not available Yes, some data < PQL

Beta particle and photo emitters

Gross Beta Not available Yes, some data < PQL

Barium-133 Not available Yes; no PQL

Cesium-134 Not available Yes, no data < PQL

Cesium-137 Not available Yes, no data < PQL

Cobalt-60 Not available Yes; no PQL

Iodine-131 Not available Yes, some data < PQL

Strontium-89 Not available Yes, no data < PQL

Strontium-90 Not available Yes, no data < PQL

Tritium Not available Yes, no data < PQL

Zinc-65 Not available Yes; no PQL

1 Radionuclides were not included in the Six-Year 1 Review; therefore, no data are available.
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page B-4 

 Exhibit B-3: Evaluation of ERA PT Data – Gross Alpha

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70

True Value (pCi/L)

% Laboratories Passing

PQL ERA Data 75% Passing Rate

Current PQL 

= 15 pCi/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page B-5 

Exhibit B-4: Evaluation of ERA PT Data – Radium-226 

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20

True Value (pCi/L)

% Laboratories Passing

PQL ERA Data 75% Passing Rate

Current PQL 

= 5 pCi/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page B-6 

Exhibit B-5: Evaluation of ERA PT Data – Radium-228 

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20

True Value (pCi/L)

% Laboratories Passing

PQL ERA Data 75% Passing Rate

Current PQL 

= 5 pCi/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page B-7 

Exhibit B-6: Evaluation of ERA PT Data – Uranium

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70

True Value (pCi/L)

% Laboratories Passing

PQL ERA Data 75% Passing Rate

Current PQL 

= 5 pCi/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page B-8 

Exhibit B-7: Evaluation of ERA PT Data – Gross Beta

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70

True Value (pCi/L)

% Laboratories Passing

PQL ERA Data 75% Passing Rate

Current PQL 

= 30 pCi/L

75%
Exhibit B-8: Evaluation of ERA PT Data – Barium-133 

0

10

20

30

40

50

60

70

80

90

100

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0

True Value (pCi/L)

% Laboratories Passing

ERA Data 75% Passing Rate

75%

EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page B-9 
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page B-10

Exhibit B-9: Evaluation of ERA PT Data – Cobalt-60 

0

10

20

30

40

50

60

70

80

90

100

0.0 20.0 40.0 60.0 80.0 100.0 120.0

True Value (pCi/L)

% Laboratories Passing

ERA Data 75% Passing Rate

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page B-11

Exhibit B-10: Evaluation of ERA PT Data – Cesium-134 

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70 80 90 100

True Value (pCi/L)

% Laboratories Passing

PQL ERA Data 75% Passing Rate PQL

Current PQL

= 10 pCi/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page B-12

Exhibit B-11: Evaluation of ERA PT Data – Cesium-137 

0

10

20

30

40

50

60

70

80

90

100

0 25 50 75 100 125 150 175 200 225 250

True Value (pCi/L)

% Laboratories Passing

PQL ERA Data 75% Passing Rate

Current PQL 

= 10 pCi/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page B-13

Exhibit B-12: Evaluation of ERA PT Data – Iodine-131 

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30

True Value (pCi/L)

% Laboratories Passing

PQL ERA Data 75% Passing Rate

Current PQL 

= 20 pCi/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page B-14

Exhibit B-13: Evaluation of ERA PT Data – Strontium-89 

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60

True Value (pCi/L)

% Laboratories Passing

PQL ERA Data 75% Passing Rate

Current PQL 

= 5 pCi/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page B-15

Exhibit B-14: Evaluation of ERA PT Data – Strontium-90 

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30 35 40

True Value (pCi/L)

% Laboratories Passing

PQL ERA Data 75% Passing Rate

Current PQL 

= 5 pCi/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page B-16

Exhibit B-15: Evaluation of ERA PT Data – Tritium

0

10

20

30

40

50

60

70

80

90

100

0 5,000 10,000 15,000 20,000 25,000 30,000 35,000

True Value (pCi/L)

% Laboratories Passing

PQL ERA Data 75% Passing Rate

Current PQL 

= 1,200 pCi/L

75%
EPA – OGWDW Analytical Feasibility Support Document for the Second Six-Year Review EPA 815-B-09-003

October 2009

Page B-17

Exhibit B-16: Evaluation of ERA PT Data – Zinc-65 

0

10

20

30

40

50

60

70

80

90

100

0.0 50.0 100.0 150.0 200.0 250.0 300.0

True Value (pCi/L)

% Laboratories Passing

ERA Data 75% Passing Rate

75%