*>EPA
United States
Environmental Protection
Agency
Per- and Polyfluoroalkyl Substances
(PFAS) Occurrence and Contaminant
Background Support Document for
the Final PFAS National Primary
Drinking Water Regulation
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Office of Water (4607M)
EPA 815-R-24-013
April 2024
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
Executive Summary
On March 3, 2021 (86 FR 12272; USEPA, 2021a), the United States Environmental Protection Agency
(EPA) announced its decision to regulate perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic
acid (PFOA) under the Safe Drinking Water Act (SDWA). Subsequently, on March 14, 2023, the EPA
announced its preliminary decision to regulate four additional per- and polyfluoroalkyl substance (PFAS)
compounds including Hexafluoropropylene Oxide Dimer Acid (HFPO-DA) and its ammonium salt (also
known as "GenX Chemicals"), perfluorobutane sulfonic acid (PFBS), perfluorohexane sulfonic acid
(PFHxS), and perfluorononanoic acid (PFNA), and also proposed Maximum Contaminant Level Goals
(MCLGs) and National Primary Drinking Water Regulations (NPDWRs) for PFOA and PFOS and an MCLG
and NPDWR through a Hazard Index (HI) approach for the four additional PFAS (USEPA, 2023a). The EPA
is finalizing determinations to individually regulate PFHxS, PFNA, and HFPO-DA, as well as finalizing a
determination to regulate any combination of these three PFAS and PFBS in mixtures. Concurrently, the
agency is finalizing MCLGs and NPDWRs for PFOA, PFOS, PFNA, PFHxS, and HFPO-DA and an HI MCLG
and NPDWR for mixtures containing two or more of PFNA, PFHxS, HFPO-DA, and PFBS. The final
determination to individually regulate PFNA, PFHxS, and HFPO-DA is based on the finding that these
three contaminants meet the SDWA criteria for regulating a contaminant: 1) the contaminant may have
an adverse effect on the health of persons, 2) the contaminant is known to occur or there is a
substantial likelihood that the contaminant will occur in public water systems (PWSs) with a frequency
and at levels of public health concern, and 3) in the sole judgment of the Administrator, regulation of
such contaminant presents a meaningful opportunity for health risk reduction for persons served by
PWSs. The final determination to regulate mixtures containing two or more of PFHxS, PFNA, HFPO-DA,
and PFBS under an HI approach is similarly based on these three SDWA criteria when considering these
four contaminants in mixtures, particularly their dose additive adverse health effects, substantial
likelihood of co-occurrence, and meaningful opportunity to reduce health effects of these mixtures.
Regarding the individual regulation of PFBS, the EPA is deferring the final individual regulatory
determination for PFBS to further evaluate the three regulatory determination criteria previously
described under SDWA and consequently is not promulgating an individual NPDWR or MCLG for PFBS in
this action.
The EPA reviewed the available peer-reviewed science and supporting studies, as well as finished
drinking water data, to evaluate the occurrence of PFOA, PFOS, HFPO-DA, PFHxS, and PFNA and the co-
occurrence of these five PFAS and PFBS. To inform analyses and characterize the individual frequency
and levels of PFOA, PFOS, HFPO-DA, PFHxS, and PFNA occurrence and frequency and levels of co-
occurrence for PFOA, PFOS, HFPO-DA, PFHxS, PFNA, and PFBS, the EPA relied on multiple data sources
including the third Unregulated Contaminant Monitoring Rule 3 (UCMR 3) and available state
monitoring data. The EPA also incorporated both the UCMR 3 and applicable state data into a Bayesian
hierarchical model which further supported occurrence exposure estimates for modeled PFAS. These
data together demonstrate individual occurrence of PFOA, PFOS, HFPO-DA, PFHxS, and PFNA and co-
occurrence of these five compounds and PFBS in multiple geographic locations.
Occurrence analyses based on the UCMR 3 and state data identify individual reported detections of
PFOA, PFOS, HFPO-DA, PFHxS, and/or PFNA located in 43 states, tribes, and territories. Under the UCMR
3, reported detections of PFOA and PFOS above their UCMR 3 minimum reporting levels (MRLs) were
found in 117 (2.38 percent) and 95 (1.93 percent) PWSs, serving approximate populations of 7.6 million
and 10.4 million people, respectively. These reported detections are all above the EPA's final Maximum
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Contaminant Levels (MCLs) of 4.0 parts per trillion (ppt). Reported detections of PFHxS and PFNA above
their UCMR 3 MRLs were found in 55 and 14 PWSs, serving approximate populations of 5.7 million and
526,000 people, respectively. All of these detections exceed their final MCLs of 10 ppt each. The
available state monitoring data showed that in 32 states there are approximately 1,900 PWSs serving a
total population of more than 26 million people that have at least one result exceeding the final PFOA
MCL and approximately 1,600 PWSs serving a total population of nearly 24 million people that have at
least one result exceeding the final PFOS MCL. The available state monitoring data for PFHxS showed
there are approximately 184 PWSs serving a total population of more than 4.3 million people in 21
states that have at least one result exceeding the final MCL. For PFNA, the available state monitoring
data showed there are approximately 52 PWSs serving a total population of more than 177,000 people
in 12 states that have at least one result exceeding the final MCL, and for HFPO-DA the available state
monitoring data showed that in 5 states there are approximately 13 PWSs serving a total population of
more than 227,000 people that have at least one result exceeding the final MCL. Related to the HI MCL,
state monitoring data demonstrated that in 21 states there are at least 211 systems serving a population
of approximately 4.7 million people that exceed the final HI MCL of 1 (unitless) for mixtures containing
two or more of PFHxS, PFNA, HFPO-DA, and PFBS. Further, from the Bayesian hierarchical occurrence
model developed to explore national occurrence for PFOA, PFOS, and PFHxS, thousands of PWSs serving
populations of tens of millions of people are estimated to have mean concentrations over the final MCLs
for PFOA and PFOS. Hundreds of systems serving millions of people are anticipated to have system-level
mean concentrations over the individual MCL for PFHxS.
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Contents
Executive Summary i
Exhibits iv
Abbreviations ix
1 Introduction 12
1.1 SDWA Statutory Requirements and Rulemaking Process for PFAS in Drinking Water 13
2 Data Sources 15
2.1 Contaminant Background, Chemical, and Physical Properties 15
2.2 Contaminant Production, Use, and Release 15
2.2.1 Inventory Update Reporting (IUR) and Chemical Data Reporting (CDR) Program 15
2.2.2 Toxics Release Inventory (TRI) 16
2.3 Environmental Fate and Transport 17
2.4 Contaminant Occurrence 21
2.4.1 Detection, Quantitation, and Reporting Thresholds 21
2.4.2 Occurrence in Drinking Water 22
2.4.3 Occurrence in Ambient Water 30
2.5 Analytical Methods 31
3 Perfluorooctanoic Acid (PFOA) 33
3.1 Contaminant Background, Chemical and Physical Properties 33
3.1.1 Sources and Environmental Fate 35
3.2 PFOA Occurrence 38
3.2.1 Occurrence in Drinking Water 38
3.2.2 Other Data 74
3.2.3 Occurrence in Ambient Water 77
3.3 Analytical Methods 78
4 Perfluorooctanesulfonic Acid (PFOS) 80
4.1 Contaminant Background, Chemical and Physical Properties 80
4.1.1 Sources and Environmental Fate 82
4.2 PFOS Occurrence 85
4.2.1 Occurrence in Drinking Water 85
4.2.2 Other Data 119
4.2.3 Occurrence in Ambient Water 122
4.3 Analytical Methods 124
5 Perfluorohexane Sulfonic Acid (PFHxS) 126
5.1 Contaminant Background, Chemical and Physical Properties 126
5.1.1 Sources and Environmental Fate 128
5.2 PFHxS Occurrence 129
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5.2.1 Occurrence in Drinking Water 130
5.2.2 Other Data 154
5.2.3 Occurrence in Ambient Water 157
5.3 Analytical Methods 159
6 Perfluorononanoic Acid (PFNA) 160
6.1 Contaminant Background, Chemical and Physical Properties 160
6.1.1 Sources and Environmental Fate 162
6.2 PFNA Occurrence 163
6.2.1 Occurrence in Drinking Water 164
6.2.2 Other Data 188
6.2.3 Occurrence in Ambient Water 191
6.3 Analytical Methods 193
7 Hexafluoropropylene Oxide Dimer Acid (HFPO-DA) 194
7.1 Contaminant Background, Chemical and Physical Properties 194
7.1.1 Sources and Environmental Fate 196
7.2 HFPO-DA Occurrence 199
7.2.1 Occurrence in Drinking Water 199
7.2.2 Other Data 216
7.2.3 Occurrence in Ambient Water 217
7.3 Analytical Methods 219
8 Hazard Index MCL Analyses 220
9 Co-Occurrence Analyses 236
9.1 UCMR3 236
9.1.1 Groupwise Co-occurrence 236
9.1.2 Unique Chemical Combinations 237
9.2 State Datasets 238
9.2.1 Groupwise Co-occurrence 238
9.2.2 Pairwise Co-occurrence 242
9.3 Additional UCMR 3 Analyses from Published Studies 244
10 Model Estimates and Extrapolation 247
10.1 Model Data and Correlation Output 247
10.2 Extrapolation of System-level Means 248
10.3 National Estimate of Systems Exceeding Individual MCLs or HI MCL 248
10.3.1 Handling of Model Output 248
10.3.2 Combination of State Data with Modeled Estimates 249
11 UCMR 5 Results 252
12 References 259
Appendix A: Perfluorobutane Sulfonic Acid (PFBS) A-l
A.l Contaminant Background, Chemical and Physical Properties A-l
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A.1.1 Sources and Environmental Fate A-3
A.2 PFBS Occurrence A-5
A.2.1 Occurrence in Drinking Water A-5
A.2.2 Other Data A-27
A.2.3 Occurrence in Ambient Water A-30
A.3 Analytical Methods A-32
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Exhibits
Exhibit 2-1: Chemical Volume Production (Including Importation) Ranges Used in IUR and CDR Reporting
16
Exhibit 2-2: Persistence Scale 19
Exhibit 2-3: Mobility Scale 20
Exhibit 2-4: Summary of Available State Reported Monitoring Data 23
Exhibit 3-1: Chemical Structure of PFOA - Straight-Chain Isomer 34
Exhibit 3-2: Physical and Chemical Properties of PFOA 34
Exhibit 3-3: IUR Reported Annual Manufacture and Importation of PFOA in the United States, 1986-2006
(pounds) 36
Exhibit 3-4: CDR Reported Annual Manufacture and Importation of PFOA in the United States, 2011-
2020 (pounds) 36
Exhibit 3-5: Environmental Releases of PFOA in the United States, 2020-2022 37
Exhibit 3-6: PFOA National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data -
Summary of Samples 39
Exhibit 3-7: PFOA Occurrence Data from UCMR 3 Assessment Monitoring - Summary of Reported
Concentrations 41
Exhibit 3-8: PFOA National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data -
Summary of System and Population Served Data - Reported Detections 42
Exhibit 3-9: Summary of Available PFOA State Reported Monitoring Data 44
Exhibit 3-10: PFOA State Reported Drinking Water Occurrence Data - Summary of Finished Water
Samples 51
Exhibit 3-11: PFOA State Reported Drinking Water Occurrence Data - Summary of Detected
Concentrations 56
Exhibit 3-12: PFOA State Reported Drinking Water Occurrence Data - Summary of Systems with Finished
Water Data 61
Exhibit 3-13: PFOA State Reported Drinking Water Occurrence Data - Summary of Population Served by
Systems with Finished Water Data 67
Exhibit 3-14: Summary of PFOA Drinking Water Sampling Results Collected Post-Treatment from
Department of Defense Off-Base "Covered Areas" 75
Exhibit 3-15: PFOA NWIS Data 77
Exhibit 3-16: PFOA STORET Data - Summary of Detected Concentrations 78
Exhibit 3-17: PFOA STORET Data - Summary of Samples and Sites 78
Exhibit 4-1: Chemical Structure of PFOS - Straight-Chain Isomer 81
Exhibit 4-2: Physical and Chemical Properties of PFOS 81
Exhibit 4-3: IUR Reported Annual Manufacture and Importation of PFOS in the United States, 1986-2006
(pounds) 83
Exhibit 4-4: Environmental Releases of PFOS in the United States, 2020-2022 83
Exhibit 4-5: PFOS National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data -
Summary of Samples 86
Exhibit 4-6: PFOS Occurrence Data from UCMR 3 Assessment Monitoring - Summary of Reported
Concentrations 87
Exhibit 4-7: PFOS National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data -
Summary of System and Population Served Data - Reported Detections 88
Exhibit 4-8: Summary of Available PFOS State Reported Monitoring Data 90
Exhibit 4-9: PFOS State Reported Drinking Water Occurrence Data - Summary of Finished Water Samples
95
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Exhibit 4-10: PFOS State Reported Drinking Water Occurrence Data - Summary of Detected
Concentrations 100
Exhibit 4-11: PFOS State Reported Drinking Water Occurrence Data - Summary of Systems with Finished
Water Data 105
Exhibit 4-12: PFOS State Reported Drinking Water Occurrence Data - Summary of Population Served by
Systems with Finished Water Data Ill
Exhibit 4-13: Summary of PFOS Drinking Water Sampling Results Collected Post-Treatment from
Department of Defense Off-Base "Covered Areas" 120
Exhibit 4-14: PFOS NWIS Data 122
Exhibit 4-15: PFOS STORET Data - Summary of Detected Concentrations 123
Exhibit 4-16: PFOS STORET Data - Summary of Samples and Sites 123
Exhibit 5-1: Chemical Structure of PFHxS 126
Exhibit 5-2: Physical and Chemical Properties of PFHxS 127
Exhibit 5-3: Environmental Releases of PFHxS in the United States, 2020-2022 128
Exhibit 5-4: PFHxS National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data -
Summary of Samples 131
Exhibit 5-5: PFHxS Occurrence Data from UCMR 3 Assessment Monitoring - Summary of Reported
Detected Concentrations 132
Exhibit 5-6: PFHxS National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data -
Summary of System and Population Served Data - Reported Detections 133
Exhibit 5-7: Summary of Available PFHxS State Reported Monitoring Data 135
Exhibit 5-8: PFHxS State Reported Drinking Water Occurrence Data - Summary of Finished Water
Samples 140
Exhibit 5-9: PFHxS State Reported Drinking Water Occurrence Data - Summary of Detected
Concentrations 143
Exhibit 5-10: PFHxS State Reported Drinking Water Occurrence Data - Summary of Systems with
Finished Water Data 146
Exhibit 5-11: PFHxS State Reported Drinking Water Occurrence Data - Summary of Population Served by
Systems with Finished Water Data 150
Exhibit 5-12: Summary of PFHxS Drinking Water Sampling Results Collected Post-Treatment from
Department of Defense Off-Base "Covered Areas" 155
Exhibit 5-13: PFHxS NWIS Data 157
Exhibit 5-14: PFHxS STORET Data - Summary of Detected Concentrations 158
Exhibit 5-15: PFHxS STORET Data - Summary of Samples and Sites 158
Exhibit 6-1: Chemical Structure of PFNA - Straight-Chain Isomer 160
Exhibit 6-2: Physical and Chemical Properties of PFNA 161
Exhibit 6-3: Environmental Releases of PFNA in the United States, 2020-2022 162
Exhibit 6-4: PFNA National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data -
Summary of Samples 165
Exhibit 6-5: PFNA Occurrence Data from UCMR 3 Assessment Monitoring - Summary of Reported
Concentrations 166
Exhibit 6-6: PFNA National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data -
Summary of System and Population Served Data - Reported Detections 167
Exhibit 6-7: Summary of Available PFNA State Reported Monitoring Data 169
Exhibit 6-8: PFNA State Reported Drinking Water Occurrence Data - Summary of Finished Water Samples
174
Exhibit 6-9: PFNA State Reported Drinking Water Occurrence Data - Summary of Detected
Concentrations 177
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Exhibit 6-10: PFNA State Reported Drinking Water Occurrence Data - Summary of Systems with Finished
Water Data 180
Exhibit 6-11: PFNA State Reported Drinking Water Occurrence Data - Summary of Population Served by
Systems with Finished Water Data 183
Exhibit 6-12: Summary of PFNA Drinking Water Sampling Results Collected Post-Treatment from
Department of Defense Off-Base "Covered Areas" 189
Exhibit 6-13: PFNA NWIS Data 191
Exhibit 6-14: PFNA STORET Data - Summary of Detected Concentrations 192
Exhibit 6-15: PFNA STORET Data - Summary of Samples and Sites 192
Exhibit 7-1: Chemical Structure of HFPO-DA and its Ammonium Salt 195
Exhibit 7-2: Physical and Chemical Properties of HFPO-DA & Its Ammonium Salt 195
Exhibit 7-3: CDR Reported Annual Manufacture and Importation of HFPO-DA in the United States, 2016-
2019 (pounds) 197
Exhibit 7-4: CDR Reported Annual Manufacture and Importation of HFPO-DA Ammonium Salt in the
United States, 2016-2019 (pounds) 197
Exhibit 7-5: Environmental Releases of HFPO-DA in the United States, 2020-2022 198
Exhibit 7-6: Environmental Releases of HFPO-DA Ammonium Salt in the United States, 2020-2022 198
Exhibit 7-7: Summary of Available HFPO-DA State Reported Monitoring Data 201
Exhibit 7-8: HFPO-DA State Reported Drinking Water Occurrence Data - Summary of Finished Water
Samples 205
Exhibit 7-9: HFPO-DA State Reported Drinking Water Occurrence Data - Summary of Detected
Concentrations 208
Exhibit 7-10: HFPO-DA State Reported Drinking Water Occurrence Data - Summary of Systems with
Finished Water Data 211
Exhibit 7-11: HFPO-DA State Reported Drinking Water Occurrence Data - Summary of Population Served
by Systems with Finished Water Data 214
Exhibit 7-12: Summary of HFPO-DA Drinking Water Sampling Results Collected Post-Treatment from
Department of Defense Off-Base "Covered Areas" 217
Exhibit 7-13: HFPO-DA NWIS Data 218
Exhibit 7-14: HFPO-DA STORET Data - Summary of Samples and Sites 219
Exhibit 8-1. Hazard Index Analysis, Summary of Samples 220
Exhibit 8-2. Hazard Index Analysis, Summary of Systems and Population Served by Systems 226
Exhibit 9-1: UCMR 3 - Samples and Systems Binned According to Whether PFOS or PFOA were Reported
by States and Whether Additional Other PFAS were Reported 236
Exhibit 9-2: UCMR 3 - Counts of Systems and Samples Where PFOA/PFOS and Other PFAS Were
Reported Above the MRL According to the Number of Other PFAS Reported Above the UCMR 3
MRL 237
Exhibit 9-3: UCMR 3 - Counts of Unique Combinations of PFAS Chemicals At or Above the UCMR 3 MRL
at the Sample Level 237
Exhibit 9-4: Counts of Systems and Samples According to the Number of HI PFAS Analyzed 238
Exhibit 9-5: Non-Targeted State PFAS Finished Water Data - Samples and Systems Binned According to
Whether PFOS or PFOA were Reported by States and Whether Additional HI PFAS were
Reported 239
Exhibit 9-6: Sample counts according to HI PFAS analyzed and reported present for samples where PFOS
and PFOA were not reported present by the state 239
Exhibit 9-7: System counts according to HI PFAS analyzed and reported present for systems where PFOS
and PFOA were not reported present by the state 239
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Exhibit 9-8: Sample counts according to HI PFAS analyzed and reported present for samples where PFOS
and PFOA were reported present by the state 240
Exhibit 9-9: System counts according to HI PFAS analyzed and reported present for systems where PFOS
and PFOA were reported present by the state 240
Exhibit 9-10: Non-Targeted State PFAS Finished Water Data - Samples that Included Three or Four HI
PFAS Binned According to Whether PFOS or PFOA were Reported and Whether Any Additional
HI PFAS were Reported by State 240
Exhibit 9-11: Non-Targeted State PFAS Finished Water Data - Systems that Sampled for Three or Four HI
PFAS Binned According to Whether PFOS or PFOA were Reported and Whether Any Additional
HI PFAS were Reported by State 241
Exhibit 9-12: Sample-level counts of pairwise chemical occurrence and odds ratios calculated from
aggregated state dataset PFAS samples for PFOS, PFOA, and HI PFAS 243
Exhibit 9-13: System-level counts of pairwise chemical occurrence and odds ratios calculated from
aggregated state dataset PFAS samples for PFOS, PFOA, and HI PFAS 243
Exhibit 9-14: Co-Occurrence Matrix (Odds Ratios for Association Between PFAS Pairs) 245
Exhibit 10-1: National Occurrence Model Estimate - Median Estimated Pearson Correlation Coefficient
and 90% Credible Interval Among System-level Means 247
Exhibit 10-2: National Occurrence Model Estimate - Estimated Number of Systems With System-level
Means At or Above Various Concentrations 248
Exhibit 10-3: National Occurrence Model Estimate - Estimated Total Population Served By Systems With
System-level Means At or Above Various Concentrations 248
Exhibit 10-4: National Occurrence Estimate - Estimated Systems and Total Population Served By Systems
in Exceedance of the MCL for PFOS or PFOA 250
Exhibit 10-5: National Occurrence Estimate - Estimated Systems and Total Population Served By Systems
in Exceedance of the HI MCL 250
Exhibit 10-6: National Occurrence Estimate - Estimated Systems and Total Population Served By Systems
in Exceedance of an MCL for PFOS or PFOA or the HI MCL 251
Exhibit 11-1: Preliminary UCMR 5 Dataset1 - Summary of Sample, Entry Point, and System Counts as of
February 2024 252
Exhibit 11-2: Preliminary UCMR 5 Dataset1 - Summary of Single Samples, Entry Points with Single
Samples, and Systems with Single Samples Exceeding MCL Thresholds 253
Exhibit 11-3: Preliminary UCMR 5 Dataset1 - Summary of Systems with Entry Point Mean Concentrations
Exceeding MCL Thresholds 254
Exhibit 11-4: Preliminary UCMR 5 Dataset1 - Samples, Entry Points, and Systems Binned According to
Number of PFAS Among PFOA, PFOS, PFHxS, PFNA, HFPO-DA and PFBS That Were Reported at
or Above the Minimum Reporting Level 254
Exhibit 11-5: Preliminary UCMR 5 Dataset1 - Samples, Entry Points, and Systems Binned According to
Whether PFOS or PFOA and Additional HI PFAS were Reported At or Above their Minimum
Reporting Levels 255
Exhibit 11-6: Preliminary UCMR 5 Dataset1 - Sample, Entry Points, and System Counts According the
Number of HI PFAS Reported At or Above their Minimum Reporting Levels for Samples, Entry
Points, and Systems Where PFOS and PFOA Were Below their Minimum Reporting Levels 256
Exhibit 11-7: Preliminary UCMR 5 Dataset1 - Sample, Entry Points, and System Counts According to the
Number of HI PFAS Reported At or Above their Minimum Reporting Levels for Samples and
Systems Where PFOS and/or PFOA Were At or Above the Minimum Reporting Level 256
Exhibit 11-8: Preliminary UCMR 5 Dataset1 - Sample-level Counts of Pairwise Chemical Occurrence and
Calculated Odds Ratios 257
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Exhibit 11-9: Preliminary UCMR 5 Dataset1 - System-level Counts of Pairwise Chemical Occurrence and
Calculated Odds Ratios 257
Exhibit A-l: Chemical Structure of PFBS - Straight-Chain Isomer A-l
Exhibit A-2: Physical and Chemical Properties of PFBS A-2
Exhibit A-3: Environmental Releases of PFBS in the United States, 2022 A-4
Exhibit A-4: PFBS National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data -
Summary of Samples A-6
Exhibit A-5: PFBS Occurrence Data from UCMR 3 Assessment Monitoring - Summary of Reported
Concentrations A-8
Exhibit A-6: PFBS National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data -
Summary of System and Population Served Data - Reported Detections A-9
Exhibit A-7: Summary of Available PFBS State Reported Monitoring Data A-ll
Exhibit A-8: PFBS State Reported Drinking Water Occurrence Data - Summary of Finished Water Samples
A-16
Exhibit A-9: PFBS State Reported Drinking Water Occurrence Data - Summary of Detected
Concentrations A-19
Exhibit A-10: PFBS State Reported Drinking Water Occurrence Data - Summary of Systems and
Population Served by Systems with Finished Water Data A-22
Exhibit A-ll: Summary of PFBS Drinking Water Sampling Results Collected Post-Treatment from
Department of Defense Off-Base "Covered Areas" A-28
Exhibit A-12: PFBS NWIS Data A-30
Exhibit A-13: PFBS STORET Data - Summary of Detected Concentrations A-31
Exhibit A-14: PFBS STORET Data - Summary of Samples and Sites A-31
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Abbreviations
ADEQ Arizona Department of Environmental Quality
ADPH Alabama Department of Public Health
AF Amorphous Fluoropolymer
ATSDR Agency for Toxic Substances and Disease Registry
BF Biodegrades Fast
BFA Biodegrades Fast with Acclimation
BS Biodegrades Slowly
BSA Biodegrades Slowly with Acclimation
BST Biodegrades Sometimes/Recalcitrant
CAS Chemical Abstracts Service
CBI Confidential Business Information
CCL Contaminant Candidate List
CCL 3 Third Contaminant Candidate List
CCL 4 Fourth Contaminant Candidate List
CDPHE Colorado Department of Public Health and Environment
CDR Chemical Data Reporting
CEC Cation Exchange Capacity
CI Confidence Interval
CWS Community Water System
DL Detection Limit
DoD Department of Defense
DWTP Drinking Water Treatment Plants
eCDF Empirical Cumulative Distribution Function
EPA Environmental Protection Agency
EPCRA Emergency Planning and Community Right-to-Know Act
EPISuite™ Estimation Programs Interface Suite™
ESP Exchangeable Sodium Percentage
FEP Fluorinated Ethylene Propylene
FRN Federal Register Notice
FUDS Formerly Used Defense Site
GA EPD Georgia Environmental Protection Division
GAC Granular Activated Carbon
GWUDI Ground water Under the Direct Influence of Surface Water
HBWC Health Based Water Concentration
HFPO-DA Hexafluoropropylene Oxide Dimer Acid
HI Hazard Index
HQ Hazard Quotient
HRL Health Reference Level
HRRCA Health Risk Reduction and Cost Analysis
HSDB Hazardous Substances Data Bank
IDEM Indiana Department of Environmental Management
Iowa DNR Iowa Department of Natural Resources
ITRC Interstate Technology & Regulatory Council
IUR Inventory Update Reporting
Kd Soil Sorption Coefficient
Kh Henry's Law Constant
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Koc
Organic Carbon Partitioning Coefficient
Kow
Octanol-Water Partitioning Coefficient
LC/MS/MS
Liquid Chromatography/Tandem Mass Spectrometry
LCMRL
Lowest Concentration Minimum Reporting Level
Maine CDC
Maine Center for Disease Control and Prevention
MCL
Maximum Contaminant Level
MCLG
Maximum Contaminant Level Goal
MDE
Maryland Department of Environment
MDH
Minnesota Department of Health
Michigan EGLE
Michigan Department of Environment, Great Lakes, and Energy
Missouri DNR
Missouri Department of Natural Resources
MRL
Minimum Reporting Level
NAWQA
National Water-Quality Assessment
NCBI
National Center for Biotechnology Information
NCDEQ
North Carolina Department of Environmental Quality
NDAA
National Defense Authorization Act
NDDEQ
North Dakota Department of Environmental Quality
NHANES
National Health and Nutrition Examination Survey
NMED
New Mexico Environment Department
NPDWR
National Primary Drinking Water Regulation
NTNCWS
Non-Transient Non-Community Water System
NWIS
National Water Information System
OHA
Oregon Health Authority
PFA
Perfluoroalkoxy
PFAA
Perfluorinated Alkyl Acid
PFAS
Per- and Polyfluoroalkyl Substances
PFBS
Perfluorobutane Sulfonic Acid
PFC
Perfluorinated Compound
PFCA
Perfluoroalkyl Carboxylate
PFHpA
Perfluoroheptanoic Acid
PFHxA
Perfluorohexanoic Acid
PFHxS
Perfluorohexane Sulfonic Acid
PFNA
Perfluorononanoic Acid
PFOA
Perfluorooctanoic Acid
PFOS
Perfluorooctane Sulfonic Acid
PFSA
Perfluoroalkyl Sulfonate
pKa
Acid Dissociation Constant
POP
Persistent Organic Pollutants
PPM
Parts Per Million
PPMV
Parts Per Million by Volume
PPT
Parts Per Trillion
PQL
Practical Quantitation Level
PTFE
Polytetrafluoroethylene
PWS
Public Water System
PWSID
Public Water System Identification Number
OA
Quality Assurance
RSD
Relative Standard Deviation
SDWA
Safe Drinking Water Act
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SDWIS
Safe Drinking Water Information System
SNUR
Significant New Use Rule
STEWARDS
Sustaining the Earth's Watersheds-Agricultural Research Data System
STORET
Storage and Retrieval Data System
TOC
Total Organic Carbon
TRI
Toxics Release Inventory
TSCA
Toxic Substances Control Act
UCMR
Unregulated Contaminant Monitoring Rule
UCMR 1
First Unregulated Contaminant Monitoring Rule
UCMR 2
Second Unregulated Contaminant Monitoring Rule
UCMR 3
Third Unregulated Contaminant Monitoring Rule
UCMR 5
Fifth Unregulated Contaminant Monitoring Rule
USDA
United States Department of Agriculture
USGS
United States Geological Survey
USNLM
United States National Library of Medicine
Virginia ODW
Virginia Office of Drinking Water
WQP
Water Quality Portal
WQX
Water Quality Exchange
WTP
Water Treatment Plant
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1 Introduction
This document describes technical and background information on production and use, environmental
fate and transport, and in particular, the data and analyses used by the United States Environmental
Protection Agency (EPA) to develop national estimates of the individual occurrence of perfluorooctanoic
acid (PFOA), perfluorooctane sulfonic acid (PFOS), hexafluoropropylene oxide dimer acid (HFPO-DA) and
its ammonium salt, perfluorohexane sulfonic acid (PFHxS), and perfluorononanoic acid (PFNA) and co-
occurrence of these five per- and polyfluoroalkyl substances (PFAS) and perfluorobutane sulfonic acid
(PFBS) in public drinking water systems (PWSs). Further, this information supports both the final
determination to individually regulate HFPO-DA, PFHxS, and PFNA and the final determination to
regulate any mixture combination of these three PFAS and PFBS in drinking water, along with the
proposed National Primary Drinking Water Regulations (NPDWRs) for PFOA, PFOS, HFPO-DA, PFHxS, and
PFNA and the Hazard Index (HI) NPDWR for HFPO-DA, PFHxS, PFNA, and PFBS. Additional supplemental
PFOA, PFOS, PFHxS, PFNA, HFPO-DA, and PFBS occurrence background information and data were also
reviewed. The information, data, and analyses described in this report are organized into 8 chapters
with a brief description of each chapter presented below.
• Chapter 1: Introduction provides an overview of the rulemaking process for PFAS in the context
of public drinking water.
• Chapter 2: Data Sources provides a general overview of the sources of data that the EPA used to
evaluate PFAS.
• Chapter 3: PFOA provides information on PFOA's chemical and physical properties, sources of
PFOA, environmental fate, drinking water and ambient water occurrence data, and laboratory
analytical methods.
• Chapter 4: PFOS provides information on PFOS's chemical and physical properties, sources of
PFOS, environmental fate, drinking water and ambient water occurrence data, and laboratory
analytical methods.
• Chapter 5: PFHxS provides information on PFHxS's chemical and physical properties, sources, of
PFHxS environmental fate, drinking water and ambient water occurrence data, and laboratory
analytical methods.
• Chapter 6: PFNA provides information on PFNA's chemical and physical properties, sources of
PFNA, environmental fate, drinking water and ambient water occurrence data, and laboratory
analytical methods.
• Chapter 7: HFPO-DA provides information on HFPO-DA's chemical and physical properties,
sources of HFPO-DA, environmental fate, drinking water and ambient water occurrence data,
and laboratory analytical methods.
• Chapter 8: Hazard Index MCL Analyses presents the occurrence analysis relative to the HI
NPDWR for the regulation of PFHxS, PFNA, HFPO-DA, and PFBS when co-occurring in mixture
combinations.
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• Chapter 9: Co-Occurrence Analyses presents the co-occurrence analysis of PFAS data in the
third Unregulated Contaminant Monitoring Rule (UCMR 3) as well as in non-targeted
supplemental state datasets.
• Chapter 10: Model Estimates and Extrapolation presents the national occurrence estimates of
four PFAS derived from a Bayesian hierarchical model developed to estimate national
occurrence.
• Chapter 11: UCMR 5 Results presents the preliminary sampling results from the fifth
Unregulated Contaminant Monitoring Rule (UCMR 5) as of February 2024.
• Chapter 12: References is a list of the cited and supporting scientific literature used in
development of the document.
• Appendix A: PFBS provides information on PFBS's chemical and physical properties, sources of
PFBS, environmental fate, drinking water and ambient water occurrence data, and laboratory
analytical methods.
1.1 SDWA Statutory Requirements and Rulemaking Process for PFAS in Drinking
Water
Under the Safe Drinking Water Act (SDWA), the EPA has the authority to set enforceable NPDWRs for
drinking water contaminants and require monitoring of PWSs. On March 3, 2021 (86 FR 12272; USEPA,
2021a), the EPA published Regulatory Determinations for Contaminants on the Fourth Contaminant
Candidate List (CCL 4) which included a final determination to regulate PFOA and PFOS in drinking water.
Following that final determination and concurrent with proposing the NPDWRs for PFOA and PFOS, the
EPA made a preliminary determination to regulate PFHxS, PFNA, HFPO-DA, and PFBS and proposed an
NPDWR for these four PFAS compounds through an HI approach (USEPA, 2023a).
On March 10, 2020, the EPA announced and requested public comment on the preliminary regulatory
determinations for eight CCL 4 contaminants, including a preliminary determination to regulate PFOS
and PFOA in drinking water (USEPA, 2020a). On March 3, 2021, the EPA announced a final
determination to regulate PFOS and PFOA, marking the beginning of the drinking water regulation
development process for these two PFAS (USEPA, 2021a).
Concurrent with proposing the NPDWR for PFOA and PFOS, the EPA announced and requested public
comment on a preliminary determination to regulate PFHxS, PFNA, HFPO-DA, and PFBS and a proposed
NPDWR and Maximum Contaminant Level Goals (MCLGs) through an HI approach for these four
compounds. The EPA's final decision to regulate PFOA and PFOS and preliminary decision to regulate
PFHxS, PFNA, HFPO-DA, and PFBS was based on its finding that these contaminants meet the SDWA's
three criteria for regulating a contaminant: 1) the contaminant may have an adverse effect on the health
of persons, 2) the contaminant is known to occur or there is a substantial likelihood that the
contaminant will occur in PWSs with a frequency and at levels of public health protection, and 3) in the
sole judgement of the Administrator, regulation of such contaminant presents a meaningful opportunity
for health risk reduction for persons served by PWSs. The proposal to regulate these contaminants
included non-enforceable MCLGs and enforceable Maximum Contaminant Level (MCL) standards.
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The EPA is finalizing determinations to individually regulate HFPO-DA, PFHxS, and PFNA and finalizing a
determination to regulate any combination of these three PFAS and PFBS in mixtures. The EPA's final
decision to regulate these compounds is based on the same findings as the preliminary determination
that they individually and/or as part of a mixture meet the SDWA's three criteria for regulating a
contaminant. Concurrent with this final determination, the EPA is finalizing individual NPDWRs for PFOA,
PFOS, HFPO-DA, PFHxS, and PFNA and an NPDWR through an HI for mixtures containing two or more of
HFPO-DA, PFHxS, PFNA, and PFBS. See Section IV of the final rule Federal Register Notice (FRN) for
further discussion about the final MCLGs and Section V of the FRN for further discussion of the final
MCLs (USEPA, 2024a).
In accordance with Section 1412(b)(3)(c) of SDWA, the EPA has prepared a Health Risk Reduction and
Cost Analysis (HRRCA) of the final MCLs and proposed alternative MCLs. The EPA has assessed the
quantifiable and non-quantifiable costs that are likely to occur as a result of compliance with the MCLs.
These costs could be new treatment processes as well as incremental monitoring and administrative
costs. The EPA also provides an estimate of the health risk reduction benefits likely to occur as a result
of the treatment to comply with each PFAS concentration level assessed. For further discussion, see the
Economic Analysis of the Final NPDWR for PFAS (USEPA, 2024b).
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2 Data Sources
This chapter provides a general overview of the sources of data that the EPA used to evaluate PFAS. The
outline of this chapter mirrors the organization of the contaminant-specific chapters that follow. Section
2.1 identifies the sources used to gather contaminant background information and chemical and
physical properties. Section 2.2 describes information sources used to characterize contaminant
production, use, and release. Section 2.3 describes how environmental fate and transport were
evaluated and what information sources were used. Section 2.4 describes the primary and supplemental
sources of ambient and drinking water occurrence information used to evaluate contaminant
occurrence and exposure and provides information about occurrence data handling. Section 2.5
presents information on evaluation of analytical methods.
2.1 Contaminant Background, Chemical, and Physical Properties
The EPA consulted a number of standard sources to gather information on contaminant background and
properties. These sources include the National Center for Biotechnology Information's (NCBI) PubChem
database, which houses and displays information from a variety of formerly independent sources such
as the U.S. National Library of Medicine's (USNLM) Hazardous Substances Data Bank (HSDB) and
USNLM's ChemlDPIus database, plus Toxicity Profiles from the U.S. Agency for Toxic Substances and
Disease Registry (ATSDR), and standard chemistry reference books. To fill some information gaps,
primary literature was consulted as well, with preference given to peer-reviewed sources.
2.2 Contaminant Production, Use, and Release
Quantitative data on natural and anthropogenic sources, including data on production, use, and
industrial releases, were obtained from specific primary sources and data compilations. These data are
described below.
2.2.1 Inventory Update Reporting (IUR) and Chemical Data Reporting (CDR) Program
The Toxic Substances Control Act (TSCA) requires the EPA to compile, keep current, and publish a
Chemical Substance Inventory, a list of chemical substances that are manufactured (including imported)
or processed in the United States. Initially published in 1979, the TSCA Inventory currently lists more
than 86,000 chemicals (USEPA, 2022a). Modifications of the IUR rule in 2003 and 2005 expanded the
type of chemicals to include inorganic chemical substances, expanded the type of data reported, raised
the production volume threshold that triggers reporting from 10,000 pounds to 25,000 pounds, and
made certain further adjustments. In 2011, the agency issued the Chemical Data Reporting (CDR) Rule
which replaced the IUR Rule and established a somewhat modified program, including annual data
gathering and periodic reporting. CDR makes use of a two-tiered system of reporting thresholds, with
25,000 pounds the threshold for most chemical substances and 2,500 pounds the threshold for others
(USEPA, 2020b). In 2020, the EPA issued an update to the CDR program revising the definition of a small
manufacturer. This revision may impact the reporting requirements of some PFAS manufacturers
(USEPA, 2020c).
The EPA makes certain non-confidential information available to the public. This includes aggregated
national total annual production volumes for chemicals based on reports filed. As a result of the changes
in reporting thresholds and other program modifications, the results from 2006 onward might not be
directly comparable to results from earlier years.
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In making total annual national production volumes for chemicals available to the public, the agency
assigned production volumes to bins. Eight production and importation volume ranges were used under
IUR. The ranges used for 2006 data differ slightly from those used for earlier years. Under CDR the
number of bins was expanded from 8 to 29. Exhibit 2-1 shows the production and importation volume
categories used for 1986-2002 data, 2006 data, and more recent data.
If no reports were filed for a chemical in a particular year, the EPA indicated that the chemical had "no
reports" in the summary of IUR/CDR data presented in this document. If production quantities were
withheld from publication by the EPA so as not to compromise companies' confidential business
information (CBI), the quantities are flagged as "withheld."
Exhibit 2-1: Chemical Volume Production (Including Importation) Ranges Used in
IUR and CDR Reporting
1986-2002
2006
Post-20061
10,000 pounds - 500,000 pounds
<500,000 pounds
<25,000
>500,000- 1 million pounds
500,000 to <1 million pounds
25,000 to 100,000
>1 million -10 million pounds
1 million to <10 million pounds
100,000 to 500,000
>10 million - 50 million pounds
10 million to <50 million pounds
500,000 to 1 million
>50 million -100 million pounds
50 million to <100 million pounds
1 million to 10 million
>100 million - 500 million pounds
100 million to <500 million
10 million to 50 million
> 500 million -1 billion pounds
500 million to <1 billion pounds
50 million to 100 million
Over 1 billion pounds
1 billion pounds or greater
100 million to 250 million
250 million to 500 million
500 million to 750 million
750 million to 1 billion
1 billion to 5 billion
Source: USEPA 2021b
1CDR currently uses 29 bins for reporting volumes, including the 12 listed here and an additional 17 bins for
production quantities greater than 5 billion pounds.
Several factors should be considered when interpreting production ranges assigned to chemicals. Site-
specific production volumes less than 10,000 pounds (25,000 pounds from 2006 on) were not reported
and thus are not included in the totals. Production volume ranges for reporting changed in 2006 and
changed again in 2012. Furthermore, the data provide a snapshot of annual production (including
importation) only every four years through 2006, and therefore do not capture fluctuation from year to
year prior to initiation of the CDR in 2012.
2.2.2 Toxics Release Inventory (TRI)
The EPA established the Toxics Release Inventory (TRI) in 1987 in response to Section 313 of the
Emergency Planning and Community Right-to-Know Act (EPCRA). EPCRA section 313 requires facilities to
report to both the EPA and states annual information on toxic chemical releases and other waste
management from facilities that meet reporting criteria. EPCRA section 313 also requires the EPA to
make this information available to the public through a computer database. The database is accessible
through the EPA's TRI Explorer. In 1990 Congress passed the Pollution Prevention Act, which required
that additional data on waste management and source reduction activities be reported under TRI. The
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TRI database details not only the types and quantities of toxic chemicals released to the air, water, and
land by facilities, but also provides information on the quantities of chemicals sent to other facilities for
further management (USEPA, 2022b; USEPA, 2003).
Facilities are required to report releases and other waste management activities related to TRI chemicals
if they manufacture, process, or otherwise use more than established threshold quantities of these
chemicals. Currently, for most chemicals, reporting of releases is required if 25,000 pounds or more of
the chemical are manufactured or processed at a facility, or if 10,000 pounds or more are used at the
facility. Note that a lower reporting threshold applies to some TRI chemicals, including a threshold of
100 pounds which applies to PFAS (USEPA, 2022b).
TRI data are particularly useful for tracking trends in chemical releases and other waste management
practices. When using the data this way, consider only data that were reported under consistent TRI
reporting requirements. Using comparable data will better ensure that any changes in the data over
time are driven by actual changes in the use, release or other management of a chemical, and are not
simply due to modifications in reporting requirements. For example, the TRI Program has evolved as the
EPA extended reporting requirements to additional industry sectors, added or deleted chemicals from
the TRI list, and raised or lowered chemical activity reporting thresholds. These changes can influence
release and waste management quantities for a given year and may impact multi-year trend analyses or
year-to-year comparisons of TRI data. Further, changes in the TRI "reporting universe" may impact
multi-year trend analyses or year-to-year comparisons of TRI data. The "reporting universe" can vary
year-to-year because facilities may not be required to submit TRI forms for the same chemicals each
year and in some years, may not meet the TRI reporting criteria at all. Changes in facility operations,
production volume, and type of chemicals used, for example, can influence whether a facility meets the
reporting criteria in a given year (USEPA, 2022b).
Additionally, TRI data users should be aware of the scope of PFAS data available in the TRI database.
Section 7321 of the National Defense Authorization Act for Fiscal Year 2020 (NDAA) immediately added
172 PFAS to the list of chemicals covered by the TRI list (effective with Reporting Year 2020) and
provided a framework for additional PFAS to be added to TRI on an annual basis (USEPA, 2022c).
2.3 Environmental Fate and Transport
In the Environmental Fate section of each chapter, the initial discussion is focused on available data in
the literature regarding persistence and mobility. HSDB/PubChem is typically used as the primary
source. Other sources consulted include ATSDR Toxicological Profiles, Interstate Technology &
Regulatory Council (ITRC) documents, and journal articles. Important parameters include the organic
carbon partitioning coefficient (Koc), the octanol-water partitioning coefficient (expressed as log Kow), the
Henry's Law Constant (KH), water solubility, vapor pressure, and half-life. Note that property data are
typically provided for the acid form of the various PFAS; however, in cases where salts are common,
some properties for the salt form(s) are presented and labeled as such. Certain properties can vary
substantially for the acid and salt forms of a given PFAS. For example, the water solubility of PFOS (acid
form) and the potassium salt of PFOS may vary by approximately five orders of magnitude.
Li et al. (2018) indicated that because PFAS exhibit both hydrophilic and hydrophobic properties, organic
carbon may not be the only factor that dictates the degree to which they sorb to soil. In addition to
organic carbon content, the authors found that pH and clay content may also be important factors that
affect sorption. The degree to which these factors contribute to sorption varies among the various PFAS.
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In particular, log Kow values for PFAS may be difficult to determine and/or have limited relevance
regarding environmental partitioning. Prevedouros et al. (2006) reported that PFOA formed multiple
layers in octanol and water, thus rendering the log Kow value as questionable/uncertain.
Following this discussion of available data, qualitative conclusions about persistence and mobility are
drawn, as applicable, using Koc, log Kow, KH, water solubility, and suitable half-lives in the context of the
persistence/mobility evaluation protocol. This protocol was originally developed and used during the
third Contaminant Candidate List (CCL 3)1 to informally rank chemical contaminants' likely mobility
(understood as their tendency to partition to water rather than other media) and persistence as "high,"
"moderate," or "low" based on physical and chemical properties (see USEPA, 2021b and USEPA, 2009).
Use of the protocol helps to ensure that generalizations about the persistence and mobility of
compounds are made using standardized scales. Below is a more detailed explanation of how qualitative
conclusions about persistence and mobility are drawn using the protocol.
Persistence
Persistence refers to the length of time a contaminant remains in the environment, or in a particular
medium like soil or water, when introduced. There are two primary mechanisms of degradation that are
of greatest importance: biodegradation and hydrolysis. Of primary importance is degradation in water.
However, since release of contaminants to soil can result in migration to surface water and/or ground
water (and some contaminants, such as pesticides, are designed to be applied to crops and/or soil),
biodegradation in soil is also of importance. Chemical reactivity with soil organic matter may also be
important; however, data for this process are not common in sources such as HSDB.
Although other processes can result in either degradation of a contaminant (i.e., photolysis) or
contaminant loss from an environmental system (i.e., volatilization), they are of lesser importance in the
context of drinking water. Photolysis can occur in surface water but not in ground water; therefore,
photolytic degradation may not be applicable to all sources of drinking water. Volatilization from soil or
water to the atmosphere is a loss mechanism; however, it is not a destructive loss mechanism. Thus,
contaminants that volatilize can be re-introduced to a given environmental medium through
atmospheric deposition. Volatilization also does not occur in surface water and in ground water by
identical mechanisms or at identical rates. Values for photolysis and/or volatilization half-life are
presented when available in HSDB; however, only biodegradation, hydrolysis, and soil reactivity half-
lives are assigned a qualitative conclusion for persistence by processing them through the
persistence/mobility ranking protocol.
Exhibit 2-2 summarizes the Persistence Scale in the form of derived numerical time scales, qualitative
biodegradation codes and their corresponding qualitative textual descriptions (used for the CCL 3 and
CCL 4 process which included PFOS and PFOA), and qualitative conclusions for persistence.
1 See Exhibit A.8 from https://www.epa,eov/sites/default/files/2014-05/documents/ccl3 pccltoccl 08-31-
09 508.pdf
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Exhibit 2-2: Persistence Scale
A: Numerical Time Scale for Use
when Interpreting Literature
Values (for half-life)
B: Qualitative Code from
CCL 3 Modeling Using
BIODEG
C: Qualitative Conclusion
for Persistence
Hours-2 days
BF (Biodegrades fast)
Low persistence
>2 days-14 days
BFA (Biodegrades fast with
acclimation1)
Low persistence
>14 days-30 days
BS (Biodegrades slowly)
Moderate persistence
>30 days-59 days
BSA (Biodegrades slowly with
acclimation1)
Moderate persistence
>60 days
BST (Biodegrades
sometimes/recalcitrant)
High persistence
Source: Adapted from USEPA, 2009
1 The term "acclimation" typically means that a contaminant does not begin to biodegrade until the requisite
microorganisms have become acclimated to the metabolism of a particular contaminant under a given set of
environmental conditions. Here, "acclimation" is used in a less specific manner (i.e., "Biodegrades fast with
acclimation" is a designation to indicate that biodegradation is not as rapid as "Biodegrades fast" but not as slow as
"Biodegrades slowly" and "Biodegrades slowly with acclimation" is a designation to indicate that biodegradation is not
as rapid as "Biodegrades slowly" but not as slow as "Biodegrades sometimes/recalcitrant").
The output of the persistence evaluation is shown in Column C. The preferred input is measured or
modeled half-lives from the literature (especially HSDB), evaluated against the categories in Column A.
The numerical time scale in Column A is applicable to a range of degradation processes, including
biodegradation, hydrolysis, and soil reactivity. If no numerical values for degradation half-life that are
broadly applicable to potential drinking water resources are available from HSDB and other sources in
the literature, the next preferred input to the persistence evaluation is a qualitative biodegradation
code (corresponding to one of the codes in Column B), as derived by modeling performed during the
development of CCL 3 using the EPA's BIODEG model.
If no qualitative biodegradation code from CCL 3 modeling is available, the BIOWIN module of the EPA's
Estimation Program Interface (EPI Suite™; USEPA, 2012a) is used to provide a qualitative estimate of
persistence. The BIOWIN (v4.10) module of EPI Suite™ uses several models to predict biodegradation,
including complete degradation to a primary metabolite and complete degradation to carbon dioxide
and water. Although these predictions are not half-lives and therefore cannot be directly compared to
the categories for half-lives in the Persistence Scale, an inference regarding persistence can often be
made from the BIOWIN data relative to the protocol's duration ranges for low, medium/moderate, and
high persistence.
Mobility
Mobility refers to how readily a contaminant can partition from one environmental medium to another.
In the context of the Contaminant Candidate List (CCL) and Regulatory Determination, it is used
specifically to refer to how readily a contaminant partitions to or remains in water. That is, for CCL and
in Regulatory Determination, the way that mobility affects concentrations of a contaminant in water is
of greatest importance. Exhibit 2-3 summarizes the Mobility Scale for data elements in the form of
"bins" that establish cut-offs for low, medium/moderate and high mobility rankings. A low ranking
(Column B) minimizes the resulting concentration in water while a high ranking (Column D) maximizes
the resulting concentration in water. Thus, those contaminants with a high ranking are of relatively
greater concern for their potential to occur in water than those with a low ranking. Note that depending
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on how a parameter is defined, a large numerical value may result in either a low or a high ranking, as
explained in Column E of Exhibit 2-3. Since "mobility" can refer to the tendency to partition both into
and out of water, textual descriptions of the results of these rankings are presented not in terms of
"high mobility" and "low mobility" but "high likelihood of partitioning to water" and "low likelihood of
partitioning to water."
Exhibit 2-3: Mobility Scale
A: Parameter
B: Low
Ranking
C: Medium/
Moderate
Ranking
D: High
Ranking
E: Effect on Water Concentration
Organic Carbon
Partitioning Coefficient
(Koc)
>1,000 mL/g
100-1,000
mL/g
<100 mL/g
Lower values for Koc (Column D) favor
dissolution in water over adsorption to
soil/sediment
Log Octanol/Water
Partitioning Coefficient
(log Kow)
>4
1-4
<1
Lower values for log Kow (Column D) favor
dissolution in water over adsorption to
soil/sediment or accumulation in animal lipids
Henry's Law Constant
(Kh)
>10-3 atm-
m3/mol
10"7-10"3 atm-
m3/mol
<10"7 atm-
m3/mol
Lower values for Kh (Column D) favor
dissolution in water over volatilization to air
Water Solubility
<1 mg/L
1-1,000 mg/L
>1,000 mg/L
Larger values for water solubility (Column D)
may favor higher water concentrations unless
sorption or volatility are more important
Source: Adapted from USEPA, 2009
Koc is a chemical-specific value that represents the degree to which a chemical sorbs to soil or sediment
organic carbon relative to remaining dissolved in water. A related parameter, the soil sorption
coefficient or soil distribution coefficient (Kd), modifies Koc to account for the amount of organic carbon
that is present in soil or sediment. Koc is used in this document because values for Koc are typically more
widely available for most chemicals than are values for Kd and because Koc allows for the comparison of
one chemical's sorption potential relative to another chemical's sorption potential without regard to soil
type (e.g., a Kd value for chemical A in soil type X cannot be directly compared to a Kd for chemical B in
soil type Y). However, researchers have reported that the process of sorption of PFAS may be more
complicated than it is for many other chemicals.
Nguyen et al. (2020) indicated that alkyl chain length and charge are two primary attributes that affect
PFAS sorption. PFAS with longer alkyl chains (>C6) are associated with higher values of logKd and tend to
be sorbed to soil while PFAS with shorter alkyl chains (
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2.4 Contaminant Occurrence
2.4.1 Detection, Quantitation, and Reporting Thresholds
Several types of concentration thresholds are important in the characterization of chemical contaminant
occurrence in drinking water. This section clarifies some of the terminology used in this support
document.
Typically, an analytical method allows for low-level detection of a contaminant in water at
concentrations that cannot be reliably quantified. Thus, there is a distinction between the detection limit
(or DL, the threshold at or above which the presence or absence of an identified compound can be
distinguished with a specified degree of confidence) and a quantitation limit or reporting limit or level (a
somewhat higher threshold, at or above which the concentration of a contaminant can be measured
with a specified degree of precision and/or accuracy). Such thresholds can vary from method to method,
contaminant to contaminant, laboratory to laboratory, and even from technician to technician, based on
method limitations, chemical properties, technician skill, and the quality of analytical instrumentation.
Published analytical methods specify the standards of precision and accuracy that define acceptable
laboratory performance, and often estimate "normal" or expected DLs. In practice, the limits vary.
The reporting level is the threshold at or above which a contaminant's presence or concentration is
officially quantitated. For NPDWR development purposes, the EPA has historically called this threshold
the practical quantitation level (PQL). In some of the data sets discussed in this document, the term
reporting limit may also be used; however, the term reporting level is used in this document for the sake
of consistency with the PQL. For the purposes of occurrence data evaluation, the terms "reporting level"
and "reporting limit" are considered to be synonymous.
Reporting thresholds may be established by the laboratory or by those who design and carry out a
study. The requirements for precision and accuracy that are included in a published analytical method
help to dictate where laboratories establish a reporting threshold for a particular analyte. In the case of
the EPA's nation-wide drinking water study, the Unregulated Contaminant Monitoring Rule (UCMR), the
selected reporting level is known officially as the minimum reporting level (MRL) and is the minimum
quantitation level that the EPA believes can be achieved with specified confidence by a broad spectrum
of capable laboratories across the nation.
In the absence of an otherwise established reporting threshold, laboratories generally report results as
low as can be reliably measured based on precision and accuracy acceptance criteria and the lowest
calibration standard used in the development of their instrument calibration curve, i.e., at the
quantitation limit or level.
Knowing the reporting threshold(s) associated with a study or data set can help with interpretation of
the results. Also, knowledge of reporting thresholds can help a reader to determine whether data from
two studies are directly comparable.
To facilitate interpretation of occurrence results in the contaminant-specific chapters that follow,
reporting thresholds are provided whenever they are available. In some cases, reporting thresholds are
not known, and this too is documented. In some cases, the lowest reported concentration values can
give a rough idea of what the reporting threshold(s) might have been. (Generally, the reporting
threshold could not have been higher than the lowest reported concentration. If a sufficiently large
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number of detections are reported, the lowest reported concentration is likely a good approximation of
the reporting level.)
Frequently the word detection is used in discussions of contaminant occurrence as shorthand for a
sampling result that is equal to or exceeds a given reporting threshold, and non-detection for a result
that does not equal or exceed the reporting threshold. Thus, even a sample that exhibits a result that
exceeds the laboratory DL could, in the context of a particular study or data compilation, be considered
a non-detection. For ambient water samples and some state drinking water samples for unregulated
contaminants such as those presented within this document, laboratories will often report estimated
values that are equal to or greater than the DL but less than the reporting threshold.
2.4.2 Occurrence in Drinking Water
The primary sources of the drinking water occurrence data used to evaluate PFAS occurrence were the
UCMR 3 and state monitoring data. The agency also evaluated additional sources of drinking water
occurrence information (including information on occurrence in "source" or "untreated" water, e.g., at
the wellhead in ground water systems) to augment the primary drinking water occurrence data, to
evaluate the likelihood of contaminant occurrence, and/or to more fully characterize a contaminant's
presence in the environment. These data sources are generally narrower in geographic scope than the
primary drinking water data sources.
2.4.2.1 Third Unregulated Contaminant Monitoring Rule (UCMR 3) Data
The purpose of the EPA's unregulated contaminant monitoring program is to collect data on the
occurrence of contaminants suspected to be present in drinking water, but that do not have established
health-based national standards under SDWA. UCMR 3 monitoring, designed to provide nationally
representative contaminant occurrence data, was conducted from 2013 through 2015. UCMR 3
Assessment Monitoring occurrence data are available for six PFAS: PFOS, PFOA, PFBS, PFHxS, PFNA, and
perfluoroheptanoic acid (PFHpA). Similar in design to prior rounds of UCMR sampling, UCMR 3 required
surface water systems to monitor quarterly and ground water systems to monitor semi-annually to
capture seasonal variability. As with first and second rounds of the Unregulated Contaminant
Monitoring Rule (UCMR 1 and UCMR 2, respectively), there were multiple tiers of monitoring:
Assessment Monitoring for contaminants with commonly used analytical method technologies,
Screening Survey monitoring for contaminants that require specialized analytical method technologies
not in wide or common use, and pre-screen testing for contaminants that require newer analytical
method technologies not in wide or common use. See USEPA (2012b) and USEPA (2019a) for more
information on the UCMR 3 study design and data analysis, including a complete list of analytes.
For UCMR 3, all large and very large PWSs (serving between 10,001 and 100,000 people and serving
more than 100,000 people, respectively), plus a statistically representative national sample of 800 small
PWSs (serving 10,000 people or fewer), were required to conduct Assessment Monitoring during a 12-
month period between January 2013 and December 2015. For the individual PFAS contaminants, nearly
37,000 finished water samples were collected from 4,920 PWSs. Analysis of UCMR 3 results is found in
the chapters that follow and in Occurrence Data from the Third Unregulated Contaminant Monitoring
Regulation (UCMR 3) (USEPA, 2019a).
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2.4.2.2 State Monitoring Data
The agency supplemented the UCMR 3 data with more recent data collected by states who have made
their data publicly available. In general, these more recent state data were collected using newer
analytical methods and state results reflect lower reporting and detection limits than those in the UCMR
3. The EPA identified some available state data as part of the preliminary regulatory determination for
PFOA and PFOS, and based on public comments received following that preliminary regulatory
determination, commenters identified additional state data information and recommended the EPA
consider all readily available drinking water sampling conducted by states (USEPA, 2021a). In addition,
the EPA gathered updated and new state data as of May 2023 to support the development of the final
NPDWR. Exhibit 2-4 discusses state-specific sampling and collection dates for each state. The EPA
collected these occurrence data by downloading publicly available monitoring data from state websites.
(The EPA notes that one state voluntarily submitted their drinking water data to the EPA.) Drinking
water monitoring data for select contaminants were available online from several states, including
Alabama, Arizona, California, Colorado, Delaware, Georgia, Idaho, Illinois, Indiana, Iowa, Kentucky,
Maine, Massachusetts, Maryland, Michigan, Minnesota, Missouri, New Hampshire, New Jersey, New
Mexico, New York, North Carolina, North Dakota, Ohio, Oregon, Pennsylvania, Rhode Island, South
Carolina, Tennessee, Vermont, Virginia, West Virginia, and Wisconsin. The available state data are
varied in terms of quantity and coverage, and some represent targeted sampling efforts (i.e., monitoring
in areas of known or potential PFAS contamination). Thus, the monitoring data from each state may not
necessarily be representative of levels found in all PWSs within a state or represent occurrence in other
states.
Due to the representative and reporting limitations of some of the available state data (e.g., reporting
combined analyte results rather than individual analyte results, very limited available data), the EPA did
not utilize all of the data described below in the subsequent occurrence analyses/co-occurrence
analyses; specific data analysis criteria (e.g., separation of non-targeted and targeted monitoring results)
were applied and are described in the chapters that follow. Furthermore, there were not available data
for all six PFAS (PFOA, PFOS, PFHxS, PFNA, HFPO-DA, and PFBS) from all states listed below. See
Chapters 3 and 4 of this document for more information on state data collected for PFOA and PFOS,
specifically. Please see Chapters 5, 6, and 7 (and Appendix A) of this document for more information on
state data collected for PFHxS, PFNA, HFPO-DA, and PFBS. For system-level analyses, inventory
information (i.e., source water type and population served information) was obtained from the fourth
quarter 2022 report from the Safe Drinking Water Information System / Federal version (SDWIS/Fed)
data available online.
Exhibit 2-4: Summary of Available State Reported Monitoring Data
State
(Reference)
Date
Range
Type of Water
Tested
Notes on Overall Coverage
Survey
Type
Alabama
(ADEM, 2023)
2013-
2022
Ground Water
and Surface
Water - Finished
Water
The Alabama Department of Public Health (ADPH)
instructed water systems to carry out PFAS
monitoring at all PWSs not previously sampled
during UCMR 3. In 2022, water systems that had not
been sampled since UCMR 3 were required to
sample between January and June 2022 using
current analytical methods . Alabama conducted
sampling of 18 PFAS, including PFOS, PFOA,
HFPO-DA, PFBS, PFHxS, and PFNA. Data were
Non-
Targeted
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State
(Reference)
Date
Range
Type of Water
Tested
Notes on Overall Coverage
Survey
Type
downloaded in May 2023 which included monitoring
data through August 2022. Only results that are
above the reporting limit are posted online; thus, only
reported detections were available for use in the
occurrence analyses.
Arizona
2016-
February
2021
Ground Water
and Surface
Water - Finished
Water
The Arizona Department of Environmental Quality
(ADEQ) made publicly available PFAS sampling data
from systems near the Luke Air Force Base. Finished
water data were available from two PWSs. Arizona
conducted sampling of two PFAS, PFOS and PFOA.
Targeted
(ADEQ, 2021;
ADEQ, 2023)
2018-
2022
Ground Water
and Surface
Water - Raw and
Finished Water
ADEQ presents a PFAS Interactive Data Map that
displays the results of testing conducted by ADEQ
since 2018 at PWSs across the state. Data were
downloaded in May 2023 which included monitoring
data through July 2022. ADEQ (2023) conducted
sampling of 18 PFAS, including PFOS, PFOA,
HFPO-DA, PFBS, PFHxS, and PFNA.
Targeted
California
(CADDW,
2023)
2013-
April 2023
Ground Water
and Surface
Water - Raw,
Finished, and
Unknown Water
The EPA reviewed the California PFAS data
available online through April 2023. Finished water
data were available from approximately 120 PWSs.
For analysis purposes, the EPA only included results
that were explicitly defined as being from treated
water. Sampling in California is ongoing. California
conducted sampling of 18 PFAS, including PFOS,
PFOA, HFPO-DA, PFBS, PFHxS, and PFNA.
Targeted
Colorado
2013-
2017
Surface Water
(Finished Water)
and Drinking
Water
Distribution
Samples
Data available from 28 "drinking water distribution
zones" (one or more per PWS) in targeted sampling
efforts at a known contaminated aquifer region. Data
were collected by El Paso County Public Health,
local water districts and utilities, and the Colorado
Department of Public Health and Environment
(CDPHE). Colorado (2013-2017) conducted
sampling of six PFAS, including PFOS, PFOA,
PFBS, PFHxS, and PFNA.
Targeted
(CDPHE, 2018;
CDPHE, 2020)
2020
Ground Water
and Surface
Water - Raw and
Finished Water
CDPHE offered free testing to PWSs serving
communities, schools, and workplaces and also to
fire districts with wells. Approximately 50% of PWSs
in Colorado participated in the 2020 PFAS sampling
project. Data included in this report were collected in
March through May of 2020. Colorado (2020)
conducted sampling of 18 PFAS, including PFOS,
PFOA, HFPO-DA, PFBS, PFHxS, and PFNA.
Non-
Targeted
Delaware
(DE ODW,
2021)
2019-
2020
Surface Water -
Finished and
Unknown Water
Sampling of finished drinking water data between
January 2019 and October 2020 from one public
water system. Delaware conducted sampling of
PFOS and PFOA, the EPA notes that the data no
longer appear to be publicly available through the
Drinking Water Watch link.
Targeted
Georgia
(GA EPD,
2020)
2020
Surface Water -
Raw, Finished,
and Unknown
Water
The EPA and the Georgia Environmental Protection
Division (GA EPD) conducted joint sampling of the
City of Summerville's drinking water sources and
finished drinking water in January 2020. Georgia
conducted sampling of six PFAS, including PFOS,
PFOA, PFBS, PFHxS, and PFNA.
Targeted
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State
(Reference)
Date
Range
Type of Water
Tested
Notes on Overall Coverage
Survey
Type
Idaho
(Idaho DEQ,
2023)
2016-
April 2023
Ground Water -
Finished and
Unknown Water
Sampling of finished drinking water data between
August 2016 and April 2023 that were available on
the state's Drinking Water Watch website. Idaho
conducted sampling of 25 PFAS, including PFOS,
PFOA, HFPO-DA, PFBS, PFHxS, and PFNA.
Not
specified
Illinois
(IL EPA, 2023)
2020 - May
2023
Ground Water
and Surface
Water - Raw and
Finished Water
The EPA reviewed statewide finished drinking
water data collected between September 2020 and
May 2023 that were available on the state's Drinking
Water Watch website. Limited PFOA and PFOS data
were also available from 2017. Illinois conducted
sampling of 20 PFAS, including PFOS, PFOA,
HFPO-DA, PFBS, PFHxS, and PFNA. Sampling in
Illinois is ongoing.
Non-
Targeted
Indiana (IDEM,
2023)
2021 -
January
2023
Ground Water
and Surface
Water - Raw,
Finished, and
Unknown Water
Beginning in February 2021, the Indiana Department
of Environmental Management (IDEM) facilitated
PFAS monitoring at all community water systems
(CWSs) throughout the state of Indiana. Samples
were to be collected at all raw water (i.e., wells and
intakes) and finished (after treatment) water points in
a CWS's supply to evaluate the statewide
occurrence of PFAS compounds in CWS across the
state and determine the efficacy of conventional
drinking water treatment for PFAS. Indiana
conducted sampling of 18 PFAS, including PFOS,
PFOA, HFPO-DA, PFBS, PFHxS, and PFNA.
Non-
Targeted
Iowa
(IA DNR, 2023)
2021 -
April 2023
Ground Water
and Surface
Water - Raw and
Finished Water
In January 2020, the Iowa Department of Natural
Resources (DNR) developed an Action Plan to
protect the health of Iowa residents and the
environment from PFAS. Data were downloaded
from the PFAS Sampling Interactive Dashboard and
Map. Iowa conducted sampling of 30 PFAS,
including PFOS, PFOA, HFPO-DA, PFBS, PFHxS,
and PFNA.
Targeted
Kentucky
(KYDEP, 2019)
2019
Ground Water
and Surface
Water - Finished
Water
Sampling of finished drinking water data between
June and October 2019. Under this sampling effort,
data are available from 81 community public drinking
water treatment plants (DWTPs), representing 74
PWSs, and serving more than 2.4 million people.
Kentucky conducted sampling of eight PFAS,
including PFOS, PFOA, HFPO-DA, PFBS, PFHxS,
and PFNA.
Non-
Targeted
Maine
(Maine DEP,
2020; Maine
DHHS, 2023)
2013-
2020
Drinking Water -
Raw, Finished,
and Unknown
Water
In March 2019, the Maine PFAS Task Force was
created to review the extent of PFAS contamination
in Maine. Finished water results collected from 2013
through 2020 have been collected at 23 locations
throughout the state. Data may include results from
public and private finished drinking water sources.
Maine conducted sampling of 35 PFAS, including
PFOS, PFOA, HFPO-DA, PFBS, PFHxS, and PFNA.
Sampling in Maine is ongoing.
Targeted
2021 -
January
2023
Ground Water
and Surface
Water - Finished
Water
The EPA reviewed the finished water data reported
to the Maine Center for Disease Control and
Prevention (CDC) Drinking Water Program as
compliance samples since June 2021 and processed
in the database as of 3/10/2023. Maine conducted
sampling of 12 PFAS, including PFOS, PFOA,
Non-
Targeted
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State
(Reference)
Date
Range
Type of Water
Tested
Notes on Overall Coverage
Survey
Type
HFPO-DA, PFBS, PFHxS, and PFNA. Sampling in
Maine is ongoing.
Maryland
(MDE, 2021;
MDE, 2022a;
MDE, 2022b)
2020-
2022
Ground Water
and Surface
Water - Raw and
Finished Water
In 2020, Maryland's Department of the Environment
(MDE) initiated a project to identify potential sources
of PFAS in Maryland and to prioritize water sources
for PFAS sampling. The EPA reviewed the finished
water results from the first three phases of MDE's
Public Water System study for the occurrence of
PFAS in state drinking water sources. Under Phase
1 (September 2020 - February 2021), sites were
selected for priority sampling based on MDE's
evaluation of potential relative risk for PFAS
exposure through drinking water. Under Phase 2
(March 2021 - May 2021), MDE conducted sampling
at sites that were selected based on their geological
setting and proximity to potential sources of PFAS.
Under Phase 3 (August 2021- June 2022), MDE
tested the remaining CWSs in the state. Maryland
conducted sampling of 18 PFAS, including PFOS,
PFOA, HFPO-DA, PFBS, PFHxS, and PFNA.
Targeted
(Phase 1,
Phase 2);
Non-
Targeted
(Phase 3)
Massachusetts
(MA EE A,
2023)
2016-April
2023
Ground Water
and Surface
Water - Raw and
Finished Water
The EPA reviewed the finished water data available
online through April 2023. Data were available from
approximately 1,300 PWSs. Massachusetts
conducted sampling of 18 PFAS, including PFOS,
PFOA, HFPO-DA, PFBS, PFHxS, and PFNA.
Sampling in Massachusetts is ongoing.
Non-
Targeted
Michigan
(Michigan
EGLE, 2023)
2020-
March
2023
Ground Water
and Surface
Water -Finished
Water
The Michigan Department of Environment, Great
Lakes, and Energy (EGLE) developed MCLs for
seven PFAS compounds in Michigan, which took
effect in August 2020. The EPA reviewed available
PFAS finished water compliance monitoring results
through March 2023. Michigan conducted sampling
of 18 PFAS, including PFOS, PFOA, HFPO-DA,
PFBS, PFHxS, and PFNA. Sampling in Michigan is
ongoing.
Non-
Targeted
Minnesota
(MDH, 2023)
2020-
2023
Ground Water
and Surface
Water -Finished
Water
Through the Statewide PFAS Monitoring Project, the
Minnesota Department of Health (MDH) is testing
CWSs across the state for PFAS. The EPA reviewed
finished water data through MDH's Interactive
Dashboard for PFAS Testing in Drinking Water.
Minnesota conducted sampling of eight PFAS,
including PFOS, PFOA, PFBS, and PFHxS.
Non-
Targeted
Missouri
(Missouri DNR,
2018; Missouri
DNR, 2023)
2016-
2017
Ground Water
and Surface
Water - Raw and
Finished Water
The Missouri Department of Natural Resources
(Missouri DNR) conducted sampling of finished
drinking water data between September 2016 and
February 2017. Under this sampling effort, 30
finished water samples were collected from 15
PWSs. Missouri conducted sampling of two PFAS,
PFOS and PFOA.
Targeted
2022-
2023
Ground Water
and Surface
Water - Raw and
Finished Water
The EPA reviewed the finished water data available
online from Missouri DNR's "PFAS Viewer Tool"
which identifies the location of voluntary sampling for
PFAS in public drinking water systems in Missouri.
The EPA reviewed finished water data collected from
approximately 125 PWSs from 2022 through 2023.
Limited data were also available from 2013 through
2017. Missouri conducted sampling of 29 PFAS,
Non-
Targeted
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State
(Reference)
Date
Range
Type of Water
Tested
Notes on Overall Coverage
Survey
Type
including PFOS, PFOA, HFPO-DA, PFBS, PFHxS,
and PFNA..
New
Hampshire
(NHDES, 2021)
2016-May
2021
Ground Water
and Surface
Water - Raw and
Finished Water
The EPA reviewed the New Hampshire PFAS
drinking water data available online through May
2021. Finished water data were available from more
than 500 PWSs. New Hampshire conducted
sampling of 42 PFAS, including PFOS, PFOA,
HFPO-DA, PFBS, PFHxS, and PFNA. Sampling in
New Hampshire is ongoing.
Non-
Targeted
New Jersey
(NJDEP, 2023)
2019-May
2023
Ground Water
and Surface
Water - Raw,
Finished, and
Unknown Water
Statewide sampling of finished drinking water data
was available from 2019-2023. The EPA reviewed
finished water data available online through May
2023 from more than 1,100 PWSs. New Jersey
conducted sampling of 14 PFAS, including PFOS,
PFOA, PFBS, PFHxS, and PFNA. Sampling in New
Jersey is ongoing.
Non-
Targeted
New Mexico
(NMED, 2019)
2016
Ground Water -
Raw and
Finished Water
The New Mexico Environment Department (NMED),
Department of Health and the U.S. Air Force
conducted testing at public drinking water supplies at
or around Cannon Air Force Base up to 2019. New
Mexico conducted sampling of 21 PFAS, including
PFOS, PFOA, PFBS, PFHxS, and PFNA.
Targeted
New York
(NYDOH,
2022)
2013-
2022
Ground Water
and Surface
Water - Raw,
Finished, and
Unknown Water
The EPA reviewed finished water data voluntarily
provided by the state to the EPA. Data were
available from nearly 2,600 PWSs from 2017 through
2022. Limited data were also available from 2013
and 2016. New York conducted sampling of 29
PFAS, including PFOS, PFOA, HFPO-DA, PFBS,
PFHxS, and PFNA.
Non-
Targeted
North Carolina
(NCDEQ, 2021;
2017-
2019
Finished and
unknown water
The North Carolina Department of Environmental
Quality (NCDEQ) and the NC Department of Health
and Human Services investigated the presence of
HFPO-DA and other PFAS in the Cape Fear
River. Monthly results were collected from five WTPs
on the Cape Fear River. Data were available from
June 2017 through October 2019. North Carolina
conducted sampling of 36 PFAS, including PFOS,
PFOA, HFPO-DA, PFBS, PFHxS, and PFNA. Only
results above the DL were reported; thus, only
reported detections were available for use in the
occurrence analyses.
Targeted
NCDEQ, 2023)
September
2022-
November
2022
Ground Water
and Surface
Water - Raw,
Finished, and
Unknown Water
In late 2022, NCDEQ performed three months of
sampling at 50 municipal and county water systems
identified in the 2019 PFAS Testing Network study
with PFOA/PFOS detections above the MRL
indicated by the 2022 EPA interim health advisories.
Data for three PFAS were included: PFOS, PFOA
and HFPO-DA.
Targeted
North Dakota
(NDDEQ, 2019;
NDDEQ, date
unknown;
NDDEQ, date
unknown)
2018,
2020, 2021
Ground Water
and Surface
Water - Raw and
Finished Water
North Dakota Department of Environmental Quality
(NDDEQ) published a 2018, a 2020, and a 2021
survey report of North Dakota Statewide PFAS
Presence/Absence results. The first phase of
sampling in October of 2018 included raw and
finished water from seven drinking WTPs that were
chosen based on either the population served or
proximity to an industrial site. During the first phase
of sampling North Dakota conducted sampling of two
Targeted
(2018);
Non-
Targeted
(2020);
Non-
Targeted
(2021)
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State
(Reference)
Date
Range
Type of Water
Tested
Notes on Overall Coverage
Survey
Type
PFAS, PFOS and PFOA, The second sampling effort
in October of 2020 sought to determine if there was a
PFAS presence in a representative portion of the
state's public water supply. In 2021, sampling
conducted as part of the third phase of the survey
focused on drinking water sites not evaluated in the
first two surveys. During the second and third phases
of sampling, North Dakota conducted sampling of 22
PFAS, including PFOS, PFOA, HFPO-DA, PFBS,
PFHxS, and PFNA.
Ohio
(Ohio EPA,
2023)
December
2019-
December
2021
Ground Water
and Surface
Water - Raw and
Finished Water
The Ohio EPA coordinated sampling of raw and
finished drinking water from PWSs throughout the
state. The EPA reviewed the finished water data
available online through December 2021. During this
timeframe, data were available from 1,479 PWSs.
Ohio conducted sampling of six PFAS, including
PFOS, PFOA, HFPO-DA, PFBS, PFHxS, and PFNA.
Non-
Targeted
Oregon
(OHA-DWS,
2022)
Oct 2021 -
Jul 2022
Ground Water
and Surface
Water -Finished
Water
The Oregon Health Authority (OHA) conducted a
PFAS drinking water monitoring project in 2021 at
PWSs in Oregon identified as at risk due to their
proximity to a known or suspected PFAS use or
contamination site. The EPA reviewed the finished
water data from more than 140 PWSs. Oregon
conducted sampling of 24 PFAS, including PFOS,
PFOA, HFPO-DA, PFBS, PFHxS, and PFNA.
Targeted
Pennsylvania
(PADEP, 2019;
PADEP, 2021)
2019-
March
2021
Ground Water
and Surface
Water -Finished
Water
A PFAS Sampling Plan was developed to test PWSs
across the state. Finished water data were collected
for more than 340 PWSs. Statewide sampling began
in June 2019. Pennsylvania conducted sampling
from June 2019 through February 2020 of six PFAS,
including PFOS, PFOA, PFBS, PFHxS, and PFNA.
Sampling was suspended from March 2020 to July
2020 due to COVID-19. Sampling resumed in August
2020 and was completed by the end of March 2021.
In 2019, sampling was conducted for 6 PFAS;
however, upon monitoring resuming from 2020-2021
sampling was conducted for 18 PFAS. Pennsylvania
conducted sampling of 18 PFAS, including PFOS,
PFOA, HFPO-DA, PFBS, PFHxS, and PFNA during
this timeframe Results for the two rounds of sampling
(i.e., pre-2020 and post 2020) are presented
separately in the occurrence analyses.
Targeted
South Carolina
(SCDHEC,
2020;
SCDHEC,
2023)
2017-
March
2023
Ground Water
and Surface
Water -Raw and
Finished Water
The EPA reviewed PFAS sampling results collected
by the South Carolina Bureau of Water for
community drinking water systems. South Carolina
conducted sampling of 18 PFAS, including PFOS,
PFOA, HFPO-DA, PFBS, PFHxS, and PFNA. Data
were available from 300 PWSs.
Non-
Targeted
Tennessee
(TDEC, 2023)
2019
Surface Water -
Raw and
Finished Water
In 2019, Metro Water Services conducted a voluntary
sampling of Nashville's drinking water systems for
PFAS. Their stated goal was to go above and
beyond current federal and state monitoring
requirements to understand the potential presence of
PFAS in Nashville's drinking water. Sampling data
included results for 18 PFAS, including PFOS,
PFOA, PFBS, PFHxS, and PFNA.
Non-
Targeted
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State
(Reference)
Date
Range
Type of Water
Tested
Notes on Overall Coverage
Survey
Type
Vermont
(VT DEC,
2023)
2019 -April
2023
Ground Water
and Surface
Water - Raw,
Finished, and
Unknown Water
The Vermont Water Supply Rule required all CWSs
and non-transient non-community water systems
(NTNCWSs) to sample for PFAS. The EPA reviewed
finished water data available online from July 2019 -
April 2023 from approximately 560 PWSs. Vermont
conducted sampling of 18 PFAS, including PFOS,
PFOA, HFPO-DA, PFBS, PFHxS, and PFNA.
Sampling in Vermont is ongoing.
Non-
Targeted
Virginia
(VDH ODW,
2021)
2021
Ground Water
and Surface
Water - Raw and
Finished Water
The Virginia Department of Health Office of Drinking
Water (ODW), in conjunction with the Virginia Per
and Poly Fluoroalkyl Substances (VA PFAS) work
group, designed the sample study to prioritize sites
for measuring PFAS concentrations in drinking water
and major sources of water and generate statewide
occurrence data. Virginia ODW also selected the 17
largest waterworks in the state, which serve
approximately 4.5 million consumers, to participate in
the sampling effort. Virginia conducted sampling of
nine PFAS, including PFOS, PFOA, HFPO-DA,
PFBS, PFHxS, and PFNA.
Targeted /
Non-
Targeted
West Virginia
(WV DHHR.
2023)
2017-
2019
Ground Water
and Surface
Water - Raw,
Finished, and
Unknown Water
The EPA reviewed finished drinking water data
collected from 2017-2019 that were available on the
state's Drinking Water Viewer website. PFOS and
PFOA results were available from one PWS.
Not
specified
Wisconsin
(Wl DNR,
2023)
2022 -April
2023
Ground Water
and Surface
Water - Raw,
Finished, and
Unknown Water
The EPA reviewed the finished water data available
online from 2022 - 2023. Data were available from
nearly 250 PWSs. On Aug. 1, 2022, the state's safe
drinking water code ch. NR 809 Wis. Adm. Code was
revised to include standards for PFOA and PFOS.
Wisconsin conducted sampling of 37 PFAS,
including PFOS, PFOA, HFPO-DA, PFBS, PFHxS,
and PFNA. Sampling in Wisconsin is ongoing.
Non-
Targeted
The EPA notes that additional available state data were reviewed other than what is included in Exhibit
2-4 above, including information from Rhode Island, Alaska and Montana as well as other sampling
efforts in Georgia and Michigan. However, those data only either represented the sum of some analytes
or the EPA was not able to determine if was representative of finished drinking water data. Additionally,
the EPA is aware that since the state data described above and in Exhibit 2-4 were collected, some of
these states may have newer data available and additional states have or intend to conduct monitoring
of finished drinking water. Any data not listed were also not used within the analyses presented in this
document.
2.4.2.3 Other Data
Department of Defense (DoD) Drinking Water Sampling
In May 2016, the Department of Defense (DoD) took actions to address impacted drinking water and
developed strategies to investigate and address DoD releases of PFAS, including testing of PFOS and
PFOA at all DoD-owned and operated drinking water systems (DoD, 2020). Additionally, in accordance
with Section 345 of the NDAA for Fiscal Year 2022, the DoD was required to provide the final testing
results for off-base drinking water located in "covered areas," which are areas in the United States that
are adjacent to and down gradient from a military installation, Formerly Used Defense Site (FUDS), or
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National Guard facility (DoD, 2023a). The drinking water analytical results from Section 345 Reporting
are only for locations outside of the installation boundary. The DoD separately manages and reports on-
base drinking water where DoD is the purveyor under SDWA (DoD, 2023b). Currently, DoD uses
validated EPA methods 533, 537, 537.1, and 1633 and DoD Quality Systems Manual Table B-15 to test
for PFAS in drinking water (DoD, 2023a). The EPA summarized the final testing results for off-base
drinking water from samples marked as "post-treatment" (i.e., "finished drinking water" after the
filtration system was used and where water is actually being consumed). Note that reported results
were based on DLs which varied between both sampling sites and across different PFAS (DoD, 2023a).
2.4.3 Occurrence in Ambient Water
This section describes sources the EPA consulted to evaluate the occurrence of PFAS in U.S. ambient
water (e.g., aquifers, rivers, lakes).
2.4.3.1 National Water Information System (NWIS) Data
The National Water Information System (NWIS) is the Nation's principal repository of water resources
data collected by the United States Geological Survey (USGS) from more than 1.9 million sites in all 50
states (USGS, 2023). NWIS-Web is the general online interface to the USGS NWIS database. All USGS
water quality and flow data are stored in NWIS, including site characteristics, streamflow, groundwater
level, precipitation, and chemical analyses of water, sediment, and biological media, though not all
parameters are available for every site. NWIS houses the National Water Quality Assessment (NAWQA)
data and includes other USGS data from unspecified projects. NWIS contains many more samples at
many more sites than the NAWQA Program. Although NWIS is comprised of primarily ambient water
data, some finished drinking water data are included as well. The non-NAWQA data housed in NWIS
generally involve fewer constituents per sample than the NAWQA data. Unlike the NAWQA data, the
non-NAWQA data are a miscellaneous collection, so they are not as well-suited for making temporal and
geographic comparisons. NWIS data were downloaded from the Water Quality Portal (WQP) in
November 2023 (WQP, 2023).
2.4.3.2 Storage and Retrieval (STORET) Data System / Water Quality Exchange (WQX) / Water
Quality Portal Data System (WQP)
The EPA's Water Quality Exchange (WQX) is the data format and mechanism for publishing monitoring
data available through the WQP. In June of 2018, the WQX replaced the Storage and Retrieval Data
System (STORET) as the mechanism for data partners to submit water monitoring data to the EPA. The
Water Quality Portal is the mechanism for anyone, including the public, to retrieve water monitoring
data that were previously in STORET (referred to below as WQP STORET data), as well as the United
States Department of Agriculture (USDA) Sustaining the Earth's Watersheds-Agricultural Research Data
System (STEWARDS) and USGS NWIS/BioData. The WQP contains raw biological, chemical, and physical
data from surface and ground water sampling by federal, state and local agencies, Native American
tribes, volunteer groups, academics, and others. The WQP database includes data from monitoring
locations in all 50 states as well as multiple territories and jurisdictions of the United States. Most data
are from ambient waters, but in some cases finished drinking water data are included as well. Data
owners are responsible for providing data of documented quality, so that data users can choose to
access only those data collected and analyzed with data quality objectives that meet their study needs.
For more general WQX data information, please refer to: https://www.epa.gov/waterdata/water-
qualitv-data-wax. To retrieve the data via WQP, please refer to:
https://www.wateraualitvdata.us/portal/.
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The WQP STORET data were downloaded from the WQP in November 2023 (WQP, 2023). (STORET data
were downloaded from the WQP by selecting the STORET database from the dropdown menu of
available data sources.) The EPA reviewed WQP STORET ground water data from wells and springs and
surface water data from lakes, rivers, streams, and reservoirs (WQP, 2023).
Limitations of WQP STORET data quality include variations in the extent of national coverage and data
completeness from parameter to parameter. Data may have been collected as part of targeted, rather
than randomized, monitoring. Furthermore, there are no restrictions on submission of data based on
analytical methods or quality assurance (QA) practices.
Since reporting levels vary and are not always provided in the WQP STORET data, it is generally not
possible to present a single reporting level or even a range of reporting levels. Instead, the chapters that
follow point out the minimum detected concentration. The minimum detected concentration, being
equal to or probably no more than a little higher than one reporting level, is probably in or near the
range of reporting levels.
2.5 Analytical Methods
The EPA has evaluated the availability of drinking water analytical methods for PFOS, PFOA, PFHxS,
PFNA, HFPO-DA, and PFBS. For the purposes of compliance with the PFAS NPDWR, the EPA has currently
identified that multiple standardized and validated analytical methods are available, including EPA
Methods 533 and 537.1 (Version 2.0).
The EPA notes that laboratories participating in UCMR 3 were required to use EPA Method 537 and
were required to report values at or above the EPA-defined MRLs for UCMR 3 PFAS (77 FR 26072;
USEPA, 2012b). The MRLs were set based on the capability of multiple laboratories at the time. The EPA
Method 537.1 was originally published in November 2018 as Version 1.0 as a more sensitive update to
EPA Method 537 (with a slightly expanded target analyte list). Version 2.0 was published in March 2020
and contains minor editorial changes to Version 1.0. Use of EPA Method 537.1 is preferable to use of
EPA Method 537 (it may not be feasible to reliably quantitate down to health levels of concern for
certain PFAS when using EPA Method 537). For this reason, only EPA methods 533 and 537.1 (Version
2.0) are accepted for use in demonstrating compliance with this final rule.
The following analytical method performance metrics are useful and are typically available for assessing
method sensitivity. The Lowest Concentration Minimum Reporting Level (LCMRL) is generally
representative of the single EPA laboratory that developed the method, while the MRL is designed to be
applied nationally in the context of UCMR monitoring during a specific UCMR cycle for which that MRL
was developed. The DL represents the minimum concentration that can be distinguished from a blank
sample, i.e., the minimum concentration required to detect the present of an analyte. A quantitation
limit represents the minimum concentration at which the measured result can be reported with a
desired level of confidence.
• LCMRL - The LCMRL is a single-laboratory reporting level for selected EPA analytical methods. It
is determined via a statistical model of future analyte recovery using the method, where the
future recovery is predicted to fall between 50% to 150% with 99% confidence.
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MRL - The MRL is a reporting level used for national application in the EPA's UCMR program.
Starting with UCMR 3, the MRL was determined via a statistical model from raw LCMRL study
data from multiple laboratories (typically three).
DL - The minimum result which can be reliably discriminated from a blank (for example,
statistically determined with a 99% confidence level).
Quantitation Limit - The smallest detectable concentration of analyte greater than the DL where
the accuracy (precision & bias) achieves the objectives of the intended purpose.
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3 Perfluorooctanoic Acid (PFOA)
This chapter presents information and analysis specific to PFOA, including background information on
the contaminant, information on contaminant sources and environmental fate, an analysis of health
effects, an analysis of occurrence in ambient and drinking water, and information about the availability
of analytical methods and treatment technologies.
3.1 Contaminant Background, Chemical and Physical Properties
Synonyms for PFOA include pentadecafluorooctanoic acid; perfluorocaprylic acid; perfluoroctanoic acid;
perfluoroheptanecarboxylic acid; and octanoic acid, pentadecafluoro-, according to the Hazardous
Substances Data Bank (NCBI, 2022a).
PFOA is a perfluorinated aliphatic carboxylic acid. It has been used as an emulsifier and surfactant in
fluoropolymers (such as in the manufacture of non-stick products like Teflon), fire-fighting foams,
cosmetics, greases and lubricants, paints, polishes, and adhesives (NCBI, 2022a). Through the EPA's
2010/2015 PFOA Stewardship Program, a voluntary risk reduction program, eight major chemical
manufacturers agreed in 2006 to phase out the use of PFOA and PFOA-related chemicals in their
products and as emissions from their facilities by 2015. All participating companies state that they met
the PFOA Stewardship Program goals (USEPA, 2022d). PFOA may still be used by other companies not
participating in the PFOA Stewardship Program. In addition, PFOA can also be present in imported
articles (USEPA, 2017) or may be inadvertently formed as by-products in commercial products (USEPA,
2021c).
The EPA has taken a range of regulatory actions to address PFAS in manufacturing and consumer
products. Since 2002, the EPA has finalized a number of TSCA Section 5(a) Significant New Use Rules
(SNURs) covering hundreds of existing PFAS no longer in use. These regulatory actions require notice to
the EPA, as well as agency review and regulation, as necessary, before manufacture (including import) or
processing for significant new uses of these chemicals can begin or resume. The SNURs also apply to
imported articles containing certain PFAS, including consumer products such as carpets, furniture,
electronics, and household appliances. The EPA also has issued SNURs for dozens of PFAS that have
undergone the EPA's new chemicals review prior to commercialization; these actions ensure that any
new uses which may present risk concerns but were not part of the EPA new chemicals review, do not
commence unless the EPA is notified, conducts a risk review, and regulates as appropriate under TSCA
section 5. However, SNURs will not prevent the formation of PFAS by-product formation discussed in the
preceding paragraph.
PFOA may also be formed in the environment as a terminal degradation product of commercial PFAS
produced by fluorotelomerization and electrochemical fluorination. Perfluorooctane sulfonyl fluoride,
8:2 fluorotelomer alcohols, 8:2 fluorotelomer acrylates, and A/-alkyl sulfonamido PFAS such as A/-methyl
perfluorooctanesulfonamido ethanol and A/-ethyl perfluorooctanesulfonamido ethanol are used to
produce surfactants and polymers that may degrade to PFOA (ITRC, 2020a; ITRC, 2020b; Buck et al.,
2011).
The diagram in Exhibit 3-1 shows the straight-chain chemical structure of PFOA. PFOA and related
compounds can exist as either branched-chain or linear-chain isomers depending on their method of
manufacture (ATSDR, 2021). Physical and chemical properties and other reference information are listed
in Exhibit 3-2 (these properties typically represent mixtures of branched and linear isomers rather than
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any particular isomer). There is uncertainty as to whether values for certain physical/chemical
properties of PFOA can be measured or estimated. For example, NCBI (2022a) reports a value for the log
Kow that is estimated using the EPA's Estimation Programs Interface Suite™ (EPISuite™), while ATSDR
(2021) and Lange et al. (2006) indicate that log Kow cannot be measured since PFOA is expected to form
multiple layers in octanol and water mixtures. While uncharged and very long-chain perfluoroalkyls form
layers in water/hydrocarbon mixtures, forms that are charged/ionized at typical environmental pH (such
as PFOA) are fairly soluble in water (ATSDR, 2021). Another example of apparent uncertainty is the
Henry's Law Constant. NCBI (2022a) presents a value for KH for PFOA that indicates a very high degree of
partitioning from water to air (this value was estimated using EPISuite™), while ATSDR (2021) presents a
value that indicates a moderate to nearly high degree of partitioning from water to air.
PFOA is a perfluorinated alkyl acid (PFAA) that exists as its carboxylate anion at typical environmental pH
values. Physical and chemical property data for various PFAS often correspond to the protonated acid
form of the compound in contrast to the deprotonated anion (ITRC, 2020a). Thus, the available physical
and chemical property data for PFOA may not be representative of how PFOA partitions in the
environment.
In cases where there are different conclusions in the literature, information describing differences are
presented to highlight the uncertainty in this area.
Exhibit 3-1: Chemical Structure of PFOA - Straight-Chain Isomer
p P p IP F p p
F F f IF F F F
Source: NCBI, 2022a
Exhibit 3-2: Physical and Chemical Properties of PFOA
Property
Data
Chemical Abstracts Service (CAS)
Registry Number
335-67-1 (NCBI, 2022a)
EPA Pesticide Chemical Code
Not Applicable
Chemical Formula
C8HFi502(NCBI, 2022a)
Molecular Weight
414.069 g/mol (NCBI, 2022a)
Color/Physical State
White to off-white powder (NCBI, 2022a)
Boiling Point
192 deg C (NCBI, 2022a)
Melting Point
54.3 deg C (NCBI, 2022a)
Density
1.792 g/mL at 20 deg C (NCBI, 2022a)
1.8 g/cm3 at 20 deg C (ITRC, 2021)
Freundlich Adsorption Coefficient
-
Vapor Pressure
0.0316 mm Hg at 19 deg C (NCBI, 2022a)
0.017 mm Hg at 20 deg C (ATSDR, 2021; extrapolated)
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Property
Data
Kh
0.362 Pa-m3/mol (ATSDR, 2021; converts to 3.57E-06 atm-m3/mol)
0.0908 atm-m3/mol (NCBI, 2022a; est)3
log Kow
4.81 (est) (dimensionless)b (NCBI, 2022a)
Not applicable (ATSDR, 2021)
Koc
631 ±7.9 L/kg (mean ±1 standard deviation of selected values from
Zareitalabad et al., 2013; converted from log Koc to Koc)
Acid Dissociation Constant (pKa)
1.30, 2.80, -0.5-4.2 (NCBI, 2022a)
-0.5, 0.5 (ATSDR, 2021)
Solubility in Water
2,290 mg/L at 24 deg C (est); 3,300 mg/L at 25 deg C; 4,340 at 24.1 deg C
(NCBI, 2022a)
9,500 mg/L, 3,300 mg/L at 25 deg C (ATSDR, 2021)
Other Solvents
-
Conversion Factors
(at 25 deg C, 1 atm)
1 part per million (PPM) = 16.94 mg/m3; 1 mg/m3 = 0.059 PPM (ATSDR,
2021)
Note:indicates that no information was found.
a These values should not be used to estimate portioning between water and air.
b Surfactants are surface acting agents that contain both a hydrophilic part and a hydrophobic part which causes them
to accumulate at interfaces hampering the determination of their aqueous concentration. These surfactant properties
present difficulties in applying existing methods for the experimental determination of log Kowand produce unreliable
results.
3.1.1 Sources and Environmental Fate
3.1.1.1 Production, Use, and Release
Production data for PFOA are available from the EPA's IUR and CDR programs and industrial release data
are available from the EPA's TRI, as described below.
Inventory Update Reporting (IUR)/Chemical Data Reporting (CDR) Program
Under the authority of the TSCA, the EPA gathers information on production (including both
manufacture and importation) of industrial chemicals. As a compound with a TSCA section 5(a)(2) SNUR,
PFOA is among those contaminants to which the 2,500-pound threshold applies. See Chapter 2 for
further discussion.
Exhibit 3-3 presents the publicly available information on production of PFOA in the United States from
1986 to 2006 as reported under IUR. Production did not exceed 500,000 pounds in any year with
reported data. No data were reported in 1990 (the minimum threshold for reporting chemicals
produced was 10,000 pounds or more at a single site).
Exhibit 3-4 presents the publicly available production data for PFOA in the United States from 2011 to
2015 as reported under CDR. (No reports were available for 2016 through 2020.) From 2012 to 2015,
PFOA production was less than 1 million pounds. Note that although PFOA are not produced
domestically or imported by the companies participating in the 2010/2015 PFOA Stewardship Program,
PFOA may still be produced domestically or imported below the CDR reporting thresholds by companies
not participating in the PFOA Stewardship Program.
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Exhibit 3-3: IUR Reported Annual Manufacture and Importation of PFOA in the
United States, 1986-2006 (pounds)
Reporting Cycle
1986
1990
1994
1998
2002
2006
Range of
Production
Volume
10,000-
500,000
No Reports
10,000-
500,000
10,000-
500,000
10,000 -
500,000
< 500,000
Source: USEPA, 2008
Exhibit 3-4: CDR Reported Annual Manufacture and Importation of PFOA in the
United States, 2011-2020 (pounds)
Chemical Inventory Update Reporting Cycle
2011
2012
2013
2014
2015
2016 -2020
Range of
Production /
Importation
Volume
Withheld
<1,000,000
lbs
<1,000,000
lbs
<1,000,000
lbs
<1,000,000
lbs
No Reports
"Withheld" = results not publicly available due to confidential business information.
Source: USEPA, 2022e
Toxics Release Inventory (TRI)
The EPA established TRI in 1987 in response to section 313 of the EPCRA. EPCRA section 313 requires
the reporting of annual information on toxic chemical releases from facilities that meet specific criteria.
This reported information is maintained in a database accessible through TRI Explorer (USEPA, 2023b).
Although TRI can provide a general idea of release trends, it has limitations. Not all facilities are required
to report all releases. Facilities are required to report releases if they manufacture, process, or
otherwise use a listed toxic chemical in quantities above the respective activity threshold. For PFOA, the
reporting threshold is 100 pounds manufactured, processed, or otherwise used over the year. It should
also be noted that, as of this publication, quantities of PFOA at concentrations under 1.0 percent within
mixtures may be exempt from TRI reporting requirements. Reporting requirements have changed over
time (e.g., the chemical list has changed), so conclusions about temporal trends should be drawn with
caution. TRI data are meant to reflect releases and other waste management activities and should not
be used to estimate general public exposure to a chemical (USEPA, 2023b).
TRI data for PFOA are available for 2020 through 2022 (USEPA, 2023b). As shown in Exhibit 3-5, there
were about 780 pounds of total on-site disposals and 11,498 pounds of total off-site disposals across all
industries in 2020. Reported releases decreased in 2021 but then increased again in 2022 to more than
18,000 pounds of total on- and off-site disposal and other releases. A total of eight facilities from seven
states reported releases of PFOA in 2022 (USEPA, 2023b).
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Exhibit 3-5: Environmental Releases of PFOA in the United States, 2020-2022
Year
On-Site Releases (in pounds)
Total Off-
Site
Releases
(in pounds)
Total On-
and Off-Site
Releases
(in pounds)
Air
Emissions
Surface
Water
Discharges
Underground
Injection
Releases to
Land
2020
0
9
771
0
11,498
12,278
2021
4
0
288
0
0
292
2022
6
0
249
17,464
549
18,268
Source: USEPA, 2023b
3.1.1.2 Environmental Fate
The primary measures used by the EPA to assess mobility include (where available) Koc, log Kow, KH, water
solubility, and vapor pressure. For PFOA, pKa is also important.
Based on its vapor pressure, if PFOA is released to the atmosphere it will be present as a vapor. PFOA
can react in the atmosphere with photochemically produced hydroxyl radicals. The half-life for the
degradation in air of PFOA by photochemically produced hydroxyl radicals is estimated to be 31 days,
based on a structure estimation method (NCBI, 2022a). (Note that radical reactions typically proceed
more rapidly than chemically or microbially mediated degradation reactions in other environmental
media such as water, soil and/or sediment.) PFOA is not expected to undergo direct photolysis (NCBI,
2022a).
Based on findings from laboratory studies, Zareitalabad et al. (2013) calculate an average log Koc of 2.8
±0.9, equivalent to a Koc of 631 ±7.9 L/kg, which suggests a propensity for PFOA to be mobilized to
ground water and surface water rather than to bind to suspended solids or sediments. The authors note
that field studies indicate a greater propensity for PFOA to bind to soil and sediment than the lab-
derived Koc values would predict.
With a pKa ranging from -0.5 to 4.2 (NCBI, 2022a), PFOA will exist almost entirely in its anionic form in
the environment, which contributes to mobilization in water (NCBI, 2022a; Lange et al., 2006). An
estimated Henry's Law Constant of 0.0908 atm-m3/mol suggests that PFOA may volatilize from moist
soil, although the ionic nature of the compound at typical environmental pH may lessen its volatilization.
A vapor pressure of 0.0316 mm Hg suggests that PFOA may not volatilize from dry soil (NCBI, 2022a).
PFOA is resistant to hydrolysis, photolysis, and biodegradation (NCBI, 2022a; Lange et al., 2006).
Washington et al. (2010) found that PFOA had a modeled disappearance half-life of 1.0 years in sludge-
applied soils near Decatur, Alabama. Washington et al. (2010) noted that this disappearance half-life is
the time over which PFOA concentration in the surface soil was diminished by half due to all
environmental processes: those processes could potentially include uptake into plants (c.f. Yoo et al.,
2011), erosion, leaching, ingrowth from precursors, and degradation. Washington et al. (2014) posits
that among these possible processes, leaching was likely a leading mode of loss. However, the chemical
stability of PFOA is much longer than this disappearance half-life. Additionally, labile PFAS precursors
commonly present in sludge may degrade in soil settings, leading to ingrowth of recalcitrant PFAS such
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as PFOS, PFOA and related compounds (Wang et al., 2009; Martin et al., 2010; Washington et al., 2014;
Washington et al., 2015).
Under CCL 3, the EPA created scales2 to informally rank chemical contaminants' likely mobility
(understood as their tendency to partition to water rather than other media) and persistence as "high,"
"moderate," or "low" based on physical and chemical properties (see USEPA, 2021b and USEPA, 2009).
For PFOA, a KH of 0.0908 atm-m3/mol and a log Kow of 4.81 predict a low likelihood of partitioning to
water. A Koc value of 631 ±7.9 L/kg and a second KH value of 3.57E-06 atm-m3/mol predict a moderate
likelihood of partitioning to water. A water solubility of 2,290 mg/L at 24 degrees C to 9,500 mg/L at 25
degrees C predicts a high likelihood of partitioning to water. A resistance to essentially all forms of
degradation other than atmospheric processes predicts high persistence.
3.2 PFOA Occurrence
This section presents data on the occurrence of PFOA in drinking water and ambient water in the United
States. The EPA is finalizing an MCLG of 0 parts per trillion (ppt) for PFOA. Under SDWA, the EPA must
establish an enforceable MCL, the maximum concentration of a contaminant that is allowed in PWSs, as
close to the MCLG as feasible, taking several factors into consideration, including analytical methods
capable of measuring the contaminant, available treatment technologies to remove the contaminant,
and costs. Based on these factors, the EPA is finalizing an MCL of 4.0 ppt for PFOA. Occurrence data from
various sources presented below are analyzed with respect to the MCL and two alternative MCLs for
PFOA of 5.0 ppt and 10.0 ppt that the EPA evaluated under its HRRCA for the proposed and final rule.
When possible, estimates of the population exposed at concentrations above the MCL and alternative
MCLs are presented. Also, when possible, studies that are meant to be representative and studies that
are targeted at known or suspected sites of contamination are identified as such.
The drinking water analyses presented in this section were performed for UCMR 3 and select state data
sources. In addition, this section presents PFOA findings from occurrence analyses conducted by non-
EPA researchers. Chapter 10 describes the Bayesian hierarchical model used to extrapolate PFOA
occurrence to the nation and also points the reader to examine Cadwallader et al. (2022) for further
details.
For additional background information about data sources used to evaluate occurrence, please refer to
Chapter 2.
3.2.1 Occurrence in Drinking Water
Data sources reviewed by the agency for information on PFOA occurrence in drinking water included
UCMR 3, state drinking water monitoring programs, and the DoD PFAS drinking water testing, as well as
additional studies from the literature.
Note that there may be some overlap, as sources with different purposes and audiences may have
reported the same underlying data. UCMR 3 is a nationally representative data source. Other data
sources profiled in this section are considered "supplemental" sources. Also note that 29 PFAS, including
PFOA, are being monitored for under the fifth round of UCMR (UCMR 5), that data collection effort is
occurring from 2023 to 2025. Analysis of partial UCMR 5 results (the first three quarters of data that
2 See Exhibit A.8 here: https://www.epa.gov/sites/default/files/2014-05/documents/ccl3 pccltoccl 08-31-
09 508.pdf
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were made available as of February 2024) are discussed in section 11 of this document. The EPA notes
that the UCMR 3 MRL for PFOA is higher than that utilized within the majority of state monitoring data
and for the UCMR 5.
3.2.1.1 UCMR 3 Data
UCMR 3 monitoring, designed to provide nationally representative contaminant occurrence data, was
conducted from 2013 through 2015. UCMR 3 Assessment Monitoring occurrence data are available for
PFOA from all large and very large public water systems or PWSs (serving between 10,001 and 100,000
people and serving more than 100,000 people, respectively), plus a statistically representative national
sample of 800 small PWSs (serving 10,000 people or fewer).3 Surface water and ground water under the
direct influence of surface water (GWUDI) sampling points were monitored four times during the
applicable year of monitoring, and ground water sample points were monitored twice during the
applicable year of monitoring. See USEPA (2012b) and USEPA (2019a) for more information on the
UCMR 3 study design and data analysis.
Exhibit 3-6 through Exhibit 3-8 provide an overview of PFOA occurrence results from the UCMR 3
Assessment Monitoring. Laboratories participating in UCMR 3 were required to report values at or
above MRLs defined by the EPA. The UCMR MRLs are not intended to represent the lowest achievable
measurement level an individual laboratory may achieve. Rather, the MRLs are established to ensure
reliable and consistent results from the array of laboratories needed for a national monitoring program
and are set based on the quantitation level capability of multiple commercial laboratories prior to
beginning each UCMR round. The MRL used for PFOA in the UCMR 3 survey was 20 ng/L (77 FR 26072;
USEPA, 2012b). Exhibit 3-6 presents a sample-level summary of the results. Exhibit 3-7 shows a
statistical summary of PFOA concentrations by system size and source water type (including the
minimum, 25th percentile, median, 75th percentile, 90th percentile, 99th percentile, and maximum).
Exhibit 3-8 shows system-level results for detections greater than or equal to the MRL.
A total of 36,972 finished water samples for PFOA were collected from 4,920 PWSs. PFOA was reported
> MRL of 20 ng/L in 1.03 percent of UCMR 3 samples. Reported PFOA concentrations for these results
ranged from 20 ng/L (the MRL) to 349 ng/L. Of 4,920 systems, 117 (2.4 percent of systems, serving 3.2
percent of the PWS-served population) reported at least one detection.
Exhibit 3-6: PFOA National Occurrence Measures Based on UCMR 3 Assessment
Monitoring Data - Summary of Samples
Source Water Type
Total # of
Samples
Samples with Detections
> MRL of 20 ng/L
Number
Percent
Small Systems (serving < 10,000 people)
Ground Water
1,853
2
0.11%
Surface Water
1,421
2
0.14%
All Small Systems
3,274
4
0.12%
3 A total of 799 small systems submitted Assessment Monitoring results.
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Source Water Type
Total # of
Samples
Samples with Detections
> MRL of 20 ng/L
Number
Percent
Large Systems (serving 10,001 -100,000 people) — CENSUS
Ground Water
11,707
94
0.80%
Surface Water
14,860
198
1.33%
All Large Systems
26,567
292
1.10%
Very Large Systems (serving > 100,000 people) — CENSUS
Ground Water
2,020
7
0.35%
Surface Water
5,111
76
1.49%
All Very Large Systems
7,131
83
1.16%
All Systems
All Water Systems
36,972
379
1.03%
40
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
Exhibit 3-7: PFOA Occurrence Data from UCMR 3 Assessment Monitoring - Summary of Reported Concentrations
Source Water Type
Concentration Value of Detections (in ng/L) > MRL of 20 ng/L
Minimum
25th percentile
Median
75th percentile
90th Percentile
99th Percentile
Maximum
Small Systems (serving < 10,000 people)
Ground Water
30
30
30
30
30
30
32
Surface Water
130
150
170
190
200
210
206.05
All Small Systems
30
30
80
150
180
200
206.05
Large Systems (serving 10,001 -100,000 people) — CENSUS
Ground Water
20
20
30
40
70
320
338
Surface Water
20
20
30
40
70
290
349
All Large Systems
20
20
30
40
70
290
349
Very Large Systems (serving > 100,000 people) — CENSUS
Ground Water
21
30
40
50
50
60
65
Surface Water
20
20
30
40
50
140
140
All Very Large
Systems
20
20
30
40
50
140
140
All Systems
All Water Systems
20
20
30
40
70
290
349
41
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
Exhibit 3-8: PFOA National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data - Summary of
System and Population Served Data - Reported Detections
Source Water
Type
UCMR 3 Samples
Number With At Least
One Detection > MRL of
20 ng/L
Percent With At Least
One Detection > MRL of
20 ng/L
National Inventory
Percent of National
Inventory Included
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems (serving < 10,000 people)
Ground Water
527
1,498,845
1
536
0.19%
0.04%
55,700
38,730,597
0.95%
3.87%
Surface Water
272
1,250,215
1
8,323
0.37%
0.67%
9,728
20,007,917
2.80%
6.25%
All Small
Systems
799
2,749,060
2
8,859
0.25%
0.32%
65,428
58,738,514
1.22%
4.68%
Large Systems (serving 10,001 -100,000 people) — CENSUS
Ground Water
1,453
37,141,418
32
925,684
2.20%
2.49%
1,470
37,540,614
98.84%
98.94%
Surface Water
2,260
69,619,878
62
2,043,795
2.74%
2.94%
2,310
70,791,005
97.84%
98.35%
All Large
Systems
3,713
106,761,296
94
2,969,479
2.53%
2.78%
3,780
108,331,619
98.23%
98.55%
Very Large Systems (serving > 100,000 people) — CENSUS
Ground Water
68
16,355,951
4
603,800
5.88%
3.69%
68
16,355,951
100.00%
100.00%
Surface Water
340
115,158,260
17
4,051,738
5.00%
3.52%
343
120,785,622
99.13%
95.34%
All Very Large
Systems
408
131,514,211
21
4,655,538
5.15%
3.54%
411
137,141,573
99.27%
95.90%
All Systems
All Water
Systems
4,920
241,024,567
117
7,633,876
2.38%
3.17%
69,619
304,211,706
7.07%
79.23%
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Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
3.2.1.2 State Monitoring Data
In the development of the proposed and final NPDWR, the agency supplemented its UCMR 3 data with
more recent publicly available data collected by states. In general, these more recent state data were
collected using newer analytical methods and state results reflect lower reporting and detection limits
than those in the UCMR 3. The EPA downloaded publicly available monitoring data for PWSs from state
websites through May of 2023. Drinking water occurrence data for PFOA were available from several
states, including Alabama, Arizona, California, Colorado, Delaware, Georgia, Idaho, Illinois, Indiana, Iowa,
Kentucky, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, New Hampshire, New
Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oregon, Pennsylvania, South
Carolina, Tennessee, Vermont, Virginia, West Virginia, and Wisconsin. Note that while some states did
have available raw water data as indicated in Exhibit 3-9, for the subsequent analyses the EPA only
evaluated finished water results.
Exhibit 3-9 provides a summary of the available state reported monitoring data for PFOA, including date
range and a description of coverage and representativeness (including whether monitoring was non-
targeted or targeted (i.e., monitoring in areas of known or potential PFAS contamination). A description
of those studies is also included in Exhibit 3-9. Within state reported data, there may be overlap with
UCMR 3 results from 2013 - 2015, though the EPA notes that the large majority of the available state
data are from 2019 and later. In addition, the EPA excluded UCMR 3 results from the state data
whenever possible. State reporting thresholds are also provided, where available, in Exhibit 3-9. The EPA
notes that different states utilized various reporting thresholds when analyzing and presenting their
data, and for some states there were no clearly defined thresholds publicly provided; in these cases,
minimum detected concentrations reported may be indicative of reporting thresholds used. Further, for
some states, the thresholds varied when reporting results for the same analyte, as well as the laboratory
analyzing the data. For those states, a range of thresholds is provided. As shown in Exhibit 3-9, some
states reported at thresholds and/or presented data at concentrations below the EPA's final MCL and/or
PQL for PFOA. However, to present the best available occurrence information, the EPA collected and
evaluated the data based on the information as reported directly by the states and when conducting
data analyses incorporated individual state-specific reporting thresholds where possible. Additionally,
the EPA notes that the majority of the data were analyzed via an EPA-approved drinking water analytical
method.
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April 2024
Exhibit 3-9: Summary of Available PFOA State Reported Monitoring Data
State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
Alabama
(ADEM, 2023)
2013-2022
Ground Water and
Surface Water -
Finished Water
Not reported
ADPH instructed water systems to carry out PFAS monitoring at all
PWSs not previously sampled during UCMR 3. In 2022, water systems
that had not been sampled since UCMR 3 were required to sample
between January and June 2022 using current analytical methods.
Only results that are above the MRL are posted online; thus, only
reported detections were available for use in the occurrence analyses.
Non-
Targeted
Arizona
(ADEQ, 2021;
ADEQ, 2023)
2016-
February
2021
Ground Water and
Surface Water -
Finished Water
Not reported
ADEQ made publicly available PFAS sampling data from systems
near the Luke Airforce Base. Finished water data were available from
two PWSs.
Targeted
2018 - June
2021
Ground Water and
Surface Water -
Raw and Finished
Water
1.6-2
ADEQ presents a PFAS Interactive Data Map that displays the results
of testing conducted by ADEQ since 2018 at PWSs across Arizona.
Targeted
California
(CADDW,
2023)
2013-April
2023
Ground Water and
Surface Water -
Raw, Finished, and
Unknown Water
0.002-20
The EPA reviewed the California PFOA data available online through
April 2023. Finished water data were available from approximately 120
PWSs. For this analysis, the EPA only included results that were
explicitly marked as being from treated water. Sampling in California is
ongoing.
Targeted
Colorado
(CDPHE,
2018;CDPHE,
2020)
2013-
2017
Surface Water
(Finished Water)
and Drinking Water
Distribution
Samples
2-20
Data available from 28 "drinking water distribution zones" (one or more
per PWS) in targeted sampling efforts at a known contaminated
aquifer region. Data were collected by El Paso County Public Health,
local water districts and utilities, and the CDPHE.
Targeted
2020
Ground Water and
Surface Water -
Raw and Finished
Water
1.6-2.4
CDPHE offered free testing to PWSs serving communities, schools,
and workplaces and also to fire districts with wells. Approximately
50% of PWSs in Colorado participated in the 2020 PFAS sampling
project. Data included in this report were collected in March through
May of 2020.
Non-
Targeted
Delaware
(DE ODW,
2021)
2019-
2020
Surface Water -
Finished and
Unknown Water
2
Sampling of finished drinking water data between January 2019 and
October 2020 from one public water system. The EPA notes that the
data no longer appear to be publicly available through the Drinking
Water Watch link.
Targeted
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April 2024
State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
Georgia
(GA EPD,
2020)
2020
Surface Water -
Raw, Finished, and
Unknown Water
20
The EPA and the GA EPD conducted joint sampling of the City of
Summerville's drinking water sources and finished drinking water in
January 2020.
Targeted
Idaho
(Idaho DEQ,
2023)
2021-
April 2023
Ground Water -
Finished and
Unknown Water
0.5 -1
Sampling of finished drinking water data between August 2016 and
April 2023 that were available on the state's Drinking Water Watch
website.
Not specified
Illinois
(IL EPA, 2023)
2020 - May
2023
Ground Water and
Surface Water -
Raw and Finished
Water
1.7-8
In 2020, the IL EPA initiated a statewide investigation into the
prevalence and occurrence of PFAS in finished drinking water at
1,749 community water supplies across Illinois. The EPA
reviewed finished drinking water data collected between September
2020 and May 2023 that were available on the state's Drinking Water
Watch website. Limited PFOA data were also available from 2017.
Sampling in Illinois is ongoing.
Non-
Targeted
Indiana (IDEM,
2023)
2021 -
January
2023
Ground Water and
Surface Water -
Raw, Finished, and
Unknown Water
2
Beginning in February 2021, the IDEM facilitated PFAS monitoring at
all CWSs throughout the state of Indiana. Samples were to be
collected at all raw water (i.e., wells and intakes) and finished (after
treatment) water points in a CWS's supply to evaluate the statewide
occurrence of PFAS compounds in CWS across the state and
determine the efficacy of conventional drinking water treatment for
PFAS.
Non-
Targeted
Iowa
(IA DNR,
2023)
2021 - April
2023
Ground Water and
Surface Water -
Raw and Finished
Water
1.7-4
In January 2020, the Iowa DNR developed an Action Plan to protect
the health of Iowa residents and the environment from PFAS. Data
were downloaded from the PFAS Sampling Interactive Dashboard and
Map.
Targeted
Kentucky
(KYDEP,
2019)
2019
Ground Water and
Surface Water -
Finished Water
3.24
Sampling of finished drinking water data between June and October
2019. Under this sampling effort, data are available from 81
community public DWTPs, representing 74 PWSs, and serving more
than 2.4 million people.
Non-
Targeted
Maine
(Maine DEP,
2020; Maine
DHHS, 2023)
2013-
2020
Drinking Water -
Raw, Finished, and
Unknown Water
1.78-20
In March 2019, the Maine PFAS Task Force was created to review the
extent of PFAS contamination in Maine. Finished water results
collected from 2013 through 2020 have been collected at 23 locations
throughout the state. Data may include results from public and private
finished drinking water sources. Sampling in Maine is ongoing.
Targeted
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April 2024
State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
2021 -
January
2023
Ground Water and
Surface Water -
Finished Water
2
The EPA reviewed the finished water data reported to the Maine CDC
Drinking Water Program as compliance samples since June 2021 and
processed in the database as of 3/10/2023. Sampling in Maine is
ongoing.
Non-
Targeted
Maryland
(MDE, 2021;
MDE, 2022a;
MDE, 2022b)
2020-
2022
Ground Water and
Surface Water -
Raw and Finished
Water
1
In 2020, MDE initiated a project to identify potential sources of PFAS
in Maryland and to prioritize water sources for PFAS sampling. The
EPA reviewed the finished water results from the first three phases of
MDE's Public Water System study for the occurrence of PFAS in State
drinking water sources. Under Phase 1 (September 2020 - February
2021), sites were selected for priority sampling based on MDE's
evaluation of potential relative risk for PFAS exposure through drinking
water. Under Phase 2 (March 2021 - May 2021), MDE conducted
sampling at sites that were selected based on their geological setting
and proximity to potential sources of PFAS. Under Phase 3 (August
2021- June 2022), MDE tested the remaining CWSs in the state.
Targeted
Massachusetts
(MA EE A,
2023)
2016-April
2023
Ground Water and
Surface Water -
Raw and Finished
Water
0.56 -10
EPA reviewed the finished water data available online through April
2023. Data were available from 1,330 PWSs. Sampling in
Massachusetts is ongoing.
Targeted
Michigan
(Michigan
EGLE, 2023)
2020-
March 2023
Ground Water and
Surface Water -
Finished Water
2
The Michigan EGLE developed MCLs for seven PFAS compounds in
Michigan, which took effect in August 2020. The EPA reviewed
available finished compliance monitoring results through March 2023.
Sampling in Michigan is ongoing.
Non-
Targeted
Minnesota
(MDH, 2023)
2020 - 2023
Ground Water and
Surface Water -
Finished Water
Not reported
Through the Statewide PFAS Monitoring Project, MDH is testing
CWSs across the state for PFAS. The EPA reviewed finished water
data through MDH's Interactive Dashboard for PFAS Testing in
Drinking Water.
Non-
Targeted
Missouri
(Missouri
DNR, 2018
Missouri DNR,
2023)
2016-2017
Ground Water and
Surface Water -
Raw and Finished
Water
Not reported
The Missouri DNR conducted sampling of finished drinking water data
between September 2016 and February 2017. Under this sampling
effort, 30 finished water samples were collected from 15 PWSs.
Targeted
2022 - 2023
Ground Water and
Surface Water -
Raw and Finished
Water
Not reported
The EPA reviewed the finished water data available online from
Missouri DNR's "PFAS Viewer Tool" which identifies the location of
voluntary sampling for PFAS in public drinking water systems in
Missouri. The EPA reviewed finished water data collected from
approximately 125 PWSs from 2022 through 2023. Limited data were
also available from 2013 through 2017.
Non-
Targeted
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State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
New
Hampshire
(NHDES,
2021)
2016-May
2021
Ground Water and
Surface Water -
Raw and Finished
Water
2-5
The EPA reviewed the New Hampshire PFOA data available online
through May 2021. Finished water data were available from more than
500 PWSs. Sampling in New Hampshire is ongoing.
Non-
Targeted
New Jersey
(NJDEP, 2023)
2019- May
2023
Ground Water and
Surface Water -
Raw, Finished, and
Unknown Water
0.17-5
Statewide sampling of finished drinking water data was available from
2019-2023. The EPA reviewed data available online through May
2023 from more than 1,100 PWSs. Sampling in New Jersey is
ongoing.
Non-
Targeted
New Mexico
(NMED, 2019)
2016
Ground Water -
Raw and Finished
Water
Not reported
NMED, Department of Health and the U.S. Air Force conducted testing
at public drinking water supplies at or around Cannon Air Force Base
up to 2019.
Targeted
New York
(NYDOH,
2022)
2017-
2022
Ground Water and
Surface Water -
Raw, Finished, and
Unknown Water
0.000000001 -
2,020
The EPA reviewed finished water data voluntarily provided by the state
to the EPA. Data were available from nearly 2,600 PWSs from 2017
through 2022. Limited data were also available from 2016.
Non-
Targeted
North Carolina
(NCDEQ,
2021; NCDEQ,
2023)
2017-
2019
Finished and
unknown water
Not reported
NCDEQ and the Department of Health and Human Services
investigated the presence of HFPO-DA and other PFAS in the Cape
Fear River in June 2017. Monthly results were also collected from five
water treatment plants on the Cape Fear River. Data were available
from June 2017 through October 2019. Only results above the DL
were reported; thus, only reported detections were available for use in
the occurrence analyses.
Targeted
September
2022-
November
2022
Ground Water and
Surface Water -
Raw, Finished, and
Unknown Water
Not reported
In late 2022, NCDEQ performed three months of sampling at 50
municipal and county water systems identified in the 2019 PFAS
Testing Network study with PFOA/PFOS detections above the MRL
indicated by the 2022 EPA interim health advisories.
Targeted
North Dakota
(NDDEQ,
2019; NDDEQ,
date unknown;
NDDEQ, date
unknown)
2018, 2020,
2021
Ground Water and
Surface Water -
Raw and Finished
Water
Not reported
NDDEQ published a 2018 and a 2020 survey report of North Dakota
Statewide PFAS Presence/Absence results. The first phase of
sampling in October of 2018 included raw and finished water from
seven drinking WTPs that were chosen based on either the population
served or proximity to an industrial site. The second sampling effort in
October of 2020 sought to determine if there was a PFAS presence in
a representative portion of the state's public water supply. In 2021,
sampling conducted as part of the third phase of the survey focused
on drinking water sites not evaluated in the first two surveys.
Targeted
(2018); Non-
Targeted
(2020); Non-
Targeted
(2021)
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State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
Ohio
(Ohio EPA,
2023)
December
2019-
December
2021
Ground Water and
Surface Water -
Raw and Finished
Water
5
The Ohio EPA coordinated sampling of raw and finished drinking
water from PWSs throughout the state. The EPA reviewed the finished
water data available online through December 2021. During this
timeframe, data were available from 1,479 PWSs.
Non-
Targeted
Oregon
(OHA-DWS,
2022)
2021 - July
2022
Ground Water and
Surface Water -
Finished Water
10.1 -12.4
OHA conducted a PFAS drinking water monitoring project in 2021 at
PWSs in Oregon identified as at risk due to their proximity to a known
or suspected PFAS use or contamination site. The EPA reviewed the
finished water data from more than 140 PWSs.
Targeted
Pennsylvania
(PADEP,
2019)
2019
Ground Water and
Surface Water -
Finished Water
2
A PFAS Sampling Plan was developed to test PWSs across the state.
Finished water data were collected for 87 PWSs in 2019.
Targeted
Pennsylvania
(PADEP,
2021)
2020-
March 2021
Ground Water and
Surface Water -
Finished Water
1.7-4
Beginning in 2020 and running through March of 2021, finished water
data were collected by more than 340 PWSs.
Targeted
South Carolina
(SCDHEC,
2020;
SCDHEC,
2023)
2017-
March 2023
Ground Water and
Surface Water -
Raw and Finished
Water
2
The EPA reviewed PFAS sampling results collected by the South
Carolina Bureau of Water for community drinking water systems. Data
were available from 300 PWSs.
Non-
Targeted
Tennessee
(TDEC, 2023)
2019
Surface Water -
Raw and Finished
Water
Not reported
In 2019, Metro Water Services conducted a voluntary sampling of
Nashville's drinking water systems for PFAS. Their stated goal was to
go above and beyond current federal and state monitoring
requirements to understand the potential presence of PFAS in
Nashville's drinking water.
Non-
Targeted
Vermont
(VT DEC,
2023)
2019 -April
2023
Ground Water and
Surface Water -
Finished Water
2
The Vermont Water Supply Rule required all CWSs and NTNCWSs to
sample for PFAS. The EPA reviewed finished water data available
online from July 2019 - April 2023 from approximately 560 PWSs.
Sampling in Vermont is ongoing.
Non-
Targeted
Virginia
(VDH ODW,
2021)
2021
Ground Water and
Surface Water -
Raw and Finished
Water
3.5
The Virginia ODW, in conjunction with VA PFAS work group, designed
the sample study to prioritize sites for measuring PFAS concentrations
in drinking water and major sources of water and generate statewide
occurrence data.
Targeted /
Non-
Targeted
West Virginia
(WV DHHR.
2023)
2017-
2019
Ground Water and
Surface Water -
Raw, Finished, and
Unknown Water
Not reported
The EPA reviewed finished drinking water data collected from 2017-
2019 that were available on the state's Drinking Water Watch website.
PFOS and PFOA results were available from one PWS.
Not specified
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State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
Wisconsin
(Wl DNR,
2023)
2022-April
2023
Ground Water and
Surface Water -
Raw, Finished, and
Unknown Water
Not reported
The EPA reviewed the finished water data available online from 2022 -
2023. Data were available from nearly 250 PWSs. On Aug. 1, 2022,
the state's safe drinking water code ch. NR 809 Wis. Adm. Code was
revised to include standards for PFOA and PFOS. Sampling in
Wisconsin is ongoing.
Non-
Targeted
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A summary of state reported monitoring data from PWSs for PFOA is presented in Exhibit 3-10 through
Exhibit 3-13. As noted above, some of the monitoring data from each state are limited and may not be
representative of occurrence in the state. In addition, states have varying reporting thresholds, as
described earlier and indicated in the first column of Exhibit 3-10. For states with available reporting
thresholds, only detected concentrations greater than the reporting thresholds were counted as
detections. For states that did not provide reporting thresholds, the EPA included all detected
concentrations reported in the count of detections. Overall, state reported detected concentrations
ranged from 0.21 ppt (New Jersey) to 650 ppt (New York). Note that for a small number of systems,
population served information could not be identified. These systems were included in the counts and
analysis presented in Exhibit 3-12; however, no associated population served was included in the counts
and analysis presented in Exhibit 3-13.
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Exhibit 3-10: PFOA State Reported Drinking Water Occurrence Data - Summary of Finished Water Samples
State
(Reporting
Threshold)
Source Water
Type
Total #
Samples
All Detections
Detections
> 4.0 ppt
Detections
> 5.0 ppt
Detections
> 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Alabama1
(Not reported)
Ground Water
-
32
-
13
-
8
-
4
-
Surface Water
-
144
-
96
-
91
-
59
-
Total
--
176
-
109
-
99
-
63
-
Arizona, ADEQ
Sampling
(1.6-2 ppt)
Ground Water
24
18
75.0%
14
58.3%
11
45.8%
6
25.0%
Surface Water
2
1
50.0%
0
0.0%
0
0.0%
0
0.0%
Total
26
19
73.1%
14
53.8%
11
42.3%
6
23.1%
Arizona, Luke Air
Force Base
(Not reported)
Ground Water
263
111
42.2%
70
26.6%
56
21.3%
20
7.6%
Surface Water
16
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
279
111
39.8%
70
25.1%
56
20.1%
20
7.2%
California
(0.002 - 20 ppt)
Ground Water
1,899
385
20.3%
170
9.0%
131
6.9%
39
2.1%
Surface Water
4,138
1,009
24.4%
465
11.2%
377
9.1%
163
3.9%
Unknown
29
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
6,066
1,394
23.0%
635
10.5%
508
8.4%
202
3.3%
Colorado
(2013 -2017)
(2-20 ppt)
Distribution
(Finished)
96
33
34.4%
30
31.3%
30
31.3%
28
29.2%
Surface Water
(Finished)
11
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
107
33
30.8%
30
28.0%
30
28.0%
28
26.2%
Colorado (2020)
(1.6-2.4 ppt)
Ground Water
339
30
8.8%
15
4.4%
11
3.2%
2
0.6%
Surface Water
244
24
9.8%
5
2.0%
4
1.6%
0
0.0%
Total
583
54
9.3%
20
3.4%
15
2.6%
2
0.3%
Delaware
(2 ppt)
Ground Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
34
4
11.8%
1
2.9%
1
2.9%
1
2.9%
Total
34
4
11.8%
1
2.9%
1
2.9%
1
2.9%
Georgia
(20 ppt)
Ground Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
2
1
50.0%
1
50.0%
1
50.0%
1
50.0%
Total
2
1
50.0%
1
50.0%
1
50.0%
1
50.0%
51
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water
Type
Total #
Samples
All Detections
Detections
> 4.0 ppt
Detections
> 5.0 ppt
Detections
> 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Idaho
(0.5 -1 ppt)
Ground Water
18
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
18
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Illinois
(1.7-8 ppt)
Ground Water
1,831
187
10.2%
66
3.6%
43
2.3%
27
1.5%
Surface Water
302
111
36.8%
4
1.3%
0
0.0%
0
0.0%
Total
2,133
298
14.0%
70
3.3%
43
2.0%
27
1.3%
Indiana
(2 ppt)
Ground Water
422
7
1.7%
1
0.2%
1
0.2%
0
0.0%
Surface Water
59
1
1.7%
0
0.0%
0
0.0%
0
0.0%
Total
481
8
1.7%
1
0.2%
1
0.2%
0
0.0%
Iowa
(1.7-4 ppt)
Ground Water
154
42
27.3%
21
13.6%
15
9.7%
4
2.6%
Surface Water
65
14
21.5%
5
7.7%
4
6.2%
0
0.0%
Total
219
56
25.6%
26
11.9%
19
8.7%
4
1.8%
Kentucky
(3.24 ppt)
Ground Water
33
6
18.2%
3
9.1%
2
6.1%
1
3.0%
Surface Water
48
18
37.5%
6
12.5%
2
4.2%
0
0.0%
Total
81
24
29.6%
9
11.1%
4
4.9%
1
1.2%
Maine (PFAS Task
Force)2
(1.78-20 ppt)
Ground Water
9
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
3
3
100.0%
0
0.0%
0
0.0%
0
0.0%
Unknown
75
19
25.3%
16
21.3%
13
17.3%
10
13.3%
Total
87
22
25.3%
16
18.4%
13
14.9%
10
11.5%
Maine
(Compliance)
(2 ppt)
Ground Water
646
135
20.9%
74
11.5%
66
10.2%
31
4.8%
Surface Water
62
7
11.3%
4
6.5%
3
4.8%
1
1.6%
Total
708
142
20.1%
78
11.0%
69
9.7%
32
4.5%
Maryland
(Phase 1)
(1 ppt)
Ground Water
70
50
71.4%
18
25.7%
13
18.6%
2
2.9%
Surface Water
76
50
65.8%
18
23.7%
17
22.4%
8
10.5%
Total
146
100
68.5%
36
24.7%
30
20.5%
10
6.8%
Maryland
(Phase 2)
(1 ppt)
Ground Water
9
3
33.3%
1
11.1%
1
11.1%
1
11.1%
Surface Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
9
3
33.3%
1
11.1%
1
11.1%
1
11.1%
52
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water
Type
Total #
Samples
All Detections
Detections
> 4.0 ppt
Detections
> 5.0 ppt
Detections
> 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Maryland
(Phase 3)
(1 ppt)
Ground Water
88
20
22.7%
11
12.5%
11
12.5%
10
11.4%
Surface Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
88
20
22.7%
11
12.5%
11
12.5%
10
11.4%
Massachusetts
(0.56-10 ppt)
Ground Water
7,211
3,941
54.7%
2,793
38.7%
2,281
31.6%
557
7.7%
Surface Water
2,135
1,422
66.6%
905
42.4%
689
32.3%
114
5.3%
Total
9,346
5,363
57.4%
3,698
39.6%
2,970
31.8%
671
7.2%
Michigan
(2 ppt)
Ground Water
10,007
489
4.9%
185
1.8%
139
1.4%
43
0.4%
Surface Water
519
60
11.6%
0
0.0%
0
0.0%
0
0.0%
Unknown
164
8
4.9%
1
0.6%
0
0.0%
0
0.0%
Total
10,690
557
5.2%
186
1.7%
139
1.3%
43
0.4%
Missouri,
2016-2017
(Not reported)
Unknown
29
9
31.0%
0
0.0%
0
0.0%
0
0.0%
Total
29
9
31.0%
0
0.0%
0
0.0%
0
0.0%
Missouri,
2022 - 2023
(Not reported)
Ground Water
213
12
5.6%
9
4.2%
7
3.3%
3
1.4%
Surface Water
26
5
19.2%
0
0.0%
0
0.0%
0
0.0%
Total
239
17
7.1%
9
3.8%
7
2.9%
3
1.3%
New Hampshire
(2 - 5 ppt)
Ground Water
1,656
936
56.5%
632
38.2%
540
32.6%
192
11.6%
Surface Water
157
73
46.5%
26
16.6%
14
8.9%
1
0.6%
Unknown
1
1
100.0%
0
0.0%
0
0.0%
0
0.0%
Total
1,814
1,010
55.7%
658
36.3%
554
30.5%
193
10.6%
New Jersey
(0.17-5 ppt)
Ground Water
12,713
6,128
48.2%
4,626
36.4%
3,987
31.4%
1,459
11.5%
Surface Water
3,178
1,923
60.5%
1,545
48.6%
1,339
42.1%
647
20.4%
Unknown
16
12
75.0%
6
37.5%
5
31.3%
0
0.0%
Total
15,907
8,063
50.7%
6,177
38.8%
5,331
33.5%
2,106
13.2%
New Mexico
(Not reported)
Ground Water
2
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
2
0
0.0%
0
0.0%
0
0.0%
0
0.0%
New York
Ground Water
5,515
1,333
24.2%
666
12.1%
538
9.8%
229
4.2%
53
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
(0.000000001 -
2,020 ppt)
Source Water
Type
Total #
Samples
All Detections
Detections
> 4.0 ppt
Detections
> 5.0 ppt
Detections
> 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Surface Water
1,520
416
27.4%
90
5.9%
61
4.0%
30
2.0%
Unknown
21
2
9.5%
1
4.8%
1
4.8%
0
0.0%
Total
7,056
1,751
24.8%
757
10.7%
600
8.5%
259
3.7%
North Carolina,
Cape Fear River1
(Not Reported)
Unknown
-
372
-
353
-
352
-
342
-
Total
-
372
-
353
-
352
-
342
-
North Carolina,
2022
(Not Reported)
Ground Water
21
6
28.6%
3
14.3%
3
14.3%
0
0.0%
Surface Water
141
131
92.9%
70
49.6%
52
36.9%
9
6.4%
Total
162
137
84.6%
73
45.1%
55
34.0%
9
5.6%
North Dakota,
2018 (Not
reported)
Ground Water
4
2
50.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
3
3
100.0%
0
0.0%
0
0.0%
0
0.0%
Total
7
5
71.4%
0
0.0%
0
0.0%
0
0.0%
North Dakota,
2020 (Not
reported)
Ground Water
42
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
9
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
51
0
0.0%
0
0.0%
0
0.0%
0
0.0%
North Dakota,
2021 (Not
reported)
Ground Water
56
1
1.8%
0
0.0%
0
0.0%
0
0.0%
Surface Water
7
1
14.3%
0
0.0%
0
0.0%
0
0.0%
Total
63
2
3.2%
0
0.0%
0
0.0%
0
0.0%
Ohio3
(5 ppt)
Ground Water
1,775
104
5.9%
104
5.9%
104
5.9%
46
2.6%
Surface Water
170
12
7.1%
12
7.1%
12
7.1%
0
0.0%
Total
1,945
116
6.0%
116
6.0%
116
6.0%
46
2.4%
Oregon
(10.1 -12.4 ppt)
Ground Water
131
1
0.8%
1
0.8%
1
0.8%
1
0.8%
Surface Water
29
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
160
1
0.6%
1
0.6%
1
0.6%
1
0.6%
Pennsylvania,
2019 (2 ppt)
Ground Water
75
17
22.7%
6
8.0%
3
4.0%
1
1.3%
Surface Water
21
12
57.1%
6
28.6%
3
14.3%
1
4.8%
Total
96
29
30.2%
12
12.5%
6
6.3%
2
2.1%
Ground Water
314
83
26.4%
61
19.4%
42
13.4%
14
4.5%
54
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Pennsylvania,
2021 (1.7-4 ppt)
Source Water
Type
Total #
Samples
All Detections
Detections
> 4.0 ppt
Detections
> 5.0 ppt
Detections
> 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Surface Water
98
29
29.6%
23
23.5%
18
18.4%
4
4.1%
Total
412
112
27.2%
84
20.4%
60
14.6%
18
4.4%
South Carolina
(2 ppt)
Ground Water
572
53
9.3%
21
3.7%
13
2.3%
4
0.7%
Surface Water
197
88
44.7%
51
25.9%
33
16.8%
5
2.5%
Total
769
141
18.3%
72
9.4%
46
6.0%
9
1.2%
Tennessee
(Not reported)
Ground Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
2
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
2
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Vermont
(2 ppt)
Ground Water
1,463
224
15.3%
140
9.6%
111
7.6%
36
2.5%
Surface Water
102
1
1.0%
0
0.0%
0
0.0%
0
0.0%
Total
1,565
225
14.4%
140
8.9%
111
7.1%
36
2.3%
Virginia
(3.5 ppt)
Ground Water
5
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
36
4
11.1%
4
11.1%
2
5.6%
0
0.0%
Total
41
4
9.8%
4
9.8%
2
4.9%
0
0.0%
West Virginia
(Not reported)
Ground Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
31
24
77.4%
14
45.2%
12
38.7%
4
12.9%
Total
31
24
77.4%
14
45.2%
12
38.7%
4
12.9%
Wisconsin
(Not reported)
Ground Water
733
136
18.6%
25
3.4%
13
1.8%
0
0.0%
Surface Water
54
31
57.4%
0
0.0%
0
0.0%
0
0.0%
Total
787
167
21.2%
25
3.2%
13
1.7%
0
0.0%
55
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
1 Only reported detections were available in this state's dataset.
2 Reported data from Maine may include results from public and private finished drinking water sources. Based on available state data information, the EPA could
not verify public water system identification numbers (PWSIDs) for all included samples.
3 The reporting threshold for Ohio is 5 ppt; thus, any occurrence estimates relative to the final MCL of 4.0 ppt only include results greater than or equal to 5 ppt.
Exhibit 3-11: PFOA State Reported Drinking Water Occurrence Data - Summary of Detected Concentrations
State
(Reporting Threshold)
Source Water Type
Concentration Value of Detections (ppt)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Alabama1
(Not reported)
Ground Water
0.3
3.80
10.9
23.8
26
Surface Water
0.9
8.55
19.0
32.7
41
Total
0.3
7.30
18.5
31.8
41
Arizona, ADEQ Sampling
(1.6-2 ppt)
Ground Water
1.7
5.75
21.3
24.5
25
Surface Water
2.8
2.8
2.8
2.8
2.8
Total
1.7
5.40
21.2
24.5
25
Arizona, Luke Air Force Base
(Not reported)
Ground Water
2.5
5.10
15.0
30.7
33
Surface Water
-
-
-
-
-
Total
2.5
5.10
15.0
30.7
33
California
(0.002 - 20 ppt)
Ground Water
1.4
3.60
10.6
28.0
190
Surface Water
0.9
3.80
17.3
58.0
130
Unknown
-
-
-
-
-
Total
0.9
3.70
14.0
57.1
190
Colorado (2013-2017)
(2-20 ppt)
Distribution (Finished)
2.4
33.0
71.6
86.8
90
Surface Water (Finished)
-
-
-
-
-
Total
2.4
33.0
71.6
86.8
90
Colorado (2020)
(1.6-2.4 ppt)
Ground Water
1.7
4.00
8.67
11.0
11
Surface Water
1.9
3.20
6.34
6.75
6.8
Total
1.7
3.30
8.18
11.0
11
Delaware
Ground Water
-
-
-
-
-
56
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting Threshold)
(2 ppt)
Source Water Type
Concentration Value of Detections (ppt)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Surface Water
2.2
3.40
15.0
19.5
20
Total
2.2
3.40
15.0
19.5
20
Georgia
(20 ppt)
Ground Water
-
-
-
-
-
Surface Water
49
49
49
49
49
Total
49
49
49
49
49
Idaho
(0.5 -1 ppt)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
-
-
-
-
-
Illinois
(1.7-8 ppt)
Ground Water
2
3.10
13.4
24.7
42
Surface Water
2
2.40
3.30
4.30
4.5
Total
2
2.70
8.37
18.2
42
Indiana
(2 ppt)
Ground Water
2.4
3.20
4.49
6.13
6.317
Surface Water
2.7
2.7
2.7
2.7
2.7
Total
2.4
3.15
4.19
6.10
6.317
Iowa
(1.7-4 ppt)
Ground Water
2
4.15
8.45
31.2
32
Surface Water
2.3
3.35
5.54
6.04
6.1
Total
2
3.70
7.90
30.9
32
Kentucky
(3.24 ppt)
Ground Water
1.09
3.28
14.1
22.3
23.2
Surface Water
1.1
1.68
4.85
5.53
5.62
Total
1.09
1.98
5.07
19.2
23.2
Maine (PFAS Task Force)2
(1.78-20 ppt)
Ground Water
-
-
-
-
-
Surface Water
2.87
2.90
3.14
3.19
3.2
Unknown
3.7
11.4
32.5
51.4
55.6
Total
2.87
5.71
32.1
50.8
55.6
Maine (Compliance)
(2 ppt)
Ground Water
2
4.98
21.2
311
361
Surface Water
2
4.21
8.90
13.5
14
Total
2
4.95
19.3
301.8
361
57
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting Threshold)
Source Water Type
Concentration Value of Detections (ppt)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Maryland (Phase 1)
(1 ppt)
Ground Water
1.02
3.16
8.26
19.2
23.98
Surface Water
1.03
3.37
11.1
21.6
22.9
Total
1.02
3.34
9.49
22.9
23.98
Maryland (Phase 2)
(1 ppt)
Ground Water
2.27
3.32
17.9
21.2
21.54
Surface Water
-
-
-
-
-
Total
2.27
3.32
17.9
21.2
21.54
Maryland (Phase 3)
(1 ppt)
Ground Water
1.49
8.00
22.5
28.8
29.3
Surface Water
-
-
-
-
-
Total
1.49
8.00
22.5
28.8
29.3
Massachusetts
(0.56-10 ppt)
Ground Water
1.54
5.60
11.6
33.0
122
Surface Water
1.7
4.94
9.51
36.0
59
Total
1.54
5.40
11.0
34.4
122
Michigan
(2 ppt)
Ground Water
2
4.00
9.23
29.2
83
Surface Water
2
2.00
3.00
4.00
4
Unknown
2
3.00
4.30
4.93
5
Total
2
3.00
9.00
26.3
83
Minnesota
(Not reported)
Ground Water
0.46
-
-
-
52
Surface Water
1.6
-
-
-
1.6
Total
0.46
-
-
-
52
Missouri, 2016 - 2017
(Not reported)
Unknown
0.24
0.310
0.542
0.657
0.67
Total
0.24
0.310
0.542
0.657
0.67
Missouri, 2022 - 2023
(Not reported)
Ground Water
3.6
6.40
20.8
22.8
23
Surface Water
0.51
1.80
2.14
2.28
2.3
Total
0.51
4.60
19.8
22.7
23
New Hampshire
(2 - 5 ppt)
Ground Water
2
6.00
16.3
98.8
153
Surface Water
2
3.47
5.93
10.1
10.9
Unknown
3.82
3.82
3.82
3.82
3.82
58
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting Threshold)
Source Water Type
Concentration Value of Detections (ppt)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Total
2
5.61
15.8
96.4
153
New Jersey
(0.17-5 ppt)
Ground Water
0.21
6.55
16.1
34.0
173
Surface Water
1.5
7.48
21.8
32.7
51
Unknown
3.2
4.35
5.97
6.10
6.11
Total
0.21
6.70
18.0
34.0
173
New Mexico
(Not reported)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
-
-
-
-
-
New York
(0.000000001 -2,020 ppt)
Ground Water
0.255
4.00
14.1
69.7
426
Surface Water
0.253
2.20
6.27
589
650
Unknown
2.91
4.26
5.33
5.57
5.6
Total
0.253
3.30
13.5
460
650
North Carolina, Cape Fear
River1
(Not Reported)
Unknown
0.71
40.0
40.0
130
130
Total
0.71
40.0
40.0
130
130
North Carolina, 2022
(Not Reported)
Ground Water
1.38
4.16
7.34
8.03
8.11
Surface Water
1
4.29
8.58
19.5
25.3
Total
1
4.29
8.52
19.3
25.3
North Dakota, 2018
(Not reported)
Ground Water
0.45
0.670
0.846
0.886
0.89
Surface Water
0.77
0.800
0.840
0.849
0.85
Total
0.45
0.800
0.874
0.888
0.89
North Dakota, 2020
(Not reported)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
--
-
-
-
-
North Dakota, 2021
(Not reported)
Ground Water
1.34
1.34
1.34
1.34
1.34
Surface Water
1.2
1.2
1.2
1.2
1.2
Total
1.2
1.27
1.33
1.34
1.34
Ohio3
Ground Water
5.06
9.90
70.0
88.4
95.8
59
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting Threshold)
(5 ppt)
Source Water Type
Concentration Value of Detections (ppt)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Surface Water
5.03
5.60
6.67
6.70
6.7
Total
5.03
9.40
53.9
88.2
95.8
Oregon
(10.1 -12.4 ppt)
Ground Water
12
12
12
12
12
Surface Water
-
-
-
-
-
Total
12
12
12
12
12
Pennsylvania, 2019
(2 ppt)
Ground Water
2.1
3.20
6.96
18.0
20
Surface Water
2.1
4.10
7.68
11.5
12
Total
2.1
3.40
7.58
17.8
20
Pennsylvania, 2021
(1.7-4 ppt)
Ground Water
1.7
5.20
12.8
36.4
59.6
Surface Water
2.1
6.40
11.9
22.6
25
Total
1.7
5.30
12.8
31.3
59.6
South Carolina
(2 ppt)
Ground Water
2
3.10
7.80
79.0
130
Surface Water
2.1
4.20
9.33
13.7
18
Total
2
4.10
9.10
26.4
130
Tennessee
(Not reported)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
-
-
-
-
-
Vermont
(2 ppt)
Ground Water
2
4.95
11.5
36.6
44
Surface Water
2.7
2.7
2.7
2.7
2.7
Total
2
4.93
11.5
36.6
44
Virginia
(3.5 ppt)
Ground Water
-
-
-
-
-
Surface Water
4.2
5.00
5.50
5.50
5.5
Total
4.2
5.00
5.50
5.50
5.5
West Virginia
(Not reported)
Ground Water
-
-
-
-
-
Surface Water
0.31
5.05
11.0
12.8
13
Total
0.31
5.05
11.0
12.8
13
Wisconsin
Ground Water
0.297
1.80
4.99
9.04
9.9
60
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting Threshold)
(Not reported)
Source Water Type
Concentration Value of Detections (ppt)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Surface Water
0.58
1.80
2.40
2.74
2.8
Total
0.297
1.80
4.87
8.78
9.9
Note: With limited exceptions, calculated concentration values (i.e., median, 90th percentile and 99th percentile concentrations) were rounded to three
significant figures for consistent presentation across the datasets and may not indicate exact laboratory precision.
1 Only reported detections were available in this state's dataset.
2 Reported data from Maine may include results from public and private finished drinking water sources. Based on available state data information, the EPA
could not verify PWSIDs for all included samples.
Exhibit 3-12: PFOA State Reported Drinking Water Occurrence Data - Summary of Systems with Finished Water
Data
State
(Reporting
Threshold)
Source Water
Type
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections > 4.0 ppt
Systems with
Detections > 5.0 ppt
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Alabama1
(Not reported)
Ground Water
-
17
-
9
-
6
-
4
-
Surface Water
-
48
-
27
-
24
-
14
-
Total
-
65
-
36
--
30
--
18
-
Arizona, ADEQ
Sampling
(1.6-2 ppt)
Ground Water
6
3
50.0%
2
33.3%
2
33.3%
2
33.3%
Surface Water
1
1
100.0%
0
0.0%
0
0.0%
0
0.0%
Total
7
4
57.1%
2
28.6%
2
28.6%
2
28.6%
Arizona, Luke Air
Force Base
(Not reported)
Ground Water
1
1
100.0%
1
100.0%
1
100.0%
1
100.0%
Surface Water
1
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
2
1
50.0%
1
50.0%
1
50.0%
1
50.0%
Arizona (All
Systems)2
(Not reported)
Ground Water
6
3
50.0%
2
33.3%
2
33.3%
2
33.3%
Surface Water
2
1
50.0%
0
0.0%
0
0.0%
0
0.0%
Total
8
4
50.0%
2
25.0%
2
25.0%
2
25.0%
California
(0.002 - 20 ppt)
Ground Water
43
14
32.6%
12
27.9%
12
27.9%
10
23.3%
Surface Water
79
30
38.0%
24
30.4%
19
24.1%
16
20.3%
61
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Source Water
Type
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections > 4.0 ppt
Systems with
Detections > 5.0 ppt
Systems with
Detections > 10.0 ppt
Threshold)
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Unknown
1
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
123
44
35.8%
36
29.3%
31
25.2%
26
21.1%
Colorado
Distribution
(Finished)
23
12
52.2%
11
47.8%
11
47.8%
11
47.8%
(2013 -2017)
(2-20 ppt)
Surface Water
(Finished)
5
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
28
12
42.9%
11
39.3%
11
39.3%
11
39.3%
Colorado (2020)
(1.6-2.4 ppt)
Ground Water
221
25
11.3%
13
5.9%
10
4.5%
2
0.9%
Surface Water
176
20
11.4%
5
2.8%
4
2.3%
0
0.0%
Total
397
45
11.3%
18
4.5%
14
3.5%
2
0.5%
Delaware
(2 ppt)
Ground Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
1
1
100.0%
1
100.0%
1
100.0%
1
100.0%
Total
1
1
100.0%
1
100.0%
1
100.0%
1
100.0%
Georgia
(20 ppt)
Ground Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
1
1
100.0%
1
100.0%
1
100.0%
1
100.0%
Total
1
1
100.0%
1
100.0%
1
100.0%
1
100.0%
Idaho
(0.5 -1 ppt)
Ground Water
10
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
10
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Illinois
(1.7-8 ppt)
Ground Water
899
38
4.2%
18
2.0%
13
1.4%
7
0.8%
Surface Water
97
29
29.9%
4
4.1%
0
0.0%
0
0.0%
Total
996
67
6.7%
22
2.2%
13
1.3%
7
0.7%
Indiana
(2 ppt)
Ground Water
341
7
2.1%
1
0.3%
1
0.3%
0
0.0%
Surface Water
31
1
3.2%
0
0.0%
0
0.0%
0
0.0%
Total
372
8
2.2%
1
0.3%
1
0.3%
0
0.0%
Iowa
(1.7-4 ppt)
Ground Water
90
8
8.9%
5
5.6%
3
3.3%
1
1.1%
Surface Water
26
5
19.2%
2
7.7%
1
3.8%
0
0.0%
Total
116
13
11.2%
7
6.0%
4
3.4%
1
0.9%
62
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water
Type
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections > 4.0 ppt
Systems with
Detections > 5.0 ppt
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Kentucky
(3.24 ppt)
Ground Water
30
5
16.7%
3
10.0%
2
6.7%
1
3.3%
Surface Water
44
17
38.6%
6
13.6%
2
4.5%
0
0.0%
Total
74
22
29.7%
9
12.2%
4
5.4%
1
1.4%
Maine (PFAS
Task Force)3
(1.78-20 ppt)
Ground Water
7
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
1
1
100.0%
0
0.0%
0
0.0%
0
0.0%
Unknown
10
5
50.0%
5
50.0%
5
50.0%
4
40.0%
Total
18
6
33.3%
5
27.8%
5
27.8%
4
22.2%
Maine
(Compliance)
(2 ppt)
Ground Water
593
126
21.2%
73
12.3%
65
11.0%
31
5.2%
Surface Water
53
6
11.3%
3
5.7%
2
3.8%
1
1.9%
Total
646
132
20.4%
76
11.8%
67
10.4%
32
5.0%
Maine (All
Systems)2
(1.78-40 ppt)
Ground Water
593
126
21.2%
73
12.3%
65
11.0%
31
5.2%
Surface Water
53
6
11.3%
3
5.7%
2
3.8%
1
1.9%
Unknown
10
5
50.0%
5
50.0%
5
50.0%
4
40.0%
Total
656
137
20.9%
81
12.3%
72
11.0%
36
5.5%
Maryland
(Phase 1)
(1 ppt)
Ground Water
30
18
60.0%
9
30.0%
7
23.3%
2
6.7%
Surface Water
36
20
55.6%
8
22.2%
7
19.4%
4
11.1%
Total
66
38
57.6%
17
25.8%
14
21.2%
6
9.1%
Maryland
(Phase 2)
(1 ppt)
Ground Water
6
3
50.0%
1
16.7%
1
16.7%
1
16.7%
Surface Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
6
3
50.0%
1
16.7%
1
16.7%
1
16.7%
Maryland
(Phase 3)
(1 ppt)
Ground Water
63
10
15.9%
8
12.7%
8
12.7%
7
11.1%
Surface Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
63
10
15.9%
8
12.7%
8
12.7%
7
11.1%
Maryland
(All Systems)2
(1 PPt)
Ground Water
99
31
31.3%
18
18.2%
16
16.2%
10
10.1%
Surface Water
36
20
55.6%
8
22.2%
7
19.4%
4
11.1%
Total
135
51
37.8%
26
19.3%
23
17.0%
14
10.4%
Massachusetts
Ground Water
1,209
432
35.7%
281
23.2%
232
19.2%
108
8.9%
63
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
(0.56-10 ppt)
Source Water
Type
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections > 4.0 ppt
Systems with
Detections > 5.0 ppt
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Surface Water
122
88
72.1%
54
44.3%
48
39.3%
15
12.3%
Total
1,331
520
39.1%
335
25.2%
280
21.0%
123
9.2%
Michigan
(2 ppt)
Ground Water
2,370
115
4.9%
46
1.9%
35
1.5%
17
0.7%
Surface Water
84
17
20.2%
0
0.0%
0
0.0%
0
0.0%
Unknown
54
3
5.6%
1
1.9%
0
0.0%
0
0.0%
Total
2,508
135
5.4%
47
1.9%
35
1.4%
17
0.7%
Minnesota
(Not reported)
Ground Water
561
68
12.1%
15
2.7%
12
2.1%
4
0.7%
Surface Water
16
1
6.3%
0
0.0%
0
0.0%
0
0.0%
Total
577
69
12.0%
15
2.6%
12
2.1%
4
0.7%
Missouri,
2016-2017
(Not reported)
Unknown
15
7
46.7%
0
0.0%
0
0.0%
0
0.0%
Total
15
7
46.7%
0
0.0%
0
0.0%
0
0.0%
Missouri,
2022 - 2023
(Not reported)
Ground Water
105
4
3.8%
3
2.9%
3
2.9%
1
1.0%
Surface Water
20
3
15.0%
0
0.0%
0
0.0%
0
0.0%
Total
125
7
5.6%
3
2.4%
3
2.4%
1
0.8%
New Hampshire
(2 - 5 ppt)
Ground Water
529
296
56.0%
200
37.8%
179
33.8%
82
15.5%
Surface Water
30
13
43.3%
10
33.3%
7
23.3%
1
3.3%
Unknown
1
1
100.0%
0
0.0%
0
0.0%
0
0.0%
Total
560
310
55.4%
210
37.5%
186
33.2%
83
14.8%
New Jersey
(0.17-5 ppt)
Ground Water
1,012
535
52.9%
384
37.9%
341
33.7%
182
18.0%
Surface Water
107
88
82.2%
71
66.4%
67
62.6%
41
38.3%
Unknown
4
2
50.0%
2
50.0%
1
25.0%
0
0.0%
Total
1,123
625
55.7%
457
40.7%
409
36.4%
223
19.9%
New Mexico
(Not reported)
Ground Water
2
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
2
0
0.0%
0
0.0%
0
0.0%
0
0.0%
New York
Ground Water
1,600
436
27.3%
193
12.1%
164
10.3%
63
3.9%
Surface Water
277
120
43.3%
23
8.3%
18
6.5%
1
0.4%
64
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
(0.000000001 -
2,020 ppt)
Source Water
Type
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections > 4.0 ppt
Systems with
Detections > 5.0 ppt
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Unknown
9
2
22.2%
1
11.1%
1
11.1%
0
0.0%
Total
1,886
558
29.6%
217
11.5%
183
9.7%
64
3.4%
North Carolina,
Cape Fear River1
(Not Reported)
Unknown
-
5
-
5
-
5
-
5
-
Total
-
5
-
5
-
5
-
5
-
North Carolina,
2022
(Not Reported)
Ground Water
7
2
28.6%
1
14.3%
1
14.3%
0
0.0%
Surface Water
43
41
95.3%
26
60.5%
19
44.2%
4
9.3%
Total
50
43
86.0%
27
54.0%
20
40.0%
4
8.0%
North Dakota,
2018 (Not
reported)
Ground Water
4
2
50.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
3
3
100.0%
0
0.0%
0
0.0%
0
0.0%
Total
7
5
71.4%
0
0.0%
0
0.0%
0
0.0%
North Dakota,
2020 (Not
reported)
Ground Water
41
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
9
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
50
0
0.0%
0
0.0%
0
0.0%
0
0.0%
North Dakota,
2021 (Not
reported)
Ground Water
56
1
1.8%
0
0.0%
0
0.0%
0
0.0%
Surface Water
7
1
14.3%
0
0.0%
0
0.0%
0
0.0%
Total
63
2
3.2%
0
0.0%
0
0.0%
0
0.0%
North Dakota
(All Systems)2
(Not reported)
Ground Water
95
3
3.2%
0
0.0%
0
0.0%
0
0.0%
Surface Water
17
4
23.5%
0
0.0%
0
0.0%
0
0.0%
Total
112
7
6.3%
0
0.0%
0
0.0%
0
0.0%
Ohio4
(5 ppt)
Ground Water
1,372
27
2.0%
27
2.0%
27
2.0%
15
1.1%
Surface Water
107
6
5.6%
6
5.6%
6
5.6%
0
0.0%
Total
1,479
33
2.2%
33
2.2%
33
2.2%
15
1.0%
Oregon
(10.1 -12.4 ppt)
Ground Water
116
1
0.9%
1
0.9%
1
0.9%
1
0.9%
Surface Water
27
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
143
1
0.7%
1
0.7%
1
0.7%
1
0.7%
Pennsylvania,
2019 (2 ppt)
Ground Water
71
15
21.1%
5
7.0%
3
4.2%
1
1.4%
Surface Water
16
8
50.0%
5
31.3%
3
18.8%
1
6.3%
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April 2024
State
(Reporting
Threshold)
Source Water
Type
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections > 4.0 ppt
Systems with
Detections > 5.0 ppt
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Total
87
23
26.4%
10
11.5%
6
6.9%
2
2.3%
Pennsylvania,
2021 (1.7-4 ppt)
Ground Water
269
71
26.4%
55
20.4%
40
14.9%
14
5.2%
Surface Water
73
19
26.0%
17
23.3%
14
19.2%
4
5.5%
Total
342
90
26.3%
72
21.1%
54
15.8%
18
5.3%
Pennsylvania
(All Systems)2
(1.7-4 ppt)
Ground Water
270
77
28.5%
57
21.1%
41
15.2%
14
5.2%
Surface Water
73
22
30.1%
19
26.0%
15
20.5%
5
6.8%
Total
343
99
28.9%
76
22.2%
56
16.3%
19
5.5%
South Carolina
(2 ppt)
Ground Water
234
40
17.1%
18
7.7%
11
4.7%
4
1.7%
Surface Water
66
45
68.2%
34
51.5%
27
40.9%
4
6.1%
Total
300
85
28.3%
52
17.3%
38
12.7%
8
2.7%
Tennessee
(Not reported)
Ground Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
1
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
1
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Vermont
(2 ppt)
Ground Water
526
48
9.1%
27
5.1%
23
4.4%
7
1.3%
Surface Water
38
1
2.6%
0
0.0%
0
0.0%
0
0.0%
Total
564
49
8.7%
27
4.8%
23
4.1%
7
1.2%
Virginia
(3.5 ppt)
Ground Water
5
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
20
4
20.0%
4
20.0%
2
10.0%
0
0.0%
Total
25
4
16.0%
4
16.0%
2
8.0%
0
0.0%
West Virginia
(Not reported)
Ground Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
1
1
100.0%
1
100.0%
1
100.0%
1
100.0%
Total
1
1
100.0%
1
100.0%
1
100.0%
1
100.0%
Wisconsin
(Not reported)
Ground Water
217
48
22.1%
11
5.1%
5
2.3%
0
0.0%
Surface Water
22
18
81.8%
0
0.0%
0
0.0%
0
0.0%
Total
239
66
27.6%
11
4.6%
5
2.1%
0
0.0%
1 Only reported detections were available in this state's dataset.
2 The "All Systems" counts represent a summary of all unique systems across multiple sampling efforts within the state. For some states (e.g., CO, MO, NC), the
EPA could not verify this number due to the sample site ID reporting.
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3 Reported data from Maine may include results from public and private finished drinking water sources. Based on available state data information, the EPA could
not verify PWSIDs for all included samples.
4 The reporting threshold for Ohio is 5 ppt; thus, any occurrence estimates relative to the final MCL of 4.0 ppt only include results greater than or equal to 5 ppt.
Exhibit 3-13: PFOA State Reported Drinking Water Occurrence Data - Summary of Population Served by Systems
with Finished Water Data
State
(Reporting
Threshold)
Source Water
Type
Total
Population
Served by
Systems
Population Served by
Systems with
Detections
Population Served by
Systems with
Detections > 4.0 ppt
Population Served by
Systems with
Detections > 5.0 ppt
Population Served by
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Alabama1
(Not reported)
Ground Water
-
312,751
-
107,491
-
41,095
-
32,224
-
Surface Water
-
2,469,247
-
647,484
-
576,172
-
315,958
-
Total
-
2,781,998
-
754,975
-
617,267
-
348,182
-
Arizona, ADEQ
Sampling
(1.6-2 ppt)
Ground Water
94,712
55,853
59.0%
55,535
58.6%
55,535
58.6%
55,535
58.6%
Surface Water
50,001
50,001
100.0%
0
0.0%
0
0.0%
0
0.0%
Total
144,713
105,854
73.1%
55,535
38.4%
55,535
38.4%
55,535
38.4%
Arizona, Luke Air
Force Base
(Not reported)
Ground Water
50,770
50,770
100.0%
50,770
100.0%
50,770
100.0%
50,770
100.0%
Surface Water
234,766
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
285,536
50,770
17.8%
50,770
17.8%
50,770
17.8%
50,770
17.8%
Arizona (All
Systems)2
(Not reported)
Ground Water
94,712
55,853
59.0%
55,535
58.6%
55,535
58.6%
55,535
58.6%
Surface Water
284,767
50,001
17.6%
0
0.0%
0
0.0%
0
0.0%
Total
379,479
105,854
27.9%
55,535
14.6%
55,535
14.6%
55,535
14.6%
California
(0.002 - 20 ppt)
Ground Water
1,098,122
545,250
49.7%
538,033
49.0%
538,033
49.0%
450,292
41.0%
Surface Water
13,505,270
4,181,477
31.0%
3,491,853
25.9%
3,142,564
23.3%
2,944,399
21.8%
Unknown
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
14,603,392
4,726,727
32.4%
4,029,886
27.6%
3,680,597
25.2%
3,394,691
23.2%
Colorado
(2013 -2017)3
(2-20 ppt)
Distribution
(Finished)
-
-
-
-
-
-
-
-
-
Surface Water
(Finished)
-
-
-
-
-
-
-
-
-
Total
-
-
-
-
-
-
-
-
-
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April 2024
State
(Reporting
Threshold)
Source Water
Type
Total
Population
Served by
Systems
Population Served by
Systems with
Detections
Population Served by
Systems with
Detections > 4.0 ppt
Population Served by
Systems with
Detections > 5.0 ppt
Population Served by
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Colorado (2020)
(1.6-2.4 ppt)
Ground Water
261,162
57,385
22.0%
37,131
14.2%
33,411
12.8%
505
0.2%
Surface Water
4,191,774
920,514
22.0%
167,742
4.0%
161,914
3.9%
0
0.0%
Total
4,452,936
977,899
22.0%
204,873
4.6%
195,325
4.4%
505
0.0%
Delaware
(2 ppt)
Ground Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
231,114
231,114
100.0%
231,114
100.0%
231,114
100.0%
231,114
100.0%
Total
231,114
231,114
100.0%
231,114
100.0%
231,114
100.0%
231,114
100.0%
Georgia
(20 ppt)
Ground Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
9,993
9,993
100.0%
9,993
100.0%
9,993
100.0%
9,993
100.0%
Total
9,993
9,993
100.0%
9,993
100.0%
9,993
100.0%
9,993
100.0%
Idaho
(0.5 -1 ppt)
Ground Water
81,985
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
81,985
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Illinois
(1.7-8 ppt)
Ground Water
2,916,219
453,497
15.6%
262,840
9.0%
197,132
6.8%
121,850
4.2%
Surface Water
4,628,949
1,122,623
24.3%
169,883
3.7%
0
0.0%
0
0.0%
Total
7,545,168
1,576,120
20.9%
432,723
5.7%
197,132
2.6%
121,850
1.6%
Indiana
(2 ppt)
Ground Water
545,838
25,100
4.6%
7,125
1.3%
7,125
1.3%
0
0.0%
Surface Water
97,448
2,175
2.2%
0
0.0%
0
0.0%
0
0.0%
Total
643,286
27,275
4.2%
7,125
1.1%
7,125
1.1%
0
0.0%
Iowa
(1.7-4 ppt)
Ground Water
491,495
146,935
29.9%
88,239
18.0%
28,467
5.8%
100
0.0%
Surface Water
987,522
338,155
34.2%
111,812
11.3%
85,797
8.7%
0
0.0%
Total
1,479,017
485,090
32.8%
200,051
13.5%
114,264
7.7%
100
0.0%
Kentucky
(3.24 ppt)
Ground Water
171,212
77,953
45.5%
69,139
40.4%
67,449
39.4%
6,798
4.0%
Surface Water
1,922,023
1,380,792
71.8%
895,351
46.6%
18,073
0.9%
0
0.0%
Total
2,093,235
1,458,745
69.7%
964,490
46.1%
85,522
4.1%
6,798
0.3%
Maine (PFAS
Task Force)3 4
(1.78-20 ppt)
Ground Water
3,995
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
21,808
21,808
100.0%
0
0.0%
0
0.0%
0
0.0%
Unknown
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
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April 2024
State
(Reporting
Threshold)
Source Water
Type
Total
Population
Served by
Systems
Population Served by
Systems with
Detections
Population Served by
Systems with
Detections > 4.0 ppt
Population Served by
Systems with
Detections > 5.0 ppt
Population Served by
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Total
25,803
21,808
84.5%
0
0.0%
0
0.0%
0
0.0%
Maine
(Compliance)
(2 ppt)
Ground Water
274,866
83,393
30.3%
57,541
20.9%
42,326
15.4%
8,898
3.2%
Surface Water
464,453
45,244
9.7%
27,491
5.9%
24,923
5.4%
3,115
0.7%
Total
739,319
128,637
17.4%
85,032
11.5%
67,249
9.1%
12,013
1.6%
Maine (All
Systems)23
(1.78-40 ppt)
Ground Water
274,866
83,393
30.3%
57,541
20.9%
42,326
15.4%
8,898
3.2%
Surface Water
464,453
45,244
9.7%
27,491
5.9%
24,923
5.4%
3,115
0.7%
Unknown
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
739,319
128,637
17.4%
85,032
11.5%
67,249
9.1%
12,013
1.6%
Maryland
(Phase 1)
(1 ppt)
Ground Water
384,007
73,634
19.2%
61,428
16.0%
61,178
15.9%
10,100
2.6%
Surface Water
4,059,154
3,843,541
94.7%
94,394
2.3%
93,397
2.3%
62,481
1.5%
Total
4,443,161
3,917,175
88.2%
155,822
3.5%
154,575
3.5%
72,581
1.6%
Maryland
(Phase 2)
(1 ppt)
Ground Water
3,896
315
8.1%
50
1.3%
50
1.3%
50
1.3%
Surface Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
3,896
315
8.1%
50
1.3%
50
1.3%
50
1.3%
Maryland
(Phase 3)
(1 ppt)
Ground Water
41,063
3,203
7.8%
3,034
7.4%
3,034
7.4%
2,584
6.3%
Surface Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
41,063
3,203
7.8%
3,034
7.4%
3,034
7.4%
2,584
6.3%
Maryland
(All Systems)2
(1 PPt)
Ground Water
428,966
77,152
18.0%
64,512
15.0%
64,262
15.0%
12,734
3.0%
Surface Water
4,059,154
3,843,541
94.7%
94,394
2.3%
93,397
2.3%
62,481
1.5%
Total
4,488,120
3,920,693
87.4%
158,906
3.5%
157,659
3.5%
75,215
1.7%
Massachusetts
(0.56-10 ppt)
Ground Water
1,828,984
1,313,240
71.8%
1,021,308
55.8%
943,086
51.6%
401,076
21.9%
Surface Water
5,860,701
2,703,141
46.1%
1,628,689
27.8%
1,345,668
23.0%
368,445
6.3%
Total
7,689,685
4,016,381
52.2%
2,649,997
34.5%
2,288,754
29.8%
769,521
10.0%
Michigan3
(2 PPt)
Ground Water
1,945,734
320,806
16.5%
26,367
1.4%
11,491
0.6%
4,493
0.2%
Surface Water
1,314,601
470,947
35.8%
0
0.0%
0
0.0%
0
0.0%
Unknown
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
3,260,335
791,753
24.3%
26,367
0.8%
11,491
0.4%
4,493
0.1%
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April 2024
State
(Reporting
Threshold)
Source Water
Type
Total
Population
Served by
Systems
Population Served by
Systems with
Detections
Population Served by
Systems with
Detections > 4.0 ppt
Population Served by
Systems with
Detections > 5.0 ppt
Population Served by
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Minnesota
(Not reported)
Ground Water
2,752,594
1,095,531
39.8%
114,152
4.1%
85,828
3.1%
31,506
1.1%
Surface Water
1,106,268
89,987
8.1%
0
0.0%
0
0.0%
0
0.0%
Total
3,858,862
1,185,518
30.7%
114,152
3.0%
85,828
2.2%
31,506
0.8%
Missouri,
2016-20173
(Not reported)
Unknown
-
-
-
-
-
-
-
-
-
Total
-
-
-
-
-
-
-
-
-
Missouri,
2022 - 2023
(Not reported)
Ground Water
257,420
4,949
1.9%
4,879
1.9%
4,879
1.9%
2,377
0.9%
Surface Water
425,658
21,613
5.1%
0
0.0%
0
0.0%
0
0.0%
Total
683,078
26,562
3.9%
4,879
0.7%
4,879
0.7%
2,377
0.3%
New Hampshire
(2 - 5 ppt)
Ground Water
267,029
177,997
66.7%
149,081
55.8%
142,290
53.3%
114,635
42.9%
Surface Water
476,367
388,304
81.5%
353,804
74.3%
278,458
58.5%
140
0.0%
Unknown
10
10
100.0%
0
0.0%
0
0.0%
0
0.0%
Total
743,406
566,311
76.2%
502,885
67.6%
420,748
56.6%
114,775
15.4%
New Jersey
(0.17-5 ppt)
Ground Water
2,485,837
1,225,754
49.3%
1,072,557
43.1%
983,033
39.5%
605,447
24.4%
Surface Water
5,794,947
5,402,878
93.2%
4,636,191
80.0%
4,589,721
79.2%
3,610,604
62.3%
Unknown
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
8,280,784
6,628,632
80.0%
5,708,748
68.9%
5,572,754
67.3%
4,216,051
50.9%
New Mexico3
(Not reported)
Ground Water
-
-
-
-
-
-
-
-
-
Surface Water
-
-
-
-
-
-
-
-
-
Total
-
-
-
-
-
--
-
-
-
New York
(0.000000001 -
2,020 ppt)
Ground Water
2,109,018
791,773
37.5%
472,049
22.4%
442,389
21.0%
267,915
12.7%
Surface Water
3,850,284
2,093,183
54.4%
717,288
18.6%
621,001
16.1%
4,925
0.1%
Unknown
1,089
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
5,960,391
2,884,956
48.4%
1,189,337
20.0%
1,063,390
17.8%
272,840
4.6%
North Carolina,
Cape Fear
River13
(Not Reported)
Unknown
-
-
-
-
-
-
-
-
-
Total
-
-
-
-
-
-
-
-
-
Ground Water
26,914
3,620
13.5%
965
3.6%
965
3.6%
0
0.0%
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State
(Reporting
Threshold)
North Carolina,
2022
(Not Reported)
Source Water
Type
Total
Population
Served by
Systems
Population Served by
Systems with
Detections
Population Served by
Systems with
Detections > 4.0 ppt
Population Served by
Systems with
Detections > 5.0 ppt
Population Served by
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Surface Water
2,649,927
2,643,626
99.8%
1,883,832
71.1%
1,067,084
40.3%
193,311
7.3%
Total
2,676,841
2,647,246
98.9%
1,884,797
70.4%
1,068,049
39.9%
193,311
7.2%
North Dakota,
2018 (Not
reported)
Ground Water
67,981
51,801
76.2%
0
0.0%
0
0.0%
0
0.0%
Surface Water
250,518
250,518
100.0%
0
0.0%
0
0.0%
0
0.0%
Total
318,499
302,319
94.9%
0
0.0%
0
0.0%
0
0.0%
North Dakota,
2020 (Not
reported)
Ground Water
68,280
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
57,469
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
125,749
0
0.0%
0
0.0%
0
0.0%
0
0.0%
North Dakota,
2021 (Not
reported)
Ground Water
113,623
244
0.2%
0
0.0%
0
0.0%
0
0.0%
Surface Water
194,121
4,284
2.2%
0
0.0%
0
0.0%
0
0.0%
Total
307,744
4,528
1.5%
0
0.0%
0
0.0%
0
0.0%
North Dakota
(All Systems)2
(Not reported)
Ground Water
181,514
52,045
28.7%
0
0.0%
0
0.0%
0
0.0%
Surface Water
324,007
254,802
78.6%
0
0.0%
0
0.0%
0
0.0%
Total
505,521
306,847
60.7%
0
0.0%
0
0.0%
0
0.0%
Ohio5
(5 ppt)
Ground Water
2,883,252
99,659
3.5%
99,659
3.5%
99,659
3.5%
41,456
1.4%
Surface Water
6,215,644
86,324
1.4%
86,324
1.4%
86,324
1.4%
0
0.0%
Total
9,098,896
185,983
2.0%
185,983
2.0%
185,983
2.0%
41,456
0.5%
Oregon
(10.1 -12.4 ppt)
Ground Water
114,194
802
0.7%
802
0.7%
802
0.7%
802
0.7%
Surface Water
125,239
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
239,433
802
0.3%
802
0.3%
802
0.3%
802
0.3%
Pennsylvania,
2019 (2 ppt)
Ground Water
162,825
41,152
25.3%
12,288
7.5%
2,890
1.8%
110
0.1%
Surface Water
431,370
225,466
52.3%
134,502
31.2%
77,698
18.0%
45,013
10.4%
Total
594,195
266,618
44.9%
146,790
24.7%
80,588
13.6%
45,123
7.6%
Pennsylvania,
2021 (1.7-4 ppt)
Ground Water
471,651
201,749
42.8%
153,336
32.5%
115,882
24.6%
39,243
8.3%
Surface Water
4,296,097
1,489,172
34.7%
1,320,172
30.7%
1,229,741
28.6%
116,774
2.7%
Total
4,767,748
1,690,921
35.5%
1,473,508
30.9%
1,345,623
28.2%
156,017
3.3%
Pennsylvania
Ground Water
471,891
209,249
44.3%
153,784
32.6%
116,232
24.6%
39,243
8.3%
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State
(Reporting
Threshold)
(All Systems)2
(1.7-4 ppt)
Source Water
Type
Total
Population
Served by
Systems
Population Served by
Systems with
Detections
Population Served by
Systems with
Detections > 4.0 ppt
Population Served by
Systems with
Detections > 5.0 ppt
Population Served by
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Surface Water
4,296,097
1,581,476
36.8%
1,376,976
32.1%
1,274,754
29.7%
161,787
3.8%
Total
4,767,988
1,790,725
37.6%
1,530,760
32.1%
1,390,986
29.2%
201,030
4.2%
South Carolina
(2 ppt)
Ground Water
485,992
19,188
3.9%
12,454
2.6%
11,125
2.3%
3,424
0.7%
Surface Water
2,499,980
1,595,891
63.8%
1,377,099
55.1%
1,173,861
47.0%
72,093
2.9%
Total
2,985,972
1,615,079
54.1%
1,389,553
46.5%
1,184,986
39.7%
75,517
2.5%
Tennessee
(Not reported)
Ground Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
2,551
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
2,551
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Vermont
(2 ppt)
Ground Water
211,357
12,297
5.8%
6,155
2.9%
4,565
2.2%
1,269
0.6%
Surface Water
174,473
367
0.2%
0
0.0%
0
0.0%
0
0.0%
Total
385,830
12,664
3.3%
6,155
1.6%
4,565
1.2%
1,269
0.3%
Virginia
(3.5 ppt)
Ground Water
2,975
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
4,839,373
1,759,253
36.4%
1,759,253
36.4%
1,274,613
26.3%
0
0.0%
Total
4,842,348
1,759,253
36.3%
1,759,253
36.3%
1,274,613
26.3%
0
0.0%
West Virginia
(Not reported)
Ground Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
15,652
15,652
100.0%
15,652
100.0%
15,652
100.0%
15,652
100.0%
Total
15,652
15,652
100.0%
15,652
100.0%
15,652
100.0%
15,652
100.0%
Wisconsin
(Not reported)
Ground Water
1,514,437
857,072
56.6%
184,913
12.2%
105,466
7.0%
0
0.0%
Surface Water
1,333,737
1,277,594
95.8%
0
0.0%
0
0.0%
0
0.0%
Total
2,848,174
2,134,666
74.9%
184,913
6.5%
105,466
3.7%
0
0.0%
1 Only reported detections were available in this state's dataset.
2 The "All Systems" counts represent a summary of all unique systems across multiple sampling efforts within the state.
3 There were some instances where the population served by a system could not be identified. Thus, there are systems with detections but no associated
population served by those systems with detections.
4 Reported data from Maine may include results from public and private finished drinking water sources. Based on available state data information, the EPA could
not verify PWSIDs for all included samples.
5 The reporting threshold for Ohio is 5 ppt; thus, any occurrence estimates relative to the final MCL of 4.0 ppt only include results greater than or equal to 5 ppt.
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3.2.1.3 Additional Secondary Source Water and Drinking Water Studies
Boone et al. (2019) measured 17 PFAS in both source and treated water from 25 DWTPs in the United
States. The results indicated that only five of the sampling locations demonstrated a significant
difference in PFAS concentration between the source and treated water. The median concentration of
PFOA in source water was 6.32 ng/L and 4.15 ng/L in treated water. PFOA was detected in 76 percent of
treated drinking water samples (Boone et al., 2019).
Post et al. (2013) re-evaluated PFOA, PFOS, and perfluorinated compounds (PFC) occurrence data in
drinking water systems throughout New Jersey to update previous PFAS research in the area from 2006.
PFCs were found in 70 percent of PWSs sampled at concentrations ranging from 5-174 ng/L. PFOA was
the most commonly detected PFC which was detected in 57 percent of samples at a maximum
concentration of 100 ng/L. Post et al. (2013) found that multiple PFCs are commonly detected in raw
water from New Jersey PWSs, with even higher levels found near industrial sources.
McMahon et al. (2022) collected samples from aquifer systems in the eastern United States in 2019 to
evaluate PFAS occurrence in ground water used as a source of drinking water. The study found that 14
of the 24 analyzed PFAS were detected in ground water samples. Furthermore, at least one PFAS was
detected in 54 percent of the ground water samples and two or more PFAS were detected in 47 percent
of the ground water samples. In the public supply and domestic wells, 60 and 20 percent of the samples,
respectively, had at least one PFAS detection. Two or more PFAS were detected in 53 percent of the
public-supply wells and 10 percent of domestic wells. The six PFAS outlined in the EPA's UCMR 3
program (i.e., PFBS, PFHxS, PFOS, PFHpA, PFOA, and PFNA) were the most detected PFAS in the study's
samples. PFOA and PFOS were the two most frequently detected PFAS sampled. PFOA was detected in
30 percent of the 254 samples; 24 percent of samples were reported detections greater than 4 ng/L
(McMahon et al., 2022).
As part of a joint study by the EPA and USGS to assess human exposure to contaminants of emerging
concern, water samples were collected from 25 DWTPs in 24 states (Glassmeyer et al., 2017).
Participation in the study was voluntary, and candidate locations were selected based on nomination by
the EPA and USGS regional personnel and DWTP self-nomination as well as consideration of high
wastewater contribution and the availability of pharmaceutical concentration data. Final sample
locations were chosen to represent a wide range of geography, diversity in disinfectant type used, and a
range of production volumes. Phase I of the study (2007) analyzed a subset of contaminants and sites to
test experimental design; PFOA was not included in Phase 1. During Phase II of the study (2010-2012),
samples were collected from ground water and surface water sources and treated drinking water from
25 DWTPs and analyzed for PFOA occurrence. The LCMRL for PFOA was equal to 0.56 ng/L. PFOA was
detected in 76 percent of the 25 source water samples and 76 percent of the 25 treated drinking water
samples. The maximum detected concentrations in source water and treated water were 112 ng/L and
104 ng/L, respectively.
Reyes (2021) conducted a ground water-quality study to describe the occurrence and distribution of
PFAS in the Columbia aquifer public water-supply wells in the Delaware Coastal Plain region in 2018.
One or more PFAS were detected in 16 of the sampled wells with as many as 8 different PFAS detected
in a single sample. PFOA was most frequently detected out of the total PFAS detected during the study
(47 percent), followed by PFHxA (33 percent), and PFOS and PFHxS, both detected at 27 percent. PFOS
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was detected in 8 of the 30 public water-supply wells sampled in the study. The maximum PFOA
concentration detected was 57 ng/L.
3.2.2 Other Data
3.2.2.1 Department of Defense (DoD) Drinking Water Sampling
The DoD conducted sampling of off-base drinking water located in "covered areas" (i.e., areas that are
adjacent to and down gradient from a military installation) to identify potential impacts of PFAS
resulting from DoD activities. Sampling was conducted for multiple PFAS, including PFOA. The EPA
downloaded available DOD off-base sampling results in September 2023.
The EPA summarized off-base sampling results for PFOA collected "post treatment" from drinking water
systems and private wells located in covered areas adjacent to 47 installations located in 22 states.
Detected concentrations ranged from an estimated concentration of 0.071 ng/L to 333 ng/L. Sampling
was conducted utilizing multiple analytical methods including EPA methods 533, 537, 537.1, 1633, and
DoD Quality Systems Manual Table B-15 (DoD, 2023a). Results are based on DLs which vary between
both sampling sites and across different PFAS. Results for PFOA are presented in Exhibit 3-14.
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Exhibit 3-14: Summary of PFOA Drinking Water Sampling Results Collected Post-Treatment from Department of
Defense Off-Base "Covered Areas"
State
Installation Name
Sampling Dates
Analysis
Method
#
Samples
#
Detections
%
Detections
Range of Detections
(ng/L)
AK
Eielson AFB
11/3/2022
537
1
0
0.00%
NA
AZ
Luke AFB
3/31/2022
QSM_B15
2
2
100.00%
5.4 (est) - 6 (est)
AZ
YUMA AZ MCAS
5/26/2023
533
1
0
0.00%
NA
AR
Little Rock AFB
5/5/2022
537
3
2
66.67%
70.9-71.7
AR
Little Rock AFB
06/16/2022 - 03/22/2023
QSM_B15
6
1
16.67%
8.8 (est)
CA
Castle AFB
07/05/2022 - 04/05/2023
537
26
3
11.54%
0.45 - 0.668 (est)
CA
Castle AFB
11/17/2021 -01/11/2022
QSM_B15
12
0
0.00%
NA
CA
George AFB
03/23/2023 - 04/20/2023
1633
3
0
0.00%
NA
CA
March AFB
01/03/2023-04/10/2023
533
3
1
33.33%
0.62 (est)
CA
March AFB
01/03/2022- 12/01/2022
537.1
11
5
45.45%
CM
CO
cd
CA
March AFB
9/1/2022
QSM_B15
1
0
0.00%
NA
CA
Mather AFB
7/28/2022
537
1
0
0.00%
NA
CA
Mather AFB
01/27/2022 - 04/26/2022
QSM_B15
3
0
0.00%
NA
CA
Travis AFB
01/25/2022-01/16/2023
QSM_B15
19
1
5.26%
14.3
CO
Peterson Space Force Base
12/14/2021 - 02/07/2023
537.1
8
0
0.00%
NA
CO
Peterson Space Force Base
03/01/2022 - 09/14/2022
QSM_B15
16
0
0.00%
NA
DE
Dover AFB
01/22/2022- 10/25/2022
QSM_B15
10
0
0.00%
NA
FL
Homestead Air Reserve Base
02/21/2022 - 03/30/2023
QSM_B15
13
0
0.00%
NA
FL
WHITING FLD FL NAS
9/1/2022
537.1
2
1
50.00%
1.15 (est)
IL
Scott AFB
03/22/2022 - 03/28/2023
QSM_B15
3
0
0.00%
NA
ME
Loring AFB
7/25/2022
QSM_B15
1
0
0.00%
NA
ME
NCTAMSLANT DET CUTLER
04/20/2022 - 12/06/2022
537.1
66
4
6.06%
0.714 (est)-15.7 (est)
MA
Otis ANG (Joint Base Cape Cod -
Massachusetts Military Reservation)
02/28/2022 - 11/22/2022
QSM_B15
11
7
63.64%
0.48 (est) - 6
Ml
Kl Sawyer AFB
7/13/2022
QSM_B15
2
0
0.00%
NA
MT
Great Falls International Airport
06/15/2022-07/07/2022
537
3
1
33.33%
2.14 (est)
NH
Pease AFB
09/22/2021 - 03/30/2023
QSM_B15
16
7
43.75%
LO
LO
CD
CO
NJ
Joint Base McGuire-Dix-Lakehurst
03/03/2022 - 05/25/2022
QSM_B15
2
0
0.00%
NA
NM
Cannon AFB
11/11/2021 - 12/13/2021
QSM_B15
2
0
0.00%
NA
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State
Installation Name
Sampling Dates
Analysis
Method
#
Samples
#
Detections
%
Detections
Range of Detections
(ng/L)
NY
Pittsburgh AFB
05/20/2022-08/10/2022
537
8
1
12.50%
0.6 (est)
NY
Pittsburgh AFB
11/18/2021 -09/15/2022
537.1
16
0
0.00%
NA
NY
Pittsburgh AFB
11/29/2021 -06/27/2023
QSM_B15
15
2
13.33%
CD
CO
00
OK
Tinker AFB
2/2/2023
QSM_B15
3
0
0.00%
NA
Rl
NAVAL AUX LANDING FIELD
5/19/2022
537.1
2
0
0.00%
NA
Rl
NAVAL AUX LANDING FIELD
10/17/2022-02/28/2023
QSM_B15
31
28
90.32%
0.893 (est)-155
SD
Ellsworth AFB
3/14/2022
537
1
0
0.00%
NA
SD
Ellsworth AFB
06/09/2022 - 09/07/2022
537.1
2
0
0.00%
NA
SD
Ellsworth AFB
02/07/2022 - 06/23/2022
QSM_B15
36
4
11.11%
13.6 -164
TX
Goodfellow AFB
08/18/2022- 11/15/2022
537
11
1
9.09%
0.43 (est)
TX
Goodfellow AFB
12/06/2022 - 04/27/2023
QSM_B15
28
1
3.57%
333
TX
Reese AFB
09/14/2022-06/13/2023
1633
504
16
3.17%
0.67 (est) - 34.7
TX
Reese AFB
09/28/2021 - 08/29/2022
QSM_B15
839
23
2.74%
2 (est)-124
VA
OCEANA VA NAS
10/19/2022-04/14/2023
537.1
13
0
0.00%
NA
WA
BREMERTON WA NAVBASE
10/11/2022-07/21/2023
537.1
3
2
66.67%
12.2-12.5
WA
Fairchild AFB
09/19/2022-09/27/2022
537
87
2
2.30%
2.1 (est) -14.1
WA
Fairchild AFB
02/20/2023 - 03/06/2023
537.1
87
37
42.53%
0.071 (est) - 0.27 (est)
WA
Fairchild AFB
01/31/2022 - 07/21/2022
QSM_B15
187
2
1.07%
2.7 (est)-18.7
WA
WHIDBEY IS WANAS
04/21/2022 - 04/20/2023
537.1
11
2
18.18%
2.52-9.47
Source: DOD, 2023a
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3.2.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the ambient sources of most drinking water. Contaminant occurrence in
ambient water provides information on the potential for contaminants to adversely affect drinking
water supplies. Occurrence data for PFOA in ambient water are available from the USGS NWIS database
and the EPA's legacy STORET data available through the WQP.
3.2.3.1 National Water Information System (NWIS) Data
The NWIS is the Nation's principal repository of water resources data USGS collects from more than 1.9
million sites (USGS, 2023). NWIS-Web is the general online interface to the USGS NWIS database.
Discrete water-sample and time-series data are available from sites in all 50 States, including 5 million
water samples with 90 million water-quality results. All USGS water quality and flow data are stored in
NWIS, including site characteristics, streamflow, ground water level, precipitation, and chemical
analyses of water, sediment, and biological media, though not all parameters are available for every site.
NWIS houses the NAWQA data and includes other USGS data from unspecified projects. NWIS contains
many more samples at many more sites than the NAWQA Program. Although NWIS is comprised of
primarily ambient water data, some finished drinking water data are included as well. This section
presents analyses of non-NAWQA data in NWIS, downloaded from the WQP in November 2023 (WQP,
2023).
The results of the non-NAWQA NWIS PFOA analysis are presented in Exhibit 3-15. NWIS data for PFOA
were listed under the characteristic name "PFOA ion." PFOA was detected in approximately 55 percent
of samples (1,609 out of 2,950 samples) and at approximately 46 percent of sites (804 out of 1,759
sites). The median concentration based on detections was equal to 4.70 ng/L. (Note that the NWIS data
are presented as downloaded; potential outliers were not evaluated or excluded from the analysis.)
Exhibit 3-15: PFOA NWIS Data
Site Type
Detection Frequency
(detections are results > reporting level)
Concentration Values
(of detections, in ng/L)
No. of
Samples
No. of
Samples
with
Detections
No.
of
Sites
No. of
Sites with
Detections
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Ground
Water
1,344
373
1,233
369
1
7.20
29.8
85.0
150
Surface
Water
1,606
1,236
526
435
0.1
4.30
14.0
35.3
330
All Sites
2,950
1,609
1,759
804
0.1
4.70
16.4
55.9
330
Source: WQP, 2023
3.2.3.2 Storage and Retrieval (STORET) Data / Water Quality Portal (WQP)
From its launch in 1999 until it was decommissioned in June 2018, the EPA's STORET Data Warehouse
was collaboratively populated with raw biological, chemical, and physical data from surface water and
ground water sampling by federal, state and local agencies, Native American tribes, volunteer groups,
academics, and others. Legacy STORET data are accessible through the WQP:
https://www.wateraualitvdata.us/portal/.
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STORET data are from monitoring locations in all 50 states as well as multiple territories and jurisdictions
of the United States. Most data are from ambient waters, but in some cases finished drinking water data
are included as well. STORET's data quality limitations include variations in the extent of national
coverage and data completeness from parameter to parameter. Data may have been collected as part of
targeted, rather than randomized, monitoring.
This section presents analyses of STORET data, downloaded from the WQP in November 2023 (WQP,
2023). The EPA reviewed STORET ground water data from wells and springs and surface water data from
lakes, rivers, streams, and reservoirs (WQP, 2023). STORET data for PFOA STORET data were listed under
the characteristic name of "PFOA ion" and "Perfluorooctanoic acid." The results of the STORET analysis
for PFOA are presented in Exhibit 3-16 and Exhibit 3-17. More than 1,300 PFOA samples were available
for analysis. These PFOA samples were collected between 2005 and May 2023. Of the 763 sites sampled,
more than 70 percent reported detections of PFOA. Detected concentrations ranged from 0 to 1,200
ng/L. (Note: A minimum value of zero could represent a detection that was entered into the database as
a non-numerical value (e.g., "Present").)
Exhibit 3-16: PFOA STORET Data - Summary of Detected Concentrations
Source Water Type
Concentration Value of Detections (ng/L)
Minimum1
Median
90th Percentile
Maximum
Ground Water
0
0
100
1,200
Surface Water
0.81
7.36
28.5
256
Unknown
0
1.24
5.56
20.4
Total
0
0
90.0
1,200
Source: WQP, 2023
1A minimum value of zero may represent a detection that was entered into the database as a non-numerical value
(e.g., "Present").
Exhibit 3-17: PFOA STORET Data - Summary of Samples and Sites
Source Water
Type
Total
Number of
Samples
Samples with
Detections
Total
Number
of Sites
Sites with Detections
Number
Percent
Number
Percent
Ground Water
772
726
94.04%
520
484
93.08%
Surface Water
88
38
43.18%
73
26
35.62%
Unknown
491
28
5.70%
170
27
15.88%
Total
1,351
792
58.62%
763
537
70.38%
Source: WQP, 2023
3.3 Analytical Methods
For the purposes of compliance with the PFAS NPDWR, the EPA has published two analytical methods
that are available for the analysis of PFOA and other PFAS in drinking water. The performance metrics
that are presented, including the DL, LCMRL, mean recoveries and Relative Standard Deviation (RSDs)
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are specific to PFOA for each of the listed analytical methods. Ranges of mean recoveries and RSDs are
presented for the matrices listed; data from holding time studies are not included since these studies
are designed to demonstrate a degradation in method performance over time and thus are not
indicative of method performance that should be observed when holding times are not exceeded:
• EPA Method 537.1, Version 2.0, Determination of Selected Per- and Polyfluorinated Alkyl
Substances in Drinking Water by Solid Phase Extraction and Liquid Chromatography/Tandem
Mass Spectrometry (LC/MS/MS). The DL and LCMRL generated by the laboratory that
developed the method are 0.53 ng/L and 0.82 ng/L, respectively. Mean recoveries in
fortified reagent water, tap water from a ground water source (total organic carbon (TOC) =
0.53 mg/L and hardness = 377 mg/L), tap water from a surface water source (TOC = 2.4 mg/L
and hardness = 103 mg/L), and tap water from a private well (TOC = 0.56 mg/L and hardness
= 394 mg/L) range from 91.1 to 106%, with RSDs of 1.5 to 5.2% (USEPA, 2020d).
• EPA Method 533, Determination of Per- and Polyfluoroalkyl Substances in Drinking Water by
Isotope Dilution Anion Exchange Solid Phase Extraction and Liquid Chromatography /
Tandem Mass Spectrometry. The LCMRL generated by the laboratory that developed the
method is 3.4 ng/L (DLs were not calculated). Mean recoveries (excluding 13C isotope
analogue data) in fortified reagent water, finished drinking water from a ground water
source (hardness = 320 mg/L, pH = 7.88 at 17° C, free Cl2 = 0.64 mg/L, and total Cl2 = 0.74
mg/L) and clarified surface water (prior to granular activated carbon (GAC) treatment and
chlorinated in the laboratory; pH = 8.1 at 20 °C, free Cl2 = 0.98 mg/L, total Cl2 = 1.31 mg/L.
and TOC = 3.8 mg/L) range from 91.9 to 108%, with RSDs of 4.9 to 9.8% (USEPA, 2019b).
Laboratories participating in UCMR 3 were required to use EPA Method 537 and, as described in Section
4.4.2, were required to report PFOA values at or above the EPA-defined MRL of 20 ng/L (77 FR 26072;
USEPA, 2012b). The MRL was set based on the capability of multiple laboratories at the time. The EPA
Method 537.1 was originally published in November 2018 as Version 1.0 as a more sensitive update to
EPA Method 537 (with a slightly expanded target analyte list). Version 2.0 was published in March 2020
and contains minor editorial changes to Version 1.0. Use of EPA Method 537.1 is preferable to use of
EPA Method 537 (it may not be feasible to reliably quantitate down to health levels of concern for
certain PFAS when using EPA Method 537). For this reason, only EPA methods 533 and 537.1 are
accepted for use in demonstrating compliance with this final rule.
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4 Perfluorooctanesulfonic Acid (PFOS)
This chapter presents information and analysis specific to PFOS, including background information on
the contaminant, information on contaminant sources and environmental fate, an analysis of health
effects, an analysis of occurrence in ambient and drinking water, and information about the availability
of analytical methods and treatment technologies.
4.1 Contaminant Background, Chemical and Physical Properties
Synonyms for PFOS include perfluorooctylsulfonic acid and heptadecafluorooctanesulfonic acid. The
acronym PFOS is also used to refer to the deprotonated anionic form of the compound, perfluorooctane
sulfonate, according to the Hazardous Substances Data Bank (NCBI, 2022b).
PFOS is a perfluorinated aliphatic sulfonic acid. It has been used as a surfactant or emulsifier in
firefighting foam, circuit board etching acids, alkaline cleaners, and floor polish; and as a pesticide active
ingredient for insect bait traps (NCBI, 2022b). The sole manufacturer of PFOS In the United States
agreed to a voluntary phaseout in 2000, and the last reported production was in 2002 (USEPA, 2000;
USEPA, 2022d). There are some limited ongoing uses of PFOS and PFOS precursors (40 CFR § 721.9582)
such as use as a component of a photoresist substance, including a photo acid generator or surfactant,
or as a component of an anti-reflective coating, used in a photomicrolithography process to produce
semiconductors or similar components of electronic or other miniaturized devices.
The EPA has taken a range of regulatory actions to address PFAS in manufacturing and consumer
products. Since 2002, the EPA has finalized many TSCA Section 5(a) SNURs covering hundreds of existing
PFAS no longer in use. These regulatory actions require notice to the EPA, as well as agency review and
regulation, as necessary, before manufacture (including import) or processing for significant new uses of
these chemicals can begin or resume. The SNURs also apply to imported articles containing certain PFAS,
including consumer products such as carpets, furniture, electronics, and household appliances. The EPA
also has issued SNURs for dozens of PFAS that have undergone the EPA's new chemicals review prior to
commercialization; these actions ensure that any new uses which may present risk concerns but were
not part of the EPA new chemicals review, do not commence unless the EPA is notified, conducts a risk
review, and regulates as appropriate under TSCA section 5.
Since PFOS production ceased in the United States, serum concentrations taken in biomonitoring studies
in the United States' population have been declining (CDC, 2022). National Health and Nutrition
Examination Survey (NHANES) data show that 95th-percentile serum PFOS concentrations have
decreased from 75,700 ng/L in the 1999-2000 cycle to 14,600 ng/L in the 2017-2018 cycle (CDC, 2022).
PFOS may also be formed in the environment as a terminal degradation product of commercial PFAS
produced by electrochemical fluorination. Perfluorooctane sulfonyl fluoride and A/-alkyl sulfonamido
PFAS such as A/-methyl perfluorooctanesulfonamido ethanol and A/-ethyl perfluorooctanesulfonamido
ethanol are used to produce surfactants and polymers that may degrade to PFOS (ITRC, 2020a; ITRC,
2020b; Buck et al., 2011).
The diagram in Exhibit 4-1 shows the straight-chain chemical structure of PFOS. PFOS and related
compounds can exist as either branched-chain or straight-chain isomers depending on their method of
manufacture (ATSDR, 2021). Physical and chemical properties and other reference information are listed
in Exhibit 4-2 (these properties typically represent mixtures of branched and linear isomers rather than
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any particular isomer). There is uncertainty as to whether values for certain physical/chemical
properties of PFOS can be measured or estimated. For example, NCBI (2022b) reports a value for the log
Kow that is estimated using EPISuite™, while ATSDR (2021) and Lange et al. (2006) indicate that log Kow is
not applicable or cannot be measured since PFOS is expected to form multiple layers in octanol and
water mixtures. While uncharged and very long-chain perfluoroalkyls form layers in water/hydrocarbon
mixtures, forms that are charged/ionized at typical environmental pH (such as PFOS) are fairly soluble in
water (ATSDR, 2021). Another example of apparent uncertainty is the Henry's Law Constant. NCBI
(2022b) presents a value for KH for PFOS, while ATSDR (2021) indicates that no data are available for this
property. The value for KH was estimated from vapor pressure and water solubility using EPISuite™.
PFOS is a PFAA that exists as its sulfonate anion at typical environmental pH values. Physical and
chemical property data for various PFAS often correspond to the protonated acid form of the compound
in contrast to the deprotonated anion (ITRC, 2020a). Thus, the available physical and chemical property
data for PFOS may not be representative of how PFOS partitions in the environment.
In cases where there are different conclusions in the literature, information describing differences is
presented to highlight the uncertainty in this area.
Exhibit 4-1: Chemical Structure of PFOS - Straight-Chain Isomer
FFFFFFFFO
f. | | , . | | | . . on
FFFFFFFFO
Source: NCBI, 2022b
Exhibit 4-2: Physical and Chemical Properties of PFOS
Property
Data
Chemical Abstracts Service (CAS)
Registry Number
1763-23-1 (NCBI, 2022b)
EPA Pesticide Chemical Code
Not Applicable
Chemical Formula
CsHFi/OsS (NCBI, 2022b)
Molecular Weight
500.13 g/mol (NCBI, 2022b)
Color/Physical State
Liquid (NCBI, 2022b)
Boiling Point
249 deg C (NCBI, 2022b)
Melting Point
— (liquid)
Density
1.84-1.85 g/cm3 (ITRC, 2021)
Freundlich Adsorption Coefficient
25.1 in clay, 14.0 in clay loam, 28.2 in sandy loam, 8.70 in river
sediment (NCBI, 2022b)
Vapor Pressure
0.002 mm Hg at 25 deg C (est) (NCBI, 2022b)
Kh
4.1E-04 atm-m3/mol at 25 deg C (NCBI, 2022b; est from vapor
pressure and water solubility)3
No data (ATSDR, 2021)
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Property
Data
Log Kow
4.49 (est) (dimensionless)b (NCBI, 2022b)
Cannot be measured (Lange et al., 2006)
Not applicable (ATSDR, 2021)
Koc
1,000 ±5.0 L/kg (mean of values ±1 standard deviation from
Zareitalabad et al., 2013; converted from log Koc to Koc)
pKa
<1.0 (NCBI, 2022b)
Solubility in Water
0.0032 mg/L at 25 deg C (est) (NCBI, 2022b)
570 mg/L (ATSDR, 2021; potassium salt in pure water)
Other Solvents
-
Conversion Factors
(at 25 deg C, 1 atm)
1 PPM = 20.45 mg/m3; 1 mg/m3 = 0.049 PPM (ATSDR, 2021)
Note:indicates that no information was found.
a These values should not be used to estimate portioning between water and air.
b Surfactants are surface acting agents that contain both a hydrophilic part and a hydrophobic part which causes them
to accumulate at interfaces hampering the determination of their aqueous concentration. These surfactant properties
present difficulties in applying existing methods for the experimental determination of log Kowand produce unreliable
results.
4.1.1 Sources and Environmental Fate
4.1.1.1 Production, Use, and Release
Production data for PFOS are available from the EPA's IUR and CDR programs and industrial release data
are available from the EPA's TRI, as described below.
Inventory Update Reporting (IUR)/Chemical Data Reporting (CDR) Program
Under the authority of the TSCA, the EPA gathers information on production (including both
manufacture and importation) of industrial chemicals. As a compound with a TSCA section 5(a)(2) SNUR,
PFOS is among those contaminants to which the 2,500-pound threshold applies. See Chapter 2 for
further discussion.
Exhibit 4-3 presents the publicly available information on production of PFOS in the United States from
1986 to 2006 as reported under IUR. Production did not exceed 500,000 pounds in any year with
reported data. No data were reported in 1986, 1990, 1998, or 2006. PFOS was phased out by 3M in 2002
and the most recently reported data for PFOS are from the 2002 reporting cycle (which includes
production information from 2001 only).
Although PFOS is subject to CDR reporting, there are no reports of manufacture or importation in the
CDR dataset (USEPA, 2022e). Absence of recent reporting may indicate that production (including
import) of PFOS has halted or has been below the CDR reporting thresholds. Although PFOS is not
produced domestically or imported by the companies participating in the 2010/2015 PFOA Stewardship
Program, PFOS may still be produced domestically or imported below the CDR reporting thresholds by
companies not participating in the PFOA Stewardship Program.
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Exhibit 4-3: IUR Reported Annual Manufacture and Importation of PFOS in the
United States, 1986-2006 (pounds)
Reporting Cycle
1986
1990
1994
1998
2002
2006
Range of
Production
Volume
No Reports
No Reports
10,000-
500,000
No Reports
10,000-
500,000
No Reports
Source: USEPA, 2008
Toxics Release Inventory (TRI)
The EPA established TRI in 1987 in response to section 313 of the EPCRA. EPCRA section 313 requires
the reporting of annual information on toxic chemical releases from facilities that meet specific criteria.
This reported information is maintained in a database accessible through TRI Explorer (USEPA, 2023b).
Although TRI can provide a general idea of release trends, it has limitations. Not all facilities are required
to report all releases. Facilities are required to report releases if they manufacture, process, or
otherwise use a listed toxic chemical in quantities above the respective activity threshold. For PFOS, the
reporting threshold is 100 lbs. manufactured, processed, or otherwise used over the year. It should also
be noted that, as of this publication, quantities of PFOS at concentrations under 0.1 percent within
mixtures may be exempt from TRI reporting requirements. Reporting requirements have changed over
time (e.g., the chemical list has changed), so conclusions about temporal trends should be drawn with
caution. TRI data are meant to reflect releases and other waste management activities and should not
be used to estimate general public exposure to a chemical (USEPA, 2023b).
TRI data for PFOS are available for 2020 through 2022 (USEPA, 2023b). As shown in Exhibit 4-4, there
were 482 pounds of total on-site disposals and 362 pounds of total off-site disposals across all industries
in 2020. In 2021, a total of 16,308 on- and off-site releases were reported and in 2022, a total of 6,819
on- and off-site releases were reported. A total of five facilities from five states reported releases of
PFOS in 2022.
Exhibit 4-4: Environmental Releases of PFOS in the United States, 2020-2022
On-Site Releases (in pounds)
Year
Air
Emissions
Surface
Water
Discharges
Underground
Injection
Releases to
Land
Total Off-
Site
Releases
(in pounds)
Total On-
and Off-Site
Releases
(in pounds)
2020
0
1
5
476
362
844
2021
0
0
0
4,000
12,308
16,308
2022
0
0
0
443
6,376
6,819
Source: USEPA, 2023b
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4.1.1.2 Environmental Fate
The primary measures used by the EPA to assess mobility include (where available) Koc, log Kow, KH, water
solubility and vapor pressure. For PFOS, the log of the pKa is also important.
Modeling of atmospheric behavior at a vapor pressure of 0.002 mm Hg at 25 degrees C suggest that
PFOS will be present as a vapor if released to the atmosphere (NCBI, 2022b). PFOS can react with
photochemically produced hydroxyl radicals in the atmosphere to degrade (NCBI, 2022b). A half-life for
this reaction in air is estimated to be 115 days, based on a structure estimation method (NCBI, 2022b).
(Note that radical reactions typically proceed more rapidly than chemically- or microbially-mediated
degradation reactions in other environmental media such as water, soil, and/or sediment.) PFOS is not
expected to undergo direct photolysis (NCBI, 2022b).
Based on findings from laboratory studies, Zareitalabad et al. (2013) calculate an average log Koc of 3.0
±0.7, equivalent to a Koc of 1,000 ±5.0 L/kg, which suggests a propensity for PFOS to be mobilized to
ground water and surface water rather than to bind to suspended solids or sediments. The authors note
that field studies indicate a greater propensity for PFOS to bind to soil and sediment than the lab-
derived Koc values would predict.
Based on the vapor pressure, PFOS is not expected to volatilize from dry soil (NCBI, 2022b). With a pKa of
less than 1.0 (NCBI, 2022b), PFOS is expected to exist in its ionized form at typical environment pH
ranges of natural waters (NCBI, 2022b; Lange et al., 2006). Thus, volatilization from water at typical
environment pH is not expected (NCBI, 2022b).
PFOS is very stable chemically and is resistant to hydrolysis, photolysis, and biodegradation (NCBI,
2022b; Lange et al., 2006). Washington et al. (2010) found that PFOS had a modeled disappearance half-
life of 1.2 years in sludge-applied soils near Decatur, Alabama. Washington et al. (2010) noted that this
disappearance half-life is the time over which PFOS concentration in the surface soil was diminished by
half due to all environmental processes: these processes could potentially include uptake into plants
(c.f. Yoo et al., 2011), erosion, leaching, generation from precursors, and degradation. Washington et al.
(2010) posits that among these possible processes, leaching was likely a leading mode of loss. However,
the chemical stability of PFOS is much longer than this modeled disappearance half-life. Additionally,
labile PFAS precursors commonly present in sludge may degrade in soil settings, leading to ingrowth of
recalcitrant PFAS such as PFOS, PFOA, and related compounds (Wang et al., 2009; Martin et al., 2010;
Washington et al., 2014; Washington et al., 2015).
Under CCL 3, the EPA created scales4 to informally rank chemical contaminants' likely mobility
(understood as their tendency to partition to water rather than other media) and persistence as "high,"
"moderate," or "low" based on physical and chemical properties (see USEPA, 2021b and USEPA, 2009).
For PFOS, an estimated log Kow of 4.49, and a water solubility of 0.0032 mg/L at 25 degrees C predict a
low likelihood of partitioning to water. The water solubility of the potassium salt of PFOS, 570 mg/L,
which may be more indicative of the anionic form that occurs at typical environmental pH, predicts a
moderate likelihood of partitioning to water (certain properties can vary substantially for the acid and
salt forms of a given PFAS; for example, the water solubility of PFOS (acid form) and the potassium salt
of PFOS may vary by approximately five orders of magnitude, which can be seen in the two water
4 See Exhibit A.8 here: https://www.epa.gov/sites/default/files/2014-05/documents/ccl3 pccltoccl 08-31-
09 508.pdf
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solubility values above). The KH of <4.9E-09 atm-m3/mol predicts a high likelihood of partitioning to
water. NCBI (2022b) also lists a KH of 4.1E-04 atm-m3/mol, but this value was estimated from vapor
pressure and water solubility using EPISuite™. A Koc value of 1,000 ±5.0 L/kg predicts a moderate
likelihood of partitioning to water. A resistance to essentially all forms of degradation other than
atmospheric processes indicates high persistence.
4.2 PFOS Occurrence
This section presents data on the occurrence of PFOS in drinking water and ambient water in the United
States. The EPA is finalizing an MCLG of 0 ppt for PFOS. Under SDWA, the EPA must establish an
enforceable MCL, the maximum concentration of a contaminant that is allowed in PWSs, as close to the
MCLG as feasible, taking several factors into consideration, including analytical methods capable of
measuring the contaminant, available treatment technologies to remove the contaminant, and costs.
Based on these factors, the EPA is finalizing an MCL of 4.0 ppt for PFOS. Occurrence data from various
sources presented below are analyzed with respect to the MCL and two alternative MCLs for PFOS of 5.0
ppt and 10.0 ppt that the EPA evaluated under its HRRCA for the proposed rule. When possible,
estimates of the population exposed at concentrations above the MCL and alternative MCLs are
presented. Also, when possible, studies that are meant to be representative and studies that are
targeted at known or suspected sites of contamination are identified as such.
The drinking water analyses presented in this section were performed for UCMR 3 and select state data
sources. In addition, this section presents PFOS findings from occurrence analyses conducted by non-
EPA researchers. Chapter 10 describes the Bayesian hierarchical model used to extrapolate PFOS
occurrence to the nation and also points the reader to examine Cadwallader et al. (2022) for further
details.
For additional background information about data sources used to evaluate occurrence, please refer to
Chapter 2.
4.2.1 Occurrence in Drinking Water
Data sources reviewed by the agency for information on PFOS occurrence in drinking water included
UCMR 3, state drinking water monitoring programs, and the DoD PFAS drinking water testing, as well as
additional studies from the literature.
Note that there may be some overlap, as sources with different purposes and audiences may have
reported the same underlying data. UCMR 3 is a nationally representative data source. Other data
sources profiled in this section are considered "supplemental" sources. Also note that 29 PFAS, including
PFOS, are being monitored for under UCMR 5, that data collection effort is occurring from 2023 to 2025.
Analysis of partial UCMR 5 results (the first three quarters of data that were made available as of
February 2024) are discussed in section 11 of this document. The EPA notes that the UCMR 3 MRLfor
PFOS is higher than that utilized within the majority of state monitoring data and for the UCMR 5.
4.2.1.1 UCMR 3 Data
UCMR 3 monitoring, designed to provide nationally representative contaminant occurrence data, was
conducted from 2013 through 2015. UCMR 3 Assessment Monitoring occurrence data are available for
PFOS from all large and very large public water systems or PWSs (serving between 10,001 and 100,000
people and serving more than 100,000 people, respectively), plus a statistically representative national
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sample of 800 small PWSs (serving 10,000 people or fewer).5 Surface water and GWUDI sampling points
were monitored four times during the applicable year of monitoring, and ground water sample points
were monitored twice during the applicable year of monitoring. See USEPA (2012b) and USEPA (2019a)
for more information on the UCMR 3 study design and data analysis.
Exhibit 4-5 through Exhibit 4-7 provide an overview of PFOS occurrence results from the UCMR 3
Assessment Monitoring. Laboratories participating in UCMR 3 were required to report values at or
above MRLs defined by the EPA. The UCMR MRLs are not intended to represent the lowest achievable
measurement level an individual laboratory may achieve. Rather, the MRLs are established to ensure
reliable and consistent results from the array of laboratories needed for a national monitoring program
and are set based on the quantitation level capability of multiple commercial laboratories prior to
beginning each UCMR round. The MRL used for PFOS in the UCMR 3 survey was 40 ng/L (77 FR 26072;
USEPA, 2012b). Exhibit 4-5 presents a sample-level summary of the results. Exhibit 4-6 shows a
statistical summary of PFOS concentrations by system size and source water type (including the
minimum, 25th percentile, median, 75th percentile, 90th percentile, 99th percentile, and maximum).
Exhibit 4-7 shows system-level results for detections greater than or equal to the MRL.
A total of 36,972 finished water samples for PFOS were collected from 4,920 PWSs. PFOS was reported >
MRL of 40 ng/L in 0.79 percent of UCMR 3 samples. Reported PFOS concentrations for these results
ranged from 40 ng/L (the MRL) to 7,000 ng/L. Of 4,920 systems, 95 (1.9 percent of systems, serving 4.3
percent of the PWS-served population) reported at least one detection.
Exhibit 4-5: PFOS National Occurrence Measures Based on UCMR 3 Assessment
Monitoring Data - Summary of Samples
Source Water Type
Total # of
Samples
Samples with Detections
> MRL of 40 ng/L
Number
Percent
Small Systems (serving < 10,000 people)
Ground Water
1,853
2
0.11%
Surface Water
1,421
4
0.28%
All Small Systems
3,274
6
0.18%
Large Systems (serving 10,001 -100,000 people) — CENSUS
Ground Water
11,707
66
0.56%
Surface Water
14,860
138
0.93%
All Large Systems
26,567
204
0.77%
Very Large Systems (serving > 100,000 people) — CENSUS
Ground Water
2,020
29
1.44%
Surface Water
5,111
53
1.04%
All Very Large Systems
7,131
82
1.15%
All Systems
All Water Systems
36,972
292
0.79%
5 A total of 799 small systems submitted Assessment Monitoring results.
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Exhibit 4-6: PFOS Occurrence Data from UCMR 3 Assessment Monitoring - Summary of Reported Concentrations
Source Water Type
Concentration Value of Detections (in ng/L) > MRL of 40 ng/L
Minimum
25th percentile
Median
75th percentile
90th Percentile
99th Percentile
Maximum
Small Systems (serving < 10,000 people)
Ground Water
230
250
270
280
290
300
300
Surface Water
50
50
50
50
60
60
58.53
All Small Systems
50
50
60
190
270
300
300
Large Systems (serving 10,001 -100,000 people) — CENSUS
Ground Water
40
50
60
160
240
540
600
Surface Water
40
50
70
130
370
3,570
7,000
All Large Systems
40
50
60
140
280
1,290
7,000
Very Large Systems (serving > 100,000 people) — CENSUS
Ground Water
41
60
90
160
340
500
530
Surface Water
41
40
50
60
110
1350
1800
All Very Large
Systems
41
50
50
90
180
1,100
1,800
All Systems
All Water Systems
40
50
60
130
250
1,340
7,000
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Exhibit 4-7: PFOS National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data - Summary of
System and Population Served Data - Reported Detections
Source Water
Type
UCMR 3 Samples
Number With At Least
One Detection > MRL of
40 ng/L
Percent With At Least
One Detection > MRL of
40 ng/L
National Inventory
Percent of National
Inventory Included
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems (serving < 10,000 people)
Ground Water
527
1,498,845
1
536
0.19%
0.04%
55,700
38,730,597
0.95%
3.87%
Surface Water
272
1,250,215
3
22,363
1.10%
1.79%
9,728
20,007,917
2.80%
6.25%
All Small
Systems
799
2,749,060
4
22,899
0.50%
0.83%
65,428
58,738,514
1.22%
4.68%
Large Systems (serving 10,001 -100,000 people) — CENSUS
Ground Water
1,453
37,141,418
29
1,070,732
2.00%
2.88%
1,470
37,540,614
98.84%
98.94%
Surface Water
2,260
69,619,878
38
1,314,380
1.68%
1.89%
2,310
70,791,005
97.84%
98.35%
All Large
Systems
3,713
106,761,296
67
2,385,112
1.80%
2.23%
3,780
108,331,619
98.23%
98.55%
Very Large Systems (serving > 100,000 people) — CENSUS
Ground Water
68
16,355,951
9
4,739,185
13.24%
28.98%
68
16,355,951
100.00%
100.00%
Surface Water
340
115,158,260
15
3,279,997
4.41%
2.85%
343
120,785,622
99.13%
95.34%
All Very Large
Systems
408
131,514,211
24
8,019,182
5.88%
6.10%
411
137,141,573
99.27%
95.90%
All Systems
All Water
Systems
4,920
241,024,567
95
10,427,193
1.93%
4.33%
69,619
304,211,706
7.07%
79.23%
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Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
4.2.1.2 State Monitoring Data
In the development of the proposed and final NPDWR, the agency supplemented its UCMR 3 data with
more recent publicly available data collected by states. In general, these more recent state data were
collected using newer analytical methods and state results reflect lower reporting and detection limits
than those in the UCMR 3. The EPA downloaded publicly available monitoring data for PWSs from state
websites through May 2023. Drinking water occurrence data for PFOS were available from several
states, including Alabama, Arizona, California, Colorado, Delaware, Georgia, Idaho, Illinois, Indiana, Iowa,
Kentucky, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, New Hampshire, New
Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oregon, Pennsylvania, South
Carolina, Tennessee, Vermont, Virginia, West Virginia, and Wisconsin. Note that while some states did
have available raw water data as indicated in Exhibit 4-8, for the subsequent analyses the EPA only
evaluated finished water results.
Exhibit 4-8 provides a summary of the available state reported monitoring data for PFOS, including date
range and a description of coverage and representativeness (including whether monitoring was non-
targeted or targeted (i.e., monitoring in areas of known or potential PFAS contamination). A description
of those studies is also included in Exhibit 4-8. Within state reported data there may be overlap with
UCMR 3 results from 2013 - 2015, though the EPA notes that the large majority of the available state
data are from 2019 and later. In addition, the EPA excluded UCMR 3 results from the state data
whenever possible. State reporting thresholds are also provided, where available, in Exhibit 4-8. The EPA
notes that different states utilized various reporting thresholds when analyzing and presenting their
data, and for some states there were no clearly defined thresholds publicly provided; in these cases,
minimum detected concentrations reported may be indicative of reporting thresholds used. Further, for
some states, the thresholds varied when reporting results for the same analyte, as well as the laboratory
analyzing the data. For those states, a range of thresholds is provided. As shown in Exhibit 4-8, some
states reported at thresholds and/or presented data at concentrations below the EPA's final MCL and/or
PQL for PFOS. However, to present the best available occurrence information, the EPA collected and
evaluated the data based on the information as reported directly by the states and when conducting
data analyses incorporated individual state-specific reporting thresholds where possible. Additionally,
the EPA notes that the majority of the data were analyzed via an EPA-approved drinking water analytical
method.
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Exhibit 4-8: Summary of Available PFOS State Reported Monitoring Data
State
(Reference)
Date
Range
Type of Water Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
Alabama
(ADEM, 2023)
2013-
2022
Ground Water and
Surface Water -
Finished Water
Not reported
ADPH instructed water systems to carry out PFAS monitoring at all
PWSs not previously sampled during UCMR 3. In 2022, water systems
that had not been sampled since UCMR 3 were required to sample
between January and June 2022 using current analytical methods.
Only results that are above the MRL are posted online; thus, only
reported detections were available for use in the occurrence analyses.
Non-
Targeted
Arizona
(ADEQ, 2021;
ADEQ, 2023)
2016-
February
2021
Ground Water and
Surface Water -
Finished Water
Not reported
ADEQ made publicly available PFAS sampling data from systems
near the Luke Airforce Base. Finished water data were available from
two PWSs.
Targeted
2018-
June 2021
Ground Water and
Surface Water - Raw
and Finished Water
1.6-2
ADEQ presents a PFAS Interactive Data Map that displays the results
of testing conducted by ADEQ since 2018 at PWSs across Arizona.
Targeted
California
(CADDW, 2023)
2013-
April 2023
Ground Water and
Surface Water - Raw,
Finished, and
Unknown Water
0.002 - 40
The EPA reviewed the California PFOS data available online through
April 2023. Finished water data were available from approximately 120
PWSs. For this analysis, the EPA only included results that were
explicitly marked as being from treated water. Sampling in California is
ongoing.
Targeted
Colorado
(CDPHE,
2018;CDPHE,
2020)
2013-
2017
Surface Water
(Finished Water) and
Drinking Water
Distribution Samples
2-40
Data available from 28 "drinking water distribution zones" (one or more
per PWS) in targeted sampling efforts at a known contaminated
aquifer region. Data were collected by El Paso County Public Health,
local water districts and utilities, and the CDPHE.
Targeted
2020
Ground Water and
Surface Water - Raw
and Finished Water
1.6-2.4
CDPHE offered free testing to PWSs serving communities, schools,
and workplaces and also to fire districts with wells. Approximately
50% of PWSs in Colorado participated in the 2020 PFAS sampling
project. Data included in this report were collected in March through
May of 2020.
Non-
Targeted
Delaware
(DE ODW, 2021)
2019-
2020
Surface Water -
Finished and Unknown
Water
2
Sampling of finished drinking water data between January 2019 and
October 2020 from one public water system. The EPA notes that the
data no longer appear to be publicly available through the Drinking
Water Watch link.
Targeted
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State
(Reference)
Date
Range
Type of Water Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
Georgia
(GA EPD, 2020)
2020
Surface Water - Raw,
Finished, and
Unknown Water
18
The EPA and the GA EPD conducted joint sampling of the City of
Summerville's drinking water sources and finished drinking water in
January 2020.
Targeted
Idaho
(Idaho DEQ,
2023)
2021 -
April 2023
Ground Water -
Finished and Unknown
Water
0.5-1
Sampling of finished drinking water data between available on the
state's Drinking Water Watch website.
Not
specified
Illinois
(IL EPA, 2023)
2020-
May 2023
Ground Water and
Surface Water - Raw
and Finished Water
1.7-8
In 2020, the IL EPA initiated a statewide investigation into the
prevalence and occurrence of PFAS in finished drinking water at
1,749 community water supplies across Illinois. The EPA
reviewed finished drinking water data collected between September
2020 and May 2023 that were available on the state's Drinking Water
Watch website. Limited PFOS data were also available from 2017.
Sampling in Illinois is ongoing.
Non-
Targeted
Indiana (IDEM,
2023)
2021 -
January
2023
Ground Water and
Surface Water - Raw,
Finished, and
Unknown Water
2
Beginning in February 2021, the IDEM facilitated PFAS monitoring at
all CWSs throughout the state of Indiana. Samples were to be
collected at all raw water (i.e., wells and intakes) and finished (after
treatment) water points in a CWS's supply to evaluate the statewide
occurrence of PFAS compounds in CWS across the state and
determine the efficacy of conventional drinking water treatment for
PFAS.
Non-
Targeted
Iowa
(IA DNR, 2023)
2021 -
April 2023
Ground Water and
Surface Water - Raw
and Finished Water
1.7-4
In January 2020, the Iowa DNR developed an Action Plan to protect
the health of Iowa residents and the environment from PFAS. Data
were downloaded from the PFAS Sampling Interactive Dashboard and
Map.
Targeted
Kentucky
(KYDEP, 2019)
2019
Ground Water and
Surface Water -
Finished Water
3.24
Sampling of finished drinking water data between June and October
2019. Under this sampling effort, data are available from 81
community public DWTPs, representing 74 PWSs, and serving more
than 2.4 million people.
Non-
Targeted
Maine
(Maine DEP,
2020; Maine
DHHS, 2023)
2013-
2020
Drinking Water - Raw,
Finished, and
Unknown Water
1.78-40
In March 2019, the Maine PFAS Task Force was created to review the
extent of PFAS contamination in Maine. Finished water results
collected from 2013 through 2020 have been collected at 23 locations
throughout the state. Data may include results from public and private
finished drinking water sources. Sampling in Maine is ongoing.
Targeted
2021 -
January
2023
Ground Water and
Surface Water -
Finished Water
2
The EPA reviewed the finished water data reported to the Maine CDC
Drinking Water Program as compliance samples since June 2021 and
Non-
Targeted
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State
(Reference)
Date
Range
Type of Water Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
processed in the database as of 3/10/2023. Sampling in Maine is
ongoing.
Maryland
(MDE, 2021;
MDE, 2022a;
MDE, 2022b)
2020-
2022
Ground Water and
Surface Water - Raw
and Finished Water
2
In 2020, MDE initiated a project to identify potential sources of PFAS
in Maryland and to prioritize water sources for PFAS sampling. The
EPA reviewed the finished water results from the first three phases of
MDE's Public Water System study for the occurrence of PFAS in State
drinking water sources. Under Phase 1 (September 2020 - February
2021), sites were selected for priority sampling based on MDE's
evaluation of potential relative risk for PFAS exposure through drinking
water. Under Phase 2 (March 2021 - May 2021), MDE conducted
sampling at sites that were selected based on their geological setting
and proximity to potential sources of PFAS. Under Phase 3 (August
2021- June 2022), MDE tested the remaining CWSs in the state.
Targeted
(Phase 1,
Phase 2);
Non-
Targeted
(Phase
3)
Massachusetts
(MA EE A, 2023)
2016-April
2023
Ground Water and
Surface Water - Raw
and Finished Water
0.44-19
The EPA reviewed the finished water data available online through
April 2023. Data were available from 1,330 PWSs. Sampling in
Massachusetts is ongoing.
Targeted
Michigan
(Michigan EGLE,
2023)
2020-
March
2023
Ground Water and
Surface Water -
Finished Water
2
The Michigan EGLE developed MCLs for seven PFAS compounds in
Michigan, which took effect in August 2020. The EPA reviewed
available PFOS finished compliance monitoring results through March
2023. Sampling in Michigan is ongoing.
Non-
Targeted
Minnesota
(MDH, 2023)
2020-
2023
Ground Water and
Surface Water -
Finished Water
Not reported
Through the Statewide PFAS Monitoring Project, MDH is testing
CWSs across the state for PFAS. The EPA reviewed finished water
data through MDH's Interactive Dashboard for PFAS Testing in
Drinking Water.
Non-
Targeted
Missouri
(Missouri DNR,
2018; Missouri
DNR, 2023)
2016-
2017
Ground Water and
Surface Water - Raw
and Finished Water
Not reported
The Missouri DNR conducted sampling of finished drinking water data
between September 2016 and February 2017. Under this sampling
effort, 30 finished water samples were collected from 15 PWSs.
Targeted
2022-
2023
Ground Water and
Surface Water - Raw
and Finished Water
Not reported
The EPA reviewed the finished water data available online from
Missouri DNR's "PFAS Viewer Tool" which identifies the location of
voluntary sampling for PFAS in public drinking water systems in
Missouri. The EPA reviewed finished water data collected from
approximately 125 PWSs from 2022 through 2023. Limited data were
also available from 2013 through 2017.
Non-
Targeted
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State
(Reference)
Date
Range
Type of Water Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
New Hampshire
(NHDES, 2021)
2016-
May 2021
Ground Water and
Surface Water - Raw
and Finished Water
2-5
The EPA reviewed the New Hampshire PFOS data available online
through May 2021. Finished water data were available from more than
500 PWSs. Sampling in New Hampshire is ongoing.
Non-
Targeted
New Jersey
(NJDEP, 2023)
2019-
May 2023
Ground Water and
Surface Water - Raw,
Finished, and
Unknown Water
0.018-8.9
Statewide sampling of finished drinking water data was available from
2019-2023. The EPA reviewed data available online through May
2023 from more than 1,100 PWSs. Sampling in New Jersey is
ongoing.
Non-
Targeted
New Mexico
(NMED, 2019)
2016
Ground Water - Raw
and Finished Water
Not reported
NMED, Department of Health and the U.S. Air Force conducted testing
at public drinking water supplies at or around Cannon Air Force Base
up to 2019.
Targeted
New York
(NYDOH, 2022)
2017-
2022
Ground Water and
Surface Water - Raw,
Finished, and
Unknown Water
0.000000001
-2020
The EPA reviewed finished water data voluntarily provided by the state
to the EPA. Data were available from nearly 2,600 PWSs from 2017
through 2022. Limited data were also available from 2016.
Non-
Targeted
North Carolina
(NCDEQ, 2021;
NCDEQ, 2023)
2017-
2019
Finished and unknown
water
Not reported
NCDEQ and the Department of Health and Human Services
investigated the presence of HFPO-DA and other PFAS in the Cape
Fear River in June 2017. Monthly results were also collected from five
water treatment plants on the Cape Fear River. Data were available
from June 2017 through October 2019. Only results above the DL
were reported; thus, only reported detections were available for use in
the occurrence analyses.
Targeted
September
2022-
November
2022
Ground Water and
Surface Water - Raw,
Finished, and
Unknown Water
Not reported
In late 2022, NCDEQ performed three months of sampling at 50
municipal and county water systems identified in the 2019 PFAS
Testing Network study with PFOA/PFOS detections above the MRL
indicated by the 2022 EPA interim health advisories.
Targeted
North Dakota
(NDDEQ, 2019;
NDDEQ, date
unknown;
NDDEQ, date
unknown)
2018,
2020,
2021
Ground Water and
Surface Water - Raw
and Finished Water
Not reported
NDDEQ published a 2018, a 2020, and a 2021 survey report of North
Dakota Statewide PFAS Presence/Absence results. The first phase of
sampling in October of 2018 included raw and finished water from
seven drinking WTPs that were chosen based on either the population
served or proximity to an industrial site. The second sampling effort in
October of 2020 sought to determine if there was a PFAS presence in
a representative portion of the state's public water supply. In 2021,
sampling conducted as part of the third phase of the survey focused
on drinking water sites not evaluated in the first two surveys.
Targeted
(2018);
Non-
Targeted
(2020);
Non-
Targeted
(2021)
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State
(Reference)
Date
Range
Type of Water Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
Ohio
(Ohio EPA,
2023)
December
2019-
December
2021
Ground Water and
Surface Water - Raw
and Finished Water
5
The Ohio EPA coordinated sampling of raw and finished drinking
water from PWSs throughout the state. The EPA reviewed the finished
water data available online through December 2021. During this
timeframe, data were available from 1,479 PWSs.
Non-
Targeted
Oregon
(OHA-DWS,
2022)
2021 - July
2022
Ground Water and
Surface Water -
Finished Water
10.1 -12.4
OHA conducted a PFAS drinking water monitoring project in 2021 at
PWSs in Oregon identified as at risk due to their proximity to a known
or suspected PFAS use or contamination site. The EPA reviewed the
finished water data from more than 140 PWSs.
Targeted
Pennsylvania
(PADEP, 2019)
2019
Ground Water and
Surface Water -
Finished Water
1.9
A PFAS Sampling Plan was developed to test PWSs across the state.
Finished water data were collected for 87 PWSs in 2019.
Targeted
Pennsylvania
(PADEP, 2021)
2020-
March
2021
Ground Water and
Surface Water -
Finished Water
1.7-4
Beginning in 2020 and running through March of 2021, finished water
data were collected by more than 340 PWSs.
Targeted
South Carolina
(SCDHEC, 2020;
SCDHEC, 2023)
2017-
March
2023
Ground Water and
Surface Water -Raw
and Finished Water
2
The EPA reviewed PFAS sampling results collected by the South
Carolina Bureau of Water for community drinking water systems. Data
were available from 300 PWSs.
Non-
Targeted
Tennessee
(TDEC, 2023)
2019
Surface Water - Raw
and Finished Water
Not reported
In 2019, Metro Water Services conducted a voluntary sampling of
Nashville's drinking water systems for PFAS. Their stated goal was to
go above and beyond current federal and state monitoring
requirements to understand the potential presence of PFAS in
Nashville's drinking water.
Non-
Targeted
Vermont
(VT DEC, 2023)
2019 -April
2023
Ground Water and
Surface Water -Raw,
Finished, and
Unknown Water
2
The Vermont Water Supply Rule required all CWSs and NTNCWSs to
sample for PFAS. The EPA reviewed finished water data available
online from July 2019 - April 2023 from approximately 560 PWSs.
Sampling in Vermont is ongoing.
Non-
Targeted
Virginia
(VDH ODW,
2021)
2021
Ground Water and
Surface Water - Raw
and Finished Water
3.5
The Virginia ODW, in conjunction with VA PFAS work group, designed
the sample study to prioritize sites for measuring PFAS concentrations
in drinking water and major sources of water and generate statewide
occurrence data.
Targeted
/ Non-
Targeted
West Virginia
(WV DHHR.
2023)
2017-
2019
Ground Water and
Surface Water - Raw,
Finished, and
Unknown Water
Not reported
The EPA reviewed finished drinking water data collected from 2017-
2019 that were available on the state's Drinking Water Watch website.
PFOS and PFOA results were available from one PWS.
Not
specified
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State
(Reference)
Date
Range
Type of Water Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
Wisconsin
(Wl DNR, 2023)
2022-
April 2023
Ground Water and
Surface Water - Raw,
Finished, and
Unknown Water
Not reported
The EPA reviewed the finished water data available online from 2022 -
2023. Data were available from nearly 250 PWSs. On Aug. 1, 2022,
the state's safe drinking water code ch. NR 809 Wis. Adm. Code was
revised to include standards for PFOA and PFOS. Sampling in
Wisconsin is ongoing.
Non-
Targeted
A summary of state reported monitoring data from public water systems for PFOS is presented in Exhibit 4-9 through Exhibit 4-12. As noted
above, some of the monitoring data from each state are limited and may not be representative of occurrence in the state. In addition, states
have varying reporting thresholds, as described earlier and indicated in the first column of Exhibit 4-9. For states with available reporting
thresholds, only detected concentrations greater than the reporting thresholds were counted as detections. For states that did not provide
reporting thresholds, the EPA included all detected concentrations reported in the count of detections. Overall, state reported detected
concentrations ranged from 0.22 ppt (North Carolina) to 650 ppt (Massachusetts). Note that for a small number of systems, population served
information could not be identified. These systems were included in the counts and analysis presented in Exhibit 4-11; however, no associated
population served was included in the counts and analysis presented in Exhibit 4-12.
Exhibit 4-9: PFOS State Reported Drinking Water Occurrence Data - Summary of Finished Water Samples
State
(Reporting
Threshold)
Source Water
Type
Total #
Samples
All Detections1
Detections
> 4.0 ppt
Detections
> 5.0 ppt
Detections
> 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Alabama1
(Not reported)
Ground Water
-
73
-
53
-
51
-
27
-
Surface Water
-
176
-
117
-
103
-
77
-
Total
--
249
-
170
-
154
--
104
-
Arizona, ADEQ
Sampling
(1.6-2 ppt)
Ground Water
24
12
50.0%
9
37.5%
8
33.3%
6
25.0%
Surface Water
2
1
50.0%
1
50.0%
0
0.0%
0
0.0%
Total
26
13
50.0%
10
38.5%
8
30.8%
6
23.1%
Arizona, Luke Air
Force Base
(Not reported)
Ground Water
264
76
28.8%
60
22.7%
47
17.8%
28
10.6%
Surface Water
16
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
280
76
27.1%
60
21.4%
47
16.8%
28
10.0%
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State
(Reporting
Threshold)
Source Water
Total #
All Detections1
Detections
> 4.0 ppt
Detections
> 5.0 ppt
Detections
> 10.0 ppt
Type
Samples
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Ground Water
1,898
481
25.3%
339
17.9%
289
15.2%
204
10.7%
California
Surface Water
4,134
670
16.2%
423
10.2%
362
8.8%
201
4.9%
(0.002 - 40 ppt)
Unknown
29
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
6,061
1,151
19.0%
762
12.6%
651
10.7%
405
6.7%
Colorado
Distribution
(Finished)
96
38
39.6%
36
37.5%
34
35.4%
33
34.4%
(2013 -2017)
(2-40 ppt)
Surface Water
(Finished)
11
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
107
38
35.5%
36
33.6%
34
31.8%
33
30.8%
Colorado (2020)
(1.6-2.4 ppt)
Ground Water
339
37
10.9%
17
5.0%
12
3.5%
2
0.6%
Surface Water
244
23
9.4%
11
4.5%
8
3.3%
1
0.4%
Total
583
60
10.3%
28
4.8%
20
3.4%
3
0.5%
Delaware
(2 ppt)
Ground Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
34
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
34
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Georgia
(18 ppt)
Ground Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
2
1
50.0%
1
50.0%
1
50.0%
1
50.0%
Total
2
1
50.0%
1
50.0%
1
50.0%
1
50.0%
Idaho
(0.5 -1 ppt)
Ground Water
18
1
5.6%
0
0.0%
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
18
1
5.6%
0
0.0%
0
0.0%
0
0.0%
Illinois
(1.7-8 ppt)
Ground Water
1,831
180
9.8%
94
5.1%
47
2.6%
20
1.1%
Surface Water
302
126
41.7%
31
10.3%
18
6.0%
3
1.0%
Total
2,133
306
14.3%
125
5.9%
65
3.0%
23
1.1%
Indiana
(2 ppt)
Ground Water
422
6
1.4%
1
0.2%
1
0.2%
0
0.0%
Surface Water
59
2
3.4%
0
0.0%
0
0.0%
0
0.0%
Total
481
8
1.7%
1
0.2%
1
0.2%
0
0.0%
Iowa
Ground Water
154
46
29.9%
32
20.8%
22
14.3%
10
6.5%
(1.7-4 ppt)
Surface Water
65
11
16.9%
3
4.6%
0
0.0%
0
0.0%
96
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water
Type
Total #
Samples
All Detections1
Detections
> 4.0 ppt
Detections
> 5.0 ppt
Detections
> 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Total
219
57
26.0%
35
16.0%
22
10.0%
10
4.6%
Kentucky
(3.24 ppt)
Ground Water
33
4
12.1%
1
3.0%
1
3.0%
1
3.0%
Surface Water
48
29
60.4%
3
6.3%
2
4.2%
0
0.0%
Total
81
33
40.7%
4
4.9%
3
3.7%
1
1.2%
Maine (PFAS Task
Force)2
(1.78-40 ppt)
Ground Water
9
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
3
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Unknown
75
12
16.0%
7
9.3%
6
8.0%
5
6.7%
Total
87
12
13.8%
7
8.0%
6
6.9%
5
5.7%
Maine
(Compliance)
(2 ppt)
Ground Water
646
99
15.3%
52
8.0%
42
6.5%
12
1.9%
Surface Water
62
2
3.2%
1
1.6%
0
0.0%
0
0.0%
Total
708
101
14.3%
53
7.5%
42
5.9%
12
1.7%
Maryland
(Phase 1)
(2 ppt)
Ground Water
70
27
38.6%
14
20.0%
12
17.1%
3
4.3%
Surface Water
76
30
39.5%
19
25.0%
17
22.4%
8
10.5%
Total
146
57
39.0%
33
22.6%
29
19.9%
11
7.5%
Maryland
(Phase 2)
(2 ppt)
Ground Water
9
3
33.3%
3
33.3%
2
22.2%
2
22.2%
Surface Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
9
3
33.3%
3
33.3%
2
22.2%
2
22.2%
Maryland
(Phase 3)
(2 ppt)
Ground Water
88
17
19.3%
14
15.9%
10
11.4%
8
9.1%
Surface Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
88
17
19.3%
14
15.9%
10
11.4%
8
9.1%
Massachusetts
(0.44-19 ppt)
Ground Water
7,215
3,394
47.0%
2,197
30.5%
1,665
23.1%
521
7.2%
Surface Water
2,130
1,038
48.7%
553
26.0%
399
18.7%
85
4.0%
Total
9,345
4,432
47.4%
2,750
29.4%
2,064
22.1%
606
6.5%
Michigan
(2 ppt)
Ground Water
10,007
394
3.9%
156
1.6%
123
1.2%
72
0.7%
Surface Water
519
89
17.1%
5
1.0%
5
1.0%
1
0.2%
Unknown
164
6
3.7%
5
3.0%
5
3.0%
4
2.4%
Total
10,690
489
4.6%
166
1.6%
133
1.2%
77
0.7%
97
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water
Type
Total #
Samples
All Detections1
Detections
> 4.0 ppt
Detections
> 5.0 ppt
Detections
> 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Missouri,
2016-2017
(Not reported)
Unknown
29
12
41.4%
0
0.0%
0
0.0%
0
0.0%
Total
29
12
41.4%
0
0.0%
0
0.0%
0
0.0%
Missouri,
2022 - 2023
(Not reported)
Ground Water
213
19
8.9%
8
3.8%
6
2.8%
0
0.0%
Surface Water
26
3
11.5%
0
0.0%
0
0.0%
0
0.0%
Total
239
22
9.2%
8
3.3%
6
2.5%
0
0.0%
New Hampshire
(2 - 5 ppt)
Ground Water
1,656
465
28.1%
248
15.0%
199
12.0%
80
4.8%
Surface Water
157
30
19.1%
6
3.8%
1
0.6%
1
0.6%
Unknown
1
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
1,814
495
27.3%
254
14.0%
200
11.0%
81
4.5%
New Jersey
(0.018-8.9 ppt)
Ground Water
12,715
4,947
38.9%
3,343
26.3%
2,742
21.6%
1,050
8.3%
Surface Water
3,168
1,549
48.9%
878
27.7%
687
21.7%
188
5.9%
Unknown
16
6
37.5%
2
12.5%
1
6.3%
0
0.0%
Total
15,899
6,502
40.9%
4,223
26.6%
3,430
21.6%
1,238
7.8%
New Mexico
(Not reported)
Ground Water
2
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
2
0
0.0%
0
0.0%
0
0.0%
0
0.0%
New York
(0.000000001 -
2,020 ppt)
Ground Water
5,516
1,171
21.2%
576
10.4%
438
7.9%
160
2.9%
Surface Water
1,520
403
26.5%
63
4.1%
47
3.1%
8
0.5%
Unknown
21
2
9.5%
0
0.0%
0
0.0%
0
0.0%
Total
7,057
1,576
22.3%
639
9.1%
485
6.9%
168
2.4%
North Carolina,
Cape Fear River1
(Not Reported)
Unknown
-
372
-
347
-
347
-
339
-
Total
-
372
-
347
-
347
-
339
-
North Carolina,
2022
(Not Reported)
Ground Water
21
6
28.6%
6
28.6%
6
28.6%
4
19.0%
Surface Water
141
129
91.5%
96
68.1%
85
60.3%
34
24.1%
Total
162
135
83.3%
102
63.0%
91
56.2%
38
23.5%
Ground Water
4
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
3
3
100.0%
0
0.0%
0
0.0%
0
0.0%
98
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
North Dakota,
2018 (Not
reported)
Source Water
Type
Total #
Samples
All Detections1
Detections
> 4.0 ppt
Detections
> 5.0 ppt
Detections
> 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Total
7
3
42.9%
0
0.0%
0
0.0%
0
0.0%
North Dakota,
2020 (Not
reported)
Ground Water
42
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
9
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
51
0
0.0%
0
0.0%
0
0.0%
0
0.0%
North Dakota,
2021 (Not
reported)
Ground Water
56
2
3.6%
0
0.0%
0
0.0%
0
0.0%
Surface Water
7
1
14.3%
0
0.0%
0
0.0%
0
0.0%
Total
63
3
4.8%
0
0.0%
0
0.0%
0
0.0%
Ohio3
(5 ppt)
Ground Water
1,775
97
5.5%
97
5.5%
96
5.4%
58
3.3%
Surface Water
170
16
9.4%
16
9.4%
16
9.4%
9
5.3%
Total
1,945
113
5.8%
113
5.8%
112
5.8%
67
3.4%
Oregon
(10.1 -12.4 ppt)
Ground Water
131
5
3.8%
5
3.8%
5
3.8%
5
3.8%
Surface Water
29
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
160
5
3.1%
5
3.1%
5
3.1%
5
3.1%
Pennsylvania,
2019 (1.9 ppt)
Ground Water
75
14
18.7%
8
10.7%
7
9.3%
2
2.7%
Surface Water
21
11
52.4%
8
38.1%
6
28.6%
1
4.8%
Total
96
25
26.0%
16
16.7%
13
13.5%
3
3.1%
Pennsylvania,
2021 (1.7-4 ppt)
Ground Water
314
76
24.2%
57
18.2%
45
14.3%
20
6.4%
Surface Water
98
27
27.6%
20
20.4%
18
18.4%
5
5.1%
Total
412
103
25.0%
77
18.7%
63
15.3%
25
6.1%
South Carolina
(2 ppt)
Ground Water
572
41
7.2%
18
3.1%
16
2.8%
10
1.7%
Surface Water
197
94
47.7%
51
25.9%
32
16.2%
5
2.5%
Total
769
135
17.6%
69
9.0%
48
6.2%
15
2.0%
Tennessee
(Not reported)
Ground Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
2
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
2
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Vermont
Ground Water
1,463
192
13.1%
110
7.5%
90
6.2%
35
2.4%
99
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
(2 ppt)
Source Water
Type
Total #
Samples
All Detections1
Detections
> 4.0 ppt
Detections
> 5.0 ppt
Detections
> 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Surface Water
102
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
1,565
192
12.3%
110
7.0%
90
5.8%
35
2.2%
Virginia
(3.5 ppt)
Ground Water
5
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
36
7
19.4%
6
16.7%
4
11.1%
0
0.0%
Total
41
7
17.1%
6
14.6%
4
9.8%
0
0.0%
West Virginia
(Not reported)
Ground Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
31
24
77.4%
17
54.8%
16
51.6%
12
38.7%
Total
31
24
77.4%
17
54.8%
16
51.6%
12
38.7%
Wisconsin
(Not reported)
Ground Water
728
147
20.2%
35
4.8%
29
4.0%
22
3.0%
Surface Water
54
40
74.1%
0
0.0%
0
0.0%
0
0.0%
Total
782
187
23.9%
35
4.5%
29
3.7%
22
2.8%
1 Only reported detections were available in this state's dataset.
2 Reported data from Maine may include results from public and private finished drinking water sources. Based on available state data information, the EPA could
not verify PWSIDs for all included samples.
3 The reporting threshold for Ohio is 5 ppt; thus, any occurrence estimates relative to the final MCL of 4.0 ppt only include results greater than or equal to 5 ppt.
Exhibit 4-10: PFOS State Reported Drinking Water Occurrence Data - Summary of Detected Concentrations
State
(Reporting Threshold)
Source Water Type
Concentration Value of Detections (ppt)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Alabama1
(Not reported)
Ground Water
1.2
7.70
22.4
36.2
47
Surface Water
1
7.40
25.5
74.5
120
Total
1
7.60
24.3
65.8
120
Arizona, ADEQ Sampling
(1.6-2 ppt)
Ground Water
1.9
10.8
53.3
58.5
59
Surface Water
4.4
4.4
4.4
4.4
4.4
Total
1.9
8.50
52.6
58.4
59
Arizona, Luke Air Force Base
Ground Water
2.1
8.55
19.5
51.0
78
100
-------
EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting Threshold)
(Not reported)
Source Water Type
Concentration Value of Detections (ppt)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Surface Water
-
-
-
-
-
Total
2.1
8.55
19.5
51.0
78
California
(0.002 - 40 ppt)
Ground Water
1.7
8.10
21.0
45.0
74
Surface Water
0.4
5.40
31.9
58.9
250
Unknown
-
-
-
-
-
Total
0.4
5.90
26.0
56.5
250
Colorado (2013-2017)
(2-40 ppt)
Distribution (Finished)
2.3
60.0
103
192
210
Surface Water (Finished)
-
-
-
-
-
Total
2.3
60.0
103
192
210
Colorado (2020)
(1.6-2.4 ppt)
Ground Water
1.7
3.80
8.46
15.5
18
Surface Water
2
4.00
6.40
10.2
11
Total
1.7
3.90
7.31
13.9
18
Delaware
(2 ppt)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
--
--
--
--
-
Georgia
(18 ppt)
Ground Water
-
-
-
-
-
Surface Water
49
49
49
49
49
Total
49
49
49
49
49
Idaho
(0.5 -1 ppt)
Ground Water
1.33
1.33
1.33
1.33
1.33
Surface Water
-
-
-
-
-
Total
1.33
1.33
1.33
1.33
1.33
Illinois
(1.7-8 ppt)
Ground Water
1.9
4.10
11.0
75.8
150
Surface Water
2
2.60
5.40
11.0
15
Total
1.9
3.45
7.95
18.0
150
Indiana
(2 ppt)
Ground Water
2.451
3.35
4.80
5.52
5.6
Surface Water
2.233
2.57
2.83
2.89
2.9
Total
2.233
2.95
4.48
5.49
5.6
101
-------
EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting Threshold)
Source Water Type
Concentration Value of Detections (ppt)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Iowa
(1.7-4 ppt)
Ground Water
2.1
5.00
15.5
52.3
59
Surface Water
2
3.30
4.40
4.85
4.9
Total
2
4.60
14.4
50.6
59
Kentucky
(3.24 ppt)
Ground Water
1
2.43
14.1
18.4
18.9
Surface Water
1.01
1.40
4.11
7.54
8.35
Total
1
1.51
4.43
15.5
18.9
Maine (PFAS Task Force)2
(1.78-40 ppt)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Unknown
2.52
7.50
79.7
99.5
102
Total
2.52
7.50
79.7
99.5
102
Maine (Compliance)
(2 ppt)
Ground Water
2
4.18
11.4
32.6
138
Surface Water
2.83
3.67
4.33
4.48
4.5
Total
2
4.18
11.3
30.4
138
Maryland (Phase 1)
(2 ppt)
Ground Water
2.05
4.42
10.8
234
235
Surface Water
2.24
6.45
24.1
107
136.03
Total
2.05
5.07
21.0
233
235
Maryland (Phase 2)
(2 ppt)
Ground Water
4.7
21.2
30.8
32.9
33.18
Surface Water
-
-
-
-
-
Total
4.7
21.2
30.8
32.9
33.18
Maryland (Phase 3)
(2 ppt)
Ground Water
2.17
10.0
51.7
87.1
93.1
Surface Water
-
-
-
-
-
Total
2.17
10.0
51.7
87.1
93.1
Massachusetts
(0.44-19 ppt)
Ground Water
1.78
4.99
13.4
40.1
650
Surface Water
1.7
4.21
9.43
140
270
Total
1.7
4.80
12.0
41.3
650
Michigan
(2 ppt)
Ground Water
2
4.00
20.0
73.2
150
Surface Water
2
2.20
3.42
8.36
11
102
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting Threshold)
Source Water Type
Concentration Value of Detections (ppt)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Unknown
3
11.0
14.5
15.9
16
Total
2
3.00
17.0
70.4
150
Minnesota
(Not reported)
Ground Water
0.68
-
-
-
27
Surface Water
-
-
-
-
-
Total
0.68
--
--
--
27
Missouri, 2016 - 2017
(Not reported)
Unknown
0.24
0.500
1.03
1.19
1.21
Total
0.24
0.500
1.03
1.19
1.21
Missouri, 2022 - 2023
(Not reported)
Ground Water
0.46
3.50
6.16
7.14
7.3
Surface Water
0.6
0.720
0.984
1.04
1.05
Total
0.46
3.40
6.08
7.11
7.3
New Hampshire
(2 - 5 ppt)
Ground Water
2
4.37
16.1
193
261
Surface Water
2.12
2.76
4.41
14.7
18.8
Unknown
-
-
-
-
-
Total
2
4.15
15.9
190
261
New Jersey
(0.018-8.9 ppt)
Ground Water
0.5
5.60
16.9
78.0
359
Surface Water
0.68
4.50
11.0
22.7
64
Unknown
3.2
3.56
4.85
5.26
5.3
Total
0.5
5.30
15.0
59.6
359
New Mexico
(Not reported)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
--
--
-
-
-
New York
(0.000000001 -2,020 ppt)
Ground Water
0.24
3.94
11.8
34.2
389
Surface Water
0.4
2.68
5.58
14.8
47.5
Unknown
2.4
2.68
2.90
2.95
2.96
Total
0.24
3.30
10.6
32.7
389
North Carolina, Cape Fear
River1
(Not Reported)
Unknown
0.22
40.0
40.0
79.3
80
Total
0.22
40.0
40.0
79.3
80
103
-------
EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting Threshold)
Source Water Type
Concentration Value of Detections (ppt)
Minimum
Median
90th Percentile
99th Percentile
Maximum
North Carolina, 2022
(Not Reported)
Ground Water
8.15
13.8
20.1
21.6
21.8
Surface Water
0.739
6.54
17.7
38.6
41
Total
0.739
6.58
18.6
38.4
41
North Dakota, 2018
(Not reported)
Ground Water
-
-
-
-
-
Surface Water
0.37
0.450
0.970
1.09
1.1
Total
0.37
0.450
0.970
1.09
1.1
North Dakota, 2020
(Not reported)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
--
--
-
-
-
North Dakota, 2021
(Not reported)
Ground Water
0.805
1.14
1.40
1.46
1.47
Surface Water
1.21
1.21
1.21
1.21
1.21
Total
0.805
1.21
1.42
1.46
1.47
Ohio3
(5 ppt)
Ground Water
5
12.1
25.3
49.9
66
Surface Water
5.3
10.9
15.4
18.5
19
Total
5
12.1
24.0
49.2
66
Oregon
(10.1 -12.4 ppt)
Ground Water
13.2
16.3
17.9
18.5
18.6
Surface Water
-
-
-
-
-
Total
13.2
16.3
17.9
18.5
18.6
Pennsylvania, 2019
(1.9 ppt)
Ground Water
2.6
4.80
12.4
83.6
94
Surface Water
1.9
6.00
8.40
12.5
13
Total
1.9
5.10
11.3
74.8
94
Pennsylvania, 2021
(1.7-4 ppt)
Ground Water
1.8
6.35
13.2
93.4
187.1
Surface Water
2
7.10
11.8
19.1
19.8
Total
1.8
6.50
13.0
61.4
187.1
South Carolina
(2 ppt)
Ground Water
2
3.80
17.0
19.0
19
Surface Water
2
4.30
8.77
16.4
22
Total
2
4.20
11.0
19.0
22
104
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting Threshold)
Source Water Type
Concentration Value of Detections (ppt)
Minimum
Median
90th Percentile
99th Percentile
Maximum
Tennessee
(Not reported)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
--
--
--
--
-
Vermont
(2 ppt)
Ground Water
2
4.60
16.1
234
262
Surface Water
-
-
-
-
-
Total
2
4.60
16.1
234
262
Virginia
(3.5 ppt)
Ground Water
-
-
-
-
-
Surface Water
3.9
5.10
6.68
7.06
7.1
Total
3.9
5.10
6.68
7.06
7.1
West Virginia
(Not reported)
Ground Water
-
-
-
-
-
Surface Water
0.41
10.4
39.7
45.9
47
Total
0.41
10.4
39.7
45.9
47
Wisconsin
(Not reported)
Ground Water
0.29
1.59
15.2
31.7
47.4
Surface Water
0.31
1.58
2.10
2.30
2.3
Total
0.29
1.59
11.5
30.6
47.4
Note: With limited exceptions, calculated concentration values (i.e., median, 90th percentile and 99th percentile concentrations) were rounded to three significant
figures for consistent presentation across the datasets and may not indicate exact laboratory precision.
1 Only reported detections were available in this state's dataset.
2 Reported data from Maine may include results from public and private finished drinking water sources. Based on available state data information, the EPA
could not verify PWSIDs for all included samples.
Exhibit 4-11: PFOS State Reported Drinking Water Occurrence Data - Summary of Systems with Finished Water
Data
State
(Reporting
Threshold)
Source Water
Type
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections > 4.0 ppt
Systems with
Detections > 5.0 ppt
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Alabama1
Ground Water
-
31
-
24
-
22
-
15
-
105
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
(Not reported)
Source Water
Type
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections > 4.0 ppt
Systems with
Detections > 5.0 ppt
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Surface Water
-
57
-
40
-
31
-
19
-
Total
-
88
-
64
-
53
-
34
-
Arizona, ADEQ
Sampling
(1.6-2 ppt)
Ground Water
6
2
33.3%
2
33.3%
2
33.3%
2
33.3%
Surface Water
1
1
100.0%
1
100.0%
0
0.0%
0
0.0%
Total
7
3
42.9%
3
42.9%
2
28.6%
2
28.6%
Arizona, Luke Air
Force Base
(Not reported)
Ground Water
1
1
100.0%
1
100.0%
1
100.0%
1
100.0%
Surface Water
1
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
2
1
50.0%
1
50.0%
1
50.0%
1
50.0%
Arizona (All
Systems)2
(Not reported)
Ground Water
6
2
33.3%
2
33.3%
2
33.3%
2
33.3%
Surface Water
2
1
50.0%
1
50.0%
0
0.0%
0
0.0%
Total
8
3
37.5%
3
37.5%
2
25.0%
2
25.0%
California
(0.002 - 40 ppt)
Ground Water
43
16
37.2%
14
32.6%
14
32.6%
12
27.9%
Surface Water
79
32
40.5%
24
30.4%
23
29.1%
18
22.8%
Unknown
1
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
123
48
39.0%
38
30.9%
37
30.1%
30
24.4%
Colorado
(2013 -2017)
(2-40 ppt)
Distribution
(Finished)
23
12
52.2%
12
52.2%
12
52.2%
12
52.2%
Surface Water
(Finished)
5
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
28
12
42.9%
12
42.9%
12
42.9%
12
42.9%
Colorado (2020)
(1.6-2.4 ppt)
Ground Water
221
31
14.0%
14
6.3%
10
4.5%
2
0.9%
Surface Water
176
19
10.8%
8
4.5%
6
3.4%
1
0.6%
Total
397
50
12.6%
22
5.5%
16
4.0%
3
0.8%
Delaware
(2 ppt)
Ground Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
1
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
1
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Georgia
(18 ppt)
Ground Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
1
1
100.0%
1
100.0%
1
100.0%
1
100.0%
106
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water
Type
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections > 4.0 ppt
Systems with
Detections > 5.0 ppt
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Total
1
1
100.0%
1
100.0%
1
100.0%
1
100.0%
Idaho
(0.5 -1 ppt)
Ground Water
10
1
10.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
10
1
10.0%
0
0.0%
0
0.0%
0
0.0%
Illinois
(1.7-8 ppt)
Ground Water
899
42
4.7%
21
2.3%
17
1.9%
4
0.4%
Surface Water
97
31
32.0%
9
9.3%
6
6.2%
1
1.0%
Total
996
73
7.3%
30
3.0%
23
2.3%
5
0.5%
Indiana
(2 ppt)
Ground Water
341
5
1.5%
1
0.3%
1
0.3%
0
0.0%
Surface Water
31
2
6.5%
0
0.0%
0
0.0%
0
0.0%
Total
372
7
1.9%
1
0.3%
1
0.3%
0
0.0%
Iowa
(1.7-4 ppt)
Ground Water
90
9
10.0%
7
7.8%
6
6.7%
3
3.3%
Surface Water
26
5
19.2%
1
3.8%
0
0.0%
0
0.0%
Total
116
14
12.1%
8
6.9%
6
5.2%
3
2.6%
Kentucky
(3.24 ppt)
Ground Water
30
4
13.3%
1
3.3%
1
3.3%
1
3.3%
Surface Water
44
26
59.1%
3
6.8%
2
4.5%
0
0.0%
Total
74
30
40.5%
4
5.4%
3
4.1%
1
1.4%
Maine (PFAS Task
Force)3
(1.78-40 ppt)
Ground Water
7
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
1
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Unknown
10
5
50.0%
5
50.0%
4
40.0%
3
30.0%
Total
18
5
27.8%
5
27.8%
4
22.2%
3
16.7%
Maine
(Compliance)
(2 ppt)
Ground Water
593
92
15.5%
47
7.9%
38
6.4%
10
1.7%
Surface Water
53
2
3.8%
1
1.9%
0
0.0%
0
0.0%
Total
646
94
14.6%
48
7.4%
38
5.9%
10
1.5%
Maine (All
Systems)2
(1.78-40 ppt)
Ground Water
593
92
15.5%
47
7.9%
38
6.4%
10
1.7%
Surface Water
53
2
3.8%
1
1.9%
0
0.0%
0
0.0%
Unknown
10
5
50.0%
5
50.0%
4
40.0%
3
30.0%
Total
656
99
15.1%
53
8.1%
42
6.4%
13
2.0%
107
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water
Type
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections > 4.0 ppt
Systems with
Detections > 5.0 ppt
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Maryland
(Phase 1)
(1 ppt)
Ground Water
30
13
43.3%
7
23.3%
7
23.3%
2
6.7%
Surface Water
36
13
36.1%
8
22.2%
8
22.2%
5
13.9%
Total
66
26
39.4%
15
22.7%
15
22.7%
7
10.6%
Maryland
(Phase 2)
(2 ppt)
Ground Water
6
3
50.0%
3
50.0%
2
33.3%
2
33.3%
Surface Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
6
3
50.0%
3
50.0%
2
33.3%
2
33.3%
Maryland
(Phase 3)
(2 ppt)
Ground Water
63
9
14.3%
9
14.3%
5
7.9%
5
7.9%
Surface Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
63
9
14.3%
9
14.3%
5
7.9%
5
7.9%
Maryland
(All Systems)2
(2 ppt)
Ground Water
99
25
25.3%
19
19.2%
14
14.1%
9
9.1%
Surface Water
36
13
36.1%
8
22.2%
8
22.2%
5
13.9%
Total
135
38
28.1%
27
20.0%
22
16.3%
14
10.4%
Massachusetts
(0.44-19 ppt)
Ground Water
1,208
348
28.8%
221
18.3%
185
15.3%
97
8.0%
Surface Water
122
69
56.6%
40
32.8%
35
28.7%
15
12.3%
Total
1,330
417
31.4%
261
19.6%
220
16.5%
112
8.4%
Michigan
(2 ppt)
Ground Water
2,370
81
3.4%
36
1.5%
32
1.4%
14
0.6%
Surface Water
84
22
26.2%
3
3.6%
3
3.6%
1
1.2%
Unknown
54
2
3.7%
1
1.9%
1
1.9%
1
1.9%
Total
2,508
105
4.2%
40
1.6%
36
1.4%
16
0.6%
Minnesota
(Not reported)
Ground Water
561
55
9.8%
8
1.4%
7
1.2%
2
0.4%
Surface Water
16
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
577
55
9.5%
8
1.4%
7
1.2%
2
0.3%
Missouri,
2016-2017
(Not reported)
Unknown
15
7
46.7%
0
0.0%
0
0.0%
0
0.0%
Total
15
7
46.7%
0
0.0%
0
0.0%
0
0.0%
Missouri,
2022 - 2023
(Not reported)
Ground Water
105
9
8.6%
3
2.9%
2
1.9%
0
0.0%
Surface Water
20
2
10.0%
0
0.0%
0
0.0%
0
0.0%
Total
125
11
8.8%
3
2.4%
2
1.6%
0
0.0%
108
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water
Type
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections > 4.0 ppt
Systems with
Detections > 5.0 ppt
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
New Hampshire
(2 - 5 ppt)
Ground Water
529
180
34.0%
103
19.5%
85
16.1%
38
7.2%
Surface Water
30
9
30.0%
4
13.3%
1
3.3%
1
3.3%
Unknown
1
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
560
189
33.8%
107
19.1%
86
15.4%
39
7.0%
New Jersey
(0.018-8.9 ppt)
Ground Water
1,012
459
45.4%
302
29.8%
260
25.7%
135
13.3%
Surface Water
107
81
75.7%
53
49.5%
45
42.1%
24
22.4%
Unknown
4
1
25.0%
1
25.0%
1
25.0%
0
0.0%
Total
1,123
541
48.2%
356
31.7%
306
27.2%
159
14.2%
New Mexico
(Not reported)
Ground Water
2
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
2
0
0.0%
0
0.0%
0
0.0%
0
0.0%
New York
(0.000000001 -
2,020 ppt)
Ground Water
1,601
395
24.7%
177
11.1%
137
8.6%
53
3.3%
Surface Water
277
99
35.7%
24
8.7%
17
6.1%
4
1.4%
Unknown
9
2
22.2%
0
0.0%
0
0.0%
0
0.0%
Total
1,887
496
26.3%
201
10.7%
154
8.2%
57
3.0%
North Carolina,
Cape Fear River1
(Not Reported)
Unknown
-
5
-
5
-
5
-
5
-
Total
-
5
-
5
-
5
-
5
-
North Carolina,
2022
(Not Reported)
Ground Water
7
2
28.6%
2
28.6%
2
28.6%
2
28.6%
Surface Water
43
41
95.3%
31
72.1%
29
67.4%
11
25.6%
Total
50
43
86.0%
33
66.0%
31
62.0%
13
26.0%
North Dakota, 2018
(Not reported)
Ground Water
4
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
3
3
100.0%
0
0.0%
0
0.0%
0
0.0%
Total
7
3
42.9%
0
0.0%
0
0.0%
0
0.0%
North Dakota, 2020
(Not reported)
Ground Water
41
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
9
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
50
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Ground Water
56
2
3.6%
0
0.0%
0
0.0%
0
0.0%
109
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
North Dakota, 2021
(Not reported)
Source Water
Type
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections > 4.0 ppt
Systems with
Detections > 5.0 ppt
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Surface Water
7
1
14.3%
0
0.0%
0
0.0%
0
0.0%
Total
63
3
4.8%
0
0.0%
0
0.0%
0
0.0%
North Dakota (All
Systems)2
(Not reported)
Ground Water
95
2
2.1%
0
0.0%
0
0.0%
0
0.0%
Surface Water
17
4
23.5%
0
0.0%
0
0.0%
0
0.0%
Total
112
6
5.4%
0
0.0%
0
0.0%
0
0.0%
Ohio4
(5 ppt)
Ground Water
1,372
24
1.7%
24
1.7%
24
1.7%
18
1.3%
Surface Water
107
5
4.7%
5
4.7%
5
4.7%
3
2.8%
Total
1,479
29
2.0%
29
2.0%
29
2.0%
21
1.4%
Oregon
(10.1 -12.4 ppt)
Ground Water
116
3
2.6%
3
2.6%
3
2.6%
3
2.6%
Surface Water
27
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
143
3
2.1%
3
2.1%
3
2.1%
3
2.1%
Pennsylvania, 2019
(1.9 ppt)
Ground Water
71
12
16.9%
6
8.5%
5
7.0%
2
2.8%
Surface Water
16
8
50.0%
6
37.5%
5
31.3%
1
6.3%
Total
87
20
23.0%
12
13.8%
10
11.5%
3
3.4%
Pennsylvania, 2021
(1.7-4 ppt)
Ground Water
269
65
24.2%
51
19.0%
39
14.5%
20
7.4%
Surface Water
73
20
27.4%
15
20.5%
14
19.2%
4
5.5%
Total
342
85
24.9%
66
19.3%
53
15.5%
24
7.0%
Pennsylvania
(All Systems)2
(1.7 -4 ppt)
Ground Water
270
68
25.2%
51
18.9%
39
14.4%
20
7.4%
Surface Water
73
22
30.1%
16
21.9%
15
20.5%
5
6.8%
Total
343
90
26.2%
67
19.5%
54
15.7%
25
7.3%
South Carolina
(2 ppt)
Ground Water
234
33
14.1%
16
6.8%
14
6.0%
8
3.4%
Surface Water
66
47
71.2%
29
43.9%
22
33.3%
4
6.1%
Total
300
80
26.7%
45
15.0%
36
12.0%
12
4.0%
Tennessee
(Not reported)
Ground Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
1
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
1
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Vermont
Ground Water
526
38
7.2%
20
3.8%
16
3.0%
7
1.3%
110
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
(2 ppt)
Source Water
Type
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections > 4.0 ppt
Systems with
Detections > 5.0 ppt
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Surface Water
38
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
564
38
6.7%
20
3.5%
16
2.8%
7
1.2%
Virginia
(3.5 ppt)
Ground Water
5
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
20
6
30.0%
5
25.0%
4
20.0%
0
0.0%
Total
25
6
24.0%
5
20.0%
4
16.0%
0
0.0%
West Virginia
(Not reported)
Ground Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
1
1
100.0%
1
100.0%
1
100.0%
1
100.0%
Total
1
1
100.0%
1
100.0%
1
100.0%
1
100.0%
Wisconsin
(Not reported)
Ground Water
217
51
23.5%
12
5.5%
10
4.6%
8
3.7%
Surface Water
22
19
86.4%
0
0.0%
0
0.0%
0
0.0%
Total
239
70
29.3%
12
5.0%
10
4.2%
8
3.3%
1 Only reported detections were available in this state's dataset.
2 The "All Systems" counts represent a summary of all unique systems across multiple sampling efforts within the state. For some states (e.g., CO, MO, NC), the
EPA could not verify this number due to the sample site ID reporting.
3 Reported data from Maine may include results from public and private finished drinking water sources. Based on available state data information, the EPA could
not verify PWSIDs for all included samples.
4 The reporting threshold for Ohio is 5 ppt; thus, any occurrence estimates relative to the final MCL of 4.0 ppt only include results greater than or equal to 5 ppt.
Exhibit 4-12: PFOS State Reported Drinking Water Occurrence Data - Summary of Population Served by Systems
with Finished Water Data
State
(Reporting
Threshold)
Source Water
Type
Total
Population
Served by
Systems
Population Served by
Systems with
Detections
Population Served by
Systems with
Detections > 4.0 ppt
Population Served by
Systems with
Detections > 5.0 ppt
Population Served by
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Alabama1
(Not reported)
Ground Water
-
427,167
-
265,818
-
251,631
-
145,653
-
Surface Water
-
2,378,180
-
1,139,921
-
929,142
-
286,273
-
Total
-
2,805,347
-
1,405,739
-
1,180,773
-
431,926
-
in
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water
Type
Total
Population
Served by
Systems
Population Served by
Systems with
Detections
Population Served by
Systems with
Detections > 4.0 ppt
Population Served by
Systems with
Detections > 5.0 ppt
Population Served by
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Arizona, ADEQ
Sampling
(1.6-2 ppt)
Ground Water
94,712
55,535
58.6%
55,535
58.6%
55,535
58.6%
55,535
58.6%
Surface Water
50,001
50,001
100.0%
50,001
100.0%
0
0.0%
0
0.0%
Total
144,713
105,536
72.9%
105,536
72.9%
55,535
38.4%
55,535
38.4%
Arizona, Luke Air
Force Base
(Not reported)
Ground Water
50,770
50,770
100.0%
50,770
100.0%
50,770
100.0%
50,770
100.0%
Surface Water
234,766
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
285,536
50,770
17.8%
50,770
17.8%
50,770
17.8%
50,770
17.8%
Arizona (All
Systems)2
(Not reported)
Ground Water
94,712
55,535
58.6%
55,535
58.6%
55,535
58.6%
55,535
58.6%
Surface Water
284,767
50,001
17.6%
50,001
17.6%
0
0.0%
0
0.0%
Total
379,479
105,536
27.8%
105,536
27.8%
55,535
14.6%
55,535
14.6%
California
(0.002 - 40 ppt)
Ground Water
1,098,122
692,464
63.1%
647,726
59.0%
647,726
59.0%
536,584
48.9%
Surface Water
13,505,270
4,330,203
32.1%
3,672,550
27.2%
3,633,656
26.9%
2,961,439
21.9%
Unknown
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
14,603,392
5,022,667
34.4%
4,320,276
29.6%
4,281,382
29.3%
3,498,023
24.0%
Colorado
(2013 -2017)3
(2-40 ppt)
Distribution
(Finished)
-
-
-
-
-
-
-
-
-
Surface Water
(Finished)
-
-
-
-
-
-
-
-
-
Total
-
-
-
-
-
--
-
-
-
Colorado (2020)
(1.6-2.4 ppt)
Ground Water
261,162
82,186
31.5%
38,715
14.8%
37,359
14.3%
302
0.1%
Surface Water
4,191,774
843,845
20.1%
136,028
3.2%
132,578
3.2%
4,495
0.1%
Total
4,452,936
926,031
20.8%
174,743
3.9%
169,937
3.8%
4,797
0.1%
Delaware
(2 ppt)
Ground Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
231,114
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
231,114
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Georgia
(18 ppt)
Ground Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
9,993
9,993
100.0%
9,993
100.0%
9,993
100.0%
9,993
100.0%
Total
9,993
9,993
100.0%
9,993
100.0%
9,993
100.0%
9,993
100.0%
Idaho
Ground Water
81,985
303
0.4%
0
0.0%
0
0.0%
0
0.0%
112
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
(0.5 -1 ppt)
Source Water
Type
Total
Population
Served by
Systems
Population Served by
Systems with
Detections
Population Served by
Systems with
Detections > 4.0 ppt
Population Served by
Systems with
Detections > 5.0 ppt
Population Served by
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Surface Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
81,985
303
0.4%
0
0.0%
0
0.0%
0
0.0%
Illinois
(1.7-8 ppt)
Ground Water
2,916,219
397,990
13.6%
195,498
6.7%
192,087
6.6%
64,406
2.2%
Surface Water
4,628,949
1,150,863
24.9%
269,340
5.8%
227,657
4.9%
1,595
0.0%
Total
7,545,168
1,548,853
20.5%
464,838
6.2%
419,744
5.6%
66,001
0.9%
Indiana
(2 ppt)
Ground Water
545,838
15,732
2.9%
1,758
0.3%
1,758
0.3%
0
0.0%
Surface Water
97,448
5,768
5.9%
0
0.0%
0
0.0%
0
0.0%
Total
643,286
21,500
3.3%
1,758
0.3%
1,758
0.3%
0
0.0%
Iowa
(1.7-4 ppt)
Ground Water
491,495
151,869
30.9%
88,143
17.9%
88,038
17.9%
5,934
1.2%
Surface Water
987,522
338,155
34.2%
85,797
8.7%
0
0.0%
0
0.0%
Total
1,479,017
490,024
33.1%
173,940
11.8%
88,038
6.0%
5,934
0.4%
Kentucky
(3.24 ppt)
Ground Water
171,212
72,019
42.1%
6,798
4.0%
6,798
4.0%
6,798
4.0%
Surface Water
1,922,023
1,453,530
75.6%
105,914
5.5%
42,977
2.2%
0
0.0%
Total
2,093,235
1,525,549
72.9%
112,712
5.4%
49,775
2.4%
6,798
0.3%
Maine (PFAS
Task Force)3 4
(1.78-40 ppt)
Ground Water
3,995
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
21,808
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Unknown
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
25,803
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Maine
(Compliance)
(2 ppt)
Ground Water
274,866
69,753
25.4%
39,942
14.5%
38,379
14.0%
3,073
1.1%
Surface Water
464,453
12,365
2.7%
3,115
0.7%
0
0.0%
0
0.0%
Total
739,319
82,118
11.1%
43,057
5.8%
38,379
5.2%
3,073
0.4%
Maine (All
Systems)23
(1.78-40 ppt)
Ground Water
274,866
69,753
25.4%
39,942
14.5%
38,379
14.0%
3,073
1.1%
Surface Water
464,453
12,365
2.7%
3,115
0.7%
0
0.0%
0
0.0%
Unknown
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
739,319
82,118
11.1%
43,057
5.8%
38,379
5.2%
3,073
0.4%
Maryland
(Phase 1)
Ground Water
384,007
68,126
17.7%
61,816
16.1%
61,816
16.1%
13,350
3.5%
Surface Water
4,059,154
3,717,211
91.6%
94,394
2.3%
94,394
2.3%
64,053
1.6%
113
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
(1 ppt)
Source Water
Type
Total
Population
Served by
Systems
Population Served by
Systems with
Detections
Population Served by
Systems with
Detections > 4.0 ppt
Population Served by
Systems with
Detections > 5.0 ppt
Population Served by
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Total
4,443,161
3,785,337
85.2%
156,210
3.5%
156,210
3.5%
77,403
1.7%
Maryland
(Phase 2)
(2 ppt)
Ground Water
3,896
315
8.1%
315
8.1%
230
5.9%
230
5.9%
Surface Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
3,896
315
8.1%
315
8.1%
230
5.9%
230
5.9%
Maryland
(Phase 3)
(2 ppt)
Ground Water
41,063
3,138
7.6%
3,138
7.6%
2,380
5.8%
2,380
5.8%
Surface Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
41,063
3,138
7.6%
3,138
7.6%
2,380
5.8%
2,380
5.8%
Maryland
(All Systems)2
(2 ppt)
Ground Water
428,966
71,579
16.7%
65,269
15.2%
64,426
15.0%
15,960
3.7%
Surface Water
4,059,154
3,717,211
91.6%
94,394
2.3%
94,394
2.3%
64,053
1.6%
Total
4,488,120
3,788,790
84.4%
159,663
3.6%
158,820
3.5%
80,013
1.8%
Massachusetts
(0.44-19 ppt)
Ground Water
1,828,934
1,235,488
67.6%
975,530
53.3%
847,476
46.3%
400,766
21.9%
Surface Water
5,860,701
2,050,074
35.0%
1,109,099
18.9%
886,464
15.1%
551,731
9.4%
Total
7,689,635
3,285,562
42.7%
2,084,629
27.1%
1,733,940
22.5%
952,497
12.4%
Michigan3
(2 ppt)
Ground Water
1,945,734
312,213
16.0%
220,902
11.4%
219,910
11.3%
6,897
0.4%
Surface Water
1,314,601
631,716
48.1%
55,087
4.2%
55,087
4.2%
8,184
0.6%
Unknown
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
3,260,335
943,929
29.0%
275,989
8.5%
274,997
8.4%
15,081
0.5%
Minnesota
(Not reported)
Ground Water
2,752,594
1,015,561
36.9%
57,612
2.1%
52,892
1.9%
7,881
0.3%
Surface Water
1,106,268
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
3,858,862
1,015,561
26.3%
57,612
1.5%
52,892
1.4%
7,881
0.2%
Missouri,
2016-20173
(Not reported)
Unknown
-
-
-
-
-
-
-
-
-
Total
-
-
-
-
-
-
-
-
-
Missouri,
2022 - 2023
(Not reported)
Ground Water
257,420
35,399
13.8%
3,549
1.4%
2,447
1.0%
0
0.0%
Surface Water
425,658
20,613
4.8%
0
0.0%
0
0.0%
0
0.0%
Total
683,078
56,012
8.2%
3,549
0.5%
2,447
0.4%
0
0.0%
New Hampshire
(2 - 5 ppt)
Ground Water
267,029
150,228
56.3%
117,670
44.1%
88,836
33.3%
42,925
16.1%
Surface Water
476,367
148,257
31.1%
51,507
10.8%
6,131
1.3%
6,131
1.3%
114
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water
Type
Total
Population
Served by
Systems
Population Served by
Systems with
Detections
Population Served by
Systems with
Detections > 4.0 ppt
Population Served by
Systems with
Detections > 5.0 ppt
Population Served by
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Unknown
10
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
743,406
298,485
40.2%
169,177
22.8%
94,967
12.8%
49,056
6.6%
New Jersey
(0.018-8.9 ppt)
Ground Water
2,485,837
1,185,337
47.7%
901,937
36.3%
790,511
31.8%
633,615
25.5%
Surface Water
5,794,947
5,031,191
86.8%
4,079,848
70.4%
3,604,820
62.2%
2,480,425
42.8%
Unknown
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
8,280,784
6,216,528
75.1%
4,981,785
60.2%
4,395,331
53.1%
3,114,040
37.6%
New Mexico3
(Not reported)
Ground Water
-
-
-
-
-
-
-
-
-
Surface Water
-
-
-
-
-
-
-
-
-
Total
-
-
-
-
-
--
-
-
-
New York
(0.000000001 -
2,020 ppt)
Ground Water
2,109,118
938,685
44.5%
469,275
22.2%
438,891
20.8%
152,686
7.2%
Surface Water
3,850,284
1,765,447
45.9%
407,968
10.6%
106,987
2.8%
4,710
0.1%
Unknown
1,089
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
5,960,491
2,704,132
45.4%
877,243
14.7%
545,878
9.2%
157,396
2.6%
North Carolina,
Cape Fear
River13
(Not Reported)
Unknown
-
-
-
-
-
-
-
-
-
Total
-
-
-
-
-
-
-
-
-
North Carolina,
2022
(Not Reported)
Ground Water
26,914
3,620
13.5%
3,620
13.5%
3,620
13.5%
3,620
13.5%
Surface Water
2,649,927
2,643,626
99.8%
1,806,794
68.2%
1,806,794
68.2%
1,067,028
40.3%
Total
2,676,841
2,647,246
98.9%
1,810,414
67.6%
1,810,414
67.6%
1,070,648
40.0%
North Dakota,
2018 (Not
reported)
Ground Water
67,981
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
250,518
250,518
100.0%
0
0.0%
0
0.0%
0
0.0%
Total
318,499
250,518
78.7%
0
0.0%
0
0.0%
0
0.0%
North Dakota,
2020 (Not
reported)
Ground Water
68,280
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
57,469
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
125,749
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Ground Water
113,623
15,671
13.8%
0
0.0%
0
0.0%
0
0.0%
Surface Water
194,121
4,284
2.2%
0
0.0%
0
0.0%
0
0.0%
115
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
North Dakota,
2021 (Not
reported)
Source Water
Type
Total
Population
Served by
Systems
Population Served by
Systems with
Detections
Population Served by
Systems with
Detections > 4.0 ppt
Population Served by
Systems with
Detections > 5.0 ppt
Population Served by
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Total
307,744
19,955
6.5%
0
0.0%
0
0.0%
0
0.0%
North Dakota
(All Systems)2
(Not reported)
Ground Water
181,514
15,671
8.6%
0
0.0%
0
0.0%
0
0.0%
Surface Water
324,007
254,802
78.6%
0
0.0%
0
0.0%
0
0.0%
Total
505,521
270,473
53.5%
0
0.0%
0
0.0%
0
0.0%
Ohio5
(5 ppt)
Ground Water
2,883,252
202,301
7.0%
202,301
7.0%
202,301
7.0%
155,606
5.4%
Surface Water
6,215,644
194,156
3.1%
194,156
3.1%
194,156
3.1%
52,449
0.8%
Total
9,098,896
396,457
4.4%
396,457
4.4%
396,457
4.4%
208,055
2.3%
Oregon
(10.1 -12.4 ppt)
Ground Water
114,194
279
0.2%
279
0.2%
279
0.2%
279
0.2%
Surface Water
125,239
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
239,433
279
0.1%
279
0.1%
279
0.1%
279
0.1%
Pennsylvania,
2019 (1.9 ppt)
Ground Water
162,825
36,798
22.6%
25,588
15.7%
22,406
13.8%
5,693
3.5%
Surface Water
431,370
225,466
52.3%
138,966
32.2%
87,966
20.4%
45,013
10.4%
Total
594,195
262,264
44.1%
164,554
27.7%
110,372
18.6%
50,706
8.5%
Pennsylvania,
2021 (1.7-4 ppt)
Ground Water
471,651
190,979
40.5%
150,193
31.8%
120,915
25.6%
87,988
18.7%
Surface Water
4,296,097
1,383,930
32.2%
1,073,662
25.0%
1,069,198
24.9%
112,694
2.6%
Total
4,767,748
1,574,909
33.0%
1,223,855
25.7%
1,190,113
25.0%
200,682
4.2%
Pennsylvania
(All Systems)2
(1.7-4 ppt)
Ground Water
471,891
191,719
40.6%
150,193
31.8%
120,915
25.6%
87,988
18.6%
Surface Water
4,296,097
1,470,430
34.2%
1,124,662
26.2%
1,073,662
25.0%
157,707
3.7%
Total
4,767,988
1,662,149
34.9%
1,274,855
26.7%
1,194,577
25.1%
245,695
5.2%
South Carolina
(2 ppt)
Ground Water
485,992
17,569
3.6%
4,399
0.9%
4,268
0.9%
3,893
0.8%
Surface Water
2,499,980
1,675,562
67.0%
1,347,102
53.9%
933,419
37.3%
211,385
8.5%
Total
2,985,972
1,693,131
56.7%
1,351,501
45.3%
937,687
31.4%
215,278
7.2%
Tennessee
(Not reported)
Ground Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
2,551
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
2,551
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Vermont
Ground Water
211,357
7,061
3.3%
3,029
1.4%
2,754
1.3%
1,304
0.6%
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State
(Reporting
Threshold)
(2 ppt)
Source Water
Type
Total
Population
Served by
Systems
Population Served by
Systems with
Detections
Population Served by
Systems with
Detections > 4.0 ppt
Population Served by
Systems with
Detections > 5.0 ppt
Population Served by
Systems with
Detections > 10.0 ppt
Number
Percent
Number
Percent
Number
Percent
Number
Percent
Surface Water
174,473
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Total
385,830
7,061
1.8%
3,029
0.8%
2,754
0.7%
1,304
0.3%
Virginia
(3.5 ppt)
Ground Water
2,975
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
4,839,373
2,000,972
41.3%
1,841,772
38.1%
1,688,772
34.9%
0
0.0%
Total
4,842,348
2,000,972
41.3%
1,841,772
38.0%
1,688,772
34.9%
0
0.0%
West Virginia
(Not reported)
Ground Water
0
0
0.0%
0
0.0%
0
0.0%
0
0.0%
Surface Water
15,652
15,652
100.0%
15,652
100.0%
15,652
100.0%
15,652
100.0%
Total
15,652
15,652
100.0%
15,652
100.0%
15,652
100.0%
15,652
100.0%
Wisconsin
(Not reported)
Ground Water
1,514,437
880,722
58.2%
131,753
8.7%
62,883
4.2%
52,619
3.5%
Surface Water
1,333,737
1,290,335
96.7%
0
0.0%
0
0.0%
0
0.0%
Total
2,848,174
2,171,057
76.2%
131,753
4.6%
62,883
2.2%
52,619
1.8%
1 Only reported detections were available in this state's dataset.
2 The "All Systems" counts represent a summary of all unique systems across multiple sampling efforts within the state.
3 There were some instances where the population served by a system could not be identified. Thus, there are systems with detections but no associated
population served by those systems with detections.
4 Reported data from Maine may include results from public and private finished drinking water sources. Based on available state data information, the EPA could
not verify PWSIDs for all included samples.
5 The reporting threshold for Ohio is 5 ppt; thus, any occurrence estimates relative to the final MCL of 4.0 ppt only include results greater than or equal to 5 ppt.
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4.2.1.3 Additional Secondary Source Water and Drinking Water Studies
Boone et al. (2019) measured 17 PFAS in both source and treated water from 25 DWTPs in the United
States. The results indicated that only five of the sampling locations demonstrated a significant
difference in PFAS concentration between the source and treated water. The median concentration of
PFOS in source water was 2.28 ng/L and 1.62 ng/L in treated water. PFOS was detected in 80 percent of
treated drinking water samples (Boone et al., 2019).
Post et al. (2013) re-evaluated PFOA, PFOS, and PFC occurrence data in drinking water systems
throughout New Jersey to update previous PFAS research in the area from 2006. The EPA notes that
PFCs is a term that some researchers use to refer to the group of chemicals that includes PFOA, PFOS,
and other PFAS. PFCs were found in 70 percent of PWSs sampled at concentrations ranging from 5-174
ng/L. PFOS was detected in 30 percent of samples at a maximum concentration of 43 ng/L. Post et al.
(2013) found that multiple PFCs are commonly detected in raw water from New Jersey PWSs, with even
higher levels found near industrial sources.
McMahon et al. (2022) collected samples from aquifer systems in the eastern United States in 2019 to
evaluate PFAS occurrence in ground water used as a source of drinking water. The study found that 14
of the 24 analyzed PFAS were detected in ground water samples. Furthermore, at least one PFAS was
detected in 54 percent of the ground water samples and two or more PFAS were detected in 47 percent
of the ground water samples. In the public supply and domestic wells, 60 and 20 percent of the samples,
respectively, had at least one PFAS detection. Two or more PFAS were detected in 53 percent of the
public-supply wells and 10 percent of domestic wells. The six PFAS outlined in the EPA's UCMR 3
program (i.e., PFBS, PFHxS, PFOS, PFHpA, PFOA, and PFNA) were the most detected PFAS in the study's
samples. PFOA and PFOS were the two most frequently detected PFAS sampled. PFOS was detected in
30 percent of the 254 samples; 27 percent of samples were reported detections greater than 4 ng/L
(McMahon et al., 2022).
As part of a joint study by the EPA and USGS to assess human exposure to contaminants of emerging
concern, water samples were collected from 25 DWTPs in 24 states (Glassmeyer et al., 2017).
Participation in the study was voluntary, and candidate locations were selected based on nomination by
the EPA and USGS regional personnel and DWTP self-nomination as well as consideration of high
wastewater contribution and the availability of pharmaceutical concentration data. Final sample
locations were chosen to represent a wide range of geography, diversity in disinfectant type used, and a
range of production volumes. Phase I of the study (2007) analyzed a subset of contaminants and sites to
test experimental design; PFOS was not included in Phase 1. During Phase II of the study (2010-2012),
samples were collected from ground water and surface water sources and treated drinking water from
25 DWTPs and analyzed for PFOS occurrence. The LCMRL for PFOS was equal to 0.13 ng/L. PFOS was
detected in 88 percent of the 25 source water samples and 80 percent of the 25 treated drinking water
samples. The maximum detected concentrations in source water and treated water were 48.3 ng/L and
46.9 ng/L, respectively.
Reyes (2021) conducted a ground water-quality study to describe the occurrence and distribution of
PFAS in the Columbia aquifer public water-supply wells in the Delaware Coastal Plain region in 2018.
One or more PFAS were detected in 16 of the sampled wells with as many as 8 different PFAS detected
in a single sample. PFOA was most frequently detected out of the total PFAS detected during the study
(47 percent), followed by perfluorohexanoic acid (PFHxA) (33 percent), and PFOS and PFHxS, both
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detected at 27 percent. PFOS was detected in 8 of the 30 public water-supply wells sampled in the
study. The maximum PFOS concentration detected was 59 ng/L.
4.2.2 Other Data
4.2.2.1 Department of Defense (DoD) Drinking Water Sampling
The DoD conducted sampling of off-base drinking water located in "covered areas" (i.e., areas that are
adjacent to and down gradient from a military installation) to identify potential impacts of PFAS
resulting from DoD activities. Sampling was conducted for multiple PFAS, including PFOS. The EPA
downloaded available DOD off-base sampling results in September 2023.
The EPA summarized off-base sampling results for PFOS collected "post treatment" from drinking water
systems and private wells located in covered areas adjacent to 47 installations located in 22 states.
Detected concentrations ranged from an estimated concentration of 0.063 ng/L to 8,750 ng/L. Sampling
was conducted utilizing multiple analytical methods including EPA methods 533, 537, 537.1, 1633, and
DoD Quality Systems Manual Table B-15 (DoD, 2023a). Results are based on DLs which vary between
both sampling sites and across different PFAS. Results for PFOS are presented in Exhibit 4-13.
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Exhibit 4-13: Summary of PFOS Drinking Water Sampling Results Collected Post-Treatment from Department of
Defense Off-Base "Covered Areas"
State
Installation Name
Sampling Dates
Analysis
Method
#
Samples
#
Detections
%
Detections
Range of Detections
(ng/L)
AK
Eielson AFB
11/3/2022
537
1
0
0.00%
NA
AZ
Luke AFB
3/31/2022
QSM_B15
2
2
100.00%
26.2-28.3
AZ
YUMA AZ MCAS
5/26/2023
533
1
0
0.00%
NA
AR
Little Rock AFB
5/5/2022
537
3
2
66.67%
47.7 (est)-50.3 (est)
AR
Little Rock AFB
6/16/2022 - 3/22/2023
QSM_B15
6
1
16.67%
24.2 (est)
CA
Castle AFB
7/5/2022 - 4/5/2023
537
26
2
7.69%
0.479 (est) - 0.76 (est)
CA
Castle AFB
11/17/2021 - 1/11/2022
QSM_B15
12
2
16.67%
0.397 (est)-0.91 (est)
CA
George AFB
3/23/2023 - 4/20/2023
1633
3
0
0.00%
NA
CA
March AFB
1/3/2023-4/10/2023
533
3
0
0.00%
NA
CA
March AFB
1/3/2022- 12/1/2022
537.1
11
2
18.18%
2.4-4.2
CA
March AFB
9/1/2022
QSM_B15
1
0
0.00%
NA
CA
Mather AFB
7/28/2022
537
1
0
0.00%
NA
CA
Mather AFB
1/27/2022 - 4/26/2022
QSM_B15
3
0
0.00%
NA
CA
Travis AFB
1/25/2022 - 1/16/2023
QSM_B15
19
1
5.26%
18.4 (est)
CO
Peterson Space Force Base
12/14/2021 -2/7/2023
537.1
8
0
0.00%
NA
CO
Peterson Space Force Base
3/1/2022 - 9/14/2022
QSM_B15
16
0
0.00%
NA
DE
Dover AFB
1/22/2022- 10/25/2022
QSM_B15
10
1
10.00%
2.2 (est)
FL
Homestead Air Reserve Base
2/21/2022 - 3/30/2023
QSM_B15
13
0
0.00%
NA
FL
WHITING FLD FL NAS
9/1/2022
537.1
2
1
50.00%
2.22
IL
Scott AFB
3/22/2022 - 3/28/2023
QSM_B15
3
1
33.33%
8.1
ME
Loring AFB
7/25/2022
QSM_B15
1
1
100.00%
1.1 (est)
ME
NCTAMSLANT DET CUTLER
4/20/2022 - 12/6/2022
537.1
66
3
4.55%
1.71 (est) -238
MA
Otis ANG (Joint Base Cape Cod -
Massachusetts Military
Reservation)
2/28/2022 - 11/22/2022
QSM_B15
11
7
63.64%
0.45 (est) - 9.2
Ml
Kl Sawyer AFB
7/13/2022
QSM_B15
2
0
0.00%
NA
MT
Great Falls International Airport
6/15/2022-7/7/2022
537
3
1
33.33%
2.39 (est)
NH
Pease AFB
9/22/2021 - 3/30/2023
QSM_B15
16
7
43.75%
8.3-440
NJ
Joint Base McGuire-Dix-
Lakehurst
3/3/2022 - 5/25/2022
QSM_B15
2
0
0.00%
NA
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State
Installation Name
Sampling Dates
Analysis
Method
#
Samples
#
Detections
%
Detections
Range of Detections
(ng/L)
NM
Cannon AFB
11/11/2021 - 12/13/2021
QSM_B15
2
0
0.00%
NA
NY
Pittsburgh AFB
5/20/2022-8/10/2022
537
8
0
0.00%
NA
NY
Pittsburgh AFB
11/18/2021 -9/15/2022
537.1
16
1
6.25%
0.46 (est)
NY
Pittsburgh AFB
11/29/2021 -6/27/2023
QSM_B15
15
5
33.33%
0.494 (est) - 5.4 (est)
OK
Tinker AFB
2/2/2023
QSM_B15
3
0
0.00%
NA
Rl
NAVAL AUX LANDING FIELD
5/19/2022
537.1
2
0
0.00%
NA
Rl
NAVAL AUX LANDING FIELD
10/17/2022-2/28/2023
QSM_B15
31
23
74.19%
0.805 (est)-5.9
SD
Ellsworth AFB
3/14/2022
537
1
0
0.00%
NA
SD
Ellsworth AFB
6/9/2022 - 9/7/2022
537.1
2
0
0.00%
NA
SD
Ellsworth AFB
2/7/2022 - 6/23/2022
QSM_B15
36
5
13.89%
0.732 (est) -1370
TX
Goodfellow AFB
8/18/2022- 11/15/2022
537
11
5
45.45%
1.2 (est)-2.5 (est)
TX
Goodfellow AFB
12/6/2022 - 4/27/2023
QSM_B15
28
2
7.14%
32 - 8750
TX
Reese AFB
9/14/2022-6/13/2023
1633
504
13
2.58%
0.77 (est)-8.5
TX
Reese AFB
9/28/2021 - 8/29/2022
QSM_B15
839
15
1.79%
2.4 (est) - 433
VA
OCEANA VA NAS
10/19/2022-4/14/2023
537.1
13
0
0.00%
NA
WA
BREMERTON WA NAVBASE
10/11/2022-7/21/2023
537.1
3
2
66.67%
25.8 -25.9
WA
Fairchild AFB
9/19/2022 - 9/27/2022
537
87
2
2.30%
5.6 (est) - 285
WA
Fairchild AFB
2/20/2023 - 3/6/2023
537.1
87
72
82.76%
0.063 (est) -1.3
WA
Fairchild AFB
1/31/2022-7/21/2022
QSM_B15
187
11
5.88%
1.7 (est)-40.6
WA
WHIDBEY IS WANAS
4/21/2022 - 4/20/2023
537.1
11
0
0.00%
NA
Source: DOD, 2023a
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4.2.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the ambient sources of most drinking water. Contaminant occurrence in
ambient water provides information on the potential for contaminants to adversely affect drinking
water supplies. Occurrence data for PFOS in ambient water are available from the USGS NWIS database
and the EPA's legacy STORET data available through the WQP. Occurrence data for PFOS in ambient
water are available from one published study is summarized below.
4.2.3.1 National Water Information System (NWIS) Data
The NWIS is the Nation's principal repository of water resources data USGS collects from more than 1.9
million sites (USGS, 2023). NWIS-Web is the general online interface to the USGS NWIS database.
Discrete water-sample and time-series data are available from sites in all 50 States, including 5 million
water samples with 90 million water-quality results. All USGS water quality and flow data are stored in
NWIS, including site characteristics, streamflow, ground water level, precipitation, and chemical
analyses of water, sediment, and biological media, though not all parameters are available for every site.
NWIS houses the NAWQA data and includes other USGS data from unspecified projects. NWIS contains
many more samples at many more sites than the NAWQA Program. Although NWIS is comprised of
primarily ambient water data, some finished drinking water data are included as well. This section
presents analyses of non-NAWQA data in NWIS, downloaded from the WQP in November 2023 (WQP,
2023).
The results of the non-NAWQA NWIS PFOS analysis are presented in Exhibit 4-14. NWIS data for PFOS
were listed under the characteristic name "Perfluorooctanesulfonate." PFOS was detected in
approximately 49 percent of samples (1,456 out of 2,945 samples) and at approximately 40 percent of
sites (708 out of 1,756 sites). The median concentration based on detections was equal to 4.65 ng/L.
(Note that the NWIS data are presented as downloaded; potential outliers were not evaluated or
excluded from the analysis.)
Exhibit 4-14: PFOS NWIS Data
Site Type
Detection Frequency
(detections are results > reporting level)
Concentration Values
(of detections, in ng/L)
No. of
Samples
No. of
Samples
with
Detections
No.
of
Sites
No. of
Sites with
Detections
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Ground
Water
1,341
321
1,230
318
0.7
6.70
63.0
328
1300
Surface
Water
1,604
1,135
526
390
0.1
4.31
17.8
140
1900
All Sites
2,945
1,456
1,756
708
0.1
4.65
26.5
300
1900
Source: WQP, 2023
4.2.3.2 Storage and Retrieval (STORET) Data / Water Quality Portal (WQP)
From its launch in 1999 until it was decommissioned in June 2018, the EPA's STORET Data Warehouse
was collaboratively populated with raw biological, chemical, and physical data from surface water and
ground water sampling by federal, state and local agencies, Native American tribes, volunteer groups,
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academics, and others. Legacy STORET data are accessible through the WQP:
https://www.waterqualitvdata.us/portal/.
STORET data are from monitoring locations in all 50 states as well as multiple territories and jurisdictions
of the United States. Most data are from ambient waters, but in some cases finished drinking water data
are included as well. STORET's data quality limitations include variations in the extent of national
coverage and data completeness from parameter to parameter. Data may have been collected as part of
targeted, rather than randomized, monitoring.
This section presents analyses of STORET data, downloaded from the WQP in November 2023 (WQP,
2023). The EPA reviewed STORET ground water data from wells and springs and surface water data from
lakes, rivers, streams, and reservoirs (WQP, 2023). STORET data for PFOS were listed under the
characteristic name of "Perfluorooctanesulfonate (PFOS)", "1-Octanesulfonic acid,
1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-heptadecafluoro-, sodium salt (1:1)" and "Perfluorooctanesulfonate."
The results of the STORET analysis for PFOS are presented in Exhibit 4-15 and Exhibit 4-16. Almost 1,300
PFOS samples were available for analysis. These PFOS samples were collected between 2005 and 2023.
Of the 705 sites sampled, more than 70 percent reported detections of PFOS. Detected concentrations
ranged from 0 to 500 ng/L. (Note: A minimum value of zero could represent a detection that was
entered into the database as a non-numerical value (e.g., "Present").)
Exhibit 4-15: PFOS STORET Data - Summary of Detected Concentrations
Source Water Type
Concentration Value of Detections (ng/L)
Minimum1
Median
90th Percentile
Maximum
Ground Water
0
0
100
500
Surface Water
5.16
23.3
104
115
Unknown
0
0
3.79
8.17
Total
0
0
100
500
Source: WQP, 2023
1A minimum value of zero may represent a detection that was entered into the database as a non-numerical value
(e.g., "Present").
Exhibit 4-16: PFOS STORET Data - Summary of Samples and Sites
Source Water
Type
Total
Number of
Samples
Samples with
Detections
Total
Number
of Sites
Sites with Detections
Number
Percent
Number
Percent
Ground Water
771
706
91.57%
519
470
90.56%
Surface Water
58
19
32.76%
46
13
28.26%
Unknown
460
18
3.91%
140
15
10.71%
Total
1,289
743
57.64%
705
498
70.64%
Source: WQP, 2023
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4.2.3.3 Additional Ambient Water Studies
Jarvis et al. (2021) summarized the current literature on PFOS occurrence in the surface waters across
the United States and highlighted data gaps. The study reportedly found that concentrations of detected
PFOS varied widely among sample sites, ranging from picograms to milligrams per liter. The median
concentration of samples was 3.6 ng/L, though the author cautioned this may not be representative of
all measured PFOS concentrations in the United States. Approximately 91 percent of measured PFOS
concentrations in the literature were below 300 ng/L. The author attributed the higher frequency of
PFOS concentrations below 300 ng/L to the increased tendency of studies to include sites with no known
previous exposures to PFAS and compare them to sites with known previous exposure to PFOS. PFOS
were widely reported across the United States and their presence in surface water is dependent on the
presence of a nearby source and positively correlated with increased levels of urbanization. Jarvis et al.
(2021) noted that some studies suggested that PFOS concentrations are decreasing since the 2002 PFOS
voluntary phaseout.
4.3 Analytical Methods
For the purposes of compliance with the PFAS NPDWR, the EPA has published two analytical methods
that are available for the analysis of PFOS and other PFAS in drinking water. The performance metrics
that are presented, including the DL, LCMRL, mean recoveries and RSDs are specific to PFOS for each of
the listed analytical methods. Ranges of mean recoveries and RSDs are presented for the matrices listed;
data from holding time studies are not included since these studies are designed to demonstrate a
degradation in method performance over time and thus are not indicative of method performance that
should be observed when holding times are not exceeded:
• EPA Method 537.1, Version 2.0, Determination of Selected Per- and Polyfluorinated Alkyl
Substances in Drinking Water by Solid Phase Extraction and Liquid Chromatography/Tandem
Mass Spectrometry (LC/MS/MS). The DL and LCMRL generated by the laboratory that
developed the method are 1.1 ng/L and 2.7 ng/L, respectively. Mean recoveries in fortified
reagent water, tap water from a ground water source (TOC = 0.53 mg/L and hardness = 377
mg/L), tap water from a surface water source (TOC = 2.4 mg/L and hardness = 103 mg/L),
and tap water from a private well (TOC = 0.56 mg/L and hardness = 394 mg/L) range from
93.5 to 111%, with RSDs of 1.9 to 5.9% (USEPA, 2020d).
• EPA Method 533, Determination of Per- and Polyfluoroalkyl Substances in Drinking Water by
Isotope Dilution Anion Exchange Solid Phase Extraction and Liquid Chromatography /
Tandem Mass Spectrometry. The LCMRL generated by the laboratory that developed the
method is 4.4 ng/L (DLs were not calculated). Mean recoveries (excluding 13C isotope
analogue data) in fortified reagent water, finished drinking water from a ground water
source (hardness = 320 mg/L, pH = 7.88 at 17° C, free Cl2 = 0.64 mg/L, and total Cl2 = 0.74
mg/L) and clarified surface water (prior to GAC treatment and chlorinated in the laboratory;
pH = 8.1 at 20 °C, free Cl2 = 0.98 mg/L, total Cl2 = 1.31 mg/L. and TOC = 3.8 mg/L) range from
95.1 to 109%, with RSDs of 4.3 to 11% (USEPA, 2019b).
Laboratories participating in UCMR 3 were required to use EPA Method 537 and were required to report
PFOS values at or above the EPA-defined MRL of 40 ng/L (77 FR 26072; USEPA, 2012b). The MRL was set
based on the capability of multiple laboratories at the time. EPA Method 537.1 was originally published
in November 2018 as Version 1.0 as a more sensitive update to EPA Method 537 (with a slightly
expanded target analyte list). Version 2.0 was published in March 2020 and contains minor editorial
changes to Version 1.0. Use of EPA Method 537.1 is preferable to use of EPA Method 537 (it may not be
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feasible to reliably quantitate down to health levels of concern for certain PFAS when using EPA Method
537). For this reason, only EPA methods 533 and 537.1 are accepted for use in demonstrating
compliance with this final rule.
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5 Perfluorohexane Sulfonic Acid (PFHxS)
This chapter presents information and analysis specific to PFHxS, including background information on
the contaminant, information on contaminant sources and environmental fate, an analysis of health
effects, an analysis of occurrence in ambient and drinking water, and information about the availability
of analytical methods and treatment technologies.
5.1 Contaminant Background, Chemical and Physical Properties
Synonyms for PFHxS include perfluorohexane-l-sulphonic acid, and tridecafluorohexane-l-sulfonic acid
according to NCBI (2022c). PFHxS is a long chain perfluorinated aliphatic sulfonic acid. Its salts differ
from PFHxS by being associated with either a potassium ion, sodium ion, or lithium ion. For the purposes
of this document PFHxS will signify the ion, acid, or any salt of PFHxS.
PFHxS is used mainly as a raw material for the production of PFAS (NCBI, 2022c). PFHxS is contained in
legacy PFOS aqueous film-forming foam used for firefighting (ITRC, 2021). It has also been used as a
surfactant stain and water repellant for carpet treatment solutions (NCBI, 2022c) and in the
semiconductor industry (UNEP, 2019). It may have also been used for electroplating applications, or in
uses such as pesticides, flame retardants, cook wear or in the paper industry (UNEP; 2017; UNEP, 2019)
The sole manufacturer of PFOS In the United States agreed to a voluntary phaseout in 2000, and the last
reported production of PFHxS was in 2002 (ITRC, 2021) although international imports continued after
that date. In 2019, PFHxS was recommended to the United Nations' Stockholm Convention on Persistent
Organic Pollutants (POPs) for consideration of a full manufacturing ban (UNEP, 2019).
The diagram of Exhibit 5-1 shows the straight-chain chemical structure of PFHxS. Depending on their
method of manufacture, PFHxS and related compounds can exist as either branched-chain or straight-
chain isomers (ATSDR, 2021). The chemical and physical properties of PFHxS are listed in Exhibit 5-2 and
typically represent mixtures of branched and linear isomers rather than any particular isomer.
Although chemical properties commonly are reported for PFAS in the acid form, PFHxS does not have
available laboratory standards in the acid form and is commonly reported as the corresponding
potassium or sodium salts (ITRC, 2021). When looking at the physical and chemical properties, whether
the compound exists as an acid, an anion, or a salt (cation) will affect how they behave in the
environment (ITRC, 2021).
Exhibit 5-1: Chemical Structure of PFHxS
F F F F F F O
I > [ If
F ' j | -OH
lii li
F F F F F F O
Source: NCBI, 2022c
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NCBI (2022c) reports a value of 3.16 for the log Kow that is estimated using the EPA's EPISuite™, while
ATSDR (2021) indicated that log Kow is not applicable or cannot be measured since PFHxS is expected to
form multiple layers in octanol and water mixtures. Although very long-chain perfluoroalkyls that are
uncharged form layers in water/hydrocarbon mixtures, PFHxS is charged/ionized and at typical
environmental pH can have low to moderate solubility in water (ITRC, 2021; NCBI, 2022c). ATSDR
reports no data available for Henry's Law Constant while ITRC and HSDB present a value for KH. The KH
value presented by HSDB was estimated from vapor pressure and water solubility using EPISuite™.
Where there are different conclusions in the literature for the properties of PFHxS, information is
presented to highlight the range of uncertainty for this compound.
Exhibit 5-2: Physical and Chemical Properties of PFHxS
Property
Data
Chemical Abstracts Service
(CAS) Registry Number
355-46-4 (NCBI, 2022c)
EPA Pesticide Chemical Code
Not Applicable
Chemical Formula
CeHFisOsS (NCBI, 2022c)
Molecular Weight
400.12 g/mol (NCBI, 2022c)
Color/Physical State
No data (NCBI, 2022c)
Boiling Point
238-239 deg C (NCBI, 2022c)
95-452 deg C (ITRC, 2021)
Melting Point
190 deg C (ITRC, 2021)
No data (ATSDR, 2021)
Density
1.841 g/mL (NCBI, 2022c)
Freundlich Adsorption
Coefficient
-
Vapor Pressure
0.36 mm Hg at 25 deg C (ITRC, 2021; converted from 1.68 log-Pa)
0.0046 mm Hg at 25 deg C (est) (NCBI, 2022c)
Kh
3.5 atm-m3/mol at 25 deg C (ITRC, 2021; converted from 2.15 log)
4.0E-04 atm-m3/mol at 25 deg C (est)
(NCBI, 2022c)a
No data (ATSDR, 2021)
Log Kow
3.16 (est) (dimensionless) (NCBI, 2022c)b
Not applicable (ATSDR, 2021)
Koc
50 - 1.3E04 soil (dimensionless) (ITRC, 2021; converted from Log Koc 1.7 - 4.1)
14 - 3.2E04 sediment (dimensionless) (ITRC, 2021; converted from Log Koc 1.15 -4.5)
320 (dimensionless) (ATSDR, 2021; converted from Log Koc 2.28 avg (n=7))
9.3 (dimensionless) (est) (NCBI, 2022c)
pKa
0.14 (est) (NCBI, 2022c)
0.14 (est) (ATSDR, 2021)
Solubility in Water
236 mg/L (ITRC, 2021; converted from
-3.23 log-mol/L)
6.2 mg/L at 25 deg C (est) (NCBI, 2022c)
Other Solvents
-
Conversion Factors
(at 25 deg C, 1 atm)
1 PPM = 16.36 mg/m3; 1 mg/m3 = 0.061 PPM (ATSDR, 2021)
Note:indicates that no information was found.
a These values should not be used to estimate portioning between water and air.
b Surfactants are surface acting agents that contain both a hydrophilic part and a hydrophobic part which causes them
to accumulate at interfaces hampering the determination of their aqueous concentration. These surfactant properties
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present difficulties in applying existing methods for the experimental determination of log Kowand produce unreliable
results.
5.1.1 Sources and Environmental Fate
5.1.1.1 Production, Use, and Release
No production data for PFHxS are available from the EPA's IUR and CDR programs.6 Industrial release
data are available from the EPA's TRI, described below.
Toxics Release Inventory (TRI)
The EPA established TRI in 1987 in response to section 313 of the EPCRA. EPCRA section 313 requires
the reporting of annual information on toxic chemical releases from facilities that meet specific criteria.
This reported information is maintained in a database accessible through TRI Explorer (USEPA, 2023b).
Although TRI can provide a general idea of release trends, it has limitations. Not all facilities are required
to report all releases. Facilities are required to report releases if they manufacture, process, or
otherwise use a listed toxic chemical in quantities above the respective activity threshold. For PFHxS, the
reporting threshold is 100 lbs. manufactured, processed, or otherwise used over the year. It should also
be noted that, as of this publication, quantities of PFHxS at concentrations under 1.0 percent within
mixtures may be exempt from TRI reporting requirements. Reporting requirements have changed over
time (e.g., the chemical list has been updated), so conclusions about temporal trends should be drawn
with caution. TRI data are meant to reflect releases and other waste management activities and should
not be used to estimate general public exposure to a chemical (USEPA, 2023b).
TRI data for PFHxS are available for 2020 through 2022 (USEPA, 2023b). As shown in Exhibit 5-3, there
were 7 pounds of total on-site disposals and 115 pounds of total off-site disposals across all industries in
2020. A total of two facilities from two states reported releases of PFHxS. In 2021, there were 500
pounds of total on-site releases and no off-site releases reported. PFHxS releases were reported by one
facility in one state in 2021. In 2022, a total of 3,400 pounds of total on-site releases were reported and
no off-site releases were reported. PFHxS releases were reported by one facility in Alabama in 2022.
Exhibit 5-3: Environmental Releases of PFHxS in the United States, 2020-2022
On-Site Releases (in pounds)
Year
Air
Emissions
Surface
Water
Discharges
Underground
Injection
Releases to
Land
Total Off-
Site
Releases
(in pounds)
Total On-
and Off-Site
Releases
(in pounds)
2020
0
6
1
0
115
123
2021
0
0
0
500
0
500
2022
0
0
0
3,400
0
3,400
6 Note that there are 2020 CDR data listed for "Perfluoro compounds, C5-18." Those data are not summarized in
this report.
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Source: USEPA, 2023b
5.1.1.2 Environmental Fate
The primary measures used by the EPA to assess mobility include (where available) Koc, log Kow, KH, water
solubility and vapor pressure. For PFHxS, pKa is also important.
Modeling of atmospheric behavior of PFHxS suggest that PFHxS will be present as a vapor if released to
the atmosphere (NCBI, 2022c). PFHxS can react with photochemically produced hydroxyl radicals in the
atmosphere to degrade (NCBI, 2022c). A half-life for this reaction in air is estimated to be 115 days
(NCBI, 2022c). (Note that radical reactions typically proceed more rapidly than chemically- or
microbially-mediated degradation reactions in other environmental media such as water, soil, and/or
sediment.) PFHxS is not expected to undergo direct photolysis (NCBI, 2022c).
Based on findings from laboratory studies as reported by ITRC (2021) for soil, experimental log Koc which
suggests a moderate propensity for PFHxS to be mobilized to ground water and surface water rather
than to bind to suspended solids or sediments. PFHxS is expected to have low mobility to sediment
based upon estimates of log Koc having an estimated value ranging from 1.15 - 4.5.
Based on the vapor pressure, PFHxS is not expected to volatilize from dry soil (NCBI, 2022c). With a pKa
of less than 1.0, PFHxS is expected to exist in its ionized form at typical environment pH ranges of
natural waters (NCBI, 2022c). Thus, volatilization from water at typical environment pH is not expected
(NCBI, 2022c).
PFHxS is very stable chemically and is resistant to hydrolysis, photolysis; biodegradation data in soil or
water were not available (NCBI, 2022c).
Under CCL 3, the EPA created scales7 to informally rank chemical contaminants' likely mobility
(understood as their tendency to partition to water rather than other media) and persistence as "high,"
"moderate," or "low" based on physical and chemical properties (see USEPA, 2021b and USEPA, 2009).
For PFHxS, a log Kow of 3.16, and a moderate water solubility of more than 6.2 mg/L at 25 degrees C
(NCBI, 2022c) predict a moderate favorability of partitioning to water.
A resistance to essentially all forms of degradation other than atmospheric processes indicates high
persistence.
5.2 PFHxS Occurrence
This section presents data on the occurrence of PFHxS in drinking water and ambient water in the
United States. The EPA is finalizing an MCLG of 10 ppt for PFHxS. Under SDWA, the EPA must establish
an enforceable MCL, the maximum concentration of a contaminant that is allowed in PWSs, as close to
the MCLG as feasible, taking several factors into consideration, including analytical methods capable of
measuring the contaminant, available treatment technologies to remove the contaminant, and costs.
Based on these factors, the EPA is finalizing an MCL of 10 ppt for PFHxS. Occurrence data from various
sources presented below are analyzed with respect to the MCL. When possible, estimates of the
7 See Exhibit A.8 here: https://www.epa.gov/sites/default/files/2014-05/documents/ccl3 pccltoccl 08-31-
09 508.pdf
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population exposed at concentrations above the MCL are presented. Also, when possible, studies that
are meant to be representative and studies that are targeted at known or suspected sites of
contamination are identified as such.
The drinking water analyses presented in this section were performed for UCMR 3 and select state data
sources. In addition, this section presents PFHxS findings from occurrence analyses conducted by non-
EPA researchers. Chapter 10 describes the Bayesian hierarchical model used to extrapolate PFHxS
occurrence to the nation and also points the reader to examine Cadwallader et al. (2022) for further
details. For additional background information about data sources used to evaluate occurrence, please
refer to Chapter 2.
The EPA is also finalizing an HI MCL for the regulation of PFHxS, PFNA, HFPO-DA, and PFBS when co-
occurring in mixture combinations containing two or more of these four PFAS. Refer to Chapter 8 for
more information on the HI MCL and chapter 9 for co-occurrence information.
5.2.1 Occurrence in Drinking Water
Data sources reviewed by the agency for information on PFHxS occurrence in drinking water included
UCMR 3, more recent state drinking water monitoring programs, and the DoD PFAS drinking water
testing, as well as additional studies from the literature.
Note that there may be some overlap, as sources with different purposes and audiences may have
reported the same underlying data. UCMR 3 is a nationally representative data source. Other data
sources profiled in this section are considered "supplemental" sources. Also note that PFHxS is being
monitored for under UCMR 5, which is occurring from 2023 to 2025. Analysis of partial UCMR 5 results
(the first three quarters of data that were made available as of February 2024) are discussed in section
11 of this document. Additionally, the EPA notes that the UCMR 3 MRLfor PFHxS is higher than that
utilized within the majority of state monitoring data and for the UCMR 5.
5.2.1.1 UCMR 3 Data
PFHxS was included as part of the nationally representative UCMR 3 monitoring from 2013 through
2015. UCMR 3 Assessment Monitoring occurrence data are available for PFHxS from all large and very
large PWSs (serving between 10,001 and 100,000 people and serving more than 100,000 people,
respectively), plus a statistically representative national sample of 800 small PWSs (serving 10,000
people or fewer).8 Surface water and GWUDI sampling points were monitored four times during the
applicable year of monitoring, and ground water sample points were monitored twice during the
applicable year of monitoring. See USEPA (2012b) and USEPA (2019a) for more information on the
UCMR 3 study design and data analysis.
Exhibit 5-4 through Exhibit 5-6 provide an overview of PFHxS occurrence results from the UCMR 3
Assessment Monitoring. Laboratories participating in UCMR 3 were required to report values at or
above MRLs defined by the EPA. The UCMR MRLs are not intended to represent the lowest achievable
measurement level an individual laboratory may achieve. Rather, the MRLs are established to ensure
reliable and consistent results from the array of laboratories needed for a national monitoring program
and are set based on the quantitation level capability of multiple commercial laboratories prior to
8 A total of 799 small systems submitted Assessment Monitoring results.
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beginning each UCMR round. The MRL used for PFHxS in the UCMR 3 survey was 30 ng/L (77 FR 26072;
USEPA, 2012b). Exhibit 5-4 presents a sample-level summary of the results. Exhibit 5-5 shows a
statistical summary of PFHxS concentrations by system size and source water type (including the
minimum, 25th percentile, median, 75th percentile, 90th percentile, 99th percentile, and maximum).
Exhibit 5-6 shows system-level results for detections greater than or equal to the MRL.
A total of 36,971 finished water samples for PFHxS were collected from 4,920 PWSs. PFHxS was reported
> MRL of 30 ng/L in 0.56 percent of UCMR 3 samples. Reported PFHxS concentrations for these results
ranged from 30 ng/L (the MRL) to 1,600 ng/L. Of 4,920 systems, 55 (1.12 percent of systems, serving
2.36 percent of the PWS-served population) reported at least one detection.
Exhibit 5-4: PFHxS National Occurrence Measures Based on UCMR 3 Assessment
Monitoring Data - Summary of Samples
Source Water Type
Total # of
Samples
Samples with Detections
> MRL of 30 ng/L
Number
Percent
Small Systems (serving < 10,000 people)
Ground Water
1,853
4
0.22%
Surface Water
1,421
0
0.00%
All Small Systems
3,274
4
0.12%
Large Systems (serving 10,001 -100,000 people) — CENSUS
Ground Water
11,707
49
0.42%
Surface Water
14,859
103
0.69%
All Large Systems
26,566
152
0.57%
Very Large Systems (serving > 100,000 people) - CENSUS
Ground Water
2,020
27
1.34%
Surface Water
5,111
24
0.47%
All Very Large Systems
7,131
51
0.72%
All Systems
All Water Systems
36,971
207
0.56%
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Exhibit 5-5: PFHxS Occurrence Data from UCMR 3 Assessment Monitoring - Summary of Reported Detected
Concentrations
Source Water Type
Concentration Value of Detections (in ng/L) > MRL of 30 ng/L
Minimum
25th percentile
Median
75th percentile
90th Percentile
99th Percentile
Maximum
Small Systems (serving < 10,000 people)
Ground Water
100
112.975
403.65
700
718
728.8
730
Surface Water
-
-
-
-
-
-
-
All Small Systems
100
112.975
403.65
700
718
728.8
730
Large Systems (serving 10,001 -100,000 people) — CENSUS
Ground Water
30
40
62
100
152
256.08
270
Surface Water
30
59.75
100
235
348
884
1600
All Large Systems
30
52.825
77.55
187.75
329
737
1,600
Very Large Systems (serving > 100,000 people) — CENSUS
Ground Water
30
44.5
68
95
156
378.4
420
Surface Water
34
48.465
59.5
91
117
624.8
680
All Very Large
Systems
30
45.93
60
93
140
560
680
All Systems
All Water Systems
30
50.5
73
160
324
727.6
1,600
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Exhibit 5-6: PFHxS National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data - Summary of
System and Population Served Data - Reported Detections
Source Water
Type
UCMR 3 Samples
Number With At Least
One Detection > MRL of
30 ng/L
Percent With At Least
One Detection > MRL of
30 ng/L
National Inventory
Percent of National
Inventory Included
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems (serving < 10,000 people)
Ground Water
527
1,498,845
2
7,963
0.38%
0.53%
55,700
38,730,597
0.95%
3.87%
Surface Water
272
1,250,215
0
0
0.00%
0.00%
9,728
20,007,917
2.80%
6.25%
All Small
Systems
799
2,749,060
2
7,963
0.25%
0.29%
65,428
58,738,514
1.22%
4.68%
Large Systems (serving 10,001 -100,000 people) — CENSUS
Ground Water
1,453
37,141,418
21
591,679
1.45%
1.59%
1,470
37,540,614
98.84%
98.94%
Surface Water
2,260
69,619,878
18
580,941
0.80%
0.83%
2,310
70,791,005
97.84%
98.35%
All Large
Systems
3,713
106,761,296
39
1,172,620
1.05%
1.10%
3,780
108,331,619
98.23%
98.55%
Very Large Systems (serving > 100,000 people) — CENSUS
Ground Water
68
16,355,951
6
2,416,685
8.82%
14.78%
68
16,355,951
100.00%
100.00%
Surface Water
340
115,158,260
8
2,083,447
2.35%
1.81%
343
120,785,622
99.13%
95.34%
All Very Large
Systems
408
131,514,211
14
4,500,132
3.43%
3.42%
411
137,141,573
99.27%
95.90%
All Systems
All Water
Systems
4,920
241,024,567
55
5,680,715
1.12%
2.36%
69,619
304,211,706
7.07%
79.23%
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5.2.1.2 State Monitoring Data
In the development of the proposed and final NPDWR, the agency supplemented its UCMR 3 data with
more recent publicly available data collected by states. In general, these more recent state data were
collected using newer analytical methods and state results reflect lower reporting and detection limits
than those in the UCMR 3. Drinking water occurrence data from PWSs for PFHxS were available from
several states, including Alabama, Arizona, California, Colorado, Georgia, Idaho, Illinois, Indiana, Iowa,
Kentucky, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, New Hampshire, New
Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oregon, Pennsylvania, South
Carolina, Tennessee, Vermont, Virginia, and Wisconsin. The EPA downloaded publicly available
monitoring data from state websites through May 2023. Note that while some states did have available
raw water data as indicated in Exhibit 5-7, for the subsequent analyses the EPA only evaluated finished
water results.
Exhibit 5-7 provides a summary of the available state reported monitoring data for PFHxS, including date
range and a description of coverage and representativeness (including whether monitoring was non-
targeted or targeted (i.e., monitoring in areas of known or potential PFAS contamination)). A description
of those studies is also included in Exhibit 5-7. State reporting thresholds are also provided, where
available, in Exhibit 5-7. The EPA notes that different states utilized various reporting thresholds when
analyzing and presenting their data, and for some states there were no clearly defined thresholds
publicly provided; in these cases, minimum detected concentrations reported may be indicative of
reporting thresholds used. Further, for some states, the thresholds varied when reporting results for the
same analyte, as well as the laboratory analyzing the data. For those states, a range of thresholds is
provided. As shown in Exhibit 5-7, some states reported at thresholds and/or presented data at
concentrations below the EPA's final MCL and/or PQL for PFHxS. However, to present the best available
occurrence information, the EPA collected and evaluated the data based on the information as reported
directly by the states and when conducting data analyses incorporated individual state-specific reporting
thresholds where possible. Additionally, the EPA notes that the majority of the data were analyzed via
an EPA-approved drinking water analytical method.
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Exhibit 5-7: Summary of Available PFHxS State Reported Monitoring Data
State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
Alabama
(ADEM, 2023)
2013 -
2022
Ground Water and
Surface Water -
Finished Water
Not reported
ADPH instructed water systems to carry out PFAS monitoring at all PWSs not
previously sampled during UCMR 3. In 2022, water systems that had not been
sampled since UCMR 3 were required to sample between January and June
2022 using current analytical methods. Only results that are above the MRL
are posted online; thus, only reported detections were available for use in the
occurrence analyses.
Non-
Targeted
Arizona
(ADEQ, 2023)
2021
Ground Water and
Surface Water -
Raw and Finished
Water
1.6-2
ADEQ presents a PFAS Interactive Data Map that displays the results of
testing conducted by ADEQ since 2018 at PWSs across Arizona.
Targeted
California
(CADDW,
2023)
2016-
April 2023
Ground Water and
Surface Water -
Raw, Finished,
and Unknown
Water
0.002-30
The EPA reviewed the California PFHxS data available online through April
2023. Finished water data were available from approximately 120 PWSs. For
this analysis, the EPA only included results that were explicitly marked as
being from treated water. Sampling in California is ongoing.
Targeted
Colorado
(CDPHE,
2018;CDPHE,
2020)
2013 -
2017
Surface Water
(Finished Water)
and Drinking
Water Distribution
Samples
2-30
Data available from 28 "drinking water distribution zones" (one or more per
PWS) in targeted sampling efforts at a known contaminated aquifer region.
Data were collected by El Paso County Public Health, local water districts and
utilities, and the CDPHE.
Targeted
2020
Ground Water and
Surface Water -
Raw and Finished
Water
1.6-2.4
CDPHE offered free testing to PWSs serving communities, schools, and
workplaces and also to fire districts with wells. Approximately 50% of PWSs in
Colorado participated in the 2020 PFAS sampling project. Data included in this
report were collected in March through May of 2020.
Non-
Targeted
Georgia
(GA EPD,
2020)
2020
Surface Water -
Raw, Finished,
and Unknown
Water
18
The EPA and the GA EPD conducted joint sampling of the City of
Summerville's drinking water sources and finished drinking water in January
2020.
Targeted
Idaho
(Idaho DEQ,
2023)
2021 -
April 2023
Ground Water -
Finished and
Unknown Water
0.5-1
Sampling of finished drinking water data between September 2021 and April
2023 that were available on the state's Drinking Water Watch website.
Not
specified
135
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April 2024
State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
Illinois
(IL EPA, 2023)
2020 - May
2023
Ground Water and
Surface Water -
Raw and Finished
Water
1.7-3.7
In 2020, the IL EPA initiated a statewide investigation into the prevalence and
occurrence of PFAS in finished drinking water at 1,749 community water
supplies across Illinois. The EPA reviewed finished drinking water data
collected between September 2020 and May 2023 that were available on the
state's Drinking Water Watch website. Sampling in Illinois is ongoing.
Non-
Targeted
Indiana (IDEM,
2023)
2021 -
January
2023
Ground Water and
Surface Water -
Raw, Finished,
and Unknown
Water
2
Beginning in February 2021, the IDEM facilitated PFAS monitoring at all CWSs
throughout the state of Indiana. Samples were to be collected at all raw water
(i.e., wells and intakes) and finished (after treatment) water points in a CWS's
supply to evaluate the statewide occurrence of PFAS compounds in CWS
across the state and determine the efficacy of conventional drinking water
treatment for PFAS.
Non-
Targeted
Iowa
(IA DNR, 2023)
2021 -
April 2023
Ground Water and
Surface Water -
Raw and Finished
Water
1.7-3
In January 2020, the Iowa DNR developed an Action Plan to protect the health
of Iowa residents and the environment from PFAS. Data were downloaded
from the PFAS Sampling Interactive Dashboard and Map.
Targeted
Kentucky
(KYDEP, 2019)
2019
Ground Water and
Surface Water -
Finished Water
3.24
Sampling of finished drinking water data between June and October 2019.
Under this sampling effort, data are available from 81 community public
DWTPs, representing 74 PWSs, and serving more than 2.4 million people.
Non-
Targeted
Maine
(Maine DEP,
2020; Maine
DHHS, 2023)
2013 -
2020
Drinking Water -
Raw, Finished,
and Unknown
Water
1.78-30
In March 2019, the Maine PFAS Task Force was created to review the extent
of PFAS contamination in Maine. Finished water results collected from 2013
through 2020 have been collected at 23 locations throughout the state. Data
may include results from public and private finished drinking water sources.
Sampling in Maine is ongoing.
Targeted
2021 -
January
2023
Ground Water and
Surface Water -
Finished Water
2
The EPA reviewed the finished water data reported to the Maine CDC Drinking
Water Program as compliance samples since June 2021 and processed in the
database as of 3/10/2023. Sampling in Maine is ongoing.
Non-
Targeted
Maryland
(MDE, 2021;
MDE, 2022a;
MDE, 2022b)
2020 -
2022
Ground Water and
Surface Water -
Raw and Finished
Water
1
In 2020, MDE initiated a project to identify potential sources of PFAS in
Maryland and to prioritize water sources for PFAS sampling. The EPA
reviewed the finished water results from the first three phases of MDE's Public
Water System study for the occurrence of PFAS in State drinking water
sources. Under Phase 1 (September 2020 - February 2021), sites were
selected for priority sampling based on MDE's evaluation of potential relative
risk for PFAS exposure through drinking water. Under Phase 2 (March 2021 -
May 2021), MDE conducted sampling at sites that were selected based on
their geological setting and proximity to potential sources of PFAS. Under
Phase 3 (August 2021- June 2022), MDE tested the remaining CWSs in the
state.
Targeted(
Phase 1,
Phase 2);
Non-
Targeted
(Phase 3)
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April 2024
State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
Massachusetts
(MA EE A,
2023)
2016-April
2023
Ground Water and
Surface Water -
Raw and Finished
Water
0.43 - 25
The EPA reviewed the finished water data available online through April 2023.
Data were available from 1,330 PWSs. Sampling in Massachusetts is ongoing.
Targeted
Michigan
(Michigan
EGLE, 2023)
2020 -
March
2023
Ground Water and
Surface Water -
Finished Water
2
The Michigan EGLE developed MCLs for seven PFAS compounds in
Michigan, which took effect in August 2020. The EPA reviewed available
finished compliance monitoring results through March 2023. Sampling in
Michigan is ongoing.
Non-
Targeted
Minnesota
(MDH, 2023)
2020 -
2023
Ground Water and
Surface Water -
Finished Water
Not reported
Through the Statewide PFAS Monitoring Project, MDH is testing CWSs across
the state for PFAS. The EPA reviewed finished water data through MDH's
Interactive Dashboard for PFAS Testing in Drinking Water.
Non-
Targeted
Missouri
(Missouri DNR,
2023)
2022 -
2023
Ground Water and
Surface Water -
Raw and Finished
Water
Not reported
The EPA reviewed the finished water data available online from Missouri
DNR's "PFAS Viewer Tool" which identifies the location of voluntary sampling
for PFAS in public drinking water systems in Missouri. The EPA reviewed
finished water data collected from approximately 113 PWSs from 2022 through
2023. Limited data were also available from 2013 through 2017.
Non-
Targeted
New
Hampshire
(NHDES, 2021)
2016-May
2021
Ground Water and
Surface Water -
Raw and Finished
Water
Not reported
The EPA reviewed the New Hampshire PFHxS data available online through
May 2021. Finished water data were available from more than 500 PWSs.
Sampling in New Hampshire is ongoing.
Non-
Targeted
New Jersey
(NJDEP, 2023)
2019 - May
2023
Ground Water and
Surface Water -
Raw, Finished,
and Unknown
Water
0.43-6
Statewide sampling of finished drinking water data was available from 2019-
2023. The EPA reviewed data available online through May 2023 from more
than 660 PWSs. Sampling in New Jersey is ongoing.
Non-
Targeted
New Mexico
(NMED, 2019)
2016
Ground Water -
Raw and Finished
Water
Not reported
NMED, Department of Health and the U.S. Air Force conducted testing at
public drinking water supplies at or around Cannon Air Force Base up to 2019.
Targeted
New York
(NYDOH,
2022)
2017 -
2022
Ground Water and
Surface Water -
Raw, Finished,
and Unknown
Water
0.000000001
-2,020
The EPA reviewed finished water data voluntarily provided by the state to the
EPA. Data were available from nearly 700 PWSs from 2017 through 2022.
Limited data were also available from 2013 through 2016.
Non-
Targeted
North Carolina
(NCDEQ,
2021)
2017 -
2019
Finished and
unknown water
Not reported
NCDEQ and the Department of Health and Human Services investigated the
presence of HFPO-DA and other PFAS in the Cape Fear River in June
2017. Monthly results were also collected from five water treatment plants on
the Cape Fear River. Data were available from June 2017 through October
Targeted
137
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April 2024
State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
2019. Only results above the DLwere reported; thus, only reported detections
were available for use in the occurrence analyses.
North Dakota
(NDDEQ, date
unknown;
NDDEQ, date
unknown)
2020, 2021
Ground Water and
Surface Water -
Raw and Finished
Water
Not reported
NDDEQ published a 2020 and a 2021 survey report of North Dakota Statewide
Per- and Polyfluoroalkyl Substances (PFAS) Presence/Absence results. The
sampling effort in October of 2020 sought to determine if there was a PFAS
presence in a representative portion of the state's public water supply. In 2021,
sampling conducted as part of the third phase of the survey focused on
drinking water sites not evaluated in the first two surveys.
Non-
Targeted
Ohio
(Ohio EPA,
2023)
December
2019 -
December
2021
Ground Water and
Surface Water -
Raw and Finished
Water
5
The Ohio EPA coordinated sampling of raw and finished drinking water from
PWSs throughout the state. The EPA reviewed the finished water data
available online through December 2021. During this timeframe, data were
available from 1,479 PWSs.
Non-
Targeted
Oregon
(OHA-DWS,
2022)
2021 - July
2022
Ground Water and
Surface Water -
Finished Water
10.1 -12.4
OHA conducted a PFAS drinking water monitoring project in 2021 at PWSs in
Oregon identified as at risk due to their proximity to a known or suspected
PFAS use or contamination site. The EPA reviewed the finished water data
from more than 140 PWSs.
Targeted
Pennsylvania
(PADEP, 2019)
2019
Ground Water and
Surface Water -
Finished Water
1.9
A PFAS Sampling Plan was developed to test PWSs across the state.
Finished water data were collected for 87 PWSs in 2019.
Targeted
Pennsylvania
(PADEP, 2021)
2020 -
March
2021
Ground Water and
Surface Water -
Finished Water
1.7-4
Beginning in 2020 and running through March of 2021, finished water data
were collected by more than 340 PWSs.
Targeted
South Carolina
(SCDHEC,
2020;
SCDHEC,
2023)
2017 -
March
2023
Ground Water and
Surface Water -
Raw and Finished
Water
2.1
The EPA reviewed PFAS sampling results collected by the South Carolina
Bureau of Water for community drinking water systems. Data were available
from 300 PWSs.
Non-
Targeted
Tennessee
(TDEC, 2023)
2019
Surface Water -
Raw and Finished
Water
Not reported
In 2019, Metro Water Services conducted a voluntary sampling of Nashville's
drinking water systems for PFAS. Their stated goal was to go above and
beyond current federal and state monitoring requirements to understand the
potential presence of PFAS in Nashville's drinking water.
Non-
Targeted
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April 2024
State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
Vermont
(VT DEC,
2023)
2019 -April
2023
Ground Water and
Surface Water -
Raw, Finished,
and Unknown
2
The Vermont Water Supply Rule required all CWSs and NTNCWSs to sample
for PFAS. The EPA reviewed finished water data available online from July
2019 - April 2023 from approximately 560 PWSs. Sampling in Vermont is
ongoing.
Non-
Targeted
Virginia
(VDH ODW,
2021)
2021
Ground Water and
Surface Water -
Raw and Finished
Water
3.5
The Virginia ODW, in conjunction with VA PFAS work group, designed the
sample study to prioritize sites for measuring PFAS concentrations in drinking
water and major sources of water and generate statewide occurrence data.
Targeted /
Non-
Targeted
Wisconsin
(Wl DNR,
2023)
2022 -April
2023
Ground Water and
Surface Water -
Raw, Finished,
and Unknown
Water
Not reported
The EPA reviewed the finished water data available online from 2022 - 2023.
Data were available from nearly 250 PWSs. Sampling in Wisconsin is ongoing.
Non-
Targeted
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Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
A summary of state reported monitoring data from PWSs for PFHxS is presented in Exhibit 5-8 through
Exhibit 5-10. As noted above, some of the monitoring data from each state are limited and may not be
representative of occurrence in the state. In addition, states have varying reporting thresholds, as
indicated in the first column of Exhibit 5-8. For states with available reporting thresholds, only detected
concentrations greater than the reporting thresholds were counted as detections. For states that did not
provide reporting thresholds, the EPA included all detected concentrations reported in the count of
detections. Overall, state reported detected concentrations ranged from 0.2 ppt (Alabama) to 856 ppt
(New York). Note that for a small number of systems, population served information could not be
identified. These systems were included in the counts and analysis presented in Exhibit 5-10; however,
no associated population served was included in the counts and analysis presented in Exhibit 5-10.
Exhibit 5-8: PFHxS State Reported Drinking Water Occurrence Data - Summary of
Finished Water Samples
State
(Reporting
Threshold)
Source Water Type
Total
Number of
Samples
All Detections
All Detections
> 10 ppt
Number
Percent
Number
Percent
Alabama1
(Not reported)
Ground Water
-
42
-
5
-
Surface Water
-
82
-
4
-
Total
-
124
-
9
-
Arizona
(1.6-2 ppt)
Ground Water
23
18
78.3%
5
21.7%
Surface Water
2
1
50.0%
0
0.0%
Total
25
19
76.0%
5
20.0%
California
(0.002 - 30 ppt)
Ground Water
1,883
489
26.0%
180
9.6%
Surface Water
3,947
610
15.5%
109
2.8%
Unknown
4
0
0.0%
0
0.0%
Total
5,834
1,099
18.8%
289
5.0%
Colorado
(2013-2017)
(2 - 30 ppt)
Distribution (Finished)
94
46
48.9%
33
35.1%
Surface water (Finished)
11
0
0.0%
0
0.0%
Total
105
46
43.8%
33
31.4%
Colorado (2020)
(1.6-2.4 ppt)
Ground Water
339
36
10.6%
1
0.3%
Surface Water
244
27
11.1%
1
0.4%
Total
583
63
10.8%
2
0.3%
Georgia
(18 ppt)
Ground Water
0
0
0.0%
0
0.0%
Surface Water
2
0
0.0%
0
0.0%
Total
2
0
0.0%
0
0.0%
Idaho
(0.5 -1 ppt)
Ground Water
18
2
11.1%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Total
18
2
11.1%
0
0.0%
Illinois
(1.7-3.7 ppt)
Ground Water
1,823
258
14.2%
16
0.9%
Surface Water
302
27
8.9%
0
0.0%
Total
2,125
285
13.4%
16
0.8%
Indiana
Ground Water
422
7
1.7%
0
0.0%
140
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April 2024
State
(Reporting
Threshold)
(2 ppt)
Source Water Type
Total
Number of
Samples
All Detections
All Detections
> 10 ppt
Number
Percent
Number
Percent
Surface Water
59
0
0.0%
0
0.0%
Total
481
7
1.5%
0
0.0%
Iowa
(1.7-3 ppt)
Ground Water
152
29
19.1%
3
2.0%
Surface Water
63
4
6.3%
4
6.3%
Total
215
33
15.3%
7
3.3%
Kentucky
(3.24 ppt)
Ground Water
33
4
12.1%
0
0.0%
Surface Water
48
3
6.3%
0
0.0%
Total
81
7
8.6%
0
0.0%
Maine (PFAS Task
Force)2
(1.78-30 ppt)
Ground Water
9
0
0.0%
0
0.0%
Surface Water
3
0
0.0%
0
0.0%
Unknown
75
6
8.0%
3
4.0%
Total
87
6
6.9%
3
3.4%
Maine
(Compliance)
(2 ppt)
Ground Water
646
21
3.3%
1
0.2%
Surface Water
62
0
0.0%
0
0.0%
Total
708
21
3.0%
1
0.1%
Maryland (Phase 1)
(1 ppt)
Ground Water
70
33
47.1%
3
4.3%
Surface Water
76
35
46.1%
3
3.9%
Total
146
68
46.6%
6
4.1%
Maryland (Phase 2)
(1 ppt)
Ground Water
9
3
33.3%
1
11.1%
Surface Water
0
0
0.0%
0
0.0%
Total
9
3
33.3%
1
11.1%
Maryland (Phase 3)
(1 ppt)
Ground Water
88
16
18.2%
3
3.4%
Surface Water
0
0
0.0%
0
0.0%
Total
88
16
18.2%
3
3.4%
Massachusetts
(0.43 - 25 ppt)
Ground Water
7,215
1,771
24.5%
125
1.7%
Surface Water
2,136
437
20.5%
11
0.5%
Total
9,351
2,208
23.6%
136
1.5%
Michigan
(2 ppt)
Ground Water
10,007
446
4.5%
49
0.5%
Surface Water
519
2
0.4%
0
0.0%
Unknown
164
13
7.9%
3
1.8%
Total
10,690
461
4.3%
52
0.5%
Missouri,
2022 - 2023
(Not reported)
Ground Water
192
7
3.6%
1
0.5%
Surface Water
22
0
0.0%
0
0.0%
Total
214
7
3.3%
1
0.5%
New Hampshire
(Not reported)
Ground Water
1,656
293
17.7%
34
2.1%
Surface Water
157
11
7.0%
0
0.0%
Unknown
1
0
0.0%
0
0.0%
Total
1,814
304
16.8%
34
1.9%
New Jersey
(0.43 - 6 ppt)
Ground Water
5,346
1,169
21.9%
99
1.9%
Surface Water
1,770
697
39.4%
14
0.8%
141
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April 2024
State
(Reporting
Threshold)
Source Water Type
Total
Number of
Samples
All Detections
All Detections
> 10 ppt
Number
Percent
Number
Percent
Unknown
3
0
0.0%
0
0.0%
Total
7,119
1,866
26.2%
113
1.6%
New Mexico
(Not reported)
Ground Water
2
1
50.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Total
2
1
50.0%
0
0.0%
New York
(0.000000001-
2,020 ppt)
Ground Water
1,839
423
23.0%
15
0.8%
Surface Water
401
63
15.7%
2
0.5%
Unknown
9
0
0.0%
0
0.0%
Total
2,249
486
21.6%
17
0.8%
North Carolina1
(Not Reported)
Unknown
-
372
-
327
-
Total
-
372
-
327
-
North Dakota
(2020)
(Not reported)
Ground Water
42
1
2.4%
0
0.0%
Surface Water
9
0
0.0%
0
0.0%
Total
51
1
2.0%
0
0.0%
North Dakota
(2021)
(Not reported)
Ground Water
56
4
7.1%
0
0.0%
Surface Water
7
1
14.3%
0
0.0%
Total
63
5
7.9%
0
0.0%
Ohio
(5 ppt)
Ground Water
1,775
117
6.6%
55
3.1%
Surface Water
170
11
6.5%
0
0.0%
Total
1,945
128
6.6%
55
2.8%
Oregon
(10.1 -12.4 ppt)
Ground Water
131
3
2.3%
1
0.8%
Surface Water
29
0
0.0%
0
0.0%
Total
160
3
1.9%
1
0.6%
Pennsylvania
(2019)
(1.9-2 ppt)
Ground Water
75
11
14.7%
1
1.3%
Surface Water
21
6
28.6%
0
0.0%
Total
96
17
17.7%
1
1.0%
Pennsylvania
(2021)
(1.7-4 ppt)
Ground Water
314
38
12.1%
6
1.9%
Surface Water
98
14
14.3%
0
0.0%
Total
412
52
12.6%
6
1.5%
South Carolina
(2.1 ppt)
Ground Water
572
42
7.3%
2
0.3%
Surface Water
193
20
10.4%
0
0.0%
Total
765
62
8.1%
2
0.3%
Tennessee
(Not reported)
Ground Water
0
0
0.0%
0
0.0%
Surface Water
2
0
0.0%
0
0.0%
Total
2
0
0.0%
0
0.0%
Vermont
(2 ppt)
Ground Water
1,463
65
4.4%
10
0.7%
Surface Water
102
0
0.0%
0
0.0%
Total
1,565
65
4.2%
10
0.6%
Virginia
(3.5 ppt)
Ground Water
5
0
0.0%
0
0.0%
Surface Water
36
1
2.8%
0
0.0%
142
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April 2024
State
(Reporting
Threshold)
Source Water Type
Total
Number of
Samples
All Detections
All Detections
> 10 ppt
Number
Percent
Number
Percent
Total
41
1
2.4%
0
0.0%
Wisconsin
(Not reported)
Ground Water
733
189
25.8%
14
1.9%
Surface Water
54
25
46.3%
0
0.0%
Total
787
214
27.2%
14
1.8%
1 Only reported detections were available in this state's dataset.
2 Reported data from Maine may include results from public and private finished drinking water sources. Based
on available state data information, the EPA could not verify PWSIDs for all included samples.
Exhibit 5-9: PFHxS State Reported Drinking Water Occurrence Data - Summary of
Detected Concentrations
State
(Reporting
Threshold)
Source Water Type
Concentration Value of Detections (ppt)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Alabama1
(Not reported)
Ground Water
0.8
5.70
15.8
23.0
23
Surface Water
0.2
2.60
8.49
22.4
24
Total
0.2
3.00
12.7
23.0
24
Arizona
(1.6-2 ppt)
Ground Water
3.7
7.15
30.3
34.3
35
Surface Water
3
3
3
3
3
Total
3
7.10
30.2
34.3
35
California
(0.002 - 30 ppt)
Ground Water
1.1
9.40
24.0
35.4
50
Surface Water
1.7
4.70
24.0
109
160
Unknown
-
-
-
-
-
Total
1.1
6.30
24.0
91.1
160
Colorado
(2013-2017)
(2 - 30 ppt)
Distribution (Finished)
3.9
76.0
380
523
590
Surface water (Finished)
-
-
-
-
-
Total
3.9
76.0
380
523
590
Colorado (2020)
(1.6-2.4 ppt)
Ground Water
1.8
3.75
8.95
15.9
18
Surface Water
1.6
2.80
5.80
27.3
34
Total
1.6
3.60
8.28
24.1
34
Georgia
(18 ppt)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
-
-
-
-
-
Idaho
(0.5 -1 ppt)
Ground Water
1.11
1.32
1.48
1.52
1.52
Surface Water
-
-
-
-
-
Total
1.11
1.32
1.48
1.52
1.52
Illinois
(1.7-3.7 ppt)
Ground Water
1.9
4.05
12.0
109
200
Surface Water
2.2
3.80
7.46
11.3
12
Total
1.9
4.00
11.0
93.8
200
Indiana
Ground Water
2.1
2.30
2.62
2.78
2.8
143
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
(2 ppt)
Source Water Type
Concentration Value of Detections (ppt)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Surface Water
-
-
-
-
-
Total
2.1
2.30
2.62
2.78
2.8
Iowa
(1.7-3 ppt)
Ground Water
2
4.00
14.2
41.9
43
Surface Water
36
39.0
44.2
45.8
46
Total
2
5.50
38.8
45.0
46
Kentucky
(3.24 ppt)
Ground Water
1.62
2.65
8.54
10.8
11
Surface Water
1.74
1.96
2.15
2.20
2.2
Total
1.62
2.20
6.08
10.5
11
Maine (PFAS Task
Force)2
(1.78-30 ppt)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Unknown
5.81
25.9
58.2
71.0
72.4
Total
5.81
25.9
58.2
71.0
72.4
Maine
(Compliance)
(2 ppt)
Ground Water
2.02
3.18
7.94
21.8
24
Surface Water
-
-
-
-
-
Total
2.02
3.18
7.94
21.8
24
Maryland (Phase 1)
(1 ppt)
Ground Water
1
1.80
7.17
58.6
61.49
Surface Water
1
2.49
9.21
91.6
123.18
Total
1
2.43
9.01
81.8
123.18
Maryland (Phase 2)
(1 ppt)
Ground Water
2.05
9.26
18.4
20.4
20.66
Surface Water
-
-
-
-
-
Total
2.05
9.26
18.4
20.4
20.66
Maryland (Phase 3)
(1 ppt)
Ground Water
1.46
3.78
53.0
143
158
Surface Water
-
-
-
-
-
Total
1.46
3.78
53.0
143
158
Massachusetts
(0.43 - 25 ppt)
Ground Water
0.72
3.08
11.5
57.5
222
Surface Water
1.66
2.70
5.76
18.3
31
Total
0.72
2.92
11.0
56.9
222
Michigan
(2 ppt)
Ground Water
2
3.40
16.0
260
347
Surface Water
3.2
3.40
3.56
3.60
3.6
Unknown
3
8.00
22.6
26.6
27
Total
2
3.50
16.0
257
347
Minnesota
(Not reported)
Ground Water
0.74
-
-
-
31
Surface Water
0.65
-
-
-
0.65
Total
0.65
-
--
-
31
Missouri,
2022 - 2023
(Not reported)
Ground Water
2
2.40
12.1
24.6
26
Surface Water
-
-
-
-
-
Total
2
2.40
12.1
24.6
26
New Hampshire
(Not reported)
Ground Water
0.7
3.22
18.5
235
269
Surface Water
1.7
2.67
6.20
7.84
8.02
144
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water Type
Concentration Value of Detections (ppt)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Unknown
-
-
-
-
-
Total
0.7
3.17
17.9
234
269
New Jersey
(0.43 - 6 ppt)
Ground Water
0.46
3.20
12.7
77.3
260
Surface Water
1.74
3.45
7.80
34.1
100
Unknown
-
-
-
-
-
Total
0.46
3.30
9.60
65.0
260
New Mexico
(Not reported)
Ground Water
2.6
2.6
2.6
2.6
2.6
Surface Water
-
-
-
-
-
Total
2.6
2.6
2.6
2.6
2.6
New York
(0.000000001-
2,020 ppt)
Ground Water
0.33
2.33
5.58
29.9
856
Surface Water
0.52
2.00
7.92
15.8
16.2
Unknown
-
-
-
-
-
Total
0.33
2.31
5.80
27.5
856
North Carolina1
(Not Reported)
Unknown
0.26
40.0
40.0
80.0
80
Total
0.26
40.0
40.0
80.0
80
North Dakota
(2020)
(Not reported)
Ground Water
2.14
2.14
2.14
2.14
2.14
Surface Water
-
-
-
-
-
Total
2.14
2.14
2.14
2.14
2.14
North Dakota
(2021)
(Not reported)
Ground Water
0.751
1.01
1.62
1.79
1.81
Surface Water
1.47
1.47
1.47
1.47
1.47
Total
0.751
1.17
1.67
1.80
1.81
Ohio
(5 ppt)
Ground Water
5
13.5
32.4
120
140
Surface Water
5.28
7.68
9.56
11.1
11.3
Total
5
12.1
31.4
113
140
Oregon
(10.1 -12.4 ppt)
Ground Water
12.5
12.7
15.8
16.5
16.6
Surface Water
-
-
-
-
-
Total
12.5
12.7
15.8
16.5
16.6
Pennsylvania
(2019)
(1.9-2 ppt)
Ground Water
2.3
2.90
7.40
66.4
73
Surface Water
2.4
3.35
12.5
13.0
13
Total
2.3
3.00
12.4
63.4
73
Pennsylvania
(2021)
(1.7-4 ppt)
Ground Water
1.9
4.60
23.6
118
140
Surface Water
1.9
4.05
5.82
6.35
6.4
Total
1.9
4.50
17.0
109
140
South Carolina
(2.1 ppt)
Ground Water
2.1
3.85
7.56
238
380
Surface Water
2.1
3.25
4.81
4.98
5
Total
2.1
3.55
7.03
169
380
Tennessee
(Not reported)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
-
-
-
-
-
145
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water Type
Concentration Value of Detections (ppt)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Vermont
(2 ppt)
Ground Water
2
3.84
54.9
134
134
Surface Water
-
-
-
-
-
Total
2
3.84
54.9
134
134
Virginia
(3.5 ppt)
Ground Water
-
-
-
-
-
Surface Water
4.9
4.9
4.9
4.9
4.9
Total
4.9
4.9
4.9
4.9
4.9
Wisconsin
(Not reported)
Ground Water
0.276
1.60
9.44
37.5
43.3
Surface Water
0.43
0.680
0.876
1.00
1
Total
0.276
1.44
6.35
36.3
43.3
Note: With limited exceptions, calculated concentration values (i.e., median, 90th percentile and 99th percentile
concentrations) were rounded to three significant figures for consistent presentation across the datasets and may
not indicate exact laboratory precision.
1 Only reported detections were available in this state's dataset.
2 Reported data from Maine may include results from public and private finished drinking water sources. Based on
available state data information, the EPA could not verify PWSIDs for all included samples.
Exhibit 5-10: PFHxS State Reported Drinking Water Occurrence Data - Summary
of Systems with Finished Water Data
State
(Reporting
Threshold)
Source Water Type
Total
Number of
Systems
Systems with
Detections
Systems with
Detections
> 10 ppt
Number
Percent
Number
Number
Alabama1
(Not reported)
Ground Water
-
20
-
3
-
Surface Water
-
33
-
1
-
Total
-
53
-
4
-
Arizona
(1.6-2 ppt)
Ground Water
5
3
60.0%
2
40.0%
Surface Water
1
1
100.0%
0
0.0%
Total
6
4
66.7%
2
33.3%
Ground Water
43
17
39.5%
7
16.3%
California
Surface Water
78
30
38.5%
12
15.4%
(0.002-30 ppt)
Unknown
1
0
0.0%
0
0.0%
Total
122
47
38.5%
19
15.6%
Colorado
Distribution (Finished)
22
13
59.1%
11
50.0%
(2013-2017)
Surface water (Finished)
5
0
0.0%
0
0.0%
(2 - 30 ppt)
Total
27
13
48.1%
11
40.7%
Colorado (2020)
(1.6-2.4 ppt)
Ground Water
221
31
14.0%
1
0.5%
Surface Water
176
22
12.5%
1
0.6%
Total
397
53
13.4%
2
0.5%
Georgia
Ground Water
0
0
0.0%
0
0.0%
(18 ppt)
Surface Water
1
0
0.0%
0
0.0%
146
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water Type
Total
Number of
Systems
Systems with
Detections
Systems with
Detections
> 10 ppt
Number
Percent
Number
Number
Total
1
0
0.0%
0
0.0%
Idaho
(0.5 -1 ppt)
Ground Water
10
2
20.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Total
10
2
20.0%
0
0.0%
Illinois
(1.7-3.7 ppt)
Ground Water
899
44
4.9%
7
0.8%
Surface Water
97
2
2.1%
0
0.0%
Total
996
46
4.6%
7
0.7%
Indiana
(2 ppt)
Ground Water
341
5
1.5%
0
0.0%
Surface Water
31
0
0.0%
0
0.0%
Total
372
5
1.3%
0
0.0%
Iowa
(1.7-3 ppt)
Ground Water
90
10
11.1%
2
2.2%
Surface Water
26
1
3.8%
1
3.8%
Total
116
11
9.5%
3
2.6%
Kentucky
(3.24 ppt)
Ground Water
30
4
13.3%
0
0.0%
Surface Water
44
3
6.8%
0
0.0%
Total
74
7
9.5%
0
0.0%
Maine (PFAS Task
Force)2
(1.78-30 ppt)
Ground Water
7
0
0.0%
0
0.0%
Surface Water
1
0
0.0%
0
0.0%
Unknown
10
4
40.0%
3
30.0%
Total
18
4
22.2%
3
16.7%
Maine
(Compliance)
(2 ppt)
Ground Water
593
18
3.0%
1
0.2%
Surface Water
53
0
0.0%
0
0.0%
Total
646
18
2.8%
1
0.2%
Maine
(All Systems)3
(1.78-30 ppt)
Ground Water
593
18
3.0%
1
0.2%
Surface Water
53
0
0.0%
0
0.0%
Unknown
10
4
40.0%
3
30.0%
Total
656
22
3.4%
4
0.6%
Maryland (Phase 1)
(1 ppt)
Ground Water
30
15
50.0%
2
6.7%
Surface Water
36
18
50.0%
2
5.6%
Total
66
33
50.0%
4
6.1%
Maryland (Phase 2)
(1 ppt)
Ground Water
6
3
50.0%
1
16.7%
Surface Water
0
0
0.0%
0
0.0%
Total
6
3
50.0%
1
16.7%
Maryland (Phase 3)
(1 ppt)
Ground Water
63
8
12.7%
2
3.2%
Surface Water
0
0
0.0%
0
0.0%
Total
63
8
12.7%
2
3.2%
Maryland
(All Systems)3
(1 PPt)
Ground Water
99
26
26.3%
5
5.1%
Surface Water
36
18
50.0%
2
5.6%
Total
135
44
32.6%
7
5.2%
147
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water Type
Total
Number of
Systems
Systems with
Detections
Systems with
Detections
> 10 ppt
Number
Percent
Number
Number
Massachusetts
(0.43-25 ppt)
Ground Water
1,209
201
16.6%
24
2.0%
Surface Water
122
40
32.8%
4
3.3%
Total
1,331
241
18.1%
28
2.1%
Ground Water
2,370
98
4.1%
13
0.5%
Michigan
Surface Water
84
1
1.2%
0
0.0%
(2 ppt)
Unknown
54
3
5.6%
1
1.9%
Total
2,508
102
4.1%
14
0.6%
Minnesota
(Not reported)
Ground Water
561
60
10.7%
2
0.4%
Surface Water
16
1
6.3%
0
0.0%
Total
577
61
10.6%
2
0.3%
Missouri,
Ground Water
95
3
3.2%
1
1.1%
2022 - 2023
Surface Water
18
0
0.0%
0
0.0%
(Not reported)
Total
113
3
2.7%
1
0.9%
Ground Water
529
122
23.1%
14
2.6%
New Hampshire
Surface Water
30
4
13.3%
0
0.0%
(Not reported)
Unknown
1
0
0.0%
0
0.0%
Total
560
126
22.5%
14
2.5%
Ground Water
599
180
30.1%
15
2.5%
New Jersey
Surface Water
65
39
60.0%
3
4.6%
(0.43-6 ppt)
Unknown
1
0
0.0%
0
0.0%
Total
665
219
32.9%
18
2.7%
New Mexico
(Not reported)
Ground Water
2
1
50.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Total
2
1
50.0%
0
0.0%
Ground Water
568
148
26.1%
9
1.6%
New York
(0.000000001-
2,020 ppt)
Surface Water
123
26
21.1%
2
1.6%
Unknown
4
0
0.0%
0
0.0%
Total
695
174
25.0%
11
1.6%
North Carolina1
Unknown
-
5
-
5
-
(Not Reported)
Total
-
5
-
5
-
North Dakota
Ground Water
41
1
2.4%
0
0.0%
(2020)
Surface Water
9
0
0.0%
0
0.0%
(Not reported)
Total
50
1
2.0%
0
0.0%
North Dakota
Ground Water
56
4
7.1%
0
0.0%
(2021)
Surface Water
7
1
14.3%
0
0.0%
(Not reported)
Total
63
5
7.9%
0
0.0%
North Dakota
Ground Water
95
5
5.3%
0
0.0%
(All Systems)3
Surface Water
16
1
6.3%
0
0.0%
(Not reported)
Total
111
6
5.4%
0
0.0%
148
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water Type
Total
Number of
Systems
Systems with
Detections
Systems with
Detections
> 10 ppt
Number
Percent
Number
Number
Ohio
(5 ppt)
Ground Water
1,372
29
2.1%
15
1.1%
Surface Water
107
3
2.8%
0
0.0%
Total
1,479
32
2.2%
15
1.0%
Oregon
(10.1 -12.4 ppt)
Ground Water
116
2
1.7%
1
0.9%
Surface Water
27
0
0.0%
0
0.0%
Total
143
2
1.4%
1
0.7%
Pennsylvania
(2019)
(1.9-2 ppt)
Ground Water
71
8
11.3%
1
1.4%
Surface Water
16
5
31.3%
0
0.0%
Total
87
13
14.9%
1
1.1%
Pennsylvania
(2021)
(1.7-4 ppt)
Ground Water
269
32
11.9%
6
2.2%
Surface Water
73
10
13.7%
0
0.0%
Total
342
42
12.3%
6
1.8%
Pennsylvania
(All Systems)3
(1.7-4 ppt)
Ground Water
270
35
13.0%
6
2.2%
Surface Water
73
12
16.4%
0
0.0%
Total
343
47
13.7%
6
1.7%
South Carolina
(2.1 ppt)
Ground Water
234
30
12.8%
2
0.9%
Surface Water
65
11
16.9%
0
0.0%
Total
299
41
13.7%
2
0.7%
Tennessee
(Not reported)
Ground Water
0
0
0.0%
0
0.0%
Surface Water
1
0
0.0%
0
0.0%
Total
1
0
0.0%
0
0.0%
Vermont
(2 ppt)
Ground Water
526
15
2.9%
1
0.2%
Surface Water
38
0
0.0%
0
0.0%
Total
564
15
2.7%
1
0.2%
Virginia
(3.5 ppt)
Ground Water
5
0
0.0%
0
0.0%
Surface Water
20
1
5.0%
0
0.0%
Total
25
1
4.0%
0
0.0%
Wisconsin
(Not reported)
Ground Water
217
62
28.6%
7
3.2%
Surface Water
22
14
63.6%
0
0.0%
Total
239
76
31.8%
7
2.9%
1 Only reported detections were available in this state's dataset.
2 Reported data from Maine may include results from public and private finished drinking water sources. Based on
available state data information, the EPA could not verify PWSIDs for all included samples.
3 The "All Systems" counts represent a summary of all unique systems across multiple sampling efforts within the
state. For some states (e.g., CO), the EPA could not verify this number due to the sample site ID reporting.
149
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Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
Exhibit 5-11: PFHxS State Reported Drinking Water Occurrence Data - Summary
of Population Served by Systems with Finished Water Data
State
(Reporting
Threshold)
Source Water
Type
Total
Population
Served by
Systems
Total Population
Served by Systems
with Detections
Total Population
Served by Systems
with Detections
> 10 ppt
Number
Percent
Number
Number
Alabama1
(Not reported)
Ground Water
-
331,485
-
35,991
-
Surface Water
-
1,230,184
-
4,350
-
Total
-
1,561,669
-
40,341
-
Arizona
(1.6-2 ppt)
Ground Water
94,569
55,853
59.1%
55,535
58.7%
Surface Water
50,001
50,001
100.0%
0
0.0%
Total
144,570
105,854
73.2%
55,535
38.4%
California
(0.002 - 30 ppt)
Ground Water
1,098,122
693,964
63.2%
134,039
12.2%
Surface Water
13,500,188
4,269,361
31.6%
2,665,573
19.7%
Unknown
0
0
0.0%
0
0.0%
Total
14,598,310
4,963,325
34.0%
2,799,612
19.2%
Colorado
(2013 -201 If
(2 - 30 ppt)
Distribution
(Finished)
-
-
-
-
-
Surface water
(Finished)
-
-
-
-
-
Total
-
-
--
--
-
Colorado (2020)
(1.6-2.4 ppt)
Ground Water
261,162
81,445
31.2%
70
0.0%
Surface Water
4,191,774
904,295
21.6%
4,495
0.1%
Total
4,452,936
985,740
22.1%
4,565
0.1%
Georgia
(18 ppt)
Ground Water
0
0
0.0%
0
0.0%
Surface Water
9,993
0
0.0%
0
0.0%
Total
9,993
0
0.0%
0
0.0%
Idaho
(0.5 -1 ppt)
Ground Water
81,985
14,977
18.3%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Total
81,985
14,977
18.3%
0
0.0%
Illinois
(1.7-3.7 ppt)
Ground Water
2,916,219
536,360
18.4%
83,168
2.9%
Surface Water
4,628,949
123,073
2.7%
0
0.0%
Total
7,545,168
659,433
8.7%
83,168
1.1%
Indiana
(2 ppt)
Ground Water
545,838
6,571
1.2%
0
0.0%
Surface Water
97,448
0
0.0%
0
0.0%
Total
643,286
6,571
1.0%
0
0.0%
Iowa
(1.7-3 ppt)
Ground Water
491,495
77,979
15.9%
5,834
1.2%
Surface Water
987,522
85,797
8.7%
85,797
8.7%
Total
1,479,017
163,776
11.1%
91,631
6.2%
Kentucky
(3.24 ppt)
Ground Water
171,212
12,391
7.2%
0
0.0%
Surface Water
1,922,023
70,010
3.6%
0
0.0%
Total
2,093,235
82,401
3.9%
0
0.0%
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State
(Reporting
Threshold)
Source Water
Type
Total
Population
Served by
Systems
Total Population
Served by Systems
with Detections
Total Population
Served by Systems
with Detections
> 10 ppt
Number
Percent
Number
Number
Maine (PFAS Task
Force)23
(1.78-30 ppt)
Ground Water
3,995
0
0.0%
0
0.0%
Surface Water
21,808
0
0.0%
0
0.0%
Unknown
0
0
0.0%
0
0.0%
Total
25,803
0
0.0%
0
0.0%
Maine
(Compliance)
(2 ppt)
Ground Water
274,866
24,012
8.7%
140
0.1%
Surface Water
464,453
0
0.0%
0
0.0%
Total
739,319
24,012
3.2%
140
0.0%
Maine
(All Systems)24
(1.78-30 ppt)
Ground Water
274,866
24,012
8.7%
140
0.1%
Surface Water
464,453
0
0.0%
0
0.0%
Unknown
0
0
0.0%
0
0.0%
Total
739,319
24,012
3.2%
140
0.0%
Maryland
(Phase 1)
(1 ppt)
Ground Water
384,007
72,696
18.9%
7,000
1.8%
Surface Water
4,059,154
3,829,519
94.3%
40,656
1.0%
Total
4,443,161
3,902,215
87.8%
47,656
1.1%
Maryland
(Phase 2)
(1 ppt)
Ground Water
3,896
315
8.1%
180
4.6%
Surface Water
0
0
0.0%
0
0.0%
Total
3,896
315
8.1%
180
4.6%
Maryland
(Phase 3)
(1 ppt)
Ground Water
41,063
3,034
7.4%
295
0.7%
Surface Water
0
0
0.0%
0
0.0%
Total
41,063
3,034
7.4%
295
0.7%
Maryland
(All Systems)4
(1 PPt)
Ground Water
428,966
76,045
17.7%
7,475
1.7%
Surface Water
4,059,154
3,829,519
94.3%
40,656
1.0%
Total
4,488,120
3,905,564
87.0%
48,131
1.1%
Massachusetts
(0.43 - 25 ppt)
Ground Water
1,828,984
1,086,532
59.4%
245,748
13.4%
Surface Water
5,860,701
1,329,491
22.7%
175,785
3.0%
Total
7,689,685
2,416,023
31.4%
421,533
5.5%
Michigan2
(2 PPt)
Ground Water
1,945,734
430,649
22.1%
221,394
11.4%
Surface Water
1,314,601
42,271
3.2%
0
0.0%
Unknown
0
0
0.0%
0
0.0%
Total
3,260,335
472,920
14.5%
221,394
6.8%
Minnesota
(Not reported)
Ground Water
2,752,594
1,290,853
46.9%
35,115
1.3%
Surface Water
1,106,268
61,747
5.6%
0
0.0%
Total
3,858,862
1,352,600
35.1%
35,115
0.9%
Missouri,
2022 - 2023
(Not reported)
Ground Water
190,274
4,410
2.3%
1,963
1.0%
Surface Water
405,045
0
0.0%
0
0.0%
Total
595,319
4,410
0.7%
1,963
0.3%
New Hampshire
(Not reported)
Ground Water
267,029
144,523
54.1%
33,551
12.6%
Surface Water
476,367
47,826
10.0%
0
0.0%
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State
(Reporting
Threshold)
Source Water
Type
Total
Population
Served by
Systems
Total Population
Served by Systems
with Detections
Total Population
Served by Systems
with Detections
> 10 ppt
Number
Percent
Number
Number
Unknown
10
0
0.0%
0
0.0%
Total
743,406
192,349
25.9%
33,551
4.5%
New Jersey
(0.43 - 6 ppt)
Ground Water
1,520,763
589,240
38.7%
157,170
10.3%
Surface Water
4,783,734
3,900,556
81.5%
180,066
3.8%
Unknown
0
0
0.0%
0
0.0%
Total
6,304,497
4,489,796
71.2%
337,236
5.3%
New Mexico2
(Not reported)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
-
-
-
-
-
New York
(0.000000001-
2,020 ppt)
Ground Water
1,459,428
624,391
42.8%
2,313
0.2%
Surface Water
2,850,536
494,790
17.4%
11,200
0.4%
Unknown
1,024
0
0.0%
0
0.0%
Total
4,310,988
1,119,181
26.0%
13,513
0.3%
North Carolina1'2
(Not Reported)
Unknown
-
-
-
-
-
Total
-
-
--
--
--
North Dakota
(2020)
(Not reported)
Ground Water
68,280
50
0.1%
0
0.0%
Surface Water
57,469
0
0.0%
0
0.0%
Total
125,749
50
0.0%
0
0.0%
North Dakota
(2021)
(Not reported)
Ground Water
113,623
64,496
56.8%
0
0.0%
Surface Water
194,121
4,284
2.2%
0
0.0%
Total
307,744
68,780
22.3%
0
0.0%
North Dakota
(All Systems)4
(Not reported)
Ground Water
181,514
64,546
35.6%
0
0.0%
Surface Water
251,590
4,284
1.7%
0
0.0%
Total
433,104
68,830
15.9%
0
0.0%
Ohio
(5 ppt)
Ground Water
2,883,252
95,659
3.3%
66,341
2.3%
Surface Water
6,215,644
152,856
2.5%
0
0.0%
Total
9,098,896
248,515
2.7%
66,341
0.7%
Oregon
(10.1 -12.4 ppt)
Ground Water
114,194
344
0.3%
289
0.3%
Surface Water
125,239
0
0.0%
0
0.0%
Total
239,433
344
0.1%
289
0.1%
Pennsylvania
(2019)
(1.9-2 ppt)
Ground Water
162,825
25,756
15.8%
110
0.1%
Surface Water
431,370
134,502
31.2%
0
0.0%
Total
594,195
160,258
27.0%
110
0.0%
Pennsylvania
(2021)
(1.7-4 ppt)
Ground Water
471,651
102,203
21.7%
5,170
1.1%
Surface Water
4,296,097
1,046,132
24.4%
0
0.0%
Total
4,767,748
1,148,335
24.1%
5,170
0.1%
Pennsylvania
(All Systems)4
Ground Water
471,891
105,553
22.4%
5,170
1.1%
Surface Water
4,296,097
1,098,879
25.6%
0
0.0%
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State
(Reporting
Threshold)
(1.7-4 ppt)
Source Water
Type
Total
Population
Served by
Systems
Total Population
Served by Systems
with Detections
Total Population
Served by Systems
with Detections
> 10 ppt
Number
Percent
Number
Number
Total
4,767,988
1,204,432
25.3%
5,170
0.1%
South Carolina
(2.1 ppt)
Ground Water
485,992
8,376
1.7%
709
0.1%
Surface Water
2,489,351
344,016
13.8%
0
0.0%
Total
2,975,343
352,392
11.8%
709
0.0%
Tennessee
(Not reported)
Ground Water
0
0
0.0%
0
0.0%
Surface Water
2,551
0
0.0%
0
0.0%
Total
2,551
0
0.0%
0
0.0%
Vermont
(2 ppt)
Ground Water
211,357
2,185
1.0%
120
0.1%
Surface Water
174,473
0
0.0%
0
0.0%
Total
385,830
2,185
0.6%
120
0.0%
Virginia
(3.5 ppt)
Ground Water
2,975
0
0.0%
0
0.0%
Surface Water
4,839,373
407,300
8.4%
0
0.0%
Total
4,842,348
407,300
8.4%
0
0.0%
Wisconsin
(Not reported)
Ground Water
1,514,437
1,028,037
67.9%
56,862
3.8%
Surface Water
1,333,737
649,446
48.7%
0
0.0%
Total
2,848,174
1,677,483
58.9%
56,862
2.0%
1 Only reported detections were available in this state's dataset.
2 There were some instances where the population served by a system could not be identified. Thus, there are
systems with detections but no associated population served by those systems with detections.
3 Reported data from Maine may include results from public and private finished drinking water sources. Based on
available state data information, the EPA could not verify PWSIDs for all included samples.
4 The "All Systems" counts represent a summary of all unique systems across multiple sampling efforts within the
state.
5.2.1.3 Additional Secondary Source Water and Drinking Water Studies
Boone et al. (2019) measured 17 PFAS in both source and treated water from 25 DWTPs in the United
States. The results indicated that only five of the sampling locations demonstrated a significant
difference in PFAS concentration between the source and treated water. The median concentration of
PFHxS in source water was 0.86 ng/L and 0.79 ng/L in treated water. PFHxS was detected in 80 percent
of treated drinking water samples (Boone et al., 2019).
Post et al. (2013) re-evaluated PFOA, PFOS, and PFC occurrence data in drinking water systems
throughout New Jersey to update previous PFAS research in the area from 2006. PFCs were found in 70
percent of PWSs sampled at concentrations ranging from 5-174 ng/L. PFHxS was detected in 13 percent
of samples at a maximum concentration of 46 ng/L.
McMahon et al. (2022) collected samples from aquifer systems in the eastern United States in 2019 to
evaluate PFAS occurrence in ground water used as a source of drinking water. The study found that 14
of the 24 analyzed PFAS were detected in ground water samples. Furthermore, at least one PFAS was
detected in 54 percent of the ground water samples and two or more PFAS were detected in 47 percent
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of the ground water samples. In the public supply and domestic wells, 60 and 20 percent of the samples,
respectively, had at least one PFAS detection. Two or more PFAS were detected in 53 percent of the
public-supply wells and 10 percent of domestic wells. The six PFAS outlined in the EPA's UCMR 3
program (i.e., PFBS, PFHxS, PFOS, PFHpA, PFOA, and PFNA) were the most detected PFAS in the study's
samples. PFHxS was detected in 20 percent of the 254 samples (McMahon et al., 2022).
As part of a joint study by the EPA and USGS to assess human exposure to contaminants of emerging
concern, water samples were collected from 25 DWTPs in 24 states (Glassmeyer et al., 2017).
Participation in the study was voluntary, and candidate locations were selected based on nomination by
the EPA and USGS regional personnel and DWTP self-nomination as well as consideration of high
wastewater contribution and the availability of pharmaceutical concentration data. Final sample
locations were chosen to represent a wide range of geography, diversity in disinfectant type used, and a
range of production volumes. Phase I of the study (2007) analyzed a subset of contaminants and sites to
test experimental design; PFHxS was not included in Phase 1. During Phase II of the study (2010-2012),
samples were collected from ground water and surface water sources and treated drinking water from
25 DWTPs and analyzed for PFHxS occurrence. The LCMRL for PFHxS was equal to 0.034 ng/L. PFHxS was
detected in 92 percent of the 25 source water samples and 84 percent of the 25 treated drinking water
samples. The maximum detected concentrations in source water and treated water were 44.8 ng/L and
38.4 ng/L, respectively.
Reyes (2021) conducted a ground water-quality study to describe the occurrence and distribution of
PFAS in the Columbia aquifer public water-supply wells in the Delaware Coastal Plain region in 2018.
One or more PFAS were detected in 16 of the sampled wells with as many as 8 different PFAS detected
in a single sample. PFHxS was detected in 8 of the 30 public water-supply wells sampled in the study.
The maximum PFHxS concentration detected was 130 ng/L.
5.2.2 Other Data
5.2.2.1 Department of Defense (DoD) Drinking Water Sampling
The DoD conducted sampling of off-base drinking water located in "covered areas" (i.e., areas that are
adjacent to and down gradient from a military installation) to identify potential impacts of PFAS
resulting from DoD activities. Sampling was conducted for multiple PFAS, including PFHxS. The EPA
downloaded available DOD off-base sampling results in September 2023.
The EPA summarized off-base sampling results for PFHxS collected "post treatment" from drinking water
systems and private wells located in covered areas adjacent to 47 installations located in 22 states.
Detected concentrations ranged from an estimated concentration of 0.38 ng/L to 2,900 ng/L. Sampling
was conducted utilizing multiple analytical methods including EPA methods 533, 537, 537.1, 1633, and
DoD Quality Systems Manual Table B-15 (DoD, 2023a). Results are based on DLs which vary between
both sampling sites and across different PFAS. Results for PFHxS are presented in Exhibit 5-12.
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Exhibit 5-12: Summary of PFHxS Drinking Water Sampling Results Collected Post-Treatment from Department of
Defense Off-Base "Covered Areas"
State
Installation Name
Sampling Dates
Analysis
Method
#
Samples
#
Detections
%
Detections
Range of Detections
(ng/L)
AK
Eielson AFB
11/3/2022
537
1
0
0.00%
NA
AZ
Luke AFB
3/31/2022
QSM_B15
2
2
100.00%
4.9 (est) - 5 (est)
AZ
YUMA AZ MCAS
5/26/2023
533
1
0
0.00%
NA
AR
Little Rock AFB
5/5/2022
537
3
2
66.67%
163-164
AR
Little Rock AFB
6/16/2022 - 3/22/2023
QSM_B15
6
1
16.67%
30.9 (est)
CA
Castle AFB
7/5/2022 - 4/5/2023
537
26
4
15.38%
1.37 (est)-2.22
CA
Castle AFB
11/17/2021 - 1/11/2022
QSM_B15
12
2
16.67%
1.12 (est) -1.86 (est)
CA
George AFB
3/23/2023 - 4/20/2023
1633
3
0
0.00%
NA
CA
March AFB
1/3/2023-4/10/2023
533
3
1
33.33%
1.4 (est)
CA
March AFB
1/3/2022 - 12/1/2022
537.1
11
6
54.55%
2-63
CA
March AFB
9/1/2022
QSM_B15
1
0
0.00%
NA
CA
Mather AFB
7/28/2022
537
1
0
0.00%
NA
CA
Mather AFB
1/27/2022 - 4/26/2022
QSM_B15
3
0
0.00%
NA
CA
Travis AFB
1/25/2022 - 1/16/2023
QSM_B15
19
1
5.26%
22.6
CO
Peterson Space Force Base
12/14/2021 -2/7/2023
537.1
8
0
0.00%
NA
CO
Peterson Space Force Base
3/1/2022 - 9/14/2022
QSM_B15
16
0
0.00%
NA
DE
Dover AFB
1/22/2022 - 10/25/2022
QSM_B15
10
0
0.00%
NA
FL
Homestead Air Reserve Base
2/21/2022 - 3/30/2023
QSM_B15
13
0
0.00%
NA
FL
WHITING FLD FL NAS
9/1/2022
537.1
2
1
50.00%
3.36
IL
Scott AFB
3/22/2022 - 3/28/2023
QSM_B15
3
0
0.00%
NA
ME
Loring AFB
7/25/2022
QSM_B15
1
0
0.00%
NA
ME
NCTAMSLANT DET CUTLER
4/20/2022 - 12/6/2022
537.1
66
2
3.03%
34.9 (est) -147
MA
Otis ANG (Joint Base Cape Cod -
Massachusetts Military Reservation)
2/28/2022 -11/22/2022
QSM_B15
11
4
36.36%
0.81 (est)-4.5 (est)
Ml
Kl Sawyer AFB
7/13/2022
QSM_B15
2
0
0.00%
NA
MT
Great Falls International Airport
6/15/2022-7/7/2022
537
3
1
33.33%
3.26 (est)
NH
Pease AFB
9/22/2021 - 3/30/2023
QSM_B15
16
8
50.00%
0.84 (est) -190
NJ
Joint Base McGuire-Dix-Lakehurst
3/3/2022 - 5/25/2022
QSM_B15
2
0
0.00%
NA
NM
Cannon AFB
11/11/2021 - 12/13/2021
QSM_B15
2
0
0.00%
NA
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State
Installation Name
Sampling Dates
Analysis
Method
#
Samples
#
Detections
%
Detections
Range of Detections
(ng/L)
NY
Pittsburgh AFB
5/20/2022-8/10/2022
537
8
1
12.50%
2.2
NY
Pittsburgh AFB
11/18/2021 -9/15/2022
537.1
16
1
6.25%
0.56 (est)
NY
Pittsburgh AFB
11/29/2021 -6/27/2023
QSM_B15
15
2
13.33%
2.8-3.1
OK
Tinker AFB
2/2/2023
QSM_B15
3
0
0.00%
NA
Rl
NAVAL AUX LANDING FIELD
5/19/2022
537.1
2
0
0.00%
NA
Rl
NAVAL AUX LANDING FIELD
10/17/2022-2/28/2023
QSM_B15
31
17
54.84%
0.38 (est)-7.03
SD
Ellsworth AFB
3/14/2022
537
1
0
0.00%
NA
SD
Ellsworth AFB
6/9/2022 - 9/7/2022
537.1
2
0
0.00%
NA
SD
Ellsworth AFB
2/7/2022 - 6/23/2022
QSM_B15
36
4
11.11%
10.3 -1,320
TX
Goodfellow AFB
8/18/2022 - 11/15/2022
537
11
1
9.09%
0.58 (est)
TX
Goodfellow AFB
12/6/2022 - 4/27/2023
QSM_B15
28
2
7.14%
6.6 (est) -2,900
TX
Reese AFB
9/14/2022-6/13/2023
1633
504
24
4.76%
0.64 (est) -104
TX
Reese AFB
9/28/2021 - 8/29/2022
QSM_B15
839
33
3.93%
2.1 (est)-551
VA
OCEANA VA NAS
10/19/2022-4/14/2023
537.1
13
0
0.00%
NA
WA
BREMERTON WA NAVBASE
10/11/2022-7/21/2023
537.1
3
2
66.67%
18.4-18.9
WA
Fairchild AFB
9/19/2022-9/27/2022
537
87
1
1.15%
4.6 (est)
WA
Fairchild AFB
2/20/2023 - 3/6/2023
537.1
87
0
0.00%
NA
WA
Fairchild AFB
1/31/2022-7/21/2022
QSM_B15
187
2
1.07%
2.2 (est)-46.3
WA
WHIDBEY IS WANAS
4/21/2022 - 4/20/2023
537.1
11
2
18.18%
1.24 (est)-4.51
Source: DOD, 2023a
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5.2.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the ambient sources of most drinking water. Contaminant occurrence in
ambient water can provide useful information on the potential for contaminants to adversely affect
drinking water supplies. Occurrence data for PFHxS in ambient water are available from the USGS NWIS
database and the EPA's legacy STORET data available through the WQP.
5.2.3.1 National Water Information System (NWIS) Data
The NWIS is the Nation's principal repository of water resources data USGS collects from more than 1.9
million sites (USGS, 2023). NWIS-Web is the general online interface to the USGS NWIS database.
Discrete water-sample and time-series data are available from sites in all 50 States, including 5 million
water samples with 90 million water-quality results. All USGS water quality and flow data are stored in
NWIS, including site characteristics, streamflow, ground water level, precipitation, and chemical
analyses of water, sediment, and biological media, though not all parameters are available for every site.
NWIS houses the NAWQA data and includes other USGS data from unspecified projects. NWIS contains
many more samples at many more sites than the NAWQA Program. Although NWIS is comprised of
primarily ambient water data, some finished drinking water data are included as well. This section
presents analyses of non-NAWQA data in NWIS, downloaded from the WQP in November 2023 (WQP,
2023).
The results of the non-NAWQA NWIS PFHxS analysis are presented in Exhibit 5-13. NWIS data for PFHxS
were listed under the characteristic name "Perfluorohexanesulfonate." PFHxS was detected in
approximately 38 percent of samples (1,122 out of 2,951 samples) and at approximately 34 percent of
sites (594 out of 1,759 sites). The median concentration based on detections was equal to 2.50 ng/L.
(Note that the NWIS data are presented as downloaded; potential outliers were not evaluated or
excluded from the analysis.)
Exhibit 5-13: PFHxS NWIS Data
Site Type
Detection Frequency
(detections are results > reporting level)
Concentration Values
(of detections, in ng/L)
No. of
Samples
No. of
Samples
with
Detections
No.
of
Sites
No. of
Sites with
Detections
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Ground
Water
1,344
305
1,233
300
0.9
3.10
62.0
340
680
Surface
Water
1,607
817
526
294
0
2.35
16.0
420
3100
All Sites
2,951
1,122
1,759
594
0
2.50
22.0
356
3100
Source: WQP, 2023
5.2.3.2 Storage and Retrieval (STORET) Data / Water Quality Portal (WQP)
From its launch in 1999 until it was decommissioned in June 2018, the EPA's STORET Data Warehouse
was collaboratively populated with raw biological, chemical, and physical data from surface water and
ground water sampling by federal, state and local agencies, Native American tribes, volunteer groups,
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academics, and others. Legacy STORET data are accessible through the WQP:
https://www.waterqualitvdata.us/portal/.
STORET data are from monitoring locations in all 50 states as well as multiple territories and jurisdictions
of the United States. Most data are from ambient waters, but in some cases finished drinking water data
are included as well. STORET's data quality limitations include variations in the extent of national
coverage and data completeness from parameter to parameter. Data may have been collected as part of
targeted, rather than randomized, monitoring.
This section presents analyses of STORET data, downloaded from the WQP in November 2023 (WQP,
2023). The EPA reviewed STORET ground water data from wells and springs and surface water data from
lakes, rivers, streams, and reservoirs (WQP, 2023). STORET data for PFHxS were listed under the
characteristic name of "Perfluorohexanesulfonate" and "Perfluorohexanesulfonic acid." The results of
the STORET analysis for PFHxS are presented in Exhibit 5-14 and Exhibit 5-15. Approximately 860
samples were available for analysis. These PFHxS samples were collected between 2006 and 2022. Of
the 614 sites sampled, nearly 78 percent reported detections of PFHxS. Detected concentrations ranged
from 0 to 667 ng/L. (Note: A minimum value of zero could represent a detection that was entered into
the database as a non-numerical value (e.g., "Present").)
Exhibit 5-14: PFHxS STORET Data - Summary of Detected Concentrations
Source Water Type
Concentration Value of Detections (ng/L)
Minimum1
Median
90th Percentile
Maximum
Ground Water
0
0
0
200
Surface Water
0.54
4.00
28.4
667
Unknown
0
0
2.62
3.7
Total
0
0
0.929
667
Source: WQP, 2023
1A minimum value of zero may represent a detection that was entered into the database as a non-numerical value
(e.g., "Present").
Exhibit 5-15: PFHxS STORET Data - Summary of Samples and Sites
Source Water
Type
Total
Number of
Samples
Samples with
Detections
Total
Number
of Sites
Sites with Detections
Number
Percent
Number
Percent
Ground Water
729
655
89.85%
495
447
90.30%
Surface Water
88
24
27.27%
73
19
26.03%
Unknown
47
12
25.53%
46
11
23.91%
Total
864
691
79.98%
614
477
77.69%
Source: WQP, 2023
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5.3 Analytical Methods
For the purposes of compliance with the PFAS NPDWR, the EPA has published two analytical methods
that are available for the analysis of PFHxS and other PFAS in drinking water. The performance metrics
that are presented, including the DL, LCMRL, mean recoveries and RSDs are specific to PFHxS for each of
the listed analytical methods. Ranges of mean recoveries and RSDs are presented for the matrices listed;
data from holding time studies are not included since these studies are designed to demonstrate a
degradation in method performance over time and thus are not indicative of method performance that
should be observed when holding times are not exceeded:
• EPA Method 537.1, Version 2.0, Determination of Selected Per- and Polyfluorinated Alkyl
Substances in Drinking Water by Solid Phase Extraction and Liquid Chromatography/Tandem
Mass Spectrometry (LC/MS/MS). The DL and LCMRL generated by the laboratory that
developed the method are 1.4 ng/L and 2.4 ng/L, respectively. Mean recoveries in fortified
reagent water, tap water from a ground water source (TOC = 0.53 mg/L and hardness = 377
mg/L), tap water from a surface water source (TOC = 2.4 mg/L and hardness = 103 mg/L),
and tap water from a private well (TOC = 0.56 mg/L and hardness = 394 mg/L) range from
93.5 to 110%, with RSDs of 0.9 to 6.7% (USEPA, 2020d).
• EPA Method 533, Determination of Per- and Polyfluoroalkyl Substances in Drinking Water by
Isotope Dilution Anion Exchange Solid Phase Extraction and Liquid Chromatography /
Tandem Mass Spectrometry. The LCMRL generated by the laboratory that developed the
method is 3.7 ng/L (DLs were not calculated Mean recoveries (excluding 13C isotope
analogue data) in fortified reagent water, finished drinking water from a ground water
source (hardness = 320 mg/L, pH = 7.88 at 17° C, free Cl2 = 0.64 mg/L, and total Cl2 = 0.74
mg/L) and clarified surface water (prior to GAC treatment and chlorinated in the laboratory;
pH = 8.1 at 20 °C, free Cl2 = 0.98 mg/L, total Cl2 = 1.31 mg/L. and TOC = 3.8 mg/L) range from
78.5 to 108%, with RSDs of 5.3 to 18% (USEPA, 2019b).
Laboratories participating in UCMR 3 were required to use EPA Method 537 and were required to report
PFHxS values at or above the EPA-defined MRL of 30 ng/L (77 FR 26072; USEPA, 2012b). The MRL was
set based on the capability of multiple laboratories at the time. EPA Method 537.1 was originally
published in November 2018 as Version 1.0 as a more sensitive update to EPA Method 537 (with a
slightly expanded target analyte list). Version 2.0 was published in March 2020 and contains minor
editorial changes to Version 1.0. Use of EPA Method 537.1 is preferable to use of EPA Method 537 (it
may not be feasible to reliably quantitate down to health levels of concern for certain PFAS when using
EPA Method 537). For this reason, only EPA methods 533 and 537.1 are accepted for use in
demonstrating compliance with this final rule.
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6 Perfluorononanoic Acid (PFNA)
This chapter presents information and analysis specific to PFNA, including background information on
the contaminant, information on contaminant sources and environmental fate, an analysis of health
effects, an analysis of occurrence in ambient and drinking water, and information about the availability
of analytical methods and treatment technologies.
6.1 Contaminant Background, Chemical and Physical Properties
Synonyms for PFNA include, perfluoro-n-nonanoic acid, heptadecafluorononanoic acid (NCBI, 2022d),
and perfluorononan-l-oic acid (ATSDR, 2021). The acronym PFNA is also used to refer to the
deprotonated anionic form of the compound, perfluorononanoate, also known as
heptadecafluorononanoic acid anion (NCBI, 2022d).
PFNA is a long chain perfluorinated aliphatic carboxylic acid. Its salts differ from PFNA by being
associated with either an ammonium, potassium ion, sodium ion, or lithium ion. For the purposes of this
document PFNA will signify the ion, acid, or any salt of PFNA.
As a long chain perfluoroalkane carboxylic acid, PFNA is a surfactant that could be used as a wetting
dispersing, emulsifying or foaming agent (NCBI, 2022d). The ammonium salt of PFNA was historically
used to make fluoropolymers including polyvinylidene fluoride (ITRC, 2021) and may be present as a
trace contaminant. PFNA has also been found in semiconductor waste streams (ITRC, 2021).
Eight participating PFNA manufacturers committed to cease PFNA production in the United States by
2015 (ITRC, 2021). Products manufactured and imported prior to 2015 may still contain PFNA and
international manufacturing continued after that date. In 2021, PFNA was petitioned to the United
Nations' Stockholm Convention on POPs for consideration of a manufacturing ban or best available
techniques recommendation (UNEP, 2021). In addition, PFNA may be inadvertently formed as by-
products in commercial products (USEPA, 2021c).
The diagram of Exhibit 6-1 shows the straight-chain chemical structure of PFNA. Depending on their
method of manufacture, PFNA and related compounds may exist as either branched-chain or straight-
chain isomers (ATSDR, 2021). The chemical and physical properties of PFNA are listed in Exhibit 6-2 and
typically represent mixtures of branched and linear isomers rather than any particular isomer.
Exhibit 6-1: Chemical Structure of PFNA - Straight-Chain Isomer
PFNA Structure
Source: NCBI, 2022d
NCBI (2022d) reports a value of 5.48 for the log Kow that is estimated using the EPA's EPISuite™, while
ATSDR (2021) indicated that log Kow is not applicable or cannot be measured since PFBS is expected to
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form multiple layers in octanol and water mixtures. Although long-chain perfluoroalkyls that are
uncharged form layers in water/hydrocarbon mixtures, PFNA is charged/ionized and at typical
environmental pH and has low to moderate solubility in water (NCBI, 2022d; ITRC, 2021). ATSDR reports
no data available for this property while ITRC and HSDB present a value for KH. The KH value presented
by HSDB was estimated from vapor pressure and water solubility using EPISuite™.
Where there are different conclusions in the literature for the properties of PFNA, information is
presented to highlight the range of uncertainty for this compound.
Exhibit 6-2: Physical and Chemical Properties of PFNA
Property
Data
Chemical Abstracts Service (CAS)
Registry Number
375-95-1 (NCBI, 2022d)
EPA Pesticide Chemical Code
Not Applicable
Chemical Formula
C9HFi702(NCBI, 2022d)
Molecular Weight
464.08 g/mol (NCBI, 2022d)
Color/Physical State
Beige Crystalline solid (NCBI, 2022d)
Boiling Point
218 deg C (ITRC, 2021)
Melting Point
53.2-66.5 deg C (ITRC, 2021)
No data (ATSDR, 2021)
Density
1.75-1.80 g/mL (est) (ITRC, 2021)
Freundlich Adsorption Coefficient
-
Vapor Pressure
0.010 mm Hg at 25 deg C (ITRC, 2021; converted from 0.12 log-Pa)
8.4 mm Hg at 99.63 deg C (ITRC, 2021; converted from 1.12 kPa)
0.083 mm Hg at 25 deg C (est) (NCBI, 2022d)
Kh
33.8 atm-m3/mol at 25 deg C (ITRC, 2021; converted from 3.14 log)
No data (ATSDR, 2021 )a
Log Kow
5.48 (est) (dimensionless) (NCBI, 2022d)b
Not applicable0 (ATSDR, 2021)
Koc
2.09E02 - 7.9E03 soil (dimensionless)
(ITRC, 2021; converted from Log Koc 2.32 - 3.9)b
2.0E02 - 7.9E05 sediment (dimensionless)
(ITRC, 2021; Log Koc 2.3-5.9)
2.45E02 (ATSDR, 2021; converted from Log Koc 2.39)
1.2E05 (dimensionless) (est) (NCBI, 2022d)d
pKa
-0.21 (NCBI, 2022d)
-0.21 (est) (ATSDR, 2021)
<1.6 (dimensionless) (ITRC, 2021)
0.82 (est) (ECHA, 2015)
Solubility in Water
12 mg/L (ITRC, 2021; converted from -4.6 log-mol/L)
6.25E-02 mg/L at 25 deg C (est) (NCBI, 2022d)
Other Solvents
-
Conversion Factors
(at 25 deg C, 1 atm)
1 PPM = 18.98 mg/m3; 1 mg/m3 = 0.053 PPM (ATSDR, 2021)
Note:indicates that no information was found.
aThese values should not be used to estimate portioning between water and air.
bSurfactants are surface acting agents that contain both a hydrophilic part and a hydrophobic part which causes them
to accumulate at interfaces hampering the determination of their aqueous concentration. These surfactant properties
present difficulties in applying existing methods for the experimental determination of log Kowand produce unreliable
results.
c The log K0w is not measurable since these substances are expected to form multiple layers in an octanol-water
mixture (3M 1999, 2008).
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d An experimental value for log Koc (0.62 to 1.9) was not included due to an incomplete mass balance (ITRC, 2021).
6.1.1 Sources and Environmental Fate
6.1.1.1 Production, Use, and Release
No production data for PFNA are available from the EPA's IUR and CDR programs.9 Industrial release
data are available from the EPA's TRI, described below.
Toxics Release Inventory (TRI)
The EPA established TRI in 1987 in response to section 313 of the EPCRA. EPCRA section 313 requires
the reporting of annual information on toxic chemical releases from facilities that meet specific criteria.
This reported information is maintained in a database accessible through TRI Explorer (USEPA, 2023b).
Although TRI can provide a general idea of release trends, it has limitations. Not all facilities are required
to report all releases. Facilities are required to report releases if they manufacture, process, or
otherwise use a listed toxic chemical in quantities above the respective activity threshold. For PFNA, the
reporting threshold is 100 lbs. manufactured, processed, or otherwise used over the year. It should also
be noted that, as of this publication, quantities of PFNA at concentrations under 1.0 percent within
mixtures may be exempt from TRI reporting requirements. Reporting requirements have changed over
time (e.g., the chemical list have been updated), so conclusions about temporal trends should be drawn
with caution. TRI data are meant to reflect releases and other waste management activities and should
not be used to estimate general public exposure to a chemical (USEPA, 2023b).
TRI data for PFNA are available for 2020 through 2022 (USEPA, 2023b). As shown in Exhibit 3-5, no
releases were reported for 2020 or 2021. In 2022, 3,400 pounds of on-site releases to land were
reported by one facility in Alabama (USEPA, 2023b).
Exhibit 6-3: Environmental Releases of PFNA in the United States, 2020-2022
On-Site Releases (in pounds)
Year
Air
Emissions
Surface
Water
Discharges
Underground
Injection
Releases to
Land
Total Off-
Site
Releases
(in pounds)
Total On-
and Off-Site
Releases
(in pounds)
2020
0
0
0
0
0
0
2021
0
0
0
0
0
0
2022
0
0
0
3,400
0
3,400
Source: USEPA, 2023b
9 Note that there are 2020 CDR data listed for "Perfluoro compounds, C5-18." Those data are not summarized in
this report.
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6.1.1.2 Environmental Fate
The primary measures used by the EPA to assess mobility include (where available) Koc, log Kow, KH, water
solubility and vapor pressure. For PFNA, pKa is also important.
Modeling of atmospheric behavior of PFNA suggest that PFNA will be present predominantly as a vapor
if released to the atmosphere (NCBI, 2022d). PFNA can react with photochemically produced hydroxyl
radicals in the atmosphere to degrade (NCBI, 2022d). A half-life for this reaction in air is estimated to be
31 days (NCBI, 2022d). (Note that radical reactions typically proceed more rapidly than chemically- or
microbially-mediated degradation reactions in other environmental media such as water, soil, and/or
sediment.) PFNA is not expected to undergo direct photolysis (NCBI, 2022d).
Based on findings from laboratory studies and estimation methods, log Koc suggests a propensity for
PFNA to adsorb to suspended solids or sediments (NCBI, 2022d). Based on the vapor pressure, PFNA is
not expected to volatilize from dry soil (NCBI, 2022d). With a pKa of less than 1.0, PFNA is expected to
exist in its ionized form at typical environment pH ranges of natural waters (NCBI, 2022d). Thus,
volatilization from water at typical environment pH is not expected (NCBI, 2022d).
PFNA is very stable chemically and is resistant to hydrolysis, photolysis, and biodegradation (NCBI,
2022d; ECHA, 2015). A resistance to essentially all forms of degradation other than atmospheric
processes indicates high persistence.
Under CCL 3, the EPA created scales10 to informally rank chemical contaminants' likely mobility
(understood as their tendency to partition to water rather than other media) and persistence as "high,"
"moderate," or "low" based on physical and chemical properties (see USEPA, 2021b and USEPA, 2009).
For PFNA, a log Kow of 5.48, and a water solubility of 12 mg/L (ITRC, 2021) at 25 degrees C predict a
moderate favorability of partitioning to water.
6.2 PFNA Occurrence
This section presents data on the occurrence of PFNA in drinking water and ambient water in the United
States. The EPA is finalizing an MCLG of 10 ppt for PFNA. Under SDWA, the EPA must establish an
enforceable MCL, the maximum concentration of a contaminant that is allowed in PWSs, as close to the
MCLG as feasible, taking several factors into consideration, including analytical methods capable of
measuring the contaminant, available treatment technologies to remove the contaminant, and costs.
Based on these factors, the EPA is finalizing an MCL of 10 ppt for PFNA. Occurrence data from various
sources presented below are analyzed with respect to the MCL. When possible, estimates of the
population exposed at concentrations above the MCL are presented. Also, when possible, studies that
are meant to be representative and studies that are targeted at known or suspected sites of
contamination are identified as such.
The drinking water analyses presented in this section were performed for UCMR 3 and select state data
sources. In addition, this section presents PFNA findings from occurrence analyses conducted by non-
EPA researchers. For additional background information about data sources used to evaluate
occurrence, please refer to Chapter 2.
10 See Exhibit A.8 here: https://www.epa.gov/sites/default/files/2014-05/documents/ccl3 pccltoccl 08-31-
09 508.pdf
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The EPA is also finalizing an HI MCL for the regulation of PFHxS, PFNA, HFPO-DA, and PFBS when co-
occurring in mixture combinations containing two or more of these four PFAS. Refer to Chapter 8 for
more information on the HI MCL and chapter 9 for co-occurrence information.
6.2.1 Occurrence in Drinking Water
Data sources reviewed by the agency for information on PFNA occurrence in drinking water included
UCMR 3, more recent state drinking water monitoring programs, and the DoD PFAS drinking water
testing, as well as additional studies from the literature. Note that there may be some overlap, as
sources with different purposes and audiences may have reported the same underlying data. UCMR 3 is
a nationally representative data source. Other data sources profiled in this section are considered
"supplemental" sources. Also note that PFNA is being monitored for under UCMR 5, which is occurring
from 2023 to 2025. Analysis of partial UCMR 5 results (the first three quarters of data that were made
available as of February 2024) are discussed in section 11 of this document. Additionally, the EPA notes
that the UCMR 3 MRL for PFNA is higher than that utilized within the majority of state monitoring data
and for the UCMR 5.
6.2.1.1 UCMR 3 Data
PFNA was included as part of the nationally representative UCMR 3 monitoring from 2013 through 2015.
UCMR 3 Assessment Monitoring occurrence data are available for PFNA from all large and very large
PWSs (serving between 10,001 and 100,000 people and serving more than 100,000 people,
respectively), plus a statistically representative national sample of 800 small PWSs (serving 10,000
people or fewer).11 Surface water and GWUDI sampling points were monitored four times during the
applicable year of monitoring, and ground water sample points were monitored twice during the
applicable year of monitoring. See USEPA (2012b) and USEPA (2019a) for more information on the
UCMR 3 study design and data analysis.
Exhibit 6-3 through Exhibit 6-5 provide an overview of PFNA occurrence results from the UCMR 3
Assessment Monitoring. Laboratories participating in UCMR 3 were required to report values at or
above MRLs defined by the EPA. The UCMR MRLs are not intended to represent the lowest achievable
measurement level an individual laboratory may achieve. Rather, the MRLs are established to ensure
reliable and consistent results from the array of laboratories needed for a national monitoring program
and are set based on the quantitation level capability of multiple commercial laboratories prior to
beginning each UCMR round. The MRL used for PFNA in the UCMR 3 survey was 20 ng/L (77 FR 26072;
USEPA, 2012b). Exhibit 6-3 presents a sample-level summary of the results. Exhibit 6-4 shows a
statistical summary of PFNA concentrations by system size and source water type (including the
minimum, 25th percentile, median, 75th percentile, 90th percentile, 99th percentile, and maximum).
Exhibit 6-5 shows system-level results for detections greater than or equal to the MRL.
A total of 36,972 finished water samples for PFNA were collected from 4,920 PWSs. PFNA was reported
> MRL of 20 ng/L in 0.05 percent of UCMR 3 samples. Reported PFNA concentrations for these results
ranged from 22 ng/L to 55.88 ng/L. Of 4,920 systems, 14 (0.28 percent of systems, serving 0.22 percent
of the PWS-served population) reported at least one detection.
11A total of 799 small systems submitted Assessment Monitoring results.
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Exhibit 6-4: PFNA National Occurrence Measures Based on UCMR 3 Assessment
Monitoring Data - Summary of Samples
Source Water Type
Total # of
Samples
Samples with Detections
> MRL of 20 ng/L
Number
Percent
Small Systems (serving < 10,000 people)
Ground Water
1,853
0
0.00%
Surface Water
1,421
1
0.07%
All Small Systems
3,274
1
0.03%
Large Systems (serving 10,001 -100,000 people) — CENSUS
Ground Water
11,707
11
0.09%
Surface Water
14,860
5
0.03%
All Large Systems
26,567
16
0.06%
Very Large Systems (serving > 100,000 people) — CENSUS
Ground Water
2,020
1
0.05%
Surface Water
5,111
1
0.02%
All Very Large Systems
7,131
2
0.03%
All Systems
All Water Systems
36,972
19
0.05%
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Exhibit 6-5: PFNA Occurrence Data from UCMR 3 Assessment Monitoring - Summary of Reported Concentrations
Source Water Type
Concentration Value of Detections (in ng/L) > MRL of 20 ng/L
Minimum
25th percentile
Median
75th percentile
90th Percentile
99th Percentile
Maximum
Small Systems (serving < 10,000 people)
Ground Water
-
-
-
-
-
-
-
Surface Water
26
26
26
26
26
26
26
All Small Systems
26
26
26
26
26
26
26
Large Systems (serving 10,001 -100,000 people) — CENSUS
Ground Water
22
26.8
28.1
34.9
52.1
52.64
52.7
Surface Water
29
30
46.16
46.6
52.168
55.5088
55.88
All Large Systems
22
27.75
31.15
46.27
52.4
55.403
55.88
Very Large Systems (serving > 100,000 people) — CENSUS
Ground Water
32
32
32
32
32
32
32
Surface Water
53.8
53.8
53.8
53.8
53.8
53.8
53.8
All Very Large
Systems
32
37.45
42.9
48.35
51.62
53.582
53.8
All Systems
All Water Systems
22
27.5
32
46.38
52.92
55.5056
55.88
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Exhibit 6-6: PFNA National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data - Summary of
System and Population Served Data - Reported Detections
Source Water
Type
UCMR 3 Samples
Number With At Least
One Detection > MRL of
20 ng/L
Percent With At Least
One Detection > MRL of
20 ng/L
National Inventory
Percent of National
Inventory Included
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems (serving < 10,000 people)
Ground Water
527
1,498,845
0
0
0.00%
0.00%
55,700
38,730,597
0.95%
3.87%
Surface Water
272
1,250,215
1
8,323
0.37%
0.67%
9,728
20,007,917
2.80%
6.25%
All Small
Systems
799
2,749,060
1
8,323
0.13%
0.30%
65,428
58,738,514
1.22%
4.68%
Large Systems (serving 10,001 -100,000 people) — CENSUS
Ground Water
1,453
37,141,418
7
140,373
0.48%
0.38%
1,470
37,540,614
98.84%
98.94%
Surface Water
2,260
69,619,878
4
148,645
0.18%
0.21%
2,310
70,791,005
97.84%
98.35%
All Large
Systems
3,713
106,761,296
11
289,018
0.30%
0.27%
3,780
108,331,619
98.23%
98.55%
Very Large Systems (serving > 100,000 people) — CENSUS
Ground Water
68
16,355,951
1
120,000
1.47%
0.73%
68
16,355,951
100.00%
100.00%
Surface Water
340
115,158,260
1
109,000
0.29%
0.09%
343
120,785,622
99.13%
95.34%
All Very Large
Systems
408
131,514,211
2
229,000
0.49%
0.17%
411
137,141,573
99.27%
95.90%
All Systems
All Water
Systems
4,920
241,024,567
14
526,341
0.28%
0.22%
69,619
304,211,706
7.07%
79.23%
167
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April 2024
6.2.1.2 State Monitoring Data
In the development of the proposed and final NPDWR, the agency supplemented its UCMR 3 data with
more recent publicly available data collected by states. In general, these more recent state data were
collected using newer analytical methods and state results reflect lower reporting and detection limits
than those in the UCMR 3. Drinking water occurrence data from PWSs for PFNA were available online
from several states, including Alabama, Arizona, California, Colorado, Georgia, Idaho, Illinois, Indiana,
Iowa, Kentucky, Maine, Maryland, Massachusetts, Michigan, Missouri, New Hampshire, New Jersey,
New Mexico, New York, North Carolina, North Dakota, Ohio, Oregon, Pennsylvania, South Carolina,
Tennessee, Vermont, Virginia, and Wisconsin. The EPA downloaded publicly available monitoring data
from state websites through May 2023. Note that while some states did have available raw water data
as indicated in Exhibit 6-6, for the subsequent analyses the EPA only evaluated finished water results.
Exhibit 6-6 provides a summary of the available state reported monitoring data for PFNA, including date
range and a description of coverage and representativeness (including whether monitoring was non-
targeted or targeted (i.e., monitoring in areas of known or potential PFAS contamination)). A description
of those studies is also included in Exhibit 6-6. State reporting thresholds are also provided, where
available, in Exhibit 6-6. The EPA notes that different states utilized various reporting thresholds when
analyzing and presenting their data, and for some states there were no clearly defined thresholds
publicly provided; in these cases, minimum detected concentrations reported may be indicative of
reporting thresholds used. Further, for some states, the thresholds varied when reporting results for the
same analyte, as well as the laboratory analyzing the data. For those states, a range of thresholds is
provided. As shown in Exhibit 6-6, some states reported at thresholds and/or presented data at
concentrations below the EPA's final MCL and/or PQL for PFNA. However, to present the best available
occurrence information, the EPA collected and evaluated the data based on the information as reported
directly by the states and when conducting data analyses incorporated individual state-specific reporting
thresholds where possible. Additionally, the EPA notes that the majority of the data were analyzed via
an EPA-approved drinking water analytical method.
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Exhibit 6-7: Summary of Available PFNA State Reported Monitoring Data
State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
Alabama
(ADEM, 2023)
2020-2022
Ground Water and
Surface Water -
Finished Water
Not reported
ADPH instructed water systems to carry out PFAS monitoring at all
PWSs not previously sampled during UCMR 3. In 2022, water systems
that had not been sampled since UCMR 3 were required to sample
between January and June 2022 using current analytical methods .
Only results that are above the MRL are posted online; thus, only
reported detections were available for use in the occurrence analyses.
Non-
Targeted
Arizona
(ADEQ, 2023)
2021
Ground Water and
Surface Water - Raw
and Finished Water
1.6-2
ADEQ presents a PFAS Interactive Data Map that displays the results
of testing conducted by ADEQ since 2018 at PWSs across Arizona.
Targeted
California
(CADDW, 2023)
2013-
April 2023
Ground Water and
Surface Water -
Raw, Finished, and
Unknown Water
0.002 -20
The EPA reviewed the California PFNA data available online through
April 2023. Finished water data were available from approximately 120
PWSs. For this analysis, the EPA only included results that were
explicitly marked as being from treated water. Sampling in California is
ongoing.
Targeted
Colorado
(CDPHE,
2018;CDPHE,
2020)
2013-
2017
Surface Water
(Finished Water)
and Drinking Water
Distribution Samples
2-30
Data available from 28 "drinking water distribution zones" (one or more
per PWS) in targeted sampling efforts at a known contaminated aquifer
region. Data were collected by El Paso County Public Health, local
water districts and utilities, and the CDPHE.
Targeted
2020
Ground Water and
Surface Water - Raw
and Finished Water
1.6-2.4
CDPHE offered free testing to PWSs serving communities, schools,
and workplaces and also to fire districts with wells. Approximately 50%
of PWSs in Colorado participated in the 2020 PFAS sampling project.
Data included in this report were collected in March through May of
2020.
Non-
Targeted
Georgia
(GA EPD, 2020)
2020
Surface Water -
Raw, Finished, and
Unknown Water
20
The EPA and the GA EPD conducted joint sampling of the City of
Summerville's drinking water sources and finished drinking water in
January 2020.
Targeted
Idaho
(Idaho DEQ,
2023)
2021 -
April 2023
Ground Water -
Finished and
Unknown Water
0.5-1
Sampling of finished drinking water data between September 2021 and
April 2023 that were available on the state's Drinking Water Watch
website.
Not
specified
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State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
Illinois
(IL EPA, 2023)
2020-
May 2023
Ground Water and
Surface Water - Raw
and Finished Water
1.7-2
In 2020, the IL EPA initiated a statewide investigation into the
prevalence and occurrence of PFAS in finished drinking water at 1,749
community water supplies across Illinois. The EPA reviewed finished
drinking water data collected between September 2020 and May 2023
that were available on the state's Drinking Water Watch website.
Sampling in Illinois is ongoing.
Non-
Targeted
Indiana (IDEM,
2023)
2021 -
January
2023
Ground Water and
Surface Water -
Raw, Finished, and
Unknown Water
2
Beginning in February 2021, the IDEM facilitated PFAS monitoring at all
CWSs throughout the state of Indiana. Samples were to be collected at
all raw water (i.e., wells and intakes) and finished (after treatment)
water points in a CWS's supply to evaluate the statewide occurrence of
PFAS compounds in CWS across the state and determine the efficacy
of conventional drinking water treatment for PFAS.
Non-
Targeted
Iowa
(IA DNR, 2023)
2021 -
April 2023
Ground Water and
Surface Water - Raw
and Finished Water
1.7-4
In January 2020, the Iowa DNR developed an Action Plan to protect the
health of Iowa residents and the environment from PFAS. Data were
downloaded from the PFAS Sampling Interactive Dashboard and Map.
Targeted
Kentucky
(KYDEP, 2019)
2019
Ground Water and
Surface Water -
Finished Water
3.24
Sampling of finished drinking water data between June and October
2019. Under this sampling effort, data are available from 81 community
public DWTPs, representing 74 PWSs, and serving more than 2.4
million people.
Non-
Targeted
Maine
(Maine DEP,
2020; Maine
DHHS, 2023)
2013-
2020
Drinking Water -
Raw, Finished, and
Unknown Water
1.78-20
In March 2019, the Maine PFAS Task Force was created to review the
extent of PFAS contamination in Maine. Finished water results collected
from 2013 through 2020 have been collected at 23 locations throughout
the state. Data may include results from public and private finished
drinking water sources. Sampling in Maine is ongoing.
Targeted
2021 -
January
2023
Ground Water and
Surface Water -
Finished Water
2
The EPA reviewed the finished water data reported to the Maine CDC
Drinking Water Program as compliance samples since June 2021 and
processed in the database as of 3/10/2023. Sampling in Maine is
ongoing.
Non-
Targeted
Maryland
(MDE, 2021;
MDE, 2022a;
MDE, 2022b)
2020-
2022
Raw and Finished
Water
2
In 2020, MDE initiated a project to identify potential sources of PFAS in
Maryland and to prioritize water sources for PFAS sampling. The EPA
reviewed the finished water results from the first three phases of MDE's
Public Water System study for the occurrence of PFAS in State drinking
water sources. Under Phase 1 (September 2020 - February 2021), sites
were selected for priority sampling based on MDE's evaluation of
potential relative risk for PFAS exposure through drinking water. Under
Phase 2 (March 2021 - May 2021), MDE conducted sampling at sites
that were selected based on their geological setting and proximity to
Targeted
(Phase 1,
Phase 2);
Non-
Targeted
(Phase
3)
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State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
potential sources of PFAS. Under Phase 3 (August 2021- June 2022),
MDE tested the remaining CWSs in the state.
Massachusetts
(MA EE A, 2023)
2016-April
2023
Ground Water and
Surface Water - Raw
and Finished Water
0.43-10
The EPA reviewed the finished water data available online through April
2023. Data were available from 226 PWSs. Sampling in Massachusetts
is ongoing.
Targeted
Michigan
(Michigan EGLE,
2023)
2020-
March
2023
Ground Water and
Surface Water -
Finished Water
2
The Michigan EGLE developed MCLs for seven PFAS compounds in
Michigan, which took effect in August 2020. The EPA reviewed
available finished compliance monitoring results through March 2023.
Sampling in Michigan is ongoing.
Non-
Targeted
Minnesota
(MDH, 2023)
2020-
2023
Ground Water and
Surface Water -
Finished Water
Not reported
Through the Statewide PFAS Monitoring Project, MDH is testing CWSs
across the state for PFAS. The EPA reviewed finished water data
through MDH's Interactive Dashboard for PFAS Testing in Drinking
Water.
Non-
Targeted
Missouri
(Missouri DNR,
2023)
2022-
2023
Ground Water and
Surface Water - Raw
and Finished Water
Not reported
The EPA reviewed the finished water data available online from
Missouri DNR's "PFAS Viewer Tool" which identifies the location of
voluntary sampling for PFAS in public drinking water systems in
Missouri. The EPA reviewed finished water data collected from
approximately 113 PWSs from 2022 through 2023. Limited data were
also available from 2013 through 2017.
Non-
Targeted
New Hampshire
(NHDES, 2021)
2016-
May 2021
Ground Water and
Surface Water - Raw
and Finished Water
Not reported
The EPA reviewed the New Hampshire PFNA data available online
through May 2021. Finished water data were available from more than
500 PWSs. Sampling in New Hampshire is ongoing.
Non-
Targeted
New Jersey
(NJDEP, 2023)
2019-
May 2023
Ground Water and
Surface Water -
Raw, Finished, and
Unknown Water
0.019-2,000
Statewide sampling of finished drinking water data was available from
2019-2023. The EPA reviewed data available online through May 2023.
Sampling in New Jersey is ongoing.
Non-
Targeted
New Mexico
(NMED, 2019)
2016
Ground Water - Raw
and Finished Water
Not reported
NMED, Department of Health and the U.S. Air Force conducted testing
at public drinking water supplies at or around Cannon Air Force Base
up to 2019.
Targeted
New York
(NYDOH, 2022)
2017-
2022
Ground Water and
Surface Water -
Raw, Finished, and
Unknown Water
0.000000001 -
2,020
The EPA reviewed finished water data voluntarily provided by the state
to the EPA. Data were available from nearly 2,600 PWSs from 2017
through 2022. Limited data were also available from 2013 and 2016.
Non-
Targeted
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State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
North Carolina
(NCDEQ, 2021)
2017-
2019
Finished and
unknown water
Not reported
NCDEQ and the Department of Health and Human Services
investigated the presence of HFPO-DA and other PFAS in the Cape
Fear River in June 2017. Monthly results were also collected from five
water treatment plants on the Cape Fear River. Data were available
from June 2017 through October 2019. Only results above the DL were
reported; thus, only reported detections were available for use in the
occurrence analyses.
Targeted
North Dakota
(NDDEQ, date
unknown;
NDDEQ, date
unknown)
2020,
2021
Ground Water and
Surface Water - Raw
and Finished Water
Not reported
NDDEQ published a 2020 and a 2021 survey report of North Dakota
Statewide PFAS Presence/Absence results. The sampling effort in
October of 2020 sought to determine if there was a PFAS presence in a
representative portion of the state's public water supply. In 2021,
sampling conducted as part of the third phase of the survey focused on
drinking water sites not evaluated in the first two surveys.
Non-
Targeted
Ohio
(Ohio EPA,
2023)
December
2019-
December
2021
Ground Water and
Surface Water - Raw
and Finished Water
5
The Ohio EPA coordinated sampling of raw and finished drinking water
from PWSs throughout the state. The EPA reviewed the finished water
data available online through December 2021. During this timeframe,
data were available from 1,479 PWSs.
Non-
Targeted
Oregon
(OHA-DWS,
2022)
2021 - July
2022
Ground Water and
Surface Water -
Finished Water
10.1 -12.4
OHA conducted a PFAS drinking water monitoring project in 2021 at
PWSs in Oregon identified as at risk due to their proximity to a known
or suspected PFAS use or contamination site. The EPA reviewed the
finished water data from more than 140 PWSs.
Targeted
Pennsylvania
(PADEP, 2019)
2019
Ground Water and
Surface Water -
Finished Water
1.9
A PFAS Sampling Plan was developed to test PWSs across the state.
Finished water data were collected for 87 PWSs in 2019.
Targeted
Pennsylvania
(PADEP, 2021)
2020-
March
2021
Ground Water and
Surface Water -
Finished Water
1.7-4
Beginning in 2020 and running through March of 2021, finished water
data were collected by more than 340 PWSs.
Targeted
South Carolina
(SCDHEC, 2020;
SCDHEC, 2023)
2017-
March
2023
Ground Water and
Surface Water -Raw
and Finished Water
2.1
The EPA reviewed PFAS sampling results collected by the South
Carolina Bureau of Water for community drinking water systems Data
were available from 300 PWSs..
Non-
Targeted
Tennessee
(TDEC, 2023)
2019
Surface Water - Raw
and Finished Water
Not reported
In 2019, Metro Water Services conducted a voluntary sampling of
Nashville's drinking water systems for PFAS. Their stated goal was to
go above and beyond current federal and state monitoring requirements
to understand the potential presence of PFAS in Nashville's drinking
water.
Non-
Targeted
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State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
Vermont
(VT DEC, 2023)
2019 -April
2023
Ground Water and
Surface Water -
Raw, Finished, and
Unknown Water
2
The Vermont Water Supply Rule required all CWSs and NTNCWSs to
sample for PFAS. The EPA reviewed finished water data available
online from July 2019 - April 2023 from approximately 560 PWSs.
Sampling in Vermont is ongoing.
Non-
Targeted
Virginia
(VDH ODW,
2021)
2021
Ground Water and
Surface Water - Raw
and Finished Water
3.5
The Virginia ODW, in conjunction with VA PFAS work group, designed
the sample study to prioritize sites for measuring PFAS concentrations
in drinking water and major sources of water and generate statewide
occurrence data.
Targeted
/ Non-
Targeted
Wisconsin
(Wl DNR, 2023)
2022-
April 2023
Ground Water and
Surface Water -
Raw, Finished, and
Unknown Water
Not reported
The EPA reviewed the finished water data available online from 2022 -
2023. Data were available from nearly 250 PWSs. Sampling in
Wisconsin is ongoing.
Non-
Targeted
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April 2024
A summary of state reported monitoring data from PWSs for PFNA is presented in Exhibit 6-7 through
Exhibit 6-9. As noted above, some of the monitoring data from each state are limited and may not be
representative of occurrence in the state. In addition, states have varying reporting thresholds, as
indicated in the first column of Exhibit 6-7. For states with available reporting thresholds, only detected
concentrations greater than the reporting thresholds were counted as detections. For states that did not
provide reporting thresholds, the EPA included all detected concentrations reported in the count of
detections. Overall, state reported detected concentrations ranged from 0.22 ppt (North Carolina) to
330 ppt (New York). Note that for a small number of systems, population served information could not
be identified. These systems were included in the counts and analysis presented in Exhibit 6-9; however,
no associated population served was included in the counts and analysis presented in Exhibit 6-9.
Exhibit 6-8: PFNA State Reported Drinking Water Occurrence Data - Summary of
Finished Water Samples
State
(Reporting
Threshold)
Source Water Type
Total
Number of
Samples
All Detections
All Detections
> 10 ppt
Number
Percent
Number
Percent
Alabama1
(Not reported)
Ground Water
-
2
-
1
-
Surface Water
-
17
-
0
-
Total
-
19
-
1
-
Arizona
(1.6-2 ppt)
Ground Water
23
1
4.3%
0
0.0%
Surface Water
2
1
50.0%
0
0.0%
Total
25
2
8.0%
0
0.0%
California
(0.002 - 20 ppt)
Ground Water
1,882
24
1.3%
0
0.0%
Surface Water
3,946
49
1.2%
0
0.0%
Unknown
4
0
0.0%
0
0.0%
Total
5,832
73
1.3%
0
0.0%
Colorado
(2013-2017)
(2 - 30 ppt)
Distribution (Finished)
94
5
5.3%
4
4.3%
Surface water (Finished)
11
0
0.0%
0
0.0%
Total
105
5
4.8%
4
3.8%
Colorado (2020)
(1.6-2.4 ppt)
Ground Water
339
4
1.2%
0
0.0%
Surface Water
244
1
0.4%
0
0.0%
Total
583
5
0.9%
0
0.0%
Georgia
(20 ppt)
Ground Water
0
0
0.0%
0
0.0%
Surface Water
2
0
0.0%
0
0.0%
Total
2
0
0.0%
0
0.0%
Idaho
(0.5 -1 ppt)
Ground Water
18
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Total
18
0
0.0%
0
0.0%
Illinois
(1.7-2 ppt)
Ground Water
1,823
3
0.2%
0
0.0%
Surface Water
302
10
3.3%
0
0.0%
Total
2,125
13
0.6%
0
0.0%
Indiana
Ground Water
422
0
0.0%
0
0.0%
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State
(Reporting
Threshold)
(2 ppt)
Source Water Type
Total
Number of
Samples
All Detections
All Detections
> 10 ppt
Number
Percent
Number
Percent
Surface Water
59
1
1.7%
0
0.0%
Total
481
1
0.2%
0
0.0%
Iowa
(1.7-4 ppt)
Ground Water
151
0
0.0%
0
0.0%
Surface Water
63
0
0.0%
0
0.0%
Total
214
0
0.0%
0
0.0%
Kentucky
(3.24 ppt)
Ground Water
33
0
0.0%
0
0.0%
Surface Water
48
2
4.2%
0
0.0%
Total
81
2
2.5%
0
0.0%
Maine (PFAS Task
Force)2
(1.78-20 ppt)
Ground Water
9
0
0.0%
0
0.0%
Surface Water
3
0
0.0%
0
0.0%
Unknown
75
6
8.0%
0
0.0%
Total
87
6
6.9%
0
0.0%
Maine
(Compliance)
(2 ppt)
Ground Water
646
23
3.6%
3
0.5%
Surface Water
62
2
3.2%
0
0.0%
Total
708
25
3.5%
3
0.4%
Maryland (Phase 1)
(2 ppt)
Ground Water
70
2
2.9%
0
0.0%
Surface Water
76
3
3.9%
0
0.0%
Total
146
5
3.4%
0
0.0%
Maryland (Phase 2)
(2 ppt)
Ground Water
9
1
11.1%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Total
9
1
11.1%
0
0.0%
Maryland (Phase 3)
(2 ppt)
Ground Water
88
2
2.3%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Total
88
2
2.3%
0
0.0%
Massachusetts
(0.43-10 ppt)
Ground Water
7,201
245
3.4%
8
0.1%
Surface Water
2,133
28
1.3%
0
0.0%
Total
9,334
273
2.9%
8
0.1%
Michigan
(2 ppt)
Ground Water
10,007
64
0.6%
6
0.1%
Surface Water
519
1
0.2%
0
0.0%
Unknown
164
1
0.6%
0
0.0%
Total
10,690
66
0.6%
6
0.1%
Missouri,
2022 - 2023
(Not reported)
Ground Water
192
0
0.0%
0
0.0%
Surface Water
22
0
0.0%
0
0.0%
Total
214
0
0.0%
0
0.0%
New Hampshire
(Not reported)
Ground Water
1,656
59
3.6%
14
0.8%
Surface Water
157
1
0.6%
0
0.0%
Unknown
1
0
0.0%
0
0.0%
Total
1,814
60
3.3%
14
0.8%
New Jersey
(0.019-2,000 ppt)
Ground Water
12,891
888
6.9%
40
0.3%
Surface Water
3,356
360
10.7%
30
0.9%
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State
(Reporting
Threshold)
Source Water Type
Total
Number of
Samples
All Detections
All Detections
> 10 ppt
Number
Percent
Number
Percent
Unknown
18
0
0.0%
0
0.0%
Total
16,265
1,248
7.7%
70
0.4%
New Mexico
(Not reported)
Ground Water
2
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Total
2
0
0.0%
0
0.0%
New York
(0.000000001-
2,020 ppt)
Ground Water
1,827
171
9.4%
8
0.4%
Surface Water
397
21
5.3%
0
0.0%
Unknown
9
0
0.0%
0
0.0%
Total
2,233
192
8.6%
8
0.4%
North Carolina1
(Not Reported)
Unknown
-
372
-
323
-
Total
-
372
-
323
-
North Dakota
(2020)
(Not reported)
Ground Water
42
0
0.0%
0
0.0%
Surface Water
9
0
0.0%
0
0.0%
Total
51
0
0.0%
0
0.0%
North Dakota
(2021)
(Not reported)
Ground Water
56
0
0.0%
0
0.0%
Surface Water
7
0
0.0%
0
0.0%
Total
63
0
0.0%
0
0.0%
Ohio
(5 ppt)
Ground Water
1,775
5
0.3%
2
0.1%
Surface Water
170
1
0.6%
0
0.0%
Total
1,945
6
0.3%
2
0.1%
Oregon
(10.1 -12.4 ppt)
Ground Water
131
0
0.0%
0
0.0%
Surface Water
29
0
0.0%
0
0.0%
Total
160
0
0.0%
0
0.0%
Pennsylvania
(2019)
(1.9 ppt)
Ground Water
75
4
5.3%
0
0.0%
Surface Water
21
2
9.5%
0
0.0%
Total
96
6
6.3%
0
0.0%
Pennsylvania
(2021)
(1.7-4 ppt)
Ground Water
314
16
5.1%
1
0.3%
Surface Water
98
7
7.1%
1
1.0%
Total
412
23
5.6%
2
0.5%
South Carolina
(2.1 ppt)
Ground Water
572
0
0.0%
0
0.0%
Surface Water
188
1
0.5%
0
0.0%
Total
760
1
0.1%
0
0.0%
Tennessee
(Not reported)
Ground Water
0
0
0.0%
0
0.0%
Surface Water
2
0
0.0%
0
0.0%
Total
2
0
0.0%
0
0.0%
Vermont
(2 ppt)
Ground Water
1,463
39
2.7%
10
0.7%
Surface Water
102
0
0.0%
0
0.0%
Total
1,565
39
2.5%
10
0.6%
Virginia
(3.5 ppt)
Ground Water
5
0
0.0%
0
0.0%
Surface Water
36
0
0.0%
0
0.0%
176
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water Type
Total
Number of
Samples
All Detections
All Detections
> 10 ppt
Number
Percent
Number
Percent
Total
41
0
0.0%
0
0.0%
Wisconsin
(Not reported)
Ground Water
690
13
1.9%
0
0.0%
Surface Water
47
3
6.4%
0
0.0%
Total
737
16
2.2%
0
0.0%
1 Only reported detections were available in this state's dataset.
2 Reported data from Maine may include results from public and private finished drinking water sources. Based
on available state data information, the EPA could not verify PWSIDs for all included samples.
Exhibit 6-9: PFNA State Reported Drinking Water Occurrence Data - Summary of
Detected Concentrations
State
(Reporting
Threshold)
Source Water
Type
Concentration Value of Detections (ppt)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Alabama1
(Not reported)
Ground Water
7.2
12.6
16.9
17.9
18
Surface Water
0.5
2.10
6.40
6.48
6.5
Total
0.5
3.70
6.64
16.1
18
Arizona
(1.6-2 ppt)
Ground Water
4.1
4.1
4.1
4.1
4.1
Surface Water
4.5
4.5
4.5
4.5
4.5
Total
4.1
4.30
4.46
4.50
4.5
California
(0.002-20
PPt)
Ground Water
0.23
2.40
3.00
7.24
8.3
Surface Water
1.8
3.50
5.90
7.07
7.5
Unknown
-
-
-
-
-
Total
0.23
3.20
4.26
7.72
8.3
Colorado
(2013-2017)
(2 - 30 ppt)
Distribution
(Finished)
9.2
78.0
160
178
180
Surface water
-
-
-
-
-
Total
9.2
78.0
160
178
180
Colorado
(2020)
(1.6-2.4 ppt)
Ground Water
1.9
2.20
5.20
6.28
6.4
Surface Water
2.4
2.4
2.4
2.4
2.4
Total
1.9
2.40
4.80
6.24
6.4
Georgia
(20 ppt)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
-
--
--
--
-
Idaho
(0.5 -1 ppt)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
-
--
--
--
-
Illinois
(1.7-2 ppt)
Ground Water
2.1
2.10
2.26
2.30
2.3
Surface Water
2
2.70
3.06
3.55
3.6
Total
2
2.60
3.00
3.53
3.6
177
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water
Type
Concentration Value of Detections (ppt)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Indiana
(2 ppt)
Ground Water
-
-
-
-
-
Surface Water
4.823
4.823
4.823
4.823
4.823
Total
4.823
4.823
4.823
4.823
4.823
Iowa
(1.7-4 ppt)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
-
-
--
--
-
Kentucky
(3.24 ppt)
Ground Water
-
-
-
-
-
Surface Water
0.99
1.29
1.52
1.57
1.58
Total
0.99
1.29
1.52
1.57
1.58
Maine (PFAS
Task Force)2
(1.78-20 ppt)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Unknown
2.19
9.58
12.0
12.0
12
Total
2.19
9.58
12.0
12.0
12
Maine
(Compliance)
(2 ppt)
Ground Water
2.05
5.84
62.5
116
127
Surface Water
2.1
2.84
3.42
3.56
3.57
Total
2.05
5.65
50.5
115
127
Maryland
(Phase 1)
(2 ppt)
Ground Water
2.09
2.59
2.98
3.07
3.08
Surface Water
2.27
2.66
8.66
10.0
10.16
Total
2.09
2.66
7.33
9.88
10.16
Maryland
(Phase 2)
(2 ppt)
Ground Water
2.03
2.03
2.03
2.03
2.03
Surface Water
-
-
-
-
-
Total
2.03
2.03
2.03
2.03
2.03
Maryland
(Phase 3)
(2 ppt)
Ground Water
2.43
3.50
4.35
4.54
4.56
Surface Water
-
-
-
-
-
Total
2.43
3.50
4.35
4.54
4.56
Massachusetts
(0.43-10 ppt)
Ground Water
0.816
3.74
8.19
24.6
35.1
Surface Water
1.83
2.57
8.62
9.22
9.3
Total
0.816
3.66
8.43
24.2
35.1
Michigan
(2 ppt)
Ground Water
2
4.00
9.70
32.7
34
Surface Water
2
2
2
2
2
Unknown
3
3
3
3
3
Total
2
4.00
9.50
32.7
34
Missouri,
2022 - 2023
(Not reported)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
-
-
--
--
-
New
Hampshire
(Not reported)
Ground Water
0.51
3.49
43.8
88.8
94.2
Surface Water
1.7
1.7
1.7
1.7
1.7
Unknown
-
-
-
-
-
Total
0.51
3.21
43.2
88.7
94.2
178
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water
Type
Concentration Value of Detections (ppt)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
New Jersey
(0.019-2,000
PPt)
Ground Water
0.24
3.23
10.0
31.3
57
Surface Water
0.386
2.20
11.3
54.6
64
Unknown
-
-
-
-
-
Total
0.24
2.83
10.0
40.9
64
New Mexico
(Not reported)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
-
-
"
--
-
New York
(0.000000001-
2,020 ppt)
Ground Water
0.41
2.20
9.76
22.3
330
Surface Water
0.432
1.02
2.20
5.34
5.62
Unknown
-
-
-
-
-
Total
0.41
2.10
9.23
21.2
330
North
Carolina1
(Not Reported)
Unknown
0.22
40.0
40.0
79.3
80
Total
0.22
40.0
40.0
79.3
80
North Dakota
(2020)
(Not reported)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
-
--
--
--
-
North Dakota
(2021)
(Not reported)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
-
--
--
--
-
Ohio
(5 ppt)
Ground Water
5.6
6.61
23.1
23.9
24
Surface Water
8.3
8.3
8.3
8.3
8.3
Total
5.6
7.46
22.9
23.9
24
Oregon
(10.1 -12.4
PPt)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
-
--
--
--
-
Pennsylvania
(2019)
(1.9 ppt)
Ground Water
2.4
4.10
5.84
5.89
5.9
Surface Water
4.3
9.15
13.0
13.9
14
Total
2.4
5.00
9.95
13.6
14
Pennsylvania
(2021)
(1.7-4 ppt)
Ground Water
1.8
5.35
14.0
17.5
18.1
Surface Water
2.1
5.90
11.1
14.6
15
Total
1.8
5.60
14.0
17.4
18.1
South Carolina
(2.1 ppt)
Ground Water
-
-
-
-
-
Surface Water
2.5
2.5
2.5
2.5
2.5
Total
2.5
2.5
2.5
2.5
2.5
Tennessee
(Not reported)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
-
--
--
--
-
Vermont
(2 PPt)
Ground Water
2
4.97
19.9
31.6
36.2
Surface Water
-
-
-
-
-
179
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water
Type
Concentration Value of Detections (ppt)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Total
2
4.97
19.9
31.6
36.2
Virginia
(3.5 ppt)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
-
-
--
--
-
Wisconsin
(Not reported)
Ground Water
0.225
0.39
2.35
3.97
4.17
Surface Water
0.3
0.33
0.338
0.340
0.34
Total
0.225
0.350
2.07
3.93
4.17
Note: With limited exceptions, calculated concentration values (i.e., median, 90th percentile and 99th percentile
concentrations) were rounded to three significant figures for consistent presentation across the datasets and may
not indicate exact laboratory precision.
1 Only reported detections were available in this state's dataset.
2 Reported data from Maine may include results from public and private finished drinking water sources. Based on
available state data information, the EPA could not verify PWSIDs for all included samples.
Exhibit 6-10: PFNA State Reported Drinking Water Occurrence Data - Summary of
Systems with Finished Water Data
State
(Reporting
Threshold)
Source Water Type
Total
Number of
Systems
Systems with
Detections
Systems with
Detections
> 10 ppt
Number
Percent
Number
Percent
Alabama1
(Not reported)
Ground Water
-
2
-
1
-
Surface Water
-
5
-
0
-
Total
-
7
-
1
-
Arizona
(1.6-2 ppt)
Ground Water
5
1
20.0%
0
0.0%
Surface Water
1
1
100.0%
0
0.0%
Total
6
2
33.3%
0
0.0%
California
(0.002 - 20 ppt)
Ground Water
43
7
16.3%
0
0.0%
Surface Water
78
11
14.1%
0
0.0%
Unknown
1
0
0.0%
0
0.0%
Total
122
18
14.8%
0
0.0%
Colorado
(2013 -2017)
(2 - 30 ppt)
Distribution (Finished)
22
5
22.7%
4
18.2%
Surface water (Finished)
5
0
0.0%
0
0.0%
Total
27
5
18.5%
4
14.8%
Colorado (2020)
(1.6-2.4 ppt)
Ground Water
221
3
1.4%
0
0.0%
Surface Water
176
1
0.6%
0
0.0%
Total
397
4
1.0%
0
0.0%
Georgia
(20 ppt)
Ground Water
0
0
0.0%
0
0.0%
Surface Water
1
0
0.0%
0
0.0%
Total
1
0
0.0%
0
0.0%
Idaho
Ground Water
10
0
0.0%
0
0.0%
180
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
(0.5 -1 ppt)
Source Water Type
Total
Number of
Systems
Systems with
Detections
Systems with
Detections
> 10 ppt
Number
Percent
Number
Percent
Surface Water
0
0
0.0%
0
0.0%
Total
10
0
0.0%
0
0.0%
Illinois
(1.7-2 ppt)
Ground Water
899
2
0.2%
0
0.0%
Surface Water
97
3
3.1%
0
0.0%
Total
996
5
0.5%
0
0.0%
Indiana
(2 ppt)
Ground Water
341
0
0.0%
0
0.0%
Surface Water
31
1
3.2%
0
0.0%
Total
372
1
0.3%
0
0.0%
Iowa
(1.7-4 ppt)
Ground Water
89
0
0.0%
0
0.0%
Surface Water
26
0
0.0%
0
0.0%
Total
115
0
0.0%
0
0.0%
Kentucky
(3.24 ppt)
Ground Water
30
0
0.0%
0
0.0%
Surface Water
44
2
4.5%
0
0.0%
Total
74
2
2.7%
0
0.0%
Maine (PFAS Task
Force)2
(1.78-20 ppt)
Ground Water
7
0
0.0%
0
0.0%
Surface Water
1
0
0.0%
0
0.0%
Unknown
10
2
20.0%
0
0.0%
Total
18
2
11.1%
0
0.0%
Maine
(Compliance)
(2 ppt)
Ground Water
593
23
3.9%
3
0.5%
Surface Water
53
2
3.8%
0
0.0%
Total
646
25
3.9%
3
0.5%
Maine
(All Systems)3
(1.78-20 ppt)
Ground Water
593
23
3.9%
3
0.5%
Surface Water
53
2
3.8%
0
0.0%
Unknown
10
2
20.0%
0
0.0%
Total
656
27
4.1%
3
0.5%
Maryland (Phase 1)
(2 ppt)
Ground Water
30
1
3.3%
0
0.0%
Surface Water
36
2
5.6%
0
0.0%
Total
66
3
4.5%
0
0.0%
Maryland (Phase 2)
(2 ppt)
Ground Water
6
1
16.7%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Total
6
1
16.7%
0
0.0%
Maryland (Phase 3)
(2 ppt)
Ground Water
63
2
3.2%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Total
63
2
3.2%
0
0.0%
Maryland
(All Systems)3
(2 ppt)
Ground Water
99
4
4.0%
0
0.0%
Surface Water
36
2
5.6%
0
0.0%
Total
135
6
4.4%
0
0.0%
Massachusetts
(0.43-10 ppt)
Ground Water
1,209
48
4.0%
4
0.3%
Surface Water
122
10
8.2%
0
0.0%
181
-------
EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water Type
Total
Number of
Systems
Systems with
Detections
Systems with
Detections
> 10 ppt
Number
Percent
Number
Percent
Total
1,331
58
4.4%
4
0.3%
Michigan
(2 ppt)
Ground Water
2,370
13
0.5%
1
0.0%
Surface Water
84
1
1.2%
0
0.0%
Unknown
54
1
1.9%
0
0.0%
Total
2,508
15
0.6%
1
0.0%
Missouri,
2022 - 2023
(Not reported)
Ground Water
95
0
0.0%
0
0.0%
Surface Water
18
0
0.0%
0
0.0%
Total
113
0
0.0%
0
0.0%
New Hampshire
(Not reported)
Ground Water
529
30
5.7%
5
0.9%
Surface Water
30
1
3.3%
0
0.0%
Unknown
1
0
0.0%
0
0.0%
Total
560
31
5.5%
5
0.9%
New Jersey
(0.019-2,000 ppt)
Ground Water
1,012
141
13.9%
15
1.5%
Surface Water
107
44
41.1%
5
4.7%
Unknown
5
0
0.0%
0
0.0%
Total
1,124
185
16.5%
20
1.8%
New Mexico
(Not reported)
Ground Water
2
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Total
2
0
0.0%
0
0.0%
New York
(0.000000001-
2,020 ppt)
Ground Water
565
58
10.3%
5
0.9%
Surface Water
120
9
7.5%
0
0.0%
Unknown
4
0
0.0%
0
0.0%
Total
689
67
9.7%
5
0.7%
North Carolina1
(Not Reported)
Unknown
-
5
-
5
-
Total
-
5
-
5
-
North Dakota
(2020)
(Not reported)
Ground Water
41
0
0.0%
0
0.0%
Surface Water
9
0
0.0%
0
0.0%
Total
50
0
0.0%
0
0.0%
North Dakota
(2021)
(Not reported)
Ground Water
56
0
0.0%
0
0.0%
Surface Water
7
0
0.0%
0
0.0%
Total
63
0
0.0%
0
0.0%
North Dakota
(All Systems)3
(Not reported)
Ground Water
95
0
0.0%
0
0.0%
Surface Water
16
0
0.0%
0
0.0%
Total
111
0
0.0%
0
0.0%
Ohio
(5 ppt)
Ground Water
1,372
3
0.2%
1
0.1%
Surface Water
107
1
0.9%
0
0.0%
Total
1,479
4
0.3%
1
0.1%
Oregon
(10.1 -12.4 ppt)
Ground Water
116
0
0.0%
0
0.0%
Surface Water
27
0
0.0%
0
0.0%
182
-------
EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water Type
Total
Number of
Systems
Systems with
Detections
Systems with
Detections
> 10 ppt
Number
Percent
Number
Percent
Total
143
0
0.0%
0
0.0%
Pennsylvania
(2019)
(1.9 ppt)
Ground Water
71
4
5.6%
0
0.0%
Surface Water
16
2
12.5%
0
0.0%
Total
87
6
6.9%
0
0.0%
Pennsylvania
(2021)
(1.7-4 ppt)
Ground Water
269
14
5.2%
1
0.4%
Surface Water
73
6
8.2%
1
1.4%
Total
342
20
5.8%
2
0.6%
Pennsylvania
(All Systems)3
(1.7-4 ppt)
Ground Water
270
17
6.3%
1
0.4%
Surface Water
73
6
8.2%
1
1.4%
Total
343
23
6.7%
2
0.6%
South Carolina
(2.1 ppt)
Ground Water
234
0
0.0%
0
0.0%
Surface Water
64
1
1.6%
0
0.0%
Total
298
1
0.3%
0
0.0%
Tennessee
(Not reported)
Ground Water
0
0
0.0%
0
0.0%
Surface Water
1
0
0.0%
0
0.0%
Total
1
0
0.0%
0
0.0%
Vermont
(2 ppt)
Ground Water
526
5
1.0%
1
0.2%
Surface Water
38
0
0.0%
0
0.0%
Total
564
5
0.9%
1
0.2%
Virginia
(3.5 ppt)
Ground Water
5
0
0.0%
0
0.0%
Surface Water
20
0
0.0%
0
0.0%
Total
25
0
0.0%
0
0.0%
Wisconsin
(Not reported)
Ground Water
213
6
2.8%
0
0.0%
Surface Water
20
3
15.0%
0
0.0%
Total
233
9
3.9%
0
0.0%
1 Only reported detections were available in this state's dataset.
2 Reported data from Maine may include results from public and private finished drinking water sources. Based on
available state data information, the EPA could not verify PWSIDs for all included samples.
3 The "All Systems" counts represent a summary of all unique systems across multiple sampling efforts within the
state. For some states (e.g., CO), the EPA could not verify this number due to the sample site ID reporting.
Exhibit 6-11: PFNA State Reported Drinking Water Occurrence Data - Summary of
Population Served by Systems with Finished Water Data
State
(Reporting
Threshold)
Source Water Type
Total
Population
Served by
Systems
Total Population
Served by Systems
with Detections
Total Population
Served by Systems
with Detections
> 10 ppt
Number
Percent
Number
Percent
Alabama1
(Not reported)
Ground Water
-
73,311
-
13,827
-
Surface Water
-
363,847
-
0
-
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State
(Reporting
Threshold)
Source Water Type
Total
Population
Served by
Systems
Total Population
Served by Systems
with Detections
Total Population
Served by Systems
with Detections
> 10 ppt
Number
Percent
Number
Percent
Total
-
437,158
-
13,827
-
Arizona
(1.6-2 ppt)
Ground Water
94,569
50,770
53.7%
0
0.0%
Surface Water
50,001
50,001
100.0%
0
0.0%
Total
144,570
100,771
69.7%
0
0.0%
California
(0.002 - 20 ppt)
Ground Water
1,098,122
360,254
32.8%
0
0.0%
Surface Water
13,500,188
1,975,526
14.6%
0
0.0%
Unknown
0
0
0.0%
0
0.0%
Total
14,598,310
2,335,780
16.0%
0
0.0%
Colorado
(2013 -2017)2
(2 - 30 ppt)
Distribution (Finished)
-
-
-
-
-
Surface water (Finished)
-
-
-
-
-
Total
-
-
-
-
-
Colorado (2020)
(1.6-2.4 ppt)
Ground Water
261,162
765
0.3%
0
0.0%
Surface Water
4,191,774
1,505
0.0%
0
0.0%
Total
4,452,936
2,270
0.1%
0
0.0%
Georgia
(20 ppt)
Ground Water
0
0
0.0%
0
0.0%
Surface Water
9,993
0
0.0%
0
0.0%
Total
9,993
0
0.0%
0
0.0%
Idaho
(0.5 -1 ppt)
Ground Water
81,985
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Total
81,985
0
0.0%
0
0.0%
Illinois
(1.7-2 ppt)
Ground Water
2,916,219
70,518
2.4%
0
0.0%
Surface Water
4,628,949
4,740
0.1%
0
0.0%
Total
7,545,168
75,258
1.0%
0
0.0%
Indiana
(2 ppt)
Ground Water
545,838
0
0.0%
0
0.0%
Surface Water
97,448
4,158
4.3%
0
0.0%
Total
643,286
4,158
0.6%
0
0.0%
Iowa
(1.7-4 ppt)
Ground Water
490,955
0
0.0%
0
0.0%
Surface Water
987,522
0
0.0%
0
0.0%
Total
1,478,477
0
0.0%
0
0.0%
Kentucky
(3.24 ppt)
Ground Water
171,212
0
0.0%
0
0.0%
Surface Water
1,922,023
55,135
2.9%
0
0.0%
Total
2,093,235
55,135
2.6%
0
0.0%
Maine (PFAS Task
Force)23
(1.78-20 ppt)
Ground Water
3,995
0
0.0%
0
0.0%
Surface Water
21,808
0
0.0%
0
0.0%
Unknown
0
0
0.0%
0
0.0%
Total
25,803
0
0.0%
0
0.0%
Maine
(Compliance)
(2 ppt)
Ground Water
274,866
6,369
2.3%
1,060
0.4%
Surface Water
464,453
12,365
2.7%
0
0.0%
Total
739,319
18,734
2.5%
1,060
0.1%
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State
(Reporting
Threshold)
Source Water Type
Total
Population
Served by
Systems
Total Population
Served by Systems
with Detections
Total Population
Served by Systems
with Detections
> 10 ppt
Number
Percent
Number
Percent
Maine
(All Systems)24
(1.78-20 ppt)
Ground Water
274,866
6,369
2.3%
1,060
0.4%
Surface Water
464,453
12,365
2.7%
0
0.0%
Unknown
0
0
0.0%
0
0.0%
Total
739,319
18,734
2.5%
1,060
0.1%
Maryland (Phase 1)
(2 ppt)
Ground Water
384,007
6,600
1.7%
0
0.0%
Surface Water
4,059,154
50,881
1.3%
0
0.0%
Total
4,443,161
57,481
1.3%
0
0.0%
Maryland (Phase 2)
(2 ppt)
Ground Water
3,896
50
1.3%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Total
3,896
50
1.3%
0
0.0%
Maryland (Phase 3)
(2 ppt)
Ground Water
41,063
145
0.4%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Total
41,063
145
0.4%
0
0.0%
Maryland
(All Systems)4
(2 ppt)
Ground Water
428,966
6,795
1.6%
0
0.0%
Surface Water
4,059,154
50,881
1.3%
0
0.0%
Total
4,488,120
57,676
1.3%
0
0.0%
Massachusetts
(0.43-10 ppt)
Ground Water
1,828,984
203,986
11.2%
6,927
0.4%
Surface Water
5,860,701
315,115
5.4%
0
0.0%
Total
7,689,685
519,101
6.8%
6,927
0.1%
Michigan2
(2 ppt)
Ground Water
1,945,734
4,651
0.2%
385
0.0%
Surface Water
1,314,601
36,542
2.8%
0
0.0%
Unknown
0
0
0.0%
0
0.0%
Total
3,260,335
41,193
1.3%
385
0.0%
Missouri,
2022 - 2023
(Not reported)
Ground Water
190,274
0
0.0%
0
0.0%
Surface Water
405,045
0
0.0%
0
0.0%
Total
595,319
0
0.0%
0
0.0%
New Hampshire
(Not reported)
Ground Water
267,029
61,102
22.9%
1,198
0.4%
Surface Water
476,367
2,450
0.5%
0
0.0%
Unknown
10
0
0.0%
0
0.0%
Total
743,406
63,552
8.5%
1,198
0.2%
New Jersey
(0.019-2,000 ppt)
Ground Water
2,485,837
469,265
18.9%
46,687
1.9%
Surface Water
5,794,947
2,097,046
36.2%
82,675
1.4%
Unknown
0
0
0.0%
0
0.0%
Total
8,280,784
2,566,311
31.0%
129,362
1.6%
New Mexico2
(Not reported)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
--
--
-
-
-
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State
(Reporting
Threshold)
Source Water Type
Total
Population
Served by
Systems
Total Population
Served by Systems
with Detections
Total Population
Served by Systems
with Detections
> 10 ppt
Number
Percent
Number
Percent
New York
(0.000000001-
2,020 ppt)
Ground Water
1,441,706
546,904
37.9%
3,762
0.3%
Surface Water
2,845,715
104,478
3.7%
0
0.0%
Unknown
1,024
0
0.0%
0
0.0%
Total
4,288,445
651,382
15.2%
3,762
0.1%
North Carolina1'2
(Not Reported)
Unknown
-
-
-
-
-
Total
--
--
-
-
-
North Dakota
(2020)
(Not reported)
Ground Water
68,280
0
0.0%
0
0.0%
Surface Water
57,469
0
0.0%
0
0.0%
Total
125,749
0
0.0%
0
0.0%
North Dakota
(2021)
(Not reported)
Ground Water
113,623
0
0.0%
0
0.0%
Surface Water
194,121
0
0.0%
0
0.0%
Total
307,744
0
0.0%
0
0.0%
North Dakota
(All Systems)4
(Not reported)
Ground Water
181,514
0
0.0%
0
0.0%
Surface Water
251,590
0
0.0%
0
0.0%
Total
433,104
0
0.0%
0
0.0%
Ohio
(5 ppt)
Ground Water
2,883,252
3,595
0.1%
2,830
0.1%
Surface Water
6,215,644
7,425
0.1%
0
0.0%
Total
9,098,896
11,020
0.1%
2,830
0.0%
Oregon
(10.1 -12.4 ppt)
Ground Water
114,194
0
0.0%
0
0.0%
Surface Water
125,239
0
0.0%
0
0.0%
Total
239,433
0
0.0%
0
0.0%
Pennsylvania
(2019)
(1.9 ppt)
Ground Water
162,825
6,393
3.9%
0
0.0%
Surface Water
431,370
55,464
12.9%
0
0.0%
Total
594,195
61,857
10.4%
0
0.0%
Pennsylvania
(2021)
(1.7-4 ppt)
Ground Water
471,651
70,381
14.9%
12,800
2.7%
Surface Water
4,296,097
981,760
22.9%
4,464
0.1%
Total
4,767,748
1,052,141
22.1%
17,264
0.4%
Pennsylvania
(All Systems)4
(1.7 -4 ppt)
Ground Water
471,891
71,191
15.1%
12,800
2.7%
Surface Water
4,296,097
981,760
22.9%
4,464
0.1%
Total
4,767,988
1,052,951
22.1%
17,264
0.4%
South Carolina
(2.1 ppt)
Ground Water
485,992
0
0.0%
0
0.0%
Surface Water
2,246,954
9,070
0.4%
0
0.0%
Total
2,732,946
9,070
0.3%
0
0.0%
Tennessee
(Not reported)
Ground Water
0
0
0.0%
0
0.0%
Surface Water
2,551
0
0.0%
0
0.0%
Total
2,551
0
0.0%
0
0.0%
Vermont
(2 ppt)
Ground Water
211,357
689
0.3%
50
0.0%
Surface Water
174,473
0
0.0%
0
0.0%
Total
385,830
689
0.2%
50
0.0%
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State
(Reporting
Threshold)
Source Water Type
Total
Population
Served by
Systems
Total Population
Served by Systems
with Detections
Total Population
Served by Systems
with Detections
> 10 ppt
Number
Percent
Number
Percent
Virginia
(3.5 ppt)
Ground Water
2,975
0
0.0%
0
0.0%
Surface Water
4,839,373
0
0.0%
0
0.0%
Total
4,842,348
0
0.0%
0
0.0%
Wisconsin
(Not reported)
Ground Water
1,433,854
52,284
3.6%
0
0.0%
Surface Water
1,297,605
266,275
20.5%
0
0.0%
Total
2,731,459
318,559
11.7%
0
0.0%
1 Only reported detections were available in this state's dataset.
2 There were some instances where the population served by a system could not be identified. Thus, there are
systems with detections but no associated population served by those systems with detections.
3 Reported data from Maine may include results from public and private finished drinking water sources. Based on
available state data information, the EPA could not verify PWSIDs for all included samples.
3 The "All Systems" counts represent a summary of all unique systems across multiple sampling efforts within the
state.
6.2.1.3 Additional Secondary Source Water and Drinking Water Studies
Boone et al. (2019) measured 17 PFAS in both source and treated water from 25 DWTPs in the United
States. The results indicated that only five of the sampling locations demonstrated a significant
difference in PFAS concentration between the source and treated water. The median concentration of
PFNA in source water was 0.86 ng/L and 0.74 ng/L in treated water. PFNA was detected in 88 percent of
treated drinking water samples (Boone et al., 2019).
Post et al. (2013) re-evaluated PFOA, PFOS, and PFC occurrence data in drinking water systems
throughout New Jersey to update previous PFAS research in the area from 2006. PFCs were found in 70
percent of PWSs sampled at concentrations ranging from 5-174 ng/L. PFNA was detected in 30 percent
of samples at a maximum concentration of 96 ng/L.
McMahon et al. (2022) collected samples from aquifer systems in the eastern United States in 2019 to
evaluate PFAS occurrence in ground water used as a source of drinking water. The study found that 14
of the 24 analyzed PFAS were detected in ground water samples. Furthermore, at least one PFAS was
detected in 54 percent of the ground water samples and two or more PFAS were detected in 47 percent
of the ground water samples. In the public supply and domestic wells, 60 and 20 percent of the samples,
respectively, had at least one PFAS detection. Two or more PFAS were detected in 53 percent of the
public-supply wells and 10 percent of domestic wells. The six PFAS outlined in the EPA's UCMR 3
program (i.e., PFBS, PFHxS, PFOS, PFHpA, PFOA, and PFNA) were the most detected PFAS in the study's
samples. PFNA was detected in 6 percent of the 254 samples (McMahon et al., 2022).
As part of a joint study by the EPA and USGS to assess human exposure to contaminants of emerging
concern, water samples were collected from 25 DWTPs in 24 states (Glassmeyer et al., 2017).
Participation in the study was voluntary, and candidate locations were selected based on nomination by
the EPA and USGS regional personnel and DWTP self-nomination as well as consideration of high
wastewater contribution and the availability of pharmaceutical concentration data. Final sample
locations were chosen to represent a wide range of geography, diversity in disinfectant type used, and a
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range of production volumes. Phase I of the study (2007) analyzed a subset of contaminants and sites to
test experimental design; PFNA was not included in Phase 1. During Phase II of the study (2010-2012),
samples were collected from ground water and surface water sources and treated drinking water from
25 DWTPs and analyzed for PFNA occurrence. The LCMRL for PFNA was equal to 0.094 ng/L. PFHxS was
detected in 96 percent of the 25 source water samples and 88 percent of the 25 treated drinking water
samples. The maximum detected concentrations in source water and treated water were 41.4 ng/L and
38.6 ng/L, respectively.
Reyes (2021) conducted a ground water-quality study to describe the occurrence and distribution of
PFAS in the Columbia aquifer public water-supply wells in the Delaware Coastal Plain region in 2018.
One or more PFAS were detected in 16 of the sampled wells with as many as 8 different PFAS detected
in a single sample. PFNA was not detected in any of the 30 public water-supply wells sampled in the
study.
6.2.2 Other Data
6.2.2.1 Department of Defense (DoD) Drinking Water Sampling
The DoD conducted sampling of off-base drinking water located in "covered areas" (i.e., areas that are
adjacent to and down gradient from a military installation) to identify potential impacts of PFAS
resulting from DoD activities. Sampling was conducted for multiple PFAS, including PFNA. The EPA
downloaded available DOD off-base sampling results in September 2023.
The EPA summarized off-base sampling results for PFNA collected "post treatment" from drinking water
systems and private wells located in covered areas adjacent to 47 installations located in 22 states.
Detected concentrations ranged from an estimated concentration of 0.457 ng/L to 27.8 ng/L. Sampling
was conducted utilizing multiple analytical methods including EPA methods 533, 537, 537.1, 1633, and
DoD Quality Systems Manual Table B-15 (DoD, 2023a). Results are based on DLs which vary between
both sampling sites and across different PFAS. Results for PFNA are presented in Exhibit 6-11.
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Exhibit 6-12: Summary of PFNA Drinking Water Sampling Results Collected Post-Treatment from Department of
Defense Off-Base "Covered Areas"
State
Installation Name
Sampling Dates
Analysis
Method
#
Samples
#
Detections
%
Detections
Range of Detections
(ng/L)
AK
Eielson AFB
11/3/2022
537
1
0
0.00%
NA
AZ
Luke AFB
3/31/2022
QSM_B15
2
0
0.00%
NA
AZ
YUMA AZ MCAS
5/26/2023
533
1
0
0.00%
NA
AR
Little Rock AFB
5/5/2022
537
3
0
0.00%
NA
AR
Little Rock AFB
6/16/2022 - 3/22/2023
QSM_B15
6
0
0.00%
NA
CA
Castle AFB
7/5/2022 - 4/5/2023
537
26
1
3.85%
0.5 (est)
CA
Castle AFB
11/17/2021 - 1/11/2022
QSM_B15
12
0
0.00%
NA
CA
George AFB
3/23/2023 - 4/20/2023
1633
3
0
0.00%
NA
CA
March AFB
1/3/2023-4/10/2023
533
3
0
0.00%
NA
CA
March AFB
1/3/2022 - 12/1/2022
537.1
11
0
0.00%
NA
CA
March AFB
9/1/2022
QSM_B15
1
0
0.00%
NA
CA
Mather AFB
7/28/2022
537
1
0
0.00%
NA
CA
Mather AFB
1/27/2022 - 4/26/2022
QSM_B15
3
0
0.00%
NA
CA
Travis AFB
1/25/2022 - 1/16/2023
QSM_B15
19
0
0.00%
NA
CO
Peterson Space Force Base
12/14/2021 -2/7/2023
537.1
8
0
0.00%
NA
CO
Peterson Space Force Base
3/1/2022 - 9/14/2022
QSM_B15
16
0
0.00%
NA
DE
Dover AFB
1/22/2022 - 10/25/2022
QSM_B15
10
0
0.00%
NA
FL
Homestead Air Reserve Base
2/21/2022 - 3/30/2023
QSM_B15
13
0
0.00%
NA
FL
WHITING FLD FL NAS
9/1/2022
537.1
2
0
0.00%
NA
IL
Scott AFB
3/22/2022 - 3/28/2023
QSM_B15
3
0
0.00%
NA
ME
Loring AFB
7/25/2022
QSM_B15
1
0
0.00%
NA
ME
NCTAMSLANT DET CUTLER
4/20/2022 - 12/6/2022
537.1
66
2
3.03%
0.457 (est)-1.18 (est)
MA
Otis ANG (Joint Base Cape Cod -
Massachusetts Military Reservation)
2/28/2022 -11/22/2022
QSM_B15
11
1
9.09%
1.5 (est)
Ml
Kl Sawyer AFB
7/13/2022
QSM_B15
2
0
0.00%
NA
MT
Great Falls International Airport
6/15/2022-7/7/2022
537
3
0
0.00%
NA
NH
Pease AFB
9/22/2021 - 3/30/2023
QSM_B15
16
5
31.25%
1.9 (est)-3.6
NJ
Joint Base McGuire-Dix-Lakehurst
3/3/2022 - 5/25/2022
QSM_B15
2
0
0.00%
NA
NM
Cannon AFB
11/11/2021 - 12/13/2021
QSM_B15
2
0
0.00%
NA
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State
Installation Name
Sampling Dates
Analysis
Method
#
Samples
#
Detections
%
Detections
Range of Detections
(ng/L)
NY
Pittsburgh AFB
5/20/2022-8/10/2022
537
8
0
0.00%
NA
NY
Pittsburgh AFB
11/18/2021 -9/15/2022
537.1
16
0
0.00%
NA
NY
Pittsburgh AFB
11/29/2021 -6/27/2023
QSM_B15
15
0
0.00%
NA
OK
Tinker AFB
2/2/2023
QSM_B15
3
0
0.00%
NA
Rl
NAVAL AUX LANDING FIELD
5/19/2022
537.1
2
0
0.00%
NA
Rl
NAVAL AUX LANDING FIELD
10/17/2022-2/28/2023
QSM_B15
31
8
25.81%
0.545 (est) - 3.63
SD
Ellsworth AFB
3/14/2022
537
1
0
0.00%
NA
SD
Ellsworth AFB
6/9/2022 - 9/7/2022
537.1
2
0
0.00%
NA
SD
Ellsworth AFB
2/7/2022 - 6/23/2022
QSM_B15
36
2
5.56%
1.18 (est) -10.4
TX
Goodfellow AFB
8/18/2022 - 11/15/2022
537
11
0
0.00%
NA
TX
Goodfellow AFB
12/6/2022 - 4/27/2023
QSM_B15
28
1
3.57%
27.8
TX
Reese AFB
9/14/2022-6/13/2023
1633
504
1
0.20%
1.3 (est)
TX
Reese AFB
9/28/2021 - 8/29/2022
QSM_B15
839
1
0.12%
7.9 (est)
VA
OCEANA VA NAS
10/19/2022-4/14/2023
537.1
13
0
0.00%
NA
WA
BREMERTON WA NAVBASE
10/11/2022-7/21/2023
537.1
3
2
66.67%
0.855 (est)-0.872
(est)
WA
Fairchild AFB
9/19/2022-9/27/2022
537
87
1
1.15%
14.5
WA
Fairchild AFB
2/20/2023 - 3/6/2023
537.1
87
0
0.00%
NA
WA
Fairchild AFB
1/31/2022-7/21/2022
QSM_B15
187
0
0.00%
NA
WA
WHIDBEY IS WANAS
4/21/2022 - 4/20/2023
537.1
11
0
0.00%
NA
Source: DOD, 2023a
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6.2.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the ambient sources of most drinking water. Contaminant occurrence in
ambient water can provide useful information on the potential for contaminants to adversely affect
drinking water supplies. Occurrence data for PFNA in ambient water are available from the USGS NWIS
database and the EPA's legacy STORET data available through the WQP.
6.2.3.1 National Water Information System (NWIS) Data
The NWIS is the Nation's principal repository of water resources data USGS collects from more than 1.9
million sites (USGS, 2023). NWIS-Web is the general online interface to the USGS NWIS database.
Discrete water-sample and time-series data are available from sites in all 50 States, including 5 million
water samples with 90 million water-quality results. All USGS water quality and flow data are stored in
NWIS, including site characteristics, streamflow, ground water level, precipitation, and chemical
analyses of water, sediment, and biological media, though not all parameters are available for every site.
NWIS houses the NAWQA data and includes other USGS data from unspecified projects. NWIS contains
many more samples at many more sites than the NAWQA Program. Although NWIS is comprised of
primarily ambient water data, some finished drinking water data are included as well. This section
presents analyses of non-NAWQA data in NWIS, downloaded from the WQP in November 2023 (WQP,
2023).
The results of the non-NAWQA NWIS PFNA analysis are presented in Exhibit 6-12. NWIS data for PFNA
were listed under the characteristic name "Perfluorononanoate." PFNA was detected in approximately
26 percent of samples (770 out of 2,950 samples) and at approximately 21 percent of sites (365 out of
1,759 sites). The median concentration based on detections was equal to 1.40 ng/L. (Note that the NWIS
data are presented as downloaded; potential outliers were not evaluated or excluded from the analysis.)
Exhibit 6-13: PFNA NWIS Data
Site Type
Detection Frequency
(detections are results > reporting level)
Concentration Values
(of detections, in ng/L)
No. of
Samples
No. of
Samples
with
Detections
No.
of
Sites
No. of
Sites with
Detections
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Ground
Water
1,344
114
1,233
112
0.9
2.40
16.0
83.0
160
Surface
Water
1,606
656
526
253
0.138
1.30
3.00
12.0
17
All Sites
2,950
770
1,759
365
0.138
1.40
4.00
18.9
160
Source: WQP, 2023
6.2.3.2 Storage and Retrieval (STORET) Data / Water Quality Portal (WQP)
From its launch in 1999 until it was decommissioned in June 2018, the EPA's STORET Data Warehouse
was collaboratively populated with raw biological, chemical, and physical data from surface water and
ground water sampling by federal, state and local agencies, Native American tribes, volunteer groups,
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academics, and others. Legacy STORET data are accessible through the WQP:
https://www.waterqualitvdata.us/portal/.
STORET data are from monitoring locations in all 50 states as well as multiple territories and jurisdictions
of the United States. Most data are from ambient waters, but in some cases finished drinking water data
are included as well. STORET's data quality limitations include variations in the extent of national
coverage and data completeness from parameter to parameter. Data may have been collected as part of
targeted, rather than randomized, monitoring.
This section presents analyses of STORET data, downloaded from the WQP in November 2023 (WQP,
2023). The EPA reviewed STORET ground water data from wells and surface water data from lakes,
rivers/streams, and reservoirs (WQP, 2023). STORET data for PFNA were listed under the characteristic
name of "Perfluorononanoate" and "Perfluorononanoic acid." The results of the STORET analysis for
PFNA are presented in Exhibit 6-13 and Exhibit 6-14. Nearly 700 PFNA samples were available for
analysis. These PFNA samples were collected between 2006 and 2023. Of the 324 sites sampled, more
than 7 percent reported detections of PFNA. Detected concentrations ranged from 0 to 13 ng/L. (Note:
A minimum value of zero could represent a detection that was entered into the database as a non-
numerical value (e.g., "Present").)
Exhibit 6-14: PFNA STORET Data - Summary of Detected Concentrations
Source Water Type
Concentration Value of Detections (ng/L)
Minimum1
Median
90th Percentile
Maximum
Ground Water
0.426
0.822
2.20
4.16
Surface Water
0.56502
2.10
4.77
13
Unknown
0
0
1.10
3.65
Total
0
0.671
3.71
13
Source: WQP, 2023
1A minimum value of zero may represent a detection that was entered into the database as a non-numerical value
(e.g., "Present").
Exhibit 6-15: PFNA STORET Data - Summary of Samples and Sites
Source Water
Type
Total
Number of
Samples
Samples with
Detections
Total
Number
of Sites
Sites with Detections
Number
Percent
Number
Percent
Ground Water
102
10
9.80%
82
10
12.20%
Surface Water
88
10
11.36%
73
6
8.22%
Unknown
488
8
1.64%
169
8
4.73%
Total
678
28
4.13%
324
24
7.41%
Source: WQP, 2023
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6.3 Analytical Methods
For the purposes of compliance with the PFAS NPDWR, the EPA has published two analytical methods
that are available for the analysis of PFNA and other PFAS in drinking water. The performance metrics
that are presented, including the DL, LCMRL, mean recoveries and RSDs are specific to PFNA for each of
the listed analytical methods. Ranges of mean recoveries and RSDs are presented for the matrices listed;
data from holding time studies are not included since these studies are designed to demonstrate a
degradation in method performance over time and thus are not indicative of method performance that
should be observed when holding times are not exceeded:
• EPA Method 537.1, Version 2.0, Determination of Selected Per- and Polyfluorinated Alkyl
Substances in Drinking Water by Solid Phase Extraction and Liquid Chromatography/Tandem
Mass Spectrometry (LC/MS/MS). The DL and LCMRL generated by the laboratory that
developed the method are 0.7 ng/L and 0.83 ng/L, respectively. Mean recoveries in fortified
reagent water, tap water from a ground water source (TOC = 0.53 mg/L and hardness = 377
mg/L), tap water from a surface water source (TOC = 2.4 mg/L and hardness = 103 mg/L),
and tap water from a private well (TOC = 0.56 mg/L and hardness = 394 mg/L) range from
92.4 to 110%, with RSDs of 1.3 to 6.9% (USEPA, 2020d).
• EPA Method 533, Determination of Per- and Polyfluoroalkyl Substances in Drinking Water by
Isotope Dilution Anion Exchange Solid Phase Extraction and Liquid Chromatography /
Tandem Mass Spectrometry. The LCMRL generated by the laboratory that developed the
method is 4.8 ng/L (DLs were not calculated). Mean recoveries (excluding 13C isotope
analogue data) in fortified reagent water, finished drinking water from a ground water
source (hardness = 320 mg/L, pH = 7.88 at 17° C, free Cl2 = 0.64 mg/L, and total Cl2 = 0.74
mg/L) and clarified surface water (prior to GAC treatment and chlorinated in the laboratory;
pH = 8.1 at 20 °C, free Cl2 = 0.98 mg/L, total Cl2 = 1.31 mg/L. and TOC = 3.8 mg/L) range from
89.7 to 109%, with RSDs of 2.8 to 9.5% (USEPA, 2019b).
Laboratories participating in UCMR 3 were required to use EPA Method 537 and were required to report
PFNA values at or above the EPA-defined MRL of 20 ng/L (77 FR 26072; USEPA, 2012b). The MRL was set
based on the capability of multiple laboratories at the time. EPA Method 537.1 was originally published
in November 2018 as Version 1.0 as a more sensitive update to EPA Method 537 (with a slightly
expanded target analyte list). Version 2.0 was published in March 2020 and contains minor editorial
changes to Version 1.0. Use of EPA Method 537.1 is preferable to use of EPA Method 537 (it may not be
feasible to reliably quantitate down to health levels of concern for certain PFAS when using EPA Method
537). For this reason, only EPA methods 533 and 537.1 are accepted for use in demonstrating
compliance with this final rule.
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7 Hexafluoropropylene Oxide Dimer Acid (HFPO-DA)
This chapter presents information and analysis specific to HFPO-DA, including background information
on the contaminant, information on contaminant sources and environmental fate, an analysis of health
effects, an analysis of occurrence in ambient and drinking water, and information about the availability
of analytical methods and treatment technologies.
7.1 Contaminant Background, Chemical and Physical Properties
Synonyms for HFPO-DA include Perfluoro(2-methyl-3-oxahexanoic) acid; 2,3,3,3-Tetrafluoro-2-
(heptafluoropropoxy)propanoic acid and Perfluoro-2-propoxypropionic acid, according to NCBI (2022e).
The acronym HFPO-DA can also be used to refer to the deprotonated anionic form of the compound,
2,3,3,3-Tetrafluoro-2-(heptafluoropropoxy) propanoate also known as 2-
(Heptafluoropropoxy)tetrafluoropropionic acid anion (NCBI, 2022e).
HFPO refers to hexafluoropropylene oxide, the compound used to manufacture HFPO-DA (USEPA,
2021d). HFPO-DA can react with HFPO to form HFPO trimer acid, HFPO tetramer acid and longer
polymer fluorides (USEPA, 2021d). For the purposes of this document HFPO-DA will signify the ion, acid,
or any salt of HFPO-DA.
HFPO-DA is a perfluoroalkyl ether carboxylic acid. Its predominant salt, HFPO-DA ammonium salt
(NH4+HFPO-DA) differs from HFPO-DA by being associated with an ammonium ion. The technology used
by Chemours Company for manufacturing HFPO-DA and NH4+HFPO-DA is referred to with the trade
name GenX (USEPA, 2021d). GenX Chemicals include other perfluoroalkyl ether carboxylic acids that are
used as a surfactant and polymerization aid in the processing of polytetrafluoroethylene. Chemours
Company reports countless applications of GenX Chemicals and uses GenX Chemicals to produce four
trademarked fluoropolymers Teflon™ polytetrafluoroethylene (PTFE), Teflon™ perfluoroalkoxy (PFA),
Teflon™ fluorinated ethylene propylene (FEP), and Teflon™ amorphous fluoropolymer (AF) (Chemours,
2022; USEPA, 2022f).
HFPO-DA and NH4+HFPO-DA are used in the production of fluoropolymers as replacement chemicals for
PFOA following the phase-out period of 2006 to 2015. Fluoropolymers have many uses due to their
unique properties such as resistance to high and low temperatures, resistance to degradation and non-
stick properties. Fluoropolymers are found in electrical, electronic and architectural applications and
many manufacturing processes: fabrics, automotive, cable materials, food processing, electronics,
pharmaceutical, biotech and semiconductors (USEPA, 2021d).
The diagram of Exhibit 7-1 shows the branched-chain chemical structure of HFPO-DA and NH4+HFPO-DA.
The chemical and physical properties of HFPO-DA and its ammonium salt are listed in Exhibit 7-2.
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Exhibit 7-1: Chemical Structure of HFPO-DA and its Ammonium Salt
J
F F F
OH
J
Figure 1 HFPO-DA Structure
nh;
Figure 2 HFPO-DA Ammonium Salt Structure
Source: NCBI, 2022e and 2022f
DuPont reports a value of >751,000 mg/Lfor the solubility in water which represents the highest tested
values, while the actual solubility is described as "infinite" (Dupont-24128, 2008). The uncertainty of the
Henry's Law Constant builds upon the uncertainty of the measured water solubility. Log Kow is not
applicable or cannot be measured since HFPO-DA is expected to form multiple layers in octanol and
water mixtures.
Where there are different conclusions in the literature for the properties of HFPO-DA, information is
presented to highlight the range of uncertainty for this compound.
Exhibit 7-2: Physical and Chemical Properties of HFPO-DA & Its Ammonium Salt
Property
Data
HFPO-DA
NH4+HFPO-DA
Chemical Abstracts Service (CAS)
Registry Number
13252-13-6 (NCBI, 2022e)
62037-80-3 (NCBI, 2022f)
EPA Pesticide Chemical Code
Not Applicable
-
Chemical Formula
CeHFuOs (NCBI, 2022e)
C6H4F11NO3 (NCBI, 2022f)
Molecular Weight
330.05 g/mol (NCBI, 2022e)
347.08 g/mol (NCBI, 2022f)
Color/Physical State
Clear, Colorless Liquid
(DuPont-24698, 2008)
Solid (USEPA, 2021 d)
Boiling Point
129 deg C (exp) (DuPont-24698, 2008)
143-145 deg C (exp) (ITRC, 2021)
108 deg C (exp) (DuPont-24637,
2008)
Melting Point
< -40.0 deg C (exp)
(DuPont-24698, 2008)
-21.0 deg C (as 86% salt solution
in water) (exp) (DuPont-24637,
2008)
No data available for salt form.
27.8 deg C (est) (ITRC, 2021)
Density
1.69 g/mL (est) (ITRC, 2021)
1.85 g/mL (est) (ITRC, 2021)
-
Freundlich Adsorption Coefficient
-
-
Vapor Pressure
2.30 mm Hg (exp) (Dupont-24128,
2008; converted from 306 Pa)
2.9 mm Hg (est)
(ITRC, 2021; converted from 2.59 log-
Pa)
0.24 mm Hg at 25 deg C (est)
(ITRC, 2021)
-1.49 ± 0.01 log (Pa) solid vapor
pressure (est) (NCBI, 2022f)
No measurement available3 (exp)
(DuPont-24129, 2008)
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Property
Data
HFPO-DA
NH4+HFPO-DA
Kh
<2.5E-04 atm-m3/molb (est)
(USEPA, 2021 d)
1.8E-04 atm-m3/mol (est)
(ITRC, 2021; converted from - 2.13 log)
2.37E-10 atm-m3/mol at 25 deg C (est)
(ITRC, 2021)
-
Log Kow
Not applicable0
Not applicable0
Koc
11.2 (dimensionless) (est)
(ITRC, 2021; Log Koc 1.05)
83.2 (dimensionless) (est)
(ITRC, 2021; Log Koc 1.92)
Soil -12 L/Kg (exp) (log 1.10)
Sludge -12.6 L/kg (exp) (log 1.08)
(DuPont-17568-1675, 2008)
pKa
2.84 (20 deg C) (exp)
(DuPont-26349, 2008)
-0.77 (est) (ITRC, 2021)
3.82 (20 deg C) (exp)
(DuPont-26349, 2008)
Solubility in Water
>751,000 mg/Ld(exp)
(DuPont-24128, 2008)
7,059 mg/L (est) (ITRC, 2021;
converted from -1.67 log-mol/L)
>739,000 mg/Ld (exp)
(DuPont-24129, 2008)
Other Solvents
-
-
Conversion Factors
(at 25 deg C, 1 atm)
1 PPMV =13.50 mg/m3; 1 mg/m3 =
0.074 PPMV (calculated)
N/A (salts do not volatilize)
Note:indicates that no information was found.
a No experimental value was reported for the vapor pressure of NhVHFPO-DA because the measured vapor
pressure was reported to primarily be resultant of water and ammonia present in the substance.
b These values should not be used to estimate portioning between water and air. Estimated from measured vapor
pressure and highest measured water solubility (Dupont-24128, 2008). The actual Kh is expected to be lower
because the water solubility is reported to be infinite (USEPA, 2021 d).
c Surfactants are surface acting agents that contain both a hydrophilic part and a hydrophobic part which causes
them to accumulate at interfaces hampering the determination of their aqueous concentration. These surfactant
properties present difficulties in applying existing methods for the experimental determination of log K0w and produce
unreliable results.
d Highest tested values. Actual solubility not determined but described as "infinite" (DuPont-24128, 2008; DuPont-
24129, 2008).
7.1.1 Sources and Environmental Fate
7.1.1.1 Production, Use, and Release
Production data for HFPO-DA are available from the EPA's IUR and CDR programs and industrial release
data are available from the EPA's TRI, as described below.
Inventory Update Reporting (IUR)/Chemical Data Reporting (CDR) Program
Under the authority of the TSCA, the EPA gathers information on production (including both
manufacture and importation) of industrial chemicals. As a compound with a TSCA section 5(a)(2) SNUR,
HFPO-DA and its ammonium salt is among those contaminants to which the 2,500-pound threshold
applies. See Chapter 2 for further discussion.
Exhibit 7-3 presents the publicly available production data for HFPO-DA in the United States from 2016
to 2019 as reported under CDR. From 2016 to 2019, HFPO-DA production was less than 1 million
pounds.
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Exhibit 7-3: CDR Reported Annual Manufacture and Importation of HFPO-DA in
the United States, 2016-2019 (pounds)
Chemical Inventory Update Reporting Cycle
2016
2017
2018
2019
2020
Range of
Production /
Importation
Volume
<1,000,000 lbs
<1,000,000 lbs
<1,000,000 lbs
<1,000,000 lbs
No Reports
Exhibit 7-4: CDR Reported Annual Manufacture and Importation of HFPO-DA
Ammonium Salt in the United States, 2016-2019 (pounds)
Chemical Inventory Update Reporting Cycle
2016
2017
2018
2019
2020
Range of
Production /
Importation
Volume
<1,000,000 lbs
<1,000,000 lbs
<1,000,000 lbs
<1,000,000 lbs
No Reports
Toxics Release Inventory (TRI)
The EPA established TRI in 1987 in response to section 313 of the EPCRA. EPCRA section 313 requires
the reporting of annual information on toxic chemical releases from facilities that meet specific criteria.
This reported information is maintained in a database accessible through TRI Explorer (USEPA, 2023b).
Although TRI can provide a general idea of release trends, it has limitations. Not all facilities are required
to report all releases. Facilities are required to report releases if they manufacture, process, or
otherwise use a listed toxic chemical in quantities above the respective activity threshold. For HFPO-DA,
the reporting threshold is 100 lbs. manufactured, processed, or otherwise used over the year. It should
also be noted that, as of this publication, quantities of HFPO-DA at concentrations under 1.0 percent
within mixtures may be exempt from TRI reporting requirements. Reporting requirements have changed
over time (e.g., the chemical list has changed), so conclusions about temporal trends should be drawn
with caution. TRI data are meant to reflect releases and other waste management activities and should
not be used to estimate general public exposure to a chemical (USEPA, 2023b).
TRI data for HFPO-DA are available for 2020 through 2022 (USEPA, 2023b). As shown in Exhibit 7-5,
there were 3,861 pounds of total on-site disposals and 314 pounds of total off-site disposals across all
industries in 2020. In 2021, there were 3,252 pounds of total on-site disposals and 10,389 pounds of
total off-site disposals across all industries. In 2022, there were 2,055 pounds of total on-site disposals
and 1,347 pounds of total off-site disposals across all industries. A total of six facilities from six states
reported releases of HFPO-DA in 2022 (USEPA, 2023b).
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Exhibit 7-5: Environmental Releases of HFPO-DA in the United States, 2020-2022
On-Site Releases (in pounds)
Year
Air
Emissions
Surface
Water
Discharges
Underground
Injection
Releases to
Land
Total Off-
Site
Releases
(in pounds)
Total On-
and Off-Site
Releases
(in pounds)
2020
61
12
3,788
0
314
4,176
2021
64
0
3,188
0
10,389
13,641
2022
59
0
1,596
400
1,347
3,402
Source: USEPA, 2023b
TRI data from 2020 through 2022 are also available for HFPO-DA ammonium salt (USEPA, 2023c). As
shown in Exhibit 7-6, there were 624 pounds of total on-site disposals and no off-site disposals across all
industries in 2020. Similarly, in 2021, all reported releases (820 pounds) were on-site releases. In 2022, a
total of 171 on-site releases were reported and 56 off-site releases were reported. Releases were
reported from one facility in West Virginia.
Exhibit 7-6: Environmental Releases of HFPO-DA Ammonium Salt in the United
States, 2020-2022
On-Site Releases (in pounds)
Year
Air
Emissions
Surface
Water
Discharges
Underground
Injection
Releases to
Land
Total Off-
Site
Releases
(in pounds)
Total On-
and Off-Site
Releases
(in pounds)
2020
218
406
0
0
0
624
2021
147
673
0
0
0
820
2022
46
126
0
0
56
227
Source: USEPA, 2023b
7.1.1.2 Environmental Fate
The primary measures used by the EPA to assess mobility include (where available) Koc, log Kow, KH, water
solubility and vapor pressure. For HFPO-DA, pKa is also important. HFPO-DA is very stable chemically and
is resistant to hydrolysis, photolysis, and biodegradation (USEPA, 2021d). HFPO-DA is considered
persistent, having a half-life [tl/2] longer than six months in air, water, soil and sediments (USEPA,
2022f).
Findings from laboratory studies suggests a propensity for HFPO-DA to be infinitely soluble in water
(DuPont-24128, 2008; DuPont-24129, 2008). In freshwater, HFPO-DA will dissociate to the HFPO
carboxylate anion (USEPA, 2022f). With a pKa of 2.84, HFPO-DA is expected to predominantly exist in its
ionized form at typical environment pH ranges of natural waters (USEPA, 2021d). Based upon estimated
Log Koc 1.05 to 1.92 for HFPO-DA (ITRC, 2021) and Log Koc of 1.10 for HFPO-DA ammonium salt, HFPO-DA
would remain largely in ground water and surface water rather than to bind to suspended solids or
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sediments, although they can bind to the soil particle surfaces in areas of positive charge (USEPA,
2021d).
Based on the vapor pressure of 2.7 mm Hg (DuPont-24128, 2008), HFPO-DA could volatilize from dry
soil. Also, volatilization from water at typical environment pH is possible (USEPA, 2021d).
Modeling of atmospheric behavior of HFPO-DA suggest that it will not exist solely as a vapor if released
to the atmosphere based upon the HFPO-DA vapor pressure. HFPO-DA can very slowly react with
photochemically produced hydroxyl radicals in the atmosphere to degrade (USEPA, 2021d). HFPO-DA is
not expected to undergo direct photolysis (USEPA, 2021d).
Under CCL 3, the EPA created scales12 to informally rank chemical contaminants' likely mobility
(understood as their tendency to partition to water rather than other media) and persistence as "high,"
"moderate," or "low" based on physical and chemical properties (see USEPA, 2021b and USEPA, 2009).
Based upon the chemical properties of HFPO-DA, infinite solubility, and relative low vapor pressure of
2.7 mm Hg predict a favorability of partitioning to water.
7.2 HFPO-DA Occurrence
This section presents data on the occurrence of HFPO-DA in drinking water in the United States. The EPA
is finalizing an MCLG of 10 ppt for HFPO-DA. Under SDWA, the EPA must establish an enforceable MCL,
the maximum concentration of a contaminant that is allowed in PWSs, as close to the MCLG as feasible,
taking several factors into consideration, including analytical methods capable of measuring the
contaminant, available treatment technologies to remove the contaminant, and costs. Based on these
factors, the EPA is finalizing an MCL of 10 ppt for HFPO-DA. Occurrence data from various sources
presented below are analyzed with respect to the MCL. When possible, estimates of the population
exposed at concentrations above the MCL are presented. Also, when possible, studies that are meant to
be representative and studies that are targeted at known or suspected sites of contamination are
identified as such.
The drinking water analyses presented in this section were performed for select state data sources. In
addition, this section presents HFPO-DA findings from occurrence analyses conducted by non-EPA
researchers. For additional background information about data sources used to evaluate occurrence,
please refer to Chapter 2.
The EPA is also finalizing an HI MCL for the regulation of PFHxS, PFNA, HFPO-DA, and PFBS when co-
occurring in mixture combinations containing two or more of these four PFAS. Refer to Chapter 8 for
more information on the HI MCL and chapter 9 for co-occurrence information.
7.2.1 Occurrence in Drinking Water
Data sources reviewed by the agency for information on HFPO-DA occurrence in drinking water included
state drinking water monitoring programs, the DoD PFAS drinking water testing, and additional studies
from the literature. The EPA notes that HFPO-DA were not monitored for a part of the UCMR 3. HFPO-
12 See Exhibit A.8 here: https://www.epa.gov/sites/default/files/2014-05/documents/ccl3 pccltoccl 08-31-
09 508.pdf
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DA is being monitored for under UCMR 5 which is occurring from 2023 to 2025. Analysis of partial UCMR
5 results (the first three quarters of data that were made available as of February 2024) are discussed in
section 11 of this document.
7.2.1.1 State Monitoring Data
Drinking water occurrence data from PWSs for HFPO-DA are available from several states, including
Alabama, Arizona, California, Colorado, Idaho, Illinois, Indiana, Iowa, Kentucky, Maine, Maryland,
Massachusetts, Michigan, Missouri, New Hampshire, New York, North Carolina, North Dakota, Ohio,
Oregon, Pennsylvania, South Carolina, Vermont, Virginia, and Wisconsin. (Note: Some states reported
monitoring for "GenX Chemicals" while other states reported monitoring for HFPO-DA.) The EPA
downloaded publicly available monitoring data from state websites. Note that while some states did
have available raw water data as indicated in Exhibit 7-7, for the subsequent analyses the EPA only
evaluated finished water results.
Exhibit 7-7 provides a summary of the available state reported monitoring data for HFPO-DA, including
date range and a description of coverage and representativeness (including whether monitoring was
non-targeted or targeted (i.e., monitoring in areas of known or potential PFAS contamination)). A
description of those studies is also included in Exhibit 7-7. State reporting thresholds are also provided,
where available, in Exhibit 7-7. The EPA notes that different states utilized various reporting thresholds
when analyzing and presenting their data, and for some states there were no clearly defined thresholds
publicly provided; in these cases, minimum detected concentrations reported may be indicative of
reporting thresholds used. Further, for some states, the thresholds varied when reporting results for the
same analyte, as well as the laboratory analyzing the data. For those states, a range of thresholds is
provided. As shown in Exhibit 7-7, some states reported at thresholds and/or presented data at
concentrations below the EPA's final MCL and/or PQL for HFPO-DA. However, to present the best
available occurrence information, the EPA collected and evaluated the data based on the information as
reported directly by the states and when conducting data analyses incorporated individual state-specific
reporting thresholds where possible. Additionally, the EPA notes that the majority of the data were
analyzed via an EPA-approved drinking water analytical method.
200
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Exhibit 7-7: Summary of Available HFPO-DA State Reported Monitoring Data
State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
Alabama
(ADEM, 2023)
2020
Ground Water and
Surface Water -
Finished Water
Not reported
ADPH instructed water systems to carry out PFAS monitoring at all PWSs
not previously sampled during UCMR 3. In 2022, water systems that had
not been sampled since UCMR 3 were required to sample between
January and June 2022 using current analytical methods . Only results that
are above the MRL are posted online; thus, only reported detections were
available for use in the occurrence analyses.
Non-
Targeted
Arizona
(ADEQ, 2023)
2021
Ground Water and
Surface Water -
Raw and Finished
Water
1.6-2
ADEQ presents a PFAS Interactive Data Map that displays the results of
testing conducted by ADEQ since 2018 at PWSs across Arizona.
Targeted
California
(CADDW, 2023)
2019-
April 2023
Ground Water and
Surface Water -
Raw, Finished, and
Unknown Water
0.002- 17
The EPA reviewed the California HFPO-DA data available online through
April 2023. Finished water data were available from approximately 100
PWSs. For this analysis, the EPA only included results that were explicitly
marked as being from treated water. Sampling in California is ongoing.
Targeted
Colorado
(CDPHE, 2020)
2020
Ground Water and
Surface Water -
Raw and Finished
Water
1.6-3.7
The CDPHE offered free testing to PWSs serving communities, schools,
and workplaces and also to fire districts with wells. Approximately 50% of
PWSs in Colorado participated in the 2020 PFAS sampling project. Data
included in this report were collected in March through May of 2020.
Non-
Targeted
Idaho
(Idaho DEQ,
2023)
2021 -
April 2023
Ground Water -
Finished and
Unknown Water
0.5 -1
Sampling of finished drinking water data between August 2016 and April
2023 that were available on the state's Drinking Water Watch website.
Not
specified
Illinois
(IL EPA, 2023)
2020-
May 2023
Ground Water and
Surface Water -
Raw and Finished
Water
1.7 -12
In 2020, the IL EPA initiated a statewide investigation into the prevalence
and occurrence of PFAS in finished drinking water at 1,749 community
water supplies across Illinois. The EPA reviewed finished drinking water
data collected between September 2020 and May 2023 that were available
on the state's Drinking Water Watch website. Sampling in Illinois is
ongoing.
Non-
Targeted
Indiana (IDEM,
2023)
2021 -
January
2023
Ground Water and
Surface Water -
Raw, Finished, and
Unknown Water
10
Beginning in February 2021, the IDEM facilitated PFAS monitoring at all
CWSs throughout the state of Indiana. Samples were to be collected at all
raw water (i.e., wells and intakes) and finished (after treatment) water
points in a CWS's supply to evaluate the statewide occurrence of PFAS
compounds in CWS across the state and determine the efficacy of
conventional drinking water treatment for PFAS.
Non-
Targeted
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State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
Iowa
(IA DNR, 2023)
2021 -
April 2023
Ground Water and
Surface Water -
Raw and Finished
Water
1.7-5
In January 2020, the Iowa DNR developed an Action Plan to protect the
health of Iowa residents and the environment from PFAS. Data were
downloaded from the PFAS Sampling Interactive Dashboard and Map.
Targeted
Kentucky
(KYDEP, 2019)
2019
Ground Water and
Surface Water -
Finished Water
3.96
Sampling of finished drinking water data between June and October 2019.
Under this sampling effort, data are available from 81 community public
DWTPs, representing 74 PWSs, and serving more than 2.4 million people.
Non-
Targeted
Maine
(Maine DEP,
2020)
2020
Drinking Water -
Raw, Finished, and
Unknown Water
3.69-4.31
In March 2019, the Maine PFAS Task Force was created to review the
extent of PFAS contamination in Maine. Finished water results collected
from 2013 through 2020 have been collected at 23 locations throughout
the state. Data may include results from public and private finished drinking
water sources. Sampling in Maine is ongoing.
Targeted
Maryland
(MDE, 2021;
MDE, 2022a;
MDE, 2022b)
2020-
2022
Ground Water and
Surface Water -
Raw and Finished
Water
1
In 2020, MDE initiated a project to identify potential sources of PFAS in
Maryland and to prioritize water sources for PFAS sampling. The EPA
reviewed the finished water results from the first three phases of MDE's
Public Water System study for the occurrence of PFAS in State drinking
water sources. Under Phase 1 (September 2020 - February 2021), sites
were selected for priority sampling based on MDE's evaluation of potential
relative risk for PFAS exposure through drinking water. Under Phase 2
(March 2021 - May 2021), MDE conducted sampling at sites that were
selected based on their geological setting and proximity to potential
sources of PFAS. Under Phase 3 (August 2021- June 2022), MDE tested
the remaining CWSs in the state.
Targeted
(Phase 1,
Phase 2);
Non-
Targeted
(Phase
3)
Massachusetts
(MA EE A, 2023)
2019-April
2023
Ground Water and
Surface Water -
Raw and Finished
Water
0.41 -20
The EPA reviewed the finished water data available online through April
2023. Data were available from more than 1,300 PWSs. Sampling in
Massachusetts is ongoing.
Targeted
Michigan
(Michigan EGLE,
2023)
2020-
February
2023
Ground Water and
Surface Water -
Finished Water
2
The Michigan EGLE developed MCLs for seven PFAS compounds in
Michigan, which took effect in August 2020. The EPA reviewed available
finished compliance monitoring results through March 2023. Sampling in
Michigan is ongoing.
Non-
Targeted
Missouri
(Missouri DNR,
2023)
2022-
2023
Ground Water and
Surface Water -
Raw and Finished
Water
Not reported
The EPA reviewed the finished water data available online from Missouri
DNR's"PFAS Viewer Tool" which identifies the location of voluntary
sampling for PFAS in public drinking water systems in Missouri. The EPA
reviewed finished water data collected from approximately 125 PWSs from
2022 through 2023. Limited data were also available from 2013 through
2017.
Non-
Targeted
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State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
New Hampshire
(NHDES, 2021)
2019-
May 2021
Ground Water and
Surface Water -
Raw and Finished
Water
Not reported
The EPA reviewed the New Hampshire HFPO-DA data available online
through May 2021. Finished water data were available from more than 130
PWSs. Sampling in New Hampshire is ongoing.
Non-
Targeted
New York
(NYDOH, 2022)
2020-
2022
Ground Water and
Surface Water -
Raw, Finished, and
Unknown Water
0.00000000
1 -2,020
The EPA reviewed finished water data voluntarily provided by the state to
the EPA. Data were available from nearly 2,600 PWSs from 2020 through
2020.
Non-
Targeted
North Carolina
(NCDEQ, 2021;
NCDEQ, 2023)
2017-
2019
Finished and
unknown water
Not reported
NCDEQ and the Department of Health and Human Services investigated
the presence of HFPO-DA and other PFAS in the Cape Fear River in June
2017. Monthly results were also collected from five water treatment plants
on the Cape Fear River. Data were available from June 2017 through
October 2019. Only results above the DLwere reported; thus, only
reported detections were available for use in the occurrence analyses.
Targeted
September
2022-
November
2022
Ground Water and
Surface Water -
Raw, Finished, and
Unknown Water
Not reported
In late 2022, NCDEQ performed three months of sampling at 50 municipal
and county water systems identified in the 2019 PFAS Testing Network
study with PFOA/PFOS detections above the MRL indicated by the 2022
EPA interim health advisories.
Targeted
North Dakota
(NDDEQ, date
unknown;
NDDEQ, date
unknown)
2020,
2021
Ground Water and
Surface Water -
Raw and Finished
Water
Not reported
NDDEQ published a 2020 and a 2021 survey report of North Dakota
Statewide PFAS Presence/Absence results. The sampling effort in October
of 2020 sought to determine if there was a PFAS presence in a
representative portion of the state's public water supply. In 2021, sampling
conducted as part of the third phase of the survey focused on drinking
water sites not evaluated in the first two surveys.
Non-
Targeted
Ohio
(Ohio EPA,
2023)
December
2019-
December
2021
Ground Water and
Surface Water -
Raw and Finished
Water
25
The Ohio EPA coordinated sampling of raw and finished drinking water
from PWSs throughout the state. The EPA reviewed the finished water
data available online through December 2021. During this timeframe, data
were available from 1,479 PWSs.
Non-
Targeted
Oregon
(OHA-DWS,
2022)
2021 - July
2022
Ground Water and
Surface Water -
Finished Water
101 -124
OHA conducted a PFAS drinking water monitoring project in 2021 at PWSs
in Oregon identified as at risk due to their proximity to a known or
suspected PFAS use or contamination site. The EPA reviewed the finished
water data from more than 140 PWSs.
Targeted
Pennsylvania
(PADEP, 2021)
2020-
March
2021
Ground Water and
Surface Water -
Finished Water
1.7-4
Beginning in 2020 and running through March of 2021, finished water data
were collected by more than 340 PWSs.
Targeted
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State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
South Carolina
(SCDHEC, 2020;
SCDHEC, 2023)
2017-
March
2023
Ground Water and
Surface Water -
Raw and Finished
Water
2.1
The EPA reviewed PFAS sampling results collected by the South Carolina
Bureau of Water for community drinking water systems. Data were
available from 300 PWSs.
Non-
Targeted
Vermont
(VT DEC, 2023)
2019 -April
2023
Ground Water and
Surface Water -
Finished Water
2
The Vermont Water Supply Rule required all CWSs and NTNCWSs to
sample for PFAS. The EPA reviewed finished water data available online
from July 2019 - April 2023 from approximately 560 PWSs. Sampling in
Vermont is ongoing.
Non-
Targeted
Virginia
(VDH ODW,
2021)
2021
Ground Water and
Surface Water -
Raw and Finished
Water
3.5
The Virginia ODW, in conjunction with VA PFAS work group, designed the
sample study to prioritize sites for measuring PFAS concentrations in
drinking water and major sources of water and generate statewide
occurrence data.
Targeted
/ Non-
Targeted
Wisconsin
(Wl DNR, 2023)
2022-
April 2023
Ground Water and
Surface Water -
Raw, Finished, and
Unknown Water
Not reported
The EPA reviewed the finished water data available online from 2022 -
2023. Data were available from nearly 250 PWSs. Sampling in Wisconsin
is ongoing.
Non-
Targeted
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A summary of state reported monitoring data from PWSs for HFPO-DA is presented in Exhibit 7-8
through Exhibit 7-10. As noted above, some of the monitoring data from each state are limited and may
not be representative of occurrence in the state. In addition, states have varying reporting thresholds, as
described earlier and indicated in the first column of Exhibit 7-8. For states with available reporting
thresholds, only detected concentrations greater than the reporting thresholds were counted as
detections. For states that did not provide reporting thresholds, the EPA included all detected
concentrations reported in the count of detections. Overall, state reported detected concentrations
ranged from 0.193 ppt (North Carolina) to 1,100 ppt (North Carolina). Note that for a small number of
systems, population served information could not be identified. These systems were included in the
counts and analysis presented in Exhibit 7-10; however, no associated population served was included in
the counts and analysis presented in Exhibit 7-10.
Exhibit 7-8: HFPO-DA State Reported Drinking Water Occurrence Data - Summary
of Finished Water Samples
State
(Reporting
Threshold)
Source Water Type
Total
Number of
Samples
All Detections
All Detections
> 10 ppt
Number
Percent
Number
Percent
Alabama1
(Not reported)
Ground Water
-
1
-
0
-
Surface Water
-
5
-
0
-
Total
-
6
-
0
-
Arizona
(1.6-2 ppt)
Ground Water
23
0
0.0%
0
0.0%
Surface Water
2
0
0.0%
0
0.0%
Total
25
0
0.0%
0
0.0%
California
(0.002- 17 ppt)
Ground Water
1,618
0
0.0%
0
0.0%
Surface Water
3,844
0
0.0%
0
0.0%
Unknown
4
0
0.0%
0
0.0%
Total
5,466
0
0.0%
0
0.0%
Colorado (2020)
(1.6-3.7 ppt)
Ground Water
339
0
0.0%
0
0.0%
Surface Water
244
1
0.4%
0
0.0%
Total
583
1
0.2%
0
0.0%
Idaho
(0.5 -1 ppt)
Ground Water
18
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Total
18
0
0.0%
0
0.0%
Illinois
(1.7 -12 ppt)
Ground Water
1,666
0
0.0%
0
0.0%
Surface Water
277
0
0.0%
0
0.0%
Total
1,943
0
0.0%
0
0.0%
Indiana
(10 ppt)
Ground Water
414
0
0.0%
0
0.0%
Surface Water
56
0
0.0%
0
0.0%
Total
470
0
0.0%
0
0.0%
Iowa
(1.7-5 ppt)
Ground Water
152
5
3.3%
0
0.0%
Surface Water
63
0
0.0%
0
0.0%
Total
215
5
2.3%
0
0.0%
205
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April 2024
State
(Reporting
Threshold)
Source Water Type
Total
Number of
Samples
All Detections
All Detections
> 10 ppt
Number
Percent
Number
Percent
Kentucky
(3.96 ppt)
Ground Water
33
0
0.0%
0
0.0%
Surface Water
48
11
22.9%
2
4.2%
Total
81
11
13.6%
2
2.5%
Maine (PFAS Task
Force)2
(3.69-4.31 ppt)
Ground Water
0
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Unknown
11
0
0.0%
0
0.0%
Total
11
0
0.0%
0
0.0%
Maryland (Phase 1)
(1 ppt)
Ground Water
70
0
0.0%
0
0.0%
Surface Water
76
0
0.0%
0
0.0%
Total
146
0
0.0%
0
0.0%
Maryland (Phase 2)
(1 ppt)
Ground Water
9
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Total
9
0
0.0%
0
0.0%
Maryland (Phase 3)
(1 ppt)
Ground Water
88
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Total
88
0
0.0%
0
0.0%
Massachusetts
(0.41 -20 ppt)
Ground Water
6,750
6
0.1%
0
0.0%
Surface Water
1,888
0
0.0%
0
0.0%
Total
8,638
6
0.1%
0
0.0%
Michigan
(2 ppt)
Ground Water
10,007
8
0.1%
3
0.0%
Surface Water
519
0
0.0%
0
0.0%
Unknown
164
0
0.0%
0
0.0%
Total
10,690
8
0.1%
3
0.0%
Missouri,
2022 - 2023
(Not reported)
Ground Water
190
0
0.0%
0
0.0%
Surface Water
20
0
0.0%
0
0.0%
Total
210
0
0.0%
0
0.0%
New Hampshire
(Not reported)
Ground Water
191
8
4.2%
0
0.0%
Surface Water
46
1
2.2%
0
0.0%
Total
237
9
3.8%
0
0.0%
New York
(0.000000001-
2,020 ppt)
Ground Water
947
4
0.4%
0
0.0%
Surface Water
252
4
1.6%
0
0.0%
Unknown
9
0
0.0%
0
0.0%
Total
1,208
8
0.7%
0
0.0%
North Carolina1
(Not Reported)
Unknown
-
438
-
428
-
Total
-
438
-
428
-
206
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April 2024
State
(Reporting
Threshold)
Source Water Type
Total
Number of
Samples
All Detections
All Detections
> 10 ppt
Number
Percent
Number
Percent
North Carolina
(2023)
Ground Water
21
3
14.3%
2
9.5%
Surface Water
141
46
32.6%
0
0.0%
Total
162
49
30.2%
2
1.2%
North Dakota (2020)
(Not reported)
Ground Water
42
0
0.0%
0
0.0%
Surface Water
9
0
0.0%
0
0.0%
Total
51
0
0.0%
0
0.0%
North Dakota (2021)
(Not reported)
Ground Water
56
0
0.0%
0
0.0%
Surface Water
7
0
0.0%
0
0.0%
Total
63
0
0.0%
0
0.0%
Ohio
(25 ppt)
Ground Water
1,775
0
0.0%
0
0.0%
Surface Water
170
1
0.6%
1
0.6%
Total
1,945
1
0.1%
1
0.1%
Oregon
(101 -124 ppt)
Ground Water
131
0
0.0%
0
0.0%
Surface Water
29
0
0.0%
0
0.0%
Total
160
0
0.0%
0
0.0%
Pennsylvania (2021)
(1.7-4 ppt)
Ground Water
314
0
0.0%
0
0.0%
Surface Water
98
0
0.0%
0
0.0%
Total
412
0
0.0%
0
0.0%
South Carolina
(2.1 ppt)
Ground Water
572
0
0.0%
0
0.0%
Surface Water
185
10
5.4%
0
0.0%
Total
757
10
1.3%
0
0.0%
Vermont
(2 ppt)
Ground Water
1,456
3
0.2%
0
0.0%
Surface Water
102
0
0.0%
0
0.0%
Total
1,558
3
0.2%
0
0.0%
Virginia
(3.5 ppt)
Ground Water
5
0
0.0%
0
0.0%
Surface Water
36
1
2.8%
1
2.8%
Total
41
1
2.4%
1
2.4%
Wisconsin
(Not reported)
Ground Water
683
0
0.0%
0
0.0%
Surface Water
47
0
0.0%
0
0.0%
Total
730
0
0.0%
0
0.0%
1 Only reported detections were available in this state's dataset.
2 Reported data from Maine may include results from public and private finished drinking water sources. Based on
available state data information, the EPA could not verify PWSIDs for all included samples.
207
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Exhibit 7-9: HFPO-DA State Reported Drinking Water Occurrence Data - Summary
of Detected Concentrations
State
(Reporting
Threshold)
Source
Water
Type
Concentration Value of Detections (ppt)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Alabama1
(Not reported)
Ground
Water
4.4
4.4
4.4
4.4
4.4
Surface
Water
2
2.40
3.70
3.88
3.9
Total
2
2.90
4.15
4.38
4.4
Arizona
(1.6-2 ppt)
Ground
Water
-
-
-
-
-
Surface
Water
-
-
-
-
-
Total
-
-
-
-
-
California
(0.002- 17
PPt)
Ground
Water
-
-
-
-
-
Surface
Water
-
-
-
-
-
Unknown
-
-
-
-
-
Total
-
-
-
-
-
Colorado
(2020)
(1.6-3.7 ppt)
Ground
Water
-
-
-
-
-
Surface
Water
2.2
2.2
2.2
2.2
2.2
Total
2.2
2.2
2.2
2.2
2.2
Idaho
(0.5 -1 ppt)
Ground
Water
-
-
-
-
-
Surface
Water
-
-
-
-
-
Total
-
-
-
-
-
Illinois
(1.7 -12 ppt)
Ground
Water
-
-
-
-
-
Surface
Water
-
-
-
-
-
Total
--
-
-
--
-
Indiana
(10 ppt)
Ground
Water
-
-
-
-
-
Surface
Water
-
-
-
-
-
Total
-
-
-
-
-
Iowa
(1.7-5 ppt)
Ground
Water
2.1
2.4
2.5
2.5
2.5
Surface
Water
-
-
-
-
-
Total
2.1
2.4
2.5
2.5
2.5
Kentucky
(3.96 ppt)
Ground
Water
-
-
-
-
-
Surface
Water
3.57
5.75
18.3
28.6
29.7
Total
3.57
5.75
18.3
28.6
29.7
208
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April 2024
State
(Reporting
Threshold)
Source
Water
Type
Concentration Value of Detections (ppt)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Maine (PFAS
Task Force)2
(3.69-4.31
PPt)
Ground
Water
-
-
-
-
-
Surface
Water
-
-
-
-
-
Unknown
-
-
-
-
-
Total
-
-
-
-
-
Maryland
(Phase 1)
(1 ppt)
Ground
Water
-
-
-
-
-
Surface
Water
-
-
-
-
-
Total
-
-
-
-
-
Maryland
(Phase 2)
(1 ppt)
Ground
Water
-
-
-
-
-
Surface
Water
-
-
-
-
-
Total
-
-
-
-
-
Maryland
(Phase 3)
(1 ppt)
Ground
Water
-
-
-
-
-
Surface
Water
-
-
-
-
-
Total
-
-
-
-
-
Massachusetts
(0.41 -20 ppt)
Ground
Water
1.75
2.17
2.69
2.91
2.94
Surface
Water
-
-
-
-
-
Total
1.75
2.17
2.69
2.91
2.94
Michigan
(2 PPt)
Ground
Water
2
7.25
95.1
99.5
100
Surface
Water
-
-
-
-
-
Unknown
-
-
-
-
-
Total
2
7.25
95.1
99.5
100
Missouri,
2022 - 2023
(Not reported)
Ground
Water
-
-
-
-
-
Surface
Water
-
-
-
-
-
Total
--
-
-
--
-
New
Hampshire
(Not reported)
Ground
Water
1.7
1.75
1.93
1.99
2
Surface
Water
1.7
1.7
1.7
1.7
1.7
Total
1.7
1.70
1.92
1.99
2
New York
(0.000000001-
2,020 ppt)
Ground
Water
1.4
3.24
4.38
4.49
4.5
Surface
Water
0.722
1.50
3.28
3.93
4
Unknown
-
-
-
-
-
Total
0.722
1.99
4.22
4.47
4.5
North
Carolina1
(Not Reported)
Unknown
9.52
40.0
80.0
693
1100
Total
9.52
40.0
80.0
693
1100
209
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source
Water
Type
Concentration Value of Detections (ppt)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
North Carolina
(2023)
Ground
Water
13.4
17.3
19.1
19.5
19.5
Surface
Water
0.193
0.715
4.98
10.5
11
Total
0.193
0.846
8.81
18.4
19.5
North Dakota
(2020)
(Not reported)
Ground
Water
-
-
-
-
-
Surface
Water
-
-
-
-
-
Total
--
-
-
--
-
North Dakota
(2021)
(Not reported)
Ground
Water
-
-
-
-
-
Surface
Water
-
-
-
-
-
Total
-
-
-
-
-
Ohio
(25 ppt)
Ground
Water
-
-
-
-
-
Surface
Water
29.6
29.6
29.6
29.6
29.6
Total
29.6
29.6
29.6
29.6
29.6
Oregon
(101 -124 ppt)
Ground
Water
-
-
-
-
-
Surface
Water
-
-
-
-
-
Total
-
-
-
-
-
Pennsylvania
(2021)
(1.7-4 ppt)
Ground
Water
-
-
-
-
-
Surface
Water
-
-
-
-
-
Total
-
-
-
-
-
South Carolina
(2.1 ppt)
Ground
Water
-
-
-
-
-
Surface
Water
2.2
4.65
6.15
6.56
6.6
Total
2.2
4.65
6.15
6.56
6.6
Vermont
(2 ppt)
Ground
Water
2.5
3.1
3.1
3.1
3.1
Surface
Water
-
-
-
-
-
Total
2.5
3.1
3.1
3.1
3.1
Virginia
(3.5 ppt)
Ground
Water
-
-
-
-
-
Surface
Water
54
54
54
54
54
Total
54
54
54
54
54
Wisconsin
(Not reported)
Ground
Water
-
-
-
-
-
Surface
Water
-
-
-
-
-
Total
-
-
-
-
-
210
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
Note: With limited exceptions, calculated concentration values (i.e., median, 90th percentile and 99th percentile
concentrations) were rounded to three significant figures for consistent presentation across the datasets and may
not indicate exact laboratory precision.
1 Only reported detections were available in this state's dataset.
2 Reported data from Maine may include results from public and private finished drinking water sources. Based on
available state data information, the EPA could not verify PWSIDs for all included samples.
Exhibit 7-10: HFPO-DA State Reported Drinking Water Occurrence Data -
Summary of Systems with Finished Water Data
State
(Reporting
Threshold)
Source Water Type
Total
Number
of
Systems with
Detections
Systems with
Detections
> 10 ppt
Systems
Number
Percent
Number
Percent
Alabama1
(Not reported)
Ground Water
-
1
-
0
-
Surface Water
-
3
-
0
-
Total
--
4
-
0
-
Arizona
(1.6-2 ppt)
Ground Water
5
0
0.0%
0
0.0%
Surface Water
1
0
0.0%
0
0.0%
Total
6
0
0.0%
0
0.0%
Ground Water
39
0
0.0%
0
0.0%
California
Surface Water
74
0
0.0%
0
0.0%
(0.002- 17 ppt)
Unknown
1
0
0.0%
0
0.0%
Total
114
0
0.0%
0
0.0%
Colorado (2020)
(1.6-3.7 ppt)
Ground Water
221
0
0.0%
0
0.0%
Surface Water
176
1
0.6%
0
0.0%
Total
397
1
0.3%
0
0.0%
Idaho
(0.5 -1 ppt)
Ground Water
10
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Total
10
0
0.0%
0
0.0%
Illinois
(1.7 -12 ppt)
Ground Water
899
0
0.0%
0
0.0%
Surface Water
97
0
0.0%
0
0.0%
Total
996
0
0.0%
0
0.0%
Indiana
(10 ppt)
Ground Water
333
0
0.0%
0
0.0%
Surface Water
30
0
0.0%
0
0.0%
Total
363
0
0.0%
0
0.0%
Iowa
(1.7-5 ppt)
Ground Water
90
1
1.1%
0
0.0%
Surface Water
26
0
0.0%
0
0.0%
Total
116
1
0.9%
0
0.0%
Kentucky
(3.96 ppt)
Ground Water
30
0
0.0%
0
0.0%
Surface Water
44
9
20.5%
2
4.5%
Total
74
9
12.2%
2
2.7%
211
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water Type
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections
> 10 ppt
Number
Percent
Number
Percent
Maine (PFAS Task
Force)2
(3.69-4.31 ppt)
Ground Water
0
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Unknown
2
0
0.0%
0
0.0%
Total
2
0
0.0%
0
0.0%
Maryland (Phase 1)
(1 ppt)
Ground Water
30
0
0.0%
0
0.0%
Surface Water
36
0
0.0%
0
0.0%
Total
66
0
0.0%
0
0.0%
Maryland (Phase 2)
(1 ppt)
Ground Water
6
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Total
6
0
0.0%
0
0.0%
Maryland (Phase 3)
(1 ppt)
Ground Water
63
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Total
63
0
0.0%
0
0.0%
Maryland
(All Systems)3
(1 PPt)
Ground Water
99
0
0.0%
0
0.0%
Surface Water
36
0
0.0%
0
0.0%
Total
135
0
0.0%
0
0.0%
Massachusetts
(0.41 -20 ppt)
Ground Water
1,192
4
0.3%
0
0.0%
Surface Water
122
0
0.0%
0
0.0%
Total
1,314
4
0.3%
0
0.0%
Michigan
(2 PPt)
Ground Water
2,370
8
0.3%
3
0.1%
Surface Water
84
0
0.0%
0
0.0%
Unknown
54
0
0.0%
0
0.0%
Total
2,508
8
0.3%
3
0.1%
Missouri,
2022 - 2023
(Not reported)
Ground Water
94
0
0.0%
0
0.0%
Surface Water
16
0
0.0%
0
0.0%
Total
110
0
0.0%
0
0.0%
New Hampshire
(Not reported)
Ground Water
127
6
4.7%
0
0.0%
Surface Water
11
1
9.1%
0
0.0%
Total
138
7
5.1%
0
0.0%
New York
(0.000000001-
2,020 ppt)
Ground Water
465
3
0.6%
0
0.0%
Surface Water
94
3
3.2%
0
0.0%
Unknown
4
0
0.0%
0
0.0%
Total
563
6
1.1%
0
0.0%
North Carolina1
(Not Reported)
Unknown
-
5
-
5
-
Total
-
5
-
5
-
212
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water Type
Total
Number
of
Systems
Systems with
Detections
Systems with
Detections
> 10 ppt
Number
Percent
Number
Percent
North Carolina
(2023)
Ground Water
7
1
14.3%
1
14.3%
Surface Water
43
18
41.9%
0
0.0%
Total
50
19
38.0%
1
2.0%
North Dakota
(2020)
(Not reported)
Ground Water
41
0
0.0%
0
0.0%
Surface Water
9
0
0.0%
0
0.0%
Total
50
0
0.0%
0
0.0%
North Dakota
(2021)
(Not reported)
Ground Water
56
0
0.0%
0
0.0%
Surface Water
7
0
0.0%
0
0.0%
Total
63
0
0.0%
0
0.0%
North Dakota
(All Systems)3
(Not reported)
Ground Water
95
0
0.0%
0
0.0%
Surface Water
16
0
0.0%
0
0.0%
Total
111
0
0.0%
0
0.0%
Ohio
(25 ppt)
Ground Water
1,372
0
0.0%
0
0.0%
Surface Water
107
1
0.9%
1
0.9%
Total
1,479
1
0.1%
1
0.1%
Oregon
(101 -124 ppt)
Ground Water
116
0
0.0%
0
0.0%
Surface Water
27
0
0.0%
0
0.0%
Total
143
0
0.0%
0
0.0%
Pennsylvania
(2021)
(1.7-4 ppt)
Ground Water
269
0
0.0%
0
0.0%
Surface Water
73
0
0.0%
0
0.0%
Total
342
0
0.0%
0
0.0%
South Carolina
(2.1 ppt)
Ground Water
234
0
0.0%
0
0.0%
Surface Water
61
6
9.8%
0
0.0%
Total
295
6
2.0%
0
0.0%
Vermont
(2 ppt)
Ground Water
526
3
0.6%
0
0.0%
Surface Water
38
0
0.0%
0
0.0%
Total
564
3
0.5%
0
0.0%
Virginia
(3.5 ppt)
Ground Water
5
0
0.0%
0
0.0%
Surface Water
20
1
5.0%
1
5.0%
Total
25
1
4.0%
1
4.0%
Wisconsin
(Not reported)
Ground Water
213
0
0.0%
0
0.0%
Surface Water
20
0
0.0%
0
0.0%
Total
233
0
0.0%
0
0.0%
1 Only reported detections were available in this state's dataset.
2 Reported data from Maine may include results from public and private finished drinking water sources. Based on
available state data information, the EPA could not verify PWSIDs for all included samples.
3 The "All Systems" counts represent a summary of all unique systems across multiple sampling efforts within the
state. For some states (e.g., NC), the EPA could not verify this number due to the sample site ID reporting.
213
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Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
Exhibit 7-11: HFPO-DA State Reported Drinking Water Occurrence Data -
Summary of Population Served by Systems with Finished Water Data
State
(Reporting
Threshold)
Source Water Type
Total
Population
Served by
Systems
Total Population
Served by Systems
with Detections
Total Population
Served by Systems
with Detections
> 10 ppt
Number
Percent
Number
Percent
Alabama1
(Not reported)
Ground Water
-
7,248
-
0
-
Surface Water
-
57,905
-
0
-
Total
--
65,153
-
0
-
Arizona
(1.6-2 ppt)
Ground Water
94,569
0
0.0%
0
0.0%
Surface Water
50,001
0
0.0%
0
0.0%
Total
144,570
0
0.0%
0
0.0%
California
(0.002- 17 ppt)
Ground Water
1,086,727
0
0.0%
0
0.0%
Surface Water
13,163,194
0
0.0%
0
0.0%
Unknown
0
0
0.0%
0
0.0%
Total
14,249,921
0
0.0%
0
0.0%
Colorado (2020)
(1.6-3.7 ppt)
Ground Water
261,162
0
0.0%
0
0.0%
Surface Water
4,191,774
1,505
0.0%
0
0.0%
Total
4,452,936
1,505
0.0%
0
0.0%
Idaho
(0.5 -1 ppt)
Ground Water
81,985
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Total
81,985
0
0.0%
0
0.0%
Illinois
(1.7 -12 ppt)
Ground Water
2,916,219
0
0.0%
0
0.0%
Surface Water
4,628,949
0
0.0%
0
0.0%
Total
7,545,168
0
0.0%
0
0.0%
Indiana
(10 ppt)
Ground Water
505,212
0
0.0%
0
0.0%
Surface Water
93,290
0
0.0%
0
0.0%
Total
598,502
0
0.0%
0
0.0%
Iowa
(1.7-5 ppt)
Ground Water
491,495
4,570
0.9%
0
0.0%
Surface Water
987,522
0
0.0%
0
0.0%
Total
1,479,017
4,570
0.3%
0
0.0%
Kentucky
(3.96 ppt)
Ground Water
171,212
0
0.0%
0
0.0%
Surface Water
1,922,023
1,130,006
58.8%
55,665
2.9%
Total
2,093,235
1,130,006
54.0%
55,665
2.7%
Maine (PFAS Task
Force)23
(3.69-4.31 ppt)
Ground Water
0
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Unknown
0
0
0.0%
0
0.0%
Total
0
0
0.0%
0
0.0%
Maryland (Phase 1)
(1 ppt)
Ground Water
384,007
0
0.0%
0
0.0%
Surface Water
4,059,154
0
0.0%
0
0.0%
214
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water Type
Total
Population
Served by
Total Population
Served by Systems
with Detections
Total Population
Served by Systems
with Detections
> 10 ppt
Systems
Number
Percent
Number
Percent
Total
4,443,161
0
0.0%
0
0.0%
Maryland (Phase 2)
(1 ppt)
Ground Water
3,896
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Total
3,896
0
0.0%
0
0.0%
Maryland (Phase 3)
(1 ppt)
Ground Water
41,063
0
0.0%
0
0.0%
Surface Water
0
0
0.0%
0
0.0%
Total
41,063
0
0.0%
0
0.0%
Maryland
(All Systems)4
Ground Water
428,966
0
0.0%
0
0.0%
Surface Water
4,059,154
0
0.0%
0
0.0%
(1 PPt)
Total
4,488,120
0
0.0%
0
0.0%
Massachusetts
(0.41 -20 ppt)
Ground Water
1,777,376
45,470
2.6%
0
0.0%
Surface Water
5,860,701
0
0.0%
0
0.0%
Total
7,638,077
45,470
0.6%
0
0.0%
Ground Water
1,945,734
2,538
0.1%
966
0.0%
Michigan
Surface Water
1,314,601
0
0.0%
0
0.0%
(2 PPt)
Unknown
0
0
0.0%
0
0.0%
Total
3,260,335
2,538
0.1%
966
0.0%
Missouri
Ground Water
189,904
0
0.0%
0
0.0%
2022 - 2023
Surface Water
347,928
0
0.0%
0
0.0%
(Not reported)
Total
537,832
0
0.0%
0
0.0%
New Hampshire
(Not reported)
Ground Water
69,445
852
1.2%
0
0.0%
Surface Water
237,720
2,450
1.0%
0
0.0%
Total
307,165
3,302
1.1%
0
0.0%
Ground Water
464,701
9,250
2.0%
0
0.0%
New York
(0.000000001-
2,020 ppt)
Surface Water
1,326,928
14,421
1.1%
0
0.0%
Unknown
1,024
0
0.0%
0
0.0%
Total
1,792,653
23,671
1.3%
0
0.0%
North Carolina1'2
Unknown
-
-
-
-
-
(Not Reported)
Total
--
--
-
-
-
North Carolina
(2023)
Ground Water
26,914
3,889
14.4%
3,889
14.4%
Surface Water
2,649,927
956,842
36.1%
0
0.0%
Total
2,676,841
960,731
35.9%
3,889
0.1%
North Dakota
Ground Water
68,280
0
0.0%
0
0.0%
(2020)
Surface Water
57,469
0
0.0%
0
0.0%
(Not reported)
Total
125,749
0
0.0%
0
0.0%
North Dakota
Ground Water
113,623
0
0.0%
0
0.0%
(2021)
Surface Water
194,121
0
0.0%
0
0.0%
(Not reported)
Total
307,744
0
0.0%
0
0.0%
215
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water Type
Total
Population
Served by
Systems
Total Population
Served by Systems
with Detections
Total Population
Served by Systems
with Detections
> 10 ppt
Number
Percent
Number
Percent
North Dakota
(All Systems)4
(Not reported)
Ground Water
181,514
0
0.0%
0
0.0%
Surface Water
251,590
0
0.0%
0
0.0%
Total
433,104
0
0.0%
0
0.0%
Ohio
(25 ppt)
Ground Water
2,883,252
0
0.0%
0
0.0%
Surface Water
6,215,644
11,129
0.2%
11,129
0.2%
Total
9,098,896
11,129
0.1%
11,129
0.1%
Oregon
(101 -124 ppt)
Ground Water
114,194
0
0.0%
0
0.0%
Surface Water
125,239
0
0.0%
0
0.0%
Total
239,433
0
0.0%
0
0.0%
Pennsylvania
(2021)
(1.7-4 ppt)
Ground Water
471,651
0
0.0%
0
0.0%
Surface Water
4,296,097
0
0.0%
0
0.0%
Total
4,767,748
0
0.0%
0
0.0%
South Carolina
(2.1 ppt)
Ground Water
485,992
0
0.0%
0
0.0%
Surface Water
2,200,008
138,147
6.3%
0
0.0%
Total
2,686,000
138,147
5.1%
0
0.0%
Vermont
(2 ppt)
Ground Water
211,357
305
0.1%
0
0.0%
Surface Water
174,473
0
0.0%
0
0.0%
Total
385,830
305
0.1%
0
0.0%
Virginia
(3.5 ppt)
Ground Water
2,975
0
0.0%
0
0.0%
Surface Water
4,839,373
155,000
3.2%
155,000
3.2%
Total
4,842,348
155,000
3.2%
155,000
3.2%
Wisconsin
(Not reported)
Ground Water
1,433,854
0
0.0%
0
0.0%
Surface Water
1,297,605
0
0.0%
0
0.0%
Total
2,731,459
0
0.0%
0
0.0%
1 Only reported detections were available in this state's dataset.
2 There were some instances where the population served by a system could not be identified. Thus, there are
systems with detections but no associated population served by those systems with detections.
3 Reported data from Maine may include results from public and private finished drinking water sources. Based on
available state data information, the EPA could not verify PWSIDs for all included samples.
4 The "All Systems" counts represent a summary of all unique systems across multiple sampling efforts within the
state.
7.2.2 Other Data
7.2.2.1 Department of Defense (DoD) Drinking Water Sampling
The DoD conducted sampling of off-base drinking water located in "covered areas" (i.e., areas that are
adjacent to and down gradient from a military installation) to identify potential impacts of PFAS
resulting from DoD activities. Sampling was conducted for multiple PFAS, including HFPO-DA. The EPA
downloaded available DOD off-base sampling results September 2023.
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The EPA summarized off-base sampling results for HFPO-DA collected "post treatment" from drinking
water systems and private wells located in covered areas adjacent to 18 installations located in 10
states. No detections were reported "post treatment." Sampling was conducted utilizing multiple
analytical methods including EPA methods 533, 537, 537.1, 1633, and DoD Quality Systems Manual
Table B-15 (DoD, 2023a). Results are based on DLs which vary between both sampling sites and across
different PFAS. Results for HFPO-DA are presented in Exhibit 7-12.
Exhibit 7-12: Summary of HFPO-DA Drinking Water Sampling Results Collected
Post-Treatment from Department of Defense Off-Base "Covered Areas"
State
Installation Name
Sampling Dates
Analysis
Method
#
Samples
#
Detections
%
Detections
AZ
YUMA AZ MCAS
5/26/2023
533
1
0
0.00%
CA
Castle AFB
7/5/2022 - 4/5/2023
537
26
0
0.00%
CA
Castle AFB
11/17/2021 - 1/11/2022
QSM_B15
12
0
0.00%
CA
George AFB
3/23/2023 - 4/20/2023
1633
3
0
0.00%
CA
March AFB
1/3/2023-4/10/2023
533
3
0
0.00%
CA
March AFB
1/3/2022- 12/1/2022
537.1
11
0
0.00%
CA
March AFB
9/1/2022
QSM_B15
1
0
0.00%
DE
Dover AFB
1/22/2022
QSM_B15
6
0
0.00%
FL
WHITING FLD FL NAS
9/1/2022
537.1
2
0
0.00%
ME
NCTAMSLANT DET CUTLER
4/20/2022 - 12/6/2022
537.1
66
0
0.00%
NH
Pease AFB
6/23/2022
QSM_B15
2
0
0.00%
NY
Plattsburgh AFB
3/1/2022-9/15/2022
537.1
10
0
0.00%
NY
Plattsburgh AFB
11/29/2021 -6/27/2023
QSM_B15
9
0
0.00%
Rl
NAVAL AUX LANDING FIELD
5/19/2022
537.1
2
0
0.00%
Rl
NAVAL AUX LANDING FIELD
10/17/2022-2/28/2023
QSM_B15
31
0
0.00%
VA
OCEANA VA NAS
10/19/2022-4/14/2023
537.1
13
0
0.00%
WA
BREMERTON WA NAVBASE
10/11/2022-7/21/2023
537.1
3
0
0.00%
WA
WHIDBEY IS WA NAS
4/21/2022 - 4/20/2023
537.1
11
0
0.00%
Source: DOD, 2023a
7.2.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the ambient sources of most drinking water. Contaminant occurrence in
ambient water can provide useful information on the potential for contaminants to adversely affect
drinking water supplies. Occurrence data for HFPO-DA in ambient water are available from the USGS
NWIS database and the EPA's legacy STORET data available through the WQP.
7.2.3.1 National Water Information System (NWIS) Data
The NWIS is the Nation's principal repository of water resources data USGS collects from more than 1.9
million sites (USGS, 2023). NWIS-Web is the general online interface to the USGS NWIS database.
Discrete water-sample and time-series data are available from sites in all 50 States, including 5 million
water samples with 90 million water-quality results. All USGS water quality and flow data are stored in
NWIS, including site characteristics, streamflow, ground water level, precipitation, and chemical
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analyses of water, sediment, and biological media, though not all parameters are available for every site.
NWIS houses the NAWQA data and includes other USGS data from unspecified projects. NWIS contains
many more samples at many more sites than the NAWQA Program. Although NWIS is comprised of
primarily ambient water data, some finished drinking water data are included as well. This section
presents analyses of non-NAWQA data in NWIS, downloaded from the WQP in November 2023 (WQP,
2023).
The results of the non-NAWQA NWIS HFPO-DA analysis are presented in Exhibit 7-13. NWIS data for
HFPO-DA were listed under the characteristic name "Hexafluoropropylene oxide dimer acid." HFPO-DA
was not detected in any of the 170 samples collected from 60 sites. (Note that the NWIS data are
presented as downloaded; potential outliers were not evaluated or excluded from the analysis.)
Exhibit 7-13: HFPO-DA NWIS Data
Site Type
Detection Frequency
(detections are results > reporting level)
Concentration Values
(of detections, in ng/L)
No. of
Samples
No. of
Samples
with
Detections
No.
of
Sites
No. of
Sites with
Detections
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Ground
Water
2
0
2
0
-
-
-
-
-
Surface
Water
168
0
58
0
-
-
-
-
-
All Sites
170
0
60
0
-
-
-
-
-
Source: WQP, 2023
7.2.3.2 Storage and Retrieval (STORET) Data / Water Quality Portal (WQP)
From its launch in 1999 until it was decommissioned in June 2018, the EPA's STORET Data Warehouse
was collaboratively populated with raw biological, chemical, and physical data from surface water and
ground water sampling by federal, state and local agencies, Native American tribes, volunteer groups,
academics, and others. Legacy STORET data are accessible through the WQP:
https://www.waterqualitydata.us/portal/.
STORET data are from monitoring locations in all 50 states as well as multiple territories and jurisdictions
of the United States. Most data are from ambient waters, but in some cases finished drinking water data
are included as well. STORET's data quality limitations include variations in the extent of national
coverage and data completeness from parameter to parameter. Data may have been collected as part of
targeted, rather than randomized, monitoring.
This section presents analyses of STORET data, downloaded from the WQP in November 2023 (WQP,
2023). The EPA reviewed STORET ground water data from wells and springs and surface water data from
lakes, rivers, streams, and reservoirs (WQP, 2023). STORET data for HFPO-DA were listed under the
characteristic name of "Hexafluoropropylene oxide dimer acid" and "Perfluoro(2-propoxypropanoate)."
The results of the STORET analysis for HFPO-DA are presented in Exhibit 7-14. More than 130 HFPO-DA
samples were available for analysis. These HFPO-DA samples were collected between 2019 and 2023. Of
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the 118 sites sampled, less than 1 percent reported detections of HFPO-DA. One detected concentration
was listed in the database as a non-numerical value (i.e., "Present Below Quantification Limit").
Exhibit 7-14: HFPO-DA STORET Data - Summary of Samples and Sites
Source Water
Type
Total
Number of
Samples
Samples with
Detections
Total
Number
of Sites
Sites with Detections
Number
Percent
Number
Percent
Ground Water
51
0
0.00%
48
0
0.00%
Surface Water
26
0
0.00%
26
0
0.00%
Unknown
59
1
1.69%
44
1
2.27%
Total
136
1
0.74%
118
1
0.85%
Source: WQP, 2023
7.3 Analytical Methods
For the purposes of compliance with the PFAS NPDWR, the EPA has published two analytical methods
that are available for the analysis of HFPO-DA and other PFAS in drinking water. The performance
metrics that are presented, including the DL, LCMRL, mean recoveries and RSDs are specific to HFPO-DA
for each of the listed analytical methods. Ranges of mean recoveries and RSDs are presented for the
matrices listed; data from holding time studies are not included since these studies are designed to
demonstrate a degradation in method performance over time and thus are not indicative of method
performance that should be observed when holding times are not exceeded:
• EPA Method 537.1, Version 2.0, Determination of Selected Per- and Polyfluorinated Alkyl
Substances in Drinking Water by Solid Phase Extraction and Liquid Chromatography/Tandem
Mass Spectrometry (LC/MS/MS). The DL and LCMRL generated by the laboratory that
developed the method are 1.9 ng/L and 4.3 ng/L, respectively. Mean recoveries in fortified
reagent water, tap water from a ground water source (TOC = 0.53 mg/L and hardness = 377
mg/L), tap water from a surface water source (TOC = 2.4 mg/L and hardness = 103 mg/L),
and tap water from a private well (TOC = 0.56 mg/L and hardness = 394 mg/L) range from
88.6 to 102%, with RSDs of 1.3 to 5.1% (USEPA, 2020d).
• EPA Method 533, Determination of Per- and Polyfluoroalkyl Substances in Drinking Water by
Isotope Dilution Anion Exchange Solid Phase Extraction and Liquid Chromatography /
Tandem Mass Spectrometry. The LCMRL generated by the laboratory that developed the
method is 3.7 ng/L (DLs were not calculated). Mean recoveries (excluding 13C isotope
analogue data) in fortified reagent water, finished drinking water from a ground water
source (hardness = 320 mg/L, pH = 7.88 at 17° C, free Cl2 = 0.64 mg/L, and total Cl2 = 0.74
mg/L) and clarified surface water (prior to GAC treatment and chlorinated in the laboratory;
pH = 8.1 at 20 °C, free Cl2 = 0.98 mg/L, total Cl2 = 1.31 mg/L. and TOC = 3.8 mg/L) range from
102 to 109%, with RSDs of 4.7 to 9.7% (USEPA, 2019b).
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8 Hazard Index MCL Analyses
The EPA is making a final regulatory determination and finalizing an HI NPDWR for the regulation of
mixture combinations containing two or more of PFHxS, PFNA, HFPO-DA, and PFBS (collectively referred
to as "HI PFAS"). As such, the EPA is finalizing to calculate the HI as the sum total of component four
PFAS hazard quotients (HQs), calculated by dividing the measured component PFAS concentration in
water by the relevant Health Based Water Concentration (HBWC). The EPA is finalizing the HBWCs to be
10 ppt for PFHxS; 10 ppt for PFNA; 10 ppt for HFPO-DA; and 2,000 ppt for PFBS. The EPA notes these
HBWCs are identical to the final individual MCLs for PFHxS, PFNA, and HFPO-DA. Exhibit 8-1 below
presents the sample-level results of the HI analysis for mixtures containing two or more of PFHxS, PFNA,
HFPO-DA, and PFBS using available finished water data from the state reported data sets. The EPA notes
that while nearly all states included in Exhibit 8-1 conducted monitoring of all four PFAS as a part of their
overall PFAS sampling effort, in a subset of those states (e.g., California, Massachusetts) some samples
did not include reported data on all four HI PFAS (i.e., values of one or more of the HI PFAS were not
reported as non-detect, rather no value was reported). Therefore, for that subset of states, to fully
conduct the HI analysis, the EPA also analyzed samples even if those samples did not contain reported
values (including non-detects) of all four HI PFAS (i.e., exceeding the HI based on only two or three HI
PFAS with reported values included within a sample). Accordingly, for water samples with a reported
result of all four analytes included, an HQ is calculated for each analyte and the resulting ratios are
summed and compared to the HI of 1 (unitless). For water samples with fewer than all four analytes (as
indicated in the first column of Exhibit 8-1), the HQs for any of the four PFAS with available results are
also calculated and then summed and compared to the HI of 1 (unitless). The HI MCL equation is
calculated as follows:
jjj Mr, _ f[HFP0 ~ DAwater\\ f[PFBSwater]\ f[PFNAwater]\
- ^ [10 ppt] ) + y [2,000 ppt] J V [10 ppt] )
hPFHxSwater]\
\ [10 ppt] )
Where HFPO-DAwater = monitored ppt concentration of HFPO-DA;
PFBSwater = monitored ppt concentration of PFBS;
PFNAwater= monitored ppt concentration of PFNA; and
PFHxSwater = monitored ppt concentration of PFHxS
Exhibit 8-1. Hazard Index Analysis, Summary of Samples
Samples
with "X"
number of
analytes
State
Source Water Type
Total # Samples
Hazard Index (HI)
Calculation
# Samples
with HI > 1
% of Samples
with HI > 1
4
Arizona
Ground Water
23
5
21.74%
4
Surface Water
2
0
0.00%
4
Total
25
5
20.00%
4
California
Ground Water
1,601
63
3.94%
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Samples
with "X"
number of
analytes
State
Source Water Type
Total # Samples
Hazard Index (HI)
Calculation
# Samples
with HI > 1
% of Samples
with HI > 1
4
Surface Water
3,803
82
2.16%
4
Unknown
4
0
0.00%
4
Total
5,408
145
2.68%
3
Ground Water
267
115
43.07%
3
California
Surface Water
117
12
10.26%
3
Total
384
127
33.07%
2
Ground Water
1
0
0.00%
2
California
Surface Water
0
0
0.00%
2
Total
1
0
0.00%
3
Distribution (Finished)
66
27
40.91%
3
Colorado
(2013-2017)
Surface Water
(Finished)
11
0
0.00%
3
Total
77
27
35.06%
4
Ground Water
339
1
0.29%
4
Colorado (2020)
Surface Water
244
1
0.41%
4
Total
583
2
0.34%
3
Ground Water
0
0
0.00%
3
Georgia
Surface Water
2
0
0.00%
3
Total
2
0
0.00%
4
Ground Water
18
0
0.00%
4
Idaho
Surface Water
0
0
0.00%
4
Total
18
0
0.00%
4
Ground Water
1,666
13
0.78%
4
Illinois
Surface Water
277
0
0.00%
4
Total
1,943
13
0.67%
3
Ground Water
157
3
1.91%
3
Illinois
Surface Water
25
0
0.00%
3
Total
182
3
1.65%
4
Ground Water
414
0
0.00%
4
Indiana
Surface Water
56
0
0.00%
4
Total
470
0
0.00%
3
Ground Water
8
0
0.00%
3
Indiana
Surface Water
3
0
0.00%
3
Total
11
0
0.00%
4
Ground Water
151
3
1.99%
4
Iowa
Surface Water
63
4
6.35%
4
Total
214
7
3.27%
3
Iowa
Ground Water
1
0
0.00%
3
Surface Water
0
0
0.00%
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Samples
with "X"
number of
analytes
State
Source Water Type
Total # Samples
Hazard Index (HI)
Calculation
# Samples
with HI > 1
% of Samples
with HI > 1
3
Total
1
0
0.00%
4
Ground Water
33
0
0.00%
4
Kentucky
Surface Water
48
2
4.17%
4
Total
81
2
2.47%
4
Ground Water
0
0
0.00%
4
Maine
Surface Water
0
0
0.00%
4
Unknown
9
0
0.00%
4
Total
9
0
0.00%
3
Ground Water
7
0
0.00%
3
Maine
Surface Water
2
0
0.00%
3
Unknown
45
3
6.67%
3
Total
54
3
5.56%
3
Ground Water
640
3
0.47%
3
Maine (Compliance)
Surface Water
62
0
0.00%
3
Total
702
3
0.43%
2
Ground Water
6
1
16.67%
2
Maine (Compliance)
Surface Water
0
0
0.00%
2
Total
6
1
16.67%
4
Ground Water
70
3
4.29%
4
Maryland (Phase 1)
Surface Water
76
3
3.95%
4
Total
146
6
4.11%
4
Ground Water
9
1
11.11%
4
Maryland (Phase 2)
Surface Water
0
0
0.00%
4
Total
9
1
11.11%
4
Ground Water
88
3
3.41%
4
Maryland (Phase 3)
Surface Water
0
0
0.00%
4
Total
88
3
3.41%
4
Ground Water
6,522
85
1.30%
4
Massachusetts
Surface Water
1,751
7
0.40%
4
Total
8,273
92
1.11%
3
Ground Water
238
34
14.29%
3
Massachusetts
Surface Water
130
4
3.08%
3
Total
368
38
10.33%
2
Ground Water
192
6
3.13%
2
Massachusetts
Surface Water
93
0
0.00%
2
Total
285
6
2.11%
4
Ground Water
9,973
62
0.62%
4
Michigan
Surface Water
516
0
0.00%
4
Unknown
164
3
1.83%
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Samples
with "X"
number of
analytes
State
Source Water Type
Total # Samples
Hazard Index (HI)
Calculation
# Samples
with HI > 1
% of Samples
with HI > 1
4
Total
10,653
65
0.61%
4
Missouri,
2022 - 2023
Ground Water
190
1
0.53%
4
Surface Water
20
0
0.00%
4
Total
210
1
0.48%
3
Missouri,
2022 - 2023
Ground Water
19
0
0.00%
3
Surface Water
23
0
0.00%
3
Total
42
0
0.00%
4
Ground Water
181
4
2.21%
4
New Hampshire
Surface Water
45
0
0.00%
4
Total
226
4
1.77%
3
Ground Water
338
11
3.25%
3
New Hampshire
Surface Water
14
0
0.00%
3
Total
352
11
3.13%
2
Ground Water
1,107
25
2.26%
2
New Hampshire
Surface Water
92
0
0.00%
2
Unknown
1
0
0.00%
2
Total
1,200
25
2.08%
3
Ground Water
5,344
119
2.23%
3
New Jersey
Surface Water
1,769
20
1.13%
3
Unknown
3
0
0.00%
3
Total
7,116
139
1.95%
2
Ground Water
2
0
0.00%
2
New Jersey
Surface Water
1
0
0.00%
2
Total
3
0
0.00%
3
Ground Water
2
0
0.00%
3
New Mexico
Surface Water
0
0
0.00%
3
Total
2
0
0.00%
4
Ground Water
874
6
0.69%
4
New York
Surface Water
239
2
0.84%
4
Unknown
4
0
0.00%
4
Total
1,117
8
0.72%
3
Ground Water
822
19
2.31%
3
New York
Surface Water
115
0
0.00%
3
Total
937
19
2.03%
2
Ground Water
16
0
0.00%
2
New York
Surface Water
5
0
0.00%
2
Total
21
0
0.00%
3
North Dakota (2020)
Ground Water
42
0
0.00%
3
Surface Water
8
0
0.00%
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Samples
with "X"
number of
analytes
State
Source Water Type
Total # Samples
Hazard Index (HI)
Calculation
# Samples
with HI > 1
% of Samples
with HI > 1
3
Total
50
0
0.00%
2
Ground Water
0
0
0.00%
2
North Dakota (2020)
Surface Water
1
0
0.00%
2
Total
1
0
0.00%
4
Ground Water
56
0
0.00%
4
North Dakota (2021)
Surface Water
7
0
0.00%
4
Total
63
0
0.00%
4
Ground Water
1,775
57
3.21%
4
Ohio
Surface Water
170
1
0.59%
4
Total
1,945
58
2.98%
4
Ground Water
113
1
0.88%
4
Oregon
Surface Water
27
0
0.00%
4
Total
140
1
0.71%
3
Ground Water
18
0
0.00%
3
Oregon
Surface Water
2
0
0.00%
3
Total
20
0
0.00%
3
Ground Water
75
1
1.33%
3
Pennsylvania (2019)
Surface Water
21
1
4.76%
3
Total
96
2
2.08%
4
Ground Water
314
9
2.87%
4
Pennsylvania (2021)
Surface Water
98
1
1.02%
4
Total
412
10
2.43%
4
Ground Water
572
2
0.35%
4
South Carolina
Surface Water
185
0
0.00%
4
Total
757
2
0.26%
3
Ground Water
0
0
0.00%
3
South Carolina
Surface Water
3
0
0.00%
3
Total
3
0
0.00%
2
Ground Water
0
0
0.00%
2
South Carolina
Surface Water
6
0
0.00%
2
Total
6
0
0.00%
3
Ground Water
0
0
0.00%
3
Tennessee
Surface Water
2
0
0.00%
3
Total
2
0
0.00%
4
Ground Water
1,456
20
1.37%
4
Vermont
Surface Water
101
0
0.00%
4
Total
1,557
20
1.28%
3
Vermont
Ground Water
1
0
0.00%
3
Surface Water
0
0
0.00%
224
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
Samples
with "X"
number of
analytes
State
Source Water Type
Total # Samples
Hazard Index (HI)
Calculation
# Samples
with HI > 1
% of Samples
with HI > 1
3
Total
1
0
0.00%
2
Ground Water
6
0
0.00%
2
Vermont
Surface Water
1
0
0.00%
2
Total
7
0
0.00%
4
Ground Water
5
0
0.00%
4
Virginia
Surface Water
34
1
2.94%
4
Total
39
1
2.56%
4
Ground Water
675
14
2.07%
4
Wisconsin
Surface Water
47
0
0.00%
4
Total
722
14
1.94%
3
Ground Water
9
0
0.00%
3
Wisconsin
Surface Water
0
0
0.00%
3
Total
9
0
0.00%
2
Ground Water
36
0
0.00%
2
Wisconsin
Surface Water
7
0
0.00%
2
Total
43
0
0.00%
1 New Jersey only conducted monitoring for PFHxS, PFNA, and PFBS.
The EPA notes that there are other states (e.g., Alabama, North Carolina) that conducted monitoring of
all four PFAS; however, for the entirety of their results, only detections were reported. Thus, conducting
the HI analysis for those states may not be fully representative. An analysis of the HI data for those two
states showed the following results: 5 percent of Alabama samples including two or more PFAS had an
HI > 1 (4 of 80 samples) and 99 percent of North Carolina samples including two or more PFAS had an HI
> 1 (367 of 372 samples).
Exhibit 8-2 presents similar results to Exhibit 8-1 but at the system-level, including population served
estimates. For the states with a varying number of analytes included in the HI calculation, a summary of
the unique count of systems with data is also presented (e.g., California, Massachusetts, etc.).
225
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
Exhibit 8-2. Hazard Index Analysis, Summary of Systems and Population Served by Systems
Samples
with "X"
number of
analytes
State
Source Water Type
Total #
Systems with
Data for the
HI Calculation
#
Systems
with HI >1
%of
Systems
with HI > 1
Total Pop.
Served by
Systems
with Data for
the HI
Calculation1
Pop. Served
by Systems
with HI >1
%of
Systems
with HI > 1
Ground Water
5
2
40.00%
94,569
55,535
58.72%
4
Arizona
Surface Water
1
0
0.00%
50,001
0
0.00%
Total
6
2
33.33%
144,570
55,535
38.41%
Ground Water
37
6
16.22%
1,085,674
132,539
12.21%
4
California
Surface Water
Unknown
74
1
11
0
14.86%
0.00%
13,163,194
0
2,491,347
0
18.93%
0.00%
Total
112
17
15.18%
14,248,868
2,623,886
18.41%
Ground Water
12
3
25.00%
122,333
84,840
69.35%
3
California
Surface Water
22
5
22.73%
3,319,040
754,159
22.72%
Total
34
8
23.53%
3,441,373
838,999
24.38%
Ground Water
1
0
0.00%
26,355
0
0.00%
2
California
Surface Water
0
0
0.00%
0
0
0.00%
Total
1
0
0.00%
26,355
0
0.00%
Ground Water
43
7
16.28%
1,098,122
134,039
12.21%
Unique
System
Count
California
Surface Water
Unknown
78
1
12
0
15.38%
0.00%
13,500,188
0
2,665,573
0
19.74%
0.00%
Total
122
19
15.57%
14,598,310
2,799,612
19.18%
Distribution (Finished)
22
11
50.00%
-
-
-
O
Colorado
Surface Water
C.
0
11
0.00%
40.74%
(2013-2017)
(Finished)
Total
27
Ground Water
221
1
0.45%
261,162
70
0.03%
4
Colorado (2020)
Surface Water
176
1
0.57%
4,191,774
4,495
0.11%
Total
397
2
0.50%
4,452,936
4,565
0.10%
3
Georgia2
Ground Water
0
0
0.00%
0
0
0.00%
226
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
Samples
with "X"
number of
analytes
State
Source Water Type
Total #
Systems with
Data for the
HI Calculation
#
Systems
with HI >1
%of
Systems
with HI > 1
Total Pop.
Served by
Systems
with Data for
the HI
Calculation1
Pop. Served
by Systems
with HI >1
%of
Systems
with HI > 1
Surface Water
1
0
0.00%
9,993
0
0.00%
Total
1
0
0.00%
9,993
0
0.00%
Ground Water
10
0
0.00%
81,985
0
0.00%
4
Idaho
Surface Water
0
0
0.00%
0
0
0.00%
Total
10
0
0.00%
81,985
0
0.00%
Ground Water
899
7
0.78%
2,916,219
83,168
2.85%
4
Illinois
Surface Water
97
0
0.00%
4,628,949
0
0.00%
Total
996
7
0.70%
7,545,168
83,168
1.10%
Ground Water
26
1
3.85%
531,087
3,000
0.56%
3
Illinois
Surface Water
13
0
0.00%
315,395
0
0.00%
Total
39
1
2.56%
846,482
3,000
0.35%
Unique
System
Ground Water
899
7
0.78%
2,916,219
83,168
2.85%
Illinois
Surface Water
97
0
0.00%
4,628,949
0
0.00%
Count
Total
996
7
0.70%
7,545,168
83,168
1.10%
Ground Water
333
0
0.00%
505,212
0
0.00%
4
Indiana
Surface Water
30
0
0.00%
93,290
0
0.00%
Total
363
0
0.00%
598,502
0
0.00%
Ground Water
8
0
0.00%
40,626
0
0.00%
3
Indiana
Surface Water
1
0
0.00%
4,158
0
0.00%
Total
9
0
0.00%
44,784
0
0.00%
Unique
System
Ground Water
341
0
0.00%
545,838
0
0.00%
Indiana
Surface Water
31
0
0.00%
97,448
0
0.00%
Count
Total
372
0
0.00%
643,286
0
0.00%
Ground Water
89
2
2.25%
490,955
5,834
1.19%
4
Iowa
Surface Water
26
1
3.85%
987,522
85,797
8.69%
Total
115
3
2.61%
1,478,477
91,631
6.20%
227
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
Samples
with "X"
number of
analytes
State
Source Water Type
Total #
Systems with
Data for the
HI Calculation
#
Systems
with HI >1
%of
Systems
with HI > 1
Total Pop.
Served by
Systems
with Data for
the HI
Calculation1
Pop. Served
by Systems
with HI >1
%of
Systems
with HI > 1
Ground Water
1
0
0.00%
540
0
0.00%
3
Iowa
Surface Water
0
0
0.00%
0
0
0.00%
Total
1
0
0.00%
540
0
0.00%
Ground Water
90
2
2.22%
491,495
5,834
1.19%
Unique
Iowa
Surface Water
26
1
3.85%
987,522
85,797
8.69%
Total
116
3
2.59%
1,479,017
91,631
6.20%
Ground Water
30
0
0.00%
171,212
0
0.00%
4
Kentucky
Surface Water
44
2
4.55%
1,922,023
55,665
2.90%
Total
74
2
2.70%
2,093,235
55,665
2.66%
Ground Water
0
0
0.00%
0
0
0.00%
4
Maine
Surface Water
Unknown
0
2
0
0
0.00%
0.00%
0
0
0
0
0.00%
0.00%
Total
2
0
0.00%
0
0
0.00%
Ground Water
7
0
0.00%
3,995
0
0.00%
3
Maine
Surface Water
Unknown
1
10
0
3
0.00%
30.00%
21,808
0
0
0
0.00%
0.00%
Total
18
3
16.67%
25,803
0
0.00%
Ground Water
7
0
0.00%
3,995
0
0.00%
Unique
System
Count
Maine
Surface Water
Unknown
1
10
0
3
0.00%
0.00%
21,808
0
0
0
0.00%
0.00%
Total
18
3
16.67%
25,803
0
0.00%
Ground Water
588
3
0.51%
274,216
1,060
0.39%
3
Maine (Compliance)
Surface Water
53
0
0.00%
464,453
0
0.00%
Total
641
3
0.47%
738,669
1,060
0.14%
2
Maine (Compliance)
Ground Water
Surface Water
5
0
1
0
20.00%
0.00%
650
0
140
0
21.54%
0.00%
228
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
Samples
with "X"
number of
analytes
State
Source Water Type
Total #
Systems with
Data for the
HI Calculation
#
Systems
with HI >1
%of
Systems
with HI > 1
Total Pop.
Served by
Systems
with Data for
the HI
Calculation1
Pop. Served
by Systems
with HI >1
%of
Systems
with HI > 1
Total
5
1
20.00%
650
140
21.54%
Unique
Ground Water
593
4
0.67%
274,866
1,200
0.44%
System
Maine (Compliance)
Surface Water
53
0
0.00%
464,453
0
0.00%
Count
Total
646
4
0.62%
739,319
1,200
0.16%
Ground Water
593
4
0.67%
274,866
1,200
0.44%
Unique
System
Count
Maine (All)
Surface Water
Unknown
53
10
0
3
0.00%
0.00%
464,453
0
0
0
0.00%
0.00%
Total
656
7
1.07%
739,319
1,200
0.16%
Ground Water
30
2
6.67%
384,007
7,000
1.82%
4
Maryland (Phase 1)
Surface Water
36
2
5.56%
4,059,154
40,656
1.00%
Total
66
4
6.06%
4,443,161
47,656
1.07%
Ground Water
6
1
16.67%
3,896
180
4.62%
4
Maryland (Phase 2)
Surface Water
0
0
0.00%
0
0
0.00%
Total
6
1
16.67%
3,896
180
4.62%
Ground Water
63
2
3.17%
41,063
295
0.72%
4
Maryland (Phase 3)
Surface Water
0
0
0.00%
0
0
0.00%
Total
63
2
3.17%
41,063
295
0.72%
Unique
System
Ground Water
99
5
5.05%
428,966
7,475
1.74%
Maryland (All)
Surface Water
36
2
0.00%
4,059,154
40,656
1.00%
Count
Total
135
7
5.19%
4,488,120
48,131
1.07%
Ground Water
1,187
21
1.77%
1,776,646
129,909
7.31%
4
Massachusetts
Surface Water
122
2
1.64%
5,860,701
56,285
0.96%
Total
1,309
23
1.76%
7,637,347
186,194
2.44%
Ground Water
69
7
10.14%
386,252
86,397
22.37%
3
Massachusetts
Surface Water
24
2
8.33%
1,007,330
119,500
11.86%
Total
93
9
9.68%
1,393,582
205,897
14.77%
229
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
Samples
with "X"
number of
analytes
State
Source Water Type
Total #
Systems with
Data for the
HI Calculation
#
Systems
with HI >1
%of
Systems
with HI > 1
Total Pop.
Served by
Systems
with Data for
the HI
Calculation1
Pop. Served
by Systems
with HI >1
%of
Systems
with HI > 1
Ground Water
93
5
5.38%
541,579
73,361
13.55%
2
Massachusetts
Surface Water
31
0
0.00%
3,681,189
0
0.00%
Total
124
5
4.03%
4,222,768
73,361
1.74%
Unique
System
Ground Water
1,204
27
2.24%
1,828,254
216,323
11.83%
Massachusetts
Surface Water
122
4
3.28%
5,860,701
175,785
3.00%
Count
Total
1,326
31
2.34%
7,688,955
392,108
5.10%
Ground Water
2,370
16
0.68%
1,945,734
222,360
11.43%
4
Michigan
Surface Water
Unknown
84
54
0
1
0.00%
1.85%
1,314,601
0
0
0
0.00%
0.00%
Total
2,508
17
0.68%
3,260,335
222,360
6.82%
Ground Water
94
1
1.06%
189,904
1,963
1.03%
4
Missouri
Surface Water
16
0
0.00%
347,928
0
0.00%
Total
110
1
0.91%
537,832
1,963
0.36%
Ground Water
3
0
0.00%
23,470
0
0.00%
3
Missouri
Surface Water
4
0
0.00%
384,959
0
0.00%
Total
7
0
0.00%
408,429
0
0.00%
Unique
System
Ground Water
96
1
1.04%
212,274
1,963
0.92%
Missouri
Surface Water
19
0
0.00%
417,202
0
0.00%
Count
Total
115
1
0.87%
629,476
1,963
0.31%
Ground Water
127
3
2.36%
69,445
4,145
5.97%
4
New Hampshire
Surface Water
11
0
0.00%
237,720
0
0.00%
Total
138
3
2.17%
307,165
4,145
1.35%
Ground Water
121
8
6.61%
122,407
29,486
24.09%
3
New Hampshire
Surface Water
10
0
0.00%
302,520
0
0.00%
Total
131
8
6.11%
424,927
29,486
6.94%
2
New Hampshire
Ground Water
434
10
2.30%
225,885
2,368
1.05%
230
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
Samples
with "X"
number of
analytes
State
Source Water Type
Total #
Systems with
Data for the
HI Calculation
#
Systems
with HI >1
%of
Systems
with HI > 1
Total Pop.
Served by
Systems
with Data for
the HI
Calculation1
Pop. Served
by Systems
with HI >1
%of
Systems
with HI > 1
Surface Water
20
0
0.00%
149,742
0
0.00%
Unknown
1
0
0.00%
10
0
0.00%
Total
455
10
2.20%
375,637
2,368
0.63%
Ground Water
529
17
3.21%
267,029
34,736
13.01%
Unique
System
Count
New Hampshire
Surface Water
Unknown
30
1
0
0
0.00%
0.00%
476,367
10
0
0
0.00%
0.00%
Total
560
17
3.04%
743,406
34,736
4.67%
Ground Water
598
22
3.68%
1,520,663
181,605
11.94%
3
New Jersey2
Surface Water
Unknown
65
1
5
0
7.69%
0.00%
4,783,734
0
216,145
0
4.52%
0.00%
Total
664
27
4.07%
6,304,397
397,750
6.31%
Ground Water
2
0
0.00%
2,520
0
0.00%
2
New Jersey2
Surface Water
1
0
0.00%
335,449
0
0.00%
Total
3
0
0.00%
337,969
0
0.00%
Ground Water
599
22
0.00%
1,520,763
181,605
11.94%
Unique
System
Count
New Jersey2
Surface Water
Unknown
65
1
5
0
7.69%
0.00%
4,783,734
0
216,145
0
4.52%
0.00%
Total
665
27
4.06%
6,304,497
397,750
6.31%
Ground Water
1
0
0.00%
-
-
-
3
New Mexico2
Surface Water
Total
0
1
0
0
0.00%
0.00%
—
—
—
Ground Water
452
5
1.11%
459,067
3,643
0.79%
4
New York
Surface Water
Unknown
91
3
2
0
2.20%
0.00%
1,280,497
1,024
11,200
0
0.87%
0.00%
Total
546
7
1.28%
1,740,588
14,843
0.85%
3
New York
Ground Water
153
13
8.50%
1,195,261
154,077
12.89%
231
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
Samples
with "X"
number of
analytes
State
Source Water Type
Total #
Systems with
Data for the
HI Calculation
#
Systems
with HI >1
%of
Systems
with HI > 1
Total Pop.
Served by
Systems
with Data for
the HI
Calculation1
Pop. Served
by Systems
with HI >1
%of
Systems
with HI > 1
Surface Water
35
0
0.00%
1,818,235
0
0.00%
Total
188
13
6.91%
3,013,496
154,077
5.11%
Ground Water
13
0
0.00%
30,296
0
0.00%
2
New York
Surface Water
4
0
0.00%
5,251
0
0.00%
Total
17
0
0.00%
35,547
0
0.00%
Ground Water
550
16
2.91%
1,451,812
157,170
10.83%
Unique
System
Count
New York
Surface Water
Unknown
120
3
2
0
1.67%
0.00%
2,805,924
1,024
11,200
0
0.40%
0.00%
Total
673
18
2.67%
4,258,760
168,370
3.95%
Ground Water
56
0
0.00%
113,623
0
0.00%
4
North Dakota (2021)
Surface Water
7
0
0.00%
194,121
0
0.00%
Total
63
0
0.00%
307,744
0
0.00%
Ground Water
41
0
0.00%
68,280
0
0.00%
3
North Dakota (2020)
Surface Water
8
0
0.00%
56,016
0
0.00%
Total
49
0
0.00%
124,296
0
0.00%
Ground Water
0
0
0.00%
0
0
0.00%
2
North Dakota (2020)
Surface Water
1
0
0.00%
1,453
0
0.00%
Total
1
0
0.00%
1,453
0
0.00%
Unique
System
Ground Water
41
0
0.00%
68,280
0
0.00%
North Dakota (2020)
Surface Water
9
0
0.00%
57,469
0
0.00%
Count
Total
50
0
0.00%
125,749
0
0.00%
Unique
Ground Water
95
0
0.00%
181,514
0
0.00%
System
North Dakota (All)
Surface Water
16
0
0.00%
251,590
0
0.00%
Count
Total
111
0
0.00%
433,104
0
0.00%
4
Ohio
Ground Water
Surface Water
1,372
107
15
1
1.09%
0.93%
2,883,252
6,215,644
66,341
11,129
2.30%
0.18%
232
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Samples
with "X"
number of
analytes
State
Source Water Type
Total #
Systems with
Data for the
HI Calculation
#
Systems
with HI >1
%of
Systems
with HI > 1
Total Pop.
Served by
Systems
with Data for
the HI
Calculation1
Pop. Served
by Systems
with HI >1
%of
Systems
with HI > 1
Total
1,479
16
1.08%
9,098,896
77,470
0.85%
Ground Water
100
1
1.00%
100,162
289
0.29%
4
Oregon
Surface Water
25
0
0.00%
106,912
0
0.00%
Total
125
1
0.80%
207,074
289
0.14%
Ground Water
16
0
0.00%
14,032
0
0.00%
3
Oregon
Surface Water
2
0
0.00%
18,327
0
0.00%
Total
18
0
0.00%
32,359
0
0.00%
Unique
System
Ground Water
116
1
0.86%
114,194
289
0.25%
Oregon
Surface Water
27
0
0.00%
125,239
0
0.00%
Count
Total
143
1
0.70%
239,433
289
0.12%
Ground Water
71
1
1.41%
162,825
110
0.07%
3
Pennsylvania (2019)
Surface Water
16
1
6.25%
431,370
51,000
11.82%
Total
87
2
2.30%
594,195
51,110
8.60%
Ground Water
269
9
3.35%
471,651
37,553
7.96%
4
Pennsylvania (2021)
Surface Water
73
1
1.37%
4,296,097
4,464
0.10%
Total
342
10
2.92%
4,767,748
42,017
0.88%
Ground Water
270
9
3.33%
471,891
37,553
7.96%
Unique
Pennsylvania
Surface Water
73
2
2.74%
4,296,097
55,464
1.29%
Total
343
11
3.21%
4,767,988
93,017
1.95%
Ground Water
234
2
0.85%
485,992
709
0.15%
4
South Carolina
Surface Water
61
0
0.00%
2,200,008
0
0.00%
Total
295
2
0.68%
2,686,000
709
0.03%
Ground Water
0
0
0.00%
0
0
0.00%
3
South Carolina
Surface Water
3
0
0.00%
46,946
0
0.00%
Total
3
0
0.00%
46,946
0
0.00%
2
South Carolina
Ground Water
0
0
0.00%
0
0
0.00%
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Samples
with "X"
number of
analytes
State
Source Water Type
Total #
Systems with
Data for the
HI Calculation
#
Systems
with HI >1
%of
Systems
with HI > 1
Total Pop.
Served by
Systems
with Data for
the HI
Calculation1
Pop. Served
by Systems
with HI >1
%of
Systems
with HI > 1
Surface Water
1
0
0.00%
242,397
0
0.00%
Total
1
0
0.00%
242,397
0
0.00%
Unique
System
Ground Water
234
2
0.85%
485,992
709
0.15%
South Carolina
Surface Water
65
0
0.00%
2,489,351
0
0.00%
Count
Total
299
2
0.67%
2,975,343
709
0.02%
Ground Water
0
0
0.00%
0
0
0.00%
3
Tennessee2
Surface Water
1
0
0.00%
2,551
0
0.00%
Total
1
0
0.00%
2,551
0
0.00%
Ground Water
526
2
0.38%
211,357
170
0.08%
4
Vermont
Surface Water
38
0
0.00%
174,473
0
0.00%
Total
564
2
0.35%
385,830
170
0.04%
Ground Water
1
0
0.00%
302
0
0.00%
3
Vermont
Surface Water
0
0
0.00%
0
0
0.00%
Total
1
0
0.00%
302
0
0.00%
Ground Water
6
0
0.00%
1,722
0
0.00%
2
Vermont
Surface Water
1
0
0.00%
64
0
0.00%
Total
7
0
0.00%
1,786
0
0.00%
Unique
System
Ground Water
526
2
0.38%
211,357
170
0.08%
Vermont
Surface Water
38
0
0.00%
174,473
0
0.00%
Count
Total
564
2
0.35%
385,830
170
0.04%
Ground Water
5
0
0.00%
2,975
0
0.00%
4
Virginia
Surface Water
19
1
5.26%
4,680,173
155,000
3.31%
Total
24
1
4.17%
4,683,148
155,000
3.31%
Ground Water
211
7
3.32%
1,407,629
56,862
4.04%
4
Wisconsin
Surface Water
20
0
0.00%
1,297,605
0
0.00%
Total
231
7
3.03%
2,705,234
56,862
2.10%
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April 2024
Samples
with "X"
number of
analytes
State
Source Water Type
Total #
Systems with
Data for the
HI Calculation
#
Systems
with HI >1
%of
Systems
with HI > 1
Total Pop.
Served by
Systems
with Data for
the HI
Calculation1
Pop. Served
by Systems
with HI >1
%of
Systems
with HI > 1
Ground Water
7
0
0.00%
10,058
0
0.00%
3
Wisconsin
Surface Water
0
0
0.00%
0
0
0.00%
Total
7
0
0.00%
10,058
0
0.00%
Ground Water
11
0
0.00%
480,084
0
0.00%
2
Wisconsin
Surface Water
7
0
0.00%
361,347
0
0.00%
Total
18
0
0.00%
841,431
0
0.00%
Unique
System
Ground Water
215
7
3.26%
1,488,212
56,862
3.82%
Wisconsin
Surface Water
22
0
0.00%
1,333,737
0
0.00%
Count
Total
237
7
2.95%
2,821,949
56,862
2.01%
1 There were some instances where the population served by a system could not be identified. Thus, there are systems with detections but no associated
population served by those systems with detections.
2 The following states only conducted monitoring for PFHxS, PFNA, and PFBS: Georgia, New Jersey, New Mexico, and Tennessee. These states did not conduct
monitoring for HFPO-DA.
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9 Co-Occurrence Analyses
This chapter presents co-occurrence analysis of PFAS data in the UCMR 3 as well as in non-targeted
supplemental state datasets. The UCMR 3 included monitoring for PFOA, PFOS, PFBS, PFHxS, PFHpA, and
PFNA. The EPA notes that PFHpA is not included as a part of the final regulation and HFPO-DA was not
monitored for under the UCMR 3. The state datasets included monitoring for a broader suite of PFAS
but the analysis presented here is limited to PFAS included in the final regulation: PFOA, PFOS, HFPO-DA,
PFBS, PFHxS, and PFNA. Since reporting thresholds differed both across chemicals (for both the UCMR 3
dataset and the aggregated state datasets) and within chemicals (in the aggregated state datasets)
continuous approaches relying on relationships between chemical concentrations were not used.
Instead, the reported absence or presence of chemicals were used to conduct categorical analyses. Co-
occurrence was assessed both groupwise and pairwise.
9.1 UCMR 3
The UCMR 3 dataset included 36,965 complete sample sets (i.e., sample sets where results were
reported for all six PFAS analytes included in UCMR 3). Co-occurrence for these sample sets was
assessed using groupwise methods as well as counting instances of the occurrence of specific
combinations of PFAS chemicals reported to be present.
9.1.1 Groupwise Co-occurrence
The six UCMR 3 PFAS were separated into two groups. The first group consisted of PFOA and PFOS. The
second group consisted of the remaining UCMR 3 PFAS (PFHpA, PFHxS, PFNA, and PFBS). The second
group is collectively referred to in this section as "Other PFAS." Exhibit 9-1 provides the counts and
percentages of UCMR 3 samples and systems according to whether a) they reported the presence of
PFOS or PFOA and b) they reported the presence of Other PFAS.
Exhibit 9-1: UCMR 3 - Samples and Systems Binned According to Whether PFOS
or PFOA were Reported by States and Whether Additional Other PFAS were
Reported
No PFOS or PFOA
PFOS or PFOA
Reported
Reported
Type
No Other
Other
No Other
Other
Total Count
PFAS
PFAS
PFAS
PFAS
Reported
Reported
Reported
Reported
Samples
36,368
(98.4%)
91
(0.2%)
255
(0.7%)
251
(0.7%)
36,965
Systems
4,722
(96.0%)
36
(0.7%)
80
(1.6%)
82
(1.7%)
4,920
Exhibit 9-2 further examines systems and samples that detected both PFOS and/or PFOA and Other
PFAS according to how many Other PFAS were reported above the MRL.
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Exhibit 9-2: UCMR 3 - Counts of Systems and Samples Where PFOA/PFOS and
Other PFAS Were Reported Above the MRL According to the Number of Other
PFAS Reported Above the UCMR 3 MRL
Additional
PFAS
Reported
Samples
Systems
1
127
44
(50.6%)
(53.7%)
113
32
(45.0%)
(39.0%)
11
6
O
(4.4%)
(7.3%)
Total
251
82
Results of a pairwise PFAS co-occurrence analysis conducted using UCMR 3 data can be found in the
discussion of Guelfo and Adamson (2018) in Section 9.3.
9.1.2 Unique Chemical Combinations
Exhibit 9-3 provides the unique combinations of PFAS that were observed at or above the MRL in the
UCMR 3 dataset. Also presented is the percentage contribution of each unique combination of PFAS to
the total number of sample sets that had any PFAS reported at or above the respective UCMR 3 MRL.
Exhibit 9-3: UCMR 3 - Counts of Unique Combinations of PFAS Chemicals At or
Above the UCMR 3 MRL at the Sample Level
Chemicals Reported Present
Number of
Occurrences
Percentage Among
All Samples with a
PFAS Reported At or
Above MRL
PFOA
149
25.0%
PFOS/PFOA/PFHxS/PFHpA
76
12.7%
PFOS
75
12.6%
PFHpA
48
8.0%
PFOA/PFHpA
41
6.9%
PFOS/PFHxS
33
5.5%
PFOS/PFOA
31
5.2%
PFHxS
27
4.5%
PFOS/PFOA/PFHxS
19
3.2%
PFOS/PFOA/PFHpA
18
3.0%
P FOS/P F HxS/P F H p A
17
2.8%
PFOA/PFHxS
11
1.8%
PFNA
11
1.8%
P F O A/P F HxS/P F H p A
10
1.7%
PFOS/PFOA/PFHxS/PFHpA/PFBS
7
1.2%
PFOS/PFOA/PFHpA/PFBS
7
1.2%
PFOS/PFOA/PFNA/PFHxS/PFHpA
4
0.7%
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April 2024
Chemicals Reported Present
Number of
Occurrences
Percentage Among
All Samples with a
PFAS Reported At or
Above MRL
PFOS/PFHpA
3
0.5%
PFBS
3
0.5%
PFOA/PFNA/PFHpA
2
0.3%
PFOA/PFBS
2
0.3%
PFOS/PFOA/PFNA/PFHxS
1
0.2%
PFHxS/PFHpA
1
0.2%
PFNA/PFHpA
1
0.2%
9.2 State Datasets
The aggregated state monitoring dataset used to conduct these analyses includes data from Colorado,
Illinois, Indiana, Kentucky, Maine, Maryland, Massachusetts, Michigan, Missouri, New Hampshire, New
Jersey, New York, North Dakota, Ohio, South Carolina, Tennessee, Vermont, and Wisconsin and consists
of 54,198 sample sets. System-level data were also included for Minnesota. As noted previously, states
utilized various reporting thresholds both across and within chemicals. Co-occurrence was assessed with
groupwise and pairwise methods.
9.2.1 Groupwise Co-occurrence
The six chemicals the EPA is finalizing regulation of individually and/or as part of the HI were separated
into two groups. The first group consisted of PFOA and PFOS. The second group consisted of HFPO-DA,
PFBS, PFHxS, and PFNA (collectively referred to in this section as "HI PFAS"). Different state data
collection efforts included different numbers of HI PFAS. Exhibit 9-4 below shows the number of systems
and samples according to the number of HI PFAS that were sampled at the sample and system levels.
Exhibit 9-4: Counts of Systems and Samples According to the Number of HI PFAS
Analyzed
Number of
HI PFAS
Analyzed
Samples
Systems
0
4,826
1,202
1
9,231
466
2
1,609
934
3
9,739
1,554
4
28,793
9,198
Total
54,198
13,354
Among these, 48,889 samples and 12,145 systems included analysis for at least one HI PFAS as well as
sufficient analysis to examine whether PFOS or PFOA were present. Exhibit 9-5 provides the counts and
percentages of these samples and systems according to whether: a) they reported the presence of PFOS
or PFOA, and b) they reported the presence of HI chemicals.
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Exhibit 9-5: Non-Targeted State PFAS Finished Water Data - Samples and
Systems Binned According to Whether PFOS or PFOA were Reported by States
and Whether Additional HI PFAS were Reported
Type
No PFOS or PFOA
Reported
PFOS or PFOA
Reported
Total Count
No Other
PFAS
Reported
HI PFAS
Reported
No HI PFAS
Reported
HI PFAS
Reported
Samples
28,249
(57.8%)
1,321
(2.7%)
7,365
(15.1%)
11,954
(24.5%)
48,889
Systems
8,576
(70.6%)
401
(3.3%)
1,079
(8.9%)
2,089
(17.2%)
12,145
The number of HI that were analyzed for may impact whether any HI PFAS were reported as present as
well as how many HI PFAS were reported present. Exhibit 9-6 through Exhibit 9-9 present the HI PFAS
reported according to how many HI PFAS were analyzed for and whether PFOS or PFOA were detected
at the system and sample level.
Exhibit 9-6: Sample counts according to HI PFAS analyzed and reported present
for samples where PFOS and PFOA were not reported present by the state
HI PFAS
Analyzed
HI PFAS Reported Present
0
1
2
3
4
Total
1
4,629
(99.8%)
8
(0.2%)
-
-
-
4,637
2
640
(97.3%)
12
(1.8%)
6
(0.9%)
-
-
658
3
4,435
(97.2%)
116
(2.5%)
13
(0.3%)
0
(0.0%)
-
4,564
4
18,545
(94.1%)
939
(4.8%)
226
(1.1%)
1
(0.0%)
0
(0.0%)
19,711
Total
28,249
1,075
245
1
0
Exhibit 9-7: System counts according to HI PFAS analyzed and reported present
for systems where PFOS and PFOA were not reported present by the state
HI PFAS
Analyzed
HI PFAS Reported Present
0
1
2
3
4
Total
1
235
(99.2%)
2
(0.8%)
-
-
-
237
2
626
(96.6%)
17
(2.6%)
5
(0.8%)
-
-
648
3
-799
(97.3%)
21
(2.6%)
1
(0.1%)
0
(0.0%)
-
821
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April 2024
HI PFAS
Analyzed
HI PFAS Reported Present
0
1
2
3
4
Total
4
6,916
(95.1%)
285
(3.9%)
69
(0.9%)
1
(0.0%)
0
(0.0%)
7,271
Total
8,576
325
75
1
0
Exhibit 9-8: Sample counts according to HI PFAS analyzed and reported present
for samples where PFOS and PFOA were reported present by the state
HI PFAS
Analyzed
HI PFAS Reported Present
0
1
2
3
4
Total
1
3,383
(81.2%)
785
(18.8%)
-
-
-
4,168
2
483
(53.0%)
294
(32.3%)
134
(14.7%)
-
-
911
3
1,829
(35.4%)
1,670
(32.4%)
1,424
(27.6%)
239
(4.6%)
-
5,162
4
1,670
(18.4%)
1,750
(19.3%)
3,947
(43.5%)
1,680
(18.5%)
31
(0.3%)
9,078
Total
7,365
4,499
5,505
1,919
31
Exhibit 9-9: System counts according to HI PFAS analyzed and reported present
for systems where PFOS and PFOA were reported present by the state
HI PFAS
Analyzed
HI PFAS Reported Present
0
1
2
3
4
Total
1
148
(65.5%)
78
(34.5%)
-
-
-
226
2
138
(48.6%)
85
(29.9%)
61
(21.5%)
-
-
284
3
282
(38.5%)
183
(25.0%)
183
(25.0%)
84
(11.5%)
-
732
4
511
(26.5%)
449
(23.3%)
668
(34.7%)
278
(14.4%)
20
(1.0%)
1,926
Total
1,079
795
912
362
20
Exhibit 9-10 and Exhibit 9-11 provide categorical results similar to Exhibit 9-5; however these results are
broken down by state and restricted to systems and samples that included data for at least three of the
HI PFAS.
Exhibit 9-10: Non-Targeted State PFAS Finished Water Data - Samples that
Included Three or Four HI PFAS Binned According to Whether PFOS or PFOA
were Reported and Whether Any Additional HI PFAS were Reported by State
State
No PFOS or PFOA
PFOS or PFOA
Total Sample
Reported
Reported
Count
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No HI PFAS
HI PFAS
No HI PFAS
HI PFAS
detected
detected
detected
detected
CO
422
30
14
117
583
(72.4%)
(5.1%)
(2.4%)
(20.1%)
IL
1,531
199
112
283
2,125
(72.0%)
(9.4%)
(5.3%)
(13.3%)
IN
435
22
7
7
471
(92.4%)
(4.7%)
(1.5%)
(1.5%)
KY
40
4
20
17
81
(49.4%)
(4.9%)
(24.7%)
(21.0%)
MA
2,041
158
716
5,740
8,655
(23.6%)
(1.8%)
(8.3%)
(66.3%)
MD
66
0
3
19
88
(75.0%)
(0.0%)
(3.4%)
(21.6%)
ME
517
14
89
82
702
(73.6%)
(2.0%)
(12.7%)
(11.7%)
Ml
9,422
516
287
458
10,683
(88.2%)
(4.8%)
(2.7%)
(4.3%)
MO
191
2
10
11
214
(89.3%)
(0.9%)
(4.7%)
(5.1%)
ND
102
9
0
3
114
(89.5%)
(7.9%)
(0.0%)
(2.6%)
NH
148
18
225
174
565
(26.2%)
(3.2%)
(39.8%)
(30.8%)
NJ
2,940
57
1,450
2,669
7,116
(41.3%)
(0.8%)
(20.4%)
(37.5%)
NY
1,109
64
283
666
2,122
(52.3%)
(3.0%)
(13.3%)
(31.4%)
OH
1,658
97
99
91
1,945
(85.2%)
(5.0%)
(5.1%)
(4.7%)
SC
574
23
51
112
760
(75.5%)
(3.0%)
(6.7%)
(14.7%)
TN
2
0
0
0
(100.0%)
(0.0%)
(0.0%)
(0.0%)
z
VT
1,274
26
105
153
1,558
(81.8%)
(1.7%)
(6.7%)
(9.8%)
Wl
508
56
28
139
731
(69.5%)
(7.7%)
(3.8%)
(19.0%)
Exhibit 9-11: Non-Targeted State PFAS Finished Water Data - Systems that
Sampled for Three or Four HI PFAS Binned According to Whether PFOS or PFOA
were Reported and Whether Any Additional HI PFAS were Reported by State
No PFOS or PFOA
PFOS or PFOA
State
Reported
Reported
Total Sample
No HI PFAS
HI PFAS
No HI PFAS
HI PFAS
Count
detected
detected
detected
detected
CO
270
26
11
90
397
(68.0%)
(6.5%)
(2.8%)
(22.7%)
IL
880
28
25
63
996
(88.4%)
(2.8%)
(2.5%)
(6.3%)
IN
339
19
6
7
371
(91.4%)
(5.1%)
(1.6%)
(1.9%)
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KY
38
3
17
16
74
(51.4%)
(4.1%)
(23.0%)
(21.6%)
MA
479
33
146
655
1,313
(36.5%)
(2.5%)
(11.1%)
(49.9%)
MD
51
0
3
9
63
(81.0%)
(0.0%)
(4.8%)
(14.3%)
ME
469
12
84
76
641
(73.2%)
(1.9%)
(13.1%)
(11.9%)
Ml
2,205
130
66
107
2,508
(87.9%)
(5.2%)
(2.6%)
(4.3%)
MO
102
2
4
5
113
(90.3%)
(1.8%)
(3.5%)
(4.4%)
ND
99
9
0
3
111
(89.2%)
(8.1%)
(0.0%)
(2.7%)
NH
64
13
68
92
237
(27.0%)
(5.5%)
(28.7%)
(38.8%)
NJ
227
7
142
289
665
(34.1%)
(1.1%)
(21.4%)
(43.5%)
NY
275
15
132
264
686
(40.1%)
(2.2%)
(19.2%)
(38.5%)
OH
1,397
31
25
26
1,479
(94.5%)
(2.1%)
(1.7%)
(1.8%)
SC
187
11
28
72
298
(62.8%)
(3.7%)
(9.4%)
(24.2%)
TN
1
0
0
0
1
(100.0%)
(0.0%)
(0.0%)
(0.0%)
VT
492
14
26
32
564
(87.2%)
(2.5%)
(4.6%)
(5.7%)
Wl
140
24
10
59
233
(60.1%)
(10.3%)
(4.3%)
(25.3%)
9.2.2 Pairwise Co-occurrence
To examine pairwise relationships among PFAS, odds ratios were calculated. In this analysis, odds ratios
represent the change in the odds of observing a first chemical given that a second chemical is known to
be present relative to the odds of observing the first chemical given that the second chemical is not
present. For example, an odds ratio of 2 would indicate that the presence of the second chemical would
be expected to double the odds of the first chemical being reported present. Odds ratios were
calculated as follows.
„ „ nAB * n\A\B
Where n indicates the number of samples that fell into a given bin. Subscript AB indicates both
chemicals were detected while A!B, for example, indicates that chemical A was detected but chemical B
was not. Since this equation is symmetrical, chemical A and chemical B are interchangeable (as long as it
is the same pair of chemicals, it does not matter which is A and which is B). Exhibit 9-12 and Exhibit 9-13
below present the calculated odds ratios for each unique pair of PFAS chemicals among the six included
in the final rule, as well as the lower and upper limits for the approximate 95% confidence intervals (CI)
for the odds ratios determined based on the score statistic.
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Exhibit 9-12: Sample-level counts of pairwise chemical occurrence and odds
ratios calculated from aggregated state dataset PFAS samples for PFOS, PFOA,
and HI PFAS
Chem A
Chem B
Chems A
and B
Reported
Only
Chem B
Reported
Only
Chem A
Reported
Neither
Chem
Reported
Odds Ratio
[95% CI]
HFPO-DA
PFBS
54
7,708
26
21,055
5.7
[3.6-9.01
HFPO-DA
PFHxS
41
6,458
39
22,280
3.6
[2.3-5.61
HFPO-DA
PFNA
31
1,885
49
26,869
9.0
f5.8-14.1l
HFPO-DA
PFOA
61
8,319
20
20,428
7.5
[4.5-12.41
HFPO-DA
PFOS
61
7,678
20
21,070
8.4
[5.1-13.81
PFBS
PFHxS
7,330
1,555
2,989
26,693
42.1
[38.3-46.31
PFBS
PFNA
2,059
354
8,206
27,897
19.8
[17.6-22.21
PFBS
PFOA
9,105
4,280
1,228
23,967
41.5
[37.7-45.71
PFBS
PFOS
8,488
3,262
1,842
24,986
35.3
[32.1-38.81
PFHxS
PFNA
2,192
308
7,003
30,503
31.0
[27.4-35.01
PFHxS
PFOA
8,413
5,780
853
25,026
42.7
[38.8-47.01
PFHxS
PFOS
8,226
4,074
1,036
26,733
52.1
[47.4-57.31
PFNA
PFOA
3,190
14,983
74
30,542
87.9
[69.7-110.71
PFNA
PFOS
3,086
12,380
182
33,136
45.4
[39.0-52.81
PFOA
PFOS
15,024
1,203
3,974
33,324
104.7
[95.2-115.21
Exhibit 9-13: System-level counts of pairwise chemical occurrence and odds
ratios calculated from aggregated state dataset PFAS samples for PFOS, PFOA,
and HI PFAS
Chem A
Chem B
Chems A
and B
Reported
Only
Chem B
Reported
Only
Chem A
Reported
Neither
Chem
Reported
Odds Ratio
[95% CI]
HFPO-DA
PFBS
33
1,532
21
7,614
7.8
[4.5-13.51
HFPO-DA
PFHxS
23
1,137
31
8,007
5.2
[3.1-8.91
HFPO-DA
PFNA
20
327
34
8,818
15.9
[9.1-27.71
HFPO-DA
PFOA
39
1,665
16
7,480
11.0
[6.2-19.51
HFPO-DA
PFOS
37
1,530
18
7,613
10.2
[5.9-17.91
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Chem A
Chem B
Chems A
and B
Reported
Only
Chem B
Reported
Only
Chem A
Reported
Neither
Chem
Reported
Odds Ratio
[95% CI]
PFBS
PFHxS
1,282
245
721
9,093
66.0
[56.4-77.21
PFBS
PFNA
423
85
1,510
8,735
28.8
[22.7-36.61
PFBS
PFOA
1,605
852
401
8,485
39.9
[35.0-45.41
PFBS
PFOS
1,497
692
509
8,645
36.7
[32.4-41.71
PFHxS
PFNA
415
108
1,115
9,455
32.6
[26.1-40.71
PFHxS
PFOA
1,374
1,259
230
8,820
41.9
[35.9-48.71
PFHxS
PFOS
1,369
939
235
9,140
56.7
[48.6-66.21
PFNA
PFOA
575
2,190
23
8,764
100.1
[65.9-151.81
PFNA
PFOS
555
1,864
43
9,089
62.9
[46.0-86.11
PFOA
PFOS
2,304
341
729
9,972
92.4
[80.6-106.01
Estimates of correlation between system-level means across chemicals modeled in the national
occurrence model can be found in Section 10.1.
9.3 Additional UCMR 3 Analyses from Published Studies
Adamson et al. (2017) and Guelfo and Adamson (2018) conducted independent analyses of UCMR 3
data for six PFASs (PFOA and PFOS, PFHpA, PFNA, PFBS, and PFHxS) and other contaminants. Some care
should be taken when comparing their UCMR 3 occurrence findings with results presented elsewhere in
this document. Note, for example, that these researchers appeared to have been working with a "near-
final" data set of 36,139 samples (Guelfo and Adamson, 2018), whereas the final UCMR 3 data set
included 36,972 samples for most PFAS.
Guelfo and Adamson (2018) examined PFAS results from UCMR 3 in detail, addressing co-occurrence
among the six PFAS compounds, relationships to sources, and temporal trends over the UCMR 3
sampling period. They found that approximately 50 percent of samples with reportable levels of one or
more PFAS detections contained at least two PFAS and 72 percent of detections occurred in ground
water. Large PWSs (>10,000 customers) were 5.6 times more likely than small PWSs (<10,000
customers) to exhibit PFAS detections; however, when detected, median total PFAS concentrations
were higher in small PWSs (0.12 ng/L) than in large (0.053 ng/L). The authors performed pairwise co-
occurrence analyses using both a categorical (chi square) analysis based on sample detections and a
calculation of odds ratios for co-occurring pairs also based on sample detections. All of the pairwise
categorical results showed statistically significant co-occurrence, with the exception of PFBS and PFNA
for which there was no observed co-occurrence. The odds ratio results, presented in Exhibit 9-14, also
showed a strong likelihood of co-occurrence between all PFAS pairs other than PFNA and PFBS. (Odds
ratios > 1 suggest co-occurrence greater than that expected by chance; odds ratios of 0 to <1 indicate
co-occurrence less than that expected by chance. While the magnitude of the values shown in Exhibit
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9-14 suggest the odds ratios are likely to be statistically significant given the sample size, the authors did
not specifically present p value results for these odds ratios.)
Exhibit 9-14: Co-Occurrence Matrix (Odds Ratios for Association Between PFAS
Pairs)
PFOS
PFOA
PFHxS
PFHpA
PFBS
PFNA
PFOS
-
216
876
295
371
46
PFOA
216
-
242
407
538
57
PFHxS
876
242
-
389
107
65
PFHpA
295
407
389
-
463
94
PFBS
371
538
107
463
-
0
PFNA
46
57
65
94
0
-
Guelfo and Adamson (2018) also conducted a cluster analysis for assessing co-occurrence relationships
between PFAS based on both detection and concentration. The authors identified two notable clusters
among co-occurring PFAS, one involving PFOA and PFHpA and the other involving PFOS and PFHxS. The
authors also noted that the lack of co-occurrence between PFNA and PFBS could have been an artifact
of low individual detection rates but also could be attributed to factors related to use and
environmental transport for these two compounds.
With respect to sources, the authors observed that perfluoroalkyl sulfonates, PFSAs (i.e., PFOS, PFHxS,
PFBS) tended to dominate over perfluoroalkyl carboxylates, or PFCAs (i.e., PFOA, PFHpA, PFNA) in
ground water, while PFCAs tended to dominate over PFSAs in surface water. PFSAs tend to be
associated with uses such as fire-fighting foam, mist suppressants, and surface protection products,
while PFCA releases tend to be associated with fluoropolymer manufacturing, landfills, and water
treatment plant effluent.
Guelfo and Adamson (2018) evaluated temporal trends using two different methodologies: linear
regression and a Mann-Kendall test. In an examination of quarterly detection rates for all six PFAS
together, both analyses showed an increasing trend over twelve quarters; however, only the Mann-
Kendall results were statistically significant (p = 0.03). Further analysis (apparently using the Mann-
Kendall test alone) showed increasing trends as well for PFOA alone (statistically significant; p = 0.01)
and PFOS alone (not statistically significant; p = 0.1).
In an earlier related study, Adamson et al. (2017) calculated odds ratios to examine co-occurrence
between 1,4-dioxane and other UCMR 3 contaminants, including PFOS and PFOA. Statistically significant
(at a 95 percent confidence level) co-occurrence was observed with both PFOS and PFOA. Based on
calculated odds ratios, samples with a 1,4-dioxane detection were 14.2 times more likely to occur with a
PFOS detection than without a PFOS detection when adjusted for system size. Similarly, samples with a
1,4-dioxane detection were 13.4 times more likely to occur with a PFOA detection than without a PFOA
detection when adjusted for system size.
Hu et al. (2016) presented a spatial analysis of PFAS concentrations under UCMR 3 and found that the
number of industrial sites that manufacture or use these compounds, the number of military fire
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training areas, and the number of wastewater treatment plants are all significant predictors of PFAS
detection frequencies and concentrations in public water supplies. The authors found that for PFAS
monitored under UCMR 3, the detection frequency in drinking water sourced from ground water was
more than twice that from surface water. Additionally, PFOA and PFOS were more frequently detected
in ground water whereas UCMR 3 PFAS compounds with shorter chain lengths were detected more
frequently in surface waters. Hu et al. (2016) noted that this observation could be due to the original
mode of environmental release (aerosol, application to soil, and aqueous discharge).
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10 Model Estimates and Extrapolation
10.1 Model Data and Correlation Output
A Bayesian hierarchical model was developed to estimate national occurrence of four PFAS that were
included in the UCMR 3 monitoring effort. These PFAS were PFOA, PFOS, PFHxS, and PFHpA. While PFNA
and PFBS were also monitored for in UCMR 3, each chemical was limited to 19 results (among nearly
37,000 samples per chemical) that were reported as concentrations over the MRL. The limited number
of reported concentrations for these two chemicals was insufficient for these chemicals to be included
in the Bayesian model. The EPA also notes that while PFHpA was included in the model because of its
UCMR 3 data availability; however, the EPA is not including it in this final regulation. A total of 65,537
samples from 28 state datasets were included to supplement the UCMR 3 dataset. State datasets were
generally collected more recently than the UCMR 3 dataset with improved analytical methods capable
of measuring PFOA, PFOS, PFHxS, and/or PFHpA at concentrations lower than the UCMR 3 MRLs. These
data provided valuable information regarding the occurrence of PFAS at sub-UCMR 3 MRL
concentrations to the model. From the state datasets, only samples that were collected at systems that
monitored as part of UCMR 3 were incorporated in the model fitting. This decision was made because
the UCMR sampling program selects a set of systems to monitor that is statistically representative of
PWS in the United States as a whole (i.e., a nationally representative set of PWS). The inclusion of non-
UCMR 3 systems would have biased model results towards states which had subsequent state datasets
available. Additional information on the model design, including detailed discussion of the model's
methods, can be found in Cadwallader et al. (2022) which is included in the docket for this final
regulation and incorporated by reference into this document.
The fitted model was examined to assess the correlation of system-level means across the four
chemicals. The median estimates for the Pearson correlation coefficients (which indicate the strength of
a linear relationship) between untransformed system-level means are shown in Exhibit 10-1.
Exhibit 10-1: National Occurrence Model Estimate - Median Estimated Pearson
Correlation Coefficient and 90% Credible Interval Among System-level Means
Chemical Pair
Pearson Correlation
Coefficient
[90% CI]
PFOS-PFOA
0.73
[0.63-0.801
PFOS-PFHpA
0.67
T0.56-0.75l
PFOS-PFHxS
0.82
[0.72-0.89]
PFOA-PFHpA
0.83
[0.79-0.871
PFOA-PFHxS
0.51
[0.39-0.601
PFHpA-PFHxS
0.58
[0.44-0.67]
The fitted model produced high-level distributions of system-level means as well as within and between-
system standard deviations for each chemical included. These high-level distributions were sampled to
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perform extrapolation to a national inventory of active CWSs and NTNCWSs. This inventory was
extracted from SDWIS and included 66,782 systems.
10.2 Extrapolation of System-level Means
Exhibit 10-2 shows the median estimate of the number of systems anticipated to have system-level
means above various thresholds for the four modeled PFAS contaminants. Exhibit 10-3 shows the
median estimate of the total population served by systems that were estimated to have system-level
means over the respective thresholds.
Exhibit 10-2: National Occurrence Model Estimate - Estimated Number of Systems
With System-level Means At or Above Various Concentrations
Concentration
(PPt)
PFHpA
[90% CI]
PFHxS
[90% CI]
PFOA
[90% CI]
PFOS
[90% CI]
4.0
466
[299-735]
1,828
[1,226-2,6891
3,260
[2,416-4,3491
3,368
[2,461-4,5661
5.0
264
[166-4291
1,252
[823-1,8881
2,194
[1,588-2,9941
2,447
[1,757-3,3861
10.0
41
[24-691
340
[209-5551
523
[354-7711
793
[537-1,1661
Exhibit 10-3: National Occurrence Model Estimate - Estimated Total Population
Served By Systems With System-level Means At or Above Various
Concentrations
Concentrations
PFHpA
PFHxS
PFOA
PFOS
(PPt)
[90% Cll
[90% Cll
[90% Cll
[90% Cll
8,660,000
20,386,000
34,343,000
34,313,000
4.0
[7,111,000-
[17,436,000-
[30,897,000-
[30,703,000-
10,209,0001
24,351,0001
40,600,0001
41,110,0001
6,082,000
15,436,000
24,287,000
26,594,000
5.0
[3,614,000-
[12,524,000-
[21,551,000-
[23,793,000-
7,002,0001
18,458,0001
28,222,0001
31,240,0001
713,000
4,645,000
7,132,000
10,205,000
10.0
[507,000-
[3,557,000-
[4,871,000-
[7,552,000-
2,933,0001
7,205,0001
8,987,0001
12,232,0001
10.3 National Estimate of Systems Exceeding Individual MCLs or HI MCL
The model output for PFOS, PFOA, and PFHxS was combined with characteristics observed in the state
datasets for the three remaining HI PFAS to generate estimates of the national counts of systems (CWS
and NTNCWS) anticipated to exceed either the MCL for PFOS, the MCL for PFOA, or the HI MCL for
HFPO-DA, PFBS, PFHxS and PFNA.
10.3.1 Handling of Model Output
The extrapolation results in Section 10.2 are shown at the system mean level. In order to account for
within-system variability, each entry point concentration was simulated using the system-level mean
and within-system standard deviation of the log transformed, normal distribution (i.e., with the
assumption of lognormality). Here all within-system variability was assumed to be attributable to
differences across entry points (rather than temporal variations within entry points) (USEPA, 2023c).
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Thus, for each system included in the extrapolation, a concentration was simulated for each entry point.
The maximum entry point concentration of PFOA or PFOS was selected to examine whether the system
would exceed a final MCL. The maximum value of PFHxS was also selected for each system for
subsequent combination with PFNA, PFBS, and HFPO-DA data. Finally, the highest sum value of the four
modeled PFAS (PFOA, PFOS, PFHxS, and PFHpA) was retained for probabilistic weighting of which
systems to assign additional PFAS concentrations to (described in Section 10.3.2).
10.3.2 Combination of State Data with Modeled Estimates
The aggregated non-targeted state monitoring dataset was used to extract information regarding the
occurrence of HFPO-DA, PFBS, and PFNA. This information included the fraction of systems with data for
the individual chemicals that reported any measurement of the chemical at or above its respective
UCMR 5 MRL. The MRLs for HFPO-DA, PFBS, and PFNA in UCMR 5 are equivalent to 5.0 ppt, 3.0 ppt, and
4.0 ppt, respectively (USEPA, 2021e). For each of these systems, the system-level maximum
concentration observed of the chemical of interest was selected, providing a list (an empirical
cumulative distribution function or eCDF) of system-level maximums for PFNA, PFBS, and HFPO-DA.
These eCDFs were used to superimpose PFNA, PFBS, and HFPO-DA concentrations onto the model
output for each iteration.
Given potential uncertainty of extrapolating the aggregated state datasets to the nation, multiple
methods were examined. Common elements across these methods included randomly sampling each
chemical's eCDF for concentrations to apply to a fraction of national systems equivalent to the fraction
of systems that observed the presence of the chemical in the aggregated state dataset. In most cases,
this fraction of systems was selected from systems that were not already exceeding the MCLs for PFOS
or PFOA.
Systems were selected using the following methods:
• Among systems not already exceeding an MCL for PFOS or PFOA, add chemical
concentration to the remaining systems with the highest maximum sum of modeled
PFAS (PFOA, PFOS, PFHxS, PFHpA)
• Among systems not already exceeding an MCL for PFOS or PFOA, select systems
randomly but with probability of selection proportionate to the system's maximum sum
of modeled PFAS
• Among systems not already exceeding an MCL for PFOS or PFOA that had sum of
modeled PFAS at or above 2.0 ppt, select systems randomly but with probability of
selection proportionate to the system's maximum sum of modeled PFAS
• Select systems randomly with a probability proportionate to the system's maximum
sum of modeled PFAS (including systems already exceeding an MCL for PFOA or PFOS)
• Select equal percentages of systems among systems that a) are already exceeding an
MCL for PFOA or PFOS and b) are not exceeding an MCL for PFOA or PFOS. Within a
group, probability of being selected is proportionate to the system's maximum sum of
modeled PFAS
Systems were selected separately for each chemical and were assigned a concentration that was
randomly sampled from that chemical's eCDF. This concentration was added to the modeled
concentration for PFHxS at the selected system. After this was completed for PFBS, PFNA, and HFPO-DA,
a simulated value of the system's maximum HI could be produced. The output from this analysis was
used to anticipate how many systems would either exceed an MCL for PFOA, an MCL for PFOS, or the HI
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MCLfor PFHxS, PFBS, PFNA, and HFPO-DA. This approach requires the assumption that a system's
maximum concentration for each chemical would occur at the same location. This assumption was
deemed reasonable given the extensive co-occurrence among PFAS observed in state data and the
UCMR 3 dataset and that systems selected using a probability weight and were not necessarily the same
across the 3 additional HI chemicals.
Because the approach used to generate national estimates of systems exceeding the HI MCL included
multiple methods for comparison, strict quantiles and central estimates are not provided. Instead, the
"Low" estimate indicates the results of the lowest 5th percentile estimate across methods, rounded
down, while the "High" estimate indicates the highest 95th percentile estimate across methods, rounded
up. Since PFOA and PFOS were included in the model, output related to systems exceeding PFOA or
PFOS MCLs did not vary by method. Exhibit 10-4 provides estimates for the number of systems
anticipated to be in exceedance of the PFOS or PFOA MCLs of 4.0 ppt, as well as the total population
served by these systems. Exhibit 7-5 provides estimates for the number of systems estimated to exceed
the HI MCL, as well as the total population served. The systems counts and population totals provided in
Exhibit 10-4 and Exhibit 10-5 are not mutually exclusive and thus cannot be added to estimate total
systems exceeding either the HI MCL or the MCLs for PFOS or PFOA. Instead, Exhibit 10-6 presents the
number of systems estimated to be exceeding either the HI MCL, the MCL for PFOA, or the MCL for
PFOS. Among systems not exceeding the MCLs for PFOA or PFOS, approximately 100-300 are anticipated
to exceed the HI MCL.
Exhibit 10-4: National Occurrence Estimate - Estimated Systems and Total
Population Served By Systems in Exceedance of the MCL for PFOS or PFOA
Estimate
Low
High
Systems Exceeding
MCLs for PFOS or PFOA
4,000
6,500
Population Served by
Systems Exceeding
MCLs for PFOS or PFOA
82,000,000
103,000,000
Exhibit 10-5: National Occurrence Estimate - Estimated Systems and Total
Population Served By Systems in Exceedance of the HI MCL
Estimate
Low
High
Systems Exceeding the HI MCL
300
700
Population Served by Systems
Exceeding the HI MCL
9,000,000
18,000,000
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Exhibit 10-6: National Occurrence Estimate - Estimated Systems and Total
Population Served By Systems in Exceedance of an MCL for PFOS or PFOA or
the HI MCL
Estimate
Low
High
Systems Exceeding MCLs
4,100
6,700
Population Served by
Systems Exceeding MCLs
83,000,000
105,000,000
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11 UCMR 5 Results
This chapter presents the preliminary sampling results from the fifth Unregulated Contaminant
Monitoring Rule (UCMR 5) as of February 2024 (USEPA, 2024c). The UCMR 5 data collection effort will
run from January 2023 through December 2025, with the final dataset anticipated to be available in
2026. The results described here account for approximately 24 percent of the results anticipated to be
available in the final dataset. Since the UCMR 5 dataset is currently incomplete, it does not serve as the
basis for informing the agency's decisions for the regulatory determinations and NPDWRs. While 29
PFAS chemicals are being monitored under UCMR 5, only results for the six PFAS included in the final
NPDWRs are shown. Most summaries are presented at the sample, entry point, and system levels.
Exhibit 11-1 shows the sample counts, entry point counts, system counts, and the percentages of
samples, entry points, and systems that had concentrations at or above the minimum reporting levels
for UCMR 5.
Exhibit 11-1: Preliminary UCMR 5 Dataset1 - Summary of Sample, Entry Point, and
System Counts as of February 2024
Chemical
Samples
Collected
Sample
Results At
or Above
Minimum
Reporting
Level
Entry Points
With Results
Entry Points
With Results
At or Above
Minimum
Reporting
Level
Systems
with Results
Systems
With Results
At or Above
Minimum
Reporting
Level
PFOA
16,772
1,076
(6.4%)
9,536
744
(7.8%)
3,720
429
(11.5%)
PFOS
16,768
1,149
(6.9%)
9,535
796
(8.3%)
3,720
477
(12.8%)
PFHxS
16,768
933
(5.6%)
9,534
670
(7.0%)
3,721
374
(10.1%)
PFNA
16,778
48
(0.3%)
9,539
35
(0.4%)
3,722
26
(0.7%)
PFBS
16,766
1,443
(8.6%)
9,534
981
(10.3%)
3,720
570
(15.3%)
HFPO-DA
16,777
24
(0.1%)
9,538
17
(0.2%)
3,722
17
(0.5%)
Notes:
1 The preliminary UCMR 5 dataset contains approximately 24 percent of the samples anticipated to be available once the dataset is
complete.
These data combined for a total of 100,629 analytical results from 9,539 entry points at 3,722 PWS.
These included 16,743 completed sample sets where an analytical result was available for each of the six
PFAS and 9,528 entry points and 3,719 PWS that provided at least one analytical result for each of the
six PFAS and had at least one sample set for which the HI could be calculated. Among these 16,743
sample sets, 9,528 entry points, and 3,719 PWS, Exhibit 11-2 shows the count of individual samples that
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exceeded numerical thresholds for the PFOA, PFOS, PFHxS, PFNA, HFPO-DA, and/or HI MCLs as well as
the count of entry points and systems with such samples. Note that MCL violations under the final rule
are based on running annual average MCL exceedance rather than a single sample MCL exceedance (see
section XIII of the final rule preamble for monitoring and compliance requirements).
Exhibit 11-2: Preliminary UCMR5 Dataset1 - Summary of Single Samples, Entry
Points with Single Samples, and Systems with Single Samples Exceeding MCL
Thresholds
MCL
Threshold2
Samples
Exceeding
Entry Points
With At Least
One Sample
Exceeding
Systems With
At Least One
Sample
Exceeding
PFOA
(4.0 ng/L)
1,024
(6.1%)
719
(7.5%)
415
(11.2%)
PFOS
(4.0 ng/L)
1,100
(6.6%)
766
(8.0%)
462
(12.4%)
PFHxS
(10 ng/L)
66
(0.4%)
53
(0.6%)
42
(1.1%)
PFNA
(10 ng/L)
5
(<0.1 %)
5
(<0.1)
5
(0.1%)
HFPO-DA
(10 ng/L)
2
(<0.1 %)
1
(<0.1 %)
1
(<0.1 %)
HI (1)
76
(0.5%)
60
(0.6%)
48
(1.3%)
Any
1,504
(9.0%)
1,043
(10.9%)
589
(15.8%)
Notes:
1 The preliminary UCMR 5 dataset contains approximately 24 percent of the samples anticipated to be available once the dataset is
complete.
2 MCL thresholds for PFOA and PFOS were assessed to two significant figures while MCL thresholds for PFHxS, PFNA, HFPO-DA,
and the HI were assessed with one significant figure. Analytical results had to be equal to or exceed the following values to be
treated as exceeding an MCL: 4.05 for PFOA and PFOS; 15 for PFHxS, PFNA, and HFPO-DA; 1.5 forthe HI. See Section V ofthe
final rule preamble for more information.
Entry points with means and systems with entry point-level mean concentrations exceeding MCL
thresholds were also assessed. For this analysis, only sample sets with analytical results for all six PFAS
were included when calculating entry point-level means. Further, only entry points at which multiple
complete sample sets were available were included. Results meeting these criteria were available for
5,269 entry points and 2,498 systems. When calculating entry point mean concentrations, analytical
results below the respective minimum reporting limits were treated as zero to maximize consistency
with the NPDWR. Exhibit 11-3 shows the count and percentages of entry points and systems with data
meeting the described criteria that had an observed entry point mean concentration exceeding an MCL
threshold.
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Exhibit 11-3: Preliminary UCMR 5 Dataset1 - Summary of Systems with Entry
Point Mean Concentrations Exceeding MCL Thresholds
MCL
Threshold2
Entry Points
With Mean
Exceeding
Systems With At
Least One Entry
Point Mean
Exceeding
PFOA
(4.0 ng/L)
253
(4.8%)
149
(6.0%)
PFOS
(4.0 ng/L)
278
(5.3%)
179
(7.2%)
PFHxS
(10 ng/L)
15
(0.3%)
11
(0.4%)
PFNA
(10 ng/L)
1
(<0.1 %)
1
(<0.1 %)
HFPO-DA
(10 ng/L)
1
(<0..1%)
1
(<0.1 %)
HI (1)
18
(0.3%)
14
(0.6%)
Any
381
(7.2%)
235
(9.4%)
Notes:
1 The preliminary UCMR 5 dataset contains approximately 24 percent of the samples anticipated to be available once the dataset is
complete.
2 MCL thresholds for PFOA and PFOS were assessed to two significant figures while MCL thresholds for PFHxS, PFNA, HFPO-DA,
and the HI were assessed with one significant figure. Calculated means had to be equal to or exceed the following values to be
treated as exceeding an MCL: 4.05 for PFOA and PFOS; 15 for PFHxS, PFNA, and HFPO-DA; 1.5 forthe HI. See Section V ofthe
final rule preamble for more information.
PFAS co-occurrence was also examined in the partial UCMR 5 dataset. Exhibit 11-4 shows sample, entry
point, and system counts according to how many PFAS were reported at or above their minimum
reporting levels for the 16,743 samples for which all six analytes had results and 9,529 entry points and
3,719 systems which had at least one analytical result for each analyte.
Exhibit 11-4: Preliminary UCMR 5 Dataset1 - Samples, Entry Points, and Systems
Binned According to Number of PFAS Among PFOA, PFOS, PFHxS, PFNA, HFPO-
DA and PFBS That Were Reported at or Above the Minimum Reporting Level
PFAS
Observed
Samples
Entry
Points
Systems
0
14,408
(86.1%)
7,954
(83.5%)
2,877
(77.4%)
1
1,077
(6.4%)
676
(7.1%)
313
(8.4%)
2
541
(3.2%)
379
(4.0%)
191
(5.1%)
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PFAS
Observed
Samples
Entry
Points
Systems
3
393
(2.3%)
289
(3.0%)
172
(4.6%)
4
303
(1.8%)
215
(2.3%)
148
(4.0%)
5
21
(0.1%)
16
(0.2%)
18
(0.5%)
6
0
(0.0%)
0
(0.0%)
0
(0.0%)
Notes:
1 The preliminary UCMR 5 dataset contains approximately 24 percent of the samples anticipated to be available once the dataset is
complete.
The partial UCMR 5 dataset was also separated for groupwise analysis using the same approach
described in subsection 9.2.1. Exhibit 11-5 provides the counts and percentages of samples, entry
points, and systems according to whether: a) they reported the presence of PFOS or PFOA, and b) they
reported the presence of HI chemicals.
Exhibit 11-5: Preliminary UCMR 5 Dataset1 - Samples, Entry Points, and Systems
Binned According to Whether PFOS or PFOA and Additional HI PFAS were
Reported At or Above their Minimum Reporting Levels
Type
No PFOS or PFOA
Reported
PFOS or PFOA
Reported
Total Count
No Other
PFAS
Reported
HI PFAS
Reported
No HI PFAS
Reported
HI PFAS
Reported
Samples
14,408
(86.1%)
786
(4.7%)
498
(3.0%)
1,051
(6.3%)
16,743
Entry Points
7,954
(83.5%)
508
(5.3%)
317
(3.3%)
750
(7.9%)
9,529
Systems
2,877
(77.4%)
242
(6.5%)
145
(3.9%)
455
(12.2%)
3,719
Notes:
1 The preliminary UCMR 5 dataset contains approximately 24 percent of the samples anticipated to be available once the dataset is
complete.
Samples, entry points, and systems were also separated according to how many HI PFAS were reported
at or above the minimum reporting level. Exhibit 11-6 and Exhibit 11-7 present these results when PFOA
or PFOS were not reported present and for when they were reported present, respectively.
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Exhibit 11-6: Preliminary UCMR 5 Dataset1 - Sample, Entry Points, and System
Counts According the Number of HI PFAS Reported At or Above their Minimum
Reporting Levels for Samples, Entry Points, and Systems Where PFOS and PFOA
Were Below their Minimum Reporting Levels
HI PFAS
Observed
Samples
Entry
Points
Systems
0
14,408
(94.8%)
7,954
(94.0%)
2,877
(92.2%)
1
686
(4.5%)
429
(5.1%)
202
(6.5%)
2
100
(0.7%)
79
(0.9%)
40
(1.3%)
3
0
(0.0%)
0
(0.0%)
0
(0.0%)
4
0
(0.0%)
0
(0.0%)
0
(0.0%)
Total
15,194
8,462
3,119
Notes:
1 The preliminary UCMR 5 dataset contains approximately 24 percent of the samples anticipated to be available once the dataset is
complete.
Exhibit 11-7: Preliminary UCMR 5 Dataset1 - Sample, Entry Points, and System
Counts According to the Number of HI PFAS Reported At or Above their Minimum
Reporting Levels for Samples and Systems Where PFOS and/or PFOA Were At or
Above the Minimum Reporting Level
HI PFAS
Observed
Samples
Entry
Points
Systems
0
498
(32.2%)
317
(29.7%)
145
(24.2%)
1
573
(37.0%)
403
(37.8%)
223
(37.2%)
2
453
(29.2%)
329
(30.8%)
214
(35.7%)
3
25
(1.6%)
18
(1.7%)
18
(3.0%)
4
0
(0.0%)
0
(0.0%)
0
(0.0%)
Total
1,549
1,067
600
Notes:
1 The preliminary UCMR 5 dataset contains approximately 24 percent of the samples anticipated to be available once the dataset is
complete.
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Pairwise co-occurrence was also assessed through odds ratios, as seen in subsection 9.2.2. The results
are shown at the sample level and the system level in Exhibit 11-8 and Exhibit 11-9, respectively.
Exhibit 11-8: Preliminary UCMR 5 Dataset1 - Sample-level Counts of Pairwise
Chemical Occurrence and Calculated Odds Ratios
Chem A
Chem B
Chems A
and B
Reported
Only
Chem B
Reported
Only
Chem A
Reported
Neither
Chem
Reported
Odds Ratio
[95% CI]
HFPO-DA
PFBS
12
1,427
12
15,309
10.7
[4.9-23.51
HFPO-DA
PFHxS
4
925
20
15,812
3.4
[1.2-9.61
HFPO-DA
PFNA
0
48
24
16,704
0.0
[0.0-56.21
HFPO-DA
PFOA
16
1,057
8
15,686
29.7
[13.0-67.91
HFPO-DA
PFOS
15
1,128
9
15,608
23.1
[10.3-51.71
PFBS
PFHxS
559
373
882
14,938
25.4
[21.9-29.41
PFBS
PFNA
30
18
1,409
15,305
18.1
[10.2-32.31
PFBS
PFOA
626
450
816
14,872
25.4
[22.0-29.21
PFBS
PFOS
714
433
728
14,882
33.7
[29.3-38.81
PFHxS
PFNA
25
23
905
15,810
19.0
[10.8-33.41
PFHxS
PFOA
432
642
500
15,186
20.4
[17.6-23.81
PFHxS
PFOS
594
553
339
15,270
48.4
[41.3-56.71
PFNA
PFOA
36
1,037
12
15,684
45.4
[23.8-86.61
PFNA
PFOS
33
1,111
15
15,603
30.9
[16.9-56.61
PFOA
PFOS
669
478
407
15,209
52.3
[44.9-61.01
Notes:
1 The preliminary UCMR 5 dataset contains approximately 24 percent of the samples anticipated to be available once the dataset is
complete.
Exhibit 11-9: Preliminary UCMR 5 Dataset1 - System-level Counts of Pairwise
Chemical Occurrence and Calculated Odds Ratios
Chem A
Chem B
Chems A
and B
Reported
Only
Chem B
Reported
Only
Chem A
Reported
Neither
Chem
Reported
Odds Ratio
[95% CI]
HFPO-DA
PFBS
10
560
7
3,143
8.0
[3.1-20.51
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Chem A
Chem B
Chems A
and B
Reported
Only
Chem B
Reported
Only
Chem A
Reported
Neither
Chem
Reported
Odds Ratio
[95% CI]
HFPO-DA
PFHxS
3
371
14
3,333
1.9
F0.6-6.31
HFPO-DA
PFNA
0
26
17
3,679
0.0
r0.0-32.6l
HFPO-DA
PFOA
12
417
5
3,286
18.9
[6.9-51.81
HFPO-DA
PFOS
13
464
4
3,239
22.7
[7.7-66.41
PFBS
PFHxS
259
115
311
3,034
22.0
[17.1-28.21
PFBS
PFNA
19
7
551
3,143
15.5
[6.6-36.11
PFBS
PFOA
290
139
280
3,011
22.4
[17.7-28.41
PFBS
PFOS
327
150
243
2,999
26.9
[21.3-34.01
PFHxS
PFNA
17
9
357
3,338
17.7
[8.0-39.21
PFHxS
PFOA
204
225
170
3,120
16.6
[13.0-21.21
PFHxS
PFOS
273
204
101
3,142
41.6
[31.8-54.51
PFNA
PFOA
22
407
4
3,287
44.4
[15.9-123.91
PFNA
PFOS
20
457
6
3,237
23.6
[9.7-57.41
PFOA
PFOS
306
171
123
3,119
45.4
[35.0-58.91
Notes:
1 The preliminary UCMR 5 dataset contains approximately 24 percent of the samples anticipated to be available once the dataset is
complete.
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Appendix A: Perfluorobutane Sulfonic Acid (PFBS)
This appendix presents information and analysis specific to PFBS, including background information on
the contaminant, information on contaminant sources and environmental fate, an analysis of health
effects, an analysis of occurrence in ambient and drinking water, and information about the availability
of analytical methods and treatment technologies.
A.l Contaminant Background, Chemical and Physical Properties
Synonyms for PFBS include nonafluorobutanesulfonic acid and 1-perfluorobutanesulfonic acid,
according to NCBI (2022g). The acronym PFBS is also used to refer to the deprotonated anionic form of
the compound, perfluorobutane sulfonate (NCBI, 2022g) also known as pentyl perfluorobutanoate
(ATSDR, 2021).
PFBS is a short-chain perfluorinated aliphatic sulfonic acid (ITRC, 2021). Its predominant salt K+PFBS
differs from PFBS by being associated with a potassium ion. For the purposes of this document PFBS will
signify the ion, acid, or any salt of PFBS (USEPA, 2022g).
PFBS is a replacement chemical for PFOS. It has been used as a surfactant in alkaline cleaners, paints and
water- and stain-repellant products (USEPA, 2021f). It has also been found in semiconductor waste
streams (ITRC, 2021), floor wax, firefighting foam, and carpeting (USEPA, 2021f; USEPA, 2022g). While
PFBS is not authorized for use in food packaging, it has been detected in grease-proofing agents in other
countries (USEPA, 2022g). It is possible that some of these compounds, notably the potassium salt,
potassium perfluorobutane sulfonate, used as a flame retardant for polycarbonate resin may result in
the presence of PFBS in the environment (ITRC, 2021).
The diagram of Exhibit A-l shows the straight-chain chemical structure of PFBS. Currently PFBS is not
known to exist as branched-chain isomers. As more analytical standards become available, PFBS may be
reported as either linear or branched in the future (ITRC, 2021). The chemical and physical properties of
PFBS are listed in Exhibit A-2 and would represent mixtures of branched and linear isomers, if present,
rather than any particular isomer.
Exhibit A-1: Chemical Structure of PFBS - Straight-Chain Isomer
¦OH
Source: NCBI, 2022g
NCBI (2022g) reports a value of 1.82 for the log octanol/water partitioning coefficient (log Kow) that is
estimated using the EPA's EPISuite™, while ATSDR (2021) indicated that log Kow is not applicable or
cannot be measured since PFBS is expected to form multiple layers in octanol and water mixtures. PFBS
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is charged/ionized and at typical environmental pH can be moderately to very soluble in water (NCBI,
2022g; ITRC, 2021). ATSDR reports no data available for Henry's Law Constant while ITRC and NCBI
present a value for KH. The KH value presented by NCBI was estimated from vapor pressure and water
solubility using EPISuite™.
Where there are different conclusions in the literature for the properties of PFBS, information is
presented to highlight the range of uncertainty for this compound.
Exhibit A-2: Physical and Chemical Properties of PFBS
Property
Data
PFBS
Chemical Abstracts Service
(CAS) Registry Number
375-73-5 (NCBI, 2022g)
EPA Pesticide Chemical
Code
Not Applicable
Chemical Formula
C4HF9O3S (ATSDR, 2021)
Molecular Weight
300.1 g/mol (ATSDR, 2021)
Color/Physical State
Colorless Liquid (NCBI, 2022g)
Boiling Point
210-212 deg C (NCBI, 2022g)
80-211 deg C (ITRC, 2021)
152 deg C (USEPA, 2021f)
Melting Point
20.4-70.4 deg C (est) (ITRC, 2021)
No data (ATSDR, 2021)
Density
1.811 g/mL at 25 deg C (NCBI, 2022g)
Freundlich Adsorption
Coefficient
-
Vapor Pressure
1.0 mm Hg at 25 deg C (ITRC, 2021; converted from 2.12 log-Pa)
0.0268 mm Hg at 25 deg C (est) (NCBI, 2022g)
0.104 mm Hg (est) (USEPA, 2021 f)
Kh
0.26 atm-m3/mol at 25 deg C (ITRC, 2021; converted from 1.02 log)
1.44E-05 atm-m3/mol at 25 deg C (est) (NCBI, 2022g)a
No data (ATSDR, 2021)
Log Kow
1.82 (est) (dimensionless) (NCBI, 2022g)b
Not applicable (ATSDR, 2021)
Koc
<1 - 1.6E02 soil (dimensionless)
(ITRC, 2021 :Log Koc -0.7 to 2.2)
6.3 - 3.2E03 sediment (dimensionless)
(ITRC, 2021; Log Koc 0.8 to 3.5)
1.15E02 (ATSDR, 2021; Log Koc 2.06 avg (n=7))
180 (dimensionless) (est) (NCBI, 2022g)
pKa
-3.31 (est) (NCBI, 2022g)
0.14 (est) (ATSDR, 2021)
Solubility in Water
6,875 mg/L (ITRC, 2021; converted from -1.64 log-mol/L)
344 mg/L at 25 deg C (est) (NCBI, 2022g)
Other Solvents
-
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Property
Data
PFBS
Conversion Factors
(at 25 deg C, 1 atm)
1 PPM = 12.27 mg/m3; 1 mg/m3 = 0.081 PPM (ATSDR, 2021)
Note:indicates that no information was found.
aThese values should not be used to estimate portioning between water and air.
bSurfactants are surface acting agents that contain both a hydrophilic part and a hydrophobic part which causes them
to accumulate at interfaces hampering the determination of their aqueous concentration. These surfactant properties
present difficulties in applying existing methods for the experimental determination of log Kowand produce unreliable
results.
A.l.l Sources and Environmental Fate
A. 1.1.1 Production, Use, and Release
No production data for PFBS are available from the EPA's IUR and CDR programs.13 Industrial release
data are available from the EPA's TRI, as described below.
Toxics Release Inventory (TRI)
The EPA established TRI in 1987 in response to section 313 of the EPCRA. EPCRA section 313 requires
the reporting of annual information on toxic chemical releases from facilities that meet specific criteria.
This reported information is maintained in a database accessible through TRI Explorer (USEPA, 2023b).
Although TRI can provide a general idea of release trends, it has limitations. Not all facilities are required
to report all releases. Facilities are required to report releases if they manufacture, process, or
otherwise use a listed toxic chemical in quantities above the respective activity threshold. For PFOA, the
reporting threshold is 100 pounds manufactured, processed, or otherwise used over the year. It should
also be noted that, as of this publication, quantities of PFOA at concentrations under 1.0 percent within
mixtures may be exempt from TRI reporting requirements. Reporting requirements have changed over
time (e.g., the chemical list has changed), so conclusions about temporal trends should be drawn with
caution. TRI data are meant to reflect releases and other waste management activities and should not
be used to estimate general public exposure to a chemical (USEPA, 2023b).
TRI data for PFBS are available for 2022 (USEPA, 2023b). As shown in Exhibit A-3, there were 40 pounds
of total on-site disposals and 4 pounds of total off-site disposals reported across all industries in 2022.
Releases were reported by one facility in Alabama (USEPA, 2023b).
13 Note that there are 2020 CDR data listed for "Perfluoro compounds, C5-18." Those data are not summarized in
this report.
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Exhibit A-3: Environmental Releases of PFBS in the United States, 2022
On-Site Releases (in pounds)
Year
Air
Emissions
Surface
Water
Discharges
Underground
Injection
Releases to
Land
Total Off-
Site
Releases
(in pounds)
Total On-
and Off-Site
Releases
(in pounds)
2022
10
30
0
0
4
44
Source: USEPA, 2023b
A.l.1.2 Environmental Fate
The primary measures used by the EPA to assess mobility include (where available) Koc, log Kow, KH, water
solubility and vapor pressure. For PFBS, pKa is also important.
PFBS is expected to be stable to oxidation, hydrolysis, photodegradation in the atmosphere and abiotic
degradation under environmental conditions (ECHA, 2019; USEPA, 2022g).
Modeling of atmospheric behavior of PFBS suggest that PFBS will be present as a vapor if released to the
atmosphere (NCBI, 2022g). PFBS can react with photochemically produced hydroxyl radicals in the
atmosphere to degrade (NCBI, 2022g), although PFBS has the potential for long range transport (ECHA,
2019). A half-life for this reaction in air is estimated to be 115 days (NCBI, 2022g) and 76.4 days (ECHA,
2019) based upon EPISuite™ models. Caution should be applied while interpreting these results since
half-life estimation is based on "reaction with N, S and OH-" and does not fully cover perfluoroalkyl
substances (ECHA, 2019). Note that radical reactions typically proceed more rapidly than chemically- or
microbially-mediated degradation reactions in other environmental media such as water, soil, and/or
sediment. PFBS is not expected to undergo direct photolysis (NCBI, 2022g).
Log Koc suggests a propensity for PFBS to be mobilized to ground water and surface water rather than to
bind to soil. The relative hydrophobicity of PFAS control their sorption to soils, with PFBS exhibiting
lower sorption affinity than PFOS and PFOA, due to PFBS of relative low value of log K0w and its shorter
carbon chain. PFBS is expected to have moderate mobility to sediment as Koc was found to range up to
Log Koc 3.2 ±0.3, equivalent to 790 - 3160 in sediment (dimensionless) (ITRC, 2021).
PFBS is considered hydrolytically stable having a hydrolytic half-life or more than 1 year based upon a
study of K+PFBS hydrolysis at varying pHs of 4.0, 7.0 and 9.0 (ECHA, 2019). PFBS is also not expected to
undergo photolysis in water based upon testing of PFOS and structural similarities between PFBS and
PFOS (ECHA, 2019).
PFBS was modelled by ECHA using the seven separate models of EPISuite™ BIOWIN v4.10 to estimate
the probability of aerobic and anaerobic biodegradation in water. Although the models provide varying
biodegradation results based upon varying methods of structural carbon stability, all of the methods
found that PFBS would not biodegrade fast, having results below the screening criteria for being "readily
biodegradable" (ECHA, 2019). This finding is corroborated by a 28-day test of PFBS inoculated surface
water which biodegraded less than 3 percent (NCBI, 2022g).
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No significant oxidation of PFBS by abiotic degradation is expected based on a study using various
advanced oxidation methods (ultraviolet radiation, hydrogen peroxide and both methods combined)
(ECHA, 2019).
Based on the vapor pressure, PFBS is not expected to volatilize from dry soil (NCBI, 2022g). With a pKa of
less than 1.0, PFBS is expected to exist in its ionized form at typical environment pH ranges of natural
waters (NCBI, 2022g). Thus, volatilization from water at typical environment pH is not expected (NCBI,
2022g).
Under CCL 3, the EPA created scales14 to informally rank chemical contaminants' likely mobility
(understood as their tendency to partition to water rather than other media) and persistence as "high,"
"moderate," or "low" based on physical and chemical properties (see USEPA, 2021b and USEPA, 2009).
For PFBS, a log Kow of 1.82, and a water solubility of more than 300 mg/L at 25 degrees C predict a
moderate favorability of partitioning to water. The water solubility of the potassium salt of PFBS, 2.7E05
mg/L, which may be more indicative of the anionic form that occurs at typical environmental pH,
predicts a high likelihood of partitioning to water. The experimental value of KH of 0.26 atm-m3/mol
(ITRC, 2021) predicts a high likelihood of partitioning to water. NCBI (2022g) lists a KH of 1.44E-05 atm-
m3/mol, but this value was estimated from vapor pressure and water solubility using EPISuite™.
PFBS is very stable chemically and is resistant to hydrolysis, photolysis, and biodegradation (NCBI,
2022g). A resistance to essentially all forms of degradation other than recalcitrant atmospheric
processes indicates high persistence.
A.2 PFBS Occurrence
In this action, the EPA is deferring the final determination to individually regulate PFBS for further
evaluation under the SDWA statutory criteria. The EPA is making a final determination to regulate PFBS
as part of an HI approach when co-occurring in mixture combinations containing two or more of PFHxS,
PFNA, HFPO-DA, and PFBS. Refer to chapter 8 for more information on the HI and chapter 9 for co-
occurrence information. For reference only, this appendix presents data on the individual occurrence of
PFBS in drinking water and ambient water in the United States. The drinking water analyses presented in
this section were performed for UCMR 3 and select state data sources. For additional background
information about data sources used to evaluate occurrence, please refer to Chapter 2.
A.2.1 Occurrence in Drinking Water
Data sources reviewed by the agency for information on PFBS occurrence in drinking water included
UCMR 3, more recent state drinking water monitoring programs, and the DoD PFAS drinking water
testing, as well as additional studies from the literature. Note that there may be some overlap, as
sources with different purposes and audiences may have reported the same underlying data. UCMR 3 is
a nationally representative data source. Other data sources profiled in this section are considered
"supplemental" sources. Also note that PFBS is being monitored for under UCMR 5, which is occurring
from 2023 to 2025. Analysis of partial UCMR 5 results (the first three quarters of data that were made
available as of February 2024) are discussed in section 11 of this document. Additionally, the EPA notes
14 See Exhibit A.8 here: https://www.epa.gov/sites/default/files/2014-05/documents/ccl3 pccltoccl 08-31-
09 508.pdf
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that the UCMR 3 MRLfor PFBS is higher than that utilized within the majority of state monitoring data
and for the UCMR 5.
A.2.1.1 UCMR 3 Data
PFBS was included as part of the nationally representative UCMR 3 monitoring from 2013 through 2015.
UCMR 3 Assessment Monitoring occurrence data are available for PFBS from all large and very large
PWSs (serving between 10,001 and 100,000 people and serving more than 100,000 people,
respectively), plus a statistically representative national sample of 800 small PWSs (serving 10,000
people or fewer).15 Surface water and GWUDI sampling points were monitored four times during the
applicable year of monitoring, and ground water sample points were monitored twice during the
applicable year of monitoring. See USEPA (2012b) and USEPA (2019a) for more information on the
UCMR 3 study design and data analysis.
Exhibit A-4 through Exhibit A-6 provide an overview of PFBS occurrence results from the UCMR 3
Assessment Monitoring. Laboratories participating in UCMR 3 were required to report values at or
above MRLs defined by the EPA. The UCMR MRLs are not intended to represent the lowest achievable
measurement level an individual laboratory may achieve. Rather, the MRLs are established to ensure
reliable and consistent results from the array of laboratories needed for a national monitoring program
and are set based on the quantitation level capability of multiple commercial laboratories prior to
beginning each UCMR round. The MRL used for PFBS in the UCMR 3 survey was 90 ng/L (77 FR 26072;
USEPA, 2012b). Exhibit A-4 presents a sample-level summary of the results. Exhibit A-5 shows a
statistical summary of PFBS concentrations by system size and source water type (including the
minimum, 25th percentile, median, 75th percentile, 90th percentile, 99th percentile, and maximum).
Exhibit A-6 shows system-level results for detections greater than or equal to the MRL.
A total of 36,972 finished water samples for PFBS were collected from 4,920 PWSs. PFBS was reported >
MRL of 90 ng/L in 0.05 percent of UCMR 3 samples. Reported PFBS concentrations for these results
ranged from 90 ng/L (the MRL) to 370 ng/L. Of 4,920 systems, 8 (0.16 percent of systems, serving 0.15
percent of the PWS-served population) reported at least one detection.
Exhibit A-4: PFBS National Occurrence Measures Based on UCMR 3 Assessment
Monitoring Data - Summary of Samples
Source Water Type
Total # of
Samples
Samples with Detections
> MRL of 90 ng/L
Number
Percent
Small Systems (serving < 10,000 people)
Ground Water
1,853
0
0.00%
Surface Water
1,421
0
0.00%
All Small Systems
3,274
0
0.00%
Large Systems (serving 10,001 -100,000 people) — CENSUS
Ground Water
11,707
0
0.00%
Surface Water
14,860
19
0.13%
15 A total of 799 small systems submitted Assessment Monitoring results.
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Source Water Type
Total # of
Samples
Samples with Detections
> MRL of 90 ng/L
Number
Percent
All Large Systems
26,567
19
0.07%
Very Large Systems (serving > 100,000 people) — CENSUS
Ground Water
2,020
0
0.00%
Surface Water
5,111
0
0.00%
All Very Large Systems
7,131
0
0.00%
All Systems
All Water Systems
36,972
19
0.05%
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Exhibit A-5: PFBS Occurrence Data from UCMR 3 Assessment Monitoring - Summary of Reported Concentrations
Source Water Type
Concentration Value of Detections (in ng/L) > MRL of 90 ng/L
Minimum
25th percentile
Median
75th percentile
90th Percentile
99th Percentile
Maximum
Small Systems (serving < 10,000 people)
Ground Water
-
-
-
-
-
-
-
Surface Water
-
-
-
-
-
-
-
All Small Systems
-
-
-
-
-
-
-
Large Systems (serving 10,001 -100,000 people) — CENSUS
Ground Water
-
-
-
-
-
-
-
Surface Water
90
115
170
205
336
368.2
370
All Large Systems
90
115
170
205
336
368.2
370
Very Large Systems (serving > 100,000 people) — CENSUS
Ground Water
-
-
-
-
-
-
-
Surface Water
-
-
-
-
-
-
-
All Very Large
Systems
-
-
-
-
-
-
-
All Systems
All Water Systems
90
115
170
205
336
368.2
370
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Exhibit A-6: PFBS National Occurrence Measures Based on UCMR 3 Assessment Monitoring Data - Summary of
System and Population Served Data - Reported Detections
Source Water
Type
UCMR 3 Samples
Number With At Least
One Detection > MRL of
90 ng/L
Percent With At Least
One Detection > MRL of
90 ng/L
National Inventory
Percent of National
Inventory Included
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Systems
Population
Small Systems (serving < 10,000 people)
Ground Water
527
1,498,845
0
0
0.00%
0.00%
55,700
38,730,597
0.95%
3.87%
Surface Water
272
1,250,215
0
0
0.00%
0.00%
9,728
20,007,917
2.80%
6.25%
All Small
Systems
799
2,749,060
0
0
0.00%
0.00%
65,428
58,738,514
1.22%
4.68%
Large Systems (serving 10,001 -100,000 people) — CENSUS
Ground Water
1,453
37,141,418
0
0
0.00%
0.00%
1,470
37,540,614
98.84%
98.94%
Surface Water
2,260
69,619,878
8
349,933
0.35%
0.50%
2,310
70,791,005
97.84%
98.35%
All Large
Systems
3,713
106,761,296
8
349,933
0.22%
0.33%
3,780
108,331,619
98.23%
98.55%
Very Large Systems (serving > 100,000 people) — CENSUS
Ground Water
68
16,355,951
0
0
0.00%
0.00%
68
16,355,951
100.00%
100.00%
Surface Water
340
115,158,260
0
0
0.00%
0.00%
343
120,785,622
99.13%
95.34%
All Very Large
Systems
408
131,514,211
0
0
0.00%
0.00%
411
137,141,573
99.27%
95.90%
All Systems
All Water
Systems
4,920
241,024,567
8
349,933
0.16%
0.15%
69,619
304,211,706
7.07%
79.23%
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A.2.1.2 State Monitoring Data
In the development of the proposed and final NPDWR, the agency supplemented its UCMR 3 data with
more recent publicly available data collected by states. In general, these more recent state data were
collected using newer analytical methods and state results reflect lower reporting and detection limits
than those in the UCMR 3. Drinking water occurrence data from PWSs for PFBS were available from
several states, including Alabama, Arizona, California, Colorado, Georgia, Idaho, Illinois, Indiana, Iowa,
Kentucky, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, New Hampshire, New
Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oregon, Pennsylvania, South
Carolina, Tennessee, Vermont, Virginia, and Wisconsin. The EPA downloaded publicly available
monitoring data from state websites. Note that while some states did have available raw water data as
indicated in Exhibit A-7, for the subsequent analyses the EPA only evaluated finished water results.
Exhibit A-7 provides a summary of the available state reported monitoring data for PFBS, including date
range and a description of coverage and representativeness (including whether monitoring was non-
targeted or targeted (i.e., monitoring in areas of known or potential PFAS contamination)). A description
of those studies is also included in Exhibit A-7. State reporting thresholds are also provided, where
available, in Exhibit A-7. The EPA notes that different states utilized various reporting thresholds when
analyzing and presenting their data, and for some states there were no clearly defined thresholds
publicly provided; in these cases, minimum detected concentrations reported may be indicative of
reporting thresholds used. Further, for some states, the thresholds varied when reporting results for the
same analyte, as well as the laboratory analyzing the data. For those states, a range of thresholds is
provided. As shown in Exhibit A-7, some states reported at thresholds and/or presented data at
concentrations below the EPA's final HBWC and/or PQL for PFBS. However, to present the best available
occurrence information, the EPA collected and evaluated the data based on the information as reported
directly by the states and when conducting data analyses incorporated individual state-specific reporting
thresholds where possible. Additionally, the EPA notes that the majority of the data were analyzed via
an EPA-approved drinking water analytical method.
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Exhibit A-7: Summary of Available PFBS State Reported Monitoring Data
State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
Alabama
(ADEM, 2023)
2013-
2022
Ground Water and
Surface Water -
Finished Water
Not reported
ADPH instructed water systems to carry out PFAS monitoring at all PWSs not
previously sampled during UCMR 3. In 2022, water systems that had not been
sampled since UCMR 3 were required to sample between January and June
2022 using current analytical methods. Only results that are above the MRL
are posted online; thus, only reported detections were available for use in the
occurrence analyses.
Non-
Targeted
Arizona
(ADEQ, 2023)
2021
Ground Water and
Surface Water -
Raw and Finished
Water
1.6-2
ADEQ presents a PFAS Interactive Data Map that displays the results of
testing conducted by ADEQ since 2018 at PWSs across Arizona.
Targeted
California
(CADDW,
2023)
2016-
April 2023
Ground Water and
Surface Water -
Raw, Finished, and
Unknown Water
0.002-90
The EPA reviewed the California PFBS data available online through April
2023. Finished water data were available from approximately 120 PWSs. For
this analysis, the EPA only included results that were explicitly marked as
being from treated water. Sampling in California is ongoing.
Targeted
Colorado
(CDPHE,
2018;CDPHE,
2020)
2013-
2017
Surface Water
(Finished Water)
and Drinking Water
Distribution
Samples
2-90
Data available from 28 "drinking water distribution zones" (one or more per
PWS) in targeted sampling efforts at a known contaminated aquifer region.
Data were collected by El Paso County Public Health, local water districts and
utilities, and the CDPHE.
Targeted
2020
Ground Water and
Surface Water -
Raw and Finished
Water
1.6-2.4
CDPHE offered free testing to PWSs serving communities, schools, and
workplaces and also to fire districts with wells. Approximately 50% of PWSs in
Colorado participated in the 2020 PFAS sampling project. Data included in this
report were collected in March through May of 2020.
Non-
Targeted
Georgia
(GA EPD,
2020)
2020
Surface Water -
Raw, Finished, and
Unknown Water
18
The EPA and the GA EPD conducted joint sampling of the City of
Summerville's drinking water sources and finished drinking water in January
2020.
Targeted
Idaho
(Idaho DEQ,
2023)
2021 -
April 2023
Ground Water -
Finished and
Unknown Water
0.5-1
Sampling of finished drinking water data between September 2021 and April
2023 that were available on the state's Drinking Water Watch website.
Not
specified
Illinois
(IL EPA, 2023)
2020 - May
2023
Ground Water and
Surface Water -
Raw and Finished
Water
1.7-5
In 2020, the IL EPA initiated a statewide investigation into the prevalence and
occurrence of PFAS in finished drinking water at 1,749 community water
supplies across Illinois. The EPA reviewed finished drinking water data
Non-
Targeted
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State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
collected between September 2020 and May 2023 that were available on the
state's Drinking Water Watch website. Sampling in Illinois is ongoing.
Indiana (IDEM,
2023)
2021 -
January
2023
Ground Water and
Surface Water -
Raw, Finished, and
Unknown Water
2
Beginning in February 2021, the IDEM facilitated PFAS monitoring at all CWSs
throughout the state of Indiana. Samples were to be collected at all raw water
(i.e., wells and intakes) and finished (after treatment) water points in a CWS's
supply to evaluate the statewide occurrence of PFAS compounds in CWS
across the state and determine the efficacy of conventional drinking water
treatment for PFAS.
Non-
Targeted
Iowa
(IA DNR, 2023)
2021 -
April 2023
Ground Water and
Surface Water -
Raw and Finished
Water
1.7-3
In January 2020, the Iowa DNR developed an Action Plan to protect the health
of Iowa residents and the environment from PFAS. Data were downloaded
from the PFAS Sampling Interactive Dashboard and Map.
Targeted
Kentucky
(KYDEP, 2019)
2019
Ground Water and
Surface Water -
Finished Water
3.96
Sampling of finished drinking water data between June and October 2019.
Under this sampling effort, data are available from 81 community public
DWTPs, representing 74 PWSs, and serving more than 2.4 million people.
Non-
Targeted
Maine
(Maine DEP,
2020; Maine
DHHS, 2023)
2013-
2020
Drinking Water -
Raw, Finished, and
Unknown Water
1.78-90
In March 2019, the Maine PFAS Task Force was created to review the extent
of PFAS contamination in Maine. Finished water results collected from 2013
through 2020 have been collected at 23 locations throughout the state. Data
may include results from public and private finished drinking water sources.
Sampling in Maine is ongoing.
Targeted
2021 -
January
2023
Ground Water and
Surface Water -
Finished Water
2
The EPA reviewed the finished water data reported to the Maine CDC Drinking
Water Program as compliance samples since June 2021 and processed in the
database as of 3/10/2023. Sampling in Maine is ongoing.
Non-
Targeted
Maryland
(MDE, 2021;
MDE, 2022a;
MDE, 2022b)
2020-
2022
Raw and Finished
Water
1
In 2020, MDE initiated a project to identify potential sources of PFAS in
Maryland and to prioritize water sources for PFAS sampling. The EPA
reviewed the finished water results from the first three phases of MDE's Public
Water System study for the occurrence of PFAS in State drinking water
sources. Under Phase 1 (September 2020 - February 2021), sites were
selected for priority sampling based on MDE's evaluation of potential relative
risk for PFAS exposure through drinking water. Under Phase 2 (March 2021 -
May 2021), MDE conducted sampling at sites that were selected based on
their geological setting and proximity to potential sources of PFAS. Under
Phase 3 (August 2021- June 2022), MDE tested the remaining CWSs in the
state.
Targeted
(Phase 1,
Phase 2);
Non-
Targeted
(Phase 3)
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State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
Massachusetts
(MA EE A,
2023)
2016-April
2023
Ground Water and
Surface Water -
Raw and Finished
Water
0.26 - 42
The EPA reviewed the finished water data available online through April 2023.
Data were available from 1,319 PWSs. Sampling in Massachusetts is ongoing.
Targeted
Michigan
(Michigan
EGLE, 2023)
2020-
March
2023
Ground Water and
Surface Water -
Finished Water
2
The Michigan EGLE developed MCLs for seven PFAS compounds in
Michigan, which took effect in August 2020. The EPA reviewed available
finished compliance monitoring results through March 2023. Sampling in
Michigan is ongoing.
Non-
Targeted
Minnesota
(MDH, 2023)
2020-
2023
Ground Water and
Surface Water -
Finished Water
Not reported
Through the Statewide PFAS Monitoring Project, MDH is testing CWSs across
the state for PFAS. The EPA reviewed finished water data through MDH's
Interactive Dashboard for PFAS Testing in Drinking Water.
Non-
Targeted
Missouri
(Missouri DNR,
2023)
2022-
2023
Ground Water and
Surface Water -
Raw and Finished
Water
Not reported
The EPA reviewed the finished water data available online from Missouri
DNR's "PFAS Viewer Tool" which identifies the location of voluntary sampling
for PFAS in public drinking water systems in Missouri. The EPA reviewed
finished water data collected from approximately 113 PWSs from 2022 through
2023. Limited data were also available from 2013 through 2017.
Non-
Targeted
New
Hampshire
(NHDES, 2021)
2016-
May 2021
Ground Water and
Surface Water -
Raw and Finished
Water
Not reported
The EPA reviewed the New Hampshire PFBS data available online through
May 2021. Finished water data were available from more than 200 PWSs.
Sampling in New Hampshire is ongoing.
Non-
Targeted
New Jersey
(NJDEP, 2023)
2019- May
2023
Ground Water and
Surface Water -
Raw, Finished, and
Unknown Water
0.43-44
Statewide sampling of finished drinking water data was available from 2019-
2023. The EPA reviewed data available online through May 2023 from more
than 660 PWSs. Sampling in New Jersey is ongoing.
Non-
Targeted
New Mexico
(NMED, 2019)
2016
Ground Water -
Raw and Finished
Water
Not reported
NMED, Department of Health and the U.S. Air Force conducted testing at
public drinking water supplies at or around Cannon Air Force Base up to 2019.
Targeted
New York
(NYDOH,
2022)
2017-
2022
Ground Water and
Surface Water -
Raw, Finished, and
Unknown Water
0.000000001
-1,790
The EPA reviewed finished water data voluntarily provided by the state to the
EPA. Data were available from nearly 2,600 PWSs from 2017 through 2022.
Limited data were also available from 2016.
Non-
Targeted
North Carolina
(NCDEQ,
2021)
2017-
2019
Finished and
unknown water
Not reported
NCDEQ and the Department of Health and Human Services investigated the
presence of HFPO-DA and other PFAS in the Cape Fear River in June
2017. Monthly results were also collected from five water treatment plants on
the Cape Fear River. Data were available from June 2017 through October
2019. Only results above the DLwere reported; thus, only reported detections
were available for use in the occurrence analyses.
Targeted
A-13
-------
EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
North Dakota
(NDDEQ, date
unknown;
NDDEQ, date
unknown)
2020, 2021
Ground Water and
Surface Water -
Raw and Finished
Water
Not reported
NDDEQ published a 2020 and a 2021 survey report of North Dakota Statewide
PFAS Presence/Absence results. The sampling effort in October of 2020
sought to determine if there was a PFAS presence in a representative portion
of the state's public water supply. In 2021, sampling conducted as part of the
third phase of the survey focused on drinking water sites not evaluated in the
first two surveys.
Non-
Targeted
Ohio
(Ohio EPA,
2023)
December
2019-
December
2021
Ground Water and
Surface Water -
Raw and Finished
Water
5
The Ohio EPA coordinated sampling of raw and finished drinking water from
PWSs throughout the state. The EPA reviewed the finished water data
available online through December 2021. During this timeframe, data were
available from 1,479 PWSs.
Non-
Targeted
Oregon
(OHA-DWS,
2022)
2021 - July
2022
Ground Water and
Surface Water -
Finished Water
40.2-49.6
OHA conducted a PFAS drinking water monitoring project in 2021 at PWSs in
Oregon identified as at risk due to their proximity to a known or suspected
PFAS use or contamination site. The EPA reviewed the finished water data
from more than 140 PWSs.
Targeted
Pennsylvania
(PADEP, 2019)
2019
Ground Water and
Surface Water -
Finished Water
1.9
A PFAS Sampling Plan was developed to test PWSs across the state. Finished
water data were collected for 87 PWSs in 2019.
Targeted
Pennsylvania
(PADEP, 2021)
2020-
March
2021
Ground Water and
Surface Water -
Finished Water
1.7-4
Beginning in 2020 and running through March of 2021, finished water data
were collected by more than 340 PWSs.
Targeted
South Carolina
(SCDHEC,
2020;
SCDHEC,
2023)
2017-
March
2023
Ground Water and
Surface Water -
Raw and Finished
Water
2.1
The EPA reviewed PFAS sampling results collected by the South Carolina
Bureau of Water for community drinking water systems . Data were available
from 300 PWSs.
Non-
Targeted
Tennessee
(TDEC, 2023)
2019
Surface Water -
Raw and Finished
Water
Not reported
In 2019, Metro Water Services conducted a voluntary sampling of Nashville's
drinking water systems for PFAS. Their stated goal was to go above and
beyond current federal and state monitoring requirements to understand the
potential presence of PFAS in Nashville's drinking water.
Non-
Targeted
Vermont
(VT DEC,
2023)
2019 -April
2023
Ground Water and
Surface Water -
Raw, Finished, and
Unknown Water
2
The Vermont Water Supply Rule required all CWSs and NTNCWSs to sample
for PFAS. The EPA reviewed finished water data available online from July
2019 - April 2023 from approximately 560 PWSs. Sampling in Vermont is
ongoing.
Non-
Targeted
A-14
-------
EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reference)
Date
Range
Type of Water
Tested
Reporting
Threshold
(PPt)
Notes on Coverage
Survey
Type
Virginia
(VDH ODW,
2021)
2021
Ground Water and
Surface Water -
Raw and Finished
Water
3.5
The Virginia ODW, in conjunction with VA PFAS work group, designed the
sample study to prioritize sites for measuring PFAS concentrations in drinking
water and major sources of water and generate statewide occurrence data.
Targeted /
Non-
Targeted
Wisconsin
(Wl DNR,
2023)
2022-
April 2023
Ground Water and
Surface Water -
Raw, Finished, and
Unknown Water
Not reported
The EPA reviewed the finished water data available online from 2022 - 2023.
Data were available from nearly 250 PWSs. Sampling in Wisconsin is ongoing.
Non-
Targeted
A-15
-------
EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
A summary of state reported monitoring data from PWSs for PFBS is presented in Exhibit A-8 through
Exhibit A-10. As noted above, some of the monitoring data from each state are limited and may not be
representative of occurrence in the state. In addition, states have varying reporting thresholds, as
indicated in the first column of Exhibit A-8. For states with available reporting thresholds, only detected
concentrations greater than the reporting thresholds were counted as detections. For states that did not
provide reporting thresholds, the EPA included all detected concentrations reported in the count of
detections. Overall, state reported detected concentrations ranged from 0.22 ppt (North Carolina) to
720 ppt (Alabama). Note that for a small number of systems, population served information could not
be identified. These systems were included in the counts and analysis presented in Exhibit A-10;
however, no associated population served was included in the counts and analysis presented in Exhibit
A-10.
Exhibit A-8: PFBS State Reported Drinking Water Occurrence Data - Summary of
Finished Water Samples
State
(Reporting
Threshold)
Source Water Type
Total Number
of Samples
All Detections
Number
Percent
Alabama1
(Not reported)
Ground Water
-
29
-
Surface Water
-
171
-
Total
-
200
--
Arizona
(1.6-2 ppt)
Ground Water
23
15
65.22%
Surface Water
2
0
0.00%
Total
25
15
60.00%
California
(0.002 - 90 ppt)
Ground Water
1,882
448
23.80%
Surface Water
3,950
735
18.61%
Unknown
4
0
0.00%
Total
5,836
1,183
20.27%
Colorado
(2013-2017)
(2 - 90 ppt)
Distribution (Finished)
94
26
27.66%
Surface water (Finished)
11
0
0.00%
Total
105
26
24.76%
Colorado (2020)
(1.6-2.4 ppt)
Ground Water
339
43
12.68%
Surface Water
244
21
8.61%
Total
583
64
10.98%
Georgia
(18 ppt)
Ground Water
0
0
0.00%
Surface Water
2
0
0.00%
Total
2
0
0.00%
Idaho
(0.5 -1 ppt)
Ground Water
18
1
5.56%
Surface Water
0
0
0.00%
Total
18
1
5.56%
Illinois
(1.7-5 ppt)
Ground Water
1,823
298
16.35%
Surface Water
302
75
24.83%
Total
2,125
373
17.55%
A-16
-------
EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water Type
Total Number
of Samples
All Detections
Number
Percent
Indiana
(2 ppt)
Ground Water
422
25
5.92%
Surface Water
59
2
3.39%
Total
481
27
5.61%
Iowa
(1.7-3 ppt)
Ground Water
153
40
26.14%
Surface Water
64
14
21.88%
Total
217
54
24.88%
Kentucky
(3.96 ppt)
Ground Water
33
4
12.12%
Surface Water
48
6
12.50%
Total
81
10
12.35%
Maine (PFAS Task
Force)2
(1.78-90 ppt)
Ground Water
9
0
0.00%
Surface Water
3
0
0.00%
Unknown
75
3
4.00%
Total
87
3
3.45%
Maine
(Compliance)
(2 ppt)
Ground Water
640
70
10.94%
Surface Water
62
1
1.61%
Total
702
71
10.11%
Maryland (Phase 1)
(1 ppt)
Ground Water
70
45
64.29%
Surface Water
76
47
61.84%
Total
146
92
63.01%
Maryland (Phase 2)
(1 ppt)
Ground Water
9
2
22.22%
Surface Water
0
0
0.00%
Total
9
2
22.22%
Maryland (Phase 3)
(1 ppt)
Ground Water
88
17
19.32%
Surface Water
0
0
0.00%
Total
88
17
19.32%
Massachusetts
(0.26 - 42 ppt)
Ground Water
7,013
2,734
38.98%
Surface Water
2,014
863
42.85%
Total
9,027
3,597
39.85%
Michigan
(2 ppt)
Ground Water
10,007
775
7.74%
Surface Water
519
20
3.85%
Unknown
164
6
3.66%
Total
10,690
801
7.49%
Missouri
(Not reported)
Ground Water
192
12
6.25%
Surface Water
22
1
4.55%
Total
214
13
6.07%
New Hampshire
(Not reported)
Ground Water
539
184
34.14%
Surface Water
60
8
13.33%
Total
599
192
32.05%
New Jersey
(0.43 - 44 ppt)
Ground Water
5,345
1,529
28.61%
Surface Water
1,770
471
26.61%
A-17
-------
EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water Type
Total Number
of Samples
All Detections
Number
Percent
Unknown
3
0
0.00%
Total
7,118
2,000
28.10%
New Mexico
(Not reported)
Ground Water
2
1
50.00%
Surface Water
0
0
0.00%
Total
2
1
50.00%
New York
(0.000000001-
1,790 ppt)
Ground Water
1,843
565
30.66%
Surface Water
400
83
20.75%
Unknown
10
0
0.00%
Total
2,253
648
28.76%
North Carolina1
(Not Reported)
Unknown
-
372
-
Total
-
372
--
North Dakota
(2020)
(Not reported)
Ground Water
42
0
0.00%
Surface Water
9
0
0.00%
Total
51
0
0.00%
North Dakota
(2021)
(Not reported)
Ground Water
56
8
14.29%
Surface Water
7
2
28.57%
Total
63
10
15.87%
Ohio
(5 ppt)
Ground Water
1,775
93
5.24%
Surface Water
170
5
2.94%
Total
1,945
98
5.04%
Oregon
(40.2-49.6 ppt)
Ground Water
131
0
0.00%
Surface Water
29
0
0.00%
Total
160
0
0.00%
Pennsylvania
(2019)
(1.9 ppt)
Ground Water
75
12
16.00%
Surface Water
21
8
38.10%
Total
96
20
20.83%
Pennsylvania
(2021)
(1.7-4 ppt)
Ground Water
314
46
14.65%
Surface Water
98
20
20.41%
Total
412
66
16.02%
South Carolina
(2.1 ppt)
Ground Water
572
48
8.39%
Surface Water
194
57
29.38%
Total
766
105
13.71%
Tennessee
(Not reported)
Ground Water
0
0
0.00%
Surface Water
2
0
0.00%
Total
2
0
0.00%
Vermont
(2 ppt)
Ground Water
1,457
108
7.41%
Surface Water
102
3
2.94%
Total
1,559
111
7.12%
Virginia
(3.5 ppt)
Ground Water
5
0
0.00%
Surface Water
36
3
8.33%
A-18
-------
EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water Type
Total Number
of Samples
All Detections
Number
Percent
Total
41
3
7.32%
Wisconsin
(Not reported)
Ground Water
728
193
26.51%
Surface Water
54
26
48.15%
Total
782
219
28.01%
1 Only reported detections were available in this state's dataset.
2 Reported data from Maine may include results from public and private finished drinking water sources. Based
on available state data information, the EPA could not verify PWSIDs for all included samples.
Exhibit A-9: PFBS State Reported Drinking Water Occurrence Data - Summary of
Detected Concentrations
State
(Reporting
Threshold)
Source Water Type
Concentration Value of Detections (ppt)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Alabama1
(Not reported)
Ground Water
1.1
3.80
5.30
17.4
22
Surface Water
0.7
4.50
81.0
154
720
Total
0.7
4.30
71.5
131
720
Arizona
(1.6-2 ppt)
Ground Water
1.6
3.70
9.88
13.4
14
Surface Water
-
-
-
-
-
Total
1.6
3.70
9.88
13.4
14
California
(0.002 - 90 ppt)
Ground Water
1
4.90
10.0
31.5
45
Surface Water
1.7
3.60
15.0
36.0
47
Unknown
-
-
-
-
-
Total
1
4.10
12.9
35.2
47
Colorado
(2013-2017)
(2 - 90 ppt)
Distribution (Finished)
2.9
46.5
86.0
138
150
Surface water (Finished)
-
-
-
-
-
Total
2.9
46.5
86.0
138
150
Colorado (2020)
(1.6-2.4 ppt)
Ground Water
1.8
3.70
7.72
9.54
10
Surface Water
1.7
3.60
9.00
14.7
16
Total
1.7
3.65
7.87
12.2
16
Georgia
(18 ppt)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
-
-
-
--
-
Idaho
(0.5 -1 ppt)
Ground Water
2.47
2.47
2.47
2.47
2.47
Surface Water
-
-
-
-
-
Total
2.47
2.47
2.47
2.47
2.47
Illinois
(1.7-5 ppt)
Ground Water
1.8
3.50
9.48
34.0
37
Surface Water
2.1
2.70
4.08
6.20
6.2
Total
1.8
3.30
8.46
25.4
37
A-19
-------
EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water Type
Concentration Value of Detections (ppt)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Indiana
(2 ppt)
Ground Water
2
3.20
6.14
12.4
14
Surface Water
2.3
7.75
12.1
13.1
13.2
Total
2
3.20
7.10
13.8
14
Iowa
(1.7-3 ppt)
Ground Water
2
6.35
14.9
46.2
47
Surface Water
1.9
4.95
24.7
27.6
28
Total
1.9
6.10
24.7
45.9
47
Kentucky
(3.96 ppt)
Ground Water
1.39
1.99
6.62
8.36
8.55
Surface Water
1.35
1.85
2.62
2.72
2.73
Total
1.35
1.99
3.31
8.03
8.55
Maine (PFAS Task
Force)2
(1.78-90 ppt)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Unknown
19
44
44
44
44
Total
19
44
44
44
44
Maine
(Compliance)
(2 ppt)
Ground Water
2.01
3.71
9.78
34.9
72.8
Surface Water
2.8
2.8
2.8
2.8
2.8
Total
2.01
3.70
9.72
34.4
72.8
Maryland (Phase 1)
(1 ppt)
Ground Water
1.08
3.59
8.97
18.7
21.29
Surface Water
1.08
2.57
6.60
10.3
11.32
Total
1.08
2.77
7.63
15.9
21.29
Maryland (Phase 2)
(1 ppt)
Ground Water
3.32
5.68
7.56
7.98
8.03
Surface Water
-
-
-
-
-
Total
3.32
5.68
7.56
7.98
8.03
Maryland (Phase 3)
(1 ppt)
Ground Water
1.22
3.31
10.2
12.7
12.9
Surface Water
-
-
-
-
-
Total
1.22
3.31
10.2
12.7
12.9
Massachusetts
(0.26 - 42 ppt)
Ground Water
1.15
3.24
7.57
43.3
414
Surface Water
1.68
2.80
5.34
9.04
11.1
Total
1.15
3.11
6.90
27.0
414
Michigan
(2 ppt)
Ground Water
2
3.80
15.0
53.0
110
Surface Water
2
3.45
4.17
6.35
6.5
Unknown
2
2.5
5
5
5
Total
2
3.70
15.0
52.0
110
Minnesota
(Not reported)
Ground Water
0.76
-
-
-
11
Surface Water
-
-
-
-
-
Total
0.76
-
-
-
11
Missouri
(Not reported)
Ground Water
2
4.75
6.95
7.62
7.7
Surface Water
2.3
2.3
2.3
2.3
2.3
Total
2
4.60
6.90
7.62
7.7
New Hampshire
Ground Water
1.6
2.80
7.12
16.3
26.8
A-20
-------
EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
(Not reported)
Source Water Type
Concentration Value of Detections (ppt)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Surface Water
1.7
2.78
17.3
18.1
18.2
Total
1.6
2.80
7.20
18.0
26.8
New Jersey
(0.43 - 44 ppt)
Ground Water
0.47
3.30
7.66
17.7
310
Surface Water
0.68
2.80
5.30
11.2
18.8
Unknown
-
-
-
-
-
Total
0.47
3.20
7.19
15.8
310
New Mexico
(Not reported)
Ground Water
4.1
4.1
4.1
4.1
4.1
Surface Water
-
-
-
-
-
Total
4.1
4.1
4.1
4.1
4.1
New York
(0.000000001-
1,790 ppt)
Ground Water
0.25
2.99
8.05
33.6
126
Surface Water
0.36
1.97
4.58
9.76
12.1
Unknown
-
-
-
-
-
Total
0.25
2.80
7.81
33.4
126
North Carolina1
(Not Reported)
Unknown
0.22
40.0
40.0
79.3
80
Total
0.22
40.0
40.0
79.3
80
North Dakota
(2020)
(Not reported)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
-
-
-
-
-
North Dakota
(2021)
(Not reported)
Ground Water
0.499
0.741
1.46
1.51
1.51
Surface Water
0.522
1.02
1.42
1.51
1.52
Total
0.499
0.741
1.51
1.52
1.52
Ohio
(5 ppt)
Ground Water
5.08
7.14
16.0
21.9
28.2
Surface Water
5.1
117
165
183
185
Total
5.08
7.39
17.3
136
185
Oregon
(40.2-49.6 ppt)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
-
-
-
-
-
Pennsylvania
(2019)
(1.9 ppt)
Ground Water
2.2
3.10
6.93
7.6
7.7
Surface Water
2
4.00
7.89
12.5
13
Total
2
3.75
7.25
12.0
13
Pennsylvania
(2021)
(1.7-4 ppt)
Ground Water
1.7
4.40
14.9
49.2
64
Surface Water
1.8
3.90
8.12
11.8
12
Total
1.7
4.15
10.4
42.6
64
South Carolina
(2.1 ppt)
Ground Water
2.1
4.00
7.45
12.1
14
Surface Water
2.1
3.10
4.23
9.50
10
Total
2.1
3.20
6.28
10.0
14
Tennessee
(Not reported)
Ground Water
-
-
-
-
-
Surface Water
-
-
-
-
-
Total
-
-
-
-
-
A-21
-------
EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water Type
Concentration Value of Detections (ppt)
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Vermont
(2 ppt)
Ground Water
2
3.17
6.18
17.8
19.2
Surface Water
2.44
2.56
3.33
3.50
3.52
Total
2
3.14
6.18
17.8
19.2
Virginia
(3.5 ppt)
Ground Water
-
-
-
-
-
Surface Water
4.2
4.80
5.44
5.58
5.6
Total
4.2
4.80
5.44
5.58
5.6
Wisconsin
(Not reported)
Ground Water
0.251
1.50
5.11
18.2
25.4
Surface Water
0.32
0.400
0.785
2.61
3.2
Total
0.251
1.30
4.73
17.6
25.4
Note: With limited exceptions, calculated concentration values (i.e., median, 90th percentile and 99th percentile
concentrations) were rounded to three significant figures for consistent presentation across the datasets and may
not indicate exact laboratory precision.
1 Only reported detections were available in this state's dataset.
2 Reported data from Maine may include results from public and private finished drinking water sources. Based on
available state data information, the EPA could not verify PWSIDs for all included samples.
Exhibit A-10: PFBS State Reported Drinking Water Occurrence Data - Summary of
Systems and Population Served by Systems with Finished Water Data
State
(Reporting
Threshold)
Source Water
Type
Total
Number
of
Systems
Systems with
Detections
Total
Population
Served by
Systems
Total Population
Served by Systems
with Detections
Number
Percent
Number
Percent
Alabama1
(Not reported)
Ground Water
-
18
-
-
203,924
-
Surface Water
-
54
-
-
2,437,360
-
Total
--
72
--
-
2,641,284
-
Arizona
(1.6-2 ppt)
Ground Water
5
2
40.00%
94,569
55,535
58.72%
Surface Water
1
0
0.00%
50,001
0
0.00%
Total
6
2
33.33%
144,570
55,535
38.41%
California
(0.002 - 90 ppt)
Ground Water
43
12
27.91%
1,098,122
647,605
58.97%
Surface Water
78
32
41.03%
13,500,188
4,468,482
33.10%
Unknown
1
0
0.00%
0
0
0.00%
Total
122
44
36.07%
14,598,310
5,116,087
35.05%
Colorado
(2013 -201 If
(2 - 90 ppt)
Distribution
(Finished)
22
9
40.91%
-
-
-
Surface water
(Finished)
5
0
0.00%
-
-
-
Total
27
9
33.33%
-
-
-
Colorado (2020)
(1.6-2.4 ppt)
Ground Water
221
35
15.84%
261,162
91,478
35.03%
Surface Water
176
18
10.23%
4,191,774
926,253
22.10%
Total
397
53
13.35%
4,452,936
1,017,731
22.86%
A-22
-------
EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water
Type
Total
Number
of
Systems
Systems with
Detections
Total
Population
Served by
Systems
Total Population
Served by Systems
with Detections
Number
Percent
Number
Percent
Georgia
(18 ppt)
Ground Water
0
0
0.00%
0
0
0.00%
Surface Water
1
0
0.00%
9,993
0
0.00%
Total
1
0
0.00%
9,993
0
0.00%
Idaho
(0.5 -1 ppt)
Ground Water
10
1
10.00%
81,985
150
0.18%
Surface Water
0
0
0.00%
0
0
0.00%
Total
10
1
10.00%
81,985
150
0.18%
Illinois
(1.7-5 ppt)
Ground Water
899
66
7.34%
2,916,219
787,544
27.01%
Surface Water
97
14
14.43%
4,628,949
823,327
17.79%
Total
996
80
8.03%
7,545,168
1,610,871
21.35%
Indiana
(2 ppt)
Ground Water
341
22
6.45%
545,838
53,136
9.73%
Surface Water
31
2
6.45%
97,448
5,050
5.18%
Total
372
24
6.45%
643,286
58,186
9.05%
Iowa
(1.7-3 ppt)
Ground Water
90
12
13.33%
491,495
107,099
21.79%
Surface Water
26
5
19.23%
987,522
338,155
34.24%
Total
116
17
14.66%
1,479,017
445,254
30.10%
Kentucky
(3.96 ppt)
Ground Water
30
4
13.33%
171,212
13,041
7.62%
Surface Water
44
6
13.64%
1,922,023
433,845
22.57%
Total
74
10
13.51%
2,093,235
446,886
21.35%
Maine (PFAS
Task Force)2 3
(1.78-90 ppt)
Ground Water
7
0
0.00%
3,995
0
0.00%
Surface Water
1
0
0.00%
21,808
0
0.00%
Unknown
10
3
30.00%
0
0
0.00%
Total
18
3
16.67%
25,803
0
0.00%
Maine
(Compliance)
(2 ppt)
Ground Water
588
65
11.05%
274,216
34,345
12.52%
Surface Water
53
1
1.89%
464,453
3,115
0.67%
Total
641
66
10.30%
738,669
37,460
5.07%
Maine
(All Systems)24
(1.78-90 ppt)
Ground Water
588
65
11.05%
274,216
34,345
12.52%
Surface Water
53
1
1.89%
464,453
3,115
0.67%
Unknown
10
3
30.00%
0
0
0.00%
Total
651
69
10.60%
738,669
37,460
5.07%
Maryland
(Phase 1)
(1 ppt)
Ground Water
30
16
53.33%
384,007
73,237
19.07%
Surface Water
36
18
50.00%
4,059,154
3,834,319
94.46%
Total
66
34
51.52%
4,443,161
3,907,556
87.95%
Maryland
(Phase 2)
(1 ppt)
Ground Water
6
2
33.33%
3,896
135
3.47%
Surface Water
0
0
0.00%
0
0
0.00%
Total
6
2
33.33%
3,896
135
3.47%
Maryland
(Phase 3)
(1 ppt)
Ground Water
63
8
12.70%
41,063
2,940
7.16%
Surface Water
0
0
0.00%
0
0
0.00%
Total
63
8
12.70%
41,063
2,940
7.16%
A-23
-------
EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water
Type
Total
Number
of
Systems
Systems with
Detections
Total
Population
Served by
Systems
Total Population
Served by Systems
with Detections
Number
Percent
Number
Percent
Maryland
(All Systems)4
(1 PPt)
Ground Water
99
26
26.26%
428,966
76,312
17.79%
Surface Water
36
18
50.00%
4,059,154
3,834,319
94.46%
Total
135
44
32.59%
4,488,120
3,910,631
87.13%
Massachusetts
(0.26 - 42 ppt)
Ground Water
1,197
308
25.73%
1,828,117
1,200,412
65.66%
Surface Water
122
59
48.36%
5,860,701
1,694,183
28.91%
Total
1,319
367
27.82%
7,688,818
2,894,595
37.65%
Michigan2
(2 PPt)
Ground Water
2,370
187
7.89%
1,945,734
500,134
25.70%
Surface Water
84
6
7.14%
1,314,601
185,162
14.09%
Unknown
54
4
7.41%
0
0
0.00%
Total
2,508
197
7.85%
3,260,335
685,296
21.02%
Minnesota
(Not reported)
Ground Water
561
60
10.7%
2,752,594
869,034
31.6%
Surface Water
16
0
0.0%
1,106,268
0
0.0%
Total
577
60
10.4%
3,858,862
869,034
22.5%
Missouri
(Not reported)
Ground Water
95
6
6.32%
190,274
9,825
5.16%
Surface Water
18
1
5.56%
405,045
1,000
0.25%
Total
113
7
6.19%
595,319
10,825
1.82%
New Hampshire
(Not reported)
Ground Water
223
87
39.01%
156,573
93,968
60.02%
Surface Water
16
4
25.00%
393,475
45,090
11.46%
Total
239
91
38.08%
550,048
139,058
25.28%
New Jersey
(0.43 - 44 ppt)
Ground Water
599
200
33.39%
1,520,763
515,709
33.91%
Surface Water
65
34
52.31%
4,783,734
3,728,587
77.94%
Unknown
1
0
0.00%
0
0
0.00%
Total
665
234
35.19%
6,304,497
4,244,296
67.32%
New Mexico2
(Not reported)
Ground Water
2
1
50.00%
-
-
-
Surface Water
0
0
0.00%
-
-
-
Total
2
1
50.00%
-
-
-
New York
(0.000000001-
1,790 ppt)
Ground Water
570
221
38.77%
1,458,927
308,051
21.11%
Surface Water
123
35
28.46%
2,850,536
792,304
27.79%
Unknown
5
0
0.00%
1,024
0
0.00%
Total
698
256
36.68%
4,310,487
1,100,355
25.53%
North Carolina12
(Not Reported)
Unknown
-
5
-
-
-
-
Total
-
5
-
-
-
-
North Dakota
(2020)
(Not reported)
Ground Water
41
0
0.00%
68,280
0
0.00%
Surface Water
9
0
0.00%
57,469
0
0.00%
Total
50
0
0.00%
125,749
0
0.00%
North Dakota
(2021)
(Not reported)
Ground Water
56
8
14.29%
113,623
69,449
61.12%
Surface Water
7
2
28.57%
194,121
5,530
2.85%
Total
63
10
15.87%
307,744
74,979
24.36%
A-24
-------
EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
State
(Reporting
Threshold)
Source Water
Type
Total
Number
of
Systems
Systems with
Detections
Total
Population
Served by
Systems
Total Population
Served by Systems
with Detections
Number
Percent
Number
Percent
North Dakota
(All Systems)4
(Not reported)
Ground Water
95
8
8.42%
181,514
69,449
38.26%
Surface Water
16
2
12.50%
251,590
5,530
2.20%
Total
111
10
9.01%
433,104
74,979
17.31%
Ohio
(5 ppt)
Ground Water
1,372
34
2.48%
2,883,252
131,013
4.54%
Surface Water
107
2
1.87%
6,215,644
7,600
0.12%
Total
1,479
36
2.43%
9,098,896
138,613
1.52%
Oregon
(40.2-49.6 ppt)
Ground Water
116
0
0.00%
114,194
0
0.00%
Surface Water
27
0
0.00%
125,239
0
0.00%
Total
143
0
0.00%
239,433
0
0.00%
Pennsylvania
(2019)
(1.9 ppt)
Ground Water
71
10
14.08%
162,825
56,541
34.73%
Surface Water
16
6
37.50%
431,370
138,966
32.22%
Total
87
16
18.39%
594,195
195,507
32.90%
Pennsylvania
(2021)
(1.7-4 ppt)
Ground Water
269
42
15.61%
471,651
161,556
34.25%
Surface Water
73
14
19.18%
4,296,097
1,300,279
30.27%
Total
342
56
16.37%
4,767,748
1,461,835
30.66%
Pennsylvania
(All Systems)4
(1.7-4 ppt)
Ground Water
270
45
16.67%
471,891
161,766
34.28%
Surface Water
73
15
20.55%
4,296,097
1,351,279
31.45%
Total
343
60
17.49%
4,767,988
1,513,045
31.73%
South Carolina
(2.1 ppt)
Ground Water
234
38
16.24%
485,992
9,485
1.95%
Surface Water
65
28
43.08%
2,489,351
1,322,343
53.12%
Total
299
66
22.07%
2,975,343
1,331,828
44.76%
Tennessee
(Not reported)
Ground Water
0
0
0.00%
0
0
0.00%
Surface Water
1
0
0.00%
2,551
0
0.00%
Total
1
0
0.00%
2,551
0
0.00%
Vermont
(2 ppt)
Ground Water
526
32
6.08%
211,357
16,254
7.69%
Surface Water
38
2
5.26%
174,473
4,598
2.64%
Total
564
34
6.03%
385,830
20,852
5.40%
Virginia
(3.5 ppt)
Ground Water
5
0
0.00%
2,975
0
0.00%
Surface Water
20
3
15.00%
4,839,373
1,433,813
29.63%
Total
25
3
12.00%
4,842,348
1,433,813
29.61%
Wisconsin
(Not reported)
Ground Water
217
66
30.41%
1,514,437
1,002,980
66.23%
Surface Water
22
15
68.18%
1,333,737
660,373
49.51%
Total
239
81
33.89%
2,848,174
1,663,353
58.40%
1 Only reported detections were available in this state's dataset.
2 There were some instances where the population served by a system could not be identified. Thus, there are
systems with detections but no associated population served by those systems with detections.
3 Reported data from Maine may include results from public and private finished drinking water sources. Based on
available state data information, the EPA could not verify PWSIDs for all included samples.
4 The "All Systems" counts represent a summary of all unique systems across multiple sampling efforts within the
state. For some states (e.g., CO), the EPA could not verify this number due to the sample site ID reporting.
A-25
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
A.2.1.3 Additional Secondary Source Water and Drinking Water Studies
Boone et al. (2019) measured 17 PFAS in both source and treated water from 25 DWTPs in the United
States. The results indicated that only five of the sampling locations demonstrated a significant
difference in PFAS concentration between the source and treated water. The median concentration of
PFBS in source water was 1.12 ng/L and 1.17 ng/L in treated water. PFBS was detected in 96 percent of
treated drinking water samples (Boone et al., 2019).
Post et al. (2013) re-evaluated PFOA, PFOS, and PFC occurrence data in drinking water systems
throughout New Jersey to update previous PFAS research in the area from 2006. PFCs were found in 70
percent of PWSs sampled at concentrations ranging from 5-174 ng/L. PFBS was detected in 10 percent
of samples at a maximum concentration of 6 ng/L.
McMahon et al. (2022) collected samples from aquifer systems in the eastern United States in 2019 to
evaluate PFAS occurrence in ground water used as a source of drinking water. The study found that 14
of the 24 analyzed PFAS were detected in ground water samples. Furthermore, at least one PFAS was
detected in 54 percent of the ground water samples and two or more PFAS were detected in 47 percent
of the ground water samples. In the public supply and domestic wells, 60 and 20 percent of the samples,
respectively, had at least one PFAS detection. Two or more PFAS were detected in 53 percent of the
public-supply wells and 10 percent of domestic wells. The six PFAS outlined in the EPA's UCMR 3
program (i.e., PFBS, PFHxS, PFOS, PFHpA, PFOA, and PFNA) were the most detected PFAS in the study's
samples. PFBS was detected in 22 percent of the 254 samples (McMahon et al., 2022).
As part of a joint study by the EPA and USGS to assess human exposure to contaminants of emerging
concern, water samples were collected from 25 DWTPs in 24 states (Glassmeyer et al., 2017).
Participation in the study was voluntary, and candidate locations were selected based on nomination by
the EPA and USGS regional personnel and DWTP self-nomination as well as consideration of high
wastewater contribution and the availability of pharmaceutical concentration data. Final sample
locations were chosen to represent a wide range of geography, diversity in disinfectant type used, and a
range of production volumes. Phase I of the study (2007) analyzed a subset of contaminants and sites to
test experimental design; PFBS was not included in Phase 1. During Phase II of the study (2010-2012),
samples were collected from ground water and surface water sources and treated drinking water from
25 DWTPs and analyzed for PFBS occurrence. The LCMRL for PFBS was equal to 0.032 ng/L. PFBS was
detected in 96 percent of the 25 source water samples and 96 percent of the 25 treated drinking water
samples. The maximum detected concentrations in source water and treated water were 11.1 ng/L and
11.9 ng/L, respectively.
Reyes (2021) conducted a ground water-quality study to describe the occurrence and distribution of
PFAS in the Columbia aquifer public water-supply wells in the Delaware Coastal Plain region in 2018.
One or more PFAS were detected in 16 of the sampled wells with as many as 8 different PFAS detected
in a single sample. PFBS was detected in 6 of the 30 public water-supply wells sampled in the study. The
maximum PFBS concentration detected was 100 ng/L.
A-26
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
A.2.2 Other Data
A.2.2.1 Department of Defense (DoD) Drinking Water Sampling
The DoD conducted sampling of off-base drinking water located in "covered areas" (i.e., areas that are
adjacent to and down gradient from a military installation) to identify potential impacts of PFAS
resulting from DoD activities. Sampling was conducted for multiple PFAS, including PFBS. The EPA
downloaded available DoD off-base sampling results in September 2023.
The EPA summarized off-base sampling results for PFBS collected "post treatment" from drinking water
systems and private wells located in covered areas adjacent to 47 installations located in 22 states.
Detected concentrations ranged from an estimated concentration of 0.18 ng/L to 476 ng/L. Sampling
was conducted utilizing multiple analytical methods including EPA methods 533, 537, 537.1, 1633, and
DoD Quality Systems Manual Table B-15 (DoD, 2023a). Results are based on DLs which vary between
both sampling sites and across different PFAS. Results for PFBS are presented Exhibit A-ll.
A-27
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EPA-OGWDW
Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
Exhibit A-11: Summary of PFBS Drinking Water Sampling Results Collected Post-Treatment from Department of
Defense Off-Base "Covered Areas"
State
Installation Name
Sampling Dates
Analysis
Method
#
Samples
#
Detections
%
Detections
Range of Detections
(ng/L)
AK
Eielson AFB
11/3/2022
537
1
0
0.00%
NA
AZ
Luke AFB
3/31/2022
QSM_B15
2
0
0.00%
NA
AZ
YUMA AZ MCAS
5/26/2023
533
1
0
0.00%
NA
AR
Little Rock AFB
5/5/2022
537
3
2
66.67%
9.9-10.2
AR
Little Rock AFB
6/16/2022 - 3/22/2023
QSM_B15
6
0
0.00%
NA
CA
Castle AFB
7/5/2022 - 4/5/2023
537
26
4
15.38%
0.331 (est) -2.41
CA
Castle AFB
11/17/2021 - 1/11/2022
QSM_B15
12
2
16.67%
1.05 (est)-1.6 (est)
CA
George AFB
3/23/2023 - 4/20/2023
1633
3
0
0.00%
NA
CA
March AFB
1/3/2023-4/10/2023
533
3
2
66.67%
6.9 -13
CA
March AFB
1/3/2022 - 12/1/2022
537.1
11
7
63.64%
4-35
CA
March AFB
9/1/2022
QSM_B15
1
1
100.00%
10
CA
Mather AFB
7/28/2022
537
1
1
100.00%
1.4 (est)
CA
Mather AFB
1/27/2022 - 4/26/2022
QSM_B15
3
0
0.00%
NA
CA
Travis AFB
1/25/2022 - 1/16/2023
QSM_B15
19
0
0.00%
NA
CO
Peterson Space Force Base
12/14/2021 -2/7/2023
537.1
8
0
0.00%
NA
CO
Peterson Space Force Base
3/1/2022 - 9/14/2022
QSM_B15
16
0
0.00%
NA
DE
Dover AFB
1/22/2022 - 10/25/2022
QSM_B15
10
0
0.00%
NA
FL
Homestead Air Reserve Base
2/21/2022 - 3/30/2023
QSM_B15
13
0
0.00%
NA
FL
WHITING FLD FL NAS
9/1/2022
537.1
2
0
0.00%
NA
IL
Scott AFB
3/22/2022 - 3/28/2023
QSM_B15
3
0
0.00%
NA
ME
Loring AFB
7/25/2022
QSM_B15
1
0
0.00%
NA
ME
NCTAMSLANT DET CUTLER
4/20/2022 - 12/6/2022
537.1
66
2
3.03%
10.4 (est) -17.2 (est)
MA
Otis ANG (Joint Base Cape Cod -
Massachusetts Military Reservation)
2/28/2022 -11/22/2022
QSM_B15
11
6
54.55%
0.33 (est)-1.7 (est)
Ml
Kl Sawyer AFB
7/13/2022
QSM_B15
2
0
0.00%
NA
MT
Great Falls International Airport
6/15/2022-7/7/2022
537
3
0
0.00%
NA
NH
Pease AFB
9/22/2021 - 3/30/2023
QSM_B15
16
7
43.75%
1.7 (est) -13
NJ
Joint Base McGuire-Dix-Lakehurst
3/3/2022 - 5/25/2022
QSM_B15
2
0
0.00%
NA
NM
Cannon AFB
11/11/2021 - 12/13/2021
QSM_B15
2
0
0.00%
NA
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April 2024
State
Installation Name
Sampling Dates
Analysis
Method
#
Samples
#
Detections
%
Detections
Range of Detections
(ng/L)
NY
Pittsburgh AFB
5/20/2022-8/10/2022
537
8
0
0.00%
NA
NY
Pittsburgh AFB
11/18/2021 -9/15/2022
537.1
16
0
0.00%
NA
NY
Pittsburgh AFB
11/29/2021 -6/27/2023
QSM_B15
15
2
13.33%
1 (est) -1 (est)
OK
Tinker AFB
2/2/2023
QSM_B15
3
0
0.00%
NA
Rl
NAVAL AUX LANDING FIELD
5/19/2022
537.1
2
0
0.00%
NA
Rl
NAVAL AUX LANDING FIELD
10/17/2022-2/28/2023
QSM_B15
31
22
70.97%
0.326 (est) -13.4
SD
Ellsworth AFB
3/14/2022
537
1
0
0.00%
NA
SD
Ellsworth AFB
6/9/2022 - 9/7/2022
537.1
2
0
0.00%
NA
SD
Ellsworth AFB
2/7/2022 - 6/23/2022
QSM_B15
36
4
11.11%
20.7 -273
TX
Goodfellow AFB
8/18/2022 - 11/15/2022
537
11
0
0.00%
NA
TX
Goodfellow AFB
12/6/2022 - 4/27/2023
QSM_B15
28
1
3.57%
476
TX
Reese AFB
9/14/2022-6/13/2023
1633
504
27
5.36%
0.52 (est)-24.8
TX
Reese AFB
9/28/2021 - 8/29/2022
QSM_B15
839
39
4.65%
2 (est)-71.3
VA
OCEANA VA NAS
10/19/2022-4/14/2023
537.1
13
0
0.00%
NA
WA
BREMERTON WA NAVBASE
10/11/2022-7/21/2023
537.1
3
2
66.67%
11 -11.3
WA
Fairchild AFB
9/19/2022-9/27/2022
537
87
2
2.30%
7 (est)-14.1
WA
Fairchild AFB
2/20/2023 - 3/6/2023
537.1
87
2
2.30%
0.18 (est)-0.2 (est)
WA
Fairchild AFB
1/31/2022-7/21/2022
QSM_B15
187
5
2.67%
3 (est)-5.5 (est)
WA
WHIDBEY IS WANAS
4/21/2022 - 4/20/2023
537.1
11
2
18.18%
9.14-12.7
Source: DOD, 2023a
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Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
A.2.3 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the ambient sources of most drinking water. Contaminant occurrence in
ambient water provides information on the potential for contaminants to adversely affect drinking
water supplies. Occurrence data for PFBS in ambient water are available from the USGS NWIS database
and the EPA's legacy STORET data available through the WQP.
A.2.3.1 National Water Information System (NWIS) Data
The NWIS is the Nation's principal repository of water resources data USGS collects from more than 1.9
million sites (USGS, 2023). NWIS-Web is the general online interface to the USGS NWIS database.
Discrete water-sample and time-series data are available from sites in all 50 States, including 5 million
water samples with 90 million water-quality results. All USGS water quality and flow data are stored in
NWIS, including site characteristics, streamflow, ground water level, precipitation, and chemical
analyses of water, sediment, and biological media, though not all parameters are available for every site.
NWIS houses the NAWQA data and includes other USGS data from unspecified projects. NWIS contains
many more samples at many more sites than the NAWQA Program. Although NWIS is comprised of
primarily ambient water data, some finished drinking water data are included as well. This section
presents analyses of non-NAWQA data in NWIS, downloaded from the WQP in November 2023 (WQP,
2023).
The results of the non-NAWQA NWIS PFBS analysis are presented in Exhibit A-12. NWIS data for PFBS
were listed under the characteristic name of "Perfluorobutanesulfonate." PFBS was detected in
approximately 47 percent of samples (1,385 out of 2,952 samples) and at approximately 38 percent of
sites (676 out of 1,759 sites). The median concentration based on detections was equal to 3.60 ng/L.
(Note that the NWIS data are presented as downloaded; potential outliers were not evaluated or
excluded from the analysis.)
Exhibit A-12: PFBS NWIS Data
Site Type
Detection Frequency
(detections are results > reporting level)
Concentration Values
(of detections, in ng/L)
No. of
Samples
No. of
Samples
with
Detections
No.
of
Sites
No. of
Sites with
Detections
Minimum
Median
90th
Percentile
99th
Percentile
Maximum
Ground
Water
1,344
321
1,233
315
0
2.50
10.0
64.4
370
Surface
Water
1,608
1,064
526
361
0
3.82
12.0
87.1
460
All Sites
2,952
1,385
1,759
676
0
3.60
12.0
86.8
460
Source: WQP, 2023
A.2.3.2 Storage and Retrieval (STORET) Data / Water Quality Portal (WQP)
From its launch in 1999 until it was decommissioned in June 2018, the EPA's STORET Data Warehouse
was collaboratively populated with raw biological, chemical, and physical data from surface water and
ground water sampling by federal, state and local agencies, Native American tribes, volunteer groups,
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Technical Support Document for PFAS Occurrence and Contaminant Background
April 2024
academics, and others. Legacy STORET data are accessible through the WQP:
https://www.waterqualitvdata.us/portal/.
STORET data are from monitoring locations in all 50 states as well as multiple territories and jurisdictions
of the United States. Most data are from ambient waters, but in some cases finished drinking water data
are included as well. STORET's data quality limitations include variations in the extent of national
coverage and data completeness from parameter to parameter. Data may have been collected as part of
targeted, rather than randomized, monitoring.
This section presents analyses of STORET data, downloaded from the WQP in November 2023 (WQP,
2023). The EPA reviewed STORET ground water data from wells and surface water data from lakes,
rivers/streams, and reservoirs (WQP, 2023). STORET data for PFBS were listed under the characteristic
name of "1-Butanesulfonic acid, 1,1,2,2,3,3,4,4,4-nonafluoro-, potassium salt (1:1)",
"Perfluorobutanesulfonate", and "Perfluorobutanesulfonic acid." The results of the STORET analysis for
PFBS are presented in Exhibit A-13 and Exhibit A-14. Nearly 900 PFBS samples were available for
analysis. These PFBS samples were collected between 2006 and 2023. Of the 628 sites sampled,
approximately 76 percent reported detections of PFBS. Detected concentrations ranged from 0 to 68
ng/L. (Note: A minimum value of zero could represent a detection that was entered into the database as
a non-numerical value (e.g., "Present").)
Exhibit A-13: PFBS STORET Data - Summary of Detected Concentrations
Source Water Type
Concentration Value of Detections (ng/L)
Minimum1
Median
90th Percentile
Maximum
Ground Water
0
0
0
50
Surface Water
0.93
2.05
61.2
68
Unknown
0
0
2.09
4.25
Total
0
0
0
68
Source: WQP, 2023
1A minimum value of zero may represent a detection that was entered into the database as a non-numerical value
(e.g., "Present").
Exhibit A-14: PFBS STORET Data - Summary of Samples and Sites
Source Water
Type
Total
Number of
Samples
Samples with
Detections
Total
Number
of Sites
Sites with Detections
Number
Percent
Number
Percent
Ground Water
729
654
89.71%
495
450
90.91%
Surface Water
88
16
18.18%
73
11
15.07%
Unknown
76
21
27.63%
60
16
26.67%
Total
893
691
77.38%
628
477
75.96%
Source: WQP, 2023
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April 2024
A.3 Analytical Methods
The EPA has published two analytical methods that are available for the analysis of PFBS and other PFAS
in drinking water. The performance metrics that are presented, including the DL, LCMRL, mean
recoveries and RSDs are specific to PFBS for each of the listed analytical methods. Ranges of mean
recoveries and RSDs are presented for the matrices listed; data from holding time studies are not
included since these studies are designed to demonstrate a degradation in method performance over
time and thus are not indicative of method performance that should be observed when holding times
are not exceeded:
• EPA Method 537.1, Version 2.0, Determination of Selected Per- and Polyfluorinated Alkyl
Substances in Drinking Water by Solid Phase Extraction and Liquid Chromatography/Tandem
Mass Spectrometry (LC/MS/MS). The DL and LCMRL generated by the laboratory that
developed the method are 1.8 ng/L and 6.3 ng/L, respectively. Mean recoveries in fortified
reagent water, tap water from a ground water source (TOC = 0.53 mg/L and hardness = 377
mg/L), tap water from a surface water source (TOC = 2.4 mg/L and hardness = 103 mg/L),
and tap water from a private well (TOC = 0.56 mg/L and hardness = 394 mg/L) range from
85.1 to 104%, with RSDs of 2.1 to 7.1% (USEPA, 2020d).
• EPA Method 533, Determination of Per- and Polyfluoroalkyl Substances in Drinking Water by
Isotope Dilution Anion Exchange Solid Phase Extraction and Liquid Chromatography /
Tandem Mass Spectrometry. The LCMRL generated by the laboratory that developed the
method is 3.5 ng/L (DLs were not calculated). Mean recoveries (excluding 13C isotope
analogue data) in fortified reagent water, finished drinking water from a ground water
source (hardness = 320 mg/L, pH = 7.88 at 17° C, free Cl2 = 0.64 mg/L, and total Cl2 = 0.74
mg/L) and clarified surface water (prior to GAC treatment and chlorinated in the laboratory;
pH = 8.1 at 20 °C, free Cl2 = 0.98 mg/L, total Cl2 = 1.31 mg/L. and TOC = 3.8 mg/L) range from
96.2 to 111%, with RSDs of 2.7 to 17% (USEPA, 2019b).
Laboratories participating in UCMR 3 were required to use EPA Method 537 and were required to report
PFBS values at or above the EPA-defined MRL of 90 ng/L (77 FR 26072; USEPA, 2012b). The MRL was set
based on the capability of multiple laboratories at the time. The EPA Method 537.1 was originally
published in November 2018 as Version 1.0 as a more sensitive update to EPA Method 537 (with a
slightly expanded target analyte list). Version 2.0 was published in March 2020 and contains minor
editorial changes to Version 1.0. Use of EPA Method 537.1 is preferable to use of EPA Method 537 (it
may not be feasible to reliably quantitate down to health levels of concern for certain PFAS when using
EPA Method 537).
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