Health Effects Support 

Document for 

Perfluorooctane Sulfonate 

(PFOS) 

United States 

Environmental Protection 

Agency 

Office of Water

Mail Code 4304T

EPA 822-R-16-002

May 2016

Perfluorooctane sulfonate (PFOS) –May 2016 i 
Health Effects Support Document

for

Perfluorooctane Sulfonate (PFOS)

U.S. Environmental Protection Agency 

Office of Water (4304T)

Health and Ecological Criteria Division

Washington, DC 20460 

http://www.epa.gov/dwstandardsregulations/drinking-water-contaminant-human-health-effectsinformation. 

EPA Document Number: 822-R-16-002

May 2016 

Perfluorooctane sulfonate (PFOS) –May 2016 ii
BACKGROUND

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

the U.S. Environmental Protection Agency (EPA) to establish a list of unregulated 

microbiological and chemical contaminants known or anticipated to occur in public water 

systems and that might require control in the future through national primary drinking water 

regulations. The SDWA also requires the Agency to make regulatory determinations on at least 

five contaminants on the Contaminant Candidate List (CCL) every 5 years. For each contaminant 

on the CCL, before EPA makes a regulatory determination, the Agency needs to obtain sufficient 

data to conduct analyses on the extent to which the contaminant occurs and the risk it poses to 

populations via drinking water. Ultimately, this information will assist the Agency in 

determining the most appropriate course of action in relation to the contaminant (e.g., developing 

a regulation to control it in drinking water, developing guidance, or deciding not to regulate it). 

The PFOS health assessment was initiated by the Office of Water, Office of Science and 

Technology in 2009. The draft Health Effects Support Document for Perfluorooctane Sulfonate 

Acid (PFOS) was completed in 2013 and released for public comment in February 2014. An 

external peer-review panel meeting was held on August 21 and 22, 2014. The final document 

reflects input from the panel as well as public comments received on the draft document. Both 

the peer-reviewed draft and this document include only the sections of a health effects support 

document (HESD) that cover the toxicokinetics and health effects of PFOS. If a decision is made 

to regulate the contaminant, this document will be expanded. 

One of the challenges inherent in conducting this assessment was the wealth of experimental 

data published before and during its development. This section provides a synopsis of the 

approach used in identifying and selecting the publications reflected in the final assessment. 

Data were identified through the following:

Monthly/bimonthly literature searches conducted by EPA library staff (2009–2015) and New 

Jersey Department of Environmental Protection library staff (2012–2015). 

• Papers identified by EPA internal and external peer reviewers.

• Papers identified through public comments on the draft assessments.

• Papers submitted to EPA by the public. 

In mid-2013, the EPA library searches were expanded to cover other members of the 

perfluorocarboxylic acids (C-4 to C-12) and sulfonate families (C-4, C-6, C-8). Appendix A 

describes the literature search strategy used by the libraries. Through the literature search, 

documents were identified for retrieval, review, and inclusion in the HESD using the following 

criteria:

• The study examines a toxicity endpoint or population not examined by studies already 

included in the draft document. 

• Aspects of the study design such as the size of the population exposed or quantification 

approach make it superior to key studies already included in the draft document. 

• The data contribute substantially to the weight of evidence for any of the toxicity 

endpoints covered by the draft document. 

• Elements of the study design merit its inclusion in the draft document based on its 

contribution to the mode of action or the quantification approach. 

Perfluorooctane sulfonate (PFOS) –May 2016 iii
• The study elucidates the mode of action for any toxicity endpoint or toxicokinetic 

property associated with PFOS exposure. 

• The effects observed differ from those in other studies with comparable protocols.

In addition to each publication being evaluated against the criteria above, the relevance of the 

study to drinking water exposures and to the U.S. population also were considered.

The studies included in the final draft were determined to provide the most current and 

comprehensive description of the toxicological properties of PFOS and the risk it poses to 

humans exposed to it in their drinking water. Appendix B summarizes the studies evaluated for 

inclusion in the HESD following the August 2014 peer review and identifies those selected for 

inclusion in the final assessment. Appendix B includes epidemiology data that provide a highlevel summary of the outcomes across the studies evaluated.

Development of the hazard identification and dose-response assessment for PFOS has 

followed the general guidelines for risk assessment forth by the National Research Council 

(1983) and EPA’s Framework for Human Health Risk Assessment to Inform Decision Making 

(USEPA 2014a). Other EPA guidelines used in the development of this assessment include the 

following: 

• Guidelines for the Health Risk Assessment of Chemical Mixtures (USEPA 1986a) 

• Guidelines for Mutagenicity Risk Assessment (USEPA 1986b) 

• Recommendations for and Documentation of Biological Values for Use in Risk 

Assessment (USEPA 1988)

• Guidelines for Developmental Toxicity Risk Assessment (USEPA 1991) 

• Interim Policy for Particle Size and Limit Concentration Issues in Inhalation Toxicity 

Studies (USEPA 1994a) 

• Methods for Derivation of Inhalation Reference Concentrations and Application of 

Inhalation Dosimetry (USEPA 1994b) 

• Use of the Benchmark Dose Approach in Health Risk Assessment (USEPA 1995) 

• Guidelines for Reproductive Toxicity Risk Assessment (USEPA 1996) 

• Guidelines for Neurotoxicity Risk Assessment (USEPA 1998) 

• Science Policy Council Handbook: Peer Review (2nd edition) (USEPA 2000a) 

• Supplemental Guidance for Conducting Health Risk Assessment of Chemical Mixtures 

(USEPA 2000b) 

• A Review of the Reference Dose and Reference Concentration Processes (USEPA 2002)

• Guidelines for Carcinogen Risk Assessment (USEPA 2005a) 

• Supplemental Guidance for Assessing Susceptibility from Early-Life Exposure to 

Carcinogens (USEPA 2005b) 

• Science Policy Council Handbook: Peer Review (USEPA 2006a)

• A Framework for Assessing Health Risks of Environmental Exposures to Children 

(USEPA 2006b) 

• Highlights of the Exposure Factors Handbook (USEPA 2011)

• Benchmark Dose Technical Guidance Document (USEPA 2012)

• Child-Specific Exposure Scenarios Examples (USEPA 2014b) 

Perfluorooctane sulfonate (PFOS) –May 2016 iv
AUTHORS, CONTRIBUTORS, AND REVIEWERS

Joyce Morrissey Donohue, Ph.D. (Chemical Manager) 

Office of Water

U.S. Environmental Protection Agency, Washington, D.C.

Amal Mahfouz, Ph.D. (Chemical Manager, pre-retirement). 

Office of Water

U.S. Environmental Protection Agency, Washington, D.C.

Tina Moore Duke, M.S. (previously with Office of Water, U.S. Environmental Protection 

Agency) 

John Wambaugh, Ph.D. 

Office of Research and Development 

U.S. Environmental Protection Agency, Research Triangle Park, NC 

The following contractor authors supported the development of this document:

Dana F. Glass-Mattie, D.V.M. 

Environmental Sciences Division

Oak Ridge National Laboratory, Oak Ridge, TN

Carol S. Wood, Ph.D., D.A.B.T. 

Environmental Sciences Division

Oak Ridge National Laboratory, Oak Ridge, TN 

This document was prepared under the U.S. EPA Contract No. DW-8992342701, Work 

Assignment No. 2011-001 with Oak Ridge National Laboratory. The Lead U.S. EPA Scientist is 

Joyce Morrissey Donohue, Ph.D., Health and Ecological Criteria Division, Office of Science and 

Technology, Office of Water. 

The Oak Ridge National Laboratory is managed and operated by UT-Battelle, LLC., for the 

U.S. Department of Energy under Contract No. DE-AC05-00OR22725. 

CONTRIBUTORS AND REVIEWERS

Internal Contributors and Reviewers

Office of Water, U.S. Environmental Protection Agency 

Elizabeth Doyle, Ph.D. (retired) 

Edward Hackett

Office of Research and Development, U.S. Environmental Protection Agency 

Glinda Cooper, Ph.D. 

Barbara Glenn, Ph.D. 

Erin Hines, Ph.D.

Christopher Lau, Ph.D.

Matthew Lorber, Ph.D. 

Jaqueline Moya 

Linda Phillips, Ph.D. 

Perfluorooctane sulfonate (PFOS) –May 2016 v 
Paul White, Ph.D. 

Michael Wright, Sc.D. 

Office of Chemical Safety and Pollution Prevention, U.S. Environmental Protection Agency 

E. Laurence Libelo

Andrea Pfehales-Hutchens, Ph.D. 

Tracy Williamson

David Lai, Ph.D. (retired) 

Jennifer Seed, Ph.D. (retired) 

Office of Children’s Health Protection, U.S. Environmental Protection Agency 

Gregory Miller 

Office of Land and Emergency Management, U.S. Environmental Protection Agency 

External Reviewers

James Bruckner, Ph.D. 

Department of Pharmacology and Toxicology 

University of Georgia, Athens, GA 

Deborah Cory-Slechta, Ph.D.

Department of Environmental Medicine

University of Rochester Medical Center, Rochester, NY

Jamie DeWitt, Ph.D. 

Pharmacology and Toxicology 

East Carolina University, Greenville, NC

Jeffrey Fisher, Ph.D. 

Biochemical Toxicology, National Center for Toxicological Research

U.S. Food and Drug Administration, Jefferson, AK 

William Hayton, Ph.D. 

College of Pharmacy (Emeritus)

The Ohio State University, Columbus, OH 

Matthew Longnecker, M.D., Sc.D. 

Biomarker-based Epidemiology Group 

National Institute of Environmental Health Sciences, Research Triangle Park, NC

Angela Slitt, Ph.D. 

Biomedical and Pharmaceutical Sciences

University of Rhode Island, Kingston, RI 

Perfluorooctane sulfonate (PFOS) –May 2016 vi
CONTENTS

BACKGROUND ........................................................................................................................... iii

ABBREVIATIONS AND ACRONYMS .................................................................................... xiii

EXECUTIVE SUMMARY .......................................................................................................ES-1

1. IDENTITY: CHEMICAL AND PHYSICAL PROPERTIES .............................................. 1-1

2. TOXICOKINETICS ............................................................................................................. 2-1

2.1 Absorption.................................................................................................................... 2-1

2.1.1 Oral Exposure ........................................................................................................ 2-1

2.1.2 Inhalation Exposure ............................................................................................... 2-2

2.1.3 Dermal Exposure ................................................................................................... 2-2

2.2 Distribution .................................................................................................................. 2-2

2.2.1 Oral Exposure ........................................................................................................ 2-4

2.2.2 Inhalation and Dermal Exposure ......................................................................... 2-15

2.2.3 Other Routes of Exposure .................................................................................... 2-15

2.3 Metabolism ................................................................................................................ 2-16

2.4 Excretion .................................................................................................................... 2-17

2.4.1 Oral Exposure ...................................................................................................... 2-17

2.4.2 Inhalation Exposure ............................................................................................. 2-19

2.5 Pharmacokinetic Considerations ................................................................................ 2-20

2.5.1 Pharmacokinetic models ...................................................................................... 2-20

2.5.2 Half-life data ........................................................................................................ 2-30

2.5.3 Volume of Distribution Data ............................................................................... 2-34

2.6 Toxicokinetic Summary ............................................................................................. 2-36

3. HAZARD IDENTIFICATION ............................................................................................ 3-1

3.1 Human Effects ............................................................................................................. 3-1

3.1.1 Long-Term Noncancer Epidemiological Studies ................................................... 3-2

3.1.1.1 Serum Lipids and Cardiovascular Diseases ...................................................... 3-2

3.1.1.2 Liver Enzymes and Liver Disease .................................................................. 3-10

3.1.1.3 Biomarkers of Kidney Function and Kidney Disease ..................................... 3-11

3.1.1.4 Reproductive Hormones and Reproductive/Developmental Studies .............. 3-13

3.1.1.5 Thyroid Effect Studies .................................................................................... 3-30

3.1.1.6 Immunotoxicity ............................................................................................... 3-36

3.1.1.7 Other Effects ................................................................................................... 3-41

3.1.1.8 Summary and conclusions from the human epidemiology studies ................. 3-41

3.1.2 Carcinogenicity Studies ....................................................................................... 3-44

3.1.2.1 Summary and Conclusions from the Human Cancer Epidemiology Studies ... 3-49

3.2 Animal Studies ........................................................................................................... 3-49

3.2.1 Acute Toxicity ..................................................................................................... 3-50

3.2.2 Short-Term Studies .............................................................................................. 3-51

3.2.3 Subchronic Studies............................................................................................... 3-56

3.2.4 Neurotoxicity ....................................................................................................... 3-60

Perfluorooctane sulfonate (PFOS) –May 2016 vii
3.2.5 Developmental/Reproductive Toxicity ................................................................ 3-62

3.2.6 Specialized Developmental/Reproductive Studies .............................................. 3-73

3.2.7 Chronic Toxicity .................................................................................................. 3-78

3.2.8 Carcinogenicity .................................................................................................... 3-79

3.3 Other Key Data .......................................................................................................... 3-81

3.3.1 Mutagenicity and Genotoxicity ............................................................................ 3-81

3.3.2 Protein binding ..................................................................................................... 3-82

3.3.3 Immunotoxicity .................................................................................................... 3-83

3.3.4 Physiological or Mechanistic Studies of Noncancer Effects ............................... 3-89

3.3.5 Structure-Activity Relationship ......................................................................... 3-102

3.3.6 ToxCast Assays .................................................................................................. 3-102

3.4 Hazard Characterization ........................................................................................... 3-104

3.4.1 Synthesis and Evaluation of Major Noncancer Effects ..................................... 3-104

3.4.1.1 Liver Effects, Cholesterol, and Uric Acid .................................................... 3-104

3.4.1.2 Developmental/Reproductive Toxicity ......................................................... 3-107

3.4.1.3 Immunotoxicity ............................................................................................. 3-109

3.4.1.4 Neurotoxicity ................................................................................................ 3-110

3.4.1.5 Thyroid Effects ............................................................................................. 3-111

3.4.2 Synthesis and Evaluation of Carcinogenic Effects ............................................ 3-113

3.4.3 Mode of Action and Implications in Cancer Assessment .................................. 3-114

3.4.4 Weight of Evidence Evaluation for Carcinogenicity ......................................... 3-114

3.4.5 Potentially Sensitive Populations ....................................................................... 3-115

4. DOSE-RESPONSE ASSESSMENT .................................................................................... 4-1

4.1 Dose-Response for Noncancer Effects ........................................................................ 4-1

4.1.1 RfD Determination ................................................................................................. 4-1

4.1.1.1 Pharmacokinetic Model .................................................................................... 4-7

4.1.1.2 RfD Quantification .......................................................................................... 4-14

4.1.2 RfC Determination ............................................................................................... 4-17

4.2 Dose-Response for Cancer Effects ............................................................................ 4-17

5. REFERENCES ..................................................................................................................... 5-1

Appendix A: Literature Search Strategy Developing the Search ............................................... A-1

Appendix B: Studies Evaluated Since August 2014 ....................................................................B-1

Appendix C: Summary of Data ....................................................................................................C-1

Perfluorooctane sulfonate (PFOS) –May 2016 viii
TABLES

Table 1-1. Chemical and Physical Properties of PFOS ............................................................... 1-2

Table 2-1. Mean % (± SE) of 14C-K+PFOS in Rats After a Single Dose of 4.2 mg/kg .............. 2-2

Table 2-2. Percent (%) Binding of PFOS to Human Plasma Protein Fractions .......................... 2-2

Table 2-3. Average PFOS Level (μg/mL or ppm) in Serum Of Monkeys .................................. 2-6

Table 2-4. Levels of PFOS in Serum and Bile of Rats Treated for 5 Days ................................. 2-7

Table 2-5. Mean (± SD) Daily PFOS Consumption and Tissue Residue Levels in Rats 

Treated for 28 Days ................................................................................................... 2-7

Table 2-6. Concentrations of PFOS in Male Rats’ Whole Blood (μg/mL) and Various 

Tissues (μg/g) After 28 Days ..................................................................................... 2-8

Table 2-7. PFOS Levels in the Serum and Liver of Rats ............................................................. 2-8

Table 2-8. Mean Concentration of PFOS (± SD) in Various Tissues of Mice ............................ 2-9

Table 2-9. Levels of PFOS (Means ± SE) in Mouse Serum Following Treatment for 10 

Days ......................................................................................................................... 2-10

Table 2-10. PFOS Concentrations (Mean ± Standard Deviation [SD]) in Samples from 

Pregnant Dams and Fetuses (GD 21 only) in μg/mL (ppm) for Serum and Urine 

and μg/g for Liver and Feces ................................................................................... 2-11

Table 2-11. Mean PFOS (± Standard Error) Concentrations in Serum, Liver, snd Brain 

Tissue in Dams and Offspring ................................................................................. 2-12

Table 2-12. PFOS Contents in Serum, Hippocampus, and Cortex of Offspring (n = 6) ........... 2-13

Table 2-13. Mean PFOS Content in Serum and Lungs of Rat Offspring (n = 6) ...................... 2-14

Table 2-14. Ratios (Means ± SD) Between the Concentrations Of 35S-Labeled PFOS in 

Various Organs and Blood of Mouse Dams, Fetuses, and Pups Versus the 

Average Concentration in Maternal Blood .............................................................. 2-14

Table 2-15. Percent Distribution (%) of PFOS in Mice After a 50 mg/kg Subcutaneous 

Injection ................................................................................................................... 2-16

Table 2-16. Pharmacokinetic Parameters from Wambaugh et al. (2013) Meta-Analysis of 

Literature Data ......................................................................................................... 2-30

Table 2-17. PFOS Pharmacokinetic Data Summary for Monkeys ............................................ 2-32

Table 2-18. PFOS Pharmacokinetic Data Summary for Rats .................................................... 2-33

Table 2-19. PFOS Pharmacokinetic Data Summary for Mice ................................................... 2-33

Table 2-20. Summary of Half-Life Data .................................................................................... 2-34

Table 3-1. Association of Serum PFOS with Serum Lipids ........................................................ 3-6

Table 3-2. Summary of Epidemiology Studies of PFOS and Liver Enzymes ........................... 3-10

Table 3-3. Summary of Epidemiology Studies of PFOS and Measures of Kidney Function ... 3-12

Table 3-4. Summary of Epidemiology Studies of PFOS and Pregnancy Outcomes ................. 3-14

Table 3-5. Summary of Epidemiology Studies of PFOS and Fetal Growth .............................. 3-16

Perfluorooctane sulfonate (PFOS) –May 2016 ix
Table 3-6. Summary of Epidemiology Studies of PFOS and Thyroid Effects .......................... 3-34

Table 3-7. Summary of Epidemiology Studies of PFOS and Immune Suppression 

(Infectious Disease and Vaccine Response) ............................................................ 3-38

Table 3-8. Summary of PFOS Epidemiology Studies of Cancer ............................................... 3-47

Table 3-9. Mean (± SD) Values for Select Parameters in Rats Treated for 4 Weeks ................ 3-52

Table 3-10. Mean (± SD) Values for Select Parameters in Rats Treated for 28 Days .............. 3-53

Table 3-11. Mean (± SD) Values for Select Parameters in Monkeys Treated for 182 Days ..... 3-58

Table 3-12. Mean (± SD) Values for Select Parameters in Rats Treated for 14 Weeks ............ 3-60

Table 3-13. Fertility and Litter Observations in Dams Administered 0 to 2.0 mg 

PFOS/kg/day ............................................................................................................ 3-66

Table 3-14. Effects Observed in the Mice Administered PFOS from GD 0 to GD 17/18 ........ 3-72

Table 3-15. Incidence of Nonneoplastic Liver Lesions in Rats (Number Affected/Total 

Number) ................................................................................................................... 3-79

Table 3-16. Tumor Incidence (%) .............................................................................................. 3-80

Table 3-17. Genotoxicity of PFOS in vitro ................................................................................ 3-82

Table 3-18. Genotoxicity of PFOS in vivo ................................................................................. 3-82

Table 3-19. Summary of SRBC and NK Cell Findings in Mice after PFOS Exposure ............ 3-89

Table 3-20. Thyroid Hormone Levels in PFOS Treated Rats ................................................... 3-91

Table 3-21. Summary of PFAS Transactivation of Mouse and Human PPARα, β/δ, and γ ..... 3-94

Table 4-1. NOAEL/LOAEL and Effects for Longer-Term Duration Studies of PFOS .............. 4-4

Table 4-2. NOAEL/LOAEL Data for Short-Term Oral Studies of PFOS ................................... 4-6

Table 4-3. Predicted Final Serum Concentration and Time Integrated Serum Concentration 

(AUC) for Different Treatments of Rat ..................................................................... 4-9

Table 4-4. Predicted Final Serum Concentration and Time Integrated Serum Concentration 

(AUC) for the Mouse ................................................................................................. 4-9

Table 4-5. Predicted Final Serum Concentration and Time Integrated Serum Concentration 

(AUC) for the Monkey ............................................................................................. 4-10

Table 4-6. Average serum Concentrations for the Duration of Dosing ..................................... 4-10

Table 4-7. Comparison of Average Serum Concentration and Steady-State Concentration ..... 4-12

Table 4-8. Human Equivalent Doses Derived from the Modeled Animal Average 

Serum Values ........................................................................................................... 4-14

Table 4-9. POD Outcomes for the HEDs from the Pharmacokinetic Model Average Serum 

Values ...................................................................................................................... 4-15

Table B-1. PFOS Epi Papers—Post Peer Review (Retrieved and Reviewed) ............................B-1

Table B-2. PFOA Post Peer Review Animal Toxicity Studies ....................................................B-3

Table B-3. Toxicokinetics: Post Peer Review .............................................................................B-5

Perfluorooctane sulfonate (PFOS) –May 2016 x 
Table B-4. Association of Serum PFOS with Serum Lipids and Uric Acid ................................B-6

Table B-5. Association of Serum PFOS with Reproductive and Developmental Outcomes ......B-8

Table B-6. Association of PFOS Level with the Prevalence of Thyroid Disease and Thyroid 

Hormone Levels .......................................................................................................B-11

Table B-7. Association of Serum PFOS with Markers of Immunotoxicity ...............................B-12

Table C-1. PFOS Toxicokinetic Information ...............................................................................C-2

Table C-2. Summary of Animal Studies with Exposure to PFOS ...............................................C-7

Perfluorooctane sulfonate (PFOS) –May 2016 xi
FIGURES

Figure 1-1. Chemical Structure of PFOS ..................................................................................... 1-1

Figure 2-1. Distribution of Radiolabeled PFOS in Dams and in Fetuses/Pups in the 

Liver, Lung, Kidney, and Brain (Figure from Borg et al. 2010) ............................. 2-15

Figure 2-2. PFOS Contents in Urine, Feces, and Overall Excretion in Male Rats Treated 

for 28 Days ............................................................................................................... 2-19

Figure 2-3. Schematic for a Physiologically-Motivated Renal Resorption Pharmacokinetic 

Model ....................................................................................................................... 2-21

Figure 2-4. Structure of Model for PFOS in Rats and Monkeys ............................................... 2-22

Figure 2-5. Structure of the PFOS PBPK Model in Monkeys and Humans .............................. 2-22

Figure 2-6. Structure of the PBPK Model for PFOS in the Adult Sprague-Dawley Rat ........... 2-25

Figure 2-7. Predicted Daily Average Concentration of PFOS in Maternal (Black Line) and 

Fetal (Gray Line) Plasma at External Doses to the Dam ......................................... 2-26

Figure 2-8. PBPK Model Structure for Simulating PFOA and PFOS Exposure During 

Pregnancy in Humans (Maternal, Left; Fetal, Right) .............................................. 2-27

Figure 3-1. Functional Categories of Genes Modified by PFOS in Wild-Type and Null 

Mice ......................................................................................................................... 3-98

Figure 3-2. Function Distribution and Category Enrichment Analysis of the Differential 

Proteins .................................................................................................................... 3-99

Perfluorooctane sulfonate (PFOS) –May 2016 xii
ABBREVIATIONS AND ACRONYMS

ACh acetylcholine

ADHD attention deficit hyperactivity disorder

ALP alkaline phosphatase

ALT alanine transaminase

ANOVA analysis of variance

AP activation protein

AST aspartate aminotransferase

AUC area under the curve 

BMD benchmark dose 

BMDL benchmark dose – lower 95th percentile confidence bound 

BMI body mass index 

BUN blood urea nitrogen 

°C degrees Celsius

CAR constitutive androstane receptor

CAS Chemical Abstracts Service

CASRN Chemical Abstracts Service Registry Number

CCL Chemical Contaminants List

CD circular dichroism

CFSE 6-carboxyfluorescein succinimidyl ester 

CHMS Canadian Health Measures Survey

CI confidence interval

CL clearance

CoA coenzyme A

Conc. Concentration 

Css Steady-state concentration

CSF cerebrospinal fluid

CSM cholestyramine 

Cte acyl CoA thioesterase

d day 

DA dansylamide 

DAUDA 11-(5-dimethylaminoapthalenesulphonyl)-undecanoic acid 

DCDQ Developmental Coordination Disorder Questionnaire

DIO1 type 1 deiodinase 

DIO3 type 3 deiodinase 

dL deciliter

DMEM Dulbecco’s Minimal Essential Medium

DMSO dimethyl sulfoxide 

DNA deoxyribonucleic acid 

DNBC Danish National Birth Cohort 

DP dansyl-L-proline 

DR dose rate

E estradiol

EAA excitatory amino acid

EC50 half maximal effective concentration

ECF Electro-Chemical Fluorination

ED equilibrium dialysis

Perfluorooctane sulfonate (PFOS) –May 2016 xiii
eGFR estimated glomerular filtration rate

EMM Estimated Marginal Mean

EPA U.S. Environmental Protection Agency 

FABP fatty acid binding proteins 

FAI free androgen index 

FR fecundability ratio 

FSH Follicle-stimulating hormone 

FT free testosterone

FT3 free triiodothyronine 

FT4 free thyroxin 

g gram 

GABA gamma-aminobutyric acid 

GAP-43 growth-associated protein-43 

GD gestation day 

GFAP glial fibrillary acidic protein

GFR glomerular filtration rate

GGT gamma-glutamyl transpeptidase 

GI gastrointestinal

GJIC gap junction intercellular communication 

GLP good laboratory practice 

Glu glutamate

GS glutamine synthetase 

HDL high density lipoprotein

HED human equivalent dose 

HESD Health Effects Support Document 

HL-60 human promyelocytic leukemia cell line 

HMG-CoA 3-hydroxy-3-methylglutaryl coenzyme A 

HOMA homeostatic model assessment

HPT hypothalamic-pituitary-thyroid 

HPLC/MS/MS High-performance liquid chromatography/tandem mass spectrometry

h hour 

HSDB Hazardous Substances Database

HSI hepatosomatic index 

ICa inward calcium currents

IC50 half-maximal Inhibiting Concentration

ICR imprinting control region

IgE Immunoglobulin E 

IL interleukin

INUENDO Biopersistent Organochlorines in Diet and Human Fertility study 

IQR interquartile range

IRR incidence rate ratio

IU international unit 

IV intravenous 

Kow octanol-water partition coefficient

Kt affinity constant 

kg kilogram 

KO knockout 

L liter

LBW low birth weight 

Perfluorooctane sulfonate (PFOS) –May 2016 xiv
LC50 Lethal concentration for 50% (statistical median) of animals

LC/MS/MS liquid chromatography/tandem mass spectrometry

LD lactation day

LD50 Lethal dose for 50% (statistical median) of animals

LDL low density lipoprotein

L-FABP liver fatty acid binding protein

LI labeling index 

LIFE Longitudinal Investigation of Fertility and the Environment 

LLOQ lower limit of quantitation 

LOAEL lowest observed adverse effect level

LOEC lowest observed effect concentration

LOQ Limit of quantitation

LPS Lipopolysaccharide 

m meter

MDA malondialdehyde 

ME malic enzyme

μg microgram

mg milligram

min minute 

mL milliliter

mmol millimole

μmol micromole

MOA mode of action 

mol mole

MRP multidrug resistance-associated protein

NA not applicable 

NCEH1 Neutral Cholesterol Ester Hydrolase 1

ND not detected or not determined 

ng nanogram 

NHANES National Health and Nutrition Examination Survey 

NIS sodium iodide symporter 

NJDEP New Jersey Department of Environmental Protection 

NK natural killer

nmol nanomole 

NMRI Naval Medical Research Institute

NOAEL no observed adverse effect level

NOEC no observed effect concentration 

NR1H3 Nuclear Receptor Subfamily 1, Group H, Member 3 

NS no sample 

NSP newborn screening program 

NT not tested

OAT organic anion transporter

OATp organic anion transporting peptide 

OR odds ratio 

p probability 

PB phenobarbital 

PBDE polybrominated diphenyl ether 

PBMC peripheral blood mononuclear cells 

PBPK physiologically-based pharmacokinetic

Perfluorooctane sulfonate (PFOS) –May 2016 xv
PCB polychlorinated biphenyl 

PCNA proliferating cell nuclear antigen

PCoAO palmitoyl CoA oxidase 

PFAS perfluoroalkyl substance

PFBA perfluorobutyric acid 

PFBS perfluorobutane sulfonate 

PFHxS Perfluorohexanesulfonic acid 

PFNA perfluorononanoic acid 

PFOA Perfluorooctanoic acid 

PFOS perfluoroocatane sulfonate 

PFOSA perfluorooctane sulfamide 

pg picogram 

PI proliferation index

PK pharmacokinetic 

pKa acid dissociation constant

pmol picomole 

PND postnatal day 

POD point of departure 

POSF perfluorooctanesulfonyl fluoride

PPAR peroxisome proliferator activated receptor 

ppb parts per billion

ppm parts per million

mPSC miniature post-synaptic current 

mRNA messenger ribonucleic acid

PTU propylthiouracil 

PUFA polyunsaturated fatty acid

PXR pregnane X receptor

Q flow in and out of tissues 

RBC red blood cell 

RfC reference concentration 

RfD reference dose

RIA radio immunoassay

RNA ribonucleic acid

RR rate ratio

RSI renal-somatic index

SD standard deviation

SDQ Strengths and Difficulties Questionnaire

SDWA Safe Drinking Water Act

SHBG sex hormone-binding globulin 

SIR standardized incidence ratio

SMR standardized mortality ratio

SOD superoxide dismutase

SPC saponin compound 

SRBC sheep red blood cells 

Syn 1 synapsin 1 

Syp synaptophysin 

T total testosterone

T-AOC total antioxidation capability

T3 triiodothyronine 

Perfluorooctane sulfonate (PFOS) –May 2016 xvi
T4 thyroxine

t1/2 chemical half-life

T1/2 elimination half-time

Tm transport maximum

TBG thyroxine-binding globulin 

TC total cholesterol

TG triglycerides

TH thyroid hormone 

TNF-α tumor necrosis factor-α

TNP trinitrophenol

TPO thyroid peroxidase 

TPOAb thyroid peroxidase antibody

TRH thyrotropin releasing hormone

TSH thyroid stimulating hormone 

TSHR thyroid stimulating hormone receptor 

TT3 total triiodothyronine 

TT4 total thyroxin

TTP time to pregnancy 

TTR thyroid hormone transport protein, transthyretin 

TUNEL Terminal deoxynucleotidyl transferase dUTP nick end labeling 

UCB umbilical cord blood

UF uncertainty factor 

UGT uridine diphosphoglucuronosyl transferase 

UK United Kingdom 

U.S. United States

Vd volume of distribution 

VLDL very low density lipoprotein 

WHO World Health Organization 

Perfluorooctane sulfonate (PFOS) –May 2016 xvii
EXECUTIVE SUMMARY

Perfluorooctane sulfonate (PFOS) is a fluorinated organic compound with an eight-carbon 

backbone and a sulfonate functional group. PFOS-related chemicals are used in a variety of 

products, including surface treatments for soil/stain resistance; surface treatments of textiles, 

paper, and metals; and in specialized applications such as firefighting foams. Because of strong 

carbon-fluorine bonds, PFOS is stable to metabolic and environmental degradation and is 

resistant to biotransformation. Data in humans and animals demonstrate ready absorption of 

PFOS and distribution of the chemical throughout the body by noncovalent binding to serum 

albumin and other plasma proteins. Both experimental data and pharmacokinetic models show 

higher levels of PFOS in fetal serum and brain compared with the maternal compartments. PFOS 

is not readily eliminated from humans as evidenced by the estimated average half-life values of 

4.1–8.67 years. In contrast, half-life values for the monkey, rat, and mouse are 121 days, 48 days, 

and 37 days, respectively. The long half-lives appear to be the result of saturable resorption from 

the kidney. In other words, after initial PFOS removal from blood by the kidney, a substantial 

fraction of what would normally be eliminated in urine is resorbed from the renal tubules and 

returned to the blood. A number of published toxicokinetic models use saturable resorption as a 

basis for predicting serum values in animals and humans, including one developed by the 

U.S. Environmental Protection Agency (EPA) to support this assessment.

Peroxisome proliferation as a result of binding to and activation of peroxisome proliferatoractivated receptor-alpha (PPARα), is usually associated with hepatic lesions in the rat, but some 

uncertainties exist as to whether this is true for liver effects induced by PFOS. Increased hepatic 

lipid content in the absence of a strong PPARα response is a characteristic of exposure to PFOS.

In two studies, mice administered PFOS showed differential expression of proteins mainly 

involved in lipid metabolism, fatty acid uptake, transport, biosynthetic processes, and response to 

stimulus. Many of the genes activated by PFOS are associated with nuclear receptors other than 

PPARα. 

Numerous epidemiology studies have examined occupational populations at large-scale 

PFOS production plants in the United States and a residential population living near a PFOA 

production facility in an attempt to determine the relationship between serum PFOS 

concentration and various health outcomes. Epidemiology data report associations between 

PFOS exposure and high cholesterol and reproductive and developmental parameters. The 

strongest associations are related to serum lipids with increased total cholesterol and high density 

lipoproteins (HDLs). Data also suggest a correlation between higher PFOS levels and decreases 

in female fecundity and fertility, in addition to decreased body weights in offspring, and other 

measures of postnatal growth. Several human epidemiology studies evaluated the association 

between PFOS and cancers including bladder, colon, and prostate, but these data present a small 

number or cases and some are cofounded by failure to adjust for smoking. The associations for 

most epidemiology endpoints are mixed. While mean serum values are presented in the human 

studies, actual estimates of PFOS exposure (i.e., doses/duration) are not currently available.

Thus, the serum level at which the effects were first manifest and whether the serum had 

achieved steady state at the point the effect occurred cannot be determined. It is likely that some 

of the human exposures that contribute to serum PFOS values come from PFOS derivatives or 

precursors that break down metabolically to PFOS. These compounds may originate from PFOS 

in diet and materials used in the home, thus, there is potential for confounding. Additionally, 

most of the subjects of the epidemiology studies have many perfluoroalkyl substances (PFAS),

other contaminants, or both in their blood. Taken together, the weight of evidence for human 

Perfluorooctane sulfonate (PFOS) – May 2016 ES-1 
studies supports the conclusion that PFOS exposure is a human health hazard. At this time, EPA 

concludes that the human studies are adequate for use qualitatively in the identification hazard 

and are supportive of the findings in laboratory animals. 

Short-term and chronic exposure studies in animals demonstrate increases in liver weight 

consistently at doses generally ≥ 0.5 milligrams per kilogram per day (mg/kg/day). Co-occurring 

effects in these studies include decreased cholesterol, hepatic steatosis, lower body weight, and 

liver histopathology. 

One and two generation toxicity studies also show decreased pup survival and body weights. 

Additionally, developmental neurotoxicity studies show increased motor activity and decreased 

habituation and increased escape latency in the water maze test following in utero and lactational 

exposure to PFOS. Gestational and lactational exposures were also associated with higher serum 

glucose levels and evidence of insulin resistance in adult offspring. Limited evidence suggests 

immunological effects in mice.

EPA derived a reference dose (RfD) for PFOS of 0.00002 mg/kg/day based on decreased 

neonatal rat body weight from the two-generation study by Luebker et al. (2005b). A 

pharmacokinetic model was used to predict an area under the curve (AUC) for the no observed 

adverse effect level (NOAEL) and used to calculate a human equivalent dose (HED)NOAEL. The 

total uncertainty factor (UF) applied to the HEDNOAEL from the rat study was 30, which included 

a UF of 10 for intrahuman variability and a UF of 3 to account for toxicodynamic differences 

between animals and humans. The HED for effects on pup body weight in the two generation 

study is supported by comparable values derived from the lowest observed adverse effect level 

for the same effect in the one-generation study and the NOAEL for effects seen in a 

developmental neurotoxicity study. 

Applying the U.S. EPA Guidelines for Carcinogen Risk Assessment, there is suggestive 

evidence of carcinogenic potential for PFOS (USEPA 2005a). In a chronic oral toxicity and 

carcinogenicity study of PFOS in rats, liver, thyroid, and mammary fibroadenomas were 

identified. The biological significance of the mammary fibroadenomas and thyroid tumors was 

questionable as a linear response to dose was not observed. The liver tumors also showed a 

slight, but statistically-significant increase only in high-dose males and females. The liver tumors 

most found were adenomas (7/60 and 5/60 in high-dose males and females, respectively, versus

none in the controls of either sex). Only one hepatocellular carcinoma was found in a high-dose 

female. The genotoxicity data are uniformly negative. Human epidemiology studies did not find 

a direct correlation between PFOS exposure and the incidence of carcinogenicity in workerbased populations. Although one worker cohort found an increase in bladder cancer, smoking 

was a major confounding factor, and the standardized incidence ratios were not significantly 

different from the general population. Other worker and general population studies found no 

statistically-significant trends for any cancer type. Thus, the weight of evidence for the 

carcinogenic potential to humans was judged to be too limited to support a quantitative cancer 

assessment. 

Perfluorooctane sulfonate (PFOS) – May 2016 ES-2 
1. IDENTITY: CHEMICAL AND PHYSICAL PROPERTIES

Perfluorooctane sulfonate, commonly known as PFOS, and its salts are fluorinated organic 

compounds and are part of the group of chemicals called perfluoroalkyl substances (PFAS). The 

two most widely known PFAS have an eight-carbon backbone with either a sulfonate (PFOS) or 

carboxylate (perfluorooctanoic acid, PFOA) attached (Lau et al. 2007). PFOS-related chemicals 

are used in a variety of products including surface treatments for soil/stain resistance, coating of 

paper as a part of a sizing agent formulation, and in specialized applications such as firefighting

foams. PFOS is produced commercially from perfluorooctanesulfonyl fluoride (POSF), which is 

primarily used as an intermediate to synthesize other fluorochemicals.

POSF is manufactured through a process called Simons Electro-Chemical Fluorination (ECF) 

in which an electric current is passed through a solution of anhydrous hydrogen fluoride and an 

organic feedback of 1-octanesulfonyl fluoride, causing the carbon-hydrogen bonds on molecules 

to be replaced with carbon-fluorine bonds (OECD 2002). This process yields a mixture of linear 

and branched chain isomers (Beesoon and Martin 2015). The isomer ratio is about 70% linear 

and 30% branched chain. Yu et al. (2015) measured the isomer profiles of drinking water 

samples collected from 10 locations in China and found that the levels of the branched isomers

accounted for 31.8% to 44.6% of the PFOS present using limits of quantification (LOQ) that 

ranged from 0.04 to 0.06 nanograms per liter (ng/L). Some systems had 1-methyl and 6-methyl 

isomers that were > 2% of the total. Levels of the other isomers were lower. Isomer 

concentrations are important because half-life decreases as the percentage of branched isomers

increases.

A second process for preparing PFOS is called telomerization. It produces linear chains and 

was the favored process in the United States until the time 3M voluntarily ceased production in 

2002 (Beesoon et al. 2011). PFOS can also be formed in the environment by the degradation of 

other POSF-derived fluorochemicals such as N-methyl or N-ethyl perfluorooctane sulfonamides 

(PFOSAs) often referred to as precursors.

Because of strong carbon-fluorine bonds, PFOS is stable to metabolic and environmental 

degradation. It is a solid at room temperature and has a low vapor pressure. Because of the 

surface-active properties of PFOS, it forms three layers in octanol/water making determination of 

an n-octanol/water partition coefficient (Kow) impossible. No direct measurement of the acid 

dissociation constant (pKa) of the acid has been located; however, the chemical is considered to 

have a low pKa and exist as a highly dissociated anion. The chemical structure is provided in 

Figure 1-1, and the physical properties for PFOS are provided in Table 1-1. 

Source: Environment Canada (2006)

Figure 1-1. Chemical Structure of PFOS

The branched chain isomers have a 7 carbon linear chain with methyl groups located on carbons 

1, 3, 4, 5, or 6 (Beesoon and Martin 2015).

Perfluorooctane sulfonate (PFOS) – May 2016 1-1 
Table 1-1. Chemical and Physical Properties of PFOS

Property PFOS, acidic form* Source

Chemical Abstracts Service 

Registry Number (CASRN) 

1763-23-1

Chemical Abstracts Index 

Name

1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-

heptadecafluoro-1-octanesulfonic acid

Synonyms Perfluorooctane sulfonic acid; 

heptadecafluoro-1-octane sulfonic acid; 

PFOS acid

Chemical Formula C8HF17O3S

Molecular Weight (grams 

per mole [g/mol])

500.13 Lewis (2004); Hazardous Substances 

Database (HSDB) (2012); SRC (2016)

Color/Physical State White powder

(potassium salt)

OECD (2002)

Boiling Point 258–260 oC SRC (2016)

Melting Point No data

Vapor Pressure 2.0 x 10-3 milligrams Mercury (mm Hg)

at 25 oC (estimate)

HSDB (2012)

Henry’s Law Constant Not measureable ATSDR (2015)

Kow Not measurable EFSA (2008); ATSDR (2015)

organic carbon water 

partitioning coefficient (Koc)

2.57 Higgins and Luthy (2006) 

Solubility in Water 680 mg/L OECD (2002)

Half-life in Water Stable UNEP (2006) 

Half-life in Air Stable UNEP (2006)

Notes: *PFOS is commonly produced as a potassium salt (CASRN 2795-39-3). Properties specific to the salt are not included.

This CASRN given are for linear PFOS, respectively, but the toxicity studies are based on a mixture of linear and branched, and 

thus the RfD applies to the total linear and branched.

Perfluorooctane sulfonate (PFOS) – May 2016 1-2 
2. TOXICOKINETICS

Because of strong carbon-fluorine bonds, PFOS is stable to metabolic and environmental 

degradation. It is not readily eliminated and can have a long half-life in humans and animals. 

However, the toxicokinetic profile and the underlying mechanism for the chemical’s long halflife are not completely understood. In the case of another perfluorinated compound (PFAS), 

PFOA, membrane transporter families appear to play an important role in absorption, 

distribution, and excretion. The transporter families identified for PFOA include organic anion 

transporters (OATs), organic anion transporting peptides (OATps), multidrug resistanceassociated proteins (MRPs), and urate transporters. Transporters play a critical role in 

gastrointestinal absorption, uptake by the tissues, and excretion via the kidney. Limited data are 

available regarding the transporters and PFOS, however the toxicokinetic properties of PFOS 

suggest facilitated transport functions in tissue uptake and renal resorption. Hepatic OATp1, 

OATp2, and MRP2 messenger ribonucleic acid (mRNA) respond to PFOA exposure in a doserelated manner. Some inhibition studies suggest that PFOS with its similar chain length, renal 

excretion properties and liver accumulation could involve the same transporters. However, 

transporter-specific data related to PFOS are minimal.

Animal studies indicate that PFOS is well-absorbed orally and distributes primarily to the 

blood and liver. While PFOS can form as a metabolite from other perfluorinated compounds, 

PFOS itself does not undergo further metabolism after absorption takes place. PFAS are known 

to activate peroxisome proliferator activated receptor (PPAR) pathways by increasing 

transcription of mitochondrial and peroxisomal lipid metabolism, as well as sterol and bile acid 

biosynthesis based on transcriptional activation of many genes in PPARα-null mice, the effects 

of PFAS involve more than activation of PPAR receptors (Andersen et al. 2008). A summary of 

toxicokinetic data are provided in Appendix C, Table C-1. 

2.1 Absorption

The absorption process requires transport across the tissue interface with the external 

environment. PFOS displays both hydrophobic and oleophobic properties, indicating that 

movement across the membrane surface is likely to be associated with transporters rather than 

simple diffusion. Unfortunately no information on the interaction of PFOS with intestinal, lung, 

or skin transporters in mammals was identified. 

While there are no absorption studies available that quantify absorption in humans, extensive 

data on serum PFOS demonstrate uptake from the environment but not the exposure route. 

Studies that provide the basis for human half-life estimates rely on changes in serum levels over 

time. Section 2.5.2 of this document provides serum levels measured in humans. 

2.1.1 Oral Exposure 

Chang et al. (2012) administered a single dose of 4.2 milligrams per kilogram (mg/kg) of 

PFOS14C in solution to 3 male rats. At 48 hours after dosing, 3.32% of the total dose was found 

in the digestive tract and 3.24% in the feces, indicating that most of the dose had been absorbed 

with some of the unabsorbed material excreted in fecal matter (Table 2-1). 

Perfluorooctane sulfonate (PFOS) – May 2016 2-1 
Table 2-1. Mean % (± SE) of 14C-K+PFOS in Rats after a Single Dose of 4.2 mg/kg 

Compartment

% 14C of dose recovered

24 hr 48 hr

carcass 79.0 ± 1.8 94.2 ± 5.1

digestive tract 3.58 ± 0.23 3.32 ± 0.12

feces 1.55 ± 0.15 3.24 ± 0.08

urine 1.57 ± 0.25 2.52 ± 0.31

plasma 11.02 ± 0.64 (estimated)* 10.01 ± 0.62(estimated)*

red blood cell (RBC) 2.29 ± 0.18 (estimated)* 3.25 ± 0.92 (estimated)*

Total 99.0 116.5

Source: Data from Chang et al. 2012

Note: *A mean body weight of 300g was used to estimate the red blood cell (RBC) and plasma volume.

2.1.2 Inhalation Exposure

An acute lethal concentration for 50% (statistical median) of animals (LC50) study in rats 

indicates that PFOS absorption occurs after inhalation exposures. However, pharmacokinetic 

data were not included in the published report (Rusch et al. 1979). The analytical methods for 

measuring PFOS in animals were limited at the time the study was conducted. 

2.1.3 Dermal Exposure

No data are available on dermal absorption of PFOS. 

2.2 Distribution

PFOS is distributed within the body by non-covalently binding to plasma proteins, most 

commonly albumin. The in vitro protein binding of PFOS in rat, monkey, and human plasma at 

concentrations of 1–500 parts per million (ppm) PFOS was investigated by Kerstner-Wood et al. 

(2003). PFOS was bound to plasma protein in all three species at all concentrations with no sign 

of saturation (99.0–100%). When incubated with separate human-derived plasma protein

fractions, PFOS was highly bound (99.8%) to albumin and showed affinity for low density 

lipoproteins (LDLs, formerly beta-lipoproteins) (95.6%) with some binding to alpha-globulins 

(59.4%) and gamma-globulins (24.1%). Low levels of binding to alpha-2-macroglobulin and 

transferrin were measured when the protein concentrations were approximately 10% of 

physiological concentration (Table 2-2).

Table 2-2. Percent (%) Binding of PFOS to Human Plasma Protein Fractions

Fraction

~ 10% Physiological 

Concentration (Conc.) 100% Physiological Conc.

Albumin 99.0 99.8

Gamma-globulin 6.3 24.1

Alpha-globulin 49.9 59.4

Fibrinogen < 0.1 < 0.1

Alpha-2-macroglobulin 12.5 < 0.1

Transferrin 7.2 < 0.1

LDLs 90.1 95.6

Source: Data from Kerstner-Wood et al. 2003. 

Perfluorooctane sulfonate (PFOS) – May 2016 2-2 
Zhang et al. (2009) used equilibrium dialysis, fluorophotometry, isothermal titration 

calorimetry and circular dichroism (CD) to characterize interactions between PFOS and serum 

albumin and deoxyribonucleic acid (DNA). Solutions containing known amounts of serum 

albumin or DNA were placed in dialysis tubing and suspended in solutions with varying 

concentrations of PFOS. The solutions were allowed to equilibrate while measuring the change 

in the PFOS concentration in the dialysis solution. During dialysis, the PFOS concentration in 

the solution decreased reflecting its ability to cross the dialysis membrane and bind to the 

biopolymer within the dialysis bag. Based on the data, the serum albumin could bind up to 45 

moles of PFOS per mole of protein and 0.36 moles per base pair of DNA. The binding ratio 

increased with increasing PFOS concentrations and decreasing solution pH (i.e., capable of 

promoting protein and DNA denaturation), thus providing an increased number of binding sites. 

It is important to remember that these studies were conducted in vitro and may not reflect in vivo 

situations.

The authors concluded that the interactions between serum albumin and PFOS were the 

results of surface electrostatic interactions between the sulfonate functional group and the 

positively charged side chains of lysine and arginine. Hydrogen binding interactions between the 

negative dipoles (fluorine) of the PFOS carbon-fluorine bonds could also play a role in the noncovalent bonding of PFOS with serum albumin. Intrinsic fluorescence analysis of tryptophan 

residues in serum albumin suggested a potential interaction of PFOS with tryptophan, an amino 

acid likely to be found in a hydrophobic portion of the albumin. In the case of DNA, the authors 

postulated that the interaction with PFOS occurred along the major or minor grooves of the 

double helix and was stabilized by the hydrogen bonding and van der Waals interactions. 

Serum albumin plays an important role in the transport of a number of endogenous and 

exogenous compounds, such as fatty acids, bile acids, some medications and pesticides (Zhang et 

al. 2009). Accordingly, changes in conformation could change its transporting activity. CD 

spectrometry was used to determine if PFOS changed the conformation of the albumin or DNA 

in solution. The results of both analyses indicated conformational changes as a result of PFOS 

binding. However, the CD results did not demonstrate whether there was a change in transport 

function as a result of the conformational change. 

Binding of five perfluoroalkyl acids, including PFOS, to human serum albumin was 

investigated by using site-specific fluorescence (Chen and Guo, 2009). Intrinsic fluorescence of 

trytophan-214 in human serum albumin was monitored upon addition of the perfluoroalkyl acids. 

PFOS induced fluorescence quenching indicative of binding. A binding constant of 2.2 x 104 M-1

and a binding ratio of PFOS to human albumin of 14 moles PFOS/mole albumin were calculated.

Human serum albumin has two high-affinity drug binding sites which are known as Sudlow’s 

drug Site I and Site II. Past experiments have shown that two fluorescence probes, dansylamide 

(DA) and dansyl-L-proline (DP), are specific for the two drug binding sites on human serum 

albumin. Alone these two probes emit negligible fluorescence; after binding with albumin, 

fluorescence increases. The titration of PFOS into human serum albumin pretreated with DA 

(site I), showed that at low concentrations of PFOS (0.07 mmol), DA emission increased as the 

PFOS concentration increased until it was at 140% the original intensity. At the higher PFOS 

concentrations (0.7–4 mmol), however, the fluorescence dropped. The author speculated that the 

rise in fluorescence was induced by the conformational changes of the protein after PFOS binds 

to it at a site different from Site I, and the decrease at higher concentrations was from 

displacement of DA by PFOS. For Site II, PFOS caused a fluorescence reduction that was quick 

at first, but then became more gradual suggesting the possibility that PFOS was binding to this 

Perfluorooctane sulfonate (PFOS) – May 2016 2-3 
site with two different affinities. The binding constant calculated at Site II was 7.6 x 106

 M-1. 

These findings indicate PFOS has binding sites that are similar to those identified for fatty acids.

Structure and the energy of PFOS binding sites were determined for human serum albumin 

using molecular modeling (Salvalaglio et al. 2010). Calculations were based on a compound 

approach docking, molecular dynamics simulations, and estimating free binding energies by 

adopting the weighted histogram analysis method umbrella sampling and semiempirical 

methodology. The binding sites impacted were ones identified as human serum albumin fatty 

acid binding sites. The PFOS binding site with the highest energy (−8.8 kilocalories per mole 

[kcal/mol]) was located near the tip of the tryptophan-214 binding site, and the maximum 

number of ligands that could bind to human serum albumin for PFOS was 11. The most 

populated albumin binding site for PFOS was dominated by van der Waals interactions. The 

author indicated that eleven PFOS molecules were adsorbed on the surface of the albumin. 

PFOS binding to bovine serum albumin was evaluated using electrospray ionization mass 

spectrometry by D’Alessandro et al. (2013). Using this approach, the estimate for the maximum 

number of PFOS binding sites was also 11, but the data on collision-induced PFOS removal was 

more consistent with 7 binding sites. Two of the potential binding sites (Sudlow’s sites I and II) 

are binding sites for a number of pharmaceuticals.

D’Alessandro et al. (2013) also examined whether PFOS could prevent binding of ibuprofen 

to its Sudlow II site and whether it was also able to displace bound ibuprofen. The study showed 

that PFOS competes with ibuprofen for its site when the PFOS:ibuprofen ratio is ≥ 0.5 moles:1

mole. In addition, when the binding site is occupied by PFOS, ibuprofen is unable to bind. Zhang 

et al. (2009) conducted a similar study of the impact of PFOS on the ability of serum albumin to 

bind vitamin B2 (riboflavin). The study found that at normal physiological conditions, 

1.2 mmol/L of PFOS decreased the binding ratio of serum albumin for riboflavin in vitro by 

> 30%. These data suggest that PFOS can alter the pharmacokinetics and pharmacodynamics of 

medicinal and natural substances that share a common site on albumin. 

Beesoon and Martin (2015) examined differences in the binding of the linear and branched 

chain isomers to serum albumin and human serum proteins. The linear PFOS molecule was 

found to bind more strongly to calf serum albumin than the branched chain isomers. When 

arranged in order of increasing binding the order was 3m < 4m < 1m < 5m < 6m (iso) <linear. In 

the isomer-specific binding to spiked total human serum protein, the 1m appeared to bind most 

strongly and the 4m the least. Binding was estimated based on the concentrations in the 

ultrafiltrate after spiking with 5 to 60 mg/L technical PFOS. The human serum was diluted tenfold before spiking. 

2.2.1 Oral Exposure 

PFOS entry from serum into tissues appears to be controlled by several families of membrane 

transporters based on PFOA studies. Yu et al. (2011) administered PFOS to rats and extracted 

the mRNAs for OATp1, OATp2, and MRP2 from the liver to determine if they were involved in 

hepatic uptake. Approximately six female Wistar rats per group were administered vehicle 

(0.5% Tween 20), or PFOS at 0.2, 1.0, or 3.0 mg/kg in Tween 20 once daily by gavage for 

5 consecutive days. Blood, bile, and liver tissue were collected 24 hours after the last dose.

Exposure to 3.0 mg/kg of PFOS increased hepatic OATp2 mRNA expression (1.43 times 

control) while MRP2 was increased approximately 1.80 and 1.69 times that of controls in the 

Perfluorooctane sulfonate (PFOS) – May 2016 2-4 
1.0 and 3.0 mg/kg groups, respectively. No effect with treatment was observed on OATp1. No 

additional information on PFOS tissue transport was identified. 

Humans. In humans, PFOS distributes mostly to the liver and blood. Olsen et al. (2003a) 

sampled both liver and serum from cadavers for PFOS. There was a good correlation between 

samples from the same subject. There was no difference in the PFOS concentrations identified in 

males and females or between age groups. Kärrman et al. (2010) identified PFOS in postmortem 

liver samples (n = 12; 6 males and 6 females 27–79 years old) with a mean concentration of 

26.6 ng/g tissue. 

Pérez et al. (2013) collected tissue samples from 20 adult subjects (aged 28–83) who had 

been living in Catalonia, Spain for 10 years and died of a variety of causes. Autopsies and tissue 

collection (liver, kidney, brain lung, and bone) were carried out in the first 24 hours after death. 

The tissues were analyzed for 21 perfluorinated compounds. PFOS was present in 90% of the 

samples but could be quantified in only 20% (median 1.9 ng/g). PFOS accumulated primarily in

the liver (104 ng/g), kidney (75.6 ng/g), and lung (29.1 ng/g), and it was low in brain (4.9 ng/g) 

and bone (not detected) based on the mean wet weight tissue concentration. Detection levels 

varied with the tissue evaluated.

Stein et al. (2012) compared PFAS levels in maternal serum and amniotic fluid paired 

samples from 28 females in their second trimester of pregnancy. PFOS (0.0036–0.0287 μg/mL) 

was detected in all serum samples and in nine amniotic fluid samples (0.0002–0.0018 μg/mL). 

The Spearman correlation coefficient between the serum and amniotic fluid levels was 0.76 and 

is significant (p = 0.01), indicating a direct relationship between the levels in blood and amniotic 

fluid. The median ratio of maternal serum:amniotic fluid concentration was 25.5:1. Based on a 

simple regression between the levels in each compartment, PFOS was rarely detected in amniotic 

fluid unless the serum concentration was ≥ 0.0055 μg/mL.

Harada et al. (2007) obtained cerebrospinal fluid (CSF) from seven patients (6 males and 

1 female; aged 56–80) to evaluate the partitioning of PFOS between serum and the CSF. The 

median concentration of PFOS in the serum was 0.0184 μg/mL, compared to the concentration 

in the CSF (0.00010 μg/mL). The CSF to serum ratio was 9.1 x 10-3. The levels identified 

indicate that PFOS does not easily cross the adult blood-brain barrier.

PFOS has been detected in both umbilical cord blood and breast milk indicating that maternal 

transfer occurs (Apelberg et al. 2007; Von Ehrenstein et al. 2009; Völkel et al. 2008). Kärrman et 

al. (2010) identified PFOS in breast milk samples from healthy females (n = 10; females 30–39 

years old). The levels in milk (mean 0.12 ng/mL) were low compared to liver levels.

Animals 

Monkey. Seacat et al. (2002) administered 0, 0.03, 0.15, or 0.75 mg/kg/day potassium PFOS 

orally in a capsule by intragastric intubation to six young-adult to adult cynomolgus 

monkeys/sex/group, except for the 0.03 mg/kg/day group which was 4/sex, daily for 26 weeks 

(182 days). Serum and tissues were collected at the time of sacrifice. The dosing was followed 

by a 52-week recovery period in 2 animals in the control, 0.15 and 0.75 mg/kg/day groups. 

Levels of PFOS were recorded in the serum and liver. Serum PFOS measurements demonstrate a 

linear increase with dosing duration in the 0.03 and 0.15 mg/kg/day groups and a non-linear 

increase in the 0.75 mg/kg/day group. Levels in the high-dose group appeared to plateau after 

about 100 days (14 weeks). Serum levels of PFOS decreased with recovery in the two highest 

Perfluorooctane sulfonate (PFOS) – May 2016 2-5 
dosed groups. The average percent of the cumulative dose of PFOS in the liver at the end of 

treatment ranged from 4.4% to 8.7% with no difference by dose group or gender. The 

concentration of PFOS in the liver decreased during the recovery period. Serum levels are 

provided in Table 2-3. 

Table 2-3. Average PFOS Level (μg/mL or ppm) in Serum of Monkeys 

Time

(weeks)

Group 1

0.0 milligram 

(mg)/kilogram (kg)/day

Group 2

0.03 mg/kg/day

Group 3

0.15 mg/kg/day

Group 4

0.75 mg/kg/day

Males Females Males Females Males Females Males Females

1 < LOQ < LOQ 0.869

± 0.147

0.947 ±

0.110

4.60 ± 

0782

3.71 ± 

0.455

21.0 ± 

1.57

20.4 ± 

2.71

4 < LOQ < LOQ 3.20 ±

0.577

3.40 ± 

0.291

17.8 ± 

1.68

16.5 ± 

1.87

95.3 ± 

70.4

92.7 ± 

39.6

16 0.04 ± 

0.01

0.04 ±

0.008

11.2 ±

2.44

10.5 ±

1.90

56.2 ± 

5.84

42.1 ± 

4.04

189 ± 

15.9

162 ± 

19.3

27 0.05 ± 

0.01

0.04 ± 

0.01

15.9 ±

5.54

11.1 ±

1.52

68.1 ±

5.75

58.5 ±

4.67

194 ±

8.93

160 ±

23.9

35 0.05 ± 

0.003

0.07 ± 

0.004

Not 

Determined

Not 

Determined

84.5 ± 

12.0

74.7 ± 

9.53

181 ± 

19.5

171 ± 

10.1

57 0.03 ± 

0005

0.0445 ± 

0.00385

Not 

Determined

Not 

Determined

30.2 ± 

2.36

32.3 ± 

1.34

78.0 ± 

16.3

106 ± 

3.84

79 0.02 ± 

0.003

0.02 ± 

0.003

Not 

Determined

Not 

Determined

19.1 ± 

0.805

21.4 ± 

2.01

41.1 ± 

25.9

41.4 ± 

1.15

Source: Data from p. 304 in OECD 2002.

Note: LOQ = limit of quantitation (value not stated)

At the two low doses, serum levels were comparable in the males and females, whereas at the 

high dose, the levels were higher in the males than females. Only for the highest dose group did 

the animals appear to reach serum steady state (week 16 for both males and females). In the 

lower dose groups, the serum levels continued to increase with dose across the dosing period. 

Once dosing ceased serum levels declined in all animals monitored.

Rat. Martin et al. (2007) administered 10 mg PFOS/kg to adult male Sprague-Dawley rats 

(n = 5) for 1, 3, or 5 days by gavage and determined the liver and serum levels. Blood was 

collected via cardiac puncture and PFOS concentration was determined by high-performance 

liquid chromatography-electrospray tandem mass spectrometry. The mean liver PFOS 

concentration was 83 ± 5, 229 ± 10, and 401 ± 21 μg/g after 1, 3, or 5 daily doses, respectively.

The mean serum concentration was 23 ± 2.8 and 87.7 ± 4.1 μg/mL, after 1 and 3 days of dosing, 

respectively. Serum PFOS concentration was not determined after 5 days of dosing due to 

sample unavailability (not further explained by the authors). 

Yu et al. (2011) administered the doses of 1, 0.2, 1.0, or 3.0 mg PFOS/kg dissolved in 0.5% 

Tween 20 as the vehicle to 6 female Wistar rats/group once daily by gavage for 5 consecutive 

days as part of a study of the effects of PFOS on the thyroid. Blood and bile were collected 24 

hours after the last dose (Table 2-4). The data demonstrate a dose-related distribution to both 

serum and bile.

Perfluorooctane sulfonate (PFOS) – May 2016 2-6 
Table 2-4. Levels of PFOS in Serum and Bile of Rats Treated for 5 Days

PFOS (mg/kg bw)

Serum PFOS (microgram 

[μg]/milliliter [mL]) Bile PFOS (μg/mL)

0.0 < LOQ < LOQ

0.2 1.09 ± 0.12 1.51 ± 0.42

1.0 8.20 ± 0.13 3.58 ± 0.66

3.0 33.5 ± 1.79 6.51 ± 0.67

Source: Data from Table 2 in Yu et al. 2011.

Note: LOQ = limit of quantification, 0.5 μg/L

Groups of 15 Sprague-Dawley rats/sex/group were administered 0, 20, 50 or 100 mg 

PFOS/kg diet (Curran et al. 2008). Tissues were analyzed for PFOS residue by liquid 

chromatography negative electrospray tandem mass spectrometry. Distribution of PFOS is 

provided in Table 2-5 and indicates that the highest levels were distributed to the liver and 

spleen. There were no consistent differences between sexes for the liver tissues, however levels 

in the spleen and heart tended to be higher in females (F) than males (M) at all doses. The levels 

in the liver were considerably higher than those in the heart and spleen in both sexes for all 

doses.

Table 2-5. Mean (± SD) Daily PFOS Consumption and Tissue Residue Levels in Rats 

Treated for 28 Days 

Parameter

0 mg/kg diet 2 mg/kg diet 20 mg/kg diet 50 mg/kg diet 100 mg/kg diet

M F M F M F M F M F

PFOS 

consumption 

(mg/kg 

bw/day)

0 0 0.14 ± 

0.02

0.15 ± 

0.02

1.33 ± 

0.24

1.43 ± 

0.24

3.21 ± 

0.57

3.73 ± 

0.57

6.34 ± 

1.35

7.58 ± 

0.68

Serum

(μg PFOS/g 

serum)

0.47 ± 

0.27

0.95 ± 

0.51

0.95 ± 

0.13

1.50 ± 

0.23

13.45 ± 

1.48

15.40 ± 

1.56

20.93 ± 

2.36

31.93 ± 

3.59

29.88 ± 

3.53

43.20 ± 

3.95

Liver

(μg 

PFOS/gram (g) 

liver)

0.79 ± 

0.49

0.89 ± 

0.44

48.28 ± 

5.81

43.44 ± 

6.79

560.23 

± 

104.43

716.55 

± 59.15

856.90 

± 

353.83

596.75 

± 

158.01

1030.40 

± 

162.80

1008.59 

± 49.41

Ratio 

liver:serum 

PFOS

2.04 ± 

1.39

1.30 ± 

1.32

51.34 ± 

9.20

29.99 ± 

8.11

42.10 ± 

9.20

46.81 ± 

5.26

41.42 ± 

16.95

20.23 ± 

7.50

35.23 ± 

8.50

23.48 ± 

1.98

Spleen

(μg PFOS/g 

spleen)

0.27 ± 

0.36

2.08 ± 

4.17

6.07 ± 

1.85

7.94 ± 

3.76

45.27 ± 

2.16

70.03 ± 

36.66

122.51 

± 7.83

139.45 

± 15.44

230.73 

± 11.47

294.96 

± 26.66

Heart

(μg PFOS/g 

heart)

0.10 ± 

0.14

1.42 ± 

2.91

4.67 ± 

1.73

6.54 ± 

3.07

33.00 ± 

3.44

54.65 ± 

30.89

90.28 ± 

4.95

107.53 

± 6.24

154.13 

± 11.78

214.45 

± 17.58

Source: Data from Table 1 on in Curran et al. 2008

Note: M = male; F = female; SD = standard deviation

Ten three-month old male Sprague-Dawley rats/group were administered 0 (Milli-Q water 

only), 5, or 20 mg/kg/day of PFOS by oral gavage for 28 days (Cui et al. 2009). Rats were 

sacrificed after the exposure and blood and tissue samples obtained. Concentrations identified in 

rat whole blood and various tissues at the end of the exposure are provided in Table 2-6. The 

study indicated that the highest levels of PFOS were identified in the liver after 28 days of 

exposure. 

Perfluorooctane sulfonate (PFOS) – May 2016 2-7 
Table 2-6. Concentrations of PFOS in Male Rats’ Whole Blood (μg/mL) and Various 

Tissues (μg/g) after 28 Days

Tissues Controls 5 mg/kg/day PFOS 20 mg/kg/day PFOS

blood ND 72.0 ± 25.7 No sample

liver ND 345 ± 40 648 ± 17

kidney ND 93.9 ± 13.6 248 ± 26

lung ND 46.6 ± 17.8 228 ± 122

heart ND 168 ± 17 497 ± 64

spleen ND 38.5 ± 11.8 167 ± 64

testicle ND 39.5 ± 10.0 127 ± 11

brain ND 13.6 ± 1.0 146 ± 34

Source: Data from Table 1 in Cui et al. 2009.

Note: ND = not detected

A combined chronic toxicity/carcinogenicity good laboratory practice (GLP) study was 

performed in 40–70 male and female Sprague-Dawley Crl:CD (SD)IGS BR rats administered 0, 

0.5, 2, 5, or 20 ppm of PFOS for 104 weeks (Thomford 2002/Butenhoff et al. 20121

). Doses 

were approximately 0, 0.018–0.023, 0.072–0.099, 0.184–0.247 and 0.765–1.1 mg/kg/day. A 

recovery group was administered the test substance at 20 ppm for 52 weeks and observed until 

sacrifice at 106 weeks. Serum and liver samples were obtained during and at the end of the study 

to determine the concentration of PFOS. Dose-dependent increases in the PFOS level in the 

serum and liver were observed, with values slightly higher in females. Further study details are 

described in section 3.2.7 Chronic Toxicity. Levels of PFOS identified in the liver and serum are 

included in Table 2-7. 

Table 2-7. PFOS Levels in the Serum and Liver of Rats

Timepoint

(weeks)

0 ppm PFOS 

(0 mg/kg/day) 

0.5 ppm

(0.024–0.029

mg/kg/day)

2 ppm

(0.098–0.120 

mg/kg/day)

5 ppm

(0.242–0.299 

mg/kg/day)

20 ppm

(0.984–1.251

mg/kg/day)

M F M F M F M F M F

Serum PFOS levels (μg/mL)

0 < LOQ* 0.0259 0.907 1.61 4.33 6.62 7.57 12.6 41.8 54.0

14 < LOQ** 2.67 4.04 6.96 17.1 27.3 43.9 64.4 148 223

53 0.0249 0.395 146 220

105 0.0118 0.0836 1.31 4.35 7.60 22.5 75.0 69.3 233

106 2.42a 9.51a

Liver PFOS levels (μg/g)

0 0.104 0.107 11.0 8.71 31.3 25.0 47.6 83.0 282 373

10 0.459 12.0 23.8 19.2 74.0 69.2 358 370 568 635

53 0.635 0.932 435 560

105 0.114 0.185 7.83 12.9 26.4 70.5 131 189 381

106 3.12a 12.9a

Source: Data from Tables 4 and 5 on pp. 38 and 39 in OECD 2002

Notes: a These samples were obtained from the recovery group administered 20 ppm for 52 weeks and then observed until death. *LOQ = limit of quantification = 0.00910 picogram (pg)/mL **LOQ = 0.0457 pg/mL

M = male; F = female

1 Thomford (2002) is unpublished, but it contains the raw data. Butenhoff et al. (2012) is the published study.

Perfluorooctane sulfonate (PFOS) – May 2016 2-8 

 
Mouse. Adult male C57/BL6 mice (3 mice/group) were administered 35S-PFOS in the feed at a 

low and high dose for 1, 3, and 5 days. The dose equivalents were 0.031 mg/kg/day in the low 

dose group and 23 mg/kg/day in the high dose group. Tissue contents were determined by liquid 

scintillation (Bogdanska et al. 2011). At 23 mg/kg/day after 5 days, mice had hypertrophy of the 

liver, atrophy of fat pads, and atrophy of epididymal fat when compared to the mice at 

0.013 mg/kg/day at 5 days. To determine the amount of radioactivity recovered that was due to 

blood in the tissues, the hemoglobin content was determined in all of the samples. By correcting 

for PFOS in the blood, the actual tissue levels were then calculated.

At both doses and at all time-points, the liver contained the highest amount of PFOS. At the 

low dose, the liver PFOS level relative to blood concentration increased with time, whereas at 

the high dose, the ratio plateaued after three days. The autoradiography indicated that the 

distribution within the liver did not appear to favor one area to a greater extent than any other. 

The liver contained 40% to 50% of the recovered PFOS at the high dose. The authors 

hypothesized that this could possibly reflect high levels of binding to tissue proteins. 

In the high dose mice, the next highest level was found in the lungs. Distribution was fairly 

uniform with some favoring of specific surface areas. The tissue to blood ratio for the lung was 

greater than that for all other tissues except the liver. The lowest PFOS levels were in the brain 

and fat deposits.

While the levels in Table 2-8 report the PFOS in the whole bone, when the authors did a 

whole body autoradiogram of a mouse 48 hours after a single oral dose of 35S-PFOS 

(12.5 mg/kg), the results indicated that most PFOS was found in the bone marrow and not the 

calcified bone. Levels for the kidney roughly equal those values observed in the blood at both 

concentrations and all timepoints (see Table 2-8). 

Table 2-8. Mean Concentration of PFOS (± SD) in Various Tissues of Mice

Tissues 1 day 3 days 5 days

Dose of 0.013 mg/kg/day (PFOS in tissue reported as picomole [pmol]/g)

Blood 61(6) 129 (41)# 99 (21)

Liver 114 (13)** 343 (24)**# 578 (39)**#

Kidney 38 (19) 65 (13) 93 (11)#

Lung 39 (29) 88 (6)# 141 (10)*#

Whole bone 113 (15)** 98 (24) 109 (6)

Dose of 23 mg/kg/day (PFOS in tissue reported as nanomole [nmol]/g)

Blood 67 (4) 171 (21)# 287 (9)#

Liver 246 (31)** 698 (71)**# 1044 (114)**#

Kidney 62 (3) 166 (8)# 233 (12)**#

Lung 135 (18)** 336 (69)*# 445 (42)**#

Whole bone 55 (6)* 155 (17)# 207 (8)**#

Source: Data from Tables 2 and 3 in Bogdanska et al. 2011

Notes: *significantly different (p < 0.05) than blood at the same time-point as evaluated by an independent t-test **significantly different (p <0.01) than blood at the same time-point as evaluated by an independent t-test #significantly different (p < 0.05) from the value for the same tissue at day 1 as determined by one-way analysis of variance 

(ANOVA) followed by Duncan’s test

Perfluorooctane sulfonate (PFOS) – May 2016 2-9 
In an immunotoxicity study, four to six C57BL/6 male mice/group were administered diets 

with 0% to 0.02% PFOS for 10 days. Levels in the serum increased as the concentration 

increased (Table 2-9) (Qazi et al. 2009a).

Table 2-9. Levels of PFOS (Means ± SE) in Mouse Serum Following Treatment for 10 Days

Dietary level (% w/w) Number of mice ppm

PFOS (0) 4 0.0287 ± 0.01

PFOS (0.001%) 4 50.8 ± 2.5

PFOS (0.005%) 4 96.7 ± 5.2

PFOS (0.02%) 4 340 ± 16

Source: Data from study report by Qazi et al. 2009a

Distribution during Reproduction and Development

The availability of distribution data from pregnant females plus animal pups and neonates is 

a strength of the PFOS pharmacokinetic database, because it helps to identify those tissues 

receiving the highest concentration of PFOS during development. For this reason the information 

on tissue levels during reproduction and development are presented separately from those that 

are representative of other life stages.

Humans. T. Zhang et al. (2013) recruited pregnant females for a study to examine the 

distribution of PFOS between maternal blood, cord blood, the placenta, and amniotic fluid. 

Thirty two females from Tianjin, China volunteered to take part in the study. Samples were 

collected at time of delivery. Maternal ages ranged from 21 to 39 years, and periods ranged from 

35 to 37 weeks. It was the first child for 26 of the females and the second child for 6. The study 

yielded 31 maternal whole blood samples, 30 cord blood samples, 29 amniotic fluid samples, and 

29 placentas. The maternal blood contained variable levels of 10 PFAS, 8 acids and 2 sulfonates. 

The mean maternal blood concentration was highest for PFOS (14.6 ng/mL), followed by PFOA 

(3.35 ng/mL). In both cases, the mean was greater than the median, indicating a distribution 

skewed toward the higher concentrations. 

PFOS was found in all fluids/tissues sampled. It was transferred to the amniotic fluid to a 

lesser extent than PFOA based on their relative proportions in the maternal blood and cord blood 

(21% versus 58%, respectively). Compared to the mean PFOS value in maternal blood, the mean 

levels in the cord blood, placenta, and amniotic fluid were 21%, 56%, and 0.14% of the mean 

levels in the mother’s blood, respectively. The correlation coefficients between the maternal 

PFOS blood levels and placenta, cord blood, and amniotic fluid levels were good (0.7 to 0.9), 

and the relationships were statistically-significant (p < 0.001). 

Rat. To determine the dose-response curve for neonatal mortality in rat pups born to PFOS 

exposed dams and to investigate associated biochemical and pharmacokinetic parameters, 5 

groups of 16 female Sprague-Dawley Crl:CD(SD)IGS VAF/Plus rats each were administered 0, 

0.1, 0.4, 1.6, or 3.2 mg PFOS/kg bw/day by oral gavage beginning 42 days prior to cohabitation 

and continuing through gestation day (GD) 14 or 20 (Luebker et al. 2005b). Eight rats from each 

group were randomly chosen and sacrificed on GD 15, followed by Caesarean removal of the 

pups. All remaining animals were sacrificed and C-sectioned on GD 21. Urine and feces were 

collected overnight from dams on the eve of cohabitation day 1 and during GDs 6–7, 14–15, and 

20–21. Serum samples were collected just prior to cohabitation and on GD 7, GD 15, and GD 21. 

Fetal liver and blood samples were obtained on GD 21 and pooled by litter. 

Perfluorooctane sulfonate (PFOS) – May 2016 2-10
The urine, feces, and liver of the control animals all contained PFOS at small concentrations.

In treated rats, the highest concentration of PFOS was in the liver. Serum levels in the dams for 

each dose were consistent between GD 1 and GD 15, indicating achievement of steady state prior 

to conception (Table 2-10). The GD 21 levels in the dams had dropped below those observed 

earlier in the pregnancy. Serum levels in the GD,21 fetuses were higher than those in the dams. 

In contrast, the liver levels in the dams on GD 21 were about three times higher than in the 

fetuses. Fecal excretion was greater than urinary excretion by the dams. 

Table 2-10. PFOS Concentrations (Mean ± Standard Deviation [SD]) in Samples from 

Pregnant Dams and Fetuses (GD 21 Only) in μg/mL (ppm) for Serum and Urine and μg/g 

for Liver and Feces

Parameter

Dose

(mg/kg/day) GD 1 GD 7 GD 15 GD 21

Dams Fetuses

Serum 0.1 8.90 ± 1.10 7.83 ± 1.11 8.81 ± 1.47 4.52 ± 1.15 9.08

0.4 40.7 ± 4.46 40.9 ± 5.89 41.4 ± 4.80 26.2 ± 16.1 34.3

1.6 160 ± 12.5 154 ±14.0 156 ± 25.9 136 ± 86.5 101

3.2 318 ± 21.1 306 ± 32.1 275 ± 26.7 155 ± 39.3 164

Liver 0.1 - - - 29.2 ± 10.5 7.92

0.4 - - - 107 ± 22.7 30.6

1.6 - - - 388 ± 167 86.5

3.2 - - - 610 ± 142 230

Urine 0.1 0.05 ± 0.02 0.06 ± 0.03 0.07± 0.04 0.06 ± 0.01 -

0.4 0.28 ± 0.19 0.31 ± 0.20 0.53 ± 0.23 0.55 ± 0.16 -

1.6 0.96 ± 0.39 1.10 ± 0.57 0.36 ± 0.35 2.71 ± 2.07 -

3.2 1.53 ± 0.87 1.60 ± 0.97 0.52 ± 0.28 1.61 ± 0.53 -

Feces 0.1 0.50 ± 0.14 0.49 ± 0.11 0.66 ± 0.10 0.42 ± 0.10 -

0.4 2.42 ± 0.49 2.16 ± 0.43 2.93 ±0.62 2.39 ± 1.21 -

1.6 10.3 ± 3.01 9.20 ± 2.68 11.1 ± 3.28 9.94 ± 4.51 -

3.2 23.9 ± 4.16 33.0 ± 10.0 29.5 ± 8.92 20.1 ± 4.21 -

Source: Data from Luebker et al. 2005b 

Note: - = no sample obtained

This same study also included a subset of dams allowed to litter naturally and dosed through 

lactation day (LD) 4. Liver and serum samples were collected from dams and pups on LD 5. In 

this sampling, serum PFOS levels were similar between the dam and offspring, but the liver 

values were now higher in the neonates than in their dams. 

Twenty five female Sprague-Dawley rats/group were administered 0, 0.1, 0.3, or 

1.0 mg/kg/day potassium PFOS by gavage from GD 0 through postnatal day (PND) 20. An 

additional 10 mated females served as satellite rats to each of the four groups and were used to 

collect additional blood and tissue samples. Further details from this study are provided in 

section 3.2.6 as reported in Butenhoff et al. (2009). Samples were taken from the dams, fetuses, 

and pups for serum and tissue PFOS concentrations and the results reported by Chang et al. 

(2009). The blood and tissue sampling results are provided in Table 2-11. 

Perfluorooctane sulfonate (PFOS) – May 2016 2-11
Table 2-11. Mean PFOS (± Standard Error) Concentrations in Serum, Liver, and Brain 

Tissue in Dams and Offspring

Time

Dose 

(mg/kg)

Serum PFOS (μg/mL) Liver PFOS (μg/g) Brain PFOS (μg/g)

Dam Offspring Dam Offspring Dam Offspring

GD 20a Control < LLOQ 0.009 ± 0.001 < LLOQ < LLOQ < LLOQ < LLOQ

0.1 1.722 ± 

0.068

3.906 ± 0.096 8.349 ± 

0.344

3.205 ± 0.217 0.151 ± 

0.012

1.233 ± 0.067

0.3 6.245 ± 

0.901

10.446 ± 0.291 21.725 ± 

0.721

5.814 ± 0.245 0.368 ± 

0.043

3.126 ± 0.238

1.0 26.630 ± 

3.943

31.463 ± 1.032 48.875 ± 

72.733

20.025 ± 2.021 0.999 ± 

0.083

12.984 ± 1.122

PND 4a Control 0.008 ± 

0.000

< LLOQ NS < LLOQ NS < LLOQ

0.1 3.307 ± 

0.080

2.236 ± 0.070 NS 9.463 ± 0.512 NS 0.680 ± 0.033

0.3 10.449 ± 

0.234

6.960 ± 0.163 NS 20.130 ± 0.963 NS 1.910 ± 0.074

1.0 34.320 ± 

31.154

22.440 ± 0.723 NS 50.180 ± 1.124 NS 6.683 ± 0.428

PND 21 Control 0.007 ± 

0.000

< LLOQ – m/f NS < LLOQ – m/f NS < LLOQ – m/f

0.1 3.159 ± 

0.081

1.729 ± 0.079 (M)

1.771 ± 0.076 (F)

NS 5.980 ± 0.614 (M)

5.278 ± 0.174 (F)

NS 0.220 ± 0.014 (M)

0.229 ± 0.011 (F)

0.3 8.981 ± 

0.275

5.048 ± 0.108 (M)

5.246 ± 0.138 (F)

NS 14.780 ± 0.832 (M)

13.550 ± 0.298 (F)

NS 0.649 ± 0.053 (M)

0.735 ± 0.039 (F)

1.0 30.480 ± 

1.294

18.611 ± 1.011 (M)

18.010 ± 0.744 (F)

NS 44.890 ± 2.637 (M)

41.230 ± 2.295 (F)

NS 2.619 ± 0.165 (M)

2.700 ± 0.187 (F)

PND 72 Control NA < LLOQ – m/f NA < LLOQ – m/f NA NS – M/F

0.1 NA 0.042 ± 0.004 (M)

0.207 ± 0.042 (F)

NA 0.981± 0.091 (M)

0.801 ± 0.082 (F)

NA NS – M/F

0.3 NA 0.120 ± 0.009 (M)

0.556 ± 0.062 (F)

NA 2.464 ± 0.073 (M)

2.252 ± 0.095 (F)

NA NS – M/F

1.0 NA 0.560 ± 0.105 (M)

1.993 ± 0.293 (F)

NA 7.170 ± 0.382 (M)

7.204 ± 0.414 (F)

NA NS – M/F

Source: Data from Table 2 in Chang et al. 2009

Notes: a Data are from samples pooled by litters in the fetuses/pups

< LLOQ = sample less than lower limit of quantitation, serum = 0.01 μg/mL; liver = 0.05 μg/g; brain = 0.025 μg/g

NS = no sample obtained

NA = not applicable; all dams sacrificed on PND 21

m = male; f = female

On GD 20, PFOS concentration in maternal serum, liver, and brain correlated with the daily 

doses administered. Maternal liver-to-serum PFOS ratios ranged from 1.8 to 4.9, while the 

maternal brain-to-serum ratios were 0.04 to 0.09 (Chang et al. 2009). The concentrations in the 

brains of fetuses was about ten times higher than in their dams for all doses.

Perfluorooctane sulfonate (PFOS) – May 2016 2-12
Based on the maternal and offspring data on GD 20, there is placental transfer of PFOS from 

rat dams to developing fetuses. Serum values were approximately 1–2 times greater in the 

fetuses than in the dams at GD 20. The concentration of PFOS in fetal liver was less than that of 

dams, and the brain values were much higher; this is possibly due to the lack of development of 

the blood-brain barrier at this stage of offspring development. PFOS serum concentrations in the 

offspring were lower than those for the dams on PND 4 and continued to drop through PND 72. 

However, based on the concentrations still present in the neonate serum, lactational transfer of 

PFOS was occurring. At PND 72, the males appeared to be eliminating PFOS more quickly as 

the serum values were lower than those in the females; this difference was not observed at earlier 

time-points. In the liver, PFOS was the greatest in the offspring at PND 4 and decreased 

significantly by PND 72. Liver values were similar at all time-points between males and females.

On GD 20, the brain levels for the pups were ten-fold higher than those for the dam. The levels 

in pup brain gradually declined between PND 4 and PND 21. 

In a study by Zeng et al. (2011) ten pregnant Sprague-Dawley rats/group were administered 

0, 0.1, 0.6, or 2.0 mg/kg/day of PFOS by oral gavage in 0.5% Tween 80 from GD 2 to GD 21. 

On GD 21, dams were monitored for parturition, and the day of delivery was designated PND 0. 

On PND 0, five pups/litter were sacrificed and the trunk blood, cortex, and hippocampus were 

collected for examination. The other pups were randomly redistributed to dams within the dosage 

groups and allowed to nurse until PND 21, when they were sacrificed with the same tissues 

collected as previously described. PFOS concentration in the hippocampus, cortex, and serum 

increased in a dose-dependent manner but overall was lower in all tissues on PND 21 when 

compared to PND 0. Levels of PFOS are included in Table 2-12. 

Table 2-12. PFOS Contents in Serum, Hippocampus, and Cortex of Offspring (n = 6) 

Time Dose group (mg/kg/day) Serum (μg/mL) Hippocampus (μg/g) Cortex (μg/g)

PND 0 Control ND ND ND

0.1 1.50 ± 0.43* 0.63 ± 0.19* 0.39 ± 0.09*

0.6 24.60 ± 3.02** 7.43 ± 1.62* 5.23 ± 1.58**

2.0 45.69 ± 4.77** 17.44 ± 4.12* 13.43 ± 3.89**

PND 21 Control ND ND ND

0.1 0.37 ± 1.12* 0.25 ± 0.14* 0.06 ± 0.04*

0.6 1.86 ± 0.35** 1.59 ± 0.78** 1.03 ± 0.59**

2.0 4.26 ± 1.73*** 6.09 ± 1.30*** 3.69 ± 0.95***

Source: Data from Table 2 in Zeng et al. 2011

Notes: ND = not detected *

 p < 0.05 compared with control in the same day ** p < 0.05 compared with 0.1 mg/kg group in the same day *** p < 0.05 compared with 0.6 mg/kg group in the same day

Sprague-Dawley rats were administered PFOS in 0.05% Tween (in deionized water) once 

daily by gavage from GD 1 to GD 21 at 0, 0.1, or 2.0 mg/kg/day. There was a postnatal decline 

in the serum and brain PFOS levels between PND 0 and PND 21. PFOS concentrations were 

higher in the serum when compared to the lung in offspring on both PND 0 and 21 (Chen et al.

2012) (see Table 2-13). 

Perfluorooctane sulfonate (PFOS) – May 2016 2-13
Table 2-13. Mean PFOS Content in Serum and Lungs of Rat Offspring (n = 6) 

Age Treatment PFOS in serum (μg/mL) PFOS in lung (μg/g)

PND 0 0 mg/kg/day ND ND

0.1 mg/kg/day 1.7 ± 0.35* 0.92 ± 0.04*

2.0 mg/kg/day 47.52 ± 3.72* 22.4 ± 1.03*

PND 21 0 mg/kg/day ND ND

0.1 mg/kg/day 0.41 ± 0.11* 0.21 ± 0.04*

2.0 mg/kg/day 4.46 ± 1.82** 3.16 ± 0.11**

Source: Data from Table 2 in Chen et al. 2012

Notes: ND = not detected *

 p < 0.05 compared with control ** p < 0.01 compared with control

Mouse. Borg et al. (2010) administered a single dose of 12.5 mg/kg 35S-PFOS by intravenous 

injection (n = 1) or gavage (n = 5) on GD 16 to C57Bl/6 dams. Using whole-body 

autoradiography and liquid scintillation, counting distribution of PFOS was determined for the 

dams/fetuses (GD 18 and 20) and the neonates on PND 1. Distribution in the dams was similar 

regardless of the route of exposure, with the hepatic level being approximately four times greater 

than the serum. Maternal PFOS levels were highest in the liver and lungs at all timepoints. In 

dams, the concentration of PFOS in the liver was approximately 4 times and in the lung was 

approximately 2 times the blood concentrations, respectively. The distribution of PFOS in the 

kidneys was similar and the amount in the brain was lower than that of the blood. In the fetuses, 

the highest concentrations of PFOS were found in the kidneys and liver. In the fetuses on GD 18, 

values in the lungs were similar to the maternal lungs, and this value increased by GD 20. In the 

kidneys, the highest concentration of PFOS was observed in the fetuses on GD 18 (3 times

higher than maternal levels)

In the offspring at all timepoints, PFOS was homogeneously distributed in the liver at a level 

2.5 times higher than maternal blood and 1.7 times lower than maternal liver. In pups on PND 1, 

PFOS was mostly concentrated in the lungs and liver. Pups on PND 1 had PFOS levels that were 

3 times higher in the lungs, compared to maternal blood with a heterogeneous distribution. In the 

kidneys, the levels in pups on PND 1 were similar to their dams despite being higher on GD 18.

Levels in the brain were similar at all timepoints in the offspring and higher than in the maternal 

brain, likely due to an immature brain-blood barrier. Select data are provided in Table 2-14 and 

Figure 2-1. 

Table 2-14. Ratios (Means ± SD) Between the Concentrations of 35S-Labeled PFOS in 

Various Organs and Blood of Mouse Dams, Fetuses, and Pups versus the Average 

Concentration in Maternal Blood 

[

35S-PFOS]organ/[35S-PFOS]maternal blood

Subject

Liver 

(n = 6–8)

Lungs 

(n = 5–6)

Kidneys 

(n = 3–6)

Brain 

(n = 6–9)

Blood 

(n = 1–6)

Dams 4.2** ± 0.7 2.0* ± 0.4 0.9 ± 0.1 0.2** ± 0.05 1.0

Fetus on GD 18 2.6** ± 0.8 2.1* ± 0.6 2.8** ± 0.3 1.2 ± 0.3 2.3

Fetus on GD 20 2.4** ± 0.5 2.5** ± 0.4 1.4 ± 0.2 0.9 ± 0.1 1.1 ± 0.04

Pups on PND 1 2.4* ± 0.4 3.0** ± 0.5 1.0 ± 0.5 0.9 ± 0.2 1.7** ± 0.3

Source: Data from Table 1 in Borg et al. 2010

Notes: *

Statistically-significant (p ≤ 0.01) in comparison to maternal blood **Statistically-significant (p ≤ 0.001) in comparison to maternal blood

Perfluorooctane sulfonate (PFOS) – May 2016 2-14
 Filled symbols are representative after oral exposure; open after intravenous exposure.

A = p ≤ 0.001 and a = p ≤ 0.01, compared to maternal blood

B = p ≤ 0.001 and b = p ≤ 0.05, compared to maternal tissue

C = p ≤ 0.001 and c = p ≤ 0.05, comparing between fetuses/pups on GD 20/PND 1 with corresponding value on GD 18; 

Figure 2-1. Distribution of Radiolabeled PFOS in Dams and in Fetuses/Pups in the 

Liver, Lung, Kidney, and Brain

(Figure from Borg et al. 2010)

2.2.2 Inhalation and Dermal Exposure

No data on distribution following inhalation or dermal exposures were identified. 

2.2.3 Other Routes of Exposure

Male and female mice were administered PFOS by subcutaneous injection one time on PNDs 

7, 14, 21, 28, or 35 at concentrations of 0 or 50 mg/kg bodyweight (bw) (Liu et al. 2009). 

Animals were killed 24 hours after treatment and the PFOS concentration levels obtained. The 

percent distribution found in the blood, brain, and liver are provided in Table 2-15. The 

distribution shows that beyond PND 14 the levels in the liver are approximately two to four 

times greater than those found on PND 7. 

Perfluorooctane sulfonate (PFOS) – May 2016 2-15
Table 2-15. Percent Distribution (%) of PFOS in Mice after a 50 mg/kg Subcutaneous 

Injection

PND

Males Females

Blood Brain Liver Blood Brain Liver

7 11.78 ± 2.88 5.04 ± 1.49 14.84 ± 4.01 10.77 ± 1.16 4.17 ± 1.17 16.23 ± 4.84

14 13.78 ± 1.52 1.61 ± 0.80** 26.50 ± 7.36 12.31 ± 2.24 3.26 ± 0.58 26.30 ± 4.54

21 9.85 ± 2.74 2.40 ± 0.60** 51.35 ± 11.06** 12.37 ± 3.80 2.14 ± 0.38** 51.48 ± 3.44**

28 9.89 ± 2.94 0.85 ± 0.19** 63.39 ± 19.78** 12.16 ± 2.32 2.10 ± 0.73** 51.05 ± 10.59**

35 13.33 ± 0.89 1.02 ± 0.28** 73.68 ± 6.86** 11.54 ± 1.28 0.90 ± 0.23** 69.92 ± 18.52**

Source: Data from Table 4 in Liu et al. 2009.

Note: **Statistically significant from PND 7 (p < 0.01)

2.3 Metabolism

No studies on the metabolism of PFOS were identified as it does not appear to be further 

metabolized once absorbed. However, electrostatic interactions with biopolymers are indicated 

by the Kerstner-Wood et al. (2003) data on binding to plasma proteins, in addition to the Zhang 

et al. (2009) and Chen and Guo (2009) data from albumin-binding investigations. PFOS binding 

to other serum and intracellular proteins also occurs. 

Weiss et al. (2009) screened the binding of PFOS to the thyroid hormone transport protein 

transthyretin (TTR) in a radioligand-binding assay to determine if it could compete with 

thyroxine (T4), the natural ligand of TTR. Human TTR was incubated with 125I-labeled T4, 

unlabeled T4, and 10–10,000 nanomoles (nmol) competitor (PFOS) overnight. The unlabeled T4 

was used as a reference compound, and the levels of T4 in the assay were close to the lower 

range of total T4 measured in healthy adults. PFOS had a high binding potency to TTR. The 50% 

inhibition concentration was 940 nmol. The authors concluded that PFOS demonstrates an 

affinity to TTR and had a greater affinity than the compounds with shorter chain lengths. 

Luebker et al. (2002) investigated the possibility that PFOS could interfere with the binding 

affinity of liver-fatty acid binding protein (L-FABP), an intracellular lipid-carrier protein, with 

long chain fatty acids (e.g., palmitic and oleic acid). This study was performed in vitro with a 

fluorescent fatty acid analogue 11-(5-dimethylaminoapthalenesulphonyl)-undecanoic acid 

(DAUDA). The concentration that can inhibit fifty percent of specific DAUDA-L-FABP binding 

(half-maximal Inhibiting Concentration, or IC50) was determined. PFOS demonstrated inhibition 

of L-FABP in competitive binding assays; with 10 micromoles (μmols) PFOS added, 69% of 

specific DAUDA-L-FABP binding was inhibited with the calculated IC50 of 4.9 μmol. 

L. Zhang et al. (2013) cloned the human L-FABP gene and used it to produce purified 

protein for evaluation of the binding of PFOA and other PFASs. Nitrobenzoxadizole-labeled 

lauric acid was the fluorescent substrate used in the displacement assays. IC50 values and 

dissociation constants were generated for the PFAS studied. Oleic and palmitic acids served as 

the normal substrates for L-FABP binding. The nitrobenzoxadiazole labeled lauric acids 

indicated that there were two distinct binding sites for fatty acids in human FABP, with the 

primary site having a 20-fold higher affinity than the secondary site. The IC50 value for PFOS 

was 3.3 ±1 μmol, suggesting that it has a higher binding affinity than PFOA. 

Perfluorooctane sulfonate (PFOS) – May 2016 2-16
2.4 Excretion

2.4.1 Oral Exposure 

Humans. Urinary excretion of PFOS in humans is impacted by the isomeric composition of the 

mixture present in blood and the gender/age of the individuals. The half-lives of the branched 

chain PFOS isomers are shorter than those for the linear molecule, an indication that renal 

resorption is less likely with the branched chains.

Y. Zhang et al. (2013) determined half-lives for PFOA isomers based on paired serum 

samples and early morning urine samples collected from healthy volunteers in two large Chinese 

cities. Half-lives were determined using a one compartment model and an assumption of first 

order clearance. The volume of distribution (Vd) applied in the analysis as determined by 

Thompson et al. (2010) was 170 mL/kg. Clearance was estimated from the concentration in urine 

normalized for creatinine and assuming excretion of 1.2 and 1.4 L/day of urine and 0.9 and 

1.1 mg creatinine/day for males and females, respectively. The mean half-life for the sum of all 

PFOS isomers in younger females (n = 20) was 6.2 years (range: 5.0–10 years), while that for all 

males and older females (n = 66) was 27 (range: 14–90 years); the medians were 6.0 and 18 

years, respectively.

The mean half-life values for the six branched chain isomers of PFOS were lower than the 

value for the linear chain with the exception of the 1-methyl heptane sulfonate, suggesting that 

resorption transporters may favor uptake of the linear chain and 1-methyl branched chain over 

the other isomers. Older females and males have longer half-lives than young females, 

suggesting the importance of monthly menstruation as a pathway for excretion (Y. Zhang et al. 

2013). The mean half-life for the 1-methylheptane sulfonate in the males and older females 

(n = 43) was considerably greater than that for the sum of all isomers (90 years versus 27 years). 

For males and older females there were considerable inter-individuals differences, with 100-fold 

differences between the minimum and maximum values among the males and older females 

compared to < 10-fold differences for the younger females. 

T. Zhang et al. (2014) derived estimates for PFOA’s urinary excretion rate using paired urine 

and blood samples from 54 adults (29 male, 25 female) in the general population and 27 

pregnant females in Tainjin, China The age range for the general population was 22–62 and that 

for the pregnant females was 21–39. Urinary excretion was calculated based on the concentration 

in the urine times volume of urine, wherein a urinary volume of 1200 mL/day was applied to all 

females and 1600 mL/day applied to all males. Urine samples were first draw morning samples. 

Total daily intakes for PFOS were calculated from the concentration in blood using first order 

assumptions, a half-life of 5.4 years (Olsen et al. 2007) and a volume of distribution of 

170 mL/kg (Thompson et al. 2010; Egeghy and Lorber 2011). Urinary elimination rate was then 

calculated from the urine levels and the modeled total daily intake. Total daily intake, and thus 

the urinary elimination rate, was not calculated for pregnant females due to the highly variable 

blood levels of PFOS during pregnancy. PFOS was detected in the blood samples for all 

participants but only for 48% of the urine samples from the general population and 11% of 

samples from the pregnant females. Unfortunately the urinary PFOS was below detection for 

most of the females in the study. 

The calculated geometric mean total daily intake for PFOS was 89.2 ng/day for the adult 

general population, resulting in a daily urinary excretion rate of 16% of the estimated intake; 

there was no significant difference between males and females. From the limited number of urine 

Perfluorooctane sulfonate (PFOS) – May 2016 2-17
samples available, the urine:blood ratio was lower for pregnant females than nonpregnant 

females (0.0004 versus 0.0013) suggesting other removal pathways such as placenta and cord 

blood. There was a difference between the younger menstruating females (21–50 years versus 

51–61 years), with a higher ratio for the younger females (0.0018 versus 0.0006). There is no 

indication that data were collected from the participants relative to menstruation status on the day 

of blood and urine collection. There was a significant difference between PFOS urinary excretion 

in older adults compared to younger adults (p = 0.015), with a higher elimination rate in the 

younger adults compared to the older age group. 

Wong et al. (2014) looked at the role of menstrual blood as an excretory pathway to explain 

the shorter half-life of PFOS in females than males. They fit a population-based pharmacokinetic 

model to six cross-sectional National Health and Nutrition Examination Survey (NHANES) data 

sets (1999–2012) for males and females. They concluded that menstruation could account for 

about 30% of the elimination half-life difference between females and males. Verner and 

Longnecker (2015) suggested a need to consider the nonblood portion of the menstrual fluid and 

its albumin content in the Wong et al. (2014) estimate for the menstrual fluid volume. A yearly 

estimate for serum loss of 868 mL/year by Verner and Longnecker (2015) compared to the 

432 mL/year estimate of Wong et al. (2014) suggests that the menstrual fluid loss can account 

for > 30% of the difference in the elimination half-life between females and males. 

Harada et al. (2007) obtained serum and bile samples from patients (2 male and 2 female; 

aged 63–76) undergoing gallstone surgery to determine the bile to serum ratio and biliary 

resorption rate. The median concentration for PFOS in the serum was 23.2 ng/mL (0.023 ppm), 

compared to the bile, 27.9 ng/mL (0.028 ppm). The fact that the levels in bile concentrations are 

higher than in serum is supportive of bile as a route of excretion. The biliary resorption rate was 

0.97, which could contribute to the long half-life in humans. Method of exposure to PFOS was 

unknown. 

Biliary excretion in humans and the potential for resorption from bile discharged to the 

gastrointestinal (GI) tract is supported by the Genuis et al. (2010) self-study of the potential for 

cholestyramine to lower the levels of PFAS in blood. Ingestion of 4 g/day cholestyramine (a bile 

acid sequestrant) in three doses for 20 weeks decreased the PFOS serum levels from 23 ng/g 

serum to 14.4 ng/g serum. 

Animals. In a study by Chang et al. (2012), three Sprague-Dawley rats/sex/timepoint were 

administered 14C-PFOS as the potassium salt, one time by oral gavage at a dose of 4.2 mg/kg. 

Urine and feces were collected after 24 and 48 hours. The amounts recovered in urine and feces 

were approximately equivalent at each time point: 1.57% and 1.55%, respectively, at 24 hours 

and 2.52% and 3.24%, respectively, at 48 hours. 

Ten male Sprague-Dawley rats (~ 9 weeks old)/group were administered 0, 5, or 

20 mg/kg/day of either PFOA or PFOS by gavage once daily, 7 days a week for 4 weeks (Cui et 

al. 2010). The dose groups were identified as the following: Group (G) 0 = ultrapure water; 

G1 = 5 mg/kg/day PFOA; G2 = 20 mg/kg/day PFOA; G3 = 5 mg/kg/day PFOS; and 

G4 = 20 mg/kg/day PFOS. Urine and fecal samples were obtained after the daily gavage by 

placing the rats in metabolism cages for 24 hour intervals on the following days: prior to 

treatment (day 0), day 1, and days 3, 5, 7, 10, 14, 18, 21, 24, and 28. Urine was collected three 

times daily, and the volume of the urine sample and weight of the fecal sample were recorded. 

Samples were stored at −40 degrees Celsius (°C) prior to analyzing. Target analytes were 

Perfluorooctane sulfonate (PFOS) – May 2016 2-18
determined by using a high-performance liquid chromatography-electrospray tandem mass 

spectrometry system with separation of PFOS and PFOA achieved by the analytical column. 

An upward trend of increased excretion was observed in the rats administered 5 mg/kg/day 

PFOS during the study and a similar trend was observed in the rats administered 20 mg/kg/day 

PFOS. However, in the third week, mortalities occurred. By study day 24, there were only 2 out 

of 10 rats in the 20 mg/kg/day group surviving. The range of PFOS excreted in urine by rats 

treated with 20 mg/kg/day was 0.080 mg on day 1 to 0.673 mg on day 14. In the feces, the lowest 

amount of PFOS was at 5 mg/kg/day on day 1 (0.0015 mg) and the highest on day 28 

(0.355 mg). A similar trend in feces was observed in the rats treated with 20 mg/kg/day until the 

deaths occurred; however, the fecal excretion reached a steady state after a maximum on day 18 

(0.519 mg). This steady state could have been the result of lower feces volume because the rats 

had decreased food intake as well. The mean fecal excretion rates of PFOS between the two dose 

groups was comparable as 1.2% and 1.3% of the oral doses were eliminated by fecal excretion in 

the 5 mg/kg/day and 20 mg/kg/day groups on day 1, respectively, indicating a majority of the 

dose was absorbed. Overall, more PFOS was eliminated in the urine rather than the feces, but 

there was not a notable difference in total excretion between the two PFOS dose groups. When 

the average elimination rates (urinary, fecal, and overall) of PFOA versus PFOS were compared, 

the amount of PFOA being eliminated was higher than PFOS, especially on the first day. The 

elimination rates on the first day were 2.6% and 2.8% in rats at 5 mg PFOS/kg/day and 20 mg 

PFOS/kg/day, respectively (see Figure 3.2). 

Notes: No urine was available after day 18 in the 20 mg/kg/day group due to high mortality in this group. *Statistically-significant at p < 0.05 **Statistically-significant at p < 0.01

Figure 2-2. PFOS Contents in Urine, Feces, and Overall Excretion in Male Rats Treated 

for 28 Days 

Five groups of 16 female Crl:CD(SD)IGS VAF/Plus rats each were administered 0, 0.1, 0.4, 

1.6, or 3.2 mg PFOS/kg bw/day by oral gavage beginning 42 days prior to cohabitation and 

continuing through GD 14 or 20 (Luebker et al. 2005b). Urine and feces were collected 

overnight from dams on the eve of cohabitation day 1 and during GDs 6–7, 14–15, and 20–21. 

The concentrations in the feces were consistently about 5 times greater than in the urine (see 

Table 2-10). 

2.4.2 Inhalation Exposure

In a case report, a 51-year old asymptomatic male researcher lived in a home with carpet 

flooring that had been treated intermittently with soil/dirt repellants. The carpeting also had an 

Perfluorooctane sulfonate (PFOS) – May 2016 2-19
in-floor heating system under the carpets (Genuis et al. 2010). Because of his work, the man 

knew that he had an unusually high amount of PFASs in his serum, primarily 

perfluorohexanesulfonic acid (PFHxS), PFOS, and PFOA. The level of PFOS in his serum was 

26 ng/g, the level in his urine was < 0.50 ng/mL, and it was < 0.50 ng/g in sweat and stool 

samples. The man began treatment with two bile acid sequestrants, cholestyramine (CSM) and 

saponin compounds (SPCs) to see if they would lower the serum PFAS levels. Stool samples 

were evaluated for PFOS levels after administration of each compound. The concentration of 

PFOS was increased after CSM treatment, suggesting that it may help with removing PFOS that 

gains access to the GI tract with bile. The first stool sample after approximately 20 weeks of 

CSM treatment showed PFOS levels of 9.06 ng/g and the second, 7.94 ng/g. The treatment with 

SPCs did not increase the PFOS found in the stool. Serum levels of PFOS decreased to 15.6 ng/g 

after 12 weeks of treatment with CSM and to 14.4 ng/g after 20 weeks of treatment even though 

the man’s exposure at his home had not changed. 

2.5 Pharmacokinetic Considerations

2.5.1 Pharmacokinetic models

Toxicokinetic models that can accommodate half-life values that are longer than would be 

predicted based on standard absorption, distribution, metabolism, and excretion concepts have 

been published as tools to estimate internal doses for humans, monkeys, and rats. The underlying 

assumption for all of the models is saturable resorption from the kidney filtrate, which 

consistently returns a portion of the excreted dose to the systemic circulation and prolongs both 

clearance from the body (e.g., extends half-life) and the time needed to reach steady state.

One of the earliest physiologically-based pharmacokinetic (PBPK) models (Andersen et al. 

2006) was developed for PFOS using two dosing situations in cynomolgus monkeys. In the first, 

three male and three female monkeys received a single intravenous dose of potassium PFOS at 

2 mg/kg (Noker and Gorman 2003). For oral dosing, groups of four to six male and female 

monkeys were administered daily oral doses of 0, 0.03, 0.15, or 0.75 mg/kg PFOS for 26 weeks 

(Seacat et al. 2002). 

This model was based on the hypothesis that saturable resorption capacity in the kidney 

would account for the unique half-life properties of PFOS across species. The model structure 

(Figure 2-3; Andersen et al. 2006) was derived from a published model for glucose resorption 

from the glomerular filtrate via transporters on the apical surface of renal tubule epithelial cells.

The model was parameterized using the body weight and urine output for cynomolgus 

monkeys (Butenhoff et al. 2002, 2004) and a cardiac output of 15 liters (L)/hour (h)-kg from the 

literature (Corley et al. 1990). Other parameters were assumed or optimized to fit the best for 

monkeys. In the intravenous time course data, some time and/or dose-dependent changes 

occurred in distribution of PFOS between the blood and tissue compartments, and these changes 

were less noticeable in the females, therefore, only the female data were used. The simulation 

captured the overall time course scenario but did not provide good correspondence with the 

initial rapid loss from plasma and the apparent rise in plasma concentrations over the first 

20 days. For the oral dosing, the 0.15 mg/kg dose simulation was uniformly lower, and the 

0.75 mg/kg dose simulation was higher than the data. When compared to PFOA, PFOS had a 

longer terminal half-life and more rapid approach to steady-state with repeated oral 

administration. 

Perfluorooctane sulfonate (PFOS) – May 2016 2-20
Figure 2-3. Schematic for a Physiologically-Motivated Renal Resorption 

Pharmacokinetic Model

Tan et al. (2008) developed a physiologically-based pharmacokinetic model by modifying 

the model by Andersen et al. (2006). The new model included time-dependent descriptions and a 

liver compartment for rats and monkeys to simulate the data on plasma and urine concentrations 

of PFOS in male and female cynomolgus monkeys after a single intravenous (IV) injection of 

2 mg PFOS/kg bw (Noker and Gorman, 2003), and to simulate the time course data on plasma 

concentrations of PFOS in rats after single oral dosing (see Figure 2-4 below). Only one timedependent function (protein binding) was needed to fit the plasma data from male monkeys 

exposed to PFOS, while two functions (protein binding and volume of distribution) were needed 

to fit the male rat data. The PFOS retention in the liver appeared to occur only in male rats but

not in male monkeys because of the higher liver:blood partition coefficient and additional 

binding in the rat liver. The liver:blood partition coefficient was 1 in the monkey and 6.51 in the 

rat. Comparing the renal resorption parameters, the transport maximum (Tm) was about 1,500 

times higher in the monkey than the rat. Comparing PFOA and PFOS, the model suggested that 

PFOS was retained in the tissues longer by the higher liver:blood partition coefficient and renal 

filtration. The author stated that development of a human model was feasible.

Loccisano et al. (2011) developed a PFOS PBPK model for monkeys based on the Andersen 

et al. (2006) and Tan et al. (2008) models, and they extrapolated it for use in humans (Figure 

2-5). The model reflects saturable renal absorption of urinary PFOS by the proximal tubule of the 

kidney. This is represented in Figure 2-5 by the interactions between the plasma and kidney, plus 

the interaction of the filtrate compartment with both plasma and kidney. A second route for 

PFOS resorption is represented by the gut plasma interaction that allows for resorption of PFOS 

from bile secreted into the gastrointestinal tract.

The fraction of PFOS free in plasma and available for glomerular filtration was based on data 

fit and was considered to decrease over time. Lacking primary data on transporter resorption 

kinetics, the rate was based on the best fit to the plasma/urine data. Binding to serum albumin 

allowed for less than a tenth of the plasma concentration to be available for glomerular filtration. 

A storage compartment was added to the model between the filtrate compartment and urine 

because PFOS appears in the urine at a slower rate than it disappears from the plasma.

Perfluorooctane sulfonate (PFOS) – May 2016 2-21
Notes: Tm = transport maximum, Kt = affinity constant, and Q = flow in and out of tissues

Figure 2-4. Structure of Model for PFOS in Rats and Monkeys

Notes: Tm = transport maximum, Kt = affinity constant, and Q = flow in and out of tissues

Figure 2-5. Structure of the PFOS PBPK Model in Monkeys and Humans

Perfluorooctane sulfonate (PFOS) – May 2016 2-22
Existing data sets for the cynomolgus monkey were used to develop the monkey model. The 

IV data came from monkeys administered a single dose of 2 mg/kg, and the concentrations in 

plasma and urine were monitored for up to 161 days after dosing (Noker and Gorman 2003). The 

repeat-dose oral data were from Seacat et al. (2002) with exposures to 0, 0.03, 0.15, or 

0.75 mg/kg by capsule for 26 weeks with follow-up monitoring of plasma levels in two monkeys 

per group at the two highest doses for a year after the cessation of dosing. Both data sets show 

that the plasma and liver are the primary target tissues for PFOS. The model projections for the 

repeat dose oral study were in good agreement with the Seacat et al. (2002) data for the 

0.15 mg/kg dose, but overestimated the plasma values for the 0.75 mg/kg/day dose. The model 

projected a sharper rise in plasma levels with achievement of steady state more rapidly than 

indicated by the experimental results.

Human data for PFOS are limited, although serum concentrations were collected from retired 

workers (Olsen et al. 2007) and from residents (n = 25) in Little Hocking, Ohio. The structure of 

the human model was similar to that used for the monkeys (Loccisano et al. 2011). The fact that 

the serum data applied to measurements made following uncertain exposure routes and uncertain 

exposure durations presented a challenge in the assessment of model fit. The human half-life 

used for the model (5.4 years) came from an occupational study (Olsen et al. 2007, see section 

2.5.2). No measures of PFOS concentration were available for the drinking water at Little 

Hocking, so the authors estimated the value that could account for the average population serum 

concentration. The value for the drinking water was estimated to be 0.34 parts per billion (ppb). 

The model results can be characterized as good when compared to the reported average serum 

measurements. The average daily exposure, consistent with the serum value, was estimated as 

0.003 μg/kg/day during the period from 1999 to 2000, and about 0.002 μg/kg/day for the 2003 to 

2009 time period. The authors concluded that in order to refine the human model more data are 

needed on the kinetics of renal transporters and intrahuman variability, as well as definitive 

information on exposures. 

Additional projections of human exposures consistent with measured average serum levels 

from selected human populations have also been published (Egeghy and Lorber 2011; Thompson 

et al. 2010). Both papers used a first-order, one-compartment model to assess PFOS exposure 

from both an intake and body burden perspective using the following equations to determine 

clearance (CL) with information on Vd and chemical half-life (t1⁄2).

CL = Vd x (ln2 ÷ t1⁄2) 

Human dose = average serum concentration x CL

Egeghy and Lorber (2011) estimated PFOS exposures from both intake and serum 

measurements for both typical and contaminated scenarios for adults and children, using 

available data from peer-reviewed publications. A range of intakes was estimated from the PFOS 

serum concentrations reported by NHANES, as well as published concentrations in various 

media including dust, air, water, and foods. In the absence of human data, high and low 

bounding estimates of 3 L/kg and 0.2 L/kg were used for volume of distribution. Total PFOS 

intakes over all pathways were estimated to be 160 and 2,200 ng/day for adults and 50 and 

640 ng/day for children in typical and contaminated scenarios, respectively, with food ingestion 

being the main exposure source in adults and food and dust ingestion being the two main sources 

in children. Based on the model predictions, the range of intake of PFOS consistent with the 

serum levels was 1.6 to 24.2 ng/kg-bw/day for adults, assuming a 70 kg body weight. 

Perfluorooctane sulfonate (PFOS) – May 2016 2-23
Thompson et al. (2010) predicted PFOS concentration in blood serum as a function of dose, 

elimination rate, and volume of distribution. The volume of distribution in this study, 0.23 L/kg 

bw, was adjusted by 35% from the calibrated data for PFOA in accordance with the differences 

in PFOA and PFOS volumes of distribution calculated by Andersen et al. (2006). The volume of 

distribution from PFOA was obtained by calibrating human serum and exposure data collected 

from two communities in the Little Hocking, Ohio area (see section 2.5.3). Applying the volume 

of distribution and elimination rate values for PFOS calculated from the Little Hocking 

population to serum data collected from members of the Australian population, the predicted 

intake by the Australian population was calculated to be 1.7 to 3.6 ng/kg bw/day.

Fàbrega et al. (2014) adapted the Loccisano et al. (2011) model to include compartments for 

the brain and lung and remove the skin. They applied the adjusted model to humans by using 

intake and body burden data from residents in Tarragona County, Spain. Food and drinking 

water were the major vehicles of exposure. Body burden information came from blood samples 

from 48 residents, and tissue burdens came from 99 samples of autopsy tissues. The adjusted 

model over-predicted serum levels by a factor of about two for PFOS but under-predicted the 

levels in both liver (slightly) and kidney (by a factor of about 4). 

The authors also looked at the value of using partition coefficients from human tissues in 

place of the Loccisano et al. (2011) rat data. The PFOS simulation values were closer to the 

human experimental data when using the human partition coefficients values for liver, brain, and 

kidney but not for the lung PFOS results. However, the Loccisano et al. (2011) model 

demonstrated better performance overall. The authors suggested that both saturable resorption 

and variations in protein binding are important parameters for pharmacokinetic models. With the 

exception of serum albumin, the existing models have not considered protein binding constants 

within tissues. Even though the use of human partition coefficients improved the steady state 

predictions overall for tissues there were still considerable differences between the experimental 

values and the predictions for both models. 

Loccisano et al. (2012a) utilized the saturable resorption hypothesis and pharmacokinetic 

data from Chang et al. (2012), 3M Environmental Laboratory (2009), and Seacat et al. (2003) for 

adult Sprague-Dawley rats to develop the model depicted in Figure 2-6. The structure of the 

model is similar to that for the monkey/human model depicted in Figure 2-5 but lacks the fat and 

skin compartments and includes a storage compartment to accommodate fecal loss of unabsorbed 

dietary PFOS as well as that from biliary secretions. Partition coefficients for liver:plasma, 

kidney:plasma, and rest of the body:plasma were derived from unpublished data on mice by 

DePierre (2009) through personal communication to authors (Loccisano et al. 2012a); most of 

the other kinetic parameters were based on values providing the best fit to the experimental data. 

The free fraction in plasma was allowed to decrease with time suggesting a strong binding to 

serum proteins. 

The agreement between the experimental data and the model output was good but requires 

additional data from experimental studies on plasma binding and renal tubular transporters to 

support further refinement of the parameters derived from model fit. In general, liver and plasma 

concentrations after daily dosing were overestimated by a factor of about two. Male and female 

rats did not differ significantly in their ability to move PFOS from tissues to urine or in 

resorption capability. PFOS appeared to have a greater capacity to bind to sites in the liver than 

PFOA.

Perfluorooctane sulfonate (PFOS) – May 2016 2-24
Figure 2-6. Structure of the PBPK Model for PFOS in the Adult Sprague-Dawley Rat 

Loccisano et al. (2012b) expanded their adult Sprague-Dawley rat model described above to 

cover gestational and lactational exposure to the fetus and pups. The data from Thibodeaux et al. 

(2003) and Chang et al. (2012) for GDs 0 to 20 were used in model development. Both studies 

used multiple dose levels in addition to data on serum and selected tissue concentrations (liver, 

brain) from the dams and fetuses at one or more time points. The gestational model structure for 

the dams is similar to Figure 2-6. The model was expanded to include the fetuses linked to the 

dams by way of the placenta. Uptake from the placenta was described by simple diffusion; the 

fetal plasma compartment was separate from the dams as was distribution to fetal tissues and 

amniotic fluid. The model allowed for saturable binding of PFOS within the liver and to serum 

proteins. Model performance was judged by its ability to predict 24-hour area under the curve 

(AUC) for plasma, liver, and brain for both the fetus and dam. Brain data were only available 

from the Chang et al. (2012) study. 

According to the model, liver concentrations for the dam are six to seven times greater than 

those for the fetus, and the brain levels for the fetus about eight times greater than those for the 

dam. Model performance in comparison to the experimental data was judged to be good. The 

model was used to project the maternal and fetal plasma levels expected at the doses employed in 

the Butenhoff et al. (2009), Luebker et al. (2005a, 2005b), Yu et al. (2009a), and Lau et al. 

(2003) studies as depicted in Figure 2-7. 

Perfluorooctane sulfonate (PFOS) – May 2016 2-25
Figure 2-7. Predicted Daily Average Concentration of PFOS in Maternal (Black Line) and 

Fetal (Gray Line) Plasma at External Doses to the Dam

The lactational component of the Loccisano et al. (2012b) model allowed for PFOS transport 

to neonates via mammary-tissue secretion and consequent ingestion by the pups. Pup tissues 

included in the lactational model included the gut, liver, kidney, and the remainder of the body. 

A renal filtrate compartment linked to plasma and the kidney allowed for neonate PFOS 

resorption. PFOS transfer to milk via the mammary gland was assumed to be controlled by 

simple diffusion. Pup urine returned PFOS from the kidney filtrate to the dam. 

Loccisano et al. (2013) extended their model development to cover humans during pregnancy 

and lactation, building on the work done with rodents and recognizing the limitations of the 

human data available for evaluating the model predictions. Figure 2-8 illustrates the structure of 

the model used. The basic structure was derived from the rat model discussed above. Some of the 

key features of the model are summarized below: 

• The fetus is exposed via the placenta through simple bidirectional diffusion.

• Transfer rates to the fetus from the amniotic fluid are governed by bidirectional diffusion. 

• Transfer from the fetal plasma to tissues is flow-limited. 

• Maternal plasma is directly linked to the milk compartment and considered to be flow 

limited; only the free fraction in plasma is transferred to maternal milk. 

• The neonate is exposed to PFOS only via maternal milk for the first 6 months 

postpartum. 

• The infant in the model is treated as one compartment with a volume of distribution. 

Perfluorooctane sulfonate (PFOS) – May 2016 2-26
Figure 2-8. PBPK Model Structure for Simulating PFOA and PFOS Exposure During 

Pregnancy in Humans (Maternal, Left; Fetal, Right)

Limitations to the model are acknowledged and attributed primarily to lack of data to support 

a more mechanistic approach. Physiological parameters applicable to a pregnant or lactating 

woman, the fetus, and the nursing infant were obtained from a variety of referenced publications. 

In order to obtain a plasma value at the time of conception, the model was run until it reached 

a prepregnancy steady state concentration. The model predicted 30 years as the exposure 

necessary to reach steady state (1 x 10-4 to 2 x 10-3 μg/kg bw/day) for the general female 

population. The model performance simulations for PFOS were run using an exposure of 

1.35 × 10-3 μg/kg bw/day. Projections were developed for maternal plasma, fetal plasma, infant 

plasma, and maternal milk. Agreement between the observed concentrations (μg/L) and the 

predicted values was considered satisfactory if the predicted value was within 1% of the 

observed value. Model output was compared to maternal and fetal plasma values at delivery or at 

specific time points, and for the infant plasma and milk data where available. Predicted 

maternal:fetal plasma (cord blood) concentration ratios were more variable for PFOS than PFOA 

in the comparisons to the published data. The projections for fetal internal dose were reasonable, 

and there was good agreement between the model and the available human lactation data. When 

modeled, the maternal plasma was 14 μg/L at conception, slowly decreased across the gestation 

period, and increased slightly at delivery. For the most part the modeled results fell within ± 1 

SD of the observed data. 

Perfluorooctane sulfonate (PFOS) – May 2016 2-27
During lactation there was a gradual, very-slight, decline in maternal plasma across the six 

months of lactation. Thereafter, plasma values slowly increased and stabilized at about 12.5 μg/L 

at six months postpartum. The fetal plasma was about 6.5 μg/L at the start of gestation, and 

declined to about 5.5 μg/L at the time of delivery. Maternal plasma values are about twice those 

for the fetus. During the lactation period, the infant plasma increased in a linear fashion to a 

terminal value of about 13 μg/L. Milk concentrations declined very slightly across the lactation 

period with an initial concentration of 0.16 μg/L and a final value of 0.15 μg/L. These 

concentrations were estimated from the graphic data presentation. 

The projections for PFOS differed from those for PFOA in several respects. Most 

importantly maternal and fetal plasma values were similar for PFOA but for PFOS, maternal 

levels were approximately two-fold greater than fetal levels. Compared with PFOS, there was a 

much greater decline in maternal PFOA plasma values during lactation accompanied by a 

comparable decline in the PFOA concentration in milk. The increase in infant plasma across the 

lactation period was comparable for PFOA and PFOS with the concentration at 6 months 

postpartum about 2.5 times higher than that at 1 month. 

The authors compared the human pregnancy lactation model results to published data, and 

they identified several important research needs as follows:

• Are there differences in the transporter preferences and transfer rates for the individuals 

PFASs? Do those differences correlate with half-life differences?

• Are there qualitative or quantitative differences between the transporters favored by 

PFOS compared to PFOA?

• What physiological factors influence clearance for the mother, the fetus, and the infant 

during gestation and lactation? 

• Are placental transport processes active, facilitated, or passive? 

These research needs are more pronounced for PFOS than PFOA, because the information 

supporting renal resorption and tissue uptake via membrane transporters for PFOS is very 

limited. Most models infer that PFOS and PFOA are similar based on their half-lives rather than 

on published research on transporters. 

The authors acknowledged the lack of primary experimental data on PFOS transport and 

potential transporters. Similarity to PFOA was assumed in model development, and PFOS was 

transparently described as lacking supporting transporter data. The authors concluded that 

additional research on PFOS binding to serum proteins and liver tissues, its biliary excretion and 

resorption, and information on renal resorption transporters in dams and pups are needed to 

accomplish further refinements to the published model (Loccisano et al. 2012b, 2013).

Building on the work of other researchers, Wambaugh et al. (2013) developed and published 

a pharmacokinetic model to support the development of an EPA reference dose for PFOS. The 

model was applied to data from studies conducted in monkeys, rats, or mice that demonstrated an 

assortment of systemic, developmental, reproductive, and immunological effects. A saturable 

renal resorption pharmacokinetic (PK) model was again used. This concept has played a 

fundamental role in the design of all of the published PFOS models summarized in this section. 

In this case, an oral dosing version of the original model introduced by Andersen et al. (2006) 

and summarized early in section 2.5.3 was selected for having the fewest number of parameters 

that would need to be estimated. A unique feature of the Wambaugh et al. (2013) approach was 

to use a single model for all species in the toxicological studies in order to examine the 

Perfluorooctane sulfonate (PFOS) – May 2016 2-28
consistency in the average serum values associated with effects and with no effects from 13 

animal studies of PFOS. The model structure is that depicted in Figure 2-3 with minor 

modifications.

Wambaugh et al. (2013) placed bounds on the estimated values for some parameters of the 

Andersen et al. (2006) model to support the assumption that serum carries a significant portion of 

the total PFOS body load. The Andersen et al. (2006) model is a modified two-compartment 

model in which a primary compartment describes the serum and a secondary deep tissue 

compartment acts as a specified tissue reservoir. Wambaugh et al. (2013) constrained the total 

volume of distribution to a value of not > 100 times that in the serum. As a result, the ratio of the 

two volumes (serum versus total) was estimated in place of establishing a rate of transfer from 

the tissue to serum. 

A nonhierarchical model for parameter values was assumed. Under this assumption a single 

numeric value represents all individuals of the same species, gender, and strain. The gender 

assumption was applied to the monkeys and mice, while male and female rats were treated 

separately because of the established gender toxicokinetic differences. Body weight, the number 

of doses, and magnitude of the doses were the only parameters to vary. In place of external 

doses, serum concentrations as measured at the time of euthanasia were used as the metric for 

dose magnitude. Measurement errors were assumed to be log-normally distributed. Table 2-16 

provides the estimated and assumed PK parameters applied in the Wambaugh et al. (2013) model 

for each of the species evaluated.

The PK data that supported the analysis were derived from two PFOS PK in vivo studies. The 

monkey PK data were derived from Seacat et al. (2002) and Chang et al. (2012). Data for the rats 

(male/females) and mice were both from Chang et al. (2012). The data were analyzed within a 

Bayesian framework using a Markov Chain Monte Carlo sampler implemented as an R package 

developed by EPA to allow predictions across species, strains, and genders and identify serum 

levels associated with the no observed adverse effect level (NOAEL) and lowest observed 

adverse effect level (LOAEL) external doses. The model chose vague, bounded prior 

distributions on the parameters being estimated allowing them to be significantly informed by 

the data. The values were assumed to be log normally distributed constraining each parameter to 

a positive value. 

The model predictions were evaluated by comparing each predicted final serum 

concentration to the serum value in the supporting animal studies. The predictions were generally 

similar to the experimental values. There were no systematic differences between the 

experimental data and the model predictions across species, strain, or gender, and median model 

outputs uniformly appeared to be biologically plausible despite the uncertainty reflected in some 

of the 95th percentile credible intervals. The application of the model outputs in the derivation of 

a human RfD is the focus of section 4 of this document. 

Perfluorooctane sulfonate (PFOS) – May 2016 2-29
Table 2-16. Pharmacokinetic Parameters from Wambaugh et al. (2013) Meta-Analysis of 

Literature Data

Parameter Units CD1 Mouse (F)a 

CD1 Mouse 

(M)a 

SpragueDawley Rat (F)a 

SpragueDawley Rat 

(M)a 

Cynomolgus 

Monkey

(M/F)a 

Bodyweightb kg 0.02 0.02 0.203 0.222 3.42

Cardiac 

Outputc

L/h/kg0.74 8.68 8.68 12.39 12.39 19.8

ka L/h 1.16 (0.617–

42,400)

433.4 (0.51–

803.8)

4.65 (3.02–

1,980)

0.836 (0.522–

1.51)

132 (0.225–

72,100)

Vcc L/kg 0.264 (0.24–

0.286)

0.292 (0.268–

0.317)

0.535 (0.49–

0.581)

0.637 (0.593–

0.68)

0.303 (0.289–

0.314)

k12 L/h 0.0093 (2.63 x

e-10 – 38,900)

2,976 (2.8 x e-10

–4.2 x e4)

0.0124 (3.1 x

e-10 –46,800)

0.00524 (2.86 x

e-10–43,200)

0.00292 (2.59 x 

e-10–34,500)

RV2:V1 Unitless 1.01 (0.251–

4.06)

1.29 (0.24–4.09) 0.957 (0.238–

3.62)

1.04 (0.256–

4.01)

1.03 (0.256–

4.05)

Tmaxc μmol/h 57.9 (0.671–

32,000)

1.1 x e4 (2.1–7.9

x e4)

1,930 (4.11–

83,400)

1.34 x e-6 (1.65 x 

e-10–44)

15.5 (0.764–

4,680)

KT μmol 0.0109 (1.44 x e-5

–1.45)

381 (2.6 x e-5–

2.9 x e3)

9.49 (0.00626–

11,100)

2.45 (4.88 x e-10

–60,300)

0.00594 (2.34 x 

e-5–0.0941)

Free Unitless 0.00963 

(0.00238–

0.0372)

0.012 (0.0024–

0.038)

0.00807 

(0.00203–

0.0291)

0.00193 

(0.000954–

0.00249)

0.0101 

(0.00265–0.04)

Qfilc Unitless 0.439 (0.0125–

307)

27.59 (0.012–

283)

0.0666 (0.0107–

8.95)

0.0122 (0.0101–

0.025)

0.198 (0.012–

50.5)

Vfilc L/kg 0.00142 (4.4 x

e-10 –6.2)

0.51 (3.5 x e-10

–6.09)

0.0185 (8.2 x e-7

–7.34)

0.000194 (1.48 x 

e-9–5.51)

0.0534 (1.1 x

e-7–8.52)

Notes: Means and 95% confidence interval (in parentheses) from Bayesian analysis are reported. For some parameters the 

distributions are quite wide, indicating uncertainty in that parameter (i.e., the predictions match the data equally well for a wide 

range of values). a Data sets modeled for the mouse and rat were from Chang et al. 2012 and for the monkey from Seacat et al. 2002 and Chang et 

al. 2012

b Average bodyweight for species:individual-specific bodyweights c Cardiac outputs obtained from Davies and Morriss 1993

Qfilc = median fraction of blood flow to the filtrate

Tmax = time of maximum plasma concentration

M = male; F = female

2.5.2 Half-life data

Differences between species were observed in studies determining the elimination half-life 

(T1/2) of PFOS in rats, mice, monkeys, and humans. Gender differences in rats do not appear to 

be as dramatic for PFOS as they are for PFOA (Loccisano et al. 2012a, 2012b). 

Humans 

Occupational Population. Blood sampling was performed on retirees from the 3M plant in 

Decatur, Alabama where PFOS was produced. These samples were taken approximately every 6 

months over a 5-year period to predict the half-life of PFOS. Results ranged from approximately 

4 years to 8.67 years (3M Company 2000; Burris et al. 2002). Both of these studies exhibited 

some deficiencies in sample collection and methods. 

Perfluorooctane sulfonate (PFOS) – May 2016 2-30
More recently, Olsen et al. (2007) obtained samples from 26 retired fluorochemical 

production workers (24 males and 2 females) from the 3M plant in Decatur, Alabama to 

determine the half-life of PFOS. Periodic serum samples (total of 7–8 samples per person) were 

collected over a period of 5 years, stored at −80 °C, and at the end of the study, Highperformance liquid chromatography/mass spectrometry was used to analyze the samples. The 

study took place from 1998 to 2004. The mean number of years worked at the plant was 31 years 

(range: 20–36 years), the mean age of the participants at the initial blood sampling was 61 years 

(range: 55–75 years), and the average number of years retired was 2.6 years (range: 0.4–11.5 

years). The initial arithmetic mean serum concentration of PFOS was 0.799 μg/mL (range: 

0.145–3.490 μg/mL), and when samples were taken at the end of the study the mean serum 

concentration was 0.403 μg/mL (range: 0.037–1.740 μg/mL). Semi-log graphs of concentration 

versus time for each of the 26 individuals were created, and individual serum elimination halflives were determined using first-order elimination. The arithmetic and geometric mean serum 

elimination half-lives of PFOS were 5.4 years (95% confidence interval [CI]: 3.9–6.9 years) and 

4.8 years (95% CI: 4.1–5.4 years), respectively.

General Population. No data on the half-life of PFOS in the general population were identified. 

Infants. Newborn Screening Programs (NSPs) collect whole blood as dried spots on filter paper 

from almost all infants born in the United States. One hundred and ten of the NSPs collected in 

the state of New York from infants born between 1997 and 2007 were analyzed for PFOS 

(Spliethoff et al. 2008). The analytical methods were validated by using freshly drawn blood 

from healthy adult volunteers. The mean whole blood concentration for PFOS ranged from 

0.00081 to 0.00241 μg/mL. The study grouped the blood spots by two different time-points; 

those collected in 1999–2000 and in 2003–2004, which corresponded to the intervals reported by 

NHANES. The PFOS concentrations decreased with a mean value of 0.00243 μg/mL reported in 

1999–2000 and 0.00174 μg/mL in 2003–2004. The study authors determined the half-life of 

PFOS using the regression slopes for natural log blood concentrations versus the year 2000 and 

after. The calculated half-life for PFOS was 4.1 years.

Animal Data 

A series of studies was performed to determine the pharmacokinetic parameters of PFOS in 

rats, mice, and monkeys following administration of single doses (Chang et al. 2012). Another 

study provided half-life information from monkeys administered PFOS for 26 weeks (Seacat et 

al. 2002). Minimal gender-related differences were observed in the species examined.

Monkeys. In the study by Chang et al. (2012), three male and three female monkeys were 

administered a single IV dose of PFOS of 2 mg/kg and followed for 161 days. All monkeys were 

observed twice daily for clinical signs, and body weights were obtained weekly. Urine and serum 

samples were taken throughout the study. There was no indication that elimination was different 

from males versus females. Serum elimination half-lives ranged 122–146 days in male monkeys 

and 88–138 days in females. Mean values are shown in Table 2-17. The Vd values suggest that 

distribution was predominately extracellular.

Perfluorooctane sulfonate (PFOS) – May 2016 2-31
Table 2-17. PFOS Pharmacokinetic Data Summary for Monkeys 

Species

Time 

evaluated 

after last dose Route Sex

Amount

K+PFOS 

(mg/kg)

Mean serum 

T1/2 by sex 

(days)

Mean serum 

T1/2 by 

species

(days)

Mean 

serum Vd

by sex 

(mL/kg)

Cynomolgus 

monkeys 23 weeks IV

M 2 132.0 ± 7

120.8

202

F 2 110.0 ± 15 274

Source: Data from Chang et al. 2012

M = male; F = female

Seacat et al. (2002) administered 0, 0.03, 0.15, or 0.75 mg/kg/day potassium PFOS orally in a 

capsule by intragastric intubation to 6 young-adult to adult cynomolgus monkeys/sex/group, 

except for the 0.03 mg/kg/day group which had 4/sex, daily for 26 weeks (182 days) in a GLP 

study. Two monkeys/sex/group in the control, 0.15, and 0.75 mg/kg/day groups were monitored 

for 1 year after the end of the treatment period for reversible or delayed toxicity effects. The 

elimination half-life for potassium PFOS in monkeys was estimated from the elimination curves 

as approximately 200 days. This value is consistent with that reported by Chang et al. (2012) 

above. 

Rats. Chang et al. (2012) conducted a series of pharmacokinetic studies in rats (Table 2-18).

First, a single oral dose of 4.2 mg 14C-K+PFOS/kg was administered to male Sprague-Dawley

rats (3/timepoint). Urine and fecal samples were collected for 24 and 48 hours. Interim sacrifices 

to obtain plasma samples were obtained at 1, 2, 6, 12, 24, 48, 96, and 144 hours post-dosing. In 

the next study, 3 rats/sex were administered 2.2 mg PFOS/kg once by oral gavage or IV 

administration. The rats had a jugular cannula in place and serum samples from it were obtained 

at 0.25, 0.5, 1, 2, 4, 8, 18, and 24 hours post-dosing. The T1/2 values should be viewed with 

caution because the blood samples were limited to a 24-hour post-dose observation period in 

contrast to the 144-hour (6-day) period from the first study. 

In a third study, serum uptake and elimination of PFOS were evaluated at two dose levels: 2 

mg/kg and 15 mg/kg. PFOS was administered as a single oral dose in a 0.5% Tween 20 vehicle 

to 3 rats/sex or 5/sex at the low and high dose, respectively. Periodic serum, urine, and fecal 

samples were taken for up to 10 weeks. Liver concentrations were evaluated at termination. Halflife estimates (Table 2-18) did not differ significantly with dose, but there was a difference by 

sex, with values for the males about half those for the females. There were also gender related 

differences in the volume of distribution values. PFOS concentrations in the liver exceeded those 

for paired serum concentrations. 

The studies by Chang et al. (2012) described above are limited in that they each reflect 

pharmacokinetic features associated with a single dose. In an unpublished study by 3M 

(Butenhoff and Chang 2007), 5 rats/sex were administered 1 mg/kg/day of PFOS orally for 28 

days. Interim blood, urine, and feces were obtained for up to 10 weeks. There was no effect on 

body weight, and PFOS elimination was more prominent in the urine than the feces. The 

elimination of PFOS in this study approximated first order kinetics with a ‘stair-stepping’ 

pattern. Using nonlinear, noncompartmental software for computation, the half-lives for males 

ranged 35–53 days and that for females ranged 33–55 days. 

Perfluorooctane sulfonate (PFOS) – May 2016 2-32
Table 2-18. PFOS Pharmacokinetic Data Summary for Rats 

Species

Time 

evaluated 

after last 

dose Route Sex

Amount

K+PFOS 

(mg/kg)

Mean 

serum T1/2

by dose 

(days)

Mean 

serum 

T1/2 by 

sex (days)

Mean 

serum T1/2

by

species

(days)

Mean serum 

Vd by dose 

(mL/kg)

SD rats 144 hours Oral M 4.2 8.2 ± 1.5 275

SD rats 24 hours

Oral M

2.2

3.1ab

Not determined due to 

study design.

765 a

F 1.9b 521

IV

M 8.0b 649

F 5.6a 586 a

SD rats 10 weeks Oral M 1 x 28 days 35–53 48.2 47.6 -

F 1 x 28 days 33–55 46.9 -

SD rats 10 weeks Oral

M 

2 38.3 ± 2.3 39.8

53.3

1,228

15 41.2 ± 2.0 666

F 

2 62.3 ± 2.1 66.7 484

15 71.1 ± 11.3 468

Source: Data from Chang et al. 2012 and Butenhoff and Chang 2007

Notes: a Data reflected a single value derived from one rat only b Within limits of the study design and a follow-up duration of only 24 hours 

NA= not available

M = male; F = female

Mice. CD-1 male and female mice were administered PFOS as a single oral dose of 1 or 20 

mg/kg (Chang et al. 2012). At designated times (2, 4, 8 hours and 1, 8, 15, 22, 36, 50, 64, and 

141 days) post-dosing, four mice/sex were sacrificed and blood, kidneys, and liver samples were 

obtained. Urine and feces were collected for each 24-hour period up until sacrifice. At the end of 

the observation period, the daily urinary and fecal excretion was < 0.1% of the administered 

dose. Results are shown in Table 2-19. Serum elimination values were similar for males and 

females, independent of dose administered (distribution appeared to be mostly extracellular). 

Table 2-19. PFOS Pharmacokinetic Data Summary for Mice

Species

Time 

evaluated 

after last 

dose Route Sex

Amount

K+PFOS 

(mg/kg)

Mean 

serum 

T1/2 by 

dose 

(days)

Mean 

serum 

T1/2 by 

sex (days)

Mean 

serum 

T1/2 by

species

(days)

Mean 

serum Vd

by dose 

(mL/kg)

CD-1 mice 20 weeks Oral

M 

1 42.8 39.6

36.9

290.0

20 36.4 263.0

F 

1 37.8 34.2 258.0

20 30.5 261.0

Source: Data from Chang et al. 2012

M = male; F = female

Table 2-20 summarizes the half-life data from the studies discussed above. Despite the 

limitation that the half-life values from most animal studies were derived from administration of 

only one dose (Chang et al. 2012), consistency was found in the half-lives for males and females 

for the monkeys, rats, and mice. In rats, this is in contrast to the results observed for PFOA, 

where there is a much longer half-life in males than in females. However, similar to PFOA, the 

half-life of PFOS in humans is much greater than that in laboratory animals. A measure of PFOS 

Perfluorooctane sulfonate (PFOS) – May 2016 2-33
half-life in a retired worker population is 5.4 years (Olsen et al. 2007), compared with several 

months in the laboratory animals.

Table 2-20. Summary of Half-Life Data

Source Human Monkey Rat Mouse Strain

Spliethoff et al. 2008 4.1 years ND ND ND Infants

3M Company 2000 4–8.67 years ND ND ND Occupational

Olsen et al. 2007 5.4 years ND ND ND Occupational

Butenhoff and Chang 2007 ND ND 48.2 days (M)

46.9 days (F)

ND SD; 28 days oral

Chang et al. 2012 ND ND 39.8 days (M)

66.7 days (F)

ND SD; single oral 

dose

ND ND ND 39.6 days (M)

34.2 days (F)

CD-1; single oral 

dose

ND 132 days (M)

110 days (F)

ND ND Cynomolgus; 

single IV dose

Seacat et al. 2002 ND 200 days (M/F) ND ND Cynomolgus; 

oral, 182 days

Note: ND = No Data

M = male; F = female

The animal data summarized in Table 2-20 show fairly consistent half-life values following 

single and multiple dosing regimens in both the rat and monkey, probably due to the relatively 

long follow-up in both species after the last dosing was given. In the rat, half-lives for males and 

females were nearly identical at 48.2 and 46.9 days, respectively, after 28 days of dosing and 10 

weeks of follow-up (Butenhoff and Chang 2007). These results for rats were more consistent 

between sexes than those half-life values calculated after a single oral dose (Chang et al. 2012). 

In male and female monkeys, half-life values were similar for either a single intravenous dose 

(Chang et al. 2012) or repeated oral dosing for 182 days (Seacat et al. 2002). Half-life values for 

male and female monkeys from Chang et al. (2012) were calculated from the serum 

concentrations measured over 23 weeks, while the value from Seacat et al. (2002) was estimated 

from the elimination curves. 

2.5.3 Volume of Distribution Data

Humans. None of the available studies provide data for calibration of volume of distribution of 

PFOS in humans. However, several researchers have attempted to characterize PFOS exposure 

and intake in humans (Thompson et al. 2010; Egeghy and Lorber 2011) through pharmacokinetic 

modeling. In the models discussed below, volume of distribution was defined as the total amount 

of PFOS in the body divided by the blood or serum concentration. 

Both research groups defined a volume of distribution for humans using a simple, first-order, 

one-compartment pharmacokinetic model (Thompson et al. 2010; Egeghy and Lorber 2011). The 

models developed were designed to estimate intakes of PFOS by young children and adults 

(Egeghy and Lorber 2011) and the general population of urban areas on the east coast of 

Australia (Thompson et al. 2010). In both models, the volume of distribution was calibrated 

using human serum concentration and exposure data from NHANES, and it was assumed that 

most PFOS intake was from contaminated drinking water. Thus, the value for volume of 

distribution was calibrated so that model prediction of elevated blood levels of PFOS matched 

those seen in the study population. 

Perfluorooctane sulfonate (PFOS) – May 2016 2-34
Thompson et al. (2010) used a first-order, one-compartment pharmacokinetic model, as 

described previously, to predict PFOS concentration in blood serum as a function of dose, 

elimination rate, and volume of distribution. The volume of distribution was first obtained for 

PFOA by calibrating human serum and exposure data. The volume of distribution for PFOS 

(230 mL/kg) was adjusted from the calibrated PFOA data by 35% in accordance with the 

differences in PFOA and PFOS volumes of distribution calculated by Andersen et al. (2006). The 

original Andersen et al. (2006) model was developed from oral data in monkeys and optimized a 

volume of distribution of 220 mL/kg for PFOS and 140 mL/kg for PFOA. Thus, the volume of 

distribution in monkeys for PFOS was approximately 35% greater than that for PFOA in the 

optimized models. Therefore, Thompson et al. (2010) used a volume of distribution of 

230 mL/kg for humans in their model. 

Egeghy and Lorber (2011) used high and low bounding estimates of 3,000 mL/kg and 

200 mL/kg for volume of distribution since data in humans were not available. The two separate 

estimates of volume of distribution were used in a first-order, one-compartment model to 

estimate a range of intakes of PFOA. They concluded that the volume of distribution was likely 

closer to the lower value based on a comparison of predicted modeled intake with estimates of 

intakes based on exposure pathway analyses. Use of the lower value gave a modeled intake 

prediction similar to that obtained by a forward-modeled median intake based on an exposure 

assessment. The authors concluded that the lower value of 200 mL/kg was appropriate for their 

analysis.

Both of the models described above used a volume of distribution calibrated from actual 

human data on serum measurements and intake estimates. A calibration parameter obtained from 

human studies, where constant intake was assumed and blood levels were measured, is 

considered a more robust estimate for volume of distribution than that optimized within a model 

developed from animal data.

Animals. The Chang et al. (2012) series of pharmacokinetic studies on rats, mice, and monkeys 

described above, included volume of distribution calculations. Values for all species were 

calculated following a single oral or IV dose of PFOS. As discussed below, the volume of 

distribution values reported for male and female monkeys, female rats, and male and female

mice were reasonably similar.

The volume of distribution was 202 and 274 mL/kg, for male and female cynomolgus 

monkeys, respectively (Table 2-17), following a single IV dose of 2 mg/kg (Chang et al. 2012). 

Animals were evaluated up to 23 weeks after dosing, and the resulting volumes of distribution 

are similar to the 230 mL/kg calibrated from human data by Thompson et al. (2010) described 

above. 

The Chang et al. (2012) volume of distribution findings for rats are in Table 2-18. Those 

values calculated from a follow-up duration of only 24 hours are not considered reliable. In 

studies with a longer follow-up after dosing, the values for male rats were 275, 666, and 

1228 mL/kg and, for female rats, values were 468 and 484 mL/kg. The volume of distribution 

was notably greater for male rats than that of female rats or other species including humans, with 

the exception of one value. The authors could not explain the higher value for the male rat but 

concluded that the volume of distribution for monkeys, rats, and mice is likely in the range of 

200–300 mL/kg.

Perfluorooctane sulfonate (PFOS) – May 2016 2-35
Data for mice (Chang et al. 2012) are shown in Table 2-19. For males and females the 

volume of distribution was 263–290 mL/kg and 258–261 mL/kg, respectively, following a single 

oral dose. 

Pharmacokinetic models based on animal data described previously in this section generally 

optimized the value for volume of distribution based on model output. The original Andersen et 

al. (2006) model was developed using data from Seacat et al. (2002) on serum PFOS 

concentrations in cynomolgus monkeys following oral dosing. The volume of distribution in this 

model was 220 mL/kg. 

2.6 Toxicokinetic Summary

Uptake and egress of PFOS from cells is largely regulated by transporters in cell membranes 

based on data collected for PFOA, a structurally similar chemical. On the basis of the tissue 

concentrations found in the pharmacokinetic studies (Cui et al. 2009; Curran et al. 2008), PFOS 

is absorbed from the gastrointestinal tract, as indicated by the serum measurements in treated 

animals, and distributed to the tissues. The highest tissue concentrations are usually those in the 

liver. Post mortem tissues samples collected from 20 adults in Spain found PFOS in liver, 

kidney, and lung (Pérez et al. 2013). The levels in brain and bone were low. In serum, PFOS is 

electrostatically bound to albumin occupying up to eleven sites (Weiss et al. 2009). Linear PFOS 

chains display stronger binding than branched chains (Beesoon and Martin 2015). Binding 

causes a change in the conformation of serum albumin (Weiss et al. 2009) thereby changing its 

affinity for the endogenous compounds also transported by serum albumin. PFOS binds to other 

serum proteins including immunoglobulins and transferrin (Kerstner-Wood et al. 2003). It is not 

metabolized, thus any effects observed in toxicological studies are not the effects of metabolites.

Electrostatic interactions with proteins are an important toxicokinetic feature of PFOS.

Studies demonstrate binding or interactions with nuclear receptors (e.g., PPARα), transport 

proteins (e.g., transthyretin [TTR]), FABP), and enzymes (Luebker et al. 2002; Ren et al. 2015; 

L. Wang et al. 2014; Weiss et al. 2009; Wolf et al. 2008; L. Zhang et al. 2013, 2014). Saturable 

renal resorption of PFOS from the glomerular filtrate via transporters in the kidney tubules is 

believed to be a major contributor to the long half-life of this compound. No studies were

identified on specific renal tubular transporters for PFOS, but many are available for PFOA. All 

toxicokinetic models for PFOS and PFOA are built on the concept of saturable renal resorption 

first proposed by Anderson et al. (2006). Some PFOS is removed from the body with bile (Chang 

et al. 2012; Harada et al. 2007), a process that is also transporter-dependent. Accordingly, the 

levels in fecal matter represent both unabsorbed material and that discharged with bile.

The arithmetic mean half-life in humans for occupationally exposed workers (Olsen et al.

2007) was 5.4 years (95% CI: 3.9–6.9 years). Half-lives from animals include 120.8 days for 

monkeys, 33–35 days for male and female Sprague-Dawley rats, and 36.9 days for male and 

female CD1 mice (Chang et al. 2012). The half-life differences between male and female rats 

observed for PFOA were not observed with PFOS. This indicates a lack of sex-related 

differences in renal excretion in rats and implies that the renal excretion and/or resorption 

transporters for PFOS differ from those for PFOA. No comprehensive studies of PFOS 

transporters in humans or laboratory animals were identified. 

Perfluorooctane sulfonate (PFOS) – May 2016 2-36
3. HAZARD IDENTIFICATION

The Hazard Identification section provides a summary and synthesis of the data from a large 

number of human epidemiology studies accompanied by studies in laboratory animals designed 

to identify both the dose-response and critical effects that result from exposures to PFOS and to 

examine the mode of action leading to toxicity. 

3.1 Human Effects

There is a substantial body of research on the adverse effects of PFOS in both humans and 

animals. The human database lacks data on acute effects and short term exposures, but it 

includes many epidemiology studies. The database of human studies is large, in part, due to the 

extensive research program conducted by the C8 Science Panel on residents of communities in 

Ohio and West Virginia that were impacted by PFOA discharges from the DuPont Washington 

Works plant in Parkersburg, West Virginia. The purpose of the C8 Health Project is to assess if 

there are any probable links between PFOA (and PFOS) exposure and disease. During the period 

August 2005–July 2006, about 69,000 study participants were identified. Eligible participants 

included those who had consumed drinking water for at least one year up to and including 

December 4, 2004 from the (1) Lubeck and Mason County water districts in West Virginia; 

(2) the Belpre, Little Hocking, Tuppers Plains-Chester, and Pomeroy water districts in Ohio; or 

(3) private water source within the geographical boundaries of the public water sources. The 

participants (n = 69,030; 33,242 males, 35,788 females; aged < 10 to 70 years and older) donated 

a blood sample, filled out an extensive questionnaire, and received $400 in compensation. 

Although the project was designed to examine the impact of PFOA on health effects among 

residents of the impacted community, the serum was analyzed for other perfluorochemicals, 

including PFOS. Medical records were used to validate diseases reported by participants. The C8 

Science panel studies were funded by DuPont under a consent decree. Some of the studies 

evaluated the impact of PFOS (or PFOA) on outcome. 

Commercial use of PFOS and other PFASs began over 60 years ago, resulting in global 

release of this family of compounds. As a result, population monitoring of serum is widespread 

and has supported multiple epidemiological investigations of the general population within the 

United States and abroad. Occupational epidemiology studies are available from 3M, a U.S. 

manufacturer of PFOS. Studies investigating the association between PFOS levels and health 

effects in the U.S. general population have also been conducted using the NHANES data set. The 

NHANES examined representative members of the U.S. population through their surveys 

focusing on different health topics. These studies consist of an interview (demographic, 

socioeconomic, dietary, and medical questions) and examination (medical including blood and 

urine collection, dental, and physiological parameters). 

A study by Jain (2014) examined the influence of diet and other factors on the levels of 

serum PFOS and other PFASs using the NHANES 2003–2004, 2005–2006, and 2007–2008 data. 

Significantly higher serum PFOS levels were found in males (0.020 μg/mL) compared to 

females (0.014 μg/mL). There was a significant decreasing trend in serum PFOS concentration 

between 2003 and 2008. There was a positive association of PFOS with increases in serum 

cholesterol (p < 0.01) and serum albumin (p < 0.01) in the 5,591 records used for the assessment. 

Intakes of meat and fish were positively associated with serum PFOA (p < 0.01). 

Perfluorooctane sulfonate (PFOS) – May 2016 3-1 
3.1.1 Long-Term Noncancer Epidemiological Studies

3.1.1.1 Serum Lipids and Cardiovascular Diseases

Occupational studies. Cross-sectional, as well as a longitudinal analyses of medical surveillance 

data from the 3M Decatur, Alabama and Antwerp, Belgium plants were conducted to evaluate 

possible associations between PFOS levels and hematology, clinical chemistry, and hormonal 

parameters (Olsen et. al 2001a, 2001b, 2003b). In the cross-sectional study, male (n = 215) and 

female (n = 48) volunteers working at the Decatur plant and male (n = 206) and female (n = 49) 

volunteers working at the Antwerp plant underwent clinical chemistry tests to evaluate hepatic 

enzyme activity, renal function, thyroid activity, and cholesterol levels. Data on employees from 

both plants appeared to be combined for the regression analyses; however, it was not clear 

whether females were included or whether the analyses only included males. The mean PFOS 

level in all employees from the Decatur and Antwerp plants was 1.40 μg/mL (range: 0.11–

10.06 μg/mL) and 0.96 μg/mL (range: 0.04–6.24 μg/mL), respectively. Positive significant 

associations were reported between serum PFOS and cholesterol (probability [p] = 0.04) and 

between serum PFOS and triglycerides (p = 0.01); similar results were found for PFOA. Age was 

also significant in both analyses. Alcohol consumed per day was significant in the cholesterol 

model, while body mass index (BMI) and cigarettes smoked per day was significant for 

triglycerides. PFOS was positively associated with alkaline phosphatase (ALP). Hepatic enzymes 

and bilirubin were not associated with PFOA. However, there were many limitations to 

combining and comparing the data from the two plants. 

A longitudinal analysis of the above data was performed to determine whether occupational 

exposure to fluorochemicals over time was related to changes in clinical chemistry and lipids 

(Olsen et al. 2001b, 2003b). The medical surveillance data from 175 individuals who had 

participated in two or more medical exams in 1995, 1997, and 2000 were analyzed using 

multivariable regression. Mean PFOS levels at the beginning and end of the surveillance period 

were 2.62 μg/mL and 1.67 μg/mL, respectively, in Decatur employees and 1.87 μg/mL and 

1.16 μg/mL, respectively, in Antwerp employees. When male employees from both plants were 

combined, no statistically-significant (p < 0.05) associations were observed over time between 

PFOS and serum cholesterol or triglycerides. There were no significant associations between 

PFOS and changes over time in HDL, ALP, gamma-glutamyl transpeptidase (GGT), aspartate 

aminotransferase (AST), or alanine transaminase (ALT) activities, total bilirubin, or direct 

bilirubin. PFOA was positively associated with cholesterol and triglycerides in the Antwerp 

employees.

High-exposure community studies. The C8 Health Project conducted in 2005–2006 on 

approximately 69,000 residents in Ohio and West Virginia evaluated general population 

exposures to PFOS and other perfluorochemicals. Public drinking water was contaminated in six 

water districts surrounding the plant (≥ 0.05 ng/mL of PFOA). Residents were eligible to 

participate in the study if they had consumed water from any of the 6 water districts for at least 

one year prior to the study. Blood samples were collected from the participants to determine 

PFOA and PFOS serum levels and clinical chemistry was performed. Extensive questionnaires 

were administered as well. The levels of PFOA were elevated, however, levels of PFOS in this 

population were similar to those reported in the general U.S. population (median 0.02 μg/mL). 

Steenland et al. (2009) examined serum PFOS and PFOA levels and lipids among 46,294 

residents, ≥ 18 years old, participating in the C8 Health Project. The mean serum PFOS level 

among participants was 0.022 μg/mL, with a range of 0.00025–0.7592 μg/mL. Lipid outcomes 

Perfluorooctane sulfonate (PFOS) – May 2016 3-2 
(total cholesterol, HDL cholesterol, LDL cholesterol, and triglycerides) were examined in 

relation to PFOS and PFOA serum levels. All lipid outcomes, except for HDL, showed 

significant increasing trends with increasing PFOS levels (similar for PFOA). The predicted 

increase in cholesterol from lowest to highest PFOS decile was 11–12 mg/deciliter (dL). Logistic 

regression analyses indicate statistically-significant incidence of hypercholesterolemia 

(≥ 240 mg/dL) with increasing PFOS serum levels. Cholesterol levels ≥ 240 mg/dL are 

characterized as high, and medical intercession is recommended. The odds ratios (ORs) across 

quartiles for cholesterol ≥ 240 mg/dL were 1.00, 1.14 (95% CI: 1.05–1.23), 1.28 (95% CI: 1.19–

1.39) and 1.51 (95% CI: 1.40–1.64). The cross-sectional design of this study, as well as the lack 

of cumulative exposure measurements, are limitations in the study design.

Frisbee et al. 2010 evaluated 12,476 children ≤ 18 years old who lived in the C8 Health 

Project communities for total cholesterol, LDLs, HDLs, and fasting triglycerides. The mean level 

of PFOS was 0.023 μg/mL. PFOS was significantly associated with increased total cholesterol, 

HDL-cholesterol, and LDL- cholesterol in a linear regression analysis after adjustment for covariables. A statistically-significant increased risk of high total cholesterol [OR 1.6 (1.4–1.9)] 

and LDL-cholesterol [OR 1.6 (1.3–1.9)] was also observed between the first and fifth quintiles of 

PFOS serum levels. No trends were observed with triglycerides. Total cholesterol, LDL, and 

triglycerides were also positively associated with serum PFOA concentration. As with the other 

C8 project data, the authors acknowledge that the cross-sectional nature of this study limits 

causal inference.

A cohort of 521 adult members of the C8 Health Project was evaluated for an association 

between changes in serum PFOS levels and changes in serum LDL-cholesterol, HDLcholesterol, total cholesterol, and triglycerides over a 4.4-year period (Fitz-Simon et al. 2013). 

Linear regression models were fit to the logarithm (base 10) of ratio change in each serum lipid 

measurement in relation to the logarithm of ratio change in PFOS. Mean serum PFOS 

concentration decreased by approximately one-half between baseline (0.023 ± 0.014 μg/mL) and 

follow-up (0.011 ± 0.007 μg/mL). No corresponding changes in serum lipids were found. 

However, those individuals with the greatest declines in serum PFOS had a tendency for a slight 

decrease in LDL-cholesterol. Similar results were found with PFOA.

A subset of 290 individuals in the C8 Health Project was evaluated for evidence that PFOS 

exposure can influence the transcript expression of genes involved in cholesterol metabolism, 

mobilization, or transport (Fletcher et al. 2013). Ribonucleic acid (RNA) was extracted from 

whole blood samples taken from 144 males and 146 females aged 20–60 years; serum collected 

at the same time was used to measure PFOS concentration. The association between candidate 

gene expression levels and PFOS levels was assessed by multivariable linear regression with 

adjustments for confounders. A positive association was seen between PFOS and a transcript 

involved in cholesterol mobilization (Neutral Cholesterol Ester Hydrolase 1 [NCEH1]; 

p = 0.018), and a negative relationship with a transcript involved in cholesterol transport 

(Nuclear Receptor Subfamily 1, Group H, Member 3 [NR1H3]; p = 0.044). When sexes were 

analyzed separately, PFOS was positively associated with expression of genes involved in 

cholesterol mobilization and transport in females (NCEH1 and Peroxisome ProliferatorActivated Receptor alpha [PPARα]; p = 0.003 and 0.039, respectively), but no effects were 

evident in males. Similar associations were also found for PFOA.

General population studies. Nelson et al. (2010) used NHANES 2003–2004 data to analyze 

PFOS and three other perfluorinated chemicals and total cholesterol, HDLs, non-HDL 

lipoproteins, and LDL. LDL was available only for a subsample of the fasting population and 

Perfluorooctane sulfonate (PFOS) – May 2016 3-3 
was not measured directly, but was estimated by the Friedewald formula2

 as recommended by 

Centers for Disease Control and Prevention. Homeostatic model assessment (HOMA) was used 

to assess insulin resistance (calculated from fasting insulin and fasting glucose measurements 

collected in NHANES). BMI and waist circumference were used to measure body size.

Exclusion criteria included current use of cholesterol-lowering medications, participants over the 

age of 80, pregnant/breastfeeding females or insulin use. After exclusion criteria, approximately

860 participants were included in the analyses. The mean PFOS serum concentration for 

participants 20–80 years old was 0.025 μg/mL (range: 0.0014–0.392 μg/mL). 

A positive association was identified between total serum cholesterol and serum PFOS 

concentrations. When analyzed by PFOS serum quartiles, adults in the highest PFOS quartile had 

total cholesterol levels of 13.4 mg/dL (95% CI: 3.8–23.0), higher than those in the lowest 

quartile. As expected, non-HDL cholesterol accounted for most of the total cholesterol. 

Consistent trends were not observed for HDL or LDL. Adjusting the cholesterol models for 

serum albumin produced similar results. Body weight and insulin resistance were not 

consistently associated with serum PFOS levels. Similar results were found for PFOA.

Lin et al. (2009) explored associations of serum lipid levels with NHANES PFOA data from 

1999–2000 and 2003–2004. Serum HDL was inversely associated with serum PFOS 

concentration OR ((95% CI): 1.61 (1.15–2.26), p < 0.05). Triglycerides did not show an 

association with PFASs.

Effects of PFOS on plasma lipid levels in the Inuit population of Northern Quebec were 

examined in a cross-sectional epidemiology study (Château-Degat et al. 2010). The relationship 

between consumption of PFOS-contaminated fish and wild game with blood lipids was assessed 

in 723 Inuit adults (326 man and 397 females). This traditional diet is also rich in n-3-

polyunsaturated fatty acids (n-3 PUFAs) which are known to have hypolipidemic effects; 

therefore, the n-3 PUFAs were considered as a confounder in the analyses. Multivariate linear 

regression modeling was used to evaluate the relationship of PFOS levels and blood lipids, 

including total cholesterol (TC), HDL cholesterol, LDL cholesterol, and triacylglycerols. Plasma 

levels of HDL cholesterol were positively associated with PFOS levels, even after adjustment for 

circulating levels of n-3 PUFAs, but the other blood lipids were not associated with PFOS levels. 

The geometric mean level of PFOS in plasma for females and males was 0.019 μg/mL. 

Eriksen et al. (2013) examined the association between plasma PFOS levels and total 

cholesterol levels in a middle-aged Danish population. This cross-sectional study included 

663 males and 90 females aged 50–65 years who were enrolled in the Danish Diet, Cancer and 

Health cohort. Generalized linear models were used to analyze the association between PFOS 

and total cholesterol levels and adjusted regression analyses were performed. The mean plasma 

PFOS level was 0.0361 μg/mL. A significant, positive association was found between PFOS 

(and PFOA) and total cholesterol such that in the fully adjusted model, a 4.6 mg/dL (95% CI: 

0.8–8.5) higher concentration of total cholesterol was found per interquartile range of plasma 

PFOS. The quartiles of PFOS used in the analyses were not defined and no comparison was 

made for cholesterol levels between the highest and lowest PFOS quartile.

2 Friedewald formula: [LDL-cholesterol] = [total cholesterol] – [HDL-cholesterol] – [triglycerides/5]. All values are 

expressed in mg/dL units.

Perfluorooctane sulfonate (PFOS) – May 2016 3-4 

 
A cross-sectional study of 891 pregnant females evaluated the association between plasma 

PFOS levels and plasma lipids (Starling et al. 2014). Six other perfluoroalkyl substances were 

also quantified and evaluated. The females were a cohort of the Norwegian Mother and Child 

Cohort Study, and the majority of blood samples were drawn during weeks 14–26 of gestation. 

Weighted multiple linear regression was used to estimate the association between PFOS level 

and each lipid level. The median plasma PFOS level was 0.013 μg/mL. No association was 

observed between PFOS and triglycerides. PFOS was positively associated with total cholesterol, 

HDL-cholesterol, and LDL-cholesterol, although confidence intervals were broad for all 

associations. Each ln-unit increase in PFOS was associated with an increase of 8.96 mg/dL 

(95% CI: 1.70–16.22) in total cholesterol and for each interquartile range (IQR)-unit increase in 

the ln-PFOS concentration, total cholesterol increased by 4.25 mg/dL (95% CI: 0.81–7.69). With 

HDL-cholesterol, each IQR-unit increase in ln-PFOS was associated with an increase of 

2.08 mg/dL (95% CI: 1.12–3.04). For LDL-cholesterol, each IQR-unit shift in ln-PFOS was 

associated with a change of 3.07 mg/dL LDL (95% CI: −0.03–6.18). Five of the seven PFASs 

studied were positively associated with HDL cholesterol, and all seven had elevated HDL 

associated with the highest quartile.

Fisher et al. (2013) examined the association of plasma PFAS levels, including PFOS, with 

metabolic function and plasma lipid levels. This cross-sectional study included 2,700 

participants, aged 18–74 years (approximately 50% male), in the Canadian Health Measures 

Survey. Multivariate linear and logistic regression models were used for analyses of associations 

between PFOS levels and cholesterol outcomes, metabolic syndrome, and glucose homeostasis.

The geometric mean PFOS concentration was 0.0084 ± 0.002 μg/mL. In weighted analyses, no 

association was found between PFOS (or PFOA) and total cholesterol, HDL- and LDLcholesterol, and metabolic syndrome and glucose homeostasis parameters. Hypercholesterolemia 

(cholesterol greater than 240 mg/dL), was associated with PFOS exposure in unadjusted analyses 

of this cohort. 

Multiple epidemiologic studies have evaluated serum lipid status in association with PFOS 

concentration (Table 3-1). These studies provide support for an association between PFOS and 

small increases in total cholesterol in the general population at mean serum levels of 0.0224–

0.0361 μg/mL (Frisbee et al. 2010; Nelson et al. 2010; Eriksen et al. 2013). 

Hypercholesterolemia, (clinically defined as cholesterol greater than 240 mg/dL), was associated 

with PFOS exposure in a Canadian cohort (Fisher et al. 2013) and in the C8 cohort (Steenland et 

al. 2009). Cross-sectional occupational studies demonstrated an association between PFOS and 

total cholesterol (Olsen et al. 2001a, 2001b, 2003b). Evidence for associations between other 

serum lipids and PFOS is mixed, including HDL cholesterol, LDL, very low density lipoprotein 

(VLDL), non-HDL cholesterol, and triglycerides. The studies on serum lipids in association with 

PFOS serum concentrations are largely cross-sectional in nature and were largely conducted in 

adults, but some studies exist on children and pregnant females. The location of these cohorts 

varied from the U.S. population including NHANES volunteers, to the Avon cohort in the United 

Kingdom (UK), to Scandinavian countries. Limitations to these studies include the frequently 

high correlation between PFOA and PFOS exposure; not all studies control for PFOA in study 

design. Studies also included populations with known elevated exposure to other environmental 

chemicals including PFOA in the C8 population or polybrominated diphenyl ethers (PBDEs) and 

other persistent organic compounds among the Inuit population. Overall, the epidemiologic 

evidence supports an association between PFOS and increased total cholesterol. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-5 
Table 3-1. Association of Serum PFOS with Serum Lipids

Reference and Study 

Details

PFOS Level 

(μg/mL) Total Cholesterol (TC)

Low Density 

Lipoprotein (LDL)

High Density 

Lipoprotein (HDL) Triglycerides (TG)

Occupational Populations

Olsen et al. 2001a, 2003b

Cross-sectional from 

manufacturing plant 

workers 

n = 263 (Decatur)

n = 255 (Antwerp)

Mean 1.40 Decatur

Mean 0.96 Antwerp

Beta = 0.010 (95% CI)

(−0.005, 0.025)

NM No association Beta = 0.025 (95% CI) (−0.015, 0.065)

Olsen et al. 2001b, 2003b 

Longitudinal; ~ 5 years

n = 175 

(Decatur and Antwerp 

combined for analysis)

Mean

2.62 

(baseline)

1.67 (follow-up) 

(Decatur) 

1.87 (baseline)

1.16 

(follow-up) 

(Antwerp) 

PFOS Quartiles

Q1: 0.04–0.42

Q2: 0.43–0.81

Q3: 0.82–1.68

Q4: 1.69–10.06 ppm

TC by quartile of PFOS 

mean (SD):

Q1: 214 (41) 

Q2: 214 (43)

Q3: 215 (39)

Q4: 222 (44)

NM HDL by quartile of PFOS 

mean (SD):

Q1:54 (15) 

Q2:47 (11) 

Q3:48 (13) 

Q4: 48 (15)

TG by quartile of PFOS mean (SD):

Q1:131 (95) 

Q2: 155 (102) 

Q3: 169 (123) 

Q4: 177 (123)

p < 0.05 Q4 v Q1

General Populations with high environmental exposure to other PFASs

Steenland et al. 2009

Cross-sectional (C8), 

Logistic regression 

analysis, 2005–2006 n =

46,294 

Age: 18–80 yrs (not 

taking cholesterollowering medications)

Mean duration: not 

provided 

Linear regression, 

quartiles and continuous

Mean 0.022

Quartiles of PFOS 

(ng/mL): 

Q1: 0–13.2 

Q2: 13.3–19.5

Q3: 19.6–28.0

Q4: ≥ 28.1 

Odds Ratio (95% CI) for 

high cholesterol by 1 IQR 

increase in PFOS

Q1: 1 (referrant)

Q2: 1.14 (1.05, 1.23)

Q3: 1.28 (1.19, 1.39)

Q4: 1.51 (1.40, 1.64)

Beta 0.02660

(SD 0.00140)

[log PFOS and lipids]

Nearly monotonic increase 

in association with PFOS

Beta 0.04176 

(SD 0.00221)

[log PFOS and lipids]

Null associations

Beta 0.00355

(SD 0.00173)

[log PFOS and lipids]

Increased

Beta 0.01998

(SD 0.00402)

[log PFOS and lipids]

Perfluorooctane sulfonate (PFOS) – May 2016 3-6 
Reference and Study 

Details

PFOS Level 

(μg/mL) Total Cholesterol (TC)

Low Density 

Lipoprotein (LDL)

High Density 

Lipoprotein (HDL) Triglycerides (TG)

Fitz-Simon et al. 2013

Longitudinal (C8);

n = 521 

Duration: 4.4 years

Within-individual changes 

in PFOS & lipids over 

time, 2005–2006 versus 

2010 serum 

concentrations. 

Linear regression fit to log 

of ratio change in lipid in 

relation to change in 

PFOS

0.023 (baseline)

0.011 (follow-up)

Tertiles of PFOS ng/ml 

(ratio follow 

up/baseline) 

T1: < 0.4

T2: 0.4–0.54 

T3: > 0.54

Geometric mean (mg/dL): 

baseline, follow-up 

192.5, 192.8

Percent decrease (95% CI) in 

lipid per halving PFOS

3.20 (1.63–4.76) 

Geometric mean (mg/dL): 

baseline, follow-up 

107.8, 109.2

Percent decrease (95% CI) 

in lipid per halving PFOS

4.99 (2.46–7.44) 

Geometric mean (mg/dL): 

baseline, follow-up 

48.6, 47.2

Percent decrease (95% CI) 

in lipid per halving PFOS

1.28 (−0.59–3.12) 

Geometric mean (mg/dL): baseline, 

follow-up 

144.1, 146.9

Percent decrease (95% CI) in lipid per 

halving PFOS

2.49 (−2.88–7.57) 

Nelson et al. 2010

Cross-sectional 

(NHANES), USA. n =

860 (20–80 yrs old)

Linear regression analysis 

for PFOS and serum lipids

0.025

Serum PFOS by 

quartile 

Q1: 1.4–13.6

Q2: 13.8–19.7

Q3: 19.8–28.1

Q4: 28.2–392.0 

TC by PFOS Quartile 

(mg/dl): 

Q1: 198.6 

Q2: 201.6 

Q3: 202 

Q4: 205.7 

Beta 0.27

(95% CI; 0.05–0.48)

LDL by PFOS Quartile 

(mg/dl): 

Q1: 113.6 

Q2: 116.4 

Q3: 113.4 

Q4: 123.1

Beta 0.12 (95% CI; −0.17– 

0.41)

HDL by PFOS Quartile 

(mg/dl): 

Q1: 54.3

Q2: 56.0 

Q3: 52.7 

Q4 : 55.2

Beta 0.02 (95% CI; −0.05–

0.09)

NM

Château-Degat et al. 2010

Cross-sectional, Inuit 

population (Quebec). 

PFOS effect on total 

lipids. Effect modification 

of n-3 PUFAs, which can 

be hypolipidemic

n = 723 

Multiple linear regression

modeling

0.019

Geometric mean (95% 

CI) μg/L 

Women: 

16.8 (15.8–17.8) 

Men: 

20.4 (19.1–21.8) 

Adjusted models

R2, Beta (p value)

0.17, 0.0009 (0.086)

Adjusted models

R2, Beta (p value)

0.17, −0.0020 (0.242)

Adjusted models

R2, Beta (p value)

Women: 

0.12, 0.0042 (0.001)

Men: 0.12, 0.0016 (< 0.001) 

Adjusted models

R2, Beta (p value)

Women: 

0.20, −0.0014 (0.04)

Men: 0.16, −0.0009 (0.162)

Perfluorooctane sulfonate (PFOS) – May 2016 3-7 
Reference and Study 

Details

PFOS Level 

(μg/mL) Total Cholesterol (TC)

Low Density 

Lipoprotein (LDL)

High Density 

Lipoprotein (HDL) Triglycerides (TG)

Eriksen et al. 2013 Crosssectional, Middle aged 

Danish population

n = 753 (663 men and 90 

women) 

Generalized linear models 

used for analysis

0.036 Differences in TC (mg/dl) 

per 1 IQR increase

Beta (95% CI):

Total population:

3.7 (0.1, 7.3)

Women: 

11.7 (−0.2, 23.6)

Men: 2.9 (−0.9, 6.7) 

NM NM NM

Fisher et al. 2013

Cross-sectional, 2007–

2009, Canadian Health 

Measures Survey (CHMS) 

Cycle 1. n = 2700 (aged

18–74) 

Used multivariate linear 

and logistic regression 

models to assess 

associations between 

PFOS and serum lipids.

0.0084 Unadjusted OR for high 

cholesterol compared to Q1 

of PFOS exposure: 

OR (95% CI)

Q1: Referrent

Q2: 1.12 (0.89, 1.41)

Q3: 1.15(0.91, 1.45)

Q4: 1.66 (1.32, 2.09)

p trend = 0.03 

Null effects in adjusted 

model

Null effects Null effects NM

Children and Adolescents

Frisbee et al. 2010

Cross-sectional (C8, 

children) 

GLM Analysis,

n = 12,476 

Differences of Estimated 

Marginal Mean (EMM) 

between Q1 and Q5 and 

regression analysis for Q 

trend

0.023 Differences in Estimated 

Marginal Mean (EMM), 

Beta (SE), p for trend:

Age 1 to < 12: 5.5,

1.3 (0.3), < 0.001 

Age 12 to < 18: 9.5, 

2.1 (0.4), < 0.001

Differences in EMM, 

B(SE) p for trend:

Age 1 to < 12: 3.4,

0.9 (0.3), .002

Age 12 to < 18: 7.5,

1.7 (0.2), < 0.001 

Differences in EMM, 

B(SE), p for trend:

Age 1 to < 12: 1.6,

0.3 (0.1), 0.007

Age 12 to < 18: 1.5,

0.4 (0.1), 0.001 

Differences in EMM, B(SE), p for trend:

Age 1 to < 12: 2.8,

0.1 (1.4), 0.99

Age 12 to <1 8: 2.8,

−0.1 (1.0), 0.90

Geiger et al. 2014a

Cross-sectional, 

NHANES, 1999–2008, 

dyslipidemia (TC, LDL, 

HDL, TG).

n = 815 (Age < 18) 

Multivariate regression 

analysis.

n = 815 

T1: < 12.1

T2: 12.1–21.8 

T3: > 21.8 ppb

TC (mg/dL) association with 

PFOS by tertiles

T1: 1 

T2: 1.73 (−2.89, 6.36)

T3: 3.91 (−1.32, 9.14)

p trend: 0.15

log transformed PFOS

Beta 0.04 (95% CI: 0.00– 0.08)

Association between 

PFOS and LDL:

T1: 1 (referent)

T2: 0.49 (−3.41, 4.38)

T3: 4.59 (−0.17, 9.35)

P trend: 0.0632

log transformed PFOS

Beta 2.83 (95% CI: 0.03– 5.37)

Association between PFOS 

and HDL:

T1: 1

T2: 2.86 (0.44, 5.28)

T3: 1.11 (−0.93, 3.15)

P trend: 0.2931

Association between PFOS and TG:

T1: 1

T2:−8.13 (−15.50, −0.77) 

T3: −8.89 (−15.67, −2.11) 

P trend: 0.0126

log transformed PFOS

Beta −3.90 (95% CI: −7.72 to −0.08) 

Perfluorooctane sulfonate (PFOS) – May 2016 3-8 
Reference and Study 

Details

PFOS Level 

(μg/mL) Total Cholesterol (TC)

Low Density 

Lipoprotein (LDL)

High Density 

Lipoprotein (HDL) Triglycerides (TG)

Lin et al. 2009

Cross-sectional, 

NHANES, 1999–2000, 

2003–2004. Adolescents 

and adults aged > 12 yrs 

n = 3,685

Mean (SEM) Log 

PFOS

12 to < 20 yrs olds: 

3.11 (0.05) ng/mL

20 yrs old and older: 

3.19 (0.04) ng/mL

NM NM OR (95% CI), p

1.61 (1.15–2.26), p < 0.05 

in those 20 yrs or older

Null findings

Maisonet et al. 2015

Avon Longitudinal Study 

of Parents and Children. 

Prenatal PFOS compared 

to serum lipids in female 

offspring. 

n = 111 (age 7), n = 88 

(age 15) 

Mean (SD)

22.2 (11.4) mg/dl

Non-linear associations of 

TC with PFOS.

Non-linear associations of 

LDL with PFOS.

Null findings Null findings

Timmermann et al. 2014

Danish children, aged 8–

10 years old. Linear 

regression models. 1997.

n = 499

Median 41.5 ng/mL Null findings in normal 

weight children.

Null findings in normal 

weight children.

Null findings in normal 

weight children.

Null findings in normal weight children.

In overweight children, 10 ng increase 

PFOS/mL plasma associated with 8.6% 

(95% CI: 1.2%–16.5%) higher 

triglyceride concentrations

Pregnant Women

Starling et al. 2014

Cross-sectional (maternal 

at 14–26 weeks gestation), 

Norwegian Mother and 

Child Cohort (MoBa) 

2003–2004. 

n = 891 

0.013

Quartiles (ng/mL):

Q1: < 10.31 

Q2: 10.31–13.03 

Q3: 13.04–16.59 

Q4: > 16.60 

B (95% CI) PFOS (ng/ml) 

and TC (mg/dL). 

Q1: Referrent 

Q2: −3.35 (−10.34, 3.64)

Q3: 3.06 (−4.93, 11.05)

Q4: 7.59 (−0.42, 15.60)

TC change per IQR change 

in PFOS: 4.25 (0.81, 7.69)

B (95% CI) PFOS (ng/ml) 

and LDL(mg/dL).

Q1: referrent

Q2: −3.23 (−9.28, 2.83)

Q3: 2.60 (−4.49, 9.70)

Q4: 5.51 (−1.62, 12.64)

LDL change per IQR 

PFOS change: 3.07 

(−0.03, 6.18)

B (95% CI) PFOS (ng/ml) 

and HDL (mg/dL). 

Q1: Referrent 

Q2: 1.96 (−0.39, 4.31)

Q3: 2.49 (0.00, 4.97)

Q4: 4.45 (2.04, 6.86)

HDL change per IQR 

change in PFOS: 2.08 (1.12, 

3.04) 

B (95% CI) PFOS (ng/ml) and TG

(mg/dL). 

Q1: Referrent

Q2: 0.00 (−0.06, 0.07)

Q3: −0.03 (−0.10, 0.05)

Q4: 0.00 (−0.07, 0.07)

TG change per IQR PFOS change:

−0.01 (−0.04, 0.02)

NM = Not Measured

Perfluorooctane sulfonate (PFOS) – May 2016 3-9 
Some of the studies that examined serum LDL and HDL cholesterol also found significant 

increases these measures. Neither of these lipoprotein complexes is a stand-alone indicator for 

cardiovascular decrease risk. Rather, it is the relationship across the lipoprotein complexes 

within the same individuals that is important with HDLs considered as protective and LDLs a 

biomarker for potential atherosclerosis. Relatively few studies of triglycerides noted a significant 

increase with the serum PFOS levels.

3.1.1.2 Liver Enzymes and Liver Disease

Cross-sectional studies and longitudinal studies of PFOS and liver enzymes in various 

populations are described below and summarized in Table 3-2. 

Table 3-2. Summary of Epidemiology Studies of PFOS and Liver Enzymes

Reference and Study Details PFOS Level (μg/mL) Results

Lin et al. 2010

n = 2,216 adults (1,076 men and 1,140 

women) 

Age: > 20 years old

Data from 1999–2000 and 2003–2004 

NHANES

Regression models used to analyze data 

and adjust for confounders

Mean levels

Women: 0.0222

Men: 0.0274

Linear regression coefficients (standard 

error), p-value (adjusted for age, gender, 

race, lifestyle, measurement data, etc.)

ALT (U/L): 1.01 (0.53), 0.066 (slight pos. 

association)

GGT (U/L): 0.01 (0.03), p = 0.81

Total bilirubin (μmol): 0.30 (0.24), p = 0.22

Gallo et al. 2012

n = 47,092

Data from those enrolled in C8 Health 

Project

Linear and logistic regression models 

used. 

Mean level: 0.0233 Linear regression coefficients, (partial R2)

Ln-ALT: 0.020, 95% CI: 0.014–0.026 

(< 0.001)

Raised ALT in logistic regression odds ratio, 

(p-value)

OR: 1.13, 95% CI: 1.07–1.18 (p < 0.001)

GGT: no association

Direct bilirubin: less consistent results

Lin et al. (2010) investigated the association between low-dose serum PFOS (along with 

three other individual PFAS) and liver enzymes in the adult population of the United States by 

analyzing data from the 1999–2000 and 2003–2004 NHANES. The study population included 

2,216 adults (1,076 males, 1,140 females) older than 20 years who were not pregnant or nursing; 

had fasted > 6 hours at the time of examination; were negative for hepatitis B or C virus; had 

body weight, height, educational attainment, and smoking status data available; and had serum 

tests for PFAS, liver function, and metabolic syndrome. Regression models were used to analyze 

the data and adjust for confounding factors. Mean PFOS levels were 0.0274 and 0.0222 μg/mL 

for males and females, respectively.

Serum PFOS concentration was divided into quartiles. Unadjusted liver enzymes, serum 

ALT, and log-GGT increased across quartiles of PFOS (p ≤ 0.03), but total bilirubin showed no 

trend. The linear regression models were adjusted for:

• Age, gender, and race/ethnicity. 

• Lifestyle (smoking status, drinking status, education level). 

• Biomarker data (BMI, metabolic syndrome, iron saturation status, insulin resistance).

Perfluorooctane sulfonate (PFOS) – May 2016 3-10
In the fully adjusted model, a slight positive association was found between serum PFOS 

concentration and serum ALT (p = 0.066). A positive association was also found between serum 

PFOA concentration and serum ALT and PFOA concentration and serum GGT. Data 

interpretation was limited by the cross-sectional study design, and the fact that other 

environmental chemicals (possible covariates or explanatory variables) and medication use were 

not included in the study. 

Gallo et al. (2012) investigated the correlation between serum PFOS levels and liver enzymes 

in a total of 47,092 samples collected from members enrolled in the C8 Health Project. The 

association of ALT, GGT, and direct bilirubin with PFOS was assessed using linear regression 

models adjusted for age, physical activity, body mass index, average household income, 

education level, race, alcohol consumption, and cigarette smoking. Median PFOS level was 

0.0233 μg/mL with an interquartile range of 0.0137–0.0294 μg/mL. The ln-transformed values 

of ALT were significantly associated with ln-transformed PFOS levels (and PFOA) and showed 

a steady increase in fitted levels of ALT per decile of PFOS, leveling off after approximately 

0.030 μg PFOS/mL. Fitted values of GGT showed no overall association with ln-transformed 

PFOS levels. A positive association was seen with direct bilirubin and PFOS levels in linear 

regression models, but this was not evident with logistic regression models. Limitations of the 

study include the cross-sectional design and self-reported lifestyle characteristics. Only a small 

number of ALT values were outside the normal range, making the results difficult to interpret in 

terms of health.

The epidemiological data supporting liver damage based on serum ALT and GGT as reported 

by Gallo et al. (2012) are not strong enough to support an association of serum PFOS alone with 

liver damage in humans, because in most of the epidemiology studies the serum contains a 

mixture of PFASs and possibly other exogenous chemicals.

3.1.1.3 Biomarkers of Kidney Function and Kidney Disease

Epidemiology studies of PFOS and kidney function and biomarkers in various populations 

are described below and summarized in Table 3-3. 

Shankar et al. (2011) used data from the NHANES to determine whether there was a 

relationship between serum PFOS levels and chronic kidney disease. A total of 4,587 adult 

participants (51.1% females) with PFOS measurements available from the 1999–2000 and 2003–

2008 cycles of the survey were examined. Chronic kidney disease was defined as glomerular 

filtration rate (GFR) < 60 mL/minute (min)/1.73 m2

. Serum PFOS levels were categorized into 

quartiles: quartile 1 = < 0.012 μg/mL; quartile 2 = 0.012–0.019 μg/mL; quartile 3 = 0.019–0.030 

μg/mL; quartile 4 = > 0.030 μg/mL. The multivariable odds ratio for chronic kidney disease for 

individuals in quartile 4 was 1.82 (95% CI: 1.01–3.27; p for trend = 0.019) compared with 

individuals in quartile 1. This association was shown to be independent for confounders of age, 

sex, race/ethnicity, body mass index, diabetes, hypertension, and serum cholesterol level. 

However, the authors noted that because of the cross-sectional nature of the study, the possibility 

of reverse causality could not be excluded. A low GFR would diminish the removal of PFOS 

from serum for excretion by the kidney, thus increasing the serum PFOS levels. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-11
Table 3-3. Summary of Epidemiology Studies of PFOS and Measures of Kidney Function

Reference and Study Details PFOS levels (μg/mL) Results

Shankar et al. 2011

USA, NHANES

n = 4587 adults

PFOS from 1999–2000 and 

2003–2008

Quartiles, μg/mL, n

1: < 0.012 μg/mL, 1,152

2: 0.012–0.019 μg/mL, 1,151

3: 0.019–0.030 μg/mL, 1,137

4: > 0.030 μg/mL, 1,147

Estimated glomerular filtration rate (eGFR) 

Chronic kidney disease defined as eGFR < 60 

mL/minute/1.73 m2 

Quartile, OR (95% CI)

1: Referent

2: 1.12 (0.64, 1.99) 

3: 1.53 (0.87, 2.67) 

4: 1.82 (1.01, 3.27)

p = 0.02

Logistic regression adjusting for age, gender, 

race/ethnicity, education, smoking, alcohol, 

BMI, systolic blood pressure, diastolic blood 

pressure, diabetes, serum total cholesterol and 

glycohemoglobin

Adjustment for PFOS did not alter association 

with PFOA

Multivariate regression of association PFOS 

with eGFR among subjects with and without 

chronic kidney disease

β (SE) with −1.8 (0.8) and without −3.2 (0.6) 

chronic kidney disease (p < 0.05)

Steenland et al. 2010

USA, C8 Health Project 

participants

n = 54,591 (≥ 20 yrs old)

Mean: 0.0234 ± 0.0161 Increased predicted uric acid of 0.2 to 0.3 

μg/dL with increasing deciles of PFOS.

Odds Ratio, p-value

Hyperuricemia (> 6.0 mg/dL for women and >

6.8 mg/dL for men):

1.00

1.02 (95% CI: 0.95−1.10), p < 0.0001

1.11 (95% CI: 1.04−1.20), p < 0.0001

1.19 (95% CI: 1.11−1.27), p < 0.0001

1.26 (95% CI: 1.17−1.35), p < 0.0001

Trend for increase uric acid more prominent 

with PFOA

Children

Watkins et al. 2013

USA, C8 Health Project 

participants

n = 9,660 (1 to < 18 yrs old)

Median: 0.020 β (95% CI) change in unit eGFR (mL/min/1.73 

m2 ) per ln serum PFOS,

−1.10 (−1.66 to −0.53), p = 0.0001

Linear regression adjusting for age, gender, 

race, smoking, and household income.

Geiger et al. 2014b

USA, NHANES

n = 1644 (12–18 yrs old)

Mean: 0.018 ± 0.005 Multivariable-adjusted OR (95% CI) between 

PFOS and hypertension 

Quartile 1: 1 (referent)

Quartile 2: 0.99 (0.55, 1.78)

Quartile 3: 0.73 (0.36, 1.61)

Quartile 4: 0.77 (0.37, 1.61)

p = 0.36

Log transformed PFOS = 0.83 (0.58, 1.19)

Perfluorooctane sulfonate (PFOS) – May 2016 3-12
Steenland et al. (2010) reported on another analysis of the C8 Health Project participants 

≥ 20 years old (n = 54,591) for a possible association between PFOS (and PFOA) serum levels 

and uric acid. Elevated uric acid is a risk factor for hypertension and may be an independent risk 

factor for stroke. The mean PFOS level was 0.0234 ± 0.0161 μg/mL. A statistically-significant 

(p < 0.0001) trend was observed between increasing PFOS levels (untransformed) and uric acid 

levels. A 0.2–0.3 μg/dL increase in uric acid was associated with an increase from the lowest to 

highest PFOS decile (0.010–0.050 μg/mL). Hyperuricemia (> 6.0 mg/dL for females and 

> 6.8 mg/dL for males) risk by quintiles increased slightly with PFOS levels (OR 1.00, 1.02, 

1.11, 1.19, and 1.26). The serum of C8 study participants included several PFASs; PFOA 

appeared to have a greater influence on uric acid trends than PFOS in the models employed by 

Steenland et al. (2010). 

Children. Watkins et al. (2013) evaluated the cross-sectional association between PFOS 

exposure and kidney function among children aged 1 to <18 years (mean 12.4 ± 3.8 years) 

enrolled in the C8 Health Project. A total of 9,660 participants had data available on serum PFOS 

(median = 0.020 μg/mL), serum creatinine, and height, which were used to calculated an 

estimated glomerular filtration rate (eGFR). Linear regression was used to evaluate the 

association between quartiles of measured serum PFOS concentration and eGFR. A shift from 

the lowest to the highest quartile of measured, natural log–transformed concentrations of PFOS 

in serum [IQR ln-(PFOS) = 0.64] was associated with a decrease in eGFR of 1.10 mL/min/1.73 

m2 (95% CI: −1.66 to −0.53; p = 0.0001) adjusting for age, sex, race, smoking status, and household income. With increasing quartile of serum PFOS concentrations, eGFR decreased monotonically with a decrease of 2.3, 2.6, and 2.9 mL/min/1.73 m2

 for the second, third, and fourth 

quartile of serum PFOS, respectively, compared with the lowest quartile (p for trend across 

quartiles = 0.0001).

Geiger et al. (2014b) used data from the NHANES to determine whether there was a 

relationship between serum PFOS levels and hypertension in children. A total of 1,655 

participants (aged 12–18 years) with PFOS measurements available from the 1999–2000 and 

2003–2008 cycles of the survey were examined. Blood pressure was measured to determine the 

presence of hypertension and linear regression modeling was used to study the association 

between increasing quartiles of serum PFOS and mean changes in systolic and diastolic blood 

pressures. Mean PFOS level was 0.018 ± 0.005 μg/mL. No association was found between 

serum PFOS levels and hypertension in either unadjusted or multivariable-adjusted analyses.

Compared with the lowest quartile, the multivariable-adjusted odds ratio (95% confidence 

interval) of hypertension in the highest quartile of exposure was 0.77 (0.37–1.61) (p-trend > 

0.30). 

3.1.1.4 Reproductive Hormones and Reproductive/Developmental Studies

Many of the studies of PFOS focused on pregnancy-related outcomes, including measures of 

fetal growth retardation, puberty, and other developmental endpoints, as well as pregnancyrelated hypertension, preeclampsia, and gestational diabetes. Reproductive outcomes such as 

measures affecting fertility were also evaluated. Within each section, the discussion is divided 

into occupational exposure studies (if applicable) and general population studies. Epidemiology 

studies of PFOS and pregnancy-related outcomes in various populations are described below and 

summarized in Table 3-4. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-13
Table 3-4. Summary of Epidemiology Studies of PFOS and Pregnancy Outcomes

Study

PFOS level 

(μg/mL) Results

Stein et al. 2009

United States (C8 Health Project)

n = 5,262 pregnancies

Self-reported pregnancy outcomes 

in mid-Ohio Valley in 2000–2006.

Median: 0.014 OR (95% CI), preeclampsia

per IQR(lnPFOS) increase in PFOS: 1.1 (0.9, 1.3)

< 50th percentile 1.0 (referent)

≥ 50th percentile 1.3 (1.1, 1.7)

< 50th percentile 1.0 (referent)

50th–<75th percentile 1.3 (1.0, 1.7)

75th–90th percentile 1.1 (0.8, 1.6)

≥ 90th percentile 1.6 (1.2, 2.3)

Darrow et al. 2013

United States (C8 Health Project)

n = 1,630 live births from 1,330 

women after January 1, 2005

Geometric mean: 

0.0132

Pregnancy induced hypertension

OR (95% CI) per log unit increase in PFOS: 1.47 (1.06, 

2.04)

By quintile:

Q1 up to 0.0086 μg/mL 1.0 (referent)

Q2 0.0086– < 0.0121 1.46 (0.69, 3.11)

Q3 0.0121– < 0.0159 2.71 (1.33, 5.52)

Q4 0.0159– < 0.0214 2.21 (1.07, 4.54)

Q5 ≥ 0.0214 1.56 (0.72, 3.38)

Q1 up to 0.0086 μg/mL 1.0 (referent)

First pregnancy after

PFOS measure 2.02 (1.11, 3.66)

Zhang et al. 2015

n = 258 women as part of LIFE 

study. Blood samples taken during 

2005–2009.

Mean: 0.0131 

with gestational 

diabetes and 

0.012 without

Gestational diabetes

OR (95% CI) associated with SD increment of 

preconception PFOS log-transformed concentration

OR 1.13 (0.75, 1.72) (fully adjusted for age, BMI, 

smoking, etc.)

Pregnancy-related Outcomes. Stein et al. (2009) examined serum levels of PFOS and selfreported pregnancy outcomes of a population of females (5,262 pregnancies; aged 15–55 years) 

in the mid-Ohio Valley in 2000–2006. These females were enrollees in the C8 Health Project, a 

community health study of residents near a chemical plant that used PFOA in the manufacture of 

fluoropolymers. Pregnancies within the 5 years preceding the exposure measurements were 

analyzed. The mean level of PFOS in the serum of these females was 0.014 μg/mL. There was 

no association between PFOS levels and miscarriages. PFOS was associated with preeclampsia 

(adjusted odds ratio = 1.3; 95% CI: 1.1–1.7). Similarly, PFOA was not associated with 

miscarriage and only weakly associated with preeclampsia. The self-reported nature of 

pregnancy outcomes is a recognized limitation with uncertain impact on study results.

Darrow et al. (2013; 2014) analyzed pregnancy outcomes for the five years following 

enrollment in the C8 Health Project. Among the 69,030 females who provided serum for PFOS 

measurement in 2005–2006, 32,354 provided follow-up interviews on reproductive histories.

After exclusions, 1,630 singleton live births from 1,330 females after January 1, 2005 were 

linked to birth records to identify outcomes of preterm birth (i.e., < 37 gestational weeks), 

pregnancy-induced hypertension, low birth weight (LBW) (i.e., < 2500 grams), and birth weight 

among full-term infants (Darrow et al. 2013). Effects on fetal growth measures are described in 

that section below. Another subset of 1,129 females with a total of 1,438 pregnancies was 

evaluated for an association between PFOS levels and miscarriage (Darrow et al. 2014). The 

baseline mean PFOS level for these females was 0.016–0.017 μg/mL. Confounders that were 

adjusted in each model for every outcome in the 2013 Darrow et al. study included maternal age, 

Perfluorooctane sulfonate (PFOS) – May 2016 3-14
educational level, smoking status, parity, BMI, self-reported diabetes, time between conception 

and serum measurement. Parity was excluded, and race was included in the miscarriage analysis 

(Darrow et al. 2014). 

An increased risk of pregnancy-induced hypertension was detected per log unit increase in 

PFOS (OR = 1.47; 95% CI: 1.06−2.04) and PFOA (OR = 1.27; 95% CI: 1.05−1.55). Although 

monotonicity was not evident, consistently increased odds were found across all upper PFOS 

(OR range: 1.46–2.72) and PFOA (OR range: 2.39–3.43) quintiles. 

The odds of miscarriage per each log unit increase in PFOS was 1.21 (95% CI: 0.94−1.55) 

for all reported prospective pregnancies and 1.34 (95% CI: 1.02−1.76) when restricted the 

analysis to each woman’s first pregnancy. Miscarriage results were comparable across all PFOS 

quintiles in the primary analysis (OR range: 1.34–1.59) and those restricted to first pregnancy 

(OR range: 1.68–1.94). PFOA was not associated with miscarriage and was not a confounder of 

the observed association with PFOS. To address the potential for reverse causality related to 

PFAS levels decreasing from prior pregnancies, analyses were restricted to nulliparous and 

nulligravid females. Adjusted odds ratios were higher across all four quintiles for nulliparous 

(OR range: 1.88–3.08) and nulligravid females (OR range: 2.04–3.73). These studies represent 

prospective assessment of PFASs in relation to adverse pregnancy outcomes, which address 

some of the limitations in the available cross-sectional studies. The impact of measurement error 

resulting from unknown critical exposure windows and the time lag (> 99% of births were within 

3 years) between the estimated conception date and the serum collection is unclear in these 

studies.

Preconception serum levels of PFOS (and other PFASs) were evaluated in females

attempting pregnancy in relation to risk of developing gestational diabetes (Zhang et al. 2015). 

The 258 participants were members of the Longitudinal Investigation of Fertility and the 

Environment (LIFE) study with blood samples taken during 2005–2009. The ORs and 95% CIs 

of gestational diabetes associated with each SD increment of preconception serum PFOS 

concentration (log-transformed) (and six other PFAS) were estimated with the use of logistic 

regression after adjusting for age, pre-pregnancy body mass index, smoking, and parity, each 

conditional on the number of times a woman had been pregnant. Preconception mean serum 

PFOS levels were 0.0131 μg/mL in females with gestational diabetes and 0.012 μg/mL in 

females without gestational diabetes (p-value for mean difference = 0.10). A positive association 

was found between PFOS and risk of gestational diabetes in the fully adjusted model (OR = 

1.13; 95% CI: 0.75−1.72). PFOA was the only PFAS that was significantly associated with 

developing gestational diabetes in this analysis. 

Fetal Growth. Many different measures of fetal growth can be used in epidemiology studies. 

Birth weight is widely available (as it is routinely collected in medical records and birth 

certificates). LBW (defined as < 2500 g) can be a proxy measure for preterm birth (particularly 

when accurate gestational age dating is not available). Other measures of fetal growth, such as 

small for gestation age, tend to more accurately reflect fetal growth retardation. Epidemiology 

studies of PFOS and fetal growth are described below and summarized in Table 3-5. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-15
Table 3-5. Summary of Epidemiology Studies of PFOS and Fetal Growth

Study PFOS level (μg/mL) Results

Grice et al. 2007

United States (C8 Health Project)

n = 263 women reporting 429 

births 

Self-reported pregnancy 

outcomes in workers associated 

with perfluorinated chemical 

production factory.

Exposure to PFOS was based on job 

assignment and varied

Never exposed: 0.11–0.29 ppm

Low exposure: 0.39–0.89 ppm

High exposure: 1.30–1.97 ppm

No association between PFOS exposure and mean birth 

weight 

Regression coefficients for birth weight compared to neverexposed pregnancies, 95% CI (adjusted for maternal age, 

smoking, gravidity)

Ever exposed, low exposure −0.08 (−0.25, 0.09)

Ever exposed, high exposure 0.07 (−0.14, 0.28)

High exposure, > 1 yr 0.11 (−0.11, 0.33)

Low or high exposure, > 1 yr −0.03 (−0.19, 0.13)

Ever exposed, low or high - 0.05 (−0.20, 0.11)

Apelberg et al. 2007

United States (Baltimore)

n = 293 newborns born between 

November 2004 and March 2005

Cord blood samples

Geometric mean: 0.005 Change in birth weight (g) per log unit increase (95% CI)

−69 (−149, 10) 

Fei et al. 2007

n = 1,400 women and their 

infants randomly selected from 

the group enrolled in the DNBC

Mean: 0.035 LBW

OR (95% CI) for LBW by quartile

Q1 0.0064 to 0.026 μg/dL 1.0 (referent)

Q2 0.026 to 0.033 μg/dL 3.5 (0.37, 31.16)

Q3 0.033 to 0.043 μg/dL 6.0 (0.73, 49.34)

Q4 ≥ 0.043 μg/dL 4.8 (0.56, 41.16)

Trend: p = 0.13

Andersen et al. 2010

n = 1,010 women and their 

infants randomly selected from 

the group enrolled in the DNBC

Median: 0.0334 (range: 0.0064–

0.1067) 

PFOS concentrations per each 0.001 μg/mL increase 

inversely associated with:

birth weight in girls: Beta = −3.2; 95% CI: −6.0 to −0.3

weight at 12 months in boys: Beta = −9.0; 95% CI:

−15.9 to −2.2

Monroy et al. 2008

n = 101 pregnant women as part 

of a larger cohort study 

conducted at McMaster 

University Medical Center

Mean:

0.0183 in maternal serum (24–28 wks)

0.0162 in maternal serum at delivery

0.0072 in umbilical cord blood

No association between PFOS levels and infant birth weight

Change in PFOS per g change in birth weight

Beta = 0.000853 (p = 0.73)

Washino et al. 2009

Japan

n = 428 women and their infants 

between July 2002 and October 

2005

Mean: 0.006 Change in birth weight per log unit increase (95% CI)

For all: Beta = −149 g (−297.0, −0.5)

For female infants: Beta = −269.4 g (−465.7, −73.0)

Hamm et al. 2010

Canada 

n = 252 women with blood 

samples taken between December 

2005 and June 2006

Mean: 0.009 Change in birth weight per Ln unit increase (95% CI)

31.3 g (−43.3, 105.9)

Stein et al. 2009 Mean: 0.014 OR (95% CI), birth weight < 5.5 lbs.

per IQR(lnPFOS) increase in PFOS: 1.3 (1.1, 1.6)

< 50th percentile 1.0 (referent)

≥ 50th percentile 1.5 (1.1, 1.9)

< 50th percentile 1.0 (referent)

50th–<75th percentile 1.3 (0.9, 1.8)

75th–90th percentile 1.6 (1.1, 2.3)

≥ 90th percentile 1.8 (1.2, 2.8)

Perfluorooctane sulfonate (PFOS) – May 2016 3-16
Study PFOS level (μg/mL) Results

Darrow et al. 2013

United States (C8 Health Project)

n = 1,630 live births from 1,330 

women after January 1, 2005

Geometric mean: 0.0132 LBW

OR (95% CI) per LBW (< 2,500 g) per log unit increase: 

1.12 (0.75, 1.67)

By quintile:

Q1 up to 0.0086 μg/mL 1.0 (referent)

Q2 0.0086– < 0.0121 1.48 (0.71, 3.08)

Q3 0.0121– < 0.0159 1.23 (0.57, 2.65)

Q4 0.0159– < 0.0214 1.31 (0.59, 2.94)

Q5 ≥ 0.0214 1.33 (0.60, 2.96)

First pregnancy after

PFOS measure 0.97 (0.61, 1.54)

An occupational cohort study by Grice et al. (2007) examined the relationship between PFOS 

exposure and self-reported adverse pregnancy outcomes in employees at a perfluorinated 

chemical production facility in Decatur, Alabama. Current and former female employees of the 

facility completed a questionnaire and provided a brief pregnancy history. The level of exposure 

was categorized according to a job-specific exposure matrix. A total of 263 females participated 

(participation rate = 73%) and reported 439 births, of which there were 421 live births, 

14 stillbirths, and 4 with missing outcome data. The birth weight models of single births were 

adjusted for maternal age, smoking status, and gravidity. No associations were detected between 

PFOS exposure and the pregnancy outcomes that were examined (i.e., stillbirth and mean birth 

weight).

Apelberg et al. (2007) measured PFOS in the cord blood of 293 newborns (singleton births 

without congenital anomalies) born November 26, 2004 through March 16, 2005 at Johns 

Hopkins Hospital in Baltimore, Maryland. Maternal and infant data, including maternal birth 

cohort, social class, place of residence, past pregnancies, insurance type, BMI, age, race, 

education, marital status, parity, gestational age, smoking status, and infant sex were collected 

from the hospital database and forms filled out at time of delivery. PFOS was found in > 99% of 

the cord blood samples (geometric mean 0.005, range < level of detection [0.2]–0.035 μg/mL). 

PFOS concentrations were evenly distributed across larger maternal age categories. The nonsmoker and passively exposed individuals (5.2 ng/mL) had higher mean PFOS levels than 

smokers (4.1 ng/mL), as did Asians (6.5 ng/mL) and Blacks (5.2 ng/mL) compared to 

Caucasians (4.5 ng/mL). No associations were observed between PFOS and maternal age, 

gestational age, BMI, or various socioeconomic measures (e.g., education, insurance, marital 

status, living in Baltimore City). Birth weight, head circumference, and ponderal index were 

inversely associated with both cord PFOS and PFOA levels. For example, large deficits in mean 

birth weight per one ln-unit increase were found for both PFOS (β = −69; 95% CI: −149–10) and 

PFOA (β = −104 g; 95% CI: −213–5). 

A series of longitudinal, population-based studies was conducted in a subset of 91,827 

females aged 25–35 enrolled in the Danish National Birth Cohort (DNBC) from March 1996 to 

November 2002 (Andersen et al. 2013; Fei et al. 2007, 2008a, 2008b, 2009, 2010a). This 

prospective birth cohort was comprised of a random sample of 1,400 females who were recruited 

through general practitioners around weeks 6–12 of gestation to investigate the association 

between blood levels of perfluorinated chemicals and adverse reproductive and developmental 

outcomes in the females and their children. This subset was sampled from 43,035 females with 

singleton live births without congenital malformation who provided the first blood sample 

between gestational weeks 4 and 14 and who responded to all four telephone interviews. Study 

data were collected by telephone interviews at 12 and 30 weeks of gestation, approximately 

Perfluorooctane sulfonate (PFOS) – May 2016 3-17
6 and 18 months after birth, and when the children were 7 years of age. A food frequency 

questionnaire was filled out at home during approximately week 25 of pregnancy. Maternal 

blood samples were taken in the first and second trimester, and infant cord blood was sampled 

just after birth. Only blood results from the 1,400 females in the first trimester were reported.

Mean plasma PFOS levels by age groups were: < 25 years: 0.039 μg/mL; 25–29 years: 

0.037 μg/mL; 30–34 years: 0.034 μg/mL and ≥ 35 years: 0.033 μg/mL. 

Potential confounders for which adjustments were made included: maternal age, maternal 

occupation and educational status, parity, pre-pregnancy BMI, smoking/alcohol consumption 

during pregnancy, gestational weeks at blood draw, child’s sex, child’s age at interview with 

mother, breast-feeding > 6 months (for 18-month interview), out-of-home child care, hours 

mother spent with child per day, and home density (the total number of rooms divided by the 

total number of people in the household). Although dietary data were available for at least 80% 

of the births, it is unclear why some of these studies did not examine these data as confounders 

(e.g., Fei et al. 2009). Although the DNBC had a low participation rate (31%), a previous study 

of various exposures in relation to three different outcomes (preterm birth, small-for-gestationalage, infancy and antepartum stillbirth) did not provide any evidence of non-participation bias 

(Nohr et al. 2006). 

Using data from the DNBC, Fei et al. (2007) investigated the association between plasma 

levels of PFOS in pregnant females, length of gestation, preterm birth (i.e., < 37 gestational 

weeks), and infant birth weight. The average PFOS levels in maternal plasma were 0.035μg/mL 

(range: 0.0064–0.107 μg/mL). The data were adjusted for confounding factors that might also 

influence fetal growth or length of gestation and analyzed by analysis of variance and linear 

regression using both continuous PFOS concentrations and PFOS quartiles. No associations 

between PFOS and birth weight were found. PFOA concentrations based on the continuous 

exposure measures were inversely associated with birth weight (β= −10.6; 95% CI: −20.8 to 

−0.5) following adjustment for confounding (unadjusted β= −20.5; 95% CI: −31.5 to −9.6). 

Although most were not statistically-significant, ORs for preterm birth were consistent in 

magnitude (OR range: 1.43–2.94) across both the upper three PFOS and PFOA quartiles. 

Consistently elevated ORs were also detected (OR range: 3.39–6.00) for LBW across the upper 

three PFOS and PFOA quartiles, but all of these analyses were limited by very small cell sizes 

given low incidence of these outcomes. Although these ORs often lacked statistical significance 

due to low statistical power, the elevated odds detected between PFOS levels and various 

outcomes including preterm delivery and LBW warrant further research, especially given the 

potential generalizability limitations of this low-risk study population. 

Fei et al. (2008a) also investigated the association between PFOS levels and placental 

weight, birth length, and head and abdominal circumference in the DNBC study population. 

Maternal PFOS levels were not associated with any of the fetal growth indicators when the 

lowest quartile was compared to the highest. In a stratified analysis of PFOS, inverse 

associations were found with birth length for post-term and pre-term infants and with ponderal 

index (relationship between mass and height) in multiparous females. In nulliparous females the 

association was positive. These associations were not statistically-significant. 

Andersen et al. (2010) examined the association between maternal plasma PFOS 

concentration and offspring weight, length, and BMI at 5 and 12 months of age from participants 

in the DNBC. The mothers (n = 1,010) reported the information during an interview and weight 

and length measurements were used to calculate BMI. Median maternal plasma PFOS level was 

0.0334 μg/mL with a range of 0.0064–0.1067 μg/mL. PFOS concentrations (per each 0.001 

Perfluorooctane sulfonate (PFOS) – May 2016 3-18
μg/mL increase) were inversely associated with birth weight in girls (β= −3.2; 95% CI: −6.0 to

−0.3), weight at 12 months in boys (β= −9; 95% CI: −15.9 to −2.2), and BMI at 12 months in 

boys (β= −0.017; 95% CI: −0.028 to −0.005) in models adjusted for maternal age, parity, 

prepregnancy BMI, smoking, gestational age at blood draw, socioeconomic status, and 

breastfeeding. Similar inverse associations were found with PFOA only in boys. 

Monroy et al. (2008) examined the relationship between the maternal serum levels of PFOS 

and PFOA and infant birth weight from neonates born to 101 pregnant females enrolled in a 

large cohort study, the Family Study, conducted at McMaster University Medical Center in 

Ontario, Canada. Linear regression analyses were adjusted for parity, gestational length, BMI, 

gender, and smoking status as confounding factors. PFOS was measured in maternal serum from 

24–28 weeks of gestation and at delivery and in umbilical cord blood (UCB) from 105 babies. 

PFOS was detected in all of the collected samples with mean levels of 0.0183, 0.0162, and 

0.0072 μg/mL in maternal serum at 24–28 weeks, maternal serum at delivery, and in UCB, 

respectively. The concentration of PFOS in maternal serum was significantly higher than in UCB 

(mean ratio of UCB/maternal serum at delivery was 0.45). No statistically-significant 

associations were detected between levels of PFOS in the maternal serum or UCB and infant 

birth weight. Maternal PFOS levels were also not associated with maternal body mass index, 

gestational length, or gender. Results were similar for PFOA.

A prospective cohort study was conducted on birth weight between July 2002 and October 

2005 at the Sapporo Toho Hospital in Hokkaido, Japan that included 428 native Japanese 

females and their infants (Washino et al. 2009). Females enrolled were at 23–35 weeks of 

gestation with a mean age of 30.5 years. Exclusion criteria included maternal pregnancy-induced 

hypertension, diabetes mellitus, fetal heart failure, and multiple births (i.e., restricted to 

singletons). A self-administered questionnaire survey after the second trimester of pregnancy 

was used by the subjects to report dietary habits, smoking status, alcohol consumption, caffeine 

intake, household income, and educational level. Other potential confounding factors collected 

from medical records included prepregnancy BMI, pregnancy complications, gestational age, 

infant sex, parity, infant disease, birth weight, and birth size. A blood sample was collected for 

measurement of PFOS and PFOA during the second trimester when the questionnaire was 

administered or after pregnancy for anemic mothers. The mean concentration of PFOS in the 

females was 0.006 μg/mL with detection in 100% of samples. The highest PFOS concentration 

identified was 0.016 μg/mL. The results indicated that large reductions in mean birth weight 

(β = −149 g; 95% CI: −297.0 to −0.5) were detected for each log-10 change in maternal serum 

PFOS exposure, especially among female infants (β = −269.4 g; 95% CI: −465.7 to −73.0).

Large birth weight deficits were also detected per each unit increase in PFOA for both males 

(−68.1 g; 95% CI: −246.2–110.0) and females (−76.7 g; 95% CI: −234.7–81.3), with an overall 

change in mean birth weight of 75 grams (95% CI: −191.8–41.6). 

A cohort study on pregnant females (≥ 18 years old) at 15–16 weeks gestation in the city of 

Edmonton, Alberta, Canada was undertaken to examine a possible association between 

perfluorinated chemicals, fetal growth, and gestational age (Hamm et al. 2010). The study 

population included 252 pregnant females who elected to undergo a second trimester prenatal 

triplescreen at 15–16 weeks of gestation for Down’s syndrome, trisomy 18, and open spina 

bifida. This population was restricted to mothers > 18 years of age who gave birth to live 

singletons without evidence of malformations, and who delivered at greater than or equal to 

22 weeks of gestation. Serum samples collected from December 2005 to June 2006 during the 

second trimester had PFOS levels ranging from nondetectable to 0.035 μg/mL, with the mean 

Perfluorooctane sulfonate (PFOS) – May 2016 3-19
and geometric mean being 0.009 μg/mL and 0.0074 μg/mL, respectively. Potential confounders 

included maternal age, maternal weight, maternal height, maternal smoking status, maternal race, 

gravida, gestational age at the time of serum collection, infant sex, infant birth weight, and infant 

gestational age at birth. Overall, there was no association with the level of PFOS and birth 

weight or length of gestation. Mean birth weight increased slightly by increasing PFOS tertiles

(3,278 g for < 0.006 μg/mL; 3,380 g for 0.006–0.010 μg/mL; 3,387 g for > 0.010–0.035 μg/mL). 

The mean length of gestation for all groups was 38 weeks; the preterm delivery percentage was 

similar between groups. Similar associations were found for other PFASs, which were correlated 

with serum PFOS including PFOA (Spearman correlation coefficient = 0.52) and 

perfluorohexane sulfonate (Spearman correlation coefficient = 0.54). 

In addition to the pregnancy-related outcomes discussed previously, Stein et al. (2009) 

examined fetal growth outcomes among females enrolled in the C8 Health Project. Pregnancies 

within the 5 years preceding the exposure measurements were analyzed. The mean level of 

PFOS in the serum of these females was 0.014 μg/mL at the time of measurement. There was no 

association between PFOS levels and preterm births. PFOS was, however, associated with an 

increased risk above the median (adjusted odds ratio = 1.5: 95% CI: 1.1–1.9) for LBW, and a 

dose-response relationship was reported for the 50th–75th, 75th–90th and > 90th percentile serum 

PFOS exposure concentrations (adjusted ORs = 1.3, 1.6, and 1.8, respectively). Similarly, PFOA 

was not associated with LBW and preterm birth. The self-reported nature of pregnancy outcomes 

is a recognized limitation with uncertain impact on study results. Although this 5-year window 

was intended to ensure that measured PFAS values at the time of study enrollment reflected 

exposure level at the time of pregnancy, this could have resulted in exposure misclassification 

given changes in maternal PFAS levels that could have occurred between the time of serum 

collection and pregnancy and lactation because measures had been implemented to decrease 

population exposures. 

Darrow et al. (2013, 2014) analyzed pregnancy outcomes for the 5 years after enrollment in 

the C8 Health Project. Among the 69,030 females who provided serum for PFOS measurement 

in 2005–2006, 32,354 provided follow-up interviews on reproductive histories. After exclusions, 

1,630 singleton live births from 1,330 females after January 1, 2005 were linked to birth records 

to identify outcomes of preterm birth (i.e., < 37 gestational weeks), LBW, and birth weight 

among full-term infants (Darrow et al. 2013). Another subset of 1,129 females with a total of 

1,438 pregnancies was evaluated for an association between PFOS levels and miscarriage 

(Darrow et al. 2014). The baseline mean PFOS level for these females was 0.016–0.017 μg/mL. 

Confounders that were adjusted in each model for every outcome in the 2013 Darrow et al. study 

included maternal age, educational level, smoking status, parity, BMI, self-reported diabetes, and 

time between conception and serum measurement. Parity was excluded and race was included in 

the miscarriage analysis (Darrow et al. 2014). Maternal serum PFOS levels were not associated 

with preterm birth or LBW. An inverse association was found between PFOS and mean birth 

weight in full-term infants (−29 g per log unit increase; 95% CI: –66–7). PFOA was not 

associated with mean birth weight, and therefore was not a confounder of this association. These 

studies represent prospective assessments of PFASs in relation to adverse pregnancy outcomes 

thereby avoiding some of the limitations of the cross-sectional studies. The impact of 

measurement error resulting from unknown critical exposure windows and the time lag (> 99% 

of births were within 3 years) between the estimated conception date and the serum collection is 

unclear. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-20
Preeclampsia is a condition where the pregnant female is hypertensive because of reduced 

renal excretion associated with a decrease in GFR. Preecampsia is often accompanied by LBW

(Whitney et al. 1987). Morken et al. (2014) used a subset of the Norwegian Mother and Child 

Cohort to evaluate the relationship between GFR and fetal size. Participants included 470 

preeclamptic patients and 483 non-preeclamptic females; plasma creatinine measured during the 

second trimester was used to estimate GFR. For the overall cohort, for each mL/min increase in 

GFR, infant weight at birth increased 0.73–0.83 g depending on the method used to calculate 

GFR. The increases in body weight with increased GFR were greater, and statisticallysignificant, in females with preeclampsia. Differences were not statistically-significant for the 

nonpreeclamptic group. Morken et al. (2014) was not a study of perfluorochemicals, and there 

were no serum measurements of any PFAS. However because PFOA/PFOS serum levels are 

expected to be higher with a lower GFR, the finding stimulated examination of the GFR as it 

relates to serum PFAS levels and the LBW identified in the epidemiology studies (Vesterinen et 

al. 2014; Verner et al. 2015). 

Evidence for an inverse association between PFAS levels and birth weight raised the 

question of reverse causality linked to maternal GFR. PFOS excretion by the kidney is 

dependent, in part, by the GFR. Conditions that result in impairment of GFR (and, thus, 

increased serum PFOS) and are also related to fetal growth restriction could result in a 

confounded observation of an association between PFOS and decreased birth weight. Vesterinen 

et al. (2014), using the Navigation Guide systematic review methods, examined evidence 

pertaining to the relation between fetal growth and maternal GFR. They identified relevant 

studies that met the Navigation Guide criteria for inclusion in the analysis; none included 

consideration of PFOS or other PFASs. All studies were rated as low or very low quality leading 

to the conclusion that data were inadequate to determine an association between fetal growth and 

GFR.

Verner et al. (2015) modified the PK model of PFOS during pregnancy by Loccisano et al. 

(2013) described in section 2.5.1 to evaluate the association between GFR, serum PFOS levels 

and birth weight. When low GFR was accounted for in the model simulations, the reduction in 

birth weight associated with increasing serum PFOS was less than that found by the author’s 

meta-analysis of the same data. This finding suggests that a portion of the association between 

prenatal PFOS and birth weight could be confounded by maternal GFR differences within the 

populations studied. The true association for each 1 ng/mL increase in PFOS could be closer to a 

2.72 g reduction (95% CI: −3.40 to −2.04) in body weight compared to the 5.00 g reduction 

(95% CI: −21.66 to −7.78) predicted by meta-analysis of the epidemiology data without a 

correction for low GFR.

Other Developmental Effects. Fei et al. (2010a) reported on the effects of PFOS and PFOA on 

the length of breastfeeding. Self-reported data on the duration of breastfeeding were collected 

during the telephone interviews at 6 and 18 months after birth of the child. Statisticallysignificant higher levels of PFOS were associated with a shorter duration of breastfeeding 

following adjustment for confounding. This is an expected consequence because PFOS is 

transferred from the mother during breast feeding; thus, the shorter the lactation period the 

greater the proportion of the serum PFOS at the time of birth remains with the mother. A 

20% increase risk for the mother in weaning before 6 months was noted in both primiparous 

[OR = 1.20; 95% CI: 1.04–1.37] and multiparous females, [OR = 1.20; 95% CI: 1.06–1.37]) for 

each 0.010 μg/mL increase in PFOS concentration in the maternal blood. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-21
A dose-response relationship was noted only among multiparous females (OR range: 

1.55–2.64) based on categorical PFOS exposures, as only the highest PFOS quartile showed an 

elevated effect estimate [OR = 1.52; 95% CI: 0.89–2.60]) among primiparous females. For 

analyses based on termination of exclusive breastfeeding before 4 months, associations were 

only seen among multiparous females for both PFOS and PFOA exposures. Given that the 

associations between length of breastfeeding and PFOA and PFOS exposures were largely only 

seen among multiparous females, reverse causality is a possible explanation since reductions of 

current PFOS and PFOA levels may have resulted from longer lactation periods for previous 

children.

Andersen et al. (2013) evaluated the association between maternal plasma PFOS levels and 

the children’s body mass index, waist circumference, and risk of being overweight at 7 years of 

age. From the subset of 1,400 randomly selected females from the DNBC who provided blood 

samples during their first trimester, only those children with weight and height information 

(n = 811) or waist measurements (n = 804) at age 7 years were included in the analysis. Maternal 

plasma PFOS levels were evaluated as both continuous and categorical exposures. Maternal 

PFOS concentrations were inversely associated with all of the children’s anthropometric 

endpoints, but statistical significance was not attained and a dose-response relationship was not 

observed. Neither maternal PFOS nor PFOA levels were associated with anthropometric 

measures in either boys or girls at age 7 in this prospective birth cohort. 

A case-cohort study from the DNBC population was used to evaluate the relationship 

between prenatal PFAS exposure and the risk of congenital cerebral palsy (Liew et al. 2014). 

From a source population of 83,389 mother-child pairs, 156 cases of cerebral palsy were 

identified and matched to 550 randomly selected controls (including 440 boys). Stored maternal 

plasma samples collected in early or mid-pregnancy were analyzed for 16 PFAS; six compounds 

were quantifiable in > 90% of the samples. For the cerebral palsy cases and matched controls, 

median maternal PFOS levels were 0.0289 and 0.0276 μg/mL, respectively, for boys and 0.0275 

and 0.0262 μg/mL, respectively, for girls. A statistically-significant increased risk of developing 

cerebral palsy in boys (rate ratio [RR] = 1.7; 95% CI: 1.0–2.8) was detected per each natural-log 

unit increase in maternal PFOS level. A dose-response relationship between cerebral palsy and 

categorical PFOS exposures was detected in boys. Positive associations were also found with 

PFOA and perfluoroheptanesulfonate (PFHpS), and the results for PFOS remained unchanged 

after adjusting for multiple PFAS in the regression models. No association was found between 

any PFAS level and risk of cerebral palsy in girls, although this analysis was much more limited 

by smaller numbers.

Fei and Olsen (2011) examined the association between prenatal PFOS (and PFOA) exposure 

and behavior or coordination problems in children aged 7 enrolled in the DNBC study. 

Behavioral problems were assessed using the Strengths and Difficulties Questionnaire (SDQ), 

and coordination problems were assessed using the Developmental Coordination Disorder 

Questionnaire (DCDQ) completed by the mothers. A total of 787 mothers completed the SDQ 

and 537 completed the DCDQ for children aged 7.01–8.47 years (mean age 7.15 years). The 

mean maternal PFOS concentration was 0.036 μg/mL, and PFOS levels were divided into 

quartiles: <LLOQ–0.00395, 0.00396–0.00532, 0.00535–0.00711, and 0.00714–0.02190 μg/mL. 

The primary analyses of dichotomized outcomes were examined using logistic regression. Linear 

regression and ordinal logistic regression were also used to examine the full scale of behavioral 

scores. There were no statistically-significant associations detected between 4th quartile PFAS 

exposures and various outcomes, including total difficulties, emotional symptoms, hyperactivity 

Perfluorooctane sulfonate (PFOS) – May 2016 3-22
score, conduct problems, or peer problems. Odds ratios adjusted for different outcomes were 

adjusted for the following confounders: parity, maternal age, pre-pregnancy BMI, smoking and 

alcohol consumption during pregnancy, sex of the child, breastfeeding, birth year, housing 

density, gestational age at blood draw, and parental behavioral problem scores during their 

childhood. Overall, no associations between behavioral or coordination problems in children 7 

years of age and prenatal PFOS (and PFOA) exposure were found. 

A prospective birth cohort study called INUENDO3

 was designed to examine biopersistent 

organochlorines in diet and human fertility (Høyer et al. 2015b). Pregnant females were enrolled 

between May 2002 and February 2004 with a total of 1,106 mother-child pairs at follow-up 

between January 2010 and May 2012 when the children were 7–9 years old. The study 

population consisted of 526 pairs from Greenland, 89 from Poland, and 491 from Ukraine. Since 

maternal blood samples for measurement of plasma PFOS levels were taken any time during 

pregnancy, median gestational age at time of collection varied by country (range: 23–33). 

Behavior of children was assessed with SDQ score, and logistic regression models were used in 

the analyses of PFOS tertiles and behavioral problems. Motor development was assessed with 

DCDQ score, and linear regression was used for analyses. All analyses were performed on the 

entire cohort, as well as by country although not all analyses could be performed on the Polish 

subset due to the small number of cases. Analyses were adjusted for the following potential 

confounders: maternal cotinine level during pregnancy, maternal alcohol consumption at 

conception, maternal age at pregnancy, gestational age at blood-sampling, and child gender. 

The median maternal plasma PFOS level was 0.01 μg/mL for the combined population and 

0.02, 0.005, and 0.008 μg/mL for the pregnant females from Greenland, Ukraine, and Poland, 

respectively. No associations were found between PFOS (and PFOA) levels and motor 

development score. Total SDQ score was not associated with PFOS levels; however, PFOS 

concentrations were associated with higher total SDQ score only in Greenland. The highest 

PFOS tertile was associated with a 0.5 point higher hyperactivity scores in the combined analysis 

in Greenland (0.3) and Poland (1.3), but no association was found in Ukraine. The adjusted OR 

for hyperactive behavior in the combined analysis was 1.4 (95% CI: 0.4–4.9) for the highest 

tertile compared to the lowest PFOS tertile, with comparable results found for Greenland and 

Ukraine. Although statistical adjustment in the regression models included country of 

participant, inter-country differences complicate interpretation of the study results especially 

given variability in exposure data collection periods and vastly different participation rates (e.g., 

37% in Poland and 86% in Greenland). In addition to the potential for selection and information 

biases, the unknown critical exposure window(s), including the impact of unmeasured post-natal 

exposures, for these outcomes increases the uncertainty of these study results.

Fei et al. (2008b) examined the association between plasma levels of PFOS in pregnant 

females and the motor and mental development in their children. The developmental measures 

examined in the infants included Apgar score of child at birth and maternal reported 

questionnaire responses about child development milestones at 6 and 18 months. Using linear 

regression, no significant association between PFOS and Apgar score was observed after 

adjustment for potential confounders (OR = 1.20; 95% CI: 0.57–2.25). Although these data were 

limited by maternal reporting of the outcome data, there was no association between PFOS levels 

and motor or mental development as reported in the questionnaire at 6 months. In children at 

18 months, mothers with higher PFOS levels were slightly more likely to report that their babies 

3 Biopersistent Organochlorines in Diet and Human Fertility study. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-23

 
started sitting without support at a later age and “did not use word-like sounds to tell what he/she 

wants.” No statistically-significant associations were found with PFOA. 

Hoffman et al. (2010) examined the associations between perfluorochemicals, including 

PFOS, and diagnosis of attention deficit hyperactivity disorder (ADHD) using the NHANES data 

from 1999–2000 and 2003–2004. The study population included 571 children aged 12–15 years 

including those who had been diagnosed as having ADHD (n = 48) and/or taking ADHD 

medications (n = 21). Various potential confounders were considered, including birth weight, 

admittance to a neonatal intensive-care unit, socioecomonic status, health insurance coverage, 

having a routine health care provider, preschool attendance, and lead exposure. NHANES 

sample cycle, age, sex, race/ethnicity, living with a smoker, and maternal smoking were adjusted 

for in the logistic regression models. The median serum PFOS levels were 0.023 μg/mL and 

ranged from 0.002 to 0.09 μg/mL. Serum PFOS was positively associated with parental report of 

ADHD (OR = 1.03, 95% CI: 1.01–1.05). The adjusted odds ratio per each 1 μg/L increase in

serum PFOA for parental report of ADHD and ADHD medication use was 1.05 (95% CI: 1.02–

1.08). Both PFOA and perfluorohexane sulfonate were also positively associated with parentallyreported ADHD. Data interpretation were limited by the cross-sectional study design, other 

potential confounders (e.g., alcohol consumption) that were not included in the available data, 

and measurement error resulting from using current PFOS levels as proxy measures of 

etiologically relevant exposures.

In a prospective study, Halldorsson et al. (2012) examined prenatal exposure to PFASs, 

including PFOS, and the risk of being overweight at 20 years of age. A birth cohort consisting of 

965 singleton pregnancies were recruited from a midwife center in Aarhus, Denmark. Maternal 

PFOS levels were measured in serum samples collected during week 30 of gestation for 

assessment of in utero PFOS exposure and offspring anthropometry at 20 years of age. Among 

the 965 study subjects, 915 of their offspring were located and 665 agreed to participate. The 

median PFOS concentration was 0.0215 ± 0.0019 μg/mL with quartiles of 0.016 ± 0.0056, 

0.0202 ± 0.0057, 0.0236 ± 0.0068, and 0.0285 ± 0.0021 μg/mL. Four PFASs, including PFOA, 

PFOS, PFOSA, and perfluorononanoic acid (PFNA) exhibited sufficient contrasts to examine 

quartiles of exposure; while eight of the other quantified PFASs did not. PFOS was positively 

associated with female offspring BMI at 20 years. Maternal PFOS concentrations were not 

associated with offspring anthropometry at 20 years. Associations of PFOS and other variables 

including smoking status; waist circumference; or insulin, leptin, or adiponectin concentrations 

at 20 years were not reported. Therefore, possible confounding cannot be assessed. Study 

strengths include a high rate of participation (69%) in the offspring analysis and for sample 

collection from the original cohort (72%).

The relationship between maternal PFOS (and PFOA) levels and prevalence of offspring 

overweight and waist-to-height ratio > 0.5 was investigated in a subset of the INUENDO 

(biopersistent organochlorines in diet and human fertility) prospective birth cohort (Høyer et al.

2015a). Pregnant females were enrolled between May 2002 and February 2004 with a total of 

1,022 mother-child pairs at follow-up between January 2010 and May 2012 when the children 

were 7–9 years old. The study population consisted of 531 pairs from Greenland and 491 from 

Ukraine. The maternal blood samples for measurement of plasma PFOS levels were taken at a 

mean gestational age of 24 weeks, but there was a substantial range of collection windows in 

both Greenland (5–42 weeks) and Ukraine (9–40 weeks). The child’s weight and height were 

measured and used to calculate BMI. All analyses were performed on the entire cohort as well as 

by country. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-24
The median maternal plasma PFOS level was 0.0202 μg/mL in the pregnant females from 

Greenland and 0.0050 μg/mL in the pregnant females from Ukraine. No associations were found 

between PFOS (and PFOA) levels and risk of being overweight in the combined analysis or in 

Ukraine. No associations were observed between PFOS and BMI score in either country. In the 

combined analysis, an association was detected for having waist-to-height ratio > 0.5 and the 

continuous (per each ln-unit increase) exposure (RR = 1.38, 95% CI: 1.05–1.82). Comparable 

results were noted for PFOA also and waist-to-height ratio > 0.5 in the combined analysis (Høyer 

et al. 2015a), although this was not statistically-significant (RR = 1.30, 95% CI: 0.97–1.74).

Reproductive Outcomes in Females. Using the C8 Health Project data, blood samples from a 

population of females aged 18–65 years (n = 25,957) were analyzed to determine whether the 

onset of menopause, levels of serum estradiol, and the amount of PFAS in the blood were interrelated (Knox et al. 2011). These data were cross-sectional, with a one-time serum measurement 

collected for participants. The mean PFOS level of all the females was 0.018 μg/mL. The 

analyses of menopause excluded participants who reported undergoing a hysterectomy. Logistic 

regression models were adjusted for age, smoking, alcohol consumption, BMI, and exercise. The 

analysis for menopause was determined upon three groups of females: childbearing (aged 30–

42), perimenopausal (aged > 42–51) and menopausal (aged > 51– ≤ 65). These same groups 

were used for the estradiol concentrations except the childbearing group was extended to include 

those > 18 years; exclusions for this analyses included pregnant females, females with a full 

hysterectomy, or females taking hormones, fertility drugs, or selective estrogen receptor 

modulators. 

Among females aged 51–65, statistically-significant ORs for menopause were detected 

across PFOS quintiles, including a monotonic dose-response relationship. Similar results were 

found with PFOA quintiles (OR range: 1.5–1.7). Although dose-response relationships were not 

evident, consistent ORs for menopause were detected among the perimenopausal age group, as 

well for both PFOS and PFOA exposures (OR range: 1.2–1.4). Inverse associations were 

detected between estradiol concentrations and PFOS in the perimenopausal group (β = −3.65; 

p < 0.0001) and menopausal group (β = −0.83; p < 0.007). Serum PFOA and estradiol 

concentrations were not associated. Despite the contaminated water supplies, the PFOS exposure 

levels were comparable to those from NHANES and likely represented general population levels.

A study limitation was the one-time serum measurement and cross-sectional study design; thus, 

exposure misclassification is likely despite long half-lives reported for PFAS. The level of PFOS 

was significantly higher in the set of females that had undergone a hysterectomy. Menopause and 

having undergone a hysterectomy, therefore, may be associated with increased serum PFAS due 

to the loss of menstruation as a route for removing PFOS with the associated menstrual blood 

loss. Thus, reverse causation cannot be ruled out as an alternative explanation for the study 

findings. 

Lopez-Espinosa et al. (2011) evaluated the relationship between pubertal timing and PFOS 

levels among 2,931 girls and 3,076 boys aged 8–18 years from the C8 study. A high proportion 

of available participants provided serum biomarkers among both boys (66%) and girls (67%). 

The median serum PFOS level was 0.018 μg/mL among these female participants, and exposures 

were examined continuous and categorical (quartiles) variables. Pubertal development was based 

on hormone levels (total > 50 ng/dL and free > 5 pg/mL testosterone in boys and estradiol 

> 20 pg/mL in girls) or onset of menarche. although participant age at survey and time of day of 

blood sampling were the only confounders that were identified and adjusted for, other covariates 

considered as potential confounders included BMI z-score, height annual household family 

Perfluorooctane sulfonate (PFOS) – May 2016 3-25
income, ethnicity, ever smoking, and ever alcohol consumption. A reduced odds of having 

reached puberty was found with increasing PFOS levels, with girls having a difference of 

138 days between the highest and lowest PFOS quartile. A reduced odds of postmenarche was 

found for both PFOS (138 days of delay) and PFOA (130 days of delay). 

Christensen et al. (2011) used data from a prospective cohort study in the United Kingdom to 

conduct a nested case-control study examining the association between age at menarche and 

gestational exposure to perfluorinated chemicals including PFOS and PFOA. The study 

population from the Avon Longitudinal Study of Parents and Children included single-birth 

female subjects who had completed at least two puberty staging questionnaires between the ages 

of 8 and 13 years and whose mothers provided at least one prenatal serum sample. If more than 

one serum sample were available, the earliest sample provided was used for analysis. The study 

does not provide information as to when samples were collected. The females were divided into 

two groups, including those who experienced menarche prior to age 11.5 years (n = 218 cases), 

and a sample of those who experienced menarche after age 11.5 (n = 230 controls) from the 

5,756 female offspring enrolled in the Avon study. Confounders including the mother’s prepregnancy BMI, age at delivery, age at menarche, educational level, and the child’s birth order 

and ethnic background were included in linear and logistic regression models used to analyze the 

data. The median maternal serum PFOS concentrations were 0.019 and 0.02 μg/mL for the early 

menarche and non-early menarche groups, respectively. 

Although not statistically-significant, decreased adjusted odds ratios for earlier age at 

menarche were found for the prenatal PFOS examined as a continuous [OR = 0.68; 95% 

CI: 0.40–1.13] and the categorical [OR = 0.83; 95% CI: 0.56–1.23] exposure dichotomized as 

the median value (0.0198 μg/mL). Results were null for the continuous PFOA exposure measure 

and slightly elevated for the categorical exposure [OR = 1.29; 95% CI: 0.86–1.93] above the 

median value of 0.0037 μg/mL. The limitations of the study included having a small sample size, 

using a single maternal gestational serum sample for perfluorinated chemical measurement, and 

the self-reported nature of some covariates including menarche status and age at menarche.

The relationship between prenatal exposure to PFOS (and PFOA) and female and male 

reproductive function was evaluated in 343 females and 169 males whose mothers participated in 

an Aarhus, Denmark cohort in 1988–1989 (Kristensen et al. 2013; Vested et al. 2013). Maternal 

blood samples were collected during week 30 of gestation. Follow-up was initiated in 2008 when 

the offspring were approximately 20 years old. Median serum PFOS level was 0.0211 μg/mL for 

the mothers with daughters evaluated. Potential confounders adjusted for included maternal 

smoking during pregnancy, social class, and daughter’s BMI. No statistically-significant

association was found between prenatal exposure to PFOS and age of menarche. In adjusted 

regression analysis, daughters from mothers in the highest PFOA tertile had a later age at 

menarche compared with those in the lowest tertile. No statistically-significant relationships 

were found between PFOS (or PFOA) exposure and cycle length, reproductive hormone levels, 

and number of follicles assessed by ultrasound (Kristensen et al. 2013). Study limitations 

included retrospective collection of some health outcome data, such as age of the menarche, 

which was queried 2–10 years afterward.

Fei et al. (2009) evaluated associations with PFOS levels and fecundity as indicated by the 

time to pregnancy (TTP) in the DNBC study population. In females who had a planned 

pregnancy (n = 1,240), there was a longer TTP with higher levels of PFOS (p < 0.001). PFOS 

was also associated with irregular menstrual periods (11.6% in the lowest quartile versus 

14.2% in the upper three exposure quartiles). The proportion of females with infertility 

Perfluorooctane sulfonate (PFOS) – May 2016 3-26
(TTP > 12 months) was higher in the upper three quartiles of PFOS versus the lowest quartile. 

These trends were statistically-significant. In females who had planned pregnancies (n = 1,240), 

there was a longer TTP with higher levels of PFOS (p < 0.001). Females with longer TTP were 

also older and had a history of spontaneous miscarriages or irregular menstrual cycles. The 

biological mechanism by which PFOS may reduce fecundity is unknown. Both TTP and 

infertility were also positively associated with serum PFOA levels. The selection of females who 

gave birth among only those with planned or partly planned pregnancies may limit study 

generalizability. Selection bias is also possible if excluded fertile females who did not plan their 

pregnancy had differentially higher or lower PFAS exposures. Additional analyses of unplanned 

pregnancies actually resulted in stronger association between PFAS levels and TTP.

Participants enrolled in the Maternal-Infant Research on Environmental Chemicals Study, a 

Canadian pregnancy and birth cohort, were evaluated for an association between serum PFOS 

levels (as well as PFOA and PFHxS) and TTP (Vélez et al. 2015). Females (n = 1,743) recruited 

from prenatal clinics across 10 Canadian cities between 2008 and 2011 (39% participation rate) 

were included in this analysis if they provided a first trimester blood sample collected between 

6 and 14 gestational weeks. Infertility was defined as having a TTP of > 12 months or requiring 

infertility treatment for the current pregnancy. The geometric mean plasma PFOS level was 

0.00459 μg/mL. No statistically-significant associations with fecundity were observed, although 

an increased risk was observed for infertility (OR = 1.14; 95% CI: 0.98–1.34) per one SD 

increased in PFOS. In contrast, statistically-significant associations were detected for infertility 

and reduced fecundity and both PFOA and PFHxS. 

Reproductive Outcomes in Males. Lopez-Espinosa et al. (2011) also included 3,076 boys aged

8–18 years from the C8 database in their analysis, with a high proportion of available 

participants providing serum biomarkers (66%). The median serum PFOS level was 0.020 

μg/mL among these male participants. Pubertal development was based on hormone levels (total 

> 50 ng/dL and free > 5 pg/mL testosterone). Reduced odds of reaching puberty in boys (i.e., 

raised testosterone) was detected with increasing PFOS (delay of 190 days between the highest 

and lowest quartile).

Reproductive function and other reproductive endpoints also were evaluated in the sons of 

the mothers who participated in the Aarhus, Denmark cohort (Kristensen et al. 2013). The 

median (25th–75th percentile) serum PFOA level was 0.0212 μg/mL (0.017.4–0.026.5 ng/mL) for 

the mothers with sons who were evaluated. PFOS was not associated with any outcome of 

reproductive function analyzed with multivariable regression models. No associations were 

found between PFOS (and PFOA) levels and percentage of progressive sperm, sperm 

morphology, semen volume, or testicular volume. Monotonic exposure-response relationships 

were detected for in utero PFOA exposure and sperm concentration, total sperm count, and 

percentage of progressive spermatozoa (based on the computer-assisted semen analysis), and 

positive associations for follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels 

were associated with PFOA (Vested et al. 2013). 

Joensen et al. (2009) investigated the relationship between PFAS and semen quality in a 

cross-sectional study of 105 Danish males. The study participants were recruited in 2003 from a 

sample of 546 males from a compulsory medical examination for all young Danish males being 

considered for military service. They represented the individuals with the lowest and highest 

testosterone levels in that study population. Nine PFAS were measured from frozen, archived 

(5 years) samples, while the semen samples were collected during the 2003 examination.

Confounders adjusted for in the various regression models included duration of abstinence and 

Perfluorooctane sulfonate (PFOS) – May 2016 3-27
time between ejaculation and semen analysis. The median PFOS serum level in the 105 study 

participants was 0.025 μg/mL. Males with high combined levels of PFOA/PFOS had a median 

level of 6.2 million morphologically normal spermatozoa compared to 15.5 million in males with 

low PFOA/PFOS levels (p = 0.030). 

There was no statistically significant association between testosterone levels and PFAS

exposures and no difference in PFAS levels between high and low testosterone groups. To 

address previous study limitations and expand the generalizability of the findings, a later study 

by Joensen et al. (2013) was conducted to investigate the associations between serum PFOS 

concentration and reproductive hormones and semen quality. Study participants included a 

random sample of 247 healthy young Danish males (mean age 19.6 years) recruited in 2008–

2009 from the same study population. Serum samples were analyzed for PFOS, as well as total 

testosterone (T), estradiol (E), sex hormone-binding globulin (SHBG), LH, FSH, and inhibin-B.

Semen samples were collected the same morning as the blood samples, and self-administered 

questionnaires were also completed by the study participants. Confounders adjusted for in the 

various regression models included time to semen analysis, abstinence time, BMI, and smoking. 

The mean PFOS level was 0.0085 μg/mL. Inverse associations were detected for PFOS and 

various outcomes including T, calculated free T (FT), free androgen index (FAI), and ratios of 

T/LH, FT/LH, and FAI/LH (all p-values ≤ 0.05). PFOS was also inversely associated with 

estradiol, T/E ratio, and inhibin-B/FSH ratio, and positively associated with SHBG, LH, FSH, 

and inhibin-B, although statistical significance was not attained. No associations were detected 

between PFOS levels and any semen quality parameters. Study strengths included improved 

generalizability due to the random selection of subjects from the general population and a higher 

participation rate was (30%) compared to other population-based semen quality studies.

The relationship between serum PFOS exposures and 35 semen quality parameters was 

evaluated in 462 males enrolled in the LIFE Study cohort (Buck Louis et al. 2015). The males

were recruited from 501 couples discontinuing contraception for the purposes of becoming 

pregnant and residing in 16 counties from Michigan and Texas. Forty-two percent of eligible 

couples enrolled in the study, and the 462 males provided at least one semen sample. Linear

mixed models were adjusted for age, BMI, smoking, abstinence time, sample age, and study site.

The study participants had a mean age of 31.8 years and mean PFOS levels were 0.017 μg/mL 

for Michigan residents and 0.021 μg/mL for Texas residents. Statistically-significant associations 

were detected between PFOS exposures and for a lower percentage of sperm with coiled tails; no 

associations were found for any other endpoint. In total, six PFAS (including PFOS) were 

associated with changes in 17 semen quality endpoints. Study strengths included improved 

generalizability, since participants were from the general population and had a higher 

participation rate (42%) compared to other population-based semen quality studies. A key study 

limitation of this and many of these types of epidemiology studies is the uncertainty related to 

the critical exposure window(s) relative to timing of the collected samples and the multiple 

comparisons (n = 245) that were examined. 

Raymer et al. (2012) conducted a cross-sectional study of the relationships between PFAS 

and semen quality and reproductive hormones. The study population included 256 males

recruited between 2002 and 2005 from Duke University Medical Center’s IVF Clinic. 

Reproductive health questionnaires were administered to participants. Blood and semen samples 

were used to detect PFAS and were both collected at the time of evaluation. Linear and logistic 

regression models were used to calculate effect estimates and were adjusted for age, period of 

abstinence, and tobacco use. The average PFOS levels in plasma were 0.0374 μg/mL and 

Perfluorooctane sulfonate (PFOS) – May 2016 3-28
0.0008 μg/mL in semen. The strongest correlations detected between PFAS and hormones were 

between plasma PFOS and LH (r = 0.12), plasma PFOA and LH (r = 0.16), plasma PFOS and 

triiodothyronine (r = 0.14), as well as semen PFOS and FSH (r = 0.13). No statisticallysignificant associations were detected between PFOS and PFOA concentrations and reproductive 

hormones or different semen quality outcomes. The older population (mean age = 42 years) may 

limit comparability with previous studies and generalizability of study findings. 

The INUENDO prospective birth cohort study of persistent organic pollutants and fertility 

was used to examine the relationship between PFAS and semen quality parameters (Toft et al.

2012). The study population included 588 males (97%) from Greenland, Poland and Ukraine 

who provided a semen sample among the underlying 607 male partners of 1710 pregnant 

females. PFOS levels were quantified from serum samples; these were categorized into tertiles 

and also examined as continuous exposures. Linear regression models and categorical analyses 

were adjusted for the following potential confounders: age, abstinence time, spillage, smoking, 

urogenital infections, BMI, and country of origin. For the categorical analysis combining the 

three cohorts, compared to the first tertile, the percent of normal sperm cells was decreased in the 

upper two serum PFOS tertiles with a decrease of 22% (95% CI: 1%–44%) and 35% (95% CI: 

4%–66%) in the second and third PFOS tertiles, respectively. Exposure-response relationships 

were detected for the overall population based on the continuous PFOS exposure data, although 

this was only evident among the Polish and Ukrainian populations. No other associations 

between PFOS exposure and semen quality parameters were noted. The variable participation 

rates across study sites and potential for participation bias (i.e., if participation was related to 

fertility status and exposure levels) complicate interpretation of these results. The cross-sectional 

nature of this study also limits the ability to draw causal inference from these types of studies, 

especially since temporality could not be established some of the study population based on the 

timing of the blood and semen samples (e.g., nearly 60% of the Greenland samples were 

collected approximately a year before the semen samples).

Summary. Fetal growth retardation was examined through measures including mean birth 

weight, LBW, and small for gestational age. Mean birth weight examined as a continuous 

outcome was the most commonly examined endpoint for epidemiology studies of serum/cord 

PFOS exposures. Although three studies were null (Fei et al. 2008a; Hamm et al. 2010; Monroy 

et al. 2008), birth weight deficits ranging from 29 to 149 grams were detected in five studies 

(Apelberg et al. 2007; Chen et al. 2015; Darrow et al. 2013; Maisonet et al. 2012; Washino et al. 

2009). Larger reductions (from 69 to 149 grams) were noted in three of these studies (Apelberg 

et al. 2007; Chen et al. 2015; Washino et al. 2009) on the basis of per unit increases in 

serum/cord PFOS exposures, while the lone categorical data showed an exposure-response 

deficit in mean birth weight up to 140 grams across the PFOS tertiles (Maisonet et al. 2012). 

Two (Chen et al. 2015; Whitworth et al. 2012) out of four (Fei et al. 2007; Hamm et al. 2009) 

studies of SGA and serum/cord PFOS exposures showed some suggestion of increased ORs 

(range: 1.3–2.3), while three (Chen et al. 2012; Fei et al. 2007; Stein et al. 2009) out of four 

(Darrow et al. 2014) studies of LBW showed increased risks (OR range: 1.5–4.8). Although a 

few of these studies showed some suggestion of dose-response relationships across different fetal 

growth measures (Fei et al. 2007; Maisonet et al. 2012; Stein et al. 2009), study limitations, 

including the potential for exposure misclassification, likely precluded the ability to adequately 

examine exposure-response patterns. While there is some uncertainty in the interpretation of the 

observed association between PFOS and birth weight given the potential impact of low GFR, the 

available information indicates that the association between PFOS exposure and birth weight for 

the general population cannot be ruled out. In humans with low GFR (which includes females

Perfluorooctane sulfonate (PFOS) – May 2016 3-29
with pregnancy induced hypertension or preeclampsia) the impact on body weight is likely due 

to a combination of the low GFR and the serum PFOS. 

A small set of studies observed an association with gestational diabetes (preconception serum 

PFOS; Zhang et al. 2015), pre-eclampsia (Stein et al. 2009) and pregnancy-induced hypertension 

(Darrow et al. 2013) in populations with serum PFOS concentrations of 0.012 – 0.017 μg/mL. 

Zhang et al. (2015) and Darrow et al. (2013) used a prospective assessment of adverse pregnancy 

outcomes in relation to PFASs which addresses some of the limitations the available crosssectional studies. Associations with these outcomes and serum PFOA also were observed.

Although there was some suggestion of an association between PFOS exposures and semen 

quality parameters in a few studies (Joensen et al. 2009; Toft et al. 2012), most studies were 

largely null (Buck Louis et al. 2015; Ding et al. 2013; Joensen et al. 2013; Raymer et al. 2012; 

Specht et al. 2012; Vested et al. 2013). For example, morphologically abnormal sperm associated 

with PFOS were detected in three (Buck Louis et al. 2015; Joensen et al. 2009; Toft et al. 2012) 

out of nine (Buck Louis et al. 2015; Ding et al. 2013; Joensen et al. 2013; Raymer et al. 2012; 

Specht et al. 2012; Vested et al. 2013) studies.

Small increased odds of infertility was found for PFOS exposures in studies by Jørgensen et 

al. (2014) [OR = 1.39; 95% CI: 0.93–2.07] and Vélez et al. (2015) [OR = 1.14; 95% CI: 0.98–

1.34]. Although one study was null (Vestergaard et al. 2012), PFOS exposures were associated 

with decreased fecundability ratios (FRs), indicative of longer time to pregnancy, in studies by 

Fei et al. (2009) [FR = 0.74 (95% CI: 0.58–0.93) and in studies by Jørgensen et al. (2014) 

[FR = 0.90; 95% CI: 0.76–1.07]. Whitworth et al. (2012) data suggested that reverse causality 

may explain their observation of subfecundity odds of 2.1 (95% CI: 1.2–3.8) for the highest 

PFOS quartile among parous females, but a reduced odds among nulliparous females (OR = 0.7; 

95% CI: 0.4–1.3). A recent analysis of the pooled DNBC study samples found limited evidence 

of reverse causality with an overall FR of 0.83 (95% CI: 0.72–0.97) for PFOS exposures, as well 

as comparable ratios for parous (0.86; 95% CI: 0.70–1.06) and nulliparous (0.78; 95% CI: 0.63–

0.97) females (Bach et al. 2015). The same authors reported an increased infertility OR of 1.75 

(95% CI: 1.21–2.53) and OR for parous (OR = 1.51; 95% CI: 0.86–2.65) and nulliparous 

(OR = 1.83; 95% CI: 1.10–3.04) females. Although there remains some concern over the 

possibility of reverse causation explaining some previous study results, these collective findings 

indicate a consistent association with fertility and fecundity measures and PFOS exposures.

3.1.1.5 Thyroid Effect Studies

Occupational Populations. In the cross-sectional study described above for production workers, 

thyroid hormone (TH) levels were also measured in male (n = 215) and female (n = 48) 

volunteers working at the Decatur, Alabama plant and male (n = 206) and female (n = 49) 

volunteers working at the Antwerp, Belgium plant (Olsen et al. 2001a). The mean PFOS level in 

all employees from the Decatur and Antwerp plants was 1.40 μg/mL (range: 0.11–10.06 μg/mL) 

and 0.96 μg/mL (range: 0.04–6.24 μg/mL), respectively. No significant associations were found 

for quartile of PFOS level and thyroid-stimulating hormone (TSH), serum thyroxine (T4), free 

thyroxine (FT4), triiodothyronine (T3), and thyroid hormone binding ratio. 

General Population. The relationship between exposure to polyhalogenated compounds, 

including PFOS, and thyroid hormone homeostasis was examined in a cross-sectional study of 

the adult Inuit population of Nunavik, Quebec, Canada (Dallaire et al. 2009). Those using 

medication for thyroid disease and pregnant females were not included in the study. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-30
Concentrations of TSH, FT4, total triiodothyronine (TT3), and thyroxine-binding globulin 

(TBG) were measured in 623 individuals. Participants were given a survey to indicate smoking 

status, frequency of alcohol consumption, medications taken, and dietary fish consumption. The 

study detected PFOS in 100% of individuals, with a mean plasma PFOS concentration of 

0.018 μg/mL (95% CI: 0.017–0.019 μg/mL). PFOS was negatively associated with circulating 

levels of TSH, TT3, and TBG and positively associated with FT4. The results suggest that 

human thyroid hormone levels could be affected by PFOS exposure. However, because the 

majority of individuals were reported by the authors to have normal thyroid gland function and 

the thyroid hormone levels were in the normal range, it is uncertain that these relationships are 

connected to thyroid disease or are a reflection of hormone variability in the human population. 

NHANES data from three independent cross-sectional cycles (1999–2000; 2003–2004, and 

2005–2006) were analyzed by Melzer et al. (2010) to estimate associations between serum 

PFOA and PFOS concentrations and thyroid disease in the general U.S. population. Overall, a 

total of 3,966 individuals ≥ 20 years of age (1,900 males and 2,066 females) were included. Of 

these, 292 females and 69 males reported thyroid disease. Overall mean PFOS levels were 

0.025 μg/mL for males and 0.019 μg/mL for females. The data showed that males with PFOS 

levels in the highest quartile ≥ 0.037 μg/mL were more likely to report currently treated thyroid 

disease than males with PFOS levels in the lowest two quartiles combined, ≤ 0.026 μg/mL (OR

= 2.68; 95% CI: 1.03–6.98; p = 0.043). Females had lower levels of PFOS than males and higher 

prevalence of thyroid disease, but serum PFOS concentration was not significantly associated 

with treated thyroid disease. With PFOA, the opposite was found, with females in the highest 

quartile, but not males, more likely to report thyroid disease. Further studies measuring thyroid 

hormone levels in a larger sample population could clarify whether pathology, changes in 

exposure, or altered pharmacokinetics can explain the association. Thyroid hormone levels were 

not reported by Melzer et al. (2010). 

Another study of 1,181 members of NHANES for survey years 2007–2008 and 2009–2010 

examined the association between serum PFOS levels (and 12 other PFASs) and thyroid 

hormone levels (Wen et al. 2013). Multivariable linear regression models were used with serum 

thyroid measures as the dependent variable and individual natural log-transformed PFAS

concentration as a predictor along with confounders. The geometric mean serum PFOS level was 

0.0142 μg/mL. No associations between PFOS level and thyroid hormones were found in males

and females. However in 23 individuals defined as subclinical hypothyroid (TSH above normal 

range), a 1-unit increase in natural log-PFOS was positively associated with hypothyroidism (OR 

= 3.03; 95% CI: 1.14–8.07 in females; OR = 1.98; 95% CI: 1.19–3.28 for males; both p < 0.05). 

Webster et al. (2015) also used NHANES 2007–2008 data from 1,525 adults to explore the 

contribution of PFOS exposure to those with risk factors for thyroid disease, low iodide status 

and/or high thyroid peroxidase antibody (TPOAb). Webster et al. 2015 saw that people with both 

elevated TPOAb and low iodide (those at risk for thyroid insufficiency) were more susceptible to 

PFOS associated disruption of thyroid hormone concentrations than were people without these 

two risk factors.

Bloom et al. (2010) examined the potential association between serum concentrations of 

eight polyhalogenated compounds, including PFOS, and human thyroid function. Levels of TSH 

and FT4 were measured in a subsample of participants in the cross-sectional New York State 

Angler Cohort Study (27 males and 4 females). A survey was conducted to determine smoking 

status, history of thyroid disease, medications used, and dietary fish consumption. None of the 

participants reported a thyroid condition or the use of thyroid medication. PFOS occurred at a 

Perfluorooctane sulfonate (PFOS) – May 2016 3-31
high concentration compared to the other PFASs measured with a mean concentration of 

0.0196 μg/mL (95% CI: 0.0163–0.0235). The results indicated no significant association 

between PFOS serum concentration (or PFOA) and thyroid hormone levels, potentially due to 

the study’s small sample size.

The relationship between thyroid biomarkers and serum levels of PFOS, PFOA, and other 

persistent organic pollutants was investigated in older adults (Shrestha et al. 2015). Levels of 

TSH, FT4, T4, and T3 were measured in 51 males and 36 females with a mean age of 63.6 years. 

None of the participants had thyroid disease or were taking thyroid medication. Covariates in the 

analysis included age, sex, education level, polychlorinated biphenyl (PCB) and PBDE exposure, 

smoking status, and alcohol consumption. The mean PFOS serum level was 0.0366 ± 0.023 μg/mL 

for all participants. In both unadjusted and adjusted models, PFOS was significantly (p < 0.05 or 

0.01) and positively associated with FT4 and T4; a possible dose-response was not evaluated in 

this small sample.

The potential relationship between PFOS exposure and thyroid disease was investigated by 

Pirali et al. (2009) in a sample of 28 patients undergoing thyroid surgery (22 benign and 6 

malignant) and a control group of 7 patients with no evidence of thyroid disease. PFOS was 

detected in thyroid tissue in 100% of the 8 males and 20 females with thyroid disease, with a 

median PFOS concentration of 5.3 ng/g, and no significant difference in levels between benign 

and malignant patients. The median PFOS concentration (4.4 ng/g) in the healthy glands of the 

control group was similar to that found in the diseased thyroid samples indicating that there was 

no association between PFOS concentration and thyroid disease. 

A cross-sectional study of 903 pregnant females evaluated the association between plasma 

PFOS levels and plasma TSH (Wang et al. 2013). Twelve other perfluoroalkyl substances were 

also quantified and evaluated. The females were a cohort of the Norwegian Mother and Child 

Cohort Study, and the blood samples were drawn at approximately week 18 of gestation. The 

median PFOS concentration was 0.013 μg/mL with an interquartile range of 0.010–0.017 μg/mL. 

A trend was observed for increasing TSH across PFOS quartiles, with females in the third and 

fourth quartiles having significantly higher TSH levels compared with the first quartile. After 

adjustment, each 0.001 μg/mL increase in PFOS concentration was associated with a 0.8% (95% 

CI: 0.1%–1.6%) rise in TSH. The odds ratio of having an abnormally high TSH, however, was 

not increased. The plasma levels of other perfluoroalkyl substances were not related to TSH 

levels.

Expanding on the above study, Berg et al. (2015) investigated the association between a 

number of perfluoroalkyl substances, including PFOS, and TSH, T3, T4, free triiodothyronine 

(FT3), and FT4. A subset of 375 females on the Norwegian Mother and Child Cohort Study with 

blood samples at about gestational week 18 and at 3 days and 6 weeks after delivery were 

included. Seven compounds were detected in > 80% of the blood samples with PFOS present in 

the greatest concentration. The median PFOS level was 0.00803 μg/mL and the females were 

assigned to quartiles based on the first blood sample at week 18 of gestation. After adjustment 

for covariates (parity, age, thyroxin binding capacity, BMI), TSH was positively associated with 

PFOS. Females in the highest quartile had significantly higher mean TSH at all three time points 

compared to females in the first quartile. No associations were found between PFOS and the 

other thyroid hormone levels. 

Maternal and umbilical cord blood concentrations of a number of fluorinated organic 

compounds, including PFOS, were determined in 15 females (17–37 years of age) and their 

Perfluorooctane sulfonate (PFOS) – May 2016 3-32
newborns at Sapporo Toho Hospitals in Hokkaido, Japan from February 2003 to July 2003 

(Inoue et al. 2004). PFOS was detected in 100% of the maternal and cord blood samples, with 

maternal blood PFOS ranging from 0.0049 to 0.0176 μg/mL, and cord blood PFOS ranging from 

0.0016 to 0.0053 μg/mL. TSH and FT4 levels in the infants between days 4 and 7 of age were 

not related to cord blood PFOS concentration in this small study. 

Chan et al. (2011) used blood from 974 serum samples collected in 2005–2006 from females

in Canada (mean age 31.3 years) at 15–20 weeks gestation and measured thyroid hormones, FT4

and the level of PFAS to determine whether PFAS levels were associated with hypothyroxinemia. 

From the samples, there were 96 identified as cases of hypothyroxinemia and 175 identified as 

controls. The cases had normal TSH concentrations and free T4 concentrations in the lowest 10th

percentile (≤ 8.8 pmol/L). The controls had normal TSH concentrations and free T4 

concentrations between the 50th and 90th percentiles (12–14.1 pmol/L). The geometric mean for 

PFOS was 0.0074 μg/mL. The mean free T4 levels were 7.7 pmol/L in the cases and 12.9 in the 

controls. The mean TSH concentrations were 0.69 milli-Units/L in the cases and 1.13 in the 

controls. Analysis by conditional logistic regression indicated that the concentration of PFOS (or 

PFOA) was not significantly associated with hypothyroxinemia. For PFOS, the odds ratio for 

association of hypothyroxinemia with exposure to PFOS was 0.88 with a 95% CI of 0.63–1.24. 

A similar study of 152 Canadian females evaluated maternal serum PFOS levels (and 

PFHxS, PFNA, PFOA) for associations with thyroid hormone levels during the early second 

trimester of pregnancy, weeks 15–18 (Webster et al. 2014). Mixed effects linear models were 

used to examine associations between PFOS levels and FT4, total T4, and TSH; associations 

were made for all females and separately for females with high levels of thyroid peroxidase 

antibody, a marker of autoimmune hypothyroidism. Median serum PFOS was 0.0048 μg/mL. No 

associations were found between levels of PFOS (or PFOA and PFHxS), and thyroid hormone 

levels in females with normal antibody levels. PFNA was positively associated with TSH.

Clinically elevated thyroid peroxidase antibody levels were found in 14 (9%) of the study 

population. In the females with high antibody levels, PFOS, PFNA, and PFOA were strongly and 

positively associated with TSH. An IQR increase in maternal PFOS concentrations was associated 

with a 69% increase in maternal TSH compared to the median TSH level. PFNA and PFOA 

concentrations were associated with 46% and 54% increases, respectively, in maternal TSH.

Numerous epidemiologic studies have evaluated thyroid hormone levels, thyroid disease, or 

both in association with serum PFOS concentrations (Table 3-6). These epidemiologic studies 

provide limited support for an association between PFOS exposure and incidence or prevalence 

of thyroid disease, and they include large studies of representative samples of the general U.S. 

adult population (Melzer et al. 2010; Wen et al. 2013). These highly powered studies reported 

associations between PFOS exposure (serum PFOS concentrations) and thyroid disease but not 

thyroid hormone status. Melzer et al. (2010) studied thyroid disease with medication and Wen et 

al. (2013) studied subclinical thyroid disease. In studies of pregnant females, PFOS was 

associated with increased TSH levels (Berg et al. 2015; Wang et al. 2013; Webster et al. 2014). 

Thyroid function can be affected by iodide sufficiency and by autoimmune disease. Pregnant 

females testing positive for the anti-thyroid peroxidase (TPO) biomarker showed a positive 

association with PFOS and TSH (Webster et al. 2014). An association with PFOS and TSH and 

T3 was found in a subset of the NHANES population with both low iodide status and positive 

anti-TPO antibodies (Webster et al. 2015). These studies used anti-TPO antibody levels as an 

indication of stress to the thyroid system, not a disease state. Thus, the association between 

PFOS and altered thyroid hormone levels is stronger in people at risk for thyroid insufficiency. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-33
Table 3-6. Summary of Epidemiology Studies of PFOS and Thyroid Effects

Study

PFOS level 

(μg/mL) TSH T3 T4

Olsen et al. 2001a

n = 263 Decatur, AL plant

n = 255 Antwerp, Belgium 

plant

Decatur plant: 1.4

Antwerp plant: 0.96

No effect observed. No effect observed. No effects observed.

Dallaire et al. 2009

Canada 

n = 623 (adult Inuit 

population) 

Adjusted for sex, age, BMI, 

education, lipids and smoking

0.018 Adjusted Beta = −0.102 (p 

≤ 0.05)

Adjusted Beta = 

−0.017 (p ≤ 0.05)

Adjusted Beta = 0.014 

(p≤0.05)

Melzer et al. 2010

n = 3,966 adults, 

≥ 20 yrs old

NHANES (1999–2000; 

2003–2004 and 2005–2006) 

0.025 (men)

0.019 (women) 

Men (μg/mL) 

Q1: 0.0003–0.018

Q2: 0.0182–0.0255

Q3: 0.0256–0.0367

Q4: 0.0368–0.435

Similar cut-points in 

women

Self-Reported on thyroid disease, with medication use (fully adjusted); 

OR (95% CI), p-value

Men Women

Q1: 1 (referent) Q1: 1 (referent)

Q2: 0.43 (0.17, 1.08), p = 0.073 Q2: 1.05 (0.55, 2.00), p = 0.89

Q3: 0.95 (0.34, 2.70), p = 0.926 Q3: 0.81 (0.44, 1.51), p = 0.496

Q4: 1.89 (0.72, 4.93), p = 0.190 Q4: 1.31 (0.72, 2.36), p = 0.269

Q4 vs Q1&2: 2.68 (1.03, 6.98), p = 0.043 Q4 vs Q1&2: 1.27 (0.82, 1.97)

Wen et al. 2013

United States, NHANES 

2007–2008, 2009–2010 

n = 1,181 adults, aged ≥ 20 

yrs 

Linear regression, adjusted, 

with sampling weights

0.0142 Subclinical hypothyroidism (fully adjusted); OR (95% CI), p-value

Men Women

1.98 (1.19, 3.28), p < 0.05 3.03 (1.14, 8.07)

No associations between serum PFOS and thyroid hormones.

Webster et al. 2015

n = 1,525 adults

NHANES (2007–2008) 

Results are on those with 

high TPOAb and low iodinen = 26

Geometric mean: 

0.014 

% difference in serum 

thyroid hormones for each 

IQ ratio increase in PFOS 

(95% CI), p-value (n = 26)

17.1 (6.6, 28.7), p < 0.05

% difference in serum 

thyroid hormones for 

each IQ ratio increase 

in PFOS (95% CI), 

p-value (n = 26)

4.7 (3.9,5.5), p < 0.05

% difference in serum 

thyroid hormones for 

each IQ ratio increase in 

PFOS (95% CI), p-value 

(n = 26)

−4.4 (−7.6,−1.1), p < 

0.05

Bloom et al. 2010

n = 31 adults, subset of New 

York Angler Cohort study

0.0196 Log-PFOS and log-TSH, 

(95% CI), p-value

Beta = 0.04 (−0.52,0.59), p 

= 0.90

NM Log-PFOS and log-FT4, 

(95% CI), p-value

Beta = 0.03 (−0.17, 

0.10), p = 0.62

Shrestha et al. 2015

n = 87 adults (mean age of 

64) 

United States

Geometric mean: 

0.036 

Log-PFOS and log-TSH, 

(95% CI), p-value

Beta = 0.129 (−0.02, 0.28), 

p= 0.09

Log-PFOS and log-T3, 

(95% CI), p-value

Beta = 2.631 (−2.25, 

7.51), p= 0.29

Log-PFOS and log-FT4, 

(95% CI), p-value

Beta = 0.054 (0.002, 

0.11), p = 0.04

Log-PFOS and log-T4, 

(95% CI), p-value

Beta = 0.766 (0.33, 

1.21), p = 0.001

Pirali et al. 2009

n = 28 patients undergoing 

thyroid surgery

n = 7 control group

5.3 ng/g thyroid 

tissue

No association with 

PFOS concentration 

and thyroid disease

NM NM NM

Perfluorooctane sulfonate (PFOS) – May 2016 3-34
Study

PFOS level 

(μg/mL) TSH T3 T4

Wang et al. 2013

n = 903 women

Norway (from case-control 

study of subfecundity in the 

Norwegian Mother and 

Child Cohort Study; cases 

and controls combined)

Blood sample (mean 18 

weeks pregnancy) 

Median: 0.013 PFOS and ln-TSH (95% 

CI) 

Beta= 0.012 (0.005, 0.019)

NM NM

Berg et al. 2015

n = 375 women in the 

Norwegian Mother and 

Child Cohort Study

Blood samples at week 18, 

and 3 days/6 weeks postdelivery

Median: 0.00803

(μg/mL) 

Q1: 0.0003–0.0057

Q2: 0.0058–0.008

Q3: 0.0081–0.011

Q4: 0.0111–0.0359

PFOS and ln-TSH mLU/L 

(95% CI), p-value

Q1: 1 (referent)

Q2: 0.18 (0.06, 0.31), p = 

0.11

Q3: 0.26 (0.13, 0.40), p = 

0.03

Q4: 0.35 (0.21, 0.50), p = 

0.00

No association No association

Inoue et al. 2004

n = 15 women (17–37 yrs 

old) 

Japan

0.0016–0.0053 

(cord blood)

0.0049–0.0176 

(maternal blood)

No correlation between 

PFOS and TSH

NM No correlation between 

PFOS and free T4

Chan et al. 2011

n = 96 identified as cases of 

hypothyroxinemia 

n = 175 controls

Canada (2005–2006) 

Geometric mean: 

0.0074

Association of 

hypothyroxinemia with 

PFOS exposure, OR (95% 

CI), adjusted

OR = 0.88 (0.63, 1.24)

NM No association

Webster et al. 2014

n = 152 women

Canada 

Blood samples taken during 

weeks 15–18 of pregnancy

Median: 0.0048 Beta per IQR PFOS and 

TSH, (95% CI, p-value) 

Normal TPOAb

0.07 (−0.06, 0.2), p = 0.28

High TPOAb

0.9 (0.2, 2), p = 0.02

[IQR PFOS = 0.0033 

μg/mL]

NM Beta per IQR PFOS and 

free T4, (95% CI), pvalue 

Normal TPOAb

0.05 (−0.1, 0.2), p = 0.58

High TPOAb

−0.7 (−2, 0.3), p = 0.18

[IQR PFOS = 0.0033 

μg/mL]

In people without diagnosed thyroid disease or without biomarkers of thyroid disease, 

thyroid hormones (TSH, T3, or T4) show mixed effects across cohorts. Studies of thyroid disease 

and thyroid hormone concentrations in children and pregnant females found mixed effects. TSH 

was the indicator most frequently associated with PFOS in studies of pregnant females. In crosssectional studies where thyroid hormones were measured in association with serum PFOS, 

increased TSH was associated with PFOS exposure in the most cases (Berg et al. 2015; Wang et 

al. 2013; Webster et al. 2014), but this association was null in a smaller study with 15 

participants (Inoue et al. 2004).

A case-control study of hypothyroxinemia (normal TSH and low free T4) in pregnant 

females (Chan et al. 2011), did not show associations of disease with PFOS exposure; in most 

other thyroid diseases, T4 and its compensatory TSH co-vary. In children from the C8 cohort, 

increasing PFOS was associated with increased T4 in children aged 1 to 17 years (LopezEspinosa et al. 2011); PFOS was not associated with hypothyroidism. A small South Korean 

study examined correlations between maternal PFASs during pregnancy and fetal thyroid 

Perfluorooctane sulfonate (PFOS) – May 2016 3-35
hormones in cord blood (Kim et al. 2011). PFOS was associated with increased fetal TSH and 

with decreased fetal T3 (Kim et al. 2011). Studies of pregnant females show associations 

between TSH and PFOS, and studies in children show mixed results. 

3.1.1.6 Immunotoxicity

Immune suppression 

Immune function, and specifically immune system suppression, can affect numerous health 

outcomes, including risk of common infectious diseases (e.g., colds, flu, otitis media) and some 

types of cancer. The World Health Organization (WHO) guidelines for immunotoxicity risk 

assessment recommend measures of vaccine response as a measure of immune effects, with 

potentially important public health implications (WHO 2012). 

Okada et al. (2012) investigated the relationship between maternal PFOS concentration (and 

PFOA) and otitis media (and allergic conditions), as well as cord blood Immunoglobulin E (IgE) 

levels during the first 18 months of life. The prospective birth cohort was based on infants 

delivered at the Sapporo Toho Hospital in Sapporo, Hokkaido, Japan between July 2002 and 

October 2005. PFOS levels were measured in maternal serum taken after the second trimester 

(n = 343) and total IgE concentration was measured in cord blood (n = 231) at the time of 

delivery. Infectious diseases and infant allergies were assessed through a self-administered 

questionnaire in mothers at 18 months post-delivery. Polynomial regression analyses, adjusted 

for potential confounders, were performed on log-transformed data. Mean maternal PFOS 

concentration was 0.0056 μg/mL and cord blood IgE level was 0.62 international units (IU)/mL.

No significant associations were observed between maternal PFOS levels (or PFOA) and cord 

blood IgE levels or incidence of otitis media, wheeze, food allergy, or eczema in infants at 18 

months of age. 

The population from the DNBC studies evaluated by Fei et al. (2010b) was used to determine 

whether prenatal exposure to PFOS caused an increased risk of infectious diseases leading to 

hospitalization in early childhood. Information was collected by telephone interview. No clear 

pattern was identified when results were stratified by child’s age at the time of hospitalization for 

an infectious disease and the level of PFASs in the maternal blood, although effect modification 

by sex was indicated (i.e., associations were seen in girls but not in boys). Hospitalizations 

among girls increased with higher prenatal PFOS concentration (incidence rate ratio [IRR] for 

trend across PFOS quartiles = 1.18, 95% CI: 1.03–1.36). Mean maternal plasma levels were 

0.0353 μg/mL, with a range of 0.0064–0.107 μg/mL. 

Two other studies, described below, examined reported history of colds and gastroenteritis in 

children (up to age 3 years) (Granum et al. 2013) or colds and flu in adults (Looker et al. 2014). 

Neither study reported associations with PFOS concentration. 

Three studies have examined response to one or more vaccine (e.g., measured by antibody 

titer) in relation to higher exposure to PFOS in children (Grandjean et al. 2012; Granum et al.

2013) or adults (Looker et al. 2014); the latter study was conducted in the high-exposure C8 

community population (Table 3-7).

Perfluorooctane sulfonate (PFOS) – May 2016 3-36
Antibody responses to diphtheria and tetanus toxoids following childhood vaccinations were 

assessed in context of exposure to perfluorinated compounds (Grandjean et al. 2012). The 

prospective study included a birth cohort of 587 singleton births during 1999–2001 from the 

National Hospital in the Faroe Islands. Serum antibody concentrations were measured in children 

at age 5 years prebooster, approximately 4 weeks after the booster, and at age 7 years. Prenatal 

exposures to perfluorinated compounds were assessed by analysis of serum collected from the 

mother during week 32 of pregnancy (geometric mean 0.0273 μg/mL; IQR 0.0232–0.0331); 

postnatal exposure was assessed from serum collected from the child at 5 years of age (geometric 

mean 0.0167 μg/mL; IQR 0.0135–0.0211). Multiple regression analyses with covariate 

adjustments were used to estimate the percent difference in specific antibody concentrations per 

2-fold increase in PFOS concentration in both maternal and 5-year serum.

Maternal PFOS serum concentration was inversely associated with antidiphtheria antibody 

concentration (−39%) at age 5 before booster. In addition, an association of antibody 

concentrations at age 7 was found with serum PFOS concentrations at age 5. A 2-fold increase in 

PFOS was associated with a difference in diphtheria antibody of −28% (95% CI: −46% to −3%).

Additionally at ages 5 and 7, a small percentage of children had antibody concentrations below 

the clinically protective level of 0.1 IU/mL. At age 5, the odds ratios of antibody concentrations 

falling below this level for diphtheria were 2.48 (95% CI: 1.55–3.97) compared with maternal 

and 1.60 (95% CI: 1.10–2.34) compared with age 5 serum PFOS concentrations. For age 7 

antibody levels associated with age 5 PFOS serum concentrations, odds ratios for inadequate 

antibody concentration were 2.38 (95% CI: 0.89–6.35) for diphtheria and 2.61 (95% CI: 0.77–

8.92) for tetanus. Models were adjusted for maternal serum PCB concentration. Similar 

associations were also observed with PFOA concentrations. 

The effects of prenatal exposure to perfluorinated compounds on vaccination responses and 

clinical health outcomes in early childhood were investigated in a subcohort of the Norwegian 

Mother and Child Cohort Study (Granum et al. 2013). A total of 56 mother-child pairs, for whom 

both maternal blood samples at delivery and blood samples from the children at 3 years of age, 

were evaluated. Antibody titers specific to measles, rubella, tetanus, and influenza were 

measured as these vaccines are part of the Norwegian Childhood Vaccination Program. Serum 

IgE levels were also measured. Mean maternal plasma PFOS concentration was 0.0056 μg/mL at 

delivery; the PFOA level was 0.0011 μg/mL and PFNA and PFHxS were below the limit of 

quantitation. PFOS levels in the children were not measured. A slight, but significant, inverse 

relationship between maternal PFOS level and anti-rubella antibodies in children at 3 years was 

found (β = −.08 [95% CI: −0.14 to −0.02]). No associations were found with PFOS or any 

perfluorinated compound and antibody levels to the other vaccines. 

A cohort of 411 adult members of the C8 Health Project was evaluated in 2010 to determine 

whether there was an association between serum PFOS levels and antibody response following 

vaccination with an inactivated trivalent influenza vaccine (Looker et al. 2014). A prevaccination 

serum sample was collected at the time of vaccination and a post-vaccination serum sample was 

collected 21 ± 3 days later. The geometric mean serum PFOS level was 0.0083 μg/mL (95% CI: 

0.0077–0.0091), and participants were divided into quartiles for analyses. Vaccine response, as 

measured by geometric mean antibody titer rise, was not affected by PFOS exposure. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-37
Table 3-7. Summary of Epidemiology Studies of PFOS and Immune Suppression 

(Infectious Disease and Vaccine Response) 

Reference and Study Details PFOS level Results

General Population: Children

Okada et al. 2012

Japan, birth cohort study, July 

2002–October 2005 enrollment; 

follow-up to 18 months; n = 343 

Log-transformed PFOS in blood 

after second trimester

Logistic regression adjusting for 

maternal age, maternal 

educational level, parity, infant 

gender, breast-feeding period, 

environmental tobacco smoke at 

18 months, day care attendance, 

period of blood sampling.

Mean 0.0056 

μg/mL

Incidence otitis media 17.8% (n = 61)

OR (95% CI) n 

Overall 1.40 (0.33, 6.00) n = 343

Males 1.38 (0.18, 10.60) n = 169

Females 1.43 (0.17, 12.30) n = 174 

Fei et al. 2010b

Denmark, birth cohort study, 

1996–2002, follow-up through 

2008; Number hospitalizations 

219 girls, 358 boys

Maternal blood sample median 8 

weeks gestation

Poisson regression adjusting for 

parity, maternal age, prepregnancy BMI, breastfeeding, 

smoking during pregnancy, sociooccupational status, home density, 

child’s age, gender of child, 

sibling age difference, gestational 

age at blood draw, birth year, and 

birth season.

Mean 0.0353 

μg/mL

Quartiles 

Q1 0.0064 – 0.026 

Q2 0.0261 – 0.0333 

Q3 0.0334 – 0.0432 

Q4 ≥ 0.433

Adjusted IRR for hospitalization for infectious diseases by gender, 

IRR (95% CI) n

Overall

Q1 1.0 n = 147

Q2 0.93 (0.71, 1.21) n = 142

Q3 0.90 (0.68, 1.18) n = 136

Q4 1.00 (0.76, 1.32) n = 152

Trend 1.00 (0.91, 1.09)

Girls

Q1 1.0 n = 39

Q2 1.14 (0.73, 1.791) n = 48

Q3 1.61 (1.05, 2.47) n = 67

Q4 1.59 (1.02, 2.49) n = 65

Trend 1.18 (1.03, 1.36)

Boys

Q1 1.0 n = 108

Q2 0.80 (0.57, 1.13) n = 94

Q3 0.61 (0.42, 0.89) n = 69

Q4 0.77 (0.54, 1.12) n = 87

Trend 0.90 (0.80, 1.02)

Grandjean et al. 2012

Faroe Islands

Birth cohort, follow-up to age 7 

yrs 

n = 587 

Age 5 pre-booster (e.g., tetanus, 

diphtheria) and 4 weeks after 

booster and age 7

PFOS in 3rd trimester blood 

sample and in child (age 5)

Linear regression, adjusted for 

sex, age, birth weight, maternal 

smoking, breastfeeding, and PCBs 

[and time since booster for postbooster analysis]

Geometric mean

Maternal sample

0.027 μg/mL

Child’s sample

0.0167 μg/mL 

Log PFOS and Log antibody Beta (95% CI) [% change in antibody 

titer per 2-fold increase in PFOS]

Maternal PFOS Tetanus Diptheria

Pre-booster −10.1 (−31.9, 18.7) −38.6 (−54.7, −16.9)

Post-booster −2.3 (−28.6, 33.6) −20.6 (−37.5, 0.9)

Year 7 35.3 (−3.9, 90.6) −19.7 (−41.8, 10.7)

Year 7

(adjusted for age 5) 33.1 (1.5, 74.6) −10.0 (−32.6, 20.0)

Child’s PFOS Tetanus Diptheria

Pre-booster −11.9 (−30.0, 10.9) −16.0 (−34.9, 8.3)

Post-booster −28.5 (−45.5, −6.1) −15.5 (−31.5, 4.3)

Year 7 −23.8 (−44.3, 4.2) −27.6 (−45.8, −3.3)

Year 7

(adjusted for age 5) −11.4 (−30.5, 12.8) −20.6 (−38.2, 2.1)

Similar results seen with PFOA

Perfluorooctane sulfonate (PFOS) – May 2016 3-38
Reference and Study Details PFOS level Results

Granum et al. 2013

Norway

Birth cohort, Norwegian Mother 

and Child Cohort Study

n = 56 with maternal blood at 

delivery and child blood samples 

at 3 yrs

Linear regression, considered 

potential confounders

Mean 0.0056

μg/mL

Beta (95% CI ) (p-value), PFOS and antibody titer

Rubella −0.08 (−0.14, −0.02) (p = 0.007)

Measles −0.05 (−0.10, 0.01) (p = 0.09)

Tetanus −0.002 (−0.03, 0.02) (p = 0.87)

Hib −0.16 (−1.02, 0.70) (p = 0.71)

Similar results for other PFASs 

General Population: Adults

Looker et al. 2014

C8 Health Project, West Virginia

2005–2005 enrollment and 

baseline blood sample and 

questionnaires; 2010 follow-up n 

= 411 with pre-vaccination blood 

sample – flu vaccination – 21 day 

post vaccination blood sample

Linear regression: antibody titer 

rise

Logistic regression: 

seroconversion and seroprotection 

Considered possible confounders, 

retained in final model: age, 

gender, mobility (# addresses), 

and history of previous influenza 

vaccination 

Geometric mean 

0.0083 μg/mL

Q1: 0.001–0.0058

Q2: 0.0059–0.0092

Q3: 0.0093–0.0145

Q4: 0.0147–0.0423

Percentage positive) OR (95% CI), by influenza strain: 

Seroconversion Seroproection

(4-fold increase (antibody titer 1:40

in antibody titer) following vaccine)

Influenza B (62%) (66%)

PFOS continuous 1.17 (0.63, 2.17) 0.85 (0.44, 1.64)

Q1 1.0 (referent) 1.0 (referent)

Q2 0.72 (0.39, 1.33) 0.67 (0.35, 1.25)

Q3 0.81 (0.42, 1.53) 0.82 (0.42, 1.59)

Q4 0.87 (0.43, 1.74) 0.73 (0.36, 1.47)

A/H1Na (84%) (96%)

PFOS continuous 1.10 (0.51, 2.37) 0.93 (0.23, 3.71)

Q1 1.0 (referent) 1.0 (referent)

Q2 0.97 (0.44, 2.14) 0.55 (0.13, 2.37)

Q3 0.78 (0.35, 1.75) 1.81 (0.32, 10.22)

Q4 0.94 (0.38, 2.31) 1.26 (0.24, 6.61)

A/H3N2 (65%) (84%)

PFOS continuous 1.17 (0.63, 2.15) 0.63 (0.26, 1.49)

Q1 1.0 (referent) 1.0 (referent)

Q2 1.08 (0.59, 1.97) 0.85 (0.38, 1.88)

Q3 1.10 (0.59, 2.06) 1.09 (0.47, 2.56)

Q4 1.41 (0.72, 2.78) 0.56 (0.24, 1.28)

Asthma

Humblet et al. (2014) evaluated a cohort from NHANES to investigate children’s PFAS

serum levels, including PFOS, and their association with asthma-related outcomes. Sera were 

analyzed for 12 PFAS with focus on PFOA, PFOS, PFHxS, and PFNA. A total of 1,877 children 

12–19 years old with at least one serum sample available were included. Asthma and related 

outcomes were self-reported. Median serum PFOS levels were 0.017 μg/mL for those ever 

having asthma and 0.0168 μg/mL for children without asthma. In the multivariable adjusted 

model, a doubling of PFOS level was inversely associated with the odds of ever having asthma 

(OR = 0.88, 95% CI: 0.74–1.04), but statistical significance was not attained. PFOA was 

significantly associated with asthma and no associations were found between the other PFASs 

and outcome. 

The association between serum levels of perfluorinated compounds and childhood asthma 

was investigated by Dong et al. (2013). The cross-sectional study included a total of 231 children 

aged 10–15 years with physician-diagnosed asthma and 225 age-matched non-asthmatic 

controls. Between 2009 and 2010, asthmatic children were recruited from two hospitals in 

Northern Taiwan, while the controls were part of a cohort population in seven public schools in 

Northern Taiwan. Serum was collected for measurement of ten perfluorinated compounds, 

Perfluorooctane sulfonate (PFOS) – May 2016 3-39
absolute eosinophil counts, total IgE, and eosinophilic cationic protein. A questionnaire was 

administered to asthmatic children to assess asthma control and to calculate an asthma severity 

score (including frequency of attacks, use of medicine, and hospitalization) during the previous 4 

weeks. Associations of perfluorinated compound quartiles with concentrations of immunological 

markers and asthma outcomes were estimated using multivariable regression models.

Nine of ten perfluorinated compounds were detectable in ≥ 84.4% of all children with levels 

generally higher in asthmatic children compared with non-asthmatics. Serum concentrations of 

PFOS in asthmatic and non-asthmatic children were 0.0455 ± 0.0373 and 0.0334 ± 0.0264 

μg/mL, respectively; similar levels were measured for perfluorotetradecanoic acid with much 

lower concentrations of the remaining six perfluorinated carboxylated and two sulfonates 

sulfonates. The adjusted odds ratios for asthma association with the highest versus lowest 

quartile levels were significantly elevated for seven of the PFAS compounds. For PFOS, the 

odds ratio was 2.63 (95% CI: 1.48–4.69). In asthmatic children, absolute eosinophil counts, total 

IgE, and eosinophilic cationic protein concentration were positively associated with PFOS levels 

with a significant monotonic trend with increasing serum concentration. None of these 

biomarkers was significantly associated with PFOS levels in non-asthmatic children. Serum 

PFOS levels, as well as three other compounds, were significantly associated with higher asthma 

severity scores.

A summary of the studies that examined the relationship between PFOS serum levels and 

markers of immunotoxicity in humans is presented in Table 3-7. A few studies have evaluated 

associations with measures indicating immunosuppression. Two studies reported decreases in 

response to one or more vaccines in children aged 3, 5, and 7 years (e.g., measured by antibody 

titer) in relation to increasing maternal serum PFOS levels during pregnancy or at 5 years of age 

(Grandjean et al. 2012; Granum et al. 2013). Decreased rubella and mumps antibody 

concentrations in relation to serum PFOS concentration were found among 12–19 year old 

children in the NHANES, particularly among seropositive children (Stein et al. 2015). A third 

study of adults found no associations with antibody response to influenza vaccine (Looker et al.

2014). In the three studies examining exposures in the background range among children (i.e., 

general population exposures, geometric means < 0.02 μg/ml), the associations with PFOS were 

also seen with other correlated PFAS, complicating conclusions specifically for PFOS. No clear 

associations were reported between prenatal PFOS exposure and incidence of infectious disease 

among children (Fei et al. 2010b; Okada et al. 2012), although an elevation in risk of 

hospitalizations for an infectious disease was found among girls suggesting an effect at the 

higher maternal serum levels measured in the Danish population (mean maternal plasma levels 

were 0.0353 μg/mL). 

With regard to other immune dysfunction, serum PFOS levels were not associated with risk 

of ever having had asthma among children in the NHANES with median levels of 0.017 μg/mL 

(Humblet et al. 2014). A study among children in Taiwan with higher serum PFOS 

concentrations (median with and without asthma 0.0339 and 0.0289 μg/mL, respectively) found 

higher odds ratios for physician-diagnosed asthma with increasing serum PFOS quartile (Dong et 

al. 2013). Associations also were found for other PFASs. Among asthmatics, serum PFOS was 

also associated with higher severity scores, serum total IgE, absolute eosinophil counts and 

eosinophilic cationic protein levels.

Perfluorooctane sulfonate (PFOS) – May 2016 3-40
3.1.1.7 Other Effects

Metabolic syndrome is a combination of medical disorders and risk factors that increase the 

risk of developing cardiovascular disease and diabetes. Lin et al. (2009) investigated the 

association between serum PFOS (plus three other PFASs) and glucose homeostasis and 

metabolic syndrome in adolescents (12–20 years) and adults (> 20 years) by analyzing the 1999–

2000 and 2003–2004 NHANES data. The National Cholesterol Education Program Adult 

Treatment Panel III guidelines were used to define adult metabolic syndrome and the modified 

guidelines were used to define adolescent metabolic syndrome. The study population included 

1,443 subjects (474 adolescents, 969 adults) at least 12 years of age who had a morning 

examination and triglyceride measurement. There were 266 male and 208 female adolescents 

and 475 male and 493 female adults. Multiple linear regression and logistic regression models 

were used to analyze the data. Covariates included age, sex, race, smoking status, alcohol

consumption, and household income. Log-transformed PFOS concentration was 3.11 ng/mL and 

3.19 ng/mL for adolescents and adults, respectively. In adults, serum PFOS concentration was 

associated with increased β-cell function (β coefficient 0.15, p < 0.01). Serum PFOS 

concentration was not associated with metabolic syndrome, glucose concentration, homeostasis 

model of insulin resistance, or insulin levels in adults or adolescents. 

3.1.1.8 Summary and conclusions from the human epidemiology studies

Numerous epidemiology studies have been conducted evaluating occupational PFOS 

exposure and environmental PFOS exposure including a large community highly-exposed to 

PFOA (the C8 Health Project) and background exposures in the general population in several 

countries. Occupational and general populations have evaluated the association of PFOS 

exposure to a variety of health endpoints. Health outcomes assessed include blood lipid and 

clinical chemistry profiles, thyroid effects, immune function, reproductive effects, pregnancyrelated outcomes, fetal growth and developmental outcomes, and cancer. 

Serum Lipids. Multiple epidemiologic studies have evaluated serum lipid status in association 

with PFOS concentration (Table 3-1). These studies provide support for an association between 

PFOS and small increases in total cholesterol. Hypercholesterolemia, which is clinically defined 

as cholesterol > 240 mg/dL, was associated with PFOS exposure in a Canadian cohort (Fisher et 

al. 2013) and in the C8 cohort (Steenland et al. 2009). Cross-sectional occupational studies 

demonstrated an association between PFOS and total cholesterol (Olsen et al. 2001a, 2001b, 

2003b). Evidence for associations between other serum lipids and PFOS is mixed, including 

HDL cholesterol, LDL, VLDL, and non-HDL cholesterol, as well as triglycerides. The studies on 

serum lipids in association with PFOS serum concentrations are largely cross-sectional in nature 

and were largely conducted in adults, but some studies exist on children and pregnant females. 

The location of these cohorts varied from the U.S. population including NHANES volunteers, to 

the Avon cohort in the UK, to Scandinavian countries. Limitations to these studies include the 

frequently high correlation between PFOA and PFOS exposure; not all studies control for PFOA 

in study design. Also studied were populations with known elevated exposure to other 

environmental chemicals including PFOA in the C8 population and PBDEs and other persistent

organic chemicals in the Inuit population. 

Liver. Cross-sectional and longitudinal studies evaluated PFOS and liver enzymes in adults. Lin 

et al. (2010) looked at data from the NHANES, which is representative of the U.S. national 

population, and Gallo et al. (2012) reported an analysis of data from the C8 Health Project, 

reflective of a highly-exposed community. Both studies saw a slight positive association between 

Perfluorooctane sulfonate (PFOS) – May 2016 3-41
serum PFOS levels and increased serum ALT values. The association between PFOS levels and 

increased serum GGT levels was less defined and overall did not appear to be affected. Total or 

direct bilirubin showed no association with PFOS in either study. In the Gallo et al. (2012) study, 

the cross-sectional design and self-reported lifestyle characteristics are limitations to the study, 

and while both studies showed a trend, it was not large in magnitude. 

Kidney. Shankar et al. (2011) and Watkins et al. (2013) analyzed sub-sets or the entire 

population for an association between PFOS serum levels and either kidney disease or 

biomarkers that may be associated with kidney function. Shankar et al. (2011) used NHANES 

data and showed a positive association between increasing levels of PFOS and chronic kidney 

disease, as defined as an eGFR of < 60 mL/min/1.73 m2

. The odds ratio for chronic kidney 

disease at > 0.030 μg/mL of PFOS was 1.82 (95% CI: 1.01–3.27), and while the possibility of 

reverse causality could not be excluded, the association between PFOS and eGFR when 

examined in those with and without chronic kidney disease supports an effect. Watkins et al. 

(2013) evaluated C8 Health Project children to look at PFOS levels and kidney function in 

children, as defined as decreased eGFR, and found a dose-related trend: the decrease was 

1.10 mL/min/1.73 m2 (95% CI: −1.66 to −0.53). Geiger et al. (2014b) found no association in 

children between serum PFOS levels and hypertension. Steenland et al. (2010) evaluated C8 

Health Project adults and found a positive association between PFOS serum levels and an 

increase in uric acid with odds ratios increasing from 1.02 to 1.26 with each decile. Overall, 

studies do suggest an association between chronic kidney disease, as defined by estimated 

glomerular filtration rate; however, reverse causality cannot be excluded. 

Fertility, Pregnancy, and Birth Outcomes. Fetal growth retardation was examined through 

measures including mean birth weight, LBW, and small for gestational age. Mean birth weight 

examined as a continuous outcome was the most commonly examined endpoint for 

epidemiology studies of serum/cord PFOS exposures. Although three studies were null (Fei et al.

2008b; Hamm et al. 2010; Monroy et al. 2008), birth weight deficits ranging 29–149 grams were 

detected in five studies (Apelberg et al. 2007; Chen et al. 2015; Darrow et al. 2013; Maisonet et 

al. 2012; Washino et al. 2009). Larger reductions (69–149 grams) were noted in three of these 

studies (Apelberg et al. 2007; Chen et al. 2015; Washino et al. 2009) based on per unit increases 

in serum/cord PFOS exposures, while the lone categorical data showed an exposure-response 

deficit in mean birth weight up to 140 grams across the PFOS tertiles (Maisonet et al. 2012). 

Two (Chen et al. 2015; Whitworth et al. 2012) out of four (Fei et al. 2007; Hamm et al. 2009) 

studies of SGA and serum/cord PFOS exposures showed some suggestion of increased ORs 

(range: 1.3–2.3), while three (Chen et al. 2012; Fei et al. 2007; Stein et al. 2009) out of four 

(Darrow et al. 2014) studies of LBW showed increased risks (OR range: 1.5–4.8). Although a 

few of these studies showed some suggestion of dose-response relationships across different fetal 

growth measures (Fei et al. 2007; Maisonet et al. 2012; Stein et al. 2009), study limitations, 

including the potential for exposure misclassification, likely precluded the ability to adequately 

examine the exposure-response pattern. 

Recent data also indicate an association between low maternal GFR and infant birth weight, 

supporting GFR as a confounder in epidemiology studies (Morken et al. 2014; Verner et al.

2015). In such cases the increased serum PFOS could be the result of the developmental 

milestone rather than a cause. However, while a proportion of the association between prenatal 

PFOS and birth weight may be confounded by low maternal GFR, a direct effect of PFOS on 

neonatal weight cannot be entirely dismissed based on the available data.

Perfluorooctane sulfonate (PFOS) – May 2016 3-42
A small set of studies observed an association with gestational diabetes (Zhang et al. 2015, 

preconception serum PFOS), pre-eclampsia (Stein et al. 2009) and pregnancy-induced 

hypertension (Darrow et al. 2013) in populations with serum PFOS concentrations of 0.012–

0.017 μg/mL. Zhang et al. (2015) and Darrow et al. (2013) used a prospective assessment of 

adverse pregnancy outcomes in relation to PFASs which addresses some of the limitations in the 

available cross-sectional studies. Associations with these outcomes and serum PFOA also were 

observed. 

Although there was some suggestion of an association between PFOS exposures and semen 

quality parameters in a few studies (Joensen et al. 2009; Toft et al. 2012), most studies were 

largely null (Buck Louis et al. 2015; Ding et al. 2013; Joensen et al. 2013; Vested et al. 2013; 

Raymer et al. 2012; Specht et al. 2012; Vested et al. 2013). For example, morphologically 

abnormal sperm associated with PFOS were detected in three (Buck Louis et al. 2015; Joensen et 

al. 2009; Toft et al. 2012) out of eight (Buck Louis et al. 2015; Ding et al. 2013; Joensen et al.

2013; Raymer et al. 2012; Specht et al. 2012; Vested et al. 2013) studies.

Small increased odds of infertility was found for PFOS exposures in studies by Jørgensen et 

al. (2014) [OR = 1.39; 95% CI: 0.93–2.07] and Vélez et al. (2015) [OR = 1.14; 95% CI: 0.98–

1.34]. Although one study was null (Vestergaard et al. 2012), PFOS exposures associated with 

decreased FRs, indicative of longer time to pregnancy, were noted in studies by Fei et al. (2009) 

[FR = 0.74 (95% CI: 0.58–0.93) and in studies by Jørgensen et al. (2014) [FR = 0.90; 95% CI: 

0.76–1.07]. Whitworth et al. (2012) data suggested that reverse causality may explain their 

observation of subfecundity odds of 2.1 (95% CI: 1.2–3.8) for the highest PFOS quartile among 

parous females, but a reduced odds among nulliparous females (OR = 0.7; 95% CI: 0.4–1.3). A 

recent analysis of the pooled DNBC study samples did not find strong evidence of differences by 

parity status with an overall fecundability ratio of 0.83 (95% CI: 0.72–0.97) for PFOS exposures, 

as well as comparable ratios for parous (0.86; 95% CI: 0.70–1.06) and nulliparous (0.78; 95% : 

0.63–0.97) females (Bach et al. 2015). The same authors reported an increased infertility OR of 

1.75 (95% CI: 1.21–2.53) and OR for parous (OR = 1.51; 95% CI: 0.86–2.65) and nulliparous 

(OR = 1.83; 95% CI: 1.10–3.04) females. Although there remains some concern over the 

possibility of reverse causation explaining some previous study results, these collective findings 

indicate a consistent association with fertility and fecundity measures and PFOS exposures.

Thyroid. Numerous epidemiologic studies have evaluated thyroid hormone levels and/or thyroid 

disease in association with serum PFOS concentrations. These epidemiologic studies provide 

limited support for an association between PFOS exposure and incidence or prevalence of 

thyroid disease, and include large studies of representative samples of the general U.S. adult 

population (Melzer et al. 2010; Wen et al. 2013). These highly powered studies reported 

associations between PFOS exposure (serum PFOS concentrations) and thyroid disease but not 

thyroid hormone status. Melzer et al. (2010) studied thyroid disease with medication and Wen et 

al. (2013) studied subclinical thyroid disease. Thyroid function can be affected by iodide 

sufficiency and by autoimmune disease. People testing positive for the anti-TPO biomarker 

showed associations with PFOS and TSH or T4 (Webster et al. 2014); this association was 

stronger in people with both low iodide status and positive anti-TPO antibodies (Webster et al.

2015). These studies used anti-TPO antibody levels as an indication of stress to the thyroid 

system, not a disease state. Thus, the association between PFOS and altered thyroid hormone 

levels is stronger in people at risk for thyroid insufficiency. In people without diagnosed thyroid 

disease or without biomarkers of thyroid disease, thyroid hormones (TSH, T3, or T4) show 

mixed effects across cohorts.

Perfluorooctane sulfonate (PFOS) – May 2016 3-43
Immune Function. A few studies have evaluated associations with measures indicating 

immunosuppression. Two studies reported decreases in response to one or more vaccines in 

children aged 3, 5, and 7 years (e.g., measured by antibody titer) in relation to increasing prenatal 

serum PFOS levels or at 5 years of age (Grandjean et al. 2012; Granum et al. 2013). Decreased 

rubella and mumps antibody concentrations in relation to serum PFOS concentration were found 

among 12–19 year old children in the NHANES, particularly among seropositive children (Stein 

et al. 2015). A third study of adults found no associations with antibody response to influenza 

vaccine (Looker et al. 2014). In the three studies examining exposures in the background range 

among children (i.e., general population exposures, geometric means < 0.02 μg/ml), the 

associations with PFOS were also seen with other correlated PFASs, complicating conclusions 

specifically for PFOS.

No clear associations were reported between prenatal PFOS exposure and incidence of 

infectious disease among children (Fei et al. 2010b; Okada et al. 2012), although an elevation in 

risk of hospitalizations for an infectious disease was found among girls suggesting an effect at 

the higher maternal serum levels measured in the Danish population (mean maternal plasma 

levels were 0.0353 μg/mL). With regard to other immune dysfunction, serum PFOS levels were 

not associated with risk of ever having had asthma among children in the NHANES with median 

levels of 0.017 μg/mL (Humblet et al. 2014). A study among children in Taiwan with higher 

serum PFOS concentrations (median with and without asthma 0.0339 μg/mL and 0.0289 μg/mL, 

respectively) found higher odds ratios for physician-diagnosed asthma with increasing serum 

PFOS quartile (Dong et al. 2013). Associations also were found for other PFASs. Among 

asthmatics, serum PFOS was also associated with higher severity scores, serum total IgE, 

absolute eosinophil counts and eosinophilic cationic protein levels. 

3.1.2 Carcinogenicity Studies

Occupational Exposure. Several analyses of various health outcomes have occurred on cohorts 

of workers at the 3M Decatur, Alabama plant (Alexander et al. 2003; Alexander and Olsen 2007; 

Mandel and Johnson 1995). Cause-specific mortality was examined in a cohort of 2,083 workers 

employed for at least 1 year among workers grouped into three PFOS exposure categories: nonexposed, low exposed, and high exposed. Exposure classifications were determined using PFOS 

serum concentrations measured in a subset of workers linked to specific jobs and work histories. 

Cumulative exposures were also estimated by applying a weight to each of the exposure 

categories and multiplying by the number of years of employment for that job for each 

individual. The geometric mean serum PFOS levels were 0.941 μg/mL for chemical plant 

employees and 0.136 μg/mL for non-exposed workers. Results of these studies are summarized 

in Table 3-8.

A total of 145 deaths were identified with 65 of them in high-exposure jobs. Standardized 

mortality ratios (SMRs) were calculated using the state of Alabama reference data and when 

analyzing the entire cohort, SMRs were not elevated for most of the cancer types and for nonmalignant causes. SMRs that were above 1 included cancer of the esophagus, liver, breast, 

urinary organs, bladder, and skin. However, the number of cases was very small (1–3), resulting 

in wide confidence intervals. The SMRs for these causes (except breast cancer) were also 

elevated when the cohort was limited to the 65 employees ever employed in a high exposure job. 

The SMR for bladder cancer was 4.81 (95% CI: 0.99–14.06). Three male employees in the 

cohort died of bladder cancer (0.62 expected). All were employed at the Decatur plant for 

> 20 years and had worked in high exposure jobs for at least 5 years. The SMR for bladder 

Perfluorooctane sulfonate (PFOS) – May 2016 3-44
cancer for workers who were ever employed in a high exposure job was 12.77 (0.23 expected, 

CI: 2.63–37.35). When the data were analyzed for workers with > 5 years of employment in a 

high exposure job, the SMR was 24.49. This effect remained when the data were analyzed using 

county death rates. 

While the three deaths from bladder cancer were greater than the expected number observed 

in the general population, the small number of deaths (especially for females in all categories) 

precludes a definitive conclusion regarding an association with PFOS exposure. In addition, six 

death certificates were not obtained, and smoking status was not known for the cohort increasing 

the uncertainty with regard to the estimated risk.

Based on these results, another study of this cohort was conducted to evaluate bladder cancer 

incidence (Alexander and Olsen 2007). Cancer deaths were ascertained from death certificates 

and via questionnaire for bladder cancer cases, year of diagnosis, and smoking history. Eleven 

bladder cancer cases were identified: five deaths and six incident cases. Only two of the six selfreported cases were confirmed with medical records. Five of the six incident cases had a history 

of cigarette smoking. Standardized incidence ratios (SIR) were estimated for the three exposure 

categories described for the mortality study and compared to U.S. cancer rates. SIRs were 0.61, 

2.26, and 1.74 for the nonexposed, ever low, and ever high exposure categories, respectively. 

Rate ratios by cumulative exposure index were increased in the higher categories (5 to < 10 and 

≥ 10) when using either the U.S. population rates or an internal referent population, however the 

number of cases were few and confidence intervals were wide including the null. These results, 

while suggestive of an elevated risk of bladder cancer, were not conclusive.

Grice et al. (2007) evaluated associations between PFOS exposure at the 3M Decatur, 

Alabama plant and various malignant or benign tumors reported by the same study group 

evaluated by Alexander and Olsen (2007). Current and past employees at the plant answered 

questionnaires (n = 1,400; 1,137 male and 263 female) about diagnosis of cancers or noncancerous conditions. Data were analyzed by PFOS exposure category: unexposed 

(< 0.29 μg/mL), low (0.39–0.89 μg/mL), or high exposure (1.30–1.97 μg/mL) and by categories 

of estimated cumulative exposure using the same weighted approach described in the previous 

studies of this cohort. Prostate, melanoma, and colon cancer were the most frequently reported 

malignancies. When cumulative exposure measures were analyzed, elevated odds ratios were 

reported for both colon and prostate cancer, however, they did not reach statistical significance. 

Length of follow-up may not have been adequate to detect cancer incidence in this cohort as 

approximately one-third of the participants had worked < 5 years in their jobs, and only 41.7% 

were employed ≥ 20 years.

C8 Health Project Community. Members of the C8 Health Project, 47,151 cancer-free adults 

and 203 cases, were evaluated for an association between serum PFOS levels and incidence of 

colorectal cancers (Innes et al. 2014). This cross-sectional study compared serum PFOS (and 

PFOA) levels at enrollment with diagnosis of primary colorectal cancer. Serum PFOS levels 

ranged from < 0.0005 to 0.759 μg/mL, with an average of 0.0234 μg/mL. A concentrationrelated inverse relationship was found between PFOS level and diagnosis of colorectal cancer 

with OR = 0.24 (95% CI 0.16, 0.37; highest to lowest quartile, p for trend < 0.00001). An inverse 

association was also found between PFOA and colorectal cancer.

General Population. A subset of females enrolled in the DNBC was evaluated for an 

association between plasma PFOS levels (as well as 15 other perfluoroalkylated substances) 

measured during pregnancy and risk of breast cancer during a follow-up period of 10–15 years 

Perfluorooctane sulfonate (PFOS) – May 2016 3-45
(Bonefeld-Jørgensen et al. 2014). A total of 250 females diagnosed with breast cancer were 

matched for age and parity with 233 controls. The mean PFOS level in the controls was 

0.0306 μg/mL while levels in the cases were divided into quintiles ranging from < 0.0204 up to 

> 0.0391 μg/mL. No association was found between PFOS levels and breast cancer risk in 

logistic regression models adjusted for age at blood draw, BMI before pregnancy, gravidity, use 

of oral contraceptives, age at menarche, smoking, alcohol consumption, maternal education and 

physical activity. A weak positive Relative Risk (1.04; 95% CI: 0.99–1.08) was found only with 

perfluorooctane-sulfonamide. 

These same researchers had previously observed a borderline significant positive association 

with PFOS levels and breast cancer (adjusted OR = 1.03, 95% CI: 1.001–1.07) in a small cohort 

from Greenland (Bonefeld-Jørgensen et al. 2011). Logistic regression models were adjusted for 

age, BMI, total number of full-term pregnancies, breastfeeding, menopausal status, and serum 

cotinine, but the unadjusted results that included the entire study group were not different. 

Median serum PFOS levels were 0.0456 μg/mL (range: 0.0116–0.124 μg/mL) among 31 breast 

cancer patients and 0.0219 μg/mL (range: 0.0015–0.172 μg/mL) among 98 controls. A weak 

positive odds ratio of 1.03 (95% CI: 1.00–1.05) was also found for the sum of 

perfluorosulfonated compounds which included PFOS along with perfluorohexane sulfonate and 

perfluorooctane sulfonamide. 

Eriksen et al. (2009) examined the association between plasma PFOS concentration and the 

risk of cancer in the general Danish population. The study population was chosen from 

individuals (50–65 years of age) who had enrolled in the prospective Danish cohort Diet, Cancer, 

and Health study between December 1, 1993 and May 31, 1997. The Danish Cancer Registry 

and Danish Pathology Data Bank were used to identify cancer patients diagnosed between 

December 1, 1993, and July 1, 2006. The cancer patients (n = 1,240) consisted of 1,111 males

and 129 females whose median age was 59 years having prostate cancer (n = 713), bladder 

cancer (n = 332), pancreatic cancer (n = 128), and liver cancer (n = 67). The individuals 

(n = 772) in the subcohort comparison group were randomly chosen from the cohort study and 

consisted of 680 males and 92 females whose median age was 56 years. The participants 

answered a questionnaire upon enrollment in the cohort study, and data on known confounders 

were obtained from the questionnaires. The plasma PFOS concentrations, based on blood 

samples provided at enrollment (1993–1997) for cancer patients were as follows: males

0.0351 μg/mL, females 0.0321 μg/mL, prostate cancer 0.0368 μg/mL, bladder cancer 

0.0323 μg/mL, pancreatic cancer 0.0327 μg/mL, and liver cancer 0.0310 μg/mL. The plasma 

PFOS concentrations for the subcohort comparison group were 0.0350, 0.0293, and 

0.0343 μg/mL for the males, females, and combined, respectively. Incidence rate ratios, crude 

and adjusted for confounders, did not indicate an association between plasma PFOS 

concentration and bladder, pancreatic, or liver cancer in models adjusting for potential 

confounders. For prostate cancer, increased odds ratios 30% above the comparison group for 

quartiles 2 through 4 were observed, but there was no increasing trend in the analysis using 

PFOS concentration as a continuous variable. The plasma PFOS levels in the population were 

lower than those observed in occupational cohorts. 

Hardell et al. (2014) investigated an association between prostate cancer and levels of PFAS

in whole blood. Patients with newly diagnosed prostate cancer (n = 201) had median PFOS 

levels of 0.009 μg/mL, while the control group (n = 186) had a median level of 0.0083 μg/mL. 

PFOS levels, which were measured 1–3 years after cancer diagnosis, were not associated with 

higher risks of prostate cancer in logistic regression models adjusted for age, BMI, and year of 

Perfluorooctane sulfonate (PFOS) – May 2016 3-46
blood sampling, or when analyzed according to Gleason score (pathology grade) and prostatespecific antigen. A significantly higher risk for prostate cancer was found for a group with PFOS 

levels above the median and a first-degree relative with prostate cancer indicating a potential 

genetic risk factor.

A small study found no differences in blood PFOS levels between cancer and non-cancer 

patients; the types of cancer in the patients were not defined. Vassiliadou et al. (2010) found 

median serum PFOS concentrations among 40 cancer patients (0.0113 μg/mL, males; 

0.008 μg/mL, females) were similar to two control groups (0.0105 and 0.0137 μg/mL, males; 

0.007 and 0.0085 μg/mL, females). 

Results of the cancer epidemiology studies in the highly exposed and general populations are 

summarized in Table 3-8. 

Table 3-8. Summary of PFOS Epidemiology Studies of Cancer

Reference and Study Details Analysis Group Relative Risk Estimates

Occupational Exposure Studies

Alexander et al. 2003

Fluorochemical production, Decatur, 

Alabama

Film plant and chemical plant 

employees (current, retired and former), 

n = 2,083, follow-up through 1998

83% male, median age 50.9 yrs at 

follow-up, median 13.2 yrs of 

employment

Mortality

Comparisons by exposure group 

classified using matrix of work history 

(1961–1997) and job-specific serum 

PFOS concentration: No exposure, low 

and high potential workplace exposure;

Cumulative exposure level based on 

exposure category weight (1,3, or 10) 

and years spent in specific jobs

Mortality through 1998

All (Alabama referent)

Non-exposed jobs

(0.11–0.29 μg/ml)

Low exposure jobs

(0.39–0.89 μg/ml)

High exposure jobs

(1.30–1.97 μg/ml)

All (Alabama referent)

Non-exposed jobs

(0.11–0.29 μg/ml)

Low exposure jobs

(0.39–0.89 μg/ml)

High exposure jobs

(1.30–1.97 μg/ml)

Liver Cancer

SMR (95% CI)

1.61 (0.20, 5.82) (n = 2) 

No cases

3.94 (0.10, 21.88) (n = 1) 

2.00 (0.05, 11.01) (n = 1) 

Bladder Cancer

SMR (95% CI)

4.81 (0.99, 14.06)(n = 3) 

No cases

No cases

12.77 (2.63, 37.35) (n = 3)

Alexander and Olsen 2007; Grice et al. 

2007) 

Fluorochemical production, Decatur, 

Alabama

Film plant and chemical plant 

employees, n = 1,400 of 2,083 who 

completed questionnaire in 2002 and 

188 decedents since mortality analysis. 

495 declined; participation 73.9% of 

eligible, 43,739 person-years of followup. 81.2% male, Incidence (via 

questionnaire) with confirmation by 

physician for some 

Incidence through 2002

All (U.S. population referent)

Non-exposed jobs

(0.11–0.29 μg/ml)

Low exposure jobs

(0.39–0.89 μg/ml)

High exposure jobs

(1.30–1.97 μg/ml)

Ever low or high

Low or high (≥ 1 yr)

Bladder cancer (2 of 6 reported confirmed; 5 deaths)

SIR (95% CI) (n cases)

1.28 (0.64, 2.29) (n = 11)

0.61 (0.07, 2.19) (n = 2)

2.26 (0.91, 4.67) (n = 7)

1.74 (0.64, 3.79) (n = 6)

1.7 (0.77, 3.22) (n = 9)

1.31 (0.48, 2.85) (n = 6)

Non-exposed jobs

Ever low or high

Low or high (≥ 1 yr)

High (> 1 yr)

Colon cancer (12 of 22 reported confirmed)

OR, 95% CI, (n cases)

1.0 (n = 8)

1.21 (0.51, 2.87) (n = 15)

1.37 (0.57, 3.30) (n = 14)

1.69 (0.68, 4.17) (n = 7)

Perfluorooctane sulfonate (PFOS) – May 2016 3-47
Reference and Study Details Analysis Group Relative Risk Estimates

Non-exposed jobs

Ever low or high

Low or high (≥ 1 yr)

High (> 1 yr)

Prostate cancer (22 of 29 reported confirmed)

OR (95% CI) (n cases)

1.0 (n = 10)

1.34 (0.62, 2.91) (n = 19)

1.36 (0.61, 3.02) (n = 16)

1.08 (0.44, 2.69) (n = 9)

General Population Studies

Bonefeld-Jørgensen et al. 2014

Denmark; case-control study nested in 

prospective cohort; DNBC, 1996–2002, 

follow-up to 2010. 250 women with 

breast cancer identified using cancer 

registry (mean age at blood draw 30.4 

yr) and 233 controls (mean age at blood 

draw 29.6 yr), frequency matched on 

age and parity, selected at random from 

cohort at baseline. PFOS (and other 

perfluorochemicals) in blood drawn 

between gestation weeks 6 and 14.

Mean serum PFOS in controls

0.031 μg/mL; correlation PFOS 

and PFOA 0.69

Continuous PFOS

Quintiles

< 0.02

0.02–0.025 

0.025–0.030 

0.030–0.039 

> 0.039

Breast Cancer

Adjusted RR (95% CI) (n cases)

0.99 (0.98, 1.01) (n = 221) 

1.0 (n = 42)

1.51 (0.081, 2.71) (n = 52) 

1.51 (0.82, 2.84) (n = 49) 

1.13 (0.59, 2.04) (n = 43) 

0.90 (0.47, 1.7) (n = 35) 

Hardell et al. 2014

Denmark; case-control study

Prostate cancer cases from hospital 

admissions, 2007–2011 (n = 201, 

participation 79%, median age 67 yr); 

population-based controls matched on 

age geographical location (n = 186, 

participation 54%); Blood sampling for 

perfluorinated alkyl acids 2007–2011

Median blood PFOS in cases 

0.009 μg/mL, controls 0.0083 

μg/mL

Prostate Cancer

Adjusted RR (95% CI) (n cases)

1.0 (0.60, 1.5) (n = 109) 

Bonefeld-Jørgensen et al. 2011

Greenland, case-control study

Inuit women with breast cancer 

registered at hospital (n = 31, 80% of 

all cases) in 2000–2003 (median age 50 

yr). Age and district-matched 

(frequency) controls selected from 

cross-sectional biomonitoring study (n 

= 115, median age 54 yr) 

Median serum PFOS (range)

Cases: 0.0456 μg/mL 

(0.0116−0.124) 

Controls: 0.0219 μg/mL 

(0.0015–0.172) 

Breast Cancer

OR (95% CI), p-value, (n cases/n controls)

Unadjusted 1.01 (1.003, 1.02), p = 0.02, (98 cases/31 

controls) 

Adjusted 1.03 (1.001, 1.07), p = 0.05, (69 cases/9 

controls) 

Eriksen et al. 2009

Denmark Diet, Cancer and Health 

Study; enrolled December 1, 1993–

May 31, 1997; cancer diagnoses 

between December 1, 1993–July 1, 

2006. 1,240 cancer cases (1,111 male, 

129 female), median age 59 years 

compared to 772 participants selected 

at random from cohort, median age 56 

years. Analysis using Cox proportional 

hazards model stratified by sex (IRR)

Plasma PFOS concentrations at 

enrollment; range: 0.001–0.131 

μg/mL. 

Quartiles PFOS IRR (95% CI)

Q1

Q2

Q3

Q4

Trend per 10 ng/mL increase 

Bladder Cancer (n = 332)

1.0 

0.76 (0.50, 1.16)

0.93 (0.61, 1.41)

0.70 (0.446, 1.07)

0.93 (0.83, 1.03)

Q1

Q2

Q3

Q4

Trend per 10 ng/mL increase 

Liver Cancer (67)

1.0 

0.62 (0.29, 1.33)

0.72 (0.33, 1.56) 

0.59 (0.27, 1.27)

0.97 (0.79, 1.19) 

Q1

Q2

Q3

Q4

Trend per 10 ng/mL increase

Prostate Cancer (n = 713)

1.0 

1.35 (0.97, 1.87)

1.31 (0.94, 1.82)

1.38 (0.99, 1.93)

1.05 (0.97, 1.14)

Perfluorooctane sulfonate (PFOS) – May 2016 3-48
3.1.2.1 Summary and Conclusions from the Human Cancer Epidemiology Studies

A small number of epidemiology studies of PFOS exposure and cancer risk are available.

While these studies do report elevated risk of bladder and prostate cancers, limitations in design 

and analysis preclude the ability to make definitive conclusions. While an elevated risk of 

bladder cancer mortality was associated with PFOS exposure in an occupational study 

(Alexander et al. 2003), a subsequent study to ascertain cancer incidence in the cohort observed 

elevated but statistically insignificant incidence ratios that were 1.7- to 2-fold higher among 

workers with higher cumulative exposure (Alexander and Olsen 2007). The risk estimates lacked 

precision because the number of cases was small. Smoking prevalence was higher in the bladder 

cancer cases, but the analysis did not control for smoking because data were missing for 

deceased workers, and therefore positive confounding by smoking is a possibility. Mean PFOS 

serum levels were 0.941 μg/mL. No elevated bladder cancer risk was observed in a nested casecontrol study in a Danish cohort with plasma PFOS concentrations at enrollment of 0.001–

0.1305 μg/mL (Eriksen et al. 2009). 

Elevated odds ratios for prostate cancer were reported for the occupational cohort examined 

by Alexander and Olsen (2007) and the Danish population-based cohort examined by Eriksen et 

al. (2009). However, the confidence intervals included the null, and no association was reported 

by another case-control study in Denmark (Hardell et al. 2014). A case-control study of breast 

cancer among Inuit females in Greenland with similar serum PFOS levels to those of the Danish 

population (0.0015–0.172 μg/mL) reported an association of low magnitude that could not be 

separated from other perfluorsulfonated acids, and the association was not confirmed in a Danish 

population (Bonefeld-Jørgensen et al. 2011, 2014). Some studies evaluated associations with 

serum PFOS concentration at the time of cancer diagnosis, and the impact of this potential 

exposure misclassification on the estimated risks is unknown (Bonefeld-Jørgensen et al. 2011; 

Hardell et al. 2014). No associations were adjusted for other perfluorinated chemicals in serum in 

any of the occupational and population-based studies.

3.2 Animal Studies

Acute and short-term studies in rats and mice provide data on lethality, systemic toxicity, 

neurotoxicity, and mode of action. Subchronic studies in monkeys and rats found decreased body 

weight, increased liver weight accompanied by microscopic lesions, and decreased serum 

cholesterol. The most prominent microscopic lesion of the liver in both monkeys and rats was 

centrilobular hepatocellular hypertrophy. In a chronic bioassay, rats had decreased body weight, 

increased liver weight with microscopic lesions, and an increased incidence of hepatocellular 

adenomas. Effects on development and reproduction were found in both rats and mice, including 

increased neonatal mortality. Other developmental and reproductive toxicity effects included 

decreased gestation length, lower birth weight, and developmental delays. Postnatal effects of 

gestational and lactational exposure included evidence of developmental neurotoxicity, changes 

in thyroid and reproductive hormones, altered lipid and glucose metabolism, and decreased 

immune function. Each of these studies is described in detail below, and a tabular summary of 

the animal studies is provided in Appendix C, Table C-2. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-49
3.2.1 Acute Toxicity

The few available acute toxicity studies of PFOS indicate a lethal dose for 50% (statistical 

median) of animals (LD50) of 251 mg/kg and an LC50 of 5.2 ppm in rats (Dean et al. 1978; Rusch 

et al. 1979). PFOS caused no irritation in a dermal irritation study although limited study details 

were available (OECD 2002). An eye irritation study was also conducted but few details were 

provided on effects observed (OECD 2002). 

Oral Exposure 

Dean et al. (1978) exposed 5 CD rats/sex/dose by gavage to a single dose of 0, 100, 215, 464, 

or 1,000 mg/kg of PFOS suspended in a 20% acetone/80% corn oil mixture. Rats were observed 

for abnormal signs for 4 hours after exposure and then daily for up to 14 days. All rats died in the 

464 and 1,000 mg/kg group, and 3 of 10 rats died in the 215 mg/kg group. Clinical signs observed 

included hypoactivity, decreased limb tone, and ataxia. Necropsy results indicated stomach 

distension, lung congestion, and irritation of the glandular mucosa. Based on the findings, the acute 

oral LD50 was 233 mg/kg in males, 271 mg/kg in females, and 251 mg/kg combined.

Male Wistar rats and male ICR mice (n = 2–3 per group) were administered a single oral 

dose of PFOS at 0, 125, 250, or 500 mg/kg and monitored for any neurological signs (Sato et al.

2009). Animals of both species treated with ≥ 250 mg/kg had decreased body weight or delay of 

body weight gain during the 14 days post-exposure. One of three rats in the 250 mg/kg group and 

both rats in the 500 mg/kg group died. One mouse in each dose group died. No neurological 

signs were observed. No histopathological changes were observed in the neuronal or glial cells 

of the cerebrum and cerebellum in rats killed 24 hours after exposure. In these same rats, the 

highest concentration of PFOS was in the liver and the lowest was in the brain. Rats 

administered 250 mg/kg bw did not show any differences in the levels of catecholamines 

(norepinephrine, dopamine, and serotonin) or amino acids (glutamic acid, glycine, and gammaaminobutyric acid [GABA]) when compared to the controls at 24 and 48 hours post-exposure. 

Inhalation Exposure 

Rusch et al. (1979) exposed Sprague-Dawley rats (5/sex/dose) to PFOS dust (in air) at 

concentrations of 0, 1.89, 2.86, 4.88, 6.49, 7.05, 13.9, 24.09, or 45.97 mg/L for 1 hour. Rats were 

observed for abnormal signs prior to exposure, every 15-min during exposure, at removal from 

the chamber, hourly for 4 hours after exposure, and then daily for up to 14 days. The 45.97 mg/L 

group was not used in determining the LC50 as this portion of the study was terminated on day 2 

due to high mortality; the 13.9 mg/L group was also not part of the calculation as this group was 

terminated early due to mechanical problems. All rats in the 24.09 mg/L group died by day 6. 

Mortality for the other groups was 0%, 10%, 20%, 80%, and 80% in the 1.89, 2.86, 4.88, 6.49, 

and 7.05 mg/L groups, respectively. Clinical signs observed included emaciation, red material 

around the nose or other nasal discharges, dry rales, breathing disturbances, and general poor 

condition. Necropsy results indicated discoloration of the liver and lung. Based on the findings, 

the acute inhalation LC50 was 5.2 mg/L (ppm). 

Dermal/Ocular Exposure 

The only dermal and ocular irritation PFOS studies were performed by Biesemeier and 

Harris (1974) and were summarized in OECD (2002) with few details. In the dermal study, six 

albino rabbits were treated by placing 0.5 grams of the test material on their intact or abraded 

backs and covered. Erythema and edema were scored after 24 and 72 hours. The primary 

Perfluorooctane sulfonate (PFOS) – May 2016 3-50
irritation score was zero indicating no irritation or edema. No information was provided on the 

guidelines followed, sex of the animals, and the vehicle used. 

In the ocular study, six albino New Zealand White rabbits, fitted with Elizabethan collars, 

were treated with one tenth of a gram of the test substance instilled in one eye; the other eye was 

used as the untreated control. Reaction to the test material was recorded at 1, 24, 48, and 72 

hours after treatment; however, the scale criteria were not presented or referenced. Scores were 

maximal at 1 hour and 24 hours after treatment, then decreased over the rest of the study. The 

raw data were not provided in the OECD (2002) report. 

3.2.2 Short-Term Studies

Short-term oral toxicity studies in rats and mice included data on lethality, body weight, liver 

weight, and histopathology, as well as serum lipids. Body weight was decreased and liver weight 

increased at > 2 mg/kg/day in rats. Higher doses resulted in hepatocyte hypertrophy and 

decreased cholesterol in rats and mice. Mechanistic studies in mice indicate changes suggestive 

of hepatic hyperlipidemia or fatty liver disease.

Oral Exposure 

Rat. Forty to seventy Sprague-Dawley Crl:CD (SD) IGS BR rats/sex/dose were administered 

PFOS in the diet at concentrations of 0, 0.5, 2.0, 5.0, or 20 ppm as part of a long term chronic 

cancer bioassay (Seacat et al. 2003). Five animals per dose group were sacrificed for interim 

necropsies at 4 weeks. Doses were equivalent to 0, 0.05, 0.18, 0.37, and 1.51 mg/kg in males and 

0, 0.05, 0.22, 0.47, and 1.77 mg/kg in females. Animals were observed twice daily for mortality 

and moribundity, with a clinical exam performed weekly. Body weight and food consumption 

data were recorded weekly. Food efficiency was determined, and mean daily intake of PFOS, 

cumulative dose, and percentage of dose were identified in the liver and sera. Blood and urine 

were obtained from 10 animals/sex/dose during week 4 for clinical chemistry, hematology, and 

urinalysis evaluation. A thorough necropsy was performed on five animals/ sex/dose at the end 

of 4 weeks of treatment and liver samples were collected for palmitoyl CoA oxidase (PCoAO) 

activity, liver weight, cell proliferation index (PI), and PFOS concentration analysis. 

Microscopic analysis of tissues was performed on the control and high-dose animals. Analysis of 

PFOS in the liver and sera were determined by HPLC/MS/MS and results were considered 

quantitative to ± 30%. 

A summary of findings in the study is provided in Table 3-9. For the animals treated for 

4 weeks, terminal body weight in the 20 ppm animals was decreased, although not statisticallysignificant. Absolute liver weight was not affected, but relative liver weight was increased in the 

high dose males and females; the increase was significant only for males. Food consumption and 

food efficiency were decreased only in the 20 ppm females. No treatment-related effects were 

observed on hematology or urinalysis; male rats treated with 20 ppm had significant decreases in 

serum glucose. Analysis of PCoAO activity was weakly increased (< 2-fold) when compared to 

controls in the 20 ppm dose group males in one laboratory and similar to controls in another 

laboratory analysis. The 20 ppm (1.5 mg/kg/day) dose group was a LOAEL for males following 

a 4 week exposure.

Perfluorooctane sulfonate (PFOS) – May 2016 3-51
Table 3-9. Mean (± SD) Values for Select Parameters in Rats Treated for 4 Weeks 

Parameter PFOS (mg/kg/day)

Males

0 0.05 0.18 0.37 1.51

Body wt (g) 323 ± 34 315 ± 16 303 ± 25 309 ± 19 296 ± 21

Liver/body wt (%) 3.6 ± 0.2 4.1 ± 0.4 3.9 ± 0.2 3.5 ± 0.3 4.4* ± 0.3

PCNA LI (%) 0.042 ± 0.024 0.038 ± 0.014 0.069 ± 0.028 0.043 ± 0.025 0.065 ± 0.029

Glucose (mg/dL) 97 ± 11 97 ± 5 91 ± 11 94 ± 9 84* ± 5

AST (IU/L) 122 ± 26 146 ± 29 104 ± 23 114 ± 17 131 ± 20

PCoAO (IU/g) 9.0 ± 2.2 9.0 ± 2.3 7.0 ± 4.0 8.0 ± 0.8 6.0 ± 1.4

Females

0 0.05 0.22 0.47 1.77

Body wt (g) 213 ± 21 192 ± 11 202 ±15 206 ± 29 193 ± 17

Liver/body wt (%) 3.8 ± 0.2 3.7 ± 0.2 3.8 ± 0.2 3.7 ± 0.4 4.1 ± 0.3

PCNA LI (%) 0.53 ± 0.032 0.055 ± 0.015 0.059 ± 0.013 0.097 ± 0.036 0.183 ± 0.085

Glucose (mg/dL) 114 ± 7 11 ± 7a 113 ± 18 109 ± 11 107 ± 8

AST (IU/L) 123 ± 28 120 ± 37 101 ± 12 112 ± 24 92 ± 16

PCoAO (IU/g) 5.0 ± 1.5 6.0 ± 1.1 3.0 ± 1.7 2.0** ± 1.1 4.0 ± 1.1

Source: Data from Seacat et al. 2003 

Notes: a Reviewer suspects this is a typo and should be 111 mg/dL as it was not marked significant and is not in the text. *

Statistically-significant from controls, p < 0.05

PCNA LI = proliferating cell nuclear antigen labeling index

IU = international unit

Curran et al. (2008) conducted two 28-day studies in groups of 15 Sprague-Dawley

rats/sex/dose. In both studies, the animals were administered 0, 2, 20, 50, or 100 mg PFOS/kg

diet which was equivalent to 0, 0.14, 1.33, 3.21, or 6.34 mg PFOS/kg body weight/day, 

respectively, in males and 0, 0.15, 1.43, 3.73, or 7.58 mg/kg body weight/day, respectively, in 

females. In the first study (Study 1), rats were assessed for changes in clinical chemistry, 

hematology, histopathology, and gene expression. In Study 2, blood pressure, erythrocyte 

deformability and liver fatty acid composition were assessed. Tissues were also analyzed for 

PFOS residues by LC/MS/MS. Tissue residue results showed a dose-dependent increase with 

most of the PFOS identified in the liver; values for the PFOS residue levels are reported in 

section 2.2, Distribution.

There were no treatment-related differences observed in hematology and urinalysis 

parameters. Statistically-significant (p ≤ 0.05) decreases in body weight and food consumption 

were observed in the males and females administered ≥ 50 mg PFOS/kg diet. Food consumption 

was also statistically decreased in males during week 3 of treatment in the 20 mg PFOS/kg diet 

group. No differences in blood pressure measurements were observed across the groups.

Deformability index values in red blood cells over a range of shear stress levels were 

significantly lower in both males and females exposed to 100 mg PFOS/kg diet, relative to 

controls.

Absolute and relative liver weights were statistically-significantly increased in the male and 

female rats at ≥ 20 mg PFOS/kg diet. Relative liver weight was also statistically increased in the 

2 mg PFOS/kg diet females. Histopathological changes were observed in the liver of the males 

treated with ≥ 50 mg PFOS/kg diet and included hepatocyte hypertrophy and an apparent 

increase in cytoplasmic homogeneity. Increased hepatocyte hypertrophy and cytoplasmic 

homogeneity in the females was seen at ≥ 50 mg PFOS/kg diet. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-52
Both males and females showed a significant increase in expression of the gene for peroxisomal 

acyl-coenzyme A oxidase at concentrations ≥ 50 mg PFOS/kg diet. Cytochrome P-450 4A22 

(CYP4A22) expression was increased 4%–15% greater than controls in the males in the ≥ 20 mg/kg 

diet groups and 3%–7% greater in the females administered ≥ 50 mg PFOS/kg diet. Liver fatty acid 

profiles showed increased total monounsaturated fatty acid levels and decreased total 

polyunsaturated fatty acids. A total of 67 fatty acid profiles were examined. The authors stated that 

the profile changes were similar to those induced by weak peroxisome proliferators.

At the high doses, the serum levels of conjugated bilirubin and total bilirubin were increased 

significantly. Serum cholesterol was significantly decreased for males and females at ≥ 50 mg 

PFOS/kg diet. Serum T4 and T3 levels were also decreased in males and females, with T4 levels 

being statistically-significantly decreased at ≥ 20 mg PFOS/kg diet, when compared to the 

control levels. Significant differences as observed in this study are provided in Table 3-10. 

Table 3-10. Mean (± SD) Values for Select Parameters in Rats Treated for 28 Days 

Parameter PFOS (mg/kg diet)

0 2 20 50 100

Males

Final body wt (g) 415.1 ± 40.1 412.3 ± 32.0 386.2 ± 25.9 363.7* ± 25.7 327.0* ± 21.6

Liver wt (g) 17.7 ± 2.7 17.1 ± 2.8 18.4 ± 3.2 20.8* ± 1.5 21.7* ± 2.3

Liver/body wt (%) 4.24 ± 0.41 4.13 ± 0.48 4.75* ± 0.67 5.73* ± 0.21 6.64* ± 0.41

Thyroid wt (g) 0.021± 0.004 0.022 ± 0.005 0.020 ± 0.004 0.020 ± 0.003 0.021 ± 0.055

Conjugated bilirubin 

(μmol/L)

0.57 ± 0.18 0.65 ± 0.22 0.62 ± 0.19 0.75 ± 0.27 2.13* ± 0.44

Total bilirubin

(μmol/L)

2.75 ± 0.63 2.75 ± 0.89 2.47 ± 0.82 2.55 ± 0.91 4.01* ± 0.87

Cholesterol (mmol/L) 2.54 ± 0.63 2.46 ± 0.55 2.06 ± 0.43 1.63* ± 0.31 0.31* ± 0.18

Triglycerides 

(mmol/L)

1.74 ± 0.93 1.92 ± 0.78 1.77 ± 0.57 1.00* ± 0.42 0.20* ± 0.08

T4 (nmol/L) 80.94 ± 11.83 66.97 ± 14.75 14.36* ± 4.18 12.88* ± 2.67 13.29* ± 2.59

T3 (nmol/L) 1.60 ± 0.33 1.81 ± 0.19 1.36 ± 0.26 1.29 ± 0.26 1.21* ± 0.23

Females

Final body wt (g) 247.2 ± 27.5 251.2 ± 13.1 245.9 ± 10.5 217.6* ± 15.1 197.6* ± 10.4

Liver wt (g) 9.1 ± 1.5 10.2 ± 1.2 11.0* ± 1.2 11.2* ± 1.2 12.2* ± 1.4

Liver/body wt (%) 3.64 ± 0.38 4.06* ± 0.39 4.45* ± 0.40 5.12* ± 0.38 6.24* ± 0.67

Thyroid wt (g) 0.016 ± 0.003 0.017 ± 0.004 0.018 ± 0.003 0.017 ± 0.003 0.018 ± 0.005

Conjugated bilirubin 

(μmol/L)

0.52 ± 0.14 0.47 ± 0.14 0.49 ± 0.17 0.85* ± 0.18 2.60* ± 0.73

Total bilirubin

(μmol/L)

2.00 ± 0.75 1.67 ± 0.43 1.51 ± 0.54 2.20 ± 0.43 4.69* ± 1.04

Cholesterol (mmol/L) 2.06 ± 0.36 2.02 ± 0.51 1.66 ± 0.28 1.37* ± 0.24 0.52* ± 0.16

Triglycerides 

(mmol/L)

0.99 ± 0.46 1.68 ± 0.99 1.11 ± 0.70 0.65 ± 0.30 0.37* ± 0.30

T4 (nmol/L) 37.71 ± 15.41 32.39 ± 10.40 19.62* ± 2.49 15.05* ± 1.99 16.40* ± 4.61

T3 (nmol/L) 1.83 ± 0.17 1.72 ± 0.14 1.75 ± 0.27 1.41* ± 0.22 1.27* ± 0.20

Source: Data from Tables 2-3 and 6-7 in Curran et al. 2008

Note: *

Statistically-significant from controls, p < 0.05 or p ≤ 0.05

The LOAEL was the 20 mg/kg dietary level (males: 1.33 mg PFOS/kg/day; females: 1.43 mg 

PFOS/kg/day) for a significant increase in absolute (females) and relative (males and females) 

liver weights and significant decrease in serum T4 (males and females). The NOAEL was the 2 

mg/kg diet level (0.14–0.15 mg PFOS/kg/day). 

Perfluorooctane sulfonate (PFOS) – May 2016 3-53
Ten three-month old male Sprague-Dawley rats/group were administered 0 (Milli-Q water 

only), 5, or 20 mg/kg/day PFOS by oral gavage for 28 days (Cui et al. 2009). Rats were 

sacrificed after exposure, and blood and tissue samples were obtained. All rats (10/10) 

administered 20 mg/kg/day of PFOS died by study day 26. At necropsy, rats had bleeding around 

the eye socket and nose and yellow staining in the urogenital region. Prior to death, rats 

displayed significant weight loss and a decrease in food consumption when compared to 

controls. Rats administered 5 mg/kg/day also had a significant decrease in body weight when 

compared to controls at the study termination. Viscera indices were calculated including the 

hepatosomatic index (HSI), renal-somatic index (RSI), and gonad-somatic index to evaluate the 

hyperplasia, swelling and/or atrophy of the organs, and all three indices were statisticallysignificantly increased in all of the treated groups. The increases in the HSI and RSI showed a 

dose dependency. Rats administered 20 mg/kg/day had swelling and discoloration of the liver, 

with hepatocyte hypertrophy and cytoplasmic vacuolation observed on histopathological exam. 

Rats administered 20 mg/kg/day had congestion and thickened walls in the lungs with the 

pulmonary congestion also observed in the 5 mg/kg rats. Based on the results, a LOAEL of 5 

mg/kg/day in rats was identified based on a significant decrease in body weight, dose-related 

effects in the liver and pulmonary congestion. A NOAEL could not be identified. 

Mouse. The variability in the serum lipid profiles in humans suggests that response to PFOS 

exposure could be impacted by individual physiological differences and that environmental 

factors such as diet might contribute to intraspecies variability in response. L. Wang et al. (2014) 

reported on the differences in response of male BALB/c mice (4–5 weeks old) administered 

PFOS (0, 5, or 20 mg/kg) for 14 days while concurrently given diets that varied in fat [regular fat 

(RF) versus high fat (HF) content]. The high fat diet contained 10% more lard and 3% more 

cholesterol than the regular fat diet. Liver and serum responses were evaluated after a 14 day 

exposure period. The data were for the endpoints monitored were presented graphically. 

Following PFOS exposure, there was an increase in liver fat content in both groups and a 

decrease in liver glycogen in rats on both diets. For the mice on the regular fat diet, the addition 

of PFOS led to a significant increase in liver fat content (an approximately two-fold increase). 

For the mice on the high fat diet, the addition of PFOS caused a slight a slight and nonsignificant 

increase in the liver fat content. 

The fat content of the diet alone was associated with significantly higher serum levels of 

glucose, HDL cholesterol, LDL cholesterol, total cholesterol, and triglycerides. The differences 

were significant for glucose, albumin, and total cholesterol (p < 0.01). For glucose, cholesterol, 

HDL, and LDL, the serum levels declined as the dose of PFOS increased; for triglycerides the 

levels increased at a dose of 5 mg PFOS/kg/day and decreased at 20 mg PFOS/kg/day. PPARα 

expression at the end of 14 day PFOS treatment increased for the RF group, but it decreased for 

the HF groups (significant for the high dose). 

The authors examined the expression of several genes involved with lipid metabolism 

(CPT1A and CYP7A1). CPT1A plays a role in transport of fatty acid into the mitochondria for 

beta oxidation, and CYP7A1 is involved with the transformation of cholesterol into bile acids. 

The high fat diet alone increased the expression of both genes. On the RF diet, the exposure to 

PFOS was associated with a significant dose-related increase in CPT1A expression, whereas for 

the high fat diet plus PFOS there was a significant decrease in expression. For CYP7A1 

expression there was no significant impact of PFOS with the RF diet, whereas with the high fat 

diet there was a highly significant decrease in expression with PFOS. The study demonstrates a 

clear influence of diet alone on the liver and lipid profile of the treated mice, combined with 

Perfluorooctane sulfonate (PFOS) – May 2016 3-54
some dose-related differences in the responses to PFOS exposure. The data support a possible 

role for PFOS in inhibiting pathways for cholesterol metabolism and export of liver lipids and 

identify some PFOS associated liver responses that are independent of PPARα activation.

A 21-day study by Wan et al. (2012) examined mechanistic aspects related to the role of 

PFOS in leading to hepatic steatosis in male CD-1 mice (4/dose). Animals were given PFOS in 

corn oil by gavage at doses of 0, 1, 5, or 10 mg/kg/day with sacrifice after 3, 7, 14, or 21 days. 

Liver weights were significantly (p < 0.05) increased for the highest two dose groups across the 

duration of the study and only at day 7 for the 1 mg/kg/day dose. The size of the liver was 

significantly increased (p < 0.0003) at 5 and 10 mg/kg/day and a yellowish coloration of the 

tissues was visually apparent. Histologically there was microvesicular steatosis on day 14 and 

macrovesicular steatosis on day 21 at 10 mg/kg/day. The level of liver triglycerides was 

significantly (p < 0.001) increased compared to control for the 5 and 10 mg/kg/day dose groups. 

The Wan et al. (2012) study included a series of mechanistic components to investigate the 

mode of action for the effects observed. Both mRNA and protein expression for fatty acid 

translocase and lipoprotein lipase were significantly increased for the 10 mg/kg/day dose. Levels 

of mRNA in adipose tissue from the fat pad were not increased for either enzyme. Export of liver 

lipids appeared to decrease, leading to lower serum LDL/VLDL levels on days 14 and 21. The 

change correlated with increased liver weight and decreased expression of liver apolipoprotein 

B-100 (apob). By day 21, apob expression was significantly decreased (p < 0.001) even in the 

low dose group. Formation of hepatic VLDLs requires apob; the VLDLs are carriers of liver 

triglycerides and other lipids from liver to serum. 

The authors also examined total hepatic β oxidation, peroxisomal β oxidation, and 

mitochondrial β oxidation using d31 palmitic acid. The results of this assay indicated that the 

PFOS was primarily responsible for a decrease in mitochondrial β oxidation as monitored on day 

14. While total and peroxisomal β oxidation were slightly, but significantly, increased (p < 0.01) 

at 10 mg/kg/day, mitochondrial β oxidation was markedly decreased (p < 0.05 or 0.01) in all 

dose groups. Transcripts for mRNA for peroxisomal acyl-CoA oxidase, Cyp 4a14, and acyl-Co 

A dehydrogenase were significantly increased in the 5 and 10 mg/kg/day dose groups, suggesting 

breakdown of long chain fatty acids by peroxisomes. Increases in peroxisomal oxidation in the 

absence of increased mitochondrial beta oxidation can lead to accumulation of fatty acids in the 

liver (steatosis). The LOAEL identified for this study is 5 mg/kg/day. At 1 mg/kg/day there was 

increased liver weight in the absence of histopathological correlates. The 1 mg/kg/day dose is 

accordingly a NOAEL. The authors concluded that the hepatic changes observed in mice were 

similar to those associated with nonalcoholic fatty liver disease in humans and were not totally a 

reflection of PPARα activation. 

Bijland et al. (2011) examined the molecular biology for the hepatic hyperlipidemia in 

APOE*3-Leiden.CETP mice, a strain that exhibits human-like lipoprotein metabolism. The 

experimental animals were fed a western-type diet containing 0.25% cholesterol, 1% corn oil, 

and 14% bovine fat for 4 weeks with or without 3 mg PFOS/kg/day. The diet contained 0.25% 

cholesterol, 1% corn oil, and 14% bovine fat. Plasma samples were collected via tail vein 

bleeding and analyzed for a variety of lipid related endpoints including TC, triglycerides, VLDL, 

and HDL. Following terminal sacrifice, the liver, heart, perigonadal fat, spleen, and skeletal 

femoralis muscle were collected for analysis. Fecal samples were collected for measurement of 

bile acids and neutral sterols.

Perfluorooctane sulfonate (PFOS) – May 2016 3-55
Significant decreases in triglycerides (−50%), total cholesterol (−60%), HDL (−74%), and 

non-HDL (−60%) were found in mice given PFOS compared with controls. VLDL was also 

significantly less than that of controls, but the level was only presented graphically. Radiolabeled 

VLDL-like emulsion particles showed the plasma half-life of VLDL was reduced by 52% in 

PFOS treated mice compared with controls accompanied by significantly increased uptake by 

liver, heart, and muscle. VLDL production by the liver was markedly decreased (−87%) in 

treated animals. Liver weight and hepatic triglyceride content were significantly greater 

(p < 0.0001) and perigonadal fat pad weight was significantly less (p < 0.05) in PFOS treated 

mice compared to those of controls. Thus, PFOS was found to decrease hepatic VLDL 

production leading to increased retention of triglycerides (steatosis) and hepatomegaly. As a 

consequence, there was a decrease in plasma-free fatty acids and glycerol and the mass of 

perigonadal fat pad. Neutral sterols in the feces were not altered, but the presence of bile acids 

was decreased by 50%. Hepatic clearance of VLDL and HDL cholesterol were decreased 

primarily because of impaired hepatic production and clearance of these lipoprotein complexes. 

Compared with the controls, PFOS treated animals had 3,986 differentially expressed genes. 

Impacted hepatic genes involved with lipid metabolism included those involved with VLDL 

metabolism, fatty acid uptake and transport, fatty acid oxidation, and triglyceride synthesis.

Overall, the genes upregulated (1- to 2-fold) were those involved with fatty acid uptake and 

transport and catabolism; triglyceride synthesis; cholesterol storage; and VLDL synthesis. Genes 

involved with HDL synthesis, maturation, clearance, and bile acid formation and secretion were 

downregulated (1-fold for most genes to almost 4-fold for genes involved in secretion). These 

changes are consistent with increased hepatic hyperlipidemia, decrease in bile acid secretion, and 

serum hypolipidemia. Many of the genes activated are associated with the nuclear pregnane X 

receptor (PXR) to a greater extent than PPARα. Lipoprotein lipase activity and mRNA 

expressions were increased in the liver. This enzyme facilitates removal of TGs from serum

LDLs, as well as uptake into the liver and other organs as free fatty acids and glycerol. 

Lipoprotein lipase activity in the liver is relatively low compared to that of peripheral tissues.

3.2.3 Subchronic Studies

Three monkey studies of oral PFOS exposure (two with rhesus- and one with cynomolgusstrains) and two rat subchronic studies are available. The study with cynomolgus monkeys was a 

GLP study. There are no subchronic studies by dermal or inhalation routes of exposure with 

PFOS. In monkeys, clinical signs of toxicity were observed at 0.5 mg/kg/day, while lower body 

weight, increased liver weight with hepatocellular hypertrophy, and decreased serum cholesterol 

occurred at 0.75 mg/kg/day. Rats given 1.3–1.6 mg/kg/day had increased liver weight with 

hepatocyte hypertrophy and decreased cholesterol. 

Oral Exposure 

Monkey. Two monkey studies were performed with rhesus monkeys (Goldenthal et al. 1978a 

and 1979). In the first study, 2 monkeys/sex/dose were administered 0, 10, 30, 100, or 

300 mg/kg/day of PFOS in distilled water by gavage. The study was terminated on day 20 as all 

of the 300 mg/kg treated monkeys died beginning on day 4; deaths were also observed at all 

lower doses, but whether it was one or both of the animals was not stated. Clinical signs of 

toxicity were observed in all groups and included decreased activity, emesis, body stiffening, 

general body trembling, twitching, weakness, and convulsions. At necropsy, several of the 

Perfluorooctane sulfonate (PFOS) – May 2016 3-56
100 and 300 mg/kg/day monkeys had a yellowish-brown discoloration of the liver although there 

were no microscopic lesions. A NOAEL or LOAEL was not determined for this study. 

In the second study, 2 rhesus monkeys/sex/dose were administered 0, 0.5, 1.5, or 

4.5 mg/kg/day of PFOS in distilled water by gavage for 90 days. All monkeys in the 

4.5 mg/kg/day group died or were euthanized in extremis by week 7 and exhibited decreased 

body weight, signs of gastrointestinal tract toxicity (anorexia, emesis, black stool), decreased 

activity, and marked to severe rigidity and had a significant decrease in serum cholesterol.

Histopathology of the 4.5 mg/kg/day monkeys showed diffuse lipid depletion in the adrenals 

(4/4), diffuse atrophy of the pancreatic exocrine cells (3/4) and moderate diffuse atrophy of the 

serous alveolar cells (3/4). All monkeys in the 0.5 and 1.5 mg/kg/day treated groups survived, 

but they exhibited occasional diarrhea, soft stools, and anorexia. These clinical signs showed a 

dose-related increase, and 1/4 of the 1.5 mg/kg/day monkeys had low serum cholesterol. Body 

weight was decreased in males and females at 1.5 mg/kg/day. There were no treatment-related 

effects observed in any of the 0.5 or 1.5 mg/kg/day monkeys at necropsy. Based on the findings, 

the LOAEL was 0.5 mg/kg/day, and the NOAEL could not be determined. 

Seacat et al. (2002) administered 0, 0.03, 0.15, or 0.75 mg/kg/day of potassium PFOS orally 

in a capsule by intragastric intubation to 6 young-adult to adult cynomolgus monkeys/sex/dose, 

except for the 0.03 mg/kg/day group (4 monkeys/sex), daily for 26 weeks (182 days) in a GLP 

study. Two monkeys per sex in the control, 0.15, and 0.75 mg/kg/day groups were monitored for 

1 year post-exposure for reversible or delayed toxic effects. Monkeys were observed twice daily 

for mortality, morbidity, clinical signs, and qualitative food consumption. Body weights were 

recorded pre-dosing and weekly thereafter, and ophthalmic examinations were performed preand post-treatment. PFOS levels were determined in serum and liver tissue and hematology and 

clinical chemistry were performed. Urine and fecal analyses were done and full histopathology 

performed at the scheduled sacrifice. Liver samples were also obtained for hepatic peroxisome 

proliferation determination and immunohistochemistry was performed by PCNA to look for cell 

proliferation. Selected results are shown in Table 3-11. 

Two of the 0.75 mg/kg/day males died; one died on day 155 and one was found moribund and 

was sacrificed on day 179. The monkey that died had pulmonary necrosis and severe acute 

recurrences of pulmonary inflammation as its cause of death. The specific cause of the moribund 

condition was not established, however, the clinical chemistry results were suggestive of 

hyperkalemia. Overall mean body weight gain was significantly (p ≤ 0.05) less in the 

0.75 mg/kg/day males and females (lost 8 ± 8% and 4 ± 5%, respectively) after the treatment when 

compared to controls (gained 14 ± 11% and 5 ± 5%, respectively). Mean absolute and relative (to 

body weight) liver weight was increased significantly in the 0.75 mg/kg/day males and females.

Males and females at 0.75 mg/kg/day had lower total serum cholesterol beginning on day 91 

(27%–68% [males] and 33%–49% [females] lower than controls) and lower high density 

lipoprotein cholesterol beginning on day 153 (72%–79% and 61%–68% lower than controls) when 

compared to the control values. This effect was reversible, however, as the total cholesterol levels 

were similar to controls by week 5 during recovery and the total high density lipoprotein 

cholesterol was similar to controls by week 9. Estradiol values were lower at 0.75 mg/kg in males 

and females on day 182; however, the data were highly variable and the study authors stated that 

the change was not well understood. Total triiodothyronine (T3) values were significantly 

decreased and TSH was increased on day 182 in the high-dose monkeys, but a true dose-response 

was not observed and the monkeys had no indication of clinical hypothyroidism (TSH values 

within reference range, no hyperlipidemia, and no thyroid gland histopathological lesions). 

Perfluorooctane sulfonate (PFOS) – May 2016 3-57
Table 3-11. Mean (± SD) Values for Select Parameters in Monkeys Treated for 182 Days 

Parameter PFOS (mg/kg/day)

Males

0 0.03 0.15 0.75

Body wt (g) 3.7 ± 0.7 3.9 ± 0.6 3.3 ± 0.3 3.2 ± 0.8

Body wt change (%) 14 ± 11 16 ± 8 8 ± 7 −8 ± 8*

Liver wt (g) 54.9 ± 8.1 62.1 ± 5.3 57.3 ± 5.5 85.3 ± 38.4

Liver/body wt (%) 1.6 ± 0.2 1.7 ± 0.3 1.8 ± 0.1 2.7 ± 0.3*

Cholesterol (mg/dL) 152 ± 28 110 ±17** 147 ± 24 48 ± 19**

HDL (mg/dL) 63 ± 11 42 ± 4** 48 ± 14 13 ± 5**

Total T3 (ng/dL) 146 ± 19.8 145 ± 18.0 129 ± 4.8 76 ± 22**

TSH (μU/mL) 0.55 ± 0.44 0.56 ± 0.10 1.38 ± 0.78 1.43 ± 0.25*

Estradiol (pg/mL) 23.0 ± 11.5 24.1 ± 14.2 23.2 ± 7.4 0.8 ± 1.0**

Females

0 0.03 0.15 0.75

Body wt (g) 3.0 ± 0.4 3.2 ± 0.7 3.1 ± 0.5 2.8 ± 0.4

Body wt change (%) 5 ± 5 6 ± 7 4 ± 5 −4 ± 5

Liver wt (g) 51.1 ± 9.4 56.8 ± 12.6 57.0 ± 3.1 75.3 ± 13.3*

Liver/body wt (%) 1.8 ± 0.2 1.9 ± 0.0 2.1 ± 0.2 2.9 ± 0.3*

Cholesterol (mg/dL) 160 ± 47 122 ± 22 129 ± 22 82 ± 15**

HDL (mg/dL) 56 ± 16 42 ± 9 36 ± 12** 21 ± 7**

Total T3 (ng/dL) 148 ± 21.6 139 ± 11.5 116 ± 16.8 99 ± 16.8*

TSH (μU/mL) 1.02 ± 0.69 2.01 ± 2.09 1.33 ± 1.13 1.86 ± 1.29

Estradiol (pg/mL) 148.5 ± 110.1 125.2 ± 101.2 70.6 ± 62.7 39.9 ± 33.6

Source: Data from Seacat et al. 2002 

Notes: *Statistically-significant from controls: *p < 0.05 ** Statistically-significant from controls: p < 0.01. 

Hepatic peroxisome proliferation was measured by PCoAO activity and was increased 

significantly in the 0.75 mg/kg/day females; however, the increase was not dose-related and it 

was < two-fold. There were no treatment-related effects on cell proliferation in the liver, 

pancreas, or testes when analyzed by proliferating cell nuclear antigen immunohistochemistry 

cell labeling index. Two high dose males and one high-dose female had mottled livers on gross 

examination at sacrifice; this was also observed in the high-dose male that died during the study. 

All females and 3/4 males at the high-dose had centrilobular or diffuse hepatocellular 

hypertrophy. 

Serum and liver samples collected during the study were analyzed for PFOS and animals 

showed a dose-dependent increase in concentrations. Values decreased with recovery but never 

returned to control levels. There was not any gender difference in the amount of PFOS identified 

in the sera or liver. Based on the decreased body weight gain, decreased serum cholesterol, 

increased absolute and relative liver weight and histopathological lesions in the liver, the 

LOAEL in male and female monkeys treated with potassium PFOS was 0.75 mg/kg/day and the 

NOAEL was 0.15 mg/kg/day. Serum concentrations associated with no adverse effect 

(0.15 mg/kg/day) were 82.6 μg/mL in males and 66.8 μg/mL in females. Serum concentrations 

associated with adverse effects (0.75 mg/kg/day) were 173 μg/mL in males and 171 μg/mL in 

females.

Perfluorooctane sulfonate (PFOS) – May 2016 3-58
Rat. Goldenthal et al. (1978b) administered 0, 30, 100, 300, 1,000, or 3,000 ppm of PFOS in the 

diet to five CD rats/sex/group for 90 days. Dietary levels were equivalent to 0, 2, 6, 18, 60, and 

200 mg/kg/day, respectively. All rats at ≥ 300 ppm died starting on day 7 after exhibiting 

emaciation, convulsions, hunched back, increased sensitivity to stimuli, reduced activity, and red 

material around the nose/mouth At 100 ppm body weights were decreased (~ 16.5%), as was 

food consumption, when compared to controls. Relative liver weight and relative/absolute liver 

weight was significantly increased in the 100 ppm males and females, respectively. Both sexes 

had significant increases in relative kidney weight at 100 ppm. Three males and 2 females from 

the 100 ppm group died. All rats survived at 30 ppm, but there was a significant decrease in food 

consumption (males) and significant increase in absolute and relative liver weight (females). All 

treated animals had very slight to slight cytoplasmic hypertrophy of hepatocytes in the liver. 

Based on the significant decrease in food consumption and increase in absolute and relative liver 

weight, the LOAEL was 30 ppm (2 mg/kg/day) and the NOAEL could not be determined. 

Seacat et al. (2003) also performed an interim sacrifice for five Sprague-Dawley Crl:CD 

(SD) IGS BR rats/sex/dose at the end of 14 weeks as part of the long-term cancer bioassay. The 

animals were administered PFOS in the diet at concentrations of 0, 0.5, 2.0, 5.0, or 20 ppm. 

Doses were equivalent to 0, 0.03, 0.13, 0.34, and 1.33 mg/kg in males and 0, 0.04, 0.15, 0.40, 

and 1.56 mg/kg in females, respectively for those sacrificed at 14 weeks. Animals were observed 

twice daily for mortality and moribundity with a clinical exam performed weekly. Body weight 

and food consumption data were recorded weekly. Other parameters recorded were food 

efficiency, mean daily intake of PFOS, and cumulative/percentage of dose in the liver and sera. 

Blood and urine were obtained from 10 animals/sex/dose during week 14 for clinical chemistry, 

hematology, and urinalysis evaluation. A thorough necropsy was performed at the end of 14 

weeks of treatment for 5 animals/sex/dose, and liver samples were collected for PCoAO activity, 

cell PI, and PFOS concentration analysis. Microscopic analysis of tissues was performed on the 

control and high-dose animals. Analysis of PFOS in the liver and sera were determined by 

HPLC/MS/MS, and results were considered quantitative to ± 30%.

No effects were observed on body weight, food efficiency, urinalysis evaluation, or peroxisome 

proliferation (hepatic PCoAO was unchanged) at 14 weeks. All significant changes, when 

compared to controls, were observed in the highest dose group. Food consumption was 

decreased. Absolute and relative (to body weight) liver weights were increased significantly in 

the males and males/females, respectively. All hematology parameters were similar to controls.

Clinical chemistry parameters that were significantly affected, compared to controls, included 

decreased serum cholesterol (males), increased alanine aminotransferase [ALT] (males), and 

increased urea nitrogen (males/females). Select data are provided in Table 3-12. 

Histopathological changes were not observed in the kidney; however, centrilobular 

hepatocyte hypertrophy and mid-zonal to centrilobular vacuolization were observed in the livers 

of the males and females. Based on the findings, the LOAEL for male and female rats 

administered PFOS in the diet for up to 14 weeks was 20 ppm (1.33 mg/kg in males and 

1.56 mg/kg in females), and the NOAEL was 5 ppm (0.34 mg/kg in males and 0.40 mg/kg in 

females).

Perfluorooctane sulfonate (PFOS) – May 2016 3-59
Table 3-12. Mean (± SD) Values for Select Parameters in Rats Treated for 14 Weeks 

Parameter PFOS (mg/kg/day)

Males

0 0.03 0.13 0.34 1.33

Body wt (g) 496 ± 56 481 ± 51 434 ± 31 424 ± 44 470 ± 40

Liver wt (g) 15.5 ± 1.1 15.5 ± 2.7 14.0 ± 1.4 18.8 ± 3.0 20.3*± 2.2

Liver/body wt (%) 3.2 ± 0.3 3.2 ± 0.2 3.2 ± 0.2 3.6 ± 0.3 4.3* ± 0.4

Seg. neutrophils (103/μL) 1.1 ± 0.4 1.3 ± 0.3 1.2 ± 0.3 1.2 ± 0.4 1.6* ± 0.4

Glucose (mg/dL) 102 ± 6.2 106 ± 11 91 ± 14 99 ± 9 95 ± 10

Cholesterol (mg/dL) 63 ± 13 53 ± 17 51 ± 15 57 ± 7 37* ± 13

ALT (IU/L) 36 ± 7 41 ± 6 41 ± 5 44 ± 14 65* ± 53

Urea nitrogen (mg/dL) 13 ± 2 14 ± 2 13 ± 2 14 ± 1 16* ± 2

PCoAO (IU/g) 4.6 ± 1.3 4.8 ± 3.3 5.4 ± 3.0 1.8 ± 1.8 5.4 ± 1.9

Females

0 0.04 0.15 0.40 1.56

Body wt (g) 284 ± 39 298 ± 41 266 ± 16 247 ± 18 249 ± 26

Liver wt (g) 9.3 ± 1.6 9.2 ± 1.3 8.4 ± 0.7 8.7 ± 1.0 10.6 ± 0.7

Liver/body wt (%) 3.3 ± 0.2 3.1 ± 0.1 3.2 ± 0.3 3.5 ± 0.3 4.3* ± 0.4

Seg. neutrophils (103/μL) 1.0 ± 0.5 1.0 ± 0.5 0.7 ± 0.2 0.9 ± 0.6 1.0 ± 0.6

Glucose (mg/dL) 106 ± 12 106 ± 9 108 ± 6 95* ± 8 99 ± 7

Cholesterol (mg/dL) 75 ± 15 88 ± 27 87 ± 24 70 ± 13 66 ± 14

ALT (IU/L) 34 ± 2.4 36 ± 9 37 ± 18 34 ± 5 39 ± 18

Urea nitrogen (mg/dL) 12 ± 2 13 ± 2 13 ± 2 14 ± 3 17* ± 2

PCoAO (IU/g) 1.8 ± 1.6 3.0 ± 2.6 1.0 ± 0.8 1.6 ± 2.6 5.0 ± 2.9

Source: Data from Table 1 in Seacat et al. 2003 

Note: *Statistically-significant from controls, p < 0.05

3.2.4 Neurotoxicity 

Available in vivo and in vitro studies focused on mechanistic endpoints to a greater extent 

neurobehavioral indications of neurotoxicity. Effects observed included altered levels of 

excitatory amino acids in the brain, changes in neurotransmitter levels and increases in miniature 

post-synaptic currents along with inward calcium currents. One study found effects on learning 

and memory in mice at approximately 2 mg/kg/day. 

In vivo

Rat. Yang et al. (2009) determined the effect of PFOS on excitatory amino acids (EAAs) and 

glutamine synthetase (GS) in the rat central nervous system. Adult male Wistar rats (5/group) 

were administered a single dose of 0, 12.5, 25, or 50 mg/kg bw PFOS by oral gavage. The 

animals were sacrificed 5 days after administration. The EAAs analyzed in brain tissue were 

glutamate (Glu), aspartate, glycine, and GABA. 

Rats in the 12.5, 25, and 50 mg/kg groups had significantly (p < 0.05) decreased body 

weights, by 15%, 22%, and 27%, respectively, compared to controls. Among the EAAs, the Glu 

content was significantly decreased in the hippocampus at the high dose (decrease of 77% 

compared to controls; p <0.05); no other significant differences were recorded. In the cortex, Glu 

was the only excitatory amino acid (EAA) affected with significant decreases at 25 (decrease of 

33% compared to controls) and 50 (decrease of 47 compared to controls) mg/kg. GS activity was 

Perfluorooctane sulfonate (PFOS) – May 2016 3-60
significantly increased in the hippocampus at 25 and 50 mg/kg bw. The study had a LOAEL of 

12.5 mg/kg/day in rats based on the decreased body weight. 

Mouse. Groups of 15 adult C57BL6 mice (8 weeks old; number of each sex not specified) were 

administered PFOS at doses of 0, 0.43, 2.15, or 10.75 mg/kg/day by gavage for three months 

(Long et al. 2013). Learning and memory were assessed in the Morris water maze. The apoptosis 

profile of hippocampal cells, as well as the levels of glutamate, GABA, dopamine, 3,4-

dihydrophenylacetic acid (DOPAC), and homovanillic acid (HVA) were evaluated. In the water 

maze trial, animals in the mid- and high-dose groups exhibited a significantly longer latency to 

escape and spent significantly less time in the target quadrant. A significant increase in the 

percentage of apoptotic cells was observed in the hippocampus of the mid- and high-dose 

animals. Neurotransmitter levels were affected only in the high-dose group as based on 

decreased dopamine and DOPAC levels plus increased glutamate levels. HVA and GABA levels 

were unchanged by PFOS treatment. 

Differential protein expression at the high dose included down-regulation of Mib1 protein (an 

E3 ubiquitin-protein ligase), Herc5 (hect domain and RLD 5 isoform 2), and Tyro3 (TYRO3 

protein tyrosine kinase 3). Succinate dehydrogenase flavoprotein subunit (SDHA), Gzma 

(Isoform HF1 of Granzyme A precursor), Plau (Urokinase-type plasminogen activator 

precursor), and Lig4 (DNA ligase 4) were upregulated. The 0.43 mg/kg/day dose group was the 

NOAEL, and the 2.15 mg/kg/day dose group the LOAEL based on water maze performance. 

In vitro. Slotkin et al. (2008) evaluated 10–250 μmol PFOS, PFOA, perfluorooctane sulfamide 

(PFOSA), and perfluorobutane sulfonate (PFBS) in vitro in differentiated and undifferentiated 

PC12 cells, a neurotypic cell line. The study evaluated the following endpoints as indications of 

effects:

• Inhibition of DNA synthesis. 

• Deficits in cell numbers and growth. 

• Oxidative stress. 

• Cell viability. 

• Shifts in differentiation toward or away from the dopamine and acetylcholine (ACh) 

neurotransmitter phenotypes. 

No effects on cell size, cell number, or neurocyte outgrowth were observed. PFOS decreased cell 

viability at 250 μmol and promoted differentiation into the ACh phenotype at the expense of the 

DA phenotype. The study suggests that the mechanisms for the observed effects in the 

neurotypic cell lines are not the same for the individual perfluoroalkyl acids tested. The rank 

order for the adverse effects measured in vitro was as follows: PFOSA > PFOS > PFBS = PFOA.

Liao et al. (2009) assessed the effect of varying chain lengths of the perfluorinated 

compounds on cultured Sprague-Dawley rat hippocampal neurons. Spontaneous miniature postsynaptic currents (mPSCs) were recorded in gap-free mode from hippocampal neurons at 8–15 

days in vitro. The compounds were tested at 100 μmol and included a variety of perfluorinated 

compounds including PFOS. Testing showed the frequency of mPSCs increased in proportion to 

the increase in carbon chain length. PFOS had a statistically-significant (p < 0.001) increase in 

the mPSCs when compared to the four carbon PFBS. Inward calcium currents (ICa) were 

recorded in the presence or absence of the individual compounds with a ramp depolarization 

pulse. Voltage values were recorded and plotted versus the corresponding ICa every 5 mV and the 

resulting current-voltage relationship curve established. All three sulfonic compounds increased 

Perfluorooctane sulfonate (PFOS) – May 2016 3-61
the ICa. The longer the chain length the greater was the effect. PFOS caused the greatest increase 

in ICa (% increase not provided). 

In the same study, the chronic effects of perfluorinated compounds (50 μmol) on neuronal 

development were evaluated by measuring neurite outgrowth and branching. Among the sulfonic 

compounds, only PFOS statistically suppressed the length of neurites (p < 0.001; 25% below that 

of controls) and sum length of neurites per neuron (p < 0.001; 31% below that of controls). The 

study suggested that the effects of perfluorinated sulfonates on neurons were greater than the 

perfluorinated carboxylates. The study authors hypothesized that this reflects the fact that PFOS 

was more likely to be incorporated into the lipid bilayer of cell membranes. This is consistent 

with the results from a study by Matyszewska et al. (2008) who found that PFOS incorporation 

into a model biological membrane was superior to PFOA and that it caused a change in 

membrane fluidity and thickness depending on the amount incorporated. 

3.2.5 Developmental/Reproductive Toxicity

Rats and mice were found to be affected in developmental/reproductive studies with orallyadministered PFOS. Prenatal exposure of rats to PFOS caused an increase in neonatal mortality 

when dams were given doses ≥ 1 mg/kg/day and lowered pup body weight occurred at maternal 

doses of 0.4 mg/kg/day. Neonatal death was shown to be a direct effect of PFOS on the lung 

surfactant. Other developmental and reproductive toxicity effects included decreased gestation 

length and developmental delays. Higher doses resulted in fetal sternal defects and cleft palate in 

both rats and mice. 

Many specialized developmental studies have also been conducted with PFOS to assess longterm effects in offspring (see section 3.2.6). Postnatal effects of gestational and lactational 

exposure included evidence of developmental neurotoxicity, changes in thyroid and reproductive 

hormones, altered lipid and glucose metabolism, and decreased immune function. 

Reproductive Effects

Rat. A two-generation reproductive study was conducted in Crl:CD(SD)IGS VAF rats with five 

groups of 35 rats/sex/group administered 0, 0.1, 0.4, 1.6, or 3.2 mg/kg/day of PFOS by gavage 

for 6 weeks prior to and during mating (Luebker et al. 2005b). Treatment in males continued 

through the cohabitation interval, and females were treated throughout gestation, parturition, and 

lactation.

F0 Generation: Parental animals (F0) were observed twice daily for clinical signs, and body 

weight and food consumption monitored. Two sets of females in each dose group were treated 

and had Caesarean-sections (C-sections) performed on GD 10; others delivered naturally and 

were killed on LD 21. Typical reproductive parameters were monitored in the females. The F0 

male rats were sacrificed and necropsied after the cohabitation interval, with the testes, 

epididymides, prostate, and seminal vesicles weighed. All livers from adults were removed, 

weighed, and examined. Blood samples were collected from five male rats at sacrifice and five 

female rats on LD 21 for pharmacokinetic analysis; livers of pups from the litters of these five 

dams were also collected for analysis.

In the F0 generation male rats, mortality, clinical signs, and mating/fertility parameters were 

unaffected. During pre-mating, decreases in terminal body weight, body weight gain, and food 

consumption occurred at 1.6 and 3.2 mg/kg/day in males. The only effect on weight of the 

Perfluorooctane sulfonate (PFOS) – May 2016 3-62
organs evaluated was a significant reduction in the absolute weight of the seminal vesicles (with 

fluid) and prostate in males administered 3.2 mg/kg/day. In the F0 generation female rats, there 

were no deaths and no effects on the reproductive parameters measured in both dams sacrificed 

on GD 10 and those allowed to deliver naturally. The F0 dams administered ≥ 0.4 mg/kg/day had

localized alopecia during pre-mating, gestation, and lactation, and a decrease in body weight and 

food consumption. 

F1 Generation: The F1 generation pup viability was significantly reduced at 1.6 and 3.2 

mg/kg/day, therefore only the 0.1 and 0.4 mg/kg/day dose groups were carried into the second 

generation. Twenty-five F1 rats/sex/dose were administered 0, 0.1, or 0.4 mg/kg/day of PFOS by 

oral gavage beginning at weaning on post-natal day (PND) 22 and continuing until sacrifice. One 

rat/sex/litter was tested in a passive avoidance paradigm at 24 days of age and one rat/sex/litter 

was evaluated in a water-filled M-maze on PND 70. On PND 28, females were evaluated for 

vaginal patency and on PND 34 males were examined for preputial separation. On PND 90, rats 

were assigned within each dose group to cohabitation, and once confirmed pregnant, the females 

were housed individually. The F1 generation male rats were sacrificed after mating, necropsied, 

and evaluated as described in the F0 generation. All F1 generation females were allowed to 

deliver and were sacrificed and necropsied on LD 21. 

Mortality occurred in the F1 offspring of dams administered 1.6 or 3.2 mg/kg/day. At 

1.6 mg/kg/day, over 26% of the pups were found dead between LDs 2 and 4. At 3.2 mg/kg/day, 

45% of the pups were found dead on LD 1, with 100% dead by LD 2. The dams dosed with 

3.2 mg/kg/day also had a significant increase in stillborn pups and the viability index was 0% at 

3.2 mg/kg/day and 66% at 1.6 mg/kg/day. The lactation index was 94.6% at 1.6 mg/kg/day. At 

3.2 mg/kg/day, there were significant decreases in gestation length and number of implantation 

sites, and reductions in litter size. Statistically-significant decreases in pup body weight were 

also observed at the two highest doses. Additional adverse effects in pups at 3.2 mg/kg/day 

included impacts on lactation (i.e., high number [~ 75%] of pups not nursing and not having milk 

present in the stomach), an increased incidence of stillborn pups, and a high incidence of 

maternal cannibalization of the pups. 

In the F1 generation offspring, pups administered 3.2 mg/kg/day could only be evaluated on 

LD 1 due to the high mortality. All viable pups from the 1.6 mg/kg/day group had significantly 

(p < 0.05 or 0.01) delayed eye opening, pinna unfolding, surface righting, and air righting during 

lactation. No delays were observed in rats administered doses ≤ 0.4 mg/kg/day. Sexual 

maturation was not affected in the 0.1 and 0.4 mg/kg/day groups after weaning. The results from 

the passive avoidance (beginning at 24 days of age) and water maze tests (beginning at 70 days 

of age) for neurobehavioral effects showed no dose-related effects on learning and memory. 

F2 Generation: F1 parental animals displayed no clinical signs or mortality. Food consumption 

was transiently decreased in F1 males, but it was not affected in F1 females. Reproductive 

performance was unaffected in the F1 dams.

All F2 generation pups were sacrificed, necropsied, and examined on LD 21 as previously 

described for the F1 generation pups. In the F2 generation pups, decreases in mean pup body 

weights were observed at 0.1 mg/kg/day on LDs 4 and 7, but mean pup body weights were

similar to controls by LD 14. The pups in the 0.4 mg/kg/day group displayed significant 

decreases in body weight on LDs 7–14; after LD 21, body weights remained lower than controls, 

but were not statistically-significant. No other treatment-related effects were observed.

Perfluorooctane sulfonate (PFOS) – May 2016 3-63
Based on the decreases in body weight gain and food consumption, the LOAEL for both the 

F0 male and female rats was 0.4 mg/kg/day and the NOAEL was 0.1 mg/kg/day. For the F1 rats, 

the NOAEL was 0.4 mg/kg/day and the LOAEL was not identified. For the F1 offspring, the 

LOAEL was 1.6 mg/kg/day based on the significant decrease in the pup viability, pup weight, 

and survival; the NOAEL was 0.4 mg/kg/day. In the F2 generation offspring, the LOAEL was 

0.4 mg/kg/day, based on the significant decreases in mean pup body weight; the NOAEL was 

0.1 mg/kg/day. 

Because of the significant reductions in pup viability observed at 1.6 and 3.2 mg/kg/day, a 

cross-fostering study was conducted as a means of determining whether the effects observed in 

pups were a result of in utero exposure to PFOS or as a result of exposure during lactation 

(Luebker et al. 2005b). Twenty five female Sprague-Dawley rats/group were administered 0 or 

1.6 mg/kg/day PFOS in 0.5% Tween-80 by gavage, beginning 42 days prior to mating with 

untreated males, and continuing throughout gestation until LD 21. Parental females were 

observed twice daily for viability and clinical observations were recorded. Maternal body weight 

and food consumption were recorded. All maternal rats were sacrificed on LD 22 and gross 

necropsy was performed; the number and distribution of implantation sites were recorded. After 

parturition, litters were immediately removed from their respective dams and placed with either a 

control- or PFOS-treated dam for rearing. This cross-fostering procedure resulted in four groups 

as follows:

• Control dams with litters from control dams (negative control). 

• Control dams with litters from PFOS-treated dams (in utero exposure only). 

• PFOS-treated dams with litters from control dams (post-natal exposure only). 

• PFOS-treated dams with litters from PFOS-treated dams (both in utero and post-natal 

exposure). 

There were no mortality or clinical signs associated with treatment in the dams. Mean 

maternal body weight gain and food consumption at 1.6 mg/kg/day was reduced compared to 

controls during premating and continuing throughout gestation, but not lactation. Significant 

reductions in gestation length, the average number of implantation sites, total litter size (live and 

dead), and live litter size were observed for treated dams. 

Live litter sizes were comparable between treated and control groups following crossfostering. However, on LDs 2–4, approximately 19% of the pups in the group exposed 

gestationally and lactationally were either found dead or presumed cannibalized compared to 

1.6% for the negative control. For pups only exposed prenatally, mortality was 9% compared to 

1.1% for those exposed during lactation only. Reductions in pup body weights on LD 1 were 

observed in groups exposed both gestationally and lactationally and in those with gestational 

exposure only. On LDs 4–21, pup body weights were reduced in all exposed groups when 

compared to the negative control (p < 0.05 or 0.01). The greatest deficit in body weight 

compared to controls was the group exposed during both gestation and lactation. 

Sex ratios and the lactation index were comparable among all groups. Electron microscopic 

examination of the livers revealed an increase in the number of peroxisomes in pups from treated 

dams. No significant differences in pup lung histopathology were observed between the negative 

control group and the treated animals. 

Serum PFOS concentrations in untreated dams ranged from below the limit of detection 

(0.05 μg/mL) to 5.34 μg/mL. Serum PFOS concentrations in the pups from the negative controls 

Perfluorooctane sulfonate (PFOS) – May 2016 3-64
were below the limit of detection. Serum PFOS concentrations in the pups from treated dams, 

fostered with untreated dams (in utero exposures) ranged 47.6–59.2 μg/mL. Serum PFOS 

concentrations of treated dams ranged 59.2–157 μg/mL. Serum PFOS concentrations in the pups 

from untreated dams, fostered with treated dams (lactational exposure), ranged from below the 

limit of detection to 35.7 μg/mL. Serum PFOS concentrations in the pups from treated dams, 

fostered with treated dams (in utero plus lactational exposures), ranged 79.5–96.9 μg/mL. These 

data indicate that exposure to PFOS can occur both in utero and via milk from treated dams (3M 

Environmental Laboratory 1999). The accuracy of quantitation for the analyses was ± 30%. 

In conclusion, pups from control dams that were cross-fostered with PFOS-treated dams 

(lactational exposure only) had the same low mortality rate (1.1%) as pups from control dams 

cross-fostered with control dams (1.6%; negative control). Mortality rates in the remaining two 

groups (gestational exposures and gestational plus lactational exposures) were much higher at 

9% and 19%, respectively. Although the study is limited, the data to indicate that reduced pup 

survival is mainly a result of in utero exposure to PFOS and that post-natal exposure via milk in 

conjunction with in utero exposure increases the risk of mortality. In contrast, when the pups 

were nursed by dams that had been exposed there was no significant effect on pup viability even 

though the dams continued to receive PFOS during the period of lactation. 

The dose-response curve for neonatal mortality in rat pups born to PFOS exposed dams and 

the associated biochemical and pharmacokinetic parameters were investigated in a companion 

study (Luebker et al. 2005a). At 6 weeks prior to mating, female Crl:CD(SD)IGS VAF/Plus rats 

were administered 0, 0.4, 0.8, 1.0, 1.2, 1.6, or 2.0 mg PFOS/kg bw/day by oral gavage. Dosing 

continued during the mating interval and through GD 20 for dams assigned to C-section which 

included eight dams in the control, 1.6, and 2.0 mg/kg/day groups, but none from the other dose 

groups. Another group (~ 20 dams per dose group) was allowed to deliver and nurse their pups 

through LD 4. These dams and their pups were sacrificed on LD 5.

The dams in the C-section group were examined for the number of corpora lutea, number of 

implantation sites, live/dead fetuses, and early/late resorptions. Maternal liver weights were 

determined and the maternal organs examined by gross necropsy. Fetuses were pooled by litter 

and mean weight recorded. For the dams that were allowed to deliver, reproductive and fetal 

parameters (Table 3-13) were measured and recorded. Biochemical parameters investigated in 

the dams and litters included: serum lipids, glucose, mevalonic acid, thyroid hormones (TT4 and 

FT4, TT3, and FT3, and TSH), milk cholesterol, and liver lipids. Mevalonic acid was included as it 

is a biomarker of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity. Some 

chemicals that are inhibitors of this enzyme are known to cause developmental effects in rats.

No mortality occurred and no effects were observed in reproductive parameters (corpora 

lutea, implantations, fetuses/litter) in those dams receiving C-sections. Overall absolute body 

weights of the dams were reduced slightly (5%–7% of that for the controls) in the 1.6 and 

2.0 mg/kg/day group dams during gestation; the changes, although slight, were statisticallysignificant. Body weight change was significantly reduced (p < 0.05 or 0.01) during premating at 

2 mg/kg/day and during lactation at ≥ 0.8 mg/kg/day. Food consumption showed a decreasing 

trend with increasing dose during pre-mating, gestation and lactation. For dams allowed to 

deliver, the fertility index, implantations per delivered litter, gestation index, live births, and 

delivered pups/litter were similar between treated and control dams. Based on the decreased 

body weight gain, the LOAEL for the F0 dams was 0.8 mg/kg/day and the NOAEL was 

0.4 mg/kg/day. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-65
Table 3-13. Fertility and Litter Observations in Dams Administered 0 to 2.0 mg 

PFOS/kg/day

0.0 0.4 0.8 1.0 1.2 1.6 2.0

Fertility indexa (%) 96.4 100.0 89.5 95.0 94.7 92.6 96.4

Implantations per 

delivered litter

14.7 ± 2.3 16.2 ± 1.8 15.1 ± 2.2 15.9 ± 2.0 15.3 ± 2.5 14.3 ± 2.1 14.4 ± 1.9

Gestation length 

(days)

22.9 ± 0.3 22.6 ± 0.5 22.5 ± 0.5* 22.4 ± 0.6** 22.3 ± 0.5** 22.0 ± 0.0** 22.2 ± 0.4**

Gestation indexb (%) 100 100 100 100 100 100 100

Delivered pups/litter 13.9 ± 2.6 15.0 ± 2.3 14.5 ± 2.3 15.1 ± 2.3 14.0 ± 2.9 13.6 ± 2.8 13.3 ± 2.5

Live births (%) 98.1 97.0 99.2 99.3 99.6 98.3 99.6

Dams with all pups 

dying on LDs 1–5

0 0 0 1 0 4 14**

Viability indexc (%) 97.3 97.6 93.1 88.8 81.7 49.3** 17.1**

Source: Data from Luebker et al. 2005a 

Notes: a Number of dams pregnant/number of dams mated x 100 b Number of dams with live offspring/number of pregnant dams x 100

c Number of live pups on day 5 postpartum/number of live births x 100

*Statistically-significant at p ≤ 0.05 ** Statistically-significant at p ≤ 0.01

In the group sacrificed on LD 5, a significant decrease in gestation length was observed at 

doses ≥ 0.8 mg/kg. Offspring viability was decreased starting at 0.8 mg/kg and was statisticallysignificant at 1.6 and 2.0 mg/kg. The viability indices were 97.3%, 97.6%, 93.1%, 88.8%, 

81.7%, 49.3%, and 17.1% at 0, 0.4, 0.8, 1.0, 1.2, 1.6, and 2.0 mg/kg, respectively (Table 3-13).

Lipids, glucose utilization, and thyroid hormones were similar or slightly different for treated 

animals compared to controls. In all treated groups, pup body weight at birth on PND 5 was 

significantly less than that of controls. In one male and one female pup at 2.0 mg/kg/day, the 

heart and thyroid were collected and examined microscopically. No lesions were found when 

compared to the controls. The LOAEL for the F1 generation was 0.4 mg/kg/day based on 

decreased body weight and a NOAEL was not identified. 

Several benchmark dose (BMD) estimates (BMD5 and benchmark dose for the lower 95th

percentile confidence bound [BMDL5]) were presented in the study. They were as follows:

• Effect on gestation length: BMD5 = 0.45 mg/kg/day, BMDL5 = 0.31 mg/kg/day. 

• Birth weight effect: BMD5 = 0.63 mg/kg/day, BMDL5 = 0.39 mg/kg/day. 

• Decreased pup weight (day 5): BMD5 = 0.39 mg/kg/day, BMDL5 = 0.27 mg/kg/day. 

• Pup weight gain (day 5): BMD5 = 0.41 mg/kg/day, BMDL5 = 0.28 mg/kg/day. 

• Decreased survival of pups to day 6: BMD5 = 1.06 mg/kg/day, BMDL5 = 0.89 

mg/kg/day. 

The impact of PFOS exposure on the hypothalamic-pituitary-testicular axis in groups of 19 

adult male rats was studied by López-Doval et al. (2014) following dosing at levels of 0, 0.5, 1, 

3, or 6 mg/kg/day by gavage for 28 days. Serum LH, FSH, and testosterone were measured in all 

animals. The histology of the hypothalamus, pituitary gland, and testes were examined by light 

microscopy and by electron microscopy (two animals/dose group using each method). 

Noradrenaline concentration in the anterior and medial hypothalamus and median eminence and 

GnRH in the whole hypothalamus were also determined in five animals/dose group each. For the 

Perfluorooctane sulfonate (PFOS) – May 2016 3-66
remaining five animals/dose group, GnRH gene expression in the hypothalamus and LH and 

FSH gene expression in the pituitary gland were assayed. 

The pituitary gonadotrophic cells examined using an electron microscope showed structural 

abnormalities in all exposed animals, although under light microscopy, the cells at the lowest 

exposure levels appeared normal. At doses ≥ 3 mg/kg/day the most active gonadotrophic cells

were classified as inactive based on the lack of homogeneous endoplasmic reticulum and a welldeveloped Golgi complex. Many cells in the process of degeneration were observed. The 

hypothalamus appeared to be normal at the two lowest doses, but not for doses ≥ 3 mg/kg/day at 

which basophilia, vacuolation, and irregular nuclear borders were seen. Histological 

abnormalities (edema around seminiferous tubules and malformed spermatids) in the testes were 

seen at doses ≥ 1 mg/kg/day. Gene expression for LH and FSH were increased compared to 

controls at the two lowest doses, with subsequent decreases at the higher doses. Serum LH and 

testosterone were significantly decreased and FSH was significantly increased at all doses. Gene 

expression for GnRH was significantly decreased compared to controls at all doses, while GnRH 

levels in the hypothalamus were increased at the high dose. The results are consistent with 

inhibition of the reproductive hypothalamus-pituitary-testicular axis at doses of 0.5 mg/kg/day 

and above. The 0.5 mg/kg/day was the LOAEL based on significantly decreased LH and 

testosterone concentration and increased FSH concentration. The authors stated that the various 

biochemical changes observed are linked and could be due to PFOS antiandrogenic and/or 

estrogenic properties as has been proposed by other researchers.

Developmental Studies 

Rat. Thibodeaux et al. (2003) administered 0, 1, 2, 3, 5, or 10 mg/kg PFOS in 0.5% Tween-20 

daily by gavage during gestational days (GDs) 2–20 to groups of 9–16 pregnant Sprague-Dawley

rats. Maternal weight gain, food and water consumption, and serum clinical chemistries were 

monitored and recorded. Rats were euthanized on GD 21 and uterine contents examined. At 

sacrifice, PFOS levels were measured in the serum and maternal and fetal livers.

Maternal body weight, food consumption and water consumption were significantly 

decreased (p < 0.0001) in a dose-dependent manner at ≥ 2 mg/kg; these data were presented 

graphically. A dose-dependent increase in the serum PFOS concentration was observed with 

liver concentrations approximately four times higher than serum at each dose. Liver weight was 

not affected in the treated rats. Serum chemistry showed significant decreases in cholesterol 

(decrease of 14% compared to controls) and triglycerides (decrease of 34% compared to 

controls) at 10 mg/kg. Serum thyroxine (T4) and T3 were significantly decreased in all treated 

rats when compared to controls, however, a feedback response on TSH was not observed. The 

number of implantations or live fetuses at term was not affected by treatment. There was a 

decrease in fetal weight, and birth defects such as cleft palate, ventricular septal defect, and 

enlargement of the right atrium were observed at 10 mg/kg, but the litter incidence rates were not 

given. Benchmark dose estimates provided for different parameters were as follows:

• Maternal weight reduction BMD5 = 0.22 mg/kg and BMDL5 = 0.15 mg/kg (polynomial 

model). 

• T4 effects on GD 7 BMD5 = 0.23 mg/kg and BMDL5 = 0.05 mg/kg (Hill model). 

• Fetal sternal defects BMD5 = 0.31 mg/kg and BMDL5 = 0.12 mg/kg (logistic model). 

• Fetal cleft palate BMD5 = 8.85 mg/kg and BMDL5 = 3.33 mg/kg (logistic model). 

Perfluorooctane sulfonate (PFOS) – May 2016 3-67
Lau et al. (2003) conducted a companion study to the one by Thibodeaux et al. (2003) in 

order to examine the post-natal impact of in utero exposure to PFOS. Sprague-Dawley rats were 

administered 0, 1, 2, 3, 5, or 10 mg/kg/day PFOS in 0.5% Tween-20 by gavage on GDs 2–21. On 

GD 22, dams were monitored for signs of parturition. The day after parturition was designated 

PND 1. The number of pups per litter, number of live pups in the litter and body weight were 

monitored. All pups were weaned on PND 21 and separated by gender. Additional pregnant rats 

were dosed in the same manner to 0, 1, 2, 3, or 5 mg/kg/day of PFOS, and four pups from each 

litter were sacrificed within 2–4 hours after birth and used to determine blood and liver PFOS 

concentrations and thyroid hormone analysis. The other pups were maintained in the study and 

used for serum collection and thyroid hormone analysis and as the subjects for the

neurobehavioral tests.

In dams administered 10 mg/kg/day, the neonates became pale, inactive, and moribund 

within 30–60 minutes of birth and all died. In 5 mg/kg/day dams, the neonates became moribund 

after 8–12 hours, with 95% dying within the first 24 hours. A 50% fetal mortality was observed 

in dams administered 3 mg/kg/day. Pups from dams treated with 2 mg/kg/day still had 

significant increases in mortality, but those from dams administered 1 mg/kg/day were similar to 

controls (these data were presented graphically). No differences were observed in liver weight in 

the neonates. Pup body weight was significantly decreased in dams administered ≥ 2 mg/kg/day. 

A significant (p < 0.05) delay in eye opening was observed at the same dose in the pups, but no 

differences in onset of puberty were observed at that dose. On PND 2, serum levels of both total 

T4 and free T4 were decreased significantly in all the treated groups, but total T4 recovered to 

levels similar to those of controls by weaning. No changes were observed in serum T3 or TSH.

The thyroid hormone data were presented graphically. Choline acetyltransferase activity in the 

prefrontal lobe, which is sensitive to thyroid status, was slightly reduced in rat pups, but activity 

in the hippocampus was not. T-maze testing did not demonstrate any learning deficiencies.

Based on the findings, the developmental LOAEL is 2 mg/kg/day PFOS for mortality, decreased 

body weight, and a significant 1-day delay in eye opening; the NOAEL is 1 mg/kg/day. The 

authors calculated a BMDL5 for a 6 day survival of 7.02 mg/kg/day. 

Because of the high number of fetal deaths, a sub-study was performed with newborns from 

the 5 mg/kg/day PFOS group wherein they were cross-fostered with control dams immediately 

after parturition. Survival was monitored for 3 days. Cross-fostering the pups from PFOS-treated 

rats (5 mg/kg/day) with control dams did not increase their survival. Conversely, all control pups 

fostered by PFOS treated dams survived, supporting the Luebker et al. (2005a) observations. 

Grasty et al. (2003) exposed pregnant rats to 25 mg/kg/day by gavage for four consecutive 

days during critical windows of development (GDs 2–5, 6–9, 10–13, 14–17, or 17–20) or at 25 

or 50 mg/kg/day on GDs 19–20. Litter size at birth was unaffected, but pup weight was 

decreased in dams exposed for each of the 4 day intervals. Neonates died after dosing in all the 

gestation time periods tested and the number of deaths increased as the time of dosing moved 

closer to the end of gestation period. Mortality was 100% when administered on GD 17–20. 

Most deaths occurred within 24 hours; all pups had died by PND 4. 

In the dams treated only on GDs 19–20, survival of the pups was 98%, 66%, and 3% in the 

control, 25, and 50 mg/kg/day groups on PND 5, respectively. Histological examination of the 

lungs showed differences in the level of maturation between the control and treated pups. 

Grasty et al. (2005) performed a study with a comparable design to their 2003 study in order 

to determine whether delayed lung surfactant maturation was responsible for neonatal deaths.

Perfluorooctane sulfonate (PFOS) – May 2016 3-68
Dams were given 25 or 50 mg/kg/day on GDs 19–20 and offspring evaluated on GD 21 or PND 

0 immediately after birth. The newborns had normal pulmonary surfactant profiles.

Morphometric measurements of the histological lung sections of newborns showed significantly 

(p < 0.05) increased proportion of solid tissue and decreased proportion of small airway space at 

both doses. Co-treatment of dams with dexamethasone or trans-retinol palmitate as rescue agents 

did not improve survival of newborns. These agents are used therapeutically to promote lung 

maturation and surfactant production. 

While lung surfactant maturation did not appear to be the cause of death in the Grasty et al.

(2003) study, some data support effects of PFOS on lung surfactants. Xie et al. (2007, 2010a,

2010b) found that PFOS interacts with dipalmitoylphosphatidylcholine, a major lung surfactant. 

As discussed in the distribution section, Borg et al. (2010) found that radiolabeled PFOS was 

localized in the perinatal lung on GD 18 after it was administered to the dams on GD 16. In these 

same pups, the PFOS levels in the lungs were three-fold higher than what was in the maternal 

blood on PND 1. 

Chen et al. (2012) administered 0, 0.1, or 2.0 mg/kg/day PFOS in 0.05% Tween 80 in 

deionized water by gavage to 10 pregnant Sprague-Dawley rats/group on GDs 1–21. After 

parturition (PND 0), pups were counted and weighed, and 2 male and 2 female pups/litter were 

randomly selected for sacrifice and serum and lung collection. Six offspring/litter were kept until 

PND 21 when they were sacrificed for serum and lung collection. Lung tissue was assessed for

markers of oxidative stress and cytoplasmic protein and examined histologically. The serum and 

lungs were also analyzed for PFOS concentration. Three additional groups of 10 rats/dose were 

treated as described above and the number of deaths/litter recorded until PND 4. 

Body weight of the pups was decreased and postnatal pup mortality (by PND 3) was 

increased significantly (p < 0.05 and 0.01, respectively) at 2.0 mg/kg/day, when compared to the 

control litters. No treatment-related findings were observed at 0.1 mg/kg/day. Postnatal pup 

mortality in the control, 0.1, and 2.0 mg/kg/day groups on PND 3 was approximately 4%, 3%, 

and 23%, respectively. On PND 0, PFOS concentrations in the pup serum (μg/mL) were 

approximately 2 times greater than that found in the pup lung (μg/g) at both 0.1 and 0.2 

mg/kg/day. PFOS concentrations decreased in both the serum and lungs on PND 21, but they 

were still greater compared to serum. PFOS was not detected in control pups at either timepoint.

Histopathological changes observed in pup lungs at 2.0 mg/kg/day on PND 0 included 

marked alveolar hemorrhage, thickened interalveolar septum, and focal lung consolidation. On 

PND 21, the lungs also had alveolar hemorrhage, thickened septum, and inflammatory cell 

infiltration. Numerous apoptotic cells were observed. No abnormalities were observed on 

examination of the control rats or the pups from dams receiving 0.1 mg/kg/day.

An increase in biomarkers associated with oxidative stress was found in pups from the 

2.0mg/kg/day dams. The levels of malondialdehyde (MDA) were 473% and 305% of controls on 

PND 0 and 21, respectively, and glutathione levels and superoxide dismutase (SOD) activity 

decreased at both time-points compared to controls. Cytochrome c release from the inner 

mitochondrial membrane and increased caspase −3, −8, and −9 are biomarkers for apoptotic cell 

death. Each of these factors was significantly increased above that for controls at 2.0 mg/kg/day 

on both PNDs 0 and 21. No changes were observed in the pups from dams receiving 

0.1 mg/kg/day. The NOAEL for histopathological lesions in the lung, oxidative stress, and 

apoptosis was 0.1 mg/kg/day with a LOAEL of 2 mg/kg/day. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-69
Ye et al. (2012) administered 0, 5, or 20 mg PFOS/kg/day by gavage in 0.5% Tween-20 to 

Sprague-Dawley rats on GDs 12–18. Animals were sacrificed on GD 18.5 and the lungs 

analyzed for histological lesions and gene expression profiles. Maternal treatment with PFOS did 

not result in any apparent microscopic changes in the fetal lung. However, gene expression 

profiling showed a dose-dependent upregulated expression of 21 genes at 5 mg/kg/day and of 

43 genes at 20 mg/kg/day. The genes included five PPARα target genes, four of which are 

involved in lipid metabolism; the remaining upregulated genes were involved in significant 

cytoskeletal, extracellular matrix remodeling, and transport and secretion of proteins. 

Lv et al. (2013) investigated the impact of gestational and lactational exposure to PFOS on 

glucose and lipid homeostasis in offspring. Groups of 6 pregnant SPF Wistar rats were given 

doses of 0, 0.5, or 1.5 mg/kg/day dissolved in 0.5% Tween 20 from GD 0 to PND 20. After birth, 

pups were sexed, randomly selected and cross-fostered to insure there were equal pups per litter 

(5 male and 5 female). Pup weights were determined on PNDs 0, 5, 10, 15, and 21. Serum and 

liver samples were also collected at PND 0 and 21 from an unspecified number of pups. The 

remaining pups were maintained for 19 weeks after weaning before final sacrifice. Blood 

samples were collected at 10 and 15 weeks after weaning and examined for fasting serum 

triglycerides, total cholesterol, and fasting blood glucose. A glucose tolerance test was 

administered after a 16-hour overnight fast. The adult pups were sacrificed at 22 weeks of age 

for collection of total liver RNA with analysis for hepatic transcription factor SREBP-1c (sterol 

regulatory element binding protein 1c) as a reflection of lipogenesis linked to glucose. Other 

parameters evaluated included serum insulin, leptin, and adiponectin, and gonadal fat weight, 

pancreatic beta cell area, fat accumulation in the liver as monitored through oil red and 

hematoxylin and eosin staining. 

Body weight of pups from treated dams was significantly reduced (p < 0.05) at birth, 

throughout lactation, and persisted until week 8 post-weaning. A dose-related increase in glucose 

intolerance was observed at 10 weeks post-weaning in pups from treated dams with statistical 

significance attained at 1.5 mg/kg/day. At 15 weeks, pups from the 0.5 mg/kg/day dams had 

significantly increased glucose intolerance, while that for high-dose pups was increased but did 

not attain statistical significance. Fasting glucose levels and serum glycosylated serum protein 

concentrations were similar between pups from treated and control dams at 10 and 15 weeks 

post-weaning. At 18 weeks after weaning, pups from dams given 1.5 mg/kg/day had significant 

increases in serum insulin, insulin resistance index, and serum leptin. Serum adiponectin was 

significantly decreased in pups from both treated groups compared with that of controls. At 

sacrifice, pups from both treated groups had a significant increase in epigonadal fat pad weight, 

and fat accumulation was observed in the liver of high-dose animals. The lowest dose tested 

(0.5 mg/kg/day) was a LOAEL for a significant decrease in birth weight that persisted until week 

8 of the post-lactation period, a significant increase of the epigonadal fat pad weight at 19 weeks 

after weaning, impaired glucose tolerance at 15 weeks after weaning, and decreased serum 

adiponectin. 

Mouse. As described for rats, a two-part developmental study with PFOS was performed in mice 

by Thibodeaux et al. (2003) and Lau et al. (2003). In the first study, groups of 20–29 CD-1 mice 

were administered 0, 1, 5, 10, 15, or 20 mg/kg/day PFOS during GDs 1–17 (Thibodeaux et al.

2003). Maternal weight gain, food and water consumption, and serum clinical chemistries were 

monitored and recorded. Mice were euthanized on GD 18. Parameters as described for the rat 

were also measured in the mice.

Perfluorooctane sulfonate (PFOS) – May 2016 3-70
Maternal body weight gain was significantly decreased at 20 mg/kg/day. Food and water 

consumption were not affected by treatment. Increases in serum PFOS were comparable to the 

rat. PFOS treatment increased (p < 0.05) the liver weight in a dose-dependent manner in the 

mice. T4 was decreased in a dose-dependent manner on GD 6 with statistical significance 

(p < 0.05) attained for the 20 mg/kg/day group; levels of T3 and TSH were not affected by 

treatment. A significant increase in post-implantation loss was observed in animals administered 

20 mg/kg/day, and reduced fetal weight (p < 0.05) was observed from dams in the 10 and 

15 mg/kg/day groups. Birth defects such as cleft palate, ventricular septal defect, and 

enlargement of the right atrium were observed at doses ≥ 10 mg/kg.

In the second part of the developmental study, the post-natal effects of in utero exposure to 

PFOS were evaluated in the mouse (Lau et al. 2003). CD-1 mice were administered 0, 1, 5, 10, 

15 or 20 mg/kg/day of PFOS in 0.5% Tween-20 by gavage on GDs 1–17. 

Most mouse pups from dams administered 15 or 20 mg/kg/day did not survive for 24 hours 

after birth. Fifty percent mortality was observed at 10 mg/kg/day. Survival of pups in the 1 and 

5 mg/kg/day treated dams was similar to controls. A significant (p < 0.0001) increase in absolute 

liver weight was observed at ≥ 5 mg/kg/day. A significant delay in eye opening was observed at 

≥ 5 mg/kg/day. No dose- or treatment-related effects were observed on T4, T3, and TSH levels 

in the pups. The LOAEL for this study in mice was 5 mg/kg/day and the NOAEL was 1 

mg/kg/day. The authors calculated a BLDL5 for survival at 6 days of 3.88 mg/kg/day. 

Ten pregnant ICR mice/group were administered 0, 1, 10, or 20 mg/kg of PFOS daily by 

gavage from GD 1 to GD 17 or 18 (Yahia et al. 2008). Five dams/group were sacrificed on GD 

18 for fetal external and skeletal effects and histological examination of the maternal liver, 

kidneys, lungs and brain; the other five were left to give birth. Body weight, food consumption, 

and water consumption were monitored in the dams. In the dams sacrificed on GD 18, the gravid 

uterus was removed and the number of live/dead fetuses, fetal body weight, and number of 

resorptions were recorded. Four pups/litter were sacrificed immediately after birth for 

examination of their lungs. 

All dams survived and exhibited no clinical signs. A statistically-significant (p < 0.05 or 

p < 0.01) decrease in body weight was observed in the dams administered 20 mg/kg/day 

beginning on GD 10. Water consumption was increased. Maternal absolute liver weight 

increased in a dose-dependent manner, significantly in the 10 (59%) and 20 (60%) mg/kg/day 

groups. 

All neonates in the 20 mg/kg/day dose group were born pale, weak, and inactive, and all died 

within a few hours of birth. At 10 mg/kg/day, 45% of those born died within 24 hours. Survival 

of the 1 mg/kg/day group was similar to that of controls. Neonatal weight was significantly 

decreased at 10 and 20 mg/kg/day. In the fetuses from dams treated with 20 mg/kg/day, there 

were large numbers of cleft palates (98.56%), sternal defects (100%), delayed ossification of 

phalanges (57.23%), wavy ribs (84.09%), spina bifida occulta (100%), and curved fetus 

(68.47%). Similar defects were observed in the fetuses from dams treated with 10 mg/kg/day 

except at a lower incidence. Results from this study are summarized in Table 3-14. 

Histopathological exam showed that all fetuses examined on GD 18 from dams treated with 

20 mg/kg were alive and had normal lung structures but mild to severe intracranial dilatation of 

the blood vessels. Neonates from the 20 mg/kg treated dams had fetal lung atelectasis (partial or 

complete collapse of the lung or a lobe of the lung) with reduction of alveolar space and 

Perfluorooctane sulfonate (PFOS) – May 2016 3-71
intracranial blood vessel dilatation when examined histopathologically. Three neonates from 

each of the five dams treated with 10 mg/kg were examined, and 27% had slight lung atelectasis 

and 87% had mild to severe dilatation of the brain blood vessel. Based on the significant increase 

in liver organ weight, the maternal LOAEL was 10 mg/kg/day and the NOAEL was 

1 mg/kg/day. Based on the abnormalities observed in the fetuses and decreased survival rate, the 

developmental LOAEL was 10 mg/kg/day and the NOAEL was 1 mg/kg/day. 

Table 3-14. Effects Observed in the Mice Administered PFOS from GD 0 to GD 17/18 

Effects Control 1 mg/kg 10 mg/kg 20 mg/kg

Number of dams 5 5 5 5

Total # of fetuses 80 76 79 71

Live fetuses (%) 98.75 ± 1.25 98.88 ± 1.12 96.85 ± 1.97 90.06 ± 3.02*

Body weight of fetuses (g) 1.49 ± 0.01 1.46 ± 0.01 1.41 ± 0.01** 1.10 ± 0.02**

# of fetuses examined 60 44 68 60

Cleft palate (%) 0 1.96 ± 1.96 23.36 ± 8.27** 98.56 ± 1.44**

Sternal defects (%) 0 15.77 ± 0.99** 52.44 ± 2.79** 100**

Delayed ossification of 

phalanges (%)

0 1.96 ± 1.96 4.34 ± 1.80 57.23 ± 9.60**

Wavy ribs (%) 0 0 7.31 ± 0.34* 84.09 ± 2.56**

Curved fetus (%) 3.55 ± 2.11 4.94 ± 2.47 33.38 ± 8.47** 68.47 ± 6.71**

Spina bifida occulta (%) 0 1.96 ± 1.96 23.13 ± 3.94** 100**

Survival rate at PND 4 (%) 98.18 ± 1.82 100 55.20 ± 18.98* 0**

Source: Data from Tables 2-3 in Yahia et al. 2008

Notes: *Statistically-significant difference between control and treated groups, p < 0.05 ** Statistically-significant difference between control and treated groups, p < 0.01

The effects of developmental PFOS exposure during gestation and lactation on glucose 

metabolism in adult CD-1 mice were studied by Wan et al. (2014b). The effects observed are 

consistent with those in Wistar rats (Lv et al. 2013) discussed above. The dams were exposed to 

doses of 0, 0.3, or 3 mg/kg/day dissolved in dimethyl sulfoxide (DMSO) and then in corn oil 

from GD 3 to sacrifice on PND 21. The final concentration of DMSO was < 0.05% throughout 

gestation and lactation. At PND 21, all dams and 2 pups per litter were sacrificed. The remaining 

pups were randomly divided into two groups that were fed with either a standard diet or a high 

fat diet until PND 63. Dams had increased liver weight at 3 mg/kg/day but no differences in 

fasting serum glucose or insulin levels.

There were no significant differences in pup weights at PND 21 although liver weights were 

increased significantly (p < 0.05) at the highest dose for both the male and female pups. Both 

sexes also had significant changes in genes regulating lipids and glucose at the highest dose.

Expression of CYP4A14, lipoprotein lipase, fatty acids translocase, the hepatic insulin receptor, 

and insulin-like growth factor-1 receptor were significantly increased (p < 0.05) in males and 

females from high-dose dams. The genes for prolactin receptor and insulin-like growth factor-1 

were significantly decreased (p < 0.05) in males and females at 3 mg/kg/day. 

When evaluated at PND 63, liver weight in the pups was significantly increased at the high 

dose in males, but not females. In the animals on the standard diet, fasting serum glucose was 

significantly (p < 0.05) higher for males and females at both doses, but fasting serum insulin 

attained statistical significance only for the animals in the highest dose group. There were no 

significant differences in oral glucose tolerance. The HOMA-IR index was increased 

significantly for the high-dose group receiving the standard diet. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-72
The results from the glucose tolerance test (fasting blood glucose levels and blood glucose 

levels over 2 hours following oral glucose challenge) became statistically-significant (p < 0.05) 

at the high dose in both sexes fed high fat diets on PND 63. Fasting serum insulin was 

significantly increased (p < 0.05) at 3 mg/kg/day in males and females on both diets, with the 

effects more pronounced in mice on the high fat diet than in mice on the standard diet. The 

HOMA-IR index was significantly increased (p < 0.01) at both doses for males and females on 

the high fat diet. 

3.2.6 Specialized Developmental/Reproductive Studies

Hormonal Disruption 

Rat. Yu et al. (2009a) fed pregnant adult Wistar rats (n = 20/group) a control diet or a diet 

containing 3.2 mg PFOS/kg feed. Doses to the dams were not calculated, and body weight and 

feed consumption data were not presented. Treatment continued for both groups throughout 

gestation and lactation. Dams were allowed to deliver, and on the day of delivery (PND 0) 

samples were collected from two control litters and two PFOS treated litters. The remaining 

litters were cross-fostered within 12 hours of birth to make the following groups: 

• Litters from control dams fostered by control dams (CC, unexposed control; n = 8). 

• Litters from treated dams fostered by control dams (TC, prenatal exposure; n = 8). 

• Litters from control dams fostered by treated dams (CT, post-natal exposure; n = 8). 

• Litters from treated dams fostered by treated dams (TT, prenatal + postnatal exposure;

n = 10). 

The pups were weaned on PND 21 and then fed the same diet as the foster dam. Pups were 

weighed and sacrificed on PNDs 0, 7, 14, 21, or 35. Serum thyroid hormone analysis was 

performed and included total thyroxine (T4), total triiodothyronine (T3), reverse T3 (rT3), and 

hepatic expression of genes involved in thyroid hormone (TH) transport, metabolism, and 

receptors. The genes associated with thyroid metabolism included type 1 deiodinase (DI01) and 

uridine diphosphoglucuronosyl transferase 1A1 and 1A6 (UGT1A1 and UGT1A6). Those 

associated with thyroid hormone transport included transthyretin (TTR). The genes for the 

thyroid hormone receptors α and β (TRα and TRβ) were also studied.

No mortality or clinical signs were observed in the dams. Body weight in offspring from 

PFOS treated groups did not differ significantly from controls. Liver weights in pups from the 

pre- and postnatal exposure (group TT) were significantly increased on PNDs 21 and 35. As 

observed in other studies, levels of PFOS in the dams and offspring were higher in the liver when 

compared to the serum. The levels of PFOS in both the serum and liver increased with time in 

the pups exposed postnatally (group CT) but decreased with time in those exposed only 

prenatally (group TC). The levels increased in those in the TT group. These results indicate that 

PFOS can be transferred by the placenta and through lactation. 

The total T3 and rT3 were not affected by PFOS treatment of the pups. Compared to 

controls, pups in all treated groups had significant (p < 0.05 or 0.01) decreases in total T4 on 

PNDs 21 and 35, with the response in the CT and TT groups larger than that of the TC group. On 

PNDs 21 and 35, T4 levels were 71%–75% and 63%–64% of controls for the CT and TT groups, 

respectively, compared with 80%–81% of control for the TC group on both days. Pups in the TT 

group (exposed pre- and postnatally) had T4 levels that were significantly lower than the controls

at PND 14. For gene expression, no statistically-significant differences were observed between 

Perfluorooctane sulfonate (PFOS) – May 2016 3-73
litters born to control dams or litters born to treated dams on PND 0. The only significant finding 

in gene expression at the other sacrifice time-points was a significant (p < 0.01) increase (1.5 

times greater than the controls) in TTR on PND 21 in the pups that had been treated both in the 

prenatal and postnatal interval. Lactational exposure appears to be an important contributor to the 

observed thyroid effects given that the serum PFOS levels were higher, and T4 levels lower, in 

the CT group than in the TC group. 

The effects of PFOS on testosterone production by fetal Leydig cells were investigated 

following prenatal exposures (Zhao et al. 2014). Pregnant Sprague-Dawley rats (n = 4) were 

administered PFOS by gavage at doses of 0, 5, or 20 mg/kg/day on GDs 11–19; controls received 

the 0.05% Tween 20 vehicle. Dams were killed on GD 20 and the male pups removed, weighed, 

and measured for length and anogenital distance. The fetal testes were removed for analysis of 

testosterone production, fetal Leydig cell numbers, ultrastructure, and gene and protein 

expression levels. Dams given 20 mg/kg/day had significantly lower body weight and serum 

cholesterol levels on GD 20. Male fetuses had significantly lower body weight at 5 and 

20 mg/kg/day. At 20 mg/kg/day there were significant differences in body length, anogenital 

distance, and testes weight; all measures were lower than those for controls. 

Testicular mRNA levels of growth factors (Kitl), cholesterol transporters (Scarb1 and Star), 

steroidogenic enzymes (Cyp11a1, Cyp17a, and Hsd3b1), junction protein (Trmp2), and LH 

receptor (Lhcgr) were significantly reduced in fetuses from dams given 20 mg/kg/day. Fetuses 

from high-dose dams also had significantly lower testicular testosterone levels, enzyme activity, 

and protein levels for 3β-hydrosteroid dehydrogenase and 17α-hydroxylase/20-lyase. Liver 

cholesterol and testes HDL-cholesterol levels were reduced in fetuses from high dose dams.

Histologically, the number of fetal Leydig cells was reduced and showed a decreased number of 

lipid droplets and features of apoptosis at 20 mg/kg/day. The 5 mg/kg/day dose was a LOAEL 

for effects on male fetal body weight. 

Developmental Neurotoxicity

Rat. Twenty five female Sprague-Dawley rats/group were administered 0, 0.1, 0.3, or 

1.0 mg/kg/day of potassium PFOS by gavage from GD 0 through PND 20 (Butenhoff et al.

2009). An additional 10 mated females/group were used to collect additional blood and tissue 

samples. Offspring were monitored through PND 72 for growth, maturation, motor activity, 

learning and memory, acoustic startle reflex, and brain weight. 

There were no treatment-related effects on the pregnancy rates, gestation length, number of 

implantation sites, number of pups born, sex ratio, birth to PND 4 survival, PND 4–21 survival, 

pup body weights through PND 72, and gross internal findings. Maternal body weight and body 

weight gain during gestation were comparable between the treated and control groups. On LDs 

1–4, dams in the 1.0 mg/kg/day group had slightly, but not significantly, lower weight gain and 

food consumption than those of controls resulting in significantly lower (p < 0.05 or 0.01) 

absolute body weight throughout lactation. Food consumption was transiently decreased 

(p < 0.05 or 0.01) on GDs 6–9 for the 0.3 mg/kg/day group and on GDs 6–12 for the 

1.0 mg/kg/day group. These findings in the treated dams are not considered to be treatmentrelated or adverse. Based on results, the maternal toxicity NOAEL was 1.0 mg/kg/day and the 

LOAEL could not be determined. 

No treatment related effects were observed on functional observational battery assessments 

performed on PNDs 4, 11, 21, 35, 45, and 60. Male offspring from dams administered 0.3 and 

Perfluorooctane sulfonate (PFOS) – May 2016 3-74
1.0 mg/kg/day had statistically-significant (p < 0.05) increases in motor activity on PND 17, but 

this was not observed on PND 13, 21 or 61. No effect on habituation was observed in the 0.1 and 

0.3 mg/kg/day males or in the 1.0 mg/kg/day females. On PND 17, males at 1.0 mg/kg/day 

showed a lack of habituation as evidenced by significantly (p < 0.05) increased activity counts 

for the sequential time intervals of 16–30, 31–45, and 46–60 minutes. The normal habituation 

response is for motor activity to be highest when the animals are first exposed to a new 

environment and to decline during later exposures to the same environment as they have learned 

what to expect. There were no effects in males or females on acoustic startle reflexes or in the 

Biel swimming maze trials. Mean absolute and relative (to body weight) brain weight and brain 

measurements (length, width) were similar between the control and treated animals. Based on the 

increased motor activity observed reflecting decreased habituation, the LOAEL for 

developmental neurotoxicity in male rats was 1.0 mg/kg/day and the NOAEL was 

0.3 mg/kg/day. 

Y. Wang et al. (2015) examined the effects of PFOS on spatial learning and memory 

following pre- and post-natal exposure. Pregnant Wistar rats were administered PFOS in the 

drinking water at 0, 5, or 15 mg/L beginning on GD 1 and continuing through lactation. Doses to 

the animals were not calculated, and body weight and water consumption data were not 

presented. Doses were estimated as 0, 0.8, or 2.4 mg/kg/day using subchronic values for female 

Wistar rats from USEPA (1988). Maternal serum levels in the treated groups were 25.7 and 

99.3 μg/mL, respectively, on PND 7 and 64.3 and 207.7 μg/mL, respectively, on PND 35. On 

PND 1 pups were cross-fostered to establish groups for unexposed controls, only prenatal 

exposure, only post-natal exposure, and continuous exposure. After weaning, pups were given 

the same treated or control water as their foster dam. Three pups per group were sacrificed on 

PNDs 7 and 35 for measurement of protein and RNA levels in the hippocampus. On PND 35, 

8–10 pups per group were tested in the Morris Water Maze which consisted of one day of visible 

platform tests, seven days of hidden platform tests, and a probe trial 24 hours after the last 

hidden platform test. 

Offspring survival on PND 1 was significantly reduced from high-dose dams before crossfostering; survival on PND 5 was not given. On water maze testing day 1, swimming speed and 

the time to reach the visible platform were similar between all treated and control groups.

Thereafter, escape latency was significantly increased for all treated groups on one or more 

testing days. The most pronounced and significant effect was in pups exposed prenatally from 

dams given 15 mg/L and cross-fostered to control dams. Similar trends were observed for escape 

distance. During the probe trial for memory testing, pups continuously exposed pre- and postnatally to 15 mg/L spent less time in the target quadrant than the unexposed controls but 

statistical significance was not achieved as consistently as that for the group exposed only during 

gestation. Protein levels of growth-associated protein-43, neural cell adhesion molecule 1, nerve 

growth factor, and brain-derived neurotrophic factor were significantly decreased in the 

hippocampus on PND 35, especially in pups exposed prenatally to 15 mg/L and cross-fostered to 

control dams. 

Ten pregnant Sprague-Dawley rats/group were administered 0, 0.1, 0.6, or 2.0 mg/kg/day of 

PFOS in 0.5% Tween 80 by oral gavage from GD 2 to GD 21 (Zeng et al. 2011). On GD 21, 

dams were monitored for parturition and the day of delivery was designated PND 0. On PND 0, 

five pups/litter were sacrificed and the trunk blood, cortex, and hippocampus were collected for 

examination. Astrocyte activation markers, glial fibrillary acidic protein (GFAP) and S100 

calcium binding protein B, which are associated with morphological changes inside the cell, 

Perfluorooctane sulfonate (PFOS) – May 2016 3-75
were evaluated with immunohistochemistry. The other pups were randomly redistributed to dams 

within the dosage groups and allowed to nurse until PND 21, when they were sacrificed with the 

same tissues collected as described for PND 0. PFOS concentration in the hippocampus, cortex, 

and serum increased in a dose-dependent manner, but overall was lower in all tissues on PND 21 

than on PND 0.

The number of GFAP positive cells was significantly increased in the hippocampus and 

cortex of offspring from treated dams on PND 21. The protein levels of GFAP in PND 21 

offspring were also increased in the hippocampus and cortex on Western Blot tests. The S100 

calcium binding protein B was increased in the offspring’s hippocampus and cortex on PND 21 

in those from dams treated with 0.6 and 2.0 mg/kg/day. 

In other tests, PFOS increased the mRNA expression of two inflammatory cytokines, 

interleukin 1 beta (IL-1β) and tumor necrosis factor-α(TNF) The expression of IL-1β and TNF-α 

was significantly increased compared to controls in all treated offspring in the hippocampus on 

PND 0 and in those from dams administered ≥ 0.6 mg/kg on PND 21. In the cortex, IL-1β and 

TNF-α were only significantly increased in the 0.6 mg/kg group and 2.0 mg/kg group, 

respectively, on PND 0. On PND 21 in the cortex, IL-1β was increased at ≥ 0.6 mg/kg and TNFα was increased in the high dose group. 

To determine the mechanisms leading to the inflammatory effect after PFOS exposure, 

mRNA levels of three pro-inflammatory transcription factors in both brain tissues were 

examined. The greatest increase was observed in the hippocampus on with a significant increase 

in activation protein-1 (AP-1) in all dose groups and an increase in nuclear factor-ĸB (NF-ĸB) 

and cAMP response element-binding protein at ≥ 0.6 mg/kg groups at PND 0. Two synaptic 

proteins, synapsin 1 (Syn 1) and synaptophysin (Syp) were also affected; Syn 1 was decreased 

with PFOS exposure primarily in the hippocampus. Syp was decreased in the hippocampus, but 

increased in the cortex.

Mouse. Fuentes et al. (2007) treated 8–10 pregnant Charles River CD-1 mice/group to 0 or 

6 mg/kg/day of PFOS dissolved in 0.5% Tween-20 daily by gavage on gestation days (GDs) 

12–18. After treatment, mice were either left alone or restrained (immobilized) three times per 

day for 30 minutes to induce maternal stress. Maternal body weight and food and water 

consumption were monitored. At birth, the length of gestation, number of live/dead pups, and 

sex/weight of pups were recorded.

During the post-natal period, the body weight of the pups was recorded, landmarks for 

development were monitored, and neuromotor maturation tests (i.e., surface righting reflex, 

forelimb grip strength) were conducted. At 3 months of age, the pups were tested in open-field 

and rotarod tests to further assess development. The PFOS treatment had no effect on maternal 

body weight or food/water consumption. On PNDs 4 and 8, pups from dams treated with 

6 mg/kg of PFOS had reduced body weight, as well as delayed (p < 0.05) eye opening, pinna 

detachment, and surface righting reflex. Female pups from dams exposed to 6 mg/kg of PFOS 

and stressed by immobilization exhibited reduced open-field activity. No differences in activity 

were observed for male pups and rotarod performance was not affected in any group by PFOS 

alone or combined with maternal stress.

Ten-day old male neonatal Naval Medical Research Institute (NMRI) mice (4–7/group) were 

exposed once to 0, 0.75, or 11.3 mg/kg bw of PFOS by oral gavage (Johansson et al. 2008). 

Spontaneous behavior (locomotion, rearing, and total activity) and habituation were examined in 

Perfluorooctane sulfonate (PFOS) – May 2016 3-76
the mice at 2 and 4 months old. Behavior was tested in an automated device equipped with 

horizontal infrared beams. Motor activity was measured during a 60-minute period divided into 

three 20-minute sessions. Locomotion, rearing, and total activity were recorded.

No effects were observed on body weight. At 2 months old, mice exposed to 0.75 and 

11.3 mg/kg bw of PFOS exhibited significant (p ≤ 0.01) decreases in locomotion, rearing, and 

total activity during the first 20 minutes compared to controls. After 60 minutes, activity was 

significantly increased in the 11.3 mg/kg bw dose group when compared to controls. The 

expected habituation response is for the highest activity pattern to occur in the first 20-minute 

period not the last period. The same trend was observed at 4 months in the mice exposed to 

11.3 mg/kg bw. At 4 months the responses in the 0.75 mg/kg bw dose group were similar to the 

controls. Overall, a single PFOS treatment on PND 10 affected habituation even up to 4 months 

of age for mice in the high dose group (11.3 mg/kg/day). The LOAEL was 0.75 mg/kg based on 

decreased locomotion, rearing, and total activity in 2 month old mice. 

Johansson et al. (2009) administered a single oral dose of 0 (3 litters) or 11.3 mg/kg (four 

litters) to NMRI male mice (10 days old). The exact number of male mice in each litter was not 

provided. Sacrifice occurred 24 hours after treatment and the brain was dissected. The cerebral 

cortex and hippocampus were homogenized to determine if PFOS affected the protein levels of 

calcium/calmodulin-dependent protein kinase II (CaMKII), growth-associated protein-43 (GAP43), synaptophysin, and tau, which are all proteins involved in neuronal survival, growth, and 

synaptogenesis change during the brain growth spurt. 

There were no clinical signs of acute toxicity, and no treatment-related body weight 

differences. The CaMKII and GAP-43 protein levels in the hippocampus were both increased in 

the PFOS treated males; levels were increased 57% (p < 0.001) and 22% (p < 0.01), respectively, 

when compared to controls. Protein values in the cerebral cortex were similar between the 

control and treated mice. Synaptophysin protein levels were increased significantly (p < 0.001; 

48%) in the hippocampus and (p < 0.01; 59%) in the cerebral cortex of the treated mice. The tau 

protein levels in the cerebral cortex were increased significantly (p < 0.05; 80%) in treated 

animals compared to controls. Overall, the study indicates that a one-time treatment with 

11.3 mg//kg PFOS had a significant effect on the neuronal proteins evaluated. 

Tissue and Metabolic effects

Zeng et al. (2014) examined cardiac mitochondria mediated apoptosis in weaned rats 

exposed by way of their dams (10 per dose group) to 0, 0.1, 0.6, or 2 mg/kg/day in 0.05% Tween 

80 by gavage on GDs 2–21. The pups were sacrificed at the end of the lactation period. Trunk 

blood and the heart were recovered. Apoptotic cells in the heart tissue from six animals per dose 

group were measured using a Terminal deoxynucleotidyl transferase dUTP nick end labeling 

(TUNEL) staining assay by an individual pathologist blinded to the exposure group. The 

apoptosis index was recorded as percent apoptotic cells per 1,000 cells in the same section.

PFOS exposure was associated with a dose dependent increase in the percentage of TUNEL 

positive nuclei (p < 0.05). The 0.6 mg/kg/day dose was the LOAEL and the 0.1 mg/kg/day dose 

the NOAEL. The researchers found that biomarkers for apoptosis were supportive of the TUNEL 

results. The expression of BCL2-associated X protein and cytochrome c were upregulated and 

bcl-2 downregulated. The concentration of caspase 9 was significantly increased above the 

control levels at all doses and caspase 3 levels were significantly increased for all but the lowest 

dose level. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-77
3.2.7 Chronic Toxicity 

Only a single chronic exposure study in animals is available (Thomford 2002/Butenhoff et al.

2012). It is the long term component of the Seacat et al. (2002) subchronic study reported in 

section 3.2.3. Sprague-Dawley Crl:CD (SD)IGS BR, rats (n = 40–70) were dosed using a PFOS

containing diet for up to 105 weeks. Five per sex per dose group were sacrificed at 4 and 14 

weeks as described earlier. Treatment resulted in decreased body weight, with increased liver 

weight with hepatocellular hypertrophy. A satellite group of animals received 20 ppm of the 

PFOS containing diet for 52 weeks, followed by the control diet until sacrifice at week 106. 

The animals received dietary levels of 0, 0.5, 2, 5, or 20 ppm PFOS as the potassium salt. 

Corresponding PFOS doses were 0, 0.024, 0.098, 0.24, and 0.984 mg/kg/day, respectively, for 

males and 0, 0.029, 0.120, 0.299, 1.251 mg/kg/day, respectively, for females. Five animals/sex in 

the treated groups were sacrificed during week 53 and liver samples were obtained for 

mitochondrial activity, hepatocellular proliferation rate, and determination of palmitoyl-CoA 

oxidase activity; liver weight was recorded. The results from the 4-week and 14-week sacrifices 

(Seacat et al. 2002) from this study are provided in sections 3.2.2 and 3.2.3, respectively. Serum 

samples were collected at weeks 27 and 53 from 10 rats/sex/dose group and were examined for 

clinical effects associated with systemic toxicity; liver samples were obtained during and at the end 

of the study for determination of PFOS concentration. Data on chronic effects were not reported 

for the recovery group. The concentration of PFOS in serum was measured at weeks 4, 14, and 

105. In males the serum levels decreased between week 14 and 105 by 50% for all but the 0.5 ppm 

group where the decrease in serum concentration was larger. A serum measurement was available 

at 53 weeks for the high dose males and was comparable to the value at 14 weeks. In females 

serum levels serum levels remained relatively constant at 14 and 105 weeks. In both males and 

females the concentrations in the liver were lower at 105 weeks than they were at 14 weeks.

The clinical serum observations for ALT at 53 weeks were consistent with those at 14 weeks 

in demonstrating significant (p < 0.05) increases for the high dose males but not females. At 

week 27, ALT was increased for high-dose males, but did not attain statistical significance. For 

males at 53 weeks in the 0, 0.5, 2, 5, and 20 ppm groups, ALT values were 54 ± 66, 62 ± 52, 

40 ± 7.5, 44 ± 8.3, and 83 ± 84 IU/L, respectively. The large SDs were the result of high values 

in one animal in each of the control and 0.5 ppm groups and two animals in the 20 ppm group. 

Thus, some animals may be more sensitive to liver damage as a result of exposure than others. 

AST levels were not increased for either sex. Serum blood urea nitrogen (BUN) was 

significantly (p ≤ 0.05) increased at 20 ppm for males and females at weeks 14, 27, and 53 and in 

5 ppm males and females at 27 and 53 weeks. The males in the 2 ppm group also had a 

significant (p ≤ 0.05) increase in BUN at 53 weeks. These data were presented graphically in 

Butenhoff et al. (2012). 

Nonneoplastic lesions in the liver are shown in Table 3-15. At sacrifice, males at 2 ppm had a 

significant (p < 0.05) increase in hepatocellular centrilobular hypertrophy. In the males and 

females at 5 and 20 ppm, there were significant (p < 0.05) increases in centrilobular hypertrophy, 

centrilobular eosinophilic hepatocytic granules (females only), and centrilobular hepatocytic 

vacuolation (males only). At the high dose, there was a significant increase in the number of 

animals with single cell hepatic necrosis in both males and females at 53 weeks. Necrosis in the 

recovery animals was comparable to the controls.

Perfluorooctane sulfonate (PFOS) – May 2016 3-78
Table 3-15. Incidence of Nonneoplastic Liver Lesions in Rats

(Number Affected/Total Number)

Lesion

0 ppm

0 mg/kg/day (d)

0.5 ppm

0.024 mg/kg/d

2.0 ppm

0.098 mg/kg/d

5.0 ppm

0.242 mg/kg/d

20 ppm

0.984 mg/kg/d

Males

Centrilobular hypertrophy 0/65 2/55 4/55* 22/55** 42/65**

Eosinophilic granules 0/65 0/55 0/55 0/55 14/65*

Vacuolation 3/65 3/55 6/55 13/55** 19/65**

Single cell necrosis 5/65 4/55 6/55 5/55 14/65*

Females

0 mg/kg/d 0.029 mg/kg/d 0.120 mg/kg/d 0.299 mg/kg/d 1.251 mg/kg/d

Centrilobular hypertrophy 2/65 1/55 4/55 16/55** 52/65**

Eosinophilic granules 0/65 0/55 0/55 7/55** 36/65**

Single cell necrosis 7/65 6/55 6/55 6/55 15/65*

Source: Data from Thomford 2002/Butenhoff et al. 2012

Notes: *Significantly increased over control: p < 0.05 ** Significantly increased over control: p < 0.01.

No effects were observed on hepatic palmitoyl-CoA oxidase activity or increases in 

proliferative cell nuclear antigen (PCNA) at weeks 4 and 14 or bromodeoxyuridine at week 53. 

PFOS was identified in the liver and serum samples of the treated animals and trace amounts 

were identified in the control animals. The LOAEL at termination for male rats was 2 ppm 

(0.098 mg/kg/day) and for female rats was 5 ppm (0.299 mg/kg/day) based on the liver 

histopathology. The NOAEL for the males was 0.5 ppm (0.024 mg/kg/day) and 2 ppm 

(0.120 mg/kg/day) for females. Additional details from the study in regard to carcinogenicity are 

provided in section 3.2.8. 

Survival was not affected by PFOS administration. Males and females administered 20 ppm 

had statistically-significantly decreased mean body weight compared to controls during weeks 

9–37 and 3–101, respectively, but was similar to controls by week 105. The females at 20 ppm 

had decreased food consumption during weeks 2–44. At the week 14 and 53 sacrifices, absolute 

and relative liver weights were significantly increased at 20 ppm in males and relative liver 

weight was increased at 20 ppm in females. At week 53, liver weight data were given only for 

the control and 20 ppm groups such that a dose-response could not be evaluated. 

3.2.8 Carcinogenicity

Rat. Tumor data were collected as part of the chronic study (Thomford 2002/Butenhoff et al. 2012) 

described above. The tumor results are provided in Table 3-16. A significant positive trend 

(p = 0.0276) was noted in the incidence of hepatocellular adenoma in male rats. This was 

associated with a significant increase (p < 0.0456) in the high-dose group (7/60, 11.7%) over the 

control (0/60, 0%). No hepatocellular tumors were observed in the recovery group exposed for 52 

weeks and sacrificed at 106 weeks. Liver tumors were observed in males at all doses (0%, 6%, 6%, 

2%, and 11.7%). In females, significant positive trends were observed in the incidences of 

hepatocellular adenoma (p = 0.0153) and combined hepatocellular adenoma and carcinoma 

(p = 0.0057) at sacrifice. Here too, the response was not linear to dose with sequential values of 

0%, 2%, 2%, 2%, and 8.3%. These cases were associated with significant increases in the highdose group 5/60 (p = 0.0386; 8.3%) for adenomas and 6/60 (p = 0.0204; 10%) for combined 

adenomas and carcinomas compared to the control. The female recovery group had 2/20 liver 

adenomas (5%) and no carcinomas. The presence of increased levels of ALT in the males of the 

Perfluorooctane sulfonate (PFOS) – May 2016 3-79
high dose group at 14, 27, and 53 weeks supports hepatic tissue damage with compensatory repair 

as a probable a possible mode of action (MOA) for the liver tumors. In all cases the SDs about the 

means are broad suggesting that some animals could be less resilient than others to the liver effects.

Table 3-16. Tumor Incidence (%)

Tumors

0 ppm

0 mg/kg/d

0.5 ppm

0.024 mg/kg/d

2.0 ppm

0.098 mg/kg/d

5.0 ppm

0.242 mg/kg/d

20 ppm

0.984 mg/kg/d

20 ppm

recovery

1.144 mg/kg/day

Males

Liver

hepatocellular adenoma+ 0 (0/60) 6.0 (3/50) 6.0 (3/50) 2.0 (1/50) 11.7* (7/60) 0 (0/40)

Thyroid

follicular cell adenoma 5.0 (3/60) 10.2 (5/49) 8.0 (4/50) 8.2 (4/49) 6.8 (4/59) 23.1* (9/39)

follicular cell carcinoma 5.0 (3/60) 2.0 (1/49) 2.0 (1/50) 4.1 (2/49) 1.7 (1/59) 2.6 (1/39)

combined 10.0 (6/60) 12.2 (6/49) 10.0 (5/50) 10.2 (5/49) 8.5 (5/59) 25.6 (10/39)

Females

0 mg/kg/d 0.029 mg/kg/d 0.120 mg/kg/d 0.299 mg/kg/d 1.251 mg/kg/d 1.385 mg/kg/d

Liver

hepatocellular adenoma+ 0 (0/60) 2.0 (1/50) 2.0 (1/49) 2.0 (1/50) 8.3* (5/60) 5.0 (2/40)

hepatocellular carcinoma 0 (0/60) 0 (0/50) 0 (0/49) 0 (0/50) 1.7 (1/60) 0 (0/40)

combined+ 0 (0/60) 2.0 (1/50) 2.0 (1/49) 2.0 (1/50) 10.0* (6/60) 5.0 (2/40)

Thyroid

follicular cell adenoma 0 (0/60) 0 (0/50) 0 (0/49) 4.0 (2/50) 1.7 (1/60) 2.5 (1/40)

follicular cell carcinoma 0 (0/60) 0 (0/50) 0 (0/49) 2.0 (1/50) 0 (0/60) 0 (0/40)

follicular cell combined 0 (0/60) 0 (0/50) 0 (0/49) 6.0* (3/50) 1.7 (1/60) 2.5 (1/40)

C-cell adenomas 20.0 (12/60) 12.0 (6/50) 12.2 (6/49) 16.0 (8/50) 8.3* (5/60) 15.0 (6/40)

C-cell Carcinomas 0 (0/60) 2.0 (1/50) 0 (0/49) 0 (0/50) 0 (0/60) 2.5 (1/40)

C-cell combined 20.0 (12/60) 14.0 (7/50) 12.2 (6/49) 16.0 (8/50) 8.3* (5/60) 17.5 (7/40)

Mammary

Fibroma/Adenoma 33.3 (20/60) 54.0* (27/50) 39.6 (19/48) 48.0 (24/50) 18* (11/60) 37.5 (15/40)

Adenoma 11.7 (7/60) 12.0 (6/50) 10.4 (5/48) 14.0 (7/50) 6.7 (4/60) 10.0 (4/40)

Combined adenomas 38.3 (23/60) 60.0* (30/50) 45.8 (22/48) 52.0 (26/50) 25.0* (15/60) 40.0 (16/40)

carcinoma 18.3 (11/60) 24.0 (12/50) 31.3 (15/48) 22.0 (11/50) 23.3 (14/60) 10.0 (4/40)

Source: Data from Thomford 2002/Butenhoff et al. 2012.

Notes: +Significant positive trend.

* Significantly increased over the control: p < 0.05

** Significantly increased over the control: p < 0.01.

There were cases of thyroid follicular cell adenomas and carcinomas in both the male and 

female rats but no pattern of dose-response or significant increases compared to controls. The 

incidence of thyroid follicular cell adenomas in the male recovery group was increased 

significantly (p = 0.028) over controls (23.1% vs 5%). The incidence of combined thyroid 

follicular cell adenoma and carcinoma in the recovery group males (10/39, 25.6%) did not attain 

statistical significance compared to that of the control group (6/60, 10%). The males that were 

continually dosed for 105 weeks had a much lower adenoma incidence than the recovery group 

(6.8% versus 23.1%). In no case were thyroid tumors determined to be a cause of death. 

In females, there was a significant increase (p = 0.0471) for combined thyroid follicular cell 

adenoma and carcinoma in the mid-high (5.0 ppm) group (3/50, 6%) compared to the control 

group (0/60, 0%). The incidence data for thyroid follicular tumors lacked dose-response. C-cell 

thyroid adenomas had a higher incidence than the follicular cell tumors in female rats. The 

Perfluorooctane sulfonate (PFOS) – May 2016 3-80
highest incidence was in the control group (20%); there was a lack of dose-response across 

groups (8%–18%). As was the case with the combined adenomas and carcinomas, the C-cell 

tumors were not identified as a cause of death.

There was a high background incidence in mammary gland tumors in the female rats, 

primarily combined fibroma adenoma and adenoma (25%–60%), but the incidence lacked doseresponse for all tumor classifications. Significant (p = 0.0318) increases combined mammary 

fibroadenoma/adenoma (30/50, 60%; p = 0.0318) were observed in the low–dose (0.5 ppm) 

group compared to the respective controls but there was a lack of dose response with the high 

dose group having a lower incidence (25%) than the controls (38%). Mammary gland 

carcinomas also lacked dose-response and had a relatively comparable incidence across dose 

groups including the controls. 

Mouse. The mouse model C57BL/6J-Min/+ for intestinal neoplasia was used to study the 

obesogenic and tumorigenesis effects of PFOS following in utero exposure (Ngo et al. 2014). 

The C57BL/6J-ApcMin/+ mouse has a heterozygote mutation in the tumor suppressor gene 

adenomatous polyposis coli (Apc), and is therefore a sensitive model in which to test whether 

chemicals can affect intestinal tumorigenesis. Wild-type females (Apc+/+), mated to heterozygous 

males (ApcMin/+), were given 0, 0.01, 0.1, or 3 mg/kg/day by gavage on GDs 1–17 and allowed to 

litter naturally. Offspring with ApcMin/+ genotype were terminated at 11 weeks of age for study 

of intestinal tumorigenesis and obesogenic effect while wild-type (Apc+/+) offspring were

sacrificed at 20 weeks to assess any obesogenic effect at an older age. In the treated groups, 

whole litter loss occurred in 6/16, 10/28, and 7/14 dams, respectively, compared with 2/22 

controls; the timing of loss, late, or early gestation, was not stated. No clinical signs of toxicity 

were observed during dosing and maternal body weight was similar between treated and control 

groups. For offspring of either genotype, terminal body weight, liver and spleen weights, and 

plasma glucose were not affected by in utero exposure. PFOS did not increase intestinal 

tumorigenesis in susceptible, ApcMin/+, offspring. 

3.3 Other Key Data

3.3.1 Mutagenicity and Genotoxicity

Results of genotoxicity testing with PFOS are summarized in Tables 3-17 and 3-18. PFOS 

was tested for mutation in the Ames Salmonella/Microsome plate test and in the D4 strain of 

Saccharomyces cerevisiae (Litton Bionetics, Inc. 1979). It was also tested in a SalmonellaEscherichia coli/Mammalian-microsome reverse mutation assay with and without metabolic 

activation (Mecchi 1999), in an in vitro assay for chromosomal aberrations in human whole 

blood lymphocytes with and without metabolic activation (Murli 1999), and in an unscheduled 

DNA synthesis assay in rat liver primary cell cultures (Cifone 1999). In all these assays, PFOS 

was negative. In an in vivo mouse micronucleus assay, PFOS did not induce any micronuclei in 

the bone marrow of Crl:CD-1 BR mice (Murli 1996). A 50% w/w solution of the 

diethanolammonium salt of PFOS in water (T-2247 CoC) was also tested to determine whether 

induction of gene mutation in five strains of S. typhimurium and in S. cerevisiae strain D3 would 

take place with and without metabolic activation (Simmon 1978). The results were negative.

Governini et al. (2015) collected semen samples from 59 healthy-nonsmoking patients 

attending a Center for Couple Sterility at the University in Siena, Italy. The subjects were 

divided into those that were normozoospermic (13) and those that were oligoasthenoteratoPerfluorooctane sulfonate (PFOS) – May 2016 3-81
zoospermic (46). PFOS was present in 25% of the seminal plasma samples and 84% of the serum 

samples. Conversely PFOA was present in 75% of the seminal plasma samples and only 16% of 

the blood samples. Sperm were evaluated for the presence of aneuploidy and diploidy, and sperm 

DNA was evaluated for fragmentation using the TUNEL assay. The frequencies of aneuploidy 

and diploidy were significantly greater in the PFAS positive samples than in the PFC negative 

samples (p < 0.001 and p < 0.05, respectively) suggesting the possibility for errors in cell 

division. The levels of fragmented chromatin were significantly increased (p < 0.001) for the 

PFC positive group compared with the PFAS negative group.

Table 3-17. Genotoxicity of PFOS in vitro

Species

(test system) End-point With activation Without activation Reference

Salmonella strains and D4 

strain of Saccharomyces 

cerevisiae

Gene mutation negative negative Litton Bionetics, Inc. 

1979

Salmonella strains and 

Escherichia coli WP2uvr

Gene mutation negative negative Mecchi 1999

5 strains of S. typhimurium 

and S. cerevisiae strain D3

Gene mutation negative negative Simmon 1978

Human lymphocytes Chromosome 

aberrations

negative negative Murli 1999

Hepatocytes from Fisher 

344 male rats

DNA synthesis negative Cifone 1999

Table 3-18. Genotoxicity of PFOS in vivo

Species

(test system) End-point Results Reference

Crl:CD-1 BR mice Presence of micronuclei in bone marrow negative Murli 1996

3.3.2 Protein binding

The ability of PFOS to bind to serum proteins for distribution is discussed in section 2.2. PFC 

protein binding can also impact cellular function in cases where the proteins in question are 

transporters (serum albumin and fatty acid binding protein), enzymes (lysine decarboxylase), or 

membrane receptors such as members of the PPAR family and thyroid hormone receptors. The 

mechanistic studies of the membrane receptors are described in section 3.3.4. 

Ren et al. (2015) examined the relative binding affinities of 16 perfluoroalkyl compounds for 

the human thyroid hormone receptor’s α ligand binding domain (TRα-LBD) using a fluorescence 

competitive binding assay. Solutions of 1μmol TRα-LBD were prepared in DMSO. Changes in 

TRα-LBD tryptophan fluorescence after binding to 10 μmol T3 in the absence or presence of the 

PFAS was used to determine the binding properties of the PFAS. IC50 values were calculated by 

linear extrapolation between two responses located in the vicinity of a 50% inhibition level. All 

the PFAS had a lower affinity for the receptor than T3, but the binding affinity of PFOS was 

greater than that for PFOA and the other sulfonates tested. The IC50 value for PFOS was 

16 μmol, compared with 0.3 μmol for T3.

Perfluorooctane sulfonate (PFOS) – May 2016 3-82
Lysine decarboxylase is a key enzyme involved in the production of cadaverine from the 

amino acid lysine. S. Wang et al. (2014) studied the impact of a series of 16 PFAS on the activity 

and conformation of this enzyme because of its involvement in growth and development. The 

interaction assays were carried out in vitro using a fluorescent probe to measure enzyme activity. 

The impact of a PFAS on enzyme activity caused a decrease in fluorescence that represented 

enzyme inhibition. Varying the PFAS concentrations provided the data for determining 

inhibition constants for each compound tested. Members of the sulfonate family were stronger 

inhibitors than the carboxylic acids, and enzyme inhibition increased as did the length of the 

carbon chain. Only the 4, 6, and 8 carbon members of the sulfonate family were tested. 

Circular dichroism was used as a tool for determining changes in enzyme conformation in the 

presence of the tested PFAS (S. Wang et al. 2014). PFOS caused a greater change in enzyme 

conformation than PFOA. Cellular cadaverine production was decreased indicating the potential 

for PFOS to alter metabolism by way of enzyme inhibition as a consequence of its protein 

binding properties. To date there has been scant investigation of PFOS or other PFASs as 

enzyme inhibitors. 

An in vitro study of the impact of PFOS (and other PFASs) on the conformation of several 

proteins (BSA, ovalbumin, and β-galactosidase) in solution found that the denaturing effect of 

the PFAS depended on the amino acid composition and conformation of the protein as well as 

the individual PFAS (Ospinal-Jiménez and Pozzo 2012). The PFOS concentration (1 millimole 

[mmol]) was higher than one would expect in vivo because the study was designed to examine 

denaturing potential. 

Enzymes targeted by PFOS can vary. Molecular docking analysis of PFOS’s potential to bind 

with and change the activity of enzymes along metabolic pathways associated with its critical 

effects could provide important insights related to toxicity. The importance of the S. Wang et al. 

(2014) and Ospinal-Jiménez and Pozzo (2012) studies are the evidence they produced showing 

that the protein binding properties of a PFAS can impact the conformation, thereby possibly 

changing activity. 

3.3.3 Immunotoxicity

Human–in vitro. In a pilot study, Brieger et al. (2011) examined the effects of PFOS on human 

leukocytes. Peripheral blood mononuclear cells (PBMC) were obtained from 11 voluntary 

donors (n = 6 females, 5 males). The mean plasma concentrations of PFOS were 0.004, 0.0028, 

and 0.0055 μg/mL for all, female, and male volunteers, respectively. PBMCs were incubated 

with varying concentrations of PFOS followed by assays for cell viability, proliferation, and 

natural killer (NK) cell activity. The human promyelocytic leukemia cell line, HL-60, was also 

used in cell viability and monocyte differentiation assays. The various components of the assays 

employed and the results are identified as follows:

1. In the cell viability assay, the PBMCs and HL-60 cells were incubated with 0–125 μg/mL 

of PFOS for 24 hours. Viability was determined after incubation by measuring neutral red 

uptake. No significant reduction of viability was observed up to 125 μg/mL; however, the 

highest concentration for PFOS could not be evaluated due to limited solubility. 

Therefore, 100 μg/mL was the highest concentration used thereafter. 

2. In the proliferation assay, the PBMCs were incubated with 0, 1, 10, or 100 μg/mL of 

PFOS for 24 hours; labeled with 6-carboxyfluorescein succinimidyl ester (CFSE); 

stimulated with concanavalinA, a T-cell mitogen (ConA, 5 μg/mL to half of all samples); 

Perfluorooctane sulfonate (PFOS) – May 2016 3-83
and incubated for an additional 72 hours. Proliferation was slightly increased at 

100 μg/mL and slightly reduced with the presence of ConA, but neither effect was 

statistically-significant. 

3. For the NK cell assays, PBMCs were incubated with 0, 1, 10, or 100 μg/mL of PFOS for 

24 hours followed by incubation for 3 hours with K562 target cells (12.5:1 ratio) labeled

with CFSE. K562 cells are a chronic myelogenous leukemia cell line known to be 

susceptible to NK cell induced cytotoxicity. PFOS significantly (p < 0.001) reduced NK 

cell cytotoxicity to K562 cells by 32% at 100 μg/mL. 

4. In the monocyte differentiation assay, HL-60 cells were incubated with 0, 1, 10, or 

100 μg/mL of PFOS for 72 hours. Half of each sample was stimulated with 25 nmol 

calcitrol, 1α,25-dehydroxyvitamin D3 (1,25D3) 24 hours into the incubation period. 

Expression of CD11b and CD14 were measured as markers of differentiation. In the 

presence of 1,25D3, PFOS had no significant effect on the percentage of HL-60 cells 

expressing CD11b and CD14. No differences in monocyte differentiation were observed 

in the absence of 1,25D3. 

5. Whole blood was incubated with 0–100 μg/mL of PFOS in the presence or absence of 

25 μg/mL phytohemagglutinin (PHA), a T-cell cytokine secretion stimulator, for 

48 hours. Lipopolysaccharide (LPS, 0 or 250 ng/mL), a monocyte stimulator, was added 

to whole blood incubated with 0.1–100 μg/mL of PFOS either 4 or 24 hours prior to the 

end of the 48 hour incubation period. Release of the cytokines TNF-α and IL-6 from 

T-cells or monocytes was quantified. Cytokine release from T-cells was not affected by 

PFOS. PFOS significantly (p < 0.001) reduced the release of the pro-inflammatory 

cytokine TNF-α after monocyte LPS stimulation. The authors also looked at the 

correlation between basal PFOS concentration of the blood donor and cytokine release. A 

significant association was observed between PFOS concentration and the release of 

LPS-induced IL-6 by peripheral monocytes. 

This study suggests some effects on immunity in humans; however the sample size used is 

small and the concentrations at which effects were observed are much higher than the levels of 

PFOS in human blood samples. 

Midgett et al. (2014) examined the effects on IL-2 production using stimulated cultured 

human Jurkat cells and CD4+ T cells recovered from 11 healthy volunteers. Both cell types were 

stimulated with PHA/phorbal myristate acetate (PMA) or anti-CD3 to produce IL-2 and 

incubated with 0–100 μg PFOS/mL; separate experiments were conducted with human Jurkat 

cells in the presence or absence of a PPAR antagonist. Cell viability was not affected in either 

cell type up to and including the highest concentration of PFOS. In the human Jurkat cells 

stimulated with PHA/PMA a concentration of 10 μg/mL was a NOEL and 50 μg/mL a LOEL for 

inhibition of IL-2 production in the absence and presence of a PPARα inhibitor. In the presence 

of anti-CD3, the NOEL was 1 μg/mL and the LOEL 5 μg/mL. In primary human CD4+ T cells 

stimulated with PHA/PMA, the NOEL was the 10 μg/mL concentration and the LOEL 

100 μg/mL for inhibition of IL-2 production. A decrease in T cell IL-2 production is a 

characteristic associated with autoimmune disorders, suggesting that this population could be 

sensitive to PFOS exposures. However, the authors caution that the results from the in vitro 

studies do not reflect any potential decrease in circulating PFOS as the result of protein binding 

to albumin or other serum proteins. In this study the observed IL-2 effects in the Jurkat cells 

were demonstrated to be independent of PPARα activation as the inhibition was similar with and 

without the PPAR antagonist. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-84
Mouse. Qazi et al. (2009a) administered diets containing 0, 0.001%, 0.005% , 0.02% (40 mg/kg 

bw/day), 0.05% (100 mg/kg bw/day), 0.1%, 0.25%, 0.5%, or 1% PFOS and 0.02% PFOA for 

10 days to 4–6 six male (6–8 weeks old) C57Bl/6 mice/group. Doses for all dietary levels were 

not presented by the study authors. PFOS and PFOA were dissolved in 20 mL of acetone prior to 

being mixed with the chow and then dried to allow the odor of the acetone to dissipate prior to 

administration. At the end of 10 days, mice were bled for analysis of PFOA and PFOS, and then 

killed. Weights were obtained for the thymus, spleen, liver, and epididymal fat. The number of 

thymocytes and splenocytes were measured and checked for viability. Histology was also 

performed on the thymus and spleen. 

The mice treated with dietary concentrations of > 0.02% (~ 40 mg PFOS/kg bw/day) PFOS 

exhibited pronounced weight loss (> 20%), a decrease in food consumption (> 40%), and 

lethargy and were withdrawn from the experiment after 5 days of exposure. The author stated 

that this was not due to taste aversion since it is also observed when PFOS is administered 

intraperitoneally or subcutaneously. The background levels of PFOS and PFOA were both 

similar in the control mice; however, after administration of 0.02% in the diet, the serum level of 

PFOS was approximately twice that of PFOA. Only the animals treated with 0.02% PFOS had a 

significant decrease in total body weight and in the wet weights of the thymus, spleen, and 

epididymal fat pads compared to the controls. However, all three doses resulted in a significant 

increase (p < 0.05 or 0.01) in liver weight, compared to controls. Similar findings slightly more 

pronounced were observed in mice administered PFOA. The mice administered 0.02% of PFOS 

demonstrated a marked decrease in the total number of thymocytes (84% of controls) and 

splenocytes (43% of controls), and they had thymocytes and splenocytes that were reduced in 

size. Finally, in the mice administered 0.02% PFOS or PFOA, the thymic cortex was small and 

devoid of cells and the cortical/medullary junction was not distinguishable. No obvious 

histological differences in the spleen of the mice administered any dose of PFOA or PFOS were 

observed. 

Qazi et al. (2009b) also performed a study to see if exposure to PFOS influenced the cells of 

the innate immune system. Four male C57Bl/6 mice per dose were exposed to rat chow 

supplemented with 0%, 0.001%, or 0.02% PFOS for 10 consecutive days. A second, similar 

study was performed to determine if the PFAS exposure influenced innate immune response to 

bacterial LPS. Mice were exposed to PFOS as described above. On day 10, some mice were 

injected intravenously with 0.1 mL sterile saline containing 300 μg LPS (E. coli), while others 

received vehicle only. In the first study, mice were bled directly after the 10 day exposure and in 

the second study mice were bled 2 hours after administration of LPS. The spleen, thymus, 

epididymal fat, liver, and peritoneal and bone marrow cells were collected.

No effects were observed in any of the mice exposed to 0.001% PFOS. Exposure to 

0.02% PFOS caused an increase in liver weight and a decrease in the weight of other organs and 

overall body weight. Food consumption in these mice was also decreased 25% when compared 

to control mice. The total intake of PFOS over the 10 days was approximately 6 mg 

(0.6 mg/kg/day), and the total concentration of PFOS in the serum was 340 ± 16 μg/mL (ppm). 

The overall total number of white blood cells and lymphocytes were decreased while the 

neutrophil counts were similar to controls. The number of macrophages in the bone marrow was 

increased but not those of the peritoneum and spleen. Cells isolated from the peritoneal cavity 

and bone marrow, but not spleen, of mice exposed to the high level of PFOS had enhanced levels 

of the pro-inflammatory cytokines, TNF-α, and IL-6 in response to stimulation by LPS. The 

levels of these cytokines in the serum were not elevated. This study indicates that PFOS can have 

Perfluorooctane sulfonate (PFOS) – May 2016 3-85
an effect on the innate immune responses in mice following a 10-day exposure to about 

0.6 mg/kg/day. 

In Qazi et al. (2010), male C57BL/6 (H-2b

) mice (n = 7) were administered PFOS in the diet 

at 0.005% (w/w) for 10 days to determine the effect on the histology and immune status of the 

liver. There was no effect on body weight, food intake, thymus, spleen or fat pad mass, serum 

levels of ALT or AST, hematocrit, hemoglobin, or the numbers of thymocytes and splenocytes. 

However, the liver mass was increased 1.6-fold when compared to untreated controls, and 

hypertrophic hepatocytes surrounded the central vein. No necrosis was noted. Total serum 

cholesterol was decreased and there was a moderate increase in serum ALP. At the end of the 

study, the total mean serum PFOS concentration for four mice was 125.8 μg/mL. PFOS 

increased only one type of intrahepatic immune cells (TER119+). The treated mice also had 

lower levels of the hepatic cytokines, TNF-α, IFN-γ, and IL-4, when compared to the control 

mice and an increase in hepatic erythropoietin. The IgM response of the intrahepatic B and T 

cells was normal. 

Peden-Adams et al. (2008) gave PFOS in Milli-Q water containing 0.5% Tween 20, daily by 

gavage for 28 days to five adult male and female B6C3F1 mice/group. Equivalent daily PFOS 

doses to the seven dose groups were 0, 0.00017, 0.0017, 0.0033, 0.017, 0.033, and 

0.166 mg/kg/day, respectively. Animals were euthanized at the end of treatment. Various 

immune parameters, including lymphocytic proliferation, NK cell activity, lysozyme activity, 

antigen specific IgM production, lymphocyte immunophenotypes, and serum PFOS 

concentrations were determined after exposure.

Survival, behavior, body weight, spleen, thymus, kidney, gonad and liver weights, and 

lymphocytic proliferation were not affected by treatment. Lysozyme activity increased 

significantly in females, but not males, at 0.0033 and 0.166 mg/kg/day, respectively compared to 

the control group; however, the response as not dose-related. NK cell activity was increased 

significantly (p ≤ 0.05) 2- to 2.5-fold in males at 0.017, 0.033, and 0.166 mg/kg/day, but was not 

affected in any of the females. Splenic T-cell immunophenotypes were slightly affected in 

females, but they were significantly altered in males treated with ≥ 0.0033 mg/kg/day. In both 

genders, thymus cell populations were less sensitive to PFOS. Male thymic T-cell 

subpopulations were not affected with PFOS treatment and in females were increased only at 

0.033 and 0.166 mg/kg/day. 

Because IgM suppression can result from effects on both T- and B-cells, antibody production 

was measured in response to sheep red blood cells (SRBC) (T-dependent) and a trinitrophenyl 

(TNP) LPS conjugate (T-independent). The SRBC plaque-forming response was suppressed and 

demonstrated a dose-response in males beginning at 0.0017 mg/kg/day and in females at 

0.017 mg/kg/day. In males it was suppressed by 52%–78% and females by 50%–74%. For 

evaluation of T-independent (TI) responses, an additional group of female mice was treated with 

0 or 0.334 mg/kg/day of PFOS orally for 21 days and challenged with a TI antigen TNP-LPS 

conjugate. Serum TNP-specific IgM titers were decreased after the TNP-LPS challenge with 

serum levels of TNP-specific IgM significantly suppressed by 62% compared with controls. 

Based on the IgM suppression observed in both the T-cell independent and dependent tests, 

humoral immune effects can be attributed to B-cells, rather than T-cells. Serum levels of PFOS 

were similar between males and females. Based on the results the LOAEL in mice is 

0.0017 mg/kg/day in males and 0.017 mg/kg/day in females. The NOAELs are 

0.00017 mg/kg/day in males and 0.0033 mg/kg/day in females. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-86
Potassium PFOS suspensions were made with deionized water with 2% Tween 80 and 

administered orally by gavage at doses of 0, 5, 20, or 40 mg/kg bw to twelve male (8–10 weeks 

old) C57BL/6 mice/group daily for 7 days (Zheng et al. 2009). Food consumption and body 

weight were measured daily for 7 days. Mice were bled on the eighth day (24 hours after the last 

treatment) and subsequently sacrificed. The blood was analyzed for corticosterone and PFOS 

concentration. Spleen, thymus, liver, and kidneys were collected and weighed, and the spleen 

and thymus were processed into suspensions to look at functional immune endpoints and T-cell 

immunophenotype determinations. 

Starting on about day 3, mean body weights were significantly decreased compared to the 

controls for the 20 and 40 mg/kg bw/day doses. However, food consumption decreased with 

treatment. At the end of treatment, the body weight, splenic, and thymic weights were all 

decreased at 20 and 40 mg/kg bw/day, compared to the controls. Liver weight was increased by 

34%, 79%, and 117% over controls at 5, 20, and 40 mg/kg bw/day, respectively. A dosedependent increase in PFOS was observed in the serum samples; levels in the controls were 

below the limit of detection. Serum corticosterone levels increased significantly in mice treated 

with doses ≥ 20 mg/kg/day. Splenic and thymic cellularity were significantly decreased 

(p ≤ 0.05) at 20 and 40 mg/kg bw/day; cellularity in the spleen and thymus in the mice 

administered 40 mg/kg/day was decreased by 51% and 61%, respectively, compared to the 

control mice. To determine population changes in functional cell types of spleen and thymic 

lymphocytes, CD4/CD8 marker analysis was performed. Significant decreases in CD4+ and 

CD8+ cells were observed in both the spleen and thymus in the mice administered 

≥ 20 mg/kg/day PFOS. 

A lactate-dehydrogenase release assay was performed to determine NK cell activity. The 

average NK-cell activity was decreased at 20 and 40 mg/kg/day compared to control mice, 

18.04 ± 1.42 and 13.08 ± 1.11, respectively compared to 50.33 ± 4.08 in controls. No numeric 

data were provided for the 5 mg/kg/day group. Treatment in all groups of mice resulted in a 

significant suppression of the plaque-forming cell response after 7 days of treatment; results 

were 63%, 77%, and 86% that of controls at 5, 20, and 40 mg/kg bw/day, respectively. Based on 

the increase in liver weight and the suppression of the plaque-forming cell response, the LOAEL 

was 5 mg/kg/day in mice and the NOAEL could not be determined. 

In order to observe chronic effects of immunotoxicity, adult male C57BL/6 mice (10/group) 

were administered 0, 0.008, 0.083, 0.417, 0.833, and 2.083 mg/kg/day PFOS with 2% Tween 80 

in de-ionized water daily by gavage for 60 days (Dong et al. 2009). Parameters similar to those 

described above for Zheng et al. (2009) were measured.

At sacrifice, mice treated with ≥ 0.417 mg/kg/day had significantly lower body weight 

compared to the control mice, as well as significant decreases in spleen, thymus and kidney 

weight. Food consumption in the study was decreased in mice at 0.833 and 2.083 mg/kg/day. 

Liver weight was increased significantly in all dose groups compared to controls, 5.17 ± 0.12 g 

(control), 5.21 ± 0.17 g, 5.78 ± 0.13 g, 6.67 ± 0.11 g, 8.17 ± 0.21 g, and 11.47 ± 0.12 g, 

respectively. Serum corticosterone was decreased in mice at the two higher doses. As in the 

shorter-term study, thymic and splenic cellularity was decreased in a dose-dependent trend, with 

significant decreases observed in mice receiving ≥ 0.417 mg/kg/day. The CD4/CD8 marker 

analysis performed on splenic and thymic lymphocytes demonstrated that the numbers of T cell 

and B cell CD4/CD8 subpopulations were decreased starting at 0.417 mg PFOS/kg/day. Splenic 

NK cell activity was increased significantly compared to controls (31.14 ± 1.93%) in the mice at 

0.083 mg/kg/day (45.43 ± 4.74%) with significant marked decreases at 0.833 mg/kg/day 

Perfluorooctane sulfonate (PFOS) – May 2016 3-87
(20.28 ± 2.51%) and 2.083 mg/kg/day (15.67 ± 1.52%). The SRBC-specific IgM plaque forming 

cell response showed a dose-related decrease with statistical significance at 0.083 mg/kg/day and 

higher. Based on the findings in the 60 day study, the NOAEL was 0.008 mg/kg/day and the 

LOAEL was 0.083 mg/kg/day. The serum concentration at the LOAEL was 7.132 mg/L. 

Keil et al. (2008) treated pregnant C57BL/6N females (bred with male C3H/HeJ mice) with 

PFOS to evaluate developmental immunity in their inbred B6C3F1 offspring. The females 

(10–12/group) were administered 0, 0.1, 1, or 5 mg/kg of PFOS in 0.5% Tween-20 by gavage 

daily on gestation days (GDs) 1–17. Pups remained with the dam for approximately 3 weeks 

with immunotoxicity evaluations performed at 4 and 8 weeks. Body weight was recorded for

dams during the study and pups after delivery. Organ weights (spleen, liver, thymus and uterus) 

from the pups were recorded at sacrifice. Only litters with 6 to 9 pups were retained for the 

immunotoxicity studies. One male and one female were selected from the retained litters (total of 

6 male and 6 female pups) for testing of the immunotoxicity parameters; positive controls were 

included for each assay.

NK cell activity was not altered in any pups at 4 weeks old. At 8 weeks, however, NK cell 

activity was suppressed in males treated with 1 and 5 mg/kg/day (42.5% and 32.1% decreases 

compared to controls, respectively) and in females at 5 mg/kg/day (35.1%, compared to 

controls). The positive control for NK cell activity produced the appropriate response. The 

plaque-forming cell response for SRBC IgM production by B cells was only assessed at 8 weeks 

and was significantly suppressed in the 5 mg/kg/day males (53%); no effect was observed in the 

females. The only significant differences in lymphocyte immunophenotypes was a 21% decrease 

in absolute numbers of B220+ cells in 4-week-old females in the 5 mg/kg/day group compared to 

controls; this effect was not observed at 8 weeks. The other significant change was a 25% 

decrease in CD3+ and 28% decrease in CD4+ thymocytes at 5 mg/kg/day in males at the 8-week 

evaluation. Functional responses (nitrite production) to LPS and interferon-gamma by peritoneal 

macrophages were not affected with treatment in the 8-week-old mice (not evaluated at 

4 weeks). Based on the changes in the immunotoxicity parameters evaluated, the LOAEL in 

mice is 1 mg/kg/day in males and 5 mg/kg/day in females. The NOAEL is 0.1 mg/kg/day in 

males and 1 mg/kg/day in females. 

Guruge et al. (2009) administered 0, 5, or 25 μg/kg PFOS (0, 0.005, or 0.025 mg/kg, 

respectively) in 30 female B6C3F1 mice/group for 21 days and then exposed them intranasally to 

100 plaque forming units (pfu; in 30 μL of phosphate buffered saline) influenza A virus 

suspension. Mice were observed for 20 days past inoculation. Concentrations of PFOS in the 

plasma, spleen, thymus, and lung all showed a dose-dependent increase; however, there was not 

a significant change in body or organ weights (spleen, thymus, liver, kidney, and lung) of the 

treated mice compared to the controls. Survival rate was significantly decreased in the mice at 

25 μg/kg PFOS after viral exposure. Survival rate in the mice on day 20 was 46% in the controls 

and 17% in the high-dose group. 

The four studies in mice discussed above examined NK cell activity and SRBC response.

The results from those studies are summarized in Table 3-19. Three of the studies showed effects 

on SRBC response, NK cell activity, or both at the same dose that caused increased liver weight. 

Based on the limited evidence, neither response appeared more sensitive than the other. The NK 

cell activity was enhanced at very low PFOS doses, while it was depressed at higher doses. The 

animal studies indicate that females are less susceptible to impacts on NK cell activity and the 

SRBC response than males. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-88
Table 3-19. Summary of SRBC and NK Cell Findings in Mice after PFOS Exposure

Study Strain

Duration

Days

SRBC NK Cell activity

Increased 

Liver wt.

NOAEL

mg/kg/day

LOAEL

mg/kg/day

NOAEL

mg/kg/day

LOAEL 

mg/kg/day

LOAEL

mg/kg/day

Dong et 

al. (2009)

C57BL/6 

(M)

60 0.008 0.083 (↓) 0.008 0.083 (↑)

0.833 (↓)

0.083

Keil et al. 

(2008)

B6C3F1

(M, F pups)

GDs 1–17

Dams 

only*

1 (M)

5 (F) 

5 (↓M)

- 

-

1 (F) 

1 (↓M)

5 (↓F) 

5 (M at 4 

wks only)

PedenAdams et 

al. (2008) 

B6C3F1 

(M, F) 

28 0.00017 (M)

0.0033 (F) 

0.0017(↓M)

0.017 (↓M) 

0.0033 (M)

0.166 (F) 

0.017 (↑M) None

Zheng et 

al. (2009) 

C56BL/6 

(M)

7 5 (↓) 5 20 (↓) 5

Notes: Direct dosing of the dams did not continue during the lactation period. The immune system response was evaluated in 

pups at 4 and 8 weeks. Effects were seen at 8 weeks but not at 4 weeks.

The direct ion of the arrow indicates if the change from control was an increase or a decrease.

M = male; F = female

3.3.4 Physiological or Mechanistic Studies of Noncancer Effects

Hormone Disruption 

Martin et al. (2007) administered 10 mg PFOS/kg to adult male Sprague-Dawley rats (n = 5) 

for 1, 3, or 5 days by oral gavage and determined the impact of PFOS on hormone levels. Blood 

was collected via cardiac puncture, and the serum was analyzed for cholesterol, testosterone, free 

and total T4, and total T3. RNA extracted from the livers was used for gene expression profiling, 

genomic signatures, and pathway analyses to determine a mechanism of toxicity. 

Following a 1-day, 3-day, and 5-day dose, a significant decrease (p < 0.05) was observed in 

total T4 (~ decrease of 47–80%) and free T4 (~ decrease of 60–82%). The total T3 was only 

significantly deceased after day 5 (decrease of ~ 23%). Serum cholesterol was significantly 

decreased (p < 0.05) after dosing for 3 and 5 days. Serum testosterone was similar to controls at 

all timepoints. PFOS treatment caused hepatomegaly, hepatocellular hypertrophy, and 

macrovesicular steatosis. Genes associated with the thyroid hormone release and synthesis 

pathway included type 3 deiodinase DIO3, which catalyzes the inactivation of T3 and type 1 

deiodinase DIO1, which deiodinates prohormone T4 to bioactivate T3. Treatment with PFOS 

caused significant (p < 0.05) DIO1 repression and Dio3 induction only on day 5. 

Chang et al. (2007) investigated whether the decrease of FT4 often observed in animals upon 

PFOS exposure was due to competition for carrier protein binding interference. The study used 

equilibrium dialysis radioimmunoassay (ED-RIA) for FT4 measurements in in vitro and in vivo 

protocols. PFOS did not decrease serum total thyroxine (TT4) or FT4 at concentrations up to 

200 μmol in vitro. Female rats administered three daily 5 mg/kg oral doses of PFOS also had no 

changes to serum TSH and FT4 when checked by ED-RIA. However, FT4 was significantly 

decreased in the animals when measured with two analog methods, chemiluminescence 

immunoassay and simple RIA. The authors suggested that further testing for thyroid hormone 

parameters should use a reference method such as ED-RIA for determining serum FT4 as analog 

methods may falsely appear to decrease free thyroid hormones.

Perfluorooctane sulfonate (PFOS) – May 2016 3-89
Chang et al. (2008) investigated whether PFOS competed with thyroxine for serum binding 

proteins in rats. Three different experimental designs were employed. In the first part, five to 

fifteen female Sprague-Dawley rats/group were given either a single oral dose of vehicle (0.5% 

Tween 20 in distilled water; three groups) or 15 mg potassium PFOS/kg bw (three groups) 

suspended in vehicle. Rats were killed at 2, 6, and 24 hours post-dosing, and blood samples were 

obtained. Serum FT4, total thyroxine (TT4), triiodothyronine (TT3), reverse triiodothyronine 

(rT3), and thyrotropin were measured at each timepoint. TSH was measured only at the 6 and 24 

hour timepoints. PFOS concentrations in the blood and liver were also measured along with 

hepatic transcripts for UDP-glucuronosyltransferase 1A (UGT1A) (involved in glucuronidation 

and T4 turnover) and malic enzyme (ME). ME activity is an indicator for tissue response to 

thyroid hormone. 

Serum TT4 decreased significantly (p < 0.05) compared to controls after 2 hours (decrease of 

24%), 6 hours (decrease of 38%), and 24 hours (decrease of 53%). The TT3 and rT3 only 

decreased significantly at the 24-hour time-point, while FT4 was increased significantly at 2 and 

6 hours (68% and 90% over control, respectively) before becoming similar to that of controls at 

the 24-hour time-point. Serum levels of PFOS were significantly (p < 0.05) higher than controls 

at all time-points (control: < LOQ; treated: 37.28, 66.90, and 61.58 μg/mL at 2, 6, and 24 hours, 

respectively). A similar trend was observed with the concentration of PFOS in the liver (control: 

< LOQ; treated: 30.60, 44.84, 45.00 μg/g at 2, 6, and 24 hours, respectively). The ME and 

UGT1A mRNA transcripts were significantly increased (p < 0.05) only at the 2 hour time-point, 

compared to controls, and the ME activity was increased significantly only at the 24-hour 

sampling. 

In the second part of the study, Sprague-Dawley rats were injected intravenously with either 

9.3 μCi (females; n = 5/group) or 11 μCi (males; n = 4/group) of 125I-T4 followed by a single oral 

dose of either vehicle or 15 mg potassium PFOS/kg bw. Urine and feces were collected for 24 

hours after administration to determine the 125I elimination. At the end of the 24 hours, the animals 

were killed and liver and serum samples collected. Serum TT4 concentration was decreased by 

55% in the PFOS treated males and females compared to controls. There was also a decrease in 

serum 125I in the treated males. Liver 125I radioactivity decreased by 40% and 30% in males and 

females, respectively, but the urine and feces 125I radioactivity increased, with the males exhibiting 

the most activity. This indicates a loss of thyroid hormones and increased turnover.

In the last part of the study, adult male Sprague-Dawley rats (4–6/group) were administered 

either vehicle only by gavage, 3 mg/kg bw of potassium PFOS suspended in vehicle by gavage, 

10 μg/mL (10 ppm) propylthiouracil (PTU) in drinking water, or 10 ppm PTU in drinking water 

+ 3 mg PFOS/kg bw for 7 consecutive days. PTU is an inhibitor of thyroid hormone synthesis. 

On days 1, 3, 7, and 8, TT4, TT3, and TSH were monitored and on day 8, the pituitaries were 

removed and placed in static culture to assess thyrotropin releasing hormone- (TRH)-mediated 

release of TSH. During the days of dosing with PFOS, TSH levels did not increase, but TT4 and 

TT3 were decreased. Pituitary response to TRH-mediated TSH release was not affected or 

lessened after the PFOS-only administration. 

Results suggest that oral PFOS administration results in a transiently increased tissue 

availability of thyroid hormones, increased turnover of T4, and a reduction in TT4, but PFOS 

administration does not induce a typical hypothyroid state or alter the hypothalamic-pituitarythyroid axis.

Perfluorooctane sulfonate (PFOS) – May 2016 3-90
In the study by Curran et al. (2008) (see section 3.2.2 of this document) where SpragueDawley rats (15/sex/group) were administered 0, 2, 20, 50, or 100 mg PFOS/kg diet for 28 days, 

T4 and T3 levels were decreased. T4 levels were statistically-significantly decreased at ≥ 20 mg 

PFOS/kg diet, when compared to the control levels, in both males and females. T3 levels were 

decreased significantly at ≥ 50 mg/kg diet in the females and 100 mg/kg diet in the males. There 

were no treatment-related changes observed with absolute thyroid weight. 

Yu et al. (2009a) fed adult pregnant Wistar rats (n = 20/group) a control diet or a diet 

containing 3.2 mg PFOS/kg feed. Treatment continued for both groups throughout gestation and 

lactation. Dams were allowed to deliver naturally and on the day of delivery (PND 0), samples 

were collected from two control litters and two PFOS treated litters. Litters were cross-fostered 

to help determine whether PFOS had more effect when administered prenatally, postnatally, or 

both. The total T3 and rT3 were not affected with PFOS treatment in the pups. Pups in all 

groups, except the controls, had significant (p < 0.05 or 0.01) decreases in total T4 on PNDs 21 

and 35. Pups exposed pre- and postnatally were also significantly T4-deficient at PND 14. 

Male Sprague-Dawley rats (8–10/group) were administered 0, 1.7, 5.0, or 15.0 mg/L PFOS 

in drinking water for 91 days (Yu et al. 2009b). At the end of exposure, serum was collected and 

analyzed for total thyroxine (T4), FT4, total triiodothyronine (T3), and TSH. Liver and thyroid 

organ weights were obtained as well. Also measured were messenger RNA (mRNA) levels for 

two isoforms of uridine diphosphoglucuronosyl transferase (UGT1A6 and UGT1A1) and DIO1 

in liver; sodium iodide symporter (NIS), TSH receptor (TSHR), and DIO1 in thyroid; and 

activity of thyroid peroxidase (TPO).

No treatment-related effects were observed on body weight or thyroid absolute and relative 

weight. Absolute and relative (to body weight) liver weights were increased significantly 

(p < 0.05 or 0.01) in the rats administered 5 and 15 mg/L. Levels of the thyroid hormone activity 

measured are in Table 3-20 and show that total T4 decreased in a significant dose-dependent 

manner in the treated rats. Serum FT4 was only decreased at 5 mg/L, total T3 was only increased 

at 1.7 mg/L, and there was no effect on TSH. 

Table 3-20. Thyroid Hormone Levels in PFOS Treated Rats

Dose administered 

mg/L

Total T3

(μg/L)

Total T4

(μg/L)

Free T4 

(pmol/L)

TSH

(IU/L)

PFOS

(mg/L)

0 0.29 ± 0.04 40.9 ± 1.8 19.0 ± 1.3 0.72 ± 0.30 < LOQ

1.7 0.48* ± 0.08 23.9** ± 1.3 16.7 ± 1.4 0.67 ± 0.27 5.0 ± 0.3

5.0 0.23 ± 0.05 16.4** ± 5.4 12.6* ± 1.5 1.12 ± 0.34 33.6 ± 2.1

15.0 0.23 ± 0.03 8.5**± 1.6 17.3 ± 1.1 1.62 ± 0.67 88.2 ± 4.2

Source: Data from Table 3 in Yu et al. 2009b 

Notes: *statistically-significant at p < 0.05 ** statistically-significant at p < 0.01 

LOQ = limit of quantification

Hepatic UGT1A6 was not affected with treatment, but hepatic UGT1A1 mRNA expression 

was upregulated in the rats treated with 5 and 15 mg/L. Exposure to PFOS at ≥ 5 mg/L also 

lowered DIO1 mRNA in the liver when compared to controls. The DIO1 levels in the thyroid 

increased in these same treatment groups by 1.8- and 2.9-fold, respectively, compared to 

controls. PFOS treatment had no effect on NIS, TSHR, or TPO activity.

Perfluorooctane sulfonate (PFOS) – May 2016 3-91
Six female Wistar rats/dose were administered 0, 0.2, 1.0, or 3.0 mg/kg of PFOS by oral 

gavage daily for 5 consecutive days (Yu et al. 2011). Groups of six were also administered 

propylthiouracil at 10 mg/kg or PTU (10 mg/kg) + PFOS (3.0 mg/kg) in the same manner. 

Serum and bile were evaluated for total T4 (TT4), TT3, transthyretin, and thyroglobulin. Serum 

TT4 and TT3 both decreased significantly at 1.0 and 3.0 mg/kg for the TT4 (~ 63.7% and 58.9% 

of controls) and 3.0 mg/kg for the TT3 (~ 62.9% of the control value). The values in bile were 

not affected and were similar to controls. Serum transthyretin and thyroglobulin were also 

similar to controls. As stated earlier (section 2.2.1), Yu et al. (2011) found that liver OATp2 was 

increased significantly (143% compared to controls) in rats at 3.0 mg/kg, indicating that this

transporter may be involved in hepatic T4 uptake and could potentially lead to the decrease 

observed in serum TT3 and TT4. Relative liver weight and absolute and relative thyroid weight 

were all increased significantly with treatment of PFOS, PTU, and PFOS + PTU. In the thyroid, 

PTU had the most effect followed by the PFOS/PTU mixture and then the PFOS alone. In the 

liver, PFOS alone had the most effect.

Ren et al. (2015) examined the comparative agonist and antagonist properties of the PFCs as 

revealed using a T3 cell proliferation assay in GH2 cancer cells. Antagonist activity was 

measured using cell proliferation response in the presence of 0.2 nmol T3 and the PFAS. PFOS 

had the strongest potency as an agonist among the PFAS compounds tested but was still less 

potent than T3. PFOS also upregulated three thyroid hormone response genes and downregulated 

another three, one of those being the fatty acid binding protein gene in tadpoles. Molecular 

docking analysis was used to examine the mode of interaction between the PFOS and the TRαligand binding domain protein. PFOS and T3 both hydrogen bonded with Arg-228, with the 

PFOS sulfonate functional group facing into the pocket and the perfluorinated carbon chain 

oriented towards the exterior of the pocket.

Kjeldsen and Bonefeld-Jørgensen (2013) conducted an in vitro study in an attempt to 

elucidate the mechanisms by which PFAS, including PFOS, affect the estrogen receptor (ER) 

and androgen receptor (AR) transactivity, as well as aromatase activity. Estrogenic and 

antiestrogenic activities were assessed using the stably transfected MVLN cell line carrying an 

estrogen response element luciferase reporter vector. Androgenic and antiandrogenic activities 

were assessed using the Chinese hamster ovary cell line CHO-K1 transiently co-transfected with 

an MMTV-LUC reporter vector and an AR expression plasmid pSVAR0. Effects on aromatase 

activity were assessed using the human choriocarcinoma JEG-3 cell line. PFOS had no effect on 

aromatase activity, but it was cytotoxic at ≥ 1 × 10-4 M. 

In the ER transactivation assay, PFOS was cytotoxic to MVLN cells at concentrations 

≥ 6 × 10-5 M. The half maximal effective concentration (EC50) for PFOS was 2.9 × 10-5 M 

compared with 4.8 × 10-11 M for 17β-estradiol (E2). Co-exposure of cells with E2 and PFOS 

enhanced the E2-induced ER response at the highest non-cytotoxic PFOS concentration. No 

evidence of antagonism was observed. 

In the AR transactivation assay, PFOS was cytotoxic to CHO-K1 cells at concentrations 

≥ 1 × 10-4 M. PFOS did not act as an agonist, however, it elicited a significant (p < 0.05) 

inhibiting effect (76%) on AR function at a relative high test concentration of 5 × 10-5 M.

Co-exposure of cells with dihydrotestosterone and PFOS elicited a significant (p < 0.05) 

concentration-dependent antagonistic effect on DHT-induced AR transactivity; the IC50 was 

4.7 × 10-6 M. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-92
PPAR activity

Studies have been conducted in order to determine if PFOS activates PPARs. The PPARs are 

members of the nuclear hormone receptor superfamily of ligand-activated transcription factors.

These factors can alter gene expression in response to endogenous and exogenous ligands and 

are associated with lipid metabolism, energy homeostasis, and cell differentiation. The three 

types, PPARα, β/δ, or γ, are encoded by different genes, expressed in many tissues, and have 

specific roles during development as well as in the adult (Takacs and Abbott 2007). 

In vitro. Shipley et al. (2004) tested PFOS to determine whether it activated human or mouse 

PPARα in a COS-1 cell-based luciferase reporter trans-activation assay. The COS-1 is a 

fibroblast-like cell line derived from monkey kidney. Concentrations at 8, 16, 32, 64, 125, 250, 

500, and 1000 μmol were tested. The COS-1 cells were transfected with either a mouse or 

human PPARα expression plasmid along with the reporter plasmid, pHD(x3)luc, which has three 

PPAR binding sites that are linked to a minimal promoter controlling the gene for Firefly 

luciferase. Cells were also cotransfected with a plasmid encoding Renilla luciferase to serve as a 

control. A positive control, WY-14,643, was also used. In the experiments, PFOS activated both 

human and mouse PPARα. The highest PFOS-activation was 4- to 6-fold and was similar to that 

obtained with the positive control. The average EC50 was 13 μmol in the mouse and 15 μmol in 

the human PPARα.

Both PFOS and PFOA were tested to determine whether they could activate PPARs in a 

transient transfection cell assay (Takacs and Abbott 2007). The Cos-1 cells were cultured in 

Dulbecco’s Minimal Essential Medium (DMEM) with fetal bovine serum in 96-well plates and 

transfected with mouse or human PPARα, β/δ, or γ reporter plasmids. Transfected cells were 

then exposed to PFOS (1–250 μmol), positive controls (known agonists and antagonists), or 

negative controls (DMEM, 0.1% water and 0.1% dimethyl sulfoxide). The positive control 

agonists and antagonists were WY-14,643 and MK-886, respectively, for PPARα, and 

troglitazone and GW9662, respectively, for PPARγ. Only the agonist L165,041 was used for 

PPARβ/δ. After treatment for 24 hours, activity was measured using the Luciferase reporter 

assay. WY-14,643 was used for mouse and human PPARα, and it exhibited 15- and 1-fold 

increase, respectively over the luciferase response of the negative controls. L165,041 was the 

agonist for mouse and human PPARβ/δ. It exhibited 28- and 13-fold increases in the luciferase 

response, respectively, compared to the negative controls. Finally, troglitazone, the agonist for 

mouse and human PPARγ, increased the luciferase response 3- and 2-fold over the negative 

controls, respectively. The antagonists showed appropriate inhibitory responses with maximum 

inhibition of agonist activity of 90% and 60% for mouse and human PPAR α, respectively, and 

47% and 45% for mouse and human PPARγ.

In this study, PFOS activated the mouse PPARα with a significant (p < 0.01) 1.5-fold 

increase in activity at 120 μmol PFOS, compared to the negative control. PFOS did not 

significantly increase activity in the human PPARα construct. PFOS activated the mouse 

PPARβ/δ but not the human PPARβ/δ construct. It did not activate the mouse or human PPARγ 

construct. Table 3-21 shows summary data. The authors concluded that PFOA activated PPARα 

more than PFOS and that the mouse was more responsive than the human. PFOA and PFOS both 

activated mouse but not human PPARβ/δ, and neither chemical activated human or mouse 

PPARγ.

Perfluorooctane sulfonate (PFOS) – May 2016 3-93
Table 3-21. Summary of PFAS Transactivation of Mouse and Human PPARα, β/δ, and γ

PPAR isoform PFAS Mouse LOECa Human LOECa

α PFOA

PFOS

10 μmol

120 μmol

30 μmol

NAb 

β/δ PFOA

PFOS

40 μmol

20 μmol

NA

NA

γ PFOA

PFOS

NA

NA

NA

NA

Source: Data from Table 1 in Takacs and Abbott 2007

Notes: a LOEC = lowest observed effect concentration; lowest concentration (μmol) at which there was a significant difference 

compared to the negative control (p < 0.05) c NA = not activated

Wolf et al. (2008) tested PFAS, including PFOS, to determine whether mouse and human 

PPARα activity could be induced in transiently transfected COS-1 cell assays. COS-1 cells were 

transfected with either a mouse or human PPAR-α receptor-luciferase reporter plasmid and after 

24-hours were exposed to either negative controls (water or 0.1% DMSO), a positive control 

(WY-14,643), or PFOS at 1–250 μmol. At the end of 24-hours of exposure, the luciferase 

activity was measured. The no observed effect concentration (NOEC) for PFOS was 60 μmol in 

the mouse; the LOEC was 90 μmol (48.4 μg/mL), and the C20max was 94 μmol. The 

corresponding values for humans were: NOEC = 20 μmol, LOEC = 30 μmol (16.2 μg/mL), and 

C20max = 262 μmol. 

Wolf et al. (2012) incubated transfected cells with PFAS at concentrations of 0.5 to 

100 μmol, vehicle (water or 0.1% DMSO as negative control), or with 10 μmol WY-14,643 

(positive control). Assays were performed with three identical plates per compound per species, 

with nine concentrations per plate and eight wells per concentration. Cell viability was assessed 

using the Cell Titer Blue cell viability kit and read in a fluorometer. The positive and negative 

controls had the expected results. All PFAS significantly induced human and mouse PPARα. The 

study also provided the C20max, which was the concentration at which a PFAS produced 20% of 

the maximal response elicited by the most active PFAS. For PFOS, this was 94 μmol in mouse 

PPARα and 262 μmol in human PPARα. For comparison, PFOA was 6 μmol and 7 μmol, 

respectively.

Several studies have suggested that PFOS may target PPARγ and influence metabolism via 

pathways under its control. L. Zhang et al. (2014) examined the direct binding properties of 

PFOS and other PFASs using the ligand binding domain of human PPARγ. Interactions between 

transfected B1.21(DE3) E. coli supported derivation of IC50 values for the different PFAS

examined. The IC50 values were derived using a fluorescence displacement method and 

comparing the results from the tested chemicals with those of decanoic and octanoic acid. The 

PFAS binding increased with carbon chain length (C4 to C11). The authors also examined the 

PFAS binding to the PPARγ ligand binding domain. For compounds with fewer than 11 carbons 

there was a correlation between binding and chain length. The authors interpreted this as an 

indication that hydrophobic interactions between the amino acids of the binding domain and the 

PFAS are responsible for the stability of the complex. PFOA and PFOS induced receptor 

activation to a similar extent, 2.8 and 2.5 times greater than the control, respectively. The authors 

concluded that PFASs induce disruption of lipid homeostasis and inflammation by the PPARγ 

pathway as well as the PPARα pathway. Among the three members of the sulfonate family tested 

(4, 6, and 8 carbons), PFOS displayed the strongest activation potency. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-94
In vivo

Rats. Martin et al. (2007) administered PFOS to male Sprague-Dawley rats by oral gavage at 

doses of 0 or 10 mg/kg/day for 1, 3, or 5 consecutive days. Clinical chemistry, hematology, 

histopathology, and gene expression profiling of the livers from three rats/group were performed. 

Body weight was not affected with treatment, but relative liver weight increased after 5 days of 

treatment. PFOS exhibited peroxisome proliferator-activated receptor alpha agonist-like effects 

on genes associated with fatty acid homeostasis. Exposure also caused down-regulation of 

cholesterol biosynthesis genes. PFOS caused significant DIO1 repression and Dio3 induction on 

day 5 of exposure, which corresponded to decreases of T3 only on day 5 and total and free T4 

decreases. DIO1 deiodinates thyroxine (T4) to bioactivate T3 and Dio3 catalyzes the inactivation 

of T3. PFOS was poorly correlated with peroxisome proliferators in the global gene expression 

patterns and indicated weak matches with hepatotoxicity related signatures and weak correlation 

to PPARα agonist treatment. Expression of HMG-CoA reductase was significantly upregulated, 

and cholesterol biosynthesis was downregulated in a manner suggesting a mechanism distinct 

from the statins. The authors suggested a link between PFOS, PPAR, and thyroid hormone 

homeostasis based on work by Miller et al. (2001) who observed decreased serum T4 and T3 

levels and increased hepatic proliferation following exposure to peroxisome proliferators. They 

also noted that PFOS exhibited similarities to compounds that induce xenobiotic metabolizing 

enzymes through PPARγ and constitutive androstane receptor (CAR). 

Wang et al. (2010) dosed albino Wistar female rats with 3.2 mg PFOS/kg diet from GD 1 to 

weaning (PND 21). Pups were allowed access to the treated feed until PND 35. To determine if 

prenatal or lactational exposure had more effect on altering gene expression, pups were divided 

into cross fostering groups on PND 2. These groups are listed below: 

• Pups born to treated dams fostered by control dams. 

• Pups born to control dams fostered by treated dams. 

• Pups born to control dams fostered by other control dams. 

• Pups born to treated dams fostered by other treated dams. 

Gene expression changes were examined on PNDs 1, 7, and 35. Significant effects were 

observed on genes involved in neuroactive ligand-receptor interaction, calcium signaling 

pathways, cell communication, the cell cycle, and peroxisome proliferator-activated receptor 

(PPAR) signaling. Transthyretin (TTR) which is a serum and cerebrospinal fluid carrier of 

thyroxine (T4) was decreased after PND 1. Based on analysis of PFOS in the serum, the half-life 

of PFOS in the neonates was approximately 14 days, and overall, prenatal exposure altered gene 

expression more than lactational exposure.

In a 4-week study in rats, the hepatic effects of PFOS, WY-14,648 and phenobarbital (PB) 

were compared (Elcombe et al. 2012). Groups of 30 male Sprague-Dawley rats were 

administered either 20 ppm PFOS, 100 ppm PFOS, 50 ppm WY-14,648, or 500 ppm PB in the 

diet ad libitum for either 1, 7, or 28 days. Control animals received only diet ad libitum for the 

duration of the study. Ten animals from each group were sacrificed on days 2, 8, and 29 for 

evaluation of liver weights, peroxisome proliferation, enzyme induction, cell proliferation, 

apoptosis, and other clinical and pathological parameters. The study showed that PFOS exhibits 

the combined effects of WY-14,643 and PB, behaving as a combined peroxisome proliferator 

and phenobarbital-like enzyme inducer. The data suggested that PFOS may activate not only 

PPARα, but also CAR and PXR.

Perfluorooctane sulfonate (PFOS) – May 2016 3-95
Mice. To assess PPAR involvement in developmental effects of PFOS, male and female 

129S1/Svlm wild-type and PPARα knockout (KO) mice were bred and pregnancy confirmed 

(Abbott et al. 2009). The females (n = 8–20 dams/group) were administered either vehicle (0.5% 

Tween-20) or PFOS by gavage on GDs 15–18; the wild-type mice were administered 4.5, 6.5, 

8.5, or 10.5 mg/kg/day PFOS and the KO mice, 8.5 or 10.5 mg/kg/day. Dams and pups were 

observed daily, and pups were weighed on PNDs 1 and 15. Eye opening was recorded on PNDs 

12–15. Dams and pups were killed on PND 15, and body and liver weights were recorded and 

serum collected.

Reproductive parameters measured included maternal body weight, maternal body weight 

gain, implantation sites, total number of pups at birth, and the percent litter loss from 

implantation to birth. Pup body weight and pup body weight gain were not affected with 

treatment in either the KO or wild-type mice. PFOS exposure had no effect on absolute or 

relative liver weight in any of the dams. In both strains of pups, PFOS exposure at 10.5 

mg/kg/day caused a significant increase in relative liver weight (sexes were combined). Survival 

of the pups was affected with treatment. Most post-natal deaths occurred between PNDs 1 and 2.

Survival of the wild-type pups was significantly (p < 0.001) decreased and was 65% ± 10 (n = 

16), 45% ± 14 (n = 8), 55% ± 6 (n = 7), 43% ± 9 (n = 20), and 26% ± 9 (n = 17) in the control, 

4.5, 6.5, 8.5, and 10.5 mg/kg/day groups, respectively. Survival of the KO pups was significantly 

(p < 0.001) decreased and was 84% ± 9 (n = 12), 56% ± 12 (n = 13), and 62% ± 8 (n = 14) in the 

control, 8.5, and 10.5 mg/kg/day groups, respectively. 

Post-natal development was also affected in the wild-type and KO pups. On PND 13, 44% of 

the control pups and none in the 8.5 mg/kg/day wild-type group had experienced their eye 

opening. In the KO mice, open eyes were reported in 23% of the 10.5 mg/kg pups and 59% of 

the controls on PND 14. All serum samples (pups and adults) showed a linear relationship 

between the amount of PFOS administered and the amount found in the serum, with levels in 

treated groups being significantly increased compared to the controls. As the results from the 

wild-type and KO pups were similar, the author concluded that PFOS-induced neonatal lethality 

and delayed eye opening were not dependent on the PPARα activation.

In another mechanistic developmental study, a PFOS solution with 0.5% Tween-20 was 

administered to timed-pregnant CD-1 mice by oral gavage at 0, 5, or 10 mg/kg/day for GD 1–17 

(Rosen et al. 2009). Five dams per group were euthanized at term, and three fetuses per litter 

were collected for preparation of total RNA from liver and lung. Additional liver and lungs were 

collected from two more fetuses/litter for histological examination.

Treatment with PFOS had no effect on body weight, general appearance, or litter size. 

Hematoxylin and eosin stained sections from treated and control fetal livers showed eosinophilic 

granules characteristic of peroxisome proliferation in the PFOS treated dose groups. At 5 

mg/kg/day, 753 fully annotated genes were altered in the fetal liver. In the fetal liver, PFOS 

upregulated a number of markers for fatty acid metabolism, xenobiotic metabolism, peroxisome 

biogenesis, cholesterol biosynthesis, bile acid biosynthesis, and glucose and glycogen metabolism. 

In the fetal lungs, up-regulation only occurred in a limited group of genes including: Cyp4a14, 

enoyl-Coenzyme A hydratase (Ehhadh), and fatty acid binding protein 1 (FABP1).

Qazi et al. (2009a) tested the effects of 0, 0.005%, or 0.02% PFOS on wild-type and PPARαnull 129/Sv mice. Dietary administration of 0.02% PFOS for 10 days resulted in a significant 

increase in liver weight and a reduction in the weight of the spleen in both the wild-type and null 

mice; the thymus and epididymal fat pad weights were both decreased in the wild-type mice 

Perfluorooctane sulfonate (PFOS) – May 2016 3-96
only. The wild-type mice administered 0.02% PFOS in the diet had a pronounced decrease in the 

total number of thymocytes (by 84%) and splenocytes (by 43%), as well as a decrease in the size 

of all subpopulations of thymocytes and splenocytes. In the knock-out mice, the reduction in the 

total number of thymocytes and subpopulations was partially or almost totally attenuated; effects 

on splenocytes were mostly eliminated. There were no effects in the wild-type or knock-out mice 

administered 0.005%. The study indicated that the immunomodulation was partially dependent 

on PPARα activation. 

Changes in gene expression were examined in wild-type and PPARα-null mice administered 

PFOS by gavage at 0, 3, or 10 mg/kg/day for 7 days (Rosen et al. 2010). At sacrifice, liver 

tissues were processed for histopathology and total RNA; microarray analysis was conducted 

using Affymetrix GeneChip 430_2 mouse genome arrays. Liver weight was increased at 

10 mg/kg/day in both wild-type and null mice. Overall gene expression showed dose-related 

changes in wild-type mice, while the number of transcripts influenced by PFOS in null mice was 

similar across the dose groups. This finding suggests that there are PPARα-independent effects 

in null mice that also occur in wild-type mice. Thus, some of the liver effects in the wild-type 

animals are not necessarily a reflection of PPARα activation.

In wild-type mice, PFOS altered the expression of PPARα-regulated genes including those 

involved in lipid metabolism, peroxisome biogenesis, proteasome activation, and inflammatory 

response. Altered PPARα-independent genes included those associated with xenobiotic 

metabolism in both wild-type and null mice. PFOS caused induction of a constitutive androstane 

receptor (CAR) inducible gene, Cyp2b10, indicating the likelihood that PFOS also activates 

CAR. In null mice, changes induced by PFOS included up-regulation of genes in the cholesterol 

biosynthesis pathway and modest down-regulation of genes associated with oxidative 

phosphorylation and ribosome biogenesis (Figure 3-1). Unique in null mice, PFOS upregulated 

Cyp7a1, an important gene related to bile acid/cholesterol homeostasis. The results support those 

from other studies that indicate PFOS exposure results in metabolic changes both linked to, and 

independent of, PPAR-α.

The variability in the serum lipid profiles in humans suggests that response to PFOS 

exposure could be impacted by individual physiological differences and that environmental 

factors such as diet could contribute to intraspecies differences in response. L. Wang et al. (2014) 

reported on the differences in response of male BALB/c mice (4–5 weeks old) administered 

PFOS (0, 5, or 20 mg/kg) for 14 days while concurrently given diets that varied in dietary fat 

[regular fat (RF) versus high fat (HF)] content. Following PFOS exposure, there was an increase 

in liver fat content in both groups and a decrease in liver glycogen. However, the increase in fat 

content was more pronounced with the RF mice than in the mice on the HF diet. This study is 

described in more detail in section 3.2.2. 

The fat content of the diet alone was associated with significantly higher serum levels of 

glucose, HDL cholesterol, LDL cholesterol, and total cholesterol. For glucose, cholesterol, HDL, 

and LDL the levels declined as the dose of PFOS increased. In the case of triglycerides, the 

levels increased with 5 mg/kg/day PFOS and decreased at 20 mg/kg/day. PPARα expression at 

the end of the 14-day PFOS treatment increased for the RF group but decreased for the HF 

groups (significant for the high dose). 

Perfluorooctane sulfonate (PFOS) – May 2016 3-97
Figure 3-1. Functional Categories of Genes Modified by PFOS in Wild-Type and Null Mice

The high fat diet alone increased the expression of CPT1A and CYP7A1 genes involved with 

lipid metabolism. On the RF diet, the exposure to PFOS was associated with a significant doserelated increase in CTP1A expression, whereas for the high fat diet plus PFOS there was a 

significant decrease in expression. For CYP7A1 expression there was no significant impact of 

PFOS with the RF diet, whereas with the high fat diet there was a highly significant decrease in 

expression with PFOS. 

The L. Wang et al. (2014) study demonstrates a clear influence of diet alone on the liver and 

lipid profile that was combined with some dose-related differences in the responses to PFOS 

exposure. The data support a possible role for PFOS in inhibiting pathways for metabolism and 

export of liver lipids and identify some PFOS associated liver responses that are independent of 

PPARα activation.

Tan et al. (2012) conducted a dose-response study of hepatic proteonomic responses 

following exposure of male Kunming mice (5/dose group) to PFOS at levels of 0.1, 1.5, or 

5 mg/kg/day by interperitoneal (ip) injection for 7 days. Twenty-four hours after the last dose, 

Perfluorooctane sulfonate (PFOS) – May 2016 3-98
the animals were sacrificed and the livers harvested, weighed, and preserved in liquid nitrogen. 

Body weight was recorded at study initiation and immediately before sacrifice.

Liver tissues were pooled for each dose group and homogenized for proteonomic analysis. 

The liver proteins were extracted and grouped using iTRAQ labeling guidelines, digested with 

trypsin, and labeled with iTRAQ reagent. The iTRAQ proteonomic analysis is a novel, 

MS-based approach for the relative quantification of proteins. It relies on the derivatization of 

primary amino groups in intact proteins using isobaric tags for relative and absolute quantitation 

(Wiese et al. 2007). The tryptic peptides were separated using reverse phase liquid 

chromatography, identified following LC/MS/MS analysis, and correlated to intact proteins 

based on peptide structures. 

Treatment with PFOS caused a slight deficit in body weight for the high dose group and a 

significant dose-related increase in liver weight for the two highest dose groups. The iTRAQ 

process identified 1,502 unique proteins; 71 showed a greater than 1.5-fold change in expression. 

Sixty-two proteins showed increased expression, and nine showed decreased expression. Figure 

3-2 illustrates the impact of the PFOS exposure on identified proteins as associated with 

subcompartments within the liver cells compared to the proteins in the reference data base.

Enrichment was greatest for peroxisomes and endoplasmic reticulum, mitochondrial, and cell 

membrane proteins. Relative to biochemical processes, Figure 3-2 shows that the majority of 

enriched proteins were involved with lipid metabolism, transport, biosynthetic processes, 

catabolic processes, and carbohydrate metabolic processes.

Top: cellular component; Bottom: biological process

npro: the number of proteins belongs to one category in the proteome database

Expect: the number of proteins having an ontology annotation in the reference database.

Figure 3-2. Function Distribution and Category Enrichment Analysis of the 

Differential Proteins

Perfluorooctane sulfonate (PFOS) – May 2016 3-99
Sixteen proteins were identified that showed dose-response for the increase in expression. 

Four of these were related to peroxisomal beta-oxidation, four were related to CYP-450 

aromatase activity, and three had transferase activity including GSTmu3 and GSTmu6. A GTP 

binding protein (GTP sar-1b) also displayed a dose-related response. One of the remaining four 

proteins exhibiting dose-response, cysteine sulfinic acid decarboxylase, is the rate limiting 

enzyme in taurine production and has been proposed as a biomarker for hepatocarcinogenesis. 

In the developmental study by Butenhoff et al. (2009), mRNA transcript data for the control 

and 1.0 mg/kg/day dose group (GD 20 dams and fetuses and PND 21 male pups) was obtained 

by quantitative reverse transcription polymerase chain reaction. Results for this part of the study 

were reported by Chang et al. (2009). Statistically-significant changes included: 

• Increased Cyp2b2 levels in dams and male pups (2.8-fold and 1.8-fold, respectively) than 

in controls on GD 20 and PND 21. 

• Higher mean acyl CoA (ACoA) and Cyp4a1 levels in male pups (1.5-fold and 2.1-fold, 

respectively) than those of controls. 

• Lower mean Cyp7a1 (3.5-fold) than that for controls. 

These results suggest induction of PPARα as well as hepatic CAR. Transcripts possibly related 

to thyroid status were all similar between the treated dams and pups and the controls. 

Oxidative Damage 

Liu et al. (2009) conducted a study of KM mice in which 3–6 pups/sex/group were 

administered one subcutaneous injection of 0 or 50 mg PFOS/kg bw on PNDs 7, 14, 21, 28, or 

35. The study was done in an attempt to determine the effects of treatment on the oxidationantioxidation system by measuring MDA content, SOD activity, and total antioxidation 

capability (T-AOC). Animals were sacrificed 24 hours post-treatment, blood was collected, and 

liver and brain were removed and weighed. 

No treatment-related effects were observed on body weight. Relative liver weight was 

significantly increased (p < 0.01 or p <0.05) when compared to controls in both males and 

females at most time-points. The levels of MDA in the brain and liver and SOD activity were 

similar between treated mice and the controls at most time-points. On PNDs 7 and 21 in the 

treated males, brain SOD activity was significantly lower when compared to controls by 19% 

and 13%, respectively. Liver SOD activity was lower (decrease of 19%) in the treated females on 

PND 14 when compared to controls. Male brain T-AOC was decreased at all stages of post-natal 

development but only significantly at PND 21 (decrease of 15%). Male liver T-AOC was 

decreased significantly at PND 7 (decrease of 25%) and 14 (decrease of 27%). Female brain 

T-AOC had no significant differences from controls and the liver T-AOC was decreased only at 

PND 21 (decrease of 15%). The study also demonstrated that distribution increased in the liver 

and lessened in the blood and brain with postnatal development in both the males and females.

On PND 7, PFOS concentrations were 11.78%, 5.04%, and 14.84% in the male mouse blood, 

brain, and liver, respectively. On PND 28, the PFOS concentrations were 9.89%, 0.85%, and 

63.39% in the male mouse blood, brain, and liver, respectively. PFOS brain levels were about 

5-fold higher on PND 7 than they were on PND 28. A similar trend was observed in the females.

The study suggested that oxidative damage from PFOS can occur, is more prominent in the 

younger neonates, and is slightly more pronounced in the males. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-100
Gap Junctional Intercellular Communication (GJIC) 

Gap junctions are found in the cell’s plasma membrane and formed by proteins that connect 

to form an intercellular connection that allows a direct exchange of chemicals from the interior 

of one cell to that of adjacent cells without passage into the extracellular space. The GJIC is 

considered to be essential in maintaining healthy cells and thus disruptions are thought to cause 

abnormal cell growth, including tumor formation. They also appear to be linked to some 

neurological, reproductive or endocrine abnormalities. 

Hu et al. (2002) tested PFOS exposure in vitro and in vivo to determine whether disruption to 

the GJIC could possibly be a mechanism for the effects observed with PFOS exposure. The study 

exposed a rat epithelial cell line (WB-F344) and a dolphin kidney epithelial cell line (CDK) to 

PFOS at concentrations of 0, 3.1, 6.25, 12.5, 50, 100, or 160 μmol for 30 minutes. GJIC effects 

were measured using the scrape loading dye technique. PFOS inhibited GJIC rapidly in a dosedependent method starting at 12.5 μmol, but it was reversible once exposure ended. Additionally, 

4 to 6 Sprague-Dawley rats/sex/group were exposed to 0 or 5 mg/kg PFOS by gavage for either 3 

or 21 days. GJIC was significantly reduced in the liver tissue after 3 days of exposure. Inhibition 

also occurred in rats exposed for 21 days, but it was comparable to that seen after 3 days. No 

differences were observed between the male and female rats.

Wan et al. (2014a) isolated and cultured Sertoli cells from testes of 20-day old rats to 

examine PFOS’s effects on blood testes barrier function. By day 3 the cultures had established a 

functional tight junction barrier. Gap junction communication was assayed by means of 

fluorescence recovery using a photo bleaching assay that measured the ability of a fluorescent 

dye to move from one cell to another in the presence or absence of PFOS (20 μmol; a 3-hour 

exposure) in a 120 second period. Cells treated with PFOS displayed significantly lower

fluorescence recovery than the control cells in the absence of cytotoxicity. The assays were 

performed in triplicate. The authors identified this as a matter of concern because it represents 

diminished function of the blood testes barrier in coordinating an intercellular junction necessary 

for intercellular communication during spermatogenesis. The authors also examined other 

characteristics of the blood testes barrier finding effects of PFOS on the cytoskeleton manifest in 

the form of shortened F-actin filaments.

Mitochondrial Function 

Starkov and Wallace (2002) isolated mitochondria from the livers of adult male SpragueDawley rats and used them to measure mitochondrial membrane potential and oxygen 

consumption when exposed to PFOS. PFOS appeared to be a weak mitochondrial toxicant. At 

higher concentrations, PFOS caused a small increase in resting respiration rate and slightly 

decreased the membrane potential. The observed effects were attributed to a slight increase in 

nonselective permeability of the mitochondria membranes caused by the surface-active property 

of the compound. 

Wallace et al. (2013) also examined the impact of 16 different PFASs on mitochondrial 

respiration rate and oxidative phosphorylation as measured in vitro using isolated rat liver 

mitochondria. Inhibition was determined through the reduction in oxygen consumption in 

response to the addition of ADP to isolated mitochondria. PFOS displayed a 20–30 times more 

potent inhibitory effect among the other sulfonates evaluated (PFBS and PFHxS). PFOS was 

three times more potent than PFOA. The inhibition mode of action seemed to vary across 

different PFAS families. In the case of PFOS, its impact on membrane fluidity appeared to be 

Perfluorooctane sulfonate (PFOS) – May 2016 3-101
responsible for the observed respiratory inhibition. The authors’ proposed mode of action for this 

effect from PFOS is consistent with the findings of Matyszewska et al. (2008) that PFOS 

increased the membrane fluidity and thickness of a model biological membrane in a manner 

similar to that resulting from cholesterol insertion into a lipid by-layer.

3.3.5 Structure-Activity Relationship

In vitro. Bjork and Wallace (2009) performed a study to see whether the PPARα agonism was 

relevant in human cell lines and whether effects differed with various chain lengths. Primary rat 

and human hepatocytes and HepG2/C3A hepatoma cells were exposed to 25 μmol PFAS for 24 

hours to determine the structure-activity relationships across various chain lengths. The 

concentration used was the maximum concentration that did not lead to cell injury in any of the 

cell lines. The PFAS tested included perfluorinated carboxylic acids with carbon chain lengths of 

2 to 8 and perfluorinated sulfonic acids with chain lengths of 4 to 8. 

The PFAS stimulated mRNA expression of either acyl CoA oxidase (Acox) or acyl CoA 

thioesterase (Cte-rats or Acot 1-humans) only in rat hepatocytes and within both series and 

transcripts; the degree of stimulation of gene expression increased with increasing carbon 

number. Maximum stimulation of Acox gene expression was 3-fold over control for PFOS; 

maximum stimulation for Cte/Acot 1 gene expression was 4-fold for PFOS. PFOS did not cause 

any significant stimulation of Acox or Cte/Acot 1 gene expression in human hepatocytes. The 

Cyp4a11 gene was not expressed or stimulated by any of the PFASs in HepG2/C3A cells. 

However, this gene expression was stimulated by PFAS exposure in both rat and human 

hepatocytes with the perfluorocarboxylates indicating a chain-length dependent structure activity 

relationship. Maximum gene expression stimulation was in the longer carbon PFAS, but the 

variability was large with little statistical difference between the 6 and 8 carbon molecules. Study 

results suggested that the PPARα related gene expression by PFAS was induced in primary rat 

hepatocytes, increased with carbon chain length, and appeared to be greater in the carboxylic 

acids (such as PFOA) when compared to the sulfonates (such as PFOS). There was no induction 

of peroxisome-related fatty acid oxidation gene expression (Acox and Cte/Acot 1) in either 

primary or transformed human liver cells in culture. This suggests that the PPARα mediated 

peroxisome proliferation observed in rodent liver may not be relevant as an indicator of human 

risk.

3.3.6 ToxCast Assays 

The Toxicity Forecaster (ToxCast) database is a large high throughput screening compilation 

of public in vitro and in vivo assays on over 9,000 chemicals. PFOS was tested in 1,087 assays 

and was active in 175. Assay activation defines the occurrence of the molecular event within the 

assay (cytotoxicity, induction, binding, and so forth.) with the concentration resulting in 50% 

activity, AC50, used for comparison to other assays. Assays with < 50% reported efficacy or 

over-fitting issues are not included in the results discussed. Some of the data from the ToxCast 

assays such as the interactions with PPAR and CAR support the experimental data for PFOS and 

PFOA. In cases where effects were only observed at concentrations greater than those causing 

cytotoxicity, attributing the outcome to PFOS rather than the cytotoxicity is less certain. 

Cytotoxicity. Of the active assays, 20 were examining endpoints based on cytotoxicity. Most 

cell types offered at least one cytotoxicity AC50 for comparison to other in vitro assays. If no 

cytotoxicity AC50 was reported for a specific cell type, the minimum in vitro cytotoxicity 

Perfluorooctane sulfonate (PFOS) – May 2016 3-102
endpoint for PFOS was used for comparison. The lowest PFOS induced AC50 recorded in the 

ToxCast database is 5.34 μM in the assay for induction of tumor protein 53 using liver cells and 

the highest AC50 recorded is 172.02 μM for measuring tumor protein in intestinal cells 

(SD = 45.15; standard error = 9.9). 

Endocrine Disruption. Four different estrogen receptor (ESR) assays reported activation 

following PFOS treatment, all of which were Estrogen Receptor 1- (ESR1-) related. Estrogen 

and its receptors are essential for sexual development and reproductive function, but they also 

play a role in other tissues, such as bone. Estrogen receptors are also involved in pathological 

processes including breast cancer, endometrial cancer, and osteoporosis (NCBI 2016). Two 

assays of the same cell type were related to ESR1 induction with the lowest AC50, 18.06 μM. 

This is lower than the cytotoxicity AC50 reported for the cell type used, 23.76 μM, and is 

indicative of ESR1 induction. In a different ESR1 assay, antagonism was recorded at an AC50 of 

83.57 μM, a value higher than the cytotoxicity AC50 for that cell type, 66.31 μM. PFOS induced 

the estrogen DNA binding site with an AC50 of 87.42 μM. There was no cell-specific reference 

cytotoxicity value for comparison. The ToxCast assays suggest that PFOS has the ability to 

induce ESR1.

PFOS antagonized the androgen receptor (AR) at 12.57 μM in human cells and 4.27 μM in 

rats. Although there is no direct cellular cytotoxicity value to compare, PFOS rat AR antagonism 

occurred at lower concentrations than the minimum cytotoxicity value (5.34 μM). This implies 

that PFOS reacts with the AR receptor in the rat and perhaps the human. The progesterone 

receptor (PR) was also antagonized within the same human cell type, and had a higher AC50, 

22.2 μM, than the minimum cytotoxicity AC50. Thyroid receptor (TR) antagonism AC50, 

91.24 μM, was also higher than its respective cell specific cytotoxicity AC50 (33.323 μM). This 

signifies that assay activation (i.e., positive results) might have occurred due to cytotoxicity 

rather than PR, TR, or human AR antagonism. However, PFOS-induced ESR1 and antagonized 

rat AR was observed. 

Immunotoxicity. PFOS activated a variety of genes related to immunotoxicity in the ToxCast 

database. These genes include: chemokine ligand (CXCL) 10, CXCL8, collagen type II alpha 

(COL3A), interleukin-1 alpha (IL-1α), plasminogen activator (PLA), plasminogen activator 

urokinase (PLAUR), vascular cell adhesion molecule (VCAM1), and the TNF receptor 

subfamily gene CD40 (CD40). All of the immunological assays were performed by the vendor 

BioSeek. The vendor did not have a cytotoxicity AC50 for every cell type utilized and used only 

two cytotoxicity AC50 values for comparison. Genes that had lower AC50 values than cell or 

BioSeek specific cytotoxicity AC50 were: CD40, PLAUR, PLA, VCAM1, and CXCL8. Given 

the limited cytotoxicity reference values it is difficult to determine if all gene activity can be 

attributed to PFOS. For PLAUR and VCAM1, AC50 results were lower than their cell specific 

cytotoxicity AC50 and have stronger translational potential. VCAM1 and PLAUR play a role in 

inducing chronic inflammation and vascularization in vivo (Kleinstreuer et al. 2014). This 

implies PFOS may play a role in inducing chronic inflammation and/or vascularization, both of 

which are important for the development of rheumatoid arthritis (Khansari et al. 2009).

Neurotoxicity (in vitro). PFOS activated five different neurological receptor families with seven

different receptor types in cell-based assays. The receptors activated were: 5-hydroxytryptamine 

receptor (5HT) 5a, 6, and 7, the adenosine A2a receptor (ADORA2), the adrenoceptor alpha 2C 

(ADRA2C), and beta 1 (ADRB1), as well as the dopamine receptor D4 (DRD4). Cell-specific 

cytotoxicity AC50 values for reference were lacking for all of the in vitro assays; only ADORA2 

had an activation AC50 lower than the lowest PFOS cytotoxicity AC50 of 5.34 μM. Therefore, it 

Perfluorooctane sulfonate (PFOS) – May 2016 3-103
is difficult to draw any conclusions on the potential neurotoxicity of PFOS using the ToxCast 

data.

Fish Toxicity (in vivo). Oregon State University conducted a large number of toxicity studies 

using a zebrafish model. PFOS gave positive results in nine assays. Positive effects were 

recorded for limb malformations 5 days after a 1-time exposure during embryonic development. 

Other assays with positive results were those for Axis Malformation, Jaw Malformation, 

Pericaradiac Edema, Snout Malformation, Touch Response, Trunk Malformation, Yolk Sac 

Edema, and Mortality. Mortality had the lowest reported AC50 at 0.54 μmol. The results provide 

strong evidence for PFOS developmental toxicity in fish and suggest a potential for human 

developmental human toxicity. 

PPAR/PXR/RAR Receptors. PFOS activated PPARs, PXR, constitutive adrostane receptor 

(CAR), and retinoic acid receptor (RAR) in assays conducted under the ToxCast program. PFOS 

induced the DNA sequences for PPAR alpha (PPARα), peroxisome proliferator hormone 

response elements (PPRE), and PPAR gamma (PPARγ) and antagonized the PPARγ receptor.

The only PPAR assay AC50 that was above the cell-specific cytotoxicity AC50 was PPARγ

antagonism at 5.91 μM. However, it is possible that cytotoxicity occurs due to PPAR induction 

or that the PPAR antagonism contributes to cytotoxicity. PFOS induced DNA sequences for 

PXR, AC50 9.42 μM, at concentrations lower than the cell-specific cytotoxicity AC50. CAR and 

RAR alpha antagonism were also observed but not at levels below the cell specific cytotoxicity 

values of 17.57 μM and 28.45 μM respectively. PPAR, PXR, CAR, and RAR pathways are all 

nuclear receptors that can form heterodimers with one another to induce translation of linked 

genes. Some of these genes are important for development, reproduction, waste degradation, and 

even induction of cytotoxicity. Therefore, PFOS induction of these assays are consistent with the 

experimental data on PPAR and CAR receptor activation. 

Cytochrome P450s Activation. Cytochrome P450 (CYP) enzyme bindings were also examined 

within the ToxCast database in order to understand any metabolic potential for a chemical. 

Though PFOS is not known to be metabolically active, it showed activation in four acceptable 

CYP assays: CYP2C18, CYP2C19, and CYP2C9 in human cells, and CYP2C11 in rat. All of the 

CYP assays had activation at concentrations lower than the lowest cytotoxic AC50. The CYP2C 

class is known to be involved in the metabolism of xenobiotics including drugs, such as the antiseizure medication diazepam, the beta blocker propranolol, and the selective serotonergic 

reuptake inhibitor citalopram. Though there is no evidence of metabolism of PFOS by these 

CYPs, it is possibly acting as a competitive or allosteric inhibitor for other substrates. This, 

coupled with PFOS’s high affinity for albumin, could significantly alter the pharmacokinetics of 

various necessary and habitual pharmaceuticals.

3.4 Hazard Characterization

3.4.1 Synthesis and Evaluation of Major Noncancer Effects 

3.4.1.1 Liver Effects, Cholesterol, and Uric Acid

Good correlation between serum and hepatic levels of PFOS has been shown for human 

samples (Kärrman et al. 2010; Olsen et al. 2003a). However, no consistent adverse effects on the 

liver were found in epidemiology studies. Biomonitoring studies performed at the 3M Decatur, 

Alabama plant (Olsen et al. 2001a, 2001b, 2003b) identified occasional differences in hepatic 

Perfluorooctane sulfonate (PFOS) – May 2016 3-104
clinical chemistry values but no associated hepatic disease and or hepatic carcinogenicity was 

reported. 

Multiple epidemiologic studies have evaluated serum lipid status in association with PFOS 

concentration. These studies provide support for an association between PFOS and small 

increases in total cholesterol. Hypercholesterolemia, which is clinically defined as cholesterol 

greater than 240 mg/dL, was associated with PFOS exposure in a Canadian cohort (Fisher et al.

2013) and in the C8 cohort (Steenland et al. 2009). PFOS levels in these studies were 

0.0084 μg/mL and 0.022 μg/mL, respectively. Cross-sectional occupational studies demonstrated 

an association between PFOS and total cholesterol (Olsen et al. 2001a, 2001b, 2003b), with 

much higher PFOS serum levels of up to 1.40 μg/mL. Evidence for associations between other 

serum lipids and PFOS is mixed, with some studies showing an association with measurements 

of concurrent HDL and/or LDL and others failing to measure the serum lipoprotien complexes. 

The studies on serum lipids in association with PFOS serum concentrations are largely crosssectional in nature and were largely conducted in adults, but some studies exist on children and 

pregnant females. The location of these cohorts varied from the U.S. population including 

NHANES volunteers, to the Avon cohort in the UK, to Scandanivian countries. Limitations to 

these studies include the frequently high correlation between PFOA and PFOS exposure; not all 

studies control for PFOA in study design. 

There are several characteristics of HDLs that explain the association of increased serum 

concentration of HDL with PFOS or PFOA levels. HDLs accept cholesterol from other serum 

lipoprotein complexes and bring it to the liver for degradation and conversion to bile salts 

(Montgomery et al. 1990). Competition between PFOS and bile salts for biliary transport could 

result in impeded removal of HDL lipids from serum and increase both HDL cholesterol and 

total cholesterol. The liver is the only tissue that can rid the body of excess cholesterol by 

secreting it in bile for removal with the feces (Montgomery et al. 1990). In addition, HDLs have 

the highest ratio of protein to lipid (50:50) among the serum lipoprotein complexes 

(Montgomery et al. 1990). Binding of PFOS to HDL protein could impede the HDL interaction 

with liver tissue receptors resulting in increased serum levels of HDL. LDLs contain 21% 

protein. LDL uptake by tissues is mediated by binding of the LDL apo-B-100 protein and by a 

receptor independent route (Montgomery et al. 1990). Thus, conformational changes in the 

lipoprotein proteins as a result of PFOS binding can also impact serum LDL levels. 

PFOS, when absorbed, is primarily found in the liver tissue. In monkeys, rats, and mice, 

PFOS levels in the liver showed a dose-dependent increase that was consistently greater than 

serum levels (Curran et al. 2008; Goldenthal et al. 1978a; Liu et al. 2009; Seacat et al. 2002; 

Thomford 2002/Butenhoff et al. 2012). Chang et al. (2009) identified PFOS levels in the liver of 

rat offspring as early as GD 20, and Stein et al. (2012) measured PFOS in human amniotic fluid 

supporting placental transfer.

In experimental studies, increased absolute liver weight was observed in monkeys exposed to 

0.75 mg/kg/day for 182 days (Seacat et al. 2002), in rats at ≥ 1.33 mg/kg/day for 14 weeks 

(Curran et al. 2008; Seacat et al. 2003), and in rats at ≥ 0.77 mg/kg/day for 53 weeks (Thomford 

2002/Butenhoff et al. 2012). Microscopic lesions of the liver were observed in rats and monkeys. 

Lesions were found in rats at 1.33–1.56 mg/kg/day after 14 weeks (Seacat et al. 2003), in rats at 

0.098–0.299 mg/kg/day after 104 weeks (Thomford 2002/Butenhoff et al. 2012), and in monkeys 

at 0.75 mg/kg/day after 53 weeks (Seacat et al. 2002). Liver lesions were similar in both species 

and included centrilobular hypertrophy and vacuolation after the subchronic and chronic 

exposures with eosinophilic granules also observed after chronic duration. Single cell necrosis 

Perfluorooctane sulfonate (PFOS) – May 2016 3-105
was also found in rats at 0.984–1.251 mg/kg/day after 104 weeks (Thomford 2002/Butenhoff et 

al. 2012; Table 3-15). In these studies, no evidence of peroxisome proliferation was found in 

either species.

Hepatomegaly and increased liver weight alone are not considered adverse in cases where a 

chemical such as PFOA causes stimulation of PPAR-α, CAR, and/or PXR cellular receptors

(Hall et al. 2012). However, when accompanied by necrosis (Thomford 2002/Butenhoff et al.

2012) and/or fatty acid steatosis (Bijland et al. 2011; Wan et al. 2012), liver weight increases are 

considered adverse. 

In contrast with humans, rats, mice, and monkeys displayed a decrease in cholesterol levels 

and high density lipoprotein cholesterol following PFOS administration in short and long term 

studies (Curran et al. 2008; Seacat et al. 2003; L. Wang et al. 2014) when compared to the 

controls. Male rats had decreased serum cholesterol after 14 weeks at a dose of about 

1.4 mg/kg/day (Curran et al. 2008). Wan et al. (2012) found evidence for hepatic macrovesicular 

steatosis in mice given ≥ 5 mg/kg/day that was not entirely due to PPARα activation. Steatosis 

was exacerbated when PFOS exposure was combined with a high fat diet.

As discussed above in section 3.3.4, mice administered PFOS showed differential expression 

of genes or proteins mainly involved in lipid metabolism, transport, biosynthetic processes, and 

response to stimulus (Tan et al. 2012; L. Wang et al. 2014) and in genes involved in cholesterol 

biosynthesis and xenobiotic metabolism (Rosen et al. 2010). More specific investigations into the 

genes involved in lipoprotein metabolism were conducted by Bijland et al. (2011) as described 

below. In addition, the nuclear hormone receptors CAR and PXR have been shown to be 

activated in mice (Bijland et al. 2011; Rosen et al. 2010) and rats (Elcombe et al. 2012). Taken 

together, these studies consistently show an effect on expression of genes involved in lipid 

metabolism and cholesterol transport and biosynthesis following in vivo PFOS exposure. 

To further examine PFOS-specific effects on lipid metabolism, Bijland et al. (2011) 

examined the molecular biology of hepatic hyperlipidemia in APOE*3-Leiden.CETP mice, a 

strain that exhibits human-like lipoprotein metabolism. Details of the experimental procedure 

were given in section 3.2.2. Animals fed 3 mg/kg/day for 4 weeks had decreased hepatic VLDL 

production leading to increased retention of triglycerides and hepatomegaly, with concomitant 

decreased hepatic clearance of VLDL and HDL cholesterol. Fecal bile acid content was 

decreased by 50%. 

Overall the genes upregulated were those involved with fatty acid uptake, transport, and 

catabolism; triglyceride synthesis; cholesterol ester synthesis; and VLDL synthesis and secretion.

Genes involved with HDL synthesis, maturation, clearance, and bile acid formation were 

downregulated. Lipoprotein lipase activity and mRNA expression, both normally low in the 

liver, were increased.

Many of the genes activated are associated with the nuclear PXR receptor to a greater extent 

than PPARα. Lipoprotein lipase activity facilitates removal of TGs from serum LDLs, and 

uptake into the liver and other organs as free fatty acids and glycerol. 

No animal studies were identified that examined serum uric acid levels following PFOS 

exposures. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-106
3.4.1.2 Developmental/Reproductive Toxicity

PFOS has been detected in amniotic fluid samples indicating that the chemical crosses the 

placenta. The median ratio of maternal serum:amniotic fluid concentration was 25.5:1, and PFOS 

was rarely detected in amniotic fluid until the serum concentration reached at least 0.0055 μg/mL 

(Stein et al. 2012). Studies evaluating the reproductive and developmental health in humans 

exposed to PFOS have been performed in both occupational settings and in the general 

population. 

Although not entirely consistent, the set of studies evaluating fetal growth retardation suggest 

an association of prenatal serum PFOS with deficits in mean birth weight and with LBW. 

Although three studies were null (Fei et al. 2008a; Hamm et al. 2010; Monroy et al. 2008), birth 

weight deficits ranging from 29 to 149 grams were detected in 5 studies (Apelberg et al. 2007; 

Chen et al. 2015; Darrow et al. 2013; Maisonet et al. 2012; Washino et al. 2009). In these 

studies, PFOS serum levels ranged from 0.005 to 0.0132 μg/mL. Three (Chen et al. 2012; Fei et 

al. 2007; Stein et al. 2009) out of four (Darrow et al. 2014) studies of LBW showed increased 

risks (OR range: 1.5–4.8). Studies have questioned whether low maternal GFR is a positive 

confounder in epidemiology studies of birth weight and PFAS (Morken et al. 2014; Verner et al.

2015). The Verner et al. (2015) comparison between a meta-analysis and PBPK simulations 

suggests that the some but not all of the association reported between PFOS and birth weight 

could be attributable to low GFR.

A small set of studies observed an association with gestational diabetes (Zhang et al. 2015, 

preconception serum PFOS), pre-eclampsia (Stein et al. 2009), and pregnancy-induced 

hypertension (Darrow et al. 2013) in populations with serum PFOS concentrations of 0.012–

0.017 μg/mL. Zhang et al. (2015), and Darrow et al. (2013) used a prospective assessment of 

adverse pregnancy outcomes in relation to PFAS which addresses some of the limitations the 

available cross-sectional studies. Associations with these outcomes and serum PFOA also were 

observed. 

There also is generally consistent evidence of associations of serum PFOS with decreased 

fertility and fecundity (Bach et al. 2015; Fei et al. 2009; Jørgensen et al. 2014; Vélez et al. 2015); 

there was one null study (Vestergaard et al. 2012). While a concern over the possibility of 

reverse causation explaining observed associations has been raised (Whitworth et al. 2012), the 

collective findings, particularly from a more recent study (Bach et al. 2015), support a consistent 

association with fertility and fecundity measures and PFOS exposures. Although there was some 

suggestion of an association between PFOS exposures and semen quality parameters in a few 

studies (Joensen et al. 2009; Toft et al. 2012), most studies were largely null (Buck Louis et al. 

2015; Ding et al. 2013; Joensen et al. 2013; Raymer et al. 2012; Specht et al. 2012; Vested et al. 

2013).

No animal studies were identified that suggested effects on fertility in males or females.

However, López-Doval et al. (2014) found structural effects on the hypothalamic-pituitary axis 

in adult male rats after exposure to PFOS. There were histopathological lesions of the testes at 

doses ≥ 1 mg/kg/day and only a few active gonadotrophic cells at doses ≥ 3 mg/kg/day. The 

lowest dose tested, 0.5 mg/kg/day, was accompanied by decreased LH and testosterone levels 

and increased FSH levels. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-107
Increased pup mortality was observed when rat dams were treated only during gestation as 

part of developmental toxicity studies (Chen et al. 2012; Lau et al. 2003; Thibodeaux et al.

2003). Chen et al. (2012) found increased mortality, decreased body weight, and 

histopathological changes in the lungs (alveolar hemorrhage, thickened interalveolar septum) in 

rat offspring from dams treated with 2.0 mg/kg/day from GD 1 to 21. No effects were observed 

in those administered 0.1 mg/kg/day. Developmental delays were found in rat offspring at a 

lower dose than that affecting survival (1 mg/kg/day; Butenhoff et al. 2009) and in mice at a 

slightly higher dose (5 mg/kg/day; Lau et al. 2003; Thibodeaux et al. 2003).

Rat dams were treated with PFOS for 63 or 84 days in a one- or two-generation reproductive 

study, respectively (Luebker et al. 2005a, 2005b). No changes in maternal liver weight were 

observed on either protocol. The most sensitive endpoint was decreased pup body weight, with 

reduced survival also observed at higher maternal doses. A NOAEL for pup body weight effects 

is 0.1 mg/kg/day in the two-generation study (Luebker et al. 2005b); this dose was not tested in 

the one-generation study (Luebker et al. 2005a) where the LOAEL was 0.4 mg/kg/day for 

decreased pup body weight, decreased maternal body weight, and decreased gestation length. A 

0.4 mg/kg/day dose was a LOAEL in the both the one and two generation studies. The dose 

associated with a significant decrease in pup survival for the two generation study was 

1.6 mg/kg/day and the dose for a decreased viability index was 0.8 mg/kg/day (BMDL5 = 

0.89 mg/kg/day) in the one-generation study. 

To help characterize the mechanism of PFOS induced neonatal mortality, Grasty et al. (2003) 

examined critical windows of exposure by treating rats with a high dose of PFOS (25 mg/kg/day) 

for a 4-day period during various stages of pregnancy. Mortality was highest when treatment 

occurred on GDs 17–20, identifying late gestation as the sensitive window for neonatal death. In 

a subsequent experiment, exposure to 50 mg/kg/day of PFOS on GDs 19 and 20 alone was 

sufficient to produce almost 100% mortality to pups at birth. 

Studies by Grasty et al. (2003, 2005) and Chen et al. (2012) describe significant histological 

and morphometric differences in the lungs between control and PFOS-exposed newborn pups, 

suggesting that lung maturation and pulmonary surfactant interactions are potential MOAs. 

Changes in lung morphology were noted in rat pups, but prenatal exposure to PFOS did not 

affect lung phospholipids or alter the expression of marker genes for alveolar differentiation 

associated with lung maturation (Grasty et al. 2005). Chen et al. (2012) found that PFOS caused 

oxidative stress and cell apoptosis in the lungs of offspring from mothers treated with 

2.0 mg/kg/day during GDs 1–21. 

Currently, the leading hypothesis for the MOA of PFOS-induced neonatal mortality is that 

PFOS interacts directly with components of natural lung surfactants (Grasty et al. 2005; Xie et 

al. 2010a, 2010b). PFOS interacts with the major phosphatidylcholine components of pulmonary 

surfactants and cell membranes and, therefore, has the potential to alter the dynamic properties of 

lung surfactant (Xie et al. 2010a). PFOS partitions into phospholipid membranes to increase 

membrane fluidity in several cell types (Xie et al. 2010b). This high tendency of PFOS to 

partition into phosphatidylcholine lipid bilayers is consistent with its resemblance to medium 

chain fatty acids and may be responsible for interfering with the normal physiological function of 

pulmonary surfactant.

Prenatal PFOS exposures appear to influence hormones during gestation, as well as in 

neonate and adult animals. Zhao et al. (2014) examined the testes from male Sprague-Dawley rat 

fetuses on GD 20 following maternal exposure to 0, 5, or 20 mg/kg/day on GDs 11–19. Fetal 

Perfluorooctane sulfonate (PFOS) – May 2016 3-108
Leydig cells were found to be reduced in number with evidence of apoptosis. Levels of 

testosterone were reduced along with the levels of key enzymes or mRNA for proteins involved 

with testosterone production. 

Studies have examined the impact of gestational and lactational exposures on the pups as 

adults (Lv et al. 2013 rats; Wan et al. 2014b, mice). In both cases early life exposure through 

maternal treatment with PFOS was associated with abnormal glucose control in the mature 

offspring. In both cases, serum glucose was significantly higher in the adult animals exposed 

during gestation and lactation than in controls and there was evidence of insulin resistance. The 

LOAEL was 0.5 mg/kg/day in the Lv et al. (2013) study and 3 mg/kg/day for pups fed a diet 

with normal fat levels (Wan et al. 2014b). In the Wan et al. (2014b) study, the NOAEL was 

0.3 mg/kg/day. When accompanied by a high fat diet, 0.3 mg/kg/day was a LOAEL for increased 

insulin resistance.

3.4.1.3 Immunotoxicity

A few studies have evaluated associations with measures indicating immunosuppression. 

Two studies reported decreases in response to one or more vaccines (diphtheria, rubella) in 

children aged 3, 5, and 7 years (e.g., measured by antibody titer) in relation to increasing 

maternal serum PFOS levels (maternal levels ranging from 0.0056 to 0.027 μg/mL) during 

pregnancy or in the children at 5 years of age (mean child 0.0167 μg/mL) (Grandjean et al. 2012; 

Granum et al. 2013). Decreased rubella and mumps antibody concentrations in relation to serum 

PFOS concentration were found among 12–19 year old children in the NHANES, particularly 

among seropositive children (Stein et al. 2015). A third study of adults found no associations 

with antibody response to influenza vaccine (Looker et al. 2014). In the three studies examining 

exposures in the background range among children (i.e., general population exposures, geometric 

means < 0.02 μg/mL), the associations with PFOS were also seen with other correlated PFAS, 

complicating conclusions specifically for PFOS.

No clear associations were reported between prenatal PFOS exposure and incidence of 

infectious disease among children (Fei et al. 2010b; Okada et al. 2012), although there might be 

effect modification by sex. With regard to other immune dysfunction, serum PFOS levels were 

not associated with risk of ever having had asthma among children in the NHANES with median 

levels of 0.017 μg/mL (Humblet et al. 2014). A study among children in Taiwan with higher 

serum PFOS concentrations (median with and without asthma 0.0339 and 0.0289 μg/mL, 

respectively) found higher odds ratios for physician-diagnosed asthma with increasing serum 

PFOS quartile (Dong et al. 2013). Associations also were found for other PFASs. Among 

asthmatics, serum PFOS was also associated with higher severity scores, serum total IgE, 

absolute eosinophil counts, and eosinophilic cationic protein levels. 

Other data on the immunotoxicity of PFOS in humans are limited to in vitro studies using 

cells recovered from human blood (PBMCs; Brieger et al. 2011 or CD4+ T cells; Midgett et al.

2014). In both cases the concentration of PFOS with a demonstrated significant effect was 

100 μg/mL, and the concentration that lacked any effects was 10 μg/mL. A significant 

(p < 0.001) decrease in TNFα and a nonsignificant trend towards increasing IL-6 release from 

stimulated monocytes were seen, but no effects were measured on stimulated T cells (Brieger et 

al. 2011). T cell IL-2 production was decreased in the Midgett et al. (2014) study. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-109
Studies in mice examined NK cell activity and SRBC response following oral dosing with 

PFOS. Three of four studies showed effects on SRBC response and/or NK cell activity at the 

same dose that caused increased liver weight (Dong et al. 2009; Keil et al. 2008; Zheng et al.

2009). Based on the limited evidence, neither response appeared more sensitive than the other. 

The animal studies indicate that females are less susceptible to impacts on NK cell activity and 

the SRBC response than males.

The NK cell activity was enhanced at very low PFOS doses, while it was depressed at higher 

doses. Peden-Adams et al. (2008) and Dong et al. (2009) showed increased NK cell activity in 

male mice following exposure to 0.0017 mg/kg/day and 0.083 mg/kg/day, respectively. The 

increased activity in Dong et al. (2009) correlated with a PFOS serum level of approximately 

7.1 μg/mL. In the Dong et al. (2009) study, the NK cell activity was significantly decreased at a 

higher dose of 0.833 mg/kg/day, demonstrating a U-shaped response to dose. Doses 

≥ 1 mg/kg/day resulted in decreased NK cell activity in offspring of dams treated during 

gestation (Keil et al. 2008) and in adult male mice (Zheng et al. 2009). 

In the Peden-Adams et al. (2008) study, IgM suppression occurred after 28 days of treatment 

with 0.0017 mg/kg/day although there were not any overt signs of toxicity. Further investigation 

found that the IgM suppression was observed in both the T-cell independent and dependent tests 

making the humoral immune effects caused by B-cells. Other studies also showed a suppression 

of the SRBC response at higher doses of PFOS (Dong et al. 2009; Keil et al. 2008; Zheng et al.

2009). Guruge et al. (2009) found a decrease in survival in mice exposed to 0.025 mg/kg of 

PFOS after exposure to influenza A virus. 

Qazi et al. (2009a) reported that approximately 40 mg/kg/day in the diet for 10 days in wildtype and PPARα-null 129/Sv knock-out mice caused a pronounced decrease in the total number 

of thymocytes and splenocytes, as well as a decrease in size of the those present in wild-type 

mice. Knock-out mice had a reduction in the total number of thymocytes that was less than that 

seen in the wild-type mice. Effects on splenocytes were mostly eliminated in knock-out mice.

The study, thus, indicated that the immunomodulation was partially dependent on PPARα.

Mechanisms that could cause these effects other than PPAR activation are not known. At the 

same dose, Qazi et al. (2009b) did not find elevated levels in serum or spleen of TNF-α and IL-6 

in response to stimulation by LPS in C57Bl/6 mice, but levels were increased in the cells from 

the peritoneal cavity and bone marrow 

3.4.1.4 Neurotoxicity 

Developmental neurotoxicity and adult neurotoxicity studies have been conducted in rats and 

mice. Mechanistic studies have examined effects on excitatory amino acids and gene profiles 

following PFOS exposures. 

Butenhoff et al. (2009) found significantly increased motor activity and decreased 

habituation of male offspring at one time point (PND 17) following gestational and lactational 

dosing of dams with 1.0 mg/kg/day. No effects were found on learning and memory with the 

Biel swimming maze. Luebker et al. (2005b) found no effects on passive avoidance behavior or 

water maze learning and memory in F1 offspring at a daily dose of 0.4 mg/kg/day. Y. Wang et 

al. (2015) used water maze testing on offspring from treated dams who were cross-fostered with 

either control or treated dams, and continued on the treatment of their lactational dam. Escape 

latency was significantly increased for all treated groups on one or more testing days with the 

most pronounced effect in pups exposed prenatally from dams given 15 mg/L drinking water and 

Perfluorooctane sulfonate (PFOS) – May 2016 3-110
cross-fostered to control dams. Y. Wang et al. (2015) did not provide data on water intake or 

body weight data. A drinking water concentration of 5 mg/L was a NOAEL, and a concentration 

of 15 mg/L was a LOAEL for offspring. Estimated adult doses are 0.8 and 2.4 mg/kg/day, 

respectively, using the subchronic USEPA (1988) conventions for water intake and body weight. 

Long et al. (2013) found a significantly longer latency to escape, with significantly less time 

spent in the target quadrant in the Morris water maze test for learning and memory at a dose of 

2.5 mg/kg/day in 8-week-old C57BL6 mice. The NOAEL for these effects was 0.43 mg/kg/day. 

Effects were observed on excitatory amino acids in the central nervous systems of rats when 

administered 25 mg/kg/day of PFOS one time (Yang et al. 2009). Wang et al. (2010) found that 

pre-natal exposure to 3.2 mg/kg/day of PFOS in the feed had some effect on gene expression 

involved in neuroactive ligand-receptor interaction, calcium signaling pathways and PPAR 

signaling. Zeng et al. (2011) also found PFOS administered to pregnant rats as low as 0.1 mg/kg 

from GD 2 to 21 caused significant increases of PFOS in the brain (hippocampus and cortex) of 

the offspring, with effects on inflammatory markers and transcription factors. Two-month-old 

mice exposed to 0.75 mg/kg of PFOS when they were 10 days old (Johansson et al. 2008) 

displayed abnormal habituation responses in motor activity testing. Cultured hippocampal 

neurite growth and branching were suppressed by exposure to 50 μmol PFOS. The authors 

hypothesized that this was a consequence of PFOS incorporation into the neuronal lipid bilayer 

membrane (Liao et al. 2009). The effect of PFOS was greater than that of PFOA. PFOS was the 

only member of the sulfonate family to exhibit this effect.

3.4.1.5 Thyroid Effects

Numerous epidemiologic studies have evaluated thyroid hormone levels and/or thyroid 

disease in association with serum PFOS concentrations. These epidemiologic studies provide 

limited support for an association between PFOS exposure and incidence or prevalence of 

thyroid disease, and include large studies of representative samples of the general U.S. adult 

population (Melzer et al. 2010; Wen et al. 2013). These highly powered studies reported 

associations between PFOS exposure (serum PFOS concentrations) and thyroid disease but not 

thyroid hormone status. Melzer et al. (2010) studied thyroid disease with medication (PFOS level 

of 0.025 μg/mL in males and 0.019 μg/mL in females) and Wen et al. (2013) studied subclinical 

thyroid disease (mean serum 0.0142 μg/mL). Thyroid function can be affected by iodide 

sufficiency and by autoimmune disease. People testing positive for the anti-TPO biomarker for 

autoimmune thyroid disease showed associations with PFOS (0.0048 μg/mL) and TSH or T4 

(Webster et al. 2014); this association was stronger in people with both low iodide status and 

positive anti-TPO antibodies, with a PFOS level of 0.014 μg/mL (Webster et al. 2015). These 

studies used anti-TPO antibody levels as an indication of stress to the thyroid system, not a 

disease state. Thus, the association between PFOS and altered thyroid hormone levels is stronger 

in people at risk for iodine deficiency than those receiving adequate dietary iodine. In people 

without diagnosed thyroid disease or without biomarkers of thyroid disease, thyroid hormones 

(TSH, T3, or T4) show mixed effects across cohorts.

Several animal models have described changes in thyroid hormone levels after administration 

of PFOS. In contrast to the human epidemiology studies, the most consistent finding in animals 

treated with PFOS was a decrease in T4 with slight, or no, changes in T3. Any changes found in 

T3 and T4 levels failed to activate the hypothalamic-pituitary-thyroid (HPT) feedback 

mechanism to produce significant elevations of serum TSH. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-111
Rats treated orally with PFOS for 1–5 days had significant decreases in total T4 at doses of 

10 and 15 mg/kg, but not at 5 mg/kg (Chang et al. 2007, 2008; Martin et al. 2007). With 

treatment for 7 days, total T4 was decreased at 1 and 3 mg/kg (Yu et al. 2011). 

In Cynomolgus monkeys treated with 0.03, 0.15, or 0.75 mg/kg/day of PFOS for 26 weeks, 

Seacat et al. (2002) saw significant reductions of total triiodothyronine (T3) (~ 50%), and a less 

consistent effect in total thyroxine (TT4, females only). This was more pronounced at the end of 

exposure period in the high-dose group but neither a dose-response nor evidence of 

hypothyroidism was observed. TSH levels were variable during the study, but increased 2-fold in 

the high-dose males at the end of exposure.

Exposure of pregnant rats to PFOS at 1 mg/kg/day, which corresponded to maternal serum 

concentrations of 14–26 μg/mL, resulted in decreases in T4 and T3 in dams (Thibodeaux et al.

2003) and decreased T4 in pups (Lau et al. 2003). No effect was observed on serum TSH. In 

contrast, no effects were found on thyroid hormones in either dams or pups when females were 

treated prior to mating and through LD 4 (Luebker et al. 2005a). Histological and morphometric 

evaluations of the fetal and neonatal thyroid glands indicated normal number and size 

distribution of follicles, and normal follicular epithelial cell heights and colloid areas (Chang et 

al. 2009). 

In addition to the evaluation of PFOS’s effects on serum TT4, several studies have examined 

the levels of circulating FT4 (Lau et al. 2003; Luebker et al. 2005a; Thibodeaux et al. 2003; Yu 

et al. 2011). In these studies, FT4 was reduced after PFOS administration when measured by 

analog radioimmunoassays (RIA). However, when the FT4 was measured by an equilibrium 

dialysis step prior to the standard RIA (ED-RIA), FT4 levels in the PFOS-treated rats were 

comparable to those of controls (Luebker et al. 2005a). 

Mechanisms underlying the PFOS-induced alterations in thyroid hormones are still under 

active investigation, but do not likely involve altered de novo biosynthesis of the hormones or 

compromised integrity of the HPT axis. Yu et al. (2009b) reported no significant effects of PFOS 

on the sodium iodide symporter gene expression (for iodide uptake) or thyroid peroxidase 

activity in the thyroid gland. Chang et al. (2008) showed that release of TSH from the pituitary in 

response to ex vivo TRH stimulation was not altered by PFOS exposure. 

Weiss et al. (2009) demonstrated that perfluorinated chemicals (including PFOS) are capable 

of competing with T4 and displacing the hormone from binding to the human thyroid hormone 

transport protein transthyretin (TTR). In fact, PFOS ranks the second highest in binding potency 

among all perfluorinated compounds examined, although its TTR binding potency is only onefifteenth of that for T4. Similarly, Ren et al. (2015) demonstrated that PFOS bound to the ligand 

binding domain of the human thyroid hormone receptor, although with a much lower affinity 

than T3. 

Several possibilities might account for the differential findings of thyroid hormone disruption 

between animal models and human biomonitoring data. First, decreased T3 or T4 was observed 

in adult monkeys and rodents only when serum PFOS reached the 70–90 μg/mL range. Pregnant 

rats and neonatal rats appeared to be more sensitive, exhibiting TT4 depression when serum 

PFOS reached about 20 and 40 μg/mL, respectively. However, serum PFOS in general 

populations of humans is estimated to be 0.018–0.037 μg/mL, about three orders of magnitude 

lower than the effective body burden for thyroid hormone disruption in animal models. 

Secondly, TBG (rather than TTR as in rodents) is the major thyroid hormone transporter in 

Perfluorooctane sulfonate (PFOS) – May 2016 3-112
humans. Although PFOS can bind to human TTR and effectively displaces T4 as illustrated in 

the rat model, its binding affinity to TBG is unknown. PFOS has been shown to have much a 

lower binding affinity for both TTR and the thyroid hormone receptor than do T4 and T3, 

respectively (Ren et al. 2015; Weiss et al. 2009).

3.4.2 Synthesis and Evaluation of Carcinogenic Effects

The small set of epidemiology studies of PFOS exposure do not suggest that there is an 

association with cancer, but the breadth and scope of the studies are not adequate to make 

definitive conclusions. While an elevated risk of bladder cancer mortality was associated with 

PFOS exposure in an occupational study (Alexander et al. 2003), a subsequent study to ascertain 

cancer incidence in the cohort observed elevated but statistically insignificant incidence ratios 

that were 1.7- to 2-fold higher among exposed workers (Alexander and Olsen 2007). Mean 

PFOS serum levels were 0.941 μg/mL. No elevated bladder cancer risk was observed in a nested 

case-control study in a Danish cohort with plasma PFOS concentrations at enrollment ranging 

0.001–0.1305 μg/mL (Eriksen et al. 2009). 

Elevated odds ratios for prostate cancer were reported for the occupational cohort examined 

by Alexander and Olsen (2007) and the Danish population-based cohort examined by Eriksen et 

al. (2009), however the confidence intervals included the null, and no association was reported 

by another case-control study in Denmark (Hardell et al. 2014). A case-control study of breast 

cancer among Inuit females in Greenland with similar serum PFOS levels to those of the Danish 

population (0.0015–0.172 μg/mL) reported an association of low magnitude that could not be 

separated from other perfluorsulfonated acids, and the association was not confirmed in a Danish 

population (Bonefeld-Jørgensen et al. 2011, 2014). Some studies evaluated associations with 

serum PFOS concentration at the time of cancer diagnosis and the impact of this potential 

exposure misclassification on the estimated risks is unknown (Bonefeld-Jørgensen et al. 2011; 

Hardell et al. 2014). No associations were adjusted for other perfluorinated chemicals in serum in 

any of the occupational and population-based studies. 

The only chronic toxicity/carcinogenicity study in animals was a rat study (Thomford 

2002/Butenhoff et al. 2012). Increased incidence of hepatocellular adenomas in the male (12% at 

the high dose) and female rats (8% at the high dose) and combined adenomas/carcinomas in the 

females (10% at the high dose) were observed, but they did not display a clear dose-related 

response. In males but not females the serum ALT levels were increased at 14, 27, and 53 weeks. 

At 105 weeks there was an increase in eosinophilic clear cell foci, and cystic hepatocellular 

degeneration in males given 2, 5, and 20 ppm PFOS. Low levels of single cell necrosis in all 

dose groups (males and females) were identified; the increase compared to controls was

significant at the high dose in males and females (Table 3-15). 

Thyroid tumors (adenomas and carcinomas) were seen in males receiving 0, 0.5, 2, 5, or 

20 ppm and in females receiving 5 or 20 ppm in their diet. The tumor (adenomas + carcinomas) 

prevalence for males was consistent across dose groups. In males the incidence of thyroid tumors 

was significantly elevated only in the high-dose, recovery group males exposed for 52 weeks 

(10/39) but not in the animals receiving the same dose at 105 weeks. There were very few 

follicular cell acenomas/carcinomas in the females (5 total) with no dose-response. The most 

frequent thyroid tumor type in the females was C-cell adenomas, but the highest incidence was 

that for the controls and there was a lack of dose response among the exposed groups. C-cell 

adenomas were not observed in males (Thomford 2002/Butenhoff et al. 2012). 

Perfluorooctane sulfonate (PFOS) – May 2016 3-113
There was a high background incidence in mammary gland tumors in the female rats, 

primarily combined fibroma adenoma and adenoma, but the incidence lacked dose-response for 

all tumor classifications. Mammary gland carcinomas also lacked dose-response and had a 

relatively comparable incidence across dose groups including the controls (Thomford 

2002/Butenhoff et al. 2012). 

All genotoxicity studies including an Ames test, mammalian-microsome reverse mutation 

assay, an in vitro assay for chromosomal aberrations, an unscheduled DNA synthesis assay, and 

mouse micronucleus assay were negative.

3.4.3 Mode of Action and Implications in Cancer Assessment

Short-term genotoxicity assays suggested that PFOS is not a DNA-reactive compound. The 

results from five in vitro studies (Cifone 1999; Litton Bionetics, Inc. 1979; Mecchi 1999; Murli 

1999; Simmon 1978) were negative, as was the result from an in vivo bone marrow micronucleus 

assay (Murli 1996). 

Induction of peroxisome proliferation has been suggested as the mode of action for an 

increasing number of non-genotoxic carcinogens that induce liver tumors upon chronic 

administration to rats, mice, or both (Ashby et al. 1994; Rao and Reddy 1996). The liverexpressed peroxisome PPARα regulates the transcription of genes involved in peroxisome 

proliferation, cell cycle control, apoptosis, and lipid metabolism. The data for PFOS illustrate the 

ability of PFOS to activate PPARα (Martin et al. 2007; Shipley et al. 2004; Wolf et al. 2008, 

2012). However, data are generally lacking for increased cell proliferation. No increase in 

hepatic cell proliferation was detected in the subchronic study (Seacat et al. 2003) or the cancer 

bioassay (Thomford 2002/Butenhoff et al. 2012); limited necrosis was observed across all doses 

and significantly (p < 0.05) increased for the 20 ppm males and females. In addition, no 

subchronic or longer term studies revealed evidence of preneoplastic foci in the liver. Liu et al. 

(2009) studied biomarkers for oxidative stress in the liver and brain in KD mice. Levels of MDA 

did not differ between controls and exposed animals; SOD activity was lower than that observed 

in the controls.

Other possible MOAs for carcinogenicity have been explored, including mitochondrial 

biogenetics and GJIC. While PFOS was shown to be a weak toxicant to isolated mitochondria 

(Starkov and Wallace 2002), it inhibited GJIC in a dose-dependent manner in two cell lines and 

in liver tissue from rats exposed orally (Hu et al. 2002). These are not clearly defined MOAs, and 

their importance relative to PFOS exposure is not certain. Ngo et al. (2014) used the mouse 

model C57BL/6J –Min/+ for intestinal neoplasia to determine effects following in utero

exposure. Maternal treatment with PFOS at doses up to 0.3 mg/kg/day during gestation did not 

result in an increase of intestinal tumors in either wildtype or susceptible offspring up to 20 

weeks of age. 

3.4.4 Weight of Evidence Evaluation for Carcinogenicity 

Under the EPA Guidelines for Carcinogen Risk Assessment (USEPA 2005a) there is 

suggestive evidence of carcinogenic potential of PFOS in humans. A single chronic cancer 

bioassay in animals is available for PFOS. Although liver adenomas were significantly increased 

in males and females at the highest dose and a positive trend was observed (p = 0.03), a doseresponse pattern was not observed. In males the incidence of thyroid follicular tumors was 

Perfluorooctane sulfonate (PFOS) – May 2016 3-114
elevated only in the high-dose, recovery group exposed for 52 weeks, where it was about 3 times 

greater than the incidence in rats given the same dose for 104 weeks. As was the case for the 

liver tumors, the thyroid adenoma data did not show a direct response to dose. Based on the 

available evidence, the data are inadequate to support a PPARα-linked MOA for the liver and 

thyroid adenomas observed by Thomford (2002)/Butenhoff et al. (2012) in the chronic 2 year 

bioassay in Sprague-Dawley Crl:CD(SD)IGS BR rats.

3.4.5 Potentially Sensitive Populations

In humans, single blood samplings of different populations within the United States do not 

support major gender differences in half-life or sensitivity to PFOS. Gender differences could not 

be determined by those exposed by occupational exposure, as the majority of those tested were 

males. Serum monitoring among the NHANES populations (2004–2008) found significantly 

(p < 0.05) higher PFOS levels in males (0.020 μg/L) than females (0.014 μg/L). However, this 

difference is more likely to be related to exposures than to sensitivity.

Evidence from animal studies does not suggest major differences between genders in the 

amount of PFOS identified in the serum and liver tissue of animals or in the toxicity. In the 

monkey studies and most developmental rat studies, there do not appear to be any differences 

between the males and females after administration of PFOS. However, in the 

chronic/carcinogenicity study in rats, the male rats do appear to be slightly more sensitive to liver 

toxicity. In animal studies of immunological effects, the response to NK cell suppression 

occurred at a lower dose in males than in females (Peden-Adams et al. 2008). 

Animal studies clearly show that developmental exposure of rats or mice to PFOS 

administered during gestation results in rapid, dose-dependent effects on neonatal survival (Lau 

et al. 2003; Luebker et al. 2005a, 2005b). Additional long term effects on postnatal growth and 

delays in developmental landmarks (eye opening, pinna unfolding, surface righting, air righting) 

occur in surviving rat pups. The mechanistic cause of this developmental toxicity is unknown, 

but investigations of several potential modes of action are summarized here. Generally, there is a 

lack of consistency among the epidemiology studies regarding potential associations between 

PFOS levels during pregnancy and developmental birth outcomes. Some studies indicate a 

potential impact on birth weight, but this finding is not consistent across studies. 

The animal data on LBW receive support from the epidemiolgy (Apelberg et al. 2007; Chen 

et al. 2015; Darrow et al. 2013; Maisonet et al. 2012; Washino et al. 2009). For humans with low 

GFR (females with pregnancy-induced hypertension or preeclampsia in late pregnancy), the 

impact on body weight is likely due to a combination of the low GFR and the serum PFOS 

(Verner et al. 2015). Low GFR in pregnant females will tend to cause an increase in serum PFOS 

compared to individuals with a normal GFR. Females with hypertension during pregnancy could 

have an increased risk for having a LBW baby. 

The fat content of the diet appears to be an important variable that influences the effects from 

PFOS exposures. Elevated total cholesterol, HDL, and sometimes triglycerides are effects seen 

in a number of the human epidemiology studies. However, none of the studies evaluated 

appeared to control for fat content in the typical diet of the subjects. Martin et al. (2007), Bijland 

et al. (2011), and Wan et al. (2012) found hepatic steatosis in PFOS-treated animals. Liver fat 

increased with both a high fat diet alone and with a high fat diet plus PFOS (Wan et al. 2012). In 

the same study, significant increases in the expression of fatty acid translocase and lipoprotein 

lipase was observed at the 10 mg/kg/day PFOS dose. Mobilization of liver lipids appeared to 

Perfluorooctane sulfonate (PFOS) – May 2016 3-115
decrease following the PFOS exposure leading to lower serum LDL/VLDL levels; VLDLs are 

carriers of liver triglycerides and other lipids from liver to serum.

To help characterize the mechanism of PFOS induced neonatal mortality, Grasty et al. (2003) 

examined critical windows of exposure by treating rats with a high dose of PFOS (25 mg/kg/day) 

for a 4-day period during various stages of pregnancy. Neonatal mortality occurred after all 

treatment periods, but the incidence of neonatal death increased when exposure occurred later in 

gestation. Mortality was highest when treatment occurred on gestation days (GDs) 17–20, 

identifying late gestation as a critical exposure window for increasing the risk of neonatal 

survival. The effects of PFOS at this stage of development could be related to an impact of PFOS 

on lung surfactants leading to respiratory distress syndrome. Both Luebker et al. (2005a) and Lau 

et al. (2003) identified pup mortality as adverse effects of gestational PFOS exposures. 

Perfluorooctane sulfonate (PFOS) – May 2016 3-116
4. DOSE-RESPONSE ASSESSMENT

A Reference Dose (RfD) or Reference Concentration (RfC) is used as a benchmark for the 

prevention of long-term toxic effects other than carcinogenicity. RfD/RfC determination assumes 

that thresholds exist for toxic effects, such as cellular necrosis, significant body or organ weight 

changes, blood disorders, and so on. The RfD is expressed in terms of milligrams per kilogram 

per day (mg/kg/day), and the RfC is expressed in milligrams per cubic meter (mg/m3). The RfD 

and RfC are estimates (with uncertainties spanning perhaps an order of magnitude) of the daily 

exposure to the human population (including sensitive subgroups) that is likely to be without an 

appreciable risk of deleterious effects during a lifetime.

4.1 Dose-Response for Noncancer Effects

4.1.1 RfD Determination

Human Data. In humans, data have been obtained from studies evaluating both occupational 

and general population exposure scenarios. Some studies monitored similar populations over 

time to determine whether or not a trend was present. Pathways of exposure in the general 

population appear to be from drinking water, food (especially fish/seafood), and some 

environmental exposures (e.g., carpets, house dust). In general, PFOS levels in the serum of the 

general population have decreased since production was stopped in the United States.

Multiple epidemiology studies evaluated serum lipid status in association with PFOS 

concentration. These studies provide support for an association between PFOS and small 

increases in total cholesterol. Hypercholesterolemia, (clinically defined as cholesterol 

> 240 mg/dL) was associated with PFOS exposure in a Canadian cohort (Fisher et al. 2013) and 

in the C8 cohort (Steenland et al. 2009); PFOS levels in these studies were 0.0084 μg/mL and 

0.022 μg/mL, respectively. Cross-sectional occupational studies demonstrated an association 

between PFOS and total cholesterol (Olsen et al. 2001a, 2001b, 2003b), with much higher PFOS 

serum levels of up to 1.40 μg/mL. Evidence for associations between PFOS and other serum 

lipids including HDL cholesterol, LDL, VLDL, non-HDL cholesterol, and triglycerides is mixed. 

The studies on serum lipids in association with PFOS serum concentrations are largely crosssectional in nature and were largely conducted in adults. Some studies exist on children and 

pregnant females. The location of these cohorts varied from the U.S. population including 

NHANES volunteers, to the Avon cohort in the UK, to and Scandanivian countries. Limitations 

to these studies include the frequently high correlation between PFOA and PFOS exposure; not 

all studies control for PFOA in study design. 

Studies that evaluated thyroid hormone levels and/or thyroid disease in association with 

serum PFOS concentrations include large representative samples of the general U.S. adult 

population and provide limited support for an association between PFOS exposure and the 

incidence or prevalence of thyroid disease. PFOS levels in Melzer et al. (2010) were

0.025 μg/mL in males and 0.019 μg/mL in females, and in Wen et al. (2013) they were 

0.0142 μg/mL. Pregnant females testing positive for the anti-TPO biomarker for autoimmune 

thyroid disease showed a positive association with PFOS (0.0048 μg/mL) and TSH (Webster et 

al. 2014). In a second study, Webster et al. (2015) found an association with PFOS 

(0.014 μg/mL) and TSH and T3 in a subset of the NHANES population with both low iodide 

status and positive anti-TPO antibodies. Anti-TPO antibody levels are an indication of stress to 

Perfluorooctane sulfonate (PFOS) – May 2016 4-1 
the thyroid system, not a disease state. Thus, the association between PFOS and altered thyroid 

hormone levels is stronger in people at risk for thyroid insufficiency or disease. In people 

without diagnosed thyroid disease or without biomarkers of thyroid disease, thyroid hormones 

(TSH, T3, or T4) show mixed effects across cohorts.

A few studies evaluated associations with measures of immunosuppression. Two studies 

reported decreases in response to one or more vaccines (diphtheria, rubella) in children aged 3, 5, 

and 7 years (e.g., measured by antibody titer) in relation to increasing maternal serum PFOS 

levels (ranging 0.0056–0.027 μg/mL) during pregnancy or at 5 years of age (Grandjean et al.

2012; Granum et al. 2013). Decreased rubella and mumps antibody concentrations in relation to 

serum PFOS concentration were found among 12–19 year old children in the NHANES, 

particularly among seropositive children (Stein et al. 2015). A study of adults found no 

associations with antibody response to influenza vaccine (Looker et al. 2014). In the three studies 

examining exposures in the background range among children (i.e., general population 

exposures, geometric means < 0.02 μg/ml), the associations with PFOS were also correlated with 

other PFASs, complicating conclusions as they applied to PFOS.

No clear associations were reported between prenatal PFOS exposure and incidence of 

infectious disease among children (Fei et al. 2010b; Okada et al. 2012), although an elevation in 

risk of hospitalizations for infectious disease was found among girls, suggesting effect 

modification by sex. PFOS levels were not associated with risk of ever having had asthma 

among children in the NHANES with median levels of 0.017 μg/mL (Humblet et al. 2014). A 

study among children in Taiwan with higher serum PFOS concentrations (median with and 

without asthma 0.0339 and 0.0289 μg/mL, respectively) found higher odds ratios for physiciandiagnosed asthma with increasing serum PFOS quartile (Dong et al. 2013). Associations with 

other PFASs were also positive. Among asthmatics, serum PFOS was associated with higher 

severity scores, serum total IgE, absolute eosinophil counts, and eosinophilic cationic protein 

levels.

The set of studies evaluating fetal growth retardation suggest an association of prenatal 

serum PFOS with deficits in mean birth weight and with LBW, however it is not entirely 

consistent. Birth weight deficits ranging from 29 to 149 grams were detected in five studies 

(Apelberg et al. 2007; Chen et al. 2015; Darrow et al. 2013; Maisonet et al. 2012; Washino et al. 

2009). In these studies, PFOS serum levels ranged from 0.005 to 0.0132 μg/mL. Three (Chen et 

al. 2012; Fei et al. 2007; Stein et al. 2009) out of four (Darrow et al. 2014) studies of LBW 

showed increased risks (OR range: 1.5–4.8). Studies have questioned whether low maternal GFR 

is a confounder in epidemiology studies of birth weight and PFOS (Morken et al. 2014; Verner et 

al. 2015). The Verner et al. (2015) study compared the results from a meta-analysis of the 

epidemiology data with PBPK simulations and concluded that the some, but not all, of the 

association reported between PFOS and birth weight is attributable to low GFR. Thus, the 

interpretation of the observed associations is unclear.

A small set of studies observed an association with gestational diabetes (Zhang et al. 2015, 

preconception serum PFOS), pre-eclampsia (Stein et al. 2009), and pregnancy-induced 

hypertension (Darrow et al. 2013) in populations with serum PFOS concentrations of 0.012 – 

0.017 μg/mL. Zhang et al. (2015) and Darrow et al. (2013) used a prospective assessment of 

adverse pregnancy outcomes in relation to serum PFAS thereby avoiding some of the limitations 

of the available cross-sectional studies. Associations with serum PFOA and adverse pregnancy 

outcome were identified. 

Perfluorooctane sulfonate (PFOS) – May 2016 4-2 
There is consistent evidence of associations of serum PFOS with decreased fertility and 

fecundity (Bach et al. 2015; Fei et al. 2009; Jørgensen et al. 2014; Vélez et al. 2015). While a 

concern over the possibility of reverse causation explaining observed associations has been 

raised (Whitworth et al. 2012), the collective findings, particularly from a more recent study 

(Bach et al. 2015), support a consistent association with fertility and fecundity measures and 

PFOS exposures. Although there was some suggestion of an association between PFOS 

exposures and semen quality parameters in a few studies (Joensen et al. 2009; Toft et al. 2012), 

most studies were largely null (Buck Louis et al. 2015; Ding et al. 2013; Joensen et al. 2013; 

Raymer et al. 2012; Specht et al. 2012; Vested et al. 2013).

Animal Data. Adequate studies were available for short-term, subchronic, chronic, 

developmental, and reproductive parameters in rats, mice, and primates. Subchronic, chronic, 

and reproductive toxicity animal studies, all with exposure duration greater than 60 days, have 

been summarized in Table 4-1. Shorter duration studies that focused on immunotoxicity 

endpoints and developmental toxicity studies are summarized in Table 4-2. Although the 

exposure durations are shorter in developmental studies, they are important in quantification of 

dose-response because the exposures occur during critical windows of development and are often 

symptomatic of effects that can occur later in life. It is noted, however, that in some of these 

studies, steady states of PFOS might not have been achieved due to the long half-life of PFOS in 

animal models (see discussion of steady state in section 4.1.1.1) 

Seacat et al. (2002) treated monkeys with PFOS for up to 6 months and found increased liver 

weight and centrilobular or diffuse hepatocellular hypertrophy at 0.75 mg/kg/day, but no clear 

evidence of peroxisomal or cell proliferation. Hepatic peroxisome proliferation, measured by 

PCoAO activity, was increased significantly in the females at 0.75 mg/kg/day; however, the 

magnitude was less than the 2-fold increase typically indicating biological significance and 

PPARα activation. There were no treatment-related effects on cell proliferation in the liver, 

pancreas, or testes; survival was decreased among the males. At the dose with no effects 

observed (0.15 mg/kg/day), the serum concentration was 83 μg/mL in males and 67 μg/mL in 

females. At the effect level (0.75 mg/kg/day), the serum concentrations were 173 μg/mL in 

males and 171 μg/mL in females, about twice those for the no-effect serum level despite a 5-fold 

increase in dose. 

Microscopic lesions of the liver were observed at doses of 1.33 mg/kg/day in males and 

1.56 mg/kg/day in females after 14 weeks (Seacat et al. 2003) and at 0.098 mg/kg/day in males 

and 0.299 mg/kg/day in females after 105 weeks (Thomford 2002/Butenhoff et al. 2012). Liver 

lesions included centrilobular hypertrophy and vacuolation after the subchronic and chronic 

exposures with eosinophilic granules observed after 104 weeks. No evidence of peroxisome 

proliferation was found during either phase of the study. Mean no effect levels in males and 

females were 0.34 mg/kg/day and 0.40 mg/kg/day, respectively, after 14 weeks and 0.024 mg/

kg/day and 0.120 mg/kg/day, respectively, after 104 weeks. 

Rat dams were treated with PFOS for 63 or 84 days in one- and two-generation reproductive 

studies, respectively (Luebker et al. 2005a, 2005b). No changes in maternal liver weight were 

observed with either protocol. The most sensitive endpoint was decreased pup body weight at 

0.4 mg/kg/day in both the one- and two-generation study. A NOAEL for pup body weight effects 

was 0.1 mg/kg/day in the two-generation study; the one-generation study (Luebker et al. 2005a) 

lacked a NOAEL, as pup body weight was impacted at the lowest dose tested (0.4 mg/kg/day). 

Perfluorooctane sulfonate (PFOS) – May 2016 4-3 
Table 4-1. NOAEL/LOAEL and Effects for Longer-Term Duration Studies of PFOS

Species Study Duration

NOAEL

(mg/kg/day)

LOAEL

(mg/kg/day) Critical Effect(s) Reference

Monkey 90 days ND 0.5 diarrhea, anorexia Goldenthal et al. 

1979 

Monkey 182 days (6 

months)

0.15 0.75 ↓ survival, body wt gain

↑ liver wt; hepatocyte 

hypertrophy,

↓T3 and ↑TSH

Seacat et al. 

2002

Rat 90 days ND 2.0 ↑ liver wt

hepatocyte hypertrophy

Goldenthal et al. 

1978b

Rat 98 days (14 

weeks)

0.40 (F)

0.34 (M)

1.56 (F)

1.33 (M)

↑ liver wt

↓ cholesterol (M)

↑ ALT (M), ↑BUN (M/F) 

↑ liver hypertrophy

hepatic centrilobular

vacuolization

Seacat et al. 

2003

Rat 2 generation

(84 days; 12 

weeks) 

0.1 0.4 ↓ adult body wt gain

↓ pup body wt

Luebker et al. 

2005b

Rat 1 generation

(females only)

(63 days)

0.4 0.8 ↓ maternal wt gain

↓ gestation length

↓ pup survival

Luebker et al. 

2005a

Rat 1 generation

(females only)

(63 days)

ND 0.4 ↓ pup body weight Luebker et al. 

2005a

Rat 728 days

(104 weeks; 2 yrs)

0.120 (F)

0.024 (M)

0.299 (F)

0.098 (M)

Cystic degeneration, 

centrilobular vacuolation (M)

and centrilobular eosinophilic 

granules (F); ↑hepatic necrosis 

centrilobular vacuolation at 

higher doses

Thomford 

2002/Butenhoff 

et al. 2012

Mouse 60 days 0.008 0.083 ↑ liver wt

↑ splenic NK cell activity; ↓ 

SRBC response

Dong et al. 

2009

Mouse 90 days 0.43 2.15 Impaired spatial learning and 

memory

Long et al. 2013

Notes: ND = not determined

BUN = blood urea nitrogen

M = male; F = female

Offspring survival was affected in a dose-related manner in the one-generation study, with a 

biologically important decrease in viability index attained at 0.8 mg/kg/day and statistical 

significance reached at 1.6 mg/kg/day (Luebker et al. 2005a). In the two generation study 

(Luebker et al. 2005b), F1 offspring viability was markedly impacted at a dose of 1.6 mg/kg/day, 

resulting in discontinuation of that dose for production of the F2 generation 

Some effects on thyroid-related parameters were noted in animals, but there did not appear to 

be any increase in hypothyroid or hyperthyroid disorders. In the Seacat et al. monkey study 

(2002), trends for reduced total triiodothyronine (T3) and increased TSH (males only) were 

observed and reached statistical significance for T3 in males and females. In the case of TSH, the 

decrease was significant only for males. The trend in females lacked clear dose-response. There 

was no evidence of hypothyroidism. PFOS-induced alterations of thyroid hormones were also 

seen studies on adult rats (Martin et al. 2007; Thibodeaux et al. 2003; Yu et al. 2009b, 2011); 

Perfluorooctane sulfonate (PFOS) – May 2016 4-4 
however, most reductions involved circulating TT4, instead of T3. In most animal studies, 

however, the changes in T3 and TT4 failed to activate the HPT feedback mechanism to produce 

significant elevations of serum TSH.

Across the range of longer-term studies, the lowest LOAEL is 0.098 mg/kg/day for 

histopathological changes in the liver of male Sprague-Dawley rats following a 104-week 

(2-year) exposure (Thomford 2002/Butenhoff et al. 2012). Histological changes observed 

included centrilobular eosinophilic granules, centrilobular vacuolation, and centrilobular 

hypertrophy with single cell necrosis at a higher dose. Significant increases in absolute and 

relative liver weights were not observed. The LOAEL for comparable effects in females was 

about 3 times higher. After 14 weeks, Seacat et al. (2003) reported increased absolute and 

relative liver weights in male and absolute liver weight in female Sprague-Dawley rats, 

accompanied by centrilobular hypertrophy and decreased cholesterol levels at a dose of 

1.33 mg/kg/day for the males and 1.56 mg/kg/day for the females. An increase in serum ALT at 

the same dose is suggestive of liver damage, but these data were highly variable and did not 

notably progress in the Thomford 2002/Butenhoff et al. 2012 study at 27 and 53 weeks. In 

monkeys, decreased survival, increased relative liver weight, and decreased cholesterol were 

seen at a LOAEL of 0.75 mg/kg/day administered for 6 months (Seacat et al. 2002). 

In the Dong et al. (2009) study, an increase in splenic NK cell activity, a decrease in the 

SRBC response, and increased liver weight were seen in male mice after 60 days of treatment 

with 0.083 mg/kg/day; resulting PFOS serum concentrations were approximately 7.1 mg/L. At a 

10-fold higher dose, NK response was decreased and indicative of a U-shaped response to dose. 

No other studies of an immunological endpoint with a comparable exposure duration were 

identified. 

The most severe of the effects observed in the longer-term studies was the decrease pup 

survival in the one-generation study by Luebker et al. (2005a) in rats at a LOAEL of 0.8 

mg/kg/day, a dose not evaluated in the two-generation study. The LOAEL for the less serious 

effect of decreased pup body weight was 0.4 mg/kg/day in the one- and two-generation studies. 

The short-term and developmental exposure studies compiled in Table 4-2 below support the 

concern for low dose-effects on pup body weight and survival. The majority of the short-term, 

dose-response studies of PFOS were designed to examine developmental end-points. 

Similar to the decreased offspring survival described in the one-generation reproductive 

toxicity study (Luebker et al. 2005a), increased pup mortality was observed when rat dams were 

treated only during gestation as part of developmental toxicity studies (Chen et al. 2012; Lau et 

al. 2003; Thibodeaux et al. 2003). Chen et al. (2012) found increased mortality, decreased body 

weight, and histopathological changes in the lungs (alveolar hemorrhage, thickened interalveolar 

septum) in rat offspring from dams treated with 2.0 mg/kg/day from GD 1 to 21. No effects were 

observed in those administered 0.1 mg/kg/day. Data from Borg et al. (2010) demonstrated 

significantly increased levels of fetal and neonatal PFOS concentrations in the lung between GD 

18 and PND 1 compared with their dams, providing a possible link to the changes observed by 

Chen et al. (2012). Thibodeaux et al. (2003) and Lau et al. (2003) both found decreased maternal 

and pup weight, but no effects on maternal liver weight, when dams were dosed at 2 mg/kg/day 

from GD 2 to 20. 

Perfluorooctane sulfonate (PFOS) – May 2016 4-5 
Table 4-2. NOAEL/LOAEL Data for Short-Term Oral Studies of PFOS

Species Study Duration

NOAEL

(mg/kg/day)

LOAEL

(mg/kg/day) Critical Effect(s) Reference

Rat 28 days ND (F)

0.14 (M)

0.15 (F)

1.33 (M)

↑ relative liver wt (M/F), ↓T4 

(M/F)

Curran et al.

2008

Rat GDs 1–21 0.1 2.0 ↓ pup survival histopathological 

changes to lungs (pups)

Chen et al.

2012

Rat GD 0 to PND 20 - 0.5 ↓ body weight impaired glucose 

tolerance

Lv et al. 2013

Rat GDs 11–19 - 5 ↓body weight, ↓ fetal Leydig 

cells, and ↓testosterone

Zhao et al.

2014

Rat GDs 2–20 1.0 2.0 ↓ dam and pup body weight

↓ pup survival

Thibodeaux et 

al. 2003; Lau 

et al. 2003

Rat GD 0–PND 20 0.3 1.0 ↑ motor activity and decreased 

habituation in male pups

Butenhoff et 

al. 2009

Rat GDs 0–20 0.8 2.5 ↑water maze escape distance 

and escapre latency

Y. Wang et 

al. 2015

Rat GD 0–LD 21 0.8 2.5 ↑water maze escape distance 

and escapre latency

Y. Wang et 

al. 2015

Mouse GDs 1–17 1.0 5.0 ↑ liver wt, dams and pups; 

delayed eye opening

Thibodeaux et 

al. 2003; Lau 

et al. 2003

Mouse GD 3–PND 21 

(dams)

(offspring 

evaluated on PND 

63)

0.3 3.0 ↑ liver weight, increased insulin 

resistance

Wan et al.

2014a 

Mouse 21 days 1 5 ↑liver weight

hepatic steatosis

Wan et al.

2012

Mouse 28 days 0.00017 (M)

0.0033 (F)

0.0017 (M)

0.017 (F)

↓ SRBC plaque-forming cell 

response

Peden-Adams 

et al. 2008

Mouse GDs 1–17 (M)

1 (F)

1 (M)

5 (F)

↓ NK cell activity at postnatal 

week 8

Keil et al.

2008

Note: M = male; F = female

In the standard developmental neurotoxicity study by Butenhoff et al. (2009), male offspring 

showed increased motor activity and decreased habituation on PND 17 following a maternal 

dose of 1 mg/kg/day; no effects on body weight were reported. In Y. Wang et al. (2015), the 

NOAEL for learning and memory as reflected in Morris water maze results for rats exposed 

during gestation and gestation/lactation was 0.8 mg/kg/day and the LOAEL was 2.4 mg/kg/day. 

In the longer-term 90-day study by Long et al. (2013), the NOAEL for effects on learning and 

memory was 0.43 mg/kg/day with a LOAEL of 2.12 in mice first exposed at 8 weeks. Evaluating 

postnatal effects of in utero exposure in the mouse, Lau et al. (2003) reported increased liver 

weight and delayed eye opening in offspring from dams treated with 5 mg/kg/day. 

The studies by Lv et al. (2013) in rats and Wan et al. (2014b) in mice provide evidence for 

long lasting impacts on blood glucose control in adult animals exposed to PFOS gestationally 

and lactationally. In both studies, dams were exposed throughout gestation and lactation, but the 

offspring were not directly treated. In the Lv et al. (2013) study, the animals were evaluated at

22 weeks of age and in the Wan et al. (2014b) study animals were evaluated at 63 days of age 

Perfluorooctane sulfonate (PFOS) – May 2016 4-6 
(9 weeks). In both cases, the rats exposed during gestation had signs of insulin resistance, 

resulting in elevated serum glucose levels. 

Peden-Adams et al. (2008) identified immunotoxicity in male mice exposed to 0.0017 

mg/kg/day. IgM production was suppressed after 28 days of treatment although no overt signs of 

toxicity were observed at any dose. In the Keil et al. (2008) study, crossbred mice exposed 

during gestation had decreased NK cell activity in males and females at postnatal week 8. The 

SRBC IgM response was suppressed in males at a higher dose (5 mg/kg/day), but not in females. 

The 52%–78% decrease in the SRBC plaque-forming cell response in male mice in the study by 

Peden-Adams et al. (2008) with a LOAEL of 0.0017 mg/kg/day and an NOAEL of 

0.00017 mg/kg/day is the only effect at a LOAEL less than that in male rats (0.072 mg/kg/day) 

from the Thomford (2002)/Butenhoff et al. (2012) chronic study. The number of animals per 

dose group utilized by Peden-Adams et al. (2008) was small (n = 5). The SRBC response 

suppression in male pups (n = 6) from the Keil et al. (2008) developmental exposure was higher 

at 5 mg/kg/d; females showed no response. The longer duration study by Dong et al. (2009) also 

had a higher LOAEL at 0.083 mg/kg/day for SRBC suppression and increased liver weight. 

Decreased NK cell activity occurred at a lower dose than the SRBC response in the Keil et al. 

(2008) study, at a higher dose in the Peden-Adams et al. (2008) study, and at the same dose in 

the Dong et al. (2009) study. The NK cell activity was enhanced at very low PFOS doses, while 

it was depressed at higher doses. These differences highlight the need for additional research to 

confirm the NOAEL and LOAEL for the immunological endpoints. In all three studies with the 

low dose responses, males responded at lower doses than females. 

Studies in mice examined NK cell activity and SRBC response. Three of four studies showed 

effects on SRBC response, NK cell activity, or both at the same dose that caused increased liver 

weight (0.083 mg/kg/day, Dong et al. 2009; 5 mg/kg/day, Keil et al. 2008; Zheng et al. 2009). 

The extremely low-dose effects found in Peden-Adams et al. (2008) with a LOAEL for SRBC 

response of 0.0017 mg/kg/day after 28 days are not supported by the LOAEL of 0.083 

mg/kg/day for a dosing duration of 60 days from Dong et al. (2009). 

Taken together, the lower antibody titers associated with PFOS levels in humans and the 

consistent suppression of SRBC response in animals indicates a concern for adverse effects on 

the immune system. However, lack of human dosing information and lack of low-dose 

confirmation of effects in animals for the short-duration study precludes the use of these 

immunotoxicity data in setting the RfD. 

4.1.1.1 Pharmacokinetic Model

Among the studies summarized in Tables 4-1 and 4-2, a number reported low-dose adverse 

effects and had data on measured serum concentrations that made them suitable for

pharmacokinetic modeling in order predict a time-integrated average serum concentration for the 

exposure duration and experimental doses. Because of the complexities of the pharmacokinetic 

differences between animals and humans and across animal species, the average serum values 

are a superior point of departure (POD) for RfD derivation, rather than the external doses in the 

studies. Generally, it was assumed that animals were observed at the end of dosing. The 

published Wambaugh et al. (2013) model described in section 2.5.1 was applied to the selected

studies. The use of the animal data and the available PK model allows for the incorporation of 

species differences in saturable renal resorption, dosing duration, and serum measurements for 

Perfluorooctane sulfonate (PFOS) – May 2016 4-7 
doses administered to determine human equivalent doses based on average serum concentration 

and clearance.

The results for studies in the rats are summarized in Table 4-3. For the Butenhoff et al. 

(2009) study two different AUCs were calculated—gestational only (for the male offspring 

endpoint) and gestational plus 20 days postnatal (for the maternal endpoint). This separation of 

the two exposures neglects lactational transfer of compound, which was not modeled. 

The predicted results from studies in mice and the monkey are provided in Tables 4-4 and 

4-5, respectively. The Lau et al. (2003) data on mice are representative of the impact of PFOS on 

developmental endpoints. Although the duration of this study is relatively short at 19 days, the 

average serum levels associated with the observed effects on pup body weight and 

developmental milestones merit consideration. The Seacat et al. (2002) study on monkeys is a 

long term (6 month), multiple dose study of systemic toxicity in which the LOAEL for effects on 

liver weight, liver histopathology, cholesterol, body weight gain, T3, and TSH was accompanied 

by early death in two of six monkeys. 

The AUC for the LOAEL or NOAEL of each data set can be used to determine an average 

serum concentration by dividing it by the duration of the study in days with adjustment for the 

number of hours in a day. The average serum concentration given in Table 4-6 for the LOAEL or 

NOAEL was determined through numeric simulation. Averaging the serum concentrations for 

the duration of exposure is important because of the variability in the times of exposure across 

the studies (17–182 days). 

Average serum concentration has the advantage of normalizing across the exposure durations 

to generate a uniform metric for internal dose in situations where the dosing durations varied and 

serum measurements were taken immediately prior to sacrifice. The averaged serum 

concentration is a hybrid of the AUC and the maximum serum concentration. As applied to the 

database for PFOS, average serum concentration appears to be a stable reflection of internal 

dosimetry. 

Table 4-6 provides dosing duration and the predicted average serum concentration from each 

of the modeled studies. Internal doses associated with developmental toxicity were 19.9–25 

μg/mL for reduced pup body weight (Luebker et al. 2005a, 2005b), 34.6 μg/mL for changes in 

motor activity (Butenhoff et al. 2009), and 35.1–39.7 μg/mL for pup survival (Lau et al. 2003; 

Luebker et al. 2005a). In comparison, internal doses associated with increased liver weight were 

64.6–157 μg/mL (Seacat et al. 2002, 2003). Thus, the internal doses associated with the 

developmental and liver effect levels (LOAELs) differ by less than an order of magnitude 

(19.9–157 μg/mL), while the corresponding AUC values (Tables 4-3 through 4-5) differ by more 

than an order of magnitude (30,100 μg/mL*h–684,000 μg/mL*h). 

Perfluorooctane sulfonate (PFOS) – May 2016 4-8 
Table 4-3. Predicted Final Serum Concentration and Time Integrated Serum 

Concentration (AUC) for Different Treatments of Rat

Study

Species / 

Strain

Study 

Duration

Oral Doses

mg/kg/day

Measured 

Serum

Concentration 

μg/mL

Species / 

Strain Used 

for 

Prediction

Predicted 

Final Serum 

Concentration

μg/mL

Predicted AUC 

μg/mL*h

Seacat et al. 

2003 

Male Rat/ 

Crl:CD(SD) 

IGS BR

98 Days 0.03 4.04 (0.80) Male 

Rat/SpragueDawley

2.29 (0.0888) 3,430 (108)

0.13 17.1 (1.22) 9.94 (0.386) 14,900 (480)

0.34 43.9 (4.9) 25.9 (0.976) 38,900 (1,230)

1.33 148 (14) 101 (3.94) 152,000 (4,860)

Seacat et al. 

2003 

Female Rat/ 

Crl:CD(SD) 

IGS BR

98 Days 0.04 6.96 (0.99) Female 

Rat/SpragueDawley

4.86 (0.0978) 6,620 (143)

0.15 27.3 (2.3) 18.2 (0.364) 24,800 (561)

0.40 64.4 (5.5) 48.3 (1.07) 65,800 (1,500)

1.56 223 (22) 187 (7.98) 256,000 (7,500)

Butenhoff et 

al. 2009 and 

Chang et al. 

2009

Rat/SpragueDawleyGestation (22 

Days)

0.1 1.722 (0.068) Female 

Rat/SpragueDawley

3.7 (0.121) 1,060 (37.7)

0.3 6.245 (0.096) 11.1 (0.367) 3,180 (114)

1 26.630 (3.943) 37.1 (1.2) 10,600 (376)

Butenhoff et 

al. 2009 and 

Chang et al. 

2009

Rat/SpragueDawleyGestation (21 

Days) + 

Postnatal (20 

Days)

0.1 3.159 (0.081) Female 

Rat/SpragueDawley

6.36 (0.167) 3,410 (105)

0.3 8.981 (0.275) 19.1 (0.512) 10,300 (323)

1 30.480 (1.294) 63.5 (1.67) 34,100 (1,040)

Thibodeaux et 

al. 2003 and 

Lau et al. 

2003 

Rat/SpragueDawleyGDs 2–20

(19 days)

1 19.69a Female 

Rat/SpragueDawley

32.4 (1.05) 8,020 (279)

2 44.33a 64.8 (2.23) 16,000 (594)

3 70.62a 97 (3.26) 24,000 (866)

5 79.39a 162 (5.61) 40,100 (1,430)

10 189.4a 321 (15) 79,800 (3,070)

Luebker et al. 

2005b 

Rat/Crl:CD 

(SD)IGS 

VAF/Plus

6 wks prior to 

mating through 

gestation and 

lactation

(84 Days)

0.1 4.52 (1.15) Female 

Rat/SpragueDawley

11 (0.226) 12,600 (312)

0.4 26.2 (16.1) 43.8 (0.882) 50,400 (1,180)

1.6 136 (86.5) 174 (5.73) 201,000 (5,250)

3.2 155 (39.3) 342 (24.5) 398,000 (17,700)

Luebker et al. 

2005a 

Rat/Crl:CD 

(SD)IGS 

VAF/Plus

6 wks prior to 

mating through 

gestation

(63 Days) 

0.4 NT Female 

Rat/SpragueDawley

35.7 (0.765) 30,100 (794)

0.8 NT 71.3 (1.65) 60,100 (1,640)

1.0 NT 88.9 (2.25) 75,000 (2,060)

1.2 NT 107 (2.91) 90,000 (2,600)

1.6 NT 142 (4.13) 120,000 (3,400)

2.0 NT 177 (6.38) 150,000 (4,530)

Notes: Numbers in parentheses indicate SD

GD = gestation day; NT = not tested

a Thibodeaux et al. (2003) data available only in a graph in the published paper; the values for the model obtained from author.

Table 4-4. Predicted Final Serum Concentration and Time Integrated Serum 

Concentration (AUC) for the Mouse

Study

Species / 

Strain

Study 

Duration

And Type

Administere

d Doses

mg/kg/day

Measured Final 

Serum

Concentration 

μg/mL

Species / 

Strain Used 

for 

Prediction

Predicted Final 

Serum 

Concentration

μg/mL

Predicted AUC 

μg/mL*h

Lau et 

al. 2003

Female 

Mouse/CD-1

GDs 1–17 

(17 days)

1 NT Female 

Mouse / 

CD1

54.8 (1.78) 13,500 (460)

5 NT 195 (38.4) 57,700 (5,220)

10 NT 259 (103) 88,900 (19,700)

15 NT 289 (158) 106,000 (35,000)

20 NT 312 (217) 118,000 (50,300)

Notes: Numbers in parentheses indicate SD

GD = gestation day; NT = not tested

Perfluorooctane sulfonate (PFOS) – May 2016 4-9 
Table 4-5. Predicted Final Serum Concentration and Time Integrated Serum 

Concentration (AUC) for the Monkey

Study

Species / 

Strain

Study 

Duration

And Type

Administered 

Doses

mg/kg/day

Measured Final 

Serum

Concentration 

μg/mL

Species / 

Strain Used 

for 

Prediction

Predicted Final 

Serum 

Concentration

μg/mL

Predicted AUC 

μg/mL*h

Seacat et 

al. 2002

Monkey / 

Cynomolgus

182 days 0.03 F: 13.2 (1.4)

M: 15.8 (1.4)

Monkey / 

Cynomol-gus

14.3 (0.228) 33,800 (547)

0.15 F: 66.8 (10.8)

M: 82.6 (25.2)

68.8 (0.978) 166,000 (2460)

0.75 F: 171 (22)

M: 173 (37)

225 (6.28) 684,000 (10,700)

Notes: Numbers in parentheses indicate SD

M = male; F = female

Table 4-6. Average Serum Concentrations for the Duration of Dosing 

Study

Dosing 

duration

days

NOAEL 

mg/kg/day

NOAEL

(Av serum

μg/mL)a 

LOAEL 

mg/kg/day

LOAEL

(Av serum

μg/mL)a 

Seacat et al. 2002 

monkey: ↑liver weight + 

histopathology; ↓body 

weight; ↓T3; ↑TSH

182 0.15 38

(0.564) 0.75 157(2.45)

Seacat et al. 2003 male 

rat: ↑liver weight,

centrilobular 

vacuolization,↑ ALT, 

↑BUN 

98 0.34 16.5 

(0.522) 1.33 64.6(2.06)

Luebker et al. 2005b: ↓ 

rat pup body weightb 84 0.1 6.26(0.155) 0.4 25(0.583)

Luebker et al. 2005a: ↓ 

rat pup body weightb 63 None None 0.4 19.9(0.525)

Luebker et al. 2005a rat:

↓ maternal body weight, 

gestation length and pup 

survivalb 

63 0.4 19.9

(0.525) 0.8 39.7(1.09)

Butenhoff et al. 2009 rat 

developmental 

neurotoxictiy: ↑increased 

motor activity↓ 

habituation

41 0.3 10.4 

(0.328) 1.0 34.6(1.05)

Lau et al. 2003: ↓rat pup 

survival; ↓maternal and 

pup body weight

19 1.0 17.5

(0.609) 2.0 35.1 (1.3)

Notes: a Average serum concentrations predicted from PK simulations of dose regimens were performed using species-specific 

parameter distributions. The number in parentheses is the SD. b Multiple effects are included for the Luebker et al. (2005a, 2005b) studies to distinguish between the effects quantified for doseresponse. 

Perfluorooctane sulfonate (PFOS) – May 2016 4-10
The internal doses associated with no adverse effects on developmental and liver endpoints 

(NOAELs) were very similar with overlapping ranges; the average serum concentrations ranged 

6.26–19.9 μg/mL for developmental/neurodevelopmental endpoints (Butenhoff et al. 2009; Lau 

et al. 2003; Luebker et al. 2005a, 2005b) and 16.5–38 μg/mL for liver weight changes and 

accompanying liver pathology and changes in serum biochemistry (Seacat et al. 2002, 2003). 

Despite the similarity in average serum concentrations, the AUC values differ by an order of 

magnitude (12,600 μg/mL*h–166,000 μg/mL*h). Given the differences in external doses, the 

projected serum levels are proportionally quite similar. Table 4-6 identifies 6.26 and 10.4 μg/mL 

as the lowest average serum concentrations associated with a NOAEL for offspring effects; the 

associated LOAELs were based on decreased pup body weight (Luebker et al. 2005b) and 

increased motor activity in male pups (Butenhoff et al. 2009). Average serum values for no 

increases in liver weight, liver histopathology, changes in body weight, and serum biochemistry

in monkeys (38 μg/mL; Seacat et al. 2002) and male rats (16.5 μg/mL; Seacat et al. 2003) are 

very similar to the average no effect serum value in Lau et al. (2003) for decreased pup survival 

with a shorter averaging time (17.5 μg/mL). Thus, it appears that the NOAELs are consistent 

across gender, species, and treatment with respect to average serum concentration. Assuming 

that mode of action and susceptibility to toxicity do not vary and that pharmacokinetics alone 

explain variation, it is reasonable to expect similar concentrations to cause similar effects in 

humans. 

The Wambaugh et al. (2013) model employed here to generate the average serum 

concentrations shown in Table 4-6 does not include a gestational or lactational component.

However the results are in good agreement with those of Loccisano et al. (2012b) from their 

gestational and lactational model. Comparison of the average maternal serum concentrations 

calculated for developmental endpoints (Butenhoff et al. 2009; Lau et al. 2003; Luebker et al.

2005a) with those depicted graphically in Figure 3-7 (from Loccisano et al. 2012b), demonstrates 

good agreement between the two models. For example the LOAEL of 1 mg/kg/day for 

developmental neurotoxicity (Butenhoff et al. 2009) yields a calculated average maternal serum 

of 34.6 μg/mL as seen in Table 4-6, which is very similar to the approximately 25 μg/mL for the 

dams that can be estimated from the graph (Loccisano et al. 2012b). The slightly higher value 

calculated from the Wambaugh et al. (2013) model might be due to the longer dosing interval, 

41 days, used by Butenhoff et al. (2009), versus GD 20 levels presented graphically by 

Loccisano et al. (2012b). Fetal PFOS serum concentration on GD 20 was published by Chang et 

al. (2009), but because the Wambaugh et al. (2013) model predicts maternal values, a direct 

comparison to the fetal plasma predicted by Loccisano et al. (2012b; Figure 3-7) cannot be made. 

However, despite the limitations in the fetal data, values generated by the Wambaugh et al. 

(2013) model can be accepted with reasonable confidence that the predicted AUC values 

accurately represent maternal levels during gestational and lactational exposures.

The Andersen et al. (2006) model, used to make the predictions in Tables 4-3 through 4-6, 

calls for numerical simulation in order to make predictions for serum concentrations resulting 

from a regimen of discrete doses. However, one can predict the steady-state concentration (Css) 

resulting from a fixed infusion dose rate (DR, in units of μmol/h): 

Css = DR

free ∗ Qfil

�1 +

Tmax

Qfil ∗ kT + DR�

The Css depends non-linearly on DR. The PFOS studies in Tables 4-1 and 4-2, used discrete, 

daily doses that can be converted to DR by dividing the daily dose (mg/kg/day) by 24 hours to 

Perfluorooctane sulfonate (PFOS) – May 2016 4-11
give and approximate measure of DR. For each DR and species a range of Css values can be 

calculated by using species-specific combinations of parameters from the Bayesian analysis of 

the available PK data. In Table 4-7, the Css is compared with the average serum concentration 

predicted for each of the studies in Table 4-6. The average serum concentration fraction of the 

Css for the 182-day Seacat et al. (2002) study in monkeys is approximately 69% of the steadystate concentration. The 19-day average serum concentration from Thibodeaux et al. (2003) is 

only approximately 9% of Css, while the average serum concentration for the rest of the modeled 

studies ranges 17%–50% of Css. 

The shortest duration study in Table 4-7 had a higher administered LOAEL dose than the 

longest studies (0.75 mg/kg/day for 182 days versus 2.0 mg/kg/day for 19 days). Despite the 

higher administered dose, the short 19-day study resulted in effects at a lower serum 

concentration than that for the longest duration of exposure, the one closest to steady state. In 

fact, the average serum values from the studies that do not approach steady state have lower 

average serum LOAELs for endpoints of toxicological concern. Thus, the data do not appear to 

indicate increasing sensitivity as steady-state is approached. If anything, the average serum 

values appear to be more protective than serum concentrations at steady state. 

Table 4-7. Comparison of Average Serum Concentration and Steady-State Concentration

Study

Dosing 

duration

days

LOAEL 

mg/kg/day

Css (mg/L) for 

constant infusion 

of LOAEL

Average Serum 

Conc. for Study

(mg/L)

Fraction of Css

(Average / Css)

Seacat et al. 2002: monkey: 

↑liver weight + 

histopathology; ↓body 

weight; ↓T3; ↑TSH

182 0.75 227 (6.95) 157 (2.45) 0.689 (0.0131)

Seacat et al. 2003: male rat:

↑liver weight, centrilobular 

vacuolization,↑ ALT, ↑BUN

98 1.33 128 (7.9) 64.6 (2.06) 0.504 (0.0211)

Luebker et al. 2005b: ↓ rat 

pup body weight 84 0.4 83.4 (6.96) 25 (0.583) 0.302 (0.027)

Luebker et al. 2005a: ↓rat 

pup body weight 63 0.4 83.3 (7.08) 19.9 (0.525) 0.24 (0.0232)

Luebker et al. 2005a: rat pup 

survival and ↓maternal body 

weight

63 0.8 163 (15.9) 39.7 (1.09) 0.246 (0.0273)

Butenhoff et al. 2009: ↓rat 

pup body weight 41 1.0 203 (22.5) 34.6 (1.05) 0.173 (0.0245)

Lau et al. 2003rat: pup 

survival; ↓maternal and pup 

body weight

19 2.0 397 (57.6) 35.1 (1.3) 0.0911 (0.0202) 

Notes: Average serum concentrations from PK simulations of toxicity study treatment regimens and Css were both predicted 

using species-specific parameter distributions. The number in parentheses is the SD. 

For human exposure to PFOS one needs to rely on average serum calculations since there is a 

lack of both the sufficient PK and exposure knowledge to make more complicated estimates. The 

average serum concentrations of the LOAEL in Table 4-7 range from 19.9 to 157 μg/mL; all are

within one order of magnitude. The predicted toxic serum concentrations can be converted into 

an oral equivalent dose at steady state by recognizing that, at steady state, clearance from the 

body must equal dose to the body. Clearance can be calculated if the rate of elimination (derived 

from half-life) and the volume of distribution are both known. 

Perfluorooctane sulfonate (PFOS) – May 2016 4-12
A reliable measure of half-life in humans is available from a retired worker population 

followed for 5 years. Olsen et al. (2007) calculated the PFOS half-life in this former worker 

population as 5.4 years (see section 2.5.2). Thompson et al. (2010) give a volume of distribution 

of 0.23 L/kg bw (see section 2.5.3). These values combined give a clearance of 8.1×10-5 L/kg 

bw/day as determined by the following equation: 

CL = Vd x (ln 2 ÷ t1/2) = 0.23 L/kg bw x (0.693 ÷ 1,971 days) = 0.000081 L/kg bw/day

Where:

Vd = 0.23 L/kg 

ln 2 = 0.693 

t1/2 = 1,971 days (5.4 years x 365 days/year = 1,971 days) 

These values combined give a clearance of 8.1 x 10-5 L/kg bw/day. 

Scaling the derived average concentrations (in μg/mL) for the NOAELs and LOAELs in 

Table 4-6 gives predicted oral HEDs in mg/kg bw/day for each corresponding serum 

measurement. The HED values are the predicted human oral exposures necessary to achieve 

serum concentrations equivalent to the NOAEL or LOAEL in the animal toxicity studies. Note 

that this scaling uses linear human kinetics in contrast to the non-linear phenomena observed at 

high doses in animals. 

Thus, HED = average serum concentration (in μg/mL) x CL

Where:

 Average serum is from model output in Table 4-6 

 CL = 0.000081 L/kg bw/day 

The resulting HED values are shown in Table 4-8. Endpoints considered as critical effects in 

multiple studies include offspring growth and survival, liver weight changes, liver 

histopathology, and changes in serum biochemistry indicative of systemic effects. Each study 

selected for modeling was of high quality and show effects at low doses. In all cases but one 

(Luebker et al. 2005a) the POD for the analysis was a NOAEL rather than a LOAEL. The 

developmental effects of reduced pup body weight and survival occurred in the absence of 

changes in maternal liver weight, indicating that maternal toxicity and PPARα were not

confounding variables. 

The external dose NOAELs and LOAELs from other studies summarized in Tables 4-1 and 

4-2 that lacked serum information are comparable to those in the modeled studies. For example, 

the NOAEL in the Long et al. (2013) 90-day mouse study for effects on learning and memory is 

0.43 mg/kg/day (Table 4-1) compared to the 0.3 mg/kg/day for Butenhoff et al. (2009) in rats 

and the LOAEL for mice is 2.15 mg/kg/day compared to the value of 1 mg/kg/day for rats. The 

LOAEL from Luebker et al. (2005a) of 0.4 mg/kg/day for decreased pup body weight is not 

unlike the 0.5 mg/kg/day observed by Lv et al. (2013) for decreased pup body weight and 

increased insulin resistance (Table 4-2). The 1.0 mg/kg/day NOAEL and 2.0 mg/kg/day LOAEL 

for decreased body weight in rat dams and pups combined with decreased pup survival (Lau et 

al. 2003; Thibodeaux et al. 2003) are quite similar to the corresponding values of 1 and 

5 mg/kg/day, respectively, in the study of mice conducted by the same authors (increased 

maternal liver weight and delayed pup eye opening). 

Perfluorooctane sulfonate (PFOS) – May 2016 4-13
Table 4-8. Human Equivalent Doses Derived from the Modeled Animal Average 

Serum Values

Study

Dosing 

duration

days

NOAEL

mg/kg/d

NOAEL

Av serum

μg/mL

HED

mg/kg/d

LOAEL

mg/kg/d

LOAEL

Av serum

μg/mL

HED

mg/kg/d

Seacat et al. 2002 monkey:

↑liver weight + 

histopathology; ↓body 

weight; ↓T3; ↑TSH

182 0.15 38 0.0031 0.75 157 0.013

Seacat et al. 2003 male rat:

↑liver weight, centrilobular 

vacuolization,↑ ALT, ↑BUN

98 0.34 16.5 0.0013 1.33 64.6 0.0052

Luebker et al. 2005b rat: 

↓pup body weight 84 0.1 6.26 0.00051 0.4 25 0.002

Luebker et al. 2005a rat: ↓

pup body weight 63 None None None 0.4 19.9 0.0016

Luebker et al. 2005a rat:

↓maternal body weight, 

gestation length and pup 

survival

63 0.4 19.9 0.0016 0.8 39.7 0.0032

Butenhoff et al. 2009 rat 

developmental neurotoxictiy: 

↑motor activity, ↓habituation

41 0.3 10.4 0.00084 1.0 34.6 0.0028

Lau et al. 2003 rat: ↓ pup 

survival; maternal and pup 

body weight

19 1.0 17.5 0.0014 2.0 35.1 0.0028

4.1.1.2 RfD Quantification

Several acceptable PODs can be used in the process of RfD development based on the 

modeled human equivalent doses (Table 4-9). 

All modeled studies identified a NOAEL for PFOS except for the endpoint of offspring 

growth as measured by body weight in the one-generation study by Luebker et al. (2005a) with a 

LOAEL of 0.4 mg/kg/day. The same external dose was also a LOAEL for the same effect in the 

two-generation study by Luebker et al. (2005b), with a NOAEL of 0.1 mg/kg/day, a dose not 

tested in the one-generation study. The calculated HED values associated with no adverse effects 

on developmental and liver endpoints (NOAELs) were very similar with a range of 0.00051–

0.0031 mg/kg/day. 

Two effect-level doses were modeled from the Luebker et al. (2005a) one-generation rat 

study: (1) the NOAEL for the effects on pup survival (0.4 mg/kg/day), which was the LOAEL 

for the body weight effect, and (2) the LOAEL (0.8 mg/kg/day) for the pup survival effect to 

illustrate the importance of the body weight LOAEL in both the one- and two-generation 

Luebker et al. (2005a, 2005b) studies. In the two-generation study, 1.6 mg/kg/day resulted in the 

death of > 26% of the pups between LD 2 and 4. Support for the pup survival serum level 

LOAEL is provided by the Lau et al. (2003) rat study, with a HED for the same end point that is 

comparable to that in the Luebker et al. (2005b) study (0.0028 mg/L and 0.0032 mg/L, 

respectively). 

Perfluorooctane sulfonate (PFOS) – May 2016 4-14
Table 4-9. POD Outcomes for the HEDs from the Pharmacokinetic Model 

Average Serum Values

POD 

POD Value

mg/kg/day UFH UFA UFL UFS UFD UFtotal

Candidate

RfD

mg/kg/day

PK-HED (Seacat et al.

2003; rat, NOAEL,↑ ALT, 

↑BUN 

0.0013 10 3 1 1 1 30 0.00004 

PK-HED (Lau et al. 2003; 

rat, NOAEL ↓pup 

survival)

0.0014 10 3 1 1 1 30 0.00005

PK-HED (Butenhoff et al.

2009; rat, NOAEL ↑motor 

activity ↓habituation)

0.00084 10 3 1 1 1 30 0.00003

PK-HED (Luebker et al. 

2005b; rat, NOAEL↓pup 

body wt)

0.00051 10 3 1 1 1 30 0.00002

PK-HED LOAEL 

(Luebker et al. 2005a; rat, 

LOAEL↓pup body wt)

0.0016 10 3 3 1 1 100 0.00002

PK-HED (Luebker et al.

2005a; rat, NOAEL ↓pup 

survival)

0.0016 10 3 1 1 1 30 0.00005

Notes: UFH: Intra-individual uncertainty factor, UFA: Interspecies uncertainty factor, UFS: Subchronic to chronic uncertainty 

factor, UFL: LOAEL to NOAEL uncertainty factor, UFD: incomplete database uncertainty factor, UFtotal: Total (multiplied) 

uncertainty factor

The pharmacokinetically-modeled average serum values from the animal studies are 

restricted to the animal species selected for their low dose response to oral PFOS intakes. 

However, the modeled average serum values from animals are several orders of magnitude 

greater than measured values in humans. Thus, extrapolation to humans adds a layer of 

uncertainty that needs to be accommodated in deriving the RfD. 

HED PODs. The PK HEDs derived from Seacat et al. (2003), Lau et al. (2003), Butenhoff et al. 

(2009), and Luebker et al. (2005a, 2005b) were each examined as the potential basis for the RfD 

(ph). The Seacat et al. (2002) results for male monkeys were not utilized in the derivation of the 

RfD because of the premature deaths in two of the six males at the LOAEL. Each of these 

studies, except one, contained a NOAEL from which the HED could be derived. The outcomes 

for potential RfD values are similar demonstrating the ability of the model to normalize the 

animal data across species, gender, and exposure duration.

Uncertainty Factors 

An uncertainty factor for intraspecies variability (UFH) of 10 is assigned to account for 

variability in the responses within the human populations because of both intrinsic (genetic, life 

stage, health status) and extrinsic (life style) factors that can influence the response to exposure. 

No information was available relative to variability in the human population that supports a 

factor other than 10. 

An uncertainty factor for interspecies variability (UFA) of three was applied to account for 

uncertainty in extrapolating from laboratory animals to humans (i.e., interspecies variability).

The 3-fold factor is applied to account for toxicodynamic differences between the animals and 

Perfluorooctane sulfonate (PFOS) – May 2016 4-15
humans. The HEDs were derived using average serum values from a model to account for 

pharmacokinetic differences between animals and humans.

An uncertainty factor for LOAEL to NOAEL extrapolation (UFL) of one was applied to all 

PODs, except the LOAEL of 0.4 mg/kg/day for effects on pup body weight in the one-generation 

Luebker et al. (2005a) study. A value of three is assigned for this study based on the fact that the 

NOAEL for this effect was 0.1 mg/kg/day in the two-generation (Luebker et al. 2005b) study, a 

dose that was not used in the one-generation study. The LOAEL in the two-generation study was 

0.4 mg/kg/day, demonstrating that the difference between a NOAEL and LOAEL for the body 

weight is not a factor of 10, the default value for NOAEL/LOAEL extrapolation. 

An uncertainty factor for extrapolation from a subchronic to a chronic exposure duration 

(UFS) of one was applied because the PODs are based on average serum concentrations for all 

studies except Seacat et al. (2013). The studies for developmental endpoints are not adjusted for 

lifetime exposures because they cover a critical window of exposure with lifetime consequences. 

The average serum value associated with the developmental (Luebker et al. 2005b) POD is lower 

than that for any of the other modeled studies including those with systemic effects after longer 

exposures. It is accordingly more protective of adverse effects than the POD for any of the 

longer-term studies despite the limited exposure duration. The serum from the Seacat et al. 

(2013) study was collected at 14 weeks. Some of the animals in the study continued to be dosed 

for a total of 105 weeks, but the effects observed at the LOAEL did not increase in magnitude. 

Serum measurements taken before sacrifice were 2-fold higher at 14 weeks in males than they 

were at 105 weeks. Concentrations of PFOS in the liver were lower at 105 weeks than they were 

at 14 weeks. The PFOS concentrations in the diet were constant. SDs about the monitored ALT 

and BUN were broad indicating higher sensitivity is some animals than others. The serum and 

effects data for the male rats justify the subchronic to chronic adjustment to the study NOAEL 

for this study. 

A database uncertainty factor (UFD) of one was applied to account for deficiencies in the 

database for PFOS. The epidemiology data provide strong support for the identification of 

hazards observed following exposure to PFOS in the laboratory animal studies and human 

relevance. However, uncertainties in the use of the available epidemiology data precluded their 

use at this time in the quantification of the effect level for derivation of the drinking water health 

advisory. In animals, comprehensive oral short term, subchronic, and chronic studies in three 

species and several strains of laboratory animals have been conducted and published in the peer 

reviewed literature. Additionally, there are several neurotoxicity studies (including 

developmental neurotoxicity) and several reproductive (including one- and two-generation 

reproductive toxicity studies) and developmental toxicity studies including assessment of 

immune effects following developmental exposure. 

RfD Selection

Based on the consistency of the response and of the use of the most sensitive endpoint, 

developmental toxicity, as the critical effect, the RfD of 0.00002 mg/kg/day from Luebker et al. 

(2005a) is selected as the RfD for PFOS. This RfD is derived from reduced pup body weight in 

the two-generation study in rats. The POD for the derivation of the RfD for PFOS is the HED of 

0.00051 mg/kg/day that corresponds to a NOAEL that represents approximately 30% of steadystate concentration. An UF of 30 (10 UFH and 3 UFA) was applied to the HED NOAEL to derive 

an RfD of 0.00002 mg/kg/day. This is supported by the 0.00002 mg/kg/day value derived from 

the LOAEL for the same effect in the one-generation Luebker et al. (2005a) study and the 

Perfluorooctane sulfonate (PFOS) – May 2016 4-16
0.00003 mg/kg/day value for neonatal neurodevelopmental effects in the Butenhoff et al. (2009) 

study. 

Low body weights in neonates are a biomarker for developmental deficits and linked to 

problems often manifest later in life. A study by Lv et al. (2013) that lacked serum data for 

pharmacokinetic modeling identified 0.5 mg/kg/day as a LOAEL for effects on body weight in 

Wistar rat pups exposed during gestation, an observation that was accompanied by increased 

insulin resistance, problems with glucose homeostasis, and hepatic fat accumulation in the pups 

as adults. A similar effect on glucose homeostasis was observed in CD-1 mice at PND 63 in a 

study by Wan et al. (2014b), with a dose of 3 mg/kg/day for animals receiving a diet with regular 

fat content. For animals receiving a high fat diet, the LOAEL was 0.3 mg/kg/day. Support for the 

neurodevelopmental effects in Butenhoff et al. (2009) at a dose 1 mg/kg/day kg/day is provided 

by the NOAEL (0.43 mg/kg/day) in the Long et al. (2013) 90-day mouse study for effects on 

learning and memory.

Use of the developmental toxicity endpoint is directly relevant to human health because in 

utero and lactational exposures have been demonstrated. PFOS has been measured in the blood 

of newborns (Spliethoff et al. 2008), in human breast milk (Kärrman et al. 2010), and in serum 

samples from children aged 5–15 years (Dong et al. 2013; Grandjean et al. 2012). A human 

epidemiology study found no association with maternal PFOS levels and motor or mental 

development of their children; the mean maternal serum concentration was approximately 

0.035 μg/mL (Fei et al. 2008b). 

4.1.2 RfC Determination

The only inhalation study available is an acute lethality inhalation study in rats (Rusch et al.

1979); no inhalation data are available in humans. Thus, data are insufficient for the development 

of an RfC for PFOS. 

4.2 Dose-Response for Cancer Effects

Under the EPA (2005a) Guidelines for Carcinogen Risk Assessment, when the evidence from 

the epidemiology studies and the cancer bioassays is suggestive for carcinogenicity, a 

quantitative estimate of risk is generally not performed unless there is a well-conducted study 

that could serve a useful purpose by providing a sense of the magnitude and uncertainty of 

potential risks, ranking potential hazards, or setting research priorities. In the case of PFOS, the 

existing evidence does not support a strong correlation between the tumor incidence and dose to 

justify a quantitative assessment.

Perfluorooctane sulfonate (PFOS) – May 2016 4-17
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Appendix A: Literature Search Strategy Developing the Search

The literature search strategy was planned with input from EPA library services staff. CAS 

numbers served as the basis for identification of relevant search terms. Trial searches were 

conducted and results were evaluated to refine the search strategy (e.g., to prevent retrieval of 

citations unrelated to health and occurrence). The search string was refined to improve the 

relevancy of the results. All searches were conducted in the PubMed database, which contains 

peer-reviewed journal abstracts and articles in various biological, medical, public health, and 

chemical topics. The first search string (as well as future iterations) is presented below.

Every two weeks, a search was run in PubMed and a bibliography of the search results was 

compiled. 

In 2012, the State of New Jersey Department of Environmental Protection (NJDEP) initiated a 

monthly search in PubMed for emerging literature on perfluorinated chemicals primarily from 

the carboxylic acid and sulfonate families. These searches were provided to the EPA on a 

monthly basis. There was a high degree of overlap with the results from the EPA search, thus 

increasing the confidence in the search strategy.

In 2013, the EPA search strategy was expanded to cover other members of the 

perfluorocarboxylic acids (C-4 to C-12) and sulfonate families (C-4, C-6, C-8). The search string 

was altered in June of 2013 to rely more on the search features offered by PubMed. 

A change in the PubMed database structure in 2015 required some modification to the search 

strategy. A search in August 2015 returned more than 4,000 records, a number that was 

inconsistent with prior searches. The cause was PubMed’s lack of recognition of the search term, 

“Heptadecafluorooctane-1-sulphonic acid” and interpreting the term as “ACID.” The 

resolution is highlighted in the search strings below.

All search iterations are noted below. 

Search Strategy Examples: (Arranged from most recent to oldest).

2015 

Search: perfluorooctanoate OR “perfluorooctanoic acid” OR “perfluoroctanoic acid” OR pfoa 

OR “perfluorinated chemicals” OR “perfluorinated compounds” OR “perfluorinated homologue 

groups” OR “perfluorinated contaminants” OR “perfluorinated surfactants” OR perfluoroalkyl 

acids OR “perfluorinated alkylated substances” OR “perfluoroalkylated substances” OR pfba OR 

“perfluorobutanoic acid” OR perfluorochemicals OR “telomer alcohol” OR “telomer alcohols” 

OR “fluorotelomer alcohols” OR “polyfluoroalkyl compounds” OR “perfluorooctane sulfonate” 

OR pfos OR “perfluorooctanesulfonic acid” OR “perfluorooctane sulfonic acid” OR 

“perfluorooctane sulphonate” OR perfluorooctane sulfonate OR “perfluorooctanyl sulfonate” OR 

“Heptadecafluorooctane-1-sulphonic” OR “Heptadecafluoro-1-octanesulfonic acid” OR 

perfluorononanoate OR pfhxa OR “perfluorohexanoic acid” OR “fluorinated surfactants” 

Filters: English. 

Frequency: Every 2 weeks

September 2013 

Perfluorooctane sulfonate (PFOS) – May 2016 A-1 
Search: perfluorooctanoate OR “perfluorooctanoic acid” OR “perfluoroctanoic acid” OR pfoa 

OR “perfluorinated chemicals” OR “perfluorinated compounds” OR “perfluorinated homologue 

groups” OR “perfluorinated contaminants” OR “perfluorinated surfactants” OR perfluoroalkyl 

acids OR “perfluorinated alkylated substances” OR “perfluoroalkylated substances” OR pfba OR 

“perfluorobutanoic acid” OR perfluorochemicals OR “telomer alcohol” OR “telomer alcohols” 

OR “fluorotelomer alcohols” OR “polyfluoroalkyl compounds” OR “perfluorooctane sulfonate” 

OR pfos OR “perfluorooctanesulfonic acid” OR “perfluorooctane sulfonic acid” OR 

“perfluorooctane sulphonate” OR perfluorooctane sulfonate OR “perfluorooctanyl sulfonate” OR 

“Heptadecafluorooctane-1-sulphonic acid” OR “Heptadecafluoro-1-octanesulfonic acid” OR 

perfluorononanoate OR pfhxa OR “perfluorohexanoic acid” OR “fluorinated surfactants” 

Filters: English. 

Frequency: Every 2 weeks

June 2013 

Search: (PFOA[tw] OR perfluorooctanoic acid[tw] OR 335-67-1[tw] OR PFBA[tw] OR 

perfluorobutanoate[tw] OR 3794-64-7[tw] OR PFDA[tw] OR perflurordecanoic acid[tw] OR 

335-76-2[tw] OR PFHpA[tw] OR perfluoroheptanoic acid[tw] OR 375-85-9[tw] OR PFHxA[tw] 

OR perfluorohexanoic acid[tw] OR 307-24-4[tw] OR PFNA[tw] OR perfluorononanoic acid[tw] 

OR 375-95-1[tw] OR PFPtA[tw] OR perfluoropentanoic acid[tw] OR 2706-90-3[tw] OR 

PFPA[tw] OR pentafluoropropionic acid[tw] OR 422-64-0[tw]) AND (human* [tw] OR 

mammal*[tw]) NOT (environment* OR ecolog*) 

Filters: English. 

Frequency: Every 2 weeks 

February 2013 

Search: perfluorooctanoate OR “perfluorooctanoic acid” OR “perfluoroctanoic acid” OR pfoa 

OR “perfluorinated chemicals” OR “perfluorinated compounds” OR “perfluorinated homologue 

groups” OR “perfluorinated contaminants” OR “perfluorinated surfactants” OR perfluoroalkyl 

acids OR “perfluorinated alkylated substances” OR “perfluoroalkylated substances” OR pfba OR 

“perfluorobutanoic acid” OR perfluorochemicals OR “telomer alcohol” OR “telomer alcohols” 

OR “fluorotelomer alcohols” OR “polyfluoroalkyl compounds” OR “perfluorooctane sulfonate” 

OR pfos OR “perfluorooctanesulfonic acid” OR “perfluorooctane sulfonic acid” OR 

“perfluorooctane sulphonate” OR perfluorooctane sulfonate OR “perfluorooctanyl sulfonate” OR 

“Heptadecafluorooctane-1-sulphonic acid” OR “Heptadecafluoro-1-octanesulfonic acid” OR 

perfluorononanoate OR pfhxa OR “perfluorohexanoic acid” OR “fluorinated surfactants” 

Filters: English. 

Frequency: Every 2 weeks 

June 2011 

Search (perfluorooctanoate OR “perfluorooctanoic acid” OR “perfluoroctanoic acid” OR pfoa 

OR “perfluorinated chemicals” OR “perfluorinated compounds” OR “perfluorinated homologue 

groups” OR “perfluorinated contaminants” OR “perfluorinated surfactants” OR 

perfluoroalkylacids OR “perfluorinated alkylated substances” OR “perfluoroalkylated 

substances” OR pfba OR “perfluorobutanoic acid” OR perfluorochemicals OR “telomer alcohol” 

OR “telomer alcohols” OR “fluorotelomer alcohols” OR “polyfluoroalkyl compounds” OR 

Perfluorooctane sulfonate (PFOS) – May 2016 A-2 
“perfluorooctane sulfonate” OR pfos OR “perfluorooctanesulfonic acid” OR “perfluorooctane 

sulfonic acid” OR “perfluorooctane sulphonate” OR perfluorooctanesulfonate OR 

“perfluorooctanyl sulfonate” OR “Heptadecafluorooctane-1-sulphonic acid” OR 

“Heptadecafluoro-1-octanesulfonic acid” OR perfluorononanoate OR pfhxa OR 

“perfluorohexanoic acid” OR “fluorinated surfactants” OR 335-67-1 [rn])

Limits: Publication Date [Dates will change for each search], English Language only. 

June 2009 

Search (perfluorooctanoate OR “perfluorooctanoic acid” OR “perfluoroctanoic acid” OR pfoa 

OR “perfluorinated chemicals” OR “perfluorinated compounds” OR “perfluorinated homologue 

groups” OR “perfluorinated contaminants” OR “perfluorinated surfactants” OR 

perfluoroalkylacids OR “perfluorinated alkylated substances” OR “perfluoroalkylated 

substances” OR pfba OR “perfluorobutanoic acid” OR perfluorochemicals OR “telomer alcohol” 

OR “telomer alcohols” OR “fluorotelomer alcohols” OR “polyfluoroalkyl compounds” OR 

“perfluorooctane sulfonate” OR pfos OR “perfluorooctanesulfonic acid” OR “perfluorooctane 

sulfonic acid” OR “perfluorooctane sulphonate” OR perfluorooctanesulfonate OR 

perfluorononanoate OR pfhxa OR “perfluorohexanoic acid” OR “fluorinated surfactants” OR 

335-67-1 [rn] OR 1763-23-1 [rn])

Limits: Entrez Date from 2009/04/07 to 2009/04/12. 

New Jersey Search Terms

Search: perfluorinated OR perfluorooctanoate OR perfluorononanoate OR 

perfluorooctanesulfonate OR perfluorooctanesulphonate OR perfluoroalkylated OR 

perfluoroalkyl OR polyfluoroalkyl OR polyfluorinated OR PFBA OR PFBS OR PFDA OR 

PFHA OR PFHPA OR PFHXA OR PFHXS OR PFNA OR PFOA OR PFOAs OR PFOS OR 

PFUNDA OR “perfluorooctanoic acid” OR “perfluoro octanoic acid” OR “perfluorooctane 

sulfonate” OR “perfluorooctane sulfonic acid” OR “perfluorooctanesulfonic acid” OR 

“perfluorooctane sulphonate” OR “perfluorooctanyl sulfonate” OR “perfluorobutanoic acid” OR 

“perfluoroalkyl acids” OR “perfluorononanoic acid” OR “perfluorohexanoic acid” OR 

“perfluorohexane sulfonate” OR “perfluorohexane sulphonate” OR perfluorobutanoate OR 

“perfluoro butanoate” OR perfluorohexanoate OR “perfluoro hexanoate” 

Filters: 1

Perfluorooctane sulfonate (PFOS) – May 2016 A-3 
Appendix B: Studies Evaluated Since August 2014 

The tables that follow identify the papers that were retrieved and reviewed for inclusion 

following the August 2014 peer review for the draft PFOS Health Effects Support Document. 

The papers listed include those recommended by the peer reviewers or public commenters, as 

well as those identified from the literature searches between the completion of the peer review 

draft and December 2015. Papers included in the final Health Effects Support Document (HESD) 

are noted and reasons provided for those that were not included in the final document. 

The tables for document retrieval and review are followed by updated versions of the 

summaries of the epidemiology summary tables from the peer reviewed draft as recommended 

by the peer reviewers. They are a useful tool to facilitate a high level comparison of the study 

outcomes for each of the epidemiological study groupings. 

The criteria utilized in determining the papers that were included in the HESD after the peer 

review and presented in the Background were the following: 

1. The study examines a toxicity endpoint or population that had not been examined by 

studies already present in the draft assessment.

2. Aspects of the study design, such as the size of the population exposed or quantification 

approach, make it superior to key studies already included in the draft document. 

3. The data contribute substantially to the weight of evidence for any of the toxicity 

endpoints covered by the draft document. 

4. There are elements of the study design that merit its inclusion in the draft assessment 

based on its contribution to the mode of action or the quantification approach. 

5. The study elucidates the mode of action for any toxicity endpoint or toxicokinetic 

property associated with PFOS exposure. 

6. The effects observed differ from those in other studies with comparable protocols.

Table B-1. PFOS Epi Papers—Post Peer Review (Retrieved and Reviewed)

Authors and year Topic—key words Status/Notes

Andersen et al. 2013 Postnatal growth Added PFOA/PFOS

Back et al. 2015 Time to pregnancy Added PFOA

Barrett et al. 2015 Ovarian hormone Not Added—No association observed for 

PFOA; PFOS was not included in the 

assessment

Berg et al. 2015 Thyroid Added PFOA/PFOS

Bonefeld-Jørgenson et al. 2014 Breast cancer Added PFOA/PFOS

Bonefeld-Jørgenson et al. 2011 Breast cancer Added PFOA/PFOS

Brieger et al. 2011 Immune effects Already presented in PFOS/PFOA

Buck Louis et al. 2015 Semen quality Added PFOA/PFOS

Chang et al. 2014 Analysis of human cancer 

studies 

Added PFOA in the cancer weight of 

evidence section

Chen et al. 2015 Birth weight Added PFOS

Dankers et al. 2013 Blood-testis barrier Reviewed,—not added; Study of an assay 

that used PFOA as one chemical in the test 

battery

Darrow et al. 2013 Reproductive outcome Added PFOA/PFOS

Darrow et al. 2014 Miscarriage Added PFOA/PFOS

Perfluorooctane sulfonate (PFOS) – May 2016 B-1 
Authors and year Topic—key words Status/Notes

Donauer et al. 2015 Infant Neurobehavior Not added—negative for PFOS; No 

statistical differences in PFOA levels 

during pregnancy and any neuro endpoint. 

Better studies.

Eriksen et al. 2013 Total cholesterol—Danish Added PFOA/PFOS

Fitz-Simon et al. 2013 Serum lipids Added PFOA/PFOS

Fisher et al. 2013 Plasma lipids Added PFOA/PFOS

Fletcher et al. 2013 Cholesterol–genes Added PFOA/PFOS

Fu et al. 2014 Serum lipids in Chinese 

subjects

Not added: Chinese population, dataset

available on U.S. population. More 

branched chain isomers found among the 

people in China.

Geiger et al. 2014a Lipids/children Added PFOA/PFOS

Geiger et al. 2014b Hypertension/children Added PFOA/PFOS

Ghisari et al. 2014 Breast cancer—Inuit Not added; same population as BonefeldJørgensen et al. 2014; this study focuses on 

gene polymorphisms

Governini et al. 2015 DNA effects in sperm Added PFOA/PFOS

Grandjean and Clapp 2015 Health Risks Not added; the primary studies are already 

included in the documents.

Granum et al. 2013 Immune children Added PFOA/PFOS

Hardell et al. 2014 Prostate cancer Added PFOA/PFOS

Høyer et al. 2015a Human weight Added PFOA/PFOS

Høyer et al. 2015b Behavior motor development Added PFOA/PFOS

Humblet et al. 2014 Asthma Added PFOA/PFOS

Jain 2014 NHANES Added PFOA/PFOS

Innes et al. 2014 Colorectal cancer Added PFOA/PFOS

Joensen et al. 2013 Sperm Added PFOA/PFOS

Kerger et al. 2011 Cholesterol C8 Added; demographics for cholesterol and 

PFOS in summary section of epi studies

Kjeldsen and Bonefeld-Jørgensen 

2013

Sex hormones Covered multiple PFAS in vitro no impact 

on weight of evidence

Kristensen et al. 2013 Prenatal female repro Added PFOA/PFOS

Liew et al. 2014 Cerebral palsy children Added PFOA/PFOS

Looker et al. 2014 Immune Added PFOA/PFOS

López-Doval et al. 2014 Male repro Added PFOS

Maisonet et al. 2015 Gestational diabetes Added PFOA/PFOS

Maisonet et al. 2012 Birth weight Added PFOA/PFOS

Mørck et al. 2015 PFAS levels in children Not added; No significant impact

Okada et al. 2014 Allergy children Added PFOS

Osuna et al. 2014 Antibodies PFOS PFOA Not added; focus more on methylHg and 

PCB than PFAS; only n = 38 as 

preliminary study

Roth and Wilks 2014 Neurodevelopmental . Not added; no significant impact

Shrestha et al. 2015 Thyroid Added PFOA/PFOS

Starling et al. 2014 Plasma lipids Added PFOA/PFOS

Steenland et al. 2015 Workers Added PFOA

Perfluorooctane sulfonate (PFOS) – May 2016 B-2 
Authors and year Topic—key words Status/Notes

Stein et al. 2009 Pregnancy Added PFOA

Taylor et al. 2014 Menopause Added PFOA/PFOS

Vanden Heuvel 2013 Serum lipids Not added; is a rebuttal of Fletcher et al. 

2013 conclusions. No significant impact

Vassiliadou et al. 2010 PFOS in cancer vs non-cancer 

patients

Added PFOA/PFOS

Vélez et al. 2015 Fertility Added PFOA/PFOS

Verner et al. 2015 Fetal growth GFR Added PFOA/PFOS

Verner and Longnecker 2015 Menstruation/excretion Added PFOS

Vested et al. 2013 Semen quality and hormones Added PFOS/PFOS

Vesterinen et al. 2014 Fetal Growth GFR Added PFOA/PFOS

Wang et al. 2013 Thyroid Added PFOA/PFOS

Watkins et al. 2013 Kidney function Added PFOA/PFOS

Webster et al. 2014 Maternal thyroid Added PFOA/PFOS

Webster et al. 2015 Thyroid—iodine statue Added PFOS

Wen et al. 2013 Thyroid Added PFOA/PFOS 

Yeung et al. 2013 Liver cancer Added PFOA/PFOS

Zhang et al. 2015 Gestational diabetes Added PFOA/PFOS

Table B-2. PFOA Post Peer Review Animal Toxicity Studies

Authors and year Topic Action notes

Bjork et al. 2011 Nuclear receptor activation In vitro, mechanistic findings comparable to 

studies already included

Corsini et al. 2014 Immune data review Not added; no significant impact

Corsini et al. 2012 Immune in vitro data review Not added; no significant impact

Dewitt et al. 2015 Immunotoxicity Added PFOA

Fenton 2015 Repro editorial Not added 

Filgo et al. 2015 Liver tumors in females 

developmentally exposed

Added PFOA

Hall et al. 2012 PPARα and cancer Cited in synthesis. Paper on adversity of liver 

hypertrophy PFOA/ PFOS

Koustas et al. 2014 Fetal growth (animal studies) 

navigation guide

Added PFOA

Liu et al. 2015 Testes Added PFOA

Long et al. 2013 Neurotoxicity adult PFOS Added PFOS

Lu et al. 2015 Testes Added PFOA

Ngo et al. 2014 Tumors mice Min/+ PFOS Added PFOS 

Post et al. 2012 Review paper Not added. Key studies included in the document; 

no significant impact

Quist et al. 2015 Liver histopathology/high fat 

diet post weaning exposure

Added PFOA

Rigden et al. 2015 Acute liver effects Added PFOA

Shabalina et al. 2015 Brown fat uncoupling protein 1 Not added. Mechanistic; no significant impact

Sheng et al. 2016 Binding to liver fatty acid 

binding protein

Not added; no significant impact, topic covered by 

other papers

Perfluorooctane sulfonate (PFOS) – May 2016 B-3 
Authors and year Topic Action notes

Tan et al. 2012 Gene activation Added PFOA/PFOS

Tan et al. 2013 Gene activation dietary fat Added PFOA

Tucker et al. 2015 Mammary gland Added PFOA

Wallace et al. 2013 Mitochodrial respiration Not added. No significant impact, topic covered 

by other papers

Wan et al. 2014b Glucose metabolism Added PFOS

Wan et al. 2012 Hepatic steatosis Added PFOS

Wan et al. 2014a Sertoli cells Added PFOS

F. Wang et al. 2015 MiRNA liver PFOS early life Not added; no significant impact

S. Wang et al. 2014 Lysine decarboxylase Added PFOA/PFOS

L. Wang et al. 2014 Inhibition of LDL Added PFOS

Y. Wang et al. 2015 Special learning and memory Added PFOS

Yan et al. 2015 Glucose homeostasis Not added. Dose-response in Wan (2014b)

presented (more robust). Single dose for whole 

animal

Yu et al. 2015 Thyroid PFOS isomers Added PFOS

Zeng et al. 2014 Mitochondrial mediated 

apoptosis of the heart

Added PFOS

L. Zhang et al. 2013 Fatty acid binding protein Added PFOA/PFOS

Y. Zhang et al. 2013 Biological half-life Added PFOA/PFOS

W. Zhang et al. 2014 Breast cancer cell invasion—

mechanistic 

Not added; in vitro, no significant impact

Zhao et al. 2014 Testosterone reduction in 

Leydig cells PFOS

Added PFOS

Perfluorooctane sulfonate (PFOS) – May 2016 B-4 
Table B-3. Toxicokinetics: Post Peer Review 

Authors and year Topic Action Notes

D’Alessandro et al. 2013 Serum albumin Added PFOS

Augustine et al. 2005 Transporter expression testes Not added background paper on testes transporters 

–no relationship to PFOA PFOA or any PFAS

Beesoon et al. 2011 Isomer profile Added PFOA

Beesoon and Martin 2015 Albumin binding Added PFOA

Cui et al. 2010 Excretion subchronic Added PFOA/PFOS

Fàbrega et al. 2014 PK model Added PFOA/PFOS

Kerstner-Wood et al. 2003 Plasma protein binding Added—PFOA/PFOS

Klaassen and Aleksunes 

2010

Transporter paper—Provided 

diagram of kidney transporters

Added PFOA

Loccisano et al. 2013 PK model—Human Added PFOA/PFOS

Mondal et al. 2014 Breast milk Added PFOS/PFOA 

Ospinal-Jimenez and Pozzo 

2012

Protein denaturation Added PFOS

Pérez et al. 2013 Human tissue levels New PFOA/PFOS

Ren et al. 2015 Thyroid hormone receptor 

binding (in vitro)

Added PFOA/PFOS

Rigden et al. 2015 Liver and excretion Added PFOA

Shabalina et al. 2015 Brown fat Not added; No information on MOA for body 

weight effects in the animal or human studies

Slitt et al. 2007 Transporter expression PFOA Not added. Reported on transporters during 

extrahepatic cholestasis. No data on PFOA and 

PFOS. No significant impact.

Tucker et al. 2015 Menstruation-excretory route Added PFOA

Verner and Longnecker 

2015

Excretion PFOS Added PFOS

Wambaugh et al. 2013 PK model Added PFOA/PFOS

Wong et al. 2014 Menstrual blood as excretory 

route

Added PFOA/PFOS

T. Zhang et al. 2014 Excretion general population 

and pregnancy

Added PFOA/PFOS

L. Zhang et al. 2014 PPAR gamma Added PFOS

Y. Zhang et al. 2013 Excretion, half-life Added PFOA/PFOS 

T. Zhang et al. 2013 Maternal transfer Added PFOA/PFOS

Perfluorooctane sulfonate (PFOS) – May 2016 B-5 
Table B-4. Association of Serum PFOS with Serum Lipids and Uric Acid

Reference Study type n

Mean or median 

serum PFOS (μg/mL) TC VLDL LDL HDL Non-HDL TG UA

Occupational Populations

Olsen et al.

2001a, 2003b

Cross-sectional 263 (Decatur)

255 (Antwerp)

1.40

0.96

↑ NM NM ↔ NM ↑ NM

Olsen et al.

2001b, 2003b

Longitudinal; 

~5 years

175

(Decatur and 

Antwerp 

combined for 

analysis)

2.62

(baseline)

1.67 (follow-up)

(Decatur)

1.87 (baseline)

1.16

(follow-up)

(Antwerp)

↔ NM NM ↔ NM ↔ NM

General Populations

Steenland et 

al. 2009

Cross-sectional 

(C8)

46,294 0.022 ↑ NM ↑ ↔ NM ↑ NM

Steenland et 

al. 2010

Cross-sectional 

(C8)

54,951 0.023 NM NM NM NM NM NM ↑

Frisbee et al.

2010

Cross-sectional 

(C8, children)

12,476 0.023 ↑ NM ↑ ↑ NM ↔ NM

Fitz-Simon et 

al. 2013

Longitudinal; 

4.4 years (C8)

521 0.023 (baseline)

0.011 (follow-up)

↔ NM ↔ ↔ NM ↔ NM

Nelson et al.

2010

Cross-sectional 

(NHANES)

860 0.025 ↑ NM ↔ ↔ ↑ NM NM

Lin et al. 

2009

Cross-sectional

(NHANES)

3,685 0.0031 (12–< 20 yrs)

0.0032 (≥ 20 yrs)

NM NM NM ↑ NM ↔ NM

Maisonet et 

al. 2015

Longitudinal; 

prenatal and 

aged 7 and 15

years

111 (age 7 years)

88 (age 15 years) 

0.022 ↔ NM ↔ ↔ NM ↔ NM

Timmermann 

et al. 2014

Cross-sectional

(children 8–10 

years)

499 0.0412 ↔ NM ↔ ↔ NM ↔ (normal wt)

↑ (overweight)

NM

ChâteauDegat et al.

2010

Cross-sectional 723 0.019 ↔ NM ↔ ↑ NM ↔ NM

Eriksen et al.

2013

Cross-sectional 663 0.036 ↑ NM NM NM NM NM NM

Perfluorooctane sulfonate (PFOS) – May 2016 B-6 
Reference Study type n

Mean or median 

serum PFOS (μg/mL) TC VLDL LDL HDL Non-HDL TG UA

Starling et al.

2014

Cross-sectional 

(maternal at 

14–26 weeks 

gestation)

891 0.013 ↑ NM ↑ ↑ NM ↔ NM

Fisher et al.

2013

Cross-sectional 2,700 0.0084 ↔ NM ↔ ↔ NM NM NM

Notes: ↑ = positive association; ↓= negative association; ↔ = no association; TC = total cholesterol; VLDL= very low density lipoprotein; LDL= low density lipoprotein; non-HDL= 

TC(VLDL,IDL, LDL)-HDL; HDL= high density lipoprotein; TG = triglycerides; UA = uric acid; NM = not measured

Perfluorooctane sulfonate (PFOS) – May 2016 B-7 
Table B-5. Association of Serum PFOS with Reproductive and Developmental Outcomes

Study Study type n

Mean or median 

serum PFOS 

(μg/mL) Outcome

Measures at 

birth

Growth/ 

Development

Fecundity/ 

Fertility

Occupational Populations

Grice et al. 2007 Survey 263 Not measured; 

exposure 

categorized by job

↔ (any adverse) NM NM NM

General Populations—Measures at Birth

Fei et al. 2007,

2008a, 2010a

Cross-sectional 1,400 0.033–0.039 (first 

trimester)

↔ (gestation 

length)

↓ (length of 

breastfeeding)

↔ (weight)

↔ (size)

↔ (Apgar score)

NM NM

Monroy et al. 2008 Cross-sectional 101 0.018 (maternal at 

24–28 weeks)

0.016

(maternal at 

delivery)

0.0072 (umbilical 

cord blood)

↔ (gestation 

length)

↔ (weight) NM NM

Washino et al.

2009

Cross-sectional 428 0.0056 (maternal) NM ↑ (low weight 

females only)

NM NM

Hamm et al. 2009 Cross-sectional 252 0.009 (maternal) ↔ (gestation 

length)

↔ (weight) NM NM

Stein et al. 2009 Cross-sectional 

(C8)

5,262 0.014 ↔ (miscarriage) ↑ (low weight) NM NM

Darrow et al.

2013, 2014

Cross-sectional 

(C8)

1330 0.016–0.017 ↔ (preterm)

↑ (miscarriage)

↔ (low weight)

↑ (birth weight 

decreased)

NM ↑ (hypertension)

Apelberg et al.

2007

Cross-sectional 293 0.005 (cord blood) ↔ (gestational 

age)

↓ (weight, head 

circumference, 

ponderal index)

NM NM

General Populations—Measures of Postnatal Growth

Fei et al. 2008b Cross-sectional 1,400 0.033–0.039 (first 

trimester)

NM NM ↔ (at 6 months)

↑ (at 18 months; 

sitting up later)

MN

Liew et al. 2014 Cross-sectional 156 cases

550 controls

0.026–0.029 (first 

trimester)

NM NM ↑ (cerebral palsy 

in boys)

NM

Perfluorooctane sulfonate (PFOS) – May 2016 B-8 
Study Study type n

Mean or median 

serum PFOS 

(μg/mL) Outcome

Measures at 

birth

Growth/ 

Development

Fecundity/ 

Fertility

Andersen et al.

2010

Cross-sectional 1,010 0.0334 (first 

trimester)

NM ↓ (birth weight in 

girls)

↓ (weight and 

BMI at 12 

months in boys)

NM

Andersen et al.

2013

Cross-sectional 811 (children at 

age 7 years)

0.033–0.039 (first 

trimester)

NM NM ↔ (height, 

weight, waist 

measurement, 

risk of 

overweight)

NM

Fei and Olsen 

2011

Cross-sectional 787 (behavior)

537 

(coordination)

0.036 (first

trimester)

NM NM ↔ (behavior and 

coordination at 7 

years)

NM

Høyer et al. 2015b Cross-sectional 1,106 0.01 (maternal) NM NM ↔ (motor skills, 

hyperactivity)

NM

Hoffman et al.

2010

Cross-sectional 

(NHANES)

571 (children) 0.023 NM NM ↑ (ADHD) NM

Høyer et al. 2015a Cross-sectional 1,022 (children) 0.005–0.0202 

(maternal)

NM NM ↔ (overweight)

↑ (waist-to-height 

ratio)

NM

Lopez-Espinosa et 

al. 2011

Cross-sectional 

(C8)

3,076 boys

2,931 girls

0.0098–0.036 NM NM ↑ (delayed 

puberty)

NM

Kristensen et al.

2013; Vested et al.

2013

Cross-sectional 343 women

169 men

(~ 20 years)

0.0211–0.0212 

(maternal)

NM NM NM ↔ (measures of 

reproductive 

function)

Christensen et al.

2011

Cross-sectional 448 girls 0.019–0.02 

(maternal)

NM NM ↔ (age at 

menarche)

NM

Halldorsson et al.

2012

Cross-sectional 665 0.0285 (maternal) NM NM ↑ (overweight in 

females at 20 

years)

NM

General Populations—Male and Female Fertility

Zhang et al. 2015 Cross-sectional 258 0.012–0.0131 

(preconception)

↑ (gestational 

diabetes)

NM NM NM

Vélez et al. 2015 Cross-sectional 1,743 0.005 NM NM NM ↔ (time to 

pregnancy)

↔ (infertility)

Fei et al. 2009 Cross-sectional 1,400 0.033–0.039 (first 

trimester)

NM NM NM ↑ (time to 

pregnancy)

↑ (infertility)

Perfluorooctane sulfonate (PFOS) – May 2016 B-9 
Study Study type n

Mean or median 

serum PFOS 

(μg/mL) Outcome

Measures at 

birth

Growth/ 

Development

Fecundity/ 

Fertility

Knox et al. 2011 Cross-sectional 

(C8)

25,957 0.018 NM NM NM ↑ (early 

menopause)

Joensen et al. 2009

(PFOA/PFOS 

combined)

Cross-sectional 105 0.025 NM NM NM ↑ (lower number 

normal sperm)

↔ (testosterone)

Joensen et al. 2013 Cross-sectional 247 0.0085 NM NM NM ↔ (semen 

parameters)

↓ (testosterone)

Buck Louis et al.

2014

Cross-sectional 462 0.017–0.021 NM NM NM ↑ (lower % sperm 

with coiled tail) 

(total of six PFAS

associated with 

changes in sperm 

quality)

Notes: ↑ = positive association; ↓= negative association; ↔ = no association; NM = Not Measured

Perfluorooctane sulfonate (PFOS) – May 2016 B-10
Table B-6. Association of PFOS Level with the Prevalence of Thyroid Disease and Thyroid Hormone Levels

Study Study type Population (n)

Mean serum PFOS 

(μg/mL)

Thyroid 

Disease TSH T3 T4

Olsen et al. 2001a Cross-sectional Adult workers

(263 Decatur)

(255 Antwerp)

1.4

0.96

NM ↔ ↔ ↔

Dallaire et al. 2009 Cross-sectional Adults (623) 0.018 ↔ ↓ ↓ ↑

Bloom et al. 2010 Cross-sectional Adults (31) 0.0196 ↔ ↔ NM ↔

Melzer et al. 2010 Cross-sectional Adult (NHANES; 

3,966)

0.025 (men)

0.019 (women)

↔ (women)

↑ (men)

NM NM NM

Shrestha et al. 2015 Cross-sectional Adults (51 men, 36 

women)

0.036 ↔ ↔ ↔ ↑

Pirali et al. 2009 Cross-sectional Adults (28) 5.3 ng/g thyroid tissue ↔ NM NM NM

Wang et al. 2013 Cross-sectional Women at gestation 

week 18 (Norwegian 

Mother/Child 

Cohort; 903)

0.0128 NM ↑ NM NM

Berg et al. 2015 Cross-sectional Women at gestation 

week 18, day 3 and 

week 6 after delivery 

(Norwegian 

Mother/Child 

Cohort; 375)

0.00803 NM ↑ ↔ ↔

Inoue et al. 2004 Cross-sectional Newborns (15) 0.0016–0.0053 (cord 

blood)

NM ↔ NM ↔

Chan et al. 2011 Cross-sectional Women at gestation 

week 15–20 (974)

0.0074 ↔ ↔ NM ↔

Webster et al. 2014 Cross-sectional 152 women at 

gestation week 15–

18

0.0017 NM ↔ ↔ ↔

Notes: ↑= positive association; ↓= negative association; ↔= no association; NM = Not Monitored

Perfluorooctane sulfonate (PFOS) – May 2016 B-11
Table B-7. Association of Serum PFOS with Markers of Immunotoxicity

Study Study type Population (n)

Mean or median 

serum PFOS 

(μg/mL)

Disease 

prevalence in 

children

Vaccine 

response

Okada et al. 2012 Prospective 

cohort

Maternal, third 

trimester (343)

0.0056 ↔ NM

Fei et al. 2010b Cross-sectional Maternal, first 

trimester (1,400)

0.0353 ↔ NM

Grandjean et al.

2012

Prospective 

cohort

Maternal at 

gestation week 

32 (587)

0.0273 (maternal) NM ↓ (antibody titer 

in child at age 5 

yrs)

Grandjean et al.

2012

Prospective 

cohort

Children age 5 

years (587)

0.0167 (child at 

age 5 years)

NM ↓ (antibody titer 

in child at age 7 

yrs)

Granum et al.

2013

Prospective 

cohort

Women at 

delivery (56)

0.0056 (maternal) ↔ ↓ (antibody titer 

in child at age 3 

years)

Humblet et al.

2014

Cross-sectional Children at 12–

19 years (1,877)

0.017 

(asthmatics)

0.0168 (nonasthmatics)

↔ for asthma NM

Dong et al. 2013 Cross-sectional Children age 

10–15 years 

(231 asthmatics 

and 225 

controls)

0.0455 

(asthmatics)

0.0334 (nonasthmatics)

↑ for asthma NM

Looker et al. 2014 Cross-sectional Adults (411) 0.0083 NM ↔

Notes: ↑= positive association; ↓= negative association; ↔= no association; NM = Not Measured

Perfluorooctane sulfonate (PFOS) – May 2016 B-12
Appendix C: Summary of Data

Perfluorooctane sulfonate (PFOS) – May 2016 C-1 
Table C-1. PFOS Toxicokinetic Information

Species Dose

Route of 

exposure Effects observed

PFOS in liver

(μg/g)

PFOS in blood

(μg/mL)

M F M F Reference

Human NA Unknown ↑ TC; ↑ TG NS 0.96–1.40 Olsen et al.

2001b, 2003b

Human NA Unknown None observed 

on cholesterol

NS

1.16–2.62

Olsen et al.

2001b, 2003b

Human NA Drinking water ↑ TC; ↑ TG; ↑ 

LDL; ↑ UA

NS NS 0.022–0.023 Steenland et al.

2009, 2010

Human NA Drinking water ↑ TC; ↑ LDL; ↑ 

HDL

NS NS 0.023 Frisbee et al.

2010

Human NA Drinking water None observed 

on cholesterol

NS NS 0.011–0.023 Fitz-Simon et al.

2013

Human NA Unknown ↑ TC; ↑ nonHDLNS NS 0.025 Nelson et al.

2010

Human NA Unknown ↑ HDL NS NS 0.019 Château-Degat et 

al. 2010

Human NA Unknown ↑ TC NS NS 0.036 Eriksen et al.

2013

Human NA Unknown ↑ TC; ↑ LDL; ↑ 

HDL

NS NS 0.013 Starling et al.

2014

Human NA Unknown None observed 

on cholesterol

NS NS 0.0084 Fisher et al. 2013

Human NA Unknown/

drinking water

Developmental 

delays

NS NS NS 0.0098–0.039 Fei et al. 2008b; 

Lopez-Espinosa 

et al. 2011

Human NA Unknown/

drinking water

LBW NS NS NS 0.0056–0.016 Washino et al.

2009; Stein et al.

2009; Darrow et 

al. 2013

Human NA Unknown None on birth 

outcome; birth 

weight and 

length; growth to 

7 years

NS NS NS 0.009–0.039 Fei et al. 2007,

2008a; Monroy 

et al. 2008; 

Hamm et al.

2009; Andersen 

et al. 2013

Human NA Unknown ↑ time to 

pregnancy

NS NS NS 0.033–0.039 Fei et al. 2009

Perfluorooctane sulfonate (PFOS) – May 2016 C-2 
Species Dose

Route of 

exposure Effects observed

PFOS in liver

(μg/g)

PFOS in blood

(μg/mL)

M F M F Reference

Human NA Unknown Effects on sperm 

numbers and 

morphology

NS NS 0.017–0.025 NS Joensen et al.

2009; Buck 

Louis et al. 2014

Human NA Unknown None on semen 

parameters

NS NS 0.0085 NS Joensen et al.

2013

Human NA Unknown None on thyroid 

hormones

NS NS 0.96–1.4 Olsen et al.

2001b; 2003b

Human NA Unknown ↓TSH, T3; ↑T4 NS NS 0.018 Dallaire et al.

2009

Human NA Unknown None on thyroid 

hormones

NS NS 0.0196 Bloom et al.

2010

Human NA Unknown ↑ incidence of 

thyroid disease 

(men only)

NS NS 0.025 0.019 Melzer et al.

2010

Human NA Unknown ↑T4 NS NS 0.036 Shrestha et al.

2015

Human NA Unknown ↑TSH NS NS NS 0.008–0.0128

(gestation wk 18)

Wang et al.

2013; Berg et al.

2015

Human NA Unknown None on thyroid 

hormones

NS NS NS 0.0074

(gestation wk 

15–20)

Chan et al. 2011

Human NA Unknown None on diseases 

in children

NS NS NS 0.0056

(maternal, third 

trimester)

Okada et al. 2012

Human NA Unknown None on diseases 

in children

NS NS NS 0.0353

(maternal, first 

trimester)

Fei et al. 2010b

Human NA Unknown ↓ antibody titer 

in children

NS NS NS 0.0273

(maternal, 

gestation wk 32)

Grandjean et al.

2012 

0.0167 (child age 5 years)

Human NA Unknown ↓ antibody titer 

in children

NS NS NS 0.0056

(maternal at 

delivery)

Granum et al.

2013

Human NA Unknown ↑asthma NS NS 0.0455 (asthmatic children) Dong et al. 2013

Perfluorooctane sulfonate (PFOS) – May 2016 C-3 
Species Dose

Route of 

exposure Effects observed

PFOS in liver

(μg/g)

PFOS in blood

(μg/mL)

M F M F Reference

Human NA Unknown None on vaccine 

response

NS NS 0.0083 Looker et al.

2014

Monkey 0.15 mg/kg/day 

for 26 weeks 

with 52 week 

recovery

capsule None observed NS NS (serum)

wk 1: 4.60

wk 26: 82.6

wk 35: 84.5

wk 79: 19.1

(serum)

wk 1: 3.71

wk 26: 66.8

wk 35: 74.7

wk 79: 21.4

Seacat et al. 2002

Monkey 0.75 mg/kg/day 

for 26 weeks 

with 52 week 

recovery

capsule ↑ liver wt

↓ cholesterol and 

body wt

NS NS (serum)

wk 1: 21.0

wk 26: 173

wk 35: 181

wk 79: 41.1

(serum)

wk 1: 20.4

wk 26: 171

wk 35: 171

wk 79: 41.4

Seacat et al. 2002

Rat 0.018–0.023 

mg/kg/day for 

104 weeks

diet None observed

wk 0: 11.0

wk 10: 23.8

wk 105: 7.83

wk 0: 8.71

wk 10: 19.2

wk 105: 12.9

(serum)

wk 0: 0.91

wk 14: 4.04

wk 105: 1.31

(serum)

wk 0: 1.61

wk 14: 6.96

wk 105: 4.35

Thomford 2002

Rat 0.184–0.247 

mg/kg/day for 

104 weeks

diet ↑ liver histopath. 

lesions wk 0: 47.6

wk 10: 358

wk 105: 70.5

wk 0: 83.0

wk 10: 370

wk 105: 131

(serum)

wk 0: 7.57

wk 14: 43.9

wk 105: 22.5

(serum)

wk 0: 12.6

wk 14: 64.4

wk 105: 75.0

Thomford 2002

Rat 0.765–1.10 

mg/kg/day for 

104 weeks

diet ↑ body and liver 

wt

↑ hepatocellular 

adenoma

wk 0: 282

wk 10: 568

wk 105: 189

wk 0: 373

wk 10: 635

wk 105: 381

(serum)

wk 0: 41.8

wk 14: 148

wk 105: 69.3

(serum)

wk 0: 54.0

wk 14: 223

wk 105: 233

Thomford 2002

Rat

(male only)

5 mg/kg for 28 

days

oral gavage ↓ body wt 345 NS (whole blood)

72.0

NS Cui et al. 2009

Rat

(male only)

20 mg/kg for 28 

days

oral gavage 10/10 died (day 

26)

hepatic 

hypertrophy

648 NS (whole blood)

NS

NS Cui et al. 2009

Perfluorooctane sulfonate (PFOS) – May 2016 C-4 
Species Dose

Route of 

exposure Effects observed

PFOS in liver

(μg/g)

PFOS in blood

(μg/mL)

M F M F Reference

Rat 0.4 mg/kg

42 days prior to 

cohabitation 

through GD 21

oral

gavage

↓ maternal and 

pup body wt

NS GD 21:

dams = 107

fetuses = 30.6

NS (serum)

GD 1: 40.7

GD 7: 40.9

GD 21:

dams = 26.2

fetuses = 34.3

Luebker et al.

2005b

Rat 1.6 mg/kg

42 days prior to 

cohabitation 

through GD 21

oral

gavage

↓ maternal and 

pup body wt

↓ pup survival

NS GD 21:

dams = 388

fetuses = 86.5

NS (serum)

GD 1: 160

GD 7: 154

GD 21:

dams = 136

fetuses = 101

Luebker et al.

2005b

Rat 3.2 mg/kg

42 days prior to 

cohabitation 

through GD 21

oral

gavage

100% pup

mortality by 

PND 2

NS GD 21:

dams = 610

fetuses = 230

NS (serum)

GD 1: 318

GD 7: 306

GD 21:

dams = 155

fetuses = 164

Luebker et al.

2005b

Rat 0.1 mg/kg GD 0 

to PND 20

oral gavage None observed in 

dams or 

offspring

PND 21:

Offspring = 

5.98

PND 72:

Offspring = 

0.98

GD 20:

Dams = 8.35

Offspring = 

3.21

PND 21:

Dams = NS

Offspring = 

5.28

PND 72:

Dams = NS

Offspring = 

0.80

(serum)

PND 21:

Offspring = 

1.73

PND 72:

Offspring = 

0.04

(serum)

GD 20:

Dams = 1.72

Offspring = 3.91

PND 21:

Dams = 3.16

Offspring = 1.77

PND 72:

Dams = NS

Offspring = 0.21

Butenhoff et al.

2009; Chang et 

al. 2009

Perfluorooctane sulfonate (PFOS) – May 2016 C-5 
Species Dose

Route of 

exposure Effects observed

PFOS in liver

(μg/g)

PFOS in blood

(μg/mL)

M F M F Reference

Rat 1.0 mg/kg GD 0 

to PND 20

oral gavage ↑ motor activity 

and ↓ habituation 

in male offspring

PND 21:

Offspring = 

44.89

PND 72:

Offspring = 

7.17

GD 20:

Dams = 48.88

Offspring = 

20.03

PND 21:

Dams = NS

Offspring = 

41.23

PND 72:

Dams = NS

Offspring = 7.2

(serum)

PND 21:

Offspring = 

18.61

PND 72:

Offspring = 

0.56

(serum)

GD 20:

Dams = 26.63

Offspring = 

31.46

PND 21:

Dams = 30.48

Offspring = 

18.01

PND 72:

Dams = NS

Offspring = 1.99

Butenhoff et al.

2009; Chang et 

al. 2009

Rat 1.0 mg/kg/day

GDs 2–20

oral gavage none NS NS NS 19.69 Thibodeaux et al.

2003; Lau et al.

2003

Rat 2.0 mg/kg/day

GDs 2–20

oral gavage ↓ dam and pup 

wt; ↓pup survival

NS NS NS 44.33 Thibodeaux et al.

2003; Lau et al.

2003

Note: NS = no sample obtained or recorded

Perfluorooctane sulfonate (PFOS) – May 2016 C-6 
Table C-2. Summary of Animal Studies with Exposure to PFOS

Method of 

exposure Length of study Species Concentration Results Reference

oral gavage 20 days monkey 0, 10, 30, 100, or 300 

mg/kg/day

2 monkeys/sex/dose

NOAEL= NA

LOAEL= 10 mg/kg/day 

from deaths at all doses

Goldenthal et al. 

1978a

oral gavage 90 days monkey 0, 0.5, 1.5, or 4.5 

mg/kg/day

2 monkeys/sex/dose

NOAEL= NA

LOAEL= 0.5 mg/kg/day 

based on diarrhea and 

anorexia

Goldenthal et al. 

1979

oral 

(capsule)

182 days monkey 0, 0.03, 0.15, or 0.75 

mg/kg/day

4–6 

monkeys/sex/dose

NOAEL= 0.15 

mg/kg/day

LOAEL= 0.75 

mg/kg/day from ↓ body 

weight, ↑liver wt and 

↓cholesterol

Seacat et al. 2002

oral gavage single dose rat 0, 100, 215, 464, or 

1,000 mg/kg

5 rats/sex/dose

LD50 = 251 mg/kg 

(combined)

Dean et al. 1978

oral gavage single dose rat 0, 12.5, 25, or 50 

mg/kg 

5 male rats/dose

NOAEL= NA

LOAEL= 12.5 mg/kg 

based on ↓ body weight

Yang et al. 2009

oral gavage single dose

thyroid hormone 

activity

rat 0 or 15 mg/kg

5/15 female 

rats/group

Total thyroxine (TT4)-

significant ↓ at 2, 6 and 

24 hrs

Triiodothyronine (TT3) 

and reverse 

triiodothyronine (rT3)- 

significant ↓ at 24 hrs

Free thyroxinesignificant ↑ at 2 and 6 

hrs; normal at 24 hrs

Chang et al. 2008

inhalation 1 hour rat 0, 1.89, 2.86, 4.88, 

6.49, 7.05, 13.9, 

24.09, or 45.97 ppm

5 rats/sex/dose

LC50 = 5.2 ppm Rusch et al. 1979

oral (in diet) 28 days rat 0, 0.05, 0.18, 0.37, or 

1.51 mg/kg/day—

males

0, 0.05, 0.22, 0.47, or 

1.77 mg/kg/day— 

females

(0, 0.5, 2, 5, or 20 

ppm)

5 rats/sex/dose

NOAEL = 0.37 

mg/kg/day in males and 

0.47 mg/kg/day in 

females

LOAEL = 1.51 

mg/kg/day in males and 

1.77 mg/kg/day in 

females, based on ↓ body 

wt (M/F) and ↓ food 

consumption (F)

Seacat et al. 2003

oral (in diet) 28 days rat 0.14, 1.33, 3.21, 6.34 

mg/kg/day—males

0.15, 1.43, 3.73, 7.58 

mg/kg/day—females

(0, 2, 20, 50, or 100 

mg/kg diet)

15 rats/sex/dose

NOAEL = 0.14 mg 

/kg/day in males and NA 

in females

LOAEL = 1.33 mg 

/kg/day in males and 0.15

mg/kg/day in females 

based on ↑ relative liver 

wt

Curran et al. 2008

Perfluorooctane sulfonate (PFOS) – May 2016 C-7 
Method of 

exposure Length of study Species Concentration Results Reference

oral gavage 28 days rat 0, 5, or 20 mg/kg/day

10 males/dose

NOAEL= NA

LOAEL= 5 mg/kg/day 

based on ↓ body wt and 

lung congestion

Cui et al. 2009

oral gavage 28 days rat 0, 0.5, 1, 3, or 6 

mg/kg/day

19 males/dose

NOAEL = NA

LOAEL = 0.5 mg/kg/day 

based on ↓ LH and 

testosterone and ↑ FSH

López-Doval et al.

2014

oral (in diet) 90 days rat 0, 2, 6, 18, 60, or 200 

mg/kg/day

5 rats/sex/dose

NOAEL= NA

LOAEL= 2 mg/kg/day, 

from ↑ liver wt, ↓ food 

consumption

Goldenthal et al. 

1978b

oral (in diet) 98 days rat 0, 0.5, 2.0, 5.0, or 20 

ppm

0, 0.03, 0.13, 0.34 or 

1.33 mg/kg/daymales

0, 0.04, 0.15, 0.40 or 

1.56 mg/kg/dayfemales

5 rats/sex/dose

NOAEL = 0.34 

mg/kg/day in males and 

0.40 mg/kg/day in 

females

LOAEL = 1.33 

mg/kg/day in males and 

1.56 mg/kg/day in 

females, based on ↑ liver 

wt (M) and ↑ relative liver 

wt (M/F)

Seacat et al. 2003

oral gavage GD 0 to PND 20a

developmental 

neurotoxicity 

study

rat 0, 0.1, 0.3, or 1.0 

mg/kg/day

25 females/dose

Maternal

NOAEL= 1 mg/kg/day

LOAEL= NA

Developmental

NOAEL= 0.3 mg/kg/day

LOAEL= 1 mg/kg/day 

based on ↑ motor activity

Butenhoff et al. 

2009

oral gavage GDs 2–20 rat 0, 1, 2, 3, 5, or 10 

mg/kg

Maternal

NOAEL= 1 mg/kg

LOAEL= 2 mg/kg based 

on ↓ body wt

Developmental

NOAEL= 1 mg/kg

LOAEL= 2 mg/kg based 

on ↓ survival

BMDL5 corresponding to 

maternal dose for 

survival of rat pups at 

PND 8 was 0.58 mg/kg

Thibodeaux et al. 

2003 and Lau et 

al. 2003

oral gavage GDs 2–21 rat 0, 0.1, 0.6, or 2.0 

mg/kg

Offspring

NOAEL = cannot be 

determined

LOAEL= 0.1 mg/kg 

based on changes in the 

cortex and hippocampus 

(astrocyte activation 

markers, proinflammatory 

transcription factors)

Zeng et al. 2011

Perfluorooctane sulfonate (PFOS) – May 2016 C-8 
Method of 

exposure Length of study Species Concentration Results Reference

oral gavage GDs 2–21 rat 0, 0.1, 0.6, or 2 

mg/kg/day

Offspring on PND 21

NOAEL = 0.1 mg/kg/day

LOAEL = 0.6 mg/kg/day 

based on increased 

apoptosis in heart cells

Zeng et al. 2014

oral gavage GDs 1–21 rat 0, 0.1, or 2.0 

mg/kg/day

Offspring

NOAEL= 0.1 mg/kg/day

LOAEL = 2.0 mg/kg/day 

based on 

histopathological 

changes in lungs, ↓ body 

wt and ↑ mortality

Chen et al. 2012

oral gavage GD 0–PND 20 rat 0, 0.5, or 1.5 

mg/kg/day

6 dams/dose

NOAEL = NA

LOAEL = 0.5 mg/kg/day 

based on ↓ offspring 

body wt, impaired 

glucose tolerance

Lv et al. 2013

oral gavage GDs 11–19 rat 0, 5, or 20 mg/kg/day

4 dams/dose

NOAEL = NA

LOAEL = 5 mg/kg/day 

based on ↓ offspring 

body wt

Zhao et al. 2014

oral gavage 6 wks prior to 

mating and

Males—22 days

Females— 

through 

gestation, 

parturition and 

lactation

reproductive 

study

rat 0, 0.1, 0.4, 1.6, or 3.2 

mg/kg/day

35 rats/sex/dose

F0 (M/F) parents

NOAEL= 0.1 mg/kg/day

LOAEL= 0.4 mg/kg/day 

based on ↓ bwt gain/food 

consumption

F1 (M/F) parents

NOAEL = 0.4 mg/kg

LOAEL = NA, higher 

dose not tested

F1 offspring

NOAEL= 0.4 mg/kg/day

LOAEL= 1.6 mg/kg/day 

based on ↓ viability, 

body wt

F2 offspring

NOAEL= 0.1 mg/kg/day

LOAEL= 0.4 mg/kg/day 

based on ↓ body wt

Luebker et al.

2005b

Perfluorooctane sulfonate (PFOS) – May 2016 C-9 
Method of 

exposure Length of study Species Concentration Results Reference

oral gavage 6 wks prior to 

mating and 

continued 

through mating, 

gestation and 

LD 4 

reproductive

study

rat 0, 0.4, 0.8. 1.0, 1.2, 

1.6 and 2.0 

mg/kg/day

20–28 dams/dose

F0 dams

NOAEL= 0.4 mg/kg/day

LOAEL= 0.8 mg/kg/day 

based on ↓ bwt gain

F1 offspring

NOAEL= not identified

LOAEL= 0.4 mg/kg/day 

based on ↓ pup body 

weight

BMDL5 estimates for 

decreased gestation 

length was 0.31 and 

viability was 0.89 

mg/kg/day

Luebker et al.

2005a

oral (diet) 104 weeks rat 0, 0.024, 0.098, 

0.242, or 0.984

mg/kg/day—males

0, 0.029, 0.120, 

0.299, or 1.251

mg/kg/day—females

0, 0.5, 2, 5, or 20 ppm

40–70 males and 

females

Males NOAEL= 0.024

mg/kg/day

Males LOAEL= 0.098

mg/kg/day based on liver 

histopathology

Females NOAEL = 0.120

mg/kg/day

Females LOAEL = 0.299

mg/kg/day based on liver 

histopathology

Suggestive of 

carcinogenicity

Thomford 2002/ 

Butenhoff et al.

2012

oral gavage 1 time on PND 

10

developmental 

neurotoxicity

mouse 0, 0.75, or 11.3 mg/kg

4–7 males/group

Mice at both 

concentrations showed ↓ 

activity and ↑ 

neuroprotein levels in the 

hippocampus

Johansson et al. 

2008, 2009

oral gavage 7 days

immunotoxicity 

study

mouse 0, 5, 20, or 40 mg/kg

12 male mice/dose

NOAEL= NA

LOAEL= 5 mg/kg based 

on ↑ liver wt and 

suppression of the plaque 

forming cell response

Zheng et al. 2009

oral gavage GDs 1–17

developmental 

immunotoxicity

mouse 0, 0.1, 1, or 5 mg/kg

10–12 female 

mice/dose

Males NOAEL = 0.1 

mg/kg

Males LOAEL = 1 mg/kg 

based on ↓NK cell 

activity

Females NOAEL = 1 

mg/kg

Females LOAEL = 5 

mg/kg based on ↓NK cell 

activity

Keil et al. 2008

Perfluorooctane sulfonate (PFOS) – May 2016 C-10
Method of 

exposure Length of study Species Concentration Results Reference

oral gavage GDs 1–17 mouse 0, 1, 5, 10, 15, or 20 

mg/kg

Maternal

NOAEL= 1 mg/kg

LOAEL= 5 mg/kg based 

on ↑ liver wt

Developmental

NOAEL= 1 mg/kg

LOAEL= 5 mg/kg based 

on ↑ liver wt, delayed eye 

opening

BMDL5 corresponding to 

maternal dose for 

survival of mouse pups at 

PND 6 was 3.88 mg/kg

Thibodeaux et al. 

2003; Lau et al. 

2003

oral gavage GDs 12–18

developmental

mouse 0 or 6 mg/kg/day

8–10 mice/dose

Maternal

NOAEL= 6 mg/kg/day

LOAEL= NA

Developmental

NOAEL= NA

LOAEL= 6 mg/kg/day 

based on ↓ body wt

Fuentes et al. 2007

oral gavage GDs 1–17/18

developmental

mouse 0, 1, 10, or 20 

mg/kg/day

10 mice/dose

Maternal

NOAEL = 1 mg/kg/day

LOAEL= 10 mg/kg/day, 

based on ↑ liver organ 

wt.

Developmental

NOAEL= 1 mg/kg/day

LOAEL= 10 mg/kg/day, 

based on fetal 

abnormalities and 

↓survival

Yahia et al. 2008

oral gavage 14 days

With regular or 

high fat diet

mouse 0, 5, or 20 mg/kg/day

16 males/dose/diet

NOAEL = NA

LOAEL = 5 mg/kg/day 

based on wt loss on high 

fat diet

L. Wang et al.

2014

oral gavage 3–21 days mouse 0, 1, 5, or 10 

mg/kg/day

4 males/dose

NOAEL = 1 mg/kg/day

LOAEL = 5 mg/kg/day 

based on ↑ liver wt, 

changes in oxidation 

biochemical parameters

Wan et al. 2012

oral gavage GD 0–PND 21 mouse 0, 0.3, 3 mg/kg/day

6 dams/dose

NOAEL = 0.3 mg/kg/day

LOAEL = 3 mg/kg/day 

based on ↑ liver wt in 

dams and male offspring, 

↑ fasting serum insulin in 

males

Wan et al. 2014b

Perfluorooctane sulfonate (PFOS) – May 2016 C-11
Method of 

exposure Length of study Species Concentration Results Reference

oral gavage 28 days

immunotoxicity

mouse 0, 0.00017, 0.0017, 

0.0033, 0.017, 0.033, 

or 0.166 mg/kg

5 mice/dose

Males NOAEL= 0.00017

mg/kg

Males LOAEL= 0.0017

mg/kg based on ↓ plaque 

forming cell response

Females NOAEL= 

0.0033 mg/kg

Females LOAEL= 0.017

mg/kg

based on ↓ plaque 

forming cell response

Peden-Adams et 

al. 2008

oral gavage 60 days

immunotoxicity

mouse 0, 0.008, 0.083, 

0.417, 0.833, or 2.083 

mg/kg

10 male mice/group

NOAEL = 0.008 

mg/kg/day

LOAEL = 0.083 mg/kg 

based on ↑ splenic NK 

cell activity and ↑ liver 

weight

Dong et al. 2009

oral gavage 90 days

neurotoxicity

mouse 0, 0.43, 2.15, or 10.75 

mg/kg/day

15/group, sex not 

specified

NOAEL = 0.43 

mg/kg/day

LOAEL = 2.15 

mg/kg/day based on 

changes in water maze 

and histopath. in 

hippocampus

Long et al. 2013

dermal single dose rabbit 0.5 g*

(no data on gender)

No irritation Biesemeier and 

Harris 1974

ocular single dose rabbit 0.5 g*

(no data on gender)

Exact score not provided 

except maximal score at 

1 and 24 hrs

Biesemeier and 

Harris 1974

Notes: *Exact dose not provided; NA= not applicable; could not be determined a GD = gestation day and PND = post natal day

M = male; F = female

Perfluorooctane sulfonate (PFOS) – May 2016 C-12