Perfluorooctane sulfonate (PFOS) – February 2014 i 

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Health Effects Document 

for Perfluorooctane 

Sulfonate (PFOS) 
 

 

Health Effects Document 

for 

Perfluorooctane Sulfonate (PFOS) 

U.S. Environmental Protection Agency 

Office of Water (4304T) 

Health and Ecological Criteria Division
 

Washington, DC 20460 

EPA Document Number: 822R14002 

Date: February 2014 

Perfluorooctane sulfonate (PFOS) – February 2014 

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ii 
Perfluorooctane sulfonate (PFOS) – February 2014 iii

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ACKNOWLEDGMENT

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. 
Perfluorooctane sulfonate (PFOS) – February 2014 iv

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Authors, Contributors, and Reviewers

Chemical manager

Joyce Morrissey Donohue, Ph.D. 

Office of Water, Office of Science and Technology 

Health and Ecological Criteria Division

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

Authors (EPA) 

Amal Mahfouz, Ph.D. 

Office of Water, Office of Science and Technology

Health and Ecological Criteria Division

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

Joyce Morrissey Donohue, Ph.D. 

Office of Water, Office of Science and Technology

Health and Ecological Criteria Division

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

Tina Moore Duke, M.S. 

Office of Water, Office of Science and Technology

Health and Ecological Criteria Division

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

Authors (Oak Ridge National Laboratory) 

Dana 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 

Peer Reviewers

Internal

Christopher Lau, Ph.D.
Perfluorooctane sulfonate (PFOS) – February 2014 v 

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National Health and Environmental Effects Research Laboratory, Office of Research and 

Development 

Reproductive Toxicology Division 

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

Greg Miller, Ph.D.

Office of Children’s Health Protection, Office of the Administrator

U.S. Environmental Protection Agency, Washington, DC 

John Wambaugh, Ph.D. 

National Center for Computational Toxicology, Office of Research and Development 

Systems Models for Chemical Toxicity and Exposure 

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

National Center for Environmental Assessment

Office of Research and Development

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

External 
Perfluorooctane sulfonate (PFOS) – February 2014 vi 

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TABLE OF CONTENTS

ACKNOWLEDGMENT..............................................................................................................................iii

Authors, Contributors, and Reviewers.........................................................................................................iv

TABLE OF CONTENTS............................................................................................................................. vi

LIST OF TABLES.....................................................................................................................................viii

LIST OF FIGURES ...................................................................................................................................... x

ABBREVIATIONS AND ACRONYMS .................................................................................................... xi

1.0 EXECUTIVE SUMMARY............................................................................................................. 1-1

2.0 IDENTITY: CHEMICAL AND PHYSICAL PROPERTIES......................................................... 2-1

3.0 TOXICOKINETICS ........................................................................................................................ 3-1

3.1 Absorption ................................................................................................................................ 3-1

3.1.1 Oral Exposure........................................................................................................................... 3-1

3.1.2 Inhalation Exposure.................................................................................................................. 3-2

3.1.3 Dermal Exposure ...................................................................................................................... 3-2

3.2 Distribution............................................................................................................................... 3-2

3.2.1 Oral Exposure........................................................................................................................... 3-5

3.2.2 Inhalation and Dermal Exposure ............................................................................................ 3-16

3.2.3 Other Routes of Exposure....................................................................................................... 3-17

3.3 Metabolism............................................................................................................................. 3-17

3.4 Excretion................................................................................................................................. 3-18

3.4.1 Oral Exposure......................................................................................................................... 3-18

3.4.2 Inhalation Exposure................................................................................................................ 3-20

3.4.3 Dermal Exposure .................................................................................................................... 3-20

3.4.4 Other Exposure Routes........................................................................................................... 3-20

3.5 Pharmacokinetic Considerations ............................................................................................ 3-20

3.5.1 Physiologically based models................................................................................................. 3-20

3.5.2 Half-life data........................................................................................................................... 3-27

3.5.3 Volume of Distribution Data .................................................................................................. 3-31

4.0 HAZARD IDENTIFICATION........................................................................................................ 4-1

4.1 Human Effects.......................................................................................................................... 4-1

4.1.1 Short-Term Studies and Case Reports...................................................................................... 4-1

4.1.2 Long-Term and Epidemiological Studies................................................................................. 4-1

4.1.2.1 Noncancer Systemic Toxicity Studies............................................................................. 4-1

4.1.2.2 Reproductive Hormones and Reproductive/Developmental Studies............................... 4-5

4.1.2.3 Thyroid Effect Studies..................................................................................................... 4-9

4.1.2.4 Immunotoxicity.............................................................................................................. 4-11

4.1.2.5 Carcinogenicity Studies................................................................................................. 4-13

4.2 Animal Studies ....................................................................................................................... 4-14

4.2.1 Acute Toxicity ........................................................................................................................ 4-14

4.2.2 Short-Term Studies................................................................................................................. 4-16

4.2.3 Subchronic Studies................................................................................................................. 4-20

4.2.4 Neurotoxicity.......................................................................................................................... 4-24

4.2.5 Developmental/Reproductive Toxicity................................................................................... 4-26

4.2.6 Specialized Developmental Studies........................................................................................ 4-37

4.2.7 Chronic Toxicity..................................................................................................................... 4-41

4.2.8 Carcinogenicity....................................................................................................................... 4-42

4.3 Other Key Data....................................................................................................................... 4-44

4.3.1 Mutagenicity and Genotoxicity .............................................................................................. 4-44

4.3.2 Immunotoxicity ...................................................................................................................... 4-45

4.3.3 Physiological or Mechanistic Studies..................................................................................... 4-49
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4.3.3.1 Noncancer Effects.......................................................................................................... 4-49

4.3.4 Structure-Activity Relationship.............................................................................................. 4-61

4.4 Hazard Characterization ......................................................................................................... 4-61

4.4.1 Synthesis and Evaluation of Major Noncancer Effects.......................................................... 4-62

4.4.2 Synthesis and Evaluation of Carcinogenic Effects................................................................. 4-68

4.4.3 Mode of Action and Implications in Cancer Assessment....................................................... 4-69

4.4.4 Weight of Evidence Evaluation for Carcinogenicity.............................................................. 4-70

4.4.5 Potentially Sensitive Populations ........................................................................................... 4-70

5.0 DOSE-RESPONSE ASSESSMENT............................................................................................... 5-1

5.1 Dose-Response for Noncancer Effects..................................................................................... 5-1

5.1.1 RfD Determination ................................................................................................................... 5-1

5.1.1.1 Benchmark Dose Approach ............................................................................................. 5-7

5.1.1.2 Pharmacokinetic Model Approach ................................................................................ 5-11

5.1.1.3 RfD Quantitation............................................................................................................ 5-21

5.1.2 RfC Determination ................................................................................................................. 5-27

5.2 Dose-Response for Cancer Effects......................................................................................... 5-27

6.0 REFERENCES................................................................................................................................ 6-1

APPENDIX A: Summary of Data ................................................................................................................ 1

APPENDIX B............................................................................................................................................... 1
Perfluorooctane sulfonate (PFOS) – February 2014 viii

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LIST OF TABLES

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

TABLE 3-1. Percent (%) Binding of PFOS in Rat, Monkey and Human Plasmaa

................................... 3-3

TABLE 3-2. Average PFOS Level (μg/mL or ppm) in Serum of Monkeysa ........................................... 3-6

TABLE 3-3. PFOS Levels in the Serum and Liver of Ratsa

..................................................................... 3-7

TABLE 3-4. Mean (± SD) daily PFOS Consumption and Tissue Residue Levels in Rats Treated for 28 

Daysa ................................................................................................................................................. 3-8

TABLE 3-5. Concentrations of PFOS in Male Rats’ Whole Blood (μg/mL) and Various Tissues 

(μg/g) After 28 Daysa

........................................................................................................................ 3-8

TABLE 3-6. Levels of PFOS in serum and bile of rats treated for 5 daysa .............................................. 3-9

TABLE 3-7. PFOS Concentrations (Mean ± S.D.) in Samples From Pregnant Dams and Fetuses (GD 21 

only) in μg/mL (ppm) for Serum and Urine and μg/g for Liver and Fecesa ................................... 3-10

TABLE 3-8. Mean PFOS (± Standard Error) Concentrations in Serum, Liver and Brain Tissue in Dams 

and Offspringa ................................................................................................................................. 3-11

TABLE 3-9. PFOS contents in serum, hippocampus and cortex of offspring (n=6)a

............................. 3-12

TABLE 3-10. Mean PFOS content in serum and lungs of rat offspring (n=6)a

...................................... 3-12

TABLE 3-11. Levels of PFOS (Means ± SE) in Mouse Serum Following Treatment for 10 Daysa

...... 3-13

TABLE 3-12. Mean Concentration of PFOS (±SD) in Various Tissues of Micea

.................................. 3-14

TABLE 3-13. Ratios (means ± S.D.) between the concentrations of 35S-labeled PFOS in various organs 

and blood of mouse dams, fetuses and pups versus the average concentration in maternal blooda

 3-15

TABLE 3-14. Percent Distribution (%) of PFOS in Mice After a 50 mg/kg Subcutaneous Injectiona .. 3-17

TABLE 3-15. Estimation of Toxicokinetic Parameters for PFOSa

......................................................... 3-18

TABLE 3-16. Mean % (± SE) of 14C-K+PFOS in rats after a single dose of 4.2 mg/kga

....................... 3-19

TABLE 3-17. PFOS pharmacokinetic data summary for monkeysa

....................................................... 3-28

TABLE 3-18. PFOS pharmacokinetic data summary for Ratsa

.............................................................. 3-29

TABLE 3-19. PFOS pharmacokinetic data summary for micea ............................................................. 3-30

TABLE 3-20. Summary of Half-life Data .............................................................................................. 3-31

TABLE 4-1. Association of Serum PFOS with Serum Lipids and Uric Acid ......................................... 4-4

TABLE 4-2. Association of serum PFOS with reproductive and developmental outcomes.................... 4-9

TABLE 4-3. Association of serum PFOS with the prevalence of thyroid disease and thyroid hormone 

levels in studies of general and worker populations........................................................................ 4-11

TABLE 4-4. Mean (± SD) Values for Select Parameters in Rats Treated for 4 Weeksa ....................... 4-17

TABLE 4-5. Mean (± SD) Values for Select Parameters in Rats Treated for 28 Daysa

......................... 4-18

TABLE 4-6. Mean (± SD) Values for Select Parameters in Monkeys Treated for 182 Daysa

................ 4-22

TABLE 4-7. Mean (± SD) Values for Select Parameters in Rats Treated for 14 Weeksa ....................... 4-24

TABLE 4-8. Fertility and Litter Observations in Dams Administered 0 to 2.0 mg PFOS/kg/Daya

........ 4-31

TABLE 4-9. Effects Observed in the Mice Administered PFOS from GD 0 to GD 17/18a

.................... 4-36

TABLE 4-10. Incidence of nonneoplastic liver lesions in rats (number affected/total number)............ 4-42

TABLE 4-11. Tumor Incidence (%)a....................................................................................................... 4-43

TABLE 4-12. Genotoxicity of PFOS In Vitro ........................................................................................ 4-44

TABLE 4-13. Genotoxicity of PFOS In Vivo ........................................................................................ 4-44

TABLE 4-14. Thyroid hormone levels in PFOS treated rats.................................................................. 4-51
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TABLE 4-15. Summary of PFAA Transactivation of Mouse and Human PPARα, β/δ and γa............... 4-53

TABLE 5-1. NOAEL/LOAEL and Effects for Longer-term Duration Studies of PFOS ......................... 5-3

TABLE 5-2. NOAEL/LOAEL Data for Short-term Oral Studies of PFOS.............................................. 5-5

TABLE 5-3. Benchmark Dose Modeling for a 5% Increased Risk of Developmental Toxicity in Rats.. 5-7

TABLE 5-4. Benchmark Dose Modeling for a 10% Increased Incidence of Liver Lesions in Rats........ 5-8

TABLE 5-5. Benchmark Dose Modeling for a 10% Increase in Liver Weight...................................... 5-10

TABLE 5-6. Description of prior distributions used. ............................................................................. 5-13

TABLE 5-7. Pharmacokinetic parameters used in the Andersen et al. (2006) model. ........................... 5-15

TABLE 5-8. Predicted final serum concentration and time integrated serum concentration (AUC) for 

different treatments of rat................................................................................................................ 5-16

TABLE 5-9. Predicted final serum concentration and time integrated serum concentration (AUC) for the 

mouse. ............................................................................................................................................. 5-17

TABLE 5-10. Predicted final serum concentration and time integrated serum concentration (AUC) for 

the monkey. ..................................................................................................................................... 5-17

TABLE 5-11. Average Serum concentrations Derived from the AUC and the duration of Dosing....... 5-19

TABLE 5-12. Human Equivalent Doses Derived from the Modeled Animal Average Serum Values.. 5-21

TABLE 5-13. RfD Point of Departure Options from the PFOS Animal Studies ................................... 5-22

TABLE 5-14. The Impact of Quantification Approach on the RfD outcome for the PODs from the 

available NOAELs .......................................................................................................................... 5-23

TABLE 5-15. The Impact of Quantification Approach on the RfD Outcome for the BMDLs from liver 

and developmental endpoints.......................................................................................................... 5-25

TABLE 5-16. The Impact of Quantification Approach on the RfD Outcomes for the HEDs from the 

Pharmacokinetic Model Average Serum Values............................................................................. 5-26

TABLE A.1. PFOS Toxicokinetic Information ........................................................................................... 2

TABLE A.2. Key Studies Used With Effects Related to Serum Values (Condensed Version) .................. 6

TABLE A.3. Summary of Animal Studies with Exposure to PFOS ......................................................... 14
Perfluorooctane sulfonate (PFOS) – February 2014 x 

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LIST OF FIGURES

Figure 2- 1. Chemical Structure of PFOS................................................................................................. 2-1

Figure 3-1. Distribution of radiolabeled PFOS in dams and in fetuses/pups in the liver, lung, kidney and 

brain................................................................................................................................................. 3-16

Figure 3-2. PFOS Contents in Urine, Feces and Overall Excretion in Male Rats Treated for 28 Days . 3-19

Figure 3-3. Schematic for a physiologically-motivated renal resorption pharmacokinetic model. ........ 3-21

Figure 3-4. Structure of model for PFOS in rats and monkeys............................................................... 3-22

Figure 3-5. Structure of the PFOS PBPK model in monkeys and humans............................................. 3-23

Figure 3-6. Structure of the PBPK Model for PFOS in the Adult Sprague-Dawley Rat........................ 3-25

Figure 3-7. Predicted Daily Average Concentration of PFOS in Maternal (black line) and Fetal (gray 

line) Plasma at External Doses to the Dam..................................................................................... 3-26

Figure 4-1. Functional categories of genes modified by PFOS in wild type and null mice.................... 4-57

Figure 4-2. Function distribution and category enrichment analysis of the differential proteins. .......... 4-59

Figure 5-1. BMDS graphic output from selected model runs; data from Thomford, 2002. ..................... 5-9

Figure 5- 2. BMDS graphic output from liver weight model runs; data from Seacat et al., 2002, 2003 5-11
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ABBREVIATIONS AND ACRONYMS

Ach acetylcholine

ACoA Acetyl CoA

ACOX1 peroxisomal acyl-coenzyme A oxidase

ADAF Age-Dependent Agjustment Factor 

AIC Akaike's Information Criterion

ALP alkaline phosphatase

ALT alanine transaminase

ANOVA analysis of variance

AP-1 activation protein-1 

Asp aspartate

AST aspartate aninotransferase

AUC area under the curve 

AWWARF American Water Works Association Research Foundation 

BGS brain growth spurt 

BMD benchmark dose 

BMD benchmark dose – Lower 95th percentile confidence bound 

BMDS benchmark dose software 

BMI body mass index 

BQL below quantifiable limit

BrdU bromodeoxyuridine 

BUN blood urea nitrogen 

bw body weight 

°C Celsius 

C Carbon 

CaMKII calcium/calmodulin-dependent protein kinase II 

CAR constitutive androstane receptor

CAS Chemical Abstracts Service 

CCL Contaminant Candidate List 

CCL 3 Contaminant Candidate List 3 

CD circular dichroism

CFSE 6-carboxyfluorescein succinimidyl ester 

CI confidence interval 

CL clearance

CoA coenzyme A

CREB cAMP response element-binding protein 

CSF Cancer Slope Factor or cerebrospinal fluid

CSM cholestyramine 

Cte acyl CoA thioesterase

CWS community water system 

CYP4A22 cytochrome P-450 4A22 

Cyt c cytochrome c 

d day 

DA dansylamide or dopamine 

DAUDA 11-(5-dimethylaminoapthalenesulphonyl)-undecanoic acid 
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DIO1 type 1 deiodinase 

dL deciliter

DMEM Dulbecco’s Minimal Essential Medium

DMSO dimethyl sulfoxide 

DNA Deoxyribonucleic acid 

DNBC Danish National Birth Cohort 

DP dansyl-L-proline 

DPPC dipalmitoylphosphatidylcholine 

DWI drinking water intake 

EAA excitatory amino acid

EC50 half maximal effective concentration

ECF Electro-Chemical Fluorination

ED equilibrium dialysis

EFSA European Food Safety Authority 

FOB functional observational battery

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

GGT gamma-glutamyl transpeptidase 

GJIC gap junction intercellular communication 

GLP good laboratory practice 

Glu glutamate

Gly glycine 

GS glutamine synthetase 

GSH glutathione 

GSI gonad-somatic index

HDL high density lipoprotein 

HED human equivalent dose 

HL-60 human promyelocytic leukemia cell line 

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

HOMA homeostatic model assessment

HPT hypothalamic-pituitary-thyroid 

HPLC/

ESMSMS High Performance Liquid Chromatography – electrospray tandem mass 

spectrometry

HRL health reference level 

HSA Human Serum Albumin 

HSDB Hazardous Substances Database 

HSI hepatosomatic index 

IC50 half-maximal Inhibiting Concentration

ICa inward calcium currents

ICR imprinting control region

IEF induction equivalency factor 
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IL-1α interleukin

IL-6 interleukin 6

IRR incidence rate ratio

ITC isothermal titration calorimetry

IU international unit 

IV intravenous 

Ka adsorption rate constant 

kg kilogram 

KO knockout 

Koc organic carbon water partitioning coefficient 

Kow octanol-water partition coefficient

Kt affinity constant 

L liter 

LC50 Lethal concentration for 50% (statistical median) of animals

LC-ESIMS/MS liquid chromatography/electrospray ionization with tandem mass spectrometry

LC-MS liquid chromatography – mass spectrometry

LC-MS/MS liquid chromatography – negative electrospray tandem mass spectrometry

LD lactation day

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

LDH lactic dehydrogenase

LDL low density lipoprotein

L-FABP liver fatty acid binding protein

LI labeling index 

LLOQ lower limit of quantification

LOAEL lowest observed adverse effect level 

LOEC lowest observed effect concentration

LOQ Limit of Quantitation

LPS Lipopolysaccharide 

m meter 

MCLG Maximum Contaminant Level Goal 

MDA malondialdehyde 

Mdr2 multidrug resistance protein 2

ME malic enzyme

μg microgram

mg milligram

min minute 

mL milliliter

μm micrometer

MOA mode of action 

mol mole

MRL minimum reporting level 

MRP multidrug resistance-associated protein

MTBE methyl tertiary-butyl ether

NAWQA National Water Quality Assessment 

NDWAC National Drinking Water Advisory Council 

ng nanogram 
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NA not applicable 

ND not detected or not determined 

NHANES The National Health and Nutrition Examination Survey 

NIS sodium iodide symporter 

NK natural killer

NMRI Naval Medical Research Institute

NOAEL no observed adverse effect level 

NOEC no observed effect concentration 

NPDWR National Primary Drinking Water Regulation 

NRC National Research Council

NS no sample 

NSP newborn screening program 

NT not tested

OA octanoic acid

OAT organic anion transporter

OATp organic anion transporting peptide 

OGWDW Office of Ground Water and Drinking Water 

OR odds ratio

p probability 

PB phenobarbital 

PBDE polybrominated diphenyl ether 

PBMC peripheral blood mononuclear cells 

PBPK physiologically-based pharmacokinetic

PBS phosphate buffered saline

PCB polychlorinated biphenyl 

PCNA proliferating cell nuclear antigen

PCoAO palmitoyl CoA oxidase 

PFA perfluoroalkylate

PFC perfluorinated carboxylic acids 

PFAA perfluoroalkyl acid

PFBA perfluorobutyric acid 

PFBS perfluorobutane sulfonate 

PFDA perfluorododecanoic acid

PFHS perfluorohexanesulfonic acid potassium salt 

PFHxS Perfluorohexanesulfonic acid 

PFOA Perfluorooctanoic acid 

PFOC perfluorooctane 

PFOS perfluoroocatane sulfonate 

PFOSA perfluorooctane sulfamide 

PFPA perfluoropropionic acid 

PFTA perfluorotetradecanoic acid

pg picogram 

PI proliferation index

PK pharmacokinetic 

PND postnatal day 

POD point of departure 

POSF perfluorooctanesulfonyl fluoride
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pKa acid dissociation constant

PPAR peroxisome proliferator activated receptor

ppb parts per billion

ppm parts per million 

ppt parts per trillion

mPSC miniature post-synaptic current 

PTU propylthiouracil 

PUFA polyunsaturated fatty acid

PWS public water system

PXR pregnane X receptor 

Q flow in and out of tissues Qfilc median fraction of blood flow to the filtrate

RBC red blood cell 

Reg Det 2 Regulatory Determinations on the Second CCL 

RfC reference concentration 

RfD reference dose 

RIA radio immunoassay

RNA ribonucleic acid

RSC relative source contribution

RSI renal-somatic index

RT-PCR reverse transcription polymerase chain reaction

RXRα retinoid X receptor alpha 

SA serum albumin 

SPC saponin compound 

SD standard deviation

SDWA Safe Drinking Water Act

SIR standardized incidence ratio

SMR standardized mortality ratio

SOD superoxide dismutase

SRBC sheep red blood cells 

STP sewage treatment plant

Syn 1 synapsin 1 

SYP synaptophysin 

T-AOC total antioxidation capability Tmax time of maximum plasma concentration

T3 triiodothyronine 

T4 thyroxine t1/2 chemical half-life T1/2 elimination half-time Tm transporter maximum

TAD target administered dose

TBG thyroxine-binding globulin 

TC total cholesterol

TG triglycerides

TH tyrosine hydroxylase 

TNFα tumor necrosis factor α 

TNP trinitrophenol
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TPO thyroid peroxidase 

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 

UCB umbilical cord blood

UCMR 3 Unregulated Contaminant Monitoring Rule 3

UF uncertainty factor 

UGT1 uridine diphosphoglucuronosyl transferase 

URAT urate transporter

U.S. EPA U.S. Environmental Protection Agency 

USGS U.S. Geological Service 

Vd volume of distribution 

VLDL very low density lipoprotein 

VOC volatile organic compound 

WHAM weighted histogram analysis method 

WT wild type 

ww wet weight

WWTP waste water treatment plant

Wy Wy14,648 
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1.0 EXECUTIVE SUMMARY PFOS

Perfluorooctane sulfonate (PFOS) is a fluorinated organic compound with an eightcarbon 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 fire fighting 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 plasma 

proteins. Both experimental data and pharmacokinetic models show higher level of PFOS in 

fetal serum and brain compared with the maternal compartments. PFOS is not readily eliminated 

from humans as evidenced by the half-life of 5.4 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 resorption from the kidney. In other words after initial removal from 

blood by the kidney, a substantial fraction of what would normally be eliminated in urine is 

returned to the blood. 

Peroxisome proliferation is usually associated with hepatic lesions in the rats, but some 

uncertainties exist as to whether this is true for PFOS and if this is cause for concern in the 

human population. 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 are 

associated with nuclear receptors other than PPARα. 

Epidemiology studies have examined occupational and residential populations at or near 

large-scale PFOS production plants in the United States in an attempt to determine the 

relationship between serum PFOS concentration and various health outcomes suggested by 

standard animal toxicological studies. Exposures were mainly through contaminated drinking 

water and to multiple PFCs. These studies found a positive association with increased PFOS 

serum levels and an increase in total cholesterol, triglycerides, and uric acid in the general 

population. In contrast, occupational studies did not indicate consistent associations between 

PFOS and cholesterol and/or triglycerides in either cross-sectional surveys or in a longitudinal 

analysis. Results are inconclusive or inconsistent for associations between increased serum 

PFOS and affects on thyroid hormones and immunotoxicity. 

In general population studies of effects on reproduction and development, the only 

finding of note was a slight increase in the risk for low birth weight, however, this was not a 

consistent finding across the studies. 

In most animal studies with PFOS, short-term and chronic exposure resulted in an 

increase in liver weight as at least one of the critical effects. Co-occurring effects in these 

studies included decreased cholesterol, lower body weight, liver histopathology, and 

developmental toxicity. In rat and monkey repeat-dosing studies (14 or 26 weeks), increased 

liver weight was accompanied by decreased cholesterol and hepatocellular hypertrophy. As part 

of a chronic bioassay, rats had low dose liver lesions with liver weight affected at higher doses. 

The most severe effect observed in the longer-term studies was decreased pup survival in a one-
Perfluorooctane sulfonate (PFOS) – February 2014 1-2 

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generation rat study at a LOAEL of 0.8 mg/kg/day. The LOAEL for decreased pup body weight 

was 0.4 mg/kg/day in one- and two-generation studies. Developmental toxicity studies at 

slightly higher doses support the concern for low dose-effects on pup survival. In a standard 

developmental neurotoxicity study, male offspring showed increased motor activity and 

decreased habituation on PND 17 following a maternal dose of 1 mg/kg/day. Two studies 

provide evidence for immunological effects in mice. 

U.S. EPA has selected 0.00003 mg/kg/day as the RfD for PFOS based on the consistency 

of the response and with recognition of the use of developmental toxicity and liver weight as the 

most sensitive endpoints for protection against co-occurring adverse effects. This value is the 

outcome for modeled rat serum values for developmental. In the standard developmental 

neurotoxicity study, male offspring showed increased motor activity and decreased habituation 

on PND 17 following a maternal dose of 1 mg/kg/day in the absence of effects on pup body 

weight. The human equivalent dose (HED) used as the basis for the RfD, was calculated from an 

average serum concentration of 10.87 mg/L derived from the NOAEL of 0.3 mg/kg/day for 

developmental neurotoxicity. A pharmacokinetic model was used to predict an area under the 

curve (AUC) for the NOAEL and used to calculate an HEDNOAEL. 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. Comparable values derived from the HED for liver effects in rats and 

developmental effects in mice are slightly higher than the RfD indicating that it will be 

protective. 

Under the EPA 2005 cancer guidelines, the evidence for the carcinogenicity of PFOS is 

considered “suggestive of carcinogenicity,” but not sufficient to assess human carcinogenicity 

potential. 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 true dose-dependent response was not identified. The liver 

tumors also had a questionable dose-response with slight but statistically significant increases only in 

high-dose males and females. The liver tumors most found were adenomas (7/60 and 5/60 in highdose males and females vs. 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 worker-based populations. Thus, the weight of evidence for the carcinogenic potential to humans of 

these tumors was judged to be too limited to support a quantitative cancer assessment. 
Perfluorooctane sulfonate (PFOS) – February 2014 2-1 

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2.0 IDENTITY: CHEMICAL AND PHYSICAL PROPERTIES

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

organic compounds and is part of the group of chemicals called perfluoroalkyl acids (PFAAs). 

The two most widely known PFAAs have an eight-carbon backbone with either a sulfonate 

(PFOS) or carboxylate (PFOA- perfluorooctanoic acid) attached (Lau et al., 2007). PFOSrelated 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 fire fighting foams. PFOS is produced commercially from perfluorooctanesulfonyl 

fluoride (POSF) which is used primarily 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). PFOS can also be formed by the 

degradation of other POSF-derived fluorochemicals. 

 

Due to strong C-F bonds, PFOS is extremely stable and does not biodegrade in the 

environment, making it very persistent. Because of this reason, most PFOS manufactured in the 

United States was discontinued voluntarily by 3M in 2002. PFOS is soluble in fresh water at 

approximately 519 mg/L. The solubility decreases significantly as the salt content of the water 

increases. Because of the surface-active properties of PFOS, it forms three layers in 

octanol/water making an n-octanol/water (Kow) partition co-efficient unable to be determined. 

The potassium salt of PFOS has a low vapor pressure (OECD, 2002). No direct measurement of 

the pKa of the acid has been located; however, the chemical is considered to have a low pKa. 

The chemical structure is provided in Figure 2-1 and the physical properties for PFOS are 

provided in Table 2-1. 

Figure 2- 1. Chemical Structure of PFOS
Perfluorooctane sulfonate (PFOS) – February 2014 2-2 

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TABLE 2-1. Chemical and Physical Properties of PFOS

Property Information

Chemical Abstracts Registry (CAS) No. 2795-39-3*

EPA Pesticide Chemical Code

Chemical Formula C8F17O3S

Molecular Weight 500.13

Color/Physical State White powder

Boiling Point 133°C @ 0.8 kPa

Melting Point ≥ 400°C

Density

Vapor Pressure: 3.31 x 10-4 Pa @ 20°C

Henry’s Law Constant

Kow Can not be measured**

Koc

Solubility in Water 519 mg/L in fresh water @ 25°C

12.4 mg/L in salt water @ 22-23°C 

Sources: HSDB, 2009; OECD, 2002

*The CAS No. is for the potassium salt of PFOS which is the anion most commonly used in animal testing

**Because of the surface-active properties of PFOS, it forms three layers in octanol/water making this not measurable
Perfluorooctane sulfonate (PFOS) – February 2014 3-1 

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3.0 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 PFC, PFOA, transport families appear 

to play role in absorption, distribution, and excretion and include organic anion transporters 

(OATs), organic anion transporting peptides (OATps), multidrug resistance-associated proteins 

(MRPs) and urate transporters (URAT). The transporters play a critical role in gastrointestinal 

absorption, uptake by the tissues, and excretion via the kidney. Work is currently in progress to 

determine if these same transporters are involved in PFOS toxicokinetics and preliminary data 

appear to indicate that they are. Some preliminary inhibition studies suggest that PFOS has a 

similar chain length dependent renal excretion and liver accumulation pattern as PFOA, and 

would involve these same transporters. 

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

blood and liver. While PFOS can be a formed as a metabolite from other perfluocompounds, 

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

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

transcription of mitochondrial and peroxisomal lipid metabolism enzymes, sterol, and bile acid 

biosynthesis and retinol metabolism genes. However, based on transcriptional activation of 

many genes in PPARα-null mice, the effects of PFAAs involve more than activation of PPAR

(Andersen et al., 2008). 

 

 A summary of toxicokinetic data are provided in Appendix A, Table A.1 and Table A.2. 

3.1 Absorption

Absorption data are available for oral exposure in rats. While there are no absorption 

studies available for humans that quantify the amounts absorbed relative to dose, extensive data 

are available demonstrating the presence of PFOS in the serum. These data were reported in 

Section 5.0 Biomonitoring Data. 

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 probably achieved with transporters rather than 

simple diffusion. 

3.1.1 Oral Exposure 

Absorption in Animals 

Rats

 Following ingestion, PFOS is well absorbed. Three male rats were administered a single 

dose of 4.2 mg/kg of PFOS-14C in solution; 3.45% of the total dose was found in the digestive 

tract. The mean fecal excretion was 1.55% of the dose at 24 hours and 3.24% at 48 hours. At 24 

hours, the mean sum of total carbon-14 in feces and digestive tract plus contents was 5% of the 
Perfluorooctane sulfonate (PFOS) – February 2014 3-2 

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dose. Some of this 5% likely represented systemically absorbed carbon-14 present either in the 

digestive tract tissues or in the digestive tract contents as a result of excretion. The data from the 

48 hour post dose group of rats were consistent with the 24 hour data. Thus, at least 95% of the 

PFOS14C dose was absorbed from solution after administration to non-fasted rats (Chang et al., 

2012). 

3.1.2 Inhalation Exposure

An acute LC50 study in rats indicated that PFOS absorption occurs by inhalation 

exposure; however, pharmacokinetic data were not included (Rusch et al., 1979). 

3.1.3 Dermal Exposure

No data are available on dermal absorption of PFOS. 

3.2 Distribution 

 It has been suggested that PFOS is distributed within the body by non-covalently binding 

to a plasma protein, most commonly, albumin. Binding studies are provided to help support this 

hypothesis. Distribution data are provided only for rats following oral exposure. Indirect 

distribution data are provided from analysis of PFOS in tissue and blood samples from studies 

conducted in rats, monkeys and humans. 

 In humans, PFOS has been found to distribute mostly to the liver and blood, but has also 

been identified in umbilical cord blood and breast milk. In humans, the ratio of PFOS identified 

in the serum and liver tissue are similar, while in animals the amount found in the liver is higher 

than that in the serum. In a study by Cui et al. (2009) bioaccumulation of PFOS was liver > 

heart > kidney > whole blood > lung > testicle, brain and spleen in rats administered 5 or 20 

mg/kg/day. The highest level of PFOS was found in the liver of the rats exposed to 20 

mg/kg/day and was 648 ± 17 μg/g. 

Binding Studies

The in vitro protein binding of PFOS in rat, monkey and human plasma at concentrations 

of 1-500 ppm PFOS was investigated (Kerstner-Wood et al., 2003). The PFOS bound to plasma 

protein in all three species at all concentrations with no sign of saturation (Table 3-1). When 

incubated with human plasma protein, 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%). 

 
Perfluorooctane sulfonate (PFOS) – February 2014 3-3 

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TABLE 3-1. Percent (%) Binding of PFOS in Rat, Monkey and Human Plasmaa

PFOS concentration (ppm) Rat Monkey Human

1 ~100b ~100b 99.4

10 99.8 99.9 99.9

100 99.7 99.9 99.9

250 99.5 99.9 99.9

500 99.0 99.9 99.9 a Data from Kerstner-Wood et al., 2003 b % binding values reported as ~100 reflect a nonquantifiable amount of test article in the plasma water below quantifiable limit 

(BQL) < 6.25 ng/mL

Zhang et al. (2009) used equilibrium dialysis, fluorophotometry, isothermal titration 

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

serum albumin (SA) 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 decrease 

in concentration of PFOS in the dialysate. During dialysis, the PFOS concentration decreased 

reflecting its binding to the biopolymer within the dialysis bag. Based on the data, the SA 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 decreases in pH that would 

promote protein and DNA denaturation. 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 SA and PFOS were the results of 

surface electrostatic interactions between the sulfonate functional group and the positively 

charged side chains of lysine and argenine. Hydrogen binding interactions between the negative 

dipoles (fluorine) of the PFOS carbon-fluorine bonds could also play a role in the non-covalent 

bonding of PFOS with SA. Intrinsic fluorescence analysis of tryptophan residues in SA 

suggested a potential interaction of PFOS with tryptophan, an amino acid likely to be found in a 

hydrophobic portion of SA. 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 (SA) 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 the conformation of SA could change its 

transporting activity. Circular dichroism (CD) spectrometry was used to determine if PFOS 

changed the conformation of the SA 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 function as a result of the conformational change. 

Accordingly, the authors investigated the effect of PFOS on the ability of serum albumin to 

transport 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%. 

 

 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. A binding constant of 2.2 x 104 M-1 and a binding ratio 

of PFOS to human albumin of 14 were calculated. Human serum albumin also has two high-
Perfluorooctane sulfonate (PFOS) – February 2014 3-4 

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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. These two probes 

emit negligible fluorescence, but 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 mM), DA emission increased as the PFOS concentration increased 

until it was at 140% the original intensity. At the higher PFOS concentrations (0.7 to 4 mM), 

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 the Site II, PFOS caused a fluorescence reduction that was quick at first but then became 

more gradual making the possibility that PFOS was binding to this 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 binding sites were determined between PFOS and human 

serum albumin (HSA) 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 weighted histogram analysis method (WHAM)-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 

kcal/mol) was located near the tip of the Trp 214 binding site and the maximum number of 

ligands that could bind to HSA for PFOS was 11. The most populated albumin binding site for 

PFOS was dominated by van der Waals interactions. The author indicated that the number of 

molecules adsorbed on HSA for PFOA was 9, compared to the 11 for PFOS, which may explain 

why PFOS has a higher bioaccumulation than PFOA.

 Weiss et al. (2009) screened the binding of several perfluorinated compounds, including 

PFOS, to the thyroid hormone transport protein transthyretin (TTR) in a radioligand-binding 

assay to determine if the compounds can compete with thyroxine (T4), the natural ligand of TTR. 

Human TTR was incubated with 125I-labeled T4, unlabeled T4, and 10-10,000 nM 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 nM. The authors concluded 

that binding affinity for TTR did occur in perfluorinated compounds with peak binding in 

compounds having at least an eight carbon length chain, such as PFOS. 

 

Luebker et al. (2002) investigated the possibility that PFOS interferes with the binding 

affinity of liver-fatty acid binding protein (L-FABP) which is an intracellular lipid-carrier 

protein. 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 (IC50) was determined. PFOS demonstrated 

inhibition of L-FABP in competitive binding assays; with 10 μM PFOS added, 69% of specific 

DAUDA-L-FABP binding was inhibited with the calculated IC50 being 4.9 μM. 
Perfluorooctane sulfonate (PFOS) – February 2014 3-5 

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3.2.1 Oral Exposure

Distribution in Humans

No studies are available in humans on administration of a controlled dose and PFOS 

distribution. Olsen et al. (2003), however, sampled both liver and serum from cadavers for 

PFOS. Both samples contained PFOS with good correlation between the samples from the same 

subject. There was no difference in the PFOS concentrations identified in males and females or 

between age groups. 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) also identified PFOS in postmortem liver samples 

(n=12; 6 males and 6 females 27-79 years old) and in breast milk samples from healthy women 

(n=10; females 30-39 years old) in Catalonia, Spain. The human samples indicate low levels in 

the milk and good correlation between serum and hepatic levels. 

Stein et al. (2012) compared perfluoroalkyl compound levels in maternal serum and 

amniotic fluid. Concentrations of eight compounds were measured in paired samples from 28 

women in their second trimester. PFOS (3.6-28.7 ng/mL) and three other compounds were 

detected in all serum samples and PFOS was detected in nine amniotic fluid samples (0.2-1.8 

ng/mL). The Spearman correlation coefficient was 0.76 for PFOS (p = 0.01) and the median 

ratio of maternal serum:amniotic fluid concentration was 25.5:1. Based on simple regression, 

PFOS was rarely detected in amniotic fluid until the serum concentration reached at least 5.5 

ng/mL. 

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

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

median concentration of PFOS in the serum was 18.4 ng/mL (0.018 ppm), compared to the 

concentration in the CSF which was 0.10 ng/mL (0.0001 ppm). The CSF to serum ratio was 9.1 

x 10-3. The levels identified indicate that PFOS does not easily cross into the adult blood-brain 

barrier.

 

Distribution in Animals

Monkey 

Seacat et al. (2002; further described under Section 4.2.3) 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) in a good laboratory practice (GLP) study, followed by a 52-week 

recovery period. 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 dosed groups. The average percent of cumulative dose of PFOS in 

the liver ranged from 4.4 to 8.7% without any correlation to dose group or gender. The 

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

provided in Table 3-2. 
Perfluorooctane sulfonate (PFOS) – February 2014 3-6 

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

Time

(weeks)

Group 1

0.0 mg/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 a

Data from p. 304 in OECD, 2002.

LOQ = limit of quantification (value not stated)

Rat

 

In Chang et al. (2012), the three male rats administered the single dose of 4.2 mg/kg of 

PFOS14C were found to have approximately 86% of the radioactivity in the carcass at 24 and 48 

hours, indicating little had been excreted. Eighty nine days later, male rats had the following 

mean tissue C-14 concentrations: liver- 20.6 μg/g; plasma- 2.2 μg/g; kidney- 1.1 μg/g; and lung1.1 μg/g (Chang et al., 2012). Other tissues such as muscle, bone marrow, skin and spleen had 

concentrations ranging from 0.2 to 0.6 μg/g. Differences were observed in subcutaneous fat (0.2 

μg/g) and abdominal fat (≤ 0.08 μg/g). Little radiolabeled material was found in the eye and 

none was found in the brain. Liver and plasma contained 25.21% and 2.81% of the dose 

administered. 

 A combined chronic toxicity/carcinogenicity GLP study was performed in compliance 

with Good Laboratory Practice (GLP) in 40-70 male and female Crl:CD (SD)IGS BR rats 

administered 0, 0.5, 2, 5 or 20 ppm of PFOS in the diet for 104 weeks (Thomford, 2002). 

Exposure concentrations were equivalent to 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 death. 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 4.2.6 Chronic Toxicity. Levels of PFOS identified in the 

liver and serum are included in Table 3-3. 
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TABLE 3-3. PFOS Levels in the Serum and Liver of Ratsa

Timepoint

(weeks)

0 ppm 0.5 ppm 

(0.018-0.023

mg/k/day)

2 ppm

(0.072-0.099

mg/kg/day)

5 ppm

(0.184-0.247

mg/kg/day)

20 ppm

(0.765-1.1

mg/kg/day)

M F M F M F M F M F

Serum PFOS levels (ppm)

0 < LOQ* 0.0259 0.0907 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 2.42b 9.51b

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 3.12b 12.9b

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

b 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 pg/mL or ** 0.0457 pg/mL

 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 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). 

 In two consecutive 28-day studies, fifteen Sprague-Dawley rats/sex/group were 

administered 0, 20, 50 or 100 mg PFOS/kg diet (Curran et al., 2008). Tissues were also analyzed 

for PFOS residue by liquid chromatography negative electrospray tandem mass spectrometry 

(LC-MS/MS). Further discussion of the study is in Section 4.2.2 Short-term studies. 

Distribution of PFOS is provided in Table 3-4. 
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TABLE 3-4. Mean (± SD) daily PFOS Consumption and Tissue Residue Levels in Rats 

Treated for 28 Daysa 

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/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

a Data from Table 1 on p. 1531 in Curran et al., 2008

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 3-5. The 

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

exposure. 

TABLE 3-5. Concentrations of PFOS in Male Rats’ Whole Blood (μg/mL) and Various 

Tissues (μg/g) After 28 Daysa 

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 a Data from Table 1 in Cui et al., 2009.

ND = not detected 

Yu et al. (2011) administered the following doses to approximately six female Wistar 

rats/group are part of a study of PFOS on the thyroid: 

1) vehicle (0.5% Tween 20), 

2) PFOS at 0.2, 1.0 or 3.0 mg/kg, 

3) propylthiouracil (PTU) at 10 mg/kg or 
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4) PTU at 10 mg/kg and PFOS at 3.0 mg/kg once daily by gavage for 5 consecutive days. 

Blood, bile and liver tissue were collected 24 hours after the last dose. The serum was used to 

determine the level of PFOS as well as T4 (TT4) and T3 (TT3). PFOS levels in the serum as 

well as the bile are provided in Table 3-6. The data demonstrate distribution to serum and bile 

with a direct relationship to dose.

TABLE 3-6. Levels of PFOS in serum and bile of rats treated for 5 daysa

PFOS (mg/kg bw) Serum PFOS (mg/L) Bile PFOS (mg/L)

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 a Data from Table 2 in Yu et al. 2011.

LOQ = limit of quantification, 0.5 μg/L

Rat- Distribution in Reproductive/Developmental Studies

Two studies administered PFOS up to 3.2 mg/kg/day orally to Sprague-Dawley rats 

during cohabitation and either confirmed day of pregnancy or gestation day (GD) 14 or 20 (3M 

Environmental Laboratory, 2001a and 2001b). Serum, urine, liver and feces were collected. The 

studies showed that liver samples from adults and fetuses contained higher amounts of PFOS 

when compared to the serum. 

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

exposed dams and to investigate the biochemical and pharmacokinetic parameters, 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 

gestation day (GD) 14 or 20 (Luebker et al., 2005a). Eight rats from each group were randomly 

chosen and sacrificed on GD 15. Caesarean sections (C-section) were also performed. 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. Liver 

and blood samples were also obtained from the fetuses on GD 21 and pooled by litter. 

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. Compared to 

the dams, the levels of PFOS in the fetuses were similar in the serum, but much lower in the 

liver. This same study also performed a dose response study that was conducted in a similar 

manner but obtained liver and serum samples from pups on lactation day 5. In this sampling, 

serum PFOS levels were similar between the dam and offspring but the liver values were now 

higher in the neonates. The concentrations found in the pregnant dams and in the fetuses are 

provided in Table 3-7 below. 
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TABLE 3-7. PFOS Concentrations (Mean ± S.D.) in Samples From Pregnant Dams and 

Fetuses (GD 21 only) in μg/mL (ppm) for Serum and Urine and μg/g for Liver and Fecesa 

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 - a Data from Luebker et al., 2005a

- = no sample obtained

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 gestation day (GD) 0 through postnatal day (PND) 

20 (Butenhoff et al., 2009). An additional 10 mated females were used as satellite rats to each of 

the four groups and used to collect additional blood and tissue samples. Further details from this 

study are provided in Section 4.2.4. 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 3-8. 

From GD 20 to PND 21, 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). From 

GD 20 to PND 72, PFOS concentrations correlated well between fetal and pup serum, liver and 

brain and the daily litter-matched maternal PFOS levels. Comparing results from dams and 

fetuses/pups, liver PFOS concentrations were always higher for the dams than the respective 

serum levels and the brain PFOS concentrations in the dams were always lower than that of 

corresponding serum levels. 

Based on the maternal and offspring data on GD 20, placental transfer of PFOS from rat 

dams to developing fetuses does occur. Serum values were approximately 1-2 times greater in 

the fetuses than in the dams at GD 20. The fetal liver PFOS concentration 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 less during PND 4 and continued to drop through PND 72; however, based on the 
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amounts still present in the pup 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 but decreased significantly by PND 72. Values were 

similar at all time-points between males and females. The level of PFOS in the brain was the 

highest at GD 20 and had decreased by PND 21. 

TABLE 3-8. Mean PFOS (± Standard Error) Concentrations in Serum, Liver and Brain 

Tissue in Dams and Offspringa 

Time Dose

(mg/kg)

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

Dam Offspring Dam Offspring Dam Offspring

GD 20b 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 4b 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

a

Data from Table 2 in Chang et al., 2009

b 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
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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 (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. 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 3-9. 

TABLE 3-9. PFOS contents in serum, hippocampus and cortex of offspring (n=6)a

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*** a

Data from Table 2 in Zeng et al., 2011

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

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

daily by gavage from GD1 to GD21 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 3-10. 

TABLE 3-10. Mean PFOS content in serum and lungs of rat offspring (n=6)a

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** a Data from Table 2 in Chen et al., 2012

ND = not detected

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

Mouse

 In an immunotoxicity study (described in detail under Section 4.3.2. Immunotoxicity), 

four to six C57BL/6 male mice/group were administered diets with 0 to 0.02% PFOS for 10 
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days. Levels in the serum increased as the concentration increased (Qazi et al., 2009a). See 

Table 3-11. 

TABLE 3-11. Levels of PFOS (Means ± SE) in Mouse Serum Following Treatment 

for 10 Daysa 

Dietary dose (% 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 a Data from study report by Qazi et al., 2009a

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: 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 3-12 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 3-12.
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TABLE 3-12. Mean Concentration of PFOS (±SD) in Various Tissues of Micea

Tissues 1 day 3 days 5 days

Dose of 0.013 mg/kg/day (PFOS in tissue reported as 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 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)**# a

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

*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

Mouse- Distribution in Reproductive/Developmental Studies 

 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 gestation day (GD) 16 to C57Bl/6 mouse dams. Distribution 

of PFOS was determined in the dams/fetuses (GD 18 and 20) and pups (PND 1) by using wholebody autoradiography and liquid scintillation counting. Distribution in the dams was similar 

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

than the blood. At all timepoints in the dams, PFOS was most concentrated in the liver and 

lungs. In the fetuses, the highest concentrations of PFOS were found in the kidneys and liver 

and in pups on PND 1, PFOS was mostly concentrated in the lungs/liver. In dams, the 

concentration of PFOS in the liver was approximately 4x and in the lung was approximately 2x 

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

level 2.5x higher than maternal blood and 1.7x lower than maternal liver. In the fetuses on GD 

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

Pups on PND 1 had PFOS levels that were 3x higher in the lungs, compared to maternal blood 

with a heterogeneous distribution. In the kidneys, the highest concentration of PFOS was 

observed in the fetuses on GD 18 (3x higher than maternal levels) but then was similar to the 

dams on GD 20 and PND 1. 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 3-13 and Figure 3-1. 
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TABLE 3-13. Ratios (means ± S.D.) between the concentrations of 35S-labeled PFOS in 

various organs and blood of mouse dams, fetuses and pups versus the average concentration 

in maternal blooda

[

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 a Data from Table 1 in Borg et al. (2010)

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

** Statistically significant (p≤0.001) in comparison to maternal blood 
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 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 GD20/PND1 with corresponding value 

on GD18; 

Figure 3-1. Distribution of radiolabeled PFOS in dams and in fetuses/pups in the liver, 

lung, kidney and brain 

(Figure from Borg et al., 2010)

3.2.2 Inhalation and Dermal Exposure

No data on distribution following inhalation or dermal exposures were identified. 
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3.2.3 Other Routes of Exposure

Mice- Distribution in Reproductive/Developmental Studies

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

post-natal days (PNDs) 7, 14, 21, 28 or 35 (further study details provided in Section 4.2.5 

Developmental/Reproductive Toxicity) at concentrations of 0 or 50 mg/kg 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 3-14. The 

distribution shows that as the PND days increase, more PFOS is identified in the liver, and males 

appear to accumulate slightly more than females. 

TABLE 3-14. Percent Distribution (%) of PFOS in Mice After a 50 mg/kg Subcutaneous 

Injectiona

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** a Data from Table 4 in Liu et al., 2009.

*statistically significant (p< 0.01)

Tissue Transport

As described earlier, Yu et al. (2011) administered PFOS to determine what transporters 

were involved in hepatic uptake and to also determine the effect of transporters on thyroid 

hormones. Approximately six female Wistar rats/group were administered 1) vehicle (0.5% 

Tween 20), 2) PFOS at 0.2, 1.0 or 3.0 mg/kg, 3) propylthiouracil (PTU) at 10 mg/kg or 4) PTU 

at 10 mg/kg and PFOS at 3.0 mg/kg once daily by gavage for 5 consecutive days. Blood, bile 

and liver tissue were collected 24 hours after the last dose. Total mRNA as well as the mRNAs 

for the following hepatic genes were isolated from the liver tissue: OATp1, OATp2, and MRP2. 

Serum levels of PFOS were measured.

Exposure to 3.0 mg/kg of PFOS increased hepatic organic anion transporter OATp2 

mRNA expression (1.43 times of control) and increased MRP2 approximately 1.80 and 1.69 

times that of controls in the 1.0 and 3.0 mg/kg groups, respectively. No effect with treatment 

was observed on OATp1. Studies of the role of transporters in PFOA tissue distribution are 

rather extensive; that is not the case for PFOS. However, to the extent that it is like PFOA, 

import and export tissue transporters are most likely important features controlling tissue 

distribution and impacting pharmacokinetics. 

 

3.3 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 
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by the Kerstner-Wood et al. (2003) data on binding to plasma proteins plus the Zhang et al. 

(2009) and Chen and Guo (2009) data from albumin-binding investigations. 

3.4 Excretion 

Humans

 Harada et al. (2007) obtained serum and bile samples from patients (2 male and 2 female; 

ages 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 biliary resorption rate was 0.97 which could 

contribute to the long-half life in humans. Method of exposure to PFOS was unknown. See 

Table 3-15. 

TABLE 3-15. Estimation of Toxicokinetic Parameters for PFOSa

Bile

Participants Serum levels- ng/mL (ppm) Bile levels- ng/mL (ppm) Bile to serum ratio

Median (n=4) 23.2 (0.023) 27.9 (0.028) 0.60 a Data from Tables 2 and 3 in Harada et al., 2007

Animals

Studies to determine the direct excretion routes are only available for rats. Most 

excretion for PFOS occurs in the urine. 

3.4.1 Oral Exposure

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: G0 = 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°C 

prior to analyzing. Target analytes were 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; a similar trend was observed in the rats administered 20 

mg/kg/day PFOS, but in the third week, mortalities occurred. By study day 24, there were only 

2/10 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 in rats 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 could have been the result of lower feces volume because the rats had 
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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 5 

and 20 mg/kg/day 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. 

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 and ** p< 0.01

Figure 3-2. PFOS Contents in Urine, Feces and Overall Excretion in Male Rats Treated 

for 28 Days

 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, feces and tissues were collected in 24 and 48 hours and are presented below in Table 3-

16. 

TABLE 3-16. Mean % (± SE) of 14C-K+PFOS in rats after a single dose of 4.2 mg/kga

Compartment % 14C of dose recovered

0-24 hr 0-48 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)*

RBC 2.29 ± 0.18 (estimated)* 3.25 ± 0.92 (estimated)*

Total 99.0 116.5 a

Data from Chang et al., 2012

*Mean body weight of 300g was used to estimate the red blood cell (RBC) and plasma volume.
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3.4.2 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 

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 PFCs 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 < 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 PFC 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. 

3.4.3 Dermal Exposure

No data on PFOS excretion following dermal exposures were identified. 

3.4.4 Other Exposure Routes

 At 89 days after a single intravenous (IV) dose of PFOS-14C of 4.2 mg/kg to male rats, 

urinary excretion was 30.2 ± 1.5% of the total C-14 administered. Mean fecal excretion was 

12.6 ± 1.2% (Chang et al., 2012). There was also evidence of enterohepatic circulation of PFOS. 

3.5 Pharmacokinetic Considerations

3.5.1 Physiologically based models

Toxicokinetic models have been published as tools to estimate internal doses for humans, 

monkeys, and rats that can accommodate half-life values that are longer than would be predicted 

based on standard absorption, distribution, metabolism and excretion concepts. 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 possibly account for the unique half-life properties of PFOS across species. The model 
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structure (Figure 3-3; 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. 

Figure 3-3. Schematic for a physiologically-motivated renal resorption pharmacokinetic 

model.

 

 The model was parameterized using the body weight and urine output for cynomolgus 

monkeys (Butenhoff et al., 2002 and 2004) and a cardiac output of 15 L/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 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 slower terminal half-life and more 

rapid approach to steady-state with repeated oral administration. 

 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 

3.4 below). Only one time-dependent 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 and 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 1500 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 
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liver:blood partition coefficient and renal filtration. The author stated that development of a 

human model was feasible. 

Tm = transporter maximum, Kt= affinity constant and Q= flow in and out of tissues

Figure 3-4. Structure of model for PFOS in rats and monkeys

 Loccisano et al. (2011) developed a PFOS PBPK model for monkeys based on the 

Anderson et al. (2006) and Tan et al. (2008) models, and extrapolated it for use in humans 

(Figure 3-5). The model reflects saturable renal absorption of urinary PFOS by the proximal 

tubule of the kidney. This is represented in Figure 3-5 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 which 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.

 
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Tm = transporter maximum, Kt= affinity constant and Q= flow in and out of tissues

Figure 3-5. Structure of the PFOS PBPK model in monkeys and humans

Existing data sets for the cynomolgus monkey were used to develop the monkey model. 

The IV data came from a single dose of 2 mg/kg (Noker and Gorman, 2003) wherein the 

concentrations in plasma and urine were monitored for up to 161 days after dosing. The repeatdose oral data were those 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. 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. 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 3.5.2). No 

measures of PFOS concentration were available for the drinking water at Little Hocking; thus, 

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 ppb. The model results 

can be characterized as good when compared to the reported average serum measurements. The 
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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 more data are needed on the kinetics of renal transporters, 

intrahuman variability, and definitive information on exposures in order to refine the human 

model. 

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 volume of distribution (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 2200 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 70 kg. 

 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 Anderson 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, OH area (see Section 3.5.3). 

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 21.7 to 3.6 ng/kg bw/day. 

Loccisano et al. (2012a) utilized the saturable resorption hypothesis and pharmacokinetic 

data from Chang et al. (2012), 3M (2009; unpublished) and Seacat et al. (2003) for adult 

Sprague-Dawley Rats to develop the model depicted in Figure 3-6. The structure of the model is 

similar to that for the monkey/human model depicted in Figure 3-5 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; personal communication to authors), 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. 
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Figure 3-6. Structure of the PBPK Model for PFOS in the Adult Sprague-Dawley Rat

 

The agreement between the experimental data and the model output was generally 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 2. 

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.

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 GD 0 to 20 were used in model development. Both studies 

used multiple dose levels plus data on serum and selected tissue concentrations (liver, brain) 

from the dams and fetus at one or more time points. The gestational model structure for the 

dams is similar to Figure 3-6. 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 

Cheng 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 
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employed in the Butenhoff et al. (2009), Luebker et al. (2005a,b) and Lau et al. (2003) studies as 

depicted in Figure 3-7. 

Figure 3-7. 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-tissues 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. 

 The data of Luebker et al. (2005a,b) and Kuklenyik et al. (2004) were applied in model 

development. The predicted milk:plasma ratio of 0.1 was in good agreement with the 

experimental value (0.14) from Kuklenyik et al. (2004). The 24-hour AUC was used to evaluate 

model predictions. At the beginning of lactation the levels in pup liver were greater than those 

for the dam; at PND 14 they were equivalent and at PND 20 the levels for the dams were greater 

than those for the pups. PFOS levels in the pup brain remained higher than those for the dams 

throughout gestation and lactation but declined gradually across the duration of lactation. After 

cessation of dosing PFOS levels in the livers of the dams declined gradually. 

 The authors acknowledged the lack of primary experimental data on PFOS transport and 

potential transporters. Similarity to PFOA was assumed and PFOS was transparently described 
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as lacking supporting transporter data. Additional research on PFOS binding to serum proteins 

and liver tissues, its biliary excretion and resorption, plus information on renal resorption 

transporters in dams and pups, is needed to accomplish further refinements to the published 

model (Loccisano et al., 2012b). 

3.5.2 Half-life data

Differences between species were observed when studies determining the half-life (T1/2) 

of PFOS in rats, mice, monkeys, and humans were performed. Gender differences in rats do not 

appear to be as dramatic for PFOS as they are for PFOA (Loccisano et al., 2012a,b). 

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 how the samples were taken and the methods used. 

 More recently, Olsen et al. (2007) obtained samples from twenty-six (24 males and 2 

females) retired fluorochemical production workers from the 3M Company in Decatur, Alabama 

to determine the half-life of PFOS. Periodic serum samples (total of 7-8 samples) were collected 

over a period of 5 years, stored at -80°C and at the end of the study, HPLC-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 to 36 years), the mean age of the participants at 

the initial blood sampling was 61 years (range: 55 to 75 years), and the average number of years 

retired was 2.6 years (range: 0.4 to 11.5 years). The initial arithmetic mean serum concentration 

of PFOS was 799 ng/mL [0.79 ppm] (range: 145 to 3490 ng/mL), and when samples were taken 

at the end of the study, the mean serum concentration was 403 ng/mL [0.40 ppm] (range: 37 to 

1740 ng/mL). Semi-log graphs of concentration versus time for each of the 26 individuals were 

created and individual serum elimination half-lives were determined using first-order

elimination. The arithmetic and geometric mean serum elimination half-lives of PFOS were 5.4 

years (95% CI, 3.9- 6.9) and 4.8 years (95% CI, 4.1-5.4), respectively.

General Population. Data were not found for estimation of the half-life of PFOS in the general 

population. 

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 these NSPs collected 

from infants born between 1997 and 2007 in the state of New York were analyzed for PFOS 

(Spliethoff et al., 2008). The methods used for analysis were validated by using freshly drawn 

blood from healthy adult volunteers. The mean whole blood concentration for PFOS was 0.81 to 

2.41 ng/mL (0.00081 to 0.00241 ppm). The study grouped the blood spots by two different timepoints; those collected from 1999-2000 and from 2003-2004 which corresponded to the intervals 

reported by NHANES. The PFOS concentrations decreased with a mean value of 2.43 ng/mL 

(0.0024 ppm) reported in 1999-2000 and 1.74 ng/mL (0.0017 ppm) in 2003-2004. The study 

authors also used regression slopes for natural log concentration versus years since 2000 to 

calculate the half-life for PFOS. The calculated half-life for PFOS was 4.1 years. 
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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 (Seacat et al., 2002). Serum halflife estimates were obtained from short-term and long-term studies. 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 at 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 from 122-146 days in male 

monkeys and 88-138 days in females. Mean values are shown in Table 3-17. The volume of 

distribution values (Vd) suggest that distribution was predominately extracellular.

TABLE 3-17. PFOS pharmacokinetic data summary for monkeysa

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 a Data from Chang et al., 2012

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 one 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 3-18). 

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 postdosing. 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 must 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.
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In a third study, serum uptake and elimination of PFOS were evaluated at two dose 

levels: 2 mg/kg and 15 mg/kg. The 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. Half-life estimates (Table 3-18) 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 from 35 to 53 days and that for females from 33 to 55 days. 

TABLE 3-18. PFOS pharmacokinetic data summary for Ratsa

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 hrs Oral M 4.2 8.2 ± 1.5 275

SD rats 24 hrs

Oral M 2.2 3.1bc Not determined due 

to study design.

765 b

F 1.9c 521

IV M 8.0c 649

F 5.6b 586 b

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 1228

15 41.2 ± 2.0 666

F 

2 62.3 ± 2.1 66.7 484

15 71.1 ± 

11.3

468

a Data from Chang et al., 2012 and Butenhoff and Chang, 2007 (unpublished)

b

Data reflected a single value derived from one rat only

c

Within limits of the study design and a follow-up duration of only 24 hrs

NA= not available

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 
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of the observation period, the daily urinary and fecal excretion was less than 0.1% of the 

administered dose. Results are shown in Table 3-19. Serum elimination values were similar for 

males and females, independent of dose administered: distribution appeared to be mostly 

extracellular.

TABLE 3-19. PFOS pharmacokinetic data summary for micea

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 a Data from Chang et al., 2012

Table 3-20 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 

half-life in a retired worker population is 5.4 years (Olsen et al., 2007) compared with several 

months in the laboratory animals. 

The animal data summarized in Table 3-20 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 monkeys similar half-life values were found after 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.
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TABLE 3-20. Summary of Half-life Data

Source Human Monkey Rat Mouse Strain

Spliethoff et al. 

2008

4.1 years Infants

3M Co 2000 4-8.67 years Occupational

Olsen et al. 

2007

5.4 years Occupational

Butenhoff and 

Chang, 2007

48.2 days (m)

46.9 days (f)

SD; 28 days 

oral

Chang et al.

2012

39.8 days (m)

66.7 days (f)

SD; single oral 

dose

39.6 days (m)

34.2 days (f)

CD-1; single 

oral dose

132 days (m)

110 days (f)

Cynomolgus; 

single IV dose

Seacat et al. 

2002

200 days (m/f) Cynomolgus; 

oral, 182 days

3.5.3 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. As an integral part of model validation, the parameter for volume of 

distribution of PFOS within the body was calibrated from the available data. 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 for use in a simple, 

single compartment, first-order 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 assumed that 

most PFOS intake is 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. 

Thompson et al. (2010) used a the single compartment, 1st order 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 Anderson et al. (2006). 

The original Anderson 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 
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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 3000 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 exposure 

assessment. Thus, the authors concluded that the lower value of 200 mL/kg was more 

appropriate for use in 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 series of pharmacokinetic studies on rats, mice, and monkeys described above, also 

included volume of distribution calculations (Chang et al., 2012). 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 monkey, female rats, and male and female mice 

were reasonably similar. The reason for some much higher values found in male rats could not 

be explained by the study authors. 

For male and female cynomolgus monkeys, the volume of distribution was 202 and 274 

mL/kg, respectively (Table 3-17), following a single IV dose of 2 mg/kg (Chang et al., 2012). 

Animals in this pharmacokinetic study were evaluated up to 23 weeks after dosing and the 

resulting volumes of distribution are similar to that calibrated from human data described above 

for Thompson et al. (2010). 

Volume of distribution findings by Chang et al. (2012) for rats are shown above in Table 

3-18. 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, with the exception of one value, than that of 

females or other species including humans. As noted, 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. 

Data for mice (Chang et al., 2012) are shown in Table 3-20. For males and females the 

volume of distribution was 263-290 mL/kg and 258-261 mL/kg, respectively, following a single 

oral dose. 
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Pharmacokinetic models based on animal data described previously in this chapter 

(Anderson et al., 2006; Tan et al., 2008) generally optimized the value for volume of distribution 

based on model output. The original Anderson 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.
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4.0 HAZARD IDENTIFICATION 

4.1 Human Effects

Studies on PFOS exposures are available from both occupational populations and the 

general population. Several epidemiologic studies have recently reported associations with 

PFOS and cholesterol, birth weight changes and various thyroid parameters. These studies are 

discussed below.

4.1.1 Short-Term Studies and Case Reports 

Intentional and Accidental Acute Ingestion

No studies of acute accidental or intentional human exposures to PFOS by ingestion were 

identified. 

 

Acute and Short-Term Inhalation Exposure

No studies of acute and short-term inhalation human exposures to PFOS were identified. 

4.1.2 Long-Term and Epidemiological Studies 

Several long-term epidemiological studies have been conducted to investigate possible 

associations between PFOS exposures and various health outcomes. Occupational studies 

conducted at the 3M Decatur, Alabama plant that produced PFOS are available as well as studies 

from the C8 Health Project in Ohio and West Virginia. These studies and those on other 

population groupings are described below. The studies that examined systemic endpoints of 

toxicity other than cancer are described in Section 4.1.2.1 below where they are subcategorized 

according to the endpoints examined.

4.1.2.1 Noncancer Systemic Toxicity Studies

Cholesterol, Lipid Homeostasis, Uric Acid, and Biochemical Toxicity Studies

Occupational Populations 

Cross-sectional as well as a longitudinal analysis 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., 1999; Olsen et. al, 2001b, 2001c). Male volunteers working at the Decatur plant in 

1995, 1997 and 2000 and male and female Antwerp volunteers from a 2000 medical surveillance 

study underwent clinical chemistry tests which evaluated hepatic enzyme activity, renal function 

tests, thyroid activity and cholesterol levels. There were no consistent associations between 

worker PFOS levels and any of the clinical chemistry tests in the 1995 and 1997 analyses. The 

analysis of the data from the 2000 surveillance period indicated a positive association between 

PFOS and T3, cholesterol, triglycerides and the activity of several hepatic enzymes among male 

employees at the Decatur plant. However, there were many limitations to combining and 

comparing the data from the various surveillance periods. 
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 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 lipid results in employees of the Antwerp and Decatur facilities (Olsen, et al., 2001c). The 

medical surveillance data from 1995, 1997, and 2000 were analyzed using multivariable 

regression. The three subcohorts included those who participated in two or more medical exams 

between 1995 and 2000. 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 

high density lipoprotein (HDL), alkaline phosphatase, gamma-glutamyl transpeptidase (GGT), 

aspartate aminotransferase (AST), or alanine transaminase (ALT) activities, total bilirubin, or 

direct bilirubin. 

 

General Population 

Several studies on general population exposures to PFOS and other perfluorochemicals 

have been generated by the C8 Health Project. The C8 Health Project was conducted in 2005 to 

2006 to collect health data from approximately 69,000 residents in Ohio and West Virginia 

living in the vicinity of a chemical plant producing PFOA. Public drinking water was 

contaminated in six water districts surrounding the plant (≥0.05 ng/mL of PFOA). The levels of 

PFOS in this population were similar to those reported in the general U.S. population (median 

20.2 ng/mL). 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. 

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 22.4 ng/mL (0.022 ppm), range (0.25-759.2 ng/mL). Lipid outcomes 

(total cholesterol, high density lipoprotein [HDL] cholesterol, low density lipoprotein [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. The predicted increase in cholesterol from lowest to highest PFOS decile (0 to 60 ng/mL) 

was 11-12 mg/dL. Logistic regression analyses indicate statistically significant increases in 

cholesterol (≥ 240 mg/dL) with increasing PFOS serum levels. Cholesterol levels ≥ 240 mg/dL 

are characterized as high, medical intercession is recommended. The odds ratios 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. In addition, the 

mechanism by which perfluorinated compounds impact serum cholesterol is not yet understood. 

 

Steenland et al. (2010) reported on another analysis of the C8 Health Project participants 

≥ 20 years old (n= 54,951) 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. 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 (10-50 ng/mL). 

Hyperuricemia (> 6.0 mg/dL for women and > 6.8 mg/dL for men) risk by quintiles increased 
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slightly with PFOS levels (OR 1.00, 1.02, 1.11, 1.19 and 1.26). The serum of C8 study 

participants included several PFCs; PFOA appeared to have a greater influence on uric acid 

trends than PFOS in the models employed by Steenland et al. (2010). 

 Modest associations between PFOS and some lipids existed in children involved in the 

C8 Health Project (Frisbee et al. 2010). The report stated that 12,476 community children ≤ 18 

years old that lived in the C8 Health Project communities were tested for total cholesterol, LDLs, 

HDLs and fasting triglycerides. The mean level of PFOS was 22.7 ng/mL (0.023 ppm). PFOS 

was significantly associated with increased total cholesterol, HDL-cholesterol and LDLcholesterol in a linear regression analysis after adjustment for co-variables. A statistically 

significant increased risk of abnormal total cholesterol and LDL-cholesterol was also observed 

between the first and fifth quintiles of PFOS serum concentrations. No trends were observed 

with triglycerides. As with the other C8 project data, the authors acknowledge that the crosssectional nature of this study limits causal inference.

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 various confounders. The ln-transformed values of ALT were 

significantly associated with ln-transformed PFOS levels and showed a steady increase in fitted 

levels of ALT per decile of PFOS, leveling off after approximately 30 ng 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 crosssectional 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. 

 Two studies used data from the U.S. National Health and Nutrition Examination Survey 

(NHANES) to examine the relationship between perfluorinated chemicals, serum lipid 

measurements and related conditions. One study analyzed NHANES 2003-2004 data and 

examined cholesterol levels, obesity, and insulin resistance in relation to PFOS (and other PFCs) 

(Nelson et al. 2010). The other study analyzed NHANES data from 1999-2000 and 2003-2004 

in adolescents and adults and glucose homeostasis and metabolic syndrome (Lin et al. 2009). 

 Nelson et al. (2010) analyzed 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 was not measured directly, but was estimated by the Friedewald 

formula as recommended by CDC. Homeostatic model assessment (HOMA) was used to assess 

insulin resistance (calculated from fasting insulin and fasting glucose measurements collected in 

NHANES). Body mass index (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 women or insulin use. After exclusion criteria, ~ 860 

participants were included in the cholesterol analyses. The mean PFOS serum concentration for 

participants 20-80 years old was 25.3 μg/L (range, 1.4 to 392 μg/L). 

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 
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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. 

 Lin et al. (2009) analyzed the data on perfluorinated chemicals in NHANES 1999-2000 

and 2003-2004 and glucose homeostasis and metabolic syndrome. The authors reported an 

association between PFOS and metabolic syndrome; however, it was not reported how PFOS and 

other perfluorinated chemicals in the analysis were combined for the NHANES sample years. 

 

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 women). 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 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 women and men was 18.6 μg/L. 

Table 4-1 provides a summary of the results from the studies that examined the 

relationship of serum PFOS with serum lipids and uric acid. The most consistent findings are 

those for total cholesterol.

TABLE 4-1. Association of Serum PFOS with Serum Lipids and Uric Acid

Study TC VLDL LDL HDL NonHDLTG UA

Occupational Population

Olsen et al., 2001c ↔ NM NM ↔ NM ↔ NM

General Population

Steenland et al., 2009; 

2010

↑ NM ↑ ↔ NM ↑ ↑

Frisbee et al., 2010 

(children)

↑ NM ↑ ↑ NM ↔ NM

Château-Degat et al., 

2010

↔ NM ↔ ↑ NM ↔ NM

Nelson et al., 2010 ↑ NM ↔ ↔ ↑ NM NM

↑= 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 monitored 

 
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4.1.2.2 Reproductive Hormones and Reproductive/Developmental Studies

Olsen et al. (2009) recently reviewed the epidemiological literature and identified six 

studies examining potential associations between PFOS and human birth outcomes. Research 

has focused on birth weight and other measures of fetal growth. Overall, in both the general and 

occupational populations, inconsistent associations were identified between PFOS 

exposure/levels and fetal birth weight or gestational age.

An occupational cohort study by Grice et al. (2007) examined the potential association 

between PFOS exposure and 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 women participated 

and reported 439 births of which there were 421 live births, 14 stillbirths and 4 no data. Birth 

weight was adjusted for maternal age, smoking status and gravidity. No associations were 

observed between PFOS exposure and pregnancy outcomes even when birth weight was adjusted 

for maternal age, smoking status and gravidity. 

A series of longitudinal, population-based studies was conducted in a subset of women 

aged 25 to 35 enrolled in the Danish National Birth Cohort (DNBC) from March 1996 to 

November 2002 (Fei et al., 2007, 2008a, 2008b, 2009, 2010a). A random sample of 1400 

women was selected to investigate the association between blood levels of perfluorinated 

chemicals and adverse reproductive and developmental outcomes in the women and their 

children. Study data were collected by telephone interviews at 12 and 30 weeks of gestation and 

approximately 6 and 18 months after birth. 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 from the cord blood in the infant just after birth. Only blood 

results from the 1400 women in the first trimester were reported. Mean plasma PFOS levels by 

age groups were: < 25 years- 38.6 ng/mL (0.039 ppm); 25-29 years- 36.8 ng/mL (0.037 ppm); 

30-34 years- 33.9 ng/mL (0.034 ppm) and ≥ 35 years- 33.0 ng/mL (0.033 ppm). Potential 

confounders included: maternal age, maternal occupation and educational status, parity, prepregnancy 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/day, and home density (the 

total number of rooms divided by the total number of people in the household). 

 

Data from the DNBC were used to investigate the association between plasma levels of 

PFOS in pregnant women, length of gestation, and the infant’s birth weight (Fei et al., 2007). 

The average PFOS levels in maternal plasma were 35.3 ng/mL (range, 6.4-106.7 ng/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 categorical quartiles of PFOS. Elevated risk estimates were found for PFOS 

levels and preterm birth, but the odds ratio was significant only for the third quartile of exposure. 

No significant association was found between PFOS levels and length of gestation, low birth 

weight, or small for gestational age. 
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When Fei et al. (2008a) investigated the association between PFOS levels in pregnant 

women and their newborns and placental weight, birth length, and head and abdominal 

circumference, he found 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 postterm and preterm infants and 

with ponderal index in multiparous women and positive association with ponderal index in 

nulliparous women. These associations were not statistically significant.

 In the Fei et al. (2008b) report examining the association between plasma levels of PFOS 

in pregnant women and the motor and mental development in their children, regression analysis 

did not indicate any significant association between PFOS and Apgar score after adjustment for 

potential confounders (odds ratio [OR], 1.20; 95% confidence interval [CI], 0.57-2.25). The 

developmental measures examined in the infants included Apgar score of child at birth and 

questionnaire responses about child development milestones at 6 and 18 months. Data from the 

6 month interview did not show any association between PFOS levels and motor or mental 

development. In children at 18 months, mothers with higher PFOS levels were slightly more 

likely to report that their babies started sitting without support at a later age and “did not use 

word-like sounds to tell what he/she wants.”

 

Fei et al. (2009) used the same population of pregnant women to determine if there was 

any association with PFOS levels and fecundity indicated by the time to pregnancy (TTP). In 

women who had planned pregnancies (n=1240), there was a longer time to pregnancy (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 quartiles). The proportion 

of women with infertility (TTP>12 months) was higher in the upper three quartiles of PFOS 

versus the lowest quartile. These trends were significant. Women 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. 

 Fei et al. (2010a) reported on the effects of PFOS on the length of breastfeeding. Self 

reported data on the duration of breastfeeding was collected during the telephone interviews at 6 

and 18 months after birth of the child. Higher levels of PFOS were significantly associated with 

a shorter duration of breastfeeding. In multiparous women, the adjusted OR for weaning before 

6 months is 1.20 [95% CI, 1.06-1.37]) for each 10 ng/mL increase in PFOS concentration in the 

maternal blood and the increase was dose-related. A statistically significant positive trend was 

observed for women having their first child, but no consistent association was found across 

increasing blood levels of PFOS. The authors speculate that the observed associations may be 

non-causally related to previous length of breastfeeding or to reduction of PFOS through 

lactation.

 

 Monroy et al. (2008) found no association between the maternal serum levels of PFOS 

and the birth weight of the neonates in 101 pregnant women enrolled in a large cohort study, 

Family Study, conducted at McMaster University Medical Center in Canada. PFOS was 

measured in maternal serum at mid-pregnancy and delivery in 101 healthy pregnant women in 

Ontario, Canada and in umbilical cord blood (UCB) from 105 babies. PFOS was detected in 

100% of samples with mean levels of 18.3, 16.2, and 7.2 ng/L in maternal serum at 24-28 weeks, 

maternal serum at delivery, and in UCB respectively. The concentration of PFOS in maternal 
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serum was significantly higher than in UCB. No significant association between levels of PFOS 

in the maternal serum or UCB and the birth weight of the neonates was found. Maternal PFOS 

levels were also not associated with maternal body mass index, gestational length, or gender.

 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 women and their infants (Washino et al., 2009). Women enrolled were at 23-35 weeks 

of gestation with a mean age of 30.5 years. Subjects reported on dietary habits, smoking status, 

alcohol intake, caffeine intake, household income and educational level. At the time of the 

questionnaire, a blood sample was obtained. Both PFOS and PFOA were analyzed in the blood 

using liquid chromatography-tandem mass spectrometry coupled with solid-phase extraction. 

The mean concentration in the women was 5.6 ng/mL (0.006 ppm) PFOS with every sample 

having detectable PFOS. The highest PFOS concentration identified was 16.2 ng/mL (0.016 

ppm). The results indicated that in utero exposure to PFOS negatively correlated with birth 

weight in female infants only. 

 A cohort study on 252 pregnant women (≥ 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., 2009). Serum samples 

collected from December 2005 to June 2006 showed PFOS levels ranging from nondetectable to 

35 ng/mL, with the mean and geometric mean being 9.0 ng/mL (0.009 ppm) and 7.4 ng/mL 

(0.0074 ppm), respectively. Overall, there was no association with the level of PFOS and birth 

weight or length of gestation. Mean birth weight was 3278 g (n = 83; PFOS < 6.1 ng/mL); 3380 

g (n = 83; PFOS 6.1-10.0) and 3387 g (n = 86; PFOS > 10-35). Mean length of gestation for all 

groups was 38 weeks; the pre-term delivery percentage was similar between groups. 

 

 Stein et al. (2009) presented on serum levels of PFOS and self-reported pregnancy 

outcomes of a population of women (5,262 pregnancies; ages 15-55 years) in the Mid-Ohio 

Valley in 2000-2006. These women 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 women was 14.1 ng/mL (0.014 ppm). 

There was no association between PFOS levels and miscarriages or pre-term births. PFOS was, 

however, associated with an increased risk above the median (adjusted odds ratio = 1.5: 95% 

confidence interval: 1.1, 1.9) for low birth weight, and a dose-response relationship was reported 

for the 50th-75th, 75th-90th and > 90th percentile serum PFOS exposure concentrations (adjusted 

OR 1.3, 1.6, 1.8, respectively). PFOS was also weakly associated with pre-eclampsia (adjusted 

odds ratio = 1.3, 95% confidence interval: 1.1, 1.7). The self-reported nature of pregnancy 

outcomes in this study is a limitation.

 Using the C8 Health Project data, blood samples from a population of women aged 18-65 

years (n= 25, 957) were analyzed to determine if the onset of menopause, serum estradiol and the 

amount of PFCs in the blood were inter-related (Knox et al., 2011). These data were crosssectional with no variable for the length of exposure. The mean PFOS level of all the women 

was 17.6 ng/mL. Data were eliminated for those reporting undergoing a hysterectomy and 

adjusted for age within the group, smoking, alcohol consumption, body mass index and exercise. 

The analysis for menopause was determined upon three groups of women: childbearing (ages 30-
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42), perimenopausal (ages >42 but < 51) and menopausal (ages > 51 or < 65). These same 

groups were used for the estradiol concentrations except the childbearing group was extended to 

include those > 18 years. For menopause, the odds of having experienced menopause in the 

menopausal group exposed to PFOS showed a monotonic increase with all quintiles significantly 

higher relative to the lowest (PFOS odds= 2.1, CI=1.6-2.8). Also, PFOS was negatively 

associated with estradiol concentrations in all groups but significantly in the perimenapausal 

group (β = -3.65; p< 0.0001) and menopausal group (β = -0.83; p< 0.007). The level of PFOS 

was significantly higher in the set of women that had undergone a hysterectomy. While these 

relationships were associated with PFOS, the authors still recommended caution when 

interpreting results because the data are cross-sectional. Lopez-Espinosa et al. (2011) also used 

the C8 Health Project data base to indicate that in 3076 boys and 2931 girls, ages 8-18 years, 

there was a relationship of reduced odds of reaching puberty (raised testosterone) with increasing 

PFOS levels, having a delay of 190 days between the highest and lowest quartile, and reduced 

odds of postmenarche (138 days delay) in girls. This study suggested that PFOS exposure 

correlated with a delay in puberty. 

 Joensen et al. (2009) investigated the possible associations between perfluoroalkyl acids 

(PFAAs) and semen quality in 105 Danish men. The median PFOS serum level in men was 24.5 

ng/mL. Men with high levels of combined levels PFOA/PFOS had a median level of 6.2 million 

spermatozoa compared to 15.5 million in men with low PFOA/PFOS levels. There was no 

significant association between testosterone levels and PFAA levels and no difference in PFAA 

levels between high and low testosterone groups. 

 The relationships examined and outcomes from the studies that examined reproductive or 

developmental endpoints as they related to serum PFOS concentrations are summarized in Table 

4-2 that follows. For most endpoints no associations were identified. There is some evidence for 

body weight effects in neonates (2 of 5 studies). Possitive associations were also noted for some 

developmental endpoints and factors impacting fertility. 
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TABLE 4-2. Association of serum PFOS with reproductive and developmental 

outcomes 

Study Population Outcome Measures 

at birth

Growth/ 

Development

Fecundity/ 

Fertility

Grice et al., 

2007

Occupational ↔ (any 

adverse)

NM NM NM

Fei et al., 2007; 

2008a; 2008b; 

2009; 2010a 

General ↔ (gestation 

length) 

↔ (length of 

breastfeeding)

↔ 

(weight)

↔ (size) 

↔ (Apgar 

score)

↔ (at 6 

months) 

↑ (at 18 

months; sitting 

up later)

↑ (time to 

pregnancy) 

↑ (infertility)

Monroy et al., 

2008

General ↔ (gestation 

length)

↔ 

(weight)

NM NM

Washino et al., 

2009 

General NM ↑ (low 

weight 

females 

only)

NM NM

Hamm et al., 

2009

General ↔ (gestation 

length)

↔ 

(weight)

NM NM

Stein et al., 

2009

General ↔ 

(miscarriage)

↑ (low 

weight)

NM NM

Knox et al., 

2011 and 

Lopez-Espinosa 

et al., 2011

General NM NM ↑ (delayed 

puberty) 

↑ (early 

menopause) 

Joensen et al., 

2009 

(PFOA/PFOS 

combined)

General NM NM NM ↑ (lower 

sperm count) 

↔ 

(testosterone)

↑= positive association; ↓= negative association; ↔= no association; NM = Not Monitored 

4.1.2.3 Thyroid Effect Studies

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, 2009b). Concentrations of thyroidstimulating hormone (TSH), free thyroxine (fT4), total triiodothyronine (tT3) and thyroxinebinding globulin (TBG) were measured in 623 individuals. Participants were given a survey to 

indicate smoking status, frequency of alcohol use, medications taken, and dietary fish 

consumption. Those using medication for thyroid disease and pregnant women were not 

included in the results. The study detected PFOS in 100% of individuals with a mean plasma 

PFOS concentration of 18 ng/ml (95% CI, 17-19 ng/ml). PFOS was negatively associated with 

circulating levels of TSH, tT3 and TGB and positively associated with fT4. The results suggest 

that human thyroid hormone levels may be affected by PFOS exposure. However, because the 

majority of individuals had normal thyroid gland function, it is uncertain whether these 

relationships are connected to thyroid disease. 
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National Health and Nutrition Examination Survey (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 (1900 men and 2066 women) were included. Of these, 292 women and 69 men reported 

thyroid disease. The data showed that men with PFOS levels in the highest quartile ≥ 36.8 

ng/mL were more likely to report currently treated thyroid disease than men with PFOS levels in 

the lowest quartile ≤ 25.5 ng/mL (OR=2.68; 95% CI, 1.03-6.98; p=0.043). Women had lower 

levels of PFOS than men and higher prevalence of thyroid disease, but serum PFOS 

concentration was not significantly associated with treated 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. 

Bloom et al. (2010) examined the potential association between serum concentrations of 

eight polyhalogenated compounds, including PFOS, and human thyroid function. Levels of 

thyroid stimulating hormone (TSH) and free thyroxine (fT4) were measured in a subsample of 

participants in the cross-sectional New York State Angler Cohort Study (27 men and 4 women). 

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 high concentration compared to the other PFCs 

measured with a mean concentration of 19.6 ng/mL (95% CI, 16.3-23.5). The results indicated 

no significant association between PFOS serum concentration and thyroid hormone levels, 

potentially due to the study’s small sample size. 

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, with 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. 

 

Maternal and umbilical cord blood concentrations of a number of fluorinated organic 

compounds, including PFOS, were determined in 15 women (17-37 years of age) and their 

newborns at Sapporo Toho Hospitals in Hokkaido, Japan from February 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 4.9 to 17.6 ng/mL, and cord blood PFOS ranging from 1.6 to 5.3 

ng/mL. Thyroid stimulating hormone (TSH) and free thyroxine (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 from women (mean age31.3 years) at 15-20 weeks gestation in 2005-2006 in Canada and measured thyroid hormones, 

fT4 and the level of PFCs to determine if PFC levels were associated with hypothyroxinemia. 

From the samples, there were 96 cases of hypothyroxinemia (identified as ‘cases’) and 175 

controls used. The geometric mean for PFOS was 7.39 ng/mL. The mean free T4 levels were 
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7.7 pmol/L in the cases and 12.9 in the controls. The mean TSH concentrations were 0.69 mU/L 

in the cases and 1.13 in the controls. Analysis by conditional logistic regression indicated that 

the concentration of PFOS was not associated with hypothyroxinemia in this set of pregnant 

women. 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. 

The Dallaire et al (2009b) study provides the strongest evidence for effects on thyroid 

hormones as illustrated in Table 4-3. The hormone endpoints were not monitored consistently in 

a number of the other sudies of thyroid effects and where monitored exhibited no significant 

association. 

TABLE 4-3. Association of serum PFOS with the prevalence of thyroid disease and 

thyroid hormone levels in studies of general and worker populations

Study Population Thyroid Disease TSH T3 T4

Dallaire et al., 2009b General ↔ ↓ ↓ ↑

Bloom et al., 2010 General ↔ ↔ NM ↔

Melzer et al., 2010 General ↔ (women)

↑ (men)

NM NM NM

Pirali et al., 2009 General ↔ NM NM NM

Inoue et al., 2004 Newborns NM ↔ NM ↔

Chan et al., 2011 Pregnant 

women

↔ ↔ NM ↔

↑= positive association; ↓= negative association; ↔= no association; NM = Not Monitored 

4.1.2.4 Immunotoxicity

Okada et al. (2012) investigated the relationship between maternal PFOS concentration 

and infant allergies and infectious diseases during the first 18 months of life as well as cord 

blood IgE levels. 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. Infant allergies and 

infectious diseases were assessed in a maternal self-administered questionnaire at 18 months 

post-delivery. Polynomial regression analyses, adjusted for potential confounders, were 

performed on log-transformed data. Mean maternal PFOS concentration was 5.6 ng/mL and 

cord blood IgE level was 0.62 IU/mL. No significant associations were observed between 

maternal PFOS levels and cord blood IgE levels or incidence of food allergy, eczema, wheezing, 

or otitis media in infants at 18 months of age. Limitations of the study include the small sample 

size, potential selection bias of the population, and accurate diagnosis of disease in the infants.

 The population from the Danish National Birth Cohort studies 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. No clear pattern was identified when 

results were stratified by child’s age of infection and the level of PFCs in the maternal blood. 

Antibody responses to diphtheria and tetanus toxoids following childhood vaccinations 

were assessed in context of exposure to perfluorinated compounds (Grandjean et al., 2012). The 
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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; postnatal exposure was assessed from serum 

collected from the child at 5 years of age. 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 negatively associated with antidiphtheria 

antibody concentration (-39%) at age 5 before booster. An effect was also found in comparison 

of antibody concentrations at age 7 with serum PFOS concentrations at age 5 where 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 to 3.97) 

compared with maternal and 1.60 (95% CI, 1.10 to 2.34) compared with age 5 serum PFOS 

concentrations. For age 7 antibody levels correlated with age 5 PFOS serum concentrations, 

odds ratios for inadequate antibody concentration were 2.38 (95% CI, 0.89 to 6.35) for diphtheria 

and 2.61 (95% CI, 0.77 to 8.92) for tetanus. 

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, 

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 

four weeks. Associations of perflourinated 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 45.5±37.3 and 33.4±26.4 

ng/mL, respectively; similar levels were measured for perfluorotetradecanoic acid with 

concentrations of the remaining compounds much lower. The adjusted odds ratios for asthma 

association with the highest versus lowest quartile levels were significantly elevated for seven of 

the 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 nonasthmatic children. Serum PFOA levels, as well as three other compounds, were significantly 

associated with higher asthma severity scores.
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4.1.2.5 Carcinogenicity Studies

Occupational Populations 

Several analyses of various health outcomes have occurred on cohorts of workers at the 

3M Decatur, Alabama plant (Mandel and Johnson, 1995; Alexander et al., 2003; Alexander and 

Olsen, 2007). Cancer incidence and mortality have been examined periodically in these workers. 

A cohort of 2083 workers employed for at least 1 year was examined. Workers were grouped 

into three PFOS exposure categories: non-exposed, low exposed and high exposed. Cumulative 

exposures were also estimated using a weighted approach based on biomonitoring data. The 

geometric mean serum PFOS levels were 0.9 ppm for chemical plant employees and 0.1 ppm for 

non-exposed workers. 

 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 non-malignant causes. SMRs that were above 1 (cancer of the esophagus, liver, breast, 

urinary organs, bladder, and skin) were also elevated when the cohort was limited to any 

employee ever employed in a high exposure job (except breast cancer). Only 2 or 3 deaths were 

reported for each of these cause-specific categories and were not statistically significant, except 

for bladder cancer. Three male employees in the cohort died of bladder cancer (0.12 expected). 

All were employed at the Decatur plant for more than 20 years, and had worked in high exposure 

jobs for at least 5 years. The SMR for bladder 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 3 deaths from bladder cancer were greater than the expected number observed 

in the general population, there were limitations observed in this study. The number of deaths 

was small (especially for females in all categories), all death certificates were not located, 

exposures to other chemicals were not accounted for, smoking status was not established and 

animal studies do not indicate any bladder cancer.

Based on these results, 3M undertook another study of this cohort to identify 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 6 incident cases. Only 2 of 

the 6 self-reported cases were confirmed with medical records. Five of the 6 cases had a history 

of cigarette smoking. Standardized incidence ratios (SIR) were estimated for 3 exposure 

categories and compared to US cancer rates. SIRs ranged from less than 1 to 2.72 but none were 

statistically significant. The highest SIRs were for the lower exposure groups. The SIR was 

1.74 (95% CI 0.64-3.79) for those ever employed in a high exposure job. 

 

 Grice et al. (2007) looked for association with PFOS exposure at the 3M Decatur, 

Alabama plant to various malignant and benign disorders as well as adverse pregnancy outcomes 

(results reported in Section 4.1.2.2). Current and past employees at the plant answered 

questionnaires (n = 1400; 1137 male and 263 female) about any diagnosis of cancers or non-
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cancerous conditions (including liver, kidney and gastrointestinal disease). Two exposure 

models were used in this analysis. The first model grouped workers according to PFOS 

exposure: unexposed (< 0.29 ppm), low (0.39-0.89 ppm) or high exposure (1.30-1.97 ppm). The 

other model estimated cumulative exposures by using a weighted approach based on 

biomonitoring data. 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. 

None of the other health conditions were positively associated with PFOS exposures 

 

General Populations 

 A prospective Danish cohort study (1993-2006) compared plasma levels of PFOS and 

PFOA and the incidence of cancer in 57,053 native Danish individuals (ages 50-65 years) 

(Eriksen et al., 2009). The participants had no cancer diagnosis at the time of the enrollment. 

The Danish Cancer Registry and the Danish Pathology Data Bank were used to identify 713, 

332, 128 and 67 patients with prostate, bladder, pancreatic and liver cancer, respectively, 

diagnosed 0-12 years after enrollment in the cohort. A comparison group reflecting the gender 

ratio of the case group was also chosen from the original cohort (680 men, 92 women). Potential 

confounders associated with each type of cancer were addressed in questionnaires administered 

to the participants. 

One-time, PFOS and PFOA blood samples were taken at recruitment. Cancer incidence 

rate ratios (IRR) were estimated using Cox proportional hazards model, stratified by sex. 

Median PFOS levels did not differ significantly between male and female cases (35.1 ng/mL, 

males; 32.1 ng/mL, females) or controls. Adjusted IRRs for the 4 types of cancer based on 

increasing PFOS quartiles were only above 1 for prostate and pancreatic cancer; none of them 

were statistically significant, and no increasing trends were noted. 

4.2 Animal Studies 

A tabular summary of animal studies is provided in Appendix A, Table A.3. 

4.2.1 Acute Toxicity 

A limited number of acute studies are available for PFOS. The studies indicate an LD50 

of 251 mg/kg and an LC50 of 5.2 ppm in rats. PFOS caused no irritation in a dermal irritation 

study although limited study details were available. An eye irritation study was also conducted 

but few details were provided on effects observed. 

Oral Exposure 

Rat

Dean et al. (1978) exposed 5 CD rats/sex/dose by gavage to a single dose of 0, 100, 215, 

464 or 1000 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 1000 mg/kg group and 3/10 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 
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findings, the acute oral LD50 was 233 mg/kg in males, 271 mg/kg in females and 251 mg/kg 

combined. 

Male Wistar rats (n=2-3/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 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. 

Mice

 Sato et al. (2009) also studied male ICR mice (n=2-3/group) administered a single oral 

dose of PFOS at 0, 125, 250 or 500 mg/kg. Animals treated with ≥ 250 mg/kg had decreased 

body weight or delay of body weight gain during the 14 days post-exposure. One mouse in each 

dose group died.

Inhalation Exposure 

Rusch et al. (1979) exposed five Sprague-Dawley rats/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 died in the 24.09 mg/L group 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

Rabbit 

 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, covered and erythema and edema were scored after 24 and 72 hours. The primary 

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; however, the raw data were not 

provided. 
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4.2.2 Short-Term Studies 

Oral Exposure 

Rat

Five Crl:CD (SD) IGS BR rats/sex/dose level/interim necropsy were administered PFOS 

in the diet at concentrations of 0, 0.5, 2.0, 5.0 or 20 ppm for 4 or 14 weeks (further discussion of 

the 14-week results is provided in Section 4.2.3) as part of a larger 2-year cancer bioassay design 

(Seacat et al., 2003). 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, respectively. Animals were observed twice daily 

for mortality and morbundity 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/treatment during week 4 for clinical 

chemistry, hematology and urinalysis evaluation. A thorough necropsy was performed at the end 

of treatment and liver samples were collected for palmitoyl CoA oxidase (PCoAO) activity, 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 are provided in Table 4-4. For the animals treated for 

4 weeks, terminal body weight in the 20 ppm animals was decreased, although not statistically 

significant. Absolute liver weight was not affected but relative (to body weight) liver weight was 

significantly increased in the high dose males. Food consumption and food efficiency were only 

decreased in the 20 ppm females. No treatment-related effects were observed on hematology or 

urinalysis; female rats treated with 20 ppm had significant decreases in serum glucose and 

increases in aspartate aminotransferase (AST). Analysis of PCoAO activity was weakly 

increased (less than 2-fold) when compared to controls in the 20 ppm dose group males in one 

laboratory and similar to controls in another laboratory analysis. 
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TABLE 4-4. Mean (± SD) Values for Select Parameters in Rats Treated for 4 Weeksa

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 ± 7b 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 37.0 ± 1.7 2.0* ± 1.1 4.0 ± 1.1 a Data from Seacat et al., 2003

b 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 

 Curren et al. (2008) conducted two 28-day studies in groups of 15 Sprague-Dawley 

rats/sex/dose group. 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 and 6.34 mg/kg/day, respectively, in 

males and 0, 0.15, 1.43, 3.73 and 7.58 mg/kg/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 liquid 

chromatography negative electrospray tandem mass spectrometry (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 3.2 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 one week of treatment in the 20 mg PFOS/kg diet 

group. No differences in blood pressure measurements were observed across the groups. In red 

blood cells from both males and females, deformability index values over a range of shear stress 

levels were significantly lower relative to controls in animals exposed to 100 mg PFOS/kg diet.

Absolute and relative (to body weight) liver weight were statistically significantly 

increased in the male and female rats at ≥ 20 mg PFOS/kg diet. Relative (to body weight) 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 dietary 

concentrations ≥ 50 mg PFOS/kg. 
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Both males and females showed a significant increase in expression of the gene for 

peroxisomal acyl-coenzyme A oxidase (ACOX1) at concentrations ≥ 50 mg/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. At the high doses, the serum levels of 

conjugated bilirubin and total bilirubin were increased significantly. A total of 67 fatty acid 

profiles were examined. The author stated that the profile changes were similar to those induced 

by weak peroxisome proliferators. 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 were observed in this study are provided 

in Table 4-5. 

TABLE 4-5. Mean (± SD) Values for Select Parameters in Rats Treated for 28 Daysa

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 a Data from Tables 2-3 and 6-7 in Curran et al., 2008

*Statistically significant from controls, p< 0.05 or p ≤ 0.05

 Ten three-month old male Sprague-Dawley rats/group were administered by oral gavage 

0 (Milli-Q water only), 5 or 20 mg/kg/day of PFOS for 28 days (Cui et al., 2009). Rats were 

sacrificed after the exposure and blood and tissue samples 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 
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socket and nose, and tumescence/yellow staining at 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 (HSI), renal-somatic (RSI), and gonad-somatic (GSI) index to evaluate the 

hyperplasia, swelling and/or atrophy of the organs and all three indices were statistically 

significantly 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 no observed 

adverse effect level (NOAEL) could not be identified and the lowest observed adverse effect 

level (LOAEL) was 5 mg/kg/day in rats. 

Mouse

Bijand 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 with or without 3 mg PFOS/kg/day for 

periods of 4 weeks. Plasma samples were collected via tail vein bleeding and analyzed for a 

variety of lipid related endpoints including TC, triglycerides (TG), very low density lipoprotein 

(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. 

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, the mass of perigonadal fat pad, and TG uptake by skeletal muscle. 

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. 

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 were those involved with fatty acid uptake, transport 

and catabolism; triglyceride synthesis, cholesterol ester synthesis; plus VLDL synthesis and 

secretion. Genes involved with HDL synthesis, maturation and clearance plus bile acid 

formation were down regulated. 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, and 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. 
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Inhalation Exposure

 No short-term inhalation animal exposure studies of PFOS were identified. 

4.2.3 Subchronic Studies 

There are three monkey studies of PFOA exposure, two with rhesus- and one with 

cynomolgus- strains, and two rat subchronic studies. The study with cynomolgus monkeys was a 

GLP study. There are no subchronic studies by dermal or inhalation routes of exposure with 

PFOS.

Oral Exposure 

Monkey 

 Two monkey studies were performed with rhesus monkeys (Goldenthal et al., 1978a and 

1979). In the first study, 2 monkeys/sex/group 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. 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 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 set in the study. 

 In the second study, 2 rhesus monkeys/sex/group 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 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/group, except for the 0.03 mg/kg/day group (4 monkeys/sex), daily for 26 weeks 

(182 days) in a GLP study. Two monkeys/sex in the control, 0.15, and 0.75 mg/kg/day groups 

were monitored for one 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 pre- and 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 
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obtained for hepatic peroxisome proliferation determination and immunohistochemistry was 

performed by PCNA to look for cell proliferation. Selected results are shown in Table 4-6. 

 Two of the 0.75 mg/kg/day males died; one died on day 155 and one was found 

moribund and 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 after the treatment when compared to controls. The 0.75 

mg/kg/day males and females lost 8 ± 8% and 4 ± 5%, respectively, while the control males and 

females 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% and 33-49% 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 thyroid 

stimulating hormone (TSH) was increased on day 182 in the high-dose monkeys but a true doseresponse was not observed and the monkeys had no sign of hypothyroidism. 
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TABLE 4-6. Mean (± SD) Values for Select Parameters in Monkeys Treated for 182 Daysa

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 a Data from Seacat et al., 2002

Statistically significant from controls: *p< 0.05; **p<0.01. 

 Hepatic peroxisome proliferation was measured by palmitoyl CoA oxidase activity and 

was increased significantly in the 0.75 mg/kg/day females; however, it was less than the two-fold 

increase typically indicating biological significance. 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 highdose male that died during the study. On histopathology, all high-dose females and 3/4 highdose males 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 ppm in males and 66.8 ppm in females. 

Rat

 Goldenthal (1978b) administered 0, 30, 100, 300, 1000 or 3000 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 exhibited emaciation, convulsions, hunched 
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back, increased sensitivity to stimuli, reduced activity and red material around the nose/mouth 

before their deaths starting on day 7. 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. 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 for PFOS in the rats was 30 ppm (2 mg/kg/day) and the NOAEL could not be 

determined. 

Five Crl:CD (SD) IGS BR rats/sex/dose level/interim necropsy were administered PFOS 

in the diet at concentrations of 0, 0.5, 2.0, 5.0 or 20 ppm for 14 weeks as part of a larger 2-year 

cancer bioassay design (Seacat et al., 2003). 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. Animals 

were observed twice daily for mortality and morbundity 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/treatment during week 14 for 

clinical chemistry, hematology and urinalysis evaluation. A thorough necropsy was performed at 

the end of treatment and liver samples were collected for palmitoyl CoA oxidase (PCoAO) 

activity, 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%.

 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 4-7. 
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TABLE 4-7. Mean (± SD) Values for Select Parameters in Rats Treated for 14 Weeksa

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 a Data from Table 1 in Seacat et al., 2003

*Statistically significant from controls, p< 0.05 

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). 

4.2.4 Neurotoxicity 

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. Five adult male Wistar rats/group 

were administered one 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 (Asp), glycine (Gly) and gamma-aminobutyric acid (GABA). 

All treated rats had a significant (p<0.05) decrease in body weight, 15, 22 and 27% less 

than the controls in the 12.5, 25 and 50 mg/kg groups, respectively. Among the EAAs, the Glu 

content was significantly decreased at the high dose (↓77% compared to controls; p<0.05) in the 

hippocampus; no other significant differences were recorded. In the cortex, Glu was again the 

only EAA affected with significant decreases at 25 (↓33% compared to controls) and 50 (↓47 
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compared to controls) mg/kg. GS activity was 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 and indicated an effect on Glu and GS in the central nervous system starting at 25 

mg/kg/day. 

Male Wistar rats and ICR mice (n=2-3/group) were administered a single oral dose of 

PFOS at concentrations of 0, 125, 250 or 500 mg/kg bw and monitored for any neurological 

signs (Sato et al., 2009). Animals were checked daily for startle response, touch response, pain 

response, righting reflex, visual placing, abdominal tone and limb tone. No neurological signs 

were observed. However, when stimulated with ultrasound (44 kHz, 10 sec), tonic convulsions 

occurred and 1/3 rats in the 250 mg/kg group, 2/2 rats in the 500 mg/kg group and 1 mouse in 

each dose group died within 48 hours of the convulsions. 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 one time did not show any differences 

in the levels of catecholamines (norepinephrine, dopamine and serotonin) or amino acids 

(glutamic acid, glycine and GABA) when compared to the controls at 24 and 48 hours postexposure.

In vitro

Slotkin et al. (2008) evaluated 10-250 μM PFOS, PFOA, perfluorooctane sulfamide 

(PFOSA) and perfluorobutane sulfonate (PFBS) in vitro in differentiated and undifferentiated 

PC12 cells, a neurotypic cell line. In the study, inhibition of DNA synthesis, deficits in cell 

numbers and growth, oxidative stress, cell viability and shifts in differentiation toward or away 

from the dopamine (DA) and acetylcholine (ACh) neurotransmitter phenotypes were assessed. 

No effects on cell size, cell number or neurocyte outgrowth were observed. PFOS decreased cell 

viability at 250 μM and promoted differentiation into the ACh phenotype at the expense of the 

DA phenotype. The study suggests that the mechanisms of these neurotypic cell lines are not 

similar between the tested perfluoroalkyl acids. The rank order of adverse effects was PFOSA > 

PFOS > PFBS = PFOA. 

Liao et al. (2009) assessed the neurotoxic effect of varying chain lengths of the 

perfluorinated compounds on cultured Sprague-Dawley rat hippocampal neurons. Spontaneous 

miniature post-synaptic currents (mPSCs) were recorded in gap-free mode from hippocampal 

neurons at 8-15 days in vitro. The compounds tested included those in the carboxylic group: 

perfluoropropionic acid (PFPA; C-3), perfluorobutyric acid (PFBA; C-4), perfluorooctanoic acid 

(PFOA; C-8), perfluorododecanoic acid (PFDA; C-12) and perfluorotetradecanoic acid (PFTA; 

C-14); those in the sulfonic group: perfluorobutane sulfonic (PFBS; C-4), 

perfluorohexanesulfonic acid potassium salt (PFHS; C-6) and perfluorooctane sulfonate (PFOS; 

C-8) and a nonfluorinated hydrocarbon, octanoic acid (OA; C-8). Also tested was 1 Hperfluorooctane (PFOC; C-8). Testing showed frequency of mPSCs increased in proportion to 

the increase in carbon length. Eight carbon PFOS had a statistically significant (p< 0.001) 

increase in the mPSCs when compared to 4 carbon PFBS. Compounds with a carboxylic group 

also had lower frequencies than those with sulfonic groups. PFOS significantly (p< 0.001) 

increased the mPSC amplitude. The inward calcium currents (ICa) were recorded in the presence 

or absence of compounds with a ramp depolarization pulse. Voltage values were recorded and 
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plotted versus the corresponding ICa every 5 mV and the resulting current-voltage relationship 

curve established. All three sulfonic compounds increased the ICa with correlation to the chain 

length with PFOS having the most effect (% increase not provided). 

 

In the same study, the chronic effects of perfluorinated compounds on neuronal 

development were evaluated by measuring neurite outgrowth and branching. In the sulfonic 

compounds, only PFOS statistically suppressed the length of neurites (p < 0.001; 25% below that 

of controls). The lengths of the longest neurites and sum length of neurites per neuron were not 

affected with OA or PFOC but were reduced by PFOA and PFOS. 

Overall, the adverse effects on cultured neurons increased as the chain length of the test 

compound increased. The study also suggested that perfluorinated sulfonates exerted more 

potent actions on neurons when compared to perfluorinated carboxylates. The study authors 

hypothesized that this could occur because PFOS was more likely to be incorporated into the 

lipid bilayer of cell membranes.

4.2.5 Developmental/Reproductive Toxicity 

Rats, rabbits, and mice were all found to be affected in developmental/reproductive 

studies of PFOS. Prenatal exposure to PFOS caused an increase in neonatal mortality when 

dams were exposed to concentrations ≥ 2 mg/kg/day. Effects were observed on gestation length, 

birth weight, survival and developmental delays. Structural abnormalities observed include: 

ocular lens abnormalities (questionable), decreased bone ossification, cleft palate, and 

enlargement of the right atrium. Many specialized developmental studies (neurotoxicity, 

immunotoxicity) have been conducted with PFOS. 

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 six weeks prior to and during mating (Luebker et al., 2005b). Treatment in males 

continued until one day prior to sacrifice 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-section) performed on GD10; others delivered naturally and were killed 

on lactation day (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, no effects were observed on mortality, treatment-related 

clinical signs and the mating/fertility parameters evaluated. During pre-mating, decreases in 
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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 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, so 

only the 0.1 and 0.4 mg/kg/day dose groups were carried into the second generation. Twentyfive 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 through sacrifice. One 

rat/sex/litter was tested in a passive avoidance paradigm at 24 days of age and one/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 

individually housed. The F1 generation male rats were sacrificed after mating, necropsied and 

evaluated as described in the F0 generation. All F1 generation females delivered naturally 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 2-4. 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 stillborns 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, 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 signs in pups at 3.2 mg/kg/day were a 

high number of pups not nursing, not having milk present in the stomach, being stillborn and a 

high incidence of maternal cannibalization of the pups. 

 

 In the F1 generation offspring, pups administered 3.2 mg/kg/day could be evaluated only 

on LD 1 due to high mortality; all displayed decreased surface righting ability. The acoustic 

startle reflex and air righting ability were both significantly reduced at 1.6 mg/kg/day. Similar 

responses were seen for pinna unfolding and eye opening. The physical development delays 

were transient; all pups were similar to controls by the end of the observation period. No delays 

were observed in rats administered doses ≤ 0.4 mg/kg/day. 

F2 Generation: 

 F1 parental animals displayed no clinical signs or mortality. F1 male parents had a 

transient decrease in food consumption but it was not affected in F1 females. The F1 dams 

showed no effects in reproductive performance. 

 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 at 0.1 mg/kg/day on LDs 4 and 7 were transient; mean body weights were 
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similar to controls by LD 14. The pups at 0.4 mg/kg/day had 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. 

 

 Based on the decreases in body weight gain and food consumption, the LOAEL for both 

the F0 male and female parents was 0.4 mg/kg/day and the NOAEL was 0.1 mg/kg/day. For the 

F1 parents, 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 to 

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 was 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. Reductions in 

gestation length, the average number of implantation sites, delivered sizes, and live litter size 

were observed in treated animals. 

Live litter sizes were comparable between treated and control groups following crossfostering. On LDs 2-4, ~ 19% of the pups in the group exposed gestationally and lactationally 

were either found dead or presumed cannibalized. Pup mortality for the negative control was 

1.6%. For pups exposed only prenatally mortality was 9% while it was 1.1% for those exposed 

during lactation only. Reductions in pup body weights on LD 1were observed in groups exposed 

both gestationally and lactationally and those with gestational exposure only. On LDs 4-21, pup 

body weights were reduced in all exposed groups when compared to the negative control, with 

the greatest decrease in the group with gestational and lactational exposures. 
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Two litters in the group with lactational exposure and one litter exposed during gestation 

and lactation did not nurse. No milk was found in the stomachs of the pups found dead and 

necropsied from the groups with in utero plus lactational exposures (100% of pups), in utero 

exposures only (57% of pups), and lactational exposures only (87% of pups). 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 dams treated with 1.6 

mg/kg/day PFOS. No significant differences were observed between the negative control group 

and the other groups following examination of pup lungs. 

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 

were below the limit of detection. Serum PFOS concentrations in the pups from treated dams, 

fostered with untreated dams (in utero exposures) ranged from 47.6 μg/mL to 59.2 μg/mL. 

Serum PFOS concentrations of treated dams ranged from 59.2 μg/mL to 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 from 79.5 μg/mL to 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 

(post-natal 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 appear 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, 

exposure during lactation alone from exposed dams had no significant affect on pup viability. 

 

 The dose-response curve for neonatal mortality in rat pups born to PFOS exposed dams 

and the biochemical and pharmacokinetic parameters were investigated (Luebker et al., 2005a). 

At 6 weeks prior to mating, female Crl:CD(SD)IGS VAF/Plus rats/dose 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 gestation day (GD) 20 for dams assigned to C-section (eight dams in 

the control, 1.6 and 2.0 mg/kg/day groups). Another group (~20 dams per dose group were 

allowed to deliver naturally and nurse their pups through LD4. These dams and their pups were 

killed 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, early/late resorptions and placentas. Liver weights were 

determined for the dams as well and their organs examined by gross necropsy. Fetuses were 

pooled by litter and mean weight recorded. In the natural delivery dams, typical reproductive 

and fetal parameters were measured and recorded. Biochemical parameters investigated in the 

dams and litters included: serum lipids, glucose, mevalonic acid and thyroid hormones (total 

[TT4] and free thyroxin [FT4], total [TT3] and free triiodothyronine [FT3] and thyroid 

stimulating hormone [TSH]); milk cholesterol and liver lipids. Mevalonic acid was included as 
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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, dead fetuses/litter) in those C-sectioned. Mild decreases in body weight 

were observed in dams at 1.6 and 2.0 mg/kg during gestation. Body weight gain in the dams was 

affected statistically during lactation at ≥ 0.8 mg/kg and food consumption showed a general 

downward trend with increasing dose during pre-mating, gestation and lactation. For those 

allowed to deliver normally, 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. 

 In the group sacrificed on LD5, a decrease in gestation length was observed at doses ≥ 

0.8 mg/kg and decreases in viability were observed starting at 0.8 mg/kg becoming statistically 

significant at doses of 1.6 and 2.0 mg/kg. The viability indices were 97.3%, 93.1%, 88.8%, 

81.7%, 49.3% and 17.1% at 0, 0.8, 1.0, 1.2, 1.6 and 2.0 mg/kg, respectively (Table 4-8). The 

decrease in survival did not appear to be caused by a reduction in lipids, glucose utilization or 

thyroid hormones as these parameters were either only slightly affected or similar between 

treated and control animals. In all treated groups, pup body weight at birth and on postnatal day 

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, 

respectively, based on decreased body weight and the NOAEL was not identified.

Several benchmark dose estimates (BMD5 and BMDL5) were run by the author and 

provided 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 wt (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 

through day 5 BMD5 = 1.06 mg/kg/day BMDL5 = 0.89 mg/kg/day 
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TABLE 4-8. Fertility and Litter Observations in Dams Administered 0 to 2.0 mg 

PFOS/kg/Daya 

0.0 0.4 0.8 1.0 1.2 1.6 2.0

Fertility indexb (%) 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 indexc (%) 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 LD 1-5

0 0 0 1 0 4 14**

Viability indexd (%) 97.3 97.6 93.1 88.8 81.7 49.3** 17.1** a Data from Luebker et al., 2005a

b Number of dams pregnant/number of dams mated x 100

c Number of dams with live offspring/number of pregnant dams x 100

d Number of live pups on day 5 postpartum/number of live births x 100

Statistically significant at * p ≤ 0.05 or ** p ≤ 0.01

Developmental Studies

Rat

Two older developmental studies were performed on rats. Gortner (1980) administered 

0, 1, 5 or 10 mg/kg/day PFOS in corn oil by gavage to four groups of time-mated SpragueDawley rats on gestation days (GD) 6-15 and then sacrificed them on GD 20. The maternal 

LOAEL was 10 mg/kg/day based on significant decreases in body weight during GDs 12-20 and 

the maternal NOAEL was 5 mg/kg/day. The developmental LOAEL was 1 mg/kg/day based on 

abnormalities in the lens of the eye, not observed in the control fetuses. The eye abnormalities 

were localized to the area of the embryonal lens nucleus and appeared to be a lack of complete 

development of the primary lens fibers. The developmental NOAEL could not be determined. 

The author added an amendment to the study, however, suggesting that the eye lesion was an 

artifact created by sectioning and the results were not observed in the Wetzel (1983) study. 

Therefore, the developmental lesion occurring in the eye is believed to be an artifact and not 

related to PFOS.

In the second study, groups of 25 pregnant Sprague-Dawley rats were administered 0, 1, 

5 or 10 mg/kg/day PFOS in corn oil by gavage on GDs 6-15 (Wetzel, 1983). In this study, the 

maternal LOAEL was 5 mg/kg/day based on clinical signs observed at 5 and 10 mg/kg/day in 

dams, including hunched posture, anorexia, uterine stains, bloody vaginal discharge, rough 

haircoat, and decreased body weight. The maternal NOAEL was 1 mg/kg/day. Two dams in the 

10 mg/kg/day group were found dead on GD 17, but information as to the cause of death was not 

provided. The developmental LOAEL was 5 mg/kg/day based on a decrease in body weight in 

fetuses; the NOAEL was 1 mg/kg/day. Statistically significant increases in the number of litters 

containing fetuses with visceral abnormalities, delayed ossifications and skeletal abnormalities 

were observed at 10 mg/kg/day. 

A two-part developmental study with PFOS was performed in rats. Thibodeaux et al. 

(2003) reported on the maternal and prenatal evaluation by administering 0, 1, 2, 3, 5 or 10 
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mg/kg PFOS daily by gavage in 0.5% Tween-20 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 decreased 

significantly (p< 0.0001) in a dose-dependent manner at doses ≥ 2 mg/kg. A dose dependent 

increase in the serum concentration of PFOS was observed with liver concentrations 

approximately four times higher. Liver weight was not affected in the treated rats. Serum 

chemistry showed significant decreases in cholesterol (↓ 14% compared to controls) and 

triglycerides (↓ 34% compared to controls) at 10 mg/kg. Serum thyroxine (T4) and 

triiodothyronine (T3) were significantly decreased in all treated rats when compared to controls, 

however, a feedback response on thyroid stimulating hormone (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 were provided for different parameters and were as follows: 

maternal weight reduction (polynomial model) BMD5 = 0.22 mg/kg and BMDL5 = 0.15 mg/kg; 

T4 effects on GD7 (Hill model) BMD5 = 0.23 mg/kg and BMDL5 = 0.05 mg/kg; fetal sternal 

defects (logistic model) BMD5 = 0.31 mg/kg and BMDL5 = 0.12 mg/kg and fetal cleft palate 

(logistic model) BMD5 = 8.85 mg/kg and BMDL5 = 3.33 mg/kg. 

In the second part of the developmental study, the post-natal effects of in utero exposure 

to PFOS were evaluated in the rat (Lau et al., 2003). Sprague-Dawley rats were administered 0, 

1, 2, 3, 5 or 10 mg/kg 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 post natal day (PND) 

1. The number of pups per litter, number of live pups in the litter daily 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 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 used for additional PFOS 

concentrations, thyroid hormone analysis and neurobehavioral tests. 

In dams administered 10 mg/kg, the neonates became pale, inactive, and moribund within 

30-60 minutes and all died. In 5 mg/kg 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. Pups from dams treated with 2 mg/kg still had significant increases in 

mortality but those from dams administered 1 mg/kg were similar to controls. No differences 

were observed in liver weight in the rats. Pup body weight was affected with PFOS treatment 

and was significantly decreased starting in dams administered 2 mg/kg. A slight but significant 

delay in eye opening was observed in the rats (≥ 2 mg/kg), but no difference was observed in 

onset of puberty. 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. 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 
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deficiencies. Based on the findings, the developmental LOAEL is 2 mg/kg PFOS and the 

NOAEL is 1 mg/kg. Benchmark dose estimates were provided for survival of the neonates on 

PND 8 (NCTR model) and were as follows: BMD5 = 1.07 mg/kg and BMDL5 = 0.58 mg/kg. 

Because of the high number of fetal deaths, a sub-study was performed with newborns 

from the 5 mg/kg PFOS group being cross-fostered with control dams immediately after 

parturition. Survival was monitored for 3 days. Cross-fostering the PFOS-treated rats (5 mg/kg) 

with control dams did not increase survival, and all control pups fostered by PFOS treated dams 

survived. 

Grasty et al. (2003) investigated the critical window for prenatal exposure to PFOS by 

administering it to pregnant rats by gavage at 25 mg/kg on four consecutive days (GDs 2-5, 6-9, 

10-13, 14-17 or 17-20) or at 25 or 50 mg/kg on GDs 19-20. In those administered PFOS in the 

4-day intervals, litter size at birth was unaffected but pup weight was decreased. Neonates died 

after dosing in all time periods but the incidence of death 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 but all occurred by PND 4. In the two-day treatment, 

survival of the pups was 98, 66 and 3% in the control, 25 and 50 mg/kg groups on PND 5. 

Histological examination of the lungs showed differences in maturation between the control and 

treated pups. Grasty et al. (2005) performed another study to determine if delayed lung 

maturation was responsible for the deaths. The newborns were found to have thick alveolar 

walls but had normal pulmonary surfactant profiles leading to doubt that lung maturation was the 

cause of death.

While the lung maturation did not appear to be the cause of death, on-going studies 

support that effects of PFOS on lung surfactant is still likely to be the reason neonatal deaths 

occurred. PFOS has been shown to interact with dipalmitoylphosphatidylcholine (DPPC) which 

is a major component of surfactant (Xie et al. 2007, 2010a and 2010b). As discussed in the 

distribution section, Borg et al. (2010) found radiolabeled PFOS 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 that in the maternal blood on PND 1. 

Chen et al. (2012) administered 0, 0.1 or 2.0 mg/kg/day PFOS to 10 pregnant SpragueDawley rats/group in 0.05% Tween 80 in deionized water on GDs 1 to 21 by gavage. After 

parturition (PND 0), pups were counted, 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 used for 

histopathological examination and assessing oxidative stress and extraction of cytoplasmic 

protein. The serum and lungs were also analyzed for PFOS concentration. To determine the 

maternal effect of PFOS on offspring survival, three additional groups of rats were treated as 

previously described and the number of deaths/litter recorded until PND 4. 

Body weight of the dams was decreased and postnatal mortality (by PND 3) increased 

significantly (p< 0.05 and 0.01) 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 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 serum (μg/mL) were approximately 2x greater than that 
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found in the 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 were still greater in the serum. PFOS was not detected in 

controls at either timepoint. Histopathological changes were observed in the lungs of rats at 2.0 

mg/kg/day on PND 0 that included marked alveolar hemorrhage, thickened interalveolar septum 

and focal lung consolidation. At this same dose, the lungs also had alveolar hemorrhage, 

thickened septum and inflammatory cell infiltration on PND 21. Numerous apoptotic cells were 

also observed in the lungs of rats at 2.0 mg/kg/day. No abnormalities were observed on 

examination of the control rats or at 0.1 mg/kg/day. An increase in biomarkers associated with 

oxidative stress was also observed in the rats at 2.0 mg/kg/day. In the pups, there was an 

increase in the level of malondialdehyde (MDA; 473% and 305% of controls on PND 0 and 21, 

respectively) and a decrease in the level of glutathione (GSH) content. Superoxide dismutase 

(SOD) activity declined also at 2.0 mg/kg/day. Cytochrome c (Cyt c) was increased in rats at 2.0 

mg/kg/day which is an apoptogenic factor in the mitochondrial pathway. To determine the 

intrinsic and extrinsic cell death pathway role in the apoptosis found in the rat offspring, caspaselike activity was measured using specific chromogenic substrates. In the lungs of those 

administered 2.0 mg/kg/day, caspase -3, -8 and -9 were activated markedly at both PND 0 and 21 

when compared to the controls. No changes were observed in the 0.1 mg/kg/day substrates. 

Overall, the results suggest that both the mitochondrial and the cell death receptor pathways were 

activated by prenatal PFOS exposure.

To further investigate the effects of PFOS on the fetal lung, 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 fetal 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 dosedependent up-regulated 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 up-regulated genes were involved in significant cytoskeletal, extracellular matrix 

remodeling, and transporting and secreted proteins in the fetal lung.

Rabbit 

Christian et al. (1999) administered 0, 0.1, 1.0, 2.5 or 3.75 mg/kg/day of PFOS in 0.5% 

Tween-80 by gavage to 22 pregnant female New Zealand White rabbits/group on GDs 7-20. 

Does were sacrificed on GD 29 and reproductive parameters measured. A satellite group of 3-5 

pregnant rabbits/group were administered the same concentration and euthanized on GD 21 for 

measurement of PFOS in blood and liver samples. Fetuses from the satellite does were removed, 

examined grossly and samples pooled by litter. All animals had PFOS in serum and liver 

although PFOS levels were higher in the liver. Maternal toxicity was observed at 1.0 mg/kg/day 

and higher. At 2.5 mg/kg/day, one doe and at 3.75 mg/kg/day, nine does aborted between GDs 

22-28. Mean maternal body weight was decreased significantly at doses ≥1.0 mg/kg/day. Based 

on the findings, the maternal rabbit LOAEL was 1.0 mg/kg/day and the NOAEL was 0.1 

mg/kg/day. The developmental LOAEL was 2.5 mg/kg/day based on decreased mean fetal body 

weight and a reduction in the ossification of the sternum of the fetuses. The developmental 

NOAEL was 1.0 mg/kg/day. 
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Mouse

As described for rats, a two-part developmental study with PFOS was performed also 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 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 recorded for the mice. 

Maternal body weight gain was decreased significantly at 20 mg/kg/day. Food and water 

consumption were also affected at the high dose. Increases in serum PFOS were comparable to 

the rat but PFOS treatment increased the liver weight in a dose-dependent manner. T4 was 

decreased but not as severely as in the rat and the effects of PFOS on the thyroid hormones were 

not as pronounced as that seen in the rat. A significant increase in post-implantation losses was 

observed in those administered 20 mg/kg/day and small reductions in fetal weight were 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 ≥ 10 mg/kg. Benchmark dose 

estimates were provided for different parameters but for most, were much higher than those for 

the rat. The estimates are as follows: maternal weight reduction (polynomial model) BMD5 = 

15.15 mg/kg and BMDL5 = 3.14 mg/kg; maternal T4 effects on GD6 (Hill model) BMD5 = 0.51 

mg/kg and BMDL5 = 0.35 mg/kg; fetal sternal defects (logistic model) BMD5 = 0.06 mg/kg and 

BMDL5 = 0.02 mg/kg and fetal cleft palate (logistic model) BMD5 = 7.03 mg/kg and BMDL5 = 

3.53 mg/kg.

In the second part of the developmental study, the post-natal effects of in utero exposure 

were evaluated in the mouse (Lau et al., 2003). CD-1 mice were administered 0, 1, 5, 10, 15 or 

20 mg/kg of PFOS in 0.5% Tween-20 by gavage on GDs 1-17. 

Most mouse pups from dams administered 15 or 20 mg/kg did not survive for 24 hours 

after birth. Fifty percent mortality was observed at 10 mg/kg. Survival of pups in the 1 and 5 

mg/kg treated dams were similar to controls. A significant (p< 0.0001) increase in absolute liver 

weight was observed at ≥ 5 mg/kg. A significant delay in eye opening was observed at ≥ 5 

mg/kg. Thyroid hormones were not affected as prominently as in the rat. The LOAEL for 

mouse pups was 5 mg/kg and the NOAEL was 1 mg/kg. Benchmark dose estimates were 

provided for survival of the neonates on PND 6 (NCTR model) and were as follows: BMD5 = 

7.02 mg/kg and BMDL5 = 3.88 mg/kg. 

Ten pregnant ICR mice/group were administered 0, 1, 10 or 20 mg/kg of PFOS daily by 

gavage from gestational day (GD) 1 to GD 17 or 18 (Yahia et al., 2008). Five dams/group were 

killed on GD 18 for prenatal evaluation 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 killed on GD 18, the gravid 

uterus was removed and the number of live/dead fetuses as well as resorptions recorded. Fetal 

weight was obtained and the bone, cartilage and skeletal morphology were examined. Four 

pups/litter were killed immediately after birth for pulmonary examination. 
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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, 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. See Table 4-9 below. The study did not distinguish or provide any 

gender differences. 

TABLE 4-9. Effects Observed in the Mice Administered PFOS from GD 0 to GD 17/18a

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 PND4 (%) 98.18 ± 1.82 100 55.20 ± 18.98* 0** a Data from Tables 2-3 in Yahia et al., 2008

*Statistically significant difference between control and treated groups, p< 0.05 or ** p< 0.01

Histopathological exam showed that all fetuses examined on GD 18 from dams treated 

with 20 mg/kg were alive, 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 

intracranial blood vessel dilatation when examined histopathologically. At 10 mg/kg, some pups 

had normal lungs and some had severe or focal atelectasis. Three neonates from each of the five 

dams treated with 10 mg/kg were examined, 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. 

 
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4.2.6 Specialized Developmental Studies

Hormonal Disruption 

Rat

 

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. The remaining litters were 

cross-fostered within 12 hours of birth to make the following groups: 

1) litters from control dams fostered by control dams (CC, unexposed control; n=8), 

2) litters from treated dams fostered by control dams (TC, prenatal exposure; n=8), 

3) litters from control dams fostered by treated dams (CT, post-natal exposure; n=8) and

4) 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 diet of their rearing dam. Pups were 

weighed and killed 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. Offspring from PFOS treated 

groups did not differ significantly from controls in body weight. Liver weights in pups from the 

TT group were significantly increased on PND 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 in those exposed only prenatally (group TC). The levels increased in 

those treated both pre- and postnatally (group TT). These results indicate that PFOS can be 

transferred by the placenta and by the milk. 

 The total T3 and rT3 were not affected by PFOS treatment of 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 with the response in the CT and TT groups being more severe. Pups in the TT group 

(exposed pre- and postnatally) were also significantly T4 deficient at PND 14. For gene 

expression, no statistically significant differences were observed between 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 

period (group TT). The author noted, however, that there are metabolic differences between rats 

and humans that may make the rat’s TH status more susceptible to exogenous exposures than 

that of humans. 
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Developmental Immunotoxicity

Mouse

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 PFOS in 0.5% Tween-20 by gavage daily 

on gestation day (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 on the 

dams during the study and pups after delivery. Organ weights (spleen, liver, thymus and uterus) 

from the pups were recorded at sacrifice.

 

Natural killer (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 sheep red blood cell (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 evaluations observed, 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. 

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 orally by gavage from gestation day (GD) 0 through postnatal day 

(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, % gender differences, birth to PND 4 survival, PND 

4-21 survival, pup body weights through PND 72, and no gross internal findings were identified 

at necropsy. A statistically significant, but not toxicologically significant, decrease in mean 

maternal body weight and food consumption was observed in rats administered 1.0 mg/kg/day. 

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 (FOB) 

assessments performed on PND 4, 11, 21, 35, 45 and 60. Male offspring from dams 

administered 0.3 and 1.0 mg/kg/day had statistically significant (p< 0.05) increases in motor 
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activity on PND 17 but this was not observed on PND 13, 21 or 61. No effect on habituation 

was observed in the 0.3 mg/kg/day males but it was decreased at 1.0 mg/kg/day. This effect was 

not observed in the females. 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 with 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. 

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 (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. 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 when compared to PND 

0. 

Astrocyte activation markers, glial fibrillary acidic protein (GFAP) and S100 calcium 

binding protein B, which are associated with morphological changes inside the cell, were 

evaluated with immunohistochemistry. 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 (IL-1β) and tumor necrosis factor (TNF)-α. 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 in those administered ≥ 0.6 mg/kg and 

TNF-α only in the highest dosed 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 most increased effect was observed in the hippocampus on PND 0 with all 

treated offspring having a significant increase in activation protein-1 (AP-1) and increases in 

nuclear factor-ĸB (NF- ĸB) and cAMP response element-binding protein (CREB) observed in 

the ≥ 0.6 mg/kg groups. 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. 
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Mouse

Fuentes et al. (2007) treated 8-10 pregnant Charles River CD-1 mice/group to 0 or 6 

mg/kg 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 each time 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 to further assess development. The PFOS treatment had no effect on maternal body 

weight or food/water consumption. Pups from dams treated with 6 mg/kg of PFOS had reduced 

body weight on PND 4 and 8. Pups from dams exposed to 6 mg/kg of PFOS and having 

exposure to restraint exhibited reduced activity in the open-field. 

 

Ten-day old male neonatal 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 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). 

 

Johansson et al. (2009), administered a single oral dose of 0 (3 litters) or 11.3 (four 

litters) mg of PFOS/kg bw to NMRI male mice (10 days old). The exact number of male mice in 

each litter was not given. 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), growthassociated protein-43 (GAP-43), synaptophysin and tau, which are all proteins involved in 

neuronal survival, growth and synaptogenesis change during the ‘brain growth spurt’ (BGS). 

 

There were no acute toxic signs, and no treatment-related body weight differences. The 

CaMKII and GAP-43 protein levels were both increased in the PFOS treated males in the 

hippocampus; 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 
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hippocampus and (p< 0.01; ↑ 59%) in the cerebral cortex in the treated mice. The tau protein 

levels were increased significantly (p< 0.05; ↑ 80%) in the cerebral cortex only when compared 

to controls. Overall the study did support that the neuronal proteins were affected with just a 

one-time treatment with PFOS.

4.2.7 Chronic Toxicity 

Oral Exposure

Rat

 

A combined chronic toxicity/carcinogenicity GLP study was performed in compliance 

with Good Laboratory Practice (GLP) in 40-70 male and female Crl:CD (SD)IGS BR rats 

administered 0, 0.5, 2, 5 or 20 ppm of PFOS in the diet for 104 weeks (Thomford, 2002). 

Interim sacrifice results after 14 weeks (Seacat et al., 2002) were described in Section 4.2.3. 

Doses were equivalent to approximately 0, 0.018, 0.072, 0.184 and 0.765 mg/kg/day, 

respectively, for males and 0, 0.023, 0.099, 0.247, and 1.10 mg/kg/day, respectively, for females. 

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

death. Five animals/sex in the treated groups were sacrificed during weeks 4, 14 and 53 and 

liver samples were obtained for mitochondrial activity, hepatocellular proliferation rate, and 

determination of palmitoyl-CoA oxidase activity. Liver weight was recorded only at weeks 14 

and 53. The results from the 4-week and 14 week sacrifices are provided in Section 4.2.2 and 

7.2.3 respectively. Serum and liver samples were obtained during and at the end of the study for 

determination of PFOS concentration. 

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 weeks 14 and 53 sacrifice, 

absolute and relative (to body weight) liver weights were significantly increased at 20 ppm in 

males and relative (to body weight) liver weight was increased at 20 ppm in females. At week 

53, organ weight data were given only for the control and 20 ppm groups such that a doseresponse could not be evaluated. 

 Nonneoplastic lesions in the liver are shown in Table 4-10. 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 and centrilobular hepatocytic 

vacuolation. The LOAEL for male rats was 2 ppm (0.072 mg/kg) and for female rats was 5 ppm 

(0.247 mg/kg) based on the liver histopathology. The NOAEL for the males was 0.5 ppm (0.018 

mg/kg) and 2 ppm (0.099 mg/kg) for females. No effects with treatment were observed on 

hepatic palmitoyl-CoA oxidase activity or increases in proliferative cell nuclear antigen (PCNA) 

at weeks 4 and 14 or bromodeoxyuridine (BrdU) 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. Additional details from the study in regard to carcinogenicity are under Section 4.2.8 

Carcinogenicity. 
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TABLE 4-10. Incidence of nonneoplastic liver lesions in rats

(number affected/total number)

Lesion 0 ppm 0.5 ppm 2.0 ppm 5.0 ppm 20 ppm

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

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*

Data from Thomford, 2002

Significantly increased over control: *p<0.05; **p<0.01.

4.2.8 Carcinogenicity 

Oral Exposure 

Rat

 As described above in Section 4.2.7, a combined chronic toxicity/carcinogenicity GLP 

study was performed in which 40-70 male and female Crl:CD (SD)IGS BR rats were 

administered 0, 0.5, 2, 5 or 20 ppm PFOS in the diet for 104 weeks (Thomford, 2002). Doses 

were equivalent to approximately 0, 0.018, 0.072, 0.184 and 0.765 mg/kg/day, respectively, for 

males and 0, 0.023, 0.099, 0.247, and 1.10 mg/kg/day, respectively, for females. A recovery 

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

Five animals/sex in the treated groups were sacrificed during weeks 4, 14 and 53, and liver 

samples were obtained for mitochondrial activity, hepatocellular proliferation rate and 

determination of palmitoyl-CoA oxidase activity. Serum and liver samples were obtained during 

and at the end of the study to determine the concentration of PFOS in them. 

Tumor incidence from the study is included in Table 4-11. 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<0.05) in the high-dose group (7/60, 11.7%) over the 

control (0/60, 0%). A significantly increased incidence was observed for thyroid follicular cell 

adenoma in the high-dose recovery group (9/39, 23.1%) compared to the control group (3/60, 

5%). There was also a significant increase in the combined thyroid follicular cell adenoma and 

carcinoma in the high-dose males (10/39, 25.6%) compared to that of the control group (6/60, 

10%). 
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TABLE 4-11. Tumor Incidence (%)a

Tumors 0 ppm 0.5 ppm 2 ppm 5 ppm 20 ppm 20 ppm

recovery

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

follicular cell

carcinoma

combined

5.0 (3/60)

5.0 (3/60)

10.0 (6/60)

10.2 (5/49)

2.0 (1/49)

12.2 (6/49)

8.0 (4/50)

2.0 (1/50)

10.0 (5/50)

8.2 (4/49)

4.1 (2/49)

10.2 (5/49)

6.8 (4/59)

1.7 (1/59) 

8.5 (5/59)

23.1** (9/39)

2.6 (1/39)

25.6 (10/39)

FEMALES

Liver

hepatocellular 

adenoma+ 

hepatocellular 

carcinoma

combined+ 

0 (0/60)

0 (0/60)

0 (0/60)

2.0(1/50)

0 (0/50)

2.0 (1/50)

2.0 (1/49)

0 (0/49)

2.0 (1/49)

2.0 (1/50)

0 (0/50)

2.0 (1/50)

8.3** (5/60)

1.7 (1/60)

10.0** (6/60)

5.0 (2/40)

0 (0/40)

5.0 (2/40)

Thyroid

follicular cell 

adenoma

follicular cell

carcinoma

combined

0 (0/60)

0(0/60)

0(0/60)

0 (0/50)

0 (0/50)

0 (0/50)

0 (0/49)

0 (0/49)

0 (0/49)

4.0 (2/50)

2.0 (1/50)

6.0* (3/50)

1.7(1/60)

0 (0/60)

1.7 (1/60)

2.5 (1/40)

0 (0/40)

2.5 (1/40)

Mammary

Fibroma/

adenoma 

carcinoma

combined

38.3 (23/60)

18.3 (11/60)

48.3 (29/60)

60.0** (30/50)

24.0 (12/50)

72.0* (36/50)

45.8 (22/48)

31.2 (15/48)

64.6** (31/48)

52.04 (26/50) 

22.0 (11/50)

58.0 (29/50)

25 (15/60)

23.3 (14/60)

40 (24/60)

40 (16/40)

10 (4/40) 

42.5 (17/40) a

Data from Thomford, 2002.

+

Significant positive trend.

Significantly increased over the control: *p < 0.05; **p < 0.01.

In the 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 the terminal sacrifice. These cases were associated with significant increases in 

the high-dose group (5/60, 8.3%, and 6/60, 10%) compared to the control (0/60, 0%). A 

significant increase (P=0.0471) for combined thyroid follicular cell adenoma and carcinoma was 

observed in the mid-high (5.0 ppm) group (3/50, 6%) compared to the control group (0/60, 0%). 

Significant increases in mammary fibroadenoma/adenoma (30/50, 60%) and combined 

mammary fibroadenoma/adenoma and carcinoma (36/50, 72%) were observed in the low–dose 

(0.5 ppm) group compared to the respective controls (23/60, 38.3%; and 29/60, 48.3%). In 

addition, the mid-high (5.0 ppm) group (31/48, 64.6%) exhibited a marginally significant 
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(P=0.066) increase in the incidence of combined mammary fibroadenoma/adenoma/carcinoma 

over the control group (29/36, 48.3%). 

 

Because the tumor incidence does not indicate a dose response, the evidence of 

carcinogenicity is suggestive but not definitive. 

4.3 Other Key Data 

4.3.1 Mutagenicity and Genotoxicity 

Results of genotoxicity testing with PFOS are given in Tables 4-12 and 4-13. PFOS was

tested for mutation inductions 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), an in vitro assay for chromosomal aberrations in human whole blood 

lymphocytes with and without metabolic activation (Murli, 1999) and 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 if 

induction of gene mutation in 5 strains of S. typhimurium and in S. cerevisiae strain D3 would 

take place with and without metabolic activation (Simmon, 1978). The results were negative. 

Overall, PFOS does not appear to be mutagenic.

TABLE 4-12. 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 rat

DNA synthesis negative Cifone, 1999

TABLE 4-13. 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
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4.3.2 Immunotoxicity 

Human- in vitro

Eleven volunteers donated blood and peripheral blood mononuclear cells (PBMCs) were 

isolated (Brieger et al., 2011). The PBMCs were incubated for 24, 48, or 72 hours and a human 

promyelocytic leukemia cell line (HL-60) was incubated for 24 hours in normal culture medium 

containing PFOS at the following concentrations: 3.9, 7.8, 15.6, 31.3, 62.5 and 125 μg/mL. 

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. The impact of PFOS on TNF-α and IL-6 release was also 

determined in whole blood. PFOS reduced the release of the pro-inflammatory cytokine TNF-α 

after lipopolysaccharide (LPS) stimulation. Natural killer cell activity was examined by culturing 

PBMCs for 24 hours in the presence of 0, 1, 10 or 100 μg/mL of PFOS with labeled K562 target 

cells (labeled with 6-carboxyfluorecein succinimidyl ester [CFSE] diacetate). PFOS decreased 

NK-cell-mediated killing of K562 cells, reducing NK-cell cytotoxicity by 32%, and was 

statistically significant at 100 μg/mL. This study suggests some effects on immunity in humans; 

however the sample size used is small and the dose in which effects were observed are much 

higher than that typically observed in humans. 

Mouse

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 

doses to the animals 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, natural killer cell activity, lysozyme activity, antigen 

specific IgM production, lymphocyte immunophenotypes, as well as serum PFOS concentrations 

were determined after exposure. 

The following were not affected with treatment: survival; behavior; body weight; spleen, 

thymus, kidney, gonad and liver weights; and lymphocytic proliferation. Lysozyme activity was 

not affected in males but increased significantly in females at 0.0033 and 0.166 mg/kg/day 

compared to the control group; however, this did not follow a dose response. Natural killer 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 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. 

The sheep red blood cell (SRBC) plaque-forming cell response (IgM production) 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%. 

Because IgM suppression can result from effects on both T- and B-cells, a T-cell independent 

test was performed after the SRBC (T-cell dependent) test and it indicated suppression. An 

additional group of female mice was treated with 0 or 0.334 mg/kg/day of PFOS orally for 21 
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days and challenged with a TI antigen [a trinitrophenyl (TNP) lipopolysaccharide (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. 

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 four to six male (six to eight week old) C57Bl/6 mice/group. The 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 ten 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 also measured and 

checked for viability. Histology was also performed on the thymus and spleen. 

 

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 as it was observed when PFOS was 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) as well as having thymocytes and splenocytes 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. 

In this same study, work was done to determine the role of PPARα which will be discussed in 

Section 4.3.4. Briefly, results of that part of the study indicated that the immunomodulation was 

partially dependent on PPARα. 

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 exposure to the chemicals influenced innate immune 

responses to bacterial lipopolysaccharide (LPS). In this study, mice were exposed as described 

and then on day 10, some mice were injected intravenously with 0.1 mL sterile saline containing 

300 μg LPS (Escherichia coli), while others received the 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 
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administration of LPS. The spleen, thymus, epididymal fat and liver were collected as well as 

peritoneal and bone marrow cells. 

 

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 and the total 

concentration of PFOS in the serum was 340 ± 16 μg/mL (ppm). In the first study of the innate 

immune system, the overall total number of white blood cells and lymphocytes were decreased; 

however, neutrophil counts were similar to controls. The number of macrophages in the bone 

marrow was increased but the peritoneal and splenic macrophages were not. The second study 

also found that 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, TNFα 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 an effect on the immunotoxicity of mice. 

 

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 wks 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 killed. The blood was analyzed for corticosterone and PFOS 

concentration. Spleen, thymus, liver and kidneys were collected, weighed and the spleen and 

thymus were processed into suspensions to look at functional immune endpoints and T-cell 

immunophenotype determinations. 

At 20 and 40 mg/kg bw/day starting about day 3, mean body weights were significantly 

decreased compared to the controls. Food consumption decreased with treatment; food 

consumption in the control animals on study day 0 was 5.9 ± 0.2 g and was similar during the 

study. In the mice treated with 20 and 40 mg/kg bw/day, day one values were 5.8 ± 0.3g and 5.9 

± 0.2 g and dropped to 2.8 ± 0.1 g and 1.6 ± 0.1 g on day 7, respectively. 

 

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 and the liver weight increased by 34, 79 

and 117% over controls at 5, 20 and 40 mg/kg bw/day, respectively. A dose-dependent increase 

in PFOS was observed in the serum samples with no PFOS identified in the control mice; serum 

corticosterone levels increased significantly in the mice treated with doses ≥ 20 mg/kg/day. 

Splenic and thymic cellularity was 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 were 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 (LDH) release 

assay was performed to determine natural killer (NK) cell activity and this was decreased 

significantly in the two highest dosed groups. The average NK-cell activity in control mice was 

50.33 ± 4.08 with the activity at 20 mg/kg/day being 18.04 ± 1.42 and at 40 mg/kg/day, 13.08 ± 

1.11. Finally, treatment in all groups of mice resulted in a significant suppression of the plaqueforming cell response after 7 days of treatment; results were 63, 77 and 86% that of controls at 5, 
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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 bw/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 PFOS delivered in de-ionized water with 2% Tween 80 daily by 

gavage for 60 days to doses of 0, 0.008, 0.083, 0.417, 0.833 and 2.083 mg/kg/day (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 treated mice starting at 0.083 mg/kg/day. The 

mean liver weight in control mice was 5.17 ± 0.12 g and the liver weights in the treated mice 

were 5.21 ± 0.17 g (0.0.008 mg/kg/day), 5.78 ± 0.13 g (0.083 mg/kg/day), 6.67 ± 0.11 g (0.417 

mg/kg/day), 8.17 ± 0.21 g (0.833 mg/kg/day) and 11.47 ± 0.12 g (2.083 mg/kg/day). Serum 

corticosterone was similar to that in controls in the mice receiving 0.008, 0.083 or 0.417 mg 

PFOS/kg/day but was decreased in those 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 PFOS/kg/day (45.43 ± 4.74%) with marked decreases at 0.833 mg/kg/day (20.28 ± 

2.51%) and 2.083 mg/kg/day (15.67 ± 1.52%). 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. 

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 [PBS]) 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. 

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 (Qazi et al., 

2010). Control mice were also used. 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 although necrosis was not observed. Total serum cholesterol was also 

decreased and there was a moderate increase in serum alkaline phosphatase (ALP). At the end of 

the study, the total mean serum PFOS concentration for four mice was 125.8 μg/mL. The livers 

of the treated mice also displayed hypertrophic hepatocytes surrounding the central vein. PFOS 
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only increased one type of intrahepatic immune cells (TER119+) while a corresponding test with 

0.002% PFOA increased all types of intrahepatic immune cells. PFOS treated mice, however, 

had normal responses in the intrahepatic B and T cells by producing enough IgM. 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. 

4.3.3 Physiological or Mechanistic Studies 

4.3.3.1 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 (~↓47- 80%) and free T4 (~↓60-82%). The total T3 was only significantly deceased 

after day 5 (↓~ 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 was 

matched to hepatomegaly and hepatocellular hypertrophy. Genes associated with the thyroid 

hormone release and synthesis pathway including Dio3, which catalyzes the inactivation of T3 

and 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) tried to determine if the decrease of free thyroxine (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 μM 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 EDRIA. 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. 

 

Chang et al. (2008) also used a study on thyroid hormone status to determine if exposure 

to PFOS in rats caused a competition with thyroxine for serum binding proteins. Three different 

experimental designs were employed in this three-part study. 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 obtained. The 

following thyroid parameters were measured: serum fT4, total thyroxine (TT4), triiodothyronine 

(TT3), reverse triiodothyronine (rT3), and thyrotropin (TSH; measured at the 6 and 24 hour 

timepoints only). PFOS concentrations in the blood and liver were also measured and the 

following hepatic biochemical markers were measured: UDP-glucuronosyltransferase 1A 
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[UGT1A] family of mRNA transcripts (involved in glucuronidation and T4 turnover), malic 

enzyme [ME] mRNA transcripts and ME activity (indicators of tissue response to thyroid 

hormone). 

 Serum TT4 decreased significantly (p<0.05) compared to controls after 2 hours (↓24%), 6 

hours (↓38%) and 24 hours (↓53%). The TT3 and rT3 only decreased significantly at the 24 

hours 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 but 

were the highest at 6 hours. A similar trend was observed with the concentration of PFOS in the 

liver except the values were slightly less and continued to increase through the 24 hour timepoint. 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 although 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 does not 

induce a typical hypothyroid state or alter the hypothalamic-pituitary-thyroid axis. 

In the study by Curren et al. (2008; Section 4.2.2) where Sprague-Dawley 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. 
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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 if 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), free thyroxine (fT4), total triiodothyronine (T3) 

and thyrotropin (TSH) as well as liver and thyroid organ weights obtained. Also measured were 

messenger RNA (mRNA) levels for two isoforms of uridine diphosphoglucuronosyl transferase 

(UGT1A6 and UGT1A1) and type 1 deiodinase (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 wt) 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 4-14 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 4-24. 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

Data from Table 3 in Yu et al. 2009b 

*statistically significant at p< 0.05 or **p< 0.01

LOQ = limit of quantification

 Hepatic UGT1A6 was not affected with treatment, but hepatic UGT1A1 mRNA 

expression was up-regulated 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. 

 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), total T3 (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, Yu et al. also found that OATp2 
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was increased significantly (143% compared to controls) in rats at 3.0 mg/kg indicating that this 

may be involved in hepatic T4 uptake and could be one reason the serum TT4 was decreased. 

This could also possibly be causing the TT3 decrease. Relative liver weight, 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. 

PPAR activity

Studies have been conducted with PFOS in order to determine if it activates peroxisome 

proliferator-activated receptors (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 if 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 100 μM 

were tested. The COS-1 cells were transfected with either 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 

coinfected 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 4-6-fold and was similar to that obtained with the positive 

control. The average EC50 was 13 μM in the mouse and 15 μM in the human PPARα. 

Both PFOS and PFOA were tested to determine whether they could activate peroxisome 

proliferator-activated receptors (PPARs) with 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 μM), 

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-14643 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. The agonist used for mouse and human PPARα 

was WY-14,643 and it exhibited 15- and one-fold increase, respectively over the luciferase 

response of the negative controls. The agonist for mouse and human PPARβ/δ, L165,041, 

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. 
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In this study, PFOS activated the mouse PPARα with a significant (p< 0.01) 1.5-fold 

increase in activity at 120 μM 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 4-15 shows summary data. The authors concluded that PFOA activated PPARα 

more than PFOS and 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.

TABLE 4-35. Summary of PFAA Transactivation of Mouse and Human PPARα, β/δ and γa

PPAR isoform PFAA Mouse LOECb Human LOECb

α PFOA

PFOS

10 μM

120 μM

30 μM

NA

β/δ PFOA

PFOS

40 μM

20 μM

NA

NA

γ PFOA

PFOS

NA

NA

NA

NA a Data from Table 1 in Takacs and Abbott, 2007

b LOEC = lowest concentration (μM) at which there was a significant difference compared to the negative control (p< 0.05)

Wolf et al. (2008) tested PFAAs, including PFOS, to determine if 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% dimethyl sulfoxide [DMSO]), 

a positive control (WY14,643) or PFOS at 1-250 μM. At the end of 24-hours of exposure, the 

luciferase activity was measured. The positive and negative controls had the expected results. A 

lowest observed effect concentration (LOEC) and no observed effect concentration (NOEC) was 

determined. In the study, the mouse PPARα was more responsive than the human. The NOEC 

for PFOS was 60 μM in the mouse and 20 μM in humans; the LOEC was 90 μM (48.4 μg/mL) 

in the mouse and 30 μM (16.2 μg/mL) in humans. 

In a study similar to that above but including additional PFAAs, Wolf et al. (2012) 

incubated transfected cells with PFAAs at concentrations of 0.5 to 100 μM, vehicle (water or 

0.1% DMSO as negative control) or with 10 μM WY14,643 (positive control). Assays were 

performed with 3 identical plates per compound per species with 9 concentrations/plate and 8 

wells/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 PFAAs 

significantly induced human and mouse PPARα. The study also provided the C20max which was 

the concentration at which a PFAA produced 20% of the maximal response elicited by the most 

active PFAA. For PFOS, this was 94 μM in mouse PPARα and 262 μM in human PPARα. For 

comparison, PFOA was 6 μM and 7 μM, respectively. 

 

Ishibashi et al. (2011) assessed the transactivation potencies of the Baikal seal 

peroxisome proliferator-activated receptor α (BS PPARα) with various PFCs using an in vitro

reporter gene assay. They tested eight perfluoroalkyl carboxylates and two perfluoroalkyl 

sulfonates, including PFOS. As found in the two Wolf studies above, the authors found that the 

number of perfluorinated carbons was one of the factors determining the transactivation 

potencies of the BS PPARα, and the carboxylates were more potent than the sulfonates with the 
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same carbon numbers. The transactivation potencies were measured between the compounds by 

estimating the PFOA induction equivalency factor (IEF) which was the ratio of the 50% effective 

concentration of PFOA to the concentration of each compound that can induce the response 

corresponding to 50% of the maximal effect of PFOA. The IEF would then be 1 and efficacy (% 

of PFOA) would be 100%. For PFOS, the IEF was 0.26 and the efficacy was 45%. 

 

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 one, three or five 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. In gene expression, 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 type 1 

iodothyronine deiodinase (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 CAR.

Wang et al. (2010) dosed albino Wistar female rats in the feed with 3.2 mg/kg of PFOS 

from gestation day (GD) 1 to weaning (postnatal day [PND] 21). Pups were allowed access to 

the treated feed until PND 35. Pups on PND 2 were divided into groups: 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 and pups born to treated dams fostered by other 

treated dams. This was done to determine if prenatal or lactational exposure had more effect on 

altering gene expression. 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 proliferatoractivated 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, Wy14,648 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 Wy14,648 or 500 ppm PB in the diet 
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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 Wy14,643 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. 

Mice

To assess PPAR involvement in developmental effects of PFOS, male and female 

129S1/Svlm wild type (WT) 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 WT 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 postnatal day (PND) 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.

Maternal body weight, maternal body weight gain, and reproductive parameters measured 

included 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 WT mice. PFOS exposure had no effect on absolute or relative (to 

body weight) liver weight in any of the dams. PFOS exposure at 10.5 mg/kg/day caused a 

significant increase in relative liver weight (sexes were combined) in both strains of pups. 

Survival of the pups was affected with treatment. Most post-natal deaths occurred between 

PNDs 1 and 2. Survival of the WT 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 WT and KO pups. On PND 13, open 

eyes were reported in 44% of the control pups and none in the 8.5 mg/kg/day WT group. In the 

KO mice, open eyes were reported in 23% of the 10.5 mg/kg pups on PND 14 and 59% of the 

controls. 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 WT 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 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 from 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 2 more fetuses/litter for histological examination. 
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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. A 

transcriptional response occurred but it was not as prolific as it had been in an earlier PFOA 

study. At 5 mg/kg/day, PFOS had 753 fully annotated genes in the fetal liver. PFOS upregulated a number of markers for PPARα activity in the fetal liver. In the fetal lungs, regulation 

only occurred in a limited group of genes including: Cyp4a14, enoyl-Coenzyme A hydratase 

(Ehhadh) and fatty acid binding protein 1 (Fabp1). The pathways or functional groups 

significantly enriched by PFOS included: fatty acid metabolism in the fetal liver and lung, 

xenobiotic metabolism, peroxisome biogenesis, cholesterol biosynthesis, bile acid biosynthesis 

and metabolism of glucose and glycogen. Overall, there was little difference in the 

transcriptional changes made by PFOS when compared to the changes activated by PFOA except 

for the up-regulation of Cyp3a11 and Cyp3a25 occurring in PFOS treated fetal livers. 

Taken together, these studies suggest PPARα-independent mechanism for PFOS-induced 

neonatal mortality. While transcription changes induced by PFOS in the fetal mouse liver and 

lung were related to activation of PPARα and were similar to profiles induced by PFOA (Rosen 

et al., 2009), neonatal mortality occurs in PPARα-null mice treated with PFOS but not with 

PFOA (Abbott et al., 2009). Thus neonatal toxicity observed with maternal PFOS administration 

may not be a result of the transcriptional alterations. 

Treatment of mice at a dietary level of 0.05% (500 ppm) PFOS for 5 days caused 

increases in relative liver weight and activities of palmitoyl-CoA oxidase, catalase and other 

peroxisomal enzymes (Sohlenius et al., 1993). Induction of peroxisome proliferation and 

peroxisomal enzyme activities in the liver were also found in rats exposed to 0.02% (200 ppm) 

PFOS in the diet for 2 weeks (Ikeda et al., 1987). 

 

Qazi et al. (2009a) tested the effects of 0, 0.005% or 0.02% PFOS on wild-type and 

PPARα-null 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 wildtype and null mice; the thymus and epididymal fat pad were both decreased in the wild-type mice 

only. The wild-type mice administered 0.02% PFOS in the diet had a pronounced decrease in 

the total number of thymocytes and splenocytes as well as a decrease in the size of the ones 

present. In the knock-out mice, there was a reduction in the total number of thymocytes and 

subpopulations that 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. 

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 seven 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 between the dose groups. This finding suggests robust PPARαindependent effects in null mice.
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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 4-1). Unique in null mice, PFOS up-regulated 

Cyp7a1, an important gene related to bile acid/cholesterol homeostasis.

Figure 4-1. Functional categories of genes modified by PFOS in wild type and null mice.

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 i.p. injection for 7 days. Twenty-four hours after the last dose, the animals were 
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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 1502 unique proteins; 71 showed a greater than 1.5-fold change in expression. 

Sixty-two proteins showed increased expression and 9 showed decreased expression. Figure 4-2 

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 4-2 shows that the majority of 

enriched proteins were involved with lipid metabolism, transport, biosynthetic processes,

catabolic processes, and carbohydrate metabolic processes.
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Figure 4-2. Function distribution and category enrichment analysis of the differential 

proteins.

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.

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), quantitative reverse transcription 

polymerase chain reaction (RT-PCR) to obtain mRNA transcript data for the control and 1.0 

mg/kg/day dose groups were recorded on GD 20 in the dams and fetuses and PND 21 in the male 

pups. Results for this part of the study were reported by Chang et al. (2009). Statistically 

significant changes included: Cyp2b2 levels in dams and male pups were higher (↑ 2.8-fold and 

1.8-fold, respectively) than controls on GD 20 and PND 21; mean acyl CoA (ACoA) and 

Cyp4a1 levels in male pups were greater (↑ 1.5-fold and 2.1-fold, respectively) than those of 

controls and the mean Cyp7a1 was lower (↓ 3.5-fold) than those of controls. This suggests 

induction of PPARα as well as hepatic constitutive androstane receptor (CAR). Transcripts 

possibly related to thyroid status were all similar between the treated dams and pups and the 

controls.
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Oxidative Damage 

Liu et al. (2009) conducted a study in which 3-6 male and female KD mice/group were 

administered one subcutaneous injection of 0 or 50 mg PFOS/kg bw on postnatal days (PNDs) 7, 

14, 21, 28 or 35. The study was done in an attempt to determine the effects of treatment on the 

oxidation-antioxidation system by measuring maleic dialdehyde (MDA) content, superoxide 

dismutase (SOD) activity and total antioxidation capability (T-AOC). Animals were killed 24 

hours post-treatment, and blood was collected as well as liver and brain removed and weighed. 

No treatment-related effects were observed on body weight. Relative (to body weight) 

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 (↓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 (↓15%). Male liver T-AOC was decreased 

significantly at PND 7 (↓25%) and 14 (↓27%). Female brain T-AOC had no significant 

differences from controls and the liver T-AOC was decreased only at PND 21 (↓15%). The 

study also demonstrated that distribution increased in the liver and lessened in the blood and 

brain with post natal 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. 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. 

Gap Junctional Intercellular Communication (GJIC) 

Gap junctions are found in the cell plasma membrane and formed by proteins that 

connect and 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 if 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), a dolphin kidney epithelial cell line (CDK) as 

well as exposing Sprague-Dawley rats orally to PFOS for 3 days and 3 weeks. GJIC effects were 

measured using the scrape loading dye technique. The in vitro cell lines were exposed to PFOS 

at concentrations of 0, 3.1, 6.25, 12.5, 50, 100 or 160 μM for 30 minutes. PFOS inhibited GJIC 

rapidly in a dose-dependent method starting at 12.5 μM, but it was reversible once exposure 

ended. Four to six 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 without an increase in magnitude of the inhibition. No 

differences were observed between the male and female rats. 
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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. 

4.3.4 Structure-Activity Relationship 

In vitro

 

Bjork and Wallace (2009) performed a study to see if 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 μM PFAAs for 24 hours 

to determine the structure-activity relationships across various chain lengths. The concentration 

was the maximum concentration not causing cell injury in any of the cell lines. The PFAAs 

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 PFAAs 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 PFAAs in HepG2/C3A cells. 

However, this gene expression was stimulated by PFAA 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 PFAAs 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 PFAAs 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 also 

was not any 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. 

4.4 Hazard Characterization 

Human information from biomonitoring as well as more long-term epidemiology studies 

is available, however, the actual dose of exposure is not known. Controlled dosing studies are 

available in a variety of species including monkey, rats, rabbits, and mice. The main toxicity 

endpoints observed are discussed below for both humans and animals with some possible known 

or speculated modes of action provided. 
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4.4.1 Synthesis and Evaluation of Major Noncancer Effects 

Liver Effects, Cholesterol and Uric Acid

Human

Few studies are available where the effects of PFOS in the liver of humans were 

examined. Olsen et al. (2003) sampled liver tissue and serum from cadavers and found 

correlation between the samples; Kärrman et al. (2010) also identified PFOS in human hepatic 

tissue in twelve subjects. Biomonitoring studies performed at the 3M Decatur, Alabama plant 

(Olsen et al., 1999; Olsen et al., 2001b, 2001c) identified occasional differences in hepatic 

clinical chemistry values but there were no reported increases in hepatic disease and or hepatic 

carcinogenicity associated with them.

 

 Several studies examining potential associations between PFOS exposures and 

cholesterol and other lipid measurements are available. Occupational studies did not reveal 

consistent associations between PFOS and cholesterol and triglycerides in either cross-sectional 

surveys or in a longitudinal analysis (Olsen et al., 1999; Olsen et al., 2001b, 2001c). However, 

community studies and an analysis of NHANES data have shown positive relationships of PFOS 

with total cholesterol (Steenland et al., 2009; Nelson et al., 2010; Lin et al., 2009), LDL, and 

triglycerides (Steenland et al., 2009). A statistically significant positive association was also 

reported in a community study between PFOS and uric acid levels (Steenland et al., 2010). 

Elevated uric acid is a risk factor for hypertension and may be an independent risk factor for 

stroke, diabetes, and metabolic syndrome. 

Animal

 

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 (Goldenthal et al., 1978a; Seacat et al., 2002; Thomford, 2002; Curran et al., 2008; 

Liu et al., 2009). Chang et al. (2009) also identified PFOS levels in the liver of offspring as early 

as GD 20 and Stein et al. (2012) measured PFOS in 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). As part of a chronic bioassay, rats were administered PFOS in the diet for up 

to 104 weeks (Thomford, 2002). Liver weight was increased in males and females at the highest 

dietary concentration after both 14 and 53 weeks. Liver weight data were not collected at the 

104 week sacrifice. 

Histopathological 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 0.072-0.247 

mg/kg/day after 104 weeks (Thomford, 2002), 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. In these studies, no evidence of peroxisome 

proliferation was found in either species. 
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Rat and monkey studies demonstrated a decrease in cholesterol levels and high density 

lipoprotein cholesterol at 0.75 mg/kg/day when compared to the controls. Serum concentrations 

increased during recovery. Male rats had decreased serum cholesterol at 14-weeks at a dose of 

about 1.4 mg/kg/day. Increased hepatic lipid content in the absence of a strong PPAR-α 

response is a characteristic of exposure to PFOS. 

As discussed above in Section 4.3.3.1, mice administered PFOS showed differential 

expression of proteins mainly involved in lipid metabolism, transport, biosynthetic processes, 

and response to stimulus (Tan et al., 2012) 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 Bijand et al. (2011) as described below. In 

addition, the nuclear hormone receptors CAR and PXR have been shown to be activated in mice 

(Bijand 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, Bijand 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 4.2.2. 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; plus VLDL synthesis and 

secretion. Genes involved with HDL synthesis, maturation and clearance plus bile acid 

formation were down regulated. 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.

 

Developmental/Reproductive Toxicity

Human

Studies evaluating the reproductive and developmental health in humans exposed to 

PFOS have been performed in both occupational settings (Grice et al., 2007) and in the general 

population (Inoue et al., 2004; Apelberg et al., 2007; Fei et al., 2007, 2008a, 2008b, 2010a and 

2010b; Monroy et al., 2008; Washino et al., 2009). No adverse correlations were found in the 

occupational workers with birth outcome. In general population studies, the most frequent 

associations were those for lower birth weight but this was not a consistent finding in all of the 

studies. PFOS has been detected in human amniotic fluid samples indicating that the chemical 

crosses the placenta. The median ratio of maternal serum:amniotic fluid concentration was 
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25.5:1 and PFOS was rarely detected in amniotic fluid until the serum concentration reached at 

least 5.5 ng/mL (Stein et al., 2012). 

Animal

Increased pup mortality was observed when rat dams were treated only during gestation 

as part of developmental toxicity studies (Chen et al., 2012; Thibodeaux, 2003; Lau 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; Thibodeaux et al., 2003; Lau 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,b). 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 was 0.1 mg/kg/day in the two-generation study (Luebker et al., 2005b); this dose was not 

tested in the one-generation study (Leubker et al., 2005a) where the LOAEL was 0.8 mg/kg/day 

for decreased pup survival, decreased maternal body weight and decreased gestation length. A 

0.4 mg/kg/day dose was a NOAEL in the one generation and LOAEL for decreased body weight 

gain in the two 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 four-day period during various stages of pregnancy. Mortality was highest 

when treatment occurred on gestation days (GD) 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 

GD 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-treated 

newborn pups, suggesting that lung maturation and pulmonary surfactant interactions are 

potential modes of action (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, b). 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 
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chain fatty acids and may be responsible for interfering with the normal physiological function of 

pulmonary surfactant. 

Immunotoxicity

Human

Limited data, which focus on infants and children, are inconclusive on the potential 

immunotoxicity from PFOS exposure to humans. No significant associations were observed 

between maternal PFOS levels and cord blood IgE levels or incidence of food allergy, eczema, 

wheezing, or otitis media in infants at 18 months of age (Okada et al., 2012). In another study, 

maternal serum PFOS concentration, measured at week 32 of pregnancy, was negatively 

associated with anitdiphtheria antibody concentration in their children at 5 years of age. The 

odds ratio was increased for a 5-year old child to have inadequate antibody concentrations to 

diphtheria when compared to both maternal PFOS and the child’s age 5 PFOS serum 

concentrations. At age 7, lower antibody concentrations to diphtheria and tetanus were 

correlated with higher serum PFOS levels at age 5 (Grandjean et al., 2012). 

Animal

Peden-Adams et al. (2008) and Dong et al. (2009) both identified immunotoxicity in male 

mice following exposure to 0.0017 mg/kg and 0.083 mg/kg, respectively. In the Peden-Adams 

study, IgM suppression occurred after 28 days of treatment 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. 

In the Dong et al. study, there was an increase in splenic natural killer (NK) cell activity after 60 

days, when PFOS serum concentrations were approximately 7.1 mg/L. Gurunge et al. (2009) 

found a decrease in survival in mice exposed to 0.025 mg/kg of PFOS after exposure to influenza 

A virus. Inbred B6C3F1 male mice offspring had a decrease in NK cell activity starting at 1 

mg/kg/day after 8 weeks of treatment. 

 

Qazi et al. (2009a) reported that 0.02% PFOS in the diet for 10 days in wild-type 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 the size of the ones present in wild-type 

mice. Knock-out mice had a reduction in the total number of thymocytes that 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 but are a 

topic of investigation. 

Neurotoxicity 

Human

No epidemiology studies of neurotoxicity as associated with PFOS exposure were identified. 
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Animal 

In animals 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). 

Butenhoff et al. (2009) and Wang et al. (2010) both looked for developmental neurotoxicity 

effects in Sprague-Dawley and Wistar rats, respectively. Butenhoff found significant increases 

in motor activity of male offspring at one time point (PND 17) and decreased habituation in the 

1.0 mg/kg/day males. Wang 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. Transthyretin (CSF carrier of T4) was also decreased. 

Zeng et al. (2011) also found PFOS administered to pregnant rats as low as 0.1 mg/kg from 

gestation day 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 PFOS (Johansson et al., 2008) displayed abnormal habituation 

responses in motor activity testing. 

Thyroid Effects

Human

Several epidemiological studies included the evaluations of circulating thyroid hormones. 

Olsen et al. (2003) reported no significant associations of TSH, TT4 and fT4 with serum PFOS 

among production workers although a positive association with T3 was apparent. PFOS was 

detected in maternal and cord blood samples in a susceptible population in Japan with no 

significant correlations between PFOS concentration and TSH or fT4 (Inoue et al., 2004). Pirali 

et al. (2009) found no relationship between intrathyroidal concentrations of PFOS and 

underlying thyroid diseases in patients. Dallaire et al. (2009b) examined a population of 

Canadian Inuit adults and noted that PFOS at mean plasma levels of 18.3 ng/mL was negatively 

associated with TSH, T3 or thyroid binding protein (TBG), but positively associated with fT4. 

The findings of Bloom et al. (2010) in a non-occupational cohort in the U.S. with mean serum 

PFOS concentrations of 19.6 ng/mL were similar. 

 

Melzer et al. (2010) examined NHANES records for thyroid disease and serum PFOS 

levels in the U.S. general population. The only significant association was for men with thyroid 

disease with PFOS levels ≥ 36.8 ng/mL compared to men with PFOS levels ≤ 25.5 ng/mL 

Animal 

Several animal models have described changes in thyroid hormone levels after 

administration of PFOS. 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 a dose-response was not 

observed and no evidence of hypothyroidism was seen. Thyroid-stimulating hormone (TSH) 

levels were variable during the study, but increased two-fold in the high-dose group at the end of 

exposure. PFOS-induced alterations of thyroid hormones were also seen in the adult rat models 

(Thibodeaux et al., 2003; Martin et al., 2007; Yu et al., 2009b; Yu et al., 2011); however, in 
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contrast to the monkey model, most reductions involved circulating TT4, instead of T3. In all 

animal studies, the changes in T3 and rT4 failed to activate the hypothalamic-pituitary-thyroid 

(HPT) feedback mechanism to produce significant elevations of serum TSH.

Typically in pregnancy, serum rT4 will decrease by 70% while TSH will increase 3-fold. 

Exposure of pregnant rats to PFOS exacerbated both of these hormonal reactions without further 

elevating the levels of TSH (Thibodeaux et al., 2003). The effective dose of PFOS on TT4 was 1 

mg/kg/day, which corresponded to maternal serum concentrations of 14-26 μg/mL. A similar 

effect of PFOS on serum TT4 was also seen in the pregnant mouse model, although this rodent 

species appears to be much less sensitive than the rat, with significant changes noted only at the 

high dose (20 mg/kg/day, corresponding to 114-261 μg/mL) (Thibodeaux et al., 2003). 

In utero exposure to PFOS led to postnatal mortality in rat neonates, in a dose-dependent 

fashion (Lau et al., 2003). Among the surviving pups, the ontogenetic increases of serum TT4 

during the first two weeks of life were delayed or attenuated. No significant changes were noted 

in the ontogenetic rises of T3 or TSH. Luebker et al. (2005a) observed significant dose-related 

reductions of TT4 (and to a lesser extent, T3) on postnatal day 5 when ≥0.4 mg/kg/day of PFOS 

was administered in the diet during gestation. No effect was observed on serum TSH. 

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, despite the PFOS-induced TT4 deficits (Chang et al., 2009). 

In addition to the evaluation of PFOS’s effects on serum TT4, several studies have 

examined the levels of circulating free T4 (fT4) (Thibodeaux et al., 2003; Lau et al., 2003, 

Luebker et al., 2005a; 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 hypothyroxinemia 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 one-fifteenth of that for T4. Hence, a plausible scenario can be constructed to 

account for the hypothyroxinemic responses in the PFOS-treated animals. PFOS in circulation 

competes with T4 and displaces the hormone from binding to TTR (the primary thyroid hormone 

transport protein in the rat), initially leading to a transient elevation of fT4 (within 6 h), and a 

brief compensatory decrease of TSH. Concomitantly, hepatic metabolism of the hormone by 

UGT1A is enhanced (presumably in response to the transient elevation of the free hormone), 

which results in an increase of hormonal clearance and urinary excretion of iodide. As the fT4 
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level returns to normal range subsequently (within 24 h), a new equilibrium is reached between 

normal complements of fT4 and TSH, but a net reduction of total T4 (resulted from protein 

binding displacement and metabolism). 

A lack of significant change in TSH receptor gene expression in the thyroid gland is also 

consistent with the transient nature of TSH depression (Yu et al., 2009b). Thus, so long as fT4 

levels are maintained, TSH levels will remain within the normal range, despite the repeated 

displacement of T4 from TTR by PFOS, which results in net loss of TT4. Because the extent of 

T3 binding to TTR is less than that of T4, the deficits of serum T3 caused by PFOS exposure are 

smaller than those of T4. Maintenance of fT4 levels despite the PFOS-induced deficits of TT4 is 

indirectly supported by a general lack of thyroid hormone-specific responses in the rat (Lau et 

al., 2003; Chang et al. 2008), suggesting that the functional thyroid status has not been 

compromised significantly by subchronic exposure to the chemical. 

 

Several possibilities may account for the differential findings of thyroid hormone 

disruption between animal models and human biomonitoring data. First, hypothyroxinemia was 

observed in adult monkeys and rodents only when serum PFOS reached the 70-90 μg/mL (ppm) 

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 the 

general populations is estimated to be 15-30 ng/mL (ppb), 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 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 and may be lower than that to TTR (suggested by the PBDE 

findings reported by Cao et al., 2010), thus leading to a weaker thyroidal effect of the chemical 

in humans. Weiss et al. (2009) have shown that most of these compounds are capable of binding 

to human TTR, and therefore effective in displacing T4 from its transporter proteins. Indeed, 

these investigators used a T4-EQ approach to estimate the combined thyroidal effects of multiple 

perfluorinated compounds, and suggested a margin of safety of 503 for European adults and 306 

for North American adults. 

Synthesis and Evaluation of Carcinogenic Effects 

4.4.2 Synthesis and Evaluation of Carcinogenic Effects 

A positive association between PFOS exposure and the incidence of cancer was not 

identified in occupational studies (Alexander et al., 2003; Alexander and Olsen, 2007; Grice et 

al., 2007), and a study of the general population (Eriksen et al., 2009). The only chronic 

toxicity/carcinogenicity study in animals was a rat study (Thomford, 2002). This study was 

‘suggestive’ of carcinogenicity. Increased incidence of hepatocellular adenomas in the male and 

female rats and combined adenomas/carcinomas in the females were observed, but did not 

display a clear dose-related response. 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. 

Epidemiological studies in occupational and general populations did not support any increases in 

the incidence of carcinogenicity with exposure to PFOS. 
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4.4.3 Mode of Action and Implications in Cancer Assessment 

Short-term genotoxicity assays suggested that PFOS is not a DNA-reactive compound 

Therefore, the induction of tumors by PFOS is probably due to non-genotoxic mechanisms. 

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 and/or mice (Rao and Reddy, 1996; Ashby et al., 1994). The liver-expressed peroxisome 

PPARα regulates the transcription of genes involved in peroxisome proliferation, cell cycle 

control, apoptosis, and lipid metabolism. Mode of action (MOA) analysis suggested that the 

liver tumors induced by PFOS in rats are not clearly related to PPARα activation. 

The mode of action (MOA) for PPARα-agonist induced liver tumors has been 

hypothesized to involve four key causal key events: 

• PPARα activation 

• Cell proliferation/decreased apoptosis

• Preneoplastic foci

• Clonal Expansion of foci

• Liver tumors

The data for PFOS are adequate to support the some but not all of the key events in the PPARαagonist induced tumorigenic MOA.

 Peroxisome proliferation can lead to oxidative stress and may contribute to the mode of 

action by causing indirect DNA damage and leading to mutations, or by stimulating cell 

proliferation. Information that would help establish that a chemical is inducing liver tumors via a 

PPARα agonist MOA includes in vitro evidence of PPARα agonism (i.e., evidence from an in 

vitro receptor assay), in vivo evidence of an increase in number and size of peroxisomes, 

increases in the activity of acyl CoA oxidase, and hepatic cell proliferation. 

Treatment of rats (Ikeda et al., 1987; Thomford, 2002), and mice (Sohlenius et al., 1993) 

caused increases in relative liver weight and increased activities of peroxisomal enzymes. 

Several studies demonstrated that PFOS activates mouse and human PPARα in a luciferase 

reporter trans-activation assay in COS-1 or 3T3-L1 cells and in a rat liver cell model where the 

induction of endogenous PPARα target genes was monitored (Shipley et al., 2004; Takacs and 

Abbott, 2007). Studies by Martin et al (2007) and Rosen et al (2010) And Tan et al (2012) 

demonstrated that PFOS exposure is associated with gene expression patterns and induction of 

proteins associated with PPARα but also to CAR and other cellular receptors. Maloney and 

Waxman (1999) found that PPARα is activated by endogenous cellular fatty acids which 

suggests that displacement of endogenous ligands from liver fatty acid binding protein may be 

one mechanism by which PFOS induces peroxisome proliferation. 

Although there are some data supporting the ability of PFOS to activate PPARα, data are 

generally lacking for increased cell proliferation, another of the key events in a peroxisome 

proliferator-induced hepatocarcinogenesis. No increase in cell proliferation in the liver was 

detected in the subchronic study (Seacat et al., 2003) or the cancer bioassay (Thomford, 2002) of 

PFOS. No studies were identified wherein evidence of preneoplastic foci were observed in the 

liver. Liu et al. (2009) studied biomarkers for oxidative stress in the liver and brain in KD mice. 
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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 gap junctional intercellular communication (GJIC). While PFOS was shown to be a 

weak toxicant to isolated mitochondria (Starkov and Wallace, 2002), it inhibited GJIC in a dosedependent manner in two cell lines and in liver tissue from rats exposed orally (Hu et al., 2002). 

However, these are not clearly defined MOAs and their importance relative to PFOS exposure is not 

certain. The results from genotoxicity studies conducted with PFOS were negative. 

PFOS was tested for its ability to induce mutation/genotoxicity in a number of in vitro

and in vivo assay systems and it was neither mutagenic or genotoxic when tested under these 

conditions (see Section on Mutagenicity and Genotoxicity). 

4.4.4 Weight of Evidence Evaluation for Carcinogenicity 

Based on the available evidence, the data are inadequate to support a PPARα-linked 

MOA for the liver and thyroid adenoma’s observed by Thomford (2002) in the chronic two year 

bioassay in Crl:CD(SD)IGS BR rats. Although liver adenomas were significantly increased in 

males and females at the highest dose, a dose-response pattern was not observed although the test 

for trend was positive (P=0.03). In males the incidence of thyroid tumors was elevated only in 

the high-dose, recovery group males 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. The classification for 

of PFOS under the U.S. EPA Guidelines for Carcinogen Risk Assessment (U.S. EPA, 2005a) is 

currently consistent with the suggestive evidence of carcinogenic potential descriptor. 

4.4.5 Potentially Sensitive Populations

 In humans, single blood samplings of different populations within the United States do 

not support major gender differences. Gender differences could not be determined by those 

exposed by occupational exposure as the majority of those tested were males. 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. Also males had lower NOAEL 

and LOAEL values in the animal studies involved in determining immunology function. 

 

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., 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 epidemiological 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. 
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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 four-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 

(GD) 17-20 identifying late gestation as the sensitive window for neonatal death. 

 The evidence for reproductive and developmental effects of PFOS in humans is unclear. 

The strength of many of the studies is reliance on direct biomonitoring data to assess exposure, 

therefore minimizing misclassification (Olsen et al., 2009). Birth weight was measured by 

medical records, birth certificates, or maternal recall within several years of birth leading to good 

accuracy and reliability of the data, but other birth outcome measures may be subject to a greater 

degree of error. A number of methodological differences across the investigations may affect the 

comparability of the risk estimates and could account for the inconsistencies between the studies. 

Differences in the reported data make comparisons difficult because some reported logtransformed data and others did not (Olsen et al., 2009). No two studies reported statistically 

significant correlations for the same birth outcome and associations were sometimes specific for 

birth gender or parity. The subjects of the studies differed substantially in nationality, ethnicity, 

and pre-pregnancy BMI. Several investigators attempted to correct for potential confounders for 

birth weight. Parity was found to be a significant confounder. Low response rates may also be a 

factor affecting the representativeness of the population sample. 
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5.0 DOSE-RESPONSE ASSESSMENT 

5.1 Dose-Response for Noncancer Effects 

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, etc. 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.

5.1.1 RfD Determination

While the database and number of studies is robust for PFOS, quantifying the dose 

response is challenging. PFOS is a unique chemical as the toxicokinetics are still not fully 

understood, the half-life differences between species are great (>100X difference between rats 

and humans), true exposure data in humans are lacking, and a difference in effects has been 

observed between animal studies and human epidemiology studies. 

Human Data. In humans, data have been obtained for occupational and general 

population exposure scenarios. Some studies have monitored similar populations over time to 

determine the trend observed. In general, PFOS levels in the serum of the general population 

have decreased since production was stopped in the United States. Some limitations associated 

with the epidemiology studies include the small population of persons evaluated, the lack of 

control over other factors that may be contributing to the effects observed, and concurrent 

exposures to other perfluorinated chemicals which were measured in serum. In most cases, the 

findings are suggestive and not conclusive of an effect. Pathways of exposure in the general 

population appear to be from drinking water, food (especially fish/seafood), and some 

environmental exposures (i.e. carpets, house dust). 

Some human epidemiology studies found an association with increased PFOS serum 

levels and an increase in total cholesterol in adults (Chateau-Degat et al., 2010; Nelson et al., 

2010; Steenland et al., 2009) as well as children (Frisbee et al., 2010). Steenland et al. (2009) 

also found a correlation between increased PFOS and higher triglycerides. Occupational studies 

did not indicate consistent associations between PFOS and cholesterol and/or triglycerides in 

either cross-sectional surveys or in a longitudinal analysis (Olsen et al., 1999; Olsen et al., 

2001b,2001c). A statistically significant positive association was also reported between PFOS 

and uric acid levels in a community study (Steenland et al., 2010). A number of the studies in 

the general population were associated with the C8 project in which the mean serum level of 

PFOS was approximately 22.4 ng/mL or derived from NHANES data in which the mean serum 

level was approximately 25.3 μg/L (25.3 ng/mL). 

The relationship between PFOS and an increase in thyroid hormones was examined in 

human populations (Bloom et al., 2010; Dallaire et al., 2009a; Chateau-Degat et al., 2010; 

Meltzer et al., 2010) with inconsistent results. While a significant increase in free T4 was 

observed in subjects with higher PFOS levels, thyroid function appeared to be either normal or 
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not affected. The mean serum concentration observed in these populations was approximately 

20 ng/mL. Limited data, which focus on infants and children, are inconclusive with regard to the 

potential immunotoxicity from PFOS exposure (Okada et al., 2012; Grandjean et al., 2012; Dong 

et al., 2013). 

Studies of the impact of PFOS on reproductive and developmental health have been 

conducted in both occupational settings (Grice et al., 2007) and for the general population (Inoue 

et al., 2004; Apelberg et al., 2007; Fei et al., 2007, 2008a, 2008b, 2010a and 2010b; Monroy et 

al., 2008; Washino et al., 2009). The researchers focused on endpoints of birth weight and other 

measures of fetal growth. No significant effects were found in the occupational workers relative 

to birth outcome. In general population studies, the only finding of note was a slight increase in 

the risk for low birth weight, however, this was not a consistent finding across the studies. Mean 

serum concentrations in pregnant females participating in these studies ranged from 14 to 30 

ng/mL. 

Animal Data. Adequate studies were available for short-term, subchronic, chronic, 

developmental and reproductive parameters in rats, mice, rabbits and primates. Subchronic, 

chronic, and reproductive toxicity animal studies, all with exposure duration greater than 60 

days, have been summarized in Table 5-1. Shorter duration studies which focused on 

immunotoxicity endpoints and developmental toxicity studies are summarized in Table 5-2. 
Perfluorooctane sulfonate (PFOS) – February 2014 5-3 

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TABLE 5-1. 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 ↓ cholesterol

↓ body wt gain

↑ liver wt; histopath.

Seacat et al., 

2002

rat 90 days ND 2.0 ↑ liver wt

↓ food consumption

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) and BUN

(m/f) 

↑ liver hypertrophy

Seacat et al., 

2003

rat 2 generation 

(84 days; 12 weeks) 

0.1 0.4 ↓ food consumption

↓ 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)

0.099 (f)

0.018 (m)

0.247 (f)

0.072 (m)

liver 

histopathological 

changes

Thomford, 

2002

mouse 60 days 0.008 0.083 ↑ liver wt

↑ splenic natural 

killer cell activity

Dong et al., 

2009

ND= not determined

BUN = blood urea nitrogen

Seacat et al. (2002) treated monkeys 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 palmitoyl 

CoA oxidase activity, was increased significantly in the females at 0.75 mg/kg/day; however, the 

magnitude was less than the two-fold increase typically indicating biological significance. 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. At the 

highest dose, 0.75 mg/kg/day, monkeys also had decreased cholesterol and 2/6 males died. At 

the concentration 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 dose where effects were present (0.75 

mg/kg/day), the serum concentrations were 173 μg/mL in males and 171 μg/mL in females. In 

the 3-month study with monkeys, Goldenthal et al. (1979) found anorexia and clinical signs, but 

no changes in liver weight at 0.5 mg/kg/day. 

As part of a chronic bioassay, rats were administered PFOS in the diet with an interim 

sacrifice after 14 weeks (Seacat et al., 2003) or continued for up to 104 weeks (Thomford, 2002). 

Liver weight was increased in males and females at the highest dietary concentration after both 

14 and 53 weeks, but a dose- and time-response could not be evaluated because data for the 

lower dose groups were not reported at week 53 and no liver weight data were reported for any 
Perfluorooctane sulfonate (PFOS) – February 2014 5-4 

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group at study termination after 104 weeks. An increase in liver weight was noted in the 

subchronic study by Goldenthal et al. (1978b) at a slightly higher dose (2 mg/kg/day) than that 

seen in Seacat et al. (2003) but a NOAEL was not determined in the older study. In mice, Dong 

et al. (2009) found a significant increase in liver weight after a 60-day exposure to a dose of 

0.083 mg/kg/day.

Histopathological 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 0.072 mg/kg/day in 

males and 0.247 mg/kg/day in females after 104 weeks (Thomford, 2002). Liver lesions 

included centrilobular hypertrophy and vacuolation after the subchronic and chronic exposures 

with eosinophilic granules also observed after chronic duration. No evidence of peroxisome 

proliferation was found during either phase of the study. No effect levels in males and females 

were 0.34 mg/kg/day and 0.40 mg/kg/day, respectively, after 14 weeks and 0.018 mg/kg/day and 

0.099 mg/kg/day, respectively, after 104 weeks. 

Rat dams were treated with PFOS for 63 or 84 days in a one- or two-generation 

reproductive study, respectively (Luebker et al., 2005a,b). 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 studies with reduced pup survival observed 

in the one generation study at higher maternal doses of ≥0.8 mg/kg/day. A NOAEL for pup 

body weight effects was 0.1 mg/kg/day in the two-generation study; the one-generation study 

(Leubeker et al., 2005a) lacked a NOAEL for decreased pup body weight because it was 

impacted at the lowest dose tested (0.4 mg/kg/day). Offspring survival was affected in a doserelated manner in the one-generation study with a biologically significant decrease attained at 0.8 

mg/kg/day and statistical significance reached at 1.6 mg/kg/day. In the two generation study 

(Luebeker 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. The highest dose 

used during production of the F2 generation was 0.4 mg/kg/day which was a NOAEL for effects 

on survival. Thus, the most sensitive endpoint was decreased offspring body weight which 

occurred at a lower dose than that resulting in reduced pup survival and was similar to the dose 

causing maternal toxicity. 

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), a significant reduction of total triiodothyronine (T3) and increased TSH were 

observed that were more pronounced at the end of exposure period in the high-dose group. 

However, a dose-response was not observed and no evidence of hypothyroidism was seen. 

PFOS-induced alterations of thyroid hormones were also seen studies on adult rats (Thibodeaux 

et al., 2003; Martin et al., 2007; Yu et al., 2009b; Yu et al., 2011); however, most reductions 

involved circulating TT4, instead of T3. In two studies (Martin et al., 2007; Yu et al., 2009b) 

when PFOS serum levels were at 88 μg/mL, TT4 levels were reduced by 75-79%, suggesting 

effects of PFOS on serum TT4 are directly related to endogenous concentrations of the chemical. 

In all animal studies, however, the changes in T3 and TT4 failed to activate the hypothalamicpituitary-thyroid (HPT) feedback mechanism to produce significant elevations of serum TSH. 

Across the range of longer-term studies the lowest LOAEL is 0.072 mg/kg/day for 

histopathological changes in the liver of male Sprague-Dawley rats following a 104-week (2-
Perfluorooctane sulfonate (PFOS) – February 2014 5-5 

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year) exposure (Thomford, 2002). Histological changes observed included centrilobular 

hypertrophy and centrilobular vacuolization in the hepatocytes, likely associated with PFOS or 

lipid accumulation. Significant increases in absolute and relative liver weights were not noted. 

The LOAEL for comparable effects in females was about 3 times higher. Increases in liver 

weight were observed in male and female rats with shorter durations of exposure. 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. Goldenthal et al. (1978b) identified 2 mg/kg/day as a LOAEL for increased 

absolute and relative liver weights in rats treated for 90 days. In monkeys, increased relative 

liver weight and decreased cholesterol were seen at a LOAEL of 0.75 mg/kg/day administered 

for six months (Seacat et al., 2002). 

In the Dong et al. (2009) study, an increase in splenic natural killer (NK) cell activity 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. No other studies of an 

immunological endpoint with a comparable exposure duration were identified. 

The most severe of the effect observed in the longer-term studies was the decrease pup 

survival in the one-generation study by Luebker et al. (2005a) in SD rats at a LOAEL of 0.8 

mg/kg/day. The LOAEL for the less serious effect of decreased pup body weight was 0.4 

mg/kg/day in one- and two-generation studies. The short-term studies compiled in Table 5-2 

below support the concern for low dose-effects on pup survival. The NOAEL for liver effects in 

male rats (0.072 mg/kg/day) appears to be protective for other effects from PFOS exposures. 

TABLE 5-2. 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 Curran et al., 

2008

Rat GD 1-21 0.1 2.0 ↑ mortality; 

histopathological 

changes to lungs 

(pups)

Chen et al., 

2012

Rat GD 2-20 1.0 2.0 ↓ dam and pup bwt

↓ pup survival

Thibodeaux et 

al., 2003; Lau 

et al., 2003

Rat GD 1-21 + 20 days 

postnatal

0.3 1.0 ↑ motor activity in 

male pups PND 17

Butenhoff et 

al., 2009

Mouse GD 1-17 1.0 5.0 ↑ liver wt, dams and 

pups; delayed eye 

opening

Thibodeaux et 

al., 2003 ; Lau 

et al., 2003

Mouse 28 days 0.00017 (m)

0.0033 (f)

0.0017 (m)

0.017 (f)

↓ SRBC plaqueforming cell responsePeden-Adams 

et al., 2008

Similar to the decreased offspring survival described in the reproductive toxicity studies 

(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; Thibodeaux et al., 

2003; Lau 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 
Perfluorooctane sulfonate (PFOS) – February 2014 5-6 

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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. Thibodeaux et al. (2003) and Lau et al. (2003) both found 

decreased maternal and pup weight gain, but no effects on maternal liver weight, when dams 

were dosed at 2 mg/kg/day from GD 2 to 20. 

Developmental neurotoxicity was found in rat offspring at a lower dose than that 

affecting survival (1 mg/kg/day; Butenhoff et al., 2009) and developmental delays were observed 

in mice at a slightly higher dose (5 mg/kg/day; Thibodeaux et al., 2003; Lau et al., 2003). 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. 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. 

Several studies (Lau et al., 2003; Thibodeaux et al., 2003; Curran et al., 2008) found 

increased liver weight generally concurrent with other endpoints. Rats treated for 28 days 

showed dose-related decreased body weight and increased liver weight with statistical 

significance beginning at 1.33 mg/kg/day for males and 0.15 mg/kg/day for females (Curran et 

al., 2008). Treatment of mice during gestation resulted in increased maternal liver weight and 

developmental delays in the offspring at 5 mg/kg/day (Thibodeaux et al., 2003; Lau et al., 2003). 

Peden-Adams et al. (2008) identified immunotoxicity in male mice exposed to 0.0017 

mg/kg/day. IgM suppression occurred after 28 days of treatment although no overt signs of 

toxicity or effects on liver weight were observed at any dose. The only effect at a LOAEL less 

than that from the Thomford (2002) chronic study was a decrease (52 to 78%) 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. The number of animals per 

dose groups in this study was small (n=5) suggesting the need for additional research to confirm 

the NOAEL and LOAEL for this endpoint. 

In the process of RfD development, all relevant endpoints must be considered within the 

context of the database as a whole. As part of that analysis, data from the mouse do not appear 

to be the best choice on which to base the risk assessment of PFOS. The in vitro measures of 

immunocompetence on mice may not be relevant to the human experience and limited human 

data from epidemiology studies are inconclusive regarding the immunotoxicity of PFOS in 

humans. Values associated with immunotoxicity endpoints in mice were markedly lower, by 

several orders of magnitude, than those from developmental and liver endpoints in monkeys and 

rats (Tables 5-1 and 5-2), but are not supported by other immunotoxicity studies in the database 

(Keil et al., 2008; Zhang et al., 2009; Dong et al., 2009; Qazi et al., 2010). Developmental 

delays occurred in mice at higher doses than those affecting development and survival in rats. 

Thus, the mouse does not appear to be the most sensitive species for evaluation of the potential 

developmental toxicity of PFOS. 
Perfluorooctane sulfonate (PFOS) – February 2014 5-7 

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5.1.1.1 Benchmark Dose Approach 

As a second step in the dose-response analysis, benchmark modeling of dose-response for 

key endpoints was evaluated. Endpoints considered as critical effects in several studies included 

decreased offspring body weight, reduced pup survival, liver histopathology, and liver weight 

changes. For the developmental endpoints, benchmark dose estimates were calculated and 

published by the authors of the studies. Liver endpoints were modeled as described below based 

on the available data. 

Benchmark dose estimates for developmental endpoints in rats were published in a twopart developmental toxicity study (Thibodeaux et al., 2003; Lau et al., 2003) and in a onegeneration study in which only dams were treated (Luebker et al., 2005a). Protocols varied 

slightly between studies, but dams were treated throughout gestation and the offspring evaluated 

either on GD 21 or by postnatal day 8 in each study. As recommended for continuous, normally 

distributed developmental toxicity endpoints, a shift in the distribution of 0.67 standard 

deviations was used as the benchmark response, which represents approximately an extra 5% of 

the individual values being greater than approximately the 99th percentile or about an extra 5% 

less than approximately the 1st percentile of the distribution in controls (U.S. EPA, 1995). 

Goodness-of-fit information was used by the authors to choose the best model for each data set. 

The estimated values from the modeling are reported as the BMD5 and its lower 95% confidence 

limit, the BMDL5 as shown in Table 5-3. 

TABLE 5-3. Benchmark Dose Modeling for a 5% Increased Risk of Developmental 

Toxicity in Rats

Maternal 

treatment

Best fit 

Model

BMD5

mg/kg/day

BMDL5

mg/kg/day

Effects Modeled Reference

GD 2-20 Polynomial 0.22 0.15 Decreased maternal body 

weight.

Thibodeaux 

et al., 2003

Hill 0.23 0.05 Decreased maternal T4.

Logistic 0.31 0.12 Fetal sternal defects.

Logistic 8.85 3.33 Fetal cleft palate

GD 2-21 NCTR 1.07 0.58 Reduced neonatal survival on 

postnatal day 8

Lau et al., 

2003

6 weeks prior 

to mating 

until lactation 

day 4

Not stated 0.45 0.31 Reduced gestation length Luebker et 

Not stated 0.63 0.39 Decreased pup birth weight al., 2005a

Not stated 0.39 0.27 Decreased pup weight on day 5

Not stated 0.41 0.28 Decreased pup weight gain

Not stated 1.06 0.89 Reduced pup survival on day 5

Benchmark dose estimates were not published in the two-generation study (Luebker et 

al., 2005b) which had the lowest NOAEL, 0.1 mg/kg/day, for decreased pup body weight and a 

LOAEL of 0.4 mg/kg/day. Significantly reduced body weight was noted in the F2 pups on 

lactation days 7 and 14 but not on days 1, 4, or 21. Data presented included mean pup 

weight/litter but number of litters was not reported. As a consequence benchmark dose analyses 

could not be run on these data. 

Benchmark dose estimates for maternal and developmental endpoints were also published 

for mice (Thibodeaux et al., 2003; Lau et al., 2003) treated similarly to the protocol for rats. The 

resulting estimates for offspring survival and malformations were approximately an order of 
Perfluorooctane sulfonate (PFOS) – February 2014 5-8 

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magnitude greater than those for the rat and are not considered further as potential points of 

departure (PODs) for use in RfD development. 

The incidence data for liver lesions were modeled by EPA using benchmark dose 

software (BMDS) v. 2.1.2 for dichotomous variables. Goodness-of-fit information (p value and 

Akaike’s Information Criterion [AIC]) was used to choose the best model for each data set. In 

the 2-year study in rats (Thomford, 2002), dose-related increased incidences were observed for 

hepatocellular centrilobular hypertrophy in males and females and centrilobular hepatocytic 

vacuolation in males (as shown in Table 4-10). These lesions are consistent with the high 

uptake/storage of PFOS by the liver. A 10% extra risk for each endpoint was selected as the 

benchmark response for the analysis. Results are shown in Table 5-4 and the modeling output is 

included in Appendix B. Figure 5-1 provides the graphic results from these datasets. Because 

the incidence of centrilobular, eosinophilic, hepatocytic granules was markedly increased in 

males and females only at the highest dose, these data were not modeled. In males, the BMDL10

for both hepatocellular hypertrophy and hepatocyte vacuolization are comparable (0.033 and 

0.028 mg/kg/day, respectively). Based on hepatocyte hypertrophy females are less responsive to 

chronic exposure to PFOS than males by a factor of about 2; thus, the data for females were not 

considered further for derivation of the RfD. 

TABLE 5-4. Benchmark Dose Modeling for a 10% Increased Incidence of Liver Lesions in 

Rats

Sex Best fit 

Model

BMD10

mg/kg/day

BMDL10

mg/kg/day

Notes Reference

Hepatocellular centrilobular hypertrophy

Males Log-Probit

(no 

restriction)

0.0521299 0.0326765 2-year dietary administration Thomford, 

2002

Females Log-Probit

(no 

restriction)

0.0981083 0.0680339 2-year dietary administration Thomford, 

2002

Centrilobular hepatocytic vacuolation

Males Log-Probit 

(no 

restriction)

0.0931649 0.0278419 2-year dietary administration Thomford, 

2002
Perfluorooctane sulfonate (PFOS) – February 2014 5-9 

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Males – hypertrophy Females – hypertrophy

Males – vacuolation

Figure 5-1. BMDS graphic output from selected model runs; data from Thomford, 2002. 

For the studies wherein liver weight was a critical effect, the data were also modeled 

using BMDS v. 2.1.2 for a continuous dataset with modeled variance where applicable. A 10% 

increase in absolute liver weight was chosen as the benchmark response for the initial analysis. 

This endpoint is considered to be a biomarker for systemic exposure in rodents when the 

chemical is an activator of PPAR-α, rather than a biomarker of adversity. Although the PFOS 

data support an increase in the expression of proteins involved in peroxisomal fatty acid 

catabolism (Tan et al., 2012) and lipid transport and metabolism (Bijland et al., 2011), those 

effects may not totally be a reflection of PPAR-α activation. Compared to PFOA, PFOS appears 

to be a relatively weak activator of the PPAR-α receptor (Shipley et al., 2004; Wolf et al., 

2008,2012; Ishibashi et al., 2011). 

 0

 0.1

 0.2

 0.3

 0.4

 0.5

 0.6

 0.7

 0.8

 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Fraction Affected

dose

LogProbit Model with 0.95 Confidence Level

14:57 10/03 2012

BMDL BMD

 

LogProbit

 0

 0.2

 0.4

 0.6

 0.8

 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Fraction Affected

dose

LogProbit Model with 0.95 Confidence Level

13:03 01/29 2013

BMDL BMD

 

LogProbit

 0

 0.05

 0.1

 0.15

 0.2

 0.25

 0.3

 0.35

 0.4

 0.45

 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Fraction Affected

dose

LogProbit Model with 0.95 Confidence Level

08:56 10/04 2012

BMDL BMD

 

LogProbit
Perfluorooctane sulfonate (PFOS) – February 2014 5-10 

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Results of the liver weight analyses are shown in Table 5-5 where goodness-of-fit 

information (p value and AIC) was used to chose the best model for each data set. The modeling 

output is included in Appendix B; Figure 5-2 provides the graphic results from these datasets. 

Liver weight data were available in the male and female monkey (Seacat et al., 2002), the male 

rat (Seacat et al., 2003), and the male mouse (Dong et al., 2009). However, the data for the male 

mouse did not adequately fit any model as indicated by values of p<0.1 and are not included 

here. For each data set, the BMD (10% increase in liver weight) and the lower-bound confidence 

limit on the BMD (BMDL) are provided. 

TABLE 5-5. Benchmark Dose Modeling for a 10% Increase in Liver Weight

Species Best fit 

Model

BMD10

mg/kg/day

BMDL10

mg/kg/day

Notes Reference

Monkey

Monkey

male

Power 

(modeled 

variance)

0.60743 0.0147931 Increased absolute liver 

weight; 26 weeks

Seacat et al., 

2002

Monkey 

female

Exponential 

Model 2

0.03338792 0.0207989 Increased absolute liver 

weight; 26 weeks

Seacat et al., 

2002

Rat

Rat male Exponential 

Model 5

0.280426 0.0585612 Increased absolute liver wt; 

98 days

Seacat et al., 

2003

The benchmark dose, liver weight response in male (BMDL10 = 0.015 mg/kg/day) and 

female (BMDL10 = 0.021 mg/kg/day) monkeys after 26-weeks of exposure is slightly more 

sensitive than both the liver weight and histopathology responses in male rats. Given that 

monkeys are less responsive than rodents to PPAR-α activation, the liver weight BMDLs for the 

monkey suggest that the increase, in this case, may not simply be a reflection of a classic PPARα response.
Perfluorooctane sulfonate (PFOS) – February 2014 5-11 

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Male monkey Female monkey

Male rat

Figure 5- 2. BMDS graphic output from liver weight model runs; data from Seacat et al., 

2002, 2003 

5.1.1.2 Pharmacokinetic Model Approach

The pharmacokinetics of PFOS are not well understood but are considered to be roughly 

similar to that of the more extensively studied PFOA (Andersen et al., 2006; Loccisano et al., 

2011, 2012a,b). Pharmacokinetic studies with PFOS have measured a serum half-life of 

approximately 48 days in rats (Butenhoff and Chang, 2007) and approximately 121 days in 

monkeys (Chang et al., 2012). Compared with a half-life of months in animals, the human PFOS 

half-life of roughly five years (Olsen et al., 2007) is clearly inconsistent with simple allometric 

scaling across species. The reasons for the contrast between the multi-year PFOS elimination 

half-life in humans and the shorter half-lives of laboratory animals are not fully understood. 

In the process of developing pharmacokinetic models for PFOS in monkeys and rats, 

several assumptions had to be made by the authors in order to fit the model outcome to the 

available pharmacokinetic data (Anderson et al., 2006; Tan et al., 2008; Loccisano et al., 2011, 

2012a,b). Parameters for transporter characteristics were assumed to be the same for both sexes 

 20

 40

 60

 80

 100

 120

 140

 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

BMDL BMD

 

Power

Mean Response

dose

Power Model with 0.95 Confidence Level

09:33 01/29 2013

 30

 40

 50

 60

 70

 80

 90

 100

 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

Mean Response

dose

Exponential Model 2 with 0.95 Confidence Level

10:17 01/29 2013

BMDL BMD

 

Exponential

 12

 14

 16

 18

 20

 22

 24

 0 0.2 0.4 0.6 0.8 1 1.2

Mean Response

dose

Exponential Model 5 with 0.95 Confidence Level

11:21 01/29 2013

BMDL BMD

 

Exponential
Perfluorooctane sulfonate (PFOS) – February 2014 5-12 

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consistent with no observed differences in elimination; a storage compartment was added 

because PFOS appears in the urine of male rats at a slower rate than it disappears from plasma. 

To account for the concentrations of PFOS found in the liver at long times (72–99 days) after 

dosing, description of saturable binding in the liver was used in the adult rat model (Loccisano et 

al., 2012a), and a time-dependent description of the free fraction of chemical in the central 

(plasma) compartment was added to describe possible changes in binding or elimination that

may be occurring over time. 

It is hypothesized that the pharmacokinetics of perfluorinated compounds, including 

PFOS, are driven by transporters, notably in kidney and liver (Kudo, 2006). All published 

pharmacokinetic models assume that perfluoroalkyl acids are rapidly eliminated into the urine, 

but then reabsorbed into the body by transporters before they can be excreted. Whenever the 

ability of transporters to reabsorb the compounds is saturated, however, the compounds can be 

rapidly eliminated.

Currently, no data characterizing the uptake kinetics of PFOS by renal organic anion 

transporters are available. The long half-life of PFOS in both the male and female rat, the 

monkey, and humans, suggests that it is most likely reabsorbed back into the plasma by a renal 

transport process, similar to the documented process for PFOA. However, because no significant 

difference is observed for the elimination half-life between male and female rats (Chang et al., 

2012), it can be assumed that the transporters responsible for reabsorption are similar in both 

sexes, and different in some way from those for PFOA. Differences could be due to either the 

kinetic interactions of the chemicals with the same transporters or differences in transporters. 

Studies characterizing the uptake and reuptake of PFOS by renal transporters will help in 

refinement of these parameters. 

Because the exposures of interest typically involve repeated doses, the saturable renal 

resorption model (Andersen et al., 2006, Section 3.5.1) was used to describe how PFOS can

reach steady state faster than the elimination half-life would indicate. Using a simpler, linear 

pharmacokinetic model (e.g. the one-compartment model) would result in estimated exposures 

due to repeated doses that are much greater than actually seem to occur (Seacat et al., 2003). 

Despite the uncertainties described above, application of this model to PFOS yielded good 

agreement between the experimental data and the model simulations.

The biological basis for the saturable resorption model parameters is uncertain (Lou et al.

2009), particularly with respect to the idea that glomerular filtration alone is responsible for the 

movement of PFOS into the renal filtrate given that PFOS is highly protein bound (KerstnerWood et al., 2003) and the interactions with the renal transporters are unknown. However, the 

saturable resorption model functions well in describing the internal doses in studies of PFOS 

(Andersen et al., 2006; Loccisano et al., 2011, 2012a,b). 

The saturable resorption model is an empirical model similar to the commonly used oneand two-compartment models. Because it is an empirical model, extrapolation between species 

is difficult. Resorption parameters cannot be directly linked to the properties of the relevant 

serum transport proteins or membrane transporters. Therefore the saturable resorption model 

parameters must be estimated using species-specific pharmacokinetic data. 
Perfluorooctane sulfonate (PFOS) – February 2014 5-13 

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Pharmacokinetic data (serial blood concentrations following treatment with known 

quantities of PFOS) were collected for three species: cynomolgus monkeys (Chang et al., 2012; 

Seacat et al., 2002), Sprague-Dawley rat (Chang et al., 2012), and CD1 mouse (Chang et al., 

2012). Given that the available pharmacokinetic studies were not necessarily designed with the 

expectation of non-linear pharmacokinetics, many parameters associated with saturable 

resorption should be expected to be uncertain. In the absence of ideal data, the question of 

parameter values becomes one of what range of values are consistent with the data, rather than 

which single value is most consistent with the data. Considering a range of possible values that 

might equally well explain the data can be addressed with Bayesian statistical analysis, which 

determines the distributions of parameter values that are likely to reproduce the observed data 

(Gelman et al., 2004). 

In this case, a non-hierarchical model for parameter values was applied in which there is 

a single value shared by all individuals of the same species and gender. Body-weight and 

treatment (number and magnitude of doses) are the only parameters that may vary between 

individuals. Body-weight was only varied when animal-specific body-weights were available.

Bayesian analysis allows formal inclusion of prior knowledge in the form of set 

distributions on the parameters being estimated (Gelman et al., 2004). Given that empirical 

pharmacokinetic parameters can have a wide range of values, vague, bounded prior distributions 

are appropriate (Wambaugh et al., 2008). For all estimated parameters, the prior knowledge was 

distributed log-normally. This constrained the parameters to positive values. The mean and 

variances used are given in Table 5-6. 

TABLE 5-6. Description of prior distributions used.

Parameter Mean Variance Bounds

Lower Upper

ka 1 1000 1/6 105

Vcc 1 1000 10-10 105

k12 1 1000 10-10 105

RV2:V1 1 0.5 10-10 100

Tmaxc 1 1000 10-10 105

kT 1 1000 10-10 105

free 0.01 0.5 10-10 1

Qfilc 1 1000 0.01 105

Vfilc 1 1000 10-10 10

Parameters were log-normally distributed with the mean and variance listed. Bounds were used to reduce the time spent sampling 

in areas thought to have low probability, and were expanded when large posterior mass at the bounds indicated that the bounds 

were too narrow.

The deep tissue compartment of the Andersen et al. (2006) model is characterized in 

terms of the rates to and from that compartment (k12 and k21, respectively). This corresponds to a 

volume of distribution V2 = k12*V1/k21, so that the ratio of the volume of the second 

compartment to the first is Rv2:v1 = k12/k21. In order to enforce the assumption that the primary 

(serum) compartment contains a significant portion of the PFOS, the volume of the deep tissue 

was constrained to be no more than 100 times greater than the volume of distribution of the 

serum. For this reason the ratio of the two volumes is estimated, rather than the rate from the 

second compartment to the first compartment. The rate of flow from the deep tissue back to the 

serum was calculated as k21 = k12/Rv2:v1. 
Perfluorooctane sulfonate (PFOS) – February 2014 5-14 

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Bayesian analysis was performed using Markov Chain Monte Carlo (Gelman et al., 

2004). The distribution of parameter values were considered to “burned in” (i.e., true draws 

from the posterior combination of the prior distributions and the available data and independent 

of the starting values) when they passed the Heidelberger and Welch Stationarity test 

(Heidelberger and Welch, 1983) as implemented in the Coda Package (Best et al., 1995) for R (R 

Development Core Team, 2010). 

The estimated parameters (median and 95% interval), presented in Table 5-7, generally 

appear plausible. The volumes of distributions were all less than 1 L/kg BW, and varied between 

species. The parameters for the male mouse were extremely uncertain, reflecting a combination 

of the limited amount of data (two single dose treatments) and perhaps inappropriateness of the 

model used. However, data to support the model assumptions are needed. Parameters such as 

the flow to and volume of the filtrate compartment were found to be very uncertain, as in 

previous studies (Andersen et al. 2006). The median fraction of blood flow to the filtrate (Qfilc) 

was physiological (less than or equal to the fraction of blood flow to the kidney) for the male and 

female rats, but appears too high for the mouse and monkeys, which might be explained by either 

a lack of sufficient data or perhaps the role of secreting transporters in the kidney. Although the 

physical interpretation is moot, the form of the saturable resorption model seems appropriate. 
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TABLE 5-7. Pharmacokinetic parameters used in the Andersen et al. (2006) model.

Parameter Units CD1 Mouse 

Femalea 

CD1 Mouse 

Malea 

SpragueDawley Rat 

Femalea 

SpragueDawley Rat 

Malea 

Cynomolgus 

Monkey Male 

and Femalea 

BWb 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 1/h 1.16 (0.617 

- 42400)

433.4 (0.51 

– 803.8

4.65 (3.02 -

1980)

0.836 (0.522 

- 1.51)

132 (0.225 -

72100)

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 1/h 0.0093 

(2.63e-10 - 

38900)

2976 (2.8e10 – 4.2e4)0.0124 (3.1e10 - 46800)0.00524 

(2.86e-10 - 

43200)

0.00292 (2.59e10 - 34500)

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 M/h 57.9 (0.671 

- 32000)

1.1e4 (2.1 –

7.9e4)

1930 (4.11 -

83400)

1.34e-06 

(1.65e-10 - 

44)

15.5 (0.764 -

4680)

kT M 0.0109 

(1.44e-05 - 

1.45)

381 (2.6e-5 

– 2.9e3)

9.49 (0.00626 

- 11100)

2.45 (4.88e10 - 60300)0.00594 (2.34e05 - 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 L/h 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 

(4.4e-10 - 

6.2)

0.51 (3.5e10 – 6.09)0.0185 (8.2e07 - 7.34)0.000194 

(1.48e-09 - 

5.51)

0.0534 (1.1e-07 -

8.52)

Means and 95% confidence interval 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.

a Average bodyweight for species -- individual-specific bodyweights b Cardiac outputs obtained from Davis & Morris, Pharmaceutical Res 10, 1093, 1993

For each study with a toxicological endpoint and NOAEL/LOAEL, the time-integrated 

serum concentration (area under the curve or AUC) was determined for the exposure duration 

investigated in that study. Generally, it was assumed that animals were observed at the end of 

dosing. The data for studies in the rats are summarized in Table 5-8. For the Butenhoff et al.

(2009) study two different AUCs were calculated – gestational only (for the male offspring 

endpoint) and gestational plus twenty days postnatal (for the maternal endpoint). This separation 

of the two exposures neglects lactational transfer of compound, which was not modeled. 
Perfluorooctane sulfonate (PFOS) – February 2014 5-16 

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TABLE 5-8. Predicted final serum concentration and time integrated serum concentration 

(AUC) for different treatments of rat.

Study Species / 

Strain 

Study

Duration 

And Type

Oral

Doses

mg/kg/day 

Measured 

Serum

Concentration 

mg/L

Species / 

Strain Used 

for 

Prediction

Predicted 

Final Serum 

Concentration 

mg/L

Predicted 

AUC mg/L*h

Curran et al. 

2008 

Male 

Rat/SpragueDawley 

28 days 0.14 No data Male 

Rat/SpragueDawley

4.88 (0.148) 1840 (56.9)

1.33 No data 46.4 (1.4) 17400 (540)

3.21 No data 112 (3.39) 42100 (1300)

6.34 No data 221 (6.7) 83100 (2580)

Curran et al. 

2008 

Female 

Rat/SpragueDawley

28 days 0.15 No data Female 

Rat/SpragueDawley

6.88 (0.212) 2500 (85.9)

1.43 No data 65.5 (2.03) 23800 (820)

3.73 No data 170 (5.76) 62100 (2170)

7.58 No data 344 (18.3) 126000 (5090

Seacat et al. 

2003 

Male Rat/ 

Crl:CD(SD) 

IGS BR

98 days 0.03 4.04 (0.80) Male 

Rat/SpragueDawley

2.64 (0.103) 3970 (128)

0.13 17.1 (1.22) 10.5 (0.408) 15900 (507)

0.34 43.9 (4.9) 26.3 (1.02) 39600 (1270)

1.33 148 (14) 105 (4.08) 158000 

(5070)

Seacat et al. 

2003 

Female Rat/ 

Crl:CD(SD) 

IGS BR

98 days 0.04 6.96 (0.99) Female 

Rat/SpragueDawley

4.24 (0.0867) 5780 (128)

0.15 27.3 (2.3) 17 (0.345) 23100 (511)

0.40 64.4 (5.5) 42.3 (0.882) 57700 (1280)

1.56 223 (22) 168 (6.38) 230000 

(6390)

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) 1060 (37.8)

0.3 6.245 (0.096) 11.1 (0.364) 3170 (114)

1 26.630 (3.943) 37 (1.21) 10600 (378)

Butenhoff et 

al. 2009 and 

Chang et al. 

2009

Rat/SpragueDawleyGestation 

(21 Days) 

+ 20 Days 

Postnatal

0.1 3.159 (0.081) Female 

Rat/SpragueDawley

6.49 (0.172) 3570 (111)

0.3 8.981 (0.275) 19.5 (0.515) 10700 (333)

1 30.480 (1.294) 64.8 (1.74) 35600 (1110)

Thibodeaux 

et al. 2003 

and Lau et 

al. 2003

Rat/SpragueDawleyGDs 2-20

(19 days)

1 19.69a Female 

Rat/SpragueDawley

32.4 (1.1) 8010 (293)

2 44.33a 64.7 (2.2) 16000 (585)

3 70.62a 97 (3.31) 24000 (879)

5 79.39a 161 (5.69) 40000 (1470)

10 189.4a 321 (15.6) 79800 (3190)

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

9.65 (0.202) 9100 (235)

0.4 26.2 (16.1) 38.5 (0.814) 36400 (942)

1.6 136 (86.5) 153 (4.74) 145000 

(4100)

3.2 155 (39.3) 303 (17.5) 288000 

(11200) 

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

38.5 (0.814) 36400 (942)

0.8 NT 76.9 (1.75) 72600 (1910)

1.0 NT 96.1 (2.32) 90700 (2410)

1.2 NT 115 (2.99) 109000 

(2940)

1.6 NT 153 (4.74) 145000 

(4100)

2.0 NT 191 (7.07) 181000 

(5460)

Numbers in parentheses indicate standard deviation

GD = gestation day; NT = not tested

a

Thibodeaux et al. (2003) data available only in a graph; values obtained from author.
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The data on the results from studies in mice and the monkey are provided in Tables 5-9 

and 5-10, respectively. The Lau et al. (2003) data on mice are representative of the impact of 

PFOS on developmental endpoints as described in Table 5-2 although the duration of this study 

is relatively short at 17 days. The Seacat et al. (2002) study on monkeys is a long term (6 

months) multiple dose study of systemic toxicity in which the LOAEL for effects on liver weight 

and cholesterol was accompanied by death of 2/6 monkeys. 

TABLE 5-9. Predicted final serum concentration and time integrated serum concentration 

(AUC) for the mouse. 

Study Species / 

Strain

Study 

Duration

And 

Type

Administered 

Doses

mg/kg/day

Measured 

Final Serum

Concentration 

mg/L

Species / 

Strain 

Used for 

Prediction

Predicted 

Final Serum 

Concentration

mg/L

Predicted 

AUC 

mg/L*h

Lau et 

al. 2003

Female 

Mouse/CD1 

GD 1-17 

(17 days)

1 NT Female 

Mouse / 

CD1

62.7 (2.28) 14700 

(533)

5 NT 287 (19.2) 70900 

(2560)

10 NT 421 (107 123000 

(14500)

15 NT 484 (186) 156000 

(32100)

20 NT 532 (257) 180000 

(49900

Numbers in parentheses indicate standard deviation

GD = gestation day; NT = not tested

TABLE 5-10. 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 mg/L

Species / 

Strain Used 

for 

Prediction

Predicted 

Final Serum 

Concentration

mg/L

Predicted AUC 

mg/L*h

Seacat 

et al. 

2002

Monkey / 

Cynomolgus

182 days 0.03 F: 13.2 (1.4)

M: 15.8 (1.4)

Monkey / 

Cynomolgus

7.58 (0.16) 22100 

(382)

0.15 F: 66.8 (10.8)

M: 82.6 (25.2)

32.9 (0.557) 102000 

(1530)

0.75 F: 171 (22)

M: 173 (37)

86.7 (2.14) 332000 

(6450)

Numbers in parentheses indicate standard deviation

M = male; F = female

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. Averaging the terminal serum concentrations for the duration 

of exposure is important because of the variability in the times of exposure across the studies 

(17-182 days). The following equation is used for the conversion: 

Average Serum Concentration = AUC (mg/L*h) × 1 day/24 hours ÷ exposure duration 

(days) 
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For example, in a case where the AUC was 30,000 mg/L*h and the study duration was 90 

days, the Average Serum Concentration would be calculated as follows: 

Average Serum Concentration = 30,000 mg/L*h ÷ (90 days × 24 h/day) = 13.89 mg/L 

This calculation has the advantage of normalizing the serum concentration 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 5-11 provides the AUC from the model, the dosing duration from each of the 

modeled studies, and the resultant average serum concentration. Internal doses associated with 

developmental toxicity were 18.06 and 24.07 mg/L for reduced pup body weight (Luebker et al., 

2005a,b), 36.18 mg/L for changes in motor activity (Butenhoff et al., 2009), and 35.09-48.02 

mg/L for pup survival (Lau et al., 2003; Luebker et al., 2005a). In comparison, internal doses 

associated with increased liver weight were 67.18-76.01 mg/L (Seacat et al., 2002; 2003). Thus, 

the internal doses associated with the developmental and liver effect levels (LOAELs) differ by 

much less than an order of magnitude (18.06 mg/L to 76.01 mg/L) while the corresponding AUC 

values differ by more than an order of magnitude (16000 mg/L*h to 332000 mg/L*h). 

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 from 4.51-24.07 mg/L for developmental endpoints (Butenhoff et al., 

2009; Lau et al., 2003; Luebker et al., 2005a,b) and from 16.84-23.35 mg/L for liver weight 

changes (Seacat et al., 2002; 2003). Despite the similarity in average serum concentrations, the 

AUC values differ by two orders of magnitude (8010 mg/L*h to 102000 mg/L*h). Given the 

differences in external doses, the projected serum levels are proportionally quite similar.
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TABLE 5-11. Average Serum concentrations Derived from the AUC and the duration of 

Dosing

Study Dosing 

duration 

days

NOAEL

mg/kg/day 

(AUC

mg/L*h)

NOAEL 

(Av serum

mg/L)

LOAEL

mg/kg/day

(AUC

mg/L*h)

LOAEL

(Av serum 

mg/L)

Seacat et al., 2002 

monkey ↑liver 

weight

182 0.15

(102000)

23.35 0.75

(332000)

76.01

Luebker et al., 

2005b ↓ rat pup 

body weight

84 0.1

(9100)

4.51 0.4

(36400)

18.06

Luebker et al., 

2005a ↓ rat pup 

body weight

63 None None 0.4

(36400)

24.07

Luebker et al., 

2005a ↓maternal 

weight, pup 

survival

63 0.4

(36400)

24.07 0.8

(72600)

48.02

Lau et al., 2003 

↓rat pup survival

19 1.0

(8010)

17.56 2.0

(16000)

35.09

Butenhoff et al., 

2009 rat ↑DNT

41 0.3

(10700)

10.87 1.0

(35600)

36.18

Seacat et al., 2003 

male ↑rat liver 

weight

98 0.34

(39600)

16.84 1.33

(158000)

67.18

Table 5-11 identifies 4.51 and 10.87 mg/L as the lowest average serum concentrations 

which were associated with a NOAEL for offspring effects; the LOAELs were associated with 

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 in monkeys 

(Seacat et al., 2002) and male rats (Seacat et al., 2003) are very similar to the average serum 

value in Butenhoff et al. (2009). Thus, it appears that the NOAELs are consistent across gender, 

species, and treatment with respect average serum concentration. Assuming that mode of action 

and susceptibility to toxicity do not vary and that pharmacokinetics alone explains variation, it is 

reasonable to expect similar concentrations to cause similar effects in humans.

The EPA model employed here to generate the predicted AUC values that became the 

basis for the average serum concentrations shown in Table 5-11, 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 36.18 mg/L as seen in Table 5-11 which is very similar to the approximately 

25 mg/L for the dams that can be estimated from the graph (Loccisano et al., 2012b). The 

slightly higher value calculated from the EPA model may 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 EPA model predicts maternal values, not fetal, a direct comparison to the fetal 
Perfluorooctane sulfonate (PFOS) – February 2014 5-20 

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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 EPA model can be accepted with reasonable 

confidence that the predicted AUC values accurately represent maternal levels during gestational 

and lactational exposures. 

The predicted 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. 

A reliable measure of half-life in humans is from a retired worker population followed for 

five years. Olsen et al. (2007) calculated the PFOS half-life in this former worker population as 

5.4 years (see Section 3.5.2). Thompson et al. (2010) gives a volume of distribution of 0.23 L/kg 

bw (see Section 3.5.3). 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/day x (0.693 ÷ 1971 days) = 0.000081 L/kg bw/day 

Where:

 Vd = 0.23 L/kg

 ln 2 = 0.693 

 t1/2 = 1971 days (5.4 years x 365 days/year = 1971 days) 

These values combined give a clearance of 8.1 x 10-5 L/kg bw/day. 

Scaling the derived average concentrations (in mg/L) for the NOAELs and LOAELs in 

Table 5-9 gives predicted oral human equivalent doses (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 mg/L) x CL 

Where:

 Average serum is from model output in Table 5-11 

 CL = 0.000081 L/kg bw/day 

The resulting HED values are shown in Table 5-12. Endpoints considered as critical 

effects in multiple studies include offspring growth and survival, liver weight changes, and liver 

histopathology. 
Perfluorooctane sulfonate (PFOS) – February 2014 5-21 

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TABLE 5-12. Human Equivalent Doses Derived from the Modeled Animal Average Serum 

Values

Study Dosing 

duration 

days

NOAEL

mg/kg/d 

NOAEL 

Av serum

mg/L

HED

mg/kg/d

LOAEL

mg/kg/d

LOAEL

Av serum 

mg/L

HED

mg/kg/d

Seacat et al., 

2002 monkey 

↑liver weight 

182 0.15 23.35 0.0019 0.75 76.01 0.0062

Luebker et al., 

2005b

84 0.1 4.51 0.00037 0.4 18.06 0.0015

Luebker et al., 

2005a↓ rat pup 

body weight

63 None None 0.4 24.07 0.0019

Luebker et al., 

2005a 

↓maternal 

weight pup 

survival

63 0.4 24.07 0.0019 0.8 48.02 0.0039

Lau et al., 2003 

↓ rat pup 

survival

19 1.0 17.56 0.0014 2.0 35.09 0.0028

Butenhoff et 

al., 2009 ↑ rat 

DNT

41 0.3 10.87 0.00088 1.0 36.18 0.0029

Seacat et al., 

2003 ↑male rat 

liver weight

98 0.34 16.84 0.0014 1.33 67.18 0.0054

5.1.1.3 RfD Quantitation 

Several acceptable points of departure (PODs) can be used in the process of identifying 

the POD for RfD development: 

 

• NOAEL or LOAEL values 

• Lower 95% confidence bounds on the BMD (BMDLs), and 

• Human Equivalent Doses (HED). 

Studies that have more than one POD for the same NOAEL or LOAEL are summarized 

in Table 5-13. All 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). The 

developmental effects of reduced pup body weight and survival occurred in the absence of 

changes in maternal liver weight. The calculated HED values associated with no adverse effects 

on developmental and liver endpoints (NOAELs) were very similar with a range of 0.00088-

0.0019 mg/kg/day.

Modeling of dose-response to identify a BMD and BMDL was successful for most

studies. All benchmark models targeted a 10% increase in liver weight or histopathology 

incidence or a 5% decrease in offspring body weight and survival. Most of the studies were 

amenable for derivation of HED based on average serum measurements from the 

pharmacokinetic model because dose and species-specific serum values were available for model 
Perfluorooctane sulfonate (PFOS) – February 2014 5-22 

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development. Entries in Table 5-13 provide at least three potential PODs for consideration; four 

studies provide five values. 

 

TABLE 5-13. RfD Point of Departure Options from the PFOS Animal Studies

Studies NOAEL

(mg/kg/ 

day)

LOAEL

(mg/kg/ 

day)

BMDL10

(mg/kg/ 

day)

HED

NOAEL

(mg/kg/ 

day)

HED

LOAEL

(mg/kg/ 

day)

Endpoint

Seacat et al., 

2002

0.15 0.75 0.015 0.0019 0.0062 Increased liver weight.

Seacat et al., 

2003

0.34 1.33 0.059 0.0014 0.0054 Increased liver weight.

Thomford, 

2002

0.018 0.072 0.033 - - Liver hypertrophy.

Thibodeaux 

et al., 2003

1.0 2.0 0.12* - - Decreased maternal and 

pup body weight 

(LOAEL); fetal sternal 

defects (BMDL5)

Lau et al., 

2003

1.0 2.0 0.58* 0.0014 0.0028 Reduced pup survival.

Butenhoff et 

al., 2009

0.3 1.0 - 0.00088 0.0029 Increased motor activity in 

male pups on PND 17.

Luebker et 

al., 2005b

0.1 0.4 - 0.00037 0.0015 Decreased pup body 

weight.

Luebker et 

al., 2005a

None 0.4 0.27* - 0.0019 Decreased pup body 

weight.

Luebker et 

al., 2005a

0.4 0.8 0.89* 0.0019 0.0039 Reduced pup survival.

* The value provided for developmental endpoints is the BMDL05 rather than the BMDL10.

As explained previously, human data have identified significant relationships between 

serum levels and specific indicators of adverse health effects but lack the exposure information 

for dose-response modeling. For this reason none of the human studies provided an appropriate 

POD for RfD derivation. 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. Extrapolation to humans adds a layer of uncertainty that must be accommodated 

in deriving the RfD. 

Each of the POD values represented in Table 5-13 requires a different quantification 

approach. Thus, EPA has systematically examined the impact of POD on outcome through three 

sets of calculations as follows:

• Derivation from the NOAEL values;

• Derivation from the BMDL values; 

• Derivation from HED values derived from modeled average serum values.

NOAEL PODs: Table 5-14 provides the potential RfDs derived from the seven studies which 

identified a NOAEL. These studies also provided a LOAEL which is critical for dose-response 

characterization. The NOAEL is used as the POD according to Agency policy instead of the 

LOAEL because lower uncertainty is applied to the NOAEL when calculating the RfD. The 

lowest NOAEL is from a chronic bioassay in the rat (Thomford, 2002) and is the dose which did 
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not cause microscopic lesions in the liver. Because it is a chronic study the uncertainty applied 

in derivation of the RfD is less than that used in the other rat studies and the monkey study. The 

NOAEL from Thomford (2002) is also protective of co-critical developmental toxicity effects 

observed in other studies. 

 

TABLE 5-14. The Impact of Quantification Approach on the RfD outcome for the PODs 

from the available NOAELs

Study POD dose 

mg/kg/day

UFH UFA UFL UFS UFD UFtotal Potential 

RfD

mg/kg/day

Seacat et al., 2002 

monkey

0.15 10 48 1 10 1 4800 0.00003

Seacat et al., 2003 rat 0.34 10 123 1 10 1 12300 0.00003

Thomford, 2002 rat 0.018 10 123 1 1 1 1230 0.00001

Thibodeaux et al., 

2003 rat

1.0 10 123 1 10 1 12300 0.00008

Lau et al., 2003 rat 1.0 10 123 1 10 1 12300 0.00008

Butenhoff et al., 

2009 rat

0.3 10 123 1 10 1 12300 0.00002

Luebker et al., 2005b 

rat

0.1 10 123 1 10 1 12300 0.000008

Luebker et al., 2005a 

rat

0.4 10 123 1 10 1 12300 0.00003

Uncertainty Factor (UF) Application

UFH A ten-fold adjustment is assigned to account for intrahuman variability and applied for all 

PODs. 

UFA. Determination of the interspecies uncertainty factor for the NOAEL requires application of 

the equation for first order kinetics in order to determine the pharmacokinetic adjustment 

associated with differences in half-life between humans and rats or monkeys. Pharmacokinetic 

studies with PFOS have measured a serum half-life of approximately 48 days in rats (Butenhoff 

and Chang, 2007) and approximately 121 days in monkeys (Chang et al., 2012). The equation 

also utilizes a volume of distribution component, which for humans has been calibrated as 230 

mL/kg (Thompson et al., 2010). This volume of distribution is similar to those reported for 

monkeys, female rats, and mice in pharmacokinetic studies (Chang et al., 2012) and utilized in 

pharmacokinetic models on monkeys (Anderson et al., 2006). 

The equation that describes first order kinetics is as follows (Medinsky and Klaassen, 1996): 

CL = Vd x (ln 2 ÷ t1/2) 

Where: 

 Vd = 0.23 L/kg

 Ln 2 = 0.693 

Half-life = 48 days for rats; 121 days for monkeys; and 1971 days for humans 

CLrat = 0.23 L/kg x (0.693 ÷ 48 days) = 0.0033 L/kg/day 
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CLmonkey = 0.23 L/kg x (0.693 ÷ 121 days) = 0.0013 L/kg/day 

CLhuman = 0.23 L/kg x (0.693 ÷ 1971 days) = 0.000081 L/kg/day 

The ratio of CLrat to CLhuman (0.0033 L/kg/day ÷ 0.000081 L/kg/day = 41) is used as the 

pharmacokinetic adjustment for differences between these species. The total UFA requires an 

additional 3-fold factor for species differences in pharmacodynamics (41 x 3 = 123).

The ratio of CLmonkey to CLhuman (0.0013 L/kg/day ÷ 0.000081 L/kg/day = 16) is used as the 

pharmacokinetic adjustment for differences between these species. The total UFA requires an 

additional 3-fold factor for species differences in pharmacodynamics (16 x 3 = 48).

UFL A UF of 1 was used for the NOAEL-derived PODs following Agency policies. 

 

UFS A ten-fold factor was applied to the NOAEL PODs to account for studies with less than 

lifetime exposure.

UFD In all cases the uncertainty factor for the strength of the database (UFD) is 1. The data base 

for oral PFOS exposure studies is essentially complete although mechanistic questions relative to 

the MOA have not yet been fully elucidated.

 

BMDL PODs. Potential PODs from benchmark dose estimates are listed in Table 5-13. The 

lowest, species-specific benchmark dose values are those from the Seacat et al. (2002; 2003) 

studies in the male monkey and male rat and the Thomford (2002) study in the male rat. For the 

Seacat et al. (2002; 2003) studies the effect modeled was a 10% change in liver weight. For the 

Thomford (2002) study the effect modeled was a 10% increase in incidence of hepatocellular 

centrilobular hypertrophy. The BMDL estimates for the liver effects are lower than those 

calculated for developmental effects, indicating that liver endpoints are protective of other cocritical endpoints. The values for developmental endpoints are included in Table 5-15 for 

comparison. 
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TABLE 5-15. The Impact of Quantification Approach on the RfD Outcome for the 

BMDLs from liver and developmental endpoints

POD Dose

mg/kg/d 

UFH UFA UFL UFS UFD UFtotal Potential 

RfD

mg/kg/day

BMDL10 

(monkey Seacat et al.,

2002)

0.015 10 48 1 10 1 4800 0.000003

BMDL10 

(rat Seacat et al., 2003)

0.059 10 123 1 10 1 12300 0.000005

BMDL10 

(rat Thomford, 2002)

0.033 10 123 1 1 1 1230 0.00003

BMDL05

(rat Thibodeaux et al., 

2003)

0.12 10 123 1 10 1 12300 0.00001

BMDL05 

(rat Lau et al., 2003)

0.58 10 123 1 10 1 12300 0.00005

BMDL05 

(rat Luebker et al., 

2005a)

0.27 10 123 1 10 1 12300 0.00002

Uncertainty Value Application

The UFH, UFA, UFS and UFD values are assigned as described for the NOAEL data in Table 5-

14. 

UFL A UF of 1 was used for the BMDL-derived PODs following Agency policies. 

HED PODs. The pharmacokinetic (PK) HEDs derived from Seacat et al. (2002; 2003), Lau et 

al. (2003), Butenhoff et al. (2009), and Luebker et al. (2005a,b) were each examined as the 

potential basis for the RfD (Table 5-16). Each of these studies contained a NOAEL from which 

the HED could be derived. The outcomes for potential RfD values are quite similar 

demonstrating the ability of the model to normalize the animal data across species, gender, and 

exposure duration. Co-critical effects of liver lesions and developmental toxicity resulted in 

similar HED values which yielded similar potential RfD values.
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TABLE 5-16. The Impact of Quantification Approach on the RfD Outcomes for the HEDs 

from the Pharmacokinetic Model Average Serum Values

POD Value

mg/kg/day

UFH UFA UFL UFS UFD UFtotal Potential 

RfD

mg/kg/day

PK-HED monkey Seacat et 

al., 2002

0.0019 10 3 1 1 1 30 0.00006

PK-HED rat Seacat et al., 2003 0.0014 10 3 1 1 1 30 0.00005

PK-HED rat Lau et al., 2003 0.0014 10 3 1 1 1 30 0.00005

PK-HED rat Butenhoff et al., 

2009

0.00088 10 3 1 1 1 30 0.00003

PK-HED rat Luebker et al., 

2005b

0.00037 10 3 1 1 1 30 0.00001

PK-HED rat Luebker et al., 

2005a

0.0019 10 3 1 1 1 30 0.00006

Uncertainty Value Application

The UFH, UFL, and UFD values are assigned as described for the NOAEL data in Table 5-14. 

The UFA is 3 for each study because the HED was derived using the steady state serum values 

from the model to account for pharmacokinetic differences between animals and humans. The 3-

fold factor is applied to account for toxicodynamic differences between the animals and humans 

The UFS is 1 bacause the point of departure is based on steady state serum concentrations.

RfD Selection 

Based on the consistency of the response and with recognition of the use of 

developmental toxicity as the sensitive endpoint, the 0.00003 mg/kg/day outcome is selected as 

the RfD for PFOS. This value is the outcome for the modeled rat serum for developmental 

neurotoxicity (Butenhoff et al., 2009) and supported by the slightly higher 0.00005 and 0.00006 

mg/kg/day values for increases in liver weight and other developmental effects. Thus, cooccurring critical endpoints are protected by the chosen RfD.

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 pup body weight were reported. Animal data 

consistently show higher PFOS levels in fetal tissues, including brain, as compared to maternal 

tissues (Chang et al., 2009; Borg et al., 2010) resulting in the higher modeled predictions for fetal 

versus maternal levels (Loccisano et al., 2012b; see Figure 3-7). 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 (So et al., 2006; Karrman et al., 2010; Tao et al., 2008), and in 

serum samples from children aged 2-12 (Olsen et al., 2002b). A human epidemiology found no 

association with maternal PFOS levels and motor or mental development of their children; the 

mean maternal serum concentration was approximately 35 mg/L (Fei et al., 2008b). The HED 

used as the basis for the RfD, was calculated from an average serum concentration of 10.87 mg/L 
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derived from the NOAEL of 0.3 mg/kg/day for developmental neurotoxicity (Butenhoff et al., 

2009; Table 5-11). This further supports the selected RfD as being protective of adverse human 

health risks. 

Use of the developmental neurotoxicity and liver weight endpoints as the basis for the 

RfD confers protection against co-occurring adverse effects on offspring body weight and 

survival. The selected RfD is supported by the results from the modeled serum value for rat 

offspring body weight (Luebker et al., 2005a) and survival (Lau et al., 2003). These supporting 

values are slightly greater than the recommended RfD, indicating that the RfD is protective of 

co-occurring effects on the offspring. For these co-occurring effects, both the modeled values 

were similar (0.00005-0.00006 mg/kg/day) adding confidence to the selected RfD. 

The most conservative potential RfD was derived from modeled serum for decreased pup 

body weight from the two-generation study (Luebker et al., 2005b). While this represents the 

most sensitive endpoint, it was described by the authors as transient because the body weights 

were significantly lower than those for controls for 2 of 5 time points monitored with the weight 

differences before and after those two time points not significantly different. Benchmark data 

for the body weight data to frame the NOAEL POD versus the LOAEL POD were not available. 

Other modeled results are in good agreement with those from a gestational and lactational model 

(Loccisano et al., 2012b) but cumulative effects from continuous exposure over multiple 

generations is unknown and not accounted for by the present model. 

5.1.2 RfC Determination 

For development of an RfC, an adequate subchronic inhalation study must be available for 

review. At this time, data are insufficient for PFOS to develop an RfC. The only inhalation study 

available is an acute lethality inhalation study in rats (Rusch et al., 1979); no inhalation data are 

available in humans. Therefore, an RfC for PFOS cannot be derived. 

5.2 Dose-Response for Cancer Effects 

In a chronic oral toxicity and carcinogenicity study of PFOS in rats, liver, thyroid and 

mammary fibroadenomas were identified (Thomford, 2002). The biological significance of the 

mammary fibroadenomas and thyroid tumors were questionable as a true dose-dependent response 

was not identified. Mammary fibroadenomas were increased only in low-dose females and the 

incidence rate showed a significant decreasing trend with dose. The incidence of thyroid follicular cell 

adenomas was increased in the high-dose males administered PFOS for 52 weeks followed by basal 

diet until natural death, but was not increased in high-dose males given PFOS for 104 weeks. The 

liver tumors also had a questionable dose-response with slight but statistically significant increases 

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 vs. none in the controls of either sex); only one hepatocellular carcinoma 

was found in a high-dose female. No evidence of cell proliferation or peroxisome proliferation was 

found as measured by hepatic palmitoyl-CoA oxidase activity, PCNA, and BrdU.

Human epidemiology studies did not find a direct correlation between PFOS exposure and the 

incidence of carcinogenicity in worker-based populations. Several studies looked at worker-related 

toxicities of PFOS including some on cancer incidence (Mandel and Johnson, 1995; Alexander et al., 

2003; Alexander and Olsen, 2007). A slight increase in bladder cancer was identified in workers; 
Perfluorooctane sulfonate (PFOS) – February 2014 5-28 

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however, the outcome was not adjusted to account for other possible causes such as cigarette smoking 

practices (Mandel and Johnson, 1995; Alexander et al., 2003). Based on these results, 3M undertook 

another study of the same cohort to examine bladder cancer incidence (Alexander and Olsen, 2007) 

and identified eleven bladder cancer cases with five deaths and 6 incident cases. Only 2 of the 6 selfreported cases were confirmed with medical records and five of the 6 cases had a history of cigarette 

smoking. Standardized incidence ratios (SIR) were estimated for 3 exposure categories and compared 

to US cancer rates. SIRs ranged from less than 1 to 2.72 but none were statistically significant. 

Grice et al. (2007) also looked for association between PFOS exposure the incidence of cancer 

at the 3M Decatur plant and found that prostate, melanoma and colon cancer were the most frequently 

reported malignancies, but none reached statistical significance. In the general population, Eriksen et 

al. (2009) compared plasma levels of PFOS to the incidence of cancer in 57,000 Danish individuals 

and found no statistically significant trends. 

As discussed in Section 4.4.3., in animals, the induction of peroxisome proliferation has been 

suggested to be the mode of action (MOA) for the tumors observed with PFOS. Evidence of this 

MOA can be identified by an increase in the number of peroxisomes, increases in the activity of CoA 

oxidase activity and hepatic cell proliferation as described by Rao and Reddy, (1996) and Ashby et al., 

(1994). While a number of short-term studies in rats and mice (Sohlenius et al., 1993; Ikeda et al., 

1987; 3M Company, 2004) have shown that PFOS is capable of inducing peroxisome proliferation, 

longer-term studies in monkeys and rats have not (Seacat et al., 2002; 2003; Thomford, 2002). 

Positive evidence for peroxisome proliferation was found in mice administered a dietary level 

of 500 ppm PFOS for 5 days (Sohlenius et al., 1993) and in rats given 200 ppm in the diet for two 

weeks (Ikeda et al., 1987). In contrast, no increases in hepatic cell proliferation (a precursor for tumor 

development) were detected in a rat subchronic study (Seacat et al., 2003), the cancer bioassay in rats 

(Thomford, 2002), or in monkeys administered PFOS for six months (Seacat et al., 2002). Also, in 

studies by Wolf et al. (2008 and 2012) and Ishibashi et al. (2011), peroxisome proliferation was 

activated less by the perfluorinated sulfonates, including PFOS, when compared to the perfluorinated 

carboxylates and mouse PPARα was more activated than human suggesting possible involvement of 

other MOAs. In contrast to PFOA, PFOS was poorly correlated with peroxisome proliferators in a 

study of global PPARα gene expression patterns following exposure (Martin et al., 2007). The weight 

of evidence for the carcinogenic potential to humans of these tumors was judged to be too limited to 

support a quantitative cancer assessment. 
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Perfluorooctane sulfonate (PFOS) – February 2014 A-1 

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APPENDIX A: Summary of Data
Perfluorooctane sulfonate (PFOS) – February 2014 A-2 

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TABLE A.1. PFOS Toxicokinetic Information

Species Dose Route of 

exposure

Effects 

observed

PFOS in liver

(μg/g)

PFOS in blood 

(ppm)

PFOS in brain

(μg/g)

M F M F M F

human

1 NA Unknown NA 0.19 (serum)

0.015 ppm

NS NS

human

2 NA Unknown None 

observed

NS 0.27 NS NS NS NS

human

3 NA Unknown ↑ total 

cholesterol

NS NS 0.022 NS NS

human

4 NA Unknown ↑ total 

cholesterol

NS NS 0.023 NS NS

human

5 NA Unknown ↑ total 

cholesterol

NS NS 0.023 0.018 NS NS

human6 NA Unknown ↑ incidence of 

thyroid 

disease

NS NS 0.037 NS NS NS

monkey7 0.15 

mg/kg/day 

for 26 weeks 

with 52 

week 

recovery

capsule None 

observed

NS NS (serum)

wk 1: 4.60

wk 35: 84.5

wk 79: 19.1

(serum)

wk 1: 3.71

wk 35: 74.7

wk 79: 21.4

NS NS

monkey7 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 35: 181

wk 79: 41.1

(serum)

wk 1: 20.4

wk 35: 171

wk 79: 41.4

NS NS

rat8 0.03

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: 0.091

wk 14: 4.04

wk 105: 1.31

(serum)

wk 0: 1.61

wk 14: 6.96

wk 105: 4.35

NS NS

rat8 0.4

mg/kg/day 

diet ↑ liver 

histopath. wk 0: 47.6 wk 0: 83.0

(serum)

wk 0: 7.57

(serum)

wk 0: 12.6

NS NS
Perfluorooctane sulfonate (PFOS) – February 2014 A-3 

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TABLE A.1. PFOS Toxicokinetic Information

Species Dose Route of 

exposure

Effects 

observed

PFOS in liver

(μg/g)

PFOS in blood 

(ppm)

PFOS in brain

(μg/g)

M F M F M F

for 104 

weeks

lesions wk 10: 358

wk 105: 70.5

wk 10: 370

wk 105: 

131

wk 14: 43.9

wk 105: 22.5

wk 14: 64.4

wk 105: 75.0

rat8 1.5

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

NS NS

rat9 2 mg/kg diet 

for 28 days

diet None 

observed

48.28 43.44 (serum)

0.95 μg/g serum

(serum)

1.50 μg/g serum

NS NS

rat9 20 mg/kg

diet for 28 

days

diet ↓T4 and ↑ 

liver wt.

560.23 716.55 (serum)

13.45 μg/g serum

(serum)

15.40 μg/g serum

NS NS

rat9 100 mg/kg

diet for 28 

days

diet ↓ body wt, T4, 

T3 and 

cholesterol

↑ hepatocyte 

hypertrophy

1030.40 1008.59 (serum)

29.88 μg/g serum

(serum)

43.20 μg/g serum

NS NS

rat10

(m only)

5 mg/kg for 

28 days

drinking

water

↓ body wt 345 NS (whole blood)

72.0

NS NS NS

rat10

(m only)

20 mg/kg for 

28 days

drinking 

water

10/10 died 

(day 26)

hepatic 

hypertrophy

648 NS (whole blood)

NS

NS NS NS

rat11 0.4 mg/kg42 days 

prior to 

cohabitation 

through GD 

21

oral

gavage

. NS GD 21: 

dams = 107 

fetuses = 

30.6

NS (serum)

GD 1: 8.90

GD 7: 7.83

GD 21: 

dams = 26.2 

fetuses = 34.3

NS NS

rat11 1.6 mg/kg42 days 

prior to 

oral 

gavage

NS GD 21: 

dams = 388 

fetuses = 

NS (serum)

GD 1: 160

GD 7: 154

NS NS
Perfluorooctane sulfonate (PFOS) – February 2014 A-4 

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TABLE A.1. PFOS Toxicokinetic Information

Species Dose Route of 

exposure

Effects 

observed

PFOS in liver

(μg/g)

PFOS in blood 

(ppm)

PFOS in brain

(μg/g)

M F M F M F

cohabitation 

through GD 

21

86.5 GD 21: 

dams = 136 

fetuses = 101

rat11 3.2 mg/kg42 days 

prior to 

cohabitation 

through GD 

21

oral 

gavage

NS GD 21: 

dams = 610 

fetuses = 

230

NS (serum)

GD 1: 318

GD 7: 306

GD 21: 

dams = 155 

fetuses = 164

NS NS

rat12 0.1 mg/kgGD 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

PND 21:

Offspring 

= 0.22

GD 20:

Dams = 

0.15

Offspring 

= 1.23

PND 21:

Dams = 

NS

Offspring 

= 0.23

rat12 1.0 mg/kgGD 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 = 

(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

PND 21:

Offspring 

= 2.62

GD 20:

Dams = 

0.99

Offspring 

= 12.98

PND 21:

Dams = 

NS

Offspring 

= 2.70
Perfluorooctane sulfonate (PFOS) – February 2014 A-5 

Draft – Do Not Cite or Quote 

TABLE A.1. PFOS Toxicokinetic Information

Species Dose Route of 

exposure

Effects 

observed

PFOS in liver

(μg/g)

PFOS in blood 

(ppm)

PFOS in brain

(μg/g)

M F M F M F

7.2

mouse

13 50 mg/kg 

one time

SQ injection ↑ liver wt. 

and signs of 

oxidative 

damage

PND 7: 15%

PND 21: 

51%

PND 35: 

74%

PND 7: 

16%

PND 21: 

52%

PND 35: 

70%

PND 7: 12%

PND 21: 10%

PND 35: 13%

PND 7: 11%

PND 21: 12%

PND 35: 12%

PND 7: 

5%

PND 21: 

2%

PND 35: 

1%

PND 7: 

4%

PND 21: 

2%

PND 35: 

1%

NS = no sample obtained or recorded; NA = not applicable

1

Olsen et al. 2003

2

Kärrman et al. 2010

3

Steenland et al. 2009

4

Frisbee et al. 2010

5

Nelson et al. 2010

6 Melzer et al. 2010

7

Seacat et al. 2002 8

Thomford 2002

9

Curran et al. 2008

10Cui et al. 2009

11Luebker et al. 2005a

12Chang et al. 2009

13Liu et al. 2009
Perfluorooctane sulfonate (PFOS) – February 2014 A-6 

Draft – Do Not Cite or Quote 

TABLE A.2. Key Studies Used With Effects Related to Serum Values (Condensed Version)

Study Species/Strain Exposure 

duration

Dose 

(mg/kg/day)

PFOS concentration

(μg/mL)

NOAEL

(mg/kg)

LOAEL

(mg/kg)

Critical Effect

M F

LIVER EFFECTS

Curran et al. 

2008

Rat/Sprague-Dawley

15/sex/group

diet

28 days

0 

M: 0.14; F: 

0.15

M: 1.33; F: 

1.43

M: 3.21; F: 

3.73

M: 6.34; F: 

7.58

serum (values 

expressed as 

μg/g serum)

0.47

0.95

13.45

20.93

29.88

serum 

(values 

expressed as 

μg/g serum)

0.95

1.50

15.40

31.93

43.20

0.14 (M)

NA (F)

1.33 (M)

0.15 (F)

F: ↑ final relative (to 

body weight) liver 

weight

M: ↑ final relative 

(to body weight) 

liver weight; ↓ 

serum T4

Seacat et al. 

2003

Rat/ Crl:CD(SD) IGS 

BR

5/sex/group

diet

98 days

(14 weeks)

0 

0.035 

0.14

0.35

1.4

serum

<LOQa 

4.04

17.1

43.9

148

serum

2.67

6.96

27.3

64.4

223

0.35 1.4 ↑ absolute liver wt 

and ALT (m) and ↑ 

relative liver wt (f)

centrilobular hepatic 

hypertrophy (m/f)

Seacat et al. 

2002

Monkey/Cynomolgus

6/sex/group

capsule

182 days 

(26 weeks) 

followed by 

52 week 

recovery

0 

serum

wk 1: NA

wk 16: 0.04

wk 27: 0.05

serum

wk 1: NA

wk 16: 0.04

wk 27: 0.04

0.15 0.75 M/F: ↑ absolute and 

relative hepatic wt; 

centrilobular or 

diffuse 

hepatocellular 
Perfluorooctane sulfonate (PFOS) – February 2014 A-7 

Draft – Do Not Cite or Quote 

TABLE A.2. Key Studies Used With Effects Related to Serum Values (Condensed Version)

Study Species/Strain Exposure 

duration

Dose 

(mg/kg/day)

PFOS concentration

(μg/mL)

NOAEL

(mg/kg)

LOAEL

(mg/kg)

Critical Effect

M F

0.03

0.15

0.75

wk 35: 0.05

wk 79: 0.02

wk 1: 0.869

wk 16: 11.2

wk 27: 15.9

wk 35: NS

wk 79: ND

wk 1: 4.60

wk 16: 56.2

wk 27: 68.1

wk 35: 84.5

wk 79: 19.1

wk 1: 21.0

wk 16: 189

wk 27: 194

wk 35: 181

wk 79: 41.1

wk 35: 0.07

wk 79: 0.02

wk 1: 0.947

wk 16: 10.5

wk 27: 11.1

wk 35: NS

wk 79: ND

wk 1: 3.71

wk 16: 42.1

wk 27: 58.5

wk 35: 74.7

wk 79: 21.4

wk 1: 20.4

wk 16: 162

wk 27: 160

wk 35: 171

wk 79: 41.4

hypertrophy

Thomford,

2002

Rat/Crl:CD

(SD)IGS BR 

diet

104 weeks

0 

0.018-0.023

0.072-0.099

serum

wk 1: <LOQ

wk 14: <LOQ

wk 53: 0.025

wk 105: 

0.012

wk 1: 0.091

wk 14: 4.04

wk 53: NS

wk 105: 1.31

wk 1: 4.33

wk 14: 17.1

serum

wk 1: 0.026

wk 14: 2.67

wk 53: 0.40

wk 105: 

0.084

wk 1: 1.61

wk 14: 6.96

wk 53: NS

wk 105: 4.35

wk 1: 6.62

wk 14: 27.3

Males 

0.018 

Females 

0.099

Males

0.072

Females

0.247

Males and Females: 

liver histopathology
Perfluorooctane sulfonate (PFOS) – February 2014 A-8 

Draft – Do Not Cite or Quote 

TABLE A.2. Key Studies Used With Effects Related to Serum Values (Condensed Version)

Study Species/Strain Exposure 

duration

Dose 

(mg/kg/day)

PFOS concentration

(μg/mL)

NOAEL

(mg/kg)

LOAEL

(mg/kg)

Critical Effect

M F

0.184-0.247

0.765-1.1 

wk 53: NS

wk 105: 7.60

wk 1: 7.57

wk 14: 43.9

wk 53: NS

wk 105: 22.5

wk 1: 41.8

wk 14: 148

wk 53: 146

wk 105: 69.3

wk 53: NS

wk 105: NS

wk 1: 12.6

wk 14: 64.4

wk 53: NS

wk 105: 75.0

wk 1: 54.0

wk 14: 223

wk 53: 220

wk 105: 233

THYROID EFFECTS

Chang et al. 

2008

Rat/Sprague-Dawley

5-15 females/group

oral gavage

Single dose

0 

15

No males 

dosed

serum

< LLOQa at 

all timepoints

2 hrs: 37.28

6 hrs: 66.90

24 hrs: 61.58

NA 15 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

Curran et al. 

2008

Rat/Sprague-Dawley

15/sex/group

diet

28 days

0 

M: 0.14; F: 

0.15

serum (values 

expressed as 

μg/g serum)

0.47

0.95

13.45

serum 

(values 

expressed as 

μg/g serum)

0.95

1.50

M: 0.14; 

F: 0.15

M: 1.33; F: 

1.43 

M/F: ↓ T4
Perfluorooctane sulfonate (PFOS) – February 2014 A-9 

Draft – Do Not Cite or Quote 

TABLE A.2. Key Studies Used With Effects Related to Serum Values (Condensed Version)

Study Species/Strain Exposure 

duration

Dose 

(mg/kg/day)

PFOS concentration

(μg/mL)

NOAEL

(mg/kg)

LOAEL

(mg/kg)

Critical Effect

M F

M: 1.33; F: 

1.43

M: 3.21; F: 

3.73

M: 6.34; F: 

7.58

20.93

29.88

15.40

31.93

43.20

DEVELOPMENTAL EFFECTS

Butenhoff et 

al. 2009 and 

Chang et al. 

2009

Rat/Sprague-Dawley

25 females/group

oral gavage

GD 0- PND 

20

Offspring 

monitored 

through PND 

72

0 

0.1

serum

PND 21:

M Offspring 

= <LLOQ

PND 72:

M Offspring 

= <LLOQ

PND 21:

M Offspring 

= 1.73

PND 72:

M Offspring 

= 0.04

serum

GD 20:

Dams = 

<LLOQ 

Fetus = 

0.009

PND 21:

Dams = 

0.007

F Offspring 

= <LLOQ

PND 72:

Dams = NA

F Offspring 

= <LLOQ

GD 20:

Dams = 1.72

Fetus = 3.91

PND 21:

Dams = 3.16

F Offspring 

= 1.77

PND 72:

Maternal: 

0.3

 

Male 

offspring: 

0.3

Female 

Offspring:

>1 mg/kg 

Maternal:

1.0

Male 

offspring: 1.0

Female 

Offspring: ND

Maternal: ↓ body wt

Male offspring: 

based on ↓ 

habituation response
Perfluorooctane sulfonate (PFOS) – February 2014 A-10 

Draft – Do Not Cite or Quote 

TABLE A.2. Key Studies Used With Effects Related to Serum Values (Condensed Version)

Study Species/Strain Exposure 

duration

Dose 

(mg/kg/day)

PFOS concentration

(μg/mL)

NOAEL

(mg/kg)

LOAEL

(mg/kg)

Critical Effect

M F

0.3

1.0

PND 21:

M Offspring 

= 5.05

PND 72:

M Offspring 

= 0.12

PND 21:

M Offspring 

= 18.61

PND 72:

M Offspring 

= 0.56

Dams = NA

F Offspring 

= 0.21

GD 20:

Dams = 6.25

Fetus = 

10.45

PND 21:

Dams = 8.98

F Offspring 

= 5.25

PND 72:

Dams = NA

F Offspring 

= 0.56

GD 20:

Dams = 

26.63

Fetus = 

31.46

PND 21:

Dams = 

30.48

F Offspring 

= 18.01

PND 72:

Dams = NA

F Offspring 

= 1.99

Thibodeaux et 

al. 2003 and 

Rat/Sprague-Dawley

16-25 females/group

GDs 2-20 serum on GD 21 Maternal 

= 1 

Maternal= 2 Maternal: ↓ body wt
Perfluorooctane sulfonate (PFOS) – February 2014 A-11 

Draft – Do Not Cite or Quote 

TABLE A.2. Key Studies Used With Effects Related to Serum Values (Condensed Version)

Study Species/Strain Exposure 

duration

Dose 

(mg/kg/day)

PFOS concentration

(μg/mL)

NOAEL

(mg/kg)

LOAEL

(mg/kg)

Critical Effect

M F

Lau et al. 

2003 oral gavage 0 

1 

2

3

5 

10

Dam: 0.24

Newborn: 0.188

Dam: 19.6

Newborn: 35.9

Dam: 45.0

Newborn: 71.9

Dam: 71.9

Newborn: 86.5

Dam: 80.6

Newborn: 108.2

Dam: 189.9

Newborn: NS

Develop

mental

= 1 

Developmental 

= 2 

Developmental: 

based on ↓ survival 

and developmental 

delays

BMDL5

corresponding to 

maternal dose for 

survival of rat pups 

at PND 8 was 0.58 

mg/kg

BMDL5

corresponding to 

fetal sternal defects 

was 0.12 and cleft 

palates was 3.33 

mg/kg

REPRODUCTIVE

Luebker et al. 

2005a and 

2005b

Rat/Crl:CD (SD)IGS 

VAF/Plus

oral gavage

6 wks prior 

to mating 

through 

gestation and 

lactation 

across 2 

generations

Due to high 

number of 

pups dying, 

only 0, 0.1 

and 0.4 

administered 

to 2nd

0 

0.1

0.4

NS

serum

NS

Dams

GD 1: 8.90

GD 7: 7.83

GD 15: 8.81

GD 21: 4.52

Fetus GD 21: 

9.08

Dams

GD 1: 40.7

GD 7: 40.9

F0 dams

0.4 

F1 pups: 

0.4

F0 dams 0.8 

F1 pups: 0.8

F0 dams: 

Decreased body wt

F1 pups: 

Decreased gestation 

length

BMDL5 for 

decreased survival of 

pups through LD5 

was 0.89 mg/kg/day

BMDL5 for pup 

weight gain was 0.28 
Perfluorooctane sulfonate (PFOS) – February 2014 A-12 

Draft – Do Not Cite or Quote 

TABLE A.2. Key Studies Used With Effects Related to Serum Values (Condensed Version)

Study Species/Strain Exposure 

duration

Dose 

(mg/kg/day)

PFOS concentration

(μg/mL)

NOAEL

(mg/kg)

LOAEL

(mg/kg)

Critical Effect

M F

generation

1.6

3.2

GD 15: 41.4

GD 21: 26.2

Fetus GD 21: 

34.3

Dams

GD 1: 160

GD 7: 154

GD 15: 156

GD 21: 136

Fetus GD 21: 

101

Dams

GD 1: 318

GD 7: 306

GD 15: 275

GD 21: 155

Fetus GD 21: 

164

mg/kg/day

IMMUNOTOXICITY

Dong et al. 

2009

Mouse/B6C3F1

10 m/dose

oral gavage

60 days

0 

0.0083

0.083 

0.42 

0.83 

2.08

serum

0.048

0.674

7.132

21.638

65.426

120.67

NS 0.0083 0.083 Based on ↑ splenic 

natural killer cell 

activity
Perfluorooctane sulfonate (PFOS) – February 2014 A-13 

Draft – Do Not Cite or Quote 

TABLE A.2. Key Studies Used With Effects Related to Serum Values (Condensed Version)

Study Species/Strain Exposure 

duration

Dose 

(mg/kg/day)

PFOS concentration

(μg/mL)

NOAEL

(mg/kg)

LOAEL

(mg/kg)

Critical Effect

M F

Peden-Adams 

et al. 2008

Mouse/B6C3F1

5 m/5 f

oral gavage 

28 days

0 

0.0017

0.0017

0.0033

0.017

0.033

0.166

serum

0.012

0.018

0.092

0.131

NS

NS

NS

serum

0.017

NS

0.088

0.123

0.666

NS

NS

Males 

0.00017

Females 

0.0033 

 

Males 0.0017

Females

0.017

Males: ↓ plaque 

forming cell 

response

Females: ↓ plaque 

forming cell 

response

a LOQ or LLOQ are below limits that can be quantified

NS = no sample; NA= not applicable
Perfluorooctane sulfonate (PFOS) – February 2014 A- 14 

Draft – Do Not Cite or Quote 

TABLE A.3. 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 

1000 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 thyroxine- significant ↑ 

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/dayfemales

(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, 2, 20, 50 or 100 mg 

PFOS/kg diet

NOAEL = 2 mg PFOS/kg in 

males and NA in females

LOAEL = 20 mg PFOS/kg 

in males and 2 mg/kg in 

females based on ↑ relative 

liver wt

Curran et 

al. 2008

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 (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
Perfluorooctane sulfonate (PFOS) – February 2014 A- 15 

Draft – Do Not Cite or Quote 

TABLE A.3. Summary of Animal Studies with Exposure to PFOS

Method of 

exposure

Length of 

study

Species Concentration Results Reference

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/day- males

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 GD 6-15

developmental 

study

rat 0, 1, 5 or 10 mg/kg/day

25 pregnant rats

Maternal

NOAEL= 1 mg/kg/day

LOAEL= 5 mg/kg/day based 

on clinical signs

Developmental

NOAEL= 1 mg/kg/day 

LOAEL= 5 mg/kg/day based 

on ↓ body wt

Wetzel 

1983

oral gavage GD 2-21 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 GD 2-21 rat 0, 0.1, 0.6 or 2.0 mg/kg Offspring

NOAEL = can’t 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

oral gavage GD 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 

Chen et al., 

2012
Perfluorooctane sulfonate (PFOS) – February 2014 A- 16 

Draft – Do Not Cite or Quote 

TABLE A.3. Summary of Animal Studies with Exposure to PFOS

Method of 

exposure

Length of 

study

Species Concentration Results Reference

changes in lungs, ↓ body wt 

and ↑ mortality

oral gavage 6 wks prior to 

mating and

Males- 22 days

Femalesthrough 

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 = 1.6 mg/kg/day 

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 

oral gavage 6 wks prior to 

mating and 

continued 

through mating, 

gestation and 

lactation day 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, 0.03, 0.1, 0.4 or 1.5 

mg/kg/day

0, 0.5, 2, 5 or 20 ppm

40-70 males and 

females

Males NOAEL= 0.5 ppm 

(0.03 mg/kg)

Males LOAEL= 2 ppm (0.1 

mg/kg) based on liver 

histopathology

Females NOAEL= 2 ppm 

(0.1 mg/kg) 

Females LOAEL= 5 ppm 

(0.4 mg/kg) based on liver 

histopathology

Suggestive of 

carcinogenicity

Thomford, 

2002

oral gavage 1 time

developmental 

mouse 0, 0.75 or 11.3 mg/kg

4-7 males/group

Mice at both concentrations 

showed ↓ activity and ↑ 

neuroprotein levels in the 

Johansson 

et al. 2008 

and 2009
Perfluorooctane sulfonate (PFOS) – February 2014 A- 17 

Draft – Do Not Cite or Quote 

TABLE A.3. Summary of Animal Studies with Exposure to PFOS

Method of 

exposure

Length of 

study

Species Concentration Results Reference

neurotoxicity hippocampus

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 GD 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

oral gavage GD 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 

and Lau et 

al. 2003

oral gavage GD 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 GD 0-17/18

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 28 days

immunotoxicity

mouse 0, 0.005, 0.05, 0.1, 0.5, 

1, or 5 mg/kg

5 mice/dose

Males NOAEL= 0.005 

mg/kg

Males LOAEL= 0.05 mg/kg 

based on ↓ plaque forming 

cell response

Females NOAEL= 0.1 

PedenAdams et 

al., 2008
Perfluorooctane sulfonate (PFOS) – February 2014 A- 18 

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TABLE A.3. Summary of Animal Studies with Exposure to PFOS

Method of 

exposure

Length of 

study

Species Concentration Results Reference

mg/kg

Females LOAEL= 0.5 mg/kg

based on ↓ plaque forming 

cell response

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

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

oral gavage GD 7-20

developmental

rabbit 0, 0.1, 1.0, 2.5 or 3.75 

mg/kg/day

22 females/dose

Maternal

NOAEL= 0.1 mg/kg/day

LOAEL= 1 mg/kg/day based 

on ↓ body wt.

Developmental

NOAEL= 1 mg/kg/day 

LOAEL= 2.5 mg/kg/day 

based on ↓ fetal body wt and 

↓ in sternum ossification

Christian et 

al. 1999

*Exact dose not provided; NA= not applicable; could not be determined

a GD = gestation day and PND = post natal day 
Perfluorooctane sulfonate (PFOS) – February 2014 B- 1 

Draft – Do Not Cite or Quote 

APPENDIX B 

Contents: Benchmark Dose Modeling Output Files 10% increased incidence of liver lesions and 

10% increase in liver weight for:

1) Thomford, 2002: male rat – hepatocellular centrilobular hypertrophy; 

2) Thomford, 2002: female rat – hepatocellular centrilobular hypertrophy; 

3) Thomford, 2002: male rat – centrilobular hepatocytic vacuolation; 

4) Seacat et al., 2002: male monkey – increased liver weight; 

5) Seacat et al., 2002: female monkey – increased liver weight; 

6) Seacat et al., 2003: male rat – increased liver weight.
Perfluorooctane sulfonate (PFOS) – February 2014 B- 2 

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1) Thomford, 2002: male rat – hepatocellular centrilobular hypertrophy 

==================================================================== 

 Probit Model. (Version: 3.2; Date: 10/28/2009) 

 Wed Oct 03 14:57:49 2012 

 ==================================================================== 

 BMDS_Model_Run 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 

 

 The form of the probability function is: 

 P[response] = Background 

 + (1-Background) * CumNorm(Intercept+Slope*Log(Dose)), 

 where CumNorm(.) is the cumulative normal distribution function 

 Dependent variable = Incidence 

 Independent variable = Dose 

 Slope parameter is not restricted 

 Total number of observations = 5 

 Total number of records with missing values = 0 

 Maximum number of iterations = 250 

 Relative Function Convergence has been set to: 1e-008 

 Parameter Convergence has been set to: 1e-008 

 User has chosen the log transformed model 

 Default Initial (and Specified) Parameter Values 

 background = 0 

 intercept = 0.551536 

 slope = 0.619893 

 Asymptotic Correlation Matrix of Parameter Estimates 

 (*** The model parameter(s) -background have been estimated at a 

boundary point, or have been specified by the user, and do not appear in the 

correlation matrix ) 

 intercept slope 

 intercept 1 0.79 

 slope 0.79 1 

 Parameter Estimates 

 95.0% Wald Confidence Interval 

Variable Estimate Std. Err. Lower Conf. Limit Upper Conf. Limit 

 Background 0 NA 

 Intercept 0.600166 0.163276 0.280151 0.92018 

 Slope 0.637003 0.0848112 0.470776 0.80323 

NA - Indicates that this parameter has hit a bound implied by some inequality 

constraint and thus has no standard error. 

 
Perfluorooctane sulfonate (PFOS) – February 2014 B- 3 

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Analysis of Deviance Table 

 Model Log(likelihood) # Param's Deviance Test d.f. P-value 

 Full model -102.179 5 

 Fitted model -104.472 2 4.58658 3 0.2047 

 Reduced model -161.64 1 118.923 4 <.0001 

 AIC: 212.944 

 Goodness of Fit 

 Scaled 

 Dose Est._Prob. Expected Observed Size Residual 

 ------------------------------------------------------------------------ 

 0.0000 0.0000 0.000 0.000 65 0.000 

 0.0180 0.0251 1.378 2.000 55 0.536 

 0.0720 0.1410 7.755 4.000 55 -1.455 

 0.1840 0.3163 17.395 22.000 55 1.335 

 0.7650 0.6662 43.305 42.000 65 -0.343 

 Chi^2 = 4.31 d.f. = 3 P-value = 0.2303 

 Benchmark Dose Computation 

Specified effect = 0.1 

Risk Type = Extra risk 

Confidence level = 0.95 

 BMD = 0.0521299 

 BMDL = 0.0326765 
Perfluorooctane sulfonate (PFOS) – February 2014 B- 4 

Draft – Do Not Cite or Quote 

2) Thomford, 2002: female rat – hepatocellular centrilobular hypertrophy; 

==================================================================== 

 Probit Model. (Version: 3.2; Date: 10/28/2009) 

 Tue Jan 29 13:03:16 2013 

 ==================================================================== 

 BMDS_Model_Run 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 

 

 The form of the probability function is: 

 P[response] = Background 

 + (1-Background) * CumNorm(Intercept+Slope*Log(Dose)), 

 where CumNorm(.) is the cumulative normal distribution function 

 Dependent variable = Incidence 

 Independent variable = Dose 

 Slope parameter is not restricted 

 Total number of observations = 5 

 Total number of records with missing values = 0 

 Maximum number of iterations = 250 

 Relative Function Convergence has been set to: 1e-008 

 Parameter Convergence has been set to: 1e-008 

 User has chosen the log transformed model 

 Default Initial (and Specified) Parameter Values 

 background = 0.0307692 

 intercept = 0.921158 

 slope = 0.875963 

 Asymptotic Correlation Matrix of Parameter Estimates 

 background intercept slope 

background 1 0.037 0.25 

 intercept 0.037 1 0.78 

 slope 0.25 0.78 1 

 Parameter Estimates 

 95.0% Wald Confidence Interval 

Variable Estimate Std. Err. Lower Conf. Limit Upper Conf. Limit 

 Background 0.0242361 0.0139844 -0.0031728 0.0516449 

 Intercept 1.11217 0.200749 0.718705 1.50563 

 Slope 1.03103 0.140636 0.755385 1.30667 

 Analysis of Deviance Table 

 Model Log(likelihood) # Param's Deviance Test d.f. P-value 

 Full model -93.9538 5 

 Fitted model -94.0971 3 0.286555 2 0.8665 

 Reduced model -167.248 1 146.589 4 <.0001 
Perfluorooctane sulfonate (PFOS) – February 2014 B- 5 

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 AIC: 194.194 

 Goodness of Fit 

 Scaled 

 Dose Est._Prob. Expected Observed Size Residual 

 ------------------------------------------------------------------------ 

 0.0000 0.0242 1.575 2.000 65 0.343 

 0.0180 0.0254 1.399 1.000 55 -0.341 

 0.0720 0.0776 4.271 4.000 55 -0.136 

 0.1840 0.2812 15.464 16.000 55 0.161 

 0.7650 0.8033 52.215 52.000 65 -0.067 

 Chi^2 = 0.28 d.f. = 2 P-value = 0.8681 

 Benchmark Dose Computation 

Specified effect = 0.1 

Risk Type = Extra risk 

Confidence level = 0.95 

 BMD = 0.0981083 

 BMDL = 0.0680339
Perfluorooctane sulfonate (PFOS) – February 2014 B- 6 

Draft – Do Not Cite or Quote 

3) Thomford, 2002: male rat – centrilobular hepatocytic vacuolation; 

==================================================================== 

 Probit Model. (Version: 3.2; Date: 10/28/2009) 

 Thu Oct 04 08:56:32 2012 

 ==================================================================== 

 BMDS_Model_Run 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 

 

 The form of the probability function is: 

 P[response] = Background 

 + (1-Background) * CumNorm(Intercept+Slope*Log(Dose)), 

 where CumNorm(.) is the cumulative normal distribution function 

 Dependent variable = incidence 

 Independent variable = dose 

 Slope parameter is not restricted 

 Total number of observations = 5 

 Total number of records with missing values = 0 

 Maximum number of iterations = 250 

 Relative Function Convergence has been set to: 1e-008 

 Parameter Convergence has been set to: 1e-008 

 User has chosen the log transformed model 

 Default Initial (and Specified) Parameter Values 

 background = 0.0461538 

 intercept = -0.349312 

 slope = 0.465561 

 Asymptotic Correlation Matrix of Parameter Estimates 

 background intercept slope 

background 1 -0.2 0.33 

 intercept -0.2 1 0.63 

 slope 0.33 0.63 1 

 Parameter Estimates 

95.0% Wald Confidence Interval 

Variable Estimate Std. Err. Lower Conf. Limit Upper Conf. Limit 

 Background 0.0409871 0.022081 -0.00229092 0.0842651 

 Intercept -0.470429 0.188805 -0.84048 -0.100379 

 Slope 0.341758 0.108985 0.128151 0.555365 

 Analysis of Deviance Table 

 Model Log(likelihood) # Param's Deviance Test d.f. P-value 

 Full model -112.104 5 

 Fitted model -112.911 3 1.61515 2 0.4459 

 Reduced model -124.265 1 24.3222 4 <.0001 

 AIC: 231.822 
Perfluorooctane sulfonate (PFOS) – February 2014 B- 7 

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 Goodness of Fit 

 Scaled 

 Dose Est._Prob. Expected Observed Size Residual 

 ------------------------------------------------------------------------ 

 0.0000 0.0410 2.664 3.000 65 0.210 

 0.0180 0.0723 3.976 3.000 55 -0.508 

 0.0720 0.1229 6.759 6.000 55 -0.312 

 0.1840 0.1821 10.013 13.000 55 1.044 

 0.7650 0.3163 20.559 19.000 65 -0.416 

 Chi^2 = 1.66 d.f. = 2 P-value = 0.4357 

 Benchmark Dose Computation 

Specified effect = 0.1 

Risk Type = Extra risk 

Confidence level = 0.95 

 BMD = 0.0931649 

 BMDL = 0.0278419 
Perfluorooctane sulfonate (PFOS) – February 2014 B- 8 

Draft – Do Not Cite or Quote 

4) Seacat et al., 2002: male monkey – increased liver weight; 

==================================================================== 

 Power Model. (Version: 2.16; Date: 10/28/2009) 

 Tue Jan 29 09:33:47 2013 

 ==================================================================== 

 BMDS Model Run 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 

 

 The form of the response function is: 

 Y[dose] = control + slope * dose^power 

 Dependent variable = Mean 

 Independent variable = Dose 

 The power is restricted to be greater than or equal to 1 

 The variance is to be modeled as Var(i) = exp(lalpha + log(mean(i)) * rho) 

 Total number of dose groups = 4 

 Total number of records with missing values = 0 

 Maximum number of iterations = 250 

 Relative Function Convergence has been set to: 1e-008 

 Parameter Convergence has been set to: 1e-008 

 Default Initial Parameter Values 

 lalpha = 6.06377 

 rho = 0 

 control = 54.9 

 slope = 18.8575 

 power = 0.447473 

 Asymptotic Correlation Matrix of Parameter Estimates 

 ( *** The model parameter(s) -power have been estimated at a 

boundary point, or have been specified by the user, and do not appear in the 

correlation matrix ) 

 lalpha rho control slope 

 lalpha 1 -1 -0.16 0.9 

 rho -1 1 0.14 -0.91 

 control -0.16 0.14 1 -0.11 

 slope 0.9 -0.91 -0.11 1 

 Parameter Estimates 

 95.0% Wald Confidence Interval 

Variable Estimate Std. Err. Lower Conf. Limit Upper Conf. Limit 

 lalpha -32.9753 21.1498 -74.4282 8.47765 

 rho 8.99283 5.16599 -1.13233 19.118 

 control 58.3909 1.82406 54.8158 61.966 

 slope 4773.05 2967.06 -1042.28 10588.4 

 power 18 NA 

NA - Indicates that this parameter has hit a bound implied by some inequality 

constraint and thus has no standard error. 
Perfluorooctane sulfonate (PFOS) – February 2014 B- 9 

Draft – Do Not Cite or Quote 

 Table of Data and Estimated Values of Interest 

 Dose N Obs Mean Est Mean Obs Std Dev Est Std Dev Scaled Res. 

------ --- -------- -------- ----------- ----------- ---------- 

 0 3 54.9 58.4 8.1 6.05 -0.999 

 0.03 4 62.1 58.4 5.3 6.05 1.23 

 0.15 4 57.3 58.4 5.5 6.05 -0.361 

 0.75 4 85.3 85.3 38.4 33.3 -7.12e-008 

 Model Descriptions for likelihoods calculated 

 Model A1: Yij = Mu(i) + e(ij) 

 Var{e(ij)} = Sigma^2 

 Model A2: Yij = Mu(i) + e(ij) 

 Var{e(ij)} = Sigma(i)^2 

 Model A3: Yij = Mu(i) + e(ij) 

 Var{e(ij)} = exp(lalpha + rho*ln(Mu(i))) 

 Model A3 uses any fixed variance parameters that 

 were specified by the user 

 Model R: Yi = Mu + e(i) 

 Var{e(i)} = Sigma^2 

 Likelihoods of Interest 

 Model Log(likelihood) # Param's AIC 

 A1 -50.652100 5 111.304201 

 A2 -39.523352 8 95.046703 

 A3 -40.563551 6 93.127102 

 fitted -41.316982 4 90.633964 

 R -53.538667 2 111.077334 

 Explanation of Tests 

 Test 1: Do responses and/or variances differ among Dose levels? 

 (A2 vs. R) 

 Test 2: Are Variances Homogeneous? (A1 vs A2) 

 Test 3: Are variances adequately modeled? (A2 vs. A3) 

 Test 4: Does the Model for the Mean Fit? (A3 vs. fitted) 

 (Note: When rho=0 the results of Test 3 and Test 2 will be the same.) 

 Tests of Interest 

 Test -2*log(Likelihood Ratio) Test df p-value 

 Test 1 28.0306 6 <.0001 

 Test 2 22.2575 3 <.0001 

 Test 3 2.0804 2 0.3534 

 Test 4 1.50686 2 0.4707 

The p-value for Test 1 is less than .05. There appears to be a 

difference between response and/or variances among the dose levels 

It seems appropriate to model the data 

The p-value for Test 2 is less than .1. A non-homogeneous variance 

model appears to be appropriate 

The p-value for Test 3 is greater than .1. The modeled variance appears 
Perfluorooctane sulfonate (PFOS) – February 2014 B- 10 

Draft – Do Not Cite or Quote 

 to be appropriate here 

The p-value for Test 4 is greater than .1. The model chosen seems 

to adequately describe the data 

 

 Benchmark Dose Computation 

Specified effect = 0.1 

Risk Type = Estimated standard deviations from the control mean 

Confidence level = 0.95 

 BMD = 0.60743 

 BMDL = 0.0147931 
Perfluorooctane sulfonate (PFOS) – February 2014 B- 11 

Draft – Do Not Cite or Quote 

5) Seacat et al., 2002: female monkey – increased liver weight; 

==================================================================== 

 Exponential Model. (Version: 1.7; Date: 12/10/2009) 

 Tue Jan 29 10:17:21 2013 

 ==================================================================== 

 BMDS Model Run 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 

 

 The form of the response function by Model: 

 Model 2: Y[dose] = a * exp{sign * b * dose} 

 Model 3: Y[dose] = a * exp{sign * (b * dose)^d} 

 Model 4: Y[dose] = a * [c-(c-1) * exp{-b * dose}] 

 Model 5: Y[dose] = a * [c-(c-1) * exp{-(b * dose)^d}] 

 Note: Y[dose] is the median response for exposure = dose; 

 sign = +1 for increasing trend in data; 

 sign = -1 for decreasing trend. 

 Model 2 is nested within Models 3 and 4. 

 Model 3 is nested within Model 5. 

 Model 4 is nested within Model 5. 

 Dependent variable = Mean 

 Independent variable = Dose 

 Data are assumed to be distributed: normally 

 Variance Model: exp(lnalpha +rho *ln(Y[dose])) 

 The variance is to be modeled as Var(i) = exp(lalpha + log(mean(i)) * rho) 

 Total number of dose groups = 4 

 Total number of records with missing values = 0 

 Maximum number of iterations = 250 

 Relative Function Convergence has been set to: 1e-008 

 Parameter Convergence has been set to: 1e-008 

 MLE solution provided: Exact 

 Initial Parameter Values 

Variable Model 2 Model 3 Model 4 Model 5 

-------- ------- ------- ------- ------- 

lnalpha -7.12771 -7.12771 -7.12771 -7.12771 

rho 2.78482 2.78482 2.78482 2.78482 

a 53.6357 53.6357 48.545 48.545 

b 0.452798 0.452798 2.77794 2.77794 

c -- -- 1.6287 1.6287 

d -- 1 -- 1 

 Parameter Estimates by Model 

Variable Model 2 Model 3 Model 4 Model 5 

-------- ------- ------- ------- ------- 

lnalpha -1.92335 -2.1108 -1.59973 -2.44766 

rho 1.54391 1.58965 1.46555 1.6722 

a 53.6802 53.8771 53.4554 54.2396 

b 0.451454 0.479691 0.00050114 0.0042198 

c -- -- 1083.43 721.127 

d -- 1.06864 -- 1.30686 

 Table of Stats From Input Data 
Perfluorooctane sulfonate (PFOS) – February 2014 B- 12 

Draft – Do Not Cite or Quote 

 Dose N Obs Mean Obs Std Dev 

 ----- --- ---------- ------------- 

 0 3 51.1 9.4 

 0.03 4 56.8 12.6 

 0.15 4 57 3.1 

 0.75 4 75.3 13.3 

 Estimated Values of Interest 

 Model Dose Est Mean Est Std Scaled Residual 

 ------- ------ ---------- --------- ---------------- 

 2 0 53.68 8.273 -0.5402 

 0.03 54.41 8.36 0.5712 

 0.15 57.44 8.717 -0.1012 

 0.75 75.31 10.74 -0.002181 

 3 0 53.88 8.276 -0.5812 

 0.03 54.46 8.347 0.5608 

 0.15 57.21 8.681 -0.04889 

 0.75 75.35 10.8 -0.008551 

 4 0 53.46 8.296 -0.4918 

 0.03 54.33 8.394 0.5896 

 0.15 57.8 8.785 -0.1832 

 0.75 75.2 10.65 0.01899 

 5 0 54.24 8.29 -0.656 

 0.03 54.55 8.33 0.5391 

 0.15 56.82 8.618 0.04191 

 0.75 75.37 10.92 -0.01305 

 Other models for which likelihoods are calculated: 

 Model A1: Yij = Mu(i) + e(ij) 

 Var{e(ij)} = Sigma^2 

 Model A2: Yij = Mu(i) + e(ij) 

 Var{e(ij)} = Sigma(i)^2 

 Model A3: Yij = Mu(i) + e(ij) 

 Var{e(ij)} = exp(lalpha + log(mean(i)) * rho) 

 Model R: Yij = Mu + e(i) 

 Var{e(ij)} = Sigma^2 

 Likelihoods of Interest 

 Model Log(likelihood) DF AIC 

 ------- ----------------- ---- ------------ 

 A1 -40.44292 5 90.88584 

 A2 -36.89929 8 89.79858 

 A3 -39.91492 6 91.82985 

 R -45.74039 2 95.48078 

 2 -40.49219 4 88.98438 

 3 -40.49157 5 90.98314 

 4 -40.51305 5 91.0261 

 5 -40.50101 6 93.00202 

 Additive constant for all log-likelihoods = -13.78. This constant added 

to the above values gives the log-likelihood including the term that does not 

 depend on the model parameters. 
Perfluorooctane sulfonate (PFOS) – February 2014 B- 13 

Draft – Do Not Cite or Quote 

 Explanation of Tests 

 Test 1: Does response and/or variances differ among Dose levels? (A2 vs. R) 

 Test 2: Are Variances Homogeneous? (A2 vs. A1) 

 Test 3: Are variances adequately modeled? (A2 vs. A3) 

 Test 4: Does Model 2 fit the data? (A3 vs. 2) 

 Test 5a: Does Model 3 fit the data? (A3 vs 3) 

 Test 5b: Is Model 3 better than Model 2? (3 vs. 2) 

 Test 6a: Does Model 4 fit the data? (A3 vs 4) 

 Test 6b: Is Model 4 better than Model 2? (4 vs. 2) 

 Test 7a: Does Model 5 fit the data? (A3 vs 5) 

 Test 7b: Is Model 5 better than Model 3? (5 vs. 3) 

 Test 7c: Is Model 5 better than Model 4? (5 vs. 4) 

 Tests of Interest 

 Test -2*log(Likelihood Ratio) D. F. p-value 

 -------- ------------------------ ------ -------------- 

 Test 1 17.68 6 0.007077 

 Test 2 7.087 3 0.06917 

 Test 3 6.031 2 0.04901 

 Test 4 1.155 2 0.5614 

 Test 5a 1.153 1 0.2829 

 Test 5b 0.001241 1 0.9719 

 Test 6a 1.196 1 0.2741 

 Test 6b -0.04172 1 N/A 

 Test 7a 1.172 0 N/A 

 Test 7b -0.01888 1 N/A 

 Test 7c 0.02408 1 0.8767 

 The p-value for Test 1 is less than .05. There appears to be a 

 difference between response and/or variances among the dose 

 levels, it seems appropriate to model the data. 

 The p-value for Test 2 is less than .1. A non-homogeneous 

 variance model appears to be appropriate. 

 The p-value for Test 3 is less than .1. You may want to 

 consider a different variance model. 

 The p-value for Test 4 is greater than .1. Model 2 seems 

 to adequately describe the data. 

 The p-value for Test 5a is greater than .1. Model 3 seems 

 to adequately describe the data. 

 The p-value for Test 5b is greater than .05. Model 3 does 

 not seem to fit the data better than Model 2. 

 The p-value for Test 6a is greater than .1. Model 4 seems 

 to adequately describe the data. 

 The p-value for Test 6b is less than .05. Model 4 appears 

 to fit the data better than Model 2. 

 Degrees of freedom for Test 7a are less than or equal to 0. 

 The Chi-Square test for fit is not valid. 
Perfluorooctane sulfonate (PFOS) – February 2014 B- 14 

Draft – Do Not Cite or Quote 

 The p-value for Test 7b is less than .05. Model 5 appears 

 to fit the data better than Model 3. 

 The p-value for Test 7c is greater than .05. Model 5 does 

 not seem to fit the data better than Model 4. 

 Benchmark Dose Computations: 

 Specified Effect = 0.100000 

 Risk Type = Estimated standard deviations from control 

 Confidence Level = 0.950000 

 BMD and BMDL by Model 

 Model BMD BMDL 

 ------- ------------ ---------- 

 2 0.0338792 0.0207989 

 3 0.0415751 0.0208011 

 4 0.0286094 0.0165794 

 5 0.0629252 0.00584753
Perfluorooctane sulfonate (PFOS) – February 2014 B- 15 

Draft – Do Not Cite or Quote 

6) Seacat et al., 2003: male rat – increased liver weight.

==================================================================== 

 Exponential Model. (Version: 1.7; Date: 12/10/2009) 

 Tue Jan 29 11:21:33 2013 

 ==================================================================== 

 BMDS Model Run 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 

 

 The form of the response function by Model: 

 Model 2: Y[dose] = a * exp{sign * b * dose} 

 Model 3: Y[dose] = a * exp{sign * (b * dose)^d} 

 Model 4: Y[dose] = a * [c-(c-1) * exp{-b * dose}] 

 Model 5: Y[dose] = a * [c-(c-1) * exp{-(b * dose)^d}] 

 Note: Y[dose] is the median response for exposure = dose; 

 sign = +1 for increasing trend in data; 

 sign = -1 for decreasing trend. 

 Model 2 is nested within Models 3 and 4. 

 Model 3 is nested within Model 5. 

 Model 4 is nested within Model 5. 

 Dependent variable = Mean 

 Independent variable = Dose 

 Data are assumed to be distributed: normally 

 Variance Model: exp(lnalpha +rho *ln(Y[dose])) 

 rho is set to 0. 

 A constant variance model is fit. 

 Total number of dose groups = 5 

 Total number of records with missing values = 0 

 Maximum number of iterations = 250 

 Relative Function Convergence has been set to: 1e-008 

 Parameter Convergence has been set to: 1e-008 

 MLE solution provided: Exact 

 Initial Parameter Values 

Variable Model 2 Model 3 Model 4 Model 5 

-------- ------- ------- ------- ------- 

lnalpha 1.35789 1.35789 1.35789 1.35789 

rho(S) 0 0 0 0 

a 15.3355 15.3355 13.3 13.3 

b 0.226423 0.226423 1.66321 1.66321 

c -- -- 1.60263 1.60263 

d -- 1 -- 1 

 (S) = Specified 

 Parameter Estimates by Model 

Variable Model 2 Model 3 Model 4 Model 5 

-------- ------- ------- ------- ------- 

lnalpha 1.7164 1.7164 1.64166 1.43222 

rho 0 0 0 0 

a 15.4453 15.4453 14.8246 15 

b 0.216725 0.216725 1.73553 2.97948 

c -- -- 1.42089 1.35333 
Perfluorooctane sulfonate (PFOS) – February 2014 B- 16 

Draft – Do Not Cite or Quote 

d -- 1 -- 18 

 Table of Stats From Input Data 

 Dose N Obs Mean Obs Std Dev 

 ----- --- ---------- ------------- 

 0 5 15.5 1.1 

 0.03 5 15.5 2.7 

 0.13 5 14 1.4 

 0.34 5 18.8 3 

 1.33 5 20.3 2.2 

 Estimated Values of Interest 

 Model Dose Est Mean Est Std Scaled Residual 

 ------- ------ ---------- --------- ---------------- 

 2 0 15.45 2.359 0.0518 

 0.03 15.55 2.359 -0.0437 

 0.13 15.89 2.359 -1.788 

 0.34 16.63 2.359 2.06 

 1.33 20.61 2.359 -0.2895 

 3 0 15.45 2.359 0.0518 

 0.03 15.55 2.359 -0.0437 

 0.13 15.89 2.359 -1.788 

 0.34 16.63 2.359 2.06 

 1.33 20.61 2.359 -0.2895 

 4 0 14.82 2.272 0.6646 

 0.03 15.14 2.272 0.3531 

 0.13 16.08 2.272 -2.052 

 0.34 17.61 2.272 1.175 

 1.33 20.44 2.272 -0.1414 

 5 0 15 2.046 0.5463 

 0.03 15 2.046 0.5463 

 0.13 15 2.046 -1.093 

 0.34 18.8 2.046 1.225e-007 

 1.33 20.3 2.046 -6.774e-008 

 Other models for which likelihoods are calculated: 

 Model A1: Yij = Mu(i) + e(ij) 

 Var{e(ij)} = Sigma^2 

 Model A2: Yij = Mu(i) + e(ij) 

 Var{e(ij)} = Sigma(i)^2 

 Model A3: Yij = Mu(i) + e(ij) 

 Var{e(ij)} = exp(lalpha + log(mean(i)) * rho) 

 Model R: Yij = Mu + e(i) 

 Var{e(ij)} = Sigma^2 

 Likelihoods of Interest 

 Model Log(likelihood) DF AIC 

 ------- ----------------- ---- ------------ 

 A1 -29.47369 6 70.94737 

 A2 -26.27122 10 72.54245 

 A3 -29.47369 6 70.94737 

 R -40.48438 2 84.96876 
Perfluorooctane sulfonate (PFOS) – February 2014 B- 17 

Draft – Do Not Cite or Quote 

 2 -33.95502 3 73.91004 

 3 -33.95502 3 73.91004 

 4 -33.02072 4 74.04144 

 5 -30.40279 5 70.80558 

 Additive constant for all log-likelihoods = -22.97. This constant added 

to the 

 above values gives the log-likelihood including the term that does not 

 depend on the model parameters. 

 Explanation of Tests 

 Test 1: Does response and/or variances differ among Dose levels? (A2 vs. R) 

 Test 2: Are Variances Homogeneous? (A2 vs. A1) 

 Test 3: Are variances adequately modeled? (A2 vs. A3) 

 Test 4: Does Model 2 fit the data? (A3 vs. 2) 

 Test 5a: Does Model 3 fit the data? (A3 vs 3) 

 Test 5b: Is Model 3 better than Model 2? (3 vs. 2) 

 Test 6a: Does Model 4 fit the data? (A3 vs 4) 

 Test 6b: Is Model 4 better than Model 2? (4 vs. 2) 

 Test 7a: Does Model 5 fit the data? (A3 vs 5) 

 Test 7b: Is Model 5 better than Model 3? (5 vs. 3) 

 Test 7c: Is Model 5 better than Model 4? (5 vs. 4) 

 Tests of Interest 

 Test -2*log(Likelihood Ratio) D. F. p-value 

 -------- ------------------------ ------ -------------- 

 Test 1 28.43 8 0.0003996 

 Test 2 6.405 4 0.1709 

 Test 3 6.405 4 0.1709 

 Test 4 8.963 3 0.02979 

 Test 5a 8.963 3 0.02979 

 Test 5b -1.421e-014 0 N/A 

 Test 6a 7.094 2 0.02881 

 Test 6b 1.869 1 0.1716 

 Test 7a 1.858 1 0.1728 

 Test 7b 7.104 2 0.02866 

 Test 7c 5.236 1 0.02213 

 The p-value for Test 1 is less than .05. There appears to be a 

 difference between response and/or variances among the dose 

 levels, it seems appropriate to model the data. 

 The p-value for Test 2 is greater than .1. A homogeneous 

 variance model appears to be appropriate here. 

 The p-value for Test 3 is greater than .1. The modeled 

 variance appears to be appropriate here. 

 The p-value for Test 4 is less than .1. Model 2 may not adequately 

 describe the data; you may want to consider another model. 

 The p-value for Test 5a is less than .1. Model 3 may not adequately 

 describe the data; you may want to consider another model. 

 Degrees of freedom for Test 5b are less than or equal to 0. 
Perfluorooctane sulfonate (PFOS) – February 2014 B- 18 

Draft – Do Not Cite or Quote 

 The Chi-Square test for fit is not valid. 

 The p-value for Test 6a is less than .1. Model 4 may not adequately 

 describe the data; you may want to consider another model. 

 The p-value for Test 6b is greater than .05. Model 4 does 

 not seem to fit the data better than Model 2. 

 The p-value for Test 7a is greater than .1. Model 5 seems 

 to adequately describe the data. 

 The p-value for Test 7b is less than .05. Model 5 appears 

 to fit the data better than Model 3. 

 The p-value for Test 7c is less than .05. Model 5 appears 

 to fit the data better than Model 4. 

Benchmark Dose Computations: 

 Specified Effect = 0.100000 

 Risk Type = Estimated standard deviations from control 

 Confidence Level = 0.950000 

 BMD and BMDL by Model 

 Model BMD BMDL 

 ------- ------------ ---------- 

 2 0.0699374 0.0498937 

 3 0.0699374 0.0498937 

 4 0.0213759 0.00939927 

 5 0.280426 0.0585612