UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

MEMORANDUM 

Date: June 29, 2015 

SUBJECT: EDSP Weight of Evidence Conclusions on the Tier 1 Screening Assays for the 

List 1 Chemicals 

PC Code: See table, Attachment A 

Decision No.: NA 

Petition No.: NA 

Risk Assessment Type: NA 

TXR No.: See table, Attachment A 

MRIDNo.:NA 

DP Barcode: NA 

Registration No.: NA 

Regulatory Action: NA 

Case No.: NA 

CAS No.: NA 

40CFR: NA 

FROM: Greg Akerman & 

Health Effects Divison 

::~:E£'~:::e f]g:ams d f 'v--

Environmental Fat~~fec~~~n ~ Office of Pesticide Program 

THROUGH: Jess Rowland ~ S ~~~ Deputy Division Director 

Health Effects Division 

Office of Pesticide Programs 

TO: Jolene Trujillo 

Chemical Review Manager 

Pesticide Re-Evaluation Division 

Office of Pesticide Programs 

Ver.Apr. 2010 

EPA has completed its Weight of Evidence (WoE) assessment evaluating results of the 

Endocrine Screening Program (EDSP) Tier l screening assays for the List l chemicals. 

The WoE documents for the 52 chemicals are listed in Attachment A along with the chemical 

and report identifiers. 

Page I of2 

Page 1 of 70
Page 2 of 2 

Attachment A. EDSP List 1 Chemicals 

Chemical Name PC Code TXR Number 

2,4-D 030001 0057151 

Abamectin 122804 0057152 

Acephate 103301 0057153 

Acetone 044101 0057154 

Atrazine 080803 0057155 

Benfluralin 084301 0057156 

Bifenthrin 128825 0057157 

Captan 081301 0057158 

Carbaryl 056801 0057159 

Carbofuran 090601 0057160 

Chlorothalonil 081901 0057161 

Chlorpyrifos 059101 0057162 

Cyfluthrin 128831 0057163 

Cypermethrin 109702 0057164 

DCPA 078701 0057165 

Diazinon 057801 0057166 

Dichlobenil 027401 0057167 

Dimethoate 035001 0057168 

EPTC 041401 0057169 

Esfenvalerate 109303 0057170 

Ethoprop 041101 0057171 

Fenbutatin-Oxide 104601 0057172 

Flutolanil 128975 0057173 

Folpet 081601 0057174 

Glyphosate 417300 0057175 

Imidacloprid 129099 0057176 

Iprodione 109801 0057177 

Isophorone 847401 0057178 

Linuron 035506 0057179 

Malathion 057701 0057180 

Metalaxyl 113501 0057181 

Methomyl 090301 0057182 

Metolachlor 108801 0057183 

Metribuzin 101101 0057184 

MGK-264 057001 0057185 

Myclobutanil 128857 0057186 

Norflurazon 105801 0057150 

o-Phenylphenol 064103 0057146 

Oxamyl 103801 0057142 

PCNB 056502 0057138 

Permethrin 109701 0057149 

Phosmet 059201 0057145 

Piperonyl Butoxide 067501 0057141 

Pronamide 101701 0057137 

Propargite 097601 0057148 

Propiconazole 122101 0057144 

Pyriproxyfen 129032 0057140 

Simazine 080807 0057136 

Tebuconazole 128997 0057143 

Tetrachlorvinphos (TCVP) 083701 0057147 

Triadimefon 109901 0057139 

Trifluralin 036101 0057135 

Page 2 of 70
 

EDSP: WEIGHT OF EVIDENCE ANALYSIS OF POTENTIAL 

INTERACTION WITH THE ESTROGEN, ANDROGEN OR THYROID 

PATHWAYS 

CHEMICAL: GLYPHOSATE 

OFFICE OF PESTICIDE PROGRAMS

OFFICE OF SCIENCE COORDINATION AND POLICY

U.S. ENVIRONMENTAL PROTECTION AGENCY

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ii 

TABLE OF CONTENTS 

Abbreviations...................................................................................................iii 

Executive Summary..........................................................................................1 

I. Introduction.......................................................................................3 

II. Sources of Scientific Data and Technical Information......................................4 

A. EDSP Tier 1 Screening Assays............................................................4 

B. Other Scientifically Relevant Information (OSRI)......................................4 

III. Weight of Evidence (WoE) Evaluation.......................................................4 

A. EDSP Tier 1 Screening Assays.............................................................7 

B. Effects on Hypothalamic-Pituitary-Gonadal (HPG) Axis..............................8 

1. Effects on Estrogen Pathway.....................................................8 

2. Effects on Androgen Pathway..................................................14 

C. Effects on Hypothalamic-Pituitary-Thyroidal (HPT) Axis...........................19 

IV. Committee’s Assessment of Weight of Evidence..........................................22 

A. Systemic/Overt Toxicity in the in vivo Tier 1 Assays and OSRI ...................22 

1. Tier 1 in vivo Assays.............................................................23 

2. OSRI...............................................................................23 

B. Estrogen Pathway...........................................................................25 

C. Androgen Pathway.........................................................................26 

D. Thyroid Pathway...........................................................................26 

E. Conclusions.................................................................................26 

V. EDSP Tier 2 Testing Recommendations....................................................26 

VI. References.......................................................................................27 

LIST OF TABLES: 

 Table 1. Tier 1 Assays for Glyphosate................................................................7 

 Table 2. Estrogenic/Anti-Estrogenic Pathway for Glyphosate ..................................10 

 Table 3. Androgenic/Anti-Androgenic Pathway for Glyphosate ................................15 

 Table 4. Thyroid Pathway for Glyphosate .........................................................20 

APPENDIX 1. EDSP Tier 1 Screening Assays..............................................................32 

APPENDIX 2. Other Scientifically Relevant Information (OSRI)....................................42 

APPENDIX 3. References Not Utilized in the Glyphosate WoE Analysis...........................62 

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GLYPHOSATE FINAL 

iii 

Abbreviations 

Abbreviation Terminology 

A Androgen (hormonal pathway) 

ADME Absorption, Distribution, Metabolism, Excretion 

ALP Alkaline Phosphatase 

ALT Alanine Aminotransferase 

AMA Amphibian Metamorphosis Assay 

ARTA Androgen Receptor Transcriptional Activation 

AST Aspartate Aminotransferase 

ANOVA Analysis of Variance 

AOP Adverse Outcome Pathway

AR Androgen Receptor

Bmax Binding at maximum

BROD Benzyloxyresorufin-O-dealkylase 

BUN Blood Urea Nitrogen

CAR Constitutive Androstane Receptor

CFR Code of Federal Regulations 

CG Cowper’s Gland 

ChE Cholinesterase 

ChEI Cholinesterase inhibition 

CMC Carboxymethyl cellulose 

CTA Comparative Thyroid Assay 

CV Coefficient of Variation 

CYP Cytochrome 450 

DER Data Evaluation Record

DMSO Dimethyl Sulfoxide

DNA Deoxyribonucleic Acid

DO Dissolved Oxygen

DP Dorsolateral Prostrate

E Estrogen hormonal pathway

EDSTAC Endocrine Disruptor Screening and Testing Advisory Committee 

EDRT Endocrine Disruptor Review Team

EDSP Endocrine Disruptor Screening Program

EE Ethinyl Estradiol

ELISA Enzyme Linked Immunosorbent Assay

EOGRTS Extended One-Generation Reproductive Toxicity Study (Rat)

ER Estrogen Receptor

EROD Ethoxyresorufin-O-dealkylase (or deethylase)

ERTA Estrogen Receptor Transcriptional Activation

EtOH Ethanol 

F Female 

F1 First filial generation 

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iv 

Abbreviation Terminology 

F2 Second filial generation 

Fcd Fecundity

FIFRA Federal Insecticide, Fungicide and Rodenticide Act 

FOB Field Observation Battery

FQPA Food Quality Protection Act

Frt Fertility

FSH Follicle Stimulating Hormone

FSTRA Fish Short-Term Reproduction Assay

FT Flutamide 

GD Gestation Day

GGT Gamma-glutamyl Transpeptidase

GnRH Gonadotropin-releasing hormone

GP Glans Penis 

GSI Gonado-Somatic Index

H High 

HLL Hind Limb Length

HPG Hypothalamic-Pituitary-Gonadal Axis

HPLC/MS/MS High Pressure Liquid Chromatography/Mass Spectroscopy

HPT Hypothalamic-Pituitary-Thyroidal Axis

I Inadequate 

IC50 Inhibitory Concentration at 50% of response

ICCVAM Interagency Coordinating Committee on the Validation of Alternative 

Kd Equilibrium Dissociation Constant 

KOW Octanol/Water Partition Coefficient 

L Low dose 

LABC Levator Ani-Bulbocavernosus

LAGDA Larval Amphibian Growth and Development Assay

LC50 Lethal Concentration in 50% of test organisms 

LD Lactation Day 

LH Luteinizing hormone 

LOAEC Lowest Observed Adverse Effect Concentration 

LOAEL Lowest Observed Adverse Effect Level 

LOQ Limit of Quantitation 

M Male 

MDL Minimum Detection Level

MEOGRT Medaka Extended One Generation Reproduction Test

MH Medium high 

ML Medium low 

MoA Mode of Action 

MOE Margin of Exposure

MRID Master Record Identifier 

MROD Methoxyresorufin-O-dealkylase 

MTC Maximum Tolerated Concentration 

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v 

Abbreviation Terminology 

MTD Maximum Tolerated Dose

N Negative 

NE Not examined/evaluated

NF stage Nieuwkoop and Faber’s Staging Atlas

NOAEC No Observed Adverse Effect Concentration

NOAEL No Observed Adverse Effect Level

NS Not Statistically Significant

NR Not Reported

OCSPP Office of Chemical Safety Pollution and Prevention

OECD Organization for Economic Co-Operation and Development 

OPP Office of Pesticide Programs 

ORD Office of Research and Development

OSCP Office of Science Coordination and Policy

OSRI Other Scientifically Relevant Information

P Positive 

P Parental generation

PC Positive Control 

PC10 Positive Control at 10% of response 

PC50 Positive Control at 50% of response 

PND Post-Natal Day

POD Point of Departure

PPS Preputial Separation 

PROD Pentaoxyresorufin-O-dealkylase (or depentylase)

PXR Pregnane X receptor

QC Quality Control 

RBA Relative Binding Affinity 

RBC Red Blood Cells 

RfD Reference Dose 

RPCmax Relative to Positive Control at maximum 

SAP Scientific Advisory Panel

SC Solvent Control 

s.c Subcutaneous 

SDH Sorbitol dehydrogenase

SDWA Safe Drinking Water Act 

SEP Standard Evaluation Procedure

SD Standard Deviation or Sprague-Dawley 

SVL Snout-to-Vent Length

SV Seminal Vesicles

T Thyroid (hormonal pathway)

T1WoERC EDSP Tier 1 Weight of Evidence Review Committee

T3 Triiodothyronine 

T4 Thyroxine (tetraiodothyronine) 

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vi 

Abbreviation Terminology 

TP Testosterone Propionate

TR Thyroid Receptor

TSH Thyroid Stimulating Hormone 

UDPGT Uridine Diphosphate Glucuronyltransferase (also known as UGT) 

VC Vehicle Control 

VO Vaginal Opening 

VP Ventral Prostate 

VTG Vitellogenin

WoE Weight-of-Evidence

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Page 1 of 62 

Executive Summary 

The Endocrine Disruptor Screening Programs (EDSP) Tier 1 assay battery is designed to provide 

the necessary empirical data to evaluate the potential of chemicals to interact with the estrogen 

(E), androgen (A) or thyroid (T) signaling pathways. This interaction includes agonism and 

antagonism at the estrogen and androgen receptors, altered steroidogenesis, as well as 

hypothalamic-pituitary-gonadal (HPG) and hypothalamic-pituitary thyroid (HPT) axes. In 

addition to the available Tier 1 assay data, other scientifically relevant information (OSRI), 

including general toxicity data and open literature studies of sufficient quality, were considered 

in this weight of evidence (WoE) assessment. 

In determining whether glyphosate interacts with E, A or T hormone pathways, the number and 

type of effects induced, the magnitude of responses, and the pattern of responses observed across 

studies, taxa, and sexes were considered. Additionally, the conditions under which effects occur 

were considered, in particular, whether or not endocrine-related responses occurred at dose(s) 

that also resulted in general systemic toxicity or overt toxicity. 

On September 17, 2014, the EDSP Tier 1 Assay Weight of Evidence Review Committee 

(T1WoERC) of the Office of Pesticide Programs (OPP) and the Office of Science Coordination 

and Policy (OSCP) conducted a weight-of-evidence (WoE) analysis of the potential interaction 

of glyphosate with the E, A or T hormone pathways. The T1WoERC conclusions from the WoE 

evaluation in this report are presented by pathway (E, A and then T) beginning with the results of 

the Tier 1 in vitro assays followed by in vivo mammalian and wildlife results, then the results of 

the cited OSRI for mammalian and wildlife studies (40 CFR Part 158 and literature).

For the estrogen pathway, while glyphosate showed estrogen receptor (ER) antagonism in vitro

with estrogen-dependent human breast cancer cells (Thongprakaisang et al., 2013), there was no 

evidence of potential interaction of glyphosate with the estrogen pathway in the EDSP Tier 1 in 

vitro assays [i.e, ER binding, ER transactivation assay (ERTA), aromatase and steroidogenesis 

assays]. Additionally, glyphosate was negative in the Tier 1 in vivo mammalian assays (i.e.,

uterotrophic or female pubertal assays). In the fish short-term reproduction assay (FSTRA), the 

non-treatment-responsive decrease [only significant at mid-treatment] in vitellogenin (VTG) was 

seen in isolation in the absence of any treatment-related effects in the other estrogen-related 

endpoints such as gonado-somatic index (GSI), gonadal staging, fecundity and fertilization. In 

addition, there were no notable gonadal histopathology. There were no treatment-related effects 

on female reproductive parameters in the existing glyphosate Part 158 mammalian or wildlife 

studies (decreases in offspring body weight observed in one avian reproduction study). 

Therefore, there is no convincing evidence of a potential interaction with the estrogen pathway 

for glyphosate. 

For the androgen pathway, there was no evidence of interaction of glyphosate with the androgen 

pathway in the Tier 1 in vitro [i.e, androgen receptor (AR) binding and steriodogenesis assays 

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Page 2 of 62 

were negative] or Tier 1 in vivo FSTRA and mammalian assays (i.e., Hershberger and male 

pubertal assays were negative in the absence of overt toxicity). In addition, glyphosate was 

negative in an AR transactivation assay (Kojima et al., 2004). The only treatment-related effects 

observed in the Part 158 mammalian studies in the absence of overt toxicity were decreases in 

sperm count in the subchronic rat study (1678 mg/kg/day) and a delay in preputial separation 

(PPS)at 1234 mg/kg/day in the post-1998 two-generation reproduction study in rats (the EDSP 

Tier 2 study). Both effects were observed at a dose that was above the limit dose (1000 

mg/kg/day) for those studies. No androgen-related effects were seen in the wildlife Part 158 

studies (decreases in offspring body weight observed in one avian reproduction study). 

For the thyroid pathway, there was no convincing evidence of potential interaction of glyphosate. 

There were no treatment-related effects on thyroid hormones (T4 and TSH), thyroid weights or 

thyroid histopathology in the male pubertal assay in the absence of overt toxicity. There were no 

thyroid-related effects observed in the female pubertal assay. In the amphibian metamorphosis 

assay (AMA), there were no developmental effects or alterations in thyroid histopathology. No 

thyroid-related effects were noted in any of the Part 158 studies.

Based on weight of evidence considerations, mammalian or wildlife EDSP Tier 2 testing is not 

recommended for glyphosate since there was no convincing evidence of potential interaction 

with the estrogen, androgen or thyroid pathways. 

 

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Page 3 of 62 

I. Introduction 

The Endocrine Disruptor Screening Programs (EDSP) Tier 1 assay battery is designed to provide 

the necessary empirical data to evaluate the potential of chemicals to interact with the estrogen 

(E), androgen (A) or thyroid (T) signaling pathways. This interaction includes agonism and 

antagonism at the estrogen and androgen receptors, altered steroidogenesis, as well as 

hypothalamic-pituitary-gonadal (HPG) and hypothalamic-pituitary thyroid (HPT) axes. In 

addition to the available Tier 1 assay data, other scientifically relevant information (OSRI), 

including general toxicity data and open literature studies of sufficient quality, were considered 

in this weight of evidence (WoE) assessment. 

In determining whether a pesticide chemical interacts with E, A or T hormone pathways, the 

number and type of effects induced, the magnitude of responses, and the pattern of responses 

observed across studies, taxa and sexes were considered. Additionally, the conditions under 

which effects occur were considered, in particular, whether or not endocrine-related responses 

occurred at dose(s) that also resulted in general systemic toxicity or overt toxicity. 

On September 17, 2014 the EDSP Tier 1 Assay Weight of Evidence Review Committee 

(T1WoERC) of the Office of Pesticide Programs (OPP) and the Office of Science Coordination 

and Policy (OSCP) conducted a weight-of-evidence (WOE) analysis of the potential interaction 

of glyphosate with the E, A or T hormone pathways. The T1WoERC conclusions from the WoE 

evaluation in this report are presented by pathway (E, A and then T) beginning with the results of 

the Tier 1 in vitro assays followed by in vivo mammalian and wildlife results, then the results of 

the cited OSRI for mammalian and wildlife studies (40 CFR Part 158 and literature).

Glyphosate has a vapor pressure of 9.8×10-8mm Hg at 25°C, with a water solubility of 10.5 g/L 

at 20°C. The octanol/water partition coefficient is log Kow = –3.2 to −3.4 with fish 

bioconcentration factors ranging from 0.2-0.63. Based on its vapor pressure and low Henry’s 

Law constant, glyphosate has low potential to volatilize from soils or from water. Glyphosate 

adsorbs strongly to soil and is stable to chemical and photochemical decomposition and 

hydrolysis; however, it is readily degraded by soil microbes. 

The available information considered in determining the potential interaction of glyphosate with 

the E, A and/or T pathways include submitted EDSP Tier 1 assays and/or other scientifically 

relevant information (OSRI) such as general toxicity studies and other published articles. These 

data are summarized in Sections III.A through III.C. An analysis of the data submitted to the 

Agency, using the WoE approach outlined by the Agency (USEPA, 2011), is presented in 

Section IV. The EDSP Tier 2 studies recommendations are presented in Section V. 

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Page 4 of 62 

II. Sources of Scientific Data and Technical Information 

A. EDSP Tier 1 Screening Assays 

The Tier 1 assays and/or other scientifically relevant information (OSRI) submitted to satisfy the 

agency’s test order are shown below in Table 1. Executive Summaries are presented in Appendix 

1. 

B. Other Scientifically Relevant Information (OSRI) 

In response to the Agency’s Test Orders, data believed to be relevant to one or more of the Tier 1 

assays were submitted as OSRI by the Test Order recipients and/or the public. This included 

studies published in the open literature and/or data submitted to support pesticide registration 

(e.g., Part 158 guideline studies), and a review of the available scientific literature conducted by 

Health Canada’s Pest Management Regulatory Agency (USEPA, 2014). The Agency’s review of 

the initial OSRI is provided in the Report of the Endocrine Disruptor Review Team on OPP 

(USEPA, 2010). Since then, the Agency has also conducted a more recent search of available 

scientific literature for any additional relevant information. Summaries of the available OSRI are 

presented in Appendix 2. Additionally, literature/studies considered but not utilized for the WoE 

analysis are listed in Appendix 3. 

III. Weight of Evidence (WoE) Evaluation 

The principles, criteria and approach used in the WoE determination on the potential of a 

substance to interact with endocrine-related processes (i.e., E, A, or T hormonal pathways) were 

as described in the WoE guidance document (USEPA, 2011) and presented at the 2013 FIFRA 

Scientific Advisory Panel (SAP) (USEPA, 2013). The weight of evidence process identifies how 

the individual lines of evidence are assembled and integrated along two concepts (i.e., 

complementarity and redundancy) within the conceptual framework of an adverse outcome 

pathway). Broadly, there are four main steps outlined in the guidance which provide the 

foundation for WoE evaluations. The first step is to evaluate the individual studies for their 

scientific quality and relevance in evaluating potential endocrine interaction(s). The second step 

is to integrate the data along different levels of biological organization while examining the 

extent of complementarity (i.e., the concordance of endpoints within an assay that measures 

multiple endpoints) and redundancy (i.e., the concordance of endpoints/responses across assays) 

in the observed responses across these different levels of biological organization. The third step 

is to characterize the main lines of evidence as well any conclusions. Finally, the last step is to 

evaluate whether additional testing is needed based on the evidence and conclusions described 

above. 

As mentioned, the first step is to assemble and evaluate the available scientific data. Data for the 

EDSP Tier 1 WoE evaluation falls into one of two categories: 1) EDSP Tier 1 data, or 2) other 

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Page 5 of 62 

scientifically relevant information (OSRI). The EDSP Tier 1 data include a battery of 11 assays 

consisting of in vitro and mammalian and wildlife in vivo assays. The Tier 1 assays were 

designed specifically to evaluate a number of key biological events including potential effects on 

receptor binding (estrogen and androgen agonist and antagonist), steroidogenesis, and other 

effects on the HPG and HPT axes. OSRI may include published literature studies as well as 

studies conducted under USEPA (often referred to as Part 158 data) or OECD guidelines 

submitted in support of pesticide registrations. Each study is evaluated for scientific quality and 

relevance for informing interactions with the E, A, or T pathway. Additionally, the consistency 

of the responses in the individual study is evaluated. For the Tier 1 in vivo assays, often multiple 

endpoints are measured in each assay. 

Evaluation of the potential confounding effects of overt toxicity in the study, as well as the 

relative degree of diagnostic utility of a specific endpoint for discerning whether or not the 

chemical has interacted with the endocrine system, are considered. The collective response of the 

individual endpoints, as well as the conditions under which they were expressed, are considered 

when evaluating an overall indication of potential interaction as measured by the study. 

The second step in this WoE process is to formulate hypotheses and integrate the available data 

along different levels of biological organization. Two keys elements in the integration of data, as 

well as characterizing the extent to which the available data support a hypothesis that a chemical 

has the potential to interact E, A or T pathways, are the concepts of complementarity and 

redundancy. These two concepts provide a basis for considering the plausibility, coherence, 

strength, and consistency of the body of evidence. The current EDSP Tier 1 screening assays are 

meant to evaluate whether or not a chemical can interact with E, A and T consisting of different 

levels of biological organization from a molecular initiating event, such as receptor binding, 

through potential adverse effects in apical endpoints such as sexual development and fecundity at 

the whole organism level. The extent of expression of responses at higher levels of biological 

organization can indirectly provide information on potential compensatory capabilities of an 

individual organism. 

After the data have been assembled and integrated, the third step is to characterize the main lines 

of evidence along with the conclusions; this characterization involves three components. The 

first component is whether the data provide relevant, robust and consistent evidence in terms of 

complementarity and redundancy as well as biological plausibility. Second, is at what level of 

biological organization were the responses observed and whether organisms exhibit 

compensatory responses at higher levels of biological organization? Finally, under what 

conditions dide the responses occur including consideration of whether the responses were 

observed in the presence of overt or systemic toxicity? The presence of overt and/or systemic 

toxicity introduces uncertainty in the ability to distinguish effects specifically related to an 

endocrine-related effect from a non-endocrine toxic response. 

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Page 6 of 62 

This uncertainty in distinguishing whether the responses were endocrine-related was discussed at 

the FIFRA SAP meeting that evaluated scientific issues associated with the WoE evaluation of 

the EDSP Tier 1 screening process. In October 2013, the SAP stated that , “In summary, the 

Panel agreed that little, if any, weight should be placed on signs of endocrine disruption in the 

presence of overt toxicity. All effects in endocrine sensitive tissues should be evaluated in terms 

of primary interactions with the endocrine system vs. secondary effects related to toxicity in nonendocrine organs or overall disruptions in homeostasis” (USEPA, 2013). 

For these WoE analyses, overt toxicity was generally defined in accordance with EPA’s current 

approach as used by OPP in reviewing 40 CFR Part 158 studies for both human and ecological 

risk assessments. Specifically, in these analyses, the effects that EPA considered to be potential 

evidence of overt toxicity included, but were not limited to: mortality; clinical signs such as 

tremors, ataxia and abnormal swimming (fish and aquatic-phase amphibians); and body weight 

decreases of ≥10% in mammals. Additionally, other effects including morphological (e.g., organ 

weights/histopathology), biochemical (e.g., blood chemistry), and other clinical signs (e.g., 

lethargy) were also considered when evaluating overt toxicity, especially if the effects were 

extreme. In some instances, one parameter (i.e., death or >10% decrease in mammalian body 

weight) was sufficient to consider a dose/concentration to be overtly toxic. However, in other 

instances, more than one parameter was needed to determine overt toxicity. For example, in the 

FSTRA, generally, body weight decreases were considered along with other responses when 

assessing potential overt toxicity. Additionally, effects which were considered to be signs of 

systemic toxicity were also captured and these effects were generally considered as less severe 

forms of toxicity (e.g., organ weights or blood chemistry). The circumstances for which a 

dose/concentration was considered overtly toxic for a particular study are described in Section 

IV.A. 

In summary, EPA considers multiple lines of evidence in including the observed responses in 

the Tier 1 assays and OSRI in the context of a chemical’s physical/chemical properties and its 

known modes of action in its overall characterization of a chemical’s potential to interact with 

the E, A or T pathway. Adequately addressing the three components described above is 

fundamental to the WoE process and in determining whether additional data are needed. In 

addition to characterizing the WoE, reviewers also considered: 1) uncertainties and their 

potential impact to conclusions; 2) discussion of key studies; 3) description of inconsistent or 

conflicting data; 4) overall strength of evidence supporting a conclusion; and, 5) what, if any, 

additional data are needed and why. Assessing the need for additional data is based on a caseby-case analysis which took all available toxicity data into account. 

The WoE approach involved consideration of data (i.e., lines of evidence) from the EDSP Tier 1 

assays and OSRI which are depicted in Tables 2 - 4. These tables contain data that are 

considered scientifically and biologically relevant with regard to a treatment-related effect 

which supports a conclusion of whether a substance has the potential to interact with the E, A, 

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Page 7 of 62 

or T pathway. Effects that occurred in the presence of overt toxicity are discussed in the text for 

each respective pathway (E, A or T) but are not reported in the table for E, A or T. 

A. EDSP Tier 1 Screening Assays 

The Tier 1 assays submitted in response to the agency’s test order for glyphosate are shown below 

in Table 1. 

Table 1 Tier 1 Screening Assays for Glyphosate 

Tier 1 Assays Test Guideline Test Order Status 

ER Binding Assay (Rat uterine cytosol) OSCPP 890.1250 Requirement Satisfied 

(MRID 48671305) 

ERα Transcriptional Activation Assay 

(Human cell line HeLa 9903) 

OSCPP 890.1300; 

OECD 455 

Requirement Satisfied 

(MRID 48671307) 

AR Binding Assay (Rat prostate cytosol) OSCPP 890.1150 Requirement Satisfied 

(MRID 48671301) 

Steroidogenesis Assay (Human cell line 

H295R) 

OSCPP 890.1550; 

OECD 456 

Requirement Satisfied by OSRI 

(Hecker et al., 2011)

Aromatase Assay (human recombinant 

microsomes) OSCPP 890.1200 Requirement Satisfied (MRID 48671303) 

Uterotrophic Assay (Rat) OSCPP 890.1600; 

OECD 440 

Requirement Satisfied 

(MRID 48677003) 

Hershberger Assay (Rat) OSCPP 890.1400; 

OECD 441 

Requirement Satisfied 

(MRID 48617001) 

Pubertal Female Assay (Rat) OSCPP 890.1450 Requirement Satisfied 

(MRID 48671315) 

Pubertal Male Assay (Rat) OSCPP 890.1500 Requirement Satisfied 

(MRID 48671313) 

Fish Short-term Reproduction Assay OSCPP 890.1350; 

OECD 229 

Requirement Satisfied 

(MRID 48671311) 

Amphibian Metamorphosis Assay (Frog) OSCPP 890.1100; 

OECD 231 

Requirement Satisfied 

(MRID 48671309) 

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B. Effects on Hypothalamic-Pituitary-Gonadal (HPG) Axis 

1. Effects on Estrogen Pathway 

The potential for glyphosate to interact with the estrogen pathway is summarized in Table 2. The 

various targets of the estrogen pathway across the relevant Tier 1 assays are delineated so as to 

facilitate determination of potential for estrogenic, anti-estrogenic or HPG axis effects. This table 

also includes HPG-relevant findings from data evaluated as OSRI. Effects that occurred in the 

presence of overt toxicity are discussed in the text but are not reported in the table and not 

considered further in the WOE assessment. 

Glyphosate was negative (or not interactive) in the in vitro estrogen receptor (ER) binding, 

aromatase, and steroidogenesis assays. In the Tier 1 ERα transcriptional activation (ERTA), the 

data for the very weak agonist control chemical (17α-methyltestosterone) did not respond 

appropriately in the assay, and therefore, this study was not considered reliable for evaluating 

potentially very weak agonists. However, it is unlikely that glyphosate is an estrogen receptor 

agonist because (1) there was no activity in an ERTA assay in which the strong and weak agonist 

reference chemicals (17β-estradiol and 17α-estradiol, respectively) showed the expected activity, 

and (2) negative responses were observed in the Tier 1 ER binding and uterotrophic assays, 

which also assess estrogen receptor-related activity. In a literature study by Thongprakaisang et 

al., 2013, glyphosate induced ERE activation in T47D-KBluc cells. Co-incubation of glyphosate 

with ICI 182780 (ER antagonist) resulted in a decreased or inhibited response in these cells.

The uterotrophic assay was negative up to the limit dose (1000 mg/kg/day). No estrogen-related 

effects were observed in the female pubertal rat assay up to the limit dose (1000 mg/kg/day). No 

estrogen-related effects were seen in the mammalian Part 158 studies. 

In the FSTRA, there was a significant decrease in plasma vitellogenin (VTG) concentrations in 

the medium high treatment group (6.2 mg a.i/L) as compared to the negative control. This 

reduction from control was 55%, with non-dose-dependent decreases in VTG concentrations of 

approximately 30-33% at all other treatment concentrations. Other female-related endpoints, 

including gonado-somatic index (GSI), gonadal staging, fecundity, and fertilization success were 

not significantly affected. Additionally, there were no notable histopathological diagnoses that 

were attributed to glyphosate exposure. 

In available Part 158 avian reproduction studies (two with the mallard duck and one with the 

bobwhite quail), there were no treatment-related effects on all reproductive parameters (tested up 

to 1000 mg/kg-diet). In another mallard duck reproduction study, test up to 2250 mg/kg-diet, 

reductions in 14-d offspring body weight were observed at 501 mg/kg-diet as well as reductions 

in male body weight; there were no other effects observed. 

Page 16 of 70
GLYPHOSATE FINAL 

Page 9 of 62 

In a OSRI fish study (Le Mer et al., 2013) with wild larval three-spined sticklebacks 

(Gasterosteus aculeatus), there was no VTG induction observed in fish treated with glyphosate 

up to 10 μg/L. Additionally, there were no effects on histology including proportions of intersex 

individuals. In a Part 158 fish life-cycle toxicity study with fathead minnow, there was no 

treatment-related effect on any of the reproductive or growth parameters up to 25.7 mg/L. 

Page 17 of 70
GLYPHOSATE FINAL 

Page 10 of 62 

Table 2. Estrogenic/Anti-Estrogenic Pathway for Glyphosate

Lines of Evidence Indicating Potential Interaction with the Estrogenic/Anti-Estrogenic Pathway for Glyphosate1Study Type/ Literature Citation 

ER Binding 

ER Activation 

Steroidogenesis 

Sex Steroid 

Hormone 

Uterine Weight 

Ovarian 

Weight/GSI 

Ovarian/Gonad 

Staging and 

Histopathology 

Pituitary Weight 

Estrous Cyclicity 

Age & Weight at 

VO 

2° Sex 

Characteristics 

Fertility(Frt) 

/Fecundity (Fcd) 

Vitellogenin (VTG) 

EDSP Tier 1 Assays 

ER Binding (MRID 48671305) N ERTA (MRID 48671307) N Aromatase (MRID 48671303) N Steroidogenesis (MRID 48617005) N Uterotrophic (MRID 48617003) N Female Pubertal Rat (MRID 48671315) N N N N N N FSTRA (MRID 48671311) NE N N N N N 

OSRI 

Receptor Transactivation Assay (Kojima et al., 2004)

 N 

Receptor Transactivation Assay (Thongprakaisang et al., 2013)

 P5

90-Day Subchronic Toxicity (Rat; MRID 40559401)

 NE N NE 
GLYPHOSATE FINAL 

Page 11 of 62 

Table 2. Estrogenic/Anti-Estrogenic Pathway for Glyphosate

Lines of Evidence Indicating Potential Interaction with the Estrogenic/Anti-Estrogenic Pathway for Glyphosate1Study Type/ Literature Citation 

ER Binding 

ER Activation 

Steroidogenesis 

Sex Steroid 

Hormone 

Uterine Weight 

Ovarian 

Weight/GSI 

Ovarian/Gonad 

Staging and 

Histopathology 

Pituitary Weight 

Estrous Cyclicity 

Age & Weight at 

VO 

2° Sex 

Characteristics 

Fertility(Frt) 

/Fecundity (Fcd) 

Vitellogenin (VTG) 

90-Day Subchronic Toxicity (Rat; NTP, 1992)

 NE N NE 

90-Day Subchronic Toxicity (Mouse; MRID 00036803)

 N N NE 

90-Day Subchronic Toxicity (Mouse; NTP, 1992)

 NE N NE N 

Developmental Toxicity (Rat; MRID 00046362)

NR N 

Developmental Toxicity (Rabbit; MRID 00046363) 

 NR N 

Three-Generation Reproduction (Rat; MRIDs 00081674, 00105995) 

 NE N N N NE N 

Two-Generation Reproduction (Rat; MRID 41621501) 

 NE N N NE N 

Two-Generation Reproduction (Rat; MRIDs 48865101-48865105) 

N N N N N N 
GLYPHOSATE FINAL 

Page 12 of 62 

Table 2. Estrogenic/Anti-Estrogenic Pathway for Glyphosate

Lines of Evidence Indicating Potential Interaction with the Estrogenic/Anti-Estrogenic Pathway for Glyphosate1Study Type/ Literature Citation 

ER Binding 

ER Activation 

Steroidogenesis 

Sex Steroid 

Hormone 

Uterine Weight 

Ovarian 

Weight/GSI 

Ovarian/Gonad 

Staging and 

Histopathology 

Pituitary Weight 

Estrous Cyclicity 

Age & Weight at 

VO 

2° Sex 

Characteristics 

Fertility(Frt) 

/Fecundity (Fcd) 

Vitellogenin (VTG) 

Chronic Toxicity (Dog; MRID 00153374) 

 NE N N N 

Carcinogenicity (Mouse; MRID, 00130406) 

 NR N N NR 

Chronic Toxicity/ Carcinogenicity (Rat; MRIDs 00093879, 00150564) 

 NE N N N 

Chronic Toxicity/ Carcinogenicity (Rat; MRID 41643801) 

 NE NE N NE 

Avian Reproduction (Duck; MRID 00036328; 00111953) 

N 

Avian Reproduction (Duck; MRID 48876602) 

P6 

Avian Reproduction (Quail; MRID 00108207) 

N 

Early Life-Stage Toxicity (Sticklebacks; Le Mer et al., 2013) 

 N 

Fish Life Cycle Toxicity (MRID 00108171) 

N 
GLYPHOSATE FINAL 

Page 13 of 62 

1. Key to responses: L=Low treatment, ML=Medium-low treatment, M=Medium treatment, MH=Medium-high treatment, H=Hi Arrows (↓ or ↑) indicate the direction of the response. A shaded cell indicates that this parameter is not routinely evaluated or is 

assay. Changes in weight are absolute unless otherwise indicated. I= Inconclusive; LW= Liver weight; I= inconclusive 

2. The systemic toxicity in the Tier 1 assays are presented in this column (e.g. KW= kidney weight). The systemic toxicity for the 

X in this column. For details see Section IV. A 

3. The overt toxicity in the Tier 1 assays are presented in this column (e.g. ↓BW). The overt toxicity for the OSRI is indicated by a

details see Section IV. A 

4. Rales was observed in medium- and high-dose animals (4/15 and 13-15, respectively) at approximately 4 hours post-dose. 5. Glyphosate caused hormone-dependent T47D cells to proliferate, approximately 15-30% of control, in the absence of E2. Glyp

activation by 5- to 13-fold in T47D-KBluc cells compared to control. Both responses were inhibited in the presence of ICI 1827

6. Reductions in 14-d offspring body weight at 501 mg/kg-diet. No effects on egg production or embryo viability were observed. 7. Reduction in male body weight gain at 501 mg/kg-diet; no effects on female body weight gain or other clinical signs of toxicityP Positive findings N Negative (in vitro)/No effect (in vivo) 

NE Not examined NR Not reported 
GLYPHOSATE FINAL 

Page 14 of 62 

2. Effects on Androgen Pathway 

The potential for glyphosate to interact with the androgen pathway is summarized in Table 3. 

The various targets of the androgen pathway across the relevant Tier 1 assays are delineated so 

as to facilitate determination of potential for androgenic, anti-androgenic, or HPG axis effects. 

This table also includes HPG-relevant findings from data evaluated as OSRI. Effects that 

occurred in the presence of overt toxicity are discussed in the text but are not reported in the 

table and not considered further in the WOE assessment. 

Glyphosate was negative (or a non-binder) in the in vitro androgen receptor (AR) binding (rat 

prostate cytosol) and steroidogenesis assay. 

Glyphosate was also classified as negative in the in vivo Hershberger assay as there were no 

treatment-related effects in accessory sex tissue (AST) weights up to the limit dose (1000 

mg/kg/day). Glyphosate had no effect on androgenic endpoints in the FSTRA, including GSI, 

gonadal histology and staging, as well as no effects on VTG. 

In the male pubertal assay, decreases were observed in the weights of the ventral prostate, 

seminal vesicle, LABC, pituitary glands as well as a 2.1 day delay in PPS at the high dose (1000 

mg/kg/day) but were concurrent with significant decreases in body weight (10%). Additionally, 

there was no treatment-related changes in serum testosterone concentrations or any 

histopathological changes in any tissues in at any dose. 

In the Part 158 two-generation rat reproduction study, a delay in attainment of PPS, and 

increased body weight at attainment, occurred in F1 male pups at 1234 mg/kg/day. In the 90-day 

subchronic rat study, relative testes weight was increased 21% at a dose of 3393 mg/kg/day 

which occurred in the presence of overt toxicity (↓18% body weight); no changes were observed 

in absolute weights. Additionally, sperm counts were decreased at 1678 and 3393 mg/kg/day; 

however, no changes in testes histopathology were observed. In the 90-day mouse study, relative 

testes weight were increased 10 and 18% at a dose of 4776 and 10,780 mg/kg/day, respectively, 

which was concurrent with decreases in body weight greater than 10%. In the carcinogenicity 

study in mice, relative testes weights were increased (17.5%; NS) at a dose (4500 mg/kg/day) 

which is approximately four-fold higher than the limit dose. 

In the fish study by Le Mer et al., 2013, there was no effect on the induction of spiggin (a protein 

secreted by males to construct nests) observed in any of the treatment groups. Additionally, 

while effects on male body weight gain and offspring body weight were observed in one Part 158 

mallard duck reproduction study, there were no other androgen-related effects observed in the 

Part 158 avian reproduction studies or fish life-cycle study.

Page 22 of 70
GLYPHOSATE FINAL 

Page 15 of 62 

Table 3. Androgenic/Anti-Androgenic Pathway for Glyphosate

Lines of Evidence Indicating Potential Interaction with the Androgenic/Anti-Androgenic Pathway for Glyphosate1Study Type/ Literature Citation 

AR Binding 

AR Activation 

Steroidogenesis 

Sex Steroid 

Hormones 

Testes Weight/GSI 

Gonad Staging and 

Histopathology 

Epididymides Weight 

Epididymides 

Histopathology 

Pituitary Weight 

Accessory Sex Organ 

Weights/ 2° Sex 

Characteristics 

Fertility(Frt) 

/Fecundity (Fcd) 

Age and Weight at 

PPS 

Vitellogenin (VTG) 

EDSP Tier 1 Assays 

AR Binding (MRID 48671301) N Steroidogenesis (MRID 48617005) N Hershberger (MRID 48617001) NE N Male Pubertal Rat (MRID 48671313) N N N N N N N N FSTRA (MRID 48671311) NE N N N N N 

OSRI 

Receptor Transactivation Assay (Kojima et al., 2004)

 N 

90-Day Subchronic Toxicity (Rat; MRID 40559401)

 N N N N NE 

90-Day Subchronic Toxicity (Rat; NTP, 1992)

 N N N N NE P5 
GLYPHOSATE FINAL 

Page 16 of 62 

Table 3. Androgenic/Anti-Androgenic Pathway for Glyphosate

Lines of Evidence Indicating Potential Interaction with the Androgenic/Anti-Androgenic Pathway for Glyphosate1Study Type/ Literature Citation 

AR Binding 

AR Activation 

Steroidogenesis 

Sex Steroid 

Hormones 

Testes Weight/GSI 

Gonad Staging and 

Histopathology 

Epididymides Weight 

Epididymides 

Histopathology 

Pituitary Weight 

Accessory Sex Organ 

Weights/ 2° Sex 

Characteristics 

Fertility(Frt) 

/Fecundity (Fcd) 

Age and Weight at 

PPS 

Vitellogenin (VTG) 

90-Day Subchronic Toxicity (Mouse; MRID 00036803)

 N N NE N NE 

90-Day Subchronic Toxicity (Mouse; NTP, 1992)

 N N N N NE 

Three-Generation Reproduction (Rat; MRIDs 00081674, 00105995) 

N N N N 

Two-Generation Reproduction (Rat; MRID 41621501) 

N N N N N N 

Two-Generation Reproduction (Rat; MRIDs 48865101-48865105) 

N N N N N N N 

Age: 

↑2.9 d 

Wt: 

↑10% 

(H)6

 

Chronic Toxicity (Dog; MRID 00153374) 

N N NE NR N 

Carcinogenicity (Mouse; MRID 00130406) 

 N N NR NR NR 
GLYPHOSATE FINAL 

Page 17 of 62 

Table 3. Androgenic/Anti-Androgenic Pathway for Glyphosate

Lines of Evidence Indicating Potential Interaction with the Androgenic/Anti-Androgenic Pathway for Glyphosate1Study Type/ Literature Citation 

AR Binding 

AR Activation 

Steroidogenesis 

Sex Steroid 

Hormones 

Testes Weight/GSI 

Gonad Staging and 

Histopathology 

Epididymides Weight 

Epididymides 

Histopathology 

Pituitary Weight 

Accessory Sex Organ 

Weights/ 2° Sex 

Characteristics 

Fertility(Frt) 

/Fecundity (Fcd) 

Age and Weight at 

PPS 

Vitellogenin (VTG) 

Chronic Toxicity/ Carcinogenicity (Rat; MRIDs 00093879, 00150564) 

N N NE N N 

Chronic Toxicity/ Carcinogenicity (Rat; MRID 41643801) 

N N N N NE 

Avian Reproduction (Duck; MRID 00036328) 

N 

Avian Reproduction (Duck; MRID 00111953) 

N 

Avian Reproduction (Duck: MRID 48876602) 

P7 

Avian Reproduction (Quail; MRID 00108207) 

N 

Early Life-Stage Toxicity (Sticklebacks; Le Mer et al., 2013) 

 N9 
GLYPHOSATE FINAL 

Page 18 of 62 

Table 3. Androgenic/Anti-Androgenic Pathway for Glyphosate

Lines of Evidence Indicating Potential Interaction with the Androgenic/Anti-Androgenic Pathway for Glyphosate1Study Type/ Literature Citation 

AR Binding 

AR Activation 

Steroidogenesis 

Sex Steroid 

Hormones 

Testes Weight/GSI 

Gonad Staging and 

Histopathology 

Epididymides Weight 

Epididymides 

Histopathology 

Pituitary Weight 

Accessory Sex Organ 

Weights/ 2° Sex 

Characteristics 

Fertility(Frt) 

/Fecundity (Fcd) 

Age and Weight at 

PPS 

Vitellogenin (VTG) 

Fish Life Cycle Toxicity (MRID 00108171) 

 N 

1. Key to responses: L=Low treatment, ML=Medium-low treatment, M=Medium treatment, MH=Medium-high treatment, H=High 

indicate the direction of the response. A shaded cell indicates that this parameter is not routinely evaluated or is not applicable in thweight are absolute unless otherwise indicated. Abbreviations for androgen sensitive tissues: Seminal vesicles (SV), Ventral prosta(DP), Levator ani-bulbocavernosus (LABC), Epididymides (E), Cowper’s gland (CG), glans penis (GP).; BW= Body weight; BWGLW= Liver weight 

2. The systemic toxicity in the Tier 1 assays are presented in this column (e.g. KW= kidney weight). The systemic toxicity for the OS

this column. For details see Section IV. A 

3. The overt toxicity in the Tier 1 assays are presented in this column (e.g. ↓BW). The overt toxicity for the OSRI is indicated by an X 

details see Section IV. A 

4. Rales were observed in 9/15 and 14/15 males in the medium- and high-dose groups, respectively, approximately 4 hours post-dosin

during the daily examinations in 7/15 high-dose males throughout the study. 

5. Sperm counts were decreased at 1678 mg/kg/day in the absence of overt toxicity; however epididymal sperm motility, total sperma

spermatid heads/g caudal tissue in the treated animals were similar to control. 

6. Delay in attainment of PPS, and increased body weight at attainment, occurred in F1 male pups at 1234 mg/kg/day. 

7. Reductions in 14-d offspring body weight at 501 mg/kg-diet. No effects on egg production or embryo viability were observed. 8. Reduction in male body weight gain at 501 mg/kg-diet; no effects on female body weight gain or other clinical signs of toxicity

9. No induction of spiggin (a protein secreted by males to construct nests) in fish 

P Positive findings N Negative (in vitro)/No effect (in vivo) 

NE Not examined NR Not reported 
GLYPHOSATE FINAL 

Page 19 of 62 

C. Effects on Hypothalamic-Pituitary-Thyroidal (HPT) Axis 

The current EDSP Tier 1 battery does not have a specific in vitro assay to detect chemicals with 

the potential to affect hypothalamic or pituitary regulation of thyroid hormone production, but it 

does include three in vivo assays that provide data to detect changes in the HPT axis, i.e., the 

pubertal female and male (rat) assays, and the AMA (frog). 

The potential for glyphosate to interact with thyroid regulation is summarized in Table 4. The 

various targets of the thyroid pathway across the relevant Tier 1 assays are delineated so as to 

facilitate determination of potential for thyroid or HPT axis effects. This table also includes 

HPT-relevant findings from data evaluated as OSRI. Effects that occurred in the presence of 

overt toxicity are discussed in the text but are not reported in the table and not considered 

further in the WOE assessment. 

In the AMA, there were no effects on median NF developmental stage and, no asynchronous 

development was observed. There was a significant decrease (p<0.05) in Day 7 normalized hind 

limb length at the middle treatment concentration (4.3 mg a.i/L) but this effect was not observed 

at Day 21 along with no significant (p>0.05) effects at any other concentration for Days 7 and 

21. There was no treatment-related effects on thyroid histopathology. There was a significant 

increase (p<0.05) in Day 21 snout-vent-length (SVL) in the middle, middle-high and high 

treatment concentrations (↑5.2, 2.5 and 6.8%, respectively). Additionally, there was a significant 

increase in Day 21 body weight at the highest treatment concentration (↑17%). In a study 

examining the chronic effects of glyphosate and its formulations to four North American frog 

species (Howe et al, 2004), treatment with glyphosate alone did not reveal any effects on growth 

(length), tail morphology, percent surviving to reach Gosner Stage 42, time to metamorphosis, 

gonadal development or thyroid gene expression relative to controls. It is noted that control 

mortality was relatively high in this study under chronic exposure (38%), and as such is not 

included in table below. 

There were no thyroid-related effects observed in the female pubertal assay. In the male pubertal 

assay, while total thyroxine (T4) and thyroid stimulating hormone (TSH) concentrations were 

decreased compared to control in all glyphosate treatment groups, they were not statistically 

significant and were not considered to be treatment-related. Additionally, there was a slight 

increase in the number of high-dose males with decreased colloid area that occurred in the 

presence of overt toxicity (↓10% body weight), and there were no treatment-related effects on 

follicular cell height at any dose compared to control. Furthermore, there were no effects on 

thyroid function observed in any of the mammalian Part 158 toxicity studies. 

Page 27 of 70
GLYPHOSATE FINAL 

Page 20 of 62 

Table 4. Thyroid Pathway for Glyphosate

Lines of Evidence Indicating Potential Interaction with the Thyroid Pathway for Glyphosate1

Study Type/ 

Literature Citation 

Thyroid Weight Thyroid: Gross and Histopathology Serum T4 Levels 

Serum TSH Levels Pituitary Weight Developmental stage (± or asynchronous, HLL) Growth (BW, BL, SVL) Systemic Toxicity 2

Overt Toxicity3

EDSP Tier 1 Assays 

Female Pubertal 

Rat 

(MRID 48671315) 

N N N N N P 

(M, H)4 N 

Male Pubertal Rat 

(MRID 48671313) N N N N N P (M, H)5 BW: 

↓10% 

(H)

AMA (Frog; MRID 

48671309) N N 

Day 21: 

SVL: 

↑5, 3,7% 

(M, MH, 

H)6

; 

BW: 

↑17% 

 (H)7 

 N 

OSRI 

90-Day Subchronic 

Toxicity (Rat; 

MRID 40559401)

NE N NE N N 

90-Day Subchronic 

Toxicity (Rat; NTP, 

1992)

NE N NE X 

(H) 

X 

(H) 

90-Day Subchronic 

Toxicity (Mouse; 

MRID 00036803)

NE N NE X 

 (H) N 

90-Day Subchronic 

Toxicity (Mouse; 

NTP, 1992)

NE N NE X 

(M, MH, H) 

X 

(MH, 

H) 

Three-Generation 

Reproduction (Rat; 

MRIDs 00081674, 

00105995) 

NE N N N N 

Two-Generation 

Reproduction (Rat; 

MRID 41621501) 

NE NE NE X 

 (H)

X 

(H) 

Two-Generation 

Reproduction (Rat; 

MRIDs 48865101-

48865105) 

N N N X 

 (H) N 

Chronic Toxicity 

(Dog; MRID 

00153374) 

N N N N N 

Page 28 of 70
GLYPHOSATE FINAL 

Page 21 of 62 

Table 4. Thyroid Pathway for Glyphosate

Lines of Evidence Indicating Potential Interaction with the Thyroid Pathway for Glyphosate1

Study Type/ 

Literature Citation 

Thyroid Weight Thyroid: Gross and Histopathology Serum T4 Levels 

Serum TSH Levels Pituitary Weight Developmental stage (± or asynchronous, HLL) Growth (BW, BL, SVL) Systemic Toxicity 2

Overt Toxicity3

Carcinogenicity 

(Mouse; MRID, 

00130406) 

N N N X 

(H) N 

Chronic Toxicity/ 

Carcinogenicity 

(Rat; MRIDs 

00093879, 

00150564) 

N N N X 

(L, M) N 

Chronic Toxicity/ 

Carcinogenicity 

(Rat; MRID 

41643801) 

NE N NE X 

(H) N 

1. Key to responses: L=Low treatment, ML=Medium-low treatment, M=Medium treatment, MH=Medium-high 

treatment, H=High treatment. Arrows (↓ or ↑) indicate the direction of the response. A shaded cell indicates 

that this parameter is not routinely evaluated or is not applicable in this assay. Changes in weight are absolute 

unless otherwise indicated. 

2. The systemic toxicity in the Tier 1 assays are presented in this column (e.g. KW= kidney weight). The systemic 

toxicity for the OSRI is indicated by an X in this column. For details see Section IV. A 

3. The overt toxicity in the Tier 1 assays are presented in this column (e.g. ↓BW). The overt toxicity for the OSRI 

is indicated by an X in this column. For details see Section IV. A 

4. Rales was observed in medium- and high-dose animals (4/15 and 13-15, respectively) at approximately 4 hours 

post-dose. 

5. Rales were observed in 9/15 and 14/15 males in the medium- and high-dose groups, respectively, approximately 

4 hours post-dosing. This finding persisted during the daily examinations in 7/15 high-dose males throughout 

the study. 

6. Snout-vent length was increased in a non-dose-dependent manner in the top three dose groups on Day 21. 

7. Body weight was increased 17% in the high-dose group on Day 21. 

P Positive findings 

N Negative findings 

NE Not examined 

Page 29 of 70
GLYPHOSATE FINAL 

Page 22 of 62 

IV. Committee’s Assessment of Weight of Evidence 

This section of the document describes the weight of evidence (WoE) determination on the 

potential of glyphosate to interact with endocrine related processes (i.e., E, A, or T hormonal 

pathways) as well as recommendations regarding Tier 2 testing. The results of the Tier 1 assays 

are considered, along with other scientifically relevant information (e.g., 40 CFR Part 158 test 

guidelines and published or publicly available peer-reviewed studies). WoE analysis in the 

context of the EDSP follows the Agency’s guidance (USEPA 2011) and is conducted on a caseby-case basis by first assessing the different lines of evidence (i.e., specific Tier 1 assays and 

OSRI), then performing an integrated analysis of those lines of evidence. 

The WoE evaluation includes considerations of biological plausibility of the findings from the 

different lines of evidence by examining the consistency, coherence, and interrelationships 

among the measured endpoints within and across studies. The available findings from standard 

toxicology studies on the substance may contribute to the WoE evaluation in helping elucidate if 

effects seen in the Tier 1 assay are related to perturbations of the endocrine system per se or 

alternatively sequelae of systemic effects. Endocrine modes of action may elicit a number of 

phenotypic consequences other than those evaluated in the Tier 1 assays. 

Endocrine-related findings in the presence of overt toxicity may result in uncertainty as to 

whether or not the responses are related through an endocrine pathway, therefore non-endocrine 

toxic responses (including but not limited to mortality or body weight changes) are also 

considered in this WoE evaluation. The FIFRA SAP that evaluated scientific issues associated 

with weight of evidence evaluation of the results of the Tier 1 assays stated that “In summary, the 

Panel agreed that little, if any, weight should be placed on signs of endocrine disruption in the 

presence of overt toxicity. All effects in endocrine sensitive tissues should be evaluated in terms 

of primary interactions with the endocrine system vs. secondary effects related to toxicity in nonendocrine organs or overall disruptions in homeostasis” (USEPA, 2013).

A. Systemic/Overt Toxicity in the in vivo Tier 1 Assays and OSRI 

Effects that were considered to be systemic or overt toxicity for the in vivo Tier 1 and OSRI 

studies are described below. Generally, one parameter (i.e., death or >10% decrease in 

mammalian body weight) is sufficient for a dose/concentration to be considered overtly toxic. 

However, in other instances, more than one parameter was needed to determine overt toxicity. 

Effects which were considered to be signs of systemic toxicity were generally less severe forms 

of toxicity (e.g., changes in organ weights or blood chemistry).

Page 30 of 70
GLYPHOSATE FINAL 

Page 23 of 62 

1. Tier 1 in vivo Assays 

In the Hershberger assay and the uterotrophic assays, all animals survived until scheduled 

termination, and no treatment-related clinical findings were noted in any of the animals during 

the study. In the female pubertal rat assay, one animal in the control group was sacrificed in 

extremis on PND 27 due to impairment of the right forelimb (due to possible mechanical injury); 

all other animals survived until scheduled sacrifice. In the male pubertal rat assay, one high-dose 

male was found dead prior to dosing on PND 24; no significant clinical or macroscopic findings 

were observed in this animal, with all other rats surviving until scheduled sacrifice. Treatmentrelated clinical signs in the pubertal studies were limited to rales in 4/15 females and 9/15 males 

at the medium dose (approximately 4 hours post-dosing), and in 13/15 females and 14/15 males 

at the high dose. This finding did not persist to the daily examinations at the medium dose, but 

were present in the daily examinations in 7/15 males at the high dose throughout the study. No 

other treatment-related clinical signs were noted during the 4-hour post-dosing or daily 

examinations at any dose level. Final body weights were decreased by 7 and 10% in the mediumand high-dose males. Moderate decreases in liver weights (p<0.05; ↓10 and 15%) also were also 

noted in the medium- and high-dose males, but considered secondary to decreased body weights. 

In the FSTRA, survival was 100% in the negative control and all treatment groups, except the 

medium-dose treatment group (one male mortality). Glyphosate did not result in any significant 

changes in weight or length for either sex at any treatment level. There were no observed effects 

on secondary sex characteristics and clinical signs (i.e., behavioral and other sub-lethal effects) 

in male or female fish at any treatment group. Additionally, glyphosate exposure also did not 

affect the survival of tadpoles at any concentration in the AMA, and no clinical signs of toxicity 

were observed. 

2. OSRI 

In a subchronic oral toxicity study in rats conducted by the National Toxicology Program (NTP; 

1992), all animals survived to necropsy. Diarrhea was noted in the high-dose animals through 

Day 50 of the study. Body weight gain was reduced in the high-dose males (3393 mg/kg/day), 

and the final body weight was decreased 18%, but statistical significance was not reported. Mean 

necropsy body weights were decreased in the 1678 and 3393 mg/kg/day males (↓12 and 21%, 

respectively). Body weight gain in high-dose females was decreased, but no effects on final or 

necropsy body weights were observed. Non-dose-dependent increases in relative liver weights 

also were observed in males in all dose groups and in females in the two highest dose groups. 

These findings, combined with clinical chemistry changes, are consistent with a hepatobiliary 

effect that can be attributed to glyphosate administration. 

In a subchronic oral toxicity study in mice, there were no treatment-related toxicological signs or 

mortalities during the study and no effects of treatment on food consumption. Body weight gains 

in the high-dose male and female groups were decreased compared to control. 

Page 31 of 70
GLYPHOSATE FINAL 

Page 24 of 62 

In a subchronic oral toxicity study in mice conducted by NTP (1992), there were two nontreatment-related mortalities in the study. In addition, no clinical signs of toxicity were reported. 

Final body weights were decreased in males and females in the two highest dose groups (↓>10% 

for males and ≤10% for females) with concomitant decreases in body weight gain; statistical 

significance was not reported. Mean necropsy body weights were decreased for the medium-high 

(4776 and 5846 mg/kg/day, respectively) and high-dose (10,780 and 11,977 mg/kg/day, 

respectively) males and females. Non-dose-dependent increases in relative liver weight also were 

noted in males of all dose groups, except at the low dose. A decrease in absolute liver weight 

also was noted in high-dose females. 

In a developmental toxicity study in rats, there were six deaths in the high-dose group, but none 

of the deaths were determined to be related to treatment. At the high-dose, the majority of the 

dams (all but three) were observed at least once with diarrhea, soft stools, breathing rattles, 

inactivity, and red matter in the region of nose, mouth, forelimbs, or dorsal head. No treatmentrelated clinical signs were observed in the low- and mid-dose groups; additionally, there were no 

treatment-related effects on maternal body weight in these groups. At the high dose, maternal 

body weight gain was decreased during the test period (GDs 0-20) due to body weight losses 

during GDs 6-20 (≤10%). In a developmental toxicity study in rabbits, five rabbits aborted and 

were sacrificed. Additionally, rabbits at the medium and the high dose died during the study; of 

these, five deaths were determined to not be related to treatment, but the cause of death for the 

remaining eight rabbits could not be determined at necropsy. Soft stool or diarrhea was noted in 

all groups, with a slight increase at the medium dose and at least one incidence in each rabbit of 

the high-dose group. In addition, an increase in nasal discharge was noted in the high-dose 

animals. There were no toxicologically significant differences in maternal mean body weight 

among control and treated groups. 

There were no treatment-related mortalities in a two-generation reproduction study with rats. 

Treatment-related clinical signs consisted of soft stools in high-dose males and females (both F0

and F1). Body weights of high-dose male and female F0 rats were decreased (<10%) during the 

pre-mating growth period. Similarly, F1 high-dose male and female adults weighed less at 

weaning compared to F0 animals with continued decreases of 10-12%. The body weights of 

high-dose females remained decreased compared to control during gestation and lactation of the 

F1, F2a, and F2b litters, although the high-dose group body weights were comparable to control 

by the end of lactation. Food consumption was generally similar to control in high-dose males 

and females during most measurement periods; consumption was decreased in the medium- and 

high-dose F1 females on pre-mating Days 0-14 (↓9 and 11%, respectively). Terminal body 

weights in the F0 and F1a generations were decreased by 8-13%. In a subsequent two-generation 

reproduction study with rats, there were no treatment-related effects on clinical signs or 

mortality. No treatment-related effects were observed on mortality, clinical signs, body weights, 

body weight gains, or food consumption. Absolute and relative (to body) liver weights were 

Page 32 of 70
GLYPHOSATE FINAL 

Page 25 of 62 

increased by 8-13% in both the P and F1 females at in the high-dose group with no 

histopathological findings. 

In a chronic oral toxicity/carcinogenicity study in rats, survival was unaffected by treatment. 

Decreased body weight gains were observed in treated males beginning at Week 26 and 

continuing to Week 102, and decreased body weight gains were present in the low- and mediumdose female rats from Weeks 84 to 92. No dose-response relationship was apparent in the 

decreased body weight gains in female rats, and the changes in body weight did not affect 

survival. In a subsequent chronic oral toxicity/carcinogenicity study in rats, there were also no 

treatment-related effects on clinical signs or mortality. The mean body weight of high-dose 

females was decreased by 13% at Week 81, with decreased a body weight gain of 23% compared 

to control. There were no decreases in body weight or body weight gain in male rats. Liver 

weight (relative to body weight) was increased (↑13%) in high-dose males at interim sacrifice, 

and absolute liver weights were increased (↑13%) in high-dose males at terminal sacrifice. In a 

carcinogenicity study in mice, there were no treatment-related toxic signs noted during the study, 

and mortality was low during the first eighteen months of the study. Body weight was 

consistently decreased for males and, to a lesser extent, females at the high-dose (4500 

mg/kg/day) during the study at several sampling intervals, with no treatment-related changes in 

body weight at the low- and mid-dose groups. 

No treatment-related mortalities, clinical signs of toxicity, or body weight/body weight gain 

changes were observed in a subchronic oral toxicity study in rats, a three-generation reproduction 

study in rats, a chronic toxicity study in dogs, or the avian reproduction studies in mallard ducks 

and bobwhite quail. In another mallard duck reproduction study, reductions in male body weight 

gain were observed at 501 mg/kg-diet and 2250 mg/kg-diet. 

B. Estrogen Pathway 

While glyphosate showed ER antagonism in vitro with estrogen-dependent human breast cancer 

cells (Thongprakaisang et al., 2013), there was no evidence of potential interaction of glyphosate 

with the estrogen pathway in the Tier 1 in vitro assays (i.e, ER binding, ERTA, aromatase and 

steroidogenesis assays). Additionally, glyphosate was negative in the Tier 1 in vivo mammalian 

assays (i.e., uterotrophic or female pubertal assays). In the fish short-term reproduction assay 

(FSTRA), the non-treatment-responsive decrease [only significant at mid-treatment] in 

vitellogenin (VTG) was seen in isolation in the absence of any treatment-related effects in the 

other estrogen-related endpoints such as gonado-somatic index (GSI), gonadal staging, fecundity 

and fertilization. In addition, there were no notable gonadal histopathology. There were no 

treatment-related effects on female reproductive parameters in the existing glyphosate Part 158 

mammalian or wildlife studies (decreases in offspring body weight observed in one avian 

reproduction study). Therefore, there is no convincing evidence of a potential interaction with 

the estrogen pathway for glyphosate. 

Page 33 of 70
GLYPHOSATE FINAL 

Page 26 of 62 

C. Androgen Pathway 

There was no evidence of interaction of glyphosate with the androgen pathway in the Tier 1 in 

vitro (i.e, AR binding and steriodogenesis assays were negative) or Tier 1 in vivo FSTRA and 

mammalian assays (i.e., Hershberger and male pubertal assays were negative in the absence of 

overt toxicity). In addition, glyphosate was negative in an AR transactivation assay (Kojima et 

al., 2004). The only treatment-related effects observed in the Part 158 mammalian studies in the 

absence of overt toxicity were decreases in sperm count in the subchronic rat study (1678 

mg/kg/day) and a delay PPS in the post 1998 2-generation reproduction study (1234 mg/kg/day) 

in the rat. Both effects were observed at a dose that was above the limit dose (1000 mg/kg/day) 

for those studies. No androgen-related effects were seen in the wildlife Part 158 studies 

(decreases in offspring body weight observed in one avian reproduction study). 

D. Thyroid Pathway 

There was no convincing evidence of potential interaction of glyphosate with the thyroid 

pathway. There were no treatment-related effects on thyroid hormones (T4 and TSH), thyroid 

weights or thyroid histopathology in the male pubertal assay in the absence of overt toxicity. 

There were no thyroid-related effects observed in the female pubertal assay. In the AMA, there 

were no developmental effects or alterations in thyroid histopathology. No thyroid-related effects 

were noted in any of the Part 158 studies.

E. Conclusions 

The conclusion of the WoE evaluation is that glyphosate demonstrates no convincing evidence 

of potential interaction with the estrogen, androgen or thyroid pathways in mammals or wildlife. 

V. EDSP Tier 2 Testing Recommendations 

Based on weight of evidence considerations, mammalian or wildlife EDSP Tier 2 testing is not 

recommended for glyphosate since there was no convincing evidence of potential interaction 

with the estrogen, androgen or thyroid pathways. 

Page 34 of 70
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Page 27 of 62 

VI. References 

Beavers, J. and Fink, R. (1978) Final Report: One-generation Reproduction study-Bobwhite 

Quail: Glyphosate Technical: Project No. 139-141. (Unpublished study received Nov 13, 1978 

under 524-308; prepared by Wildlife International, Ltd., submitted by Monsanto Co., 

Washington, DC; CDL: 235924-B). (MRID 00108207) 

Beavers, J. and Fink, R. (1978) Final Report: One-generation Reproduction Study-Mallard Duck: 

Glyphosate Technical: Project No. 139-143. (Unpublished study received Nov 13, 1978 under 

524-308; prepared by Wildlife International Ltd., submitted by Monsanto Co., Washington, DC; 

CDL:235924-A). (MRID 00111953) 

Dhinsa, N.K.; Watson, P; Brooks, P.N. (2007) Glyphosate technical: dietary two generation 

reproduction study in the rat. Unpublished study conducted by Safepharm Laboratories Limited, 

Derbyshire, UK. SPL Project Number: 2060/0013, November 6, 2007. (MRID 48865101) 

Dhinsa, N.K.; Watson, P; Brooks, P.N. (2012) Glyphosate technical: dietary two generation 

reproduction study in the rat; cortical vacuolation historical data. Unpublished study conducted 

by Safepharm Laboratories Limited, Derbyshire, UK. SPL Project Number: 2060/0013, June 18, 

2012. (MRID 48865105) 

EG & G, Bionomics. (1975) Chronic Toxicity of Glyphosate to the Fathead Minnow 

(Pimephales promelas, Rafinesque). (Unpublished study received Dec 27, 1978 under 524-308; 

submitted by Monsanto Co., Washington, DC; CDL:097759-B). (MRID 00108171) 

Frey, L.T. 2012. Glyphosate-acid: A Reproduction Study with the Mallard (Anas platyrhynchos). 

Unpublished study performed by Wildlife International Ltd., Easton, MD. Laboratory Study No. 

123-187. Study sponsored by Syngenta Crop Protection, LLC, Greensboro. NC. Study initiated 

May 26, 1998 and completed January 11, 1999. (MRID 48876602). 

Hecker, M., Hollert H., Cooper, R., et al. (2011) The OECD validation program of the H295R 

steroidogenesis assay: phase 3. Final inter-laboratory validation study. MRID 48617005. 

Published: Environ. Sci. Pollut. Res. (2011) 18:503-515. 

Howe, C. M, M. Berrill, B. D. Pauli, C. C. Helbing, K. Werry and N. Veldhoen. 2004. Toxicity 

of Glyphosate-based Pesticides to Four North American Frog Species. Society of Environmental 

Toxicology and Chemistry 23(8): 1928 - 1938. 

Kojima, H., Iida, M., Katsura, E., Kanetoshi, A., Hori, Y., and Kobayashi, K. (2003) Effects of a 

diphenyl ether-type herbicide, chlornitrofen, and its amino derivative on androgen and estrogen 

receptor activities. Environ. Health Perspect. 111:497–502. 

Page 35 of 70
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Page 28 of 62 

Kojima, H., Katsura, E., Takeuchi, S., Niiyami, K., and Kobayashi, K. (2004) Screening for 

estrogen and androgen receptor activities in 200 pesticides by in vitro reporter gene assays using 

Chinese hamster ovary cells. Environ. Health Perspect. 112 (5): 524-531. 

Knezevich, A. and Hogan, G. (1983) A Chronic Feeding Study of Glyphosate (Roundup 

Technical) in Mice: Project No. 77-2061: BDN-77420. Final rept. (Unpublished study received 

Aug 17, 1983 under 524-308; prepared by Bio/dynamics, Inc., submitted by Monsanto Co., 

Washington, DC; CDL:251007-A; 251008; 251009; 251010; 251011; 251012;251013;251014). 

(MRID 00130406) 

Lankas, G.R. and Hogan, G.K. (1981) A Lifetime Feeding Study of Glyphosate (Roundup 

Technical) in Rats: Project No. 772062. (Unpublished study received Jan 20, 1982 under 524-

308; prepared by Bio/dynamics, Inc., submitted by Monsanto Co., Washington, D.C.; 

CDL:246617-A; 246618; 246619; 246620; 246621). (MRID 00093879) 

Le Mer, C., Roy, R.L., Pellerin, J., Couillard, C.M., and Maltais, D. (2013) Effects of chronic 

exposures to the herbicides atrazine and glyphosate to larvae of the threespine stickleback 

(Gasterosteus aculeatus). Ecotoxicol. Environ. Saf. 89: 174-181. 

McConnel, R. (1985) A Chronic Feeding Study of Glyphosate (Roundup Technical in Mice): 

Pathology Report on Additional Kidney Sections: Addendum to Final Report Dated July 21, 

1983: Project No. 77-2061A. Unpublished study prepared by Bio/dynamics Inc. 59 p. (MRID 

00150564) 

National Toxicology Program. (1992) Technical Report on Toxicity Studies of Glyphosate (CAS 

No. 1071-83-6) Administered in Dosed Feed to F344/N Rats and B6C3Fl Mice, Toxicity Report 

Series Number 16, NIH Publication 92-3135, July 1992. U.S. Department of Health and Human 

Services, Research Triangle Park, NC. 

Reyna, M. (1985) Twelve Month Study of Glyphosate Administered by Gelatin Capsule to 

Beagle Dogs: Project No. ML-83-137: Study No. 830116. Unpublished study prepared by 

Monsanto Company Environmental Health. 317 p. (MRID 00153374) 

Reyna M. (1990) Two Generation Reproduction Feeding Study with Glyphosate in Sprague 

Dawley Rats: Lab Project No: MSL-10387, Study No. ML 88-106. Unpublished study prepared 

by Monsanto Agricultural Co. (MRID 41621501) 

Rodwell, D.E., Tasker, E.J., Blair, A.M. et al. (1980) Teratology Study in Rabbits: IRDC No. 

401056, Study No. IR 79-018. (Unpublished study; prepared by International Research and 

Development Corp., submitted by Monsanto Co., Washington, D.C.; CDL: 242516-B). (MRID 

00046363) 

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Page 29 of 62 

Rodwell, D.E., Tasker, E.J. Blair, A.M. et al. (l980) Teratology Study in Rats: IRDC No. 401-

054, Study No. IR 79-016. (Unpublished study including IRDC no. 999-021; received May 23, 

1980 under 524-308; prepared by International Research and Development Corp., submitted by 

Monsanto Co., Washington, D.C.; CDL:242516-A. (MRID 00046362) 

Schneider, S.Z., Kendall, T.Z., and Krueger, H.O. (2012) Glyphosate: Amphibian 

Metamorphosis Assay for the Detection of Thyroid Active Substances. Unpublished study 

conducted by Wildlife International, Ltd., Easton, Maryland 21601. Laboratory report number 

707A-103. Study sponsored by Joint Glyphosate Task Force c/o Data Group Management, Inc., 

Raleigh, North Carolina 27615. Study completed April 11, 2012. (MRID 48671309) 

Schneider, S.Z., Martin, K.H., Kendall, T.Z., and Krueger, H.O. (2012) Glyphosate: Fish ShortTerm Reproduction Assay with the Fathead Minnow (Pimephales promelas). Unpublished study 

conducted by Wildlife International, Ltd., Easton, MD 21601. Laboratory report number 707A102A. Study sponsored by Joint Glyphosate Task Force c/o Data Group Management, Inc., 

Raleigh, NC 27615. Study completed April 11, 2012. (MRID 48671311) 

Schroeder, R.E. and Hogan, G.K. (1981) A Three-Generation Reproduction Study with 

Glyphosate in Rats: Project No. 77-2, Study No. BDN 77-417 (Unpublished study received Sep 

22,1981 under 524-308; prepared by Bio/dynamics, Inc., submitted by Monsanto Co., 

Washington, D.C.; CDL: 245909-A). (MRID 00081674) 

Stout, L. and Johnson, C. (1987) 90-day Study of Glyphosate Administered in Feed to Sprague 

Dawley Rats: Proj. ID ML-86-351/EHL 86128. Unpublished study prepared by Monsanto 

Agricultural Co. (MRID 40559401) 

Stout, L. and Ruecker, F. (1990) Chronic Study of Glyphosate administered in Feed to Albino 

Rats: Lab Project Number: MSL-I0495: R.D. 1014, Study No. ML 87-148. Unpublished study 

prepared by Monsanto Agricultural Co. (MRID 41643801) 

Street, R. (1982) Letter sent to R. Taylor dated Jul 6, 1982: Roundup Herbicide: Addendum to 

pathology report for a three-generation reproduction study in rats with glyphosate. (Unpublished 

study received Jul 7, 1982 under 524-308; submitted by Monsanto Co., Washington, DC; 

CDL:247793-A). (MRID 00105995) 

Street, R.W., Conkin, R.A., Edwards, G.A., et al. (1980) A Three-Month Feeding Study of 

Glyphosate in Mice: Special Report# MSL-1154. (Unpublished study received Jul 2, 1980 under 

524308; submitted by Monsanto Co., Washington, D.C.; CDL:242799. (MRID 00036803) 

Stump, D. G. (2012) A Hershberger Assay of Glyphosate Administered Orally in Peripubertal 

Orchidoepididymectomized Rats. Unpublished study conducted by WIL Research Laboratories, 

LLC, Ashland, OH. Laboratory Report No.: WIL-843003, January 6, 2012. (MRID 48617001) 

Page 37 of 70
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Page 30 of 62 

Stump, D.G. (2012) A Pubertal Development and Thyroid Function Assay of Glyphosate 

Administered Orally in Intact Juvenile/Peripubertal Female Rats. Unpublished study conducted 

by WIL Research Laboratories, LLC, Ashland, OH, Laboratory Project ID: WIL-843007, April 

10, 2012. (MRID 48671315) 

Stump, D.G. (2012) A Pubertal Development and Thyroid Function Assay of Glyphosate 

Administered Orally in Intact Juvenile/Peripubertal Male Rats. Unpublished study conducted by 

WIL Research Laboratories, LLC, Ashland, OH. Laboratory Project ID: WIL-843005, April 10, 

2012. (MRID 48671313) 

Stump, D. G. (2012) A Uterotrophic Assay of Glyphosate Administered Orally in 

Ovariectomized Rats. Unpublished study conducted by WIL Research Laboratories, LLC, 

Ashland, OH. Laboratory Report No.: WIL-843002, January 6, 2012. (MRID 48617003) 

Thongprakaisang, S., Thiantanawat, A., Rangkadilok, N., Suriyo, T., and Satayavivad, J. (2013) 

Glyphosate induces human breast cancer cells growth via estrogen receptors. Food Chem. 

Toxicol. 59:129-136. 

USEPA (2010) Glyphosate: Report of the Endocrine Disruptor Review Team; Test Order #: 

EDSP- 417300-229; 230; 240; 241; 244; 246; 247; and 248, December 16, 2010. Office of 

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

DC. 

USEPA (2011) Endocrine Disruptor Screening Program – Weight of Evidence: Evaluating 

Results of EDSP Tier 1 Screening to Identify the Need for Tier 2 Testing. Office of Chemical 

Safety and Pollution Prevention Science Coordination and Policy. U.S. Environmental Protection 

Agency, Washington, DC. 

USEPA (2013) Transmittal of Meeting Minutes of the FIFRA Scientific Advisory Panel Meeting 

held July 30 - August 1, 2013 on Weight-of-Evidence: Evaluating Results of EDSP Tier 1 

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

Agency, Washington, DC. 

USEPA (2014) Glyphosate: Literature Search Review. March 7, 2014. Office of Chemical 

Safety and Pollution Prevention. U.S. Environmental Protection Agency, Washington, DC. 

Wilga, P.C. (2012) Glyphosate: Human Recombinant Aromatase Assay. Unpublished study 

conducted by CeeTox, Inc., Kalamazoo, MI. Laboratory Study No.: 6500V-100334AROM, 

March 9, 2012. (MRID 48671303) 

Willoughby, J.A. (2012) Estrogen Receptor Transcriptional Activation (Human Cell Line (HeLa9903)) Screening Assay with Glyphosate. Unpublished study conducted by CeeTox, Kalamazoo, 

MI. Laboratory Report No.: 6500V-100334ERTA, March 8, 2012. (MRID 48671307) 

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Page 31 of 62 

Willoughby, J.A. (2012) Glyphosate: Androgen Receptor Binding (Rat Prostate Cytosol) 

Screening Assay. Unpublished study conducted by CeeTox, Inc., Kalamazoo, MI. Laboratory 

Study No.: 6500V-100334ARB, March 8, 2012. (MRID 48671301) 

Willoughby, J.A. (2012) Glyphosate: Estrogen Receptor Binding (Rat Uterine Cytosol). 

Unpublished study conducted by CeeTox, Inc., Kalamazoo, MI. Laboratory Study No.: 6500V100364ERB, March 8, 2012. (MRID 48671305) 

Willoughby, J.A. (2012) Supplemental Information - Laboratory Proficiency Data for ERTA 

assays and Saturation Binding Data for AR and ER Binding Assays for Assorted Chemicals. 

Unpublished study conducted by CeeTox, Inc., Kalamazoo, MI. July 19, 2011. MRID 48843501) 

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APPENDIX 1. EDSP Tier 1 Screening Assays 

Amphibian Metamorphosis Assay (AMA); (OCSPP 890.1100) 

The 21-day assay (MRID 48671309) of glyphosate (85.14% purity) on amphibian 

metamorphosis of African clawed frog (Xenopus laevis) was conducted under flow-through 

conditions. Amphibian larvae at Nieuwkoop-Faber (NF) stage 51 (80 per control and treatment 

group) were exposed to nominal concentrations of 0 (negative control), 0.16, 0.80, 4.0, 20, and 

100 mg a.i./L. Mean-measured concentrations were <0.100 (<LOQ; control), 0.13, 0.79, 4.3, 20, 

and 90 mg a.i./L. The test system was maintained at 21.4 to 22.3°C and a pH of 7.0 to 8.3. 

The survival of tadpoles exposed to glyphosate was not significantly affected (p>0.05) as it was 

100% in the control group and 99% in each of the treatment concentrations. Tail curvature was 

the only observed clinical sign (i.e., behavioral and other sublethal effects) at test termination 

and occurred in 46 to 57 (out of 80 exposed) tadpoles in the control and treatment groups (64, 63, 

65, 53, 53, and 78% of tadpoles in the negative control, 0.13, 0.79, 4.3, 20, and 90 mg a.i./L 

treatment groups, respectively), and did not appear to be treatment-related. 

Glyphosate caused no significant acceleration or delay of median NF developmental stage 

throughout the test. Further, no asynchronous development was observed. No tadpoles in the 

control and treatment groups developed beyond NF stage 57. Glyphosate exposure did not cause 

significant effects on Day 7 or 21 normalized (for snout-vent length) hind-limb length (HLL) at 

any concentration tested except a significant decrease (p<0.05) at the mid (4.3 mg a.i/L) 

concentration (↓15.6%) at Day 7. This effect was not observed in any treatment group at Day 21. 

Snout-vent length (SVL) was not significantly affected at any treatment concentration at Day 7 

but was significantly increased (p<0.05) in the 4.3, 20, and 90 mg a.i/L treatment concentrations 

at Day 21 (↑5.2, 2.5, and 6.7%, respectively) compared to the control. Additionally there was a 

significant increase in Day 21 body weight at 90 mg a.i./L (⇖ 17%). 

There were no treatment-related effects on thyroid gland histopathology at any treatment level, 

with comparable incidence and severity of thyroid gland atrophy and hypertrophy, and follicular 

cell hypertrophy and hyperplasia in the control and treatment concentrations. While there 

appeared to be an increased incidence of mild thyroid gland hypertrophy at the highest treatment 

concentration, the same incidence was observed at the lowest treatment concentration and the 

effect was not concentration responsive. Similar findings were observed for follicular cell height 

increase: an apparent increase in mild severity at the top concentration with a similar incidence at 

the lowest treatment concentration and no concentration-responsive pattern. Finally, the 

pathologist report indicated that there were no treatment-related changes in the thyroid glands of 

tadpoles exposed to glyphosate when compared to those in the negative control. 

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Androgen Receptor (AR) Binding Assay; (OCSPP 890.1150) 

In an androgen receptor (AR) binding assay (MRID 48617301), ventral prostate cytosol from 

Sprague Dawley rats was used as the source of AR to conduct saturation and competitive binding 

experiments. The saturation binding experiment was conducted to demonstrate that the AR in 

the rat prostate cytosol was present in reasonable numbers and was functioning with appropriate 

affinity for the radio-labeled reference androgen (R1881). The competitive binding assay 

measured the binding of a single concentration of [3

H]-R1881 (1 nM) in the presence of 

increasing concentrations (logarithmic increase from 10−10 to 10−3

 M) of glyphosate (95.93% 

glyphosate acid, 85.14% calculated glyphosate content, Batch # GLP-1103-21149-T). Low-salt 

TEGD buffer was used as the vehicle for glyphosate. A total of 3 runs were performed, and each 

run included dexamethasone as a weak positive control, and R1881 as the ligand reference 

standard. 

Saturation binding data were not originally provided in the study report; however, summarized 

saturation binding data (MRID 48843501) from the performing laboratory were submitted 

following a request by the Agency. The dissociation constant (Kd) for [3H]-R1881 was 

0.613±0.041 nM and the estimated Bmax was 0.817±0.049 fmol/100 μg protein for the single 

batch of prostate cytosol that was prepared. The mean and individual Kd values were below the 

range reported in the EPA validation program (0.685 to 1.57 nM). Confidence in these numbers 

is high according to the goodness of fit (R2

 = 0.957-0.984) and the small variation among runs.

In the competitive binding experiment, the estimated mean log IC50s for R1881 and the weak 

positive control (dexamethasone) were −9.0 and −4.6 M, respectively, and the mean relative 

binding affinity (RBA) for the weak positive control, dexamethasone, was 0.004%. Confidence 

in the numbers for the reference standards is high as the values as variation between runs was 

small. All performance criteria were met. 

At glyphosate concentrations of 10−10 to 10−3

 M, specific binding of [3H]-R1881 was 92.4-

101.3% with the exception of one concentration (10−9

 M) in Run 1, which had an average 

binding of 66.5%. Review of the data indicated that this value was a result of a single replicate 

with a specific binding of 7.5%. Excluding this value yielded a mean specific binding of 96.0%, 

which concurs with the other runs. As the specific [3

H]-R1881 binding was >75% at all 

concentrations of glyphosate in all runs, an IC50 and RBA could not be calculated for glyphosate. 

Based on the results from the three runs, glyphosate is classified as a Non-Binder in the 

Androgen Receptor Binding Assay. 

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Aromatase Assay; (OCSPP 890.1200) 

In an in vitro aromatase (CYP 19) assay (MRID 48671303), glyphosate (95.93% glyphosate 

acid; 85.14% calculated glyphosate content in sample; Lot # GLP-1103-21149-T) was incubated 

with human recombinant aromatase and tritiated androstenedione ([1β3

H(N)]-androst-4-ene3,17-dione; [3

H]ASDN) at log concentrations of 10−10 to 10−3 M for 15 minutes to assess the 

potential of glyphosate to inhibit aromatase activity. The solvent vehicle was 0.1 M phosphate 

buffer for glyphosate, ethanol for ASDN, and dimethyl sulfoxide (DMSO) for 4-OH ASDN, with 

a final assay volume of ≤1% DMSO. 

Aromatase activity was determined by measuring the amount of tritiated water produced at the 

end of a 15-minute incubation for each concentration of chemical. Tritiated water was quantified 

using liquid scintillation counting (LSC). Four independent runs were conducted; however, the 

first run was not used because of incorrect standard preparation. The remaining three runs were 

conducted and each run included a full activity control, a background activity control, a positive 

control series (10−10 to 10−5

 M) with a known inhibitor (4-hydroxyandrostenedione; 4-OH 

ASDN), and the test chemical series (10−10 to 10−3

 M) with three repetitions per concentration. 

Aromatase activity in the full activity controls was 0.676 ± 0.072 nmol·mg-protein−1

·min−1. The 

response of each full activity control within a run was between 90 to 110% of the average full 

activity. Activity in the background controls ranged 0.23 to 0.38% and averaged 0.30% of the 

full activity control. The response of the full activity controls and background controls was 

acceptable for each run. 

For the positive control substance (4-OH ASDN), aromatase activity results were within the 

recommended ranges for the performance criteria. The estimated log IC50 for 4-OH ASDN 

averaged −7.29 M and the Hill slope was −0.96. 

For glyphosate, aromatase activity averaged 0.673 ± 0.066 nmol·mg-protein−1

·min−1 at the lowest 

tested concentration of 10−10 M and 0.741 ± 0.100 nmol·mg-protein−1

·min−1 at the highest tested 

concentration of 10−3 M. The average aromatase activity was ≥99.67% of the control at all tested 

glyphosate concentrations for all runs. 

Based on the data from the average response curve, glyphosate is classified as a Non-inhibitor of 

aromatase activity in this assay. 

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Estrogen Receptor (ER) Binding; (OCSPP 890.1250) 

In an estrogen receptor (ER) binding assay (MRID 48671305) for glyphosate (95.93% 

glyphosate acid, 85.14% calculated glyphosate content, Batch # GLP-1103-21149-T), uterine 

cytosol from Sprague Dawley rats was used as the source of ER to conduct saturation and 

competitive binding experiments. A saturation binding experiment was conducted to 

demonstrate that the ER in the rat uterine cytosol was present in reasonable numbers and was 

functioning with appropriate affinity for the radio-labeled reference estrogen prior to conducting 

ER competitive binding experiments. The competitive binding experiment measured the binding 

of a single concentration of [3

H]-17β-estradiol (1 nM) in the presence of increasing 

concentrations (10−10 to 10−3 M) of glyphosate. TEGD buffer was used as the solvent vehicle for 

glyphosate. A total of 3 runs were performed, and each run included 19-norethindrone as a 

weak positive control, octyltriethoxysilane as a negative control, and 17-β-estradiol as the natural 

ligand reference material. 

Saturation binding data were not originally provided in the study report; however, summarized 

saturation binding data (MRID 48843501) from the performing laboratory were submitted 

following a request by the Agency. The protein concentrations used in the saturation binding 

runs varied between each run, and were approximately 3- to 6-fold greater than recommended 

(160 to 320 μg versus 50±10 μg). The Kd for [3

H]-17β-estradiol was 0.331 ± 0.061 nM and the 

estimated Bmax was 74.55 ± 3.03 fmol/100 μg protein for the prepared rat uterine cytosol. The 

Kd for each run was within the expected Guideline range of 0.03 to 1.5 nM. 

In the competitive binding experiment, the estimated mean log IC50s for 17β-estradiol and 19-

norethindrone were −9.0 and −5.5 M, respectively. The mean relative binding affinity (RBA) 

was 0.032% for 19-norethindrone, compared to the natural ligand. 

 

Glyphosate was tested over a concentration range (10−10 to 10−3

 M) that fully defined the top of 

the curve. The percent binding at the top plateau (101.2-116.9%) was within 25 percentage 

points of the lowest concentration of the estradiol standard (98.6-101.8%). Across all runs, the 

lowest average percent radiolabeled estradiol binding in the presence of glyphosate was >81% 

(i.e. showed less than 25% displacement) at concentrations up to 10−3

 M indicating that 

gylphosate was not competing with the natural ligand for binding to the ER. 

Based on the results from the three runs, glyphosate is classified as Not Interactive in the 

Estrogen Receptor Binding Assay. 

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ERα Transcriptional Activation (ERTA) Assay; (OCSPP 890.1300) 

In an estrogen receptor transcriptional activation assay (MRID 48617307), hERα-HeLa-9903 

cells cultured in vitro were exposed to glyphosate (85.14% a.i. Batch # GLP-1103-21149-T) at 

logarithmically increasing concentrations from 10−10 to 10−3 M in cell culture media for 24 hours 

in three independent runs. The experiments were performed using 96-well plates and each 

glyphosate concentration was tested in 6 wells/plate in each run. The solvent vehicle was culture 

media for glyphosate and DMSO (0.1%) for the reference chemicals. Cells were exposed to the 

test agent for 24±2 hr to induce reporter (luciferase) gene products. Luciferase expression in 

response to activation of the estrogen receptor was measured using a proprietary luciferase assay. 

Glyphosate was tested up to the limit dose, with no precipitation or cytotoxicity observed at any 

tested concentration. At concentrations up to 10−3 M, the relative transcriptional activation of 

glyphosate was ≤2.4%. In the main assays, the responsiveness of the cells to the very weak 

positive control 17α-methyltestosterone was lower than the expected values, indicating a 

decreased sensitivity of the assay to very weak agonists. Although the conditions of this assay 

were not optimal to detect very weak activity, glyphosate responses were similar to those of the 

negative control corticosterone and not comparable to the responses of 17α-methyltestosterone, 

which was able to reach a maximum of 40.8-42.6% PC. Glyphosate was only able to reach a 

maximum of 0.8-2.4% PC when tested up to the highest concentration possible based on 

cytotoxicity. Because the RPCMax < PC10 in both assay runs, glyphosate was considered negative 

for estrogen receptor transcriptional activation in this test system. 

Fish Short-Term Reproduction Assay (FSTRA); (OCSPP 890.1350) 

The 21-day short-term reproduction assay (MRID 48671311) of glyphosate with Fathead 

minnow (Pimephales promelas) was conducted under flow-through conditions. Adult fish (2 

males and 4 females in each group, 4 groups/treatment, 5.5 months of age) were exposed to 

glyphosate (85.14% purity) at nominal concentrations of 0 (negative control), 0.048, 0.24, 1.2, 

6.0, and 30 mg a.i./L. Mean-measured concentrations were <0.03 (<LOQ; negative control), 

0.046, 0.23, 1.2, 6.2, and 33 mg a.i./L. The high test concentration was based on 1/3 of a 96-hr 

LC50 value. The test system was maintained at 24.3 to 29.1°C and a pH of 8.0 to 8.3. 

Survival was 100% in the negative control, 0.046, 0.23, 6.2 and 33 mg a.i./L treatment groups 

and 95.8% in the 1.2 mg a.i./L treatment group. Glyphosate did not result in any significant 

increases or decreases in weight or length for either sex at any treatment level. There were no 

observed effects on secondary sex characteristics or clinical signs (i.e., behavioral and other 

sublethal effects) in males or females in any treatment group. 

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Spawning and mean fecundity in the negative control were at least every 4 days in each replicate 

and 23.5 eggs/female/day/replicate (range: 23.2-23.9 eggs/female/day), respectively; fertilization 

success in the negative control was 97.3%. Fecundity and fertilization success were not 

significantly different from the negative control for any treatment group. 

Plasma vitellogenin (VTG) was significantly decreased 55% (p<0.05) in female fish at the mid 

high-treatment level (6.2 mg a.i./L) compared to the negative control; male VTG was unaffected 

by treatment. There were no effects in gonado-somatic index (GSI) or nuptial tubercle scores for 

male or females (none noted in females) in any treatment group relative to the negative control. 

Although there were gonadal histopathology observations reported for both males and females 

(e.g. minimal to mild granulomatous inflammation, oocyte atresia, increased mature oocytes), 

there were no treatment-related patterns in gonadal histopathology for males or females. 

Hershberger Assay; (OCSPP 890.1400) 

In a Hershberger Assay (MRID 48617001) screening for androgenic activity, glyphosate (85.1% 

a.i., Batch/lot# GLP-1103-21149-T) in 0.5% methylcellulose (w/v) was administered daily via 

oral gavage (5 mL/kg) to groups of six 54- or 55-day old, castrated male Sprague Dawley rats at 

dose levels of 0 (vehicle), 100, 300, or 1,000 (limit dose) mg/kg/day. The androgenic positive 

control group consisted of 6 castrated rats exposed to 0.2 mg/kg/day of testosterone propionate 

(TP) by subcutaneous (s.c.) injection. 

To screen for potential anti-androgenic activity, glyphosate in 0.5% methylcellulose (w/v) was 

administered daily via oral gavage to groups of six 54- or 55-day old, castrated male Sprague 

Dawley rats at dose levels of 0 (vehicle), 100, 300, or 1,000 mg/kg/day in conjunction with a 

daily dose of reference androgen TP at 0.2 mg/kg/day by s.c. injection. The anti-androgenic 

positive control group consisted of 6 castrated rats exposed to 0.2 mg/kg/day TP by s.c. injection 

and 3 mg/kg/day flutamide (FT) via oral gavage. TP alone was used as the anti-androgenic 

negative control. 

For both components of the assay, body weights were determined daily. The animals were dosed 

for 10 consecutive days and terminated approximately 24 hours after the final dose. At 

necropsy, the five androgen-dependent tissues were collected and weighed.

All animals survived until scheduled termination. No animals exhibited any dose-related clinical 

signs of toxicology and there were no treatment-related gross pathological findings. 

In the androgen agonist assay, there were no treatment-related effects on body weights, overall 

body weight gains, or the weights of accessory sex organs for any glyphosate dose group. 

Animals in the positive TP control group had increased (p<0.01) accessory sex organ weights as 

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follows: 437% in seminal vesicles; 728% in ventral prostate; 200% in levator anibulbocavernosus (LABC); 361% in Cowper’s gland; and 45% in glans penis. The performance 

criteria indicated that this assay was performing as expected. 

In the anti-androgen assay, there were no treatment-related effects on body weights, overall body 

weight gains, or the weights of accessory sex organs for any glyphosate dose group. Animals 

dosed with TP + FT (positive control) had decreased (p<0.01) accessory sex organ weights as 

follows: 76% in seminal vesicles; 80% in ventral prostate; 63% in LABC; 70% in Cowper’s 

gland; and 29% in glans penis. The performance criteria indicated that this assay was 

performing as expected. 

Statistically significant changes were not seen in two or more of the five androgen sensitive 

tissue weights. Glyphosate was negative for androgenicity and anti-androgenicity in the 

Hershberger assay. 

Female Pubertal Assay; (OCSPP 890.1450) 

In a Female Pubertal Assay (MRID 48671315), 15 Crl:CD(SD) Sprague-Dawley rats/dose group 

were treated daily via oral gavage with glyphosate technical (95.93% a.i., Lot #: GLP-1103-

21149-T) in 0.5% methylcellulose at doses of 0, 100, 300 or 1000 mg/kg/day (limit dose) from 

post-natal day (PND) 22 to 42. Animals were examined for vaginal opening (VO) daily 

beginning on PND 22, and age and weight at day of attainment were recorded. Following 

sacrifice on PND 42, blood was collected for clinical chemistry analyses, including total 

thyroxine (T4) and thyroid stimulating hormone (TSH) levels, which were analyzed using an 

electrochemiluminescent immunoassay (T4) and a magnetic [125I]rTSH gamma counter 

immunoassay (TSH). Liver, adrenal glands, thyroid, pituitary, and urogenital organ weights 

were recorded, and microscopic examinations were performed on the thyroid, kidneys, ovary and 

uterus. 

One animal in the control group was sacrificed in extremis on PND 27 due to impairment of the 

right forelimb (due to possible mechanical injury). All other animals survived until scheduled 

sacrifice. Treatment-related clinical signs were limited to rales in 4/15 and 13/15 females in the 

300 and 1000 mg/kg/day groups, respectively, at approximately 4 hours post-dosing. This 

finding did not persist to the daily examinations. No other treatment-related clinical signs were 

noted during the 4-hour post-dosing or daily examinations at any dose level. There were no 

treatment-related differences in age of attainment of VO, body weight at VO, final body weights, 

or body weight gains in the treated groups relative to controls. One female each in the control 

and 300 mg/kg/day groups failed to attain VO. There were no statistically significant differences 

in mean age at first vaginal estrus, mean cycle length, or percent cycling. The cycle status at 

necropsy was similar among all groups. Serum T4 and TSH were not affected by treatment, and 

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no adverse treatment-related effects on any clinical chemistry parameter were observed at any 

dose. There were no treatment-related microscopic findings in the thyroid, ovaries, uterus, or 

kidneys at any dose. 

The dose levels tested were adequate since the high dose was the Limit Dose (1000 mg/kg/day). 

Male Pubertal Assay; (OCSPP 890.1500) 

In a Male Pubertal Assay (MRID 48671313), 15 Crl:CD(SD) Sprague-Dawley rats/dose group 

were treated daily via oral gavage (5 mL/kg) with glyphosate technical (95.93% a.i., Lot #: GLP1103-21149-T) in 0.5% methylcellulose at doses of 0, 100, 300 or 1000 mg/kg/day (limit dose) 

from post-natal day (PND) 23 to 53. Animals were examined for preputial separation (PPS) 

daily beginning on PND 30, and age and weight at day of attainment were recorded. Following 

sacrifice on PND 53, blood was taken for total thyroxine (T4), testosterone, thyroid stimulating 

hormone (TSH), and clinical chemistry analysis. The hormones were analyzed by 

radioimmunoassay (RIA) or chemiluminescence. Weights were recorded for the liver, adrenal 

glands, thyroid, pituitary, and urogenital organs, and microscopic examinations were performed 

on the thyroid, kidneys, right testis and epididymides.

One male in the 1000 mg/kg/day group was found dead prior to dosing on PND 24; no 

significant clinical or macroscopic findings were observed in this animal. All other rats survived 

until scheduled sacrifice. Treatment-related clinical findings were limited to rales in 9/15 and 

14/15 males in the 300 and 1000 mg/kg/day groups, respectively, approximately 4 hours postdosing. This finding persisted in the daily examinations in 7/15 males at 1000 mg/kg/day 

throughout the study. 

 

Treatment-related decreases in overall (PND 23-53) body weight gains were observed at 

300 mg/kg/day (↓8%, not significant; NS) and 1000 mg/kg/day (↓12%, p<0.01). On PND 53, 

final body weights in the 300 and 1000 mg/kg/day groups were decreased (p<0.05) by 7-10%. A 

treatment-related delay in the mean age at attainment of complete PPS was noted at 1000 

mg/kg/day (48.0 days) compared to controls (45.9 days). However, it was determined that the 

delay in attainment of complete PPS at this dose was a result of the treatment-related decrease in 

body weight, rather than a direct anti-androgenic effect. 

No compound-related effects on organ weights were observed at any dose. No treatment-related 

effects on T4, TSH, or testosterone levels were observed at any dose. T4 and TSH levels were 

lower than the control group in all treated groups and testosterone was lower at 300 and 1000 

mg/kg/day. However, these changes were not statistically significant and were not associated 

with any histopathological findings. At 1000 mg/kg/day, the increases (p<0.01) in ALT (also at 

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300 mg/kg/day), sodium, albumin, ALP, AST, chloride, phosphorous, and total protein, and the 

decrease in urea nitrogen were considered to be related to treatment. 

At 1000 mg/kg/day, there was a slight increase in the number of animals with colloid area Grade 

4 (5 treated vs. 1 control) and Grade 5 (1 treated vs. 0 controls). There were no treatment-related 

effects on follicular cell height at any dose compared to controls. There were no treatmentrelated findings in the testes, epididymides or kidneys. 

The highest dose tested showed evidence of overt toxicity based on the decreases in terminal 

body weight, clinical signs, and mortality at 1000 mg/kg/day; the dose concentrations used in the 

study are considered adequate. 

Effects on androgen-related endpoints included decreased ventral prostate, seminal vesicle, 

LABC, and pituitary glands weights, as well as a 2.1 day delay in PPS at the high dose but these 

occurred with significant decreases in body weight. There were no treatment-related effects on 

thyroid-related endpoints in this assay. 

Steroidogenesis Assay; (OCSPP 890.1550) 

The purpose of this study was to validate the use of a standardized steroidogenesis assay as 

detailed in OECD Guideline for the Testing of Chemicals: Draft Proposal for a New Guideline 

4XX – The H295R Steroidogenesis Assay (available on-line at 

http://www.oecd.org/dataoecd/56/11/44285292.pdf). In this validation study, 28 chemicals were 

selected as a screen for potential effects of endocrine-disrupting chemicals on the production of 

testosterone (T) and 17β-estradiol (E2). These chemicals were selected based on their known or 

suspected endocrine activity, or lack thereof, and included inhibitors and inducers of different 

potencies as well as positive and negative controls. These chemicals were selected and approved 

by the OECD Validation and Management Group for Non-Animal Testing (VMG NA). 

Glyphosate was one of the chemicals evaluated. A total of seven laboratories from the USA, 

Denmark, Germany, Japan, Hong Kong, and Canada, each with different levels of experience in 

conducting the H295R steroidogenesis assay, were invited to participate in this validation study. 

Inclusion of laboratories with different levels of proficiency in conducting the assay was 

essential to evaluate the completeness of the test protocols and their transferability. Each 

laboratory was assigned a random code number (1–7) as part of the study. However, part way 

through the study, two of the seven laboratories decided to cease their participation in the 

validation studies. Thus, with the exception of the QC exposure data, only the data for the 

remaining five laboratories that completed the validation studies are presented (Labs 1, 2, 3, 4, 

and 6). One laboratory evaluated all 28 chemicals, and one other laboratory (#4) also evaluated 

glyphosate. The laboratories were not identified. 

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In this steroidogenesis assay (MRID 48617005), H295R cells cultured in vitro in 24-well plates 

were incubated with glyphosate (purity and lot # not provided) at seven concentrations between 

0.0001 and 100 μM (specific concentrations not reported) for 48 hours in triplicate for three 

independent experiments. The test chemical’s vehicle was not identified. The presence or 

absence of precipitation and/or cytotoxicity was not reported. A Quality Control (QC) plate was 

run concurrently with each independent run of a test chemical plate to demonstrate that the assay 

responded properly to positive control agents at two concentrations; positive controls included 

the known inhibitor (prochloraz) and inducer (forskolin) of estradiol and testosterone production. 

T and E2 levels were measured using radioimmunoassays or ELISA; responses of the QC plates 

measured by these assays were confirmed by LC-MS (at Lab 1). 

The report stated that with a few exceptions, all of the laboratories met the key quality 

performance parameters for conducting the H295R assay protocol. The report stated that two 

laboratories demonstrated that glyphosate exposure does not affect testosterone or estradiol 

levels in this assay; however, data were not presented. 

Uterotrophic Assay; (OCSPP 890.1600) 

In a Uterotrophic Assay (MRID 48617003) conducted to screen for potential estrogenic activity, 

glyphosate (85.1% a.i., Batch/lot# GLP-1103-21149-T) in 0.5% methylcellulose (w/v) was 

administered daily via oral gavage to groups of six ovariectomized female Sprague Dawley rats 

at dose levels of 0 (vehicle), 100, 300, or 1,000 (limit dose) mg/kg/day on post-natal days (PND) 

66/67 to 68/69. The positive control group was treated with a daily dose of 17α-ethynyl estradiol 

(EE) at 3 μg/kg/day by oral gavage. Body weights were determined daily. All animals were 

terminated and necropsied on PND 69/70 approximately 24 hours after the final dose 

administration to determine wet and blotted uterine weights. 

All animals survived until scheduled termination and no treatment-related clinical findings were 

observed in glyphosate dosed animals. Body weights, body weight gains, and uterine weights in 

the glyphosate groups were comparable to the vehicle control.

In the positive control (EE) group, mean body weights decreased on Days 3 and 4 (not 

significant, NS), leading to an overall body weight loss during the study of 5.6 g (p<0.01) 

compared to a gain of 11.3 g in the controls. Absolute wet and blotted uterus weights for the 

positive control (EE) group were increased (p<0.01) by 758% and 256%, respectively, as 

expected. 

No statistically significant changes were seen in uterine weight in this assay. Glyphosate is 

negative in the uterotrophic assay. 

 

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APPENDIX 2. Other Scientifically Relevant Information (OSRI) 

Published literature and Part 158 general toxicity studies considered relevant for determining the 

potential interaction of glyphosate with the endocrine system are summarized below. Given the 

breadth of toxicity data available on glyphosate, the only Part 158 studies discussed in this 

appendix are those that fulfill current guideline requirements and are directly relevant to 

assessing potential endocrine effects (i.e., multiple-generation rodent reproductive studies, 

development studies, chronic toxicity studies, etc.). 

ER Binding and Transactivation Assays

In a published, non-Guideline study (Kojima et al., 2004), the potential of glyphosate (>95% 

purity) to interact with two human ER subtypes (hERα and hERβ) and one human androgen 

receptor (hAR) in transactivation assays with Chinese hamster ovary cells (CHO-K1 cells) was 

investigated. The human ER (hERα) and AR (hAR) expression vectors (pcDNAERα and 

pZeoSV2AR, respectively) were constructed as described previously (Kojima et al., 2003). The 

hERβ expression vector was constructed by cloning the hERβ cDNA with reverse transcriptasepolymerase chain reaction from human placental RNA. The sequence was verified and inserted 

into the mammalian expression vector pcDNA3.1Zeo(-) creating pcDNAERβ. The construction 

of the estrogen or androgen responsive elements containing reporter plasmid (pGL3-tkERE and 

pIND-ARE, respectively) was described previously (Kojima et al., 2003). pRL-SV40 containing 

the Renilla luciferase gene was used as an internal control for transfection efficiency. 

For detection of hERα or hERβ activity, cells were transfected with pcDNAERα or pcDNAERβ, 

pGL3-tkERE, and pRL-SV40. For detection of hAR activity, cells were transfected with 

pZeoSV2AR, pIND-ARE, and pRL-SV40. Flutolanil was tested over a concentration range from 

10−8 to 10−5 M, and the responses were compared to the activity of 17β-estradiol (E2, >97% 

purity) or 5α-dihydrotestosterone (DHT, 95% purity) for the ER or AR assays, respectively. For 

measurement of antagonistic activity to hERα, hERβ and hAR, either 10−11 or 10−10 M E2 or 

10−10 M DHT was added to the cell cultures along with the test compound, respectively. 

Agonistic activities were evaluated by the relative activity expressed as 20% relative effective 

concentration (REC20), the concentration of the compound demonstrating 20% of the activity of 

10−10 M E2, 10−9 M E2, or 10−9

 M DHT for ERα, ERβ, and AR, respectively. Antagonistic 

activities were evaluated similarly by the relative activity expressed as 20% relative inhibitory 

concentration (RIC20), the concentration of the compound showing 20% inhibition of the activity 

of E2 or DHT against ERα, ERβ, and AR, respectively. Glyphosate did not have agonist or 

antagonist activity for ERα and ERβ, or agonist activity for AR in this study. 

Thongprakaisang et al. (2013) evaluated the estrogenic and/or anti-estrogenic effects of 

glyphosate (>98% purity) at concentrations that have been reported in environmental conditions 

and exposed humans. Effects were investigated in estrogen-dependent human breast cancer cells, 

T47D; a stably ERE (estrogen response element)-luc construct-transfected, hormone-dependent 

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breast cancer, T47D-KBluc; and a hormone-independent human breast cancer, MDA-MB231. 

To differentiate the effects of endogenous estrogen, cells were studied both in completed 

(standard) medium (medium containing fetal bovine serum) and in estrogen withdrawal medium 

(medium containing dextran-charcoal treated fetal bovine serum). 

Cells were seeded in 96-well luminometer plates and allowed to attach overnight. Media was 

then replaced with dosing media in which the final concentration of glyphosate ranged from 

10−12 to 10−6

 M. 17β-estradiol (E2) at the same range of concentrations was used as the positive 

control agonist for ER activation. The media was used as the negative control. Cells were 

allowed to incubate 24 hours. Cell growth and viability were tested with the MTT reagent assay. 

In the cell viability assay, glyphosate caused hormone-dependent T47D cells to proliferate, 

approximately 15-30% of control, in the absence of E2; the effect was significant (p≤0.05) at 

10−9

 and 10−8 M and was approximately half the E2 response in T47D cells. Glyphosate had no 

effect on the growth of hormone-independent MDA-MB231 cells in the absence or presence of 

E2. Because the proliferation effect of glyphosate on T47D cells was only observed in the 

absence of E2, the possibility that ER signaling may be involved was investigated by 

co-incubating glyphosate or E2 with the ER antagonist, ICI 182780, in T47D cells. ICI 182780 at 

a concentration of 1 nM mitigated the proliferative effect of glyphosate and E2 in T47D cells; the 

proliferative effects of glyphosate on T47D cells were completely inhibited at an ICI 182780 

concentration of 10 nM. The results suggest that the proliferative effects of glyphosate may 

involve the ER. 

The estrogenic activity of glyphosate on ERE transcription activity was investigated with 

T47D-KBluc cells. In the concentration range 10−12 to 10−6 M, glyphosate induced ERE 

activation 5- to 13-fold compared to control; the effects were <50% compared to E2 induction. 

Co-incubation of glyphosate with 1 nM ICI 182780 resulted in a decreased response, with 

complete inhibition in the presence of 10 nM ICI 182780. When cells were co-incubated with 

glyphosate and E2, the E2-induced ERE activation was suppressed, indicating that in the 

presence of endogenous agonist (E2), glyphosate acted as an antagonist. 

90-Day (Subchronic) Oral Toxicity in Rodents (Rat; OSCPP 870.3100) 

In a subchronic oral toxicity study in rats (MRID 40559401), glyphosate (95.21% purity) was 

administered to SD rats (12/sex/group) in the diet at nominal concentrations of 0, 1000, 5000, or 

20,000 ppm for three months. Mean actual intakes were 950, 4600, and 19,000 ppm 

corresponding to 63, 317, and 1267 mg/kg/day for males and 84, 404, and 1623 mg/kg/day for 

females (based on actual body weights, food consumption, and analyses of feed). Body weights 

and food consumption were measured weekly, and hematology, clinical chemistry, and urine 

analyses were conducted at the end of the study. Organs that were weighed included the liver, 

kidneys, and testes (including epididymides). For control and high-dose animals, gross and 

microscopic pathological examinations were conducted on these tissues as well as adrenals, 

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ovaries, mammary gland, prostate, pituitary, seminal vesicles, thyroid, urinary bladder, and 

uterus (corpus and cervix). The kidneys and livers of the low- and medium-dose animals were 

also examined microscopically. 

There were no mortalities or treatment-related toxic signs during the study, and there were no 

effects of treatment on body weight or food consumption. Possibly treatment-related findings in 

male rats were increased (p<0.05) serum phosphorus (low and high dose) and potassium 

(medium dose) concentrations; increased serum glucose concentrations at 317 and 1,267 

mg/kg/day at the medium and high doses; and increased (NS) serum BUN and alkaline 

phosphatase concentrations at the high dose apparently due to a single animal. In addition, 

histopathological lesions observed in the pancreas of high-dose male rats may have been 

treatment-related. Possible treatment-related findings in female rats were increased (p<0.05) 

serum phosphorus concentrations and increased (p<0.05 or NS) potassium concentrations in all 

treated females. No other histopathological findings were noted. Because clinical chemistries 

were conducted only once during the entire study, and as the pancreas was not examined 

histologically in the low- and medium-dose groups, it could not be determined whether or not 

these findings were attributable to the test material on the basis of this study alone. 

In a subchronic oral toxicity study in rats conducted by the National Toxicology Program

(NTP; 1992), glyphosate (99% purity) was administered in the diet to F344/N rats 

(10/sex/group) at nominal concentrations of 0, 3125, 6250, 12,500, 25,000, or 50,000 ppm 

(mean-measured doses of 205, 410, 811, 1678, or 3393 mg/kg/day for males and 213, 421, 844, 

1690 or 3393 mg/kg/day for females, respectively, based on food consumption and body weight 

measurements) for 90 days. Ten additional rats/sex were included at each dose level for 

evaluation of hematology and clinical chemistry parameters. Body weights were measured 

weekly. Samples for hematology and clinical chemistry determinations were collected from 

additional study animals on Study Days 5 and 21, and from the regular study animals at the end 

of the study. Organs that were weighed included kidney (right), liver, and testis (including left 

caudal and left epididymal tissue for the control and 12,500, 25,000, and 50,000 ppm dose 

groups). For control and high dose animals, gross and microscopic pathological examinations 

were conducted on these tissues as well as adrenals, mammary gland, ovaries, pituitary, 

preputial/clitoral glands, prostate, seminal vesicles, thyroid, uterus, and vagina; histopathological 

examinations of the salivary gland were conducted for rats in all dose groups. In addition, for rats 

in the control and three highest dose groups, sperm morphology (sperm motility, sperm count per 

gram caudal tissue, and spermatid head count) evaluations were conducted at the end of the 

study, and vaginal cytology evaluations were conducted during the 12 days prior to sacrifice. 

All animals survived to necropsy. Diarrhea was noted in the high-dose animals (males and 

females) through Day 50 of the study. Body weight gain was reduced in the high-dose males 

(↓25%; 3393 mg/kg/day) and the final body weight was decreased by 18%, but statistical 

significance was not reported for final body weights or body weight gains. Mean necropsy body 

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weights were decreased (p<0.05 and 0.01, respectively) for the 1678 and 3393 mg/kg/day males 

(↓12 and 21%, respectively). Body weight gain in high-dose females (3393 mg/kg/day) was 

decreased (↓10%), but no effects on final or necropsy body weights were observed. Clinical 

chemistry results showed increases in ALP and ALT in some or all of the dose groups; ALP 

concentrations in the control animals was variable over the sampling days (Days 5, 21, and 90). 

Increases (p<0.01) in ALP in males were generally dose-dependent in the top three dose groups 

on Days 5 and 21, but were similar to control by Day 90. Increases (p<0.01 or 0.05) in ALP in 

females were dose-dependent in the top three dose groups on Days 5 and 21, and still present on 

Day 90 in the top two dose groups. Increases in ALT in both sexes were generally non-dosedependent, and seen in all but the lowest dose group in males (except for Day 90) and in all dose 

groups in females (except for Day 90). In addition, effects on bile acids were noted in both sexes. 

On Day 5, variable increases (NS) were noted with a clear dose-dependent response in the two 

highest dose groups. A stronger, dose-dependent response was observed on Day 21 with 

increases (NS, p<0.05, and p<0.01) in males (↑2-70%) and females (↑23-102%). Concentrations 

of bile acids on Day 90 were more variable, with a generally non-significant, but dose-dependent 

response at the two highest doses in both sexes. Non-dose-dependent increases (p<0.01 or 0.05) 

in relative liver weights also were observed in males in all dose groups (↑6-15%) and in females 

in the two highest dose groups (↑10 and 6%). Taken together, these findings are consistent with a 

hepatobiliary effect that can be attributed to glyphosate administration. 

In the 1678 and 3393 mg/kg/day males, there were increases (p<0.01 or 0.05) in the relative right 

kidney (↑8% and 13%, respectively) and right testis weights (↑7% and 21%, respectively); 

relative right kidney weight also was increased (p<0.05) in high-dose females (↑7%). Absolute 

weights for these organs in treated rats were similar to control. Left caudal, epididymal, and 

testicular weights of treated males (811, 1678, and 3393 mg/kg/day groups) were similar to 

control. 

A dose-related increase in the incidence and severity of cytoplasmic alteration of the parotid and 

submandibular salivary glands was noted in the microscopic evaluations, beginning at the lowest 

dose in both sexes. These lesions were diagnosed as “cytoplasmic alteration” and consisted of 

basophilic change and hypertrophy of acinar cells. No other treatment-related histopathological 

findings were reported. 

Sperm counts were decreased (p<0.01) in the two high-dose groups (1678 and 3393 mg/kg/day; 

↓20%). Epididymal sperm motility, total spermatid head/testis, and total spermatid heads/g 

caudal tissue in the treated animals were similar to control. A delayed (p<0.05) estrous cycle was 

observed in the 3393 mg/kg/day group (5.4±0.21 days) compared to control (4.9±0.10 days). 

The LOAEL is the low dose (205/213 mg/kg/day for males and females, respectively) based on 

dose-related increases in the incidence and severity of cytoplasmic alterations in the parotid and 

submandibular salivary glands of male and female rats. A NOAEL is not determined. 

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90-Day (Subchronic) Oral Toxicity in Rodents (Mouse; OSCPP 870.3100) 

In a subchronic oral toxicity study in mice (MRID 00036803), glyphosate (98.7% purity) was 

administered to CD-1 albino mice (15/sex/group) at dietary concentrations of 0, 5000, 10,000, or 

50,000 ppm (0, 750, 1500, or 7500 mg/kg/day, based on standard conversion) for three months. 

The mice were sacrificed at the end of the study and complete gross necropsies were conducted. 

Organs that were weighed included the gonads, kidneys, and liver. Histopathological 

examinations included these organs, as well as adrenals, epididymis, pituitary, thyroid, 

parathyroid, urinary bladder, uterus, and prostate. 

There were no treatment-related toxicological signs or mortalities during the study, and there 

were no effects of treatment on food consumption. Body weight gains in the male and female 

high-dose groups were decreased (↓ approximately 24% and 18%, respectively) compared to 

control. There were no changes in absolute or relative organ weights at any dose, and there were 

no treatment-related histopathological findings in any organ. The LOAEL for the study is 50,000 

ppm (7500 mg/kg/day) based on reduced body weight gain and the NOAEL is 10,000 ppm (1500 

mg/kg/day). 

In a subchronic oral toxicity study in mice conducted by NTP (1992), glyphosate (99% purity) 

was administered in the diet to B6C3F1mice (10/sex/group) at nominal concentrations of 0, 

3125, 6250, 12,500, 25,000, or 50,000 ppm (equivalent to 0, 507, 1065, 2273, 4776, or 10,780 

mg/kg/day for males and 753, 1411, 2707, 5846, 11,977 mg/kg/day for females, respectively, 

based on food consumption and body weight measurements) for 90 days. Body weights were 

measured weekly. Organs that were weighed included kidney (right), liver, and testis (including 

left caudal and left epididymal tissue for the control and 12,500, 25,000, and 50,000 ppm dose 

groups). For control and high-dose animals, gross and microscopic pathological examinations 

were conducted on these tissues as well as adrenals, mammary gland, ovaries, pituitary, 

preputial/clitoral glands, prostate, seminal vesicles, thyroid, uterus, and vagina; histopathological 

examinations of the salivary gland were conducted for mice in all dose groups. In addition, for 

mice in the control and three highest dose groups, sperm morphology (sperm motility, sperm 

count per gram caudal tissue, and spermatid head count) evaluations were conducted at the end 

of the study, and vaginal cytology evaluations were conducted during the 12 days prior to 

sacrifice. 

There were two mortalities in the study; neither was related to treatment. In addition, no clinical 

signs of toxicity were reported. Final body weights were decreased in males and females in the 

two highest dose groups (↓11% and 17% for males and 6% and 10% for females) with 

concomitant decreases in body weight gain (↓35% and 63% for males and 14% and 27% for 

females); statistical significance was not reported. Mean necropsy body weights were decreased 

for the 4776/5846 mg/kg/day (p<0.05; ↓8 and 6%, respectively) and 10,780/11,977 mg/kg/day 

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(p<0.01; ↓15 and 11%) males and females. Average daily food consumption was comparable 

across the treated and control groups. 

Relative right testis weights were increased (p<0.01) at the two highest doses (↑10% at 4776 

mg/kg/day and ↑18% at 10,780 mg/kg/day); absolute weights were comparable to control. 

Absolute left caudal, epididymal, and testicular weights of treated males (2273, 4776, and 10,780 

mg/kg/day groups) were similar to control. The relative weights of the right kidney were 

increased (p<0.05), in a non-dose-related manner, in males in all dose groups except the lowest 

(↑11%, 15%, 23%, and 16%, respectively); absolute kidney weights were increased only in the 

medium-dose males (↑15%). Non-dose-dependent increases (p<0.05) in relative liver weight also 

were noted in males of all dose groups except the lowest (↑9%, 4%, 8%, and 9%, respectively). 

A decrease (p<0.01) in the absolute liver weight was noted in high-dose females (↓14%). 

Dose-related increases in the incidence and severity of lesions in the parotid salivary glands of 

male and female mice were observed, beginning at the second lowest dose (1065 and 1411 

mg/kg/day, respectively); no lesions were observed in mice in the low-dose group. These lesions 

were diagnosed as “cytoplasmic alteration” and consisted of basophilia of the acinar cells. In 

more severely affected glands, the cells and acini also appeared enlarged with an associated 

relative reduction in the number of ducts. This finding was considered adverse. 

Histopathology examination of control and high dose animals did not reveal any other related 

findings. There were no effects of treatment on sperm counts, sperm motility, total spermatid 

head/testis, and total spermatid heads/g caudal tissue in males, or on length of estrous cycle in 

females. 

Prenatal in Rodents (Rat; OCSPP 870.3700) 

In a developmental toxicity study in rats (MRID 00046362), glyphosate (98.7%) was 

administered by gavage to mated female SD rats (25/group) at doses of 0 (0.5% aqueous 

methocel), 300, 1000, or 3500 mg/kg/day on GDs 6 to 19, inclusive. Individual dam body 

weights were recorded on GDs 0, 6, 9, 12, 16, and 20; food consumption was not determined. 

The surviving rats were sacrificed on GD 20 and the uterus was weighed; the locations of viable 

and nonviable fetuses, early and late resorptions, and the total number of implantations and 

corpora lutea were recorded. All fetuses were weighed, sexed, and examined for gross external 

malformation. One-half of the fetuses in each litter were examined for visceral soft tissue 

alterations by the Wilson technique. The remaining fetuses in each litter were examined for 

skeletal alterations by the Dawson method. This study was conducted prior to the publication of 

EPA GLP Guidelines. 

There were six deaths in the high-dose group (one each on GDs 10 and 17, and two each on GDs 

11 and 12); the causes of death were not determined. At the high-dose, all of the dams (except 

three) were observed at least once with diarrhea, soft stools, breathing rattles, inactivity, and red 

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matter in the region of nose, mouth, forelimbs, or dorsal head; no treatment-related clinical signs 

were observed in the low- and mid-dose groups. There were no treatment-related effects on 

maternal body weight in the low- and mid-dose groups. At the high dose, maternal body weight 

gain was decreased (↓23%) during the test period (GDs 0-20), due to a body weight losses during 

GDs 6-20 (↓6-10%). It is not known if statistical analyses were conducted on body weights/body 

weight gains, as no statistical differences were reported for these decreases. 

At 300 and 1000 mg/kg/day, there were no effects in mean number of viable fetuses, late or early 

resorptions, postimplantation loss, corpora lutea, the fetal sex distribution, or fetal body weight. 

Decreases in viable fetuses/dam (11.9 ± 4.36; p<0.05) and total implantations/dam (12.1 ± 4.45; 

p<0.01) were noted at the low dose compared to control (14.4 ± 1.26 and 15.0 ± 1.67, 

respectively), but were not considered to be related to treatment because the decreases were not 

dose-related. At the high dose, decreases in viable fetuses/dam (11.5 ± 4.12; p<0.05), total 

implantations/dam (12.8 ± 3.77; p<0.05), and mean fetal body weight (3.2 ± 0.34 g vs. 3.0 ± 0.21 

g in control; p<0.01) were observed. There were no fetal malformations in low- and mid-dose 

groups. The number of malformed fetuses in the high-dose group (10) was increased compared 

to control (3). However, because the number of litters with malformed fetuses was the same for 

both groups, this was not considered to be an effect. There was an increase in the number of 

litters and fetuses with unossified sternebrae observed at the high dose. The maternal LOAEL is 

3500 mg/kg/day, based on mortality, toxic signs, and decreased body weight gain, and the 

maternal NOAEL is 1000 mg/kg/day. The developmental LOAEL is 3500 mg/kg/day based on 

decreases in fetal body weight, increases in the number of litters and fetuses with unossified 

sternebrae, decreases in viable fetuses/dam, and decreases in total implantations/dam; the 

developmental NOAEL is 1000 mg/kg/day. 

Prenatal Development in Non-Rodents (Rabbit; OCSPP 870.3700) 

In a developmental toxicity study in rabbits (MRID 00046363), glyphosate (98.7% purity) was 

administered to artificially-inseminated, female Dutch Belted rabbits (16/dose group) by gavage 

at doses of 0 (0.5% aqueous methocel), 75, 175, or 350 mg/kg/day from GDs 6-27, inclusive. 

Individual doe body weights were recorded on GDs 0, 6, 12, 18, 24, and 28; food consumption 

was not determined. On GD 28, all surviving does were sacrificed, and the uterus was examined 

and weighed; the number and location of viable fetuses and early and late resorptions, and the 

total number of implantations and corpora lutea were recorded. Each fetus was weighed, 

examined for external malformations, dissected, sexed, examined for visceral abnormalities, then 

eviscerated, stained with Alizarin Red S, and examined for skeletal abnormalities by the Dawson 

method. This study was conducted prior to the publication of EPA GLP Guidelines. 

One rabbit in the low-dose group died apparently of pneumonia on GD 26. Two rabbits in the 

control group, one in the low-dose group, and one in the high-dose group aborted and were 

sacrificed. Additionally, two rabbits at the medium dose and ten rabbits at the high dose died 

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during the study; of these, death was attributed to gastroenteritis for two rabbits, to enteritis for 

one rabbit, and to respiratory disease for one rabbit. The cause of death for the remaining eight 

rabbits could not be determined at necropsy. Soft stool or diarrhea was noted in all groups with a 

slight increase at the medium dose and at least once in each rabbit of the high-dose group; in 

addition, an increase in nasal discharge was noted in the high-dose animals. There were no 

toxicologically significant differences in maternal mean body weight among control and treated 

groups; however, a non-dose-dependent decrease in overall body weight gain was observed in 

the medium-dose group (↓135%). No treatment-related changes were seen in the number of 

viable fetuses, early or late resorptions, total implantations, corpora lutea, or fetal sex 

distributions at any dose. A slight decrease was noted for mean fetal body weight of all of the 

treated groups compared to the control group. However, mean fetal body weights for all groups 

were comparable to historical control mean fetal body weight values. There were no treatmentrelated malformations in fetuses from litters of treated rabbits in comparison to control. A few 

malformations were noted in each of the three treated groups. Because these did not occur in a 

dose-related pattern and their frequency was comparable to that of the historical control group, 

they were not considered treatment-related. 

The maternal LOAEL is 350 mg/kg/day, based on increased incidences of soft stool, diarrhea, 

nasal discharge, and death, and the maternal NOAEL is 175 mg/kg/day. The developmental 

LOAEL is not determined (>350 mg/kg/day), and the developmental NOAEL is 350 mg/kg/day. 

Multi-Generation Reproduction in Rodents (Rat; OCSPP 370.3800) 

In a three-generation reproduction study in rats (MRID 00081674), glyphosate (98.7% purity; 

assumed to be 100% for dosing preparations) was administered in the diet to three consecutive 

generations of CD (SD) rats (12 males and 24 females/generation/dose) at nominal doses of 0, 3, 

10, or 30 mg/kg/day. Each parent generation was mated to produce two litters. Offspring from 

the second litters of the F0 and F1 parents (F1b and F2b litters, respectively) were selected to be 

parents for the subsequent pair of generations. Parameters evaluated for each generation 

included: mortality, body weight and food consumption data, in-life physical observation data, 

maternal body weights (gestation/lactation), reproduction-fertility indices (mating, pregnancy 

and fertility indices), litter data at parturition, and organ weight data. Offspring from each litter 

interval were evaluated during a 21-day lactation period for growth, survival, sex distribution 

data, and gross postmortem observations including organ weight data (F3b offspring only). All 

parents were sacrificed after weaning of the second litters and randomly selected offspring from 

the second litters of the second generation (21-day F3b weanlings) were sacrificed; the organs 

that were weighed at sacrifice included the adrenals, gonads, kidneys, liver, and pituitary. 

Microscopic examinations of these tissues as well as mammary glands, thyroid and parathyroid, 

prostate, and uterus were conducted for 10 rats/sex from the control and high-dose groups of F0, 

F1, and F2 parents and F3b weanlings. 

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There were no treatment-related effects on adult mortality, clinical signs, body weight, or food 

consumption. Although there were some differences between control and treated groups, there 

were no consistent, dose-related effects on mating, fertility, or pregnancy indices over the entire 

study that would indicate an adverse effect of treatment. There were no consistent adverse effects 

of treatment in maternal body weight or body weight gain, gestation length, parturition data, or 

litter survival indices throughout the study. No consistent treatment-related effects were found in 

sex distribution data, body weights, survival, or gross postmortem findings in offspring. There 

were no effects of treatment on absolute or relative organ weights in F3b offspring or F0, F1, or F2

adult males. Gross postmortem evaluations of the tissues from randomly selected F0, F1, and 

F2 control and high-dose animals, and F3b control and high-dose offspring, revealed a high 

incidence of focal tubular dilation in the kidneys of the male F3b high-dose offspring. In a 

subsequent submission (MRID 00105995), the results of examination of the kidneys from the 

low- and mid-dose F3b offspring were reported, which showed that the incidence of renal focal 

tubular dilation in the low- and mid-dose F3b offspring was similar to the study control, as well 

as, historical control data. 

The reproductive LOAEL is 30 mg/kg/day based on increased focal tubular dilation in the 

kidneys of male F3b offspring. The reproductive NOAEL is 10 mg/kg/day. The systemic NOAEL 

is 30 mg/kg/day, and the LOAEL is not determined (>30 mg/kg/day). 

In a two-generation reproduction study with rats (MRID 41621501), glyphosate (97.67% purity) 

was administered in the diet to SD rats (30/sex/group) at 0, 2000, 10,000, or 30,000 ppm (0, 100, 

500, or 1500 mg/kg/day, based on standard conversion) for eleven weeks. After Week 11, the 

rats were mated to produce the F1 generation. Litters were culled to eight pups and weaned on 

Day 21, after which 30 rats/sex/group were randomly selected to continue as the second 

generation. The F1 rats were mated after approximately 14 weeks to produce the F2a and F2b 

litters. Rats were maintained on dosing diets throughout pre-mating, mating, gestation, and 

lactation until sacrifice. Parameters evaluated for each generation included: mortality, clinical 

signs, body weight, and food consumption, maternal body weights (gestation/lactation), 

reproduction-fertility indices (pre-coital interval, gestation length, litter size, dead pups/litter, and 

pup survival), and organ weight (ovaries and testes with epididymides). Microscopic 

examinations of tissues of F0 and F1 adults were conducted for selected tissues: kidneys, ovaries, 

pituitary (F1 only), prostate, seminal vesicles, mammary gland, testes, epididymides, and 

uterus/vagina. In addition, kidneys from F2b weanlings (1/sex/litter) were examined 

microscopically. 

There were no treatment-related mortalities during the study. Treatment-related clinical signs 

consisted of soft stools in high-dose males and females (both F0 and F1). Body weights of highdose male and female F0 rats were decreased (p<0.01, ↓8%) during the premating growth period. 

Similarly, F1 high-dose male and female adults weighed less at weaning compared to F0 animals 

with continued decreases (p<0.01 or 0.05) of 10-12%. The body weights of high-dose females 

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remained decreased (p<0.01 or 0.05) compared to control during gestation and lactation of the 

F1, F2a, and F2b litters, although high-dose body weights were comparable to control by the end 

of lactation. Food consumption was generally similar to control in high-dose males and females 

during most measurement periods; consumption was decreased in the medium- and high-dose F1

females on Days 0-14 (↓9 and 11%, respectively). There were no treatment-related effects on 

mating and fertility in the F0 to F1 generation, or in the F1a to F2a or F1a to F2b generations. At 

Days 14 and 21 in the F2b litter, and Day 21 in F1 and F2a litters, the mean body weights of highdose pups were decreased (p<0.01 or 0.05, ↓6-14%) and body weight gain of high-dose pups was 

decreased 15-20%. There were no consistent, dose-related effects on litter size at Day 0 or on 

pup survival during lactation. There were no treatment-related findings in gross necropsy or 

histopathology in examined treated rats compared to control. Terminal body weights in the F0

and F1a generations were decreased (p<0.01) by 8-13%. Increased relative weights of testes of 

high-dose F0 (NS, ↑6%) and F1 (p<0.01, ↑12%) rats were noted; however, this effect was 

considered to be due to the decreased terminal weights, and not be of toxicological significance 

as absolute weights were not affected by treatment. There were no treatment-related gross or 

microscopic findings in the kidneys of F2b weanlings. 

The reproductive NOAEL is 30,000 ppm (1500 mg/kg/day). The systemic LOAEL is 30,000 

ppm based on increased incidences of soft stool, and decreased food consumption and body 

weight during growth; the systemic NOAEL is 10,000 ppm (500 mg/kg/day). The developmental 

LOAEL is 30,000 ppm based on decreased pup body weight on LDs 14 and 21; the 

developmental NOAEL is 10,000 ppm. 

In a subsequent two-generation reproduction study with rats (MRIDs 48865101 through 

48865105), glyphosate (95.7% purity) was administered to Crl:CD(SD) IGS BR rats 

(28/sex/dose) in the diet at nominal doses of 0, 1500, 5000 and 15,000 ppm (equivalent to 

121/126, 408/423, and 1234/1273 mg/kg/day in males/females during pre-mating) for two 

successive generations with one litter per generation. The P generation animals were fed the test 

diets for ten weeks prior to mating to produce the F1 litters. The F1 litters were not standardized; 

litter sizes ranged from 4 to 21 pups. On PND 21, 24 pups/sex/dose were selected and fed the 

same test diet as their parents for ten weeks prior to mating to produce the F2 litters. Organs that 

were weighed in parental animals included adrenals, epididymides, kidneys, liver, ovaries, 

prostate, pituitary, seminal vesicles, testes, thymus, thyroid, and uterus; of these tissues, adrenals, 

epididymides, ovaries, prostate, pituitary, seminal vesicles, testes, and uterus of the control and 

high-dose P and F1 group were subjected to microscopic examination. 

No treatment-related effects were observed on mortality, clinical signs, body weights, body 

weight gains, food consumption, food efficiency, or gross or microscopic pathology in either the 

P or F1 generation. 

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Absolute and relative (to body) liver weights were increased (p<0.05, 0.01, or 0.001) by 8-13% 

in both the P and F1 females at in the high-dose group with no histopathological findings. 

Additionally, at this dose, absolute and relative kidney weights were increased (p<0.01 or 0.001) 

by 7-11% in the P females only. 

The LOAEL for parental toxicity was not observed. The NOAEL is 15,000 ppm (equivalent to 

1234/1273 mg/kg/day in males/females during pre-mating). 

There were no effects of treatment on the mean numbers of corpora lutea and implantations, preand post-implantation loss, numbers of pups born, litter size on PND 1, 4, 7, 14, and 21, live 

birth, viability, and lactation indices, and sex ratio at birth and on PND 1 and 21, clinical signs of 

toxicity, litter weights, pup body weights, developmental landmarks or reflexes, ano-genital 

distance, or brain, spleen or thymus weights in either the F1 or F2 offspring. 

There was a delay (p<0.01) of 2.9 days in attaining complete PPS (PND 45.9 treated vs. PND 

43.0 control) in the 15,000 ppm F1 male pups, along with a 10% increase (p<0.01) in body 

weight at attainment. 

The LOAEL for offspring toxicity is 15,000 ppm (equivalent to 1234/1273 mg/kg/day in 

males/females during pre-mating), based on delayed age and increased weight at attainment of 

PPS. The NOAEL is 5000 ppm (equivalent to 408/423 in males/females during pre-mating). 

The number of males impregnating their female partner, and the number of females not pregnant, 

with no litters observed, with total litter loss, and rearing their litters to weaning was similar in 

all groups. The pre-coital intervals were similar across all groups with the majority of pairs 

mating during the first four days of the mating period. Gestation duration, mean estrous cycle 

length and periodicity, follicle number, and sperm parameters were unaffected by treatment. 

The LOAEL for reproductive toxicity was not observed. The NOAEL is 15,000 ppm (equivalent 

to 1234/1273 mg/kg/day in males/females during pre-mating). 

Chronic Oral Toxicity/Carcinogenicity in Rodents (Rat; OCSPP 870.4300) 

In a chronic oral toxicity/carcinogenicity study in rats (MRIDs 00093879 and 00150564), 

glyphosate (98.7% purity) was administered to rats (50/sex/group) at nominal concentrations of 

0, 30, 100, or 300 ppm (3, 10, or 30 mg/kg/day based on standard conversion) for the first week 

of the study; rats were then dosed at 3.05, 10.30 and 31.49 mg/kg/day for the males and 3.37, 

11.22 and 34.02 mg/kg/day for the females for the remainder of the study. Animals were 

terminated at 26 months, when survival had decreased to 30% in one group per sex. All rats were 

observed twice daily for mortality and toxic signs and given a detailed physical examination each 

week throughout the study. Body weights and food consumption were determined at pretest, 

weekly through 14 weeks, and biweekly for the remainder of the study. Clinical and 

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hematological parameters were determined (10 rats/sex/group) at 4, 8, 12, 18, and 24 months. 

Complete necropsies were performed on all rats that died or were sacrificed during or at the end 

of the study. Organ weights determined at sacrifice included the adrenals, kidneys, liver, 

testes/ovaries, pituitary, and thyroid. Microscopic examination was conducted on these tissues, 

as well as epididymides, mammary gland, parathyroid, prostate, seminal vesicles, urinary 

bladder, and uterus for all treated and control rats. 

Survival was unaffected by treatment. Decreased (NS) body weight gains were observed in 

treated males beginning at Week 26 and continuing to Week 102, and decreased (significance 

not reported) body weight gains (↓10-15%) were present in the low- and medium-dose female 

rats from Weeks 84 to 92. No dose-response relationship was present in the decreased body 

weight gains in female rats and the changes in body weight did not affect survival. Overall food 

consumption was unaffected by treatment. Hematology, clinical chemistry, and urinalyses values 

for treated male and female rats were comparable to control values. Absolute and relative organ 

weights of treated rats also were comparable to control. No treatment-related findings were 

observed during gross necropsies. Microscopic examinations revealed lymphocytic hyperplasia 

of the thymus occurring at increased (significance not reported) incidences in the mid- and highdose female rats. In addition, focal vacuolation of liver was found with increased (significance 

not reported) incidence in high-dose male rats. Testicular interstitial cell tumors were seen in 

3/50, 1/50 and 6/50 rats at the low-, mid-, and high-dose groups when compared to control (0/50) 

with the 12% incidence at the high dose reaching statistical significance (p=0.013). However, it 

was concluded that the increased incidence was similar to the incidence observed in control 

groups of male rats in other concurrent studies and therefore was not related to treatment. C-cell 

carcinomas were seen in the thyroid of 5/47 females at the high dose (11%; p<0.001) compared 

to 1/47 control females (2%). No increases were seen in adenomas, and the incidences of C-cell 

hyperplasia were comparable between the treated and control groups. 

The LOAEL for chronic toxicity is 10.30/11.22 mg/kg/day (males/females) based on increased 

lymphocytic hyperplasia. The NOAEL for chronic toxicity is 3.05/3.37 mg/kg/day 

(males/females). The oncogenic potential is negative. 

In a subsequent chronic oral toxicity/carcinogenicity study in rats (MRID 41643801), glyphosate 

(96.5% purity) was administered to SD rats (60/sex/group) at nominal concentrations of 0, 2000, 

8000, or 20,000 ppm (89, 362, and 940 mg/kg/day in males and 113, 457, and 1183 mg/kg/day in 

females) for 24 months; 10 rats/sex/group were assigned for interim sacrifice after 12 months of 

treatment. All rats were observed twice daily for mortality and toxic signs and given a detailed 

physical examination each week throughout the study. Body weights were determined once 

weekly for 13 weeks and then monthly thereafter. Ophthalmological examinations were 

conducted pretest and twice prior to sacrifice. Clinical and hematological parameters were 

determined (10 rats/sex/group) before treatment and at 6, 12, 18, and 24 months; urinalyses also 

were conducted at 6, 12, 18, and 24 months. The organs that were weighed at sacrifice included 

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liver, kidneys, testes, epididymides, and prostate. Gross and microscopic pathological 

examinations were conducted on these and other tissues, including the seminal vesicles, ovaries, 

uterus, urinary bladder, mammary glands, pituitary, adrenals, and parathyroids/thyroids. 

There were no treatment-related effects on clinical signs or mortality. The mean body weight of 

high-dose females was decreased (p<0.05) by 3% at Day 51, 13% (p<0.01) at Week 81, and 3% 

(NS) at Week 104; at Week 81, body weight gain was decreased by 23% in high-dose females 

compared to control. There were no decreases in body weight or body weight gain in male rats. 

The incidence of cataracts and lens abnormalities in male rats in the high-dose group was 

increased (p<0.05) compared to control according to two examiners, and not significantly 

different according to two other examiners. There were no treatment-related hematology or 

clinical chemistry findings that were considered toxicologically significant. 

Liver weight (relative to body weight) was increased (p<0.05, ↑13%) in high-dose males at 

interim sacrifice, and absolute liver weights were increased (p<0.05, ↑13%) in high-dose males 

at terminal sacrifice. No treatment-related changes were seen in absolute or relative weights of 

the testes, epididymides, and prostate glands, and no treatment-related histopathological lesions 

were observed in the testes, epididymides, seminal vesicle, prostate, ovaries, uterus, and 

mammary, adrenal, and pituitary glands. The incidences of the pancreatic islet call adenomas in 

the low-, medium- and high-dose males exceeded the historical control range (1.8-8.5%); 

however, because there was no positive dose-related trend in the occurrence of these tumors in 

males, no progression to carcinoma, and the incidence of hyperplasia was not dose-related, the 

pancreatic islet cell tumors were not considered to be treatment-related. The incidences of 

thyroid C-cell adenomas were increased in animals in the medium- and high-dose groups 

compared to control; however, these increases were not considered to be treatment-related 

because none of the increases reached statistical significance, there was no dose-response in 

either sex, there was no increase in severity of grade or incidence in hyperplasia or progression 

to malignancy, and the incidences were within the historical control ranges. 

The NOAEL is 8000 ppm (362 and 467 mg/kg/day in males and females, respectively) and the 

LOAEL is 20,000 ppm (940 and 1183 mg/kg/day in males and females, respectively) due to 

decreased body weight and body weight gain in females, cataracts in males, and increased 

relative liver weight (to body) at 12 months and increased absolute liver weight at 24 months in 

males. 

In addition, the HED Carcinogenicity Peer Review Committee evaluated the carcinogenic 

potential of glyphosate in June 1991. Glyphosate was classified into Group E (evidence of noncarcinogenicity in humans) based on a lack of convincing evidence of carcinogenicity in 

adequate studies in two species. 

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Carcinogenicity in Rodents (Mouse; OCSPP 870.4200) 

In a carcinogenicity study in mice (MRIDs 00130406 and 00150564), glyphosate (99.7% purity) 

was administered in the diet to CD-1 mice (50/sex/group) at nominal concentrations of 0, 1000, 

5000, or 30,000 ppm (0, 150, 750, or 4500 mg/kg/day, based on standard conversion) for 24 

months. The parameters evaluated were clinical signs, mortality, body weight, food and water 

consumption, and hematology at 12, 18, and 24 months. At the end of the study, all animals were 

necropsied and selected organs (not specified) were weighed; tissues (not specified) were stained 

and examined microscopically. 

There were no treatment-related toxic signs noted, and mortality was low during the first 

eighteen months of the study. Body weight was consistently decreased for males and, to a lesser 

extent, females in the 30,000 ppm dose group during the study at several sampling intervals 

(extent and significance not reported). Changes in body weight at the low- and mid-dose group 

were variable and not dose-related. Food consumption showed no treatment-related or doserelated effect. Hematological values, although significant in some instances, did not show a 

consistent dose-related response. Necropsy did not show treatment-related lesions. There was 

good correlation between gross and microscopic findings. The relative (to bodyweight) testes 

weight was non-significantly increased (17.5%) at the high dose; however there were no 

significant changes in absolute or relative-to-brain weights for the testes. Absolute and relative 

ovarian weights were increased at 30000 ppm; however, the change was not statistically 

significant and attributed to a single animal in the group. There were no histopathological 

findings in the ovaries. 

Renal tubule adenomas were found in male mice in the 5000 and 30,000 ppm dose groups; 

however, it was concluded that the renal tumors were not dose-related. Trends, and effects in the 

high-dose group (p<0.01), were observed in non-neoplastic lesions. The lesions considered 

treatment-related were hepatocyte hypertrophy, central lobular hepatocyte necrosis, and chronic 

interstitial nephritis in high-dose males, and proximal tubule epithelial basophilia and 

hypertrophy in high-dose females. 

The NOAEL for systemic effects was 5000 ppm (750 mg/kg/day). At the LOAEL, 30,000 ppm 

(4500 mg/kg/day), there were increased incidences of hepatocyte hypertrophy, hepatocyte 

necrosis, and interstitial nephritis in male mice and increased incidences of proximal tubule 

epithelial basophilia and hypertrophy in female mice. Additionally, there were treatment-related 

decreases in body weights in male and female mice at 30,000 ppm. 

Chronic Oral Toxicity in Non-Rodents (Dog; OCSPP 870.4100)

In a chronic toxicity study in dogs (MRID 00153374), glyphosate (96.13% purity) was 

administered to Beagle dogs (6/sex/group) at concentrations of 0, 20, 100, or 500 mg/kg/day for 

one year. Criteria evaluated included clinical signs, mortality, body weight, food consumption, 

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ophthalmologic evaluation, hematology, clinical chemistry, urinalysis, organ weights (including 

adrenals, kidneys, liver, ovaries, testes, pituitary, and thyroid/parathyroid), and histopathology of 

selected tissues (not reported) and all gross lesions. 

All animals survived the duration of the study. There were no dose-related, clinical signs of 

toxicity, and body weight and food consumption in treated dogs were comparable to control. 

There were no dose-related changes in hematological or clinical chemistry values. Decreased 

pituitary weights (absolute and relative) were observed in mid-and high-dose male dogs, 

however, these were not considered to be treatment-related because there were no underlying 

histopathological changes in that organ and there was no dose relationship in the weight changes. 

No treatment-related changes were seen in absolute or relative weights of the other organs, 

including testes, ovaries, thyroid, and adrenal glands. There were no treatment-related 

histopathological findings, and the incidence and grade of microscopic lesions were comparable 

between treated and control dogs for all organs including testes, ovaries, thyroid, adrenals, and 

pituitary. 

The NOAEL for the study is the high dose of 500 mg/kg/day; a LOAEL was not identified. 

Avian Reproduction (OCSPP 850.2300) 

In an avian reproduction study (MRID 00111953), mature Mallard ducks were administered 

glyphosate (83% purity) at nominal concentrations of 0, 50, 200, or 1000 ppm (mg/kg) in the diet 

for 17 weeks (nine weeks prior to the start of egg production and eight weeks of egg production). 

Each treatment group was comprised of five pens, with five drakes and two hens per pen. Body 

weights were taken four times: at initiation, after five weeks, prior to onset of egg laying, and at 

termination of the study. Food consumption was recorded biweekly. Eggs were cleaned at 

weekly intervals and placed in an incubator. On Days 22 or 23 of incubation, the eggs were 

placed in a hatcher, and on Days 26 or 27, hatchlings were housed according to the appropriate 

parental grouping and maintained on control diet until 14 days of age. For the purposes of 

measuring egg weight and egg shell thickness, one egg from each pen was randomly selected on 

a weekly basis. 

Ducks treated with glyphosate up to 1000 ppm (limit dose) showed no symptoms of toxicity or 

behavioral abnormalities for the duration of the study. There was one mortality on study in the 

high-dose group during Week 12. Because the mortality occurred during the stress of egg 

production and no gross abnormalities were noted upon gross necropsy, the death was not 

considered to be treatment-related. There were no treatment-related effects on the reproductive 

parameters that were evaluated: eggs laid, eggs cracked, viable embryos, live 3-week embryos, 

normal hatchlings, 14-day-old survivors, representative hatchlings body weight, representative 

14-day-old survivors body weight, egg weight, and eggshell thickness. The NOAEC is 1000 ppm 

and the LOAEC is >1000 ppm. 

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In another avian reproduction study with the mallard duck (MRID 00036328), test animals were 

exposed to concentrations of control, 3, and 30 ppm. There were five pens per treatment group 

with 2 males and 5 females per pen. Birds receiving glyphosate at 3 and 30 ppm in the diet 

showed no signs of toxicity or behavioral abnormalities during the course of the study. All test 

and control birds appeared normal throughout the study and there were no observed mortalities. 

Additionally, there were no treatment related effects on any reproductive parameter assessed. 

In a third mallard duck reproduction study (MRID 48876602), the one-generation reproductive 

toxicity of Glyphosate-acid to 16 pairs per level of 21-week old Mallards (Anas platyrhynchos) 

was assessed over 21 weeks. Glyphosate-acid was administered to the birds in the diet at nominal 

concentrations of 0 (negative control), 500, 1000, and 2250 mg ae/kg diet. Mean-measured 

concentrations were 0 (control), 501, 987, and 2160 mg ae/kg diet. No treatment-related 

mortalities or signs of toxicity occurred during the test. One incidental mortality was observed in 

each of the control, 501, and 987 mg ae/kg groups. Significant reductions were detected at the 

low and high treatment levels for 14-day survivor body weight and adult male weight gain 

(Dunnett’s, p<0.05); no effects were detected at the 987 mg ae/kg diet level for any endpoint 

(p>0.05). Reductions in 14-day survivor body weights at the low and high dose were 10-11% of 

control body weight values and adult male birds did not gain weight at the low dose and lost 

weight during the study at the high dose. Additionally, the reviewer’s analysis detected a 

suggestively dose-dependent, significant 6% reduction from control in hatchling body weights at 

the high dose level (William’s, p<0.05). No other significant treatment-related differences were 

observed between the control group and any of the treatment groups. Based on the significant 

reductions from control in offspring survivor body weight and adult male body weight gain at the 

501 mg ae/kg diet level, the reviewer concluded that a NOAEL could not be determined in this 

study (i.e., <501 mg ai/kg diet). 

In an avian reproduction study (MRID 00108207), mature Bobwhite quail were administered 

glyphosate (83% purity) at nominal concentrations of 0, 50, 200, or 1000 ppm diet for 17 weeks 

(nine weeks prior to the start of egg production and eight weeks of egg production). Each 

treatment group was comprised of 12 pens, with one male and two females per pen. Body 

weights were recorded at the initiation of the study, after five weeks, immediately prior to the 

onset of egg laying, and at study termination. Food consumption was recorded biweekly 

throughout the study. Day 19 eggs were placed in a hatcher. All eggs on day 21 or 22 were 

removed from the incubator. Hatchlings were housed according to the appropriate parental 

grouping and maintained on a control diet until 14 days of age. One egg from every other pen 

was taken weekly for egg weight and eggshell measurements. 

Quails treated with glyphosate up to 1000 ppm (limit dose) showed no symptoms of toxicity or 

behavioral abnormalities for the duration of the study. There were three mortalities during the 

study in the control group at Weeks 13, 14, and 17. Because the mortalities occurred during the 

stress of egg production and no gross abnormalities were noted upon gross necropsy, the deaths 

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were not considered to be treatment-related. There was no effect of treatment on the following 

reproductive parameters: eggs laid, eggs cracked, viable embryos, live 3-week embryos, normal 

hatchlings, 14-day-old survivors, and representative hatchlings body weight. Decreases in 

eggshell thickness (50 ppm group; ↓5%, p<0.05) and egg weight (1000 ppm group; ↓8%, NS) 

were not considered to be biologically meaningful, as there was no dose response observed for 

eggshell thickness decreases and no effect on overall reproductive success. The NOAEC is 1000 

ppm and the LOAEC is >1000 ppm. 

Fish Early Life-Stage Toxicity (Threespine Stickleback) 

In a published non-Guideline study (Le Mer et al., 2013), the effects of glyphosate (≥96% 

purity) exposure on larval threespine sticklebacks (Gasterosteus aculeatus) was determined 

according to growth, survival, the reproductive biomarkers vitellogenin (VTG) and spiggin 

(SPG), and sexual differentiation as endpoints in exposed larvae. The tested concentrations of 

0.1, 1, and 10 μg/L were considered to be representative of environmental concentrations found 

in estuarine and coastal waters of eastern North America; a higher pharmacological 

concentration of 100 μg/L also was included. 

Adult threespine sticklebacks were collected from an uncontaminated site on the Gaspé 

Peninsula (Rivière Saint-Jean, QC) and mature adult males and females displaying secondary 

sexual characteristics were placed separately in 105-L tanks supplied with a constant flow of 

filtered seawater and maintained at 18±1°C and salinity 15±1%, with a 16:8 hour light:dark 

photoperiod. After fish were acclimated for ten days, 40 males and females were placed in 45-L 

tanks containing nesting materials. Mating trials were conducted, and fertilized egg clutches 

were transferred to 1 L beakers with aerated IML seawater, at 18-19°C, until hatching. Newly 

hatched larvae, at Day 7 after fertilization, were exposed to the treatments in 1-L glass beakers 

with 500-mL portions of aerated seawater at 18°C with a 16:8 hour light:dark photoperiod. The 

tested concentrations were 0.1, 1, 10, and 100 μg/L glyphosate, and the tests included a negative 

(seawater) control, a positive control of 17α-ethinylestradiol (EE2; 0.05 μg/L), and a positive 

control of dihydrotestosterone (DHT; 3 μg/L). Each treatment included three replicates, with 9-

10 fish per replicate for glyphosate. Fish were exposed throughout the embryo-larvae and 

juvenile life stages (from hatching to Day 42 post-hatching) until fish had a mean length of ~20 

mm. Larvae were fed once per day with Artemia nauplii; water was changed every day (>80% 

replacement) before feeding. Dissolved oxygen, temperature, and fish mortality were monitored 

daily. Experiments were conducted during the summer of 2007 and repeated during the summer 

of 2008. 

At the end of the 42-day exposure period, surviving fish were sacrificed and total body lengths 

(L; mm) and wet weights (W; mg) were determined; a condition factor (CF) was calculated as 

CF = (W/L3

)100. Half of the fish from each replicate, selected at random, were frozen at –80°C 

for VTG and SPG measurements, and the remaining fish were preserved for intersex evaluations; 

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a subset of these fish were processed for histological evaluation. Vitellogenin was isolated from 

the whole-body homogenates of juvenile sticklebacks with a previously described method and 

measured with an indirect competitive ELISA. Stickleback SPG was determined with a 

competitive ELISA that included an antibody against a synthetic peptide specific to SPG 

sequence. For histological evaluations, the gonads were examined by light microscopy; all 

sections were examined for phenotypic sex determination. 

In 2007, mean glyphosate concentrations could not be determined due to possible seawater 

interference. In 2008, mean glyphosate concentrations were 0.08, 1.0, 8, and78 mg/L (≤22% of 

nominal). 

There was <11% mortality in the fish exposed to glyphosate over the 42-day exposure period. 

There were no significant differences in wet weight, body length, or condition of juvenile fish 

between glyphosate-exposed fish and control in either test year. The study authors noted that 

there was a significant difference in the size of fish in the 2007 trials compared with those of the 

2008 trials, even though fish came from the same field site; the 2008 fish were smaller (up to 

12% less in body length) and weighed less (up to 32% less in wet weight) than the 2007 fish. For 

the 2007 trial, the condition factor for fish treated with EE2 was similar to all other treatments. In 

2008, the condition factor for EE2-treated fish was decreased (p<0.05) compared to the DHT 

treatment and the 1.0 and 100 μg/L glyphosate treatments. Treatment with EE2 resulted in 

significant (p<0.05) induction of whole-body VTG compared to other treatments. There was no 

VTG induction observed in fish treated with DHT or glyphosate, or in fish in the negative 

control groups. No induction of SPG was observed in any of the treatment groups, including the 

positive DHT control. 

Glyphosate treatment had no effect on the proportion of mixed sex individuals. A single mixed 

sex individual was found in the group exposed to 10 μg/L glyphosate. The proportion of mixed 

sex individuals was higher in the positive controls (EE2, DHT) compared to the negative control. 

The proportion of female individuals did not differ significantly among treatments, but tended to 

be higher in the fish exposed to EE2 and the lowest dose of glyphosate, and lower in fish 

exposed to DHT. For histological evaluations, all sections with gonad tissue were examined for 

phenotypic sex determination. The number of gonad sections per individual and the proportion of 

individuals without gonad sections did not differ among treatments. It was concluded that 

glyphosate exposure had no effect on larval survival or growth, and that glyphosate did not exert 

estrogenic or androgenic effects on early life-stages of sticklebacks at environmentally-realistic 

concentrations. 

Toxicity to Amphibians (Non-guideline) 

In a published non-guideline study (Howe et al, 2004), the effects of glyphosate (reported as 

technical grade) to leopard frogs (Rana pipeins) was investigated at 0.6 and 1.8 mg glyphosate 

free acid equivalents (FAE). 

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The study reports on a series of studies conducted over roughly a seven-year period examining 

the acute and chronic effects of glyphosate alone, the surfactant polyethoxylated tallowamine 

(POEA) and glyphosate based products on four aquatic-phase amphibian (anuran) species. It is 

noted that only the effects of glyphosate alone were considered in the weight of evidence for 

endocrine related(decreases in offspring body weight observed in one avian reproduction study) 

effects. 

Treatment with glyphosate alone did not reveal any effects on growth (length), tail morphology, 

percent surviving to reach Stage 42, time to metamorphosis, gonadal development or thyroid 

hormone gene expression relative to controls; however, treatment with POEA alone or 

glyphosate formulations containing POEA reduced the percentage of larvae surviving to reach 

Stage 42, decreased length at metamorphosis, increased time to metamorphosis, and resulted in 

mixed-sex gonads. 

Mortality was relatively high in chronic study control groups (38%) and suggests that 

environmental conditions were not ideal for promoting survival of leopard hogs. This may have 

been due to relatively high loading rates coupled with partial water changes every 96 hours. 

Although effects on metamorphosis and gonadal development appear to be treatment related, 

poor environmental conditions could affect development. 

Fish Life Cycle Toxicity (Fathead Minnows) (OPPTS 850.1500)

In a fish full life-cycle toxicity study (MRID 00108171), Fathead minnows (P. promelas) were 

continuously exposed to glyphosate (87.3% purity) at nominal concentrations of 0, 1.6, 3.2, 6.3, 

12.5, and 25.0 mg/L; mean-measured concentrations were 0.7, 2.8, 7.0, 13.0, and 25.7 mg/L. In 

duplicate aquaria for each treatment, two groups of thirty eggs were incubated; dead eggs were 

removed and counted each day until hatching was completed (4 days at 25°C). Percent hatch was 

based on the number of live fry from 60 eggs. Forty fish, divided into two groups of twenty each, 

were randomly selected and distributed to growth chambers in each aquarium. Two growth 

chambers were used to facilitate handling of fry for 30- and 60-day measurements by a 

photographic method. Percent survival based on cumulative mortality was also determined at 

these intervals. After the Day 60 measurements, the number of fish released to each spawning 

chamber was impartially reduced to fifteen after combining fish from the growth chambers. On 

Day 64, five spawning sites were placed in the spawning chamber. After secondary sexual 

characteristics were well developed (approximately Day 134), the number of fish in each tank 

was reduced initially to four males and four females, and finally to two males and four females 

on Day 179. Eggs were removed from the spawning sites daily and counted after spawning 

began (approximately Day 112). Fifty eggs from each of the first ten spawnings per tank were 

oscillated in their respective test waters by means of an egg cup, and dead eggs were removed 

and counted each day until hatching was completed (3-5 days at 25°C). Percent hatch was based 

on the number of live fry from 50 eggs. Twenty fry from the first two spawns in each tank in 

which at least 80% live hatch was observed were placed in their respective growth chambers. 

After thirty days of exposure, fry groups were terminated and total lengths determined by the 

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photographic method. Total wet weight and percent survival were also determined at this time 

for each fry group. 

There was no treatment effect on any of the parameters measured: survival, growth and egg 

production of first generation fish; and hatchability, survival, and growth of second generation 

eggs and fry. The NOAEC is 25.7 mg/L and the LOAEC is ≥25.7 mg/L. 

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APPENDIX 3: References Not Utilized in the Glyphosate WoE Analysis 

In 2009, after public review and comment, a final list of 67 chemicals and schedule for issuing 

Test Orders for the EDSP Tier 1 screening battery was made available in a Federal Register 

Notice issued October 21, 2009 (74 FR 54422). The agency’s review of the initial data submitted 

as “other scientifically relevant information (OSRI) was provided in the Report of the Endocrine 

Disruptor Review Team (USEPA, 2010). 

Beginning in 2011, the agency has reviewed data cited as “OSRI which included Part 158 studies 

previously submitted to the agency for registration/reregistration, published literature articles 

and/or Tier 1 assays. The agency also conducted a more recent search (2009 to 2014) of 

available scientific literature for any additional relevant information for their weight of evidence 

(WoE) evaluations. These articles were evaluated in accordance with the agencies Evaluation 

Guidelines for Ecological Toxicity Data in Open Literature, May 2011 

(http://www.epa.gov/pesticides/science/efed/policy_guidance/team_authors/endangered_species

_reregistration_workgroup/PDF_rot/esa_evaluation_open_literature.pdf) and the 2012 Guidance 

for considering and Using Open Literature Toxicity Studies to Support Human Health Risk 

Assessment (http://www.epa.gov/pesticides/science/lit-studies.pdf). 

The following published and unpublished references were considered for use in the WoE 

analysis for Glyphosate but were not utilized due to one or more of the following reasons: 1) the 

article was not available in English; 2) the compound of interest was not used in the study; 3) the 

test material was not adequately described; 4) a formulated end-use product or mixture of 

chemicals was utilized as the test material; 5) only acute mortality toxicity data were provided; 

6) the experimental conditions were not adequately described; 7) only an abstract of the study 

was available; 8) the reference is a review article or book chapter and does not contain primary 

study data; 9) insufficient information was available to adequately assess the validity of the study 

results; 10) the 40 CFR Part 158 guideline study was classified as unacceptable/inadequate; 11) 

the study dealt only with non-EDSP assay development; 12) no specific endocrine-related 

endpoints were assessed in the study; and 13) the study contained only data on invertebrates. 

Forgacs, A. L., Ding, Q., Jaremba, R. G., Huhtaniemi, I. T., Rahman, N. A., and Zacharewski, T. 

R. (2012) BLTK1 murine Leydig cells: a novel steroidogenic model for evaluating the effects of 

reproductive and developmental toxicants. Toxicol. Sci. 127(2):391-402 

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