820R92110
FINAL
DRINKING WATER CRITERIA DOCUMENT
• FOR
GLYPHOSATE
Health and Ecological Criteria Division
Office of Science and Technology
Office of Water
U.S. Environmental Protection Agency
Washington, DC 20460
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Giyphcsate C~:aria Document
TABLE OF CONTENTS
FOREWORD - iv
I. SUMMARY M
H. PHYSICAL AND CHEMICAL PROPERTIES '. H-l
A. GENERAL PROPERTIES .' 0-1
B. MANUFACTURE AND USES • 0-1
C ENVIRONMENTAL FATE O-l
D. SUMMARY 0-3
m. TOXICOKINETICS '....- m-i
A. ABSORPTION i , 01-1
B. DISTRIBUTION DM
C. METABOLISM ' ffi-1
D. EXCRETION EM
E. BIOACCUMULAHON AND RETENTION 10-2.
F; SUMMARY . . m-2:-
IV. HUMAN EXPOSURE IV-1
A. EXPOSURE ESTIMATION IV-1
1. Drinking Water "IV-1
2. Diet IV-1
3. Air '.... IV-1
B. SUMMARY IV-1
V. HEALTH EFFECTS IN ANIMALS V-l
A. SHORT-TERM EXPOSURE V-l
1. Lethality V-l
2. Sub-acute Effects V-l
3. Dermal/Ocular Effects V-l
B. LONGER-TERM EXPOSURE V-l
C. REPRODUCnVE/TERATOGENIC EFFECTS V-3
D. MUTAGENICTTY V-5
E. CARCINOGENlCrrY V-5
F. SUMMARY V-8
VL HEALTH EFFECTS IN HUMANS VI-1
VH, MECHANISMS OF TOXIOTY VIM
A, EFFECTS ON MITOCHONDRIA VH-I
B. SUMMARY VH-4
QUANTIFICATION OF TOXICOLOGICAL EFFECTS VHI-1
A. PROCEDURES FOR QUANTinCATION OF TOXICOLOGICAL EFFECTS VDI-1
1. Noncarcinogenic Effects Vffl-1
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Glyphosate Criteria Document
2. Carcinogenic Effects Vffl-2
B. QUANTIFICATION OF NONCARONOGENIC EFFECTS FOR GLYPHOSATE . . VHI-4
1. One-day Health Advisory Vm-i
2.' Ten-day Health Advisory vm-4
3. Longer-term Health Advisory .' .' Vm-i
4. Reference Dose and Drinking Water Equivalent Level vm-6
C QUANTIFICATION OF CARCINOGENIC EFFECTS FOR GLYPHOSATE . . Vm-8
1. Characterization of Carcinogenic Potential Vm-8
2. Quantitative Carcinogenic Risk Estimates VT!3-9
D. EXISTING GUIDELINES AND STANDARDS , VHI-9
E. SUMMARY VTH-9
DC. REFERENCES DC-1
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Glyphosate Criteria Document
LIST OF TABLES
Table H-1. Physical and Chemical Properties of Glyphosate (N-(phosphonornethyOglycine) . . . H-2
Table IV-1. Tolerances for Glyphosate .. •.' IV-2
Table V-l. Sister Chromatid Exchange Frequencies in Human Lymphocytes V-6
Table VIM. Respiratory Control Ratios of Mitochondria VII-2
Table VII-2. Activities of Enzymes in Mitochondria Isolated From Livers VTI-3
Table VE-1. Summary of Candidate Studies for Derivation Vffl-5
Table Vffl-2. Summary of Candidate Studies for Derivation of the DWEL for Glyphosate .. VDI-7
Table VHI-3. Summary of Quantification of Toxicological Effects for Glyphosate VTH-IO
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Giyphosate Criteria Document
FOREWORD
Section 1412 (b)(3)(A) of the Safe Drinking Water Act. as amended -in 1986, requires the
Administrator of the Environmental Protection Agency to publish Maximum Contaminant Level Goals
(MCLGs) and promulgate National Primary Drinking Water Regulations for each contaminant, which,
in the judgment of the Administrator, may have an adverse effect on public health and which is known
or anticipated to occur in public water systems. The MCLG is nonenforceable and is set at a level at
which no known or anticipated adverse health effects in humans occur and which allows for an adequate
margin of safety. Factors considered in setting the MCLG include health effects data and sources of
exposure other than drinking water. '
This document provides the health effects basis to be considered in establishing the MCLG. To
achieve this objective, data on pharmacokinetics, human exposure, acute and chronic toxicity to animals
and humans, epidemiology, and mechanisms of toxicity were evaluated. Specific emphasis is placed on
literature data providing dose-response' informatioa Thus, while the literature search and evaluation
performed in support of this document was comprehensive, only the reports considered most pertinent
in the derivation of the MCLG are cited in the .document. The comprehensive literature data base in
support of this document includes information published up to April 1987; however, more recent dai
may have been added during the review process.
When adequate health effects data exist, Health Advisory values for :less-ihan-lifetime exposures
(One-day, Ten-day, and Longer-term, approximately 10% of an individual's lifetime) are included in this
document. These values are not used in setting the MCLG, but serve as informal guidance to
municipalities and other organizations when emergency spills or contamination situations occur.
- James R. Elder Tudor T. Davies
Director Director
Office of Ground Water and Drinking Water Office of Science and Technology
IV
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Glyphosate Criteria Document
FOREWORD
Section 1412 (b)(3)(A) of the Safe Drinking Water Act, as amended in 1986, requires the
Administrator of the Environmental Protection Agency to publish Maximum Contaminant Level Goals
(MCLGs) and promulgate National Primary Drinking Water Regulations for each contaminant, which,
in the judgment of the Administrator, may have an adverse effect on public health and which is known
or anticipated to occur in public water systems. The MCLG is nonenforceable and is set at a level at
which no known or anticipated adverse health effects in humans occur and which allows for an adequate
margin of safety. Factors considered in setting the MCLG include health effects data and sources of
exposure other than drinking water.
This document provides the health effects basis to be considered in establishing the MCLG. To
achieve this objective, data on pharmacokinetics, human exposure, acute and chronic toxicity to animals
and humans, epidemiology, and mechanisms of toxicity were evaluated. Specific emphasis is placed on
literature data providing dose-response information. Thus, while the.literature search and evaluation
performed in support of this document was comprehensive, only the reports considered most pertinent
in the derivation of the MCLG are cited in the document The comprehensive literature data base in
support of this document includes information published up to April 1987; however, more recent data
may have been added during the review process. o • ,
*.
When adequate health effects data exist! Health Advisory values for less-than-lifetime exposures,
(One-day, Ten-day, and Longer-term, approximately 10% of an individual's lifetime) are included in this
document These values are not used in setting the MCLG, but serve as informal guidance to
municipalities and other organizations when emergency spills or contamination situations occur.
James R. Elder Tudor T. Davies
Director Director
Office of Ground Water and Drinking Water Office of Science and Technology
IV
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Glyphosate Criteria Document
I. SUMMARY
Glyphosate is the common name for N-(phosphonomethyl)glycine, which is a white, solid compound
that is readily soluble in water (12 g/L) and insoluble in organic solvents. Glyphosate is widely used
as a nonselective postemergence herbicide for control of grasses, broad-leaved weeds, and woody brush.
It is commercially available in formulations containing a concentrated aqueous solution of the
isopropylamine salt, sold under the trade names of Rodeo or Roundup,
Glyphosate is strongly adsorbed to soil particles and is unlikely to be present in soil leachate or
runoff. It is readily degraded by microbial action, both in soil (half-life [t^j of about 60 days) and in
water (t!/2 of 50 to 70 days). Reaction of glyphosate with nitrite to form N-nitrosoglyphosate has been
demonstrated in soil under laboratory conditions, but there is no evidence that it occurs in the field.
Toxicokinetic data indicate that oral doses of glyphosate are rapidly absorbed by rats, with females
absorbing more than males, and that over 90% is excreted within 48 hours. Peak levels of glyphosate
occurred within 30 minutes in blood and bone marrow of rats given intraperiioneal injections .of
glyphosate. Blood levels in males and females dropped rapidly with a tia of 1 hour, while bone marrow
levels remained constant over the 10 hour post-treatment period with a t,fl of 7.6 hours for males and
4.2 hours for females. Orally administered glyphosate (10 mg/kg) followed a biphasic pattern of:
excretion in the feces of treated rats, with an excretion t1/2 for the a phase of 5.9-6.2 hours and 79-106 *
hours for the 0 phase. At the higher oral dose (1000 mg/kg), the tw for the o phase remained the same,,
but for the'jS phase it was 181-337 hours. Following intravenous administration in rats, 30-36% of the
compound was eliminated in the urine unchanged and the rest in the feces. Traces (0.4%) of
aminomethylphosphonic acid were fpund to be the only metabolite in the feces. In rat tissues, 0.1 ppm
of administered glyphosate was determined to be retained in rat tissues. Feeding studies in chickens,
cows, and swiae suggest-that glyphosate does not accumulate in animal tissues during periods of oral
exposure. ' „
No data were found on levels of glyphosate in drinking water, food, or ambient air. An interim
tolerance of 100 ug/L was established by the U.S. EPA for residues of glyphosate in potable water.
This value is based on anticipated residue concentrations in bodies of water adjacent to fields where
glyphosate has been applied at the maximum recommended rate, and is not based on health effects data.
Very few data on the health effects of glyphosate in mammals have been found in the published
literature, and most information on the toxicity of this compound has been provided by the Monsanto
Company. Oral LDjo values have been reported in two different studies to be 4,873 and 5,600 mg/kg
in rats. The oral ID*, has been reported to be 1,568 mg/kg in mice. The dermal LD30 in rabbits has
been estimated to be greater than 5,000 mg/kg. Hyperemia of the lungs has been reported to be the most
prominent effect following glyphosate poisoning, with severe stress, accelerated breathing, elevated
temperature, occasional convulsive movements, and rigor preceding death. Glyphosate may be a
cumulative irritant but not a skin sensitizer in guinea pigs.
In one 90-day feeding study in rats and dogs, doses of up to 100 mg/kg/day and 60 mg/kg/day,
respectively, produced no changes as compared with controls in body weight, behavior, mortality,
hematology, blood chemistry, or urinalysis. Similar results were obtained in another 90-day study in
rats administered glyphosate in the diet up to 1,000 mg/kg/day level. A 2-year chronic feeding study
in mice produced an equivocal oncogenic response in that a slight increase in renal tubular adenomas
occurred in males ingesting glyphosate at the highest tested dietary level of 30,000 ppm. In a lifetime
feeding study conducted for approximately 26 months in male and female rats, doses of up to 31.5 and
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Glyphcsate Criteria Document,
34.0.rng/kg/day, respectively, had no significant effect on body weight, organ weight, organ/body weight
ratios, or hernatologic and clinical chemistry parameters. A recent chronic study, in which rats were
administered glyphosate in the diet at 2,000, 8,000, and 20,000 ppm for 24 months, revealed a significant
decrease in body weight gain in high-dose females suggesting a No Observed Adverse Effect Level
(NOAEL) of 8,000 ppm based on this effect. No other compound-related hematoiogical, clinical, toxico-
logical, or histopathologkal effects were revealed. Also, a 1-year feeding study in dogs produced an
apparent decrease in absolute and relative pituitary weights with no accompanying histopathologic
effects. The NOAEL for this study was reported to be greater than 500 mg/kg/day. A Low Observed
Adverse Effect Level .(LOAEL) was not established.
In a three-generation rat feeding study, doses of up to 30 mg/kg/day had no effect on reproductive
function. Based on renal effects observed in F3b male weanlings the systemic NOAEL is 10 mg/kg/day
and the LOAEL is 30 mg/kg/day. In a subsequent two-generation reproduction study, glyphosate was
administered to rats in the diet up to 30,000 ppm (about 1,500 mg/kg/day). No adverse effects were
noted on mortality, pup survival, mating, pregnancy, and fertility. Some reduction in, weight gain
occurred in F0, F^ and F2 generations in males and females ingesting glyphosate at 30,000 ppm. F0 and
F, generation males and females at the dietary level of 30,000 ppm but not at lower levels had soft
stools. No gross or microscopic pathological changes in organs were found attributable to glyphosate.
As. in the three-generation study, no renal tubular dilations were observed in F2 male weanlings. In %
reproductive study in rats, oral doses of glyphosate ."on days 6 through 19 of gestation at 3,500 mg/kg/day
produced breathing difficulty, reduced activity, diarrhea, weight loss, altered physical appearance, and
mortality in dams, but no evidence of birth defects in the offspring. Eposes ef giyphosate up to 350
mg/kg/day produced no adverse developmental effects, and doses up to 175 mg/kg/day produced ru» toxic
effects on dams when administered to pregnant rabbits on days 6 to 27 of gestation. ,
Glyphosate has been reported to be nonmutagenic in a number of bacterial and yeast test systems,.
and in Chinese hamster ovary cells. It was negative for chromosomal aberrations in the mouse dominant
lethal test, in the in vivo cytogenetics assay, in the Bacillus subtilis rec assay, and in the rat hepatocyte
DNA repair assay. High concentrations of glyphosate have been reported to cause sister chromatid
exchange in human lymphocytes in vitro.
No increase in tumor incidence was observed in male or female rats administered glyphosate in the
diet at doses of up to 31.5 and 34.0 mg/kg/day, respectively, for 26 weeks. In a 24-month chronic
feeding study in mice, dietary levels of 1.000, 5,000, and 30,000 ppm glyphosate did not elicit an
oncogenic response. However, the Agency has reviewed the data and classified this study as a chronic
toxicity study because it does not meet the guideline requirements for an oncogenicity study; the highest
dose tested was neither a toxic nor a maximum tolerated dose. Another carcinogenicity study in rats
fed glyphosate at dietary levels of 2,000, 8,000, and 20,000 ppm for 24 months revealed an increased
incidence of pancreatic islet cell adenomas, C-cell adenomas in thyroid, and hepatocellular adenomas.
Although no clearcut dose-response relationship was observed and the lesions did not progress from
adenoma to carcinoma, the observed high incidence of pancreatic islet cell adenomas in low-dose males
has prompted the U.S. EPA to recommend that the carcinogenic effects of glyphosate be addressed by
a Peer Review Committee.
No reports of glyphosate-related adverse health effects in humans were found.
Glyphosate is capable of uncoupling oxidative phosphorylation in isolated mitochondria. Five hours
after a single intraperitoneal administration of glyphosate to rats (at doses of up to 120 mg/kg),
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Glyphosate Criteria Document
respiratory control ratios of liver mitochondria were reduced as much as 46%, and activities of ATPase
and several dehydrogenases were enhanced.
The One-day Health Advisory (HA) value of 20,000 ug glyphosate/L was derived from a study used
for the derivation of ihe Ten-day HA because no suitable short-term studies on glyphosate toxicity were
found. A Ten-day HA of 20,000 ug/L was based on a reproduction study in rabbits. No suitable studies
were found to calculate the Longer-term HA values for a 10-kg child and a 70-kg adult. The adjusted
DWEL value of 1,000 ug/L is recommended for estimating the Longer-term HA for a 10-kg child, and
the DWEL value of 4,000 ug/L is recommended for estimating the Longer-term HA value for a 70-kg
adult. A three-generation feeding study in rats identified a NOAEL of 10 mg/kg/day (based on the
absence of effects on survival, histological appearance of tissues, and reproductive success), and this was
used to calculate the Reference Dose (RfD) of 100 ug/kg/day and the Drinking Water Equivalent Level
(DWEL) of 4,000 ug/L No existing exposure guidelines or standards based on health effects of
glyphosate were found, and no special considerations regarding glyphosate toxicity were identified.
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Giyphosaie Criteria Document
1 H. PHYSICAL AND CHEMICAL PROPERTIES
A. GENERAL PROPERTIES
Glyphosate is the common name for N-(phosphonomethyl)glycine, a white, odorless solid compound
that is readily soluble in water (12 g/L) at room temperature and iasolufale in organic solvents (Monsanto
Company, 1982a).
Solutions of glyphosate are known to be corrosive to iron and galvanized steel (Weed Science
Society of America, 1983). Table II-1 summarizes some important physical and chemical properties of
glyphosate. „
B. MANUFACTURE AND USES
Glyphosate is manufactured by extended refluxing of a mixture of glycine, chloromethylphosphonic
acid, and aqueous sodium hydroxide (pH of 10 to 12), followed by acidification with hydrochloric acid
and filtration. The resulting clear solution slowly deposits N-(phosphonomethyl)glycine (Sirtig, 1980).
As reported by CEH (1985), U.S. production of glyphosate reached 11.7 million pounds/year in 1982.
Glyphosate is a broad-spectrum, foliar herbicide that is absorbed through foliage and translocated.
throughout the plant .(Monsanto Company, 1980a). It is highly effective on deep-rooted perennial
species, and on annual and biennial species of grasses, sedges, and broad-leaved weeds (Weed Science
Society of America, 1983; Worthing, 1979). Roundup, a glyphosate-containing herbicide manufactured
by the Monsanto Company, also controls many tree and woody brush species in cropland and noncrop
sites such as airports, ditch banks, dry ditches, canals, fence rows, golf courses, and highways (Meister,
1983).
The principal commercial formulations of glyphosate are Roundup and Rodeo. Both are aqueous
solutions (pH 4.6 to 4.8) of the isopropylamine salt of glyphosate. Roundup contains 480 g/L of the salt
(356 g/L of glyphosate), and Rodeo contains 648 g/L of the salt (480 g/L of giyphosate) (Monsanto
Company, 1982a,b).
C ENVIRONMENTAL FATE
Glyphosate is strongly adsorbed to soil particles through the phosphoric acid moiety. Phosphate
levels in the soil influence the quantity of giyphosate adsorbed, and adsorption is greater in soils
saturated with Ar1* and Fe1* than with Na* and Ca2* (Hance, 1976; Sprankle et aL, 1975a,b). Owing to
its strong adsorption, glyphosate has little tendency to be leached in runoff water (Rueppel et al, 1977).
Analysis of glyphosate residues may be carried out by high-pressure liquid chromaiography (Worthing,
1979).
Microbial degradation of glyphosate in soil occurs with a half-life of about 60 days (Torstensson and
Aamisepp, 1977; Sprankle et aL, 1975a; Monsanto Company, 1982c). The principal metabolite, amino-
methylphosphonic acid, is also highly biodegradable (Rueppel et al., 1977). Glyphosate dissolved in
water is also rapidly degraded by microbial action. In laboratory studies, the half-lives in natural water
systems were 7 weeks in a sphagnum bog, 9 weeks in a cattail swamp, and 10 weeks in pond water
(Monsanto Company, 1983a).
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Glyphosate Criteria Document
Table D-l. Physical and Chemical Properties of Glyphosate (N-(phosphonomethyl)glycine)
Property
CAS No.
RTECS No.
Chemical formula
Molecular weight
Structure
Value
1071-83-6
MC1075000
WTCV
169.07
0 . 0
Reference
Monsanto Company (1982a)
Lewis and Tatken (1980)
Monsanto Company (1982a)
Windholz (1983)
Dissociation constants
(phosphonate)
(carboxyiate):
(phosphonatej
pK,, (amine)
Valence state
Melting point
Density
Vapor pressure
Stability in water
Solubility
Water
Organic solvents
I I
HO-C-CHrN-CHrP-QH
I I
H OH
2.6
5.6
10.6
Zwitterionic
200°C, decomposes
230°C, decomposes
0.5 g/mL
(for pure chemical)
Negligible
Completely stable in
sterile water
12 g/L at 25°C
Insoluble
Sprankle et ai (1975b)
Shovai and Yariv (1981)
Monsanto Company (1982a)
.Windholz (1983)
Monsanto Company (1982b)
Monsanto Company (1982a,b)
Monsanto Company (1983a)
Monsanto Company (1982a,b)
Monsanto Company (1982a,b)
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Criteria Document
. Khan and Young (1977), Young and Khari (1978), and Khan (1981) have reported that glyphosa^e
can be nitrosated by nitrite in an aqueous solution to form N-nitrosoglyphosate. Formation of N-
nitrosoglyphosate was also observed in soils treated with sodium nitrite and glyphosate.- At low levels
of glyphosate (5 ppm) and nitrite nitrogen (2 ppm), formation of N-nitrosoglyphosate was not observed:
Thus,'formation of N-nitrosoglyphosate in soil, and its subsequent uptake by plants under normal field
conditions, is not anticipated.
D. SUMMARY
Glyphosate is the common name for N-(phosphonomethyl)gIycine. It is a white, solid compound
that is readily soluble in water (12 g/L) and insoluble in organic solvents. Glyphosate is widely used
as a nonselective post-emergence herbicide for control of grasses, broad-leaved weeds, and woody brush.
It is commercially available as a concentrated aqueous solution of the isopropylamine salt, sold under
the trade names Rodeo and Roundup, which provides effective broad-spectrum control of emerged weeds
growing in or adjacent to aquatic sites.
d
Glyphosate is strongly adsorbed to soil particles and is unlikely to be present in soil leachate or
runoff. It is readily degraded by microbiai action, both in soil (half-life [tl/2j of about 60 days) and in
water (t1B of 35 to 70 days). Reaction of alvchosate with nitrite to form N-nitrosoelvohosate has been
demonstrated in soil under
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Glyphosace Criteria Document. " - . '.
!• ' "
m. TOXICOKINETICS
A. ABSORPTION
Toxicokinetic studies have been described in Sprague-Dawley rats (3-5/sex/group) following
oral (p.o.) or intravenous (i.v.) administration of ;4C-glyphosate (99% radiochemically pure) labeled in
the phosphonomethyl carbon (Monsanto Company, I988a.b). Animals in group 1,2, and 5 were given
a single p.o. dose of labeled glyphosate a: 10 mg/kg; groups 3 and 7 received Lv. doses at 10 mg/kg;
and group 4 received a p.o. dose of 1,000 mg/kg. Animals in group 6 were preconditioned p.o. with
unlabeled glyphosate at 10 mg/kg/day for 14 days and then given a single p.o. dose of labeled
glyphosate at 10 trig/kg. Based on radioactivity in whole blood in rats administered 14C-glyphosate p.o.
or Lv., the absorption in males was calculated to be 30.4% and in females to be 35.4% of the
administered dose. In another study (Monsanto Company, 1983b), Sprague-Dawley rats (9/sex) received
an imraperitoneal injection (Lp.) of 14C>glyphosate (98% radiochemically pure) at U50 mg/kg, after
which blood samples were collected at 0.25, 0.5, 1, 2, 4, 6, 10 hours. Peak absorption occurred at 30
minutes and then the blood plasma glyphosate level dropped rapidly following first-order kinetics.- The'
half-life of elimination from plasma was approximately 1 hour for both males and females.
B. DISTRIBUTION
After a single p.o. dose of i4C-labeled glyphosate in Sprague-Dawley rats (3/sex) at 10 mg/kg(<
0.-2-0.6% of the administered dose was found associated with the bone tissue, and after a single i.v. dose
(10 mg/kg) about 1% was associated with bone tissue (Monsanto Company, 1988a). Sprague-Dawley
rat* .(3/sex) were killed at 0.5, 4, and 10 hours after being given Lp. injections of 14C-glyphosate at a
dose of 10 mg/kg (Monsanto Company, 1983b). Peak values for glyphosate in isolated femoral bone
marrow cells were observed at 30 minutes post-treatment and remained at that level over the 10-hour
experimental period. The elimination half-life from the bone marrow was about 7.6 hours for the males
and 4.2 hours for the females.
C. METABOLISM
Following oral administration of I4C-labeled glyphosate (99% radiochemically pure) to Sprague-
Dawley rats (3-5/sex/group), no metabolite was found in the urine but the feces contained traces (£0.4%)
of aminomethylphosphonic acid as the only metabolite of glyphosate (Monsanto Company, 1988a).
D. EXCRETION
U.S. EPA (1986b) data on rats indicate that after a single p.o. or Lp. dose of glyphosate, less than
1% of the administered dose is retained at 120 hours after treatment, and that over 90% of the
administered glyphosate was excreted within 48 hours of treatment In a subsequent study (Monsanto
Company, I988a), urine and fecal data were used to estimate the kinetics of whole body elimination of
glyphosate in Sprague-Dawley rats (3-5/sex/group). When administered p.o. at 10 mg/kg, glyphosate
was excreted in the feces biphasically with an excretion tI/2 for the a phase of 5.9-6.2 hours, and for the
P phase of 79-106 hours. The percentage of excretion of administered glyphosate in the urine of males
was 31.2 and females 24.4 and in the feces the percentage of excretion was 68.1 for males and 75.1 for
females. Thus, female rats absorbed more glyphosate than males. Following repeated doses, the above
values did not change much. The percentage excretion in the urine of males was 33.4 and females 24.5,
and in the feces it was 65.9 in males and 75.1 in females. However, when administered p.o. at 1,000
mg/kg dose, the excretion tl/2 for the a phase remained same as above but for the £ phase it. was 181-
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Ghphcsate Criieria Document
337 hours. The percentage excretion of administered glyphosate in the urine of males was 19.6 and
females 15.5, and the fecal excretion values in males was 80 and in females 84. Thus, a higher oral
dose produced less absorption as revealed by urinary excretion data. When glyphosate was administered
as a single i.v. dose (10 mg/kg). the excretion of glyphosate expressed as percent of administered dose
in the urine of males was 92.7 and females 88.5, and excretion in the feces in males was 5.5 and in
females 9.9. Thus, about 90% was eliminated in the urine.
E. B10ACCUMULATION AND RETENTION
A steady-state equilibrium between intake and excretion of label was reached within 8 days when
groups of one to three rats were fed a diet containing 1, 10, or 100 ppm of MC"glyphosate for 14 days
(U.S. EPA, 1986b). The amount of radioactivity in the urine declined rapidly after cessation of
treatment. No data were given on the analysis of metabolites of glyphosate in the urine.. Detectable
amounts of radioactivity were measured in the urine and feces 10 days after cessation of glyphosate
treatment in the. 10 ppm and 100 ppm groups only. Only residues of 0.1 ppm or less remained -in the
tissues of high-dose rats after 10 days post-treatment. A -prefeTerftial accumulation of I4C was not
observed for any tissue. No evidence for bioaccumulation of glyphosate was observed following
repeated dosing of glyphosate. .Monsanto Company (1983a) reported minimal tissue retention and rapid
elimination of glyphosate fro'm several animal species including mammals, birds, and fish. Feeding
studies with chickens, cows, and swine showed that ingestion of up to 75 ppm glyphosate resulted in
nondetectable glyphosate residue levels (<0.05 ppm) in muscle tissue and fat. When milk and eggs from
cows and chickens fed diets containing glyphosate were analyzed, glyphosate residue was not detectable
(<0.025 ppm). It was concluded from these data that glyphosate does not bioaccumulate.
F. SUMMARY
Following oral or intravenous administration in rats, glyphosate is absorbed rapidly to about 30.4%
in males and 35.4% in females. Peak levels of glyphosate appeared in blood and bone marrow of
intraperitoneally treated rats 30 minutes post-administration. Blood levels fell rapidly following first-
order kinetics with a tw of about 1 hour for males and females. Bone marrow level of glyphosate
remained constant for 10 hours post-injection with a tl/2 7.6 hours for male rats and 4.2 hours for
females. Following an oral dose of 10 mg/kg, urinary excretion was 24-31% and fecal excretion was
68-75% which remained similar after repeated (14 daily doses of 10 mg/kg/day) oral doses. However,
after a single oral dose of 1,000 mg/kg/day, urinary excretion was 15-20% and fecal excretion was 80-
84%. Following intravenous administration in rats, 88-93% of administered glyphosate was excreted
in the urine and 5-10% in the feces. At all the above doses, absorption was relatively more in females
than in males. Aminomethylphosphonic acid was the only trace metabolite found in the feces of rats
orally treated with glyphosate indicating that glyphosate is metabolized to a certain extent
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Glyphosate Criteria Document
IV. HUMAN EXPOSURE,
Humans may be exposed to glyphosate from a variety of sources, including drinking water, food.
ambient air, occupational settings, and consumer products. This analysis of human exposure to
glyphosate is limited to drinking water, food, and ambient air because these media are considered to be
sources common to all individuals. Even in limiting the analysis to these three sources, it must be
recognized that individual exposures will vary widely based on personal lifestyles and on other factors
over which little control exists. Daily exposure and intake are profoundly affected by the area in which
a person lives, works, and travels; an individual's diet; and physiologic characteristics related to age, sex,
and health status. Individuals living in the same neighborhood or even the same household can
experience vastly different exposure patterns.
Information concerning occurrence of and exposure to glyphosate in the environment has been
presented in an interim draft report by Johnston et al. (1984). Information from that report relative to
glyphosate exposure from drinking water, food, and air is summarized in the following section.
A. "EXPOSURE ESTIMATION
1. Drinking Water . .
No data were found on levels of glyphosate in drinking water, although an interim tolerance of,
100 jig/L was established for residues of glyphosate in potable water (U.S. EPA, 1981). The maximum
intake of glyphosate from drinking water was estimated using this tolerance. Assuming .that a 70-kg
adult male consumes 2 liters of water/day, a maximum intake of 2.9 ug/kg/day was calculated.
However, these values do not account for variances in individual exposures or uncertainties in the
assumptions used to estimate exposure.
2. Diet
No data were found on the dietary intake of glyphosate in the United States. Tolerances for
glyphosate associated with raw agricultural commodities and in foods are listed in Table IV-1. However,
these data cannot be used to estimate typical dietary intake.
3. Air
No data were found on levels of glyphosate in ambient air. Therefore, the intake of glyphosate from
ambient air could not be estimated.
B. SUMMARY
Data on the intake of glyphosate from drinking water, food, and ambient air are insufficient for use
in determining which cf these sources is the major contributor to total intake.
IV-1
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Giyphosate Criieria Document
Table IV-1. Tolerances for Giyphosate
Food or commodity
Tolerance (ug/kg)
Food
Olives
Palm oil
«
Sugarcane, molasses
Raw agricultural commodity*
Alfalfa, fresh and hay
Almonds, hulls
Asparagus
Avocados
Cattle
Kidney
Liver
Citrus fruits
Coffee beans
Cottonseed
Cranberries
Goats
Kidney
liver
200
100
30,000
300
1,000
200
200
500
500
200
1,000
15,000
200
500
500
(continued)
TV-2
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Glyphos«..e' Criteria Document
Table IV-1. (continued)
Food or commodity
Tolerance (jig/kg)
Raw aericulturai commodity (com.)
Grain crops
Grapes
Grasses, forage
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Giyphosate Criteria Document
Table IV-1. (continued)
Food or commodity " Tolerance Qig/kg)
Raw agricultural commodity (com.)
Sheep
Kidney " .500
Liver 500
Soybeans 6,000
Forage _ 15,000
Hay 15,000
Sugarcane • 2,000
"For combined residues of glyphosate and its metabolite, aminomethylphosphonic acid.
"Negligible residue.
SOURCE: Adapted from U.S. EPA (1981); U.S. EPA (1986a).
IV-4
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Glyphosate Criteria Document
V. HEALTH EFFECTS IN ANIMALS
A. SHORT-TERM EXPOSURE
1. Lethality
The Monsanto Company (1982a) has reported that the oral LDSO for technical grade glyphosate (95?o
minimum assay) in rats is 5,600 mg/kg. and the dermal LDJO in rabbits is more than 5,000 mg/lcg.
Bababunmi et al. (1978) reported acute oral LDJO values of 4,873 mg/kg in the rat and 1,568 mg/kg
in the mouse. Acute intraperitoneal (i.p.) LDJO values were much lower (238 mg/kg in the rat, and 134
mg/kg in the mouse). Hyperemia in the lungs was the major adverse effect observed in glyphosate
poisoning. Symptoms of severe stress, accelerated breathing, elevated rectal temperature, occasional
asphyxial convulsive movements, and rigor preceded death.
2. Sub-acute Effects
Bababunmi et al. (1978) reported that daily i.p. administration of 15, 30,45, or 60 mg/kg to rats for
28 days resulted in reduced daily body weight gain; decreased blood hemoglobin; decreased red blood'
ceil count and hematocrit values; and elevated levels of serum glutamic-pyruvic transaminase and leucine*
amino peptidase during the study period
3. Dermal/Ocular Effects
No information was found in the published literature on the dermal or ocular effects of technically
pure glyphosate in humans. Application of glyphosate to Guinea pig skin produced in some animals
mild to severe irritation, erythema, edema, and necrosis beginning with the sixth exposure. Although
these results suggested some cumulative irritation potential, the response to a challenge dose indicated
no sensitization (Monsanto Company, 1983c).
B. LONGER-TERM EXPOSURE
In subacute studies reported by the Weed Science Society of America (1983), technical grade
glyphosate was fed to rats and dogs at dietary levels of 200. 600, or 2,000° ppm for 90 days. Assuming
daily consumption of 50 g food/kg body weight by rats and 30 g/kg by dogs (Arlington, 1972), this
corresponds to doses of about 10, 30, or 100 mg/kg/day, respectively, in rats and about 6, 18, or 60
mg/kg/day, respectively, in dogs. No significant differences between treated and control animals were
observed in mean body weight, food consumption, behavioral reactions, mortality, hematoiogy, blood
chemistry, or urinalysis, and no relevant gross or histopathologic changes were found (Weed Science
Society of America, 1983). No other details were provided.
A 90-day feeding study (Monsanto Company, 1987) was reported in Sprague-Dawley rats.
Glyphosate was administered in the diet at 1,000, 5,000 or 20,000 ppm levels. Neither mortality nor
treatment-related adverse effects were noted on body weights, food consumption, or clinical signs. An
increase in lymphocytes in low- and mid-dose males, and in total leukocytes in mid-dose males was
observed, but these changes were within the normal ranges when compared to concurrent controls.
Clinical chemistry findings included increased serum inorganic phosphorus and potassium values in both
sexes at ail tested doses, increased serum glucose in males at mid- and high-doses, and increased serum
V-l
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Glyphosace Criteria Document
BUN and alkaline phosphatase in males at the high-dose. No effeets were noted on organ weights. An
increase in chronic and active inflammation of the pancreatic,islets was observed in high-dose males.
Since this is a common finding in rats of this strain and age, the effect is not considered to be .
compound-related. Changes observed in the hematology, clinical chemistry, and urinalysis parameters
were slight, not dose-related, and not considered to be compound-related. Neither an effect level nor
a maximum tolerated dose (MTD) were established in this study,-
A 1-year chronic feeding study in dogs was reported (Monsanto Company, 1985). Glyphosate
(96.13% pure) was administered orally in gelatin capsules to three groups (6 dogs/sex/group) (strain not
specified) at 20, 100, and 500 mg/kg/day. All dogs survived until the termination of the study. Body
weights and food consumption were similar for control and treated groups. Neither ocular abnormalities
in the early part of the test period nor hematological abnormalities at 3,6, and 12 months after initiation
of the study were observed. Slight decreases in serum sodium and potassium concentrations in males
administered the mid- and high-doses, and in females administered the high dose, were observed only
. at the 3-month sampling period, but were considered toxicologically important. The apparent decreases >
in absolute and relative weights of pituitaries in mid- and high-dose male dogs were not correlated with
any histopathologic effects. Systemic NOAEL from this study is greater that 500 mg/kg/day.^
In a chronic feeding study, glyphosate admixed in the diet at 1,000, 5,000, and 30,000 ppm was
given to CD-I mice (50/sex/group) for 24 months (U.S. EPA, 1986b). Body weight and food
consumption were recorded weekly through the initial 14 weeks and biweekly thereafter. All survivors
at the end of the 24-month period were sacrificed, and organ weights were determined. A complete"
gross postmortem examination and histopathology study on selected tissues was carried out on all
animals. Based on food consumption over the 24-month period, the daily dietary levels of 1,000,5,000,
and 30,000 ppm in males correspond to glyphosate intakes of 111 to 250, 519 to 1,264, and 3,465 to
7,220 mg/fcg/day, respectively. The giyphosate dose ranges for females at daily dietary levels of 1,000,
5,000, and 30,000 ppm were 129-288, 690-1,322, and 4,232-9,859 mg/kg/day, respectively.
Mean body weights of high-dose males were generally lower than those of controls; the difference
was as much as 11% at week 102 of die study. Mean body weights in other treated groups were similar
to those of controls. No differences were observed in hematology parameters between control and test
groups. At terminal sacrifice, the mean absolute and relative weights of testes were elevated in the high-
dose group males, but not in the other dose groups. The nonneoplastic histopathologic changes in high-
dose male mice included hepatic centrilooular hypertrophy and necrosis of hepaiocytes. Chronic
interstitial necrosis and proximal tubule epithelial cell basophilia and hypertrophy of the kidneys were
observed in the high-dose females. The NOAEL for nonneoplastic chronic effects from this study is
5,000 ppm. Based on an average body weight of 20 g and an average dietary consumption of 3 g/day,
the 5,000-ppm dietary level corresponds to a dose of 750 mg/kg/day.
In a combined lifetime feeding and carcinogenicity study, Bio/dynamics, Inc. (198 Ib) administered
glyphosate in the diet to four groups of Sprague-Dawley rats (50/sex/dose) at dose levels of 3.1, 10.3,
or 31.5 mg/kg/day in males or 3.4, 11.3, or 34.0 mg/kg/day in females. Alter 26 months, control and
exposed animals were evaluated with respect to body weight gain, organ weights, organ/body weight
ratios, and hematologic and clinical chemistry parameters. No significant differences between control
and exposed animals were observed at any dose level. For nonneoplastic effects, 31 mg/kg/day is
considered to be the systemic NOAEL in this long-term feeding study in rats. Histopathological data
and evaluation of benign and malignant tumors for this study are further discussed in Section V.E
(Carcinogenicity).
V-2
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Glyph'oa-te Cnieria Docurr.eht'
A recent study (Stout and Ruecker, 1990) reported on the chronic effects of dietary giyphosate in
Sprague.-Dawley rats. Randomized groups (60 animals/sex/group) were administered commercial
giyphosaie (96.5% pure) in the diet at doses of 2.000, 8,000 and 20,000 ppm for a 24-month period.
Neither compound-related adverse toxic/clinical signs nor adverse growth and survival were noted. Body
weight changes were not significant in males during the study period but a significant decrease in body
weight gain occurred in high-dose females starting day 51 through month 20. This suggested a NOAEL
of 8,000 ppm (mid-dose) based on decreased body weight data.. Food consumption data revealed no
significant difference between the treated and control animals. Consumption of giyphosate based on the
target concentration were approximately 89, 362 and 940 mg/kg/day in males, and in females 113, 45
and 1183 mg/kg/day for the low-, mid-, and high-dose groups, respectively.
At terminal sacrifice, significant increases in cataracts and lens abnormalities were noted in high-
dose males (Stout and Ruecker, 1990). Hematology and clinical •chemistries did not reveal compound-
related changes. A significant decrease in urinary pH was noted in high-dose males at 18- and 24-month
sampling periods but females did not display this effect. High-dose 'males that either died or were
sacrificed on schedule revealed increased relative liver weights at interim (12 months) sacrifice and at
terminal (24 months) sacrifice. No other compound-related gross pathological findings were observed
in these males. Microscopic pathologic findings consisted of a significantly increased incidence of
inflammation of the gastric mucosa in the mid-dose females. In either sex there was no dose-related
increase in severity of the lesion. - The lesion was not considered compound related. The neoplastic^
effects described in this study are presented in Section V.E (Carcinogenicity).
C REPRODUCTTVEn'ERATOGENIC EFFECTS
—Bi0/dynamics, Inc. (198 la) investigated the reproductive toxicity of giyphosate in rats? The chemical
(98.7% pure) was administered in the diet at dose levels of 0,3,10, or 30 mg/kg/day to Sprape-Dawley
albino rats for three successive generations. Groups of 12 male and 24 female rats (F0 generation)
received test diets for* 60 days prior to breeding. Giyphosate administration was continued through
mating, gestation, and lactation for two successive litters (Fu, Ftb). Groups of 12 males and 24 females
from the Flb generation were retained at weaning for each dose level to serve as parental animals for the
succeeding generation.
The following indices of reproductive function were measured: fetal, pup, and adult survival; mean
parental and pup body weight and food consumption; and mating, pregnancy, fertility, and gestation
length. Necropsy and histopathologic evaluations were also performed. No compound-related changes
in these parameters were observed when the treated animals were compared to controls, although an
addendum (Bio/dynamics, Inc., 198la) to the pathology report for this study included an increase in
unilateral focal tubular dilation of the kidney in the male F3b pups (7/10 in treated animals compared
with 2/10 in concurrent controls) of dams treated with giyphosate at 30 mg/kg/day. According to the
authors, the historical control indices of tubular lesions varied markedly in male weanling rats. Based
on data from this three-generation reproduction study, the authors concluded that the highest dose tested
(30 mg/kg/day) had no adverse reproductive effects. However, in view of the observed kidney lesions
in the male F3b pups of dams treated with the highest dose, a more appropriate systemic NOAEL for this
study is 10 mg/kg/day. The LOAEL is 30 mg/kg/day based on renal effects observed in male F3b
weanlings.
The potential adverse effects of giyphosate were evaluated in a two-generation reproduction study
in Sprague-Dawley rats (Reyna, 1990). Giyphosaie was administered in the diet, ad libitum, to rats
(30/sex/group) at levels of 2,000, 10,000 and 30,000 ppm throughout the premating, mating, gestation,
V-3
-------
and lactation phases. After approximately 11 weeks of feeding, the animals were mated to produce the
F, generation. The Ft animals were weaned on lactation day 21, at which time 30 rats/sex/group were
selected to parent the next generation. After a growth period of about 14 weeks, these animals were
mated twice to produce F^ and Fa generations.
ff
Soft stools were observed in males and females of F0 and Ft generations ingesting glyphosate at
dietary level of 30,000 ppm but not at lower doses. In F0 animals prior to mating, body weights
decreased gradually with time to aboat 8% less than controls. The ¥l animals had 8-11% less body
weight than'controls aat weaning and this weight differential remained at the same level for the remaining
14-week post-weaning period. There were neither significant changes in the postnatal pup survival at
all tested intervals (days 0^. 4-14, and 14-21) in all generations (Ft, F^, and F^ nor in mating,
pregnancy, and fertility indices. Also, precoital and gestational lengths were unaffected. On lactation
day 0, the litter size of F[ dams was approximately two pups less than controls, and after the first Ft
mating, the litter size was one pup less than controls. However, a dose-related decrease in the litter size
was not apparent when F, parents were remated to produce the Fa litters. No treatment-related deaths
were observed. . .
*
The body weights of high-dose F^, male, and F^ male and female offspring were 4-11% below
controls on lactation day 14, and 11-14% below controls on lactation day 21 in all generations. In mid-
dose F. males and F^ male and female offspring, the body weights were 5.6-6.6% below controls. This
effect was not observed after lactation day 21. Since the effects observed in mid-dose animals wer$
small, transient, and not consistent in both sexes for all generations, they were considered to be of
questionable lexicological significance. The study author observed that the decrease in body weights
occurring during the latter pan of lactation (day 14-21) may have partly resulted from the consumption
of glyphosate-treated diet by the pups. There were no gross or microscopic pathological changes in
organs of parents or offspring related to ingestion of glyphosate in the diet. In this study, no treatment-
related renal effects were observed in male offspring (I/sex/litter) at 30,000 ppm (approximately 1,500
mg/kg/day) unlike in a previous study wherein renal tubular dilations were noted in F3b male weanlings
ingesting glyphosate in the diet at 30 mg/kg/day. Dietary glyphosate at 10,000 ppm (about 500
mg/kg/day) was considered to be the NOAEL (Bio/dynamics, Inc., 198la).
In a second study, pregnant CD rats were treated by gavage with single daily doses of glyphosate
at 300, 1.000, or 3,500 mg/kg/day on days 6 through 19 of gestation (Monsanto Company, I980b). At
the highest dose, breathing difficulty, reduced activity, diarrhea, stomach hemorrhages, weight gain
deficits, altered physical appearance, and mortality during treatment were observed in dams. Again, no
evidence of birth defects in the offspring was observed. Evidence of developmental toxicity in the form
of unossified stemebrae was noted in fetuses from dams that received the 3,500 mg/kg/day dose (U.S.
EPA, 1986b). Based on the results, the fetotoxicity and maternal toxicity NOAELs are each 1,000 mg/
kg/day. The teratogenic NOAEL is 3,500 mg/kg/day (the highest dose tested). .
Glyphosate was administered orally by gavage to pregnant Dutch Belted rabbits in single daily doses
at 75, 175, and 350 mg/kg/day on days 6 through 27 of gestation (Monsanto Company, 1980b).
Cesarean sections were performed on all surviving females on day 28 of gestation. No evidence of fetal
toxicity or birth defects in the offspring was observed. However, at the 350 mg/kg/day dose, nasal
discharge, diarrhea, and death were reported for the dams. This dose was toxic to females as evidenced
by altered physical appearance and mortality during treatment (U.S. EPA, 1986b). The NOAELs for
maternal toxicity and fetotoxicity indicated from the results 01 this study are 175 and 350 mg/kg/day,
respectively. The teratogenicity NOAEL is 350 mg/kg/day (the highest dose tested).
V-4
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Giyphcsaie Criteria Document
D. MUTAGENICITY
The Monsanto Company (I982a) reponed that glyphosate did net produce a mutagenic effect in
several microbiai test systems. A total of eight strains (seven bacterial and one yeast), including five
Salmonella typhimurium strains and one strain, each of. Bacillus subtilis, Escherichia coli, and
Saccharomyces cerevisiae (yeast), were tested. No mutagenic effects were observed in these strains.
Similarly, Njagi and Gopalan (1980) found that glyphosate did not induce reversion mutations in'
Salmonella cyphimurium histidine auxotrophs. Seiler (1977) found that nitrosated glyphosate was not
mutagenic.
Vyse and Vigfusson (1979) and Vigfusson and Vyse (1980) measured sister chromarid exchange in
two samples of lymphocytes exposed to glyphosate (Roundup) in vitro. The results (Table V-l) indicate
that high concentrations (0.65 to 6.5 mM) caused a statistically significant (p <0.00l) increase in sister
chromatid exchange. At the highest concentration tested (65 mM), however, no lymphocyte growth
occurred. Based on this limited study, the authors, concluded that glyphosate was, at most, slightly
mutagenic.
The potential for glyphosate to induce forward mutation at the hypoxamhine guanine phosphoribosyl
transferase (HGPRT) gene locus, as indicated by the induction of 6-thioguanine mutants, was determined
in cultured Chinese hamster ovary (CHO) cells (Monsanto Company, 1983d). The CHO cells were
treated with glyphosate at concentrations of 2-25 mg/mL both in the presence and absence of an Aroclor-
1254-induced rat liver homogenate activating system. While glyphosate was cytotoxic to CHO cells at
concentrations above 10 mg/mL, no mutagenic effect was observed, at die HGPRT gene locus at 10
mg/mL. It was concluded that glyphosate is not a mutagen in the mammalian system.
j» «r
«
The effect of glyphosate on chromosomal aberrations in bone marrow cells obtained from Sprague-
Dawley rats was investigated by the Monsanto Company (1983.d). The animals were injected i.p. with
a single"dose of glyphosate at 1,000 mg/kg and marrow cells obtained at 6, 12, or 24 hours after
treatment were observed for chromosomal aberrations. Glyphbsate did'not produce any clastogenic
effects at any of the treatment time points. However, this study was not considered adequate for the
successful assessment of this end point.
^
Glyphosate was negative in the mouse dominant lethal test (Monsanto Company, 1983d). No
primary DNA effects were seen with glyphosate in the Bacillus subnlis rec assay or in the rat hepatocyte
primary culture (HPQ/DNA repair assay at the highest nontoxic concentration of 0.125 mg/mL
(Monsanto Company, 1983d).
In summary, die above mentioned mutagenicity data reflect that the weight of evidence for
genotoxicity of glyphosate is negative.
E. CARCINOGENICrrY
Bio/dynamics, Inc. (198lb) conducted a 26-month study to assess the oncogenicity of glyphosate
(98.7% purity). The chemical was administered in the diet to four groups of Sprague-Dawley rats
(50/sex/group) at dose levels of 3.1,10.3, or 31.5 mg/kg/day for males, and 3.4,11.3, or 34.0 mg/kg/day
for females. After 26 months, animals were sacrificed and tissues were examined for histologic lesions.
A variety of benign and malignant tumors were observed in both the treated and control groups; the most
commonly occurring tumors were in the pituitary glands of both sexes and in the mammary glands of
females. The total number of rats from both sexes that developed tumors (benign plus malignant) was
V-5
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Ghphosate Criteria Document
Table V-l. Sister Girbmand Exchange Frequencies in Human Lymphocytes
Exposed to Roundup* In Vitro
Roundup ;oncentration
in test medium
(mg/'mL)
0.00
0.25
' 2.50
25.00
(mM)
0.00
0.65
6.50
65.00
Sister chromarid exchange
Subject No. 1
14.2 ± 2.9
16.5 ±3.7"
18.9 ±3.3"
No growth
(mean + SD>
Subject No. 2
17.1 ± 3.5
19.5 ± 2.9"
18.1 ±'3.2 ,
No growth
•Registered trademark.
."p <0.001.
SOURCE: Vigfusson and Vyse (1980).
V-6
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Glyyhcsoce Criteria Documenc
72/100 (low dose); 79/100 (middle dose); 85/100 (high dose); and 87/100 (control). An increased rate
of interstitial cell tumors of the testes was reported in the high-dose group when compared with
concurrent controls (6/50 versus 0/50), but this was not considered to be compound related, since,
according to the authors, the incidence of this tumor type was within the range found in historical
controls. Based on the data from this study, the authors concluded that the highest dose tested (31.5 or
34.0 mg/kg/day for males or females, respectively) was not carcinogenic in rats.
The possible occurrence of interstitial tumors in testes was discounted by the EPA (U.S. EPA,
1986b) after a careful consideration of all the pertinent data including the lack of a dose-dependent
response, lack of preneoplastic changes, and the similarity of response between the high-dose group and
the historical controls. A possible thyroid carcinoma in high-dose females was also discounted because
no effect of treatment on tumor latency or the combined incidence of adenoma and carcinoma was
apparent. This study suggests an oncogenic NOAEL of 31 mg/kg/day. However, in this study, there
was no evidence that the highest dose tested was a toxic or a MTD. Tumors might have been induced
if an MTD had been used. Although this study meets the U.S. EPA requirements for a chronic toxicity
study, it does not satisfy the EPA guidelines for a rat oncogenicity study (U.S. EPA, 1986c).
A chronic feeding study was carried out to assess the oncogenic potential of glyphosate in CD-I
mice (50/sex/group) given a glyphosate admixed of 1,000, 5,000, or 30,000 ppm in the diet for 24.
months (U.S. EPA, 19865); further details are presented in Section V.B. Generally, the neoplastic*
findings were similar to those commonly encountered in CD-I mice. Lymphoreticufar tumors tended,
to be more common in treated groups, especially treated females, than in controls, and renal tubular
adenomas occurred more frequently in males than in females. These changes, however, were not dose-
related and occurred sporadically. The Science Advisory Panel in 1986 reported that the kidney tumor
data in the male mice are equivocal because only a small number of tumors were found in any groups
including those at the highest dose level. The vast majority of pathologists who examined the
proliferation lesions in male control animals agreed that the lesions represented renal adenomas.
Therefore, the statistical analysis of the data should have included this information and adjusted for the
age of die animals. 9
Because of the equivocal nature of the oncogenic response in mice and lack of an acceptable study
in rats, the Agency requested a repetition of the carcinogenicity study in rats. A combined chronic
toxicity/carcinogenicity feeding study in rats was submitted by the manufacturer in 1990 (Stout and
Ruecker, 1990). In this study, randomized groups of Sprague-Dawley rats, 60/sex/dose (10/sex/dose
were interim-sacrificed at 12 months), were fed commercial technical glyphosate (96.5% pure) at dietary
levels of 2,000, 8,000, and 20,000 ppm for 24 months. The study averages for consumption of
glyphosate, based on the target concentrations, were approximately 89,362, and 940 mg/kg/day in males
and 113, 457, and 1,183 mg/kg/day in females for the low-, mid-, and high-dose groups, respectively.
Histopathological studies for neoplastic end points revealed a statistically significant increased incidence
of pancreatic islet cell adenomas in low-dose males but there was neither a dose-response relationship
nor progression to carcinoma. Similarly, C-cell adenomas in thyroid were slightly increased in male and
female mid- and high-dose groups with no dose-response relationship and no progression to carcinoma
in a dose-related manner. There was a slight dose-related increase in hepatocellular adenomas in males
but this was within the range of historical controls from the manufacturer's EHL, and there was no
progression of lesions from adenoma to carcinoma. The hepatocellular effect was not considered
compound related.
V-7
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aie Cr.ceria Document
to the high 'incidence of pancreatic islet cell adenomas in each.of the treated male groups in.
comparison-to concurrent controls', the U.S. EPA.has-recommended that the carcinogenic potential of
glyphosate be addressed Ijy the Peer Review Committee.
« \
F. SUMMARY
Few data on the health 'effects of glyphosate in mammals were found in the published literature.
Most information on the toxicity of this compound has been provided by the Monsanto Company. Oral
LDjo values have been reported to be 4,873 and 5,600 mg/kg in rats, and 5,600 mg/kg in mice. The
dermal LDJO in rabbits was reported to be greater than 5,000 mg/kg. Hyperemia'in the lungs has been
reported to be the most prominent effect, with severe stress, accelerated breathing, elevated temperature,
occasional convulsive movements, and rigor preceding death. Glyphosate may have a cumulative irrita-
tion potential but no skin sensitization in guinea pigs.
In a 90-day feeding study with rats and dogs, doses of glyphosate up to 100 mg/kg/day and 60 mg/
kg/day, respectively, produced no adverse changes in body weight, behavior, mortality, hemaiolbgy,
blood chemistry, or urinalysis. Similarly, in another 90-day feeding study in rats, dietary glyphosate up
to 20,000 ppm levels (about 1,000 mg/kg/day) produced no adverse effects. In a I-year feeding study
in which dogs ingested up to 500 mg/kg/day of glyphosate in their diet, an apparent decrease in the
absolute and relative weights of pituiiaries from dogs in the mid- to high-dose groups was observed but*
there were no correlating histopathology findings, and a LOAEL was not established. However, the^
study did indicate a NOAEL of more than 500 mg/kg/day.. In male mice fed diets containing 1,000 to
30,000 ppm of glyphosate for 24 months, centrilobular hypertrophy of liver cells and necrosis of
hepatocytes were observed at the high-dose level. In females, chronic interstitial necrosis and proximal
tubule epithelial cell basophilia and hypertrophy of kidneys were observed. This study indicated a
NOAEL of 750 mg/kg/day. In a lifetime feeding study in male and female rats, doses of glyphosate up
to 31.5 and 34.0 mg/kg/day, respectively, for about 26 weeks produced no significant effect on body
weight, organ weight, organ/body weight ratios, or hematologic and clinical chemistry parameters. A
recent 24-month feeding study in rats produced a significant decrease in .body weight gain in females
but not males starting day 51 of feeding through month 20. This suggested a NOAEL of 8,000 ppm
(mid-dose) based on body weight data. No other adverse effects—hematological, clinical, lexicological,
or histopathological—were noted.
In a three-generation study in rats, an increase in unilateral focal tubular dilation of the kidney in
male pups from the Fa generation of high-dose dams (30 mg/kg/day) was observed. The NOAEL for
this effect was 10 mg/kg/day. No effect on fertility was,noted. In a subsequent two-generation
reproduction study, rats were fed glyphosate in their diets up to 30,000 ppm, Some reduction in weight
gain in FQ, Fp and Fj generation animals of both sexes and soft stools in F0 and Fj animals of both sexes
occurred at the 30,000 ppm levels (but not lower). No other gross or histopathological effects were
seen. No renal tubular dilations were present in F2 weanlings.
Pregnant rats dosed with glyphosate on days 6-19 of gestation showed evidence of developmental
toxicity in the form of unossified stemabrae in fetuses from dams dosed at 3,500 mg/kg/day, as well as
altered physical appearance and mortality in dams. The maternal toxic NOAEL for this study is 1,000
mg/kg/day. A teratology study in rabbits showed no evidence of teratogenicity. The highest dose (350
mg/kg/day) was toxic to females as evidenced by altered physical appearance and mortality. No
treatment-related fetal effects were noted. The NOAELs for maternal toxicity and fetotoxicity are 175
and 350 mg/kg/day, respectively.
V-8
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Criteria Document
Glyphosate has been reported to be nonrnutagenic in a number of bacterial test systems and in one
yeast assay but has caused sister chromatid exchanges in human lymphocytes in vitro at high
concentrations. Glyphosate was negative for gene mutations in Chinese hamster ovary cells in the
presence or absence of rnicrosomal activation and for chromosomal aberrations in the mouse dominant
lethal test and the in vivo cytogenics assay. Glyphosate was also negative in the Bacillus subtilis DNA
rec assay and rat hepatocyte DNA repair assay.
A carcinogenicity study in rats that suggested the possible occurrence of interstitial tumors in testes
and thyroid carcinoma in female rats was critically reviewed by the EPA and discounted because of the
lack of dose-dependent responses, the lack of preneoplastic changes, the similarity of response between
the high-dose group and the historical controls, no effect of treatment on tumor latency, and no apparent
effect on the combined incidences of adenoma and carcinoma. Also, the highest dose tested was not
a MTD and, as such, the study was not considered a valid carcinogenicity study under EPA guidelines.
An oncogenicity study in CD-I mice also indicated no positive evidence for treatment-related carcino-
genic effects. Because of the lack of an acceptable rat carcinogenicity study and-the equivocal nature
of ohcogenic response in mice, the Agency requested a repeat of the rat carcinogenicity study. A new
24-month combined chronic toxicity/carcinogenicity rat feeding study has been evaluated at the U.S.
EPA. In this study, an increased .incidence of pancreatic jslet cell adenomas in low-dose males and C-
cell adenomas of the thyroid in mid- and high-dose animals of both sexes were observed, but there wast
no dose-response relationship. A slight dose-related increase in hepatocellular adenomas was also*
observed in males, but this was within the ran^e of historical controls. In this study, a progression of-
lesions from adenomas to carcinomas was not noted. In view of the high incidence of pancreatic cell
adenomas, the Agency has recommended that the carcinogenic potential of glyphosate be evaluated by
the Peer review Committee.
V-9
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Glyphosate Criteria Document." -
VI HEALTH EFFECTS EN HUMANS
•No reports were found in the av|ilable Literature on the health effects of glyphosate in humans.
VI-1
-------
O'.vohcsate Cr.ieria Document
VH. MECHANISMS OF TOXICTTY
A. EFFECTS ON MITOCHONDRIA
Olorunsogo et al. (1977) investigated the effect of glyphosate on mitochondrial energy-linked
functions. Mitochondria that were isolated from livers of rats 5 hours after intraperitoneal (i.p.)
administration of a single dose of 15, 30, 60, or 120 mg/kg glyphosate exhibited reduced acceptor
control ratios, enhanced ATPase activity, and stimulation of the rate of oxygen uptake. From these
findings, the authors suggested that an uncoupling of oxidative phosphorylarion in animal mitochondria
may be a. primary lexicological effect of glyphosate.
Olorunspgo et al. (1979a) administered single i.p. doses of 15, 30, 60, or 120 mg/kg glyphosate to
Wistar'rats (250 g). Exposure to glyphosate resulted in a dose-related decrease in respiratory control
ratios of isolated liver mitochondria (Table VE-1) and increased activity of ATPase and several dehydro-
genases (Table VIM). The -respiratory control ratio is the rate of adenosine diphosphate (ADP)-
stimulated respiration to that of the ADP-less respiration. Although the results of these studies show
a dose-related response on subtle biochemical parameters, it is not possible to derive a NOAEL or
LOAEL because of the difficulty in assessing the proportion of the in vivo dose that reached the live?
mitochondria.
t
Olorunsogo et aL (1979b) reported a significant inhibition of energy-dependent, phosphate-induced
swelling of isolated liver mitochondria 5 hours after administration of a single i.p. dose of glyphosate'
to rats. Mitochondria isolated from livers of rats (species not specified, presumably Wistar) following
single i.p. doses of 60, 120, and 240 mg/kg of glyphosate caused 20, 40, and 65% inhibition of
mitochondrial swelling, respectively, "when either sucdnate or be'ta-hydroxybutyrate was used as the
substrate.
Bababunmi et aL (1979) and Olorunsogo and Bababunmi (1980) examined the oxidative
phosphorylation uncoupling effect of glyphosate on isolated rat liver mitochondria and the inhibiting
effect of glyphosate on succinate-linked reduction of pyridine nucleoti.de in isolated rat liver
mitochondria. Their general conclusion was that the inhibitory effect of glyphosate may be due to its
uncoupling effect on oxidative phosphorylation in isolated liver mitochondria.
Olorunsogo (1982) studied the pattern of interaction of various concentrations of glyphosate with
membrane-bound nicotinamide nucleotide transhydrogenase in intact mitochondria isolated from rat liver.
Concentrations of glyphosate lower than 0.00015 mol had no significant effect (12% inhibition) on the
activity of the enzyme when the reaction was supported by energy generated from succinate oxidation.
Inhibition increased to 28 and 46% (maximum) as the concentration of (he herbicide was raised to
0.000312 and 0.00125 mol, respectively. Similar results were obtained when adenosine triphosphate
(ATP) was used as the energy source. According to Olorunsogo (1982), these observations indicate that,
like thyroxine (a known uncoupler of oxidative phosphorylation), glyphosate interacts with both oxidative
phosphorylation and energy-dependent transhydrogenase reactions.
VTT-1
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Giyphosate Cnieria Document
Table VII-1. Respiratory Control Ratios" of Mitochondria
Isolated From the Livers of Rats 5 Hours
After a Single Intraperitoneai Dose of Giyphosate
Dose of glyphosate
(mg/kg)
,
0
15
30
60
120
Respiratory control
ratio
•V
4.4510.49"
3.2510.56
3.0010.67
2.50±0.36
2.4510.24
% Decrease
27.0
32.6
43.8
46.0.
'Respiratory control ratio the rate of the ADP-stimulated respiration to that of the ADP-less respiration.
"Mean 1SD (n * 5). ' ;
SOURCE: Adapted from Otorunsogo et a! (1979a).
VH-2
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Giyphcsate Criteria Document
Table VH-2. Activities of Enzymes in Mitochondria Isolated From Livers
of Rats 5 Hours After a Single Intraperitoneal Dose of Glyphosate
Dose of
glyphosate
(me/kz'
Enzvme activities'
ATPase' ICDHC HBDH" GDHe SCH*
0
15
30
60
120
3.39±0.20*
10.98±0.18
14.33±0.20
•-17.54iO.24
' 19.64±0.27
3.75±0.26
3.79±0.25
3.90±0.21
4.71±0.11
4.17±0.10
5.14±0.31
5.20±0.34
5.81 ±0.27 .
5.94±0.29
6.16±0.28
4.00±0.28
4.17±0.30
4.57±0.35
4.91±0.21
5.59±0.26
6.24±0.17
6.89±0.20
7.10±0.19
7.68±0.19
7.94±0.22
•Mean ± SD (n = 5).
b Activity expressed as nmol inorganic phosphorus/mg protein/mirL
Tsocitrate dehydrogenase; activity expressed as umol NAD* reduced/mg
protein/min.
''Hydroxybutyrate dehydrogenase; activity expressed- as umol NAD* reduced/mg
protein/min. .... • •
*Glutamate dehydrogenase; activity expressed as umol NAD* reduced/mg
protein/min.
fSuccinate dehydrogenase; activity expressed as umol succinate/mg protein/min.
SOURCE: Adapted from Olomnsogo et al. (I979a).
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Tjiyphosate Criteria Document
B, SUMMARY .'.'..
Some reports on the mechanism of glyphosate toxicity indicate that giyphosate is capable of
uncoupling oxidative phosphorylation in isolated mitochondria. Five hours after administration of a
single i.p. dose of giyphosate (15 to 120 mg/kg) to rats, respiratory control ratios of isolated liver
mitochondria were reduced' as much as 46% and activities of ATPase and several dehydrogmases
were enhanced. Although a dose-related response was apparent, the information is not suitable for
the' derivation of a NOAEL or LOAEL based on one or more of these subtle biochemical effects
observed in isolated mitochondria.
vn-4
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GKphosate Criteria Document
. • Vm. QUANTIFICATION OF TOXICOLOGICAL EFFECTS
f
The quantification of toxicoiogical effects of a chemical consists of an assessment of
noncarcinogenic and carcinogenic effects. Chemicals that do not produce carcinogenic effects are
believed to have a threshold dose below which no adverse, noncarcinogenic health effects occor,
whereas carcinogens are assumed to act without a threshold.
A. PROCEDURES FOR QUANTIFICATION OF TOXICOLOGICAL EFFECTS
1. Noncarcinogenic Effects
In the quantification of noncarcinogenic effects, a Reference Dose (RfD), formerly called the
Acceptable Daily Intake (ADO. is calculated. The RfD is an estimate of a daily exposure to the
human population that is likely to be without appreciable risk of deleterious health effects, even if
exposure occurs over a lifetime. The RfD is derived from a No Observed Adverse Effect Level
(NOAEL), or Lowest Observed Adverse Effect Level (LOAEL), identified from a subchronic or
chronic study, and divided by an uncertainty factor (UF). The RfD is calculated as follows:
(NOAEL o
UncertintyFactors
i
Selection of the uncertainty factor to be employed in the calculation of the RfD is based on
professional judgment while considering the entire data base of toxicoiogical effects for the chemical
To ensure that uncertainty factors are selected and applied in a consistent manner, the Office of
Science and Technology (OST) employs a modification to the guidelines proposed by the National
Academy of Sciences (NAS, 1977, 1980) as follows:
• An uncertainty factor of 10 is generally used when good chronic or subchronic human exposure
data identifying a NOAEL are available and are supported by good chronic or subchronic
toxicity data in other species.
* Art uncertainty factor of 100 is generally used when good chronic toxicity data identifying a
NOAEL are available for one or more animal species (and human data are not available), or
when good chronic or subchronic toxicity data identifying a LOAEL in humans are available.
• An uncertainty factor of 1,000 is generally used when limited or incomplete chronic or
subchronic toxicity data are available, or when good chronic or subchronic toxicity data
identifying a LOAEL, but not a NOAEL, for one or more animal species are available.
The uncertainty factor used for a specific risk assessment is based principally on scientific
judgment rather than scientific fact, and accounts for possible incra- and interspecies differences.
Additional considerations not incorporated in me NAS/OST (formerly NAS/ODW) guidelines for
selection of an uncertainty factor include the use of a less-than-lifetime study for deriving an RfD,
the significance of the adverse health effect, and the counterbalancing of beneficial effects.
From the RfD, a Drinking Water Equivalent Level (DWEL) can be calculated. The DWEL
represents a medium-specific (i.e., drinking water) lifetime exposure at which adverse,
noncarcinogenic health effects are not expected to occur. The DWEL assumes 100% exposure from
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Glyphosate Criteria Document
drinking water. The DWEL provides the noncarcinogenic health effects basis for establishing a
drinking water standard: -For ingestion data, the DWEL is derived as follows:
DWEL = RfD * (body weight in kg) , __ mg/L
Drinking water volume in L/day
where:
Body weight = assumed to be 70 kg for an adult
Drinking water volume = assumed to be 2 L per day for an adulL
In addition to the RfD and the DWEL, Health Advisories (HAs) for exposures of shorter
duration (One-day, Ten-day, and Longer-term HAs) are determined. The HA values are used as
informal guidance to municipalities and other organizations when emergency spills or contamination
situations occur. The HAs are calculated using a similar equation to the RfD and DWEL; however,
the NOAELs or LOAELs are identified from acute or subchronic studies. The HAs are derived as
follows: i
HA = - . _.mgfl. (ramded
[UFO)1 x ( _ L/day) :
i
. Using the above equation, the following drinking water HAs are developed for noncarcinogenic
effects:
1. One-day HA for a 10-kg child ingesting 1 L water per day.
2. Ten-day HA for a 10-kg child ingesting 1 L water per day.
3. Longer-term HA for a 10-kg child ingesting 1 L water per day.
4. Longer-term HA for a 70-kg adult ingesting 2 L water per day.
The One-day HA, calculated for a 10-kg child, assumes a single acute exposure to the chemical
and is generally derived from a study of less than 7 days' duration. The Ten-day HA assumes a
limited exposure period of 1 to 2 weeks and is generally derived from a study of less than 30 days'
duration. The Longer-term HA is calculated for both a 10-kg child and a 70-kg adult and assumes an
exposure period of approximately 7 years (or 10% of an individual's lifetime). The Longer-term HA
is generally derived from a study of subchronic duration (exposure for 10% of an animal's lifetime).
2. Carcinogenic Effects
The EPA categorizes the carcinogenic potential of a chemical, based on the overall weight of
evidence, according to the following scheme:
• Group A: Known Human Carcinogen. Sufficient evidence exists from epidemiology studies to
support a causal association between exposure to the chemical and human cancer.
• Group B: Probable Human Carcinogen. Sufficient evidence of carcinogenicity in animals with
limited (Group Bl) or inadequate (Group B2) evidence in humans.
-------
'uts Criteria DOC u,i sent
• Group C: Possible Human Carcinogen. Limited evidence of carcinogenicity in animals in the
absence of human data.
• Group D: Not Classified as to Human Carcinogenicnv. Inadequate human and animal evidence
of carcinogenicity or for which no data are available.
• Group E: Evidence of Noncarcinogenicity for Humans. No evidence of carcinogenicity in at
least two adequate animal tests in different species or in both adequate epidemiologic
and animal studies.
If lexicological evidence leads to the classification of the contaminant as a known, probable, or
possible human carcinogen, mathematical models are used to calculate the estimate of excess cancer
risk associated with the ingestion of the contaminant in drinking water. The data used in these
estimates usually come from lifetime exposure studies in animals. To predict the risk for humans
from animal data, animal doses must be converted to equivalent human doses. This conversion
includes correction for noncontiguous exposure, less-than-lifetime studies, and for differences in size.
The factor thai compensates for the size difference is the cube root of the ratio of the animal and
human body weights. It is assumed that the average adult human body weight is 70 kg and that the
average water consumption of an adult human is 2 liters of water per day. ;
For contaminants with a carcinogenic potential, chemical levels are correlated with a
carcinogenic risk estimate by employing a cancer potency (unit risk) value together with the
assumption for lifetime exposure via ingestion of water. The cancer unit risk is usually derived from
a linearized multistage model, with a 95% upper confidence limit providing a low-dose estimate; this
means that the true risk to humans, while' not identifiable, is not likely to exceed the upper limit
estimate and, in fact, may be lower. Excess cancer risk estimates may also be calculated using other
models such as the one-hit, Weibull, logit, and probit There is little basis in the current
understanding of the biological mechanisms involved in cancer to suggest that any one of these
models is able to predict risk more accurately than any others. Because each model is based on
differing assumptions, the estimates that were derived for each model can differ by several orders of
magnitude.
The scientific data base used to calculate and support the setting of cancer risk rate levels has an
inherent uncertainty due to the systematic and random errors in scientific measurement. In most
cases, only studies using experimental animals have been performed. . Thus, there is uncertainty
when the data are extrapolated to humans. When developing cancer risk rate levels, several other
areas of uncertainty exist, such as the incomplete knowledge concerning the health effects of
contaminants in drinking water, the impact of the experimental animal's age, sex, and species; the
nature of the target organ system(s) examined; and the actual rate of exposure of the internal targets
in experimental animals or humans. Dose-response data usually are available only for high levels of
exposure, not for the lower levels of exposure closer to where a standard may be set. When there is
exposure to more than one contaminant, additional uncertainty results from a lack of information
about possible synergistic or antagonistic effects.
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G'yrhosate Criteria Document
0 >
B. QUANTIFICATION OF NONCARONOGENIC EFFECTS FOR GLYPHOSATE
i
1. One -da v Health Advisory
« *
No suitable information was found in the available literature for the determination of the One-
day- HA. It is therefore recommended that the Ten-day HA value (20,000 ug/L, calculated below) be
used. Thus, the One-day HA value is 20,000 ug/L. No existing guidelines or standards were found
for acute oral exposure to glyphosate.
2. Ten-dav Health Advisory
Table vni-l summarizes the teratology study in pregnant rabbits chosen to serve as the basis for
the determination of the Ten-day HA for glyphosate. In this study, pregnant rabbits received
glyphosate orally by gavage at doses of 75, 175, or 350 mg/kg/day on days 6-27 of gestation.
Cesarean sections were performed on all surviving animals on day 28 of gestation. No fetal toxicity
or teratogenicity was observed at these doses. The highest dose produced altered physical
appearance and mortality in females. No treatment-related effects were reported at lower doses. The
NOAEL identified in this study is, therefore, 175 mg/kg/day. While a developmental endpoint may
not be the most appropriate basis for deriving an HA for a 10-kg child, this study provides an extra,
margin of safety for the derivation of an HA.
a
f
Using this value, the Ten-day HA for a 10-kg child is calculated as follows:
Ten-day HA . <17J m^^ * <10 . n.50 mg/L (rounded to 20,000 p/L)
7 (100) x (1 Uday) .
where: .
175 mg/kg/day - NOAEL, based on absence of altered physical changes and
mortality in rabbits.
10 kg = assumed body weight of a child.
100 = uncertainty factor, chosen in accordance with NAS/OST
(formerly NAS/ODW) guidelines for use with a NOAEL
. from an animal study.
1 L/day = assumed daily water consumption of a child. '
3. Longer-term Health Advisory
No information was found in the available literature that was suitable for determination of the
Longer-term HA value for glyphosate. It is therefore recommended that the adjusted DWEL of
1 mg/L for a 10-kg child be used at this time as a conservative estimate of the Longer-term HA
value. Thus:
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Glyphosate Criteria Document
Table VTO-l. Summary of Candidate Studies for Derivation
of the One-day Health Advisory for Glyphosate
Exposure, NOAEL LOAEL
Species Route duration Endpoints (mg/kg/day) (mg/kg/day)
Reference
Rabbit Oral Gestation
gavage days 6-28
Physical
appearance,
mortality,
developmental
effects
Maternal
toxicity
Fetotoxicity
Teratogenicity
Monsanto
Company
(1980b)
175
350
350
VHI-5
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Glyphcsate Criteria Documem
(0-1 mg/fci/day) x (10 mg) , 1 (i.QOO o/L)'
1 L/day
where: -
. 0.1 mg/kg/day = NOAEL (see Section VHI.B.4, DWEL derivation).
10 kg = assumed body weight of a 10-kg child.
1 L/day = assumed daily water consumption of a 10-kg child.
D
The DWEL value of 4,000 ug/L is recommended as a conservative estimate for the Longer-term
HA for a 70-kg adult.
4. Reference Dose and Drinking Water Equivalent Level
«
Table Vin-2 summarizes the studies considered for calculating the RfD and DWEL. Trfe studjt
considered most suitable was the three-generation rat study (Bio/dynamics Inc.. 1981b). In this
study, the reproductive effects of glyphosate administered in the diet at dose levels of 3, 10, and 30
mg/kg were investigated over three generations. Although no adverse reproductive effects were
observed at the highest dose, the male weanlings of the F3b generation had more renal focal tubular
dilation than controls. The NOAEL from this study is 10 mg/kg/day. In a subsequent two-genera-
tion reproduction study in rats (Reyna, 1990), dietary ingestion of glyphosate at approximately 1,000
mg/kg/day did not produce any adverse effects. Reduction in body weights in adults and pups, and
soft stools, were present at the higher dose (1,500 mg/kg/day). This study suggests a NOAEL of
1,000 mg/kg/day. However, further Agency review is undergoing at the present time.
A chronic feeding study in mice (U.S. EPA, 1986b), in which glyphosate was administered daily
in the diet at doses of 1,000, 5,000, and 30,000 mg/kg for a period of 24 months, was not considered
as important as the three-generation rat study mainly because of the absence of data relating to the
effect on progeny. In this study, male mice treated at the 30,000 mg/kg dose generally had lower
body weights than those of the controls. Also, at the 24-month terminal sacrifice, the mean,
absolute, and relative weights of testes were elevated compared with those of controls. At this dose,
centrilobular hypertrophy of the liver and necrosis of hepatocytes were observed in male mice. In
females at the 30,000-mg/kg dose, chronic interstitial necrosis and proximal tubule epithelial
basophilia and hypertrophy of the kidney were observed. A NOAEL from this study is calculated as
750 mg/kg/day. A 1-year chronic feeding study in dogs (U.S. EPA, 1986b) was considered but was
found less appropriate than the three-generation rat study for the same reason (relating to (he absence
of data on the effect of glyphosate on progeny).
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Givphosate Criteria Document
Table yTH-2. Summary of Candidate Studies for Derivation of the DWEL for Glyphosate
p
Species
Rat
Rat
Mouse
Dog
Exposure
Route duration
Oral Three
(diet) generations
Oral Two
(diet) generations
Oral 2 years
(dietary
mix)
c
Oral 1 year
(geiatin
capsule)
NOAEL
Endpoints (mg/kg/day)
Reproductive 10
effect; fetal
effect; weanling
effect; gross
pathology;
liver, kidney
histopathology
Reduction in body 1,000
weights in adults
and pups; soft
stools
Body weight; 750
terminal gross and
histopathology;
effects on testes.
liver, and kidney
Serum sodium and . 500
potassium'
concentrations*,
pituitary weights
"LOAEL
(mg/fcg/day) Reference
30 Bio/dynamics
Inc. (1981a)
1.500 ' Reyna
(1990)
— U.S. EPA i
(1986b)
*
— U.S. EPA
(1986b)
vm-7
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Glyohosate Criteria 'Document
•• In this study, dogs were administered glyphosate orally in gelatin capsules at 20, 100, and 500
mg/kg/day." At the 3-month sampling period, a slight decrease in serum, sodium and potassium
concentrations was observed in male dogs.administered glyphosate at 100 and 500 mg/kg/day, and in
female dogs administered glyphosate at 500 mg/kg/day: In the male dogs dosed at 100 and 500 mg/
kg/day, there was an apparent decrease in the absolute and relative weights of pituitaries. This
effect, according to the EPA, needs_ further study (U.S. EPA, 1986b). A tentative NOAEL from this
study is 20 mg/kg/day. ' " . "
Using a NOAEL value of 10 mg/kg/day-derived from the three-generation rat study, the DWEL
is derived as follows:
Step 1: Determination of the Reference Dose (RfD)
.RfD - 10 myay - 0.1 mg/kg/day
100
where:
10 mg/kg/day = NOAEL, based on the absence of renal focal tubular dilation
in rats.
100 = uncertainty factor, chosen- in accordance with NAS/OST
(formerly NAS/ODW) guidelines for use with a NOAEL
from an animal study.
Step 2: Determination of the Drinking Water Equivalent Level (DWEL)
DWEL . (0.1 mg/kg/day) x (70 kg) a ^ mg/L (rounded w ^ ^
(2 L/day)
where:
0.1 mg/kg/day = RfD.
70 kg = assumed body weight of an adult
2 L/day = assumed daily water consumption of an adult
C QUANTIFICATION OF CARCINOGENIC EFFECTS FOR GLYPHOSATE
1. Characterization of Carcinogenic Potential
Applying the criteria described in EPA's guidelines for assessment of carcinogenic risk (U.S.
EPA, 1986c), glyphosate may be classified in Group E: evidence of noncarcinogenicity for humans.
This category is for substances with no evidence of carcinogenicity in at least two adequate animal
tests in different species or in both adequate epidemiologic and animal studies.
Vffi-8
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Giyphosate Criteria Document
2. Quantitative Carcinogenic Risk Estimates
e»
No quantitative carcinogenic risk estimates -are carried out at this time for glyphosatte because
there is evidence that glyphosate is not carcinogenic in animals or humans; in addition, the weight of
evidence for the mutagenic effects of this chemical is also negative.
D. EXISTING GUIDELINES AND STANDARDS
No other criteria, guidelines, or standards pertaining to glyphosate were found in the available
literature.
E. SUMMARY
The quantification of lexicological effects for glyphosate is summarized in Table VHI-3.
vm-9
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O'yphosate Catena Document
"Table Vm-3. Summary of Quantificatioft of.Toxicological Effects for Glyphosate ,
Drinking water
concentration
Value (ug/L) . Reference
One-day HA for 10-kg child —' _ —
Ten-day HA for 10-kg child 20,000 . U.S. EPA (1986a)
Longer-term HA for 10-kg child 1,000 Bio/dynamics, Inc.
(1981b)
a' *
Longer-term HA for 70-kg adult —b —
DWEL for 70-kg adult 4,000 Bio/dynamics, Inc.
(198Ib)
Excess Cancer Risk — —
The Ten-day HA value for a 10-kg child is taken as a conservative estimate
for the One-day HA.
"The DWEL value is taken as a conservative estimate for the Longer-term HA
value for a 70-kg adult
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Glyphcsate Criteria Document
IX. REFERENCES
Arrington LR. 1972. The laboratory animals. In: Introductory Laboratory Animal Science. The
Breeding, Care and Management of Experimental Animals. Danville, IL: Interstate Print i-j and
Publishers. Inc., pp. 9-11.
Bababunmi EA, Olorunsogo 00, Bassir 0.. 1978. Toxicology of glyphosate in rats and mice.
Toxicoi. Appl. PharmacoL 45:319-320. (Abstract.)
Bababunmi EA, Olorunsogo 00, Bassir 0. 1979. The uncoupling effect of N-
(phosphonomethyl)glycine on isolated rat liver mitochondria. Biochem. PharmacoL 28:925-927.
Bio/dynamics, Inc. 1981 a. A three-generation reproduction'study in rats with glyphosate-. Project
No. 77-2063 for Monsanto Co., St. Louis, MO. EPA Accession Nos. 245909 and 247793.
Bio/dynamics, Inc. 1981b. Lifetime feeding study of glyphosate (Roundup Technical). Project No.
77-2062 for Monsanto Co., St Louis, MO. EPA Accession Nos. 246617 and 24661 *.
CEH. 1985. Chemical Economics Handbook. Menio Park, CA: SRI International
*,
Hance RJ. 1976. Adsorption of glyphosate by soils. Pestic. Sci. 7:363-366.
I
Johnston P, Letkiewicz F, Borum D, Gambal N, Gemer G, et aL 1984. Occurrence of pesticides in
drinking water, food and air. Interim draft report Prepared by :JRB Associates, McLean, VA, for
Office of Science and Technology (formerly Office of Drinking Water), U.S. Environment^
Protection Agency, Washington, DC.
Khan SU. 1981. N-nitrosamine formation in soil from the herbicide glyphosate and its uptake by
plants. In: Scanlan RA, Tannenbaum SR, eds. N-Nitroso Compounds. Washington, DC:
American Chemical Society (ACS Symposium Series No. 174), pp. 275-287.
Khan SU, Young JC. 1977. N-nitrosamine formation in soil from the herbicide glyphosate. J.
Agric. Food Chem. 25:1430-1432.
Lewis RJ, Tatken RL, eds. 1980. Registry of toxic effects of chemical substances. 1979 edition.
VoL 1. Cincinnati, OH: U.S. Department of Health and Human Services, National Institute for
Occupational Safety and Health, p. 720. DHHS (NIOSH) Publication No. 80-111.
Meister RT, ed 1983. Farm Chemical Handbook. Willoughby, OH: Meister Publishing Co.,
P-C117.
Monsanto Company. 1980a. Technical bulletin for Roundup herbicide. Monsanto Agricultural
Products Company. 800 N. Lindbergh Blvd. St. Louis, MO. RU-3009-80.
Monsanto Company. 1980b. Additional toxicology studies submitted in support of the registration
of Roundup herbicide. Special report MSL-1147, EPA Accession number 242516.
Monsanto Company. 1982a. Material safety data sheet, glyphosate technical 800 N. Lindbergh
Blvd., SL Louis, MO. MSDS No. 1071-83-6.
DC-1
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Criteria Document
Monsanto Company-.- 1982b. Rodeo herbicide far aquatic'* vegetation management. Technical
manual, .St. Louis, MO. 82-L01. • • -' - - • •
-' * , ' ' -
- •* - *
Monsanto Company. I982c. The health and environmental safety aspects of Roundup herbicide:
An overview. St. Louis, MO. Roundup Herbicide Bulletin No. 3.
Monsanto Company. 1983a. Rodeo herbicide: Toxicological and environmental properties. St.
Louis, MO. Rodeo Herbicide Bulletin No. 1.
4
Monsanto Company. 1983b. Additional information submitted in support of Roundup herbicide and
glyphosate. Part D. A study of plasma and bone marrow levels of glyphosate following
intraperitoneal administration in the rat. ML-83-218. U.S. EPA Accession number* 251737, pp. 73-
74; 85.
Monsanto Company. 1983c. Additional information submitted in support of Roundup herbicide.
dermal sensitization and dermal absorption studies. Special report MSL-3279. EPA MRID 252142.
o
Monsanto Company. 1983d. Glyphosate mutagenicity studies. U.S. EPA "MRID 25137, Accession
numbers 4313010-14, 4313010-15, 4313010-16, 43130KM7.-4313010-18, 4313010-19, 4313010-20.:
i.
Monsanto Company. 1985. Twelve month study of glyphosate administered by gelatin capsules to
Beagle dogs. MS25069. EPA "MRID 260021, pp. 1-8.
Monsanto Company. 1987. 90-Day study of glyphosate administered in feed to Sprague-Dawley
rats ML-86-351/EHL86128. EPA *MRJOD 405594.01, pp. 1-7.
Monsanto Company. 1988a. The metabolism of glyphosate in Sprague-Dawley rats. Part L
Excretion and tissue distribution of glyphosate and its metabolism following intravenous and oral
administration, 86139 MSL-7215. EPA *MRID 407671-01, pp. 1-11, 15-21.
Monsanto Company. 1988b. The metabolism of glyphosate in Sprague-Dawley rats, Part H.
Identification, characterization, and quantitation of glyphosate and its metabolites after intravenous
and oral administration. MSL-7206. EPA *MRID 407671-02, pp. I-VII.
HAS. 1977. National Academy of Sciences. Drinking water and health. Washington, DC:
National Academy of Sciences.
NAS. 1980. National Academy of Sciences, National Research Council Drinking water and
health. VoL 3. Washington, DC: National Academy Press, pp. 77-80.
Njagi GDE, Gopalan HNB. 1980. Mutagenicity testing of some selected food preservatives,
herbicides and insecticides. Bangladesh J. Bot, 9:141-146. (abstract only).
Olorunsogo OO. 1982. Inhibition of energy-dependent transhydrogenase reaction by N-
(phosphonomethyl)glycine in isolated rat liver mitochondria. Toxicol Lett. 10:91-95.
Olorunsogo OO, Bababunmi EA. 1980. Inhibition of succinate-linked reduction of pyridine
nucleotide in rat liver mitochondria in vivo by N-(phosphonomethyl)glycine. ToxicoL Lett. 7:149-
152.
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GKphcsate Criteria .Document
Olorunsdgo OO; Bababunmi EA, Bassir 0. 1977. Toxicity of glyphosate. Proceedings of the 1st
IntemationaTCongress -on Toxicology. Plaa GL, Duncan WAM, eds. New York: Academic Press,
p. 597. (Abstract) .
Olorunsogo OO, Bababunmi EA, Bassir 0. I979a. Effect of glyphosate on rat liver mitochondria in
vivo. Bull. Environ. Contam. Toxicol. 22:357-364.
Olorunsogo OO, Bababunmi EA, Bassir 0. l?79b. The inhibitory effect of N-(phosRhonomethyl)-
glycine in vivo on energy-dependent, phosphate-induced swelling of isolated rat liver mitochondria.
Toxicol. Lett. 4:303-306.
Reyna MS. 1990. Two generation reproduction study with glyphosate in Sprague-Dawley rats.
Monsanto Agricultural Company. St. Louis, Missouri. MSL-10387. EPA *MRID 416215-01.
Rueppel ML, Brightwell BB, Schaefer J, Marvel JT. 1977. Metabolism and degradation of
glyphosate in soil and water. J. Agric. Food Chem. 25:517-528.
Seiler JP. 1977. Nitrosation in vitro and in vivo by sodium nitrite, and mutagenicity of nitrogenous
pesticides. Mutat Res. 48:225-236.
' *•
Shoval S, Yariv S. 1981. Infrared study of the-fine structures of glyphosate and Roundup:
Agrochimica 25:377-386. '
Sittig M. 1980. Glyphosate. In: Pesticide Manufacturing and Toxic Materials Control
Encyclopedia. Park Ridge, NJ: Noyes Data Corp., p. 441.
Sprankle P, Meggitt WF, Penner D. 1975a. Rapid inactivation of glyphosate in the soil. Weed Sci
23:224-228.
Sprankle P, Meggitt WF, Penner D. 1975b. Adsorption, mobility, and microbial degradation of
glyphosate in the soil Weed Sci 23:229-234.
Stout LD, Ruecker FA. 1990. Combined Chronic Toxicity/Carcinogeniciry - Rats. MSL-10495.
EPA *MRID No.:4I6438-01 (Volumes 1-6), pp. 1^6.
Torstensson NTL, Aanrisepp A. 1977. Detoxification of glyphosate in soil. Weed Res. 17:209-212.
U.S. EPA. 1981. U.S. Environmental Protection Agency. Code of Federal Regulations. 40 CFR
150-189, p. 512; July 1.
U.S. EPA. 1986a. U.S. Environmental Protection Agency. Code cf Federal Regulations. 40 CFR
180.364; July 1.
U.S. EPA. 1986b. U.S. Environmental Protection Agency. Guidance for the registration of
pesticide products containing glyphosate as the active ingredient Case No. 0178, June 1986. "PSD-
HC-8723 Nos. 0153374, 0153376, 46363, 46362,132681, 137640,0132683, 0132686,130406.
U.S. EPA 1986c. U.S. Environmental Protection Agency. Guidelines for carcinogenic risk
assessment Fed. Reg. 51(185): 33992-34002; September 24.
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Glyphosate'Criteria Document
. Vyse ER. 1980. The effect of the .pesticides Dexon, Captan, and Roundup, on
sister-chromaud exchanges in human lymphocytes in vitro. 'Muiat Res. 79:53-57.
"Vyse ER, Vigfusson NV. 1979. Pesticide induction of SCE in human lymphocytes jn vitro.
Genetics 91:5133-5134. (Abstract.)
Weed Science Society of America. 1983. Herbicide Handbook. 5th Ed. Champaign, E.: Weed
Science Society of America, pp. 258-263. •
WSndhoIz M, Buhawari S, Bhumeni RF, Otterbein ES, eds. 1983. The Merck Index. 10th Ed.
Rahway, NJ: Merck and Company, p. 648.
Worthing CR, ed. 1979. The Pesticide Manual: A World Compendium. 6th Ed. Croydon: British
Crop Protection Council, p. 292.
Young JC,. Khan SU. 1978. Kinetics of nitrosation of the herbicide glyphosate. J. Environ. Sci
Health 813:59-72.
•PSD-HC-8723 numbers and MRID numbers refer to data accessed from EPA's Confidential
Business Information. >
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