Was it here I saw someone screaming a couple weeks ago about glyphosate,
"Roundup", being a dangerous organo-phosphate, ala "Malathion" and
several military "nerve-agents"?  Anybody care for real information?
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                      E  X  T  O  X  N  E  T
                   EXTENSION TOXICOLOGY NETWORK
A Pesticide Information Project of Cooperative Extension Offices
at Cornell University, Michigan State University, Oregon State
University, and University of California at Davis.  Major support
and funding was provided by the USDA/Extension Service/National
Agricultural Pesticide Impact Assessment Program.
Revised 5/94.
EXTOXNET primary files maintained and archived at Oregon State
University.
                       Glyphosate
TRADE OR OTHER NAMES
     Trade names for products containing glyphosate include
Roundup, Rodeo, and Pondmaster.  It may be used in formulations
with other herbicides.
INTRODUCTION
     Glyphosate is a broad-spectrum, non-selective systemic
herbicide  It is useful on essentially all annual and perennial
plants including grasses, sedges, broad-leaved weeds and woody
plants. It can be used on non-cropland and among a great variety
of crops.
     Glyphosate is usually formulated as an isopropylamine salt.       <-
While it can be described as an organophosphorus compound,             <-
glyphosate is not an organophosphate ester but a                       <-
phosphanoglycine, and it does not inhibit cholinesterase               <-
activity.                                                              <-
     Glyphosate is a general use pesticide.
TOXICOLOGICAL EFFECTS
Acute Toxicity
     Glyphosate is a moderately toxic herbicide and carries the
signal word WARNING on the label. Even though the LD50 values
show the compound to be relatively non-toxic it can cause
significant eye irritation. The toxicity of the technical product
(glyphosate) and the formulated product (Roundup) is nearly the
same.  The acute oral LD50 in the rat is 5,600 mg/kg.  Other oral
LD50 values for glyphosate are 1,538 to greater than 10,000 mg/kg
for mice, rabbits mg/kg, and goats (1, 5).
     In a number of human volunteers, patch tests produced no
visible skin changes or sensitization.
Chronic Toxicity
     Subchronic and chronic tests with glyphosate have been
conducted with rats, dogs, mice, and rabbits in studies lasting
from 21 days to two years.  With few exceptions there were no
treatment-related gross (easily observable) or cellular changes
(5).  In a chronic feeding study with rats, no toxic effects were
observed in rats given doses as high as 31 mg/kg/day, the highest
dose tested.  No toxic effects were observed in a chronic feeding
study with dogs fed up to 500 mg/kg/day, the highest dose tested
(8).  Mice fed glyphosate for 90 days exhibited reduced body
weight gains. The lifetime administration of very high amounts of
glyphosate produced only a slight reduction of body weight and
some microscopic liver and kidney changes.  Blood chemistry,
cellular components, and organ function were not affected even at
the highest doses.
     Hens fed massive amounts over three days and again 21 days        <-
later showed no nerve related effects.                                 <-
Reproductive Effects
     Most of the field and laboratory evidence shows that
glyphosate produces no reproductive changes in test animals.  It
is unlikely that the compound would produce any reproductive
effects in humans.
Teratogenic Effects
     In a teratology study with rabbits, the maternal NOEL was
175 mg/kg/day and no developmental toxicity was observed in the
fetuses at the highest dose tested (350 mg/kg/day) (8).
     Rats given doses up to 3,500 mg/kg on days 6 to 19 of
pregnancy had offspring with no teratogenic effects, but other
toxic effects were observed in both the mothers and the fetuses. 
No toxic effects to the fetuses occurred at 1,000 mg/kg/day.
Mutagenic Effects                                                      <-
     The compound does not cause mutations in microbes.  The
tests on eight different kinds of bacterial strains and on yeast
cells were all negative.  The compound poses little mutagenic
risk to humans (6).
Carcinogenic Effects                                                   <-
     Rats and dogs and mice fed glyphosate over a wide range of
doses showed no cancer related effects directly due to the
compound (4).  EPA has stated that there is sufficient evidence
to conclude that glyphosate is not carcinogenic in humans (8).
Organ Toxicity                                                         <-
     Glyphosate caused no changes in the rate of body weight
gain, in blood, nor in kidneys or liver.  The studies were
conducted at doses up to 500 mg/kg (3).
Fate in Humans and Animals
     Glyphosate is poorly absorbed from the digestive tract and        <-
is largely excreted unchanged by mammals.  Ten days after              <-
treatment there were only minute amounts in the tissues of rats        <-
fed glyphosate for three weeks (3).                                    <-
     Cows, chickens, and pigs fed small amounts had undetectable
levels (less than 0.05 ppm) in muscle tissue and fat.  Levels in
milk and eggs were also undetectable (less than 0.025 ppm). 
Nearly all glyphosate residues were rapidly eliminated by fish
that had been exposed for 10 to 14 days once these fish were
transferred to glyphosate-free water.  Glyphosate has no
significant potential to accumulate in animal tissue (9).
ECOLOGICAL EFFECTS
     Glyphosate is only slightly toxic to wild birds.  The LC50        <-
in both mallards and bobwhite quail is greater than 4,500 ppm. 
The bioaccumulation factor in chicken muscle, fat, eggs, and
liver was as low as 1/10,000 (4).
     Glyphosate is practically non-toxic to fish.  However,            <-
Roundup was more toxic to fish than was glyphosate.  In rainbow
trout, for instance, the 96-hour LC50 was 8.3 mg/l with Roundup
and 38 ppm with glyphosate. The LC50 for glyphosate was 120 mg/l
for bluegill sunfish. An additive used in the Roundup formulation
(modified tallow amine used as a surfactant) is apparently more
toxic to fish than many common surfactants.  For this reason, the
formulation for use in aquatic situations (Rodeo) omits this
ingredient. The surfactant is used to allow the compound to
readily dissolve in solution and to keep the compound from
balling up on the leaf surface.
     There is a very low potential for the compound to build up        <-
in the tissues of aquatic invertebrates or other aquatic
organisms.  Glyphosate is relatively non-toxic to honeybees.  Its
oral and dermal LD50 is greater than 0.1 mg/ bee (7).
ENVIRONMENTAL FATE
     Glyphosate is highly adsorbed on most soils especially those
with high organic content.  The compound is so strongly attracted
to the soil that little is expected to leach from the applied
area.  Microbes are primarily responsible for the breakdown of
the product. The time it takes for half of the product to break
down ranges from 1 to 174 days.  Because glyphosate is so tightly
bound to the soil, little is transferred by rain or irrigation
water.  One estimate showed less than two percent of the applied
chemical lost to runoff (4).  The herbicide could move when
attached to soil particles in erosion run-off. 
Photodecomposition plays only a minor role in environmental
breakdown.
     In water, glyphosate is strongly adsorbed to suspended
organic and mineral matter and is broken down primarily by
microorganisms also.  Its half-life in pond water ranges from 12
days to 10 weeks.
     Glyphosate may be extensively metabolized by some plants
while remaining intact in others (2).  Once in the plant tissue,
the chemical is translocated throughout the plant, including to
the roots.
Exposure Guidelines:
NOEL (rabbit):  175 mg/kg/day
HA:  0.7 mg/l (lifetime)
ADI:  0.03 mg/kg (EPA)
-- 0.3 mg/kg (WHO)
LEL:  300 mg/kg/day (rabbit)
Physical Properties:
CAS #:  1071-83-6
Chemical name:  N-(phosphonomethyl) glycine
Chemical class/use:  Phosphanoglycine herbicide
Solubility in water:  900,000 mg/l
Solubility in other solvents:  insoluble in common organics
Melting Point:  200 degrees C
Vapor Pressure:  negligible (Monsanto)
Dissociation values:  2.27 (pKa)
Partition Coefficient: 0.17 x 10 to the minus 2 power at 20 ppm; 
0.6 x 10 to the minus 3 power at 100 ppm
BASIC MANUFACTURER
Monsanto Company
800 N. Lindbergh Blvd.
St. Louis, MO 63167    Telephone: 314/694-1000
Emergency: 314/694-4000
Review by Basic Manufacturer:
Comments solicited:  November, 1992
Comments received:  November, 1992
REFERENCES
(1)  National Library of Medicine (1992).  Hazardous Substances
Databank.  TOXNET, Medlars Management Section, Bethesda, MD.
(2)  Grossbard, E. and D. Atkinson, Editors (1985).  The
Herbicide Glyphosate, Butterworths, Boston, MA.
(3)  U.S. Environmental Protection Agency (1987).  Health
Advisory, Office of Drinking Water.
(4)  Forest Service (1984).  Pesticide Background Statements,
Vol. I Herbicides.  United States Dept. of Agriculture,
Agriculture Handbook No. 633.
(5)  Monsanto Company (1985).  Toxicology of Glyphosate and
Roundup Herbicide, Department of Medicine and Environmental
Health, St. Louis, MO.
(6)  Stevens, James T. and Darrell D. Sumner. 1991. Herbicides in
Handbook of Pesticide Toxicology Volume 3, Cases of Pesticides. 
Wayland J. Hayes and Edward R. Law editors.  Academic Press, NY.
(7)  The Agrochemicals handbook.  1991.  The Royal Society of
Chemistry, Cambridge, England.
(8)  U.S. Environmental Protection Agency (1992).  Pesticide
Tolerance for Glyphosate.  Federal Register 57 (49): 8739-40.
(9)  Malik, J., G. Barry and G. Kishore.  1989. Minireview: The
herbicide glyphosate.  BioFactors 2 (1): 17-25.
     This PIP is part of the EXTOXNET Pesticide Information
Notebook.  For more information, contact the Pesticide Management
Education Program, Cornell University, 5123 Comstock Hall,
Ithaca, N.Y.  14853-0901.
DISCLAIMER:  The information in this profile does not in any way
replace or supersede the information on the pesticide product
label/ing or other regulatory requirements.  Please refer to the
pesticide product label/ing.
... Rap is to music as Etch-A-Sketch is to art.  
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