CHEMICAL NAME: GLYPHOSATE Isopropylamine salt of N-(phosphonomethyl)
CAS REGISTRY NUMBER: 1071-83-6
CHEMICAL FAMILY: Phosphonate/organic phosphorus compound
MOLECULAR FORMULA: C3 H8 NO5 P
DESCRIPTION: Colourless or white, odourless crystals
USAGE: A Schedule 5 herbicide in the form of the mono(isopropyl ammonium) salt. A
broad spectrum (non selective) post-emergent plant growth regulator used for the control
of grasses, sedges and broadleaved weeds.
A systemic herbicide that translocates to the roots of plants. Used as the active
constituent in many commercial herbicide products. Formerly a Monsanto-held patent,
glyphosate products are now formulated by a number of pesticide producers. Used in
forestry, farming and pastoral activities, local councils, weed control and transport
agencies, as well as domestic and industrial uses.
HEALTH EFFECTS: HUMAN AND TEST ANIMAL DATA
Short Term (Acute Toxicity)
- Acute Toxicity (standard animal tests) : Oral Toxicity: low
LD50 (rat, oral): 4873 mg/kg. LD50 (mouse, oral): 1568 mg/kg.
Lethal oral doses produce severe stress, breathing difficulties, blood in the lungs,
convulsions and death.
LD50 (rabbit, dermal): Greater than 5000 mg/kg.
LC50 (rat): greater than 12.2 mg/kg in air (4 hour exposure)
- Can cause slight skin irritation, severe eye irritation. Dust may cause mild to moderate
irritation of nose and throat.
- Toxicity of glyphosate formulations may be due to presence of surfactants and other
Long Term (Chronic Toxicity)
- No chronic effects from human exposure reported in peer reviewed literature.
- Mouse feeding studies noted non-neoplastic changes including necrosis of hepatocytes
male mice and hypertrophy in female mice. (Non-cancerous liver damage)
- potential for adverse human health impacts of glyphosate formulations requires more
- Long term animal studies did not show carcinogenic activity.
- No information on human cancer risk is available.
- Glyphosate is readily nitrosated to N-nitrosoglyphosate. Whilst this compound has not
been assessed for carcinogenicity potential, at least 3/4 of another 120 N-nitroso
compounds showed carcinogenic potential. Nitrosation occurs in the stomach by reaction of
nitrite in human saliva. Standard carcinogenic tests using rats would not detect this
effect since rats do not secrete nitrite in their saliva.
- In 1986, the oncogenic potential of glyphosate was not fully understood. A review of a
mouse cancer study noted a slight increase in renal tubular adenomas and a one- year
feeding study in dogs observed a reduction of weight of pituitary gland in mid to high
doses. The United States Environment Protection Agency reveiwed thses studies and
concluded that the mice feeding study did not represent a safety concern because such high
doses of glyphosate had been administered to the test animals. (up to 3% of total diet).
They did require an additional rat study conducted at high dose levels.
- In 1991, following review of the new rat study, the US EPA placed glyphosate in Group E.
Evidence of non-carcinogenciity for humans.
- Animal studies did not produce any effects. Diets of up to 30 mg/day did not produce any
reproductive effects in male or female rats, over three generations. No teratogenic
effects were observed in rabbits given up to 350 mg/kg/day on days 6-27 of pregnancy.
Toxic effects noted at the highest dose in both treated animals and their offspring.
- No information on human reproductive risk is available.
- Not mutagenic in a standardised series of tests using bacteria, cultured mammalian cells
and whole animals. One study showed very weak mutagenic activity in an in vitro mammalian
- No information on human genetic risk.
Damage to cell structure and function
- Glyphosate, or some additive to commercial glyphosate products, may cause damage to DNA
via sister chromatid exchange.
- Glyphosate can affect the capacity of cells to produce energy. This occurs due to
disruption of cell membrane structure.
- Further investigation of potential for cell and sub-cellular impacts is required
- All commercial pesticide products are mixtures of chemical compounds. They contain the
active constituent/s (a.i.) and other compounds such as solvents, surfactants, lubricants,
preservatives, solubilizers and suspending agents. They may also contain impurities and/or
contaminants. Some commercial glyphosate products contain the solvent POEA, which is
contaminated with the carcinogen 1,4-dioxane, a common solvent used in laboratories and
contained in many consumer products. According to the manufacturer, the levels of this
contaminant are kept below 1 part per million ( ppm). Another contaminant is
N-Nitrosoglyphosate. According to the manufacturer, levels of this contaminant are kept
below 0.1 ppm.
- No information is available on the human toxicity of pesticide mixtures containing
glyphosate. It is often mixed with other pesticides.
HEALTH EFFECTS: WILDLIFE
The US EPA regards glyphosate as being slightly toxic to birds, aquatic vertebrates and
fish and moderately toxic to embryo and larvae.
- Acute toxicity to freshwater fish: Rainbow trout 86 mg/L.
- Chronic toxicity to freshwater fish: Fathead minnow with maximum threshold concentration
(MATC). >25.7 mg/L.
- Avian toxicity (reproductive study): Mallard ducks > 1000ppm.
- The use of glyphosate for vegetation control and the resulting decreased habitat
complexity caused a decrease in invertebrate populations and songbird numbers (especially
insectivores). One US study found the total abundance of songbirds was 36% lower on
clear-cut treated with herbicides for at least three years. The effect related to the
complexity of vegetation.
Toxicity to wildlife has mainly focussed on its acute toxicity to frogs. The Final
Report, Acute toxicity of a herbicide to selected frog species investigated the
toxicity of technical grade glyphosate and the glyphosate-based herbicide, Roundup
360. The method used was through acute bioassays with frog species common to the
south-west of Western Australia. The report found that:
- technical grade glyphosate and Roundup 360 can be acutely toxic to adult frogs and
tadpoles in laboratory bioassays
- tadpoles were many times more sensitive to the herbicide formulation tested than adult
- tadpoles were approximately an order of magnitude more sensitive to the formulation than
to technical grade glyphosate
- the above results and the results of other studies reported in the literature tend to
suggest that the surfactant used in the formulation is more harmful to aquatic animals
than the glyphosate
The report also stated that:
- the acute toxicity value ( 48 hour LC50 or Lethal Concentration) to the juvenile Crinia
insignifera was 51.8 mg/L for Roundup 360 (the commercial formulation
containing the solvent)
- the acute toxicity value ( 48 hour LC50 or Lethal Concentration) to the juvenile Crinia
insignifera was 83.6 mg/L for glyphosate alone
- the toxicity of Roundup to fish changes significantly with temperature and pH,
with greatest toxicity at high temperature and pH.
- a potential hazard exists for frogs and tadpoles in shallow water bodies
- further study is required to determine the actual concentrations and persistence of the
formulation in aquatic environments.
As a result of this study, commercial herbicide products containing the herbicide
glyphosate have been reformulated, with the toxic surfactant replaced by another
Limitations of the study : Replicating real world conditions in a laboratory is
impossible and as a result, laboratory studies can only provide a guide to toxicity
potential, not a definitive prediction. Professor Tyler of the University of Adelaide
- The WA toxicity trial involved placing the animals in an exposure chamber where there
would be some skin contact with the solution. However, under normal application in
the environment, the application method (of boom spraying) may result in atomised spray,
which may increase overall exposure potential for the animals.
- All bioassays were conducted at 20 +/- 2 degrees C under ambient laboratory light.
Temperatures in real world conditions may be as high as 42 degrees C (in the Northern
Territory) and certainly well above 30 degrees C in northern NSW summer months.
- The WA study looked at three frog species, with the bulk of the investigation focussed
on two species, Crinia insignifera and Litoria moorei. Under real world
conditions, many thousands of species of amphibians, invertebrates and other aquatic
creatures may be exposed to herbicides and risks to the viability of their communities is
not well understood. The studies have not been done.
- Australias biodiversity is well documented and to assert negligible risk to the
environment based on a small laboratory study on two localised frog species is not
- The WA study investigated acute poisoning potential only. No attempt was made to
investigate sub-lethal, chronic, reproductive, endocrinal or immunological effects, which
may also pose significant risks to the viability of aquatic communities.
- The WA study did indicate a 48 hour LC50 of 83.6 mg/L for glyphosate alone for Crinia
insignifera. This is a significant level if reproduced by normal applications in
the environment. Thus it is not just the formulation that may pose unacceptable risks to
wildlife. The data generated by the WA study indicates both commercial formulation and
the active constituent alone pose risks.
ENVIRONMENTAL IMPACTS: PLANT RESISTANCE
Australian research reports that fescue and perennial ryegrass cultivars, soybean and
convolvulus arvenis L. Lines displayed varying degrees of resistance to glyphosate. Genetic
engineering of crops such as soy now allows this and other commercially important food
crops to be sprayed with glyphosate, thus extending the potential global market for
ENVIRONMENTAL FATE AND TRANSPORT
Elimination, Bioaccumulation and Residues in Food and Animals.
- Slowly absorbed through the digestive system and rapidly eliminated. A urine test for
glyphosate in urine is available.
- Does not bio-accumulate in animal tissue but residues can be detected after exposure.
Glyphosate and its metabolite, aminomethylphosphonic acid (AMPA) have been identified in
the tissues, urine and faeces of rats and rabbits, in the liver in poultry, pigs and
cattle and the kidney of pigs and cattle. Has been detected in rice.
The persistence of glyphosate in the environment is variable. It is strongly
bound to clay particles and is considered moderately persistent in soil. Degradation via
microbial action is moderately slow. Half lives range from a few days to several months or
years. The more sand in the soil, the slower the inactivation via the bounding to clay.
Application of glyphosate to sandy loam resulted in weakening of subclover planted 120
days after application. A significant decrease in nodule numbers and root weights of the
plants was observed. This indicated that breakdown of glyphosate in soils with a high sand
content is slow. Study recommended care in advocating glyphosate use in soils with high
(>80%) sand content.
Nitrosation: N-nitrosoglyphosate was generated in soils treated with sodium nitrate (20
ppm) and glyphosate (740 ppm) at elevated levels. The highest level generated was noted in
soil of low organic matter and clay content. The formation of N-nitrosoglyphosate was not
observed in soils treated with lower levels, nitrite nitrogen (2ppm) and glyphosate
The manufacturer claims that the product is completely biodegradable, breaking down
into natural products in both soil and water. Stated half-life of 60 days in
the soil, a time frame described as rapid by manufacturer. Other information indicates
that breakdown time is extremely variable from a half-life of 24 days in forest soils in
Ontario to 249 days in Finland.
Very little leaching capacity. Low potential to contaminate ground water as it is
tightly bound to soil
Glyphosate and its metabolites are considered as residues of concern in plants. Maximum
Residue Limits (in mg/kg or parts per million/ppm) have been set for a number of
GENETICALLY ENGINEERED RESISTANCE TO GLYPHOSATE
Resistance has been genetically engineered into food crops such as soya beans so that
this core food crop can be sprayed with glyphosate without killing it. This means that up
to 200 times more glyphosate residue may be present in soy-based foods.
MANUFACTURER AGREES TO CHANGE ADS
In the USA, Monsanto has agreed to change its advertisements for glyphosate-based
products. As part of the agreement, Monsanto will discontinue the use of the terms
"biodegradable" and "environmentally friendly " in all advertising in
New York State.