|Chemical Abstract Number (CAS #)||
|Synonyms||Glyphosate||N-(Phosphonomethyl)glycine, isopropylamine salt||Roundup
||EPA Method 547|
Link to the National Library of Medicine's Hazardous Substances
Database for more details
on this compound.
|Use|| NON-SELECTIVE, NON-RESIDUAL POST-EMERGENCE HERBICIDE.
Very effective on deep-rooted perennial species.
Non-selective systemic herbicide, for control of a great variety of annual, biennial, and
perennial grasses, sedges, broad-leaved weeds, and woody shrubs. Used in fruit orchards,
vineyards, conifer plantations, and many plantation crops (eg coffee, tea, bananas, rubber,
coconut, palms, cocoa, mangoes); post-weed emergence but pre-crop-emergence in a wide range
of crops (including vegetables, beet, lucerne, okra, soya beans, figs, kiwi fruit, olives, cucurbits,
cereals, cotton, etc); on non crop areas; immediately pre-harvest in ripened cereals; in cereal
stubble; and in pasture renovation. Also used for pre-harvest desiccation of cotton, cereals, peas,
beans, etc; for destruction of rye sown to prevent wind erosion of the soil; for control of suckers
on fruit trees; and for aquatic weed control.
|Apparent Color|| WHITE SOLID; Colorless crystals
|Melting Point|| 230 DEG C (DECOMP)
|Molecular Weight|| 169.07
|Density|| 0.5 G/CU CM
|Environmental Impact|| Glyphosate is released to the environment in its use as a non-selective, post emergent
herbicide for controlling woody and herbaceous weeds on forestry, right-of-way, cropped and
non-cropped sites. It is applied as a spray of the isopropylamine salt and is removed from the
atmosphere by gravitational settling. After glyphosate is applied to forests, fields, and other land
by spraying, it is strongly adsorbed to soil, remains in the upper soil layers, and has a low
propensity for leaching. Glyphosate readily and completely biodegrades in soil. Its average
half-life in soil is about 60 days. Biodegradation in foliage and litter is somewhat faster. In field
studies, residues are often found the following year. Glyphosate may enter aquatic systems
through accidental spraying, spray drift, or surface runoff. It dissipates rapidly from the water
column as a result of adsorption and possibly biodegradation. The half-life in water is a few days.
Sediment is the primary sink for glyphosate. After spraying, glyphosate levels in sediment rise and
then decline to low levels in a few months. Glyphosate does not bioconcentrate in aquatic
organisms or bioaccumulate in species in higher tropic levels. Occupational workers and home
gardeners may be exposed to glyphosate by inhalation and dermal contact during spraying,
mixing, and cleanup. They may also be exposed by touching soil and plants to which glyphosate
was applied. Occupational exposure may also occur during glyphosate's manufacture, transport
storage, and disposal.
|Environmental Fate|| TERRESTRIAL FATE: APPLIED AT 2.6 KG/HA FOR QUACKGRASS ON LOAM
& FINE SILT SOILS, GLYPHOSATE WAS IMMEDIATELY DETECTABLE BY GAS
CHROMATOGRAPHY AFTER APPLICATION AS WELL AS AT 28 DAYS & 8 MO
LATER. UNCHANGED GLYPHOSATE & AMINOMETHYLPHOSPHONIC ACID WERE
IDENTIFIED BY GC IN THE SOILS.
TERRESTRIAL FATE: After 16 wk, <3% of the starting material is detectable. Strong soil
adsorption, slight washing-out or displacement.
Would not be expected to persist from one growing season to the next.
TERRESTRIAL FATE: Half-life in soil is normally less than 60 days.
TERRESTRIAL FATE: After glyphosate is applied to forests, fields, and other land by spraying,
its mobility in soil is limited and is affected by pH and phosphate levels, as well as by soil type .
In addition to binding to organic matter and clay in soil, it may also form insoluble complexes with
metal ions in the soil. Distribution data for glyphosate after spraying in a coastal forest ecosystem
indicate that glyphosate is strongly adsorbed to the upper layers of soil and has a low propensity
for leaching . Glyphosate residues dissipated with a half-life of 45-60 days. After 360 days,
residues levels were 6-18% of initial levels . Field studies on eleven different soils covering a
full range of soil types and geographical areas indicates an avg half-life of 60 days for glyphosate
in soil . Other sources also report an avg half-life of 60 days from literature surveys(1,5).
TERRESTRIAL FATE: The half-life of glyphosate applied to forest foliage was 14.4 days
and that applied to two Finnish agricultural fields were 69 and 127 days, respectively .
Persistence studies with glyphosate in sandy test sites in a boreal forest in Ontario, Canada
indicate that the half-life of glyphosate was 24 days and residues were reduced to <10% of that
applied after 78 days . More than 95% of residues were found in the upper organic layer of soil.
In aerially treated forest brush fields in the Oregon coast range, the half-life of glyphosate ranged
from 10.4-26.6 days in foliage and litter. The half-life of glyphosate on exposed soil and
litter-covered soil was 40.2 and 29.2 days, respectively . Glyphosate degrades even under low
TERRESTRIAL FATE: In a Finnish study where the glyphosate was applied to two agricultural
fields in September to control quackgrass and the fields plowed after six days, 76% and 10%
remained in the field containing loam soil after 28 days and 8 months, respectively . The
corresponding values for the field with fine silt was 92% and 53%. The loam soil in which
degradation was more rapid had a higher respiration rate. In a similar study in eight forest soils in
Sweden at higher temperatures, an avg 20% of the glyphosate applied in August was present in
samples taken the following May .
AQUATIC FATE: When glyphosate enters water as runoff or inadvertent overspray or spray
drift, it adsorbs strongly to sediment and particulate matter in the water column. It may also form
insoluble complexes with metal ions and precipitate. Evidence from microcosm studies suggests
that sediment adsorption and/or biodegradation represents the major dissipation process in aquatic
systems . Glyphosate levels in sediment rise at first and then fall to very low or undetectable
levels . After glyphosate was sprayed over two streams in the rainy coastal watershed of British
Columbia, glyphosate levels in the streams rose dramatically after the first rain event, 27 hr
postapplication, and fell to undetectable levels 96 hr postapplication . The highest residues were
associated with sediments, indicating that they were the major sink for glyphosate. Residues
persisted throughout the 171 day monitoring period. Suspended sediment is not a major
mechanism for glyphosate transport in rivers . The half-lives of glyphosate in three forest ponds
in Manitoba, Canada that were aerially spray in August was 1.51 to 1.99 days and glyphosate was
not detected in any sample by day 38 . The pond in which glyphosate had the longest half-life
had much higher levels of calcium and magnesium than the other ponds.
AQUATIC FATE: In aerially treated forest brush fields in the Oregon Coast range, the
concentration in streamwater peaked at 0.28 ppm shortly after spraying and declined sharply to
undetectable levels in about 6 days . Concentrations in sediment increased slowly to a peak
value of 0.55 ppm after 14 days and then slowly declined; at the end of the 55 day study the level
was about 0.1 ppm. The concn pattern for aminomethylphosphonic acid, a glyphosphate
metabolite in sediment was similar to that of glyphosate, but at much lower levels. Sediments
adsorb glyphosate from flowing water; once adsorbed, it is not readily eluted. In experiments
where glyphosate was added to water in two irrigation canals, the fractional reduction in load was
13 and 27% per km with uptake by the benthic sediment being 365 and 603 g/km . In two other
experiments in which glyphosate was added to flowing water to simulate contamination during
foliar spaying, 63% of the glyphosate was scavenged by sediment in 14 km and 43% was removed
in 14 km . In a field study, glyphosate was sprayed on sediment in an irrigation channel in
spring and 4 days afterwards the channel was filled with water. Based on the observed
concentration levels, less than 7% of the applied glyphosate eluted with water .
ATMOSPHERIC FATE: Glyphosate will be released into the atmosphere as an aerosol during
spraying and removed by gravitational settling. It will occur in the atmosphere only as an aerosol
and may degrade by photolysis.
|Drinking Water Impact|| GROUNDWATER: Glyphosate was detected in groundwater and water supply
monitoring programs in Texas . The concn and site details were not reported . In a survey of
farm wells in Ontario, Canada, 103 in 1986 and 76 in 1987, glyphosate was not detected in any
wells . However, glyphosate was only used on crops on 28 farms in 1986 and 1987 .