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in 1996. EXTOXNET no longer updates this information, but it may be useful
as a reference or resource.
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E X T O X N E T
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and the Institute for Environmental Toxicology, Michigan State
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USDA/Extension Service/National Agricultural Pesticide Impact
EXTOXNET primary files maintained and archived at Oregon State
Revised June 1996
Trade and Other Names:
Trade names include Beacon, CGAA 136872, Rifle, and Tell.
Primisulfuron-methyl may be found in mixes with other herbicides
such as 2,4-D, dicamba, cyanazine, bromoxynil, and atrazine.
Primisulfuron-methyl is a practically nontoxic compound in EPA
toxicity class IV. Labels for products containing it must bear
the Signal Word CAUTION. Primisulfuron-methyl is a General Use
Primisulfuron-methyl is a selective post-emergence herbicide used
to control grassy and broad leaved weeds in crop and non-crop
applications. It is the methyl ester of primisulfuron, and is
similar in its toxicological and environmental fate
characteristics. Primisulfuron-methyl is available in wettable
powders and water dispersible granules in water-soluble packets.
Primisulfuron methyl is available in wettable powders and water
dispersible granules in water-soluble packets.
- Acute toxicity: Primisulfuron-methyl is
practically non-toxic by ingestion, with a reported oral
LD50 of greater than 5050 mg/kg in rats [4,8]. Via the
dermal route, it is moderately to practically nontoxic,
with a dermal LD50 of greater than 2010 mg/kg in rats and
rabbits [4,7]. Slight skin irritation was observed in
rabbits after dermal application of primisulfuron-methyl,
but it did not cause skin sensitization in male guinea
pigs [4,15]. In rabbits, primisulfuron-methyl caused
slight eye irritation that cleared within 3 days after
contact . The 4-hour inhalation LC50 for
primisulfuron-methyl is greater than 4.8 mg/L in rats,
indicating slight toxicity by this route .
- Chronic toxicity: Doses of 125 mg/kg/day
administered in the diet to dogs over a 1-year period
produced decreased body weight gain, anemia, increased
liver weight, and thyroid hyperplasia (abnormal growth)
. Rats fed dietary doses of about 180 mg/kg/day over
90 days showed effects similar to those noted in dogs, as
well as spleen weight increases . In another study,
doses of 480 mg/kg/day in rats over 18 months produced
increased incidence of tooth disorders, chronic nephritis
(kidney damage), and testicular atrophy . In two
18-month studies in mice, testicular atrophy, chronic
nephritis, and increased tooth and bone disorders were
seen at doses of 180 mg/kg/day and 360 mg/kg/day,
- Reproductive effects: Changes in the
function of the testes were noted in rats fed high doses
(250 mg/kg/day) of primisulfuron-methyl over two
generations. There was also a decrease in the body weight
of the offspring. No compound-related effects on
reproduction were noted at doses below 50 mg/kg/day .
Testicular atrophy was seen in rats in chronic studies
(see above), which could result in reproductive effects.
The available data suggest that reproductive effects in
humans due to primisulfuron are not likely under normal
- Teratogenic effects: No teratological
effects were seen in offspring of rabbits given doses of
up to 600 mg/kg/day. In one study of rats, delayed
skeletal development and lack of ossification was seen in
offspring of pregnant rats given doses of 500 mg/kg/day,
while in another, 100 mg/kg/day produced incomplete
ossification of the pubic bone . The available
evidence suggests that primisulfuron-methyl is not
teratogenic except at very high doses.
- Mutagenic effects: Primisulfuron-methyl
did not cause mutations in extensive testing. These tests
included the Ames assay with and without metabolic
activation, the Chinese hamster ovary cell culture,
chromosomal aberration assay, and the rat liver cell
unscheduled DNA synthesis assay [4,15]. This indicates
that this compound is not mutagenic.
- Carcinogenic effects: In an 18-month
study, mice that were fed doses of 180 mg/kg/day showed
increased liver tumors, but this same dose level failed
to produce the same effect in the same species in another
investigation over the same period [4,15]. No
carcinogenic activity was seen in rats fed up to about
450 to 500 mg/kg/day . The available data suggest that
primisulfuron is not carcinogenic.
- Organ toxicity: Target organs identified
in animal studies include the liver, kidneys, spleen, and
testes, as well as the skeleton.
- Fate in humans and animals: Nearly all
of a single dose (level not noted) of
primisulfuron-methyl fed to rats was excreted unchanged
in the feces and the urine within 9 days . Relatively
low concentrations were identifiable in the feces and
urine of rats, goats, and chickens fed the compound .
- Effects on birds: Primisulfuron-methyl
is practically nontoxic to wildfowl. Both bobwhite quail
and mallard ducks show a high tolerance for the compound.
The 5-day dietary LC50 for primisulfuron-methyl in both
these species was in excess of 2150 ppm . In addition,
mallards fed moderate amounts of the compound showed no
adverse effects on reproduction at the highest dose
tested (500 ppm in their diet) .
- Effects on aquatic organisms:
Primisulfuron-methyl is only slightly toxic to freshwater
fish, aquatic organisms, and marine (estuarine) shrimp.
The reported 96-hour LC50 values are greater than 48 mg/L
in bluegill, and greater than 13 mg/L in rainbow trout
[4,15]. The compound is practically nontoxic to the
freshwater invertebrate Daphnia magna .
- Effects on other organisms:
Primisulfuron-methyl is nontoxic to honey bees [5,6].
- Breakdown in soil and groundwater:
Primisulfuron-methyl is of low to moderate persistence in
the soil environment, with a field half-life of from 4 to
60 days. A representative value is estimated to be about
30 days. Aerobic conditions enhance the breakdown in
soils [4,15]. Losses due to volatilization and
photodegradation are negligible . Acidic conditions
will accelerate the breakdown process.
Primisulfuron-methyl is poorly sorbed to most soils and
is soluble in water and thus may be mobile . However,
in field tests, no primisulfuron-methyl was detected
below 9 inches of the surface .
- Breakdown in water: Primisulfuron is
resistant to hydrolysis in alkaline and neutral solutions
. Anaerobic conditions will increase persistence. A
half-life of 22 days at a pH of 5 has been reported .
- Breakdown in vegetation: It is rapidly
absorbed by plants and translocated throughout the plant
roots and foliage . The herbicide works by blocking
cell growth in the active growing regions of the plant
(meristems) and by blocking photosynthesis .
Primisulfuron-methyl application to crops grown
previously on the same land resulted in detectable
amounts in wheat, soybeans, sugar beets, corn, and
- Appearance: Primisulfuron-methyl is a
colorless, crystalline solid under normal conditions .
- Chemical Name:
- CAS Number: 113036-87-6
- Molecular Weight: 468.30
- Water Solubility: 70 mg/L @ 20 C 
- Solubility in Other Solvents: s.s. in
acetone, cyclohexane, isopropanol, methanol, and xylene
- Melting Point: 203.1 C 
- Vapor Pressure: 0.000001 mPa 
- Partition Coefficient: 0.1987 
- Adsorption Coefficient: 50 (estimate)
- ADI: Not Available
- MCL: Not Available
- RfD: Not Available
- PEL: Not Available
- HA: Not Available
- TLV: Not Available
P.O. Box 18300
Greensboro, NC 27419-8300
- Phone: 800-334-9481
- Emergency: 800-888-8372
References for the information in this PIP can be found in
Reference List Number 9
information in this profile does not in any way replace or
supersede the information on the pesticide product labeling or
other regulatory requirements. Please refer to the pesticide