United States Office of Pesticides
Environmental Protection and Toxic Substances
Agency (H7501C) 54 O-FS-90-093
&EPA Pesticide
Fact Sheet
Name Of Chemical: Primisulf uron-methyl
Reason for Issuance: Registration
Date Issued: June 12, 1990
Fact Sheet Number: 2i4
1. DESCRIPTION OF CHEMICAL.
Generic Name: 3-[4,6-Bis-(difluoromethoxy)-pyrimidin-2-yl]-
1-(2-methoxycarbonyIphenylsulfonyl)urea
Common Name: CGA-136872 and primisulfuron-methyl
Trade Names: BeaconŽ Herbicide and Rifle Herbicide
EPA Shaughnessy Code: 128973-5
Chemical Abstracts Service (CAS) Number: 86209-51-0
Year of Initial Registration: 1990
Pesticide Type: Herbicide
Chemical Family: Sulfonylurea
U.S. Producer: CIBA-GEIGY Corporation
2. USE PATTERNS AND FORMULATIONS
Application sites: Terrestrial food crops and terrestrial
noncrop sites. Postemergence to actively growing
weeds in corn; and in noncropland areas such as fence
rows, airports, highway rights-of-way, industrial sites,
lumber yards, petroleum tank farms, pipeline rights-of-way,
plant sites, railroads, storage areas, and utility
rights-of-way.
Types of formulations: The two end-use products (75.0% a.i)
are identical in composition. They are water dispersible
granules packaged in water soluble bags. The technical
product which is a crystalline solid contain-
ing 95% a.i. is used in the manufacture of the two end-use
products. The technical product is packaged in a metal
container.
Amount and Method of Application: Maximum application
of 0.56 oz. active ingredient per acre per season is
claimed for postemergence weed cpntrol in the culture
of corn. For low maintenance turfgrass sites along
roadsides, airports, industrial sites, fence rows,
etc. in common bermudagrass and buffalograss turf,
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dosages of 0.4 to 2.5 ozs per acre may be applied.
These same dosages are claimed for noncrop sites such
as fence rows, highway rights-of-way, industrial
sites, lumberyards, petroleum tank farms, pipeline
rights-of-way, plant sites, railroads, storage areas,
and utility rights-of-way. The dosage to be used
depends on the target weed species to be controlled.
Only ground application directions are given on the
proposed labeling. Measures to avoid spray drift
and washing onto.nontarget areas are described on
the labeling.
Carrier: Water
3. SCIENCE FINDINGS
Summary Science Statements:
Adequate toxicological, product and residue chemistry
ecological effects environmental fate and ground water
data have been submitted and reviewed to support the
registration of primisulfuron-methyl for use as a
postemergence herbicide in the culture of corn and
perennial turf grasses. Registration as a postemergence,
non-selective herbicide on noncropland such as
fence rows, highway rights-of-ways, industrial sites,
lumber yards, petroleum tank farms, pipe line right-of-
ways, plant sites, railroads, storage areas, and
utility rights-of-way is also supported. Primisulfuron-
methyl is classified as a Toxicity Category III pesticide
and is labeled witn the signal word "CAUTION", based on
acute dermal, acute inhalation and eye irritation studies.
A 21-day dermal study in rabbits indicated a no observable
effect level (NOEL) of greater than 1,000 mg/kg/day
for systemic toxicity. Primisulfuron-methyl was non-
mutagenic and in developmental tox-i-city studies it did
not appear to be a potential teratogen. Based on results
of a mouse oncogenic lifetime study it was classified as
a Group D carcinogen - not classifiable as to human
carcinogenicity. Ecological effects data characterize
primisulfuron-methyl as practically nontoxic to birds on
subacute dietary and acute oral bases. Toxicological
data demonstrated that it is of low toxicity to mammals.
Low levels of contamination of ground water is possible
in vulnerable soils with high water tables. The
chemical is essentially nontoxic to honey bees. It is
stable to hydrolysis in neutral and mildly alkaline
solutions (pH 7 and 9), and hydrolyzed slowly (half-
life >30 days) in acidic (pH 5) solutions.
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Chemical Characteristics:
Phyical State:
Color:
Odor:
Melting Point:
Density:
Solubility'
Vapor Pressure:
Crystalline Solid
Colorless to yellow
Odorless
Q
ca. 200 C (Decomposition at
melting point)
1.62 gm/cm-3 at 20° (typical)
Solvent Based on gm/100 cm3/20°C
Water
N-Octanol
Acetone
Cyclohexanone
Methyl Chloride
Methanol
Toluene
Isopropanol
Xylene
1 ppm (pri 5)
9 ppm (pH 6)
70 ppm (pH 7)
600 ppm (pH 8)
4500 ppm (pH 9)
120 ppm
3.6%
2.7%
0.4%
0.35%
0.05%
0.04%
0.03%
1.5 x 10~10 Torr. at 25°C
Dissociation Constant: pKa value = 5.1 (Acid)
Octanol/Water Partition Coefficient: P = 0.059
pH: 5.56 at 25°C + or - 1°C
(Saturated Solution)
Stability
The technical material decomposes on melting. Technical
primisulfuron-raethyl is stable at room temperatures.
At 35°C it degraded less than 1.0 percent during 12 months
of storage. At 54°C there was no degradation up to
3 months of storage. The formulated products Beacon*
Herbicide.and Rifle" Herbicide were stable up to 28
weeks at 50°C and after 7 weeks at 70°C there occurred
2.0% degradation.
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Toxicology Characteristics:
Acute Toxicity (Technical, 94% ai)
Acute oral toxicity (rat): LD5Q > 5050 mg/kg,
Toxicity Category IV.
Acute dermal toxicity (rabbit): LD5Q > 2,010 mg/kg,
Toxicity Category III.
Primary dermal irritation .(rabbit) : No edema, no
erythema in male rabbits, Erythema in one
female rabbit cleared within 72 hours,
Toxicity Category IV.
Primary eye irritation (rabbit): No corneal
opacity, conjunctivitis clearing within 3 days,
Toxicity Category III.
Acute inhalation toxicity (rat): No deaths,
LC50 > 4.81 mg/L for 4 hours, Category III.
Dermal sensitization (guinea pig): Negative for skin
sensitization in male guinea pigs (not tested in
females), not a skin sensitizer.
Acute Toxicity (Beacon* Herbicide, 75% ai)
Acute dermal toxicity (rabbit): No deaths, LD5Q50
>2010 mg/kg, Category III.
Acute inhalation toxicity (rat): No deaths, LCsoSO
>3.28 mg/L for 4 hours, Category III.
Primary eye irritation (rabbit): No corneal opacity,
conjunctivitis calearing in day 4, Category III.
Primary dermal irritation (rabbit): No edema, slight
erythema in one male and one female clearing by
24 hoursr Category. IV.
Dermal sensitization (guinea pig): Negative for skin
sensitization in male guinea pigs, females not
tested, not a skin sensitizer.
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Subchronic Toxicity
A 21-day dermal study in rabbits was conducted using
levels of 0, 10, 100 and 1,000 mg/kg/day. No effect
was observed on any parameter examined, NOEL was
> 1,000 mg/kg/day.
A 13-week dog feeding study at 0, 25, 1,000 and
10,000 ppm was conducted. Effects were increased
platelet values in tema,le.s and thiokened._,g.all bladder
mucosa in one female dog macroscopicaly. One male
and three female dogs had mild epithelial hyperplasia of
the gall bladder. The NOEL was 25 ppm and the LEL
was 1,000 ppm.
A 13-week rat feeding study at 0, 10, 300, 3,000,
10,000, 20,000 ppm was conducted. The effects were
decreased body weight in males, decreased food
consumption in males, decreased absolute and relative
spleen weight in males. The NOEL was 300 ppm and
the LEL was 3,000 ppm.
A 1-year dog feeding study was conducted at 0, 25,
1,000 and 10,000/5,000 ppm (changed after week 10).
Results were decreased body weight gain at 10,000 ppm
(weeks 1 to 10); anemia at 10/5,000 ppm; liver weight
increases (absolute and relative) and vacuolar changes
at 10/5,000 ppm; thyroid hyperplasia at 10/5,000 ppm;
systemic NOEL was 1,000 (25 mg/kg/day) and the system-
ic LEL was 5,000 ppm (125 mg/kg/day). The effects
were anemia, increase in platelets, lower chloesterol
values, pale livers, moderate to trace vacuolar changes
and thyroid hyperplasia.
Reproduction
A 2-generation reproduction study in rats was conducted
at doses of 0, 10, 1,000 and 5,000 ppm. An effect
noted at 5,000 ppm was decrease in testicular/spermatic
function and decreasedjbody weight gains in males.
There was also a decrease in pup weights. The systemic
parental NOEL was 1000 ppm and the LEL was 5,000 ppm
based on decreased body weight gain. The reproductive
NOEL was 1,000 ppm and the LEL was 5,000 ppm based
on paternal decrease in testicular/spermatic function
and a decrease in pup body weight.
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Mutagenicity
The following mutagenicity studies indicated that
primisulfuron-methyl is not mutagenic at doses tested:
- Ames Assays for mutagenicity with and without metabolic
activation in Salmonella TA98, TA100, TA1535, and
TA1537 up to 1024 ug/plate.
- Chromosome Aberration (micronucleus) in Chinese hamster
up to 5,000 mg/kg. There was no evidence of toxicity.
- Unscheduled DMA synthesis (UDS) Assay with rat liver
cells (hepatocytes) up to 400' ug/ml.
- UDS Assay with human fibroblasts up to 1,000 ug/ml with-
out activation (without S-9).
Teratology
In a rabbit teratology study at doses of 0, 10, 300,
600 mg/kg/day by gavage there was no evidence of
development effects. The effect observed in this
study was abortion, decreased body weight, stool
alterations. The maternal NOEL was 10 mg/kg/day and the
LEL was 300 mg/kg/day. .
In a rat study at doses of 0, 100, 500, and 1000
mg/kg/day by gavage there was delayed skeletal
development and incomplete or lack of ossification
of several bones. The developmental NOEL was
100 mg/kg/day and the LEL was 500 mg/kg/day.
In a second rat study at doses of 0, 10, 50 and
100 mg/kg/day there was possible increase in number
of litters (not fetuses) having incomplete ossification
of the os pubis at 100 mg/kg/day. Maternal NOEL
was > 100 mg/kg/day at the highest dose tested (HOT).
These three studies indicate that primisulfuron-
raethyl is not a teratogen.
Oncogenicity
A 104-week rat feeding oncogenic study was conducted
at doses of 0, 10, 300, 3,000 and 10,000/8,000 ppm.
The systemic NOEL was 300 ppm (15 mg/kg/day) and the
systemic LEL was 3,000 ppm (150 mg/kg/day) based on
decreased weight gain in males. At 10,000/8,000 ppm
testes of males were soft and atrophied; at
1*0,000/8,000 ppm food consumption in both males
and female was decreased. The study was evaluated . (
as showing a negative oncogenicity potential in rats.
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An 80-week mouse feeding oncogenic study was conducted
at doses of 0, 300, 3,000 and 10,000 (reduced to
7,000 at week 23). The systemic NOEL was 300 ppm
(40.0 mg/kg/day) for males and less than 10 ppm
(1.4 mg/kg/day) for females. The systemic LEL was
3,000 ppm (408 mg/kg/day) for males and 10 ppm
(1.7 mg/kg/day) for females. The effects were
increased mortality, body weight gain decreases,
hypoplasia. of teeth/, liver, weight increases, chronic
nephritis and testicular degeneration/epididymal
aspermia. There was an apparent increase in hepato-
cellular adenomas and hepatocellular carcinomas in
both males and females at 3,000 and 10,000/7,000 ppm.
Tumors were statistically significantly higher than
concurrent controls, but only at dose levels exceeding
the maximum tolerated dose (MTD).
The Agency Peer Review Committee classified
primisulfuron-methyl as a Group D carcinogen -
not classifiable as to human carcinogenicity.
Physiological and Biochemical Behavioral Characteristics
Metabolism
A rat radiolabeled primisulfuron-methyl metabolism
study showed that 88 to 102% of radioactive
primisulfuron-methyl was excreted in feces and urine with-
in 9 days. Most of the radioactivity was in the form of
unchanged parent compound. There were 6 major metabolites
in the feces and urine. Hydroxylation of the pyrimidinyl
ring occurs at the 5-position, and is followed by either an
N- or O- rearrangement of a difluoromethoxy group. There
appears to be little cleavage of the sulfonylurea bridge
with the 5-hydroxylate primisulfuron-methyl to form an
oxidized and/or oxidized and rearranged modified pyrimi-
dinyl moiety. Some cleavage of the sulfonylurea bridge
of the parent is evident by the isolation of a sulfonyl-
benzoate intermediate and its cyclized counterpart,
saccharin, and the isolation of the bis(difluoromethyl)
pyrimidinyl moiety. Similar metabolism of primisulfuron-
methyl was observed in the goat and the chicken.
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Mechanism of Pesticidal Action
Primisulfuron-methyl is a photosynthesis inhibitor.
It inhibits growth and development by inhibiting the
function of chlorophyll. It inhibits growth and
development of susceptable weeds. It is applied
postemergence to corn and weed species. Its selectivity
is not completely understood. Susceptable plants become
chlorotic and then necrotic-at their growing points.
The herbicidal activity of primisulfuron-methyl
is influenced by temperature^ moi&ture-,as. associated
with optimum growth of weed species both before and
after application, weed species, weed size at time
of application, rate applied and general growing con-
ditions. Some weeds not killed are often stunted and
are less competative to corn. Primisulfuron-methyl
may provide some herbicidal activity as a premergence
herbicide. Certain corn hybrids may be sensitive to
Primisulfuron-methyl and respond to application with
temporary injury at labeled dosages. A list of
corn hybrids having good tolerance to this herbicide
is available from CIBA-GEIGY Corporation.
Environmental Characteristics:
Hydrolysis: Primisulfuron-methyl does not hydrolyze
in neutral and mildly alkaline solutions (pH 7
and 9), it hydrolized slowly (half-life > 30 days)
in acedic (pH 5) solutions.
Photodegradation: Primisulfuroa-methyl dxxes not
photodegrate in either water or on soil.
Aerobic Soil Metabolism: In aerobic soil maintained under
controlled laboratory conditions phenyl ring-labeled
[l^C] primisulfuron-methyl degraded with a half-life
of 63 days and pyrimidine ring-labeled [14C] primi-
sulfuron-methyl degraded with a half-life of 30 days.
Anaerobic Soil Metabolism: In anaerobic soil maintained
under controled conditions, phenyl ring-labeled [14C]
primisulfuron-methyl degraded with a half-life of
89 days and pyrimidine ring-labeled [14C] primisulfuron-
methyl degraded with a half-life of 41 days.
Field Dissipation: Dissipation occurred more rapidly
under fild conditions where primisulfuron-methyl
dissipated with half-lives of 3 to 12 days (detection
limits of 0.01 ppm), and total phenyl and pyrimidine
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ring-labeled [-^c] primisulfuron-methyl residues
dissipated with initial half-lives of 12 and 30
days respectively.
Leach, Adsorption/Desorption: [-^C] Primisulfuron-methyl and
its degradates were very mobile in both laboratory
and field leaching studies, however unlabeled
primisulfuron-methyl was not detected (>0.01 ppm)
below a depth of 9 inches in field studies. Detection
limits is a limiting factor in conducting such
studies.
Accumulation Studies: Primisulfuron-methyl accumulates
up to 0.011 ppm in wheat, soybeans, sugar beets,
corn, or lettuce that were planted 103-334 days
after corn plants growing in the plots had been
foliarly-treated with primisulfuron-methyl.
Potential to Contaminate Groundwater: The use of primi-
sulfuron as a postemergence herbicide in the
culture of corn, turf and in vegetation control
in low maintenance turf sites may result in low
levels of contamination in groundwater in highly
vulnerable soils with high water tables. The pre-
sent analytical methodology for primisulfuron-methyl
and its degradates with detection limits of only
0.01 ppm is not sufficiently sensitive to detect
residues resulting from the uses of this
chemical as a postemergence herbicide, as registered.
Ecological Characteristics
Avian Studies: Primisulfuron-methyl is practically
non-toxic to birds based on the following
studies:
Single Dose Oral Studies:
Bobwhite quail with 94.0% ai, LC$Q > 2150 mg/kg.
Mallard duck with 94.0% ai, LCso > 2150 mg/kg.
Subacute Dietary Study:
Bobwhite quail with. 94.0% ai, LCso >5000 ppm.
Avian Reproduction:
Mallard duck with 95.9% ai, NOEL was 500 ppm.,
No reproductive impairment occurred at 500 ppm
dietary test level.
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Aquatic Organisms: The following data indicate that primi-
sulfuron-methyl is no more than slightly toxic to
to freshwater fish, aquatic invertebrates and
estuarine shrimp:
Fish Acute Toxicity:
Bluegill sunfish, LC$Q > 48 ppm (supplementary study).
Rainbow trout, LC$Q > 13 ppm (supplementary study).
Effects on Freshwater* In.v.erJteb.r.a.tes;.
Acute Toxicity Study:
Daphnia magna, LD5Q > 100.0 ppm.
Chronic Study:
Daphnia magna, NOEL of 0.41 ppm.
Effects on esturine organisms:
Acute Toxicity Study:
Mysid shrimp, LC5Q of 16 ppm.
Effects on honey bees:
Acute Contact Toxicity Study:
Apis mellifera, LC$Q > 100 ug/bee, practically non-toxic.
Effects on Nontarget plants:
Aquatic species, ECso is 0.27 to 24.0 ppb
Terrestrial species, EC25 for:
Seed germination was 3.7 to 473.0 gm/ha,
Seed emergence was 0.15 to 44.0 gm/ha,
Vegatative vigor was 0.14 to 33.4 gm/ha.
Endangered Species Hazards:
Based on available data the registered uses of
primisulfuron-methyl is unlikely to pose a hazard to
endangered aquatic and avian species. There may be
some hazard to endangered plants.
Residue Chemistry
A tolerance regulation has been established for
residues of primisulfuron-raethyl associate with
its use as a postemergence herbicide in the
culture of corn. The regulation is found
under Section 180.452 in the Code of Federal
Regulations. The regulation establishes tolerances
for residues of primisulfuron-methyl in or on
corn (forage) at 0.10 ppm; corn (fodder) at 0.10 ppm;
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corn (grain) at 0.02 ppm; corn (sweet) (kernels
plus cobs with husks removed) at 0.10 ppm; milk at
0.02 ppm; meat, fat, meat byproducts of cattle, goats,
hogs, horses, and sheep at 0.10 ppm; poultry fat, meat
and meat by-products at 0.10 ppm; and eggs at 0.10 ppm.
4. Summary of Regulatory Position and Rationale
Available data provided adequate information to support
the conditional registration of BeaconŽ Herbicide,
.RifleŽ Herbicide, and CGA-136872 Technical, that were
first registered on May.11, 1990-.under. Section 3 of
the Federal Insecticide, Fungicide and Rodenticide Act
as amended.
Use, formulation, manufacturing process or
geographic restrictions: Crop rotation
restrictions are specified on the Beacon
Herbicide label. Aerial applications of
Beacon* and Rifle* Herbicides are not permitted.
Beacon* and RifleŽ Herbicides are water
dispersible granules that are in pre-measured
quantities in water-soluble packets.
5. Summary of Data Gaps
Environmental Fate and Groundwater Data:
a. Information on the relative mobilities of primisul-
furon-methyl in soil (EPA Guideline Date 163-1) and its
major phenyl and pyrimidine ring-labeled [^4C] degradates
must be submitted within 12 months from the date of
registration.
b. A new field dissipation study in soil (EPA Guideline
Date 164-1) in which residues at the level of 10%
of the applied rate are measured with the appropriately
sensitive methodology. In lieu of a new study,
the registrant may submit data that characterize
the residues detected in the submitted soil dis-
sipation study. This study must be submitted within
27 months form the date of registration.
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A small-scale prospective ground-water monitoring
study that addresses the mobility of the parent
compound and its degradates must be submitted
within 30 months from the date of registration.
Ecological Effects Data:
Aquatic organism testing with a warmwater freshwater
fish and a coldwater freshwater fish (EPA Guidelines
data 72-1) must be submitted -9..months, from the date
of registration.
6. Contact Person at EPA
Joanne I. Miller
Acting Product Manager 23
Fungicide-Herbicide Branch
Registation Division (KH-7505C)
Office of Pesticide Programs
Environmental Protection Agency
401 M Street SW
Washington, DC 20460
Office Location and Telephone Number
Room 237, Crystal Mall Building 12
1921 Jefferson Davis Highway
Arlington, VA 22202
(703) 557-1830
DISCLAIMER: The information presented in this Pesticide Fact
Sheet is for informational purposes only and may not be used
to fulfill data requirements for pesticide registration and
reregistration.
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r/EPA
United States
Environmental Protection Agency
Office of Pesticide Program (H7S04C)
PMSD. Information Services Branch
401 M Street. SW
Washington, DC 20460
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