nicosulfuron (Accent) EPA Chemical Fact Sheet 6/90
CHEMICAL FACT SHEET FOR
FACT SHEET NUMBER: 216
DATE ISSUED: JUNE 29, 1990
1. Description of the Chemical
Generic Name: Nicosulfuron 3-pyridinecarboxamide,
Common Name: Nicosulfuron
Code Name: DPX-V9360
Trade Name: Accent
EPA (Shaughnessy) Code: 129008
Service (CAS) Number: 111991-09-4
Year of Initial
Pesticide Type: Herbicide
Chemical Family: Sulfonylurea
U.S. and Foreign
Producers: E.I. du Pont de Nemours & Co., Inc.
2. Use Patterns and Formulations
- Field corn only. Accent is not to be used on popcorn, sweet corn,
or corn grown for seed production.
Types and Methods of Application:
- Accent is to be applied by ground equipment to young, actively
- Single application - Maximum single application is 1 1/3 ounce (oz)
of Accent per acre (A) per any crop year, (1 oz active ingredient
(ai)/A) in a minimum of 10 gallons of water.
- Split application - Application not to exceed a total of 1 1/3 oz of
Accent/A/crop year recommended 2/3 oz of Accent each (0.5 oz/ai/A)|.
- 75% water dispersible granule.
3. Science Findings
(NR - Not Required, NA - Not Applicable)
End-Use Product Technical
Molecular Weight: 410.4
Molecular Formula: C15H18N6O6S
Color: Light tan White
Physical State: Solid, granular Solid
Odor: None Paste-like
Melting Point: NR 141-144 degrees C
Boiling Point: NA NA
Density: 0.53 g/ml 0.313 g/ml
Solubility: NR 0.04* (pH 5.0 buffer);
1.2* (pH 7.0 buffer); and
3.9* (pH 9.0 buffer)
*solubility limit, g/100 g buffer at 25 degrees C
*3.8 (ethyl acetate),
*160 (methylene chloride),
*solubility limit, ppm x 10(3) at 28 plus or minus
1 degree C
Vapor Pressure: NR 1.2 x 10(-16) torr
Constant: NR pKa value = 4.3 (acid)
pH: 3.9 (1% dispersion A slurry in HPLC water caused
in water) the pH of the water to
decrease from 6.6 to 4.5.
Partition Coefficient (KOW):
NR 0.44 (pH 5)
0.017 (pH 7)
0.01 (pH 9)
Stability: NR The TGAI is solution stable
in the presence of iron
metal and ferrous (Fe +2|).
The solid TGAI is stable under
normal storage at 25 degrees C
and at 45 degrees C for 3
Reducing Action: Does not contain oxidizing or reducing agents.
Explodability: Not explosive.
Storage Stability: Ten months result showed product stability at
room temperature. Aging test continuing for
two additional months.
Characteristics: After being stored in the laboratory at room
temperature for 10 months, no physical change
was observed for either solid granules or
container material of construction (high-density
- Acute Oral: LD50>5000 mg/kg LD50>5000 mg/kg
Toxicity Category IV Toxicity Category IV
- Acute Dermal: LD50>2000 mg/kg LD50>2000 mg/kg
Toxicity Category III Toxicity Category III
- Acute Inhalation: LC50>5.9 mg/l LC50>5600 mg/m(3)
Toxicity Category III Toxicity Category IV
- Primary Dermal
Irritation: Non-irritant Mild irritant
Toxicity Category IV Toxicity Category IV
- Primary Eye
Irritation: Moderate irritant Moderate irritant
Toxicity Category III Toxicity Category III
Sensitization: Non-sensitizer Non-sensitizer
- Oncogenicity: In an 18 month oncogenicity study, mice administered
dosages of 0, 3.3/4.4, 32.7/44.8, 327/438, and 993/1312 mg/kg/day
resulted in a systemic NOEL of 993 and 1312 mg/kg/day (HDT) for
male and female mice, respectively.
- Chronic Toxicity: In a 1 year feeding study, dogs were treated with
Accent at doses of 0, 62.5, 125, and 500 mg/kg/day. The systemic
NOEL of 125 mg/kg/day for both sexes is based upon a decrease in
body weight gains and a concomitant increase in relative liver and
kidney weights in males.
- Chronic Toxicity/Oncogenicity: A 2 year chronic toxicity/
oncogenicity study with rats fed dosages of 0, 1.9/2.6, 58.1/77.1,
289/382, and 786/1098 mg/kg/day yielded a systemic NOEL of greater
than or equal to 786 mg/kg/day in males and 1098 mg/kg/day in
females, (HDT). The systemic Lowest-Observed-Effect-Level (LOEL)
is greater than 786 mg/kg/day and 1098 mg/kg/day for male and female
- Teratogenicity: A rat teratology study using doses of 0, 186, 930,
2325, and 5581 mg/kg/day had a developmental and maternal NOEL of
greater than or equal to 5581 mg/kg/day (HDT). The maternal and
developmental LOEL is greater than 5581 mg/kg/day. No treatment-
related effects were noted on maternal or developmental toxicity up
to and including 5581 mg/kg/day (HDT).
- A rabbit teratology study using doses of 0, 93, 465, 930, and 1860
mg/kg/day of Accent yielded a maternal NOEL of 93 mg/kg/day and LOEL
of 465 mg/kg/day based upon maternal toxicity occurring at 465
mg/kg/day; an increase in clinical signs, gross pathological
observations, abortions, postimplantation loss and a decrease in bod
weight gain during the dosing period. The developmental NOEL
of 465 mg/kg/day and LOEL of 930 mg/kg/day is based upon
developmental toxicity occurring at 930 mg/kg/day; reduced mean
fetal body weight and the apparent increase in postimplantation
loss at 465 mg/kg/day and above.
- Reproduction: In a multigeneration reproduction study, rats were fed
doses of 0, 12.5, 287, and 1269 mg/kg/day. The NOEL for systemic
toxicity is 287 mg/kg/day with a LOEL of 1269 mg/kg/day, based on
F1 (first mating) females with a lower body weight gain during the
final week of gestation and a similar pattern in the F0 females
during the same gestational period. The reproductive NOEL is
287 mg/kg/day with a LOEL of 1269 mg/kg/day based on minimal
reduction in litter size at birth and in pup weights at postpartum
day 14 through 21 in the F2a high dose group.
- Metabolism: The requirement for a metabolism study in rats has
been satisfied. Five groups of rats, 5 males and 5 females, were
dosed in various sequences with either 10 mg/kg or 1000 mg/kg
of pyridinyl-14C|-DPX-V9360 or pyrimidinyl-14C|DPX-V9360
either orally or intravenously. Both males and females excreted
essentially all of the radionuclide in the feces and urine.
Elimination of 14C-CO2 was not observed. No organ or tissue
showed total 14C-radioactivity >0.01 of the administered dose.
The major radioactivity was recovered as the parent which ranged from
85 to 97%. Two metabolites, pyridine sulfonamide and 5-hydroxy
pyrimidine amine, were identified. The presence of pyridine acid
sulfonamide was also suggested, but not positively identified.
Several undefined metabolites makeup <10% TRR. Based on the
metabolites identified, the major pathway in the rat is cleavage
of the parent DPX-V9360, to yield pyridine sulfonamide and
pyrimidine amine; 5-OH pyrimidine amine could be formed either
before or after the cleavage.
- No mutagenic activity was observed when tested in four strains
(TA97A, TA98, TA100, and TA1535) of Salmonella typhimurium.
In vitro chromosomal aberration tests in cultured human lymphocytes
indicated negative responses at the concentrations from 40 to 470
ug/ml. Nicosulfuron assayed with or without metabolic activation
in vitro in Chinese Hamster Ovary (CHO) cells was nonmutagenic at
the concentrations from 4 to 465 ug/ml and a micronucleus assay
in mouse bone marrow cells was negative at dose levels from 500
to 5000 mg/kg. An unscheduled DNA synthesis study in rat
hepatocytes did not cause any DNA damage in rat hepatocytes at the
concentrations from 0.04 to 470 ug/ml.
Physiological and Biochemical Characteristics
- Mechanism of Pesticidal Actio: Biodegradation is an important
degradation mechanism of nicosulfuron.
- Foliar Absorption: Foliar absorption is the primary means of
nicosulfuron uptake by plants.
- Hydrolysis: Nicosulfuron is stable in aqueous solutions at neutral
and alkaline pHs. Solubility increases with increasing pH. The
main hydrolytic mechanism involves cleavage of the sulfonylurea
bridge, but a minor mechanism involving -SO2- elimination followed
by rebridging also occurs at acidic pHs. The mail hydrolytic
degradates are pyrimidine amine and pyridine sulfonamide.
- Photodegradation in Water and on Soil: Photodegradation is not a
significant degradation mechanism for nicosulfuron.
- Aerobic Soil Metabolism: Biodegradation is an important degradation
mechanism for nicosulfuron. The half-life of nicosulfuron in a silt
clay soil is 26 days. The main degradates are pyridine sulfonamide
and pyrimidine amine.
- Anaerobic Soil/Aquatic Metabolism: Biodegradation is an important
degradation mechanism for nicosulfuron. However, anaerobic
conditions slow down the degradation process. The half-life of
nicosulfuron in silt clay soil/water is 63 days. The main degradates
are pyridine sulfonamide and pyrimidine amine.
- Mobility in Soil: Nicusulfuron is very mobile in sandy loam and
silt loam soils. The pyridine sulfonamide degradate is more
mobile than the parent. The pyrimidine amine degradate is the
- Volatility from Soil: Nicosulfuron is not likely to volatilize
- Terrestrial Field Dissipation: This study was determined to be
supplemental and cannot be used to define a depth of leaching or
to use the reported half-lives to estimate the persistence of
nicosulfuron under field conditions.
- Accumulation in Confined Rotational Crops and in Fish: Degradates
containing the pyridine ring are more readily uptaken by the plants.
The minimum rotational crop interval is 10 months. Nicosulfuron
has a low tendency to accumulate in fish.
The Environmental Fate and Ground Water Branch (EFGWB) has
determined that the following data requirements have been
satisfied: hydrolysis, photodegradation on soil and in water,
aerobic and anaerobic soil metabolism, anaerboic aquatic
metabolism, mobility in soil, and accumulation in confined
rotational crops. The volatility from soil studies and the
bioaccumulation in fish study have been waived. The terrestrial
field dissipation study was considered supplemental and a new
study must be submitted as a condition for registration.
- Spray drift studies are being requested as a part of the
conditional registration. Submission of these data will address
concerns about the potential to harm nontarget plants during
application and ways to prevent adverse effects.
- Avian Acute Toxicity:
- Bobwhite quail LD50>2000 mg/kg Practically non-toxic
- Avian Dietary Toxicity:
- Mallard duck LC50>5000 mg/kg Slightly toxic
- Bobwhite quail LC50>5000 mg/kg Slightly toxic
-Freshwater Fish Acute
- Rainbow trout LC50>1000 ppm Practically non-toxic
- Bluegill sunfish LC50>1000 ppm Practically non-toxic
- Freshwater Invertebrate
- Daphnia magna LC50>1000 ppm Practically non-toxic
- Acute Contact
- Honey bee LD50>20 ug/bee Practically non-toxic
- Available data indicates that the hazard to avian, aquatic, and
mammalian species will be minimal. The terrestrial nontarget plant
data does not fulfill data requirements. Nicosulfuron is practically
non-toxic to freshwater fish and invertebrates. This chemical is
slightly toxic to birds on an acute and dietary basis. In addition,
nicosulfuron is practically non-toxic to honey bees.
- The Agency does not believe that conditional registration of this
chemical will cause substantially greater adverse effects to the
environment than other sulfonylurea products.
- Potential Problems Related to Endangered Species: It is not
expected that nicosulfuron will pose any hazards to endangered
- Tolerances have been established for residues of the herbicide in or
on the raw agricultural commodity corn, in the form of grain, forage,
silage, and fodder (40 CFR 180.).
corn, grain 0.1 ppm
corn, fodder 0.1 ppm
corn, silage 0.1 ppm
corn, forage 0.1 ppm
There are no tolerances established for residues of nicosulfuron
in/on corn in Canada, Mexico, or by Codex.
- Summary of Other Permanent Tolerances for Nicosulfuron - The only
permanent tolerances established for nicosulfuron at this time are
the above corn raw agricultural commodities (RACs). No other
permanent tolerances have been established for nicosulfuron.
Summary Science Statement
- Review of the product chemistry, environmental fate, toxicology,
and ecological effects data have been completed. The available
data supports the conditional registration of Accent for the
proposed food use. Data deficiencies exist in the ecological
effects and environmental fate and ground water areas.
- In the area of Environmental Fate and Ground Water, new field
dissipation and spray drift studies are required. However, the
available environmental fate data supports the conditional
registration of Accent.
- With respect to ecological effects data, the Agency is requiring
the company to submit a new seedling emergence study and
additional information to upgrade the vegetative vigor study.
However, the available ecological effects data supports the
conditional registration of this chemical.
- Available ecological effects data indicates that the hazard to
avian, aquatic, and mammalian species will be minimal.
- The Agency does not believe that registration of this chemical
will cause substantially greater adverse effects the environment
than other sulfonylurea products.
4. Summary of Regulatory Position and Rationale
- As a condition of registration, the registrant must submit a new
terrestrial field dissipation study, additional information on the
photodegradation in water study, spray drift studies, a new
seedling emergence study, and additional information to upgrade
the vegetative vigor study.
- Required Unique Labeling
- Precautionary Statements:
"Do not apply where/when condition could favor runoff."
"Do not apply if rainfall or storm is expected within 24 hours."
- Use Directions:
"The minimum rotational crop interval is 10 months, except
for alfalfa which is 12 months."
"The minimum time interval for sorghum, cotton, and all other
rotational crops is 10 months on soils with pH less than or
equal to 6.5 or 18 months for all soils with pH greater than 6.5."
"Do not apply to popcorn, sweet corn, or corn grown for seed
"Single or split applications of Accent must not exceed a total
of 1 1/3 oz/A in any crop year."
"Do not graze or feed forage or grain from the treated areas to
livestock within 30 days after application of Accent."
5. Summary of Major Data Gaps
Environmental Fate Ecological Effects
164-1 Terrestrial Field Dissipation 122-1 Seedling Emergence
201-1 Droplet Size Spectrum 122-1 Vegetative Vigor
202-1 Drift Field Evaluation
6. Contact Person at EPA
- Robert J. Taylor
Product Manager (25)
Registration Division (H7505C)
Office of Pesticide Programs
Environmental Protection Agency
401 M Street, S.W.
Washington, DC 20460
- Office Location and Telephone Number:
Room 245, Crystal Mall #2
1921 Jefferson Davis Highway
Arlington, VA 22202
THE INFORMATION PRESENTED IN THIS CHEMICAL INFORMATION FACT SHEET
IS FOR INFORMATIONAL PURPOSES ONLY AND NOT TO BE USED TO FULFILL
DATA REQUIREMENTS FOR PESTICIDE REGISTRATION AND REREGISTRATION.
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