United States O.'f.ce of Pestodes
Environmental Protection and Toxic Substances
Agency (H7501C)
PA Pesticide
Fact Sheet
Name of Chemical: Nicosuifuron
Reason for Issuance: New chemical
Date Issued: June 29> "90
Fact Sheet Number: 216
54 O-FS-9 0-096
DESCRIPTION OF CHEMICAL
Generic Name:
Nicosuifuron [3-pyridinecarboxamide, 2—{(((4,6
-dimethoxypyrimidin-2-yl)aminocarbony1)
aminosulfonyl))-N,N-dimethylJ
Common and Code Name: Nicosuifuron, DPX-V9360
Trade and Other Names: Accent
EPA Shaughnessy Codes: 129008
Chemical Abstracts Service
(CAS) Number:
Year of Initial
Registration:
Pesticide Type:
Chemical Family:
U.S. and Foreign:
Producers:
111991-09-4
1990
Herbicide
Sulfonylurea
E.I. du Pont de Nemours & Co. , Inc
DSE PATTERNS AND FORMPLATTONS
Application Sites:
Types and Methods
of Application:
Application Rates:
Field corn only. Accent .is not to be used on
popcorn, sweet corn, or com grown for seed
production.
Accent is to be applied to young, actively growing
weeds with ground equipment.
Single application - Maximum single application
is 1 1/3 ounce (oz) of Accent per acre (A) per any
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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 Accent/A/crop year [recommended
2/3 oz of Accent each (0.5 oz/ai/A)].
Formulations:
75* water dispersible granule
SCIENCE FINDINGS
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, a 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 effect to the environment than
other sulfonylurea products.
Chemical Characteristics of the Technical Material
N.R. - Not Required, N.A. - Not Applicable
END USE PRODUCT
(Accent)
Molecular Weight: 410.40
TECHNICAL
(Nicosulfuron)
Molecular Formula: C.Jf.-N.O.S
18 6 6
light tan
Color:
white
Physical State: solid, granular
solid
Odor:
none
paste-like
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Melting Point:
Boiling Point:
Density:
Solubility:
END USE PRODUCT
(Accent)
N.R.
N.A.
0.53 g/ml
N.R.
TECHNICAL
(Nicosulfuron)
141-144 #C
N.A.
0.313 g/ml
~solubility limit,
•solubility limit,
0.04* (pH 5.0 buffer);
1.2* (pH 7.0 buffer); and
3.9* (pH 9.0 buffer)
g/100 g buffer at 25*C
*18 (acetone), *23
(acetonitrile), *1.7
(benzene), *64
(chloroform), *64 (N,N
-dimethylformamide),
*4.5 (ethanol), *3.8
(ethyl acetate), *<0.02
(n-hexane), *0.44
(methanol), *160
(methylene chloride),
*1.2 (2-propanol), *26
(tetrahydrofuran), *0.37
(toluene), *0.20
(xylenes)
ppm x 103at 28 + 1 *C
Vapor Pressure:
Dissociation
Constant:
N.R.
N.R.
1.2 x 10
16
torr
Octanol/Water Partition
Coefficient: N.R.
pH:
Stability:
3.9 (1% dispersion
in water)
N.R.
pKt value = 4.3 (acid)
0.44 (pH 5)
0.017 (pH 7)
0.01 (pH 9)
A slurry in HPLC
water caused the pH of
the water to decrease
from 6.6 to 4.5.
The TGAI is solution
stable in the presence
of iron metal and ferrous
(Fe ). The solid TGAI
is stable under normal
storage at 25 C and at
45 C for 3 weeks.
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END USE PRODUCT
(Accent)
Oxidizing or Reducing
TECHNICAL
(Nicosulfuron)
Action:
Flammabilrty:
Explodability:
Storage Stability:
Viscosity:
Miscibility:
Corrosion
Characteristics:
Does not contain oxidizing
or reducing agents.
N. A.
Not explosive
Ten months result showed
product stability at room
temperature. Aging test
continuing for two additional
months.
N. A.
N.A.
After being stored in the
laboratory at room temperature
for 10 month, no physical change
was observed for either solid
granules or container material of
construction (high-density
polyethylene).
Dielectric
Breakdown Voltage: N.A.
Toxicology Characteristics
Acute Testing
Acute Oral:
TECHNICAL
LDjq > 5000 mg/kg
Toxicity Category
Acute Dermal:
Acute Inhalation:
Primary Dermal
Irritation:
Primary Eye
Irritation:
LDso > 2000 mg/kg
FORMULATION
LD50 > 5000 mg/kg
- IV Toxicity Category - IV
LD50 > 2000 mg/kg
Toxicity Category - III Toxicity Category - III
LCj,, > 5.9 mg/1
Toxicity Category
Non-irritant
Toxicity Category
Moderate Irritant
Toxicity Category
LC50 > 5600 mg/m
- Ill Toxicity Category - IV
Mild Irritant
- IV Toxicity Category - IV
Moderate Irritant
- Ill Toxicity Category - III
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TECHNICAL FORMULATION
Dermal Sensitizat-
ion: Non-sensitizer Non-sensitizer
Chronic Testing
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 rat, respectively.
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 4 65
mg/kg/day; an increase in clinical signs, gross pathological
observations, abortions, postimplantation loss and a decrease in
body 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 F, (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
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gestational period. The Reproductive NOIL 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
F2i high dose group.
Special Testing
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-V9 360 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-C02 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.
Mutagenicity Testing
No mutagenic activity was observed when tested in four strains
(TA97A, TA98, TA100, and TA1535) of Salmonella tvphimurium. In
vitro chromosomal aberration test 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 Action:
Biodegradation is an important degradation mechanism of nicosulfuron.
Foliar Absorption:
Foliar absorption is the primary means of nicosulfuron uptake by
plants.
Environmental Characteristics
Hydrolysis - Nicosulfuron is stable in aqueous solutions at neutral
and alkaline pHs. Solubility increases with increasing pH. The main
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hydrolytic mechanism involves cleavage of the sulfonylurea bridge, but
a minor mechanism involving -S02- elimination followed by rebridging
also occurs at acidic pHs. The main hydrolytic degradates are
pyrimidine amine and pyridine sulfonamide.
Photodeqradation in water and on soil - Photodegradation is not a
significant degradation mechanism for nicosulfuron.
Aerobic Spjl 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 - Nicosulfuron 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 least
mobile.
Volatility from soil - Nicosulfuron is not likely to volatilize
from soil.
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, anaerobic aquatic
metabolism, mobility in soil, and accumulation in confined
rotational crops. The volatility from soil studies and the
bioaecumulation 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.
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Ecological Characteristics
Avian acute toxicity:
Bobwhite Quail
LD50 > 2000 mg/kg
Avian dietary toxicity:
Bobwhite Quail LC^ > 5000 mg/kg
Mallard Duck
Freshwater fish acute
toxicity:
Bluegill Sunfish
Rainbow Trout
LC50 > 5000 mg/kg
LC50 > 1000 ppm
LC50 > 1000 ppm
Freshwater invertebrate
toxicity:
Daphnia magna
Acute Contact toxicity:
LC50 > 1000 ppm
Honey bee
LD,
50
> 20 ug/bee
Classification
Practically Non-toxic
Slightly Toxic
Slightly Toxic
Practically Non-toxic
Practically Non-toxic
Practically Non-toxic
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 not cause substantial 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
species.
TOLERANCE A8SE88WEKT
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.
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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 of Regulatory Positions
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 Pnigue Labeling
PRECAUTIONARY STATEMENTS
"Do not apply where/when conditions 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.M
RESTRICTIONS
"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
production."
"Single or split applications of Accent must not exceed a total of
1 1/3 oz/A in any one crop year."
"Do not graze or feed forage or grain from the treated areas to
livestock within 30 days after application of Accent."
Summary of Maior Data Gaps
Environmental Fate
164-1 Terrestrial Field Dissipation
201-1 Droplet size spectrum
202-1 Drift field evaluation
Ecological Effects
122-1 Seedling Emergence
122-1 Vegetative Vigor
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COtfTACT PERSON AT EPA
Robert J. Taylor
Product Manager (25)
Fungicide-Herbicide Branch
Registration Division (H7505C)
Office of Pesticide Programs
Environmental Protection Agency
401 M Street, S. W.
Washington, D. c. 20460
Office location and telephone number:
Room 245, Crystal Mall #2
1921 Jefferson Davis Highway
Arlington, VA 22202
(703) 557-1800
DISCLAIMER: The information in this Pesticide Fact Sheet is a summary
only and is not to be used to satisfy data requirements for pesticide
registration and reregistration. The complete Registration Standard for
the pesticide may be obtained from the contact person listed above.
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