United States Office of Prevention, Pesticides
Environmental Protection and Toxic Substances
Agency (7501C)
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47.0% water dispersible granule
end-use
46.9% water dispersible granule
end-use
Types and Methods of Application: Ground application using standard commercial sprayers
Application Rates: Application rates for soybeans range from 0.25 to 0.375 pounds active
ingredient per acre in preemergency, preplant incorporated, no-till and minimum till applications.
Carrier: Water, crop oil concentrate, non-ionic surfactant
3. Science Findings
Summary Science Statements
Based upon a battery of acute toxicity studies, Authority Herbicide (technical product) is classified
as Toxicity Category IE. Sulfentrazone is not carcinogenic. However, under the conditions of the
studies reviewed, sulfentrazone caused developmental and reproductive toxicity. The results of these
studies elicited a high level of concern, since the developmental toxicity studies demonstrated
embryo/fetal toxicity at treatment levels that were not maternally toxic, and significant toxic effects
were observed primarily in the second generation animals of the reproduction study. Because these
animals had been exposed to sulfentrazone m utero. the possibility that the observed reproductive
toxicity resulted from a developmental and/or genotoxic mechanism was suggested.
Chemical Characteristics - Technical Grade
Physical State - Solid
Color - Tan
Odor - Faint sulfur-like
Melting Point - 120-122°C
Density - 0.53 g/ml at 20°C
Solubility-7.8 X102(pH 7)
Vapor Pressure - 1 X 10'9 mmHg at 25 °C
Dissociation Constant - 6.56
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3
Octanol/Water Partition Coefficient - Kow = 9.8 at pH 7
pH - 4.78
Toxicology Characteristics
Acute Toxicity - Sulfentrazone Technical
Acute Oral Toxicity in Rats - LD50 > 2855 mg/kg in males and females; Toxicity Category in
Acute Dermal Toxicity in Rats - LD50 > 2000 mg/kg in males and females; Toxicity Category in
Acute Inhalation Toxicity in Rats - LC50 > 4.13 mg/1 in males and females; Toxicity Category HI
Primary Eye Irritation in Rabbits - Corneal opacity, iritis, diffuse irritation within 24 hr., clearing by
day 4; Toxicity Category HI
Primary Dermal Irritation in Rabbits - No erythema or edema after 4-hour exposure; Toxicity
Category IV
Primary Dermal Sensitization in Guinea-Pigs - Did not exhibit any sensitization potential.
Acute Toxicity - End-Use Products
The end-use products containing sulfentrazone, Authority 4 F Herbicide, Authority 75 DF Herbicide,
Authority BL Herbicide, and Authority Broadleaf Herbicide, resulted in acute toxicity classification
of HI or IV in all areas of acute toxicity testing. The end-use products carry the signal word
"CAUTION" to reflect toxicity category HI.
Subchronic Toxicity
A 90-day feeding study in rats resulted in a lowest-observed-effect level (LOEL) of 65.8
mg/kg/day in males and 78.1 mg/kg/day in females, and a no-observed-effect level (NOEL) of
19.9 mg/kg/day in males and 23.1 mg/kg/day in females.
A 90-day feeding study in mice resulted in a LOEL of 108.4 mg/kg/day for males and 143.6
mg/kg/day in females, and a NOEL of 60.0 mg/kg/day for males and 79.8 mg/kg/day for females.
A 90-day feeding study in dogs resulted in a NOEL of 28 mg/kg/day and a LOEL of 57
mg/kg/day for males and 73 mg/kg/day for females.
Chronic Toxicitv
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A 1-year feeding oral study was performed on dogs. The induction of normochromic
microcytosis in animals fed diets containing 1800 ppm test material, although compensated by
increased red cell production, reflects an adverse treatment-related effect. The microcytosis may
have arisen from the inhibition of heme synthesis as indicated by the presence of brown to
yellow/brown pigmentation in hepatocytes and reticuloendothelial cells of the liver. The
microcytosis induced by sulfentrazone justifies an oral LOEL of 61.2 mg/kg/day for males and
61.9 mg/kg/day for females. The NOEL is 24.9 mg/kg/day for males and 29.6 mg/kg/day for
females.
A 18-month feeding/carcinogenicity study in mice resulted a LOEL of 160.5 mg/kg/day in males
and 198.0 mg/kg/day in females, based upon treatment-related decreases in hemoglobin and
hematocrit. The NOEL is 93.9 mg/kg/day in males and 116.9 mg/kg/day in females.
A 2-year feeding/carcinogenicity study in rats resulted in a LOEL of 82.8 mg/kg/day in males and
67.0 mg/kg/day in females, and a NOEL of 40.0 mg/kg/day in males and 36.4 mg/kg/day in
females. There was no evidence of carcinogenicity in this study.
Reproductive/Developmental Toxicity
A developmental toxicity study in rats resulted in a maternal (systemic) LOEL of 50.0 mg/kg/day
based upon increased relative spleen weight and splenic extramedullary hematopoiesis. The
maternal (systemic) NOEL is 25.00 mg/kg/day. The developmental (fetal) LOEL is 25.0
mg/kg/day based upon 1) decreased mean fetal weight and 2) retardation in skeletal development
as evidenced by an increased number of litters with any variation and by decreased numbers of
caudal vertebral and metacarpal ossification sites. The developmental (fetal) NOEL is 10.0
mg/kg/day.
Evidence of treatment-related developmental toxicity consisted of decreased fetal viability,
decreased fetal body weight, and increased incidence of fetal alterations, comprised, for the most
part, of skeletal malformations and variations. A supplementary prenatal oral developmental
toxicity study in rats confirmed the maternal and fetal findings of the previously conducted study
and did not alter the study conclusions.
In a dietary two-generation reproduction study in rats resulted in the systemic and
reproductive/developmental NOEL of 14 mg/kg/day for males and 16 mg/kg/day for females.
Mutagenicity
A reverse gene mutation assay in Salmonella typhimurium yielded negative results, both with
and without metabolic activation.
A mouse lymphoma forward gene mutation assay yielded negative results with equivocal results
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without activation.
A mouse micronucleus assay test was negative following intraperitoneal injection of 340 mg/kg.
Metabolism
A metabolism study in rats resulted in the administered dose and nearly all radioactivity excreted
in the urine, indicating nearly complete absorption. Most of the test article was eliminated by
urine and feces within 72 hours, and appeared to be independent of dose and sex.
Environmental Characteristics
Acceptable information from environmental fate studies with respect to the persistence and
mobility of sulfentrazone under laboratory and field conditions has been reviewed. Based on the
current environmental fate data base, sulfentrazone has the following characteristics: 1)
moderately soluble, 2) not susceptible to hydrolysis, 3) extremely susceptible to direct photolysis
in water, 4) very stable to photolysis on soil, 5) aerobic half-life of 1.5 years, 6) anaerobic half-
life of 9 years, 7) very high mobility in soil (average Koc = 43, Kd < 1), and 8) low volatility from
soils and water. With these properties, it appears that sulfentrazone is highly mobile and
persistent, and has a strong potential to leach into groundwater and move offsite to surface water.
The primary routes of dissipation are through direct aqueous photolysis and leaching. Direct
photolysis would only be an effective dissipation pathway in clear shallow waters because
sulfentrazone is stable to hydrolysis and biodegradation. Low soil/water partitioning (average
Koc = 43, Kd < 1) indicates that most sulfentrazone runoff is through dissolution in runoff water,
as opposed to adsorption to eroding soil. It also indicates that most sulfentrazone will be
partitioned in the water column instead of in the suspended and bottom sediments.
Mechanism of Pesticidal Action
Sulfentrazone control weeds by process of protoporphyrinogen oxidase inhibition (membrane
disruption), a mode-of-action commonly referred to as PPO inhibition. Sulfentrazone is
primarily taken up by the roots of treated plants. Plants emerging from treated soil turn necrotic
and die after exposure to light. Foliar contact causes rapid desiccation and necrosis of exposed
plant tissue. Shoot-root soil placement studies indicate that sulfentrazone is primarily absorbed
by the roots of the plant following soil applications.
Potential to Contaminate Groundwater
A groundwater exposure estimate for sulfentrazone was conducted based on findings from a
prospective groundwater monitoring study in North Carolina. Although the study was
incomplete, enough data were collected to confirm that sulfentrazone leaches substantially to
groundwater in areas with sandy soils.
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Ecological Characteristics
Terrestrial
Sulfentrazone is practically non-toxic to birds on an acute oral and with an LD50 greater 2250
mg/kg. Sulfentrazone is practically non-toxic to birds on an avian dietary basis with an LD50
greater 5620 ppm. Mammalian results indicate that Sulfentrazone is slightly toxic to small
mammals on an acute oral basis.
Aquatic
Sulfentrazone is practically non-toxic to the rainbow trout (LC50) greater 120 ppm) and slightly
toxic to the bluegill sunfish (93.8 ppm). The results indicate that Sulfentrazone is slightly toxic
to fish on an acute basis. The chronic results indicate that Sulfentrazone significantly affects
young fish survival and growth at aquatic concentrations as low as 5.93 ppm. Sulfentrazone is
slightly toxic to aquatic invertebrates on an acute basis.
The results from data from chronic freshwater invertebrates indicate that survival of young
daphnids is adversely affected at Sulfentrazone concentrations as low as 0.51 ppm. The results
from acute estuarine and marine animals study are incomplete but indicate that Sulfentrazone is
highly toxic to estuarine/marine organisms.
Plants
Being a pre-plant and pre-emergent herbicide, Sulfentrazone is expected to prevent the successful
emergence of non-target terrestrial and semi-aquatic plants through soil that has been exposed.
The proposed use is not expected to pose an unacceptable risk to non-target terrestrial or aquatic
animals.
For nontarget terrestrial plant Tier II seedling emergence, the results indicate that lettuce is the
most sensitive dicot and oat is the most sensitive monocot. For Tier n vegetative vigor,
cucumber is the most sensitive dicot and onion is the most sensitive monocot.
For aquatic plant testing the results indicate that duckweed is the most sensitive aquatic plant
species.
4. Summary of Regulatory Position and Rationale
Available data provide adequate information to support the conditional registration of Authority
herbicide as a technical product, Authority 4 F herbicide, Authority 75 DF herbicide, Authority
Broadleaf herbicide, and Authority BL herbicide for use on soybean seed, in cereal grains
(excluding sweet corn), forage, straw, hay, grain, stover, bran and hulls.
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The registrant will add statements to the end use labels to mitigate the risk to groundwater and
will conduct further prospective groundwater studies to further address the Agency's concerns.
Use, Formulation, Manufacturing Process or Geographic Restrictions:
Environmental Hazards
This pesticide is toxic to marine/estaurine invertebrates. Do not apply directly to water,
to areas where surface water is present or to intertidal areas below the mean high water
mark. Drift and runoff may be hazardous to terrestrial and aquatic plants in neighboring
areas. Do not contaminate water when disposing of equipment washwaters or rinsate.
Groundwater Advisory and Labeling-Off of Soil Type: This chemical is known to
leach through soil into ground water under certain conditions as a result of label use.
Use of this chemical in areas where soils are permeable, particularly where the water table
is shallow, may result in ground-water contamination.
Do not use on coarse soils classified as sand which have less than 1% organic matter."
Surface Water Advisory: Sulfentrazone can contaminate surface water through spray
drift. Under some conditions, sulfentrazone may also have a high potential for runoff into
surface water (primarily via dissolution in runoff water), for several to many months post-
application. These include poorly draining or wet soils with readily visible slopes toward
adjacent surface waters, frequently flooded areas, areas overlying extremely shallow
ground water, areas with in-field canals or ditches that drain to surface water, areas not
separated from adjacent surface waters with vegetated filter strips, and areas over-lying
tile drainage systems that drain to surface waters."
Use Directions - General Precautions
Do not use on crops other than soybeans.
Use only ground application equipment. Do not apply by air.
Do not apply this product through any type of irrigation system.
Do not flood irrigation to apply or incorporate this product.
Do not apply when wind speed exceeds 10 mph nor with a spray pressure exceeding 40
psi.
Product must be used in a manner which will prevent back siphoning in wells, spills or
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improper disposal of excess pesticide, spray mixtures or rinsates.
Proper handling instructions: This product may not be mixed or loaded within 50 feet
of any wells (including abandoned wells and drainage wells), sink holes, perennial or
intermittent streams and rivers, and natural or impounded lakes and reservoirs. This
setback does not apply to properly capped or plugged abandoned wells and does not apply
to impervious pad or properly diked mixing/loading areas."
Operations that involve mixing, loading, rinsing, or washing of this product into or from
pesticide handling or application equipment or containers within 50 feet of any well are
prohibited unless conducted on an impervious pad constructed to withstand the weight of
the heaviest load that may be positioned on or moved across the pad. Such a pad shall be
designed and maintained to contain any product spills or equipment leaks, container or
equipment rinse or washwater, and rainwater that may fall on the pad. Surface water
shall not be allowed to either flow over or from the pad, which means the pad must be
self contained. The pad shall be sloped to facilitate material removal. An unroofed pad
shall be of sufficient capacity to contain at a minimum 110% of the capacity of the largest
pesticide container or application equipment on the pad. A pad that is covered by a roof
of sufficient size to completely exclude precipitation from contact with the pad shall have
a minimum containment capacity of 100% of the capacity of the largest pesticide
container or application equipment on the pad. Containment capacities as described above
shall be maintained at all times. The above specific minimum containment capacities do
not apply to vehicles when delivering pesticide shipments to the mixing/loading site.
States may have in effect additional requirements regarding wellhead setbacks and
operational containment."
Use Directions - Soybeans - Preemergence - Apply only one preemergence application,
not to exceed 0.375 Ib ai/acre per year, up to 30 days before crop emergence. Can also be
applied during or after planting, but before the crop emerges.
Use Directions - Soybeans - Preplant Incorporated - Apply only one preplant incorporated
application, not to exceed 0.375 Ib ai/acre per year, up to 30 days prior to planting
soybeans.
5. Summary of Data Gaps
Toxicology Data:
1. 21-day dermal study in rabbits
2. In vivo cytogenetics dominant lethal assay in rats
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Residue Chemistry Data:
1. Wheat processing study
2. Additi onal ri ce fi el d tri al s
3. Residue data for sorghum aspirated grain fractions
Ecological Effect Data:
1. Acute oyster toxicity study
6. Contact Person at EPA
Joanne I. Miller
Product Manager 23
Fungicide-Herbicide Branch
Registration Division (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 #2
1921 Jefferson Davis Highway
Arlington, VA 22202
(703) 305-6224
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
reregi strati on.
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