United States Office of Prevention, Pesticides
Environmental Protection and Toxic Substances
Agency (7501C)
A
^•^^MU Fact Sheet
Name of Chemical: Cyhalofop-butyl
Reason for Issuance: Registration
Date Issued: May 23, 2002
1. Description of Chemical
Generic Name: 2-[4-(4-cyano-2-fluorophenoxy)phenoxy]propanoic acid, butyl ester (R)
Common Name: Cyhalofop-butyl
Trade Name: Clincher (Technical)
Clincher (CA)
Clincher (SF)
EPA Shaughnessy Code: 082583
Chemical Abstracts
Service (CAS) Number: 122008-85-9
Year of Initial
Registration: 2002
Pesticide Type: Herbicide
Chemical Family: Aryloxyphenoxy propionate
U.S. Producer: Dow AgroSciences LLC
2. Use Patterns and Formulations
Application Sites: Cyhalofop-butyl is registered for use on rice.
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Types of Formulations: 96.5% technical product
29.6% emulsifiable concentrate end-use product
Types and Methods
of Application:
Application Rates:
Carrier:
Aerial and ground application using standard commercial sprayers
Application rates 0.28 ozs of formulated product (0.19-0.28 pounds
active ingredient acid equivalent) per acre. Two applications are allowed
per season, with a ten-day interval for a maximum application rate of 0.46
ozs of formulated product per acre.
Water
3.
Science Findings
Summary Science Statements
Based upon a battery of acute toxicity studies, Clincher (CA) and Clincher (SF) are
classified as Toxicity Category IV. There are no risks of concern from the use of cyhalofop-butyl. An
appropriate endpoint attributable to a single dose was not identified. Therefore, cyhalofop-butyl is not
expected to pose an acute risk. The carcinogenic potential of cyhalofop-butyl has not been characterized
because the doses tested in the rat and mouse carcinogenicity studies were too low.
No dermal sensitivity was detected with cyhalofop-butyl. It does not demonstrate developmental or
reproductive toxicity. There is no evidence of neurotoxicity . None of the animal studies provided any
evidence that cyhalofop-butyl is an endocrine disrupter.
Chemical Characteristics
PROPERTY
Physical State
Color
Odor
Melting Point
Density
TECHNICAL
Waxy Solid
Off White/Buff
Faint almond odor
45.5°Cto49.5°C
1.172g/mL(S)/200C
END-USE
Liquid
Amber, clear
Mild aromatic odor
N/A
0.9662 g/ml, 0.961 5g/ml
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Solubility (Water)
Vapor Pressure
Octanol/Water Partition
Coefficient
PH
0.44 mg/1 @20°C (pH 7)
5.3xlO-8kPa(4.0x 10 @W7
mm Hg or Torr)
Log10Pow = 3.3158 @25C°
P = 2069; Log P = 3.3 158
N/A
N/A
N/A
6.73 at 23 °C
Toxicology Characteristics
Acute Toxicity (Clincher Technical)
! Acute Oral Toxicity in Rats - LD50 > 5000 mg/kg in males and females; Toxicity Category IV
! Acute Oral Toxicity in Mice - LD50 > 5000 mg/kg in males and females; Toxicity Category IV
! Acute Dermal Toxicity in Rats - LD50 > 2000 mg/kg in males and females; Toxicity Category m
! Acute Dermal Toxicity in Rats - LD50 > 5000 mg/kg in males and females; Toxicity Category IV
! Acute Inhalation Toxicity in Rats - LC50 > 5.63 mg/L in males and females; Toxicity Category IV
! Primary Eye Irritation in Rabbits - Minimally irritating, Toxicity Category IV
! Primary Skin Irritation in Rabbits - Non-irritating; Toxicity Category IV
! Primary Dermal Sensitization in Guinea-Pigs - Not a dermal sensitizer
Acute Toxicity (Clincher CA and Clincher SF)
! Acute Oral Toxicity in Rats - LD50 = 1611.7 mg/kg in males and LD50 > 2000, <5000 mg/kg in
females; Toxicity Category m
! Acute Dermal Toxicity in Rats - LD50 > 5000 mg/kg in males and females; Toxicity Category IV
! Acute Inhalation Toxicity in Rats - LC50 > 5.19 mg/L for males and females; Toxicity Category IV
! Primary Eye Irritation in Rabbits - Irritation based on findings of cornea! opacity in all three
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rabbits tested with the corneal opacity persisting through day 7 but clearing by day 10. All eyes were
positive for conjunctiva! redness through 3 days. Presence of corneal opacity in 3/3 eyes on day 7,
which was resolved by day 21.
! Primary Dermal Irritation in Rabbits - Irritation based on the effects of the 3 rabbits at 1,24, 48
and 72 hour scores for erythema which ranged from 1 to 2 and scores for edema which ranged from
1 to 2. On day 7 all 3 rabbits scored 2 for erythema, and 1 or 2 for edema. At 21 days irritation
had cleared in 2/3 rabbits, while the remaining rabbit scored 1 for erythema and 1 for edema; Toxicity
Category HI
! Primary Dermal Sensitization in Guinea-Pigs - The tests animals did not exhibit any sensitization
potential.
Subchronic Toxicity
! In a 90-day feeding study in rats, the NOAEL (male) is >400 mg/kg/day and the NOAEL (female)
is 400 mg/kg/day. In females the LOAEL for this study is 800 mg/kg/day based on perineal soiling
and reduced body weights and body weight gain.
! In a 90-day feeding study in rats, the NOAEL is 60.5/65.3 mg/kg/day (males/females) and the
LOAEL is 189.5/199.6 mg/kg/day based on kidney toxicity (males/female) and possible liver toxicity
in males. No short-term effects were observed which dould be used for a short-term endpoint.
! In a 90-day feeding study in mice, the NOAEL for males is > 30 mg/kg/day and in females at >100
mg/kg/day.
! In a 90-day feeding study in mice, no significant effects were observed at any dose level. The NOAEL
in males is >37.5 mg/kg/day and in females is 4.3 mg/kg/day. In females the LOAEL is 14.1 mg/kg/day
based on enlarged kidneys accompanied by swelling of the proximal tubule cells.
! In a feeding study in dogs, the NOAEL is 14.7/15.6 mg/kg/day (males/females) and the LOAEL is
75.2/79.4 mg/kg/day (males/females) based on brown and/or atrophied thymuses, and decreased thymus
weight.
! In a 21-day dermal study in rats, no dermal or systemic toxicity was observed at any dose level. The
systermic and dermal NOAELs are > 1000 mg/kg.day (limit dose).
Chronic Toxicity/Carcinogenicity
! In the combined chronic toxicity/carcinogenicity study in rats, there were no treatment-related increases
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in tumor incidence, compared to controls. The NOAEL in males is 0.823 mg/kg/day and 2.475 mg/kg/day
in females. The LOAEL in males is 3.44 mg/kg/day and 24.97 mg/kg/day in females. Dosing was too low
to elicit carcinogenic potential.
! In the carcinogenicity study in mice, in males the NO AEL is 0.99 mg/kg/day and the LOAEL is 10.06
mg/kg/day in males and 10.28 mg/kg/day in females. There was no evidence of carcinogenic potential
under the conditions of this study. Dosing was too low to elicit frank toxicity and inadequate to assess
carcinogenic potential. No short-term effects were observed which could be used for a short-term
endpoint.
! In a one-year chronic feeding study in dogs, no adverse effects were observed at any dose level. The
NO AEL for this study in males is >46.7 mg/kg/day and 45.9 mg/kg/day in females.
Developmental Toxicity
! In a developmental toxicity study in rats, the maternal NO AEL is 1000 mg/kg/day and the
developmental NO AEL is _> 1000 mg/kg/day
! In a developmental toxicity study in rabbits, the maternal NO AEL is 40 mg/kg/day and the maternal
LOAEL is 200 mg/kg/day based on maternal death. The developmental NO AEL for this study is > 1000
mg/kg/day.
Reproductive Toxicity
! In a 2-generation reproduction study in rats, in males the systemic NO AEL is 4.85-13.75 mg/kg/day
and the systemic LOAEL is 50.0-138.7 mg/kg/day based on kidney lesions. In females the systemic
NO AEL is 69.2-147.7 mg/kg/day. The reproductive NO AEL in males is 50.1-138.7 mg/kg/day and in
females is 69.2-147.7 mg/kg/day. The offspring NO AEL is 50-147.7 mg/kg/day.
Mutagenicity
! Five studies were available for review and all tested negative in the data submitted.
Neurotoxicity
! In a gavage acute neurotoxicity study in rats, the NO AEL is >2000 mg/kg based on the absence of
clinical signs, a lack of effects on FOB parameters and motor activity, and the absence of neuropathologic
lesions. There is no evidence of neurotoxicity.
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! In a feeding subchronic neurotoxicity study in rats the NOAEL is >75 mg/kg/day in males and >250
mg/kg/day in females based on the absence of clinical signs, lack of effects on FOB parameters and motor
activity, and absence of neuropathologic lesions. There is no evidence of neurotoxicity.
Metabolism
! Cyhalofop-butyl (labeled and nonlabeled in rats) demonstrated that absorption of gavaged test article
was 93-1000% with urinary excretion being the major route of elimination regardless of dose, label
position, or gender. Over 168-hours, 84-100% of the radioactivity was eliminated via the urine, with 86-
90% eliminated within 24 hours. Due to rapid excretion, tissue/organ levels declined to near detection limits
by 24 hours in all dose groups. There was a biphasic pattern for both labels with no substantial differences
in pharmacokinetic indices. Cyhalofop-butyl was absorbed and rapidly eliminated.
Exposures and Risks
An acute RfD was not established because an appropriate endpoint attributable to a single dose was not
identified. The chronic Reference Dose (RfD) is 0.01 mg/kg/day. Based on the supporting data, there
are no risks of concern from the use of cyhalofop-butyl. An appropriate endpoint attributable to a single
dose was not identified. Therefore, cyhalofop-butyl is not expected to pose an acute risk. No dermal
sensitivity was detected. The risk due to exposure to residues in food and water was calculated to be
below the Agency's level of concern for all population subgroups, including infants and children. The
FQPA safety factor for cyhalofop-butyl has been reduced to Ix when assessing acute and chronic dietary
exposures for all population subgroups for all exposure durations (acute and chronic). There are no
residential uses registered (or pending) for this chemical. Therefore a residential risk assessment was not
performed.
Environmental Characteristics
STUDY TYPE
Hydrolysis
Photolysis in Water
Photolysis on Soil
Aerobic Soil Metabolism
Aerobic Aquatic Metabolism
Anaerobic Aquatic Metabolism
Aquatic Field Dissipation
HALF LIFE/OTHER
88 days at pH 7, 2. 1 days at pH 9
27.9 - 159.3 days, not a significant process
0.5 days, not a significant process
3-1 1 hours, microbial metabolism is very
rapid
Ranged from 2.4 to 4.4 hours
0.2 days
Less than a dav
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Mechanism of Pesticidal Action
Cyhalofop-butyl is an inhibitor of acetyl coenzyme -A carboxylase, a pivotal enzyme in plant fatty acid
biosynthesis.
Potential to Contaminate Groundwater
Cyhalofop-butyl demonstrates the properties and characteristics associated with chemicals detected in
groundwater. The use of cyhalofop-butyl in areas where soils are permeable, particularly where the water
table is shallow, may result in groundwater contamination.
Ecological Characteristics
Terrestrial
Cyhalofop-butyl is practically non-toxic to birds on an acute exposure basis (LD50>2,250 mg/kg)
and on a subacute dietary exposure basis (LC5O5620 ppm). Cyhalofop-butyl is practically non-toxic to
small mammals on an acute exposure basis (LC50>5000 mg/kg). In addition, a rat developmental toxicity
study indicated that there were no treatment related effects up to the highest dose tested (1,000
mg/kg/day). Therefore the potential for chronic effects appears to be low. Cyhalofop-butyl is non-toxic
to adult bees (LD50>100 ug/bee).
Aquatic - Freshwater and Estuarine/Marine
Cyhalofop-butyl is highly toxic to both freshwater and estuarine/marine animals on an acute exposure
basis. However, data indicate that the major degradation products for cyhalofop-butyl are practically non-
toxic to aquatic organisms. The endangered species level of concern is exceeded for estuarine/marine fish,
estuarine/marine invertebrates, and freshwater fish. The minimal exceedance for threatened and/or
endangered aquatic species levels of concern will be mitigated by holding rice paddy water for a minimum
of 7 days to facilitate degradation of cyhalofop-butyl and by dilution of the discharge by the receiving
waters.
Plants
Cyhalofop-butyl is highly toxic to terrestrial plants. The minimal exceedance for threatened and/or
endangered aquatic species levels of concern will be mitigated by holding rice paddy water for a minimum
of 7 days to facilitate degradation of cyhalofop-butyl and by dilution of the discharge by the receiving
waters.
4. Summary of Regulatory Position and Rationale
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Available data provide adequate information to support the registrations of Clincher Technical, Clincher
CA and Clincher SF use on drill-seeded and water-seeded rice.
Use. Formulation. Manufacturing Process or Geographic Restrictions
Environmental Hazards
Do not apply directly to water, or to areas where surface water is present or to intertidal areas
below the mean high water mark except when treating rice fields as specified in this product
label. Drift and runoff may be hazardous to aquatic organisms and non-target plants in neighboring
areas. Do not contaminate water when disposing of equipment washwaters.
Do not discharge water from treated area for a period of four weeks post-treatment.
The endangered species level of concern is exceeded for estuarine/marine fish, estuarine/marine
invertebrates, freshwater water fish and terrestrial plants. The minimal exceedance for threatened
and/or endangered aquatic species levels of concern will be mitigated by holding rice paddy water
for a minimum of 7 days to facilitate degradation of cyhalofop-butyl and by dilution of the discharge
by the receiving waters. It is believed that the rapid degradation of the parent to less toxic
degradates will greatly reduce the likelihood of risk to non-target aquatic organisms.
Ground Water Advisory
Cyhalofop-butyl has properties and characteristics associated with chemicals detected in ground
water. The use of this chemical in areas where soils are permeable, particularly where the water
table is shallow, may result in ground water contamination.
Surface Water Advisory
Cyhalofop-butyl can contaminate surface water through spray drift. Under some conditios,
cyhalofop-butyl and/or its degradates may also have a high potential for runoff surface water
(primarily via dissolution in runoff water). These include poorly drained or wet soils with readily
visible slopes toward adjacent surface waters, frequently flooded areas, areas over-laying
extremely shallow ground water, area with in-field canals or ditches that drain to surface water,
areas not separated from adjacent surface waters with vegetated filter strips and areas overlaying
tile drainage systems that drain to surface water. Cyhalofop-butyl may contaminate surface water
by overflow of rice paddies, or by accidental or deliberate release of paddy water during the
growing season or at harvest.
Physical or Chemical Hazards
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Do not use or store near heat or open flame.
Drift Reduction
In general, ground sprays are considered safer than aerial applictions because there is a lower
potential for direct application to water, there is usually less drift, and typically smaller areas are
treated at any one time. However, drift from ground applications still occur. Therefore the
following drift precaution statement should be incorporated on the label.
Drift from aerial and/or ground applications of this pesticide is likely to result in damage to sensitive
aquatic organisms in water bodies adjacent to the treatment area. In addition, drift from aerial and
ground applications may damage non-target terrestrial plants or crops.
Cyhalofop-butyl cannot be applied aerially unless the nearest peach or nectarine orchard is at least
2 miles upwind or 4 miles downwind of the application site. Aerial applications may only be made
when the wind speed is ten miles per hour or less. A maximum boom width of 2/3 for fixed-wing
aircraft and less than 3/4 for helicopters is required. Buffer zone for non-target cereal and grass
crops is 50 feet for ground application and 450 feet for aerial application. Buffer zone for peaches
and nectarines is 660 feet. These restrictions were developed because of damage to peaches,
nectarines, non-target cereal and grass crops in California from use of cyhalofop-butyl on rice
under a section 18 in 2001.
Use Directions - General Precautions and Restrictions
Do not apply this product in a way that will contact workers or other persons, either directly or
through drift. Only protected handlers may be in the area during application. For any requirements
specific to your state or tribe, consult the agency responsible for pesticide regulation.
Do not apply within 60 days of rice harvest.
Do not apply more than 15 fl oz/acre in a single application. Do not make more than two
applications or apply more than 25 fl oz per acre during the growing season. Sequential
applications must be at least 10 days apart.
Do not allow discharge of paddy water from treated areas for a minimum of 7 days following the
most recent application of Clincher CA and Clincher SF.
Do not rotate treated land to crops other than rice for 3 months following application.
Do not apply where runoff or irrigation water may flow directly onto agricultural land other than
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rice fields.
Do not fish or commercially grow fish, shellfish or crustaceans entreated acres during the year of
treatment.
Use Directions - Rice
Mixers and loaders for aerial applications are limited to handling no more than the amount of
product sufficient to treat 800 acres.
Do not apply this product where drift may be a problem due to proximity to susceptible crops or
other desirable plants.
Buffer Zones- (distance between application and sensitive crop) for wind speeds between 2 and
10 miles per hour.
Sensitive crops (non-target cereal and grass crops such as corn, sugar cane, sudangrass,
sorghum, grass grown for seed, millet, and sod farm have a 50 feet ground restriction and
450 feet aerial restriction. Peaches and nectarines have a 660 feet ground restriction and
2 miles if wind blowing from treatment area away from sensitive crop, and 4 miles if wind
is blowing from treatment area toward sensitive crop.
5. Summary of Terms of Registration - Data Required
Subacute (28 day) inhalation toxicity study
Repeat Carcinogenicity study in rats (Maximum Tolerance Dose Met (MTD) Not Met
Repeat Carcinogenicity study in mice (MTD Not Met)
6. Contact Person at EPA
Joanne I. Miller
Product Manager 23
Herbicide Branch
Registration Division (7505C)
Office of Pesticide Programs
Environmental Protection Agency
1200 Pennsylvania Ave., N.W.
Washington, DC 20460
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Office Location and Telephone Number
Room 241, 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 reregistration.
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