cyhexatin (Plictran) Chemical Fact Sheet 6/85
CHEMICAL FACT SHEET FOR:
FACT SHEET NUMBER: 56
DATE ISSUED: JUNE 30, 1985
1. DESCRIPTION OF CHEMICAL
- Generic Name: Tricyclohexylhydroxystannane
- Common Name: cyhexatin
- Trade Names: Plictran, Acarstin, and Dowco 213
- EPA Shaughnessy Code: 101601
- Chemical Abstracts Service (CAS) Number: 13121-70-5
- Year of Initial Registration: 1972
- Pesticide Type: Miticide
- Chemical Family: organotins
- U S. Producer: Dow Chemical Company
2. USE PATTERNS AND FORMULATIONS
- Application sites: apples, pears, citrus, peaches, plums, nectarines,
strawberries, almonds, walnuts, hops, and ornamental plants (including
- Types and methods of applications: aerial and ground application as a
- Application rates: 0.5 lb. active ingredient (a.l.)/A to 2.0 lbs.
- Usual carriers: wettable powders
3. SCIENCE FINDINGS
- Technical cyhexatin is a white, crystalline powder, nearly odorless,
that has no true melting point, degrades to bistricyclohexyltin
oxide at 121 to 131 C, and decomposes at 228 C.
- It is soluble in some organic solvents, and is very insoluble in
- Vapor pressure is negligible at 25 C. It is stable in aqueous
suspensions in neutral and alkaline pH, reacts ionically in the
presence of a strong acid to form salts, and converts to dicyclo-
hexyltin oxide and further to cyclohexylstannoic acid by exposure to
- Acute oral LD50: 196 mg/kg (rat), Toxicity Category II.
- Acute dermal LD50: Data gap
- Primary eye irritation: Causes eye irritation -- corneal and iris
irritation (rabbit), Toxicity Category II.
- Acute inhalation: 6.35 mg/l (rat), Toxicity Category III.
- Primary skin irritation: Non-irritant, Toxicity - IV
- Skin sensitization: Not a sensitizer.
- Major routes of exposure: Human exposure from cyhexatin applica-
tions is greatest from mixing and loading of pesticide formulation
and applying it. Exposure can be reduced by the use of goggles or
face shield and gloves and other protective clothing.
- Neurotoxicity: Cyhexatin is not expected to be a delayed neuro-
toxin, because it is neither an organophosphate nor an analog of a
- Oncogenicity: Data gap. Study submitted does not meet Agency
- Metabolism: Available data suggest that cyhexatin is not readily
absorbed in tissues and is excreted in the feces. The minor amount
that is not excreted is metabolized to an organotin form and is
accumulated in the liver and kidney, with lesser levels found in the
brain, heart, adrenal, and muscle.
- Teratology: Adequate data are unavailable. Data gap.
- Reproduction: Adequate data are unavailable. Data gap.
- Mutagenicity: Adequate data are unavailable. Data gap.
Physiological and Biochemical Behavioral Characteristics
- Mechanism of pesticidal action: It is suspected that cyhexatin
inhibits adenosine triphosphate (ATP) enzymes.
- Metabolism and persistence in plants and animals: Available data
suggest that plant degradates of cyhexatin are translocated
following root exposure; however, these data are insufficient to
adequately characterize plant metabolism. Known animal metabolism
is summarized above.
- Available data are insufficient to fully assess the environmental
fate of cyhexatin. Data gaps exist for all required studies.
- The available data do suggest that cyhexatin can leach slowly in
certain soils. Data are required to assess cyhexatin's environ-
mental fate and ability to leach through soils.
- Avian acute oral LD50: Approximately 250 mg to 400 mg technical
cyhexatin/kg body weight for quail (moderately toxic).
- Avian dietary LC50: 195 ppm for bobwhite quail (highly toxic).
- Freshwater fish acute LC50: coldwater species (rainbow trout),
6 ppb for technical; warmwater species (bluegill), 4 ppb for
- Aquatic freshwater invertebrates toxicity: <<Daphnia.> 0.2 g/l
- Additional data are required to fully characterize the ecological
effects of cyhexatin.
- The Agency is unable to complete a full tolerance assessment for
the established tolerances because of certain residue chemistry and
significant toxicology data gaps.
- Established tolerances are published in 40 CFR 180.144. They are:
Commodity parts per million
Almonds 0 5
Almonds, hulls 60
Cattle, fat 0.2
Cattle, kidney 0.5
Cattle, meat byproducts (mbyp) 0.2
Cattle, meat 0.2
Citrus fruits 2
Goats, fat 0.2
Goats, kidney 0.5
Goats, liver 0.5
Goats, mbyp 0.2
Goats, meat 0.2
Hogs, fat 0.2
Hogs, liver 0.5
Hogs, mbyp 0.2
Hogs, meat 0.2
Horses, fat 0.2
Horses, kidney o.s
Horses, liver 0.5
Horses, mbyp 0.2
Horses, meat 0.2
Macadamia nuts 0.5
Milk, fat 0.05
Plums (fresh prunes) 1
Sheep, fat 0.2
Sheep, kidney 0.5
Sheep, liver 0.5
Sheep, mbyp 0.2
Sheep, meat 0.2
- The data for cyhexatin residues in or on the following agricultural
commodities are adequate to support the residue data requirements:
hops, Macadamia nuts, and strawberries.
- Additional residue data are required for the following commodities:
peaches, plums, nectarines, apples, pears, almonds, almond hulls,
walnuts, citrus fruits, dried hops, meat, milk, poultry, and eggs.
- Based on the established tolerances, the theoretical maximum residue
contribution (TMRC) for cyhexatin residues in the human diet is
0.33 mg/day (for a 60-kg person with a 1.5 kg diet). However, this
was based on an acceptable daily intake (ADI) which has been
invalidated due to the lack of a sufficient chronic toxicology data
- Compatibility of U.S. tolerances with Codex Maximum Residue Limits
will be assessed when data have been submitted and evaluated.
4. SUMMARY OF REGULATORY POSITION AND RATIONALE
- Unique warning statements required on labels: All manufacturing-use
and end-use cyhexatin products must bear appropriate labeling as
specified in 40 CFR 162.10. In addition to the above, the following
information must appear on the labeling:
- Manufacturing-use products must state that they are intended for
formulation into other manufacturing-use products or end-use
products for uses which are accepted by the Agency.
- Current labels must be revised to reduce the recommended spray
gallonage and active ingredient per acre for pears, peaches,
plums (prunes), and nectarines.
- Labels must be revised to incorporate the use of additional
protective clothing such as masks or respirators and chemically
- The Agency has determined that it should continue to allow the
registration of cyhexatin. None of the criteria for unreasonable
adverse effects listed in the regulations (162.11(a)) have been met
or exceeded. However, because of gaps in the data base, a full risk
assessment cannot be completed.
- Also, a full tolerance reassessment cannot be completed because of
major residue chemistry and toxicology data gaps. Until these gaps
are filled, cyhexatin will not be registered for significant new
- Available data are insufficient to fully assess the environmental
fate of and the ecological effects from cyhexatin. Data are required
to determine if cyhexatin will contaminate groundwater.
5. SUMMARY OF MAJOR DATA GAPS
- Additional crop residue studies on various commodities and plant and
animal metabolism studies are required to support existing
tolerances. The full complement of chronic toxicology requirements
are data gaps: chronic feeding, oncogenicity, reproduction, and
teratology and mutagenicity.
- The full complement of environmental fate data requirements are data
gaps. Studies on degradation (hydrolysis and photolysis), soil
metabolism, mobility, dissipation, and accumulation are needed to
fully characterize cyhexatin's environmental fate.
- Additional data are required on avian toxicology (acute and subacute
oral and reproduction) and freshwater and marine organism acute
- Other data gaps are product chemistry of technical cyhexatin, storage
stability of residues, and acute and subchronic dermal toxicology.
6. CONTACT PERSON AT EPA
Jay S. Ellenberger
Product Manager (12)
Registration Division (TS-767)
Office of Pesticide Programs
Environmental Protection Agency
401 M Street S.W.
Washington, DC 20460
Office location and telephone number:
Room 202, Crystal Mall Building 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.