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cyhexatin (Plictran) Chemical Fact Sheet 6/85

                          CHEMICAL FACT SHEET FOR:
                  CYHEXATIN (TRICYCLOHEXYLHYDROXYSTANNANE)

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
  greenhouse grown).
- Types and methods of applications:  aerial and ground application as a
  spray
- Application rates:  0.5 lb. active ingredient (a.l.)/A to 2.0 lbs.
  a.i./A
- Usual carriers:  wettable powders


                       3.  SCIENCE FINDINGS

Chemical Characteristics

- 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
  water.
- 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
  ultraviolet radiation.


Toxicological Characteristics

- 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
  neurotoxic compound.
- Oncogenicity:  Data gap.  Study submitted does not meet Agency
  standards.
- 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.


Environmental Characteristics

- 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.


Ecological Characteristics

- 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
  technical.
- Aquatic freshwater invertebrates toxicity:  <<Daphnia.> 0.2  g/l
- Additional data are required to fully characterize the ecological
  effects of cyhexatin.

Tolerance Assessment

- 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
Apples                                         2
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
Hops                                          30
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
Nectarines                                     4
Peaches                                        4
Pears                                          2
Plums (fresh prunes)                           1
Sheep, fat                                     0.2
Sheep, kidney                                  0.5

Sheep, liver                                   0.5
Sheep, mbyp                                    0.2
Sheep, meat                                    0.2
Strawberries                                   3
Walnuts                                        0.5

- 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
  base.
- 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
    resistant gloves.
- 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
  uses.
- 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
  toxicology.
- 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)
Insecticide-Rodenticide Branch
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
(703) 557-2386


DISCLAIMER:
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.