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paclobutrazol (Clipper 50 WP) Herbicide Profile 8/85

                        CHEMICAL FACT SHEET FOR:
                              PACLOBUTRAZOL
FACT SHEET NUMBER: 62
DATE ISSUED: AUGUST 14, 1985
                  1.  DESCRIPTION OF CHEMICAL
- Generic Name:  (+/-)-(R*,R*)-B-[(4-chlorophenyl)methyl]-alpha-
  (1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol
- Common Name:  paclobutrazol
- Code Name:   PP333
- Trade Name:  Clipper 50 WP
- EPA Shaughnessy Code:  125601
- Chemical Abstracts Service (CAS) Registry Number:  76738-62-0
- Year of Initial Registration:  1985
- Pesticide Type:  Plant growth regulator
- Chemical Family:
- U.S. Foreign Producers:  ICI Americas Inc.
             2.  USE PATTERNS AND FORMULATIONS
- Application sites:  Ornamental trees (deciduous and broadleaf
  evergreen)
- Types of formulations:  Wettable powder (50% a.i.)
- Types and methods of application:  Applied in a pressurized tree
  injection system.
- Application rates:  Rates vary depending upon tree size; dosage for
  smallest treatable tree is 0.006 oz. active ingredient per tree.
- Usual carriers:  Water
                    3.  SCIENCE FINDINGS
Chemical Characteristics
- Physical state:  solid
- Color:  white
- Odor:  not significant
- Melting point:  165-166 degrees C
- Density:  1.22g/cubic cm
- Vapor pressure:  1.5 x 10(-4) Pa at 50 degrees C
                   8 x 10(-6) Pa at 30 degrees C
                   1 x 10(-6) Pa at 20 degrees C (by extrapolation)
Solubility:
- Water                  35 ppm
- Cyclohexanone          18%
- Methanol               15%
- Acetone                11%
- Methylene dichloride   10%
- Xylene                  6%
- Propylene glycol        5%
- Hexane               <1%
Octanol/water partition coefficient:  Log P 3.2
- Unusual handling characteristics:  None
Toxicological Characteristics
- Acute toxicology results
  - Technical:
    - Acute oral toxicity (rat):  1.95 g/kg (male), 1.33 g/kg (female),
      Toxicity Category III
    - Acute dermal toxicity (rat):  Greater than 2 g/kg, Toxicity
      Category III
    - Primary skin irritation (rabbit):  Paclobutrazol caused mild skin
      irritation.  Toxicity Category III
    - Primary eye irritation (rabbit):  Paclobutrazol caused reversible
      corneal opacities with irritation lasting 72 hours.  Toxicity
      Category II
    - Dermal sensitization (guinea pig):  Paclobutrazol is not a skin
      sensitizer.
    50% Formulation:
    - Acute inhalation toxicity (rat):  Greater than 766 mg/cu. m
      (male), 359-766 mg/cu. m (female), Toxicity Category II
- Chronic toxicology results:
  - 21-day dermal (rabbit):  NOEL is 10 mg/kg/day, LEL is 100 mg/kg/
    day
  - 90-day feeding (rat):  NOEL is 250 ppm, LEL is 1,250 ppm
  - One year feeding (dog):  NOEL is 15 mg/kg/day, LEL is 75 mg/kg/day
  - Teratology (rat):  NOEL (maternal toxicity) is greater than 100
    mg/kg/day (highest dose tested).  NOEL (fetal effects) is 10
    mg/kg/day.
  - Teratology (rabbit):  Within limitations of study (low fertility),
    NOEL (maternal toxicity) is 25 mg/kg/day.  LEL is 75 mg/kg/day.
  - Mutagenicity:  Paclobutrazol does not cause mutagenic effects.
  - Metabolism:  Results from rat and dog studies indicate that
    paclobutrazol and its metabolites are rapidly eliminated.
- Major routes of exposure:  Mixers, loaders, and applicators would
  receive the most exposure via skin/eye contact and inhalation.
Physiological and Biochemical Behavioral Characteristics
- Mechanism of pesticidal action:  Paclobutrazol acts as a plant
  growth regulator and reduces regrowth in ornamental trees following
  trimming.
Environmental Characteristics
- Adsorption and leaching in basic soil types:  Paclobutrazol could
  leach in sandy soils with low organic content.  In other soil types,
  the chemical does not have a high propensity to leach.
- Loss from photodegradation:  Paclobutrazol does not photodegrade
  after exposed to 10 days of simulated sunlight.
- Resultant average persistence:  Paclobutrazol degrades aerobically
  in soil with half-lives of about 1-7 months depending upon soil
  type.  Paclobutrazol is not expected to hydrolyze in the environment.
Ecological Characteristics
- Avian acute oral toxicity (Mallard):  greater than 7,913 mg/kg
- Avian dietary toxicity (Bobwhite quail):  greater than 5,000 ppm
- Avian dietary toxicity (Mallard):  greater than 20,000 ppm
- Fish acute toxicity (Bluegill):  23.6 mg/l
- Fish acute toxicity (Rainbow trout):  27.B mg/l
- Aquatic invertebrate toxicity (Daphnia magna):  33.2 mg/l
- Potential problems related to endangered species:  Minimal hazard to
  endangered species is expected because of the low toxicity of
  paclobutrazol and proposed use (tree injection).
Summary Science Statement
     The data base for paclobutrazol (non-food uses) is well developed. 
Results of acute inhalation (50% formulation) and eye irritation studies 
indicate toxicity category II. The chemical is non-mutagenic and is 
rapidly cleared from body tissue (rat and dog studies). Except for sandy 
soils, paclobutrazol does not exhibit a tendency to leach.  The chemical 
does not photodegrade and is not expected to hydrolyze.  Hazards to 
aquatic and terrestrial wildlife are not anticipated because of low 
toxicity and low risk of exposure (tree injection system).
          4.  SUMMARY OF REGULATORY POSITION AND RATIONALE
- Use classification:  General
- Use, formulation, manufacturing process, or geographical restrictions:
  Paclobutrazol is not to be injected:  (l) into trees that do not
  appear healthy, (2) into fruit or nut trees that will be harvested
  within one year after application, and (3) into sugar maple or any
  other trees that are or could be tapped for sugar.
- Unique label warning statements:
  - End-Use Products:  Wear protective clothing, rubber gloves, and a
    mask or pesticide respirator jointly approved by the Mining
    Enforcement and Safety Administration and the National Institute
    for Occupational Safety and Health.
                   5.  SUMMARY OF MAJOR DATA GAPS
NONE
                      6.  CONTACT PERSON AT EPA
Robert J. Taylor
Product Manager (25), TS-7670
Envlronmental Protection Agency
401 M Street S.W.
Washington, DC  20460
(703)557-1800
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.