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picloram (Tordon, Grazon) Herbicide Profile 10/88

EPA Pesticide Fact Sheet
Name of Chemical  Picloram
Reason for Issuance:  Registration Standard
Date Issued:  October 24, 1988
Fact Sheet Number:  48.1
                1.  DESCRIPTION OF CHEMICAL
- Chemical Name:  4-amino-3,5,6-trichloropicolinic acid
- Common Name:  Picloram
- OPP Chemical Code:  005101
- Chemical Abstracts Service (CAS) Number:  1918-02-1
- Year of Initial Registration:  1964
- Pesticide Type:  Herbicide
- Chemical Family:  Picolinic acid
- U.S. Producer:  Dow Chemical, U.S.A.
- Chemical Name:  Potassium salt of 4-amino-3,5,6-trichloropicolinic
  acid
- Common Name:  Picloram, Potassium (K) salt
- OPP Chemical Code:  005104
- CAS No.:  2545-60-0
- Chemical Name:  Isooctyl ester of 4-amino-3,5,6-trichloropicolinic
  acid
- Common Name:  Picloram, Isooctyl ester (IOE) of picloram
- OPP Chemical Code:  005103
- Chemical Name:  Triisopropanolamine salt of 4-amino-3,5,6-trichloro-
  picolinic acid
- Common Name:  Picloram, TIPA salt
- OPP Chemical Code:  005102
- Chemical Name:  Triethylamine salt of 4-amino-3,5,6-trichloropicolinic
  acid
- Common Name:  Picloram, TEA salt
- OPP Chemical Code:  005105
- Chemical Name:  Isopropanolamine salt of 4-amino-3,5,6-trichloropico-
  linic acid
- Common Name:  Picloram, IPA salt
               2  USE PATTERNS AND FORMULATIONS
Application Sites:
- Picloram, potassium salt:  Terrestrial food crop use on small grains,
  flax, pastures and rangeland grasses; Terrestrial noncrop use
  on noncrop agricultural areas and rights-of-way; Forestry use on
  forest lands site preparation.
- Picloram, isooctyl ester:  Terrestrial noncrop use on industrial
  sites and rights-of-way; Forestry use on forest trees site
  preparation.
- Picloram triisopropanolamine salt:  Terrestrial food crop use on
  small grains and pastures and rangeland; Terrestrial nonfood crop
  use on uncultivated agricultural areas, rights-of-way, and industrial
  sites; Aquatic noncrop use on drainage ditch banks; Forestry
  use on forest trees.
- Picloram, triethylamine salt:  Terrestrial food crop use on pastures
  and rangelands.
Types and Methods of Application:
- By ground:  broadcast or spot treatment as foliar or soil spray; as a
  basal spot treatment, broadcast as pelletized spray; as tree
  injection, as frill treatment; as a stump treatment, as basal bark
  treatment, as a wick application, and as a low-volume dormant stem
  spray.
- By air: broadcast and low-volume dormant spray.
Pests Controlled:  Broadleaf weeds and woody plants.
Application Rates: (Section 3 registrations)
- Picloram, TIPA salt:  0.27 to 3.00 pounds acid equivalent (lb ae)
  per acre (A)
- Picloram, IOE:  0.5 to 3.0 lb ae/A(mixtures or MAF)
- Picloram, K salt:  1.0 to 8.5 lb ae/A
- Picloram, TEA salt:  0.25 to 1.0 lb ae/A(SLNS)
Types of Formulations: [represented Sec 3 registrations of the potassium
salt(K)]:
- Formulation Intermediate: 30% ae or 34.7% active ingredient (ai),
  Pelleted: 2% ae or 2.3 ai, 5 ae or 5.8% ai, 10% ae or 11.6 ai; Soluble
  Concentrate, Liquid: 2 lb ae or 24% ai, 24.4% ai or 29.9 ai
Usual Carrier:  Water
                         3. SCIENCE FINDINGS
Summary Science Statement
- Technical picloram is in Toxicity Category I with respect to acute
  inhalation and Categories II and IV with respect to other acute
  toxicities.  Picloram has been classified as Group D Oncogen (not
  classifiable to human carcinogenicity).  Repeat oncogenicity,
  teratology, and reproduction studies are being required.  Picloram
  does not appear to be mutagenic based on available data.
- Picloram is stable to hydrolysis, does not photodegrade under light,
  and is relatively stable in anaerobic loam soils and under anaerobic
  aquatic conditions and does not accumulate in fish.  Picloram is
  intermediately to very mobile in soils ranging in texture from
  clay to loam.  Picloram has been identified as a chemical with a
  potential to contaminate groundwater.
- The Agency is requiring that residue data depicting residues of HCB
  in plant and animal commodities be submitted.
- Picloram is practically nontoxic to avian species, slightly to
  moderately toxic to freshwater fish, and slightly toxic to freshwater
  invertebrates.
Chemical Characteristics:
- Technical Picloram (Acid):
  - Color: White
  - Physical State:  Powder
  - Odor:  Chlorine like
  - Melting Point:  215 degrees C (decomposes)
  - Bulk Density:  19.7 lb/cu ft
  - Solubility at 25 degrees C:
      0.043 g/100 mL - Water
      0.55 g/100 mL - Isopropanol
      1.05 g/100 mL - Ethanol
      1.98 g/100 mL - Acetone
      0.12 g/100 mL - Diethyl ether
      0.16 g/100 mL - Acetonitrile
      1.85 g/100 mL - Methanol
      0.06 g/100 mL - Methylene dichloride
      0.02 g/100 mL - Benzene
      0.001 g/100 mL - Kerosene
  - Vapor Pressure:  6.16 x 10-7 millimeters (mm) Hg at 35 degrees C
                     1.07 x 10-6 mm Hg at 45 degrees C
  - Storage Stability:  Stable under normal conditions.
- Picloram, Potassium (K) Salt (34.7% ai)
  - Color:  Dark brown
  - Physical State:  Liquid
  - Odor:  Alcoholic
  - Bulk Density:  1.320 at 20 degrees C
Toxicology Characteristics:
Existing data are all based on picloram (technical) or K salt.
  Further data are requested for the IOE, TIPA salt, TEA salt, and IPA
  salt.
Acute Toxicology - Technical (Acid):
- Acute Oral Toxicity (Rats):  Greater than (>) 5000 mg/kg body weight
  for males - Toxicity Category IV; = 4012 mg/kg for females - Toxicity
  Category III
- Acute Dermal Toxicity (Rabbits):  > 2000 mg/kg for males and
  females, Toxicity Category III
- Acute Inhalation (Rat):  > 0.035 mg/L for males and females, Toxicity
  Category I
- Primary Eye Irritation (Rabbit):  Moderate eye irritation, Toxicity
  Category III
- Primary Dermal Irritation (Rabbit):  Not an irritant, Toxicity
  Category IV
- Dermal Sensitization (Guinea Pig):  Not a skin sensitizer
Acute Toxicology (K Salt):
- Acute Oral Toxicity (Rat):  > 5000 mg/k for males, Toxicity Category
  IV; = 3536 mg/kg for females, Toxicity Category II
- Acute Dermal Toxicity (Rabbit):  > 2000 mg/kg for males and females,
  Toxicity Category III
- Acute Inhalation Toxicity (Rat):  > 1.5 mg/L for males and females,
  Toxicity Category II
- Primary Eye Irritation (Rabbit):  Moderate eye irritation, Toxicity
  Category III
- Primary Dermal Irritation (Rabbit):  Not a skin irritant, Toxicity
  Category IV
- Dermal Sensitization (Guinea Pig):  Skin Sensitizer*
_______________
*Requires statement for skin sensitization:  "May Cause Allergic Skin
 Reaction."
Acute Toxicology (IOE):
- Acute Oral Toxicity (Rat):  > 3500 mg/kg for males and females,
  Toxicity Category III
- Acute Dermal Toxicity (Rabbit):  > 2000 mg/kg for males and females,
  Toxicity Category III
- Acute Inhalation Toxicity (Rats): > 0.35 mg/L for males and females,
  Toxicity Category II
- Primary Eye Irritation (Rabbits): Moderate eye irritation, Toxicity
  Category III
- Primary Dermal Irritation (Rabbit):  Mild skin irritation, Toxicity
  Category III
Subchronic Toxicology Studies:
- An acceptable 13-week subchronic feeding study in rats is available
  for picloram.  The no-observed-effect level (NOEL) for this study was
  50 mg/kg.  A dose dependent increase in absolute and relative liver
  weights was seen at 150 mg/kg.
- An acceptable 6-month feeding study with dogs is available for
  picloram.  The NOEL for this study was 7 mg/kg.  A decrease in food
  consumption and increase in liver weights was noted at the highest
  dose.
- No subchronic feeding studies are available for the TIPA, TEA, IPA, or
  IOE forms of picloram.  Subchronic feeding studies are required in a
  rodent and a nonrodent for each form of picloram.
- A 21-day subchronic dermal study is not available for picloram.  This
  study is required for all forms of picloram.
Chronic Feeding Studies:
- An acceptable 2-year chronic feeding study with rats is available for
  picloram.  An increase in size and altered tinctorial properties of
  centrilobular hepatocytes occurred in males and females at the high
  (200 mg/kg/day) and mid (60 mg/kg/day) dose resulting in a NOEL of 20
  mg/kg/day for this study.
- A chronic feeding study in nonrodents is not available for picloram
  and is required.
Oncogenicity Studies:
- The available oncogenic data for picloram include mouse and rat
  studies performed by the National Toxicology Program (NTP) and a
  rat study performed by DOW Chemical U.S.A.
- An oncogenic effect (neoplastic nodules) was seen in female rats at
  the highest dose in the NTP study.  This study was unacceptable
  based on experimental design (too short exposure limit, insufficient
  information to determine if a maximum tolerated dose [MTD]
  was attained).
- No oncogenic effects were noted in either the mouse study done by NTP
  or the rat study done by Dow. These studies were not acceptable
  because the available information was insufficient for determining
  if an MTD had been reached.
- The test material in all of these studies contained the contaminant
  hexachlorobenzene (HCB), which is classified by the Agency as a
  Group B2 oncogen (probable human carcinogen). Picloram was classified
  as a Group D oncogen (not classifiable as to human carcinogenicity).
  The Agency is requiring that both the mouse and rat oncogenicity
  studies be repeated.
Teratogenicity and Reproduction:
- A teratogenicity study in rabbits is available for picloram. A small
  number of fetuses showed abnormalities such as missing ribs,
  omphalocele, and hypoplastic tail. Historical control data are
  required to evaluate the observed abnormalities.
- A teratology study in rats is available for picloram. No teratogenic
  effects were noted. Some fetotoxicity was present at the lowest
  dose. Because a NOEL cannot be set for the study a repeat teratology
  study in rats is required.
- A multigeneration reproduction study in rat is available for picloram.
  No reproductive effects were observed however, too few test animals
  were used and no toxicity was observed at the highest dose.
  Therefore, a 2-generation reproduction study is required for picloram.
- No teratology or reproduction studies are available for the ester and
  amine forms of picloram.  Teratology studies in rats and rabbits are
  required for all ester and amine forms of picloram.  Reproduction
  studies are not required at this time.
Mutagenicity:
- Picloram did not show evidence of chromosomal changes in a cytogenetic
  bone marrow study exposing rats up to 2000 mg/kg of picloram.
- No other acceptable mutagenicity studies are available for picloram,
  its salt, ester, or amine forms.  Additional mutagenicity data are
  required for picloram, its esters, and its amines.
Metabolism:
- Available rat metabolism data are not adequate to fulfill Guideline
  requirements; therefore, additional studies are required.
Manufacturing Contaminants:
- Technical picloram is contaminated with HCB, classified as a probable
  human carcinogen (Group B2).  Dietary and nondietary risk assessments
  were performed by the Agency.  The Agency considered the dietary and
  nondietary risk from HCB to be acceptable at this time.
- Nitrosoamines are a potential contaminant of tertiary amines (TEA)
  and alkanolamines (TIPA) forms of picloram.  Testing is required
  to show that the level of 1 ppm nitrosoamine contamination is not
  exceeded.
Physiological and Biochemical Characteristics:
- Foliar Absorption and Translocation:  Picloram translocates from both
  the roots and leaves of plants and accumulates in the new growth.
  Picloram is both foliar-absorbed and root-absorbed.
- Mechanism of Pesticidal Action:  Alters nucleic acid and protein
  synthesis.
- Metabolism and Persistence in Plants:  Available plant metabolism
  data indicate that picloram degrades to C02, oxalic acid, and
  the metabolites 4-amino-2,3,5-trichloropyridine and 4-amino-35-
  dichloro-6-hydroxypicolinic acid.
- Metabolism and Persistence in Animals:  Available metabolism data
  indicate that animals excrete 82 to 98 percent of the [l4C]picloram
  used in dosing the animals as picloram.
Environmental Characteristics:
- Absorption and Leaching in Basic Soil Types:  Available data indicate
  that picloram was intermediately mobile to very mobile in soils
  ranging in texture from clay to loam.  Adsorption of picloram pH.
  Addition of inorganic salts to the soil did not affect adsorption of
  picloram.
- Microbial Breakdown:  Picloram degraded with half-lives of 100 to 200
  days in loam soil, 200 to 300 days in silt loam soil, and greater than
  300 days in loamy sand, commerce loam, clay, and sandy loam soils
  under aerobic conditions.  Picloram was relatively stable in anaerobic
  loam soil under anaerobic aquatic soil conditions.
- Loss from Photodecomposition:  Does not degrade.
- Bioaccumulation in Fish:  Does not accumulate in fish.
- Potential to Contaminate Groundwater:  Picloram has been previously
  identified as a pesticide with a propensity to leach into groundwater.
  Picloram has been reported as detected in seven states.  Picloram is
  persistent and mobile and has a high potential to reach groundwater.
- Exposure to Humans:  Based on available acute toxicology data the
  major routes of exposure appear to be through inhalation and dermal
  sensitization.  Although technical picloram (free acid) is in Toxicity
  Category I based on inhalation, there is little chance of exposure to
  mixer/loaders or applicators because there are currently no products
  registered containing the free acid form of picloram.
- Risk to Humans:  The major risk to humans appears to be from the
  contaminant HCB.  Both dietary and nondietary risk assessments were
  performed.  The dietary exposure to HCB occurs from the use of
  pesticides containing picloram on small grains and secondary residues
  on animal commodities.  The oncogenic risk for the U.S. population
  based on dietary exposure was calculated to be 6. x 10-7.
- Potential nondietary exposure to HCB is to workers, mixer/loaders and
  applicators from use of picloram on wheat, forests, right-of-way, and
  pasture/rangeland. The estimated nondietary risk to mixer/loaders and 
  applicators ranged from 5.0 x 10-5 to 10-8 .
- Reentry: Reentry intervals are not required because cultural practices
  for existing uses indicate little likelihood that field workers
  would be exposed to acutely toxic levels of picloram from agricultural
  applications.
Ecological Characteristics:
- Avian Acute Oral Toxicity (Technical): Bobwhite quail > 2250
  mg/kg/day; K Salt: Bobwhite quail > 2510 mg/kg/day
- Avian Subacute Dietary Toxicity (Technical): Bobwhite quail > 5000
  ppm, mallard duck > 5000 ppm; K Salt, bobwhite quail > 5620 ppm; IOE,
  bobwhite quail > 5620 ppm
- Acute Toxicity to Freshwater Fish (Technical): Rainbow trout = 4.3
  to 19.3 ppm, bluegill sunfish = 14.5 to 23.0 ppm; K Salt, rainbow
  trout = 13 ppm, catfish = 14 ppm, bluegill sunfish = 24 ppm; IOE,
  rainbow trout = 4.0 ppm, catfish = 1.4 ppm, bluegill sunfish =
  6.3 ppm
- Fish Embryolarvae Study:  Rainbow trout with a maximum acceptable
  threshold concentration (MATC) = 0.55 < MATC < 0.88 mg/L
- Acute Toxicity to Freshwater Invertebrates Studies:  (Daphnids,
  Gammarus, Pteronarcella, and Pteronarcys) = 10 to 68.3 ppm
- Chronic Aquatic Invertebrate Study (Daphnids): 11.8 < MATC
  < 18.1 mg/L
- Acute Toxicity to Honey Bees (Technical): = 14.5 micrograms per bee
- Technical picloram appears to be moderately to slightly toxic to
  freshwater fish, slightly toxic to aquatic invertebrates, and
  practically nontoxic to birds. Chronic fish testing showed that
  picloram caused a reduction in rainbow trout larval survival at 2.02
  mg/L and a reduction in growth at 0.88 mg/L. Picloram affected the
  growth and survival in cutthroat trout at 0.29 mg/L.
- The isooctyl ester form of picloram is moderately toxic to fish, and
  practically nontoxic to birds.
- The potassium salt of picloram appears to be slightly toxic to
  freshwater fish and practically nontoxic to birds.
Phytotoxicity and Endangered Species
Picloram has been shown to be a highly phytotoxic herbicide.
Because of picloram's demonstrated toxicity to nontarget plant species
   and its intended use pattern, picloram has been identified as
   being likely to jeopardize endangered plant species when used on
   pastures/rangeland and forests.  A program is being developed by
   the Agency to reduce or eliminate exposure to these species to a
   point where use does not jeopardize these species.
Tolerance Assessment:
Tolerances are established under 40 CFR 180.292 for residues of the
   picloram.  Food and Feed additive tolerance are established
   under 40CFR 185.4580 and 40 CFR 186.4580.  These replace old
   Section 21 CFR 183.350 and 21 CFR 561.305.
The Agency has established a R.F.D or a provisional acceptable daily
   intake at 0.07 mg/kg/day based on a 6-month dog feeding study
   (NOEL of 7.0 mg/kg/day) using a safety factor of 100.  The theoret-
   ical maximum residue contribution (TMRC) is calculated to
   be 0.001847 mg/kg/day, which utilizes 2.6 percent of the PADI.
The tolerance assessment indicated that additional residue data are
   needed for wheat grain, wheat forage, wheat straw, pasture, range-
   land grasses, ar.d flax.  Data are required depicting residues of
   HCB in or on wheat grain, wheat straw, pasture and rangeland
   grasses, flax seed, and flax straw.  Additional plant and animal
   metabolism data are needed.
Reported Pesticide Incidents
Most of the reported pesticide incidents involve crop damage and
   damage to other nontarget plants resulting from drift and from
   soil contaminated with picloram.
          4. SUMMARY OF REGULATORY POSITION AND RATIONALE
A review of available data indicates that none of the risk criteria
   listed in 40 CFR 154.7 have been exceeded.  Therefore, no referral
   to Special Review is being made at this time.
The Agency will continue to require that EPs containing picloram
   retain the "Restricted Use" classification and the groundwater
   advisory against the use of picloram on well-drained soils.
The Agency is requiring that the rat and mouse oncogenicity studies
   be repeated using Osborne-Mendel rats and B6C3Fl mice of both
   sexes using a commercially available technical grade picloram
   uncontaminated with potentially tumorigenic levels of HCB.
The Agency has determined that basic toxicology studies are needed
   for the organic esters and amines of picloram in addition to the
   complete toxicological testing of the acid and/or K salt.
The Agency will continue to require manufacturers to limit the level
   of HCB in the technical to a maximum of 200 ppm.
The Agency is requiring nitrosamine testing for the tertiary amine
   and alkanoloamine forms of picloram.  The level of nitrosoamines
   permitted in these forms is a maximum of 1 ppm.
The Agency is requiring that a prospective groundwater monitoring
   study be submitted for picloram.
The Agency is requiring that Tier II phytotoxicity testing be performed
   with the technical picloram, its salts, ester, and amine forms.
The Agency is requiring that droplet size spectrum and drift field
   evaluation data be submitted for picloram.
The Agency is requiring that additional residue data be submitted for
   wheat grain, wheat forage, wheat straw, pasture and rangeland
   grasses, and flax.  The data must include residues of HCB and the
   results of analysis for HCB levels.
The Agency is requiring that additional plant metabolism data be
   submitted providing complete identification and quantitation of
   all terminal residues.
The U. S. Fish and Wildlife Service has determined that picloram
   is likely to jeopardize endangered plant species when used on
   rangeland/pastureland and forests.  the Agency is developing a
   program to reduce or eliminate exposure of this chemical to these
   species.  After the program is developed, notification of any
   additional labeling requirements will be made.
The Agency is requiring that the labels of products containing
   picloram determined to be skin sensitizers include the statement "May
   cause allergic skin reaction after multiple exposure" on the labels.
The Agency will not approve any significant new food uses for picloram
   while major data gaps exist.  When additional data are evaluated
   the Agency will determine whether significant new uses may be
   established.
                   5.  SUMMARY OF DATA GAPS
   Requirements                 Due Dates
   Product Chemistry            6 to 15 months
   Residue Data                 6 to 24 months
   Toxicology Data              9 to 40 months
   Environmental Fate           9 to 39 months
   Groundwater Monitoring       9 months
   Plant Protection             9 months
                 6.  CONTACT PERSON AT EPA
Robert J. Taylor
Product Manager 25
Fungicide-Herbicide Branch
Registration Division (TS-767C)
Office of Pesticide Programs
Environmental Protection Agency
401 M Street SW.
Washington, DC  20460
Phone:  (703) 557-1800
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.