PMEP Home Page --> Pesticide Active Ingredient Information --> Herbicides, Growth Regulators, and Desiccants --> Herbicides, F to M --> Metsulfuron Methyl --> Metsulfuron Methyl - Herbicide Profile 3/86

Metsulfuron Methyl - Herbicide Profile 3/86

                        CHEMICAL FACT SHEET FOR:
                           METSULFURON METHYL



                       1.  DESCRIPTION OF CHEMICAL

- Generic Name:  Methyl-2-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)-
  amino]carbonyl]amino] sulfonyl]benzoate
- Common Name:  metsulfuron methyl
- Trade Name:  DuPont Ally Herbicide, DuPont Escort Herbicide
- EPA Shaughnessy Code:  122010
- Chemical Abstracts Service (CAS) Number:  74223-64-6
- Year of Initial Registration:  1986
- Pesticide Type:  Herbicide
- Chemical Family:  Sulfonyl urea
- U.S. and Foreign Producers:  E. I. duPont de Nemours & Company

                    2.  USE PATTERNS AND FORMULATIONS

- Application sites:  Wheat and barley, fallow or noncropland
- Formulations:  60% dry flowable (DF)
- Types and methods of application:  Foliar postemergence application,
  soil application to fallow land.  Application may be made by ground
  or aerial equipment.
- Application rates:  1/10 ounce active ingredient/acre (oz. a.i./A)
  for wheat and barley.  1/3 to 2 oz. a.i./A for noncropland.

                          3.  SCIENCE FINDINGS

Chemical Characteristics

- Physical state:  Solid
- Color:  Technical, white to pale yellow.  60% DF formulation,
- Odor:  Technical, faint, sweet ester-like.  60% DF formulation,
- Melting point:  158 C.
- Specific gravity:  1.47 grams per cubic centimeter
- Molecular weight:  381.40
- Solubility:  In distilled water at 25 C, 109 mg/L.  In 0.05N
  sodium phosphate buffer at 25 C as a function of pH:  pH 6.7 =
  9500 mg/L; pH 5.4 = 1750 mg/L; pH 4.6  270 mg/L.  In organic
  solvents at 20 C:  n-hexane  0.79 mg/L; methylene chloride =
  121,000 mg/L; acetone  3600 mg/L; methanol s 7300 mg/L; ethanol =
  2300 mg/L; and xylene = 580 mg/L.
- Unusual handling characteristics:  No special handling needed.

Toxicological Characteristics

- Acute studies:
  - Acute oral toxicity (rat): Greater than 5,000 mg/kg, Toxicity
    Category IV
  - Acute dermal toxicity (rabbit):  Greater than 2,000 mg/kg,
    Toxicity Category III
  - Primary dermal irritation:  Slightly irritating, Toxicity
    Category IV
  - Primary eye irritation:  Corneal opacity in one unwashed eye
    at 24 hours.  Cleared in 48 hours.  Toxicity Category III.
  - Dermal sensitization (guinea pig):  No sensitization shown,
    Toxicity Category IV
  - Label statements for Toxicity Category III for acute dermal:
    Harmful if absorbed through skin.  Avoid contact with skin,
    eyes, or clothing.  Wash thoroughly with soap and water after
  - Label statements for Toxicity Category III for primary eye
    irritation:  Causes (moderate) eye injury (irritation).  Avoid
    contact with eyes or clothing.  Wash thoroughly with soap and
    water after handling.
  - No precautionary labeling statements required for Toxicity
    Category IV.
  - Major routes of exposure:  dermal and eye contact.
- Chronic studies:
  - 2-year feeding/oncogenicity (rat):  Systemic No-Observable-
    Effect-Level (NOEL) = 500 ppm.  Systemic Lowest Effect Level
    (LEL) = 5,000 ppm.  No oncogenic effects noted at 5,000 ppm
    (highest dose tested (HDT)).
  - 18-month oncogenicity (mice):  Systemic NOEL = 5,000 ppm.  No
    oncogenic effects noted at 5,000 ppm (HDT).
  - 1-year feeding (dog):  NOEL = 50 ppm. LEL = 500 ppm.
  - Teratology (rat):  Maternal toxic NOEL less than 40 mg/kg/day.
    Fetal toxic NOEL < 1,000 mg/kg/day.  No teratogenic effects at
    1,000 mg/kg/day (HOT).
  - Teratology (rabbit):  Maternal toxic NOEL  25 mg/kg/day.
    Maternal toxic LEL  100 mg/kg/day. Fetotoxic NOEL  700
    mg/kg/day.  No teratogenic effects at 700 mg/kg/day (HDT).
  - 2-generation reproduction (rat):  Fetotoxic NOEL  5,000 ppm.
    Maternal NOEL = 500 ppm.  Maternal LEL  5,000 ppm.  No
    reproductive effects at 5,000 ppm (HDT).
  - Mutagenicity (Salmonella typhimurium):  negative
  - Mutagenicity, chromosomal aberrations (CHO) in vitro:
    Aberrations in Chinese hamster chromosomes were caused with
    and without activation.
  - Mutagenicity, unscheduled DNA synthesis (rat):  Negative.  Not
  - Metabolism (rat):  Rapid elimination of radioactivity, 91% or
    over 96 hours.

Physiological and Biochemical Behavioral Characteristics

- Foliar absorption:  Rapid
- Translocation:  Systemic after absorption by foliage or roots.
- Mechanism of pesticidal action:  Inhibition of cell division in
  rapidly growing tips of roots and shoots by inhibition of
  amino acid synthesis.
- Potential to contaminate groundwater:  Metsulfuron methyl has the
  potential to contaminate groundwater at very low concentrations.
- Metabolism in plants and animals:  Metabolized to several non-
  herbicidal compounds.
- Persistence in plants and animals:  Does not persist in either
  plants or animals.

Environmental Characteristics

- Absorption and leaching in basic soil types:  Moderately to very
  mobile, depending on organic matter content and soil texture.
  Leaches through silt loam and sandy soils.
- Microbial breakdown:  Degrades under anaerobic conditions to lower
  molecular weight compounds.
- Loss from photodecomposition and volatilization:  None
- Bioaccumulation:  Does not accumulate in fish.
- Resultant average persistence:  Half-life of 120 to 180 days in
  silt loam soil.

Ecological Characteristics

- Avian acute oral toxicity (mallard duck):  2,150 mg/kg
- Avian 8-day dietary toxicity (mallard duck):  5,620 ppm
- Avian 8-day dietary toxicity (bobwhite quail):  5,620 ppm
_ fish acute 96-hour toxicity (rainbow trout):  150 ppm
- Fish acute 96-hour toxicity (bluegill sunfish):  150 ppm
- Invertebrate 48-hour acute toxicity (Daphnia magna):  150 ppm
- Honeybee acute toxicity (Apis):  25 ug/bee
- Available data indicate metsulfuron methyl is practically nontoxic
  to birds, fish, invertebrates, and honeybees.

Tolerance Assessment

- The nature of the residue in plants and animals is adequately
  understood, and adequate analytical methods are available for
  enforcement purposes.
- Tolerances are established for the combined residues of
  metsulfuron methyl (methyl 2-[[[[4-methoxy-6-methyl-1,3,5-triazin-
  2-yl)amino]carbonyl]amino]sulfonyl]benzoate) and its metabolite,
  methyl 2-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]
  amino]sulfonyl]-4-hydroxybenzoate, in or on the following raw
  agricultural commodities:

  Commodity                          Parts per million
  Wheat, grain                             0.05
  Wheat, green forage                      5.0
  Wheat, hay                              20.0
  Wheat, straw                             0.1
  Barley, grain                            0.05
  Barley, green forage                     5.0
  Barley, hay                             20.0
  Barley, straw                            0.1

- Tolerances are established for residues of metsulfuron in or on
  the following raw agricultural commodities:

  Commodity                          Parts per million
  Cattle, fat                               0.1
  Cattle meat                               0.1
  Cattle meat byproducts                    0.1
  Goats, fat                                0.1
  Goats meat                                0.1
  Goats meat byproducts                     0.1
  Hogs, fat                                 0.1
  Hogs, meat                                0.1
  Hogs, meat byproducts                     0.1
  Horses, fat                               0.1
  Horses, meat                              0.1
  Horses, meat byproducts                   0.1
  Milk                                      0.055
  Sheep, fat                                0.1
  Sheep, meat                               0.1
  Sheep, meat byproducts                    0.1
- The Acceptable Daily Intake (ADI) based on the 1-year dog feeding
  study (NOEL of 1.25 mg/kg/day) and using a 100-fold safety factor
  is calculated to be 0.0125 mg/kg/day.  The Maximum Permissible
  Intake (MPI) for a 60-kg human is calculated to be 0.75 mg/kg/day.
  The Theoretical Maximum Residue Contribution (TMRC) for these
  tolerances for a 1.5 kg diet is calculated to be 0.0455 mg/kg/day
  (1.5 kg).  The current action will use 6.06% of the ADI.  There
  are no published tolerances for this chemical.

Summary Science Statement

   All data are acceptable to the Agency.  It has low toxicity (Category
III) for acute dermal and primary eye irritation, and is even less toxic
(Category IV) for all other forms of acute toxicity.  It was not
oncogenic to rats or mice, not teratogenic to rats or rabbits, and not
mutagenic with Salmonella or unscheduled DNA synthesis in rats.  The
pesticide is foliarly and root absorbed, and translocated by the plant.
It works by inhibition of cell division in the shoots or roots.  The
pesticide will leach in some soils.  Metsulfuron methyl is practically
nontoxic to birds, fish, invertebrates, and honeybees.  The nature of
the residue in plants and animals is adequately understood. and adequate
methodology is available for enforcements of tolerances in barley and
wheat grain; green forage of barley and wheat; hay of barley and wheat;
straw of barley and wheat; meat, fat, and meat byproducts of cattle,
goats, hogs, horses, and sheep; and milk.


   The Agency has accepted the use of metsulfuron methyl for control of
weeds in wheat and barley.  All major data requirements have been

                    5.  SUMMARY OF MAJOR DATA GAPS

- None.

                      6.  CONTACT PERSON AT EPA

Robert U. Taylor (PM-25)
Office of Pesticide Programs
Registration Division (TS-767C)
401 M Street S.W.
Washington, DC  20460