United States             Office of Pesticides
                    Environmental Protection      and Toxic Substances
                    Agency                (H7501C)          54 O-FS-90-093
&EPA           Pesticide
                    Fact Sheet
                    Name Of Chemical:       Primisulf uron-methyl

                    Reason for Issuance:      Registration

                    Date Issued:             June 12,  1990

                    Fact Sheet Number:      2i4


               Generic Name: 3-[4,6-Bis-(difluoromethoxy)-pyrimidin-2-yl]-
               Common Name:   CGA-136872 and primisulfuron-methyl
               Trade Names:  BeaconŽ Herbicide and Rifle  Herbicide
               EPA Shaughnessy Code: 128973-5
               Chemical Abstracts Service  (CAS) Number: 86209-51-0
               Year of Initial Registration: 1990
               Pesticide Type: Herbicide
               Chemical Family: Sulfonylurea
               U.S. Producer: CIBA-GEIGY Corporation


               Application sites:  Terrestrial food  crops and  terrestrial
                  noncrop sites.   Postemergence to actively  growing
                  weeds in corn;  and in noncropland  areas such as fence
                  rows, airports, highway  rights-of-way,  industrial sites,
                  lumber yards, petroleum  tank farms,  pipeline rights-of-way,
                  plant sites, railroads,  storage areas,  and utility

               Types of formulations:  The two end-use products  (75.0% a.i)
                  are identical in  composition.  They are water dispersible
                  granules packaged in  water soluble bags. The technical
                  product which is  a crystalline solid contain-
                  ing 95% a.i. is used  in  the manufacture of the  two end-use
                  products.   The  technical product is packaged in a metal

               Amount and Method  of Application:  Maximum application
                  of 0.56 oz. active ingredient per  acre per season is
                  claimed for postemergence weed cpntrol in  the culture
                  of corn.   For low maintenance turfgrass sites along
                  roadsides, airports,  industrial sites,  fence rows,
                  etc. in common  bermudagrass and buffalograss turf,

       dosages of 0.4 to 2.5 ozs per acre may be applied.
       These same dosages are claimed for noncrop sites such
       as fence rows, highway rights-of-way,  industrial
       sites,  lumberyards, petroleum tank farms, pipeline
       rights-of-way, plant sites, railroads, storage areas,
       and utility rights-of-way.  The dosage to be used
       depends on the target weed species to  be controlled.
       Only ground application directions are given on the
       proposed labeling.  Measures to avoid  spray drift
       and washing onto.nontarget areas are described on
       the labeling.

   Carrier:  Water


    Summary Science Statements:

      Adequate toxicological, product and residue chemistry
      ecological effects environmental fate and ground water
      data have been submitted and reviewed to support the
      registration of primisulfuron-methyl for use as a
      postemergence herbicide in the culture  of corn and
      perennial turf grasses.  Registration as a postemergence,
      non-selective herbicide on noncropland  such as
      fence rows, highway rights-of-ways, industrial sites,
      lumber yards, petroleum tank farms, pipe line right-of-
      ways, plant sites, railroads, storage areas, and
      utility rights-of-way is also supported.  Primisulfuron-
      methyl is classified as a Toxicity Category III pesticide
      and is labeled witn the signal word "CAUTION", based on
      acute dermal, acute inhalation and eye  irritation studies.
      A 21-day dermal study in rabbits indicated a no observable
      effect level (NOEL) of greater than 1,000 mg/kg/day
      for systemic toxicity.  Primisulfuron-methyl was non-
      mutagenic and in developmental tox-i-city studies it did
      not appear to be a potential teratogen. Based on results
      of a mouse oncogenic lifetime study it  was classified as
      a Group D carcinogen - not classifiable as to human
      carcinogenicity.  Ecological effects data characterize
      primisulfuron-methyl as practically nontoxic to birds on
      subacute dietary and acute oral bases.   Toxicological
      data demonstrated that it is of low toxicity to mammals.
      Low levels of contamination of ground water is possible
      in vulnerable soils with high water tables.  The
      chemical is essentially nontoxic to honey bees.  It  is
      stable to hydrolysis in neutral and mildly alkaline
      solutions (pH 7 and 9), and hydrolyzed slowly  (half-
      life >30 days) in acidic (pH 5) solutions.

Chemical Characteristics:

      Phyical State:
      Melting Point:

Vapor Pressure:
                        Crystalline Solid
                         Colorless to yellow
                         ca. 200  C (Decomposition at
                           melting point)
                         1.62 gm/cm-3 at 20° (typical)
                  Solvent      Based on gm/100 cm3/20°C
                         Methyl Chloride
                                     1 ppm (pri 5)
                                     9 ppm (pH 6)
                                    70 ppm (pH 7)
                                   600 ppm (pH 8)
                                  4500 ppm (pH 9)
                                   120 ppm
                                 1.5 x 10~10 Torr. at 25°C
      Dissociation Constant:    pKa value = 5.1 (Acid)

      Octanol/Water Partition Coefficient:  P = 0.059

      pH:                       5.56 at 25°C + or - 1°C
                                (Saturated Solution)

     The technical material decomposes on melting.  Technical
     primisulfuron-raethyl is stable at room temperatures.
     At 35°C it degraded less than 1.0 percent during 12 months
     of storage.  At 54°C there was no degradation up to
     3 months of storage.  The formulated products Beacon*
     Herbicide.and Rifle" Herbicide were stable up to 28
     weeks at 50°C and after 7 weeks at 70°C there occurred
     2.0% degradation.


Toxicology Characteristics:

     Acute Toxicity (Technical,  94% ai)

     Acute oral toxicity (rat):  LD5Q > 5050 mg/kg,
          Toxicity Category  IV.

     Acute dermal toxicity (rabbit):  LD5Q > 2,010  mg/kg,
          Toxicity Category  III.

     Primary dermal irritation .(rabbit) :  No edema,  no
          erythema in male rabbits,  Erythema in one
          female rabbit cleared within 72 hours,
          Toxicity Category  IV.

     Primary eye irritation  (rabbit):  No corneal
          opacity, conjunctivitis clearing within 3 days,
          Toxicity Category  III.

     Acute inhalation toxicity (rat):  No deaths,
          LC50 > 4.81 mg/L for 4 hours,  Category III.

     Dermal sensitization (guinea pig):  Negative for skin
          sensitization in male guinea pigs (not tested in
          females), not a skin sensitizer.

     Acute Toxicity (Beacon* Herbicide,  75% ai)
     Acute dermal toxicity (rabbit):  No deaths,  LD5Q50
          >2010 mg/kg, Category III.

     Acute inhalation toxicity (rat):  No deaths, LCsoSO
          >3.28 mg/L for 4 hours, Category III.

     Primary eye irritation (rabbit):  No corneal opacity,
          conjunctivitis calearing in day 4, Category III.

     Primary dermal irritation (rabbit):  No edema, slight
          erythema in one male and one female clearing by
          24 hoursr Category. IV.

     Dermal sensitization (guinea pig):  Negative for skin
          sensitization in male guinea pigs, females not
          tested, not a skin sensitizer.

Subchronic Toxicity

A 21-day dermal study in rabbits was conducted using
levels of 0, 10, 100 and 1,000 mg/kg/day.  No effect
was observed on any parameter examined, NOEL was
> 1,000 mg/kg/day.

A 13-week dog feeding study at 0, 25, 1,000 and
10,000 ppm was conducted.  Effects were increased
platelet values in tema,le.s and thiokened._,g.all bladder
mucosa in one female dog macroscopicaly.  One male
and three female dogs had mild epithelial hyperplasia of
the gall bladder.  The NOEL was 25 ppm and the LEL
was 1,000 ppm.

A 13-week rat feeding study at 0, 10, 300, 3,000,
10,000, 20,000 ppm was conducted.  The effects were
decreased body weight in males, decreased food
consumption in males, decreased absolute and relative
spleen weight in males.  The NOEL was 300 ppm and
the LEL was 3,000 ppm.

A 1-year dog feeding study was conducted at 0, 25,
1,000 and 10,000/5,000 ppm (changed after week 10).
Results were decreased body weight gain at 10,000 ppm
(weeks 1 to 10); anemia at 10/5,000 ppm; liver weight
increases (absolute and relative) and vacuolar changes
at 10/5,000 ppm; thyroid hyperplasia at 10/5,000 ppm;
systemic NOEL was 1,000 (25 mg/kg/day) and the system-
ic LEL was 5,000 ppm (125 mg/kg/day).  The effects
were anemia, increase in platelets, lower chloesterol
values, pale livers, moderate to trace vacuolar changes
and thyroid hyperplasia.


A 2-generation reproduction study in rats was conducted
at doses of 0, 10, 1,000 and 5,000 ppm.  An effect
noted at 5,000 ppm was decrease in testicular/spermatic
function and decreasedjbody weight gains in males.
There was also a decrease in pup weights.  The systemic
parental NOEL was 1000 ppm and the LEL was 5,000 ppm
based on decreased body weight gain.  The reproductive
NOEL was 1,000 ppm and the LEL was 5,000 ppm based
on paternal decrease in testicular/spermatic function
and a decrease in pup body weight.


The following mutagenicity studies indicated that
primisulfuron-methyl is not mutagenic at doses tested:

- Ames Assays for mutagenicity with and without metabolic
  activation in Salmonella  TA98, TA100, TA1535, and
  TA1537 up to 1024 ug/plate.

- Chromosome Aberration (micronucleus) in Chinese hamster
  up to 5,000 mg/kg.  There was no evidence of toxicity.

- Unscheduled DMA synthesis (UDS) Assay with rat liver
  cells (hepatocytes) up to 400' ug/ml.

- UDS Assay with human fibroblasts up to 1,000 ug/ml with-
  out activation (without S-9).


In a rabbit teratology study at doses of 0, 10, 300,
600 mg/kg/day by gavage there was no evidence of
development effects.  The effect observed in this
study was abortion, decreased body weight, stool
alterations.  The maternal NOEL was 10 mg/kg/day and the
LEL was 300 mg/kg/day.                                         .

In a rat study at doses of 0, 100, 500, and 1000
mg/kg/day by gavage there was delayed skeletal
development and incomplete or lack of ossification
of several bones.  The developmental NOEL was
100 mg/kg/day and the LEL was 500 mg/kg/day.

In a second rat study at doses of 0, 10, 50 and
100 mg/kg/day there was possible increase in number
of litters (not fetuses) having incomplete ossification
of the os pubis at 100 mg/kg/day.  Maternal NOEL
was > 100 mg/kg/day at the highest dose tested  (HOT).

These three studies indicate that primisulfuron-
raethyl is not a teratogen.


A 104-week rat feeding oncogenic study was conducted
at doses of 0, 10, 300, 3,000 and 10,000/8,000 ppm.
The systemic NOEL was 300 ppm  (15 mg/kg/day) and the
systemic LEL was 3,000 ppm (150 mg/kg/day) based on
decreased weight gain in males.  At 10,000/8,000 ppm
testes of males were soft and atrophied; at
1*0,000/8,000 ppm food consumption in both males
and female was decreased.  The study was evaluated     .       (
as showing a negative oncogenicity potential  in rats.

An 80-week mouse feeding oncogenic study was conducted
at doses of 0, 300, 3,000 and 10,000 (reduced to
7,000 at week 23).  The systemic NOEL was 300 ppm
(40.0 mg/kg/day) for males and less than 10 ppm
(1.4 mg/kg/day) for females.  The systemic LEL was
3,000 ppm (408 mg/kg/day) for males and 10 ppm
(1.7 mg/kg/day) for females.  The effects were
increased mortality, body weight gain decreases,
hypoplasia. of teeth/, liver, weight increases, chronic
nephritis and testicular degeneration/epididymal
aspermia.  There was an apparent increase in hepato-
cellular adenomas and hepatocellular carcinomas in
both males and females at 3,000 and 10,000/7,000 ppm.
Tumors were statistically significantly higher than
concurrent controls, but only at dose levels exceeding
the maximum tolerated dose (MTD).

The Agency Peer Review Committee classified
primisulfuron-methyl as a Group D carcinogen -
not classifiable as to human carcinogenicity.

Physiological and Biochemical Behavioral Characteristics


A rat radiolabeled primisulfuron-methyl metabolism
study showed that 88 to 102% of radioactive
primisulfuron-methyl was excreted in feces and urine with-
in 9 days.  Most of the radioactivity was in the form of
unchanged parent compound.  There were 6 major metabolites
in the feces and urine.  Hydroxylation of the pyrimidinyl
ring occurs at the 5-position, and is followed by either an
N- or O- rearrangement of a difluoromethoxy group.  There
appears to be little cleavage of the sulfonylurea bridge
with the 5-hydroxylate primisulfuron-methyl to form an
oxidized and/or oxidized and rearranged modified pyrimi-
dinyl moiety.  Some cleavage of the sulfonylurea bridge
of the parent is evident by the isolation of a sulfonyl-
benzoate intermediate and its cyclized counterpart,
saccharin, and the isolation of the bis(difluoromethyl)
pyrimidinyl moiety.  Similar metabolism of primisulfuron-
methyl was observed in the  goat and the chicken.


     Mechanism of Pesticidal Action

     Primisulfuron-methyl is a photosynthesis inhibitor.
     It inhibits growth and development by inhibiting the
     function of chlorophyll.  It inhibits growth and
     development of susceptable weeds. It is applied
     postemergence to corn and weed species. Its selectivity
     is not completely understood.   Susceptable plants become
     chlorotic and then necrotic-at their growing points.
     The herbicidal activity of primisulfuron-methyl
     is influenced by temperature^ moi&ture-,as. associated
     with optimum growth of weed species both before and
     after application, weed species, weed size at time
     of application, rate applied and general growing con-
     ditions.  Some weeds not killed are often stunted and
     are less competative to corn.   Primisulfuron-methyl
     may provide some herbicidal activity as a premergence
     herbicide.  Certain corn hybrids may be sensitive to
     Primisulfuron-methyl and respond to application with
     temporary injury at labeled dosages.  A list of
     corn hybrids having good tolerance to this herbicide
     is available from CIBA-GEIGY Corporation.

Environmental Characteristics:

    Hydrolysis:   Primisulfuron-methyl does not hydrolyze
        in neutral and mildly alkaline solutions (pH 7
        and 9), it hydrolized slowly (half-life > 30 days)
        in acedic (pH 5) solutions.

    Photodegradation:  Primisulfuroa-methyl dxxes not
        photodegrate in either water or on soil.

    Aerobic Soil Metabolism:  In aerobic soil maintained under
        controlled laboratory conditions phenyl ring-labeled
        [l^C] primisulfuron-methyl degraded with a half-life
        of 63 days and pyrimidine ring-labeled  [14C] primi-
        sulfuron-methyl degraded with a half-life of 30 days.

    Anaerobic Soil Metabolism:  In anaerobic soil maintained
        under controled conditions, phenyl ring-labeled  [14C]
        primisulfuron-methyl degraded with a half-life of
        89 days and pyrimidine ring-labeled  [14C] primisulfuron-
        methyl degraded with a half-life of 41 days.

    Field Dissipation:  Dissipation occurred more rapidly
        under fild conditions where primisulfuron-methyl
        dissipated with half-lives of 3 to  12 days  (detection
        limits of 0.01 ppm), and total phenyl and pyrimidine


              ring-labeled [-^c] primisulfuron-methyl residues
              dissipated with initial half-lives of 12 and 30
              days respectively.

     Leach, Adsorption/Desorption:  [-^C] Primisulfuron-methyl and
              its degradates were very mobile in both laboratory
              and field leaching studies, however unlabeled
              primisulfuron-methyl was not detected (>0.01 ppm)
              below a depth of 9 inches in field studies.  Detection
              limits is a limiting factor in conducting such

     Accumulation Studies:  Primisulfuron-methyl accumulates
              up to 0.011 ppm in wheat, soybeans, sugar beets,
              corn, or lettuce that were planted 103-334 days
              after corn plants growing in the plots had been
              foliarly-treated with primisulfuron-methyl.

     Potential to Contaminate Groundwater:  The use of primi-
              sulfuron as a postemergence herbicide in the
              culture of corn, turf and in vegetation control
              in low maintenance turf sites may result in low
              levels of contamination in groundwater in highly
              vulnerable soils with high water tables.  The pre-
              sent analytical methodology for primisulfuron-methyl
              and its degradates with detection limits of only
              0.01 ppm is not sufficiently sensitive to detect
              residues resulting from the uses of this
              chemical as a postemergence herbicide, as registered.

Ecological Characteristics

     Avian Studies:  Primisulfuron-methyl is practically
              non-toxic to birds based on the following

     Single Dose Oral Studies:
              Bobwhite quail with 94.0% ai, LC$Q > 2150 mg/kg.
              Mallard duck with 94.0% ai, LCso > 2150 mg/kg.

     Subacute Dietary Study:
              Bobwhite quail with. 94.0% ai, LCso >5000 ppm.

     Avian Reproduction:
              Mallard duck with 95.9% ai, NOEL was 500 ppm.,
              No reproductive impairment occurred at 500 ppm
              dietary test level.


         Aquatic Organisms:  The following data indicate that primi-
              sulfuron-methyl is no more than slightly toxic to
              to freshwater fish, aquatic invertebrates and
              estuarine shrimp:

         Fish Acute Toxicity:
              Bluegill sunfish,  LC$Q > 48 ppm (supplementary study).
              Rainbow trout, LC$Q > 13 ppm (supplementary study).

         Effects on Freshwater* In.v.erJteb.r.a.tes;.
              Acute Toxicity Study:
              Daphnia magna,  LD5Q > 100.0 ppm.
              Chronic Study:
              Daphnia magna, NOEL of 0.41 ppm.

         Effects on esturine organisms:
              Acute Toxicity Study:
              Mysid shrimp, LC5Q of 16 ppm.

         Effects on honey bees:
              Acute Contact Toxicity Study:
              Apis mellifera, LC$Q > 100 ug/bee, practically non-toxic.

         Effects on Nontarget plants:
              Aquatic species, ECso is 0.27 to 24.0 ppb
              Terrestrial species, EC25 for:
                 Seed germination was 3.7 to 473.0 gm/ha,
                 Seed emergence was 0.15 to 44.0 gm/ha,
                 Vegatative vigor was 0.14 to 33.4 gm/ha.

Endangered Species Hazards:

     Based on available data the registered uses of
     primisulfuron-methyl is unlikely to pose a hazard to
     endangered aquatic and avian species.  There may be
     some hazard to endangered plants.

Residue Chemistry

     A tolerance regulation has been established for
     residues of primisulfuron-raethyl associate with
     its use as a postemergence herbicide in the
     culture of corn.  The regulation is found
     under Section 180.452 in the Code of Federal
     Regulations.  The regulation establishes tolerances
     for residues of primisulfuron-methyl in or on
     corn (forage) at 0.10 ppm; corn  (fodder) at 0.10 ppm;


corn (grain) at 0.02 ppm; corn (sweet) (kernels
plus cobs with husks removed) at 0.10 ppm; milk at
0.02 ppm; meat, fat, meat byproducts of cattle, goats,
hogs, horses, and sheep at 0.10 ppm; poultry fat, meat
and meat by-products at 0.10 ppm; and eggs at 0.10 ppm.

4.   Summary of Regulatory Position and Rationale

    Available data provided adequate information to support
    the conditional registration of BeaconŽ Herbicide,
    .RifleŽ Herbicide, and CGA-136872 Technical, that were
    first registered on May.11, 1990-.under. Section 3 of
    the Federal Insecticide, Fungicide and Rodenticide Act
    as amended.

         Use, formulation, manufacturing process or
         geographic restrictions:  Crop rotation
         restrictions are specified on the Beacon
         Herbicide label.  Aerial applications of
         Beacon* and Rifle* Herbicides are not permitted.
         Beacon* and RifleŽ Herbicides are water
         dispersible granules that are in pre-measured
         quantities in water-soluble packets.

5.  Summary of Data Gaps

    Environmental Fate and Groundwater Data:

      a. Information on the relative mobilities of primisul-
         furon-methyl in soil (EPA Guideline Date 163-1) and its
         major phenyl and pyrimidine ring-labeled [^4C] degradates
         must be submitted within 12 months from the date of

      b. A new field dissipation study in soil (EPA Guideline
         Date 164-1) in which residues at the level of 10%
         of the applied rate are measured with the appropriately
         sensitive methodology.  In lieu of a new study,
         the registrant may submit data that characterize
         the residues detected in the submitted soil dis-
         sipation study.  This study must be submitted within
         27 months form the date of registration.


            A small-scale prospective ground-water monitoring
            study that addresses the mobility of the parent
            compound and its degradates must be submitted
            within 30 months from the date of registration.
   Ecological Effects Data:

      Aquatic organism testing with a warmwater freshwater
      fish and a coldwater freshwater fish (EPA Guidelines
      data 72-1) must be submitted -9..months, from the date
      of registration.

6.  Contact Person at EPA

      Joanne I. Miller
      Acting Product Manager 23
      Fungicide-Herbicide Branch
      Registation Division (KH-7505C)
      Office of Pesticide Programs
      Environmental Protection Agency
      401 M Street SW
      Washington, DC  20460

   Office Location and Telephone Number

      Room 237, Crystal Mall Building 12
      1921 Jefferson Davis Highway
      Arlington, VA  22202
      (703) 557-1830
   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


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   Environmental Protection Agency
   Office of Pesticide Program (H7S04C)
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