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Phosmet - Chemical Fact Sheet 10/86

                        CHEMICAL FACT SHEET FOR:



                    1.  DESCRIPTION OF CHEMICAL

- Generic Name:  N-(mercaptomethyl) phthalimide S-(O,O-dimethyl
- Common Name:  Phosmet
- Trade Names:  Phthalofos, PMP, Appa, Imidan, Kemplate, Prolate, R-1504
- EPA Shaughnessy Code:  059201
- Chemical Abstract Service (CAS) Number:  732-11-6
- Year of Initial Registration:  1966
- Pesticide Type:  Insecticide-acaricide
- Chemical family:  Organophosphate
- U.S. Producer:  Stauffer Chemical Company


- Application sites:  Terrestrial food crops (field, vegetable and
  orchard crops such as alfalfa, apples, almonds, apricots, blueberries,
  citrus, corn, cotton, grapes, nectarines, pears, peaches, pecans,
  plums, and potatoes).  Terrestrial non-food crops (nursery and
  ornamental crops)  domestic outdoor and indoor.
- Types of formulations:  Dust (1% and 5% active ingredient (A.I.),
  wettable powders (7.5%, 12%, 12.5%, 50%, and 70% A.I.): impregnated
  resins (15% A.I.) and emulsifiable concentrates [1 pound (lb.) per
  gallon (gal.), 3 lb/gal, and 12.5% A.I.]
- Methods of Application:  Foliar applications, aerial applications,
  animal treatments, stored commodity treatments, and impregnated

                        3.  SCIENCE FINDINGS

Chemical Characteristics:  Information listed below references the
technical grade active ingredient unless specified as the pure active
ingredient (PAI).

- Physical state:  Crystalline solid
- Color:  White to greyish-white
- Odor:  Typical phosphorodithioate
- Boiling Point:  Not applicable - the technical is a solid at room
- Flash point:  Not available in Agency files
- Melting point:  72.0 - 72.7 degrees C (PAI)
- Specific gravity:  1.03 at 20 degrees C
- Solubility:  At 20 degrees C, in water, 25 ppm; acetone, >/- 1,000
  grams/liter(g/l); kerosene, 10 g/l; xylene, 200 g/l.
- Stability:  Not available in Agency files.

Toxicological Characteristics

- Acute toxicity.  Phosmet has moderate to low acute oral, dermal, and
  eye/skin irritation.  Phosmet, like other organophosphate chemicals,

  can be absorbed by inhalation and skin penetration.
  - Acute oral (rat):  113-304 mg/kg.
  - Acute dermal (rabbit):  >3,160 mg/kg
  - Primary eye irritation:  Produced mild redness when instilled in
    the unwashed eyes of 3 rabbits at 24 hours after exposure.
    Phosmet also produced corneal opacity, redness, chemosis, and
    discharge in 1 of 3 rabbits.  Eyes were normal within 7 days.
- Chronic Toxicity
  - Oncogenicity:  Phosmet has been classified as a "tentative"
    Category C carcinogen.  This conclusion was reached after review
    of two (a 2-year mouse and a 2-year rat) oncogenicity studies.

    Phosmet was associated with a significantly elevated incidence of
    liver tumors (adenomas, and adenomas plus carcinomas combined) in
    male B6C3F1 mice at the highest dose tested.  These incidences
    were associated with liver hyperplastic changes and a decrease in
    the time to tumor occurrence.  In female B6C3F1 mice, the chemical
    was associated only with positive dose-related trends for liver
    adenomas and carcinomas.  A 2-year rat oncogenicity study was
    considered inadequate (the number of animals sacrificed at the end
    of the study were too small to fully evaluate tumor responses).
    The chemical was essentially non-mutagenic (only one positive
    result occurred in a limited and inadequate battery of tests) and

    no positive correlation with respect to oncogenicity and
    mutagenicity could be made with known structural analogs.  After a
    2-year rat oncogenicity study and additional mutagenicity studies
    are submitted and evaluated, the Agency will reassess the
    oncogenicity issue and determine if dietary and worker risk
    assessments are necessary.
  - Mutagenicity:  Phosmet was evaluated in several mutagenicity
    assays.  The chemical was found to be positive only when tested in
    S. typhimurium strain TA-100.  No mutagenicity study of phosmet
    was performed in mammalian cells in culture. Additional

    mutagenicity studies are required.
  - Teratogenicity:  No teratogenic effects were reported for phosmet
    in oral teratology studies in monkeys (NOEL = 8.0 mg/kg) and
    rabbits (NOEL = 60 mg/kg).
  - Reproductive effects:  Phosmet had no adverse reproductive
    performance effects in a 3-generation oral reproduction study in
    rats.  (NOEL = 80 ppm).
  - Neurotoxicity:  Delayed neurotoxic effects were not observed at
    levels up to 2,050 mg/kg of phosmet.  Body weight, food
    consumption, and egg production were significantly decreased in
    the 2,050 mg/kg test group.
  - Metabolism:  Data indicates that phosmet is rapidly eliminated
    with 78% being eliminated in the urine and 19% in the feces within
    72 hours after administration of a single oral dose in rats.
    However, the major water soluble urinary metabolites have only
    been "tentatively" identified.  A general metabolism study will be

Physiological and Behavioral Characteristics

- Mechanism of Pesticide Action - organophosphate cholinesterase

Environmental Characteristics and Groundwater Concerns

- Few data are available on the environmental fate of phosmet. Phosmet
  appears to be moderately mobile to immobile in soils ranging in
  texture from sand to silty clay loam.  Because of phosmet's physio-
  chemical properties the potential exists for phosmet, and possibly its
  degradates, to contaminate groundwater.  To date the Agency is not
  aware of incidents where phosmet has contaminated groundwater.  To
  fully assess and complete the environmental fate profile of phosmet,
  the Agency is requiring hydrolysis, soil dissipation, anaerobic soil
  metabolism, leaching, photodegradation, rotational crop and reentry

Ecological Characteristics

- Avian acute toxicity:  Mallard duck - 2009 mg/kg
- Avian dietary toxicity:  Bobwhite quail - 501 ppm; Japanese quail -
  2000 ppm; Mallard duck - >5000 ppm
- Avian reproduction:  Bobwhite quail - 69-150 ppm; Mallard duck - 25-60
- Fish:  Rainbow trout - 230 ppb; Bluegill sunfish - 70 ppm
- Aquatic invertebrates:  Daphnia magna - 5.6 ppb; Gamma fasciatus -
  2.0-4.2 ppb
- Sufficient data are available to characterize technical phosmet as
  very highly toxic to warmwater fish and highly toxic to coldwater
  fish.  The chemical is also very highly toxic to aquatic and estuarine
  invertebrates.  Monitoring data in runoff water following terrestrial
  applications of phosmet is being required to complete the hazard
- Phosmet is practically non-toxic to slightly toxic to birds and
  mammals.  Phosmet may cause reproductive impairment in birds and
  mammals due to a buildup of residues on avian food items.  Residue
  monitoring of avian and mammalian food items (apples, corn, cotton,
  and alfalfa) will be required to complete an evaluation of the
  reproductive hazards.
- Phosmet is very highly toxic to honeybees and displays extended
  residual toxicity.
- Endangered species:  Use on apple and pear orchards, alfalfa, corn,
  and cotton crops, could place endangered species in the vicinity of
  treated areas at risk.  Also two endangered insect species in the
  vicinity of food crop uses in certain counties of California could be
  threatened.  Residue monitoring data will be required to aid in
  completion of the assessment of hazards to endangered species.

Tolerance Assessment

- Tolerances have been established for residues of phosmet in raw
  agricultural commodities, meat, fat and meat byproducts (40 CFR
  180.26) and in processed food (21 CFR 193.279) for phosmet and its
  oxygen analog at levels ranging from 0.1 to 40.0 ppm.
- The metabolism of phosmet in plants and animals is not adequately
  understood.  Additional residue data and metabolism data will be
  required to reassess the adequacy of existing tolerances and to
  issue new tolerances.  Processing studies are also being required
  for potatoes, apples, plums, peaches, grapes, field corn grain, and
- The acceptable daily intake (ADI) for humans was based on a 2-year
  chronic feeding study in rats.  The ADI in humans was calculated to
  be 0.02 mg/kg/day and the maximum permitted intake (MPI) is equal to
  1.2 mg/kg/day with a NOEL of 40 ppm and a safety factor of 100.
  Using these calculations the percent utilization of the ADI would be
  09.29 percent.  Since virtually all of the ADI has been used up by
  the TMRC and the Agency is aware of a potential oncogenic response
  to phosmet, new tolerances and/or new uses will not be issued if
  they contribute significantly to the TMRC and/or result in a
  significant increase in the dietary exposure.

- Established Phosmet Tolerances:

Commodity                            Parts Per Million
  Alfalfa                               40.0
  Almond, hulls                         10.0
  Apples                                10.0
  Apricots                               5.0
  Blueberries                           10.0
  Cattle, fat                            0.2
  Cattle, meat                           0.2
  Cattle, mby                            0.2
  Cherries                              10.0
  Citrus fruits                          5.0
  Corn, fresh (including
    sweet K + 6 WHR)                     0.5
  Corn, fodder                          10.0
  Corn, forage                          10.0
  Corn, grain                            0.5
  Cottonseed                             0.1
  Cranberries                           10.0
  Goats, fat                             0.2
  Goats, mbyp                            0.2
  Goats, meat                            0.1
  Grapes                                10.0
  Hogs, fat                              0.2
  Hogs, mbyp                             0.1
  Hogs, meat                            -0.2
  Horses, fat                            0.2

  Horses, mbyp                           0.2
  Horses, meat                           0.2
  Kiwi fruit                            25.0
  Nectarines                             5.0
  Nuts                                   0.1
  Peaches                               10.0
  Pears                                 10.0
  Peas                                   0.5
  Peas, forage                          10.0
  Peas, hay                             10.0
  Plums (fresh prunes)                   5.0
  Potatoes                               0.1
  Sheep, fat                             0.2
  Sheep, mbyp                            0.2
  Sheep, meat                            0.2
  Sweet potatoes                        10.0
  Tomatoes                               2.0
  Cottonseed oil                         0.2

Reported Pesticide Incidents

- In the period from 1978 to 1979, 67 incidents involving a flea dip
  formulation (Paramite) of phosmet were reported to the Agency.  Of
  these 67 incidents, 39 involved cats only, 16 involved dogs only, 2
  involved cats and dogs, 8 involved human reactions, and 2 involved

  dogs and human reactions.  Reported mortalities from these incidents
  were 20 cats (one leukemic) and 12 dogs.  Additional incidents of
  adverse animal reactions (primarily cats) involving the same
  formulation have been reported up through 1985.  The Agency is re-
  evaluating the use of phosmet on pets.

Summary Science Statement

- Phosmet is a member of a chemical family known as the
  organophosphates (OPs).  OP pesticides act on the nervous system by
  interfering with an enzyme acetylcholinesterase.  This effect (known
  as cholinesterase inhibition) is reversible once exposure stops.
  There are antidotes for this type of poisoning (atropine and 2-pam).
  Phosmet has a moderate to low acute oral, dermal, and eye/skin
  irritation toxicity.  It is moderately toxic (Toxicity Category II)
  to humans by ingestion.  Additional data (acute inhalation and
  dermal sensitization) is required to complete the acute toxicity
  profile for technical phosmet.  Insufficient data exists to fully
  assess the subchronic dermal, mutagenicity, oncogenicity, and general
  metabolism of phosmet.  Reentry data is necessary in order to
  establish permanent worker reentry intervals.
- Phosmet has been classified as a  tentative  category C carcinogen.
  This conclusion was reached after review of a 2-year mouse
  oncogenicity study.  Additional studies are being required to
  complete the oncogenic assessment of the chemical.  Currently
  available data indicate that phosmet does not cause neurotoxic,

  teratogenic, or reproductive effects.
- The environmental fate of phosmet is not well documented.  A review
  of preliminary data indicates phosmet is moderately mobile to
  immobile in soil and hydrolyzes rapidly in soil.  The physical-
  chemical characteristics of the chemical indicate a potential for
  phosmet and possibly its degrades to contaminate groundwater.
  Hydrolysis, soil dissipation, anaerobic soil metabolism, leaching,
  photodegradation, and rotational crop and reentry data are required
- Phosmet is practically non-toxic to slightly toxic to birds, and
  mildly toxic to mammals.  It is unlikely that phosmet would be
  lethal to birds or mammals after a single application.  Available
  data indicates the possibility of reproductive effects in birds and
  mammals due to the buildup of phosmet on avian and mammalian food
  items (apples, corn, cotton, and alfalfa) from repeat applications.
  Residue monitoring data on these food items is required to determine
  the magnitude of exposure.  Phosmet is highly toxic to honeybees,
  fish, aquatic and estuarine invertebrates.  Field monitoring studies
  are being required to determine the magnitude of exposure from the
  major crop uses.  Additional fish and aquatic invertebrate studies
  are being required to complete the evaluation of hazard.


- No referral to Special Review is being made at this time.  A repeat
  rat oncogenicity study and additional mutagenicity studies must be
  submitted.  The Agency will reassess the oncogenicity issue and
  determine if dietary and worker carcinogenicity risk assessments are
  necessary.  The available data also indicate that phosmet is highly
  toxic to fish.  Terrestrial residue analysis and aquatic runoff
  modeling indicate that certain use patterns could result in exposure
  of certain aquatic organisms to hazardous levels of the pesticide.
  Additional data are needed before the Agency can complete a full

  assessment of this hazard potential.
- The Agency will reassess the adequacy of the existing tolerances after
  required metabolism data and residue data are submitted.
- New tolerances and uses will be issued on a case-by-case basis.
  amended by depleting the reference to "cholinesterase-inhibiting"
- The Agency has determined that endangered species label restrictions
  are necessary in order to prevent unreasonable adverse effects on the
- In the absence of reports of fish kills following phosmet application
  and actual field monitoring data, the Agency will not restrict certain
  uses of phosmet to certified applicators, but has determined, based on
  the high toxicity of phosmet to aquatic organisms, that precautionary
  labeling will be required.  The restricted use classification may be
  required if additional studies indicate that phosmet use poses risks
  to aquatic organisms that could be mitigated by increased controls in
- The Agency is imposing a 24-hour reentry interval.  Foliar dissipation
  data are required on crops whose propagation requires human tasks that
  involve substantial, prolonged human contact.
- Protective clothing is required for mixers/loaders and applicators.
- The Agency will analyze the safety and efficacy data of a phosmet flea
  dip formulation (Paramite) to determine if further regulatory action
  is warranted.  A warning statement indicating that improper dilution
  of the product could cause serious injury to pets is being required.
- The Agency has determined that the tolerance for cranberries should be
  revoked because there are no registered uses for phosmet on
- The Agency is requiring processing data for the following agricultural
  commodities:  Potatoes, apples, plums, peaches, grapes, field corn
  grain, and cottonseed.
- The Agency is not requiring a rotational crop restriction.  If
  required data demonstrate that follow-up crops take up phosmet
  residues from soil, rotational crop restrictions or tolerances in
  those crops may be necessary.
- The Agency is not imposing a ground water advisory statement on
  phosmet labeling at this time, but is requiring data to fully
  characterize the potential of this chemical to reach ground water.
- While data gaps are being filled, currently registered end-use
  products containing phosmet as the sole active ingredient may be sold,
  distributed, and used, subject to the terms and conditions specified
  in the Registration Standard.

                 5. SUMMARY OF MAJOR DATA GAPS

- Product Chemistry
  - Product Chemistry                      Feb. 1987
- Residue Chemistry
  - Plant/Livestock metabolism             Feb. 1988
  - Plant/Animal Residues                  Feb. 1988
  - Storage Stability                      Feb. 1988
- Environmental Fate
  - Hydrolysis/Photodegradation            July 1987
  - Mobility Studies                       Sep. 1987
  - Accumulation (Rotational) Crops        Dec. 1989
  - Glove Permeability                     Mar. 1987 - protocol
                                           Nov. 1987 - final report

  - Anaerobic Soil Metabolism              Dec. 1988
  - Soil Dissipation                       Dec. 1988
- Toxicology
  - Acute Inhalation Toxicity (rat)        July 1987
  - Dermal Sensitization                   July 1987
  - 21-Day Dermal (rabbit)                 Sep. 1987
  - Oncogenicity (rat)                     Nov. 1990
  - Gene Mutation                          July 1987
  - Structural Chromosome Aberration       Sep. 1987
  - Other Genotoxic Effects                Sep. 1987
  - General Metabolism                     Sep. 1988
- Ecological Effects
  - Acute Toxicity to Freshwater
     Invertebrates                         July 1987
  - Acute Toxicity to Estuarine and
      Marine Organisms                     Sep. 1987

  - Fish Early Life Stage and Aquatic
      Invertebrate Life Cycle              Dec. 1987
  - Field Monitoring (avian, aquatic,
      and mammalian)                       Feb. 1988

              6.  CONTACT PERSON AT EPA

George T. LaRocca
Product Manager Number 15
U.S. Environmental Protection Agency
401 M. Street S.W.
Washington, 0. C. 20460
(703) 557-2400