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Pendimethalin - Herbicide Profile 3/85

                        CHEMICAL FACT SHEET FOR:
                              PENDIMETHALIN
FACT SHEET NUMBER: 50
DATE ISSUED: MARCH 31, 1985
                  1.  DESCRIPTION OF THE CHEMICAL
- Generic Name:  N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine
- Common Name:  pendimethalin
- Trade Names:  Prowl, Herbadox, Stomp. and AC 92553
- EPA Shaughnessy Code:  108501
- Chemical Abstracts Service (CAS) Number:  40487-42-1
- Year of Initial Registration:  1974
- Pesticide Type:  herbicide
- Chemical Family:  dinitroaniline
- U.S. Producer:  American Cyanamid Company
                 2.  USE PATTERNS AND FORMULATIONS
- Application sites:  Pendimethalin is registered for control of
  broadleaf weeds and grassy weed species on the following sites:
  soybeans, cotton, field corn, beans, peanuts, potatoes, rice, sorghum,
  sunflower, tobacco, ornamentals, non-bearing fruit and nut crops, and
  vineyards.  One site, jojoba, is registered under Section 24(c) in
  Arizona.
- Types of formulations:  Pendimethalin is available in granular,
  dispersible granular, and emulsifiable concentrate formulations.
- Types and methods of application:  Pendimethalin is mainly applied as
  a preplant incorporation (except in corn, rice, and sorghum),
  preemergence spray, early postemergence (rice), and late postemergence
  culti-spray (field corn and sorghum) applications.
- Application rates:  0.5 to 2.0 lbs. a.i./A on crop sites
- Usual carriers:  Attapulgite clay and water
                    3.  SCIENCE FINDINGS
Chemical Characteristics
     Pendimethalin is crystalline at room temperature and has a fruit-
like odor.  Its molecular weight is 281.30.  The boiling point is 330
degrees C.  Pendimethalin is soluble in water (at 20 degrees C) to <0.50
ppm, and soluble in aromatic and chlorinated hydrocarbon solvents.
Toxicological Characteristics
- Acute toxicology effects on pendimethalin are as follows:
  - Acute oral toxicity in rats:  >1,250 mg/kg body weight, Toxicity
    Category III
  - Acute dermal toxicity in rabbits:  >5,000 mg/kg body weight,
    Toxicity Category III
  - Acute inhalation toxicity in rats:  >320 mg/l (4 hour exposure),
    Toxicity Category IV
  - Skin irritation in rabbits:  slight irritant, Toxicity Category III
  - Eye irritation in rabbits:  corneal irritation clearing in less
    than seven days, Toxicity Category III
- Subchronic toxicology data, except for the 90-day rat feeding study,
  have met the current toxicity requirements.
- Chronic toxicology effects on pendimethalin have not been completely
  evaluated, because there are no valid mutagenicity and chronic rat
  studies for pendimethalin, and insufficient oncogenicity data.
- A 2-year dog feeding study indicated that pendimethalin tested at
  12.5 mg/kg, 50.0 mg/kg, and 200.0 mg/kg produced increases in
  alkaline phosphatase level and liver weight.  The NOEL is 12.5
  mg/kg/day.
- A teratology test in rats has shown that pendimethalin tested at
  500.0 mg/kg, highest dose tested (HDT), failed to induce
  teratogenic or fetotoxic effects.  A teratology test in rabbits has
  shown that pendimethalin tested at 60.0 mg/kg (HDT) failed to induce
  teratogenic or fetotoxic effects.
- A reproduction study (3-generation rat) indicated that pendimethalin
  tested at 500 ppm to 5,000 ppm induced slightly fewer offspring,
  with no corresponding increase in deaths and decreased weight gain
  from weaning to maturity.  The NOEL is 500 ppm.
- Major routes of human exposure:  Non-dietary exposure to pendi-
  methalin by a farmer as an applicator during mixing, loading,
  spraying, and flagging is probable.
Physiological and Biochemical Behavioral Characteristics
- Absorption characteristics:  Pendimethalin is absorbed in limited
  amounts by monocotyledonous plants and in moderate amounts by small
  dicotyledonous plants.
- Translocation:  Pendimethalin is taken up from the soil by plants in
  very limited amounts.
- Mechanism of pesticidal action:  Pendimethalin inhibits plant cell
  division and cell elongation.
- Metabolism in plants:  Pendimethalin is principally degradated in
  plants by oxidation of the 4-methyl group (benzene ring) and the
  N-1-ethylpropyl group in the amine moiety.
Environmental Characteristics
- Adsorption and leaching in basic soil types:  Pendimethalin is
  strongly adsorbed by soil organic matter and clay, and does not
  readily leach through the soil.
- Microbial breakdown:  Soil microorganisms do not appear to play a
  significant role in degradation of pendimethalin.
- Loss from photodecomposition and/or volatilization:  Slight losses.
- Average persistence at recommended rates:  When used at recommended
  rates under normal environmental conditions, little if any
  pendimethalin occurs in the subsequent crop.
Ecological Characteristics
- Avian acute oral toxicity:  1,421 mg/kg
- Avian 8-day dietary toxicity (Bobwhite quail):  >3,149 ppm
- Avian 8-day dietary toxicity (mallard duck):  >4,640 ppm
- 96-hour fish toxicity:  0.199 ppm for bluegill sunfish (highly
  toxic) and 0.138 ppm for rainbow trout (highly toxic)
- 48-hour aquatic invertebrate toxicity:  0.28 ppm (highly toxic)
  for Daphnia magna.
- Potential problem for endangered species:
  - The Slackwater darter and certain freshwater mussels are
  endangered species at risk from the use of pendimethalin on
  cotton.  The Agency is addressing appropriate means of labeling
  pesticides that may threaten the continued existence of endangered
  species.  The labeling should be completed by the 1986 growing
  season.  If it is not, this Standard may be amended to impose
  interim labeling to protect endangered species.
- The Agency believes that the conventional labeling approach may be
  inadequate to properly inform the users on how to protect the
  endangered species.  The Agency anticipates that appropriate
  labeling will be developed in time for the 1986 growing season
  for cotton.
Tolerance Assessment
- The Agency is unable to complete a full tolerance reassessment of
  pendimethalin because of certain residue chemistry and toxicology
  data gaps.  The additional data may cause specific tolerances to be
  revised in the future.
- The Acceptable Daily Intake (ADI) for pendimethalin was originally
  based upon a 2-year feeding study on rats, which was subsequently
  declared invalid.  Subsequently, the Provisional Acceptable Daily
  Intake (PADI) for pendimethalin was calculated, using the 90-day
  portion of the same study. The subchronic portion of this study
  was used instead of a 2-year dog study, because the (P)ADI value
  calculated for the rat is the more conservative value on a mg/kg
  basis than for the dog:
          NOEL      Safety       (P)ADI         (P)MPI
        (mg/kg)     Factor      mg/kg/day     mg/day (60 kg)
  Rat     25.0      2,000       0.0125          0.7500
  Dog     12.0        100       0.1250          7.5000
- The No Observable Effect Level (NOEL) for the rat study is 25.0
  mg/kg.  A 2,000-fold safety factor was used, and the PADI was
  calculated as 0.0125 mg/kg/day, with a Maximum Permissible Intake
  (MPI) of 0.7500 mg/day for a 60-kg person.  The Theoretical
  Maximum Residue Contribution (TMRC) for pendimethalin-based
  permanent tolerances is 0.0166 mg/day for a 1.5 kg diet.  Currently,
  the permanent tolerances utilize 2.22% of the PADI.
- In the United States, tolerances are currently established in 40
  CFR 180.361 for the combined residues of the herbicide pendimethalin,
  N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine, and its
  metabolite, 4-[1-ethylpropyl)amino]-2-methyl-3,5-dinitrobenzyl
  alcohol, in or on the raw agricultural commodities listed below:
  - *Beans (lima, dry, snap); * beans, forage; *beans, hay; corn.
     fodder; corn, forage; *corn, fresh (including sweet, K+CWHR);
     corn, grain; cottonseed; peanuts; peanut hay; peanut forage;
     soybeans; soybeans, forage; soybeans, hay; and sunflower seeds -
     0.1 ppm.
  - Rice grain - 0.05 ppm
NOTE:  *The tolerances for these commodities were established after the
        science reviews for the pendimethalin registration standard
        were completed.
International tolerances
- Presently, there are no tolerances for residues of pendimethalin
  in Canada, Mexico, or in the Codex Alimentarius.
Problems Known to Have Occurred with Use
- The Pesticide Incident Monitoring System (PIMS) indicates four
  incidents involving agricultural uses of pendimethalin alone from
  1966 through 1980.  Of the four incidents, three required medical
  attention, two involved dermal exposure during ground application,
  one involved mixer/loader exposure, and one involved a truck/
  container spill.  No fatalities were reported.
- PIMS does not include any details or consequences of these
  exposures, nor does it attempt to validate these voluntarily
  submitted reports.  The PIMS data do not provide information on
  chronic health effects from exposure to pendimethalin, but do
  support the need for precautions relating to careful handling of
  pendimethalin products.
Summary Science Statement
- Pendimethalin is not acutely toxic by the oral, dermal, inhalation,
  and ocular routes of exposure. The available data is insufficient to
  show that any of the risk criteria listed in 162.11(a) of Title 40 of
  the U.S. Code of Federal Regulations have been met or exceeded for the
  uses of pendimethalin at the present time.  There are no valid muta-
  genicity and chronic rat studies for pendimethalin, and insufficient
  oncogenicity data.  There are also extensive residue chemistry and
  environmental fate data gaps.
- Pendimethalin is highly toxic to coldwater fish, highly to moderately
  toxic to warmwater fish, and highly to moderately toxic to freshwater
  invertebrates.  A detailed ecological hazard assessment cannot be made
  until certain environmental chemistry data requirements and a
  monitoring study of aquatic sites next to treated rice fields are
  fulfilled.
         4.  SUMMARY OF REGULATORY POSITION AND RATIONALE
     Based on the review and evaluation of all available data and other
relevant ,information on pendimethalin, the Agency has made the
following determinations:
- The available data do not indicate that any of the risk criteria
  listed in 162.11(a) of Title 40 of the U.S. Code of Federal
  Regulations have been met or exceeded for the uses of pendimethalin
  at the present time.
- Pendimethalin is not acutely toxic by the oral, dermal, inhalation,
  or ocular routes of exposure.
- The chronic dog study, rat and rabbit teratology studies, and a
  3-generation reproduction study did not indicate adverse chronic
  effects.
- There are no valid mutagenicity and chronic rat studies for
  pendimethalin, and insufficient oncogenicity data.  There are also
  extensive residue chemistry and environmental fate data gaps.
- The Agency is requiring monitoring data for potential residues in
  aquatic sites next to treated rice fields.  Once the Agency has
  evaluated these additional data, it will determine if EPA should
  impose more stringent measures to minimize exposure of aquatic
  organisms to pendimethalin.  Ecological effect studies indicate
  that pendimethalin is highly toxic to certain coldwater and
  warmwater fish, and moderately to highly toxic to marine and
  estuarine organisms.
- The Agency is requiring that levels of N-nitroso-pendimethalin
  contaminant not exceed 60 ppm in the technical product and that the
  technical be analyzed for other impurities.
Specific label warning statement:
- Hazard information:
  - The human hazard statements must appear on all EP labels as
    prescribed in 40 CFR 162.10.
- Environmental hazard statements:
  - All manufacturing-use products (MPs) intended for formulation
    into end-use products (EPs) must bear the following statements:
  - This pesticide is toxic to fish.  Do not discharge effluent
    containing this product directly into lakes, streams, ponds,
    estuaries, oceans, or public waters unless this product is
    specifically identified and addressed in a National Pollutant
    Discharge Elimination System (NPDES) permit.  Do not discharge
    effluent containing this product into sewer systems without
    previously notifying the sewage treatment plant authority.  For
    guidance, contact your State Water Board or Regional Office of
    the Environmental Protection Agency.
- End-use product statements:
  - Non-aquatic uses (granular products):
    - The following environmental hazard statement must appear on all
      EPs:  This pesticide is toxic to fish.  Do not apply directly to
      water.  Runoff from treated areas may be hazardous to aquatic
      organisms in neighboring areas.  Do not contaminate water by
      cleaning of equipment or disposal of wastes.  In case of spills,
      either collect for use or dispose of properly.
  - Non-aquatic uses (nongranular products):
    - The following environmental hazard statement must appear on all
      EPs:  This pesticide is toxic to fish.  Do not apply directly to
      water.  Drift and runoff from treated areas may be hazardous to
      fish in neighboring areas.  Do not contaminate water by cleaning
      of equipment or disposal of wastes.
  - Aquatic uses (rice):
    - The following environmental hazard statement must appear on all
      EPs:  This pesticide is toxic to fish and aquatic organisms.
      Fish may be killed at application rates recommended on the
      label. Do not contaminate water by cleaning of equipment or
      disposal of wastes.  Do not apply to rice fields if fields are
      used for catfish or crayfish farming.
- Restrictions on rotational crops:
  - Pending the submission of rotational crop data, do not apply
    pendimethalin on rice fields in which crayfish or catfish farming
    are included in the cultural practices, and do not plant crops in
    pendimethalin-treated fields unless pendimethalin is registered
    for use on those crops.
- Restrictions on irrigated crops:
  - Pending the submission of irrigated crop data, do not use water
    containing pendimethalin residues from rice cultivation to
    irrigate food or feed crops which are not registered for use with
    pendimethalin.
                  5.  SUMMARY OF MAJOR DATA GAPS
- The following toxicological studies are required:
  - A dermal sensitization study in guinea pig is required by October
    30, 1985.
  - A 90-day feeding study in the rat is required by January 30, 1986.
    - A chronic toxicity study in rat is required by April 30, 1989.
    - An oncogenicity study in rat and in mouse is required by April 30,
      1989.
    - The following mutagenicity data are required by October 30, 1985:
      - Gene mutation in bacteria
      - Gene mutation in mammalian cells in culture
      - Chromosomal aberration analysis in mammalian cells in culture
      - DNA damage in mammalian cells in culture
- The following environmental fate data are required:
  - A photodegradation study in water is required by October 30, 1985.
  - A photodegradation study on soil is required by October 30, 1985.
  - A metabolism test in aerobic soil is required by April 30, 1987.
  - A metabolism test under anaerobic aquatic conditions is required by
    April 30, 1987.
  - A metabolism test under aerobic aquatic conditions is required by
    April 30, 1987.
  - A mobility study involving leaching and adsorption/desorption is
    required by October 30, 1985.
  - A mobility study involving volatility in the lab is required by
    October 30, 1985.
  - A mobility study involving volatility in the field is required by
    October 30, 1985.
  - A soil dissipation study in the field is required by April 30, 1987.
  - A dissipation study in aquatic (sediment) is required by
    April 30, 1987.
  - An accumulation study in rotational crops (confined) is required by
    October 30, 1987.
  - An accumulation study in rotational crops (field) is required by
    April 30, 1987.
  - An accumulation study in irrigated crops (field) is required by
    October 30, 1987.
  - An accumulation study in fish is required by October 30, 1985.
The following ecological effects data are required:
- An acute freshwater invertebrate toxicity study using a typical
  EP is required by October, 1985.
- An aquatic field study to monitor residues next to rice fields
  using a typical EP is required by April, 1987.
The following product chemistry data are required by October 30, 1985:
- The name and address of the manufacturer or producer of each
  starting material used in the 90% technical product.
- A discussion of each impurity believed to be present at >0.1% based
  on the beginning materials, all chemical reactions, and any
  contamination, is required by April 30, 1986.
- Five or more samples must be analyzed for the active ingredient
  (A,I.) and each impurity present for which a certified limit is
  required by April 30, 1986.
- A current Confidential Statement of Formula.
- Quantitative methods to determine the remaining impurities in the
  technical product by April 30, 1986.
- Data are required for ppm solubility in various solvents at 20 C.
- Dissociation constant data.
- Octanol/water partition coefficient data.
- Data on the pH.
- The following data are required for chemical stability:  discussion
  of sensitivity of the A.I. to metal and metal ions, stability of the
  A.I. at normal and elevated temperatures, and the sensitivity of the
  A.I. to sunlight.
The following residue chemistry data are required:
- Additional plant metabolism data are required with radio-labeled
  pendimethalin by April 30, 1987.
- Levels of metabolites remaining unextractable in plant tissues and
  in polar fractions must be determined for possible toxicological
  residue concerns by April 30, 1987.
- Metabolism studies utilizing ruminants dosed with 14C ring labeled
  pendimethalin required by April 30, 1986.  Distribution and
  characterization of residues must be determined in milk, muscle,
  kidney, and liver.  If the ruminant metabolism differs significantly
  from the rat data, then swine metabolism data will also be required.
  If the additional metabolism data show the presence of new
  metabolites, then additional methodology data may be required.
- Additional data are required by April 30, 1986, to show the
  stability of pendimethalin and its 3,5-dinitrobenzyl alcohol
  metabolite in or on representative plant and animal samples stored
  at freezing temperatures.
- Residue data are required by July 30, 1986, for carrot, radish,
  and sugar beet.
- Residue data are required by July 30, 1986, for beans and peas.
- Additional data are required by July 30, 1986, to support the
  established tolerance for soybean hay.
- Data are required by July 30, 1986, for pendimethalin and its
  metabolite in or on soybean hay and straw.
- If new metabolites are found, then additional field residue data
  for field corn may be required.  When necessary, data will be
  extrapolated from the soybean processing study to corn.
- If new residue metabolites are found, additional metabolism and
  field residue data may be required for sorghum.
- Additional processing data may be required for cottonseed.  When
  necessary, data will be extrapolated from the requested soybean
  processing study.
- Additional metabolism and processing data on peanuts may be
  required.  When necessary, data will be extrapolated from the
  soybean processing study.
- Additional processing data may be required for sunflower seeds.
  When necessary, data will be extrapolated from the requested
  soybean processing study.
- Residues of pendimethalin and its metabolite in catfish and cray-
  fish are required by July 30, 1986.
- Lactating ruminants must be dosed with pendimethalin to determine
  residue levels in milk.
- A study on metabolites of pendimethalin in poultry will be required
  if additional metabolites of concern are found in the plant
  metabolism studies.  The need for a poultry feeding study will
  depend upon the results of a poultry metabolism study.
- The following data are required by July 30, 1986, for tobacco:
  residue data involving the metabolism of pendimethalin in tobacco.
  If residues exceed 0.1 ppm, additional data on pyrolysis products
  must be submitted.
                   6.  CONTACT PERSON AT EPA
Robert J. Taylor
Office of Pesticide Programs
Fungicide-Herbicide Branch
Registration Division (TS-767C)
Environmental 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.