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DCPA (Dacthal) Herbicide Profile 6/88

EPA Pesticide
Fact Sheet
Name of Chemical:           DCPA
Reason for Issuance:        Registration Standard
Date Issued:                June 6, 1988
Fact Sheet Number:          166
                    1. DESCRIPTION OF CHEMICAL
- Generic Name:  Dimethyl tetrachloroterephthalate
- Common Names:  No common name has been assigned; DCPA is commonly
                 used; other names in use are chlorothal and chlorothal-
                 dimethyl
- Trade Names:   Dacthal
- EPA Shaughnessy Code:  078701
Chemical Abstracts Service (CAS) Number:  1861-32-1
Year of Initial Registration:  1958
Pesticide Type:  Herbicide
Chemical Family:  Chlorinated benzoic acids
U.S. Producer:  Fermenta Plant Protection Company
                  2. USE PATTERNS AND FORMULATIONS
- Application sites- Terrestrial food crops (Agricultural Crops),
  Terrestrial Nonfood Crops (Agricultural Crops), Ornamental Plants and
  Forest Trees, Domestic Outdoor (Ornamental Plants and Forest Trees).
- Types of formulations: Formulation intermediates containing 50, 75 and
  90 percent DCPA; Wettable Powders containing 25, 50, 60 75, and 90
  percent DCPA and granulars containing 1.15 to 24.0 percent DCPA.
- Types and methods of application:
  - Applied with ground or aerial equipment to soil pre-emergence to
    weed seed germination, broadcast or in bands, either post-plant,
    post-transplant or at layby. Applied to ornamental turf and lawns
    with either spray or granular equipment before weed seed
    germination.
- Usual carrier:  Water and fertilizers.
                       3. SCIENCE FINDINGS
Summary Science Statement
     DCPA and its metabolites appear to have low acute and chronic 
toxicity based on the limited studies that are available. However, these 
products contain 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) and 
hexachlorobenzene (HCB) as impurities from the manufacturing of 
technical DCPA. These impurities have chronic toxicological properties 
(including oncogenic, teratogenic, fetotoxic, mutagenic or adverse 
effects on immune response in mammals) that are of particular concern in 
the reregistration of DCPA pesticide products. The Agency has classified 
both these impurities as Probable Human Carcinogens (Group B2). The 
Agency has performed preliminary assessments of the risks posed by these 
impurities and is requiring environmental fate and residue chemistry 
studies on the impurities in order to refine these risk assessments.
Chemical characteristics:
- Physical state:  Crystalline solid
- Color:  White
- Odor:  Odorless
- Melting point:  156 degrees C
- Solubility:  Insoluble in water, high in aromatic hydrocarbon solvents
Toxicological Characteristics of DCPA:
- Acute toxicity:  Data gap.
- Dermal sensitization:  Not a sensitizer in guinea pig.
- Subchronic toxicity:  Data gap.
- Chronic toxicity:  In an acceptable chronic oral toxicity of DCPA in
  dogs, four male and four female beagle dogs were dosed with DCPA at
  100, 1,000, and 10,000 ppm in their diet. No compound-related effects
  were observed. The NOEL was 10,000 ppm.
  In a chronic toxicity study in rats, 35 male and 35 female rats were
  dosed with DCPA at 100, 1,000 and 10,000 ppm in their diets for 2
  years. At termination of the study, the kidney weights in males and
  the adrenal weights of females were significantly higher than
  controls. The NOEL was 1,000 ppm (50 mg/kg/day). The LEL was 10,000
  ppm (500 mg/kg/day).
- Oncogenicity: Data gap.
- Reproductive toxicity: Data gap.
- Teratology: Twenty-five bred female Charles River rats were fed 500,
  1,000, and 2,000 mg/kg/day. No compound related effects were observed
  in the dams or the fetuses at the highest dose tested.
- Mutagenicity: DCPA did not induce toxic effects in an in vivo dominant
  lethal study when administered to male rats in a single treatment of
  3.16, 31.6 and 316 mg/kg prior to mating.
- Metabolism: Data gap.
Physiological and Biochemical Characteristics
- Mechanism of pesticidal action: DCPA appears to inhibit the normal
  cell division of root tips of a wide spectrum of plants. The precise
  mechanism of this effect is not understood.
- Metabolism and persistence in plants and animals:
  - Plants:  Radiolabeled DCPA was not translocated from treated leaves
    of cotton plants. If applied to soil or nutrient solution roots of
    cotton plants appeared to absorb it and translocate it to the stems
    and foliage of the plants. Monomethyl tetrachloroterephthalate (MTP)
    and tetrachloroterephthalic acid (TPA) and DCPA have been detected
    in residue studies from numerous agricultural commodities.
  - Animals:  Non-radiolabeled studies have detected DCPA, MTP and TPA
    in ruminants and poultry. l4C-DCPA studies are needed for both
    metabolism of DCPA in animals and plants
Environmental Characteristics:
- Environmental fate data include a hydrolysis study which indicates
  that DCPA is stable to hydrolysis for up to 36 days.
- Data gaps exist for all other environmental fate requirements.
- DCPA and its degradates were detected in ground water samples in four
  states. The highest level detected was 1139 parts per billion (ppb).
  The Agency has proposed a drinking water health advisory level of 3500
  ppb. A ground water monitoring study is required to assess the extent
  of ground water contamination.
Ecological Characteristics:
- Acute avian oral toxicity: data gap.
- Avian dietary toxicity: data gap.
- Avian reproductive toxicity: data gap.
- Freshwater fish acute toxicity: LC50 = >100 to >320 ppm (practically
  nontoxic) for bluegill sun fish and LC50 = 30 ppm (slightly toxic) for
  rainbow trout.
- Freshwater invertebrate acute toxicity: EC50 ranged from 27 ppm to 135
  ppm (slightly to practically nontoxic) for Daphnia magna. LC50 >100
  ppm (practically nontoxic) for Chironomus plumosus. LC50 >6.2 ppm
  (moderately toxic) for Gammarus pseudolimnacus.
- Estuarine and marine organisms acute toxicity: LC50 > 1,000 ug/L
  (practically nontoxic) for Brown shrimp (Penaeus aztecus ). LC50 = 620
  ug/L (practically non-toxic) for Eastern oyster (Crassostrea
  virginica). LC50 = >1,000 ug/L (practically nontoxic) for Sheepshead
  Minnow (Cyprinodon variegatus).
- Available information suggests there is no acute hazard to endangered
  aquatic species. No terrestrial endangered species have been
  associated with the use patterns of DCPA products. No data are
  available to evaluate the hazard to endangered avian species or
  endangered aquatic plant species.
Tolerance assessment:
- Tolerances have been established for residues of DCPA on raw
  agricultural commodities. (See table on the following page for a
  listing of tolerances.)
- Using a Provisional Acceptable Daily Intake (PADI) of 0.5 mg/kg/day
  based on the NOEL of 50 mg/kg/day observed in a chronic toxicity rat
  study, the Maximum Permissible Intake (MPI) for a 60 kg person is 30.0
  mg/kg/day. Using this value, the Agency calculates that existing
  tolerances occupy 1.3 % of the ADI.
                  4. SUMMARY OF REGULATORY POSITIONS
A. The Agency will not initiate a Special Review on DCPA at this time.
  There are presently no chronic toxicological concerns for exposures to
  DCPA; however concerns for the chronic toxicological effects of the
  two manufacturing impurities 2,3,7,8-TCDD and HCB have not been
  resolved by the available information.
  At the present time the Agency does not consider the risks due to
  2,3,7,8-TCDD from the use of DCPA be unreasonable. The highest risk
  estimated was 10 to the minus 6 for agricultural applicators and PCOs.
  The Agency is concerned about the risks due to HCB from the use of
  DCPA which are 10 to the minus 6 for dietary exposure and 10 to the
  minus 4 for agricultural applicators, PCOs and a child exposed while
  playing on a treated lawn. The applicator exposures can be reduced by
  using protective clothing. The uncertainties in the exposure estimates
  used to assess the risk to children playing on a DCPA-treated lawn are
  so great that the Agency believes that the risk assessment cannot be
  used to determine whether criteria for initiating a Special Review
  have been exceeded. These exposure estimates will be refined when data
  on foliar and soil exposure to HCB become available. The Agency
  believes the dietary risk to HCB from DCPA uses is acceptable while
  required metabolism and residue data are being developed.
B. The Agency is not classifying any DCPA uses as being for restricted
  use. As discussed above, the uncertainties in the exposure estimates
  are very great. Accordingly, the Agency is unable to conclude that the
  risk posed by DCPA warrants its classification as a restricted use
  pesticide. The Agency will reconsider this position when the data it
  is requiring become available.
Table 1.  Tolerances in parts per million (ppm) for residues of DCPA and 
metabolites MTP and TPA.
________________________________________________________________________
                                Residues of DCPA       Parts per Million
Raw Agricultural Commodity      U.S.      Canada       Mexico      Codex
________________________________________________________________________
Beans, field dry                 2          -            -          -
Beans, mung, dry                 2          -            -          -
Beans, snap, succulent           2          -            -          -
Broccoli                         1          -            -          -
Brussels sprouts                 1          -            -          -
Cabbage                          1          -            -          -
Cantaloupes                      1          -            -          -
Cauliflower                      1          -            -          -
Collards                         2          -            -          -
corn, field, fodder              0.4        -            -          -
corn, field, forage              0.4        -            -          -
Corn, grain (including
  field and pop)                 0.05       -            -          -
corn, pop, fodder                0.4        -            -          -
Corn, pop, forage                0.4        -            -          -
Corn, sweet (K + CWHR)           0.05       -            -          -
Corn, sweet, fodder              0.4        -            -          -
Corn, sweet, forage              0.4        -            -          -
Cottonseed                       0.02       -            -          -
Cress, upland                    5          -            -          -
Cucumbers                        1          -            -          -
Eggplant                         1          -            -          -
Garlic                           1          -            -          -
Honeydew melons                  1          -            -          -
Horseradish                      2          -            -          -
Kale                             2          -            -          -
Lettuce                          2          -            -          -
Mustard, greens                  5          -            -          -
Onions                           1          -            -          -
Peas, southern, black-eyed       2          -            -          -
Peppers                          2          -            -          -
______________________________________________________________________
Table 1 Continued.  Tolerances in parts per million (ppm) for residues 
of DCPA and metabolites MTP and TPA.
________________________________________________________________________
                                Residues of DCPA       Parts per Million
Raw Agricultural Commodity      U.S.      Canada       Mexico      Codex
________________________________________________________________________
Pimentos                         2          -            -          -
Potatoes                         2          -            -          -
Radish, roots                    2.0        -            -          -
Radish, tops                    15.0        -            -          -
Rutabagas                        2          -            -          -
Soybeans                         2          -            -          -
Squash, summer                   1          -            -          -
Squash, winter                   1          -            -          -
Strawberries                     2          -            -          -
Sweet potatoes                   2          -            -          -
Tomatoes                         1          -            -          -
Turnips                          2          -            -          -
Turnips, greens                  5          -            -          -
Watermelons                      1          -            -          -
Yams                             2          -            -          -
______________________________________________________________________
C. The Agency is requiring registrants to certify that the levels of
   2,3,7,8-TCDD and HCB in DCPA used to formulate their products do not
   exceed 0.1 ppb and 0.3 percent, respectively. This measure will
   assure that the levels of these impurities in commercially available
   DCPA products do not exceed the reported maximum levels upon which
   the Agency based its risk assessment. Registrants must also analyze
   their products for other species of dioxins and establish certified
   limits for these impurities as well.
D. The Agency will not register any significant new uses of DCPA until
   product chemistry, toxicology and residue chemistry data gaps have
   been filled.
E. The Agency is requiring ground water monitoring studies to assess the
   extent of ground water contamination. Because of the low toxicity of
   DCPA, the low levels observed in ground water to date, and the
   limited number of observations of ground water contamination, the
   Agency finds that additional regulatory action is not warranted.
F. The Agency is requiring dietary exposure information on DCPA
   impurities in order to determine the nature and magnitude of 2,3,7,8-
   TCDD and HCB residues. If these data show that these impurities or
   their metabolites accumulate in DCPA-treated agricultural commodities
   to levels that raise concerns about dietary risk, the Agency may find
   that additional regulatory action is warranted.
G. The Agency is requiring dislodgeable residue and foliar dissipation
   data on HCB in order to estimate dermal exposure to this impurity.
   These data are needed to refine the estimates of HCB exposure to farm
   workers and to users of DCPA-treated lawns.
H. The Agency is requiring the use of protective clothing and equipment
   for all uses of DCPA. End-use products registered for agricultural
   use or for professional use on ornamental turf must be labeled as
   follows:
     USE ONLY WHEN WEARING THE FOLLOWING PROTECTIVE CLOTHING AND
     EQUIPMENT DURING MIXING/LOADING AND APPLYING, REPAIR AND CLEANING
     OF MIXING, LOADING, AND APPLICATION EQUIPMENT, DISPOSAL OF THE
     PESTICIDE, AND EARLY REENTRY INTO TREATED AREAS:
     Wear a long-sleeved shirt and long-legged pants and chemical
     resistant gloves.
     IMPORTANT! If pesticide comes in contact with skin, wash off with
     soap and water. Always wash hands, face, and arms with soap and
     water before smoking, eating, drinking, or toileting.
     AFTER WORK: Before removing gloves, wash them with soap and water.
     Take off all work clothes and shoes. Shower using soap and water.
     Do not reuse contaminated clothing. Clothing worn during work must
     be laundered separately from household articles. Clothing that
     becomes heavily contaminated or drenched must be destroyed
     according to State and local regulations. HEAVILY CONTAMINATED OR
     DRENCHED CLOTHING CANNOT BE ADEQUATELY DECONTAMINATED.
End use products registered for homeowner uses must be labeled as 
follows:
     USE ONLY WHEN WEARING THE FOLLOWING PROTECTIVE CLOTHING: Wear long-
     sleeved shirt and long-legged pants and chemical resistant gloves.
     IMPORTANT! If the pesticide comes in contact with skin wash off
     with soap and water. Always wash hands, face, and arms with soap
     and water before smoking, eating, drinking, or toileting.
     AFTER USE: Before removing gloves, wash them with soap and water.
     Take off all work clothes and shoes. Shower using soap and water.
     Do not reuse contaminated clothing. Clothing worn during use must
     be laundered separately from household articles.
I. The Agency is imposing an interim 24-hr reentry interval for
   agricultural crop uses of DCPA pesticide products until required
   reentry data have been found to support a different reentry interval.
   End-use products registered for agricultural crop use must be labeled
   as follows:
     Do not enter treated areas for 24 hours after application unless
     wearing long sleeved shirt and long pants.
J. The Agency is imposing a required precautionary statement,
   environmental hazard statements, and statement of practical
   treatment, as follows:
All products must bear the following precautionary statement:
     Causes moderate eye irritation. Avoid contact with eyes or
     clothing. Wash thoroughly with soap and water after handling.
All manufacturing use products must bear the following environmental 
hazard statement:
     Do not discharge effluent containing this product into lakes,
     streams, ponds, estuaries, oceans, or public waters unless this
     product is specifically identified and addressed in an NPDES
     permit. Do not discharge effluent containing this product to sewer
     systems without previously notifying the sewage treatment plant
     authority. For guidance, contact your State Water Board or Regional
     Office of the EPA.
All nongranular end-use products must bear the following environmental 
hazard statements:
     Do not apply directly to water or wetlands (swamps, bogs, marshes,
     and potholes). Do not contaminate water when disposing of equipment
     wastewater.
All granular end-use products must bear the following environmental 
hazard statements:
     Collect and incorporate granules spilled on the soil surface. Do
     not apply directly to water or wetlands (swamps, bogs, marshes, and
     potholes). Do not contaminate water by cleaning of equipment or
     disposal of wastes.
All products must bear the following statements of practical treatment:
     If in Eyes: Flush with plenty of water. Call a physician if
     irritation persists.
K. The Agency has determined that the following studies will receive
   priority review:
158.120 Product Chemistry
_________________________
61-2 Description of Beginning Materials and Manufacturing Process
61-3 Discussion of Formation of Impurities
62-1 Preliminary Analysis
158.125 Residue Chemistry - DCPA
________________________________
171-4 Nature of Residue (Metabolism)
      - Plants
      - Livestock
171-4 Residue Analytical Method
      - Plant Residues
      - Animal Residues
171-4 Storage Stability Data
158.125 Residue Chemistry - Impurities
______________________________________
171-4 Nature of Residue (Metabolism)
      - Plants
      - Livestock
171-4 Residue Analytical Method
      - Plant Residues
      - Animal Residues
171-4 Storage Stability Data
158.130 Environmental Fate
__________________________
163-1 Leaching and Adsorption/Desorption
132-1 Foliar Dissipation
133-3 Dermal Exposure (Conditional, at option of Registrant)
133-4 Inhalation Exposure (Conditional, at option of Registrant)
-- Ground Water Monitoring
                     5. SUMMARY OF MAJOR DATA GAPS
Product Chemistry
Toxicology:
   Acute testing
   Subchronic testing
   Chronic testing
   Special testing
Environmental Fate:
   Photodegradation
   Metabolism Studies - Laboratory
   Mobility Studies
   Dissipation Studies - Field
   Accumulation Studies
   Sub-division K, Reentry Studies
   Ground water Monitoring
Ecological Effects:
   Avian Testing
   Aquatic Organism Testing
   Nontarget Area Phytotoxicity
Residue Chemistry for DCPA Products:
   Metabolism in Plants and Livestock
   Residue Analytical Methods for Plants and Animals
   Storage Stability Data for Raw Agricultural Commodities
   Magnitude of Residues in Food and Feed Commodities
Residue Chemistry for Impurities in DCPA Products:
   Metabolism in Plants
   Residue Analytical Methods for Plant Residues
   Magnitude of Residues in Raw Agricultural Commodities
                 6. CONTACT PERSON AT EPA
Richard F. Mountfort
Product Manager (23)
Fungicide-Herbicide Branch
Registration Division (TS-767C)
Office of Pesticide Programs
Environmental Protection Agency
401 M Street, S.W.
Washington, DC 20460
Room 237, Crystal Mall Building #2
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 reregistration. The complete 
Registration Standard for DCPA may be obtained from the National 
Technical Information Service (NTIS), Port Royal Road, Springfield, VA 
22152 (Telephone No. 703-487-4650). Price for paper copies vary 
depending on the length of the document, microfiche copies are $5.95 
each. When ordering you must furnish the NTIS with the stock number. The 
stock number may be obtained from the contact person identified above.