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.
Disclaimer: Please read
the pesticide label prior to use. The information contained at this web
site is not a substitute for a pesticide label. Trade names used herein
are for convenience only; no endorsement of products is intended, nor is
criticism of unnamed products implied. Most of this information is historical
in nature and may no longer be applicable.
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