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2,4-D (Dacamine, Weed-B-Gon) Herbicide Profile 9/88

                          EPA Pesticide Fact Sheet
Name of Chemical:    2,4-Dichlorophenoxyacetic Acid (2,4-D)
Reason for Issuance:  Registration Standard
Date Issued:         September 1988
Fact Sheet Number:    94.2
DESCRIPTION OF CHEMICAL
Generic Name: 2,4-Dichlorophenoxyacetic Acid
Common Name: 2,4-D (includes parent acid as well as salt, amine and ester 
derivatives)
Trade Name: 2,4-D is available under a large selection of trade names, most 
often formulated as an inorganic salt, amine or ester.
EPA Chemical Code:  030001 (Acid)
Chemical Abstracts Service (CAS) Number:  94-75-7 (Acid)
Year of Initial Registration:  1948
Pesticide Type:  Herbicide; Plant Growth Regulator
Chemical Family:  Chlorinated phenoxy
U.S. and Foreign Producers:  2,4-D technical products are manufactured by a 
large number of companies, both U.S. and foreign.
USE PATTERNS AND FORMULATIONS
Registered Uses:  Terrestrial, food and nonfood; aquatic, food and nonfood; 
domestic; and forestry.
Predominant Uses:  Postemergent weed control in agricultural crops 
(approximately 57 percent of total usage; over 45 percent of total usage is on 
wheat and corn; 20 percent of total usage on pastures and rangelands; other 
major crops are sorghum, other small grains, rice and sugarcane); the 
remainder is used on noncrop areas, with a small amount used as a plant growth 
regulator (in filberts, citrus and potatoes).
Formulation Types Registered:  Granular; amine and ester liquids; aerosol 
spray (foam).
Methods of Application:  Aerial and ground equipment, knapsack sprayers, 
pressure and hose-end applicators, and lawn spreaders.
SCIENCE FINDINGS
Summary science Statement:  The Agency's Office of Pesticide Programs (OPP) 
has classified 2,4-D as a Group D oncogen (not classifiable as to human 
carcinogenicity) because existing data are inadequate to assess the 
carcinogenic potential of 2,4-D.  Accidental human poisoning with 2,4-D, which 
resulted in severe neurotoxicity, has been reported; adequate neurotoxicity 
studies are not available.  While published data indicate that 2,4-D may be 
teratogenic, an acceptable rat teratology study is negative; a study in 
rabbits is needed.
2,4-D is often formulated as various esters and amines.  These formulations 
may affect the physical characteristics, biological activity and environmental 
fate of the parent compound. Data are needed on each ester and amine before 
the Agency can completely assess 2,4-D.
Although laboratory data demonstrate that 2,4-D is mobile in soils, its 
potential to contaminate groundwater is limited by its rapid rate of 
degradation and uptake by target plants.  However, residues of 2,4-D have been 
detected in groundwater, mostly from point sources, such as mixing, loading 
and disposal.
Certain formulations of 2,4-D are highly toxic to fish and/or aquatic 
invertebrates.  Other formulations, for which the Agency has data, are in the 
range of moderately toxic to practically nontoxic to nontarget organisms.  The 
Office of Endangered Species has issued biological opinions indicating that 
certain endangered species may be in jeopardy from the use of 2,4-D.
Chemical Characteristics (Acid):
Physical state - Flakes, powder, and crystalline powder and solid.
Color - White to light tan.
Odor - Phenolic to odorless.
Melting point - 135-142 degrees C.
Boiling point - 160 degrees C at 0.4 mm Hg.
Solubility - Soluble in acetone, ethanol, aqueous alkali, alcohols, diethyl 
ether, ethyl ether, isopropanol, methyl isobutyl ketone, most organic 
solvents; insoluble in benzene, petroleum oils.
Vapor pressure - 0.4 mm Hg at 160 degrees C.
Stability - Stable to melting point.
Toxicology Characteristics (Acid, except as noted):
Acute Toxicity: 2.4-D Acid -
   Oral (rat):  639 mg/kg (males); 764 mg/kg (females); Toxicity Category III
       (For a description of Toxicity Categories, see 40 CFR 156.10.)
   Inhalation (rat):  1.79 mg/L; Toxicity Category III
   Dermal Sensitization (guinea pig):  Not a sensitizer.
2,4-D Sodium Salt -
   Oral (rat):  876 mg/kg (males); 975 mg/kg (females); Toxicity Category III
   Dermal (rat): >2000 mg/kg; Toxicity Category III
Diethanolamine Salt (Manufacturing-Use Product) -
   Oral (rat):  >2000 mg/kg (males); 1605 mg/kg (females); Toxicity
     Category III
   Dermal (rabbit):  >2000 mg/kg (males and females); Toxicity Category III
   Inhalation (rat): >3.8 mg/L; Toxicity Category III
   Primary Eye (rabbit): Severe irritation and corneal ulcer not resolved 21
     days post-treatment; Toxicity Category I
   Primary Dermal (rabbit): No signs of dermal irritation; Toxicity Category
     IV
   Dermal Sensitization (guinea pig): Not a dermal sensitizer.
Butoxyethyl Ester -
   Oral (rat):    866 mg/kg; Toxicity Category III
   Dermal (rabbit):  >2000 mg/kg (females: 1829 (mg/kg (males); Toxicity
     Category III
   Inhalation (rat):  >4.6 mg/L; Toxicity Category III
   Primary Eye (rabbit): Very mild eye irritation resolved in 72 hours;
     Toxicity Category III
   Primary Dermal (rabbit): Very slight erythema cleared in 72 hours; Toxicity
     Category III.
   Dermal Sensitization (guinea pig):  Was a sensitizer in two tests and not a
     sensitizer in a third test.
Isooctyl Ester -
   Oral (rat):  982 mg/kg (males); >720 <864 mg/kg (females); Toxicity
     Category III
   Dermal (rabbit):  >2000 mg/kg; Toxicity Category III 
Isobutyl Ester -
   Oral (rat):  700 mg/kg (males); 553 mg/kg (females); Toxicity Category III
   Dermal (rabbit):  >2000 mg/kg; Toxicity Category III 
Isopropyl Ester -
   Oral (rat):  640 mg/kg (males); 440 mg/kg (females); Toxicity Category II
   Dermal (rabbit):  >2000 mg/kg; Toxicity Category III 
   Inhalation (rat): >4.97 mg/L; Toxicity Category III
   Primary eye (rabbit): All irritation cleared at 4 days; Toxicity Category
     III
   Primary dermal (rabbit): No irritation at 72 hours; Toxicity Category IV
   Dermal Sensitization (guinea pig): Nonsensitizer
Subchronic Toxicity:  No acceptable data are available on 2,4-D. The 
requirement for subchronic oral studies on the acid is waived because chronic 
studies are required; a subchronic dermal study is required. Subchronic 
studies are required for the esters and amines.
Chronic Toxicity:
   Oncogenicity (rats):  No observed effects level (NOEL) for systemic effects
- 1 mg/kg/day; lowest observed effects level (LOEL) for systemic effects 
- 5 mg/kg/day; further evaluation needed to determine if maximum tolerated 
dose was reached.
   Oncogenicity (mice):  NOEL for systemic effects - 1 mg/kg/day; LOEL for 
systemic effects - 15 mg/kg/day; further evaluation needed to determine if 
maximum tolerated dose was reached.
   Teratology (rats):  Fetotoxicity (delayed ossification) LOEL 75 mg/kg/day 
and NOEL 25 mg/kg/day; Maternal toxicity NOEL 75 mg/kg/day (highest dose 
tested).
   Reproduction (rats):  NOEL 5 mg/kg/day.
Major Routes of Exposure:  The major route of exposure is dermal; respiratory 
exposure is negligible.
Physiological and Behavioral Characteristics:
   Foliar Absorption:  2,4-D is absorbed through the roots and/or leaves 
depending upon the type of formulation.  A rain-free period of 4 to 6 hours 
usually is adequate for uptake.
   Translocation:  Following foliar absorption, 2,4-D translocates within the 
phloem, probably moving with the food material. Following root absorption, it 
may move upward in the transpiration stream.  Translocation rate is influenced 
by the growth rate of the plant.  Accumulation occurs principally at the rapid 
growth regions of shoots and roots.
   Mechanism of Pesticide Action:  2,4-D acid stimulates nucleic acid and 
protein synthesis affecting the activity of enzymes, respiration and cell 
division. Broadleaf plants exhibit malformed leaves, stems and roots.
Environmental Characteristics:
   Absorption and Leaching:  2,4-D is mobile to highly mobile in five soil 
types.  Based on available data, aged 2,4-D residues are only slightly mobile.
   Microbial Breakdown:  2,4-D degrades rapidly in aerobic silty clay and loam 
soil systems.
   Bioaccumulation:  Available data indicate a low potential for 2,4-D to 
accumulate in fish.
   Resultant Average Persistence:  In aerobic silty clay and loam soils, 1.9-
2.2 percent of applied 2,4-D remained at 51 days post-treatment; in four other 
soils, only 0.7-2.5 percent remained at 150 days post-treatment.
   Environmental Fate and Surface and Groundwater Contamination Concerns: 
Although laboratory data demonstrate that 2,4-D is mobile in soils, its 
potential to contaminate groundwater is limited by its rapid rate of 
degradation and uptake by target plants.  However, residues of 2,4-D have been 
detected in groundwater, mostly from point sources, such as mixing, loading 
and disposal.
   Exposure of Humans and Nontarget Organisms:  Accidental human poisoning 
with 2,4-D, which resulted in severe neurotoxicity, has been reported.  
Reports have been received concerning off-target movement of 2,4-D resulting 
in damage to crops or other desirable plants.
   Exposure during Reentry Operations:  Based on available data, 2,4-D 
products are of low toxicity (Toxicity Categories III and IV).  Because of 
these low levels of toxicity, reentry is not a concern.
Ecological Characteristics (detailed information can be obtained from the 
Registration Standard):
   Avian Toxicity:  Acceptable data indicate that 2,4-D acid can be 
characterized as moderately toxic to practically nontoxic to avian species on 
an acute basis. Butyl ester can be characterized as practically nontoxic on an 
acute and chronic basis.
   Fish Toxicity:  Acceptable data indicate that 2,4-D acid and certain of its 
salts, esters and amines can be characterized in the range of moderately toxic 
to practically nontoxic to fish.  However, the compounds N-oleyl-1,3-
propylenediamine salt, N,N- dimethyloleyl-linoleylamine, butyl ester, 
butoxyethanol ester and propylene glycol butyl ether ester can be 
characterized as highly toxic to fish, based on the following toxicity values:
     N-oleyl-1,3-propylene- 
          diamine salt 0.3 ppm (bluegill sunfish) 
          0.8 ppm (channel catfish)
     N,N-dimethyloleyl-linoleylamine
          0.64 ppm (rainbow trout)
     Butyl ester
          0.49-2.82 ppm (cutthroat trout)
          0.5-2.8 ppm (lake trout)
          0.4-0.96 ppm (rainbow trout)
          0.29-0.3 ppm (bluegill sunfish) 
     Butoxyethanol ester
          0.65 ppm (rainbow trout)
          0.76-1.2 ppm (bluegill sunfish)
          3.3 ppm (fathead minnow)
          0.78-1.35 ppm (channel catfish)
     Butoxypropyl ester
          5.4 ppm (rainbow trout) 
     Propylene glycol butyl ether ester
          0.33-2.8 ppm (cutthroat trout)
          0.39-2.93 ppm (lake trout)
          0.95-1.44 ppm (rainbow trout)
          0.56-0.67 ppm (bluegill sunfish)
   Freshwater Invertebrates Toxicity:  Of those compounds, for which the 
Agency has data, reported toxicity values indicate that the compounds can be 
characterized as slightly toxic to practically nontoxic, excepted as noted 
below.  The compounds set forth below have toxicity values which characterize 
them as highly toxic to aquatic invertebrates.
     Dimethylamine        0.15 ppm (grass shrimp) 
     Isooctyl ester       0.5 ppm (waterflea) 
     Butoxyethanol ester  1.7-6.4 ppm (waterflea) 
                          2.2 ppm (seed shrimp) 
                          2.6 ppm (sow bug)
                          0.44-6.1 ppm (side swimmer)
                          0.39-0.79 ppm (midge)
     Propylene glycol butyl ether ester
                          0.1-14 ppm (waterflea) 
                          0.42 ppm (seed shrimp)
   Estuarine and Marine Organisms Toxicity:  Acceptable data are available 
only for the butoxyethanol ester which report toxicity values of 5.0 mg/L 
(longnose killifish), 2.6 mg/L (Eastern oyster) and 5.6 mg/L (brown shrimp), 
which indicate that the material is moderately toxic to estuarine and marine 
organisms.
   Effects on Plants:  Limited plant protection studies are available. In a 
spray drift study, two application methods were compared as to quantity and 
pattern of deposition. No difference was found between the amine derivatives 
(diethanolamine and dimethylamine). With these amines, drift was observed 
beyond 225 feet from the site of application. No residues, attributable to 
drift, were found when applied postemergent to wheat or corn.
   The toxicity of butoxyethanol ester was tested on four species of algae. 
Toxicity values ranged from 75 mg/L to 150 mg/L.
   Nontarget Insects:  There is sufficient information to characterize 2,4-D 
as relatively nontoxic to honey bees, when bees are exposed to direct 
treatment.
   Potential Problems Related to Endangered Species:  The Office of Endangered 
Species has determined that certain uses of 2,4-D may jeopardize the continued 
existence of endangered species or critical habitat of certain endangered 
species.
Tolerance Assessment:
   Tolerances Established:  Tolerances and food and feed additive regulations 
have been established for residues of 2,4-D in a variety of raw agricultural 
commodities and meat byproducts (40 CFR 180.142), and in processed food (40 
CFR 185.1450) and feed (40 CFR 186.1450).
   Results of Tolerance Assessment:  A provisional acceptable daily intake 
(PADI) of 0.003 mg/kg/day for 2,4-D acid has been established based on a two- 
year rat feeding study.  Compound-related effects were observed in the kidneys 
of both male and female rats.  The LOEL was 5 mg/kg/day and the NOEL was 1 
mg/kg/day.  An uncertainty factor of 100 was used to account for the inter- 
and intraspecies differences.  An additional uncertainty factor of 3 was used 
since there is no dog study available and no information available that 
indicates the dog is less sensitive than the rat.
   Reported Pesticide Incidents:  Based on the Pesticide Incident Monitoring 
System files, covering the period 1966 to 1979, reports were received 
concerning the off-target movement of 2,4-D in unspecified formulations, 
esters and amines.  The incidents involved drift from aerial (173 reports) and 
ground (104 reports) applications, as well as volatilization and drift (35 
reports) and resulted in damage to off-target crops or other desirable plants. 
SUMMARY OF REGULATORY POSITION AND RATIONALE
   Summary of Agency Position:  OPP has classified 2,4-D as a Group D oncogen 
(not classifiable as to human carcinogenicity).  EPA is, however, requiring 
additional data, including additional information on oncogenicity and 
teratogenicity and neurotoxicity studies, for further evaluation of 2,4-D. 
Data are being required on the ester and amine formulations of 2,4-D as well 
as on the acid.  EPA will not establish any significant new food use 
tolerances or register any significant new uses at this time.
   Additional data are needed to thoroughly evaluate the ecological effects of 
2,4-D and its potential to contaminate groundwater.
   EPA is developing a program to reduce or eliminate exposure to endangered 
species from the use of 2,4-D to a point where use does not result in 
jeopardy, and will issue notice of any labeling revisions when the program is 
developed. Endangered species labeling is not required at this time.
Unique Warning Statements Required on Labels:
   Manufacturing-Use Products:  "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."
End-Use Products:
   Aquatic Uses:  "Drift or runoff may adversely affect nontarget plants.  Do 
not apply directly to water except as specified on this label.  Do not 
contaminate water when disposing of equipment washwaters."
   Nonaquatic Uses:  "Drift or runoff may adversely affect nontarget plants. 
Do not apply directly to water or wetlands (swamps, bogs, marshes, and 
potholes).  Do not contaminate water when disposing of equipment washwaters."
   End-Use Products - Certain Formulations:  End-use products containing the 
following formulations must contain the above environmental precautions 
modified to indicate that the product is toxic either to fish or aquatic 
invertebrates:
   Toxic to Fish - N-Oleyl-1,3-Propylenediamine salt
                   N,N-Dimethyloleyl-Linoleylamine
                   Butyl ester
                   Butoxylethanol ester
                   Propylene glycol butyl ether ester
   Toxic to Aquatic Invertebrates - Dimethylamine
                                    Isooctyl ester
   All End-Use Products:  The following statements are required in the use 
directions for all end-use products:
   Liquid Formulations: "This product can reach groundwater from mixing and 
loading.  To minimize groundwater contamination from spills during mixing, 
loading and cleaning of equipment, take the following steps:
   "Mixing and Loading:  When mixing, loading or applying this product, wear 
chemical resistant gloves.  Wash nondisposable gloves thoroughly with soap and 
water before removing.
   "The mixing and loading of spray mixtures into the spray equipment must be 
carried out on an impervious pad (i.e., concrete slab, plastic sheeting) large 
enough to catch any spilled material.  If spills occur, contain the spill by 
using an absorbent material (e.g, sand, earth or synthetic absorbent).  
Dispose of the contaminated absorbent material by placing in a plastic bag and 
following disposal instructions on this label.
   "Triple rinse empty containers and add the rinsate to the mixing tank.
   "Cleaning of Equipment: When cleaning equipment, do not pour the washwater 
on the ground; spray or drain over a large area away from wells and other 
water sources."
Granular Formulations:  "This product can reach groundwater from improper 
handling. To minimize groundwater contamination from spills during loading and 
cleaning of equipment, take the following steps:
   "Handling:  When handling this product, wear chemical resistant gloves. 
Wash nondisposable gloves thoroughly with soap and water before removing.  If 
spills occur, collect the material and dispose of by following disposal 
instructions on this label.
   "Cleaning of Equipment:  When cleaning equipment, do not pour the washwater 
on the ground; spray or drain over a large area away from wells and other 
water sources."
End-Use Products - Certain Food/Feed Uses.  Labels for products registered for 
certain food/feed uses must contain revised use directions pertaining to 
appropriate preharvest, pregrazing and preslaughter intervals; allowable range 
of diluent; and/or maximum seasonal application rate and/or number of 
applications.
SUMMARY OF MAJOR GAPS.  The following data are required for 2,4-D acid.  The 
Agency is also requiring data on each individual ester and amine of 2,4-D. 
Specific requirements are detailed in the Data Tables, Appendix I of the 
Registration Standard, which can be obtained from the Product Manager listed 
below.
Study                                  Due Date - From
                                       Date of Standard
Product Chemistry                        6-15 months
Residue Chemistry:                       18-24 months
  Plant and animal metabolism
  Analytical methods
  Residue studies
Toxicology:                              9-50 months
  Primary Eye and Dermal Irritation
  21-Day Dermal
  Chronic Toxicity (nonrodent)
  Teratogenicity (rabbit)
  Mutagenicity
  Metabolism
  Special Dermal (Neurotoxicity)
  Reserved:  Oncogenicity (two species)
Ecological Effects:                      9-18 months
  Avian Dietary
  Aquatic Organism (freshwater fish and invertebrates; estuarine
    and marine organisms; accumulation)
  Phytotoxicity (Tier II)
Environmental Fate:                      9-50 months
   Hydrolysis
   Photodegradation (water, soil, air)
   Metabolism (anaerobic soil; aerobic and anaerobic aquatic)
   Leaching and Adsorption/Desorption
   Volatility (lab and field)
   Dissipation (soil, aquatic and forestry)
   Accumulation (confined rotational crops; irrigated crops; fish
     and aquatic nontarget organisms)
  Spray drift
CONTACT PERSON AT EPA:
Mr. Richard Mountfort
Product Manager (Team 23)
Fungicide-Herbicide Branch
Registration Division (TS-767C)
Office of Pesticide Programs, EPA
Washington, DC 20460
Telephone: (703) 557-1830
DISCLAIMER:  The information in this Pesticide Fact Sheet is a summary only 
and may not be used to fulfill data requirements for pesticide registration 
and reregistration.