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2,4-DB (Butoxone, Butyrac) Herbicide Profile 10/88

                         EPA Pesticide Fact Sheet
Name of Chemical:      2,4-DB (See Below)
Reason for Issuance:   Registration Standard
Date Issued:           Oct. 03, 1988
Fact Sheet Number:     179
                    1.  DESCRIPTION OF CHEMICAL(S)
Generic Name(s):  4-(2,4-dichlorophenoxy)butyric acid (2,4-DB); 2,4-DB
                  sodium salt; 2,4-DB, dimethylamine salt; 2,4-DB, butyl
                  ester; 2,4-DB, 2-butoxyethyl ester; and 2,4-DB,
                  isooctyl ester.
Common Name(s):  2,4-DB, and its sodium salt, amine and esters.
Trade Name(s):  2,4-DB is available under the trade names, Butoxone and
                Butyrac, formulated as an amine salt or ester.
EPA Shaughnessy Codes:  030801 (acid)
                        030804 (sodium salt)
                        030819 (dimethylamine salt)
                        030853 (2-butoxyethyl ester)
                        030856 (butyl ester)
                        030863 (isooctyl ester)
Chemical Abstracts Service
            (CAS) Number(s):  94-82-6 (acid)
                              10433-59-7 (sodium salt)
                              2755-42-1 (dimethylamine salt)
                              32357-46-3 (2-butoxyethyl ester)
                              6753-24-8 (butyl ester)
                              1320-15-6 (isooctyl ester)
Year of Initial Registration:  1958
Pesticide Type:  Herbicide; plant growth regulator
Chemical Family:  Chlorinated phenoxys
U.S. and Foreign Producers:  2,4-DB technical products are manufactured
                             by both U.S. and foreign companies.
                  2.  USE PATTERNS AND FORMULATIONS
- Registered Uses:  Terrestrial Food
- Predominant Uses:  Agricultural crops, alfalfa (16-67% of total
  usage), soybeans (27-68%), peanuts (5-13%), and clover (less than 2).
- Pests Controlled:  Broadleaf weeds
- Formulation Types Registered:  Liquid (emulsifiable concentrate,
  soluble concentrate)
- Method of Application:  Ground equipment and aircraft.
                         3. SCIENCE FINDINGS
- Existing data are inadequate to assess the carcinogenic potential of
  2,4-DB.  In a rat study, 2,4-DB was not oncogenic.  In a mouse
  oncogenic study there was a weak but possible dose-relationship
  involving hepatocellular carcinomas in males.  A new study or
  historical control data in certain tumor incidences in the strain
  of mice at the testing facility are required before the significance
  can be determined.   Additional data are needed to determine the
  teratogenic potential of 2,4-DB.
- 2,4-DB is generally formulated as a sodium salt, an amine salt or an
  ester.  The amine and ester forms may differ in biological activity
  and environmental fate from the parent compound.  Data are needed on
  each amine and ester to enable a complete assessment.
- Concern about possible groundwater contamination exists for the family
  of 2,4-D compounds (2,4-D, 2,4-DB, and 2,4-DP).  Additional data and
  a label warning statement are required.
Chemical Characteristics: (2,4-DB acid technical)
- Physical State:  Crystalline solid
- Color:  White to light brown
- Odor:  Slight phenolic
- Melting Point:  116 to 119 degrees C
- Solubility:  Highly soluble in acetone, benzene, carbon
  tetrachloride, diesel oil and kerosene; slightly soluble in water
- Vapor Pressure:  Negligible at 25 degrees C
- Stability:  Stable
Toxicological Characteristics:  (Note:  2,4-DP acid is test material.)
- Acute Oral Toxicity - Rats:  2.33 g/kg (males), 1.54 g/kg (females),
  1.96 g/kg (males), 1.47 g/kg (females); Toxicity Category III
- Acute Dermal Toxicity - Rabbits:  > 2 g/kg; Toxicity Category III
- Primary Eye Irritation - Rabbits:  All irritation cleared at 7 days;
  Toxicity Category III
- Primary Skin Irritation - Rabbit:  No irritation at 27 and 72 hours;
  Toxicity Category IV
- Subchronic Toxicity - Dog:
  Lowest-observed-effect level (LOEL) = 25 mg/kg/day
  No-observed-effect level (NOEL) = 8 mg/kg/day
  Mortality, body weight depression, histolopathological findings at
  LOEL and highest dose level (80 mg/kg/day)
Chronic Toxicity:
- Chronic Feeding Oncogenicity - Rats:
  - Systemic LOEL = 30 mg/kg/day for non-oncogenic effects
  - Systemic NOEL = 3 mg/kg/day for non-oncogenic effects
  - Decreased mean body weight gains, change in blood chemistry and
    hematology parameters and significantly lower heart eights than
    control.  Not oncogenic under the conditions of the study.
- Oncogenicity Study - Mice:
  - Weak, but possible dose-relationship involving hepatocellular
    carcinomas in males.  A new study is required or this study may
    be upgraded if historical control data on certain tumor incidences
    in the strain of mice at testing facility are submitted and justifi-
    cation that female mice of this strain were tested at or close to
    the Maximum Tolerated Dose (MTD).
- Teratology Study:  No acceptable data available.
- Reproduction Study:
  - NOEL = 15 mg/kg/day
  - At highest dose (75 mg/kg/day) ovarian weight was significantly less
    in dams mean body weights were lower, fewer pups were born per
    litter, and extremely high pup mortality occurred during lactation
    period.
- Mutagenicity-Study:
  - Ames study negative with and without metabolic activation.
  - Chinese Hamster Ovary assay with activation suggests a weak
    mutagen immediately below doses causing high levels of cytotoxicity.
  - In Chinese Hamster Ovary assay a significant increase in chromosomal
    aberration with 17.25-hour exposure, but no increase with 2-hour
    exposure.  Unscheduled DNA synthesis, no evidence of induction.
Physiological and Behavioral Characteristics:
- Mechanism of Pesticide Action:  Phenoxy herbicides (including 2,4-DB)
  are hormone weed killers affecting the activity of enzymes,
  respiration, and cell division.
Environmental Characteristics:  No data are available.
Ecological Characteristics:  (Note: all figures are LC50 values)
- Avian Toxicity:  No acute oral studies available.  Dietary studies
  indicate 2,4-DB acid is practically nontoxic (> 5000 ppm,
  respectively) to waterfowl and upland game birds.
- Aquatic Organism Toxicity:  2,4-DB acid is moderately to slightly
  toxic to freshwater fish (18 ppm fathead minnow, 7.5 to 17 ppm
  bluegill sunfish, 2.0 to 14 ppm rainbow trout).  No studies are
  available for freshwater invertebrates.
- Nontarget Insect Toxicity:  2,4-DB dimethylamine salt has a low
  toxicity to bees.
- Nontarget Plants/Endangered Species:  Since 2,4-DB is a broadleaf
  herbicide, a potential hazard exists for nontarget plant.  Hazard
  assessments for endangered species cannot be completed until
  additional data are received.
Tolerance Assessment:
- Tolerance Established:  Tolerances of 0.2 ppm have been established
  for 2,4-DB and its metabolite 2,4-D in or on alfalfa, clover, mint
  hay, peanuts, soybeans, soybean hay, and birdsfoot trefoil (40 CFR
  180.331).
- Results of Tolerance Assessment:  A provisional acceptable daily
  intake of 0.01 mg/kg/day for 2,4-DB acid has been established
  based on a rat chronic feeding study with NOEL of 3 mg/kg/day
  and utilizing a 300X safety factor.  A Theoretical Maximum Residue
  Contribution (TMRC) for the U.S. population was calculated to be
  0.000083 mg/kg/day which utilizes 0.83 % of the PADI
- Reported Pesticide Incidents:  Based on the Pesticide Incident
  Monitoring System files covering the period of 1966 to 1979, reports
  were received concerning off-target movement for unspecified 2,4-D
  (family) compounds.  The incidents involved drift from aerial
  (173 reports) and ground (104 reports) applications, as well as
  volatilization (35 reports) and resulted in damage to nontarget
  crops and other desirable plants.
             4.  SUMMARY OF REGULATORY POSITION AND RATIONALE
- Summary of Agency Position:  The Agency has concluded that existing
  data are inadequate to assess the carcinogenic potential of 2,4-DB.
  Under conditions of the study 2,4-DB was not oncogenic in the rat.  In
  a mouse oncogenic study with 2,4-DB acid there was no conclusive
  evidence of oncogenicity.  However, there was a weak but possible dose
  relationship involving hepatocelluar carcinomas in males.  This mouse
  oncogenicity was deficient because historical control data on certain
  tumor incidences in the strain of mice at the testing facility were
  not submitted.  Unless the data are submitted, the study must be
  repeated.
- Data are being required on the salt, ester and amine formulations of
  2,4-DB as well as on the acid.  The Agency will not establish any
  significant new food use tolerances or register any significant new
  uses at this time.
- Unique Label Warning Statements:  groundwater Advisory - (end-use
  products [EPs]):  "This product can reach ground water as a result
  of mixing and loading.  To minimize groundwater contamination from
  spill during mixing and 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 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."
                  5.  SUMMARY OF MAJOR DATA GAPS
- The following data are required for 2,4-DB acid.  The Agency is also
  requiring data on each individual salt, eater and amine of 2,4-DB.
  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: Acutes, subchronic         6 - 50 months
   oral, 21-day dermal,
   second species oncogenicity
   or historical data from mouse
   oncogenicity study, chronic
   feeding (nonrodent)
   teratogenicity, mutagenicity
Ecological Effects:                       9 - 12 months
   Avian oral/dietary,
   aquatic organisms
   (freshwater fish/
   invertebrates),
   nontest insect and
   plant studies
Environmental Fate:                       9 - 27 months
   All studies
                          6. CONTACT PERSON AT EPA
Mr. Richard F. Mountfort
Product Manager (23)
Fungicide-Herbicide Branch
Registration Division (TS-767C)
Office of Pesticide Programs
Environmental Protection Agency
401 M Street SW.
Washington, DC 20460
Telephone: (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.