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,
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,
- 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 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
- 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 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
- 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
- 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
- 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
- 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
Toxicology: Acutes, subchronic 6 - 50 months
oral, 21-day dermal,
second species oncogenicity
or historical data from mouse
oncogenicity study, chronic
Ecological Effects: 9 - 12 months
nontest insect and
Environmental Fate: 9 - 27 months
6. CONTACT PERSON AT EPA
Mr. Richard F. Mountfort
Product Manager (23)
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.