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EXTOXNET primary files maintained and archived at Oregon State
Revised June 1996
Trade and Other Names:
2,4-DB is 4-(2,4-dichlorophenoxy)butyric acid. Trade names for
products containing 2,4-DB include Butoxone, Butyrac, Butirex,
Embutone, Embutox, and Venceweed. 2,4-DB may also be found in
formulations with other herbicides such as cyanazine, MCPA,
benazolin, linuron, and mecoprop.
2,4-DB is a General Use Pesticide (GUP). The U.S. Environmental
Protection Agency has classified it as toxicity class III -
slightly toxic. Products containing it bear the Signal Word
Chemical Class: phenoxy
2,4-DB is a selective systemic herbicide in the phenoxy family.
It is used for the control of many annual and perennial
broad-leaved weeds in alfalfa, peanuts, soybeans, and other
crops. In the plant, the compound changes to 2,4-D and inhibits
growth at the tips of stems and roots.
This compound is not to be confused with another phenoxy
compound, 2,4-D, and its derivatives, or with the derivatives of
2,4-DB, such as the sodium salt, the isooctyl ester, or the butyl
ester. Each of these are slightly different compounds and thus
have different toxicities and environmental characteristics. It
is found in formulations as a soluble concentrate and as an
emulsified concentrate. All of the material in this profile
refers to the acid form of 2,4-DB unless specifically stated
otherwise. Well over 1 million pounds of 2,4-DB were used in the
U.S. in 1990.
Formulation: It is
found in formulations as a soluble concentrate and as an
- Acute toxicity: 2,4-DB is a slightly
toxic compound through oral exposure. It has an oral LD50
ranging between 370 mg/kg and 700 mg/kg in rats. The
sodium salt has a substantially lower toxicity with an
LD50 of 1500 mg/kg in rats and 400 mg/kg in mice [6,7].
In rabbits 2,4-DB is only slightly toxic when exposure is
through the skin. The acute dermal LD50 of 2,4-DB is
greater than 2000 mg/kg .
- Chronic toxicity: At 25 and 80
mg/kg/day, dogs experienced changes in body weight and
tissue effects . In a longer-term chronic feeding
study with rats, 30 mg/kg effects noted included
decreases in body weight, a decrease in heart weight, and
changes in blood chemistry .
- Reproductive effects: Female rats fed
high doses of 75 mg/kg/day of 2,4-DB, experienced a
number of chronic effects, including lower ovarian
weights and fewer offspring born . These data suggest
that reproductive effects are not likely in humans at
expected exposure levels.
- Teratogenic effects: No data are
- Mutagenic effects: Chromosome changes
occurred due to exposure to 2,4-DB in Chinese hamster
cells; however, the exposure was relatively high (just
below a threshold of significant cell toxicity) and for
relatively prolonged periods of time (17 or more hours).
Tests over 2 hours produced no chromosome changes .
The Ames test produced no chromosomal abnormalities in
bacterial cells. The data, though minimal, indicate that
2,4-DB is weakly or nonmutagenic.
- Carcinogenic effects: Preliminary
evidence suggests that 2,4-DB can cause liver cancer in
mice (hepatocellular carcinomas) . However, in
another study with rats fed lower doses (to 30
mg/kg/day), no cancer-related changes occurred . Thus
the carcinogenic status of 2,4-DB is not clear.
- Organ toxicity: Target organs identified
in long-term animal studies include the heart and liver.
- Fate in humans and animals: No data are
- Effects on birds: Several dietary
feeding tests indicate that 2,4-DB is practically
nontoxic (LC50 values in excess of 5000 ppm) to waterfowl
and upland game birds .
- Effects on aquatic organisms: 2,4-DB is
slightly to moderately toxic to fish. The LC50 value for
the compound is 18 mg/L in the fathead minnow, 7.5 to 17
mg/L in the bluegill sunfish, and 2 to 14 mg/L in the
rainbow trout [33,34]. No studies were available on the
toxicity of the compound to freshwater or marine
- Effects on other organisms: 2,4-DB is
nontoxic to bees .
- Breakdown in soil and groundwater: In
soil, 2,4-DB is broken down by the action of soil
microbes to the product 2,4-D. The half-life for 2,4-DB
is about 7 days (21). Because of the risk of groundwater
contamination from the whole family of 2,4-D related
compounds, special advisories are required on the labels
of end-use products related to 2,4-D including 2,4-DB.
2,4-DB has been detected in only 1 well in Texas (out of
928 tested) . It had a concentration of 0.002 mg/L of
- Breakdown in water: No data are
- Breakdown in vegetation: The compound is
taken up by the roots and moved throughout the plant. In
plants, the compound 2,4-DB is degraded to 2,4-D, which
is then broken down further to less toxic materials. In
plants tolerant to the herbicide, the breakdown from
2,4-DB to 2,4-D is very slow .
- Appearance: 2,4-DB is a colorless to
white crystal with a slightly phenolic odor. It is
slightly corrosive to iron .
- Chemical Name:
4-(2,4-dichlorophenoxy)butyric acid 
- CAS Number: 94-82-6
- Molecular Weight: 249.10
- Water Solubility: 46 mg/L @ 25 C 
- Solubility in Other Solvents: acetone
v.s.; ethanol v.s.; diethyl ether v.s.; benzene s.s.;
toluene s.s.; and kerosene s.s. 
- Melting Point: 117-119 C 
- Vapor Pressure: Negligible (acid and
- Partition Coefficient: Not Available
- Adsorption Coefficient: 20 (estimated)
- ADI: Not Available
- MCL: Not Available
- RfD: 8 x 10-3 mg/kg/day 
- PEL: Not Available
- HA: Not Available
- TLV: Not Available
Rhone-Poulenc Ag. Co.
P.O. Box 12014
2 T.W. Alexander Drive
Research Triangle Park, NC 27709
- Phone: 919-549-2000
- Emergency: 800-334-7577
References for the information in this PIP can be found in
Reference List Number 7
information in this profile does not in any way replace or
supersede the information on the pesticide product labeling or
other regulatory requirements. Please refer to the pesticide