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EXTOXNET primary files maintained and archived at Oregon State
Revised June 1996
Trade and Other Names:2,4-D
is used in many commercial products. Commercial names for
products containing 2,4-D include Aqua-Kleen, Barrage, Lawn-Keep,
Malerbane, Planotox, Plantgard, Savage, Salvo, Weedone, and
2,4-D is a General Use Pesticide (GUP) in the U.S. The
diethylamine salt is toxicity class III- slightly toxic orally,
but toxicity class I- highly toxic by eye exposure. It bears the
Signal Word DANGER - POISON because 2,4-D has produced serious
eye and skin irritation among agricultural workers.
Chemical Class: phenoxy
There are many forms or derivatives of 2,4-D including esters,
amines, and salts. Unless otherwise specified, this document will
refer to the acid form of 2,4-D. 2,4-D, a chlorinated phenoxy
compound, functions as a systemic herbicide and is used to
control many types of broadleaf weeds. It is used in cultivated
agriculture, in pasture and rangeland applications, forest
management, home, garden, and to control aquatic vegetation. It
may be found in emulsion form, in aqueous solutions (salts), and
as a dry compound.
The product Agent Orange, used extensively throughout Vietnam,
was about 50% 2,4-D. However, the controversies associated with
the use of Agent Orange were associated with a contaminant
(dioxin) in the 2,4,5-T component of the defoliant.
Formulation: It may be
found in emulsion form, in aqueous solutions (salts), and as a
- Acute toxicity: The acid form is of
slight to moderate toxicity. The oral LD50 of 2,4-D
ranges from 375 to 666 mg/kg in the rat, 370 mg/kg in
mice, and from less than 320 to 1000 mg/kg in guinea
pigs. The dermal LD50 values are 1500 mg/kg in rats and
1400 mg/kg in rabbits, respectively [1,5,7]. In humans,
prolonged breathing of 2,4-D causes coughing, burning,
dizziness, and temporary loss of muscle coordination .
Other symptoms of poisoning can be fatigue and weakness
with possible nausea. On rare occasions following high
levels of exposure, there can be inflammation of the
nerve endings with muscular effects .
- Chronic toxicity: Rats given high
amounts, 50 mg/kg/day, of 2,4-D in the diet for 2 years
showed no adverse effects. Dogs fed lower amounts in
their food for 2 years died, probably because dogs do not
excrete organic acids efficiently. A human given a total
of 16.3 g in 32 days therapeutically, lapsed into a
stupor and showed signs of incoordination, weak reflexes,
and loss of bladder control [1,5,7].
- Reproductive effects: High levels of
2,4-D (about 50 mg/kg/day) administered orally to
pregnant rats did not cause any adverse effects on birth
weights or litter size. Higher doses (188 mg/kg/day)
resulted in fetuses with abdominal cavity bleeding and
increased mortality [1,5,7]. DNA synthesis in the testes
was significantly inhibited when mice were fed large
amounts (200 mg/kg/day) of 2,4-D . The evidence
suggests that if 2,4-D causes reproductive effects in
animals, this only occurs at very high doses. Thus
reproductive problems associated with 2,4-D are unlikely
in humans under normal circumstances.
- Teratogenic effects: 2,4-D may cause
birth defects at high doses. Rats fed 150 mg/kg/day on
days 6 to 15 of pregnancy had offspring with increased
skeletal abnormalities, such as delayed bone development
and wavy ribs . This suggests that 2,4-D exposure is
unlikely to be teratogenic in humans at expected exposure
- Mutagenic effects: 2,4-D has been very
extensively tested and was found to be nonmutagenic in
most systems. 2,4-D did not damage DNA in human lung
cells. However, in one study, significant effects
occurred in chromosomes in cultured human cells at low
exposure levels . The data suggest that 2,4-D is not
mutagenic or has low mutagenic potential.
- Carcinogenic effects: 2,4-D fed to rats
for 2 years caused an increase in malignant tumors .
Female mice given a single injection of 2,4-D developed
cancer (reticulum-cell sarcomas) . Another study in
rodents shows a low incidence of brain tumors at moderate
exposure levels (45 mg/kg/day) over a lifetime [1,7].
However, a number of questions have been raised about the
validity of this evidence and thus about the carcinogenic
potential of 2,4-D. In humans, a variety of studies give
conflicting results. Several studies suggest an
association of 2,4-D exposure with cancer. An increased
occurrence of non-Hodgkin's lymphoma was found among a
Kansas and Nebraska farm population associated with the
spraying of 2,4-D [25,27]. Other studies done in New
Zealand, Washington, New York, Australia, and on Vietnam
veterans from the U.S. were all negative. There remains
considerable controversy about the methods used in the
various studies and their results . Thus, the
carcinogenic status of 2,4-D is not clear.
- Organ toxicity: Most symptoms of 2,4-D
exposure disappear within a few days, but there is a
report of liver dysfunction from long-term exposure
- Fate in humans and animals: The
absorption of 2,4-D is almost complete in mammals after
ingestion and nearly all of the dose is excreted in the
urine. The compound is readily absorbed through the skin
and lungs. Men given 5 mg/kg excreted about 82% of the
dose as unchanged 2,4-D. The half-life is between 10 and
20 hours in living organisms. There is no evidence that
2,4-D accumulates to significant level in mammals or in
other organisms . Between 6 and 8 hours after doses
of 1 mg/kg, peak concentrations of 2,4-D were found in
the blood, liver, kidney, lungs, and spleen of rats.
There were lower levels in muscle and brain. After 24
hours, there were no detectable tissue residues. Only
traces of the compound have been found in the milk of
lactating animals for 6 days following exposure. 2,4-D
passes through the placenta in pigs and rats. In rats,
about 20% was detected in the uterus, placenta, fetus,
and amniotic fluid . Chickens given moderate amounts
of 2,4-D in drinking water from birth to maturity had
very low levels of the compound in eggs .
- Effects on birds: 2,4-D is slightly
toxic to wildfowl and slightly to moderately toxic to
birds. The LD50 is 1000 mg/kg in mallards, 272 mg/kg in
pheasants, and 668 mg/kg in quail and pigeons [5-7].
- Effects on aquatic organisms: Some
formulations of 2,4-D are highly toxic to fish while
others are less so. For example, the LC50 ranges between
1.0 and 100 mg/L in cutthroat trout, depending on the
formulation used. Channel catfish had less than 10%
mortality when exposed to 10 mg/L for 48 hours [1,9].
Green sunfish, when exposed to 110 mg/L for 41 hours,
showed no effect on swimming response. Limited studies
indicate a half-life of less than 2 days in fish and
oysters . Concentrations of 10 mg/L for 85 days did
not adversely affect the survival of adult dungeness
crabs. For immature crabs, the 96-hour LC50 is greater
than 10 mg/L, indicating that 2,4-D is only slightly
toxic. Brown shrimp showed a small increase in mortality
at exposures of 2 mg/L for 48 hours [7,20].
- Effects on other organisms: Moderate
doses of 2,4-D severely impaired honeybees brood
production. At lower levels of exposure, exposed bees
lived significantly longer than the controls. The
honeybee LD50 is 0.0115 mg/bee [6,7].
- Breakdown in soil and groundwater: 2,4-D
has low soil persistence. The half-life in soil is less
than 7 days . Soil microbes are primarily responsible
for its disappearance . Despite its short half-life
in soil and in aquatic environments, the compound has
been detected in groundwater supplies in at least five
States and in Canada . Very low concentrations have
also been detected in surface waters throughout the U.S.
- Breakdown in water: In aquatic
environments, microorganisms readily degrade 2,4-D. Rates
of breakdown increase with increased nutrients, sediment
load, and dissolved organic carbon. Under oxygenated
conditions the half-life is 1 week to several weeks .
- Breakdown in vegetation: 2,4-D
interferes with normal plant growth processes. Uptake of
the compound is through leaves, stems, and roots.
Breakdown in plants is by a variety of biological and
chemical pathways . 2,4-D is toxic to most broad leaf
crops, especially cotton, tomatoes, beets, and fruit
- Appearance: 2,4-D is a white powder .
- Chemical Name:
(2,4-dichlorophenoxy)acetic acid 
- CAS Number: 94-75-7
- Molecular Weight: 221.04
- Water Solubility: 900 mg/L @ 25 C (acid)
- Solubility in Other Solvents: ethanol
v.s.; diethyl ether v.s.; toluene s.; xylene s. 
- Melting Point: 140.5 C 
- Vapor Pressure: 0.02 mPa @ 25 C (acid)
- Partition Coefficient: 2.81 
- Adsorption Coefficient: 20 (acid) 
- ADI: 0.3 mg/kg/day 
- MCL: 0.07 mg/L 
- RfD: 0.01 mg/kg/day 
- PEL: 10 mg/m3 (8-hour) 
- HA: Not Available
- TLV: Not Available
Rhone-Poulenc Ag. Co.
P.O. Box 12014
2 T.W. Alexander Dr.
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