|Chemical Abstract Number (CAS #)||
|Synonyms||2,4-D||2,4-Dichlorophenoxyacetic acid, salts and esters||Acetic acid, (2,4-dichlorophenoxy)-
||EPA Method 515.3||EPA Method 555
||EPA Method 615
||EPA Method 8151
Link to the National Library of Medicine's Hazardous Substances
Database for more details
on this compound.
|Use|| IT IS REGISTERED IN USA AS A HERBICIDE FOR CONTROL OF BROADLEAF
PLANTS & AS A PLANT-GROWTH REGULATOR.
HERBICIDE USED ON GRASSES, WHEAT, BARLEY, OATS, SORGHUM, CORN,
SUGARCANE, & NONCROP AREAS PASTURE AND RANGE LAND; LAWNS & TURF/
FOR POST-EMERGENT CONTROL OF CANADA THISTLE, DANDELION, ANNUAL
MUSTARDS, RAGWEED, LAMBSQUARTERS & OTHERS. SOME FORMULATIONS FOR
PINE RELEASE, WATER HYACINTH CONTROL & PREVENTION OF SEED
FORMATION; DOUBLE-GEE, WILD RADISH, TURNIP & OTHER BROADLEAF WEEDS
REGISTERED FOR USE ON RICE IN THE PHILIPINES.
2,4-D when applied properly, will incr the red color in potatoes. It is used on tomatoes to cause
all fruits to ripen at the same time for machine harvesting.
/2,4-D free acid serves as the basic material from which the soluble esters & salts are produced.
Used in forest management: Brush control; Conifer release; Tree injection.
To increase latex output of old rubber trees.
Fruit drop control
HERBICIDE FOR PASTURE & RANGELANDS; AGRICULTURAL USE-EG, WHEAT,
CORN, GRAIN SORGHUM, RICE AND OTHER GRAINS; INDUSTRIAL/COMMERCIAL
USES; LAWNS, TURF, & AQUATIC USE; OTHER FIELD CROPS-EG, NUTS;
COMPONENT OF HERBICIDE FOR JUNGLE DEFOLIATION-FORMER USE.
2,4-D, ITS SALTS AND ESTERS ARE SYSTEMIC HERBICIDES, WIDELY USED FOR
WEED CONTROL IN CEREALS & OTHER CROPS AT 0.28 to 2.3 KG/HA.
CHLOROPHENOXY COMPOUNDS INCLUDING ACIDS, SALTS, AMINES AND ESTERS
ARE USED IN AGRICULTURE FOR CONTROL OF BROAD-LEAF WEEDS & IN
CONTROL OF WOODY PLANTS ALONG ROADSIDE, RAILWAYS & UTILITIES RIGHTS
OF WAY. CHLOROPHENOXY COMPOUNDS
|Consumption Patterns|| HERBICIDE FOR PASTURE & RANGELAND, 26%; FOR WHEAT, 26%; FOR
CORN, 14%; FOR OTHER GRAINS EXCEPT SORGHUM, 12%; FOR
INDUSTRIAL/COMMERCIAL USES, 11%; FOR LAWNS & TURF, 3%; FOR AQUATIC
USES, 3%: FOR GRAIN SORGHUM, 3%; FOR OTHER FIELD CROPS-EG, CITRUS,
FRUITS, NUTS, & VEGETABLES, 2%; (1982) SRP: PREVENTION FOR FRUIT
DROPPING. RIPENING AGENT.
75% AS A SELECTIVE HERBICIDE FOR BROADLEAF WEEDS & BRUSH, ON SMALL
GRAINS, CORN, SORGHUM, RICE, OTHER MINOR CROPS, & GRAZING LAND; 13%
FOR INDUSTRIAL & COMMERCIAL USE ON NON-CROPLAND; 6% BY GOVERNMENT
AGENCIES ON NON-CROPLAND; 6% FOR HOME & GARDEN USE ON TURF (1972).
PASTURE & RANGELANDS, 26%; WHEAT, 26%; CORN, 14%;
INDUSTRIAL/COMMERCIAL USES, 11%; LAWNS & TURF, 4%; AQUATIC USES, 3%;
GRAIN SORGHUM, 3%; RICE, 1%; OTHER GRAINS, 11%; OTHER FIELD CROPS-EG,
DECIDUOUS NUTS & FRUITS, CITRUS, & VEGETABLES, 2% (1982).
|Apparent Color|| WHITE TO YELLOW CRYSTALLINE POWDER SRP: YELLOW COLOR IS
PHENOLIC IMPURITIES ; COLORLESS POWDER SRP: WHITE
|Odor|| ODORLESS WHEN PURE ; A slight phenolic odor
|Boiling Point|| 160 DEG C AT 0.4 MM HG
|Melting Point|| 138 DEG C
|Molecular Weight|| 221.04
|Density|| 1.416 @ 25 deg C
|Odor Threshold Concentration|| Detection: 3.13 mg/kg SRP: Technical grade
|Sensitivity Data|| Dust may irritate eyes.
Acute eye or skin irritation has been reported in agricultural and forestry workers following
|Environmental Impact|| 2,4-D is released into the environment through its use in herbicide formulations and as a
hydrolysis product of 2,4-D esters or from spills. If released on land, it will probably readily
biodegrade (typical half-lives <1 day to several weeks). Its adsorption to soils will depend upon
organic content and pH of the soil (2,4-D pKa= 2.64). Leaching to groundwater will likely be a
significant process in coarse-grained sandy soils with low organic content or with very basic soils.
If released to water, it will be lost primarily due to biodegradation (typical half-lives 10 to >50
days). It will be more persistent in oligotrophic waters and where high concentrations are
released. Degradation will be rapid in sediments (half-life <1 day). It will not bioconcentrate in
aquatic organisms or appreciably adsorb to sediments, especially at basic pH's. If released in air, it
will be subject to photooxidation (estimated half-life of 1 day) and rainout. Human exposure will
be primarily to those workers involved in the making and using 2,4-D compounds as herbicides as
well as those who work in and live near fields sprayed and treated with 2,4-D compounds.
Exposure may also occur through ingestion of contaminated food products and drinking water.
|Environmental Fate|| TERRESTRIAL FATE: Biodegradation is by far the most important loss process for
2,4-D in most soils, leading to various hydroxylic aromatic products . The rate of degradation is
affected by the conditions, especially the concentrations of 2,4-D and water content temperature
and the organic content of soil and the status of preexposure of the soil to 2,4-D or its salts or its
esters(1-3). Typical half-lives are short, ranging from <1 day to several weeks(4-8). Longer
half-lives in dry or sandy soils with low organic content are possible(7). Adsorption to soil will
probably not be significant but will depend on type of soil and organic content(8-11). In
coarse-grained sandy soils where both biodegradation and adsorption will be low, leaching to
groundwater may occur(12). In other soils rapid biodegradation is expected to prevent significant
leaching(4-8,SRC). Evaporation and hydrolysis will be negligible(13-14).
AQUATIC FATE: When 2,4-D is released to water, it will tend to biodegrade with the rate
especially dependent upon level of nutrients present, temperature, availability of oxygen, and
whether or not the water has a prior history of contamination by 2,4-D or other phenoxyacetic
acids . Typical half-lives of 10 to >50 days have been reported with longer half-lives expected in
oligotrophic waters and where a high concentration of 2,4-D is present(1-2). Degradation in
sediments and lake muds is expected to be rapid with half-lives of <1 day reported(3-4). Products
of biodegradation include 2,4-dichlorophenol, other hydroxylic aromatics and polymeric acids .
2,4-D will also be subject to photolysis with a reported approximate half-life of several days for
water solutions irradiated at 356 nm. Adsorption to sediments will not be expected to be
extensive and volatilization and hydrolysis will be negligible(5-6).
ATMOSPHERIC FATE: The primary source of 2,4-D in air is spray applications of the herbicide
or its mixture. Spray drift is capable of carrying it up to a few km . Any 2,4-D in the air will be
subject to photooxidation by reaction with hydroxyl radicals with an estimated half-life of 1 day.
Direct photooxidation may also be important as 2,4-D absorbs light at wavelengths >290 nm.
Gravitional settling of aerosol and rainout (due to its significant solubility in water) may also be
significant removal processes.
AQUATIC FATE: Persistence in aquatic systems depends on the water type, organic particulate
matter, rain, sunlight, temperature, microbial degradation, volatilization, and oxygen content of
the water. Accumulation in bottom sediments may also be a factor, but in general, not for the
phenoxys. Microbial activity is the major means for detoxification of the phenoxys in soils, but is
relatively unimportant in natural waters, but dominates in bottom mud sediments and in sludge.
TERRESTRIAL FATE: THE DEGRADATION KINETICS OF (14)C-LABELED 2,4-D &
2,4,5-T WERE STUDIED IN A NUMBER OF SOILS. DEGRADATION RATES IN SOILS
WERE NOT SIMPLE FIRST ORDER BUT GENERALLY INCREASED UNTIL APPROX
20% OF CHEMICAL REMAINED, AFTER WHICH THEY DECLINED. AVERAGE 50%
DECOMPOSITION TIME OF 4.0 & 14 DAYS WAS OBSERVED FOR 2,4-D & 2,4,5-T,
RESPECTIVELY. 2,4,5-TRICHLOROPHENOL AND 2,4,5-TRICHLOROANISOLE WERE
FORMED. THE ANISOLE APPARENTLY WAS FORMED FROM PHENOL THROUGH A
MICROBIAL METHYLATION PROCESS.
TERRESTRIAL FATE: 2,4-D, its salts and esters are systemic herbicides, widely used for weed
control in cereals and other crops at 0.28 to 2.3 kg/ha, the highest rate persisting in soil about 30
Various amounts of 2,4-D products applied to a target area may be distributed in the general
environment, within a few hours or days, by the movements of air, water, or soil, particularly
during periods or rain, high winds, or high temperature. Persistence or accumulation of 2,4-D
residues from normal use is occasionally possible, mainly under dry or cold conditions where there
is little biological activity.
AQUATIC FATE: Persistency: Persistence in aquatic systems depends on the water type, organic
particulate matter, rain, sunlight, temperature, microbial degradation, volatilization, and oxygen
content of the water. Accumulation in bottom sediments may also be a factor, but in general, not
for the phenoxys. Microbial activity is the major means for detoxification of the phenoxys in soils,
but is relatively unimportant in natural waters, but dominates in bottom mud sediments and in
TERRESTRIAL FATE: Laboratory studies were conducted to determine the adsorption,
desorption, hydrolysis, and breakdown of commercially formulated isooctyl ester and
dimethylamine salt of 2,4-D in a Naff silt loam soil. More 2,4-D was adsorbed to the surface soil
than to soil at lower depths, and the percentage of 2,4-D adsorbed decreased as the total amount
of 2,4-D present increased. Adsorbed 2,4-D was gradually desorbed from soil by successively
exchanging the solution in equilibrium with soil with distilled water. Formulated 2,4-D isooctyl
ester applied to moist soil underwent hydroloysis to the anionic form at a rapid rate, with 80% of
the ester hydrolyzed in 72 hr. High amounts of 2,4-D in runoff (sediment and water) retarded the
active degradation of carboxyl (14)C 2,4-D when 2,4-D was incubated in runoff from a wheat
field treated with various formulations and rates of 2,4-D. The presence of the ester formulation
at the high rate of application increased the lag period before degradation of carboxyl-(14)C and
ring-(14)C 2,4-D was initiated, however, little difference could be detected in the degradation
patterns. At the end of the 10 wk of incubation in runoff or in soil, only 1% of the (14)C 2,4-D
originally applied to the soil could be identified as 2,4-D.
|Drinking Water Impact|| Available data indicate that residues of 2,4-D rarely exceed several ug/liter in water.
Exceptions may occur in the vicinity of 2,4-D herbicide spills or when the herbicide is used in
quantities far in excess of the rates applied in normal agricultural or forestry practice.
Reported as 2,4-D equivalents. DRINKING WATER: 237 wells in Ontario Canada were sampled
over a 10 yr period and 2,4-D occurred in 23 wells as the single contaminant, 50 wells with 4
other contaminants, concentrations ranging from 0.01-14,600 ppb . In a National survey of
pesticides in groundwater, it was detected in groundwater from 5 of 50 states at a maximum and
mean concentration of 49.5 ppb and 1.2 ppb, respectively .
Reported as 2,4-D equivalents. SURFACE WATER: Georgia and Florida pond waters - max
0.345 ppm and 0.692 ppm after 28 days declined to less than 0.005 ppm. Missouri pond water -
max 0.630 ppm after 56 days declined to less than 0.005 ppm . 1-10% occurrance in streams in
a survey of 11 Ontario agricultural watersheds monitored for 81 pesticides with 66 of 949
initial stream waters being positive . Tested for but not detected in Lake Erie (Monroe Water
Treatment Plant), Lake Huron nearshore water and tributaries, or Detroit River, Lake St Clair and
St Clair River (detection limit= 0.05-5 parts/trillion) . Sciote R, Highby OH - 0.12 ppb .
Reported as 2,4-D equivalents. SURFACE WATER: Hillsboro Canal, Laxahatchu National
Wildlife Refuge, FL - 0.037 ppm on day following application of 4.48 kg/ha acid equivalent to
0.001-0.004 ppm 56 days later . Levels in Guntersville Reservoir (TVA) 6 months after
application of 20-40 pounds acid equivalent/acre - less than 0.001 ppm . 2,4-D was detected in
18 of 20 midwest streams sampled over a four year period at concentration range 0.02-0.99
ppb . Fourteen of 20 streams positive in an earlier 2 year study, 36 occurrences, concentration
0.01-0.24 ppb and not detected in 11 of 11 streams in the original 1967 study . 0.245 ppb
measured in South Skunk River Water, Iowa 1975(6). Less than 0.01 ppb measured in Rhine
River Water at km 865(7).
Reported as 2,4-D equivalents. SURFACE WATER: Following spraying in Cairn Edward Forest,
Kircudbrightshire, Great Britain (4.5 kg in 135 l water/ha), 1,2,4,7 and 28 days later, 1.5, 1.6, 2.0,
1.6, not detected ppm were measured, (detection limit= 0.005 ppm), in drainage furrows .
Detected in 17% of agricultural watersheds in Ontario, Canada monitored during 1981-85. In
Thames River, the mean concentrations in 1981, 1982, 1983, 1984 and 1985 were 0.7 ppb, 0.6
ppb, 0.3 ppb, 0.5 ppb and 0.5 ppb, respectively . In a U.S. National Surface Water Monitoring
Program conducted during 1976- 80, 2,4-D was detected in 1.6% of surface waters at a maximum
concentration of 1.9 ppb .