| Chemical Abstract Number (CAS #) |
93765
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| Synonyms | 2,4,5-T |
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2,4,5-Trichlorophenoxyacetic acid | Weedone | Acetic acid, (2,4,5-trichlorophenoxy)- |
| Analytical Methods |
EPA Method 515.1 |
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EPA Method 515.2 |
EPA Method 555 |
EPA Method 615 |
EPA Method 8150B |
EPA Method 8151 |
| Molecular Formula | C8H5Cl3O3 |
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| Use | HERBICIDE FOR INDUSTRIAL SITES, LUMBER YARDS & VACANT LOTS,
RANGELAND & RICE, LAWNS & TURF (INCL ITS ESTERS & SALTS), AQUATIC USE
(INCL ITS ESTERS & SALTS), HOME USE (FORMER USE FOR GRANULES),
RECREATION AREAS (FORMER USE FOR GRANULES), FOOD CROPS FOR HUMANS
(FORMER USE).
2,4,5-T IS USED POST-EMERGENCE ALONE OR WITH 2,4-D FOR THE CONTROL OF
SHRUBS AND TREES; IT IS ALSO USED FOR GIRDLING, INJECTION OR CUT-STUMP
TREATMENT FORMER USES/.
Has been used as a growth regulator to increase size of citrus fruits and reduce excessive drop of
deciduous fruit.
The use of 2,4,5-T in the United States has been cancelled since 1985. Some or all applications
may be classified by the USEPA as Restricted Use Pesticides.
In Canada, phenoxy herbicides (almost exclusively 2,4-D) are registered for macrophyte control in
lakes and ponds at 22-45 kg/ha, and along ditches and irrigation networks.
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| Consumption Patterns | FORMER USES: INDUSTRIAL & COMMERCIAL USES, 63%; RANGELAND,
26%; RICE (EXCLUDING ISOOCTYL ESTER) 8%; LAWNS & TURF, 3% (1983-INCL
2,4,5-TRICHOROPHENOXYACETIC ACID, ESTERS, & SALTS)
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| Apparent Color | WHITE SOLID ; LIGHT TAN SOLID
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| Odor | Odorless
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| Boiling Point | Decomposes
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| Melting Point | 153 DEG C
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| Molecular Weight | 255.49
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| Density | SP GR: 1.80 AT 20 deg C/20 deg C
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| Sensitivity Data | Irritant to eyes, nose, and throat.
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| Environmental Impact | Release of 2,4,5-T to the environment occurred during its past use as a herbicide and it
can form in the environment as a hydrolysis product of its herbicide esters. Other sources of
release may include losses during formulation, packaging or disposal of 2,4,5-T, its esters and the
acaricide, tetradifon. Since 2,4,5-T has a pKa of 2.88 it will be found in the dissociated form in all
environmental media. If released in soil, 2,4,5-T can biodegrade and its mobility is expected to
vary from highly mobile in sandy soil to slightly mobile in muck (due to adsorption to humic acids
and other organic matter). Removal by biodegradation apparently limits the extent of leaching,
however, and groundwater contamination is likely only by rapid flow through large channels and
deep soil cracks. 2,4,5-trichlorophenol and 2,4,5-trichloroanisole are the primary microbial
degradation products of 2,4,5-T. Chemical hydrolysis in moist soils and volatilization from dry
and moist surfaces should not be significant. The persistence of 2,4,5-T in soil is reported to vary
between 14 to 300 days, but usually does not exceed one full growing season regardless of the
application rate. Degradation under anaerobic conditions in flooded soils is much slower (half-life
less than or equal to 48 weeks) than in field moist soils. If released to water, photochemical
decomposition, volatilization and biodegradation of 2,4,5-T appear to be the dominant removal
mechanisms. The primary degradation product of 2,4,5-T in water is 2,4,5-trichlorophenol. The
aquatic near surface half-life for direct photolysis has been calculated to be 15 days during
summer at latitude 40 deg. Humic substances can photosensitize 2,4,5-T and humic induced
photoreactions may dominate photodegradation processes when humic substance concentrations
exceed 15 mg/l of organic C/l. Primary photodegradation products are 2,4,5-trichlorophenol and
2-hydroxy-4,5-dichlorophenoxyacetic acid. Adsorption of 2,4,5-T to humic acids in suspended
solids and sediments may be significant. Oxidation, chemical hydrolysis, volatilization and
bioaccumulation should not be significant. If released to the atmosphere, 2,4,5-T should exist as
fine droplets and adsorbed on airborne particulates. 2,4,5-T has the potential to undergo (a) direct
photolysis due to uv absorption at >290 nm, (b) a reaction with photochemically generated
hydroxyl radicals (estimated vapor phase half-life= 1.12 days) or (c) be physically removed by
settling out or washout in rainfall. The most probable route of exposure to 2,4,5-T would be
inhalation and dermal exposure of workers involved in the manufacture, handling or application of
2,4,5-T, related ester compounds or certain tetradifon formulations which contain 2,4,5-T. The
general public could potentially be exposed by inhalation of particulate matter or ingestion of
fruit, milk or drinking water contaminated with 2,4,5-T.
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| Environmental Fate | TERRESTRIAL FATE: FOUR (14)C-LABELED HERBICIDES INCLUDING 2,4,5-T
WERE APPLIED AS FOLIAR SPRAY AT 0.28 KG/HA IN A TERRESTRIAL MICROCOSM
CHAMBER TO EXAMINE THEIR TRANSPORT AND METABOLISM IN COMPARISON
TO DIELDRIN. TOTAL HERBICIDE RESIDUES IN SOIL AVERAGED 0.14 PPM FOR ALL
COMPOUNDS BY 20 DAYS POSTTREATMENT. RYE GRASS SHOOTS CONTAINED 2.5
PPM 2,4,5-T. 2,4,5-T WAS ONE OF THE MOST RAPIDLY DECOMPOSED HERBICIDES.
TERRESTRIAL FATE: If released to soil, 2,4,5-T is likely to biodegrade and its mobility is
expected to vary from highly mobile in sandy soil and moderately mobile in clay and silt loams to
slightly mobile in muck (due to adsorption to humic acids and other organic matter). Removal by
biodegradation apparently limits the extent of leaching, however, and groundwater contamination
is likely only by rapid flow through large channels and deep soil cracks . 2,4,5-Trichlorophenol
and 2,4,5-trichloroanisole the primary degradation product of 2,4,5-T in soil . The anisole is
apparently formed by microbial methylation of the phenol. Chemical hydrolysis in moist soils
should not be significant. The persistence of 2,4,5-T in soil is reported to vary from 14 to 300
days depending upon climatic conditions and population of soil microorganisms, but usually does
not exceed one full growing season regardless of the application rate(2,3,4,5). Degradation under
anaerobic conditions is much slower than under aerobic conditions, thus 2,4,5-T persists longer in
flooded soils (half-life of less than or equal to 48 weeks) than in field moist soils.
AQUATIC FATE: Since 2,4,5-T has a pKa of 2.88 at 25 degC , it will be dissociated in water.
If released to water, photochemical decomposition volatilization and biodegradation of 2,4,5-T
should be the dominant removal mechanisms. 2,4,5-Trichlorophenol is the primary degradation
product of 2,4,5-T in water. Data regarding the biodegradation of 2,4,5-T in soil suggest that
biodegradation may contribute significantly to the degradation of 2,4,5-T in aquatic systems. The
aquatic near surface half-life for direct photolysis has been calculated to be 15 days during
summer at latitude 40 deg. Humic substances can photosensitize 2,4,5-T and humic induced
photoreactions may dominate photodegradation processes when humic substance concentrations
exceed 15 mg of organic C per liter. 2,4,5-T may also be degraded by photocatalytic processes
involving iron species and peroxides. The primary products of 2,4,5-T photodegradation are
2,4,5-trichlorophenol and 2-hydroxy-4,5-dichlorophenoxyacetic acid. Adsorption of 2,4,5-T to
humic acids in suspended solids and sediments may be significant. Oxidation, chemical hydrolysis,
volatilization and bioaccumulation should not be significant.
ATMOSPHERIC FATE: If released to the atmosphere, 2,4,5-T may exist in vapor form, as fine
droplets and adsorbed on air-borne particulates as a result of vapor phase adsorption, or as a
result of wind erosion of treated soils(1,SRC). 2,4,5-T has the potential to undergo (a) direct
photolysis due to uv absorption at >290 nm, (b) reaction with photochemically generated
hydroxyl radicals (estimated vapor phase half-life= 1.12 days) or (c) be physically removed by
settling or washing out in rainfall.
TERRESTRIAL FATE: THE DEGRADATION KINETICS OF (14)C-LABELED 2,4-D &
2,4,5-T WERE STUDIED IN A NUMBERS 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.
2,4,5-T ESTERS ARE RAPIDLY HYDROLYZED AFTER SPRAYING, & THE 2,4,5-T IS
THEN FURTHER DECOMPOSED BY BACTERIAL ACTION. THE MAJOR PRODUCT OF
2,4,5-T PHOTODECOMPOSITION IS 2,4,5-TRICHLOROPHENOL. OTHER PRODUCTS
IDENTIFIED INCLUDED 4,6-DICHLORORESORCINOL, 4-CHLORORESORCINOL,
2,4,5-TRICHLOROANISOLE.
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| Drinking Water Impact | SURFACE WATER: During the 1976- 1980 national surface water monitoring program
2,4,5-T occurred in 0.4% of water samples and the maximum detectable concentration was 12.90
ug/l . In Allen County, Indiana from 1977 to 1978 - 8 samples, 100% pos - 1.0-7.7 ug/l 2,4,5-T
detected, mean value 3.0 ug/l . In western Canada from 1971 to 1977 - 1426 samples, 8.2%
pos. - <0.002 to 3.12 ug/l 2,4,5-T detected, mean value <0.002-0.090 ug/l . In Ontario, Canada
from 1975 to 1977 - 949 samples, 2.2% pos. - 0.1-1.1 ug/l 2,4,5-T detected, mean value <0.1
ug/l . In Western U.S. from 1967 to 1971, levels of 2,4,5-T ranged from ND to 0.40 ug/l (5,6).
DRINKING WATER: 2,4,5-T has been qualitatively identified in drinking water .
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