| Chemical Abstract Number (CAS #) |
93721
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| Synonyms | Silvex |
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2,4,5-TP | Propanoic acid, 2-(2,4,5-trichlorophenoxy)- | 2,4,5-Trichlorophenoxypropionic acid |
| 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 | C9H7Cl3O3 |
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| Use | PLANT HORMONE FORMER USE
USED ON PHREATOPHYTES ON FLOODWAYS, ALONG CANALS, RESERVOIRS, &
STREAMS AS LIQ SPRAY IN ESTER FORM. USED ON FLOATING & EMERSED WEEDS
IN SOUTHERN WATERWAYS AS A LIQ SPRAY. FROM TABLE; FORMER USE
FOR CONTROL OF WOODY PLANTS, BROADLEAF HERBACEOUS WEEDS, &
AQUATIC WEEDS. IT IS ALSO USEFUL AS SELECTIVE POSTEMERGENCE
HERBICIDE IN RICE & BLUEGRASS TURF. IN SUGARCANE, IT IS USED TO
CONTROL WILD LETTUCE, CHICORY, NIGHTSHADE, TIEVINE & OTHER WEEDS
NOT SUSCEPTIBLE TO 2,4-D. FOR BRUSH CONTROL IN RANGELAND
IMPROVEMENT PROGRAMS, ESPECIALLY POST, BLACKJACK, SAND SHINNERY
OAKS, YUCCA, & SALT CEDAR. FORMER USE
CONTROLS ALLIGATOR WEED IN DITCHES & RIVERBANKS. CONTROLS 2,4-D
TOLERANT WEEDS SUCH AS CHICKWEEDS, SPURGES, & BLACK MEDIC IN TURF.
(FORMER USES)
HERBICIDE FOR INDUSTRIAL/COMMERCIAL USES (FORMER USE)
HERBICIDE FOR PASTURE & RANGELAND (FORMER USE)
HERBICIDE FOR LAWNS, TURF, & AQUATIC USE (FORMER USE)
Herbicides & plant growth regulators. 2,4,5-TP esters
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 | HERBICIDE FOR INDUSTRIAL/COMMERCIAL USES, 60%; PASTURE &
RANGELAND, 40% (1982)
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| Apparent Color | WHITE POWDER
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| Odor | LOW ODOR SRP: MAY BE DUE TO PHENOLIC IMPURITIES
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| Melting Point | 181.6 DEG C
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| Molecular Weight | 269.51
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| Density | 1.2085 @ 20 deg C
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| Sensitivity Data | IRRITATING TO EYES, SKIN, MUCOUS MEMBRANES.
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| Environmental Impact | Silvex has been released into the environment during spraying operations on land or in
water using herbicide formulations containing it. It may also have been released as the result of
hydrolysis of esters of silvex.The amount of silvex used annually in the U.S. prior to 1983 was
estimated in 1985 to be 7,000 pounds. At present, however, silvex is not used in the U.S. due to
the cancellation of all registered uses effective Jan 2, 1985. When released on land, it will strongly
adsorb to soils and biodegrade (average half-lives ranging from 12-17 days). It is not expected to
leach, hydrolyze, or evaporate. It may be lost due to runoff from treated fields. If released to
water, silvex will biodegrade slowly and strongly adsorb to sediment, where slow biodegradation
will occur. It will not appreciably hydrolyze or bioconcentrate but may be subject to
photooxidation near the surface of waters. Silvex may be released to air during spraying
operations but not as a result of evaporation due to its very low vapor pressure. It will be lost
from the atmosphere mainly by rainout and dry deposition. Vapor phase photooxidation by
reaction with photochemically produced hydroxyl radicals may be significant (estimated half-life
6.3 hrs). An estimated 1130 workers in 1973-1974 in the U.S. may be exposed to silvex. General
population exposure will be through ingestion of foods contaminated with silvex including some
fruits and milk.
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| Environmental Fate | TERRESTRIAL FATE: If released on land, silvex will exhibit strong adsorption to soils.
Biodegradation may be a significant loss process with average half-lives in soil of 12-17 days
reported. 2,4,5-Trichlorophenol has been reported to be a product of biodegradation. Leaching,
hydrolysis, and evaporation will not be significant. Loss due to runoff from treated fields may be
significant.
AQUATIC FATE: If released to water, silvex will be expected to biodegrade slowly and to
strongly adsorb to sediment where slow biodegradation will be expected. Silvex will not
appreciably hydrolyze or bioconcentrate in aquatic organisms. Direct photolysis may contribute to
losses near the surface of waters.
ATMOSPHERIC FATE: If released to the air, silvex will be expected to be lost mainly by rainout
and dry deposition. Photooxidation may also contribute to losses with an estimated half-life of 6.3
hrs. for reaction with photochemically produced hydroxyl radicals(1,SRC).
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. 2,4,5-T
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| Drinking Water Impact | GROUND WATER: In the Central Platte region of Nebraska sampled during 1978
irrigation season, silvex levels were below the detection limit of 0.005 ppb . SURFACE
WATER: Tested for but not detected (limit=0.05 ppb) in Lake Superior and Lake Erie . Of 20
selected streams sampled in the western U.S., silvex was detected in 11; concentrations ranged
0.01-0.14 ppb . It was detected in 29 of 30 sampling days over a 4 year period in the Humboldt
River near Rye Patch, NV . Earlier sampling of these same streams yielded 5 of 200 samples
positive, range of 0.01-0.21 ppb with the Humboldt River having 8 of 11 sampling times over a 2
year period positive and again having the higher concentrations . Not detected in 11 midwestern
streams during the 1965-1967 sampling period . The following values are from the Ohio River
Valley - Beaver River, Beaver Falls, PA - 0.02 ppb; Wabash, New Harmony, TN - 0.03 ppb;
Allegheny, Monongahela, Muskingum, Kanawha, Big Sandy, Licking, Great Miami, Ohio, White,
and Cumberland Rivers - not detected(6).
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