United States
Environmental Protection
Agency
Office of Water
4601
EPA 811-F-95-003id-T
October 1995
National Primary Drinking
Water Regulations
2,4,5 - TP (Silvex)
CHEMICAL/ PHYSICAL PROPERTIES
CAS NUMBER: 93-72-1
COLOR/ FORM/ODOR:
White powder with little odor; available
in granules, solutions and tablets as
the amine or sodium emulsifiable salts
& various esters.
M.P.: 181.6°C B.P.: N/A
VAPOR PRESSURE: N/A
OCTANOL/WATER PARTITION (Kow): N/A
DENSITY/SPEC. GRAV.: 1.21 at 20° C
SOLUBILITY: 200 mg/L of water at 25° C;
Slightly soluble in water
SOIL SORPTION COEFFICIENT:
Koc reported at 2600; Very low
mobility in soil
ODOR/TASTE THRESHOLDS: N/A
HENRY'S LAW COEFFICIENT: N/A
BlOCONCENTRATION FACTOR:
BCF=58 in fish; not expected to
bioconcentrate in aquatic organisms.
TRADE NAMES/SYNONYMS:
2,4,5-Trichlorophenoxyproprionicacid;
Weed-B-Gon; Propon; Silvi-Rhap; Sta-
fast; Miller Nu Set; Aqua-Vex;
. Color-Set; Ded-Weed; Fenoprop;
Fenormone; Fruitone T; Garion; Kuran;
Kurosal G/SL; Silvex
DRINKING WATER STANDARDS
MCLG: 0.05 mg/L
MCL: 0.05 mg/L
HAL(child): 1-to 10-day: 0.2 mg/L
Longer-term: 0.07 mg/L
HEALTH EFFECTS SUMMARY
Acute: EPA has found 2,4,5-TP to potentially cause
the following health effects from acute exposures at
levels above the MCL: depression and other nervous
system effects, weakness, stomach irritation and minor
damage to liver and kidneys.
Drinking water levels which are considered "safe" for
short-term exposures: Fora 10-kg (22 Ib.) child consum-
ing 1 liter of water per day, a one- to ten-day exposure to
0.2 mg/L or upto a 7-year exposure to 0.07 mg/L.
Chronic: 2,4,5-TP has the potential to cause the
following health effects from long-term exposures at
levels above the MCL: minor liver and kidney damage
Cancer: There is inadequate evidence to state whether
or not 2,4,5-TP has the potential to cause cancer from a
lifetime exposure in drinking water.
USAGE PATTERNS
In 1982, 2,4,5-TP production was 500,000 pounds,
with industrial/commercial herbicide consuming 60%;
range and pastureland use consuming 40%. 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.
The greatest use of 2,4,5-TP was as a postemergence
herbicide for control of woody plants, and broadleaf
herbaceous weeds in rice and bluegrass turf, in sugar-
cane, in rangeland improvement programs, on lawns.
Aquatic uses include control of weeds in ditches and
riverbanks, on floodways, along canals, reservoirs,
streams, and along southern waterways.
RELEASE PATTERNS
Former sources of release include spraying from appli-
cation of the herbicide formulations, runoff from fields,
and direct release to water for control of aquatic weeds.
It may also have been released as the result of hydrolysis
of esters of silvex.
ENVIRONMENTAL FATE
When released on land, silvex will strongly adsorb to
soils and biodegrade, but is not expected to leach,
hydrolyze, or evaporate. It may be lost due to runoff from
treated fields. Silvex has been reported to be very well
adsorbed to essentially completely adsorbed in soils
(reported Koc value of 2600). Average half-lives for
biodegradation of silvex in soils ranged from 12 days for
3 prairie soils to 17 days. Negligible degradation was
observed in air-dried soils.
If released to water, silvex will biodegrade slowly and
strongly adsorb to sediment, where slow biodegradation
will occur. The loss due to volatilization of silvex from
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aqueous and soil systems will not be significant due to its
low vapor pressure of the acid. It will not appreciably
hydrolyze but may be subject to photooxidation near the
surface of waters.
While no data concerning the rate of biodegradation in
water were found, available information suggests that
silvex is degraded slowly both in water and sediments.
2,4,5-Trichlorophenol has been identified as a product of
the biodegradation of silvex. From limited data available,
it may be concluded that any phenoxy herbicide, whether
applied as ester or as dimethylamine salt formulations,
may be chemically transformed to the same
phenoxyalkanoic anion in soil and water at rates depen-
dent on pH. These anions would presumably reassociate
with a variety of inorganic cations present in the soil to
maintain electrical neutrality, and then undergo leaching
and biological degradation.
Silvex may be released to air during spraying opera-
tions 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 photooxida-
tion by reaction with photochemically produced hydroxyl
radicals may be significant (estimated half-life 6.3 hrs).
Bioconcentration of silvex will not be significant based
with a reported bioconcentration factor of 58 for fish in
flowing water.
Agricultural workers may have been exposed to silvex
during spraying operations using herbicides containing
this chemical. Exposure may have also occurred through
consumption of contaminated foods, including fruits and
milk. At present, however, no workers are expected to be
exposed to silvex during application of herbicides be-
cause all registered uses of silvex were canceled effec-
tive Jan 2, 1985.
OTHER REGULATORY INFORMATION •
MONITORING:
FOR GROUND/SURFACE WATER SOURCES:
INITIAL FREQUENCY- 4 quarterly samples every 3 years
REPEAT FREQUENCY- If no detections during initial round:
2 quarterly per year if serving >3300 persons;
1 sample per 3 years for smaller systems
TRIGGERS - Return to Initial Freq. if detect at > 0.0002 mg/L
METHOD NUMBERS
515.1; 515.2; 555
ANALYSIS:
REFERENCE SOURCE
EPA 600/4-88-039
TREATMENT:
BEST AVAILABLE TECHNOLOGIES
Granular Activated Charcoal
FOR ADDITIONAL INFORMATION:
* EPA can provide further regulatory and other general information:
• EPA Safe Drinking Water Hotline - 800/426-4791
* Other sources of lexicological and environmental fate data include:
• Toxic Substance Control Act Information Line - 202/554-1404
• Toxics Release Inventory, National Library of Medicine - 301/496-6531
• Agency for Toxic Substances and Disease Registry - 404/639-6000
• National Pesticide Hotline - 800/858-7378
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