Technical Factsheet on: 2,4,5 - TP
List
of Contaminants
As part of the Drinking Water and Health pages, this fact
sheet is part of a larger publication:
National Primary Drinking Water Regulations
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:
For a 10-kg (22 lb.) child consuming 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 sugarcane, 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 application 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 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 dependent 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 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).
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 because all registered uses of silvex were canceled effective
Jan 2, 1985.
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
Bioconcentration Factor: BCF=58 in fish; not expected to
bioconcentrate in aquatic organisms.
Trade Names/Synonyms: 2,4,5-Trichlorophenoxyproprionic acid;
Weed-B-Gon; Propon; Silvi-Rhap; Sta-fast; Miller Nu Set;
Aqua-Vex; Color-Set; Ded-Weed; Fenoprop; Fenormone; Fruitone T;
Garlon; Kuran; Kurosal G/SL; Silvex
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
Analysis:
| Reference Source |
Method Numbers |
| EPA 600/4-88-039 |
515.1; 515.2; 555 |
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 toxicological 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
List
of Contaminants
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