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.: 181.6C  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
October 1995
         Technical Version
             Printed on Recycled Paper

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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
 October 1995
Technical Version
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