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Ethephon (Ethrel, Florel) - Herbicide Profile 9/88

EPA Pesticide
Fact Sheet
Name of Chemical:  Ethephon
Reason for Issuance:  Registration Standard
Date Issued:  September 29, 1988
Fact Sheet Number:  176
                   1.  DESCRIPTION OF CHEMICAL
Generic Name:  Ethephon
Common Name:   Ethephon
Trade Names:   Bromeflor, Cerone, Chlorethephon (New Zealand), Ethrel,
               Florel, Prep and Flordimex
EPA Shaughnessy Code:  099801
Chemical Abstracts Service (CAS) Number:  16672-87-0
Year of Initial Registration:  1973
Pesticide Type:  Growth Regulator
U.S. and Foreign Producers:  AmChem/Union Carbide
- Application Sites:  To enhance fruit ripening, flower initiation,
  fruit and leaf abscission, and breaking of apical dominance in
  apples, barley, wheat, blackberries, boysenberry, blueberry,
  cantaloupe, cherry (tart and sweet), cotton, cucumber, squash
  and pumpkin (hybrid seed production), figs, cucumber r (pickling),
  filberts, grapes, lemon, tangerine, tangelo, pepper, pimento,
  tomato, walnut, tobacco (flue cured), ornamentals, guava,
  grapes for table and raisin production, pineapples, sugarcane,
  coffee beans, cottonseed, macadamia nuts, trees (forest and
  shelterbelt) and cranberries.
- Mechanism of Action:  Generation of ethylene after application
  (ethylene is a naturally-produced plant hormone).
- Types of Formulations:  Emulsifiable concentrate, soluble
  concentrates/liquids, ready-to-use liquids.
- Types and Methods of Application:  Broadcast by ground or aerial
- Application Rates: vary from 0.08 to 2.0 pounds of active ingredient
  per acre depending upon the use site and desired effects.
                            3. SCIENCE FINDINGS
Chemical Characteristics:
- Empirical Formula:  C2H6C1O3P
- Molecular Weight:  144.5
- Physical state:  waxy, solid
- Color:  White
- Melting Point:  74 to 75 degrees C
- Solubility:  Very soluble in water, alcohol, propylene glycol very
  slightly soluble in aromatic solvents.
Toxicology Characteristics:
- Acute Effects
  - Acute Oral Toxicity: 1.6 g/kg rats (Toxicity Category III)
  - Acute Dermal Toxicity: > 5 g/kg rabbits (Toxicity Category III)
  - Acute Inhalation: Not available
  - Primary Eye Irritation: Not available, but assumed to be corrosive
    based on the primary dermal results
  - Primary Skin Irritation: Score 6.75 (Corrosive) rabbits (Toxicity
    Category I )
  - Delayed Neurotoxicity Hen: No signs of neurotoxicity
- Sub-Chronic Effects
  - No adequate data are available on subchronic oral toxicity in
    rats or dogs. However, the requirement for subchronic studies in
    the rodent and non-rodent will be waived if the required chronic
    studies are acceptable.
- Chronic Effects
  - Sprague-Dawley Rats - 18 Months: NOEL for cholinesterase activity
    is 15 mg/kg/day ( supplementary data).
  - Beagle Dogs - 2-Year: NOEL for source A* ethephon was 7.5 mg/
    kg/day (supplementary data)
  - Swiss Albino Mouse - 18-Month oncogenicity study:  NOEL for RBC
    cholinesterase activity is < 4.5mg/kg/day which was the lowest
    dose tested (LDT) (supplementary data).
* In the study there were two, apparently different, sources of the
chemical tested and reported as source A and source B.
  The available data are not adequate to assess the oncogenic potential
  of ethephon. In the rat and mouse studies submitted, only chronic
  effects were observed and these effects are discussed under the
  chronic toxicity section.
- Rat:  NOEL for maternal and embryo/fetal toxicity is 600 mg/kg/day.
  NOEL for teratogenic effects is 600 mg/kg/day.
- Rabbit:  NOEL is 50 mg/kg/day based on fetal resorptions at
  higher dose levels tested.
- Reproduction:  No adequate data available.
- Mutagenicity: Salmonella typhimurium indicate no mutagenic effect
  up to 1000 ug/100 uL without activation. No acceptable data
  are available for chromosomal aberrations, primary DNA damage,
  or other genotoxic effects.
- Metabolism:  A rat metabolism study is required.
- Possible Presence of Contaminant of Toxicological Concern
  The Agency finds that residues of monochloroacetic acid may be
  found in ethephon-treated commodities. Monochloroacetic acid
  is a potential degradation product of an impurity in ethephon,
  monochloroethyl ester of (2-chloroethyl)-phosphonic acid.
  Monochloroacetic acid is an extremely toxic metabolic inhibitor
  and has been prohibited from addition to food under 21 CFR
  189.155. Analysis of certain food and feed crops for residues
  of this contaminant are required.
- Major Routes of Exposure:  Dermal, Inhalation
Physiological and Biochemical Behavioral Characteristics:
- Metabolism:  Acceptable metabolism data are available for plants and
  ruminants. The residue of concern in plant commodities, ruminant
  tissues and milk is ethephon per se. Additional data are required
  regarding metabolism in poultry tissues and eggs.
- Possible Presence of Impurities:  Available data indicate that
  technical ethephon products may contain 2-chloroethanol as an
  impurity.  2-Chloroethanol is extremely toxic via the inhalation route
  and has caused human deaths. Because of its volatility, 2-choroethanol
  is unlikely to be present in ethephon end use products in amounts
  high enough to pose an inhalation hazard. However, the impurity
  could pose a hazard when technical or manufacturing use products
  are stored or used in poorly ventilated spaces. Under these
  conditions, 2-chloroethanol vapors could accumulate to levels which
  may be hazardous to workers in the area. The Agency is requiring
  submission of product chemistry data to assess the extent of hazard
  posed by 2-choroethanol.
Environmental Characteristics:
- Preliminary Adsorption and Leaching Characteristics:  Data are
  required on leaching, volatility, and hydrolysis# of ethephon to
  characterize the potential to reach ground water.
Ecological Characteristics:
- Data are sufficient to characterize ethephon as slightly toxic to
  birds (LC50 804 mg/kg quail, 3750 ppm ducks). Laboratory and
  field studies indicate that ethephon is slightly toxic to fish
  (LC50 180 mg/L bluegill, 170 mg/L trout (average)).
Tolerance Assessment:
List of crops and Tolerances:  (CFR 40 180.300)
Commodity                   Tolerance (ppm)
Apples                            5
Barley, grain                     2.0
Barley, straw                    10 0
Blackberries                     30
Blueberries                      20
Cantaloupes                       2
Cattle, meat byproducts           0.1
Cattle meat                       0.1
Cattle fat                        0.1
Cherries                         10
Commodity                   Tolerance (ppm)
Coffee beans                      0.1 (N)
Cottonseed                        2.0
Cranberries                       5
Cucumbers                         0.1
Figs                              5
Filberts                          0.5
Goats, fat                        0.1
Goats, mbyp                       0.1
Goats, meat                       0.1
Grapes                            2.0
Hogs, fat                         0.1
Hogs, mbyp                        0.1
Hogs, meat                        0.1
Horses, fat                       0.1
Horses, mbyp                      0.1
Horses, meat                      0.1
Lemons                            2
Macadamia nuts                    0.5
Milk                              0.1
Peppers                          30
Pineapples                        2
Pineapple fodder                  3
Pineapple forage                  3
Pumpkins                          0.1
Sheep, fat                        0.1
Sheep, mbyp                       0.1
Sheep, meat                       0.1
Tangerines                        0.5
Tangerine hybrids                 0.5
Tomatoes                          2
Walnuts                           0.5
Wheat, grain                      2.0
Wheat, straw                     10.0
Guavas                            0.1
Sugarcane Hawaii only             0.1
40 CFR 185.2700 and 186.2700 (food and feed additive)
Commodity                   Tolerance (ppm)
Barley milling fractions
 except flour                     5.0
Wheat milling fractions
 except flour                     5.0
Raisins                          12.0
Raisin waste                     65.0
Sugarcane molasses                1.5
Barley milling fractions
 except flour                     5.0
Wheat milling fractions
 except flour                     5.0
- Results of Tolerance Assessment:  The PADI for ethephon has
  recently been revised by the Agency ADI committee and is now
  established at 0.005 mg/kg/day (0.5 /kg/day for a LEL, and an
  uncertainty factor of 100).  This value is based on an LEL of 0.5
  mg/kg/day for a decrease in plasma cholinesterase activity in a 16-day
  study in humans.  An uncertainty factor of 100 is derived from a
  factor of 10 for the variation in the susceptibility of humans, and a
  factor of 10 for the use of an LEL instead of a NOEL.  The PADI will
  be reevaluated when the required toxicity and residue chemistry data
  are submitted and evaluated .
                   4. LABEL WARNING STATEMENTS:
- All Manufacturing-Use Products
  - Do not discharge effluent containing this product
    into lakes, streams, ponds, estuaries, oceans, or public water
    unless this product is specifically identified and addressed in an
    NPDES permit. Do not discharge effluent containing this product to
    sewer systems without previously notifying the  sewage treatment
    plant authority. For guidance contact your State Water Board or
    Regional Office of the EPA.
  - Technical grade ethephon must be stored and used in ventilated areas
- End-Use Products
  - Do not apply directly to water or wetlands (swamps,
    bogs marshes, and potholes). DO not contaminate
    water when disposing of equipment washwaters.
  - Mixers, loaders and applicators must wear a full
    face shield, long trousers, long sleeved shirt,
    gloves, and boots to avoid as much skin and eye
    contact as possible.
  - Do not enter treated fields within 24-hours after
  - The following interim pre-harvest intervals (PHI)
    must be included on end use product labels for the
    raw agricultural commodities listed. These interim
    PHI's may be revised after the required field residue
    data have been submitted and evaluated.
-   Apples minimum 7 days, barley 40 days, blackberries and
    blueberries 42 days, cherries minimum 7 days, coffee
    beans 14 days, cotton 14-21 days, cranberries 17-21 days,
    cucumbers 17-21 days, figs 14 days, filberts 7 days,
    grapes 14 days, guavas 7 months, melons 2 days, peppers
    14 days, pineapples 2 days, tangerines 5-10 days,
    tomatoes 14-20 days for processing and 3-6 days fresh
    market California only, walnuts 5-10 days, wheat 40 days.
1. Ethephon does not meet any of the criteria specified in 40 CFR 154.7;
therefore a Special Review is not being initiated at this time.
2. The Agency will not require restricted use classification for
ethephon end-use products.
3. The Agency is deferring decisions concerning ethephon's potential for
contaminating ground water until information on its environmental
characteristics and fate have been submitted and and reviewed.
4. The Agency has identified certain data that will receive immediate
review when submitted.
5. The Agency has determined that foliar and soil dislodgeable residue
data are required to establish reentry intervals for all crops. An
interim reentry interval of 24 hours is being imposed for all crops
until final reentry reentry intervals are established.
6. Pre-harvest intervals are required on product labeling for a variety
of currently registered use sites.
7. The Agency is requiring data on animal metabolism as well as storage
stability studies and residue studies for poultry and eggs. In order to
remain in compliance with FIFRA, registrants must do one of the
   a. Submit data which demonstrate that no residues remain in eggs and
      poultry as a result of feeding treated commodities;
   b. Propose tolerances and provide appropriate supporting data for
      residues in poultry tissues and eggs.
8. Additional residue data, including processing data, must be submitted
for the following raw agricultural commodities:  peppers, tomatoes,
cucumbers, melons, lemons, tangerines, apples, cherries, blackberries,
boysenberries, blueberries, cranberries, grapes, filberts, walnuts,
barley (wheat data may substitute), wheat, (and wheat straw), coffee
beans, cotton seed, figs, guavas, pineapple, sugarcane, and tobacco. For
tobacco, pyrolysis data must be submitted. If residues concentrate in
any of the processed products, the appropriate food additive
tolerance(s) must be proposed. Specific data requirements may be found
in the data tables.
9. The Agency is requiring the proposal of either a tolerance for
sugarcane forage or a grazing prohibition for sugarcane forage.
10. The Agency has determined that the following revisions in the
tolerances listed in 40 CFR 180.300 and 21 CFR 193.186 are necessary.
 - The designation "N" (negligible) must be deleted from all tolerances
 - The commodity "pineapple fodder" must be deleted from 40 CFR 180.300
 - The tolerance for guava must be added to 40 CFR 180.300.
 - The tolerance for raisins must be added to 21 CFR 193.186.
11. Product chemistry and residue data are required depicting residues
of monochloroacetic acid in or on food and feed commodities following
registered applications of ethephon. Monochloroacetic acid may be a
toxic metabolic residue derived from an impurity in technical ethephon.
12. The Agency has identified 2-chloroethanol as a contaminant of
toxicological concern. The Agency is requiring data to assess the extent
of contamination with this substance. Additionally, the Agency is
requiring that manufacturing use products bear a label statement
advising users to store and use the product in well-ventilated areas.
13. While the data gaps are being filled, currently registered
manufacturing-use products and end-use products containing ethephon as
the sole active ingredient may be sold, distributed, formulated, and
used in the United States, subject to the terms and conditions specified
in this Standard. Registrants must provide or agree to develop
additional data, required in the Registration Standard.
     The Agency will issue registrations for substantially similar
products and new uses will be issued after considering the effects on
the theoretical maximum residue contribution (TMRC) and the maximum
permissible intake (MPI).
7. Summary of Major Data Gaps
                                          Due Date (After Issuance
   Data Required                              of the Standard)
   Product Chemistry                         6 - 12 Months
   Hydrolysis                                     9 Months
   Photodegradation                               9 Months
   Soil Metabolism                               27 Months
   Fish Accumulation                             12 Months
   Rotational Crops                              39 Months
   Leaching and Adsorption/                      12 Months
   Terrestrial Field Dissipation                 27 Months
   Acute Estuarine and Marine                    12 Months
   Acute Inhalation                               9 Months
   Reproduction                                  39 Months
   Mutagenicity                                  12 Months
   Animal Metabolism                             18 Months
   Magnitude of Plant Residues               6 - 24 Months
   Analytical Methods                            15 Months
   Storage Stability                             18 Months
   Chronic Toxicity Rodent                        9 Months*
   Oncogenicity data                              9 Months*
*These studies may be upgraded or they will have to be repeated.
                     6. CONTACT PERSON AT EPA
Robert J. Taylor
Product Manager 25
Fungicide-Herbicide Branch
Registration Division (TS-767C)
Office of Pesticide Programs
Environmental Protection Agency
401 M Street SW.
Washington, DC   20460
(703) 557-1800
DISCLAIMER:  The information presented in this Pesticide Fact Sheet is
for informational purposes only and may not be used to fulfill data
requirements for pesticide registration and reregistration.