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ethion EPA Pesticide Fact Sheet 9/89

EPA Pesticide
Fact Sheet

Name of Chemical:  ETHION 
Reason for Issuance:  Registration, Standard
                      (Second Round Review)
Date Issued:  September 30, 1989
Fact Sheet Number:  209

                     1.   DESCRIPTION OF CHEMICAL

- Generic (Chemical) Name:  O,O,O',O'-Tetraethyl S,S'-methylene
- Common Name:  Ethion
- Trade and Other Names:  Ethanox, Ethiol, Hylemox, Rhodiacide,
  Rhodocide, Vegfru Fosmite, RP-Thion, Tafethion.
- EPA Pesticide Chemical Code (Shaughnessy No.):  0584401
- Chemical Abstracts Service (CAS) Number:  563-12-2
- Year of Initial Registration:  1965
- Pesticide Type:  Insecticide (non-systemic)
- Chemical Family:  Organothiophosphate member of the Organophosphate
- U.S. and Foreign Producers:  Cheminova (Denmark), FMC Agricultural
  Chemical Group (USA), M/S Pesticides India (India), Rallis India Ltd.
  Rhone-Poulenc Agrochemic (France), Sintesul S.A. (Brazil), Volrho Ltd.

                      2. USE PATTERNS AND FORMULATIONS

- Application: A non-systemic insecticide for control of leaf-feeding
  insects, mites, and scale.
- Registered Uses:
  - Terrestrial Non-food Crops:  Bermudagrass, junipers, ornamental
    evergreens, pine trees, lawns, ornamental turf, and ornamental
  - Greenhouse Non-food Crops:  Ornamental plants.
  - Domestic Outdoor Uses: Domestic dwellings, and lawns.
  - Terrestrial Food Crop Use: Alfalfa (seed crop), almonds, apples,
    apricots, beans, cherries, chestnuts, corn (field), cotton,
    cucumbers, eggplants, filberts, grapefruit, grapes, lemons, limes,
    melons, nectarines, onions (dry & green), oranges, peaches, peanuts,
    pears, pecans, peppers, pimentos, plums, prunes, sorghum (grain &
    forage), sorghum (seed crop), squash (summer), strawberries,
    tangelos, tangerines, tomatoes,'and walnuts.
- Mode of Insecticidal Activity:  Toxic action is exerted by inhibiting
  enzymes of the nervous system through inhibition of cholinesterase.
- Method of Application:  Ground and aerial foliar applications, furrow
  treatments by ground equipment, and seed treatment.
- Annual Usage:  1.2 to 1.5 million pounds of active ingredient are used
  in the United States.
- Predominant Usage:  Citrus accounts for 86% to 89% of the total pounds
  of ethion used in the United States. The remaining 11% to 14% is
  applied to cotton and a variety of fruit trees, nut trees, and
  vegetables. Approximately 55% to 70% of all domestically produced
  citrus fruits are treated with ethion. Less than 2% of the domestic
  cotton acreage and fewer than 10% of the fruit (other than citrus),
  vegetable, and nut acreage is treated with ethion.
- Formulations:  Emulsifiable solution 500 g/l; Wettable Powder 25%;
  Dusts 2%,3%,and 4%; Emulsifiable concentrates 4 and 8 lbs/gal;
  Granules 5% and 10%

                            3. SCIENCE FINDINGS

Chemical Characteristics of Technical Material
- Color:  colorless to light brown or pale yellow.
- Physical state:  liquid at room temperature.
- Odor:  mild dithiophosphate
- Melting point:  -12 degrees F to -15 degrees F
- Boiling point:  164-165 degrees C at 0.3 mm Hg.
- Specific gravity: 1.215-1.230 at 20 degrees C
- Solubility:  Practically insoluble in water; soluble in most organic
- Vapor pressure:  1.5 x 10 to the minus 6mm Hg at 25 degrees C
- Dissociation constant:  Not applicable; TGAI does not disperse in
- Octanol/water partition coefficient:  10,000 [GC with FPD detector].
- pH:  5.1 in an equal volume of distilled water.
- Storage stability:  95% of ethion remained unchanged during one year
  of storage at 25 degrees C. There was <2% deterioration in three years
  of storage under the same conditions. Recommended shelf life is two
  years. Do not store below 20 degrees F to avoid crystal formation.
- Corrosion:  Ethion does not corrode stainless steel or aluminum.

Summary Science Statement

- Acute oral toxicity studies show that technical ethion is highly toxic
  to mammals, particularly to females; [Toxicity Category I (females)
  and Toxicity Category II (males)]. Ethion has moderately high acute
  dermal and inhalation toxicities; [Toxicity Category II for dermal
  toxicity and Toxicity Category II (females) and Toxicity Category III
  (males) for acute inhalation]. Ethion caused slight redness of the
  conjunctiva of the eye and slight erythema on the skin. The effects
  cleared within 48 hours, thus classifying ethion in Toxicity Category
  IV. Ethion was not found to be a dermal sensitizer and does not cause
  acute delayed neurotoxicity.
- Subchronic toxicity:  No compound-related histomorphologic changes
  were found in a 90-Day Dog Feeding Study. Based upon the inhibition of
  plasma cholinesterase activity observed, the LEL is 2.5 ppm and the
  NOEL is 0.5 ppm.
- Chronic toxicity:  In a chronic toxicity study conducted with rats, a
  decrease in serum cholinesterase was observed in high dose males and
  females. No other effects were observed. Based on the cholinesterase
  inhibition, the systemic NOEL is 4 ppm and the LEL is 40 ppm.
- Oncogenicity:  Ethion was not found to be carcinogenic in rats and
- Teratogenicity:  Studies conducted with rabbits and rats did not
  indicate that there were any structural or functional abnormalities
  in test animals. However, increases in the incidence of hyperactivity
  of dams and delayed ossification of pubes in fetuses were observed in
  the rat study. In the rabbit teratology study, there were increases in
  the incidence of orange-colored urine, decreases in body weight and
  food consumption, along with an increased incidence of fused sternal
  centra in fetuses of treated females. The three generation
  reproduction study did not show any compound related reproductive
  effects, a decrease in serum cholinesterase activity.
- Mutagenicity:  Assays on gene mutation, structural chromosomal
  aberration, and unscheduled DNA Synthesis indicate ethion is not
- Reproduction and Fertility Effects:  Ethion has a reproductive NOEL of
  25 ppm (HDT) and a systemic NOEL of 25 ppm for males and 4.0 ppm for
  females. These findings were based on tests in which ethion was
  administered to groups of F(0),F(l), F(2), male and female rats (15
  males/dose and 30 females/dose) at dietary concentrations of 0, 2, 4,
  and 25 ppm. A decrease in serum cholinesterase activity was observed
  in the F(l), and F(2) high-dose females (25 ppm).
- Gene mutation test:  An Ames assay showed that ethion at the
  concentration range of 0.625 to 10.0 nl/ml does not produce mutagenic
  effects in five strains of Salmonella typhimurium (TA-98, TA-100, TA-
  1535, TA-1537, and TA-1538).
- Structural chromosome aberration test:  An in vivo cytogenetic assay
  indicated that ethion at dose ranges of 4.7 to 47 mg/kg does not
  induce chromosome aberrations in rats.
- Test for other genotoxic effects:  An unscheduled DNA synthesis (USD)
  in rat primary hepatocytes showed no evidence of induction of UDS at
  dose levels of 100, 500, 2500, 5,000, and 10,000 ug/plate.

Information on Human Effects:

- A group of adult male volunteers (10) was randomly divided into a
  control group (3 males) and a treatment group (6 males). The treatment
  group received ethion serially and orally (gelatin capsule) at dose
  levels of 0.05, 0.075, 0.1, and 0.15 mg/kg.  Significant reduction of
  plasma cholinesterase activity was seen at doses of 0.075 mg/kg and
  above. Based upon this data a NOEL of 0.05 mg/kg and a LED of 0.075
  mg/kg/day were established.

Environmental Characteristics

- Environmental Fate:  The Agency has determined that ethion appears to
  be resistant to hydrolysis (except at very alkaline pH), photolyzes in
  water and on soil (half-life of 58 and 51 days respectively) and its
  major metabolite is C02.
- Groundwater:  The Agency presently believes that ethion is not 
  expected to leech. Available data indicate that it is immobile
  and only moderately persistent.

Ecological Characteristics

- Aquatic Toxicity: Technical ethion is very highly toxic to freshwater
  and marine fish. Acute toxicity ranges from an LC50 of 49 ppb for
  Bluegill to an LC50 of 720 ppb for Cutthroat trout and flathead
- Ethion appears to be a heavy bioaccumulator (1400 for whole fish on
  day 42).
- Ethion is very highly toxic to freshwater invertebrates. The acute
  toxicity ranged from 0.056 to 7.7 ppb. The toxicity of ethion to
  marine/estuarine invertebrates is also very high, ranging from 5.6 ppb
  to 49 ppb.
- Honeybee Acute Toxicity:  Ethion was found to be practically non-toxic
  to honeybees (LD50 20.55 ug/bee).
- Endangered Species:  Because of the demonstrated toxicity of ethion to
  nontarget fish and aquatic invertebrates, ethion has been identified
  by the Office of Endangered Species (OES), U.S. Fish and Wildlife
  Service (FWS) as being likely to negatively impact on endangered
  aquatic organisms when applied to certain crops (i.e. citrus, corn,
  sorghum and cotton). The Agency is developing a program to reduce or
  eliminate exposure to these vulnerable organisms, and will issue
  notice of any product labeling, other than those identified in this
  registration standard, when the program has been developed and

Worker Protection

Based on the acute hazard to exposed persons, the following interim 
reentry intervals will be imposed until appropriate exposure data has 
been evaluated by the Agency:

     Crop                Reentry interval from last application

    Citrus                           30 Days
    Peaches                          14 Days
    Nectarines                       14 Days
    Grapes                           14 Days
    All other crops                   2 Days

- The precautionary and protective clothing label statements listed
  below are required on all products containing ethion with the signal
  words DANGER or WARNING that are applied to agricultural sites,
  structural pest control sites, or greenhouses.

     "Do not rub eyes or mouth with hands. If you feel sick in any
      way STOP work and get help right away. See Practical Treatment
      Section of this label."

     "Do not apply this product in a way that will contact unprotected
      workers, either directly or though drift. Only protected handlers
      may be in the area during application."

      of one or two pieces covering all parts of the body except head,
      hands, and feet; chemical resistant gloves; chemical resistant
      shoes (or chemical resistant shoe covers or chemical resistant
      boots); and a NIOSH or MSA approved respirator. In addition,
      mixer/loaders must wear a chemical resistant apron and face
      shield or goggles.

      During equipment repair and cleaning, the respirator need not be
      worn. During early reentry after sprays have dried or dusts have
      settled and vapors have dispersed, the respirator need not be

      ALTERNATIVE: long-sleeved shirt and long-legged pants; shoes and
      socks. Chemical resistant gloves must be available in the cab or
      cockpit and must be worn when exiting. This clothing is
      inadequate protection during equipment repair or cleaning,
      reentry, or pesticide disposal work.

      IMPORTANT! If pesticide comes in contact with skin, immediately
      wash off with soap and water. Always wash hands, face, and arms
      with soap and water before smoking, eating, drinking, or when
      using the toilet.

      AFTER WORK:  Wash gloves with soap and water before removing them.
      Take off all work clothes and shoes. After removing clothing
      shower using soap and water, then put on clean clothes. Do not
      reuse contaminated clothing. Personal clothing worn during work
      must be laundered separately from household items. Store
      protective clothing-separate from personal clothing; Clean or
      launder protective clothing after each use. Respirators must be
      cleaned and filters replaced according to instructions included
      with the respirator. Protective clothing and equipment that
      becomes heavily contaminated or drenched must be destroyed
      according to state and local regulations. HEAVILY CONTAMINATED OR


     "Do not enter or allow entry into treated areas until
      (sprays have dried/dusts have settled/vapors have dispersed, as
      applicable) to perform hand labor tasks. A person may enter the
      area to perform other tasks only if the person is wearing the
      personal protective clothing listed on the label."

     "After (sprays have dried/dusts have settled/vapors
      dispersed, as applicable) do not enter or allow entry into the
      treated area until the reentry interval has expired, unless the
      person entering the treated area is wearing the personal
      protective equipment listed on the label for early reentry."

Tolerance Assessment

- Tolerances for ethion in or on raw agricultural commodities
  and animal products are published in 40 CFR 180.173. Food
  additive tolerances for ethion have been established for dried
  tea and raisins and are published in 40 CFR 185.2750 (formerly 21
  CFR 193.190). A feed additive tolerance for ethion has been
  established for dehydrated citrus pulp and is published in 40 CFR
  186.2750 (formerly 21 CFR 561.230). All tolerances are expressed
  in terms of ethion and its oxygen analog (s-[[diethoxyphosphino-

                   Summary of Tolerances Issued for Ethion

                             Tolerances (PPM)       MRL

Commodities         US          Canadian               International
                                                      Mexican   Codex

Almonds             0.1          0.1                  0.1       0.1(1)
Almond, hulls       5.0
Apples              2.0          2                    2         2(1)
Apricots            0.1          none                 none      0.1(1)
Beans               2.0          1                    2         none(2)
Cattle, fat         2.5          2.5                  none
Cattle, meat        2.5          2.5                  none      2.5(1)
Cattle, mbyp        1.0          2.5                  none      1(1)
Cherries            0.1          none                 none      0.1(1)
Chestnuts           0.1          none                 0.1       0.1(1)
Citrus              2.0          2                    2         2(1)
Citrus, pulp       10
Corn, fodder       14            none                 none      none(2)
Corn, forage       14            none                14         none(2)
Corn, grain         0.1          none                 0.1       0.05(3)
Cottonseed          0.5          none                 0 5       0 5(1)
Cucumbers           0.5          0.1                  0.5       0.5(1)
Eggs                0.2          none                 none      0.2
Eggplants           1.0          0.1                  1         1(1)
Filberts            0.1          none                 0.1       0.1(1)
Goats, fat          0.2          none                 none      0.2(1)
Goats, meat         0.2          none                 none      0.2(1)
Goats, mbyp         0.2          none                 none      0.2(1)
Grapes              2.0          2                    2         2(1)
Raisins             4.0
Hogs, fat           0.2          none                 none      0.2(1)
Hogs, meat          0.2          none                 none      0.2(1)
Hogs, mbyp          0.2          none                 none      0.2(1)
Horses, fat         0.2          none                 none      0.2(1)
Horses, meat        0.2          none                 none      0.2(1)
Horses, mbyp        0.2          none                 none      0.2(1)
Melons              2.0          0.1                  2         2(1)
Milk, fat           0.5          none                 none      0.2(4)
Nectarines          1.0          none                 none      1.0(1)
Onions              1.0          0 .1                 1         1(1)
Peaches             1.0          1.0                  1.0       1.0(1)
Pears               2.0          2                    1         2(1)
Pecans              0.1          none                 0.1       0.1(1)
Peppers             1.0          0.1                  1         1(1)
Pimentos            1.0          0.1                  none      none(2)
Plums (fresh prunes)2.0          1.0                            2.0(1)
Poultry, fat        0.2          none                 none      0.2(1)
Poultry, meat       0.2          none                 none      0.2(1)
Poultry, mbyp       0.2          none                 none      0.2(1)
Sheep, fat          0.2          none                 none      0.2(1)
Sheep, meat         0.2          none                 none      0.2(1)
Sheep, mbyp         0.2          none                 none      0.2(1)

           Summary of Tolerances Issued for Ethion (Continued)

                             Tolerances (PPM)       MRL

Commodities         US          Canadian               International
                                                      Mexican   Codex

Sorghum, forage      2.0         none                  2.0       none(2)
Sorghum, grain       2.0         none                  2.0       none(2)
Squash, summer       0.5         0 1                   0 5       0 5(1)
Strawberries         2.0         1.0                   2.0       2.0(1)
Tea (dried)         10.0         none                  none      5.0(5)
Tomatoes             2.0         0.5                   2         2(1)
Walnuts              0.1         none                  0.1       0.1(1)

(1) Established Codex MRL is numerically identical to U.S. Tolerance.
(2) No Codex MRL has been established, therefore, no questions of
    compatibility exist with respect to Codex MRL.
(3) Codex MRL (CXL) of 0.055 ppm exist for residues of ethion per se in
    or on maize. This level is lower than that of the U.S..
(4) U.S. Tolerance is higher.
(5) (Green, black tea):  A decision regarding the potential for 
    compatibility between the permanent Codex MRL and the U.S.
    tolerance will not be made until the adequacy of the U.S.
    tolerance has been ascertained.

Summary of Dietary Exposure Analysis

     The Agency has concluded that the use of ethion will not
result in chronic health effects. There does not appear to be a
health risk from short term exposure to ethion residue on
grapefruit, stone fruits other than peaches and plums, eggs,
grains, meat nuts, and poultry. However, based on the limited
data/information available, short term exposure to ethion from
residues on peaches, vegetables, tea, and oranges may result in
acute cholinesterase inhibition for selected TAS populations,
infants and children. Also, short term exposure to ethion
residues on apples and pears, grapes, melons, tomatoes dry beans,
succulent beans, strawberries (pooled with citrus other than
oranges and grapefruit), and plums or prunes may result in acute
cholinesterase inhibition in all TAS population groups.
     The Agency is initiating a Data Call-In to examine acute
dietary exposure; anticipated residue data are being called in
under 40 CFR 158.240 (Reduction of Residue).


- The Agency is considering further regulatory action based on dietary
  exposure concerns. The Agency has determined that certain current
  tolerances may not provide an adequate margin of safety in humans.
  Short term exposure to ethion residues on apples and pears, grapes,
  melons, tomatoes, dry beans, succulent beans, strawberries (pooled
  with citrus other than oranges and grapefruit), and plums and prunes
  may result in acute cholinesterase inhibition for all TAS population
  groups. The Agency also has determined that short term exposure to
  ethion residues on peaches, vegetables, tea, and oranges may result in
  acute cholinesterase inhibition in selected TAS populations, infants
  and children.

- The Agency is not imposing the Restricted Use Classification on all
  pesticide products containing ethion. At present three ethion products
  are classified Restricted Use because of their high dermal and
  inhalation toxicity. Two of-these products contain  81.9% active
  ingredient and the other 81% active ingredient. The Agency will make a
  decision regarding the Restricted Use Classification on a product-by-
  product basis for the remaining products after evaluating the product
  specific toxicity data submitted in response to the Registration
  Standard issued September 30, 1989. 
- No groundwater advisory labeling is required because ethion is
  not expected to leach.

  Based on the high acute toxicity and worker poisoning incidents, the
  Agency is requiring label language stipulating the use of protective
  clothing and the following reentry intervals.

  Citrus         ...........30 Days
  Nectarines         .......14 Days
  Peaches         ..........14 Days
  Grapes........... ........14 Days '
  All other crops and uses.  2 Days

- The Agency is imposing these reentry intervals as an interim measure
  until reentry data can be generated.

- No significant new food uses or increases-of tolerances for food or
  feed items treated with ethion will be considered until the
  outstanding residue chemistry studies and residue reduction
  information have been submitted and reviewed by the Agency .
                   5. CONTACT PERSON AT EPA:

Product Specific Inquiries:
William Miller
Product Manager (Team 16)
Insecticide-Rodenticide Branch
Registration Division (H7505C)
Office of Pesticide Programs, EPA
Environmental Protection Agency
401 M Street, S. W.
Washington, DC 20460

Office location and telephone number:
Room 211, Crystal Mall #2
1921 Jefferson Davis Highway
Arlington, VA 22202
(703) 557-2600

Reregistration Document Inquiries:
Richard W. King
Review Manager
Reregistration Branch
Special Review and Reregistration
Division (H-7508C)
Environmental Protection Agency
401 M Street, S.W.
Washington. D.C. 20460

Office location and telephone number:
Room 1120 Crystal Mall #2
1921 Jefferson Davis Highway
Arlington, VA 22202
(703) 557-0304