ethion EPA Pesticide Fact Sheet 9/89
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 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.
- 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
- 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
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."
"USE ONLY WHEN WEARING THE FOLLOWING PROTECTIVE CLOTHING AND
EQUIPMENT DURING MIXING/LOADING, APPLICATION, REPAIR AND CLEANING
OF MIXING, LOADING, AND APPLICATION EQUIPMENT, DISPOSAL OF THE
PESTICIDE, AND EARLY REENTRY INTO TREATED AREAS: Protective suit
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
IF MIXING/LOADING IS PERFORMED USING A CLOSED SYSTEM, THE
FOLLOWING PROTECTIVE CLOTHING AND EQUIPMENT MAY BE WORN AS AN
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
DRENCHED CLOTHING CANNOT BE ADEQUATELY DECONTAMINATED.
DURING AERIAL APPLICATION, HUMAN FLAGGERS: MUST BE IN A TOTALLY
"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."
- 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
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)
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
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).
4. SUMMARY OF REGULATORY POSITION
- 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
- 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:
Product Manager (Team 16)
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
Reregistration Document Inquiries:
Richard W. King
Special Review and Reregistration
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
DISCLAIMER: THE INFORMATION IN THIS PESTICIDE FACT SHEET IS A SUMMARY
ONLY AND IS NOT TO BE USED TO SATISFY DATA REQUIREMENTS FOR PESTICIDE
REGISTRATION AND REREGISTRATION. THE COMPLETE REREGISTRATION DOCUMENT
FOR THE PESTICIDE MAY BE OBTAINED FROM THE NATIONAL TECHNICAL
INFORMATION SERVICE. CONTACT THE REVIEW MANAGER LISTED ABOVE FOR