United States Office of Pesticides and Toxic Substai
Environmental Protection Office of Pesticide Programs (H7508<
Agency Washington, DC 20460
&EPA Pesticide
Fact Sheet
540/FS-89-051
Name of Chemical: METHOMYL
Reason for Issuance: ISSUANCE OF REGISTRATION STANDARD
Date Issued: April 1939
Fact Sheet Number: 201
l. Description of Chemical
-Generic Name: S-methyl N-[(methylcarbamoyl)oxy]-
thioacetimidate
-Common Name: Methomyl
-Trade Name and
other names: methyl N-[[(methylamino)carbonyl]oxy]-
ethanimidothioate, methyl N-[(methylcar-
bamoyl)oxy]-thioacetimidate, Lannate,
Lanox, and Nudrin
-EPA Shaughnessy Number: 090301
-Chemical Abstracts Service (CAS) Number: 16752-77-5
-Year of Initial Registration : 1968
-Pesticide Type: Insecticide
-Chemical Family: Carbamate
-U.S. Producer: E.I. duPont de Nemours and Company
2. Use Patterns and Formulations
-Application sites: Terrestrial food and non-food crops,
Greenhouse food and non-food crops,
Aquatic food crops, Forestry (ground
only), and Indoor- human and animal
premise
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-Types and method of applications: Foliar and broadcast
soil application by both ground and aircraft equipment
-Application rates: 0.1 to 1.5 Ib a.i. per acre
-Types of formulations: Wettable powders, emulsifiable
and soluble concentrates, gran-
ulars, baits, and dusts
-Usual carriers: Petroleum and clay carriers
3. Science Findings
Physicochemical Characteristics:
Technical methomyl is a white crystalline solid with a melting
point of 78-79 C. Methomyl is soluble in water and most
organic solvents. Methomyl's empirical formula is
C5H10N202S and its molecular weight is 162.2.
Toxicological Characteristics:
-Acute Oral: 17 to 24 mg/kg (rat) Toxicity Category I
-Acute Dermal: >5000 mg/kg (rabbit) Toxicity Category III
-Primary Eye Irritation: Data gap
-Acute Inhalation: 0.30 mg/liter/4 hours Toxicity Category III
-Primary Skin Irritation: Data gap
-Dermal Sensitization: Data gap
-Acute Delayed Neurotoxicity: Data shows no potential for
this effect.
-Subchronic dermal (21 day): Data gap
-Oncogenicity: A rat chronic/oncogenicity study showed no
oncogenic effects at the highest dose tested (HDT-400 ppm) .
A mouse oncogenicity study showed no oncogenic effects at
HOT 200 ppm.
-Metabolism: Data Gap- Preliminary data suggests that
methomyl may be metabolized to the possible human oncogen
acetamide. Additional metabolism data in the rat and mon-
key are required to detect the possible presence of acetamide
in the tissues.
-Teratology: Not teratogenic or embryotoxic at HOT 400 ppm
in rats. Not teratogenic or embryotoxic at HOT in rabbits
(Maternal No Observed Effect Level [NOEL] of 2 mg/kg/day).
-Reproduction: No observed effects with a NOEL of 100 ppm.
-Mutagenicity: Not a mutagen in all the required tests.
Physiological and Biochemical Characteristics:
-Mechanism of Pesticide Action: Methomyl kills by poisoning
the insects' nervous system.
-Metabolism and perisistence in plants and animals:
Plants: Available data demonstrate that methomyl is rela-
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tively persistent on leaf surfaces and fruit. There has
been some concern in the recent past that acetamide, a
suspected human carcinogen, may occur in plants following
treatment with methomyl. However, recently available data
on thiodicarb, a related insecticide that breaks down initially
to methomyl in plants, reveal that acetamide will not occur
in plants treated with methomyl. Furthermore, any acetamide
formed from acetronitrile, a known metabolite of methomyl, will
be hydrolyzed to form acetic acid and ammonium ion.
Animals: The available data are not adequate to assess the
nature of methomyl in animals. Additional metabolism data
(ruminants and poultry) are required to detect the possible
presence of acetonitrile and acetamide. These data were
requested in a FIFRA 3(c)(2)(B) letter dated March 23, 1987.
Environmental Characteristics:
-Available data are insufficient to fully assess the environ-
mental fate of methomyl. The Registration Standard issued
in 1981 did not address the aquatic uses of methomyl. Data
must now be submitted for the following: aquatic aerobic,
aquatic anaerobic, aquatic field dissipation and irrigated
crops. Vapor pressure data indicate the need for volatility
data. Monitoring data are needed to assess the potential of
this pesticide to contaminate groundwater.
Ecological Characteristics:
-Acute avian oral toxicity: LD50 24.2 mg/kg for bobwhite
quail (highly toxic).
-Avian dietary toxicity: LC50 of 1100, 1975, and 288.3 ppm
respectively for bobwhite quail, ring-necked pheasant, and
mallard duck (slightly toxic).
-Freshwater fish acute toxicity: LC50 = 1.6 ppm for Rainbow
trout. LC50 = 0.5 ppm for channel catfish (moderate to
highly toxic for fish).
Freshwater aquatic invertebrate toxicity: LC50 values of
0.0698 to 0.343 ppm suggest that is very highly toxic to
freshwater invertebrates.
Major Routes of Exposure:
-Dermal followed by inhalation. Human exposure occurs from mixing,
loading and application. Exposure can be reduced by the use of
goggles or face shield and protective clothing.
Tolerance Assessment:
-Tolerances have been established for residues of methomyl in
a variety of raw agricultural commodities (Refer to 40
CFR 180.253 for listing of tolerances). Methomyl's tolerances
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have been reassessed using the Tolerance Assessment System
(TAS). The Acceptable Daily Intake (ADI) for this chemical
is 0.025 mg/kg/day. The Theoretical Maximum Residue Contri-
bution (TMRC) for the U.S. population is 0.016188 mg/kg/day,
which occupies 65% of the ADI.
4. Summary of Regulatory Position
This review of methomyl is the second intensive evaluation
of the compound. In its original Standard, issued in 1981,
the Agency summarized the available data supporting the re-
gistration of methomyl and concluded that additional data
were needed data to fully evaluate the pesticide.
The Agency has since received and reviewed the data
and has revised its scientific and regulatory conclusions in
relative to these data. Additionally, other information on the
chemical (for example the acetimide issue) and the expanded
data requirements promulgated in 1984 at 40 CFR Part 158,
have added new data requirements. This Standard, which
supercedes the 1981 document, is the Agency's updated assess-
ment of the pesticide and the data needed to support its
continued registration.
A. Methomyl is not being placed in Special Review at this
time because none of the criteria for initiation of Special
Review listed in 40 CFR 154.7 have been met. The Agency
believes that the water soluble bag use restriction and the
increased reentry intervals provide mixer/loader and field-
worker protection. The Agency intends, however, to monitor
State pesticide incidents monitoring systems to determine
the effectiveness of labeling changes identified in the
Standard. The Agency may impose further regulatory actions
if these incidents reports indicate that these labeling changes
are inadequate.
B. The Agency is requiring the submission of acute aquatic
toxicity data and aquatic and non-aquatic field monitoring
data on the end-use formulations and aquatic life stage data
and avian reproduction data on the technical formulation in
order to complete the wildlife risk assessment.
C. Based on methomyl's use pattern and toxicity data, the
Agency has determined that methomyl may trigger the endangered
species criteria for fish, aquatic organisms and insects.
No endangered species labeling is required at this time. A
program is being developed by the Agency to reduce or elim-
inate exposure of this chemical to these species. After this
program is developed, the Agency will notify registrants of
any additional labeling that may be required to remain in
compliance with FIFRA. The labeling requirements affecting
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methomyl, e.g. those listed in PR Notices 87-4 and 87-5, have
been withdrawn pending reissuance.
D. Various methomyl formulations were classified as restrict-
ed use products by regulation in 1978 (see 40 CFR 162.13).
The Agency has now determined that the 90% water soluble bag
formulation should also be classified as a restricted use
pesticide. Labeling language for each of the restricted use
products must specify that the restriction is based.on high
acute toxicity to humans.
E. The following reentry intervals are being imposed at this
time based on the submitted reentry data: one day for beans,
cabbages, roses grown outdoors and carnations, whether grown
outdoors or in a greenhouse; three days for cotton, nectarines,
and oranges/citrus; four days for peaches; and seven days for
grapes. Because of the similarity in crops and in the work
tasks performed in those crops, a three day reentry interval
is being established for apples, and a one day reentry interval
for alfalfa, asparagus, broccoli, brussel sprouts, carrots,
cauliflower, celery, collards, cucumbers, lettuce, melons,
onions, peanuts, peas, peppers, potatoes, sorghum, soybeans,
summer squash, spinach, sugar beets, tobacco, and tomatoes.
Additional data are being requested to set reentry intervals
for mint, corn, roses grown in greenhouses, and chrysanthemums
grown in greenhouses or outdoors. Until these data are received
and evaluated, an interim seven day reentry interval is being
established for corn, and a one day reentry interval is being
established for these crops and all other crops and sites
not specifically listed above.
F. The following labeling is required for all manufacturing
use products:
This pesticide is toxic to fish. Do not discharge
effluent containing this product into lakes, streams, ponds,
estuaries, oceans, or public waters unless this product is
specifically indentified and addressed in the 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.
G. The following labeling is required for all end use pro-
ducts :
PERSONAL PROTECTIVE EQUIPMENT:
USE ONLY WHEN WEARING THE FOLLOWING PERSONAL PROTECTIVE
EQUIPMENT DURING MIXING/LOADING, APPLICATION, REPAIRING AND
CLEANING OF MIXING, LOADING, AND APPLICATION EQUIPMENT, AND
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DISPOSAL OF THE PESTICIDE: longsleeve shirt; long-legged
pants; shoes and socks, chemical resistant gloves; face
shield or goggles; NIOSH or MSHA approved respirator. During
equipment repair and cleaning, the respirator need not be
worn.
IF APPLICATION IS PERFORMED USING AN ENCLOSED CAB OR
COCKPIT, THE FOLLOWING PROTECTIVE CLOTHING AND EQUIPMENT MAY
BE WORN AS AN ALTERNATIVE: long-sleeve shirt and long-legged
pants; shoes and socks. All other protective clothing and
equipment required for use during application must be available
in the cab and must be worn when exiting the cab into treated
area. When used for this purpose, contaminated clothing may
not be brought back into the cab unless in an enclosure such
as a plastic bag.
IMPORTANT! If pesticide comes in contact with skin, wash
off with soap and water and contact a physician immediately.
ALWAYS WASH HANDS, FACE, AND ARMS WITH SOAP AND WATER BEFORE
USING TOBACCO PRODUCTS, EATING, DRINKING, OR TOILETING.
AFTER WORK: Before removing gloves, wash them with soap
and water. Take off all work clothes and shoes. Shower
using soap and water. Wear only clean clothes when leaving
job—do not wear contaminated clothing. Personal clothing
worn during work must be stored and laundered separately from
protective clothing and household articles. Store protective
clothing separately from personal clothing. Clean or launder
protective clothing after each use. Respirators must be
cleaned and filters replaced according to instructions included
with the respirators. Protective clothing and protective
equipment heavily contaminated or drenched with methomyl must
be destroyed according to state and local regulations.
HEAVILY CONTAMINATED OR DRENCHED CLOTHING CANNOT BE ADEQUATELY
DECONTAMINATED.
DURING AERIAL APPLICATION, HUMAN FLAGGERS ARE PROHIBITED.
PROTECTIVE CLOTHING LABEL STATEMENTS FOR 1% BAITS
Use only when wearing the following personal protective
equipment during loading, application, repairing and
cleaning of mixing, loading, and application equipment, and
disposal of the pesticide: longsleeve shirt; long-legged
pants; shoes and socks; gloves.
IMPORTANT! If pesticide comes in contact with skin, wash
off with soap and water.
ALWAYS WASH HANDS, FACE, AND ARMS WITH SOAP AND WATER BEFORE
USING TOBACCO PRODUCTS, EATING, DRINKING, OR TOILETING.
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OTHER LABEL STATEMENTS FOR BAITS
Do not contaminate feed and foodstuffs. Do not apply
where poultry or other animals, especially dogs and young
calves, can pick it up or lick it.
Do not use in edible product areas of food processing
plants, restaurants, or other areas where food is commercially
prepared or processed. Do not use in serving areas while
food is exposed.
REENTRY INTERVALS:
The following reentry intervals are required in the
directions for use section of all labels with terrestrial and
greenhouse food and non-food uses: three days for cotton,
nectarines, citrus and apples; four days for peaches; seven
days for grapes and corn; all other crops, one day.
The following fish and wildlife statements are required
to appear under the "Environmental Hazards" heading:
1. Granulars (including baits): This pesticide is
toxic to birds. Collect, cover or incorporate granules spilled
on the soil surface. Do not apply directly to water or wetlands
(swamps, bogs, marshes, and potholes). Do not contaminate
water when disposing of equipment washwaters.
2. Non-Granular:
a. Aquatic (Watercress): This pesticide is toxic to
fish. Drift and runoff from treated areas may be hazardous
to aquatic organisms in neighboring areas. Do not contaminate
water when disposing of equipment washwaters.
b. Terrestrial: This pesticide is toxic to fish and
wildlife. Do not apply directly to water or wetlands (swamps,
bogs, marshes, and potholes). Drift and runoff may be hazardous
to aquatic organisms in neighboring areas. Do not contaminate
water when disposing of equipment washwaters.
H. End use products (except granulars and baits) with outdoor
crop uses must have the following bee caution: This product
is highly toxic to bees exposed to direct treatment on blooming
crops or weeds. Do not apply this product or allow it to
drift to blooming crops or weeds while bees are actively
visiting the treatment area.
Products with lentil use must include a pregrazing interval
of three days and a preharvest interval of seven days.
I. Pursuant to the data requirements in 40 CFR Part 158,
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8
the Agency has determined that the following data are essential
to the Agency's assessment and should receive a priority
review when they are received by the Agency:
40 CFR 158.240 Residue Chemistry
171-4 Nature of the Residue (Metabolism-Livestock),
Meat/Mi Ik/Poultry and Eggs
40 CFR 158.390 Reentry Protection
132-1 Foliar Dissipation (Reentry)
201-1 Droplet Size Spectrum
201-1 Drift Field Evaluation
40 CFR 158.340 Toxicology
85-1 General Metabolism (Rat and Monkey)
82-2 Subchronic Dermal (21-Day)
40 CFR 158.290 Environmental Fate
162-3 Anaerobic Aquatic Metabolism
162-4 Aerobic Aquatic Metabolism
162-2 Laboratory Volatility t
164-2 Aquatic (Sediment) '
165-5 Accumulation in Non-Target Organisms
Groundwater Monitoring
40 CFR 158.490 Ecological Effects
71-4 Avian Reproduction
71-5 Simulated and Actual Field Testing- Birds
72-1 Freshwater Fish Acute Toxicity
72-2 Acute Toxicity- Freshwater Invertebrate
72-3 Acute Toxicity- Aquatic Estuarine and Marine Organism
72-5 Fish Life-Cycle
72-7 Field Testing for Aquatic Organism
5. Summary of Major Data Gaps
-The following studies are required to assess the toxicological
characteristics of technical methomyl: Eye irritation, dermal
sensitization, 21-day dermal toxicity, and general metabolism
testing (rat and monkey).
-The following data are required to fully characterize
methomyl's environmental fate: Reentry, volatility (lab),
aquatic sediment dissipation, accumulation studies in ir-
rigated crops and in fish, and groundwater monitoring.
-Additional residue and processing studies in certain commod-
ities, are required to support existing tolerances. I
-The following data are required to complete a wildlife risk
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assessment: Avian subacute dietary toxicity, avian reproduction,
freshwater fish toxicity, acute toxicity to freshwater
invertebrates, acute toxicity to estuarine and marine organisms,
fish early life stage and aquatic invertebrate life cycle,
and simulated or actual field testing for aquatic organisms and
mammals and birds.
-Product chemistry and acute toxicity data are required.
Contact person at EPA:
Dennis Edwards
Product Manager (12)
Insecticide-Rodenticide Branch
Registration Division (H7505C)
Office of Pesticide Programs
Environmental Protection Agency
401 M. Street, S.W.
Washington,D.C. 20460
Office location and telephone number:
Room 202, Crystal Mall Building #2
1921 Jefferson Davis Highway
Arlington,Va. 22202
703-557-2386
Disclaimer: The information in this Fact Sheet is a summary
only and is not to be used to satisfy data requirements for
pesticide registration and reregistration. The complete
Registration Standard for methomyl may be obtained from the
Information Services Section, Program Management and Support
Division (TS-757C), EPA, 401 M St., SW, Washington, D.C. 20460.
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