Methomyl - EPA Pesticide Fact Sheet 4/89
EPA Pesticide Fact Sheet
Name of Chemical: METHOMYL
Reason for Issuance: ISSUANCE OF REGISTRATION STANDARD
Date Issued: April 1989
Fact Sheet Number: 201
1. 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-[(methylcarbamoyl)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
- Types and method of applications: Foliar and broadcast soil
application by both ground and aircraft equipment
- Application rates: 0.1 to 1.5 lb a.i. per acre
- Types of formulations: Wettable powders, emulsifiable and soluble
concentrates, granulars, baits, and dusts
- Usual carriers: Petroleum and clay carriers
3. SCIENCE FINDINGS
Technical methomyl is a white crystalline solid with a melting point
of 78-79 degrees C. Methomyl is soluble in water and most organic
solvents. Methomyl's empirical formula is C5H10N202S and its molecular
weight is 162.2.
- 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 HDT 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 monkey are required to detect the
possible presence of acetamide in the tissues.
- Teratology: Not teratogenic or embryotoxic at HDT 400 ppm in rats.
Not teratogenic or embryotoxic at HDT 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 persistence in plants and animals:
- Plants: Available data demonstrate that methomyl is relatively
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.
- Available data are insufficient to fully assess the environmental 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.
- Acute avian oral toxicity: LD50 24.2 mg/kg for bobwhite quail (highly
- Avian dietary toxicity: LC50 of 1100, 1975, and 2883 ppm respectively
for bobwhite quail, ring-necked pheasant, and mallard duck (slightly
- Freshwater fish acute toxicity: LC50 = 1.6 ppm for Rainbow trout.
LC50 = 0.5 ppm for channel catfish (moderate to highly toxic for
- Freshwater aquatic invertebrate toxicity: LC50 values of 0.0698 to
0.343 ppm suggest that is very highly toxic to freshwater
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.
- 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 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
Contribution (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 registration of methomyl
and concluded that additional data were needed data to fully evaluate
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 supersedes the 1981 document, is the Agency's updated assessment
of the pesticide and the data needed to support its continued
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
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 eliminate 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 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 restricted 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, Brussels 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
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 identified 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 products:
- 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 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.
- 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
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
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
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
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
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, 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/Milk/Poultry
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
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 irrigated crops and in fish, and
- Additional residue and processing studies in certain commodities, are
required to support existing tolerances.
- The following data are required to complete a wildlife risk
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.
6. CONTACT PERSON AT EPA:
Product Manager (12)
Registration Division (H7505C)
Office of Pesticide Programs
Environmental Protection Agency
401 M. Street, S.W.
Office location and telephone number:
Room 202, Crystal Mall Building #2
1921 Jefferson Davis Highway
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.