Methomyl

Pesticide -> EPA IRIS

Insecticides

Active substance -> EU Pesticides database: Not approved

Pesticides -> Carbamate Insecticides

Pesticide

Pesticide (Methomyl) -> USDA PDB

log Kow= 0.60

1.24

0.6

1.2946 at 75 °F (EPA, 1998) - Denser than water; will sink

1.2946 @ 24 °C referred to water @ 4 °C

1.3 g/cm³

1.29 at 75 °F

1.2946 @ 24°C

(75 °F): 1.29

6 % at 77 °F (NIOSH, 2024)

Sol at 25 °C in wt/wt percent: water 5.8; ethanol 42; methanol 100; isopropanol 22; acetone 73

SOL IN MOST ORG SOLVENTS

In water, 58,000 mg/l @ 25 °C

Solubility in water, g/100ml at 25 °C: 5.8 (moderate)

(77 °F): 6%

When heated to decomposition it emits very toxic fumes of /nitrogen oxides & sulfur oxides/.

... /Methomyl/ decomposes rapidly in alkaline solns & in moist soils.

DT50 following leaf application /is about/ 3-5 days. Rapidly degraded to carbon dioxide & acetonitrile with incorporation into natural plant components.

172 to 174 °F (EPA, 1998)

78-79 °C

78 °C

172 °F

172 °F

5e-05 mmHg at 77 °F (EPA, 1998)

0.0000054 [mmHg]

5.4X10-6 mm Hg @ 25 °C

Vapor pressure at 25 °C: negligible

0.00005 mmHg at 77 °F

0.00005 [mm Hg] @25 °C

Methomyl is a white crystalline solid with slight sulfurous smell. Used as a nematocide, and an insecticide on vegetables, tobacco, cotton, alfalfa, soy beans, and corn. (EPA, 1998)

White, crystalline solid with a slight, sulfur-like odor. [insecticide]; [NIOSH]

WHITE CRYSTALS WITH CHARACTERISTIC ODOUR.

White, crystalline solid with a slight, sulfur-like odor.

White, crystalline solid with a slight, sulfur-like odor. [insecticide]

Danger

H300: Fatal if swallowed [Danger Acute toxicity, oral]

P264, P270, P273, P301+P316, P321, P330, P391, P405, and P501 (click each P-code to see the statement)

Danger

H300+H330 (20.4%): Fatal if swallowed or if inhaled [Danger Acute toxicity, oral; acute toxicity, inhalation]

P260, P261, P264, P270, P271, P273, P284, P301+P316, P304+P340, P316, P319, P320, P321, P330, P391, P403+P233, P405, and P501 (click each P-code to see the statement)

Commission Regulation (EC) No 451/2000

2009/115/EC, Reg. (EU) 2022/801, Reg. (EU) No 540/2011

Status: Active Update: 16-04-2020 https://echa.europa.eu/registration-dossier/-/registered-dossier/30946

Methomyl: HSNO Approval: HSR002864 Approved with controls

The New Jersey Worker and Community Right to Know Act requires public and private employers to provide information about hazardous substances at their workplaces. (N.J.S.A. 34:5A-1 et. seq.)

When heated to decomposition, it emits very toxic fumes of nitrogen oxides and sulfur oxides. Do not subject liquid formulations to temperatures below 32F. (EPA, 1998)

Combustible under specific conditions. Liquid formulations containing organic solvents may be flammable. Gives off irritating or toxic fumes (or gases) in a fire.

Classified as highly toxic, methomyl may be used only by certified applicators. The reentry interval is 1 to 7 days depending on the crop. [EXTOXNET] Allergic contact dermatitis reported in greenhouse workers; [Kanerva, p. 1812] TLV Basis: Acetylcholinesterase inhibition; male reproductive damage; Hematologic effect; [ACGIH] See CARBAMATE INSECTICIDES.

USEPA/Office of Pesticide Programs; Reregistration Eligibility Decision Document - Methomyl EPA 738-R-98-021. The RED summarizes the risk assessment conclusions and outlines any risk reduction measures necessary for the pesticide to continue to be registered in the U.S.[Available from, as of April 30, 2003: http://www.epa.gov/pesticides/reregistration/status.htm]

WHO; Environ Health Criteria 178: Methomyl (1996). The criteria monographs are intended to provide critical reviews on the effect on human health and the environment of chemicals and of combinations of chemicals and physical and biological agents.

(Non-Specific -- Carbamate Pesticide, Solid) Wear self-contained breathing apparatus.

Use water spray, foam, powder, carbon dioxide.

Fresh air, rest. Half-upright position. Refer for medical attention.

Remove contaminated clothes. Rinse skin with plenty of water or shower.

First rinse with plenty of water for several minutes (remove contact lenses if easily possible), then refer for medical attention.

Give a slurry of activated charcoal in water to drink. Refer immediately for medical attention.

Signs and Symptoms of Acute Methomyl Exposure: Acute exposure to methomyl usually leads to a cholinergic crisis. Signs and symptoms may include increased salivation, lacrimation (tearing), spontaneous defecation, and spontaneous urination. Pinpoint pupils, blurred vision, tremor, muscle twitching, and loss of muscle coordination may occur. Mental confusion, convulsions, and coma may also be noted. Gastrointestinal effects include nausea, vomiting, diarrhea, and abdominal pain. Bradycardia (slow heart rate) occurs frequently. Dyspnea (shortness of breath), pulmonary edema, and respiratory arrest may also occur.

(General first aid procedures)

Biological Exposure Indices (BEI) [ACGIH] - Acetylcholinesterase activity in red blood cells = 70% of individual's baseline; Butylcholinesterase activity in serum or plasma = 60% of individual's baseline; Sample at end of shift; [TLVs and BEIs]

A system for removing pesticides from the wash water produced by pesticide applicators as they clean their equipment has been developed. The first step is the flocculation/coagulation and sedimentation of the pesticide-contaminated wash water. The supernatant from the first step is then passed through activated carbon columns. /Pesticides/

Generators of waste (equal to or greater than 100 kg/mo) containing this contaminant, EPA hazardous waste number P066, must conform with USEPA regulations in storage, transportation, treatment and disposal of waste.

Landfill: The aqueous soln is noncorrosive. It is stable as a solid, in aqueous soln under normal conditions but is subject to decomposition in moist soil.

Hydrolysis: Alkaline hydrolysis leads to complete degradation. Carbonate, methylamine, and 5-methyl-n-hydroxylthioacetamidate are nontoxic. Recommendable methods: Incineration, landfill. Peer-review: Dissolve methomyl in water and spray into a furnace with effluent gas scrubbing. (Peer-review conclusions of an IRPTC expert consultation (May 1985))

Potential candidate for disposal by rotary kiln incineration with a temperature range of 820-1600 °C and a residence time of seconds for liquids and gases, and hours for solids. Also a potential candidate for fluidized bed incineration with a temperature range of 450-980 °C, with a residence time of seconds for liquids and gases, and longer for solids.

Personal protection: particulate filter respirator adapted to the airborne concentration of the substance. Do NOT let this chemical enter the environment. Sweep spilled substance into covered sealable containers. If appropriate, moisten first to prevent dusting. Carefully collect remainder. Then store and dispose of according to local regulations.

Smoking, eating and drinking before washing should be absolutely prohibited when any pesticide of moderate or higher toxicity is being handled or used. /Pesticides/

The worker should immediately wash the skin when it becomes contaminated.

Work clothing that becomes wet or significantly contaminated should be removed and replaced.

Workers whose clothing may have become contaminated should change into uncontaminated clothing before leaving the work premises.

SRP: The scientific literature for the use of contact lenses in industry is conflicting. The benefit or detrimental effects of wearing contact lenses depend not only upon the substance, but also on factors including the form of the substance, characteristics and duration of the exposure, the uses of other eye protection equipment, and the hygiene of the lenses. However, there may be individual substances whose irritating or corrosive properties are such that the wearing of contact lenses would be harmful to the eye. In those specific cases, contact lenses should not be worn. In any event, the usual eye protection equipment should be worn even when contact lenses are in place.

If the compound has been ingested, rapid gastric lavage should be performed using 5% sodium bicarbonate. For skin contact, the skin should be washed with soap and water. If the compound has entered the eyes, they should be washed with large quantities of isotonic saline or water. In serious cases, atropine and/or pralidoxime should be administered. Anti-cholinergic drugs work to counteract the effects of excess acetylcholine and reactivate AChE. Atropine can be used as an antidote in conjunction with pralidoxime or other pyridinium oximes (such as trimedoxime or obidoxime), though the use of '-oximes' has been found to be of no benefit, or possibly harmful, in at least two meta-analyses. Atropine is a muscarinic antagonist, and thus blocks the action of acetylcholine peripherally.

... The effects of common agricultural carbamate insecticides, aldicarb and methomyl, and a triazine herbicide, metribuzin, on hormone levels in Sprague-Dawley rats /were examined/. Fifty-four female rats were sampled at 2 and 6 wk during a 6-wk exposure to individual chemicals or to combinations of them. ... Rats treated with the herbicide (metribuzin) were hyperthyroid. The interactions of all three chemicals also significantly increased thyroxine levels. ... These experiments /were reported/ for 16 wk using 54 male rats; the results were very similar. Metribuzin alone significantly increased thyroxine throughout the second study (at 7, 13, and 16 wk). Somatotropin levels were significantly altered after 13 wk of exposure. The same concentrations and mixtures of these three pesticides have now been shown to be implicated in learning impairment and other neurological functions, immune parameter changes, and endocrine changes. These findings support the concept of the interconnectedness of the nervous, endocrine, and immune systems and raise the likelihood of impacts on all three systems if one is shown to be affected. ...

Combined effects of pesticides & ozone pollutants on pinto bean seedlings were examined. The insecticides diazinon & methomyl were applied to pinto bean seedlings at the recommended concns of 1 oz/3 gal water & 0.5 lb/100 gal water respectively. Both insecticides interacted with ozone applied at rates of 30 /part per hundred/ to produce /noteworthy/ alterations in foliar injury for the bean seedlings.

Compounds with synergistic effects (assessed as either excess mortality or greater inhibition of blood cholinesterase activity) included carbaryl, ronnel, methyl parathion, & mevinphos. Dimethoate was antagonistic; a mixture with methomyl inhibited cholinesterase 53% less than predicted. Compounds producing only additive effects included endosulfan & diflubenzuron. In mice, pretreatment with butylated hydroxyanisole (BHA) for 4 days reduced the LD50 of methomyl by a factor of 2.2-3.2.

Oximes may form a toxic complex with the carbamate & may diminish atropine effectiveness, & in many cases, are not necessary to revert the intoxication.

Immune

Eyes, respiratory system, central nervous system, cardiovascular system, liver, kidneys, blood cholinesterase

Acute exposure to cholinesterase inhibitors can cause a cholinergic crisis characterized by severe nausea/vomiting, salivation, sweating, bradycardia, hypotension, collapse, and convulsions. Increasing muscle weakness is a possibility and may result in death if respiratory muscles are involved. Accumulation of ACh at motor nerves causes overstimulation of nicotinic expression at the neuromuscular junction. When this occurs symptoms such as muscle weakness, fatigue, muscle cramps, fasciculation, and paralysis can be seen. When there is an accumulation of ACh at autonomic ganglia this causes overstimulation of nicotinic expression in the sympathetic system. Symptoms associated with this are hypertension, and hypoglycemia. Overstimulation of nicotinic acetylcholine receptors in the central nervous system, due to accumulation of ACh, results in anxiety, headache, convulsions, ataxia, depression of respiration and circulation, tremor, general weakness, and potentially coma. When there is expression of muscarinic overstimulation due to excess acetylcholine at muscarinic acetylcholine receptors symptoms of visual disturbances, tightness in chest, wheezing due to bronchoconstriction, increased bronchial secretions, increased salivation, lacrimation, sweating, peristalsis, and urination can occur. Chronically high (>10 years) exposure leads to neuropsychological consequences including disturbances in perception and visuo-motor processing (A15321).

LD50 8-MO OLD MALE MALLARD ORAL 15.9 MG/KG (95% CONFIDENCE LIMIT 11.4-22.0 MG/KG /SAMPLE PURITY 90%/

LD50 3-4-MO OLD MALE PHEASANT ORAL 15.0 MG/KG (95% CONFIDENCE LIMIT 10.0-22.3 MG/KG /SAMPLE PURITY 90%/

LD50 13-MO OLD MALE MULE DEER ORAL 11.0-22.0 MG/KG /SAMPLE PURITY 90%/

LC50 14-DAY OLD BOBWHITE QUAIL ORAL APPROX 1100 PPM IN 5-DAY DIET

For more Ecotoxicity Values (Complete) data for METHOMYL (38 total), please visit the HSDB record page.

ONE DOES NOT EXPECT TO FIND RESIDUES OF ... METHOMYL IN SOIL BEYOND GROWING SEASON DURING WHICH IT WAS APPLIED. VERY LITTLE DATA ON BEHAVIOR OF ALDICARB & METHOMYL IN WATER ARE AVAILABLE. IN STUDY OF POND & LAKE WATER, HALF-LIFE OF 5 DAYS & 6 DAYS WERE DETERMINED FOR ALDICARB & METHOMYL, RESPECTIVELY.

IN SOIL, LABELED METHOMYL WAS DEGRADED TO (14)CO2 & OTHER MATERIALS, SOME OF WHICH WERE REINCORPORATED INTO NORMAL COMPONENTS OF SOIL ORG MATTER.

TERRESTRIAL FATE: Methomyl effectively controlled fall armyworm larvae in stands of Coastal Bermuda grass. Residues of methomyl declined rapidly with time after application, and by 7 days about 7% of the initial deposit remained regardless of the rate of application. Methomyl loss during dehydration in a natural gas dryer was approx 54%. The pelletizing process caused an additional loss of approx 14%. Thus, the total loss of methomyl during processing of green hay to pellets amounted to approx 68%. Losses of residues during air curing of hay in the field amounted to approx 37%.

TERRESTRIAL FATE: Based on a classification scheme(1), a Koc value of 160(2), indicates that methomyl is expected to have moderate mobility in soil(SRC). Volatilization of methomyl from moist soil surfaces is not expected to be an important fate process(SRC) given an estimated Henry's Law constant of 1.9X10-11 atm-cu m/mole(SRC), derived from its vapor pressure, 5.4X10-6 mm Hg(3), and water solubility, 58,000 mg/l(4). Methomyl is not expected to volatilize from dry soil surfaces(SRC) based upon its vapor pressure(3). Methomyl degrades readily in soils, with half-lives of 3-14 days reported in 3 different greenhouse soils(5) and 5-6 weeks in tobacco growing soils(6).

For more Environmental Fate (Complete) data for METHOMYL (6 total), please visit the HSDB record page.

Methomyl was detected in 15 of 319 food samples analyzed between 1980 and 1983 at the following concn: cabbage, 0.02-0.41 ppm; cantaloupe, 0.02 ppm; cucumbers, 0.04 ppm; grapes, 0.01-0.04 ppm; lettuce, 0.12 ppm; romaine, 0.02 ppm; squash, 0.06 ppm; potatoes, below 0.01 ppm(1). One market basket from USA FDA's Total Diet Program for 1983 contained 0.07 ppm methomyl in boiled collards and 0.067 ppm methomyl in raw strawberries(1). Methomyl was found in 126 of 19,851 domestic and imported food and feed commodities obtained in Los Angeles, CA, 1982-86, at a concn of 0.05-2.0 ppm (4 samples at a concn >2 ppm)(2). Methomyl was identified, not quantified, in 121 of 6,391 domestic commodities and 5 of 12,044 imported commodities(3).

The substance can be absorbed into the body by inhalation of its aerosol and by ingestion.

inhalation, ingestion, skin and/or eye contact

Inhalation (L793) ; oral (L793); dermal (L793)

Methomyl is a cholinesterase or acetylcholinesterase (AChE) inhibitor. Carbamates form unstable complexes with chlolinesterases by carbamoylation of the active sites of the enzymes. This inhibition is reversible. A cholinesterase inhibitor suppresses the action of acetylcholine esterase. Because of its essential function, chemicals that interfere with the action of acetylcholine esterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses. Headache, salivation, nausea, vomiting, abdominal pain and diarrhea are often prominent at higher levels of exposure. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop.

The average daily intake of methomyl as determined by a market basket study conducted from April 1982 to April 1984 was as follows: 6-11 month olds 1.5 ng/kg body weight (bw)/day; 2 year olds 0.1 ng/kg bw/day; 14-16 year old females 1.3 ng/kg bw /day; 14- 16 year old males 1.2 ng/kg bw/day; 25-30 year old females 1.5 ng/kg bw/day; 25-30 year old males 0.9 ng/kg bw/day; 60-65 year old females 2.3 ng/kg bw/day; 60-65 year old males 2.1 ng/kg bw/day(1).

/BIRDS and MAMMALS/ Methomyl (S-methyl-N-((methylcarbamoyl)oxy) thioacetimidate) toxicity was studied in horses using iv dosages from 0.01 to 3.0 mg/kg. Doses of 1-3 mg methomyl/kg produced increased GI motility and respirations, facial fasiculations, salivation, lacrimation and convulsions. The only effect at 0.5 mg/kg was increased GI sounds in 1/4 horses. This extensively used crop insecticide had been associated with episodes of morbidity and mortality and led to speculation that it was extremely potent to the horse. This was not supported by these clinical studies.

/BIRDS and MAMMALS/ SIGNS OF INTOXICATION /IN MALLARDS FROM ACUTE ORAL EXPOSURE/: HIGH CARRIAGE, ATAXIA, DROWSINESS, TACHYPNEA, DYSPNEA, SALIVATION, TENESMUS, DIARRHEA, TREMORS, TETANY, OR WING-BEAT CONVULSIONS.

/BIRDS and MAMMALS/ 30-DAY EMLD /EMPIRICAL MINIMUM LETHAL DOSAGE/ FOR 17- TO 22-WK-OLD MALLARDS... IS 7.5 MG/KG/DAY FOR BOTH SEXES. THE RESULTING CUMULATIVE TOXICITY INDEX IS 15.9/7.5 = 2.1, INDICATING LITTLE OR NO CUMULATIVE TOXIC ACTION. /SAMPLE PURITY 90%/

/AQUATIC SPECIES/ /Data from acute toxicity studies on fathead minnows exposed to LC50 concn of 99% pure methomyl for 96 hr showed that/ affected fish lost schooling behavior, were hyperactive & swam near the tank surface. They were also overreactive to external stimuli, had incr resp, were darkly colored & lost equilibrium prior to death.

For more Ecotoxicity Excerpts (Complete) data for METHOMYL (8 total), please visit the HSDB record page.

P066; As stipulated in 40 CFR 261.33, when methomyl, as a commercial chemical product or manufacturing chemical intermediate or an off-specification commercial chemical product or a manufacturing chemical intermediate, becomes a waste, it must be managed according to federal and/or state hazardous waste regulations. Also defined as a hazardous waste is any container or inner liner used to hold this waste or any residue, contaminated soil, water, or other debris resulting from the cleanup of a spill, into water or on dry land, of this waste. Generators of small quantities of this waste may qualify for partial exclusion from hazardous waste regulations (40 CFR 261.5(e)).

Based on the reviews of the generic data for the active ingredient methomyl, the ... /United States Environmental Protection Agency/ has sufficient information on the health effects of methomyl and on its potential for causing adverse effects in fish and wildlife and the environment. The Agency has determined that methomyl products, labeled and used as specified in the Reregistration Eligibility Decision, will not pose unreasonable risks to humans or the environment.

As the federal pesticide law FIFRA directs, EPA is conducting a comprehensive review of older pesticides to consider their health and environmental effects and make decisions about their future use. Under this pesticide reregistration program, EPA examines health and safety data for pesticide active ingredients initially registered before November 1, 1984, and determines whether they are eligible for reregistration. In addition, all pesticides must meet the new safety standard of the Food Quality Protection Act of 1996. Methomyl is found on List A, which contains most food use pesticides and consists of the 194 chemical cases (or 350 individual active ingredients) for which EPA issued registration standards prior to FIFRA '88. Case No: 0028; Pesticide type: insecticide; Registration Standard Date: 01/01/81, 04/89; ... Active ingredient (AI): methomyl; Data Call-in (DCI) Date(s): 10/13/95; AI Status: The producers of the pesticide have made commitments to conduct the studies and pay the fees required for reregistration, and are meeting those commitments in a timely manner.

Tolerances are established for residues of the insecticide methomyl (S-methyl N-((methylcarbamoyl)oxy)thioacetimidate) in or on certain raw agricultural commodities as follows: alfalfa; apples; asparagus; avocado; barley (grain); barley (hay); barley (straw); beans (dry); beans (forage); beans (succulent); beets (tops); blueberry; broccoli; brussel sprouts; cabbage; cauliflower; celery; chinese cabbage; collards; corn (fodder); corn (forage); corn (fresh, including sweet Kernel and corn with husk removed; corn (grain, including pop); cottonseed; cucurbits; dandelions; endive (escarole); grapefruit; grapes; grass (Bermuda); grass (Bermuda, hay, dried and dehydrated); hop, dried cone (There are no U.S. registrations for use of methomyl on hop, dried cone, as of February 14, 1990); kale; leek; lemons; lentils; lettuce; mint (hay); mustard greens; nectarines; oats (forage); oats (grain); oats (hay); oats (straw); onions (green); oranges; parsley; peaches; peanuts; pea; pea (vines); pecans; peppers; pomegranates; rye (forage); rye (grain); rye (hay); rye (straw); sorghum (forage); sorghum (grain); soybeans; soybeans (forage); spinach; strawberries; swiss chard; tangerines; tomatoes; turnip greens (tops); vegetables, brassica, leafy, group; vegetable (fruiting); vegetables, leafy [except for beets (tops), broccoli, brussel sprouts, cabbage, cauliflower, celery, Chinese cabbage, collards, dandelions, endive (escarole), kale, lettuce, mustard greens, parsley, spinach, Swiss chard, turnip greens (tops), and watercress; vegetables (root crop); watercress; wheat (forage); wheat (grain); wheat (hay); wheat (straw).

Tolerances with regional registration are established for residues of methomyl in or on pears.

For more FIFRA Requirements (Complete) data for METHOMYL (11 total), please visit the HSDB record page.

Persons in charge of vessels or facilities are required to notify the National Response Center (NRC) immediately, when there is a release of this designated hazardous substance, in an amount equal to or greater than its reportable quantity of 100 lb or 45.4 kg. The toll free number of the NRC is (800) 424-8802; In the Washington D.C. metropolitan area (202) 426-2675. The rule for determining when notification is required is stated in 40 CFR 302.4 (section IV. D.3.b).

Releases of CERCLA hazardous substances are subject to the release reporting requirement of CERCLA section 103, codified at 40 CFR part 302, in addition to the requirements of 40 CFR part 355. Methomyl is an extremely hazardous substance (EHS) subject to reporting requirements when stored in amounts in excess of its threshold planning quantity (TPQ) of 500 or 10,000 lbs. Extremely hazardous substances that are solids are subject to either of two threshold planning quantities ... The lower quantity applies only if the solid exists in powdered form and has a particle size less than 100 microns; or is handled in solution or in molten form; or meets the criteria for a National Fire Protection Association (NFPA) rating of 2, 3 or 4 for reactivity. If the solid does not meet any of these criteria, it is subject to the upper ... threshold planning quantity ... .

(AZ) ARIZONA 180 ug/l

(ME) MAINE 175 ug/l

INHIBITION OF ACETYLCHOLINESTERASE.

Methomyl was among 24 pesticides tested for interactions with the estrogen receptor (ER) and the androgen receptor (AR) in transactivation assays. Estrogen-like effects on MCF-7 cell proliferation and effects on CYP19 aromatase activity in human placental microsomes were also investigated. Methomyl weakly stimulated aromatase activity.

Lannate 1 -(methomyl) was incubated with erythrocytes of rats at different concentrations. ... There was a decrease in the activities of superoxide dismutase and glutathione reductase after 1/2 and 16 hour of Lannate addition. There was also a decrease in the amount of glutathione. The inhibition of enzyme activities and the decrease in glutathione concentration were dose independent. The results suggest that Lannate toxicity might lead to hemolysis, oxidation of hemoglobin and finally induced erythropenia. /Lannate/

(14)C-METHOMYL ... WAS BIOTRANSFORMED IN RATS INTO (14)CO2 (ABOUT 25%), ACETONITRILE (ABOUT 50%), & UNIDENTIFIED URINARY METABOLITES (ABOUT 25%). ABSENCE IN URINE OF PARENT OXIME & ... SULFOXIDE & SULFONE OF PARENT CMPD WAS CONFIRMED BY COMPARISON STUDIES WITH AUTHENTIC MATERIAL.

... METABOLISM OF METHOMYL IS PRIMARILY BY HYDROLYTIC ROUTE. PRINCIPAL METABOLITES FOUND IN URINE FOLLOWING TREATMENT OF RATS WITH (14)C-LABELED METHOMYL WERE OXIME-O-SULFATE, FREE OXIME, OXIME GLUCURONIDE ... .

Methomyl can exist in 2 geometric configurations. ... In rats, carbonyl- or oximino-labeled syn-methomyl was metabolized to carbon dioxide & acetonitrile at a 2:1 ratio. In contrast, the anti isomer was metabolized predominately to acetonitrile. It was concluded on the basis of this & other evidence that a Beckman rearrangement of the syn & anti oximes occurs prior to formation of carbon dioxide & acetonitrile.

In rats, methomyl was rapidly converted to methomyl methylol, oxime, sulfoxide, & sulfoxide oxime; these unstable intermediates were converted to acetonitrile & carbon dioxide, which were eliminated primarily via respiration & in the urine.

For more Metabolism/Metabolites (Complete) data for METHOMYL (7 total), please visit the HSDB record page.

The carbamates are hydrolyzed enzymatically by the liver; degradation products are excreted by the kidneys and the liver. (L793)

Drugs that inhibit cholinesterases. The neurotransmitter ACETYLCHOLINE is rapidly hydrolyzed, and thereby inactivated, by cholinesterases. When cholinesterases are inhibited, the action of endogenously released acetylcholine at cholinergic synapses is potentiated. Cholinesterase inhibitors are widely used clinically for their potentiation of cholinergic inputs to the gastrointestinal tract and urinary bladder, the eye, and skeletal muscles; they are also used for their effects on the heart and the central nervous system.

Pesticides designed to control insects that are harmful to man. The insects may be directly harmful, as those acting as disease vectors, or indirectly harmful, as destroyers of crops, food products, or textile fabrics.

EXPIRED AIR COLLECTED FOLLOWING ADMIN OF /LABELLED/ METHOMYL TO RATS CONTAINED LABELED CO2 & ACETONITRILE.

... The course of therapy & symptoms for a patient who had attempted suicide by ingesting about 2.25 g of methomyl /was reported/. At 6 hr postingestion, methomyl was present in the blood at 1.61 ppm & in the urine at 10.91 ppm; at 15 hr, levels were 0.04 ppm in the blood & 0.25 ppm in the urine; & at 22 hr, methomyl was not detectable in the samples.

Near complete (95-98%) absorption of a single 5 mg/kg oral dose of 14 carbon-labeled methomyl occurred in female CD or male rats. Male rats fed 14 carbon-labeled methomyl eliminated almost all of the labeled material in 24 hr. 10% or less of the original radiolabel was found in the whole body & organs one day after treatment. Urine (25%), respiratory carbon dioxide (25%), & acetonitrile (50%) accounted for most of the recovered radioactivity. No parent methomyl appeared in the urine.

One hour after the dermal applications of (14)C-methomyl to mice ..., 2.9% of the dose was present in blood, 5% in liver and 56% in the remaining carcass. After 8 h the distribution was 6.1% in blood, 3.3% in liver, 3.8% in the gastrointestinal tract and smaller amounts (< 1%) in other individual tissues. The remaining carcass contained 15% of the original dose ... .

For more Absorption, Distribution and Excretion (Complete) data for METHOMYL (8 total), please visit the HSDB record page.

Used to kill insects on vegetables, fruits, cotton, ornamentals, and field crops; also used in animal confinement areas and to kill ticks, spiders, and flies; [EXTOXNET]

Farming (Pesticides) [Category: Industry]

For Methomyl (USEPA/OPP Pesticide Code: 090301) ACTIVE products with label matches. /SRP: Registered for use in the U.S. but approved pesticide uses may change periodically and so federal, state and local authorities must be consulted for currently approved uses./

NEMATOCIDE

INSECTICIDE ON VEGETABLES, TOBACCO, COTTON, ALFALFA, SOYBEANS, & CORN

Control of a wide range of insects and spider mites in fruit, vegetables, olives, hops, vines, ornamentals, field crops, flax, cotton, tobacco, soy beans, etc...

ABOUT 50% AS AN INSECTICIDE ON VEGETABLES; ABOUT 50% AS AN INSECTICIDE ON ALFALFA, CORN, COTTON, SOYBEANS, & TOBACCO (1974)

Alfalfa, 17.8%; Grapes, 9.8%; Lettuce, 26%; Sugarbeets, 6.1%; Tomatoes, 8.6%; Citrus, 3.9%; Other vegetables account for most of remainder, 18.1% (1984) /California use, calculated from table/

4.39X10+8 g /Used in California/

USEPA/OPP Pesticide Code 090301; Trade Names: Lannate, Nudrin, Dupont 1179, IN 1179, Insecticide 1179, Mesomile, SD 14999, WL 18236, Lanox 90, Lanox 216, Nu-Bait II, Lurectoron flybait (090301+103201).

Lannate, SP (900 g ai/kg); Lannate L, SL (220 g/l). Mixtures include: Flytek (Zoecon), RB (10 g methomyl + 0.25 g (Z)-tricos-9-ene); methomyl + fenson.

Liquid (1.8 lb ai/gal), low volatility liquid formulation (2.4 lb ai/gal), Lannate LV), 90% water-soluble powder.

"Lannate" LV Insecticide (29% methomyl contains methanol).

Methomyl is a mixture of (Z)- and (E)- isomers (the former predominating)

The WHO Recommended Classification of Pesticides by Hazard identifies Methomyl (technical grade) as Class IB: highly hazardous; Main Use: insecticide.

It was introduced, in 1966, as exptl insecticide-nematocide by EI Du Pont de nemours & Co ... under code number "Du Pont 1179", trade mark 'Lannate' & protected by US patent 3576834 & 3639633. ... following soil treatment it is taken up by roots & translocated ... this method is generally less effective than foliar treatment.

Nu-Bait III, produced by Griffin Corp, has been discontinued

An insecticide microcapsule consisting essentially of a core of methomyl surrounded by a cover of non-crosslinked, all aromatic polyurea. The polyurea is formed by dispersing a solution of methylene chloride, methomyl, and toluene-2,4-diisocyanate of at least 95% purity in aqueous medium creating a dispersion of liquid microspheres. The ratio of toluene-2,4-diisocyanate to methomyl is 1:4 to 3:1 by weight and the ratio of methylene chloride to methomyl is about 2:1 to 3:1 by weight. Hardening the liquid microspheres is achieved by adding an aqueous alkali to the dispersion with the ratio of aqueous alkali to toluene-2,4-diisocyanate being about 0.25:2 to 2:1 on a molar basis and removing the methylene chloride.