methomyl

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

H400: Very toxic to aquatic life [Warning Hazardous to the aquatic environment, acute hazard]

H410: Very toxic to aquatic life with long lasting effects [Warning Hazardous to the aquatic environment, long-term hazard]

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

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

H300 (100%): Fatal if swallowed [Danger Acute toxicity, oral]

H330 (30.6%): Fatal if inhaled [Danger Acute toxicity, inhalation]

H336 (29.3%): May cause drowsiness or dizziness [Warning Specific target organ toxicity, single exposure; Narcotic effects]

H400 (100%): Very toxic to aquatic life [Warning Hazardous to the aquatic environment, acute hazard]

H410 (100%): Very toxic to aquatic life with long lasting effects [Warning Hazardous to the aquatic environment, long-term hazard]

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)

Aggregated GHS information provided per 147 reports by companies from 8 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.

Information may vary between notifications depending on impurities, additives, and other factors. The percentage value in parenthesis indicates the notified classification ratio from companies that provide hazard codes. Only hazard codes with percentage values above 10% are shown. For more detailed information, please visit ECHA C&L website.

H301: Toxic if swallowed [Danger Acute toxicity, oral]

H312: Harmful in contact with skin [Warning Acute toxicity, dermal]

H330: Fatal if inhaled [Danger Acute toxicity, inhalation]

H370: Causes damage to organs [Danger Specific target organ toxicity, single exposure]

H373: May causes damage to organs through prolonged or repeated exposure [Warning Specific target organ toxicity, repeated exposure]

P260, P264, P270, P271, P280, P284, P301+P316, P302+P352, P304+P340, P308+P316, P316, P317, P319, P320, P321, P330, P362+P364, P403+P233, P405, and P501 (click each P-code to see the statement)

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.

Emergency Life-Support Procedures: Acute exposure to methomyl may require decontamination and life support for the victims. Emergency personnel should wear protective clothing appropriate to the type and degree of contamination. Air-purifying or supplied-air respiratory equipment should also be worn, as necessary. Rescue vehicles should carry supplies such as plastic sheeting and disposable plastic bags to assist in preventing spread of contamination.

Inhalation Exposure:

1. Move victims to fresh air. Emergency personnel should avoid self-exposure to methomyl.

2. Evaluate vital signs including pulse and respiratory rate, and note any trauma. If no pulse is detected, provide CPR. If not breathing, provide artificial respiration. If breathing is labored, administer oxygen or other respiratory support.

3. Obtain authorization and/or further instructions from the local hospital for administration of an antidote or performance of other invasive procedures.

4. Transport to a health care facility.

Dermal/Eye Exposure:

1. Remove victims from exposure. Emergency personnel should avoid self- exposure to methomyl.

3. Remove contaminated clothing as soon as possible.

4. If eye exposure has occurred, eyes must be flushed with lukewarm water for at least 15 minutes.

5. Wash exposed skin areas three times with soap and water.

6. Obtain authorization and/or further instructions from the local hospital for administration of an antidote or performance of other invasive procedures.

7. Transport to a health care facility.

Ingestion Exposure:

1. Evaluate vital signs including pulse and respiratory rate, and note any trauma. If no pulse is detected, provide CPR. If not breathing, provide artificial respiration. If breathing is labored, administer oxygen or other respiratory support.

2. Obtain authorization and/or further instructions from the local hospital for administration of an antidote or performance of other invasive procedures.

3. Vomiting may be induced with syrup of Ipecac. If elapsed time since ingestion of methomyl is unknown or suspected to be greater than 30 minutes, do not induce vomiting and proceed to Step

4.Ipecac should not be administered to children under 6 months of age.Warning: Ingestion of methomyl may result in sudden onset of seizures or loss of consciousness. Syrup of Ipecac should be administered only if victims are alert, have an active gag-reflex, and show no signs of impending seizure or coma. If ANY uncertainty exists, proceed to Step

4.The following dosages of Ipecac are recommended: children up to 1 year old, 10 mL (1/3 oz); children 1 to 12 years old, 15 mL (1/2 oz); adults, 30 mL (1 oz). Ambulate (walk) the victims and give large quantities of water. If vomiting has not occurred after 15 minutes, Ipecac may be readministered. Continue to ambulate and give water to the victims. If vomiting has not occurred within 15 minutes after second administration of Ipecac, administer activated charcoal.

4. Activated charcoal may be administered if victims are conscious and alert. Use 15 to 30 g (1/2 to 1 oz) for children, 50 to 100 g (1-3/4 to 3-1/2 oz) for adults, with 125 to 250 mL (1/2 to 1 cup) of water.

5. Promote excretion by administering a saline cathartic or sorbitol to conscious and alert victims. Children require 15 to 30 g (1/2 to 1 oz) of cathartic; 50 to 100 g (1-3/4 to 3-1/2 oz) is recommended for adults.

6. Transport to a health care facility. (EPA, 1998)

(General first aid procedures)

Eye: Irrigate immediately - If this chemical contacts the eyes, immediately wash (irrigate) the eyes with large amounts of water, occasionally lifting the lower and upper lids. Get medical attention immediately.

Skin: Water flush immediately - If this chemical contacts the skin, immediately flush the contaminated skin with water. If this chemical penetrates the clothing, immediately remove the clothing and flush the skin with water. Get medical attention promptly.

Breathing: Respiratory support

Swallow: Medical attention immediately - If this chemical has been swallowed, get medical attention immediately.

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

(Non-Specific -- Carbamate Pesticide, Solid) Use agent suitable for type of surrounding fire. Use water in flooding quantities as a fog. Use alcohol foam, carbon dioxide, or dry chemical. (EPA, 1998)

Use water spray, foam, powder, carbon dioxide.

Excerpt from ERG Guide 151 [Substances - Toxic (Non-Combustible)]:

IMMEDIATE PRECAUTIONARY MEASURE: Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters (75 feet) for solids.

SPILL: Increase the immediate precautionary measure distance, in the downwind direction, as necessary.

FIRE: If tank, rail tank car or highway tank is involved in a fire, ISOLATE for 800 meters (1/2 mile) in all directions; also, consider initial evacuation for 800 meters (1/2 mile) in all directions. (ERG, 2024)

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.

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.

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.

Caution : Flammable. Avoid sources of extreme heat or ignition including sparks or fire. Methomyl will liberate toxic nitrogen and sulfur oxide fumes when heated to decomposition.

(Non-Specific -- Carbamate Pesticide, Solid) Keep unnecessary people away; isolate hazard areas and deny entry. Stay upwind and keep out of low areas. Do not touch spilled material, or handle broken packages without protective equipment. Do not breathe dust, vapors, or the fumes from burning material. (EPA, 1998)

Store in an area without drain or sewer access. Dry. Keep in a well-ventilated room. Separated from strong bases and food and feedstuffs.

Keep /liq formulations/ away from heat, sparks, & open flame. Do not subject liquid to temperatures below 32 °F.

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]

AEGL 1: Notable discomfort, irritation, or certain asymptomatic non-sensory effects. However, the effects are not disabling and are transient and reversible upon cessation of exposure (Unit: mg/m3)

AEGL 2: Irreversible or other serious, long-lasting adverse health effects or an impaired ability to escape (Unit: mg/m3)

AEGL 3: Life-threatening health effects or death (Unit: mg/m3)

7.0 mg/m3

21 mg/m3

5.7 mg/m3

17 mg/m3

3.3 mg/m3

10 mg/m3

1.7 mg/m3

5.2 mg/m3

NOTE THAT VALUES ARE IN mg/m3. Not ppm.

AEGLs Status: Proposed

5.0 [mg/m3]

10 [mg/m3]

13 [mg/m3]

2.5 mg/m³

TWA 2.5 mg/m3

none See Appendix G

See: IDLH INDEX

0.2 [mg/m3], inhalable fraction and vapor

8 hr Time Weighted Avg (TWA): 2.5 mg/cu m.

Excursion Limit Recommendation: Excursions in worker exposure levels may exceed 3 times the TLV-TWA for no more than a total of 30 minutes during a work day, and under no circumstances should they exceed 5 times the TLV-TWA, provided that the TLV-TWA is not exceeded.

A4; Not classifiable as a human carcinogen.

Biological Exposure Index (BEI): Determinant: cholinesterase activity in red blood cells; Sampling Time: discretionary; BEI: 70% of individual's baseline. The determinant is nonspecific, since it is also observed after exposure to other chemicals. /Acetylcholinesterase inhibiting pesticides/

0.2 mg/m

0.2 mg/m³ (inhalable fraction and vapor) [2013]

A harmful contamination of the air will not or will only very slowly be reached on evaporation of this substance at 20 °C; on spraying or dispersing, however, much faster.

The substance is irritating to the eyes. The substance may cause effects on the nervous system. This may result in convulsions and respiratory depression. Cholinesterase inhibition. Exposure far above the OEL could cause death.

The substance may have effects on the blood. This may result in anaemia.

Tolerances are established for residues of the insecticide methomyl (S-methyl N-((methylcarbamoyl)oxy)thioacetimidate) in or on raw agricultural commodities as follows: alfalfa: 10 ppm; apples: 1 ppm; asparagus: 2 ppm; avocado: 2 ppm; barley (grain): 1 ppm; barley (hay): 10 ppm; barley (straw): 10 ppm; beans (dry): 0.1 ppm (negligible residues); beans (forage): 10 ppm; beans (succulent): 2 ppm; beets (tops): 6 ppm; blueberry: 6 ppm; broccoli: 3 ppm; brussel sprouts: 2 ppm; cabbage: 5 ppm; cauliflower: 2 ppm; celery: 3 ppm; chinese cabbage: 5 ppm; collards: 6 ppm; corn (fodder): 10 ppm; corn (forage): 10 ppm; corn (fresh, including sweet Kerrnel and corn with husk removed 0.1 ppm (negligible residues); corn (grain, including pop): 0.1 ppm (negligible residues); cottonseed: 0.1 ppm (negligible residues); cucurbits: 0.2 ppm (negligible residues); dandelions: 6 ppm; endive (escarole): 5 ppm; grapefruit: 2 ppm; grapes: 5 ppm; grass (Bermuda): 10 ppm; grass (Bermuda, hay, dried and dehydrated): 40 ppm; hop, dried cone: 12 ppm (There are no U.S. registrations for use of methomyl on hop, dried cone, as of February 14, 1990); kale: 6 ppm; leek: 3.0 ppm; lemons: 2 ppm; lentils: 0.1 ppm; lettuce: 5 ppm; mint (hay): 2 ppm; mustard greens: 6 ppm; nectarines: 5 ppm; oats (forage): 10 ppm; oats (grain): 1 ppm; oats (hay): 10 ppm; oats (straw): 10 ppm; onions (green): 3 ppm; oranges: 2 ppm; parsley: 6 ppm; peaches: 5 ppm; peanuts: 0.1 ppm (negligible residues); pea: 5 ppm; pea (vines): 10 ppm; pecans: 0.1 ppm; peppers: 2 ppm; pomegranates: 0.2 ppm (negligible residues); rye (forage): 10 ppm; rye (grain): 1 ppm; rye (hay): 10 ppm; rye (straw): 10 ppm; sorghum (forage): 1 ppm; sorghum (grain): 0.2 ppm (negligible residues); soybeans: 0.2 ppm (negligible residues); soybeans (forage): 10 ppm; spinach: 6 ppm; strawberries: 2 ppm; swiss chard: 6 ppm; tangerines: 2 ppm; tomatoes: 1 ppm; turnip greens (tops): 6 ppm; vegetables, brassica, leafy, group: 6.0 ppm; vegetable (fruiting): 0.2 ppm (negligible residues); 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: 0.2 ppm (negligible residues); vegetables (root crop): 0.2 ppm (negligible residues); watercress: 6 ppm; wheat (forage): 10 ppm; wheat (grain): 1 ppm; wheat (hay): 10 ppm; wheat (straw): 10 ppm.

Tolerances with regional registration ... are established for residues of methomyl in or on the following raw agricultural commodity: Pears: 4 ppm.

Excerpt from NIOSH Pocket Guide for Methomyl:

Skin: PREVENT SKIN CONTACT - Wear appropriate personal protective clothing to prevent skin contact.

Eyes: PREVENT EYE CONTACT - Wear appropriate eye protection to prevent eye contact.

Wash skin: WHEN CONTAMINATED - The worker should immediately wash the skin when it becomes contaminated.

Remove: WHEN WET OR CONTAMINATED - Work clothing that becomes wet or significantly contaminated should be removed and replaced.

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

Provide: QUICK DRENCH - Facilities for quickly drenching the body should be provided within the immediate work area for emergency use where there is a possibility of exposure. [Note: It is intended that these facilities provide a sufficient quantity or flow of water to quickly remove the substance from any body areas likely to be exposed. The actual determination of what constitutes an adequate quick drench facility depends on the specific circumstances. In certain instances, a deluge shower should be readily available, whereas in others, the availability of water from a sink or hose could be considered adequate.] (NIOSH, 2024)

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]

White crystalline solid

Slightly sulfurous

335 °C @760 [mm Hg]

172 to 174 °F (EPA, 1998)

78-79 °C

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%

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

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

(77 °F): 0.00005 mmHg

log Kow= 0.60

Stable in neutral or slightly acidic soln.

At room temp, aq solns undergo slow decomp. The rate of decomp increases at higher temps, in the presence of sunlight, on exposure to air, 7 in alkaline media.

Methomyl is stable in solid form & in aq solns at pH 7.0 or less ... .

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.

AQ SOLN NONCORROSIVE

Positive

Agilent XCT

Electrospray ionization

Water soluble.

Carbamates

Sulfides, Organic

METHOMYL is a carbamate ester. Carbamates are chemically similar to, but more reactive than amides. Like amides they form polymers such as polyurethane resins. Carbamates are incompatible with strong acids and bases, and especially incompatible with strong reducing agents such as hydrides. Flammable gaseous hydrogen is produced by the combination of active metals or nitrides with carbamates. Strongly oxidizing acids, peroxides, and hydroperoxides are incompatible with carbamates.

Strong bases.

Strong bases

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.

Methomyl

2.5 x 10 ^-2 mg/kg-day

Pesticide

Based on Acute dietary PAD for infants and children; acute endpoint is protective of chronic effects.

Smith, C.D. and Nowell, L.H., 2024. Health-Based Screening Levels for evaluating water-quality data (3rd ed.). DOI:10.5066/F71C1TWP

Cancer Classification: Group E Evidence of Non-carcinogenicity for Humans

A4; Not classifiable as a human carcinogen.

No indication of carcinogenicity to humans (not listed by IARC).

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).

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)

Pupillary constriction, muscle cramp, excessive salivation. Muscle twitching. Dizziness. Headache. Sweating. Laboured breathing. Unconsciousness.

Redness. Blurred vision.

Abdominal cramps. Convulsions. Diarrhoea. Nausea. Vomiting. Weakness. Further see Inhalation.

irritation eyes; blurred vision, miosis; salivation; abdominal cramps, nausea, vomiting; dyspnea (breathing difficulty); lassitude (weakness, exhaustion), muscle twitching; liver, kidney damage

As with organophosphates, the signs and symptoms are based on excessive cholinergic stimulation. Unlike organophosphate poisoning, carbamate poisonings tend to be of shorter duration because the inhibition of nervous tissue acetylcholinesterase is reversible, and carbamates are more rapidly metabolized. Muscle weakness, dizziness, sweating and slight body discomfort are commonly reported early symptoms. Headache, salivation, nausea, vomiting, abdominal pain and diarrhea are often prominent at higher levels of exposure. Contraction of the pupils with blurred vision, incoordination, muscle twitching and slurred speech have been reported. (L795)

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

Chemical: METHOMYL

Other Poison - Carbamate

Reproductive Toxin - A chemical that is toxic to the reproductive system, including defects in the progeny and injury to male or female reproductive function. Reproductive toxicity includes developmental effects. See Guidelines for Reproductive Toxicity Risk Assessment.

Skin Sensitizer - An agent that can induce an allergic reaction in the skin.

ACGIH Carcinogen - Not Classifiable.

FAO/WHO ADI: 0.03 mg/kg

IRIS Current

HEAST Current

LD50: 10 mg/kg (Oral, Mouse) (T14)

LD50: 9 mg/kg (Subcutaneous, Rat) (T14)

LC50: 0.45 mg/kg over 4 hours (Inhalation, Rat)

LD50 Rat (male) oral 17 mg active ingredient/kg

LD50 Rat (female) oral 24 mg active ingredient/kg

LD50 Rabbit (male) percutaneous >5000 mg ai/kg

LD50 Rat sc 9 mg/kg

For more Non-Human Toxicity Values (Complete) data for METHOMYL (11 total), please visit the HSDB record page.

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.

Basic treatment: Establish a patent airway. Suction if necessary. Aggressive airway control may be needed. Watch for signs of respiratory insufficiency and assist ventilations if necessary. Administer oxygen by nonrebreather mask at 10 to 15 L/min. Monitor for pulmonary edema and treat if necessary ... . Monitor for shock and treat if necessary ... . Anticipate seizures and treat if necessary ... . For eye contamination, flush eyes immediately with water. Irrigate each eye continuously with normal saline during transport ... . Do not use emetics. For ingestion, rinse mouth and administer 5 ml/kg up to 200 ml of water for dilution if the patient can swallow, has a strong gag reflex, and does not drool. Administer activated charcoal ... . /Carbamates and related compounds/

Advanced treatment: Consider orotracheal or nasotracheal intubation for airway control in the patient who is unconscious. Positive pressure ventilation techniques with a bag valve mask device may be beneficial. Monitor cardiac rhythm and treat arrhythmias if necessary ... . Start an IV with D5W /SRP: "To keep open", minimal flow rate/. Use lactated Ringer's if signs of hypovolemia are present. For hypotension if signs of hypovolemia are present, administer fluid cautiously. Watch for signs of pulmonary edema ... . Administer atropine. Correct hypoxia before administration ... . In severely poisoned patients, administer pralidoxime chloride (2 PAM). DIRECT PHYSICIAN ORDERS ONLY ... . Treat seizures with adequate atropinization and correction of hypoxia. Rarely is diazepam necessary ... . Use proparacaine hydrochloride to assist eye irrigation ... . /Carbamates and related compounds/

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.

/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.

1.60e+03

2.10e+04

5.00e+02

2.00e+00

1.10e-01

2.50e-02

Volatile

4.70e+03

6.20e+04

1.50e+03

The substance is very toxic to aquatic organisms. This substance may be hazardous to the environment. Special attention should be given to birds and bees. This substance does enter the environment under normal use. Great care, however, should be taken to avoid any additional release, for example through inappropriate disposal.

Methomyl's production may result in its release to the environment through various waste streams; it's use as an insecticide will result in its direct release to the environment. If released to air, a vapor pressure of 5.4X10-6 mm Hg at 25 °C indicates methomyl will exist in both the vapor and particulate phases in the ambient atmosphere. Vapor-phase methomyl will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 58 hours. Particulate-phase methomyl will be removed from the atmosphere by wet and dry deposition. Methomyl absorbs light greater than 290 nm and may undergo direct photolysis in the environment. The half-life for a thin film of methomyl exposed to laboratory lamps of environmentally significant wavelengths was 48.41 hours. If released to soil, methomyl is expected to have moderate mobility based upon a Koc of 160. Volatilization from moist soil surfaces is not expected to be an important fate process based upon an estimated Henry's Law constant of 1.9X10-11 atm-cu m/mole. Methomyl is not expected to volatilize from dry soil surfaces based on its vapor pressure. Methomyl biodegrades readily in soil with half-lives in the range of 3-14 days measured in 3 greenhouse soils and 5-6 weeks in tobacco growing soils. If released into water, methomyl is not expected to adsorb to suspended solids and sediment based upon the Koc. Hydrolysis occurs slowly in water with half-lives of 56, 54, 38, and 20 weeks at pH's of 4.5, 6.0, 7.0, and 8.0, respectively. Based on its absorption of light greater than 290 nm, methomyl may undergo photolysis in sunlit surface waters, but the kinetics of this reaction are unknown. Volatilization from water surfaces is not expected to be an important fate process based upon this compound's estimated Henry's Law constant. An estimated BCF of 3 suggests the potential for bioconcentration in aquatic organisms is low. Occupational exposure to methomyl may occur through inhalation of dust and dermal contact with this compound at workplaces where methomyl is produced or used. Monitoring data indicate that the general population may be exposed to methomyl via ingestion of food products containing methomyl. (SRC)

Methomyl's production may result in its release to the environment through various waste streams; it's use as an insecticide(1) will result in its direct release to the environment(SRC).

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 seemed to be stable for about 16 days after application to an alluvial soil, but then degraded faster in the non-autoclaved alluvial soil as compared to autoclaved soil suggesting the importance of microbial degradation(1). Soil microorganisms were found to be the primary factor responsible for methomyl conversion in various soil types(2). Laboratory studies indicated that methyl radiolabeled methomyl was rapidly degraded in soil via microbial action with carbon dioxide as the principal end product(3). Microbial transformation of methomyl in two tobacco-growing soils was found to occur after an initial lag phase of 7-14 days, but occurred with virtually no lag phase in soils previously treated with methomyl(4). After the initial lag phase, half-lives of about 5-6 weeks were determined for methomyl in these soils(4). Comparison with tests using soils sterilized with sodium azide suggested that microbial transformation is likely to be the major factor in methomyl degradation in soil(4). The half-life of methomyl in three greenhouse soils was about 3-14 days(5). The half-life of methomyl was reported as 30 days in soil(6).

The rate constant for the vapor-phase reaction of methomyl with photochemically-produced hydroxyl radicals has been estimated as 6.6X10-12 cu cm/molecule-sec at 25 °C(SRC) using a structure estimation method(1). This corresponds to an atmospheric half-life of about 58 hours at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1). Methomyl exhibited hydrolysis half-lives of 56, 54, 38, and 20 weeks at pH's of 4.5, 6.0, 7.0, and 8.0, respectively, in sterile water-ethanol (99:1) at 25 °C(2). A rate constant of 8.9X10-5 1/hr has been determined for the hydrolysis of methomyl in pure water at 25 °C (pH=7), which translates to a half-life of 262 days(3). The photodegradative half-life for a thin film of methomyl exposed to laboratory lamps of environmentally important wavelengths was 48.41 hours(4). In acetonitrile solution, methomyl strongly absorbs UV light between 295 and 305 nm indicating a potential for direct photolysis in vapor and aqueous phase(4).

An estimated BCF of 3 was calculated for methomyl(SRC), using a log Kow of 0.6(1) and a regression-derived equation(2). According to a classification scheme(3), this BCF suggests the potential for bioconcentration in aquatic organisms is low(SRC).

The measured Koc of methomyl was reported as 160(1). According to a classification scheme(2), this Koc value suggests that methomyl is expected to have moderate mobility in soil. Under field conditions and using laboratory studies, only slight movement of methomyl has been observed in soil(3,4).

The Henry's Law constant for methomyl is estimated as 1.9X10-11 atm-cu m/mole(SRC) derived from its vapor pressure, 5.4X10-6 mm Hg(1), and water solubility, 58,000 mg/l(2). This Henry's Law constant indicates that methomyl is expected to be essentially nonvolatile from water surfaces(3). Methomyl's estimated Henry's Law constant indicates that volatilization from moist soil surfaces is not expected to be an important environmental fate process(SRC). Methomyl is not expected to volatilize from dry soil surfaces(SRC) based upon its vapor pressure(1).

Methomyl was detected in 4 groundwater wells in Spain at concns of not detected to 300 ng/l(1). Methomyl was identified, not quantified, in groundwater near golf courses(2). Methomyl was detected at a max concn of 0.14 ug/l in an urban stream in Las Vegas, NV(3). Methomyl was detected in 2 of 446 surface water samples, and 25 of 1,023 groundwater samples in the US, at max concns of 2 and 10 ug/l, respectively(4).

SOURCE DOMINATED: Methomyl was detected in the aerosol phase in a greenhouse 24 hours after spraying at concns of 1-7 ppb(1).

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).

Residues of methomyl (0.04-3.4 ppm) were found in dead Honey Bees taken from poisoned apiaries in Connecticut, US, 1983-5(1).

THERE HAVE BEEN REPORTS OF OCCUPATIONAL EXPOSURE POISONINGS ... FROM METHOMYL WHEN ... INHALED BY WORKERS IN FORMULATING PLANTS. IT IS DIFFICULT ... TO EVALUATE SUCH POISONINGS, SINCE WORKERS ... ARE OCCUPATIONALLY EXPOSED ... TO ... ORGANOPHOSPHORUS INSECTICIDES AS WELL. ... NO CONTROLLED STUDIES.

Occupational exposure to methomyl may occur through inhalation of dust and dermal contact with this compound at workplaces where methomyl is produced or used. Monitoring data indicate that the general population may be exposed to methomyl via ingestion of food products containing methomyl. (SRC)

The concn of methomyl detected in the ambient air of a storage room of a commercial pest control building was 13.7 ng/cu m over a 3 hr monitoring period(1); conversion of this concn to a 40-hr work week is 0.180 ug/cu m which is far below the TLV-TWA value of 2500 ug/cu m(1).

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.

/GUIDE 131: FLAMMABLE LIQUIDS-TOXIC/ Health: TOXIC; may be fatal if inhaled, ingested or absorbed through skin. Inhalation or contact with some of these materials will irritate or burn skin and eyes. Fire will produce irritating, corrosive and/or toxic gases. Vapors may cause dizziness or suffocation. Runoff from fire control or dilution water may cause pollution. /Carbamate pesticide, liquid, flammable, poisonous; Carbamate pesticide, liquid, flammable, toxic; Carbamate pesticide, liquid, poisonous, flammable; Carbamate pesticide, liquid, toxic, flammable/

/GUIDE 131: FLAMMABLE LIQUIDS-TOXIC/ Fire or Explosion: HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames. Vapors may form explosive mixtures with air. Vapors may travel to source of ignition and flash back. Most vapors are heavier than air. They will spread along ground and collect in low or confined areas (sewers, basements, tanks). Vapor explosion and poison hazard indoors, outdoors or in sewers. Those substances designated with a "P" may polymerize explosively when heated or involved in a fire. Runoff to sewer may create fire or explosion hazard. Containers may explode when heated. Many liquids are lighter than water. /Carbamate pesticide, liquid, flammable, poisonous; Carbamate pesticide, liquid, flammable, toxic; Carbamate pesticide, liquid, poisonous, flammable; Carbamate pesticide, liquid, toxic, flammable/

/GUIDE 131: FLAMMABLE LIQUIDS-TOXIC/ Public Safety: CALL Emergency Response Telephone Number ... . As an immediate precautionary measure, isolate spill or leak area for at least 50 meters (150 feet) in all directions. Keep unauthorized personnel away. Stay upwind. Keep out of low areas. Ventilate closed spaces before entering. /Carbamate pesticide, liquid, flammable, poisonous; Carbamate pesticide, liquid, flammable, toxic; Carbamate pesticide, liquid, poisonous, flammable; Carbamate pesticide, liquid, toxic, flammable/

/GUIDE 131: FLAMMABLE LIQUIDS-TOXIC/ Protective Clothing: Wear positive pressure self-contained breathing apparatus (SCBA). Wear chemical protective clothing that is specifically recommended by the manufacturer. It may provide little or no thermal protection. Structural firefighters' protective clothing provides limited protection in fire situations ONLY; it is not effective in spill situations where direct contact with the substance is possible. /Carbamate pesticide, liquid, flammable, poisonous; Carbamate pesticide, liquid, flammable, toxic; Carbamate pesticide, liquid, poisonous, flammable; Carbamate pesticide, liquid, toxic, flammable/

For more DOT Emergency Guidelines (Complete) data for METHOMYL (16 total), please visit the HSDB record page.

2757 151(carbamate pesticide, solid, toxic)

IMO 6.1; Carbamate pesticides, solid, toxic; Carbamate pesticides, liquid, toxic, flammable, flashpoint between 23 °C and 61 °C; Carbamate pesticides, liquid, toxic

IMO 3.2; Carbamate pesticides, liquid, flammable, toxic, flashpoint less than 23 °C

UN 2757; Carbamate pesticides, solid, toxic

UN 2758; Carbamate pesticides, liquid, flammable, toxic, nos, flashpoint less than 23 °C

For more Shipping Name/ Number DOT/UN/NA/IMO (Complete) data for METHOMYL (6 total), please visit the HSDB record page.

49 105 28; Carbamate pesticide (compounds and preparations), liquid (flammable liquid)

49 216 25; Carbamate pesticide (compounds and preparations), liquid (poison B) (insecticides, agricultural, nos, liquid)

49 216 27; Carbamate pesticide (compounds and preparations), solid (poison B) (insecticides, agricultural, nec, other than liquid)

49 105 27; Carbamate pesticide (compounds and preparations), liquid (flammable liquid)

49 216 24; Carbamate pesticide (compounds and preparations), liquid (poison B) (insecticides, nec, other than agricultural)

49 216 26; Carbamate pesticide (compounds and preparations), solid (poison b) (insecticides, nec, other than agricultural)

No person may /transport,/ offer or accept a hazardous material for transportation in commerce unless that person is registered in conformance ... and the hazardous material is properly classed, described, packaged, marked, labeled, and in condition for shipment as required or authorized by ... /the hazardous materials regulations (49 CFR 171-177)./

The International Air Transport Association (IATA) Dangerous Goods Regulations are published by the IATA Dangerous Goods Board pursuant to IATA Resolutions 618 and 619 and constitute a manual of industry carrier regulations to be followed by all IATA Member airlines when transporting hazardous materials.

The International Maritime Dangerous Goods Code lays down basic principles for transporting hazardous chemicals. Detailed recommendations for individual substances and a number of recommendations for good practice are included in the classes dealing with such substances. A general index of technical names has also been compiled. This index should always be consulted when attempting to locate the appropriate procedures to be used when shipping any substance or article.

Unbreakable packaging. Put breakable packaging into closed unbreakable container. Do not transport with food and feedstuffs. Marine pollutant.

Symbol: T+, N; R: 28-50/53; S: (1/2)-22-36/37-45-60-61

UN Hazard Class: 6.1; UN Pack Group: II