Oxydemeton-methyl

Acaricides, Insecticides

Active substance -> EU Pesticides database: Not approved

Pesticides -> Organophosphate Insecticides

Insecticides

Pesticide (Oxydemeton methyl) -> USDA PDB

log Kow = -0.74 @ 21 °C

-0.74

1.289 at 68 °F (NTP, 1992) - Denser than water; will sink

1.289 g/cu cm @ 20 °C

Colorless liquid

Yellow oil

10 to 50 mg/mL at 61 °F (NTP, 1992)

Soluble in common organic solvents except petroleum ether

Completely miscible with water.

223 °F at 0.01 mmHg (NTP, 1992)

106 °C @ 0.01 mm Hg

DT50 (est.) 107 days (pH 4), 46 days (pH 7), 2 days (pH 9) (22 °C).

When heated to decomposition it emits very toxic fumes of /phosphorous and sulfur oxides/.

less than 14 °F (NTP, 1992)

<-20 °C

3.8e-05 millibar at 68 °F (NTP, 1992)

0.0000285 [mmHg]

3.8 mPa (2.85X10-5 mm Hg) @ 20 °C

Oxydemeton methyl is a clear amber liquid. (NTP, 1992)

Colorless or yellow liquid; [HSDB] Clear amber liquid; [CAMEO]

Danger

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

P262, P264, P270, P273, P280, P301+P316, P302+P352, P316, P321, P330, P361+P364, P391, P405, and P501 (click each P-code to see the statement)

Danger

H301 (97.6%): Toxic if swallowed [Danger Acute toxicity, oral]

P262, P264, P270, P273, P280, P301+P316, P302+P352, P316, P321, P330, P361+P364, P391, P405, and P501 (click each P-code to see the statement)

Hazard Traits - Developmental Toxicity; Neurotoxicity; Reproductive Toxicity

Commission Regulation (EC) No 451/2000

Oxydemeton-methyl is listed in the dataset of EPA Human Health Benchmarks for Pesticides under the Safe Drinking Water Act (40 eCFR 141)

2007/392

SYMPTOMS: This compound is a cholinesterase inhibitor. Symptoms from exposure to this compound include anorexia; nausea; vomiting; diarrhea; excessive salivation; pupillary constriction; bronchoconstriction; muscle twitching; convulsions; coma; respiratory failure; pulmonary edema; perspiration; dyspnea; and cyanosis. The effects are cumulative.

A cholinesterase inhibitor; Can be absorbed through skin; [CAMEO] A woman who was five months pregnant attempted suicide by ingestion and was hospitalized with symptoms including miosis, respiratory distress, muscular fasciculations, and coma (12 hours after admittance); Blood cholinesterase was reduced by 90%; The remainder of her pregnancy was without incident, and the baby's neurological exams at birth and 8 days later were normal; [HSDB] Occupational exposure less likely to be symptomatic or require hospitalization than exposure to other cholinesterase inhibitors; [Reference #1] The average of two baseline respective cholinesterase activity determinations three days apart, with no exposures to enzyme inhibiting pesticides for at least 30 days, is recommended for each worker prior to exposure to cholinesterase inhibitors because of large inter-individual differences in published baseline values. To be established at least once a year. Removal from workplace exposures is recommended until the cholinesterase activity returns to within 20% of baseline. [TLVs and BEIs]

USEPA/Office of Pesticide Programs; Interim Reregistration Eligibility Decision (IRED) for Oxydemeton-methyl. EPA issues an IRED for a pesticide that is undergoing reregistration, requires a reregistration eligibility decision, and also needs a cumulative assessment under FQPA. The IRED, issued after EPA completes the individual pesticide\'s aggregate risk assessment, may include taking risk reduction measures -- for example, reducing risks to workers or eliminating uses that the registrant no longer wishes to maintain -- to gain the benefits of these changes before the final RED can be issued following the Agency\'s consideration of cumulative risks.[Available from, as of July 24, 2003: http://www.epa.gov/pesticides/reregistration/status.htm]

Tolerances are established for residues of the pesticide S-(2-(ethylsulfinyl)-ethyl) O,O-dimethyl phosphorothioate and its cholinesterase-inhibiting metabolites on the following raw agricultural commodities: alfalfa, green; alfalfa, hay, grown for seed; apple; bean, lima; bean, lima, forage; bean, snap, succulent; bean, snap, forage; beet, sugar; beet, sugar, tops; broccoli; Brussels sprouts; cabbage; cattle, fat; cattle, meat byproducts; cattle, meat; cauliflower; clover, forage; clover, hay, grown for seed; clover, seed screenings; corn, forage; corn, fresh, kernel plus cob with husks removed; corn, grain; corn, stover; cotton, undelinted seed; cucumber; eggplant; filbert; goat, fat; goat, meat byproducts; goat, meat; grapefruit; grape; hog, fat; hog, meat byproducts; hog, meat; horse, fat; horse, meat byproducts; horse, meat; lemon; lettuce, head; melon; milk; mint, hay; onion, dry bulb; orange, sweet; pear; pepper; plum, prune, fresh; pumpkin; safflower, seed; sheep, fat; sheep, meat byproducts; sheep, meat; sorghum, forage; sorghum, grain; sorghum milled fractions (except flour); squash, summer; squash, winter; strawberry; turnip; turnip, greens; and walnut.

Tolerances with regional registration, as defined in section 180.1(n), are established for residues of S-(2-(ethyl-sulfinyl)ethyl) O,O-dimethyl phosphorothioate and its cholinesterase-inhibiting metabolites in or on the following raw agricultural commodities: apricot.

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. Oxydemeton-methyl 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, as amended in 1988. Case No: 0258; Pesticide type: insecticide (acaricide); Case Status: In Pre-Special Review. The pesticide is in or has completed the reregistration process and, meanwhile, is also the subject of an in-depth Special Review.; Active ingredient (AI): Oxydemeton-methyl; Data Call-in (DCI) Date(s): 09/09/92, 04/15/93, 06/12/95, 10/13/95; AI Status: The producers of the pesticide has made commitments to conduct the studies and pay the fees required for reregistration, and are meeting those commitments in a timely manner.

Organophosphates such as OXYDEMETON METHYL are susceptible to formation of highly toxic and flammable phosphine gas in the presence of strong reducing agents such as hydrides. Partial oxidation by oxidizing agents may result in the release of toxic phosphorus oxides.

/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. /Organophosphorus pesticide, liquid, flammable, poisonous; Organophosphorus pesticide, liquid, flammable, toxic; Organophosphorus pesticide, liquid, poisonous, flammable; Organophosphorus 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. /Organophosphorus pesticide, liquid, flammable, poisonous; Organophosphorus pesticide, liquid, flammable, toxic; Organophosphorus pesticide, liquid, poisonous, flammable; Organophosphorus 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. /Organophosphorus pesticide, liquid, flammable, poisonous; Organophosphorus pesticide, liquid, flammable, toxic; Organophosphorus pesticide, liquid, poisonous, flammable; Organophosphorus 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. /Organophosphorus pesticide, liquid, flammable, poisonous; Organophosphorus pesticide, liquid, flammable, toxic; Organophosphorus pesticide, liquid, poisonous, flammable; Organophosphorus pesticide, liquid, toxic, flammable/

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

Acute Tox. 3 (97.6%)

Acute toxicity - category 3

Acute toxicity (Oral) - Category 2

Acute Tox. 3 *

EYES: First check the victim for contact lenses and remove if present. Flush victim's eyes with water or normal saline solution for 20 to 30 minutes while simultaneously calling a hospital or poison control center. Do not put any ointments, oils, or medication in the victim's eyes without specific instructions from a physician. IMMEDIATELY transport the victim after flushing eyes to a hospital even if no symptoms (such as redness or irritation) develop.

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]

If material on fire or involved in fire: Do not extinguish fire unless flow can be stopped. Use water in flooding quantities as fog. Solid streams of water may be ineffective. Cool all affected containers with flooding quantities of water. Apply water from as far a distance as possible. Use "alcohol" foam, dry chemical or carbon dioxide. /Organophosphorus pesticides, liquid, flammable, toxic; Organophosphorus pesticides, liquid, toxic/

If material on fire or involved in fire: Use water in flooding quantities as fog. Extinguish fire using agent suitable for type of surrounding fire. (Material itself does not burn or burns with difficulty.) /Organophosphorus pesticides, solid, toxic/

Environmental considerations: Air spill: Apply water spray or mist to knock down vapors. /Organophosphorus pesticides, liquid, flammable, toxic; Organophosphorus pesticides, liquid, toxic; Organophosphorus pesticides, solid, toxic/

Environmental considerations: Water spill: Use natural barriers or oil spill control booms to limit spill travel. Remove trapped material with suction hoses. /Organophosphorus pesticides, liquid, flammable, toxic; Organophosphorus pesticides, liquid, toxic; Organophosphorus pesticides, solid, toxic/

Environmental considerations: Land spill: Dig a pit, pond, lagoon, holding area to contain liquid or solid material. /SRP: If time permits, pits, ponds, lagoons, soak holes, or holding areas should be sealed with an impermeable flexible membrane liner./ Dike surface flow using soil, sand bags, foamed polyurethane, or foamed concrete. Absorb bulk liquid with fly ash, cement powder, or commercial sorbents. /Organophosphorus pesticides, liquid, flammable, toxic; Organophosphorus pesticides, liquid, toxic; Organophosphorus pesticides, solid, toxic/

SMALL SPILLS AND LEAKAGE: If you spill this chemical, use absorbent paper to pick up all liquid spill material. Your contaminated clothing and absorbent paper should be sealed in a vapor-tight plastic bag for eventual disposal. Solvent wash all contaminated surfaces with alcohol followed by washing with a strong soap and water solution. Do not reenter the contaminated area until the Safety Officer (or other responsible person) has verified that the area has been properly cleaned.

SRP: The most favorable course of action is to use an alternative chemical product with less inherent propensity for occupational exposure or environmental contamination. Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air quality; potential migration in soil or water; effects on animal, aquatic, and plant life; and conformance with environmental and public health regulations.

If material not on fire and not involved in fire: Keep sparks, flames, and other sources of ignition away. Keep material out of water sources and sewers. /Organophosphorus pesticides, solid, toxic/

If material not on fire and not involved in fire: Keep sparks, flames, and other sources of ignition away. Keep material out of water sources and sewers. Build dikes to contain flow as necessary. Attempt to stop leak if without undue personnel hazard. Use water spray to knock-down vapors. /Organophosphorus pesticides, liquid, toxic/

If material not on fire and not involved in fire: Keep sparks, flames, and other sources of ignition away. Keep material out of water sources and sewers. Build dikes to contain flow as necessary. Use water spray to knock-down vapors. /Organophosphorus pesticides, liquid, flammable, toxic/

Personnel protection: Avoid breathing dusts, and fumes from burning material. Keep upwind. Avoid bodily contact with the material. Do not handle broken packages unless wearing appropriate personal protective equipment. Wash away any material which may have contacted the body with copious amounts of water or soap and water. /Organophosphorus pesticides, solid, toxic/

For more Preventive Measures (Complete) data for OXYDEMETON-METHYL (8 total), please visit the HSDB record page.

Tolerances are established for residues of the pesticide S-(2-(ethylsulfinyl)-ethyl) O,O-dimethyl phosphorothioate and its cholinesterase-inhibiting metabolites on the following raw agricultural commodities: alfalfa, green, 5 ppm; alfalfa, hay, grown for seed, 11 ppm; apple, 1 ppm; bean, lima, 0.5 ppm; bean, lima, forage, 2 ppm; bean, snap, succulent, 0.5 ppm; bean, snap, forage, 2 ppm; beet, sugar, 0.3 ppm; beet, sugar, tops, 0.5 ppm; broccoli, 1 ppm; Brussels sprouts, 1 ppm; cabbage, 1 ppm; cattle, fat, 0.01 ppm; cattle, meat byproducts, 0.01 ppm; cattle, meat, 0.01 ppm; cauliflower, 1 ppm; clover, forage, 5 ppm; clover, hay, grown for seed, 11 ppm; clover, seed screenings. 11 ppm; corn, forage, 3 ppm; corn, fresh, kernel plus cob with husks removed, 0.5 ppm; corn, grain, 0.5 ppm; corn, stover, 3 ppm; cotton, undelinted seed, 0.1 ppm; cucumber, 1 ppm; eggplant, 1 ppm; filbert, 0.05 ppm; goat, fat, 0.01 ppm; goat, meat byproducts, 0.01 ppm; goat, meat, 0.01 ppm; grapefruit, 1 ppm; grape, 0.1 ppm; hog, fat, 0.01 ppm; hog, meat byproducts, 0.01 ppm; hog, meat, 0.01 ppm; horse, fat, 0.01 ppm; horse, meat byproducts, 0.01 ppm; horse, meat, 0.01 ppm; lemon, 1 ppm; lettuce, head, 2 ppm; melon, 0.3 ppm; milk, 0.01 ppm; mint, hay, 12.5 ppm; onion, dry bulb, 0.05 ppm; orange, sweet, 1 ppm; pear, 0.3 ppm; pepper, 0.75 ppm; plum, prune, fresh, 1 ppm; pumpkin, 0.3 ppm; safflower, seed, 1.0 ppm; sheep, fat, 0.01 ppm; sheep, meat byproducts, 0.01 ppm; sheep, meat, 0.01 ppm; sorghum, forage, 2.0 ppm; sorghum, grain, 0.75 ppm; sorghum milled fractions (except flour), 2.0 ppm; squash, summer, 1 ppm; squash, winter, 0.3 ppm; strawberry, 2 ppm; turnip, 0.3 ppm; turnip, greens, 2 ppm; and walnut, 0.3 ppm.

Tolerances with regional registration, as defined in section 180.1(n), are established for residues of S-(2-(ethyl-sulfinyl)ethyl) O,O-dimethyl phosphorothioate and its cholinesterase-inhibiting metabolites in or on the following raw agricultural commodities: apricot, 0.5 ppm.

The effects of vitamin E (alpha-tocopherol) on the rate of lipid peroxidation and lipase activity ln the discrete areas of the brain and spinal cord were studied. Administration of metasystox in two different doses 1.0 and 2.0 mg/kg body weight ip daily for 10 days have shown a dose-related depletion of total lipids cholesterol and esterified fatty acids in the rat cerebral hemisphere, cerebellum brain stem and spinal cord. The rate of lipid peroxidation and lipase activity showed dose-dependent increase in different regions of the CNS. Administration of alpha-tocopherol alone caused significant reduction of lipid peroxidation and lipase activity. When it was admistered simultaneously with metasystox, alpha-tocopherol prevented the metasystox induced increase of lipid peroxidation and lipase activity.

LD50 ANAS PLATYRHYNCHOS (MALLARD), MALES 4 MO OLD, ORAL 53.9 MG/KG (95% CONFIDENCE LIMIT: 38.9-74.8 MG/KG)

LD50 PHASIANUS COLCHICUS (PHEASANT), MALES 3-4 MO OLD, ORAL 42.4 MG/KG (95% CONFIDENCE LIMIT: 30.6-58.8 MG/KG)

LD50 ALECTORIS CHUKAR MALES & FEMALES, 3-4 MO OLD, ORAL 84.7-157 MG/KG

LD50 PASSER DOMESTICUS,(HOUSE SPARROW) MALES, ORAL 70.8 MG/KG (95% CONFIDENCE LIMIT: 43.4-116 MG/KG)

For more Ecotoxicity Values (Complete) data for OXYDEMETON-METHYL (17 total), please visit the HSDB record page.

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 9(SRC), determined from a log Kow of -0.74(2) and a regression-derived equation(3), indicates that oxydemeton-methyl is expected to have very high mobility in soil(SRC). Volatilization of oxydemeton-methyl from moist soil surfaces is not expected to be an important fate process(SRC) given an estimated Henry's Law constant of 1.6X10-13 atm-cu m/mole(SRC), using a fragment constant estimation method(4). Oxydemeton-methyl is not expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 2.85X10-5 mm Hg(2). Percent degradation of oxydemeton-methyl after 14 days ranged from 65-99% by various soil microorganisms(5).

AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 9(SRC), determined from a log Kow of -0.74(2) and a regression-derived equation(3), indicates that oxydemeton-methyl is not expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is not expected(3) based upon an estimated Henry's Law constant of 1.6X10-13 atm-cu m/mole(SRC), developed using a fragment constant estimation method(4). According to a classification scheme(5), an estimated BCF of 3.1(SRC), from its log Kow(2) and a regression-derived equation(6), suggests the potential for bioconcentration in aquatic organisms is low. At 22 °C the half-lives for hydrolysis of oxydememton-methyl are estimated as 107, 46, and 2 days at pH 4, 7, and 9, respectively(2).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), oxydemeton-methyl, which has a vapor pressure of 2.85X10-5 mm Hg at 20 °C(2), will exist in both the vapor and particulate phases in the ambient atmosphere. Vapor-phase oxydemeton-methyl is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 3.6 hours(SRC), calculated from its rate constant of 1.1X10-10 cu cm/molecule-sec at 25 °C(SRC), that was derived using a structure estimation method(3). Particulate-phase oxydemeton-methyl may be removed from the air by wet and dry deposition(SRC).

In the California Department of Food and Agriculture's Priority Pesticide Program in 1989, oxydemeton-methyl was analyzed for in samples of various commodities(2). Residues were found in the following commodities (commodity, samples analyzed, samples with residues): brussel sprouts, 23, 11; cabbage, 32, 3; cauliflower, 22, 2; peppers, 12, 3; chili peppers, 4, 1; and squash (winter or unspecified), 17,1(2). All residues were within tolerance(2). No residues were found in the following commodities (commodity, samples analyzed): string beans, 16; broccoli, 11; cantaloupe, 2; sweet corn, 1; cucumber, 7; honey due, 2; lettuce, 15; summer squash, 1; zucchini, 7(2). No oxydemeton-methyl was detected in 258 vegetable samples analyzed in Ontario-grown vegetables between 1980 and 1985(1). During FDA's regulatory monitoring of domestic and imported adult food eaten by infants and children between FY 1985 and 1991 (10,000 samples), oxydemeton-methyl was only found in 9 out of 2464 samples of domestic apples, maximum residue 0.39 ppm(3). Oxydemeton-methyl was not detected in any of the 27 market baskets of infant foods and adult foods eaten by infants and children during this time period(3). Oxydemeton-methyl was not found in foods studied in the Danish National Pesticide Monitoring Program 1995-1996(4).

/BIRDS and MAMMALS/ Symptoms of acute oral toxicity /in various birds/: ataxia, salivation, lacrimation, nutation, dyspnea, masseter tenseness, severe miosis, tenesmus, prostration or immobility in prone position, tremors, tetany, terminal wing-beat convulsions or opisthotonos. Symptoms appeared as soon as 8 min and mortalities usually occurred between 10 min and 2 hr after treatment. Remission took up to 14 days.

/BIRDS and MAMMALS/ In the bobwhite quail /reproduction/ study, statistically significant differences were noted at the 6.9 /ppm/ treatment level for the 14 day old survivor weights. The number of eggs laid per hen and the number of eggs set per hen was statistically different from the control at both the 6.9 ppm and the 17.3 ppm treatment groups. Both the number of viable embryos and live 3 wk embryos per hen was significantly different at the 17.3 ppm treatment level. In the mallard duck study, statistically significant differences were noted at the 17.3 ppm treatment level for reduced food consumption. There were no treatment related effects upon reproduction in this study.

/OTHER TERRESTRIAL SPECIES/ A bee toxicity study, to determine the toxicity of residual ODM on foliage to honey bees, provided the following information: ODM was found to have short-lived toxicity to honey bees and alkali bees exposed to foliar residues. At 0.5 lbs ai/A, 3-hr old residues were low in toxicity to both species (2-20% mortality, evaluated at 24 hours). ...When honey bee larvae were exposed to oxydemeton-methyl, the 3-4 day old larvae were the most susceptible age group (LD50 = 2.15 g/larva), while 5-6 day old larvae were the least susceptible (LD50 = 24.39 g/larva). These figures compare to an adult LD50 of 3 ug/bee.

/FIELD STUDIES/ A simulated field study with English sparrows, bobwhite quail, and New Zealand rabbits was performed in 1973 (MRID 00060638) and was found to provide supplemental information. The animals were exposed to both treated and untreated alfalfa at an application rate of 2.25 lb ai/A, applied 3 times with a 2 wk application interval. The caged animals were placed on alfalfa plots for 6 weeks; they were moved to fresh alfalfa plots weekly which had received previous applications. There was no treatment-related mortality of quail during the 42 day study. Weight losses for both treated and control birds were equivalent. The treated rabbits had no toxic symptoms or deaths, although one control rabbit died. There were high mortalities of control and treated sparrows, particularly during the last week of the study. The high death rate was attributed to stress due to being caged over an extended period of time. The data indicate that a formulated product of ODM, metasystox-r, was not significantly hazardous to caged bobwhite quail, English sparrows, and New Zealand rabbits. However, issues such as repellency were not considered. Without knowing the sizes of the cages, it is difficult to know if the animals were adequately exposed to treated food.

Measurement of whole blood-AChE is the most widely adopted method for monitoring the effects of occupational exposure to organophosphorus insecticides. Physiological variations in blood ChE levels occur in a healthy person and are seen among a population. It has been estimated that the coefficient of variation for AChE activity in samples from an individual is 8-11%, and that a decrease of 23% below pre-exposure level may, therefore, be considered significant. If the average of several pre-exposure values were available, then a decrease of 17% would be significant. It has been recommended that, if measured activity is reduced by 30% or more of the pre-exposure value, AChE measurements should be repeated at appropriate intervals to confirm the results. Depressions of AChE or ChE in excess of 20-25% are considered diagnostic of exposure but not, necessarily, indicative of hazard. Depressions of 30-50% or more are considered indicators for removal of an exposed individual from further contact with pesticides until levels return to normal. /Organophosphorus Pesticides/

...Organophosphorus pesticides may undergo hydrolysis in vivo to yield substituted phosphoric acids that are subsequently excreted in urine. Advances in gas chromatography and combined gas chromatography/mass spectrometry (GC/MS) have made it possible to analyse the urine of exposed persons for the presence of appropriate metabolites. It is usually necessary to preserve the sample by the addition of chloroform, to concentrate or extract the metabolite(s), and to convert them to suitably-volatile derivatives that can be detected by GC. Obviously, access to a well-equipped analytical laboratory, capable of the quick processing of samples, is a necessary factor if monitoring by urine analysis is proposed. However, in some cases, simpler and sensitive colorimetric tests are available for screening the urine of exposed persons. Thus, 4-nitrophenol can be measured directly in the urine of workers exposed to parathion. Consideration of the concentration of metabolite(s) in the urine can be helpful in determining patterns of exposure, and these concentrations can be calibrated against the effects on AChE for a particular pesticide. However, the time-course and peak of excretion of metabolites appears to vary according to dose, so that serial sampling and analyses of urine are desirable. Levels of metabolite alone cannot be considered a guide to hazard. This is obvious when it is realized that pesticides that have very different toxicities may yield identical acidic metabolites. Thus, the level of metabolites in urine, after exposure to sufficient amounts of the very toxic parathion-methyl to depress blood-AChE to 50%, will be much lower than that of the identical metabolites, following exposure to the related fenitrothion, which is about 40 times less toxic. /Organophosphorus Pesticides/

SRP: Workers should undergo an annual medical exam. Contraindications for work with organophosporous pesticides are organic diseases of the CNS, mental disorders and epilepsy, and pronounced endocrine disorders. Blood cholinesterase, both plasma and RBC, must be determined before work starts. In the event of prolonged work periods, this activity should be determined at intervals of 3-4 days. Persons exhibiting a fall in cholinesterase activity of 25% or more must be transferred to other work where they are not exposed until cholinesterase activity is restored. /Organophosphorous pesticides/

The Koc of oxydemeton-methyl is estimated as 9(SRC), using a log Kow of -0.74(1) and a regression-derived equation(2). According to a classification scheme(3), this estimated Koc value suggests that oxydemeton-methyl is expected to have very high mobility in soil. One investigator estimated that oxydemeton-methyl would leach >35 cm in loam soil at 25 °C in a year(4).

Oxydemeton-methyl and its oxidation product, dioxydemeton-methyl were not detected in air at 5 ambient monitoring sites and during 2 application monitoring sites collected in the Salinas Valley, Monterey County, CA, during Aug-Oct 1992(1). The detection limit for oxydemeton-methyl and its oxidation product were 2.0 and 1.5 ug/cu-m, respectively(1).

/HUMAN EXPOSURE STUDIES/ ...A 41 yr old woman, who was 5 months pregnant, ...attempted to commit suicide by ingesting half a bottle (12 g) of oxydemeton methyl. She was admitted to the hospital, and conscious, about 3 and 1/2 hr later. Oxydemeton methyl was found in the gastric aspirate, blood, and urine. She experienced miosis, respiratory distress due to abundant bronchial secretions, hyperreflexia, muscular fasciculations, and diarrhea and went into a coma about 12 hr after admission. Her blood cholinesterase level was 10% of the normal level. The patient was released from the hospital to psychiatric care after 14 days and the last 4 months of pregnancy were uneventful. A neurological exam, which was normal, was given to the baby as a part of a general physical exam immediately after she was born and again on the 8th day.

/HUMAN EXPOSURE STUDIES/ Plasma and erythrocyte ChE activities were evaluated in 15 human volunteers administered ODM (97.5%) either acutely or repeated daily doses for up to 120 days. Prior to the start of the study, all subjects were given physical, hematological and urological exams. Plasma and erythrocyte ChE activities were determined prior to dosing to establish the mean activity and standard deviation for each subject; these values were used as the control values. ODM was administered orally using either undiluted in gelatin capsules or diluted with 25 mL of corn oil. In a pilot study, a single subject was treated at 0.4 mg/kg/day for 5 days; this subject formed the basis for the dose levels used in the study. For acute toxicity, 7 subjects were treated with ODM, each received a dose of 0.0125, 0.025, 0.05, 0.25, 0.5, 1.0, or 1.5 mg/kg. For these subjects, ChE activities were measured at 0.5, 1, 2, 4, 8, or 24 hr, with additional measurements at 48 and 60 hr for subjects treated at 1.0 and 1.5 mg/kg. For the subchronic portion of the study, ChE activities were evaluated in 4 subjects treated at 0.05 mg/kg/day for 25-30 days and 2 subjects treated for 60 days. A single subject was treated for 120 days at 0.1 mg/kg/day. In the pilot study, a single subject was dosed at 0.4 mg/kg/day for 5 days. At 24 hr post dosing, plasma and erythrocyte ChE activities were inhibited by 50% and 35%, respectively. Findings of the acute toxicity study showed that the NOEL was 0.5 mg/kg for both plasma and erythrocyte ChE. At 1.0 mg/kg plasma ChE was inhibited by about 18% and erythrocyte ChE by about 14%. For the subacute study, volunteers treated at 0.05 mg/kg/day for 30-60 days, did not result in inhibition of either plasma or erythrocyte ChE. Treatment at 0.1 mg/kg/day for 120 days, resulted in a progressive inhibition of ChE activities. Plasma ChE was inhibited by 40% within the first 2 wk of exposure; erythrocyte ChE was also progressively inhibited, reaching a plateau of 50% by day 60 of the 120 day exposure. No cholinergic signs were noted in any of the subjects at anytime. Based on the results of this study (inhibition of plasma ChE by 18% and erythrocyte ChE by 14%), the acute LOEL was established at 1.0 mg/kg. The NOEL was established at 0.5 mg/kg. The LOEL for subacute toxicity was established at 0.1 mg/kg/day, based on one subject showing 40% inhibition of plasma ChE at two weeks and 50% inhibition of erythrocyte ChE at 60 days. The subacute NOEL was established at 0.05 mg/kg/day, based on no effects in 6 subjects at this dose.

/HUMAN EXPOSURE STUDIES/ Electroencephalographic (EEG) changes were measured in a group of nine farmers after 30 min crop spraying using the organophosphate pesticide, oxydemeton methyl. Analysis of blood samples and an estimation of skin contamination indicated that exposure was low; cholinesterase activity remained unchanged. For EEG measurements in the closed eye condition, the spectral power of the beta2-band of a higher exposed group (4 farmers) was significantly elevated in comparison to a lower exposed group (7 farmers). Even low exposure to organophosphates may result in characteristic changes in the human EEG without a decrease in cholinesterase activity.

/SIGNS AND SYMPTOMS/ Signs and symptoms of acute intoxication by organophosphorus insecticides include muscarinic, nicotinic, and central nervous system (CNS) manifestations. Symptoms may develop rapidly, or there may be a delay of several hours after exposure before they become evident. The delay tends to be longer in the case of more lipophilic compounds, which also require metabolic activation. Symptoms may increase in severity for more than one day and may last for several days. In severe cases, respiratory failure is a dominant effect. /Organophosphorus pesticides/

For more Human Toxicity Excerpts (Complete) data for OXYDEMETON-METHYL (6 total), please visit the HSDB record page.

Tolerances are established for residues of the pesticide S-(2-(ethylsulfinyl)-ethyl) O,O-dimethyl phosphorothioate and its cholinesterase-inhibiting metabolites on the following raw agricultural commodities: alfalfa, green; alfalfa, hay, grown for seed; apple; bean, lima; bean, lima, forage; bean, snap, succulent; bean, snap, forage; beet, sugar; beet, sugar, tops; broccoli; Brussels sprouts; cabbage; cattle, fat; cattle, meat byproducts; cattle, meat; cauliflower; clover, forage; clover, hay, grown for seed; clover, seed screenings; corn, forage; corn, fresh, kernel plus cob with husks removed; corn, grain; corn, stover; cotton, undelinted seed; cucumber; eggplant; filbert; goat, fat; goat, meat byproducts; goat, meat; grapefruit; grape; hog, fat; hog, meat byproducts; hog, meat; horse, fat; horse, meat byproducts; horse, meat; lemon; lettuce, head; melon; milk; mint, hay; onion, dry bulb; orange, sweet; pear; pepper; plum, prune, fresh; pumpkin; safflower, seed; sheep, fat; sheep, meat byproducts; sheep, meat; sorghum, forage; sorghum, grain; sorghum milled fractions (except flour); squash, summer; squash, winter; strawberry; turnip; turnip, greens; and walnut.

Tolerances with regional registration, as defined in section 180.1(n), are established for residues of S-(2-(ethyl-sulfinyl)ethyl) O,O-dimethyl phosphorothioate and its cholinesterase-inhibiting metabolites in or on the following raw agricultural commodities: apricot.

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. Oxydemeton-methyl 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, as amended in 1988. Case No: 0258; Pesticide type: insecticide (acaricide); Case Status: In Pre-Special Review. The pesticide is in or has completed the reregistration process and, meanwhile, is also the subject of an in-depth Special Review.; Active ingredient (AI): Oxydemeton-methyl; Data Call-in (DCI) Date(s): 09/09/92, 04/15/93, 06/12/95, 10/13/95; AI Status: The producers of the pesticide has made commitments to conduct the studies and pay the fees required for reregistration, and are meeting those commitments in a timely manner.

Organophosphorus insecticides exert their acute effects in both insects and mammals by inhibiting acetylcholinesterase (AChE) in the nervous system with subsequent accumulation of toxic levels of acetylcholine (ACh), which is a neurotransmitter. In many cases, the organophosphorylated enzyme is fairly stable, so that recovery from intoxication may be slow. /Organophosphorus Pesticides/

In a dermal absorption study..., radiolabeled /oxydemeton-methyl/ (ODM) (14C-ODM), at a single dose level of 2 mg/kg, was administered dermally or by iv injection to 3 Sprague-Dawley rats/sex/group/time period. ...The plasma half-life of ODM was 2 hr in both males and females following iv administration, and 3 hr in males and 4 hr in females following dermal exposure. For iv administration, the urine half-live was 5-14 hr in males and 2-20 hr females; and for the dermal exposure, 5-10 hr in males and 4-9 hr in females.

Following an oral dose of 5.0 mg/kg /14C-ODM/, tissue radioactivity was evaluated from 2 hr to 10 days post-dosing. The tissue levels of radioactivity paralleled that of the blood. Peak radioactivity in the blood occurred at 1 hr with elimination half-lives of 1.5 hours for the interval of 2-6 hours followed by a longer half-life of approximately 5 days for the interval of 6-24 hours. ...

In a metabolism study..., rats were dosed with 14C-1-ethylene-labeled ODM ( 14C-ODM) at a single at dose 1 mg/kg, either iv or orally (po), a single oral dose at 20 mg/kg, or with 14 daily oral doses of unlabeled ODM at 1 mg/kg/day followed by a single oral dose of 14C-ODM at 1 mg/kg. ...The identification of major urinary and fecal metabolites were determined for each treatment group. Analysis of the urinary radioactivity revealed that most of administered 14C-ODM was not metabolized. The respective % for males and females of unmetabolized ODM were 43% and 47% for the 1 mg/kg, iv group; 38% and 47% for the 1 mg/kg, po group; 34% and 55% for the repeat, 1 mg/kg/day, po group; and 59% and 74% for the 20 mg/kg, po group. Two major metabolites and three minor ones were also identified. One major metabolite was identified as 2- (ethylsulfinyl)-1-(methylsulfinyl) ethane, and accounted for 18-21% of the administered dose at 1 mg/kg, iv; 24-25%, at 1 mg/kg, po; 15%, at 15 x 1 mg/kg/day, po; and 5-6%, at 20 mg/kg, po. The second major metabolite was identified as 2-(ethylsulfonyl)-1-(methylsulfinyl) ethane; this metabolite accounted for 11-19% of the administered dose at 1 mg/kg, iv; 16-20%, at 1 mg/kg, po; 12-23%, at 15 x 1 mg/kg/day, po; and 6-19%, at 20 mg/kg, po. One minor metabolite (as a % of the administered dose for both males and females) was identified as ODM sulfone and was present at 1.7-3.4% of the total administered dose at 1 mg/kg, iv; 1.6%, at 1 mg/kg, po; 2.4-2.6%, at 15 x 1 mg/kg/day, po; and 2.6-3.9%, at 20 mg/kg, po. Two other minor metabolites were identified as desmethyl ODM and desmethyl ODM sulfone and were detected only in the 20 mg/kg, po, group at 2.6-3.1% and 1.0-3.1%, respectively. Primary fecal metabolites included unmetabolized ODM (0.2%), ODM sulfide (0.8%) and ODM sulfone (0.2%). The differences in the metabolic profiles suggests that the biotransformation may be saturated at high doses. The results indicate that at 20 mg/kg a marked increase in urinary excretion of unmetabolized parent compound (59-74%) in conjunction with a marked decline in the urinary excretion of metabolites compared to the corresponding values for males and female rats receiving 1 mg/kg (excretion of unmetabolized parent: 34-55%).

Demeton S-methyl sulfoxide is degraded by Pseudomonas putida 1453 by cleavage of thioester bond to form 2-(ethylsulfinyl)ethanethiol, 2-(ethylsulfonyl)ethanethiol and bis(2-(ethylsulfinyl)ethyl)disulfide. Nocardia sp dsm 43252 converts it into bis(2-(ethylsulfonyl)ethyl)disulfide, bis(2-(ethylsulfinyl)ethyl)sulfide, and bis(2-(ethylsulfonyl)ethyl)sulfide. o,o-Dimethylthiophosphoric acid was detected.

Metabolism occurs principally by oxidation, hydrolysis by esterases, and by transfer of portions of the molecule to glutathione. Oxidation of organophosphorus insecticides may result in more or less toxic products. The glutathione transferase reactions produce products, that are, in most cases, of low toxicity. Hydrolytic and transferase reactions affect both thioates and their oxons. /Organophosphorus Pesticides/

Following an oral dose of 5.0 mg/kg /14C-ODM/, tissue radioactivity was evaluated from 2 hr to 10 days post-dosing. ...Measurement of tissue radioactivity at 2 hours post-dosing shows that the highest concentration of radioactivity was found in the kidney (4.8 ppm); this is understandable since the urine is the predominant route of elimination. The lowest tissue level was found in the brain (1.7 ppm). Of the other tissues analyzed, concentrations ranged from 2.2 ppm in renal fat to 3.9 ppm in the lung. The remaining tissues (muscle, skin, liver, adrenal gland and testes) concentrations were between 3.0 and 3.6 ppm. After one day the levels of tissue radioactivity were 45-106 times lower that the 2 hr values. By 10 days, residual tissue radioactivity was present and ranged from a low value of 0.00035 ppm in testes to 0.085 ppm in erythrocytes.

In a metabolism study..., rats were dosed with 14C-1-ethylene-labeled ODM ( 14C-ODM) at a single dose 1 mg/kg, either iv or orally (po), a single oral dose at 20 mg/kg, or with 14 daily oral doses of unlabeled ODM at 1 mg/kg/day followed by a single oral dose of 14C-ODM at 1 mg/kg. The results of this study show that 14C-ODM was rapidly absorbed, extensively metabolized, and rapidly excreted. Over a 3-day period, most (90-108%) of the administered dose was excreted. The radioactivity was recovered almost entirely in the urine (89-105% of the administered dose), while feces and expired CO2 accounted for 0.2-2.9% and 0.1% of the administered dose, respectively. There was no indication of bioaccumulation in any tissue or organ. ...The results indicate that at 20 mg/kg a marked increase in urinary excretion of unmetabolized parent compound (59-74%) in conjunction with a marked decline in the urinary excretion of metabolites compared to the corresponding values for males and female rats receiving 1 mg/kg (excretion of unmetabolized parent: 34-55%).

Whole body autoradiography was performed on rats dosed /with 14C-ODM/ iv at 1.0 mg/kg or orally at 10 mg/kg. Following the iv dosing the radioactivity was rapidly distributed throughout the body at 5 min post-dosing. The highest concentrations of radioactivity were found in the kidney, bladder, and accessory genital gland. Lower concentrations were found in the brain, spinal cord, and testes. The concentration in fatty tissues and boney structures were at the limit of detection. Autoradiographs taken 8 hours after the oral dose were found to be essentially the same as with iv administration.

In a dermal absorption study..., radiolabeled ODM (14C-ODM), at a single dose level of 2 mg/kg, was administered dermally or by iv injection to 3 Sprague-Dawley rats/sex/group/time period. Animals were sacrificed 2, 4, 8, 12, 24, 48 and 72 hours or until the radioactivity in urine dropped to 2 times background. For the dermally treated animals, a 12 sq cm area of the application site was removed, washed and counted. For each time period, radioactivity was counted in urine, plasma, the skin, skin solvent wash samples. ...Total recoveries for iv route of administration were 67% for males and 81% for females. For the dermal route of exposure total recoveries were 33% for males and 41% for females. Recoveries of ODM were low, probably due to metabolism and failing to include residual total body counts. Dermal absorption was calculated to be 50.4% for males and 51.8% for females. The dermal absorption rates, as calculated by regression analysis based on mg equivalents of 14C-ODM over time, were 0.15 g/sq cm/hr for males and 0.17 g/sq cm/hr for females.

Used as systemic insecticide and acaricide for cotton, vegetables, fruits, and field crops; [HSDB]

Banned in the EU for use as pesticide for plant protection; [eChemPortal: ESIS] Restricted use pesticide (RUP); [Reference #1]

Farming (Pesticides) [Category: Industry]

For oxydemeton-methyl (USEPA/OPP Pesticide Code: 058702) 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./

Systemic insecticide, acaricide, effective control by contact and systemic action of many destructive pests that attack certain vegetable, fruit and field crops. Primarily for aphids, mites, thrips, leafhoppers, and other sucking pests.

About 30% as an insecticide or acaricide on cotton; about 30% as an insecticide or acaricide on deciduous fruits and nuts; and about 30% as an insecticide or acaricide on vegetables; and about 10% as an insecticide or acaricide on other field crops (1974)

Oxidation of o,o-dimethyl-s-(2-(ethylthio)ethyl) phosphorothioate

Produced by oxidation of demeton-s-methyl...with hydrogen peroxide (West German patent 947,368) or with chlorine or bromine (West German patent 949,229)...

Metasystox R: Soluble liquid (500 g active ingredient/L)

Croneton MR: Liquid (50 g methyl oxydemeton + 250 g ethiofencarb/L)

Emulsifiable concentrate (250 g active ingredient/L)

Insecticides

INSECTICIDES

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

Introduced by Bayer AG...as code numbers Bayer 21097, R 2170, trade mark metasystox-r; oxydemeton-methyl is a systemic and contact insecticide suitable for control of sap-feeding insects and mites, with range of action similar to that of demeton-s-methyl of which it is metabolic product.

Patents: protected by West German patent 947,368; US patent 2,963,505; Canadian patent 534,370.