Dimethoat (ISO)

Pesticides

Pesticide -> EPA IRIS

Acaricides, Insecticides

Active substance -> EU Pesticides database: Not approved

Pesticides -> Organophosphate Insecticides

Environmental transformation -> Pesticides (parent, predecessor)

log Kow = 0.78

0.5/0.8

0.8

CAMPHOR-LIKE ODOR

Mercaptan odor

1.277 at 149 °F (EPA, 1998) - Denser than water; will sink

1.277 at 65 °C

1.3 g/cm³

1.277 at 149 °F

1.277 @ 65°C

White crystalline solid

Colorless crystals (Tech., white solid pellets)

1 to 10 mg/mL at 75 °F (NTP, 1992)

Readily soluble in most organic solvents, e.g. alcohols, ketones, benzene, toluene, chloroform, dichloromethane >300 g/kg at 20 °C; carbon tetrachloride, saturated hydrocarbons, n-octanol >50 g/kg at 20 °C

More than 5000 mg/L water at 20 plus or minus 1.5 °C

In water, 2.5X10+4 m/L at 25 °C

SOL IN CYCLOHEXANONE; LOW SOLUBILITY IN XYLENE, HEXANE

Solubility in water, g/100ml at 21 °C: 2.5

124 °F (EPA, 1998)

107 °C (closed cup)

107 °C c.c.

124 °F

243 °F at 0.1 mmHg (NTP, 1992)

107 °C at 0.05 mm Hg

at 0.01kPa: 117 °C

243 °F at 0.1 mmHg

Warning

H302: Harmful if swallowed [Warning Acute toxicity, oral]

P264, P270, P280, P301+P317, P302+P352, P317, P321, P330, P362+P364, and P501 (click each P-code to see the statement)

Warning

H302 (97.3%): Harmful if swallowed [Warning Acute toxicity, oral]

P264, P270, P280, P301+P317, P302+P352, P317, P321, P330, P362+P364, and P501 (click each P-code to see the statement)

Hazard Traits - Developmental Toxicity; Environmental tox; Neurotoxicity

Commission Regulation No 844/2012

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

07/25/EC, Reg. (EU) 2018/917, Reg. (EU) 2019/1090, Reg. (EU) 2019/707, Reg. (EU) No 540/2011

Dimethoate: Does not have an individual approval but may be used under an appropriate group standard

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

As with other organophosphorus pesticides, container may explode in heat of fire. The temperature of storage should not exceed 70-80F. Keep away from sources of heat, flames, or spark-generating equipment. Unstable in alkaline solution. Hydrolyzed by aqueous alkali. Stable in aqueous solutions. The compound is stable for 2 years under environmental conditions if stored in undamaged, original containers. (EPA, 1998)

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

Very toxic; the probable oral lethal dose in humans is between 50-500 mg/kg, or between 1 teaspoon and 1 ounce for a 70 kg (150 lb.) person. Dimethoate is a cholinesterase inhibitor, meaning it affects the central nervous system. Death is due to respiratory arrest arising from failure of respiratory center, paralysis of respiratory muscles, intense bronchoconstriction or all three. (EPA, 1998)

An erythema-multiforme-like contact dermatitis has been reported; [Kanerva, p. 1783] A cholinesterase inhibitor that can be absorbed through skin; May have adverse effects on human reproduction, based on animal studies; [ICSC] Has the highest reported incidence of poisonings (none life-threatening) of the organophosphates used in residential applications; No evidence of delayed neurotoxicity in hens; [Reference #2] Delayed neuropathy has been very rarely reported in humans, and seems to result from severe poisoning; Not likely to cause delayed neuropathy under normal levels of exposure; May cause an intermediate syndrome that can be life threatening; Symptoms developing 1-4 days following exposure include weakness of proximal limb muscles and neck flexors and respiratory distress; Four cases have been reported and involved ingestion of large amounts; [EFSA] 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] See Omethoate.

US Dept of Agriculture; The Biologic and Economic Assessment of Dimethoate. A Report of the Dimethoate Assessment Team to the Rebuttable Presumption Against Registration of Dimethoate. Tech Bull USDA 1663: 322 pp. (1981). A review with 425 references on the uses of dimethoate. Benefit analyses are discussed and other alternatives are /presented/.

DHEW/NCI; Bioassay of Dimethoate for Possible Carcinogenicity (1977) Technical Rpt Series No. 4 DHEW Pub No. (NIH) 77-804

WHO; Environ Health Criteria Number 90: Dimethoate (1989).

FAO/WHO; JMPR Pesticide residues in food, Dimethoate (addendum) (2003). Available from: http://www.inchem.org/documents/jmpr/jmpmono/v92pr09.htm as of January 8, 2007. This report discusses background information used to develop an ADI for dimethoate.

USEPA/Office of Pesticide Programs; Interim Reregistration Eligibility Decision (IRED) for Dimethoate. 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 February 28, 2007: http://www.epa.gov/pesticides/reregistration/status.htm]

P044; As stipulated in 40 CFR 261.33, when dimethoate, as a commercial chemical product or manufacturing chemical intermediate or an off-specification commercial chemical product or a manufacturing chemical intermediate, becomes a waste, it must be managed according to federal and/or state hazardous waste regulations. Also defined as a hazardous waste is any container or inner liner used to hold this waste or any residue, contaminated soil, water, or other debris resulting from the cleanup of a spill, into water or on dry land, of this waste. Generators of small quantities of this waste may qualify for partial exclusion from hazardous waste regulations (40 CFR 261.5(e)).

Tolerances are established for total residues of the insecticide dimethoate (O,O-dimethyl S-(N-methylcarbamoylmethyl) phosphorodithioate) including its oxygen analog (O,O-dimethyl S-(N- methylcarbamoylmethyl) phosphorothioate) in or on the following food commodities: [Table#3275]

Tolerances with regional registration, as defined in §180.1(n), are established for total residues of dimethoate including its oxygen analog in or on the following food commodities: [Table#3276]

EPA has completed its assessment of the cumulative risks from the organophosphate (OP) class of pesticides as required by the Food Quality Protection Act of 1996. In addition, the individual OPs have also been subject to review through the individual-chemical review process. The Agency's review of individual OPs has resulted in the issuance of Interim Reregistration Eligibility Decisions (IREDs) for 22 OPs /including dimethoate/, interim Tolerance Reassessment and Risk Management Decisions (TREDs) for 8 OPs, and a Reregistration Eligibility Decision (RED) for one OP, malathion. ... EPA has concluded, after completing its assessment of the cumulative risks associated with exposures to all of the OPs, that: (1) the pesticides covered by the IREDs that were pending the results of the OP cumulative assessment (listed in Attachment A) are indeed eligible for reregistration; and (2) the pesticide tolerances covered by the IREDs and TREDs that were pending the results of the OP cumulative assessment ... meet the safety standard under Section 408(b)(2) of the FFDCA.

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. Dimethoate 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: 0088; Pesticide type: insecticide (acaricide); Registration Standard Date: 04/11/83; Case Status: OPP is reviewing data from the pesticide's producers regarding its human health and/or environmental effects, or OPP is determining the pesticide's eligibility for reregistration and developing the Reregistration Eligibility Decision (RED) document.; Active ingredient (AI): Dimethoate; Data Call-in (DCI) Date(s): 06/28/91, 10/13/95, 02/09/96; 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.

This material is an organophosphate insecticide. Procedures for organophosphorus pesticides are as follows. Dike fire control water for later disposal, do not scatter the material. Wear positive pressure breathing apparatus and protective clothing. Fight fire from maximum distance.

Use water spray, powder, carbon dioxide.

Fresh air, rest. Artificial respiration may be needed. Refer for medical attention.

Remove contaminated clothes. Rinse skin with plenty of water or shower. Refer for medical attention .

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

Induce vomiting (ONLY IN CONSCIOUS PERSONS!). Rest. Refer for medical attention .

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]

Dry chemicals, carbon dioxide for small fires. Water spray or foam for larger fires.

If material on fire or involved in fire: Do not extinguish fire unless flow can be stopped or safely confined. 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, carbon dioxide or dry chemical. /Organophosphorus pesticides, liquid, NOS/

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.) Use "alcohol" foam, carbon dioxide or dry chemical. /Organophosphorus pesticides, solid, NOS/

The biological activity remains practically unvaried for 2 yr under environmental conditions, provided stored in unopened and undamaged original containers, in shaded, cool, well-aired places, inaccessible to animals & unauthorized persons. Recommended temp < 25 °C/77 °F. Crystals may form in formulations stored at < 32 °F/0 °C. Stable a minimum of 1 yr at < 25-30 °C/77-86 °F. Stack containers to permit air circulation at bottom & inside of piles. Do not contaminate food, feed products.

Liquid formulations must be stored above 45 °F.

...Must be stored in its sealed original containers, in well-aired, fresh & dry storehouses or in shaded & possibly well-aired places. It is recommended that the product's temp...not exceed 25-30 °C, & keep...away from sources of heat, free flames or spark-generating equipment. Containers must be stacked in such a way as to permit free circulation of air...at bottom & inside of piles. Storage areas must be located at suitable distance from inhabited buildings, animal shelters, & food stores; moreover, they must be inaccessible to unauthorized persons, children, & domestic animals. /Dimethoate/

Use of granular, activated carbon in the adsorption of pesticides from wastewater is presented. Dimethoate was one of the compounds studied.

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 and solid, NOS/

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 and solid, NOS/

Environmental considerations- air spill: Apply water spray or mist to knock down vapors. /Organophosphorus pesticides, liquid and solid, NOS/

Dimethoate is an organophosphate insecticide. Precautions for organophosphorus pesticides include the following. Keep unnecessary people away; isolate hazard area and deny entry. Stay upwind; keep out of low areas. Ventilate closed spaces before entering them. Remove and isolate contaminated clothing at the site. Do not touch spilled material; stop leak if you can do so without risk. Use water spray to reduce vapors.

Do not contaminate water, food or feed by storage and disposal. PESTICIDE DISPOSAL: ... If these wastes cannot be disposed of by use according to label instructions, contact your State Pesticide or Environmental Control Agency, or the Hazardous Waste representative at the nearest EPA Regional Office for guidance. CONTAINER DISPOSAL: Plastc: Triple rinse (or equivalent). Then offer for recycling or reconditioning, or puncture and dispose of in a sanitary landfill, or incineration, or if allowed by state and local authorities, by vurning. If burned, stay out of smoke. /Def-Fend E-267/

Generators of waste (equal to or greater than 100 kg/mo) containing this contaminant, EPA hazardous waste number P044, must conform with USEPA regulations in storage, transportation, treatment and disposal of waste.

Potential candidate for rotary kiln incineration with a temperature range of 820-1600 °C with residence times for liquids and gases, seconds; solids, hours. Also, a potential candidate for fluidized bed incineration with a temperature range of 450 to 980 °C with residence times for liquids and gases, seconds; solids longer. /From table/

This compound should be susceptible to removal from wastewater by air stripping.

For more Disposal Methods (Complete) data for DIMETHOATE (6 total), please visit the HSDB record page.

Do NOT wash away into sewer. Sweep spilled substance into covered containers. If appropriate, moisten first to prevent dusting. Carefully collect remainder. Then store and dispose of according to local regulations. Personal protection: chemical protection suit including self-contained breathing apparatus.

Note to Physician: For all exposures administer atropine and 2-PAM as an antidote for acetylcholinesterase inhibition.

Avoid eye, skin, clothing contact. Do not breathe dust. Use with adequate ventilation. ... Wash thoroughly after handling.

If in eyes: Hold eye open and rinse slowly and gently with water for 15-20 minutes. Remove contact lenses, if present, after the first 5 minutes, then continue rinsing eye. Call a poison control center or doctor for further treatment advice. If on skin or clothing: Take off contaminated clothing. Rinse skin immediately with plenty of water for 15-20 minutes. Call a poison control center or doctor for further treatment advice. /De-Fend E-267/

Users should: wash hands before eating, drinking, chewing gum, using tobacco, or using the toilet; remove clothing immediately if pesticide gets inside, then wash thoroughly an put on clean clothing; and remove personal protective equipment immediately after handling this product; wash the outside of gloves before removing; as soon as possible, wash thoroughly and change into clean clothing. /De-Fend E-267/

For more Preventive Measures (Complete) data for DIMETHOATE (15 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 various classes of insecticides were studied on N-demethylation of dimethylnitrosamine (DMN) by mouse liver enzymes. Organochlorine insecticides increased the activities of dimethylnitrosamine demethylases I and II. Dimethoate, an organophosphorus cmpd, was the only insecticide tested to inhibit the N-demethylation of dimethylnitrosamine, with more pronounced effect on dimethylnitrosamine demethylase I.

Organophosphates are usually found in the environment with other pesticides and with pollutants of industrial origin can cause combined exposure involving unknown interactions between the agents. In this study, female Wistar rats were given 1/25 LD50 of dimethoate by gavage, combined with the same LD50 fractions of propoxur and cypermethrin or with arsenic (6.66 mg/kg). The doses were given from day 5 to 15 of pregnancy, or that plus for the 4 weeks of lactation, or that plus 8 weeks for the male offspring after weaning. Control rats received distilled water. Electrophysiological recording was done when the male offspring reached 12 weeks of age. Spontaneous activity and evoked potentials from the somatosensory, visual and auditory cortex; and conduction velocity and absolute and relative refractory periods of the tail nerve were measured. The general trend was a shift of the spontaneous cortical activity to higher frequencies and increase in the evoked potential latency. The results showed that combined exposure to several environmental toxicants could be more harmful than the effects of each substance alone ...

Carbon disulfide pretreatment potentiated the anticholinesterase action of parathion and EPN, but suppressed that of dimethoate and diazinon. Carbon disulfide had no significant effect or a slightly suppressive effect on the other compounds. Some of these effects were contrasted with the repeated alteration of the toxicity following phenobarbital pretreatment.

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. Certain reproductive effects in fertility, growth, and development for males and females have been linked specifically to organophosphate pesticide exposure. Most of the research on reproductive effects has been conducted on farmers working with pesticides and insecticdes in rural areas. In females menstrual cycle disturbances, longer pregnancies, spontaneous abortions, stillbirths, and some developmental effects in offspring have been linked to organophosphate pesticide exposure. Prenatal exposure has been linked to impaired fetal growth and development. Neurotoxic effects have also been linked to poisoning with OP pesticides causing four neurotoxic effects in humans: cholinergic syndrome, intermediate syndrome, organophosphate-induced delayed polyneuropathy (OPIDP), and chronic organophosphate-induced neuropsychiatric disorder (COPIND). These syndromes result after acute and chronic exposure to OP pesticides.

LC50 Lepomis macrochirus (Bluegill, weight 0.3 g) 6.0 mg/L/96 hr; temp 24 °C. Static bioassay without aeration, pH 7.2-7.5, water hardness 40-50 mg/L as calcium carbonate and alkalinity of 30-35 mg/L. /Technical, 97.4%/

LC50 Lepomis macrochirus (Bluegill) 28.0 mg/L/24 hr /Conditions of bioassay not given/

LD50 Agelaius phoeniceus (Red-winged blackbird) oral 5.4 mg/kg /from table/

LD50 Starlings oral 31.6 mg/kg

For more Ecotoxicity Values (Complete) data for DIMETHOATE (49 total), please visit the HSDB record page.

FORMOTHION & DIMETHOATE SHOULD BE CONSIDERED TOGETHER SINCE THEIR SIGNIFICANT RESIDUES APPEAR TO BE IDENTICAL @ HARVEST; THAT IS, EFFECT OF APPLYING DIMETHOATE & FORMOTHION WILL BE ADDITIVE.

TERRESTRIAL FATE: Based on a classification scheme(1), experimental Koc values which range from 5.2 to 50(2-6), indicate that dimethoate is expected to have very high mobility in soil(SRC). Volatilization of dimethoate from moist soil surfaces is not expected to be an important fate process(SRC) given an estimated Henry's Law constant of 2.4X10-10 atm-cu m/mole(SRC) derived from its vapor pressure, 1.87X10-6 mm Hg(15), and water solubility, 23,300 mg/L(15). Dimethoate soil half-life values of 2.2 days(16), 7 days(7-9), 11 days(10) and as much as 122 days(11) have been reported. After 6 days, average dimethoate losses due to evaporation from uncovered soil columns were 40.4, 32.3, 23.0, and 24.9% in sand, sandy clay loam, loam, and clay loam, respectively; dimethoate losses were directly proportional to water losses(12); this study indicates that dimethoate may be removed from terrestrial surfaces via evaporation(SRC). Dimethoate will be susceptible to hydrolysis in moist alkaline soils based on a reported base catalyzed rate constant of 756 1/m-hr at pH 9 which corresponds to a half-life of 3.7 days in water(13). Biodegradation may be an important fate process in soil(SRC) with 77% degradation reported in clay loam soil in 2 wks compared to 18 and 20% degradation in the same soil that had been autoclaved or irradiated(14).

AQUATIC FATE: Based on a classification scheme(1), experimental Koc values which range range from 5.2 to 50(2-6), indicate that dimethoate is not expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is not expected(7) based upon an estimated Henry's Law constant of 2.4X10-11 atm-cu m/mole(SRC) derived from its vapor pressure, 1.87X10-6 mm Hg(8), and water solubility, 23,300 mg/L(8). According to a classification scheme(9), BCFs of 1.1-2.4 and 2.7-6(10), suggests bioconcentration in aquatic organisms is low(SRC). Dimethoate hydrolyzes very slowly in sterile buffered solutions at pHs 5 and 7 with half-lives of 156 and 68 days respectively, but hydrolyzes rapidly to desmethyl dimethoate and dimethylthiophosphoric acid with a half-life of 4.4 days at pH 9(11). Photolysis and volatilization from water do not appear to be important removal process of dimethoate from water(SRC). Half-lives of 171, 173 and 219 days were given for river water, filtered river water and sea water, respectively, at 6 °C, and 43, 29 and 36 days, respectively, at 22 °C(12), suggesting that biodegradation may be a slow environmental fate process in water(SRC).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), dimethoate, which has a vapor pressure of 1.87X10-6 mm Hg at 25 °C(2), will exist in both the vapor and particulate phases in the ambient atmosphere. Vapor-phase dimethoate 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 5 hrs(SRC), calculated from its rate constant of 7.9X10-11 cu cm/molecule-sec at 25 °C(SRC) that was derived using a structure estimation method(3). Particulate-phase dimethoate may be removed from air via dry deposition(SRC), and one monitoring study(4) indicates that dimethoate is removed from the atmosphere via wet deposition. Products of oxidation and hydrolysis accounted for 1.5 and 11%, respectively, of the dimethoate deposited on an untreated glass surface left in a greenhouse for 7 days(5). Therefore, some oxidation and hydrolysis may account for the removal of dimethoate from air(SRC). Based on a lack of absorbance of wavelengths of light above 290 nm(6), dimethoate is not expected to be susceptible to direct photolysis by sunlight(SRC).

When applied to plants, dimethoate was ... decomposed ... on surface ... by hydrolysis & oxidation. On the plant surface, dimethoate underwent non-enzymatic oxidation to the oxygen analog & hydrolysis to water sol deriv identified as dimethyl phosphoric & O,O-dimethyl phosphorothioic acids, desmethyl dimethoate ...

After applying 150 grams dimethoate/ha to lettuce, dimethoate was detected on the outer leaves at concns of 4.61, 1.36, 0.19, and 0.01 ppm, fresh weight, after 2, 4, 7, and 14 days, respectively; it was detected on the inner leaves at a concn 0.01 ppm, fresh weight, after 7 days(1). After applying 300 grams dimethoate/ha to lettuce, dimethoate was detected on the outer leaves at concns of 8.44, 1.2, 0.32, and 0.06 ppm, fresh weight, after 2, 4, 7, and 14 days, respectively; it was detected on the inner leaves at a concn of 0.04 ppm, fresh weight, after 7 days, respectively(1). Dimethoate was not detected above a detection limit of 0.01 ppm in the edible pulp of lemons and oranges 52-59 days postapplication at 1.4 kg/ha(2). Dimethoate was found on strawberries at 0.041 ppm 17 days after application of 38.1 ppm in 1986(3). Dimethoate was found on strawberries at 0.019 ppm 17 days after application of 36.186 ppm in 1987(3). One day after the application of 1.5 kg/ha of dimethoate on olives, olive concns were 1.6 mg/kg, olive oil concns were 0.33 mg/kg(4). Eight days after treatment olive oil concns were 0.22 mg/kg and 14 days after treatment olive concns were 0.17 mg/kg and dimethoate was not detected in olive oil(4). Olives in Portugal were treated with 60 g ai/ha on Feb 9, 1980 and July 10, 1980; residues in olives were 5.3, 3.1, 1.5, 0.78, 0.41, 0.28 and 0.3 mg/kg 1, 7, 14, 21, 28, 35 and 41 days after the last treatment, respectively(5). No dimethoate was detected in olive oil processed from olives harvested on the same corresponding days(5). Dimethoate was found in laboratory pressed olive oil at 0.48, 0.33, 0.19 and 0.09 mg/kg 8, 20, 32 and 47 days, respectively, after treatment on Nov 16, 1988 with 60 g ai/ha, and at 0.06 mg/kg after 53 days in industrial pressing(5).

Dimethoate was qualitatively identified in 1 large fruit sample during Fiscal Year 1976 (FY76), 16 small fruit samples during FY75-76, 33 leaf and stem vegetables, 196 vine and ear vegetable sample, and 46 bean samples during FY74-76, and 1 root vegetable sample during FY75(1). Dimethoate has been detected, by FDA's pesticide residue monitoring program, in American foods during fiscal years 1978-1992(2-6); however, the concns and the frequencies of occurrence were not reported(2-6). Dimethoate was qualitatively identified in 167 of 27,065 human food samples during FY88-89(7). In a US monitoring survey of 6970 produce samples (fruits and vegetables) collected between 1989 and 1991, dimethoate was detected in grapes, greens, lemons, and peppers(8). During October 1, 1981 and September 30, 1986, dimethoate was found in 319 U.S. agricultural commodities at a concn range of >0-0.05 ppm, 117 samples at 0.05-0.1 ppm, 192 at 0.1-0.5 ppm, 29 at 0.5-1.0 ppm, 20 at 1.0-2.0 ppm, and 8 agricultural commodities at a concn > 2.0 ppm(9). This study does not distinguish between domestic and imported commodities or between surveillance and compliance samples(9). During October 1, 1981 and September 30, 1986, dimethoate was found in 145 U.S. domestic agricultural commodities conducted by surveillance sampling at a concn range of >0-0.05 ppm, 64 at 0.05-0.1 ppm, 105 at 0.1-0.5 ppm, 22 at 0.5-1.0 ppm, 17 at 1.0-2.0 ppm, and 5 domestic agricultural commodities at a concn > 2.0 ppm(10). During October 1, 1981 and September 30, 1986, dimethoate was found in 170 U.S. imported agricultural commodities conducted by surveillance sampling at a concn range of >0-0.05 ppm, 50 at 0.05-0.1 ppm, 77 at 0.1-0.5 ppm, 4 at 0.5-1.0 ppm, 3 at 1.0-2.0 ppm, and 3 imported agricultural commodities at a concn > 2.0 ppm(10). Dimethoate was not detected in green bean, peach, sweet potato, spinch, tomato or strawberry(11). Dimethoate was not detected in acorn squash, apple, peach, strawberry, pear, apricot, spinach, lettuce, carrot, grape, tomato, orange, potato or corn, it was detected in green beans, however after washing and cooking dimethoate was no longer detected(12). Dimethoate was found in domestic and imported pears and tomatoes from a 1989-1993 US Food and Drug Administration pesticide monitoring program(13).

Dimethoate was identified between 1983 and 1984 in 1 of 47 composite samples of strawberries from Ontario, Canada at a concn of 0.04 mg/kg(1). During April 1, 1989 - December 3, 1991, dimethoate was detected in Canadian domestic commodities of fresh apples, fresh bean and fresh lettuce(2). In the same Canadian study(2), dimethoate was also detected in imported commodities of fresh beans, apples, broccoli, cucumber, grapes, lettuce, orange, pepper, and pear. Dimethoate was found in 1 imported canned spinach samples taken in a Canadian commodities study running from 1/1/1992-3/31/94 of 16,198 imported commodities and 5784 domestic commodities(3). Dimethoate was detected in 35 of 234 ready-to-eat foods items that represented about 5,000 food types sampled over 10 years by the US FDA from 1982-1991; the average concentration in the 236 food types that tested positive was 0.0094 ug/g(4). Of 802 fruit and vegetables tested in Ontario, Canada from 1991-1995 3.3% were positive for dimethoate(5). Dimethoate was found in apple, bean, celery, cherry, leaf lettuce and head lettuce in domestic fruits and vegetables from Jan 1992-Mar 1994 in Canada(6). Dimethoate was not found in apple juice, beets, blueberry, cabbage, carrot, cucumber, grape juice, mushroom, onion, parsnipe, peach, pear, pepper, plum, potato, rutabagas, spinach, strawberry or tomato from the same study(6). Imported fruits and vegetables in this same Canadian study found dimethoate in apple, bean, broccoli, celery, frozen cherry, grape, head lettuce, lim, orange, pear, pepper, spinach and tangerine(6). Dimethoate was not detected in imported apricot, artichoke, avocado, banana, beet, brussels sprout, cabbage, cantaloupe, carrot, cauliflower, cherry, cucmber, eggplant, escarole, grapefruit, kiwi, leaf lettuce, lemon, mango, melon, mushroom, nectarine, onion, parsley, peach, pimiento, pineapple, plum, potato, radish, raspberry, rutabaga, sauerkraut, snow pea, squash, star fruit, strawberry, sweet potato, tomato, turnip, ugly fruit and yam from Jan 1992-Mar 1994 in Canada(6).

In a 1995 monitoring program in Egypt dimethoate was not detected in cauliflower, carrot, courgette, onion, cantaloupe, guava or mango(1). Dimethoate was found in cabbage, cucumber, eggplant, green beans, green peas, lettuce, pepper, tomato, apple, grape, orange, peach and strawberry in the same 1995 monitoring program(1). In a 1996 monitoring program in Egypt dimethoate was not detected in cabbage, artichoke, board bean, cauliflower, okra, onion, squash, tomato, carrot, sweet potato, taro, banana, dates, fig or lemon lime(2). Dimethoate was found in grape leaf, melokhia, lettuce, watercress, spinach, cantaloupe, cucumber, eggplant, green bean, green pea, pepper, apple, apricot, grape, guava, mango, orange, peach, pear, plum, pomegranate and strawberry in the same 1996 monitoring program(2). Dimethoate was found in potato and citrus taken from local Egyptian markets Mar 1991-Jan 1992(3). Dimethoate was not detected in cumin, anise, ginger or caraway but was found in cinnamon (6 ug/kg) in Ismailia, Egypt(4). Dimethoate was found in unprocessed orange, tomato, cucumber, apple and grape from retail markets in Alexandria City, Egypt 1997-1998, but was only found in processed grape(5).

For more Food Survey Values (Complete) data for DIMETHOATE (6 total), please visit the HSDB record page.

The substance can be absorbed into the body by inhalation, through the skin and by ingestion.

Oral (L1188) ; inhalation (L1188) ; dermal (L1188)

Dimethoate was applied dermally to lactating cow. Thin-layer chromatography indicated the presence, in addition to dimethoate, of dimethoxon, dimethoate acid and desmethyl dimethoate in the blood; and of dimethoxon, dimethylthio (or dithio) phosphate and possibily desmethyl dimethoate in the milk.

When a combination of dimethoate and omethoate (dimethoxon) was given to cows in dosages of 1 and 0.1 mg/kg body weight, respectively, for 14 days, only residues of the metabolite omethoate were observed in the milk (0.004-0.125 mg/kg). Three days after the application, neither compound could be detected. When dosages of 0.5 mg dimethoate/kg and 0.05 mg omethoate/kg were given for 14 days or when corn silage containing 1-7 mg dimethoate/kg (resulting in dosages of 0.06-0.36 mg/kg body weight) was given for 28 or 42 days, no residues were detected in the milk ... .

Dimethoate was found in 1 of 96 samples taken from 4 brands of Mexican commercial pasteurized milk over a 12 month period(1). Dimethoate was not found in 6 milk products from a 10 year US Food and Drug study from 1982-1991(2). Dimethoate was not found in 14 milk samples tested in Rome, Italy(3). Dimethoate was found in 1 of 7 composite samples over a 3 month period in Monofia and Kalubia provinces in Egypt(4).

Dimethoate is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death. Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. 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. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.

P044; As stipulated in 40 CFR 261.33, when dimethoate, as a commercial chemical product or manufacturing chemical intermediate or an off-specification commercial chemical product or a manufacturing chemical intermediate, becomes a waste, it must be managed according to federal and/or state hazardous waste regulations. Also defined as a hazardous waste is any container or inner liner used to hold this waste or any residue, contaminated soil, water, or other debris resulting from the cleanup of a spill, into water or on dry land, of this waste. Generators of small quantities of this waste may qualify for partial exclusion from hazardous waste regulations (40 CFR 261.5(e)).

Tolerances are established for total residues of the insecticide dimethoate (O,O-dimethyl S-(N-methylcarbamoylmethyl) phosphorodithioate) including its oxygen analog (O,O-dimethyl S-(N- methylcarbamoylmethyl) phosphorothioate) in or on the following food commodities: [Table#3275]

Tolerances with regional registration, as defined in §180.1(n), are established for total residues of dimethoate including its oxygen analog in or on the following food commodities: [Table#3276]

EPA has completed its assessment of the cumulative risks from the organophosphate (OP) class of pesticides as required by the Food Quality Protection Act of 1996. In addition, the individual OPs have also been subject to review through the individual-chemical review process. The Agency's review of individual OPs has resulted in the issuance of Interim Reregistration Eligibility Decisions (IREDs) for 22 OPs /including dimethoate/, interim Tolerance Reassessment and Risk Management Decisions (TREDs) for 8 OPs, and a Reregistration Eligibility Decision (RED) for one OP, malathion. ... EPA has concluded, after completing its assessment of the cumulative risks associated with exposures to all of the OPs, that: (1) the pesticides covered by the IREDs that were pending the results of the OP cumulative assessment (listed in Attachment A) are indeed eligible for reregistration; and (2) the pesticide tolerances covered by the IREDs and TREDs that were pending the results of the OP cumulative assessment ... meet the safety standard under Section 408(b)(2) of the FFDCA.

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. Dimethoate 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: 0088; Pesticide type: insecticide (acaricide); Registration Standard Date: 04/11/83; Case Status: OPP is reviewing data from the pesticide's producers regarding its human health and/or environmental effects, or OPP is determining the pesticide's eligibility for reregistration and developing the Reregistration Eligibility Decision (RED) document.; Active ingredient (AI): Dimethoate; Data Call-in (DCI) Date(s): 06/28/91, 10/13/95, 02/09/96; 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.

Persons in charge of vessels or facilities are required to notify the National Response Center (NRC) immediately, when there is a release of this designated hazardous substance, in an amount equal to or greater than its reportable quantity of 10 lb or 4.54 kg. The toll free number of the NRC is (800) 424-8802. The rule for determining when notification is required is stated in 40 CFR 302.4 (section IV. D.3.b).

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

(AZ) ARIZONA 1.2 ug/l

(CA) CALIFORNIA 1 ug/l

(FL) FLORIDA 5 ug/l

(WI) WISCONSIN 2 ug/l

Organophosphorus derivatives act by combining with and inactivating the enzyme acetylcholinesterase (AChE). ... The inactivation of cholinesterase by cholinesterase inhibitor pesticides allows the accumulation of large amounts of acetylcholine, with resultant widespread effects that may be ... separated into 4 categories: (1) Potentiation of postganglionic parasympathetic activity. ... (2) Persistent depolarization of skeletal muscle ... (3) Initial stimulation following depression of cells of central nervous system ... (4) Variable ganglionic stimulation or blockade ... /Cholinesterase inhibitor pesticides/

They act principally by inhibition of acetyl cholinesterase (AChE) at the cholinergic synapses. /organophosphorus insecticides/

The signs of poisoning due to organophosphorus cmpd are those due to accumulation of acetylcholine & hence overstimulation of parasympathetic nervous system. It is usual to divide them under 3 headings: muscarinic, nicotinic & central. Muscarinic signs ... consist of hypersalivation, lacrimation, sweating & nasal discharge. Miosis, dyspnea, vomiting, diarrhea & frequency of urination ... Nicotinic effects consist of fasciculation of muscles, weakness & paralysis. Central nervous system effects include nervousness, apprehension, ataxia, convulsions & coma. Death is due to resp failure, or sometimes cardiac arrest. There is little difference between signs produced by different organophosphorus compounds, but route of absorption may influence one system more than another. /Organophosphorus cmpd/

Toxicants of this class phosphorylate almost irreversibly varying amt of acetylcholinesterase enzyme of tissues, allowing accum of acetylcholine at cholinergic neuro-effector junctions (muscarinic effects), & at skeletal muscle myoneural junctions & in autonomic ganglia (nicotinic effects). /Organophosphate pesticides/

For more Mechanism of Action (Complete) data for DIMETHOATE (6 total), please visit the HSDB record page.

... Detoxification pathway ... involves the hydrolysis of carboxyester or carboxyamide linkages in some insecticides by tissue or plasma carboxylesterases (sometimes called aliesterase). Malathion and dimethoate are examples.

Rabbit and rat liver microsomes converted dimethoate to oxygen analog and des-N-methyl derivatives.

After dimethoate was administered to rats, the following compounds were found in urine: 1. dimethoate, 2. dimethoxon, 3. dimethoate carboxylic acid, 4. dimethylphosphorodithioate, 5. dimethyl phosphorothioate, 6. dimethylphosphate, 7. monomethylphosphate, 8. phosphorothioate, 9. formate, and 10. N-methyl 2-glucuronate acetamide.

Oxidative desulfuration of dimethoate to give O-analog took place rapidly in rabbits and rats. Both dimethoate and O-analog underwent subsequent oxidative N-dealkylation coupled with formation of N-hydroxymethyl intermediates.

For more Metabolism/Metabolites (Complete) data for DIMETHOATE (28 total), please visit the HSDB record page.

Dimethoate has known human metabolites that include Omethoate.

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

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

Qualitatively, metabolism of dimethoate in mammals is essentially identical to that occurring in insects. There are... quantitative differences. In general, dimethoate, is much more rapidly degraded in mammals and eliminated via urine. For example, 87-90% of oral dose given cattle was found in urine after 24 hr, mainly as hydrolysis products.

...After ingestion of dimethoate, rats eliminate 60% of dose in 24 hr in urine and expired air.

... Dimethoate rapidly penetrated isolated sections of /mouse/ small intestine, colon, and rectum, with the highest rates of penetration occurring in the colon and rectum. The age of the mice had no significant effects on the extent of penetration. /Initial dose not specified/

... Following aerial spraying with 38% dimethoate animal tissues contained higher concentrations of dimethoate than did soil, water or plants. ... The tissue containing the highest concentrations were brain and intially, lung. ...

For more Absorption, Distribution and Excretion (Complete) data for DIMETHOATE (23 total), please visit the HSDB record page.

Used as systemic and contact insecticide; [Merck Index] A general use OP insecticide/acaricide used on various crops and ornamentals (mostly alfalfa, wheat, cotton, and corn); [Reference #2]

Residential uses cancelled in the US in 2000; [Reference #2]

Farming (Pesticides) [Category: Industry]

For dimethoate (USEPA/OPP Pesticide Code: 035001) 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./

Dimethoate ... is an indirect-acting anticholinesterase.

Acaricide, insecticide

(1978) 1.04X10+9 G (CONSUMPTION-INCL IMPORTS)

(1982) 5.90X10+8 G (CONSUMPTION-INCL IMPORTS)

(1976) 2.5x10+6 lb

Production volumes for non-confidential chemicals reported under the Inventory Update Rule. [Table#3279]

INSECTICIDE FOR VEGETABLES, 31%; CITRUS, 23%; DECIDUOUS FRUITS & NUTS, 15%; ALFALFA, 8%; COTTON, 8%; WHEAT, 8%; OTHER FIELD CROPS-EG, SORGHUM & SOYBEANS, 8% (1982)

Insecticide use: 2,959,621 lbs active ingredient per year.

REACTION OF SODIUM DIMETHYLPHOSPHORODITHIOATE WITH PHENYL CHLOROACETATE FOLLOWED BY REACTION WITH METHYLAMINE; REACTION OF METHYL ESTER OF O,O-DIMETHYL DITHIOPHOSPHORYLACETATE WITH METHYLAMINE

... O,O-Dimethyl dithiophosphoric acid ... /was/ added ... to ... anhydrous sodium carbonate suspended in ... methyl isobutyl ketone. The mixture was then heated to about 65 °C & ... N-methyl chloroacetamide ... added. The resulting mixture was held at 80 °C for 1 hr with continued stirring, then cooled to room temp & filtered. The filtrate was washed twice with water, dried over anhydrous sodium sulfate, & filtered. The filtrate was heated under vacuum to remove the methyl isobutyl ketone. The residual product /is/ S-carbamoylmethyl O,O-dimethyl dithiophosphate ...

Dimethoate is produced by reaction of the sodium salt of O,O-dimethyldithiophosphoric acid with N-methylchloroacetamide.

PRATT CYGON 2-E SYSTEMIC INSECTICIDE Active ingredient 23.4% dimethoate

DE-FEND E-267 DIMETHOATE SYSTEMIC INSECTICIDE Active Ingredient 30.5% dimethoate

Emulsifiable concentrate ... dustable powder; aerosol; ULV /ultra low vol/ liquid ...

These include: bio systemic insecticide (pan britannica ind), vitex (la littorale) ec (200, 400, or 600 g technical/L); 'rogor as' ul (300 g/L); turbair systemic insecticide (pan britannica ind), ul; wp (200 g/kg); granules (50 g/kg).

For more Formulations/Preparations (Complete) data for DIMETHOATE (6 total), please visit the HSDB record page.

Transformation products, Acaricides, Insecticides

Environmental transformation -> Pesticides (parent, predecessor)

INSECTICIDES

Phosphorodithioic acid, O,O-dimethyl S-[2-(methylamino)-2-oxoethyl] ester: ACTIVE

Use of dry formulations is not permitted.

The WHO Recommended Classification of Pesticides by Hazard identifies Dimethoate (technical grade) as Class II: moderately hazardous; Main Use: insecticide.

...Little cross-resistance /in flies/ is shown to dimethoate, and this organophosphate compound induced little or no resistance to itself.

A cholinesterase inhibitor, use has been restricted.

For more General Manufacturing Information (Complete) data for DIMETHOATE (10 total), please visit the HSDB record page.