Methidathion

Synonyms

Supracide; (O,O-Dimethyl)-S-(-2-methoxy-delta(sup 2)-1,3,4-thiadiazolin-5-on-4-ylmethyl)dithiophosphate; 3-Dimethoxyphosphinothioylthiomethyl-5-methoxy-1,3,4-thiadiazol-2(3H)-one; Ciba-Geigy GS 13005; DMTP (insecticide); Dithiophosphoric acid O,O'-dimethyl-S-((2-methoxy-1,3,4-thiadiazol-5(4H)-on-4-yl)methyl) ester; Dithiophosphoric acid O,O'-dimethyl-S-((5-methoxy-1,3,4-thiadiazol-2(3H)-on-3-yl)methyl) ester; ENT 27193; Fisons NC 2964; GS 13005; Geigy 13005; Geigy GS-13005; Methidathion 50S; Metidation [Polish]; O,O'-Dimethyl-S-((2-methoxy-1,3,4-thiadiazole-5(4H)-one-4-yl)methyl) dithiophosphate; O,O-Dimethyl S-(2,3-dihydro-5-methoxy-2-oxo-1,3,4-thiadiazol-3-ylmethyl) phosphorodithioate; O,O-Dimethyl S-(5-methoxy-1,3,4-thiadiazolinyl-3-methyl)dithiophosphate; O,O-Dimethyl-S-((2-methoxy-1,3,4(4H)thiodiazol-5-on-4-yl)-methyl)-dithiofosfaat [Dutch]; O,O-Dimethyl-S-(2-methoxy-1,3,4-thiadiazol-5(4H)-only-(4)-methyl) dithiophosphat [German]; O,O-Dimethyl-S-(2-methoxy-1,3,4-thiadiazol-5(4H)-only-(4)-methyl) phosphorodithioate; O,O-Dimethyl-S-(2-methoxy-1,3,4-thiadiazol-5-on-4-yl)-methyl-dithiophosphat [German]; O,O-Dimetil-S-((2-metossi-1,3,4-(4H)-tiadiazol-5-on-4-il)-metil)-ditiofosfato [Italian]; OMS 844; Phosphorodithioic acid, O,O-dimethyl ester, S-ester with 4-(mercaptomethyl)-2-methoxy-delta(2)-1,3,4-thiadiazolin-5-one; Phosphorodithioic acid, O,O-dimethyl ester, S-ester with 4-(mercaptomethyl)-2-methoxy-delta(sup 2)-1,3,4-thiadiazolin-5-one; Phosphorodithioic acid, S-((5-methoxy-2-oxo-1,3,4-thiadiazol-3(2H)-yl)methyl) O,O-dimethyl ester; S-((2-Methoxy-5-oxo-1,3,4-thia-diazolin-4-yl)methyl)dimethylphosphorothiolothionate; S-((5-Methoxy-2-oxo-1,3,4-thiadiazol-3(2H)-yl)methyl) O,O-dimethyl phosphorodithioate; S-(2,3-Dihydro-5-methoxy-2-oxo-1,3,4-thiadiazol-3-methyl) dimethyl phosphorothiolothionate; S-(2,3-Dihydro-5-methoxy-2-oxo-1,3,4-thiadiazol-3-methyl)dimethyl phosphorothiolothionate; S-2,3-Dihydro-5-methoxy-2-oxo-1,3,4-thiadiazol-3-ylmethyl O,O-dimethyl phosphorodithioate; S-2-Metoksy-1,3,4-tiadiazolo-5-on-N-metylo-O,O-dwumetylowy [Polish]; Somonil; Supracid; Supracide Ulvair; Suprathion; Ultracid; Ultracid 40; Ultracid EC 40; Ultracide; Ultracide Ulvair 250; [ChemIDplus] UN2783

Category

Organophosphate Insecticides

Description

Colorless solid; [ICSC] Colorless to white solid; Formulated as wettable powder in water soluble bags and emulsifiable concentrate; [Reference #1] Colorless crystalline solid; [Aldrich MSDS]

Sources/Uses

Used as insecticide/acaricide; [Merck Index] Used as a broad spectrum insecticide/acaricide on various crops and ornamentals (primarily citrus and other fruits, artichokes, nuts, and cotton); [Reference #1]

Comments

Allergic contact dermatitis reported in workers handling this pesticide; [Kanerva, p. 1812] A cholinesterase inhibitor that may cause convulsions and respiratory failure; May have cumulative effects; Can be absorbed through skin; [ICSC] Severely irritating to eyes; No reports of delayed neuropathy following ingestion poisonings; [HSDB] Human ingestion of 93 mg/kg causes miosis, lachrymation, and coma; [RTECS] A chronic dietary study of dogs produced inhibition of cholinesterase activity, increased hepatic enzymes, gross hepatic lesions, histopathology, and chronic hepatitis; [Reference #1] An irritant that may cause serious eye injury; Highly toxic by ingestion, inhalation, and skin absorption; [Aldrich MSDS] “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]

A restricted use pesticide in the US (high acute oral toxicity); All US registrations voluntarily cancelled in December 2012, with distribution of existing stocks ending in December 2014; [Reference #1]

Reference Link #1

Biomedical References

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]

3.37E-06 mm Hg

LC50 (rat) = 3,600 mg/m3/4hr

Explanatory Notes

The Guide in the Emergency Response Guidebook is for "Organophosphorus pesticide, solid, toxic."

Yes

Hepatoxic (a) from occupational exposure (secondary effect) or (b) in animal studies or in humans after ingestion

Other Poison

Organophosphate

Diseases

Occupational diseases associated with exposure to this agent:

• Contact dermatitis, allergic
• Organophosphates & carbamates, acute poisoning

Processes

Industrial Processes with risk of exposure:

• Farming (Pesticides)