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The information in this profile may be out-of-date. It was last revised in 1996. EXTOXNET no longer updates this information, but it may be useful as a reference or resource.

Please visit the National Pesticide Information Center (NPIC) to find updated pesticide fact sheets. If you don't find a fact sheet related to your question, feel free to call 1-800-858-7378. NPIC is open five days a week from 8:00am to 12:00pm Pacific Time.

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E X T O X N E T

Extension Toxicology Network

Pesticide Information Profiles

A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Oregon State University, the University of Idaho, and the University of California at Davis and the Institute for Environmental Toxicology, Michigan State University. Major support and funding was provided by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program.

EXTOXNET primary files maintained and archived at Oregon State University

Revised June 1996

Disulfoton

Trade and Other Names: Tradenames for disulfoton include Bay S276, Disyston, Disystox, Dithiodemeton, Dithiosystox, Frumin AL, Solvigram, and Solvirex.

Regulatory Status: All products formulated at greater than 2% disulfoton are classified as Restricted Use Pesticides (RUPs). RUPs may be purchased and used only by certified applicators. Disulfoton is classified as Toxicity class I- highly toxic. Products containing disulfoton bear the Signal Word DANGER.

Chemical Class: organophosphate

Introduction: Disulfoton is a selective, systemic organophosphate insecticide and acaricide that is especially effective against sucking insects. It is used to control aphids, leafhoppers, thrips, beet flies, spider mites, and coffeeleaf miners. Disulfoton products are used on cotton, tobacco, sugar beets, cole crops, corn, peanuts, wheat, ornamentals, cereal grains, and potatoes.

Formulation: Not Available

Toxicological Effects:

• Acute toxicity: Disulfoton is very highly toxic to all mammals by all routes of exposure. Whether absorbed through the skin, ingested, or inhaled, early symptoms in humans may include blurred vision, fatigue, headache, dizziness, sweating, tearing, and salivation. It inhibits cholinesterase and affects nervous system function [2,8]. Symptoms occurring at high doses include defecation, urination, fluid accumulation in the lungs, convulsions, or coma. Death can occur if high doses stop respiratory muscles or constrict the windpipe [2,8]. Ingestion of high doses can lead to rapid onset of effects on the stomach. Symptoms resulting from skin exposure may be delayed for up to 12 hours. Complete recovery from acute effects takes at least week, but complete restoration of the blood to normal cholinestrase enzyme levels may take up to 3 months [8]. The oral LD50 ranges from 6.2 to 12.5 mg/kg in male rats and from 1.9 to 2.5 mg/kg in female rats [1,59]. For weanling male rats, the oral LD50 is 5.4 mg/kg [60]. The dermal LD50 is 3.6 mg/kg in female rats and 15.9 mg/kg in male rats [60]. The inhalation LC50 for 1 hour is 0.3 mg/L in male rats [13].
• Chronic toxicity: Rats have survived daily doses of 0.5 mg/kg/day for 90 days. Some studies have shown that rats can acquire a tolerance for the chemical, so they are able to adjust to the lower cholinesterase levels resulting from chronic low level exposures [8]. In a 2-year rat study, males fed disulfoton (95.5% pure) daily at levels below the LD50 had increased spleen, liver, kidney, and pituitary weights, while females with similar treatment had decreased weights in these organs. Also, at all dietary levels, male brains decreased in weight while female brain weights increased. At the highest doses, cholinesterase activity was inhibited in both sexes in the brain, plasma, and red blood cells [59]. In a 23-month mouse study, kidney weights increased in females fed high daily doses. At that level, cholinesterase activity was decreased in both sexes [59].
• Reproductive effects: In a long-term reproduction study, 98.5% pure disulfoton was fed at a dose of 0.5 mg/kg/day to both male and female albino rats. The number of animals per litter was reduced by 21% in the first and third generations and a 10 to 25% lower pregnancy rate was noted. Some third-generation litters whose parents were exposed to this dose developed fatty deposits and swelling in their livers. Exposed adults and litters had a 60% to 70% inhibition of red blood cell cholinesterase [59]. This suggests that disulfoton is unlikely to cause reproductive effects in humans at expected exposure levels.
• Teratogenic effects: In one study, pregnant rats were given disulfoton (98.2% pure) at doses ranging from 0.1 to 1.0 mg/kg/day through a stomach tube during the sensitive period of gestation. Cholinesterase activity was decreased. In the fetuses, no developmental defects were seen except at high doses, where incomplete bone development was noted [59,60]. In another study, rabbits were given disulfoton (97.3% pure) during the sensitive period. At the higher doses (1.5 and 2.0 mg/kg/day) fetal growth was not affected [59]. These studies indicate that disulfoton is unlikely to cause birth defects.
• Mutagenic effects: Disulfoton has been shown to be mutagenic in studies on bacteria [59].
• Carcinogenic effects: There is no evidence that disulfoton is carcinogenic. Studies of rats and mice fed high doses for 2 years did not show significant tumor growth [59,60].
• Organ toxicity: Continual daily absorption may cause flu-like symptoms, loss of appetite, weakness, and uneasiness. While repeated exposure to disulfoton may inhibit the cholinesterase enzyme and thus interfere with the nervous system, 30-day human exposures have not resulted in significant enzyme inhibition [1]. Workers chronically exposed to organophosphates like disulfoton have developed irritability, delayed reaction times, anxiety, slowness of thinking, and memory defects [1]. Chronic exposure of workers may also lead to cataracts.

• Fate in humans and animals: Disulfoton is rapidly absorbed by the gastrointestinal tract, metabolized, and excreted via urine. In one study, in which both male and female rats received single doses, females excreted the chemical at a slower rate than did the males. Males excreted 50% of the dose in the urine within 4 to 6 hours after dosing, while it took females 30 to 32 hours to excrete 50% through the urine. Within 10 days after dosing, both male and female rats lost, on average, 81.6% of the initial dose via the urine, 7.0% in the feces, and 9.2% in expired air [59].

Ecological Effects:

• Effects on birds: Disulfoton is moderately toxic to birds. The 5-day acute dietary LC50 for disulfoton is 692 ppm in mallard ducks, and 544 ppm in quail [13].
• Effects on aquatic organisms: Disulfoton-containing products are highly toxic to cold and warm fish, crab, and shrimp [8]. The LC50 values for the compound are 0.038 mg/L in bluegill sunfish, 0.25 mg/L in guppies, 1.85 mg/L in rainbow trout, and 6.5 mg/L in goldfish [13]. The bioconcentration factor of 460 indicates that there is a low to moderate potential for this compound to concentrate in living organisms [60].
• Effects on other organisms: Use of disulfoton on certain crops may pose a risk to some aquatic and terrestrial endangered species [60]. Disulfoton is toxic to bees.

Environmental Fate:

• Breakdown in soil and groundwater: Disulfoton has a low to moderate persistence in soils. Disulfoton is not strongly bound to soil [8,19]. Some metabolites are more mobile than the parent disulfoton in sandy loam, clay loam, and silty clay loam soils. Mobility decreases as organic matter content of soil increases. In addition, these metabolites can persist longer than disulfoton. In a study on sandy loam soils, disulfoton had a half-life of 1 week, and 90% loss in 5 weeks. One metabolite had a half-life of 8 to 10 weeks, and another was fairly stable for 42 weeks [59]. Disulfoton has been found in groundwater in in Virginia and Wisconsin at levels up to 1 mg/L [8].
• Breakdown in water: Like other organophosphorous insecticides, disulfoton will break down in water under alkaline conditions, and is most stable at normal surface water acidities. The degradation of the compound is temperature dependent [8].
• Breakdown in vegetation: When applied to the soil, disulfoton is actively taken up by plant roots and is translocated to all parts of the plant [2]. Such systemic distribution is especially effective against sucking insects, while predators and pollinating insects are not destroyed. Control may persist for 6 to 8 weeks [60,61]. Breakdown in plants follows the same chemical pathway as in soil.

Physical Properties:

• Appearance: Disulfoton, a member of the organophosphate chemical family, is a yellowish oil [13].
• Chemical Name: O,O-diethyl S-[2-(ethylthio)ethyl]phosphorodithioate [13]
• CAS Number: 298-04-4
• Molecular Weight: 274.40
• Water Solubility: 25 mg/L @ 23 C [13]
• Solubility in Other Solvents: soluble in most organic solvents and fatty oils [13]
• Melting Point: 25 C [13]
• Vapor Pressure: 24 mPa @ 20 C [13]
• Partition Coefficient: Not Available
• Adsorption Coefficient: 600 (estimated) [19]

Exposure Guidelines:

• ADI: 3 x 10-3 mg/kg/day [38]
• MCL: Not Available
• RfD: 4 x 10-5 mg/kg/day [53]
• PEL: Not Available
• HA: 3 x 10-4 mg/L [8]
• TLV: 0.1 mg/m3 (8-hour) (skin) [47]

Basic Manufacturer:

Sanex, Inc.
5300 Harvester Road
Burlington, Ontario
L7L 5N5 Canada

• Phone: 905-639-7535
• Emergency: Not Available
  

References:

References for the information in this PIP can be found in Reference List Number 5

DISCLAIMER: The information in this profile does not in any way replace or supersede the information on the pesticide product labeling or other regulatory requirements. Please refer to the pesticide product labeling.