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The information in this profile may be out-of-date.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

Terbufos

Trade and Other Names: Trade names include AC 92100, Aragran, Contraven, Counter, and Plydox.

Regulatory Status: Products containing 15% or more terbufos are classified as Restricted Use Pesticides (RUPs). RUPs may be purchased and used only by certified applicators. Terbufos is classified as toxicity class I - highly toxic. Terbufos products are labeled with the Signal Word DANGER.

Chemical Class: organophosphate

Introduction: Terbufos is an organophosphate insecticide and nematicide used on corn, sugar beets and grain sorghum. Primarily formulated as granules, it is applied at planting in a band or directly to the seed furrow. Terbufos controls wireworms, seedcorn maggots, white grubs, corn rootworm larvae, and other pests.

Formulation: Primarily formulated as granules, it is applied at planting in a band or directly to the seed furrow.

Toxicological Effects:

• Acute toxicity: The oral LD50 of terbufos is from 1.3 to 1.57 mg/kg in female rats, and from 1.6 to 1.74 mg/kg in male rats [100]. The oral LD50 for technical terbufos is 3.5 mg/kg in male mice, 9.2 mg/kg in female mice, 4.5 mg/kg in male dogs, and 6.3 mg/kg in female dogs [101]. Rabbits given a single dose of 0.1 mg to the eyes died within 2 to 24 hours after dosing [102]. The dermal LD50 in rabbits is 1.1 mg/kg for 24 hours [8]. Terbufos is highly toxic by both dermal and oral routes of exposure. Symptoms of acute toxicity often include nausea, abdominal cramps, vomiting, salivation, excessive sweating, and diarrhea within 45 minutes of ingestion. Absorption into the bloodstream may cause inhibition of cholinesterase, an enzyme essential for normal functioning of the nervous system. This, in turn, can lead to chest tightness, wheezing, blurred vision, fatigue, headache, slurred speech, and confusion. Symptoms from skin absorption, such as localized sweating, may be delayed up to 12 hours. At high enough doses, death may result from respiratory arrest, respiratory muscle paralysis, and/or constriction of the lungs. No neurotoxic effects were observed in chickens given a single dose of 40 mg/kg, the highest dose tested [100].
• Chronic toxicity: Slow thinking, memory loss, irritability, delayed reaction times, and anxiety have been noted in workers chronically exposed to organophosphates like terbufos. When rats were fed terbufos for 90 days, no effects were observed at doses up to 0.02 mg/kg/day. Cholinesterase inhibition occurred at higher doses [101]. Similar results were obtained in a 1-year study with rats. No effects were observed at doses up to 0.025 mg/kg/day, with cholinesterase inhibition occurring at 0.05 mg/kg/day, the highest dose tested [101].
• Reproductive effects: In a long-term study in rats, no chronic reproductive effects were observed after daily exposure to low doses of terbufos [102]. In another study, when rats were fed 0.0125 or 0.05 mg/kg/day for 6 months, there was an increase in the number of litters with dead offspring at the highest dose tested [101]. Rabbits were given doses of up to 0.4 mg/kg/day on days 7 to 19 of pregnancy. Cesarean sections were performed on day 29. No adverse effects on the offspring were seen at any dose. Toxic effects on the mothers occurred at the highest dose tested [101]. These data suggest that terbufos is unlikely to cause reproductive effects in humans.
• Teratogenic effects: Available evidence indicates that terbufos does not cause birth defects. There were no birth defects in the offspring of rats given up to 0.2 mg/kg/day on days 6 to 15 of pregnancy [101]. In a similar study on rabbits, no birth defects were observed in the offspring of rabbits given 0.25 mg/kg/day, the highest dose tested. The mothers exhibited reduced body weight gain at this dose [100].
• Mutagenic effects: Several tests have shown that terbufos is not mutagenic. These include a dominant lethal study in rats, an Ames test, a DNA repair chromosomal aberration test, and a test for DNA repair in rat liver cells [100,101].
• Carcinogenic effects: No tumors were found in mice given 1.8 mg/kg/day, the highest dose tested, for 18 months. The same results occurred in a 2-year study with rats given up to 0.40 mg/kg/day, the highest dose tested [100,101]
• Organ toxicity: This pesticide can affect the eyes, lungs, skin, and central nervous system, depending on the route of exposure and the concentration.

• Fate in humans and animals: In rats given a single oral dose of terbufos, 10% remained in the liver 6 hours after dosing. Breakdown products were found in the kidney 12 hours after dosing. Of the original dose administered, 83% was excreted in the urine within 7 days after dosing, and 3.5% was found in the feces. Terbufos and its metabolites did not accumulate in tissues [101,102]. No detectable residues have been found in the eggs, milk, or body tissues of animals (hens and cows) fed very high dietary doses of terbufos and its cholinesterase inhibiting metabolites [102].

Ecological Effects:

• Effects on birds: Terbufos is extremely toxic to birds. Its acute LD50 is 28.6 mg/kg in bobwhite quail. Its dietary LC50 is 143 to 157 ppm in bobwhites [102]. Reported dietary LC50s in Japanese quail are 194 to 265 ppm in 5-day studies [14]. There were no effects on bird reproduction from chronic exposure to terbufos [101].
• Effects on aquatic organisms: Terbufos is extremely toxic to fish and aquatic invertebrates [102]. The reported 96-hour LC50 for terbufos in Daphnia magna, a small freshwater invertebrate, is 0.00031 mg/L [102]; in Gammarus psendogomnaens, also a freshwater invertebrate, it is 0.0002 mg/L [72]. Reported 96-hour LC50 values for the technical material (88%) are 0.008 to 0.0013 mg/L in rainbow trout, 0.390 mg/L in the fathead minnow, and 0.0017 to 0.0024 mg/L in bluegills [72]. The compound has a moderate potential to accumulate in living tissue in aquatic organisms. The bluegill sunfish acumulated 680 times the ambient water concentration (in whole fish); 14 days after the fish were placed in terbufos free water between 84 and 93% of the compound was eliminated [8].
• Effects on other organisms: Terbufos is expected to be extremely toxic to mammals and reptiles [102]. It is nontoxic to bees.

Environmental Fate:

• Breakdown in soil and groundwater: Terbufos is low to moderately persistent in soil. It is rapidly converted to its metabolites which tend to persist in the soil and may be detected at harvest time [103]. Terbufos and its metabolites quickly degrade during the first 15 to 30 days after application, then gradually stabilize. Only 3% of the original application stayed in field-study soils after 1 month, with 1.5% of the chemical present after 60 days [104]. In a study on silty clay loam soil in South Dakota, the half-life of terbufos was about 2 weeks. The half-life for the metabolite, terboxon sulfone, was 2 to 3 times longer [103]. Other reported field half-lives are 5 to 30 days [19]. Terbufos dissipation is generally faster in soils with very low organic carbon, while binding increases with increasing organic carbon content [104]. Soil moisture does not appear to affect the degradation of terbufos. This chemical will break down at about the same rate in soils regardless of the level of wetness [104]. As temperature increases, terbufos degrades more quickly. Terbufos is generally immobile and is therefore unlikely to leach or contaminate groundwater [102]. Much of the chemical can be recovered near the site of application. In one study, over 90% of the applied terbufos was recovered in the top 4 inches of a soil profile despite heavy rainfall, and thorough incorporation down to 2 1/2 inches [104]. Being of low water solubility, terbufos is not often found in groundwater. Terbufos has been found in a few groundwater samples collected from locations across the U.S. at concentrations of approximately 0.01 mg/L [42].
• Breakdown in water: Terbufos hydrolyzes rapidly. At a concentration of 4.6 mg/L, its hydrolysis half-lives were 4.5, 5.5, and 8.5 days at pH 5, 7, and 9 respectively [101,102]. In another study, terbufos hydrolyzed with a half-life of 2.2 weeks at pH 5, 7 and 9. Formaldehyde was the major degradate detected [101].
• Breakdown in vegetation: Terbufos moves from the soil into plants, where it is broken down rapidly. Little of the parent compound is found in plants. At 57 days after seeding and application, the total residues in broccoli were very low, while the marketable heads of broccoli harvested 90 days after seeding held only traces (less than 0.01 ppm, fresh weight) of residues. Under the same conditions, marketable cabbage and cauliflower had trace to nondetectable levels of total residues [105]. Field corn banded with 1.12 kg/ha had no detectable residues 60 days after treatment. Sweet corn and popcorn grain harvested at maturity also showed no residue, even though the surrounding soil contained 10 to 14 ppm [105].

Physical Properties:

• Appearance: Terbufos is a clear, slightly brownish-yellow liquid usually formulated into granules for agricultural applications [13].
• Chemical Name: S-tert-butylthiomethyl O,O-diethyl phosphorodithioate [13]
• CAS Number: 13071-79-9
• Molecular Weight: 288.43
• Water Solubility: 5 mg/L [13]
• Solubility in Other Solvents: s. in acetone, aromatic hydrocarbons, chlorinated hydrocarbons, and alcohols [13]
• Melting Point: -29.2 C [13]
• Vapor Pressure: 34.6 mPa @ 25 C [13]
• Partition Coefficient: 4.5185 [13]
• Adsorption Coefficient: 500 [19]

Exposure Guidelines:

• ADI: 0.002 mg/kg/day [38]
• MCL: Not Available
• RfD: 0.0001 mg/kg/day [53]
• PEL: Not Avavilable
• HA: 0.0009 mg/L (lifetime) [101]
• TLV: Not Available

Basic Manufacturer:

American Cyanamid Co.
One Cyanamid Plaza
Wayne, NJ 07470-8426

• Phone: 201-831-2000
• Emergency: 201-835-3100
  

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.