Agent Name


CAS Number




Major Category



B 1776; B-1,776; Butifos; Butiphos; Butyl phosphorotrithioate; Butyl phosphorotrithioate ((BuS)3PO); Chemagro B-1776; DEF; DEF defoliant; De-Green; E-Z-Off D; Fos-Fall A; Fossfall; Ortho phosphate defoliant; S,S,S-Tributyl phosphorotrithioate; S,S,S-Tributyl trithiophosphate; S,S,S-Tributyltrithiofosfat [Czech]; TBTP; Tribuphos; [ChemIDplus]


Organophosphate Insecticides


Colorless to pale yellow liquid; [Merck Index]


Used as cotton defoliant (for machine harvesting), synergist for insecticides, insecticide, herbicide, and growth regulator; [HSDB] Used in the US strictly for defoliating cotton prior to machine harvesting; General use pesticide; [Reference #1]


Delayed neuropathy has been reported in at least one agricultural worker; Causes moderate skin and minimal eye irritation in rabbits; Anemia observed in females during one year feeding at nominal doses (NOEL for anemia in females = 0.4 mg/kg); Effects in two year feeding study with rats include bilateral retinal and optic nerve atrophy, cataract, corneal opacity, and signs of anemia, but no adverse effects observed for oncogenicity or neurotoxicity; Reproductive toxicity observed at doses maternally toxic; No evidence of teratogenicity in two animal studies; Evidence for delayed neurotoxicity in hens exposed to single dermal dose of 250-1000 mg/kg; No evidence of mutagenicity; [HSDB] 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]

Reference Link

EPA Pesticide Chemical Search

Exposure Assessment

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]

Vapor Pressure

5.3E-6 mm Hg

Lethal Concentration

LCLo (mice) = 3,804 mg/m3/1h

Adverse Effects

Motor Neuropathy

Other Poison


Links to Other NLM Databases
Health Studies

Human Health Effects from Hazardous Substances Data Bank:

Toxicity Information


Chemical Information

Search ChemIDplus

Biomedical References

Search PubMed

Related Information in HazMap

Occupational diseases associated with exposure to this agent:


Industrial Processes with risk of exposure: