Agent Name

Paraquat dichloride

CAS Number




Major Category



1,1'-Dimethyl-4,4'-bipyridinium dichloride; N,N'-Dimethyl-4,4'-bipyridinium dichloride; Paraquat chloride; Paraquat dichloride [Note: Paraquat is a cation (C12H14N2++; 1,1-Dimethyl-4,4-bipyridinium ion); the commercial product is the dichloride salt of paraquat.]; [NIOSH] Bipyridinium, 1,1'-dimethyl-4,4'-, dichloride; Cekuquat; Crisquat; Dexuron; Dimethyl viologen chloride; Dwuchlorek 1,1'-dwumetylo-4,4'-dwupirydyniowy [Polish]; Esgram; Galokson; Goldquat 276; Gramixel; Gramoxone; Gramoxone D; Gramoxone S; Gramoxone W; Gramoxone dichloride; Gramuron; Herbaxon; Herboxone; Methyl viologen; Methyl viologen (reduced); Methyl viologen dichloride; Methylviologen chloride; OK 622; Ortho paraquat CL; Parakwat [Polish]; Paraquat CL; Pathclear; Pillarquat; Pillarxone; Toxer total; Viologen, methyl-; [ChemIDplus]


Herbicides, Bipyridyl


Yellow solid with a faint, ammonia-like odor. [herbicide] [Note: Paraquat may also be found commercially as a methyl sulfate salt C12H14N2+2CH3SO4.]; [NIOSH]


Used as a contact herbicide on weeds; [EXTOXNET] Used in animal experiments as a model of Parkinson's syndrome at doses several orders of magnitude greater than occupational exposure levels; [PMID 16217247]


Contact injuries in workers include skin rashes, burns, eye damage from splashes, nail damage, and nasal bleeding. Parquat absorption through the skin can contribute to systemic toxicity, especially when contacting damaged skin or sensitive areas like the buttocks and genitalia. Toxic ingestion: low doses (<20 mg/kg) cause local irritation to oral and GI mucosa; moderate doses (20-40 mg/kg) cause renal, liver and lung damage with respiratory failure within 2-3 weeks; high doses (>40 mg/kg) cause pulmonary fibroplasia, respiratory failure, and death within 1-7 days. [ACGIH] Classified as "highly toxic," paraquat may be used only by certified applicators. [EXTOXNET] Prolonged contact will cause blistering of skin. Poisoning usually occurs after toxic ingestion, e.g., attempted suicide. [EPA Pesticides] Phototoxic contact dermatitis reported in farmworkers; [Kanerva, p. 1823] A multigenerational study in rats given 100 ppm or 300 ppm dietary paraquat showed no effects on fertility or neonatal morbidity and mortality. In mice, maternal feeding with 125 ppm paraquat caused increased mortality in pups that was related to lung injury. [ACGIH] "Among the many herbicides in use, only the bipyridyl compounds have appeared to produce hepatic injury in humans. Even these agents have produced hepatic injury only as the result of ingestion of large amounts, not because of environmental contamination and questionably as the result of occupational exposures." [Zimmerman, p. 415] Paraquat has a chemical structure similar to MPTP, but animal studies have failed to show that paraquat causes parkinsonism. [Rosenstock, p. 1111] See "Paraquat."

Reference Link


Exposure Assessment
Skin Designation (ACGIH)



0.05 mg/m3, inhalable particulate matter, as the cation


0.5 mg/m3, respirable dust


0.1 mg/m3, inhalable fraction


1 mg/m3

Excerpts from Documentation for IDLHs

Human data: It has been stated that the high acute inhalation toxicity of paraquat is dependent wholly on the size of the particulate, with respirable sizes (i.e., <5 micrometer mass median diameter) found to be 5 to 6 times more toxic than nonrespirable dusts [McElligo 1965]. It has been reported that under paraquat spraying conditions particle sizes appear to be nonrespirable [Swan 1969].

Vapor Pressure

1.0E-7 mm Hg

Lethal Concentration

LCLo (rat) = 1 mg/m3/6H for respirable dust;

Half Life

Animal studies: less than 6 hours; other animal studies have found measurable paraquat 26 days after ingestion; [TDR, p. 991]

Reference Link

Phototoxic contact dermatitis with toxic hepatitis due to the percutaneous absorption of paraquat

Adverse Effects
Toxic Pneumonitis





Hepatotoxin, Secondary




Skin Burns

ACGIH Carcinogen

Not Classifiable

Links to Other NLM Databases
Health Studies

Human Health Effects from Hazardous Substances Data Bank:

Toxicity Information


Chemical Information

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Related Information in HazMap

Occupational diseases associated with exposure to this agent:


Industrial Processes with risk of exposure: