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The information in this profile may be out-of-date.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

Zinc phosphide

Trade and Other Names: Trade names for commercial products containing zinc phosphide include Arrex, Commando, Denkarin Grains, Gopha-Rid, Phosvin, Pollux, Ridall, Ratol, Rodenticide AG, Zinc-Tox and ZP.

Regulatory Status: Zinc phosphide is a Restricted Use Pesticide (RUP) because of its hazard to non-target organisms and its acute oral toxicity. RUPs may be purchased and used only by certified applicators. Some formulations of this rodenticide are classified as highly toxic and require the Signal Word DANGER - POISON on the label. Others are either moderately toxic or only slightly toxic, and thus require the Signal Words WARNING or CAUTION, respectively.

Chemical Class: inorganic compound

Introduction: Zinc phosphide is an inorganic chemical that is used to control rats, mice, voles, ground squirrels, prairie dogs, nutria, muskrats, feral rabbits, and gophers. It is also used as a tracking powder for the control of house mice. It is applied to crop areas and non-crop areas including lawns, golf courses, highway medians, and areas adjacent to wetlands. It may be formulated as a grain based bait, as scrap bait, or as a paste. Rodenticide baits usually contain 0.5 to 2.07% zinc phosphide, pastes approximately 5 to 10%.

Formulation: It may be formulated as a grain based bait, as scrap bait, or as a paste. Rodenticide baits usually contain 0.5 to 2.07% zinc phosphide, pastes approximately 5 to 10%.

Toxicological Effects:

• Acute toxicity: Zinc phosphide ingested orally reacts with water and acid in the stomach and produces phosphine gas, which may account in a large part for observed toxicity [160]. Symptoms of acute zinc phosphide poisoning by ingestion include nausea, abdominal pain, tightness in chest, excitement, agitation, and chills [160,8]. Other symptoms include vomiting, diarrhea, cyanosis, rales, restlessness, and fever [8,160]. The inhalation of zinc phosphide or its breadkown product phosphine gas may result in vomiting, diarrhea, cyanosis, rapid pulse, fever, and shock [160]. There are documented cases of adults dying from massive oral doses of 4000 to 5000 mg (approximately 55 to 70 mg/kg), although others have survived acute exposure of as high as 25,000 to 100,000 mg (approximately 350 to 1400 mg/kg) if vomiting occurred early and exposure to phosphine was limited [160]. In rats, the LD50 for the technical product (80 to 90% pure) is 40 mg/kg, while the LD50 values for lower concentration formulations are slightly higher, indicating lower acute toxicity [160]. In sheep the LD50 ranges from 60 to 70 mg/kg [160]. The compound is nonirritating to the skin and eyes [160].
• Chronic toxicity: Rats fed zinc phosphide over a wide range of doses experienced toxic effects. Increased liver, brain, and kidney weights, and lesions on these organs, were noted in rats exposed to around 14 mg/kg/day. Body hair loss, reduction in body weight, and reduction of food intake were all noted at 3.5 mg/kg/day. The study was conducted over 13 weeks [8]. There have been no observed symptoms of chronic poisoning due to zinc phosphide exposure in humans [1]. However, it has been suggested that chronic exposure to sublethal concentrations for extended periods of time may produce toxic symptoms [8].
• Reproductive effects: No data are currently available.
• Teratogenic effects: No data are currently available.
• Mutagenic effects: No data are currently available regarding the mutagenicity of zinc phosphide. However, its metabolite, phosphine, has shown a concentration-dependent increase in chromosomal aberrations in studies using human lymphocyte cultures [8]. Thus, its mutagenicity is unclear.
• Carcinogenic effects: No data are currently available.
• Organ toxicity: Damage to the kidneys, the liver, and the stomach have been noted in humans, but only at high acute doses of the rodenticide. Zinc phosphide reacts with water and stomach juices to release phosphine gas, which can enter the blood stream and adversely affect the lungs, liver, kidneys, heart, and central nervous system [8].

• Fate in humans and animals: Small amounts of the rodenticide fed to experimental animals may have produced an 80% absorption of zinc as well. Zinc in sufficient concentrations may have an emetic effect [8]. Hypophosphite may be excreted in the urine as a metabolite of zinc phosphide [160]. There is little tendency for the compound to concentrate in living tissue, as it is readily converted to phosphine.

Ecological Effects:

• Effects on birds: Zinc phosphide is highly toxic to wild birds The most sensitive birds are geese (LD50 of 7.5 mg/kg for the white-fronted goose). pheasants, mourning doves, quail, mallard ducks, and the horned lark are also very susceptible to this compound. Blackbirds are less sensitive [8].
• Effects on aquatic organisms: Zinc phosphide is highly toxic to freshwater fish. The fish species which have been evaluated include bluegill sunfish (LC50 of 0.8 mg/L) and rainbow trout (LC50 of 0.5 mg/L) [1]. Carp were also found to be susceptible to zinc phosphide, especially in weakly acidic water.
• Effects on other organisms: Zinc phosphide is also toxic to non-target mammals when ingested directly [8]. Nearly 60 studies have been conducted on the toxicity of this rodenticide to wild animals. Secondary toxicity to mammalian predators (animals eating other animals that had been exposed to the compound) from zinc phosphide is rather low, primarily because the compound does not significantly accumulate in the muscles of target species [8]. Some of the toxic effects to predators have been due to the ingestion of zinc phosphide that was in the digestive tract of the target organism. Studies on secondary organisms have focused on coyotes, fox, mink, weasels, and birds of prey. Under field conditions, most of the toxic effects to non-target wildlife are due to direct exposures resulting from misuse or misapplication of this rodenticide [8].

Environmental Fate:

• Breakdown in soil and groundwater: Zinc phosphide may be applied as an active ingredient in either bait or a dust. Under average conditions, toxic activitity persists for approximately 2 weeks [8]. Soil acidity and moisture tend to accelerate the breakdown of the compound [8]. Phosphine gas may be liberated as a result of this process.
• Breakdown in water: No data are currently available.
• Breakdown in vegetation: No data are currently available.

Physical Properties:

• Appearance: Zinc phosphide is an amorphous black-grey powder with a garlic-like odor [1]. It is stable when dry and decomposes in moist air [1].
• Chemical Name: trizinc diphosphide [8]
• CAS Number: 1314-84-7
• Molecular Weight: 258.09
• Water Solubility: Practically insoluble in water (decomposes slowly) [8]
• Solubility in Other Solvents: Practically i.s. in alcohol; s.s. in benzene and carbon disulfide [8]
• Melting Point: >420 C [8]
• Vapor Pressure: Negligible in the dry state (as solid) [8]
• Partition Coefficient: Not Available
• Adsorption Coefficient: Not Available

Exposure Guidelines:

• ADI: Not Available
• MCL: Not Available
• RfD: 0.0003 mg/kg/day [13]
• PEL: Not Available
• HA: Not Available
• TLV: Not Available

Basic Manufacturer:

Hacco, Inc.
P.O. Box 7190
537 Atlas Ave.
Madison, WI 53707

• Phone: 608-221-6200
• Emergency: 800-642-4699
  

References:

References for the information in this PIP can be found in Reference List Number 10

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.