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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.