Zinc phosphide is a very potent rodenticide that was very first registered in 1947. It has a broad range of uses commercially and residentially, including the protection of food crops and grasses. It may also be used as an insecticide (#NPIC).
Zinc phosphide may be sold under trade names including Arrex, Commando, Denkarin Grains, Gopha-Rid, Phosvin, Pollux, Ridall, Ratol, Rodenticide AG, Zinc-Tox and ZP (#EXTOXNET).
Zinc phosphide is a gray black powder. It has an odor similar to that of garlic. It is practically insoluble in water (#NPIC).
Zinc phosphide is commercially available as bait pellets, granules, dust, and tracking powder (#NPIC).
Zinc phosphide is used for rodent control on crops including grapes, sugarcane, artichoke, sugar beet, alfalfa, barley, berries, oats, sugar maple, wheat, corn, and hay. It is also used on grasses such as home lawns, rangeland, and golf courses (#EPA).
Zinc phosphide targets household rodent pests, such as mice and rats, in addition to field rodents including voles, ground squirrels, pocket gophers, prairie dogs, and jack rabbits (#NPIC).
Human Health Effects
Zinc phosphide very toxic in acute exposures. It is converted to phosphine gas by the moisture and acidity of the tummy. The acute oral LD50 is twenty one mg/kg for rats and 60-70 mg/kg for sheep. Zinc phosphide is converted into phosphine via ingestion, which is the compound which causes its high toxicity (#NPIC). However the EPA placed both the inhalation and oral routes of exposure in Toxicity Category I, the possible highest toxicity rating (#EPA).
People chronically exposed to petite amounts of zinc phosphide have reported weakness, anemia, toothache, necrosis of the jaw bones, weight loss, and spontaneous fractures. Blood samples taken from fumigation workers treating zinc phosphide exposed a higher rate of chromosomal abnormalities (#NPIC).
Zinc phosphide is listed as a developmental toxin in the Toxics Release Inventory (#PANNA).
Zinc phosphide is known to cause a number of symptoms such as coughing, diarrhea, headache, tiredness, nausea, vomiting, searing sensations. Exposing the eyes may cause photophobia. Specific to ingestion are abdominal ache, dizziness, unconsciousness, and ataxia (#PANNA). Failure to treat zinc phosphide poisoning may result in catastrophic outcomes.
Environmental Health Effects
The toxicity of zinc phosphide comes from phosphine after it is chemically converted in the belly. Thus, zinc phosphide must be ingested to become toxic. After phosphine is absorbed in the gastrointestinal tract, it inhibits cytochrome C oxidase, which is vital to mitochondrial respiration. It is suspected that there are other modes of activity in its toxicity (#NPIC).
Zinc phosphide has a high avian toxicity. The acute oral LD50 for northern bobwhite quail is 12.9 mg/kg. If in solution, it can also be very toxic to fish. The 96-hour LC50 for rainbow trout is .0097 ppm (#NPIC).
Zinc phosphide is expected to persist for approximately two weeks in soil. The degeneration of zinc phosphide may be accelerated by soil acidity and moisture, but this may also cause the release of toxic phosphine gas (#EXTOXNET).
Zinc phosphide is expected to have a low mobility in soil (#EPA).
Zinc phosphide is a Restricted Use Pesticide, meaning that it can only be purchased and used by certified applicators. However, formulations in lower concentrations are available for the general public to purchase.
Zinc phosphide is very toxic to humans. A single gulp of zinc phosphide rodent bait could be fatal to a youthful child (#EPA). Treated areas may release toxic phosphine gas.
Integrated Pest Management
Integrated pest management (IPM) is an treatment to pest management that can significantly reduce pesticide use. Widely used in agriculture, landscape maintenance, and structural pest control, it emphasizes prevention and monitoring of pest problems and considers pesticide applications only when nonchemical controls are ineffective or impractical.
To learn more about IPM, see Toxipedia’s sister site IPMopedia, which includes information on control of vertebrates.