Zinc phosphide (chemical formula: Zn₃P₂) is an inorganic compound that combines phosphorus with zinc. The IUPAC chemical name is trizinc diphosphide, and its CAS registry number is 1314-84-7. It is a grey-black powder with a garlic-like odour, practically insoluble in water and insoluble in alcohol.
What is Zinc Phosphide used for?
Zinc phosphide is widely used as a rodenticide. Applications include:
Grasslands: home lawns, rangelands, and golf courses.
Household pests: mice and rats.
Field rodents: voles, ground squirrels, pocket gophers, prairie dogs, and jackrabbits.
Zinc phosphide is widely used as a rodenticide in agricultural settings. It helps protect high-value crops—such as grapes, sugarcane, artichokes, sugar beets, and cereals—from rodent infestations during the growing season.
Sources and Routes of Exposure
Sources of Exposure
Direct contact with pesticide formulations containing zinc phosphide (handling bait, spills, or dust).
Ingestion of bait pellets, particularly by children or pets attracted to flavour additives (e.g., peanut butter, molasses).
Occupational exposure during application without proper PPE.
Inhalation of dust or powdered bait during handling.
Routes of Exposure
Inhalation
Skin contact
Eye contact
Ingestion
Health Risks
Acute Effects
Inhalation: Zinc phosphide dust reacts with moist tissues of the respiratory tract to release phosphine gas, leading to pulmonary oedema and cardiotoxicity.
Ingestion: Produces phosphine in the gastrointestinal tract, causing headache, dizziness, nausea, vomiting, cough, chest tightness, thirst, fatigue, and dyspnea. Severe cases progress to liver failure, jaundice, anuria, tetany, delirium, convulsions, coma, and death.
Pathology: Fatal exposures show necrosis in the liver, kidneys, myocardium, alveolar tissue; pulmonary oedema and congestion; and hypoxic brain damage.
Delayed toxicity: Death may occur up to 30 hours post-exposure due to progressive organ failure.
Other findings: Hyperglycaemia and elevated creatine phosphokinase have been reported in severe poisonings. Phosphine can inhibit acetylcholinesterase, although the role of this mechanism remains unclear.
carcinogenicity
The U.S. EPA considers chronic exposure negligible and has waived carcinogenicity testing requirements.
No human data are available on the carcinogenicity of zinc phosphide or phosphine.
Safety
First Aid Measures
General: Move victim to fresh air immediately. Emergency responders should avoid self-exposure to zinc phosphide.
Assessment: Evaluate vital signs, including pulse and respiratory rate. Note any trauma.
No pulse: Begin cardiopulmonary resuscitation (CPR).
Not breathing: Provide artificial respiration.
Laboured breathing: Administer 100% humidified oxygen or other respiratory support.
Medical care: Transport the victim promptly to a healthcare facility. Obtain authorisation and/or further instructions from the local hospital for any invasive procedures.
Workplace Controls & Practices
Always use zinc phosphide in well-ventilated areas.
Wash hands, arms and face thoroughly with soap and water after handling zinc phosphide and before eating, drinking or smoking.
Personal Protective Equipment (PPE)
When handling zinc phosphide, the following PPE is recommended:
Gloves: PVC gloves.
Respiratory protection: Full face-piece respirator with combined dust and gas cartridge, or supplied air respirator (consult AS/NZS 1715 for selection).
Maintenance: After each day’s use, wash gloves and respirator. If rubber components are used, clean with detergent and warm water.
Regulation
United States
No occupational exposure limits have been established for zinc phosphide. However, as zinc phosphide can be converted to phosphine gas the following exposure limits apply to phosphine:
OSHA Permissible Exposure Limit (PEL):
General Industry: 29 CFR 1910.1000 Table Z-1 -- 0.3 ppm, 0.4 mg/m3 TWA
Construction Industry: 29 CFR 1926.55 Appendix A -- 0.3 ppm, 0.4 mg/m3 TWA
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