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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. Zinc phosphide reacts with water and acid in the stomach and causes severe irritation (7). Symptoms of acute zinc phosphide poisoning include nausea, shock, weak heart beat and low blood pressure, loss of consciousness (3). Other symptoms include vomiting, diarrhea, cyanosis, rales, restlessness and fever. There are documented cases of adults dying from massive doses of the pesticide (4,000 to 5,000 mg) although others have survived acute exposure of as high as 25,000 mg to 100,000 mg of zinc phosphide if vomiting occurred early and absorption was limited (4).
The LD50 for the technical product (80-90% pure) is 45.7 mg/kg while the LD50 values for lower concentration formulations are slightly higher (i.e. less toxic). In sheep the LD50 ranges from 60 to 70 mg/kg (6).
The inhalation of zinc phosphide or its breakdown product phosphine gas may result in acute toxicity (7). No specific doses were mentioned in the reference. The compound is non-irritating to the skin and eyes (5).
Rats fed zinc phosphide over a wide range of doses experienced toxic effects at the lowest dose tested. Increased liver, brain and kidney weights were noted in rats exposed to around 10 mg/kg. Body hair loss, reduction in body weight, and reduction of food intake were all noted at 3.5 mg/kg. The study was conducted over thirteen weeks (7).
There have been no observed symptoms of chronic poisoning due to zinc phosphide exposure in humans (5). However another reference noted that chronic exposure to sublethal concentrations for extended periods of time may produce toxic symptoms (7). No specific note was made of the toxic symptoms or the doses required to produce them. In that the available information is inconclusive or undocumented, no definitive conclusions can be drawn to the chronic toxic potential of zinc phosphide.
Damage to the kidneys, to 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 (7).
“Outbreak of illness due to unintentional exposure to zinc phosphide rodenticide, Egypt-1996”
Authors: Ghafar, A. M. Abdela; Allam, S.a; Fikry, M.a; Barakat, M.a; Fathy, M. A.a; Hassanien, N.a; Mansour, E.a; Abdeen, F. M.a; Imam, I. Z.a; Rahka, M. A.a; Pertowski, C. A.a; Fishbein, D. B.a; Nasr, M. Abua; Hatch, D. L.a
Affiliations: a. Egyptian Field Epidemiology Training Program, Cairo, Egypt
Abstract (English): Introduction: In April 1996, local public health officials of Aswan Governorate in southern Egypt reported an outbreak of illness due to an unknown cause. Illness was characterized by vomiting without diarrhea, abdominal and back pain. 25 persons were hospitalized from three unrelated families in one village; 2 deaths occurred in children under 5 years. Officials requested the Field Epidemiology Training Program to assist the field investigation.
Methodology: A toxic etiology was considered because of the afebrile nature of illness and lack of spread to nearby households. Testing of the vomitus of persons hospitalized showed 7 of 14 specimens contained phosphide. A case-control study was conducted to determine the cause of the outbreak. Cases were defined as persons living in the affected village, treated at health facilities for vomiting without diarrhea between February and April 1996. Controls were randomly chosen from sex-matched members of households adjacent to case families.
Discussion: Prompt laboratory analysis and a collaborative field investigation promptly identified zinc phosphide as the probable cause of this outbreak.
Conclusions: Discussion of the study results with local public officials resulted in banning of the use of this material and its local distribution. Health education of community leaders and families about the cause was conducted and surveillance has been established to identify any additional cases of disease