U.S. Department of Agriculture: Animal and Plant Health Inspection Service


Date of this Version



Published in International Biodeterioration & Biodegradation 42 (1998) 109-113.


This study measured depelted-carcass residues of zinc phosphide (Zn3P2, CAS # 1314-84-7) in 8 (4 males and 4 females) gray-tailed voles (Microtus canicaudus). Six (3 males and 3 females) voles were confined individually in 1.89 dkl (5 gal) plastic pails that contained 5,2% Zn3P2 steamrolled- oat (SRO) groats; 2 voles (1 male and 1 female) served as analytical (unbaited) controls. Four test voles (3 males and 1female) died within 7.5 h after bait exposure; whereas, 2 test voles showed no signs of toxicosis and were euthanized 7.0 h after bait exposure. Whole carcasses were stored frozen and depelted carcasses were analyzed within 31 days for Zn3P2 residues using a acid-hydrolyzation, gas-chromatographic (GC) method. Analytical controls were euthanized, with carcasses stored and analyzed the same as test voles. A mean (± SD) 4.7 (±0.8) SRO groats were consumed by the test voles; this converted to a mean (±SD) intake of 2.15 (±0.38) mg Zn3P2 and dose of 73.25 mg/kg ( ± 22.95) Zn3P2. The mean (± SD) Zn3P2 residue in the 6 test vole carcasses was 0.42 mg (± 0.68); control carcasses contained <0.009 mg Zn3P2- 3P2 in voles are variable, but typically < 50% of ingested rodenticide and (2) risks of secondary poisoning posed by Zn3P2-baited voles to avian and mammalian predators/scavengers are low due to the relatively high toxic thresholds (> 20 mg/kg) required to affect these species.