Aluminum phosphide poisoning--a review

Worker exposure standard for phosphine gas

The 1998 U.S. Environmental Protection Agency Office of Pesticide Programs (OPP) re-registration eligibility decision (RED) for phosphine fumigants has generated much interest in defining safe levels of exposure for workers and worker bystanders. This report summarizes the pertinent literature on phosphine toxicity, including animal inhalation studies and human epidemiology studies, and also describes a margin-of-exposure (MOE) analysis based on available worker exposure data. In addition, a safe occupational exposure limit is estimated using typical OPP assumptions, after determination of appropriate uncertainty factors, based on quality of data in the principal study and pharmacokinetic considerations. While a conservative 8-hour time-weighted average (TWA) of 0.1 ppm was calculated, the overall weight of evidence, from a risk-management perspective, supports a conclusion that an occupational TWA of 0.3 ppm provides adequate health protection. In addition, a 15-minute short-term exposure limit (STEL) of 3 ppm was estimated. Finally, in contrast to the MOE analysis described in the OPP's phosphine RED, the MOE analysis described herein does not indicate that fumigation workers are currently being exposed to unacceptable levels of phosphine. Collectively, these findings support the occupational exposure limits of 0.3 ppm (8-hour TWA) and 1 ppm (STEL) established in the updated applicator's manuals for phosphine-generating products, which recently received approval from OPP.

Phosphine-induced oxidative damage in rats: role of glutathione

Phosphine (PH(3)), generated from aluminium, magnesium and zinc phosphide, is a widely used pesticide. PH(3) induces oxidative stress in insects, mammalian cells, animals, and humans. The involvement of glutathione (GSH) in PH(3)-induced oxidative toxicity is controversial. GSH levels in various tested tissues were reduced in aluminium phosphide-poisoned rats and humans, while the levels remained unchanged in insects and mammalian cells. This study examines the effectiveness of endogenous GSH as a protective agent against PH(3)-induced oxidative damage in rats. The association of PH(3)-induced nephrotoxicity and cardiotoxicity with free radical production was also tested. Male Wistar rats, administered intraperitoneally (I.P.) with PH(3) at 4 mg/kg, were evaluated 30 min after treatment for PH(3) toxicity to organs. PH(3) significantly decreased GSH, GSH peroxidase and catalase, while significantly increased lipid peroxidation (as malondialdehyde and 4-hydroxyalkenals), DNA oxidation (as 8-hydroxydeoxyguaonsoine) and superoxide dismutase (SOD) levels in kidney and heart. These changes were significantly alleviated by melatonin (10 mg/kg I.P., 30 min before PH(3)), with the exception of SOD activity in heart tissue. The study also found that buthionine sulfoximine (1 g/kg I.P., 24 h before PH(3)) significantly enhanced the effect of PH(3) on GSH loss and lipid peroxidation elevation in lung. These findings indicate that (1) endogenous GSH plays a crucial role as a protective factor in modulating PH(3)-induced oxidative damage, and (2) PH(3) could injure kidney and heart (as noted earlier with brain, liver and lung) via oxidative stress and the antioxidant melatonin effectively prevents the damage.

Aluminum phosphide fatalities, new local experience

Aluminum phosphide (AlP) pesticide is a highly toxic, low cost, and easily accessible rodenticidal agent. Its toxicity results from the liberation of phosphine gas upon exposure to moisture, which leads to multisystem involvement, resulting in serious consequences. The highly toxic parathion insecticide was a common cause of mortality in pesticide fatalities, prior to its banning. Its toxicity was familiar to the public as well as to physicians. Recently, ten fatalities due to AlP were encountered within a three-month period during spring, when it was used as a rodenticide in the vicinity of grain stores. The victims' ages ranged from 1-34 years. The circumstances of death were accidental in six cases, suicidal in two and possibly homicidal in two cases. Retrospectively, the clinical manifestations, scene investigation, autopsy, histological and toxicological findings supported the diagnosis of AlP intoxication. Immediate recognition was difficult due to unfamiliarity of the agent to the physicians. The occurrence of these fatalities might suggest changes of pattern in pesticide poisoning. This should raise the attention of the physician to the problem of AlP poisoning and also necessitates the awareness of the public to the hazards of this poison. Education, proper handling, strict observation and abiding by the regulations controlling this material are good protective measures against AlP poisoning.