Worker Exposure Standard for Phosphine Gas

Abstract

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.

The Tobacco Industry and Pesticide Regulations: Case Studies from Tobacco Industry Archives

“…R.J. Reynolds, Brown and Williamson, and several other tobacco companies agreed to fund most of the cost of this work (Seckar 1999e). The paper was published in Risk Analysis in 2004, with the acknowledgment that “This work was supported by the Phosphine/Metal Phosphide Coalition, consisting of the producers and users of phosphine and metal phosphides for the control of insects in stored commodities” (Pepelko et al 2004). …”

Aluminium Phosphide Poisoning

“…Two kinds of acute poisoning with these substances are reported: indirect inhalation of the phosphine generated during their approved use or direct ingestion of the salts. Pure phosphine is colorless and odorless up to toxic concentrations (200 ppm), a view accepted by the International Programme on Chemical Safety and others (Pepelko, et al, 2004;Chaudhry, 1997;IPCS, 1988;Dumas & Bond, 1974), it has an odor of garlicky or decaying fish due to the presence of substituted phosphines and diphosphines .If the former view is accepted the smell emanating from phosphide poisoned patients is probably due to contaminants in the pesticide formulations and not phosphine itself. It has been suggested that these volatile contaminants may be alkylphosphines (Fluck, 1976).…”

Phosphine Toxicity: Ethical Questions

“…In their article McDaniel et al (2005) presented three case studies, one involving an evaluation by Sciences International, Inc. (Pepelko et al 2004), of which I am the president and CEO. This case study was related to the reregistration of phosphine by the U.S. Environmental Protection Agency (EPA).…”

“…Based on this work, an article was published by scientists at my firm in 2004 on the toxicity of phosphine in Risk Analysis (Pepelko et al 2004). The article was published 5 years after the U.S. EPA made their decision (U.S.…”

“…His comments included the recommendation to consolidate them into one article. We submitted a revised and consolidated article in 2003, again handled by Travis; the article was accepted and published in October 2004 (Pepelko et al 2004). McDaniel et al (2005) made an issue of a suggestion I made that the article (Pepelko et al 2004) could be expedited in the publication process.…”