Phosphine Exposures in Grain Elevators during Fumigation with Aluminum Phosphide

Abstract

Abstract The Industrywide Studies Branch, DSHEFS, of the National Institute for Occupational Safety and Health (NIOSH) conducted a series of four industrial hygiene surveys in 1985 and 1986 to assess worker exposures to phosphine during the treatment of grain with aluminum phosphide fumigant products. Full-shift breathing zone sampling to measure workers' exposures to phosphine and area monitoring were conducted. In addition, short-term measurements were made to evaluate very brief (2–5 min) peak exposures during specific job tasks and peak concentrations from suspected sources of high concentrations. Results indicate that the use of aluminum phosphide can result in demonstrable, and frequently excessive, exposures when compared to relevant occupational evaluation criteria, even under very cold air temperatures ranging as low as −8°C (18°F). Full-shift personal exposures to phosphine ranged from non-detectable (<0.01 ppm) to 1.6 ppm, which is more than five times the current Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) and the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV) (both 0.3 ppm). Short-term personal exposures during filling and emptying an automatic phosphide tablet dispenser averaged 2.5 ppm and ranged from 0.1-52 ppm over sampling periods ranging from 2–5 minutes. Many of these greatly exceeded the recommended ACGIH short-term exposure limit of 1 ppm. Examination of the sampling data suggested that the exposures to phosphine were partially a result of uncontrolled point sources and lack of appropriate local exhaust ventilation and depended on the general level of fumigation activity. General recommendations for reducing exposures through improved local exhaust ventilation, work practices, and respiratory protection are made.