Exposure of Persons to Phosphine Gas from Aluminum Phosphide Application to Rodent Burrows
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University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Proceedings of the Fifteenth Vertebrate Pest Vertebrate Pest Conference Proceedings Conference 1992 collection March 1992 EXPOSURE OF PERSONS TO PHOSPHINE GAS FROM ALUMINUM PHOSPHIDE APPLICATION TO RODENT BURROWS Rex O. Baker California State Polytechnic University, Plant and Soil Science Department Follow this and additional works at: https://digitalcommons.unl.edu/vpc15 Part of the Environmental Health and Protection Commons Baker, Rex O., "EXPOSURE OF PERSONS TO PHOSPHINE GAS FROM ALUMINUM PHOSPHIDE APPLICATION TO RODENT BURROWS" (1992). Proceedings of the Fifteenth Vertebrate Pest Conference 1992. 5. https://digitalcommons.unl.edu/vpc15/5 This Article is brought to you for free and open access by the Vertebrate Pest Conference Proceedings collection at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Proceedings of the Fifteenth Vertebrate Pest Conference 1992 by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. EXPOSURE OF PERSONS TO PHOSPHINE GAS FROM ALUMINUM PHOSPHIDE APPLICATION TO RODENT BURROWS REX O. BAKER, Professor, California State Polytechnic University, Plant and Soil Science Department, 3801W. Temple Avenue, Pomona, California 91768 ABSTRACT: An industrial hygiene study was performed monitoring levels of phosphine gas workers are exposed to when applying aluminum phosphide tablets to rodent burrows. Clothing and gloves were monitored for phosphine gas from residual dust. Air in the breathing zone was monitored with short and long term monitoring equipment. No levels of phosphine exceeding the legal permissible exposure limits (PEL) was detected and although residues were detected on clothing, the levels were usually quite low and dissipated in open air to undetectable levels within 12 to 17 hours in all but a few cases. Hand application was also compared to a mechanical (closed system) type application device which resulted in significantly lower phosphine exposure. Proc. 15th Vertebrate Pest Conf. (J. E. Borrecco & R. E. Marsh, Editors) Published at University of Calif., Davis. 1992 INTRODUCTION found on product labels, in product literature, in Occupa- Aluminum phosphide is a fumigant used for many years tional Safety and Health Standards developed under the U.S. to eliminate stored product pests, especially insect pests of Occupational Health and Safety Act (OSHA) and in National grain and cereal products. Over the last decade this fumigant Institute for Occupational Safety and Health (NIOSH/OSHA) has become well recognized as a very effective rodent control Occupational Health Guidelines. In California, Pesticide tool when applied to burrow systems (Hayes 1982, Salmon Worker Safety laws and regulations require additional safety 1982, Baker 1986). The discovery of aluminum phosphide as precautions which are enforced by licensed County Agricul- a rodent control agent was timely, since at least three other tural Commissioner personnel under the supervision and di- fumigants, methyl bromide, carbon disulfide and hydrogen rection of the Department of Pesticide Regulation. Some of cyanide are no longer registered for use. In addition, several the requirements in the California Code of Regulations (CCR) toxic bait chemicals have also been removed from use leav- regarding worker safety are reported to be causing unsafe ing the industry with few chemical tools for controlling bur- conditions and unnecessary expense to governmental rowing rodents. agencies and private industry. Persons wearing required Agricultural producers, pest control operators and gov- goggles and long-sleeved clothing (Sections 6738 & 6736 ernmental agencies have become increasingly reliant on alu- CCR 1991) complain of fogging of glasses and excessive minum phosphide for control of burrowing rodents in perspiration, due to this required clothing being worn (Anon. “urban,” “suburban” and “rural” areas, just as the Food 199 lb). The fogged safety glasses or goggles have been cause Industry has (Anon. 1985). The material has been found to be for numerous reports of falls on slopes and rough terrain. The much more efficient, when proper soil and moisture condi- excessive respiration rate and perspiration may increase the tions exist, than many other materials for control of ground hazards associated with this water reactive material. It is also squirrels, pocket gophers, Norway rats and under some condi- felt that the cost of daily clean clothing is an unnecessary tions for moles (Hayes 1982, Shaheen 1981). When used expense. Gloves are required for all Category I materials and according to the label, the product is safe for the applicator, must be new daily or washed inside and out. Additionally, the general public and the environment (Anon. 1986, some labels suggest using rubber or cotton gloves, however, Fachmann and Gokhale 1973). However, care must be taken they do not last and provide little protection for the rough to follow the label since hydrogen phosphide (phosphine) handling burrow fumigation requires. Leather is the industry liberated from the tablets in the presence of moisture in the choice for long wear and good protection, but cannot be soil and atmosphere, is an acutely toxic gas by inhalation and washed as required. is classified as a highly toxic Category I pesticide (Anon. The CCR regulations (Section 6730) also requires per- 1981). Accidental poisoning in humans has occurred only sons applying Category I materials to either not work alone or as a result of improper application or improper handling report by phone or radio every two hours. Section 6720(b) and no incident could be found in literature review or per- exempts persons working with vertebrate pest control baits sonal interviews of human poisoning during rodent burrow from the “work clothing and not working alone” require- applications. ments and Section 6738 also exempts eye protection and Exposure to unsafe gas levels must be avoided by ob- glove requirements for these same baits. Many governmental serving proper application precautions, aeration and re-entry and private industry leaders feel that solid fumigants—to in- procedures when used in structures, according to Pestcon clude aluminum phosphide, magnesium phosphide, and product literature. Many safety precautions are required when smoke cartridges—should also be exempt when being used handling aluminum phosphide products. Most of the precau- for rodent burrow treatment. tions, however, address use for fumigation of stored products in silos, ships, grain mills and other enclosed areas, which is ALUMINUM PHOSPHIDE “TECHNICAL the primary use of the product (Anon. 1985). Use in these INFORMATION” situations is much more likely to create hazardous environ- There are several commercial brands of aluminum phos- ments for application personnel, than when used outside for phide such as Pestcon Systems Fumitoxin®, Degesch rodent burrow application. Required safety precautions are Phostoxin®, and Bernardo Chemicals Gastoxin®, but all 312 are prepared as hard pressed tablets or pellets for rodent con- or less prior to re-entry by unprotected workers. These expo- trol use. These solid products are composed of 55% finely sure limits have been developed to avoid short term acute ground aluminum phosphide, ammonium carbamate and may toxicity and low level chronic effects. The odor threshold of contain a binder or coating of paraffin. These products are the commercial products containing aluminum phosphide and classified as “Water Reactive” and “Flammable Solids” and ammonium carbonate is reported to be 0.01 to 0.02 ppm, well contact with water is to be avoided. The aluminum phosphide below the PEL suggesting the odor is an adequate warning liberates hydrogen phosphide (phosphine) gas upon exposure agent (Fluck 1976, Gibbons 1988). There are times however, to atmospheric moisture; this gas is spontaneously flamm- when the odor may not be adequate to serve as a strong able and piling of the tablets or dust should be avoided. The enough warning property (Zaebst 1988). ammonium carbamate liberates ammonia and carbon dioxide According to Dr. Jeremiah B. Sullivan, former President which reduces the fire hazard of the phosphine and the smell of Degesch of America, and literature reviewed, phosphine is of ammonia gas also serves as an initial warning agent since it either not absorbed percutaneously (through the skin) begins to smell like garlic immediately upon opening the (Fachmann and Gokhale 1972), or if it is at all, not in any container (Anon. n.d.). Exposure to phosphine must not ex- significant amount (Hayes 1982). ceed the 8 hour time weighted average (TWA) or OSHA The tablets and pellets are packaged in aluminum flasks permissible exposure limit (PEL) of 0.3 ppm (Gibbons 1988) which are resealable by re-tightening the rubber gasketed (Anon. 1975). The American Conference of Governmental screw top (Fig. 1). The rate of decomposition of the material Industrial Hygienists (ACGIH) has also established a short- depends on the moisture and temperature with total decom- term exposure limit (STEL) of 1 ppm for exposure time position of the whole tablets taking from a few days in ideal weighted over any 15 minute period with no more than four conditions to 5 days or more under low moisture content and exposures per day (Zaebst 1988). These limits were estab- low temperatures (Anon. n.d.). Decomposition of active dust lished for use in confined areas such as commodity fumiga-