Determination of airborne concentrations of dichlorvos over a range of temperatures when using commercially available pesticide strips in a simulated military guard post

ABSTRACT

Dichlorvos is a chemical compound which has been used for decades as a pesticide. Potential inhalational exposure to dichlorvos vapor associated with using commercially-based, dichlorvos-impregnated resin strips in a simulated military guard post was evaluated. A varying number of these pesticide strips, ranging from the manufacturer's guidelines ((3)-16 g strips) up to a full package of strips ((12)-16 g strips), were placed in a small, enclosed space (2.31 m x 2.26 m x 2.44 m, 12.7 m³), which was similar in size to a typical military guard post. Static air sampling was then conducted to simulate personal air sampling, followed by analysis using OSHA Method 62 (GC-ECD). Air sampling was conducted over a range of discrete temperatures (26–38˚C) which approximated average ambient temperatures expected in a variety of deployed environments. Air sampling in this range was conducted to determine the airborne concentration generated at each temperature setting. Airborne concentrations were then compared to established short term military exposure guidelines (MEGs) and the 8-hr OSHA permissible exposure limit (PEL) for dichlorvos (both criteria limits are 0.99 mg/m³). Results from air sampling indicated that exceeding the manufacturer-recommended number of strips for the workspace volume and environmental conditions produced airborne dichlorvos concentrations above established occupational standards (1.77–3.70 mg/m³). Such exposures may potentially lead to adverse effects, such as loss of mental and visual acuity for guard post watch standers who employ more strips within a space than recommended per the manufacturer for the size of the space. However, concentrations of airborne dichlorvos generated when adhering to manufacturer's guidelines based on workspace volume resulted in levels of 0.16–0.39 mg/m³ for 1-hr and 8-hr timeframes, which were below the established occupational health limits. While dichlorvos-impregnated strips are not currently recommended for use in manned workspaces for periods > 4 hr, findings suggest that prolonged use (8 hr) of similar pesticide strips within manned spaces to repel and/or kill disease-carrying insects may be possible without experiencing adverse health effects.

KEYWORDS:

• Dichlorvos
• military exposure guidelines
• military guard posts
• OSHA Method 62

Acknowledgments

We thank Captain Steve Rankin and the Armed Forces Pest Management Board for offering their time to discuss current insect borne issues affecting deployed service members. These discussions assisted us in understanding current spatial repellent products and applications under consideration, which eventually led to the development of the main objective for this project. Additionally, we thank LCDR Matthew Mercer for his assistance in reviewing and providing feedback throughout the writing process. Moreover, a very special thanks to Ms. Helen Penn and the team of professionals at the Navy Consolidated Industrial Hygiene Laboratory (CIHL, Norfolk, VA) for timely analysis of all of the air samples.

Disclaimers

The views expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense, nor the U.S. Government. The authors are military service members, or U.S. government federal employees or contractors. This work was prepared as part of their official duties. Title 17 U.S.C. §105 provides that “Copyright protection under this title is not available for any work of the United States Government.” Title 17 U.S.C. §101 defines a U.S. Government work as work prepared by military service members or employees of the U.S. Government as part of that person's official duties.

Funding

This work was funded by the Military Infectious Diseases Research Program (Project MIDRP U0340_12_WR).