A Review of Chemical Warfare Agent Simulants for the Study of Environmental Behavior

Abstract

There is renewed interest in the environmental fate of chemical warfare agents attributable to the intensified threat of chemical weapons use in a terrorist attack. Knowledge of processes that influence the fate of agents such as distilled mustard, lewisite, tabun, sarin, soman, and VX in the environment is important for development of disposal strategies and for risk and exposure assessments. However, it is often necessary to conduct studies examining chemical agent behavior using simulants due to the toxicity of the agents and usage restrictions. The objective of this study was to review the physical–chemical properties and mammalian toxicity of compounds that can be used to simulate chemical agents and to identify the most appropriate compounds to simulate specific environmental fate processes, including hydrolysis, sorption, bioavailability, and volatilization.

KEY WORDS:

• microbial degradation
• partition coefficient
• simulant
• toxicity
• warfare agent

ACKNOWLEDGEMENTS

This research was supported by the U.S. Environmental Protection Agency (EPA) through the Safe Buildings Program, Susan Thorneloe, Senior Project Officer. The input of Susan Thorneloe and Paul Lemieux of the U.S. EPA is acknowledged.

Notes

^a Data sources include. ^{10 , 14 , 16 , 19 , 29 , 56}

^b Estimated with EPISuite v.3.12. ²⁹

^c at 13 mm Hg.

^d Predicted using SPARC. ²⁵

^a Data compiled from the following sources. ¹⁴ , ¹⁶ , ¹⁹ , ²⁹ , ⁵⁶ , ⁵⁷

^b Estimated with EPISuite v.3.12. ²⁹

^c Predicted using SPARC. ²⁵

^d At 10 mm Hg.

^a Data sources include. ¹⁰ , ¹⁴ , ¹⁶ , ¹⁹ , ²⁹ , ⁵⁶ , ⁵⁸

^b Reported pK _a values for VX range from 8.6 to 9.12. ²³ , ²⁴

^c Estimated with EPISuite v.3.12. ²⁹

^d Predicted using SPARC. ²⁵

^e At 0.7 mm Hg.

^f At 0.2 mm Hg.

^g Predicted using ChemSilico software. ⁵⁹

^a Data sources include. ^{14 , 17 , 29}

^b Temperature not reported.

^c Estimated with EPISuite v.3.12. ²⁹

^a iv = intraveneous, sc = subcutaneous, ip = intraperitoneal.

^b Qualitative toxicity assessment determined by comparison of available LD₅₀ values for simulant and original CWA for a given exposure pathway and target organism. Simulant toxicity data within one order of magnitude when compared to the original CWA were determined to have “equivalent” toxicity.

^c Not determined because no LD₅₀ values were available for the simulant.