A critical review of liquid, low toxicity chemical warfare agent simulants: Enhancing accuracy, safety, and methodological approaches for sampling

The use of simulants is a crucial aspect of studying the behaviour and effects of chemical warfare agents (CWAs) and toxic industrial chemicals (TICs) without the inherent dangers associated with handling and utilising the actual hazardous substances. This review assesses the selection and application of simulants for different classes of CWAs, including nerve agents such as soman, V agents and blister agents such as sulphur and nitrogen mustards. Several simulants were examined, including diethyl malonate, malathion, methyl salicylate, and di (propylene glycol) monomethyl ether, to ascertain their structural and physiochemical properties, yet present minimal toxicity risks. A key insight from this review is the importance of aligning simulant physicochemical properties, such as hydrophobicity, volatility and solubility to those of CWAs. This ensures data relevancy in sampling accuracy and method validation. Our findings demonstrate the efficacy of utilising multiple simulants to model complex interactions within different environmental and forensic matrices, thereby enhancing the precision and reliability of detection and verification procedures. By concentrating on liquid-based simulants and excluding gaseous and solid agents, this review offers a focused assessment of existing sampling methodologies for liquid CWAs in field conditions. It concludes by proposing a unified approach to sampling standards that mitigates the risk with the objective of enhancing the practicality and reliability of detection methods while ensuring personnel safety. Furthermore, this review provides crucial insights for developing robust, field-deployable CWA sampling strategies that strike a balance between accuracy, accessibility and low toxicity.