“…Following exposure, OP pesticides and nerve agents readily interact with enzymes and proteins within the biological matrix to produce a number of relevant biomarkers, including the following: (i) OP adducts by phosphorylation of proteins, including enzymes, resulting in the loss of enzyme (e.g., cholinesterase) activity; (ii) metabolites by hydrolysis; (iii) unbound free OP in fluids . All are typical biomarkers of exposure to OP agents; therefore, some methods such as enzyme activity assays, immunoassays of OP adducts − and metabolites, and GC/LC MS analysis of OP adducts, metabolites, and free OPs have been developed for biomonitoring of exposure to OP agents. , However, for simple and rapid diagnosis/screening, especially in emergency cases, laboratory-based analytical methods (GC/LC MS) are not ideal because of lack of portability and lack of real time results. , Immunoassays of OP adducts or metabolites for diagnosis of OP exposure are challenged because of unavailability of OP-specific antibodies. Hence, the most utilized detection method is to measure enzyme activity, since it is a rapid and simple method for OP exposure evaluation and risk assessment. , Some methods, including the colorimetric Ellman assay, fluorescence assays, the Michel (ΔpH) ChE assay, radioactive assays, and the Walter Reed Army Institute of Research (WRAIR) assay, , have been developed.…”