The sources, fate, and toxicity of chemical warfare agent degradation products

We include in this review an assessment of the formation, environmental fat e, and mammalian and ecotoxicity of CW agent degradation products relevant to environmental and occupational health. These parent CW agents include se veral vesicants: sulfur mustards [undistilled sulfur mustard (H), sulfur mu stard (HD), and an HD/agent T mixture (HT)]; nitrogen mustards [ethylbis(2- chloroethyl)amine (HN1), methylbis(2-chloroethyl)amine (HN2), tris(2-chloro ethyl)amine (HN3)], and Lewisite; four nerve agents {O-ethyl S-[2-(diisopro pylamino)ethyl] methylphosphonothioate (VX), tabun (GA), sarin (GB), and so man (GD)}; and the blood agent cyanogen chloride. The degradation processes considered here include hydrolysis, microbial degradation, oxidation, and photolysis. We also briefly address decontamination but not combustion proc esses. Because CW agents are generally not considered very persistent, cert ain degradation products of significant persistence, even those that are no t particularly toxic, may indicate previous CW agent presence or that degra dation has occurred. Of those products for which there are data on both env ironmental fate and toxicity, only a few are both environmentally persisten t and highly toxic. Major degradation products estimated to be of significa nt persistence (weeks to years) include thiodiglycol for HD; Lewisite oxide for Lewisite; and ethyl methyl phosphonic acid, methyl phosphonic acid, an d possibly S-(2-diisopropylaminoethyl) methylphosphonothioic acid (EA 2192) for VX. Methyl phosphonic acid is also the ultimate hydrolysis product of both GB and GD. The GB product, isopropyl methylphosphonic acid, and a clos ely related contaminant of GB, diisopropyl methylphosphonate, are also pers istent. Of all of these compounds, only Lewisite oxide and EA 2192 possess high mammalian toxicity. Unlike other CW agents, sulfur mustard agents (e.g ., HD) are somewhat persistent; therefore, sites or conditions involving po tential HD contamination should include an evaluation of both the agent and thiodiglycol.