The penetration of the Novichok nerve agent A-234 in a human skin model and the assessment of several decontamination procedures.

The recent use of a Novichok nerve agent for an assassination attempt on Alexei Navalny underlined the importance of identifying effective countermeasures. The immediate decontamination is essential to reduce the penetration of the chemical agent into the systemic circulation. Only limited data are available about the decontamination of Novichok nerve agents on the skin. In this study, we used an in vitro model of human skin to determine the efficacy of decontaminants to remove the agent A-234. The skin was exposed towards A-234 and after 5 min or 30 min the decontamination was initiated by applying different decontamination protocols (Reactive Skin Decontamination Lotion (RSDL), the potassium salt of the acetohydroxamic acid (AHAK), sodium hypochlorite (NaOCl) 2%, soapy water 2% and tap water). Then, the amount of penetrated A-234 was calculated using an acetylcholinesterase inhibition assay. The early decontamination with AHAK was most effective resulting in a complete decontamination, i.e. 0% residual A-234. In contrast, soapy water, tap water, RSDL and NaOCl showed a lower decontamination efficacy and the penetrated amount of A-234 was reduced by 89% (soapy water, tap water), 91% (RSDL) and 95% (NaOCl). The delayed decontamination after 30 min also revealed a complete decontamination of A-234 by using AHAK and an inadequate decontamination using soapy water, tap water, RSDL and NaOCl. In conclusion, the results underline that the decontamination of the Novichok agent A-234 was similar to the V-series nerve agent VX. The relatively new AHAK was a promising decontaminant and deserves further investigation.