A computational framework for modeling VX skin penetration and RSDL-based neutralization

• A first-principles computational model evaluates VX penetration and neutralization. • Diffusion, reaction, and absorption dynamics predict the effectiveness of skin decontamination. • Early intervention limits systemic uptake, while treatment delays reduce protection. • Quantitative metrics compare the timing of interventions and treatment efficiency. VX is one of the most toxic organophosphorus nerve agents, capable of causing severe harm after dermal exposure. Rapid removal or neutralization is therefore essential in both military and civilian contexts. This study developed and validated a mechanistic skin-treatment model to evaluate the effect of delayed application of Reactive Skin Decontamination Lotion (RSDL). The model included diffusion through the stratum corneum, neutralization within the tissue, and systemic uptake. The VX diffusion coefficient in the stratum corneum was estimated at 4.3 × 10 −10 cm 2 /s, while the first-order decontamination rate constant was derived from 120-minute treatment data as 2.1 × 10 −4 s −1 . Key performance metrics included the area under the curve for the average VX concentration in the skin, the cumulative amount released, the reacted mass, the remaining amount in the dermal layer and the protection factor. Without further parameter fitting, the model predicted that RSDL applied within 5–10 min nearly eliminated penetration (cumulative absorption 155.7 µg/cm 2 vs. 2877.0 µg/cm 2 for the control), whereas treatments at 30–60 min delayed but did not prevent absorption, and treatment at 120 min provided only limited protection. These results underscore the importance of early intervention while showing that delayed action still reduces systemic uptake. The framework provides occupational and environmental hygienists with a quantitative tool for assessing dermal risk, optimizing intervention timing, and guiding response strategies in industrial or accidental exposures.