Efficient agent degradation within skin is important for decontamination of percutaneously exposed VX

Immediate dry decontamination using efficient absorbent materials is beneficial following skin exposure to low-volatile toxic chemicals

In a chemical mass casualty incident requiring skin decontamination, dry removal using absorbent materials may be beneficial to enable immediate decontamination. The efficacy of absorbent materials has therefore been evaluated, alone or procedures including both dry and wet decontamination, following skin exposure to two low volatile toxic chemicals using an in vitro human skin penetration model. Additionally, removal using active carbon wipes was evaluated with or without the Dahlgren Decon solution. All dry decontamination procedures resulted in a significantly decreased skin penetration rate of the industrial chemical 2-butoxyethanol compared to the control without decontamination. Wet decontamination following dry absorption significantly improved the efficacy compared to dry removal alone. Dry decontamination post-exposure to the chemical warfare nerve agent VX showed no decontamination efficacy. However, dry and wet decontamination resulted in a decreased agent skin penetration rate during the last hour of the experiment. At -15°C, significantly reduced VX skin penetration rates were demonstrated for both dry decontamination alone and the dry and wet decontamination procedure. The Dahlgren Decon solution significantly reduced the amount of VX penetrating the skin, but the active carbon wipe alone did not impact the skin penetration rate. In conclusion, absorbent materials are beneficial for the removal of low-volatile chemicals from the skin, but the degree of efficacy varies between chemicals. Despite the variability, immediate dry decontamination using available absorbent materials prior to wet decontamination is recommended as a general procedure for skin decontamination. The procedure should also be prioritized in cold-weather conditions to prevent patient hypothermia.

"Catch-up" therapy: combining antidotal treatment with dermal application of AHA following percutaneous VX poisoning in the domestic swine

Low-volatility organophosphorus chemical warfare agents (OP CWAs) are cholinesterase inhibitors which easily absorb into the skin, leading to the formation of a dermal depot from which they slowly enter the bloodstream. This leads to sustained cholinergic hyperstimulation, which if untreated may lead to death. However, current available countermeasures are not adequate to neutralize the agent residing in the dermal depot. Accordingly, we evaluated the efficacy of the potassium salt of acetohydroxamic acid (880 mg/ml in DMSO/H2O 1:4, AHAK), as a potential "catch-up" therapy lotion intended to neutralize the dermal depot, by penetrating the skin and decomposing it before it reaches the bloodstream. To that end, we compared the clinical outcome following skin surface decontamination combined with antidotal treatment, to that following the same antidotal treatment combined with dermal application of AHAK at the site of VX exposure, against percutaneous poisoning by a lethal neat dose (4 mg/kg) of the low-volatility nerve agent VX, in an unanesthetized swine model. Following skin surface decontamination and antidotal treatment, recurrence of intoxication signs and a prolonged recovery time were observed. In contrast, similar antidotal treatment combined with dermal application of AHAK significantly reduced intoxication signs recurrences and accordingly medical supervision duration needed, paralleled by a significantly faster recovery of whole blood cholinesterase activity. An initial evaluation demonstrated the safety of prolonged whole-body AHAK application. Hence, the AHAK lotion may act as an efficient "catch-up" therapy against percutaneous poisoning by low-volatility OP CWAs, improving the clinical outcome and reducing the burden on medical staff.

Analysis of the absorption kinetics following dermal exposure to large doses of volatile organic compounds

A mathematical method was developed to study the skin penetration of volatile organic compounds (VOCs) after exposure to a high dose of the substance. While closed-form solutions exist to describe the diffusion and evaporation from small amounts, numerical approaches are often implemented to predict dermal transport involving large doses. This work offers a Laplace transform-based method to estimate the time constant and dynamic and steady-state behaviors. First, the process was divided into two stages, separated by the time it took for excess chemicals to be depleted from the skin surface. Series solutions were written for the percutaneous VOC concentration, absorption and evaporation in the first stage. Application of Laplace transform methods yielded transient profiles after the compound dissipated from the surface of the stratum corneum. In addition, the procedure facilitated the calculation of the time constant and steady-state values. The method was validated using benchtop and fume hood experiments conducted with N,N-diethyl-3-methylbenzamide (DEET) and air velocities of 0.165 m/s and 0.72 m/s, respectively. The increase in the flow rate decreased the total amount of VOC absorbed and reduced the period required for the surface fluid to disappear.

The wash-in effect and its significance for mass casualty decontamination

Decontamination of skin by washing may increase dermal absorption, a phenomenon known as the wash-in effect. The wash-in effect is frequently discussed in studies investigating casualty decontamination where potentially life-saving interventions may enhance the dermal penetration of toxic chemicals, leading to an increase in incidence of morbidity and rates of mortality. However, the wash-in effect is seldom investigated within the context of mass casualty decontamination and real-life consequences are therefore poorly understood. This paper reviews the existing literature on the wash-in effect to highlight the proposed mechanisms for enhanced absorption and evaluate the wash-in effect within the context of mass casualty chemical decontamination.

Do cold weather temperatures affect the efficacy of skin decontamination?

Skin decontamination in cold weather temperatures might be challenging due to the aggravating circumstances. However, no information is available on the efficacy of commonly used procedures in winter conditions. Therefore, the efficacy of the reactive skin decontamination lotion (RSDL) and soapy water decontamination following skin exposure to the nerve agent VX was evaluated at three ambient air temperatures (-5°C, -15°C and room temperature). Experiments were performed in vitro using human dermatomed skin. The ability of RSDL to degrade VX at the three different air temperatures was separately evaluated. The ambient air temperature in experiments without decontamination did not influence the penetration rate of VX through skin. RSDL decontamination was highly efficient in removing VX from skin when performed in all three ambient temperatures, despite the slower agent degradation rate of VX at the lower temperatures. Decontamination with soapy water at RT resulted in an increased skin penetration of VX compared with the control without decontamination; however, in colder temperatures the VX skin penetration was similar to the corresponding control without decontamination. At RT, dry removal prior to washing with soapy water did not improve decontamination of VX compared with washing solely with soapy water. This study demonstrated high efficacy of RSDL decontamination following skin exposure to VX also at cold temperatures. The previously reported 'wash-in' effect of soapy water on VX skin penetration was reduced at cold temperatures. Altogether, this study found a scientific basis to establish guidelines for skin decontamination of chemical casualties at cold weather temperatures.