Efficacy of soap and water-based skin decontamination using in vitro animal models: A systematic review

Water and/or soap and water solutions have historically been used as first-line decontamination strategies for a wide variety of dermal contaminants from workplace exposure, environmental pesticides, and civilian chemical warfare. Although water and/or soap and water solutions are often considered a gold standard of decontamination, many studies have found other decontamination methods to be superior. This systematic review summarizes the available data on in vitro animal models contaminated with a various chemicals and their decontamination with water and/or soap and water solutions using in vitro animal models. A comprehensive literature search was performed using Concordance, Embase, PubMed, Medline, Web of Science, and Google Scholar to find in vitro animal studies that provided data on dermal decontamination using water and/or soap and water solutions. Five studies were included that analyzed 11 contaminants across two in vitro animal models (rats and pigs). Water alone was used as a decontamination method for 63.6% of the contaminants (n = 7/11) and water and soap solutions for decontamination in 54.6% of contaminants (n = 6/11). Water alone provided incomplete contaminant removal of five of seven contaminants studied; soap and water did not show significant difference in decontamination when compared with other solutions for all four contaminants and was superior to water for both contaminants studied. Water and/or soap and water are used as decontamination strategies for a variety of dermal contamination events, but for many contaminants, they do not provide complete contamination when compared with newer decontamination solutions studied with in vitro animal models.     

Efficacy of water skin decontamination in vivo in humans: A systematic review

With the constant possibility of occupational exposures, chemical warfare, and targeted attacks, increased attention has been given to determining effective and timely dermal decontamination strategies. This systematic review summarises experimental studies reporting decontamination with water-based solutions of dermal chemical contaminants with in vivo human data. Embase, MEDLINE, PubMed, Web of Science, and Google Scholar databases were comprehensively searched using search terms (“cutaneous” or “skin” or “dermal” or “percutaneous”) and (“decontamination” or “decontaminant” or “skin decontamination”) to include 10 studies, representing 18 chemical contaminants, 199 participants, and 351 decontamination outcomes. Three studies included data from decontamination with water (10.8%, n = 38/351 decontamination outcomes), seven with soap and water (68.4%, n = 240/351 decontamination outcomes), and two with 10% isopropanol distilled water (20.8%, n = 73/351 decontamination outcomes). Results of dermal decontamination using water showed complete decontamination (CD) outcomes in 52.6% (n = 20/38) and partial decontamination (PD) in 47.4% (n = 18/38); using soap and water showed PD outcomes in 92.9% (n = 223/240) and minimal to no effect in 7.1% (n = 17/240); and using 10% isopropanol distilled water achieved PD outcomes in 100.0% (n = 73/73). Available data show that decontamination with water, soap and water, and 10% isopropanol distilled water is incomplete. Much remains to be learned about decontamination of the large variety of chemical contaminants including a range of molecular weights, lipid and water solubilities, melting points, volatility, and hydrogen bonds, as well as clinically relevant anatomic sites. A major void exists in data confirming or denying the completeness of decontamination by measuring absorption and excretion. The development of effective decontamination solutions is of high priority.     

Effects of soap–water wash on human epidermal penetration

Skin decontamination is a primary interventional method used to decrease dermal absorption of hazardous contaminants, including chemical warfare agents, pesticides and industrial pollutants. Soap and water wash, the most common and readily available decontamination system, may enhance percutaneous absorption through the “wash‐in effect.” To understand better the effect of soap–water wash on percutaneous penetration, and provide insight to improving skin decontamination methods, in vitro human epidermal penetration rates of four C¹⁴‐labeled model chemicals (hydroquinone, clonidine, benzoic acid and paraoxon) were assayed using flow‐through diffusion cells. Stratum corneum (SC) absorption rates of these chemicals at various hydration levels (0–295% of the dry SC weights) were determined and compared with the results of the epidermal penetration study to clarify the effect of SC hydration on skin permeability. Results showed accelerated penetration curves of benzoic acid and paraoxon after surface wash at 30 min postdosing. Thirty minutes after washing (60 min postdosing), penetration rates of hydroquinone and benzoic acid decreased due to reduced amounts of chemical on the skin surface and in the SC. At the end of the experiment (90 min postdosing), a soap–water wash resulted in lower hydroquinone penetration, greater paraoxon penetration and similar levels of benzoic acid and clonidine penetration compared to penetration levels in the non‐wash groups. The observed wash‐in effect agrees with the enhancement effect of SC hydration on the SC chemical absorption rate. These results suggest SC hydration derived from surface wash to be one cause of the wash‐in effect. Further, the occurrence of a wash‐in effect is dependent on chemical identity and elapsed time between exposure and onset of decontamination. By reducing chemical residue quantity on skin surface and in the SC reservoir, the soap–water wash may decrease the total quantity of chemical absorbed in the long term; however, the more immediate accelerated absorption of chemical toxins, particularly chemical warfare agents, may be lethal. Copyright © 2015 John Wiley & Sons, Ltd.     

Decontamination efficacy of soapy water and water washing following exposure of toxic chemicals on human skin

Abstract

Aim of the study: Following exposure to toxic chemicals, skin uptake is a potential route of intoxication. Therefore, efficient methods for rapid skin decontamination to mitigate systemic effects are of utmost importance. In operational guidelines, skin decontamination is recommended to be performed by dry absorption and washing with water or soapy water. In the present study, evaluation of decontamination efficacy using water or soapy water was performed for five chemicals, three toxic industrial chemicals and two simulants for chemical warfare agents.

Materials and methods: Decontamination was initiated at time points 5, 15, 45 and 120 min after exposure in order to evaluate the time window for efficient decontamination. Experiments were conducted utilizing an in vitro skin penetration model to allow exposure of toxic chemicals on human skin.

Results: For all test substances, it was clearly demonstrated that decontamination had greater efficacy when initiated at the earliest time-point while decontamination after 120 min was less efficient. Adding soap to the water showed no significant improvement for any of the tested substances.

Conclusion: These results are of reledvance for the development of efficient operational decontamination procedures.     

Chemical warfare agent simulants for human volunteer trials of emergency decontamination: A systematic review

Incidents involving the release of chemical agents can pose significant risks to public health. In such an event, emergency decontamination of affected casualties may need to be undertaken to reduce injury and possible loss of life. To ensure these methods are effective, human volunteer trials (HVTs) of decontamination protocols, using simulant contaminants, have been conducted. Simulants must be used to mimic the physicochemical properties of more harmful chemicals, while remaining non‐toxic at the dose applied. This review focuses on studies that employed chemical warfare agent simulants in decontamination contexts, to identify those simulants most suitable for use in HVTs of emergency decontamination. Twenty‐two simulants were identified, of which 17 were determined unsuitable for use in HVTs. The remaining simulants (n = 5) were further scrutinized for potential suitability according to toxicity, physicochemical properties and similarities to their equivalent toxic counterparts. Three suitable simulants, for use in HVTs were identified; methyl salicylate (simulant for sulphur mustard), diethyl malonate (simulant for soman) and malathion (simulant for VX or toxic industrial chemicals). All have been safely used in previous HVTs, and have a range of physicochemical properties that would allow useful inference to more toxic chemicals when employed in future studies of emergency decontamination systems.     

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.     

Binding affinity and decontamination of dermal decontamination gel to model chemical warfare agent simulants

Six chemical warfare agent simulants (trimethyl phosphate, dimethyl adipate, 2‐chloroethyl methyl sulfide, diethyl adipate, chloroethyl phenyl sulfide and diethyl sebacate) were studied in in vitro human skin to explore relationship between dermal penetration/absorption and the mechanisms of simulant partitioning between stratum corneum (SC) and water as well as between dermal decontamination gel (DDGel) and water. Both binding affinity to and decontamination of simulants using DDGel were studied. Partition coefficients of six simulants between SC and water (Log P_SC/w) and between DDGel and water (Log P_DDGel/w) were determined. Results showed that DDGel has a similar or higher binding affinity to each simulant compared to SC. The relationship between Log P octanol/water and Log P_SC/w as well as between Log P octanol/water and Log P_DDGel/w demonstrated that partition coefficient of simulants correlated to their lipophilicity or hydrophilicity. Decontamination efficiency results with DDGel for these simulants were consistent with binding affinity results. Amounts of percentage dose of chemicals in DDGel of trimethyl phosphate, dimethyl adipate, 2‐chloroethyl methyl sulfide, diethyl adipate, chloroethyl phenyl sulfide and diethyl sebacate were determined to be 61.15, 85.67, 75.91, 53.53, 89.89 and 76.58, with corresponding amounts absorbed in skin of 0.96, 0.65, 1.68, 0.72, 0.57 and 1.38, respectively. In vitro skin decontamination experiments coupled with a dermal absorption study demonstrated that DDGel can efficiently remove chemicals from skin surface, back‐extract from the SC, and significantly reduced chemical penetration into skin or systemic absorption for all six simulants tested. Therefore, DDGel offers a great potential as a NextGen skin Decon platform technology for both military and civilian use.     

Decontamination of rat and human skin experimentally contaminated with 99mTc, 201Tl and 131I radionuclides using “Dermadecon” – a skin decontamination kit: an efficacy study

Radioactive skin contamination is one of the most likely risks which occurs after accidental or occupational radiological accidents apart from internal contamination. In such cases where the radioactive contamination has occurred, the person who is contaminated should be decontaminated as early as possible to reduce the damaging health effects of radiation. In the present study, the decontamination efficiency of a developed skin decontamination kit “dermadecon” has been evaluated in animal models and human subjects using gamma scintigraphy. Decontamination efficiency (percentage of the radioactive contaminant removed) was calculated for each radioactive isotope of the study and compared with control where general washing procedure was followed using liquid and soap. The effectiveness of the kit was calculated in animal model with respect to ^99mTc-sodium-pertechnetate (^99mTcO^4?), ²⁰¹TlCl and ¹³¹I and was found 92.84?±?4.9%, 91.18?±?3.23% and 94.67?±?2.92%, respectively. Whereas, in case of human skin, the decontamination efficiency for ^99mTcO^4? was observed to be 95.00?±?3.21%. On the basis of findings from the study, it can be concluded that the decontamination agents of the used skin decontamination kit are effective for removal of localized radioactive contaminants from skin, as compared with normal decontamination using soap and water.     

Skin penetration and decontamination efficacy following human skin exposure to fentanyl

Unintentional exposure to potent synthetic opioids during law enforcement seizures and rescue operations can potentially result in incapacitating effects or life-threatening respiratory depression. The hazard comes mainly from inhalation exposure, however, the skin contact risk should be considered. In the present study, the skin penetration of fentanyl and the efficacy of different decontamination protocols were evaluated by applying two forms of fentanyl on dermatomed human skin mounted in a diffusion cell. Studies were performed on dry skin or skin moistened by water, sweat or hand sanitizer.The free base of fentanyl displayed greater skin penetration ability than the hydrochloride salt and a higher steady state penetration rate of fentanyl in solution compared to powder on dry skin. Sweaty skin increased the penetration rate, both when applied in solution and as powder. The hand sanitizer increased skin penetration of the free base fentanyl but not the hydrochloride salt. Of the evaluated decontamination procedures, only soapy water demonstrated a general efficacy.In conclusion, the skin contact hazard of fentanyl is highly dependent on the exposure conditions and contamination density. The risk for physiological effects of fentanyl is assessed to occur only at very high exposures on sweaty skin. In such events, skin decontamination using soap and water is estimated to be a sufficient decontamination procedure.     

Development of haemostatic decontaminants for treatment of wounds contaminated with chemical warfare agents. 3: Evaluation of in vitro topical decontamination efficacy using damaged skin

Previous studies have demonstrated that haemostatic products with an absorptive mechanism of action retain their clotting efficiency in the presence of toxic materials and are effective in decontaminating chemical warfare (CW) agents when applied to normal, intact skin. The purpose of this in vitro study was to assess three candidate haemostatic products for effectiveness in the decontamination of superficially damaged porcine skin exposed to the radiolabelled CW agents, soman (GD), VX and sulphur mustard (HD). Controlled physical damage (removal of the upper 100 μm skin layer) resulted in a significant enhancement of the dermal absorption of all three CW agents. Of the haemostatic products assessed, WoundStat™ was consistently the most effective, being equivalent in performance to a standard military decontaminant (fuller's earth). These data suggest that judicious application of haemostatic products to wounds contaminated with CW agents may be a viable option for the clinical management of casualties presenting with contaminated, haemorrhaging injuries. Further studies using a relevant animal model are required to confirm the potential clinical efficacy of WoundStat™ for treating wounds contaminated with CW agents. Copyright © 2017 John Wiley & Sons, Ltd.     

Safety of dermal Diphoterine® application: An active decontamination solution for chemical splash injuries

Diphoterine (Laboratoire Prevor, Valmondois, France) is an active, amphoteric, polyvalent, chelating, slightly hypertonic decontamination solution for chemical splashes to the skin and eyes. It chemically binds a large number of chemical substances present on the skin surface without causing a significant release of heat (exothermic reactions). Because of its amphoteric properties, it can bind chemically opposite substances such as acids and bases or oxidizers and reducing agents. No adverse effects have been observed in an ongoing postmarketing surveillance program during many years of use in European industrial facilities. Diphoterine has more recently been used in hospitals for delayed management of chemical burns to the skin and eyes. There is interest in having protocols for both immediate and delayed Diphoterine use for skin decontamination. Whereas studies of Diphoterine efficacy, clinical and in vitro or ex vivo, have been published or are in the process of being prepared for publication, no review has yet been published focusing solely on the safety of this decontamination solution. Therefore, all available studies on the safety of Diphoterine are described here, including recent studies demonstrating no harmful effects on the skin. Diphoterine can be used, even on damaged skin, without toxic, irritant, allergenic, or sensitizing effects.     

In vitro skin decontamination model: comparison of salicylic acid and aminophylline

Objective: This study compared three model decontaminant solutions (distilled water, 10% distilled water and soap and methanol) for their ability to remove salicylic acid and aminophylline from an in vitro skin model.

Materials and methods: Human abdominal skin was dosed with 20?µL of either [¹⁴C]-aminophylline or [¹⁴C]-salicylic acid on 1?cm² per skin. After each exposure time (5, 30 and 60?min post-dosing, respectively), surface skin was washed three times with each solution and tape stripped 10 times. Wash solutions, tape strips, receptor fluid and remaining skin were then analyzed with liquid scintillation counting to quantify the amount of salicylic acid and aminophylline.

Results: Total mass balance recovery for each chemical at three time exposure points was between 73.6 and 101.5%, except at 60?min where aminophylline was only 42.5%. Majority of salicylic acid and aminophylline were recovered from washing solution when compared to stratum corneum, epidermis, dermis, surrounding skin and receptor fluid.

Conclusion: The three tested decontaminates possessed similar effectiveness in removing lipophilic and hydrophilic chemicals from the skin. Due to diminishing decontamination efficacy with time, it is suggested that skin should be washed as soon as possible following contamination to minimize percutaneous penetration and the deleterious effects associated with skin reservoir content.     

Water decontamination of chemical skin/eye splashes: a critical review

Skin/eye chemical splashes are a significant workplace problem. Initial water decontamination is usually recommended, but there are few well-conducted experimental animal and human studies of efficacy. An extensive review of the literature and other available information sources was performed to define the scope of the problem and critically review the evidence for water decontamination efficacy. Although water decontamination can decrease the severity of chemical skin/eye burns, it cannot completely prevent them. An ideal replacement decontamination solution would be sterile, nontoxic, chelating, polyvalent, amphoteric, and slightly hypertonic to retard skin or corneal penetration of the chemical.     

Part 2. Comparison of emergency washing solutions in 70% hydrofluoric acid-burned human skin in an established ex vivo explants model

Background: Hydrofluoric acid (HF) is a small and partially dissociated acid (pK_a 3.2), able to deeply penetrate into human skin in addition to the corrosiveness of the hydrogen ion (H⁺) and the toxicity of the fluoride ion (F^?). However, there has been a lack of experimental studies to objectively characterize the results of human HF skin exposure decontamination.

Methodology/principal findings: A previously established experimental method using a human skin explants ex vivo model (Part 1. Experimental 70% hydrofluoric acid (HF) burns: Histological observations in an established human skin explants ex vivo model) described the lesions that appeared following 70% HF penetration. Within 5?min, 70% HF penetrates to the dermis. Using the same experimental conditions, a comparison study of two different washing protocols was performed: water + topical calcium gluconate (CaG) versus Hexafluorine^®. In these conditions, washing for 15?min with running tap water followed by topical CaG ointment only delayed burn onset, while severe tissue damage appeared later. In contrast, after washing with Hexafluorine^® over 10?min, no histological lesions developed. These results are in accordance with the results of accidental human industrial case reports.

Conclusion/significance: Amphoteric and hypertonic Hexafluorine^® can deactivate H⁺ and chelate F^? ions. Based on these results, it should be considered as a promising first-aid decontamination solution to prevent or minimize significant local and systemic consequences of concentrated HF skin exposures.     

In vitro percutaneous absorption and stratum corneum binding of alachlor: Effect of formulation dilution with water

The effect of vehicle dilution on the percutaneous absorption of alachlor, 2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide, through excised human skin was determined using flowthrough design glass penetration cells and ¹⁴C radiotracer methodology. Three dilutions of alachlor (in the solubilizing commercial formulation) with distilled water were utilized: 1:20, 1:40, and 1:80 (v/v); corresponding to concentrations of 23.0, 11.8, and 5.98 mg alachlor per milliliter, respectively. Skin from the penetration studies and human powdered stratum corneum from the binding studies demonstrated a high capacity for alachlor. A soap and water (1:1, v/v) solution effectively decontaminated powdered stratum corneum. Using plasma as the receptor solution, penetration ranged from 0.5 to 4% of the applied dose for an 8-hr exposure period. Lag times of 1.2 to 1.8 hr were observed. Increasing dilution resulted in significant enhancement (p < 0.01) in the rate and extent of alachlor penetration. Although the biological significance of this observation is unclear, this phenomenon might be explored in future studies because of its ramifications for human toxicity and for decontamination opportunities.     

In vitro percutaneous penetration of organophosphorus compounds using full-thickness and split-thickness pig and human skin.

Organophosphorus compounds (OPs), such as pesticides and chemical warfare agents like sarin (GB), soman (GD) and VX, are highly toxic compounds. The OP vapours and their liquid forms are readily absorbed through the skin, therefore, protecting the skin of people who are potentially exposed to these agents is crucial. The development of effective countermeasures relies on a better knowledge of the percutaneous penetration of such molecules. The purpose of this present study is to determine the in vitro percutaneous penetration parameters of two pesticides DSM and DFP, as potential simulants of V and G agents, respectively, using four in vitro systems: full-thickness and split-thickness human abdominal and pig-ear skin membranes mounted on static diffusion cells. Based on the toxicokinetic parameters of the percutaneous penetration of DSM and DFP, we demonstrated that (a) pig-ear skin is a relevant model to predict the in vitro human skin permeability taking into account a 2-fold difference between these two species (b) both full and split-thickness skin membranes could be used indiscriminately, (c) DSM and DFP would be appropriate surrogates for V and G agents to perform skin permeation studies.     

Reducing Systemic Absorption from Monochloracetic Acid Exposure Through Dermal Decontamination: Use of the Pig Ear Organ Culture System

Abstract

Severe systemic intoxication may occur after skin contamination with monochloracetic acid (MCA). For this reason the effects of decontaminating with either water (most commonly used) or bicarbonate on the rates of percutaneous penetration and dermal accumulation of radiolabeled MCA were measured using the blood-perfused pig ear model. The rate of percutaneous penetration of a 40% solution of MCA was measured after exposure times of 1, 3, and 10 min. Maximal rates of percutaneous penetration (ng/min/cm²; mean ± SEM) were 891 ± 335 for a 1 min exposure; 947 ± 191 for a 3 min exposure; and 3221 ± 515 for a 10 min exposure. Although the initial rate of percutaneous absorption (first 30 min) was directly related to the exposure time, there was no difference in maximal rates of percutaneous penetration for 1 and 3 min exposures. It appears, that for short exposure times, the percutaneous penetration rate is determined by both the rate of penetration into the skin and the rate of diffusion from dermal stores into the blood.

A saturated sodium bicarbonate solution and water proved equally effective in decontaminating the skin after a 10 min exposure to MCA. However, a saturated bicarbonate solution was a slightly more effective decontaminant than water after a 1 min exposure. Our data indicate that decontamination should take place as soon as possible after dermal contamination with MCA. Furthermore, decontamination should continue for as long as possible in order to reduce the systemic burden. In view of the toxicity of MCA and the speed with which dermal deposits can accumulate, it is essential that decontamination facilities (e.g., a shower or bath filled with decontaminant) are available at all points in the workplace where MCA is handled.     

Design and characterisation of a novel in vitro skin diffusion cell system for assessing mass casualty decontamination systems

The efficient removal of contaminants from the outer surfaces of the body can provide an effective means of reducing adverse health effects associated with incidents involving the accidental or deliberate release of hazardous materials. Showering with water is frequently used by first responders as a rapid method of mass casualty decontamination (MCD). However, there is a paucity of data on the generic effectiveness and safety of aqueous decontamination systems. To address these issues, we have developed a new in vitro skin diffusion cell system to model the conditions of a common MCD procedure (“ladder pipe system”). The new diffusion cell design incorporates a showering nozzle, an air sampling port for measurement of vapour loss and/aerosolisation, adjustable (horizontal to vertical) skin orientation and a circulating manifold system (to maintain a specified flow rate, temperature and pressure of shower water). The dermal absorption characteristics of several simulants (Invisible Red S, curcumin and methyl salicylate) measured with the new in vitro model were in good agreement with previous in vitro and in vivo studies. Moreover, these initial studies have indicated that whilst flow rate and water temperature are important factors for MCD, the presence of clothing during showering may (under certain circumstances) cause transfer and spreading of contaminants to the skin surface.     

In vivo skin decontamination of methylene bisphenyl isocyanate (MDI): soap and water ineffective compared to polypropylene glycol, polyglycol-based cleanser, and corn oil.

In the home and workplace, decontamination of a chemical from skin is traditionally done with a soap-and-water wash, although some workplaces may have emergency showers. It has been assumed that these procedures are effective, yet workplace illness and even death occur from chemical contamination. Water, or soap and water, may not be the most effective means of skin decontamination, particularly for fat-soluble materials. This study was undertaken to help determine whether there are more effective means of removing methylene bisphenyl isocyanate (MDI), a potent contact sensitizer, from the skin. MDI is an industrial chemical for which skin decontamination, using traditional soap and water and nontraditional polypropylene glycol, a polyglycol-based cleanser (PG-C), and corn oil were all tried in vivo on the rhesus monkey, over 8 h. Water, alone and with soap (5% and 50% soap), were partially effective in the first h after exposure, removing 51-69% of the applied dose. However, decontamination fell to 40-52% at 4 h and 29-46% by 8 h. Thus, the majority of MDI was not removed by the traditional soap-and-water wash; skin tape stripping after washing confirmed that MDI was still on the skin. In contrast, polypropylene glycol, PG-C, and corn oil all removed 68-86% of the MDI in the first h, 74-79% at 4 h, and 72-86% at 8 h. Statistically, polypropylene glycol, PG-C, and corn oil were all better (p < 0.05) than soap and water at 4 and 8 h after dose application. These results indicate that a traditional soap-and-water wash and the emergency water shower are relatively ineffective at removing MDI from the skin. More effective decontamination procedures, as shown here, are available. These procedures are consistent with the partial miscibility of MDI in corn oil and polyglycols.     

Isolated human/animal stratum corneum as a partial model for 15 steps in percutaneous absorption: emphasizing decontamination,Part I

Since the advent of World War II, governments and laboratories have made a concerted effort to improve prophylactic and therapeutic interventions counteracting cutaneously directed chemical warfare agents (CWA), and by inference, common industrial and consumer dermatotoxicants. In vitro percutaneous penetration assays, first utilized by Tregear in the 1940s and presently in various modifications, have been fundamental to this effort. Percutaneous penetration, often considered a simple one‐step diffusion process, consists of at least 15 steps. The first part of this review covers the initial steps related to absorption and excretion kinetics, vehicle characteristics, and tissue disposition. Importantly, the partitioning behavior and stratum corneum (SC) diffusion by a wide physicochemical array of compounds shows that many compounds have similar diffusion coefficients determining their percutaneous absorption in vivo. After accounting for anatomical SC variation, the penetration flux value of a substance depends mainly on its SC/vehicle partition coefficient. Additionally, the SC acts as a ‘reservoir’ for topically applied molecules and application of tape stripping has been found to quantify the chemical remaining in the SC which can predict total molecular penetration in vivo. Decontamination is of particular concern and even expediting standard washing procedures after dermal chemical exposure often fails to remove chemicals. This overview summarizes knowledge of percutaneous penetration extending insights into the complexities of penetration, decontamination and potential newer assays that may be of practical importance. Copyright © 2012 John Wiley & Sons, Ltd.