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

Efficacy of soap and water based skin decontamination using in vivo animal models: a systematic review

Water-only or soap and water solutions are considered a gold standard for skin decontamination. However, there is lack of conclusive data regarding their efficacy. The aim of this study was to summarize in vivo animal model data on skin decontamination using water-only, and/or soap and water. Covidence, Embase, MEDLINE, PubMed, Web of Science, and Google Scholar were searched to identify relevant articles using water-only or soap and water decontamination methods in in vivo animals. Data extraction was completed from studies, representing three animal models, and 11 contaminants. Results demonstrated water-only decontamination solutions led to complete decontamination in 3.1% (n = 16/524) protocols, incomplete decontamination in 90.6% (n = 475/524) of protocols, and mortality in 6.3% (n = 33/524) of protocols. Soap and water decontamination solutions resulted in complete decontamination in 6.9% (n = 8/116) protocols, incomplete decontamination in 92.2% (n = 107/116) of protocols, and mortality in 6.9% (n = 8/116) of protocols. Although water only, or soap and water is considered a gold standard for skin decontamination, most papers investigated found that water only, and soap and water provided incomplete decontamination. Due to the insufficient data, and limitations that hinder the applicability of available data, evidence indicates that more contemporary studies investigating skin decontamination are needed, and compared to other model species, including humans, when practical.

Efficacy of water-based skin decontamination of occupational chemicals using in vitro human skin models: a systematic review

Percutaneous absorption of chemicals is a potential route of topical and systemic toxicity. Skin decontamination interrupts this process by removing contaminants from the skin surface. Decontamination using water-only or soap and water solutions is the current gold standard despite limited efficacy data. A summary of studies evaluating their efficacy in decontaminating occupational contaminants from in vitro human skin models is presented. Embase, MEDLINE, PubMed, Web of Science, and Google Scholar were searched for relevant articles and data extracted from 15 investigations that reported on 21 occupational contaminants, which were further classified as industrial chemicals, drugs, or pesticides. Water-only decontamination yielded no response in 4.3% (n = 6/140) and partial decontamination in 95.7% (n = 134/140) of skin samples. Soap and water decontamination yielded complete decontamination in 4.9% (n = 13/264) and partial decontamination in 95.1% (n = 251/264) of skin samples. Four studies (26.7%, n = 4/15) reported increased penetration rates or skin concentration of contaminants following decontamination, demonstrating a "wash-in" effect. Varying study methodologies hinder our ability to compare data and determine when water alone or soap and water are best used. International harmonized efficacy protocol might enhance our decontamination understanding and enable a more customized approach to decontamination clinical practice and research.

Skin decontamination procedures against potential hazards substances exposure

Decontamination of unprotected skin areas is crucial to prevent excessive penetration of chemical contaminants after criminal or accidental release. A review of literature studies was performed to identify the available decontamination methods adopted to treat skin contamination after chemical, radiological and metal exposures. In this bibliographic review, an overview of the old and recent works on decontamination procedures followed in case of potential hazards substances contaminations with a comparison between these systems are provided. Almost all data from our 95 selected studies conducted in vitro and in vivo revealed that a rapid skin decontamination process is the most efficient way to reduce the risk of intoxication. The commonly-used or recommended conventional procedures are simple rinsing with water only or soapy water. However, this approach has some limitations because an easy removal by flushing may not be sufficient to decontaminate all chemical deposited on the skin, and skin absorption can be enhanced by the wash-in effect. Other liquid solutions or systems as adsorbent powders, mobilizing agents, chelation therapy are also applied as decontaminants, but till nowadays does not exist a decontamination method which can be adopted in all situations. Therefore, there is an urgent need to develop more efficient and successful decontaminating formulations.

Evaluation of the effect of skin cleaning procedures on the dermal absorption of chemicals

To reduce the internal exposure, skin decontamination is the most important measure after dermal contact to chemicals. However, no harmonized skin cleaning procedure for experimental ex vivo studies is published. In our study, the impact of two skin cleaning techniques on dermal penetration kinetics and intradermal deposition of 1,4-dioxane, 5% hydrofluoric acid (HF, detected in terms of fluoride ions), and anisole was evaluated to develop a reliable ex vivo skin cleaning method using the diffusion cell technique. After exposure (duration: 3 min (HF); 1h (1,4-dioxane and anisole)) of excised human skin (n=6-8) decontamination was performed by (I) water-soaked cotton swabs or (II) direct application of water on the exposure area. The effect of skin cleaning was investigated by analysing the concentration time course of chemicals in the receptor fluid of diffusion cells and by determining the deposition in skin. Both skin cleaning procedures reduced the amount of fluoride in the skin compartments (p<0.05) and the receptor fluid (p<0.1). However, the effect of cleaning on the dermal absorption of the organic test compounds was not significant. The results demonstrate the suitability of the applied ex vivo protocol for investigating the effectiveness of skin cleaning measures following dermal exposure. In addition, data reveal that the determination of test compounds in both, skin compartments as well as receptor fluid as equivalent for the systemic uptake needs to be considered in studies assessing the effectiveness of skin decontamination procedures.

Current concepts for oil decontamination of crush injuries: a review

This anecdotal, non-systematic review serves to explore the principles and methods of effective oil decontamination from cutaneous wounds, particularly crush injuries. The current expansion of the petroleum industry is necessary to meet increasing world demands for oil. Most stages of oil refining and applications involve significant injury risks, particularly for crush injuries that become contaminated with petroleum compounds. A literature review regarding a standard of care for effective cutaneous oil decontamination is lacking. Based on case reports, animal models, and in vitro studies identified in our expert opinion review, standard water and soap cleansing may not be an appropriate approach. Instead, the principle of ‘like dissolves like’ guides the use of lipophilic, petroleum-derived solvents to attract and subsequently dissolve the petroleum contaminant from the skin injury. Limitations include paucity of and dated literature sources regarding the topic as well as no models specifically addressing crush injuries. Our literature review found that oil decontamination of cutaneous injuries may be best accomplished with oil-based cleansers. Certainly, this topic has significant importance for the potentially carcinogenic petroleum compounds that pervade virtually every aspect of modern human life.

Diagnosis and prevention of diseases induced by isocyanate

Isocyanates are among the most frequent causes of occupational asthma in industrialized countries. Early diagnosis of diisocyanate asthma followed by prompt termination of chemical exposure can prevent chronic morbidity due to persistent asthma. Chronic exposure to isocyanates also induces hypersensitivity pneumonitis (HP). The accurate diagnosis of diisocynate asthma requires a systematic approach that combines information obtained from the occupational history, immunologic tests and physiologic studies. The prevention of health problems from toluene diisocyanate (TDI), 4,4'-methylenediphenyl diisocyanate (MDI) and 1,6'-hexamethylene diisocyanate (HDI) is essential for all those handling the chemicals. Regulatory exposure limits should be observed. However, wheezing, coughing or even asthmatic attacks may occur after exposure much below the regulatory exposure limits especially in sensitive individuals. Preventing or minimizing exposure is of prime importance and should be supported by the installation of engineering controls, by education of the workforce, by regular monitoring of the workplace exposure and by medical surveillance. To prevent such asthma it is suggested that workers should be tested airway sensitivity and should avoid working in areas that have dust containing specific-IgE. Such tests must be periodically performed after working. Symptoms induced by isocyanate need earlier discover and early isolation of the associated individuals.

Skin decontamination

Skin decontamination is the primary intervention needed in chemical, biological and radiological exposures, involving immediate removal of the contaminant from the skin performed in the most efficient way. The most readily available decontamination system on a practical basis is washing with soap and water or water only. Timely use of flushing with copious amounts of water may physically remove the contaminant. However, this traditional method may not be completely effective, and contaminants left on the skin after traditional washing procedures can have toxic consequences. This article focuses on the principles and practices of skin decontamination.

Sulfuric Acid Burns (Corrosion and Acute Irritation): Evidence-Based Overview to Management

Concentrated sulfuric acid causes severe skin injury. To prevent skin destruction, efficient early treatment is of utmost importance. However, regimens suggested in the literature are not always supported by experimental data. Further studies are needed. To improve early management of sulfuric acid burns, future experiments need careful extrapolation between animal skin and human skin. The benefit of water, neutralizer, or alternative agents has to be established by precisely defining acid concentration and time of exposure.

Sampling and analytical method development and hand wipe measurements of dermal exposures to polycyclic aromatic hydrocarbons

This article describes the laboratory assessment of a hand and surface wipe sampling method for polycyclic aromatic hydrocarbons (PAHs). The analytical method employed extraction of the wipe samples into dimethyl sulfoxide (DMSO) and high-performance liquid chromatography (HPLC) flourometric detection of pyrene, a predominant PAH in used gasoline engine oils (UGEO). Recovery of pyrene was evaluated for two different sampling media by first contaminating the hands of a small number of volunteers with UGEO, followed by applying a small amount of corn oil to the palms, and by wiping the skin with a Whatman cellulostic filter paper or a polyester fabric wipe (i.e., Alpha wipes). In summary, using either Whatman or Alpha wipes, the mean recovery of pyrene from the UGEO that was applied to the hands and contained within three consecutive wipes was 69% and 54%, respectively. However, the relative recovery of the first to second wipe was on average 47% and 75% for the two media, respectively. These results indicate that the Alpha wipes were more efficient at recovering pyrene in the first wipe but less efficient overall when all three consecutive samples were included. Even though this sampling was performed in a controlled laboratory environment, the minimum and maximum amount of pyrene recovered in the individual composite samples using either method spanned a range of twofold. Overall, intra-and interpersonal variability, as measured by coefficient of variation, were 22% and 19%, respectively, and were not statistically different by type of media used. This method was used in a pilot field survey to sample the hands of 18 automotive repair technicians and 18 office workers. Detectable amounts of pyrene (>0.2 microg/sample) were found on the hands of 61% and 0% of these two groups, respectively, with the highest measured quantity equal to 1.06 microg. Samples from the upper surfaces of automobile motors were generally low to nondetectable (<0.027 microg/sample), while the median value of 0.047 mkcrlg/50 cm(2)(CV = 160%) and up to 0.640 microg were found on the drip pans.

Skin decontamination of glyphosate from human skin in vitro

This study compared three model decontaminant solutions (tap water, isotonic saline, and hypertonic saline) for their ability to remove a model herbicide (glyphosate) from an in vitro human skin model. Human cadaver skin was dosed (approximately 375microg) of [14C]-glyphosate on 3cm2 per skin. After each exposure time (1, 3, and 30min post-dosing, respectively), the surface skin was washed three times (4ml per time) with each solution. After washing, the skin was stripped twice with tape discs. Lastly, the wash solutions, strippings, receptor fluid, and remainder of skin were liquid scintillation analyzer counted to determine the amount of glyphosate. There were no statistical differences among these groups at any time points. The total mass balance recovery at three time exposure points was between 94.8% and 102.4%. The wash off rates (glyphosate in wash solutions) at three different exposure times is 79-101.2%. Thus the three tested decontaminants possess similar effectiveness in removing glyphosate from skin. This in vitro model is not only economic and rapid, but also provides quantitative data that may aid screening for optimal decontaminants.

Skin exposure to aliphatic polyisocyanates in the auto body repair and refinishing industry: II. A quantitative assessment

BACKGROUND

Skin exposure to isocyanates, in addition to respiratory exposures, may contribute to sensitization and asthma. Quantitative skin exposure data are scarce and quantitative methods limited.

METHODS

As part of the Survey of Painters and Repairers of Autobodies by Yale study, a method to sample and quantify human isocyanate skin exposure was developed (based on NIOSH 5525 method) and used to evaluate aliphatic isocyanate skin exposure in 81 auto body shop painters and body technicians. Wipe samples were collected from unprotected skin and from under PPE (gloves, clothing and respirator) using a polypropylene glycol-impregnated wipe. Hexamethylene diisocyanate (HDI), its polyisocyanates [HDI-derived polyisocyanates (pHDI)], isophorone diisocyanate (IPDI) and its polyisocyanates and IPDI-derived polyisocyanates (pIPDI) were quantified separately and also expressed as the total free isocyanate groups (total NCO).

RESULTS

For unprotected skin areas, 49 samples were collected for spray painting, 13 for mixing, 27 for paint-related tasks (e.g. sanding and compounding) and 53 for non-paint-related tasks. Forty-three samples were also collected under PPE. The geometric mean (GM) [geometric standard deviation (GSD)] total NCO concentrations (ng NCO cm(-2)) for unprotected skin (hands, face and forearms) was 1.9 (10.9) and range 0.0-64.4. pHDI species were the major contributor to the total NCO content. Levels were very variable, with the highest concentrations measured for clear coating and paint mixing tasks. Isocyanate skin exposure was also commonly detected under PPE, with 92% of samples above the limit of detection. Levels were very variable with the overall GM (GSD) total NCO (ng NCO cm(-2)) under PPE 1.0 (5.2) and range (0.0-47.0) and similar under the different PPE (glove, respirator and clothing). The highest concentrations were detected for mixing and spraying tasks, 6.9 (5.3) and 1.0 (5.2), respectively. Levels under PPE were generally lower than unpaired samples obtained with no PPE, but not statistically significant. Total isocyanate GM load on exposed skin and under PPE was commonly 100-300 ng NCO per sample, except for higher levels on exposed forearms during spraying (GM 5.9 mug NCO).

CONCLUSIONS

A quantitative method was developed for skin sampling of isocyanates. Using this method, the study demonstrates that skin exposure to aliphatic polyisocyanates during painting, mixing and paint-related tasks in auto body shop workers is common and also commonly detected under routine PPE.

Slow curing of aliphatic polyisocyanate paints in automotive refinishing: a potential source for skin exposure

Two-component, polyurethane paints containing aliphatic isocyanates are widely used in autobody spray painting. Such isocyanates can cause asthma, and skin exposure may be an important route of sensitization and may contribute to the development of isocyanate asthma. Autobody workers are frequently in contact with recently painted, dried auto parts. It is not known how fast the newly painted car surfaces are fully cured, that is, for how long unbound, isocyanate species remain on painted surfaces after initial drying. To address this question, scrap sections of auto bodies were painted and dried by autobody shop painters following regular practice. Routinely used paints were sprayed 23 different times on the parts. Drying was accomplished by baking the part in a paint spray booth by heating it with a heat lamp or air drying in the shop. The 23 sprayed surfaces were sampled at regular time intervals after drying to determine the presence of free NCO groups using the semiquantitative SWYPE technique. Quantitative isocyanate analysis was also performed on two sprayed parts using NIOSH method 5525. Geometric mean curing time of 23 painted surfaces was 56.4 hr (range: 0.8 hrs to 32 days). Unbound isocyanate species of similar composition to the original bulk material remained present on the majority of sampled painted surfaces for up to 120 hours for typical paint formulations and for 1 month for others. The actual curing of polyurethane paints in autobody refinishing can be a slow process. Unbound isocyanates may remain on the surface of painted car parts for prolonged periods (days to weeks) after dried. Such surfaces are an under-recognized potential source of skin exposure to autobody workers.

In vitro model for decontamination of human skin: Formaldehyde

Decontamination of a chemical from skin is often an emergency measure. This study utilized an in vitro model to compare the decontamination capacity of three model decontaminant solutions (tap water, isotonic saline, and hypertonic saline). Human cadaver skin was dosed (approximately 0.25 microg on 3 cm(2) per skin) with radio-labeled [(14)C]-formaldehyde. After a defined exposure time (1, 3, and 30 min post-dosing, respectively), the surface skin was washed three times (4ml per time) with each solution. After washing, the skin was stripped with tape discs twice. Lastly, the wash solutions, strippings, receptor fluid, and remainder of skin were liquid scintillation analyzer counted to determine the amounts of formaldehyde. Additionally, an evaporation test at different exposure times (1min, 3min, 15min, 30min, and 60min, respectively) was conducted to monitor formaldehyde % evaporation. There were no statistical differences among these groups except isotonic saline, at 3min post-exposure (in wash solutions), showed a significantly difference (p<0.05) when compared to tap water. Formaldehyde % evaporation increased linearly with extending application times, and were 7.7%, 13.6%, 19.7%, 24.4%, and 35.9% (1min, 3min, 15min, 30min, and 60min, respectively). This data suggests that isotonic saline may be effective in removing formaldehyde from skin. However, results from this model need validation in vivo. The model may provide a facile and robust method of accelerating knowledge of decontamination mechanism and lead to enhanced efficacy.

Skin exposure to isocyanates: reasons for concern

OBJECTIVE

Isocyanates (di- and poly-), important chemicals used worldwide to produce polyurethane products, are a leading cause of occupational asthma. Respiratory exposures have been reduced through improved hygiene controls and the use of less-volatile isocyanates. Yet isocyanate asthma continues to occur, not uncommonly in settings with minimal inhalation exposure but opportunity for skin exposure. In this review we evaluate the potential role of skin exposure in the development of isocyanate asthma.

DATA SOURCES

We reviewed the published animal and human literature on isocyanate skin-exposure methods, workplace skin exposure, skin absorption, and the role of skin exposure in isocyanate sensitization and asthma.

DATA EXTRACTION

We selected relevant articles from computerized searches on Medline, U.S. Environmental Protection Agency, Occupational Safety and Health Administration, National Institute for Occupational Safety and Health, and Google databases using the keywords "isocyanate," "asthma," "skin," "sensitization," and other synonymous terms, and our own extensive collection of isocyanate publications.

DATA SYNTHESIS

Isocyanate production and use continues to increase as the polyurethane industry expands. There is substantial opportunity for isocyanate skin exposure in many work settings, but such exposure is challenging to quantify and continues to be underappreciated. Isocyanate skin exposure can occur at work, even with the use of personal protective equipment, and may also occur with consumer use of certain isocyanate products. In animals, isocyanate skin exposure is an efficient route to induce sensitization, with subsequent inhalation challenge resulting in asthma-like responses. Several lines of evidence support a similar role for human isocyanate skin exposure, namely, that such exposure occurs and can contribute to the development of isocyanate asthma in certain settings, presumably by inducing systemic sensitization.

CONCLUSIONS

Integrated animal and human research is needed to better understand the role of skin exposure in human isocyanate asthma and to improve diagnosis and prevention. In spite of substantial research needs, sufficient evidence already exists to justify greater emphasis on the potential risks of isocyanate skin exposure and the importance of preventing such exposures at work and during consumer use of certain isocyanate products.

A laboratory investigation of the effectiveness of various skin and surface decontaminants for aliphatic polyisocyanates

Isocyanates may cause contact dermatitis and respiratory sensitization leading to asthma. Dermal exposure to aliphatic isocyanates in auto body shops is very common. However, little is known about the effectiveness of available commercial products used for decontaminating aliphatic polyisocyanates. This experimental study evaluated the decontamination effectiveness of aliphatic polyisocyanates for several skin and surface decontaminants available for use in the auto body industry. The efficiency of two major decontamination mechanisms, namely (i) consumption of free isocyanate groups via chemical reactions with active hydrogen components of the decontaminant and (ii) physical removal processes such as dissolution were studied separately for each decontaminant. Considerable differences were observed among surface decontaminants in their rate of isocyanate consumption, of which those containing free amine groups performed the best. Overall, Pine-Sol(R) MEA containing monoethanolamine was the most efficient surface decontaminant, operating primarily via chemical reaction with the isocyanate group. Polypropylene glycol (PPG) had the highest physical removal efficiency and the lowest reaction rate with isocyanates. All tested skin decontaminants performed similarly, accomplishing decontamination primarily via physical processes and removing 70-80% of isocyanates in one wiping. Limitations of these skin decontaminants are discussed and alternatives presented. In vitro testing using animal skins and in vivo testing with field workers are being conducted to further assess the efficiency and identify related determinants.

Analysis of markers of exposure to polymeric methylene-diphenyl diisocyanate (pMDI) in rats: a comparison of dermal and inhalation routes of exposure

Rats received polymeric methylenediphenyl-diisocyanate (pMDI) or a mixture of methylenediphenyl-4,4'-diamine (4,4'-MDA) and amino-di(aminophenylmethylene)-benzene (3-core MDA) by single inhalation or dermal exposure. The ratio of 4,4'-MDA and 3-core MDA used in this study mirrored that of 4,4'-MDI and 3-core MDI present in pMDI. The yields of the corresponding markers of exposure in hydrolyzed blood (Hb-adducts) and urine were determined. For the inhalation exposure, rats were acutely exposed for a duration of 6 h to 3.7 mg pMDI/m3 and 2.7 mg MDA/m3, respectively. Furthermore, C x t products of approximately 1200 mg pMDI/m3 x h were examined, ranging from 3 h x 6.2 mg/m3, 1.5 h x 12.7 mg/m3, 45-min x 25.1 mg/m3, and 23-min x 58.1 mg/m3. Additional groups of rats received equimolar doses of pMDI and MDA by epicutaneous exposure, i.e., 100 mg pMDI/kg bw, equivalent to approximately 50 mg 4,4'-MDI/kg bw and 34 mg 3-core MDI/kg bw or 79 mg MDA-mixture/kg bw, equivalent to 46 mg 4,4'-MDA/kg bw and 33 mg 3-core-MDA/kg bw. The biomarkers measured in this study suggest that the kind and yield of biomarkers are dependent on the route of exposure and differ markedly for MDI and MDA. This isocyanate appears to undergo reactions specific to the site of first contact (e.g., formation of adducts, conjugates and/or polyureas), suggesting that these markers of 'total body burden' can neither predict the local dose at that site nor does it provide any means to identify the route receiving the most critical dose. Similarly, it appears that the formation of biomarkers is governed by reactions requiring an intact isocyanate group rather than hydrolysis. In contrast, for MDA this type of portal-of-entry specificity was not observed. Moreover, trace amounts of diamines available to dermal contact, with respect to the isocyanate, may cause false-positive readings. Thus, in spite of the recognized advantages of biomonitoring to identify cryptic exposures not readily detected by conventional analytical sampling procedures, in regard to pMDI this technique appears to be potentially biased to overestimate exposure, i.e., results obtained from integrating dosimeters of exposure need to be verified by adequate air monitoring.

Understanding percutaneous absorption for occupational health and safety

Local and systemic toxicity from percutaneous absorption depends on a chemical's penetrating the skin, which is both a barrier to absorption and a primary route to the systemic circulation. The skin's barrier properties are such that fluids and precious chemicals are reasonably retained within the body, while foreign chemicals are restricted from entering the systemic circulation. The skin is a primary body contact with the environment and the route by which many chemicals enter the body. In most instances, the toxicity of the chemical is slight and/or its bioavailability is too low to cause an immediate response. However, some chemicals are toxic when applied to the skin, and more chemicals that come in contact with the skin are being found to be potentially toxic. This article describes percutaneous absorption, methods to determine it, and factors that can affect it.