Retention of Nickel, Cobalt and Chromium in skin at conditions mimicking intense hand hygiene practices using water, soap, and hand-disinfectant in vitro

Retention of Nickel, Cobalt and Chromium in skin at conditions mimicking intense hand hygiene practices using water, soap, and hand-disinfectant in vitro | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Retention of Nickel, Cobalt and Chromium in skin at conditions mimicking intense hand hygiene practices using water, soap, and hand-disinfectant in vitro Libe Vilela, Linda Schenk, Anneli Julander, Klara Midander This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4829304/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 06 Nov, 2024 Read the published version in Journal of Occupational Medicine and Toxicology → Version 1 posted 9 You are reading this latest preprint version Abstract Background During the COVID-19 pandemic, increased hand hygiene practices using water, soap and hand disinfectants, became prevalent, particularly among frontline workers. This study investigates the impact of these practices on the skin's ability to retain the allergenic metals nickel, cobalt, and chromium. The study constitutes three parts: I) creating an altered skin barrier, and exposing treated and untreated skin to II) nickel alone, and III) in co-exposure with cobalt and chromium. Methods Using full-thickness skin from stillborn piglets, in vitro experiments were conducted to assess retention of metals in skin at conditions mimicking intense hand hygiene practices. Treatment of skin with varying concentrations of sodium lauryl sulphate (SLS), 0.5–10%, to alter its barrier integrity was assessed. This was followed by exposure of treated and untreated skin to the metals, that were dissolved in Milli-Q water, 0.5% SLS, and ethanol respectively. Results Results showed that pre-treatment with 5% SLS altered the skin barrier with regards to the measure of trans epidermal water loss (TEWL). The highest amounts of metal retained in skin were observed for exposure to nickel in ethanol. Co-exposure to nickel, cobalt, and chromium in 0.5% SLS resulted in the highest amounts of metal retention in both untreated and treated skin. Linear regression analysis indicated that SLS treatment, exposure solvent, time, and metal combination significantly affected nickel retention. Conclusions The in vitro findings highlight the increased risk of metal retention in skin due to a compromised barrier, as a result of, for example, intensive hand hygiene practices. Hence, occupational settings with frequent exposure to water, soap and disinfectants need to consider protective measures not only for the irritant exposures themselves but also simultaneous exposure to allergenic metals. Skin Retention Penetration Metals Hygiene practices Sodium lauryl sulphate Figures Figure 1 Figure 2 1. Introduction During the Coronavirus pandemic 2019 (COVID-19), hygiene practices changed and more frequent exposure to water and hand disinfectants were observed ( 1 ). Several studies related to increased hygiene measures during this period, have focused on healthcare workers and how such COVID-19 related measures increased skin- health issues ( 2 – 5 ). Correspondingly, an increased self-reported exposure to water, soap and usage of hand disinfectant were demonstrated in frontline workers and IT personnel, i.e., occupations outside of the hospital setting that required presence at the workplace and one that could largely work from home ( 6 ). Additionally, frontline workers also reported higher frequency of hand eczema than IT personnel ( 6 ), which is in line with the associations between increased hand washing and hand eczema observed for healthcare workers ( 2 – 5 ). The most common cause of occupational skin disease has previously been reported to be occupational contact dermatitis ( 7 , 8 ), which depending on aetiology, can be divided into irritant contact dermatitis and allergic contact dermatitis. While water, detergents, and cleansers are among the most important irritants, also having the ability to impair the skin barrier ( 9 – 11 ), the allergenic metals nickel, cobalt and chromium are common causes of occupational contact dermatitis ( 12 ). Simultaneous or consecutive exposure to both irritant/barrier damaging chemicals and allergens is common, not least in wet work occupations ( 13 ), including health care workers ( 14 ). In addition, such combined exposures will affect the possibility and degree of penetration and retention of allergens into the skin, although to an unknown extent. To study how increased hand hygiene practices affect the skin barrier’s ability to retain allergenic metals, in vitro experiments were performed in accordance with the OECD Test Guideline for skin absorption ( 15 ). The aim was to elucidate to what degree skin penetration occurred at exposure to nickel alone- or in combination with cobalt and chromium, under conditions that mimicked intensive hand cleaning with water, soap, and hand sanitizer. 2. Methods In in vitro -experiments to study retention of allergenic metals in skin, conditions mimicking intense hand hygiene practices using water, soap and hand-disinfectant, was obtained by simultaneous exposure to nickel alone or in combination with cobalt and chromium, and the exposure solvents Milli-Q water, 0.5% sodium lauryl sulphate (SLS) and ethanol, respectively. In addition, skin with altered barrier properties, to further resemble damage from intensive hand hygiene, was created via pre-treatment with SLS. In practical terms, the study was divided into three different experimental parts; I - in which conditions causing an altered skin barrier were tested and evaluated, II - in which treated and untreated skin were exposed to nickel in Milli-Q water, 0.5% SLS and ethanol, and III - in which treated and untreated skin were co-exposed to nickel, cobalt and chromium in Milli-Q water, 0.5% SLS and ethanol, Fig. 1 . (Flowchart of the chronological order of the study can be found in Supplementary Material Figure S1 ). All material used in experiments were acid washed (soaked for 24 hours in 10% HNO 3 , rinsed three times with ultrapure water and dried in ambient laboratory air) or cleaned with ethanol, to avoid any possible metal contamination. 2.1 Skin for experiments Full-thickness skin of stillborn piglets from commercial breeders was used in the present study. As the animals were not bred for research purposes, the use is exempt from the Swedish Agency for Agriculture's requirements for ethical vetting of research involving animals. Although the OCED TG 428 does not specify the use of pig skin, the GD 156 ( 16 ) state the fact that pig skin is considered an appropriate alternative to human skin, which is also in line with the results from a review of in vitro penetration studies by Barbero et Frasch ( 17 ). At arrival to the laboratory, stillborn piglets were rinsed with lukewarm water, after which skin integrity was checked by measuring the transepidermal water loss (TEWL, Dermalab, Cortex Technology, Hadsund, Denmark). In an attempt to simulate experimental exposure conditions affected by intense hand hygiene practices, the skin of stillborn piglets was washed with water and soap for 5 minutes (DAX Mildtvål Oparfymerad, KiiltoClean, Hyllie Stationstorg 2, Malmö, Sweden) or repeatedly treated 25 times with hand disinfectant (DES 75 vol%, LIV by Clemondo, Helsingborg, Sweden) in situ . Based on the results from TEWL measurements following each step in the procedure, the approach was concluded to not efficiently alter the skin barrier and hence were not used for the experiments (for more information on TEWL values and the procedure see Supplementary Material Table S1 ) . Full thickness skin (mean thickness 0.86 ± 0.22 mm) was collected from the back and flank of the stillborn piglets (< 24 h post-mortem) and the effect of excision on the skin was checked measuring TEWL at four different locations in each skin piece. Skin thickness was measured with a digital micrometer (model number 293-666-20 Mitutoyo, Kawasaki, Japan). Skin with an average TEWL ≥ 11 g⋅m − 2 ⋅h − 1 was discarded ( 18 , 19 ) and the average TEWL for the skin that met the TEWL criterion was 7.25 ± 1.22 g⋅m − 2 ⋅h − 1 . Next, the skin was wrapped in polyethene film and aluminium foil and stored at − 20ºC until later use within 3 months. On the day of experiments, 3x3 cm pieces were cut from each frozen skin using a sterile scalpel (Kiato, Sylak AB, Askim, Sweden) and placed in a petri dish to thaw for 30 min at room temperature. Thereafter, the barrier integrity of each skin piece was controlled. The measured TEWL of all skin samples were < 11 g⋅m − 2 ⋅h − 1 . 2.2 Treatment of skin with SLS (I) Pre-treatment of skin to alter the barrier integrity can be performed by physical means ( 20 ), but for the purposes of this study, a pre-treatment with aqueous SLS was elaborated based on the OECD TG 439 for in vitro skin irritation ( 21 ). After the thawing of skin, 500 µl PBS (PBS, pH = 7.4, Gibco Life Technologies, Thermo Fisher Scientific, Waltham, MA, USA) was put in the petri dish underneath the 3x3 cm skin piece to prevent dehydration. The skin surface was exposed to 200 µl of SLS-solutions (diluted from 20% SLS in H 2 O, Sigma-Aldrich, Schnelldorf, Germany) at different concentrations; 0.5, 1, 2, 5, and 10% in Milli-Q water (18.2 MΩ ⋅ cm − 1 , Merck Millipore, Darmstadt, Germany) for 1h, covered by the petri dish lid ( 22 ). The SLS was removed by rinsing with 4 ml (2 ml per side) of deionized water (dH 2 O, 16.8 MΩ ⋅ cm − 1 ). In total, four replicate samples were produced for each concentration tested with skin originating from four different piglets. The experiments for the two highest concentrations 5 and 10% respectively, were repeated and the results are thus based on 8 replicate samples. The TEWL values for each skin sample was recorded 20 minutes after removing the treatment. 2.3 Franz diffusion cell experiments (II, III) A series of experiments were conducted to evaluate the ability of the skin barrier to retain metals given conditions without and with SLS pre-treatment, to alter the skin barrier, and the simultaneous exposure to Milli-Q water, 0.5% SLS and ethanol, to mimic intensive hand hygiene practices using water, soap and hand sanitizer, respectively. The OECD TG 428 for skin absorption ( 15 ) and GD 156 ( 16 ) constituted the starting point for experiments with a focus on the study of the skin barrier as boundary for exposure. Six jacketed Franz cells (orifice diameter 11.28 mm, corresponding to an exposure area of 0.95 cm 2 , receptor volume 3 ml, Permegear, Bethlehem, PA, USA) were mounted on an adapted magnetic stirrer plate (HP 6 Variomag, H + P Labortechnik, Munick, Germany) and by means of circulating water from a thermostat water bath (AT 110, Heto, Alleod, Denmark) the diffusion cells were tempered at 32ºC. PBS was used as receptor fluid and was kept stirred using Teflon coated magnetic stirring bars. Skin pieces were mounted onto the Franz cells 15 min before the start of metal exposures. This study comprises twelve different exposure scenarios each tested on both treated and untreated skin ( Supplementary Material Table 2S) , with a dose range of relevance for occupational settings and exposure time that mimic real-life work periods (short exposure and full day work shift) ( 23 – 25 ). In the experimental part II, skin was exposed to nickel (1.36 µmol corresponding to a dose of 80 µg Ni/cm 2 ) dissolved in Milli-Q water, 0.5% SLS and ethanol (≥ 96%, v/v, TechniSolv®, France) for 2 and 8 hours. In part III, skin was similarly co-exposed to equimolar amounts of nickel, cobalt and chromium (4.09 µmol corresponding to a dose of 80 µg Ni + 80 µg Co + 71 µg Cr/cm 2 ) in the three exposure solvents. The donor solutions were prepared using two metal reference materials: a standard nickel stock solution (10 000 µg Ni/ml in 2.5% HNO 3 , Spectrascan, Teknolab, Ski, Norway) and a special, equimolar high concentration reference material of nickel + cobalt + chromium (Ni + Co + Cr 200 mmol/l in 10% HNO 3 , Spectrascan, Teknolab, Ski, Norway). Once the skin exposures to metal were initiated, the donor compartment and sampling port were occluded with parafilm (PARAFILM®, American National Can™). Blank (Milli-Q) exposures were carried out in parallel to enable control for any metal baseline quantities found in the skin ( Supplementary Material Figure S2 ). 2.3 Metal quantification Post exposure, the skin surface was rinsed with 2 ml dH 2 O per side (4 ml in total). Biopsy punches (Kai medical, 8 mm diameter) were taken from the exposed area and placed in polypropylene-plastic tubes (12 ml, Sarstedt, Nümbrecht, Germany) with 1 ml of 67% HNO 3 for 48 hours (until fully digested). Prior to metal analysis, 50 µl of digested skin was diluted with 4.95 ml of dH 2 0 and spiked with 20 µl of indium (1.255 µg In/ml, diluted from stock solution of 999 ± 5 µg In/ml in 2% HNO 3 , Spectrascan, Teknolab, Ski, Norway). Quantitative analyses of Ni, Co and Cr were performed using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS iCAP Q Thermo Fisher Scientific, Qtegra version 2.10). Concentrations of 58 Ni, 60 Ni, 59 Co, and 52 Cr, were analysed in kinetic energy discrimination (KED) measurement mode using helium gas to reduce any polyatomic interference and argon as nebulizer gas, cool gas, and auxiliary gas. Matrix-matched standards for calibration with the concentrations of 0, 0.1, 1, 5, 10, 50, 100 and 500 µg/l Ni, Co, Cr and Pb in 2% HNO 3 ( 67–69% HNO3, VWR, Normatom, Leuven, Belgium) were diluted from single metal reference materials (Ni: 1001 ± 4 µg/ml in 2% HNO 3 (v/v); Co: 1000 ± 3 µg/ml in 3% HNO 3 (v/v); Cr: 1002 ± 4 µg/ml in 2% HNO 3 (v/v); Pb: 998 ± 4 µg/ml in 0.5% HNO 3 (v/v), Spectrascan, Teknolab, Ski, Norway). To ensure statistical certainty, each sample was analysed three to five times. The limit of detection (LOD) (based on 7 concentration points of the STD curve in the ICP-MS) was set at 0.079 µg/l for 58 Ni, 0.082 µg/l 60 Ni, 0.004 µg/l 59 Co, and 0.19 µg/l 52 Cr. Nickel quantities found in samples was calculated as an average of 58 Ni and 60 Ni. 2.4 Statistical analysis Any statistical relationship between the amount of metal retained in skin at exposures to nickel alone or in combination with cobalt and chromium in three exposure solvents for treated and untreated skin at two different time-points using the Mann-Whitney U-test (GraphPad Prism version 9.5.0). To determine which variable (TEWL, skin thickness, +/- SLS treatment, single nickel or Ni + Co + Cr co-exposure in Milli-Q water, 0.5% SLS or ethanol, and exposure time) affect metal retention in skin, linear regression with log-transformed metal response was performed using RStudio (Version 2023.06.2–561). 3. Results 3.1 Conditions causing an altered skin barrier (I) The median of TEWL values recorded after each step in the preparation of skin for experiments, and after treatment with five different aqueous SLS concentrations (0.5%, 1%, 2%, 5% and 10%) respectively, are compiled in Table 1 . A ∆TEWL was calculated from the difference between the measured TEWL value after freezing (post thawing) and the TEWL value after SLS treatment. The results show that among the tested concentrations, 5% aqueous SLS alters the skin barrier the most. Table 1 Median TEWL values recorded (g⋅m − 2 ⋅h − 1 ) for each step (a-d) of the skin preparation procedure including SLS treatment at different concentrations. The TEWL was measured four times at different locations on each skin piece immediately after each step of the skin preparation procedure (a-b) and three times 30 min after thawing the skin (c) and 20 min after removing the SLS treatment (d). The range of these repeated measurements, somewhat indicative of intra- and inter individual variations, is represented by min and max values. SLS concentration for skin treatment 0.5%* 1%* 2%* 5%** 10%** Median (min; max) Median (min; max) Median (min; max) Median (min; max) Median (min; max) Preparation of skin for experiment a) After rinsing with lukewarm water in situ 11.35 (5.8; 15) 8.10 (6.8; 12.2) 4.25 (3.1; 6.1) 4.85 (2.9; 15.0) 5.35 (2.9; 9.0) b) Excised skin 4.55 (4.3; 5.3) 9.20 (7.9; 9.8) 4.10 (3.8; 4.4) 5.15 (4.3; 7.4) 7.65 (5.0; 9.8) Skin stored in freezer for up to 3 months c) After thawing 7.15 (6.6; 7.8) 8.75 (6.8; 10.7) 6.95 (6.2; 8.5) 7.40 (5.5; 9.4) 6.90 (6.0; 10.8) d) After SLS treatment 11.20 (7.8; 14.8) 10.75 (9.4; 13.4) 9.15 (7.7; 10.8) 13.10 (9.3; 31.0) 11.10 (9.4; 26.2) ∆TEWL (d-c) 4.05 2.00 2.20 5.70 4.20 *skin from one piglet for each concentration, four samples, n = 4 **skin from two different piglets for each concentration, four samples from each piglet, n = 8 3.2 Skin exposure to nickel in Milli-Q water, 0.5% SLS and ethanol (II) Higher amounts of nickel were generally measured in treated skin compared to untreated (Fig. 2, top ), and the difference was statistically significant for nickel exposure in Milli-Q water. The highest degree of nickel retention was observed for the exposure in ethanol (0.20 and 0.26 µmol for the 2- and 8-hour time-points in treated skin, and 0.16 and 0.22 µmol for the 2- and 8-hour time-points in untreated skin, respectively) followed by exposure in 0.5% SLS and Milli-Q water. The same tendency, however less pronounced, was observed for the 2- and 8-hours skin exposure to nickel in 0.5% SLS (0.07 and 0.12 µmol for the treated skin and 0.06 and 0.08 µmol for the untreated skin) and Milli-Q water (0.09 and 0.11 µmol for the treated and 0.03 and 0.04 µmol for the untreated skin, respectively). 3.3 Co-exposure to nickel, cobalt and chromium in Milli-Q water, 0.5% SLS and ethanol (III) The proportion of nickel, cobalt and chromium amounts measured in treated as well as untreated skin after 2- and 8 hours of exposure respectively, consistently reflected the equimolar conditions of the co-exposure to nickel cobalt and chromium (Fig. 2, middle ). Similar as to the single exposure to nickel, larger amounts of metal were measured in the treated skin compared to untreated. When the retained amounts of nickel, cobalt and chromium were added, the total amount of metal in skin were found to be at the same level as for nickel single exposure in the cases of exposure in Milli-Q water and ethanol (Fig. 2, bottom ). For the co-exposure of nickel, cobalt and chromium in 0.5% SLS, the total amounts of metal in skin were instead approximately three times the amounts of that from nickel single exposure and in the same range as for single and co-exposure in ethanol. The difference between metal amounts retained in treated skin was statistically significant only after 8 hours of exposure to metals in 0.5% SLS (0.29 and 0.17 µmol Ni + Co + Cr in treated vs untreated skin) while in ethanol the significance was obtained for both 2- and 8 hours of exposure (0.07 and 0.16 µmol Ni + Co + Cr after 2 hours and 0.13 and 0.27 after 8 hours exposure in treated and untreated skin respectively). For metal co-exposure in Milli-Q water, there were similar amounts of the individual metals measured in skin after 2 hours (0.01–0.02 µmol), while the treatment of skin resulted in higher amounts of total metals in skin after 8 hours (0.12 µmol Ni + Co + Cr in treated compared to 0.06 µmol Ni + Co + Cr in untreated skin). 3.4 Linear regression with log-transformed metal response Among the independent variables tested, SLS pre-treatment, the exposure solvent (Milli-Q water, 0.5% SLS and ethanol), the exposure time and the metal combination have shown to affect the retention of nickel in skin in a statistically significant manner ( Supplementary Material Table S3 ). Moreover, nickel skin retention is affected negatively (coefficient − 0.997) when in the presence of cobalt and chromium, meaning that the presence of other metals in the co-exposure results in lower nickel retention in skin, although the total metal content (Ni + Co + Cr) was higher (see also Fig. 2 , bottom row). In the linear model skin thickness and TEWL (see also Supplementary Material Figure S3 and S4 ) did not have a statistically significant effect on the nickel skin retention. The model analysis thus indicates that TEWL is not a good predictor of metal in the skin. 4. Discussion The present study demonstrates how the skin's ability to resist exposure and retain allergenic metals is affected by exposure conditions mimicking intensive hand hygiene practices using water, soap and hand sanitizer and altered barrier properties. First, we found that experimental treatment of piglet skin with 5% SLS efficiently alters the barrier integrity by means of TEWL. By adopting an established OECD method for skin absorption, we then conducted in vitro experiments that confirmed the SLS treatment consistently facilitated nickel skin penetration, and that exposure to single nickel in ethanol resulted in the highest amount of nickel in skin, compared to that from exposure in Milli-Q water or 0.5% SLS. Finally, co-exposure to nickel, cobalt and chromium in Milli-Q water, 0.5% SLS or ethanol respectively, showed that the amount of metal measured in the skin reflected the equimolar conditions upon exposure and that none of the metals penetrated or retained in the skin more readily than the other. Furthermore, following metal co-exposure in Milli-Q water and ethanol, the metal amount detected in skin added up to similar levels as observed for exposure to nickel only, while for the exposure in 0.5% SLS, the total amount of metal measured in skin doubled. Altering the barrier properties of skin using SLS is recommended by OECD TG 439 for in vitro skin irritation ( 21 ) and was previously used e.g., in vivo to cause irritation in a study of skin deposition and penetration of nickel ( 26 ). In the present case, SLS treatment of skin was the preferred option since it was considered to additionally contribute to exposure conditions aimed to mimic the effect of hand hygiene practices. SLS concentrations in consumer products typically ranges from 0.01–50% in cosmetic products and 1–30% in cleaning products ( 27 ). In a series of experiments, we investigated at which concentration the SLS treatment was most effective with respect to changed barrier properties and thus increased TEWL. We found that 5% SLS was more effective than treatment with 10% SLS, despite a relatively large variability among the 8 replicates from two different piglet individuals (Table 1 ). Although the TEWL measure reflects stratum corneum integrity, i.e., the main barrier for permeation resistance, and hence serves as a predictor of solvent permeation ( 28 ), it seems not to be a good predictor of metal retention in skin, as no correlation was observed between measured amounts of metal in skin and the degree of TEWL changes ( Supplementary Material Figure S4 ). Alternative measures of e.g., natural moisturizing factor (NMF) and IL-1α are promising markers for other types of barrier properties such as permeation in deeper skin layers and inflammatory parameters ( 10 ), but more research is needed to determine their usefulness as a predictor for skin uptake of allergenic metals. The results from exposure of untreated and treated skin, confirmed that the SLS pre-treatment enhances penetration of nickel and hence higher amounts of nickel were retained in skin compared to the untreated case. This is in line with previous findings on irritancy and skin damage caused by SLS as evaluated by several methods including the TEWL measure ( 9 , 29 , 30 ) and the ability of SLS to enhance permeation of other compounds ( 31 – 33 ). Although the exact mechanism of SLS on skin barrier function has not been clarified, studies have pointed to delipidization ( 34 , 35 ), morphological changes of corneocytes ( 36 ), or to damage to the deeper nucleated layers of the epidermis ( 37 , 38 ). These changes to the lipid lamellae organization may have contributed to the higher increase of nickel into the SLS treated skin. Also, water causes skin irritancy and disruption similar to that of surfactants ( 11 ) but no study to our knowledge have investigated the permeation enhancing capacity of water. Since the results of nickel in untreated skin from exposure in Milli-Q water is the lowest that we observe in our experiments, it is anticipated that the SLS, both the pre-treatment and the exposure to 0.5% SLS have a larger influence on metal penetration and retention in skin than the other tested exposure solvents. The highest measured levels in the skin were observed for exposure to nickel in ethanol which at the same time showed a large variation between the repeated experiments which can be partially explained by inter-individual skin differences rather than the ethanol itself. In addition, ethanol interacts with stratum corneum lipids ( 39 ) and is known to be a skin permeation enhancer ( 40 ), which could contribute to the explanation of the high nickel levels measured in the skin after ethanol exposure. The measured amounts of nickel, cobalt and chromium in the skin after combined exposure showed proportionality with the equimolar composition of the metals upon exposure and thus no possible preferential retention of the allergenic metals could be demonstrated. Results show that metal penetration occur in a time-dependent manner, which is in line with previous observations of simultaneous exposure to several metals ( 41 ). The same study reported that the sum of metals in co-exposure (Ni, Co and Cr) resulted in higher metal amounts measured in skin compared to their single-metal-exposure counterparts, a tendency that was observed only for the metal co-exposure in 0.5% SLS in the current study. For exposures in Milli-Q water and ethanol, i.e., without surfactant present, the sum of metals from co-exposure is similar to the amount of nickel in the single metal exposure case. This finding indicates the possibility that the skin's ability to retain metals has a saturation limit determined by the status of the skin barrier and the magnitude of the dose, in other words, infinite or finite conditions. The present study focussed on the skin retention of nickel under different exposure conditions and skin status. A disadvantage of this study design is that, for various reasons including time and resources, metal concentrations in the receptor have not been quantified. With the information on percutaneously absorbed amounts, a better understanding of the skin’s barrier properties and ability to retain the metals that penetrated stratum corneum, could have been obtained. Having studied the single exposures to cobalt and chromium would as well have contributed to understanding potential co-exposure effects also for these metals. Another obvious limitation of the current study is the number of replicated experiments (n = 6) and the number and distribution of piglet individuals (n = 18) where a larger scale would of course be desirable in order to control for inter-individual variations. 5. Conclusion In this study, we have demonstrated that an SLS treatment of skin alters the skin barrier properties with regards to TEWL. Furthermore, we have investigated differences in nickel retention between treated and untreated skin and how it is affected by exposure to other allergenic metals and continued skin-altering treatment mimicking intensive hand hygiene practices in the form of water, a surfactant and ethanol. In all investigated exposure cases, the altered skin barrier is subject to a relatively higher level of metal retention. The exposure to nickel in ethanol and combined exposure to metals in 0.5% SLS, respectively, constitutes the most severe exposure cases. These findings are important, not least regarding the occupational exposure to allergenic metals that often co-occur with wet work and use of water, soap and hand disinfectants, and should be taken into account when developing measures to prevent harmful skin exposure to metals. Declarations Ethics approval and consent to participate Not applicaable Consent for publication All authors have approved the submission of the manuscript and consent for its publication in the Journal of Occupational Medicine and Toxicology. Availability of data and material Not applicable Competing interests Not applicable Funding The study was financed by research grants from the Afa Insurance (Dnr 200230), PI Anneli Julander. Authors’ contributions Vilela, L. and Midander, K. wrote the main manuscript text and the supplementary material. Vilela, L. prepared Figures 1-2 and Table 1 and Figures S1-S4 and Tables S1-S3 and oversaw the softwares used in the manuscript. All authors took part on the investigation, formal analysis, visualization and reviewing and editing of the manuscript. Schenk, L., Julander, A. and Midander, K. took part on the conceptualization, validation, methodology, data curation and supervision. 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Kanerva’s occupational dermatology, second edition. Springer. 2012. Diepgen TL. Occupational skin diseases. Journal der Deutschen Dermatologischen Gesellschaft = Journal of the German Society of Dermatology : JDDG . 2012;10(5):297–315. Coppeta L, De Zordo ML, Papa F, Pietroiusti A, Magrini A. Skin sensitization among night shift and daytime healthcare workers: a cross sectional study. Central European journal of public health . 2021;29(3):191–194. OECD. Test No. 428: Skin Absorption: In Vitro Method. Paris, Organisation for Economic Co-operation and Development . 2004. OECD. Guidance Notes on Dermal Absorption. Series on Testing and Assessment. No 156. Second edition. Paris, Organisation for Economic Co-operation and Development . 2022. Barbero A, Frasch H. Pig and guinea pig skin as surrogates for human in vitro penetration studies: a quantitative review. Toxicology in vitro : an international journal published in association with BIBRA . 2009;23(1):1-13. Pinnagoda J, Tupker RA, Agner T, Serup J. Guidelines for transepidermal water loss (TEWL) measurement. A report from the Standardization Group of the European Society of Contact Dermatitis. Contact dermatitis . 1990;22(3):164-178. Zhang Q, Murawsky M, LaCount T, Kasting GB, Li SK. Transepidermal water loss and skin conductance as barrier integrity tests. Toxicology in vitro : an international journal published in association with BIBRA . 2018;51:129-135. Filon FL, Boeniger M, Maina G, Adami G, Spinelli P, Damian A. Skin Absorption of Inorganic Lead (PbO) and the Effect of Skin Cleansers. Journal of occupational and environmental medicine . 2006;48(7):692–699. OECD. Test No. 439: In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method. Paris, Organisation for Economic Co-operation and Development. 2021. York M, Griffiths HA, Whittle E, Basketter DA. Evaluation of a human patch test for the identification and classification of skin irritation potential. Contact dermatitis . 1996;34(3):204-212. Kettelarij J, Midander K, Lidén C, Bottai M, Julander A. Neglected exposure route: cobalt on skin and its associations with urinary cobalt levels. Occupational and environmental medicine . 2018;75(11):837-842. Klasson M, Lindberg M, Bryngelsson IL, et al. Biological monitoring of dermal and air exposure to cobalt at a Swedish hard metal production plant: does dermal exposure contribute to uptake? Contact Dermatitis . 2017;77(4):201-207. Lidén C, Skare L, Nise G, Vahter M. Deposition of nickel, chromium, and cobalt on the skin in some occupations - assessment by acid wipe sampling. Contact Dermatitis . 2008;58(6):347-354. Ahlström MG, Midander K, Menné T, et al. Nickel deposition and penetration into the stratum corneum after short metallic nickel contact: An experimental study. Contact Dermatitis . 2019;80(2):86-93. Bondi CA, Marks JL, Wroblewski LB, Raatikainen HS, Lenox SR, Gebhardt KE. Human and Environmental Toxicity of Sodium Lauryl Sulfate (SLS): Evidence for Safe Use in Household Cleaning Products. Environmental health insights . 2015;9:27-32. Kezic S, Nielsen JB. Absorption of chemicals through compromised skin. International archives of occupational and environmental health . 2009;82(6):677-688. Laudańska H, Reduta T, Szmitkowska D. Evaluation of skin barrier function in allergic contact dermatitis and atopic dermatitis using method of the continuous TEWL measurement. Roczniki Akademii Medycznej w Bialymstoku (1995) . 2003;48:123-127. Welzel J, Metker C, Wolff HH, Wilhelm KP. SLS-irritated human skin shows no correlation between degree of proliferation and TEWL increase. Archives of dermatological research . 1998;290(11):615-620. Nielsen JB. Percutaneous penetration through slightly damaged skin. Archives of dermatological research . 2005;296(2):560-567. Benfeldt E, Serup J. Effect of barrier perturbation on cutaneous penetration of salicylic acid in hairless rats: in vivo pharmacokinetics using microdialysis and non-invasive quantification of barrier function. Archives of dermatological research . 1999;291(9):517-526. Pavlačková J, Egner P, Polašková J, et al. Transdermal absorption of active substances from cosmetic vehicles. Journal of cosmetic dermatology . 2019;18(5):1410-1415. Froebe CL, Simion FA, Rhein LD, Cagan RH, Kligman A. Stratum corneum lipid removal by surfactants: relation to in vivo irritation. Dermatologica . 1990;181(4):277–283. Imokawa G, Akasaki S, Minematsu Y, Kawai M. Importance of intercellular lipids in water-retention properties of the stratum corneum: induction and recovery study of surfactant dry skin. Archives of dermatological research . 1989;281(1):45–51. Shukuwa T, Kligman AM, Stoudemayer TJ. A new model for assessing the damaging effects of soaps and surfactants on human stratum corneum. Acta dermato-venereologica . 1997;77(1):29-34. Fartasch M, Schnetz E, Diepgen TL. Characterization of detergent-induced barrier alterations -- effect of barrier cream on irritation. The journal of investigative dermatology Symposium proceedings . 1998;3(2):121-127. Yang L, Mao-Qiang M, Taljebini M, Elias PM, Feingold KR. Topical stratum corneum lipids accelerate barrier repair after tape stripping, solvent treatment and some but not all types of detergent treatment. The British journal of dermatology . 1995;133(5):679–685. Gupta R, Badhe Y, Rai B, Mitragotri S. Molecular mechanism of the skin permeation enhancing effect of ethanol: a molecular dynamics study. RSC advances . 2020;10(21):12234–12248. Ghanem AH, Mahmoud H, Higuchi WI, Liu P, Good WR. The effects of ethanol on the transport of lipophilic and polar permeants across hairless mouse skin: Methods/validation of a novel approach. International Journal of Pharmaceutics . 1992;78(1-3):137-156. Midander K, Schenk L, Julander A. A novel approach to monitor skin permeation of metals in vitro. Regulatory toxicology and pharmacology : RTP . 2020;115:104693. Additional Declarations No competing interests reported. Supplementary Files SupplementaryMaterialforsubmission.docx Cite Share Download PDF Status: Published Journal Publication published 06 Nov, 2024 Read the published version in Journal of Occupational Medicine and Toxicology → Version 1 posted Editorial decision: Revision requested 28 Sep, 2024 Reviews received at journal 25 Sep, 2024 Reviewers agreed at journal 02 Sep, 2024 Reviews received at journal 21 Aug, 2024 Reviewers agreed at journal 15 Aug, 2024 Reviewers invited by journal 01 Aug, 2024 Editor assigned by journal 01 Aug, 2024 Submission checks completed at journal 31 Jul, 2024 First submitted to journal 30 Jul, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4829304","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":343198913,"identity":"e6690024-cc77-4eb0-89f7-906e0def01fa","order_by":0,"name":"Libe Vilela","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA3klEQVRIie2PMQrCQBBFf1hImkm23YB4hrVRu1wlEkhlYZlCRBCSK1iId7CxNixYRbxCwAtsaWHhJlpnLS32NdPMm/8HcDj+kIhRN8QIgRm6SMmq+F+FwABv3/yi4LPTKywsU3sxPwjr1ivnxBlrER7zEbi6WIpFmfRKQfHOl4jPS4LIh6PML1OBRpBUkJicC6OQtCmzZ6ckKtBYHIzC79qaAhTmMjPH660phuWg0f8iUqMIRat6e83JF/lwMc5vtdZyM+ZVdXq81lnCuWqHYzrS77z0ufZ9h8PhcNh4AwuIMR951b/qAAAAAElFTkSuQmCC","orcid":"","institution":"Karolinska Institutet","correspondingAuthor":true,"prefix":"","firstName":"Libe","middleName":"","lastName":"Vilela","suffix":""},{"id":343198914,"identity":"972486dd-c049-43be-a70a-e99df3ba70f9","order_by":1,"name":"Linda Schenk","email":"","orcid":"","institution":"Karolinska Institutet","correspondingAuthor":false,"prefix":"","firstName":"Linda","middleName":"","lastName":"Schenk","suffix":""},{"id":343198916,"identity":"9c191dda-9293-4453-b0fd-5da655b134b9","order_by":2,"name":"Anneli Julander","email":"","orcid":"","institution":"Karolinska Institutet","correspondingAuthor":false,"prefix":"","firstName":"Anneli","middleName":"","lastName":"Julander","suffix":""},{"id":343198918,"identity":"615ad940-d765-4eaa-abdd-209944d6bc88","order_by":3,"name":"Klara Midander","email":"","orcid":"","institution":"Karolinska Institutet","correspondingAuthor":false,"prefix":"","firstName":"Klara","middleName":"","lastName":"Midander","suffix":""}],"badges":[],"createdAt":"2024-07-30 13:53:35","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4829304/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4829304/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12995-024-00442-5","type":"published","date":"2024-11-06T15:57:21+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":63389668,"identity":"ffefddec-fa52-4f88-8860-b29a8f31d30a","added_by":"auto","created_at":"2024-08-27 15:18:22","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":192862,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic illustration of the three experimental parts (I, II, III) of the study.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-4829304/v1/d514bbb88a7af6c7be6565b7.png"},{"id":63390261,"identity":"1fb67eae-b556-4dd8-94b6-d9b4349e19a5","added_by":"auto","created_at":"2024-08-27 15:26:22","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":143286,"visible":true,"origin":"","legend":"\u003cp\u003eMeasured amounts of metal (µmol) in treated (grey bars) and untreated skin (white bars) following exposure to metals in Milli-Q water, 0.5% SLS and ethanol for 2 and 8 hours respectively. Results from single exposure to nickel is shown in the top row. The results for the combined exposure to equimolar amounts of nickel, cobalt and chromium are displayed per metal (middle section) and added (bottom). Data is presented as mean values of from six replicate experiments (n=6, data points) with bars showing the standard deviation. Statistically significant relationships were indicated as (*) for p-values \u0026lt; 0.01 and (**) for p-values \u0026lt; 0.001.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-4829304/v1/edc11d8fc302b5d5595a8cad.png"},{"id":68750085,"identity":"8621c4ff-5e72-441c-b001-dbdc9cc7e29c","added_by":"auto","created_at":"2024-11-11 16:09:26","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":960755,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4829304/v1/6b61b79c-bc59-4b7f-9337-57d22a686ad0.pdf"},{"id":63389671,"identity":"c7b257ea-bb6e-4c69-be8c-f0be505fde39","added_by":"auto","created_at":"2024-08-27 15:18:22","extension":"docx","order_by":5,"title":"","display":"","copyAsset":false,"role":"supplement","size":961045,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryMaterialforsubmission.docx","url":"https://assets-eu.researchsquare.com/files/rs-4829304/v1/9d30ce46edb1f655d7124ecd.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Retention of Nickel, Cobalt and Chromium in skin at conditions mimicking intense hand hygiene practices using water, soap, and hand-disinfectant in vitro","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eDuring the Coronavirus pandemic 2019 (COVID-19), hygiene practices changed and more frequent exposure to water and hand disinfectants were observed (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). Several studies related to increased hygiene measures during this period, have focused on healthcare workers and how such COVID-19 related measures increased skin- health issues (\u003cspan additionalcitationids=\"CR3 CR4\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e). Correspondingly, an increased self-reported exposure to water, soap and usage of hand disinfectant were demonstrated in frontline workers and IT personnel, i.e., occupations outside of the hospital setting that required presence at the workplace and one that could largely work from home (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e). Additionally, frontline workers also reported higher frequency of hand eczema than IT personnel (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e), which is in line with the associations between increased hand washing and hand eczema observed for healthcare workers (\u003cspan additionalcitationids=\"CR3 CR4\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe most common cause of occupational skin disease has previously been reported to be occupational contact dermatitis (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e), which depending on aetiology, can be divided into irritant contact dermatitis and allergic contact dermatitis. While water, detergents, and cleansers are among the most important irritants, also having the ability to impair the skin barrier (\u003cspan additionalcitationids=\"CR10\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e), the allergenic metals nickel, cobalt and chromium are common causes of occupational contact dermatitis (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e). Simultaneous or consecutive exposure to both irritant/barrier damaging chemicals and allergens is common, not least in wet work occupations (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e), including health care workers (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e). In addition, such combined exposures will affect the possibility and degree of penetration and retention of allergens into the skin, although to an unknown extent.\u003c/p\u003e \u003cp\u003eTo study how increased hand hygiene practices affect the skin barrier\u0026rsquo;s ability to retain allergenic metals, \u003cem\u003ein vitro\u003c/em\u003e experiments were performed in accordance with the OECD Test Guideline for skin absorption (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e). The aim was to elucidate to what degree skin penetration occurred at exposure to nickel alone- or in combination with cobalt and chromium, under conditions that mimicked intensive hand cleaning with water, soap, and hand sanitizer.\u003c/p\u003e"},{"header":"2. Methods","content":"\u003cp\u003eIn \u003cem\u003ein vitro\u003c/em\u003e-experiments to study retention of allergenic metals in skin, conditions mimicking intense hand hygiene practices using water, soap and hand-disinfectant, was obtained by simultaneous exposure to nickel alone or in combination with cobalt and chromium, and the exposure solvents Milli-Q water, 0.5% sodium lauryl sulphate (SLS) and ethanol, respectively. In addition, skin with altered barrier properties, to further resemble damage from intensive hand hygiene, was created via pre-treatment with SLS. In practical terms, the study was divided into three different experimental parts; \u003cem\u003eI\u003c/em\u003e - in which conditions causing an altered skin barrier were tested and evaluated, \u003cem\u003eII\u003c/em\u003e - in which treated and untreated skin were exposed to nickel in Milli-Q water, 0.5% SLS and ethanol, and \u003cem\u003eIII\u003c/em\u003e - in which treated and untreated skin were co-exposed to nickel, cobalt and chromium in Milli-Q water, 0.5% SLS and ethanol, Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. (Flowchart of the chronological order of the study can be found in \u003cb\u003eSupplementary Material Figure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e\u003c/b\u003e). All material used in experiments were acid washed (soaked for 24 hours in 10% HNO\u003csub\u003e3\u003c/sub\u003e, rinsed three times with ultrapure water and dried in ambient laboratory air) or cleaned with ethanol, to avoid any possible metal contamination.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Skin for experiments\u003c/h2\u003e \u003cp\u003eFull-thickness skin of stillborn piglets from commercial breeders was used in the present study. As the animals were not bred for research purposes, the use is exempt from the Swedish Agency for Agriculture's requirements for ethical vetting of research involving animals. Although the OCED TG 428 does not specify the use of pig skin, the GD 156 (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e) state the fact that pig skin is considered an appropriate alternative to human skin, which is also in line with the results from a review of \u003cem\u003ein vitro\u003c/em\u003e penetration studies by Barbero et Frasch (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAt arrival to the laboratory, stillborn piglets were rinsed with lukewarm water, after which skin integrity was checked by measuring the transepidermal water loss (TEWL, Dermalab, Cortex Technology, Hadsund, Denmark).\u003c/p\u003e \u003cp\u003eIn an attempt to simulate experimental exposure conditions affected by intense hand hygiene practices, the skin of stillborn piglets was washed with water and soap for 5 minutes (DAX Mildtv\u0026aring;l Oparfymerad, KiiltoClean, Hyllie Stationstorg 2, Malm\u0026ouml;, Sweden) or repeatedly treated 25 times with hand disinfectant (DES 75 vol%, LIV by Clemondo, Helsingborg, Sweden) \u003cem\u003ein situ\u003c/em\u003e. Based on the results from TEWL measurements following each step in the procedure, the approach was concluded to not efficiently alter the skin barrier and hence were not used for the experiments (for more information on TEWL values and the procedure see \u003cb\u003eSupplementary Material Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e)\u003c/b\u003e.\u003c/p\u003e \u003cp\u003eFull thickness skin (mean thickness 0.86\u0026thinsp;\u0026plusmn;\u0026thinsp;0.22 mm) was collected from the back and flank of the stillborn piglets (\u0026lt;\u0026thinsp;24 h post-mortem) and the effect of excision on the skin was checked measuring TEWL at four different locations in each skin piece. Skin thickness was measured with a digital micrometer (model number 293-666-20 Mitutoyo, Kawasaki, Japan). Skin with an average TEWL\u0026thinsp;\u0026ge;\u0026thinsp;11 g\u0026sdot;m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u0026sdot;h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e was discarded (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e) and the average TEWL for the skin that met the TEWL criterion was 7.25\u0026thinsp;\u0026plusmn;\u0026thinsp;1.22 g\u0026sdot;m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u0026sdot;h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Next, the skin was wrapped in polyethene film and aluminium foil and stored at \u0026minus;\u0026thinsp;20\u0026ordm;C until later use within 3 months.\u003c/p\u003e \u003cp\u003eOn the day of experiments, 3x3 cm pieces were cut from each frozen skin using a sterile scalpel (Kiato, Sylak AB, Askim, Sweden) and placed in a petri dish to thaw for 30 min at room temperature. Thereafter, the barrier integrity of each skin piece was controlled. The measured TEWL of all skin samples were \u0026lt;\u0026thinsp;11 g\u0026sdot;m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u0026sdot;h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Treatment of skin with SLS (I)\u003c/h2\u003e \u003cp\u003ePre-treatment of skin to alter the barrier integrity can be performed by physical means (\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e), but for the purposes of this study, a pre-treatment with aqueous SLS was elaborated based on the OECD TG 439 for \u003cem\u003ein vitro\u003c/em\u003e skin irritation (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAfter the thawing of skin, 500 \u0026micro;l PBS (PBS, pH\u0026thinsp;=\u0026thinsp;7.4, Gibco Life Technologies, Thermo Fisher Scientific, Waltham, MA, USA) was put in the petri dish underneath the 3x3 cm skin piece to prevent dehydration. The skin surface was exposed to 200 \u0026micro;l of SLS-solutions (diluted from 20% SLS in H\u003csub\u003e2\u003c/sub\u003eO, Sigma-Aldrich, Schnelldorf, Germany) at different concentrations; 0.5, 1, 2, 5, and 10% in Milli-Q water (18.2 MΩ\u0026thinsp;\u0026sdot;\u0026thinsp;cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, Merck Millipore, Darmstadt, Germany) for 1h, covered by the petri dish lid (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e). The SLS was removed by rinsing with 4 ml (2 ml per side) of deionized water (dH\u003csub\u003e2\u003c/sub\u003eO, 16.8 MΩ\u0026thinsp;\u0026sdot;\u0026thinsp;cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). In total, four replicate samples were produced for each concentration tested with skin originating from four different piglets. The experiments for the two highest concentrations 5 and 10% respectively, were repeated and the results are thus based on 8 replicate samples. The TEWL values for each skin sample was recorded 20 minutes after removing the treatment.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Franz diffusion cell experiments (II, III)\u003c/h2\u003e \u003cp\u003eA series of experiments were conducted to evaluate the ability of the skin barrier to retain metals given conditions without and with SLS pre-treatment, to alter the skin barrier, and the simultaneous exposure to Milli-Q water, 0.5% SLS and ethanol, to mimic intensive hand hygiene practices using water, soap and hand sanitizer, respectively. The OECD TG 428 for skin absorption (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e) and GD 156 (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e) constituted the starting point for experiments with a focus on the study of the skin barrier as boundary for exposure.\u003c/p\u003e \u003cp\u003eSix jacketed Franz cells (orifice diameter 11.28 mm, corresponding to an exposure area of 0.95 cm\u003csup\u003e2\u003c/sup\u003e, receptor volume 3 ml, Permegear, Bethlehem, PA, USA) were mounted on an adapted magnetic stirrer plate (HP 6 Variomag, H\u0026thinsp;+\u0026thinsp;P Labortechnik, Munick, Germany) and by means of circulating water from a thermostat water bath (AT 110, Heto, Alleod, Denmark) the diffusion cells were tempered at 32\u0026ordm;C. PBS was used as receptor fluid and was kept stirred using Teflon coated magnetic stirring bars. Skin pieces were mounted onto the Franz cells 15 min before the start of metal exposures.\u003c/p\u003e \u003cp\u003eThis study comprises twelve different exposure scenarios each tested on both treated and untreated skin (\u003cb\u003eSupplementary Material Table\u0026nbsp;2S)\u003c/b\u003e, with a dose range of relevance for occupational settings and exposure time that mimic real-life work periods (short exposure and full day work shift) (\u003cspan additionalcitationids=\"CR24\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e). In the experimental part II, skin was exposed to nickel (1.36 \u0026micro;mol corresponding to a dose of 80 \u0026micro;g Ni/cm\u003csup\u003e2\u003c/sup\u003e) dissolved in Milli-Q water, 0.5% SLS and ethanol (\u0026ge;\u0026thinsp;96%, v/v, TechniSolv\u0026reg;, France) for 2 and 8 hours. In part III, skin was similarly co-exposed to equimolar amounts of nickel, cobalt and chromium (4.09 \u0026micro;mol corresponding to a dose of 80 \u0026micro;g Ni\u0026thinsp;+\u0026thinsp;80 \u0026micro;g Co\u0026thinsp;+\u0026thinsp;71 \u0026micro;g Cr/cm\u003csup\u003e2\u003c/sup\u003e) in the three exposure solvents. The donor solutions were prepared using two metal reference materials: a standard nickel stock solution (10 000 \u0026micro;g Ni/ml in 2.5% HNO\u003csub\u003e3\u003c/sub\u003e, Spectrascan, Teknolab, Ski, Norway) and a special, equimolar high concentration reference material of nickel\u0026thinsp;+\u0026thinsp;cobalt\u0026thinsp;+\u0026thinsp;chromium (Ni\u0026thinsp;+\u0026thinsp;Co\u0026thinsp;+\u0026thinsp;Cr 200 mmol/l in 10% HNO\u003csub\u003e3\u003c/sub\u003e, Spectrascan, Teknolab, Ski, Norway).\u003c/p\u003e \u003cp\u003eOnce the skin exposures to metal were initiated, the donor compartment and sampling port were occluded with parafilm (PARAFILM\u0026reg;, American National Can\u0026trade;). Blank (Milli-Q) exposures were carried out in parallel to enable control for any metal baseline quantities found in the skin (\u003cb\u003eSupplementary Material Figure S2\u003c/b\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Metal quantification\u003c/h2\u003e \u003cp\u003ePost exposure, the skin surface was rinsed with 2 ml dH\u003csub\u003e2\u003c/sub\u003eO per side (4 ml in total). Biopsy punches (Kai medical, 8 mm diameter) were taken from the exposed area and placed in polypropylene-plastic tubes (12 ml, Sarstedt, N\u0026uuml;mbrecht, Germany) with 1 ml of 67% HNO\u003csub\u003e3\u003c/sub\u003e for 48 hours (until fully digested). Prior to metal analysis, 50 \u0026micro;l of digested skin was diluted with 4.95 ml of dH\u003csub\u003e2\u003c/sub\u003e0 and spiked with 20 \u0026micro;l of indium (1.255 \u0026micro;g In/ml, diluted from stock solution of 999\u0026thinsp;\u0026plusmn;\u0026thinsp;5 \u0026micro;g In/ml in 2% HNO\u003csub\u003e3\u003c/sub\u003e, Spectrascan, Teknolab, Ski, Norway).\u003c/p\u003e \u003cp\u003eQuantitative analyses of Ni, Co and Cr were performed using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS iCAP Q Thermo Fisher Scientific, Qtegra version 2.10). Concentrations of \u003csup\u003e58\u003c/sup\u003eNi, \u003csup\u003e60\u003c/sup\u003eNi, \u003csup\u003e59\u003c/sup\u003eCo, and \u003csup\u003e52\u003c/sup\u003eCr, were analysed in kinetic energy discrimination (KED) measurement mode using helium gas to reduce any polyatomic interference and argon as nebulizer gas, cool gas, and auxiliary gas.\u003c/p\u003e \u003cp\u003eMatrix-matched standards for calibration with the concentrations of 0, 0.1, 1, 5, 10, 50, 100 and 500 \u0026micro;g/l Ni, Co, Cr and Pb in 2% HNO\u003csub\u003e3\u003c/sub\u003e ( 67\u0026ndash;69% HNO3, VWR, Normatom, Leuven, Belgium) were diluted from single metal reference materials (Ni: 1001\u0026thinsp;\u0026plusmn;\u0026thinsp;4 \u0026micro;g/ml in 2% HNO\u003csub\u003e3\u003c/sub\u003e (v/v); Co: 1000\u0026thinsp;\u0026plusmn;\u0026thinsp;3 \u0026micro;g/ml in 3% HNO\u003csub\u003e3\u003c/sub\u003e (v/v); Cr: 1002\u0026thinsp;\u0026plusmn;\u0026thinsp;4 \u0026micro;g/ml in 2% HNO\u003csub\u003e3\u003c/sub\u003e (v/v); Pb: 998\u0026thinsp;\u0026plusmn;\u0026thinsp;4 \u0026micro;g/ml in 0.5% HNO\u003csub\u003e3\u003c/sub\u003e (v/v), Spectrascan, Teknolab, Ski, Norway).\u003c/p\u003e \u003cp\u003eTo ensure statistical certainty, each sample was analysed three to five times. The limit of detection (LOD) (based on 7 concentration points of the STD curve in the ICP-MS) was set at 0.079 \u0026micro;g/l for \u003csup\u003e58\u003c/sup\u003eNi, 0.082 \u0026micro;g/l \u003csup\u003e60\u003c/sup\u003eNi, 0.004 \u0026micro;g/l \u003csup\u003e59\u003c/sup\u003eCo, and 0.19 \u0026micro;g/l \u003csup\u003e52\u003c/sup\u003eCr. Nickel quantities found in samples was calculated as an average of \u003csup\u003e58\u003c/sup\u003eNi and \u003csup\u003e60\u003c/sup\u003eNi.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Statistical analysis\u003c/h2\u003e \u003cp\u003eAny statistical relationship between the amount of metal retained in skin at exposures to nickel alone or in combination with cobalt and chromium in three exposure solvents for treated and untreated skin at two different time-points using the Mann-Whitney U-test (GraphPad Prism version 9.5.0).\u003c/p\u003e \u003cp\u003eTo determine which variable (TEWL, skin thickness, +/- SLS treatment, single nickel or Ni\u0026thinsp;+\u0026thinsp;Co\u0026thinsp;+\u0026thinsp;Cr co-exposure in Milli-Q water, 0.5% SLS or ethanol, and exposure time) affect metal retention in skin, linear regression with log-transformed metal response was performed using RStudio (Version 2023.06.2\u0026ndash;561).\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1 Conditions causing an altered skin barrier (I)\u003c/h2\u003e\n \u003cp\u003eThe median of TEWL values recorded after each step in the preparation of skin for experiments, and after treatment with five different aqueous SLS concentrations (0.5%, 1%, 2%, 5% and 10%) respectively, are compiled in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. A ∆TEWL was calculated from the difference between the measured TEWL value after freezing (post thawing) and the TEWL value after SLS treatment. The results show that among the tested concentrations, 5% aqueous SLS alters the skin barrier the most.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eMedian TEWL values recorded (g\u0026sdot;m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u0026sdot;h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) for each step (a-d) of the skin preparation procedure including SLS treatment at different concentrations. The TEWL was measured four times at different locations on each skin piece immediately after each step of the skin preparation procedure (a-b) and three times 30 min after thawing the skin (c) and 20 min after removing the SLS treatment (d). The range of these repeated measurements, somewhat indicative of intra- and inter individual variations, is represented by min and max values.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"7\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" colspan=\"2\" rowspan=\"2\"\u003e\n \u003cp\u003eSLS concentration for skin treatment\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e0.5%*\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e1%*\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e2%*\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e5%**\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e10%**\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMedian\u003c/p\u003e\n \u003cp\u003e(min; max)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMedian\u003c/p\u003e\n \u003cp\u003e(min; max)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMedian\u003c/p\u003e\n \u003cp\u003e(min; max)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMedian\u003c/p\u003e\n \u003cp\u003e(min; max)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMedian\u003c/p\u003e\n \u003cp\u003e(min; max)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colspan=\"7\"\u003e\n \u003cp\u003e\u003cem\u003ePreparation of skin for experiment\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ea)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAfter rinsing with lukewarm water \u003cem\u003ein situ\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11.35\u003c/p\u003e\n \u003cp\u003e(5.8; 15)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.10\u003c/p\u003e\n \u003cp\u003e(6.8; 12.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.25\u003c/p\u003e\n \u003cp\u003e(3.1; 6.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.85\u003c/p\u003e\n \u003cp\u003e(2.9; 15.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.35\u003c/p\u003e\n \u003cp\u003e(2.9; 9.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eb)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eExcised skin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.55\u003c/p\u003e\n \u003cp\u003e(4.3; 5.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9.20\u003c/p\u003e\n \u003cp\u003e(7.9; 9.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.10\u003c/p\u003e\n \u003cp\u003e(3.8; 4.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.15\u003c/p\u003e\n \u003cp\u003e(4.3; 7.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.65\u003c/p\u003e\n \u003cp\u003e(5.0; 9.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colspan=\"7\"\u003e\n \u003cp\u003e\u003cem\u003eSkin stored in freezer for up to 3 months\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ec)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAfter thawing\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.15\u003c/p\u003e\n \u003cp\u003e(6.6; 7.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.75\u003c/p\u003e\n \u003cp\u003e(6.8; 10.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.95\u003c/p\u003e\n \u003cp\u003e(6.2; 8.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.40\u003c/p\u003e\n \u003cp\u003e(5.5; 9.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.90\u003c/p\u003e\n \u003cp\u003e(6.0; 10.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ed)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAfter SLS treatment\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11.20\u003c/p\u003e\n \u003cp\u003e(7.8; 14.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10.75\u003c/p\u003e\n \u003cp\u003e(9.4; 13.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9.15\u003c/p\u003e\n \u003cp\u003e(7.7; 10.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13.10\u003c/p\u003e\n \u003cp\u003e(9.3; 31.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11.10\u003c/p\u003e\n \u003cp\u003e(9.4; 26.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e∆TEWL (d-c)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e4.05\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e2.00\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e2.20\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e5.70\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e4.20\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"7\"\u003e*skin from one piglet for each concentration, four samples, n\u0026thinsp;=\u0026thinsp;4\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"7\"\u003e**skin from two different piglets for each concentration, four samples from each piglet, n\u0026thinsp;=\u0026thinsp;8\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2 Skin exposure to nickel in Milli-Q water, 0.5% SLS and ethanol (II)\u003c/h2\u003e\n \u003cp\u003eHigher amounts of nickel were generally measured in treated skin compared to untreated (Fig. 2, \u003cstrong\u003etop\u003c/strong\u003e), and the difference was statistically significant for nickel exposure in Milli-Q water. The highest degree of nickel retention was observed for the exposure in ethanol (0.20 and 0.26 \u0026micro;mol for the 2- and 8-hour time-points in treated skin, and 0.16 and 0.22 \u0026micro;mol for the 2- and 8-hour time-points in untreated skin, respectively) followed by exposure in 0.5% SLS and Milli-Q water. The same tendency, however less pronounced, was observed for the 2- and 8-hours skin exposure to nickel in 0.5% SLS (0.07 and 0.12 \u0026micro;mol for the treated skin and 0.06 and 0.08 \u0026micro;mol for the untreated skin) and Milli-Q water (0.09 and 0.11 \u0026micro;mol for the treated and 0.03 and 0.04 \u0026micro;mol for the untreated skin, respectively).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3 Co-exposure to nickel, cobalt and chromium in Milli-Q water, 0.5% SLS and ethanol (III)\u003c/h2\u003e\n \u003cp\u003eThe proportion of nickel, cobalt and chromium amounts measured in treated as well as untreated skin after 2- and 8 hours of exposure respectively, consistently reflected the equimolar conditions of the co-exposure to nickel cobalt and chromium (Fig. 2, \u003cstrong\u003emiddle\u003c/strong\u003e). Similar as to the single exposure to nickel, larger amounts of metal were measured in the treated skin compared to untreated. When the retained amounts of nickel, cobalt and chromium were added, the total amount of metal in skin were found to be at the same level as for nickel single exposure in the cases of exposure in Milli-Q water and ethanol (Fig. 2, \u003cstrong\u003ebottom\u003c/strong\u003e). For the co-exposure of nickel, cobalt and chromium in 0.5% SLS, the total amounts of metal in skin were instead approximately three times the amounts of that from nickel single exposure and in the same range as for single and co-exposure in ethanol. The difference between metal amounts retained in treated skin was statistically significant only after 8 hours of exposure to metals in 0.5% SLS (0.29 and 0.17 \u0026micro;mol Ni\u0026thinsp;+\u0026thinsp;Co\u0026thinsp;+\u0026thinsp;Cr in treated vs untreated skin) while in ethanol the significance was obtained for both 2- and 8 hours of exposure (0.07 and 0.16 \u0026micro;mol Ni\u0026thinsp;+\u0026thinsp;Co\u0026thinsp;+\u0026thinsp;Cr after 2 hours and 0.13 and 0.27 after 8 hours exposure in treated and untreated skin respectively). For metal co-exposure in Milli-Q water, there were similar amounts of the individual metals measured in skin after 2 hours (0.01\u0026ndash;0.02 \u0026micro;mol), while the treatment of skin resulted in higher amounts of total metals in skin after 8 hours (0.12 \u0026micro;mol Ni\u0026thinsp;+\u0026thinsp;Co\u0026thinsp;+\u0026thinsp;Cr in treated compared to 0.06 \u0026micro;mol Ni\u0026thinsp;+\u0026thinsp;Co\u0026thinsp;+\u0026thinsp;Cr in untreated skin).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n \u003ch2\u003e3.4 Linear regression with log-transformed metal response\u003c/h2\u003e\n \u003cp\u003eAmong the independent variables tested, SLS pre-treatment, the exposure solvent (Milli-Q water, 0.5% SLS and ethanol), the exposure time and the metal combination have shown to affect the retention of nickel in skin in a statistically significant manner (\u003cstrong\u003eSupplementary Material Table S3\u003c/strong\u003e). Moreover, nickel skin retention is affected negatively (coefficient \u0026minus;\u0026thinsp;0.997) when in the presence of cobalt and chromium, meaning that the presence of other metals in the co-exposure results in lower nickel retention in skin, although the total metal content (Ni\u0026thinsp;+\u0026thinsp;Co\u0026thinsp;+\u0026thinsp;Cr) was higher (see also \u003cstrong\u003eFig.\u0026nbsp;2\u003c/strong\u003e, bottom row).\u003c/p\u003e\n \u003cp\u003eIn the linear model skin thickness and TEWL (see also \u003cstrong\u003eSupplementary Material Figure S3 and S4\u003c/strong\u003e) did not have a statistically significant effect on the nickel skin retention. The model analysis thus indicates that TEWL is not a good predictor of metal in the skin.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eThe present study demonstrates how the skin's ability to resist exposure and retain allergenic metals is affected by exposure conditions mimicking intensive hand hygiene practices using water, soap and hand sanitizer and altered barrier properties. First, we found that experimental treatment of piglet skin with 5% SLS efficiently alters the barrier integrity by means of TEWL. By adopting an established OECD method for skin absorption, we then conducted \u003cem\u003ein vitro\u003c/em\u003e experiments that confirmed the SLS treatment consistently facilitated nickel skin penetration, and that exposure to single nickel in ethanol resulted in the highest amount of nickel in skin, compared to that from exposure in Milli-Q water or 0.5% SLS. Finally, co-exposure to nickel, cobalt and chromium in Milli-Q water, 0.5% SLS or ethanol respectively, showed that the amount of metal measured in the skin reflected the equimolar conditions upon exposure and that none of the metals penetrated or retained in the skin more readily than the other. Furthermore, following metal co-exposure in Milli-Q water and ethanol, the metal amount detected in skin added up to similar levels as observed for exposure to nickel only, while for the exposure in 0.5% SLS, the total amount of metal measured in skin doubled.\u003c/p\u003e \u003cp\u003eAltering the barrier properties of skin using SLS is recommended by OECD TG 439 for \u003cem\u003ein vitro\u003c/em\u003e skin irritation (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e) and was previously used e.g., \u003cem\u003ein vivo\u003c/em\u003e to cause irritation in a study of skin deposition and penetration of nickel (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e). In the present case, SLS treatment of skin was the preferred option since it was considered to additionally contribute to exposure conditions aimed to mimic the effect of hand hygiene practices. SLS concentrations in consumer products typically ranges from 0.01\u0026ndash;50% in cosmetic products and 1\u0026ndash;30% in cleaning products (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e). In a series of experiments, we investigated at which concentration the SLS treatment was most effective with respect to changed barrier properties and thus increased TEWL. We found that 5% SLS was more effective than treatment with 10% SLS, despite a relatively large variability among the 8 replicates from two different piglet individuals (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Although the TEWL measure reflects stratum corneum integrity, i.e., the main barrier for permeation resistance, and hence serves as a predictor of solvent permeation (\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e), it seems not to be a good predictor of metal retention in skin, as no correlation was observed between measured amounts of metal in skin and the degree of TEWL changes (\u003cb\u003eSupplementary Material Figure S4\u003c/b\u003e). Alternative measures of e.g., natural moisturizing factor (NMF) and IL-1α are promising markers for other types of barrier properties such as permeation in deeper skin layers and inflammatory parameters (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e), but more research is needed to determine their usefulness as a predictor for skin uptake of allergenic metals.\u003c/p\u003e \u003cp\u003eThe results from exposure of untreated and treated skin, confirmed that the SLS pre-treatment enhances penetration of nickel and hence higher amounts of nickel were retained in skin compared to the untreated case. This is in line with previous findings on irritancy and skin damage caused by SLS as evaluated by several methods including the TEWL measure (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e) and the ability of SLS to enhance permeation of other compounds (\u003cspan additionalcitationids=\"CR32\" citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e). Although the exact mechanism of SLS on skin barrier function has not been clarified, studies have pointed to delipidization (\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e), morphological changes of corneocytes (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e), or to damage to the deeper nucleated layers of the epidermis (\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e). These changes to the lipid lamellae organization may have contributed to the higher increase of nickel into the SLS treated skin. Also, water causes skin irritancy and disruption similar to that of surfactants (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e) but no study to our knowledge have investigated the permeation enhancing capacity of water. Since the results of nickel in untreated skin from exposure in Milli-Q water is the lowest that we observe in our experiments, it is anticipated that the SLS, both the pre-treatment and the exposure to 0.5% SLS have a larger influence on metal penetration and retention in skin than the other tested exposure solvents. The highest measured levels in the skin were observed for exposure to nickel in ethanol which at the same time showed a large variation between the repeated experiments which can be partially explained by inter-individual skin differences rather than the ethanol itself. In addition, ethanol interacts with stratum corneum lipids (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e) and is known to be a skin permeation enhancer (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e), which could contribute to the explanation of the high nickel levels measured in the skin after ethanol exposure.\u003c/p\u003e \u003cp\u003eThe measured amounts of nickel, cobalt and chromium in the skin after combined exposure showed proportionality with the equimolar composition of the metals upon exposure and thus no possible preferential retention of the allergenic metals could be demonstrated. Results show that metal penetration occur in a time-dependent manner, which is in line with previous observations of simultaneous exposure to several metals (\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e). The same study reported that the sum of metals in co-exposure (Ni, Co and Cr) resulted in higher metal amounts measured in skin compared to their single-metal-exposure counterparts, a tendency that was observed only for the metal co-exposure in 0.5% SLS in the current study. For exposures in Milli-Q water and ethanol, i.e., without surfactant present, the sum of metals from co-exposure is similar to the amount of nickel in the single metal exposure case. This finding indicates the possibility that the skin's ability to retain metals has a saturation limit determined by the status of the skin barrier and the magnitude of the dose, in other words, infinite or finite conditions.\u003c/p\u003e \u003cp\u003eThe present study focussed on the skin retention of nickel under different exposure conditions and skin status. A disadvantage of this study design is that, for various reasons including time and resources, metal concentrations in the receptor have not been quantified. With the information on percutaneously absorbed amounts, a better understanding of the skin\u0026rsquo;s barrier properties and ability to retain the metals that penetrated stratum corneum, could have been obtained. Having studied the single exposures to cobalt and chromium would as well have contributed to understanding potential co-exposure effects also for these metals. Another obvious limitation of the current study is the number of replicated experiments (n\u0026thinsp;=\u0026thinsp;6) and the number and distribution of piglet individuals (n\u0026thinsp;=\u0026thinsp;18) where a larger scale would of course be desirable in order to control for inter-individual variations.\u003c/p\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eIn this study, we have demonstrated that an SLS treatment of skin alters the skin barrier properties with regards to TEWL. Furthermore, we have investigated differences in nickel retention between treated and untreated skin and how it is affected by exposure to other allergenic metals and continued skin-altering treatment mimicking intensive hand hygiene practices in the form of water, a surfactant and ethanol. In all investigated exposure cases, the altered skin barrier is subject to a relatively higher level of metal retention. The exposure to nickel in ethanol and combined exposure to metals in 0.5% SLS, respectively, constitutes the most severe exposure cases. These findings are important, not least regarding the occupational exposure to allergenic metals that often co-occur with wet work and use of water, soap and hand disinfectants, and should be taken into account when developing measures to prevent harmful skin exposure to metals.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicaable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors have approved the submission of the manuscript and consent for its publication in the Journal of Occupational Medicine and Toxicology.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and material\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study was financed by research grants from the Afa Insurance (Dnr 200230), PI Anneli Julander.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eVilela, L. and Midander, K. wrote the main manuscript text and the supplementary material. Vilela, L. prepared Figures 1-2 and Table 1 and Figures S1-S4 and Tables S1-S3 and oversaw the softwares used in the manuscript. All authors took part on the investigation, formal analysis, visualization and reviewing and editing of the manuscript. Schenk, L., Julander, A. and Midander, K. took part on the conceptualization, validation, methodology, data curation and supervision. Schenk, L. and Anneli, J. were in charge of the funding acquisition, and the latter is the project administrator.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe would like to acknowledge MD.\u0026nbsp;Ina Anveden Berglind and MD.\u0026nbsp;Maria Lagrelius for their help translating high intensity hand washing practices from those observed in clinical setting to \u003cem\u003ein vitro\u003c/em\u003e experiment. \u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eSzczuka Z, Abraham C, Baban A, et al. 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Occupational skin diseases. \u003cem\u003eJournal der Deutschen Dermatologischen Gesellschaft = Journal of the German Society of Dermatology : JDDG\u003c/em\u003e. 2012;10(5):297\u0026ndash;315.\u003c/li\u003e\n\u003cli\u003eCoppeta L, De Zordo ML, Papa F, Pietroiusti A, Magrini A. Skin sensitization among night shift and daytime healthcare workers: a cross sectional study. \u003cem\u003eCentral European journal of public health\u003c/em\u003e. 2021;29(3):191\u0026ndash;194.\u003c/li\u003e\n\u003cli\u003eOECD. Test No. 428: Skin Absorption: In Vitro Method. \u003cem\u003eParis, Organisation for Economic Co-operation and Development\u003c/em\u003e. 2004.\u003c/li\u003e\n\u003cli\u003eOECD. Guidance Notes on Dermal Absorption. Series on Testing and Assessment. No 156. Second edition. \u003cem\u003eParis, Organisation for Economic Co-operation and Development\u003c/em\u003e. 2022.\u003c/li\u003e\n\u003cli\u003eBarbero A, Frasch H. Pig and guinea pig skin as surrogates for human in vitro penetration studies: a quantitative review. \u003cem\u003eToxicology in vitro : an international journal published in association with BIBRA\u003c/em\u003e. 2009;23(1):1-13.\u003c/li\u003e\n\u003cli\u003ePinnagoda J, Tupker RA, Agner T, Serup J. Guidelines for transepidermal water loss (TEWL) measurement. A report from the Standardization Group of the European Society of Contact Dermatitis. \u003cem\u003eContact dermatitis\u003c/em\u003e. 1990;22(3):164-178.\u003c/li\u003e\n\u003cli\u003eZhang Q, Murawsky M, LaCount T, Kasting GB, Li SK. Transepidermal water loss and skin conductance as barrier integrity tests. \u003cem\u003eToxicology in vitro : an international journal published in association with BIBRA\u003c/em\u003e. 2018;51:129-135.\u003c/li\u003e\n\u003cli\u003eFilon FL, Boeniger M, Maina G, Adami G, Spinelli P, Damian A. Skin Absorption of Inorganic Lead (PbO) and the Effect of Skin Cleansers. \u003cem\u003eJournal of occupational and environmental medicine\u003c/em\u003e. 2006;48(7):692\u0026ndash;699.\u003c/li\u003e\n\u003cli\u003eOECD. Test No. 439: In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method.\u003cem\u003e Paris, Organisation for Economic Co-operation and Development.\u003c/em\u003e 2021.\u003c/li\u003e\n\u003cli\u003eYork M, Griffiths HA, Whittle E, Basketter DA. Evaluation of a human patch test for the identification and classification of skin irritation potential. \u003cem\u003eContact dermatitis\u003c/em\u003e. 1996;34(3):204-212.\u003c/li\u003e\n\u003cli\u003eKettelarij J, Midander K, Lid\u0026eacute;n C, Bottai M, Julander A. Neglected exposure route: cobalt on skin and its associations with urinary cobalt levels. \u003cem\u003eOccupational and environmental medicine\u003c/em\u003e. 2018;75(11):837-842.\u003c/li\u003e\n\u003cli\u003eKlasson M, Lindberg M, Bryngelsson IL, et al. Biological monitoring of dermal and air exposure to cobalt at a Swedish hard metal production plant: does dermal exposure contribute to uptake? \u003cem\u003eContact Dermatitis\u003c/em\u003e. 2017;77(4):201-207.\u003c/li\u003e\n\u003cli\u003eLid\u0026eacute;n C, Skare L, Nise G, Vahter M. Deposition of nickel, chromium, and cobalt on the skin in some occupations - assessment by acid wipe sampling. \u003cem\u003eContact Dermatitis\u003c/em\u003e. 2008;58(6):347-354.\u003c/li\u003e\n\u003cli\u003eAhlstr\u0026ouml;m MG, Midander K, Menn\u0026eacute; T, et al. Nickel deposition and penetration into the stratum corneum after short metallic nickel contact: An experimental study. \u003cem\u003eContact Dermatitis\u003c/em\u003e. 2019;80(2):86-93.\u003c/li\u003e\n\u003cli\u003eBondi CA, Marks JL, Wroblewski LB, Raatikainen HS, Lenox SR, Gebhardt KE. Human and Environmental Toxicity of Sodium Lauryl Sulfate (SLS): Evidence for Safe Use in Household Cleaning Products. \u003cem\u003eEnvironmental health insights\u003c/em\u003e. 2015;9:27-32.\u003c/li\u003e\n\u003cli\u003eKezic S, Nielsen JB. Absorption of chemicals through compromised skin. \u003cem\u003eInternational archives of occupational and environmental health\u003c/em\u003e. 2009;82(6):677-688.\u003c/li\u003e\n\u003cli\u003eLaudańska H, Reduta T, Szmitkowska D. Evaluation of skin barrier function in allergic contact dermatitis and atopic dermatitis using method of the continuous TEWL measurement. \u003cem\u003eRoczniki Akademii Medycznej w Bialymstoku (1995)\u003c/em\u003e. 2003;48:123-127.\u003c/li\u003e\n\u003cli\u003eWelzel J, Metker C, Wolff HH, Wilhelm KP. SLS-irritated human skin shows no correlation between degree of proliferation and TEWL increase. \u003cem\u003eArchives of dermatological research\u003c/em\u003e. 1998;290(11):615-620.\u003c/li\u003e\n\u003cli\u003eNielsen JB. Percutaneous penetration through slightly damaged skin. \u003cem\u003eArchives of dermatological research\u003c/em\u003e. 2005;296(2):560-567.\u003c/li\u003e\n\u003cli\u003eBenfeldt E, Serup J. Effect of barrier perturbation on cutaneous penetration of salicylic acid in hairless rats: in vivo pharmacokinetics using microdialysis and non-invasive quantification of barrier function. \u003cem\u003eArchives of dermatological research\u003c/em\u003e. 1999;291(9):517-526.\u003c/li\u003e\n\u003cli\u003ePavlačkov\u0026aacute; J, Egner P, Pola\u0026scaron;kov\u0026aacute; J, et al. Transdermal absorption of active substances from cosmetic vehicles. \u003cem\u003eJournal of cosmetic dermatology\u003c/em\u003e. 2019;18(5):1410-1415.\u003c/li\u003e\n\u003cli\u003eFroebe CL, Simion FA, Rhein LD, Cagan RH, Kligman A. Stratum corneum lipid removal by surfactants: relation to in vivo irritation. \u003cem\u003eDermatologica\u003c/em\u003e. 1990;181(4):277\u0026ndash;283.\u003c/li\u003e\n\u003cli\u003eImokawa G, Akasaki S, Minematsu Y, Kawai M. Importance of intercellular lipids in water-retention properties of the stratum corneum: induction and recovery study of surfactant dry skin. \u003cem\u003eArchives of dermatological research\u003c/em\u003e. 1989;281(1):45\u0026ndash;51.\u003c/li\u003e\n\u003cli\u003eShukuwa T, Kligman AM, Stoudemayer TJ. A new model for assessing the damaging effects of soaps and surfactants on human stratum corneum. \u003cem\u003eActa dermato-venereologica\u003c/em\u003e. 1997;77(1):29-34.\u003c/li\u003e\n\u003cli\u003eFartasch M, Schnetz E, Diepgen TL. Characterization of detergent-induced barrier alterations -- effect of barrier cream on irritation. \u003cem\u003eThe journal of investigative dermatology Symposium proceedings\u003c/em\u003e. 1998;3(2):121-127.\u003c/li\u003e\n\u003cli\u003eYang L, Mao-Qiang M, Taljebini M, Elias PM, Feingold KR. Topical stratum corneum lipids accelerate barrier repair after tape stripping, solvent treatment and some but not all types of detergent treatment. \u003cem\u003eThe British journal of dermatology\u003c/em\u003e. 1995;133(5):679\u0026ndash;685.\u003c/li\u003e\n\u003cli\u003eGupta R, Badhe Y, Rai B, Mitragotri S. Molecular mechanism of the skin permeation enhancing effect of ethanol: a molecular dynamics study. \u003cem\u003eRSC advances\u003c/em\u003e. 2020;10(21):12234\u0026ndash;12248.\u003c/li\u003e\n\u003cli\u003eGhanem AH, Mahmoud H, Higuchi WI, Liu P, Good WR. The effects of ethanol on the transport of lipophilic and polar permeants across hairless mouse skin: Methods/validation of a novel approach. \u003cem\u003eInternational Journal of Pharmaceutics\u003c/em\u003e. 1992;78(1-3):137-156.\u003c/li\u003e\n\u003cli\u003eMidander K, Schenk L, Julander A. A novel approach to monitor skin permeation of metals in vitro. \u003cem\u003eRegulatory toxicology and pharmacology : RTP\u003c/em\u003e. 2020;115:104693.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-occupational-medicine-and-toxicology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jmet","sideBox":"Learn more about [Journal of Occupational Medicine and Toxicology](http://occup-med.biomedcentral.com/)","snPcode":"12995","submissionUrl":"https://submission.nature.com/new-submission/12995/3","title":"Journal of Occupational Medicine and Toxicology","twitterHandle":"@BioMedCentral","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Skin, Retention, Penetration, Metals, Hygiene practices, Sodium lauryl sulphate","lastPublishedDoi":"10.21203/rs.3.rs-4829304/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4829304/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eDuring the COVID-19 pandemic, increased hand hygiene practices using water, soap and hand disinfectants, became prevalent, particularly among frontline workers. This study investigates the impact of these practices on the skin's ability to retain the allergenic metals nickel, cobalt, and chromium. The study constitutes three parts: I) creating an altered skin barrier, and exposing treated and untreated skin to II) nickel alone, and III) in co-exposure with cobalt and chromium.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eUsing full-thickness skin from stillborn piglets, \u003cem\u003ein vitro\u003c/em\u003e experiments were conducted to assess retention of metals in skin at conditions mimicking intense hand hygiene practices. Treatment of skin with varying concentrations of sodium lauryl sulphate (SLS), 0.5\u0026ndash;10%, to alter its barrier integrity was assessed. This was followed by exposure of treated and untreated skin to the metals, that were dissolved in Milli-Q water, 0.5% SLS, and ethanol respectively.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eResults showed that pre-treatment with 5% SLS altered the skin barrier with regards to the measure of trans epidermal water loss (TEWL). The highest amounts of metal retained in skin were observed for exposure to nickel in ethanol. Co-exposure to nickel, cobalt, and chromium in 0.5% SLS resulted in the highest amounts of metal retention in both untreated and treated skin. Linear regression analysis indicated that SLS treatment, exposure solvent, time, and metal combination significantly affected nickel retention.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eThe \u003cem\u003ein vitro\u003c/em\u003e findings highlight the increased risk of metal retention in skin due to a compromised barrier, as a result of, for example, intensive hand hygiene practices. Hence, occupational settings with frequent exposure to water, soap and disinfectants need to consider protective measures not only for the irritant exposures themselves but also simultaneous exposure to allergenic metals.\u003c/p\u003e","manuscriptTitle":"Retention of Nickel, Cobalt and Chromium in skin at conditions mimicking intense hand hygiene practices using water, soap, and hand-disinfectant in vitro","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-08-27 15:18:17","doi":"10.21203/rs.3.rs-4829304/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-09-28T23:27:29+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-09-25T20:02:11+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"94298574958666924271888059745043709584","date":"2024-09-02T19:05:08+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-08-21T12:29:51+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"37125852375917470283937603656351788122","date":"2024-08-15T09:34:10+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-08-01T07:18:08+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-08-01T07:16:22+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-07-31T13:39:00+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Occupational Medicine and Toxicology","date":"2024-07-30T13:52:00+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-occupational-medicine-and-toxicology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jmet","sideBox":"Learn more about [Journal of Occupational Medicine and Toxicology](http://occup-med.biomedcentral.com/)","snPcode":"12995","submissionUrl":"https://submission.nature.com/new-submission/12995/3","title":"Journal of Occupational Medicine and Toxicology","twitterHandle":"@BioMedCentral","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"7762497c-a450-4786-a4e2-a09ae041e4dc","owner":[],"postedDate":"August 27th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-11-11T16:04:31+00:00","versionOfRecord":{"articleIdentity":"rs-4829304","link":"https://doi.org/10.1186/s12995-024-00442-5","journal":{"identity":"journal-of-occupational-medicine-and-toxicology","isVorOnly":false,"title":"Journal of Occupational Medicine and Toxicology"},"publishedOn":"2024-11-06 15:57:21","publishedOnDateReadable":"November 6th, 2024"},"versionCreatedAt":"2024-08-27 15:18:17","video":"","vorDoi":"10.1186/s12995-024-00442-5","vorDoiUrl":"https://doi.org/10.1186/s12995-024-00442-5","workflowStages":[]},"version":"v1","identity":"rs-4829304","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4829304","identity":"rs-4829304","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}