Surrogate Skin Research Articles

Surrogate Skin-Gelatin-Protein Complex based evaluation of Psorolin B and Psoriasis management

For the rapid evaluation of any anti-psoriatic preparations require a credible and scientifically acceptable model that should at least partially resemble the skin. The skin is composed by cholesterol, proteins like elastin, keratin etc. Therefore a semi-permeable membrane composed on most of such agents may help us to evaluate how the absorption and associated permeation of the drug happens through such membrane. We have developed a surrogate skin model using the essential chemical composition of the skin and have evaluated the absorption kinetics of Psorolin B and details are presented in the article. Keywords: Psorolin B, lipo-hydro balance, xerotic skin, psoriasis

Dermal measurement of exposure to plant protection products: Actual hand exposure from hand washing vs. wearing cotton gloves.

For the authorization of plant protection products, a quantitative non-dietary exposure risk assessment relies on established dermal exposure models, measured mainly using passive dosimetry. Exposure to the hands is determined via hand washing or using cotton gloves as a surrogate for skin. This study compared both methods using operator exposure data available from the Agricultural Operator Exposure Model (AOEM) project report. These data indicate that hand exposure determined using cotton gloves resulted in markedly higher exposure values for all exposure scenarios compared to those determined by hand washes. One explanation for this is that dermal uptake of the residues reduces the amount of residue that can be recovered by hand washing. Uncertainty due to dermal uptake can be addressed by either default assumptions or by specific dermal absorption data. However, this cannot solely account for the large difference observed between the values and is mainly likely to be due to the higher capacity of the cotton gloves vs. human skin to retain residues. The results further indicate that the variability between hand wash samples and cotton glove samples differs between the exposure scenarios. Hence, the level of conservatism related to the use of cotton gloves as surrogate skin remains unknown. In conclusion, this evaluation of the AOEM data indicates that the cotton glove method results in much higher levels of measured hand exposure than the hand wash method. It cannot be excluded that dermal uptake has contributed to that result. However, the findings suggest the higher retention capacity of cotton gloves vs. human skin to be the main impact parameter. The cotton glove method does not provide the results with regards to the protection level that can be expected from the use of protective gloves. Therefore, we believe that the application of the hand wash method is a more accurate measure of exposure levels, if either specific dermal absorption data or, in its absence, default assumptions are applied as adjustment factor.

A Versatile Simulation-Assisted Layered Mesh Analysis for Generalized Litz Wire Performance

This article introduces a semi-analytical method of predicting ac loss in commercial Litz wires. Simple finite-element simulations are used to compute the resultant proximity fields in a coil system of arbitrary geometry. The approach addresses non-ideal Litz wire construction by applying a surrogate skin effect model to inform and distribute the current over the cross Section into segmented layers. This simplifies the finite-element problem into a 2-D, dc simulation with a low number of mesh elements. Analytical solutions are then used to compute frequency-dependent loss due to skin and proximity effect. The method is demonstrated using two 14 American Wire Gauge (AWG) equivalent Litz wires with very different constructions and is validated with experimental results from several coil configurations. Finally, an appeal is made to commercial Litz wire manufacturers to provide an empirical “fabrication factor” specification that would allow consumers to predict the performance of a conductor in their application.

Transfer of bacteria between fabric and surrogate skin

Contaminated textiles serve as fomites in healthcare settings. The extent of transfer of pathogens from fabrics depends on the surface properties of the 2 contact surfaces. In the current study, the effect of surface energy and surface roughness of fabrics on the transfer of Escherichia coli and Staphylococcus aureus to and from textiles to surrogate skin were determined. Three fabrics (100% cotton, 100% polyester, and 50-50 blend of cotton and polyester) having identical constructional parameters, were characterised on the basis of surface roughness, and energy. Assessment of transfer of bacteria was carried out by bringing the matrix seeded with inoculum in contact with the sterilized matrix for a predetermined period of time, followed by dislodging of cells from the recipient surface by vortexing, and plating. Results showed that 100% polyester attracted the highest number of bacterial cells compared to the others. It also released the maximum number of bacteria upon coming in contact with surrogate skin. Properties of fabrics like absorbency, surface energy, and surface roughness, simultaneously affected transfer. It is advisable to minimize the use of 100% polyester in healthcare settings to curb the transfer load of bacteria from one surface to another.

Evaluating the Design and Repeatability of a Novel Device to Measure Friction of Mechanical Surrogate Skins in Contact with Cotton Textiles

The ability to measure the level of friction between the human skin and a given textile is critical across fashion and textiles sectors, not least for the development of sporting and protective clothing. A portable custom-made device capable of measuring friction during the skin-textile interaction across often difficult or impossible to investigate body regions with objective repeatability has been established. The friction between a pre-shrunk 100% cotton textile and a quantity of four control surfaces (transparent and patterned polycarbonate plastic, and silicon and lorica surrogate skin) was measured three times per day across five consecutive days. The results clearly demonstrated that the novel friction test device had an excellent repeatability of 0.94 and 0.93 intraclass corelation coefficient for static and dynamic friction coefficient measurement, respectively. The silicon surrogate skin control surface produced the highest friction coefficient, while the pattered polycarbonate plate demonstrated the lowest friction coefficient, suggesting that the physical features of the control surface material influenced the recorded coefficient of friction. It was also revealed that the relationship between the static and dynamic friction coefficient is dependent on the surface material.

Creation of a prototype biomimetic fish to better understand impact trauma caused by hydropower turbine blade strikes

Biomimetic model organisms could be useful surrogates for live animals in many applications if the models have sufficient biofidelity. One such application is for use in field and laboratory tests of fish mortality associated with passage through hydropower turbines. Laboratory trials suggest that blade strikes are especially injurious and often causes mortality when fish are struck by thinner blades moving at higher velocities. Dose-response relationships have been created from these data, but the exact relationship between fish mortality and the actual forces enacted on fish during simulated blade strike testing remains unknown. Here, we describe the methods used to create a prototype biomimetic model fish composed of ballistic gelatin and covered with a surrogate skin to better approximate the biomechanical properties of a fish body. Frozen fish were scanned with high-fidelity laser scanners, and a 3D-printed, reusable mold was created from which to cast our gelatin model. Computed tomography scan data, imaged directly or taken from online data repositories, were also successfully used to create CAD models for use in additive manufacturing of molds. One 3-axis accelerometer was embedded into the gelatin to compare accelerometer data to dose-response data from previous laboratory research on live fish. The resulting model (i.e., Gelfish) had a statistically indistinguishable tissue durometer to that of real fish tissue and preliminary blade strike impact testing suggested its overall flexibility was similar to that of live fish. Gelfish was designed with biofidelity as its guiding principle and our results suggest initial experimentation was successful. Future research will include replication of initial Gelfish test results, quantitative measurement of model flexibility relative to real fish, and inclusion of surrogate skeletal structures to enhance biofidelity. Use of more sophisticated sensors would also better quantify the physical forces of blade strike impact and help determine how said forces correlate with rates of mortality observed during tests on live fish.

Mechanical Behaviour of Silicone Membranes Saturated with Short Strand, Loose Polyester Fibres for Prosthetic and Rehabilitative Surrogate Skin Applications.

Silicone-based elastomers saturated with embedded, short-strand fibres are used for their ability to mimic the aesthetic qualities of skin in clinical and theatrical maxillofacial appliance design. Well-known to prostheses fabricators and technicians, the mechanical impact of fibre addition on elastomeric behaviour endures as tacit, embodied knowledge of the craft, almost unknown in the literature. To examine mechanical changes caused by fibre addition, 100 modified polydimethylsiloxane (PDMS) elastomeric compounds containing incremental amounts of loose polyester fibres were prepared and examined in a variety of mechanical tests. It was found that elasticity and strain percentage at breaking point was reduced by increasing fibre content, but Young’s modulus and ultimate tensile strength (UTS) increased. As fibre content was increased, strain hardening was seen at low strain rates, but exaggerated plastic deformation at high strain rates. PDMS hardness increased by 5 degrees of hardness (Shore-00 scale) for every additional percentage of fibres added and a strong positive linear coefficient (0.993 and 0.995) was identified to reach the hardness values given in the literature for living human skin. The apparent reorienting of loose fibres in the PDMS interrupts and absorbs stress during the loading process similar to the organic response to soft tissue loading, except in extension.

Facial skin mapping: from single point bio-instrumental evaluation to continuous visualization of skin hydration, barrier function, skin surface pH, and sebum in different ethnic skin types.

Dry skin is one of the most important concerns of consumers worldwide. Despite huge efforts over several decades, the personal care industry still does not offer a perfect solution to satisfy the unmet needs of consumers for moisturising treatments in different ethnic groups. The paucity of data for the underlying cellular and biochemical problems in, and the effects of moisturisers on photodamaged facial skin may partly explain this. Mainly, single point measurements are used to understand the effects of products on skin physiology even on surrogate skin sites such as the non‐photodamaged volar forearm. Some groups have developed discontinuous facial maps of skin biophysical properties, however, in 2014 a continuous facial analysis of bio‐instrumental evaluations was developed using a heat map approach. These maps enabled a continuous visualization of features that not only revealed an unexpected complexity of facial skin but also indicated that use of surrogate skin sites for facial skin is inappropriate. We have demonstrated that remarkable gradients of skin hydration, TEWL, skin surface pH and sebum exist within short distances across the face and the gradients are distinctive among different ethnic groups. In addition, these studies have demonstrated that darkly‐pigmented individuals do not necessarily have a better skin barrier function than their less‐pigmented counterparts and that Caucasians have a lower facial skin surface pH compared with more pigmented subjects. Overall, there are no correlations between capacitance, TEWL and skin surface pH including individual topology angle values. Novel 3D camera approaches have also been used to facilitate a more precise assignment of measurement sites and visualisation. The 3D facial colour mappings illustrated precisely the local moisturising effects of a moisturising cream. There were subtle ethnic differences in efficacy that may be related to underlying skin biochemistry and/or ethnic differences in product application. A placebo‐controlled study using conductance measurements in Chinese subjects is also reported. Finally, a new whole face statistical approach has been taken to prove differences in skin parameters but also of moisturiser treatment that adds further to our understanding of the ethnic differences in skin physiology and product application. This paper reviews the background of the development and application of this methodology.

Laboratory Validation and Field Assessment of Petroleum Laboratory Technicians' Dermal Exposure to Crude Oil Using a Wipe Sampling Method.

Crude oil may cause adverse dermal effects therefore dermal exposure is an exposure route of concern. Galea et al. (2014b) reported on a study comparing recovery (wipe) and interception (cotton glove) dermal sampling methods. The authors concluded that both methods were suitable for assessing dermal exposure to oil-based drilling fluids and crude oil but that glove samplers may overestimate the amount of fluid transferred to the skin. We describe a study which aimed to further evaluate the wipe sampling method to assess dermal exposure to crude oil, with this assessment including extended sample storage periods and sampling efficiency tests being undertaken at environmental conditions to mimic those typical of outdoor conditions in Saudi Arabia. The wipe sampling method was then used to assess the laboratory technicians' actual exposure to crude oil during typical petroleum laboratory tasks. Overall, acceptable storage efficiencies up to 54 days were reported with results suggesting storage stability over time. Sampling efficiencies were also reported to be satisfactory at both ambient and elevated temperature and relative humidity environmental conditions for surrogate skin spiked with known masses of crude oil and left up to 4 h prior to wiping, though there was an indication of reduced sampling efficiency over time. Nineteen petroleum laboratory technicians provided a total of 35 pre- and 35 post-activity paired hand wipe samples. Ninety-three percent of the pre-exposure paired hand wipes were less than the analytical limit of detection (LOD), whereas 46% of the post-activity paired hand wipes were less than the LOD. The geometric mean paired post-activity wipe sample measurement was 3.09 µg cm-2 (range 1.76-35.4 µg cm-2). It was considered that dermal exposure most frequently occurred through direct contact with the crude oil (emission) or via deposition. The findings of this study suggest that the wipe sampling method is satisfactory in quantifying laboratory technicians' dermal exposure to crude oil. It is therefore considered that this wipe sampling method may be suitable to quantify dermal exposure to crude oil for other petroleum workers.

Correlation Between Dosimetric Parameters and Acute Dermatitis of Post-operative Radiotherapy in Breast Cancer Patients.

To examine the correlation between dosimetric parameters and acute radiation dermatitis in early breast cancer patients subjected to post-operative radiotherapy. The data of 84 patients treated with post-operative radiotherapy were analyzed. The total prescribed dose was 50 Gy in 25 fractions over 5 weeks. Radiation dermatitis was assessed according to Common Terminology Criteria for Adverse Events v4.0. We set organ at risk whole body (from neck to abdomen examined by CT images) also as surrogate skin volume (3 mm thickness). A total of 28 patients showed radiation dermatitis grade equal or higher than 2 at the 50 Gy time point. These 28 patients were compared to 56 matched pair patients with grade 0-1 radiation dermatitis during the same treatment period. The mean of V5-20 and V40 in patient's whole volume and V40-50 in skin volume were significantly higher in patients who presented with acute radiation dermatitis Grades ≥2 than in the other patients who did not. The statistically most significant difference was observed for V40 for skin volume and V5 for patient whole volume. Rate of acute radiation dermatitis grade ≥2 was significantly higher for patients with V5 (whole body) >1,360 cm3 than those with V5 (whole body) <1,360 cm3 (47% vs. 27%, p=0.0353), as well as for patients with V40 (skin volume) >45 cm3 compared with those with V40 (skin volume) <45 cm3 (50% vs. 18%, p=0.0043). Dosimetric parameters were useful to predict radiation dermatitis grade ≥2. V5 (whole body) 1,360 cm3 and V40 (skin volume) 45 cm3 may be dose volume constrain for radiation dermatitis grade ≥2.

Friction between a surrogate skin (Lorica Soft) and nonwoven fabrics used in hygiene products

Incontinence pad wearers often suffer from sore skin, and a better understanding of friction between pads and skin is needed to inform the development of less damaging materials. This work investigated friction between a skin surrogate (Lorica Soft) and 13 nonwoven fabrics representing those currently used against the skin in commercial pads. All fabrics were found to behave consistently with Amontons’ law: coefficients of friction did not differ systematically when measured under two different loads. Although the 13 fabrics varied considerably in composition and structure, their coefficients of friction (static and dynamic) against Lorica Soft were remarkably similar, especially for the ten fabrics comprising just polypropylene (PP) fibres. The coefficients of friction for one PP fabric never differed by more than 15.7% from those of any other, suggesting that the ranges of fibre decitex (2.0–6.5), fabric area density (13–30 g m−2) and bonding area (11%–25%) they exhibited had only limited impact on their friction properties. It is likely that differences were largely attributable to variability in properties between multiple samples of a given fabric. Of the remaining fabrics, the one comprising polyester fibres had significantly higher coefficients of friction than the highest friction PP fabric (p < 0.005), while the one comprising PP fibres with a polyethylene sheath had significantly lower coefficients of friction than the lowest friction PP fabric (p < 10−8). However, fabrics differed in too many other ways to confidently attribute these differences in friction properties just to the choice of base polymer.

Abstract PR04: Targeting tumor-asoociated macrophages with a novel anti-CSF1R antibody in cancer patients

Abstract Myeloid cells represent the most abundant immune cell type within the tumor microenvironment of certain tumor entities, including tumor associated macrophages (TAMs). Macrophage infiltration has been identified as an independent poor prognostic factor in several cancer types. The major survival factor for TAMs is macrophage colony stimulating factor 1 (CSF1). We generated a monoclonal antibody (RG7155) that binds to the secondary dimerization interface of CSF1 receptor (CSF1R) as a specific and potent allosteric inhibitor. In vitro, RG7155 treatment results in cell death of CSF1-differentiated macrophages. In animal models, CSF1R inhibition reduced the F4/80+ TAMs infiltrate by 90% and was accompanied by an increase of the CD8+/CD4+ T cell ratio. The ability of RG7155 to reduce TAMs is currently evaluated in a first-in-man phase I clinical study in patients suffering either from pigmented villonodular synovitis (PVNS), a neoplastic disorder characterized by CSF1 overexpression, or other tumor entities. The associated biomarker program involves mandatory paired pre- and on-treatment biopsies of tumor and surrogate skin tissue as well as pharmacodynamic marker assessment in circulating blood. In patients treated with RG7155 an increase of CSF1 associated with a sustained decrease of CD14+CD16+ alternatively activated monocytes in peripheral blood was detected. In PVNS patients administration of RG7155 led to striking reductions of CSF1R+ and CD163+ macrophages in tumor tissue resulting in objective clinical responses according to RECIST (Response Evaluation Criteria in Solid Tumors) in 5 out of 6 patients. All six evaluable PVNS patients showed partial metabolic response in FDG-PET imaging and significant symptomatic improvement as early as 4 weeks after treatment initiation. Furthermore, TAM reduction was also observed in paired tumor samples of patients with various advanced solid malignancies, suggesting broad applicability of this therapeutic approach. This abstract is also presented as Poster A50. Citation Format: Michael Cannarile, Sabine Hoves, Ann-Marie Broeske, Joerg Benz, Katharina Wartha, Valeria Runza, Flora Rey-Giraud, Leon P. Pradel, Friedrich Feuerhake, Irina Klaman, Tobin Jones, Ute Jucknischke, Stefan Scheiblich, Ingo H. Gorr, Antje Walz, Keelara Abiraj, Philippe Cassier, Antonio Sica, Carlos Gomez-Roca, Christophe Le Tourneau, Jean-Pierre Delord, Antoine Italiano, Hyam Levitsky, Jean-Yves Blay, Dominik Ruettinger, Carola H. Ries. Targeting tumor-asoociated macrophages with a novel anti-CSF1R antibody in cancer patients. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr PR04. doi:10.1158/1538-7445.CHTME14-PR04

Abstract 2940: Comprehensive biomarker program demonstrates proof of mechanism and modulation of the tumor microenvironment due to RG7155, a novel therapeutic antibody targeting tumor associated macrophages

Abstract The tumor microenvironment (TME) is a dynamic, highly complex network consisting of a variety of stromal cell types which support tumorigenesis. Myeloid derived cells probably represent the most abundant cell lineage in the TME, including tumor associated macrophages (TAMs). TAMs have been identified as an independent poor prognostic factor in several cancer types. RG7155 is a novel humanized monoclonal antibody targeting colony stimulating factor-1 receptor (CSF-1R). In vitro, RG7155 treatment results in cell death of CSF1-differentiated CD163+ M2-like macrophages. The associated mode of action and clinical proof of principle was evaluated in a first-in-man phase 1 study in patients with pigmented villonodular synovitis (PVNS), a neoplastic disorder characterized by CSF1 overexpression, as well as in patients with other advanced solid tumor entities. The associated biomarker program involves mandatory paired pre- and on-treatment biopsies of tumor and surrogate skin tissue as well as pharmacodynamic marker assessment in circulating blood. Biomarker analysis in tumor and skin includes multiplex IHC assays to assess tumor associated macrophages (CD163/CD68/CSF1R), T cells (CD4/CD8), tumor proliferation (Ki67) and vascularization (CD31). Tissue analysis is complemented by systematic peripheral blood sampling allowing flow cytometric analysis of circulating white blood cells (CD45/CD3/CD4/CD8/CD19/CD56/CD14/CD16/MHCII) and profiling of cytokines and growth factors. Here, we report the initial biomarker data from representative patients from the ongoing Phase 1 study. RG7155 induced a profound reduction of TAMs both in PVNS and various solid malignancies of up to 95% vs. baseline. We also observed depletion of macrophages in the skin which therefore may qualify as a surrogate tissue for mechanistic response. In peripheral blood RG7155 induced sustained modulation of CSF-1 (increase) and alternatively activated monocytes (decrease) was detected. Furthermore, preliminary data indicates a trend for overall increase of CD8/CD4 T cell ratio in the TME following RG7155 treatment, thus a secondary effect of TAM depletion causing intratumoral T cell modulation and tumor microenvironment re-education. Taken together, the individual biomarker program accompanying the first-in-man phase 1 study of RG7155 is demonstrating proof of mechanism and identified surrogate tissue as well as circulating markers to support optimal biological dose and regimen selection for future studies. Citation Format: Ann-Marie Bröske, Irina Klaman, Jayantha Ratnayake, Georgina Meneses-Lorente, Kevin Smart, Phiippe Cassier, Carlos Gomez-Roca, Christophe Le Tourneau, Antoine Italiano, Jean-Pierre Delord, Jean-Yves Blay, Carola Ries, Dominik Ruettinger, Michael Cannarile. Comprehensive biomarker program demonstrates proof of mechanism and modulation of the tumor microenvironment due to RG7155, a novel therapeutic antibody targeting tumor associated macrophages. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2940. doi:10.1158/1538-7445.AM2014-2940

Measurement of operator exposure to chlorpyrifos

To date, no research has been conducted to establish exposure levels for occupational pesticide operators under typical use scenarios in China. Through surrogate skin techniques (the whole-body method), the authors monitored dermal and inhalation exposure of pesticide applicators in China. In addition, the exposure of pesticide mixers was analysed. The total dermal exposure of inexperienced and experienced applicators was respectively 4037 and 536 mg kg(-1) of active ingredient (AI) handled for application to maize that was <80 cm in height. The exposure level was highest on hands; the closer to the hands, the lower arms and the upper legs, the higher the exposure. The unit exposure of mixers differed according to the formulation; exposure to emulsifiable concentrate (EC) and oil-in-water emulsion (EW) was greater than exposure to wettable powder (WP) or wettable dispersible granules (WG). The unit exposure of mixers via inhalation was significantly greater than that of applicators when chlorpyrifos (48% EC) was used (P < 0.0001). The main objectives of this study were to provide an indication of the realistic exposure risk of mixers and applicators, and to contribute useful information for risk mitigation and management and epidemiological studies in China.

A study of friction mechanisms between a surrogate skin (Lorica soft) and nonwoven fabrics

Hygiene products such as incontinence pads bring nonwoven fabrics into contact with users' skin, which can cause damage in various ways, including the nonwoven abrading the skin by friction. The aim of the work described here was to develop and use methods for understanding the origin of friction between nonwoven fabrics and skin by relating measured normal and friction forces to the nature and area of the contact (fibre footprint) between them. The method development work reported here used a skin surrogate (Lorica Soft) in place of skin for reproducibility. The work was primarily experimental in nature, and involved two separate approaches. In the first, a microscope with a shallow depth of field was used to determine the length of nonwoven fibre in contact with a facing surface as a function of pressure, from which the contact area could be inferred; and, in the second, friction between chosen nonwoven fabrics and Lorica Soft was measured at a variety of anatomically relevant pressures (0.25–32.1kPa) and speeds (0.05–5mms−1). Both techniques were extensively validated, and showed reproducibility of about 5% in length and force, respectively. Straightforward inspection of the data for Lorica Soft against the nonwovens showed that Amontons' law (with respect to load) was obeyed to high precision (R2>0.999 in all cases), though there was the suggestion of sub-linearity at low loads. More detailed consideration of the friction traces suggested that two different friction mechanisms are important, and comparison with the contact data suggests tentatively that they may correspond to adhesion between two different populations of contacts, one “rough” and one “smooth”. This additional insight is a good illustration of how these techniques may prove valuable in studying other, similar interfaces. In particular, they could be used to investigate interfaces between nonwovens and skin, which was the primary motivation for developing them.

Isocyanate and VOC exposure analysis using Flexane®

Flexane® 80 is a trowelable urethane product used in combination with cleaners and primers to effect rubber conveyor belt repairs. These products are of concern due to the potential for worker exposure to isocyanates and volatile organic compounds (VOCs). Small chamber experiments were used to identify chemicals liberated to the ambient air from each of the Flexane®-related products. A new sample collection method using treated cotton sleeves as a surrogate skin surface to assess potential dermal exposure to isocyanates during mixing and application of the Flexane® product was validated. Six simulations of a worst case scenario were performed by an experienced belt repair technician in a walk-in laboratory exposure chamber. Analysis of air samples from the large chamber simulations did not detect airborne isocyanates. The average airborne VOC concentrations were below established occupational exposure levels. Dermal sleeve samples detected intermittent and low levels of isocyanates from self-application while wearing gloves having surface residues of uncured Flexane®. The data strongly suggest that the normal and intended use of Flexane® putty, and its associated products under worst case or typical working conditions is not likely to result in worker VOC or isocyanate exposure levels sufficient to produce adverse health effects.

Dermal absorption of environmental contaminants from soil and sediment: a critical review

Risk assessment of hazardous wastes sites may require characterization of the dermal availability of chemical contaminants in soil and/or sediment. Current U.S. Environmental Protection Agency guidance for assessment of dermal exposures to contaminants in water and soil was finalized in 2004 as a supplement (Part E) to the Risk Assessment Guidance for Superfund (RAGS). The soil protocol presented in RAGS Part E is less sophisticated than the water protocol and is supported by less empirical data. Investigations of dermal absorption of soil and sediment-borne contaminants that have been conducted to date include in vitro and in vivo experiments using both human and surrogate skin. A review of that literature was conducted with attention to relevant criteria including consideration of layering effects, degree of chemical saturation of soil, appropriateness of particle size distribution employed, soil-chemical contact time, and continuity of soil-skin contact (in in vivo studies). Most studies published to date are deficient by virtue of execution or reporting on one or more of the selected criteria. In addition the lack of methodological standardization evident in the literature hinders systematic evaluation of results. Since additional experimental work is needed, general agreement on acceptable approaches would be useful. Recommendations for good practice are presented.

Measuring Dust on Skin with a Small Vacuuming Sampler—A Comparison with Other Sampling Techniques

Airborne skin exposure to allergens and irritants may cause dermatitis. There are few methods for assessing skin exposure to airborne particles. We have modified and tested a vacuuming sampler for removing particles from the skin. The sampler was compared with two other skin and surface exposure sampling techniques. These were based on surrogate skin (a patch sampler-adhesive tape on an optical cover glass) and a tape stripping removal procedure. All three samplers measure the mass of dust on skin. Dust containing starch was deposited onto the skin in a whole-body exposure chamber. Samples were taken from forearms and shoulders and analysed using optical microscopy. With the different sampling techniques small differences in the results were obtained. Agreement between the vacuuming sampler and the tape stripping technique was good. The comparison between patch and tape stripping procedure indicated a slight overestimation for the patch. The three techniques are applicable for assessing skin exposure to particles and for dose-effect studies. The vacuuming method will be further developed and applied in workplace studies. The technique allows for dust sampling from large areas of skin.

An assessment of dermal exposure to semi-synthetic metal working fluids by different methods to group workers for an epidemiological study on dermatitis

Background: Assessment of exposure assessment to metal working fluids (MWF) has almost exclusively focused on inhalation exposure. Aims: To assess levels of, and factors affecting, dermal and inhalation exposure to...

Comparison of Measured Dermal Dust Exposures with Predicted Exposures Given by the EASE Expert System

Estimation and Assessment of Substance Exposure (EASE) is a rule-based computer expert system used by regulatory authorities within the European Union to assist in assessing exposure for both new and existing substances. It can provide estimates of both inhalation exposure levels and dermal exposure levels to the hands and forearms. This article describes the results of a study in which measurements of workplace dermal zinc exposures were collected for an industry-wide risk assessment and also compared with the levels predicted by EASE. Measurements were obtained from subjects in seven different workplaces that were producing or working with zinc metal or zinc compounds. The work activities were grouped a priori into one of three categories used by EASE for dermal exposure assessment: 'non-dispersive use with intermittent direct handling', 'wide dispersive use with intermittent direct handling' and 'wide dispersive use with extensive direct handling'. The predicted exposure ranges for these categories are 0.1-1, 1-5 and 5-15 mg cm(-2) day(-1). Although the average measured exposure levels for each of the categories increased in line with the predictions from EASE, the model overestimated dermal exposure to the hands by a factor of approximately 50 when the mid-point of the EASE range was compared with the measured mean exposure. Furthermore, a significant additional exposure was found on other parts of the workers' bodies for which EASE does not provide any estimates. Interpretation of the dermal exposure data was complicated by the use of protective gloves, which might have limited the amount of zinc dust adhering to the workers' skin. However, observation of the work activities suggested that the pattern of glove use was such that they would not provide a consistent level of protection. This study provided an opportunity to collect a large amount of dermal zinc exposure data for risk assessment purposes and also enabled a dermal sampling method to be developed and assessed. There is no standard method for dermal dust exposure measurement, and the choice of method was a key factor in the exposure estimation process. With regard to comparison with the EASE predictions, it is possible that EASE could appear to perform more accurately if its predictions were compared with measurements obtained using surrogate skin sampling methods. However, we believe that such sampling can provide a gross overestimate of the dust on the skin surface. We suggest that further development of the EASE system is necessary to ensure that it better reflects whole-body dermal exposures to dusts.