Anja Franken

International guidelines for the in vivo assessment of skin properties in non-clinical settings: Part 2. transepidermal water loss and skin hydration

There is an emerging perspective that it is not sufficient to just assess skin exposure to physical and chemical stressors in workplaces, but that it is also important to assess the condition, i.e. skin barrier function of the exposed skin at the time of exposure. The workplace environment, representing a non‐clinical environment, can be highly variable and difficult to control, thereby presenting unique measurement challenges not typically encountered in clinical settings.

Flow Cytometric Analysis of the Oxidative Status in Human Peripheral Blood Mononuclear Cells of Workers Exposed to Welding Fumes

Flow cytometry is a simple analytical technique that identifies, counts, and characterizes cells. The oxidative status of cells is influenced by many exogenous sources, such as occupational exposure to welding fumes. This study evaluated flow cytometry as a method to determine the oxidative status of male welders (n = 15) occupationally exposed to welding fumes. Flow cytometric analysis of reactive oxygen species (ROS) was carried out in peripheral blood mononuclear cells (PBMC) by using the probe 2, 7-dichlorodihydrofluorescein diacetate (DCFH-DA). Lipid peroxidation was measured by the decrease of fluor-DHPE fluorescence and intracellular glutathione (GSH) levels by using mercury orange. All of the parameters were also observed under a confocal microscope. The oxidative stress ratio was calculated from the oxidative damage and the antioxidant capacity to give an accurate account of the cellular oxidative status. ROS and lipid peroxidation levels were elevated by ∼ 87% and ∼ 96%, respectively, and GSH levels lowered ∼ 96% in PBMC of workers exposed to welding fumes compared with non-exposed controls. The oxidative stress ratio was significantly higher (p < 0.001) in the exposed group. Flow cytometry can be useful for the measurement of cellular oxidative stress in somatic cells of workers exposed to welding fumes and other occupational settings. Calculating an oxidative stress index may be useful in predicting disease outcomes and whether preventative control measures are efficient.

Assessment of dermal exposure and skin condition of workers exposed to nickel at a South African base metal refinery.

OBJECTIVES The objectives of this study were to assess dermal exposure of cell workers to nickel at a South African base metal refinery and to characterize their skin condition by measuring the skin hydration and trans epidermal water loss (TEWL) indices. METHODS The skin hydration index of the index finger, palm, neck, and forehead was measured before, during and at the end of the shift. The TEWL index was measured before and at the end of the shift. Dermal exposure samples were collected with Ghostwipes from the index finger and palm of the dominant hand, before, during, and at the end of the shift. Neck and forehead samples were collected before and at the end of the shift. Wipe samples of various surfaces in the workplace were also collected. Wipes were analyzed for nickel according to NIOSH method 9102, using inductively coupled plasma-atomic emission spectrometry. RESULTS Hydration indices measured on the hands decreased significantly during the shift, but recovered to normal levels by the end of the shift. TEWL indices for the index finger and palm of the hands are indicative of a low barrier function even before commencement of the shift, which further deteriorated significantly during the shift. During the shift, substantial nickel skin loading occurred on the index finger and palm of the hand. Levels on the neck and forehead were much lower. Various workplace surfaces, which workers come into contact with, were also contaminated with nickel. CONCLUSIONS The skin condition and high levels of nickel on the skin were most probably caused by inadequate chemical protection provided by protective gloves. Although, the permeability of nickel through intact skin is considered to be low, a decreased barrier function of dehydrated or slightly damaged skin will increase its permeability for nickel. The ethnicity of these exposed workers may contribute significantly toward the low incidence of allergic contact dermatitis observed. Several measures to lower dermal exposure to nickel are also recommended.

In Vitro Permeation of Metals through Human Skin: A Review and Recommendations.

During the last few decades, the interest in skin permeation of, specifically, metals has increased with the in vitro method utilizing diffusion cells as the prominent method of investigating permeability. This review provides a systematic synopsis focused on an in vitro diffusion cell method utilizing human skin and examines the differences in experimental design as this could influence the results obtained. The permeation of metals such as chromium, cobalt, copper, gold, lead, mercury, nickel, palladium, platinum, rhodium, silver, titanium, and zinc are discussed. The metals included in this review, except for titanium and zinc, can permeate through intact human skin under physiological conditions. On the basis of flux values, the order of permeability could be summarized as Cu > Pb > Cr > Ni > Co > Pt > Hg > Rh (excluding nanoparticles). Permeability of metals through human skin is highly variable with the different methodologies as a contributing factor. Furthermore, metals are retained in the skin which could lead to reservoir (depot) formation and extended exposure even after the removal thereof from the outer surface of the skin. Finally, recommendations are provided on the standardization of experimental design and format of data reporting to enable the comparison of results from future in vitro metal permeation studies.

In vitro permeation of platinum and rhodium through Caucasian skin

During platinum group metals (PGMs) refining the possibility exists for dermal exposure to PGM salts. The dermal route has been questioned as an alternative route of exposure that could contribute to employee sensitisation, even though literature has been focused on respiratory exposure. This study aimed to investigate the in vitro permeation of platinum and rhodium through intact Caucasian skin. A donor solution of 0.3mg/ml of metal, K2PtCl4 and RhCl3 respectively, was applied to the vertical Franz diffusion cells with full thickness abdominal skin. The receptor solution was removed at various intervals during the 24h experiment, and analysed with high resolution ICP-MS. Skin was digested and analysed by ICP-OES. Results indicated cumulative permeation with prolonged exposure, with a significantly higher mass of platinum permeating after 24h when compared to rhodium. The mass of platinum retained inside the skin and the flux of platinum across the skin was significantly higher than that of rhodium. Permeated and skin retained platinum and rhodium may therefore contribute to sensitisation and indicates a health risk associated with dermal exposure in the workplace.

In vitro permeation of platinum through African and Caucasian skin.

The majority of the South African workforce are Africans, therefore potential racial differences should be considered in risk and exposure assessments in the workplace. Literature suggests African skin to be a superior barrier against permeation and irritants. Previous in vitro studies on metals only included skin from Caucasian donors, whereas this study compared the permeation of platinum through African and Caucasian skin. A donor solution of 0.3 mg/ml of potassium tetrachloroplatinate (K₂PtCl₄) dissolved in synthetic sweat was applied to the vertical Franz diffusion cells with full thickness abdominal skin. Skin from three female African and three female Caucasian donors were included (n=21). The receptor solution was removed at various intervals during the 24 h experiment, and analysed with high resolution inductively coupled plasma-mass spectrometry (ICP-MS). Skin was digested and analysed by inductively coupled plasma-optical emission spectrometry (ICP-OES). Significantly higher permeation of platinum through intact African skin (p=0.044), as well as a significantly higher mass of platinum retention in African skin in comparison with Caucasian skin (p=0.002) occurred. Significant inter-donor variation was found in both racial groups (p<0.02). Results indicate that African workers have increased risk of dermal permeation and therefore possible sensitisation caused by dermal exposure to platinum salts. These results are contradictory to limited literature suggesting a superior barrier in African skin and further investigation is necessary to explain the higher permeation through African skin.

Urinary excretion of platinum from South African precious metals refinery workers

Background Urinary platinum (Pt) excretion is a reliable biomarker for occupational Pt exposure and has been previously reported for precious metals refinery workers in Europe but not for South Africa, the world’s largest producer of Pt. Objective This study aimed to quantify the urinary Pt excretion of South African precious metals refinery workers. Methods Spot urine samples were collected from 40 workers (directly and indirectly exposed to Pt) at two South African precious metals refineries on three consecutive mornings prior to their shifts. Urine samples were analysed for Pt using inductively coupled plasma-mass spectrometry and were corrected for creatinine content. Results The urinary Pt excretion of workers did not differ significantly between sampling days. Urinary Pt excretions ranged from <0.1 to 3.0 µg Pt/g creatinine with a geometric mean of 0.21 µg Pt/g creatinine (95% CI 0.17 to 0.26 µg Pt/g creatinine). The work area (P=0.0006; η2=0.567) and the number of years workers were employed at the refineries (P=0.003; η2=0.261) influenced their urinary Pt excretion according to effect size analyses. Directly exposed workers had significantly higher urinary Pt excretion compared with indirectly exposed workers (P=0.007). Conclusion The urinary Pt excretion of South African precious metals refinery workers reported in this study is comparable with that of seven other studies conducted in precious metals refineries and automotive catalyst plants in Europe. The Pt body burden of workers is predominantly determined by their work area, years of employment in the refineries and whether they are directly or indirectly exposed to Pt.

The evaluation and quantification of respirable coal and silica dust concentrations: a task-based approach

Silicosis and coal workers pneumoconiosis are serious occupational respiratory diseases associated with the coal mining industry and the inhalation of respirable dusts containing crystalline silica. The purpose of this study (funded by the Mine Health and Safety Council of South Africa) was to evaluate the individual contributions of underground coal mining tasks to the respirable dust and respirable silica dust concentrations in an underground section by sampling the respirable dust concentrations at the intake and return of each task. The identified tasks were continuous miner (CM) cutting, construction, transfer of coal, tipping, and roof bolting. The respirable dust-generating hierarchy of the tasks from highest to lowest was: transfer of coal > CM right cutting > CM left cutting > CM face cutting > construction > roof bolting > tipping; and for respirable silica dust: CM left cutting > construction > transfer of coal > CM right cutting. Personal exposure levels were determined by sampling the exposures of workers performing tasks in the section. Respirable dust concentrations and low concentrations of respirable silica dust were found at the intake air side of the section, indicating that air entering the section is already contaminated. The hierarchy for personal respirable dust exposures was as follows, from highest to lowest: CM operator > cable handler > miner > roof bolt operator > shuttle car operator, and for respirable silica dust: shuttle car operator > CM operator > cable handler > roof bolt operator > miner. Dust control methods to lower exposures should include revision of the position of workers with regard to the task performed, positioning of the tasks with regard to the CM cutting, and proper use of the line curtains to direct ventilation appropriately. The correct use of respiratory protection should also be encouraged.

Transepidermal water loss, stratum corneum hydration, and skin surface pH of female African and Caucasian nursing students

Conflicting evidence exists on how skin barrier function compares between Africans and Caucasians. This study measured skin barrier function of South African first year nursing students before their practical training started to compare skin barrier function between the racial groups.

Urinary excretion of platinum (Pt) following skin and respiratory exposure to soluble Pt at South African precious metals refineries

Adverse respiratory and skin health effects have been associated with occupational exposure to soluble platinum (Pt). However, the relationship between skin exposure and urinary Pt excretion has not yet been investigated. In this study we examined the relationship between skin and respiratory exposure to soluble Pt and urinary Pt excretion at two South African precious metals refineries. The skin and respiratory exposure to soluble Pt as well as the urinary Pt excretion of forty precious metals refinery workers was assessed simultaneously using Ghostwipes™, Methods for the Determination of Hazardous Substances method 46/2 and spot urine tests, respectively. The geometric mean for skin exposure to soluble Pt on four anatomical positions (palm, wrist, neck and forehead) was 0.008 μg/cm2 [95% confidence interval (CI): 0.005-0.013 μg/cm2], while the geometric mean for respiratory exposure was 0.301 μg/m3 (95%CI: 0.151-0.601 μg/m3) and the geometric mean for urinary Pt excretion was 0.212 μg/g creatinine (95%CI: 0.169-0.265 μg/g creatinine). Partial correlations identified significant positive correlations between skin exposure, respiratory exposure and urinary Pt excretion (r = 0.580 to 0.754). Skin and respiratory exposures to soluble Pt were both positively correlated with urinary Pt excretion, and both exposure routes should be considered when investigating occupational exposure to soluble Pt.