Last data update: Jun 11, 2024. (Total: 46992 publications since 2009)
Records 1-5 (of 5 Records) |
Query Trace: Harvey CJ [original query] |
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Dissolution of cemented carbide powders in artificial sweat: implications for cobalt sensitization and contact dermatitis
Stefaniak AB , Harvey CJ , Virji MA , Day GA . J Environ Monit 2010 12 (10) 1815-22 Skin exposure to cobalt-containing materials can cause systemic immune sensitization and upon repeat contact, elicitation of allergic contact dermatitis (ACD). Data on cobalt dissolution rates are needed to calculate uptake through skin and for development of models to understand risk of sensitization or dermatitis. The purpose of this research was to measure the dissolution kinetics of feedstock and process-sampled powders encountered in the production of hard metal alloys using artificial sweat. The physicochemical properties of each material were characterized prior to evaluation of dissolution behavior. Variations in artificial sweat solvent pH and chemistry were used to understand critical factors in dissolution. Dissolution of cobalt, tungsten, and tungsten carbide was often biphasic with the initial rapid phase being up to three orders of magnitude faster than the latter long-term phase. Artificial sweat pH did not influence dissolution of cobalt or tungsten carbide. Solvent composition had little influence on observed dissolution rates; however, vitamin E suppressed the dissolution of cobalt and tungsten carbide from sintered particles obtained from a chamfer grinder. There was no effect of particle size on dissolution of feedstock cobalt, tungsten, tungsten carbide, and admixture powders. Particle physicochemical properties influenced observed dissolution rates with more cobalt and tungsten carbide dissolving from chamfer grinder particles compared to the feedstock powders or admixture powder. Calculations using the observed dissolution rates revealed that skin exposure concentrations were similar to concentrations known to induce cobalt sensitization and elicit ACD. Observed dissolution rates for cobalt in artificial sweat indicate that dermal uptake may be sufficient to induce cobalt sensitization and allergic dermatitis. |
Formulation and stability of a novel artificial human sweat under conditions of storage and use
Harvey CJ , Lebouf RF , Stefaniak AB . Toxicol In Vitro 2010 24 (6) 1790-6 A limitation of most artificial sweat formulations used for in vitro assessment of chemical release from materials in contact with skin have little biological relevance to human sweat. The purposes of this paper are to provide guidance for preparation of a novel artificial sweat with chemical constituents at concentrations that match human sweat and to characterize chemical stability. The artificial sweat was characterized under conditions of use (with and without sebum at 36 degrees C) and storage (without sebum at -4, 4, and 23 degrees C) over 28 days by gas chromatography-mass spectroscopy, high-performance liquid chromatography, enzymatic assay kits, and ion-selective electrodes. Seven indicator constituents were tracked: sodium, chloride, glucose, lactic acid, urea, pantothenic acid, and alanine. With or without sebum at 36 degrees C, the sweat solvent was chemically stable for 14 days. Storage by refrigeration at 4 degrees C retained the chemical integrity of the solvent longest. Based on these results, the solvent should be used within 14 days of preparation. The artificial sweat model presented herein is most similar to human sweat and has applications as a dissolution solvent, donor solution in diffusion cells, or vehicle for patch testing. This sweat model may aid researchers in understanding potential release and percutaneous absorption of chemicals in contact with human skin surface liquids. |
Formulation and stability of a novel artificial sebum under conditions of storage and use
Stefaniak AB , Harvey CJ , Wertz PW . Int J Cosmet Sci 2010 32 (5) 347-55 Materials in contact with liquids on the human skin surface may dissolve and permeate into skin. Release and permeation of chemicals in contact with skin is often estimated in vitro using artificial skin liquids, although sebum lipids are generally not included in these models. The purposes of this research were to develop a representative artificial sebum that contains the appropriate types of lipids at levels that match human values and quantitatively characterize the model to understand its utility for in vitro testing. Artificial sebum that consisted of 10 lipids at proportions that closely resembled human sebum was characterized using thin layer chromatography under a variety of storage and use conditions (dry and liquid, 4 degrees C and 32 degrees C, with and without vitamin E) for 28 days. Levels of sebum constituents maintained in solution and dry at 4 degrees C were stable through the duration of the test period. Levels of all sebum lipids maintained dry at 32 degrees C were stable in the presence of vitamin E; however, squalene oxidized rapidly in the absence of vitamin E. Liquids on the human skin surface consist of sebum and sweat with minor amounts of cellular debris and intercellular lipid from the stratum corneum. The relative importance of each component for release of chemicals from materials in contact with skin will depend upon the type of material (metal, organic, etc.). A model artificial sebum was formulated and characterized to aid researchers in understanding potential release of chemicals from materials in contact with skin and subsequent partitioning and absorption. |
Influence of artificial gastric juice composition on bioaccessibility of cobalt- and tungsten-containing powders
Stefaniak AB , Abbas Virji M , Harvey CJ , Sbarra DC , Day GA , Hoover MD . Int J Hyg Environ Health 2010 213 (2) 107-15 The dissolution of metal-containing particles in the gastric compartment is poorly understood. The purpose of this study was to elucidate the influence of artificial gastric juice chemical composition on bioaccessibility of metals associated with ingestion-based health concerns. Dissolution rates were evaluated for well-characterized feedstock cobalt, tungsten metal, and tungsten carbide powders, chemically bonded pre-sintered (spray dryer material) and post-sintered (chamfer grinder) cemented tungsten carbide materials, and an admixture of pure cobalt and pure tungsten carbide, prepared by mechanically blending the two feedstock powders. Dissolution of each study material was evaluated in three different formulations of artificial gastric juice (from simplest to most chemically complex): American Society of Testing Materials (ASTM), U.S. Pharmacopoeia (USP), and National Institute for Occupational Safety and Health (NIOSH). Approximately 20% of cobalt dissolved in the first dissolution phase (t(1/2) = 0.02 days) and the remaining 80% was released in the second long-term dissolution phase (t(1/2) = 0.5 to 1 days). Artificial gastric juice chemical composition did not influence dissolution rate constant values (k, g/cm(2)day) of cobalt powder, either alone or as an admixture. Approximately 100% of the tungsten and tungsten carbide that dissolved was released in a single dissolution phase; k-values of each material differed significantly in the solvents: NIOSH > ASTM > USP (p<0.05). The k-values of cobalt and tungsten carbide in pre- and post-sintered cemented tungsten carbide powders were significantly different from values for the pure feedstock powders. Solvent composition had little influence on oral bioaccessibility of highly soluble cobalt and our data support consideration of the oral exposure route as a contributing pathway to total-body exposure. Solvent composition appeared to influence bioaccessibility of the low soluble tungsten compounds, though differences may be due to variability in the data associated with the small masses of materials that dissolved. Nonetheless, ingestion exposure may not contribute appreciably to total body burden given the short residence time of material in the stomach and relatively long dissolution half-times of these materials (t(1/2) = 60 to 380 days). |
Comparison of free radical generation by pre- and post-sintered cemented carbide particles
Stefaniak AB , Harvey CJ , Bukowski VC , Leonard SS . J Occup Environ Hyg 2010 7 (1) 23-34 Rapid generation of reactive oxygen species (ROS) may occur in response to cellular contact with metal particles. Generation of ROS by cobalt and/or tungsten carbide is implicated in causing hard metal lung disease (HMD) and allergic contact dermatitis (ACD). In this study, ROS generation and particle properties that influence radical generation were assessed for three sizes of tungsten, tungsten carbide, cobalt, admixture (tungsten carbide and cobalt powders), spray dryer, and post-sintered chamfer grinder powders using chemical (H(2)O(2) plus phosphate buffered saline, artificial lung surfactant, or artificial sweat) and cellular (RAW 264.7 mouse peritoneal monocytes plus artificial lung surfactant) reaction systems. For a given material, on a mass basis, hydroxyl (.OH) generation generally increased as particle size decreased; however, on a surface area basis, radical generation levels were more, but not completely, similar. Chamfer grinder powder, polycrystalline aggregates of tungsten carbide in a metallic cobalt matrix, generated the highest levels of .OH radicals (p < 0.05). Radical generation was not dependent on the masses of metals, rather, it involved surface-chemistry-mediated reactions that were limited to a biologically active fraction of the total available surface area of each material. Improved understanding of particle surface chemistry elucidated the importance of biologically active surface area in generation of ROS by particle mixtures. |
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