Characterization of exposures among cemented tungsten carbide workers. Part II: Assessment of surface contamination and skin exposures to cobalt, chromium and nickel

Journal of Occupational and Environmental Hygiene

Harvey

Bukowski

et al. 2009

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.

Section: Allergic Contact Dermatitismentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Comparison of Free Radical Generation by Pre- and Post-Sintered Cemented Carbide Particles

Journal of Occupational and Environmental Hygiene

Harvey

Bukowski

et al. 2009

“…The objectives of this study were to better understand hazard potential by relating mechanisms of CTC-induced adverse health to characteristics of cobalt-and tungsten-containing aerosols generated during the manufacture of hard metal with emphasis on (1) aerosol total and particle size-selective mass concentrations; (2) particle size distributions; and (3) comparison of mass concentration obtained using personal ''total'' dust and personal size-selective impactor samplers. In the companion paper, we present the results of the assessment of work surfaces contamination and skin exposure to cobalt, chromium, and nickel (Day et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Characterization of exposures among cemented tungsten carbide workers. Part I: Size-fractionated exposures to airborne cobalt and tungsten particles

J Expo Sci Environ Epidemiol

Virji

Day

2008

Self Cite

As many as 30,000 workers in the United States of America are exposed to cemented tungsten carbides (CTC), alloys composed primarily of tungsten carbide and cobalt, which are used in cutting tools. Inhalation of cobalt-containing particles may be sufficient for the development of occupational asthma, whereas tungsten carbide particles in association with cobalt particles are associated with the development of hard metal disease (HMD) and lung cancer. Historical epidemiology and exposure studies of CTC workers often rely only on measures of total airborne cobalt mass concentration. In this study, we characterized cobalt-and tungsten-containing aerosols generated during the production of CTC with emphasis on (1) aerosol ''total'' mass (n ¼ 252 closed-face 37 mm cassette samples) and particle size-selective mass concentrations (n ¼ 108 eight-stage cascade impactor samples); (2) particle size distributions; and (3) comparison of exposures obtained using personal cassette and impactor samplers. Total cobalt and tungsten exposures were highest in work areas that handled powders (e.g., powder mixing) and lowest in areas that handled finished product (e.g., grinding). Inhalable, thoracic, and respirable cobalt and tungsten exposures were observed in all work areas, indicating potential for co-exposures to particles capable of getting deposited in the upper airways and alveolar region of the lung. Understanding the risk of CTC-induced adverse health effects may require two exposure regimes: one for asthma and the other for HMD and lung cancer. All sizes of cobalt-containing particles that deposit in the lung and airways have potential to cause asthma, thus a thoracic exposure metric is likely biologically appropriate. Cobalt-tungsten mixtures that deposit in the alveolar region of the lung may potentially cause HMD and lung cancer, thus a respirable exposure metric for both metals is likely biologically appropriate. By characterizing size-selective and co-exposures as well as multiple exposure pathways, this series of papers offer an approach for developing biologically meaningful exposure metrics for use in epidemiology.

“…The duration was selected as a typical 8 hour work shift plus additional time to account for take-home exposure which is a common occurrence in the ‘real-world.’ In our experiences with dermal exposure assessments in facilities that lacked skin protection and hygiene programs, take-home contamination was evident and metals were still present on workers’ skin at the start of their shift the following day. 24 For each study material, masses equivalent to 0.05 g of metal were accurately weighed to 0.01 mg using a microbalance (Model AX-205, Mettler-Toledo) housed in a temperature- and humidity-controlled room. The chosen mass value exceeds dermal loadings that we have observed previously 24 but the high mass value was needed to exceed analytical detection limits.…”

Section: Methodsmentioning

confidence: 99%

Dissolution of the metal sensitizers Ni, Be, Cr in artificial sweat to improve estimates of dermal bioaccessibility

Environ. Sci.: Processes Impacts

Duling

Geer

et al. 2014

Dermal exposure to sensitizing metals is a serious occupational and public health problem. The usual approach to dermal exposure assessment is to process samples by chemical methods that use reactants to digest the metal particles and quantify the mass. In the case of dermal exposure assessment, these reactants are not representative of the skin surface film liquids and hence, may overestimate bioaccessibility. We hypothesize that the amount and form of sensitizer on a sample that leaches in a biological fluid, as can be estimated using artificial sweat, may be a more relevant metric for assessing health risks. Beryllium metal (Be), nickel metal (Ni), and chromium carbide (Cr3C2) particles were characterized and masses of sensitizing ions were measured using established reactant-assisted digestion procedures and extraction in artificial sweat under physiologically relevant conditions. Chromium ions released into artificial sweat were speciated to understand valence states. The ratios of the fraction of metal dissolved in artificial sweat relative to that dissolved by chemical-specific reactants were 1/2 (Be), 1/108 (Ni), and 1/2500 (Cr). The divalent Be and Ni cations were stable in artificial sweat over time (did not precipitate) whereas hexavalent chromium [Cr(vi)] ions decayed over time. Further analysis using speciated isotope dilution mass spectrometry revealed that the decay of Cr(vi) was accompanied by the formation of Cr(iii) in the sweat model. Use of reactant-assisted analytical chemistry to quantify amounts of metal sensitizers on samples could overestimate biologically relevant exposure. In addition to mass, the valence state also influences penetration through the outer stratum corneum of the skin and is an important consideration when assessing exposure to complex sensitizers such as Cr which have multiple valence states with differing penetration efficiencies.