Fabian Taube

Manganese in Occupational Arc Welding Fumes—Aspects on Physiochemical Properties, with Focus on Solubility

Physicochemical properties, such as particle sizes, composition, and solubility of welding fumes are decisive for the bioaccessibility of manganese and thereby for the manganese cytotoxic and neurotoxic effects arising from various welding fumes. Because of the diverse results within the research on welding fume solubility, this article aims to review and discuss recent literature on physicochemical properties of gas metal arc welding, shielded metal arc welding, and flux-cored arc welding fumes, with focus on solubility properties. This article also presents a short introduction to the literature on arc welding techniques, health effects from manganese, and occupational exposure to manganese among welders.

Morphological and chemical characterization of tooth enamel exposed to alkaline agents

OBJECTIVES In this study, morphological and chemical changes in teeth enamel exposed to alkaline agents, with or without surfactants, have been investigated. In addition, chemical effects of the organic surface layer, i.e. plaque and pellicle, were also investigated. METHODS The present study was conducted using several techniques: Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). RESULTS From XPS-measurements, it was found that exposure to alkaline solutions resulted in a massive removal of carbon from the tooth surface, and that the addition of surfactants increased the rate under present conditions. Based on the results from the FTIR-analysis, no substitution reactions between phosphate, carbonate and hydroxide ions in the enamel apatite could be detected. From a minor SEM-analysis, degradation and loss of substance of the enamel surface was found for the exposed samples. From XRD-analysis, no changes in crystallinity of the enamel apatite could be found between the samples. CONCLUSIONS The findings in this study show that exposure to alkaline solutions results in a degradation of enamel surfaces very dissimilar from acidic erosion. No significant erosion or chemical substitution of the apatite crystals themselves could be discerned. However, significant loss of organic carbon at the enamel surface was found in all exposed samples. The degradation of the protective organic layer at the enamel surface may profoundly increase the risk for caries and dental erosion from acidic foods and beverages.

Deviations of inorganic and organic carbon content in hypomineralised enamel

OBJECTIVES The purpose of this study was to discriminate hypomineralised enamel of permanent first molars from normal enamel by means of spectroscopic methods. METHODS The present study was conducted using Multi spot Raman Fourier Transform Spectroscopy, Diffuse Reflectance Infrared Fourier Transform Spectroscopy (FTIR) and X-ray diffraction (XRD). RESULTS Raman spectroscopy indicated significantly more B-type carbonate and hydrocarbons in hypomineralised enamel diagnosed as MIH (Molar Incisor Hypomineralisation). From XRD analysis, no changes in crystallinity of the enamel apatite could be found. CONCLUSIONS Using multi spot Raman-spectroscopy, a significant molecular discrimination between normal and hypomineralised enamel could be made. CLINICAL SIGNIFICANCE Detailed surface studies are needed in order to achieve better restorative materials, specifically designed for restoration of hypomineralised enamel, and are also needed in order to understand and predict the clinical consequences of hypomineralised enamel with the condition MIH.

17O NMR study of aqueous peroxoisopolymolybdate equilibria at lower peroxide/Mo ratios

Aqueous peroxomolybdates have been studied using 17O NMR together with equilibrium measurements and calculations, over a wide range of conditions. Ten peroxo species are identified, mostly in more than one state of protonation. Some are already known in the solid state, or from equilibrium analysis, but structural information is also obtained for MoO3(HO2)− and the new or previously tentative species Mo2O5(O2)22−, HpMo7O23(O2)2p−6 and HpMo7O23(O2)p−6 (p = 0–2). Sites of protonation are identified, as are 17O resonances from both bidentate and monodentate peroxide. Several oxygen exchange processes are also seen, including a probable dimer–tetramer exchange.

XRMA and ToF-SIMS Analysis of Normal and Hypomineralized Enamel.

Molar incisor hypomineralization (MIH) is a developmental disturbance of the enamel. This study presents analyses of hypomineralized and normal enamel in first molar teeth diagnosed with MIH, utilizing time-of-flight secondary ion mass spectrometry area analyses and X-ray microanalysis of area and spot profiles in uncoated samples between gold lines which provide electrical conductivity. Statistical analysis of mean values allows discrimination of normal from MIH enamel, which has higher Mg and lower Na and P. Inductive analysis using complete data sets for profiles from the enamel surface to the enamel-dentin junction found that Mg, Cl and position in the profile provide useful discrimination criteria. Element profiles provide a visual complement to the inductive analysis and several elements also provide insight into the development of both normal and MIH enamel. The higher Mg content and different Cl profiles of hypomineralized enamel compared with normal enamel are probably related to a relatively short period during the development of ameloblasts between birth and the 1st year of life.

Analysis of manganese and iron in exhaled endogenous particles

Background: many full-time welders experience some sort of respiratory disorder e.g., asthma, bronchitis and metal fume fever. Thus, welding aerosols are thought to cause airway inflammation. There is a need for markers of welding aerosols in exposure assessments, and as most welding aerosols contain manganese and iron, these metals may possibly be used as an indicator. We have previously developed a novel non-invasive technique to collect endogenous particles in exhaled air (PEx). This study is designed to (i) develop a method for analysis of manganese and iron in PEx and (ii) investigate whether the manganese and/or iron content of PEx changes after exposure to welding aerosols. Methods: nine individuals were experimentally exposed to welding fumes. PEx was collected at three time points for each individual; before, after and 24 hours after exposure. Analyses of PEx samples were performed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Results: four out of nine individuals showed an increase in manganese and iron levels after exposure to welding aerosols. The mean manganese and iron concentration increased from, <LOD to 82–84 pg L−1 (range from 0 to LOD for values <LOD) and 20–86 to 2600 pg L−1 of exhaled air respectively. Conclusions: an ICP-MS method for analysis of manganese and iron in PEx has been developed. The method could easily be expanded to include other trace metals of interest, such as cadmium, nickel or chromium. This first attempt to evaluate PEx as a tool for exposure assessments of airborne metals indicates that the method has potential.

Evaluation of X-Ray Microanalysis for Characterization of Dental Enamel

Elemental analysis of dental hard tissues is of importance. The aim of this study is to evaluate X-ray microanalysis (XRMA) of bovine enamel in a scanning electron microscope (SEM) with different coatings. The buccal surface of bovine incisors was polished flat, one-third was coated with carbon, one-third with gold, leaving one-third uncoated for XRMA in an SEM equipped with an energy-dispersive microanalysis system. The elements oxygen, sodium, magnesium, phosphorous, chlorine, potassium, and calcium were analyzed using their respective characteristic K X-ray series. Comparisons were made with analyses of glass produced by fusion of the bovine enamel, showing that oxygen analyses using the K X-ray series are reliable and preferable to calculating oxygen by stoichiometry for natural enamel. For the gold-coated and uncoated analyses, carbon was also measured using the K X-ray series. Small area Analyses in small areas (80 × 80 μm) in variable pressure-SEM mode with low vacuum (20 Pa), without any coating, midway between 40 μm wide gold lines 140 μm apart to avoid build-up of electrostatic charge is the preferred method, especially if carbon is included in the analysis. The analyses of bovine enamel are sufficiently reproducible to be regarded as quantitative for all elements except carbon.

Molybdate speciation in systems related to the bleaching of kraft pulp

Peroxomolybdates have shown to be efficient selective agents in the degradation of lignin in non-chlorine based bleach processes of kraft pulp. Furthermore, the process can be improved when anions ...

Lipid composition of particles in exhaled air (PEx) from workers exposed to welding fumes

More than two million workers are exposed to pneumotoxic welding aerosols and there is a need for biomarkers of effects on the respiratory system. The lipid composition of the respiratory tract lining fluid (RTLF) is such a potential marker. The most abundant pulmonary surfactant phospholipid is dipalmitoylphosphocholine (DPPC). It is specific for the airways, while palmitoyloleoylphosphatidylcholine (POPC) is a common lipid in tissues and body fluids. We hypothesize that the amounts of or ratio between DPPC and DOPC are changed due to short term and/or long term exposure to welding fumes. We have developed a method for the collection of PEx, based on counting of the exhaled particles and subsequent collection by impaction on a teflon membrane. We have also developed a method for analysis of lipids in PEx based on LC/MS. We measured the exposure to iron, manganese, chromium and nickel of 18 stainless steel welders and also analyzed DPPC and DOPC in PEx samples taken at the end of the exposure measurement day. The welders working history was also recoded and summarized as welding years. Spirometry and nitrogen multiple breath wash out were also measured but the results are not yet evaluated. There were no significant correlations between the short term exposure to either iron, manganese, chromium or nickel and the fraction of DPPC in PEx or the ratio DPPC/DOPC. However, there was a tendency of correlation (Spearman correlation coefficient= 0.407 with p-value 0.09) between welding years and the DPPC/DOPC ratio. In this pilot study we could not establish short term effects of welding exposure on the RTFL lipid composition but a tendency of change due the long time exposure.