Characterization of workplace aerosols in the manganese alloy production industry by X-ray diffraction, inductively coupled plasma optical emission spectrometry, and anion chromatography

Workers in the manganese (Mn) alloy industry are exposed to a variety of Mn compounds, which may lead to a neurological condition called manganism. To better assess health effects due to Mn exposore, it is important to know to which Mn species workers are exposed. In this thesis, three different aerosols types from ferromanganese (FeMn) and silicomanganese (SiMn) production were characterized: a) furnace fumes generated inside the FeMn and SiMn furnaces; b) workplace aerosols collected in the FeMn and SiMn tapping areas; and c) workplace aerosols collected using personal respirable cyclones worn by FeMn and SiMn tappers. Prior to sample characterization, XRD background levels of polyvinylethylene (PVC), polycarbonate (PC), and polytetrafluoroethylene (PTFE) membrane filters were checked. Further, XRD background signals of various sample plates were checked: aluminium (Al) plate, cellullose membrane filter, single-crystal Si plate manufactured by PANalytical, and a single-crystal Si plate manufactured by MTI corporation. PVC background levels were significantly lower than for PC and PTFE filters, and the two single-crystal Si plates were, as expected, of superior quality with respect to XRD background levels. Furnace fumes were characterized by X-ray diffraction (XRD), aided by inductively coupled plasma optical emission spectrometry (ICP-OES) for elemental analyses, ion chromatography (IC) for determination of water-soluble anions, and pH measurements to assess acidity and alkalinity. Workplace aerosols were studied by XRD and ICPOES, and personal exposure filters were studied by XRD only. Here it is shown that the crystalline phases are predominantly manganese(II) dimanganese (III) tetraoxide (Mn3O4), dipotassium sulfate (K2SO4), zinc(II) oxide (ZnO), and β-quartz; however, the source of detected β-quartz is not known. Minor amounts of several other phases were detected, e.g. magnesium(II) carbonate (MgCO3), magnesium(II) oxide (MgO), diiron(III) magnesium(II) tetraoxide (MgFe2O4), and zinc(II) oxide (ZnO). Elemental analysis revealed the major components of the samples to be potassium (K), Mn, and silicon (Si). Anion chromatography revealed that water-soluble anions were present as sulfate (SO 2 – 4 ), chloride (Cl – ), and fluoride (F– ), which agree well with XRD results. The FeMn and SiMn furnace-fume water-extracts were slightly alkaline. The findings of this thesis show that workers are exposed to a variety of different compunds, which agree well with previous studies. Phase identification of aerosol filters and personal exposure filters was limited by low signal-to-noise ratio, due to the low amount of sample mass on the filters. Stacking of filters resulted in a large increase of diffracted signals, but also a large increase in noise. The use of a monochromator in the XRD instrument may improve spectral purity and reduce background signals. Future investigations should focus on increasing sample material for XRD characterization of aerosol samples. One way to achieve this may be by adapting NIOSH Method 7500 to manganese-holding aerosol samples. The possible exposure to α-quartz should also be investigated further. v Preface and acknowledgements This master’s thesis is part of my master’s program in analytical chemistry, and has been written for the Department of Environmental Sciences, Norwegian University of Life Sciences, Campus Ås, Norway. The work has been carried out in co-operation with, and financed by, the National Institute of Occupational Health (NIOH), Oslo, Norway. Many people deserve recognition for the help given to me during the last year. First and foremost I would like to thank my main supervisor, Yngvar Thomassen, for insightful discussions, good ideas, and constructive feedback on my work. Next I wish to thank my co-supervisor, Elin Gjengedal, for all the helpful comments and feedback on my writing. I also wish to thank Kari Dahl, Grete Friisk, Nils Petter Skaugset, and Balazs Berlinger for helping me with my analyses — and for never (seemingly) getting bored with all of my questions. Lastly I want to thank Julian Tolchard and Martijn Fransen for being willing to help me over e-mail with various aspects of XRD analysis. Ås, May 2015 Anders M. Brakestad