The aim of this study was to estimate average occupational exposure to inhalable nickel (Ni) using the German exposure database MEGA. This database contains 8052 personal measurements of Ni collected between 1990 and 2009 in adjunct with information on the measurement and workplace conditions. The median of all Ni concentrations was 9 μg/m and the 95th percentile was 460 μg/m. We predicted geometric means (GMs) for welders and other occupations centered to 1999. Exposure to Ni in welders is strongly influenced by the welding process applied and the Ni content of the used welding materials. Welding with consumable electrodes of high Ni content (>30%) was associated with 10-fold higher concentrations compared with those with a low content (<5%). The highest exposure levels (GMs ≥20 μg/m) were observed in gas metal and shielded metal arc welders using welding materials with high Ni content, in metal sprayers, grinders and forging-press operators, and in the manufacture of batteries and accumulators. The exposure profiles are useful for exposure assessment in epidemiologic studies as well as in industrial hygiene. Therefore, we recommend to collect additional exposure-specific information in addition to the job title in community-based studies when estimating the health risks of Ni exposure.
Metal occupational exposure limits mainly focus on total content of the respective metals of interest. The methods applied for trace metal analysis in occupational health and safety laboratories are usually standardized to pragmatic consensus digestion schemes, ensuring comparability of results. The objective of the present study entailed the evaluation of a recently developed HNO3-only microwave-assisted digestion procedure by comparison with the German consensus hot-block digestion and other national digestion schemes. An inter-laboratory comparison test with participation of nine national occupational health and safety laboratories from Europe and North America was organized. For adequate emulation of what workers are at risk of inhaling four different industrial metal processing workplace dusts (electronic recycling, high-speed steel grinding, cylinder head cleaning, and battery combustion ash) were homogenized and sieved to the particle size < 100 µm diameter at IFA. The participants were asked to process air sample-typical amounts according to the German hot-plate technique, the IFA microwave-assisted digestion scheme as well as their national or in-house conventional digestion method for airborne dust and analyze for Cd, Co, Cr, Co, Fe, Mg, Ni, Pb, and Zn. Recoveries (relative to consensus open-vessel digestion) obtained for the new IFA microwave-assisted digestion were between 88 and 114% and relative reproducibility standard deviations were <10% for most metals of interest. The in-house digestion procedures applied varied widely but (whether microwave, hot block, or open vessel) yielded comparable results for the predominantly elemental alloy type dusts supplied. Results become more diverse for the combustion dust, especially if a combination of microwave-assisted digestion procedures with high temperatures and hydrofluoric acid is applied. ISO 15202-2 is currently being revised; this digestion procedure will be included as a possible variant in annex 2.
In addition to the gravimetric determination of airborne particles (total concentration), it is often necessary to selectively determine metals and their compounds in particle fractions because of their toxicological relevance. Usually, the total metal concentration is determined independently of the type of binding or oxidation state in a sample. From an occupational medical and toxicological point of view it makes sense to distinguish between different compounds of a metal, because type and extent of the toxic effect of metals depend considerably on their binding type and their solubility in the human body. In addition to the limit values of the respirable and inhalable particle fraction that must be complied, many metals have an OEL (occupational exposure limit) or MAK value that has to be checked and complied too. For cancerogenic compounds the exposure‐risk relationship has to be considered. Analysis for metals and their compounds predominantly resorts to methods, which require that the dust particle sample is brought into solution. That means the metals and their compounds contained in the sample need to be extracted, dissolved or digested. Aim of the sample preparation is the complete solution of all relevant substances to be analysed. Common digestion methods are for example acid digestion, which uses an acid mixture to digest the sample, and the suspension method, in which acetone is used to suspend the sample. An alternative sample preparation method is the microwave‐assisted pressure digestion with acid/acid mixture. In this chapter the different digestion methods are presented, discussed and compared, taking into account recent developments, in particular microwave‐assisted digestion.
In den letzten Jahren wurden die Beurteilungsmaßstäbe für die Exposition gegenüber zahlreichen Gefahrstoffen am Arbeitsplatz neu definiert. Tendenziell sind diese Werte im Vergleich zu früher geltenden Grenzwerten deutlich niedriger. Weitere Absenkungen, insbesondere auch für weitere Gefahrstoffe, sind zukünftig zu erwarten. Die Probenahme und die quantitative Analytik stellt dies vor einige Herausforderungen. Mit angepassten Probenahme- und Analysensystemen lassen sich die Mindestanforderungen an die Leistungsfähigkeit von Messverfahren heute erfüllen. Des Weiteren tritt die Speziation von Metallverbindungen im Bereich des Arbeitsschutzes aufgrund unterschiedlicher toxikologischer Wirkungen in den Vordergrund. Um in Zukunft geeignete Messverfahren für die Ermittlung und Beurteilung von Gefahrstoffexpositionen im Bereich der Metalle und Metallverbindungen nutzen zu können, bedarf es der Forschung und Entwicklung, beispielsweise für höher volumige Probenahmegeräte, sowie einer Reduzierung jeglicher Störeinflüsse und nachweisstärkerer Analysensysteme.
Anfang der 1990er-Jahre wurde die Bestimmung des Gesamtmetallgehaltes in der Luft am Arbeitsplatz in Deutschland durch die Einführung einer Aufschlusskonvention mittels offenem Aufschluss in einer Salpetersäure/Salzsäure-Mischung harmonisiert. Inzwischen haben sich Mikrowellen-Druckaufschlussverfahren aufgrund ihrer zahlreichen Vorteile in vielen Bereichen der Spuren- und Ultraspurenanalytik von Metallen als Stand der Technik durchgesetzt. Insbesondere im Hinblick auf stetig steigende Anforderungen an Bestimmungsgrenzen, Probendurchsatz und Arbeitssicherheit empfiehlt es sich, diese Technik als Alternative zum bestehenden Konventionsaufschluss im Arbeitsschutz zu etablieren. Zur Verifizierung eines im IFA entwickelten mikrowellenunterstützten Druckaufschlussverfahrens wurde sowohl ein nationaler Ringversuch mit Mitgliedern der DFG-Arbeitsgruppe „Luftanalysen” (BAuA, IGF, BGN, ALL und VW AG) als auch ein weiterer Ringversuch mit internationalen Arbeitsschutzinstituten (NIOSH, IRSST, ÖSBS, Suva, HSL, WOHL, INRS und STAMI) initiiert. Die statistische Bewertung der zusammengeführten Ergebnisse aus beiden Ringversuchen bestätigt eine gute Vergleichbarkeit zwischen dem Konventionsaufschluss und dem vorgeschlagenen Mikrowellen-Druckaufschlussverfahren.
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