Silicon dioxide (silica) is ubiquitous, and a variety of crystalline and amorphous silica polymorphs is known. They originate from both, natural and synthetic processes. Examples of silica polymorphs that are amorphous to X-rays are synthetically pure precipitated or fumed silica, gem opal, diatoms that form huge deposits of their silica skeletons, and silica fume, which is collected as by-product from silicon and ferroalloy production. All of these amorphous silica polymorphs have a fascinating origin and are used in a large number of technical applications, accordingly.

The authors respond to the points raised in the Letters to the Editor raised by Ogden and Du Clos and by Foster. Ad 1: The debate of the classification of respirable cyrstalline silica is outside the scope of the technical paper. Ad 2: A standard for the determination of SWeRF is under development, in which indeed the provision is made that for a correct determination all quartz within the fine fraction needs to be liberated. Ad 3: Dustiness tests provide useful information for occupational hygienists, but are not suitable for fulfilling classification and labelling requirements. Ad 4: Pipette effects are not discussed in the paper because the difference between calculating the SWeRF from the particle size distribution and the SWeRF from sedimentation is very small.

Since the International Agency for Research on Cancer (IARC) has classified crystalline silica (quartz and cristobalite) dust as a group 1 carcinogen in 2009, new studies and reviews on respirable crystalline silica (RCS) have been published. Evidence has been obtained in scientific literature that RCS toxicity is variable; in particular, the carcinogenic potency does not express in all industrial circumstances and in any case is secondary to fibrosis. In light of the implementation of the Globally Harmonized System (GHS) in Europe, the European Industrial Minerals Association (IMA-Europe) submitted a group notification for RCS with the classification Specific Target Organ Toxicity Repeated Exposure Category 1 (STOT RE 1) for silicosis. Consequently, generic cut-off values for hazard classification and labelling apply for products containing RCS in amounts >1 % (STOT RE 2) and >10 % (STOT RE 1), respectively. This triggers the need for a method to quantify the amount of RCS in a bulk material for classification and labelling purposes. The Metrology Working group of IMA-Europe has therefore developed the so-called SWeRF method (size-weighted relevant fine fraction), which is currently being dealt with in the European Committee for Standardization (CEN). In light of the possible setting of an EU limit value for respirable crystalline silica, the latest toxicological and epidemiological findings on exposure to RCS, as well as socio-economic assessments, provide important new information.

In accordance with the European regulation for classification, labelling and packaging of substances and mixtures (CLP) as well as the criteria as set out in the Globally Harmonized System (GHS), fine fraction of crystalline silica (CS) has been classified as a specific target organ toxicity, the specific organ in this case being the lung. Generic cut-off values for products containing a fine fraction of CS trigger the need for a method for the quantification of the fine fraction of CS in bulk materials. This article describes the so-called SWeRF method, the size-weighted relevant fine fraction. The SWeRF method combines the particle size distribution of a powder with probability factors from the EN 481 standard and allows the relevant fine fraction of a material to be calculated. The SWeRF method has been validated with a number of industrial minerals. This will enable manufacturers and blenders to apply the CLP and GHS criteria for the classification of mineral products containing RCS a fine fraction of CS.

Performing ecotoxicity tests on poorly water soluble substances and in particular metals, metalloids, and metal oxides such as silica fume, can be problematic. Such substances may not be directly toxic to aquatic organisms but often have high concentrations of impurities present, due to production processes, which may result in ecotoxicological effects. This combined with possibly testing above the limit of solubility further exacerbates the interpretation of ecotoxicity test results. One approach to overcome this is to perform a transformation/dissolution (T/D) test to determine the quantities of elemental impurities which will consequently be in solution. These data can subsequently be compared to existing data to determine if there is likely to be an effect on aquatic organisms. This paper highlights research into determining the T/D potential of 2 different grades of amorphous silica fume (low and high grade purity) with complementary chronic ecotoxicity tests of the 2 substances to validate this approach. The low grade silica fume test substance was identified in the T/D assessments as being of concern for the potential to cause acute toxicity to aquatic organisms and had levels of impurities (e.g. Pb and Zn) in the solutions which exceeded the effect limits identified in the open literature. Consequently, silica fume would be hazard classified as acute 2 according to regulatory classification schemes. However, the results of the ecotoxicity hazard validation assessments in a Daphnia magna reproduction test and the sediment dwelling organism Chironomus riparius indicated that low and high grade silica fumes are not acutely or chronically toxic up to and including an initial loading concentration of 100 mg/L and 1000 mg/kg respectively. Hence, using the T/D test data alone may have resulted in a false hazard classification of silica fume (low grade).

AbstractStoffdossiers, die entsprechend der europäischen Chemikalienverordnung Reach registriert sind, sind öffentlich zugänglich. Dies nutzen Betrüger, um ohne Aufwand eigene Dossiers zu erstellen. Damit könnten auch gefährliche Stoffe ohne entsprechende Kennzeichnung auf den Markt gelangen.

Abstract Background Respirable crystalline silica (silicon dioxide; SiO2, quartz) particles are known to induce chronic inflammation and lung disease upon long-term inhalation, whereas non-crystalline (amorphous) SiO2 particles in the submicrometre range are regarded as less harmful. Several reports have demonstrated that crystalline, but also non-crystalline silica particles induce IL-1β release from macrophages via the NALP3-inflammasome complex (caspase-1, ASC and NALP3) in the presence of lipopolysaccharide (LPS) from bacteria. Our aim was to study the potential of different non-crystalline SiO2 particles from the nano- to submicro-sized range to activate IL-1β responses in LPS-primed RAW264.7 macrophages and primary rat lung macrophages. The role of the NALP3-inflammasome and up-stream mechanisms was further explored in RAW264.7 cells. Results In the present study, we have shown that 6 h exposure to non-crystalline SiO2 particles in nano- (SiNPs, 5–20 nm, 50 nm) and submicro-sizes induced strong IL-1β responses in LPS-primed mouse macrophages (RAW264.7) and primary rat lung macrophages. The primary lung macrophages were more sensitive to Si-exposure than the RAW-macrophages, and responded more strongly. In the lung macrophages, crystalline silica (MinUsil 5) induced IL-1β release more potently than the non-crystalline Si50 and Si500, when adjusted to surface area. This difference was much less pronounced versus fumed SiNPs. The caspase-1 inhibitor zYVAD and RNA silencing of the NALP3 receptor reduced the particle-induced IL-1β release in the RAW264.7 macrophages. Furthermore, inhibitors of phagocytosis, endosomal acidification, and cathepsin B activity reduced the IL-1β responses to the different particles to a similar extent. Conclusions In conclusion, non-crystalline silica particles in the nano- and submicro-size ranges seemed to induce IL-1β release from LPS-primed RAW264.7 macrophages via similar mechanisms as crystalline silica, involving particle uptake, phagosomal leakage and activation of the NALP3 inflammasome. Notably, rat primary lung macrophages were more sensitive with respect to silica-induced IL-1β release. The differential response patterns obtained suggest that silica-induced IL-1β responses not only depend on the particle surface area, but on factors and/or mechanisms such as particle reactivity or particle uptake. These findings may suggest that bacterial infection via LPS may augment acute inflammatory effects of non-crystalline as well as crystalline silica particles.

Zeitschrift für anorganische und allgemeine ChemieVolume 638, Issue 10 p. 1565-1565 Oral Presentation Nachhaltigkeit in der Bauindustrie durch Einsatz von Microsilica Dr. Bernd Friede, Corresponding Author Dr. Bernd Friede bernd.friede@elkem.no Elkem AS, Silicon Materials, P.O. Box 8126 Vaagsbygd, 4675 Kristiansand-S, NorwegenElkem AS, Silicon Materials, P.O. Box 8126 Vaagsbygd, 4675 Kristiansand-S, NorwegenSearch for more papers by this authorPer Fidjestøl, Per Fidjestøl Elkem AS, Silicon Materials, P.O. Box 8126 Vaagsbygd, 4675 Kristiansand-S, NorwegenSearch for more papers by this author Dr. Bernd Friede, Corresponding Author Dr. Bernd Friede bernd.friede@elkem.no Elkem AS, Silicon Materials, P.O. Box 8126 Vaagsbygd, 4675 Kristiansand-S, NorwegenElkem AS, Silicon Materials, P.O. Box 8126 Vaagsbygd, 4675 Kristiansand-S, NorwegenSearch for more papers by this authorPer Fidjestøl, Per Fidjestøl Elkem AS, Silicon Materials, P.O. Box 8126 Vaagsbygd, 4675 Kristiansand-S, NorwegenSearch for more papers by this author First published: 22 August 2012 https://doi.org/10.1002/zaac.201203026Citations: 1Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume638, Issue10August 2012Pages 1565-1565 RelatedInformation

AbstractGibt es ein Mittel gegen Betonkrebs und die Zerstörung von Beton durch Meerwasser und Sulfatlösungen? Ja, allerdings nur prophylaktisch: Mikrosilica sorgt weltweit für langlebige Beton konstruktionen.

It is important that analytical results, produced to demonstrate compliance with exposure limits are comparable, to ensure controls are monitored to similar standards. Correcting a measurement result of respirable alpha-quartz for the percentage of crystalline material in the calibration dust is good analytical practice and significant changes in the values assigned to calibration materials will affect the interpretation of results by an analyst or occupational hygiene professional. The reissue of the certification for the quartz reference material NIST 1878a in 2005 and differences in comparative values obtained by other work created uncertainty about the values of crystallinity assigned to national calibration dusts for alpha-quartz. Members of an International Organization for Standardization working group for silica measurement ISO/TC146/SC2/WG7 collaborated to investigate the comparability of results by X-ray diffraction (XRD) and to reach a consensus. This paper lists the values recommended by the working group for use with XRD analysis. The values for crystallinity obtained for some of the materials (NIST 1878, Min-U-Sil5 and A9950) were 6-7% lower than the original certification or estimates reported in other comparisons. Crystallinity values obtained by XRD gave a good correlation with BET surface area measurements (r2 = 0.91) but not with mean aerodynamic particle size (r2 = 0.31). Subsamples of two of the materials (A9950 Respirable and Quin 1 Respirable) with smaller particle size distribution than their parent material did not show any significant change in their values for crystallinity, suggesting that the area XRD measurement of these materials within the particle size range collected is more dependent on how the quartz is formed geologically or how it is processed for use. A comparison of results from laboratories using the infrared (IR) and KBr disc method showed that this method is more dependent than XRD on differences in the particle size within the respirable size range, whereas the XRD values were more consistent between the different measurement values obtained on each material. It was not possible to assign a value for percentage purity to each material for users of IR analysis. This work suggests that differences are likely to exist between the results from XRD and IR analysis when measuring 'real' workplace samples and highlights the importance of matching the particle size of the calibration material to the particle size of the workplace dust for measurements of crystalline quartz.