The global variability of diatomaceous earth toxicity: a physicochemical and in vitro investigation

Abstract

BackgroundDiatomaceous earth (DE) is mined globally and is potentially of occupational respiratory health concern due to the high crystalline silica content in processed material. DE toxicity, in terms of variability related to global source and processing technique, is poorly understood. This study addresses this variability using physicochemical characterisation and in vitro toxicology assays.MethodsNineteen DE samples sourced from around the world, comprising unprocessed, calcined and flux-calcined DE, were analysed for chemical and mineral composition, particle size and morphology, and surface area. The potential toxicity of DE was assessed by its haemolytic capacity, and its ability to induce cytotoxicity or cytokine release by J774 macrophages.ResultsThe potential toxicity of DE varied with source and processing technique, ranging from non-reactive to as cytotoxic and haemolytic as DQ12. Crystalline silica-rich, flux-calcined samples were all unreactive, regardless of source. The potential toxicity of unprocessed and calcined samples was variable, and did not correlate with crystalline silica content. Calcium-rich phases, iron content, amorphous material, particle size and morphology all appeared to play a role in sample reactivity. An increased surface area was linked to an increased reactivity in vitro for some sample types.ConclusionsOverall, no single property of DE could be linked to its potential toxicity, but crystalline silica content was not a dominant factor. Occlusion of the potentially toxic crystalline silica surface by an amorphous matrix or other minerals and impurities in the crystal structure are suggested to pacify toxicity in these samples. In vivo verification is required, but these data suggest that crystalline silica content alone is not a sufficient indicator of the potential DE hazard.Electronic supplementary materialThe online version of this article (doi:10.1186/s12995-015-0064-7) contains supplementary material, which is available to authorized users.

Assessing the bioactivity of crystalline silica in heated high-temperature insulation wools

“…Due to its pathogenic behavior, DQ12 has often been used as a standard experimental quartz sample (BeruBe et al., 2009; Clouter et al., 2001). A strong pro-inflammatory cytokine response to DQ12 was observed in the present study, which aligns well with much of the existing in vitro literature (Bauer et al., 2012; Driscoll et al., 1996; Nattrass et al., 2015; Øvrevik et al., 2008; Westphal et al., 2015). Since the cytokine response to HTIW was considerably less than to DQ12, the biological significance of the HTIW induced cytokine/chemokine release observed needs to be considered since statistical significance does not always mean biological significance.…”

Industrial-Scale Decontamination Procedure Effects on the Content of Acaricides, Heavy Metals and Antioxidant Capacity of Beeswax

“…The increase in Si and As observed in the waxes after their filtration process is due to the use of diatomaceous earth as part of the filtering system. Indeed, Si represents more than 85% of diatomaceous earth composition [29], and it is possible that it is partly transferred to the filtered matrix. Furthermore, arsenic may represent around 0.2 to 0.5% of diatomaceous earth composition [29].…”

“…Indeed, Si represents more than 85% of diatomaceous earth composition [29], and it is possible that it is partly transferred to the filtered matrix. Furthermore, arsenic may represent around 0.2 to 0.5% of diatomaceous earth composition [29]. The transfer of arsenic that occurs during the filtration process with diatomaceous earth of alcoholic beverages has been described [30].…”

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“…HSCs niche in bone marrow is a complex microenvironment comprised of HSCs subpopulation and lineage-committed hematopoietic progenitors that are vital for the maintenance of haematopoiesis [ 17 , 18 ]. HSCs and hematopoietic progenitors are precursor cells that are capable to self-renew and differentiate to form a particular type of new blood cell under the regulation of intrinsic factors (e.g., signaling pathway or transcription factors) and extrinsic factors (cytokines or growth factors) [ 19 ].…”