Experimental Evaluation of the Threshold Limit∗ of Cristobalite—Calcined Diatomaceous Earth

Wagner, W.; Fraser, David A.; Wright, Patricia G.; Dobrogorski, Olga J.; Stokinger, Herbert E.

doi:10.1080/00028896809342991

Cited by 5 publications

(3 citation statements)

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“…The low reactivity of all flux-calcined samples agrees with previous reports on discrete samples [ 24 , 25 , 27 , 31 ]. Ghiazza et al [ 27 ] suggested that the low levels of cytotoxicity, lipid peroxidation and NO synthesis caused by crystalline silica-rich flux-calcined DE was due to the formation of a vitreous rim during flux-calcination, which obscured cell exposure to cristobalite in these samples.…”

Section: Discussionsupporting

confidence: 91%

“…While inhalation of unprocessed DE (170 million particles per cubic foot (mppcf)) by guinea pigs for 39–44 h/week for 24 months resulted in fibrosis, calcined, cristobalite-rich DE was seen to cause more severe fibrosis more rapidly [ 30 ]. However, in a separate study, exposure via inhalation to 5–50 mppcf flux-calcined DE, consisting of 61 % cristobalite, for 30 h/week up to 30 months caused no body weight loss or pulmonary fibrosis in rats, guinea pigs or dogs [ 31 ].…”

Section: Introductionmentioning

confidence: 99%

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

Nattrass

Horwell

Damby

et al. 2015

J Occup Med Toxicol

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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.

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Section: Discussionsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

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

Nattrass

Horwell

Damby

et al. 2015

J Occup Med Toxicol

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“…20 Few in vitro studies have been conducted on diatomaceous earths. Dusts cytotoxic towards macrophages in vitro usually cause fibrosis in animal studies2' -23; thus the crystalline silicas quartz, tridymite, and cristobalite are cytotoxic.…”

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confidence: 99%

In vitro cytotoxicity and quantitative silica analysis of diatomaceous earth products.

Bye¹,

Davies²,

Griffiths³

et al. 1984

Occupational and Environmental Medicine

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Mouse peritoneal macrophages were used to evaluate the relative cytotoxicity of a series of diatomaceous earth products in vitro. The amorphous and crystalline silica content of the products was determined by a combination of infrared spectroscopy and x ray powder diffraction techniques. The cytotoxicities of the high cristobalite content flux calcined materials were similar to that of the standard cristobalite ; both the natural and straight calcined materials had significantly greater activities than the flux calcined materials. Thus within the limitations of the macrophage cytotoxicity test the hypothesis that crystalline content is the only determinant of fibrogenicity of diatomaceous earth is not supported.

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The effect of aluminium and sodium impurities on the in vitro toxicity and pro-inflammatory potential of cristobalite

Nattrass

Horwell

Damby

et al. 2017

Environmental Research

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Experimental Evaluation of the Threshold Limit∗ of Cristobalite—Calcined Diatomaceous Earth

Cited by 5 publications

References 5 publications

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

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

In vitro cytotoxicity and quantitative silica analysis of diatomaceous earth products.

The effect of aluminium and sodium impurities on the in vitro toxicity and pro-inflammatory potential of cristobalite

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