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The in vitro respiratory toxicity of cristobalite-bearing volcanic ash

Damby, D.E.; Murphy, F.A.; Horwell, C.J.; Raftis, J.; Donaldson, K.

The in vitro respiratory toxicity of cristobalite-bearing volcanic ash Thumbnail


D.E. Damby

F.A. Murphy

J. Raftis

K. Donaldson


Ash from dome-forming volcanoes poses a unique hazard to millions of people worldwide due to an abundance of respirable cristobalite, a crystalline silica polymorph. Crystalline silica is an established respiratory hazard in other mixed dusts, but its toxicity strongly depends on sample provenance. Previous studies suggest that cristobalite-bearing volcanic ash is not as bio-reactive as may be expected for a dust containing crystalline silica. We systematically address the hazard posed by volcanic cristobalite by analysing a range of dome-related ash samples, and interpret the crystalline silica hazard according to the mineralogical nature of volcanic cristobalite. Samples are sourced from five well-characterized dome-forming volcanoes that span a range of magmatic compositions, specifically selecting samples rich in cristobalite (up to 16 wt%). Isolated respirable fractions are used to investigate the in vitro response of THP-1 macrophages and A549 type II epithelial cells in cytotoxicity, cellular stress, and pro-inflammatory assays associated with crystalline silica toxicity. Dome-related ash is minimally reactive in vitro for a range of source compositions and cristobalite contents. Cristobalite-based toxicity is not evident in the assays employed, supporting the notion that crystalline silica provenance influences reactivity. Macrophages experienced minimal ash-induced cytotoxicity and intracellular reduction of glutathione; however, production of IL-1β, IL-6 and IL-8 were sample-dependent. Lung epithelial cells experienced moderate apoptosis, sample-dependent reduction of glutathione, and minimal cytokine production. We suggest that protracted interaction between particles and epithelial cells may never arise due to effective clearance by macrophages. However, volcanic ash has the propensity to incite a low, but significant, and sample-dependent response; the effect of this response in vivo is unknown and prolonged exposure may yet pose a hazard.


Damby, D., Murphy, F., Horwell, C., Raftis, J., & Donaldson, K. (2016). The in vitro respiratory toxicity of cristobalite-bearing volcanic ash. Environmental Research, 145, 74-84.

Journal Article Type Article
Acceptance Date Nov 17, 2015
Online Publication Date Dec 6, 2015
Publication Date 2016-02
Deposit Date Nov 18, 2015
Publicly Available Date Mar 31, 2016
Journal Environmental Research
Print ISSN 0013-9351
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 145
Pages 74-84


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