The six week eruption of Eyjafjallajökull volcano in 2010 produced heavy ash fall in a sparsely populated area of southern and south eastern Iceland and disrupted European commercial flights for at least 6 days. We adopted a protocol for the rapid analysis of volcanic ash particles, for the purpose of informing respiratory health risk assessments. Ash collected from deposits underwent a multi-laboratory physicochemical and toxicological investigation of their mineralogical parameters associated with bio-reactivity, and selected in vitro toxicology assays related to pulmonary inflammatory responses. Ash from the eruption of Grímsvötn, Iceland, in 2011 was also studied. The results were benchmarked against ash from Soufrière Hills volcano, Montserrat, which has been extensively studied since the onset of eruptive activity in 1995. For Eyjafjallajökull, the grain size distributions were variable: 2-13 vol% of the bulk samples were <4 µm, with the most explosive phases of the eruption generating abundant respirable particulate matter. In contrast, the Grímsvötn ash was almost uniformly coarse (<3.5 vol%<4 µm material). Surface area ranged from 0.3 to 7.7 m2 g(-1) for Eyjafjallajökull but was very low for Grímsvötn (<0.6 m2 g(-1)). There were few fibre-like particles (which were unrelated to asbestos) and the crystalline silica content was negligible in both eruptions, whereas Soufrière Hills ash was cristobalite-rich with a known potential to cause silicosis. All samples displayed a low ability to deplete lung antioxidant defences, showed little haemolysis and low acute cytotoxicity in human alveolar type-1 like epithelial cells (TT1). However, cell-free tests showed substantial hydroxyl radical generation in the presence of hydrogen peroxide for Grímsvötn samples, as expected for basaltic, Fe-rich ash. Cellular mediators MCP-1, IL-6, and IL-8 showed chronic pro-inflammatory responses in Eyjafjallajökull, Grímsvötn and Soufrière Hills samples, despite substantial differences in the sample mineralogy and eruptive styles. The value of the pro-inflammatory profiles in differentiating the potential respiratory health hazard of volcanic ashes remains uncertain in a protocol designed to inform public health risk assessment, and further research on their role in volcanic crises is warranted.

Publisher's copyright statement:The original publication is available at www.springerlink.com Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. were available for determination of whether the ash was sufficiently fine to present a 33 respiratory hazard. In this study, we review the existing studies and carry out mineralogical, 34 geochemical and toxicological analyses to address whether the ash from Sakurajima has the 35 potential to cause respiratory health problems. The results show that the amount of respirable 36 (< 4 μm) material produced by the volcano is highly variable in different eruptions (1.1-18.8 37 vol. %). The finest samples derive from historical, plinian eruptions but considerable 38 amounts of respirable material were also produced from the most recent vulcanian eruptive 39 phase (since 1955). The amount of cristobalite, a crystalline silica polymorph which has the 40 potential to cause chronic respiratory diseases, is ~3-5 wt. % in the bulk ash. SEM and TEM 41 imaging showed no fibrous particles similar to asbestos particles. Surface reactivity tests 42showed that the ash did not produce significant amounts of highly reactive hydroxyl radicals 43

Abstract:The Soufrière Hills Volcano (SHV) crystallizes cristobalite (crystalline silica) in its lava domes, and inhalation of cristobaliterich ash may pose a chronic respiratory hazard. We investigate the causes of variation in cristobalite abundance (measured by X-ray diffraction) in ash from dome collapses, explosions and ash venting from 1997 to 2010.Cristobalite abundance in bulk dome-collapse ash varies between 4 and 23 wt%. During periods of slow lava extrusion (,5 m 3 s 21 ), cristobalite is abundant (7-23 wt%), which we attribute to extensive devitrification in slow-cooling lava; it can also form rapidly (15 wt% in 2 months), but we find no correlation between cristobalite abundance and dome residence time (DRT). By contrast, during rapid extrusion (.5 m 3 s 21), cristobalite abundance is low (4-7 wt%, similar to that associated with Vulcanian explosions), and correlates strongly with DRT. We attribute this correlation to progressive vapour-phase mineralization or devitrification, and the lack of contamination by older lava. Cristobalite abundance is expected to be .7 wt% for collapse of slowly extruded lava, for ash venting through a dome or for incorporation of hydrothermally altered edifice during explosions; cristobalite abundance is expected to be ,7 wt% for collapse of rapidly extruded lava, for ash venting without dome incorporation and from Vulcanian explosions at SHV. Gold Open Access:This article is published under the terms of the CC-BY 3.0 license.Cristobalite is a high-temperature, low-pressure crystalline silica polymorph that may crystallize as a meta-stable phase in dome lavas, and persists at ambient conditions. In industrial settings, the silica polymorphs of quartz, cristobalite and tridymite are capable of causing silicosis, a fibrotic lung disease. Crystalline silica is also classed as a Group 1 human carcinogen by the International Agency for Research on Cancer (IARC 1997). The discovery of cristobalite in the volcanic ash from the 18 May 1980 eruption of Mount St Helens, USA, prompted intensive research to determine the silicosis risk from inhaling the ash (e.g. Dollberg et al. 1986), but the evidence from a series of toxicological, epidemiological and clinical studies at the time was inconclusive on this point (see Horwell & Baxter 2006 for a review). In the event, exposure was short-lived and this substantially reduced public concern. Today, the chronic pathogenicity of cristobalite in volcanic ash is still under debate .The Soufrière Hills Volcano (SHV), Montserrat began its current eruption in July 1995. Lava dome growth started in late 1995 and has continued, intermittently, in a series of five phases (Wadge et al. 2014). Lava domes are inherently unstable, and are prone to partial or full collapses that generate pyroclastic density currents (PDCs) and associated co-PDC ash plumes. There have also been more than 100 Vulcanian explosions during the eruption. Baxter et al. (1999) observed that cristobalite is generated within the Soufrière Hills dome and is abundant in the co-P...

Mount Etna is Europe's largest and most active volcano. In recent years, it has displayed enhanced explosive activity, causing concern amongst local inhabitants who frequently have to live with, and clean up, substantial ashfall. Basaltic volcanic ash is generally considered unlikely to be a respiratory health hazard due to its often coarse nature (with few particles sub-10 μm diameter) and lack of crystalline silica. However, a previous study by the authors showed the capability of basaltic ash to generate the hydroxyl radical, a highly-reactive species which may cause cell damage. That study investigated a single sample of Etna ash, amongst others, with data giving an early indication that the Etnean ash may be uniquely reactive. In this study, we analyse a suite of Etnean samples from recent and historical eruptions. Deposits indicate that Etna's past history was much more explosive than current activity, with frequent sub-plinian to plinian events. Given the recent increase in explosivity of Etna, the potential hazard of similarly, or more-explosive, eruptions should be assessed. A suite of physicochemical analyses were conducted which showed recent ash, from 2001 and 2002 explosive phases, to be of similar composition to the historical deposits (trachy-basaltic) but rather coarser (< 2.4 c.v.% sub-10 μm material and <11.5 c.v.% sub-10 μm material, respectively), but the potential for post-depositional fragmentation by wind and vehicles should not be ignored. One recent sample contained a moderate number of fibre-like particles, but all other samples were typical of fine-grained ash (blocky, angular with electrostatic or chemical aggregation of finer particles on larger ones). The surface reactivity analyses (Fenton chemistry, on samples from recent eruptions only) showed that Etnean ash is more reactive in hydroxyl radical generation than other basaltic ash, and samples of intermediate composition. This high reactivity suggests that Etnean ash could promote oxidative stress in exposed cells. Therefore, further investigation of the potential toxicity, through cellular tests, is now warranted in order to provide a comprehensive health hazard assessment.