Physicochemical and toxicological profiling of ash from the 2010 and 2011 eruptions of Eyjafjallajökull and Grímsvötn volcanoes, Iceland using a rapid respiratory hazard assessment protocol

Our plain-English summary of Physicochemical and toxicological profiling of ash from the 2010 and 2011 eruptions of Eyjafjallajökull and Grímsvötn volcanoes, Iceland using a rapid respiratory hazard assessment protocol, by C.J. Horwell, P.J. Baxter, S.E. Hillman, et al (Environmental Research, 2013).

The study

• Authors: C.J. Horwell, P.J. Baxter, S.E. Hillman, J.A. Calkins, D.E. Damby, P. Delmelle, K. Donaldson, C. Dunster, B. Fubini, F.J. Kelly, J.S. Le Blond, K.J. Livi, F. Murphy, C. Nattrass, S. Sweeney, T.D. Tetley, T. Thordarson, M. Tomatis
• Journal: Environmental Research
• Published: 2013;127:63-73
• Cited by: 26 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

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.

Copyright © 2013 The Authors. Published by Elsevier Inc. All rights reserved.

In plain English

In this laboratory study, the authors tested volcanic ash from the 2010 Eyjafjallajökull eruption (14 samples) and the 2011 Grímsvötn eruption (12 samples) in Iceland. They compared it with 3 archived ash samples from Soufrière Hills volcano, Montserrat. They measured particle size, surface area, crystalline silica and particle shape, and ran cell-free tests and tests on human lung cells. Between 2 and 13 vol% of Eyjafjallajökull ash was finer than 4 micrometres, and Grímsvötn ash was coarser. Crystalline silica was 1.4 to 3.2 wt% in Eyjafjallajökull ash and undetectable in Grímsvötn ash, compared with 5.2 to 15.2 wt% cristobalite in Soufrière Hills ash. Very occasional fibre-like particles were found in one Eyjafjallajökull sample. They were made of glass, feldspar, gypsum or an unclassified iron/magnesium silicate that was not compositionally related to asbestos. Breakdown of red blood cells (haemolysis) was low for all samples tested. Tested ash from all three volcanoes produced a pro-inflammatory response in human lung cells lasting up to 5 days. The authors concluded that the toxicology assays they chose did not distinguish the pro-inflammatory potential of the three ash types, and that this chronic effect warrants further study.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory study: physicochemical analyses and in vitro (cell-free and human lung cell) toxicology tests on volcanic ash samples, using a rapid hazard assessment protocol
• Who was studied: Ground-deposited volcanic ash samples: 14 from Eyjafjallajökull (2010) and 12 from Grímsvötn (2011), Iceland, plus 3 archived Soufrière Hills (Montserrat) dome collapse ash samples from 1999, 2003 and 2009 used as a benchmark. Key mineralogical analyses were done on all samples and other tests on selected samples. Lung cell tests used human alveolar type-1 like epithelial cells (TT1).
• Exposure: Volcanic ash, analysed for respirable particle content, surface area, crystalline silica (cristobalite, quartz, tridymite), fibre-like particles, soluble metals, hydroxyl radical generation, oxidative capacity, haemolysis, cytotoxicity and inflammatory markers (IL-6, IL-8, MCP-1). No asbestos exposure was studied.
• Main results:
  • Eyjafjallajökull ash: 2 to 13 vol% of material was finer than 4 micrometres (respirable) and 4 to 26 vol% was finer than 10 micrometres (thoracic)
  • Grímsvötn ash was coarser: 0.0 to 3.5 vol% finer than 4 micrometres and 0.0 to 8.4 vol% finer than 10 micrometres
  • Crystalline silica was 1.4 to 3.2 wt% in Eyjafjallajökull samples and undetectable in Grímsvötn samples
  • The Soufrière Hills benchmark samples contained 5.2 to 15.2 wt% cristobalite and 1.2 to 1.6 wt% quartz
  • Very occasional respirable fibre-like particles were found in sample EYJ_10_13. They were made of glass, feldspar, gypsum or an unclassified iron/magnesium silicate not compositionally related to asbestos.
  • None of the fibre-like particles had asbestiform morphologies or compositions or contained cristobalite
  • Specific surface area of Eyjafjallajökull ash ranged from 0.3 to 7.7 square metres per gram
  • Grímsvötn ash generated between 0.6 and 2.8 micromoles per square metre of hydroxyl radicals after 30 minutes in a cell-free test
  • No tested sample showed oxidative activity in the lung lining fluid or ascorbate assays, and haemolysis was low for all samples tested (these tests were done on selected samples, not all samples)
  • Samples EYJ_10_13 and MBA20/12/09 caused significant acute TT1 cell death (30 to 40%) at doses the authors called physiologically unrealistic
  • The Eyjafjallajökull, Grímsvötn and Soufrière Hills samples tested each produced a pro-inflammatory response in TT1 cells over up to 5 days, and the effect on cytokine production persisted after the ash was removed
• The authors' conclusion: The authors concluded that the toxicology assays they chose did not discriminate between the pro-inflammatory potential of ash from the three volcanoes, and that the chronic pro-inflammatory effect seen in all three ash types warrants further study.
• Limitations the authors state:
  • Samples not collected immediately after deposition may have been exposed to moisture, which could affect particle surface composition and reactivity
  • Only 2 samples were obtained from Phase III of the Eyjafjallajökull eruption, so they may not be fully representative
  • In vitro tests are only general indicators of reactivity in the body
  • Water extraction of metals does not necessarily represent conditions in the lung
  • The TT1 cell model is new to volcanic ash studies

Topics

Medical terms in this study, explained in our Lexicon: Crystalline, Silicosis, Hydroxyl Radical, Mineralogy.

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