Dr Claire Horwell

Director of IVHHN
Associate Professor

Institute of Hazard, Risk & Resilience
Department of Earth Sciences
Durham University
Science Labs., South Road

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Research Expertise


Claire Horwell is currently involved in several areas of volcanic health hazard research:

  1. Rapid physicochemical characterisation of volcanic ash particles to determine their respiratory toxicity during volcanic crises.
  2. Fundamental research to determine the factors that control the potential toxicity of volcanic ash. This includes investigating the nature of the particles themselves (particularly crystalline silica), and external factors such as anthropogenic pollution which may interact with ash to alter its reactivity (VERTIGO).
  3. How and whether communities protect themselves from inhalation of volcanic emissions (ash and gas) around the world. This involves laboratory studies, on the effectiveness of different forms of respiratory protection, social surveys on how communities perceive the hazard and protect themselves, and a clinical trial on the health benefits of wearing respiratory protection (for asthmatics). This research is being conducted as part of the HIVE and Hawaii Vog projects.


Relevant Publications

Stewart, C., Horwell C.J., Plumlee, G., Cronin, S., Delmelle, P., Baxter, P., Calkins, J., Damby, D.E., Morman, S. & Oppenheimer, C. (2013) ‘Protocol for analysis of volcanic ash samples for assessment of hazards from leachable elements’. Available at: www.ivhhn.org/
Weinstein, P., Horwell, C. J. & Cook, A. (2013) ‘Volcanic emissions and health’, Essentials of Medical Geology, Springer Netherlands, 217-238.
Damby, D. E., Horwell, C. J., Baxter, P. J., Delmelle, P., Donaldson, K., Dunster, C., Fubini, B., Murphy, F.A., Nattrass, C., Sweeney, S., Tetley, T.D., & Tomatis, M. (2013) ‘The respiratory health hazard of tephra from the 2010 Centennial eruption of Merapi with implications for occupational mining of deposits’, Journal of Volcanology and Geothermal Research, 261, 376-387.
Horwell, C. J., Baxter, P. J., Hillman, S. E., Calkins, J. A., Damby, D. E., Delmelle, P., Donaldson, K., Dunster, C., Kelly, F.J., Le Bond, J.S., Livi, K.J., Murphy, F., Nattrass, C., Sweeney, S., Tetley, T.D., Thordarson, T., & Tomatis, M. (2013) 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’, Environmental Research, 127, 63-73.
Hillman, S.E., Horwell, C.J., Densmore, A., Damby, D.E., Fubini, B., Ishimine, Y. and Tomatis, M. (2012) ‘Sakurajima volcano: a physico-chemical study of the health consequences of long-term exposure to volcanic ash’, Bulletin of Volcanology, 74: 913–930.
Horwell, C. J., Stannett, G. W., Andronico, D., Bertagnini, A., Fenoglio, I., Fubini, B., Le Blond, J. S., & Williamson, B. J. (2010) ‘A physico-chemical assessment of the health hazard of Mt. Vesuvius volcanic ash’, Journal of Volcanology and Geothermal Research, 191(3-4), 222-232. 
Horwell, C.J., Le Blond, J.S., Michnowicz, S.A.K. and Cressey, G. (2010) ‘Cristobalite in a rhyolitic lava dome: Evolution of ash hazard’, Bulletin of Volcanology, 72: 249–253.
Martin, R. S., Mather, T. A., Pyle, D. M., Power, M., Tsanev, V. I., Oppenheimer, C., Allen, A. G., Horwell, C. J. & Ward, E.P.W. (2009) 'Size distributions of fine silicate and other particles in Masaya's volcanic plume', Journal of Geophysical Research – Atmospheres, 114, D9.
Le Blond, J.S., Cressey, G., Horwell, C.J. & Williamson, B.J. (2009) ‘A rapid method for quantifying single mineral phases in heterogeneous natural dust using X-ray diffraction’, Powder Diffraction, 24: 17-23.
Martin, R.S., Mather, T.A., Pyle, D.M, Power, M., Allen, A.G., Aiuppa, A., Horwell, C.J. and Ward E.P.W. (2008) ‘Chemical and morphological characterisation of volcanic aerosols and nanoparticles from Mt Etna’, Journal of Geophysical Research – Atmospheres, 113, D17211.
Le Blond, J.S., Williamson, B.J., Horwell, C.J., Monro, A.K., Kirk, C.A. and Oppenheimer, C. (2008) ‘Production of potentially hazardous respirable silica airborne particulate from the burning of sugarcane’, Atmospheric Environment, 44, 5558-5568.
Horwell, C.J. (2007) ‘Grain size analysis of volcanic ash for the rapid assessment of respiratory health hazard’, Journal of Environmental Monitoring, 9(10), 1107 - 1115. Also see article: “Sizing up the danger of volcanic ash” by E. Morgan, Chemical Technology, RSC Publishing, 10, 2007.
Horwell, C.J., Fenoglio, I. & Fubini, B. (2007) ‘Iron-induced hydroxyl radical generation from basaltic volcanic ash’, Earth and Planetary Science Letters, 261(3-4): 662-669.
Stewart, C., Johnston, D.M., Leonard, G.S., Horwell, C,J., Thordarson, T., & Cronin, S.J. (2006) ‘Contamination of water supplies by volcanic ashfall: A literature review and simple impact modelling’, Journal of Volcanology and Geothermal Research, 158: 296-306.
Horwell, C.J. & Baxter, P.J. (2006) ‘The respiratory health hazards of volcanic ash: a review for volcanic risk mitigation’, Bulletin of Volcanology, 69: 1-24.
Hansell, A. Horwell, C.J. and Oppenheimer. (2006) ‘The health hazards of volcanoes and geothermal areas’, Occupational Environmental Medicine, 63: 149-156.
Witham, C.S., Oppenheimer, C. and Horwell, C.J. (2005) ‘Volcanic ash leachates: a review and recommendations for sampling methods’, Journal of Volcanology and Geothermal Research, 141, 299-326.
Horwell, C. J., Patterson, J. E., Gamble, J. A., & Allen, A. G. (2005) 'Monitoring and mapping of hydrogen sulphide emissions across an active geothermal field: Rotorua, New Zealand'Journal of Volcanology and Geothermal Research, 139(3-4), 259-269.
Horwell, C. J.,  Allen, A. G., Mather, T. A. & Patterson, J. E. (2004) 'Evaluation of a simple passive sampling technique for monitoring volcanogenic hydrogen sulphide'Journal of Environmental Monitoring, 6, 630-635.
Horwell, C.J., Fenoglio, I., Ragnarsdottir, K.V., Sparks, R.S.J. and Fubini, B. (2003) ‘Surface reactivity of volcanic ash from the eruption of Soufrière Hills volcano, Montserrat, with implications for health hazards’, Environmental Research, 93(2): 202-215.
Horwell, C.J., Sparks, R.S.J., Brewer, T.S., Llewellin, E.W. and Williamson, B.J. (2003) ‘The characterisation of respirable volcanic ash from the Soufriere Hills Volcano, Montserrat, with implications for health hazard’, Bulletin of Volcanology, 65: 346-362.
Horwell, C. J., Braña, L. P., Sparks, R.S.J., Murphy, M. D. & Hards, V. L. (2001) 'A geochemical investigation of fragmentation and physical fractionation in pyroclastic flows from the Soufrière Hills volcano, Montserrat', Journal of Volcanological Geothermal Research, 109, 247-262. 


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Latest News


Download our pamphlets on preparing for ashfall and on the health hazards of ash. They are designed for mass distribution at the onset of new eruptions. They are now avaiable in English, Japanese, French Spanish, Portuguese, Swahili, Indonesian and Icelandic with Italian versions being available shortly. Please see our Pamphlets page for further infomation.





IVHHN has an article under the Guidelines tab which used to be called 'Recommended Face Masks'. This has now been updated to 'Information on face masks' and is an interim page whilst the Health Interventions in Volcanic Eruptions project investigates which types of respiratory protection are effective in protecting the general population from volcanic ash inhalation. Please note that the translations in Spanish, Japanese and Portuguese have not yet been updated.



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