ORIGINAL ARTICLE

Pulmonary epithelial response in the rat lung to instilled Montserrat respirable dusts and their major mineral components

D G Housley¹, K A Bérubé¹, T P Jones², S Anderson¹, F D Pooley³, R J Richards¹

¹ School of Biosciences, Cardiff University, PO Box 911, Museum Avenue, Cardiff CF1 3US, Wales, UK
² Department of Earth Sciences, Cardiff University, PO Box 914, Park Place, Cardiff CF10 3YE, UK
³ School of Engineering, Cardiff University, PO Box 917, The Parade, Cardiff CF2 1XH, UK

Correspondence to:
Correspondence to:
Professor Roy Richards, School of Biosciences, Cardiff University, PO Box 911, Museum Avenue, Cardiff CF1 3US, Wales, UK;
RichardsRJ{at}Cardiff.ac.uk

Background: The Soufriere Hills, a stratovolcano on Montserrat, started erupting in July 1995, producing volcanic ash, both from dome collapse pyroclastic flows and phreatic explosions. The eruptions/ash resuspension result in high concentrations of suspended particulate matter in the atmosphere, which includes cristobalite, a mineral implicated in respiratory disorders.

Aims: To conduct toxicological studies on characterised samples of ash, together with major components of the dust mixture (anorthite, cristobalite), and a bioreactive mineral control (DQ12 quartz).

Methods: Rats were challenged with a single mass (1 mg) dose of particles via intratracheal instillation and groups sacrificed at one, three, and nine weeks. Acute bioreactivity of the particles was assessed by increases in lung permeability and inflammation, changes in epithelial cell markers, and increase in the size of bronchothoracic lymph nodes.

Results: Data indicated that respirable ash derived from pyroclastic flows (20.1% cristobalite) or phreatic explosion (8.6% cristobalite) had minimal bioreactivity in the lung. Anorthite showed low bioreactivity, in contrast to pure cristobalite, which showed progressive increases in lung damage.

Conclusion: Results suggests that either the percentage mass of cristobalite particles present in Montserrat ash was not sufficient as a catalyst in the lung environment, or its surface reactivity was masked by the non-reactive volcanic glass components during the process of ash formation.

Keywords: ash; bioreactivity; cristobalite; inflammation; lung; quartz

Abbreviations: GGT, glutamyltransferase; IA, image analysis; PMN, polymorphonuclear leucocyte; TEM, transmission electron microscopy; XRD, x ray diffraction; XRF, x ray fluorescence

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