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Grain-size analysis of volcanic ash for the rapid assessment of respiratory health hazard

Horwell, C.J.



Volcanic ash has the potential to cause acute and chronic respiratory diseases if the particles are sufficiently fine to enter the respiratory system. Characterization of the grain-size distribution (GSD) of volcanic ash is, therefore, a critical first step in assessing its health hazard. Quantification of health-relevant size fractions is challenging without state-of-the-art technology such as the laser diffractometer. Here, several methods for GSD characterization for health assessment are considered, the potential for low-cost measurements is investigated and the first database of health-pertinent GSD data are presented for a suite of ash samples from around the world. Methodologies for accurate measurement of the GSD of volcanic ash by laser diffraction are presented by experimental analysis of optimal refractive indices for different magmatic compositions. Techniques for representative sampling of small quantities of ash are also experimentally investigated. GSD results for health-pertinent fractions for a suite of 49 ash samples show that the fraction of respirable (< 4 µm) material ranges from 0-17 vol. %, with the variation reflecting factors such as the style of the eruption and the distance from the source. A strong correlation between the amount of < 4 and < 10 μm material is observed for all ash types. This relationship is stable at all distances from the volcano and with all eruption styles and can be applied to volcanic plume and ash fallout models. A weaker relationship between the < 4 and < 63 μm fractions provides a novel means of estimating the quantity of respirable material from data obtained by sieving.


Horwell, C. (2007). Grain-size analysis of volcanic ash for the rapid assessment of respiratory health hazard. Journal of environmental monitoring, 9, 1107-1115.

Journal Article Type Article
Publication Date Jan 1, 2007
Deposit Date Oct 3, 2008
Journal Journal of Environmental Monitoring
Print ISSN 1464-0325
Electronic ISSN 1464-0333
Publisher Royal Society of Chemistry
Peer Reviewed Peer Reviewed
Volume 9
Pages 1107-1115
Keywords Grain size, Volcanic ash, Laser diffraction, Health, Respiratory disease, Techniques.