A Mineralogical and Geochemical Assessment of the Potential Respiratory Health Hazard of Ash from Sakurajima Volcano, Japan.

Abstract

Sakurajima Volcano, Kyushu Island is the most active volcano in Japan. Vulcanian eruptions have occurred almost constantly since 1955, and it continues to erupt hundreds of times a year, repeatedly affecting local populations and the environment. Over the past 30 years, multidisciplinary research has been carried out to determine whether volcanic ash is a respiratory health hazard. Some medical work has been carried out at Sakurajima volcano, all of which gave varying results (from toxic to inert) depending on the study design. Here, I use mineralogical and geochemical analyses to address whether the ash from Sakurajima has the potential to be toxic. Ash from the recent eruptions and also historical, plinian eruptions was examined in order to assess the current, and the possible future, potential risk.

The results show that the amount of respirable (< 4 µm) material produced by the volcano is very variable (1.10 - 18.77 vol. %). The finest samples derived from the plinian eruptions but considerable amounts of respirable material were also produced on occasion, from the most recent eruptive phase. The amount of crystalline silica was investigated to determine the potential for the development of chronic respiratory diseases. In general ~7 wt. % cristobalite was found, but no other silica polymorphs were observed. SEM imaging showed no fibrous particles that could cause symptoms similar to asbestos. Surface tests showed that the ash did not produce significant amounts of damaging hydroxyl radicals (0.02-0.1 µmol m-2). The results weakly correlated with the amount of surface iron available to react in the lungs. The findings suggest that the toxicity of the ash is low, but the potential hazard may be increased due to the long timescales for exposure.