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Respiratory effects of volcanic emissions
  1. A L Hansell
  1. Dept of Epidemiology & Public Health, Imperial College London, Norfolk Place, London W2 1PG, UK; a.hansell{at}imperial.ac.uk

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    Although at least 455 million people worldwide live within potential exposure range of a volcano active within recorded history,1 surprisingly little primary epidemiological research on the health effects of volcanic emissions has been published. The research by Forbes and colleagues2 on the respiratory effects of the eruptions in Montserrat is therefore very welcome. However, more studies are needed to determine the transferability of results to volcanic emissions elsewhere. There may be important differences between volcanoes and between events from the same volcano in terms of eruption pattern, gaseous emissions, base composition of ash (for example, cristobalite concentrations), compounds adsorbed onto ash particles (which may be volcanic in origin or derived from other pollution sources), the percentage of particles small enough to be respirable, and toxicological activity.3 For example, most respirable ash in Montserrat has originated from pyroclastic flows, with cristobalite concentrations measured at 20.1%, but Montserrat ash derived from phreatic explosions has lower cristobalite concentrations (8.6%)4 and these are higher than the 4.2% quoted for ash from the United States Mount St Helens eruptions in 1980.5 The Soufriere Hills volcano in Montserrat has produced unusually frequent pyroclastic flows, resulting in high exposures to fine ash even in residential areas distant from the volcano, but population exposure to volcanic gases such as sulphur dioxide has been low. This contrasts with volcanoes such as Sakurajima, Japan where frequent ashfalls have been accompanied by SO2 emissions6 or Kilauea, Hawaii where emissions are predominantly SO2.7

    Studies of health effects of volcanic ash exposure may help elucidate mechanisms relevant to action of anthropogenic pollution. For example, it remains unclear whether concentration or composition of anthropogenic particulate air pollution is more important for respiratory health effects.8 Montserrat children showed increased levels of wheeze and bronchial hyperreactivity following repeated exposures to high concentrations of respirable dust, with increased cristobalite content but low soluble acid content and low in vitro9 and in vivo4 bioreactivity in toxicological studies. Long term exposure to high levels of cristobalite might be expected to be associated with reductions in lung volumes, not presented in this study, rather than with increased bronchial reactivity. This raises the possibility that the effect of Montserrat ash on bronchial reactivity may have been related to the quantity rather than the quality of the particulates.

    Finally, it is unclear whether a peak flow meter or hand held spirometer was used in the Montserrat study. A hand held spirometer is suggested as the ideal measuring tool for field investigations into respiratory effects of volcanic emissions in children. It can be used reliably in children as young as 5 years, and gives a range of readings including FEV1, which has better baseline reproducibility than peak flow,10 and lung volumes, which may be particularly useful if follow up studies into long term effects are planned.

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