Volcanoes and their eruptions can result in a wide range of health impacts, arguably more varied than in any other kind of natural disaster. At least 500 million people worldwide live within potential exposure range of a volcano that has been active within recorded history. Many volcanic and geothermal regions are densely populated and several are close to major cities, threatening local populations (fig 1). Volcanic activity can also affect areas hundreds or thousands of kilometres away, as a result of airborne dispersion of gases and ash, or even on a hemispheric to global scale due to impacts on climate. Healthcare workers and physicians responding to the needs of volcanic risk management might therefore find themselves involved in scenarios as varied as disaster planning, epidemiological surveillance, treating the injured, or advising on the health hazards associated with long range transport of volcanic emissions.

The 1980 Mount St Helens eruption,¹ which resulted in fallout of ash across large areas of Washington and surrounding states, acted as a major stimulus to research into health hazards associated with volcanoes. This field, which had received little attention previously, now represents a mainstream in volcanological research, and is increasingly being addressed by multidisciplinary efforts with contributions from mineralogy, geochemistry, epidemiology, clinical medicine, toxicology, and healthcare planning, as well as volcanology. The aim of this article is to introduce the health hazards associated with volcanic phenomena and current approaches to risk management.

BASIC GEOLOGY OF VOLCANOES

Volcanoes are chiefly associated with tectonic plate margins.^2,3 The majority of destructive eruptions in history have occurred on continental margins or island arcs where the edge of one tectonic plate drops beneath another (a process known as subduction). Most are recognisably “volcano-shaped”—tall …