Volcanic and Geothermal Processes: Health Effects

Volcanic and geothermal events are among the most dramatic of all natural phenomena, and they pose numerous risks to human health. Volcanic vents and fissures provide a conduit by which magma - the molten rock, gases, and water within the earth - may disperse and cause illness in exposed communities. The majority of casualties due to volcanic activity in the past few centuries are result of pyroclastic flows, lahars, and suffocation or building collapse from ash or debris; tsunamis, which may spread for hundreds of miles; and indirect consequences of eruptions, such as famine or infectious disease outbreaks. As with many other disasters, population displacement secondary to volcanic emergencies creates attendant problems of poor sanitation, overcrowding, and contamination of food or water sources. Apart from the thermal and physical injuries resulting from an eruption, ejecta may also contain toxic elements and compounds, including silica, fluoride, and heavy metals, which may lead to risks of acute or chronic toxicity. These compounds may be carried within eruptive columns, plumes, or runoffand thus have health impacts at a significant distance from the active site. Geological data generated before, during, and subsequent to eruptions is of major importance in the public health response and can assist in minimizing death and illness.