HEALTH IMPLICATIONS OF THE MOUNT ST. HELENS' ERUPTION: LABORATORY INVESTIGATIONS

Abstract

A dry sedimented sample of Mount St. Helens volcanic ash was subjected to mineralogical and in vitro and in vivo biologic tests in order to define its potential for harm to exposed worker populations. The majority of the ash particles were within the respirable range and belonged to the plagioclase class of minerals. Free crystalline silica constituted 7.2% of the sample. In vitro biologic tests using varying concentrations of ash indicated the ash to be mildly fibrogenic. This was confirmed in vivo . Ash extracts were not mutagenic in two microbial assay systems and particulate ash had no effect on interferon production by monkey kidney cell monolayers or on the human complement system in vitro . Marked inhibition of the antibacterial substance, superoxide anion, from zymosan and ash exposed alveolar macrophages, suggests volcanic ash may impair antibacterial host defence mechanisms. Long-term inhalation and prospective autopsy studies of the exposed population are in progress.