Environmental and anthropogenic factors affecting the respiratory toxicity of volcanic ash

Abstract

The potential adverse health outcomes of exposure to inhalable volcanic ash have been a long-standing concern, especially as it is known that respirable-sized particles can potentially contribute towards the onset or exacerbation of respiratory and cardiovascular diseases. In recent years, substantial knowledge of the posed respiratory hazard, alongside extensive characterisation of the physicochemical properties of volcanic ash that may influence its biological reactivity, has been obtained. However, knowledge of how external factors, including the volcanic plume, itself, and anthropogenic pollutants, may alter potential ash toxicity and contribute to any adverse respiratory health effects is limited.
Using novel, multidisciplinary approaches and methods, across geochemistry and particle toxicology, this thesis is the first to assess whether ash particle coatings, which originate from in-plume reactions with volcanic gases, can contribute to or alter ash toxicity, as well as if concomitant exposure to volcanic and anthropogenic pollutants poses a greater respiratory hazard than the individual respiratory toxicities of either anthropogenic pollution or volcanic ash alone.
Combined exposure to respirable-sized volcanic and diesel exhaust particles was shown to induce (pro-)inflammatory response in a multicellular human lung model in vitro, implying a potentially-greater hazard of simultaneously inhaling both particle types. However, no significant toxicological effects of in-plume processing or co-exposures with complete (gasoline) exhaust were found. The fact that sulphate salts dissolve rapidly, likely prior to cellular uptake, is a finding which helps explain why the salt-laden samples had no toxicological impact.
Although further work is required to derive a more comprehensive understanding of the interactions of volcanic ash and urban pollutants in the ambient air and potential impacts of co-exposures, the findings of this thesis provide the first evidence which can be used towards the assessment of respiratory health hazard following the onset of new volcanic activity where exposed communities live in heavily polluted urban areas.