Experimental design and data relevance in a volcanic ash-leachate health study: Letter to the Editor re. Barone et al. (2021) ‘Surface reactivity of Etna volcanic ash and evaluation of health risks’

Characterizing the health hazards posed by volcanic ash is of great importance so that agencies and communities can make informed decisions regarding protection of the population during eruptions or ash resuspension after eruptions. Barone et al. (2021) set out to contribute to this important field through study of volcanic ash from Mt. Etna, Italy, an active volcano that erupts frequently and is surrounded by a relatively large population, with the aim of evaluating gastric and respiratory exposures. Their ash leachate studies are particularly important: the authors state that ‘Etna is the main aquifer in eastern Sicily’, therefore determining the impacts of eruptions on water resources is critical for safeguarding human health. However, we have concerns over aspects of the methodology, the data presented, and the conclusions reached.
From the outset, we find the title to be misleading in that the authors claim to have evaluated the health risks of Etna volcanic ash. Assessment of health risk is very different from hazard assessment, the former requiring incorporation of data on exposure concentrations, populations at risk, background morbidity and mortality rates, and the hazard of the toxicant being studied (UNISDR, 2017). Mueller et al. (2020) have recently outlined how such a risk assessment should be done for volcanic ash. Barone et al. (2021) actually attempt to evaluate the health hazard of the ash, but we find that the analysis is flawed for the reasons that we outline in this letter.