Potentially harmful elements released by volcanic ash of the 2021 Tajogaite eruption (Cumbre Vieja, La Palma Island, Spain): Implications for human health

This study assesses the potential impacts on human health of volcanic ash emitted during the 2021 Tajogaite eruption (La Palma Island, Spain). Ash samples were physically and chemically characterized and leaching tests (with deionized water and acidic solution) were performed according to the IVHHN protocols to elucidate i) the leachable elements that may affect water quality and represent a potential threat for livestock and humans through drinking water supply; and ii) the bioaccessible fraction of toxicants able to be solubilized from ash surfaces if ashes are incidentally ingested by children. The most abundant readily water-soluble compounds were SO₄, F, Cl, Na, Ca, Ba, Mg, and Zn. Fluoride and chloride (up to 1085 and 1347 mg/kg) showed higher values in distal ash samples than closer ones. The potential F availability assessed from water leachates may suggest important environmental and health implications. In addition, long-term health hazard due to a long-term weathering of tephra deposits should be possible as confirmed by the greater amount of F extracted by acidic solution. Concentration of other trace elements (e.g., As, V, Mn, Mo, Cr, Fe, Se, Ti, Pb) were low compared to global medians and within the range globally assessed. Indicative calculation of hazard for water supply showed that F concentration may exceed both the recommended value (1 mg/L) for irrigation purpose and the health-based drinking water limits of 1.5 mg/L (for humans) and 2 mg/L (for livestock). If the predicted concentrations in water were compared with the toxicologically dose, F showed a potential health-risk for children through drinking water. The indicative health-risk characterization via accidental ash ingestion showed that the direct exposure does not represent a primary source of F daily intake for children. This important outcome confirmed F as element with the greatest health threat during Tajogaite 2021 eruption.