Using the Trace Element Contents in Bronchoalveolar Lavages to Probe the Human Exposure to Inhaled Particulates

Explosive volcanic eruptions eject large volumes of high surface area, metal-rich dust and ash into the atmosphere. In areas near major volcanic eruptions, humans often interact with these materials and may bioaccumulate heavy and toxic metals. To evaluate these interactions, we examine bronchoalveolar lavage samples (BAL) collected from people exposed to the paroxysmal 2001 Etna eruption. BAL samples reveal a strong enrichment of many toxic heavy metals and the capacity for trace elements released from inhaled particles to induce crystallisation of phosphatic microcryst biominerals in intraaveolar spaces. BAL rare earth element (REE) concentration patterns normalised to shale reveal a ‘V-shaped’ feature caused by the depletion of elements from Nd to Tb (mid-REEs) as compared to the variable enrichments of heavy lanthanides, Y, La and Ce. This pattern is consistent with solutions that experience phosphate mineral crystallisation in laboratory conditions and suggests that phosphate precipitation occurs in vivo in the lungs through interactions between volcanic particles and lung fluids. The BAL trace element patterns allow us to reconstruct the source of inhaled materials and depict the fluid mineral processes that occur between lung fluids and inhaled particles.