Rare earth elements in the Loire Estuary (France): Environmental and health risk assessment

Rare Earth Elements (REEs) comprise a group of 17 metals that have seen a considerable increase in industrial and medical use over recent decades. The presence of REEs has previously been documented in both water and sediments in the Loire Estuary (France). Bioaccumulation of these elements has also been reported in European eels (Anguilla anguilla) of different life stages (yellow and silver) and in both genders. The present study focusses on determining the speciation and bioaccessibility of REEs in the estuary sediment and on assessing its influence on REE accumulation in eels. In addition, the environmental and human health risks associated with REE contamination were evaluated. Results from the sequential chemical extractions showed that 34 to 50% of the total REEs measured from triacid mineralization occurred in potentially bioaccessible fractions, with bioaccessibility increasing from light to heavy REEs. The kidneys, gills, and livers were identified as the main organs for the accumulation of light REEs and Y in all eel groups. Sediment-to-biota transfer was assessed using biota sediment accumulation factors (BSAFs), considering the concentrations measured in sediment and eel tissues. BSAF values varied according to the REE considered, the organ, gender, and life stage, but showed no clear relationship with sediment bioaccessibility. Most BSAF values were lower than unit, indicating low bioaccumulation from sediments. Finally, the environmental and sanitary risks, associated with the REE levels in the Loire Estuary, were estimated. The Risk Assessment Code revealed a potential environmental risk associated with the presence of all REEs in sediment whereas the Estimated Daily Intake indicated no significant risk to human health from consuming eel muscle.