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Rare earth elements (REEs) encompass 15 lanthanides and play a crucial role in modern technology. Despite their essential uses, REEs are emerging environmental contaminants due to their growing presence in industrial, agricultural, and medical applications. For the first time, the species sensitivity distribution (SSD) approach was applied to REEs considering 58 papers including toxicity about Ce, Dy, Er, Gd, La, Lu, Nd, Pr, Sm, and Y. SSD curves were constructed by log-logistic model providing comprehensive comparisons of the sensitivities of different species to the relative REEs deriving the hazardous concentrations (HC) at 5 % and 50 %. The review reveals that arthropods, especially Daphnia magna, and echinoderms such as Sphaerechinus granularis exhibit high sensitivity especially to Ce, Er, and Lu. Conversely, vertebrates, particularly Oncorhynchus mykiss, showed greater tolerance to REEs exposure. The general hazard perception evidenced the following prioritization list according to HC 5 values in increasing order: Dy (0.03 μg/l) > Ce (0.15 μg/l) > Sm (0.29 μg/l) > La (0.64 μg/l) > Y (0.81 μg/l) > Gd (0.95 μg/l) > Pr (1.44 μg/l) > Er (1.45 μg/l) > Nd (1.67 μg/l) > Lu (2.19 μg/l). This review highlighted gaps in REEs ecotoxicity, particularly regarding heavy REEs (HREEs), and stressed the need for more data on their long-term one-health impacts. Such knowledge is vital for developing strategies to mitigate REEs contamination, emphasizing the importance of establishing safe exposure thresholds to protect both ecosystems and human health., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Significant release of rare earth elements (REEs) into the environment is mainly due to active or abandoned mining sites, but their presence is globally increasing due to their use in several industrial sectors. The effects on primary producers as Raphidocelis subcapitata are still limited. This research focused on La and Ce as the two most widespread REEs that can be currently found up to hundreds of μg/L in water and wastewater. Microalgae were exposed to La and Ce for 3 days (pH = 7.8) (short-term exposure) to derive the effective concentrations inhibiting the growth on 10% (EC10) of the exposed population. EC10 values (0.5 mg/L of La and 0.4 mg/L of Ce) were used for the 28 days long-term exposure (renewal test) to observe after 7, 14, 21, and 28 days on a multi-endpoint basis microalgae growth inhibition (GI), biomarkers of stress (reactive oxygen species (ROS), superoxide dismutase (SOD), and catalase (CAT)), and bioconcentration. Results evidenced that La and Ce EC10 increased GI (day 28) up to 38% and 28%, respectively. ROS, CAT, and SOD activities showed differential responses from day 7 to day 14, 21, and 28, suggesting, in most of the cases, that La and Ce effects were counteracted (i.e., being the values at day 28 not significantly different, p > 0.05, from the relative negative controls), except for La-related ROS activities. La and Ce significantly bioconcentrated in microalgae populations up to 2- and 5-fold (i.e., at day 28 compared to day 7), in that order. Bioconcentrated La and Ce were up to 3157 and 1232 μg/g dry weight (day 28), respectively. These results suggested that low La and Ce concentrations can be slightly toxic to R. subcapitata having the potential to be bioaccumulated and potentially transferred along the food web., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)