Toxicity of lanthanum and yttrium oxide nanoparticles and bulk forms on Folsomia candida: a study of single versus mixture exposures.

Abstract

The intensive use of rare earth elements (REEs) raises concerns about their effects on soil organisms, particularly under mixture exposure scenarios. This study evaluated the toxicity of lanthanum oxide (La₂O₃) and yttrium oxide (Y₂O₃) nanoparticles (NPs) and bulk forms on Folsomia candida. Single (0-2500 mg/kg) and dual mixture exposures were tested for effects on survival, reproduction, avoidance behavior, and biochemical markers. No effects on survival and avoidance behavior were observed. NPs were more toxic than bulk forms. La₂O₃ NPs reduced reproduction (≥ 1250 mg/kg) and acetylcholinesterase (AChE) activity (2500 mg/kg), whereas Y₂O₃ NPs exhibited greatest toxicity, reducing reproduction (≥ 313 mg/kg) and increasing catalase (CAT) (156 and 625 mg/kg) and glutathione reductase (GR) (625 and 2500 mg/kg) activities. Mixture exposures revealed complex interactions (synergism, antagonism, or no interaction), with toxicity depending on concentration, endpoint, and material form. Besides, higher number of biochemical endpoints were affected by mixture exposures, but dissimilar responses were observed with different concentrations: 2500 mg/kg Y₂O₃ NPs + 2500 mg/kg La₂O₃ NPs decreased reproduction and increased GR, glutathione S-transferases (GST) and AChE activities; 2500 mg/kg Y₂O₃ NPs + 625 mg/kg La₂O₃ NPs increased CAT, GR, GST and AChE activities; 625 mg/kg Y₂O₃ NPs + 625 mg/kg La₂O₃ NPs increased GR activity; 156 mg/kg Y₂O₃ NPs + 2500 mg/kg La₂O₃ NPs decreased AChE activity, increased GR activity and lipid peroxidation levels. This study highlights that REE exposures, particularly mixtures, can pose risks to soil organisms and emphasizes the need to include mixture interactions in risk assessments.