Comparative analysis of rare earth elements concentrations in domestic dogs and Apennine wolves of Central Italy: Influence of biological, nutritional, and lifestyle factors

Rare Earth Elements (REEs) are strategical elements playing a crucial role in the industry, especially in producing high-tech materials. Therefore, REEs are new contaminants of emerging concerns. However, due to the lack of exposure data on REE occurrence in environmental matrices, especially in European countries, it is still tricky to establish environmental background levels to assess the ecotoxicological risk related to REEs exposure. The present study aimed to evaluate the liver concentrations of REEs in domestic dogs (Canis lupus familiaris) and Apennine wolves (Canis lupus italicus) living in the Abruzzo region, Italy. Moreover, for the scope of the present study, the dog's group was divided according to their sex, age, lifestyle, and diet. Wolves were categorized concerning their sex and genetic characteristics. Liver samples from dogs and wolves were collected during diagnostic necropsies from carcasses, sample mineralization was performed by a microwave digestion system with a single reaction chamber, and simultaneous determination of the presence of REEs was performed by Inductively Coupled Plasma Mass Spectrometer (Q-ICP-MS) using standard mode for all rare earth elements except scandium (Sc) which was acquired in kinetic energy discrimination (KED) mode. Hepatic concentrations of REEs were statistically significantly higher in wolves compared to dogs. Moreover, significant differences in REEs concentrations arose also from the genetic type of wolf, since "pure wolves" had higher liver concentrations of REEs compared to wolf -dog hybrids. Female and adult dogs also showed elevated REEs compared to male and juvenile dogs, while no significant differences were demonstrated for dogs' diet and lifestyle. The results of the present study confirm the exposure of domestic and wild carnivores to REEs, showing also the ability of REEs to accumulate in carnivore livers, suggesting the potential role of this species as an alternative bioindicator.