Comprehensive Profiling of Essential Elements and Organic and Inorganic Contaminants in Dromedary Camels from the Canary Islands: A Baseline for Nutritional and Environmental Assessment

Abstract

Dromedary camels raised under semi-extensive management can act as One Health sentinels for environmental exposures and food chain surveillance, yet serum reference information remains scarce. Our objective was to provide the most comprehensive assessment to date of physiological and toxicological serum profiles in dromedary camels (Camelus dromedarius) from the Canary Islands. We included 114 clinically healthy animals of different sex, age, and reproductive status. Serum samples were analyzed for essential, toxic, and potentially toxic elements using inductively coupled plasma mass spectrometry (ICP-MS). In addition, a high-throughput multi-residue method based on QuEChERS extraction followed by UHPLC-MS/MS and GC-MS/MS was used to screen for 360 organic compounds, including pesticides, veterinary drugs, human pharmaceuticals, and persistent organic pollutants. Essential elements showed biologically consistent variations according to sex, age group, and pregnancy status. Males had higher levels of selenium and copper, while calves showed elevated concentrations of manganese and zinc. Pregnant females exhibited lower iron, zinc, and selenium levels, consistent with increased fetal demand. These results provide preliminary reference values for healthy camels, stratified by physiological status. In contrast, classical toxic elements such as arsenic, mercury, lead, and cadmium were found at very low or undetectable concentrations. Several potentially toxic elements, including barium, strontium, and rare earth elements, were detected sporadically but without toxicological concern. Only 13 organic compounds (3.6%) were detected in any sample, and concentrations were consistently low. The most prevalent was the PAH acenaphthene (55.3%), followed by the fungicide procymidone and the PAH fluorene. Notably, no residues of the usually detected 4,4′-DDE or PCB congeners were found in any sample. These findings confirm the low environmental and dietary exposure of camels under low-intensity farming systems and highlight their value as sentinel species for food safety and environmental monitoring.