From Farm to Retail: Decoding the Elemental Landscape of Milk and Dairy Products Across Organic and Conventional Production Systems Using ICP–MS

The presence of trace and toxic elements in milk and dairy products is an important food safety issue, as contamination can occur along the dairy supply chain and may be influenced by animal species, production system, and processing conditions. This study aimed to investigate and compare the multi-elemental composition of milk and selected dairy products obtained from organic, conventional, and commercial production systems in north-western Romania. A total of 307 samples, including raw milk from different animal species (cow, goat, buffalo, donkey) as well as yogurt, cheese, and mozzarella, were collected from farms and retail outlets. Samples were subjected to standardized microwave-assisted acid digestion and analyzed for toxic and essential elements (Pb, Cd, Hg, As, Cr, Ni, Al, Sn, Cu, and Zn) using inductively coupled plasma mass spectrometry (ICP-MS), with quality assurance ensured through certified reference materials and proficiency testing. The results indicated low concentrations of toxic metals across all dairy matrices, with Pb ranging from 0.0047 to 0.0117 mg/kg, Cd from 0.0008 to 0.0011 mg/kg, and As from 0.0007 to 0.0664 mg/kg, depending on animal species and production system. Mercury was consistently below the limit of detection in all datasets (LCD = 100%). Essential and transition elements were systematically quantified, occurring within expected ranges (Al: 0.021-0.264 mg/kg; Cu: 0.078-0.270 mg/kg; Zn: 3.245-7.963 mg/kg; Sn ≈ 0.0030-0.0035 mg/kg). All toxic element concentrations were below the maximum limits established by European Union legislation. Variations in elemental profiles were observed between animal species and production systems, with organic cow milk showing the most homogeneous composition. All toxic element concentrations were below the maximum limits established by European Union legislation. Overall, the findings confirm the safety of the analyzed dairy products and emphasize the relevance of multi-elemental monitoring as a practical tool for dairy supply chain surveillance and risk assessment.