Potentially toxic elements and Pb isotope data of regional food from the Sonoran River basin: Tracing the nature of the sources

The upper Sonora River basin in northwestern Mexico is a region with active and historical mining, as well as vigorous agricultural and livestock activity. The Buenavista del Cobre mine spill that occurred in 2014 raised major concerns among residents, including food safety. In this study, potentially toxic elements, PTE, (Al, As, Ba, Cd, Cr, Cu, Fe, Ni, Pb, Zn, and Tl) and Pb isotope ratios were measured in samples of regional foods and food products [beef chorizo, shredded beef jerky, beef liver, beef top round, farmer’s cheese, and red chili (powdered dried mild pepper)] collected from representative sites along the basin. Compared to international guidelines, only two out of 20 beef samples exceeded the Pb limit of 0.1 mg/kg set by FAO/WHO and the EU, mainly in prepared products (chorizo, shredded beef jerky). One liver sample exceeded the FAO/WHO Pb limit of 0.2 mg/kg. For red chili, one sample exceeded the Pb guideline of 0.6 mg/kg (FAO/WHO). Overall, Pb levels did not surpass FAO/WHO recommendations. Pb isotope compositions in most food samples align with the range of North American rocks, indicating limited influence from mining. Variability in Pb isotope composition may be related to preparation methods and geogenic anomalies. Although the mine spill represented a major environmental disturbance, PTE concentrations measured in foods and food products are consistent with the geochemical background of the basin. This interpretation is supported by Pb isotope compositions, indicating that Pb in food and food products primarily originates from natural sources, with no clear evidence of significant contributions from mining activities.