Determination and safety assessment of lead, cadmium, arsenic, mercury, and chromium in mulberry leaves from different origins and varieties in Chongqing

Mulberry leaves are a typical medicinal and edible resource in Chongqing, yet the risks related to toxic element concentrations remain a key concern for quality control and industrial utilization. To address this issue, this study analyzed toxic elements pollution levels and associated health risks in mulberry leaves from different origins and varieties. The contents of Pb, Cd, As, Hg, and Cr in 19 mulberry leaf samples from 9 producing areas in Chongqing were determined by inductively coupled plasma mass spectrometry (ICP-MS), followed by pollution assessment, health risk evaluation, and correlation analysis. The results revealed significant regional differences in toxic element contents (P < 0.05), with Cr showing the largest variation (20.52-fold). Strong positive correlations among As–Cr (r = 0.973), Pb–As (0.851), and Pb–Cr (0.769) suggested common pollution sources. All samples were classified as clean (Nemerow composite index: 0.014 ± 0.006). The health risk assessment indicated non-carcinogenic (0.0069 ± 0.0039) and carcinogenic risks (1.9 × 10−6 ± 1.6 × 10−6) well below the thresholds. Compared with mulberry leaves from mining-impacted regions (Guangxi, Sichuan) and relatively clean areas (Hainan), Chongqing mulberry leaves exhibited lower or comparable concentrations of toxic elements. Overall, mulberry leaves in Chongqing exhibit low concentrations of toxic elements with acceptable health risks. Priority should be given to low-pollution areas (e.g. Linjiang town, Fenshui town) for planting bases, with dynamic monitoring near industrial zones to ensure quality development.