Heavy metal pollution and potential health risks of commercially available Chinese herbal medicines

A survey was conducted to investigate the pollution and health risks of copper (Cu), cadmium (Cd), lead (Pb), arsenic (As), mercury (Hg) and zinc (Zn) in 60 Chinese herbal medicines (CHMs) collected from a market in Kunming City, Yunnan Province, China. Furthermore, eight CHMs (Cyathulae radix, Drynariae rhizoma, Peucedani radix, Homalomenae rhizoma, Dryopteris setosa, Polygonati rhizoma, Lilii bulbus, and Linderae radix) containing high Cd concentrations were selected to further analyse their Cd chemical forms. Additionally, the dissolution rates of six heavy metals in decoction liquid were also analysed for four CHMs (Typhonii rhizoma, Linderae radix, Homalomenae rhizoma, and Cyathulae radix), and the health risks of heavy metals in CHMs were evaluated. The results showed that the Cd, Hg and Cu concentrations in the 60 CHMs exceeded the limiting values of the "Green Trade Standards of Importing & Exporting Medicinal Plants & Preparations" (WM2-2001), with exceedance ratios of 38.8%, 8.3% and 1.7%, respectively. The majority of Cd was integrated with pectates and protein in CHMs, and the other five Cd chemical forms followed the order of water-soluble > insoluble heavy metal phosphates > oxalate > residual > inorganic form, indicating that Cd had relatively low bioactivity and toxicity. The average dissolution rates of Zn, Cu, Cd, Hg, As and Pb in the four CHMs were 47.4%, 33.8%, 20.5%, 6.1%, 5.4% and 4.8%, respectively. The calculation results of hazard quotients (HQs) for Cd and Hg showed that the CHMs did not pose a threat to human health.