Background: Heavy metal contamination in herbal medicines is a global threat to human beings especially at levels above known threshold concentrations.
Methods: The concentrations of five heavy metals cadmium (Cd), lead (Pb), arsenic (As), mercury (Hg) and copper (Cu) were investigated using Inductively Coupled Plasma Optical Mass Spectrometry (ICP-MS) with 1773 samples. Exposure assessment, Non-carcinogenic risk assessment, and carcinogenic risk assessment were applied to measure their risks in human body.
Results: According to Chinese Pharmacopoeia, 30.51% (541) samples were detected with at least one over-limit metal. The over-limit ratio for Pb was 5.75% (102), Cd at 4.96% (88), As at 4.17% (74), Hg at 3.78% (67), and of Cu, 1.75% (31). For exposure assessment, Pb, Cd, As, and Hg have resulted in higher than acceptable risks in 25 kinds of herbs. The maximal Estimated Daily Intake (EDI) of Pb in seven herbs, of Cd in five, of Hg in four, and As in three exceeded their corresponding Provisional Tolerable Daily Intakes (PTDI). In total 25 kinds of herbs present an unacceptable risk as assessed with the HQ (Hazard Quotient) or HI (Hazard Index). Particularly, Plantaginis herba (HI = 11.47) is more than 11 times over the limit.
Conclusions: Heavy metal contamination in herbal medicines was borderline or higher than the safety level with the majority of the herbal plants were within acceptable risks. Notably, As posed the highest risk in all indicators including EDI, HI, and CR, inducing the most serious risks in all five metals. Herbal medicines Euodiae fructus, Plantaginis herba, and Desmodii styracifolii were considered the most risk-inducing herbal medicines. Therefore, it is of great advantage to establish universal standards and quality requirements for hazardous elements in herbal medicines so that this natural resource can continue and expand further, to benefit health globally.