Heavy Metals in Chinese Medicines: Lead, Mercury, Arsenic and Cadmium

Urgent first

If you or a child has taken a product that may contain heavy metals and is seriously unwell, call emergency services (US: 911). In the US, Poison Help is 1-800-222-1222. Bring the product.

Two different problems

Heavy metals reach herbal products in two ways. Some are deliberately included in traditional preparations for a medicinal purpose; others arrive accidentally through soil, water or manufacturing. A 2002 review said both occur in Asian herbal medicines, that Indian and Chinese preparations were implicated, and that most data were anecdotal and insufficient to define prevalence. [1] That limit still matters: studies below sampled certain products, not all products.

What a product survey found

A Dutch monitoring study sampled 292 traditional herbal preparations (Ayurvedic, Chinese and Tibetan) between 2004 and 2007. Mercury, arsenic or lead were detected in 186 (64%), yet fewer than 20% of labels suggested those elements were present. For 59 preparations (20%), the estimated weekly intake significantly exceeded safety limits, most often for mercury. [2] This was a survey of products on one national market, not a measure of Chinese medicine as a whole, and the sample mixed three traditions. It shows that unlabelled metals do occur. NCCIH also reports Chinese herbal products contaminated with heavy metals such as arsenic, lead and cadmium. [3]

Cinnabar and mercury

Cinnabar (mercury sulfide) has been used in traditional Chinese medicine, including in some patent medicines. A review on mercury in TCM explains that mercury-containing preparations have historically been used mainly as mercury sulfides, and that toxicity depends on the route of administration and the dosage form. [4] We do not recommend any product containing cinnabar or realgar (arsenic sulfide); treat both as a safety issue.

What this means for you

• Choose products whose full ingredient list you can read and whose maker can tell you how metals are tested. See Reading a Chinese Patent Medicine Label and Buying Chinese Herbs Safely.
• Avoid products of unknown origin, especially imported items with no ingredient list.
• Children, pregnant women and people with kidney disease should not use such products without medical advice. The NHS advises against herbal medicines in pregnancy, breastfeeding, kidney or liver problems and for children. [5]
• If you have used a product that may be contaminated and feel unwell, ask your doctor about a blood or urine metal test; we found no source for a home test.
• Metals are one of several quality issues; see Chinese Pharmacopoeia and Quality Standards and Animal and Mineral Ingredients.