Contamination/adulteration of TCM imports

Who this is about

adults using traditional Chinese herbal medicine products

Practical note

Graded moderate for the finding that measurable heavy metals and some limit exceedances occur in herbal medicine products: a 2026 meta-analysis of 70 studies from 27 countries and a 1773-sample survey agree on this. Downgraded from high for considerable heterogeneity and for indirectness, as the meta-analysis covers herbal products generally and exceedance rates depend on which limit is used. Not graded as a measure of harm to users.

Vegan note

Metal contamination concerns plant-based herbal products as well as animal-derived ones; it reflects soil, processing and manufacturing rather than the vegan status of an ingredient.

Safety note

Contamination differs by product, maker and country, so a single product's label says little about its metal content. Products sold under a national regulator's licence or listing are subject to quality standards that unlisted imports and online purchases may not meet.

Sources

• Supports “Mass spectrometry revealed heavy metals including arsenic, lead and cadmium, one with a level of arsenic >10 times the acceptable limit.” (Abstract) Coghlan ML, Maker G, Crighton E, Haile J, Murray DC, White NE, Byard RW, Bellgard MI, Mullaney I, Trengove R, Allcock RJ, Nash C, Hoban C, Jarrett K, Edwards R, Musgrave IF, Bunce M. 2015. Scientific Reports. Combined DNA, toxicological and heavy metal analyses provides an auditing toolkit to improve pharmacovigilance of traditional Chinese medicine (TCM). CC BY 4.0; credit Coghlan et al., Scientific Reports 2015
• Supports “Reported exceedance of study-specific comparators was common but varied substantially because regulatory limits, product categories, and denominators differed across studies.” (Abstract) Boulares E, Baralin AF, Yin Tan SC, Kang H. 2026. Reviews on Environmental Health. Heavy metal contamination in herbal medicines: a systematic review and meta-analysis. publisher copyright; metadata and short quotes only; Courtesy of the U.S. National Library of Medicine
• Supports “According to Chinese Pharmacopoeia, 30.51% (541) samples were detected with at least one over-limit metal.” (Abstract) Luo L, Wang B, Jiang J, Fitzgerald M, Huang Q, Yu Z, Li H, Zhang J, Wei J, Yang C, Zhang H, Dong L, Chen S. 2020. Frontiers in Pharmacology. Heavy Metal Contaminations in Herbal Medicines: Determination, Comprehensive Risk Assessments, and Solutions. CC BY 4.0; credit Luo et al., Frontiers in Pharmacology
• Context “Some Chinese herbal products have been contaminated with toxic compounds, heavy metals, pesticides, and microorganisms and may have serious side effects.” (Bottom line) National Center for Complementary and Integrative Health. 2019. NCCIH. Traditional Chinese Medicine: What You Need To Know. public domain; credit NCCIH

Who this is about

adults using traditional Chinese herbal medicine products

Practical note

Graded low: the evidence is a 2002 systematic review of 18 case reports, 2 case series and 4 analytical investigations, and a 2015 Australian audit in which 50% of 26 products contained an undeclared pharmaceutical. Small, non-random product samples from a few countries mean the true prevalence is uncertain.

Safety note

Hidden drugs can interact with prescribed medicines (warfarin is a blood thinner) or cause the side effects of the undeclared drug. National regulators publish alerts on specific products found to contain undeclared substances.

Sources

• Supports “In 50% of the TCMs, an undeclared pharmaceutical agent was detected including warfarin, dexamethasone, diclofenac, cyproheptadine and paracetamol.” (Abstract) Coghlan ML, Maker G, Crighton E, Haile J, Murray DC, White NE, Byard RW, Bellgard MI, Mullaney I, Trengove R, Allcock RJ, Nash C, Hoban C, Jarrett K, Edwards R, Musgrave IF, Bunce M. 2015. Scientific Reports. Combined DNA, toxicological and heavy metal analyses provides an auditing toolkit to improve pharmacovigilance of traditional Chinese medicine (TCM). CC BY 4.0; credit Coghlan et al., Scientific Reports 2015
• Supports “The list of adulterants contains drugs associated with serious adverse effects like corticosteroids. In several instances, patients were seriously harmed.” (Abstract) Ernst E. 2002. Journal of Internal Medicine. Adulteration of Chinese herbal medicines with synthetic drugs: a systematic review. publisher copyright; metadata and short quotes only; Courtesy of the U.S. National Library of Medicine
• Context “Some Chinese herbal products have been found to be contaminated with undeclared plant or animal material; drugs (such as the blood-thinner warfarin and the nonsteroidal anti-inflammatory agent diclofenac); heavy metals (such as arsenic, lead, and cadmium);” (What the Science Says About the Safety of Traditional Chinese Medicine) National Center for Complementary and Integrative Health. 2019. NCCIH. Traditional Chinese Medicine: What You Need To Know. public domain; credit NCCIH

Who this is about

adults using traditional Chinese herbal medicine products

Practical note

Graded low: two small Australian audits (15 and 26 products) from one research group, using DNA sequencing that detects presence but not amount. Consistent with regulator statements that undeclared plant or animal material has been found.

Vegan note

DNA from the cattle and antelope family (Bovidae), deer (Cervidae) and toads (Bufonidae) was found in many TCM samples and was rarely declared on the packaging, so a TCM product's label does not establish that it is free of animal ingredients.

Safety note

Undeclared ingredients mean the label cannot be relied on to show what a product contains, including allergens or animal material.

Sources

• Supports “Genetic analysis revealed that 50% of samples contained DNA of undeclared plant or animal taxa, including an endangered species of Panthera (snow leopard).” (Abstract) Coghlan ML, Maker G, Crighton E, Haile J, Murray DC, White NE, Byard RW, Bellgard MI, Mullaney I, Trengove R, Allcock RJ, Nash C, Hoban C, Jarrett K, Edwards R, Musgrave IF, Bunce M. 2015. Scientific Reports. Combined DNA, toxicological and heavy metal analyses provides an auditing toolkit to improve pharmacovigilance of traditional Chinese medicine (TCM). CC BY 4.0; credit Coghlan et al., Scientific Reports 2015
• Supports “Bovidae, Cervidae, and Bufonidae DNA were also detected in many of the TCM samples and were rarely declared on the product packaging.” (Abstract) Coghlan ML, Haile J, Houston J, Murray DC, White NE, Moolhuijzen P, Bellgard MI, Bunce M. 2012. PLoS Genetics. Deep sequencing of plant and animal DNA contained within traditional Chinese medicines reveals legality issues and health safety concerns. CC BY 4.0; credit Coghlan et al., PLoS Genetics 2012
• Context “Comparison of DNA sequence data to reference databases revealed the presence of 68 different plant families and included genera, such as Ephedra and Asarum, that are potentially toxic.” (Abstract) Coghlan ML, Haile J, Houston J, Murray DC, White NE, Moolhuijzen P, Bellgard MI, Bunce M. 2012. PLoS Genetics. Deep sequencing of plant and animal DNA contained within traditional Chinese medicines reveals legality issues and health safety concerns. CC BY 4.0; credit Coghlan et al., PLoS Genetics 2012

Who this is about

adults using Chinese herbal products containing aristolochic acid

Practical note

Graded moderate: the evidence is observational (outbreak investigations, population studies in Taiwan, occupational exposure) but consistent across settings, with specific DNA adducts found in tumour tissue supporting causation.

Safety note

The U.S. FDA detains imports of products made from Aristolochia and listed Asarum, Cocculus and Thottea species, and lists named Chinese formulas known to contain aristolochic acid. These products are not approved by the FDA.

Sources

• Supports “This review summarizes major epidemiologic evidence to argue for the causal association between AA exposure and urothelial carcinoma as well as nephropathy.” (Abstract) Yang HY, Chen PC, Wang JD. 2014. BioMed Research International. Chinese herbs containing aristolochic acid associated with renal failure and urothelial carcinoma: a review from epidemiologic observations to causal inference. CC BY 3.0; credit Yang et al., BioMed Research International 2014
• Supports “However, a product containing a small amount of aristolochic acid could be used for years with no apparent adverse effects until serious, irreversible effects, such as renal damage, has occurred.” (Reason for Alert) U.S. Food and Drug Administration. FDA Import Alerts. Import Alert 54-10: Detention Without Physical Examination of Bulk/Finished Dietary Supplements Products Containing Aristolochic Acid. U.S. government work, public domain; credit the U.S. Food and Drug Administration
• Context “The exposure scenarios include the following: Belgian women taking slimming pills containing single material Guang Fang Ji, consumptions of mixtures of Chinese herbal products in the general population and patients with chronic renal failure in Taiwan” (Abstract) Yang HY, Chen PC, Wang JD. 2014. BioMed Research International. Chinese herbs containing aristolochic acid associated with renal failure and urothelial carcinoma: a review from epidemiologic observations to causal inference. CC BY 3.0; credit Yang et al., BioMed Research International 2014
• Context “These products have not been approved by the U.S. Food and Drug Administration (FDA) and are often marketed as dietary supplements or “traditional medicines.”” (How are aristolochic acids used?) National Cancer Institute. 2022. National Cancer Institute (cancer.gov). Aristolochic Acids. NCI content; credit the National Cancer Institute as the source

Who this is about

adults using traditional Chinese herbal medicine products

Practical note

Graded low: the evidence is regulator summaries of outbreak investigations rather than systematic measurement of how often substitution occurs.

Safety note

Exposure to aristolochic acid can happen unknowingly, through a product whose label names a different herb.

Sources

• Supports “In each instance, the source of aristolochic acid was determined to be an aristolochia spp. plant that was used in the product for one of two reasons: (1) the plant ingredient that was listed on the label was mis-identified;” (Reason for Alert) U.S. Food and Drug Administration. FDA Import Alerts. Import Alert 54-10: Detention Without Physical Examination of Bulk/Finished Dietary Supplements Products Containing Aristolochic Acid. U.S. government work, public domain; credit the U.S. Food and Drug Administration
• Supports “Manufacturing errors, in which one herb is mistakenly replaced with another, also have resulted in serious complications.” (Bottom line) National Center for Complementary and Integrative Health. 2019. NCCIH. Traditional Chinese Medicine: What You Need To Know. public domain; credit NCCIH
• Context “Several outbreaks of renal failure in recent years have been attributed to the use of Chinese herbal medicines that were later shown to contain aristolochic acid.” (Reason for Alert) U.S. Food and Drug Administration. FDA Import Alerts. Import Alert 54-10: Detention Without Physical Examination of Bulk/Finished Dietary Supplements Products Containing Aristolochic Acid. U.S. government work, public domain; credit the U.S. Food and Drug Administration
• Context “Exposure may occur through intentionally or unknowingly eating or drinking herbal or food products that contain aristolochic acids.” (How are people exposed to aristolochic acids?) National Cancer Institute. 2022. National Cancer Institute (cancer.gov). Aristolochic Acids. NCI content; credit the National Cancer Institute as the source