Reference: Posadzki P, Watson L, Ernst E. Contamination and adulteration of herbal medicinal products (HMPs): an overview of systematic reviews. Eur J Clin Pharmacol. 2013;69(3):295-307. Abstract available at http://link.springer.com/article/10.1007%2Fs00228-012-1353-z.

Researchers from the University of Exeter, UK, performed an extensive literature search on contamination and adulteration of herbal medicinal products (HMPs). The authors distinguished between adulteration, defined as “fraudulent practices in which a HMP is substituted partially or fully with impure, extraneous, improper or inferior products/substances,” and contamination, defined as “the undesired introduction of impurities of a chemical or microbiological nature, or of foreign matter, into or onto a starting material, intermediate product or finished herbal product during production, sampling, packaging or repackaging, storage or transport.” The literature search provided 4,366 articles, but only 26 met the criteria established by the authors for systematic reviews on the issue that were included for further evaluation.

Contaminants reported included pollen, dust, microbes, parasites, toxins, pesticides, and heavy metals. Reports on adulteration were mainly due to the admixture of undisclosed prescription drugs. (In the US, the addition of prescription drugs to herbal dietary supplements is seen less as a problem of adulteration per se but is characterized more accurately as the illegal sale of drugs masquerading as dietary supplements.) The presence of contaminants and adulterants caused mild-to-severe adverse events, and was observed most often with Asian products. The authors pointed out that many of the systematic reviews were of poor quality, but indicated that “adulteration and contamination of HMPs occurs with some regularity, particularly in Asian preparations,” and that “such deficits in product quality have the potential to cause serious harm to patients.”

Comment: While the presence of excessive amounts of pollen and dust may be undesirable, finding pollen on some flowers and aerial parts material is relatively common and often unavoidable. Similarly, the presence of dust can be a by-product of processing, such as grinding, and is equally unavoidable. If these materials fall within acceptable ranges of foreign matter as established in pharmacopeial monographs, they are not regarded as contaminants. On the other hand, the detection of pharmacologically active or toxic material in herbal medicinal products is of much greater concern to human health. In the publication, the authors cited admixture of prescription drugs as a frequent cause of adverse effects, but pointed out a only a few number of cases of botanical adulteration, e.g., the isolated cases of belladonna (Atropa belladonna, Solanaceae) alkaloids and rhubarb (Rheum officinale, Polygonaceae) leaf in Essiac (a combination product containing burdock [Arctium lappa, Asteraceae] root, sheep sorrel [Rumex acetosella, Polygonaceae] leaves, slippery elm [Ulmus rubra syn. U. fulva, Ulmaceae] bark, and rhubarb root) dating back to the 1970s, or the contamination of star anise (Illicium verum, Schisandraceae) with the toxic Japanese star anise (I. anisatum). Based on the paper, the sale of prescription drugs disguised as dietary supplements, or presence of contaminants like lead or arsenic, are the major concerns, and occur more frequently than adulteration of botanical materials.