Heavy Metal and Microbial Contamination in Marketed Herbal Powders

This review summarises published evidence on heavy metal and microbial contamination of herbal powders sold over the counter, and it presents no new analytical data. It outlines how contaminants enter the supply chain, which metals and organisms are reported most often, how they are measured, and how pharmacopoeial and regulatory limits are applied. Surveys from several regions find that a minority of products exceed recommended limits for lead, cadmium, arsenic or mercury, and that moulds and enteric bacteria are frequent in powders handled and stored without control. Sampling plans, methods and limits differ between studies, which makes comparison difficult, and exposure-based risk assessments remain uncommon.