Assessment of Heavy Metal Contamination in Commonly Used Herbal Preparations in Maiduguri, Borno State, North East Nigeria

Heavy metal contamination of herbal preparations represents an emerging safety concern in Nigerian markets, particularly in areas where medicinal plants are harvested near agricultural and industrial pollution sources. This study assesses the concentrations of lead, cadmium, mercury, arsenic, and chromium in twelve commonly consumed herbal preparations purchased from open markets in Maiduguri, Borno State. Samples were digested using a wet acid digestion procedure, and metal concentrations were quantified using atomic absorption spectrophotometry (AAS). Results were compared against maximum permissible limits established by the World Health Organization and the National Agency for Food and Drug Administration and Control of Nigeria. Eleven of the twelve preparations tested contained detectable lead concentrations, with five exceeding WHO permissible limits. Cadmium was detected above permissible thresholds in three samples. No mercury or arsenic was detected above quantification limits. Preparations consisting of root and bark materials generally showed higher metal loads compared to leaf-based preparations. These findings indicate significant heavy metal contamination risks in herbal preparations available in Maiduguri markets and highlight gaps in regulatory enforcement. Recommendations include mandatory pre-market heavy metal testing for herbal products and public health campaigns targeting frequent users of traditional preparations in Borno State. Keywords: heavy metals, herbal preparations, Maiduguri, contamination, atomic absorption spectrophotometry