Medicinal herbs: a potential source of toxic metal exposure for man and animals in India.

To explore the possibility of translocation of heavy metals into humans and animals, the authors studied 28 commonly used medicinal plants and estimated their heavy metal content. The plant materials were collected from the same sources used by traditional healers and commercial drug manufacturers. The plants were identified, authenticated, and processed for the analysis of toxic metals. Lead and cadmium levels were estimated in leaf, stem bark, root, or seeds, depending on the medicinal value of the plant portion. The authors used an atomic absorption spectrophotometer to determine levels of metals. The mean lead concentration in medical herbs ranged between 2.624 ppm (standard deviation = 0.426) and 32.757 (standard deviation = 0.124 ppm), and the cadmium concentration ranged between 0.056 ppm (standard deviation = 0.002) and 0.419 ppm (standard deviation = 0.006). Interestingly, the heavy metal concentrations (i.e., lead and cadmium) were higher in leaf than in stem bark or roots, and the lowest values were recorded in seeds. No published reports on the permissible level of toxic metals in commonly used medicinal plants of India have come to the authors' attention; therefore, it was difficult for the authors to determine the role of toxic metals in drug-induced health hazards. However, the presence of toxic metals in different plants led to the conclusion that prolonged consumption of such medicinal plants may be detrimental to health.