Effect of Soil Contamination with Heavy Metals on the Production of Medicinal Plants

The study of World Health Organization (WHO) has shown that the use of herbal medicines has been increased dramatically around the world in recent years. With the expanding popularity and trade of medicinal plants, health, safety and quality of medicinal plant raw materials and processed products have become a major concern for world organizations. Environmental pollutants, including heavy metals, are one of the criteria quality control of medicinal plants and their processed products. Various studies have shown that the amount of heavy metals in medicinal plant depends on the environment growing herbs, plant species, conditions of drying, storage, transportation and processing. Herb growing environmental pollution with heavy metals may influence the biosynthesis of secondary metabolites, can lead to significant changes in the quantity and quality of these metabolites.Pollution of the growth medium of medicinal plants with heavy metals may influence the biosynthesis of secondary metabolites, can lead to significant changes in the quantity and quality of these metabolites. The WHO regulates maximum permissible limit in medicinal plant for cadmium, arsenic and lead 0.3, 1 and 10 mg kg-1, respectively. Some other elements such as copper, zinc, manganese, molybdenum and nickel can be toxic at high levels, but WHO has not to date restrictions apply to these elements. Due to increased use of fertilizers, insecticides and pesticides to improving yield of crops on one hand and increasing urbanization and industrial activities as well as the undisclosed harvest location of medicinal plants in Iran, no national regulations for monitoring and gathering wild plants and the probability of collecting contaminated with heavy metals, accumulation of these elements in medicinal plants may be occurred. Therefore, adequate oversight and quality control of medicinal plants and their processed products can be recommended.