Contamination of Heavy Metals in Herbals
A heavy metal is a member of a loosely defined subset of elements that exhibit metallic properties.
The term heavy metal has been called a “misinterpretation” in an International Union of Pure and Applied Chemistry technical report due to the contradictory definitions. There is an alternative term “toxic metal” with reference to Herbals.
Some of the Heavy metals / toxic metals are dangerous to health and damage the environment (e.g. mercury, cadmium, lead, chromium), some may cause corrosion (e.g., lead), some are harmful in other ways (e.g. arsenic may pollute catalysts). Within the European community the eleven elements of highest concern are arsenic, cadmium, cobalt, chromium, copper, mercury, manganese, nickel, lead, tin, and thallium, the emissions of which are regulated. Some of these elements are actually necessary for humans in minute / trace amounts (cobalt, copper, chromium, manganese, nickel) while others are carcinogenic i.e. produce cancer or are toxic, affecting, the central nervous system (manganese, mercury, lead, arsenic), the kidneys or liver (mercury, lead, cadmium, copper) or skin, bones, or teeth (nickel, cadmium, copper, chromium).
Depending upon the quality of soil and heavy use of agrochemicals and inorganic pesticides, for storage purposes, there is a migration or leaching of the metals in to the environment and also into the herbal materials. The heavy metals have a marked effect on the aquatic flora and fauna which through bio magnification enter the food chain and ultimately affect the human being as well.
As per the WHO / FDA /AYUSH guidelines limit for heavy metals is as follows;
Heavy Metal Maximum Permissible Limit
Arsenic (As) 3 ppm (3 mg/kg)
Cadmium (Cd) 0.3 ppm (0.3 mg/kg)
Lead (Pb) 10 ppm (10 mg/kg)
Mercury (Hg) 1 ppm (1 mg/kg)
Copper (Cu) Not specified
Zinc (Zn) Not specified
Sources of Heavy metals are not only the environmental factors or soil, but the contamination of heavy metals also comes from vessels and equipments used for the processing.
There is an increased usage (Self medication) of Complimentary / Alternative / Traditional / Herbal / Ayurvedic medicines which are freely available Over The Counter (OTC).
Manufacturer has to be extra careful and prevent heavy metal contamination and for that
there is a need to thoroughly examine the vessels, equipments and machineries for a possible leaching.
Though the Grade S. S. 316 (UNS S31600) most used, contains chromium between16 & 18% and Nickel between 10 and 14%.
It is felt that all the equipments should be of GMP grade but it is also equally necessaryand important to evaluate the intermediate and end products meant for human and animal consumption for the presence of heavy metals.
Stringent application of the norms is the need of the day to prevent heavy metal contamination and resultant toxicity.