Herbs and Heavy Metal Detoxification

Heavy metals are metallic elements which have a high atomic weight and a density much greater (at least 5 times) than water. There are more than 20 heavy metals, but four are of particular concern to human health: lead (Pb), cadmium (Cd), mercury (Hg) and inorganic arsenic (As). According to the US Agency for Toxic Substances and Disease Registry, these four heavy metals are four of the top six hazards present in toxic waste sites. They are highly toxic and can cause damaging effects even at very low concentrations. They tend to accumulate in the food chain and in the body and can be stored in soft (eg kidney) and hard tissues (eg bone). Being metals, they often exist in a positively charged form and can bind on to negatively charged organic molecules to form complexes. Chelates are a special type of complex where the organic molecule binds to the metal at two or more points (and hence quite strongly). (The term chelation comes from the Greek chēlē meaning crab or lobster claw, suggested by the way in which the metal is gripped in at least two places by the organic groups.) Chelating agents are used to produce stable compounds with relatively low toxicity and also to enhance the excretion of metals. Heavy metals can also exist covalently bound to organic molecules. In the case of As this substantially reduces its toxicity. For Hg it substantially increases toxicity, eg methyl mercury. Aluminium is not a heavy metal and considerations related to aluminium exposure, health effects and its detoxification are not always the same as for heavy metals.