Strategies for safe and effective therapeutic measures for chronic arsenic and lead poisoning.

Exposure to toxic metals remains a widespread occupational and environmental problem in world. There have been a number of reports in the recent past suggesting an incidence of childhood lead poisoning and chronic arsenic poisoning due to contaminated drinking water in many areas of West Bengal in India and Bangladesh has become a national calamity. Low level metal exposure in humans is caused by air, food and water intake. Lead and arsenic generally interferes with a number of body functions such as the central nervous system (CNS), the haematopoietic system, liver and kidneys. Over the past few decades there has been growing awareness and concern that the toxic biochemical and functional effects are occurring at a lower level of metal exposure than those that produce overt clinical and pathological signs and symptoms. Despite many years of research, we are still far from an effective treatment of chronic plumbism and arsenicosis. Medical treatment of acute and chronic lead and arsenic toxicity is furnished by chelating agents. Chelating agents are organic compounds capable of linking together metal ions to form complex ring-like structures called chelates. They have been used clinically as antidotes for acute and chronic poisoning. 2, 3-dimercaprol (BAL) has long been the mainstay of chelation therapy for lead or arsenic poisoning. Meso 2, 3, -dimercaptosuccinic acid (DMSA) has been tried successfully in animals as well as in a few cases of human lead and arsenic poisoning. DMSA could be a safe and effective method for treating lead or arsenic poisoning, but one of the major disadvantages of chelation with DMSA has been its inability to remove lead from the intracellular sites because of its lipophobic nature. Further, it does not provide protection in terms of clinical/ biochemical recovery. A new trend in chelation therapy is to use combined treatment. This includes the use of structurally different chelators or a combination of an adjuvant and a chelator to provide better clinical/biochemical recovery in addition to lead mobilization. The present review article attempts to provide update information about the current strategies being adopted for a safe, effective and specific treatment for two major toxic metals or metalloid.