Role of chelating agents for prevention, intervention, and treatment of exposures to toxic metals.

The role of chelating agents for the prevention, intervention, and treatment of exposures to toxic metals was the topic of a conference held at the National Institute of Environmental Health Sciences, 22-23 September 1994. The objective of the conference was to review experimental and clinical studies concerned with the effectiveness and potential toxicity of chelating agents used to reduce the body burden of various metals and to identify research needs in the area of chelation. The conference was prompted by emerging evidence that low-level exposures to metals may result in toxic effects not previously recognized. For example, the recent interest in use of chelation as an intervention strategy to reduce blood lead levels followed the awareness that exposure to lead in infants and young children resulting in blood lead levels as low as 10-15 )ig/dl may impair cognitive and behavioral development (1). The question increasingly asked is to what degree, if any, does increased excretion of a toxic metal reverse established toxicity? For example, does reduction in blood lead levels reverse the impairment of cognitive and behavioral development in children? Does the process of chelation cause potentially dangerous redistribution of lead to susceptible organs from those less susceptible to lead toxicity? While intervention for toxicity from any metal includes removal from exposure, what are the indications for using chelating agents that enhance excretion of metals? Complete answers to these questions may not be currently available, but discussion of benefits and problems related to chelation therapy should help identify areas needing further study. The conference participants were asked to share current data and to identify gaps in data necessary to obtain a better understanding of the proper place of chelating agents in the management of metals exposure and toxicity.