In addition to metallothionein and other proteins, exogenous chelating agents have been used to prevent metal toxicity. A review by Rooney discusses thiol-containing chelating agents for the treatment of metal toxicity [143]. Sodium 2,3-dimercaptopropane sulfate (DMPS) and meso-2,3-dimercaptosuccinic acid (DMSA) are two dithiol chelating agents that are used to treat mercury, cadmium, arsenic, and lead toxicity with some success; however, these compounds can also bind essential metals such as copper and zinc [143, 159]. In contrast, the use of NAC and glutathione as chelating agents for mercury toxicity is not recommended because these complexes are inefficiently excreted from the body. Furthermore, NAC and glutathione actually contribute to mercury uptake in the kidney and brain [143–146].