# Arsenic: A Review on a Great Health Issue Worldwide
## 8 Detoxification from Arsenic  
Chelation for heavy metal intoxication (mercury, lead, arsenic et al.) began more than 80-90 years ago. The classic antidote against acute arsenic poisoning, BAL (British Anti-Lewisite, dimercaptopropanol) (Table 3) was synthesized as an antidote for lewisite. Due to high toxicity of BAL, the clinical use of this compound is restricted to only the initial treatment for few days after arsenic intoxication. In the 1950s, water-soluble and less toxic analogs of BAL have been developed for clinical use: dimercaptouscinic acid (DMSA), 2,3-dimercaptopropane sulfonic acid (DMPS) and \(N\)-(2,3-dimercaptopropyl)-phthalamidic acid (DMPA). DMSA, DMPS, and DMPA have lower toxicity and higher therapeutic index than BAL when used in an arsenic poisoning in the proportion of 42:14:4:1, respectively. Clinical studies in chelation for the treatment of acute arsenic intoxication established that the efficacy of chelation therapy is most effective when treatment is started rapidly (within minutes or hours) after arsenic exposure [79]. Analytical and clinical results support that the endogenous dithiol dihydroate, having high affinity for arsenical compounds, are used with success in the therapy of the arsenic intoxication [64]. Arsenic-contaminated drinking water affects hundreds of millions of people in more than 50 countries. Given the high cases of affected individuals, it is not easy to provide infrastructures to remove arsenic from water for daily consumption. The reduction or the removal of arsenic from water can be done in several ways, including harvesting rainwater and digging deep well to harvesting direct groundwater. However, one of the challenges in many water and wastewater treatment plants worldwide is the selective removal of trace elements, such as arsenic, with the presence of higher concentrations of background competing solutes such as main ions. Several methods of selective arsenic removal have been developed, such as precipitation, adsorption, and modified iron and ligand exchange [80]. Besides these water sources, arsenic can be removed from water by various treatments, such as solar oxidation of arsenic in transparent containers that reduces the arsenic load by oxidizing As\({}^{3+}\) to As\({}^{5+}\). The practice of storing water for long time in clear containers reduces the arsenic level through sedimentation. Naturally dissolved Fe(OH)\({}_{2}\) in the groundwater undergoes a natural oxidation process to produce a precipitate of Fe(OH)\({}_{3}\) which attracts and adsorbs arsenic to stick to it. This adsorption produces a co-precipitate of Fe(OH)\({}_{3}\)/As that sediments to the bottom of the container. Alum [Al\({}_{2}\)(SO\({}_{4}\))\({}_{3}\)-18H\({}_{2}\)O], ferric chloride (FeCl\({}_{3}\)), and ferric sulfate [Fe\({}_{2}\)(SO\({}_{4}\))\({}_{3}\)-7H\({}_{2}\)O] are commonly used as coagulants [81]. Rice (_Oryza sativa_ L.) is the most arsenic-contaminated cereal found in water and soil. Arsenic is particularly accumulated in rice, because this cereal is grown in flooded soils, thus, the rice absorbs this toxic metal from both water and soil [82]. Rice is the main food for half of the world population, living in Asia (India, Pakistan, China, and Japan) and it grows in places where the water and soil are heavily contaminated with arsenic [83; 84]. Irrigation of rice field with arsenic-contaminated groundwater poses a major health problem for those peoples who eat rice with high levels of arsenic [85]. Different agronomic irrigation techniques allow to reduce the accumulation of this toxic element. We should intervene \"upstream\" at the environmental level by improving irrigation techniques, controlling the arsenic level of the waters that irrigate the rice fields, drawing the water in depth and fertilizing with silica, that is antagonist for arsenic. Rice grown aerobically has lower arsenic levels compared to the one grown in flooded conditions [86].