Poison in Groundwater Arsenic

Elemental arsenic and its insoluble compoimds are non-toxic, whereas soluble inorganic and organic forms of the element may be poisonous. Needless to say, the amount (or dose) matters a lot. Trivalent arsenic is often toxic, the most common form is arsenite (As03 ) salts. Pentavalent arsenates (AsO ) are less of a concern, many of them are insoluble. This is also tme in general the properties of a certain element (including toxicity) very much depend on the form (most commonly the oxidation state) found in the compound. Determining which of the possible forms occur in a sample is called speciation. 

Salvarsan (606, Arsphenamine) is probably the most well-known organic compound of arsenic. It was first prepared by Sahachiro Hata and Paul Ehrlich in 1909, and was used as a cure of syphihs and sleeping sickness imtil penicillin was discovered. An infamous organic substance containing arsenic is the chemical weapon Lewisite, which is very toxic and is readily absorbed through skin (Fig. 4.3). 

Arserric is rraturally preserrt in foods, it is rrrrlikely to be completely eliminated from them. Its corrtrol, however, preserrts a big challenge all over the world in the years corrring. Yet this corrtrol arrd efforts to remove arsenic should be based on ratiorral arguments and a detailed irrrderstarrding of what risks the different forms arsenic actually pose. Otherwise, even rrtajor efforts may resirlt in no hitman health benefit at all. 

In his Book of explanation, prominent Islamic polymath Abn Musa Jabir ibn Hayyan (722-815, name Latinized as Gebei ) writes  

In fact, all sulfur powder can do on spilled mercury is to decrease its surface tension a little bit. This may help control the otherwise quite mobile drops of mercury, but does not transform mercury chemically. The liquid metal does in fact react with sulfur to form mercuric sulfide under suitable conditions according to the chemical equation Hg+S=HgS. Mercuric sulfide has two forms red cinnabar and black metacinnabarite. The latter slowly converts to the former if left alone. The reaction of mercury and sulfur is a favorable one in terms of energy, but it does not occur at room temperature. 

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Anawar, H. M., J. Akai, K. M. G. Mostofa, et al. 2002. Arsenic Poisoning in Groundwater Health Risk and Geochemical Sources in Bangladesh. Environment International 27 597-604. 

Severe water problems are also faced in southeast Asia. For example, Bangladesh and adjacent parts of India suffer from arsenic contamination of groundwater. Specifically, arsenic poisoning of groundwater has affected more than 50% of the total area of Bangladesh. The gradual introduction of arsenic inyo the food chain is more than a possibility. Nitrate pollution is also a problem in these areas. 

Adeel, Z. (2002) The disaster of arsenic poisoning of groundwater in south Asia — A focus on research needs and UNU s role. Global Environmental Change, 12(1), 69-72. 

By far the most significant cause of arsenic poisoning in humans from an environmental source is contamination of groundwater in countries like Bangladesh, India, and China. The situation in Bangladesh has attracted particular attention and illustrates how one problem can be exchanged for another. 

AH Welch, DB Westjohn, DR Helsel, RB Wanty. Arsenic in groundwater of the United States Occurrence and geochemistry. Ground Water 38 589-604, 2000. C Choprapawon, A Rodchne. Chronic arsenic poisoning in Ronpibool Nakhon Sri Thammarat, the Southern Province of Thailand. In CO Abernathy, RL Calderon, WR Chappell, eds. Arsenic Exposure and Health Effects. London Chapman HaU, 1997, pp 69-77. 

The nature of the rock that contains the groundwater has a large influence on the water s chemical composition. If minerals in the rock are water soluble to some extent, ions can leach out of the rock and remain dissolved in the groundwater. Arsenic in the form of HAsO/, H2As04, and H3ASO3 is found in many groundwater sources across the world, most infamously in Bangladesh, at concentrations poisonous to humans. 

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