Changes

'''Arsenic contamination of groundwater''' is a natural occurring high concentration of [[arsenic]] in deeper levels of groundwater. It is a high-profile problem due to the use of deep tubewells for water supply in the Ganges Delta, causing serious [[arsenic poisoning]] to large numbers of people. A 2007 study found that over 137 million people in more than 70 countries are probably affected by arsenic poisoning of drinking water. Arsenic contamination of ground water is found in many countries throughout the world, including the USA.<ref>{{cite journal| title = A review of the source, behaviour and distribution of arsenic in natural waters | author = Smedley PL, Kinniburgh DG| journal = [[Applied Geochemistry]]| year = 2002| volume = 17| issue = 5| pages = 517&ndash;568| doi = 10.1016/S0883-2927(02)00018-5 }}</ref>  Approximately 20 incidents of groundwater arsenic contamination have been reported from all over the world.<ref>{{cite journal| title = Arsenic contamination in groundwater: A global perspective with emphasis on the Asian scenario | author = Mukherjee A., Sengupta M. K., Hossain M. A.| journal = [[Journal of Health Population and Nutrition]]| year = 2006| volume = 24| issue = 2| pages = 142&ndash;163| url = http://202.136.7.26/images/jhpn242_Arsenic-contamination.pdf}}</ref> Of these, four major incidents were in Asia, including locations in Thailand, Taiwan, and People's Republic of China|Mainland China.<ref name=chowdhury>{{cite journal| title = Groundwater arsenic contamination in Bangladesh and West Bengal, India| author = Chowdhury U. K., Biswas B. K., Chowdhury T. R.| journal = [[Environmental Health Perspectives]]| year = 2000| volume = 108| issue = 4| pages = 393&ndash;397| url = http://www.ehponline.org/members/2000/108p393-397chowdhury/chowdhury-full.html| doi = 10.2307/3454378| jstor = 3454378| publisher = Brogan &#38}}</ref>In South America, Argentina and Chile are affected. There are also many locations in the United States where the groundwater contains arsenic concentrations in excess of the United States Environmental Protection Agency|Environmental Protection Agency standard of 10 parts per billion adopted in 2001. According to a recent film funded by the US Superfund, {{cite web |url=http://www.youtube.com/watch?v=hi5DfRy01vE |title=In Small Doses |format= |work= |accessdate=}}, millions of private wells have unknown arsenic levels, and in some areas of the US, over 20% of wells may contain levels that are not safe.