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Arsenic: An Abundant Natural Poison
(Released March 2009)

  by Andreas Saldivar & Vicki Soto  


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Case Studies: Bangladesh & the USA


Situated on the Ganges - Brahmaputra delta, Bangladesh is a densely populated country with approximately 140 million people and a primarily agricultural economy. (UNDP Project Access to Information Programme n.d. ) Prior to 1970, after which Bangladesh became independent from Pakistan, surface water was the area's primary source of drinking water. However, contamination caused many cases of waterborne diseases with high mortality, notably cholera. To prevent this, throughout the 1970s tube wells were installed in Bangladesh to access shallow (10-50 meters) groundwater as an alternate drinking water supply. (Smith, Lingas and Rahman 2000) (Mead 2005)

map of Bangladesh
In the mid-1980's patients from Bangladesh were showing the characteristic skin lesions that appear from chronic exposure to high arsenic concentrations. In the early 1990s the groundwater of regions of Bangladesh was tested for arsenic. (Smith, Lingas and Rahman 2000) (UNICEF n.d.) High concentrations were found, ranging from less than 1 µg/L to greater than 300 µg/L. (British Geological Survey 2001) (Mead 2005) A regional variation grading to higher concentration of arsenic was found in groundwater in the south - southeast [see map]. In addition, other metals were present in concentrations higher than the recommended WHO guidelines. For instance, 35% of sampled wells had concentrations exceeding the WHO guidelines for manganese of 50 µg/L . (British Geological Survey 2001)

Map of arsenic distribution in groundwater in Bangladesh

Out of the over 8 million tube wells in Bangladesh, more than half have been tested for arsenic. It is estimated that about 20% of the tube wells have unsafe levels of arsenic over 50 µg/L - the national standard for Bangladesh. It is estimated that over 35 million people are exposed to contaminated drinking water with concentrations of 50 µg/L or higher and 57 million people exposed to drinking water with concentrations greater than 10 µg/L. (UNICEF n.d. ) (Smith, Lingas and Rahman 2000) (British Geological Survey 2001) In addition, over 10,000 people have shown evidence of arsenicosis with this number expected to rise. (World Health Organization 2001)

well & pump with red mark
A Tube Well
Various programs for identification and mitigation of arsenic in groundwater have been and are being carried out in Bangladesh, beginning with well testing to determine the level of arsenic concentration. Measurement is done in the field with test kits or in a laboratory. Tube wells with arsenic concentrations higher than the national standard of 50 µg/L are painted red. Tube wells with arsenic concentrations lower than the national standard are painted green. (World Bank 2005) Once a well has been deemed unsafe, users are steered towards another source of safe drinking water, which could include another, deeper groundwater source, surface water supply or rainwater harvesting. Other options for a safe water supply have other inherent problems such as microbiological quality of surface water sources and economic limitations relating to drinking water treatment. In many cases, people are directed to use other tube wells shown to have arsenic concentrations below the national standard.

Social problems exist with this approach. Public awareness and education campaigns need to be diligent to explain the color difference between safe or contaminated water supply represented in the green or red painted tube wells. Furthermore, many wells are privately owned and therefore less likely to be shared, people believe that boiling will improve water quality, and there is a belief that after many years of presentation and education, groundwater is a "safe" water supply. (The World Bank. Environment and Social Unit - South Asia Region 2005)

In Bangladesh, many government, nongovernmental and international organizations, such as UNICEF, the World Bank, the World Health Organization and WaterAid, are involved in all aspects of arsenic monitoring and mitigation performing projects from well screening, awareness and education campaigns, to various treatment options and decision and policy making. (World Bank, 2005)

In the United States, arsenic concentrations are generally less than 1 µg/L but can be higher locally in parts of the northeast and midwest and in the western states. (U.S. Geological Survey 2000) As part of the National Water Quality Assessment Program (NAWQA) of the United States Geological Survey, the Trace Element National Synthesis Project is studying various metals and other elements, including arsenic, in the United States. This project includes collecting data on arsenic concentrations in water supplies in databases and producing data sets and maps of arsenic concentrations. For more information, visit

map with arsenic concentrations
Concentration of arsenic in the United States

When the new MCL went into effect in 2001, the EPA estimated that there were 54,000 community water systems and 20,000 non-community water systems in the United States. Out of these, about 3,000 community water systems and 1,100 non-community water systems would be affected by the change in water quality standard where the drinking water quality would fall outside of the new limit. These 4,000 systems served approximately 13 million people. The cost of compliance to the new rule was estimated to be about $181 million, with the highest percentage going to new treatment technologies. The EPA also estimated that reducing the standard would lead to 19-31 fewer cases of bladder cancer per year and 19-25 fewer cases of lung cancer per year. (U.S. Environmental Protection Agency 2001) Private well owners are responsible for testing their own well and each state has information and guidance to assist owners.

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