Arsenic contamination of groundwater

From Wikipedia, the free encyclopedia

Main article: Water pollution

Arsenic contamination of groundwater has occurred in various parts of the world, most notably the Ganges Delta of Bangladesh and West Bengal, India, causing serious arsenic poisoning among large numbers of people. It is a natural occurring high concentration of arsenic in deeper levels of groundwater, which became a high-profile problem in recent years due to the use of deep tubewells for water supply in the Ganges Delta .

Parts of Thailand,^{[citation needed]} Taiwan, Argentina, Chile and China have also been affected.^[1] Approximately 20 incidents of groundwater arsenic contamination have been reported from all over the world. Of these, four major incidents were in Asia.^[2]

Roger Smith, Professor of Pharmacology and Toxicology Emeritus, Dartmouth Medical School, has confirmed that natural arsenic contamination of drinking water has also been a problem in wells in New Hampshire.^{[citation needed]}

1 Bangladesh and West Bengal
2 Water purification solutions
3 Dietary intake
4 See also
5 Notes and references
6 External links

[edit] Bangladesh and West Bengal

In the Ganges Delta, the affected wells are typically more than 20 m and less than 100 m deep. Groundwater closer to the surface typically has spent a shorter time in the ground, and so has not absorbed a high concentration of arsenic; water deeper than 100 m is exposed to much older sediments which have already been depleted of arsenic.^[1]

Dipankar Chakraborti from West Bengal brought the crisis to international attention in a research paper published in The Analyst in 1995 and reported on by David Bradley (The Guardian, January 5, 1995, "Drinking the water of death"). Beginning his investigation in West Bengal in 1988, he eventually published, in 2000, the results of a study conducted in Bangladesh which involved the analysis of thousands of water samples and hair, nail and urine samples. They found 900 villages with arsenic above the government limit. Chakraborti described this as "only the tip of the iceberg."^[1]

Chakraborti has criticized aid agencies, saying that they denied the problem during the 1990s while millions more tube wells were sunk, and later hired foreign experts who recommended treatment plants which were not appropriate to the conditions, regularly breaking down or not removing the arsenic.^[3]

Chakraborti says that the arsenic situation in Bangladesh and West Bengal is due to negligence. However, he also says that in West Bengal, water is mostly supplied from rivers. Groundwater comes from deep tubewells, which are few in the state. So the risk of arsenic patients in West Bengal is comparatively less. ^[4]

According to the World Health Organisation, “In Bangladesh, West Bengal (India) and some other areas, most drinking-water used to be collected from open dug wells and ponds with little or no arsenic, but with contaminated water transmitting diseases such as diarrhoea, dysentery, typhoid, cholera and hepatitis. Programmes to provide ‘safe’ drinking-water over the past 30 years have helped to control these diseases, but in some areas they have had the unexpected side-effect of exposing the population to another health problem - arsenic.” ^[5] WHO has defined the area under threat: Seven of 16 districts of West Bengal have been reported to have ground water arsenic concentrations above 0.05 mg/L; the total population in these seven districts is over 34 million and it has been estimated that the population actually using arsenic-rich water is more than 1 million (above 0.05 mg/L) and is 1.3 million (above 0.01 mg/L). According to a British Geological Survey study in 1998 on shallow tube-wells in 61 of the 64 districts in Bangladesh, 46% of the samples were above 0.010 mg/L and 27% were above 0.050 mg/L. When combined with the estimated 1999 population, it was estimated that the number of people exposed to arsenic concentrations above 0.05 mg/l is 28-35 million and the number of those exposed to more than 0.01 mg/l is 46-57 million (BGS, 2000). ^[6]

The solution according to Chakraborti, “By using surface water and instituting effective withdrawal regulation. West Bengal and Bangladesh are flooded with surface water. We should first regulate proper watershed management. Treat and use available surface water, rain-water and others. The way we're doing at present is not advisable. ^[7]

[edit] Water purification solutions

Chakraborti claims that arsenic removal plants (ARPs) installed in Bangladesh by UNDP and WHO were a colossal waste of funds due to breakdowns, inconvenient placements and lack of quality control.^[8]

A simpler and less expensive form of arsenic removal is known as the 3-Kolshi system, using 3 pitchers containing cast iron turnings and sand in the first pitcher, and wood charcoal and sand in the second.^[9] Plastic buckets can also be used.^[10] It is claimed that thousands of these systems are in use, and that they can last for years, while avoiding the toxic waste disposal problem inherent to conventional arsenic removal plants.

[edit] Dietary intake

Researchers from Bangladesh and the United Kingdom have recently claimed that dietary intake of arsenic adds a significant amount to total intake, where contaminated water is used for irrigation.^[11]