Arsenic contamination of groundwater

Arsenic contamination of groundwater 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, 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. [ [http://www.newsvine.com/_news/2007/08/30/931411-arsenic-in-drinking-water-seen-as-threat Arsenic in drinking water seen as threat] , Associated Press, 8/30/07. ]

Approximately 20 incidents of groundwater arsenic contamination have been reported from all over the world. [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 = 142–163
url = http://202.136.7.26/images/jhpn242_Arsenic-contamination.pdf] Of these, four major incidents were in Asia, including locations in Thailand, Taiwan, and Mainland China.The UNESCO Courier, [http://www.unesco.org/courier/2001_01/uk/planet.htm Bangladesh's arsenic poisoning: who is to blame?] ] 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 = 393–397
url = http://www.ehponline.org/members/2000/108p393-397chowdhury/chowdhury-full.html
doi = 10.2307/3454378] South American countries like Argentina and Chile have also been affected. There are also many locations in the United States where the groundwater contains arsenic concentrations in excess of the new Environmental Protection Agency standard of 10 parts per billion.

Arsenic is a carcinogen which causes many cancers including skin, lung, and bladder as well as cardiovascular disease.

Some research concludes that even at the lower concentrations, there is still a risk of arsenic contamination leading to major causes of death. A study was conducted in a contiguous six-county study area of southeastern Michigan to investigate the relationship between moderate arsenic levels and twenty-three selected disease outcomes. Disease outcomes included several types of cancer, diseases of the circulatory and respiratory system, diabetes mellitus, and kidney and liver diseases. Elevated mortality rates were observed for all diseases of the circulatory system. The researchers acknowledged a need to replicate their findings. [, Jaymie R. Meliker, [http://www.ehjournal.net/content/6/1/4 "Arsenic in drinking water and cerebrovascular disease, diabetes mellitus, and kidney disease in Michigan: a standardized mortality ratio analysis"] Environmental Health Magazine. Volume 2:4. 2007. Accessed 9 Sept. 2008.]

A study preliminarily shows a relationship between arsenic exposure measured in urine and Type II diabetes. The results supported the hypothesis that low levels of exposure to inorganic arsenic in drinking water may play a role in diabetes prevalence. [Ana Navas-Acien, "Arsenic Exposure and Prevalence of Type 2 Diabetes in US Adults," "Journal of American Medical Association", v.300, n.7 (August 2008).]

Contamination specific nations and regions

Bangladesh and West Bengal

The story of the arsenic contamination of the groundwater in Bangladesh is a tragic one. Many people have died from this contamination. Diarrheal diseases have long plagued the developing world as a major cause of death, especially in children. Prior to the 1970s, Bangladesh had one of the highest infant mortality rates in the world. Ineffective water purification and sewage systems as well as periodic monsoons and flooding exacerbated these problems. As a solution, UNICEF and the World Bank advocated the use of wells to tap into deeper groundwater for a quick and inexpensive solution. Millions of wells were constructed as a result. Because of this action, infant mortality and diarrheal illness were reduced by fifty percent. However, with over 8 million wells constructed, it has been found over the last two decades that approximately one in five of these wells is now contaminated with arsenic above the government's drinking water standard.

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, therefore likely absorbing a lower concentration of arsenic; water deeper than 100 m is exposed to much older sediments which have already been depleted of arsenic. [cite journal
title = Chemistry of arsenic in groundwater of Ganges-Brahmaputra river basin
author = Singh A. K.
journal = Current Science
year = 2006
volume = 91
issue = 5
pages = 599–606
url = http://www.ias.ac.in/currsci/sep102006/599.pdf]

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"). [cite journal
title = Arsenic in ground water in six districts of West Bengal, India: the biggest arsenic calamity in the world. Part I. Arsenic species in drinking water and urine of the affected people
author = Amit Chatterjee, Dipankar Das, Badal K. Mandal, Tarit Roy Chowdhury, Gautam Samanta and Dipankar Chakraborti
journal = Analyst
year = 1995
volume = 120
issue =
pages = 643–651
doi = 10.1039/AN9952000643] [cite journal
title = Arsenic in ground water in six districts of West Bengal, India: the biggest arsenic calamity in the world. Part 2. Arsenic concentration in drinking water, hair, nails, urine, skin-scale and liver tissue (biopsy) of the affected people
author = Dipankar Das, Amit Chatterjee, Badal K. Mandal, Gautam Samanta, Dipankar Chakraborti and Bhabatosh Chanda
journal = Analyst
year = 1995
volume = 120
issue =
pages = 917–925
doi = 10.1039/AN9952000917] 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 as well as hair, nail and urine samples. They found 900 villages with arsenic above the government limit.

Chakraborti has criticized aid agencies, saying that they denied the problem during the 1990s while millions of tube wells were sunk. The aid agencies later hired foreign experts, who recommended treatment plants which were not appropriate to the conditions, were regularly breaking down, or were not removing the arsenic. [New Scientist, [http://www.newscientist.com/article/mg19025450.600.html Interview: Drinking at the west's toxic well] 31 May 2006.]

Chakraborti says that the arsenic situation in Bangladesh and West Bengal is due to negligence. He also adds that in West Bengal water is mostly supplied from rivers. Groundwater comes from deep tubewells, which are few in number in the state. Because of the low quantity of deep tubewells, the risk of arsenic patients in West Bengal is comparatively less. The Times of India, [http://timesofindia.indiatimes.com/articleshow/864169.cms 'Use surface water. Stop digging'] , interview, 26 Sep, 2004.] 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.” World Health Organization, [http://www.who.int/mediacentre/factsheets/fs210/en/index.html Arsenic in Drinking Water] , accessed 5 Feb 2007.] WHO has defined the areas under threat: Seven of the nineteen 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, with the number using arsenic-rich water is more than 1 million (above 0.05 mg/L). That number increases to 1.3 million when the concentration is 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 0.01 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).

The solution, according to Chakraborti, is “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."

United States

There are many locations across the United States where the groundwater contains naturally high concentrations of arsenic. Cases of groundwater-caused acute arsenic toxicity, such as those found in Bangladesh, are unknown in the United States where the concern has focused on the role of arsenic as a carcinogen. The problem of high arsenic concentrations has been subject to greater scrutiny in recent years because of changing government standards for arsenic in drinking water.

Some locations in the United States, such as Fallon, Nevada, have long been known to have groundwater with relatively high arsenic concentrations (in excess of 0.08 mg/L). [Frederick Rubel Jr. and Steven W. Hathaway (1985) "Pilot Study for removal of arsenic from drinking water at the Fallon, Nevada, Naval Air Station", Environmental Protection Agency, EPA/600/S2-85/094.] Even some surface waters, such as the Verde River in Arizona, sometimes exceed 0.01 mg/L arsenic, especially during low-flow periods when the river flow is dominated by groundwater discharge. [M. Taqueer A. Qureshi (1995) "Sources of Arsenic in the Verde River and Salt River Watersheds, Arizona", M.S. thesis, Arizona State University, Tempe.]

A drinking water standard of 0.05 mg/L (equal to 50 parts per billion, or ppb) arsenic was originally established in the United States by the Public Health Service in 1942. The Environmental Protection Agency (EPA) studied the pros and cons of lowering the arsenic Maximum Contaminant Level (MCL) for years in the late 1980s and 1990s. No action was taken until January 2001, when the Clinton administration in its final weeks promulgated a new standard of 0.01 mg/L (10 ppb) to take effect January 2006. ["The history of arsenic regulation", Southwest Hydrology, May/June 2002, p.16.] The incoming Bush administration suspended the new regulation, but after some months of study, the new EPA administrator Christine Todd Whitman approved the new 10 ppb arsenic standard and its original effective date of January 2006. ["EPA announces arsenic standard for drinking water of 10 parts per billion", EPA press release, 10/31/2001.]

Many public water supply systems across the United States obtained their water supply from groundwater that had met the old 50 ppb arsenic standard but exceeded the new 10 ppb MCL. These utilities searched for either an alternative supply or an inexpensive treatment method to remove the arsenic from their water. In Arizona, an estimated 35% of water-supply wells were put out of compliance by the new regulation; in California, the percentage was 38%. [Alison Bohlen (2002) "States move forward to meet new arsenic standard", Southwest Hydrology, May/June 2002, p.18-19.]

The proper arsenic MCL continues to be debated. Some have argued that the 10 ppb federal standard is still too high, while others have argued that 10 ppb is needlessly strict. Individual states are able to establish lower arsenic limits; New Jersey has done so, setting a maximum of 0.005 mg/L for arsenic in drinking water. [Megan A. Ferguson and others, Lowering the detection limit for arsenic: implications for a future practical quantitation limit, American Water Works Association Journal, Aug. 2007, p.92-98.]

Water purification solutions

mall-scale water treatment

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.

A simpler and less expensive form of arsenic removal is known as the Sono arsenic filter, using 3 pitchers containing cast iron turnings and sand in the first pitcher and wood activated carbon and sand in the second. [PDFlink| [http://www.unu.edu/env/Arsenic/Munir.pdf Evaluation of Performance of Sono 3-Kolshi Filter for Arsenic Removal from Groundwater Using Zero Valent Iron Through Laboratory and Field Studies] |272 KiB ] Plastic buckets can also be used as filter containers. [PDFlink| [http://phys4.harvard.edu/~wilson/arsenic/remediation/SONO/As%20filtration%20pictures.pdf SONO ARSENIC FILTER FROM BANGLADESH - 1] |102 KiB - pictures with descriptions.] It is claimed that thousands of these systems are in use can last for years while avoiding the toxic waste disposal problem inherent to conventional arsenic removal plants. Although novel, this filter has not been certified by any sanitary standards such as NSF, ANSI, WQA and does not avoid toxic waste disposal similar to any other iron removal process.

In the United States small "under the sink" units have been used to remove arsenic from drinking water. This option is called "point of use" treatment. The most common type of domestic treatment unit uses the technologies of adsorption i.e. granular media such as Bayoxide E33, GFH, Titanium Dioxide and reverse osmosis, To a less extent ion exchange and activated alumina have been considered but not commonly used.

Large-scale water treatment

In some places, such as the United States, all the water supplied to residences by water utilities must meet primary (health-based) drinking water standards. This may necessitate large-scale treatment systems to remove arsenic from the water supply. The effectiveness of any method depends on the chemical makeup of a particular water supply. The aqueous chemistry of arsenic is complex, and may affect the removal rate that can be achieved by a particular process.

Some large utilities with multiple water supply wells could shut down those wells with high arsenic concentrations, and produce only from wells or surface water sources that meet the arsenic standard. Other utilities, however, especially small utilities with only a few wells, may have no available water supply that meets the arsenic standard. Coagulation/filtration removes arsenic by coprecipitation and adsorption using iron coagulants. Coagulation/filtration using alum is already used by some utilities to remove suspended solids and may be adjusted to remove arsenic.

Iron oxide adsorption filters the water through a granular medium containing ferric oxide. Ferric oxide has a high affinity for adsorbing dissolved metals such as arsenic. The iron oxide medium eventually becomes saturated, and must be replaced.

Activated alumina is another filter medium known to effectively remove dissolved arsenic. It has also been used to remove undesirably high concentrations of fluoride.

Ion Exchange has long been used as a water-softening process, although usually on a single-home basis. It can also be effective in removing arsenic with a net ionic charge. (Note that arsenic oxide, As₂O₃, is a common form of arsenic in groundwater that is soluble, but has no net charge.)

Both Reverse osmosis and electrodialysis (also called "electrodialysis reversal") can remove arsenic with a net ionic charge. (Note that arsenic oxide, As₂O₃, is a common form of arsenic in groundwater that is soluble, but has no net charge.) Some utilities presently use one of these methods to reduce total dissolved solids and therefore improve taste. A problem with both methods is the production of high-salinity waste water, called brine, or concentrate, which then must be disposed of.

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. [cite news | url = http://www.scidev.net/News/index.cfm?fuseaction=readNews&itemid=2975&language=1 | author = Mustak Hossain | title = Toxic rice harvested in southwestern Bangladesh | publisher = SciDev.Net | date = 2006-07-13] [cite journal | title = Increase in Rice Grain Arsenic for Regions of Bangladesh Irrigating Paddies with Elevated Arsenic in Groundwaters | journal = Environ. Sci. Technol | volume = 40 | issue = 16 | pages = 4903–4908 |doi = 10.1021/es060222i | year = 2006 | author = Williams, P.N.] [* cite journal
title = Screening of Rice Cultivars for Grain Arsenic Concentration and Speciation
author Raghvan T
journal = American Society of Agronomy Proceding ]

ee also

*Arsenic poisoning
*Grainger challenge
*Groundwater
*Water pollution

Notes and references

*http://www.usatoday.com/news/world/2007-08-30-553404631_x.htm, http://www.pcrwr.gov.pk/Arsenic_CP.htm
*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 = 517–568
doi = 10.1016/S0883-2927(02)00018-5
*cite journal
title = Mechanism of arsenic release to groundwater, Bangladesh and West Bengal
author = Nickson RT, McArthur JM, Ravenscroft P
journal = Applied Geochemistry
year = 2000
volume = 15
issue = 4
pages = 403–413
doi = 10.1016/S0883-2927(99)00086-4
*cite journal
title = A Review of Arsenic(III) in Groundwater
author = Korte N. E., Fernando Q.
journal = Critical Reviews in Environmental Control
year = 1991
volume = 21
issue = 1
pages = 1–39
doi =
*cite journal
title = Contamination of drinking-water by arsenic in Bangladesh: a public health emergency
author = Smith AH, Lingas EO, Rahman M
journal = Bulletin of the World Health Organization
year = 2000
volume = 78
issue = 9
pages = 1093–1103
url = http://www.scielosp.org/scielo.php?script=sci_arttext&pid=S0042-96862000000900005&lng=en&nrm=iso
*cite journal
title = Arsenic mobility and groundwater extraction in Bangladesh
author = Harvey CF, Swartz CH, Badruzzaman ABM
journal = Science
year = 2002
volume = 298
issue = 5598
pages = 1602–1606
doi = 10.1126/science.1076978
pmid = 12446905
* cite journal
title = Screening of Rice Cultivars for Grain Arsenic Concentration and Speciation
author Raghvan T
journal = American Society of Agronomy Proceding
*cite journal
title = Arsenic contamination in Bangladesh - An overview
author = Hossain MF
journal = Agriculture Ecosystem & Environment
year = 2006
volume = 113
issue = 1-4
pages = 1–16
doi = 10.1016/j.agee.2005.08.034