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Groundwater pollution remediation and protection 273

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Arsenic pollution of groundwater in southern Bangladesh
7. 6

The Quaternary alluvial aquifers of Bangladesh provide drinking a variety of ailments including melanosis (a darkening of the
water for 95% of the population and also most of the water used skin), keratosis (a thickening of the skin, mostly on hands and feet),
for irrigation (Rahman & Ravenscroft 2003). Relative to surface damage to internal organs and, ultimately, cancer of the skin
water, the groundwater is bacteriologically safe, and its increased or lungs. Groundwater studies have demonstrated the wide extent
exploitation since the late 1970s has probably saved many of arsenic occurrence in Bangladesh (Dhar et al., 1997; DPHE
millions of lives that would otherwise have been lost to water-borne 1999) at concentrations greater than the Bangladesh regulatory
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diseases resulting from the use of contaminated surface water limit for arsenic in drinking water of 50 mgL and the World Health
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sources. Organization (1994) recommended limit of 10 mgL . These
Arsenic was first detected in groundwater in Bangladesh in regional surveys have shown that aquifers of the Ganges, Meghna
1993, when analysis was prompted by increasing reports of con- and Brahmaputra floodplains are all affected in parts, making this
tamination and sickness in the adjoining state of West Bengal in the most extensive occurrence of groundwater pollution in the
India. Prolonged exposure to inorganic arsenic in water causes world (Table 1, Fig. 1). It is estimated that at least 21 million people
(a) (b)

Fig. 1 Distribution of arsenic pollution in the main aquifer system in Bangladesh. (a) The map represents the results of the DPHE (1999)
survey showing the percentage of contaminated wells in the subdistricts (upazilas) of Bangladesh that exceed the Bangladesh regulatory
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limit for arsenic in drinking water of 50 µgL . The map may misrepresent the true percentage of wells that are contaminated by arsenic
because of sampling bias (many samples were collected at wells where arsenic poisoning was suspected) and measurement inaccuracies
−1
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(field test kits where used do not reliably indicate values exceeding 50 µgL when arsenic concentrations are in the range 50–200 µgL ).
Although the affected areas are unlikely to change, the percentages shown may be revised in the future. (b) The interpolated surface,
generated using arcview spatial analyst software on log-transformed data, shows the spatial distribution of groundwater arsenic
concentrations in wells less than 150 m deep using data based on the surveys of DPHE (1999, 2000) which are available from
http://www.bgs.ac.uk/arsenic/Bangladesh.