Paul et.al.

Greiber 1971). Occurrence of As in groundwater of

small amount of As (Ratnaike 2013). The chronic

the Bengal Delta Plain in West Bengal, India and

effects of inorganic As exposure via drinking water

Bangladesh, is the region’s single largest emerging

include skin lesions, such as hyperpigmentation,

societal and environmental problem of the present

and respiratory symptoms, such as cough and

century (Bagla and Kaiser 1996; Dhar et al. , 1997).

bronchitis and reproductive disorders (Smith et al. ,

According to a study led by the British Geological

2000; Ahsan et al. , 2000; Milton and Rahman 2002,

Survey in 1998, shallow tube wells in 61 of the 64

Sen and Chaudhuri 2008). The cardiovascular,

districts in Bangladesh had As concentration above

gastrointestinal, neurological and urinary systems

0.010 mg L-1 in 46% of the samples and above 0.050

are some of the other systems most affected in

mg L-1 in 27% of the samples. When combined with

humans (Lee et al. , 2002; Mukherjee et al. , 2003).

the estimated 1999 population, it was speculated that

Arsenic is known to have mutagenic and genotoxic

the number of people exposed to As concentrations

effects on humans, and it has been associated with

above 0.05 mg L-1 was 28-35 million and the number

increased risk of skin, lung, liver and other cancers,

of those exposed to more than 0.01 mg L-1 was 46-

type 2 diabetes, and reproductive and developmental

57 million (British Geological Survey 2000. In India,

problems (Hopenhayn-Rich et al. , 1998; Steinmaus

As contamination was first discovered as late as

et al. , 2000; Karagas et al. , 2001; Bodwell et al. , 2006;

1982. By then 6.97 million people were estimated

Navas-Acien et al. , 2006; Liu et al. , 2008; Prozialeck et

to be exposed to high As content in drinking

al. , 2008). The International Agency for Research on

water. At present some 3, 00,000 people are likely

Cancer (IARC) has listed As as a human carcinogen

to be suffering from various stages of Arsenosis

since 1980. Due to toxic and carcinogenic effects of As

(Chakraborti et al. , 2002; Mukherjee et al. , 2006). The

World Health Organization has set the permissible

first report of As groundwater contamination and its

limit of As in drinking water as 0.01 mg L-1, which

health effects in the Ganga plain from West Bengal

is equivalent to 10 ppb (Chakraborti et al. , 2002;

was published in 1984 (Garai et al. , 1984). As affected

Prozialeck et al. , 2008). Recently, however, it has

areas in West Bengal have been classified into three

been reported that there is an increased risk of As

zones: highly affected (9 districts mainly in eastern

toxicity, even at the low and permissible dose of 10

side of Bhagirathi River), mildly affected (5 districts

ppb (Prozialeck et al. , 2008). In certain areas in the

in northern part), and unaffected (5 districts in

Indian subcontinent, the maximum As concentration

western part).

in ground water was found to be around 3700 ppb to

4700 ppb (Chakraborti et al. , 2002), leading to several

Toxicity and Human Health Effects

physiological damages to human beings. Presently,

Toxicity and Health effects associated with

the extent of groundwater As contamination in

significant exposure to As are dependent on the

West Bengal has reached an alarming situation as

duration and dose of exposure. Depending on that

nine districts of West Bengal have been reported

As induced toxicity can be classified as acute toxicity

to have groundwater As concentrations above 0.05

and chronic toxicity (Ratnaike 2013). Acute toxicity

mg L-1 and several people have been affected by As

involves harmful effects in an organism through a

poisonings (Chakraborti et al. , 2009).

single or short-term exposure. Acute As poisoning

Arsenite can bind to sulfhydryl groups and dithiols

mainly occurs in two distinct forms acute paralytic

groups of proteins, whereas arsenate can act as

syndrome and acute gastrointestinal syndrome

a chemical analog of phosphate and can inhibit

(Brouwer et al. , 1992; Civantos et al. , 1995). Other

oxidative phosphorylation (Ordon et al. , 2005).

clinical features of acute poisoning include nausea,

Arsenic does not directly react with DNA or cause

vomiting, profuse watery diarrhoea, and diffuse skin

gene mutations, except to a small extent at high

rash etc (Ratnaike 2013). ChronicAs poisoning occurs

doses. However, it does cause gene amplification

usually upon repeated or continuous exposure to

and chromosomal damage at lower doses and can

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