Arsenic distribution in environment and its bioremediation: A review
the ingested As compounds are rapidly excreted in
Review works covering the As contamination
uncharged forms (Tamaki and Frankenberger 1992).
scenario around the world have reported many
countries with As concentration in drinking water
The Extent of Arsenic Pollution
greater than the WHO Guideline Value of 10 μg/L or
As contamination in groundwater and its subsequent
the prevailing national standards. These incorporate
health effects has become a worldwide concern over
Afghanistan, Argentina, Australia, Bangladesh,
the past two to three decades. Untreated, highly
Brazil, Bulgaria, Canada, Cambodia, Chile, China,
toxic As in soil and effluent has been disposed of in
Germany, Ghana, Greece, Hungary, India, Iran,
rivers and has ended up in groundwater, leading to
Japan, Mexico, Myanmar, Nepal, New Zealand,
toxicity to humans and other biota. Groundwater is
Pakistan, Romania, Switzerland, Taiwan, the United
more vulnerable to As contamination than surface
States of America, and Vietnam (Mukherjee et al. ,
water because of the interaction of groundwater
2006).ThefirstincidenceofAspoisoningwasreported
with aquifer minerals and the increased potential in
in Chile in 1962. It was estimated that about 7% of
aquifersforgeneratingthephysiochemicalconditions
the deaths were caused by previous exposure to As
favourable for As release (Smedley 2006). Arsenic in
in this country (Borgono and Greiber 1972; Zaldivar
drinking water is one of the topmost environmental
1974). The Natural occurrence of As in groundwater
threats worldwide, based on the potential exposure
(>10 μg L-1) is reported from many parts of the
of people to As and the numerous diseases with
United States, such as California, Alaska, Arizona,
which it has been associated (Smith et al. , 1992;
Indiana, Idaho, Nevada, Washington, Missouri,
Abernathy et al. , 2003; Watanabe et al. , 2003; Tapio et
Ohio, Wisconsin, and New Hampshire (Moncure et
al. , 2006). Long term use of As enriched groundwater
al. , 1992; Frost et al. , 1993; Welch et al. , 1998; Welch
for drinking has resulted in severe health problems
et al. , 2000; Chiou et al. , 2001). With the discovery of
in majority of As affected regions across the world.
newer sites in the recent past, the As-con tamination
The United States Environmental Protection Agency
scenario around the world, especially in Asian
(US EPA) drinking water standard for As was set at
countries, has changed considerably. Before 2000,
50 µg L-1 in 1975, based on a Public Health Service
there were five major incidents of As contamination
standard originally established in 1942 (USEPA,
in groundwater in Asian countries: Bangladesh,
1996). On the basis of investigations initiated by the
West Bengal, India, Inner Mongolia (PR China) and
National Academy of Sciences, it was concluded
Taiwan. Between 2000 and 2005, As-related ground-
that this standard did not eliminate the risks of skin,
water problems have emerged in different Asian
lung, and prostate cancer from long-term exposure
countries, including new sites in China, Mongolia,
to low As concentrations in drinking water. In
Nepal, Cambodia, Myanmar, Afghanistan, DPR
order to achieve the EPA’s goal of protecting public
Ko rea, Iran, Pakistan and Viet Nam (Suk et al. ,
health, recommendations were made to lower the
2003; Mukherjee et al. , 2006). Arsenic problem was
safe drinking water limit to 5 μgL-1, slightly higher
reported in 1968 in Taiwan. More than 19% of tube
than what is considered the technically feasible
wells among 83,000 tested tube wells were reported
measurable level (3 µg L-1) (National Research
to be contaminated with As with concentrations
Council 1999). However the current drinking water
above 50 mg L-1 (Tseng 1977; Thornton and Farago
guideline for As adopted by both the World Health
1997; Tsai et al. , 1998). Blackfoot disease due to As
Organisation (WHO) and the US EPA is 10 μg L-1.
contamination is of common occurrence in this
This is higher than the proposed Canadian and
country (Tseng 2003). An estimated 5.63 and 14.66
Australian maximum permissible concentrations of
million people in 29 out of 32 provinces of China are
5 and 7 μg As L-1, respectively. The ground water
drinking water which contains As exceeding 50 and
As contamination problem has been recognized and
10 mg L-1, respectively. More than 30,000 cases of
documented across the world over the last decade.
Asosis have been diagnosed in China (Borgono and
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