Arsenic (As) is mostly found in the earth’s core and in clay- and
sulphide-rich portions of the earth’s crust (Henken, 2009b). Being a
metalloid in group 15 on the periodic table (along with antimony,
bismuth, nitrogen and phosphorus), arsenic is well known for its
chronic toxicity, particularly when exposure occurs over prolonged
periods. Arsenic exposure via drinking-water is related to lung,
kidney, bladder and skin cancer. For example, drinking-water arsenic
concentrations in excess of 50 lg L1 have been associated
with increased risks of cancer in the bladder and lung, whilst
drinking-water arsenic levels even below 50 lg L1 have been
associated with precursors of skin cancer (IPCS, 2001). Therefore,
the presence of arsenic in water supply poses a serious risk to human
health.