Arsenic is a toxic substance with acute as well as chronic
effects. In 2001, the US arsenic drinking water limit of 50 ppb
was lowered to 10 ppb (∼130 nM), the same as in the EU.
An upper limit of 10 ppb, as in drinking water has an estimated
cancer risk of 1 in 500 while 1 in 10,000 is usually the
highest cancer risk the US Environmental Protection Agency
(EPA) allows in tap water [1]. Assuming a linear dose–response
relationship between arsenic and lung and bladder cancer the
drinking water standard would have to be lowered to 0.5 ppb
(7 nM) As to achieve a 1 in 10,000 risk estimate, which is difficult
to detect using existing analytical methods. Furthermore, it
has been demonstrated that arsenic acts as an endocrine disruptor
at concentrations 20× less than the 10 ppb drinking water standard
[2]. The arsenic limit has been set at this level in spite of the
health risks because of measurement limitations [3]. In addition