Arsenic contamination has been found in regional water supplies in Argentina,
Bangladesh, Cambodia, Canada, Chile, China, Ghana, Hungary, India, Laos,
Mexico, Mongolia, Nepal, Pakistan, Poland, Taiwan, Thailand, the UK, the United
States, and Vietnam. Even in advanced countries such as the United States, nearly
10% of groundwater resources exceed arsenic levels of 10 ppb. Recognizing the
fact that inorganic arsenic is a documented human carcinogen, the World Health
Organization (WHO) set a standard at no more than 10 μg/L (or 10 parts per billion) of arsenic (As) in drinking water in 1993. This standard was finally adopted
by the United States in 2006; however, 50 μg/L (50 ppb or 0.05 mg/L) is the
maximum contamination level (MCL) considered acceptable in Bangladesh. The
population at risk approaches 100 million in Bangladesh at the MCL set by
the WHO.