1. IntroductionIn some countries, arsenic is the most important chemical pollutant in groundwater and drinking water. The Bengal delta region is particularly affected as an estimated 35 million people have been drinking arsenic-rich water for the past 20–30 years (Smedley and Kinniburgh, 2002). Examination for arsenical dermatologic symptoms in 29 thousand people showed that 15% had skin lesions (Chowdhury et al., 2000). Regions with arsenic-rich drinking water can be found around the globe (Smedley and Kinniburgh, 2002). Natural contamination of groundwater by arsenic is also an emerging issue in some countries of Southeast Asia, including Vietnam, Thailand, Cambodia, and Myanmar (Berg et al., 2001; Buschmann et al., submitted for publication; Polya et al., 2005). Vulnerable areas for arsenic contamination are typically young Quaternary deltaic and alluvial sediments comprising highly reducing aquifers. Chronic levels of 50 μg arsenic/L can cause health problems after 10–15 years of exposure (Smith et al., 2000). The development of symptoms of chronic arsenicpoisoning (arsenicosis) is strongly dependent on exposure time and the resulting accumulation in the body. The various stages of arsenicosis are characterized by skin pigmentation, keratosis, skin cancer, effects on the cardiovascular and nervous system, and increased risk of lung, kidney and bladder cancer. The European Union
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