THE OCCURRENCE, BIOAVAILABILITY AND TOXICITY OF ARSENIC FROM DRINKING OR IRRIGATION WATER – A WIDESPREAD HEALTH ISSUE

Toxicity from arsenic in drinking and irrigation waters, especially from ground water sources, is affecting human populations on a global scale. In a most severe instance, the Bengal Delta, an estimated 47-53 million people are exposed to concentrations of arsenic above the WHO provisional guideline of 10 µg As/L; globally, the population is thought to exceed 120 M, with elevated concentrations of As in drinking water documented in Bangladesh, Brazil, Chile, China, Ghana, Hungary, Mexico, Nepal, Nicaragua, Pakistan, Taiwan, Tajikistan, Thailand, and the USA. Although the Bangladesh/West Bengal geohydrologic regime is deltaic, with its special considerations, other natural sources of arsenic in drinking water come from metasedimentary bedrock aquifers, such as found in the Zimap¨¢n Valley of Mexico, or geohydrologic situations in which high concentrations of arsenic is found in coalbed aquifers or anthropogenically influenced agricultural and mined areas. Where this water is also used for irrigation of food crops, arsenic from these foods is thought to cause an additional toxicity burden. The co-occurrence, or absence, of physiologically synergistic elements, such as dissolved organic compounds or dietary sources of the essential micronutrient, selenium, play a role in the health of populations exposed to arsenic. A synopsis of the arsenic toxicity concerns of intergovernmental agencies and NGOs given at the IV World Water Forum, March 2006 in Mexico City will be presented.