DIETARY ARSENIC INTAKE IN TAIWANESE DISTRICTS WITH ELEVATED ARSENIC IN DRINKING-WATER

Inorganic arsenic in dietary staples (i.e., yams and rice) may have su bstantially contributed to exposure and adverse health effects observe d in an endemic Taiwanese population historically exposed to arsenic i n drinking water. Observations of this population were used by the U.S . Environmental Protection Agency to derive toxicity values that form the basis for arsenic risk assessment and various regulations in the U nited States. However, data were previously insufficient to accurately estimate dietary intake. Rice and yam samples collected in 1993 and 1 995 from Taiwanese districts with endemic arsenic were analyzed for to tal arsenic and for inorganic and organic mono- and dimethylarsenic. T he acid digestion techniques used in the analyses are among the best t o preserve organic arsenic in the test sample. Furthermore, concurrent analyses of the proportion of inorganic arsenic in split samples of r ice and yams collected in the 1995 investigation were in good agreemen t, despite using a different digestion method. These data support a li kely mean dietary intake of 50 mu g/day with a range of 15 to 211 mu g /day. Consideration of dietary intake may result in a downward revisio n of the assumed potency of ingested arsenic as reflected in EPA's tox icity values.