Dietary arsenic intake estimates based on surveys of total arsenic concentrations appear to be dominated by intake of the relatively non-toxic, organic arsenic forms found in seafood. Concentrations of inorganic arsenic in food have not been not well characterized. Accurate dietary intake estimates for inorganic arsenic are needed to support studies of arsenic's status as an essential nutrient, and to establish background levels of exposure to inorganic arsenic. In the market basket survey reported here, 40 commodities anticipated to provide at least 90% of dietary inorganic arsenic intake were identified. Four samples of each commodity were collected. Total arsenic was analysed using an NaOH digestion and inductively coupled plasma-mass spectrometry. Separate aliquots were analysed for arsenic species using an HCl digestion and hydride atomic absorption spectroscopy. Consistent with earlier studies, total arsenic concentrations (all concentrations reported as elemental arsenic per tissue wet weight) were highest in the seafoods sampled (ranging from 160 ng/g in freshwater fish to 2360 ng/g in saltwater fish). In contrast, average inorganic arsenic in seafood ranged from less than 1 ng/g to 2 ng/g. The highest inorganic arsenic values were found in raw rice (74 ng/g), followed by flour (11 ng/g), grape juice (9 ng/g) and cooked spinach (6 ng/g). Thus, grains and produce are expected to be significant contributors to dietary inorganic arsenic intake.

Background exposures to inorganic arsenic have been estimated to be in the range of 16-19 mu g/day with diet being the primary source. However, data on concentrations of inorganic arsenic in food are scanty. Existing literature includes data for a limited number of foods, and suggests that daily dietary inorganic arsenic intake for various age groups ranges from 8 to 14 mu g/day in the United States and from 5 to 13 mu g/day in Canada. The current study was conducted to obtain data for a larger number and variety of foods, and to more precisely estimate background dietary exposure ranges in the United States. This analysis presents results of a market basket survey of 40 commodities selected to represent samples of most major food types and to account for the majority of dietary exposure to inorganic arsenic. Samples were analyzed for total arsenic using NaOH digestion and inductively coupled plasma-mass spectrometry. Separate aliquots were analyzed for As3+, As5+, MMA, and DMA using an HCl digestion and hydride atomic absorption. The highest inorganic arsenic concentrations were found in grains and produce. Total arsenic concentrations were highest in seafood, and were consistent with results from previous studies; however, average inorganic arsenic concentrations in seafood were lower than previously reported. Data from the foods surveyed were coupled with a United States food consumption database to estimate the distribution of the dietary inorganic arsenic intake among adults. For most adults, dietary inorganic arsenic intake is predicted to fall within the range of 1-20 mu g/day.