Estimating Inorganic Arsenic Exposure from U.S. Rice and Total Water Intakes.

BACKGROUND: Among nonoccupationally exposed U.S. residents, drinking water and diet are considered primary exposure pathways for inorganic arsenic (iAs). In drinking water, iAs is the primary form of arsenic (As), while dietary As speciation techniques are used to differentiate iAs from less toxic arsenicals in food matrices. OBJECTIVES: Our goal was to estimate the distribution of iAs exposure rates from drinking water intakes and rice consumption in the U.S. population and ethnic- and age-based subpopulations. METHODS: The distribution of iAs in drinking water was estimated by population, weighting the iAs concentrations for each drinking water utility in the Second Six-Year Review data set. To estimate the distribution of iAs concentrations in rice ingested by U.S. consumers, 54 grain-specific, production-weighted composites of rice obtained from U.S. mills were extracted and speciated using both a quantitative dilute nitric acid extraction and speciation (DNAS) and an in vitro gastrointestinal assay to provide an upper bound and bioaccessible estimates, respectively. Daily drinking water intake and rice consumption rate distributions were developed using data from the What We Eat in America (WWEIA) study. RESULTS: Using these data sets, the Stochastic Human Exposure and Dose Simulation (SHEDS) model estimated mean iAs exposures from drinking water and rice were 4.2 µg/day and 1.4 µg/day, respectively, for the entire U.S. population. The Tribal, Asian, and Pacific population exhibited the highest mean daily exposure of iAs from cooked rice (2.8 µg/day); the mean exposure rate for children between ages 1 and 2 years in this population is 0.104 µg/kg body weight (BW)/day. CONCLUSIONS: An average consumer drinking 1.5 L of water daily that contains between 2 and 3 ng iAs/mL is exposed to approximately the same amount of iAs as a mean Tribal, Asian, and Pacific consumer is exposed to from rice. https://doi.org/10.1289/EHP418. BACKGROUND: Among nonoccupationally exposed U.S. residents, drinking water and diet are considered primary exposure pathways for inorganic arsenic (iAs). In drinking water, iAs is the primary form of arsenic (As), while dietary As speciation techniques are used to differentiate iAs from less toxic arsenicals in food matrices. OBJECTIVES: Our goal was to estimate the distribution of iAs exposure rates from drinking water intakes and rice consumption in the U.S. population and ethnic- and age-based subpopulations. METHODS: The distribution of iAs in drinking water was estimated by population, weighting the iAs concentrations for each drinking water utility in the Second Six-Year Review data set. To estimate the distribution of iAs concentrations in rice ingested by U.S. consumers, 54 grain-specific, production-weighted composites of rice obtained from U.S. mills were extracted and speciated using both a quantitative dilute nitric acid extraction and speciation (DNAS) and an in vitro gastrointestinal assay to provide an upper bound and bioaccessible estimates, respectively. Daily drinking water intake and rice consumption rate distributions were developed using data from the What We Eat in America (WWEIA) study. RESULTS: Using these data sets, the Stochastic Human Exposure and Dose Simulation (SHEDS) model estimated mean iAs exposures from drinking water and rice were [Formula: see text] and [Formula: see text], respectively, for the entire U.S. population. The Tribal, Asian, and Pacific population exhibited the highest mean daily exposure of iAs from cooked rice ([Formula: see text]); the mean exposure rate for children between ages 1 and 2 years in this population is [Formula: see text] body weight (BW)/day. CONCLUSIONS: An average consumer drinking 1.5 L of water daily that contains between 2 and [Formula: see text] is exposed to approximately the same amount of iAs as a mean Tribal, Asian, and Pacific consumer is exposed to from rice. https://doi.org/10.1289/EHP418.

Development of an ion chromatography-inductively coupled plasma-mass spectrometry method to determine inorganic arsenic in liver from chickens treated with roxarsone.

Roxarsone, (4-hydroxy-3-nitrophenyl)arsonic acid, is an arsenic-containing compound that has been approved as a feed additive for poultry and swine since the 1940s; however, little information is available regarding residual arsenic species present in edible tissues. We developed a novel method for the extraction and quantification of arsenic species in chicken liver. A strongly basic solution solubilized the liver, and ultrafiltration removed macromolecules and particulate material. Ion chromatography separated the species [arsenite, arsenate, monomethylarsonic acid, dimethylarsinic acid, (4-hydroxy-3-aminophenyl)arsonic acid, (4-hydroxy-3-acetaminophenyl)arsonic acid, and roxarsone] in the extracts, which were then detected by inductively coupled plasma-mass spectrometry. The extraction oxidized most arsenite to arsenate. For fortification concentrations at 2 µg kg(-1) and above, recoveries ranged from 70 to 120%, with relative standard deviations from 7 to 34%. We detected roxarsone, its 3-amino and 3-acetamido metabolites, inorganic arsenic, and additional unknown arsenic species in livers from roxarsone-treated chickens. Both the originating laboratory and a second laboratory validated the method.

Arsenic speciation and identification of monomethylarsonous acid and monomethylthioarsonic acid in a complex matrix.

Anion-exchange chromatography was utilized for speciation of arsenite (As(III)), arsenate (As(V)), dimethylarsinic acid (DMA(V)), monomethylarsonic acid (MMA(V)), monomethylarsonous acid (MMA(III)), and the new As species monomethylthioarsonic acid (MMTA), using inductively coupled plasma mass spectrometric (ICPMS) detection. MMA(III) and MMTA were identified for the first time in freeze-dried carrot samples that were collected over 25 years ago as part of a joint U.S. EPA, U.S. FDA, and USDA study on trace elements in agricultural crops. The discovery of MMA(III) and MMTA in terrestrial foods necessitated the analytical characterization of synthetic standards of both species, which were used for standard addition in carrot extracts. The negative ion mode, high-resolution electrospray mass spectrometry (HR-ESI-MS) data produced molecular ions of m/z 122.9418 and 154.9152 for MMA(III) and MMTA, respectively. However, ESI-MS was not sensitive enough to directly identify MMA(III) and MMTA in the carrot extracts. Therefore, to further substantiate the identification of MMA(III) and MMTA, two additional separations using an Ion-120 column were developed using the more sensitive ICPMS detection. The first separation used 20 mM tetramethylammonium hydroxide at pH 12.2 with MMA(III) eluting in less than 7 min. In the second separation, MMTA eluted at 11.2 min by utilizing 40 mM ammonium carbonate at pH 9.0. Oxidation of MMA(III) and MMTA to MMA(V) with hydrogen peroxide was observed for standards and carrot extracts alike. Several samples of carrots collected from local markets in 2006 were also analyzed and found to contain low levels of inorganic arsenic species.