Probabilistic Modeling of Dietary Arsenic Exposure and Dose and Evaluation with 2003-2004 NHANES Data

Article excerpt

BACKGROUND: Dietary exposure from food to toxic inorganic arsenic (iAs) in the general U.S. population has not been well studied.

OBJECTIVES: The goal of this research was to quantify dietary As exposure and analyze the major contributors to total As (tAs) and iAs. Another objective was to compare model predictions with observed data.

METHODS: Probabilistic exposure modeling for dietary As was conducted with the Stochastic Human Exposure and Dose Simulation-Dietary (SHEDS-Dietary) model, based on data from the National Health and Nutrition Examination Survey. The dose modeling was conducted by combining the SHEDS-Dietary model with the MENTOR-3P (Modeling ENvironment for TOtal Risk with Physiologically Based Pharmacokinetic Modeling for Populations) system. Model evaluation was conducted via comparing exposure and dose-modeling predictions against duplicate diet data and biomarker measurements, respectively, for the same individuals.

RESULTS: The mean modeled tAs exposure from food is 0.38 [micro]g/kg/day, which is approximately 14 times higher than the mean As exposures from the drinking water. The mean iAs exposure from food is 0.05 [micro]g/kg/day (1.96 [micro]g/day), which is approximately two times higher than the mean iAs exposures from the drinking water. The modeled exposure and dose estimates matched well with the duplicate diet data and measured As biomarkers. The major food contributors to iAs exposure were the following: vegetables (24%); fruit juices and fruits (18%); rice (17%); beer and wine (12%); and flour, corn, and wheat (11%). Approximately 10% of tAs exposure from foods is the toxic iAs form.

CONCLUSIONS: The general U.S. population may be exposed to tAs and iAs more from eating some foods than from drinking water. In addition, this model evaluation effort provides more confidence in the exposure assessment tools used.

KEY WORDS: arsenic, dietary, drinking water, exposure, MENTOR, model, probabilistic, SHEDS. Environ Health Perspect 118:345-350 (2010). doi:10.1289/ehp.0901205 available via http://dx.doi.org/[Online 23 November 2009]

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Human exposure to arsenic (As) can occur via different routes. A well-known early medical report about As exposure and adverse health effects discussed cancer associated with dermal exposure to As-containing medication used for treating some forms of skin diseases (Hutchinson 1887). Later studies on occupational populations exposed to As compounds in industrial environments demonstrated that respiratory inhalation is a primary route of occupational As exposure, but ingestion and dermal exposure can be significant in specific situations (Occupational Safety and Health Administration 2005; World Health Organization 2004).

Compared with the simpler As chemistry and easily identified As exposure in medical and occupational fields, As chemistry and exposure routes for the general population are much more complex. General population As exposure varies according to local geochemistry, environmental pollution, living conditions, lifestyles, and activity patterns of the exposed populations. Better characterization of environmental As levels and human activity patterns is critical for accurately assessing the human exposure to As in the general population and the related health risks.

Many efforts in studying As exposure of and regulating As intake by the general population have been focused on the ingestion of As-contaminated water (Abernathy et al. 1999, 2003; Anetor et al. 2007; Chen et al. 1988a, 1988b; Chiou et al. 2001; National Research Council 2001; Tchounwou et al. 2003). This drinking water-focused As regulation also reflects a common understanding that inorganic As (iAs) is more harmful than organic As (oAs) (Tchounwou et al. 2003). A recent publication concluded that typical and high-end background exposures to iAs in the U.S. population do not present elevated risks of carcinogenicity (Boyce et al. …