Impact/Purpose:

To develop sensitive arsenic speciation methodology for determining background exposure levels of inorganic arsenic in dietary samples, with an emphasis on infant diets, and to apply this to in vitro bioaccessibility studies.

Description:

Ingestion of arsenic is the primary route of exposure for most people, with dietary intake and drinking water as the primary sources of that exposure. Traditionally, measurements of arsenic dietary intake are based on food consumption data coupled with total arsenic data from a market basket survey of a large variety of foods or composite diet samples. The daily total arsenic intake determined in these surveys is generally dominated by arsenic from seafood, the consumption of which varies by country and age group. Arsenic in seafood is generally greater than 80% organically-bound, nontoxic forms with the remainder potentially being toxic arsenic. The Joint Expert Committee on Food Additives (JECFA) of the Food and Agriculture Organization of the United Nations and the World Health Organization (FAO/WHO) have set a Provisional Tolerable Weekly Intake (PTWI) for inorganic arsenic of 15 µg/kg body weight and Provisional Tolerable Daily Intake (PTDI) level of 2.1 µg/kg body weight/day of inorganic arsenic. While the dietary intake of arsenic for most age groups is well below the PTWI and PTDI levels, it was reported that intake for infants approached the PTDI level. In addition, several studies now indicate that children may metabolize arsenic differently than adults. For example, it has been reported that total arsenic excretion per kg body weight is higher for children than adults and that the ratio of dimethylarsinic acid (DMA) / monomethylarsonic acid (MMA) in urine indicates a difference in the way adults and children methylate arsenic. Therefore, their risk from dietary arsenic may be different than the typical adult population. As a result, infant foods are of interest because a much larger percentage of the total arsenic intake for infants comes from a terrestrial-based (non-seafood) diet. The problems associated with speciation of arsenic in infant foods are the same as those associated with many terrestrial foods. The arsenic concentrations are low and unfortunately, much of the data available regarding total arsenic and inorganic arsenic levels in terrestrial foods is clouded by the lack of sensitive methodology. Methods for the accurate determination of background total arsenic levels and speciation in dietary samples will require detection limits approaching 20 µg/kg in the food. Thus, studies on the other infant foods will first require improvements in the arsenic speciation methodology to decrease method detection limits.

The U.S. FDA recently published the results of an initial study on arsenic speciation in infant foods, and infant foods containing rice were found to have the highest levels of both total and inorganic arsenic. Significant levels of DMA were also detected, but studies on the bioaccessibility of arsenic in infant foods were not reported. Infant rice cereals are generally enriched with iron and other vitamins and minerals which may affect the bioaccessibility of arsenic. In addition, the arsenic in all these foods can be bound to protein or starch and the human digestive tract's ability to release the arsenic is a measure of the bioaccessibility of the arsenic. Therefore, an additional goal of this task is to estimate the bioaccessibility of the arsenic in these terrestrial foods. Ultimately, this extramural task will utilize the U.S. FDA's knowledge to develop sensitive arsenic speciation methodology for determining background exposure levels of inorganic arsenic in terrestrial -based dietary samples, with an emphasis on infant diets, and apply this to in vitro bioaccessibility studies. This will produce an improved understanding of infant exposure in support of sensitive sub-population concerns in the 6-year review of the Arsenic Rule and provide a more complete exposure assessment for adults from terrestrial foods.

Record Details:

Record Type:PROJECT

Start Date:06/01/2004

Projected Completion Date:09/01/2007

OMB Category:Other

Record ID: 114556

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Project Information:

Progress :This task was peer reviewed by the Office of Ground Water and Drinking Water (Irene Dooley) and by Spiros Pergantis (Assistant Professor of Analytical Chemistry at the University of Crete). An Interagency Agreement with the U.S. FDA was funded in late FY04. Procurement of the ICP-MS instrument described in the Statement of Work was initiated.

Relevance :Relevance: The Office of Research and Development (ORD) has designated the study of arsenic as a high priority research area because of the health risk associated with exposure to this element. This task is relevant to the Agency's mission in that it addresses high priority research needs identified in ORD's Arsenic Research Plan (Exposure Issue 6) which ultimately will improve drinking water regulations and minimize exposure to arsenic from drinking water ingestion. The ability to estimate arsenic dietary exposure has also been identified by research groups such as the American Water Works Association Research Foundation and the National Research Council as a critical need in establishing accurate exposure estimates in future epidemiology (EPI) studies. In addition, drinking water regulations require an evaluation of sensitive subpopulations. Infants are considered a sensitive sub-population based on exposure per unit body weight. In summary, this research will lead to improved design and interpretation of EPI studies and US population dietary exposure estimates which, in turn, will lead to a more accurate cancer dose-response estimates and more accurate risk characterizations, as well as more accurate health risk reduction benefit analyses supporting future rulemakings (i.e., Arsenic Rule 6-year review, CCA reanalyses and herbicides re-registrations. Significance / Impact: This data should improve exposure source estimates (water vs. diet) which are used in establishing Safe Drinking Water Regulations. This data could be used by the FDA to support exposure estimates under the Food Quality Protection Act and the analytical capability refined under this task can be used in improving dietary exposure estimates in future epidemiology studies. Collaboration and Customer Interaction: The research within this task is being conducted through an Interagency Agreement (IAG) with the U.S. FDA. The Statement of Work for the IAG was reviewed by Irene Dooley in the Office of Ground Water and Drinking Water in order to determine research needs and provide information which could impact future arsenic drinking water regulations. Customer interaction is accomplished through teleconferences, through communication with NERL's Assistant Laboratory Director for Drinking Water or through exchange of research results.

Clients :Office of Ground Water and Drinking Water (Irene Dooley, Hiba Shukairy, Valerie Blank, Kesha Forrest)

Project IDs:

ID Code :20522

Project type :OMIS