Description:
The FDA's market basket study reports total arsenic concentrations from composite diet samples. The use of composite diets, based on market basket sampling, is the most cost effective means of obtaining a generic arsenic exposure estimate for a population. For example, the total arsenic concentrations generated from a composite are used extensively as an estimator of arsenic exposure within the US population. However, the severity of exposure is related to the chemical form of arsenic which was not determined in these types of studies. Therefore, the need to collect speciation data is of prime importance and is outlined as a high priority research need in ORD's Arsenic Research Plan. Due to the limited availability of species specific data, estimates based on total arsenic continue to be used. Recently, the ability to predict risk has improved through the availability of speciation data for target foods, but the ability to predict cumulative risk based on composite diets is virtually nonexistent. In fact, the peer reviewed literature is void of any citations utilizing composite diets while target food speciation continues to be a rapidly growing research area. This is due to the fact that the complex sample matrix which results from the blending of proteins, fats, starches, fruits and vegetables produces many unique extraction problems. This task is aimed at overcoming these extraction problems and is driven by the potential cost savings of compositing, the need to support exposure assessment studies which collect duplicate diet samples and the need to support future epidemiology studies which also collect duplicate diet samples. Preliminary research has been conducted on composite diets as a collaborative effort with the FDA and the magnitude of the analytical problems associated with compositing are still difficult to predict. Given that this research is in its infancy (i.e., the chemical literature is void of a single citation) and the target food approach has proven effective in previous research, the target food approach will also be continued until the composite diet approach has produced similar extraction efficiencies. A second means of approaching a composite is to computationally estimate it by utilizing known arsenic concentrations in target foods. This approach will be utilized only in the case where the speciation results in the composite diet sample are severely compromised because of low analytical extraction efficiencies and/or low chromatographic recoveries. The product of this research will be a preliminary arsenic speciation database for seafoods (necessary for seafood estimates and computational composites which contain seafood), an arsenic speciation protocol for the analysis of dietary components, and preliminary information on the limitations associated with composite diets. This should provide a more accurate assessment of human exposure to arsenicals.
Keywords:
ARSENIC SPECIATION, COMPOSITE DIETARY SAMPLE, ARSENIC EXPOSURE,
Project Information:
Progress
:-This work builds upon an analytical approach that has been outlined in a completed task (Speciation of Arsenic in Edible Biota to Support Risk Assessment Determination of exposure source estimates for Arsenic - Task 4030). To date, the use of a tetramethylammonium hydroxide (TMAOH) based extraction has proven an effective means to extracting arsenicals from seafoods. These results were presented at the 2001 Winter Conference. The Winter Conference presentation focused on a comparison between a synthetic stomach extraction and a TMAOH extraction. The TMAOH extraction was found to produce a more quantitative extraction relative to the synthetic stomach. In addition, the TMAOH extraction minimized the formation of degradation products relative to the synthetic stomach. The TMAOH extraction protocol has been evaluated on a wider variety of seafoods (ISEA 2002). These data indicated that up to 40% of the chromatographable arsenic in shellfish can be arsenosugars. Data presented at the Pittsburgh Conference in March, 2002 indicated that a 2 stage extraction (base followed by acid) was necessary to liberate the maximum concentration of arsenosugars. The application of the two stage extraction provides a good mass balance between the arsenic extracted and the arsenic chromatographed. This procedure has been applied to 15 seafood samples including clams, oysters, and cockle. These samples represent a fairly broad range of shellfish but do not provide a good representation of finfish such as salmon and halibut. Therefore, data collection continues on finfish.
- An exposure study was conducted in association with a tribe in USEPA's Region 10. This study was done in collaboration with the USEPA's National Health and Environmental Effects Research Laboratory (NHEERL). Seafood sample collection and arsenic speciation of these samples was conducted by NERL while NHEERL collected blood and urine samples to assess the exposure. Data was presented to the tribe in October 2003.
- A brief summary of the arsenic speciation research being conducted in this task was presented to USEPA's Office of Pesticide Programs (OPP) and National Center for Environmental Assessment.
- In FY04, twenty different seafood samples were analyzed by using the two step (base followed by weak acid) extraction procedure. The primary focus was to identify the unchromatographable species. This was accomplished and the data for these twenty samples were condensed into a single table for presentation and publication purposes.
- Attempts to extract poultry samples produced a number of unchromatographic arsenicals from chicken liver samples. Currently, the identification of these compounds is a priority of the FDA. Preliminary results indicate that one of these species is roxasone, an arsenic based "growth promoter" (it kills parasites in the stomach of the chicken and "promotes" weight gain per unit food intake). Therefore, roxasone and its metabolites need to be added to the arsenic analyte list for true composites. The identification of sulfur analogs of existing arsenicals in seafood further expands the list of analytes. A complete chromatographic resolution of these newly identified species is currently impossible. The development of a new separation approach would require considerable effort and thus, reduce the number of target foods that could be analyzed under this task. Therefore, as a result of FY04 results, research was redirected towards target foods with the objective to model or estimate the "composite" exposure based on target food components within the composite.
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 from exposure to this element. This task is relevant to the Agency's mission in that it addresses research needs identified in the ORD's Arsenic Research Plan (Exposure issues 2, 5 and 6) which ultimately will improve drinking water regulations and minimize exposure to arsenic from drinking water ingestion. The ability to estimate species specific arsenic concentrations in dietary samples is required to support a number of arsenic research agendas within the agency. First, the exposure source estimate (water vs. diet) is used in formulating the arsenic related drinking water regulations. Improved dietary assessments provides the scientific foundation of this estimate. In setting the 2001 Arsenic Rule, EPA assumed that the average adult in the U.S. got 10 Fg/day of inorganic arsenic from food, mostly seafood, (Note: this estimate considers only the easily extracted inorganic arsenic, and excludes the various organic-bound forms), compared to an average intake from drinking water (at the Maximum Contaminant Level - MCL) of 10-12 Fg/day. Second, the epidemiology (EPI) studies which are used in formulating MCLs for drinking water often utilize default assumptions to estimate the dietary component of the arsenic exposure. Replacement of these default assumptions will improve the quality of the EPI exposure estimate. As a result, improved EPI studies will lead to more accurate cancer dose-response estimates and more accurate risk characterizations, as well as more accurate health risk reduction benefit analyses will help to support future rulemakings (e.g., 6 year review, CCA reanalyses and herbicides re-registrations). Third, dietary exposure assessments are conducted utilizing composite diets. Speciation of composite diets is currently undocumented in the literature and research is needed to improve these studies (i.e., a composite diet sample provides a "snap shot" of actual exposure which would be difficult to obtain from target food analyses alone.) Significance: The data collected under this task will aid in providing speciated arsenic dietary exposure data in seafoods. Speciated arsenic is significant because it provides a direct indicator of the toxicity of an exposure. The toxicity of drinking waters exposures to arsenic cannot be correlated with dietary exposures because water contains almost exclusively toxic arsenic whereas dietary exposures are made up of both toxic and nontoxic arsenic. Impact: These data will help the Office of Ground Water and Drinking Water (OGWDW) formulate exposure source estimates and provide regional support to assessing acute sub-population exposures. These data will provide guidance to the FDA in assessing risk based exposures to arsenic in seafoods under the Food Quality Protection Act. These data may also be useful to USEPA's Office of Pesticide Programs because DMA and other arsenic containing pesticides are under review for continued use in the United States. Collaboration and Customer Interaction: CERB has collaborated with NHEERL in the collection of daily intake samples from a Region 10 tribal study. The interaction allowed CERB scientists to communicate some of the limitations associated with compositing dietary samples. The analyses of these samples provided NHEERL with dietary exposure data on a sub-population with high seafood ingestions. Communication is maintained with OGWDW in order to determine research needs and provide information which could impact future arsenic drinking water regulations. This exchange is accomplished through teleconferences, through communication with NERL's Assistant Laboratory Director for Drinking Water or through exchange of research results. A teleconference was held in FY03 between ORD and OGWDW to review the individual tasks and how they would feed into the MCL reasse
Clients
:Office of Ground Water and Drinking Water (Irene Dooley, Hiba Shukairy, Valerie Blank, Kesha Forrest)
Research Component
:ARSENIC
Risk Paradigm
:EXPOSURE
Project IDs:
ID Code
:none
Project type
:ORD-DW Plan
ID Code
:5881
Project type
:OMIS