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Elemental Speciation as Essential Part of Formulating Exposure Assessments that Support Risk Estimates
Oral Presentation
Prepared by J. Creed1, T. Pinyayev2, M. Mantha3, P. Creed4, J. Trent5, E. Yeary6, J. Xue7
1 - USEPA, NERL, Mail Stop: 593, Cincinnati, OH, 45268
3 - Oak Ridge Institute for Science and Education Scholar, U.S. EPA, NERL, Cincinnati, OH, 45268
5 - Student Services Contractor, NERL, MCEARD, Cincinnati, OH, 45268
6 - Student Services Contractor, NERL, MCEARD, Cinncinnati, OH, 45268
7 - U.S. EPA, NERL, HEASD, -, Research Triangle Park, NC,
Contact Information: creed.jack@epa.gov; 513-569-7833
ABSTRACT
The chemical form specific toxicity of arsenic has caused scientists to move toward species specific assessments with an emphasis on biological relevance of an exposure. For example, numerous studies on the occurrence of arsenic in rice have documented the exposure potential from this commonly consumed crop, but few have addressed the bioaccessibility question essential to converting occurrence into risk. The first part of this presentation will discuss the use of a speciation based gastrointestinal based assay to estimate the bioaccessibility of arsenicals in rice. Utilizing these estimates within a modeling framework allows for population based exposure (µg/kg of body weight/day) assessment. The approach will be discussed with an emphasis on risk predictive advantages / limitations and how this information can inform decision making.
The second part of this presentation will discuss the need to incorporate gastrointestinal biotransformation of arsenic oxides in order to accurately estimate the pre-systemic species specific distribution available for uptake in the intestine. The methylation and thiolation of the parent arsenic oxide will be estimated using an in vitro anaerobic incubation of the arsenical in the cecum content of a mouse. The analytical techniques used to confirm the identity of these arsenicals will be discussed along with the need to incorporate the microbiological aspects of the intestine within any in vitro assay that intends to predict species specific exposures.
Oral Presentation
Prepared by J. Creed1, T. Pinyayev2, M. Mantha3, P. Creed4, J. Trent5, E. Yeary6, J. Xue7
1 - USEPA, NERL, Mail Stop: 593, Cincinnati, OH, 45268
3 - Oak Ridge Institute for Science and Education Scholar, U.S. EPA, NERL, Cincinnati, OH, 45268
5 - Student Services Contractor, NERL, MCEARD, Cincinnati, OH, 45268
6 - Student Services Contractor, NERL, MCEARD, Cinncinnati, OH, 45268
7 - U.S. EPA, NERL, HEASD, -, Research Triangle Park, NC,
Contact Information: creed.jack@epa.gov; 513-569-7833
ABSTRACT
The chemical form specific toxicity of arsenic has caused scientists to move toward species specific assessments with an emphasis on biological relevance of an exposure. For example, numerous studies on the occurrence of arsenic in rice have documented the exposure potential from this commonly consumed crop, but few have addressed the bioaccessibility question essential to converting occurrence into risk. The first part of this presentation will discuss the use of a speciation based gastrointestinal based assay to estimate the bioaccessibility of arsenicals in rice. Utilizing these estimates within a modeling framework allows for population based exposure (µg/kg of body weight/day) assessment. The approach will be discussed with an emphasis on risk predictive advantages / limitations and how this information can inform decision making.
The second part of this presentation will discuss the need to incorporate gastrointestinal biotransformation of arsenic oxides in order to accurately estimate the pre-systemic species specific distribution available for uptake in the intestine. The methylation and thiolation of the parent arsenic oxide will be estimated using an in vitro anaerobic incubation of the arsenical in the cecum content of a mouse. The analytical techniques used to confirm the identity of these arsenicals will be discussed along with the need to incorporate the microbiological aspects of the intestine within any in vitro assay that intends to predict species specific exposures.