Human Exposure Modeling for Mercury using the MENTOR Framework
P.G. Georgopoulos1 , S-W. Wang1 , S. Isukapalli1 , A. Sasso1 , S. Tong1 , J. Xue2 , T. McCurdy2 , M. Zhang2 and L. Sheldon2
1Environmental and Occupational Health Sciences Institute, a Joint Institute of UMDNJ-Robert Wood Johnson Medical School and Rutgers, the State University of New Jersey, Piscataway, NJ;
2National Exposure Research Laboratory (NERL), USEPA, Research Triangle Park , NC , USA
A preliminary assessment of human exposure to Hg and MeHg is presented for selected subpopulations living in the Great Lakes area of New York State . This study employs a probabilistic source-to-dose implementation of the MENTOR/SHEDS-4M system [Modeling ENvironment for TOtal Risk studies (MENTOR) incorporating the Stochastic Human Exposure and Dose Simulation (SHEDS) approach for Multiple co-occurring contaminants and Multimedia, Multipathway, Multiroute exposures (4M)]. The MENTOR/SHEDS-4M system allows simulations through both "Individual Based Exposure Modeling" (IBEM) and "Population Based Exposure Modeling" (PBEM) approaches. Both these approaches employ a "Person Oriented Modeling" (POM) formulation, i.e. they are driven by the attributes and activities of exposed "real" and/or "virtual" individual(s). The MENTOR/SHEDS-4M combines microenvironmental and human activities characterization to assess the relative contribution of (1) media (e.g., water, food, dust); (2) pathways (e.g., drinking water, diet, hand-to-mouth) and (3) routes (e.g., oral, inhalation, dermal) to (4) exposures to multiple contaminants (e.g. VOCs and heavy metals), for individuals or populations. Results from a preliminary analysis of dietary exposure to Hg and MeHg are presented here. A dietary exposure module was developed by USEPA NERL based upon work undertaken by other USEPA offices; this module combines information about food consumption by age and gender with data about mercury residues in specific food items. The approach is probabilistic in nature, explicitly addressing both variability and uncertainly in the concentration and consumption databases. This dietary module has been linked with other exposure relevant modules within the MENTOR/SHEDS-4M system. The preliminary dietary assessment indicates that the major contribution of mercury exposure is due to consumption of fish (fresh and canned) in the diet. Minor sources are liver, chicken, and some vegetables. The subpopulation-specific mercury intake distributions calculated by the dietary exposure model are to be used as inputs for the calculation of target tissue doses employing the "multi-metal" Physiologically Based Toxicokinetic (PBTK) module of the MENTOR/SHEDS-4M system, currently under on-going development. This offers the advantage of allowing estimation of biologically relevant doses as well as model evaluation against biomarker measurements.
This work had been funded in part by the US Environmental Protection Agency under Cooperative Agreement # EPAR-827033 to the Environmental and Occupational Health Sciences Institute (EOHSI). The viewpoints expressed here are the responsibility of the authors and do not necessarily reflect the views of the USEPA or its contractors.