Assessing Multimedia/Multipathway Human Exposures to Mercury and Methylmercury Using a Probabilistic Source-to-Dose Framework
S.W. Wang1, A. Sasso1, S. Isukapalli1, Y.C. Yang1, P.G. Georgopoulos1, V. Zartarian2, J. Xue2, T. McCurdy2, H. Ozkaynak2
1Environmental and Occupational Health Sciences Institute, UMDNJ - R.W. Johnson Medical School and Rutgers University, Piscataway, NJ;
2National Exposure Research Laboratory (NERL), USEPA, Research Triangle Park, NC
A preliminary assessment of human dietary exposure to Hg and MeHg is presented for the general population in Oswego County, NY. 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)]. It dynamically links biologically-based modules with environmental, microenvironmental, and human activity modules to estimate exposures and target tissue doses. Databases for food consumption patterns (CSFII 1994-1996, 1998), food residue (TDS 1991-2003), food frequency survey (NHANES 2001-2002), and related auxiliary data were used to model one-day and one-month dietary exposures for the population under consideration. The results show that the major contribution of Hg and MeHg exposure is due to consumption of fish. The one-month simulation can characterize dietary intake distributions above the level of 10-3 µg/kg/day for a larger portion of the study population than the one-day simulation. These distributions were then used as inputs for the calculation of target tissue doses employing the Physiologically Based Toxicokinetic (PBTK) module of the MENTOR/SHEDS-4M system. This offers the advantage of allowing estimation of biologically relevant doses as well as model evaluation against biomarker measurements. The predicted distributions of MeHg biomarker (blood and hair) concentrations calculated from MENTOR/SHEDS-4M are comparable to the observed concentrations reported in the NHANES-2002 and NHEXAS-V databases. Future efforts will focus on case studies characterizing exposures of selected subpopulations (e.g. sport and subsistence anglers).
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.