Modeling cumulative and aggregate exposures of co-occurring multimedia contaminants in a probabilistic source-to-dose framework
S.W. Wang1 , S. Isukapalli1 , A. Sasso1 ,Y.C. Yang1 , V. Zartarian2, J. Xue2, H. Ozkaynak2, and P.G. Georgopoulos1
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 modular application of MENTOR [Modeling ENvironment for TOtal Risk studies] is presented comparing the contributions of different routes to individual and population exposures to mixtures of heavy metals such as arsenic, lead, and mercury. This study employs a probabilistic source-to-dose modeling framework of the MENTOR/SHEDS-4M system [a MENTOR implementation that uses the Stochastic Human Exposure and Dose Simulation (SHEDS) approach for Multiple co-occurring contaminants and Multimedia, Multipathway, Multiroute exposures (4M)]. 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) multiple contaminant (e.g. mixtures of heavy metals) exposures for individuals or populations. It addresses aggregate and cumulative exposures to co-occurring pollutants in a consistent manner, and provides the ability to focus on mechanism-relevant time scales and subpopulations of interest. It also proceeds a major step further, to calculate target tissue dose (and corresponding biomarker levels) employing Physiologically Based Pharmacokinetic (PBPK) modeling. This offers the advantage of allowing model evaluation against field measurements. Case studies testing the MENTOR/SHEDS-4M approach are conducted using available environmental, demographic, human activity, biomarker etc. data for selected populations in the Great Lakes region; data from both the CDC's NHANES-III and the USEPA's NHEXAS (region-V) surveys are used.
This work is 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.