Assessing multimedia/multipathway exposures in the MENTOR framework. Preliminary case study: Arsenic
P.G. Georgopoulos, S.W. Wang, V.M. Vyas (EOHSI, UMDNJ - R.W. Johnson Medical
School and Rutgers University);
E. Vowinkel (U.S. Geological Survey & EOHSI)
J. Xue, H. Ozkaynak (US EPA - NERL)
MENTOR (the Modeling Environment for Total Risk studies) is an open and extensible multiscale framework that links new and existing (mechanistic or data-driven) models, databases, and numerical and analytic tools for probabilistically assessing exposures to individuals, populations, and susceptible subpopulations, as well as for diagnosing potentially complex relationships between sources and dose.
The present study demonstrates a preliminary application of the MENTOR framework to the study of multimedia/multipathway exposures to arsenic. This application aims to test and refine computational methods and tools for assessing 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 total arsenic exposures for individuals and populations. In this work existing, national and local, databases are used to test the regional and local validity of various hypotheses. One such commonly accepted, hypothesis is that, for non-occupationally exposed individuals, uptake of arsenic via dermal exposures from soil and water and inhalation are minor contributors to total exposure whereas intake from food and water are most significant; here, case studies consider potential exceptions, such as populations in the vicinity of arsenic emitting industrial facilities or areas where soils are contaminated with arsenic.
A major objective is to compare the relative contributions of food to total regional population exposures to those of drinking water; the significance of factors such as local food consumption habits and local drinking water quality (as well as of the associated ground and surface water supplies) are studied and discussed. Issues of arsenic speciation (organic versus inorganic) and the limitations of existing databases are also discussed. This assessment of multimedia/multipathway population exposures to arsenic employs a combination of newly developed modules of MENTOR and of EPA's SHEDS (Stochastic Human Exposure and Dose Simulation) system, as well as various standard modeling approaches, such as the EPANET water distribution model.
Assessment of the drinking water contribution to exposure in this study relies on the recently completed USEPA Arsenic Occurrence and Exposure Database (AOED) and WITF (Water Industry Technical Fund) National Arsenic Occurrence Survey (NAOS), and on primary databases such as the USGS National Water Information System (NWIS) and Water Quality Network (WQN) and the USEPA Safe Drinking Water Information System (SDWIS). The assessment of exposures through food utilizes primarily the 1994-1996 USDA Continuing Survey of Food Intakes by Individuals (CSFII) data, supplemented by data from NHEXAS (National Human Exposure Assessment Survey) studies. Data for assessing inhalation and dermal exposures are derived from a variety of information sources, including the USGS National Geochemical Atlas (for soil compositions); the USEPA Aerometric Information Retrieval System (AIRS); the 1996 National Toxics Inventory (NTI) and the associated annual average airborne concentration estimates of the National Air Toxics Assessment (NATA); the HazDat database; etc. The Consolidated Human Activities Database (CHAD) was used to develop activity patterns; demographic information was derived from Census 2000 data.
Disclaimer: This abstract has been reviewed in accordance with the U.S. Environmental Protection Agency's peer and administrative review policies and approved for presentation and publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.