The Center for Exposure and Risk Modeling (CERM)


The principal mission of CERM’s cooperative research effort is the development and application of computational tools for source-to-dose exposure assessments.


Modeling Environment for Total Risk studies

MENTOR is an evolving open “modeling support system” which can also be described as an expandable computational toolbox. It is intended to facilitate the consistent multiscale, source-to-dose, modeling of exposures to contaminants for both individuals and populations, employing a combination of existing and new approaches to enhance evaluation and application of existing and new models to understand environmental and biological processes.


To provide “user-oriented” implementations of MENTOR for specific applications, a number of “customized” versions have been developed:

  • MENTOR-1A  employs a “one atmosphere” approach to characterize simultaneous exposures of individuals or populations to multiple, co-occurring atmospheric contaminants (e.g. ozone, fine particles, air toxics, etc.). The “one atmosphere” approach places emphasis on accounting for the dynamic physical and chemical interactions of the contaminants, in both ambient air and in specific residential, occupational, and vehicular microenvironments.
  • MENTOR-4M  provides a unified multiroute/multipathway modeling framework for aggregate and cumulative exposure assessments. The focus is on contaminants that are present in multiple environmental media and on mixtures of such contaminants.
  • MENTOR-3P  is a modular, “generalized” physiologically-based pharmacokinetic modeling framework for human populations that allows simultaneous consideration of multiple, co-occurring chemicals in a consistent manner, while incorporating information for attributes of intra- and inter-individual variation and variability, either physiological or biochemical, from various recent databases.
  • MENTOR-2E  provides computational tools appropriate for characterizing exposures specifically for emergency events, as a means for improving planning for emergency response. Accordingly, emphasis is given to the critical attributes of physicochemical processes across the various temporal and spatial scales that are relevant to the evolution of the emergency event.
  • MENTOR-DOT  provides a wide range of state-of-the-art diagnostic tools, such as the Stochastic Response Surface Method (SRSM), the High Dimensional Model Representation (HDMR), and Bayesian Markov Chain Monte Carlo (MCMC) optimization techniques, which allow comprehensive sensitivity/uncertainty analysis of complex system models, systematic complex model reduction to obtain Fast Equivalent Operational Models (FEOMs), and efficient model/data fusion.

Citation:  Georgopoulos P. (2008). A multiscale approach for assessing the interactions of environmental and biological systems in a holistic health risk assessment framework. Water, Air, and Soil Pollution: Focus 8 (1): 3-21


Prioritization/Ranking of Toxic Exposures with GIS Extension 

While MENTOR is a comprehensive simulation platform that has been evolving over the past several years, PRoTEGE is a new framework that utilizes simplified versions of MENTOR components to provide screening level analyses, employing extant data and modules and a chemical Life-Cycle Assessment (LCA) approach for the screening assessment of human exposures associated with toxics in various (micro)environments and products.



PRoTEGE  derives from and complements MENTOR, which supports detailed person-oriented (“bottom-up”) source-to-dose exposure modeling for mixtures of multiple multimedia contaminants. MENTOR allows a study to focus on specific locations and sub-populations, but is both data and resource intensive. The simplified population-oriented approach of PRoTEGE provides estimates of exposures, allowing calculations up to county-level resolution, and is intended to complement the more commonly used source-oriented approaches for screening level exposure characterization. The PRoTEGE system is currently being tested with case studies spanning a broad spectrum of contaminants present in the ambient, residential, and occupational environments, including consumer products and foodstuffs.

The PRoTEGE Tiered Exposure Ranking ( PRoTEGE/TiER ) framework is designed to utilize available and on-going advances in (a) informatics methods and computational tools, (b) extant database content and availability, and (c) integrative environmental/exposure/biological modeling, to support analyses of data in either an exploratory context or in relation to various specific health-related hypotheses.


  • Royce S.G., Mukherjee D., Cai T., Xu S.S., Alexander J.A., Mi Z., Calderon L., Mainelis G., Lee K., Lioy P.J., Tetley T.D., Chung K.F., Zhang J. and Georgopoulos P.G. (2014). Modeling population exposures to silver nanoparticles present in consumer products. Journal of Nanoparticle Research. 16(11): 2724. DOI:10.1007/s11051-014-2724-4. PMCID:PMC4346165.
  • Georgopoulos P.G., Brinkerhoff C.J., Isukapalli S., Dellarco M., Landrigan P.J. and Lioy P.J. (2013). A tiered framework for risk-relevant characterization and ranking of chemical exposures: Applications to the National Children’s Study (NCS). Risk Analysis 34(7): 1299-316. DOI:10.1111/risa.12165.
  • Mitchell J., Arnot J.A., Jolliet O., Georgopoulos P., Isukapalli S., Dasgupta S., Pandian M., Wambaugh J., Egeghy P., Cohen-Hubal E.A. and Vallero D.A. (2013). Comparison of modeling approaches to prioritize chemicals based on estimates of exposure and exposure potential. Science of the Total Environment 458-460: 555-567. DOI: 10.1016/j.scitotenv.2013.04.051

Base funding for the operation of CERM was provided by USEPA-NERL through a University Partnership Agreement, 2000-2010.

This web page is a temporary placeholder for a link to the CERM website which is under revision and will be available soon.