Papers by Panos Georgopoulos
Environmental Health Perspectives, 1995
The Clean Air Act Amendments (CAAA) of 1990 have established selected comprehensive, three-dimens... more The Clean Air Act Amendments (CAAA) of 1990 have established selected comprehensive, three-dimensional, Photochemical Air Quality Simulation Models (PAQSMs) as the required regulatory tools for analyzing the urban and regional problem of high ambient ozone levels across the United States. These models are currently applied to study and establish strategies for meeting the National Ambient Air Quality Standard (NAAQS) for ozone in nonattainment areas; State Implementation Plans (SIPs) resulting from these efforts must be submitted to the U.S. Environmental Protection Agency (U.S. EPA) in November 1994. The following presentation provides an overview and discussion of the regulatory ozone modeling process and its implications. First, the PAQSM-based ozone attainment demonstration process is summarized in the framework of the 1994 SIPs. Then, following a brief overview of the representation of physical and chemical processes in PAQSMs, the essential attributes of standard modeling systems currently in regulatory use are presented in a nonmathematical, self-contained format, intended to provide a basic understanding of both model capabilities and limitations. The types of air quality, emission, and meteorological data needed for applying and evaluating PAQSMs are discussed, as well as the sources, availability, and limitations of existing databases. The issue of evaluating a model's performance in order to accept it as a tool for policy making is discussed, and various methodologies for implementing this objective are summarized. Selected interim results from diagnostic analyses, which are performed as a component of the regulatory ozone modeling process for the Philadelphia-New Jersey region, are also presented to provide some specific examples related to the general issues discussed in this work. Finally, research needs related to a) the evaluation and refinement of regulatory ozone modeling, b) the characterization of uncertainty in photochemical modeling, and c) the improvement of the model-based ozone-attainment demonstration process are presented to identify future directions in this area.
Journal of Exposure Science & Environmental Epidemiology
Background Disparities in adverse COVID-19 health outcomes have been associated with multiple soc... more Background Disparities in adverse COVID-19 health outcomes have been associated with multiple social and environmental stressors. However, research is needed to evaluate the consistency and efficiency of methods for studying these associations at local scales. Objective To assess socioexposomic associations with COVID-19 outcomes across New Jersey and evaluate consistency of findings from multiple modeling approaches. Methods We retrieved data for COVID-19 cases and deaths for the 565 municipalities of New Jersey up to the end of the first phase of the pandemic, and calculated mortality rates with and without long-term-care (LTC) facility deaths. We considered 84 spatially heterogeneous environmental, demographic and socioeconomic factors from publicly available databases, including air pollution, proximity to industrial sites/facilities, transportation-related noise, occupation and commuting, neighborhood and housing characteristics, age structure, racial/ethnic composition, povert...
The extractability of contaminants affecti its transport into various organ systems within the bo... more The extractability of contaminants affecti its transport into various organ systems within the body. Assuming the contaminants will undergo dissolution and absorption by specific target tissues and organs, artificially high estimations of the bioavailable fiction or 100'%bioavailability will alter internal dose estimates. The ratio of the total amount of material present in the soil/waste matrix to that which is available for dissolution in a bio-fluid extractant gives an indication of the bioavailability of the contaminant.
Journal of Allergy and Clinical Immunology, 2013
Environmental Science & Technology, 1998
Atmospheric chemistry mechanisms are the most computationally intensive components of photochemic... more Atmospheric chemistry mechanisms are the most computationally intensive components of photochemical air quality simulation models (PAQSMs). The development of a photochemical mechanism, that accurately describes atmospheric chemistry while being computationally efficient for use in PAQSMs, is a difficult undertaking that has traditionally been pursued through semiempirical ("diagnostic") lumping approaches. The limitations of these diagnostic approaches are often associated with inaccuracies due to the fact that the lumped mechanisms have typically been optimized to fit the concentration profile of a specific species. Formal mathematical methods for model reduction have the potential (demonstrated through past applications in other areas) to provide very effective solutions to the need for computational efficiency combined with accuracy. Such methods, that can be used to "condense" a chemical mechanism, include "kinetic lumping" and "domain separation". An application of the kinetic lumping method, using the direct constrained approximate lumping (DCAL) approach, to the atmospheric photochemistry of alkanes is presented in this work. It is shown that the lumped mechanism generated through the application of the DCAL method has the potential to overcome the limitations of existing semiempirical approaches, especially in relation to the consistent and accurate calculation of the timeconcentration profiles of multiple species.
The 4th Annual CMAS Models-3 User′ s Conference, Sep 26, 2005
past studies with air quality modeling have used very few Monte Carlo runs for studying uncertain... more past studies with air quality modeling have used very few Monte Carlo runs for studying uncertainties∗ of the order of 20-200 simulations involving 10-100 parameters• Direct Decoupled Method (DDM)–provides accurate local sensitivity information–significant memory requirements as number of parameters increase–large number of simulations for global sensitivity/uncertainty analysis–requires re-coding major portions of a model (not a black-box tool)
Motivation: In microarray experiments, missing entries arise from blemishes on the chips. In larg... more Motivation: In microarray experiments, missing entries arise from blemishes on the chips. In large-scale studies, virtually every chip contains some missing entries and more than 90 % of the genes are affected. Many analysis methods require a full set of data. Either those genes with missing entries are excluded, or the missing entries are filled with estimates prior to the analyses. This study compares methods of missing value estimation. Results: Two evaluation metrics of imputation accuracy are employed. First, the root mean squared error measures the difference between the true values and the imputed values. Second, the number of misclustered genes measures the difference between clustering with true values and that with imputed values; it examines the bias introduced by imputation to clustering. The Gaussian mixture clustering with model averaging imputation is superior to all other imputation methods, according to both evaluation metrics, on both time-series (correlated) and n...
We are building three simulation models that will help us better understand the kinds of events t... more We are building three simulation models that will help us better understand the kinds of events that can cause serious cascading impacts in passenger rail and interconnected light rail, bus and road systems, the consequences of those events, and investments that could increase system resilience. An industrial systems model will allow us to simulate rail passenger traffic through a key rail station in New Jersey under normal operating conditions. Then, using plume and other models, several serious spatially and temporally characterized events will be introduced that will upset normal operations. Impacts of these events will be followed into the surrounding environment as they disrupt light rail, bus, and other auto traffic in the region. The economic model will be used to estimate the economic consequences of the events and also the consequences of making investments that could reduce the impact of these events over both short-and long-term horizon.
Environmental, dietary, demographic, and activity variables associated with biomarkers of exposur... more Environmental, dietary, demographic, and activity variables associated with biomarkers of exposure for benzene and lead
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Papers by Panos Georgopoulos