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Society For Risk Analysis Annual Meeting 2008

Risk Analysis: the Science and the Art

Session Schedule & Abstracts

* Disclaimer: All presentations represent the views of the authors, and not the organizations that support their research. Please apply the standard disclaimer that any opinions, findings, and conclusions or recommendations in abstracts, posters, and presentations at the meeting are those of the authors and do not necessarily reflect the views of any other organization or agency. Meeting attendees and authors should be aware that this disclaimer is intended to apply to all abstracts contained in this document. Authors who wish to emphasize this disclaimer should do so in their presentation or poster. In an effort to make the abstracts as concise as possible and easy for meeting participants to read, the abstracts have been formatted such that they exclude references to papers, affiliations, and/or funding sources. Authors who wish to provide attendees with this information should do so in their presentation or poster.

Common abbreviations

Air Quality Exposure Assessment

Room: Commonwealth C   10:30 AM-Noon

Chair(s): Jonathan Levy

M2-F.1  10:30  Predictors of Heterogeneity in Aircraft Emissions of Air Toxics Associated With Individual and Population Cancer Risks. Zhou Y*, Levy JI; Harvard School of Public Health

Abstract: Airports represent a complex source type of increasing importance that may contribute appreciably to air toxics risks. Given the increasing interest among community groups and other stakeholders in including air toxics risks when considering the marginal contribution of airports or proposed airport expansions to health risks, it would be valuable to be able to predict the exposure and health risk of emissions or emissions changes at an airport, both from an individual and a population perspective. In this study, we apply a high-resolution atmospheric dispersion model (AERMOD) to a sample of 33 airports, including small and large airports in urban and rural settings across the U.S.. We estimate the emission rates required at these airports to exceed a specified individual risk threshold (i.e., 10-6 for the lifetime cancer risk for the maximally exposed individual), and we additionally calculate the total population risk to determine whether prioritization based on maximum individual exposure and risk would correspond with that based on total population exposure and risk. Furthermore, we develop models to explain the heterogeneity in these emission rates across airports, based on meteorological and population data. We focus on air toxics with different chemical characteristics—benzene, 1,3-butadiene, and particle-bound PAHs. We apply AERMOD and estimate incremental concentrations from airports at the centroids of census tracts or block groups within 50 km. Our findings indicate that the minimum emissions threshold varies significantly across airports and that optimization based on individual exposure and risk thresholds will differ from optimization based on total population exposure and risk. These results provides a method to quickly but reasonably determine the likelihood of public health impacts of concern for airport modifications or expansions, and can be expanded to include non-cancer or criteria pollutant effects in future assessments.

M2-F.2  10:50  Airborne Cr(VI) Monitoring During Building Demolition. Brenner D*, Olliges S, Anderson T, Jimenez A; 1. Neptune and Company, Inc.,2. NASA, 3. ISSi, 4.ISSi

Abstract: Building N218 at NASA Ames Research Center (ARC) and its associated wind tunnel structure underwent demolition between mid-July and the end of December 2007. Because the wind tunnel and its associated structural elements were coated with chromium containing paints and coatings there was concern that Cr (VI) dust and particulates would be released during the demolition process. Because the chromium was released during demolition as solid particulates, sampling for Cr (VI) involved collecting airborne particulates over a 24-hr period and sending the collected sample to an outside laboratory for analysis of TSP weight and Cr (VI) content. Samples were collected during three different phases of the demolition process. Prior to demolition samples were collected to establish a baseline Cr (VI) concentration in the Moffett Field area. Knowing the normal baseline concentration allowed comparisons to be made to the measured Cr (VI) concentrations during the demolition process. The second phase of sampling was during the demolition itself and the third phase was after demolition was complete but site cleanup and grading and filling activities were taking place. Due to limitations in available equipment PM10 samples could not be collected during Phase 2, consequently one of the other goals of the Phase 1 sampling was to collect both PM10 and TSP samples, so that the TSP samples collected during Phase 2 could be calibrated relative to the PM10 concentration for risk assessment purposes. Data from all three phases of the sampling will be presented. The comparison of the PM10 and TSP results from Phase 1 to establish the utility of TSP Phase 2 sample results for risk assessment purposes will be presented. Additional data showing the relationship of the results to meteorological conditions, type and level of demolition activities and proximity of sample locations to the demolition site will also be presented.

M2-F.3  11:10  Modeling variability in environmental tobacco smoke exposure and health risk at fine spatial resolution. Chahine T*, Levy JI; Harvard School of Public Health

Abstract: Communities are increasingly involved in identifying and addressing environmental hazards and exposures, but data are inadequate to allow communities to quickly but reasonably prioritize across disparate exposures and endpoints. National-scale risk assessments are available for some stressors but may not be readily scaled to a community given variability in exposure patterns and vulnerability attributes. One of the stressors of concern in many communities involves indoor air pollution, for which community-specific factors may be particularly significant. The objective of our analysis is to characterize at a community level across the United States the magnitude and distribution of adverse health outcomes associated with residential exposure to environmental tobacco smoke (ETS). Based on mass balance principles, residential ETS exposure can be approximated as a function of time spent at home, frequency of smoking at home, air exchange rate, and home volume. We use previously derived models and publicly available data to estimate each of these parameters as a function of demographic characteristics, housing characteristics, and behavioral characteristics, taking account of correlations among parameters given common socioeconomic and geographic drivers. Combining these parameters, we determine residential ETS exposure by community, stratified by a proxy for socioeconomic status which is a common predictor across these parameters. We link ETS exposure with dose-response functions for key health outcomes, taking account of effect modifiers previously determined in the epidemiological literature and spatial patterns of age and disease state. We characterize total population risk and average per capita risk and determine parameters that drive variability in these and other risk measures. The result is a risk characterization for each geographic location, which will inform community awareness, risk prioritization efforts, and action toward mitigating indoor air pollution from ETS.

M2-F.4  11:30  Air Pollution Exposure Model for Individuals (EMI) in Health Studies: Model Evaluation of Residential Air Exchange Rates. Breen MS*, Breen M, Williams RW; (1,3) National Exposure Research Laboratory, US EPA; (2) National Center for Computational Toxicology, US EPA; Biomathematics Program, Department of Statistics, North Carolina State University

Abstract: Air pollution epidemiology studies have observed statistically significant associations between particulate matter (PM) concentrations and increased rates of morbidity and mortality. These studies often use air pollution measurements from central ambient monitoring sites as exposure surrogates. To better understand the linkages between ambient concentrations and exposures, we are developing an air pollution exposure model for individuals (EMI) in health studies to predict personal exposures from ambient concentrations and questionnaire information such as building operation, indoor sources, and time-activity patterns. A critical aspect of the EMI is the estimation of the air exchange rate (AER) within individual homes where people spend most of their time. The balanced flow of air into and out of a residence is the primary mechanism for the entry of outdoor pollutants, and the removal of indoor source emissions. We developed an AER model to predict daily residential AER from infiltration airflows created by indoor outdoor temperature differences and wind speed, natural ventilation from opening of windows, and mechanical ventilation from operation of whole house or attic fans. Model parameters were estimated using questionnaires and AER measurements from the Research Triangle Park (RTP) PM Panel Study. The RTP study collected daily questionnaires and residential AER for seven consecutive days during each of four seasons in 36 homes within the RTP area of North Carolina. The individual model predicted AER closely correspond to the measured AER with an absolute difference of 0.34 ± 0.44 h-1 (mean ± SD). Our study demonstrates the feasibility of using the AER model to help reduce the uncertainty of AER estimates in air pollution exposure models, such as the EMI, in support of human health risk assessments. This work was reviewed by the U.S. EPA and approved for publication but does not necessarily reflect Agency policy.

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